bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photochemical Evidence of Electronic Interwall Communication in Double‐Wall Carbon Nanotubes
Authors: Vizuete María , Gómez‐Escalonilla María J. , García‐Rodriguez Sergio , Fierro José Luis G. , Atienzar Pedro , García Hermenegildo , Langa Fernando 
Published: November 2012

AbstractSingle‐ and double‐wall carbon nanotubes (CNTs) having dimethylanilino (DMA) units covalently attached to the external graphene wall have been prepared by the reaction of the dimethylaminophenylnitronium ion with the corresponding CNT. The samples have been characterized by Raman and XPS spectroscopies, thermogravimetry, and high‐resolution transmission electron microscopy in which the integrity of the single or double wall of the CNT and the percentage of substitution (one dimethylanilino group every 45 carbons of the wall for the single‐ and double‐wall samples) has been determined. Nanosecond laser flash photolysis has shown the generation of transients that has been derived from the charge transfer between the dimethylanilino (as the electron donor) to the CNT graphene wall (as the electron acceptor). Importantly, the lifetime of the double‐wall CNT is much shorter than that monitored for the single‐wall CNT. Shorter‐lived transients were also observed for the pentyl‐esterified functionalized double‐wall CNT with respect to the single‐wall analogue in the presence of hole (CH3OH) and electron quenchers (O2, N2O), which has led to the conclusion that the inner, intact graphene wall that is present in double‐wall CNT increases the charge mobility significantly, favoring charge recombination processes. Considering the importance that charge mobility has in microelectronics, our finding suggests that double‐wall CNT or two‐layer graphene may be more appropriate to develop devices needing fast charge mobility.
A Chiral Self‐Assembled Monolayer Derived from a Resolving Agent and its Performance as a Crystallization Template for an Organic Compound from Organic Solvents
Authors: Bejarano‐Villafuerte Ángela , van der Meijden Maarten W. , Lingenfelder Magalí , Wurst Klaus , Kellogg Richard M. , Amabilino David B. 
Published: November 2012

AbstractA new chiral nonracemic thiol derived from a popular acidic resolving agent that incorporates a cyclic disubstituted phosphate group (phencyphos) has been prepared in enantiomerically pure form. The stereochemistry and absolute configuration were established by performing a single‐crystal X‐ray structural analysis of a synthetic intermediate. The thiol compound was used for the preparation of self‐assembled monolayers (SAMs) on both monocrystalline and polycrystalline metallic gold, which have very different surface roughness. The monolayers were used to promote the nucleation and growth of crystals from nonaqueous solutions of an organic molecule (the parent phencyphos) of similar structure to the compound present in the monolayer. The template layers influence the nucleation and growth of the phencyphos crystals despite the lack of two‐dimensional order in the surfaces. Heterogeneous nucleation of phencyphos takes place upon evaporation of either CHCl3 or isopropanol solutions of the compound on the SAM surfaces, where the evaporation rate merely influences the size and homogeneity of the crystals. The roughness of the surface also plays an important role; the polycrystalline gold produces more homogeneous samples because of the greater number of nucleation sites. Clear evidence for nucleation and growth on the surfaces is shown by scanning electron microscopy. The variation in crystal form achieved by using different surfaces and solvents suggests that the layers are applicable for the preparation of organic crystals from organic solutions.
New Liquid Crystalline Materials Based on Two Generations of Dendronised Cyclophosphazenes
Authors: Jiménez Josefina , Laguna Antonio , Gascón Elena , Sanz José Antonio , Serrano José Luis , Barberá Joaquín , Oriol Luis 
Published: November 2012

AbstractA divergent approach was used for the synthesis of dendritic structures based on a cyclotriphosphazene core with 12 or 24 hydroxyl groups, by starting from [N3P3(OC6H4OH‐4)6] and using an acetal‐protected 2,2‐di(hydroxymethyl)propionic anhydride as the acylating agent. Hydroxyl groups in these first‐ and second‐generation dendrimers, G1‐(OH)12 or G2‐(OH)24, were then condensed in turn with mono‐ or polycatenar pro‐mesogenic acids to study their ability to promote self‐assembly into liquid crystalline structures. Reactions were monitored by using 31P{1H} and 1H NMR spectroscopy and the chemical structure of the resulting materials was confirmed by using different spectroscopic techniques and mass spectrometry (MALDI‐TOF MS). The results were in accordance with monodisperse, fully functionalised cyclotriphosphazene dendrimers. Thermal and liquid crystalline properties were studied by using optical microscopy, differential scanning calorimetry and X‐ray diffraction. The dendrimer with 12 4‐pentylbiphenyl mesogenic units gives rise to columnar rectangular organisation, whereas the one with 24 pentylbiphenyl units does not exhibit mesomorphic behaviour. In the case of materials that contain polycatenar pro‐mesogenic units with two aromatic rings (A4 vs. A5), the incorporation of a short flexible spacer connected to the periphery of the dendron (acid A5) was needed to achieve mesomorphic organisation. In this case, both dendrimer generations G1 A5 and G2 A5 exhibit a hexagonal columnar mesophase.
Chirality of Anisotropic Metal Nanowires with a Distinct Multihelix
Authors: Xie Junjie , Che Shunai 
Published: November 2012

AbstractTwo‐dimensional (2D) anisotropic silver nanowire (AgNW) arrays, fabricated inside chiral mesoporous silica (CMS), exhibited strong and tunable plasmon circular dichroism (CD) signals in the visible and near‐IR regions due to collective dipole coupling between the anisotropic AgNWs. The multihelix with a helical channel orientation and helical arrays of opposite handedness in CMS played a predominant effects on the transversal and longitudinal chirality of the AgNWs, respectively.This behavior differs from both isotropic‐nanoparticle and single‐helix‐induced CD responses. This system will provide new insight into the optical activity of metal inorganic nanoparticles capped with chiral organic molecules and assembled in chiral environments.
Spiroketal‐Based Phosphorus Ligands for Highly Regioselective Hydroformylation of Terminal and Internal Olefins
Authors: Jia Xiaofei , Wang Zheng , Xia Chungu , Ding Kuiling 
Published: November 2012

AbstractA new class of bidentate phosphoramidite ligands, based on a spiroketal backbone, has been developed for the rhodium‐catalyzed hydroformylation reactions. A range of short‐ and long‐chain olefins, were found amenable to the protocol, affording high catalytic activity and excellent regioselectivity for the linear aldehydes. Under the optimized reaction conditions, a turnover number (TON) of up to 2.3×104 and linear to branched ratio (l/b) of up to 174.4 were obtained in the RhI‐catalyzed hydroformylation of terminal olefins. Remarkably, the catalysts were also found to be efficient in the isomerization–hydroformylation of some internal olefins, to regioselectively afford the linear aldehydes with TON values of up to 2.0×104 and l/b ratios in the range of 23.4–30.6. X‐ray crystallographic analysis revealed the cis coordination of the ligand in the precatalyst [Rh(3 d)(acac)], whereas NMR and IR studies on the catalytically active hydride complex [HRh(CO)2(3 d)] suggested an eq–eq coordination of the ligand in the species.
Q‐learning for estimating optimal dynamic treatment rules from observational data
Authors: Moodie Erica E. M. , Chakraborty Bibhas , Kramer Michael S. 
Published: November 2012

AbstractThe area of dynamic treatment regimes (DTR) aims to make inference about adaptive, multistage decision‐making in clinical practice. A DTR is a set of decision rules, one per interval of treatment, where each decision is a function of treatment and covariate history that returns a recommended treatment. Q‐learning is a popular method from the reinforcement learning literature that has recently been applied to estimate DTRs. While, in principle, Q‐learning can be used for both randomized and observational data, the focus in the literature thus far has been exclusively on the randomized treatment setting. We extend the method to incorporate measured confounding covariates, using direct adjustment and a variety of propensity score approaches. The methods are examined under various settings including non‐regular scenarios. We illustrate the methods in examining the effect of breastfeeding on vocabulary testing, based on data from the Promotion of Breastfeeding Intervention Trial. The Canadian Journal of Statistics 40: 629–645; 2012 © 2012 Statistical Society of Canada
Variable selection and estimation in generalized linear models with the seamless ${\it L}_{{\rm 0}}$ penalty
Authors: Li Zilin , Wang Sijian , Lin Xihong 
Published: November 2012

AbstractIn this paper, we propose variable selection and estimation in generalized linear models using the seamless $L_0$ (SELO) penalized likelihood approach. The SELO penalty is a smooth function that very closely resembles the discontinuous $L_0$ penalty. We develop an efficient algorithm to fit the model, and show that the SELO‐GLM procedure has the oracle property in the presence of a diverging number of variables. We propose a Bayesian information criterion (BIC) to select the tuning parameter. We show that under some regularity conditions, the proposed SELO‐GLM/BIC procedure consistently selects the true model. We perform simulation studies to evaluate the finite sample performance of the proposed methods. Our simulation studies show that the proposed SELO‐GLM procedure has a better finite sample performance than several existing methods, especially when the number of variables is large and the signals are weak. We apply the SELO‐GLM to analyze a breast cancer genetic dataset to identify the SNPs that are associated with breast cancer risk. The Canadian Journal of Statistics 40: 745–769; 2012 © 2012 Statistical Society of Canada
A black‐box decomposition approach for coupling heterogeneous components in hemodynamics simulations
Authors: Blanco Pablo J. , Leiva Jorge S. , Buscaglia Gustavo C. 
Published: November 2012

SUMMARYThis work presents a generic and efficient black‐box approach for the strong iterative coupling of dimensionally heterogeneous flow models in computational hemodynamics. A heterogeneous model of the cardiovascular system is formed by several vascular black‐box components, which are connected through coupling equations. The associated system of equations is solved using the Broyden algorithm. In addition, a multiple time‐stepping strategy is introduced to meet different component requirements. The proposed algorithm is employed to split a 3D–1D–0D closed‐loop model of the cardiovascular system into corresponding black‐box components standing for the 3D (specific vessels), 1D (systemic arteries/peripheral vessels), and 0D (venous/cardiac/pulmonary circulation) components. Examples of application are presented showing the robustness and suitability of this novel approach. Copyright © 2012 John Wiley & Sons, Ltd.
Reproduction of pressure field in ultrasonic‐measurement‐integrated simulation of blood flow
Authors: Funamoto Kenichi , Hayase Toshiyuki 
Published: November 2012

SUMMARYUltrasonic‐measurement‐integrated (UMI) simulation of blood flow is used to analyze the velocity and pressure fields by applying feedback signals of artificial body forces based on differences of Doppler velocities between ultrasonic measurement and numerical simulation. Previous studies have revealed that UMI simulation accurately reproduces the velocity field of a target blood flow, but that the reproducibility of the pressure field is not necessarily satisfactory. In the present study, the reproduction of the pressure field by UMI simulation was investigated. The effect of feedback on the pressure field was first examined by theoretical analysis, and a pressure compensation method was devised. When the divergence of the feedback force vector was not zero, it influenced the pressure field in the UMI simulation while improving the computational accuracy of the velocity field. Hence, the correct pressure was estimated by adding pressure compensation to remove the deteriorating effect of the feedback. A numerical experiment was conducted dealing with the reproduction of a synthetic three‐dimensional steady flow in a thoracic aneurysm to validate results of the theoretical analysis and the proposed pressure compensation method. The ability of the UMI simulation to reproduce the pressure field deteriorated with a large feedback gain. However, by properly compensating the effects of the feedback signals on the pressure, the error in the pressure field was reduced, exhibiting improvement of the computational accuracy. It is thus concluded that the UMI simulation with pressure compensation allows for the reproduction of both velocity and pressure fields of blood flow. Copyright © 2012 John Wiley & Sons, Ltd.
A buffer management algorithm for improving up/down transmission congestion protocol fairness in IEEE 802.11 wireless local area networks
Authors: Huang Jiawei , Wang Jianxin , Ye Jin 
Published: November 2012

SUMMARYThe fair allocation of the resources is an important issue in wireless local area network (WLAN) because all wireless nodes compete for the same wireless radio channel. When uplink and downlink transmission congestion protocol (TCP) flows coexist in WLAN, the network service is biased toward the uplink TCP flows, and the downlink TCP flows tend to starve. In this article, we investigate the special up/down TCP unfairness problem and point out that the direct cause is the uplink acknowledgement (ACK) packets occupy most buffer space of access point. We thus propose a buffer management algorithm to ensure the fairness among uplink and downlink TCP flows. In order to limit the greedy behavior of ACK packets, the proposed algorithm adjusts the maximum size of buffer allocated for the ACK packets. Analysis and simulation results show that the proposed solution not only provides the fairness but also achieves 10–20% lower queue delay and higher network goodput than the other solutions. Copyright © 2012 John Wiley & Sons, Ltd.
Functionalized N‐Heterocyclic Carbene Ligands for Dual Enantioselective Control in the Cu‐Catalyzed Conjugate Addition of Dialkylzinc Compounds to Acyclic Enones
Authors: Dohi Kenta , Kondo Junko , Yamada Haruka , Arakawa Ryuichi , Sakaguchi Satoshi 
Published: November 2012

AbstractA series of highly tunable, functionalized azolium compounds have been synthesized from chiral α‐amino acid derivatives such as β‐amino alcohols or α‐amino esters. The combination of a Cu salt and a chiral azolium efficiently facilitated the asymmetric conjugate addition (ACA) reactions of acyclic enones with dialkylzinc under ambient conditions without temperature control. Of the (hydroxy amide)‐functionalized azolium ligand precursors, which were derived from β‐amino alcohols, an azolium salt containing a tert‐butyl group as the stereodirecting group was found to be the best choice of ligand. Ligand screening revealed that the use of an azolium salt containing a sterically bulky alkyl substituent such as N‐CHRR′ on the azolium ring led to a marked increase in the enantioselectivity of the ACA reaction. Thus, a new efficient (hydroxy amide)‐functionalized azolium ligand precursor such as 26, which was prepared from 1‐(diphenylmethyl)benzimidazole and (S)‐tert‐leucinol, has been developed. The treatment of benzalacetone (30) with Et2Zn in the presence of catalytic amounts of [Cu(OTf)]2(C6H6) and 26 at room temperature gave the corresponding 1,4‐adduct 31 with excellent enantioselectivity (92 % ee). On the other hand, the enantioselectivity of the ACA reactions of acyclic enones with dialkylzinc was successfully reversed by the use of (ester amide)‐functionalized azolium salts, which were obtained from α‐amino esters. Several functionalized azolium ligand precursors from readily available serine esters have been designed and synthesized. Finally, it was found that 30 could react with Et2Zn under the influence of a bis(hexafluoroacetylacetonato)copper(II) salt and C2‐symmetric azolium salt 36 to afford ent‐31 in almost quantitative yield with 89 % ee. A plausible reaction mechanism for the switching of the stereoselectivity in the ACA reaction by these two functionalized azolium compounds is described.
21st century climate change: where has all the geomorphology gone?
Authors: Lane Stuart N. 
Published: November 2012

ABSTRACTThis Commentary draws together recently published work relating to the relationship between climate change and geomorphology to address the surprising observation that geomorphic work seems to have had little impact upon the work of the Intergovernmental Panel for Climate Change. However, recent papers show that methodological innovation has allowed geomorphological reconstruction over timescales highly relevant to late 20th century and 21st century climate change. In turn, these and other developments are allowing links to be made between climatic variability and geomorphology, to begin to predict ‘geomorphic futures’ and also to appreciate the role that geomorphic processes play in the flux of carbon and the carbon cycle. Copyright © 2012 John Wiley & Sons, Ltd.
Relaying techniques for enhancing the physical layer secrecy in cooperative networks with multiple eavesdroppers
Authors: Al‐nahari Azzam Y. , Krikidis Ioannis , Ibrahim Ahmed S. , Dessouky Moawad I. , Abd El‐Samie Fathi E. 
Published: November 2012

ABSTRACTPhysical layer security has recently attracted considerable attention in the context of information‐theoretic point of view. In this paper, we investigate relay selection schemes for security‐constrained half‐duplex cooperative wireless networks with multiple eavesdroppers, which have the ability to cooperate to overhear the source transmission. The proposed techniques select a trusted decode‐and‐forward relay to assist the source transmission and maximize the achievable secure rate for different eavesdropper policies (cooperation or not); for the two cases, we assume that the channel is always available. In addition, a jamming method that selects two relay nodes to create an intentional interference at both phases of the decode‐and‐forward protocol to confound the eavesdropper nodes is also considered. Both the source–destination and source–eavesdroppers links are taken into account in the proposed analysis. Secrecy rate and secrecy outage probability are the two performance metrics that are used to verify the effectiveness of the proposed schemes while asymptotic approximations of the secrecy outage probability are also derived. Simulation and analytical results demonstrate the performance improvement of the proposed schemes. Copyright © 2012 John Wiley & Sons, Ltd.
Wall–bounded flow and heat transfer around a circular cylinder at low Reynolds and Hartmann numbers
Authors: Chatterjee Dipankar , Chatterjee Kanchan 
Published: November 2012

AbstractA two–dimensional numerical simulation is performed following a finite volume approach to analyze the forced convection heat transfer for the hydromagnetic flow around a circular cylinder at low Reynolds numbers. The cylinder is placed within a rectangular channel subjected to externally applied magnetic fields and acted upon by the magnetohydrodynamic (MHD) flow of a viscous incompressible and electrically conductive fluid. The magnetic field is applied either along the streamwise or transverse directions. The simulation is carried out for the range of Reynolds number 10 ≤ Re ≤ 80 with Hartmann number 0 ≤ Ha ≤ 10 and for different Prandtl numbers, Pr = 0.02 (liquid metal), 0.71 (air), and 7 (water) for a blockage ratio β = 0.25. The flow is steady for the above range of conditions. Apart from the channel wall, the magnetic field provides additional stability to the flow as a result of which the recirculation region behind the obstacle reduces with increasing magnetic field strength for a particular Reynolds number. The rate of heat transfer is found almost invariant at low Re whereas it increases slightly for higher Re with the applied magnetic field. The heat transfer increases as usual with the Reynolds number for all Hartmann numbers. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21025
Numerical investigation on the flow field of an axial flow fan in a direct air‐cooled condenser for a large power plant
Authors: Zhao Wanli , Qu Qiulin , Li Qiuyan 
Published: November 2012

AbstractThe flow field of an axial fan in a direct air‐cooled condenser for a large power plant is modeled numerically. In order to improve the efficiency of heat exchange of the air‐cooled condenser, methods of increasing the rotational velocity of the fan and laying out the guide blade at the outlet of the fan are adopted. Results show that increasing the rotational velocity of the fan can effectively increase the flux of the fan, and can improve the efficiency of an air‐cooled condenser; laying out the guide blade at the fan outlet can ameliorate the flow field in an A‐flame. This causes the rotational kinetic energy to change into static pressure at the fan outlet, so the ability of the heat exchange of the air‐cooled condenser is improved. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21027
A study on heat transfer in a second‐grade fluid through a porous medium with the modified differential transform method
Authors: Rashidi M.M. , Hayat T. , Keimanesh T. , Yousefian H. 
Published: November 2012

AbstractThis study investigates the boundary‐layer flow and heat transfer characteristics in a second‐grade fluid through a porous medium. The similarity transformation for the governing equations gives a system of nonlinear ordinary differential equations which are analytically solved by the differential transform method (DTM) and the DTM‐Padé. The DTM‐Padé is a combination of the DTM and the Padé approximant. The convergence analysis elucidates that the DTM does not give accurate results for large values of independent variables. Hence the DTM is not applicable for the solution of boundary‐layer flow problems having boundary conditions at infinity. Comparison between the solutions obtained by the DTM and the DTM‐Padé with numerical solution (fourth‐order Runge–Kutta with shooting method) illustrates that the DTM‐Padé is the most effective method for solving the problems that have boundary conditions at infinity. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library (wileyonlinelibrary.com/journal/htj). DOI 10.1002/htj.21030
Near‐infrared imaging of breast cancer using optical contrast agents
Authors: Poellinger Alexander 
Published: November 2012

AbstractBreast cancer is the most common malignancy in women worldwide and the second leading cause of cancer death. On the basis of three studies performed by our group, this article reviews the current status of optical breast imaging using extrinsic contrast agents. To date, only two contrast agents have been applied in human studies, indocyanine green (ICG) and omocianine. Both contrast media were used for absorption and fluorescence imaging. Generally speaking, malignant breast lesions exhibited higher absorption contrast as well as higher fluorescence contrast compared to benign lesions or non‐diseased breast tissue. Some groups consider early enhancement characteristics helpful for differentiation between malignant and benign lesions. Late fluorescence ICG imaging – capitalizing on the extravasation of the dye through the wall of tumorous vessels – seems to be a promising technique to distinguish malignant from benign breast lesions. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)