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Three conjugated small molecules with different planarity which were tailored by the alkyl chain (from methyl to cyclic alkyl chain) were designed and successfully synthesized. The memory devices based on each molecule exhibited similar write-once-read-many-times characteristics but different switch threshold voltages. Atomic force microscopy and X-ray diffraction results indicated that the film surface morphology became more planar and intermolecular packing more closer as improving the molecular planarity, which led to the lower switch threshold voltages and the higher ON/OFF current ratios. Mechanism analysis demonstrated that one charge trap arising from the benzoquinoline group in the molecular backbone was injected by charge carriers as the external bias increased, resulting in OFF and ON distinct current states. This work not only demonstrated a new memory device with low-power consumption but also offered fundamental insight for the rational design of small molecules for organic memory devices.

We report the synthesis of two imidazole-based small molecules with different planarity of terminal aromatic rings and their application in memory devices with a sandwich configuration. The optical, electric, and the on-based device performances were systematically investigated. Surprisingly, the device based on BT-PMZ exhibited volatile static random access memory (SRAM) behavior, whereas that based on BT-BMZ showed nonvolatile write-once-read-many-times (WORM) behavior. Further studies on the film morphology and the molecular electronic structure were carried out to investigate the underlying mechanism for the large difference in their performance. Moreover, the performance of the device that incorporates a LiF buffer layer (5 nm) embedded at the interface between the BT-BMZ active layer and the Al top electrode as well as that of the device with a cold-deposited top electrode of mercury droplet was further investigated. At that point a dramatic change in memory performance of the devices from the WORM to SRAM type was observed. The intrinsic volatile SRAM performance for the two molecules results from the moderate electron-withdrawing strength of the acceptor moieties and thus weak trapping of the charge carriers.

According to the accuracy of BP (Back Propagation) neural network in leveling fitting, an improved BP neural network model is proposed. In order to overcome the defect of the low convergence rate and local minimal in leveling fitting. The BP neural network is improved by using Relu (Rectified Linear Units) function as network activation function and Adam (Adaptive Moment Estimation) algorithm as network optimization function. The experimental results show that the improved BP neural network can effectively improve the accuracy.

The contact mechanics of individual, very small particles with other particles and walls is studied using a nanoindenter setup that allows normal and lateral displacement control and measurement of the respective forces. The sliding, rolling and torsional forces and torques are tested with borosilicate microspheres, featuring radii of about 10μm. The contacts are with flat silicon substrates of different roughness for pure sliding and rolling and with silicon based, ion-beam crafted rail systems for combined rolling and torsion. The experimental results are discussed and compared to various analytical predictions and contact models, allowing for two concurrent interpretations of the effects of surface roughness, plasticity and adhesion. This enables us to determine both rolling and torsion friction coefficients together with their associated length scales. Interestingly, even though normal contacts behave elastically (Hertzian), all other modes of motion display effects due to surface roughness and consequent plastic deformation. The influence of adhesion is interpreted in the framework of different models and is very different for different degrees of freedom, being largest for rolling.

Two conjugated small molecules were synthesized by Heck coupling reaction, wherein 1,8-naphthalimide acted as an electron acceptor, while either carbazole or triphenylamine, which contributed the different coplanarity, acted as electron donors, respectively. The devices based on both materials show non-volatile flash memory characteristics, and the effect of molecular coplanarity of the donor groups on the device performance was precisely studied. The results indicated that the reproducibility of the switching phenomenon for the memory device based on the carbazole containing naphthalimide derivative was much better than that based on the triphenylamino based naphthalimide due to the rigid carbazole moiety which improved the surface morphology as revealed by atomic force microscopy measurement. Therefore, the significance of the coplanarity of the donor moiety on improving reproducibility of switching phenomenon for memory device applications was revealed.

In this work, three new organic donor–acceptor small-molecules, in which bicarbazole served as the electron donor, and benzothiazole, nitryl or 1,1′-dicyanovinyl were used as the electron acceptor, were designed and synthesized in order to fabricate sandwiched memory devices. Acceptors with a variable electron-delocalized extent and electron-withdrawing strength were attached to the molecular backbone in order to investigate the effect on the devices switching behavior. The bi-n-butylcarbazole benzothiazole (BCZ-BT) based memory device exhibited volatile static random access memory (SRAM) switching behaviour, while the devices based on bi-n-butylcarbazole nitryl (BCZ-NO2) was found to exhibit stable nonvolatile write-once-read-many-times (WORM) data storage characteristics and the bi-n-butylcarbazole dicyanovinyl (BCZ-CN) device acted as rewritable flash memory with a higher ON/OFF current ratio of about 104. Therefore, tunable data storage devices synthesized by adjusting the terminal acceptor groups offer feasible guidance for the rational design of organic molecules to achieve superior memory performance.

Y-doped PbWO4 mesocrystals with controllable morphologies, from convex quadrangle to concave erythrocyte, which exhibit tunable optical properties, are obtained by simply increasing the Y3+ doping concentrations. A doping-induced structural disorder mechanism was tentatively proposed to understand the evolutions of PbWO4 mesocrystals.

In this study, two D-A molecules NACANA and CANACA, based on carbazole (CA) donor and naphthalimide (NA) acceptor, with different D-A arrangement (A-D-A and D-A-D) were synthesized. The photophysical and electrochemical properties, microstructure and memory behaviors of both A-D-A and D-A-D molecules were systematically investigated. The fabricated devices ITO/NACANA or CANACA layer/Al with a simple sandwich configuration both exhibited volatile nature after shutting off the external electric field. Interestingly, NACANA showed ON-state retention time of ca. 12 min, longer than that of CANACA (ca. 6 min). The difference in retention ability of the programmed states could be assigned to the difference of the D-A arrangement. This type of retention ability adjustment by varying the arrangement of donor and acceptor segments may provide a guide of structure design for future organic-based specific memory devices with tunable volatile property.

A catalyst-free N–H insertion/Mannich-type reaction cascade of α-nitrodiazoesters with anilines has been developed to afford a variety of α-amino-α-aryl esters in 60–83% yields and under mild reaction conditions (23 or 40 °C).

Global ontology and local ontologies can be built to effectively implement data semantic access in integration environment of multiple data sources based on grid computing. Data sources, as a kind of resource in grid, can join and quit grid environment dynamically. In order to ensure consistency between global ontology and local ontologies, we present joining and quitting algorithms for data sources in grid system. During processing of joining and quitting algorithms, global ontology elements were divided into two types of AES(Active Elements Set) and SES(Suspended Elements Set),and we stipulate that only mappings formed by AES can be employed for semantic data processing.

Vorinostat, a histone deacetylase inhibitor, has been used clinically as an anticancer drug and also has immunosuppressive properties. However, the underlying mechanisms of effects of vorinostat on central nervous system (CNS) inflammatory diseases remain incomplete. Here, this study investigates the effects of vorinostat on human CD14 + monocyte-derived dendritic cells (DCs) and mouse immature DC in vitro . Furthermore, we explore the therapeutic effects and cellular mechanisms of vorinostat on animal model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE) in vivo . Our findings demonstrate that vorinostat inhibited human CD14 + monocyte-derived DCs differentiation, maturation, endocytosis, and further inhibited mDCs' stimulation of allogeneic T-cell proliferation. In addition, vorinostat inhibited DC-directed Th1- (Type 1T helper) and Th17-polarizing cytokine production. Furthermore, vorinostat ameliorated Th1- and Th17-mediated EAE by reducing CNS inflammation and demyelination. What's more, Th1 and Th17 cell functions were suppressed in vorinostat-treated EAE mice. Finally, vorinostat suppressed expression of costimulatory molecules of DC in EAE mice. These suggest therapeutic effects of vorinostat on EAE which may by suppress DCs and DCs-mediated Th1 and Th17 cell functions. Our findings warrant further investigation in the potential of vorinostat for the treatment of human multiple sclerosis.

Olfactory dysfunction is among the signs of Alzheimer's disease (AD) and cognitive impairment. It has been demonstrated Aβ was associated with olfactory impairment observed in both transgenic mice and in AD patients. In this study, we evaluated amyloid deposition in the olfactory circuit of APP/PS1 transgenic mouse model of AD, which showed olfactory dysfunction in olfactory behavior tests. We found amyloid depositions were widely distributed in the whole olfactory circuit. Moreover, we think these amyloid depositions contribute to neuronal atrophy, dendritic abnormalities, synapse loss and axonal degeneration. Therefore, there was a correlation between olfactory deficits and amyloid deposition. Our findings provide initial insights into the pathological basis of AD-related olfactory dysfunction.

BACKGROUND We designed this study to investigate the influence of different ratios of n-6/n-3 polyunsaturated fatty acid in the diet of reflux esophagitis (RE) rats' and the effect on the PI3K/Akt pathway. MATERIAL AND METHODS RE rats were randomly divided into a sham group and modeling groups of different concentrations of n-6/n-3 polyunsaturated fatty acid (PUFA): 12:1 group, 10:1 group, 5:1 group, and 1:1 group. RT-PCR and Western-blot were used to detect the expression of PI3K, Akt, p-Akt, NF-κBp50, and NF-κBp65 proteins in esophageal tissue. RESULTS In the n-6/n-3 PUFAs groups the expression of PI3K, Akt, p-Akt, nf-κbp50, and NF-κBp65 mRNA decreased with the decrease in n-6/n-3 ratios in the diet. The lowest expression of each indicator occurred in the 1:1 n-6/n-3 group compared with other n-6/n-3 groups, the difference was statistically significant (p

By Hao Zhuang, Lei Zhang, Thorsten Staedler, and Xin Jiang*Microwave plasma (MW)CVD is used for the first time in the low-temperature, hetero-epitaxial growth of 3C-SiC films on Siusing a gas mixture of tetramethylsilane (TMS) and hydrogen. Good epitaxial matching between the 3C-SiC film and Sisubstrate is obtained in the epitaxially grown 3C-SiC films. Further investigation reveals that microwave powder density andsubstratetemperatureplayanimportantroleinthedeterminationoftheorientation,SiC/Siinterfacestructure,andmorphologyof 3C-SiC films. The presented results show MWCVD might be a potent approach in the future in obtaining large-scale, high-quality, single-crystalline 3C-SiC films.Keywords: Coating, Epitaxy, Low temperature, Plasma-enhanced (PE)CVD, SiC

Public cloud platforms might start with homogeneous hardware; nevertheless, because of inevitable hardware upgrades, or adding more capacity, the initial homogeneous platform will gradually evolve into heterogeneous as time passes by. The consequent performance heterogeneity is of concern to cloud users. In this article, we evaluate performance variations from hardware heterogeneity and scheduling mechanisms of public clouds. Amazon Elastic Compute Cloud (Amazon EC2) and Rackspace Cloud are used as the representatives because of their relatively long record and wide usage among small and medium enterprises (SMEs). A comprehensive set of micro-benchmarks and application-level macro-benchmarks have been used to investigate performance variation. Several major contributions have been made. Firstly, we find out that heterogeneous hardware is a commonality among the relatively long-lasting cloud platforms, although the level of heterogeneity varies. Secondly, we observe that heterogeneous hardware is the primary culprit of performance variation of cloud platforms. Thirdly, we discover that varied CPU acquisition percentages and different virtual machine scheduling mechanisms exacerbate the performance variation problem, especially for network related operations. Finally, based on the observations, we propose cost-saving approaches and analyze Nash equilibrium from cloud user perspective. By using a simple "trial-and-error" approach, i.e., keep good-performing instances and discard bad-performing instances, cloud users can achieve up to 30% cost saving.

As a potential material for biosensing applications, gallium nitride (GaN) films have attracted remarkable attention. In order to construct GaN biosensors, a corresponding immobilization of biolinkers is of great importance in order to render a surface bioactive. In this work, two kinds of n-alkenes with different carbon chain lengths, namely allylamine protected with trifluoroacetamide (TFAAA) and 10-aminodec-1-ene protected with trifluoroacetamide (TFAAD), were used to photochemically functionalize single crystalline GaN films. The successful linkage of both TFAAA and TFAAD to the GaN films is confirmed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) measurement. With increased UV illumination time, the intensity of the secondary ions corresponding to the linker molecules initially increases and subsequently decreases in both cases. Based on the SIMS measurements, the maximum coverage of TFAAA is achieved after 14 h of UV illumination, while only 2 h is required in the case of TFAAD to reach the situation of a fully covered GaN surface. This finding leads to the conclusion that the reaction rate of TFAAD is significantly higher compared to TFAAA. Measurements by atomic force microscopy (AFM) indicate that the coverage of GaN films by a TFAAA layer leads to an increased surface roughness. The atomic terraces, which are clearly observable for the pristine GaN films, disappear once the surface is fully covered by a TFAAA layer. Such TFAAA layers will feature a homogeneous surface topography even for reaction times of 24 h. In contrast to this, TFAAD shows strong cross-polymerization on the surface, this is confirmed by optical microscopy. These results demonstrate that TFAAA is a more suitable candidate as biolinker in context of the GaN surfaces due to its improved controllability.

In the designed copolymers of poly(9-(4-vinyl benzyl)-9H-carbazole) (PVCz)-random-poly(1-(4-nitro-azo-phenyl)-pyrrole-2, 5-dione) (PMIDO3), carbazole donor and nitro-azobenzene acceptor are introduced into the lateral chains to induce charge transfer under an electric field, and the resulting copolymers have a progressive increase in the nitrogen content to induce filamentary conduction. The fabricated devices with a simple sandwich configuration distinctively exhibit three conductivity states when a negative bias is applied which can be encoded as “0”, “1” and “2” for future ternary data storage. The fabricated devices could endure 108 read cycles and showed a long retention time of 104 s. It is worth noting that the switch-OFF voltages and the OFF-currents are significantly affected by the MIDO3 content within the polymers. The experimental results indicate that charge transfer between the donor and acceptor is responsible for the first switching and the second switching can be attributed to the filamen...

Three donor–acceptor and twisted anthraquinone azo molecules were synthesized, and the effects of conjugated backbones length, alkyl chains length, and the thermal annealing temperature on the memory characteristics were explored. The device based on Azo-02, which has longer conjugated backbone and alkyl chains, exhibited stable nonvolatile ternary memory behavior as the thermal annealing temperature increased, with basically the same switching threshold voltages and current ratios being ∼1:103.43:105.50. For the “counterpart” molecules (Azo-01 and Azo-03) film, defects appeared or disordered, crystal packing formed as the thermal annealing temperature increased, and the corresponding devices exhibited no obvious conductance switching behaviors. The mechanism related to electrical switching properties and WORM (write-once-read-many-times) behaviors were elucidated through molecular simulation. The results demonstrated that the long-term thermally stable high-density data-storage devices can be fabricated ...

Cetuximab is a chimeric immunoglobulin G1 mono-clonal antibody that targets the ligand-binding domain of the epidermal growth factor receptor and inhibits downstream intra- cellular signals. Research has shown that etuximab can stimulate the autoimmune system and produce antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity reactions, which can recruit cytotoxic lymphocytes to attack and kill cancer cells. Cetuximab is mainly indicated for patients with epidermal growth factor receptor-positive metastatic colorectal cancer who fail to respond to both irinotecan- and oxaliplatin-based regimens. The efficacy and safety of cetuximab as monotherapy or in combination with other treatment options were evaluated in a series of phase II and phase III trials. Identifying the clinical and molecular markers that can predict which patient groups may best benefit from cetuximab treatment is key to improving patient outcomes and avoiding unnecessary toxicities and costs. Herein, we discuss the mechanisms of action by which cetuximab exerts its antitumor effects, as well as the possible clinical and molecular markers that may help predict therapeutic benefits for patients with metastatic colorectal cancer.

By combining microcontact printing with a nanodiamond seeding technique, a precise micrometer-sized chemical vapor deposition (CVD) diamond pattern have been obtained. On the basis of the guidance of basic theoretical calculations, monodisperse detonation nanodiamonds (DNDs) were chosen as an "ink" material and oxidized poly(dimethylsiloxane) (PDMS) was selected to serve as a stamp because it features a higher interaction energy with the DNDs compared to that of the original PDMS. The adsorption kinetics shows an approximately exponential law with a maximum surface DND density of 3.4 × 10(10) cm(-2) after 20 min. To achieve a high transfer ratio of DNDs from the PDMS stamp to a silicon surface, a thin layer of poly(methyl methacrylate) (PMMA) was spin coated onto the substrates. A microwave plasma chemical vapor deposition system was used to synthesize the CVD diamond on the seeded substrate areas. Precise diamond patterns with a low expansion ratio (3.6%) were successfully prepared after 1.5 h of deposition. Further increases in the deposition time typically lead to a high expansion rate (∼0.8 μm/h). The general pattern shape, however, did not show any significant change. Compared with conventional diamond pattern deposition methods, the technique described here offers the advantages of being simple, inexpensive, damage-free, and highly compatible, rendering it attractive for a broad variety of industrial applications.

Utilizing a high atomic hydrogen concentration, highly selective formation of micrometer-sized diamond and β-SiC crystals is achieved in a microwave plasma chemical vapour deposition process. The high atomic hydrogen concentration, generated by a high microwave power density, hinders secondary heterogeneous nucleation and therefore enhances the selectivity of CH3 and SiH3 deposition onto diamond and β-SiC crystals, respectively. Based on experimental observation, an H-induced selective growth model is proposed that explains the mechanisms.

A computation efficient yet accurate surface potentialbased analytic model for the symmetric double-gate MOSFETs is proposed to simulate double-gate device current-voltage characteristics in this paper. This model consists of a surface potential versus voltage input equation and a drain current expression, which are very similar to that proposed by J. R. Brews for the single-gate (SG) Bulk MOSFET. The model gets rid of requirement of the transcendent trigonometric function used in the previous model, thus, result in the computation efficiency. The model is also verified by extensive comparisons with rigorous numerical solutions under different operation conditions and geometry structures, thus, the new set of surface potential equation and drain current is the framework of a complete DG MOSFET model for computer-aided-design circuit purpose.

Silicon carbide has been proved as a candidate for power and high-frequency devices. In this paper, we show the application of nanocrystalline 3C-SiC as an electrochemical electrode and its electrochemical functionalization for biosensing applications. SiC electrodes show a wider potential window and lower background current than glassy carbon electrodes. The surface can be electrochemically functionalized with diazonium salts, as confirmed by electrochemical techniques and X-ray photoelectron spectroscopy. The nitrophenyl film is used as linker layer to bond DNA molecule to SiC. These results show that 3C-SiC can be an interesting transducer material for applications in electro- and bioelectrochemical applications.

China's flourishing economy is contributing to rapid development throughout the country, but prosperity is not evenly distributed and rural communities are experiencing social and ecological problems. Ecotourism has potential to foster both local economic development and environmental conservation. Capacity to promote and deliver ecotourism services is, however, poorly developed at present, particularly at the level of rural communities. We assess such capacity through an institutional analysis, focusing on interactions among public agencies, businesses, and civil society actors. Specifically, we study the roles and potential of non-governmental organisations (NGOs) as an emerging class of development actors within China's civil society. We present a case study of an ecotourism demonstration project in the Laojunshan area of northwestern Yunnan Province in western China. A review of project documents and field interviews supported analysis of Strengths, Weakness, Opportunities, and Threats that the releva...

Anodic stripping voltammetry (ASV) is an effective approach in monitoring heavy metal ions in the environment, in which, a poisonous mercury electrode is conventionally employed. In this paper, we demonstrate the nanocrystalline 3C–SiC thin film as an environmental friendly alternative electrode material for ASV trace metal analysis. Low detection limits of 6 ppb and 4 ppb have been achieved in the model analyte systems containing individual Cu2+ and Ag+, respectively, with good electrode renewability. In addition to the detection of individual metals, the 3C–SiC electrode also shows good capability in the simultaneous co-detection of Cu2+ and Ag+ in the analyte. Keywords: SiC, ASV, Heavy metal ion analysis

The wettability of different diamond/β-SiC composite thin film surfaces has been studied before and after chemical treatment by measuring contact angles in both static and dynamic modes; the water contact angle varies from 92.6 ± 2.5° to 32.7 ± 2.8° as the β-SiC content in the composite films (after chemical treatment) increases. The thermodynamic surface tension components of the film surfaces are calculated by using Owens−Wendt−Rabel−Kaelble’s and van Oss’s methods. The increase in hydrophilicity is attributed to the increase in the total surface energy, which is induced by the increase of the Lewis acid−base surface tension component (γAB). The point of zero charge (PZC) of the film surfaces was determined to be at pH 4. Additionally, a composite film surface with a wettability gradient was also fabricated; here, the water contact angle varies from 86.7° at the left edge to 25.1° at the right edge of the film surface. To analyze the molecular scale origin of the observed contact angle variations, time-...

The H-terminated polycrystalline diamond thin film surface is photochemically functionalized using allylamine. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) aided by principal components analysis (PCA) is then employed to systematically elucidate (i) the photochemical grafting of trifluoroacetamide group protected allylamine (TFAAA) onto the diamond thin film surface and (ii) the deprotection of the amine group. PCA of the SIMS shows that the diamond surface is fully covered by TFAAA after 24 h of UV illumination. SIMS spectra (in the high mass range) show that TFAAA cross-polymerizes on the diamond surface before the whole surface is covered by TFAAA. PCA of the SIMS also shows that the deprotection reaction follows approximately an exponential law with a time constant of 1 h. Additionally, the unchanged CN− intensity in the deprotection step shows that the allylamine linkage to diamond is stable. A shadow mask was employed during the photochemical grafting of allylamine, leaving the masked r...

To understand the role of ATP underlying the enhanced amyloidosis of hen egg white lysozyme (HEWL), the synchrotron radiation circular dichroism, combined with tryptophan fluorescence, dynamic light-scattering, and differential scanning calorimetry, is used to examine the alterations of the conformation and thermal unfolding pathway of the HEWL in the presence of ATP, Mg(2+)-ATP, ADP, AMP, etc. It is revealed that the binding of ATP to HEWL through strong electrostatic interaction changes the secondary structures of HEWL and makes the exposed residue W62 move into hydrophobic environments. This alteration of W62 decreases the beta-domain stability of HEWL, induces a noncooperative unfolding of the secondary structures, and produces a partially unfolded intermediate. This intermediate containing relatively rich alpha-helix and less beta-sheet structures has a great tendency to aggregate. The results imply that the ease of aggregating of HEWL is related to the extent of denaturation of the amyloidogenic region, rather than the electrostatic neutralizing effect or monomeric beta-sheet enriched intermediate.

The new 4B8 beamline provides UV-VUV light in the wavelength range from 360 to 120 nm. It uniquely enables two kinds of spectroscopy measurements: synchrotron radiation circular dichroism spectroscopy and VUV excited fluorescence spectroscopy. The former is mainly used in protein secondary structure studies, and the latter in VUV excited luminescent materials research. Remote access to fluorescence measurement has been realised and users can collect data online. Besides steady-state measurements, fluorescence lifetime measurements have been established using the time domain method, while a laser-induced temperature jump is under development for protein folding dynamics using circular dichroism as a probe.

Microwave dielectric composite ceramics with compositions of (1-x)Ba(Zn 1/3 Nb 2/3 )O 3 -BaWO 4 (x = 0.1∼ 0.4) were prepared. The increasing BaWO 4 content can effectively lower the sintering temperature of the composite ceramics from 1400°C to 1250°C. XRD indicated that Ba(Zn 1/3 Nb 2/3 )O 3 and BaWO 4 coexisted. SEM observation revealed that the grain size increased with the sintering temperature rising up. The microwave dielectric properties of the sintered ceramics varied with the BaWO 4 content. The samples with x = 0.4 sintered at 1225°C exhibited the best microwave dielectric property: a near zero temperature coefficient of resonant frequency of τ f = −2.1 ppm/°C, ϵ r = 24.0, Q×f = 65300 GHz was obtained.

Microwave dielectric composite ceramics with compositions of (1 − x )Ba 5 Nb 4 O 15 – x BaWO 4 ( x = 0–1) were prepared by firing the mixture of Ba 5 Nb 4 O 15 and BaWO 4 . The sintering temperature of the composite ceramics was reduced from 1400 to 1100 °C with increasing BaWO 4 content. XRD patterns indicate that Ba 5 Nb 4 O 15 and BaWO 4 coexisted and no secondary phase was detected in sintered bodies. The composite ceramics have the finer grained microstructure compared with the pure Ba 5 Nb 4 O 15 ceramics. TEM observation and EDS analysis reveal that a very thin interfacial area (∼60 nm in width) was formed due to the limited solid solution between Ba 5 Nb 4 O 15 and BaWO 4 grains. With increasing BaWO 4 (from x = 0 to x = 0.65), the dielectric constants ( ɛ r ) and the temperature coefficient of resonant frequency ( τ f ) of the ceramics decrease from 39.2 to 16.9 and from +78 to −4.3 ppm/°C, respectively, while the quality factors ( Q × f value) increase from 26,000 to 56,700 GHz. The samples with x = 0.54–0.65 sintered at 1100 °C exhibit good microwave dielectric properties: ɛ r = 21.0–16.9, Q × f = 49,500–56,700 GHz, and τ f = 8.9–−4.3 ppm/°C.

(1−x)Zn2SiO4–xTiO2 (x=0, 5, 8, 11, and 15 wt%) ceramics have been successfully prepared through a sol–gel process. The thermal gravimetry-differential thermal analysis and X-ray diffraction analysis showed that the addition of TiO2 can lower the nucleation temperature of Zn2SiO4 and enhance the sinterability of the powders synthesized. Dense ceramics with a pure phase could be achieved at a lower temperature. The pure Zn2SiO4 ceramics sintered at 1325°C exhibited microwave dielectric properties: a dielectric constant (ɛr) of 6.6, a quality factor Q×f of 198 400 GHz, and a temperature coefficient of resonant frequency (τf) of −41.6 ppm/°C. The τf value can be adjusted to near zero by adding an appropriate amount of TiO2. The Zn2SiO4 ceramics containing 11 wt% of TiO2 sintered at 1200°C showed excellent microwave dielectric properties: an ɛr value of 9.1, a Q×f value of 150 800 GHz, and a τf value of −1.0 ppm/°C. Our results show that the sol–gel process can achieve pure phase as well as ultrafine powders, which is beneficial to optimize the performance of Zn2SiO4 ceramics. Zn2SiO4 ceramics containing 11 wt% of TiO2 are a promising candidate for microwave and millimeter-wave applications.

New low-temperature co-fired microwave dielectric composites with compositions of (1–x)Ba3(VO4)2–xBaWO4 (x=0–1) were prepared by firing mixtures of Ba3(VO4)2 and BaWO4. Thermal mechanical analysis indicated the ceramic composites had relatively low densification temperatures and could be sintered in the temperature range 925°∼950°C. X-ray diffraction patterns showed that Ba3(VO4)2 and BaWO4 coexisted and no secondary phase was detected in the sintered bodies, implying good chemical compatibility between the two phases. Near-zero temperature coefficients of the resonant frequency (τf) could be achieved by changing the relative content of the two phases, due to their positive and negative τf values, respectively. With increasing BaWO4 (x from 0.50 to 0.65), the τf value of the composites decreased from +10.9 to −1.9 ppm/°C, and the quality factor (Q×f value) increased from 66 700 to 79 100 GHz. The best microwave dielectric properties were obtained for x=0.65 samples sintered at 925°C with a dielectric constant of 11.1, a Q×f value of 79 100 GHz, and a τf value of −1.9 ppm/°C. Chemical compatibility experiments showed the ceramics are compatible with silver during cofiring process.

Low-temperature-sintered composite ceramics in Ba5Nb4O15–BaWO4 system were prepared by cofiring mixtures of Ba5Nb4O15 and BaWO4 powders. Thermo-mechanical analysis indicated that a small amount of B2O3 addition significantly promoted the densification process and lowered the sintering temperature to ∼900°C. X-ray diffraction analysis revealed that Ba5Nb4O15 and BaWO4 coexisted in the sintered ceramics. With increasing B2O3 content, a secondary phase, BaNb2O6, appeared which affects the microwave dielectric properties. Microwave dielectric properties of the aforementioned compositions were as follows: dielectric constant of 16.8–19.2, Q×f values of 33 900–50 300 GHz, and a temperature coefficient of the resonant frequency of −3.4 to −8.6 ppm/°C. The chemical compatibility of BNW6502 ceramics with silver during the cofiring process has also been investigated, and no evidence of chemical reaction between Ag and ceramics was observed, indicating that the as-prepared composite ceramics are suitable for low-temperature cofired ceramics applications.

W,Ti co-doped Ba5Nb4O15 microwave dielectric ceramics with compositions of Ba5Nb4-x(W1/2Ti1/2)xO15 (x =0–2) were prepared by solid-state reaction method. W6+ and Ti4+ substitution for Nb5+ can markedly lower the sintering temperature of Ba5Nb4O15 from 1450 to 1250 °C. X-ray powder diffraction (XRD) analysis reveals that BaWO4 formed as a secondary phase due to the limited solubility of WO3 in perovskite Ba5Nb4O15 when x>0.4. Scanning electron microscopy (SEM) observation suggests that a small amount of W and Ti co-doping can suppress the grain growth of Ba5Nb4O15 ceramics, indicating that the grain size decreases from ~25 to ~3 µm. The microwave dielectric properties of Ba5Nb4O15 ceramics is largely improved by W,Ti co-doping. With increasing x, the Q×f value increases from 25,200 GHz for undoped samples (x=0) to 38,600 GHz for x=0.4, and then declines to 19,500 GHz for x=1.2. In the composition range x=0–1.2, the dielectric constant increases slightly from 39.2 to 44, while the temperature coefficient decreases from ~78 to ~50 ppm/°C. The reasons for the improvement of the dielectric properties were investigated by SEM, XRD, and AC impedance spectrum analysis.

Microwave dielectric ceramics with the composition of Ba[Ti 1-x (Ni 1/2 W 1/2 )]O 3 (x = 0.4-0.6) were prepared by a solid-state reaction method. The evolution of the crystalline phases was investigated by X-ray powder diffraction analysis. A cubic-to-hexagonal phase transition occurred between 1000° and 1300°C. The phase transition is irreversible; thus, the hexagonal phase remains stable at room temperature. The X-ray powder diffraction data for x = 0.5 were refined using the Rietveld method. It was identified as a h-BaTiO 3 -type hexagonal perovksite with the space group of P6 3 /mmc. It also reveals that random occupancy of Ti 4+ and W 6+ ions occurs in the B-site substructures, whereas N1 2+ ions exclusively occupy the octahedral site in the corner-sharing octahedron. The dielectric properties of dense-sintered ceramics were characterized at microwave frequencies. With an increase in x from 0.4 to 0.6, the Q x f value increased from 26700 to 42000 GHz, whereas e r decreased from 29.8 to 20.0, and τ f from +6.5 to -9.9 ppm/°C.

In this work, we demonstrate a one-step approach to create graphene/3C-SiC nanolaminate structure using microwave plasma chemical vapor deposition technique. Layer-by-layer arrangement of thin 3C-SiC layers and graphene sheets is obtained with the thicknesses of the individual 3C-SiC layers and graphene sheets being 5-10 nm and 2-5 nm, respectively. An intimate contact between 3C-SiC and the graphene sheets is achieved and the nanolaminate film shows a high room temperature conductivity of 96.1 S/cm. A dedicated structural analysis of the nanolaminates by means of high-resolution transmission electron microscopy (HRTEM) reveals that the growth of the nanolaminates follows an iterative process: preferential graphene nucleation around the planar defects at the central region of the SiC layer, leading to the "splitting" of the SiC layer; and the thickening of the SiC layer after being "split". A growth mechanism based on both kinetics and thermodynamics is proposed. Following the proposed mechanism, it is possible to control the layer thickness of the graphene/3C-SiC hybrid nanolaminate by manipulating the carbon concentration in the gas phase, which is further experimentally verified. The high electrical conductivity, large surface area porous structure, feasible integration on different substrates (metal, Mo; semiconductor, Si and 2H-SiC; insulator, diamond) of the graphene/3C-SiC hybrid nanolaminate as well as other unprecedented advantages of the nanolaminate structure make it very promising for applications in mechanical, energy, and sensor-related areas.

We propose an efficient algorithmic framework for time domain circuit simulation using exponential integrator. This work addresses several critical issues exposed by previous matrix exponential based circuit simulation research, and makes it capable of simulating stiff nonlinear circuit system at a large scale. In this framework, the system's nonlinearity is treated with exponential Rosenbrock-Euler formulation. The matrix exponential and vector product is computed using invert Krylov subspace method. Our proposed method has several distinguished advantages over conventional formulations (e.g., the well-known backward Euler with Newton-Raphson method). The matrix factorization is performed only for the conductance/resistance matrix G, without being performed for the combinations of the capacitance/inductance matrix C and matrix G, which are used in traditional implicit formulations. Furthermore, due to the explicit nature of our formulation, we do not need to repeat LU decompositions when adjusting the length of time steps for error controls. Our algorithm is better suited to solving tightly coupled post-layout circuits in the pursuit for full-chip simulation. Our experimental results validate the advantages of our framework., 6 pages; ACM/IEEE DAC 2015

Many schemes have been recently advanced for storing data on multiple clouds. Distributing data over different cloud storage providers (CSPs) automatically provides users with a certain degree of information leakage control, as no single point of attack can leak all user's information. However, unplanned distribution of data chunks can lead to high information disclosure even while using multiple clouds. In this paper, to address this problem we present StoreSim, an information leakage aware storage system in multicloud. StoreSim aims to store syntactically similar data on the same cloud, thus minimizing the user's information leakage across multiple clouds. We design an approximate algorithm to efficiently generate similarity-preserving signatures for data chunks based on MinHash and Bloom filter, and also design a function to compute the information leakage based on these signatures. Next, we present an effective storage plan generation algorithm based on clustering for distributing data chunks with minimal information leakage across multiple clouds. Finally, we evaluate our scheme using two real datasets from Wikipedia and GitHub. We show that our scheme can reduce the information leakage by up to 60\% compared to unplanned placement.