bluuebunny/crossref_metadata_2025_split huggingface dataset:
Response of surface processes to climatic change in the dunefields and Loess Plateau of North China during the late Quaternary
Authors: Lu Huayu , Mason Joseph A. , Stevens Thomas , Zhou Yali , Yi Shuangwen , Miao Xiaodong 
Published: April 2011

ABSTRACTThis paper draws on recent optically stimulated luminescence (OSL) dating to evaluate the long‐held assumption that dust accumulation rates in the Loess Plateau and the extent of active aeolian sand in the dunefields to the north have varied together over time, because both are controlled by the strength of the Asian monsoons and also possibly because the dunefields are proximal loess sources. The results show there is little evidence that high rates of loess accumulation coincided with well‐dated episodes of extensive dune activity in the Mu Us, Otindag, and Horqin dunefields, at 11–8 ka and 1–0 ka. Explanations for the apparent lack of coupling include local variation in the trapping of dust and post‐depositional preservation of the loess and dune sediments, in response to varying local environmental conditions. In addition, a substantial portion of the loess may be transported directly from source areas where dust emission has somewhat different climatic and geomorphic controls than aeolian sand activity within the dunefields. The results of this study cast doubt on the use of loess accumulation rate as a palaeoclimatic proxy at millennial timescale. The dunefield and loess stratigraphic records are interpreted as primarily recording changes in effective moisture at a local scale, but the timing of late Quaternary dune activity, along with a variety of other evidence, indicates that moisture changes in many of the drylands of northern China may not be in phase with precipitation in core regions of the Asian monsoons. Copyright © 2011 John Wiley & Sons, Ltd.
Variance risk premiums and predictive power of alternative forward variances in the corn market
Authors: Wang Zhiguang , Fausti Scott W. , Qasmi Bashir A. 
Published: April 2011

AbstractWe propose a fear index for corn using the variance swap rate synthesized from out‐of‐the‐money call and put options as a measure of implied variance. We find negative and time‐varying variance risk premiums (realized variance minus implied variance) in the corn market from 1987 to 2009. Our results contrast with Egelkraut, Garcia, and Sherrick (2007), but are in line with the findings of Simon (2002). We conclude that our synthesized model‐free implied variance estimation procedure contains superior information about future realized variance relative to traditional model‐dependent estimating procedures: the implied variance model by Black (1976) and the seasonal GARCH(1, 1) forecasted variance model. © 2011 Wiley Periodicals, Inc. Jrl Fut Mark 32:587–608, 2012
Molecular Recognition of Amino Acids, Peptides, and Proteins by Cucurbit[n]uril Receptors
Authors: Urbach Adam R. , Ramalingam Vijayakumar 
Published: April 2011

AbstractAt the forefront of the endeavor to understand and manipulate living systems is the design and study of receptors that bind with high affinity and selectivity to specific amino acids, peptides, and proteins. Cucurbit[n]urils are among the most promising class of synthetic receptors for these targets due to their high affinities and selectivities in aqueous media and to the unique combination of electrostatic and hydrophobic interactions that govern binding. The fundamental supramolecular chemistry in this area has been explored in depth, and novel, useful applications are beginning to emerge.
Negotiating a flexible work arrangement: How women navigate the influence of power and organizational context
Authors: Greenberg Danna , Landry Elaine M. 
Published: April 2011

AbstractPrior work‐life research has highlighted that while organizations may be introducing more work‐life policies, organizational members are not necessarily using these policies. Empirical research is needed that focuses on the individual and provides insight into who is taking advantage of these policies and how they go about negotiating access. In this study, we explore this issue as we investigate the behavioral dynamics that underlie women's experiences negotiating a flexible work arrangement. Focusing on the individual, we examine the influence that perceptions of power and organizational work‐life support have on flexible work arrangement negotiations. The results of our research indicate that both macro level factors such as perceived work life support and micro level factors such as perceptions of power affect both the process and outcomes of these negotiations. We explore the implications these findings have for work‐life and negotiation research. Copyright © 2011 John Wiley & Sons, Ltd.
Incorporation of carbon nanotubes in a silica HPLC column to enhance the chromatographic separation of peptides: Theoretical and practical aspects
Authors: André Claire , Aljhani Rania , Gharbi Tijani , Guillaume Yves C. 
Published: April 2011

AbstractThe retention mechanism of a series of peptides on a single‐wall carbon nanotube (SWCNT) stationary phase inside an HPLC column was investigated over a wide range of mobile phase compositions. While the similar size C18 column exhibited an efficiency of 11.5 μm, the SWCNT column increased the efficiency, i.e. 7.10 μm at a flow rate of 0.8 mL/min, and significantly affected the separation quality of the peptides. The values of enthalpy (ΔH) and entropy (ΔS*) of transfer of the peptides from the mobile to the SWCNT stationary phase were determined. The method studied each factor, i.e. ACN fraction x in the ACN/water mixture and column temperature. The changes in retention factor, ΔH and ΔS* as a function of the ACN fraction in the mobile phase were examined. These variations are explained using the organization of ACN in clusters in the ACN/water mixture and on the steric and electronic forces implied in the retention process. The information obtained in this work makes this SWCNT stationary phase useful for peptide research and demonstrated the role of ACN to improve the separation quality.
Mesh‐independent matrix cracking and delamination modeling in laminated composites
Authors: Iarve Endel V. , Gurvich Mark R. , Mollenhauer David H. , Rose Cheryl A. , Dávila Carlos G. 
Published: April 2011

AbstractThe initiation and evolution of transverse matrix cracks and delaminations are predicted within a mesh‐independent cracking (MIC) framework. MIC is a regularized extended finite element method (x‐FEM) that allows the insertion of cracks in directions that are independent of the mesh orientation. The Heaviside step function that is typically used to introduce a displacement discontinuity across a crack surface is replaced by a continuous function approximated by using the original displacement shape functions. Such regularization allows the preservation of the Gaussian integration schema regardless of the enrichment required to model cracking in an arbitrary direction. The interaction between plies is anchored on the integration point distribution, which remains constant through the entire simulation. Initiation and propagation of delaminations between plies as well as intra‐ply MIC opening is implemented by using a mixed‐mode cohesive formulation in a fully three‐dimensional model that includes residual thermal stresses. The validity of the proposed methodology was tested against a variety of problems ranging from simple evolution of delamination from existing transverse cracks to strength predictions of complex laminates withouttextita priori knowledge of damage location or initiation. Good agreement with conventional numerical solutions and/or experimental data was observed in all the problems considered. Published 2011. This article is a US Government work and is in the public domain in the USA.
Identification of the major constituents in Xuebijing injection by HPLC‐ESI‐MS
Authors: Huang Hao , Ji Lanxin , Song Shengyou , Wang Jing , Wei Na , Jiang Min , Bai Gang , Luo Guoan 
Published: April 2011

AbstractIntroduction – Xuebijing injection (XBJ) is a traditional Chinese herbal prescription widely used in the treatment of sepsis. This is the first report concerning the identification of XBJ constituents. In addition, to evaluate XBJ's quality, partial least square discrimination analysis (PLS‐DA) was performed on chemical fingerprint data.Objective – Establish an LC‐MS method to identify the components in XBJ for the purpose of quality control.Methodology – Compounds were separated by HPLC using a C18 column and gradient elution of acetonitrile–methanol (60:40, v/v) and water–acetic acid (100 : 0.5, v/v) in 80 min. HPLC equipped with diode array detector (DAD) coupled with time‐of‐flight (TOF) tandem mass spectrometry and HPLC electrospray ionisation (ESI) multi‐stage tandem ion‐trap mass spectrometry (IT‐MSn) method was developed to analyse XBJ's major components. Both positive and negative ionisation modes were employed.Results – Twenty‐one compounds including amino acids, phenolic acids, flavonoid glycoside, terpene glycoside and phthalide were identified or tentatively characterised. Their retention times, UV and MS spectra were compared with those of authentic compounds or literature data. The score plot of PLS‐DA clearly revealed variations among samples produced in different commercial batches.Conclusion – The analytical method developed is highly effective for the discrimination and quality control of XBJ.
Photoluminescence of epoxy/clay nanocomposites
Authors: Mondragón Margarita , Cortes Miguel Angel , Arias Eduardo , Falcony Ciro , Zelaya‐Angel Orlando 
Published: April 2011

AbstractPolymer nanocomposites of an epoxy resin with natural montmorillonite (MMT), organically modified montmorillonite(OMMT), and halloysite nanotubes(HNTs) were prepared by the solvent casting method. Photoluminescence (PL) measurements showed that the epoxy nanocomposites with OMMT and HNTs give rise to a red‐shift of the emission band associated to bisphenol groups and to well resolved emission spectra, attributable to coplanar packing of the polymer chains in the excited states. A significant PL quenching in all the nanocomposites was observed, which depended on type and clay concentration. Atomic force microscopy (AFM) images showed a greater penetration of the epoxy resin only into the OMMT and HNT agglomerates. A relationship between the PL behavior and both the extent of confinement of polymer chains in clays agglomerates and the changes in the formation of trapping sites produced from hydroxyl groups could be revealed by AFM images and Fourier transform infrared spectroscopy (FTIR) studies. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Effect of processing conditions on the development of morphological features of banded or nonbanded spherulites of poly(3‐hydroxybutyrate) (PHB) and polylactic acid (PLLA) blends
Authors: El‐Hadi Ahmed Mohamed 
Published: April 2011

AbstractTwo semicrystalline poly(3‐hydroxybutyrate) (PHB) and polylactic acid (PLLA) blends with and without poly(vinyl acetate) (PVAc) were prepared by dissolving different ratios in hot chloroform at 50 °C to obtain promising alternative biodegradable materials for eliminating plastic waste. The miscibility, crystallization, melting behavior and vibration modes of the prepared samples were characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM), Fourier transform infrared spectroscopy (FTIR), and wide angle X‐ray diffraction (WAXD) techniques. DSC analysis showed that only one crystallization temperature for blends with PVAc (single homogeneous phase) and two crystallization temperatures for blends without PVAc (immiscible blends) were obtained. The POM results indicated that the morphological structures of B381, B551, and B831 samples consist of two types of spherulites (fibrils and banded) which created at different crystallization temperatures. The irrelevant interaction between PHB and PLLA structures was detected from FTIR spectra. The addition of PVAc caused an obvious decrease in the peak position of the carboxyl group CO from 1752 to 1724 cm−1 due to dipole‐dipole interactions. WAXD indicated that the lattice parameters are changed in blends with PVAc and unchanged without PVAc. Our results indicated that, the PVAc can be used as compatibilizer and improved the compatibility between PHB and PLLA. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers
Studies of implanted boron emitters for solar cell applications
Authors: Pawlak B. J. , Janssens T. , Singh S. , Kuzma‐Filipek I. , Robbelein J. , Posthuma N. E. , Poortmans J. , Cristiano F. , Bazizi E. M. 
Published: April 2011

ABSTRACTB implanted emitters are investigated in the back junction cell configuration and their material properties are tested in double side implanted Si wafers. B has been implanted at 5 keV at various dose conditions varying from 1 × 1014 up to 3 × 1015 at./cm2 and activated at 1000°C for 10 min. N‐type 8 × 8 cm2 mono‐crystalline cells are fabricated and measured. Both fill factor and efficiency increase for high‐B doses. However, at 1015 at./cm2 B dose the Voc drops, which is in agreement with lifetime degradation in the wafer. Defect evolution simulations of BnIm clusters formation is correlated with lifetime degradation. Copyright © 2011 John Wiley & Sons, Ltd.
Plasma Induced Multiwalled Carbon Nanotube Grafted with 2‐Vinylpyridine for Preconcentration of Pb(II) from Aqueous Solutions
Authors: Ren Xuemei , Shao Dadong , Zhao Guixia , Sheng Guodong , Hu Ju , Yang Shitong , Wang Xiangke 
Published: April 2011

AbstractMultiwalled carbon nanotubes (MWCNTs) are grafted with 2‐vinylpyridine (VP) by using N2 plasma technique. The VP grafted MWCNTs (MWCNT‐g‐VP) are characterized by using X‐ray diffraction, X‐ray photoelectron spectroscopy, and thermo‐gravimetric analysis‐differential thermal analysis. The application of MWCNTs and MWCNT‐g‐VP in the removal of Pb(II) from large volumes of wastewater is investigated under ambient conditions. The results indicate that the grafted VP improved MWCNT sorption capacity obviously in the removal of Pb(II). The VP molecules grafted on the surfaces of MWCNT‐g‐VP can prevent the entanglement of MWCNT‐g‐VP and provide more functional groups, promoting the sorption of Pb(II) onto MWCNT‐g‐VP. According to the results simulated by Langmuir model, the maximum sorption capacities (Csmax) of Pb(II) are ∼15.9 mg·g−1 on MWCNTs and ∼37.0 mg·g−1 on MWCNT‐g‐VP at pH = 6.0. The variation of separation factors indicates that the sorption of Pb(II) on MWCNTs and MWCNT‐g‐VP is favorable. The relatively high sorption capacity shows that MWCNT‐g‐VP is a suitable material for the preconcentration and immobilization of heavy metal ions from large volumes of aqueous solutions in environmental pollution management. magnified image
A life cycle framework for the investigation of environmentally benign nanoparticles and products
Authors: Theis Thomas L. , Bakshi Bhavik R. , Durham Delcie , Fthenakis Vasilis M. , Gutowski Timothy G. , Isaacs Jacqueline A. , Seager Thomas , Wiesner Mark R. 
Published: April 2011

AbstractWhile significant advances in our understanding of the behavior of engineered nanoparticles in the environment continue, there remains a need to engage the nanoparticle research community directly in the development and evaluation of environmentally benign nanoparticles to ensure that nanomaterial‐based industries emerge as tools for sustainability rather than environmental liabilities. Current research efforts aimed at understanding the environmental implications of nanotechnology emphasize existing groups of nanoparticles and products already in commercial distribution. While this is clearly necessary, this approach fails to identify and address the many tradeoffs associated with product performance and environmental quality. We believe this to be a critical gap in the ongoing exploration of nanostructured materials and their properties and applications. We posit that a number of issues are not being holistically addressed, including resource availability and allocation, manufacturing energy requirements and embodied energy, material efficiency, environmental properties of nanomaterials and nanoproducts, and waste generation. An interdisciplinary approach to research, based on the life cycle paradigm and devoted to the identification, investigation, synthesis, testing, and analysis of groups of new, more environmentally conscious nanoparticles is needed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Light confinement in e‐beam evaporated thin film polycrystalline silicon solar cells
Authors: Soderstrom T. , Wang Q. , Omaki K. , Kunz O. , Ong D. , Varlamov S. 
Published: April 2011

AbstractPolycrystalline Si thin‐film (poly‐Si) solar cells need effective light‐trapping to compensate for the moderate absorption. Recent developments in the poly‐Si cell technology focus on film fabrication by e‐beam evaporation due to its manufacturing benefits, such as a very high deposition rate above 15 nm/s and inline compatible process. However, evaporated poly‐Si cells exhibit limited compatibility with textured glass. In this Letter, the coupling of the light in the absorber layer is enhanced by introducing a rough interface at the back of the solar cells. This increases the conversion efficiency from 6% to 7.1% for, respectively, planar and back textured interface with current density of 26.6 mA/cm2 for only 3.6 μm absorber thickness. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bias in estimating accuracy of a binary screening test with differential disease verification
Authors: Alonzo Todd A. , Brinton John T. , Ringham Brandy M. , Glueck Deborah H. 
Published: April 2011

AbstractSensitivity, specificity, positive and negative predictive value are typically used to quantify the accuracy of a binary screening test. In some studies, it may not be ethical or feasible to obtain definitive disease ascertainment for all subjects using a gold standard test. When a gold standard test cannot be used, an imperfect reference test that is less than 100 per cent sensitive and specific may be used instead. In breast cancer screening, for example, follow‐up for cancer diagnosis is used as an imperfect reference test for women where it is not possible to obtain gold standard results. This incomplete ascertainment of true disease, or differential disease verification, can result in biased estimates of accuracy. In this paper, we derive the apparent accuracy values for studies subject to differential verification. We determine how the bias is affected by the accuracy of the imperfect reference test, the percent who receive the imperfect reference standard test not receiving the gold standard, the prevalence of the disease, and the correlation between the results for the screening test and the imperfect reference test. It is shown that designs with differential disease verification can yield biased estimates of accuracy. Estimates of sensitivity in cancer screening trials may be substantially biased. However, careful design decisions, including selection of the imperfect reference test, can help to minimize bias. A hypothetical breast cancer screening study is used to illustrate the problem. Copyright © 2011 John Wiley & Sons, Ltd.
Two‐stage instrumental variable methods for estimating the causal odds ratio: Analysis of bias
Authors: Cai Bing , Small Dylan S. , Have Thomas R. Ten 
Published: April 2011

AbstractWe present closed‐form expressions of asymptotic bias for the causal odds ratio from two estimation approaches of instrumental variable logistic regression: (i) the two‐stage predictor substitution (2SPS) method and (ii) the two‐stage residual inclusion (2SRI) approach. Under the 2SPS approach, the first stage model yields the predicted value of treatment as a function of an instrument and covariates, and in the second stage model for the outcome, this predicted value replaces the observed value of treatment as a covariate. Under the 2SRI approach, the first stage is the same, but the residual term of the first stage regression is included in the second stage regression, retaining the observed treatment as a covariate. Our bias assessment is for a different context from that of Terza (J. Health Econ. 2008; 27(3):531–543), who focused on the causal odds ratio conditional on the unmeasured confounder, whereas we focus on the causal odds ratio among compliers under the principal stratification framework. Our closed‐form bias results show that the 2SPS logistic regression generates asymptotically biased estimates of this causal odds ratio when there is no unmeasured confounding and that this bias increases with increasing unmeasured confounding. The 2SRI logistic regression is asymptotically unbiased when there is no unmeasured confounding, but when there is unmeasured confounding, there is bias and it increases with increasing unmeasured confounding. The closed‐form bias results provide guidance for using these IV logistic regression methods. Our simulation results are consistent with our closed‐form analytic results under different combinations of parameter settings. Copyright © 2011 John Wiley & Sons, Ltd.
Chemical Reaction Between Ag Nanoparticles and TCNQ Microparticles in Aqueous Solution
Authors: Xiao Jinchong , Yin Zongyou , Wu Yuechao , Guo Jun , Cheng Yuhua , Li Hong , Huang Yizhong , Zhang Qing , Ma Jan , Boey Freddy , Zhang Hua , Zhang Qichun 
Published: April 2011

AbstractThe chemical reaction between Ag nanoparticles (Ag NPs) and 7,7′,8,8′‐ tetracycanoquinodimethane (TCNQ) microparticles (MPs) in aqueous solution for the formation of Ag‐NP‐decorated Ag–TCNQ nanowires is reported. Based on the results obtained by UV–vis spectroscopy and scanning electron microscopy (SEM), it is proposed that the reaction between Ag NPs and TCNQ MPs includes three stages, namely, aggregation of NPs and MPs, diffusion and reaction between NPs and MPs, and formation of Ag–TCNQ nanowires. The as‐synthesized semiconducting Ag–TCNQ nanowires show good performance in nonvolatile memory devices with multiple write‐read‐erase‐read (WRER) cycles in air.
The Betz–Joukowsky limit: on the contribution to rotor aerodynamics by the British, German and Russian scientific schools
Authors: Okulov Valery L. , van Kuik Gijs A.M. 
Published: April 2011

ABSTRACTThe derivation of the efficiency of an ideal wind turbine has been attributed to the three famous scientists of the three aerodynamic research schools in Europe during the first decades of the previous century: Lanchester, Betz and Joukowsky. However, detailed reading of their classical papers has shown that Lanchester did not accept Froude's result that the velocity through the disc is the average of the velocities far upstream and far downstream, by which his solution is not determined. Betz and Joukowsky used vortex theory to support Froude's result and derived the ideal efficiency of a wind turbine at the same time. This efficiency has been known as the Joukowsky limit in Russia and as the Betz limit everywhere else. Because of the contribution of both scientists, this result should be called the Betz–Joukowsky limit everywhere. Copyright © 2011 John Wiley & Sons, Ltd.