Tunable Photocatalytic Activity of PEO‐Stabilized ZnO–Polyoxometalate Nanostructures in Aqueous Solution

Abstract The photocatalytic activity and selectivity of novel binary and ternary composite nanostructures from polyethylene oxide‐stabilized zinc oxide (PEO–ZnO) with and without polyoxometalate (H4[Si(W3O10)4], POM) are determined in aqueous solution under UV‐light. Mono‐ and di‐COOH‐end‐functionalized PEO polymers are used as surface modifiers, influencing the morphology and stability of the ZnO nanoparticles being synthesized in water. POM acts as an additional versatile photocatalytically active building block resulting in a ternary hybrid structure with tunable photocatalytic activity. Catalytic selectivity is demonstrated by studying photocatalytic dye degradations as model reactions, where the chemical backbone of the dyes and their charge turn out to be the basis for the selectivity. All samples are characterized with dynamic light scattering, transmission electron microscopy, scanning electron microscopy, light microscopy, and ζ‐potential measurements. With the functionalized PEOs, large ZnO clusters consisting of leaves are formed while 2‐[2‐(2‐methoxyethoxy) ethoxy] acetic acid (TODA) yields ZnO flower‐like structures

Taxonomy of fundamental concepts of localization in cyber-physical and sensor networks

Localization is a fundamental task in Cyber-Physical Systems (CPS), where data is tightly coupled with the environment and the location where it is generated. The research literature on localization has reached a critical mass, and several surveys have also emerged. This review paper contributes on the state-of-the-art with the proposal of a new and holistic taxonomy of the fundamental concepts of localization in CPS, based on a comprehensive analysis of previous research works and surveys. The main objective is to pave the way towards a deep understanding of the main localization techniques, and unify their descriptions. Furthermore, this review paper provides a complete overview on the most relevant localization and geolocation techniques. Also, we present the most important metrics for measuring the accuracy of localization approaches, which is meant to be the gap between the real location and its estimate. Finally, we present open issues and research challenges pertaining to localization. We believe that this review paper will represent an important and complete reference of localization techniques in CPS for researchers and practitioners and will provide them with an added value as compared to previous surveys

Development and validation of HPLC and CE methods for simultaneous determination of amlodipine and atorvastatin in the presence of their acidic degradation products in tablets

Two methods were developed for separation and quantitation of amlodipine (AML) and atorvastatin (ATV) in the presence of their acidic degradation products. The first method was a simple isocratic RP-HPLC method while the second was capillary electrophoresis (CE). Degradation products were obtained by acidic hydrolysis of the two drugs and their structures were elucidated for the first time by IR and MS spectra. Degradation products did not interfere with the determination of either drug and the assays were therefore stability-indicating. The linearity of the proposed methods was established over the ranges 1–50 μg mL–1 for AML and ATV in the HPLC method and in the range of 3–50 and 4–50 μg mL-1 for AML and ATV, respectively, in the CE method. The proposed methods were validated according to ICH guidelines. The methods were successfully applied to estimation of AML and ATV in bulk powder and in pharmaceutical dosage forms

Development and validation of HPLC and CE methods for simultaneous determination of amlodipine and atorvastatin in the presence of their acidic degradation products in tablets

Two methods were developed for separation and quantitation of amlodipine (AML) and atorvastatin (ATV) in the presence of their acidic degradation products. The first method was a simple isocratic RP-HPLC method while the second was capillary electrophoresis (CE). Degradation products were obtained by acidic hydrolysis of the two drugs and their structures were elucidated for the first time by IR and MS spectra. Degradation products did not interfere with the determination of either drug and the assays were therefore stability-indicating. The linearity of the proposed methods was established over the ranges 1-50 μg mL-1 for AML and ATV in the HPLC method and in the range of 3-50 and 4-50 μg mL-1 for AML and ATV, respectively, in the CE method. The proposed methods were validated according to ICH guidelines. The methods were successfully applied to estimation of AML and ATV in combined tablets

Respiratory Selenite Reductase from Bacillus selenitireducens Strain MLS10

The putative respiratory selenite [Se(IV)] reductase (Srr) from Bacillus selenitireducens MLS10 has been identified through a polyphasic approach involving genomics, proteomics, and enzymology. Nondenaturing gel assays were used to identify Srr in cell fractions, and the active band was shown to contain a single protein of 80 kDa. The protein was identified through liquid chromatography-tandem mass spectrometry (LC-MS/MS) as a homolog of the catalytic subunit of polysulfide reductase (PsrA). It was found to be encoded as part of an operon that contains six genes that we designated srrE, srrA, srrB, srrC, srrD, and srrF SrrA is the catalytic subunit (80 kDa), with a twin-arginine translocation (TAT) leader sequence indicative of a periplasmic protein and one putative 4Fe-4S binding site. SrrB is a small subunit (17 kDa) with four putative 4Fe-4S binding sites, SrrC (43 kDa) is an anchoring subunit, and SrrD (24 kDa) is a chaperon protein. Both SrrE (38 kDa) and SrrF (45 kDa) were annotated as rhodanese domain-containing proteins. Phylogenetic analysis revealed that SrrA belonged to the PsrA/PhsA clade but that it did not define a distinct subgroup, based on the putative homologs that were subsequently identified from other known selenite-respiring bacteria (e.g., Desulfurispirillum indicum and Pyrobaculum aerophilum). The enzyme appeared to be specific for Se(IV), showing no activity with selenate, arsenate, or thiosulfate, with a Km of 145 ± 53 μM, a V max of 23 ± 2.5 μM min-1, and a k cat of 23 ± 2.68 s-1 These results further our understanding of the mechanisms of selenium biotransformation and its biogeochemical cycle.IMPORTANCE Selenium is an essential element for life, with Se(IV) reduction a key step in its biogeochemical cycle. This report identifies for the first time a dissimilatory Se(IV) reductase, Srr, from a known selenite-respiring bacterium, the haloalkalophilic Bacillus selenitireducens strain MLS10. The work extends the versatility of the complex iron-sulfur molybdoenzyme (CISM) superfamily in electron transfer involving chalcogen substrates with different redox potentials. Further, it underscores the importance of biochemical and enzymological approaches in establishing the functionality of these enzymes