bluuebunny/crossref_metadata_2025 huggingface dataset:
Patient Preference for Triptan Formulations: A Prospective Study With Zolmitriptan
Authors: Dowson Andrew , Bundy Michael , Salt Rebecca , Kilminster Shaun
Published: May 2007

Objectives.—To investigate patterns of patient preference for 3 formulations of zolmitriptan, in a primary care study utilizing a naturalistic longitudinal design.

Background.—Although differences in efficacy between individual triptans tend to be small, migraine patients show clear preferences for individual triptans and formulations. The groups of patients suitable for the different triptan formulations, and the reasons underlying individual preferences, are not clearly understood.

Methods.—Migraine patients entered a prospective, randomized, open, crossover, longitudinal design study, with patients receiving zolmitriptan formulations according to UK prescribing recommendations. Patients naïve to zolmitriptan received zolmitriptan 2.5‐mg film‐coated tablets or 2.5‐mg Orally Disintegrating Tablets (ODT) for 1 month, before being crossed over to receive the alternative formulation for Month 2. All patients then received zolmitriptan nasal spray 5 mg for Month 3. Patients could then choose the formulation(s) of their choice for a further 7 months. Patients recorded their preferences for individual formulations, the reasons for their preferences, and also the headache‐related disability (measured by the Migraine Disability Assessment [MIDAS] score) at clinic visits. Primary endpoints were the individual preferences and changes in MIDAS scores. Adverse events were also recorded.

Results.—Forty‐eight patients took part in the study. At baseline, most patients expressed a preference for conventional tablets. After 4 months, 46.9% of patients preferred zolmitriptan ODT, 43.8% zolmitriptan nasal spray, and 6.3% the conventional tablet. The most common reasons given for preferring conventional tablets were personal reasons: for zolmitriptan ODT, convenience and, to a lesser extent, speed of onset: for zolmitriptan nasal spray, speed of onset, and overall efficacy. MIDAS scores decreased significantly following treatment with zolmitriptan. Zolmitriptan was well tolerated.

Conclusions.—Patient experience of newer zolmitriptan formulations influenced a change in preference away from conventional tablets. Speed and efficacy were the key drivers of preference for zolmitriptan nasal spray, while convenience mostly drove preference for the ODT formulation. Open, longitudinal, naturalistic studies may, allowing for biases, sometimes be an appropriate way of conducting migraine studies in primary care.
BIOCHEMICAL CHARACTERIZATION OF PARALYTIC SHELLFISH TOXIN BIOSYNTHESIS IN VITRO1
Authors: Kellmann Ralf , Neilan Brett A.
Published: May 2007

Saxitoxin (STX) and its analogs are voltage‐gated sodium‐channel blockers that cause paralytic shellfish poisoning (PSP) and negatively affect human health and seafood industries worldwide. Little is known about the molecular biology of PSP‐toxin synthesis. Saxitoxin precursors were identified 25 years ago, and a hypothetical biosynthesis pathway was proposed; however, the correct sequence of reactions and enzymes involved in their catalysis remains to be identified. This study describes the optimization of in vitro biosynthesis of PSP toxins by cellular lysates of the toxic cyanobacterium Cylindrospermopsis raciborskii (Wołosz.) Seenaya et Subbaraju T3 and the characterization of its biochemical requirements. Enzymes involved in PSP‐toxin synthesis are located in the cytosol. The molecular components of in vitro biosynthesis reactions could not be completely defined because of the requirement of an unknown cofactor. Evidence is presented that supports the previous suggestion that STX biosynthesis involves a Claisen condensation between arginine and acetate. In addition, carbamoyl phosphate was identified as a likely precursor for carbamated PSP toxins. Predictions have been made regarding the enzymes that may be involved in the biosynthesis of PSP toxins. These included class II aminotransferase; nonheme iron oxygenase, containing flavin, and possibly ferredoxin, as the prosthetic groups; and an O‐carbamoyltransferase. On the other hand, the involvement of cytochrome P450 monooxygenase was excluded.
MOLECULAR CLONING AND CHARACTERIZATION OF HIGH‐AFFINITY NITRATE TRANSPORTERS IN MARINE PHYTOPLANKTON1
Authors: Song Bongkeun , Ward Bess B.
Published: May 2007

Nitrate transporter systems initiate nitrate uptake in photoautotrophic organisms including marine phytoplankton. The functional genes encoding high‐affinity nitrate transporters (Nrt2) in marine phytoplankton were investigated in this study. Direct PCR amplification with newly developed primers was used to detect Nrt2 genes in cultured marine phytoplankton species: Dunaliella tertiolecta Butcher (Chlorophyceae); Emiliania huxleyi (Lohmann) W. H. Hay et H. Mohler (Haptophyceae); and four diatoms, including Thalassiosira weissflogii (Grunow) G. A. Fryxell et Hasle, Skeletonema costatum (Grev.) Cleve, Ditylum brightwellii (T. West) Grunow, and Chaetoceros muelleri Lemmerm. (Bacillariophyceae). Phylogenetic analysis of the detected Nrt2 genes identified three distinct clusters grouped by each class of phytoplankton species. Transcriptional abundance (mRNA) of Nrt2 genes in D. tertiolecta, E. huxleyi, T. weissflogii, and C. muelleri were measured using quantitative reverse transcriptase‐PCR assays under various nitrogen conditions. The diatoms and E. huxleyi induced Nrt2 gene transcripts both in the presence of nitrate and under nitrogen (N) starvation, while the Nrt2 transcript in D. tertiolecta was induced only when nitrate was present. Chaetoceros muelleri exhibited the highest transcript induction of the Nrt2 gene. The transcriptional abundance of the Nrt2 genes in C. muelleri was further examined with short‐term nitrate incubation of cells grown under N‐sufficient or N‐starved conditions. The maximum induction of Nrt2 gene transcripts was observed within 1 h after nitrate was added. Thus, we report differential induction and regulation of Nrt2 genes in the selected phytoplankton species to varying conditions of external N.
Consumer Selection of Food‐Safety Information Sources
Authors: Kornelis Marcel , De Jonge Janneke , Frewer Lynn , Dagevos Hans
Published: May 2007

The aim of this study is to examine the preferences of consumers for different information sources when they have a question about food safety. On the basis of a nationally representative survey conducted in the Netherlands, five distinct consumer groups are identified that not only differ on the reported use of information sources but also regarding several personality characteristics and sociodemographic variables. The empirical results show that two‐thirds of the consumers are selective in their use of information sources and prefer either institutional or social sources. So, multiple information‐acquisition patterns exist among the general public. The study illustrates how these findings can help to develop effective risk communication strategies.
Semiparametric Modeling of the Spatial Distribution of Occupational Accident Risk in the Casual Labor Market, Piracicaba, Southeast Brazil
Authors: Bailey Trevor C. , Cordeiro Ricardo , Lourenço Roberto W.
Published: May 2007

The objective of this study was to estimate the spatial distribution of work accident risk in the informal work market in the urban zone of an industrialized city in southeast Brazil and to examine concomitant effects of age, gender, and type of occupation after controlling for spatial risk variation. The basic methodology adopted was that of a population‐based case‐control study with particular interest focused on the spatial location of work. Cases were all casual workers in the city suffering work accidents during a one‐year period; controls were selected from the source population of casual laborers by systematic random sampling of urban homes. The spatial distribution of work accidents was estimated via a semiparametric generalized additive model with a nonparametric bidimensional spline of the geographical coordinates of cases and controls as the nonlinear spatial component, and including age, gender, and occupation as linear predictive variables in the parametric component. We analyzed 1,918 cases and 2,245 controls between 1/11/2003 and 31/10/2004 in Piracicaba, Brazil. Areas of significantly high and low accident risk were identified in relation to mean risk in the study region (p < 0.01). Work accident risk for informal workers varied significantly in the study area. Significant age, gender, and occupational group effects on accident risk were identified after correcting for this spatial variation. A good understanding of high‐risk groups and high‐risk regions underpins the formulation of hypotheses concerning accident causality and the development of effective public accident prevention policies.
Risk Management, Capital Budgeting, and Capital Structure Policy for Insurers and Reinsurers
Authors: Froot Kenneth A.
Published: May 2007

Abstract

This article builds on Froot and Stein in developing a framework for analyzing the risk allocation, capital budgeting, and capital structure decisions facing insurers and reinsurers. The model incorporates three key features: (i) value‐maximizing insurers and reinsurers face product‐market as well as capital‐market imperfections that give rise to well‐founded concerns with risk management and capital allocation; (ii) some, but not all, of the risks they face can be frictionlessly hedged in the capital market; and (iii) the distribution of their cash flows may be asymmetric, which alters the demand for underwriting and hedging. We show these features result in a three‐factor model that determines the optimal pricing and allocation of risk and capital structure of the firm. This approach allows us to integrate these features into: (i) the pricing of risky investment, underwriting, reinsurance, and hedging; and (ii) the allocation of risk across all of these opportunities, and the optimal amount of surplus capital held by the firm.
Robustly Hedging Variable Annuities With Guarantees Under Jump and Volatility Risks
Authors: Coleman T. F. , Kim Y. , Li Y. , Patron M.
Published: May 2007

Abstract

Recent variable annuities offer participation in the equity market and attractive protection against downside movements. Accurately quantifying this additional equity market risk and robustly hedging options embedded in the guarantees of variable annuities are new challenges for insurance companies. Due to sensitivities of the benefits to tails of the account value distribution, a simple Black–Scholes model is inadequate in preventing excessive liabilities. A model which realistically describes the real world price dynamics over a long time horizon is essential for the risk management of the variable annuities. In this article, both jump risk and volatility risk are considered for risk management of lookback options embedded in guarantees with a ratchet feature. We evaluate relative performances of delta hedging and dynamic discrete risk minimization hedging strategies. Using the underlying as the hedging instrument, we show that, under a Black–Scholes model, local risk minimization hedging can be significantly better than delta hedging. In addition, we compare risk minimization hedging using the underlying with that of using standard options. We demonstrate that, under a Merton's jump diffusion model, hedging using standard options is superior to hedging using the underlying in terms of the risk reduction. Finally, we consider a market model for volatility risks in which the at‐the‐money implied volatility is a state variable. We compute risk minimization hedging by modeling at‐the‐money Black–Scholes implied volatility explicitly; the hedging effectiveness is evaluated, however, under a joint model for the underlying price and implied volatility. Our computational results suggest that, when implied volatility risk is suitably modeled, risk minimization hedging using standard options, compared to hedging using the underlying, can potentially be more effective in risk reduction under both jump and volatility risks.
A Test of the Eclectic Paradigm: Evidence From the U.S. Reinsurance Market
Authors: Cole Cassandra R. , Lee Ryan B. , McCullough Kathleen A.
Published: May 2007

Abstract

This study provides a test of the eclectic paradigm with data from U.S. reinsurers. The U.S. reinsurance industry provides a unique setting to test the eclectic paradigm due to the extensive data available on U.S. reinsurers and the well‐developed literature related to reinsurance. The ability to test the hypotheses related to the eclectic paradigm in a service industry and incorporate industry‐specific factors adds to the eclectic paradigm literature which has traditionally focused primarily on manufacturing firms. In addition, the application of the eclectic paradigm to the reinsurance industry provides an empirical framework that combines several prior streams of literature which examine the reinsurer's decision to internationalize. The current study includes firm‐specific factors, country‐specific factors of the international markets, and factors related to the U.S. reinsurance industry. This article finds support for traditional factors impacting globalization such as host market size, loss experience, and competitiveness as well as reinsurer's ability to expand based on available capacity. Understanding the importance of firm‐, country‐, and industry‐specific factors is key for managers, as analyzing these issues in isolation may lead to an incomplete picture of the factors impacting the internationalization decision, hindering managers' ability to make decisions that are in the best interest of the firm. With the continued interdependence of the world reinsurance marketplace, as well as the recent expansion of the European Union, internationalization issues are of critical importance not only to U.S. insurers, reinsurers, and regulators, but also to their global counterparts.
The Effect of Antihistamine Cetirizine on Ventricular Repolarization in Congenital Long QT Syndrome
Authors: HEKKALA ANNA‐MARI , SWAN HEIKKI , VÄÄNÄNEN HEIKKI , VIITASALO MATTI , TOIVONEN LAURI
Published: May 2007

Introduction: Many drugs are known to block cardiac potassium channels, thus prolonging QT interval and predisposing to malignant arrhythmias. Patients with congenital long QT syndrome are particularly vulnerable, but usually electrophysiological effects of drugs have not been assessed in these patients at risk.

Methods: Fifteen asymptomatic patients with type 1 (LQT1), 15 patients with type 2 (LQT2) long QT syndrome, and 15 healthy volunteers took a placebo and cetirizine 10 mg. In addition, healthy volunteers took cetirizine 50 mg. The study was single‐blinded and randomized. Exercise tests were performed during stable plasma concentrations. The electrocardiogram was recorded with a body surface potential mapping system (BSPM). Data were analyzed with an automated analyze program. QT intervals to the T wave apex and T wave end and their difference (Tp‐e) were determined at rest and at specified heart rates during and after exercise.

Results: Cetirizine did not lengthen the QT intervals at rest or during exercise and recovery in any group. It shortened Tp‐e at rest in LQT1 and LQT2 patients and during exercise test in LQT1 patients, thus slightly decreasing electrocardiographic transmural dispersion of repolarization.

Conclusions: Cetirizine does not adversely modify ventricular repolarization in types 1 and 2 long QT syndrome, suggesting that it might be used safely in these long QT syndrome patients.
Synthesis and Optical Properties of Mullite Nanowires
Authors: Seong Han‐Kyu , Kim Ungkil , Kim Myoung‐Ha , Choi Heon‐Jin , Lee Youngho , Seo Won‐Seon
Published: May 2007

Single‐crystalline mullite (3Al2O3·2SiO2) nanowires have been synthesized on silicon substrates by forcing aluminum and chromium chloride powders to react under an ammonia gas flow. The diameter and length of the nanowires have uniform diameters of <100 nm and several micrometers, respectively. High‐resolution transmission electron microscope and selected‐area electron diffraction analyses indicated that the nanowires were almost structural defect free and had a single‐crystalline phase with a 〈0001〉 growth direction. The photoluminescence spectra showed that the mullite nanowires reached an emission peak at the center wavelength of 442 nm originating from the Al–O bonds in preference to the Al–O and Si–O bonds in the mullite bonding structure. Comparison of the photoluminescence between as‐synthesized, oxygen–annealed, and plasma‐etched nanowires indicates that the nanowires have few defects (i.e., oxygen vacancies).
Voluntary consumption of substances of unknown palatability by vervet monkeys: a refinement
Authors: Seier J.V. , Mdhluli M. , Collop T. , Davids A. , Laubscher R.
Published: May 2007

Background  Pure compounds and herbal medicines, had to be administered orally to vervet monkeys for testing. A reliable method was sought to avoid daily gavaging.

Methods  Substances were incorporated into the maize meal based diet of this facility for voluntary consumption. Food intake was monitored.

Results  In all but one case, consumption of the treated food was in excess of 90%. In all cases, the purpose of the study was achieved. Habituation was usually only required to the vehicle, and was accomplished by incremental increases to the desired concentration. Aversion was overcome by the addition of a small amount of honey. Plasma concentrations of a compound metabolite could be measured in one case after gavage and food consumption, and were similar for both methods.

Conclusion  The method enables reliable voluntary consumption of diverse substances. Since stressful gavaging is avoided, it is a valuable contribution to the 3Rs.
Modulation of Cargo Release from Dense Core Granules by Size and Actin Network
Authors: Felmy Felix
Published: May 2007

During regulated fusion of secretory granules with the plasma membrane, a fusion pore first opens and then dilates. The dilating pore allows cargo proteins from the dense core to be released into the extracellular space. Using real‐time evanescent field fluorescence microscopy of live PC12 cells, it was determined how rapidly proteins of different sizes escape from single granules after fusion. Tissue plasminogen activator (tPA)‐Venus is released 40‐fold slower than the three times smaller neuropeptide Y [NPY‐monomeric GFP (mGFP)]. An NPY bearing two mGFPs in tandem [NPY‐(mGFP)2] as an intermediate‐sized fusion probe is released most slowly. Although, the time–course of release varies substantially for a given probe. Coexpression of β‐actin, actin‐related protein 3 or mAbp1 slowed the release of the two larger cargo molecules but did not affect release of NPY‐mGFP or of the granule‐membrane‐bound probe Vamp‐pHluorin. Additionally, high concentrations of cytochalasin D slowed release of the tPA‐Venus. Together these results suggest that fusion pore dilation is not the only determinate of release time–course and that actin rearrangements similar to those mediating actin‐mediated motility influences the time–course of release without directly interfering with the granule membrane to cell membrane connection.
Quality Changes of Fresh‐Cut Kohlrabi Sticks under Modified Atmosphere Packaging
Authors: Escalona V.H. , Aguayo E. , Artés F.
Published: May 2007

ABSTRACT:  The aim of this study was to determine the effect of different gas compositions on quality attributes and shelf life of kohlrabi sticks stored in modified atmosphere up to 14 d at 0 °C. Two commercial films were tested: oriented polypropylene (OPP) and amide‐polyethylene (amide‐PE). As a control, a microperforated OPP film was used. In order to study the changes in metabolic activity by minimal processing, the respiration rate and ethylene production at 0 °C were monitored for both intact stems and sticks. Changes in color, chemical parameters, sugars and organic acid contents, and sensorial quality of kohlrabi sticks were evaluated. An initial ethylene production of sticks was 13‐fold higher than that of intact stems; meanwhile CO2 production was 2‐fold higher. However after 4 d of storage, a similar respiration rate for stems and sticks was found. Also the ethylene production of sticks and stems was steady around 15 to 20 nL/kg/h after 10 d. Kohlrabi sticks showed a little change in chemical parameters and very low weight losses during cold storage. Sticks under an equilibrium atmosphere of 7 kPa O2 and 9 kPa CO2 at 0 °C reached by amide‐PE kept an acceptable sensorial quality for 14 d.
Effects of Freezing and Thawing Processes on the Quality of Atlantic Salmon (Salmo salar) Fillets
Authors: Alizadeh E. , Chapleau N. , De Lamballerie M. , LeBail A.
Published: May 2007

ABSTRACT:  High‐pressure processing is finding a growing interest in the food industry. Among the advantages of this emerging process is the ability to favorably freeze and thaw food. This study aims at comparing the effect of different freezing and thawing processes on the quality of Atlantic salmon fillets. Atlantic salmon (Salmo salar) samples were frozen by Pressure‐Shift Freezing (PSF, 200 MPa, −18 °C) and Air‐Blast Freezing (ABF, −30 °C, 4 m/s). Samples were stored 1 mo at −20 °C and then subjected to different thawing treatments: Air‐Blast Thawing (ABT, 4 °C, 4 m/s), Immersion Thawing (IMT, 20 °C), and Pressure‐Assisted Thawing (PAT, 200 MPa, 20 °C). Changes in texture, color, and drip loss were investigated. The toughness of the PSF samples was higher than that of the ABF sample. The modification of color was more important during high‐pressure process than during the conventional process. The PSF process reduced thawing drip compared with ABF. The presence of small ice crystals in the pressure‐shift frozen sample is probably the major reason leading to the reduced drip volumes. The freezing process was generally much more influent on quality parameters than the thawing process. These results show the interaction between freezing and thawing processes on selected quality parameters.
Comparative Study of Aromatic Compounds in Young Red Wines from Cabernet Sauvignon, Cabernet Franc, and Cabernet Gernischet Varieties in China
Authors: Zhang M. , Xu Q. , Duan C. , Qu W. , Wu Y.
Published: May 2007

ABSTRACT:  The aromatic composition and key odorants of young red wines produced from Cabernet Sauvignon, Cabernet Franc, and Cabernet Gernischet wines were compared and the reasons for the difference in their aromatic compounds were discussed. Forty‐three odorants were detected in Cabernet Sauvignon and Cabernet Franc wines compared to 50 in Cabernet Gernischet wine. Quantitatively, acids formed the most abundant group in the aromatic components of the 3 wines, followed by alcohols and esters. Compared to Cabernet Sauvignon and Cabernet Franc wines, the profiles of alcohols and esters for Cabernet Gernischet wine were more diverse. Monoterpenes, namely, 4‐terpinenol, citronellol, and nerol, were found solely in Cabernet Gernischet wine. Only 10 compounds, namely, ethyl octanoate, ethyl hexanoate, isoamyl acetate, ethyl butyrate, β‐damascenone, ethyl decanoate, isoamyl alcohol, acetic acid, octanoic acid, and phenylethyl acetate, were always present in the 3 wines at concentrations higher than their threshold values. However, ethyl octanoate, ethyl hexanoate, and isoamyl acetate were found to jointly contribute to 97%, 98.9%, and 99% of the global aroma of Cabernet Sauvignon, Cabernet Franc, and Cabernet Gernischet wines, respectively. This result showed that the aroma indistinguishableness of the 3 wines was mainly due to the dominance of the fruity notes exerted by the ethyl esters and, to a lesser extent, to the contribution of varietal aromatic compounds to the global aroma of the wines.
How Far Are Direct Alcohol Fuel Cells From Our Energy Future?
Authors: Song Shuqin , Maragou Vasiliki , Tsiakaras Panagiotis
Published: May 2007

Direct alcohol fuel cells (DAFCs) have been attracting more and more attention and interest during the last decade due to their simplicity, the easy handle and the high power density of the liquid alcohol fuels. However, along with DAFCs’ development several problems related to their performance optimizations have arisen that are well established and researches are already in progress for their solutions. These problems are responsible for the short lifetime and low cell performance and can be summarized as follows: (a) low alcohol electro-oxidation kinetics, (b) alcohol crossover, and (c) electrode delamination. This article briefly reviews DAFCs’ state of the art, the pertinent work done for the localization and quantification of the above-mentioned problems and the work aiming at the identification and use of novel materials which could catalyze the rate-determining step for the DAFCs’ development and further commercialization. Furthermore, taking into account that fuel choice is still a disputed issue, the alcohols suitable as potential fuels for DAFCs are also summarized and compared.
Boundary Condition Dependent Natural Convection in a Rectangular Pool With Internal Heat Sources
Authors: Lee Seung Dong , Lee Jong Kuk , Suh Kune Y.
Published: May 2007

This paper presents results of steady-state experiments concerned with natural convection heat transfer of air in a rectangular pool in terms of the Nusselt number (Nu) versus the modified Rayleigh number (Ra′) varying from 109 to 1012. Cartridge heaters were immersed in the working fluid to simulate uniform volumetric heat generation. Two types of boundary conditions were adopted in the test: (I) top cooled, and (II) top and bottom cooled. The other sides were kept insulated. In the case of boundary condition II, the upward heat transfer ratio, Nuup∕(Nuup+Nudn), turned out to be 0.7–0.8 in the range of Ra′ between 1.05×1010 and 3.68×1011.
Effect of Hydraulic Jump on Hydrodynamics and Heat Transfer in a Thin Liquid Film Flowing Over a Rotating Disk Analyzed by Integral Method
Authors: Basu S. , Cetegen B. M.
Published: May 2007

Flow and heat transfer in a liquid film flowing over the surface of a rotating disk was analyzed by integral technique. The integral analysis includes the prediction of the hydraulic jump and its effects on heat transfer. The results of this analysis are compared to the earlier results that did not include this effect. At low inlet Reynolds numbers and high Rossby numbers, corresponding to low film inertia and low rotation rates, respectively, a hydraulic jump appears on the disk surface. The location of the jump and the liquid film height at this location are predicted. A scaling analysis of the equations governing the film thickness provided a semi-empirical expression for these quantities that was found to be in very good agreement with numerical results. Heat transfer analysis shows that the Nusselt numbers for both constant disk surface temperature and constant disk surface heat flux boundary conditions are lowered in the vicinity of the hydraulic jump due to the thickened liquid film. This effect can be more pronounced for the constant heat flux case depending on the location of the hydraulic jump. The Nusselt number exhibits a turning point at the jump location and can have higher values downstream of the hydraulic jump compared to those obtained from the analysis that does not include the gravitational effects.
Experimental Analysis of the Voltage and Temperature Behavior of a Solid Oxide Fuel Cell Generator
Authors: Santarelli M. G. , Leone P. , Cali M. , Orsello G.
Published: May 2007

A solid oxide fuel cell (SOFC) laboratory has been installed in Torino, Italy, in order to analyze the operation, in a cogenerative configuration, of the CHP-100 SOFC Field Unit built by Siemens Power Corporation (SPG) Stationary Fuel Cells (SFC), within the framework of the EOS Project. An experimental session was performed, varying the setpoint temperature TGEN and the fuel consumption (FC), with the aim of characterizing the behaviour of the local voltages and temperatures. A design of experiments procedure was applied to obtain first (simple 22) and second-order (spherical central composite design (CCD)) regression models, which were then used in subsequent constrained optimization procedures. A sensitivity analysis was also performed: FC revealed as the prevailing control factor of the operation, and it was shown that the analysis of the local voltage and temperature sensitivity to FC can be used as a diagnostic tool for the fuel distribution within a SOFC generator (the homogeneity of the sensitivity of the various cells was ∼10%, depending strongly on the cell bundle arrangement in the stack). Finally, the effect of any changes in the control factors on the tube temperature profile was evaluated and discussed; a link between a high terminal voltage and a more uniform temperature along the cell tube has been pointed out.
Thermo-Economic Optimization of a Solid Oxide Fuel Cell, Gas Turbine Hybrid System
Authors: Autissier N. , Palazzi F. , Marechal F. , van Herle J. , Favrat D.
Published: May 2007

Large scale power production benefits from the high efficiency of gas-steam combined cycles. In the lower power range, fuel cells are a good candidate to combine with gas turbines. Such systems can achieve efficiencies exceeding 60%. High-temperature solid oxide fuel cells (SOFC) offer good opportunities for this coupling. In this paper, a systematic method to select a design according to user specifications is presented. The most attractive configurations of this technology coupling are identified using a thermo-economic multi-objective optimization approach. The SOFC model includes detailed computation of losses of the electrodes and thermal management. The system is integrated using pinch based methods. A thermo-economic approach is then used to compute the integrated system performances, size, and cost. This allows to perform the optimization of the system with regard to two objectives: minimize the specific cost and maximize the efficiency. Optimization results prove the existence of designs with costs from 2400$∕kW for a 44% efficiency to 6700$∕kW for a 70% efficiency. Several design options are analyzed regarding, among others, fuel processing, pressure ratio, or turbine inlet temperature. The model of a pressurized SOFC–μGT hybrid cycle combines a state-of-the-art planar SOFC with a high-speed micro-gas turbine sustained by air bearings.
Energy Savings for Silent Camp™ Hybrid Technologies
Authors: Holcomb Franklin H. , Bush Joseph , Knight James L. , Whipple Jason
Published: May 2007

In military base camp operations, the standard method of power generation is via the use of diesel generators. Unfortunately, these generators are often noisy and inefficient. Base camps could benefit from a “silent camp™” operation, in which power is supplied via low-noise, low-impact methods such as fuel cells. Base camps have a variable load profile (they use more power during peak hours than at other times), and low loading levels (their generators’ rated capacity is normally much greater than the load). Consequently, the generators only operate at peak efficiency for short, intermittent intervals. Under these conditions, the generators’ fuel use is less than optimal, they require frequent maintenance, and their life cycle is shortened. Approximately 60–70% of maintenance problems for diesel generators are directly attributable to “wetstacking,” which occurs when these generators are operated at less than 50% of their rated capacity (Commerce Business Daily, Feb. 16, 2000). One solution to address these issues is to institute a hybrid power system, consisting of: a fuel cell (with inverter), an electrolyzer, and a metal hydride storage system, all coupled and packaged with a diesel generator. This system would enable the generator to operate at peak efficiency while increasing the capabilities of the power generation system. Such a system could offer numerous benefits over the base case stand alone generator as follows: (1) the ability for Silent Camp™ operation (by using the fuel cell output exclusively); (2) potential for reduced fuel consumption; (3) reduced instances of “wetstacking,” thereby decreasing generator maintenance costs; (4) the ability to have backup power from fuel cells; (5) refueling capability for hydrogen devices or vehicles; and (6) reduced environmental impact in terms of pollutant, acoustic, and thermal emissions.
Association of ground hardness with injuries in rugby union
Authors: Takemura Masahiro , Schneiders Anthony G , Bell Melanie L , Milburn Peter D
Published: May 2007

Background:

Ground hardness is considered one of the possible risk factors associated with rugby injuries.

Objectives:

To examine the contribution of ground hardness, rainfall and evapotranspiration to the incidence of injury, and to investigate seasonal injury bias throughout one full season of rugby union.

Methods:

A prospective epidemiological study of rugby injuries was performed on 271 players from rugby union teams involved in the premier grade rugby competition in Dunedin, New Zealand. Ground hardness was measured before each match over 20 rounds with an industrial penetrometer, and local weather information was collected through the National Institute of Weather and Atmospheric Research and the Otago Regional Council. Poisson mixed models were used to describe injury incidence as a function of ground hardness throughout the season.

Results:

The overall injury incidence during the season was 52 injuries per 1000 match player-hours (95% CI 42 to 65). Although injury incidence decreased gradually by round with a rate ratio of 0.98 (95% CI 0.96 to 0.99) (p = 0.036), and the hardness of match grounds decreased significantly over the season (0.16 MPa/round, 95% CI 0.12 to 0.21, p<0.001), a non-significant association was demonstrated between injury incidence and ground hardness. Injury incidence was not associated with a combination of ground hardness, rainfall and evapotranspiration on the day of the match or cumulative rainfall and evapotranspiration before each match.

Conclusions:

Seasonal change in ground hardness and an early-season bias of injuries was demonstrated. Although the contribution of ground hardness to injury incidence was not statistically significant, match round and injury incidence were highly correlated, confirming a seasonal bias, which may confound the relationship of injury to ground condition.
MODELLING AND ANALYSIS OF PKI-BASED SYSTEMS USING PROCESS CALCULI
Authors: AZIZ BENJAMIN , HAMILTON GEOFF
Published: May 2007

In this paper, we present a process algebra aimed at modelling PKI-based systems. The new language, SPIKY, extends the spi-calculus by adding primitives for the retrieval of certified/uncertified public keys as well as private keys belonging to users of the PKI-based system. SPIKY also formalises the notion of process ownership by PKI users, which is necessary in controlling the semantics of the key retrieval capabilities. We also construct a static analysis for SPIKY that captures the property of term substitutions resulting from message-passing and PKI/cryptographic operations. This analysis is shown to be safe and computable. Finally, we use the analysis to define the term secrecy and peer participation properties for a couple of examples of authentication protocols.
THE FIRING SQUAD SYNCHRONIZATION PROBLEM ON SQUARES, TORUSES AND RINGS
Authors: GRUSKA JOZEF , LA TORRE SALVATORE , PARENTE MIMMO
Published: May 2007

It is well known that a solution for the Firing Squad Synchronization Problem (FSSP) takes time 2n - 1, n being the number of soldiers. It is also known that a solution on a square of n × n soldiers takes the same time. The main result of this paper is a new solution for the FSSP on networks shaped as squares. Our solution is optimal in two aspects: it is communication optimal (the so-called 1-bit solution) and is also time optimal, as it takes 2n - 1 time. It is also used as a building block to construct a very efficient solution on the square torus. Our approach applies also to linearly shaped networks and yields on the ring almost optimal time & communication solutions. In particular, for the square torus with n rows and rings of n processors, if n is even our solution is time & communication optimal. Otherwise, it is communication-optimal but does not match the lower bound on the time of a synchronization just by 1 time unit.
COLLECTIVE EXCITATIONS OF DIRAC ELECTRONS IN GRAPHENE
Authors: Apalkov Vadim , Wang Xue-Feng , Chakraborty Tapash
Published: May 2007

Two-dimensional electrons in graphene are known to behave as massless fermions with Dirac-Weyl type linear dispersion near the Dirac crossing points. We have investigated the collective excitations of this system in the presence or absence of an external magnetic field. Unlike in the conventional two-dimensional electron system, the [Formula: see text] fractional quantum Hall state in graphene was found to be most stable in the n = 1 Landau level. In the zero field case, but in the presence of the spin-orbit interaction, an undamped plasmon mode was found to exist in the gap of the single-particle continuum.
The Spin Excitation Spectrum in Quantum Hall Systems: Insights from Light Scattering Experiments
Authors: GALLAIS YANN , KIRSCHENMANN THOMAS H. , YAN JUN , PINCZUK ARON , PFEIFFER LOREN N. , WEST KEN W.
Published: May 2007

Collective spin excitations in quantum Hall systems are studied via inelastic light scattering. In the fractional quantum Hall effect regime, composite fermion spin excitations are observed in the range 1/3< ν <2/5. They reveal a transition from free to strongly interacting composite fermions. At ν=1, a shift of the spin-wave energy at finite wavevector from the bare Zeeman energy is observed. It allows us to evaluate the spin-stiffness of the quantum Hall ferromagnet.
THE MEGA-GAUSS FACILITY AT KASHIWA: RECENT MAGNETO-OPTICAL STUDIES
Authors: TAKEYAMA SHOJIRO , KOJIMA EIJI , KINDO KOICHI , YOKOI HIROYUKI
Published: May 2007

We review recent activities at the mega-gauss facility at Kashiwa mega-gauss facility. The plan of introducing a giant DC generator is now under process for aiming at 100 T nondestructive magnetic field achievement in near future. Our current progress in the destructive mega-gauss magnetic fields and some of the selected topics focusing on the magneto-optical subjects are described.
MAGNETO-TRANSPORT IN OPEN QUANTUM DOT ARRAYS AT THE TRANSITION FROM LOW TO HIGH MAGNETIC FIELDS: REGULARITY AND CHAOS
Authors: BRUNNER R. , MEISELS R. , KUCHAR F. , AKIS R. , FERRY D. K. , BIRD J. P.
Published: May 2007

The mixed phase space in an open quantum dot array with a soft confining potential is studied in low and high magnetic fields. Chaos occurs due to the perturbations by the constrictions connecting the dots of the array. Regular orbits and the areas of Kalmogorov-Arnold-Moser islands in phase space become increasingly dominating with increasing magnetic field. The correspondence to the high-field quantum-mechanical picture in a 2D electron system with boundaries is discussed.
MAGNETOTRANSPORT SPECTROSCOPY OF DUAL ONE-DIMENSIONAL ELECTRON SYSTEMS
Authors: Fischer Saskia F.
Published: May 2007

A review is given on the merits of magnetotransport spectroscopy for investigations of the subband structure of dual one-dimensional electron systems (1DES). In particular, spatially coincident and tunnel-coupled vertically stacked dual 1DES are discussed which were prepared by nanolithography with subband spacings of more than 10 meV. Mode coupling between degenerate one-dimensional (1D) subbands depends on the symmetry of the confining potential and the coupling strength. In dual 1DES with different 1D confining potentials each subband structure can be identified by magnetotransport spectroscopy on behalf of the distinct magnetic field dispersions. Exemplarily, mode spectra in longitudinal and transversal applied magnetic fields are discussed for spatially coincident 1DES with an asymmetric vertical component in the 1D confinement. Nearly identical confinement, instead, can be prepared for example in vertically stacked tunnel-coupled 1DES. Here, longitudinal magnetic fields have strong influence on tunnel-coupled modes.
QUANTUM HALL EFFECT IN A MULTI-VALLEY TWO-DIMENSIONAL ELECTRON SYSTEM
Authors: SHAYEGAN M. , DE POORTERE E. P. , GUNAWAN O. , SHKOLNIKOV Y. P. , TUTUC E. , VAKILI K.
Published: May 2007

Two-dimensional electrons in an AlAs quantum well occupy multiple conduction-band minima at the X-points of the Brillouin zone. These valleys have large effective mass and g-factor compared to the standard GaAs electrons, and are highly anisotropic. With proper choice of well width and by applying symmetry-breaking strain in the plane, one can control the occupation of different valleys thus rendering a system with tuneable effective mass, g-factor, Fermi contour anisotropy, and valley degeneracy. Here we review some of the rich physics that this system has allowed us to explore.
STEREOSCOPIC OSCILLATIONS OF THE n-InGaAs/GaAs DOUBLE QUANTUM WELL MAGNETORESISTANCE UNDER TILTED MAGNETIC FIELDS
Authors: YAKUNIN M. V. , ARAPOV Yu. G. , NEVEROV V. N. , PODGORNYH S. M. , SHELUSHININA N. G. , HARUS G. I. , ZVONKOV B. N. , USKOVA E. A.
Published: May 2007

Precise scanning of the (B⊥,B‖)-plane while measuring magnetoresistance of the n - InGaAs/GaAs double quantum well (DQW) reveals a number of peculiarities connected with intricate DQW energy spectrum, which are analyzed on the basis of quasiclassical calculations. Magnetic breakdown effects are also considered. Peaks due to the latter mechanism reveal spin-splittings (in spite of lower mobilities as compared with the traditional n - GaAs/AlGaAs DQWs) corresponding to an enhanced effective Lande g-factor.
WEAKLY INTERACTING SYMMETRIC AND ANTI-SYMMETRIC STATES IN THE BILAYER SYSTEMS
Authors: MARCHEWKA M. , SHEREGII E. M. , TRALLE I. , TOMAKA G. , PLOCH D.
Published: May 2007

We have studied the parallel magneto-transport in DQW-structures of two different potential shapes: quasi-rectangular and quasi-triangular. The quantum beats effect was observed in Shubnikov-de Haas (SdH) oscillations for both types of the DQW structures in perpendicular magnetic filed arrangement. We developed a special scheme for the Landau levels energies calculation by means of which we carried out the necessary simulations of beating effect. In order to obtain the agreement between our experimental data and the results of simulations, we introduced two different quasi-Fermi levels which characterize symmetric and anti-symmetric states in DQWs. The existence of two different quasi Fermi-Levels simply means, that one can treat two sub-systems (charge carriers characterized by symmetric and anti-symmetric wave functions) as weakly interacting and having their own rate of establishing the equilibrium state.
HIGH MAGNETIC FIELD STUDY OF EXCITON COMPLEXES IN DILUTED MAGNETIC CdZnTe/(Cd,Zn,Mn)Te QUANTUM WELLS
Authors: KOJIMA E. , NATORI Y. , TAKEYAMA S. , ARISHIMA Y. , MINO H.
Published: May 2007

We measured the polarization selective photo-luminescence (PL) and the reflection spectra in the diluted magnetic semiconductor CdZnTe /( Cd , Zn , Mn ) Te quantum well under the high magnetic field of up to 40 T. A double peak structure was observed in PL spectra. The higher energy peak could be assigned to the exciton level from the behavior of Zeeman shift or polarization degree. The lower energy peak could not be explained by J=0 biexciton state. We could determined that this peak was due to the charged exciton from the results of the polarization selective reflection measurement.
EDGE AND BULK MERONS IN DOUBLE QUANTUM DOTS WITH SPONTANEOUS INTERLAYER PHASE COHERENCE
Authors: YANG S.-R. ERIC , HWANG N. Y.
Published: May 2007

We have investigated nucleation of merons in double quantum dots when a lateral distortion with a reflection symmetry is present in the confinement potential. We find that merons can nucleate both inside and at the edge of the dots. In addition to these merons, our results show that electron density modulations can be also present inside the dots. An edge meron appears to have approximately a half integer winding number.
BIFURCATION ANALYSIS OF CURRENT COUPLED BVP OSCILLATORS
Authors: TSUJI SHIGEKI , UETA TETSUSHI , KAWAKAMI HIROSHI
Published: May 2007

The Bonhöffer–van der Pol (BVP) oscillator is a simple circuit implementation describing neuronal dynamics. Lately the diffusive coupling structure of neurons attracts much attention since the existence of the gap-junctional coupling has been confirmed in the brain. Such coupling is easily realized by linear resistors for the circuit implementation, however, there are not enough investigations about diffusively coupled BVP oscillators, even a couple of BVP oscillators. We have considered several types of coupling structure between two BVP oscillators, and discussed their dynamical behavior in preceding works. In this paper, we treat a simple structure called current coupling and study their dynamical properties by the bifurcation theory. We investigate various bifurcation phenomena by computing some bifurcation diagrams in two cases, symmetrically and asymmetrically coupled systems. In symmetrically coupled systems, although all internal elements of two oscillators are the same, we obtain in-phase, anti-phase solution and some chaotic attractors. Moreover, we show that two quasi-periodic solutions disappear simultaneously by the homoclinic bifurcation on the Poincaré map, and that a large quasi-periodic solution is generated by the coalescence of these quasi-periodic solutions, but it disappears by the heteroclinic bifurcation on the Poincaré map. In the other case, we confirm the existence a conspicuous chaotic attractor in the laboratory experiments.
SHILNIKOV-TYPE MULTIPULSE ORBITS AND CHAOTIC DYNAMICS OF A PARAMETRICALLY AND EXTERNALLY EXCITED RECTANGULAR THIN PLATE
Authors: YAO M. H. , ZHANG W.
Published: May 2007

The Shilnikov-type multipulse orbits and chaotic dynamics for a simply supported rectangular thin plate under combined parametric and external excitations are studied in this paper for the first time. The rectangular thin plate is subjected to spatially and temporally varying transversal and in-plane excitations, simultaneously. The formulas of the rectangular thin plate are derived from the von Kármán equation and Galerkin's method. The method of multiple scales is used to find the averaged equation in the case of 1:2 internal resonance. Based on the averaged equation, the theory of normal form is used to obtain the explicit expressions of normal form associated with a double zero and a pair of purely imaginary eigenvalues using the Maple program. The dissipative version of the energy-phase method is utilized to analyze the multipulse global bifurcations and chaotic dynamics of a parametrically and externally excited rectangular thin plate. The global dynamical analysis indicates that there exist the multipulse jumping orbits in the perturbed phase space of the averaged equation for a parametrically and externally excited rectangular thin plate. These results show that the chaotic motions of the multipulse Shilnikov-type can occur for a parametrically and externally excited rectangular thin plate. Numerical simulation results are presented to verify the analytical predictions. It is also found from the results of numerical simulation that the Shilnikov-type multipulse orbits exist for a parametrically and externally excited thin plate.