bluuebunny/crossref_metadata_2025_split huggingface dataset:
Actinides: Photoelectron Spectroscopy
Authors: Gouder Thomas , Eloirdi Rachel 
Published: September 2018

AbstractA short review of photoemission studies of the early actinides is given. Emphasis is put on the gradual evolution of the actinide 5f states from bonding (delocalization) to nonbonding (localization) behavior. Localization is depicted by the withdrawal of the f states from screening of the photohole. Valence band and core level photoemission will be discussed. In the valence band, the transition from band like to localized states is seen in the appearance of multiplet peaks. Depending of the degree of f‐localization, two different final states are reached (well and poorly screened), each with characteristic multiplet peaks. Core level spectra also show two different final states, depending of f‐localization. Using photoemission data, the 5f transition to localization will be discussed for the pure elements. The effect on f‐localization of dilution, that is, isolation in a matrix, confinement to reduced dimensions (surface layers), and chemical bonding with ligand atoms will be discussed. 5f Participation in ionic bonding and its consequences on the chemical reactions of actinide surfaces will then be addressed. 5f States are responsible for the multiple valence of actinides and are of high technological relevance. We will compare the oxidation behavior of U, Np, and Pu and focus on unusual intermediate and the highest oxidation states, which are all related to the number and the degree of localization of the 5f electrons. We then discuss the reduction of high oxidation states by reaction with hydrogen and the photocatalytic reduction by water.
Actinides: Computational Chemistry
Authors: Dolg Michael , Cao Xiaoyan 
Published: September 2018

AbstractRelativistic quantum chemical ab initio methods for calculations of the electronic structures of actinide and transactinide atoms and molecules are briefly reviewed. The importance of relativistic and electron correlation effects for heavy‐element quantum chemical investigations is emphasized. In addition, the need to go beyond the Dirac one‐electron relativity and to include, for example, the Breit interaction for the relativistic two‐electron interaction or even low‐order contributions from quantum electrodynamics is shown for specific examples. The possible entries on the three axes of the coordinate system of ab initio quantum chemical calculations—Hamiltonian axis, one‐, and many‐particle basis set axes—are summarized. Several choices for relativistic Hamiltonians at the all‐electron and valence‐only level are introduced and compared, and the principal strategies to account for relativistic effects, including spin–orbit interaction and electron correlation effects in calculations, are discussed. Some remarks on problems when applying density functional theory to actinide and transactinide systems are made. Finally, a few selected examples show the range of applicability of the currently available methods for theoretical investigations of the heaviest known elements and their chemistry.
Actinides: Pnictogen Complexes
Authors: Vilanova Sean P. , Walensky Justin R. 
Published: September 2018

Abstract
The chemistry of the heavier congeners of nitrogen is not well understood and has only been explored in more depth in the past 5 years. We examine the history of this chemistry with emphasis on molecular complexes, and the synthesis and reactivity of actinide–pnictogen complexes involving phosphorus, arsenic, and bismuth.
Actinide Speciation and Bioavailability in Fresh and Marine Waters
Authors: Markich Scott J. , Brown Paul L. 
Published: September 2018

AbstractThe actinides comprise a group of 15 metals (with atomic numbers ranging from 89 to 103) that are all radioactive and occur as cations in natural surface waters. Only the first 10 actinides are covered in this study, as these are the most environmentally relevant, where the dominant oxidation states are as follow: actinium(III), thorium(IV), protactinium(V), uranium(VI), neptunium(V), plutonium(IV) and (V), americium(III), curium(III), berkelium(III), and californium(III). The physicochemical form, or speciation, of an actinide (e.g., free metal ion, or complexes with inorganic or organic ligands) in natural surface waters can be determined using a range of analytical techniques. However, such methods are seldom commercially available and rarely determine a complete distribution of all metal species. A complementary approach, which is more cost effective, time efficient, and predictive, is the application of geochemical speciation modeling, which calculates the percentage distribution ofallactinide species based on known or postulated chemical reactions. The general consensus is that geochemical speciation models can provide useful results if applied correctly with an understanding of the differences between simulated and real systems. This is the first study to use an internally consistent equilibrium database within a geochemical model (WHAM) to calculate the speciation of the first 10 actinides across fresh, estuarine, and marine waters that incorporates natural dissolved organic matter (DOM) (i.e., fulvic acid). The speciation of a metal (actinide) largely governs its uptake and/or toxicity (bioavailability) in aquatic organisms. The general consensus is that bioavailability is best predicted by the concentration of the free metal ion (Mz+) and that metals complexed with most inorganic ligands (e.g., carbonate or sulfate) or natural DOM, typically have low bioavailability. There is also evidence to suggest that colloidal thorium is bioavailable to freshwater organisms. The study correlates observed actinide speciation with bioavailability (where available) or utilizes predicted actinide speciation to determine the likely magnitude of bioavailability, as applied to aquatic organisms. This study also addresses the likely effects of global ocean acidification and increased natural DOM concentrations in fresh surface waters on actinide speciation and bioavailability.
Actinides: Biogeochemistry
Authors: Boukhalfa Hakim , Neu Mary 
Published: September 2018

AbstractTransuranic elements are highly reactive and form multiple oxidation states and complex species that can co‐exist, which underlies their fascinating inorganic, bioinorganic, and environmental chemistry. Because they are ubiquitous, microorganisms through their natural processes can interact with transuranic elements to change their speciation through both direct microbe‐transuranics interactions and indirect change of physical and chemical conditions in their environment. Understanding how microbial processes affect transuranic elements broadens our knowledge of fundamental transuranic chemistry, increases our understanding of the impact of biological and environmental receptors and metals on each other, and enables the development of applications in separation, remediation technologies, mammalian decorporation strategies, and nuclear repository design. Microorganisms and biogeochemical processes transform metals via numerous and varied chemical, biological, and geological processes, many of which have yet to be characterized in detail even for main group elements. The focus of this article is a brief overview of transuranic species that form in the environment and the biogeochemical processes that transform them. The primary processes that have been well studied for transuranic species are as follows: (i) complexation with inorganic/bioinorganic ligands within, and produced by, bacteria; (ii) complexation by organic ligands, including microbial metabolites, and transuranic bio‐associations; and (iii) biomineralization to form transuranic materials and mineral analogs.
Metal Ions and Complexes inAlzheimer's Disease: From Fundamental to Therapeutic Perspectives
Authors: Hureau Christelle 
Published: September 2018

AbstractIn this article, the author reviews the structural, thermodynamic, and kinetic data on metal ions (copper and zinc) binding to the amyloid‐β peptides of various sequences involved in Alzheimer's disease. Metal ions are indeed regarded as key players in Alzheimer's disease because they may contribute to the oxidative stress and modulate the aggregation propensity of the amyloid‐β peptides, two key processes in the etiology of the disease. An analogy with the influence of the interaction between metal ions and other intrinsically disordered peptides in different pathologies is also drawn. In a second part, several therapeutic and diagnostic approaches based on the role of metal ions are described and discussed. A selection of chelators, metallophores, prodrugs as well as inorganic compounds is proposed that illustrates the various strategies developed by inorganic medicinal chemists to fight Alzheimer's disease.
Tuning Charge Transport in Aromatic‐Ring Single‐Molecule Junctions via Ionic‐Liquid Gating
Authors: Xin Na , Li Xingxing , Jia Chuancheng , Gong Yao , Li Mingliang , Wang Shuopei , Zhang Guangyu , Yang Jinlong , Guo Xuefeng 
Published: September 2018

AbstractAchieving gate control with atomic precision, which is crucial to the transistor performance on the smallest scale, remains a challenge. Herein we report a new class of aromatic‐ring molecular nanotransistors based on graphene–molecule–graphene single‐molecule junctions by using an ionic‐liquid gate. Experimental phenomena and theoretical calculations confirm that this ionic‐liquid gate can effectively modulate the alignment between molecular frontier orbitals and the Fermi energy level of graphene electrodes, thus tuning the charge‐transport properties of the junctions. In addition, with a small gate voltage (|VG|≤1.5 V) ambipolar charge transport in electrochemically inactive molecular systems (EG>3.5 eV) is realized. These results offer a useful way to build high‐performance single‐molecule transistors, thus promoting the prospects for molecularly engineered electronic devices.
Engineered Biosynthesis of β‐Alkyl Tryptophan Analogues
Authors: Boville Christina E. , Scheele Remkes A. , Koch Philipp , Brinkmann‐Chen Sabine , Buller Andrew R. , Arnold Frances H. 
Published: September 2018

AbstractNoncanonical amino acids (ncAAs) with dual stereocenters at the α and β positions are valuable precursors to natural products and therapeutics. Despite the potential applications of such bioactive β‐branched ncAAs, their availability is limited due to the inefficiency of the multistep methods used to prepare them. Herein we report a stereoselective biocatalytic synthesis of β‐branched tryptophan analogues using an engineered variant of Pyrococcus furiosus tryptophan synthase (PfTrpB), PfTrpB7E6. PfTrpB7E6 is the first biocatalyst to synthesize bulky β‐branched tryptophan analogues in a single step, with demonstrated access to 27 ncAAs. The molecular basis for the efficient catalysis and broad substrate tolerance of PfTrpB7E6 was explored through X‐ray crystallography and UV/Vis spectroscopy, which revealed that a combination of active‐site and remote mutations increase the abundance and persistence of a key reactive intermediate. PfTrpB7E6 provides an operationally simple and environmentally benign platform for the preparation of β‐branched tryptophan building blocks.
Specific and Oriented Encapsulation of Fullerene C70 into a Supramolecular Double‐Decker Cage Composed of Shape‐Persistent Macrocycles
Authors: Kawano Shin‐ichiro , Fukushima Tomoaki , Tanaka Kentaro 
Published: September 2018

AbstractAn efficient strategy for the specific recognition of ellipsoidal fullerenes uses molecular containers with well‐designed three‐dimensional (3D) nanospaces. We describe the synthesis of a supramolecular double‐decker cage composed of shape‐persistent metallomacrocycles and pillar ligands. A discrete 3D nanospace was built within the molecular framework of the shape‐persistent‐macrocycle/bidentate‐pillar molecule. The single‐crystal structure of the supramolecular cage reveals a uniquely shaped inner cavity with a size and net volume (>670 Å3) that are well matched to the shape and size of C70. The cage exhibited higher selectivity for C70 over C60, the smaller carbon allotrope. We suggest that such C70‐selective recognition is derived from multiple CH–π interactions between hydrogen atoms inside the cage and C70.
Working with traumatized refugees on the Balkan route
Authors: Jović Vladimir 
Published: September 2018

AbstractIn the past several years Serbia has been in the center of the so‐called “Balkan route”, a pathway for refugees from the Middle East and Central Asia. In March 2016 the Balkan route was closed and this measure reduced the number of daily arrivals and prolonged the stay of refugees in Serbia. A brief overview of the current situation is given, together with some previous experiences in psychosocial programs for the displaced population during wars in former Yugoslavia and current psychosocial programs and interventions. Several short examples are presented to point out some aspects of those experiences that might have relevance to our understanding of the psychological trauma and possible ways of treatment.
Ultra‐performance liquid chromatography tandem mass spectrometry for the rapid, simultaneous analysis of ziprasidone and its impurities
Authors: Čarapić Marija , Nikolic Katarina , Marković Bojan , Petković Miloš , Pavlovic Milena , Agbaba Danica 
Published: September 2018

AbstractThe separation and characterization of the unknown degradation product of second‐generation antipsychotic drug ziprasidone are essential for defining the genotoxic potential of the compound. The aim of this study was to develop a simple UHPLC method coupled with tandem mass spectrometry (MS/MS) for chemical characterization of an unknown degradant, and the separation and quantification of ziprasidone and its five main impurities (I–V) in the raw material and pharmaceuticals. Chromatographic conditions were optimized by experimental design. The MS/MS fragmentation conditions were optimized individually for each compound in order to obtain both specific fragments and high signal intensity. A rapid and sensitive UHPLC–MS/MS method was developed. All seven analytes were eluted within the 7 min run time. The best separation was obtained on the Acquity UPLC BEH C18 (50 × 2.1 mm × 1.7 μm) column in gradient mode with ammonium‐formate buffer (10 mm; pH 4.7) and acetonitrile as mobile phase, with the flow rate of 0.3 mL min−1 and at the column temperature of 30°C. The new UHPLC–MS/MS method was fully validated and all validation parameters were confirmed. The fragmentation pathways and chemical characterization of an unknown degradant were proposed and it was confirmed that there are no structural alerts concerning genotoxicity.
Jack of many trades: Multifaceted role of neuropilins in pancreatic cancer
Authors: Matkar Pratiek N. , Jong Eric D. , Ariyagunarajah Ramya , Prud'homme Gerald J. , Singh Krishna K. , Leong‐Poi Howard 
Published: September 2018

AbstractNeuropilins (NRPs) have been described as receptors for class 3 semaphorins and coreceptors for a plethora of ligands, such as members of the vascular endothelial growth factor (VEGF) family of angiogenic cytokines and transforming growth factor (TGF). Initial studies using genetic models have indicated that neuropilin‐1 (NRP‐1) is essential for axonal guidance during neuronal and cardiovascular development, regulated via semaphorins and VEGF, respectively, whereas the other homolog of neuropilin, NRP‐2, has been shown to play a more specific role in neuronal patterning and lymphangiogenesis. Pancreatic ductal adenocarcinoma (PDAC) remains a significant cause of cancer mortality with the lowest five‐year survival rate compared to other types of cancer. Recent findings have indicated that NRPs are abundantly expressed in pancreatic cancer cell lines and pancreatic tumor tissues, where they mediate several essential cancer‐initiating and cancer‐promoting functional responses through their unique ability to bind multiple ligands. Specifically, NRPs have been implicated in numerous biological processes such as cancer cell proliferation, survival, invasion, and tumor growth. More recently, several other protumorigenic roles mediated by NRPs have emerged, advocating NRPs as ideal therapeutic targets against PDAC.
RNA versus DNA G‐Quadruplex: The Origin of Increased Stability
Authors: Zaccaria Francesco , Fonseca Guerra Célia 
Published: September 2018

AbstractDNA quadruplexes have been the subject of investigation because of their biological relevance and because of their potential application in supramolecular chemistry. Similarly, RNA quadruplexes are now gaining increasing attention. Although DNA and RNA quadruplexes are structurally very similar, the latter show higher stability. In this study we report dispersion‐corrected density functional theory (DFT‐D) quantum chemical calculations that were undertaken to understand the difference in stabilities of RNA and DNA quadruplexes. The smallest meaningful model of a stack of quartets, interacting with alkali metal cations, was simulated in an aqueous environment. The energy decomposition analysis allows for in‐depth examination of the interaction energies, emphasising the role of noncovalent interactions and better electrostatics in determining RNA‐GQs higher stabilities, particularly pinpointing the role of the extra 2′‐OH groups. Furthermore, our computations present new insights on why the cation is required for self‐assembly: unexpectedly the cation is not necessary to relieve the repulsion between the oxygen atoms in the central cavity, but it is needed to overcome the entropic penalty.
Synthesis of Ribo‐Azanucleosides by Anodic Oxidation: Reactivity Control of Intermediate for Efficient Access to Pharmacophores
Authors: Okamoto Kazuhiro , Shoji Takao , Tsutsui Mizuki , Shida Naoki , Chiba Kazuhiro 
Published: September 2018

AbstractAzanucleosides, the sugar‐modified nucleoside analogues, have various biological activities, while their efficient synthetic strategy is still under development. Herein, a novel method for the synthesis of pharmaceutically relevant azanucleosides, β‐anomers of ribo‐azanucleosides, by means of site‐specific anodic C−H activation by using a nitroalkane–lithium perchlorate medium is reported. A mechanistic study of the electrochemical reaction and the armed/disarmed concept from traditional glycochemistry revealed that the 2′‐substituent has a significant effect on the reactivity of prolinol derivative, and suitable carboxylic acid additives can control the reactivity of the intermediate species, an iminium cation equivalent. Finally, this method was demonstrated to be applicable for the synthesis of β‐anomers of ribo‐azanucleosides with all four nucleobases in a stereoselective manner.
Efficient Photoelectrochemical Water Oxidation on Hematite with Fluorine‐Doped FeOOH and FeNiOOH as Dual Cocatalysts
Authors: Deng Jiujun , Zhang Qingzhe , Feng Kun , Lan Huiwen , Zhong Jun , Chaker Mohamed , Ma Dongling 
Published: September 2018

AbstractAn effective cocatalyst is usually required to improve the performance of photoelectrochemical (PEC) water splitting catalysts. A fluorine‐doped FeOOH (F:FeOOH) cocatalyst on a hematite photoanode was used to lower the onset potential by 140 mV and significantly improve the PEC performance. Moreover, a more effective dual cocatalytic system was prepared by subsequent loading of a FeNiOOH cocatalyst, which resulted in a further decrease of the onset potential by 270 mV. The final onset potential of the Fe2O3/F:FeOOH/FeNiOOH photoanode was lowered to 0.45 V versus the reversible hydrogen electrode (RHE), which is one of the lowest onset potential values ever reported for hematite photoanodes. The photocurrent also dramatically increased by a factor of approximately 3 to 0.9 mA cm−2 at 1.0 V versus RHE. Based on the structural, chemical, and electrochemical impedance spectroscopy characterization, the enhanced performance was attributed to the F:FeOOH overlayer, which reduced the surface recombination and accelerated the oxygen evolution reaction activity, and the FeNiOOH cocatalyst, which further enhanced the reaction kinetics. The facile preparation of the F:FeOOH cocatalyst and the design of the dual cocatalytic system will allow the development of high‐performance hematite photoanodes.
A congestion control method of SDN data center based on reinforcement learning
Authors: Jin Rong , Li Jiaojiao , Tuo Xin , Wang Weiming , Li Xiaolin 
Published: September 2018

SummaryWith the development of cloud computing and big data, the internal communication business in data center has increased dramatically, and then the traffic in data center has also significantly increased. The bandwidth of data center is difficult to meet the bandwidth requirements of those intensive applications, and data center is facing a risk of network congestion. Under the background of the development of network intelligence, software‐defined network (SDN) should demonstrate its intelligence as a future network architecture. In this paper, we introduce reinforcement learning into the SDN data center to implement congestion control based on flow. We improve the Q‐learning and Sarsa algorithms and propose two methods of congestion control based on the algorithms. Test results show that these two congestion control methods can control congestion effectively. And Sarsa method has a better performance of link utilization. The average link utilization of the Sarsa method is 2.4% higher than the Q‐learning method and is 4.48% higher than the on‐demand method.
Partial feedback impact on achievable rate region in multiple‐access relay channels
Authors: Moeen Taghavi Ehsan , Abed Hodtani Ghosheh 
Published: September 2018

SummaryFor discrete memoryless Slepian‐Wolf multiple‐access relay channel with relay‐sources feedback (SW‐MARC‐RSF), an achievable rate region via partial decode and forward strategy at the relay is proposed, and by extending the results to the continuous alphabet version, the corresponding achievable rate region of the Gaussian SW‐MARC‐RSF is obtained. It is shown that our results include the important previous works on multiple‐access channel (MAC) with feedback (Cover‐Leung rate region) and without feedback (Slepian‐Wolf [SW] rate region, etc) as special cases. Finally, through comparison of the achievable rate regions, with and without feedback, the impact of feedback on achievability is analyzed. The derived achievable rate region is shown to resolve the residual uncertainty at the receiver in an efficient way and demonstrates that in the partial decode and forward strategy, relay‐sources feedback increases the achievable rate region in both discrete memoryless and Gaussian multiple‐access relay channels.