bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ag Nanoparticles/AgX (X=Cl, Br and I) Composites with Enhanced Photocatalytic Activity and Low Toxicological Effects
Authors: Assis Marcelo , Groppo Filho Francisco C. , Pimentel Dayene S. , Robeldo Thaiane , Gouveia Amanda F. , Castro Tassia F. D. , Fukushima Hirla C. S. , de Foggi Camila C. , da Costa João P. C. , Borra Ricardo C. , Andrés Juan , Longo Elson 
Published: April 2020

AbstractPeriodic structures induced by electron irradiation are a unique phenomenon when electron beams irradiate on the surface of some materials. These periodic structures have potential for technological applications. However, the fuzzy nature of the electron‐induced structuring hinders its further exploration in such applications. In this paper, novel Ag nanoparticle/AgX (X=Cl, Br and I) composites, with enhanced photocatalytic activity and low toxicological effects, were prepared, for the first time, using electron beam irradiation. The remarkable advantage of this approach is that the Ag nanoparticles/AgX composites can be easily prepared in one‐step without the need for high‐pressure conditions, surfactants, ionic liquids, or reducing agents. Furthermore, our method does not involve any toxic substances, which makes the as‐synthesized samples highly applicable for technological applications. The structure, morphology and physicochemical properties of the Ag nanoparticles/AgX composites were studied using various characterization techniques. Using first‐principles calculations based on density functional theory and the quantum theory of atoms in molecules, we reveal how the concentration of excess electrons in the AgX materials induces the formation of the Ag nanoparticles under electron beam irradiation. These results extend the fundamental understanding of the atomic process underlying the mechanism of Ag−X bond rupture observed during the transformation induced via electron irradiation of the AgX crystals by increasing the total number of electrons in the bulk structure. Thus, our findings provide viable guidance for the realization of new materials for the degradation of contaminated wastewater with low toxicity.
High Stability of Immobilized Acetylcholinesterase on Chitosan Beads
Authors: Işık Mesut 
Published: April 2020

AbstractThe enzymes are unstable and have a short lifetime; this causes a decrease in the number of enzyme usage and increases the cost. In the study, the acetylcholinesterase (AChE) enzyme was covalently immobilized to the surface of chitosan via glutaraldehyde by cross‐linking method, where glutaraldehyde contains functional amine group. The immobilized enzyme was characterized by scanning electron microscopy‐energy dispersive X‐ray analysis (SEM‐EDX). The operational and storage stability of immobilized AChE was found higher than the free enzyme by the spectrophotometric method. The storage stability of the immobilized AChE was found 81% for 60 days, while the free AChE lost a high ratio of its activity in 30 days. It was observed that 93% activity was preserved for the immobilized enzyme after reusing it approximately 30 times. Moreover, kinetic parameters, the Km and Vmax, were found 0.073 mM and 0.244 EU/mL for immobilized AChE and 0.044 mM and 0.362 EU/mL for free AChE, respectively. The AChE enzyme is used in the analysis of pesticides; that is why the high stability and reusability of the enzyme as a result of immobilization proses are important in biotechnological applications.
Pantoprazole Derivatives: Synthesis, Urease Inhibition Assay and In Silico Molecular Modeling Studies
Authors: Azizian Homa , Esmailnejad Atefeh , Fathi Vavsari Vaezeh , Mahernia Shabnam , Amanlou Massoud , Balalaie Saeed 
Published: April 2020

AbstractA number of pantoprazole derivatives were synthesized and screened for their urease inhibitory properties. Some of them showed potent inhibitions against jack bean urease. All compounds showed varying degree of IC50 in the range of 25.85 to 181 μMol as compared to standard acetohydroxamic acid (AHA) (100±2.02 μMol). Derivatives bearing 5‐aryl‐1,3,4‐oxadiazole ring substitutions (aryl= pyrazyl, pyridyl and phenyl) were found to be more potent inhibitors than AHA and pantoprazole. The most promising compound, 2‐((3,4‐dimethoxypyridin‐2‐yl)methylthio)‐5‐(pyrazin‐2‐yl)‐1,3,4‐oxadiazole 12, with IC50 value of 25.85±1.21 showed remarkable urease inhibition activity. In silico molecular modeling investigation performed to rationalize the possible binding interaction and ADME properties of compounds over the active site of urease enzyme. The induced fit docking study showed that compound 12 interacted with conserved residues His593 and Arg609 located at the mouth of the urease active site flap and are essential for enzyme catalytic activity. These target compounds could be further studied as a lead skeleton for discovery of novel urease inhibitors.
Preparation of Curcubit[6]uril functionalized CuO Nanoparticles: A New Nanosensing Scheme Based on Fluorescence recovery after FRET for the Label Free Determination of Dopamine
Authors: Qasem Mayada , El Kurdi Riham , Patra Digambara 
Published: April 2020

AbstractIn this manuscript, the aim is to functionalize CuO nanoparticles with the supramolecular host molecule, in this case curcubit[6]uril to have a host guest interaction between the CuO nanoparticles and probe (guest) molecules. Acridine Orange (AO) is applied as a guest molecule. Acridine orange binds with curcubit[6]uril via its carbonyl rims. In the presence of curcubit[6]uril conjugated CuO nanoparticles, the fluorescence intensity of AO is quenched by the CuO NPs through fluorescence resonance energy transfer phenomenon. However, dopamine adsorbs on the surface of CuO nanoparticles by getting incorporated into CB[6] host molecules and kicks out AO from curcubit[6]uril pocket, thus, discouraging fluorescence resonance energy transfer phenomenon and thus enhancing fluorescence intensity of AO by a factor of 3. This fluorescence recovery has been utilized to design a new detection system for dopamine. The assay, measured at fluorescence excitation and emission wavelengths of 480 nm and 520 nm respectively, works in the 0–40 μM concentration range of dopamine with 40 nM limit of detection. This method is not interfered by ascorbic acid, uric acid, glucose, tryptophan and acetaminophen. The proposed method provides a good recovery from synthetic samples and shows good stability.
A New Facial Homoleptic Tris‐cyclometalated Iridium(III) Complex with Oxygen‐bridged Triarylamine Units
Authors: Zhang Xinghua , Cao Yibo , Song Jialiang , Li Kang , Jiang Qibin , Yuan Aihua , Shi Chao 
Published: April 2020

AbstractA new facial homoleptic tris‐cyclometalated phosphorescent iridium(III) complex Ir(ppyNO)3 featuring three oxygen‐bridged triarylamine units has been synthesized via an efficient Suzuki–Miyaura cross‐coupling reaction of oxygen‐bridged triarylamine unit based boron reagent 1‐b with corresponding tribrominated iridium(III) complex Ir‐Br. It can not only show an effective green light emission, but also display a narrower full width at half maximum (FWHM=57 nm) and better solubility than that of the classical complex fac‐Ir(ppy)3 (FWHM=82 nm, ppy=2‐phenylpyridine). Furthermore, a longer emission lifetime (τ=1201 ns) of Ir(ppyNO)3 in polystyrene (PS) film can be found than that (τ=45 ns) in CH2Cl2 solution. In addition, the lowest triplet state (T1) of Ir(ppyNO)3 can exhibit both metal‐to‐ligand charge transfer (3MLCT) and intraligand charge transfer (3ILCT) excited state character according to DFT calculations.
Interaction of a Weak Acid Cation Exchange Resin (Dowex Mac 3H) with the Belousov‐Zhabotinsky Reaction and Estimation of Metal Ions
Authors: Rashid Sna , Ganaie Nadeem B. , Peerzada Ghulam M. 
Published: April 2020

AbstractThe work pertains to the study on direct and indirect interaction of a macroporous weak acid cation exchange resin‐Dowex Mac 3H form with Belousov‐Zhabotinsky (BZ) reaction based on malonic acid‐cerium‐bromate‐sulfuric acid system. In the direct mode, the above reaction was perturbed by adding 10% (w/w) of Dowex Mac 3H at three different time intervals, i. e., before the start of induction period, during the induction period and after the commencement of oscillations. This mode of interaction was studied to investigate the effect of heterogeneity on the dynamics of BZ reaction. The indirect interaction of the resin was studied by interacting the resin individually with the optimized metal catalyst for a particular period of time after which the supernatant was used as initial reagent in the otherwise optimized BZ system. The interaction was monitored with respect to the change in oscillatory parameters before and after loading the resin with metal catalyst. The selectivity of the resin towards cerium and iron (ferroin) was studied through the said BZ reaction using potentiometry as the main technique. It was found that resin is more selective towards ferroin. The selectivity of the resin towards the various metal ions was followed by their estimation using UV‐Visible spectrophotometry. The effect of solvents on the ion exchange capacity (IEC) of the resin was also studied through the BZ reaction. Some solvents increased its IEC while others decreased it. The potentiometric results obtained were validated by spectroscopic findings and electrochemical studies.
Water‐Promoted Synthesis of Azepino[3,4,5‐cd]indole Analogues via Pictet‐Spengler Reaction
Authors: Zhang Shuaizhong , Cai Yunrui , Zou Hongbin 
Published: April 2020

AbstractPictet‐Spengler reaction is an important strategy for the chemical or biosynthetic construction of alkaloids. Various suitable catalysts have thus been developed to drive the reaction. We herein report for the first time that water could directly catalyze the Pictet‐Spengler reactions of 2‐(1H‐indol‐4‐yl)ethanamines with aldehydes or ketones to generate azepino[3,4,5‐cd]indoles. Notably, this protocol is environmentally benign and highly practical with a wide substrate scope and promising gram‐scale applications. A plausible mechanism for this catalytic reaction is proposed to provide insights and potentially open a new avenue for organic synthesis.
Electrochemically Oxidative Coupling of S‐H/S‐H for S‐S Bond Formation: A Facile Approach to Diacid‐disulfides
Authors: Sun Xue‐Jie , Yang Shang‐Feng , Wang Zhi‐Tong , Liang Sen , Tian Hong‐Yu , Yang Shao‐Xiang , Liu Yong‐Guo , Sun Bao‐Guo , Zeng Cheng‐Chu 
Published: April 2020

AbstractA green electrochemical method of preparing diacid‐disulfides has been developed, in which an S−S bond is formed by electrochemically oxidative coupling of S−H/S−H employing redox active NaI as mediator. The reactions are carried out in a simple undivided cell under constant current condition at room temperature and complete in 1.3 h to afford a series of diacid‐disulfides with up to 97 % yields.
Silver Nanoparticles Derived from Albizia lebbeck Bark Extract Demonstrate Killing of Multidrug‐Resistant Bacteria by Damaging Cellular Architecture with Antioxidant Activity
Authors: Das Mahapatra Ananya , Patra Chiranjit , Mondal Joy , Sinha Chittaranjan , Chandra Sadhukhan Provash , Chattopadhyay Debprasad 
Published: April 2020

AbstractSilver nanoparticles (Ag‐NP‐AE) are synthesized and stabilized by the extract of an ethnomedicine, Albizia lebbeck bark aqueous extract (AE). Ag‐NP‐AE is active against several multidrug‐resistant (MDR) clinical isolates. The nanoparticles are characterized by UV‐vis spectroscopy, Fourier‐transform infrared spectroscopy (FTIR), Dynamic light scattering (DLS), Scanning electron microscope (SEM), Transmission electron microscope (TEM) and X‐ray diffraction (XRD) studies. The antibacterial potency of Ag‐NP‐AE is determined by Disc diffusion, Agar and Broth dilution assays against 14 MDR isolates along with their minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). The growth kinetics was determined by quantification of colonies; while toxicity by quantification of viable cells. The Ag‐NP‐AE shows free‐radical scavenging activity at 15–20 μM and is non‐toxic up to 50 μM but demonstrated significant antibacterial activity against all the test isolates with zone diameter of 10.4–19.5 mm and MIC of 0.5–0.84 μM (0.085‐0.143 μg); while the zone diameter with AE was 10.2–15 mm and MIC of 128–1024 μg/mL, respectively; while 100 % killing was observed at 0.50 μM within 2–4 h of exposure due to damage of cellular architectures.
Electric Field Effects on the Adsorption of Dopamine Species on Ag(111): DFT Investigation of Interaction Mechanism
Authors: Rossi‐Fernández Ana C. , Meier Lorena A. , Domancich Nicolás F. , Castellani Norberto J. 
Published: April 2020

AbstractThe study of interactions between dopamine (DA) and noble metal surfaces as Ag, is envisaged as a fundamental factor to attain more efficient electrochemical sensor materials. We describe, in the framework of Density Functional Theory, the adsorption of four dopamine species, neutral (NDA), zwitterionic (ZDA), protonated (PDA) and deprotonated (DPDA) species on Ag(111), upon the application of an external electric field (E), a fact of pertinence for electrochemistry tests. The ZDA and PDA species show relatively large binding energies of about 2.9 eV to 4.6 eV and suffer a significant flatting upon adsorption, compared with DPDA and NDA. The adsorbates binding energy is an increasing function of the applied E for ZDA and PDA species, showing a great change when the results for positive and negative E are compared. An electron transfer is produced from NDA, ZDA and PDA species to Ag, while in the case of DPDA an opposite behavior is obtained. As the sign of E is modified, an increase of charge values in all DA species is observed. The theoretical results obtained here show that ZDA and PDA species are the most affected DA species upon adsorption on Ag(111) and when non‐zero electric fields are applied.
The association of occupational stress and sleep duration with anxiety symptoms among healthy employees: A cohort study
Authors: Kim Sun‐Young , Shin Young‐Chul , Oh Kang‐Seob , Shin Dong‐Won , Lim Weon‐Jeong , Kim Eun‐Jin , Cho Sung Joon , Jeon Sang‐Won 
Published: April 2020

AbstractThe aim of this study is to identify occupational stress associated with the development of new‐onset anxiety symptoms and the dose–response relationship between sleep duration and the onset of anxiety symptoms. Data from 29,251 healthy employees who had undergone at least two comprehensive health examinations at Kangbuk Samsung Hospital Health Screening Center were analysed. Anxiety symptoms were assessed using the Beck Anxiety Inventory. Occupational stress and sleep duration were measured using a self‐reported questionnaire about total sleep time and the Korean Occupational Stress Scale‐Short Form (KOSS‐SF), respectively. Flexible parametric proportional hazards model used to estimate the hazard ratios. Compared with the groups without case‐level anxiety, discomfort in an organizational climate, high job demands, job insecurity, organizational injustice and lack of reward were associated with the onset of case‐level anxiety. Compared with less than 6 hr of sleep per day, the beneficial level of sleep duration was 7 ≤ to <9 hr a day. Almost all subscales of job stress were associated with the development of anxiety symptoms. In addition, the efficacious level of sleep duration for reducing the onset of future anxiety symptoms was 7 ≤ to <9 hr a day.
Global software development governance: Challenges and solutions
Authors: Manjavacas Antonio , Vizcaíno Aurora , Ruiz Francisco , Piattini Mario 
Published: April 2020

AbstractGlobal software development (GSD) has become a rising software development model in the last few years. Although much research has been performed in terms of GSD management, GSD governance research is scarce at the present time and presents multiple challenges that need to be addressed. In this paper, a systematic mapping study has been conducted, the aim of which was to discover the main issues dealt with in GSD governance literature, as well as to point out the particular research gaps that are still present in this domain. This allowed us to find out new challenges to be addressed, along with possible solutions to these. The results reveal a lack of research in key aspects such as tools, culture, people, and information, all of which provides a great opportunity for future approaches while also highlighting new opportunities in GSD governance research.
Adversarial machine learning for cybersecurity and computer vision: Current developments and challenges
Authors: Xi Bowei 
Published: April 2020

AbstractWe provide a comprehensive overview of adversarial machine learning focusing on two application domains, that is, cybersecurity and computer vision. Research in adversarial machine learning addresses a significant threat to the wide application of machine learning techniques—they are vulnerable to carefully crafted attacks from malicious adversaries. For example, deep neural networks fail to correctly classify adversarial images, which are generated by adding imperceptible perturbations to clean images. We first discuss three main categories of attacks against machine learning techniques—poisoning attacks, evasion attacks, and privacy attacks. Then the corresponding defense approaches are introduced along with the weakness and limitations of the existing defense approaches. We notice adversarial samples in cybersecurity and computer vision are fundamentally different. While adversarial samples in cybersecurity often have different properties/distributions compared with training data, adversarial images in computer vision are created with minor input perturbations. This further complicates the development of robust learning techniques, because a robust learning technique must withstand different types of attacks.This article is categorized under:
Statistical Learning and Exploratory Methods of the Data Sciences > Clustering and Classification
Statistical Learning and Exploratory Methods of the Data Sciences > Deep Learning
Statistical and Graphical Methods of Data Analysis > Robust Methods
Image‐guided mathematical modeling for pharmacological evaluation of nanomaterials and monoclonal antibodies
Authors: Dogra Prashant , Butner Joseph D. , Nizzero Sara , Ruiz Ramírez Javier , Noureddine Achraf , Peláez María J. , Elganainy Dalia , Yang Zhen , Le Anh‐Dung , Goel Shreya , Leong Hon S. , Koay Eugene J. , Brinker C. Jeffrey , Cristini Vittorio , Wang Zhihui 
Published: April 2020

AbstractWhile plasma concentration kinetics has traditionally been the predictor of drug pharmacological effects, it can occasionally fail to represent kinetics at the site of action, particularly for solid tumors. This is especially true in the case of delivery of therapeutic macromolecules (drug‐loaded nanomaterials or monoclonal antibodies), which can experience challenges to effective delivery due to particle size‐dependent diffusion barriers at the target site. As a result, disparity between therapeutic plasma kinetics and kinetics at the site of action may exist, highlighting the importance of target site concentration kinetics in determining the pharmacodynamic effects of macromolecular therapeutic agents. Assessment of concentration kinetics at the target site has been facilitated by non‐invasive in vivo imaging modalities. This allows for visualization and quantification of the whole‐body disposition behavior of therapeutics that is essential for a comprehensive understanding of their pharmacokinetics and pharmacodynamics. Quantitative non‐invasive imaging can also help guide the development and parameterization of mathematical models for descriptive and predictive purposes. Here, we present a review of the application of state‐of‐the‐art imaging modalities for quantitative pharmacological evaluation of therapeutic nanoparticles and monoclonal antibodies, with a focus on their integration with mathematical models, and identify challenges and opportunities.This article is categorized under:
Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease
Diagnostic Tools > in vivo Nanodiagnostics and Imaging
Nanotechnology Approaches to Biology > Nanoscale Systems in Biology
Dynamic in vitro intestinal barrier model coupled to chip-based liquid chromatography mass spectrometry for oral bioavailability studies
Authors: Santbergen Milou J. C. , van der Zande Meike , Gerssen Arjen , Bouwmeester Hans , Nielen Michel W. F. 
Published: April 2020

AbstractIn oral bioavailability studies, evaluation of the absorption and transport of drugs and food components across the intestinal barrier is crucial. Advances in the field of organ-on-a-chip technology have resulted in a dynamic gut-on-a-chip model that better mimics the in vivo microenvironment of the intestine. Despite a few recent integration attempts, ensuring a biologically relevant microenvironment while coupling with a fully online detection system still represents a major challenge. Herein, we designed an online technique to measure drug permeability and analyse unknown product formation across an intestinal epithelial layer of Caco-2 and HT29-MTX cells cultured on a flow-through Transwell system, while ensuring the quality and relevance of the biological model. Chip-based ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) was coupled to the dynamic Transwell system via a series of switching valves, thus allowing alternating measurements of the apical and basolateral sides of the in vitro model. Two trap columns were integrated for online sample pre-treatment and compatibility enhancement. Temporal analysis of the intestinal permeability was successfully demonstrated using verapamil as a model drug and ergotamine epimers as a model for natural toxins present in foods. Evidence was obtained that our newly developed dynamic system provided reliable results versus classical static in vitro models, and moreover, for the first time, epimer-specific transport is shown for ergotamine. Finally, initial experiments with the drug granisetron suggest that metabolic activity can be studied as well, thus highlighting the versatility of the bio-integrated online analysis system developed.
Determination of fiber saturation point of rattan (Calamus simplicifolius) using the LF-NMR and two conventional methods
Authors: Yang Limei , Tian Genlin , Yang Shumin , Shang Lili , Liu Xing’e , Jiang Zehui 
Published: April 2020

AbstractWater exists in lignocellulosic materials throughout the whole process from the plant growth to raw materials processing and utilization. The fiber saturation point (FSP) is the inflection point of the physical and mechanical properties of lignocellulosic materials and has an important influence on their physical and mechanical properties. This paper investigates the FSP of Calamus simplicifolius by the low-field nuclear magnetic resonance (LF-NMR) method and two conventional methods including the saturated salt solution method and dynamic vapor sorption (DVS) method. The average FSP values determined by the LF-NMR method, the saturated salt solution method and the DVS method are 38.15%, 32.54% and 28.96%, respectively. The study showed that the FSP values determined by the LF-NMR method were higher than those determined by the two conventional methods. The two conventional methods are simple and cost-effective and are able to directly measure whether the rattan properties are changing with moisture content. From the thermodynamics standpoint, even within the ideal solution limit, free water is present at relative humidity (RH) of less than 100%. Therefore, extrapolation to 100% RH was not strictly correct. The amount of water in rattan in different states could be quantified by the LF-NMR method, and the FSP value was determined by the ratio of the measurements above and below the water melting point. Furthermore, the LF-NMR method is faster and non-destructive compared to the two conventional methods.