CrI3-WTe2: A Novel Two-Dimensional Heterostructure as Multisensor for BrF3 and COCL2 Toxic Gases.

A new multisensor (i.e. resistive and magnetic) CrI3-WTe2 heterostructure (HS) to detect the toxic gases BrF3 and COCl2 (Phosgene) has been theoretically studied in our present investigation. The HS has demonstrated sensitivity towards both the gases by varying its electronic and magnetic properties when gas molecule interacts with the HS. Fast recovery time (<0.14 fs) under UV radiation has been observed. We have considered two configurations of BrF3 adsorbed HS; (1) when F ion interacts with HS (C1) and (2) when Br ion interacts with HS (C2). In C1 case the adsorption energy Ead is observed to be -0.66 eV while in C2 it is -0.95 eV. On the other hand in case of COCl2 Ead is found to be -0.42 eV. Magnetic moments of atoms are also found to vary upon gas adsorption indicates the suitability of the HS as a magnetic gas sensor. Our observations suggest the suitability of CrI3-WTe2 HS to respond detection of the toxic gases like BrF3 and COCl2.

An ab initio study of sensing applications of MoB2 monolayer: a potential gas sensor.

Using first principles density functional theory, we have studied the interaction mechanism of NO2 and SO2 gas molecules on an MoB2 monolayer, for gas sensing applications. The selectivity for a particular gas by the sensor has been analyzed through electronic structure calculations and adsorption studies. The calculations have been performed by considering the fact that the MoB2 monolayer as a sensing material encounters a change in its electrical properties, when gas molecules with different orientations get adsorbed on the surface. From the density of states study, we find better selectivity for NO2 as compared to SO2, as the latter leaves the electronic structure of the sensing material unaffected. Further, the adsorption curves support the above fact as the larger value of adsorption energy (Ead ∼ -1 eV) for NO2 indicates stronger adsorption. The chemisorptive nature for NO2, in contrast with the relatively weaker physisorption for SO2, additionally supports the fact that NO2 gas has a better perspective for MoB2 sensor application. Charge density plots for each case are in good agreement with the above conclusions. The faster recovery time attributes the MoB2 monolayer better as a sensor material for NO2 interaction.

MoB2 Driven Metallic Behavior and Interfacial Charge Transport Mechanism in MoS2/MoB2 Heterostructure: A First-Principles Study.

We have performed the density functional theory calculations on heterostructure (HS) of MoS2 and MoB2 monolayers. The aim of this study is to assess the influence of MoB2 on electron transport of adjacent MoS2 layer. In present investigation we predict that the electronic properties of MoS2 monolayer is influenced by 4d-states of Mo in MoB2 monolayer. Whereas, the B atoms of MoB2 and S atoms of MoS2 exhibit overlapping of intermediate atomic orbitals thereby collectively construct the interfacial electronic structure observed to be metallic in nature. From charge density calculations, we have also determine that the charge transfer is taking place at the interface via B-2p and S-3p states. The bonds at the interface are found to be metallic which is also confirmed by adsorption analysis. Thermoelectric performance of this HS is found be in good agreement with available literature. Low Seebeck coefficient and high electrical conductivity further confirms the existence of metallic state of the HS.

Interfacial Coupling Effect on Electron Transport in MoS2/SrTiO3 Heterostructure: An Ab-initio Study.

A variety of theoretical and experimental works have reported several potential applications of MoS2 monolayer based heterostructures (HSs) such as light emitting diodes, photodetectors and field effect transistors etc. In the present work, we have theoretically performed as a model case study, MoS2 monolayer deposited over insulating SrTiO3 (001) to study the band alignment at TiO2 termination. The interfacial characteristics are found to be highly dependent on the interface termination. With an insulating oxide material, a significant band gap (0.85eV) is found in MoS2/TiO2 interface heterostructure (HS). A unique electronic band profile with an indirect band gap (0.67eV) is observed in MoS2 monolayer when confined in a cubic environment of SrTiO3 (STO). Adsorption analysis showed the chemisorption of MoS2 on the surface of STO substrate with TiO2 termination which is justified by the charge density calculations that shows the existence of covalent bonding at the interface. The fabrication of HS of such materials paves the path for developing the unprecedented 2D materials with exciting properties such as semiconducting devices, thermoelectric and optoelectronic applications.

How Harmful Can Herbal Remedies Be? A Case of Severe Acute Tubulointerstitial Nephritis.

Acute interstitial nephritis (AIN) is a condition in which acute kidney injury (AKI) is characterized by the histological finding of interstitial inflammation. Hyponidd is an ayurvedic drug containing Momordica charantia, Gymnema sylvestre, Swertia chirata, etc., used for the treatment of Type 2 diabetes mellitus (DM) and polycystic ovarian disease as an insulin sensitizer. There are no case reports of AIN caused by this drug yet. We report a biopsy-proven case of AKI due to severe AIN associated with the use of hyponidd tablet in a 60-year-old male with DM and hypertension. As these types of various indigenous compounds are used as home remedies in our country, awareness about the possible adverse effects of these agents among physicians is very important in the early diagnosis and management.

Lateral displacement induced disorder in L1(0)-FePt nanostructures by ion-implantation.

Ion implantation is a promising technique for fabricating high density bit patterned media (BPM) as it may eliminate the requirement of disk planarization. However, there has not been any notable study on the impact of implantation on BPM fabrication of FePt, particularly at nano-scale, where the lateral straggle of implanted ions may become comparable to the feature size. In this work, implantation of antimony ions in patterned and unpatterned L1(0)-FePt thin films has been investigated. Unpatterned films implanted with high fluence of antimony exhibited reduced out-of-plane coercivity and change of magnetic anisotropy from perpendicular direction to film-plane. Interestingly, for samples implanted through patterned masks, the perpendicular anisotropy in the unimplanted region was also lost. This noteworthy observation can be attributed to the displacement of Fe and Pt atoms from the implantation sites to the unimplanted areas, thereby causing a phase disorder transformation from L1(0) to A1 FePt.

Tellurium nano-structure based NO gas sensor.

Tellurium nanotubes were grown on bare and silver/gold nanoparticle (nucleation centers) deposited silicon substrates by vacuum deposition technique at a substrate temperature of 100 degrees C under high vacuum conditions. Silver and gold nanoparticles prepared on (111) oriented silicon substrates were found to act as nucleation centers for growth of Tellurium nanostructures. Density of nanotubes was found to increase while their diameter reduced when grown using metallic nanoparticle template. These Te nanostructures were investigated for their gas sensitivity. Tellurium nanotubes on Ag templates showed better response to NO in comparison to H2S and NH3 gases. Selectivity in response to NO was improved in comparison to Te thin film sensors reported earlier. The gas sensing mechanism was investigated using Raman and X-ray photoelectron spectroscopy techniques. The interaction of NO is seen to yield increased adsorption of oxygen that in turn increases hole density and conductivity in the material.

Chlorine gas sensors using one-dimensional tellurium nanostructures.

Tellurium nanotubes have been grown by physical vapor deposition under inert environment at atmospheric pressure as well as under vacuum conditions. Different techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and optical absorption have been utilized for characterization of grown structures. Films prepared using both types of tellurium nanotubes were characterized for sensitivity to oxidizing and reducing gases and it was found that the relative response to gases depends on the microstructure. Nanotubes prepared at atmospheric pressure (of argon) showed high sensitivity and better selectivity to chlorine gas. Impedance spectroscopy studies showed that the response to chlorine is mainly contributed by grain boundaries and is therefore enhanced for nanotubes prepared under argon atmosphere.

The role of lattice distortions in determining the thermal properties of electron doped CaMnO(3).

We have investigated the thermal properties of electron doped perovskite manganite CaMnO(3), the end member ([Formula: see text]) of the Ruddlesden-Popper (RP) calcium manganates series with cation doping at the A-site. In this paper the functional relation between the lattice distortions and the thermal properties is determined and compared to available reports. The temperature dependence of the lattice specific heat (C(v(lattice))) of Ca(1-x)Ln(x)MnO(3) (x = 0.05, 0.10, 0.15, 0.20) with Ln(= La, Ce, Pr, Nd, Th, Bi) doping at the A-site has been studied as a function of temperature (10 K≤T≤500 K) by means of a rigid ion model (RIM) after modifying its framework to incorporate the van der Waals interactions. Strong electron-phonon interactions are present in these compounds, which are responsible for the variation of the lattice specific heat with cation doping of varying size and valency. We have found that the calculated thermal properties reproduce well the corresponding experimental data, implying that modified RIM represents properly the nature of these perovskite manganite systems. We demonstrate that the electron concentration, size mismatch and Jahn-Teller (JT) effects are the dominant factors, whereas charge mismatch and buckling of Mn-O-Mn angle influence the thermal properties to a lesser degree in the ferromagnetic state. In the insulating paramagnetic state, JT distortions vary linearly and influence the thermal properties. These specific heat results can be further improved by including the ferromagnetic spin wave and charge order contributions to the specific heat.

Lattice dynamics of orthorhombic perovskite yttrium manganite, YMnO(3).

The lattice dynamics of yttrium manganite (YMnO(3)) has been investigated by means of a shell model with pair-wise interionic interaction potential. The experimental data of crystal structure and Raman and infrared frequencies compare well with the lattice dynamical calculations. The phonon dispersion curves found along three high symmetry directions and the density of states of YMnO(3) have also been calculated from this model. The computed phonon density of states is used to derive the macroscopic thermodynamic quantities like the Debye temperature and specific heat. The crystal structure data computed from this model are in good agreement with the available experimental data measured by neutron powder diffraction. We have made a comparative study of the structures derived from the potential model calculations for both LaMnO(3) and YMnO(3). Symmetry vectors obtained through group theoretical analysis at the zone centre point were employed to classify the phonon frequencies obtained into their irreducible representations. The computed Raman and infrared frequencies have shown good agreement with the measured data.

The biochemical womb of schizophrenia: A review.

The conclusive identification of specific etiological factors or pathogenic processes in the illness of schizophrenia has remained elusive despite great technological progress. The convergence of state-of-art scientific studies in molecular genetics, molecular neuropathophysiology, in vivo brain imaging and psychopharmacology, however, indicates that we may be coming much closer to understanding the genesis of schizophrenia. In near future, the diagnosis and assessment of schizophrenia using biochemical markers may become a "dream come true" for the medical community as well as for the general population. An understanding of the biochemistry/ visa vis pathophysiology of schizophrenia is essential to the discovery of preventive measures and therapeutic intervention.

Efflux pumps in drug resistance of Candida.

The incidences of human pathogenic yeast Candida albicans and its related species acquiring resistance to antifungals have increased considerably, which poses serious problems towards its successful chemotherapy. The resistance of these pathogenic fungi is not restricted to the commonly used triazole compounds but is even encountered, though not often, with polyene derivatives as well. The efflux pump proteins belonging to ABC (ATP Binding Cassette) and MFS (Major Facilitators) super family are the most prominent contributors of multidrug resistance (MDR) in yeasts. The abundance of the drug transporters and their wider specificity suggest that these transporters may not be exclusively drug exporters in yeasts and may have other cellular functions. In this article we focus on some of the recent advances on the structure and function, evolution and transcriptional control of drug efflux proteins of Candida. A short discussion on the physiological relevance of drug transporters is also included.

Overexpression of the Candida albicans ALA1 gene in Saccharomyces cerevisiae results in aggregation following attachment of yeast cells to extracellular matrix proteins, adherence properties similar to those of Candida albicans.

Candida albicans maintains a commensal relationship with human hosts, probably by adhering to mucosal tissue in a variety of physiological conditions. We show that adherence due to the C. albicans gene ALA1 when transformed into Saccharomyces cerevisiae, is comprised of two sequential steps. Initially, C. albicans rapidly attaches to extracellular matrix (ECM) protein-coated magnetic beads in small numbers (the attachment phase). This is followed by a relatively slower step in which cell-to-cell interactions predominate (the aggregation phase). Neither of these phases is observed in S. cerevisiae. However, expression of the C. albicans ALA1 gene from a low-copy vector causes S. cerevisiae transformants to attach to ECM-coated magnetic beads without appreciable aggregation. Expression of ALA1 from a high-copy vector results in both attachment and aggregation. Moreover, transcriptional fusion of ALA1 with the galactose-inducible promoters GALS, GALL, and GAL1, allowing for low, moderate, and high levels of inducible transcription, respectively, causes attachment and aggregation that correlates with the strength of the GAL promoter. The adherence of C. albicans and S. cerevisiae overexpressing ALA1 to a number of protein ligands occurs over a broad pH range, is resistant to shear forces generated by vortexing, and is unaffected by the presence of sugars, high salt levels, free ligands, or detergents. Adherence is, however, inhibited by agents that disrupt hydrogen bonds. The similarities in the adherence and aggregation properties of C. albicans and S. cerevisiae overexpressing ALA1 suggest a role in adherence and aggregation for ALA1 and ALA1-like genes in C. albicans.

A zinc finger homeodomain transcription factor binds specific thyroid hormone response elements.

Thyroid hormone receptors can act through response elements (TREs) having a wide variation of sequence. We screened for transcription factors that bind the rat (r) glycoprotein hormone alpha-subunit TRE (alpha-sub), and isolated a cDNA, termed zinc finger homeodomain enhancer-binding protein (Zfhep), which encodes two separate zinc finger domains (ZD1 and ZD2), and a region similar to homeodomains. DNA-binding assays show that ZD1 or ZD2 can bind the alpha-subunit, rat growth hormone, or thyrotropin beta (TSHbeta) gene TREs, but do not bind DR4 or palindromic (pal) TREs. Methylation interference footprinting demonstrates that Zfhep binds the alpha-sub overlapping the TR-binding site. Similarly, the ZD1 protein footprints over TR-binding halfsites of the rat growth hormone (rGH) and TSHbeta TREs. Hence, Zfhep binding is dependent on sequences within and outside the AGGTCA TR-binding halfsite. Interactions of non-receptor transcription factors (such as Zfhep) with certain TREs are important to modify gene-specific regulation by thyroid hormones.

Expression, cloning, and characterization of a Candida albicans gene, ALA1, that confers adherence properties upon Saccharomyces cerevisiae for extracellular matrix proteins.

Adherence of Candida albicans to host tissues is a necessary step for maintenance of its commensal status and is likely a necessary step in the pathogenesis of candidiasis. The extracellular matrix (ECM) proteins are some of the host tissue and plasma proteins to which C. albicans adheres through adhesins located on the fungal cell surface. To isolate genes encoding ECM adhesins, an assay was developed based on the ability of yeast cells to adhere to magnetic beads coated with the ECM protein fibronectin, type IV collagen, or laminin. A C. albicans genomic library was constructed by cloning XbaI-partially-digested and size-selected fragments into pAUR112, an Escherichia coli-yeast low-copy-number shuttle vector. The C. albicans library was transformed into Saccharomyces cerevisiae YPH 499, and clones capable of adherence were selected by using ECM protein-coated magnetic beads. A plasmid containing an approximately 8-kb insert was isolated from 29 adherent clones. These clones exhibited adherence to all ECM protein-coated magnetic beads and to human buccal epithelial cells. The ALA1 gene (for agglutinin-like adhesin) was localized by subcloning it into a 5-kb XbaI fragment which retained the adherence phenotype in both orientations. The complete DNA sequence of the 5-kb insert was determined, and an open reading frame (ORF) encoding 1,419 amino acid residues was identified. Deletions from the 5' and 3' ends extending into the DNA sequence encoding the 1,419-amino-acid ORF product inactivated the adherence phenotype, suggesting that it is the coding region of the ALA1 gene. A database search identified ALA1 to be similar to the C. albicans ALS1 (for agglutinin-like sequence 1) protein and the S. cerevisiae agglutinin protein (AG alpha1), although the homology at the primary amino acid sequence level is limited to the first half of each of these proteins. ALA1 contains a central domain of six tandem repeats of 36 amino acids. We discuss the significance of various predicted ALA1 structural motifs and their relationships to function in the adherence process.

Hemopexin in the human retina: protection of the retina against heme-mediated toxicity.

The existence of the blood-retinal barrier means that proteins that protect the retina from damage by reactive oxygen species must either be made locally or specifically transported across the barrier cells; however, such transepithelial transport does not seem to occur. Among the circulatory proteins that protect against iron-catalyzed production of free radicals are apo-transferrin, which binds ferric iron and has previously been shown to be made by cells of the neural retina (Davis and Hunt, 1993, J. Cell Physiol., 156:280-285), and the extracellular antioxidant, apo-hemopexin, which binds free heme (iron-protoporphyrin IX). Since hemorrhage and heme release can be important contributing factors in retinal disease, evidence of a hemopexin-based retinal protection system was sought. The human retina has been shown to contain apo-hemopexin which is probably synthesized locally since its mRNA can be detected in retinal tissue dissected from human donor eyes. It is likely that the retina contains a mechanism for the degradation of hemopexin-bound heme since the blood-retinal barrier also precludes the exit of heme-hemopexin from the retina. Retinal pigment epithelial cells have been found to bind and internalize heme-hemopexin in a temperature-dependent, saturable, and specific manner, analogous to the receptor-mediated endocytic system of hepatoma cells. Moreover, the binding of heme-hemopexin to the cells stimulates the expression of heme oxygenase-1, metallothionein-1, and ferritin.

Sin, a stage-specific repressor of cellular differentiation.

Sin is a Bacillus subtilis DNA-binding protein which is essential for competence, motility, and autolysin production but also, if expressed on a multicopy plasmid, is inhibitory to sporulation and alkaline protease synthesis. We have now examined the physiological role of Sin in sporulation and found that this protein specifically represses three stage II sporulation genes (spoIIA, spoIIE, and spoIIG) but not the earlier-acting stage 0 sporulation genes. sin loss-of-function mutations cause higher expression of stage II genes and result in a higher frequency of sporulation, in general. Sin binds to the upstream promoter region of spoIIA in vitro and may thus gate entry into sporulation by directly repressing the transcription of stage II genes. In vivo levels of Sin increase rather than decrease at the time of stage II gene induction, suggesting that posttranslational modification may play a role in downregulation of negative Sin function.

The role of negative control in sporulation.

Negative controls play an important role in the regulation of differentiation in many organisms. Sporulation in Bacillus subtilis is also regulated by DNA-binding proteins which exert a repressive effect on genes which are essential for this process. AbrB represses spo0H, coding for sigma H. One of the earliest events in the initiation of sporulation is the lifting of this repression so that more sigma H can be made. As part of an RNA polymerase holoenzyme, this positive transcription factor is responsible for the elevated synthesis of sufficient phosphorylated Spo0A to activate the expression of several stage II genes. Sin, another DNA-binding protein, represses the same genes, spoIIA, spoIIE and spoIIG, that are activated by Spo0A. Thus sporulation is controlled at the two earliest stages by at least two repressors. Sin and AbrB are repressors of other late growth functions but are essential for competence development. Sin is also a positive regulator for motility and autolysin production. These results suggest that AbrB and Sin act as developmental switches, enabling cells at the beginning of stationary growth to choose different developmental fates.

The Bacillus subtilis sin gene, a regulator of alternate developmental processes, codes for a DNA-binding protein.

The sin gene of Bacillus subtilis encodes a dual-function regulatory protein, Sin, which is a negative as well as a positive regulator of alternate developmental processes that are induced at the end of vegetative growth in response to nutrient depletion. Sin has been purified to homogeneity by using a simple two-step procedure. It was found to bind to the developmentally regulated aprE (alkaline protease) gene at two sites in vitro. The stronger Sin-binding site (SBS-1) is located more than 200 bp upstream from the transcription start site. It is required for Sin repression of aprE expression in vivo, as strains bearing SBS-1 deletions were not affected by the sin gene. The second, weaker Sin-binding site lies on a DNA fragment that contains the aprE promoter. Results of DNase I, exonuclease III, and dimethyl sulfate footprinting analysis of SBS-1 suggested that Sin binding involves two adjacent binding sites which appear to contain two different partial dyad symmetries. An analysis of the predicted amino acid sequence of Sin revealed a potential leucine zipper protein dimerization motif which is flanked by two helix-turn-helix motifs that could be involved in recognizing two different dyad symmetries.