Showing papers by "Wei Ji published in 2014"
TL;DR: A detailed theoretical investigation of the atomic and electronic structure of few-layer black phosphorus (BP) is presented to predict its electrical and optical properties, finding that the mobilities are hole-dominated, rather high and highly anisotropic.
Abstract: Two-dimensional crystals are emerging materials for nanoelectronics. Development of the field requires candidate systems with both a high carrier mobility and, in contrast to graphene, a sufficiently large electronic bandgap. Here we present a detailed theoretical investigation of the atomic and electronic structure of few-layer black phosphorus (BP) to predict its electrical and optical properties. This system has a direct bandgap, tunable from 1.51 eV for a monolayer to 0.59 eV for a five-layer sample. We predict that the mobilities are hole-dominated, rather high and highly anisotropic. The monolayer is exceptional in having an extremely high hole mobility (of order 10,000 cm(2) V(-1) s(-1)) and anomalous elastic properties which reverse the anisotropy. Light absorption spectra indicate linear dichroism between perpendicular in-plane directions, which allows optical determination of the crystalline orientation and optical activation of the anisotropic transport properties. These results make few-layer BP a promising candidate for future electronics.
3,622 citations
TL;DR: An equiatomic CoCrFeNiAl high-entropy alloy was synthesized by mechanical alloying, and phase evolutions, microstructure, thermal properties and annealing behaviors were investigated as discussed by the authors.
193 citations
TL;DR: This study isolated MSCs from several mammalian species, each of a different genus, and investigated the involvement of indoleamine 2,3-dioxygenase and iNOS during MSC-mediated immunosuppression, providing critical guidance for choosing appropriate animal models for preclinical studies of M SCs.
Abstract: Mammalian mesenchymal stem cells (MSCs) have been shown to be strongly immunosuppressive in both animal disease models and human clinical trials. We have reported that the key molecule mediating immunosuppression by MSCs is species dependent: indoleamine 2,3-dioxygenase (IDO) in human and inducible nitric oxide synthase (iNOS) in mouse. In the present study, we isolated MSCs from several mammalian species, each of a different genus, and investigated the involvement of IDO and iNOS during MSC-mediated immunosuppression. The characterization of MSCs from different species was by adherence to tissue culture plastic, morphology, specific marker expression, and differentiation potential. On the basis of the inducibility of IDO and iNOS by inflammatory cytokines in MSCs, the tested mammalian species fall into two distinct groups: IDO utilizers and iNOS utilizers. MSCs from monkey, pig, and human employ IDO to suppress immune responses, whereas MSCs from mouse, rat, rabbit, and hamster utilize iNOS. Interestingly, based on the limited number of species tested, the iNOS-utilizing species all belong to the phylogenetic clade, Glires. Although the evolutionary significance of this divergence is not known, we believe that this study provides critical guidance for choosing appropriate animal models for preclinical studies of MSCs.
177 citations
TL;DR: In this paper, the authors report first-principles theoretical investigations of possible metal contacts to monolayer black phosphorus (BP) by analyzing lattice geometry, and conclude that Cu(111) is the best candidate to form excellent Ohmic contact to monoline BP.
Abstract: We report first-principles theoretical investigations of possible metal contacts to monolayer black phosphorus (BP). By analyzing lattice geometry, five metal surfaces are found to have minimal lattice mismatch with BP: Cu(111), Zn(0001), In(110), Ta(110), and Nb(110). Further studies indicate Ta and Nb bond strongly with monolayer BP causing substantial bond distortions, but the combined Ta-BP and Nb-BP form good metal surfaces to contact a second layer BP. By analyzing the geometry, bonding, electronic structure, charge transfer, potential, and band bending, it is concluded that Cu(111) is the best candidate to form excellent Ohmic contact to monolayer BP. The other four metal surfaces or combined surfaces also provide viable structures to form metal/BP contacts, but they have Schottky character. Finally, the band bending property in the current-in-plane (CIP) structure where metal/BP is connected to a freestanding monolayer BP, is investigated. By both work function estimates and direct calculations of the two-probe CIP structure, we find that the freestanding BP channel is $n$ type.
126 citations
TL;DR: An equiatomic CoCrFeNiMnAl high-entropy alloy was synthesized by mechanical alloying, and alloying behaviors, microstructure and annealing behaviors were investigated as discussed by the authors.
98 citations
TL;DR: In this paper, the effect of intermolecular hydrogen bonding on surface-enhanced Raman scattering (SERS) spectra was investigated and it was shown that the vibrational frequencies and intensities of some characteristic peaks of p-mercaptobenzoic acid (MBA) change with varying concentrations of aniline.
Abstract: We report the significant effect of intermolecular hydrogen bonding (H-bonding) on surface-enhanced Raman scattering (SERS) spectra in which the vibrational frequencies and intensities of some characteristic peaks of p-mercaptobenzoic acid (MBA) change with varying concentrations of aniline. These changes can be attributed to modifications in the electronic structure of the MBA molecule and the conjugation of the system under the influence of H-bonding. Of remarkable note is that the nontotally symmetric (b2) mode of MBA is dramatically enhanced, which can be considered as a manifestation of the charge-transfer (CT) transition process in the system. By comparing SERS spectra obtained under normal and basic conditions, the effect caused by H-bonding can be further understood. These results manifest that the CT resonance between MBA and Ag NPs through Herzberg–Teller contributions can be promoted by H-bonding. The current work may, therefore, be instructive for studying the influence of H-bonding on the ele...
77 citations
TL;DR: A particular advantage of this approach is that it is label-free and does not employ any chiral reagents, including chiral light, which opens a new avenue leading to the development of novel enantiosensing strategies.
Abstract: Efficient and generic enantioselective discrimination of various chiral alcohols is achieved by using surface-enhanced Raman scattering (SERS) spectroscopy through charge-transfer (CT) contributions. The relative intensities of the peaks in the SERS spectra of a chiral selector are strongly dependent on the chirality of its surroundings. This highly distinct spectral discrepancy may be due to the tendency of chiral isomers to form intermolecular hydrogen-bonding complexes with the chiral selector in different molecular orientations, resulting in different CT states and SERS intensities of the adsorbates in the system. This study opens a new avenue leading to the development of novel enantiosensing strategies. A particular advantage of this approach is that it is label-free and does not employ any chiral reagents, including chiral light.
74 citations
TL;DR: Temperature-dependent SERS experiments and their two-dimensional (2D) correlation analysis confirmed that the formation of H-bonds facilitated the CT transition between the adsorbed molecules and substrate and the degree of CT was reduced by H- bond breakage that occurred with increasing temperature.
Abstract: We investigated the influence of hydrogen bonds (H-bonds) on the intermolecular interactions of a system comprising p-aminothiophenol (PATP) and benzoic acid (BA) using surface-enhanced Raman scattering (SERS) for the first time. In this system, H-bonds form through intermolecular interactions between the –NH2 and –COOH groups and promote the charge-transfer (CT) transition from the Ag substrate to the adsorbed PATP molecules. Accordingly, the intensities of the non-totally symmetric vibrations (the b2-type bands) of PATP are influenced through the Herzberg–Teller contribution. This is clearly a BA concentration-dependent phenomenon. This behaviour can be attributed to an increase in the degree of conjugation of the system, which facilitates the CT process in the system with H-bonds. Furthermore, temperature-dependent SERS experiments and their two-dimensional (2D) correlation analysis confirmed that the formation of H-bonds facilitated the CT transition between the adsorbed molecules and substrate. The degree of CT was reduced by H-bond breakage that occurred with increasing temperature. An additional SERS experiment involving substituted BA molecules yielded similar conclusions.
46 citations
TL;DR: In this paper, the effect of Fe3Al additions on the microstructure and mechanical properties of B4C has been studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalyzer (EPMA) equipped with WDS and EDS.
Abstract: B4C based ceramics were fabricated with different Fe3Al contents as sintering aids by spark plasma sintering at relatively low temperature (1700 °C) in vacuum by applying 50 MPa pressure and held at 1700 °C for 5 min. The effect of Fe3Al additions (from 0 to 9 wt%) on the microstructure and mechanical properties of B4C has been studied. The composition and microstructure of as-prepared samples were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalyzer (EPMA) equipped with WDS (wavelength dispersive spectrometry) and EDS. The mixtures of B4C and Fe3Al underwent a major reaction in which the metal borides and B4C were encountered as major crystallographic phases. The sample with 7 wt% of Fe3Al as a sintering aid was found to have 32.46 GPa Vickers hardness, 483.40 MPa flexural strength, and 4.1 MPa m1/2 fracture toughness which is higher than that of pure B4C.
34 citations
TL;DR: The up-regulation expression of gcMR, IL-1β and TNF-α in liver, spleen, head kidney and intestine after Aeromonas hydrophila infection indicating it involved in innate immune regulation during bacterial infections.
Abstract: Mannose receptor C type 1 (MRC1) is a pattern-recognition receptor (PRR) which plays a significant role in immune responses. Much work on MRC1 has been done in mammals and birds while little in fish. In this study, we cloned and characterized MRC1 in grass carp (gcMR). The full-length gcMR contained 5291bp encoding a putative protein of 1432 amino acids. The predicted amino acid sequences showed that gcMR contained a signal peptide, a cysteine-rich (CR) domain, a fibronectin type II (FN II) domain, eight C-type lectin-like domains (CTLDs), a transmembrane domain and a short cytoplasmic domain. gcMR were constitutively expressed in different organs with the higher expression in spleen and head kidney. During embryonic development, gcMR transcript levels were highest at cleavage stage. The up-regulation expression of gcMR, IL-1β and TNF-α in liver, spleen, head kidney and intestine after Aeromonas hydrophila infection indicating it involved in innate immune regulation during bacterial infections.
31 citations
TL;DR: ARCHERRT was developed successfully to perform fast and accurate MC dose calculation for radiotherapy using PSFs and patient CT phantoms and achieves a fast speed for PSF-based dose calculations.
Abstract: Purpose: Using the graphical processing units (GPU) hardware technology, an extremely fast Monte Carlo (MC) code ARCHERRT is developed for radiation dose calculations in radiation therapy. This paper describes the detailed software development and testing for three clinical TomoTherapy cases: the prostate, lung, and head & neck. Methods: To obtain clinically relevant dose distributions, phase space files (PSFs) created from opti- mized radiation therapy treatment plan fluence maps were used as the input to ARCHERRT. Patient- specific phantoms were constructed from patient CT images. Batch simulations were employed to facilitate the time-consuming task of loading large PSFs, and to improve the estimation of statistical uncertainty. Furthermore, two different Woodcock tracking algorithms were implemented and their relative performance was compared. The dose curves of an Elekta accelerator PSF incident on a ho- mogeneous water phantom were benchmarked against DOSXYZnrc. For each of the treatment cases, dose volume histograms and isodose maps were produced from ARCHERRT and the general-purpose code, GEANT4. The gamma index analysis was performed to evaluate the similarity of voxel doses obtained from these two codes. The hardware accelerators used in this study are one NVIDIA K20 GPU, one NVIDIA K40 GPU, and six NVIDIA M2090 GPUs. In addition, to make a fairer compari- son of the CPU and GPU performance, a multithreaded CPU code was developed using OpenMP and tested on an Intel E5-2620 CPU. Results: For the water phantom, the depth dose curve and dose profiles from ARCHERRT agree well with DOSXYZnrc. For clinical cases, results from ARCHERRT are compared with those from GEANT4 and good agreement is observed. Gamma index test is performed for voxels whose dose is greater than 10% of maximum dose. For 2%/2mm criteria, the passing rates for the prostate, lung case, and head & neck cases are 99.7%, 98.5%, and 97.2%, respectively. Due to specific architecture of GPU, modified Woodcock tracking algorithm performed inferior to the original one. ARCHERRT achieves a fast speed for PSF-based dose calculations. With a single M2090 card, the simulations cost about 60, 50, 80 s for three cases, respectively, with the 1% statistical error in the PTV. Using the latest K40 card, the simulations are 1.7–1.8 times faster. More impressively, six M2090 cards could finish the simulations in 8.9–13.4 s. For comparison, the same simulations on Intel E5-2620 (12 hyperthreading) cost about 500–800 s. Conclusions: ARCHERRT was developed successfully to perform fast and accurate MC dose cal- culation for radiotherapy using PSFs and patient CT phantoms.
TL;DR: AT-MSCs showed significantly higher osteogenic potential compared to AT- MSCs/HUVECs both in vitro and in vivo, and superior bone formation was observed in AT-MSCS compared to At-MSC/H UVECs in rat cranial defects.
Abstract: The aim of this study was to compare the osteogenic capacity between human adipose tissue-derived mesenchymal stem cells (AT-MSCs) and their cocultures with human umbilical vein endothelial cells (HUVECs) in vitro and their biological performance in vivo. First, the optimal cell ratio in cocultures for osteogenic differentiation was determined by seeding AT-MSCs and HUVECs in ratios varying from 100:0 to 0:100 on tissue culture plates. Afterward, AT-MSCs and AT-MSCs/HUVECs (50:50) were seeded on porous titanium fiber mesh scaffolds (Ti) for both in vitro and in vivo osteogenic evaluation. For in vitro evaluation, cell osteogenic differentiation was assessed by alkaline phosphatase (ALP) activity and calcium assay. For in vivo evaluation, the scaffolds were implanted bilaterally into rat cranial defects (5 mm diameter) and bone formation was assessed histologically and histomorphometrically after 8 weeks. The ratio of 50:50 was chosen in the cocultures because this coculture condition retained similar amount of calcium deposition while using the least amount of AT-MSCs. Moreover, AT-MSCs showed higher osteogenic differentiation in comparison to AT-MSCs/HUVECs on Ti in vitro. Furthermore, superior bone formation was observed in AT-MSCs compared to AT-MSCs/HUVECs in rat cranial defects. In conclusion, AT-MSCs showed significantly higher osteogenic potential compared to AT-MSCs/HUVECs both in vitro and in vivo.
TL;DR: Investigation of the effect of fiber alignment and hydroxyapatite content in biodegradable electrospun PLGA scaffolds found nHA incorporation does have an effect on cell proliferation, differentiation and ECM production, and should be regarded as a bioactive component of dental bioengineered scaffolds.
Abstract: In stem cell-based dental tissue engineering, the goal is to create tooth-like structures using scaffold materials to guide the dental stem cells. In this study, the effect of fiber alignment and hydroxyapatite content in biodegradable electrospun PLGA scaffolds have been investigated. Fiber orientation of the scaffolds was random or aligned in bundles. For scaffolds with prefabricated orientation, scaffolds were fabricated from PLGA polymer solution containing 0, 10 or 20 % nano-hydroxyapatite. The scaffolds were seeded with porcine cells isolated from tooth buds (dental mesenchymal, dental epithelial, and mixed dental mesenchymal/epithelial cells). Samples were collected at 1, 3 and 6 weeks. Analyses were performed for cell proliferation, ALP activity, and cell morphology. Fiber alignment showed an effect on cell orientation in the first week after cell seeding, but had no long-term effect on cell alignment or organized calcified matrix deposition once the cells reach confluency. Scaffold porosity was sufficient to allow migration of mesenchymal cells. Hydroxyapatite incorporation did not have a positive effect on cell proliferation, especially of epithelial cells, but seemed to promote differentiation. Concluding, scaffold architecture is important to mesenchymal cell morphology, but has no long-term effect on cell alignment or organized ECM deposition. nHA incorporation does have an effect on cell proliferation, differentiation and ECM production, and should be regarded as a bioactive component of dental bioengineered scaffolds.
Posted Content•
20 Jan 2014
TL;DR: Wang et al. as discussed by the authors presented a theoretical investigation of geometric and electronic structures of few-layer black phosphorus, based on which, associated electric and optical properties were predicted, and showed that it has a direct band gap, which is tunable from 1.51 eV of monolayer to 0.59 eV for 5-layer; while the hole mobility is 337 cm2/V·s (monolayer) and the smallest electron mobility is 299 cm2
Abstract: Two-dimensional crystals are emerging materials for future nanoelectronics, the community of which has been seeking for candidate channel materials that have sufficient electronic band gap, high carrier mobility, and good channel-lead contact. We present a theoretical investigation of geometric and electronic structures of few-layer black phosphorus, based on which, associated electric and optical properties were predicted. Our results show that it has a direct band gap, which is tunable from 1.51 eV of monolayer to 0.59 eV of 5-layer; while the hole mobility, for example, increase from 337 cm2/V•s of monolayer to 2722 cm2/V•s of 5-layer. In addition, directionally selective optical transitions were found that significant light absorption happens at energies in the infrared range along a certain direction, while there are no appreciable absorption below 2.0 eV for the other two directions. These results make few-layer black phosphorus a promising candidate for future electronics and optoelectronics. __________ § These authors equally contributed to this work * wji@ruc.edu.cn, http://sim.phys.ruc.edu.cn The discovery of graphene opened many new areas of research, among them twodimensional (2D) atomic layers, including graphene, transition metal dichalcogenides (TMD) and others, were intensively investigated as emergent materials for future electronics.1-13 To realize a high performance device, e.g. field effect transistor (FET), it requires a sufficient electronic band gap and a reasonably high carrier mobility of the channel material and excellent electrode-channel contact.5-8,10-13 Graphene offers extremely high carrier mobility, due to its Dirac-like linear dispersion, which thus lead to graphene a promising candidate for, e.g. high speed FET, however, it is gapless.1-7 Although tremendous research efforts have been made on how to open a gap in graphene nanostructures, it is still an open issue of relatively large off current and low on-off ratio.5,6,14 The emergence of monolayer TMDs, e.g. MoS2, as its first FET recently demonstrated,8 has attracted substantial research interest. Unlike graphene, monolayer MoS2 is a direct band gap semiconductor with a carrier mobility of approximately 200 cm2/V·s, improvable up to 500 cm2/V·s,8 which is fairly good, but orders of magnitude lower than that of graphene.5,6 Germanane is another candidate for 2D electronics that theory predicts a high carrier mobility of 18195 cm2/V·s and a finite band gap of 1.56 eV.15 It is, however, covered by H atoms, rather electronically inert, which doubts whether a good contact can be made between electrode materials and germanane. Therefore, a very important open problem is to seek for a 2D material which is a, preferably direct gap, semiconductor with considerably high carrier mobility and potentially can form excellent contact with known electrode materials. In this work, we report a discovery of high carrier mobility in a novel category of layered direct band gap semiconductors, namely, few-layer black phosphorus (BP), an allotrope of phosphorus, as shown in Fig. 1(a). In particular, by density functional theory calculations we show that few-layer BPs, from monolayer up to 5-layer, are thermally stable, with interlayer interaction energy of -0.44 eV. The bandgap-thickness relation follows an exponentially decay law that it goes from ~1.5 eV of monolayer down to ~0.6 eV of 5-layer. Effective masses in the range from 0.14 m0 to 0.18 m0 for electron and hole were found along the b direction. Carrier mobilities along the same direction at 300K were theoretically derived that the smallest hole mobility is 337 cm2/V·s (monolayer) and the smallest electron mobility is 299 cm2/V·s (bilayer) among all considered few-layers, while they are over or close to a thousand cm2/V·s for the 5layer BP. The corresponding values considered in an 1D model are an order of magnitude higher. A sufficient optical absorbance peak was found at 1.72 eV in the monolayer, or at lower energies in thicker layers, only along the b direction. All these results strongly suggest that few-layer BP is a new category of 2D semiconductors that is promising in the applications of nanoelectronics and optoelectronics.
TL;DR: This work shows that the Von Hippel-Lindau gene product, pVHL, physically interacts with AR and inhibits AR transcription activity but does not induce AR turnover, implicating a physiological role of pV HL in androgen-induced signaling pathway and uncovering a noncanonical role in the ubiquitin proteasome pathway.
Abstract: The androgen receptor (AR) plays a pivotal role in prostate homeostasis and prostate cancer development. To understand the mechanism underlying the regulation of the AR holds a promise for developing novel therapeutic approaches for prostate cancer. Here, we show that the Von Hippel-Lindau gene product, pVHL, physically interacts with AR and inhibits AR transcription activity but does not induce AR turnover. Moreover, pVHL also suppresses androgen-induced cell proliferation, implicating a physiological role of pVHL in androgen-induced signaling pathway. In addition, we provide evidence to show that pVHL actually enhanced AR de-ubiquitination instead of inducing AR ubiquitination, uncovering a noncanonical role of pVHL in the ubiquitin proteasome pathway. Our data reveal a novel function of pVHL in the regulation of AR transcription activity, which may expand the scope of pVHL in tumor suppression and provide mechanistic insight into prostate cancer initiation and progression.
TL;DR: The results suggested that Microcystin-LR can stimulate c-myc transcription and stabilize c- myc protein, which might contribute to hepatic tumorigenesis in animals and humans.
TL;DR: In this paper, a fitting approach in temperature is investigated that allows for the efficient evaluation of the thermal neutron scattering physics at an arbitrary temperature within a predefined range, and the functional fits are able to accurately reproduce the scattering probabilities.
TL;DR: A new family of coumarin-based supramolecular hydrogelators without conventional gelating motifs have been designed and synthesized in a one-step reaction and fluorescent nanofibers self-assembled from these hydrogels could be used as potential scaffolds for better visualization of the interaction between substrates and cells.
TL;DR: In this article, a facile method has been proposed to synthesize dendritic silver nanostructures without any template, and the results showed that the synthesized DBSs gave an intense signal when p-aminobenzenethiol at very low concentration is used as a probe molecule.
Abstract: A facile method has been proposed to synthesize dendritic silver nanostructures without any template. UV-vis and TEM images revealed that the dendritic silver nanostructures with pronounced trunks and branches have been synthesized. Surface-enhanced Raman scattering (SERS) experiments showed that the synthesized dendritic silver gives an intense signal when p-aminobenzenethiol at very low concentration is used as a probe molecule.
TL;DR: In this article, a dual-sphere model is proposed to evaluate the Dancoff factor of TRISO fuel kernels based on the chord method, which can be used as a routine method for the neutronic design and analysis of reactors loaded with TRISO particle fuel.
TL;DR: It is shown that knockdown of zebrafish eaf1 by morpholinos caused serious defects in both primitive and definitive hematopoiesis, and a novel regulatory pathway is revealed that may shed light on the role of EAF1 in MLL-ELL induced leukemogenesis.
TL;DR: The first teleost MR from Megalobrama amblycephala, named maMR and its expression patterns were investigated and it was found that transcripts of maMR significantly increased at the late stages of embryo and continued to be at the high levels after hatching.
Abstract: Mannose receptor (MR) plays a significant role in innate immune responses to pathogens in vertebrates. Here we characterized the first teleost MR from Megalobrama amblycephala, named maMR and its expression patterns were investigated. The full-length maMR consists of 5,295 bp encoding a putative protein of 1,433 amino acids. The predicted amino acid sequences showed that maMR contained a signal peptide, a cysteine-rich domain, a single fibronectin type II domain, eight tandemly arranged C-type lectin-like domains, a transmembrane domain and a C-terminal cytoplasmic domain. Phylogenetic analysis revealed the highest similarity of maMR with Danio rerio MR predicted by computational analysis. The maMR-mRNAs were ubiquitously transcribed in different tissues, However the highest transcripts were observed in head kidney. Transcripts of maMR significantly increased at the late stages of embryo and continued to be at the high levels after hatching. The maMR transcripts were significantly increased in M. amblycephala after stimulation with killed Aeromonas hydrophila.
TL;DR: This molecular marker technique is a simple and efficient method to quantify genetic diversity within and among fish populations, and is employed here to help manage and conserve germplasm variability of blunt snout bream and to support the ongoing selective breeding programme for this fish.
Abstract: The blunt snout bream (Megalobrama amblycephala) is an important freshwater aquaculture fish throughout China. Because of widespread introductions of this species to many regions, the genetic diversity of wild and natural populations is now threatened. In the present study, SRAP (sequence-related amplified polymorphism) markers were used to assess genetic diversity of blunt snout bream. Three natural populations (Liangzi Lake, Poyang Lake and Yuni Lake, one cultured population (Nanxian) and one genetic strain (‘Pujiang No. 1’) of blunt snout bream were screened with 88 SRAP primer combinations, of which 13 primer pairs produced stable and reproducible amplification patterns. In total, 172 bands were produced, of which 132 bands were polymorphic. Nei's gene diversity (h) and Shannon's information index (I) values provided evidence of differences in genetic diversity among the five populations (Poyang Lake>Liangzi Lake>Nanxian>‘Pujiang No. 1’>Yuni Lake). Based on cluster analysis conducted on genetic distance values, the five blunt snout bream populations were divided into three groups, Poyang Lake and Liangzi Lake (natural populations), Nanxian and ‘Pujiang No. 1’ (cultured population and genetically selected strain), and Yuni Lake (natural population). Significant genetic differentiation was found among the five populations using analysis of molecular variance (AMOVA), with more genetic divergence existing among populations (55.49%), than within populations (44.51%). This molecular marker technique is a simple and efficient method to quantify genetic diversity within and among fish populations, and is employed here to help manage and conserve germplasm variability of blunt snout bream and to support the ongoing selective breeding programme for this fish.
TL;DR: A Density Functional Theory study is reported to revisit early studies of the dissociative adsorption of CH3X (X = Br and Cl) on Si(100) and identifies a new reaction pathway, which involves a flip of a silicon dimer; this new pathway agrees better with experiments.
Abstract: During the dissociative adsorption on a solid surface, the substrate usually participates in a passive manner to accommodate fragments produced upon the cleavage of the internal bond(s) of a (transient) molecular adsorbate. This simple picture, however, neglects the flexibility of surface atoms. Here, we report a Density Functional Theory study to revisit our early studies of the dissociative adsorption of CH3X (X = Br and Cl) on Si(100). We have identified a new reaction pathway, which involves a flip of a silicon dimer; this new pathway agrees better with experiments. For our main exemplar of CH3Br, insights have been gained using a simple model that involves a three-atom reactive center, Br-C-Si. When the silicon dimer flips, the interaction between C and Si in the Br-C-Si center is enhanced, evident in the increased energy-split of the frontier orbitals. We also examine how the dissociation dynamics of CH3Br is altered on a heterodimer (Si-Al, Si-P, and Si-Ge) in a Si(100) surface. In each case, we conclude, on the basis of computed reaction pathways, that no heterodimer flipping is involved before the system transverses the transition state to dissociative adsorption.
TL;DR: The molecular electrostatic potential surface calculation was performed and the result suggested that the 4-MPH has two hydrogen bond donors and three hydrogen bond acceptors.
TL;DR: STM studies combined with dynamical modeling can be seen as a way to improve understanding of the role of surface alignment in determining reactive outcomes in induced reaction at asymmetric crystalline surfaces.
Abstract: There has been much interest in the effect of adsorbate alignment in a surface reaction. Here we show its significance for an electron-induced reaction occurring along preferred axes of the asymmetric Cu(110) surface, characterized by directional copper rows. By scanning tunneling microscopy (STM), we found that the heterocyclic aromatic reagent, physisorbed meta-iodopyridine, lay with its carbon-iodine either along the rows of Cu(110), "A", or perpendicular, "P". Electron-induced dissociative attachment with the C-I bond initially along "A" gave a chemisorbed I atom and chemisorbed vertical pyridyl, singly surface-bound, whereas that with C-I along "P" gave a chemisorbed I atom and a horizontal pyridyl, doubly bound. An impulsive two-state model, involving a short-lived antibonding state of C-I, accounted for the different product surface binding in terms of closer Cu···Cu atomic spacing along "A" accommodating only one binding site of the pyridyl ring recoiling from I and wider spacing along "P" accommodating simultaneously both binding sites, N-Cu and C-Cu, in the meta-position on the recoiling pyridyl ring. STM studies combined with dynamical modeling can be seen as a way to improve understanding of the role of surface alignment in determining reactive outcomes in induced reaction at asymmetric crystalline surfaces.
01 Jun 2014
TL;DR: It is found that although the vectorized MC algorithm greatly reduces the occurrence of thread divergence thus enhancing the warp execution efficiency, the overall simulation speed is roughly ten times slower than the history-based MC code on GPUs.
Abstract: For nuclear reactor analysis such as the neutron eigenvalue calculations, the time consuming Monte Carlo (MC) simulations can be accelerated by using graphics processing units (GPUs) However, traditional MC methods are often history-based, and their performance on GPUs is affected significantly by the thread divergence problem In this paper we describe the development of a newly designed event-based vectorized MC algorithm for solving the neutron eigenvalue problem The code was implemented using NVIDIA’s Compute Unified Device Architecture (CUDA), and tested on a NVIDIA Tesla M2090 GPU card We found that although the vectorized MC algorithm greatly reduces the occurrence of thread divergence thus enhancing the warp execution efficiency, the overall simulation speed is roughly ten times slower than the history-based MC code on GPUs Profiling results suggest that the slow speed is probably due to the memory access latency caused by the large amount of global memory transactions Possible solutions to improve the code efficiency are discussed
TL;DR: These findings not only connect ELL to E2F1 function and uncover a novel role of ELL in response to DNA damage but also provide an insight into the mechanism for MLL-ELL-associated leukemogenesis.
Abstract: ELL (eleven-nineteen lysine-rich leukemia protein) was first identified as a translocation partner of MLL in acute myeloid leukemia; however, the exact mechanism of its action has remained elusive. In this study, we identified ELL as a direct downstream target gene of E2F1. Coimmunoprecipitation assays showed that ELL interacted with E2F1 in vitro and in vivo, leading to inhibition of E2F1 transcriptional activity. In addition, ELL enhanced E2F1 deacetylation via recruitment of histone deacetylase 1 (HDAC1). Notably, the MLL-ELL fusion protein lost the inhibitory role of ELL in E2F1 transcriptional activity. Furthermore, DNA damage induced ELL in an E2F1-dependent manner and ELL protected cells against E2F1-dependent apoptosis. Our findings not only connect ELL to E2F1 function and uncover a novel role of ELL in response to DNA damage but also provide an insight into the mechanism for MLL-ELL-associated leukemogenesis.
TL;DR: In this article, the role of interfacial bonding mechanism and its resulting structures to quantum transport in molecular wires was investigated, and two bonding mechanisms for the Au-S bond in an Au(111)/1,4-benzenedithiol(BDT)/Au(111) junction were identified by ab initio calculation, confirmed by a recent experiment.
Abstract: We report theoretical investigations on the role of interfacial bonding mechanism and its resulting structures to quantum transport in molecular wires. Two bonding mechanisms for the Au-S bond in an Au(111)/1,4-benzenedithiol(BDT)/Au(111) junction were identified by ab initio calculation, confirmed by a recent experiment, which, we showed, critically control charge conduction. It was found, for Au/BDT/Aujunctions, the hydrogen atom, bound by a dative bond to the Sulfur, is energetically non-dissociativeafter the interface formation. The calculated conductance and junction breakdown forces of H-non-dissociative Au/BDT/Au devices are consistent with the experimental values, while the H-dissociated devices, with the interface governed by typical covalent bonding, give conductance more than an order of magnitude larger. By examining the scattering states that traverse the junctions, we have revealed that mechanical and electric properties of a junction have strong correlation with the bonding configuration. This work clearly demonstrates that the interfacial details, rather than previously believed many-body effects, is of vital importance for correctly predicting equilibrium conductance of molecular junctions; and manifests that the interfacial contact must be carefully understood for investigating quantum transport properties of molecular nanoelectronics.
01 Jun 2014
TL;DR: The development of a software, called ARCHER (Accelerated Radiation-transport Computations in Heterogeneous EnviRonments), which is designed as a versatile testbed for future Monte Carlo codes.
Abstract: The Monte Carlo radiation transport community faces a number of challenges associated with peta- and exa-scale computing systems that rely increasingly on heterogeneous architectures involving hardware accelerators such as GPUs. Existing Monte Carlo codes and methods must be strategically upgraded to meet emerging hardware and software needs. In this paper, we describe the development of a software, called ARCHER (Accelerated Radiation-transport Computations in Heterogeneous EnviRonments), which is designed as a versatile testbed for future Monte Carlo codes. Preliminary results from five projects in nuclear engineering and medical physics are presented.