bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structures and Reactivity of Oxygen‐Rich Scandium Cluster Anions ScO3–5−
Authors: Tian Li‐Hua , Zhao Yan‐Xia , Wu Xiao‐Nan , Ding Xun‐Lei , He Sheng‐Gui , Ma Tong‐Mei 
Published: February 2012

AbstractOxygen‐rich scandium cluster anions ScO3–5− are prepared by laser ablation and allowed to react with n‐butane in a fast‐flow reactor. A time‐of‐flight mass spectrometer is used to detect the cluster distribution before and after the reactions. The ScO3− and ScO4− clusters can react with n‐butane to produce ScO3H−, ScO3H2−, and ScO4H−, while the more oxygen‐rich cluster ScO5− is inert. The experiment suggests that unreactive cluster isomers of ScO3− and ScO4− are also present in the cluster source. Density functional theory and ab initio methods are used to calculate the structures and reaction mechanisms of the clusters. The theoretical results indicate that the unreactive and reactive cluster isomers of ScO3,4− contain peroxides (O22−) and oxygen‐centered radicals (O.−), respectively. The mechanisms and energetics for conversion of unreactive O22− to reactive O.− species are also theoretically studied.
Microheterogeneities in Ionic‐Liquid–Methanol Solutions Studied by FTIR Spectroscopy, DFT Calculations and Molecular Dynamics Simulations
Authors: Roth Christian , Appelhagen Andreas , Jobst Niels , Ludwig Ralf 
Published: February 2012

AbstractThe interest in ionic liquids (ILs) is steadily increasing because of their fascinating physicochemical properties and because of their broad range of applications in synthesis, separation, catalysis and electrochemistry. However, the multiplicity of their uses strongly depends on a molecular understanding of their exceptional properties. One key to a better understanding of their unique properties are spectroscopic studies of ionic liquids in conventional organic solvents in combination with DFT calculations and molecular dynamics simulations. Therefore we investigated the mixtures of the imidazolium‐based ionic liquid [C2mim][NTf2] with methanol. Caused by the amphiphilic character of methanol both liquids are miscible over the whole mixture range. The scope of this work is to study the changes in the IL network upon dilution and to investigate the formation of methanol clusters embedded in the IL matrix. The mixtures were studied by FTIR spectroscopy in the mid‐infrared region. The formation of methanol clusters was studied from the OD stretching vibrational bands between 2300 and 2800 cm−1. The cluster populations of methanol could be derived from molecular dynamics simulations for the same mixtures. Weighting the DFT calculated frequencies by the cluster populations we could reproduce the measured spectra in the OD stretching region up to XMeOH=0.5. Above XMeOH=0.8, strong formation of self‐methanol clusters takes place resulting in increasing diffusion coefficients related to decreasing dynamical heterogeneities. Thus we obtained a deep understanding of the solute–solvent and solute–solute interactions as well as information about the presence of microheterogeneities in the mixtures.
An MD Study of the Applicability of the Walden Rule and the Nernst–Einstein Model for Ionic Liquids
Authors: Liu Hongjun , Maginn Edward 
Published: February 2012

AbstractSix different ionic liquids containing imidazolium, pyrrolidinium and ammonium cations paired with bis[(trifluoromethyl)sulfonyl]imide and bis[(perfluoroethyl)sulfonyl]imide anions were studied using molecular dynamics simulations. Ionic conductivities, shear viscosities and self‐diffusivities were computed and compared to see what relationships exist between these three transport properties. The simulations suggest that these ionic liquids follow closely the Walden rule, which relates ionic conductivity to fluidity. The computed ionic conductivities agree well with those predicted from the Nernst–Einstein model, suggesting that long‐time correlation among ion velocities is small, or that the “ionicity” of these ionic liquids is high.
Heterostructured TiO2 Nanoparticles/Nanotube Arrays: In Situ Formation from Amorphous TiO2 Nanotube Arrays in Water and Enhanced Photocatalytic Activity
Authors: Huo Kaifu , Wang Hairong , Zhang Xuming , Cao Yue , Chu Paul K. 
Published: February 2012

AbstractHeterostructured TiO2 nanoparticles/nanotube arrays (NPs/NTAs) are produced from as‐anodized amorphous TiO2 nanotube arrays in water at a temperature as low as 90 °C. The phase and morphology transformation of the as‐anodized amorphous TiO2 nanotube in water can be attributed to a water‐induced dissolution and recrystallization mechanism in which the as‐anodized amorphous TiO2 NTAs are gradually self‐sacrificed, and then spontaneously morphing into the composite NPs/NTAs structure consisting of anatase NPs and thinner amorphous NTs. The composite can be further crystallized into anatase TiO2 NPs/NTAs consisting of anatase NT and anatase NPs by annealing in air at 450 °C for 3 hours. The composite anatase TiO2 NPs/NTAs have a surface area that is 1.4 times larger than that of the anatase TiO2 NTAs and possess enhanced photocatalytic activity in the photodecomposition of organic pollutants and water splitting. The photodecomposition rate of the organic pollutant rhodamine B by the anatase TiO2 NPs/NTAs photocatalyst is two times higher than that by the annealed anatase TiO2 NTAs. The enhanced photocatalytic activity of the hererostructured TiO2 NPs/NTAs arises from the large surface area of the TiO2 NPs and superior electron transport in anatase TiO2 NT. The in situ hydrothermal conversion of the microstructure from amorphous TiO2 NTAs into hererostructured TiO2 NPs/NTAs in water is very simple thereby enabling the design and fabrication of highly photoactive one‐dimensional TiO2‐based functional materials applicable to photocatalysis and solar energy conversion.
Resin‐Derived Hierarchical Porous Carbon Spheres with High Catalytic Performance in the Oxidative Dehydrogenation of Ethylbenzene
Authors: Wang Lifeng , Delgado Juan J. , Frank Benjamin , Zhang Zhe , Shan Zhichao , Su Dang Sheng , Xiao Feng‐Shou 
Published: February 2012

AbstractPre‐shaped hierarchical porous carbon (HPC) spheres have been synthesized through a facile anion exchanged route. An industrial polymeric anion‐exchange resin with a hierarchical pore structure was used as the carbon precursor. Its high porosity was conserved using an aluminate/silicate precursor forming a hard support to prevent the structural collapse during the carbonization process. Physicochemical bulk and surface properties of the obtained HPC spheres were characterized by X‐ray diffraction, scanning and transmission electron microscopy, N2 physisorption, and X‐ray photoemission spectroscopy. Results obtained indicate that HPC keeps the abundant hierarchical porosity including meso‐ and macropores as well as the high surface area of the resin precursor. The as‐synthesized HPC spheres were tested as a catalyst for oxidative dehydrogenation of ethylbenzene to styrene. The oxygen‐rich catalyst surface formed under reaction conditions shows a high catalytic performance and stability, making HPC to a potential catalyst for this type of reaction.
Adsorption and Separation of Light Gases on an Amino‐Functionalized Metal–Organic Framework: An Adsorption and In Situ XRD Study
Authors: Couck Sarah , Gobechiya Elena , Kirschhock Christine E. A. , Serra‐Crespo Pablo , Juan‐Alcañiz Jana , Martinez Joaristi Alberto , Stavitski Eli , Gascon Jorge , Kapteijn Freek , Baron Gino V. , Denayer Joeri F. M. 
Published: February 2012

AbstractThe NH2‐MIL‐53(Al) metal–organic framework was studied for its use in the separation of CO2 from CH4, H2, N2 C2H6 and C3H8 mixtures. Isotherms of methane, ethane, propane, hydrogen, nitrogen, and CO2 were measured. The atypical shape of these isotherms is attributed to the breathing properties of the material, in which a transition from a very narrow pore form to a narrow pore form and from a narrow pore form to a large pore form occurs, depending on the total pressure and the nature of the adsorbate, as demonstrated by in situ XRD patterns measured during adsorption. Apart from CO2, all tested gases interacted weakly with the adsorbent. As a result, they are excluded from adsorption in the narrow pore form of the material at low pressure. CO2 interacted much more strongly and was adsorbed in significant amounts at low pressure. This gives the material excellent properties to separate CO2 from other gases. The separation of CO2 from methane, nitrogen, hydrogen, or a combination of these gases has been demonstrated by breakthrough experiments using pellets of NH2‐MIL‐53(Al). The effect of total pressure (1–30 bar), gas composition, temperature (303–403 K) and contact time has been examined. In all cases, CO2 was selectively adsorbed, whereas methane, nitrogen, and hydrogen nearly did not adsorb at all. Regeneration of the adsorbent by thermal treatment, inert purge gas stripping, and pressure swing has been demonstrated. The NH2‐MIL‐53(Al) pellets retained their selectivity and capacity for more than two years.
Edge‐Enriched, Porous Carbon‐Based, High Energy Density Supercapacitors for Hybrid Electric Vehicles
Authors: Kim Yong Jung , Yang Cheol‐Min , Park Ki Chul , Kaneko Katsumi , Kim Yoong Ahm , Noguchi Minoru , Fujino Takeshi , Oyama Shigeki , Endo Morinobu 
Published: February 2012

AbstractSupercapacitors can store and deliver energy by a simple charge separation, and thus they could be an attractive option to meet transient high energy density in operating fuel cells and in electric and hybrid electric vehicles. To achieve such requirements, intensive studies have been carried out to improve the volumetric capacitance in supercapacitors using various types and forms of carbons including carbon nanotubes and graphenes. However, conventional porous carbons are not suitable for use as electrode material in supercapacitors for such high energy density applications. Here, we show that edge‐enriched porous carbons are the best electrode material for high energy density supercapacitors to be used in vehicles as an auxiliary powertrain. Molten potassium hydroxide penetrates well‐aligned graphene layers vertically and consequently generates both suitable pores that are easily accessible to the electrolyte and a large fraction of electrochemically active edge sites. We expect that our findings will motivate further research related to energy storage devices and also environmentally friendly electric vehicles.
Hydrogen Production from Glucose and Sorbitol by Sorption‐Enhanced Steam Reforming: Challenges and Promises
Authors: He Li , Chen De 
Published: February 2012

AbstractConcerning energy and environmental sustainability, it is appealing to produce hydrogen from sugars or sugar alcohols that are readily obtained from the hydrolysis of cellulosic biomass. Nevertheless, the conversion of such compounds for hydrogen production poses great technical challenges. In this paper, we report that hydrogen purity and yield can be significantly improved by integrating in situ CO2 capture into the steam reforming reaction of the model compounds—glucose and sorbitol. The experimental assessment was conducted at a steam‐to‐carbon ratio of 1.8 for sorbitol and 6 for glucose from 450–625 °C. As predicted by thermodynamic analysis, combining CO2 capture and reforming reactions at favorable operating conditions yielded very high purity hydrogen, for instance, 98.8 mol % from sorbitol and 99.9 mol % from glucose. However, there are trade‐offs between hydrogen purity and yield in practice. The lower operating temperatures in the examined range helped to increase the hydrogen purity and reduce the CO content in the gas product, whereas a high hydrogen yield was more likely to be obtained at higher temperatures. Coupling CO2 capture lowered the risk of coke formation during the steam reforming of glucose. Coke accumulated in the reactor for the sorption‐enhanced steam reforming of glucose was mostly from the slow pyrolysis of glucose before it came into contact with the catalyst–acceptor bed. This problem may be solved by improving heat transfer or reconstructing the reactor, for instance, by using a fluidized‐bed reactor.
A hierarchical mobile‐agent‐based security operation center
Authors: Li Jung‐Shian , Hsieh Che‐Jen , Lin Husan‐Yeh 
Published: February 2012

SUMMARYThe continuous evolvement of the e‐domain has led to a significant increase in the amount of sensitive personal information stored on networked hosts. These hosts are invariably protected by security mechanisms such as intrusion detection systems, Intrusion Prevention System (IPS), antivirus software, firewalls, and so forth. However, they still remain vulnerable to the threat of malicious attacks, theft and intrusion. The high false positive alarm rate of such mechanisms is particularly troublesome because false alarms greatly degrade the efficiency of the security framework. Security operation centers (SOCs) provide an automated solution for analyzing the threat to a network such that appropriate protective measures can be put in place. This paper proposes a novel hierarchical mobile‐agent‐based SOC to overcome the vulnerability of traditional static SOCs to single point of failure attacks. In addition, the network is partitioned into multiple divisions, each with its own alert detection and aggregation methodology to improve the computational efficiency of the data collection and fusion process. The data acquired in the various divisions are fused and correlated in an efficient manner via intrusion detection message exchange format, XML, session and timer methods The experimental results confirm the effectiveness and efficiency of the proposed hierarchical mobile‐agent‐based SOC framework. Copyright © 2012 John Wiley & Sons, Ltd.
Performance analysis of decision directed maximum likelihood MIMO channel tracking algorithm
Authors: Karami Ebrahim 
Published: February 2012

SUMMARYIn this paper, the performance of decision directed (DD) maximum likelihood (ML) channel tracking algorithm is analyzed. The ML channel tracking algorithm presents efficient performance especially in the decision directed mode of the operation. In this paper, after introducing the method for analysis of DD algorithms, the performance of ML MIMO channel tracking algorithm in the DD mode of operation is analyzed. In this method channel tracking error is evaluated for a given decision error rate. Then, the decision error rate is approximated for a given channel tracking error. By solving these two derived equations jointly, both the decision error rate and the channel tracking error are computed. The presented analysis is compared with simulation results for different channel ranks, Doppler frequency shifts, and signal‐to‐noise ratios, and it is shown that the analysis is a good match for simulation results especially in high rank MIMO channels and high Doppler shifts. Copyright © 2012 John Wiley & Sons, Ltd.
Localized role of CRMP1 and CRMP2 in neurite outgrowth and growth cone steering
Authors: Higurashi Masakazu , Iketani Masumi , Takei Kohtaro , Yamashita Naoya , Aoki Reina , Kawahara Nobutaka , Goshima Yoshio 
Published: February 2012

AbstractCollapsin response mediator protein 1 (CRMP1) and CRMP2 have been known as mediators of extracellular guidance cues such as semaphorin 3A and contribute to cytoskeletal reorganization in the axonal pathfinding process. To date, how CRMP1 and CRMP2 focally regulate axonal pathfinding in the growth cone has not been elucidated. To delineate the local functions of these CRMPs, we carried out microscale‐chromophore‐assisted light inactivation (micro‐CALI), which enables investigation of localized molecular functions with highly spatial and temporal resolutions. Inactivation of either CRMP1 or CRMP2 in the neurite shaft led to arrested neurite outgrowth. Micro‐CALI of CRMP2 in the central domain of the growth cones consistently arrested neurite outgrowth, whereas micro‐CALI of CRMP1 in the same region caused significant lamellipodial retraction, followed by retardation of neurite outgrowth. Focal inactivation of CRMP1 in its half region of the growth cone resulted in the growth cone turning away from the irradiated site. Conversely, focal inactivation of CRMP2 resulted in the growth cone turning toward the irradiated site. These findings suggest different functions for CRMP1 and CRMP2 in growth cone behavior and neurite outgrowth. © 2012 Wiley Periodicals, Inc. Develop Neurobiol, 2012
EuLiGe2 and YbLiGe2 – A Divalent and an Intermediate‐Valent Compound with CaLiSi2‐Type Structures
Authors: Iyer Abishek K. , Peter Sebastian C. 
Published: February 2012

AbstractSingle‐phase EuLiGe2 and YbLiGe2 compounds were synthesized using a high frequency heating method. The crystal structure of EuLiGe2 was determined; it is an orthorhombic system, in space group Pnma, which crystallizes with aCaLiSi2‐type structure: a = 7.7880(10) Å, b = 3.9385(10) Å, c = 10.6436(10) Å. RELiGe2 (RE = Eu, Yb) is made up of lithium and germanium atoms forming a ten‐membered ring with channels occupied by two rare earth atoms. The Ge atoms are arranged in a zigzag manner and form the backbone of the structure. The magnetic susceptibility of EuLiGe2 obeys the Curie–Weiss law above 40 K (Eu2+) and shows antiferromagnetic ordering at 29 K followed by spin reordering at 23 K. Electrical resistivity measurements revealed the metallic nature of EuLiGe2 and confirmed the two magnetic orderings at low temperature. The divalent nature of Eu was confirmed by X‐ray absorption near edge spectroscopy (XANES). Magnetic measurements of YbLiGe2 showed that it is paramagnetic without long‐range magnetic ordering down to 2 K. The magnetic susceptibility deviates from the Curie–Weiss law below 100 K, presumably because of crystal field effects from Yb3+ ions. Magnetic susceptibility measurements of YbLiGe2 show a mixed‐valent ytterbium atom, and a magnetic moment within the linear region (<100 K) of 2.16 μB/Yb is very well supported by XANES.
Vertical flame spread on charring materials at different ambient temperatures
Authors: Mangs Johan , Hostikka Simo 
Published: February 2012

SUMMARYA new flame spread apparatus for the measurement of flame spread rates at different ambient temperatures is presented. A 2‐m long sample is pre‐heated with air to the desired temperature and ignited from its lower end with a small propane burner. The flame spread is traced with thermocouples in contact with the sample surface. The features and function of the new apparatus are described, as well as series of vertical flame spread experiments on cylindrical birch rods and electrical cables made of polyvinylchloride (PVC) and flame retardant non‐corrosive (FRNC) materials. Vertical flame spread rates 6–62 mm/s (temperature range 22–271 °C) were determined for birch samples, 3–24 mm/s (22–190 °C) for PVC cable samples, and 0–4 mm/s (22–293 °C) for FRNC cable samples. Small‐scale experiments with thermogravimetric analysis and cone calorimeter were performed to characterize the sample materials in terms of their thermal and fire behaviour. Copyright © 2012 John Wiley & Sons, Ltd.
Experimental Investigation of Air Relative Humidity (RH) Cycling Tests on MEA/Cell Aging in PEMFC Part II: Study of Low RH Cycling Test with Air RH at 62%/0%
Authors: Huang B. T. , Chatillon Y. , Bonnet C. , Lapicque F. , Leclerc S. , Hinaje M. , Raël S. 
Published: February 2012

AbstractThe effect of low relative humidity (RH) cycling (RHC 62%/0%) on the degradation mechanisms of a single proton exchange membrane fuel cell (5 × 5 cm2) was investigated and compared to a cell operated at constant humidification (RHC = 62%). The overall cell performance loss was near 33 μV h–1, which is greater than the voltage decay under constant RH condition near 3 μV h–1. The electroactive surface was reduced but to an acceptable level. Impedance spectroscopy revealed that the ohmic and charge transfer resistances were reduced by the likely improved hydration of the ionomeric layer at the catalyst due to hydrogen crossover. This was so important that H2 starvation was finally responsible for the collapse of the cell after 650 h. Transmission electron microscopy showed occurrence of various phenomena, e.g., bubbles and pinholes formation in the membrane due to local overheat from hydrogen combustion at the cathode, and thickness reduction of catalytic layers. The water up take obtained by 1H NMR within the membrane electrode assembly (MEA) after low RH cycling reduced by 24% compared to a fresh MEA. Observations are also compared to those obtained at high RH cycling (RHC 62%/100%) presented in Part I of this study [1].
Heterogeneities of Aging within a PEMFC MEA
Authors: Dubau L. , Durst J. , Maillard F. , Chatenet M. , André J. , Rossinot E. 
Published: February 2012

AbstractIn this study, we investigated the long‐term morphological and chemical changes of PEMFC cathode materials, with a special focus on the homogeneity of aging in different operating conditions (stationary or intermittent). The spatially‐resolved physico‐chemical analyses, performed at the cathode inlet/outlet region of the membrane electrode assembly, put in evidence that the cathode inlet ages much more rapidly than the cathode outlet in counter‐flow mode, this effect being exacerbated at high cell current. The rationale for such observation is the existence of heterogeneities of local current density, essentially caused by the depletion in air partial pressure and the increase in water content along the gas‐channel. We also evidenced heterogeneities of aging through the catalytic layer (CL). These heterogeneities are explained by the fact that Ptz+ ions produced by the corrosion of the Pt–Co/C nanoparticles are evacuated by the produced water exiting the CL [at the gas‐diffusion layer (GDL)|CL interface] or consumed by H2 crossing‐over from the anode through the cathode [at the CL|proton‐exchange membrane (PEM) interface], resulting in the formation of the so‐called “platinum‐band” in the PEM.
Effects of pH Value on Composition Structure and Catalytic Activity of Pt‐SnOx/C Prepared by Ethylene Glycol Method
Authors: Liu Y. H. , Wu F. , Wu C. 
Published: February 2012

AbstractPt‐SnOx nanoparticles were synthesized by the ethylene glycol (EG) method in solution of H2PtCl6 and SnCl2, with the same concentrations of Pt and Sn, but different pH values. The pH value after the end of platinum reduction reaction was not changed any more, except that a certain amount of water was added to deposit the Pt‐SnOx nanoparticles on the carbon support. The pre‐nanocatalysts were characterized by X‐ray photoelectron spectroscopy (XPS) to investigate the contents of Pt and Sn, and their catalytic activities for ethanol electrooxidation were tested by cyclic voltammetry (CV). The result was that the Sn contents were increasing as the Pt/Sn atomic ratios of 2.2, 2.6, 5.1, 7.4, 8.7, with the decreasing end pH values of 4.5, 5.0, 5.5, 6.5, 7.5, and the Pt contents became less than the addition in the preparation solution while the end pH values were <5.5, but the catalytic activities for ethanol electrooxidation were not so much regularly changed. Besides, from the end pH value of 5.5 to the increasing 9.0, all the platinum nanoparticles could be completely deposited on the carbon support, under the condition that only a certain amount of water was added.