bluuebunny/crossref_metadata_2025_split huggingface dataset:
Altitude‐resolved shortwave and longwave radiative effects of desert dust in the Mediterranean during the GAMARF campaign: Indications of a net daily cooling in the dust layer
Authors: Meloni D. , Junkermann W. , di Sarra A. , Cacciani M. , De Silvestri L. , Di Iorio T. , Estellés V. , Gómez‐Amo J. L. , Pace G. , Sferlazzo D. M. 
Published: March 2015

AbstractDesert dust interacts with shortwave (SW) and longwave (LW) radiation, influencing the Earth radiation budget and the atmospheric vertical structure. Uncertainties on the dust role are large in the LW spectral range, where few measurements are available and the dust optical properties are not well constrained. The first airborne measurements of LW irradiance vertical profiles over the Mediterranean were carried out during the Ground‐based and Airborne Measurements of Aerosol Radiative Forcing (GAMARF) campaign, which took place in spring 2008 at the island of Lampedusa. The experiment was aimed at estimating the vertical profiles of the SW and LW aerosol direct radiative forcing (ADRF) and heating rates (AHR), taking advantage of vertically resolved measurements of irradiances, meteorological parameters, and aerosol microphysical and optical properties. Two cases, characterized respectively by the presence of a homogeneous dust layer (3 May, with aerosol optical depth, AOD, at 500 nm of 0.59) and by a low aerosol burden (5 May, with AOD of 0.14), are discussed. A radiative transfer model was initialized with the measured vertical profiles and with different aerosol properties, derived from measurements or from the literature. The simulation of the irradiance vertical profiles, in particular, provides the opportunity to constrain model‐derived estimates of the AHR. The measured SW and LW irradiances were reproduced when the model was initialized with the measured aerosol size distributions and refractive indices. For the dust case, the instantaneous (solar zenith angle, SZA, of 55.1°) LW‐to‐SW ADRF ratio was 23% at the surface and 11% at the top of the atmosphere (TOA), with a more significant LW contribution on a daily basis (52% at the surface and 26% at TOA), indicating a relevant reduction of the SW radiative effects. The AHR profiles followed the aerosol extinction profile, with comparable peaks in the SW (0.72 ± 0.11 K d−1) and in the LW (−0.52 ± 0.12 K d−1) for the considered SZA. On a daily basis, the absolute value of the heating rate was larger in the LW than in the SW, producing a net cooling effect at specific levels. These are quite unexpected results, emphasizing the important role of LW radiation.
An observational analysis of warm‐sector rainfall characteristics associated with the 21 July 2012 Beijing extreme rainfall event
Authors: Zhong Lingzhi , Mu Rong , Zhang Dalin , Zhao Ping , Zhang Zhiqiang , Wang Nan 
Published: March 2015

AbstractAn observational analysis of the multiscale processes leading to the extreme rainfall event in Beijing on 21 July 2012 is performed using rain gauge records, Doppler radar, and satellite products, radiosondes, and atmospheric analysis. This rainstorm process included two heavy rainfall stages in the early afternoon [1300–1400 Beijing Standard time (BST) (0500–0600 UTC)] and the evening (1600–1900 BST), respectively. The first stage exhibited warm‐sector rainfall characteristics as it occurred under low‐level warm and moist southeasterly flows ahead of a synoptic‐scale vortex and a cold front. When the southeasterly flows turned northeastward along a southwest‐northeast oriented mountain range in western Beijing, mesoscale convergence centers formed on the windward side of the mountain range in the early afternoon, initiating moist convection. Radar echo showed a northeastward propagation as these flows extended northward. Despite the shallowness of moist convection in the warm sector, atmospheric liquid water content showed the rapid accumulation, and a large amount of supercooled water and/or ice particles was possibly accumulated above the melting level. These appeared to contribute to the occurrence of the largest rainfall rate. During the second stage, as the synoptic‐scale vortex moved across Beijing, with southeastward intrusion of its northwesterly flows, the vortex‐associated lifting caused the generation of strong updrafts aloft and formed deep convection. This facilitated the further accumulation of supercooled water and/or ice particles above the melting level. Radar echo propagated southeastward. Liquid water showed a decrease in the lower troposphere, and there were strong downdrafts due to evaporation of liquid water particles, which resulted in the relatively weak hourly rainfall rates.
New model fit functions of the plasmapause location determined using THEMIS observations during the ascending phase of Solar Cycle 24
Authors: Cho Junghee , Lee Dae‐Young , Kim Jin‐Hee , Shin Dae‐Kyu , Kim Kyung‐Chan , Turner Drew 
Published: March 2015

AbstractIt is well known that the plasmapause is influenced by the solar wind and magnetospheric conditions. Empirical models of its location have been previously developed such as those by O'Brien and Moldwin (2003) and Larsen et al. (2006). In this study, we identified the locations of the plasmapause using the plasma density data obtained from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites. We used the data for the period (2008–2012) corresponding to the ascending phase of Solar Cycle 24. Our database includes data from over a year of unusually weak solar wind conditions, correspondingly covering the plasmapause locations in a wider L range than those in previous studies. It also contains many coronal hole stream intervals during which the plasmasphere is eroded and recovers over a timescale of several days. The plasmapause was rigorously determined by requiring a density gradient by a factor of 15 within a radial distance of 0.5 L. We first determined the statistical correlation of the plasmapause locations with several solar wind parameters as well as geomagnetic indices. We found that the plasmapause locations are well correlated with the solar wind speed and the interplanetary magnetic field Bz, therefore the y component of the convective electric field, and some energy coupling functions such as the well‐known Akasofu's epsilon parameter. The plasmapause locations are also highly correlated with the geomagnetic indices, Dst, AE, and Kp, as recognized previously. Finally, we suggest new model fit functions for the plasmapause locations in terms of the solar wind parameters and geomagnetic indices. When applied to a new data interval outside the model training interval, our model fit functions work better than existing ones. The new model fit functions developed here extend the range of conditions from those used in previous works.
Synthesis of 2,6‐Dihalogenated Purine Nucleosides by Thermostable Nucleoside Phosphorylases
Authors: Zhou Xinrui , Szeker Kathleen , Jiao Lin‐Yu , Oestreich Martin , Mikhailopulo Igor A. , Neubauer Peter 
Published: March 2015

AbstractThe enzymatic transglycosylation of 2,6‐dichloropurine (26DCP) and 6‐chloro‐2‐fluoropurine (6C2FP) with uridine, thymidine and 1‐(β‐D‐arabinofuranosyl)‐uracil as the pentofuranose donors and recombinant thermostable nucleoside phosphorylases from G. thermoglucosidasius or T. thermophilus as biocatalysts was studied. Selection of 26DCP and 6C2FP as substrates is determined by their higher solubility in aqueous buffer solutions compared to most natural and modified purines and, furthermore, synthesized nucleosides are valuable precursors for the preparation of a large number of biologically important nucleosides. The substrate activity of 26DCP and 6C2FP in the synthesis of their ribo‐ and 2′‐deoxyribo‐nucleosides was closely similar to that of related 2‐amino‐ (DAP), 2‐chloro‐ and 2‐fluoroadenines; the efficiency of the synthesis of β‐D‐arabinofuranosides of 26DCP and 6C2FP was lower vs. that of DAP under similar reaction conditions. For a convenient and easier recovery of the biocatalysts, the thermostable enzymes were immobilized on MagReSyn® epoxide beads and the biocatalyst showed high catalytic efficiency in a number of reactions. As an example, 6‐chloro‐2‐fluoro‐(β‐D‐ribofuranosyl)‐purine (9), a precursor of various antiviral and antitumour drugs, was synthesized by the immobilized enzymes at 60 °C under high substrate concentrations (uridine:purine ratio of 2:1, mol). The synthesis was successfully scaled‐up [uridine (2.5 mmol), base (1.25 mmol); reaction mixture 50 mL] to afford 9 in 60% yield. The reaction reveals the great practical potential of this enzymatic method for the efficient production of modified purine nucleosides of pharmaceutical interest.magnified image
Chemo‐Controlled Cross‐Coupling of Di(hetero)aryl Disulfides with Grignard Reagents: CC vs. CS Bond Formation
Authors: Du Bao‐Xin , Quan Zheng‐Jun , Da Yu‐Xia , Zhang Zhang , Wang Xi‐Cun 
Published: March 2015

AbstractA general protocol for the chemoselectivity‐controlled CC and CS coupling reactions of di(hetero)aryl disulfides with Grignard reagents catalyzed by ferrocene and palladium acetate has been developed. Ferrocene favored the formation of CS coupled products at low temperature, whereas CC bond couplings were favored when palladium acetate was used. All the reactions proceeded with excellent chemoselectivity and in good yields under mild conditions, and a library of molecules with pyridine and pyrimidine scaffolds was produced.magnified image
Enantiopure Helical Ferrocene–Triazole–Quinone Triads: Synthesis and Properties
Authors: Hoyo Ana M. del , Latorre Alfonso , Díaz Raúl , Urbano Antonio , Carreño M. Carmen 
Published: March 2015

AbstractThe copper(I)‐catalyzed (2+3) cycloaddition between azido (or azidomethylene) ferrocenes and enantiopure (P)‐14‐(p‐ethynylphenyl)‐[5]‐tetrahydro‐helicenequinone afforded ferrocene–triazole–quinone triads, whereas diazido ferrocenes gave rise to the corresponding double triads. In reactions with 1,1′‐diazidoferrocene, the use of CuI/CH3CN or CuSO4/sodium ascorbate/THF conditions allowed the divergent formation of an open chain dimeric structure or a 1,4‐diaza‐[4]‐ferrocenophane resulting from an intramolecular oxidative coupling of the two triazole units formed after the double cycloaddition process.magnified image
Direct Coupling of Arylacetonitriles and Primary Alcohols to α‐Alkylated Arylacetamides with Complete Atom Economy Catalyzed by a Rhodium Complex–Triphenylphosphine– Potassium Hydroxide System
Authors: Li Feng , Zou Xiaoyuan , Wang Nana 
Published: March 2015

AbstractA direct synthesis of α‐alkylated arylacetamides from arylacetonitriles and primary alcohols has been accomplished for the first time. In the presence of the rhodium complex [Rh(cod)Cl]2/triphenylphosphine/potassium hydroxide system, the desired α‐alkylated arylacetamides were obtained in 74–92% yield under microwave conditions. The experimental results in this paper are in sharp contrast with previous reports, where the coupling of arylacetonitriles and primary alcohols produced the α‐alkylated arylacetonitriles. Mechanistic investigations show that arylacetonitriles are first α‐alkylated with primary alcohols to produce α‐alkylated arylacetonitriles, which are further hydrated with the water resulting from the α‐alkylation step to produce α‐alkylated arylacetamides. More importantly, this research shows the potential of developing completely atom‐economical reactions that involve the hydrogen autotransfer (or hydrogen borrowing) process.magnified image
Rhodium‐Catalyzed Decarbonylative Direct Olefination of Arenes with Vinyl Carboxylic Acids
Authors: Qiu Ruiying , Zhang Lingjuan , Xu Conghui , Pan Yixiao , Pang Hongze , Xu Lijin , Li Huanrong 
Published: March 2015

AbstractA rhodium(I)‐catalyzed direct CH bond olefination of pyridyl‐substituted arenes with readily available vinyl carboxylic acids has been realized. This reaction occurred efficiently without the need for any external oxidant, affording the ortho‐olefinated products in high yields and excellent regioselectivities. Diversely substituted vinyl carboxylic acids behaved as efficient olefination reagents under the reaction conditions, and a range of functional groups in both coupling partners was well tolerated. Mechanistic studies indicated that a decarbonylation step is involved in this catalytic process, and pivalic anhydride [(t‐BuCO)2O] acts as the activator of the carboxylic acids for the in situ generation of highly active anhydrides.magnified image
Voxel‐based morphometric magnetic resonance imaging (MRI) postprocessing in MRI‐negative epilepsies
Authors: Wang Z. Irene , Jones Stephen E. , Jaisani Zeenat , Najm Imad M. , Prayson Richard A. , Burgess Richard C. , Krishnan Balu , Ristic Aleksandar , Wong Chong H. , Bingaman William , Gonzalez‐Martinez Jorge A. , Alexopoulos Andreas V. 
Published: March 2015

ObjectiveIn the presurgical workup of magnetic resonance imaging (MRI)‐negative (MRI− or “nonlesional”) pharmacoresistant focal epilepsy (PFE) patients, discovering a previously undetected lesion can drastically change the evaluation and likely improve surgical outcome. Our study utilizes a voxel‐based MRI postprocessing technique, implemented in a morphometric analysis program (MAP), to facilitate detection of subtle abnormalities in a consecutive cohort of MRI− surgical candidates.MethodsIncluded in this retrospective study was a consecutive cohort of 150 MRI− surgical patients. MAP was performed on T1‐weighted MRI, with comparison to a scanner‐specific normal database. Review and analysis of MAP were performed blinded to patients' clinical information. The pertinence of MAP+ areas was confirmed by surgical outcome and pathology.ResultsMAP showed a 43% positive rate, sensitivity of 0.9, and specificity of 0.67. Overall, patients with the MAP+ region completely resected had the best seizure outcomes, followed by the MAP− patients, and patients who had no/partial resection of the MAP+ region had the worst outcome (p < 0.001). Subgroup analysis revealed that visually identified subtle findings are more likely correct if also MAP+. False‐positive rate in 52 normal controls was 2%. Surgical pathology of the resected MAP+ areas contained mainly non–balloon‐cell focal cortical dysplasia (FCD). Multiple MAP+ regions were present in 7% of patients.InterpretationMAP can be a practical and valuable tool to: (1) guide the search for subtle MRI abnormalities and (2) confirm visually identified questionable abnormalities in patients with PFE due to suspected FCD. A MAP+ region, when concordant with the patient's electroclinical presentation, should provide a legitimate target for surgical exploration. Ann Neurol 2015;77:1060–1075
Activation of Water in Titanium Dioxide Photocatalysis by Formation of Surface Hydrogen Bonds: An In Situ IR Spectroscopy Study
Authors: Sheng Hua , Zhang Hongna , Song Wenjing , Ji Hongwei , Ma Wanhong , Chen Chuncheng , Zhao Jincai 
Published: March 2015

AbstractThe hole‐driving oxidation of titanium‐coordinated water molecules on the surface of TiO2 is both thermodynamically and kinetically unfavorable. By avoiding the direct coordinative adsorption of water molecules to the surface Ti sites, the water can be activated to realize its oxidation. When TiO2 surface is covered by the H‐bonding acceptor F, the first‐layer water adsorption mode is switched from Ti coordination to a dual H‐bonding adsorption on adjacent surface F sites. Detailed in situ IR spectroscopy and isotope‐labeling studies reveal that the adsorbed water molecules by dual H‐bonding can be oxidized to O2 even in the absence of any electron scavengers. Combined with theoretical calculations, it is proposed that the formation of the dual H‐bonding structure can not only enable the hole transfer to the water molecules thermodynamically, but also facilitate kinetically the cleavage of OH bonds by proton‐coupled electron transfer process during water oxidation.
Synthese BN‐isosterer Verbindungen von Azofarbstoffen durch Ringerweiterung von Borolen mit Aziden
Authors: Braunschweig Holger , Celik Mehmet Ali , Hupp Florian , Krummenacher Ivo , Mailänder Lisa 
Published: March 2015

AbstractWir stellen hier die Ergebnisse unserer Untersuchungen bezüglich des Effekts der ortho‐Substitution von Arylaziden auf die Ringerweiterung von Borolen, fünfgliedrigen, ungesättigten Borheterocyclen, vor. Die Studien führten zu der Isolierung der ersten 1,2‐Azaborinin‐substituierten Azofarbstoffe, bei denen es sich um leuchtend gelbe Feststoffe handelt. In Lösung stellte sich eines der Derivate, (E)‐2‐Mesityl‐1‐(mesityldiazenyl)‐3,4,5,6‐tetraphenyl‐1,2‐azaborinin, als nicht stabil heraus, sondern geht eine Jacobsen‐Reaktion zu einem Indazol und einem 1‐Hydro‐1,2‐azaborinin ein. Um den Mechanismus der unerwarteten Bildung der Azo‐Azaborinine nachvollziehen zu können und um Rückschlüsse auf die Rolle der ortho‐Substitution auf den Reaktionsverlauf zu ziehen, wurden Dichtefunktionalrechnungen durchgeführt.
Secondary Crystal Nucleation: Nuclei Breeding Factory Uncovered
Authors: Anwar Jamshed , Khan Shahzeb , Lindfors Lennart 
Published: March 2015

AbstractSecondary nucleation, wherein crystal seeds are used to induce crystallization, is widely employed in industrial crystallizations. Despite its significance, our understanding of the process, particularly at the molecular level, remains rudimentary. An outstanding question is why do a few seeds give rise to a many‐fold increase in new crystals? Using molecular simulation coupled with experiments we have uncovered the molecular processes that give rise to this autocatalytic behavior. The simulations reveal formation of molecular aggregates in solution, which on coming in contact with the surface of the seed undergo nucleation to form new crystallites. These crystallites are weakly bound to the crystal surface and can be readily sheared by fluid, making the seed surfaces available again to repeat the process. Further, the new crystallites on development can in turn serve as seeds. This mechanistic insight will enable better control in engineering crystalline products to design.
Unprecedented Quassinoids with Promising Biological Activity from Harrisonia perforata
Authors: Fang Xin , Di Ying Tong , Zhang Yu , Xu Zhi Ping , Lu Yang , Chen Qian Qian , Zheng Qi Tai , Hao Xiao Jiang 
Published: March 2015

AbstractPerforalactone A (1), a new 20S quassinoid with a unique cagelike 2,4‐dioxaadamantane ring system and a migrated side chain, was isolated from the plant Harrisonia perforata together with two biosynthetically related new quassinoids. The structures of these natural products were elucidated by NMR spectroscopy, X‐ray diffraction analysis, computational modeling, and the CD excitation chirality method. The compounds exhibited notable biological properties, including insecticidal activity against Aphis medicaginis Koch and antagonist activity at the nicotinic acetylcholine receptor of Drosophila melanogaster. The structural features of these compounds may be related to their promising biological characteristics. Their biosynthesis and an alternative origin of quassinoid‐type natural products are also discussed.
Superstructure of a Substituted Zeolitic Imidazolate Metal–Organic Framework Determined by Combining Proton Solid‐State NMR Spectroscopy and DFT Calculations
Authors: Baias Maria , Lesage Anne , Aguado Sonia , Canivet Jerome , Moizan‐Basle Virginie , Audebrand Nathalie , Farrusseng David , Emsley Lyndon 
Published: March 2015

AbstractWe report the supercell crystal structure of a ZIF‐8 analog substituted imidazolate metal–organic framework (SIM‐1) obtained by combining solid‐state nuclear magnetic resonance and powder X‐ray diffraction experiments with density functional theory calculations.
Lack of Association of Oral Calcium Supplementation With Coronary Artery Calcification in Rheumatoid Arthritis
Authors: Geraldino‐Pardilla Laura , Dhaduvai Shanthi , Giles Jon T. , Bathon Joan M. 
Published: March 2015

ObjectiveTo investigate the association between oral calcium supplementation and coronary artery calcification among rheumatoid arthritis (RA) patients without known cardiovascular disease (CVD).MethodsThis study was conducted as a nested, prospective cohort study of RA patients without known CVD. The daily supplemental calcium dose was ascertained from each patients’ list of prescription and over‐the‐counter medications at baseline and at visit 2 (median 20 months postbaseline). The coronary artery calcium (CAC) score, a measure of coronary atherosclerosis, was assessed by cardiac multidetector row computed tomography at baseline and at visit 3 (median 39 months postbaseline). The association between calcium supplementation and CAC was explored.ResultsAmong the 145 RA patients studied, 42 (28%) were taking ≥1,000 mg/day of supplemental calcium at baseline. A CAC score of >100 units was seen in 44 patients (30%) at baseline and 50 patients (34%) at followup. Baseline CAC scores of >100 units were significantly less frequent in patients receiving the higher dosage (≥1,000 mg/day) of supplemental calcium than in those receiving the lower dosage (<1,000 mg/day) (odds ratio [OR] 0.28, 95% confidence interval [95% CI] 0.11–0.74); this association remained significant after adjustment for relevant confounders (adjusted OR 0.30, 95% CI 0.09–0.93). Similarly, at the third study visit, CAC scores of >100 units were less frequent in the higher supplemental calcium dose group compared to the lower dose group (OR 0.41, 95% CI 0.18–0.95); however, after adjustment for relevant confounders, the statistical significance of this association was lost (adjusted OR 0.39, 95% CI 0.14–1.12). No effect of sex heterogeneity was seen in the association of calcium supplementation with coronary artery calcification, and no change in the CAC score over time was observed.ConclusionHigher levels of oral calcium supplementation were not associated with an increased risk of coronary atherosclerosis, as measured by the CAC score, in this RA cohort.
Sibling Exposure and Risk of Juvenile Idiopathic Arthritis
Authors: Miller Jessica , Ponsonby Anne‐Louise , Pezic Angela , Kemp Andrew , Piper Susan E. , Akikusa Jonathan D. , Allen Roger C. , Munro Jane E. , Ellis Justine A. 
Published: March 2015

ObjectiveSusceptibility to juvenile idiopathic arthritis (JIA) is presumed to be determined by both genes and environment. However, the environmental factors remain largely unknown. The hygiene hypothesis suggests that exposure to siblings, as a marker of exposure to microbes in early life, may protect against the development of later immune disorders. Some prior evidence suggests this may also be true for JIA. The present study was undertaken to test this hypothesis in detail.MethodsWe conducted a comprehensive analysis of the role of sibling exposure in JIA risk within the Childhood Arthritis Risk Factor Identification Study JIA case–hospital control sample (302 cases and 676 controls) from Victoria, Australia.ResultsWe found that, compared to being an only child, having any siblings was protective against JIA, with an adjusted odds ratio (OR) of 0.46 (95% confidence interval [95% CI] 0.28–0.74) (P = 0.001). The protective association appeared to increase with increasing number of siblings (e.g., for ≥3 siblings, adjusted OR 0.25 [95% CI 0.13–0.48], P < 0.001). A protective association of siblings was also observed when we considered cumulative sibling years by age 6 (e.g., for ≥3 years of exposure versus no exposure, adjusted OR 0.49 [95% CI 0.30–0.79], P = 0.003). We also compared cases to a second control sample (n = 341) collected from the community and weighted to represent the child population of Victoria. Data remained supportive of an association between sibling exposure and protection against JIA, particularly for exposure to younger siblings.ConclusionIncreased exposure to siblings is associated with a reduced risk of disease in our sample. This suggests that increased microbial exposure in childhood may confer protection against the development of JIA.