Impurity scattering and Friedel oscillations in mono-layer black phosphorus

We study the effect of impurity scattering effect in black phosphorurene (BP) in this work. For single impurity, we calculate impurity induced local density of states (LDOS) in momentum space numerically based on tight-binding Hamiltonian. In real space, we calculate LDOS and Friedel oscillation analytically. LDOS shows strong anisotropy in BP. Many impurities in BP are investigated using $T$-matrix approximation when the density is low. Midgap states appear in band gap with peaks in DOS. The peaks of midgap states are dependent on impurity potential. For finite positive potential, the impurity tends to bind negative charge carriers and vise versa. The infinite impurity potential problem is related to chiral symmetry in BP

Visual information processing through the interplay between fine and coarse signal pathways

Object recognition is often viewed as a feedforward, bottom-up process in machine learning, but in real neural systems, object recognition is a complicated process which involves the interplay between two signal pathways. One is the parvocellular pathway (P-pathway), which is slow and extracts fine features of objects; the other is the magnocellular pathway (M-pathway), which is fast and extracts coarse features of objects. It has been suggested that the interplay between the two pathways endows the neural system with the capacity of processing visual information rapidly, adaptively, and robustly. However, the underlying computational mechanism remains largely unknown. In this study, we build a two-pathway model to elucidate the computational properties associated with the interactions between two visual pathways. Specifically, we model two visual pathways using two convolution neural networks: one mimics the P-pathway, referred to as FineNet, which is deep, has small-size kernels, and receives detailed visual inputs; the other mimics the M-pathway, referred to as CoarseNet, which is shallow, has large-size kernels, and receives blurred visual inputs. We show that CoarseNet can learn from FineNet through imitation to improve its performance, FineNet can benefit from the feedback of CoarseNet to improve its robustness to noise; and the two pathways interact with each other to achieve rough-to-fine information processing. Using visual backward masking as an example, we further demonstrate that our model can explain visual cognitive behaviors that involve the interplay between two pathways. We hope that this study gives us insight into understanding the interaction principles between two visual pathways

A methylation-switchable conformational probe for the sensitive and selective detection of RNA demethylase activity

We describe a novel methylation-sensitive nucleic acid (RNA) probe which switches conformation according to its methylation status. When combined with a differential scanning fluorimetry technique, it enables highly sensitive and selective detection of demethylase activity at a single methylated-base level. The approach is highly versatile and may be adapted to a broad range of RNA demethylases

Controllable molecular packing motif and overlap type in organic nanomaterials for advanced optical properties

The optical properties of organic materials are very sensitive to subtle structural modification, and a proper understanding of the structure-property relationship is essential to improve the performance of organic electronic devices. The phase transitions of the η-CuPc to the α-CuPc, then to the β-CuPc were investigated using In situ X-ray diffraction and the differential scanning calorimetry (DSC). The five stages in the phase-transition process from low to high-temperature were observed, which consisted of (1) the η-CuPc; (2) a mixture of the η- and α-CuPc; (3) a mixture of the η-, α- and β-CuPc; (4) a mixture of the α- and β-CuPc; and (5) the β-CuPc. The vibrational and optical properties at different phase-transition stages were correlated to molecular packing motif and molecule overlap type through systematic analyses of the Fourier–transform infrared, Raman and UV-VIS spectra. Moreover, the mechanism for the morphology evolution was also discussed in detail

Determination of mechanical properties of historical paper based on NIR spectroscopy and chemometrics - a new instrument

Due to sampling restrictions in the analysis of cultural heritage materials, non-destructive approaches are intensively sought for. While NIR spectrometry has rarely been used for this purpose due to the complexity of the spectra, chemometric methods can be used to extract the necessary information. For the purpose of determination of mechanical properties of historical paper, partial least squares approach was used and it is shown that tensile strength, and tensile strength after folding, can be estimated based on NIR spectra. As the mechanical properties of paper-based objects define their accessibility, a new dispersive portable instrument was built, which will enable us to rapidly survey the condition of library and archival collections

Construction and analysis of subtractive hybridization library of differentially expressed genes in spleen of C57BL/6 and A/J mice with Streptococcus suis serotype 2 infection

Streptococcus suis is an important swine and human pathogen, and it has presented a considerable challenge to the global public health community. Domínguez-Punaro et al. (2007) showed that two strains of mice were differentially susceptible to S. suis. The attainment of information on the differential expression of host response genes following S. suis infection is relevant to the understanding of the molecular mechanism of this disease. The intent of this study was to select and isolate differentially expressed genes from A/J and C57BL/6 mice that are associated with the host response to S. suis infection. These baseline data will allow for the screening and cloning of specific resistance genes, and further our understanding of the molecular mechanism of S. suis infection. Eightweek- old C57BL/6 and A/J mouse were infected with S. suis serotype 2, a 200-μL volume of a bacterial suspension (1 × 108 CFU/mL) was administrated by intraperitoneal injection to the mice, and cDNA subtraction libraries were constructed by suppression subtraction hybridization (SSH). Genes involved in immune function, such as lysozyme, interferon-active protein, macrophage activation 2-like protein, complement component-3 and Ly108 protein were up-regulated in the spleen of C57BL/6 mice to a greater extent than they were in the spleen of A/J mice, subsequent to infection with S. suis serotype 2. Interestingly, we observed that several splenic signaling factors associated with phospholipid metabolism were up-regulated to a greater extent as well in C57BL/6 mice than they were in A/J mice following infection with S. suis serotype 2. These data suggest that phospholipid metabolism may be involved in the host defense response to S. suis invasion, thereby contributing to the organism’s overall immune response to this pathogen.Key words: Streptococcus suis serotype 2, suppression, subtractive hybridization, differentially expressed genes, mouse spleen