bluuebunny/crossref_metadata_2025 huggingface dataset:
Tidal barrier and the asymptotic mass of proto gas-giant planets
Authors: Dobbs-Dixon Ian , Li ShuLin , Lin Douglas N.C.
Published: May 2008

Although late stage gap formation reduces the surface density in the vicinity of protoplanets, simulations suggest gas may continue to leak through the protoplanets tidal barrier, replenishing the gas supply and allowing protoplanets to acquire masses comparable to or larger than that of Jupiter. Global gas depletion is a possible explanation for gaseous planets with lower masses in weak-line T-Tauri disks and ice giants in our own solar system, but it is unlikely to have stalled the growth of multiple systems around nearby stars that contain relatively low-mass, close-in planets along with more massive and longer period companions. Here, we suggest a potential solution. We show that supersonic infall of surrounding gas onto a protoplanet is only possible interior to both its Bondi and Roche radii. Although the initial Bondi radius is much smaller than its Roche radius, the former overtakes the latter during its growth. Thereafter, a positive pressure gradient is required to induce the gas to enter the Roche lobe of the protoplanet and flow is significantly reduced. We present the results of analysis and numerical simulations to show that the accretion rate increases rapidly with the ratio of the protoplanets Roche to Bondi radii. Based on these results we suggest that in regions with low geometric aspect ratios gas accretion is quenched, resulting in relatively low protoplanetary masses.
Formation of heavy element rich giant planets by giant impacts
Authors: Genda H. , Ikoma M. , Guillot T. , Ida S.
Published: May 2008

We have performed the smoothed particle hydrodynamic (SPH) simulations of collisions between two gas giant planets. Changes in masses of the ice/rock core and the H/He envelope due to the collisions are investigated. The main aim of this study is to constrain the origin and probability of a class of extrasolar hot Jupiters that have much larger cores and/or higher core/envelope mass ratios than those predicted by theories of accretion of gas giant planets. A typical example is HD 149026b. Theoretical models of the interior of HD 149026b (Sato et al. 2005; Fortney et al. 2006; Ikoma et al. 2006) predict that the planet contains a huge core of 50-80 Earth masses relative to the total mass of 110 Earth masses. Our SPH simulations demonstrate that such a gas giant is produced by a collision with an impact velocity of typically more than 2.5 times escape velocity and an impact angle of typically less than 10 degrees, which results in an enormous loss of the envelope gas and complete accretion of both cores.
Formation and detectability of Earth-like planets around Alpha-Centauri B
Authors: Davis Erica
Published: May 2008

We simulate the late stages of planet formation around Alpha Centauri B and analyze the detectability of the resulting terrestrial planet systems. The N-body accretionary evolution of a Σ ∝ r−-1 disk populated with 400–900 lunar-mass oligarchs is followed for 200 Myr for each simulation. All of eight runs result in the formation of multiple-planet systems with at least one planet in the 1–2 M⊕ mass range at 0.5–1.5 AU. We examine the detectability of our simulated planetary systems by generating synthetic radial velocity observations including noise based on the radial velocity residuals to the recently published three planet fit to the nearby K0V star HD 69830. Using these synthetic observations, we find that we can reliably detect a 1.8 M⊕ planet in the habitable zone of α Centauri B after only three years of high cadence observations. We also find that the planet is detectable even if the radial velocity precision is 3 ms−1, as long as the noise spectrum is white.
On the formation age of the first planetary system
Authors: Hara T. , Kunitomo S. , Shigeyasu M. , Kajiura D.
Published: May 2008

Recently, it has been observed the extreme metal-poor stars in the Galactic halo, which must be formed just after Pop III objects. On the other hand, the first gas clouds of mass ∼ 106 M⊙ are supposed to be formed at z ∼ 10, 20, and 30 for the 1σ, 2σ and 3σ, where the density perturbations are assumed of the standard ΛCDM cosmology. Usually it is approximated that the distribution of the density perturbation amplitudes is gaussian where σ means the standard deviation. If we could apply this gaussian distribution to the extreme small probability, the gas clouds would be formed at z ∼40, 60, and 80 for the 4σ, 6σ, and 8σ where the probabilities are approximately 3 × 10−5, 10−9, and 10−15. Within our universe, there are almost ∼ 1016 (∼ 1022M⊙/106M⊙) clouds of mass 106M⊙. Then the first gas clouds must be formed around z ∼ 80, where the time is ∼ 20 Myr (∼ 13.7/(1 + z)3/2 Gyr). Even within our galaxy, there are ∼ 105 (∼ 1011M⊙/106M⊙) clouds, then the first gas clouds within our galaxy must be formed around z ∼ 40, where the time is ∼ 54 Myr (∼ 13.7/(1+z)3/2Gyr).

The evolution time for massive star (∼ 102M⊙) is ∼ 3 Myr and the explosion of the massive supernova distributes the metal within a cloud. The damping time of the supernova shock wave in the adiabatic and isothermal era is several Myr and stars of the second generation (Pop II) are formed within a free fall time ∼ 20 Myr. Even if the gas cloud is metal poor, there is a lot of possibility to form the planets around such stars. The first planetary systems could be formed within ∼ 6 × 107 years after the Big Bang in the universe. Even in our galaxies, the first planetary systems could be formed within ∼ 1.7 × 108 years. If the abundance of heavy elements such as Fe is small compared to the elements of C, N, O, the planets must be the one where the rock fraction is small. It is interesting to wait the observations of planets around metal-poor stars. For the panspermia theory, the origin of life could be expected in such systems.
Origin of debris disks and the supply of metals in DZ white dwarfs
Authors: Wang Y. , Dong R. B. , Lin D. N. C. , Liu X. W.
Published: May 2008

We discuss the dynamical evolution of minor planetary bodies in the outer regions of planetary systems around the progenitors of DZ white dwarfs. We show that during the planetary-nebula phase of these stars, mass loss can lead to the expansion of all planetary bodies. The orbital eccentricity of the minor bodies, as relics of planetesimals, may be largely excited by the perturbation due to both gas drag effects and nearby gas giant planets. Some of these bodies migrate toward the host star, while others are scattered out of the planetary system. The former have modest probability of being captured by the sweeping secular resonances of giant planets, and induced to migrate toward the host star. When they venture close to their host stars, their orbits are tidally circularized so that they form compact disks where they may undergo further collisionally driven evolution. During the subsequent post main sequence evolution of their host stars, this process may provide an avenue which continually channels heavy elements onto the surface of the white dwarfs. We suggest that this scenario provides an explanation for the recently discovered Calcium line variation in G29-38.
Dynamics and instabilities in exoplanetary systems
Authors: Ford Eric B.
Published: May 2008

Extrasolar planet surveys have discovered over two dozen multiple planet systems. As radial velocity searches push towards higher precisions and longer survey durations, they can be expected to discover an even higher fraction of multiple planet systems. Combined with radial velocity data, dynamical studies of these systems can constrain planet masses and inclinations, measure the significance of resonant and secular interactions, and provide insights into the formation and evolution of these systems. Here, we review the dynamical properties of known extrasolar multiple planet systems and their implications for planet formation theory. We conclude by outlining pressing questions to be addressed by a combination of future observations and theoretical research.
Analysis of near-separatrix motion in planetary systems
Authors: Wang Su , Zhou Ji-Lin
Published: May 2008

Near-separatrix motion is a kind of motion of two planets with their relative apsidal longitude near the boundary between libration and circulation. Observed multiple planetary systems seem to favor near-separatrix motions between neighboring planets. In this report, we study the probability that near-separatrix motion occurs with both the linear secular system and full three-body systems. We find that generally the ratio of near-separatrix motion is small unless the eccentricities of the two planets differ from each other by an order of magintude, or they are in mean motion resonance. To explore the dynamical procedures causing the near-separatrix motion, we suppose a modification to scattering model by adding a mass-accretion process during the protoplanet growth. Statistics on the modified scattering model indicate that the probability of the final planet pairs in near-separatrix motion is high (∼ 85%), which may explain the high occurrence of near-separatrix motions in observed planetary systems.
Retrograde resonances in compact multi-planetary systems: a feasible stabilizing mechanism
Authors: Gayon Julie , Bois Eric
Published: May 2008

Multi-planet systems detected until now are in most cases characterized by hot-Jupiters close to their central star as well as high eccentricities. As a consequence, from a dynamical point of view, compact multi-planetary systems form a variety of the general N-body problem (with N ≥ 3), whose solutions are not necessarily known. Extrasolar planets are up to now found in prograde (i.e. direct) orbital motions about their host star and often in mean-motion resonances (MMR). In the present paper, we investigate a theoretical alternative suitable for the stability of compact multi-planetary systems. When the outer planet moves on a retrograde orbit in MMR with respect to the inner planet, we find that the so-called retrograde resonances present fine and characteristic structures particularly relevant for dynamical stability. We show that retrograde resonances and their resources open a family of stabilizing mechanisms involving specific behaviors of apsidal precessions. We also point up that for particular orbital data, retrograde MMRs may provide more robust stability compared to the corresponding prograde MMRs.
Coupling between density structures, electromagnetic waves and ionospheric feedback in the auroral zone
Authors: Streltsov A. V. , Lotko W.
Published: May 2008

This paper presents results from a numerical study of nonlinear interactions between ultra‐low‐frequency (ULF) electromagnetic waves and the magnetospheric‐ionospheric plasma at high latitudes. The study is motivated by observations of density cavities in the ionosphere in regions of downward field‐aligned current adjacent to auroral arcs. The role of active ionospheric feedback in the development of intense, small‐scale electromagnetic waves with frequencies of 0.1–1 Hz is considered, together with the effects of the waves on the ion dynamics. The numerical results are based on a reduced two‐fluid MHD model that self‐consistently describes shear Alfvén waves, ion parallel dynamics, and effects of ionospheric E‐region activity and magnetosphere‐ionosphere feedback instability. Numerical simulations performed in dipole magnetic field geometry with realistic parameters of the ambient plasma show that, under some conditions, ionospheric feedback gives rise to intense ULF electromagnetic waves, which, via the ponderomotive force, produce density cavities in the bottomside ionosphere (between the E‐ and F‐region peaks) and an associated upwelling of the topside ionosphere. The simulated magnitude and spatial and temporal scales of the cavities match the corresponding parameters of cavities observed with ground‐based radars.
Estimation of shelf‐slope exchanges induced by frontal instability near submarine canyons
Authors: Jordi A. , Klinck J. M. , Basterretxea G. , Orfila A. , Tintoré J.
Published: May 2008

The dynamics associated with the propagation of unstable waves along a density front and their interaction with submarine canyons are simulated and analyzed with a fine‐resolution three‐dimensional primitive equation coastal ocean model. Simulations consider flow in an alongshore density front over two bottom topographies: an idealized straight shelf and a shelf incised by a canyon. The stationary circulation over the idealized shelf exhibits a geostrophic balance that is perturbed when the canyon topography is introduced. Enhanced cross‐shore and vertical motions are produced as a result of the front‐canyon interaction. A second set of simulations consider the effect of a small perturbation superimposed on the frontal circulation which develops growing meanders. In this case, the perturbation over the shelf grows rapidly by baroclinic instability into a steepened backward breaking wave characterized by significant cross‐shore and vertical motions. The canyon topography accelerates or slows the development of the perturbation depending on the relative position of the unstable waves and the canyon. Finally, we use model results to determine the shelf‐slope exchanges based on two methodologies. The first method computes the water transported across the shelf break while the second accounts for cross‐shore displacements of water. The application of both approaches reveals that not all water transported across the shelf break is effectively exchanged between the shelf and the open ocean. However, cross‐shore and vertical motions are enhanced by the unstable front and the submarine canyon leading to a large exchange between shelf and open ocean waters.
Persistent downregulation of hippocampal CREB mRNA parallels a Y‐maze deficit in adolescent rats following semi‐chronic amphetamine administration
Authors: Featherby T , Van Den Buuse M , Lubman D I , Lawrence A J
Published: May 2008

Background and purpose:

We investigated possible differences in the impact of chronic amphetamine administration during adolescence and adulthood on aspects of behaviour and brain chemistry.

Experimental approach:

Adult (n=32) and adolescent (n=32) male Sprague–Dawley rats were given either D‐amphetamine sulphate (10 mg kg−1 daily, i.p.) or saline (1 mL kg−1, i.p.) for 10 days. Rats were subsequently tested for anxiety‐like behaviour, learning and memory, and sensorimotor gating. Nine weeks later, rats received saline (1 mL kg−1) or acute amphetamine challenge (1.5 mg kg−1) and the expression levels of mRNA for tyrosine kinase B (TrkB) or cAMP response element‐binding protein (CREB) were measured in the hippocampus.

Key results:

The adolescent amphetamine pretreated group revealed a deficit in exploration on the Y‐maze during a 6 h retention test. The frequency of visits to the novel arm was 35% lower for the amphetamine group compared with controls. In parallel, a 43% decrease in hippocampal CREB mRNA, but not TrkB mRNA, was observed in periadolescent rats treated chronically with amphetamine 9 weeks earlier. None of the effects were detected in the adult treated cohort.

Conclusions and implications:

Chronic amphetamine treatment during periadolescence resulted in altered behaviour on the Y‐maze and persistent downregulation of hippocampal CREB mRNA expression. Given that this group had intact spatial learning and reference memory, it would appear that the deficits observed on the Y‐maze reflect a dysfunction in response to novelty. Because no effects of amphetamine treatment were observed in the adult cohort, these data suggest idiosyncratic sensitivity of periadolescence to the long‐term effects of psychostimulants.

British Journal of Pharmacology (2008) 154, 417–428; doi:10.1038/bjp.2008.126
From ultrasocial to antisocial: a role for oxytocin in the acute reinforcing effects and long‐term adverse consequences of drug use?
Authors: McGregor I S , Callaghan P D , Hunt G E
Published: May 2008

Addictive drugs can profoundly affect social behaviour both acutely and in the long‐term. Effects range from the artificial sociability imbued by various intoxicating agents to the depressed and socially withdrawn state frequently observed in chronic drug users. Understanding such effects is of great potential significance in addiction neurobiology. In this review we focus on the ‘social neuropeptide’ oxytocin and its possible role in acute and long‐term effects of commonly used drugs. Oxytocin regulates social affiliation and social recognition in many species and modulates anxiety, mood and aggression. Recent evidence suggests that popular party drugs such as MDMA and gamma‐hydroxybutyrate (GHB) may preferentially activate brain oxytocin systems to produce their characteristic prosocial and prosexual effects. Oxytocin interacts with the mesolimbic dopamine system to facilitate sexual and social behaviour, and this oxytocin‐dopamine interaction may also influence the acquisition and expression of drug‐seeking behaviour. An increasing body of evidence from animal models suggests that even brief exposure to drugs such as MDMA, cannabinoids, methamphetamine and phencyclidine can cause long lasting deficits in social behaviour. We discuss preliminary evidence that these adverse effects may reflect long‐term neuroadaptations in brain oxytocin systems. Laboratory studies and preliminary clinical studies also indicate that raising brain oxytocin levels may ameliorate acute drug withdrawal symptoms. It is concluded that oxytocin may play an important, yet largely unexplored, role in drug addiction. Greater understanding of this role may ultimately lead to novel therapeutics for addiction that can improve mood and facilitate the recovery of persons with drug use disorders.

British Journal of Pharmacology (2008) 154, 358–368; doi:fn1
Crocetin improves the insulin resistance induced by high‐fat diet in rats
Authors: Sheng L , Qian Z , Shi Y , Yang L , Xi L , Zhao B , Xu X , Ji H
Published: May 2008

Background and purpose:

The amelioration of insulin resistance by treatment with crocetin is closely related to the hypolipidaemic effect. The present study is designed to clarify the insulin‐sensitizing mechanism of crocetin by elucidating the mechanism of regulation of lipid metabolism by crocetin.

Experimental approach:

Rats given a high‐fat diet were treated with crocetin for 6 weeks before hyperinsulinaemic–euglycaemic clamp. 14C‐palmitate was used as tracer to track the fate of non‐esterified fatty acids or as substrate to measure β‐oxidation rate. Triglyceride clearance in plasma and lipoprotein lipase activity in tissues were tested. Content of lipids in plasma and tissues was determined. Real‐time PCR was used to assay the level of mRNA from genes involved in non‐esterified fatty acid and triglyceride uptake and oxidation.

Key results:

Crocetin prevented high‐fat‐diet induced insulin resistance (increased clamp glucose infusion rate), raised hepatic non‐esterified fatty acid uptake and oxidation, accelerated triglyceride clearance in plasma, enhanced lipoprotein lipase activity in liver, and reduced the accumulation of detrimental lipids (DAG and long‐chain acyl CoA) in liver and muscle. Genes involved in hepatic lipid metabolism which are regulated by peroxisome proliferator‐activated receptor‐α, were modulated to accelerate lipid uptake and oxidation.

Conclusions and implications:

Through regulating genes involved in lipid metabolism, crocetin accelerated hepatic uptake and oxidation of non‐esterified fatty acid and triglyceride, and reduced lipid availability to muscle, thus decreasing lipid accumulation in muscle and liver, and consequently improving sensitivity to insulin.

British Journal of Pharmacology (2008) 154, 1016–1024; doi:10.1038/bjp.2008.160; published online 12 May 2008
In vivopharmacological evaluation of compound 48/80‐induced airways oedema by MRI
Authors: Karmouty‐Quintana H , Blé F‐X , Cannet C , Zurbruegg S , Fozard J R , Page C P , Beckmann N
Published: May 2008

Background and purpose:

Allergen‐induced airways oedema in actively sensitized rats has been studied earlier by magnetic resonance imaging (MRI). We used MRI to follow the consequences of non‐immunological mast cell activation induced by compound 48/80 in the rat lungsin vivo.

Experimental approach:

Male naïve rats were scanned by MRI prior to and at several time points following intratracheal administration of the mast cell secretagogue, compound 48/80. The effects of a range of drugs on the response induced by compound 48/80 were studied.

Key results:

Strong fluid signals were detected by MRI in the lungs at 24 h after compound 48/80, correlating with increased protein concentration and inflammatory cell infiltration in bronchoalveolar lavage, and with perivascular oedema observed histologically. Pharmacological intervention demonstrated that the increase in MRI signal volume induced by compound 48/80 24 h after challenge was blocked by disodium cromoglycate and the glucocorticoid, budesonide. Pretreatment with wortmannin, capsazepine, DNK333 (a dual neurokinin (NK) 1 and NK2 antagonist) or the anti‐allergy drug CGS8515, but not indomethacin, resulted in partial inhibition.

Conclusions and implications:

Compound 48/80 induced a complex inflammatory reaction which did not solely involve mast cell degranulation but also activation of sensory nerves and was qualitatively similar to allergen challenge. Changes observed by MRI correlated with decreases in protein concentration in BAL fluid. However, the magnitude of the changes detected was greater using MRI. Our results demonstrate that MRI is a sensitive and efficient tool to assess the effects of drugs on lung inflammation.

British Journal of Pharmacology(2008)154, 1063–1072; doi:10.1038/bjp.2008.174; published online 12 May 2008
Brain oxytocin receptors mediate ejaculation elicited by 7‐hydroxy‐2‐(di‐N‐propylamino) tetralin (7‐OH‐DPAT) in anaesthetized rats
Authors: Clément P , Peeters M , Bernabé J , Denys P , Alexandre L , Giuliano F
Published: May 2008

Background and purpose:

The involvement of the neuropeptide oxytocin in the control of male sexual responses is documented although its exact mechanisms of action, and especially the site(s) of action, are not fully delineated. In order to clarify this issue, we tested the effects of a peptide oxytocin antagonist delivered through different routes on sexual responses elicited, in anaesthetized male rats, by i.c.v. 7‐hydroxy‐2‐(di‐N‐propylamino) tetralin (7‐OH‐DPAT), a dopamine agonist, preferentially active on D3receptors.

Experimental approach:

Seminal vesicle pressure (SVP) and bulbospongiosus muscle (BS) electromyograms were recorded as physiological markers of emission and expulsion phases of ejaculation respectively and intracavernosal pressure (ICP) was monitored as a physiological marker of erection.

Key results:

When injected i.v., the oxytocin antagonist did not impair 7‐OH‐DPAT‐induced SVP and ICP responses while BS burst frequency was diminished. When delivered i.c.v., the oxytocin antagonist dose‐dependently inhibited occurrence of 7‐OH‐DPAT‐induced sexual responses. When delivered intrathecally (i.t.) at the level of the 6thlumbar (L6) segment, but not the 13ththoracic (T13) segment, the oxytocin antagonist reduced the duration of BS responses and the occurrence of ejaculation without impairing ICP responses.

Conclusions and implications:

Brain oxytocin receptors mediate male sexual responses elicited by i.c.v. 7‐OH‐DPAT in anaesthetized rats whereas L6 spinal oxytocin receptors only impair the occurrence of ejaculation. Peripheral oxytocin receptors are marginally involved in 7‐OH‐DPAT‐induced sexual responses. These findings should be considered for the development of potential pharmacological treatment of premature ejaculation in man.

British Journal of Pharmacology(2008)154, 1150–1159; doi:10.1038/bjp.2008.176; published online 12 May 2008
Endothelial nitric oxide attenuates Na+/Ca2+exchanger‐mediated vasoconstriction in rat aorta
Authors: Zhao J , Majewski H
Published: May 2008

Background and purpose:

The Na+/Ca2+exchanger (NCX) may be an important modulator of Ca2+entry and exit. The present study investigated whether NCX was affected by prostacyclin and nitric oxide (NO) released from the vascular endothelium, as NCX contains phosphorylation sites for PKA and PKG.

Experimental approach:

Rat aortic rings were set up in organ baths. Tension was measured across the ring with a force transducer.

Key results:

Lowering extracellular [Na+] ([Na+]o) to 1.18 mMinduced vasoconstriction in rat endothelium‐denuded aortic rings. This effect was blocked by the NCX inhibitor KB‐R7943 (2‐2‐[4‐(4‐nitrobenzyloxy)phenyl] ethyl isothiourea methanesulphonate; 1 μM). In endothelium‐intact aortic rings, decreasing [Na+]odid not constrict the aortic rings significantly, but after treatment with the guanylate cyclase inhibitor ODQ (1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one; 1 μM) or the NOS inhibitorL‐NAME (Nω‐nitro‐L‐arginine methyl ester; 50 μM), a vasoconstriction that was similar in size to that in endothelium‐denuded preparations was evident. The vasorelaxation induced by the NO donor sodium nitroprusside sodium nitroprusside dihydrate (30 nM) was the same in the endothelium‐denuded aortic rings preconstricted with either low Na+(1.18 mM), the thromboxane A2 agonist U46619 (9,11‐dideoxy‐9α, 11α‐methanoepoxy prostaglandin F2α; 0.1 μM) or high K+(80 mM).

Conclusions and implications:

The results suggest that the endothelium inhibits NCX operation via guanylate cyclase/NO. This is stronger than for other constrictors such as phenylephrine and may relate to concomitant NCX‐stimulated NO release from the endothelium. This finding may be important where NCX operates in reverse mode, such as during ischaemia, and highlights a new mechanism whereby the endothelium modulates Ca2+homoeostasis in vascular smooth muscle.

British Journal of Pharmacology(2008)154, 982–990; doi:10.1038/bjp.2008.178; published online 12 May 2008
Interactions between cell death induced by statins and 7‐ketocholesterol in rabbit aorta smooth muscle cells
Authors: Martinet W , Schrijvers D M , Timmermans J‐P , Bult H
Published: May 2008

Background and purpose:

7‐Ketocholesterol, an oxysterol present in atherosclerotic lesions, induces smooth muscle cell (SMC) death, thereby destabilizing plaques. Statins protect patients from myocardial infarction, though they induce SMC apoptosis. We investigated whether statins and 7‐ketocholesterol exerted additive cell death effects.

Experimental approach:

Cultured rabbit aorta SMCs (passage 2–6) were exposed to 7‐ketocholesterol with or without fluvastatin, simvastatin or pravastatin. Uptake of neutral red (NR), monolayer protein, cleavage of the pan‐caspase substrate Asp‐Glu‐Val‐Asp‐rhodamine110, cell morphology (light and electron microscopy) and processing of microtubule‐associated protein 1 light chain 3 (LC3, immunoblot) were determined.

Key results:

NR uptake declined upon 18 h exposure to 25 μM 7‐ketocholesterol (−41±3%, n=13), 100 μM fluvastatin (−59%) or 30–100 μM simvastatin (−28 to −74%). Oxysterol and high statin concentrations exerted additive effects, but lower concentrations (fluvastatin 10–30 μM, simvastatin 1–10 μM) partly reversed viability loss. 7‐Ketocholesterol caused intense cytoplasmic vacuolization, processing of LC3‐I to LC3‐II, but little caspase activation (increase 29.5%). Fluvastatin (10–100 μM, 70–545% increase) and simvastatin (3–100 μM 43–322% increase) induced caspase activation without LC3 processing, but failed to activate caspases in 7‐ketocholesterol‐treated SMCs. Pravastatin up to 100 μM was always inactive.

Conclusions and implications:

7‐Ketocholesterol caused SMC death, mainly via autophagic vesicle formation with LC3 processing, whereas lipophilic statins evoked SMC apoptosis. Cell death following 7‐ketocholesterol and low statin concentrations were not additive, presumably because the autophagic process interfered with statin‐induced caspase activation. This further illustrates that drug effects in normal SMCs are not necessarily predictive for activities in atherosclerotic settings.

British Journal of Pharmacology (2008) 154, 1236–1246; doi:10.1038/bjp.2008.181; published online 12 May 2008
The dimeric form of Ca2+-ATPase is involved in Ca2+ transport in the sarcoplasmic reticulum
Authors: Ushimaru Makoto , Fukushima Yoshihiro
Published: May 2008

To identify the functional unit of Ca2+-ATPase in the sarcoplasmic reticulum, we assessed Ca2+-transport activities occurring on sarcoplasmic reticulum membranes with different combinations of active and inactive Ca2+-ATPase molecules. We prepared heterodimers, consisting of a native Ca2+-ATPase molecule and a Ca2+-ATPase molecule inactivated by FITC labelling, by fusing vesicles loaded with each type of Ca2+-ATPase. The heterodimers exhibited neither Ca2+ transport nor ATP hydrolysis, suggesting that Ca2+ transport by the Ca2+-ATPase requires an interaction between functional Ca2+-ATPase monomers. This finding implies that the functional unit of the Ca2+-ATPase is a dimer.
Plant plasma membrane water channels conduct the signalling molecule H2O2
Authors: Dynowski Marek , Schaaf Gabriel , Loque Dominique , Moran Oscar , Ludewig Uwe
Published: May 2008

H2O2 is a relatively long-lived reactive oxygen species that signals between cells and organisms. H2O2 signalling in plants is essential for response to stress, defence against pathogens and the regulation of programmed cell death. Although H2O2 diffusion across membranes is often considered as a passive property of lipid bilayers, native membranes represent significant barriers for H2O2. In the present study we addressed the question of whether channels might facilitate H2O2 conduction across plasma membranes. The expression of several plant plasma membrane aquaporins in yeast, including PIP2;1 from Arabidopsis (where PIP is plasma membrane intrinsic protein), enhanced the toxicity of H2O2 and increased the fluorescence of dye-loaded yeast when exposed to H2O2. The sensitivity of aquaporin-expressing yeast to H2O2 was altered by mutations that alter gating and the selectivity of the aquaporins. The conduction of water, H2O2 and urea was compared, using molecular dynamics simulations based on the crystal structure of SoPIP2;1 from spinach. The calculations identify differences in the conduction between the substrates and reveal channel residues critically involved in H2O2 conduction. The results of the calculations on tetramers and monomers are in agreement with the biochemical data. Taken together, the results strongly suggest that plasma membrane aquaporin pores determine the efficiency of H2O2 signalling between cells. Aquaporins are present in most species and their capacity to facilitate the diffusion of H2O2 may be of physiological significance in many organisms and particularly in communication between different species.
Molecular control of the glucan synthase-like protein NaGSL1 and callose synthesis during growth of Nicotiana alata pollen tubes
Authors: Brownfield Lynette , Wilson Sarah , Newbigin Ed , Bacic Antony , Read Steve
Published: May 2008

The protein NaGSL1 (Nicotiana alata glucan synthase-like 1) is implicated in the synthesis of callose, the 1,3-β-glucan that is the major polysaccharide in the walls of N. alata (flowering tobacco) pollen tubes. Here we examine the production, intracellular location and post-translational processing of NaGSL1, and relate each of these to the control of pollen-tube callose synthase (CalS). The 220 kDa NaGSL1 polypeptide is produced after pollen-tube germination and accumulates during pollen-tube growth, as does CalS. A combination of membrane fractionation and immunoelectron microscopy revealed that NaGSL1 was present predominantly in the endoplasmic reticulum and Golgi membranes in younger pollen tubes when CalS was mostly in an inactive (latent) form. In later stages of pollen-tube growth, when CalS was present in both latent and active forms, a greater proportion of NaGSL1 was in intracellular vesicles and the plasma membrane, the latter location being consistent with direct deposition of callose into the wall. N. alata CalS is activated in vitro by the proteolytic enzyme trypsin and the detergent CHAPS, but in neither case was activation associated with a detectable change in the molecular mass of the NaGSL1 polypeptide. NaGSL1 may thus either be activated by the removal of a few amino acids or by the removal of another protein that inhibits NaGSL1. These findings are discussed in relation to the control of callose biosynthesis during pollen germination and pollen-tube growth.
Measurement of the junction temperature in high-power light-emitting diodes from the high-energy wing of the electroluminescence band
Authors: Vaitonis Z. , Vitta P. , Žukauskas A.
Published: May 2008

By using pulsed driving currents with a small duty cycle, the high-energy wing of the electroluminescence band in AlGaInP and InGaN high-power light-emitting diodes (LEDs) was calibrated to measure the junction temperature in the range of 223–358K. In a red AlGaInP LED with a thick active layer, an accuracy of 2% was achieved for the junction temperature derived from the high-energy slope in the spectral range free from parasitic absorption by taking into account the three-dimensional density of band states. Meanwhile, the far high-energy region of the slope distorted by parasitic absorption can be used for the extraction of the junction temperature by using only an appropriate linear correction procedure (∼7% accuracy). In a blue InGaN LED with multiple-quantum-well active layers, the junction temperature can be determined with an accuracy of 2% from the inverse derivative of the spectra in a narrow spectral region ∼150meV above the peak energy by using a linear correction.
Wireless drive of a piezoelectric plate by capacitorlike structure in electric resonance with an inductor
Authors: Bhuyan Satyanarayan , Hu Junhui , Sun Chang Qing
Published: May 2008

A new technique of wirelessly transmitting electric energy to piezoelectric components is explored. In the design, an ac electric field is focused to a piezoelectric plate placed between plate-shaped live and needle ground electrodes which form a capacitorlike electric field generator in series with an inductor. The transmission of electric energy is enhanced when the capacitorlike electric field generator and inductor are in electric resonance. Experimentally it has been found that the real output power delivered to the piezoelectric plate depends on the electrode pattern, vibration mode, and electrical load of the piezoelectric component and the electric field focused by the needle ground and live electrodes. When the operating frequency is close to mechanical resonance frequency of the piezoelectric plate operating in the thickness vibration mode, a maximum output power of 0.264W and energy conversion efficiency of 1.02% have been achieved with an input voltage 150Vrms and 10mm electrode separation.
Damping of sound waves in the terahertz range and strength of the boson peak
Authors: Bove Livia E. , Petrillo C. , Fontana A. , Sokolov A. P.
Published: May 2008

By applying a new two-step line-shape analysis to inelastic neutron and x-ray scattering spectra of glassy systems, we were able to resolve the acoustic excitations from the low-frequency excess modes and to accurately estimate the damping of sound waves in the terahertz frequency range. Using this approach, we estimated the damping parameter for terahertz acoustic waves in a wide class of chemically different glasses and did a quantitative comparison of the results with prediction of theoretical models. By comparing the estimates of the mean-free path of the acoustic modes in different glasses and the corresponding boson peak strengths, we show the existence of a simple correlation between these two quantities. The relationship between attenuation of the terahertz acoustic modes, strength of the boson peak, and fragility is discussed.
Saturation of tearing modes in reversed field pinches with locally linear force-free magnetic fields and its application to quasi-single-helicity states
Authors: Tassi E. , Militello F. , Porcelli F. , Hastie R. J.
Published: May 2008

A simple formula for predicting the width of a saturated island, formed as a consequence of tearing perturbation of linear force-free fields in cylindrical geometry, is derived. The formula makes it possible to calculate the saturated island width in terms of the values of parameters characterizing the initial force-free equilibrium and can be applied to equilibria of interest for reversed field pinches. In particular it is applied, in this paper, to force-free equilibria with piecewise constant radial profile of the pinch parameter, which have been recently suggested to be relevant for the formation of quasi-single-helicity states. The main result is that the island width becomes larger as a parameter, that quantifies the departure from a relaxed Taylor state, increases.
Static tuning band gaps of three-dimensional photonic crystals in subterahertz frequencies
Authors: Chen Weiwu , Kirihara Soshu , Miyamoto Yoshinari
Published: May 2008

Microscale three-dimensional photonic crystals with different dielectric volume fractions (β) were fabricated to tune the band gaps in the subterahertz frequency range. When changed β from 33% to 20% in the SiO2–Al2O3 ceramic-resin photonic crystals with a lattice constant of 500μm, the measured first band gaps were increased from 380–450to450–520GHz. After dewaxing and sintering, the lattice constant of SiO2–Al2O3 ceramic photonic crystals were shrunk to 380μm, and the observed band gaps correspondingly appeared from 470–540GHzto520–600GHz. These experimental results were further confirmed by calculation of band diagrams using the plan wave expansion method.
Magnetization behavior of ordered and high density Co nanowire arrays with varying aspect ratio
Authors: Kartopu G. , Yalçın O. , Es-Souni M. , Başaran A. C.
Published: May 2008

Densely packed and ordered cobalt nanowire (NW) arrays with aspect ratios (wire length/diameter) varying between 5 and 250 have been fabricated via electrodeposition into alumina templates. The wire length and diameter were controlled by monitoring the total deposited charge or by adjusting the template pore size, respectively. It is observed from room temperature magnetization curves that the magnetic properties of a given array is largely dependent on the aspect ratio and packing factor. It is shown that behavior of magnetic NW arrays are governed to a large extent by the magnetostatic interactions between NWs and that magnitude of the interaction field increases not only with NW diameter (or packing factor) but also with NW length.
Oxygen defect accumulation at Si:HfO2 interfaces
Authors: Tang C. , Ramprasad R.
Published: May 2008

It has been shown earlier that thermodynamic and kinetic driving forces exist for an isolated oxygen defect to segregate to Si:HfO2 interfaces. In the present work, using the first principles calculations, we show that the accumulation of multiple point defects (O vacancies and interstitials) at Si:HfO2 interfaces is also thermodynamically favored and this preference is relatively insensitive to the areal density of interfacial defects. These results indicate that the O point defect chemistry can provide a rationale for the formation of interfacial phases.
Relating on-shell and off-shell formalisms in perturbative quantum field theory
Authors: Brouder Christian , Dütsch Michael
Published: May 2008

In the on-shell formalism (mostly used in perturbative quantum field theory), the entries of the time-ordered product T are on-shell fields (i.e., the basic fields satisfy the free field equations). With that, (multi)linearity of T is incompatible with the action Ward identity. This can be circumvented by using the off-shell formalism in which the entries of T are off-shell fields. To relate on- and off-shell formalisms correctly, a map σ from on-shell fields to off-shell fields was axiomatically introduced by Dütsch and Fredenhagen [Common. Math. Phys. 243, 275 (2003)]. In that paper it is shown that, in the case of one real scalar field in N=4 dimensional Minkowski space, these axioms have a unique solution. However, this solution is only recursively given there. We solve this recurrence relation and give a fully explicit expression for σ in the cases of the scalar, Dirac, and gauge fields for arbitrary values of the dimension N.
Influence of synthetic nucleation layers on the microstructure, magnetic properties, and recording performance of CoCrPt–SiO2 perpendicular recording media
Authors: Srinivasan Kumar , Wong Seng Kai , Piramanayagam S. N. , Kay Yew Seng
Published: May 2008

The performance of CoCrPt–SiO2 perpendicular recording media, which incorporate synthetic nucleation layers for inducing grain size control, was evaluated with regard to the crystallographic, microstructural, magnetic, interfacial, and recording properties. The media structure consisted of a 14 nm thick CoCrPt–SiO2 recording layer sputtered on two stacked Ru intermediate layers. When a submonolayer thick synthetic nucleation layer was inserted between the two Ru intermediate layers, the grain size and grain size dispersion were significantly reduced in both the upper Ru layer and the recording layer. An average grain size of 5.8 nm with 20% dispersion was achieved for the recording layer. The crystallographic growth of the Co (00·2) perpendicular texture remained unaffected with the Δθ50 at ∼4.4°; the coercivity was ∼2800 Oe and the coercivity squareness was ∼0.6. The roughness of the interface between the synthetic nucleation layer and the upper Ru intermediate layer did not significantly change, and the surface roughness was also relatively unchanged at ∼2.5 Å. An improvement in the signal-to-noise ratio by 1.5 dB was observed due to the synthetic nucleation layer. The effectiveness of the synthetic nucleation layer approach toward achieving grain size control and improving the performance of the CoCrPt–SiO2 perpendicular recording media is demonstrated.
Extended longitudinal vector and Bragg magneto-optic Kerr effect for the determination of the chirality distribution in magnetic vortices
Authors: Lee Min-Sang , Westphalen Andreas , Remhof Arndt , Schumann Alexandra , Zabel Harmut
Published: May 2008

We have measured longitudinal magneto-optic Kerr effect (MOKE) for off-specular beams diffracted by a square array of Permalloy nanodots outside the plane of incidence and found that only the measurements performed outside the plane of incidence are sensitive to the distribution of rotational sense of vortices (vortex chirality) in the dot array. An asymmetry was introduced into the dot shape to ensure a uniform vortex chirality distribution in the dot array and to obtain a clear, well-defined chirality contrast in the MOKE signal. We also demonstrate an alternative method to measure the vortex chirality in dots of asymmetric shape without switching the chirality during magnetization reversal. In addition to the experiment, we have developed a general formalism that can be used to describe MOKE measured for off-specular beams inside as well as outside of the plane of incidence in all three Kerr geometries (polar, longitudinal, and transversal) with an arbitrary polarization state of incident light. Combined with micromagnetic simulation, this formalism reproduces the experimental results well.
Surface-plasmon-enhanced frequency upconversion in Pr3+ doped tellurium-oxide glasses containing silver nanoparticles
Authors: Rai Vineet Kumar , Menezes Leonardo de S. , de Araújo Cid B. , Kassab Luciana R. P. , da Silva Davinson M. , Kobayashi Renata A.
Published: May 2008

A frequency upconversion process in Pr3+ doped TeO2–ZnO glasses containing silver nanoparticles is studied under excitation with a nanosecond laser operating at 590 nm, in resonance with the H34→D12 transition. The excited Pr3+ ions exchange energy in the presence of the nanoparticles, originating efficient conversion from orange to blue. The enhancement in the intensity of the luminescence at ∼482 nm, corresponding to the P30→H34 transition, is due to the influence of the large local field on the Pr3+ ions, which are located near the metallic nanoparticles.
Anomalous lattice relaxation mechanics in ZnO/SiC heterostructure
Authors: Ashrafi Almamun , Segawa Yusaburo
Published: May 2008

Anomalous lattice relaxation mechanics in ZnO epitaxy deposited on 6H-SiC substrates has been addressed. Thickness-dependent ZnO epitaxy showed that the lattice/strain relaxes into two steps for the layer thicknesses of (i) 10–20 nm, after overcoming the critical thickness of <6 nm and (ii) 480–1000 nm, after the complete strain relaxation. This lattice relaxation contrast has been represented with a schematic model by emphasizing on the tensile and compressive strains associated with the lattice mismatches in ZnO/SiC heterostructure of <5%. These asymmetric consequences were found also in the optical and structural properties of ZnO layers by squeezing the bandgap energy and disordering the x-ray spectral broadening and reciprocal maps. These anomalous behaviors and the consequences have been attributed to the presence of local mosaics and competition of elastic and plastic deformation kinetics in ZnO epitaxy that finally released by inducing misfit and threading dislocations diffracted in transmission electron microscopy.
Stress-induced morphology and fine-line stability enhancement of NiSi on poly-SiGe with a buffer polycrystalline silicon interlayer
Authors: Wu Chi-Chang , Wu Wen-Fa , Ko Fu-Hsiang , You Hsin-Chiang , Yang Wen-Luh
Published: May 2008

The thermal and morphological stability of NiSi is enhanced by inserting a polycrystalline (poly-Si) buffer layer between the Ni and poly-SiGe films. NiSi films formed on poly-Si/poly-SiGe stack layers possessed continuous, smooth structures after annealing at 500–850°C. Moreover, nickel germanosilicide [Ni(Si, Ge)] lines formed on the poly-SiGe exhibited a fine-line effect, i.e., the sheet resistance increased upon decreasing the linewidth, whereas the sheet resistance of NiSi lines formed on the poly-Si/poly-SiGe stack layers remained less than 5Ω∕square. A model for the stress-confined grain growth and recrystallization is proposed to explain the improved properties of the poly-Si-buffered film.
DX centers in CdTe: A density functional study
Authors: Du Mao-Hua
Published: May 2008

DX centers induced by both group-III and group-VII donors in CdTe are studied using density functional calculations. The results show that, for group-VII donors, the DX centers with a cation-cation bond (α- and β-CCB-DX centers) are more stable than the previously proposed broken-bond DX (BB-DX) center and the β-CCB-DX center is the most stable. The stability trend found for the CCB-DX centers for different donors in CdTe is consistent with that for GaAs and GaSb, which suggests a general rule that the CCB-DX centers are favored for small donor atoms on anion site especially for semiconductors with large anion size.
The Laplacian on homogeneous spaces
Authors: Hu Liangzhong
Published: May 2008

The solution of the eigenvalue problem of the Laplacian on a general homogeneous space G∕H is given. Here, G is a compact, semisimple Lie group, H is a closed subgroup of G, and the rank of H is equal to the rank of G. It is shown that the multiplicity of the lowest eigenvalue of the Laplacian on G∕H is just the degeneracy of the lowest Landau level for a particle moving on G∕H in the presence of the background gauge field. Moreover, the eigenspace of the lowest eigenvalue of the Laplacian on G∕H is, up to a sign, equal to the G-equivariant index of the Kostant’s Dirac operator on G∕H.
A visible light-sensitive tungsten carbide/tungsten trioxde composite photocatalyst
Authors: Kim Young-ho , Irie Hiroshi , Hashimoto Kazuhito
Published: May 2008

A photocatalyst composed of tungsten carbide (WC) and tungsten oxide (WO3) has been prepared by the mechanical mixing of each powder. Its photocatalytic activity was evaluated by the gaseous isopropyl alcohol decomposition process. The photocatalyst showed high visible light photocatalytic activity with a quantum efficiency of 3.2% for 400–530nm light. The photocatalytic mechanism was explained by means of enhanced oxygen reduction reaction due to WC, which may serve as a multielectron reduction catalyst, as well as the photogeneration of holes in the valence band of WO3.