bluuebunny/crossref_metadata_2025_split huggingface dataset:
In vitro characterization of the serotonin biosynthesis pathway by CEST MRI
Authors: Oglesby Ryan T. , Lam Wilfred W. , Stanisz Greg J. 
Published: April 2020

PurposeThe diagnosis of monoamine‐related psychiatric disorders is based on the phenomenological evaluation of symptoms and behavior by trained clinicians. The CEST technique can be sensitive to monoamines such as serotonin. This study quantifies the CEST properties of the compounds in the serotonin biosynthesis pathway with the goal of developing noninvasive techniques aimed at advancing the diagnostic assessment of serotonin dysfunction.MethodsSaturation transfer‐weighted images of L‐tryptophan, 5‐hydroxytryptophan, serotonin, 5‐hydroxyindoleacetic acid, and melatonin phantoms were acquired over a range of saturation amplitudes and frequency offsets along with observed T1, T2, and B1 efficiency maps at physiological temperature and pH of 5.5, 6.7, and 7.4. The CEST and MT data were fitted to a three‐pool Bloch–McConnell model of exchange to estimate the model parameters.ResultsAt a pH of 5.5, tryptophan, 5‐hydroxytryptophan and serotonin exhibited significant CEST contrast at resonance frequency offset, Δω between 2.64 ppm and 2.71 ppm, and magnetization transfer ratio asymmetry amplitudes up to 20% per 30 mM. At a pH of 7.4, all molecules exhibited significant CEST contrast between 5.11 ppm and 5.47 ppm, and magnetization transfer ratio asymmetry amplitudes up to 9.5% per 30 mM. At a pH of 6.7, all studied compounds except melatonin exhibited a CEST peak from each of the preceding two pHs.ConclusionAt a pH of 5.5, tryptophan, 5‐hydroxytryptophan, and serotonin CEST contrast originates from the
side chain, whereas at a pH of 7.4, CEST contrast is due to the chemical exchange between water and the NH proton on the indole ring. The data in this study could be used to inform future investigations aimed at detecting and measuring in vivo serotonin.
Accelerating GluCEST imaging using deep learning for B0 correction
Authors: Li Yiran , Xie Danfeng , Cember Abigail , Nanga Ravi Prakash Reddy , Yang Hanlu , Kumar Dushyant , Hariharan Hari , Bai Li , Detre John A. , Reddy Ravinder , Wang Ze 
Published: April 2020

PurposeGlutamate weighted Chemical Exchange Saturation Transfer (GluCEST) MRI is a noninvasive technique for mapping parenchymal glutamate in the brain. Because of the sensitivity to field (B0) inhomogeneity, the total acquisition time is prolonged due to the repeated image acquisitions at several saturation offset frequencies, which can cause practical issues such as increased sensitivity to patient motions. Because GluCEST signal is derived from the small z‐spectrum difference, it often has a low signal‐to‐noise‐ratio (SNR). We proposed a novel deep learning (DL)‐based algorithm armed with wide activation neural network blocks to address both issues.MethodsB0 correction based on reduced saturation offset acquisitions was performed for the positive and negative sides of the z‐spectrum separately. For each side, a separate deep residual network was trained to learn the nonlinear mapping from few CEST‐weighted images acquired at different ppm values to the one at 3 ppm (where GluCEST peaks) in the same side of the z‐spectrum.ResultsAll DL‐based methods outperformed the “traditional” method visually and quantitatively. The wide activation blocks‐based method showed the highest performance in terms of Structural Similarity Index (SSIM) and peak signal‐to‐noise ratio (PSNR), which were 0.84 and 25dB respectively. SNR increases in regions of interest were over 8dB.ConclusionWe demonstrated that the new DL‐based method can reduce the entire GluCEST imaging time by ˜50% and yield higher SNR than current state‐of‐the‐art.
Imidazolium functionalized poly(vinyl alcohol) membranes for direct methanol alkaline fuel cell applications
Authors: Albayrak Arı Gülşen , Şimşek Öykü 
Published: April 2020

AbstractIn this study, imidazolium functionalized poly(vinyl alcohol) (PVA) was synthesized by acetalization and direct quaternization reaction. Afterwards, composite anion exchange membranes based on imidazolium‐ and quaternary ammonium‐ functionalized PVA were used for direct methanol alkaline fuel cell applications. 1H NMR and Fourier transform infrared spectroscopy data indicated that imidazole functionalized PVA was successfully synthesized. Inductively coupled plasma mass spectrometry data demonstrated that the imidazolium structure was efficiently obtained by direct quaternization of the imidazole group. Composite anion exchange membranes were fabricated by application of the functionalized PVA solution on the surface of porous polycarbonate (PC) membranes. Fuel cell related properties of all prepared membranes were investigated systematically. The imidazolium functionalized composite membrane (PVA‐Im/PC) exhibited higher ionic conductivity (7.8 mS cm−1 at 30 °C) despite a lower water uptake and ion exchange capacity value compared to that of quaternary ammonium. In addition, PVA‐Im/PC showed the lowest methanol permeation rate and the highest membrane selectivity as well as high alkaline and oxidative stability. Dynamic mechanical analysis results reveal that both composite membranes were mechanically resistant up to 107 Pa at 140 °C. The superior performance of imidazolium functionalized PVA composite membrane compared to quaternary ammonium functionalized membrane makes it a promising candidate for direct methanol alkaline fuel cell applications. © 2020 Society of Chemical Industry
Crystal Morphology of 3,4‐Bis(3‐nitrofurazan‐4‐yl)furoxan in Methanol and Acetic Acid/Water Solutions by Spiral Growth Mechanism
Authors: Song Liang , Zhao Feng‐Qi , Xu Si‐Yu , Ju Xue‐Hai , Ye Cai‐Chao 
Published: April 2020

AbstractThe crystal morphologies of 3,4‐bis(3‐nitrofurazan‐4‐yl)furoxan (DNTF) are diamond‐shaped in methanol as well as in acetic acid/water (7 : 3) solutions. There is a possibility that the two solutions have similar effects on the morphologies of DNTF. To explain this phenomenon, a spiral growth model in consideration of adhesion energy, temperature, solubility, and supersaturation was implemented to predict the crystal morphologies of the DNTF in the two solutions. The interface model based on the experimental situation was constructed as a periodic supercell. The molecular dynamics simulation was performed to obtain the attachment energy at the equilibrium structure. The results indicate that the (001), (111) and (11
) faces become dominantly exposed faces, while the (011), (101) and (110) faces disappear or occupy a very small area in both solutions. The prediction results are in remarkable agreement with the experimental observations in cooling crystallization. The simulation method can provide theoretical support for the crystallization process of DNTF.
Relative bioavailability and pharmacokinetic comparison of calcium glucoheptonate with calcium carbonate
Authors: Wiria MSS , Tran Hung Manh , Nguyen Phuc H. B. , Valencia Olivia , Dutta Surajit , Pouteau Etienne 
Published: April 2020

AbstractAdequate calcium intake is important for the prevention of bone loss and osteoporosis. For some populations such as those of Southeast Asia where calcium intake is very low, supplements represent a suitable dietary source of calcium. The objective of this study was to compare the relative oral bioavailability of calcium from calcium glucoheptonate, a highly soluble calcium salt containing 8.2% of elemental calcium, to that of calcium carbonate. A single‐dose, randomized‐sequence, open‐label, two‐period crossover study, with a 7‐day washout period, was conducted in 24 Indonesian healthy adult volunteers. After a 12‐hour (overnight) fast, subjects received either two oral ampoules of 250 mg/10 mL of calcium glucoheptonate each or one effervescent tablet of calcium carbonate containing 500 mg of elemental calcium. The relative oral bioavailability of calcium from calcium glucoheptonate as compared to calcium carbonate was 92% within 6 hours and 89% within 12 hours after study drug administration. The 90% confidence intervals for the mean test/reference ratios of the maximum plasma concentration and the area under the concentration‐time curve at 12 hours post‐administration were 77.09%–120.31% and 60.58%–122.30%, respectively. Five subjects experienced a total of eight adverse events which were all mild and transient; no serious adverse events or deaths were reported. These results indicate that calcium glucoheptonate is associated with a high relative bioavailability of calcium compared to calcium carbonate, and is well‐tolerated. Calcium glucoheptonate might thus be a potential choice for calcium supplementation in Southeast Asian populations.
Position of Disulfide Bond Determines the Properties of Novel Stimuli‐Responsive Cationic Lipids
Authors: Puchkov Pavel A. , Shmendel Elena V. , Luneva Anastasia S. , Zenkova Marina A. , Maslov Michael A. 
Published: April 2020

AbstractEffective release of nucleic acids from the lipoplexes to the cytoplasm is one of the challenges of gene delivery systems. Stimuli‐responsive groups such as disulfide linkages offer an attractive solution. We designed two novel polycationic amphiphiles with disulfide links (2S3 and 2S4) and compared their transfection efficiency with their nonredox‐sensitive analogue 2X3. The stability and redox sensitivity of lipoplexes formed by cationic liposomes 2X3, 2S3, and 2S4 with plasmid DNA were studied using different destabilizing agents, such as glutathione, 1,4‐dithiothreitol, and heparin using electrophoresis and fluorescent titration assays. Further, we performed size and ζ‐potential analysis of cationic liposomes and lipoplexes, and also compared their transfection efficiencies in the presence of the destabilizing agents. Depending on their structure, disulfide lipoplexes exhibited different sensitivity towards the destabilizing agents. Moreover, high redox‐sensitivity correlated well with higher transfection activity into HEK293 cells.
CuII‐Tyrosinase Enzyme Catalyst‐Mediated Synthesis of 2‐Thioxopyrimidine Derivatives with Potential Mosquito Larvicidal Activity: Spectroscopic and Computational Investigation as well as Molecular Docking Interaction with OBPs of Culex quinquefasciatus
Authors: SathishKumar Chidambaram , Keerthana Selvaraj , Ahamed Anis , Arif Ibrahim A. , SurendraKumar Radhakrishnan , Idhayadhulla Akbar 
Published: April 2020

AbstractA series of 2‐thioxo pyrimidine derivatives 1, (1 a‐1 e) and 2, (2 a‐2 e) were synthesized via Biginelli reaction by using CuII‐tyrosinase (CuII‐Tyr) as an enzyme catalyst in up to 80–92% yield. The compounds 1, (1 a‐1 e) and 2, (2 a‐2 e) were characterized by IR, 1H NMR, 13C NMR, mass spectra and elemental analyses. The synthesized compounds 1, (1 a‐1 e) and 2, (2 a‐2 e) were screened for mosquito larvicidal activity against Culex quinquefasciatus. The compound 2 a was 80% mortality at 100 μg/mL with the LD50 value of 55.94 μg/mL than the control Permethrin 60.03 μg/mL respectively. Molecular docking studies of synthesized compounds were carried out and the results proposed that the compound 2 a as a potential candidate to mosquito odorant‐binding protein 3OGN inhibitors. In addition, computational studies, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies showed that the charge transfer occurs in the inside of the molecule and also gives the chemical reactivity descriptors, and molecular electrostatic potential (MESP) is also calculated. Therefore, experimental and theoretical studies were well supported for the compound 2 a as a potential larvicide activity aganist mosquito larvae of Culex quinquefasciatus.
Synthesis, Characterization, Photophysical and Photochemical Properties of Novel Phthalocyanines
Authors: Demirbaş Ümit 
Published: April 2020

AbstractThe benzothiazole substituted phthalonitrile (3) and non‐peripherally tetra benzothiazole substituted metal‐free (4), zinc(II) (5) and lead(II) phthalocyanine (6) complexes were prepared. The compounds (3‐6) were characterized by IR, NMR, UV‐Vis and mass spectroscopy data. After synthesis, photochemical and photophysical parameters of the compounds (4‐6) were analyzed to determine photosensitizer performance of them for PDT applications. Firstly, the most suitable solvent for compounds (4‐6) was found by aggregation studies. Then, fluorescence properties were measured in DMF at 1x10−6 M. Singlet oxygen properties were measured in DMF by using 1,3‐diphenylisobenzofuran (DPBF) as a singlet oxygen quencher. Photodegradation properties were measured under light irradiation in DMF at 1x10−5 M. The zinc(II) phthalocyanine (5) had the highest singlet oxygen production capacity (Φ▵=0.62), fluorescence (ΦF=0.25) and photodegradation quantum yield (Φd=3.28x10‐4). The results showed that zinc(II) phthalocyanine (5) has potential for photodynamic therapy applications.
Electrosynthesis of Poly(aniline‐co‐pyrrole‐co‐N‐methylpyrrole) Terpolymer and Poly(aniline‐co‐pyrrole‐co‐N‐methylpyrrole)‐TiO2 Nanocomposite on Steel
Authors: Akdag Abdurrahman 
Published: April 2020

AbstractPoly(aniline‐co‐pyrrole‐co‐N‐methylpyrrole) (P(ANI‐co‐PY‐co‐NMP)) terpolymer film was synthesized in 0.30 M oxalic acid solutions containing 0.05 M aniline +0.05 M pyrrole +0.05 M N‐methylpyrrole. Poly(aniline‐co‐pyrrole‐co‐N‐methylpyrrole)‐TiO2 nanocomposites were synthesized in 0.30 M oxalic acid solutions containing 0.05 M aniline +0.05 M pyrrole+0.05 M N‐methylpyrrole+0.1/0.4/1.0 gL−1 TiO2. Electrochemical syntheses were performed on the carbon steel (CS) elctrode using cyclic voltammetry technique. The terpolymer and nanocomposites were characterized by SEM, EDX, electrochemical impedance spectroscopy (EIS), open circuit potential‐time and anodic polarization techniques. Nanocomposite structures were observed after the addition of TiO2 nanoparticles into terpolymer films and these results was verified via EDX analysis. The results driven by EIS and anodic polarization suggest that, terpolymer and nanocomposite coated electrodes have been shown to have a protective effect against the corrosion of the CS electrode. The nanocomposite coated electrode synthesized in an environment containing 0.4 gL−1 TiO2 was found to have higher corrosion resistance in comparison to uncoated electrode, terpolymer coated electrode and electrodes coated with nanocomposites that is synthesized in environments containing 0.1/1.0 gL−1 TiO2. These results showed that the amount of TiO2 affects the anticorrosive properties of the synthesized nanocomposite.
Synthesis of 2‐Arylbenzoselenazoles from Se‐mediated Redox Condensation of 2‐Chloronitrobenzene and Arylmethyl Chloride
Authors: Gan Haifeng , Cao Mengru , Wu Hongli 
Published: April 2020

AbstractA selenium‐mediated redox condensation of 2‐chloronitrobenzene and arylmethyl chloride to obtain 2‐arylbenzoselenazoles has been realized under metal‐free condition. The reactions proceeded in moderate‐to‐good yields with good functional compatibility and gram‐scale achievement. Primarily mechanistic investigation suggested that key intermediate Bn(Se)nBn II, was first isolated and confirmed by NMR.
Sulfonylation of Five‐Membered Aromatic Heterocycles Compounds through Nucleophilic Aromatic Substitution: Concerted or Stepwise Mechanism?
Authors: Adolfo Cuesta Sebastián , Cordova‐Sintjago Tania , Ramón Mora José 
Published: April 2020

AbstractHeterocyclic sulfones are relevant in medicinal chemistry, drug design and organic synthesis, and the mechanism of sulfonylation of five‐membered heterocycles is not clear. In this work, it is presented a computational study on the mechanism of sulfonylation of five‐membered heterocycles compounds. Concerted and stepwise mechanisms for the nucleophilic aromatic substitution (SNAr) involved in the reaction were examined. Effect of the neighbouring group (NG), heteroatom in the ring (HT), nucleophile (NU), and leaving group (LG) in fourteen reactions were examined. Analysis of the intrinsic reaction coordinate, reaction force, natural bond orbital (NBO) charges and bond indexes give a reasonable insight about the mechanism for the reactions studied. Results revealed activation free energies ranging from 20.8 kcal/mol up to 38.6 kcal/mol. Reaction force analysis showed that structural changes in the reactant are the most important component associated with the energy of activation with more than 60 % of the contribution. Most sulfonylation reactions in this study proceed through a concerted mechanism; only two occur though a stepwise‐Meisenheimer‐intermediate mechanism.
An Overview of Microwave‐Assisted Kabachnik‐Fields Reactions
Authors: Shilpa Thomas , Ann Harry Nissy , Ujwaldev Sankuviruthiyil M. , Anilkumar Gopinathan 
Published: April 2020

AbstractA comprehensive evaluation of MW‐assisted Kabachnik‐Fields reactions (phospha‐Mannich condensation) is done to draw the attention of synthetic chemists towards a greener, solvent‐free and catalyst‐free protocol. The review encompasses the diverse class of α‐aminophosphonates and its derivatives synthesized via one‐pot three component KF reaction, which finds application in various disciplines of chemistry and covers literature up to 2020.
CuO Nanoparticles as a Simple and Efficient Green Catalyst for the Aziridine Ring‐Opening: Examination of a Broad Range of Nucleophiles
Authors: Chatterjee Rana , Santra Sougata , Chakraborty Ghosal Nirnita , Giri Kousik , Zyryanov Grigory V. , Majee Adinath 
Published: April 2020

AbstractIt has been observed that CuO nanoparticles act as effective and reusable catalyst for the ring‐opening reaction of aziridines with a wide range of nucleophiles such as alcohols, thiols, and indoles. The catalytic activity has been tested in large scale reactions. The methodology is applicable in very low catalyst loading. The reaction proceeds under solvent‐free conditions. The catalyst has been used for six consecutive cycles with comparable efficiency. The present methodology could be considered as environmentally benign as indicated by the calculation of E‐factors which are very low in the range of 0.37–1.31.
Crystallinity Variation in Seeded Growth of Gold Nanocrystals: the Role of Additive Ag+
Authors: Zhang Gongguo , Fu Xiaowei , Liu Zhiang , Luan Xiaoqian , Qu Fengli , Zheng Yiqun 
Published: April 2020

AbstractA synthetic case is reported that demonstrates the cationic additive, Ag+, can influence the crystallinity and thus shape of final product during seeded growth of Au nanocrystals. Using single‐crystal Au seeds as reference, the crystallinity difference between seed and final product could be directly compared. In particular, three different types of crystallinity/morphology can be obtained by varying the concentration of Ag+ in the particle growth solutions: single‐crystal quasi‐spheres, multiply twinned particles (MTPs), and protruded MTPs, with no Ag+ added and solution Ag+ /Au3+ ratios of 1 : 20 and 1 : 5, respectively. The reaction kinetics are investigated using extinction spectroscopy, indicating the presence of Ag+ leads to a dampened growth of Au nanocrystals. This principle is validated using single‐crystal Au seeds with different morphology and amounts. We also test the anti‐corrosion performance of as‐prepared Au nanocrystals with different crystallinity by treating them with sodium thiosulfate. Interestingly, in addition to reduction in size, the morphology of single‐crystal ones varies from quasi‐sphere to cube, indicating the anisotropy in oxidative etching of Au nanocrystals.
Iron‐Catalyzed Synthesis of Polyfunctional Pyridines from Ketoxime Carboxylates and Nitrones
Authors: Jiang Rui , Liu Xiang , Mu Yangxiu , Iqbal Zafar , He Lili , Zhai Lijuan , Hou Jing , Yang Minghua , Yang Zhixiang , Tang Dong 
Published: April 2020

AbstractPolyfunctional pyridines are backbone of numerous natural products and pharmaceutical reactive intermediates. We have developed an iron‐catalyzed cyclization reaction between ketoxime carboxylates and nitrones to afford trisubstituted pyridines. Employing this strategy, we have synthesized a number of trisubstituted pyridines with various functional groups in good yields under simple reaction conditions. It is worth mentioning that the nitrones can serve as a novel C1 unit in organic synthesis.
Hybridized 2D Nanomaterials Toward Highly Efficient Photocatalysis for Degrading Pollutants: Current Status and Future Perspectives
Authors: Guan Guijian , Ye Enyi , You Mingliang , Li Zibiao 
Published: April 2020

AbstractOrganic pollutants including industrial dyes and chemicals and agricultural waste have become a major environmental issue in recent years. As an alternative to simple adsorption, photocatalytic decontamination is an efficient and energy‐saving technology to eliminate these pollutants from water environment, utilizing the energy of external light, and unique function of photocatalysts. Having a large specific surface area, numerous active sites, and varied band structures, 2D nanosheets have exhibited promising applications as an efficient photocatalyst for degrading organic pollutants, particularly hybridization with other functional components. The novel hybridization of 2D nanomaterials with various functional species is summarized systematically with emphasis on their enhanced photocatalytic activities and outstanding performances in environmental remediation. First, the mechanism of photocatalytic degradation is given for discussing the advantages/shortcomings of regular 2D materials and identifying the importance of constructing hybrid 2D photocatalysts. An overview of several types of intensively investigated 2D nanomaterials (i.e., graphene, g‐C3N4, MoS2, WO3, Bi2O3, and BiOX) is then given to indicate their hybridized methodologies, synergistic effect, and improved applications in decontamination of organic dyes and other pollutants. Finally, future research directions are rationally suggested based on the current challenges.
Verifying Visibility-Based Weak Consistency
Authors: Krishna Siddharth , Emmi Michael , Enea Constantin , Jovanović Dejan 
Published: April 2020

AbstractMultithreaded programs generally leverage efficient and thread-safe concurrent objects like sets, key-value maps, and queues. While some concurrent-object operations are designed to behave atomically, each witnessing the atomic effects of predecessors in a linearization order, others forego such strong consistency to avoid complex control and synchronization bottlenecks. For example, contains (value) methods of key-value maps may iterate through key-value entries without blocking concurrent updates, to avoid unwanted performance bottlenecks, and consequently overlook the effects of some linearization-order predecessors. While such weakly-consistent operations may not be atomic, they still offer guarantees, e.g., only observing values that have been present.In this work we develop a methodology for proving that concurrent object implementations adhere to weak-consistency specifications. In particular, we consider (forward) simulation-based proofs of implementations against relaxed-visibility specifications, which allow designated operations to overlook some of their linearization-order predecessors, i.e., behaving as if they never occurred. Besides annotating implementation code to identify linearization points, i.e., points at which operations’ logical effects occur, we also annotate code to identify visible operations, i.e., operations whose effects are observed; in practice this annotation can be done automatically by tracking the writers to each accessed memory location. We formalize our methodology over a general notion of transition systems, agnostic to any particular programming language or memory model, and demonstrate its application, using automated theorem provers, by verifying models of Java concurrent object implementations.