bluuebunny/crossref_metadata_2025 huggingface dataset:
Screening and confirmation of 100 pesticides in food samples by liquid chromatography/tandem mass spectrometry
Authors: Ferrer Imma , Thurman E. Michael , Zweigenbaum Jerry A.
Published: November 2007

An analytical method for screening, quantitation and confirmation of a group of 100 pesticides in vegetable and fruit samples was developed using liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS). The pesticides studied belonged to different chemical families of herbicides, insecticides and fungicides; some degradation products were included as well. A thorough optimization was performed for each analyte to achieve individual optimum fragmentor and collision energy voltages. Two transitions per parent compound were monitored in a single chromatographic run containing two time segments. A small particle size C18 column (1.8 µm) was used for the chromatographic separation of the mixture, providing very narrow peaks and allowing an excellent separation of all the analytes in a 30‐min period for maximum peak capacity. The method was validated with blank matrices of green pepper, tomato and orange spiked from 0.1 to 100 µg/kg with the pesticide mix. Quantitation was carried out using matrix‐matched standard calibration and linearity of response over 3 orders of magnitude was demonstrated (r > 0.99). Limits of detection based on two transitions and ion‐ratio requirements ranged between 0.3 and 50 µg/kg. In general, the sensitivity obtained meets the maximum residue levels (MRLs) established by the European Union regulation for food monitoring programs. The analytical performance of the method was evaluated for different types of vegetables and fruits, showing little or no matrix effects, and examples of screening and confirmation of pesticides in these samples are shown here. Copyright © 2007 John Wiley & Sons, Ltd.
Towards a deeper understanding of test coverage
Authors: Kanstrén Teemu
Published: November 2007

Test coverage is traditionally considered as how much of the code is covered by the test suite in whole. However, test suites typically contain different types of tests with different roles, such as unit tests, integration tests and functional tests. As traditional measures of test coverage make no distinction between the different types of tests, the overall view of test coverage is limited to what is covered by the tests in general. This paper proposes a quantitative way to measure the test coverage of the different parts of the software at different testing levels. It is also shown how this information can be used in software maintenance and development to further evolve the test suite and the system under test. The technique is applied to an open‐source project to show its application in practice. Copyright © 2007 John Wiley & Sons, Ltd.
Burj Dubai: an architectural technical design case study
Authors: Weismantle Peter A. , Smith Gregory L. , Sheriff Mohamed
Published: November 2007

Beyond the aesthetics of the architectural design, the realization of Burj Dubai is very much a technical design effort. Every system in the Tower must be optimized because of the physical and economic constraints of a super high rise building. It is the intent of this paper to discuss the SOM design teams' approach in conceptualizing, investigating and resolving several of these technical topics outlined as follows.

As an introduction; the aesthetic, functional and structural advantages of Burj Dubai's tri‐axial ‘Y’ shaped plan, suggested by the ‘desert flower’, are discussed. Following that, the vertical stacking of the Tower's mixed use program is described and likened to a small, vertically arranged, city containing residences, places of work, hotels, restaurants, retail shops, amusement areas, revenue generating lease areas. The arrangement of the various functions has been rationalized along with the means and methods of transportation of people, energy, goods and materials. From the standpoint of fire and life safety; Burj Dubai has been designed with additional features in order to compensate for challenges it presents to occupant evacuation and fire fighting. Specialist wind tunnel tests were conducted not only for structural reasons, but also to asses the effectiveness of wind mitigation measures on the accessible terraces. The high outdoor temperature in Dubai and cool indoor condition create a difference in air density that makes the indoor air want to travel downward out the bottom of the building. This ‘stack effect’ was the subject of a separate study, the results of which were applied to the design. Finally, the author discusses SOM's approach to the design of the exterior wall cladding and cleaning systems. Copyright © 2007 John Wiley & Sons, Ltd.
Oral Administration of Dihomo‐γ‐Linolenic Acid Prevents Development of Atopic Dermatitis in NC/Nga Mice
Authors: Kawashima H. , Tateishi N. , Shiraishi A. , Teraoka N. , Tanaka T. , Tanaka A. , Matsuda H. , Kiso Y.
Published: November 2007

Disorders of the metabolism of essential fatty acids (EFAs) are related to atopic dermatitis (AD). Concentrations of dihomo‐γ‐linolenic acid (DGLA), an EFA, in the serum of AD patients are lower than those in healthy volunteers. Recently we developed a fermented DGLA oil, and examined whether oral administration of DGLA prevents development of dermatitis in NC/Nga mice, which spontaneously develop human AD‐like skin lesions. NC/Nga mice were fed a diet either containing or not containing DGLA for 8 weeks under in air‐uncontrolled conventional circumstances. Clinical skin severity scores were significantly lower in mice fed DGLA than in mice not fed it. Scratching behavior and plasma total IgE levels were also reduced in the DGLA group, in association with histological improvement. DGLA suppressed clinical severity of skin lesions dose‐dependently, with an increase in DGLA contents in phospholipids of skin, spleen, and plasma. Discontinuation of DGLA administration resulted in the onset of dermatitis and a decrease in DGLA contents in skin, spleen, and plasma. These findings indicate that oral administration of DGLA effectively prevents the development of AD in NC/Nga mice, and that DGLA in phospholipids is a compound of key importance in the development and prevention of dermatitis.
Physical Properties of trans‐Free Bakery Shortening Produced by Lipase‐Catalyzed Interesterification
Authors: Lee Jeung Hee , Akoh Casimir C. , Lee Ki‐Teak
Published: November 2007

Lipase‐catalyzed interesterified solid fat was produced with fully hydrogenated soybean oil (FHSBO), and rapeseed oil (RSO) and palm stearin (PS) in a weight ratio of 15:20:65, 15:40:45 and 15:50:35. The interesterified fats contained palmitic (27.8–44.6%), stearic (15.6–16.2%), oleic (27.5–36.5%) and linoleic acids (8.0–13.5%). After interesterification of the blends, the physical properties of the products changed and showed lower melting points and solid fat contents, different melting and crystallization behaviors as well as the formation of more stable crystals. The produced interesterified fats (FHSBO:RSO:PS 15:20:65, 15:40:45 and 15:50:35 blends) contained desirable crystal polymorphism (β′ form) as determined by X‐ray diffraction spectroscopy, a long plastic range with solid fat content of 51–63% at 10 °C to 4–12% at 40 °C, and melting points of 39 (15:50:35), 42 (15:50:45) and 45 °C (15:20:65). However, a reduction in tocopherols (α and γ) content and a reduced oxidative stability were observed in the interesterified fats. The physical properties of the interesterifed fats were influenced by the amount of PS, resulting in more hardness and higher solid fat contents for 15:20:65 than 15:40:45 and 15:50:35 blends. The present study suggested that the produced interesterified fats containing trans‐free fatty acids could be used as alternatives to hydrogenated types of bakery shortenings.
Banking on change: information systems and technologies in UK high street banking, 1919–1969
Authors: Bátiz-Lazo Bernardo , Wardley Peter
Published: November 2007

This article looks at the experience of management of technological innovation and mechanisation by British financial institutions. It highlights the indigenous assessment of technology, reflecting on local and American influences in two types of business organisations within the financial sector to demonstrate the nature of responses and the timing of the introduction of new methods and machinery. The adoption of Information Technology (IT) and computer applications in particular play a crucial role, though one that is intimately connected with a strategic expansion of corporate business, this growth being reflected in terms of size of business and also territorial expansion, as each of the institutions considered here constructed a national network of retail branch outlets. Discussion of established literature for the high street banks is combined with archivally informed analysis of similar, but previously undocumented, developments on the part of building societies. By taking a long-term view of these developments in the twentieth century, and by comparing the experiences of two different sets of institutions, the article highlights the strategic factors that influenced the decisions taken by senior managers in their transformation of British retail financial services.
On the visibility and zenithal confinement of 150 km (F1) radar echoes
Authors: Tsunoda Roland T. , Ecklund Warner L.
Published: November 2007

Five‐beam radar measurements of the so‐called 150 km (or F1) echoes, from Pohnpei (7.0°N, 158.2°E, geographic; 0.6°N dip latitude), are used to show, for the first time, that they are weaker and occur much less frequently at zenith angles of ±30°, than those that are observed overhead or at zenith angles of ±14°, in the vertical east‐west plane. This confinement of F1 echoes to a narrow range of zenith angles is interpreted in terms of an angular spectrum of plane plasma waves with wave vectors that are similarly restricted in zenith angle. Another manifestation of this viewing aspect sensitivity could be the appearance of F1 echoes as bands, when plotted as a function of altitude and local time. Although the exact nature of this process is not known, a two‐step interchange process acting on a solar‐produced gradient in plasma density is suggested as a working hypothesis.
Inconsistency between atmospheric dynamics and temperatures during the exceptional 2006/2007 fall/winter and recent warming in Europe
Authors: Yiou P. , Vautard R. , Naveau P. , Cassou C.
Published: November 2007

Europe witnessed unprecedented warmth persisting throughout fall and winter 2006–2007, with only a few cold breaks. Whether this anomaly and recent warming in Europe can be linked to changes in atmospheric dynamics is a key question in the climate change prospective. We show that despite the fall/winter atmospheric flow was favorable to warmth, it cannot explain alone such an exceptional anomaly. Observed temperatures remained well above those found for analogue atmospheric circulations in other fall and winter seasons. Such an offset is also found during the last decade and culminates in 2006/2007. These observational results suggest that the main drivers of recent European warming are not changes in regional atmospheric flow and weather regimes frequencies, contrasting with observed changes before 1994.
In vitroandin vivopharmacological profile of UFP‐512, a novel selective δ‐opioid receptor agonist; correlations between desensitization and tolerance
Authors: Aguila B , Coulbault L , Boulouard M , Lιveillι F , Davis A , Tσth G , Borsodi A , Balboni G , Salvadori S , Jauzac P , Allouche S
Published: November 2007

Background and purpose:

δ‐Opioid receptors (DOP receptors) could represent a novel target in the treatment of depressive disorders. To explore this new field of interest, the development of highly selective DOP receptor agonists is essential. UFP‐512 [H‐Dmt‐Tic‐NH‐CH(CH2‐COOH)‐Bid], was recently shown to behavein vitroas a selective and potent DOP receptor agonist and to promote antidepressant‐ and anxiolytic‐like effectsin vivo(Verguraet al., 2007). Here, we have characterized the pharmacological properties of UFP‐512 and established a link between desensitization and tolerance.

Experimental approach:

Studies were performed in the human neuroblastoma SK‐N‐BE cells to establish i) binding parameters for UFP‐512 ii) signalling pathways activated after acute and chronic treatment iii) regulation (phosphorylation and trafficking) of human DOP (hDOP) receptors after sustained activation by UFP‐512.In vivo, we studied UFP‐512‐induced antidepressant‐like effects after acute or chronic treatment in the mouse forced swimming test.

Key results:

In vitro, UFP‐512 was a high affinity agonist for DOP receptors. While UFP‐512 induced marked phosphorylation of DOP receptors on Ser363, we observed a low desensitization of the cAMP pathway, associated with receptor endocytosis and recycling without any reduction on extracellular signal‐regulated protein kinase 1/2 activation.In vivo, acute administration of UFP‐512 produced an antidepressant‐like effect, without any sign of tolerance after chronic administration.

Conclusions and implications:

There was a correlation between weak desensitization, significant internalization and recycling of the human DOP receptors and lack of tolerance to UFP‐512. This suggests that this compound would be a promising drug prototype for exploring innovative treatments for mood disorders.

British Journal of Pharmacology(2007)152, 1312–1324; doi:10.1038/sj.bjp.0707497; published online 5 November 2007
Analysis of the pharmacokinetic/pharmacodynamic relationship of a small molecule CXCR3 antagonist, NBI‐74330, using a murine CXCR3 internalization assay
Authors: Jopling L A , Watt G F , Fisher S , Birch H , Coggon S , Christie M I
Published: November 2007

Background and purpose:

Pharmacokinetic/pharmacodynamic (PK/PD) models are necessary to relate the degree of drug exposure in vivo to target blockade and pharmacological efficacy. This manuscript describes a murine agonist‐induced CXCR3 receptor internalization assay and demonstrates its utility for PK/PD analyses.

Experimental approach:

Activated murine DO11.10 cells were incubated with agonist in the presence or absence of a CXCR3 antagonist and changes in surface CXCR3 expression were detected by flow cytometry. For PK/PD analysis, mice were dosed with a small molecule CXCR3 antagonist, NBI‐74330, (100 mg kg−1) orally or subcutaneously and plasma samples taken at specified timepoints for the CXCR3 internalization assay.

Key results:

Surface CXCR3 expression was specifically decreased in response to CXCL9, CXCL10 and CXCL11. CXCL11 was the most potent CXCR3 agonist in buffer (pA50=9.23±0.26) and the pA50 for CXCL11 was unaltered in murine plasma (pA50=9.17±0.15). The affinity of a small molecule CXCR3 antagonist, NBI‐74330, was obtained in the absence or presence of plasma (buffer pA2 value: 7.84±0.14; plasma pKB value 6.36±0.01). Administration of NBI‐74330 to mice resulted in the formation of an N‐oxide metabolite, also an antagonist of CXCR3. Both antagonists were detectable up to 7 h post oral dose and 24 h post subcutaneous dose. Measurement of CXCR3 internalization demonstrated significant antagonism of this response ex vivo, 24 h following subcutaneous administration of NBI‐74330.

Conclusions and implications:

The CXCR3 receptor internalization assay provides a robust method for determining agonist potency orders, antagonist affinity estimates and PK/PD analyses, which discriminate between dosing regimens for the CXCR3 antagonist NBI‐74330.

British Journal of Pharmacology (2007) 152, 1260–1271; doi:10.1038/sj.bjp.0707519; published online 5 November 2007
Contribution of the active metabolite M1 to the pharmacological activity of tesofensine in vivo: a pharmacokinetic‐pharmacodynamic modelling approach
Authors: Lehr T , Staab A , Tillmann C , Nielsen E Ø , Trommeshauser D , Schaefer H G , Kloft C
Published: November 2007

Background and purpose:

Tesofensine is a centrally acting drug under clinical development for Alzheimer's disease, Parkinson's disease and obesity. In vitro, the major metabolite of tesofensine (M1) displayed a slightly higher activity, which however has not been determined in vivo. The aims of this investigation were (i) to simultaneously accomplish a thorough characterization of the pharmacokinetic (PK) properties of tesofensine and M1 in mice and (ii) to evaluate the potency (pharmacodynamics, PD) and concentration‐time course of the active metabolite M1 relative to tesofensine and their impact in vivo using the PK/PD modelling approach.

Experimental approach:

Parent compound, metabolite and vehicle were separately administered intravenously and orally over a wide dose range (0.3–20 mg kg−1) to 228 mice. Concentrations of tesofensine and M1 were measured; inhibition of the dopamine transporter was determined by co‐administration of [3H]WIN35,428 as the pharmacodynamic measure.

Key results:

Pharmacokinetics of tesofensine and M1 were best described by one‐compartment models for both compounds. Nonlinear elimination and metabolism kinetics were observed with increasing dose. The PK/PD relationship was described by an extended Emax model. Effect compartments were used to resolve observed hysteresis. EC50 values of M1, as an inhibitor of the dopamine transporter, were 4–5‐fold higher than those for tesofensine in mice.

Conclusions and implications:

The lower potency of M1 together with ∼8‐fold higher trough steady‐state concentrations suggest that M1 did contribute to the overall activity of tesofensine in mice.

British Journal of Pharmacology (2008) 153, 164–174; doi:10.1038/sj.bjp.0707539; published online 5 November 2007
The use of the Chandler loop to examine the interaction potential of NXY‐059 on the thrombolytic properties of rtPA on human thrombi in vitro
Authors: Mutch N J , Moore N R , Mattsson C , Jonasson H , Green A R , Booth N A
Published: November 2007

Background and purpose:

Recombinant tissue‐type plasminogen activator (rtPA) is the only globally approved treatment for acute ischaemic stroke. Other potential treatments might be administered with rtPA, making it important to discover whether compounds interfere with rtPA‐induced lysis. We evaluated methods for examining the effect of the neuroprotectant NXY‐059 on the lytic property of rtPA.

Experimental approach:

Plasma clot formation and lysis in the presence of rtPA and NXY‐059 was measured as the change in plasma turbidity. The effect of NXY‐059 on rtPA‐induced lysis was similarly assessed on preformed clots. Lysis of the thrombus formed in a Chandler loop measured release of fluorescent‐tagged fibrinogen that had been incorporated during thrombus formation. Thrombi were exposed to both rtPA and NXY‐059 throughout lysis in the presence of 80% autologous plasma and the release of label during lysis was measured.

Key results:

Data interpretation is limited in the clot lysis experiments because either the rtPA was present during clot formation or the drug was added to a clot formed in static conditions. In contrast, thrombi were formed in dynamic flow conditions in the Chandler loop and the time course of lysis in plasma was examined. rtPA increased thrombolysis and the antifibrinolytic trans‐4‐(aminomethyl) cyclohexane carboxylic acid (AMCA) inhibited lysis. Lysis induced by rtPA was unaltered by NXY‐059.

Conclusions and implications:

The Chandler loop method provides a reliable technique for examining the effect of compounds on rtPA‐induced lysis in vitro and demonstrated that NXY‐059 does not alter rtPA‐induced lysis at clinically relevant concentrations of either drug.

British Journal of Pharmacology (2008) 153, 124–131; doi:10.1038/sj.bjp.0707543; published online 5 November 2007
In vivoeffects of CB2receptor‐selective cannabinoids on the vasculature of normal and arthritic rat knee joints
Authors: McDougall J J , Yu V , Thomson J
Published: November 2007

Background and purpose:

Cannabinoids (CBs) are known to be vasoactive and to regulate tissue inflammation. The present study examined thein vivovasomotor effects of the CB2receptor agonists JWH015 and JWH133 in rat knee joints. The effect of acute and chronic joint inflammation on CB2receptor‐mediated responses was also tested.

Experimental approach:

Blood flow was assessed in rat knee joints by laser Doppler imaging both before and following topical administration of CB2receptor agonists. Vasoactivity was measured in normal, acute kaolin/carrageenan inflamed and Freund's complete adjuvant chronically inflamed knees.

Key results:

In normal animals, JWH015 and JWH133 caused a concentration‐dependent increase in synovial blood flow which in the case of JWH133 was blocked by the selective CB2receptor antagonist AM630 as well as the transient receptor potential vanilloid‐1 (TRPV1) antagonist SB366791. The vasodilator effect of JWH133 was significantly attenuated in both acute and chronically inflamed knees. Given alone, AM630 had no effect on joint blood flow.

Conclusion and implications:

In normal joints, the cannabinomimetic JWH133 causes hyperaemia via a CB2and TRPV1 receptor mechanism. During acute and chronic inflammation, however, this vasodilatatory response is significantly attenuated.

British Journal of Pharmacology(2008)153, 358–366; doi:10.1038/sj.bjp.0707565; published online 5 November 2007
Probing molecular conformations in momentum space: The case of n-pentane
Authors: Knippenberg S. , Huang Y. R. , Hajgató B. , François J.-P. , Deng J. K. , Deleuze M. S.
Published: November 2007

A comprehensive study, throughout the valence region, of the electronic structure and electron momentum density distributions of the four conformational isomers of n-pentane is presented. Theoretical (e,2e) valence ionization spectra at high electron impact energies (1200eV+electron binding energy) and at azimuthal angles ranging from 0° to 10° in a noncoplanar symmetric kinematical setup are generated according to the results of large scale one-particle Green’s function calculations of Dyson orbitals and related electron binding energies, using the third-order algebraic-diagrammatic construction [ADC(3)] scheme. The results of a focal point analysis (FPA) of relative conformer energies [A. Salam and M. S. Deleuze, J. Chem. Phys. 116, 1296 (2002)] and improved thermodynamical calculations accounting for hindered rotations are also employed in order to quantitatively evaluate the abundance of each conformer in the gas phase at room temperature and reliably predict the outcome of experiments on n-pentane employing high resolution electron momentum spectroscopy. Comparison with available photoelectron measurements confirms the suggestion that, due to entropy effects, the trans-gauche (tg) conformer strongly dominates the conformational mixture characterizing n-pentane at room temperature. Our simulations demonstrate therefore that experimental measurements of (e,2e) valence ionization spectra and electron momentum distributions would very consistently and straightforwardly image the topological changes and energy variations that molecular orbitals undergo due to torsion of the carbon backbone. The strongest fingerprints for the most stable conformer (tt) are found for the electron momentum distributions associated with ionization channels at the top of the inner-valence region, which sensitively image the development of methylenic hyperconjugation in all-staggered n-alkane chains.
Coupled-cluster study of the electronic structure and energetics of tetrasulfur, S4
Authors: Matus Myrna H. , Dixon David A. , Peterson Kirk A. , Harkless John A. W. , Francisco Joseph S.
Published: November 2007

Ab initio electronic structure calculations are reported for S4. Geometric and energetic parameters are calculated using the singles and doubles coupled-cluster method, including a perturbutional correction for connected triple excitation, CCSD(T), together with systematic sequences of correlation consistent basis sets extrapolated to the complete basis set limit. The geometry for the ground state singlet C2v structure of S4 is in good agreement with the microwave structure determined for S4. There is a low-lying D2h transition state at 1.6kcal∕mol which interchanges the long S–S bond. S4 has a low-lying triplet state (B1u3) in D2h symmetry which is 10.8kcal∕mol above the C2v singlet ground state. The S–S bond dissociation energy for S4 into two S2(∑g−3) molecules is predicted to be 22.8kcalmol−1. The S–S bond energy to form S3+S(P3) is predicted to be 64kcal∕mol.
Self-consistent high-Reynolds-number asymptotics for zero-pressure-gradient turbulent boundary layers
Authors: Monkewitz Peter A. , Chauhan Kapil A. , Nagib Hassan M.
Published: November 2007

The asymptotic behavior of mean velocity and integral parameters in flat plate turbulent boundary layers under zero pressure gradient are studied for Reynolds numbers approaching infinity. Using the classical two-layer approach of Millikan, Rotta, and Clauser with a logarithmic velocity profile in the overlap region between “inner” and “outer” layers, a fully self-consistent leading-order description of the mean velocity profile and all integral parameters is developed. It is shown that this description fits most high Reynolds number data, and in particular their Reynolds number dependence, exceedingly well; i.e., within experimental errors.
Boundary homogenization for spherical surfaces randomly covered with nonoverlapping partially absorbing disks
Authors: Marcelli Gianluca
Published: November 2007

A common signaling mechanism used by cells involves producing soluble extracellular ligands, which diffuse and bind to specific receptors covering the cell surface. This mechanism can be modeled with point particles (ligands) diffusing in a medium containing reflective spheres (cells) randomly covered by nonoverlapping partially absorbing disks (receptors). In order to simplify the modeling, it is desirable to replace the patchy cell surface with a spherical surface where absorption is uniform. In this Note, we use a Brownian dynamics model to test an approximating formula reported by Berezhkovkii et al. [J. Chem. Phys.121, 11390 (2004)] designed for boundary homogenization problems. We also use the model to solve the more general problem of diffusion to reactive spherical sinks.
Bifurcation diagrams and Turing patterns in a chemical self-replicating reaction-diffusion system with cross diffusion
Authors: Chung Jessica M. , Peacock-López Enrique
Published: November 2007

Chemical self-replication of oligonucleotides and helical peptides exhibits the so-called square root rate law. Based on this rate we extend our previous work on ideal replicators to include the square root rate and other possible nonlinearities, which we couple with an enzymatic sink. For this generalized model, we consider the role of cross diffusion in pattern formation, and we obtain exact general relations for the Poincaré-Adronov-Hopf and Turing bifurcations, and our generalized results include the Higgins, Autocatalator, and Templator models as specific cases.
Calculation of conformation-dependent biomolecular forces
Authors: Hwang Wonmuk
Published: November 2007

We develop a numerical scheme that calculates forces under given conformational states of a biomolecule by using a harmonic sampling potential. It can also be used for calculating the potential of mean force, as tested by random walks on Gaussian enthalpy barriers. Further, Brownian dynamics simulations of a finite-length freely jointed chain confirm the analytic expressions for its entropic elasticity that we derive. Our method, while generally applicable to many systems, will be particularly useful for studying the elasticity of biopolymers where various types of ensembles differ due to the finite size effect.
Nonpolar (11-20) plane AlGaN∕GaN heterojunction field effect transistors on (1-102) plane sapphire
Authors: Kuroda Masayuki , Ishida Hidetoshi , Ueda Tetsuzo , Tanaka Tsuyoshi
Published: November 2007

GaN-based compound semiconductors have been investigated for use in future power switching devices with high breakdown voltages and low on-state resistances due to their high breakdown field and high saturation electron velocity. To date, conventional AlGaN∕GaN heterojunction field effect transistors (HFETs) are fabricated on c-plane across which the spontaneous and piezoelectric polarization fields produce extraordinarily high sheet carrier concentrations. In this paper, we report on the epitaxial growth and fabrication of AlGaN∕GaN HFETs on (11-20) a-plane which are not affected by the polarization fields. The a-plane’s epitaxial layers are grown on (1-102) r-plane sapphire substrates by metal organic chemical vapor deposition. The sheet carrier concentrations can be controlled by simply doping the AlGaN in the nonpolar devices. The a-plane devices exhibit nearly normally-off characteristics in which the threshold voltage is −0.5V, while that of the conventional c-plane device is −4.0V. The HFET on nonpolar planes easily enables normally-off operation which is highly desirable in power switching applications.
Trap filled limit voltage (VTFL) and V2 law in space charge limited currents
Authors: Jain Anubha , Kumar Pankaj , Jain S. C. , Kumar Vikram , Kaur R. , Mehra R. M.
Published: November 2007

There is no signature of the trap filled limit voltage (VTFL) in the J-V characteristics of a sample containing exponentially distributed traps. We show that VTFL and the voltage at which V2 dependence sets in (VMott) can be determined accurately. These voltages are independent of the energy distributions of the traps and depend strongly on the trap density Hb. Contrary to the literature results, it turns out that VTFL is significantly smaller than the VMott. In a specific case with Hb=1.6×1018cm−3 and for a 5% accuracy in the current the value of VMott is about 400V whereas VTFL is 13.5V. Universal J-V curves in reduced units are derived and plotted. The reduced value of VTFL is 0.5. These curves are valid for all organics and inorganic semiconductors and for all energy distributions of traps. It is shown mathematically that all J-V curves approached Mott’s V2 law asymptotically as V increases to infinity. To validate the theory, the experimental J-V curves in polycrystalline undoped and Al doped ZnO thin films are made. The experimental results show good agreement with the theory. In the undoped ZnO films the traps are exponentially distributed and the trap concentration is calculated to be 1.7×1017cm−3. The trap distribution in Al doped ZnO films is found to be discrete at a single level with trap concentration of 8×1016cm−3.
Photoluminescence-free photoreflectance spectra using dual frequency modulation
Authors: Plaza J. , Ghita D. , Castaño J. L. , Garcia B. J.
Published: November 2007

Photoreflectance (PR) spectra are usually obtained by measuring the relative change on the reflectivity of a semiconducting sample induced by a chopped laser beam. The laser beam can also produce photoluminescence (PL) emission at the sample surface which, detected at its same frequency, could appear as an offset distorting the PR spectrum. This parasitic and intrinsically noisy PL signal, not easily discriminated electronically nor optically filtered, can become the dominant part of the PR spectrum at low sample temperatures, hiding spectrum features under its associated noise, or even avoiding data acquisition. An alternative method for PL signal discrimination is proposed in this work, using a different chopping frequency for each light beam: PL and reflected signals will appear each one at its own chopping frequency, while PR signal will be detected at its frequency sum, allowing signal separation by frequency. Both experimental setups are compared using a highly luminescent quantum well structure at low temperatures. While the standard setup suffers the PL limitation, the proposed method overcomes this constraint, allowing good quality spectra to be measured at temperatures as low as 12K.
Narrow-band single photons from a single-resonant optical parametric oscillator far below threshold
Authors: Scholz M. , Wolfgramm F. , Herzog U. , Benson O.
Published: November 2007

We present a single-resonant optical parametric oscillator pumped far below threshold as a source for narrow-band single photons. Spontaneous generation of single photons via parametric downconversion is modified and follows the cavity transfer function. Cross-correlation measurements between signal and idler beams show a cavity bandwidth of 62MHz. As the main improvement to prior realizations, our cavity is locked to the pump beam via the Hänsch-Couillaud method and therefore allows the continuous generation of heralded single photons with long-term stability.
Grain size effect on the switching current in soft ferroelectric lead zirconate titanate
Authors: Kamel Talal M. , de With Gijsbertus
Published: November 2007

Recently, we reported on the appearance of a double peak in the switching current during the reverse poling. In the present paper, the switching current measurements have been carried out on a soft lead zirconate titanate as a function of grain size. While in small grains only a small single switching peak is observed, large grains, however, showed double peak switching, as commonly observed in this material. The pyroelectric coefficient curves show a consistent trend with the switching curves. This behavior is attributed to non-180° domain switching during the reversed poling case as a result of residual stresses developed during forward poling.
Controllable effective complex permittivity of functionally graded composite materials: A numerical investigation
Authors: Mejdoubi Abdelilah , Brosseau Christian
Published: November 2007

A ubiquitous issue in dielectric heterostructures is to understand the relation between unconventional materials and their effective polarization properties (complex permittivity, polarizability, factor of depolarization). In this context, graded composite materials (GCMs), in which the constituent material properties can vary continuously in space, provide an interesting playground. We report effective permittivity calculations of two-phase GCM, using finite-element (FE) calculations, to understand the effects of shape, size, and intrinsic permittivity of the different components of the material. Our analysis shows that purposely introduced gradients in the permittivity of inclusion can be used to tune the effective permittivity of the GCM. Our FE calculations quantitatively test recent predictions of the effective permittivity of GCM having general power-law gradient inclusions based on the recently developed Wei-Poon-Shin theory [Phys. Lett. A 336, 264 (2005)]. The agreement between the FE data and the predicted curves is excellent only in the dilute limit. In addition, we quantify the complex effective permittivity of several representative GCMs and show that Maxwell Garnett equation is not, in general, appropriate to represent its volume fraction dependence. Numerics furthermore show that selected lossy GCM with negative permittivity can have specific features which distinguish them from composite materials (CMs) containing homogeneous isotropic inclusions. This information is potentially useful for understanding the dielectric properties of GCM which are abundant in nature. Collectively, the results are also relevant for exploiting artificially engineered CM in technologies for such applications as microwave biosensors, nanophotonics, and heterogeneous catalysis.
Decoherence of nuclear spins due to dipole-dipole interactions probed by resistively detected nuclear magnetic resonance
Authors: Ota T. , Yusa G. , Kumada N. , Miyashita S. , Fujisawa T. , Hirayama Y.
Published: November 2007

We study decoherence of nuclear spins in a GaAs quantum well structure using resistively detected nuclear magnetic resonance. The transverse decoherence time T2 of As75 nuclei is estimated from Rabi-type coherent oscillations as well as by using spin-echo techniques. By analyzing T2 obtained by decoupling techniques, we extract the role of dipole-dipole interactions as sources of decoherence in GaAs. Under the condition that the device is tilted in an external magnetic field, we exhibit enhanced decoherence induced by the change in strength of the direct dipole-dipole interactions between first nearest-neighbor nuclei. The results agree well with simple numerical calculations.
Defect behavior induced by helium cluster growth in titanium crystals
Authors: Wang Jun , Hou Qing , Sun Tieying , Long Xinggui , Wu Xingchun , Luo Shunzhong
Published: November 2007

The growth of helium cluster in titanium crystals is simulated in great detailed approach using molecular dynamics. We observe that, as the helium cluster grows, defects around the cluster are formed and the local pressure increases. However, at certain point in the growth process, the defects are found to rapidly escape as a whole from the helium cluster, accompanied by the relief of local high pressure and the recovery of Ti crystal structure around the helium cluster.
Electromigration-induced Coble creep in polycrystalline materials
Authors: Li Zhonghua , Dong Yan , Li Shu , Xu Limin , Sun Jun
Published: November 2007

A simple expression has been derived for the prediction of the creep rate controlled by electromigration-induced grain boundary diffusion. The creep rate depends linearly on the current density and the grain boundary diffusivity, and inversely on grain size squared. It is also demonstrated that the electromigration-induced creep can be fully suppressed by a critical compressive stress gradient.
Hidde Ploegh: Immunologist, journeyman
Authors: LeBrasseur Nicole
Published: November 2007

From the moment he finished his Ph.D., Hidde Ploegh has been a wanted man. Invited to join one institution after another, he always packed with him his keen interests in the immune system.
Very-KIND, a KIND domain–containing RasGEF, controls dendrite growth by linking Ras small GTPases and MAP2
Authors: Huang Jinhong , Furuya Asako , Furuichi Teiichi
Published: November 2007

The regulation of cytoskeletal components in the dendritic shaft core is critical for dendrite elongation and branching. Here, we report that a brain-specific Ras guanine nucleotide exchange factor (RasGEF) carrying two kinase non-catalytic C-lobe domains (KINDs), very-KIND (v-KIND), regulates microtubule-associated protein 2 (MAP2). v-KIND is expressed in developing mouse brain, predominantly in the cerebellar granule cells. v-KIND not only activates Ras small GTPases via the C-terminal RasGEF domain, but also specifically binds to MAP2 via the second KIND domain (KIND2), leading to threonine phosphorylation of MAP2. v-KIND overexpression suppresses dendritic extension and branching of hippocampal neurons and cerebellar granule cells, whereas knockdown of endogenous v-KIND expression promotes dendrite growth. These findings suggest that v-KIND mediates a signaling pathway that links Ras and MAP2 to control dendrite growth.
Functional multivesicular bodies are required for autophagic clearance of protein aggregates associated with neurodegenerative disease
Authors: Filimonenko Maria , Stuffers Susanne , Raiborg Camilla , Yamamoto Ai , Malerød Lene , Fisher Elizabeth M.C. , Isaacs Adrian , Brech Andreas , Stenmark Harald , Simonsen Anne
Published: November 2007

The endosomal sorting complexes required for transport (ESCRTs) are required to sort integral membrane proteins into intralumenal vesicles of the multivesicular body (MVB). Mutations in the ESCRT-III subunit CHMP2B were recently associated with frontotemporal dementia and amyotrophic lateral sclerosis (ALS), neurodegenerative diseases characterized by abnormal ubiquitin-positive protein deposits in affected neurons. We show here that autophagic degradation is inhibited in cells depleted of ESCRT subunits and in cells expressing CHMP2B mutants, leading to accumulation of protein aggregates containing ubiquitinated proteins, p62 and Alfy. Moreover, we find that functional MVBs are required for clearance of TDP-43 (identified as the major ubiquitinated protein in ALS and frontotemporal lobar degeneration with ubiquitin deposits), and of expanded polyglutamine aggregates associated with Huntington's disease. Together, our data indicate that efficient autophagic degradation requires functional MVBs and provide a possible explanation to the observed neurodegenerative phenotype seen in patients with CHMP2B mutations.
Regulation of atrial natriuretic peptide secretion by a novel Ras-like protein
Authors: Rybkin Igor I. , Kim Mi-Sung , Bezprozvannaya Svetlana , Qi Xiaoxia , Richardson James A. , Plato Craig F. , Hill Joseph A. , Bassel-Duby Rhonda , Olson Eric N.
Published: November 2007

Atrial cardiomyocytes, neurons, and endocrine tissues secrete neurotransmitters and peptide hormones via large dense-core vesicles (LDCVs). We describe a new member of the Ras family of G-proteins, named RRP17, which is expressed specifically in cardiomyocytes, neurons, and the pancreas. RRP17 interacts with Ca2+-activated protein for secretion-1 (CAPS1), one of only a few proteins known to be associated exclusively with LDCV exocytosis. Ectopic expression of RRP17 in cardiomyocytes enhances secretion of atrial natriuretic peptide (ANP), a regulator of blood pressure and natriuresis. Conversely, genetic deletion of RRP17 in mice results in dysmorphic LDCVs, impaired ANP secretion, and hypertension. These findings identify RRP17 as a component of the cellular machinery involved in regulated secretion within the heart and potential mediator of the endocrine influence of the heart on other tissues.
Inheritance of cortical ER in yeast is required for normal septin organization
Authors: Loewen Christopher J.R. , Young Barry P. , Tavassoli Shabnam , Levine Timothy P.
Published: November 2007

How cells monitor the distribution of organelles is largely unknown. In budding yeast, the largest subdomain of the endoplasmic reticulum (ER) is a network of cortical ER (cER) that adheres to the plasma membrane. Delivery of cER from mother cells to buds, which is termed cER inheritance, occurs as an orderly process early in budding. We find that cER inheritance is defective in cells lacking Scs2, a yeast homologue of the integral ER membrane protein VAP (vesicle-associated membrane protein–associated protein) conserved in all eukaryotes. Scs2 and human VAP both target yeast bud tips, suggesting a conserved action of VAP in attaching ER to sites of polarized growth. In addition, the loss of either Scs2 or Ice2 (another protein involved in cER inheritance) perturbs septin assembly at the bud neck. This perturbation leads to a delay in the transition through G2, activating the Saccharomyces wee1 kinase (Swe1) and the morphogenesis checkpoint. Thus, we identify a mechanism involved in sensing the distribution of ER.
Revisiting the role of microtubules in C. elegans polarity
Authors: Motegi Fumio , Seydoux Geraldine
Published: November 2007

Cells must break symmetry to acquire polarity. Microtubules have been implicated in the induction of asymmetry in several cell types, but their role in the Caenorhabditis elegans zygote, a classic polarity model, has remained uncertain. One study (see Tsai and Ahringer on p. 397 of this issue) brings new light to this problem by demonstrating that severe loss of microtubules impairs polarity onset in C. elegans.
Postexposure Immunization and Prophylaxis of Bloodborne Pathogens Following a Traumatic Explosive Event: Preliminary Recommendations
Authors: Subbarao Italo , Steinbrecher Ruth , Tan Litjen , Peleg Kobi , Zeiger Jessica , James James J.
Published: November 2007

Background: No definitive guidelines have been established in the United States for postexposure immunization and prophylaxis (PEP) to hepatitis B and C viruses (HBV, HCV) and human immunodeficiency virus (HIV) in the event of a traumatic explosive event.

Methods: The American Medical Association’s Center for Public Health Preparedness and Disaster Response assembled a US-Israeli panel of experts, including representatives from disaster medicine, trauma surgery, occupational health, and infectious disease to determine guidelines for adult and pediatric victims following a traumatic explosive event. The panel reviewed the existing Israeli and United Kingdom protocols, previously published Centers for Disease Control and Prevention guidance on occupational and nonoccupational exposures to HBV, HCV, and HIV, before reaching consensus on preliminary guidelines for the United States.

Results: These guidelines recommend an age-appropriate dose and schedule for HBV PEP for individuals presenting from the scene with nonintact skin or mucous membrane exposure, and they also consider HCV and HIV testing in individuals presenting with possible nonintact skin or mucous membrane exposure. The guidelines do not recommend PEP for individuals presenting from the scene with possible superficial skin exposure.

Conclusions: These recommendations offer PEP guidance for bloodborne pathogens and are limited in scope. These recommendations do not address general wound PEP such as tetanus or the need for antibiotics. It is hoped that these guidelines will fill an urgent gap in preparedness until definitive, comprehensive guidelines from the Centers for Disease Control and Prevention are published. (Disaster Med Public Health Preparedness. 2007;1:106–109)
A mechanism of benefit of soy genistein in asthma: inhibition of eosinophil p38‐dependent leukotriene synthesis
Authors: Kalhan R. , Smith L. J. , Nlend M. C. , Nair A. , Hixon J. L. , Sporn P. H. S.
Published: November 2007

Background
Dietary intake of the soy isoflavone genistein is associated with reduced severity of asthma, but the mechanisms responsible for this effect are unknown.

Objective
To determine whether genistein blocks eosinophil leukotriene C4 (LTC4) synthesis and to evaluate the mechanism of this effect, and to assess the impact of a 4‐week period of soy isoflavone dietary supplementation on indices of eosinophilic inflammation in asthma patients.

Methods
Human peripheral blood eosinophils were stimulated in the absence and presence of genistein, and LTC4 synthesis was measured. 5‐lipoxygenase (5‐LO) nuclear membrane translocation was assessed by confocal immunofluorescence microscopy. Mitogen‐activated protein (MAP) kinase activation was determined by immunoblot. Human subjects with mild‐to‐moderate persistent asthma and minimal or no soy intake were given a soy isoflavone supplement (100 mg/day) for 4 weeks. The fraction of exhaled nitric oxide (FENO) and ex vivo eosinophil LTC4 production were assessed before and after the soy isoflavone treatment period.

Results
Genistein inhibited eosinophil LTC4 synthesis (IC50 80 nm), blocked phosphorylation of p38 MAP kinase and its downstream target MAPKAP‐2, and reduced translocation of 5‐LO to the nuclear membrane. In patients with asthma, following 4 weeks of dietary soy isoflavone supplementation, ex vivo eosinophil LTC4 synthesis decreased by 33% (N=11, P=0.02) and FENO decreased by 18% (N=13, P=0.03).

Conclusion
At physiologically relevant concentrations, genistein inhibits eosinophil LTC4 synthesis in vitro, probably by blocking p38‐ and MAPKAP‐2‐dependent activation of 5‐LO. In asthma patients, dietary soy isoflavone supplementation reduces eosinophil LTC4 synthesis and eosinophilic airway inflammation. These results support a potential role for soy isoflavones in the treatment of asthma.