bluuebunny/crossref_metadata_2025 huggingface dataset:
Mass spectrometric investigations of α‐ and β‐cyclodextrin complexes with ortho‐, meta‐ and para‐coumaric acids by negative mode electrospray ionization
Authors: Kralj Bogdan , Šmidovnik Andrej , Kobe Jože
Published: December 2008

The mass spectrometric characterization of aqueous solutions of α‐ and β‐cyclodextrins (CDs) and o‐, m‐ and p‐coumaric acids (CAs) by negative ion electrospray ionization (ESI) indicates that the [CD+CA]− ions were sourced from the inclusion complex present in solution and from the anion attached to CD molecules formed in the spray processes. The anion adducts formed in the spray process contribute significantly to the signal intensity of an ionized inclusion complex thus overestimating the calculated stability constant (K) of solution‐phase complexes by one to two orders of magnitude. The relative intensities of anion adducts in mass spectra depend on the concentration ratio of the anion and the CD in spray droplets, while the relative intensity of the ionized inclusion complex depends on CD and CA concentrations in solutions and the value of K. Ion Mobility Spectrometry Mass Spectrometry [IMS‐MS] measurements show that the collision cross‐section (Ω) values of the [CD+CA]− or [(CD)2+CA]2− and [CD+CA] complex ions are 5–6% larger than or equal to CD− or [CD], respectively. Therefore, in the gas phase the anion adducts [CD+CA−] on cyclodextrin molecules possess the same conformations as the ionized inclusion complexes [CD+CA]−. Copyright © 2008 John Wiley & Sons, Ltd.
Robustness assessment via stability radii in delay parameters
Authors: Michiels Wim , Fridman Emilia , Niculescu Silviu‐Iulian
Published: December 2008

This paper focuses on the robust stability analysis of a class of linear systems including multiple delays subjected to constant or time‐varying perturbations. The approach considered makes use of appropriate stability radius concepts (dynamic, static) and relies on a feedback interconnection interpretation of the uncertain system. Various computable bounds on stability radii are obtained that exploit the structure of the problem. Systems including perturbations on both system matrices and delays are also dealt with. Copyright © 2008 John Wiley & Sons, Ltd.
Age‐ and size‐related reference ranges: A case study of spirometry through childhood and adulthood
Authors: Cole T. J. , Stanojevic S. , Stocks J. , Coates A. L. , Hankinson J. L. , Wade A. M.
Published: December 2008

Age‐related reference ranges are useful for assessing growth in children. The LMS method is a popular technique for constructing growth charts that model the age‐changing distribution of the measurement in terms of the median, coefficient of variation and skewness. Here the methodology is extended to references that depend on body size as well as age, by exploiting the flexibility of the generalised additive models for location, scale and shape (GAMLSS) technique. GAMLSS offers general linear predictors for each moment parameter and a choice of error distributions, which can handle kurtosis as well as skewness. A key question with such references is the nature of the age‐size adjustment, additive or multiplicative, which is explored by comparing the identity link and log link for the median predictor.

There are several measurements whose reference ranges depend on both body size and age. As an example, models are developed here for the first four moments of the lung function variables forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and FEV1/FVC in terms of height and age, in a data set of 3598 children and adults aged 4 to 80 years. The results show a strong multiplicative association between spirometry, height and age, with a large and nonlinear age effect across the age range. Variability also depends nonlinearly on age and to a lesser extent on height. FEV1and FVC are close to normally distributed, while FEV1/FVC is appreciably skew to the left. GAMLSS is a powerful technique for the construction of such references, which should be useful in clinical medicine. Copyright © 2008 John Wiley & Sons, Ltd.
Catching two rabbits: adaptive real‐time support for embedded Linux
Authors: Seo Euiseong , Jeong Jinkyu , Park Seonyeong , Kim Jinsoo , Lee Joonwoon
Published: December 2008

The trend of digital convergence makes multitasking common in many digital electronic products. Some applications in those systems have inherent real‐time properties, while many others have few or no timeliness requirements. Therefore the embedded Linux kernels, which are widely used in those devices, provide real‐time features in many forms. However, providing real‐time scheduling usually induces throughput degradation in heavy multitasking due to the increased context switches. Usually the throughput degradation becomes a critical problem, since the performance of the embedded processors is generally limited for cost, design and energy efficiency reasons. This paper proposes schemes to lessen the throughput degradation, which is from real‐time scheduling, by suppressing unnecessary context switches and applying real‐time scheduling mechanisms only when it is necessary. Also the suggested schemes enable the complete priority inheritance protocol to prevent the well‐known priority inversion problem. We evaluated the effectiveness of our approach with open‐source benchmarks. By using the suggested schemes, the throughput is improved while the scheduling latency is kept same or better in comparison with the existing approaches. Copyright © 2008 John Wiley & Sons, Ltd.
Modelling methods for web application verification and testing: state of the art
Authors: Alalfi Manar H. , Cordy James R. , Dean Thomas R.
Published: December 2008

Models are considered an essential step in capturing different system behaviours and simplifying the analysis required to check or improve the quality of software. Verification and testing of web software requires effective modelling techniques that address the specific challenges of web applications. In this study we survey 24 different modelling methods used in web site verification and testing. Based on a short catalogue of desirable properties of web applications that require analysis, two different views of the methods are presented: a general categorization by modelling level, and a detailed comparison based on property coverage. Copyright © 2008 John Wiley & Sons, Ltd.
Analysis and design of optimum interleaver for iterative receivers in IDMA scheme
Authors: Shukla M. , Srivastava V.K. , Tiwari S.
Published: December 2008

In this paper, we propose a new tree based interleaver (TBI) to generate different chip‐level interleaving sequences for different users in an interleave division multiple access (IDMA) system, which reduces computational complexity. This method of generation also solves the memory cost problem and reduces the amount of information exchange between mobile stations (MSs) and base stations (BSs) required to specify the interleaver. Simulation results are presented to show that the proposed interleavers perform well as compared to random interleavers in an IDMA system. Copyright © 2008 John Wiley & Sons, Ltd.
Familial forms of nephrotic syndrome
Authors: Caridi Gianluca , Trivelli Antonella , Sanna-Cherchi Simone , Perfumo Francesco , Ghiggeri Gian Marco
Published: December 2008

The recent discovery of genes involved in familial forms of nephrotic syndrome represents a break-through in nephrology. To date, 15 genes have been characterized and several new loci have been identified, with a potential for discovery of new genes. Overall, these genes account for a large fraction of familial forms of nephrotic syndrome, but they can also be recognized in 10–20% of sporadic cases. These advances increase diagnostic and therapeutic potentials, but also add higher complexity to the scenario, requiring clear definitions of clinical, histopathological and molecular signatures. In general, genetic forms of nephrotic syndrome are resistant to common therapeutic approaches (that include steroids and calcineurin inhibitors) but, in a few cases, drug response or spontaneous remission suggest a complex pathogenesis. Finally, syndromic variants can be recognized on the basis of the associated extra-renal manifestations. In this educational review, clinical, histological and molecular aspects of various forms of familial nephrotic syndrome have been reviewed in an attempt to define a rational diagnostic approach. The proposed model focuses on practical and economic issues, taking into consideration the impossibility of using genetic testing as starting diagnostic tool. The final objective of this review is to outline a diagnostic flow-chart for clinicians and geneticists and to generate a rational scheme for molecular testing.
Differences in Tendon Graft Healing between the Intra-articular and Extra-articular Ends of a Bone Tunnel
Authors: Bedi Asheesh , Kawamura Sumito , Ying Liang , Rodeo Scott A.
Published: December 2008

The basic biology of healing between a tendon graft and bone tunnel remains incompletely understood. Distinct variability in the morphological characteristics of the healing tendon–bone attachment site has been reported. We hypothesized that spatial and temporal differences in tendon-to-bone healing exist at different regions of a surgically created bone tunnel. Twenty-four male, Sprague–Dawley rats underwent anterior cruciate ligament (ACL) reconstruction in the left knee using a flexor digitorum longus tendon graft secured using suspensory periosteal fixation. Animals were sacrificed at 4, 7, 11, 14, 21, and 28 days after surgery and prepared for routine histology and immunohistochemical analysis of the healing enthesis at the intra-articular aperture (IAA), mid-tunnel, and extra-articular aperture (EAA). Six animals were used to measure mineral apposition rate (MAR) along the healing bone tunnel by double fluorochrome labeling at 14 and 28 days after surgery. The total area of calcified bone matrix was assessed with von Kossa staining and Goldner-Masson trichrome staining, respectively. The healing tendon–bone interface tissue exhibited a wide chondroid matrix at the IAA, in contrast to a narrow, fibrous matrix at the EAA. There were significantly more osteoclasts at the IAA compared to EAA throughout the study period, except 4 days after surgery ( p < 0.05). Collagen continuity between the tendon graft and bone tunnel increased over time, with a more parallel orientation and increased collagen fiber continuity between tendon and bone at the EAA compared to the IAA. MAR was also significantly greater at the EAA at 4 weeks ( p < 0.001). Significant differences in healing between the tendon graft and bone exist along the length of bone tunnel secured with suspensory fixation. The etiology of these differences is likely multifactorial in nature, including variable biological and biomechanical environments at different ends of the tunnel. Understanding these differences may ultimately allow surgeons to improve the quality of graft fixation and long-term outcomes after ACL reconstruction.
High Activity of Hexagonal Ag/Pt Nanoshell Catalyst for Oxygen Electroreduction
Authors: Lee Chien-Liang , Tseng Chun-Ming , Wu Chen-Chung , Chou Tsung-Chia , Syu Ciou-Mei
Published: December 2008

Hexagonal Ag/Pt nanoshells were prepared by using a hexagonal Ag nanoplate as the displacement template and by introducing Pt ions. The prepared Ag/Pt nanoshells played the role of an electrocatalyst in an oxygen reduction process. Compared to spherical Pt and Ag/Pt nanoparticles, the hexagonal Ag/Pt nanoshells showed higher activity for oxygen electroreduction.
Isolation and expansion of equine umbilical cord‐derived matrix cells (EUCMCs)
Authors: Passeri Simona , Nocchi Francesca , Lamanna Roberta , Lapi Simone , Miragliotta Vincenzo , Giannessi Elisabetta , Abramo Francesca , Stornelli Maria Rita , Matarazzo Micheletino , Plenteda Daniele , Urciuoli Patrizia , Scatena Fabrizio , Coli Alessandra
Published: December 2008

Stem cells from extra‐embryonic sources can be obtained by non‐invasive procedures. We have standardized a method for the expansion of equine umbilical cord‐derived matrix cells (EUCMCs) for potential therapy.

EUCMCs were isolated from the umbilical cord of five mares immediately after delivery. For expansion, cells were grown in α‐MEM and MSCBM. Moreover, to measure the effect of growth factor supplementation, epidermal growth factor (EGF) was added to α‐MEM.

α‐MEM and MSCBM media performed similarly in terms of population doubling and CFU number value. EGF supplementation of α‐MEM determined a significant increase of the population doubling value. EGF supplementation did not affect the adipogenic and chondrogenic differentiation while bone nodule sizes an increased with the osteogenic protocol.

Both α‐MEM and MSCBM can be used to cultivate EUCMCs. α‐MEM supplemented with EGF might represent an advantage for EUCMCs expansion. The results could be useful in choosing the culture medium since α‐MEM is more cost‐effective than MSCBM.
Intraluminal hydrogen peroxide induces a permeability change of the endoplasmic reticulum membrane
Authors: Margittai Éva , Löw Péter , Szarka András , Csala Miklós , Benedetti Angelo , Bánhegyi Gábor
Published: December 2008

Gulonolactone treatment of mice resulted in the elevation of hepatic ascorbate and hydrogen peroxide levels accompanied by transient liver swelling and reversible dilatation of endoplasmic reticulum cisternae. Although a decrease in glutathione (reduced form)/total glutathione ratio was observed in microsomes, the redox state of luminal foldases remained unchanged and the signs of endoplasmic reticulum stress were absent. Increased permeability of the microsomal membrane to various compounds of low molecular weight was substantiated. It is assumed that Gulonolactone‐dependent luminal hydrogen peroxide formation in the endoplasmic reticulum provokes a temporary increase in non‐selective membrane permeability, which results in the dilation of the organelle and in enhanced transmembrane fluxes of small molecules.
Simplified estimation of forage degradability in the rumen assuming zero-order degradation kinetics
Authors: DHANOA M. S. , LÓPEZ S. , SANDERSON R. , FRANCE J.
Published: December 2008

In the present paper, a simplified procedure using few in situ data points is derived and then evaluated (using a large database) against reference values estimated with the standard nylon bag first-order kinetics model. The procedure proposed involved a two-stage mathematical process, with a statistical prediction of some degradation parameters (such as lag time) and then a kinetic model derived by assuming degradation follows zero-order kinetics to determine effective degradability in the rumen (E). In addition to the estimation of washout fraction and discrete lag, which is common to both procedures, the simplified procedure requires measurement of dry matter losses at one incubation time point only. Thus, interference of the animal rumen will be much reduced, which will lead to increased capacity for feed evaluation. Calibration of the zero-order model against the first-order model showed that suitable estimates of E can be obtained with disappearance at 24, 48 or 72 h as the single incubation end time point. The strength of the calibration is such that an end incubation time point as low as 24 h may be sufficient, which may reduce substantially the total incubation time required and thus the impact on the experimental animal. Relevant regression equations to predict reference values of parameters such as lag time or E are also developed and validated.
Biological Innovation and Productivity Growth in the Antebellum Cotton Economy
Authors: OLMSTEAD ALAN L. , RHODE PAUL W.
Published: December 2008

The cliometrics literature on slave efficiency has generally focused on static questions. We take a decidedly more dynamic approach. Drawing on the records of 142 plantations with 509 crops years, we show that the average daily cotton-picking rate increased about fourfold between 1801 and 1862. We argue that the development and diffusion of new cotton varieties were the primary sources of the increased efficiency. These findings have broad implications for understanding the South's preeminence in the world cotton market, the pace of westward expansion, and the importance of indigenous technological innovation.
Farming systems education: Case study of Swedish test pilots
Authors: Salomonsson Lennart , Nilsson Anna , Palmer Sofia , Roigart Adam , Francis Charles
Published: December 2008

We describe and analyze a pedagogical experiment that introduced a broad and holistic perspective on complete farming systems, systemic learning tools, and a participatory learning strategy at an early stage in agronomy education. The paper describes the adventure of three students, who came from a conventional agronomy program at the Swedish University of Agricultural Sciences (SLU), who were frustrated with the lack of integrated approaches to the study of agricultural systems and a strong focus on molecular-level processes in their first year of education. They encountered a narrow focus in most courses and the overall curricula of agricultural education that is a function of specialization and university organization in unique departments that concentrate on small pieces of the large puzzle, that is the production milieu. In the current educational environment, it is difficult for students to make connections, integrate information and theories, and to create relevance to the challenges they observe in the practical world of farming and food systems. The three students agreed to put on pilots' costumes and climb into an experimental vehicle calledexperiential learning, one that providesjust-in-time educationand a very high degree of self-responsibility for the learning process. The paper describes, analyzes, and evaluates the comprehensive and exhausting pedagogical process they followed in one semester in Sweden and Viet Nam, with positive and negative aspects of the program. We provide reflective recommendations from students and advisors for future agronomic education programs with the focus on developing renewable agriculture, selecting students and evaluating performance, and designing practical programs that will motivate highly committed and action-oriented students.
Stress field evolution in the northwest Himalayan syntaxis, northern Pakistan
Authors: Pêcher A. , Seeber L. , Guillot S. , Jouanne F. , Kausar A. , Latif M. , Majid A. , Mahéo G. , Mugnier J. L. , Rolland Y. , van der Beek P. , Van Melle J.
Published: December 2008

We have conducted a systematic inversion of striated fault planes throughout northern Pakistan in order to better depict the temporal and spatial variations in stress patterns. Two domains are evidenced at a regional scale, separated by the active Raikhot fault, the western boundary of the Nanga Parbat spur. West of this fault, a wrench‐type stress field withσ1 axis oriented around N–S predominates in the Karakorum and in Kohistan. It predates Pliocene‐Quaternary exhumation of Nanga Parbat and corresponds to the Miocene or earlier regional stress field related to Indian‐Asian convergence. East of the Raikhot fault, compression parallel to the belt accounts for initiation of the Nanga Parbat anticlinorium after 5 Ma. It is followed by predominant post‐2 Ma extension, both parallel to the belt and NNE–SSW oriented. Thus, in the N–W Himalayan syntaxis, multidirectional extension is juxtaposed on short timescales to shortening either parallel or perpendicular to the belt. Such juxtaposition could be characteristic of strain and stress partitioning during oblique convergence.
Influence of terrestrial weathering on ocean acidification and the next glacial inception
Authors: Uchikawa Joji , Zeebe Richard E.
Published: December 2008

Ocean uptake of anthropogenic CO2 causes a decline in seawater pH, a process known as ocean acidification, which may adversely affect marine organisms. We investigate whether continental weathering can mitigate future ocean acidification by sequestering atmospheric CO2. We conducted simulations under a suite of carbon emission scenarios with different weathering parameterizations. The short‐term impact of a strong weathering feedback was only notable for large emissions with slow injection. This mitigation by enhanced weathering, however, is an order of magnitude smaller than the expected maximum pH decline based on the default parameterizations. Thus on short timescales, weathering has little effect on future atmospheric CO2 and ocean acidification, regardless of the assumed weathering feedback strength. But on longer timescales and for large emissions, different weathering parameterizations introduce large uncertainties regarding the time when pCO2 will return to climatically relevant levels of, say, 400 μatm in the future.
An analytical solution and case study of groundwater head response to dual tide in an island leaky confined aquifer
Authors: Sun Pingping , Li Hailong , Boufadel Michel C. , Geng Xiaolong , Chen Shi
Published: December 2008

This paper presents an analytical solution of groundwater head response to dual‐tide fluctuation in the transect of an island leaky aquifer system comprising a confined aquifer and its overlying semipermeable confining layer. Both layers terminate at the coastlines on two sides of the island. Solution analysis indicates that the tidal waves from the two sides of the island transect interfere at the middle of the island and the interference decreases to zero as the horizontal length of the aquifer increases to infinity. The leakage of the overlying confining layer enhances the landward attenuation of the tidal head fluctuation and shortens the time lag between the head and tide fluctuations. The solution agreed well with the observations in eight piezometers in Garden Island on the continental shelf of Western Australia reported by Trefry and Bekele (2004).
Impact of Behavior Genetics on Medicine and Society
Authors: Hamer Dean
Published: December 2008

Understanding the role of genes in human behavior will impact both medicine and society, but not always in the manner expected. Knowledge about behavioral genes can be used for the good, for example by improving psychiatric diagnoses, developing new drugs to treat mental illnesses, and dispelling harmful myths about certain types of human variation. However, the same sort of information could be used to discriminate against people, to provide quick fixes for social problems, or to support eugenics. How we use the new knowledge about molecular behavior genetics will depend on the legal, ethical and social policies that we develop.To watch Dr. Hamer's presentation, please see the "Google Video posting.":http://video.google.com/videoplay?docid=-9036771709057660539&hl=en To watch the deliberative discussion concluding the Symposium after this last presentation, please see the "Google Video posting.":http://video.google.com/videoplay?docid=-4540711705005631053&hl=en
Medications That Exacerbate or Induce Cognitive-Communication Deficits
Authors: Youse Kathleen M.
Published: December 2008

Purpose
: Some medications can cause or exacerbate cognitive-communication deficits and thus complicate, rather than facilitate, restoration of health. Unfortunately, the literature regarding the negative cognitive or communicative side effects of medications is limited because a variety of methodologies are used in such research, making outcomes difficult to compare. It is recommended that speech-language pathologists (SLPs) thoroughly investigate any medication a patient may be prescribed to determine if and how it may affect cognitive-communicative ability.

Method
: The current literature and reliable internet sources (e.g., National Institutes of Health, Mayo Clinic) were searched to provide examples of commonly used classes of drugs (e.g., antidepressants, diabetic medications) and the possible effect they may have on cognition and communication. This was followed by recommendations for finding current medication information using the internet.

Results and Conclusions
: Clinicians play an important role in monitoring medications and reporting their effects to the health care team. SLPs should make every effort to know the medications that a patient is prescribed and how each medication may affect cognitive-communicative ability. Moreover, the interaction between medications should also be considered, as many individuals who are receiving medical treatment are prescribed more than one medication for concomitant disease processes.
A remark on the infinite-volume Gibbs measures of spin glasses
Authors: Arguin Louis-Pierre
Published: December 2008

In this note, we point out that infinite-volume Gibbs measures of spin glass models on the hypercube can be identified as random probability measures on the unit ball of a Hilbert space. This simple observation follows from a result of Dovbysh and Sudakov on weakly exchangeable random matrices. Limiting Gibbs measures can then be studied as single well-defined objects. This approach naturally extends the space of random overlap structures as defined by Aizenman et al. We discuss the Ruelle probability cascades and the stochastic stability within this framework. As an application, we use an idea of Parisi and Talagrand to prove that if a sequence of finite-volume Gibbs measures satisfies the Ghirlanda–Guerra identities, then the infinite-volume measure must be singular as a measure on a Hilbert space.
Activation of room-temperature ferromagnetism in nonstoichiometric TiO2-δ powders by oxygen vacancies
Authors: Zhao Q. , Wu P. , Li B. L. , Lu Z. M. , Jiang E. Y.
Published: December 2008

Anatase and rutile TiO2-δ powders are synthesized by the sol-gel method. The hysteresis loops and the zero field-cooled and the field-cooled magnetization curves indicate that reduced TiO2-δ powders exhibit the room-temperature ferromagnetism that becomes stronger with prolonging annealing time in H2/Ar mixture. Analysis of Ti 2p x-ray photoelectron spectroscopy spectra indicates that Ti ions are all in the Ti4+ state and that Ti3+ or Ti2+ ions do not exist in all samples. In addition, analysis of O 1s x-ray photoelectron spectroscopy spectra indicates that the concentration of oxygen vacancies increases with prolonging annealing time. Analysis of ultraviolet-visible absorption spectra also further confirms that the concentration of oxygen vacancies increases with prolonging annealing time. These results indicate that ferromagnetism in pure TiO2-δ powders stems from oxygen vacancies. The possible mechanism on ferromagnetism is discussed.
Dielectrophoresis of ionized gas microbubbles: Dipole reversal due to diffusive double-layer polarization
Authors: Gagnon Zachary R. , Chang Hsueh-Chia
Published: December 2008

Gas bubbles generated by electrolysis reactions are shown to exhibit anomalous induced ac dipoles and dielectrophoretic behavior that cannot be described by classical Maxwell–Wagner theory. Normal charging and screening of conducting ionized gas in the gas-phase double layer are shown to render the bubble insulating at low ac field frequencies to affect negative dielectrophoresis. This screening effect couples with dielectric polarization at high frequencies to produce no crossover frequency for small bubbles and two crossover frequencies for bubbles larger than a critical size of 40 μm. A double-layer theory accurately captures the two crossover frequencies and critical bubble size behavior.
Dissociative dynamics of spin-triplet and spin-singlet O2 on Ag(100)
Authors: Alducin M. , Busnengo H. F. , Muiño R. Díez
Published: December 2008

We study the dissociative dynamics of O2 molecules on the Ag(100) surface. Initially, the impinging molecules are either in the spin-triplet ground state or in the spin-singlet excited state. The molecule-surface interaction is obtained in each case by constructing the six-dimensional potential energy surface (PES) from the interpolation of the energies calculated with spin-polarized and non-spin-polarized density functional theories, respectively. Classical trajectory calculations performed in both PESs show that O2 molecules initially in the spin-triplet ground state only dissociate for incidence energies above 1.05 eV. This result is consistent with molecular beam experiments performed in this system. Interestingly, our results also suggest that for the spin-singlet O2 dissociation occurs even for incidence energies as low as 50 meV. We propose the use of spin-singlet excited O2 molecules to improve the otherwise low dissociative reactivity of O2 at clean Ag(100).
Magnetic anisotropy, interlayer coupling, and magneto-optical effects in single-crystalline Fe/Cr/Fe/MgO/Fe magnetotunnel structures grown on GaAs(001) substrates
Authors: Grabowski J. , Przybylski M. , Nyvlt M. , Kirschner J.
Published: December 2008

Fe/MgO/Fe single-crystalline magnetotunneling structures were epitaxially grown on GaAs(001). An independent magnetization switching in the Fe electrodes was achieved by pinning the magnetization of the Fe-top electrode by antiferromagnetic coupling across a Cr spacer to another Fe film. Such Fe/Cr/Fe/MgO/Fe/GaAs(001) structures exhibit in-plane anisotropy, which ensures a discrete switching behavior of magnetization simplifying the shape of the hysteresis loop. The field dependence of magnetization was measured along the [110] and [100] crystallographic directions of GaAs(001) substrate and modeled by minimizing the total magnetic energy of the system. A peculiar magneto-optical behavior (similar to a reversed hysteresis loop) is explained by magneto-optical phase angles, which are determined mainly by the optical properties of the semiconducting GaAs substrate.
Temperature dependence of conformation, chemical state, and metal-directed assembly of tetrapyridyl-porphyrin on Cu(111)
Authors: Klappenberger F. , Weber-Bargioni A. , Auwärter W. , Marschall M. , Schiffrin A. , Barth J. V.
Published: December 2008

We present a combined scanning tunneling microscopy (STM), near-edge x-ray-absorption fine-structure, and x-ray photoemission spectroscopy (XPS) study on the bonding and ordering of tetrapyridyl-porphyrin molecules on the Cu(111) surface in the 300–500 K temperature range. Following deposition at 300 K the molecules are adsorbed with a pronounced conformational adaptation of the anchored species featuring a saddle-shaped macrocycle and terminal groups pointing toward the substrate. Upon moderate annealing supramolecular chains evolve that are stabilized by metal-ligand interactions between the mesopyridyl substituents and copper adatoms resulting in twofold copper coordination. Annealing to temperatures exceeding 450 K strongly alters the molecular appearance in high-resolution STM data. This modification was also induced by controlled voltage pulses and related to a deprotonation of the molecule by XPS. Under appropriate conditions a novel binding motif leads to honeycomb structures coexisting with the chain segments. The conformation withstands annealing without large modification.
Permeability calculations in three-dimensional isotropic and oriented fiber networks
Authors: Stylianopoulos Triantafyllos , Yeckel Andrew , Derby Jeffrey J. , Luo Xiao-Juan , Shephard Mark S. , Sander Edward A. , Barocas Victor H.
Published: December 2008

Hydraulic permeabilities of fiber networks are of interest for many applications and have been studied extensively. There is little work, however, on permeability calculations in three-dimensional random networks. Computational power is now sufficient to calculate permeabilities directly by constructing artificial fiber networks and simulating flow through them. Even with today’s high-performance computers, however, such an approach would be infeasible for large simulations. It is therefore necessary to develop a correlation based on fiber volume fraction, radius, and orientation, preferably by incorporating previous studies on isotropic or structured networks. In this work, the direct calculations were performed, using the finite element method, on networks with varying degrees of orientation, and combinations of results for flows parallel and perpendicular to a single fiber or an array thereof, using a volume-averaging theory, were compared to the detailed analysis. The detailed model agreed well with existing analytical solutions for square arrays of fibers up to fiber volume fractions of 46% for parallel flow and 33% for transverse flow. Permeability calculations were then performed for isotropic and oriented fiber networks within the fiber volume fraction range of 0.3%–15%. When drag coefficients for spatially periodic arrays were used, the results of the volume-averaging method agreed well with the direct finite element calculations. On the contrary, the use of drag coefficients for isolated fibers overpredicted the permeability for the volume fraction range that was employed. We concluded that a weighted combination of drag coefficients for spatially periodic arrays of fibers could be used as a good approximation for fiber networks, which further implies that the effect of the fiber volume fraction and orientation on the permeability of fiber networks are more important than the effect of local network structure.
Drug binding and mobility relating to the thermal fluctuation in fluid lipid membranes
Authors: Okamura Emiko , Yoshii Noriyuki
Published: December 2008

Drug binding and mobility in fluid lipid bilayer membranes are quantified in situ by using the multinuclear solution NMR combined with the pulsed-field-gradient technique. One-dimensional and pulsed-field-gradient F19 and H1 NMR signals of an anticancer drug, 5-fluorouracil (5FU) are analyzed at 283–313 K in the presence of large unilamellar vesicles (LUVs) of egg phosphatidylcholine (EPC) as model cell membranes. The simultaneous observation of the membrane-bound and free 5FU signals enables to quantify in what amount of 5FU is bound to the membrane and how fast 5FU is moving within the membrane in relation to the thermal fluctuation of the soft, fluid environment. It is shown that the mobility of membrane-bound 5FU is slowed down by almost two orders of magnitude and similar to the lipid movement in the membrane, the movement closely related to the intramembrane fluidity. The mobility of 5FU and EPC is, however, not similar at 313 K; the 5FU movement is enhanced in the membrane as a result of the loose binding of 5FU in the lipid matrices. The membrane-bound fraction of 5FU is ∼0.1 and almost unaltered over the temperature range examined. It is also independent of the 5FU concentration from 2 to 30 mM with respect to the 40–50 mM LUV. The free energy of the 5FU binding is estimated at −4 to −2 kJ/mol, the magnitude always close to the thermal fluctuation, 2.4–2.6 kJ/mol.
Selective switch made from a graded nanosandwich chain
Authors: Wang S. M. , Li T. , Liu H. , Wang F. M. , Zhu S. N. , Zhang X.
Published: December 2008

The magnetic plasmon (MP) modes in a metallic nanosandwich chain with a linearly increasing spacing along the chain has been investigated. Because of the graded coupling between nanosandwiches, the MP gradon with special field localization and large field amplitude can be found in the chain as well as the extended mode, which differs from the case of periodic chain. Using this property, we can precisely control the field in the chain and guide it to different ports at different frequencies, which works as a selective switch and may have potential application in integrated optics. Finally, we give out the underlying physical mechanism to help better understand and apply this graded chain.
Implementation of transition moments between excited states in the approximate coupled-cluster singles and doubles model
Authors: Pabst Mathias , Köhn Andreas
Published: December 2008

An implementation of transition moments between excited states for the approximate coupled-cluster singles and doubles model (CC2) using the resolution of the identity (RI) approximation is reported. The accuracy of the RI approximation is analyzed for a testset of 7 molecules and 76 transitions. The RI error is found to be very small for both transition moments and oscillator strengths. Furthermore, the performance of the CC2 model in comparison with coupled-cluster singles and doubles (CCSD) is studied for 40 transitions of the same testset, yielding deviations of about 12% for the transition moments and 24% for the oscillator strengths. In addition, for 13 transitions of the testset the behavior of the transition moments with respect to seven different basis sets (Dunnings xaug-cc-pVXZ, with x=0,1,2 for X=D,T and x=2 for X=5) is analyzed, showing a strong dependence on the degree of augmentation x and a rather small effect of the cardinal number X. First applications are presented for the triplet-triplet transition moments of benzene and polyacenes (naphthalene to pentacene), showing good agreement with experimental and theoretical results for transitions between single excitation dominated states. Somewhat problematic is the insufficient description of double-excitation dominated states by the CC2 model. As transitions to such states may be strongly allowed, unlike for excitations out of the ground state, important features of transient spectra may be missed. For triplet-triplet excitations the problem is less evident as the lowest doubly excited triplet states are expected at higher energies.
Characteristics of streamer discharge development between the dielectric-coated sphere-plane electrodes in water
Authors: Zhu Taiyun , Yang Lanjun , Jia Zhijie , Zhang Qiaogen
Published: December 2008

This paper presents the characteristics of the streamer discharge development between the dielectric-coated sphere-plane electrodes in water. In order to study the streamer propagation mechanism, the factors such as polarities, water conductivity, and ambient pressure were taken into consideration. Experimental results demonstrate that the water conductivity and amplitude of applied voltage both have a great influence on mean velocity and brightness of the streamer. When the ambient pressure decreases from 0.1 to 0.0065 MPa, the pressure has little influence on the mean velocities of the streamer in both distilled and tap water for fast streamer. The existence of dielectric coating causes a lower initiation voltage of the streamer for negative polarity than that for positive one. Also, the 10% breakdown voltage (U10%) is decreased by 20% under the pressure of 0.0065 MPa than that under the pressure of 0.1 MPa in distilled water, while the U10% is almost the same under different pressures in tap water. Based on the analysis of the discharge images and current waveforms as well as the above experimental results, it can be concluded that the streamer propagation is composed of the generation of the microbubbles and the discharge in the bubbles. For subsonic streamer, the generation of the bubbles is more likely a thermal process, whereas for supersonic streamer, the ionization and dissociation of water molecules in high electric field are involved in the bubble generation process.
On collisional energy transfer in recombination and dissociation reactions: A Wiener–Hopf problem and the effect of a near elastic peak
Authors: Zhu Zhaoyan , Marcus R. A.
Published: December 2008

The effect of the large impact parameter near-elastic peak of collisional energy transfer for unimolecular dissociation/bimolecular recombination reactions is studied. To this end, the conventional single exponential model, a biexponential model that fits the literature classical trajectory data better, a model with a singularity at zero energy transfer, and the most realistic model, a model with a near-singularity, are fitted to the trajectory data in the literature. The typical effect of the energy transfer on the recombination rate constant is maximal at low pressures and this region is the one studied here. The distribution function for the limiting dissociation rate constant k0 at low pressures is shown to obey a Wiener–Hopf integral equation and is solved analytically for the first two models and perturbatively for the other two. For the single exponential model, this method yields the trial solution of Troe. The results are applied to the dissociation of O3 in the presence of argon, for which classical mechanical trajectory data are available. The k0’s for various models are calculated and compared, the value for the near-singularity model being about ten times larger than that for the first two models. This trend reflects the contribution to the cross section from collisions with larger impact parameter. In the present study of the near-singularity model, it is found that k0 is not sensitive to reasonable values for the lower bound. Energy transfer values ⟨ΔE⟩’s are also calculated and compared and can be similarly understood. However, unlike the k0 values, they are sensitive to the lower bound, and so any comparison of a classical trajectory analysis for ⟨ΔE⟩’s with the kinetic experimental data needs particular care.
Vibrational signatures of hydrogen bonding in the protonated ammonia clusters NH4+(NH3)1−4
Authors: Yang Y. , Kühn O. , Santambrogio G. , Goebbert D. J. , Asmis K. R.
Published: December 2008

The gas phase vibrational spectroscopy of the protonated ammonia dimer N2H7+, a prototypical system for strong hydrogen bonding, is studied in the spectral region from 330 to 1650 cm−1 by combining infrared multiple photon dissociation and multidimensional quantum mechanical simulations. The fundamental transition of the antisymmetric proton stretching vibration is observed at 374 cm−1 and assigned on the basis of a six-dimensional model Hamiltonian, which predicts this transition at 471 cm−1. Photodissociation spectra of the larger protonated ammonia clusters NH4+(NH3)n with n=2–4 are also reported for the range from 1050 to 1575 cm−1. The main absorption features can be assigned within the harmonic approximation, supporting earlier evidence that hydrogen bonding in these clusters is considerably weaker than for n=1.
3.4 THz heterodyne receiver using a hot electron bolometer and a distributed feedback quantum cascade laser
Authors: Khosropanah P. , Zhang W. , Hovenier J. N. , Gao J. R. , Klapwijk T. M. , Amanti M. I. , Scalari G. , Faist J.
Published: December 2008

We report a heterodyne receiver using a superconducting NbN hot electron bolometer (HEB) integrated with a tight winding spiral antenna as mixer and a distributed feedback (DFB) terahertz quantum cascade laser (QCL) operating at 3.42 THz as local oscillator. The aim is to demonstrate the readiness of both devices for the detection of OH lines at 3.5 THz in a real instrument. We show that the improved single-spot beam of the terahertz QCL can easily pump the HEB mixer. We measured a double sideband receiver noise temperature of 2100 K at the optimum local oscillator power of 290 nW. This noise temperature can be further reduced to 1100 K if we correct the loss due to the use of an uncoated lens, and the losses of the window and the air. Therefore, the combination of a HEB and such a DFB QCL can in principle be used to detect an OH line at 3.5 THz. However, a high input power of several watts, which is needed to operate the QCL in a liquid-helium cryostat, poses a big challenge to the receiver stability.
Strong physisorption site for H2 in K- and Li-doped porous carbons
Authors: Pellenq Roland J.-M. , Marinelli Francis , Fuhr Javier D. , Fernandez-Alonso Felix , Refson Keith
Published: December 2008

Molecular hydrogen adsorption between two Li, K-doped coronene molecules (taken as local environment of carbon microporous materials) is studied by first-principles DFT-B3LYP calculations. These cluster calculations are complemented with periodic DFT-LDA/GGA calculations on extended Li- and K-doped structures. In all cases, energy minimization calculations unravel that there is a stable adsorption site for molecular hydrogen in these Li- and K-doped sp2 carbon structures with large adsorption energies. This is the direct consequence of the significant charge transfer from the doping agents on neighboring slab carbon atoms, which allows the coupling of the molecular H2 polarizability with the resulting substrate electric field (polarization interaction) that in turn induces the stabilization of molecular hydrogen. These calculations also give an insight on the atomic configurations of interlayer species (H2 and Li∕K) as the interlayer spacing increases. It can be shown that large positional changes correlate with electronic properties of interlayer species. The confined hydrogen molecule does not show any tendency for dissociation and adopts a position in the interlayer void that is deeply related to that of doping ions.
Layered high-gain lens antennas via discrete optical transformation
Authors: Jiang Wei Xiang , Cui Tie Jun , Ma Hui Feng , Yang Xin Mi , Cheng Qiang
Published: December 2008

In reality, the optical-transformation media with complicated and continuous electromagnetic parameters are difficult to realize. In this work, we propose a discrete embedded optical transformation from which a layered high-gain lens antenna is designed. All layers of the lens antenna are composed of homogeneous and uniaxially anisotropic metamaterials, which are simple and realizable. When the layered lens is embedded in a horn antenna, the lens antenna provides a high-directivity radiation beam. We also use the discrete optical transformation to design a multibeam high-gain antenna.
Electric field assisted dissolution of Au rods in gold-doped silicate glass
Authors: Zou Zhiyu , Chen Xiangjun , Wang Qiang , Qu Shiliang , Wang Xinyu
Published: December 2008

Dissolution of Au rods in gold-doped silicate glass is observed experimentally during the dc electric field thermal poling. Scanning electron microscopy characterizations show that some Au rods with a high aspect ratio are dissolved to spherelike particles and others still keep an elongated structure, which is well accorded with the absorption spectroscopy results. The mechanism for dissolution of Au particles is attributed to electron tunneling conduction and Au cationic conduction, based on electrical measurements during the electric field assisted dissolution process. Electric field thermal poling provides a promising method for the controlling of structural and optical properties of noble metal-doped silicate glass.
Composition dependence of magnetocaloric effect in Sm1−xSrxMnO3(x=0.3–0.5)
Authors: Rebello A. , Mahendiran R.
Published: December 2008

We investigated magnetic and magnetocaloric properties in Sm1−xSrxMnO3(x=0.3–0.5). We report a magnetic field-driven first-order metamagnetic transition in the paramagnetic state in x=0.4 and 0.5 and a second-order transition in x=0.3. The highest magnetic entropy (−ΔSm=1.41 J/mol K for ΔH=5 T at T=125 K) that occurs in x=0.4 is associated with the metamagnetic transition resulting from the field-induced growth and coalescence of ferromagnetic nanoclusters pre-existing in the paramagnetic state. Our results suggest that manganites with intrinsic nanoscale phase separation can be exploited for magnetic refrigeration.