bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calculating the velocity of a fast‐moving snow avalanche using an infrasound array
Authors: Havens Scott , Marshall Hans‐Peter , Johnson Jeffrey B. , Nicholson Bill 
Published: August 2014

AbstractOn 19 January 2012, a large D3 avalanche (approximately 103 t) was recorded with an infrasound array ideally situated for observing the avalanche velocity. The avalanche crossed Highway 21 in Central Idaho during the largest avalanche cycle in the 15 years of recorded history and deposited approximately 8 m of snow on the roadway. Possible source locations along the avalanche path were estimated at 0.5 s intervals and were used to calculate the avalanche velocity during the 64 s event. Approximately 10 s prior to the main avalanche signal, a small infrasound signal originated from the direction of the start zone. We infer this to be the initial snow pack failure, a precursory signal to the impending avalanche. The avalanche accelerated to a maximum velocity of 35.9 ± 7.6m s−1 within 30 s before impacting the highway. We present a new technique to obtain high spatial and temporal resolution velocity estimates not previously demonstrated with infrasound for avalanches and other mass wasting events.
Inertial Alfvén wave localization and turbulent spectrum
Authors: Sharma R. P. , Kumari Anju , Yadav Nitin 
Published: August 2014

AbstractThe localization of pump inertial Alfvén wave (IAW) in low β plasmas (β ≪ me/ mi) has been investigated by developing a model based on weak IAW and finite amplitude background density fluctuations. When IAW is perturbed by these fluctuations which are in the form of magnetosonic and ion acoustic waves, its phase velocity gets modified and IAW breaks up into localized structures of very high intensity. Numerical simulation has been carried out to analyze the localized structures and magnetic fluctuation spectrum of pump IAW. We have also developed a simplified model to understand the physical insight into evolution pattern of IAW. Results obtained from simulation reveal that turbulent spectrum up to k⊥λe ≈ 1 follows Kolmogorov power law. Furthermore, at shorter wavelengths, dispersion starts and spectrum steepens with power law index ∼ − 3.8. Energy transport to smaller length scales through this mechanism may be accountable for the observed parallel electron heating in low β plasmas. Results obtained from the numerical simulation are consistent with the observations of various spacecraft like FAST and Hawkeye.
Distribution of vertical velocity inferred from secondary flow in a curved tidal channel
Authors: Russell P. , Vennell R. 
Published: August 2014

AbstractHigh‐resolution observations from the curved tidal channel of the Otago Harbour shows secondary flows up to 20% of the primary flow and vertical velocity inferred from secondary flow up to 1% of the primary flow. This vertical velocity is inferred on a much finer scale than previous works. The spatial pattern of this vertical velocity is upward on the inside and downward on the outside of the bend, consistent with previous laboratory flume measurements. Linear regression, rp = 0.95, shows the cross‐channel distribution of the observed secondary flow can be resolved from the horizontal ADCP measurements well enough to be consistent with the cross‐channel distribution of secondary flow derived from the observed primary flow using the model of Kalkwijk and Booij (1986). Linear regression, rp = 0.80, shows the vertical velocity inferred from observed secondary flow is consistent with vertical velocity derived from the observed primary flow using the model of Kalkwijk and Booij (1986). This also shows the cross‐channel distribution of the observed secondary flow is resolved well enough from the horizontal ADCP measurements to be able to infer the vertical velocity from mass continuity. The required horizontal resolution is made possible by Radial Basis Function (RBF) smoothing and spatial interpolation that allows for continuity of the spatial derivatives. Modeling trajectories using channel dimensions and velocity field values equivalent to the observations show that 3‐dimensional secondary circulation forms a loose helical flow pattern.
Humidity variability revealed by a sounding array and its implications for cloud representation in GCMs
Authors: Lin Yanluan 
Published: August 2014

AbstractSubgrid‐scale humidity variability is critical for statistical cloud schemes. The Atmospheric Radiation Measurement (ARM) sounding array, covering a comparable size to a grid box of current global climate models (GCMs), provides estimates of subgrid‐scale humidity variability. Using radiosonde measurements from ARM sounding arrays, humidity variabilities at a tropical and a midlatitude site are analyzed. Normalized moisture variance is small in the lower troposphere but tends to be large in the middle troposphere. Moisture variability dominates relative humidity (RH) variability at the tropical site, but the contribution by temperature variability cannot be ignored at the midlatitude site. Based on the analysis, a simple linear relationship between RH variance and mean is proposed. Cloud schemes assuming Gaussian distributions give comparable cloudiness as those assuming a beta distribution considering both moisture variance and skewness. A probability distribution function scheme assuming a Gaussian distribution of RH has more flexibility than a RH threshold scheme, which tends to overestimate cloudiness in the moist boundary layer over the tropics. Supersaturation with respect to ice needs to be allowed in the upper troposphere over the tropics to reduce the persistent overestimated cloudiness there. Similar comparison results are found from analysis of cloud resolving model simulations. The study suggests that measurements from sounding arrays would be valuable for statistical cloud scheme evaluation and development.
Surface Polarization Matters: Enhancing the Hydrogen‐Evolution Reaction by Shrinking Pt Shells in Pt–Pd–Graphene Stack Structures
Authors: Bai Song , Wang Chengming , Deng Mingsen , Gong Ming , Bai Yu , Jiang Jun , Xiong Yujie 
Published: August 2014

AbstractSurface charge state plays an important role in tuning the catalytic performance of nanocrystals in various reactions. Herein, we report a synthetic approach to unique Pt–Pd–graphene stack structures with controllable Pt shell thickness. These unique hybrid structures allow us to correlate the Pt thickness with performance in the hydrogen‐evolution reaction (HER). The HER activity increases with a decrease in the Pt thickness, which is well explained by surface polarization mechanism as suggested by first‐principles simulations. In this hybrid system, the difference in work functions of Pt and Pd results in surface polarization on the Pt surface, tuning its charge state for hydrogen reduction. Meanwhile, the supporting graphene provides two‐dimensional channels for efficient charge transport, improving the HER activities. This work opens up possibilities of reducing Pt usage while achieving high HER performance.
A Lightweight Polymer Solar Cell Textile that Functions when Illuminated from Either Side
Authors: Zhang Zhitao , Li Xueyi , Guan Guozhen , Pan Shaowu , Zhu Zhengju , Ren Dayong , Peng Huisheng 
Published: August 2014

AbstractAn all‐solid‐state, lightweight, flexible, and wearable polymer solar cell (PSC) textile with reasonable photovoltaic performance has been developed. A metal textile electrode made from micrometer‐sized metal wires is used as the cathode, and the surfaces of the metal wires are dip‐coated with the photoactive layers. Two ultrathin, transparent, and aligned carbon nanotube sheets that exhibit remarkable electronic and mechanical properties were coated onto the modified metal textile at both sides as the anode to produce the desired PSC textile. Because of the designed sandwich structure, the PSC textile displays the same energy conversion efficiencies regardless of which side it is irradiated from. As expected, the PSC textiles are highly flexible, and their energy conversion efficiencies varied by less than 3 % after bending for more than 200 cycles. The PSC textile shows an areal density (5.9 mg cm−2) that is lower than that of flexible film‐based PSCs (31.3 mg cm−2).
A Universal Procedure for the [18F]Trifluoromethylation of Aryl Iodides and Aryl Boronic Acids with Highly Improved Specific Activity
Authors: van der Born Dion , Sewing Claudia , Herscheid J. (Koos) D. M. , Windhorst Albert D. , Orru Romano V. A. , Vugts Danielle J. 
Published: August 2014

AbstractHerein, we describe a valuable method for the introduction of the [18F]CF3 group into arenes with highly improved specific activity by the reaction of [18F]trifluoromethane with aryl iodides or aryl boronic acids. This [18F]trifluoromethylation reaction is the first to be described in which the [18F]CF3 products are generated in actual trace amounts and can therefore effectively be used as PET tracers. The method shows broad scope with respect to possible aryl iodide and aryl boronic acid substrates, as well as good to excellent conversion. In particular, the [18F]trifluoromethylation of boronic acids was found to outperform [18F]trifluoromethylation reactions of halogenated aryl precursors with regard to conversion, reaction conditions, and kinetics.
Energy Dissipation Rates of Newtonian and Non‐Newtonian Fluids in a Stirred Vessel
Authors: Wang Xu , Feng Xin , Yang Chao , Mao Zai‐Sha 
Published: August 2014

AbstractEnergy dissipation rates of water and glycerol as Newtonian fluids and carboxyl methyl carbonate solution as non‐Newtonian fluid in a stirred vessel are investigated by 2D particle image velocimetry and compared. Mean velocity profiles reflect the Reynolds (Re) number similarity of two flow fields with different rheological properties, but the root mean square velocity profiles differ in rheology at the same Re‐number. Energy dissipation rates are estimated by direct calculation of fluctuating velocity gradients. The varying energy dissipation rates of Newtonian and non‐Newtonian fluids result from the difference in fluid rheology and apparent viscosity distribution which decides largely the flow pattern, circulation intensity, and rate of turbulence generation.
Reactivity of Metal Catalysts in Glucose–Fructose Conversion
Authors: Loerbroks Claudia , van Rijn Jeaphianne , Ruby Marc‐Philipp , Tong Qiong , Schüth Ferdi , Thiel Walter 
Published: August 2014

AbstractA joint experimental and computational study on the glucose–fructose conversion in water is reported. The reactivity of different metal catalysts (CrCl3, AlCl3, CuCl2, FeCl3, and MgCl2) was analyzed. Experimentally, CrCl3 and AlCl3 achieved the best glucose conversion rates, CuCl2 and FeCl3 were only mediocre catalysts, and MgCl2 was inactive. To explain these differences in reactivity, DFT calculations were performed for various metal complexes. The computed mechanism consists of two proton transfers and a hydrogen‐atom transfer; the latter was the rate‐determining step for all catalysts. The computational results were consistent with the experimental findings and rationalized the observed differences in the behavior of the metal catalysts. To be an efficient catalyst, a metal complex should satisfy the following criteria: moderate Brønsted and Lewis acidity (pKa=4–6), coordination with either water or weaker σ donors, energetically low‐lying unoccupied orbitals, compact transition‐state structures, and the ability for complexation of glucose. Thus, the reactivity of the metal catalysts in water is governed by many factors, not just the Lewis acidity.
Absorption of carbon dioxide into sterically hindered amines: Kinetics analysis and the influence of promoters
Authors: Vaidya Prakash D. , Jadhav Santosh G. 
Published: August 2014

AbstractThe sterically hindered amines 2‐amino‐2‐methyl‐1‐propanol (AMP) and 2‐piperidineethanol (PE) are promising candidate absorbents for CO2 capture. Although reaction kinetics of the CO2‐AMP system is extensively studied, there exists some deviations in the reported kinetic parameters and there is some uncertainty about the reaction mechanism. Contrarily, kinetic data on the CO2‐PE reaction system is scarce. In this work, these reaction systems were revisited to set right the discrepancy of previous works and facilitate and deepen fundamental understanding of these reaction systems. Kinetic data were obtained experimentally at 298, 303, and 308 K by using a stirred‐cell reactor. The molarities of AMP and PE in the aqueous solutions were varied from 1 to 3 M and 0.05 to 0.25 M. Second order rate constants for the reactions with AMP and PE were equal to 809 and 899 m3/(kmol s) at 303 K. The increase in temperature and amine concentration caused the expected increase in the values of the observed pseudo‐first order reaction rate constants. Finally, it was found that the investigated reactions were accelerated by the addition of two sterically hindered secondary amines comprising an alkyl group, viz., N‐methyl‐ and N‐ethyl‐monoethanolamine, even at low additive concentrations (0.05–0.1 M).
Nucleophilic Difluoro(phenylsulfonimidoyl)methylation of Unactivated Alkyl Bromides with PhSO(NTBS)CF2H: Facile Entry into gem‐Difluoroalkenes
Authors: Shen Xiao , Liu Qinghe , Ni Chuanfa , Hu Jinbo 
Published: August 2014

AbstractAn efficient nucleophilic difluoro(phenylsulfonimidoyl)methylation of unactivated primary alkyl bromides with PhSO(NTBS)CF2H has been developed. It is particularly remarkable that, when 1.5 equiv. of alkyl bromides are used, the substitution products are obtained in moderate to excellent yields. The prepared difluoro(phenylsulfonimidoyl)methylated alkanes can be readily transformed to gem‐difluoroalkenes via base‐mediated β‐elimination reaction.
On Desilylation of 13‐Vertex Carborane 1,2‐Me2Si(CH2)2‐1,2‐C2B11H11
Authors: Zhang Jian , Xie Zuowei 
Published: August 2014

AbstractThe reasons for facile double desilylation of 13‐vertex carborane 1,2‐Me2Si(CH2)2‐1,2‐C2B11H11 (2) are discussed in this article. New 13‐ and 14‐vertex ruthenacarboranes bearing the same ‐CH2SiMe2CH2‐ linkage have been prepared and structurally characterized for comparison. Structural analyses of 13‐ and 14‐vertex heteroboranes as well as control experiments suggest that the facile double desilylation of 2 on silica gel can be attributed to the joint actions of several factors involving the high ring‐strain of exo five‐membered C4Si ring, Lewis acidity of Si atom and Br⊘nsted acidity of silica surface.
Markov chain order estimation based on the chi‐square divergence
Authors: Baigorri Angel Rodolfo , Gonçalves Cátia Regina , Resende Paulo Angelo Alves 
Published: August 2014

AbstractIn the selection model context, several alternatives for estimating the order of a Markov chain have been proposed. The Akaike's information criterion, AIC, is the best known and most used alternative, in spite of its inconsistency. The Bayesian information criterion (BIC) and the efficient determination criterion (EDC) have been stated as strong consistent approaches. The success of the AIC is mainly a result of its better performance when compared with the widely known consistent alternatives. In this work, we define a few objects which capture relevant information from the sample of a finite Markov chain and we use the chi‐square divergence to define a new estimator for the Markov chain order, named GDL. Finally, we show numerical simulations and a simple application to compare the proposed alternative with AIC, BIC and EDC.The Canadian Journal of Statistics42: 563–578; 2014 © 2014 Statistical Society of Canada
Outcome in Patients With Left‐Sided Native‐Valve Infective Endocarditis and Isolated Large Vegetations
Authors: Desch Steffen , Freund Anne , de Waha Suzanne , Eitel Ingo , Lurz Philipp , Stiermaier Thomas , Fuernau Georg , Schuler Gerhard , Thiele Holger 
Published: August 2014

AbstractBackgroundIn patients with left‐sided native‐valve infective endocarditis (IE), the risk of embolism is increased with a vegetation size ≥10 mm. For this reason—according to guidelines—surgery may be considered in patients with isolated large vegetations (without any other indication for surgery). However, the value of surgery in this patient subset has never been systematically studied.HypothesisWe hypothesized that surgery may be superior to medical therapy in terms of clinical outcome in the aforementioned patients.MethodsAll patients who presented at our institution between January 2000 and July 2012 with isolated left‐sided native‐valve IE and large vegetations (≥10 mm) were examined. Patients with conventional indications for surgical treatment were excluded. Follow‐up for clinical events was performed according to predefined definitions.ResultsA total of 71 patients with left‐sided native‐valve IE and isolated large vegetations qualified for inclusion into the study cohort. Mean vegetation length was 17 ± 5 mm. A total of 59 patients underwent surgery after a mean of 5 ± 6 days following the initiation of antibiotic treatment. Mean follow‐up duration was 6.0 ± 2.9 years. Surgical compared to purely medical treatment was associated with a significant increase in long‐term all‐cause mortality (P = 0.03 by log‐rank test, unadjusted analysis). Upon multivariable Cox regression analysis, surgical treatment, affection of mitral valve, blood cultures positive for Staphylococcus aureus, and increasing age showed trends as independent predictors of long‐term mortality.ConclusionsSurgical treatment in patients with left‐sided native‐valve IE and isolated large vegetations without any other indication for surgery seems to be associated with excess mortality. A randomized controlled trial of surgery vs conservative treatment in this subset of patients is justified.
The Nature of the Active Site in Ziegler–Natta Olefin Polymerization Catalysis Systems – A Computational Investigation
Authors: Kumawat Jugal , Kumar Gupta Virendra , Vanka Kumar 
Published: August 2014

AbstractFull quantum chemical calculations with density functional theory (DFT) show that a principal role of donors in Ziegler–Natta (ZN) olefin polymerization catalysts is to coordinate to the metal center at the active sites on the MgCl2 surface. Thereby, the behavior of the catalyst is modulated to favor insertion over termination and, thus, polymerization occurs. This is shown to be true for a range of different donors. The calculations indicate that active sites that feature anionic chloride ligands at the titanium center (the conventional model for the active site) would lead to lower‐molecular‐weight polymers. If an –OC2H5 group were present instead of a chloride ligand, the active site would much more effectively produce long chain polymers. Therefore, the current work provides important new insights into the nature of the ZN polymerization process.
Chiral MnIII–salalen and –salan Complexes Derived from (S)‐Pyrrolidin‐2‐ylmethanamine and Their Catalytic Activity in the Asymmetric Strecker Reaction
Authors: Kumar Pramod , Saravanan S. , Khan Noor‐ul Hasan , Hussain Firasat , Singh Surendra 
Published: August 2014

AbstractThe salalen and salan ligands have been synthesized by the reactions of (S)‐pyrrolidin‐2‐ylmethanamine and salicylaldehyde derivatives. These ligands were treated with Mn(CH3COO)2·4H2O followed by air oxidation to give (S,R)‐MnIII–salalen and –salan complexes in yields of 84–88 %. The absolute configuration of (S,R)‐MnIII–salalen was determined by single‐crystal X‐ray diffraction and CD analysis of the ligands and complexes showed similiar Cotton effects. The MnIII–salalen and –salan complexes were screened for their catalytic activity in the asymmetric Strecker reaction. (S,R)‐2,4‐Di‐tert‐butyl‐6‐({[1‐(3,5‐di‐tert‐butyl‐2‐hydroxybenzyl)pyrrolidin‐2‐yl]methylimino}methyl)phenolatomanganese(III) chloride (5 mol‐%) was found to be a suitable catalyst for the asymmetric Strecker reaction of N‐(4‐methoxybenzylidene)diphenylmethanamine with ethyl cyanoformate, which gave 89 % yield and 55 % ee of 2‐(benzhydrylamino)‐2‐(4‐methoxyphenyl)acetonitrile at –15 °C after 24 h.
Unprecedented Borylene Insertion into a C–N Bond
Authors: Ghadwal Rajendra S. , Schürmann Christian J. , Engelhardt Felix , Steinmetzger Christian 
Published: August 2014

AbstractCarbenes are well established reactive intermediates and play an important role in organic synthesis, whereas the scope of borylenes is rather limited. Selective borylene insertion into a C–N bond to yield boryl‐functionalized N‐heterocyclic olefins (NHOs), [{N(Dipp)N(DippBH)CHCH}CCH2]2 (6) and [{N(Dipp)N(DippBPh)CHCH}CCH2][{N(Dipp)N(2‐iPr‐6‐CHMeCH2BC6H3)CHCH}CCH2] (8) (Dipp = 2,6‐iPr2C6H3) is reported for the first time. KC8 reduction of (IPrCH2)BRX2 adducts (IPrCH2 = {N(Dipp)CH}2CCH2; R = X = I (2); R = Ph, X = Cl (4)) affords compounds 6 and 8. Surprisingly, treatment of (IPrCH2)BHCl2 (3) with KC8 yields completely unexpected diborane compound (IPr)BH2BH2(IPr) (7). Compound 2 is unstable in THF and induces ring opening reaction to form the borenium ion [(IPrCH2)B{O(CH2)4I}2]I (5).
Syntheses of 4‐Substituted 2‐(Trichloromethyl)quinazolines under Mild Conditions by Benzyne [4+2] Cycloaddition
Authors: Lechuga‐Eduardo Harim , Olivo Horacio F. , Romero‐Ortega Moises 
Published: August 2014

AbstractAn experimentally simple and convenient synthesis of 4‐susbstituted 2‐(trichloromethyl)quinazolines by cycloaddition of benzyne with 2‐(trichloromethyl)‐1,3‐diazabutadienes was developed. The 2‐(trichloromethyl)‐1,3‐diazabutadienes (R1 = H and Me) were prepared from trichloroacetamidine and the appropriate N,N‐dimethylamide dimethyl acetal or from trichloroacetamidine and a Vilsmeier–Haack reagent containing an aryl group.
Study of the Complexation of Pb(II) with meso‐2,3‐ Dimercaptosuccinic Acid (DMSA) and 2,3‐Dimercapto‐1‐propanesulfonic acid (DMPS) Using a Bismuth‐Bulk Rotating Disk Electrode
Authors: de la Gala Morales María , Ariño Cristina , Díaz‐Cruz José Manuel , Esteban Miquel 
Published: August 2014

AbstractFor the first time, the suitability of bismuth bulk rotating disk electrode (BiB‐RDE) for the study of metal complexation has been tested. Cyclic (CV) and differential pulse (DPV) voltammetry have been used to study the complexation of Pb(II) with two of the most effective chelating agents for the treatment of Pb(II) poisoning (meso‐2,3‐dimercaptosuccinic acid, DMSA, and 2,3‐dimercapto‐1‐propanesulfonic acid, DMPS). Multivariate curve resolution has been applied to voltammetric data to obtain the stoichiometries and stability constants of the complexes formed. In both systems, the ML2 complex was predominant, with log β2 values of 10.13 and 8.80 for DMSA‐Pb(II) and DMPS‐Pb(II), respectively.