bluuebunny/crossref_metadata_2025_split huggingface dataset:
Branched dart leaders preceding lightning return strokes
Authors: Stolzenburg Maribeth , Marshall Thomas C. , Karunarathne Sumedhe , Karunarathna Nadeeka , Orville Richard E. 
Published: March 2014

AbstractThis study describes the occurrence of branches in lightning dart leaders, based on data acquired in Florida using a high‐speed video camera and electric field change sensors. More than half (57%) of 72 flashes with analyzable dart leaders show at least one successful branched dart leader (BDL), and nine flashes have two successful BDLs. Overall, 18% of 282 visible successful dart leaders are branched. Most (42 of 50) cases of BDLs occur in the first dart leader after a stepped leader/return stroke sequence, and the data indicate that 55% of first dart leaders are visibly branched. Compared to first dart leaders in the 31 flashes without any branched dart leaders, BDLs tend to follow stepped leader/return strokes with significantly larger average peak currents (−31.3 versus −20.6 kA) and shorter average interstroke intervals (71.94 versus 94.64 ms). Average peak current of BDL strokes is 62% larger (−17.8 versus −11 kA) than that for unbranched first dart leader strokes. Branched dart leaders generally travel in the some of the most recently used lightning channels, but they are not always within the main channel of the prior return stroke. Successful BDLs may dart all the way to ground when in a prior stroke channel, or they may become stepped leaders when they reach the lower end of the prior stroke branch. Electric field change data for all the BDL cases exhibit an erratic pulse character for at least part of the leader duration; in some cases, the erratic character ends when the branches vanish.
Cauchy data requirement of the inverse problem of the mean age equation
Authors: Nassar Mohamed K. , Ginn Timothy R. 
Published: March 2014

AbstractA classical theoretical inverse problem in groundwater hydraulics is the calibration of a heterogeneous isotropic hydraulic conductivity field using known hydraulic head data at each point in the domain. It has been long known that a necessary condition for the uniqueness of the solution to this theoretical inverse problem is the Cauchy data, i.e., the hydraulic conductivity values (or, equivalently, flux) along a line crossing all streamtubes in the entire domain. This result has been cited in identifying the value of boundary flux data in practical inverse problems, although in general such data are generally not available. In this work, we show that groundwater mean age data replace this Cauchy data requirement.
A modeling approach reveals differences in evapotranspiration and its partitioning in two semiarid ecosystems in Northwest Mexico
Authors: Méndez‐Barroso Luis A. , Vivoni Enrique R. , Robles‐Morua Agustin , Mascaro Giuseppe , Yépez Enrico A. , Rodríguez Julio C. , Watts Christopher J. , Garatuza‐Payán Jaime , Saíz‐Hernández Juan A. 
Published: March 2014

AbstractSeasonal vegetation changes during the North American monsoon play a major role in modifying water, energy, and momentum fluxes. Nevertheless, most models parameterize plants as a static component or with averaged seasonal variations that ignore interannual differences and their potential impact on evapotranspiration (ET) and its components. Here vegetation parameters derived from remote sensing data were coupled with a hydrologic model at two eddy covariance (EC) sites with observations spanning multiple summers. Sinaloan thornscrub (ST) and Madrean woodland (MW) sites, arranged at intermediate and high elevations along mountain fronts in northwest Mexico, occupy specific niches related to climate conditions and water availability that are poorly understood. We found that simulations with a dynamic representation of vegetation greening tracked well the seasonal evolution of observed ET and soil moisture (SM). A switch in the dominant component of ET from soil evaporation (E) to plant transpiration (T) was observed for each ecosystem depending on the timing and magnitude of vegetation greening that is directly tied to rainfall characteristics. Differences in vegetation greening at the ST and MW sites lead to a dominance of transpiration at ST (T/ET = 57%), but evaporation‐dominant conditions at MW (T/ET = 19%). Peak transpiration occurred at 5 and 20 days after the full canopy development in the ST and MW sites, respectively. These results indicate that evapotranspiration timing and partitioning varies considerably in the two studied ecosystems in accordance with different modes of vegetation greening. Intermediate‐elevation ecosystems follow an intensive water use strategy with a rapid and robust transpiration response to water availability. In contrast, higher elevation sites have delayed and attenuated transpiration, suggesting an extensive water use strategy persisting beyond the North American monsoon.
Suppression of Void Formation in Si0.5Ge0.5 Alloy Nanowire during Ni Germanosilicidation
Authors: Li Yida , Buddharaju Kavitha , Wang Xin‐Peng , Lee Sung‐Joo , Thong Thiam‐Leong 
Published: March 2014

ABSTRACTThe growth mechanism of Ni‐germanosilicide in Si0.5Ge0.5 NW with and without silicon dioxide shell encapsulation was investigated using transmission electron microscope imaging with in situ annealing of SiGe NW array samples capped with Ni. At 200 and 400 °C, the interfacial reaction is minimal while at 600 °C, we can observe the gradual formation of a thin Ni‐germanosilicide filament for the unconstrained SiGe NW. This observation is concomitant with material loss from the sides of the SiGe NW, which eventually leads to void formation. Energy dispersive X‐ray spectroscopy analysis along the SiGe NW shows that Ge atoms out‐diffused from the NW toward the Ni source during annealing. Excessive out‐diffusion of Ge atoms and void formation are shown to be retarded in the encapsulated SiGe NW with compressive stress.
Catalytic Oxidation of C(sp3)H Bonds Induced by a Radical Cation Salt: Construction of 1,4‐Dihydropyridines Using a Fragment‐Reassembly Strategy
Authors: Jia Xiaodong , Wang Yaxin , Peng Fangfang , Huo Congde , Yu Liangling , Liu Jing , Wang Xicun 
Published: March 2014

AbstractA fragment‐reassembly strategy was applied to the construction of 1,4‐dihydropyridines and phosphorus‐substituted 1,4‐dihydropyridines under catalytic radical cation salt‐induced C(sp)3H functionalization of glycine derivatives. Mechanistic studies show that domino C(sp)3H bond oxidation and CN bond cleavage reactions are involved.magnified image
Fine‐tuning the Local Symmetry to Attain Record Blocking Temperature and Magnetic Remanence in a Single‐Ion Magnet
Authors: Ungur Liviu , Le Roy Jennifer J. , Korobkov Ilia , Murugesu Muralee , Chibotaru Liviu F. 
Published: March 2014

AbstractRemanence and coercivity are the basic characteristics of permanent magnets. They are also tightly correlated with the existence of long relaxation times of magnetization in a number of molecular complexes, called accordingly single‐molecule magnets (SMMs). Up to now, hysteresis loops with large coercive fields have only been observed in polynuclear metal complexes and metal‐radical SMMs. On the contrary, mononuclear complexes, called single‐ion magnets (SIM), have shown hysteresis loops of butterfly/phonon bottleneck type, with negligible coercivity, and therefore with much shorter relaxation times of magnetization. A mononuclear ErIII complex is presented with hysteresis loops having large coercive fields, achieving 7000 Oe at T=1.8 K and field variation as slow as 1 h for the entire cycle. The coercivity persists up to about 5 K, while the hysteresis loops persist to 12 K. Our finding shows that SIMs can be as efficient as polynuclear SMMs, thus opening new perspectives for their applications.
A Chiral Thioxanthone as an Organocatalyst for Enantioselective [2+2] Photocycloaddition Reactions Induced by Visible Light
Authors: Alonso Rafael , Bach Thorsten 
Published: March 2014

AbstractThioxanthone 1, which was synthesized in a concise fashion from methyl thiosalicylate, exhibits a significant absorption in the visible light region. It allows for an efficient enantioselective catalysis of intramolecular [2+2] photocycloaddition reactions presumably by triplet energy transfer.
K4[PbSe4]⋅en⋅NH3: A Non‐Oxide, Non‐Halide Inorganic Lead(IV) Compound
Authors: Thiele Günther , Krüger Thomas , Dehnen Stefanie 
Published: March 2014

AbstractThe first inorganic lead(IV) compound without oxygen, nitrogen or halogen ligands attached to the lead atom was obtained as the potassium salt of the tetraselenidoplumbate(IV) anion [PbIVSe4]4−. It is stable under inert conditions which may enable the transfer of the chemistry of chalcogenidogermanate(IV) or chalcogenidostannate(IV) materials, to the lead homologues.
Characterization of an Environmental DNA‐Derived Gene Cluster that Encodes the Bisindolylmaleimide Methylarcyriarubin
Authors: Chang Fang‐Yuan , Brady Sean F. 
Published: March 2014

AbstractBisindolylmaleimides represent a naturally occurring class of metabolites that are of interest because of their protein kinase inhibition activity. From a metagenomic library constructed with soil DNA, we identified the four gene mar cluster, a bisindolylmaleimide gene cluster that encodes for methylarcyriarubin (1) production. Heterologous expression of the mar gene cluster in E. coli revealed that the Rieske dioxygenase MarC facilitates the oxidative decarboxylation of a chromopyrrolic acid (CPA) intermediate to yield the bisindolylmaleimide core. The characterization of the mar cluster defines a new role for CPA in the biosynthesis of structurally diverse bacterial tryptophan dimers.
Polymer‐Stabilized Palladium Nanoparticles for the Chemoselective Transfer Hydrogenation of α,β‐Unsaturated Carbonyls: Single‐Step Bottom‐Up Approach
Authors: Mahato Sanjit K. , Ul Islam Rafique , Acharya Chiranjit , Witcomb Michael J. , Mallick Kaushik 
Published: March 2014

AbstractPolypyrrole stabilised palladium nanoparticles show good catalytic efficiency for the chemoselective transfer hydrogenation of α,β‐unsaturated carbonyl compounds. The catalyst is very specific and selectively hydrogenates the olefins or acetylenes only, without affecting the carbonyl moiety, with an excellent yield of products for a wide range of substrates.
Structures and Properties of Molecular Torsion Balances to Decipher the Nature of Substituent Effects on the Aromatic Edge‐to‐Face Interaction
Authors: Gardarsson Haraldur , Schweizer W. Bernd , Trapp Nils , Diederich François 
Published: March 2014

AbstractVarious recent computational studies initiated this systematic re‐investigation of substituent effects on aromatic edge‐to‐face interactions. Five series of Tröger base derived molecular torsion balances (MTBs), initially introduced by Wilcox and co‐workers, showing an aromatic edge‐to‐face interaction in the folded, but not in the unfolded form, were synthesized. A fluorine atom or a trifluoromethyl group was introduced onto the edge ring in ortho‐, meta‐, and para‐positions to the CH group interacting with the face component. The substituents on the face component were varied from electron‐donating to electron‐withdrawing. Extensive X‐ray crystallographic data allowed for a discussion on the conformational behavior of the torsional balances in the solid state. While most systems adopt the folded conformation, some were found to form supramolecular intercalative dimers, lacking the intramolecular edge‐to‐face interaction, which is compensated by the gain of aromatic π‐stacking interactions between four aryl rings of the two molecular components. This dimerization does not take place in solution. The folding free enthalpy ΔGfold of all torsion balances was determined by 1H NMR measurements by using 10 mM solutions of samples in CDCl3 and C6D6. Only the ΔGfold values of balances bearing an edge‐ring substituent in ortho‐position to the interacting CH show a steep linear correlation with the Hammett parameter (σmeta) of the face‐component substituent. Thermodynamic analysis using van′t Hoff plots revealed that the interaction is enthalpy‐driven. The ΔGfold values of the balances, in addition to partial charge calculations, suggest that increasing the polarization of the interacting CH group makes a favorable contribution to the edge‐to‐face interaction. The largest contribution, however, seems to originate from local direct interactions between the substituent in ortho‐position to the edge‐ring CH and the substituted face ring.
Saddlepoint approximations for rank‐invariant permutation tests and confidence intervals with interval‐censoring
Authors: Abd‐Elfattah Ehab , Butler Ronald 
Published: March 2014

AbstractInterval‐censored data occur when subjects are assessed by using regular follow‐up. In such instances, we consider rank‐invariant permutation tests to test the significance of a treatment versus a control. For a wide class of such tests, which includes the Peto & Peto class, we present saddlepoint approximations for the exact permutation mid‐P‐values which achieve extremely small relative errors. The speed and stability of these saddlepoint computations make them practicable for inverting the permutation tests and we compute nominalconfidence intervals for the treatment effect. Such confidence intervals are of substantial clinical importance since, more than simply stating the level of statistical significance, they quantify the significant benefit of the treatment by providing a confidence interval for the percentage increase in mean (or median) treatment survival time as compared to control. Our methodology makes heavy use of nonparametric MLEs (NPMLEs) for survival functions and some limitations of existing algorithms, such as the hybrid ICM algorithm, are noted and accommodated.The Canadian Journal of Statistics42: 308–324; 2014 © 2014 Statistical Society of Canada
Paul Harteck (1902–1985) – führender Physikochemiker des letzten Jahrhunderts
Authors: Stegmann Annalena , Habekost Achim 
Published: March 2014

AbstractDer Nachweis der Umwandlung von ortho/para Wasserstoff, die Entdeckung des Tritiums in der Atmosphäre, die Herstellung von Schwerem Wasser, der Bau von Isotopentrennanlagen und Versuche zur Uran‐Kettenreaktion, die Entwicklungen auf dem Gebiete der Photochemie – all diese Arbeiten gehen auf den österreichisch‐deutschen Physikochemiker Paul Harteck zurück. Harteck war zudem im Uranverein einer derjenigen, der die experimentelle Entwicklung einer „Uranmaschine“ am intensivsten voran trieb.
Management of Patients With Atrial Fibrillation by Primary‐Care Physicians in Germany: 1‐Year Results of the ATRIUM Registry
Authors: Kirchhof Paulus , Schmalowsky Janine , Pittrow David , Rosin Ludger , Kirch Wilhelm , Wegscheider Karl , Meinertz Thomas ,   for the ATRIUM Study Group
Published: March 2014

ABSTRACTBackgroundPatients with atrial fibrillation (AF) in Germany are often managed jointly by primary‐care physicians in cooperation with cardiologists. We aimed to investigate the management and 1‐year outcomes of AF patients in this setting.HypothesisWe set out to describe the current management of AF patients in primary care settings in Germany.MethodsObservational registry with 1‐year follow‐up, performed by a representative, randomly selected sample of 781 primary‐care physicians in Germany.ResultsOf 3781 patients with electrocardiographically documented AF, 3163 patients (age 71.9 ± 9.2 years, 57.9% males) were followed for 1 year; 28.4% had paroxysmal, 27.0% persistent, and 43.3% permanent AF. Comorbid conditions were common (mean CHA2DS2‐VASc score 3. 8 ± 1.7). Rhythm‐control therapy was used in 16.4%. Although oral anticoagulation was often used (82.7% at baseline), stroke rate during follow‐up was high (2.7% stroke, 3.0% transient ischemic attack). Despite a long duration of AF (mean duration 61 months at enrollment), 18.5% of patients were hospitalized during the 1‐year follow‐up.ConclusionsIn this unselected group of patients with long‐standing AF managed in primary care, hospitalizations and cardiovascular complications including strokes are frequent, illustrating the need to improve management of AF patients.
Hepatocellular Carcinoma Targeting Agents: Conjugates of Nitroimidazoles with Trimethyl Nordihydroguaiaretic Acid
Authors: Hsu Ming‐Hua , Wu Szu‐Chun , Pao Kuan‐Chuan , Unlu Irem , Gnabre John N. , Mold David E. , Huang Ru Chih C. , Hwu Jih Ru 
Published: March 2014

AbstractCancer has been a primary global health issue for decades, with hepatocellular carcinoma (HCC) resulting in more than half a million new cases annually. With survival rates as low as <5 % after five years, it remains a poorly treated cancer. Nordihydroguaiaretic acid (NDGA), an antioxidant, was previously proven effective against cancer cells. Nitroimidazole derivatives convert into reactive compounds under hypoxic conditions. In this study, eight methylated NDGAs containing a 2‐ or 4‐nitroimidazole moiety were synthesized as leads against HCC. Four of these conjugates, possessing a poly(ethylene glycol) tether, had superior aqueous solubility. These four NDGA–nitroimidazole conjugates were found to inhibit the proliferation HCC Hep3B cells with IC50 values between 10 and 15 μM. Furthermore, nitroimidazole‐conjugated NDGA derivatives exhibit better antiproliferative activity under hypoxic conditions.
Gold(I) Biscarbene Complexes Derived from Vascular‐Disrupting Combretastatin A‐4 Address Different Targets and Show Antimetastatic Potential
Authors: Muenzner Julienne K. , Biersack Bernhard , Kalie Hussein , Andronache Ion C. , Kaps Leonard , Schuppan Detlef , Sasse Florenz , Schobert Rainer 
Published: March 2014

AbstractGold N‐heterocyclic carbene (NHC) complexes are an emerging class of anticancer drugs. We present a series of gold(I) biscarbene complexes with NHC ligands derived from the plant metabolite combretastatin A‐4 (CA‐4) that retain its vascular‐disrupting effect, yet address different cellular and protein targets. Unlike CA‐4, these complexes did not interfere with tubulin, but with the actin cytoskeleton of endothelial and cancer cells. For the highly metastatic 518A2 melanoma cell line this effect was accompanied by a marked accumulation of cells in the G1 phase of the cell cycle and a suppression of active prometastatic matrix metalloproteinase‐2. Despite these mechanistic differences the complexes were as strongly antivascular as CA‐4 both in vitro in tube formation assays with human umbilical vein endothelial cells, and in vivo as to blood vessel disruption in the chorioallantoic membrane of chicken eggs. The antiproliferative effect of the new gold biscarbene complexes in a panel of six human cancer cell lines was impressive, with low sub‐micromolar IC50 values (72 h) even against CA‐4‐refractory HT‐29 colon and multidrug‐resistant MCF‐7 breast carcinoma cells. In preliminary studies with a mouse melanoma xenograft model the complexes led to significant decreases in tumor volume while being very well tolerated.
Synthesis and Electrocatalytic Properties of H2SO4‐Induced (100) Pt Nanoparticles Prepared in Water‐in‐Oil Microemulsion
Authors: Martínez‐Rodríguez Roberto A. , Vidal‐Iglesias Francisco J. , Solla‐Gullón José , Cabrera Carlos R. , Feliu Juan M. 
Published: March 2014

AbstractThe increasing number of applications for shape‐controlled metal nanoparticles (NPs) has led to the need for easy, cheap, and scalable methodologies. We report the synthesis of (100) preferentially oriented Pt NPs, with a particle size of 9 nm, by using a water‐in‐oil microemulsion method. The specific surface structure of the NPs is induced by the presence of H2SO4 in the water phase of the microemulsion. Interestingly, the results reported herein show how increasing amounts of H2SO4 lead to the formation of Pt NPs containing a larger amount of (100) sites on their surface. This preferential surface orientation is confirmed electrochemically by using the so‐called hydrogen adsorption/desorption process. In addition, transmission electron microscopy measurements confirm the presence of cubic‐like Pt NPs. Finally, the electrocatalytic properties of the Pt NPs are evaluated towards ammonia and CO electro‐oxidations, which are (100) structure‐sensitive reactions.
Unified subharmonic oscillation conditions for peak or average current mode control
Authors: Fang Chung‐Chieh 
Published: March 2014

SummaryThis paper is an extension of the author's recent research in which only buck converters were analyzed. Similar analysis can be equally applied to other types of converters. In this paper, a unified model is proposed for buck, boost, and buck–boost converters under peak or average current mode control to predict the occurrence of subharmonic oscillation. Based on the unified model, the associated stability conditions are derived in closed forms. The same stability condition can be applied to buck, boost, and buck–boost converters. Based on the closed‐form conditions, the effects of various converter parameters including the compensator poles and zeros on the stability can be clearly seen, and these parameters can be consolidated into a few ones. High‐order compensators such as type‐II and PI compensators are considered. Some new plots are also proposed for design purpose to avoid the instability. The instability is found to be associated with large crossover frequency. A conservative stability condition, agreed with the past research, is derived. The effect of the voltage loop ripple on the instability is also analyzed. Copyright © 2014 John Wiley & Sons, Ltd.
Clinician adherence to guidelines in the delivery of family‐based therapy for eating disorders
Authors: Kosmerly Stacey , Waller Glenn , Robinson Adele Lafrance 
Published: March 2014

ABSTRACTObjectiveClinicians have been shown to drift away from protocol in their delivery of evidence‐based treatments. This study explores this phenomenon in the delivery of family‐based therapy (FBT) for eating disorders, and the clinician characteristics that might explain such therapist drift.MethodThe participants were 117 clinicians who reported using FBT for eating disorders. They completed an online survey, which included questions relating to clinician characteristics, caseload, and reported use of FBT manuals and core therapeutic tasks, as well as a measure of anxiety.ResultsThe use of core FBT tasks was higher than for other therapies, but there were still noteworthy gaps between recommended and reported practice. Approximately a third of clinicians reported delivering “FBT” that deviated very substantially from evidence‐based protocols, often appearing to be on an individual therapy basis. Using an FBT manual to guide treatment delivery was associated with greater adherence to recommended techniques. Clinician caseload and anxiety were associated with differences in the use of specific FBT tasks.DiscussionConsistent with previous research regarding clinicians' use of other therapies, the delivery of FBT for the eating disorders is not homogeneous.ConclusionFurther investigation of this phenomenon is needed to determine the impact of deviating from treatment protocols on the effectiveness of FBT for the eating disorders. © 2014 Wiley Periodicals, Inc. (Int J Eat Disord 2015; 48:223–229)