Grain Boundary Effects on Microstructural Stability of Nanocrystalline Metallic Materials

Grain boundaries play an important role in dictating the mechanical and physical properties of nanocrystalline (NC) materials because of the increased volume fraction of intercrystalline components as the grain size decreases. In general, grain boundaries have a high energy level and there exists a thermodynamic driving force to reduce the overall area of grain boundaries through grain coarsening, making NC material systems intrinsically unstable. Recent investigations also indicate that mechanical deformation can promote grain growth in NC material even at the cryogenic temperatures. In this chapter, first, the current investigation on the grain boundary structures of NC metallic materials is briefly reviewed and then the state-of-the-art of experimental results on the microstructural stability during deformation processes is discussed. Finally, several key issues for improving the microstructure stability of NC metallic materials and possible future work are discussed

Evaluation of portable colposcopy and human papillomavirus testing for screening of cervical cancer in rural China

OBJECTIVE: To evaluate the use of a portable, rechargeable colposcope combined with human papillomavirus (HPV) testing, as compared with HPV testing alone, for screening of cervical cancer and pre-cancerous lesions. METHODS: This was a cross-sectional study among 488 women in Baoshan County, Yunnan. The women underwent HPV testing followed by Gynocular portable colposcopy with visual inspection with acetic acid. Obvious lesions were biopsied. If portable colposcopy testing was negative but HPV testing was positive, the women underwent follow-up testing with thin-prep cytology and traditional colposcopy. Cervical biopsies were performed for any abnormalities. Histopathology was followed up with diagnosis and treatment. RESULTS: Among 488 women screened with portable colposcopy, 24 women underwent biopsy based on positive colposcopy screening. Of these 24 women, three were HPV positive and 21 were HPV negative. Five women had cervical intra-epithelial neoplasia (CIN) I and one had advanced cervical cancer. Forty-six women tested positive for HPV. Three of these women had screened positive on preliminary colposcopy, with one positive for CIN III/squamous cell carcinoma and one woman with CIN I. Forty-three women underwent follow-up testing with thin-prep cytology. Two women had atypical squamous cells of undetermined significance and five had low-grade squamous intra-epithelial lesions and were biopsied; three women had CIN I, one had CIN II and one had CIN III. HPV testing and portable colposcopy was more sensitive but slightly less specific than portable colposcopy or HPV testing alone. CONCLUSION: While HPV testing has high sensitivity and specificity for the detection of pre-cancerous and cancerous lesions and portable colposcopy has lower specificity, both methods of detection have low positive predictive value and high negative predictive value. In tandem, HPV testing and portable colposcopy had higher sensitivity for detection among women who underwent biopsies. In clinical practice, portable colposcopy was an effective, easy and affordable tool to transport to villages where cytology is not currently feasible

Increased Neutralizing Antibody Production and Interferon-γ Secretion in Response to Porcine Reproductive and Respiratory Syndrome Virus Immunization in Genetically Modified Pigs

T cell-mediated immunity plays a prominent role in combating pathogens infection. Both the engagement of the T cell receptor with the peptide-bound major histocompatibility complex and a costimulatory signal are needed for the complete activation of the T cell. To determine whether host immune responses to vaccination could be improved by enhancing CD28-mediated costimulation and verify whether the boosted immune responses could protect the host against viral challenge, we produced a transgenic pig line expressing an extra copy of the CD28 gene controlled by its own promoter at the Rosa26 locus. As expected, in response to porcine reproductive and respiratory syndrome virus (PRRSV) strain vaccination, CD4+ T cells was remarkably increased in CD28 transgenic pigs and a similar response in CD8+ T cells was elicited after challenge. Importantly, because of increased T cell frequencies, the virus-neutralizing antibody against JXA-1 (a highly pathogenic Chinese PRRSV strain), as well as interferon-γ secretion, were enhanced in transgenic pigs. These findings in our translational study provide a novel concept for farm animal breeding in disease resistance, in which we may use the transgenic technology to force overexpression of confirmed immunity-promoting molecules like CD28 and produce an animal with enhanced immune responses to vaccination and broad-spectrum resistance to infectious diseases

Investigation of the Mode Structures of Multiphoton Induced Ultraviolet Laser in a ZnO Microrod

Hexagonal wurtzite structural ZnO microrods were fabricated by vapor-phase transport method. Under the excitation of a pulse laser with 1200 nm wavelength, the multiphoton induced ultraviolet (UV) laser was observed in a microrod. The dependence of the laser mode structures on pump intensity was investigated. The result indicates that the laser belongs to whispering gallery mode (WGM) at low pump intensity and Fabry-Perot (FP) mode at high pump intensity. The corresponding positive feedback mechanisms were discussed

Underwater multi-sensor Bayesian distributed detection and data fusion

The relationship of decision rule of sensor for each other is relevant to data fusion, so different topological network of sensors usually results in different performance. This paper considers the parallel and sequential topological data fusion in some detail and applies it to detect underwater signal with three sensors which respectively detects the energy, impulse width and frequency. In this paper, the signal detection model is specified for binary hypotheses testing problem. This paper compares the probabilities of error and Bayesian risk under both topologies corresponding to different value of priori probabilities of two hypotheses. Usually, the parallel architecture of detection and fusion with three sensors as specified in this paper needs to solve eleven nonlinear equations to determine the thresholds of three sensors and fusion rules, as to sequential architecture, five nonlinear equations need to be solved. So, this paper attempts to search numerical solutions for the parallel and sequential architecture of distributed detection and data fusion. Finally, this signal detection problem is simulated

Research on the air supply adjustment technology of breath-following powered air-purifying respirators

Abstract In the hope of reducing the air supply flow of the powered air-purifying respirator (PAPR) and extending the service life of the filter, a breath-following powered air-purifying respirator (BF-PAPR) that can dynamically adjust the air supply flow according to the breathing flow is proposed. The BF-PAPR changes the air supply flow by adjusting the speed of the variable-frequency centrifugal fan according to the air velocity at the half mask outlet (v hm ) monitored by the modular wind speed transmitter. In the study, the air supply flow adjustment model of the BF-PAPR is developed. It is found that the filtration resistance barely influences v hm . In addition, under the same mean inhalation flow, the minimum outlet air velocity increases first and then decreases with the increase of the duty cycle variation coefficient (λ), while the maximum outlet air velocity decreases first and then increases. Moreover, the minimum air supply flow of the BF-PAPR is achieved when the standard value of the air velocity is 13.4 m/s and the value of λ is 1. The BF-PAPR can reduce the air supply flow by 6.5%-8.6% and the energy consumption by approximately 20% compared with the PAPR, which is beneficial for reducing the usage cost and extending the continuous working time

Moving Target Detection Using Dynamic Mode Decomposition

It is challenging to detect a moving target in the reverberant environment for a long time. In recent years, a kind of method based on low-rank and sparse theory was developed to study this problem. The multiframe data containing the target echo and reverberation are arranged in a matrix, and then, the detection is achieved by low-rank and sparse decomposition of the data matrix. In this paper, we introduce a new method for the matrix decomposition using dynamic mode decomposition (DMD). DMD is usually used to calculate eigenmodes of an approximate linear model. We divided the eigenmodes into two categories to realize low-rank and sparse decomposition such that we detected the target from the sparse component. Compared with the previous methods based on low-rank and sparse theory, our method improves the computation speed by approximately 4–90-times at the expense of a slight loss of detection gain. The efficient method has a big advantage for real-time processing. This method can spare time for other stages of processing to improve the detection performance. We have validated the method with three sets of underwater acoustic data

A numerical simulation method for pressure drop and normal air velocity of pleated filters during dust loading

Pressure drop is an important indicator that affects the filtration performance of the pleated filter, and the deposition of dust particles within the pleats is crucial to the evolution of the pressure drop. In this study, the pressure drop during PM10 loading process was investigated for a series of V-shaped and U-shaped filters with a pleat height of 20 mm and different pleat ratios (the ratio of pleat height to pleat width: α = 0.71–3.57). In the numerical simulations, numerical models suitable for different pleated geometries were obtained through experimental verification on the local air velocity. Then, assuming that the dust cake thickness is proportional to the normal air velocity of the filters, the variation of the pressure drop with the dust deposition is derived by means of successive numerical simulations. This simulation method saved a significant amount of CPU time required for the growth of dust cake. It was found that the relative average deviations between experimental and simulated pressure drops were 3.12% and 1.19% for V-shaped and U-shaped filters, respectively. Furthermore, it was found that under the same pleat ratio and the mass of dust deposition per unit area, both the pressure drop and unevenness of normal air velocity of the U-shaped filter were lower than the V-shaped filter. Therefore, the U-shaped filter is recommended due to its better filtration performance