Bake stability of CdTe and ZnS on HgCdTe: An x-ray photoelectron spectroscopy study

Mercury cadmium telluride (Hg_1?xCd_xTe or MCT) has been commonly used in devices for infrared (IR) detection. For the optimum performance of the device, a compatible surface-passivation technology that provides long-term stability is required. Using x-ray photoelectron spectroscopy (XPS), the present study examines the effects on Hg_0.8Cd_0.2Te passivated with CdTe and ZnS undergoing baking in vacuum at temperatures typically used for dewar bakeout. Spectra recorded as a function of depth in both cases clearly show out-diffusion of Hg from the substrate toward the surface, even before the bakeout. On baking in vacuum, dramatic changes are observed in the ZnS/MCT case with complete loss of Hg from the sample up to the tested depth of more than 1,000 Å. Compositions of the HgCdTe matrix, formed after Hg out-diffusion, before and after the bakeout are also calculated at selected depths (from 250 Å to 700 Å), which is vital information from a device point of view, as it affects the bandgap of this narrow-band semiconductor.     

Light-Control over Casein Kinase 1δ Activity with Photopharmacology: A Clear Case for Arylazopyrazole-Based Inhibitors

Protein kinases are responsible for healthy cellular processes and signalling pathways, and their dysfunction is the basis of many pathologies. There are numerous small molecule inhibitors of protein kinases that systemically regulate dysfunctional signalling processes. However, attaining selectivity in kinase inhibition within the complex human kinome is still a challenge that inspires unconventional approaches. One of those approaches is photopharmacology, which uses light-controlled bioactive molecules to selectively activate drugs only at the intended space and time, thereby avoiding side effects outside of the irradiated area. Still, in the context of kinase inhibition, photopharmacology has thus far been rather unsuccessful in providing light-controlled drugs. Here, we present the discovery and optimisation of a photoswitchable inhibitor of casein kinase 1δ (CK1δ), important for the control of cell differentiation, circadian rhythm, DNA repair, apoptosis, and numerous other signalling processes. Varying the position at which the light-responsive azobenzene moiety has been introduced into a known CK1δ inhibitor, LH846, revealed the preferred regioisomer for efficient photo-modulation of inhibitory activity, but the photoswitchable inhibitor suffered from sub-optimal (photo)chemical properties. Replacement of the bis-phenyl azobenzene group with the arylazopyrazole moiety yielded a superior photoswitch with very high photostationary state distributions, increased solubility and a 10-fold difference in activity between irradiated and thermally adapted samples. The reasons behind those findings are explored with molecular docking and molecular dynamics simulations. Results described here show how the evaluation of privileged molecular architecture, followed by the optimisation of the photoswitchable unit, is a valuable strategy for the challenging design of the photoswitchable kinase inhibitors.     

Viscosity Stabilization of Tapioca Starch

Two samples of Tapioca starch of different viscosities have been crosslinked with sodium trimetaphosphate, epichlorohydrin, and phosphorus oxychloride. Of these crosslinking agents, epichlorohydrin is the most efficient, requiring only 0.01 to 0.15% of the reagent on the weight of starch. It is noted that tapioca starch having initially a high viscosity requires less amount of the crosslinking agent for stabilization of its paste viscosity as compared to the starch sample having low initial viscosity.     

Molecularly imprinted polymer-matrix nanocomposite for enantioselective electrochemical sensing of d- and l-aspartic acid

A new molecularly imprinted polymer-matrix (titanium dioxide nanoparticle/multiwalled carbon nanotubes) nanocomposite was developed for the modification of pencil graphite electrode as an enantioselective sensing probe for aspartic acid isomers, prevalent at ultra trace level in aqueous and real samples. The nanocomposite having many shape complementary cavities was synthesized adopting surface initiated-activators regenerated by electron transfer for atom transfer radical polymerization. The proposed sensor has high stability, nanocomposite uniformity, good reproducibility, and enhanced electrocatalytic activity to respond oxidative peak current of l-aspartic acid quantitatively by differential pulse anodic stripping voltammetry, without any cross-reactivity in real samples. Under the optimized operating conditions, the l-aspartic acid imprinted modified electrode showed a wide linear response for l-aspartic acid within the concentration range 9.98–532.72 ng mL^? 1, with the minimum detection limit of 1.73–1.79 ng mL^? 1 (S/N = 3) in aqueous and real samples. Almost similar stringent limit (1.79 ng mL^? 1) was obtained with cerebrospinal fluid which is typical for the primitive diagnosis of neurological disorders, caused by an acute depletion of l-aspartic acid biomarker, in clinical settings.     

Placement of FACTS controllers using modal controllability indices to damp out power system oscillations

Flexible ac transmission systems (FACTS) controllers are being used to damp out the power system oscillations. The effectiveness of these controllers depends on their optimal location in the power system network. A controllability index has been proposed to find the optimal location of the FACTS controllers to damp out the inter-area mode of oscillations. Three types of FACTS controllers have been considered, which include static var compensator, thyristor-controlled series compensator and unified power flow controller. The proposed controllability index is based on the relative participation of the parameters of FACTS controllers to the critical mode. A simple approach of computing the controllability indices has been proposed, which combines the linearised differential algebraic equation model of the power system and the FACTS output equations. The placements of FACTS controllers have been obtained for the base case as well as for the critical contingency cases. The effectiveness of the proposed method is demonstrated on New England 39-bus system and 16-machine, 68-bus system     

Deriving Object Oriented Federated Databases and Processing Federated Queries

In this paper, we present a federated query processing approach to evaluate queries on an Object-Oriented (OO) federated database. This approach has been designed and implemented in the OO-Myriad project, which is an OO extension to the Myriad FDBS researchmyriad:94. Since data integration is performed as part of federated query processing, we have proposed outerjoin, outer-difference and generalized attribute derivation operations together with the traditional relational operations, to be used for integration purposes. To define an OO federated database as a virtual view on multiple OO export databases, we adopt a database mapping strategy that systematically derives each of the class extents, deep class extents and relationships of the federated database using an operator tree consisting of the integration operations. By augmenting federated database queries with this algebraic mapping information, query execution plans can be generated. Based on the original Myriad query processing framework, we have realized the proposed OO federated query processing approach in the OO-Myriad prototype.     

Macroscopic Properties of Restacked,Redox‐Liquid Exfoliated Graphite and Graphite Mimics Produced in Bulk Quantities

The excellent properties exhibited by monolayer graphene have spurred the development of exfoliation techniques using bulk graphite to produce large quantities of pristine monolayer sheets. Development of simple chemistry to exfoliate and intercalate graphite and graphite mimics in large quantities is required for numerous applications. To determine the macroscopic behavior of restacked, exfoliated bulk materials, a systematic approach is presented using a simple, redox‐liquid sonication process along to obtain large quantities of 2D and 3D hexagonally layered graphite, molybdenum disulfide, and boron nitride, which are subsequently characterized to observe chemical and structural changes. For MoS₂ sonicated with the antioxidant sodium bisulfite, results from Raman spectroscopy, X‐ray diffraction, and electron microscopy indicate the presence of distorted phases from different polymorphs, and apparent nanotube structures in the bulk, restacked powder. Furthermore, using thermograviemtric analysis, the antioxidant enhances the resistance to oxidative degradation of MoS₂, upon thermal treatment up to 900 °C. The addition of the ionic antioxidant decreased dispersion stability in non‐polar solvent, suggesting decreased compatibility with non‐polar systems. Using simple chemical methods, the ability to generate tailored multidimensional layered materials with unique macroscopic properties is critical for numerous applications, including electrical devices, reinforced polymer composites, lithium–ion capacitors, and chemical sensing.     

Polymer-antibody fragment conjugates for biomedical applications

Many proteins benefit from improved solubility, immunocompatibility, pharmacokinetics or stability upon conjugation to polymers. For protein-conjugates used in delivery or imaging in vivo, this can mean increased efficacies due to longer circulatory half-lives or increased intracellular stability. In vitro, conjugation to polymers can increase stability, reduce aggregation, or mediate multimerization or phase separation of proteins to increase assay sensitivities or improve signal detection. The emergence of recombinant antibody technologies over the past two decades has allowed relatively simple isolation in vitro of (human) antibody fragments, such as Fabs and single chain variable fragments (scFvs), that retain the binding properties of their parent molecules and may exhibit additional properties such as reduced immunogenicity, improved tissue penetration or increased packing density on sensor surfaces due to their small sizes. In addition, protein engineering approaches that facilitate their chemical functionalization have seen antibody fragments linked to a broad spectrum of chemically and functionally diverse polymeric molecules. Of the varied strategies used in polymer–protein coupling, amine and cysteine conjugation are the most widely applied chemistries with antibody fragments. Simple conjugation to poly(ethyleneglycol) can increase half-life, decrease renal clearance, improve stability and reduce aggregation of antibody fragments without compromising their antigen binding. Meanwhile, engineering of antibody fragments can be used to control conjugation to polymers and coupling to responsive polymers can enable intracellular delivery or context responsive release of a drug payload from a polymer–antibody fragment complex. Recent years have seen polymer–antibody fragment conjugates increasingly encroach into areas traditionally associated with monoclonal antibody–polymers and we discuss the potential of such conjugates, in vivo and in vitro, in applications such as drug delivery, tissue engineering, diagnostics and bioseparation.     

Protein functionalized Pt nanoparticles-conducting polymer nanocomposite film: Characterization and immunosensor application

We report an electrochemically prepared 3-mercaptopropionic acid (MPA) capped Pt nanoparticles-Polypyrrole (PPy) nanocomposite film based bioelectrode for the detection of human C-reactive protein (αCRP). The electrochemical deposition provides homogeneous distribution of ultrafine Pt(MPA)-NPs within the uniform and adherent PPy film with high degree of geometrical conformity and controllable film thickness. Protein antibody, Ab-αCRP, was covalently immobilized through the site specific carboxyl groups of Pt(MPA)-NPs within the polymer nanocomposite film by carbodiimide coupling reaction. The bioelectrode interfacial surface electron transport study towards protein antigen, Ag-αCRP, was carried out by electrochemical impedance spectroscopy (EIS). The value of ‘n’, a Constant Phase Element exponent used as a gauge of the heterogeneity, for Pt(MPA)-PPy nanocomposite film was found to be 0.88∼1 which is indicative of a homogeneous morphology of the composite film with minimal defects. The EIS of the bioelectrode exhibited significant changes in charge transfer resistance (R_et) component at a low ac frequency of <20 Hz towards Ag-αCRP detection over a linear range of 10 ng mL⁻¹–10 μg mL⁻¹ in PBS with a sensitivity of 109.74 Ωcm² per decade.