Mobility driven thermoelectric and optical properties of two-dimensional halide-based hybrid perovskites: impact of organic cation rotation.

The pivotal impact of organic cation rotation may result in structural complexity in two-dimensional (2D) halide-based hybrid perovskites. The crucial role of the orientation of the organic cation (MA = CH3NH3+) in the 2D Ruddlesden-Popper phase (2DRP) is explored using density functional theory (DFT) calculations. Our results propose that the MA cation rotation imposes the structural distortion in the PbI6 network, which is further responsible for the changes in nature and value of the electronic bandgap, charge density and optical absorption. The spin-orbit coupling effect results in a wide range of Rashba splitting parameters being obtained from 0.04 to 0.278 eV Å. The simulated optical absorption spectra suggest that absorption edge for the alignment of the MA molecule along the X-axis (having unidirectional hydrogen bonds) is higher than that of the alignment of the MA cation in the z-direction. Furthermore, the unidirectional hydrogen bonds between the MA cation and Pb-I framework significantly help to achieve the highest mobility of charge carriers up to ∼1437 cm2 V-1 s-1. Such high mobility leads to supremacy in the thermoelectric transport properties, which are investigated for the first time with the rotation of the MA cation. The calculated thermoelectric power factor at room temperature shows exceptionally high values (up to 2.04 mW m-1 K-2), leading to desired applications in thermoelectric devices. The rotation of the MA cation might be utilized as a useful tool for variation in optical absorption and transport coefficients. Therefore, our results spark the idea to develop 2D perovskites for real-time perspective in solar and heat energy utilization.

Selective and sensitive toxic gas-sensing mechanism in a 2D Janus MoSSe monolayer.

With an inspiration of sensing toxic gases, this study is aimed at exploring the potential of a Janus MoSSe monolayer as a gas sensor. Here, we focused on the adsorption mechanism after the exposure to NH3, NO2, NO, HCN, CO2, CO, H2, H2S and SO2 on both the S and Se sites of MoSSe. We investigated the structural geometries and electronic, sensing and electron-transport properties before and after adsorption of the aforementioned gases by applying DFT calculations. The results revealed the higher binding strength of NO2/SO2 and NO on Se and S sites, respectively, among all the gas adsorptions on the MoSSe monolayer. Moreover, DOS revealed strong orbital contributions at EF, which confirmed the n/p-type semiconducting character for the NO/NO2 adsorbed MoSSe monolayer. Further, the specific work function alteration after the adsorption of NO2, SO2 and NO indicated that the MoSSe monolayer could be a potential candidate for Φ-type gas sensor at 300 K. Additionally, the higher electron transmission and prominent electrical response values of 76.4/56 µA and 82 µA suggested a maximum sensitivity of 98%/89% and 93% at a particular voltage for NO2/SO2 and NO on Se and S sites, respectively. Thus, our results promote surface selectivity, i.e. S or Se site, and better sensitivity with recycling potential could enable sensing application of the Janus MoSSe monolayer for toxic gases detection.

Occupational lead exposure is an independent modulator of hypertension and poor pulmonary function: A cross-sectional comparative study in lead-acid battery recycling workers.

Blood lead level (BLL) is the primary biomarker for lead-exposure monitoring in occupationally exposed workers. We evaluated occupational lead-exposure (OE) impact on cardiopulmonary functions in lead-acid battery recycling unit workers. Seventy-six OE cases and 30 control subjects were enrolled for questionnaire-based socio-demographic, dietary, tobacco usage, and medical history data. Anthropometric measurements, systolic and diastolic blood pressure (SBP and DBP), and pulmonary function tests were performed. Venous blood was collected for BLL, hematological analysis, and biochemical analysis. OE caused a significant increase in BLL, SBP, DBP, and small airways obstruction in lung function tests. It also impaired platelet indices, affected renal and liver biochemical measurements, and promoted oxidative stress and DNA damage. Multilinear regression analysis suggested that BLL affected SBP (ß = 0.314, p = .034) and increased small airways obstruction (FEV1/FVC, ß = -0.37, p = .05; FEV25-75%, ß = -0.351, p = .016). Higher BLL appears to be an independent modulator of hypertension and poor pulmonary function upon occupational lead exposure in lead-acid battery recyclers.

A Recombinant Fragment of Human Surfactant Protein D Binds Spike Protein and Inhibits Infectivity and Replication of SARS-CoV-2 in Clinical Samples.

Coronavirus disease (COVID-19) is an acute infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Human SP-D (surfactant protein D) is known to interact with the spike protein of SARS-CoV, but its immune surveillance against SARS-CoV-2 is not known. The current study aimed to examine the potential of a recombinant fragment of human SP-D (rfhSP-D) as an inhibitor of replication and infection of SARS-CoV-2. The interaction of rfhSP-D with the spike protein of SARS-CoV-2 and human ACE-2 (angiotensin-converting enzyme 2) receptor was predicted via docking analysis. The inhibition of interaction between the spike protein and ACE-2 by rfhSP-D was confirmed using direct and indirect ELISA. The effect of rfhSP-D on replication and infectivity of SARS-CoV-2 from clinical samples was assessed by measuring the expression of RdRp gene of the virus using quantitative PCR. In silico interaction studies indicated that three amino acid residues in the receptor-binding domain of spike protein of SARS-CoV-2 were commonly involved in interacting with rfhSP-D and ACE-2. Studies using clinical samples of SARS-CoV-2-positive cases (asymptomatic, n = 7; symptomatic, n = 8) and negative control samples (n = 15) demonstrated that treatment with 1.67 µM rfhSP-D inhibited viral replication by ∼5.5-fold and was more efficient than remdesivir (100 µM) in Vero cells. An approximately two-fold reduction in viral infectivity was also observed after treatment with 1.67 µM rfhSP-D. These results conclusively demonstrate that the rfhSP-D mediated calcium independent interaction between the receptor-binding domain of the S1 subunit of the SARS-CoV-2 spike protein and human ACE-2, its host cell receptor, and significantly reduced SARS-CoV-2 infection and replication in vitro.

Review: An insight into coronaviruses: Challenges, security and scope.

SARS-CoV2 is a novel coronavirus; the seventh of its species to infect humans. The spread of this virus emerged in Wuhan, China in late December, 2019. Since then, this virus has spread to more than 200 countries and has caused a worldwide pandemic. Being a new species of coronaviruses, any cure or vaccines for this virus has not yet been obtained. A large amount of scientific studies and clinical trials are being carried out across the world to find a potential vaccine for this virus. Current work reports a review of potential drugs and vaccines that may be effective against this virus. Different scientific therapies that may potentially be effective against the SARS-CoV2 virus are also reviewed. The mechanisms of various drugs, their efficiency in various clinical trials and their side effects are also studied.

Thermal conductivity of free-standing silicon nanowire using Raman spectroscopy.

Low dimensional systems, nanowires (NWs), in particular, have exhibited excellent optical and electronic properties. Understanding the thermal properties in semiconductor NWs is very important for their applications in electronic devices. In the present study, the thermal conductivity of a freestanding silicon NW is estimated by employing Raman spectroscopy. The advantage of this technique is that the excitation source (laser) acts as both the heater and probe. The variations of the first-order Raman peak position of the freestanding silicon NW with respect to temperature and laser power are recorded. From the analysis of effective laser power absorbed by exposed silicon NW and a detailed Raman study along with the concept of longitudinal heat distribution in silicon NW, the thermal conductivity of the freestanding silicon NW of ∼112 nm diameter is estimated to be ∼53 W m-1 K- 1.

Exploration of the strain and thermoelectric properties of hexagonal SiX (X = N, P, As, Sb, and Bi) monolayers.

Materials with moderate bandgap, high carrier mobilities and high thermoelectric efficiencies show robust performance in microelectronic and thermoelectric applications. We investigated the structural, electronic and thermoelectric properties of Si-based group IV-V monolayers using density functional theory and the semi-classical Boltzmann transport theory. The electronic band structure of SiX monolayers calculated with the PBE functional indicates moderate band gap characteristics. All the studied systems are indirect band gap semiconductors except for SiBi. The electronic band gap of these monolayers increases initially up to a certain limit and then decreases, becoming metallic at higher strain. This suggests the possibility of tuning the electronic band gap by applying strain. Carrier mobility is calculated using the deformation potential theory to get the relaxation time. Remarkable values of carrier mobility indicate p-type semiconducting nature for SiN, SiP and SiBi, while SiAs and SiSb indicate n-type semiconducting nature. The maximum ZT values at 300 K of n-type SiSb and SiAs are 1.01 and 0.98, whereas for p-type SiN, SiP, and SiBi they are 0.99, 0.98, and 0.94, respectively. Higher Seebeck coefficients, higher power factors, and a lower value of electronic thermal conductivity could be achieved in these binary compounds. These findings indicate that the new two-dimensional hexagonal SiX (X = N, P, As, Sb, and Bi) systems are promising candidates for thermoelectric materials at room temperature.

Free-standing Pt and Pd nanowires: strain-modulated stability and magnetic and thermoelectric properties.

We studied the Lagrangian strain-induced colossal magnetism and thermoelectric performance of platinum (Pt) and palladium (Pd) nanowires (NWs) using first-principles density functional calculations. Pt and Pd NWs were found to be dynamically stable for both strain-free and strained situations. Their cohesive energy and magnetic moment showed decrease and increase, respectively, with an increase in tensile Lagrangian strain (2% to 10%) in the (001) plane. Furthermore, we analyzed the thermodynamic properties using the quasi-harmonic approximation (QHA), heat capacity and internal energy of both NWs originating at 0 K, where their internal energy (E) remained high. For the NWs with the (100) and (010) planes, magnetism exist in the strain-free case, whereas it decreases rapidly on increasing the value of strain. Our results predict the excellent stability, colossal magnetism, and thermoelectric properties of the studied NWs; therefore, these NWs can be used as potential thermoelectric materials for device applications.

Achieving ultrahigh carrier mobilities and opening the band gap in two-dimensional Si2BN.

Recently, a two-dimensional (2D) Si2BN monolayer material made of silicon, boron and nitrogen, was theoretically predicated and has attracted interest in the scientific community. Due to its 2D planar nature with high formation energy, Si2BN monolayers can be flexible and strong like graphene and also exhibit captivating properties like those of other 2D materials. Motivated by this fascinating graphene-like monolayer of Si2BN, we have investigated its structural and electronic properties based on first-principles calculations. The electronic band structure of pure Si2BN shows metallic behaviour. We have discovered that the band gap of Si2BN monolayer can be tuned to 102 meV by applying external electric fields and mechanical strain. The band gap opening occurs at 5% strain, where the bond angles between the nearest neighbours become nearly equal. The band gap opening occurs at a small external electric field of 0.4 V Å-1. More interestingly, at room temperature, the electron mobility of Si2BN is 4.73 × 105 cm2 V-1 s-1, which is much larger than that of graphene, while the hole mobility is 1.11 × 105 cm2 V-1 s-1, slightly smaller than the electron mobility. The ultrahigh carrier mobility of Si2BN may lead to many novel applications in high-performance electronic and optoelectronic devices. These theoretical results suggest that the Si2BN monolayer exhibits multiple effects that may significantly enhance the performance of Si2BN based electronic devices.

Highly infrared sensitive VO2 nanowires for a nano-optical device.

Recent studies on the electronic, magnetic and optical properties of VO2 (vanadium dioxide) materials have motivated the exploration of one dimensional VO2 nanowires. First principles calculations were performed to investigate the structural, electronic, magnetic and optical properties of the monoclinic (M) and rutile (R) phases of VO2 nanowires. The monoclinic phase shows semiconducting behaviour with a band gap of 1.17 eV, whereas the rutile phase of VO2 nanowires behaves as a spin gapless semiconducting material, as band lines cross the Fermi level due only to up spin contribution. The monoclinic structure of VO2 nanowires is found to be paramagnetic and the rutile structure shows ferromagnetic half metal behavior. The conductivity calculation for VO2 nanowires shows the metal-insulator transition (MIT) temperature to be 250 K. The possible mechanism of VO2 nanowires to be used as smart windows has been discussed, as the nanowires are highly sensitive in the infrared (IR) region. Interestingly, at low temperature, the VO2 monoclinic structure allows infrared light to be transmitted, while VO2 with the rutile phase blocks light in the IR region. Furthermore, we adsorbed CO2, N2 and SO2 gas molecules on 1D VO2 monoclinic nanowire to investigate their interaction behaviour. It was observed that the absorption and transmission properties of VO2 dramatically change upon the adsorption of CO2 and SO2 gas molecules, which is likely to open up its application as an optical gas sensor.

Glycosylation control technologies for recombinant therapeutic proteins.

Protein glycosylation is a very important quality attribute of any biopharmaceutical product as it affects the efficacy, serum half-life, and antigenicity of a molecule. The present expression hosts commercially utilized for a recombinant glycoprotein production generally cannot produce a desired and uniform glycan composition and generally exhibit non-human glycans that can lead to unwanted side effects. The authors provide a comprehensive review of various approaches which can be implemented to minimize the glycan heterogeneity for the production of the desired protein with improved glycoforms. The authors also describe that the industry standard expression systems such as mammalian, insect, and yeast are glycoengineered to produce human-like glycan composition of a recombinant product. This review summarizes the recent technologies used for the improvement of the glycan composition of the biotherapeutics, focusing largely on the selection of an appropriate expression host, glycoengineering, and upstream process optimization to control protein glycosylation and thus enhanced biological activity with fewer side effects. Here, we also suggest various approaches such as host and clone selection to achieve expected glycosylation in a recombinant protein. The cell culture, biochemical, and physical process parameters play a key role in the manufacturing of the desired glycoform of a therapeutic protein. Hence, these components are to be considered very carefully while developing such glycoproteins. Also, glycoengineering of production host to modulate the protein glycosylation is also recommended in the present review.

Eye donation and eye banking in India.

Corneal blindness is a priority condition under the National Programme for Control of Blindness and an important cause of avoidable blindness in India. A multipronged approach is needed to eliminate corneal blindness. Curable or treatable blindness requires a spectrum of care including medication, optical rehabilitation and corneal transplantation. Corneal transplantation is dependent on the availability of safe, donor eyes; however, there is scarcity of donor corneal tissues in India. To improve the eye banking system, the Government of India supports eye banks through recurring grants for operational costs and non-recurring grants for infrastructure costs. Strategic interventions by the government and non-governmental organizations include awareness by health promotion and education, community participation, sustainable source of donor cornea, quality medical standards, accreditation and endeavours to strengthen eye banking systems and procedures through training and research. A model eye banking system in India can be achieved only when it is linked with the targeted infrastructure proposed under 'Vision 2020: Right to Sight- India'. Considering these targets, there is a requirement of at least 20 eye bank training centres, 200 eye banks with corneal transplant facility (collection of nearly 500 corneas per year) and 2000 eye donation centres in the country. This would become a reality if the Hospital Cornea Retrieval Programme is strengthened at all private and government hospitals, uniform medical standards are made mandatory for all eye banks and eye donation centres and the process of registration and eye donation is simplified to enhance community participation.

Gene editing for cell engineering: trends and applications.

Gene editing with all its own advantages in molecular biology applications has made easy manipulation of various production hosts with the discovery and implementation of modern gene editing tools such as Crispr (Clustered regularly interspaced short palindromic repeats), TALENs (Transcription activator-like effector nucleases) and ZFNs (Zinc finger nucleases). With the advent of these modern tools, it is now possible to manipulate the genome of industrial production hosts such as yeast and mammalian cells which allows developing a potential and cost effective recombinant therapeutic protein. These tools also allow single editing to multiple genes for knocking-in or knocking-out of a host genome quickly in an efficient manner. A recent study on "multiplexed" gene editing revolutionized the knock-out and knock-in events of yeast and CHO, mammalian cells genome for metabolic engineering as well as high, stable, and consistent expression of a transgene encoding complex therapeutic protein such as monoclonal antibody. The gene of interest can either be integrated or deleted at single or multiple loci depending on the strategy and production requirement. This review will give a gist of all the modern tools with a brief description and advances in genetic manipulation using three major tools being implemented for the modification of such hosts with the emphasis on the use of Crispr-Cas9 for the "multiplexing gene-editing approach" for genetic manipulation of yeast and CHO mammalian hosts that ultimately leads to a fast track product development with consistent, improved product yield, quality, and thus affordability for a population at large.

Modulating the electronic and optical properties of monolayer arsenene phases by organic molecular doping.

Recently, arsenene monolayer structure of the arsenic with two phases has displayed semiconducting behavior. We have systematically investigated the electronic and optical properties of single-layer arsenene with two types of functionalized organic molecules; an electrophilic molecule [tetracyanoquinodimethane (TCNQ)] and a nucleophilic molecule [tetrathiafulvalene (TTF)], as an electron acceptor and electron donor, respectively. The interfacial charge transfer between the arsenene monolayer and TCNQ/TTF molecules extensively reduces the band gap of arsenene and accordingly resulted in a p- or n-type semiconducting behavior, respectively. We have also performed the interfacial charge transfer from organic molecules to monolayer arsenene and vice versa. The interfacial surface molecular modification has established an efficient way to develop the light harvesting of arsenene in different polarization directions. Our theoretical investigation suggests that such n- and p-type arsenene semiconductors would broaden the applications in the field of nanoelectronic and optoelectronic devices such as photodiodes and it is also useful for constructing functional electronic systems.

Spin-dependent electron transport in C and Ge doped BN monolayers.

Recent advances in the synthesis and characterization of h-BN monolayers offer opportunities to tailor their electronic properties via aliovalent substitutions in the lattice. In this paper, we consider a h-BN monolayer doped with C or Ge, and find that dopants modify the Fermi level of the pristine monolayer. Three-fold coordinated dopants relax to the convex-shaped structures, while four-fold coordinated ones retain the planar structures. These modifications, in turn, lead to unique features in the electron transport characteristics including significant enhancement of current at the dopant site, diode-like asymmetric current-voltage response, and spin-dependent current. We find that the spin-polarized transport properties of the doped BN monolayers could be used for the next-generation devices at the nanoscale.

Modeling of diameter-dependent Fe and Co ultrathin nanowires from first-principles calculations.

We present the electronic, magnetic, thermoelectric and optical properties of ferromagnetic metal nanowires (NWs) made of iron (Fe) and cobalt (Co) atoms using a first principles approach. Each property has been investigated as a function of atomic arrangement and nanowire diameter. Magnetic anisotropy is predicted originating from the spin-orbit coupling. Significant delocalization of electronic charge density is found in Fe nanowires with the increase in nanowire diameter, while the charge distribution anisotropy manifests in all the studied nanowire configurations. The thermoelectric properties exhibit strong coupling to the nanowire configuration and diameter. Thermal conductivity shows large divergence from the bulk iron and cobalt. The optical properties show the strongest increase for nanowires with large diameters. The theoretical modeling of configuration- and diameter-dependent nanowire properties serves as a cornerstone for future utilization of nanowire films in a variety of applications.

Advanced technologies for improved expression of recombinant proteins in bacteria: perspectives and applications.

Prokaryotic expression systems are superior in producing valuable recombinant proteins, enzymes and therapeutic products. Conventional microbial technology is evolving gradually and amalgamated with advanced technologies in order to give rise to improved processes for the production of metabolites, recombinant biopharmaceuticals and industrial enzymes. Recently, several novel approaches have been employed in a bacterial expression platform to improve recombinant protein expression. These approaches involve metabolic engineering, use of strong promoters, novel vector elements such as inducers and enhancers, protein tags, secretion signals, high-throughput devices for cloning and process screening as well as fermentation technologies. Advancement of the novel technologies in E. coli systems led to the production of "difficult to express" complex products including small peptides, antibody fragments, few proteins and full-length aglycosylated monoclonal antibodies in considerable large quantity. Wacker's secretion technologies, Pfenex system, inducers, cell-free systems, strain engineering for post-translational modification, such as disulfide bridging and bacterial N-glycosylation, are still under evaluation for the production of complex proteins and peptides in E. coli in an efficient manner. This appraisal provides an impression of expression technologies developed in recent times for enhanced production of heterologous proteins in E. coli which are of foremost importance for diverse applications in microbiology and biopharmaceutical production.

Increased expression of endosomal members of toll-like receptor family abrogates wound healing in patients with type 2 diabetes mellitus.

The inflammatory phase of wound healing cascade is an important determinant of the fate of the wound. Acute inflammation is necessary to initiate proper wound healing, while chronic inflammation abrogates wound healing. Different endosomal members of toll-like receptor (TLR) family initiate inflammatory signalling via a range of different inflammatory mediators such as interferons, internal tissue damaged-associated molecular patterns (DAMPs) and hyperactive effector T cells. Sustained signalling of TLR9 and TLR7 contributes to chronic inflammation by activating the plasmacytoid dendritic cells. Diabetic wounds are also characterised by sustained inflammatory phase. The objective of this study was to analyse the differential expression of endosomal TLRs in human diabetic wounds compared with control wounds. We analysed the differential expression of TLR7 and TLR9 both at transcriptional and translational levels in wounds of 84 patients with type 2 diabetes mellitus (T2DM) and 6 control subjects without diabetes using quantitative real-time polymerase chain reaction (RT-PCR), western blot and immunohistochemistry. TLR7 and TLR9 were significantly up-regulated in wounds of the patients with T2DM compared with the controls and were dependent on the infection status of the diabetic wounds, and wounds with microbial infection exhibited lower expression levels of endosomal TLRs. Altered endosomal TLR expression in T2DM subjects might be associated with wound healing impairment.

Modulation of band gap by an applied electric field in silicene-based hetero-bilayers.

Electronic properties of the hetero-structures consisting of silicene, graphene and BN monolayers under the influence of an electric field were investigated using density functional theory. With no electric field, both silicene/graphene and silicene/BN were shown to have a finite gap of about ∼50 meV, though silicene is a zero-gap two-dimensional material. Application of the field perpendicular to the bilayer system was found to facilitate modulation of the band gap, exhibiting an approximately linear relationship with the gap energy, in contrast to what was seen for the constituent monolayers. Also, the degree of the modulation was mainly determined by the Si-pz electronic states at the interface of the silicene/graphene and silicene/BN bilayers.

Detection of dengue virus in individual Aedes aegypti mosquitoes in Delhi, India.

BACKGROUND & OBJECTIVES: Delhi, the capital city of India, has so far witnessed several outbreaks of dengue fever since 1967 (last one reported in 2013). Improved virological and entomological surveillance are the only tools that can help in prevention of dengue as well as in the development of dengue control programmes. The aim of the study was to conduct a prospective field study to detect dengue virus in adult Aedes aegypti mosquitoes collected from various localities represented by different socioeconomic groups in Delhi. METHODS: The study areas were selected and categorized into high, medium and low income groups on the basis of socioeconomical characteristics of the resident population, where dengue cases were reported during the past three years by MCD. Dengue viral infection was detected in the head squash of each adult mosquito by immunofluorescent assay (IFA) employing monoclonal antibodies against dengue virus (DENV). A total of 2408 females and 1206 males of Ae. aegypti were collected and tested by IFA. RESULTS: Out of 2408 Ae. aegypti females, 14 were found positive, with minimum infection rate (MIR) of 5.8 per 1000 mosquitoes. Among the 18 study areas, 11 localities were found positive for dengue virus infection. Low income group (LIG) areas showed highest mosquito infectivity (9.8), followed by medium income group (MIG), i.e. 6.2; while least was observed in high income group (HIG), i.e. 1.3. No vertical transmission of dengue virus could be detected in 1206 Ae. aegypti males collected. INTERPRETATION & CONCLUSION: The study concludes that there was high MIR in the identified localities of low and medium income groups. Estimation of MIR in a female Aedes mosquito in the existing arsenals for dengue surveillance would be an added advantage for early warning of dengue outbreak. The presence of infected mosquitoes in identified localities of Delhi was alarming and require rigorous vector surveillance so that the severe outbreaks can be prevented.