bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rare‐Earth‐Metal Alkylaluminates Supported by N‐Donor‐Functionalized Cyclopentadienyl Ligands: CH Bond Activation and Performance in Isoprene Polymerization
Authors: Jende Lars N. , Maichle‐Mössmer Cäcilia , Anwander Reiner 
Published: October 2013

AbstractHomoleptic tetramethylaluminate complexes [Ln(AlMe4)3] (Ln=La, Nd, Y) reacted with HCpNMe2 (CpNMe2=1‐[2‐(N,N‐dimethylamino)‐ethyl]‐2,3,4,5‐tetramethyl‐cyclopentadienyl) in pentane at −35 °C to yield half‐sandwich rare‐earth‐metal complexes, [{C5Me4CH2CH2NMe2(AlMe3)}Ln(AlMe4)2]. Removal of the N‐donor‐coordinated trimethylaluminum group through donor displacement by using an equimolar amount of Et2O at ambient temperature only generated the methylene‐bridged complexes [{C5Me4CH2CH2NMe(μ‐CH2)AlMe3}Ln(AlMe4)] with the larger rare‐earth‐metal ions lanthanum and neodymium. X‐ray diffraction analysis revealed the formation of isostructural complexes and the CH bond activation of one aminomethyl group. The formation of Ln(μ‐CH2)Al moieties was further corroborated by 13C and 1H‐13C HSQC NMR spectroscopy. In the case of the largest metal center, lanthanum, this CH bond activation could be suppressed at −35 °C, thereby leading to the isolation of [(CpNMe2)La(AlMe4)2], which contains an intramolecularly coordinated amino group. The protonolysis reaction of [Ln(AlMe4)3] (Ln=La, Nd) with the anilinyl‐substituted cyclopentadiene HCpAMe2 (CpAMe2=1‐[1‐(N,N‐dimethylanilinyl)]‐2,3,4,5‐tetramethylcyclopentadienyl) at −35 °C generated the half‐sandwich complexes [(CpAMe2)Ln(AlMe4)2]. Heating these complexes at 75 °C resulted in the CH bond activation of one of the anilinium methyl groups and the formation of [{C5Me4C6H4NMe(μ‐CH2)AlMe3}Ln(AlMe4)] through the elimination of methane. In contrast, the smaller yttrium metal center already gave the aminomethyl‐activated complex at −35 °C, which is isostructural to those of lanthanum and neodymium. The performance of complexes [{C5Me4CH2CH2NMe(μ‐CH2)AlMe3}‐ Ln(AlMe4)], [(CpAMe2)Ln(AlMe4)2], and [{C5Me4C6H4NMe(μ‐CH2)AlMe3}Ln(AlMe4)] in the polymerization of isoprene was investigated upon activation with [Ph3C][B(C6F5)4], [PhNMe2H][B(C6F5)4], and B(C6F5)3. The highest stereoselectivities were observed with the lanthanum‐based pre‐catalysts, thereby producing polyisoprene with trans‐1,4 contents of up to 95.6 %. Narrow molecular‐weight distributions (Mw/Mn<1.1) and complete consumption of the monomer suggested a living‐polymerization mechanism.
Surfactant Hydrogels for the Dispersion of Carbon‐Nanotube‐Based Catalysts
Authors: Di Crescenzo Antonello , Bardini Luca , Sinjari Bruna , Traini Tonino , Marinelli Lisa , Carraro Mauro , Germani Raimondo , Di Profio Pietro , Caputi Sergio , Di Stefano Antonio , Bonchio Marcella , Paolucci Francesco , Fontana Antonella 
Published: October 2013

AbstractNovel hydrogel phases based on positively charged and zwitterionic surfactants, namely, N‐[p‐(n‐dodecyloxybenzyl)]‐N,N,N‐trimethylammonium bromide (pDOTABr) and p‐dodecyloxybenzyldimethylamine oxide (pDOAO), which combine pristine carbon nanotubes (CNTs), were obtained, thus leading to stable dispersions and enhanced cross‐linked networks. The composite hydrogel featuring a well‐defined nanostructured morphology and an overall positively charged surface was shown to efficiently immobilise a polyanionic and redox‐active tetraruthenium‐substituted polyoxometalate (Ru4POM) by complementary charge interactions. The resulting hybrid gel has been characterised by electron microscopy techniques, whereas the electrostatic‐directed assembly has been monitored by means of fluorescence spectroscopy and ζ‐potential tests. This protocol offers a straightforward supramolecular strategy for the design of novel aqueous‐based electrocatalytic soft materials, thereby improving the processability of CNTs while tuning their interfacial decoration with multiple catalytic domains. Electrochemical evidence confirms that the activity of the catalyst is preserved within the gel media.
Efficient Access to Enantiopure γ4‐Amino Acids with Proteinogenic Side‐Chains and Structural Investigation of γ4‐Asn and γ4‐Ser in Hybrid Peptide Helices
Authors: Jadhav Sandip V. , Misra Rajkumar , Singh Sumeet K. , Gopi Hosahudya N. 
Published: October 2013

AbstractHybrid peptides composed of α‐ and β‐amino acids have recently emerged as new class of peptide foldamers. Comparatively, γ‐ and hybrid γ‐peptides composed of γ4‐amino acids are less studied than their β‐counterparts. However, recent investigations reveal that γ4‐amino acids have a higher propensity to fold into ordered helical structures. As amino acid side‐chain functional groups play a crucial role in the biological context, the objective of this study was to investigate efficient synthesis of γ4‐residues with functional proteinogenic side‐chains and their structural analysis in hybrid‐peptide sequences. Here, the efficient and enantiopure synthesis of various N‐ and C‐terminal free‐γ4‐residues, starting from the benzyl esters (COOBzl) of N‐Cbz‐protected (E)‐α,β‐unsaturated γ‐amino acids through multiple hydrogenolysis and double‐bond reduction in a single‐pot catalytic hydrogenation is reported. The crystal conformations of eight unprotected γ4‐amino acids (γ4‐Val, γ4‐Leu, γ4‐Ile, γ4‐Thr(OtBu), γ4‐Tyr, γ4‐Asp(OtBu), γ4‐Glu(OtBu), and γ‐Aib) reveals that these amino acids adopted a helix favoring gauche conformations along the central CγCβ bond. To study the behavior of γ4‐residues with functional side chains in peptide sequences, two short hybrid γ‐peptides P1 (Ac‐Aib‐γ4‐Asn‐Aib‐γ4‐Leu‐Aib‐γ4‐Leu‐CONH2) and P2 (Ac‐Aib‐γ4‐Ser‐Aib‐γ4‐Val‐Aib‐γ4‐Val‐CONH2) were designed, synthesized on solid phase, and their 12‐helical conformation in single crystals were studied. Remarkably, the γ4‐Asn residue in P1 facilitates the tetrameric helical aggregations through interhelical H bonding between the side‐chain amide groups. Furthermore, the hydroxyl side‐chain of γ4‐Ser in P2 is involved in the interhelical H bonding with the backbone amide group. In addition, the analysis of 87 γ4‐residues in peptide single‐crystals reveal that the γ4‐residues in 12‐helices are more ordered as compared with the 10/12‐ and 12/14‐helices.
Copper‐Catalyzed Aerobic Oxidative CH Functionalization of Substituted Pyridines: Synthesis of Imidazopyridine Derivatives
Authors: Yu Jipan , Jin Yunhe , Zhang Hao , Yang Xiaobo , Fu Hua 
Published: October 2013

AbstractA novel, efficient, and practical method for the synthesis of imidazopyridine derivatives has been developed through the copper‐catalyzed aerobic oxidative CH functionalization of substituted pyridines with N‐(alkylidene)‐4H‐1,2,4‐triazol‐4‐amines. The procedure occurs by cleavage of the NN bond in the N‐(alkylidene)‐4H‐1,2,4‐triazol‐4‐amines and activation of an aryl CH bond in the substituted pyridines. This is the first example of the preparation of imidazopyridine derivatives by using pyridines as the substrates by transition‐metal‐catalyzed CH functionalization. This method should provide a novel and efficient strategy for the synthesis of other nitrogen heterocycles.
Reactivity of Yttrium Carboxylates Toward Alkylaluminum Hydrides
Authors: Schädle Christoph , Fischbach Andreas , Herdtweck Eberhardt , Törnroos Karl W. , Anwander Reiner 
Published: October 2013

AbstractYttrocene‐carboxylate complex [Cp*2Y(OOCArMe)] (Cp*=C5Me5, ArMe=C6H2Me3‐2,4,6) was synthesized as a spectroscopically versatile model system for investigating the reactivity of alkylaluminum hydrides towards rare‐earth‐metal carboxylates. Equimolar reactions with bis‐neosilylaluminum hydride and dimethylaluminum hydride gave adduct complexes of the general formula [Cp*2Y(μ‐OOCArMe)(μ‐H)AlR2] (R=CH2SiMe3, Me). The use of an excess of the respective aluminum hydride led to the formation of product mixtures, from which the yttrium‐aluminum‐hydride complex [{Cp*2Y(μ‐H)AlMe2(μ‐H)AlMe2(μ‐CH3)}2] could be isolated, which features a 12‐membered‐ring structure. The adduct complexes [Cp*2Y(μ‐OOCArMe)(μ‐H)AlR2] display identical 1J(Y,H) coupling constants of 24.5 Hz for the bridging hydrido ligands and similar 89Y NMR shifts of δ=−88.1 ppm (R=CH2SiMe3) and δ=−86.3 ppm (R=Me) in the 89Y DEPT45 NMR experiments.
Three‐Dimensional P‐Wave Velocity Structure Around the Xiaojiang Fault Zone and Its Tectonic Implications
Authors: Jian‐Ping WU , Ting YANG , Wei‐Lai WANG , Yue‐Hong MING , Tian‐Zhong ZHANG 
Published: October 2013

AbstractAs the southeastern margin of the Tibetan Plateau, the Xiaojiang fault zone plays an important role in the lateral escape of Tibetan Plateau materials. In this work, the 3‐D P‐wave velocity structure of the Xiaojiang fault zone and its surrounding areas was imaged by using travel time data from permanent seismic stations and a dense temporal seismic array. The results show that in the upper and middle crust, the Xiaojiang fault zone is mainly of low velocity, while high velocity anomalies exist to its east. In the middle and lower crust, a low velocity anomaly is shown in the central portion of the Xiaojiang fault zone, and high velocity anomalies exist both in the northern and southern areas. The northern high velocity anomaly near Panzhihua extends from lower crust to the surface, and the southern one in the lower crust extends to the upper mantle. We consider that the low velocity anomaly in the central portion of the Xiaojiang fault zone is caused by high temperature derived from upper mantle. The high anomalies in the northern area are most likely related to the late Paleozoic mantle plume activity which caused a large number of basic and ultrabasic mantle materials intruding into the crust. These high‐velocity anomalies, with greater mechanical strength, play a certain impediment to southward escaping of Tibetan Plateau materials, and lead to the rapid uplift of the northern sub‐block of the Sichuan‐Yunnan active block. The north‐dipping high velocity anomaly in the southern area is a further barrier for southward extrusion of the Sichuan‐Yunnan active block, leading to strong deformation and intense seismicity within the low‐velocity area in the overlaying upper and middle crust. Meantime, this high‐velocity block contributes to stabilization of the upper mantle, which makes mantle materials of its southern region less affected by the southward escape of Tibetan Plateau materials.
Accurate Location of the Lushan, Sichuan M7.0 Earthquake on 20 April 2013 and Its Aftershocks and Analysis of the Seismogenic Structure
Authors: Jin‐Rong SU , Yu ZHENG , Jian‐Si YANG , Tian‐Chang CHEN , Peng WU 
Published: October 2013

AbstractThe M7.0 Lushan earthquake and its aftershocks in 9 days were relocated by the double difference algorithm and a layered velocity model, using the seismic phases recorded at stations within 150 km including the fixed stations of the Sichuan earthquake network center, temporary stations, and reservoir stations. The events analyzed include the main shock and its 3324 aftershocks. The results show that the origin time of the main shock is 8:02:46.8 on 20 April 2013, hypocenter location 30.278°N, 102.989°E and the focal depth 16.67 km. The main rupture is about 40 km long, 20 km wide with an apparent area 800 km2. It strikes in southwest and dips about 40°. Most aftershocks occurred at depths 10∼22 km, concentrating on the hanging wall of the Dayi‐Mingshan fault, forming a southwest‐trending belt on the surface. Based on these and other data, this paper makes a preliminary analysis of the seismogenic structure of the Lushan event.
Mechanism of Postseismic Deformation of Ground Surface Following the 1999 Chi‐Chi Earthquake, Taiwan
Authors: Zhen FU , Hai‐Ming ZHANG , Yong‐En CAI 
Published: October 2013

AbstractGPS measurements of 450 days after the 1999 Chi‐Chi, Taiwan, earthquake revealed large postseismic displacement from dozens to hundreds of millimeters. Two possible mechanisms responsible for the postseismic deformation of the surface are the viscous relaxation of the lower crust and the afterslip caused by the aseismic creep of the earthquake fault. In this study, the finite element method (LDDA) for the viscoelastic contact problems is used to simulate the postseismic deformation process of the 1999 Chi‐Chi earthquake with the GPS data as constraints. And the two possible mechanisms, viscous relaxation and afterslip, are discussed. The results indicate that the postseismic deformation observed by GPS can be well explained by the viscous relaxation mechanism. The viscosity of the lower crust below the Taiwan area is estimated as 1017 Pa·s by the trial‐and‐error method. The effect of afterslip mechanism on the postseismic deformation of the Chi‐Chi earthquake is investigated by the numerical method with rate‐and‐state dependent frictional law. The results suggest that the GPS data cannot be explained by the afterslip mechanism alone, which only affects the postseismic deformation in the early 50 days after the mainshock. These studies will throw light on understanding the mechanism of the postseismic deformation of the 1999 Chi‐Chi, Taiwan, earthquake.
Full Waveform Inversion Based on Modified Quasi‐Newton Equation Quasi‐Newton Equation
Authors: Lu LIU , Hong LIU , Heng ZHANG , Yong‐Fu CUI , Fei LI , Wen‐Sheng DUAN , Geng‐Xin PENG 
Published: October 2013

AbstractWaveform inversion is a kind of method to reveal the underground structure and lithology through minimizing the residual error between predicted wavefield and true seismic record using full‐wavefield information. In this paper, we briefly present the principle of the conventional Quasi‐Newton algorithm, and then exploit a new modified Quasi‐Newton equation to modify the conventional Davidon‐Fletcher‐Powell (DFP) and Broyden‐Fletcher‐Goldfarb‐Shanno (BFGS) algorithms. Different from past Quasi‐Newton methods, this modified BFGS considers gradient values, model information and objective function values to approximate the inverse matrix of Hessian matrix. Moreover, it almost does not increase the calculation amount for each iteration. The numerical experiment shows that compared with the conventional Quasi‐Newton method, the modified BFGS algorithm can not only preserve the inverse accuracy, but also significantly improve calculation efficiency.
Three‐Dimensional Magnetotelluric Parallel Inversion Algorithm Using the Data‐Space Method
Authors: Xiang‐Yun HU , Yan LI , Wen‐Cai YANG , Wen‐Bo WEI , Rui GAO , Bo HAN , Rong‐Hua PENG 
Published: October 2013

AbstractUp until now, the key issue in practical applications of three‐dimensional magnetotelluric (3D MT) inversion is low efficiency of computation. By further analysis of the data‐space inversion approach of 3D MT, we develop a massively parallel inversion scheme on the basis of frequency division and matrix decomposition, and implement its procedure by using MPI on the Dawn TC5000A high‐performance computing platform. The algorithm we develop includes the parallel calculation of 3D forward modeling, sensitivity matrix and cross‐product matrix, as well as the update of model parameters. The algorithm has the advantages of higher efficiency in computation and lower memory storage in which the storage amount of sensitivity matrix at every single computing node is 2/N times as much amount as a PC (N is the number of nodes included in parallel computation). Furthermore, we test the implemented scheme with synthetic data from two 3D theoretical models and analyze the computational efficiency under multiple‐nodes computing. The numerical experiment results show that the 3D data‐space parallel inversion algorithm is feasible and efficient. Compared with the implementation on single PC, the parallel scheme is not only able to improve the computing speed and shorten the computation time, but also enlarge the calculational scale, which would advance greatly the utility of 3D MT inversion.
Thermal Evolution Patterns and Primary Controlling Factors of Sinian‐Lower Paleozoic Source Rocks in the Sichuan Basin, Southwestern China
Authors: Song RAO , Chuan‐Qing ZHU , Qiang WANG , Xiao‐Yin TANG , Wei‐Wei LI , Guang‐Zheng JIANG , Sheng‐Biao HU , Ji‐Yang WANG 
Published: October 2013

AbstractThermal evolution is an essential part of evaluation to source rocks as well as of research of hydrocarbon dynamic accumulation in oil‐gas‐bearing basins. The purpose of this work is to use the Easy%Ro chemical kinetic model to simulate the thermal evolution history of source rocks of Sinian‐Paleozoic ages in the Sichuan basin. It is based on analysis of styles of stratum deposition, recovery of thermal history of the basin, and the data from 86 representative drilling boreholes and more than 200 man‐made wells. The results show that the varied tectonic units of the basin have distinct feature of thermal evolution of the Lower Cambrian and Lower Silurian source rocks. Thus four models of thermal evolution are established: (1) Being mature during the Caledonian epoch and rapidly developed and shaped up in the early Late Permian period, as represented by the Lower Cambrian source rocks in the southern basin; (2) Not being mature during the Caledonian epoch and rapidly developed and shaped up in the early Late Permian period, as represented by the Lower Cambrian source rocks in the southwestern basin and Lower Silurian source rocks in the southern basin; (3) Being mature during the Caledonian epoch and mature again in the Late Hercynian‐Yanshanian epochs, as indicated by the Lower Cambrian source rocks in the northern basin; and (4) Not mature during the Caledonian epoch and steady maturity in the Late Hercynian‐Yanshanian epochs, as shown by the Lower Cambrian source rocks in the central basin and Lower Silurian source rocks in the eastern and northern basin. By comparison of relationship among the deposition rate heat flow and temperature increase rate, we infer the controlling factors of the thermal evolution of the source rocks above. For the southwestern and local southern Sichuan basin, the mantle plume and abnormal heat effect of basalt at the Emeishan during the early Late Permian period had exerted an major influence on the source rocks. In the rest of the basin, heating of sediments at depth and heat flow of the basin has a joint effect, especially the former had greatly increased the temperature of source rocks.
Computer‐Aided Design, Synthesis and Validation of 2‐Phenylquinazolinone Fragments as CDK9 Inhibitors with Anti‐HIV‐1 Tat‐Mediated Transcription Activity
Authors: Sancineto Luca , Iraci Nunzio , Massari Serena , Attanasio Vanessa , Corazza Gianmarco , Barreca Maria Letizia , Sabatini Stefano , Manfroni Giuseppe , Avanzi Nilla Roberta , Cecchetti Violetta , Pannecouque Christophe , Marcello Alessandro , Tabarrini Oriana 
Published: October 2013

AbstractThe activity of the cyclin‐dependent kinase 9 (CDK9) is critical for HIV‐1 Tat‐mediated transcription and represents a promising target for antiviral therapy. Here we present computational studies that, along with preliminary synthetic efforts, allowed us to identify and characterize a new class of nontoxic anti‐CDK9 chemotypes based on the 2‐phenylquinazolinone scaffold. Inhibition of CDK9 translated into the ability to interfere selectively with Tat‐mediated transactivation of the viral promoter and in the inhibition of HIV‐1 reactivation from latently infected cells, with the most potent derivative 37 (2‐(4‐aminophenyl)‐7‐chloroquinazolin‐4(3H)‐one) showing an IC50 value of 4.0 μM. Because the herein reported 2‐phenylquinazolinones are merely fragments, they are largely optimizable, paving the way to derivatives with improved potency.
What factors influence minority use of National Cancer Institute‐designated cancer centers?
Authors: Huang Lyen C. , Ma Yifei , Ngo Justine V. , Rhoads Kim F. 
Published: October 2013

BACKGROUNDNational Cancer Institute (NCI) cancer centers provide high‐quality care and are associated with better outcomes. However, racial and ethnic minority populations tend not to use these settings. The current study sought to understand what factors influence minority use of NCI cancer centers.METHODSA data set containing California Cancer Registry (CCR) data linked to patient discharge abstracts identified all patients with colorectal cancer (CRC) who were treated from 1996 through 2006. Multivariable models were generated to predict the use of NCI settings by race. Geographic proximity to an NCI center and patient sociodemographic and clinical characteristics were assessed.RESULTSApproximately 5% of all identified patients with CRC (n = 79,231) were treated in NCI settings. The median travel distance for treatment for all patients in all hospitals was ≤ 5 miles. A higher percentage of minorities lived near an NCI cancer center compared with whites. A baseline multivariable model predicting use showed a negative association between Hispanic ethnicity and NCI center use (odds ratio, 0.71; 95% confidence interval, 0.64‐0.79). Asian/Pacific Islander patients were more likely to use NCI centers (odds ratio, 1.41; 95% confidence interval, 1.28‐1.54). There was no difference in use noted among black patients. Increasing living distance from an NCI cancer center was found to be predictive of lower odds of use for all populations. Medicare and Medicaid insurance statuses were positively associated with NCI center use. Neighborhood‐level education was found to be a more powerful predictor of NCI use than poverty or unemployment.CONCLUSIONSSelect minority groups underuse NCI cancer centers for CRC treatment. Sociodemographic factors and proximity to NCI centers are important predictors of use. Interventions to address these factors may improve minority attendance to NCI cancer centers for care. Cancer 2014;120:399–407. © 2013 American Cancer Society.
Clinical and economic outcomes of patients with brain metastases based on symptoms: An argument for routine brain screening of those treated with upfront radiosurgery
Authors: Lester Scott C. , Taksler Glen B. , Kuremsky J. Griff , Lucas John T. , Ayala‐Peacock Diandra N. , Randolph David M. , Bourland J. Daniel , Laxton Adrian W. , Tatter Stephen B. , Chan Michael D. 
Published: October 2013

BACKGROUNDInsurers have started to deny reimbursement for routine brain surveillance with magnetic resonance imaging (MRI) after stereotactic radiosurgery (SRS) for brain metastases in favor of symptom‐prompted imaging. The authors investigated the clinical and economic impact of symptomatic versus asymptomatic metastases and related these findings to the use of routine brain surveillance.METHODSBetween January 2000 and December 2010, 442 patients underwent upfront SRS for brain metastases. In total, 127 asymptomatic patients and 315 symptomatic patients were included. Medical records were used to determine the presenting symptoms, distant and local brain failure, retreatment, and need for hospital and rehabilitative care. Cost‐of‐care estimates were based on Medicare payment rates as of January 2013.RESULTSSymptomatic patients had an increased hazard for all‐cause mortality (hazard ratio, 1.448) and were more likely to experience neurologic death (42% vs 20%; P < .0001). Relative to asymptomatic patients, symptomatic patients required more craniotomies (43% vs 5%; P < .0001), had more prolonged hospitalization (2 vs 0 days; P < .0001), were more likely to have Radiation Therapy Oncology Group grade 3 and 4 post‐treatment symptoms (24% vs 5%; P < .0001), and required $11,957 more on average to manage per patient. Accounting for all‐cause mortality rates and the probability of diagnosis at each follow‐up period, the authors estimated that insurers would save an average $1326 per patient by covering routine surveillance MRI after SRS to detect asymptomatic metastases.CONCLUSIONSPatients who presented with symptomatic brain metastases had worse clinical outcomes and cost more to manage than asymptomatic patients. The current findings argue that routine brain surveillance after radiosurgery has clinical benefits and reduces the cost of care. Cancer 2014;120:433–441. © 2013 American Cancer Society.