Nanodot to Nanowire: A strain-driven shape transition in self-organized endotaxial CoSi2 on Si (100)

We report a phenomenon of strain-driven shape transition in the growth of nanoscale self-organized endotaxial CoSi2 islands on Si (100) substrates. Small square shaped islands as small as 15\times15 nm2 have been observed. Islands grow in the square shape following the four fold symmetry of the Si (100) substrate, up to a critical size of 67 \times 67 nm2. A shape transition takes place at this critical size. Larger islands adopt a rectangular shape with ever increasing length and the width decreasing to an asymptotic value of ~25 nm. This produces long wires of nearly constant width.We have observed nanowire islands with aspect ratios as large as ~ 20:1. The long nanowire heterostructures grow partly above (~ 3 nm) the surface, but mostly into (~17 nm) the Si substrate. These self-organized nanostructures behave as nanoscale Schottky diodes. They may be useful in Si-nanofabrication and find potential application in constructing nano devices.Comment: 9 pages, 7 figure

Low pH enhances the action of maximin H5 against Staphylococcus aureus and helps mediate lysylated phosphatidylglycerol induced resistance

Maximin H5 (MH5) is an amphibian antimicrobial peptide specifically targeting Staphylococcus aureus. At pH 6, the peptide showed an increased ability to penetrate (∆П = 6.2 mN m-1) and lyse (lysis = 48 %) S. aureus membrane mimics, which incorporated physiological levels of lysylated phosphatidylglycerol (Lys-PG, 60 %) as compared to pH 7 (∆П = 5.6 mN m-1 and lysis = 40 % at pH 7) where levels of Lys-PG are lower (40 %). The peptide therefore appears to have optimal function at pH levels known to be optimal for the organism’s growth. MH5 killed S. aureus (minimum inhibitory concentration = 90 µM) via membranolytic mechanisms that involved the stabilization of α-helical structure (circa 45-50 %) and which showed similarities to the ‘Carpet’ mechanism based on its ability to increase the rigidity (Cs-1 = 109.94 mN m-1) and thermodynamic stability (∆Gmix = -3.0) of physiologically relevant S. aureus membrane mimics at pH 6. Based on theoretical analysis this mechanism may involve the use of a tilted peptide structure and efficacy was noted to vary inversely with the Lys-PG content of S. aureus membrane mimics for each pH studied (R2 circa 0.97), which led to the suggestion that under biologically relevant conditions, low pH helps mediate Lys-PG induced resistance in S. aureus to MH5 antibacterial action. The peptide showed a lack of haemolytic activity (< 2 % haemolysis) and merits further investigation as a potential template for development as an anti-staphylococcal agent in medically and biotechnically relevant areas

Using Local Public Goods to Attract and Retain the Creative Class: A Tale of Two Cities

We study the impact that the provision of a local public good (LPG) by two cities has on their ability to attract and retain members of the creative class. This creative class consists of two types of members known as engineers and artists. Engineers are wealthier than artists and they also value the LPG more. We first focus on each city in isolation. We compute the marginal value and the marginal cost of the LPG and then determine the provision of this LPG when the provision is determined by uniform contributions and majority voting. Next, we allow the creative class members to migrate between the two cities and analyze whether engineers or artists migrate, the equilibrium distribution of the creative class, and the efficiency of the LPG provision. Finally, we consider the situation in each city just before migration and study how much of the LPG is provided when proportional contributions and majority voting determine this provision. A related question we address is whether engineers or artists now have an incentive to migrate and, if yes, we identify who would like to migrate and to which city

MOLECULAR CHARA CTERIZATION OF METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) ISOLATED FROM BOVINE MASTITIS IN AND AROUND KOLKATA, INDIA

The present investigation was carried out on 118 milk samples collected from suspected clinical and subclinical mastitis affected indigenous and cross-bred cattle in and around Kolkata and North 24 Parganas districts. A total of 38 samples were positive for Staphylococcus aureus. This indicates that considerable proportion of cattle with intramammary infection was colonized with S. aureus. However, sizeable populations of those pathogens (15 of 38) were methicillin resistant (MRSA) by phenotypic detection method. Methicillin resistance gene (mecA) was detected from 6 samples out of those 15 samples. Overuse or inadvertent use of antibiotics may be the cause of development of such resistant strains in livestock. This may have huge public health significance as these resistant strains may enter the food chain and infect the consumer with consequences of life-threatening infections

BOVINE PLASMA FIBRINOGEN AS MARKER IN CLINICAL AND SUB-CLINICAL MASTITIS

Plasma samples were collected from healthy as well as clinical and sub-clinical mastitis affected cows from Barasat, West Bengal, India. Plasma samples, after ammonium sulphate precipitation, were dialyzed against several changes of PBS (pH 7.2) to remove the excess ammonium sulphate. Then plasma fibrinogens were purified by gel filtration chromatography on Sephacryl S-200 HR. SDS-PAGE (10%) of purified fibrinogen from plasma of healthy cow revealed polypeptide bands of 74, 67 and 57 kDa which represent the α (alpha), β (beta) and γ (gamma)- chains respectively. On the other hand, purified fibrinogen from plasma of sub-clinical and clinical mastitis affected cow revealed polypeptide bands of 73 (α-chain), 68 kDa (β-chain) and 72 (γ-chain), 68 kDa (β-chain) respectively. The SDS-PAGE analysis showed the absence of gamma (γ)- chain of fibrinogen in both the samples of sub-clinical and clinical mastitis positive cow. Single precipitin line was observed in double immunodiffusion test when purified fibrinogen from healthy, clinical and subclinical mastitis positive cows reacted with hyper immune sera raised in rabbit. No precipitin line was found against the normal control serum. These purified fibrinogens also showed cross reactivity against antibody raised in rabbit when analyzed by western blot technique

Kramers nodal line in the charge density wave state of YTe3_3 and the influence of twin domains

Recent studies have focused on the relationship between charge density wave (CDW) collective electronic ground states and nontrivial topological states. Using angle-resolved photoemission and density functional theory, we establish that YTe$_3$ is a CDW-induced Kramers nodal line (KNL) metal, a newly proposed topological state of matter. YTe$_3$ is a non-magnetic quasi-2D chalcogenide with a CDW wave vector ($q_{\rm cdw}$) of 0.2907c$^*$. Scanning tunneling microscopy and low energy electron diffraction revealed two orthogonal CDW domains, each with a unidirectional CDW and similar YTe$_3$. The effective band structure (EBS) computations, using DFT-calculated folded bands, show excellent agreement with ARPES because a realistic x-ray crystal structure and twin domains are considered in the calculations. The Fermi surface and ARPES intensity plots show weak shadow bands displaced by $q_{\rm cdw}$ from the main bands. These are linked to CDW modulation, as the EBS calculation confirms. Bilayer split main and shadow bands suggest the existence of crossings, according to theory and experiment. DFT bands, including spin-orbit coupling, indicate a nodal line along the $\Sigma$ line from multiple band crossings perpendicular to the KNL. Additionally, doubly degenerate bands are only found along the KNL at all energies, with some bands dispersing through the Fermi level

Detection and characterization of pathogenic Pseudomonas aeruginosa from bovine subclinical mastitis in West Bengal, India

Aim: Subclinical mastitis in bovines is mainly responsible for the huge economic loss of the dairy farmers, of which Pseudomonas aeruginosa is one of the causative agents. The study was aimed at a screening of suspected milk samples from different cattle farms of West Bengal for detection and confirmation of P. aeruginosa strains followed by their characterization. Materials and Methods: Around 422 milk samples were screened from different dairy farms primarily by on-spot bromothymol blue (BTB) test and then in the lab by somatic cell counts (SCC) to finally consider 352 samples for detection of P. aeruginosa. Selective isolation and confirmation of the isolates were done using selective media, viz., cetrimide and Pseudomonas agar followed by confirmation by fluorescent technique. Molecular characterization of the strains was done by polymerase chain reaction for the presence of toxA (enterotoxin A, 352 bp) and exoS (exoenzyme S, 504 bp) genes. Results: Approximately, 371 (87.9%) samples were positive in on-spot BTB test among which 352 (94.8%) samples revealed high SCC values (more than 3 lakh cells/ml) showing infection when screened. Among these, 23 (6.5%) samples yielded typical Pseudomonas sp. isolates out of which only 19 (5.4%) isolates were confirmed to be P. aeruginosa which showed characteristic blue-green fluorescence due to the presence of pigment pyoverdin under ultraviolet light. Out of these 19 isolates, 11 isolates were positive for toxA, 6 isolates for exoS, and 2 for both these pathogenic genes. Conclusion: Approximately, 5.4% cases of bovine subclinical mastitis infections in South Bengal were associated with P. aeruginosa which possess pathogenic genes such as toxA (63.2%) and exoS (36.8%)