bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comprehensive Microscopic Picture of the Benzhydryl Radical and Cation Photogeneration and Interconversion through Electron Transfer
Authors: Sailer Christian F. , Thallmair Sebastian , Fingerhut Benjamin P. , Nolte Christoph , Ammer Johannes , Mayr Herbert , Pugliesi Igor , de Vivie‐Riedle Regina , Riedle Eberhard 
Published: March 2013

AbstractBond cleavage and bond formation are central to organic chemistry. Carbocations play a key role in our understanding of nucleophilic substitution reactions that involve both processes. The precise understanding of the mechanism and dynamics of the photogeneration of carbocations and carbon radicals is therefore an important quest. In particular, the role of electron transfer for the generation of carbocations from the radical pair is still unclear. A quantitative femtosecond absorption study is presented, with ultrabroad probing on selected donor and acceptor substituted benzhydryl chlorides irradiated with 270 nm (35 fs) pulses. The ultrafast bond cleavage within 300 fs is almost exclusively homolytic, thus leading to a radical pair. The carbocations observable in the nanosecond regime are generated from these radicals by electron transfer from the benzhydryl to the chlorine radical within the first tens of picoseconds. Their concentration is reduced by geminate recombination within hundreds of picoseconds. In moderately polar solvents this depletion almost extinguishes the cation population; in highly polar solvents free ions are still observable on the nanosecond timescale. The explanation of the experimental findings requires the microscopic realm of the intermediates to be accounted for, including their spatial and environmental distributions. The distance dependent electron transfer described by Marcus theory is combined with Smoluchowski diffusion. The depletion of the radical pair distribution at small distances causes a temporal increase of the mean distance and the observed stretched exponential electron transfer. A close accord with experiment can only be reached for a broad distribution of the nascent radical pairs. The increase in the inter‐radical and inter‐ion pair distance is measured directly as a shift of the UV/Vis absorption of the products. The results demonstrate that, at least for aprotic solvents, traditional descriptions of reaction mechanisms based on the concept of contact and solvent‐separated pairs have to be reassessed.
Hydrodesulfurization of Thiophene over Few‐Layer MoS2 Covered with Cobalt and Nickel Nanoparticles
Authors: Rao Bolla Govinda , Matte H. S. S. Ramakrishna , Chaturbedy Piyush , Rao C. N. R. 
Published: March 2013

AbstractThe hydrodesulfurization reaction of thiophene has been investigated over graphene‐like few‐layer MoS2 as well as over Co‐ and Ni‐nanoparticle‐covered few‐layer MoS2. Conversion of thiophene to n‐butane over few‐layer MoS2 is superior to that over bulk MoS2; the percent conversion is approximately 64 % at 450 °C. However, over few‐layer MoS2 covered with Co or Ni nanoparticles the conversion increases to approximately 98 % at around 375 °C as a result of the smaller nanoparticles being more effective.
Lanthanide(III) Complexes of Diethylenetriaminepentaacetic Acid (DTPA)–Bisamide Derivatives as Potential Agents for Bimodal (Optical/Magnetic Resonance) Imaging
Authors: Debroye Elke , Eliseeva Svetlana V. , Laurent Sophie , Vander Elst Luce , Petoud Stéphane , Muller Robert N. , Parac‐Vogt Tatjana N. 
Published: March 2013

AbstractDiethylenetriaminepentaacetic acid (DTPA)–bisamide derivatives functionalized with p‐toluidine, 6‐aminocoumarin, 1‐naphthalene methylamine and 4‐ethynylaniline were synthesized and fully characterized by mass spectrometry, NMR spectroscopy, FTIR spectroscopy and elemental analysis. LnIII complexes (Ln = Gd, Eu, Tb, Y) of the ligands DTPA–bis‐p‐toluidineamide (DTPA–BTolA), DTPA–bis‐6‐coumarinamide (DTPA–BCoumA), DTPA–bis‐1‐naphthylmethylamide (DTPA–BNaphA) and DTPA–bis‐4‐ethynylphenylamide (DTPA–BEthA) were prepared and studied for their bimodal magnetic resonance imaging/optical properties. EuIII and TbIII derivatives in aqueous solutions exhibit characteristic red and green emission, respectively, with quantum yields of 0.73 % for EuIII–DTPA–BNaphA and 2.5 % for TbIII–DTPA–BEthA. Ligand‐centred photophysical properties of the GdIII complexes were investigated to gain insight into energy‐transfer processes that take place in these systems. The GdIII complexes were also analyzed by nuclear magnetic relaxation dispersion (NMRD) techniques. The relaxivity (r1) at 20 MHz and 310 K equals 4.1 s–1 mM–1 for Gd–DTPA–BTolA, 5.1 s–1 mM–1 for Gd–DTPA–BCoumA, 6.4 s–1 mM–1 for Gd–DTPA–BNaphA and 5.7 s–1 mM–1 for Gd–DTPA–BEthA. These values are higher than the value of 3.8 s–1 mM–1 for Gd–DTPA (Magnevist). The improved relaxivity is due to the increase in the rotational tumbling time τR with a factor of 1.6 for Gd–DTPA–BTolA, 2.1 for Gd–DTPA–BCoumA, 3.1 for Gd–DTPA–BNaphA and 6.5 for Gd–DTPA–BEthA. In a 4 % human serum albumin solution, the apparent relaxivity at 20 MHz increases to values of 13.9 and 19.1 s–1 mM–1 for Gd–DTPA–BNaphA and Gd–DTPA–BEthA, respectively. All these features assist the search for optimal bimodal optical and magnetic resonance imaging probes.
Synthesis and Characterization of β‐Trifluoromethyl‐Substituted Pyrrolidines
Authors: Yarmolchuk Vladimir S. , Shishkin Oleg V. , Starova Viktoriia S. , Zaporozhets Olga A. , Kravchuk Olga , Zozulya Sergey , Komarov Igor V. , Mykhailiuk Pavel K. 
Published: March 2013

AbstractA practical synthetic approach to the construction of a library of three isomeric/homologous β‐trifluoromethyl‐substituted pyrrolidines is disclosed. All products were prepared in multigram quantities from a common precursor. The key synthetic step was a [3+2] cycloaddition reaction. The influence of the trifluoromethyl group on the physicochemical characteristics of the pyrrolidine fragment was studied.
Novel Ag–Glass Composite Interconnect Materials for Anode‐Supported Flat‐Tubular Solid Oxide Fuel Cells Operated at an Intermediate Temperature
Authors: Pi S.‐H. , Lee S.‐B. , Song R.‐H. , Lee J.‐W. , Lim T.‐H. , Park S.‐J. , Shin D.‐R. , Park C.‐O. 
Published: March 2013

AbstractWe developed novel Ag–glass composite interconnect materials for anode‐supported flat‐tubular solid oxide fuel cells (SOFCs) operated at 700 °C by optimization of the glass content. For this purpose, the variations of phase stability, area specific resistance (ASR), microstructure, gas leak rate, cell performance, and open circuit voltage (OCV) were determined for the Ag–glass composite materials with respect to the glass content. The Ag–glass composite materials maintain phase stability without chemical reactions. The ASR increased as the glass content increases due to glass existing as an insulator between the Ag phases. All the composite materials showed dense coating layers on the anode support and had a low gas leak. The cell performance and OCV were measured to identify the optimum composition of the Ag–glass composites. Our results confirm that Ag–glass composites are suitable for high performance interconnects in anode‐supported flat‐tubular fuel cells operated below 700 °C.
Tectonic overpressure in weak crustal‐scale shear zones and implications for the exhumation of high‐pressure rocks
Authors: Schmalholz Stefan M. , Podladchikov Yuri Y. 
Published: March 2013

AbstractA two‐dimensional numerical simulation of lithospheric shortening shows the formation of a stable crustal‐scale shear zone due to viscous heating. The shear zone thickness is controlled by thermomechanical coupling that is resolved numerically inside the shear zone. Away from the shear zone, lithospheric deformation is dominated by pure shear, and tectonic overpressure (i.e., pressure larger than the lithostatic pressure) is proportional to the deviatoric stress. Inside the shear zone, deformation is dominated by simple shear, and the deviatoric stress decreases due to thermal weakening of the viscosity. To maintain a constant horizontal total stress across the weak shear zone (i.e., horizontal force balance), the pressure in the shear zone increases to compensate the decrease of the deviatoric stress. Tectonic overpressure in the weak shear zone can be significantly larger than the deviatoric stress at the same location. Implications for the geodynamic history of tectonic nappes including high‐pressure/ultrahigh‐pressure rocks are discussed.
Characterization and intercomparison of global moderate resolution leaf area index (LAI) products: Analysis of climatologies and theoretical uncertainties
Authors: Fang Hongliang , Jiang Chongya , Li Wenjuan , Wei Shanshan , Baret Frédéric , Chen Jing M. , Garcia‐Haro Javier , Liang Shunlin , Liu Ronggao , Myneni Ranga B. , Pinty Bernard , Xiao Zhiqiang , Zhu Zaichun 
Published: March 2013

AbstractLeaf area index (LAI) is a critical variable for land surface and climate modeling studies. Several global LAI products exist, and it is important to know how these products perform and what their uncertainties are. Five major global LAI products—MODIS, GEOV1, GLASS, GLOBMAP, and JRC‐TIP—were compared between 2003 and 2010 at a 0.01° spatial resolution and with a monthly time step. The daily Land‐SAF product was used as a regional reference in order to evaluate the performance of other global products in Africa. Cross‐sensor LAI conversion equations were derived for different biome types. Product uncertainties were assessed by looking into the product quantitative quality indicators (QQIs) attached to MODIS, GEOV1, and JRC‐TIP. MODIS, GEOV1, GLASS, and GLOBMAP are generally consistent and show strong linear relationships between the products (R2 > 0.74), with typical deviations of < 0.5 for nonforest and < 1.0 for forest biomes. JRC‐TIP, the only effective LAI product, is about half the values of the other LAI products. The average uncertainties and relative uncertainties are in the following order: MODIS (0.17, 11.5%) < GEOV1 (0.24, 26.6%) < Land‐SAF (0.36, 37.8%) < JRC‐TIP (0.43, 114.3%). The highest relative uncertainties usually appear in ecological transition zones. More than 75% of MODIS, GEOV1, JRC‐TIP, and Land‐SAF pixels are within the absolute uncertainty requirements (± 0.5) set by the Global Climate Observing System (GCOS), whereas more than 78.5% of MODIS and 44.6% of GEOV1 pixels are within the threshold for relative uncertainty (20%). This study reveals the discrepancies mainly due to differences between definitions, retrieval algorithms, and input data. Future product development and validation studies should focus on areas (e.g., sparsely vegetated and savanna areas) and periods (e.g., winter time) with higher uncertainties.
K‐t GRAPPA accelerated phase contrast MRI: Improved assessment of blood flow and 3‐directional myocardial motion during breath‐hold
Authors: Bauer Simon , Markl Michael , Föll Daniela , Russe Maximilian , Stankovic Zoran , Jung Bernd 
Published: March 2013

PurposeTo evaluate spatiotemporal parallel imaging with R = 5 in comparison to conventional parallel imaging with R = 2 applied to phase contrast (PC) magnetic resonance imaging (MRI). This was motivated by the fact that scan times for PC imaging often exceed breath‐hold capabilities of patients even with standard parallel imaging using typical reduction factors of R = 2.Materials and MethodsK‐t generalized autocalibrating partially parallel acquisition (GRAPPA) acquisition was validated in phantom measurements and then applied in 10 volunteer and three patient examinations. Due to the higher reduction factor compared to conventional GRAPPA, k‐t GRAPPA measurements could be performed during breath‐hold with high spatial and temporal resolution. K‐t GRAPPA scans were compared to GRAPPA acquired during free‐breathing with navigator respiration control. In addition, spatiotemporally accelerated PC imaging was acquired during free‐breathing for comparison of k‐t‐accelerated breath‐held scans.ResultsSubstantial improvements in image quality for the breath‐hold measurements were observed. Significantly reduced peak velocities were found for the GRAPPA protocol compared to the k‐t‐accelerated breath‐hold scans for both flow (8%) and myocardial motion (up to 30%) measurements.ConclusionSpatiotemporal acceleration allows the performance of high temporal or spatial resolution PC imaging during breath‐hold while providing high image quality and robust acquisition of functional information that cannot be achieved during breath‐hold with standard techniques. J. Magn. Reson. Imaging 2013;38:1054–1062. © 2013 Wiley Periodicals, Inc.
Low‐molecular contrast agent dynamic contrast‐enhanced (DCE)‐MRI and diffusion‐weighted (DW)‐MRI in early assessment of bevacizumab treatment in breast cancer xenografts
Authors: Moestue Siver A. , Huuse Else M. , Lindholm Evita M. , Bofin Anna , Engebraaten Olav , Mælandsmo Gunhild M. , Akslen Lars A. , Gribbestad Ingrid S. 
Published: March 2013

PurposeTo investigate the effect of bevacizumab treatment on vascular architecture and function in two xenograft models with different angiogenic properties using diffusion‐weighted magnetic resonance imaging (DW‐MRI) and dynamic contrast‐enhanced MRI (DCE‐MRI).Materials and MethodsMice carrying basal‐like (MAS98.12) or luminal‐like (MAS98.06) orthotopic breast cancer xenografts were treated with bevacizumab (5 mg/kg), doxorubicin (8 mg/kg), or both drugs in combination. DW‐MRI and DCE‐MRI were performed before and 3 days after treatment using a Bruker 7T preclinical scanner. Mean microvessel density (MVD) and proliferating microvessel density (pMVD) in the tumors were determined for evaluation of vascular response to bevacizumab treatment.ResultsNo changes in DCE‐MRI or DW‐MRI parameters were observed in untreated controls during the experiment period. DW‐MRI showed increased apparent diffusion coefficient (ADC) values in all treatment groups in both basal‐like and luminal‐like xenografts. DCE‐MRI showed increased contrast agent uptake, particularly in central regions of the tumors, after bevacizumab/combination treatment in both xenograft models. This was accompanied by decreased MVD and pMVD in basal‐like xenografts. Doxorubicin treatment had no effect on DCE‐MRI parameters in any of the xenograft models.ConclusionBoth DW‐MRI and DCE‐MRI demonstrated an early response to bevacizumab treatment in the xenograft tumors. Increased contrast agent uptake and reduced MVD/pMVD is consistent with a normalization of vascular function. J. Magn. Reson. Imaging 2013;38:1043–1053. © 2013 Wiley Periodicals, Inc.
Masters athletes exhibit larger regional brain volume and better cognitive performance than sedentary older adults
Authors: Tseng Benjamin Y. , Uh Jinsoo , Rossetti Heidi C. , Cullum C. Munro , Diaz‐Arrastia Ramon F. , Levine Benjamin D. , Lu Hanzhang , Zhang Rong 
Published: March 2013

PurposeTo investigate differences in the age‐related decline in brain tissue concentration between Masters athletes and sedentary older adults.Materials and MethodsTwelve Masters athletes (MA) (three females, age = 72.4 ± 5.6 years, endurance training >15 years), 12 sedentary elderly (SE) similar in age and educational level (four females, age = 74.6 ± 4.3 years), and nine young controls (YC) (four females, age = 27.2 ± 3.6 years) participated. T1‐weighted high‐resolution (1 × 1 × 1mm3) images were acquired. Voxel‐based analysis was conducted to identify clusters showing tissue concentration differences with t‐tests. Cognitive function was assessed using a standard clinical battery focused on executive function and memory.ResultsTwo MA and two SE were unable to complete the magnetic resonance imaging (MRI) study. Both SE and MA showed lower gray matter (GM) concentrations than YC in the superior, inferior and middle frontal gyrus, superior temporal gyrus, postcentral gyrus, and the cingulate gyrus (PFDR‐corrected < 0.001) and lower white matter (WM) concentrations in the inferior frontal gyrus and precentral gyrus (PFDR‐corrected < 0.005). Notably, MA showed higher GM and WM concentrations than SE in the subgyral, cuneus, and precuneus regions related to visuospatial function, motor control, and working memory (PFDR‐corrected < 0.005). After controlling for estimated intelligence, MA outperformed SE on tasks of letter (P < 0.01) and category (P < 0.05) fluency.ConclusionLife‐long exercise may confer benefits to some aspects of executive function and age‐related brain tissue loss in the regions related to visuospatial function, motor control, and working memory in older adults. J. Magn. Reson. Imaging 2013;38:1169–1176. © 2013 Wiley Periodicals, Inc.
Bioactive lipids in the butter production chain from Parmigiano Reggiano cheese area
Authors: Verardo Vito , Gómez‐Caravaca Ana M , Gori Alessandro , Losi Giuseppe , Caboni Maria F 
Published: March 2013

AbstractBACKGROUNDBovine milk contains hundreds of diverse components, including proteins, peptides, amino acids, lipids, lactose, vitamins and minerals. Specifically, the lipid composition is influenced by different variables such as breed, feed and technological process. In this study the fatty acid and phospholipid compositions of different samples of butter and its by‐products from the Parmigiano Reggiano cheese area, produced by industrial and traditional churning processes, were determined.RESULTSThe fatty acid composition of samples manufactured by the traditional method showed higher levels of monounsaturated and polyunsaturated fatty acids compared with industrial samples. In particular, the contents of n‐3 fatty acids and conjugated linoleic acids were higher in samples produced by the traditional method than in samples produced industrially. Sample phospholipid composition also varied between the two technological processes. Phosphatidylethanolamine was the major phospholipid in cream, butter and buttermilk samples obtained by the industrial process as well as in cream and buttermilk samples from the traditional process, while phosphatidylcholine was the major phospholipid in traditionally produced butter. This result may be explained by the different churning processes causing different types of membrane disruption. Generally, samples produced traditionally had higher contents of total phospholipids; in particular, butter produced by the traditional method had a total phospholipid content 33% higher than that of industrially produced butter.CONCLUSIONThe samples studied represent the two types of products present in the Parmigiano Reggiano cheese area, where the industrial churning process is widespread compared with the traditional processing of Reggiana cow's milk. This is because Reggiana cow's milk production is lower than that of other breeds and the traditional churning process is time‐consuming and economically disadvantageous. However, its products have been demonstrated to contain more bioactive lipids compared with products obtained from other breeds and by the industrial process. © 2013 Society of Chemical Industry
A new methodology for rain identiﬁcation from passive microwave data in the Tropics using neural networks
Authors: Kacimi Sahra , Viltard Nicolas , Kirstetter Pierre‐Emmanuel 
Published: March 2013

AbstractThe detection of rainfall remains a challenge for the monitoring of precipitation from space. A methodology is presented to identify rain events from spaceborne passive microwave data using neural networks. We focus on BRAIN, the algorithm that provides instantaneous quantitative precipitation estimates at the surface, based on the MADRAS radiometer onboard the Megha‐Tropiques satellite. A version of BRAIN using data from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) has been used to compare several multilayer perceptrons (MLP) trained on different combinations of TMI brightness temperatures with the conventional GSCAT‐2 algorithm approach used for rainfall detection. These classiﬁers were compared at a global scale to reference values from the TRMM Precipitation Radar (PR). They were also compared to ground measurements using two 1° × 1° dense rain‐gauge networks from different climatic zones in West Africa to assess the inﬂuence of rainfall types. At the global scale the MLPs provide better Probability of Detection than the GSCAT‐2 decision tree but tend to have a higher False Alarm Rate. While no unique solution exists given the strong regional dependence of the classiﬁers' performances, the screen based on the 19, 21 and 85 GHz channels provides the best detection results at the instantaneous scales. As to accumulated rainfall, the screen that exhibits the lower bias relative to the PR makes use of the 37 and 85 GHz channels. The evaluation over West Africa using 10 years of TRMM overpasses shows that MLPs are in better agreement with both the PR and the gauges than GSCAT‐2. The MLP trained on the 37 and 85 GHz channels increases the Probability of Detection by nearly 35% compared to the former screening over the two studied regions. Better results are obtained in the case of organized systems. Copyright © 2013 Royal Meteorological Society
The geometric norm improves ensemble forecasting with the breeding method
Authors: Pazó D. , López J. M. , Rodríguez M. A. 
Published: March 2013

AbstractError breeding is a popular and simple method to generate flow‐adapted perturbations for use in ensemble forecasting. It has traditionally been believed that the norm type used in periodic normalizations of bred vectors (BVs) does not have an important effect on the performance of BVs within ensemble forecasting systems. However, we have recently reported that the geometric norm has nice properties (e.g. enhancement of the ensemble diversity) that in principle render it more adequate to construct ensembles than other norm types like the Euclidean one. These advantages are clearly demonstrated here in a simple experiment of ensemble forecasting for the Lorenz‐96 model with ensembles of BVs. Our simple numerical assimilation experiment shows how the increased statistical diversity of geometric BVs leads to improved scores regarding forecasting capabilities as compared with BVs constructed with the standard Euclidean norm. Moreover, we provide a theoretical basis for all these results by resorting to generic properties of spatially extended chaotic systems.
Using operational weather radar to assess high‐resolution numerical weather prediction over the British Isles for a cold air outbreak case‐study
Authors: McBeath K. , Field P. R. , Cotton R. J. 
Published: March 2013

AbstractExamination of weather radar data from the Constrain field campaign during January 2010 is presented, and comparisons between the radar data and reflectivity data computed from the Met Office high‐resolution British Isles NWP model (UKV Δx = 1.5 km) are shown. Cluster analysis was used to identify and track cells of precipitation in the two datasets; this allowed characteristics of the cloud field to be examined. Cells of precipitation were identified in the data using a reflectivity threshold of 10 dBz which allowed these cells to be tracked as they moved through the region of interest. The mean cell area identified in the radar data was found to be 37.5±1.3 km2, while the mean area of cells identified in the model data was 63.5±2.0 km2. Significant differences between the model and radar data were seen in the shape of the cells, with the cells identified in the model found to be more circular than those seen in the radar data.