bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pivotal Role of the Basic Character of Organic and Salt Catalysts in C−N Bond Forming Reactions of Amines with CO2
Authors: Hulla Martin , Dyson Paul J. 
Published: July 2019

AbstractOrganocatalysts promote a range of C−N bond forming reactions of amines with CO2. Herein, we review these reactions and attempt to identify the unifying features of the catalysts that allows them to promote a multitude of seemingly unrelated reactions. Analysis of the literature shows that these reactions predominantly proceed by carbamate salt formation in the form [BaseH][RR′NCOO]. The anion of the carbamate salt acts as a nucleophile in hydrosilane reductions of CO2, internal cyclization reactions or after dehydration as an electrophile in the synthesis of urea derivatives. The reactions are enhanced by polar aprotic solvents and can be either promoted or hindered by H‐bonding interactions. The predominant role of all types of organic and salt catalysts (including ionic liquids, ILs) is the stabilization of the carbamate salt, mostly by acting as a base. Catalytic enhancement depends on the combination of the amine, the base strength, the solvent, steric factors, ion pairing and H‐bonding. A linear relationship between the base strength and the reaction yield has been demonstrated with IL catalysts in the synthesis of formamides and quinazoline‐2,4‐diones. The role of organocatalysts in the reactions indicates that all bases of sufficient strength should be able to catalyze the reactions. However, a physical limit to the extent of a purely base catalyzed reaction mechanism should exist, which needs to be identified, understood and overcome by synergistic or alternative methods.
Hydrophobic Poly(tert‐butyl acrylate) Photonic Crystals towards Robust Energy‐Saving Performance
Authors: Wu Xingjiang , Hong Ri , Meng Jinku , Cheng Rui , Zhu Zhijie , Wu Guan , Li Qing , Wang Cai‐Feng , Chen Su 
Published: July 2019

AbstractPhotonic crystals (PCs) have been widely applied in optical, energy, and biological fields owing to their periodic crystal structure. However, the major challenges are easy cracking and poor structural color, seriously hindering their practical applications. Now, hydrophobic poly(tert‐butyl acrylate) (P(t‐BA)) PCs have been developed with relatively lower glass transition temperature (Tg), large crack‐free area, excellent hydrophobic properties, and brilliant structure color. This method based on hydrophobic groups (tertiary butyl groups) provides a reference for designing new kinds of PCs via the monomers with relatively lower Tg. Moreover, the P(t‐BA) PCs film were applied as the photoluminescence (PL) enhanced film to enhance the PL intensity of CdSe@ZnS QDs by 10‐fold in a liquid‐crystal display (LCD) device. The new‐type hydrophobic force assembled PCs may open an innovative avenue toward new‐generation energy‐saving devices.
Polymer Nanocontainers for Intracellular Delivery
Authors: Pottanam Chali Sharafudheen , Ravoo Bart Jan 
Published: July 2019

AbstractCarriers for intracellular delivery are required to overcome limitations of therapeutic agents such as low specificity, systemic toxicity, high clearance rate, and low therapeutic index. Nanocontainers comprised of an aqueous core and a polymer shell have received increasing attention because they readily combine stimuli response to improve intracellular payload release and surface modification to enhance selectivity towards the desired region of action. This Minireview summarizes the design and properties of polymer nanocontainers for intracellular delivery, classified according to the polymer architecture.
Luminescence study of LiMgBO3:Dy for γ‐ray and carbon ion beam exposure
Authors: Yerpude Mangesh M. , Chopra Vibha , Dhoble N.S. , Kadam R.M. , Krupski Aleksander R. , Dhoble S.J. 
Published: July 2019

AbstractLiMgBO3:Dy3+, a low Zeff material was prepared using the solution combustion method and its luminescence properties were studied using X‐ray diffraction (XRD), scanning electron microscopy (SEM), thermoluminescence (TL), photoluminescence (PL), Fourier transform infrared spectroscopy, and electron paramagnetic resonance (EPR) techniques. Reitvield refinement was also performed for the structural studies. The PL emission spectra for LiMgBO3:Dy3+ consisted of two peaks at 478 due to the 4F9/2→6H15/2 magnetic dipole transition and at 572 nm due to the hypersensitive 4F9/2→6H13/2 electric dipole transition of Dy3+, respectively. A TL study was carried out for both the γ‐ray‐irradiated sample and the C5+ irradiated samples and was found to show high sensitivity for both. Moreover the γ‐ray‐irradiated LiMgBO3:Dy3+ sample showed linearity in the dose range 10 Gy to 1 kGy and C5+‐irradiated samples show linearity in the fluence range 2 × 1010 to 1 × 1011 ions/cm2. In the present study, the initial rise method, various heating rate method, the whole glow curve method, glow curve convolution deconvolution function, and Chen's peak shape method were used to calculate kinetic parameters to understand the TL glow curve mechanism in detail. Finally, an EPR study was performed to examine the radicals responsible for the TL process.
Distinct gene alterations between Fos‐expressing striatal and thalamic neurons after withdrawal from methamphetamine self‐administration
Authors: Li Xuan , Davis Ian R. , Lofaro Olivia M. , Zhang Jianjun , Cimbro Raffaello , Rubio F. Javier 
Published: July 2019

AbstractBackgroundMethamphetamine (Meth) seeking progressively increases after withdrawal (incubation of Meth craving). We previously demonstrated a role of anterior intralaminar nucleus of thalamus (AIT) to dorsomedial striatum (DMS) projections in this incubation. Here, we examined molecular alterations in DMS and AIT neurons activated (identified by neuronal activity marker Fos) during “incubated” Meth‐seeking relapse test after prolonged withdrawal.MethodsWe trained male rats to self‐administer Meth or saline (control condition) for 10 days (6 hr/day). Using fluorescence‐activated cell sorting, we examined gene expression in Fos‐positive (activated during a 2‐hr relapse test) and Fos‐negative (nonactivated) DMS and AIT neurons.ResultsIn DMS, we found increased mRNA expressions of immediate early genes (IEGs) (Arc, Egr1, Npas4, Fosb), Trkb, glutamate receptors subunits (Gria3, Grin1, Grin2b, Grm1), and epigenetic enzymes (Hdac3, Hdac5, Crebbp) in Fos‐positive neurons, compared with Fos‐negative neurons. In AIT, we found that fewer genes (Egr1, Fosb, TrkB, Grin1, and Hdac5) exhibited increased mRNA expression in Fos‐positive neurons. Unexpectedly, in both brain regions, gene alterations described above also occurred in drug‐naïve saline self‐administration control rats.ConclusionsThese results demonstrated that transcriptional regulations in Fos‐positive neurons activated during the relapse tests are brain region‐specific but are not uniquely associated with drug exposure during the self‐administration training.
HOXA10 induces BCL2 expression, inhibits apoptosis, and promotes cell proliferation in gastric cancer
Authors: Song Chenlong , Han Yang , Luo Huan , Qin Zhiwei , Chen Zhengqian , Liu Yuan , Lu Su , Sun Huimin , Zhou Chongzhi 
Published: July 2019

AbstractHomeobox A10 (HOXA10) has been implicated critical for the promotion of carcinogenesis, but the underlying mechanism between HOXA10 and malignant gastric cancer (GC) phenotype remains elusive. In the present study, we analyzed and validated that HOXA10 and BCL2 expressions were elevated both at the mRNA and protein levels in GC tissues. Upregulated HOXA10 promoted GC cell proliferation with reduced apoptosis in vitro and accelerated GC tumor growth in vivo. Bioinformatics analysis and quantitative real‐time polymerase chain reaction (qRT‐PCR) experiment inferred that HOXA10 might upregulate the expression of BCL2. By performing western blot, chromatin immunoprecipitation and quantitative PCR (ChIP‐qPCR), and rescue experiment, we found that HOXA10 might bind to BCL2 promoter region, induce its expression, and thus inhibit intrinsic apoptosis pathway. Moreover, higher expression of HOXA10 and BCL2 predicted poor overall survival (OS) in GC patients. In summary, our study indicated that HOXA10 was upregulated in GC, and that HOXA10 might promote cell proliferation by elevating BCL2 expression and inhibiting apoptosis.
Repurposing the Pummerer Rearrangement: Determination of Methionine Sulfoxides in Peptides
Authors: Woodroofe Carolyn C. , Ivanic Joseph , Monti Sarah , Levine Rodney L. , Swenson Rolf E. 
Published: July 2019

AbstractThe reversible oxidation of methionine residues in proteins has emerged as a biologically important post‐translational modification. However, detection and quantitation of methionine sulfoxide in proteins is difficult. Our aim is to develop a method for specifically derivatizing methionine sulfoxide residues. We report a Pummerer rearrangement of methionine sulfoxide treated sequentially with trimethylsilyl chloride and then 2‐mercaptoimidazole or pyridine‐2‐thiol to produce a dithioacetal product. This derivative is stable to standard mass spectrometry conditions, and its formation identified oxidized methionine residues. The scope and requirements of dithioacetal formation are reported for methionine sulfoxide and model substrates. The reaction intermediates have been investigated by computational techniques and by 13C NMR spectroscopy. These provide evidence for an α‐chlorinated intermediate. The derivatization allows for detection and quantitation of methionine sulfoxide in proteins by mass spectrometry and potentially by immunochemical methods.
New Type of Columnar Liquid Crystal Superlattice in Double‐Taper Ionic Minidendrons
Authors: Li Ya‐Xin , Fan Fang‐Fang , Wang Jie , Cseh Liliana , Xue Min , Zeng Xiang‐Bing , Ungar Goran 
Published: July 2019

AbstractWedge‐shaped molecules, such as dendrons, are among the most important building blocks for directed supramolecular self‐assembly. Here we present a new approach aimed at widening the range and complexity of potential mesophases by introducing double‐tapered mesogens. Two series of compounds are presented, both alkali metal salts (Li, Na, Cs) of 3,4,5‐tris‐alkoxybenzoic acid with a second taperedtris‐alkoxyaryl group attached at the end of an alkoxy chain. The double‐tapered compounds all display an unusual hexagonal columnar phase consisting of one ionic and three non‐ionic columns per unit cell. The cation size has an unexpectedly drastic effect on unit cell size. Unlike most columnar phases, the current phases show unusually high dimensional stability on heating, and high stiffness in spite of being 80–85 % aliphatic, attributed to their molecular topology. The described approach may lead to co‐assemblies of multifunctional materials, for example, parallelp‐ andn‐semiconducting nanowires or parallel ionic and electronic conductors.
Abnormal Nucleophilic Substitution on Methoxytropone Derivatives: Steric Strategy to Synthesize 5‐Substituted Azulenes
Authors: Kumar Neha Rani , Agrawal Abhijeet R. , Zade Sanjio S. 
Published: July 2019

AbstractAzulene is a non‐alternant non‐benzenoid aromatic system, and in turn, it possesses unusual photophysical properties. Azulene‐based conjugated systems have received increasing interest in recent years as optoelectronic materials. Despite the routes available for the preparation of substituted azulene derivatives, there remain few methods that allow regioselective substitution on the seven‐membered ring of azulenes due to the subtle reactivity difference among the various positions. This report explores the reactivity of substituted tropolones as the azulene precursors and also provides a new method to create 5‐substituted azulenes. The reaction of cyanoacetate enolate with unsubstituted 2‐methoxytropone affords azulene through the attack of the nucleophile on the C‐2 center (normal pathway). We have observed that 3‐substituted 2‐methoxytropones undergo steric‐guided nucleophilic addition at the C‐7 center (abnormal pathway) to afford 5‐substituted azulene derivatives. Based on this observation and DFT calculation, a new synthetic strategy is devised for the regioselective synthesis of 5‐substituted multifunctional azulenes, which cannot be accessed by any other method.
The effects of modes of hydrogen input and reactor configuration on reaction rate and H2 efficiency in the catalytic hydrogenation of alkynol to alkenol
Authors: Navarro‐Fuentes Francisca , Keane Mark , Ni Xiong‐Wei 
Published: July 2019

AbstractHydrogenation often involves three phases where hydrogen‐on‐demand is the typical mode of operation in industrial scale reactors. In research labs and publications, however, continuous hydrogen flow has been used. This paper investigates the effect of such modes of operation on reaction rate using a selective hydrogenation of 3‐butyn‐2‐ol over Pd/Al2O3 to obtain 3‐buten‐2‐ol as the model reaction. The two modes of operation were first tested in a commercial PARR stirred tank reactor and then repeated in an oscillatory baffled reactor (OBR) in order to validate the experimental results. Our investigation demonstrates that an enhanced reaction performance and 10 times better H2 efficiency were obtained when the pressure was maintained constant during the reaction by feeding gas as required, ie hydrogen‐on‐demand mode. The method of a continuous flow of hydrogen in hydrogenation means that excess hydrogen is vented out when operating at ambient pressures or builds up at elevated pressures. Our work also enables a comparison of reactor designs on reactor performance, and three times higher H2 efficiency and 2.3 times shorter residence time were achieved when using the OBR instead of the PARR due to its enhanced and uniform mixing, regardless of the mode of operation.
Toward Microfluidic Label‐Free Isolation and Enumeration of Circulating Tumor Cells from Blood Samples
Authors: Raillon Camille , Che James , Thill Sandy , Duchamp Margaux , Desbiolles Benoît X. E. , Millet Arnaud , Sollier Elodie , Renaud Philippe 
Published: July 2019

AbstractThe isolation, analysis, and enumeration of circulating tumor cells (CTCs) from cancer patient blood samples are a paradigm shift for cancer patient diagnosis, prognosis, and treatment monitoring. Most methods used to isolate and enumerate these target cells rely on the expression of cell surface markers, which varies between patients, cancer types, tumors, and stages. Here, we propose a label‐free high‐throughput platform to isolate, enumerate, and size CTCs on two coupled microfluidic devices. Cancer cells were purified through a Vortex chip and subsequently flowed in‐line to an impedance chip, where a pair of electrodes measured fluctuations of an applied electric field generated by cells passing through. A proof‐of‐concept of the coupling of those two devices was demonstrated with beads and cells. First, the impedance chip was tested as a stand‐alone device: (1) with beads (mean counting error of 1.0%, sizing information clearly separated three clusters for 8, 15, and 20 um beads, respectively) as well as (2) with cancer cells (mean counting error of 3.5%). Second, the combined setup was tested with beads, then with cells in phosphate‐buffered saline, and finally with cancer cells spiked in healthy blood. Experiments demonstrated that the Vortex HT chip enriched the cancer cells, which then could be counted and differentiated from smaller blood cells by the impedance chip based on size information. Further discrimination was shown with dual high‐frequency measurements using electric opacity, highlighting the potential application of this combined setup for a fully integrated label‐free isolation and enumeration of CTCs from cancer patient samples. © 2019 International Society for Advancement of Cytometry
Bandwidth estimation in high mobility scenarios of IEEE 802.11 infrastructure‐less mobile ad hoc networks
Authors: Pal Pankaj , Tripathi Sachin , Kumar Chiranjeev 
Published: July 2019

SummaryBandwidth estimation in mobile ad hoc networks (MANET), where each node can move randomly and is capable of frequently changing its link with other nodes, is a challenging task. Motivation of this work is in contrast with TCP new‐reno which decreases the congestion window both in the event of link failure and congestion, which in the case of packet loss due to link failure should be close to available channel bandwidth. The proposed novel approach capture the node's mobility behavior in broadcast and unicast scenarios of IEEE 802.11 standard to efficiently estimate the sender's window size. This proposal introduces a data structure and source‐to‐destination path stability metric to imitate the mobility behavior of network and presents the analytic characterization of steady‐state throughput as a function of packet loss, round trip time, and path stability over IEEE 802.11 infrastructure‐less MANET. The performance is evaluated over random‐walk, random‐waypoint, and Gauss‐Markov mobility models in 2D and 3D environments using QualNet 7.4 network simulator. The proposed analytical model is also evaluated through two‐tailed statistical test. Analytical, statistical, and simulation‐based comparisons demonstrate the effectiveness of proposed method in high‐mobility scenarios.
SEBAP: A secure and efficient biometric‐assisted authentication protocol using ECC for vehicular cloud computing
Authors: Kumar Vinod , Ahmad Musheer , Kumari Adesh , Kumari Saru , Khan M. K. 
Published: July 2019

SummaryVehicular cloud computing (VCC) is an emerging research area of cloud and vehicular networking. It equips vehicles with networking and sensing capacities for vehicle‐to‐vehicle or vehicle‐to‐infrastructure communication with available roadside infrastructure. It is significantly utilized in traffic management and road safety using cloud applications. To obtain impressive networking in vehicular communication, there is a need of hybrid technological approach in the form of VCC utilizing vehicular resources, cloud infrastructure, and Internet of Things (IoT) environment. VCC presents smart vehicular communication structure and maintains autonomous traffic, improved vehicle control, and enhanced system security. Security and privacy has appeared to be a major concern in VCC because of involvement of unknown vehicles and infrastructure via public network. In this article, we propose a biometric and elliptic curve cryptography (ECC)‐assisted authentication framework for VCC. The presented framework obtains most of security features and attributes for secure communication in the presence of active and passive attackers. Further, we provide formal security model and its proof, which is based on random oracle model. We compare the performance of our protocol with similar frameworks in the same environment. Our analysis indicates that the presented framework is secure and efficient in terms of communication and computation overheads. As a result, the presented protocol can be utilized in VCC.
Dependability analysis for characterizing Google cluster reliability
Authors: Mesbahi Mohammad Reza , Rahmani Amir Masoud , Hosseinzadeh Mehdi 
Published: July 2019

SummaryCloud solutions are emerging as a new suitable way of transforming traditional IT data centers to highly available and reliable computing resources for hosting critical applications and data. However, software and hardware failures are a common problem in cloud datacenters that can lead to harmful damages. In this paper, we analyze the physical server failures in the Google cloud datacenter. We study the Google cluster properties to investigate the relationship among physical servers' failure rate and jobs failure events. The failure rate of Google cluster executed jobs and servers is taken into consideration during a 29‐day period.We present a reliability model for Google cluster physical machines using the continuous time Markov chains according to this observation. We attempt to analyze the obtained model through SHARPE software packages to improve the understanding of failure events in the Google cloud cluster. We also explore the cluster availability based on parameters like steady‐state availability, steady‐state unavailability, mean time to failure, and mean time to repair in the Google cluster.
Enhanced Electrocatalytic Activity of Ni‐CNT Nanocomposites for Simultaneous Determination of Epinephrine and Dopamine
Authors: Manivel Perumal , Thamilselvan Annadurai , Rajagopal Venkatachalam , Nesakumar Noel , Suryanarayanan Vembu 
Published: July 2019

AbstractA promising electrochemical sensor based nickel‐carbon nanotube (Ni‐CNT) modified on glassy carbon (GC) electrode had been developed and the properties of the modified electrode were characterized by multispectroscopic analysis. The fabricated sensor (GC/Ni‐CNT) electrode was utilized to determine the catecholamines such as epinephrine and dopamine simultaneously. Differential pulse voltammetry and amperometry were used to verify the electrochemical behavior of the studied compounds. The GC/Ni‐CNT based amperometric sensor showed a wide linear range and low detection limit with high analytical sensitivity of 8.31 and 6.61 μA μM−1 for EP and DA, respectively which demonstrates better characteristics compared to other electrodes reported in the literature. Further, no significant change in amperometric current response was observed in presence of biological interference species such as glucose, cysteine, citric acid, uric acid and ascorbic acid in the detection of EP and DA. The utility of this GC/Ni‐CNT electrode was well established for the determination of EP and DA in human urine samples.
Ecosystem Controls on Methylmercury Production by Periphyton Biofilms in a Contaminated Stream: Implications for Predictive Modeling
Authors: Schwartz Grace E. , Olsen Todd A. , Muller Katherine A. , Brooks Scott C. 
Published: July 2019

Abstract
Periphyton biofilms produce a substantial fraction of the overall monomethylmercury (MMHg) flux in East Fork Poplar Creek, an industrially contaminated, freshwater creek in Oak Ridge, Tennessee. We examined periphyton MMHg production across seasons, locations, and light conditions using mercury stable isotopes. Methylation and demethylation rate potentials (km, trans av and kd, trans av, respectively) were calculated using a transient availability kinetic model. Light exposure and season were significant predictors of km, trans av, with greater values in full light exposure and in the summer. Season, light exposure, and location were significant predictors of kd, trans av, which was highest in dark conditions, in the spring, and at the upstream location. Light exposure was the controlling factor for net MMHg production, with positive production for periphyton grown under full light exposure and net demethylation for periphyton grown in the dark. Ambient MMHg and km, trans av were significantly correlated. Transient availability rate potentials were 15 times higher for km and 9 times higher for kd compared to full availability rate potentials (km, full av and kd, full av) calculated at 1 d. No significant model for the prediction of km, full av or kd, full av could be constructed using light, season, and location. In addition, there were no significant differences among treatments for the full availability km, full av, kd, full av, or net MMHg calculated using the full availability rate potentials. km, full av was not correlated with ambient MMHg concentrations. The present results underscore the importance of applying transient availability kinetics to MMHg production data when estimating MMHg production potential and flux. Environ Toxicol Chem 2019;38:2426–2435. © 2019 SETAC
Abstract
The transient availability kinetic model predicts net positive MMHg production in light conditions and net negative MMHg production in dark conditions, across seasons and locations in East Fork Poplar Creek periphyton.