7,165 results on '"whisker"'
Search Results
252. Effect of SiC whisker on densification and mechanical properties of hot-pressed TiC-based composites
- Author
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Mohammed Abdullahi Mu'azu, Zongjie Lyu, and Loke Kok Foong
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010302 applied physics ,Materials science ,Precipitation (chemistry) ,Process Chemistry and Technology ,Whiskers ,Composite number ,Nucleation ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Flexural strength ,Whisker ,visual_art ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Relative density ,Ceramic ,Composite material ,0210 nano-technology - Abstract
The impact of adding 40 vol% SiC whiskers on the sinterability, flexural strength, and hardness of TiC ceramics was studied. The hot-pressing route was employed to fabricate the TiC–SiC composite, as well as the monolithic TiC ceramic. The microstructural studies and X-ray diffractometry revealed the precipitation of carbon within the TiC matrix owing to the formation of non-stoichiometric TiCx during the hot-pressing. The addition of SiC whiskers noticeably improved the sinterability of TiC, attaining a fully dense composite sample. The nucleation and growth of new SiC grains were identified as the dominant factors in enhancing the relative density of the TiC-40 vol% SiC composite. Moreover, the SiC additive had an effective impact on both flexural strength and hardness of TiC, standing at 543 MPa and 2280 HV0.5 kg, respectively.
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- 2020
253. Multiscale mullite fiber/whisker reinforced silica aerogel nanocomposites with enhanced compressive strength and thermal insulation performance
- Author
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Xinghe Yao, Anran Guo, Xiang Zhang, Zhehan Yi, Liwen Yan, Shan Liu, Jiachen Liu, Tao Zhang, and Feng Hou
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Materials science ,Process Chemistry and Technology ,Whiskers ,Composite number ,Mullite ,Aerogel ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Thermal barrier coating ,Compressive strength ,Whisker ,Materials Chemistry ,Ceramics and Composites ,Fiber ,Composite material - Abstract
The multiscale architecture of the mullite fiber/mullite whisker was fabricated and applied for reinforcing silica aerogel. The mullite whisker could successfully grow on the mullite fiber, with a length of 5–10 μm and a diameter of about 100 nm. The mullite fiber/mullite whisker could be well-embedded in silica aerogel, which hold a mesoporous structure and a high specific surface area of 916.67 m2/g. The as-prepared mullite fiber/mullite whisker/silica aerogel possessed a low thermal conductivity of 0.034 W/(m·K) and a low density of 0.270 g/cm3. Thanks to the interface enhancement and the stress dispersion from the introduction of mullite whisker, the compressive stress of mullite fiber/mullite whisker/silica aerogel composite was 1.32 MPa (30% compression strain), 187% higher than that of the composite without mullite whiskers, meanwhile, a high resilience rate of 88.5% was maintained. The lightweight, heat-insulating, compression resilient composite exhibits huge prospects as the thermal barrier in the heat preservation field, especially in aerospace and aviation insulation.
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- 2020
254. Optimization in Process Parameters of Calcium Sulfate Whisker Modified Asphalt Using Response Surface Methodology
- Author
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Tao-tao Fan and Xiu-shan Wang
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Materials science ,Softening point ,0211 other engineering and technologies ,020101 civil engineering ,02 engineering and technology ,Penetration (firestop) ,Work in process ,Geotechnical Engineering and Engineering Geology ,0201 civil engineering ,Whisker ,Asphalt ,Response surface methodology ,Composite material ,021101 geological & geomatics engineering ,Civil and Structural Engineering - Abstract
To optimize the process parameters of calcium sulfate whisker (CSW) modified asphalt, the response surface methodology (RSM) was adopted to determine the optimum values of process parameters. Three influence factors, stirring time, stirring temperature, and development temperature (i.e., the temperature set by the forced-air oven to stabilize the internal structure of the modified asphalt sample after stirring), were selected to determine the process of modification. Three performances including high-temperature performance, low-temperature performance, and deformation resistance relating to the service of asphalt were analyzed as responses by testing in the Box–Behnken model. The results showed that, within the scope of this study, the optimum process parameters were stirring time of 32 min, stirring temperature of 175 °C, and development temperature of 175 °C, which have reliable accuracy compared with actual experimental results. In addition, the effect of three process parameters on asphalt performances was also researched, and it was found that stirring time has a more significant influence on the softening point, penetration at 25 °C and ductility at 10 °C interacting with other two factors.
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- 2020
255. Calcium Phosphate Cement Plus 10% Wollastonite Whiskers: An In Vivo Study
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José Ângelo Camilli, Craig McNulty, Celso Aparecido Bertran, Ana Cláudia de Souza, and Mariana Motisuke
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Biocompatibility ,Chemistry ,Biomaterial ,Connective tissue ,02 engineering and technology ,Bone healing ,engineering.material ,021001 nanoscience & nanotechnology ,Wollastonite ,Bone resorption ,03 medical and health sciences ,0302 clinical medicine ,medicine.anatomical_structure ,Whisker ,030220 oncology & carcinogenesis ,engineering ,medicine ,0210 nano-technology ,Parietal bone ,Biomedical engineering - Abstract
Biomaterials can be used in several areas of regenerative bioengineering, and is a viable option in the repair of bone injuries. A number of different types of biomaterials have been studied in relation to bone repair. Ceramics such as α-TCP have low fracture toughness compared to natural bone, so reinforcements such as wollastonite whiskers are developed so that they can be used in places with greater overload. This study aimed to evaluate the biocompatibility and bone neoformation of α-TCP plus 10% wollastonite whiskers, in vivo. To obtain the cement, α-TCP powders with or without 10% wollastonite whiskers were added to an aqueous solution containing 2.5% by weight of Na2HPO4 (anhydrous bibasic sodium phosphate). The biomaterial then became a paste, which was molded into the critical 5 mm defect made in the parietal bone of Wistar rats. Ten rats were divided into two groups. The animals from each group were euthanized within 30 days. Calvaries were removed and subjected to histological processing with Eosin and Hematoxylin. The implementation of the whisker biomaterial revealed the formation of intensely vascularized connective tissue in the implemented region; however, animals with the biomaterial α-TCP showed the formation of this tissue around the implemented region. On the other hand, intense bone resorption was observed only in the animals with Wollastonite Whiskers, but new bone formation in both groups. The biomaterial evaluated was shown to be non-cytotoxic, resorbable, and capable of inducing bone neoformation; however, more studies should be carried out to assess the application of this biomaterial in bone injuries.
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- 2020
256. Fabrication and mechanical properties of ZrO2–Al2O3–SiC(w) composites by oscillatory pressure sintering
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Tianbin Zhu, Di An, Yong Cheng, Shaobai Sang, Jie Zhang, Yawei Li, and Zhipeng Xie
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010302 applied physics ,Materials science ,Process Chemistry and Technology ,Whiskers ,Sintering ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Microstructure ,Hot pressing ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Fracture toughness ,Whisker ,visual_art ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Cubic zirconia ,Ceramic ,Composite material ,0210 nano-technology - Abstract
Tetragonal zirconia polycrystalline (TZP) ceramics have been considered as the important structural materials in many key technology fields, but some of their mechanical properties do not meet the requirement under the extreme environmental conditions. In this work, SiC whiskers and Al2O3 particles were used as reinforcement additives to synergistically toughen TZP ceramics, and a newly developed oscillatory pressure sintering (OPS) technique was employed to fabricate the new zirconia-based ceramics. For comparison, the traditional hot pressing (HP) method was also used to prepare these composites. The results showed that with 15 vol% SiC whiskers addition, the toughening mechanisms such as whisker bridging, whisker pulling-out, crack deflection, and crack branching appeared apparently, thereby improving fracture toughness of such composites. In contrast to HP, OPS can eliminate defects, improve densification, obtain more uniform microstructure, and significantly enhance mechanical properties of the composites.
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- 2020
257. Electrical and Physical Properties of Ceramic Whiskers from the Al2O3-CaB6 System
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M.M. Gomaa and S.H. Kenawy
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Materials science ,Whiskers ,Sintering ,chemistry.chemical_element ,Dielectric ,Conductivity ,Microstructure ,Inorganic Chemistry ,chemistry ,Whisker ,Aluminium ,visual_art ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Ceramic ,Composite material - Abstract
In this study physical properties were determined for ceramic whiskers based on the Al2O3-CaB6 system. Through a wet method and a sintering process between 1400 °C and 1500 °C, aluminium borate (Al18B4O33) was developed from the binary Al2O3 (95-85 %)-CaB6 (5-15 %) system. The whisker microstructure from interlocked fibres (between 8 and 30 µm in width) developed after the sintering process. The addition of CaB6 at the expense of alumina at all additions resulted in an increase of the conductivity and the dielectric constant of the corresponding ceramic materials. The relationships between the phases formed, the conductivity and the dielectric values of the studied specimens were found to differ according to the complicated void structure (pores) in the specimens as detected in SEM images.
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- 2020
258. Tin Whisker Growth on Electronic Assemblies Soldered with Bi-Containing, Pb-Free Alloys
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Zohreh Bagheri, Jeff Kennedy, Stephan J. Meschter, Polina Snugovsky, and André M. Delhaise
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010302 applied physics ,Materials science ,Whiskers ,Metallurgy ,chemistry.chemical_element ,Recrystallization (metallurgy) ,Electroless nickel immersion gold ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Bismuth ,chemistry ,Whisker ,Soldering ,0103 physical sciences ,Materials Chemistry ,Dynamic recrystallization ,Electrical and Electronic Engineering ,0210 nano-technology ,Tin - Abstract
With the introduction of environmental legislation, lead (Pb)-free materials have made their way into the electronics supply chain. As a result, tin whiskers may initiate and grow under specific conditions. Sufficiently long whiskers may cause in-field short circuit failures, which are a serious concern in many high-reliability applications such as aerospace, automotive, and medical. There are efforts in developing third generation Pb-free solder alloys to replace tin-silver-copper (Sn-Ag-Cu, or SAC). Bismuth (Bi) has been considered for inclusion in SAC alloys to reduce melting point and improve reliability. In this study, we examine whisker formation on small outline transistor (SOT) components assembled with SAC-Bi alloys after ambient temperature (25°C) or high temperature (85°C), high humidity (85% RH) storage. Four alloys were considered—Senju M42 (Sn-2.0Ag-0.7Cu-3.0Bi), Violet (Sn-2.25Ag-0.5Cu-6.0Bi), Sunflower (Sn-0.7Cu-7.0Bi), and SAC305 (Sn-3.0Ag-0.5Cu). The assemblies were finished with immersion tin (ImmSn) or electroless nickel immersion gold (ENIG), and some were intentionally contaminated prior to exposure. It was found that SAC305 tended to grow longer whiskers than SAC-Bi alloys, though more whiskers were found on the latter. Particle Stimulated Nucleation (PSN) of recrystallization of the β-Sn matrix, influenced by Bi precipitation, appears to influence dynamic recrystallization (DRX), the mechanism for whisker growth.
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- 2020
259. Thermal and dielectric properties of epoxy-based composites filled with flake and whisker type hexagonal boron nitride materials
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Xinfeng Zhang, Yujun Zhang, Xiao Lin, Rongkun Yang, Mingming Sheng, Yaran Pei, and Hongyu Gong
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Filler (packaging) ,Materials science ,Polymers and Plastics ,Whiskers ,Organic Chemistry ,Flake ,02 engineering and technology ,Dielectric ,Epoxy ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Thermal conductivity ,Whisker ,visual_art ,Thermal ,Materials Chemistry ,visual_art.visual_art_medium ,Composite material ,0210 nano-technology - Abstract
In this work, the epoxy-based composites filled with 3-Aminopropyltriethoxysilane (KH-550) modified binary filler of hexagonal boron nitride (h-BN) flakes and h-BN whiskers were fabricated, and the thermal and dielectric properties of composites were systematically investigated. Adding h-BN whiskers to the filler could effectively form heat conduction paths and improve the phonon transmission efficiency, thereby improving the thermal conductivity of the composites. According to our results, the thermal conductivity of composite with 27 wt% h-BN flakes and 3 wt% h-BN whiskers reached up to 0.819 W·m−1·K−1, which was 3.9 times that of pure epoxy resin. At the same time, the dielectric loss value and dielectric constant of this composite at 1 MHz were 0.02678 and 4.55, respectively, while pure epoxy resin were 0.03602 and 4.33. In addition, introducing h-BN whiskers into the matrix could effectively improve the thermal stability and heat dissipation performance of composites.
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- 2020
260. Selective growth of tin whiskers from its alloys on Ti2SnC
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ZhengMing Sun, Yushuang Liu, Yan Zhang, Wei He, Wei Zhang, Wubian Tian, Chengjie Lu, Peigen Zhang, and Jingwen Tang
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Materials science ,Polymers and Plastics ,Whiskers ,Nanowire ,chemistry.chemical_element ,02 engineering and technology ,Substrate (electronics) ,Crystal structure ,010402 general chemistry ,01 natural sciences ,Metal ,Whisker ,Materials Chemistry ,Composite material ,Mechanical Engineering ,Metals and Alloys ,021001 nanoscience & nanotechnology ,Surface energy ,0104 chemical sciences ,chemistry ,Mechanics of Materials ,visual_art ,Ceramics and Composites ,visual_art.visual_art_medium ,0210 nano-technology ,Tin - Abstract
The spontaneous growth of metal whiskers has been investigated for more than 70 years. However, there is still no agreement on its growth mechanism, and moreover, new characteristics of this whiskering phenomenon continue to emerge. In this study, Ti2SnC is found to be capable of extracting Sn out of its alloys (SnBi, SnAg) by selectively growing Sn whiskers, and the Sn whiskers share the features of the traditional whiskers on platings and solders. Replacing the Ti2SnC substrate with TiC or SiC, under the same conditions, however, the selective growth of Sn whisker does not happen, which means Ti2SnC plays a critical role in it. Based on the unique crystal structure of Ti2SnC, active Sn atoms diffusing through the basal planes of Ti2SnC is proposed to explain the selectivity. The driving force is suggested to be the high interfacial energy between Ti2SnC and tin. This study is of importance to further understand the growth mechanism of metallic whiskers, and it may be also possible to be harnessed to develop paradigm-shifting technologies of metal purification and metallic whisker/nanowire preparation.
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- 2020
261. Influence of cBN content, Al2O3 and Si3N4 additives and their morphology on microstructure, properties, and wear of PCBN with NbN binder
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O. Zaporozhets, V. V. Garashchenko, Iu Melnichuk, Volodymyr Bushlya, Yu. Yu. Rumiantseva, and Vladimir Z. Turkevich
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010302 applied physics ,Materials science ,Process Chemistry and Technology ,Whiskers ,Metallurgy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Hardened steel ,chemistry.chemical_compound ,Fracture toughness ,chemistry ,Machining ,Boron nitride ,Whisker ,visual_art ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Ceramic ,0210 nano-technology - Abstract
Polycrystalline cubic boron nitride (PCBN) tool materials with NbN binder without additives and PCBN with Al2O3 or Si3N4 micropowder and whisker additives were manufactured and compared. PCBN materials with Si3N4 whisker reinforcement have the best mechanical properties of all the evaluated materials. Composites reinforced with Al2O3 whiskers have the lowest fracture toughness. However, Al2O3 whisker-reinforced tools outperform both commercial and Si3N4 reinforced tools when machining hardened steel. Thus Al2O3 whisker-reinforced PCBN materials are promising for industrial applications, likely due to their higher resistance to oxidation and diffusional wear mechanisms during cutting operations. (Less)
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- 2020
262. Effect of SiO2 Coating on Microstructure and Mechanical Behavior of Al-ABOw Composite Synthesized by Powder Metallurgy Technique
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Manas Ranjan Majhi, Indrajit Chakrabarty, Neeraj Pandey, and S.C. Ram
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010302 applied physics ,Materials science ,Composite number ,chemistry.chemical_element ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,chemistry ,Coating ,Flexural strength ,Aluminium ,Whisker ,Powder metallurgy ,0103 physical sciences ,Ceramics and Composites ,engineering ,Composite material ,0210 nano-technology ,Boron - Abstract
In this investigation, powder metallurgy route was employed to synthesize SiO2 (5, 10 and 15 vol%) coated aluminium borate whisker (ABOw) reinforced aluminium composites. Commercial pure aluminium ...
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- 2020
263. Local variations in grain formation, grain boundary sliding, and whisker growth along grain boundaries in large-grain Sn films
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Wei-Hsun Chen, Congying Wang, Carol A. Handwerker, Pylin Sarobol, and John E. Blendell
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010302 applied physics ,Materials science ,Mechanical Engineering ,Whiskers ,Metals and Alloys ,Nucleation ,02 engineering and technology ,Temperature cycling ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Mechanics of Materials ,Whisker ,0103 physical sciences ,General Materials Science ,Grain boundary ,Composite material ,0210 nano-technology ,Grain Boundary Sliding - Abstract
Two grain boundaries (GBs) in a Sn-alloy film exhibited different morphological changes during thermal cycling: whisker growth and GB sliding. Along GB-I, pervasive nucleation of high-angle and low-angle GBs occurred, with whisker growth of some shallow grains depending on sub-surface GB geometry. Most whiskers showed substantial changes of crystallographic orientation and surface normal relative to the parent grains. Along GB-II, GB sliding was characterized by mass accumulation, crystallographic rotation, and localized yielding. Results for two GBs suggest that grain crystallography and GB geometry, particularly GB inclination, are critical in determining the extent of new grain formation and subsequent whisker growth.
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- 2020
264. Crystalline-Phase Switching in Heterostructured Ga(As,P) Nanowires under the Impact of Elastic Strains
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V. N. Sibirev, Yu. S. Berdnikov, and N. V. Sibirev
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010302 applied physics ,Materials science ,Nanowire ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Nanocrystal ,Whisker ,Phase (matter) ,Metastability ,0103 physical sciences ,Composite material ,0210 nano-technology ,Phase switching - Abstract
The effect of elastic stresses on the Ga(As, P) crystalline phase of nanowires is studied. It is shown that the elastic stresses can lead to the stable growth of whisker nanocrystals in the metastable phase. The possibility of crystal-phase switching inside a GaP nanowire after the appearance of a Ga(As, P) insert is described.
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- 2020
265. Synergistic Effect between CaCO3 Whisker and Steel-PVA Fiber Cocktail in Cement-Based Material at Elevated Temperature
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Mingli Cao, Chaopeng Xie, Zongli Li, Xiongxiong Zhou, and Li Li
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Cement ,Materials science ,Building and Construction ,Microstructure ,Polyvinyl alcohol ,chemistry.chemical_compound ,Calcium carbonate ,chemistry ,Mechanics of Materials ,Whisker ,General Materials Science ,Fiber ,Composite material ,Civil and Structural Engineering - Abstract
A new fiber cocktail reinforced cement–based materials (NFCRCM) with steel, polyvinyl alcohol (PVA) fiber, and calcium carbonate whisker (CCW) was developed to obtain powerful fire resistan...
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- 2022
266. Novel whisker-reinforced Al2O3–SiO2 aerogel composites with ultra-low thermal conductivity.
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Hou, Xianbo, Zhang, Rubing, and Fang, Daining
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AEROGEL synthesis , *ALUMINUM oxide , *SUPERCRITICAL fluids , *SUPERCRITICAL drying , *THERMAL conductivity - Abstract
Novel aluminium borate whisker (ABOw)/Al 2 O 3 –SiO 2 aerogel composites were prepared by adding ABOw into an Al 2 O 3 –SiO 2 solution using a quick gel and supercritical fluid drying method. The microstructures and thermal and mechanical properties of the prepared ABOw/Al 2 O 3 –SiO 2 aerogel composites were investigated. The ABOw is randomly and homogeneously dispersed in the Al 2 O 3 –SiO 2 aerogel and the well-integrated nature of the material leads to enhanced mechanical properties and smaller linear shrinkage compared to those determined for pure Al 2 O 3 –SiO 2 aerogels. The compressive strength of the aerogel composites exhibit lightweight, ultra-low thermal conductivity (i.e. 0.040 W/(m·K)) and high compressive strength (i.e. 1.40 MPa at 10% strain), which is five times higher than the strength of pure Al 2 O 3 –SiO 2 aerogels. This aerogel composite prepared in this study makes a potential application in thermal insulation materials. [ABSTRACT FROM AUTHOR]
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- 2017
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267. Green synthesis of the excellent magnesium oxysulfate whiskers under controlled reaction conditions.
- Author
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Tang, Zhilei, Zhu, Chaoliang, Fan, Faying, Qing, Binju, Shao, Fei, Lei, Fengpeng, and Deng, Xiaochuan
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MAGNESIUM sulfate , *COMPOSITE materials , *CHEMICAL reactions , *CHEMICAL synthesis , *METALLIC whiskers - Abstract
Magnesium oxysulfate (MgSO 4 ·5Mg(OH) 2 ·3H 2 O, abbreviated as 153MOS) whiskers with high aspect ratio, high purity, and favorable dispersibility without the sector-like whiskers has been prepared via a simple hydrothermal method. In this method, only MgSO 4 ·7H 2 O and Mg(OH) 2 is used as the starting raw materials without by-products detected in the final production, which can decrease the cost and reduce the discharge of pollutant. The diameter and length of the whiskers is 0.1–0.7 μm and 70–150 μm, respectively. In addition, the molar ratio of MgSO 4 ·7H 2 O to Mg(OH) 2 , reaction temperature, reaction time, and the solid content of Mg(OH) 2 have influence on the purity, structure, and morphology of the 153MOS whiskers. This 153MOS whiskers obtained in this research may be further used in the polymer matrix composites as reinforcing materials, flame retardant, and composite materials additive. [ABSTRACT FROM AUTHOR]
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- 2017
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268. Eliminating Whisker Growth by Indium Addition in Electroplated Sn on Copper Substrate.
- Author
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Das Mahapatra, S., Majumdar, B., Dutta, I., and Bhassyvasantha, S.
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METALLIC whiskers ,METAL crystals ,TIN ,LEAD ,PHYSICAL metallurgy - Abstract
Whisker growth from Sn coatings is a reliability concern in electronic packages, until recently mitigated by Pb addition. Recently, it was demonstrated that doping with In dramatically reduces whisker growth in 1 μm thick Sn. Here, we present the results of In-doping on whisker growth from 3 μm and 6 μm thick Sn-films and explore the reasons behind this mitigation, and compare the results with a baseline sample of pure Sn and a control sample of tri-layer Sn-In-Sn, all subjected to identical thermal treatments. It is shown that In addition completely stops whisker growth from electroplated Sn. The impact of In addition on the film microstructure and the role of the surface oxide coating are investigated. Previous work had shown that while In addition reduces grain boundary diffusivity, it does not fully account for the observed dramatic reduction of whisker growth. In this work, it is shown by Auger electron spectroscopy and x-ray photoelectron spectroscopy that In is incorporated in the surface-oxide. Since whisker-growth is contingent on the presence of a tenacious surface-oxide, this suggests that the alteration of the oxide properties may be responsible for the observed reduction in whisker growth. Finite element modeling is utilized to demonstrate that a reduction of the elastic modulus of the surface oxide would reduce the driving force of Sn whisker growth, thus proffering a rationale for the effect of In incorporation. [ABSTRACT FROM AUTHOR]
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- 2017
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269. Effect of solution treatment on the texture and tensile properties of Mg2B2O5W/2024Al composite.
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Sheng, J., Wang, L.D., Zhao, Y., Xu, S.C., Liu, X.L., and Fei, W.D.
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MAGNESIUM alloys , *SOLUTION (Chemistry) , *CRYSTAL texture , *TENSILE tests , *METALLIC composites - Abstract
A 2024 aluminum matrix composite reinforced by Mg 2 B 2 O 5 whiskers was fabricated by squeeze casting method. The effects of solution time on the texture and tensile properties are investigated. The results show that solution time has significant effect on the texture type and tensile properties of the composite. Fiber texture of 2024Al matrix was found in the as-cast composite and its evolution during solution process was analyzed. The results indicate that recrystallization process of 2024Al matrix is the main reason for the evolution of texture and the change of mechanical properties after solution treatment. [ABSTRACT FROM AUTHOR]
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- 2017
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270. Antagonizing the different stages of kappa opioid receptor activation selectively and independently attenuates acquisition and consolidation of associative memories.
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Loh, Ryan, Chau, Lily, Aijaz, Ali, Wu, Kevin, and Galvez, Roberto
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OPIOID receptors , *SOMATOSENSORY cortex , *PERTUSSIS toxin , *GUANIDINES , *PROTEIN expression - Abstract
Previous work from our laboratory has shown that nonspecific kappa opioid receptor (KOR) antagonism in primary somatosensory cortex (S1) can inhibit acquisition for the forebrain-dependent associative task, Whisker-Trace Eyeblink conditioning (WTEB). Although studies have demonstrated that KOR activation can alter stimuli salience, our studies controlled for these factors, demonstrating that KOR also plays a role in facilitating learning. KOR has two distinct phases of activation followed by internalization/downregulation, that each independently activate kinases and transcription factors known to mediate task acquisition and memory consolidation respectively. The current study demonstrated that antagonism of the initial phase of KOR activation in S1 via local injections of the g-protein inhibitor, pertussis toxin (PTX), blocked initial WTEB acquisition without affecting retention of the association. In contrast, KOR late phase antagonism in S1 via local injections of the GRK3-specific antagonist, guanidinonaltrindole (GNTI), blocked retention of the WTEB association without affecting task acquisition. Consistent with the known mechanism for KOR activation, KOR protein expression in S1 was found to be decreased following WTEB training, further supporting the involvement of neocortical KOR activation with learning. Prior studies have shown that task acquisition and memory consolidation are mediated by distinct molecular processes; however, little is known regarding a potential mechanism driving these processes. The current study suggests that neocortical KOR activation mediates activation of these processes with learning. This study provides the first evidence for a time- and learning-dependent property of neocortical KOR in facilitating acquisition and consolidation of associative memories, while elucidating an unexplored neocortical learning mechanism. [ABSTRACT FROM AUTHOR]
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- 2017
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271. Variations in vibrissal geometry across the rat mystacial pad: base diameter, medulla, and taper.
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Belli, Hayley M., Hartmann, Mitra J. Z., Yang, Anne E. T., and Bresee, Chris S.
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VARIATIONS (Aesthetics) , *GEOMETRY , *CONFORMAL geometry , *CURVES , *DIAMETER - Abstract
Many rodents tactually sense the world through active motions of their vibrissae (whiskers), which are regularly arranged in rows and columns (arcs) on the face. The present study quantifies several geometric parameters of rat whiskers that determine the tactile information acquired. Findings include the following. 1) A meta-analysis of seven studies shows that whisker base diameter varies with arc length with a surprisingly strong dependence on the whisker’s row position within the array. 2) The length of the whisker medulla varies linearly with whisker length, and the medulla’s base diameter varies linearly with whisker base diameter. 3) Two parameters are required to characterize whisker “taper”: radius ratio (base radius divided by tip radius) and radius slope (the difference between base and tip radius, divided by arc length). A meta-analysis of five studies shows that radius ratio exhibits large variability due to variations in tip radius, while radius slope varies systematically across the array. 4) Within the resolution of the present study, radius slope does not differ between the proximal and distal segments of the whisker, where “proximal” is defined by the presence of the medulla. 5) Radius slope of the medulla is offset by a constant value from radius slope of the proximal portion of the whisker. We conclude with equations for all geometric parameters as functions of row and column position. [ABSTRACT FROM AUTHOR]
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- 2017
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272. Neuronal adaptation in the somatosensory system of rodents.
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Lampl, I. and Katz, Y.
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SOMATOSENSORY cortex , *NEUROPLASTICITY , *BRAIN stem , *THALAMUS , *LABORATORY rodents - Abstract
The sensory systems in animals constantly monitor the environment and process salient and relevant features while subtracting background activity. This process requires continuous recalibration of neuronal gain based on recent history. Adaptation has been postulated to be the key mechanism by which neurons rapidly tune their response curves to represent the entire dynamic range of external inputs. Rodents heavily rely on their vibrissa system while gathering information about their surroundings using whisking. Neuronal adaptation is observed in all stages of sensory processing, from the whisker follicle through the brainstem and thalamus up to the barrel cortex. In this review, we discuss the intrinsic, synaptic and network mechanisms of adaptation such as short-term synaptic depression, inhibitory suppression, balance between excitation and inhibition as well as the role of cascading adaptation. Furthermore, we describe recent findings about the different intensity dependent adaptation properties in the two major somatosensory pathways and their possible implications about coding. [ABSTRACT FROM AUTHOR]
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- 2017
- Full Text
- View/download PDF
273. Fabrication and mechanical properties of composite based on β-chitin and polyacrylic acid.
- Author
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Bogdanova, Olga I., Polyakov, Dmitry K., Streltsov, Dmitry R., Kulebyakina, Alevtina I., Orekhov, Anton S., Vasiliev, Alexander L., Blackwell, John, and Chvalun, Sergey N.
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CHITIN , *POLYACRYLIC acid , *MICROFIBRILS , *ACRYLIC acid , *HUMIDITY - Abstract
Squid β-chitin has been exfoliated in aqueous acrylic acid (AA), after which a composite film of chitin microfibrils in polyacrylic acid (PAA) has been prepared by in situ polymerization of the AA. The segregated chitin fibrils in the composite are 4–6 nm in diameter, with an aspect ratio >250. After drying cast films of the composites containing 1, 2 and 3% (w/w) chitin at 140 °C for four hours, there was a dramatic resistance to swelling in water, in that the dried films showed only small changes in shape and properties after four hours immersed in water.The most profound impact of the reinforcement on the mechanical properties is observed at high relative humidity (RH), when the PAA is in the rubbery state. At 97.5% RH and room temperature, the elastic moduli of the composites with 1, 2 and 3% (w/w) chitin were 150, 230 and 2100 MPa respectively, compared to 65 MPa for pure PAA. The main contribution to the filler-reinforcing effect is the high aspect ratio of fibrils and non-covalent interactions, but the stability in water suggests the presence of chemical bonding between the PAA and chitin. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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274. Whisker touch guides canopy exploration in a nocturnal, arboreal rodent, the Hazel dormouse ( Muscardinus avellanarius).
- Author
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Arkley, Kendra, Tiktak, Guuske, Breakell, Vicki, Prescott, Tony, and Grant, Robyn
- Subjects
- *
HAZEL mouse , *WHISKERS , *PLANT canopies , *HABITATS , *INFORMATION theory - Abstract
Dormouse numbers are declining in the UK due to habitat loss and fragmentation. We know that dormice are nocturnal, arboreal, and avoid crossing open spaces between habitats, yet how they navigate around their canopy is unknown. As other rodents use whisker touch sensing to navigate and explore their environment, this study investigates whether Hazel dormice ( Muscardinus avellanarius) employ their whiskers to cross between habitats. We analysed high-speed video footage of dormice exploring freely in flat and climbing arenas in near darkness and using infrared light illumination. We confirm that, like rats and mice, dormice move their whiskers back and forth continuously (~10 Hz) in a motion called whisking and recruit them to explore small gaps (<10 cm) by increasing the amplitude and frequency of whisking and also the asymmetry of movement between the left and right whisker fields. When gaps between platforms are larger than 10-15 cm, dormice spend more time travelling on the floor. These findings suggest that dormice can actively and purposively move their whiskers to gather relevant information from their canopy at night. As this species is vulnerable to threats on the ground, we also provide evidence that joining habitat patches between dormouse populations is important for promoting natural behaviours and movement between patches. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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275. Synergistic effect of graphene and β-Si3N4 whisker enables Si3N4 ceramic composites to obtain ultra-low friction coefficient.
- Author
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Chen, Fei, Yan, Ke, Hong, Jun, and Song, Jingdong
- Subjects
- *
CERAMICS , *GRAPHENE , *FRICTION , *CRYSTAL whiskers , *CERAMIC-matrix composites , *WEAR resistance - Abstract
This work aimed to further enhance the tribological properties of Si 3 N 4 -based ceramics by introducing β-Si 3 N 4 whisker (β-Si 3 N 4w) into multilayer graphene (MLG)/Si 3 N 4 ceramics to inhibit the reduction in the hardness of ceramic matrix induced by MLG. Therefore, the Si 3 N 4 ceramics containing 1 wt% MLG and 1–5 wt% β-Si 3 N 4w were prepared. The tribological properties of specimens at room temperature were evaluated using a ball-disk rotating tribo-tester. The coefficient of friction (COF) and wear resistance of MLG/β-Si 3 N 4w /Si 3 N 4 ceramic composites (MwSNCC) were analyzed. The existence of MLG and β-Si 3 N 4w enabled the dry sliding COF of MwSNCC to notably reduce to 0.04–0.07, which was 89.43–95.40% lower than that of monolithic Si 3 N 4 ceramics, and the wear resistance was enhanced by 33–62.40%. [Display omitted] • Friction coefficient of Si 3 N 4 ceramics with MLG/β-Si 3 N 4w is reduced to 0.04. • Friction coefficient was 89.43–95.40% lower than that of monolithic Si 3 N 4 ceramics. • The wear resistance of Si 3 N 4 -based ceramics was improved by 33–62.40%. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
276. Whiskers provide time-series of toxic and essential trace elements, Se:Hg molar ratios, and stable isotope values of an apex Antarctic predator, the leopard seal.
- Author
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Charapata, Patrick, Clark, Casey T., Miller, Nathan, Kienle, Sarah S., Costa, Daniel P., Goebel, Michael E., Gunn, Heather, Sperou, Emily S., Kanatous, Shane B., Crocker, Daniel E., Borras-Chavez, Renato, and Trumble, Stephen J.
- Published
- 2023
- Full Text
- View/download PDF
277. Whisker Sensing by Force and Moment Measurements at the Whisker Base.
- Author
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Starostin EL, Goss VGA, and van der Heijden GHM
- Abstract
We address the theoretical question which forces and moments measured at the base of a whisker (tactile sensor) allow for the prediction of the location in space of the point at which a whisker makes contact with an object. We deal with the general case of three-dimensional deformations as well as with the special case of planar configurations. All deformations are treated as quasi-static, and contact is assumed to be frictionless. We show that the minimum number of independent forces or moments required is three but that conserved quantities of the governing elastic equilibrium equations prevent certain triples from giving a unique solution in the case of contact at any point along the whisker except the tip. The existence of these conserved quantities depends on the material and geometrical properties of the whisker. For whiskers that are tapered and intrinsically curved, there is no obstruction to the prediction of the contact point. We show that the choice of coordinate system (Cartesian or cylindrical) affects the number of suitable triples. Tip and multiple point contact are also briefly discussed. Our results explain recent numerical observations in the literature and offer guidance for the design of robotic tactile sensory devices.
- Published
- 2023
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278. Associations of Unilateral Whisker and Olfactory Signals Induce Synapse Formation and Memory Cell Recruitment in Bilateral Barrel Cortices: Cellular Mechanism for Unilateral Training Toward Bilateral Memory.
- Author
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Zilong Gao, Lei Chen, Ruicheng Fan, Wei Lu, Dangui Wang, Shan Cui, Li Huang, Shidi Zhao, Sudong Guan, Yan Zhu, and Jin-Hui Wang
- Subjects
MEMORY ,SYNAPSES ,WHISKERS ,ODORS ,SOMATOSENSORY cortex ,NEURAL transmission ,GABA - Abstract
Somatosensory signals and operative skills learned by unilateral limbs can be retrieved bilaterally. In terms of cellular mechanism underlying this unilateral learning toward bilateral memory, we hypothesized that associative memory cells in bilateral cortices and synapse innervations between them were produced. In the examination of this hypothesis, we have observed that paired unilateral whisker and odor stimulations led to odorant-induced whisker motions in bilateral sides, which were attenuated by inhibiting the activity of barrel cortices. In the mice that showed bilateral cross-modal responses, the neurons in both sides of barrel cortices became to encode this new odor signal alongside the innate whisker signal. Axon projections and synapse formations from the barrel cortex, which was co-activated with the piriform cortex, toward its contralateral barrel cortex (CBC) were upregulated. Glutamatergic synaptic transmission in bilateral barrel cortices was upregulated and GABAergic synaptic transmission was downregulated. The associative activations of the sensory cortices facilitate new axon projection, glutamatergic synapse formation and GABAergic synapse downregulation, which drive the neurons to be recruited as associative memory cells in the bilateral cortices. Our data reveal the productions of associative memory cells and synapse innervations in bilateral sensory cortices for unilateral training toward bilateral memory. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
279. Calibrating the time span of longitudinal biomarkers in vertebrate tissues when fine-scale growth records are unavailable.
- Author
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Rogers, Tracey L., Fung, Jeffery, Slip, David, Steindler, Lisa, and O'connell, Tamsin C.
- Subjects
BIOLOGICAL tags ,LEOPARD seal ,STABLE isotopes ,WHISKERS ,VERTEBRATE development - Abstract
Biological markers (biomarkers) are invaluable and widely adopted in ecology, archaeology, and anthropology. Serially sampling biomarkers along continuously growing inert tissue, such as vibrissae, hair, nail, horn, or baleen, is an ideal method by which to capture the changes in an individual's diet, environment, climate, health, and stress levels. However, there are complications in calibrating the time periods that samples represent. Here, we assess how the choice of model and the input data used affect the prediction of time span. We use the Antarctic leopard seal, Hydrurga leptonyx, as our model, with stable isotope data from the vibrissae of captive and wild animals. We show that for tissues with nonlinear growth, and where fine-scale data on tissue growth are unavailable, modeling over the life span of the tissue is a simple and easily adopted approach. In this method, growth parameters are derived from surveys of the study population and the shed-replacement cycle to calibrate the time span of the biomarker data. This model performed better than linear and nonlinear models, which use parameters that have been derived from growth measurements documented over short periods relative to the life span of the tissue. These latter approaches performed in a similar fashion to each other as they tended to overestimate the life span of the tissue. Whether growth is linear or nonlinear, not accounting for position-specific differences in growth (rates or coefficients) and asymptotic length ( L
∞ ) resulted in different interpretations of biomarker data across the samples collected from the same individual. In species where metabolically inert tissue grows in a progressive fashion, the ability to account for time-specific information refines our ability to interpret the biomarker data. We recommend that this approach be adapted for tissue, such as the vibrissae and hair of mammals and the hair of humans, which exhibit the predictable growth. [ABSTRACT FROM AUTHOR]- Published
- 2016
- Full Text
- View/download PDF
280. Electromigration induced spontaneous Ag whisker growth in fine Ag-alloy bonding interconnects: Novel polarity effect.
- Author
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Hsu, Tzu-Yu, Chang, Jing-Yao, Chang, Hsiao-Min, and Ouyang, Fan-Yi
- Subjects
- *
ELECTRODIFFUSION , *METALLIC whiskers , *CRYSTAL growth , *WIRE , *SILVER alloys , *METAL bonding , *POLARITY (Chemistry) - Abstract
Ag-alloy wire has been recognized to be a good candidate for interconnect in light-emitting diode (LED) technology. This study employed fine Ag-alloy wires bonded on Al-Si pad to investigate their failure mechanism under current stressing of 8×10 4 A/cm 2 at ambient temperature of 150 °C and 175 °C, respectively. We report a novel polarity effect that the spontaneous whisker growth of Ag near bonded area only happens when electrons flowed from Al to Ag, while surface of bond joints remains intact with electrons flowed from Ag to Al, suggesting that the nucleation and growth of Ag whisker is strongly affected by the direction of electron flow. We proposed that the different behaviors on the whisker growth is because compressive stress caused by current crowding effect only builds up with electrons flowed from Al to Ag. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
281. HDAC1 negatively regulates Bdnf and Pvalb required for parvalbumin interneuron maturation in an experience-dependent manner.
- Author
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Koh, Dawn X. P. and Sng, Judy C. G.
- Subjects
- *
PARVALBUMINS , *INTERNEURONS , *SENSORY receptors , *NEURAL circuitry , *SENSORY deprivation , *GENETIC transcription - Abstract
During early postnatal development, neuronal circuits are sculpted by sensory experience provided by the external environment. This experience-dependent regulation of circuitry development consolidates the balance of excitatory-inhibitory (E/I) neurons in the brain. The cortical barrel-column that innervates a single principal whisker is used to provide a clear reference frame for studying the consolidation of E/I circuitry. Sensory deprivation of S1 at birth disrupts the consolidation of excitatory-inhibitory balance by decreasing inhibitory transmission of parvalbumin interneurons. The molecular mechanisms underlying this decrease in inhibition are not completely understood. Our findings show that epigenetic mechanisms, in particular histone deacetylation by histone deacetylases, negatively regulate the expression of brain-derived neurotrophic factor ( Bdnf) and parvalbumin ( Pvalb) genes during development, which are required for the maturation of parvalbumin interneurons. After whisker deprivation, increased histone deacetylase 1 expression and activity led to increased histone deacetylase 1 binding and decreased histone acetylation at Bdnf promoters I-IV and Pvalb promoter, resulting in the repression of Bdnf and Pvalb gene transcription. The decrease in Bdnf expression further affected parvalbumin interneuron maturation at layer II/III in S1, demonstrated by decreased parvalbumin expression, a marker for parvalbumin interneuron maturation. Knockdown of HDAC1 recovered Bdnf and Pvalb gene transcription and also prevented the decrease of inhibitory synapses accompanying whisker deprivation. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
282. Precision mapping of the vibrissa representation within murine primary somatosensory cortex.
- Author
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Knutsen, Per M., Mateo, Celine, and Kleinfeld, David
- Subjects
- *
BRAIN imaging , *SOMATOSENSORY cortex , *ELECTROENCEPHALOGRAPHY , *NEUROPLASTICITY , *BRAIN waves - Abstract
The ability to form an accurate map of sensory input to the brain is an essential aspect of interpreting functional brain signals. Here, we consider the somatotopic map of vibrissa-based touch in the primary somatosensory (vS1) cortex of mice. The vibrissae are represented by a Manhattan-like grid of columnar structures that are separated by inter-digitating septa. The development, dynamics and plasticity of this organization is widely used as a model system. Yet, the exact anatomical position of this organization within the vS1 cortex varies between individual mice. Targeting of a particular column in vivo therefore requires prior mapping of the activated cortical region, for instance by imaging the evoked intrinsic optical signal (eIOS) during vibrissa stimulation. Here, we describe a procedure for constructing a complete somatotopic map of the vibrissa representation in the vS1 cortex using eIOS. This enables precise targeting of individual cortical columns. We found, using C57BL/6 mice, that although the precise location of the columnar field varies between animals, the relative spatial arrangement of the columns is highly preserved. This finding enables us to construct a canonical somatotopic map of the vibrissae in the vS1 cortex. In particular, the position of any column, in absolute anatomical coordinates, can be established with near certainty when the functional representations in the vS1 cortex for as few as two vibrissae have been mapped with eIOS. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
283. Whisking kinematics enables object localization in head-centered coordinates based on tactile information from a single vibrissa
- Author
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Anne En-Tzu Yang and Mitra J Z Hartmann
- Subjects
Biomechanics ,Touch ,whisker ,Orienting ,superior colliculus ,trigeminal ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
During active tactile exploration with their whiskers (vibrissae), rodents can rapidly orient to an object even though there are very few proprioceptors in the whisker muscles. Thus a long-standing question in the study of the vibrissal system is how the rat can localize an object in head-centered coordinates without muscle-based proprioception. We used a three-dimensional model of whisker bending to simulate whisking motions against a peg to investigate the possibility that the 3D mechanics of contact from a single whisker are sufficient for localization in head-centered coordinates. Results show that, for nearly all whiskers in the array, purely tactile signals at the whisker base – as would be measured by mechanoreceptors, in whisker-centered coordinates – could be used to determine the location of a vertical peg in head-centered coordinates. Both the roll and the elevation components of whisking kinematics contribute to the uniqueness and resolution of the localization. These results offer an explanation for a behavioral study showing that rats can more accurately determine the horizontal angle of an object if one column, rather than one row, of whiskers is spared.
- Published
- 2016
- Full Text
- View/download PDF
284. Decoupling kinematics and mechanics reveals coding properties of trigeminal ganglion neurons in the rat vibrissal system
- Author
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Nicholas E Bush, Christopher L Schroeder, Jennifer A Hobbs, Anne ET Yang, Lucie A Huet, Sara A Solla, and Mitra JZ Hartmann
- Subjects
active touch ,neural coding ,somatosensation ,whisker ,natural behavior ,mechanics ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
Tactile information available to the rat vibrissal system begins as external forces that cause whisker deformations, which in turn excite mechanoreceptors in the follicle. Despite the fundamental mechanical origin of tactile information, primary sensory neurons in the trigeminal ganglion (Vg) have often been described as encoding the kinematics (geometry) of object contact. Here we aimed to determine the extent to which Vg neurons encode the kinematics vs. mechanics of contact. We used models of whisker bending to quantify mechanical signals (forces and moments) at the whisker base while simultaneously monitoring whisker kinematics and recording single Vg units in both anesthetized rats and awake, body restrained rats. We employed a novel manual stimulation technique to deflect whiskers in a way that decouples kinematics from mechanics, and used Generalized Linear Models (GLMs) to show that Vg neurons more directly encode mechanical signals when the whisker is deflected in this decoupled stimulus space.
- Published
- 2016
- Full Text
- View/download PDF
285. Long-range population dynamics of anatomically defined neocortical networks
- Author
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Jerry L Chen, Fabian F Voigt, Mitra Javadzadeh, Roland Krueppel, and Fritjof Helmchen
- Subjects
two-photon ,calcium ,whisker ,cortex ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
The coordination of activity across neocortical areas is essential for mammalian brain function. Understanding this process requires simultaneous functional measurements across the cortex. In order to dissociate direct cortico-cortical interactions from other sources of neuronal correlations, it is furthermore desirable to target cross-areal recordings to neuronal subpopulations that anatomically project between areas. Here, we combined anatomical tracers with a novel multi-area two-photon microscope to perform simultaneous calcium imaging across mouse primary (S1) and secondary (S2) somatosensory whisker cortex during texture discrimination behavior, specifically identifying feedforward and feedback neurons. We find that coordination of S1-S2 activity increases during motor behaviors such as goal-directed whisking and licking. This effect was not specific to identified feedforward and feedback neurons. However, these mutually projecting neurons especially participated in inter-areal coordination when motor behavior was paired with whisker-texture touches, suggesting that direct S1-S2 interactions are sensory-dependent. Our results demonstrate specific functional coordination of anatomically-identified projection neurons across sensory cortices.
- Published
- 2016
- Full Text
- View/download PDF
286. Manual Whisker Annotator (MWA): A Modular Open-Source Tool
- Author
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Brett M. Hewitt, Moi Hoon Yap, and Robyn A. Grant
- Subjects
Whisker ,Annotator ,Manual ,Tracker ,Curvature ,Angle ,Velocity ,Animal Behaviour ,Computer Vision ,Analysis ,Computer software ,QA76.75-76.765 - Abstract
Rodents are key to generating translational data for healthcare research. Behavioural analyses, in particular, are integral to the non-invasive monitoring of rodent health and welfare. Finding quantitative behavioural measures mitigates stress, allowing for the animal behave freely while also enabling the same animal to be studied over the time-course of its life. Locomotion and whisking are both such quantitative behavioural measures, and have been found to be significantly impacted in rodent models of neurodegenerative disease. While automatic trackers of whiskers and locomotion exist, a manual tracker is required to validate these approaches, and also to annotate complex videos where these automatic versions fail. Manually annotating whiskers for research purposes is a long and tedious task and current software does little to provide an intuitive and simple interface to carry out this task. This led to the creation of the Manual Whisker Annotator (MWA). MWA is an open source, portable whisker annotation tool developed for the Windows platform. Not only does MWA make the process much quicker, it also provides added statistical tools to analyse the data. MWA was developed in C# and WPF using the .NET framework, and could be used in any situation where annotating or tracking multiple targets is desired.
- Published
- 2016
- Full Text
- View/download PDF
287. Prediction of primary somatosensory neuron activity during active tactile exploration
- Author
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Dario Campagner, Mathew Hywel Evans, Michael Ross Bale, Andrew Erskine, and Rasmus Strange Petersen
- Subjects
neural coding ,active sensation ,whisker ,Generalized Linear Model ,trigeminal ganglion ,Medicine ,Science ,Biology (General) ,QH301-705.5 - Abstract
Primary sensory neurons form the interface between world and brain. Their function is well-understood during passive stimulation but, under natural behaving conditions, sense organs are under active, motor control. In an attempt to predict primary neuron firing under natural conditions of sensorimotor integration, we recorded from primary mechanosensory neurons of awake, head-fixed mice as they explored a pole with their whiskers, and simultaneously measured both whisker motion and forces with high-speed videography. Using Generalised Linear Models, we found that primary neuron responses were poorly predicted by whisker angle, but well-predicted by rotational forces acting on the whisker: both during touch and free-air whisker motion. These results are in apparent contrast to previous studies of passive stimulation, but could be reconciled by differences in the kinematics-force relationship between active and passive conditions. Thus, simple statistical models can predict rich neural activity elicited by natural, exploratory behaviour involving active movement of sense organs.
- Published
- 2016
- Full Text
- View/download PDF
288. Spatiotemporal patterns of contact across the rat vibrissal array during exploratory behavior
- Author
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Jennifer Anne Hobbs, R. Blythe Towal, and Mitra J Z Hartmann
- Subjects
Trigeminal Ganglion ,haptics ,active touch ,whisker ,tactile ,mechanics ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
The rat vibrissal system is an important model for the study of somatosensation, but the small size and rapid speed of the vibrissae have precluded measuring precise vibrissal-object contact sequences during behavior. We used a laser light sheet to quantify, with 1 ms resolution, the spatiotemporal structure of whisker-surface contact as five naïve rats freely explored a flat, vertical glass wall. Consistent with previous work, we show that the whisk cycle cannot be uniquely defined because different whiskers often move asynchronously, but that quasi-periodic (~8 Hz) variations in head velocity represent a distinct temporal feature on which to lock analysis. Around times of minimum head velocity, whiskers protract to make contact with the surface, and then sustain contact with the surface for extended durations (~25 – 60 ms) before detaching. This behavior results in discrete temporal windows in which large numbers of whiskers are in contact with the surface. These sustained collective contact intervals (SCCIs) were observed on 100% of whisks for all five rats. The overall spatiotemporal structure of the SCCIs can be qualitatively predicted based on information about head pose and the average whisk cycle. In contrast, precise sequences of whisker-surface contact depend on detailed head and whisker kinematics. Sequences of vibrissal contact were highly variable, equally likely to propagate in all directions across the array. Somewhat more structure was found when sequences of contacts were examined on a row-wise basis. In striking contrast to the high variability associated with contact sequences, a consistent feature of each SCCI was that the contact locations of the whiskers on the glass converged and moved more slowly on the sheet. Together, these findings lead us to propose that the rat uses a strategy of windowed sampling to extract an object’s spatial features: specifically, the rat spatially integrates quasi-static mechanical signals across whiskers during the period of sustained contact, resembling an enclosing haptic procedure.
- Published
- 2016
- Full Text
- View/download PDF
289. Si-Ge whiskers for thermoelectric sensors design
- Author
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I. Ostrovskii, A. A. Druzhinin, Yu.M. Khoverko, and Natalia Liakh-Kaguy
- Subjects
Materials science ,seebeck coefficient ,Whiskers ,Doping ,whiskers ,chemistry.chemical_element ,figure of merit ,Atmospheric temperature range ,Condensed Matter Physics ,lcsh:QC1-999 ,Thermal conductivity ,chemistry ,sensor ,Whisker ,Seebeck coefficient ,Thermoelectric effect ,thermal conductivity ,General Materials Science ,Physical and Theoretical Chemistry ,Composite material ,Boron ,lcsh:Physics ,si-ge - Abstract
The paper deals with studies of thermoelectric properties for Si1-xGex (x=0.01-0.05) whiskers doped with boron during their growth by CVD method. Temperature dependences of the resistance and the Seebeck coefficient for Si1-xGex whiskers were measured in the temperature range 275–550 K. A method for determination of thermoelectric parameters of the whisker was proposed with use of the whisker joints, which allows us to define a ratio of Seebeck coefficient to thermal conductivity a/k. Taking into account the obtained values of Seebeck coefficient, the whisker conductance and estimated values of thermal conductivity, parameter ZT was calculated for the whiskers and consists of 0.15 for T=200oC. The obtained value of ZT is in good coincidence with literature data for hop pressed Si-Ge nanocomposites. The humidity sensor was designed base on Si-Ge whiskers.
- Published
- 2020
290. Whisker Growth in Sn Coatings: A Review of Current Status and Future Prospects
- Author
-
Praveen Kumar and Piyush Jagtap
- Subjects
010302 applied physics ,Future studies ,Materials science ,Nanotechnology ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Whisker ,0103 physical sciences ,Materials Chemistry ,Electrical and Electronic Engineering ,0210 nano-technology ,Crystal anisotropy - Abstract
Whiskering is a spontaneous filamentary growth of material, and it is a major long-term reliability issue affecting microelectronic packages comprising Sn plating and Sn-rich solders. In particular, whisker growth out of Sn-plated surfaces has been studied extensively in recent years due to the advent of next-generation, environment-friendly, Pb-free microelectronic packaging. Here, we review this scientifically challenging and technologically important problem, especially in the light of relatively new insights gained in the recent past, intending to provide a quick overview of the important results and stimulating future studies. In particular, we discuss the mechanisms of whisker growth by critically examining the roles of stress and its regeneration, oxide layer, diffusion conduits, and crystal anisotropy in creating conditions conducive for whiskering. We also discuss the recent proposals for effectively mitigating whisker growth in Sn coatings. Finally, an outlook is provided, with details of important unresolved issues related to whisker growth.
- Published
- 2020
291. Characterization of Ni-doped pyrolyzed phenolic resin and its addition to the Al2O3–C refractories
- Author
-
Nasser Pourmohammadie Vafa, Mohammad Bavand Vandchali, Mahdi Ghassemi Kakroudi, Sina Darban, Firouz Rezaei, and Vahid Charkhesht
- Subjects
010302 applied physics ,Materials science ,Process Chemistry and Technology ,Reducing atmosphere ,technology, industry, and agriculture ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Nickel ,stomatognathic system ,chemistry ,Amorphous carbon ,Whisker ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,Graphite ,0210 nano-technology ,Carbon ,Pyrolysis ,Nuclear chemistry - Abstract
The catalytic graphitization of the phenolic resin was investigated in the presence of various amounts of nickel nitrate at 600–1200 °C in a reducing atmosphere for 3 h. For comparison, the effect of catalyzed phenolic resin versus none-catalyzed one was explored on the microstructure and mechanical properties of the Al2O3–C refractory specimens within a range of 800–1400 °C. The phase composition and microstructure evolution were investigated using X-ray diffraction and SEM, respectively. RAMAN spectroscopy was used to measure the graphitization level of phenolic resin. Results indicated that crystalline carbon (graphite) was achieved only from Ni-catalyzed phenolic resin at a high temperature ( ~ 1200 °C ), while non-catalyzed resin led to the formation of amorphous carbon. Mechanical properties of the Al2O3–C specimens were improved due to the presence of catalyzed phenolic resin. SEM results illustrated that the enhancement was associated with the in-situ formation of the SiC phase in whisker shape in the microstructure of specimens containing Ni-catalyzed phenolic resin.
- Published
- 2020
292. Fabrication and thermal shock behavior of Si3N4 whiskers toughened γ-Y2Si2O7 coating on porous Si3N4 ceramics
- Author
-
Xingyu Fan, Qiushi Wang, Runjun Sun, Jie Dong, and Liang Wei
- Subjects
010302 applied physics ,Thermal shock ,Materials science ,Absorption of water ,Process Chemistry and Technology ,Whiskers ,02 engineering and technology ,engineering.material ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Coating ,Whisker ,visual_art ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,engineering ,Ceramic ,Composite material ,0210 nano-technology ,Porosity - Abstract
In order to prevent water from entering the porous Si3N4 ceramics, α-Si3N4 whiskers toughened γ-Y2Si2O7 coatings were prepared by a liquid infiltration and filling method. Effects of α-Si3N4 whiskers content on the microstructure, waterproof performance, mechanical properties and thermal shock behavior of the ceramic coatings were systematically studied in this paper. Results indicated that the addition of whiskers could effectively improve the performance of the coatings under thermal shock due to the toughening mechanism of whiskers including crack deflection, whisker bridging, whisker pulling out and other energy dissipation processes. The coating with a α-Si3N4 whisker/γ-Y2Si2O7 mass ratio of 1/9 possessed a flat, dense and defect-free surface microstructure. After five thermal cycles under a thermal shock temperature difference of 1200 °C, water absorption of the coating increased slightly from ~3.2% to ~6.0%. The whisker reinforced coating is promising to be used for high temperature wave-transmitting materials in long-time service.
- Published
- 2020
293. Tuning the physicochemical properties of apple pectin films by incorporating chitosan/pectin fiber
- Author
-
Heba G.R. Younis, Fayin Ye, Hassan R.S. Abdellatif, and Guohua Zhao
- Subjects
Hot Temperature ,food.ingredient ,Materials science ,Pectin ,02 engineering and technology ,Biochemistry ,Chitosan ,03 medical and health sciences ,chemistry.chemical_compound ,food ,Structural Biology ,Whisker ,Uv blocking ,Thermal stability ,Fiber ,Molecular Biology ,Edible Films ,030304 developmental biology ,Shearing (physics) ,0303 health sciences ,General Medicine ,021001 nanoscience & nanotechnology ,chemistry ,Chemical engineering ,Malus ,Pectins ,Stress, Mechanical ,0210 nano-technology ,Layer (electronics) - Abstract
Various biodegradable or edible films were designed to deal with the environmental threats from plastic films. To overcome the defects of pectin film, the feasibility for the incorporation of CH/PE fiber was explored. Micron-scale novel artificial CH/PE fibers in needle, spindle or whisker shape with a diameter around 25 μm were fabricated via a shearing regime in virtue of electrostatic complexing. The incorporation of CH/PE fiber (mixture) and its size-fractioned portions (small and large) substantially changed PE films in diverse ways. Structurally, the fiber-incorporated films were heterogeneous with the fibers concentrated in the upper layer, although they presented similar FT-IR spectra and XRD pattern to PE film. Regarding the film performance, the incorporation of CH/PE fibers, especially the small portion, rendered the PE film with higher values in water-proof ability, thermal stability, break resistibility, stretchability and UV blocking capacity. More importantly, this work provided an innovative strategy to improve the performance of edible films.
- Published
- 2020
294. Formation mechanism of whiskers in Al–MgAl2O4–MgO refractories at 1400 °C under N2 atmosphere
- Author
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Lingyan Yu, Shanghao Tong, Rongrong Wang, Jizeng Zhao, Yucui Zhang, Yong Li, and Fuqian Yang
- Subjects
Thermal shock ,Materials science ,Whiskers ,Sintering ,chemistry.chemical_element ,02 engineering and technology ,engineering.material ,01 natural sciences ,Metal ,Whisker ,0103 physical sciences ,Materials Chemistry ,Composite material ,010302 applied physics ,Magnesium ,Process Chemistry and Technology ,Spinel ,021001 nanoscience & nanotechnology ,Microstructure ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,visual_art ,Ceramics and Composites ,visual_art.visual_art_medium ,engineering ,0210 nano-technology - Abstract
Al–MgAl2O4–MgO refractories were prepared using fused magnesia, metal Al, fused spinel and sintered high purity magnesia as raw materials. The phase composition and microstructure of Al–MgAl2O4–MgO refractories treated at 1400 °C under N2 atmosphere were investigated by means of XRD, SEM and EDS. The results showed that magnesia (MgO) whiskers and MgAlON whiskers were formed on the surface and in the inner area of the Al–MgAl2O4–MgO refractories, respectively. The MgO whiskers grew preferentially along the axial direction, forming cylindrical shape MgO whiskers. Then the cylindrical MgO whiskers further absorbed Mg(g) and O2(g), and grew along the radial direction to form the square columnar shape MgO whiskers. The MgAlON whiskers firstly grew in one-dimensional direction, forming whisker shape MgAlON, then some whisker shape MgAlON gradually developed and grew into two-dimensional flake shape MgAlON. The sintering and thermal shock resistance was significantly improved by the whiskers. The growth process of magnesia whiskers and MgAlON whiskers were dominated by a vapor-solid (VS) mechanism.
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- 2020
295. Fabrication and mechanical properties of α-Al2O3 whisker reinforced cu-graphite matrix composites
- Author
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Zhenyi Shao, Xiaosong Jiang, Zhiping Luo, Hongliang Sun, Tan Wenyue, Tingfeng Song, Chinese Academy of Sciences, and China Postdoctoral Science Foundation
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Materials science ,General Chemical Engineering ,Spark plasma sintering ,Composite number ,Mechanical properties ,Alumina whisker ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Microstructure ,Diffusion layer ,Compressive strength ,020401 chemical engineering ,Whisker ,Relative density ,0204 chemical engineering ,Composite material ,0210 nano-technology ,Copper-graphite ,Strengthening mechanisms of materials - Abstract
In this work, α-Al2O3 whisker reinforced Cu-graphite matrix composites were prepared by spark plasma sintering. Results show that the surface modification of α-Al2O3 whiskers with sodium dodecyl sulfate solution can improve its dispersibility, and the composites obtained are basically completely dense. The relative density of all composite materials is above 95%. The interface bonding mode in the composite is mainly mechanical bonding, and the formation of a diffusion layer is also observed from interfaces. With the increase of α-Al2O3 whisker content, mechanical properties of the composites increase first and then decrease. The composite with 1.0 wt% α-Al2O3 whisker has the best performance. The corresponding relative density, hardness and compressive strength are 96.35%, 56.20 HV, 139.12 MPa, respectively. By analyzing microstructure and fracture morphology of the composites, it is determined that the strengthening mechanisms are mainly fine grain strengthening, particle strengthening and load transfer. Simultaneously, the fracture type is brittle fracture., This work was supported by Key Laboratory of Infrared Imaging Materials and Detectors, Shanghai Institute of Technical Physics, Chinese Academy of Sciences (No.IIMDKFJJ-19-08) and China Postdoctoral Science Foundation (No. 2015M570794, No. 2018T110993).
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- 2020
296. A note on the effect of surface energy on the growth of a tin whisker
- Author
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Fuqian Yang
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010302 applied physics ,Mass transport ,Materials science ,chemistry.chemical_element ,02 engineering and technology ,Dissipation ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Surface energy ,chemistry ,Whisker ,0103 physical sciences ,Grain boundary diffusion coefficient ,Composite material ,0210 nano-technology ,Tin - Abstract
In this communication, we report theoretical analysis of the contribution of surface energy to the energy dissipation during the growth of a tin whisker in a tin film. The mass transport of tin for...
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- 2020
297. Kinetics of Sn whisker growth from Sn thin-films on Cu substrate
- Author
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Agata Skwarek, David Busek, Oliver Krammer, Balázs Illés, Tamas Hurtony, and Karel Dusek
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010302 applied physics ,animal structures ,Materials science ,integumentary system ,Scanning electron microscope ,Whiskers ,Intermetallic ,02 engineering and technology ,Substrate (electronics) ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Whisker ,0103 physical sciences ,Stress relaxation ,Electrical and Electronic Engineering ,Thin film ,Composite material ,0210 nano-technology ,Layer (electronics) - Abstract
The kinetics of Sn whisker growth was investigated on vacuum-evaporated Sn thin-films. Sn film layers were deposited on a Cu substrate with 0.5 and 1 µm thicknesses. The samples were stored in room conditions (22 ± 1 °C/50 ± 5RH%) for 60 days. The Sn whiskers and the Cu–Sn layer structure underneath them were investigated with both scanning electron and ion microscopy. Fast Cu–Sn intermetallic formation resulted in considerable mechanical stress in the Sn layer, which initiated intensive whisker growth right after the layer deposition. The thinner Sn layer produced twice many whiskers compared to the thicker one. The lengths of the filament-type whiskers were similar, but the growth characteristics differed. The thinner Sn layer performed the highest whisker growth rates during the first 7 days, while the thicker Sn layer increased the growth rate only after 7 days. This phenomenon was explained by the cross-correlation of the stress relaxation ability of Sn layers and the amount of Sn atoms for whisker growth. The very high filament whisker growth rates might be caused by the interface flow mechanism, which could be initiated by the intermetallic layer growth itself. Furthermore, a correlation was found between the type of the whiskers and the morphology of the intermetallic layer underneath.
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- 2020
298. Liquid crystalline and rheological properties of chitin whiskers with different chemical structures and chargeability
- Author
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Wenjun Liu, Ken Liu, Binghong Luo, Changren Zhou, Mingxian Liu, Ling Zhu, Hong Li, Wenyan Li, Kun Liu, and Wei Wen
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Materials science ,Whiskers ,Chitin ,Protonation ,02 engineering and technology ,Biochemistry ,03 medical and health sciences ,Deprotonation ,Biomimetics ,Structural Biology ,Liquid crystal ,Whisker ,Zeta potential ,Molecular Biology ,030304 developmental biology ,0303 health sciences ,Aqueous solution ,Water ,General Medicine ,Hydrogen-Ion Concentration ,021001 nanoscience & nanotechnology ,Liquid Crystals ,Chemical engineering ,Ionic strength ,Rheology ,0210 nano-technology - Abstract
The liquid crystalline and rheological properties of chitin whiskers (CHWs) are significant for their application in fabrication of highly ordered composite materials and optical components. The aim of this work was to elucidate the influence of chemical structure and chargeability (zeta potential, electropositivity, electronegativity or zwitterionic character) on the liquid crystalline and rheological properties of CHWs. Firstly, CHWs with different chemical structure, including positively charged whiskers (CHWs and CHWs-D/60 min) and negatively charged whiskers (mCHWs), were designed via acid hydrolysis, deacetylation, and maleation, respectively. Subsequently, the chargeability of the above whiskers was further regulated by protonation or deprotonation. The whisker aqueous suspensions with high zeta potential behaved as nematic liquid crystals or chiral nematic liquid crystals, whereas those with low zeta potential had no liquid crystal characteristics. The viscosity, G', and G" values of the CHWs and CHWs-D/60 min aqueous suspensions treated with protonation were lower than those of the corresponding whiskers treated with deprotonation. However, the mCHWs exhibited different changes in their rheological properties under protonation or deprotonation due to the electronegativity and zwitterionic characteristics. In addition, the effects of ionic strength and pH on the liquid crystalline and rheological properties of CHWs, CHWs-D/60 min, and mCHWs aqueous suspensions varied since the chemical structure and chargeability of whiskers differ.
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- 2020
299. Insights into the structures, energies and electronic properties of nesquehonite surfaces by first-principles calculations
- Author
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Shuaishuai Lu, Yujuan Gao, Pingke Yan, Jiwei Lu, and Caie Zhang
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Surface (mathematics) ,Materials science ,Hexagonal crystal system ,General Chemical Engineering ,Dangling bond ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surface energy ,0104 chemical sciences ,Crystal ,Mechanics of Materials ,Chemical physics ,Whisker ,Positive relationship ,0210 nano-technology ,Electronic properties - Abstract
By using the first-principles calculations, the structure, energies and electronic properties of four commonly exposed surfaces for the nesquehonite crystal were investigated. The needle-like nesquehonite whisker is well developed with smooth side faces and irregular hexagonal end faces. Surface energy results indicate that the (1 0 1) surface is the most stable surface and corresponds to the side face. The density of dangling bond has a positive relationship with surface energy and the (1 0 1) surface has the least dangling bonds. In terms of relaxed surface energy, the order of relaxed surfaces is (1 0 1)
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- 2020
300. Construction of C-Si heterojunction interface in SiC whisker/reduced graphene oxide aerogels for improving microwave absorption
- Author
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Qingqiang Kong, Zhi-Hui Hou, Cheng-Meng Chen, Jing-Peng Chen, Zhuo Liu, Hui Jia, Shouchun Zhang, Lijing Xie, and Guohua Sun
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Materials science ,Graphene ,Reflection loss ,Oxide ,Heterojunction ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,chemistry ,Whisker ,law ,General Materials Science ,Composite material ,0210 nano-technology ,Absorption (electromagnetic radiation) ,Polarization (electrochemistry) ,Microwave - Abstract
The SiC/graphene aerogels have been widely studied in microwave absorption, but the influence mechanism of SiC microwave absorption was not clear. Herein, we prepared the SiC whiskers/reduced graphene oxide aerogels (SiCw/rGOA) by in-situ growth (IS) and physical mixing (PM) methods and investigated the influence of the C-Si heterojunction on microwave absorption performance. The results show that the incorporation of SiCw can improve the interfacial impedance between free space and absorber compare to the pure rGOA, resulting in the excellent microwave absorption property. The polarization loss induced by defects and interfaces is an important factor for microwave attenuation. Especially, the formation of the C-Si heterojunction interface between SiCw and reduced graphene oxide in SiCw/rGOA-IS enhances the polarization loss at low frequency (2–6 GHz). The minimum reflection loss (RL) value of SiCw/rGOA-IS reaches to −60.05 dB at 17.12 GHz with a thickness of 2.00 mm, and its effective absorption bandwidth (EAB, below −10 dB) is up to 6.72 GHz, covering whole Ku band. Furthermore, this as-prepared absorbing material exhibits excellent mechanical and thermal properties after compound with polydimethylsiloxane.
- Published
- 2020
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