bluuebunny/crossref_metadata_2025_split huggingface dataset:
Light‐Induced Mechanistic Divergence in Gold(I) Catalysis: Revisiting the Reactivity of Diazonium Salts
Authors: Taschinski Svenja , Döpp René , Ackermann Martin , Rominger Frank , de Vries Folkert , Menger Maximilian F. S. J. , Rudolph Matthias , Hashmi A. Stephen K. , Klein Johannes E. M. N. 
Published: September 2019

AbstractIn a systematic study of the Au‐catalyzed reaction of o‐alkynylphenols with aryldiazonium salts, we find that essentially the same reaction conditions lead to a change in mechanism when a light source is applied. If the reaction is carried out at room temperature using a AuI catalyst, the diazonium salt undergoes electrophilic deauration of a vinyl AuI intermediate and provides access to substituted azobenzofurans. If the reaction mixture is irradiated with blue LED light, C−C bond formation due to N2‐extrusion from the diazonium salt is realized selectively, using the same starting materials without the need for an additional photo(redox) catalyst under aerobic conditions. We report a series of experiments demonstrating that the same vinyl AuI intermediate is capable of producing the observed products under photolytic and thermal conditions. The finding that a vinyl AuI complex can directly, without the need for an additional photo(redox) catalyst, result in C−C bond formation under photolytic conditions is contrary to the proposed mechanistic pathways suggested in the literature till date and highlights that the role of oxidation state changes in photoredox catalysis involving Au is thus far only poorly understood and may hold surprises for the future. Computational results indicate that photochemical activation can occur directly from a donor–acceptor complex formed between the vinyl AuI intermediate and the diazonium salt.
Expedient Synthesis of Core Disaccharide Building Blocks from Natural Polysaccharides for Heparan Sulfate Oligosaccharide Assembly
Authors: Pawar Nitin J. , Wang Lei , Higo Takuya , Bhattacharya Chandrabali , Kancharla Pavan K. , Zhang Fuming , Baryal Kedar , Huo Chang‐Xin , Liu Jian , Linhardt Robert J. , Huang Xuefei , Hsieh‐Wilson Linda C. 
Published: September 2019

AbstractThe complex sulfation motifs of heparan sulfate glycosaminoglycans (HS GAGs) play critical roles in many important biological processes. However, an understanding of their specific functions has been hampered by an inability to synthesize large numbers of diverse, yet defined, HS structures. Herein, we describe a new approach to access the four core disaccharides required for HS/heparin oligosaccharide assembly from natural polysaccharides. The use of disaccharides rather than monosaccharides as minimal precursors greatly accelerates the synthesis of HS GAGs, providing key disaccharide and tetrasaccharide intermediates in about half the number of steps compared to traditional strategies. Rapid access to such versatile intermediates will enable the generation of comprehensive libraries of sulfated oligosaccharides for unlocking the “sulfation code” and understanding the roles of specific GAG structures in physiology and disease.
Autonome Entdeckung in den chemischen Wissenschaften, Teil I: Fortschritt
Authors: Coley Connor W. , Eyke Natalie S. , Jensen Klavs F. 
Published: September 2019

AbstractIn dem zweiteiligen Aufsatz wird der Beitrag von Automation zu verschiedenen Aspekten der chemischen Entdeckung untersucht. In Teil 1 definieren wir die Arten von Entdeckung in den chemischen Wissenschaften – Entdeckung von Materie (Molekülen, Materialien, Gegenständen), Entdeckung von Prozessen und Entdeckung von Modellen – und beschreiben ihre Vereinheitlichung als Suchproblem. Anschließend formulieren wir eine Reihe von Fragen, die für die Bewertung des Autonomiegrads einer Entdeckung relevant sind. Den Abschluss bilden zahlreiche Fallstudien in den Bereichen Synthesechemie, Wirkstoffentdeckung, anorganische Chemie und Materialwissenschaften, bei denen Entdeckungen durch Rechenunterstützung und Automation beschleunigt oder erst ermöglicht werden. Die Studien machen deutlich, wie die rasanten Entwicklungen in der Hardware‐Automation und im maschinellen Lernen unaufhörlich die Art der experimentellen Forschung und der Modellierung verändern. Im zweiten Teil werden anhand der Fallstudien die noch ungelösten Aufgaben auf dem Gebiet benannt und diskutiert.
Autonome Entdeckung in den chemischen Wissenschaften, Teil II: Ausblick
Authors: Coley Connor W. , Eyke Natalie S. , Jensen Klavs F. 
Published: September 2019

AbstractIn dem zweiteiligen Aufsatz wird der Beitrag von Automation zu verschiedenen Aspekten der chemischen Entdeckung untersucht. In Teil 2 betrachten wir ausgewählte Beispiele. Eine Diskussion der Rolle von Automation und Rechnung im wissenschaftlichen Prozess und deren Einfluss auf die Beschleunigung von Entdeckungsaufgaben wird immer wichtiger. Selbst wenn automatisierte Systeme die Laborarbeit immens unterstützen können, kann man argumentieren, dass auch die besten Roboter noch nicht wirklich etwas “entdecken”. Zur effektiven Entwicklung autonomer Plattformen müssen wir ihren bisherigen Einsatz evaluieren und herausfinden, wie sie sich auf künftige Probleme anwenden lassen. Den Hauptteil dieses Aufsatzes nimmt die Definition von weiterführenden Forschungsrichtungen ein: Verarbeitung komplexer Daten, Erstellung empirischer Modelle, Automation experimenteller und rechnerischer Validierung, Versuchsauswahl und Evaluation des Fortschritts auf dem Weg zur autonomen Entdeckung.
Autonomous Discovery in the Chemical Sciences Part I: Progress
Authors: Coley Connor W. , Eyke Natalie S. , Jensen Klavs F. 
Published: September 2019

AbstractThis two‐part Review examines how automation has contributed to different aspects of discovery in the chemical sciences. In this first part, we describe a classification for discoveries of physical matter (molecules, materials, devices), processes, and models and how they are unified as search problems. We then introduce a set of questions and considerations relevant to assessing the extent of autonomy. Finally, we describe many case studies of discoveries accelerated by or resulting from computer assistance and automation from the domains of synthetic chemistry, drug discovery, inorganic chemistry, and materials science. These illustrate how rapid advancements in hardware automation and machine learning continue to transform the nature of experimentation and modeling. Part two reflects on these case studies and identifies a set of open challenges for the field.
Engaging Aldehydes in CuH‐Catalyzed Reductive Coupling Reactions: Stereoselective Allylation with Unactivated 1,3‐Diene Pronucleophiles
Authors: Li Chengxi , Shin Kwangmin , Liu Richard Y. , Buchwald Stephen L. 
Published: September 2019

AbstractRecently, CuH‐catalyzed reductive coupling processes involving carbonyl compounds and imines have become attractive alternatives to traditional methods for stereoselective addition because of their ability to use readily accessible and stable olefins as surrogates for organometallic nucleophiles. However, the inability to use aldehydes, which usually reduce too rapidly in the presence of copper hydride complexes to be viable substrates, has been a major limitation. Shown here is that by exploiting relative concentration effects through kinetic control, this intrinsic reactivity can be inverted and the reductive coupling of 1,3‐dienes with aldehydes achieved. Using this method, both aromatic and aliphatic aldehydes can be transformed into synthetically valuable homoallylic alcohols with high levels of diastereo‐ and enantioselectivities, and in the presence of many useful functional groups. Furthermore, using a combination of theoretical (DFT) and experimental methods, important mechanistic features of this reaction related to stereo‐ and chemoselectivities were uncovered.
Adjusting Simon's optimal two‐stage design for heterogeneous populations based on stratification or using historical controls
Authors: Edelmann Dominic , Habermehl Christina , Schlenk Richard F. , Benner Axel 
Published: September 2019

AbstractIn many cancer studies, the population under consideration is highly heterogeneous in terms of clinical, demographical, and biological covariates. As the covariates substantially impact the individual prognosis, the response probabilities of patients entering the study may strongly vary. In this case, the operating characteristics of classical clinical trial designs heavily depend on the covariates of patients entering the study. Notably, both type I and type II errors can be much higher than specified. In this paper, two modifications of Simon's optimal two‐stage design correcting for heterogeneous populations are derived. The first modification assumes that the patient population is divided into a finite number of subgroups, where each subgroup has a different response probability. The second approach uses a logistic regression model based on historical controls to estimate the response probabilities of patients entering the study. The performance of both approaches is demonstrated using simulation examples.
Exploring the Influence of Halogen Coordination Effect of Stable Bimetallic MOFs on Oxygen Evolution Reaction
Authors: Lu Jia‐Ni , Liu Jiang , Dong Long‐Zhang , Li Shun‐Li , Kan Yu‐He , Lan Ya‐Qian 
Published: September 2019

AbstractThe energy crisis and environmental pollution have forced scientists to explore alternative energy conversion and storage devices. The anodic reactions of these devices are all oxygen evolution reactions (OER), so the development of efficient OER electrocatalysts is of great significance. At the same time, understanding the reaction mechanism of OER is conducive to the rational design of efficient OER electrocatalysts. In general, catalytic active centers play a direct role in OER performance. In this paper, a series of stable bimetallic metal–organic frameworks (MOFs, named as Fe3‐Con‐X2, n=2, 3 and X=F, Cl, Br) with similar structure were synthesized by changing the halogen coordinated with the cobalt metal active center, aiming to investigate the influence of halogen substitution effect on OER performance. It was found that the OER activity of Fe3‐Co3‐F2 is much better than Fe3‐Co2‐Cl2 and Fe3‐Co2‐Br2, indicating that the regulation of the electronegativity change of the coordination halogen atom can regulate the coordination electron structure of the metal active center, thereby achieving effective regulation of OER performance.
Investigation of Active and Inactivated Yeast Cells by Scanning Electrochemical Impedance Microscopy
Authors: Valiūnienė Aušra , Petronienė Jūratė , Dulkys Mindaugas , Ramanavičius Arūnas 
Published: September 2019

AbstractScanning electrochemical microscopy (SECM), electrochemical impedance spectroscopy (EIS) and scanning electrochemical impedance microscopy (SEIM) were used to investigate electrochemical activity of active and inactivated yeast Saccharomyces cerevisiae cells. SEIM experiment was performed using a unique electrochemical impedance spectrometer with a fast Fourier transform (FFT‐EIS) function, which enabled simultaneously perturb/evaluate electrochemical system at 50 frequencies. This allowed very quick observing the differences between impedance spectra, which were taken every few seconds. Therefore, we were able to apply SEIM for relatively fast determination of electrochemical impedance dependence on the distance between ultramicroelectrode (UME) and surface modified by immobilized yeast cells. It was determined that electrochemical activity and ‘breathing’ (a consumption of dissolved oxygen) of yeast can be electrochemically observed when the distance between UME and surface of yeast cells is in the range from 0 μm to 25 μm. Therefore, 25 μm is the maximum distance suitable for efficient investigation of yeast cell activity when experiments are performed in FFT‐SEIM mode. Charge transfer resistance of active and inactivated yeast cells was determined using EIS. It was calculated that charge transfer resistance of active yeast cells is 1.5 times lower than that of inactivated yeast cells. Lipophilic vitamin K3 (Vit‐K3) and hydrophilic vitamin K1 (Vit‐K1) were mixtured and used as redox mediators for charge transfer from yeast cells.
QSAR-Based Estimation of Species Sensitivity Distribution Parameters: An Exploratory Investigation
Authors: Hoondert Renske P.J. , Oldenkamp Rik , de Zwart Dick , van de Meent Dik , Posthuma Leo 
Published: September 2019

Abstract
Ecological risk assessments are hampered by limited availability of ecotoxicity data. The present study aimed to explore the possibility of deriving species sensitivity distribution (SSD) parameters for nontested compounds, based on simple physicochemical characteristics, known SSDs for data-rich compounds, and a quantitative structure–activity relationship (QSAR)-type approach. The median toxicity of a data-poor chemical for species assemblages significantly varies with values of the physicochemical descriptors, especially when based on high-quality SSD data (from either acute median effect concentrations or chronic no-observed-effect concentrations). Beyond exploratory uses, we discuss how the precision of QSAR-based SSDs can be improved to construct models that accurately predict the SSD parameters of data-poor chemicals. The current models show that the concept of QSAR-based SSDs supports screening-level evaluations of the potential ecotoxicity of compounds for which data are lacking. Environ Toxicol Chem 2019;38:2764–2770. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC
Abstract
Extrapolation of data for species sensitivity distribution (SSD) parameters (mu and sigma) using a QSAR approach (estimating SSD parameters based on physicochemical characteristics) may in the end result in filling in data gaps for - in theory - all chemicals. QSAR = quantitative structure–activity relationship; SSD = species sensitivity distribution.
Low antithrombin activity before delivery predicts subsequent hypertensive disorders in pregnancy
Authors: Morikawa Mamoru , Umazume Takeshi , Nakagawa Kinuko , Chiba Kentaro , Kawaguchi Satoshi , Watari Hidemichi 
Published: September 2019

AbstractObjectiveTo examine whether laboratory parameters can predict the onset of recurrent hypertensive disorders of pregnancy (HDP).MethodsA retrospective study of 257 women with consecutive deliveries at a hospital in Sapporo, Japan, between 2009 and 2017. Women were divided into four groups according to whether or not they had HDP in the first and second peripartum periods (HDP‐HPD, HDP‐Non, Non‐HDP, Non‐Non). HDP was defined as gestational hypertension and/or proteinuria. Laboratory parameters measured on the day of or 1 day before delivery were compared between peripartum‐1 and peripartum‐2.ResultsFrequency of HDP in peripartum‐2 was higher among the 24 (9.3%) women with HPD in peripartum‐1 (6/24, 25.0%) than among the 233 (90.7%) women without (3/233, 1.3%) (P<0.001). In peripartum‐1, women with HDP had lower median antithrombin activity than those without (74% vs 89%, P=0.021). Antithrombin activity in peripartum‐1 was also lower in the HDP‐HDP (67%) than in the HDP‐Non (79%) group (P=0.021). Antithrombin activities of 77% or less at the first delivery predicted HDP in peripartum‐1 (P<0.001) and 70% or less predicted HDP in peripartum‐2 (P=0.018).ConclusionWomen with HDP in peripartum‐1 had a higher incidence of HDP recurrence. Low antithrombin before a first delivery might predict recurrent HDP in a second pregnancy.
Periodontal disease, sleep duration, and white blood cell markers in the 2009 to 2014 National Health and Nutrition Examination Surveys
Authors: Beydoun Hind A. , Hossain Sharmin , Beydoun May A. , Weiss Jordan , Zonderman Alan B. , Eid Shaker M. 
Published: September 2019

AbstractBackgroundElevated levels of inflammatory biomarkers are consistently associated with chronic conditions, for which periodontitis and sleep are established risk factors. We examined the relationships between periodontitis, hours of sleep and white blood cell (WBC) markers among a nationally representative sample of US adults.MethodsCross‐sectional study using existing demographic, examination, laboratory and questionnaire data on 11,813 participants (5,814 men and 5,999 women, mean age ± SE; range: 52.74 ± 0.24; 30 to 80 years) from the 2009 to 2014 National Health and Nutrition Examination Surveys. Unadjusted, sex‐ and age‐adjusted, as well as fully adjusted linear and logistic regression models were conducted in addition to generalized structural equations models, while considering sampling design complexity. β, odds ratios with their 95% confidence intervals, indirect effects and mediation proportions were estimated.ResultsThe weighted mean WBC count was 7,130 cells/µL, with the WBC 5‐part differential estimated in terms of percentages of lymphocytes (29.50%), monocytes (7.99%), neutrophils (59.03%), eosinophils (2.84%), and basophils (71.88%). Furthermore, 36.2% of participants reported <7 hours of sleep and 49.8% had periodontitis. In fully adjusted models controlling for sociodemographic, lifestyle, and health characteristics, neither WBC markers nor periodontitis were related to hours of sleep. By contrast, periodontitis was directly related to WBC count and %neutrophils and inversely related to %lymphocytes, especially among men. However, the relationship of periodontitis with %neutrophils and %lymphocytes may be modified by hours of sleep, as it was specific to individuals reporting ≥7 hours of sleep.ConclusionPeriodontitis may be directly related to WBC count and %neutrophils and inversely related to %lymphocytes, especially among men and individuals reporting ≥7 hours of sleep, with implications for primary and secondary prevention.
Resource Loss and Stress Outcomes in a Setting of Chronic Conflict: The Conservation of Resources Theory in the Eastern Congo
Authors: Snyder Jordan D. , Boan David , Aten Jamie D. , Davis Edward B. , Van Grinsven Leif , Liu Tao , Worthington Everett L. 
Published: September 2019

AbstractThe purpose of this cross‐sectional study was to examine conservation of resources (COR) theory in the context of armed conflict in Africa. Specifically, within the setting of ongoing chronic conflict in the eastern Democratic Republic of the Congo (DRC), we tested the COR theory prediction that resource loss contributes to various stress outcomes. A randomly selected sample of 312 adults (125 men, 187 women) from villages in North Kivu, DRC completed orally administered measures of resource loss, daily stressors, and four stress outcomes: depression symptoms, anxiety symptoms, posttraumatic distress, and general distress. Consistent with COR theory, resource loss predicted all four stress outcomes above and beyond the contribution of demographics, relocation experiences, and daily stressors; however, this effect was small, ΔR2 = .02–.06. The most consistent and strongest predictors of stress outcomes were daily stressors, βs = .42–.62; number of relocation experiences, βs = .33–.43; and psychosocial resource loss (e.g., loss of hope, meaning or purpose in life, intimacy with friends and family, physical health of family), βs = .17–.26. Additionally, male sex predicted depression, anxiety, and trauma symptoms, and lower educational status predicted anxiety symptoms and general distress. Our exploratory mediation analysis showed that daily stressors partially mediated all four pairs of associations between psychosocial resource loss and mental health outcomes. We discuss the findings with consideration of research on disasters generally and armed conflicts specifically. We also discuss implications for humanitarian interventions with conflict‐affected populations in Africa and beyond.
Chemoselective Thioacetalisation and Transthioacetalisation of Aldehydes Catalyzed by PVP‐I
Authors: Hu Peng‐Fei , Dong Bin , Zhou Zhi‐Peng , Chen Wei‐Dong , Zeng Bu‐Bing 
Published: September 2019

AbstractThioacetals of various aldehydes were obtained directly from aldehydes or by a transthioacetalisation process from O,O‐acetals catalyzed by Povidone‐iodine (PVP−I) with good to excellent yields. Attractive features of this method include mild reaction conditions, low catalyst loading, recyclability of catalyst, facile purification of products, and high synthetic efficiency.
Maiaspora: a new miospore genus with enigmatic sculpture from the late Visean of European Russia
Authors: Mamontov Dmitriy A. , McLean Duncan , Orlova Olga A. , Gavrilova Olga A. 
Published: September 2019

AbstractA new miospore genus, Maiaspora, is described from the upper Visean (middle Mississippian) of the southern wing of Moscow Syneclise (European Russia). Applying a combination of methods (optical light microscopy (LM), scanning‐electron microscopy, confocal laser microscopy (CLSM) and image analysis) to the same individual miospore specimens revealed a remarkable sculptural type for which we propose the new term ‘metareticuloid’. Metareticuloid sculpture is defined as a complex arrangement of muri with apiculate elements, polygonal lumina and circular scrobiculae at the base of the lumina. The discovery of fossil spores with metareticuloid sculpture allows the recognition of clear morphological differences between microreticulate and foveolate sculptures, which palynologists have historically had difficulty in separating. Virtual cross‐sections provided by CLSM show that miospores with metareticuloid sculpture display perfectly preserved, funnel‐shaped tunnels (like a gallery of cave stalactites) in the deep exospore. In contrast, miospores with microreticulate or reticulate and partly vermiculate sculpture lack such vertical tunnels (termed scrobiculae). The morphology of Maiaspora gen. nov. is considered in comparison with Microreticulatisporites (Knox non sensu Potonié & Kremp) Bhardwaj emended Oshurkova, Pseudoreticulatispora Bharadwaj & Srivastava emended Price & Foster, Vadaszisporites (Deák & Combaz) emended Juhász, Foveosporites Balme, Foveotriletes van der Hammen ex Potonié, Garotriletes Singh & Singh, Assamiasporites Mehrota & Sah, and Margotriletes Mehrota & Sah. The morphological conceptions of Microreticulatisporites and Foveotriletes are reinterpreted by numerical typification. The adaptative significance of metareticuloid sculpture is discussed in relation to modern and fossil spores, and in terms of harmomegathic mechanisms of angiosperm pollen.
Ruling Parties in Authoritarian Regimes: Rethinking Institutional Strength
Authors: Meng Anne 
Published: September 2019

AbstractA key finding in the literature on authoritarian regimes is that leaders frequently rely on ruling parties to stay in power, but the field lacks systematic ways to measure autocratic party strength. As a result, it is not clear how often ruling parties are actually strong and capable of carrying out important functions. This article demonstrates that strong ruling parties are much rarer than is typically assumed. Using a global sample of dictatorships from 1946–2008, the author shows that most ruling parties are unable to survive the death or departure of the founding leader. This is true even of many ruling parties that have been coded as leading single-party regimes. While strong parties may be key to durable authoritarianism, relatively few parties are truly strong.