bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of dust-charge fluctuation on the damping of Alfvén waves in dusty plasmas
Authors: de Juli M. C. , Schneider R. S. , Ziebell L. F. , Jatenco-Pereira V.
Published: May 2005

Using a completely kinetic description to analyze wave propagation in dusty plasmas, the case of propagation of waves exactly parallel to the external magnetic field and Maxwellian distributions for electrons and ions in the equilibrium is considered. A model for the charging process of dust particles which depends on the frequency of inelastic collisions between dust particles and electrons and ions is used. The dispersion relation and damping rates for Alfvén waves are obtained. For the numerical solutions, the average value of the inelastic collision frequency is used as an approximation. The results show that the presence of dust particles with variable charge in the plasma produces significant additional damping of the Alfvén wave. A novel process of mode coupling of low-frequency waves is demonstrated to occur due to the presence of dust particles.
Confinement analyses of the high-density field-reversed configuration plasma in the field-reversed configuration experiment with a liner
Authors: Zhang Shouyin , Intrator T. P. , Wurden G. A. , Waganaar W. J. , Taccetti J. M. , Renneke R. , Grabowski C. , Ruden E. L.
Published: May 2005

The focus of the field-reversed configuration (FRC) experiment with a liner (FRX-L) is the formation of a target FRC plasma for magnetized target fusion experiments. An FRC plasma with density of 1023m−3, total temperature in the range of 150–300 eV, and a lifetime of ≈20μs is desired. Field-reversed θ-pinch technology is used with programed cusp fields at θ-coil ends to achieve non-tearing field line reconnections during FRC formation. Well-formed FRCs with density between (2–4)×1022m−3, lifetime in the range of 15–20μs, and total temperature between 300–500 eV are reproducibly created. Key FRC parameters have standard deviation in the mean of 10% during consecutive shots. The FRCs are formed at 50 mTorr deuterium static fill using 2 kG net reversed bias field inside the θ-coil confinement region, with external main field unexpectedly ranging between 15–30 kG. The high-density FRCs confinement properties are approximately in agreement with empirical scaling laws obtained from previous experiments with fill pressure mostly less than 20 mTorr. Analyses in this paper reveal that reducing the external main field modulation and∕or extending the θ-coil length in the FRX-L device are critical in achieving higher FRC parameters for application in magnetized target fusion.
Noether’s second theorem for BRST symmetries
Authors: Bashkirov D. , Giachetta G. , Mangiarotti L. , Sardanashvily G.
Published: May 2005

We present Noether’s second theorem for graded Lagrangian systems of even and odd variables on an arbitrary body manifold X in a general case of BRST symmetries depending on derivatives of dynamic variables and ghosts of any finite order. As a preliminary step, Noether’s second theorem for Lagrangian systems on fiber bundles Y→X possessing gauge symmetries depending on derivatives of dynamic variables and parameters of arbitrary order is proved.
The motion of a point vortex around multiple circular islands
Authors: Crowdy Darren G. , Marshall Jonathan S.
Published: May 2005

A new constructive method for computing the motion of a single point vortex around an arbitrary finite number of circular islands in the special case when the circulations around all the islands are zero is presented. In this case, explicit representations for the governing Hamiltonians can be found and used to study the vortex trajectories. An example application is to geophysical flows and this study provides a simple model of the interaction of ocean eddies with topography. A wide range of illustrative examples are given, including the case of various multi-island configurations lying off an infinite coastline as well as in an unbounded ocean. The critical trajectories (or separatrices) dividing the flow domain into regions of qualitatively different dynamics of the vortices can be computed in a systematic and unified fashion irrespective of the number of islands present.
Even harmonics generation of high frequency radiation in current-carrying plasmas
Authors: Ferrante G. , Zarcone M. , Uryupin S. A.
Published: May 2005

Generation of high frequency radiation harmonics in a current-carrying plasma is studied. The physical mechanism responsible for harmonics generation is provided by electron-ion collisions. The current in the plasma is sustained by a constant electric field. It is shown that the electron distribution function anisotropy due to the static field yields generation of even harmonics. As a result, the radiation spectrum emitted by the current-carrying plasma contains both even and odd harmonics, the latter being attributed to currentless plasma. For a broad range of plasma and high frequency radiation parameters, a detailed analysis of the even harmonics properties is reported.
Retention of nativelike conformation by proteins embedded in high external electric fields
Authors: Pompa P. P. , Bramanti A. , Maruccio G. , Cingolani R. , De Rienzo F. , Corni S. , Di Felice R. , Rinaldi R.
Published: May 2005

In this Communication, we show that proteins embedded in high external electric fields are capable of retaining a nativelike fold pattern. We have tested the metalloprotein azurin, immobilized onto SiO2 substrates in air with proper electrode configuration, by applying static fields up to 106–107V∕m. The effects on the conformational properties of protein molecules have been determined by means of intrinsic fluorescence measurements. Experimental results indicate that no significant field-induced conformational alteration occurs. Such results are also discussed and supported by theoretical predictions of the inner protein fields.
Ferroelectricity at room temperature in Pr-doped SrTiO3
Authors: Durán A. , Martínez E. , Díaz J. A. , Siqueiros J. M.
Published: May 2005

The influence of Pr ion on the structural and dielectric properties was studied in Sr1−xPrxTiO3 for 0<x<0.075 composition from room temperature to 375°C. X-ray diffraction and x-ray photoelectron spectroscopy studies revealed that the praseodymium ion enters substitutionally in the Sr site with mixed valence in a Pr+3∕Pr+4=2:1 ratio. This substitution yields compressive chemical pressure in the lattice. The polarization measurements at room temperature display hysteresis loops, indicating that the Pr ion induces ferroelectric behavior at room temperature. The permittivity shows a well-defined peak at about 240°C, indicative of a ferroelectric-paraelectric transition with Curie temperature of ∼118°C.
Shear flow generation and energetics in electromagnetic turbulence
Authors: Naulin V. , Kendl A. , Garcia O. E. , Nielsen A. H. , Rasmussen J. Juul
Published: May 2005

Zonal flows are recognized to play a crucial role for magnetized plasma confinement. The genesis of these flows out of turbulent fluctuations is therefore of significant interest. Here the relative importance of zonal flow generation mechanisms via the Reynolds stress, Maxwell stress, and geodesic acoustic mode (GAM) transfer in drift-Alfvén turbulence is investigated. By means of numerical computations the energy transfer into zonal flows owing to each of these effects is quantified. The importance of the three driving ingredients in electrostatic and electromagnetic turbulence for conditions relevant to the edge of fusion devices is revealed for a broad range of parameters. The Reynolds stress is found to provide a flow drive, while the electromagnetic Maxwell stress is in the cases considered a sink for the flow energy. In the limit of high plasma β, where electromagnetic effects and Alfvén dynamics are important, the Maxwell stress is found to cancel the Reynolds stress to a high degree. The geodesic oscillations, related to equilibrium pressure profile modifications due to poloidally asymmetric transport, can act as both sinks as drive terms, depending on the parameter regime. For high-β cases the GAMs are the main drive of the flow. This is also reflected in the frequency dependence of the zonal flows, showing a distinct peak at the GAM frequency in that regime.
Terahertz wave detection performance of photoconductive antennas: Role of antenna structure and gate pulse intensity
Authors: Yano R. , Gotoh H. , Hirayama Y. , Miyashita S. , Kadoya Y. , Hattori T.
Published: May 2005

We studied the receiver performance of two photoconductive antennas (bow tie and dipole antennas) fabricated on the same low-temperature-grown GaAs substrate to clarify the effect of the antenna structure and gate pulse intensity on terahertz wave detection. We observed the gate pulse intensity dependence of the temporal profiles of the terahertz waves or terahertz spectra. For both antennas, the sensitivity in the low-frequency regime (<0.5THz) was enhanced compared to that in the high-frequency regime for large gate pulse intensities. This is because the carrier trap time increased due to the saturation of the GaAs defect levels. We also observed that the peak-to-peak amplitude of the terahertz wave detected by one antenna was not always larger than that detected by the other antenna, and the peak-to-peak amplitude of the bow tie antenna was larger (smaller) than that of the dipole antenna when the gate pulse intensity was high (low). This was explained by the gate pulse intensity dependence of the frequency-dependent detection sensitivity and also by the resonance frequency of the antenna structure.
Feasibility of static induction transistor with organic semiconductors
Authors: Zorba Serkan , Gao Yongli
Published: May 2005

We have fabricated and studied static induction transistors (SITs) with various organic semiconductor materials, such as pentacene, perylene, tris(quinoline-8-hydroxylate)aluminum (Alq), and N,N′-di(4-methylphenyl)-N,N′-diphenylbenzidine (TPD), used as the active element. The former two resulted in unsuccessful operation due to a short caused by pinholes formed in the films. Modification of the deposition rates did not change the outcome. The latter two provided successful operation. No fatal pinholes were observed in the thin films of the latter two. It is thus shown that the morphology has crucial effect in the operation of SITs. A transition from linear to nonlinear behavior has been observed in the drain-source I–V characteristics of Alq and TPD.
Stretching and mixing of non-Newtonian fluids in time-periodic flows
Authors: Arratia P. E. , Voth Greg A. , Gollub J. P.
Published: May 2005

The stretching of fluid elements and the dynamics of mixing are studied for a variety of polymer solutions in nearly two-dimensional magnetically driven flows, in order to distinguish between the effects of viscoelasticity and shear thinning. Viscoelasticity alone is found to suppress stretching and mixing mildly, in agreement with some previous experiments on time-periodic flows. On the other hand, the presence of shear thinning viscosity (especially when coupled with elasticity) produces a dramatic enhancement in stretching and mixing compared to a Newtonian solution at the same Reynolds number. In order to understand this observation, we study the velocity field separately in the sheared and elongational regions of the flow for various polymer solutions. We demonstrate that the enhancement is accompanied by a breaking of time-reversal symmetry of the particle trajectories, on the average. Finally, we discuss possible causes for the time lags leading to this temporal symmetry breaking, and the resulting enhanced mixing.
Spectral properties of laser-accelerated mid-Z MeV∕u ion beams
Authors: Hegelich B. M. , Albright B. , Audebert P. , Blazevic A. , Brambrink E. , Cobble J. , Cowan T. , Fuchs J. , Gauthier J. C. , Gautier C. , Geissel M. , Habs D. , Johnson R. , Karsch S. , Kemp A. , Letzring S. , Roth M. , Schramm U. , Schreiber J. , Witte K. J. , Fernández J. C.
Published: May 2005

Collimated jets of beryllium, carbon, oxygen, fluorine, and palladium ions with >1MeV∕nucleon energies are observed from the rear surface of thin foils irradiated with laser intensities of up to 5×1019W∕cm2. The normally dominant proton acceleration is suppressed when the target is subjected to Joule heating to remove hydrogen-bearing contaminant. This inhibits screening effects and permits effective energy transfer to and acceleration of heavier ion species. The influence of remnant protons on the spectral shape of the next highest charge-to-mass ratio species is shown. Particle-in-cell simulations confirming the experimental findings are presented.
An interface-proximity model for switchable interfacial uncompensated antiferromagnetic spins and their role in exchange bias
Authors: Lee Ki-Suk , Yu Young-Sang , Kim Sang-Koog
Published: May 2005

We propose an interface-proximity model that allows us to solve a longstanding puzzle regarding large discrepancies between the experimentally observed and theoretically estimated values of exchange-bias field Heb in coupled ferromagnetic∕antiferromagnetic (F∕AF) metallic films. In this proposed model, switchable uncompensated (UC) AF spins in contact with an F layer are taken into account as an additionally inserting layer that is chemically or magnetically distinguishable from each of the nominal AF and F layers. Reductions in Heb, enhancements in coercivity, and other exchange-bias behaviors typically observed in experiments are very well reproduced from this model. The switchable interfacial UC region with a sizable thickness, heretofore ignored, plays a crucial role in the exchange bias phenomenon.
Rapid heating of solid density material by a petawatt laser
Authors: Evans R. G. , Clark E. L. , Eagleton R. T. , Dunne A. M. , Edwards R. D. , Garbett W. J. , Goldsack T. J. , James S. , Smith C. C. , Thomas B. R. , Clarke R. , Neely D. J. , Rose S. J.
Published: May 2005

Time-resolved x-ray spectra from solid targets irradiated by the VULCAN Petawatt laser focused to 1020Wcm−2 show that material at solid density is heated to temperatures above 500 eV to a depth of about 15 μm and for a duration of more than 30 ps. Modeling with the implicit hybrid plasma code LSP shows that the heating is sensitive to the laser prepulse through resistive inhibition of the laser accelerated electrons in the blow off layer.
Quantum confinement in Volmer–Weber-type self-assembled ZnO nanocrystals
Authors: Hur Tae-Bong , Hwang Yoon-Hwae , Kim Hyung-Kook
Published: May 2005

We have studied the quantum confinement effect on Volmer–Weber-type self-assembled ZnO nanocrystals. Volmer–Weber-type self-assembled ZnO nanocrystals were grown on the Pt(111) substrate by using a rf-magnetron sputtering method and were confirmed by the Auger electron spectroscopy. The free exciton transition energies of 57-, 38-, and 24-nm-size nanocrystals were found to be roughly 3.298, 3.311, and 3.337eV, respectively, by photoluminescence measuremnets at room temperature. The blueshift of the photoluminescence peak energy of ZnO nanocrystals of 24nm in diameter roughly varied by 40meV compared to bulk ZnO.
Versatile buffer layer architectures based on Ge1−xSnx alloys
Authors: Roucka R. , Tolle J. , Cook C. , Chizmeshya A. V. G. , Kouvetakis J. , D’Costa V. , Menendez J. , Chen Zhihao D. , Zollner S.
Published: May 2005

We describe methodologies for integration of compound semiconductors with Si via buffer layers and templates based on the GeSn system. These layers exhibit atomically flat surface morphologies, low defect densities, tunable thermal expansion coefficients, and unique ductile properties, which enable them to readily absorb differential stresses produced by mismatched overlayers. They also provide a continuous selection of lattice parameters higher than that of Ge, which allows lattice matching with technologically useful III-V compounds. Using this approach we have demonstrated growth of GaAs, GeSiSn, and pure Ge layers at low temperatures on Si(100). These materials display extremely high-quality structural, morphological, and optical properties opening the possibility of versatile integration schemes directly on silicon.
Effects of temperature on good rectifying characteristic of manganite-based p-n junction
Authors: Cai Tian-Yi , Li Zhen-Ya
Published: May 2005

The good rectifying characteristic of manganite-based p-n junction are reproduced. Different from conventional p-n junctions, the variation of electronic structure of doped manganite with temperature is considered. It is obtained that the diffusion potential of a manganite-based p-n junction decreases with the increasing temperature. It is in good agreement with experimental results.
Highly Si-doped AlN grown by plasma-assisted molecular-beam epitaxy
Authors: Hermann M. , Furtmayr F. , Bergmaier A. , Dollinger G. , Stutzmann M. , Eickhoff M.
Published: May 2005

We have studied the influence of the growth conditions on the Si incorporation in AlN films grown by plasma-assisted molecular-beam epitaxy. Nitrogen-rich growth conditions allow controlled incorporation of Si up to a concentration of 5.2×1021cm−3, determined by elastic recoil detection analysis, whereas Si incorporation is supressed under Al-rich growth conditions. The structural and morphological properties determined by x-ray diffraction and atomic force microscopy were not affected up to Si concentrations of 1.2×1021cm−3. The electrical conductivity for the N-rich growth regime first increases with Si concentration followed by a decrease due to an increase of the activation energy up to 570meV for a Si content of 1.2×1021cm−3. For higher silicon concentrations, we have observed a sharp decrease in activation energy and an increase in conductivity by four orders of magnitude, attributed to the onset of impurity band conduction.
Simulations of composite carbon films with nanotube inclusions
Authors: Fyta M. G. , Kelires P. C.
Published: May 2005

We study the interfacial structure, stability, and elastic properties of composite carbon films containing nanotubes. Our Monte Carlo simulations show that van der Waals forces play a vital role in shaping up the interfacial geometry, producing a curved graphitic wall surrounding the tubes. The most stable structures are predicted to have intermediate densities, high anisotropies, and increased elastic moduli compared to pure amorphous carbon films.
Texture formation in FePt thin films via thermal stress management
Authors: Rasmussen P. , Rui X. , Shield J. E.
Published: May 2005

The transformation variant of the fcc to fct transformation in FePt thin films was tailored by controlling the stresses in the thin films, thereby allowing selection of in- or out-of-plane c-axis orientation. FePt thin films were deposited at ambient temperature on several substrates with differing coefficients of thermal expansion relative to the FePt, which generated thermal stresses during the ordering heat treatment. X-ray diffraction analysis revealed preferential out-of-plane c-axis orientation for FePt films deposited on substrates with a similar coefficients of thermal expansion, and random orientation for FePt films deposited on substrates with a very low coefficient of thermal expansion, which is consistent with theoretical analysis when considering residual stresses.
Néel temperature enhancement in nanostructured nickel zinc ferrite
Authors: Ponpandian N. , Narayanasamy A. , Chinnasamy C. N. , Sivakumar N. , Greneche J.-M. , Chattopadhyay K. , Shinoda K. , Jeyadevan B. , Tohji K.
Published: May 2005

The Néel temperature of Ni0.5Zn0.5Fe2O4 spinel ferrite increases significantly from 538K in the bulk state to 592K when the grain size is reduced to 16nm by milling in a high-energy ball mill. This has been attributed to an increase in the AB superexchange interaction strength due to a possible enhancement in the magnetic ion concentration in the A-site on milling, as is evident from extended x-ray absorption fine structure and in-field Mössbauer measurements.
Observation of ultrahigh quality factor in a semiconductor microcavity
Authors: Sanvitto D. , Daraei A. , Tahraoui A. , Hopkinson M. , Fry P. W. , Whittaker D. M. , Skolnick M. S.
Published: May 2005

Observation of a very high-quality factor (Q) of ∼30,000 is reported for a planar semiconductor microcavity grown by molecular-beam epitaxy using in situ optical monitoring. The very high Qs are measured in pillars of 5–10μm diameter, and are approximately a factor of 3 higher than measured in planar structures before etching. The higher values in the pillars are ascribed to the elimination of the effects of in-plane dispersion, diffraction, and lateral inhomogeneities, thus allowing the intrinsic Q of the planar structure to be observed. Spectrally resolved mode mapping is reported, accounting qualitatively for the decrease of Q with increasing mode number in the pillars.
Potential white-light long-lasting phosphor: Dy3+-doped aluminate
Authors: Liu Bo , Shi Chaoshu , Qi Zeming
Published: May 2005

The white-light long-lasting phosphor CaAl2O4:Dy3+ was prepared and investigated. The white-light afterglow spectra under the irradiation of 254 or 365nm are comprised of the blue light emission and the yellow light emission, originating from the transitions of F9∕24→H15∕26, F9∕24→H13∕26 in the 4f9 configuration of Dy3+. The afterglow can last 32min for the best sample with Dy-doped concentration of 2at.%. The decay curve and the thermoluminescence curve show to be a second-order process. Thermoluminescence curves exhibit a complicated structure in the range of 230–450K with the peaks at 244, 280, 310, and 346K. The two thermoluminescence bands peaking above room temperature have corresponding traps with the depths of 0.54 and 0.61eV, which are responsible for the afterglow emission at room temperature. This work provides a promising approach for the development of white-light long-lasting phosphor.
Structural stability and magnetic properties of SmCo7−xGax
Authors: Guo Yongquan , Li Wei , Feng Weichun , Luo Jun , Liang Jingkui , He Qijun , Yu Xiaojun
Published: May 2005

We have studied the structural stability and magnetic properties of SmCo7−xGax compounds using powder x-ray diffraction and magnetic measurements. Gallium as a dopant not only stabilizes the SmCo 1:7 phase but also induces a strong uniaxial magnetocrystalline anisotropy. An anisotropy field as high as 30.7 T is observed at 5 K in the SmCo6Ga compound. The strong anisotropy field might be due to the occupation of Ga atom. The structural stability of SmCo7−xGax compounds is related to the effective Sm/(Co,Ga) atomic radius ratio (RA) and the difference in electronegativity (XA) between Sm and (Co,Ga). According to our calculation, the SmCo 1:7 type structure can be stabilized in range from 1.08(5) to 1.12(9) for RA and −1.04(4) to −0.94(4) for XA.
Self-assembled growth and enhanced blue emission of SiOxNy-capped silicon nanowire arrays
Authors: Qiu T. , Wu X. L. , Wan G. J. , Mei Y. F. , Siu G. G. , Chu Paul K.
Published: May 2005

Unique structured SiOxNy-capped Si nanowire arrays were fabricated via electroless metal deposition on α-SiOxNy-covered Si wafer in ionic silver HF solution through selective chemical etching. A self-assembled localized microscopic electrochemical cell model and a diffusion-limited aggregation process are associated with the formation of the SiOxNy-capped Si nanowire arrays. An enhanced blue photoluminescence band has been recorded. Emission and excitation spectral analyses suggest that generation of photoexcited carriers takes place mainly in the quantum confined Si nanowires, whereas their radiative recombination occurs in the Si–N binding states of SiOxNy nanocaps.
Low-glycaemic diets and health: implications for obesity
Authors: Livesey Geoffrey
Published: May 2005

The present review considers the background to terminology that relates foods, glycaemia and health, including ‘available carbohydrate’, ‘glycaemic index’ (GI), 'glycaemic glucose equivalent', 'glycaemic response index' and 'net carbohydrate', and concludes that central to each of these terms is 'glycaemic load' (GL). GL represents the acute increase in exposure of tissue to glucose determined by foods; it is expressed in ingested glucose equivalents (per 100 g fresh weight or per serving), and is regarded as independent of the state of glucose metabolism from normal to type 2 diabetes mellitus (T2DM). Ad libitum studies in overweight or obese adults and children show that low-GL diets are associated with marked weight benefits, loss of adiposity and reduced food intake. Weight benefits appear on low-glycaemic v. high-glycaemic available carbohydrates, unavailable v. available carbohydrates and protein v. available carbohydrate. Energy intake immediately after lowering of meal GL via carbohydrate exchanges is apparent only after a threshold cumulative intake of >2000 MJ. Various epidemiological and interventional studies are discussed. A relationship between GL and the development of T2DM and CHD is evident. Studies that at first seem conflicting are actually consistent when data are overlaid, such that diets with a GL of >120 glucose equivalents/d would appear to be inadvisable. Whereas certain studies might place GI as being slightly stronger than GL in relationto T2DM risk, this situation appears to be associated with observations in a lower range of GL or when the range of GI is too narrow for accuracy; nevertheless, authors emphasise the importance of GL. Among the studies reviewed, GL offers a better or stronger explanation than GI in various observations including body weight, T2DM in nurses, CHD, plasma triacylglycerols, HDL-cholesterol, high-sensitivity C-reactive protein and protein glycation. Where information is available, the associations between risk factors and GL are either similar or stronger in the overweight or obese, as judged by BMI, and apply to both body weight and blood risk factors. The implications tend to favour a long-term benefit of reducing GL, for which further study is necessary to eliminate any possibility of publication bias and to establish results in clinical trials with overweight and obese patients.
Cost-effective measures to prevent obesity: epidemiological basis and appropriate target groups
Authors: Seidell Jacob C. , Nooyens Astrid J. , Visscher Tommy L. S.
Published: May 2005

Cost-effective prevention strategies to prevent weight gain and the development of obesity should be based on appropriate knowledge of the determinants of weight gain. The body of evidence on the dietary determinants of weight gain is, however, fragmentary at best, partly because inappropriate research methods are used to study the determinants of obesity under normal circumstances. Evidence from studies using experimental diets have shortcomings because of their short duration and selection of highly-motivated subjects and because the outcomes can be easily influenced by the choice of foods to be used in the intervention. Of the observational studies, many have severe methodological shortcomings, e.g. ecological studies, cross-sectional surveys and classical cohort studies in which the baseline diet is linked to subsequent weight development over long periods of time. Longitudinal studies with repeated measurements in which changes in diet and physical activity are linked to changes in weight are probably the most informative, but these studies are relatively rare. There is a great interest in interventions that are effective and efficient for the prevention of obesity. Many countries and research funding agencies seem to show a strong tendency to develop interventions for children and adolescents exclusively. It can be easily shown, however, that intervention programmes are much more likely to be cost-effective in older adults than in children, which indicates that adults should not be neglected as target populations for obesity prevention. Obesity prevention should follow a life-course approach, as currently recommended for non-communicable diseases in general by the WHO.
Obesity and metabolic disease: is adipose tissue the culprit?
Authors: Frayn Keith N.
Published: May 2005

Obesity is a risk factor for the development of type 2 diabetes and CVD. Is adipose tissue the culprit in the relationship between obesity and metabolic disease? It iscertainly possible to argue that adipose tissue function is disturbed in obesity in sucha way that adverse consequences may follow. For instance, lipolysis is down regulated, the sensitivity of lipolysis to insulin is reduced and there are disturbances in the regulation of adipose tissue blood flow. However, when examined critically these changes canbe seen as adaptations to the increased adipose tissue mass, making the situation betterrather than worse. In terms of the many peptide and other factors now known to be secreted from adipose tissue, it is easier to argue that adipose tissue is the culprit. However, for no single ‘adipokine’ is there as yet unequivocal evidence of a link between adipose tissue secretion and adverse metabolic events in other tissues. The bestdocumented of these adipokines in relation to insulin resistance is adiponectin. Here, unusually, adiponectin confers insulin sensitivity, and its secretion is down regulated in obesity. It could be again that adipose tissue has down regulated its function in an attempt to compensate for itsincreased mass, although certainly that down-regulation is too extreme. On balance, it is clear that adipose tissue is a link in the chain of events leading to metabolic disease, but in many respects it is an innocent intermediary trying to deal with the consequences of positive energy balance, the real culprit.
Brain–adipose tissue cross talk
Authors: Bartness Timothy J. , Song C. Kay , Shi Haifei , Bowers Robert R. , Foster Michelle T.
Published: May 2005

While investigating the reversible seasonal obesity of Siberian hamsters, direct sympathetic nervous system (SNS) postganglionic innervation of white adipose tissue (WAT) has been demonstrated using anterograde and retrograde tract tracers. The primary function of this innervation is lipid mobilization. The brain SNS outflow to WAT has been defined using the pseudorabies virus (PRV), a retrograde transneuronal tract tracer. These PRV-labelled SNS outflow neurons are extensively co-localized with melanocortin-4 receptor mRNA, which, combined with functional data, suggests their involvement in lipolysis. The SNS innervation of WAT also regulates fat cell number, as noradrenaline inhibits and WAT denervation stimulates fat cell proliferationin vitroandin vivorespectively. The sensory innervation of WAT has been demonstrated by retrograde tract tracing, electrophysiological recording and labelling of the sensory-associated neuropeptide calcitonin gene-related peptide in WAT. Local injections of the sensory nerve neurotoxin capsaicin into WAT selectively destroy this innervation. Just as surgical removal of WAT pads triggers compensatory increases in lipid accretion by non-excised WAT depots, capsaicin-induced sensory denervation triggers increases in lipid accretion of non-capsaicin-injected WAT depots, suggesting that these nerves convey information about body fat levels to the brain. Finally, parasympathetic nervous system innervation of WAT has been suggested, but the recent finding of no WAT immunoreactivity for the possible parasympathetic marker vesicular acetylcholine transporter (VAChT) argues against this claim. Collectively, these data suggest several roles for efferent and afferent neural innervation of WAT in body fat regulation.
Clinical treatment of obesity: are drugs and surgery the answer?
Authors: Kopelman Peter G.
Published: May 2005

Obesity treatment remains a ‘Cinderella’ of all clinical management programmes, but generally without a happy ending. The great expectation for new therapeutic agents has not been fulfilled in clinical practice, whilst the restriction of eating through surgical division of the upper bowel seems strange in an age of advanced and sophisticated technology. The better understanding of the neuro-regulation of appetite, and its application as part of evidence-based clinical interventions, could lead to a more coherent approach to obesity treatment. Nevertheless, investigation of potential neuroendocrine targets for appetite suppression suggests redundancy in the systems, which make development of effective agents against single receptors impractical. Importantly, the progressive rise in the prevalence of obesity will inevitably mean that only a small proportion of afflicted patients will actually be treated by long-term drugs and surgery. Drugs and surgery are not currently the answer for the majority of obese individuals. What is required is a better way of identifying patients who may particularly benefit from such approaches. However, the major emphasis must be the development of effective population-wide interventions that halt the increase in fatness and ensure that future generations maintain and enjoy a healthy body weight.
Lifestyle strategies for weight control: experience from the Finnish Diabetes Prevention Study
Authors: Lindström Jaana , Peltonen Markku , Tuomilehto Jaakko ,   for the Finnish Diabetes Prevention Study Group
Published: May 2005

Currently, in many European countries more than half the adult population is overweight; it hass become ‘abnormal’ to be of ‘normal weight’. The risk of type 2 diabetes, CVD, hypertension and certain forms of cancer increase with increasing weight. Biological evolution has produced body-fat-regulating mechanisms that are more powerful in protecting against weight loss than against weight gain. The current environment offers constant availability of affordable palatable energy-rich foods, with no need to consume the energy through physical activity. The ‘obesogenic’ environment is to some extent a political issue, but it has been shown that the healthcare system can also have a role in preventing obesity-related morbidity. The Finnish Diabetes Prevention Study was the first controlled randomised study to show that individualised lifestyle counselling of individuals with high risk of developing type 2 diabetes can influence diet, physical activity and body weight, and that type 2 diabetes can be prevented, or at least postponed. Most importantly, lifestyle changes do not have to be extreme. If the population would adopt a lifestyle in line with the official nutrition recommendations, the obesity and diabetes trend could at least be stabilised.
Helping individuals to help themselves
Authors: Costain Lyndel , Croker Helen
Published: May 2005

Obesity is a serious and increasing health issue. Approximately two-thirds of adults in the UK are now overweight or obese. Recent public health reports firmly reinforce the importance of engaging individuals to look after their health, including their weight. They also spell out the need for individuals to be supported more actively, on many levels, to enable this ‘engagement’. Meanwhile, national surveys indicate that approximately two-thirds of adults are concerned about weight control, with one-third actively trying to lose weight. This finding is hardly surprising considering current weight statistics, plus the plethora of popular diets on offer. Weight-loss methods include diet clubs, diet books, exercise, meal replacements, advice from healthcare professionals and following a self-styled diet. Obesity is a multi-factorial problem, and losing weight and, in particular, maintaining weight loss is difficult and often elusive. It is argued that the modern obesogenic or ‘toxic’ environment has essentially taken body-weight control from an instinctive ‘survival’ process to one that needs sustained cognitive and skill-based control. The evidence suggests that health professionals can help individuals achieve longer-term weight control by supporting them in making sustainable lifestyle changes using a range of behavioural techniques. These techniques include: assessing readiness to change; self-monitoring; realistic goal setting; dietary change; increased physical activity; stimulus control; cognitive restructuring; relapse management; establishing ongoing support. Consistently working in a client-centred way is also being increasingly advocated and incorporated into practice to help motivate and encourage, rather than hinder, the individual's progress.
Weight management in primary care: how can it be made more effective?
Authors: Maryon-Davis Alan
Published: May 2005

Obesity is often difficult to tackle in primary care. Pressure of time in the consultation, a lack of appropriately-trained primary care staff, a shortage of community dietitians or nutritionists, the potentially enormous caseload, language or cultural barriers and the sheer intractability of patients' eating habits, exercise behaviour and their clinical condition, all conspire to make general practitioners, other team members and often the patients themselves lose heart and stop even trying. However, there are ways of overcoming these difficulties. Examples of changes that evidence suggests are able to support and enhance basic one-to-one interventions in general practice include: improved clinical guidelines; better training of primary care staff; at-risk patient registers; smarter database search tools; new quality incentives; closer working with dietitians, counsellors and pharmacists; more hospital outreach clinics; designated general practitioner specialists and practice clustering; expanded exercise referral schemes and links with leisure providers; subsidised referral to commercial slimming groups; better use of patient groups and voluntary and community workers. The present paper describes a proposed ‘triple-tier’ pathway for weight management incorporating most of the elements mentioned earlier. With a more joined-up and creative approach to the development and organisation of primary care, more comprehensive training and workforce planning, and better integration with social care, voluntary groups and the commercial sector, weight management in general practice has the potential to be much more effective.
The role of plant secondary metabolites in mammalian herbivory: ecological perspectives
Authors: Iason Glenn
Published: May 2005

Plant secondary metabolites (PSM) have many ecological functions, but have long been considered as defences against pathogens or herbivores (vertebrate or invertebrate), reducing the likelihood and extent of attack. However, mammalian herbivores ingest many foods containing PSM and use both behavioural methods and physiological strategies to limit their negative effects. Most physiological counter-adaptations are inducible in response to ingested PSM, providing efficient protection against toxic effects. Possible positive effects of PSM include antioxidant and anthelminthic properties and complex formation between protein and condensed tannins that protects dietary protein from degradation by the symbiotic microflora of foregut fermenters, increasing its utilisation by the animal. This protein effect is probably only beneficial to animals under a narrow range of nutrient-rich conditions found mainly in agricultural systems. There are many examples of PSM causing food avoidance or reducing food intake, but there is as yet relatively little evidence for positive selection of them by herbivores. Although the feedback mechanisms relating the post-ingestive consequences of PSM to subsequent foraging behaviour are beginning to be understood, knowledge of the integration of behavioural and physiological strategies for regulating the effects of PSM is relatively poor. The opportunities for learned avoidance of PSM may be restricted in animals with complex diets that cannot associate a particular feedback signal with a given food type. A greater emphasis on the study of subclinical effects of PSM rather than acute effects, on pharmaco-kinetic studies in relation to behavioural studies and on the use of realistic experimental models is advocated.
Vav1 and Rac Control Chemokine-promoted T Lymphocyte Adhesion Mediated by the Integrin α4β1
Authors: García-Bernal David , Wright Natalia , Sotillo-Mallo Elena , Nombela-Arrieta César , Stein Jens V. , Bustelo Xosé R. , Teixidó Joaquin
Published: May 2005

The chemokine CXCL12 promotes T lymphocyte adhesion mediated by the integrin α4β1. CXCL12 activates the GTPase Rac, as well as Vav1, a guanine-nucleotide exchange factor for Rac, concomitant with up-regulation of α4β1-dependent adhesion. Inhibition of CXCL12-promoted Rac and Vav1 activation by transfection of dominant negative Rac or Vav1 forms, or by transfection of their siRNA, remarkably impaired the increase in T lymphocyte attachment to α4β1 ligands in response to this chemokine. Importantly, inhibition of Vav1 expression by RNA interference resulted in a blockade of Rac activation in response to CXCL12. Adhesions in flow chambers and soluble binding assays using these transfectants indicated that initial ligand binding and adhesion strengthening mediated by α4β1 were dependent on Vav1 and Rac activation by CXCL12. Finally, CXCL12-promoted T-cell transendothelial migration involving α4β1-mediated adhesion was notably inhibited by expression of dominant negative Vav1 and Rac. These results indicate that activation of Vav1-Rac signaling pathway by CXCL12 represents an important inside-out event controlling efficient up-regulation of α4β1-dependent T lymphocyte adhesion.
ACT-5 Is an Essential Caenorhabditis elegans Actin Required for Intestinal Microvilli Formation
Authors: MacQueen A. J. , Baggett J. J. , Perumov N. , Bauer R. A. , Januszewski T. , Schriefer L. , Waddle J. A.
Published: May 2005

Investigation of Caenorhabditis elegans act-5 gene function revealed that intestinal microvillus formation requires a specific actin isoform. ACT-5 is the most diverged of the five C. elegans actins, sharing only 93% identity with the other four. Green fluorescent protein reporter and immunofluorescence analysis indicated that act-5 gene expression is limited to microvillus-containing cells within the intestine and excretory systems and that ACT-5 is apically localized within intestinal cells. Animals heterozygous for a dominant act-5 mutation looked clear and thin and grew slowly. Animals homozygous for either the dominant act-5 mutation, or a recessive loss of function mutant, exhibited normal morphology and intestinal cell polarity, but died during the first larval stage. Ultrastructural analysis revealed a complete loss of intestinal microvilli in homozygous act-5 mutants. Forced expression of ACT-1 under the control of the act-5 promoter did not rescue the lethality of the act-5 mutant. Together with immuno-electron microscopy experiments that indicated ACT-5 is enriched within microvilli themselves, these results suggest a microvillus-specific function for act-5, and further, they raise the possibility that specific actins may be specialized for building microvilli and related structures.
Dynamin Forms a Src Kinase–sensitive Complex with Cbl and Regulates Podosomes and Osteoclast Activity
Authors: Bruzzaniti Angela , Neff Lynn , Sanjay Archana , Horne William C. , De Camilli Pietro , Baron Roland
Published: May 2005

Podosomes are highly dynamic actin-containing adhesion structures found in osteoclasts, macrophages, and Rous sarcoma virus (RSV)-transformed fibroblasts. After integrin engagement, Pyk2 recruits Src and the adaptor protein Cbl, forming a molecular signaling complex that is critical for cell migration, and deletion of any molecule in this complex disrupts podosome ring formation and/or decreases osteoclast migration. Dynamin, a GTPase essential for endocytosis, is also involved in actin cytoskeleton remodeling and is localized to podosomes where it has a role in actin turnover. We found that dynamin colocalizes with Cbl in the actin-rich podosome belt of osteoclasts and that dynamin forms a complex with Cbl in osteoclasts and when overexpressed in 293VnR or SYF cells. The association of dynamin with Cbl in osteoclasts was decreased by Src tyrosine kinase activity and we found that destabilization of the dynamin-Cbl complex involves the recruitment of Src through the proline-rich domain of Cbl. Overexpression of dynamin increased osteoclast bone resorbing activity and migration, whereas overexpression of dynK44A decreased osteoclast resorption and migration. These studies suggest that dynamin, Cbl, and Src coordinately participate in signaling complexes that are important in the assembly and remodeling of the actin cytoskeleton, leading to changes in osteoclast adhesion, migration, and resorption.
Synaptic Clusters of MHC Class II Molecules Induced on DCs by Adhesion Molecule–mediated Initial T-Cell Scanning
Authors: de la Fuente Hortensia , Mittelbrunn María , Sánchez-Martín Lorena , Vicente-Manzanares Miguel , Lamana Amalia , Pardi Ruggero , Cabañas Carlos , Sánchez-Madrid Francisco
Published: May 2005

Initial adhesive contacts between T lymphocytes and dendritic cells (DCs) facilitate recognition of peptide-MHC complexes by the TCR. In this report, we studied the dynamic behavior of adhesion and Ag receptors on DCs during initial contacts with T-cells. Adhesion molecules LFA-1- and ICAM-1,3-GFP as well as MHC class II-GFP molecules were very rapidly concentrated at the DC contact area. Binding of ICAM-3, and ICAM-1 to a lesser extent, to LFA-1 expressed by mature but not immature DC, induced MHC-II clustering into the immune synapse. Also, ICAM-3 binding to DC induced the activation of the Vav1-Rac1 axis, a regulatory pathway involved in actin cytoskeleton reorganization, which was essential for MHC-II clustering on DCs. Our results support a model in which ICAM-mediated MHC-II clustering on DC constitutes a priming mechanism to enhance antigen presentation to T-cells.
Structural and Functional Dissection of the Abp1 ADFH Actin-binding Domain Reveals Versatile In Vivo Adapter Functions
Authors: Quintero-Monzon Omar , Rodal Avital A. , Strokopytov Boris , Almo Steven C. , Goode Bruce L.
Published: May 2005

Abp1 is a multidomain protein that regulates the Arp2/3 complex and links proteins involved in endocytosis to the actin cytoskeleton. All of the proposed cellular functions of Abp1 involve actin filament binding, yet the actin binding site(s) on Abp1 have not been identified, nor has the importance of actin binding for Abp1 localization and function in vivo been tested. Here, we report the crystal structure of the Saccharomyces cerevisiae Abp1 actin-binding actin depolymerizing factor homology (ADFH) domain and dissect its activities by mutagenesis. Abp1-ADFH domain and ADF/cofilin structures are similar, and they use conserved surfaces to bind actin; however, there are also key differences that help explain their differential effects on actin dynamics. Using point mutations, we demonstrate that actin binding is required for localization of Abp1 in vivo, the lethality caused by Abp1 overexpression, and the ability of Abp1 to activate Arp2/3 complex. Furthermore, we genetically uncouple ABP1 functions that overlap with SAC6, SLA1, and SLA2, showing they require distinct combinations of activities and interactions. Together, our data provide the first structural and functional view of the Abp1–actin interaction and show that Abp1 has distinct cellular roles as an adapter, linking different sets of ligands for each function.