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Truncated Sequential Non-Parametric Hypothesis Testing Based on Random Distortion Testing
No full textIn this paper, we propose a new algorithm for sequential non-parametric hypothesis testing based on Random Distortion Testing (RDT). The data-based approach is non-parametric in the sense that the underlying signal distributions under each hypothesis are assumed to be unknown. Our previously proposed non-truncated sequential algorithm, SeqRDT, was show n to achieve desired error probabilities under a few assumptions on the signal model. In this paper, we show that the proposed truncated sequential algorithm, T-SeqRDT, requires even fewer assumptions on the signal model, while guaranteeing the error probabilities to he below pre-specified levels and at the same time makes a decision faster compared to its optimal fixed-sample-size counterpart, BlockRDT. We derive bounds on the error probabilities and the average stopping times of the algorithm. Via numerical simulations, we compare the performance of T-SeqRDT with SeqRDT, BlockRDT, sequential probability ratio test, and composite sequential probability ratio tests. We also show the robustness of the proposed approach compared with the standard likelihood ratio based approaches
2D layering of silicon nanocrystals at TiO2/CuI heterojunction for enhanced charge transport
No full textWe prepared a two-dimensional layer of silicon nanoparticles at the CuI/TiO2 p-n junction heterophase interface by spray coating of colloidal ink of nanoparticles. The particles are prepared by a physical process of milling at room temperature and further etched to obtain a nanometric size distribution with a mode at similar to 2nm. These particles at the interface act as traps for electrons. However, the traps fill up quickly in a diode configuration due to the dense band structure of the nanoparticles, and overflowed electrons can tunnel through the junction, thereby significantly increasing the efficiency as reflected by a large increase in the diode current. A qualitative model is developed in terms of discrete band states at the interface to explain the above phenomena. The results offer opportunities for developing high-performance semiconducting devices
Organic Imine Cages: Molecular Marriage and Applications
No full textImine condensation has been known to chemists for more than a century and is used extensively to synthesize large organic cages of defined shapes and sizes. Surprisingly, in the context of the synthetic methods for organic imine cages (OICs), a self-sorting/self-selection (molecular marriage) process has been overlooked over the years. Such processes are omnipresent in nature, from the creation of galaxies to the formation of the smallest building blocks of life (the cell). Such processes have the incredible ability to guide a system toward the formation of a specific product or products out of a collection of equally probable multiple possibilities. This Minireview sheds light on new opportunities in cage design offered by the self-sorting/self-selection protocol in OICs. Recent efforts to explore organic cages for various exciting new applications are discussed; for example, for detection of harmful small organic molecules, as templates for nucleation of metal nanoparticles (MNPs), and as proton-conducting materials
La1.5Sr0.5NiMn0.5Ru0.5O6 Double Perovskite with Enhanced ORR/OER Bifunctional Catalytic Activity
No full textPerovskites (ABO(3)) with transition metals in active B sites are considered alternative catalysts for the water oxidation to oxygen through the oxygen evolution reaction (OER) and for the oxygen reduction through the oxygen reduction reaction (ORR) back to water. We have synthesized a double perovskite (A(2)BB'O-6) with different cations in A, B, and B' sites, namely, ((La15Sr0.5)-Sr-.)(A)(Ni0.5Mn0.5)(B)(Ni0.5Ru0.5)(B)O-6 (LSNMR), which displays an outstanding OER/ORR bifunctional performance. The composition and structure of the oxide has been determined by powder X-ray diffraction, powder neutron diffraction, and transmission electron microscopy to be monoclinic with the space group P2(1)/n and with cationic ordering between the ions in the B and B' sites. X-ray absorption near-edge spectroscopy suggests that LSNMR presents a configuration of similar to Ni2+, similar to Mn4+, and similar to Ru5+. This bifunctional catalyst is endowed with high ORR and OER activities in alkaline media, with a remarkable bifunctional index value of similar to 0.83 V (the difference between the potentials measured at -1 mA cm(-2) for the ORR and +10 mA cm(-2) for the OER). The ORR onset potential (E-onset) of 0.94 V is among the best reported to date in alkaline media for ORR-active perovskites. The ORR mass activity of LSNMR is 1.1 A g(-1) at 0.9 V and 7.3 A g(-1) at 0.8 V. Furthermore, LSNMR is stable in a wide potential window down to 0.05 V. The OER potential to achieve a current density of 10 mA cm(-2) is 1.66 V. Density functional theory calculations demonstrate that the high ORR/OER activity of LSNMR is related to the presence of active Mn sites for the ORR- and Ru-active sites for the OER by virtue of the high symmetry of the respective reaction steps on those sites. In addition, the material is stable to ORR cycling and also considerably stable to OER cycling
Probing the Formation of a Seleninic Acid in Living Cells by the Fluorescence Switching of a Glutathione Peroxidase Mimetic
No full textGlutathione peroxidase (GPx) is a selenoenzyme that protects cells against oxidative damage. Although the formation of a seleninic acid (-SeO2H) by this enzyme during oxidative stress has been proposed, a selenic acid has not been identified in cells. Herein, we report that the formation of a seleninic acid can be monitored in living cells by using a redox-active ebselen analogue with a naphthalimide fluorophore. The probe reacts with H2O2 to generate the highly fluorescent seleninic acid. The electron withdrawing nature of the -SeO2H moiety and strong SeO interactions, which prevent the photoinduced electron transfer, are responsible for the fluorescence
A comprehensive review on analysis of nanocomposites: from manufacturing to properties characterization
No full textThe study of nanocomposites in its diverse scientific fields has increased dramatically over the years with numerous theoretical and experimental techniques emerging and redefining the process of synthesis, analysis and cost control methodologies of nanocomposites. The present review is an attempt to identify the various methodologies, techniques, theories and formulations that are used in nanocomposite technology. As an overall qualitative appreciation it is possible to conclude that the diversity of processes involved in the manufacture and analysis of nanocomposites, impacts them differently, influencing their physical nature, chemical behaviour, biological interactions, optical properties and production costs which consequently may introduce some constraints to their application. Hence, a critical review on the best methodology would remain inconclusive. This work intends to collect and relate publications on different fields of the nanocomposites technology and application fields, aiming at contributing to achieve a wide perspective of different aspects of the nanocomposites processes and theories and with this, being an aid to ease and raise the production and analysis of nanocomposites to a higher level
In silico modeling of Plasmodium falciparum chloroquine resistance transporter protein and biochemical studies suggest its key contribution to chloroquine resistance
No full textChloroquine (CQ) has been used for decades as the primary chemotherapeutic drug for the treatment of malaria. The emergence of drug resistance in Plasmodium falciparum has been considered to be because of the excessive use of antimalarial drugs worldwide. Moreover, the intense distribution and prevalence of chloroquine-resistant strains in endemic regions has aided the incidence of more complications to malaria treatment and control. Due to the lack of literature that portrays evident molecular mechanisms of drug resistance, it has been difficult to understand the drug resistance conferred by Plasmodium species. Intensive research on CQ drug resistance has identified the association of P. falciparum chloroquine resistance transporter protein (PfCRT), which belongs to the drug/metabolite transporter and EamA-like superfamily. Additionally, it has shown that K76 T mutation in PfCRT protein has mainly attributed to CQ resistance than other mutations. This study deals with the development of an in silica model of the PfCRT protein and its interaction with the CQ ligand molecule as well as the biochemical and biophysical characterization of the transmembrane domain 1 (TMD 1) peptide of the PfCRT protein. The physiochemical analysis of the PfCRT protein identified basic differences between the wild and mutant forms of the protein, as well as identifying the high hydrophobic nature of the mutant-type protein. The tertiary structure of the PfCRT protein was predicted and interaction with CQ revealed different active pocket binding regions in both the wild and mutant form of PfCRT proteins. The CQ2 molecule interacts with TMD 10 of the wild-type PfCRT protein, whereas it interacts with TMD 1 of the mutant-type protein. Studies on the TMD 1 peptide revealed the insertion of the peptide in the micelles adopting stable alpha-helical structure. Binding studies with the CQ molecule detected high binding affinity toward the mutant-type TMD 1 peptide rather than the wild-type, thus confirming that the TMD 1 peptide is involved in substrate selectivity. Our findings help to characterize the structure of the PfCRT protein and the role played by the TMD 1 region in CQ resistance using in silica and biochemical approaches. Molecular docking and ligand binding studies confirm that TMD 1 is involved in substrate selectivity and aids in CQ efflux, thereby contributing to the parasites CQ drug resistance mechanism
Ag/ZnO/Au 3D hybrid structured reusable SERS substrate as highly sensitive platform for DNA detection
No full textUltra-sensitive hybrid Silver/Zinc oxide/Gold (Ag/ZnO/Au) structure based three dimensional (3D) surface enhanced Raman scattering (SERS) substrates have been prepared by three step fabrication process using thermal evaporation, hydrothermal growth, and sputtering techniques. The size and inter-particle (IP) gap of decorated Au nanoparticles (NPs) on ZnO nanorods (NRs) in the sub-nanometer range have been achieved through varying the sputtering time of Au. The superhydrophobic nature, the formation of the Schottky barrier at ZnO/Au interface and the broad optical absorption spectrum facilitated towards higher SERS activity of Ag/ZnO/Au hybrid structures. The higher SERS activity of 3D SERS substrate as compared with two dimensional (2D) SERS substrate has been studied. The good SERS signal reproducibility of 3D hybrid structures have been explored through Raman mapping. Higher SERS enhancement factor (EF) of 1 x 10(10) has been achieved with a limit of detection (LOD) up to 10(-16) M and 10 ng/mu L for Rhodamine-6 G (Rh6G) and lambda DNA (lambda-DNA), respectively. The degradation of Rh6G and lambda-DNA molecules have been studied through photocatalytic degradation process to explore the reusability of the SERS substrates up to 10 and 4 times, respectively, with maintaining good SERS signal reproducibility. This metal/semiconductor/metal hybrid structure based SERS substrate with reusable capability indicates potential application towards biosensor for the detection of biologically important molecules at very low concentration level
4-Hydroxy-2-pyridone Derivatives and the delta-pyrone Isostere as Novel Agents Against Mycobacterium smegmatis Biofilm Inhibitors
No full textBackground: The treatment of a bacterial infection when the bacterium is growing in a biofilm is a vexed issue. This is because the bacteria in a biofilm behaves differently compared to the individual planktonic free-form. As a result, traditional antibacterial agents lose their activity. Objective: Presently, there are not many drugs that are effective against bacteria growing in biofilms. Based on literature reports, we have sought to develop novel derivatives of 4-hydroxy-2-pyridone as both antimycobacterial and antibiofilm agents. Methods: The pyridone derivatives were synthesized by reacting 4-hydroxy-6-methyl-2H-pyran-2-one with appropriate amines and followed by reaction with substituted phenyl isocyanates as reported in the literature. Results: Four compounds in this series significantly inhibit the growth and formation of biofilm by Mycobacterium smegmatis (mc(2) 155 strain) at 50 mu g/ml. Further, in silico evaluation of the ADME parameters shows that these compounds possess good drug-like properties and have the potential to be developed both as antibiofilm and as oral antimycobacterial agents. Conclusion: This finding is of significance as presently very few small molecules are known to inhibit biofilm formation in mycobacteria. These compounds are unique in the sense that they are more potent against Mycobacterium smegmatis in the biofilm state compared to the planktonic form
A modified peridynamics correspondence principle: Removal of zero-energy deformation and other implications
No full textWe look for an enhancement of the correspondence model of peridynamics, emphasizing the elimination of zero-energy deformation modes. We propose an approach based on the notion of sub-horizons. The most useful feature of this proposal is the setup which, whilst providing solutions with the necessary stability, deviates only marginally from the original correspondence formulation. A thorough analysis of the sub-horizon based method is furnished based on the well-posedness of integral equations and energy spectrum, which clearly demonstrate a removal of zero energy modes. We also show how other forms of unphysical deformation modes, e.g. material collapse within horizon, jump discontinuities and vanishing energy modes, can be prevented with the present proposal. Finally, a set of numerical simulations are undertaken that attest to the remarkable efficacy of the sub-horizon based approach. (C) 2018 Elsevier B.V. All rights reserved