2D and 3D cubic monocrystalline and polycrystalline materials: their stability and mechanical properties

We consider 2- and 3-dimensional cubic monocrystalline and polycrystalline materials. Expressions for Young's and shear moduli and Poisson's ratio are expressed in terms of eigenvalues of the stiffness tensor. Such a form is well suited for studying properties of these mechanical characteristics on sides of the stability triangles. For crystalline high-symmetry directions lines of vanishing Poisson's ratio are found. These lines demarcate regions of the stability triangle into areas of various auxeticity properties. The simplest model of polycrystalline 2D and 3D cubic materials is considered. In polycrystalline phases the region of complete auxetics is larger than for monocrystalline materials.Comment: 9 pages, 3 figures, in proceedings of the Tenth International School on Theoretical Physics, Symmetry and Structural Properties of Condensed Matter, Myczkowce 200

Heat capacity and phonon mean free path of wurtzite GaN

We report on lattice specific heat of bulk hexagonal GaN measured by the heat flow method in the temperature range 20-300 K and by the adiabatic method in the range 5-70 K. We fit the experimental data using two temperatures model. The best fit with the accuracy of 3 % was obtained for the temperature independent Debye's temperature $\theta_{\rm D}=365$ {\rm K} and Einstein's temperature $\theta_{\rm E}=880$ {\rm K}. We relate these temperatures to the function of density of states. Using our results for heat conduction coefficient, we established in temperature range 10-100 K the explicit dependence of the phonon mean free path on temperature $\it{l}_{\rm ph}\propto T^{-2}$. Above 100 K, there is the evidence of contribution of the Umklapp processes which limit phonon free path at high temepratures. For phonons with energy $k_{\rm B}\times 300$ {\rm K} the mean free path is of the order 100 {\rm nm}Comment: 5 pages, 4 figure

Influence of the columnar structure of heteroepitaxial nitride layers on the transport of electrons

The influence of the columnar structure of heteroepitaxial nitride layers on electronic transport has been described within the model of thermionic emission of carriers through potential barriers formed at grain boundaries. Dependence of the potential barrier height on the material properties and applied external voltage has been calculated. Potential barriers heights for gallium nitride layers grown by the metalorganic vapour phase epitaxy method has been estimated to be in the range of 20-60 meV and 10-40 meV in the dark and under illumination, respectively

Increase in bacteraemia cases in the East Midlands region of the UK due to MDREscherichia coliST73: high levels of genomic and plasmid diversity in causative isolates

Objectives: To determine the population structure of E. coli ST73 isolated from human bacteraemia and urinary tract infections. Methods: The genomes of 22 E.coli ST73 isolates were sequenced using the Illumina HiSeq platform. High resolution SNP typing was used to create a phylogenetic tree. Comparative genomics were also performed using a pangenome approach. In silico and S1-PFGE plasmid profiling was conducted, and isolates were checked for their ability to survive exposure to human serum. Results: E.coli ST73 isolates circulating in clinically unrelated episodes show a high degree of diversity at a whole genome level, though exhibit conservation in gene content, particularly in virulence associated gene carriage. The isolates also contain a highly diverse plasmid pool that confers multi-drug resistance via carriage of CTX-M genes. All strains are highly serum resistant and uniformly carry genes shown to be essential for serum resistance. Conclusions: Our data shows that a rise in incidence of multi-drug resistant E.coli ST73 clinical isolates is not due to a circulating outbreak strain as in E.coli ST131. Rather the ST73 circulating strains are distantly related and carry a diverse set of resistance plasmids. This suggests that the evolutionary events behind emergence of drug resistant E.coli differ between lineages

Local adsorption structure and bonding of porphine on Cu(111) before and after self-metalation

We have experimentally determined the lateral registry and geometric structure of free-base porphine (2H-P) and copper-metalated porphine (Cu-P) adsorbed on Cu(111), by means of energy-scanned photoelectron diffraction (PhD), and compared the experimental results to density functional theory (DFT) calculations that included van der Waals corrections within the Tkatchenko-Scheffler approach. Both 2H-P and Cu-P adsorb with their center above a surface bridge site. Consistency is obtained between the experimental and DFT-predicted structural models, with a characteristic change in the corrugation of the four N atoms of the molecule's macrocycle following metalation. Interestingly, comparison with previously published data for cobalt porphine adsorbed on the same surface evidences a distinct increase in the average height of the N atoms above the surface through the series 2H-P, Cu-P, cobalt porphine. Such an increase strikingly anti-correlates the DFT-predicted adsorption strength, with 2H-P having the smallest adsorption height despite the weakest calculated adsorption energy. In addition, our findings suggest that for these macrocyclic compounds, substrate-to-molecule charge transfer and adsorption strength may not be univocally correlated

Quantum effects in electrical conductivity and photoconductivity of single SbSI nanowire

For the first time current quantization is reported for antimony sulfoiodide (SbSI) nanowires. It has been registered in current responses on electric eld switching as well as on illumination on and o . Current steps determined in all experiments have been equal to each other within the experimental error. It has been explained by the quantized change of free carrier concentration in nanowire. Lateral dimensions of SbSI nanowires estimated from quantum steps are comparable with geometrical data reported for the same technology of material preparation

Correction: Studholme et al., Draft Genome Sequences of Xanthomonas sacchari and Two Banana-Associated Xanthomonads Reveal Insights into the Xanthomonas Group 1 clade. Genes 2011, 2, 1050-1065

Published ErratumThis is the final version of the article. Available from MDPI via the DOI in this record.NOTE: the original article is in ORE at http://hdl.handle.net/10036/3880Following publication of our article [1], we found errors in analyses performed by the corresponding author (DJS) related to the phylogenetic relationship between Xylella species and the other xanthomonads. These errors do not make any difference to the main findings and conclusions reported in our paper. For example, the phylogenetic positions of NCPPB1131, NCPPB1132 and NCPPB4393 within the Group 1 Xanthomonas species are unaffected. However, we wish to apologize to the authors of a previous work [2] for creating any negative impression on the quality of their phylogenetic analyses and to take this opportunity to rectify the errors. [...]

Draft Genome Sequence of Beneficial Rice Rhizosphere Isolate Pseudomonas aeruginosa PUPa3.

Published onlinePseudomonas aeruginosa PUPa3 is a rhizosphere-colonizing and plant growth-promoting strain isolated from the rhizosphere of rice. This strain has, however, been shown to be pathogenic in two nonmammalian infection models. Here we report the draft genome sequence of P. aeruginosa PUPa3.G.U. and M.K. were funded by the Ministry of Education, Science and Technological Development, Republic of Serbia (grant no. 173019). G.U. is also the beneficiary of FEMS Research Fellowship 2014-1. The laboratory of V.V. was financed by ICGEB core funding

Genome Sequencing of Xanthomonas vasicola Pathovar vasculorum Reveals Variation in Plasmids and Genes Encoding Lipopolysaccharide Synthesis, Type-IV Pilus and Type-III Secretion Effectors

This is the final version. Available on open access from MDPI via the DOI in this recordXanthomonas vasicola pathovar vasculorum (Xvv) is the bacterial agent causing gumming disease in sugarcane. Here, we compare complete genome sequences for five isolates of Xvv originating from sugarcane and one from maize. This identified two distinct types of lipopolysaccharide synthesis gene clusters among Xvv isolates: one is similar to that of Xanthomonas axonopodis pathovar citri (Xac) and is probably the ancestral type, while the other is similar to those of the sugarcane-inhabiting species, Xanthomonas sacchari. Four of six Xvv isolates harboured sequences similar to the Xac plasmid, pXAC47, and showed a distinct Type-IV pilus (T4P) sequence type, whereas the T4P locus of the other two isolates resembled that of the closely related banana pathogen, Xanthomonas campestris pathovar musacearum (Xcm). The Xvv isolate from maize has lost a gene encoding a homologue of the virulence effector, xopAF, which was present in all five of the sugarcane isolates, while xopL contained a premature stop codon in four out of six isolates. These findings shed new light on evolutionary events since the divergence of Xvv and Xcm, as well as further elucidating the relationships between the two closely related pathogens.This study was supported in part by the National Agriculture Research Organisation, Uganda, under the MSI/World Bank grant 2009