Energetics and kinetics of Li intercalation in irradiated graphene scaffolds

In the present study we investigate the irradiation-defects hybridized graphene scaffold as one potential building material for the anode of Li-ion batteries. Designating the Wigner V22 defect as a representative, we illustrate the interplay of Li atoms with the irradiation-defects in graphene scaffolds. We examine the adsorption energetics and diffusion kinetics of Li in the vicinity of a Wigner V22 defect using density functional theory calculations. The equilibrium Li adsorption sites at the defect are identified and shown to be energetically preferable to the adsorption sites on pristine (bilayer) graphene. Meanwhile the minimum energy paths and corresponding energy barriers for Li migration at the defect are determined and computed. We find that while the defect is shown to exhibit certain trapping effects on Li motions on the graphene surface, it appears to facilitate the interlayer Li diffusion and enhance the charge capacity within its vicinity because of the reduced interlayer spacing and characteristic symmetry associated with the defect. Our results provide critical assessment for the application of irradiated graphene scaffolds in Li-ion batteries.Comment: 23 pages, 5 figure

Investigation of ion induced bending mechanism for nanostructures

Ion induced bending is a promising controlled technique for manipulating nanoscale structures. However, the underlying mechanism of the process is not well understood. In this letter, we report a detailed study of the bending mechanism of Si nanowires (NWs) under Ga+ irradiation. The microstructural changes in the NW due to ion beam irradiation are studied and molecular dynamics simulations are used to explore the ion–NW interaction processes. The simulation results are compared with the microstructural studies of the NW. The investigations inform a generic understanding of the bending process in crystalline materials, which we suggest to be feasible as a versatile manipulation and integration technique in nanotechnology

Genomic analysis and relatedness of P2-like phages of the Burkholderia cepacia complex

<p>Abstract</p> <p>Background</p> <p>The <it>Burkholderia cepacia </it>complex (BCC) is comprised of at least seventeen Gram-negative species that cause infections in cystic fibrosis patients. Because BCC bacteria are broadly antibiotic resistant, phage therapy is currently being investigated as a possible alternative treatment for these infections. The purpose of our study was to sequence and characterize three novel BCC-specific phages: KS5 (vB_BceM-KS5 or vB_BmuZ-ATCC 17616), KS14 (vB_BceM-KS14) and KL3 (vB_BamM-KL3 or vB_BceZ-CEP511).</p> <p>Results</p> <p>KS5, KS14 and KL3 are myoviruses with the A1 morphotype. The genomes of these phages are between 32317 and 40555 base pairs in length and are predicted to encode between 44 and 52 proteins. These phages have over 50% of their proteins in common with enterobacteria phage P2 and so can be classified as members of the <it>Peduovirinae </it>subfamily and the "P2-like viruses" genus. The BCC phage proteins similar to those encoded by P2 are predominantly structural components involved in virion morphogenesis. As prophages, KS5 and KL3 integrate into an AMP nucleosidase gene and a threonine tRNA gene, respectively. Unlike other P2-like viruses, the KS14 prophage is maintained as a plasmid. The P2 <it>E+E' </it>translational frameshift site is conserved among these three phages and so they are predicted to use frameshifting for expression of two of their tail proteins. The <it>lysBC </it>genes of KS14 and KL3 are similar to those of P2, but in KS5 the organization of these genes suggests that they may have been acquired via horizontal transfer from a phage similar to λ. KS5 contains two sequence elements that are unique among these three phages: an IS<it>Bmu</it>2-like insertion sequence and a reverse transcriptase gene. KL3 encodes an EcoRII-C endonuclease/methylase pair and Vsr endonuclease that are predicted to function during the lytic cycle to cleave non-self DNA, protect the phage genome and repair methylation-induced mutations.</p> <p>Conclusions</p> <p>KS5, KS14 and KL3 are the first BCC-specific phages to be identified as P2-like. As KS14 has previously been shown to be active against <it>Burkholderia cenocepacia in vivo</it>, genomic characterization of these phages is a crucial first step in the development of these and similar phages for clinical use against the BCC.</p

Nutrition and cancer: A review of the evidence for an anti-cancer diet

It has been estimated that 30–40 percent of all cancers can be prevented by lifestyle and dietary measures alone. Obesity, nutrient sparse foods such as concentrated sugars and refined flour products that contribute to impaired glucose metabolism (which leads to diabetes), low fiber intake, consumption of red meat, and imbalance of omega 3 and omega 6 fats all contribute to excess cancer risk. Intake of flax seed, especially its lignan fraction, and abundant portions of fruits and vegetables will lower cancer risk. Allium and cruciferous vegetables are especially beneficial, with broccoli sprouts being the densest source of sulforophane. Protective elements in a cancer prevention diet include selenium, folic acid, vitamin B-12, vitamin D, chlorophyll, and antioxidants such as the carotenoids (α-carotene, β-carotene, lycopene, lutein, cryptoxanthin). Ascorbic acid has limited benefits orally, but could be very beneficial intravenously. Supplementary use of oral digestive enzymes and probiotics also has merit as anticancer dietary measures. When a diet is compiled according to the guidelines here it is likely that there would be at least a 60–70 percent decrease in breast, colorectal, and prostate cancers, and even a 40–50 percent decrease in lung cancer, along with similar reductions in cancers at other sites. Such a diet would be conducive to preventing cancer and would favor recovery from cancer as well

Substrate-induced magnetism in epitaxial graphene

Magnetism in graphene is of fundamental as well as technological interest, with potential applications in molecular magnets and spintronic devices. While defects and/or adsorbates in freestanding graphene nanoribbons and graphene sheets have been shown to cause itinerant magnetism, controlling the density and distribution of defects and adsorbates is in general difficult. We show from first principles calculations that graphene buffer layers on SiC(0001) can also show intrinsic magnetism. The formation of graphene-substrate chemical bonds disrupts the graphene pi-bonds and causes localization of graphene states near the Fermi level. Exchange interactions between these states lead to itinerant magnetism in the graphene buffer layer. We demonstrate the occurrence of magnetism in graphene buffer layers on both bulk-terminated as well as more realistic adatom-terminated SiC(0001) surfaces. Our calculations show that adatom density has a profound effect on the spin distribution in the graphene buffer layer, thereby providing a means of engineering magnetism in epitaxial graphene

Atomistic Mechanisms of Mg Insertion Reactions in Group XIV Anodes for Mg-Ion Batteries

Magnesium (Mg) metal has been widely explored as an anode material for Mg-ion batteries (MIBs) owing to its large specific capacity and dendrite-free operation. However, critical challenges, such as the formation of passivation layers during battery operation and anode− electrolyte−cathode incompatibilities, limit the practical application of Mg-metal anodes for MIBs. Motivated by the promise of group XIV elements (namely, Si, Ge, and Sn) as anodes for lithium- and sodium-ion batteries, here, we conduct systematic first-principles calculations to explore the thermodynamics and kinetics of group XIV anodes for MIBs and to identify the atomistic mechanisms of the electrochemical insertion reactions of Mg ions. We confirm the formation of amorphous MgxX phases (where X = Si, Ge, and Sn) in anodes via the breaking of the stronger X−X bonding network replaced by weaker Mg−X bonding. Mg ions have higher diffusivities in Ge and Sn anodes than in Si, resulting from weaker Ge−Ge and Sn−Sn bonding networks. In addition, we identify thermodynamic instabilities of MgxX that require a small overpotential to avoid aggregation (plating) of Mg at anode/electrolyte interfaces. Such comprehensive first-principles calculations demonstrate that amorphous Ge and crystalline Sn can be potentially effective anodes for practical applications in MIBs.Mingchao Wang, Jodie A. Yuwono, Vallabh Vasudevan, Nick Birbilis, and Nikhil V. Medheka

Ion Agglomeration and Transport in MgCl2-Based Electrolytes for Rechargeable Magnesium Batteries.

Magnesium halide salts are an exciting prospect as stable and high-performance electrolytes for rechargeable Mg batteries (RMBs). By nature of their complex equilibria, these salts exist in solution as a variety of electroactive species (EAS) in equilibrium with counterions such as AlCl₄‾. Here we investigated ion agglomeration and transport of several such EAS in MgCl₂ salts dissolved in ethereal solvents under both equilibrium and operating conditions using large-scale atomistic simulations. We found that the solute morphology is strongly characterized by the presence of clusters and is governed by the solvation structures of EAS. Specifically, the isotropic solvation of MgCl²⁺ results in the slow formation of a bulky cluster, compared with chainlike analogues observed in the Cl-containing EAS such as Mg₂Cl₃⁺, MgCl⁺, and Mg₂Cl₃⁺. We further illustrate these clusters can reduce the diffusivity of charge-carrying species in the MgCl₂-based electrolyte by at least an order of magnitude. Our findings for cluster formation, morphology, and kinetics can provide useful insight into the electrochemical reactions at the anode-electrolyte interface in RMBs.Vallabh Vasudevan, Mingchao Wang, Jodie A. Yuwono, Jacek Jasieniak, Nick Birbilis, and Nikhil V. Medheka

Blood stream infections in cancer patients: A single center experience of isolates and sensitivity pattern

Background : Up to 10% of patients who develop a nosocomial blood stream infection (BSI) in the hospital have an underlying malignancy. The treatment of infections in patients with malignancy often relies on the use of established guidelines along with the consideration of the local microbiology and antibiotic sensitivity patterns of possible etiologic agents. AIMS: This study attempts to identify the likely etiologic agents and the antibiotic sensitivity profile of BSIs in cancer patients. Settings and Design: This was a retrospective study. Methods and Material: The study was conducted at a tertiary care center for cancer patients, in which samples representing blood stream infections sent from the Medical Oncology services of the hospital during the year of 2007 were analysed. The microbiological profile and antibiotic sensitivity pattern of these isolates was studied. Results: There were 484 isolates that represented BSIs. The most common bacterial isolates from patients with cancer were Pseudomonas spp. (30.37%), Staphylococcus aureus (12.6%) and Acinetobacter spp. (11.57%). Meropenem was the most effective antibiotic with 71.2% sensitivity to the bacterial isolates it was tested against. Oxacillin resistance was seen in 18% of S. aureus isolates. Conclusion: Gram-negative bacteria were more common as etiologic agents of BSIs in cancer patients. The poor activity of the primary empirical agents for infections in cancer namely ceftazidime and piperacillin-tazobactam is alarming.Strict regulation of vancomycin use should be considered in areas where there is a low prevalence of methicillin-resistant S. aureus (MRSA)

The effect of age on the bacteria isolated and the antibiotic-sensitivity pattern in infections among cancer patients

Background: Patients with cancer are predisposed to infections. Antimicrobial patterns and antibiotic sensitivity change with increasing age, making choice of empirical therapy more complicated. Materials and Methods: This single-center study aims to try and assess the influence of age on microbiology and antibiotic sensitivity of organisms causing infection in patients with malignant disease. Results : The five most common bacterial pathogens isolated were Pseudomonas sp (245, 26.2%) > Enterocococcus sp (109, 11.66%) > Staphylococcus aureus (107, 11.44%) > Escherichia coli (106, 11.34%) > Klebsiella sp (99, 10.59%). There was no significant change in the distribution of Gram-positive and Gram-negative bacteria with age. However, there was an increase in the occurrence of the Enterobacteriacea group and a decrease in infections caused by nonlactose fermenters with increasing age. The ESBL production increased from 10.52% (12-19 years) to 24.88% (>50 years) as did oxacillin resistance (from 14.3% to 28.1%) among S. aureus isolates. The activity of most antimicrobial agents decreased with increasing age. The decreasing trend of activity was statistically significant for meropenam (73.3-41.2%) against Pseudomonas sp. and for the activity of the aminoglycosides for Acinetobacter sp (61.1-17.4% for amikacin). Conclusions : This suggests that empirical antibiotic therapy needs to be changed on the basis of the age of the patient. It also appears that combination therapy is essential for the empirical treatment of infections in elderly patients with cancer