bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aluminum Complexes Stabilized by Piperazidine‐Bridged Bis(phenolate) Ligands: Syntheses, Structures, and Application in the Ring‐Opening Polymerization of ε‐Caprolactone
Authors: Li Wenyi , Yao Yingming , Zhang Yong , Shen Qi 
Published: February 2012

AbstractThe synthesis and characterization of aluminum alkoxide and alkyl complexes stabilized by piperazidine‐bridged bis(phenolate) ligands are described. Treatment of ligand precursors H2[ONNO]1 {H2[ONNO]1=1,4‐bis(2‐hydroxy‐3‐tert‐butyl‐5‐methylbenzyl)piperazidine} and H2[ONNO]2 {H2[ONNO]2=1,4‐bis(2‐hydroxy‐3,5‐di‐tert‐butylbenzyl)piperazidine} with AlEt2(OCH2Ph) and AlEt2(OPr‐i), which were generated in situ by the reactions of AlEt3 with equivalent of the corresponding alcohols, in a 1&colon;1 molar ratio in THF gave the corresponding aluminum alkoxide complexes [ONNO]1Al(OCH2Ph) (1) and [ONNO]2Al(OPr‐i) (2), respectively. The reaction of H2[ONNO]1 with AlEt2(OCH2Ph) in a 1&colon;2 molar ratio in THF afforded a mixture of monometallic aluminum ethyl complex [ONNO]1AlEt (3) and complex 1, which can be isolated by stepwise crystallization. Similarly, H2[ONNO]2 reacted with AlEt2(OPr‐i) in a 1&colon;2 molar ratio in THF to give a mixture of aluminum ethyl complex [ONNO]2AlEt (4) and complex 2. Complexes 1 and 2 were also available via treatment of complexes 3 and 4 with 1 equiv. of benzyl alcohol and isopropyl alcohol, respectively. All of these complexes were fully characterized including X‐ray structural determination. It was found that complexes 1 to 4 can initiate the ring‐opening polymerization of ε‐caprolactone, and complexes 1 and 2 showed higher catalytic activity in comparison with complexes 3 and 4.
A Deliberation on Nanobubbles at Surfaces and in Bulk
Authors: Seddon James R. T. , Lohse Detlef , Ducker William A. , Craig Vincent S. J. 
Published: February 2012

AbstractSurface and bulk nanobubbles are two types of nanoscopic gaseous domain that have recently been discovered in interfacial physics. Both are expected to be unstable to dissolution because of the high internal pressure driving diffusion and the surface tension which squeezes the gas out, but there is a rapidly growing body of experimental evidence that demonstrates both bubble types to be stable. However, the two types of bubbles also differ in many respects: surface nanobubble stability is most probably assisted by the nearby wall, which can repel the water (in the case of hydrophobicity), accept physisorbed gas molecules, and reduce the surface area through which outfluxing can occur; bulk nanobubbles, on the other hand, must stabilise themselves. This is perhaps through ionic shielding, perhaps through diffusive shielding, or perhaps through both. Herein, the features of both bubble types are described individually, their common and disparate features are discussed, and emerging applications are examined.
Conformational Analysis of Green Apple Flavour: The Gas‐Phase Structure of Ethyl Valerate Validated by Microwave Spectroscopy
Authors: Mouhib H. , Stahl W. 
Published: February 2012

AbstractWe report on the microwave spectrum of ethyl valerate, C4H9‐COO‐C2H5, observed by molecular beam Fourier transform microwave spectroscopy (MB‐FTMW). Highly accurate rotational and centrifugal distortion constants of the two most abundant conformers were determined. Their structure was investigated by comparison of the experimental rotational constants with those obtained by quantum chemical calculations. MP2/ 6‐311++G(d,p) calculations failed to give a proper description of the observed conformers in the supersonic jet. Therefore, also other basis sets were tried using Hartree–Fock, second‐order Møller–Plesset (MP2), and B3LYP methods to predict the observed gas‐phase structures of the molecule. The quantum chemical results guided the conformer assignment of the rotational constants, obtained from the microwave experiment. One of the two observed conformers has Cs symmetry, while the most abundant conformer has C1 symmetry. The main conformer possesses a strong spectrum with high intensities. Additionally, harmonic frequency calculations at different levels of theory where carried out and a low lying vibration of the entire n‐butyl group against the rest of the molecule was identified. The symbiotic interplay of microwave gas‐phase investigations and quantum chemical calculations becomes evident in our results.
On the Origin of the Enhanced Acidity of Chalcocyclopentadienes (Cyclopentadiene Chalcogenols) in the Gas Phase
Authors: Hurtado Marcela , Lamsabhi Al M. , Mó Otilia , Yáñez Manuel , Guillemin Jean‐Claude 
Published: February 2012

AbstractThe intrinsic acidity of chalcocyclopentadienes (CpXH; X=O, S, Se, Te) is investigated by high‐level G3B3 and G2 ab initio as well as B3LYP DFT calculations, which show that, independent of the nature of the heteroatom, all chalcocyclopentadienes are stronger acids in the gas phase than cyclopentadiene. However the acidity does not increase regularly down the group, and the acidity enhancement for Te derivatives is five times larger than for O derivatives, but only twice that of S‐containing compounds. The most favorable deprotonation process corresponds to loss of the proton attached to the heteroatom, with the sole exception of the 5‐substituted 1,3‐cyclopentadienes, for which the O and S derivatives are predicted to behave as carbon acids. No matter the nature of the heteroatom, the 1‐substituted 1,3‐cyclopentadienes are the strongest acids. The intrinsic acidity of all isomers, namely, 1‐substituted, 2‐substituted, and 5‐substituted 1,3‐cyclopentadienes, increases with increasing aromaticity of the anion formed on deprotonation, and therefore the Te compound is the strongest acid for the three series. However, the intrinsic acidity of chalcocyclopentadienes is not dictated by aromaticity, so that, in general, the most stable deprotonated species do not coincide with the most aromatic ones.
Performance analysis of multi‐antenna relay communication systems with MRC
Authors: Guan Zhang‐Jun , Zhang Wei‐Jiong , Zhou Xi‐Lang 
Published: February 2012

SUMMARYThe performance of multi‐antenna relay communication systems is investigated in this letter. The source broadcasts the signal to all the relays and the destination. Decode‐and‐forward scheme is adopted at the relays, and the destination employs maximum ratio combining (MRC) technique to maximize the received signal‐to‐noise ratio. Closed‐form expressions of outage probability are derived in the MRC case and minimum routes MRC case. An adaptive grouping algorithm of relay antennas is also presented under the constraint of total antenna number. Simulation results show that the analytical curves agree with the simulated ones very well, and the performance of the proposed grouping algorithm is very close to the upper bound mentioned in other papers. Copyright © 2012 John Wiley & Sons, Ltd.
Programming and reprogramming neuronal subtypes in the central nervous system
Authors: Rouaux Caroline , Bhai Salman , Arlotta Paola 
Published: February 2012

AbstractRecent discoveries in nuclear reprogramming have challenged the dogma that the identity of terminally differentiated cells cannot be changed. The identification of molecular mechanisms that reprogram differentiated cells to a new identity carries profound implications for regenerative medicine across organ systems. The central nervous system (CNS) has historically been considered to be largely immutable. However, recent studies indicate that even the adult CNS is imparted with the potential to change under the appropriate stimuli. Here, we review current knowledge regarding the capability of distinct cells within the CNS to reprogram their identity and consider the role of developmental signals in directing these cell fate decisions. Finally, we discuss the progress and current challenges of using developmental signals to precisely direct the generation of individual neuronal subtypes in the postnatal CNS and in the dish. © 2012 Wiley Periodicals, Inc. Develop Neurobiol 72: 1085–1098, 2012
Generation of Fbn1 conditional null mice implicates the extracellular microfibrils in osteoprogenitor recruitment
Authors: Cook Jason R. , Smaldone Silvia , Cozzolino Carmine , del Solar Maria , Lee‐Arteaga Sui , Nistala Harikiran , Ramirez Francesco 
Published: February 2012

AbstractLoss‐of‐function experiments in mice have yielded invaluable mechanistic insights into the pathogenesis of Marfan syndrome (MFS) and implicitly, into the multiple roles fibrillin‐1 microfibrils play in the developing and adult organism. Unfortunately, neonatal death from aortic complications of mice lacking fibrillin‐1 (Fbn1−/− mice) has limited the scope of these studies. Here, we report the creation of a conditional mutant allele (Fbn1fneo) that contains loxP sites bordering exon1 of Fbn1 and an frt‐flanked neo expression cassette downstream of it. Fbn1fneo/+ mice were crossed with FLPeR mice and the resulting Fbn1Lox/+ progeny were crossed with Fbn1+/−;CMV‐Cre mice to generate Fbn1CMV−/− mice, which were found to phenocopy the vascular abnormalities of Fbn1−/− mice. Furthermore, mating Fbn1Lox/+ mice with Prx1‐Cre or Osx‐Cre mice revealed an unappreciated role of fibrillin‐1 microfibrils in restricting osteoprogenitor cell recruitment. Fbn1Lox/+ mice are, therefore, an informative genetic resource to further dissect MFS pathogenesis and the role of extracellular fibrillin‐1 assemblies in organ development and homeostasis. genesis 50:635–641, 2012. © 2012 Wiley Periodicals, Inc.
Statistical classification of vegetation and water depths in montane wetlands
Authors: Sharp Julia L. , Sojda Richard S. , Greenwood Mark , Rosenberry Donald O. , Warren Jeffrey M. 
Published: February 2012

ABSTRACTRelationships between water depths and density of submergent vegetation were studied in montane wetlands using statistical techniques based on clustering and an extension of regression trees. Sago pondweed (Stuckenia pectinata) was associated with lower average water depths than water milfoil (Myriophyllum sibiricum). We detected a nonlinear relationship when average water depths were used to predict percent cover in S. pectinata, with depths of 30–40 cm, producing the highest predicted average percent cover of S. pectinata; higher and lower depths resulted in lower percent cover predictions. For M. sibiricum, higher water depths were monotonically associated with higher average percent cover. To foster more S. pectinata and less M. sibiricum, managers might employ water control structures to reduce water depths below 1 m, using both temporary drawdowns and average depths of 30–40 cm. Other species responded less markedly to water depth variation. Should decreased water depths become more common, these results suggest an increase in S. pectinata and a decrease in M. sibiricum. Published in 2012. This article is a US Government work and is in the public domain in the USA.
N‐Doped Nb2O5 Sensitized by Carbon Nitride Polymer – Synthesis and High Photocatalytic Activity under Visible Light
Authors: Wang Xu , Chen Gang , Zhou Chao , Yu Yaoguang , Wang Gang 
Published: February 2012

AbstractN‐doped Nb2O5 sensitized by carbon nitride polymer (CNNO) was synthesized as a yellowish powder by using urea as a carbon–nitrogen precursor. CNNO was tested as a catalyst for the visible‐light‐responsive photodegradation of dyes. HNbO3, one of the precursors of CNNO, was obtained from LiNbO3 by a H+–Li+ ion‐exchange reaction and then pyrolyzed at 400 °C to produce a Nb2O5 substrate. The photocatalytic activities of as‐prepared samples were evaluated by the degradation of Rhodamine B (RhB) under Xe lamp irradiation (λ > 400 nm), for which the photocatalysts showed relatively high activities. XRD, thermogravimetry and differential scanning calorimetry (TG–DSC), scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDS), TEM, X‐ray photoelectron spectroscopy (XPS), UV/Vis diffuse reflectance spectroscopy (DRS), and Brunauer–Emmett–Teller (BET) measurements were utilized to explore the characteristics of the obtained samples. The results demonstrated that the surface of Nb2O5 was successfully coated, as a semitransparent layer of CN polymer surrouding the dark substrate was observed. UV/Vis DRS showed that the absorption edges of CNNO were shifted remarkably to the visible region relative to those of naked Nb2O5. These results revealed that the significantly enhanced photocatalytic activities of the CNNO samples originate from the CN polymer. The coating led to an efficient electron transfer between the CN polymer, which acted as a photosensitizer, and the N‐doped Nb2O5. The degradation mechanism that underlies the excellent photocatalytic activity of CNNO was discussed extensively.
Biscyclohexane‐Annulated Diethyl Dipyrrindicarboxylates: Observation of a Dipyrrin Form with Absent Visible Absorption
Authors: Tikhomirova Ksenia , Anisimov Alexander , Khoroshutin Andrey 
Published: February 2012

AbstractA series of 2,3;7,8‐biscyclohexano‐fused diethyl 5‐aryldipyrrin‐1,9‐dicarboxylates have been synthesized [aryl = phenyl, 3,4‐dimethoxyphenyl and 2,3,5,6,8,9,11,12‐octahydro‐1,4,7,10,13‐benzopentaoxacyclopentadecine‐15‐yl (m‐benzo‐15‐crown‐5)]. The obtained compounds were shown to exist in two equilibrium forms in solution, with one exhibiting a visible absorption band (λabs 468–485 nm), and the other, “vis‐silent” form, having no absorption band in the visible region. The “vis‐silent” form has been isolated and characterized by NMR analysis, including two‐dimensional techniques. Quantum chemical calculations have also been performed, yielding two main conformations with proximate and distant arrangements of the nitrogen atoms. In the latter conformation the pyrrole–pyrrolene fragments were found to be nearly orthogonal, with no long chain of conjugation. Computational results confirm the spectroscopic findings. Two different forms were also characterized as their Mg2+ complex and investigated by UV/Vis and by NMR spectroscopic analyses and a clear difference was noted.
Pelletization of biochar from hydrothermally carbonized wood
Authors: Reza M. Toufiq , Lynam Joan G. , Vasquez Victor R. , Coronella Charles J. 
Published: February 2012

AbstractHydrothermal carbonization (HTC) is a pretreatment process for making a homogenized, carbon rich, and energy dense solid fuel, called biochar, from underutilized lignocellulosic biomass. Compared to raw biomass, HTC biochar is both more hydrophobic for better storage and more friable for better processing. In this pretreatment method, the biomass is treated with hot compressed water in the temperature range of 200–260°C. Hemicelluloses and water extractives react very quickly compared to cellulose. Lignin is relatively inert, resulting in a biochar with increased lignin content. Lignin acts as a binder for pelletization of pretreated lignocellulosic biomass. A hydraulic press with a controllable heated die was used for pelletization studies. The materials used to make pellets were raw loblolly pine and pine pretreated at different temperatures. The presence of solid bridges was observed in both raw pine pellets and HTC biochar pellets. Pellets made from HTC biochar exhibit favorable properties, including increased hydrophobicity, abrasion resistance, energy density, and mass density compared to pellets produced from raw pine or from dry torrefied pine. Pellets produced from biomass pretreated at 260°C have a volumetric fuel value 70% greater than pellets produced from untreated pine (38.8 MJ/m3 vs. 22.8 GJ/m3), a mass density of 1468 kg/m3, and a higher heating value of 26.4 MJ/kg. © 2012 American Institute of Chemical Engineers Environ Prog, 2012
Multi‐user coherent beamforming in packet‐based wireless systems
Authors: Oh Dong‐Chan , Lee Yong‐Hwan 
Published: February 2012

ABSTRACTIn this paper, we propose a multi‐antenna technique that can simultaneously achieve spatial multiplexing and multi‐user diversity gain with the use of coherent beam weight of scheduled users. Multiple beams are utilised to maximise the spatial multiplexing gain while fully achieving the multi‐user diversity gain through each channel. Combined use of a beamforming and zero‐forcing encoding can suppress the inter‐stream interference at the transmitter. We also consider seamless adjustment of the number of beams for data transmission to maximise the sum‐rate capacity according to the operating condition. Simulation results show the effectiveness of the proposed scheme. Copyright © 2012 John Wiley & Sons, Ltd.
On the Compressibility of Gas Diffusion Layers in Proton Exchange Membrane Fuel Cells
Authors: Ismail M. S. , Hassanpour A. , Ingham D. B. , Ma L. , Pourkashanian M. 
Published: February 2012

AbstractThe mechanical behavior under compression for a number of gas diffusion layers (GDLs) and a sealing gasket used in proton exchange membrane fuel cells (PEMFCs) has been investigated. The results show that the stiffness of the carbon substrate increases with increasing polytetrafluoroethylene (PTFE) loading. Also, coating the carbon substrate with the microporous layer (MPL) significantly enhances the stiffness of the GDL. On the other hand, the stiffness of the GDL appears to slightly decrease with an increase in the PTFE loading present in the MPL. For a given practical compressive pressure, the mechanical behavior of the GDLs is hugely controlled by the less compressible sealing gaskets. Furthermore, it has been found that the compression curves for the tested materials must be corrected for machine compliance. Otherwise, the stiffness of the tested materials is significantly underestimated.
Investigation on Proton Conductivity of La2Ce2O7 in Wet Atmosphere: Dependence on Water Vapor Partial Pressure
Authors: Sun W. , Fang S. , Yan L. , Liu W. 
Published: February 2012

AbstractThe AC conductivity of fluorite‐structured La2Ce2O7 ceramic was measured under air and argon with different humidity between 250 and 550 °C. It was observed that the total conductivity in wet air and argon was higher than that under dry atmospheres. The effect of water vapor partial pressure ($ {P_{\rm {H_2{\rm O}}}} $) on the conductivity of La2Ce2O7 in air was investigated in detail. The total conductivity increased remarkably with the water vapor partial pressure, and this phenomenon became more notable at lower temperatures. The enhancement of the conductivity was attributed to the proton conduction behavior of La2Ce2O7 in wet atmospheres, and the proton conductivity reached 6.68 × 10–5 S cm–1 in wet air (3% H2O) at 550 °C. The relationship between the proton conductivity (σH) and $ {P_{\rm {H_2{\rm O}}}} $ in wet air could be fitted to $ \sigma_{\rm H} \propto {P_{\rm {H_2{\rm O}}}^{1/2}} $. The estimated proton transport number increased with increasing water vapor partial pressure and decreasing temperature, and varied between 0.05 and 0.89 in this study.
Aquaporin‐4 and epilepsy
Authors: Binder Devin K. , Nagelhus Erlend A. , Ottersen Ole Petter 
Published: February 2012

AbstractRecent studies have implicated glial cells in modulation of synaptic transmission, so it is plausible that glial cells may have a functional role in the hyperexcitability characteristic of epilepsy. Indeed, alterations in distinct astrocyte membrane channels, receptors, and transporters have all been associated with the epileptic state. This review focuses on the potential roles of the glial water channel aquaporin‐4 (AQP4) in modulation of brain excitability and in epilepsy. We will review studies of mice lacking AQP4 (Aqp4−/− mice) or α‐syntrophin (an AQP4 anchoring protein) and discuss the available human studies demonstrating alterations of AQP4 in human epilepsy tissue specimens. We will conclude with new studies of AQP4 regulation and discuss the potential role of AQP4 in the development of epilepsy (epileptogenesis). While many questions remain unanswered, the available data indicate that AQP4 and its molecular partners may represent important new therapeutic targets. © 2012 Wiley Periodicals, Inc.
Seeking huntington disease biomarkers by multimodal, cross‐sectional basal ganglia imaging
Authors: Sánchez‐Castañeda Cristina , Cherubini Andrea , Elifani Francesca , Péran Patrice , Orobello Sara , Capelli Giovanni , Sabatini Umberto , Squitieri Ferdinando 
Published: February 2012

AbstractNeurodegeneration of the striatum in Huntington disease (HD) is characterized by loss of medium‐spiny neurons, huntingtin nuclear inclusions, reactive gliosis, and iron accumulation. Neuroimaging allows in vivo detection of the macro‐ and micro‐structural changes that occur from presymptomatic stages of the disease (preHD). The aim of our study was to evaluate the reliability of multimodal imaging as an in vivo biomarker of vulnerability and development of the disease and to characterize macro‐ and micro‐structural changes in subcortical nuclei in HD. Macrostructure (T1‐weighted images), microstructure (diffusion tensor imaging), and iron content (R relaxometry) of subcortical nuclei and medial temporal lobe structures were evaluated by a 3 T scanner in 17 preHD carriers, 12 early‐stage patients and 29 matched controls. We observed a volume reduction and microstructural changes in the basal ganglia (caudate, putamen, and globus pallidus) and iron accumulation in the globus pallidus in both preHD and symptomatic subjects; all these features were significantly more pronounced in patients, in whom degeneration extended to the other subcortical nuclei (i.e., thalamus and accumbens). Mean diffusivity (MD) was the most powerful predictor in models explaining more than 50% of the variability in HD development in the caudate, putamen, and thalamus. These findings suggest that the measurement of MD may further enhance the well‐known predictive value of striatal volume to assess disease progression as it is highly sensitive to tissue microimpairment. Multimodal imaging may detect brain changes even in preHD stages. Hum Brain Mapp, 2013. © 2012 Wiley Periodicals, Inc.
Abrupt behaviours of streamflow and sediment load variations of the Yangtze River basin, China
Authors: Zhang Qiang , Singh Vijay P. , Xu Chong‐Yu , Chen Xiaohong 
Published: February 2012

AbstractMonthly sediment load and streamflow series spanning 1963–2004 from four hydrological stations situation in the main stem of the Yangtze River, China, are analysed using scanning t‐test and the simple two‐phase linear regression scheme. Results indicate significant changes in the sediment load and streamflow from the upper reach to the lower reach of the Yangtze River. Relatively consistent positive coherency relations can be detected between streamflow and sediment load in the upper reach and negative coherency in the middle and lower reaches. Interestingly, negative coherency is found mainly for larger time scales. Changes in sediment load are the result mainly of human influence; specifically, the construction of water reservoirs may be the major cause of negative coherency. Accentuating the human influence from the upper to the lower reach results in inconsistent correlations between sediment load and streamflow. Decreasing sediment load being observed in recent years has the potential to alter the topographical properties of the river channel and the consequent development and recession of the Yangtze Delta. Results of this study are of practical significance for river channel management and evaluation of the influence of human activities on the hydrological regimes of large rivers. Copyright © 2012 John Wiley & Sons, Ltd.