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Shiv Nadar University

(SoNS) School of Natural Sciences

A novel work on several aspects of current conduction mechanism for resistive switching (RS) of a reactive electrode-based memristor (Al/ZnO/Al) against generally used inert electrode-based devices has been illustrated. Compliance current (I cc ), i.e. maximum current through device and stop voltage (V stop ), i.e. maximum V stop upon device, has been used as bias characteristics to evaluate the effect upon conduction behavior. Effect of change in I cc for constant V stop and vice-versa upon high resistance state (HRS) and low resistance state (LRS) has been evaluated in terms of change in bulk defects, i.e. oxygen vacancy and interface inhomogenity, i.e. AlO x formation/dissolution. The device shows unipolar resistive switching (URS) at lower I cc (&lt; = 0.1 mA) and transits irreversibly into bipolar resistive switching (BRS) at higher I cc (&gt; = 1 mA). The dominant conduction behavior of the device is found to be homogenous resistive switching (HoRS). The conduction in HRS and LRS is found to be space-charge limited current conduction. Conductive atomic force microscopy results of the thin film switching layer support the HoRS mechanism and also illustrate the role of interfacial oxide in attributing BRS behavior in the Al/ZnO/Al resistive switch. Studies can be utilized in future to further understand the RS conduction mechanism in reactive electrode-based RS and can be applied for multi-state memory applications. © 2019 IOP Publishing Ltd.

World University root node

Physics

Semiconductor Science and Technology

Resistive switching in reactive electrode-based memristor: Engineering bulk defects and interface inhomogeneity through bias characteristics

Background: Diabetes mellitus (DM) is burgeoning as a global chronic health condition. Some studies suggest that tuberculosis (TB) can even cause diabetes in those not previously known to be diabetic, which as a corollary can add to the already heavy global DM burden. The World Health Organization (WHO) recommends screening for DM at the start of TB treatment; however, it remains to be elucidated which patients with TB-induced hyperglycaemia are at risk for developing DM and who would benefit from a more regular follow-up. This systematic review will aim to firstly synthesise literature on the irreversibility of TB-induced hyperglycaemia in individuals with previously undiagnosed type 2 diabetes mellitus and secondly to synthesise literature on risk factors for progression from TB-induced hyperglycaemia to overt DM in previously undiagnosed. Methods: We will search for relevant studies in electronic databases such as PubMed, EMBASE, PROQUEST, and SCOPUS. Furthermore, references will be hand searched to identify other studies. A flow diagram will be drawn to identify the studies retrieved from each database. We will review all publications that include studies containing data on impaired glucose metabolism upon TB diagnosis, and the quality of all eligible studies will be assessed using the Newcastle-Ottawa Scale. We will further conduct a meta-analysis to pool estimates on the risk of progression of persistent hyperglycaemia to overt DM within this population group, as well as the risk factors for this progression. We will use a random effect model to assess heterogeneity, will carry out sensitivity analysis to explore the influence of a single study on the overall estimate, and will report our findings from our systematic review and meta-analysis according to PRISMA guidelines. Egger's test will be performed to explore the presence of selective reporting bias. If data allow, we will perform a subgroup/meta-regression analysis. Summary effects will be reported using odds ratio, hazard ratio, and relative risk ratios. Furthermore, any clinical, epidemiological, and public health research gaps we identify will be described in a research proposal. © 2019 The Author(s).

Mathematics

Fulltext

Systematic Reviews

The epidemiology of intransient TB-induced hyperglycaemia in previously undiagnosed diabetes mellitus 2 individuals: A protocol for a systematic review and meta-analysis

Bioisosterism is a useful strategy in rational drug design to improve pharmacodynamic and pharmacokinetic properties of lead compounds. Imidazolidinones have been reported as potent kinase inhibitors and antileishmanial agents. In this study, bioisosteres of imidazolidinones (compounds 1–3) were evaluated for their antileishmanial properties. The modified imidazolidinones exhibited potent antileishmanial activity against extracellular as well as intracellular Leishmania donovani parasites in nanomolar concentrations. The selectivity index of these compounds on host cells was found to be more than 1000, emphasizing their specificity toward the parasite. Using SwissTargetPrediction software, we assessed the potential targets of these compounds and found MAPK as the most probable target. To in vitro validate, we developed a novel in vitro kinase assay that mimics the in vivo nature of the functional kinome. Compounds 1–3 displayed specific inhibition of parasite kinase activity accompanied by an increase in intracellular sodium levels in the parasites. This might be the effect of kinase inhibition that regulates sodium homeostasis through Na-ATPases. Finally, the compound-treated parasites underwent apoptosis-like death. This study represents bioisoterism as a novel approach for drug design to establish the structure–activity relationship, which in turn helps to improve the therapeutic activity of lead compounds. © 2019 Deutsche Pharmazeutische Gesellschaft

Chemistry

Archiv der Pharmazie

Design and synthesis of imidazolidinone derivatives as potent anti-leishmanial agents by bioisosterism

ConspectusThis Account addresses the catalytic cycle of the enzyme cytochrome P450 (CYP450) as a prototypical biological machine with automatic features. CYP450 is a nanomachine that uses dioxygen and two reducing and two proton equivalents to oxidize a plethora of molecules (so-called substrates) as a means of supplying bio-organisms with essential molecules (e.g., brain neurotransmitters, sex hormones, etc.) and protecting biosystems against poisoning. An enticing property of CYP450s is that entrance of an oxidizable substrate into the active site initiates a series of events that constitute the catalytic cycle, which functions "automatically" in a regulated sequence of events culminating in the production of the oxidized substrates (e.g., hydroxylated, epoxidized, etc.), oftentimes with remarkable stereo- and regioselectivities. It is timely to demonstrate how theory uses molecular dynamics (MD) simulations and quantum-mechanical/molecular-mechanical (QM/MM) calculations to complement experiments and elucidate the choreography by which the protein regulates the catalytic cycle.CYP450 is a heme enzyme that contains a ferric ion (Fe III ) coordinated by a porphyrin ligand, a water molecule, and a cysteinate ligand that is provided by a strategic residue of the encapsulating protein. While many of the individual steps are sufficiently well-understood, we shall provide here an overview of the factors that cause all of the steps to be sequentially coordinated. To this end, we use examples from three different CYP450 enzymes: the bacterial ones CYP450 BM3 and CYP450 CAM and the mammalian enzyme CYP450 3A4 . The treatment is limited to the catalytic cycle, as aspects of two-state reactivity were reviewed previously (e.g., Shaik, S.; et al. Chem. Rev. 2005, 105, 2279).What are the principles that govern the seeming automatic feature? For example, how do substrate entrance and binding gate the enzyme? How does the reductase attachment to the enzyme affect the next steps? What triggers the attachment of the reductase? How does the electron transfer (ET) that converts Fe III to Fe II occur? Is the ET coordinated with the entrance of O 2 into the active site? What is the mechanism of the latter step? Since the entrance of the substrate expels the water molecules from the active site, how do water molecules re-enter to form a proton channel, which is necessary for creating the ultimate oxidant Compound I? How do mutations that disrupt the water channel nevertheless create a competent oxidant? By what means does the enzyme produce regio- and stereoselective oxidation products? What triggers the departure of the oxidized product, and how does the exit occur in a manner that generates the resting state ready for the next cycle? This Account shows that the entrance of the substrate triggers all of the ensuing events. © Copyright 2019 American Chemical Society.

Accounts of Chemical Research

Cytochrome P450 - The Wonderful Nanomachine Revealed through Dynamic Simulations of the Catalytic Cycle

Prediction of crystal structure and study of transport and optoelectronic properties of NH2 substituted trans-stilbene derivative: A new promising ambipolar organic semiconductor

A lightweight organic material, trans-4′-dimethylamino-4-nitro-α-cyanostilbene, exhibits notable charge carrier mobility (∼10 -4 cm 2 V -1 s -1 ). The non-centrosymmetric material also displays moderate second harmonic generation activity. This is one of the rarest examples of small organic materials displaying semiconductor characteristics. The charge-transfer pathway as elucidated via high-resolution single-crystal X-ray diffraction data based "energy frameworks" and "experimental charge density" analyses is assessed by measuring the charge carrier mobility using the space charge limited current technique on pure single-crystal diode devices. These advanced structural analyses clearly demonstrate that charge transport in organic crystals is purely governed by its molecular packing, especially the π-π stacking geometry. The balanced ambipolar charge transport behavior makes this highly soluble and thermally stable organic crystal promising for applications in optoelectronic devices. Moreover, this report introduces the crucial role of energy frameworks and charge density analyses for fundamental understanding of the structure-property relationship in organic semiconductors. Copyright © 2019 American Chemical Society.

Crystal Growth and Design

Structure-Property Relationship in an Organic Semiconductor: Insights from Energy Frameworks, Charge Density Analysis, and Diode Devices

Ever since the discovery of two-dimensional (2D) material graphene, there has been huge interest in the exploration of low-dimensional materials that can be exfoliated from their three-dimensional counterpart with enriched properties due to quantum confinement. Two members of the Sn-S family, Pnma-SnS and P3Im1-SnS 2 that possess a layered structure with 2D nanosheets stacked via weak van der Waals (vdW) interactions, have widely been studied in this regard. The other member, Pnma-Sn 2 S 3 , comprising one-dimensional (1D) nanochains bound via vdW interactions, has never been investigated in the view of exfoliated 1D analogue. In this work, we therefore comprehensively studied 1D-Sn 2 X 3 (X = S and Se) nanochains and demonstrated them to be stable and exfoliable from their bulk counterpart. Further, it is also shown that the exfoliated 1D nanochains can easily be identified from their bulk counterpart using Raman, infrared, and X-ray spectroscopies. Our calculations predict a direct band gap of 2.35 eV (1.67 eV) for 1D-Sn 2 S 3 (1D-Sn 2 Se 3 ) nanochains under the Heyd, Scuseria, and Ernzerhof functional, with a broad absorption region lying between 2 and 8 eV, lower reflection, high charge-carrier mobility with ambipolar characteristics, as well as a larger value of the Seebeck coefficient and a smaller value of the thermal conductivity, resulting in a better thermoelectric figure of merit. These interesting electronic, optical, transport, and thermoelectric properties make 1D-Sn 2 X 3 nanochains a potential candidate for the application in future optoelectronic and thermoelectronic devices, in fact, better than three-dimensional (3D)-Sn 2 X 3 for few of the applications. Moreover, 3D-Sn 2 Se 3 is also investigated in detail in this work, which to the best of our knowledge has not been done before. © 2019 American Chemical Society.

ACS Applied Materials and Interfaces

One-Dimensional-Sn 2 X 3 (X = S, Se) as Promising Optoelectronic and Thermoelectronic Materials: A Comparison with Three-Dimensional-Sn 2 X 3

Wildlife habitat corridors are components of landscapes, which facilitate the movement of organisms and processes between areas of intact habitat, and thus provide landscape corridor as well as serve as an ideal component to study and understand physiological ecology. Corridors are thus regions within a given landscape that generally comprise native vegetation, and connect otherwise fragmented, disconnected, non-contiguous wildlife habitat patches in the landscape. The purpose of designing corridors as a conservation strategy is primarily to counter, and to the extent possible, mitigate the impacts of habitat fragmentation and loss on the biodiversity of the landscape, as well as support continuance of land use for essential local and global economic activities in the region of reference. In this paper, we use game theory and graph theory to model and design a wildlife corridor in the Central India – Eastern Ghats landscape complex, with tiger (Panthera tigris tigris) as the focal species. We construct a graph using the habitat patches supporting wild tiger populations in the landscape complex as vertices and the possible paths between these vertices as edges. A cost matrix is constructed to indicate the cost incurred by the tiger for passage between the habitat patches in the landscape (based on Shelford's Law of Tolerance), by modelling a two-person Prisoner's Dilemma game. A minimum spanning tree is then obtained by employing Kruskal's algorithm, which would suggest a feasible tiger corridor network for the tiger population within the landscape complex. Additionally, analysis of the graph is done using various centrality measures, in order to identify and focus on potentially important habitat patches, and their potential community structure. Correlation analysis is performed on the centrality indices to draw out interesting trends in the network. © 2019 Elsevier B.V.

Ecological Informatics

A graph theoretic approach for modelling tiger corridor network in Central India-Eastern Ghats landscape complex, India

Charge transport properties of common donor copolymers in organic photovoltaics, poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7) and poly([2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene]{3-fluoro-2[(2-ethylhexyl) carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7-Th), with molecular structures differing only in the pendant group, are studied. This is the first report of field-effect transistor mobility (µ FET ) of PTB7-Th (0.14 cm 2 V −1 s −1 ) and the highest µ FET for PTB7 (0.01 cm 2 V −1 s −1 ). µ FET of PTB7-Th is found to be almost one order of magnitude higher than PTB7. To understand the influence of molecular structure on charge transport, hole reorganization energy (λ h ) is calculated from first-principles. λ h of PTB7-Th (≈150 meV) is found to be lower than PTB7 (≈346 meV). Further, the ratio of hopping rate versus square of charge transfer integral calculated from Marcus theory using λ h for these systems is found to indicate a higher rate of hole transfer across dimers or homojunction interface for PTB7-Th. These results are supplemented by experimentally determined λ using bulk-heterojunction organic solar cells, where λ PTB7-Th ≈200 meV and λ PTB7 ≈310 meV follow a similar trend. The effective hole-mobility estimation from BHJ devices correlates well with these λ values. This study provides understanding of charge transport properties via reorganization energy, as a function of pendant group without altering the backbone of the chains. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Advanced Functional Materials

Influence of Pendant Group on Mobility of Organic Thin Film Transistor in Correlation with Reorganization Energy of Molecules

We propose a new form of Lagrangian that shows branching for the associated Hamiltonian and has relevance to the quadratic type and mixed linear-quadratic Liénard-type nonlinear dynamical equations on adjusting the underlying parameters. Non-uniqueness of the Lagrangian is pointed out and a particular one when Fourier transform is demonstrated to depict a momentum-dependent quantum-like mass system when expanded binomially. © 2019 World Scientific Publishing Company.