bluuebunny/crossref_metadata_2025_split huggingface dataset:
The self‐assembled of cyclic D,L‐α‐peptide systems: Insights into the structure and energetics
Authors: Qu Wenwen , Tan Hongwei , Chen Guangju , Liu Ruozhuang 
Published: October 2009

AbstractCyclic D,L‐α‐peptides are able to self‐assemble to nanotubes, although the inherent reason of the stability of this kind of nanotube as well as the intrinsic driving force of self‐assembly of the cyclic D,L‐α‐peptides still remain elusive. In this work, using several computational approaches, we investigated the structural and energy characteristics of a series of cyclo[(‐L‐Phe‐D‐Ala‐)4] and cyclo[(‐L‐Ala‐D‐Ala‐)4] oligomers. The results reveal that the thermodynamic stability, cooperativity, and self‐assembly patterns of cyclic D,L‐α‐peptide nanotubes are mainly determined by the interactions between cross‐strand side chains instead of those between backbones. For cyclo[(‐L‐Phe‐D‐Ala‐)4] oligomers, the steric interaction between cross‐strand side chains, especially the electrostatic repulsion between the phenyls in Phe residues, brings anticooperative effect into parallel stacking mode, which is responsible for the preference of self‐assembling nanotube in antiparallel vs. parallel stacking orientation. Based on our results, a novel self‐assembling mechanism is put forward—it is the L‐L antiparallel dimer of cyclo[(‐L‐Phe‐D‐Ala‐)4], instead of the commonly presumed monomer, that acts as the basic building block in self assembly. It explains why these cyclic peptides uniquely self‐assemble to form antiparallel nanotubes. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Theoretical study of electron transfer in uranyl(VI)–uranyl(V) complexes in solution
Authors: Lu Shen‐Zhuang 
Published: October 2009

AbstractThe rates of the electron self‐exchange between uranyl(VI) and uranyl(V) complexes in solution have been investigated in detail with quantum chemical methods. The calculations have shown that the bond length of UOyl is elongated by 0.1 Å when the extra electron is localized on the sites. The diabatic potential surfaces are obtained. The inner reorganization energies are 212.6 and 226.8 kJ mol−1 for hydroxide and fluoride bridge systems, respectively. The solvent reorganization energies are 28.12 and 31.60 kJ mol−1 for hydroxide and fluoride bridge systems, respectively. The nuclear frequency factors are 3.17 × 1013 and 3.12 × 1013 s−1 for hydroxide and fluoride bridge systems, respectively. The electronic coupling matrix elements are 1.89 and 4.06 kJ mol−1 for hydroxide and fluoride bridge systems, respectively. The electron‐transfer rates of our calculations are 12.95 and 0.819 M−1 s−1 for hydroxide and fluoride bridge systems, respectively. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Effect of the interelectronic repulsion on the information content of position and momentum atomic densities
Authors: Angulo J. C. , López‐Rosa S. , Antolín J. 
Published: October 2009

AbstractThe interelectronic repulsion is strongly responsible of the main structural characteristics of the atomic densities and, in particular, of their level of information content. In this work, the effect of such a repulsion on some information‐theoretic descriptors is quantified and analyzed by considering different complexities and distances between the Bare Coulomb Field (BCF) and the Hartree–Fock (HF) position and momentum densities of neutral atoms throughout the Periodic Table. In doing so, the Quantum Similarity Index (QSI), the Quadratic Distance (QD), the Jensen‐Shannon (JSD) and Fisher (FD) Divergences as well as complexity measures are employed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Effect of solvents having different dielectric constants on reactivity: A conceptual DFT approach
Authors: Kar Rahul , Pal Sourav 
Published: October 2009

AbstractConceptual density functional theory is exploited to understand the reactivity in a medium of solvents with increasing dielectric constants. Aprotic as well as protic solvents are used for this study. It is found that the global parameters, such as chemical potential and hardness, decrease from gas phase to solvent phase with increasing dielectric constant. However, it is observed that the Fukui functions of the reactive atoms increase significantly with the dielectric constants of the aprotic solvents while for the protic solvents the variation of the reactivity indices is insignificant. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Theoretical prediction on HBeN− and HNBe− anions using multiconfiguration second‐order perturbation theory
Authors: Li Wen‐Zuo , Cheng Jian‐Bo , Zhong Li Qing‐ , Gong Bao‐An , Sun Jia‐Zhong 
Published: October 2009

AbstractThe HBeN− and HNBe− anions have been investigated for the first time using the CASSCF, CASPT2, and DFT/B3LYP methods with the contracted atomic natural orbital (ANO) and cc‐pVTZ basis sets. The geometries of all stationary points along the potential energy surfaces were optimized at the CASSCF/ANO and B3LYP/cc‐pVTZ levels. The ground and the first excited states of HBeN− are predicted to be X2Π and A2Σ+ states, respectively. It was predicted that the ground state of HNBe− is X2Σ+ state. The A2Π state of HNBe− has unique imaginary frequency. A bend local minimum M1 was found along the 12A″ potential energy surface and the A2Π state of HNBe− should be the transition state of the isomerization reactions for M1 ↔ M1. The CASPT2/ANO potential energy curves of isomerization reactions were calculated as a function of HBeN bond angle. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Recombinant immobilized rhizopuspepsin as a new tool for protein digestion in hydrogen/deuterium exchange mass spectrometry
Authors: Rey Martial , Man Petr , Brandolin Gérard , Forest Eric , Pelosi Ludovic 
Published: October 2009

AbstractHydrogen/deuterium (H/D) exchange coupled to mass spectrometry is nowadays routinely used to probe protein interactions or conformational changes. The method has many advantages, e.g. very low sample consumption, but offers limited spatial resolution. One way to higher resolution leads through the use of different proteases or their combinations. In the present work we describe recombinant production, purification and use of aspartic protease zymogen from Rhizopus chimensis, protease type XVIII (EC 3.4.23.6), commonly referred to as rhizopuspepsinogen (Rpg). The enzyme was expressed in Escherichia coli, refolded and purified to homogeneity. A typical yield was approximately 100 mg of pure enzyme per 1 L of original bacterial culture. The kinetics of protease activation, i.e. removal of the propeptide achieved by autolysis in an acidic environment, was followed by mass spectrometry. The digestion efficiency was tested for the protease in solution as well as for the immobilized enzyme. Apomyoglobin was successfully digested under all conditions tested and the protease displayed very low or no autodigestion. The results outperformed those obtained with commercial protease where the digestion of apomyoglobin was incomplete and accompanied by many contaminating peptides. Taken together, the recombinant protease type XVIII can be considered as a new and highly efficient tool for H/D exchange followed by mass spectrometry. Copyright © 2009 John Wiley & Sons, Ltd.
Optimizing mass spectrometric detection for ion chromatographic analysis. I. Common anions and selected organic acids
Authors: Wang Jinyuan , Schnute William C. 
Published: October 2009

AbstractWe describe a systematic method of optimizing mass spectrometric (MS) detection for ion chromatographic (IC) analysis of common anions and three selected organic acids using response surface methodology (RSM). RSM was utilized in this study because it minimized the number of experiments required to achieve the optimum MS response and included the interactions between individual parameters for multivariable optimization. Five MS parameters, including probe temperature, nebulizer gas, assistant makeup flow, needle voltage and cone voltage, were screened and systematically optimized by two steps. Central composite design (CCD) was used to design the experiment points and a quadratic model was applied to fit the experimental data. Analysis of variance (ANOVA) was carried out to evaluate the validity of the statistical model and to determine the most significant parameters for MS response. The optimum MS conditions for each analyte were summarized and the method optimum condition was achieved by applying desirability function. Our observation showed good agreements between statistically predicted optimum response and the responses collected at the predicted optimum condition. Operable range of each parameter (with normalized MS response greater than 0.8 for each analyte) was provided for general anionic IC/MS applications. Copyright © 2009 John Wiley & Sons, Ltd.
HIV fusion inhibitors
Authors: Qadir M. I. , Malik S. A. 
Published: October 2009

AbstractDrugs based on amino acid sequence of Heptad Repeats of gp41 of HIV have been explored in search of anti‐HIV drugs acting by inhibition of the gp41 6‐helix formation and subsequent cellular infection. These are classified under a distinct discipline called HIV fusion inhibitors. Resistance to HIV fusion inhibitors and their solutions have also been discussed in this review. Copyright © 2009 John Wiley & Sons, Ltd.
Improved nonlinear trajectory tracking using RBFNN for a robotic helicopter
Authors: Lee Chi‐Tai , Tsai Ching‐Chih 
Published: October 2009

AbstractThis paper presents a backstepping control method using radial‐basis‐function neural network (RBFNN) for improving trajectory tracking performance of a robotic helicopter. Many well‐known nonlinear controllers for robotic helicopters have been constructed based on the approximate dynamic model in which the coupling effect is neglected; their qualitative behavior must be further analyzed to ensure that the unmodeled dynamics do not destroy the stability of the closed‐loop system. In order to improve the controller design process, the proposed controller is developed based on the complete dynamic model of robotic helicopters by using an RBFNN function approximation to the neglected dynamic uncertainties, and then proving that all the trajectory tracking error variables are globally ultimately bounded and converge to a neighborhood of the origin. The merits of the proposal controller are exemplified by four numerical simulations, showing that the proposed controller outperforms a well‐known controller in (J. Robust Nonlinear Control2004;14(12):1035–1059). Copyright © 2009 John Wiley & Sons, Ltd.
Decentralized control of discrete‐time linear time invariant systems with input saturation
Authors: Deliu Ciprian , Malek Babak , Roy Sandip , Saberi Ali , Stoorvogel Anton A. 
Published: October 2009

AbstractWe study decentralized stabilization of discrete‐time linear time invariant (LTI) systems subject to actuator saturation using LTI controllers. The requirement of stabilization under both saturation constraints and decentralization imposes obvious necessary conditions on the open‐loop plant, namely that its eigenvalues are in the closed unit disc and further that the eigenvalues on the unit circle are not decentralized fixed modes. The key contribution of this work is to provide a broad sufficient condition for decentralized stabilization under saturation. Specifically, we show through an iterative argument that the stabilization is possible: whenever (1) the open‐loop eigenvalues are in the closed unit disc; (2) the eigenvalues on the unit circle are not decentralized fixed modes; and (3) these eigenvalues on the unit circle have algebraic multiplicity of 1. Copyright © 2009 John Wiley & Sons, Ltd.
Observer‐based H∞ control for systems with repeated scalar nonlinearities and multiple packet losses
Authors: Dong Hongli , Wang Zidong , Gao Huijun 
Published: October 2009

AbstractThis paper is concerned with the H∞ control problem for a class of systems with repeated scalar nonlinearities and multiple missing measurements. The nonlinear system is described by a discrete‐time state equation involving a repeated scalar nonlinearity, which typically appears in recurrent neural networks. The measurement missing phenomenon is assumed to occur, simultaneously, in the communication channels from the sensor to the controller and from the controller to the actuator, where the missing probability for each sensor/actuator is governed by an individual random variable satisfying a certain probabilistic distribution in the interval [0 1]. Attention is focused on the analysis and design of an observer‐based feedback controller such that the closed‐loop control system is stochastically stable and preserves a guaranteed H∞ performance. Sufficient conditions are obtained for the existence of admissible controllers. It is shown that the controller design problem under consideration is solvable if certain linear matrix inequalities (LMIs) are feasible. Three examples are provided to illustrate the effectiveness of the developed theoretical results. Copyright © 2009 John Wiley & Sons, Ltd.
Direct sequence spectrum spreading techniques for next generation mobile broadband satellite services
Authors: Kim Pansoo , Vanelli‐Coralli Alessandro , Villanti Marco , Pedone Raffaella , Cioni Stefano , Neri Massimo , Palestini Claudio , Papaleo Marco , Lee Ho‐Jin , Corazza Giovanni E. 
Published: October 2009

AbstractThe recently approved mobile version of the Digital Video Broadcasting Return Channel via Satellite (DVB‐RCS+M) foresees the use of direct sequence spectrum spreading (DS‐SS) in the forward link. The addition of a spreading mode, on top of the conventional time division signaling structure of the fixed DVB‐S2, allows in fact for the efficient extension of DVB‐S2 to mobile terminals with small aperture antennas operating in Ku (11–14 GHz) and Ka (20–30 GHz) bands. Spectrum spreading has been introduced to augment the received energy without increasing the transmitted power density, which is limited by regulatory constraints, and to enhance the waveform resilience to co‐channel interference. In this paper, we report on the design and assessment of the DS‐SS technique that we carried out for its inclusion in the DVB‐RCS+M standard. In particular, by comparing the physical layer performance of the spread and nonspread modes in the specific DVB‐RCS+M mobile scenarios, we show that the proposed DS‐SS technique has no impact on the DVB‐RCS+M data detection performance, while satisfying the requirements on interference resilience and received energy augmentation. In order to deal with the acquisition issues raised by the introduction of the DS‐SS technique, we then propose and evaluate several synchronization sub‐systems able to deal with the specific impairments of the mobile satellite scenarios, that is, large frequency offsets, phase noise, link obstructions, etc. Finally, a possible implementation of the DS‐SS technique that fully accommodates the reuse of the specific hardware compatible with conventional DVB‐S2 is also reported. Copyright © 2009 John Wiley & Sons, Ltd.
Fabrication of nanodot plasmonic waveguide structures using FIB milling and electron beam‐induced deposition
Authors: Dhawan Anuj , Gerhold Michael , Madison Andrew , Fowlkes Jason , Russell Phillip E. , Vo‐Dinh Tuan , Leonard Donovan N. 
Published: October 2009

AbstractFabrication of metallic Au nanopillars and linear arrays of Au‐containing nanodots for plasmonic waveguides is reported in this article by two different processes—focused ion beam (FIB) milling of deposited thin films and electron beam‐induced deposition (EBID) of metallic nanostructures from an organometallic precursor gas. Finite difference time domain (FDTD) modeling of electromagnetic fields around metallic nanostructures was used to predict the optimal size and spacing between nanostructures useful for plasmonic waveguides. Subsequently, a multi‐step FIB fabrication method was developed for production of metallic nanorods and nanopillars of the size and geometry suggested by the results of the FDTD simulations. Nanostructure fabrication was carried out on planar substrates including Au‐coated glass, quartz, and mica slides as well as cleaved 4‐mode optical fibers. In the second fabrication process, EBID was utilized for the development of similar nanostructures on planar Indium Tin Oxide and Titanium‐coated glass substrates. Each method allows formation of nanostructures such that the plasmon resonances associated with the nanostructures could be engineered and precisely controlled by controlling the nanostructure size and shape. Linear arrays of low aspect ratio nanodot structures ranging in diameter between 50–70 nm were fabricated using EBID. Preliminary dark field optical microscopy demonstrates differences in the plasmonic response of the fabricated structures. SCANNING 31: 139–146, 2009. © 2009 Wiley Periodicals, Inc.
DISA: Detection and isolation of sneaky attackers in locally monitored multi‐hop wireless networks
Authors: Khalil Issa , Bagchi Saurabh , AbuAli Najah , Hayajneh M. 
Published: October 2009

AbstractLocal monitoring has been demonstrated as a powerful technique for mitigating security attacks in multi‐hopad hocnetworks. In local monitoring, nodes overhear partial neighborhood communication to detect misbehavior such as packet drop or delay. However, local monitoring as presented in the literature is vulnerable to a class of attacks that we introduce here calledstealthy packet dropping. Stealthy packet dropping disrupts the packet from reaching the destination by malicious behavior at an intermediate node. However, the malicious node gives the impression to its neighbors that it performed the legitimate forwarding action. Moreover, a legitimate node comes under suspicion. We introduce four ways of achieving stealthy packet dropping, none of which is currently detectable. We provide a protocol called DISA, based on local monitoring, to remedy each attack. DISA incorporates two techniques—having the neighbors maintain additional information about the routing path, and adding some checking responsibility to each neighbor. We show through analysis and simulation that basic local monitoring (BLM) fails to efficiently mitigate any of the presented attacks while DISA successfully mitigates them. Copyright © 2009 John Wiley & Sons, Ltd.
Hierarchical testing of multiple endpoints in group‐sequential trials
Authors: Glimm Ekkehard , Maurer Willi , Bretz Frank 
Published: October 2009

AbstractWe consider the situation of testing hierarchically a (key) secondary endpoint in a group‐sequential clinical trial that is mainly driven by a primary endpoint. By ‘mainly driven’, we mean that the interim analyses are planned at points in time where a certain number of patients or events have accrued on the primary endpoint, and the trial will run either until statistical significance of the primary endpoint is achieved at one of the interim analyses or to the final analysis. We consider both the situation where the trial is stopped as soon as the primary endpoint is significant as well as the situation where it is continued after primary endpoint significance to further investigate the secondary endpoint. In addition, we investigate how to achieve strong control of the familywise error rate (FWER) at a pre‐specified significance level α for both the primary and the secondary hypotheses. We systematically explore various multiplicity adjustment methods. Starting point is a naive strategy of testing the secondary endpoint at level α whenever the primary endpoint is significant. Hung et al. (J. Biopharm. Stat. 2007; 17:1201–1210) have already shown that this naive strategy does not maintain the FWER at level α. We derive a sharp upper bound for the rejection probability of the secondary endpoint in the naive strategy. This suggests a number of multiple test strategies and also provides a benchmark for deciding whether a method is conservative or might be improved while maintaining the FWER at α. We use a numerical example based on a real case study to illustrate the results of different hierarchical test strategies. Copyright © 2009 John Wiley & Sons, Ltd.
Hypertensive disorders in pregnancy: screening by uterine artery Doppler imaging and blood pressure at 11–13 weeks
Authors: Poon L. C. Y. , Karagiannis G. , Leal A. , Romero X. C. , Nicolaides K. H. 
Published: October 2009

AbstractObjectivesTo examine the performance of screening for hypertensive disorders in pregnancy at 11–13 weeks by a combination of the maternal history, uterine artery Doppler imaging and blood pressure.MethodsThis was a prospective screening study for pre‐eclampsia (PE) requiring delivery before 34 weeks (early PE), late PE and gestational hypertension (GH) in women attending for their routine first hospital visit in pregnancy at 11 + 0 to 13 + 6 weeks of gestation. Maternal history was recorded, color flow Doppler imaging was used to identify the uterine artery with the lowest pulsatility index (L‐PI) and automated devices were used to measure the mean arterial pressure (MAP). The performance of screening for PE and GH by a combination of the maternal factor‐derived a‐priori risk, the uterine artery L‐PI and MAP was determined.ResultsThere were 8061 (96.4%) cases unaffected by PE or GH, 165 (2.0%) that developed PE including 37 that required delivery before 34 weeks (early PE) and 128 with late PE, and 140 (1.7%) that developed GH. The MAP was higher in early PE, late PE and GH than in the unaffected group (P < 0.0001), and in early PE than in GH (P = 0.002). The uterine artery L‐PI was significantly higher in early PE and late PE than in the unaffected group (P < 0.0001), in early PE than late PE or GH (P < 0.0001), and in GH than in the unaffected group (P = 0.014). In screening by a combination of the maternal factor‐derived a‐priori risk, uterine artery L‐PI and MAP, the estimated detection rate at a 10% false‐positive rate was 89.2% (95% CI, 74.6–96.9%) for early PE, 57.0% (95% CI, 48.0–65.7%) for late PE and 50.0% (95% CI, 41.4–58.6%) for GH.ConclusionsEffective screening for hypertensive disorders in pregnancy is provided by a combination of maternal history, uterine artery Doppler imaging and blood pressure at 11–13 weeks. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.
Does pre‐eclampsia influence fetal cardiovascular function in early‐onset intrauterine growth restriction?
Authors: Crispi F. , Comas M. , Hernández‐Andrade E. , Eixarch E. , Gómez O. , Figueras F. , Gratacós E. 
Published: October 2009

AbstractObjectivesIncreasing evidence shows that intrauterine growth restriction (IUGR) is associated with fetal cardiac dysfunction. Most studies group IUGR with and without pre‐eclampsia (PE) altogether. Our objective was to evaluate whether the association with PE has any impact on cardiac function in IUGR fetusesMethodsThirty‐one normotensive IUGR cases and 31 IUGR cases with pre‐eclampsia (PE + IUGR) below 34 weeks of gestation were included. IUGR was defined as a birth weight below the 10th centile together with an umbilical artery pulsatility index above 2 SD. Fetal cardiac function was assessed by measuring ductus venosus pulsatility index, modified myocardial performance index, aortic isthmus blood flow, E/A ratios and cardiac output. The presence of fetal cardiac dysfunction was also assessed by measuring cord blood B‐type natriuretic peptide (BNP) levels collected at birth. Echocardiographic data were compared with those in 80 term appropriate‐for‐gestational age (AGA) fetuses from normotensive mothers. Cord blood BNP levels were compared with those in 40 AGA cases that delivered preterm.ResultsAll IUGR cases (with or without PE) showed echocardiographic and biochemical signs of cardiac dysfunction compared with AGA cases. However, no differences were observed between IUGR and PE + IUGR cases either in echocardiographic or in biochemical parameters. IUGR cases with or without PE had similar perinatal results.ConclusionsIUGR fetuses showed echocardiographic and biochemical signs of cardiac dysfunction. Pre‐eclampsia per se does not influence cardiac function in IUGR fetuses. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.