A comparative study of CO adsorption on flat, stepped and kinked Au surfaces using density functional theory

Our ab initio calculations of CO adsorption energies on low miller index (111), (100), stepped (211), and kinked (532) gold surfaces show a strong dependence on local coordination with a reduction in Au atom coordination leading to higher binding energies. We find trends in adsorption energies to be similar to those reported in experiments and calculations for other metal surfaces. The (532) surface provides insights into these trends because of the availability of a large number of kink sites which naturally have the lowest coordination (6). We also find that, for all surfaces, an increase in CO coverage triggers a decrease in the adsorption energy. Changes in the work-function upon CO adsorption, as well as the frequencies of the CO vibrational modes are calculated, and their coverage dependence is reported.Comment: 18 pages, 4 figure

C and S induces changes in the electronic and geometric structure of Pd(533) and Pd(320)

We have performed ab initio electronic structure calculations of C and S adsorption on two vicinal surfaces of Pd with different terrace geometry and width. We find both adsorbates to induce a significant perturbation of the surface electronic and geometric structure of Pd(533) and Pd(320). In particular C adsorbed at the bridge site at the edge of a Pd chain in Pd(320) is found to penetrate the surface to form a sub-surface structure. The adsorption energies show almost linear dependence on the number of adsorbate-metal bonds, and lie in the ranges of 5.31eV to 8.58eV for C and 2.89eV to 5.40eV for S. A strong hybridization between adsorbate and surface electronic states causes a large splitting of the bands leading to a drastic decrease in the local densities of electronic states at the Fermi-level for Pd surface atoms neighboring the adsorbate which may poison catalytic activity of the surface. Comparison of the results for Pd(533) with those obtained earlier for Pd(211) suggests the local character of the impact of the adsorbate on the geometric and electronic structures of Pd surfaces.Comment: 14 pages 9 figs, Accepted J. Phys: Conden

Broadband spin-controlled focusing via logarithmic-spiral nanoslits of varying width

This work presents analytical, numerical and experimental demonstrations of light diffracted through a logarithmic spiral (LS) nanoslit, which forms a type of switchable and focus-tunable structure. Owing to a strong dependence on the incident photon spin, the proposed LS-nanoslit converges incoming light of opposite handedness (to that of the LS-nanoslit) into a confined subwavelength spot, while it shapes light with similar chirality into a donut-like intensity profile. Benefitting from the varying width of the LS-nanoslit, different incident wavelengths interfere constructively at different positions, i.e., the focal length shifts from 7.5 μm (at λ = 632.8 nm) to 10 μm (at λ = 488 nm), which opens up new opportunities for tuning and spatially separating broadband light at the micrometer scale

Spiniform phase-encoded metagratings entangling arbitrary rational-order orbital angular momentum

Quantum entanglements between integer-order and fractional-order orbital angular momentums (OAMs) have been previously discussed. However, the entangled nature of arbitrary rational-order OAM has long been considered a myth due to the absence of an effective strategy for generating arbitrary rational-order OAM beams. Therefore, we report a single metadevice comprising a bilaterally symmetric grating with an aperture, creating optical beams with dynamically controllable OAM values that are continuously varying over a rational range. Due to its encoded spiniform phase, this novel metagrating enables the production of an average OAM that can be increased without a theoretical limit by embracing distributed singularities, which differs significantly from the classic method of stacking phase singularities using fork gratings. This new method makes it possible to probe the unexplored niche of quantum entanglement between arbitrarily defined OAMs in light, which could lead to the complex manipulation of microparticles, high-dimensional quantum entanglement and optical communication. We show that quantum coincidence based on rational-order OAM-superposition states could give rise to low cross-talks between two different states that have no significant overlap in their spiral spectra. Additionally, future applications in quantum communication and optical micromanipulation may be found

Systems genomics of nucleoporins provides prognostic insights into breast cancer

Background: Nucleoporins (Nups) constitute a large group of proteins that are structurally arranged at the nuclear envelope and facilitate the bidirectional movement of molecules across the nuclear membrane. In addition to regulating the shuttling of ribonucleoprotein complexes, RNAs and proteins, various Nups interact with chromatin either directly or indirectly, thus regulating gene expression. Any mutations or expression anomalies of Nups may lead to abnormal localization of critical molecules, or dysregulated expression of genes that they interact with. A comprehensive genomic study encompassing all Nup genes in relation to breast cancer is lacking. Methods: We used genomic and transcriptomic datasets from Pan-Cancer TCGA (The Cancer Genome Atlas), Genotype-Tissue Expression (GTEx) and microarray platforms and conducted in silico analysis of all the genes encoding nucleoporins that are associated with the Nuclear Pore Complexes (NPCs). For mutation detection, we used cBioportal; for expression analysis, we used Xena and for patient survival plots, KMPlot was utilized. Results: The genetic and molecular profile of nucleoporin genes identified multiple mutations and detected aberrant expression in breast cancer. Interestingly, NUP133, AHCTF1, TPR, Nup121L showed simultaneous gene amplification in nearly 10% of breast cancer patients. In addition, deregulated expression of some of the nucleoporins, namely, NUP62, NUP 93, NUP98, NUP155, POM121L12, RAE1, SEC13, TPR were correlated with patient prognosis. Conclusion: The current study is the first one that unravels a comprehensive molecular and genetic profile of nucleoporins genes in breast cancer and underscores the critical roles of various nucleoporins in cancer progression. The identified molecules may advance our understanding of the etiology of the disease and serve as possible targets for novel therapeutic strategies in cancer

Counteracting Selfish Nodes Using Reputation Based System in Mobile Ad Hoc Networks

A mobile ad hoc network (MANET) is a group of nodes constituting a network of mobile nodes without predefined and pre-established architecture where mobile nodes can communicate without any dedicated access points or base stations. In MANETs, a node may act as a host as well as a router. Nodes in the network can send and receive packets through intermediate nodes. However, the existence of malicious and selfish nodes in MANETs severely degrades network performance. The identification of such nodes in the network and their isolation from the network is a challenging problem. Therefore, in this paper, a simple reputation-based scheme is proposed which uses the consumption and contribution information for selfish node detection and cooperation enforcement. Nodes failing to cooperate are detached from the network to save resources of other nodes with good reputation. The simulation results show that our proposed scheme outperforms the benchmark scheme in terms of NRL (normalized routing load), PDF (packet delivery fraction), and packet drop in the presence of malicious and selfish attacks. Furthermore, our scheme identifies the selfish nodes quickly and accurately as compared to the benchmark scheme

Highly selective O2 reduction to H2O2 catalyzed by cobalt nanoparticles supported on nitrogen-doped carbon in alkaline solution

We report the synthesis of cobalt nanoparticles supported on nitrogen-doped carbon (CoNPs@N/C), which can reduce O2 into H2O2 with high selectivity (up to 93%) in 0.1 M KOH electrolyte and retains >90% activity even after 10 h polarization. The catalyst achieves a current density of 1 mA cm–2 at 0.76 V(RHE) and a peroxide production rate of ∼3.8molH2O2 gCo–1 h–1 over a 10 h period. Our study also highlights the requirement for good peroxide production catalysts to be poor hydrogen peroxide disproportionation catalysts. We show how the high activity of the CoNPs@N/C catalyst is correlated with low activity toward the peroxide disproportionation reaction

Development and pilot implementation of a locally developed Trauma Registry: lessons learnt in a low-income country

Background Trauma registries (TRs) play an integral role in the assessment of trauma care quality. TRs are still uncommon in developing countries owing to awareness and cost. We present a case study of development and pilot implementation of “Karachi Trauma Registry” (KITR), using existing medical records at a tertiary-care hospital of Karachi, Pakistan to present results of initial data and describe its process of implementation. Methods KITR is a locally developed, customized, electronic trauma registry based on open source software designed by local software developers in Karachi. Data for KITR was collected from November 2010 to January 2011. All patients presenting to the Emergency Department (ED) of the Aga Khan University Hospital (AKUH) with a diagnosis of injury as defined in ICD-9 CM were included. There was no direct contact with patients or health care providers for data collection. Basic demographics, injury details, event detail, injury severity and outcome were recorded. Data was entered in the KITR and reports were generated. Results Complete data of 542 patients were entered and analysed. The mean age of patients was 27 years, and 72.5% were males. About 87% of patients had sustained blunt injury. Falls and motor vehicle crashes were the most common mechanisms of injury. Head and face, followed by the extremities, were the most frequently injured anatomical regions. The mean Injury Severity Score (ISS) was 4.99 and there were 8 deaths. The most common missing variables in the medical records were ethnicity, ED notification prior to transfer, and pre-hospital IV fluids. Average time to review each chart was 14.5 minutes and entry into the electronic registry required 15 minutes. Conclusion Using existing medical records, we were able to enter data on most variables including mechanism of injuries, burden of severe injuries and quality indicators such as length of stay in ED, injury to arrival delay, as well as generate injury severity and survival probability but missed information such as ethnicity, ED notification. To make the data collection process more effective, we propose provider based data collection or making a standardized data collection tool a part of medical records

Collaborative Virtual Environment for Advanced Computing

Synchronous collaborative systems allow geographically distributed participants to form a virtual work environment enabling cooperation between peers and enriching the human interaction. The technology facilitating this interaction has been studied for several years and various solutions can be found at present. In this paper, we discuss our experiences with one such widely adopted technology, namely the Access Grid. We describe our experiences with using this technology, identify key problem areas and propose our solution to tackle these issues appropriately. Moreover, we propose the integration of Access Grid with an Application Sharing tool, developed by the authors. Our approach allows these integrated tools to utilise the enhanced features provided by our underlying dynamic transport layer