bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of the magnetic properties of GeMn thin films through Mn L-edge x-ray absorption
Authors: Ahlers S. , Stone P. R. , Sircar N. , Arenholz E. , Dubon O. D. , Bougeard D.
Published: October 2009

X-ray absorption spectroscopy of epitaxial GeMn thin films reveals an experimentally indistinguishable electronic configuration of Mn atoms incorporated in Ge1−xMnx nanoclusters and in precipitates of the intermetallic compound Mn5Ge3, respectively. However, the average magnetic response of thin films containing Ge1−xMnx nanoclusters is lower than the response of films containing Mn5Ge3 precipitates. This reduced magnetic response of Ge1−xMnx nanoclusters is explained in terms of a fraction of Mn atoms being magnetically inactive due to antiferromagnetic coupling or the presence of structural disorder. A determination of the role of magnetically inactive Mn atoms in the self-assembly of the thermodynamically metastable Ge1−xMnx nanoclusters seems to be an essential ingredient for an enhanced control of this promising high Curie temperature magnetic semiconductor.
Comparison between Mach 2 rarefied airflow modification by an electrical discharge and numerical simulation of airflow modification by surface heating
Authors: Parisse J. D. , Léger L. , Depussay E. , Lago V. , Burtschell Y.
Published: October 2009

This study is devoted to numerical and experimental investigations about the influence of an electrical discharge over a flat plate immersed in a rarefied Mach 2 airflow. Regarding the experimental work, a negative dc discharge is created by applying a potential difference gap between two spanwise aluminum electrodes flush mounted on the plate. The electrode placed close to the leading edge is connected to the negative dc voltage, the second one is grounded. The influence due to the presence of the electric discharge is investigated with a glass Pitot tube by measuring the pressure proles above the flat plate. These experimental results are compared to the numerical work, where the effect of a surface temperature increase is simulated. Different effects can be attributed to the electrical discharge: the ionization of the gas above the plate with the creation of charged species, the acceleration of the positive charged species, the heat of the gas volume above the flat plate, and the heating of the surface of the flat plate. The Pitot probe measurements have shown a thickening of the boundary layer and the increasing of the angle of the shock wave, and the simulation of the surface temperature increase shows the same effect. These arguments let to think that the heating effect due to the temperature increase in the flat plate is the major one among the other effects mentioned above.
X-ray linear dichroism of defects in GaN:Mg using hard x-ray nanoprobe
Authors: Martínez-Criado G. , Tucoulou R. , Cloetens P. , Sans J. A. , Susini J.
Published: October 2009

In this study, we report the application of synchrotron radiation nanoprobe techniques to the structural analysis of pyramidal defects in Mg doped GaN. A combination of fluorescence mapping with spectroscopic techniques enabled us to examine not only the elemental nature but also their crystallographic orientation on the submicron scale. Our observations provide strong evidence for the diffusion and subsequent segregation of background impurities of Fe and Cr on the sample surface, with the absence of pronounced sequential stacking compared with Ga atoms. The strong polarization-dependent x-ray absorption near-edge structure features showed the preservation of the hexagonal crystalline structure in both defect-free and hexagonal pyramids. From the spatially resolved x-ray linear dichroism, no preferential disorder was observed in the direction parallel or perpendicular to the crystal growth.
Temperature dependence of the band gap of ZnSe1−xOx
Authors: Broesler R. , Haller E. E. , Walukiewicz W. , Muranaka T. , Matsumoto T. , Nabetani Y.
Published: October 2009

We have studied the temperature dependence of the band gap of molecular-beam-epitaxy-grown ZnSe1−xOx films (x=0–0.021) using photoluminescence spectroscopy from 15 to 280 K. The temperature dependence of the band gap decreases with increasing oxygen concentration, which can be quantitatively explained by an anticrossing interaction between the highly localized oxygen defect states and the extended states of the conduction band.
Diagnostic based modeling for determining absolute atomic oxygen densities in atmospheric pressure helium-oxygen plasmas
Authors: Niemi K. , Reuter S. , Graham L. M. , Waskoenig J. , Gans T.
Published: October 2009

Absolute atomic oxygen ground state densities in a radio-frequency driven atmospheric pressure plasma jet, operated in a helium-oxygen mixture, are determined using diagnostic based modeling. One-dimensional numerical simulations of the electron dynamics are combined with time integrated optical emission spectroscopy. The population dynamics of the upper O 3p P3 (λ=844 nm) atomic oxygen state is governed by direct electron impact excitation, dissociative excitation, radiation losses, and collisional induced quenching. Absolute values for atomic oxygen densities are obtained through comparison with the upper Ar 2p1 (λ=750.4 nm) state. Results for spatial profiles and power variations are presented and show excellent quantitative agreement with independent two-photon laser-induced fluorescence measurements.
Coherent optical control of the ultrafast dephasing and mobility in a polar semiconductor
Authors: Lee J. D. , Gomi H. , Hase Muneaki
Published: October 2009

Using the nonperturbative many-body time-dependent approach, we investigate the nonequilibrium dynamics of the coherent longitudinal optical phonon-plasmon coupled (LOPC) modes in a polar semiconductor and explore their coherent optical control and eventually the carrier mobility of the semiconductor. The basic idea for a control of the carrier mobility is to manipulate the ultrafast dephasing of the coherent carrier-relevant LOPC mode. We theoretically propose two possible options to realize the idea and reach the final goal. One is to optimize a semiconductor by finely balancing two kinds of carrier densities by chemical doping and optical doping (or photodoping), where the relaxation of the coherent carrier-relevant LOPC mode would respond in a (weak) singular way. It is found that, in this way, the carrier mobility could be enhanced by a few tens of percent. The other is to optimize the optical pumping laser. In this option, the pulse train creating pure virtual carriers through the below-band-gap excitation would be incorporated for an optical pumping, which can make possible the dephasing-free dynamics of the coherent carrier-relevant LOPC mode. The carrier mobility can then be efficiently controlled and dramatically enhanced by synchronizing the pulse train with its coherent oscillation. This might imply one of ultimate ways to control the carrier mobility of the semiconductor.
Chemical stability and transport properties of ultrathin La1.2Sr1.8Mn2O7 Ruddlesden–Popper films
Authors: Matvejeff M. , Yoshimatsu K. , Kumigashira H. , Oshima M. , Lippmaa M.
Published: October 2009

Epitaxial La1.2Sr1.8Mn2O7 films with n=2 Ruddlesden–Popper structure were grown on SrTiO3 (001) substrates. Decomposition through water intercalation led to the disappearance of the metal-insulator transition in samples exposed to ambient atmosphere. Crystal damage was limited to the surface layer only, demonstrating the anisotropic nature of the water intercalation process. By protecting films with a SrTiO3 capping layer, the metal-insulator transition persisted down to 2.5 unit cell thick films. In thinner films, we propose a mechanism related to the loss of interlayer ferromagnetic order in favor of in-plane antiferromagnetism as a reason for the loss of the metallic state.
On-demand positioning of a preselected quantum emitter on a fiber-coupled toroidal microresonator
Authors: Gregor Markus , Henze Rico , Schröder Tim , Benson Oliver
Published: October 2009

The coupling of a quantum emitter to the modes of a silica toroid is presented. A fiber taper is used to manipulate and transfer a preselected diamond nanocrystal onto the toroid. Optical coupling of few nitrogen vacancy (NV) color centers contained inside the nanocrystal to the resonator modes is demonstrated by detecting the fluorescence via a tapered optical fiber coupler. A clear antibunching in the photon correlation measurement is observed indicating emission from only six NV centers residing inside the nanocrystal. The latter is confirmed by a photoluminescence spectrum at liquid helium temperature resolving individual zero phonon lines.
Electronic structure and optical properties of Sb-doped SnO2
Authors: Li Z. Q. , Yin Y. L. , Liu X. D. , Li L. Y. , Liu H. , Song Q. G.
Published: October 2009

The electronic structures and optical properties of pure and Sb-doped SnO2 are investigated by first-principles calculations based on the density functional theory. The calculation results show that the Fermi level of SnO2 is located in the band gap, and the maximum of the valence band and minimum of the conduction band are both located at Γ point (the Brillouin zone center), indicating that SnO2 is a direct band gap semiconductor. When one of the 16 Sn atoms in the SnO2 supercell is replaced by one Sb atom, the Fermi level moves into the conduction band and the compound displays metallic characteristics in electronic band structure. For the case of an Sb impurity coexisting with oxygen vacancies, the Fermi level is also located in the conduction band and the density of states near the Fermi level is increased comparing to that without oxygen vacancies. Moreover, some impurity bands depart from the top of the valence band, which narrows the band gap of the compound. With respect to the optical properties, the presence of an Sb impurity in the supercell of SnO2 leads to the occurrence of weak absorptions in the visible region, while the presence of oxygen vacancies reinforces the absorptions.
Equation of state and phase transition of deuterated ammonia monohydrate (ND3⋅D2O) measured by high-resolution neutron powder diffraction up to 500 MPa
Authors: Fortes A. Dominic , Suard Emmanuelle , Lemée-Cailleau Marie–Hélène , Pickard Christopher J. , Needs Richard J.
Published: October 2009

We describe the results of a neutron powder diffraction study of perdeuterated ammonia monohydrate (AMH, ND3⋅D2O) carried out in the range 102<P<502 MPa at T=180 K using the D2B high-resolution diffractometer at the Institut Laue-Langevin. This paper reports observations of the phase transformation from the low-pressure P212121 phase (AMH I) to the high-pressure Pbca phase (AMH II) at 351 MPa, and measurements which have allowed us to determine the volumetric and axial incompressibilities of both polymorphs. At 180 K, the fitted third order Birch–Murnaghan equation of state of AMH I has parameters, V0=248.00(2) Å3, K0=7.33(3) GPa with the first pressure derivative of K0 fixed at the value obtained in ab initio calculations, (∂K0/∂P)T=K0′=5.3; the implied value of the second derivative is therefore (∂2K0/∂P2)T=K0″=−0.94(1) GPa−1. At 351 MPa, we observed that the transition from AMH I to AMH II occurred over a period of 90 min, with an associated reduction in molar volume of 4.6% and an increase in the incompressibility of 19.6%.
The ground state van der Waals potentials of the calcium dimer and calcium rare-gas complexes
Authors: Yang D. D. , Li P. , Tang K. T.
Published: October 2009

The entire potential energy curve of the Ca2 ground state generated by the Tang–Toennies potential model with its parameters specified by the three theoretical dispersion coefficients and the experimentally determined equilibrium distance and well depth is in excellent agreement with the accurate experimental potential of Allard et al. [Phys. Rev. A 66, 042503 (2002)]. The reduced potential of Ca2 is almost identical with that of Hg2. This leads to the conjecture that the ground state van der Waals dimer potentials of group IIA, except Be, and group IIB elements have the same shape, which is different from that of the rare-gas dimers. The potentials of Ca-RG complexes (RG=He,Ne,Ar,Kr,Xe) are generated by the same potential model with its parameters calculated from the homonuclear potentials of calcium and rare-gas dimers with combining rules. The predicted spectroscopic constants are comparable to other theoretical computations.
Single-fluid stability of stationary plasma equilibria with velocity shear and magnetic shear
Authors: Miura Akira
Published: October 2009

By using incompressible single-fluid equations with a generalized Ohm’s law neglecting the electron inertia, a linear eigenmode equation for a magnetic field perturbation is derived for stationary equilibria in a slab geometry with velocity and magnetic shears. The general eigenmode equation contains a fourth-order derivative of the perturbation in the highest order and contains Alfvén and whistler mode components for a homogeneous plasma. The ratio of the characteristic ion inertia length to the characteristic inhomogeneity scale length is chosen as a small parameter for expansion. Neglecting whistler mode in the lowest order, the eigenmode equation becomes a second-order differential equation similar to the ideal magnetohydrodynamic eigenmode equation except for the fact that the unperturbed perpendicular velocity contains both electric and ion diamagnetic drifts. A sufficient condition for stability against the Kelvin–Helmholtz instability driven by shear in the ion diamagnetic drift velocity is derived and then applied to tokamaks.
Self-assembly of cholesterol DNA at liquid crystal/aqueous interface and its application for DNA detection
Authors: Lai Siok Lian , Hartono Deny , Yang Kun-Lin
Published: October 2009

In this letter, we report a strategy of detecting the DNA targets by using a thin layer of self-assembled cholesterol-labeled DNA probes at the liquid crystal (LC)/aqueous interface. When the system is exposed to 51 μg/ml of complementary DNA targets, the optical appearance of LC shows a continuous change from dark to bright under the crossed polars within 15 min. No obvious change can be observed when the system is exposed to one or two base-pair mismatch DNA targets. This system provides a principle for label-free and real-time detection of DNA targets without any fluorescent labeling.
Long term thermoelectric module testing system
Authors: D’Angelo Jonathan , Hogan Timothy
Published: October 2009

Thermoelectric generators can be used for converting waste heat into electric power. Significant interest in developing new materials in recent years has led to the discovery of several promising thermoelectrics, however, there can be considerable challenges in developing the materials into working devices. Testing and feedback is needed at each step to gain valuable information for identification of difficulties, quality of the materials and modules, repeatability in fabrication, and longevity of the devices. This paper describes a long-term module testing system for monitoring the output power of a module over extended testing times. To evaluate the system, we have tested commercially available thermoelectric modules over a one month time period.
Role of copper in light induced minority-carrier lifetime degradation of silicon
Authors: Savin H. , Yli-Koski M. , Haarahiltunen A.
Published: October 2009

We investigate the impact of copper on the light induced minority-carrier lifetime degradation in various crystalline silicon materials. We demonstrate here that the presence of neither boron nor oxygen is necessary for the degradation effect. In addition, our experiments reveal that copper contamination alone can cause the light induced minority-carrier lifetime degradation.
An inverted organic solar cell with an ultrathin Ca electron-transporting layer and MoO3 hole-transporting layer
Authors: Zhao D. W. , Liu P. , Sun X. W. , Tan S. T. , Ke L. , Kyaw A. K. K.
Published: October 2009

An inverted organic solar cell based on poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) was fabricated with an ultrathin Ca electron-transporting layer and MoO3 hole-transporting layer. The 1 nm Ca on indium tin oxide (ITO) electrode modifies the work function of ITO suitable for electron extraction. An appropriate thickness of MoO3 hole extraction layer is also essential to effectively prevent exciton quenching at the Ag anode, yet not introduce much voltage loss and series resistance. The optical field distribution across the active layer was also simulated to discuss the effect of MoO3 thickness on the photocurrent. The maximum power conversion efficiency obtained was 3.55% under simulated 100 mW/cm2 (AM 1.5G) solar irradiation.
Characterization of room temperature metal microbolometers near the metal-insulator transition regime for scanning thermal microscopy
Authors: Gaitas Angelo , Zhu Weibin , Gulari Ning , Covington Elizabeth , Kurdak Cagliyan
Published: October 2009

Metal microbolometers, used in scanning thermal microscopy, were microfabricated from <20nm titanium thin films on SiO2∕Si3N4∕SiO2 cantilevers. These thin films are near the metal-insulator transition regime such that as the film thickness decreases—the resistance increases and the current-voltage characteristics cross over from sublinear to superlinear. In addition, the temperature coefficient of resistance transitions from positive to negative before it plateaus at a negative value. Thin titanium films exhibit negative temperature coefficient of resistance as high as −0.0067∕K which is higher than that of bulk titanium films.
The role of the reference state in long-range random phase approximation correlation
Authors: Janesko Benjamin G. , Scuseria Gustavo E.
Published: October 2009

We recently presented a combination of a short-range density functional approximation with long-range random phase approximation (RPA) correlation [B. G. Janesko, T. M. Henderson, and G. E. Scuseria, J. Chem. Phys. 130, 081105 (2009)]. Here we explore how this approximation’s performance is affected by the choice of reference state, i.e., the orbitals and orbital energy differences entering the RPA energy expression. Our previous results built the reference state using a nonlocal exchange potential. Rescaling the RPA correlation energy by an empirical factor >1 gave very accurate results for a wide range of properties. We show here that reference states constructed from approximate local exchange-correlation potentials give their best results with smaller rescaling factors ∼1. However, the tested potentials yield artifacts in some systems.
Tracing ultrafast hydrogen migration in allene in intense laser fields by triple-ion coincidence momentum imaging
Authors: Xu Huailiang , Okino Tomoya , Yamanouchi Kaoru
Published: October 2009

Ultrafast hydrogen migration in allene (CH2=C=CH2) in intense laser fields was investigated by triple-ion coincidence momentum imaging. The migrating proton covering the entire range of an allene molecule was visualized by the momentum correlation maps and by the geometrical structure of triply charged allene reconstructed from the observed momentum vectors of fragment ions. The extent of hydrogen migration was found to play a decisive role in breaking selectively one of the two initially equivalent C–C chemical bonds that become inequivalent in the course of the hydrogen migration.
Emission of Tamm plasmon/exciton polaritons
Authors: Symonds C. , Lemaître A. , Homeyer E. , Plenet J. C. , Bellessa J.
Published: October 2009

We report on the observation of the strong coupling regime occurring between a Tamm plasmon (TP) mode and an exciton from inorganic quantum wells (QWs). The sample is formed by a silver thin film deposited onto an AlAs/GaAlAs Bragg reflector containing InGaAs QWs located in the high refractive index layers. Angular resolved reflectometry experiments evidence a clear anticrossing in the dispersion relations, a signature of the strong coupling regime. The Rabi splitting energy is 11.5 meV. The experimental data are in very good agreement with simple transfer matrix calculations. The emission from low and high energy TP/exciton polaritons is also demonstrated.
Two-directional lasing from a dye-doped two-dimensional hexagonal photonic crystal made of holographic polymer-dispersed liquid crystals
Authors: Luo D. , Sun X. W. , Dai H. T. , Liu Y. J. , Yang H. Z. , Ji W.
Published: October 2009

Lasing actions are demonstrated in two high-symmetry directions (ΓM and ΓK) of a two-dimensional hexagonal photonic crystal from dye-doped holographic polymer-dispersed liquid crystals. The group velocity anomaly, which is peculiar to two-dimensional and three-dimensional photonic crystals, leads to substantial enhancement in local fields in the two-dimensional photonic crystal with a low-index contrast. The difference on the lasing thresholds between the two directions is interpreted as the result of different group velocities of the flat bands where laser oscillation occurred.
Potential to increase yield in lucerne (Medicago sativa subsp. sativa) through introgression of Medicago sativa subsp. falcata into Australian adapted material
Authors: Mackie J. M. , Pepper P. M. , Lowe K. F. , Musial J. M. , Irwin J. A. G.
Published: October 2009

The effect of interspecific heterosis in crosses between Medicago sativa subsp. sativa and M. sativa subsp. falcata was assessed. Three sativa and 3 falcata plants were crossed in a diallel design. Progeny dry matter yield and natural plant height were assessed in a replicated field experiment at Gatton, Queensland. Yield data were analysed using the method of residual maximum likelihood (REML) and Griffing’s model 1. There were significant differences between the reciprocal, general combining ability (GCA), and specific combining ability (SCA) effects. As expected, S1 populations were lower yielding than their respective intraspecific cross and falcata × falcata crosses were significantly lower yielding than sativa × sativa crosses. Some of the interspecific crosses indicated substantial SCA effects, yielding at least as well as the best sativa × sativa crosses. We have demonstrated the potential usefulness of unselected M. sativa subsp. falcata as a heterotic group in the improvement of yield in northern Australian adapted lucerne material, and discuss how it could be incorporated into future breeding to overcome the yield stagnation currently being experienced in Australian programs.
Paddling mechanism for the substrate translocation by AAA+ motor revealed by multiscale molecular simulations
Authors: Koga Nobuyasu , Kameda Tomoshi , Okazaki Kei-ichi , Takada Shoji
Published: October 2009

Hexameric ring-shaped AAA+ molecular motors have a key function of active translocation of a macromolecular chain through the central pore. By performing multiscale molecular dynamics (MD) simulations, we revealed that HslU, a AAA+ motor in a bacterial homologue of eukaryotic proteasome, translocates its substrate polypeptide via paddling mechanism during ATP-driven cyclic conformational changes. First, fully atomistic MD simulations showed that the HslU pore grips the threaded signal peptide by the highly conserved Tyr-91 and Val-92 firmly in the closed form and loosely in the open form of the HslU. The grip depended on the substrate sequence. These features were fed into a coarse-grained MD, and conformational transitions of HslU upon ATP cycles were simulated. The simulations exhibited stochastic unidirectional translocation of a polypeptide. This unidirectional translocation is attributed to paddling motions of Tyr-91s between the open and the closed forms: downward motions of Tyr-91s with gripping the substrate and upward motions with slipping on it. The paddling motions were caused by the difference between the characteristic time scales of the pore-radius change and the up-down displacements of Tyr-91s. Computational experiments on mutations at the pore and the substrate were in accord with several experiments.
Pulmonary Vascular Complications in Asymptomatic Children With Portal Hypertension
Authors: Whitworth John R , Ivy D Dunbar , Gralla Jane , Narkewicz Michael R , Sokol Ronald J
Published: October 2009

Objectives:

To determine the prevalence of portopulmonary hypertension, hepatopulmonary syndrome (HPS), and intrapulmonary vascular shunting (IPVS) in children with clinically stable portal hypertension and to assess the value of vasoactive peptide levels, biochemical tests and clinical signs or symptoms to predict these conditions.

Patients and Methods:

A prospective, cross‐sectional analysis was conducted on 33 children, ages 4 to 17 years, with stable cirrhosis (n = 28) or extrahepatic portal hypertension (n = 5). The children were screened for IPVS and hypoxia with contrast‐enhanced echocardiography (cECHO) and pulse oximetry, and screened for pulmonary hypertension with Doppler echocardiography. Chemistries, radiographs, physical examinations, and levels of vasoactive peptides were compared between subjects with IPVS and those with normal cECHO.

Results:

No subject had pulmonary hypertension. Six (19%) had IPVS, all of which had intrahepatic causes of portal hypertension, and 1 of whom had HPS. Compared with subjects with normal cECHO, those with IPVS had biochemical evidence of more advanced liver disease and higher b‐type natriuretic peptide levels.

Conclusions:

Prevalence of portopulmonary hypertension and HPS appear to be rare in clinically stable children with portal hypertension. Intrapulmonary vascular shunting was present in 19% of these patients. A novel finding of this study is the elevation of b‐type natriuretic peptide in children with IPVS.
Crohn Disease and Mycobacterial Infection in Children: An Intriguing Relationship
Authors: Chiappini Elena , de Martino Maurizio , Mangiantini Franscesca , Lionetti Paolo
Published: October 2009

The relation between Crohn disease (CD) and mycobacterial infection is complex and intriguing. The 2 conditions share common immunopathogenic features, and the hypothesis that Mycobacterium avium subspecies paratuberculosis may cause CD is still under debate. Moreover, differential diagnosis between CD and intestinal tuberculosis (TB) may be challenging, especially in the growing proportion of children immigrating from countries with a high prevalence of TB. Thus, in Western countries, paediatricians who are involved in the diagnosis and management of children with CD are expected to face intestinal TB more frequently than in the past and should always consider the differential diagnosis between these 2 conditions. In addition, the use of biological agents in the treatment of CD, which may reactivate latent TB, requires the development of targeted diagnostic algorithms. Children with CD who are candidates for treatment with antitumour necrosis factor‐α agents should be screened for latent or active TB and closely followed over time, also considering possible failure of antitubercular prophylaxis and the frequent uncharacteristic presentation of TB in children receiving antitumour necrosis factor‐α agents. In the present review, the most recent literature findings on these topics are reported, focusing particularly on the paediatric age group.
Cope's Rule and Romer's theory: patterns of diversity and gigantism in eurypterids and Palaeozoic vertebrates
Authors: Lamsdell James C. , Braddy Simon J.
Published: October 2009

Gigantism is widespread among Palaeozoic arthropods, yet causal mechanisms, particularly the role of (abiotic) environmental factors versus (biotic) competition, remain unknown. The eurypterids (Arthropoda: Chelicerata) include the largest arthropods; gigantic predatory pterygotids (Eurypterina) during the Siluro-Devonian and bizarre sweep-feeding hibbertopterids (Stylonurina) from the Carboniferous to end-Permian. Analysis of family-level originations and extinctions among eurypterids and Palaeozoic vertebrates show that the diversity of Eurypterina waned during the Devonian, while the Placodermi radiated, yet Stylonurina remained relatively unaffected; adopting a sweep-feeding strategy they maintained their large body size by avoiding competition, and persisted throughout the Late Palaeozoic while the predatory nektonic Eurypterina (including the giant pterygotids) declined during the Devonian, possibly out-competed by other predators including jawed vertebrates.
Rate-dependent control strategies stabilize limb forces during human locomotion
Authors: Yen Jasper T. , Chang Young-Hui
Published: October 2009

A spring-mass model accurately predicts centre of mass dynamics for hopping and running animals and is pervasive throughout experimental and theoretical studies of legged locomotion. Given the neuromechanical complexity of the leg, it remains unclear how joint dynamics are selected to achieve such simple centre of mass movements consistently from step to step and across changing conditions. Human hopping is a tractable experimental model to study how net muscle moments, or joint torques, are coordinated for spring-mass dynamics, which include stable, or invariant, vertical ground forces. Subjects were equally able to stabilize vertical forces at all hopping frequencies (2.2, 2.8, 3.2 Hz) by selecting force-equivalent joint torque combinations. Using a hybrid-uncontrolled manifold permutation analysis, however, we discovered that force stabilization relies less on interjoint coordination at greater hopping frequencies and more on selection of appropriate ankle joint torques. We conclude that control strategies for selecting the joint torques that stabilize forces generated on the ground are adjusted to the rate of movement. Moreover, this indicates that legged locomotion may involve the differential regulation of several redundant motor control strategies that are accessed as needed to match changing environmental conditions.
Nonlinear secondary whirl of an overhung rotor
Authors: Nandakumar K. , Chatterjee Anindya
Published: October 2009

Gravity critical speeds of rotors have hitherto been studied using linear analysis, and ascribed to rotor stiffness asymmetry. Here, we study an idealized asymmetricnonlinearoverhung rotor model of Crandall and Brosens, spinning close to its gravity critical speed. Nonlinearities arise from finite displacements, and the rotor’s static lateral deflection under gravity is taken as small. Assuming small asymmetry and damping, slow modulations of whirl amplitudes are studied using the method of multiple scales. Inertia asymmetry appears only at second order. More interestingly, even without stiffness asymmetry, the gravity-induced resonance survives through geometric nonlinearities. The gravity resonant forcing does not influence the resonant mode at leading order, unlike the typical resonant oscillations. Nevertheless, the usual phenomena of resonances, namely saddle–node bifurcations, jump phenomena and hysteresis, are all observed. An unanticipated periodic solution branch is found. In the three-dimensional space of two modal coefficients and a detuning parameter, the full set of periodic solutions is found to be an imperfect version of three mutually intersecting curves: a straight line, a parabola and an ellipse.
Effects of environmental change on wildlife health
Authors: Acevedo-Whitehouse Karina , Duffus Amanda L. J.
Published: October 2009

Environmental change has negatively affected most biological systems on our planet and is becoming of increasing concern for the well-being and survival of many species. At an organism level, effects encompass not only endocrine disruptions, sex-ratio changes and decreased reproductive parameters, but also include teratogenic and genotoxic effects, immunosuppression and other immune-system impairments that can lead directly to disease or increase the risk of acquiring disease. Living organisms will strive to maintain health by recognizing and resolving abnormal situations, such as the presence of invading microorganisms or harmful peptides, abnormal cell replication and deleterious mutations. However, fast-paced environmental changes may pose additional pressure on immunocompetence and health maintenance, which may seriously impact population viability and persistence. Here, we outline the importance of a functional immune system for survival and examine the effects that exposure to a rapidly changing environment might exert on immunocompetence. We then address the various levels at which anthropogenic environmental change might affect wildlife health and identify potential deficits in reproductive parameters that might arise owing to new immune challenges in the context of a rapidly changing environment. Throughout the paper, a series of examples and case studies are used to illustrate the impact of environmental change on wildlife health.
Effects of heat stress on mammalian reproduction
Authors: Hansen Peter J.
Published: October 2009

Heat stress can have large effects on most aspects of reproductive function in mammals. These include disruptions in spermatogenesis and oocyte development, oocyte maturation, early embryonic development, foetal and placental growth and lactation. These deleterious effects of heat stress are the result of either the hyperthermia associated with heat stress or the physiological adjustments made by the heat-stressed animal to regulate body temperature. Many effects of elevated temperature on gametes and the early embryo involve increased production of reactive oxygen species. Genetic adaptation to heat stress is possible both with respect to regulation of body temperature and cellular resistance to elevated temperature.
A novel membrane fusion-mediated plant immunity against bacterial pathogens
Authors: Hatsugai Noriyuki , Iwasaki Shinji , Tamura Kentaro , Kondo Maki , Fuji Kentaro , Ogasawara Kimi , Nishimura Mikio , Hara-Nishimura Ikuko
Published: October 2009

Plants have developed their own defense strategies because they have no immune cells. A common plant defense strategy involves programmed cell death (PCD) at the infection site, but how the PCD-associated cell-autonomous immunity is executed in plants is not fully understood. Here we provide a novel mechanism underlying cell-autonomous immunity, which involves the fusion of membranes of a large central vacuole with the plasma membrane, resulting in the discharge of vacuolar antibacterial proteins to the outside of the cells, where bacteria proliferate. The extracellular fluid that was discharged from the vacuoles of infected leaves had both antibacterial activity and cell death-inducing activity. We found that a defect in proteasome function abolished the membrane fusion associated with both disease resistance and PCD in response to avirulent bacterial strains but not to a virulent strain. Furthermore, RNAi plants with a defective proteasome subunit PBA1 have reduced DEVDase activity, which is an activity associated with caspase-3, one of the executors of animal apoptosis. The plant counterpart of caspase-3 has not yet been identified. Our results suggest that PBA1 acts as a plant caspase-3-like enzyme. Thus, this novel defense strategy through proteasome-regulating membrane fusion of the vacuolar and plasma membranes provides plants with a mechanism for attacking intercellular bacterial pathogens.
Nucleotide Polymorphism in the Wheat Transcriptional ActivatorSpaInfluences Its Pattern of Expression and Has Pleiotropic Effects on Grain Protein Composition, Dough Viscoelasticity, and Grain Hardness
Authors: Ravel Catherine , Martre Pierre , Romeuf Isabelle , Dardevet Mireille , El-Malki Redouane , Bordes Jacques , Duchateau Nathalie , Brunel Dominique , Balfourier François , Charmet Gilles
Published: October 2009

Storage protein activator (SPA) is a key regulator of the transcription of wheat (Triticum aestivum) grain storage protein genes and belongs to the Opaque2 transcription factor subfamily. We analyzed the sequence polymorphism of the three homoeologous Spa genes in hexaploid wheat. The level of polymorphism in these genes was high particularly in the promoter. The deduced protein sequences of each homoeolog and haplotype show greater than 93% identity. Two major haplotypes were studied for each Spa gene. The three Spa homoeologs have similar patterns of expression during grain development, with a peak in expression around 300 degree days after anthesis. On average, Spa-B is 10 and seven times more strongly expressed than Spa-A and Spa-D, respectively. The haplotypes are associated with significant quantitative differences in Spa expression, especially for Spa-A and Spa-D. Significant differences were found in the quantity of total grain nitrogen allocated to the gliadin protein fractions for the Spa-A haplotypes, whereas the synthesis of glutenins is not modified. Genetic association analysis between Spa and dough viscoelasticity revealed that Spa polymorphisms are associated with dough tenacity, extensibility, and strength. Except for Spa-A, these associations can be explained by differences in grain hardness. No association was found between Spa markers and the average single grain dry mass or grain protein concentration. These results demonstrate that in planta Spa is involved in the regulation of grain storage protein synthesis. The associations between Spa and dough viscoelasticity and grain hardness strongly suggest that Spa has complex pleiotropic functions during grain development.
In vitro and in vivo evidence that a combination of lapatinib plus S‐1 is a promising treatment for pancreatic cancer
Authors: Komoto Masahiro , Nakata Bunzo , Nishii Takafumi , Kawajiri Hidemi , Shinto Osamu , Amano Ryosuke , Yamada Nobuya , Yashiro Masakazu , Hirakawa Kosei
Published: October 2009

Lapatinib is a small molecule inhibitor of both HER2 and the epidermal growth factor receptor (EGFR). We investigated the effect of treatment with lapatinib alone or in combination with a fluoropyrimidine derivative S‐1 against pancreatic cancer. The HER2/EGFR expression in each of the four pancreatic cancer cell lines MiaPaca‐2, PANC‐1, Capan‐1 and Capan‐2 was measured by flow cytometry. The anti‐tumor effects of lapatinib (30 mg/kg) and/or S‐1 (10 mg/kg) were evaluated using female BALB/c nude mice xenografts generated using these four cell lines. Synergy between lapatinib and S‐1 was examined by median effect analysis in vitro. Resected pancreatic cancer tissues from 137 patients were immunohistochemically stained with anti‐human HER2 and EGFR antibodies. The administration of lapatinib as a single agent substantially suppressed tumor growth in vivo of all pancreatic cancer cell lines examined. A strong correlation was observed between HER2 expression and the anti‐tumor effect of lapatinib in vivo. Lapatinib synergized with S‐1 to inhibit the tumor growth of MiaPaca‐2 and PANC‐1 xenografts. When used as a single agent in vitro, lapatinib barely inhibit the cell growth of any cell line. However, lapatinib synergized with the anti‐tumor activity of the S‐1 components 5‐fluorouracil and 5‐chloro‐2,4‐dihydrogenase against all cell lines. Immunohistochemical staining demonstrated that 70% of the pancreatic cancers overexpressed HER2 and/or EGFR. Both lapatinib monotherapy and combined treatment with S‐1 may be promising treatments for patients with pancreatic cancers; the majority these cancers express lapatinib target molecules. (Cancer Sci 2009; 00: 000–000)
Histoplasmosis: cytodiagnosis and review of literature with special emphasis on differential diagnosis on cytomorphology
Authors: Gupta N. , Arora S. K. , Rajwanshi A. , Nijhawan R. , Srinivasan R.
Published: October 2009

N. Gupta, S. K. Arora, A. Rajwanshi, R. Nijhawan and R. Srinivasan Histoplasmosis: cytodiagnosis and review of literature with special emphasis on differential diagnosis on cytomorphology

Background:  Human infection with Histoplasma capsulatum runs the gamut from asymptomatic to disseminated disease. In immunocompromised patients, a tiny inoculum can lead to widespread disseminated infection. Early diagnosis and initiation of treatment is therefore important.

Objective:  To review the cases of histoplasmosis diagnosed on fine needle aspiration cytology (FNAC) and to discuss the clinical presentation, associated inflammatory response, load of organisms and differential diagnosis on cytomorphology in these cases.

Methods:  Retrospective review of seven cases of histoplasmosis at a tertiary‐care centre during the period from 1998 to 2009 was performed. Clinical presentation along with cytomorphological features were studied and discussed in detail.

Results:  The mean age of patients was 48.6 years and six out of seven were male. History of immunodeficiency (HIV) was available in five cases. Six patients presented with peripheral and/or abdominal lymphadenopathy. One patient had nodular shadows in both lungs and two also had skin lesions. On cytological smears, a variable load of uniform round to oval, about 2–4 μm in diameter, budding yeasts were seen intracellularly (within histiocytes) as well as extracellularly. In one case (HIV positive), these organisms were also seen within neutrophil polymorphonuclear leucocytes. In two cases, an inflammatory response in the form of epithelioid cell granulomas along with multinucleated giant cells was seen.

Conclusions:  FNAC is a reliable tool to recognize infection with H. capsulatum in tissues. This infection can cause a variable inflammatory response, which should be considered while reporting on such cases.
Groundfish species diversity and assemblage structure in Icelandic waters during recent years of warming
Authors: STEFANSDOTTIR LILJA , SOLMUNDSSON JÓN , MARTEINSDOTTIR GUÐRÚN , KRISTINSSON KRISTJÁN , JONASSON JÓNAS PÁLL
Published: October 2009

Elevated ocean temperatures have been predicted to lead to a poleward shift in the latitudinal distribution ranges of fish species. Different responses of fish species to increased temperatures might lead to changes in assemblage structure and local species richness. In this study, the assemblage structure and diversity of groundfish in Icelandic waters were examined using data from a standardized groundfish survey conducted annually in 1996–2007. We used hierarchical cluster analysis to define assemblages in two time periods and canonical correspondence analysis to explore the relationships between the assemblages and temperature, depth, latitude, longitude and year. We further used two estimates of diversity, species richness and the Shannon index. Four major species assemblages were identified. Assemblages in the hydrographically stable deep waters north of the country were consistent during the study, while assemblage structure in the more variable shallow waters underwent some changes. For this period of generally increasing sea temperature, the canonical correspondence analysis also revealed a shift towards species representative of warmer temperatures. Diversity was shown to be highly variable both temporally and spatially, and also to vary with depth and temperature. Species richness increased with temperature and time southwest of the country, but decreased northeast of the country. The different trends detected between the northern and southern areas illustrate the importance of performing analyses at the most appropriate scale.
Characterization of the carbon fluxes of a vegetated drained lake basin chronosequence on the Alaskan Arctic Coastal Plain
Authors: ZONA D. , OECHEL W. C. , PETERSON K. M. , CLEMENTS R. J. , PAW U K. T. , USTIN S. L.
Published: October 2009

Greenhouse gas fluxes from vegetated drained lake basins have been largely unstudied, although these land features constitute up to 47% of the land cover in the Arctic Coastal Plain in northern Alaska. To describe current and to better predict future sink/source activity of the Arctic tundra, it is important to assess these vegetated drained lake basins with respect to the patterns of and controls on gross primary production (GPP), net ecosystem exchange, and ecosystem respiration (ER). We measured CO2 fluxes and key environmental variables during the 2007 growing season (June through August) in 12 vegetated drained lake basins representing three age classes (young, drained about 50 years ago; medium, drained between 50 and 300 years ago; and old, drained between 300 and 2000 years ago, as determined by Hinkel et al., 2003) in the Arctic Coastal Plain. Young vegetated drained lake basins had both the highest average GPP over the summer (11.4 gCO2 m−2 day−1) and the highest average summer ER (7.3 gCO2 m−2 day−1), while medium and old vegetated drained lake basins showed lower and similar GPP (7.9 and 7.2 gCO2 m−2 day−1, respectively), and ER (5.2 and 4 gCO2 m−2 day−1, respectively). Productivity decreases with age as nutrients are locked up in living plant material and dead organic matter. However, we showed that old vegetated drained lakes basins maintained relatively high productivity because of the increased development of ice‐wedge polygons, the formation of ponds, and the re‐establishment of very productive species. Comparison of the seasonal CO2 fluxes and concomitant environmental factors over this chronosequence provides the basis for better understanding the patterns and controls on CO2 flux across the coastal plain of the North Slope of Alaska and for more accurately estimating current and future contribution of the Arctic to the global carbon budget.
Neural cadherin is expressed in human gametes and participates in sperm–oocyte interaction events
Authors: Marín‐Briggiler C. I. , Lapyckyj L. , González Echeverría M. F. , Rawe V. Y. , Alvarez Sedó C. , Vazquez‐Levin M. H.
Published: October 2009

Neural cadherin (N‐cadherin) is a transmembrane glycoprotein involved in calcium‐dependent cell–cell adhesion and signalling events. The previous evidence shows N‐cadherin expression in the human gonads and gametes; however, N‐cadherin subcellular localization in human spermatozoa and oocytes, and its involvement in fertilization remain to be characterized. In this study, expression of N‐cadherin in human spermatozoa and testis was confirmed by RT‐PCR and protein forms were identified using Western immunoblotting. N‐cadherin localization in testicular and ejaculated spermatozoa, in cells that had undergone capacitation and acrosomal exocytosis, as well as in oocytes was assessed using immunocytochemistry. Participation of the adhesion protein in fertilization was evaluated using the HemiZona Assay (HZA) and the zona pellucida (ZP)‐free hamster oocyte sperm penetration assay (SPA). Both the N‐cadherin transcript and the mature protein form (135 kDa) were found in spermatozoa and testis. The protein was mainly immunolocalized in the acrosomal region of testicular, non‐capacitated and capacitated spermatozoa, and was found in the equatorial segment after acrosomal exocytosis. N‐cadherin was also detected in oocytes, in conjunction with β‐catenin, a member of the adhesion complex. Sperm incubation with anti N‐cadherin antibodies did not affect their ability to interact with homologous ZP in the HZA; by contrast, presence of the antibodies in the SPA led to a significant (p < 0.01) reduction in the percentage of penetrated oocytes. In conjunction, results indicate that N‐cadherin is a sperm protein of testicular origin localized in cellular regions involved in gamete interaction. N‐cadherin would not participate in sperm–ZP interaction, but it would have a role in sperm–oolemma adhesion/fusion events.