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Based on the eavesdropping model of non-line-of-sight (NLOS) scattering channel in mid-infrared (MIR) free-space optical (FSO) communication system, the physical-layer security is analyzed theoretically by considering the effects of the atmospheric turbulence, atmospheric attenuation, and beam divergence attenuation. The effects of atmospheric turbulence, transmission distance, and visibility on secrecy capacity and interception probability are investigated. Secrecy capacity and interception probability of near-infrared (NIR) system are compared with those of MIR system. It is theoretically demonstrated that the secrecy capacity of the NIR system is smaller than that of the MIR system. Closed-form expression of interception probability is derived. Furthermore, in the same visibility condition, the interception probability of the MIR system is much lower than that of the NIR system. Therefore, compared with the NIR system, MIR system has much better performance of physical-layer security. [ABSTRACT FROM AUTHOR]

In the process of high-efficient milling titanium alloy(Ti6Al4V) workpieces, the ICS (instantaneous contact stiffness) and its distribution between flank face of milling cutter tooth and workpiece change instantaneously due to cutting vibration, which makes tool flank friction and wear status be of instability. In this work, the tool flank micro-convex body stiffness model was developed considering the influence of cutting vibration on instantaneous tool cutting angles. The distribution of the ICS and its effect on instantaneous tool flank friction and wear increment were analyzed. The results showed that the changes in positive pressure on tool flank under cutting vibration was the primary reason for the non-uniform distribution of ICS; the friction and wear increment of different areas on tool flank were in direct proportion to the ICS. [ABSTRACT FROM AUTHOR]

Uniaxial compression acoustic emission (AE) tests were conducted on low-strength molybdenum ore (LSMO) to investigate its deformation and failure laws and AE characteristics. The stress–strain curve and AE parameter data of LSMOs were obtained by uniaxial compression AE test, and the relationships of stress, AE parameter, amplitude fractal dimension, and AE b value with loading time were analyzed accordingly to obtain the general law of their deformation and failure and a series of AE characteristics. The research shows that under the action of uniaxial stress, the failure mode of LSMOs mainly shows brittle failure, and the failure form mainly shows monoclinic shear failure. The stress–strain curve shows obvious plastic-elastic deformation, the plastic deformation time is long, and the division of each stage of deformation failure is not obvious. The simultaneous occurrence of large surges in ringing count and energy to higher orders of magnitude can be used as precursor information for failure destabilization of LSMOs. The evolution process of AE parameters of LSMO corresponds well with its deformation and failure process, and the variation pattern of ringing counts and energy shows a high consistency. With increasing stress, the amplitude correlation dimension and b value are mainly in the form of "falling-rising-falling-fluctuating". The results of the study can provide some theoretical basis for the assessment of the stability of the mine surrounding rock and the determination of a reasonable and effective reinforcement plan. [ABSTRACT FROM AUTHOR]

Due to its low density, high tensile strength and excellent energy absorption capability, 7B52 laminated (7A52/7A01/7A62 layers) aluminum alloy is a promising material for the application of armored vehicles and tanks. With the rapid development of anti-armor weapons, there is an increasing need for 7B52 laminates with excellent impact resistance. However, the impact failure behaviors and related mechanisms of this laminated alloy remain unclear. In this work, the macro–micro–nonuniform deformation behaviors of a 7B52 laminated aluminum alloy after high-speed impacts (from 2700 to 5000 s−1) were investigated. The results revealed that the plastic deformation was mainly concentrated in the 7A01 and 7A52 layers of the 7B52 laminated aluminum alloy under high-speed impact, indicating nonuniform deformation of this alloy. The ductile 7A01 layer led to the blunting and deflection of cracks formed in the interlaminar 7A62 and 7A01 layers and thus prevented cracks from propagating into the 7A52 layer. Meanwhile, the nonuniform deformation between the 7A52 and 7A62 layers could be justified from adiabatic shear bands and precipitates. Deformation shear bands, transformation shear bands and then both were successively observed in the 7A52 layer, while only slight deformation was present in the 7A62 layer due to a much larger amount of η' precipitates effectively hindering dislocation movement. Therefore, nonuniform deformation was observed in the 7B52 alloy under high-speed impact. [ABSTRACT FROM AUTHOR]

This study aims to explore the effects of different Ca(OH)2 contents on the mechanical performance and corrosion behaviors of steel in Calcium sulfoaluminate (CSA) cement, where compressive strength, corrosion potentials of reinforcements, corrosion current density, pH of pore solution as well as mortar resistivity of CSA/Ca(OH)2 mortar were researched, and the corrosion behaviors were further interpreted by the clarification of hydration phases through microstructural analyses. The initial results highlighted the positive effects of using adequate Ca(OH)2 (~ 6%) in CSA mortar in terms of strength, yet its excessive addition could delay the subsequent hydration reaction of CSA. Meanwhile, with an increased quantity of Ca(OH)2, the amount of some hydration phases, such as Al(OH)3 reduced, resulting from their reaction with Ca(OH)2. Finally, the corrosion current density increased with the reduced mortar resistivity when the reinforcement in CSA/Ca(OH)2 system was corroded, and their relationship was also provided in this study. [ABSTRACT FROM AUTHOR]

To enhance the reliability and physical layer security of free space optical (FSO) communication system simultaneously, we propose an EDFA-based all-optical relaying FSO-CDMA wiretap channel model. Two-dimensional optical encoder and decoder are designed and constructed by wavelength selective switch Add/Drop and optical delay lines. A 10 Gb/s experimental system of EDFA-based all-optical relaying FSO-CDMA wiretap channel is built and investigated for the first time. Experimental results show that the BER of the legitimate user is greatly affected by the turbulence effect, and the reliability of EDFA-based all-optical relaying FSO-CDMA can be improved significantly. Compared with the uncoded system, the optical coding scheme can enhance the physical layer security. In the experimental system, with the enhancement of turbulence, the secrecy capacity of the system will increase. At the received power -22 dBm, the secrecy capacity is 0.28 bit/symbol in weak turbulence, while the secrecy capacity is 0.35 bit/symbol in moderate turbulence. [ABSTRACT FROM AUTHOR]

To study the damage evolution laws and damage constitutive model of low-strength molybdenum ores, uniaxial compression tests on low-strength molybdenum ores were conducted in combination with acoustic emission technology. The damage variables were defined based on the accumulative ringing counts, and the pre-peak correction factor was introduced to derive a modified damage constitutive model for low-strength molybdenum ores under uniaxial compression, and analyze their acoustic emission characteristics and damage evolution laws. The results showed that the accumulative ringing count and accumulative energy had a sharp increase before the stress peak of low-strength molybdenum ores, which can be used as basis for judging that low-strength molybdenum ores are about to enter the failure stage. The damage evolution process of low-strength molybdenum ores can reasonably reflect their deformation and failure characteristics in different fracture evolution stages. The stress–strain curve was up-concave, and the pre-peak correction factor in the form of logarithmic function is proposed to establish a more reasonable modified damage constitutive model based on accumulative ringing counts under uniaxial compression. The theoretical curve can well simulate the deformation process of low-strength molybdenum ores before the peak stress, and the obtained theoretical curve is basically consistent with the text curve. The results can provide a reference for the stability evaluation and control of the surrounding rock of low-strength molybdenum mines. [ABSTRACT FROM AUTHOR]

To ensure the safe and efficient mining of the tantalum–niobium mine body No. 69 in an underground metal mine in Jiangxi province, Brazilian splitting tests were performed on sandy slate, metamorphosed sandstone and granite surrounding rocks in the middle + 417 m section of the mine, and the deformation process, failure mode and evolution law of acoustic emission of splitting failure were studied. The relationships among acoustic emission ringing count, energy, cumulative ringing count, accumulated energy, and stress and time in the process of splitting and failure of the three types of surrounding rocks were obtained. The acoustic emission ringing count and energy were generally at low levels and increased with stress. When failure occurred, the ringing count and energy both reached a peak, which can be regarded as the precursor signal characteristics of rock tensile failure. On this basis, the fractal characteristics of acoustic emission were studied. The fractal dimension of the three rock samples varied roughly in the same way, exhibiting four stages: rise → fall → rise → fall. Among them, in the period of approximately 310–425 s, the sharp decrease in the fractal dimension of acoustic emission of metamorphosed sandstone was the longest, and the acoustic emission ringing count and energy surge were the most significant. Before failure, most of the three surrounding rocks experienced a continuous decline from the largest to the smallest fractal dimension, and the change rule of the ringing count and the fractal dimension value of energy from the largest to the smallest continuous decline was obtained, which can be used as the precursor characteristics of rock instability failure. The results of this study have reference value for the analysis and prediction of rock mass stability during mining design and construction of tantalum–niobium mines. [ABSTRACT FROM AUTHOR]

This study aims to ensure the safe and efficient mining of No.69 tantalum–niobium ore bodies in an underground metal mine in Jiangxi Province. Brazilian splitting tests were conducted on disc samples of two types of surrounding rocks (sandy slate and granite) from the + 417 m middle section of the mine at different loading rates (0.002, 0.005, and 0.01 mm/s). The tensile strength, failure mode, acoustic emission (AE) characteristics, and fractal features of disc samples during splitting failure were analyzed in relation to the loading rate. The study demonstrates that with an increase in the loading rate, the duration of splitting failure of both sandy slate and granite significantly decreases, and the corresponding ultimate load at the time of failure significantly increases. The tensile strength of the sandy slate and granite increases linearly with the loading rate, and the growth rate of the tensile strength of the granite samples was slightly larger than that of the sandy slate. The loading rate has a significant effect on the failure pattern of the splitting process of rock disc samples. The AE ringing counts and energy of the sandy slate and granite both show an increasing trend with the loading rate. Under low loading rate, the AE ringing count signal is generally of "solitary vibration" type, and under high loading rate, the ringing count curve is generally of "group vibration" type. The peak mean values of ringing counts and energy of the sandy slate were larger than those of granite under different loading rates. The maximum values of the AE fractal dimension of both sandy slate and granite appeared between 60 and 80% of the peak stress. The research results can provide a reference for the analysis and prediction of rock stability during the design and construction of ore body mining. [ABSTRACT FROM AUTHOR]

The dynamic mechanical behaviors of 7B52 laminated aluminum alloy under different impact deformation conditions were investigated using split Hopkinson pressure bar, optical microscopy, electron backscatter diffraction and transmission electron microscopy. The results show that the 7B52 laminated aluminum alloy displays positive strain rate sensitivity and negative temperature sensitivity. Cracks are formed firstly at the interface between the 7A62 hard layer and the 7A01 middle layer under a low strain rate of 2200 s−1. When the strain rate increases to 3500 s−1, the deformation shear band is firstly formed in the 7A52 soft layer. The deformation shear band transformed to the transition shear band with the increase of strain rate, and then crack initiated. Adiabatic shear bands and cracks are formed in both of the hard and soft layers when samples impacted at a high strain rate (5500 s−1). Most of the cracks and adiabatic shear bands are unable to penetrate the middle layer due to the good toughness of the 7A01 alloy. The deformation of each layer of 7B52 laminated aluminum alloy becomes more uniform when the temperature increases, which was attributed to the reduction of difference in strength among the three layers and the coordinating effect of grain boundary on deformation. [ABSTRACT FROM AUTHOR]

Depletion of shallow mineral resources caused by deep mining has become an inevitable trend, and deep mining can increase safety accidents and geological hazards. Overburden in a mined-out area is affected by mining disturbances, resulting in its subsidence or collapse, posing a threat to downhole safety and surface ecology. To identify the limitations of existing models, they were studied and analyzed for predicting the overburden movement in a current goaf. Based on the actual dynamic settlement of the overburden at a mine project site, the type and time relationship of the overburden settlement in the goaf is studied. Considering the influence of the deep overburden by self-gravity and tectonic stresses and combining with the Knothe time function, the overburden settlement is classified into four types: (I) sinking at a constant speed, (II) accelerated sinking until collapse, (III) initial accelerated sinking, followed by deceleration of sinking, and finally reaching a stable state, and (IV) initial accelerated sinking, followed by decelerated sinking, and finally accelerated sinking until collapse. A new method for predicting the dynamics of overburden settlement in mined-out areas is proposed based on the relationship between the settlement time, space, and volume. A dynamic prediction model of the settlement dynamics in the mining overburden in a mined-out area was constructed, which can predict the settlement patterns of various types of mine overburden. Finally, the results predicted by the model were validated by real engineering cases and were found to be in good agreement with the actual test results. [ABSTRACT FROM AUTHOR]

Due to the low density and high fatigue strength, Al-Cu-Mg alloy has become an attractive material for aerospace and navigation applications. However, the relatively high residual stress and low micro-yield strength after the fabrication process restrict its further application in the field of inertial instruments. The objective of this work is to investigate the effect of Ni plating on the residual stress and micro-yield strength in an Al-Cu-Mg alloy under different diffusion treatments. Compared with properties of the alloy without diffusion treatment, the micro-yield strength of the alloy after diffusion treatment increases 9.5%, and the corresponding residual stress decreases > 70%. This can be attributed to the increase of diffusion layer thickness and release of elastic energy. [ABSTRACT FROM AUTHOR]

1,3-Dihydroxyacetone, a common cosmetic material and food additive, has been successfully explored as an efficient electrochemiluminescence coreactant of Ru(bpy)32+ for the first time. It is about 25 times more effective than the well-known coreactant sodium oxalate. The high electrochemiluminescence efficiency allows sensitive detection of 1,3-dihydroxyacetone without any derivatization. The electrochemiluminescence method shows two linear electrochemiluminescence responses over the range of 5.0-500 μM and 500 μM-6.0 mM with a detection limit of 1.79 μM. The proposed method is at least two orders of magnitude more sensitive than other reported methods.ECL intensity-potential profile of 1,3-dihydroxyacetone (DHA) and oxalate [ABSTRACT FROM AUTHOR]

Key message: Nicotiana sylvestris calcineurin B-like protein NsylCBL10 improves tolerance to high-salt stress through better maintenance of Na balance. Abstract: The calcineurin B-like (CBL) proteins represent a unique group of plant calcium sensors and play an important role in regulating the response of a plant cell to the stress. Although many studies have been made in Arabidopsis ( Arabidopsis thaliana), rice ( Oryza sativa) and poplar ( Populus trichocarpa), the characterization and elucidation of the functions of CBLs in tobacco have not yet been reported. In this study, NsylCBL10, a CBL gene showing higher similarities to other CBL10 genes, was cloned from Nicotiana sylvestris. NsylCBL10 is expressed in most of the tobacco tissues, and the protein targets to the plasma membrane specifically. Over-expression of NsylCBL10 enhanced the salt tolerance of Arabidopsis wild type plants greatly, and rescued the high-salt-sensitive phenotype of Arabidopsis cbl10 mutant. The analysis of ion content indicated that over-expressing NsylCBL10 in plants is able to maintain a lower Na/K ratio in roots and higher Na/K ratio in shoots, compared with cbl10 mutant. The results suggest that NsylCBL10 might play an important role in response to high salinity stress in N. sylvestris, by keeping a better ionic homeostasis to reduce the damage of toxic ion to the plant cell. [ABSTRACT FROM AUTHOR]

Copper (Cu) is an essential micronutrient required for plant growth and development. However, excess Cu can inactivate and disturb protein structure as a result of unavoidable binding to proteins. To understand better the mechanisms involved in Cu toxicity and tolerance in plants, we developed a new immobilized metal affinity chromatography (IMAC) method for the separation and isolation of Cu-binding proteins extracted from roots of rice seedling exposed to excess Cu. In our method, IDA-Sepharose or EDDS-Sepharose column (referred as pre-chromatography) and Cu-IDA-Sepharose column (referred as Cu-IMAC) were connected in tandem. Namely, protein samples were pre-chromatographed with IDA-Sepharose column to removal metal ions, then protein solution was flowed into Cu-IMAC column for enriching Cu-binding proteins in vitro. Compared with the control (Cu-IMAC without any pre-chromatography), IDA-Sepharose pre-chromatography method markedly increased yield of the Cu-IMAC-binding proteins, and number of protein spots and the abundance of 40 protein spots on two-dimensional electrophoresis (2-DE) gels. Thirteen protein spots randomly selected from 2-DE gel and 11 proteins were identified using MALDI-TOF-TOF MS. These putative Cu-binding proteins included those involved in antioxidant defense, carbohydrate metabolism, nucleic acid metabolism, protein folding and stabilization, protein transport and cell wall synthesis. Ten proteins contained one or more of nine putative metal-binding motifs reported by Smith et al. (J Proteome Res 3:834-840, ) and seven proteins contained one or two of top six motifs reported by Kung et al. (Proteomics 6:2746-2758, ). Results demonstrated that more proteins specifically bound with Cu-IMAC could be enriched through removal of metal ions from samples by IDA-Sepharose pre-chromatography. Further studies are needed on metal-binding characteristics of these proteins in vivo and the relationship between Cu ions and protein biological activities to fully understand the mechanisms of Cu tolerance and toxicity in plants. [ABSTRACT FROM AUTHOR]

Background and aims: Copper (Cu) is an essential micronutrient required for growth and development of plants. However, excess Cu is toxic to plants. To understand the mechanisms involved in copper stress response, a proteomic approach was used to investigate the differences in Cu stress-induced protein expression between a Cu-tolerant variety (B1139) and a Cu-sensitive one (B1195) of rice. Methods: Rice seedlings were exposed to 8 μM Cu for 3 days, with plants grown in the normal nutrient solution containing 0.32 μM Cu serving as the control. Proteins were extracted from the roots and separated by two-dimensional PAGE. Thirty four proteins were identified using MALDI-TOF mass spectrometry. Results: Thirty-four protein spots were found to be differently expressed in the Cu-stressed roots in at least one variety of rice, including those involved in antioxidative defense, redox regulation, stress response, sulfur and glutathione (GSH) metabolism, carbohydrate metabolism, signal transduction, and some other proteins with various functions. Nine proteins, including putative cysteine synthase, probable serine acetyltransferase 3, L-ascorbate peroxidase 1, putative glutathione S-transferase 2, and thioredoxin-like 3-3, exhibited a greater increase in response to Cu stress in the Cu-tolerant variety B1139 compared with the Cu-sensitive variety B1195. Conclusion: The majority of the proteins showing differential expression in response to Cu exposure are involved in the redox regulation, and sulfur and GSH metabolism, suggesting that these proteins, together with antioxidant enzymes, play an important role in the detoxification of excess Cu and maintaining cellular homeostasis. [ABSTRACT FROM AUTHOR]

Cytochrome P450 (CYP) 1A1 Ile462Val (exon7) polymorphism has been suggested to be a risk factor for several cancers. Published data on its association with oral cancer risk have generated conflicting results. Our previous meta-analysis containing data from prior to Jan 2008 regarding this issue failed to find a significant association between CYP1A1 Ile462Val variation and oral cancer susceptibility. An updated meta-analysis with eligible studies for the period up to May 2012 was conducted. Separate analyses on ethnicity and source of controls were also performed. A total of 13 case-control studies comprising 1,515 cases and 2,233 controls were lastly selected for analysis. Compared with the previous meta-analysis, the overall data also failed to indicate a significant association of CYP1A1 Ile462Val polymorphism with oral cancer risk (Val/Val vs. Ile/Ile-OR = 1.46; 95 % CI = 0.96-2.24; dominant model-OR = 1.01; 95 % CI = 0.81-1.25; and recessive model-OR = 1.46; 95 % CI = 0.96-2.23). However, in the subgroup analysis by ethnicity, increased cancer risk was observed among Asians under the additive and recessive models (Val/Val vs. Ile/Ile-OR = 1.74; 95 % CI = 1.04-2.90 and recessive model-OR = 1.73; 95 % CI = 1.04-2.87), inconsistent with the previous meta-analysis. Collectively, the data of the present study suggest that CYP1A1 variant Val/Val alleles might modify the susceptibility to oral cancer among Asians. Further well-designed investigations with large sample sizes are required to confirm this conclusion. [ABSTRACT FROM AUTHOR]

Protein extraction is a critical step in a two-dimensional electrophoresis (2-DE)-based proteomic analysis. Dimethyl sulfoxide (DMSO), a small organic molecule, is widely used as a solvent in biological sciences. In this study, we modified the cleanup step of the commonly used trichloroacetic acid (TCA)/acetone method of protein extraction by using 20 % DMSO/acetone as a solvent to wash TCA-acetone-precipitated pellets. The improved protocol (TCA/acetone-DMSO) was compared with the TCA/acetone and phenol extraction method based on the protein yield, the number of spots, and resolution on 2-DE maps. TCA/acetone-DMSO washing increased protein yield, and improved the resolution in 2-DE with less background, streaking, and smearing. This method also produced the highest number of protein spots. To our knowledge, the present study is the first to use DMSO as a cleanup solvent for TCA/acetone-precipitated proteins to enhance their quality prior to 2-DE. [ABSTRACT FROM AUTHOR]

To investigate the significance and relationship between matrix metalloproteinase 9 (MMP-9) and infiltration of macrophages in the process of invasion and metastasis in oral squamous cell carcinoma (OSCC). The immunohistochemical SABC method was used to detect the expression of MMP-9 and CD68 (for labeling macrophages) in 42 cases of OSCC and in 10 normal tissues. The expression of MMP-9 and macrophage counts in the OSCC cases were significantly higher compared to normal tissues ( P<0.05). The expression of MMP-9 and macrophage counts were related to lymphnode metastasis and the TNM stage ( P<0.05), showing that there was a positive correlation among these parameters ( γ = 0.443, P<0.01). Both MMP-9 and macrophages may play an important role in the process of invasion and metastasis in OSCC, and this cellular activity may relate to the macrophages which affect the tumor cells and up-regulate the expression of MMP-9. [ABSTRACT FROM AUTHOR]

Objective: To investigate the expression of angiopoietin-2 (Ang-2) and vascular endothelialcell growth factor (VEGF) in oral squamous cell carcinoma (OSCC) and their correlations with clinicopathologic parameters, angiogenesis and vessel maturation of OSCC. Methods: The expression of Ang-2 and VEGF was detected in 41 speciments of human OSCC, 30 adjacent noncancerous oral tissues and 10 specimens of normal oral mucosa by conventional immumohistochemistry. Microvessel density (MVD) and vessel maturation index (VMI) were also assessed by double-labelling immumohistochemistry staining against CD34, a marker of pan-endothelial cells, and that against alpha-smooth muscle actin (α-SMA), a marker of mural cells (pericytes/smooth muscle cells). Results: The positive expression rate of Ang-2 and VEGF in 41 OSCC tissues was 51.22% and 63.42%, respectively. The expression of Ang-2 and VEGF was significantly higher in OSCC than in adjacent noncancerous oral tissues (all P<0.05) and normal oral mucosa (all P<0.05). In the clinicopathologic parameters, the Ang-2 expression was closely correlated with tumor lymph node metastasis (P<0.01) and the VEGF expression was correlated with tumor differentiated degree (P<0.05), but there was no significant correlation among the Ang-2 and VEGF expression and patients’ sex, age and TNM stages (all P>0.05). The MVD of OSCC positive for both Ang-2 and VEGF was significantly higher than that of OSCC negative for both Ang-2 and VEGF (P<0.05). The VMI of OSCC positive for Ang-2 was significantly lower than that of OSCC negative for Ang-2 (P<0.05). When Ang-2 expression was combined with the staus of VEGF expression, MVD of OSCC positive for both Ang-2 and VEGF was the highest (51.08±2.99) as compared with that of other status in patient with OSCC (all P<0.05). Conclusion: The overexpression of Ang-2 and VEGF may play a crucial role in the development of OSCC. They are closely associated with angiogenesis and vessel maturation of tumor. [ABSTRACT FROM AUTHOR]

Seed germination, an early and important process for the growth and development of plants, is hypersensitive to environmental changes. Copper (Cu) is a necessary micronutrient for plants; however, an excessive dose of Cu had an extremely negative effect at the cellular level as a result of inevitable binding to proteins. In contrast, some structural motifs of proteins can bind free Cu ions and relieve Cu toxicity. This study aimed to understand the expression characteristics of Cu-binding proteins induced by excess Cu during rice seed germination. We investigated Cu-binding proteins in germinating rice embryos treated with 200 µM Cu using a Sephadex G-50 column or immobilized Cu affinity chromatography combined with two-dimensional gel electrophoresis. Proteomics analysis indicated that 12 protein spots exhibited a > 2.0-fold increase in intensity in response to Cu toxicity as compared with controls. Among nine proteins in ten spots identified as Cu-binding proteins, three proteins (from four spots) were involved in antioxidative defense: copper, zinc superoxide dismutase, glutathione S-transferase and protein disulfide isomerase. These results show that reactive oxygen species may be involved in the expression regulation of Cu-binding proteins in germinating rice in response to Cu stress. [ABSTRACT FROM AUTHOR]