bluuebunny/crossref_metadata_2025 huggingface dataset:
Photoemission studies from metal by UV lasers
Authors: Caretto G. , Doria D. , Nassisi V. , Siciliano M. V.
Published: April 2007

Studies of electron emission by photoelectric process from pure Zn cathodes by UV laser beams were performed. As UV sources, two different wavelength excimer lasers were utilized in order to investigate the photoemission as pure photoelectric process and multiphoton process. The Schottky effect was also considered. The utilized laser sources were a KrF operating at 248nm wavelength (5eV), 23ns full width at half maximum (FWHM), and a XeCl operating at 308nm wavelength (4.02eV), 10ns FWHM. The cathode work function was 4.33eV, a value lower and higher than the photon energies of KrF and XeCl lasers, respectively. The photocathodes were tested in a vacuum photodiode cell at 10−7mbar. The cathodes were irradiated at normal incidence and the anode-cathode distance was set to 3.7mm. Due to the electrical breakdown into the photodiode gap, the maximum applied accelerating voltage was 20kV. Under the above experimental conditions a maximum of 5.4MV∕m electric field resulted. Under the space charge effect, the electron emission was higher than the one expected by the Child-Langmuir law. In saturation regime the electron emission increased with the accelerating voltage owing to the Schottky effect and plasma formation. The highest output current was achieved with the KrF laser at 14mJ laser energy. Its value was about 12A, corresponding to a global quantum efficiency of approximately 1×10−4, while the temporal quantum efficiency presented a maximum value of 1.1×10−4 located at the tail of the laser pulse. The estimated efficiencies with the XeCl laser were lower than the KrF ones as well as the output current and the plasma formation, although higher energy values than the KrF ones were utilized. By the results obtained, we conclude that the plasma generation is strongly due to the extracted current but weakly to the used laser intensity.
Vector network analyzer ferromagnetic resonance of thin films on coplanar waveguides: Comparison of different evaluation methods
Authors: Bilzer C. , Devolder T. , Crozat P. , Chappert C. , Cardoso S. , Freitas P. P.
Published: April 2007

We have carried out two-port network analyzer ferromagnetic resonance measurements on a coplanar waveguide. We present a detailed description on how to calculate from the raw measurement data a value proportional to the complex susceptibility and permittivity of the ferromagnetic material. Necessary corrections for errors due to imprecise sample placement on the waveguide and the sample dimensions are presented. Evaluated data up to 15 GHz are provided for two model samples: a 40 nm Co80Fe20 layer showing a large linewidth (≈900 MHz) and a 40 nm Co72Fe18B10 layer yielding a small linewidth (≈360 MHz). Using these experimental data the presented evaluation scheme based on all four scattering parameters is then compared to commonly used approximate evaluation schemes relying on only one S parameter. These approximate methods show close agreement for the ferromagnetic resonance frequencies (the relative error is below 1%). However, the resonance linewidths show a relative error that can reach 10% in comparison with the presented evaluation method.
Theoretical modeling of the kinetics of fibrilar aggregation of bovine β-lactoglobulin at pH 2
Authors: Arnaudov Luben N. , de Vries Renko
Published: April 2007

The authors propose a kinetic model for the heat-induced fibrilar aggregation of bovine β-lactoglobulin at pH 2.0. The model involves a nucleation step and a simple addition reaction for the growth of the fibrils, as well as a side reaction leading to the irreversible denaturation and inactivation of a part of the protein molecules. For the early stages of the aggregation reaction, the authors obtain an analytical solution of the model. In agreement with their experimental results, the model predicts a critical protein concentration below where almost no fibrils are formed. The model agrees well with their experimental data from in situ light scattering. By fitting the experimental data with the model, the authors obtain the ionic strength dependent kinetic rate constants for β-lactoglobulin fibrilar aggregation and the size of the critical nucleus.
Plasmon modes of curvilinear metallic core/shell particles
Authors: Brandl Daniel W. , Nordlander Peter
Published: April 2007

The plasmon hybridization method is generalized to calculate the plasmon modes and optical properties of solid and dielectric-core/metallic-shell particles of geometrical structures that can be described using separable curvilinear coordinates. The authors present a detailed discussion of the plasmonic properties of hollow metallic nanowires with dielectric cores and core/shell structures of oblate and prolate spheroidal shapes. They show that the plasmon frequencies of these particles can be expressed in a common form and that the plasmon modes of the core/shell structures can be viewed as resulting from the hybridization of the solid particle plasmons associated with the outer surface of the shell and of the cavity plasmons associated with the inner surface.
Nonequilibrium molecular dynamics simulation to describe the rotation of rigid, low aspect ratio carbon nanotubes in simple shear flow
Authors: Tang Wenzhong , Advani Suresh G.
Published: April 2007

In this paper, the rotation of short carbon nanotubes in simple shear liquid argon flow was investigated by nonequilibrium molecular dynamics (MD) simulation. In their simulations, nanotubes were described as rigid cylinders of carbon atoms. Lennard-Jones potential was employed to represent both argon-argon and argon-carbon interactions. Results show that time period of a nanotube as calculated from MD simulations is longer than what would be calculated from Jeffery’s equation based on the aspect ratio of the cylinder. The difference is much higher at low shear rates and for small aspect ratios. Results also reveal that adding caps to an open-ended nanotube speeds up its rotation.
Driven polymer transport through a nanopore controlled by a rotating electric field: Off-lattice computer simulations
Authors: Tsai Y.-S. , Chen C.-M.
Published: April 2007

The driven translocation kinetics of a single strand polynucleotide chain through a nanopore is studied using off-lattice Monte Carlo simulations, by which the authors demonstrate a novel method in controlling the driven polymer transport through a nanopore by a rotating electric field. The recorded time series of blockade current from the driven polynucleotide transport are used to determine the sequence of polynucleotides by implementing a modified Monte Carlo algorithm, in which the energy landscape paving technique is incorporated to avoid trapping at deep local minima. It is found that only six-time series of block current are required to completely determine the polynucleotide sequence if the average missing rate (AMR) of current signals in these time series is smaller than 20%. For those time series with AMR greater than 20%, the error rate in sequencing an unknown polynucleotide decreases rapidly by increasing the number of time series. To find the most appropriate experimental conditions, the authors have investigated the dependence of AMR of current signals and qualified rate of measured time series of blockade current on various controllable experimental variables.
Low-variance deviational simulation Monte Carlo
Authors: Homolle Thomas M. M. , Hadjiconstantinou Nicolas G.
Published: April 2007

We present and discuss a particle simulation method for solving the Boltzmann equation which incorporates the variance reduction ideas presented in L. L. Baker and N. G. Hadjiconstantinou [Physics of Fluids 17, 051703 (2005)]. The variance reduction, achieved by simulating only the deviation from equilibrium, results in a significant computational efficiency advantage for low speed flows compared to traditional particle methods such as the direct simulation Monte Carlo (DSMC). More specifically, the proposed method can efficiently simulate arbitrarily small deviations from equilibrium (e.g., low flow speed) at a computational cost that does not scale with the magnitude of the deviation from equilibrium, while maintaining the basic algorithmic structure of DSMC.
Electromagnetic global gyrokinetic simulation of shear Alfven wave dynamics in tokamak plasmas
Authors: Nishimura Y. , Lin Z. , Wang W. X.
Published: April 2007

Electromagnetic gyrokinetic simulation in toroidal geometry is developed based on a fluid-kinetic hybrid electron model. The Alfven wave propagation in a fully global gyrokinetic particle simulation is investigated. In the long-wavelength magnetohydrodynamic limit, shear Alfven wave oscillations, continuum damping, and the appearance of the frequency gap in toroidal geometries are demonstrated. Wave propagation across the magnetic field (kinetic Alfven wave) is examined by comparing the simulation results with the theoretical dispersion relation. Furthermore, finite-beta stabilization of the ion temperature gradient mode and the onset of the kinetic ballooning mode are demonstrated.
Dynamics of free chains in polymer nanocomposites
Authors: Picu R. C. , Rakshit A.
Published: April 2007

The dynamics of entangled polymeric chains in a polymer filled with nanoparticles is studied by means of molecular dynamics simulations of a model system. The primary objective is to study to what extent the reptation of polymers not in direct contact with fillers is modified with respect to the neat material. To this end, two systems are considered: A regular filled material in which the filler-polymer affinity is controlled, and a system in which the beads in contact with the filler at the beginning of the production phase of the simulation are tethered to the filler surface. This second system represents the limit case of long polymer-filler attachment time. In this case attention is focused on the free chains of the melt. The dynamics in the two models is different. In the filled system uniform slowing down for all Rouse modes is observed. The effect varies monotonically with the filler-polymer affinity. Up to saturation, this behavior may be captured by usual models with an effective, affinity-dependent, friction coefficient. In the system with grafted chains, the free chain Rouse dynamics is identical to that in the neat material, except for the longest modes which are significantly slowed down. More interestingly, the dynamics of the free chains depends in a nonmonotonic way on the polymer-filler affinity, although the free chains do not come in direct contact with the filler. This effect is due to small changes in the structure of the polydisperse brush upon modification of the affinity. Specifically, the density of the brush and the amount of interpenetration of free and grafted chains depend on the filler-polymer affinity. The use of a reptation model with modified tube diameter to capture this behavior is discussed.
Short range scattering effect of InAs quantum dots in the transport properties of two dimensional electron gas
Authors: Kannan E. S. , Kim Gil-Ho , Kumar Sanjeev , Farrer I. , Ritchie D. A. , Son Jun Ho , Baik Jeong Min , Lee Jong-Lam , Youn D. H. , Kang Kwang-Yong
Published: April 2007

Short range interaction between two dimensional electron gas (2DEG) and InAs quantum dots embedded in the GaAs∕AlGaAs quantum well is investigated as a function of carrier density. At low carrier density the interaction is significantly characterized by a transport to quantum lifetime ratio of less than 5. However, with an increase in carrier density, quantum lifetime is observed to undergo a sharp transition from 0.17to0.25ps. This is attributed to the screening of short range repulsive scattering due to InAs quantum dots by the 2DEG.
Nondestructive and noncontact method for determining the spring constant of rectangular cantilevers
Authors: Golovko Dmytro S. , Haschke Thomas , Wiechert Wolfgang , Bonaccurso Elmar
Published: April 2007

We present here an experimental setup and suggest an extension to the long existing added-mass method for the calibration of the spring constant of atomic force microscope cantilevers. Instead of measuring the resonance frequency shift that results from attaching particles of known masses to the end of cantilevers, we load them with water microdrops generated by a commercial inkjet dispenser. Such a device is capable of generating drops, and thus masses, of extremely reproducible size. This makes it an ideal tool for calibration tasks. Moreover, the major advantage of water microdrops is that they allow for a nearly contactless calibration: no mechanical micromanipulation of particles on cantilevers is required, neither for their deposition nor for removal. After some seconds the water drop is completely evaporated, and no residues are left on the cantilever surface or tip. We present two variants: we vary the size of the drops and deposit them at the free end of the cantilever, or we keep the size of the drops constant and vary their position along the cantilever. For the second variant, we implemented also numerical simulations. Spring constants measured by this method are comparable to results obtained by the thermal noise method, as we demonstrate for six different cantilevers.
Raman spectroscopy evidence of strong spin-phonon coupling in epitaxial thin films of the double perovskite La2NiMnO6
Authors: Iliev M. N. , Guo H. , Gupta A.
Published: April 2007

The Raman spectra of epitaxial thin films of La2NiMnO6 on (001)-oriented LaAlO3 substrates have been measured in several exact scattering configurations between 12 and 773K. The evolution of the spectra with increasing temperature is consistent with a transition from the monoclinic P121∕n1 to rhombohedral R3¯ structure. The spin-phonon coupling results in significant softening of the phonon mode involving stretching vibrations of the (Ni∕Mn)O6 octahedra. The anomalous softening extends above TC=275K, indicating the presence of short range ordering up to 400K.
Doping level and work function control in oxidative chemical vapor deposited poly (3,4-ethylenedioxythiophene)
Authors: Im Sung Gap , Gleason Karen K. , Olivetti Elsa A.
Published: April 2007

Control over doping level and work function is achieved for poly(3,4-ethylenedioxythiophene) (PEDOT) films deposited by oxidative chemical vapor deposition (oCVD). Surface analysis reveals the equivalence of the surface and bulk compositions for the oCVD films. The oCVD PEDOT polymer chains doped solely with Cl− ions. By increasing the substrate temperature used for deposition, the doping level was monotonically increased from 17to33at.%, resulting in a corresponding ability to tune the work function from 5.1to5.4eV. The controllability of doping level and work function of oCVD PEDOT offers great potential advantages for organic devices.
Subsecond sintering of ice
Authors: Szabo Denes , Schneebeli Martin
Published: April 2007

Ice grains bond together in less than 1s. The tensile strength of the resulting bond was measured above −25°C in the contact time range of 10–1000ms as a function of temperature and contact load. The bond strength increases nonlinearly with time and with increasing temperature. The results indicate that the most likely mechanism of ice sintering on this time scale is the freezing of the liquidlike layer present on the surface of the ice. A model based on the plastic behavior of ice and the complete freezing of the entire contact patch well describes the observations.
Nanoscopic Coulomb explosion in ultrafast graphite ablation
Authors: Lenner M. , Kaplan A. , Palmer R. E.
Published: April 2007

The authors report single-shot femtosecond laser ablation experiments on the highly oriented pyrolitic graphite surface. The yield of positively charged carbon clusters has been measured by time-of-flight mass spectrometry. The reconstructed velocity distribution of atomic carbon ions indicates that the observed Coulomb explosion is most pronounced for fluences slightly above the damage threshold. Atomic force microscopy studies of the damage spots indicate nanoscopic removal of intact monolayers. The results imply a significant degree of charge localization on the surface graphite layers.
Focusing of high-current laser-driven ion beams
Authors: Badziak J. , Jabłoński S.
Published: April 2007

Using a two-dimensional relativistic hydrodynamic code, it is shown that a dense high-current ion beam driven by a short-pulse laser can be effectively focused by curving the target front surface. The focused beam parameters essentially depend on the density gradient scale length of the preplasma Ln and the surface curvature radius RT. When Ln⩽0.5λL (λL is the laser wavelength) and RT is comparable with the laser beam aperture dL, a significant fraction of the accelerated ions is focused on a spot much smaller than dL, which results in a considerable increase in the ion fluence and current density. Using high-contrast multipetawatt picosecond laser pulses of relativistic intensity (∼1020W∕cm2), focused ion (proton) current densities approaching those required for fast ignition of DT fuel seem to be feasible.
Double interfacial layers for highly efficient organic light-emitting devices
Authors: Park Jin Ho , Oh Seung Seok , Kim Sun Woong , Choi Eun Ha , Hong Byoung Hee , Seo Yoon Ho , Cho Guang Sup , Park Byoungchoo , Lim Jongsun , Yoon Sung Cheol , Lee Changjin
Published: April 2007

The authors report on a highly efficient phosphorescent organic light-emitting device (PHOLED) achieved by introducing nanoscale double interfacial layers, made by ultrathin surfactant and low work-function metal layers. It is shown that double interfacial layers play multiple roles in the enhancement of device performance: increasing electron injection, hole blocking, and reducing surface roughness of electroluminescent layer. With double interfacial layers, a PHOLED has shown efficiency as high as ∼60cd∕A with a current density of 1.6mA∕cm2 and a luminance of 1000cd∕m2 at 6.5V, which is higher than that of a control device with a single CsF interfacial layer.
Enhancement of Alq3 fluorescence by nanotextured silver films deposited on porous alumina substrates
Authors: Wang Ziyao , Chen Zhijian , Lan Zhihao , Zhai Xiaofeng , Du Weimin , Gong Qihuang
Published: April 2007

Enhanced photoluminescence was found in tris-8-hydroxyquinoline aluminum deposited onto nanotextured silver films with porous alumina substrates. The surface-enhanced Raman signals and shortened lifetimes suggested the presence of enhanced local electromagnetic field due to the plasmon resonance of nanotextured silver films. The photoluminescence enhancement was attributed to the increase in absorption and quantum yield. The authors analyzed the increase in quantum yield and found that the highest quantum yield was enhanced by 2.3 times compared with the samples based on flat Ag film with the same thickness. The enhancement of quantum yield has potential applications in electro-optic devices.
“Quill” writing with ultrashort light pulses in transparent materials
Authors: Kazansky Peter G. , Yang Weijia , Bricchi Erica , Bovatsek James , Arai Alan , Shimotsuma Yasuhiko , Miura Kiyotaka , Hirao Kazuyuki
Published: April 2007

A remarkable phenomenon in ultrafast laser processing of transparent materials, in particular, silica glass, manifested as a change in material modification by reversing the writing direction is observed. The effect resembles writing with a quill pen and is interpreted in terms of anisotropic trapping of electron plasma by a tilted front of the ultrashort laser pulse along the writing direction.
Corrigendum to: Target and non-target effects on the invertebrate community of Vip cotton, a new insecticidal transgenic
Authors: Whitehouse M. E. A. , Wilson L. J. , Constable G. A.
Published: April 2007

A new transgenic cotton producing the Vegetative Insecticidal Protein (Vip) is being developed to control Lepidopteran pests, especially Helicoverpa larvae. Before its introduction its efficacy against Helicoverpa larvae under field conditions needs to be confirmed, and any non-target effects it may have on the arthropod community need to be identified. We conducted field trials to compare the arthropod community in unsprayed conventional (Sicala 40) and Vip (Coker 312 Vip3A, event 102) cotton using visual searches, beatsheets, and suction samplers at 2 sites in Australia. At both sites, Vip controlled Helicoverpa larvae leading to much higher boll counts. There were no major differences in either species richness or diversity of the beneficial and non-target communities between Vip and conventional cotton, although cotton cultivar accounted for 2.7% of the variance in arthropod communities. There was no detrimental effect of Vip cotton on egg parasitoids. The number of predatory beetles and the pest mirid Creotiades dilutus (St�l) was higher in the Vip, although the increase in mirids was probably the result of more food (bolls) in the Vip crop. In a small plot experiment, we found higher numbers of whitefly in Vip, but this may be driven by differences in leaf hair between the cotton cultivars. Vip cotton appeared to have little effect on the arthropod community other than on Helicoverpa. As such it has the potential to be a useful tool in the management of Helicoverpa and may relieve resistance pressure on existing Bt cultivars (transgenic cotton containing genes for insecticidal Cry proteins), thereby increasing the durability of both technologies.
The limit to wheat water-use efficiency in eastern Australia. I. Gradients in the radiation environment and atmospheric demand
Authors: Rodriguez D. , Sadras V. O.
Published: April 2007

In the wheatbelt of eastern Australia, rainfall shifts from winter dominated in the south (South Australia, Victoria) to summer dominated in the north (northern New South Wales, southern Queensland). The seasonality of rainfall, together with frost risk, drives the choice of cultivar and sowing date, resulting in a flowering time between October in the south and August in the north. In eastern Australia, crops are therefore exposed to contrasting climatic conditions during the critical period around flowering, which may affect yield potential, and the efficiency in the use of water (WUE) and radiation (RUE). In this work we analysed empirical and simulated data, to identify key climatic drivers of potential water- and radiation-use efficiency, derive a simple climatic index of environmental potentiality, and provide an example of how a simple climatic index could be used to quantify the spatial and temporal variability in resource-use efficiency and potential yield in eastern Australia.
Around anthesis, from Horsham to Emerald, median vapour pressure deficit (VPD) increased from 0.92 to 1.28 kPa, average temperature increased from 12.9 to 15.2°C, and the fraction of diffuse radiation (FDR) decreased from 0.61 to 0.41. These spatial gradients in climatic drivers accounted for significant gradients in modelled efficiencies: median transpiration WUE (WUEB/T) increased southwards at a rate of 2.6% per degree latitude and median RUE increased southwards at a rate of 1.1% per degree latitude. Modelled and empirical data confirmed previously established relationships between WUEB/T and VPD, and between RUE and photosynthetically active radiation (PAR) and FDR. Our analysis also revealed a non-causal inverse relationship between VPD and radiation-use efficiency, and a previously unnoticed causal positive relationship between FDR and water-use efficiency.
Grain yield (range 1–7 t/ha) measured in field experiments across South Australia, New South Wales, and Queensland (n = 55) was unrelated to the photothermal quotient (Pq = PAR/T) around anthesis, but was significantly associated (r2 = 0.41, P < 0.0001) with newly developed climatic index: a normalised photothermal quotient (NPq = Pq . FDR/VPD). This highlights the importance of diffuse radiation and vapour pressure deficit as sources of variation in yield in eastern Australia. Specific experiments designed to uncouple VPD and FDR and more mechanistic crop models might be required to further disentangle the relationships between efficiencies and climate drivers.
Reliability of canola production in different rainfall zones of Western Australia
Authors: Farré Imma , Robertson Michael , Asseng Senthold
Published: April 2007

The area of canola in the wheat-based farming systems of the wheatbelt of Western Australia (WA) expanded rapidly during the 1990s and has subsequently decreased. Due to the short history of canola production in WA, there is little information on yield and oil content expectations in relation to rainfall, location, and soil type. In this paper we: (1) present the recent history of canola production in the context of the long-term climate record; (2) assess the effect of location, rainfall, soil type, and soil water at sowing on yield and oil content; and (3) determine cut-off sowing dates for profitable canola production. Simulations were run using the APSIM-Canola model with long-term climate records for 3 selected locations from the low-, medium-, and high-rainfall zones and different soil types. Analysis of recent trends in canola area showed that poor seasons and price volatility in the last few years have contributed to farmers’ perception of risk and hence the decline in area sown. Long-term simulations showed the importance of location, sowing date, soil type, and stored soil water at sowing on grain yield. Yield was negatively related to sowing date. Light-textured soils had lower yields and larger yield penalties with delayed sowing than heavy-textured soils. Soil water at sowing gave a yield advantage in most years in all locations studied, but especially in low- and medium-rainfall locations. Variation in oil content was most strongly affected by sowing date and location, while soil type and soil water at sowing had a minor effect. Long-term simulation analysis can be used as a tool to establish the latest possible sowing date to achieve profitable canola for different locations and soil types, given different canola prices and growing costs. Given the vulnerability of profitability to seasonal conditions, in the low- and medium-rainfall zone, the decision to grow canola should be tactical depending on stored soil water, sowing opportunities, seasonal climate outlook, prices, and costs. In contrast, in the high-rainfall zone, canola production is relatively low risk, and could become a reliable component of rotations.
Comparing the potassium requirements of canola and wheat
Authors: Brennan R. F. , Bolland M. D. A.
Published: April 2007

Most sandy soils used for cropping in south-western Australia are now deficient in potassium (K) due to removal of K from soil in hay and grain, and profitable grain yield responses to applied fertiliser K are commonly obtained for spring wheat (Triticum aestivum L.) and canola (oilseed rape, Brassica napus L.). However, there are only limited data comparing the K requirements of these 2 species in the region. In a glasshouse experiment we compared the K requirements of wheat (cv. Westonia), conventional canola cv. Outback (cultivars of canola not produced by classical breeding techniques to be tolerant of specific herbicides), triazine-tolerant (TT) canola cvv. Pinnacle and Surpass 501, and imidazolinone-tolerant (IT) canola cv. Surpass 603. The following measures were used: yield of 54-day-old dried shoots and seed (grain) without added K, applied K required to produce 90% of the maximum yield of shoots and grain, K required to attain a K concentration in shoots of 30 g/kg, and K required to achieve a K content in shoots (K concentration multiplied by yield) of 40 mg/pot. We also determined for each species and cultivar the concentration of K in dried shoots that was related to 90% of the maximum grain yield, to estimate critical concentration in shoots below which K deficiency was likely to reduce grain production.
All 4 canola cultivars produced similar results. Both canola and wheat produced negligible shoot yields and no grain when no K was applied. For each species and cultivar the amount of applied K required to produce 90% of the maximum yield was similar for shoots and grain, and was ~121 mg K/pot for the 4 canola cultivars and 102 mg K/pot for wheat, so ~19% more K was required for canola than for wheat. For each amount of K applied, the concentration of K in shoots was greater for canola than for wheat. The amount of applied K required to attain a K concentration of 30 g K/kg in shoots was ~96 mg K/pot for canola and 142 mg K/pot for wheat, so ~48% more K was required by wheat than by canola. The amount of K applied required to achieve a K content of 40 mg K/pot in shoots was ~46 mg K/pot for canola and 53 mg K/pot for wheat, so ~13% more applied K was required by wheat than by canola. The data suggest that canola roots were better able to obtain K from soil than wheat roots, but wheat used the K taken up more effectively than canola to produce shoots and grain. The concentration of K in dried shoots of 54-day-old plants that was related to 90% of the maximum dried shoot yield or grain was ~32 g/kg for canola and ~23 g/kg for wheat.
Relationships between metabolic endocrine systems and voluntary feed intake in Merino sheep fed a high salt diet
Authors: Blache Dominique , Grandison Micaela J. , Masters David G. , Dynes Robyn A. , Blackberry Margaret A. , Martin Graeme B.
Published: April 2007

Grazing saltbush reduces productivity in sheep mostly because the high salt intake decreases feed intake and challenges the metabolism of the animal. However, little is known of the effect of salt load on the endocrine control systems that regulate voluntary feed intake and metabolism. Plasma concentrations of leptin, insulin and cortisol and blood glucose were monitored in wethers fed for 2 weeks with either a control diet (adequate salt) fed ad libitum, a high salt diet (20% of dry matter) fed ad libitum or a group fed the control diet with an intake restricted to that of the high salt ad libitum group (control pair-fed). High salt intakes reduced voluntary feed intake within 1 day and circulating concentrations of insulin and glucose within 2 weeks. Liveweight and leptin concentrations were not specifically affected by the high intake of salt but decreased in response to the decrease in intake. Cortisol secretion was not affected. Although salt intake had a specific effect on insulin and glucose (over and above the effect of reduced feed intake alone), the reduction in insulin would be expected to increase rather than decrease appetite and feed intake. Therefore, insulin, leptin and cortisol do not appear to play major roles in the control of feed intake in sheep consuming high levels of salt.
Mutant torsinA interferes with protein processing through the secretory pathway in DYT1 dystonia cells
Authors: Hewett Jeffrey W. , Tannous Bakhos , Niland Brian P. , Nery Flavia C. , Zeng Juan , Li Yuqing , Breakefield Xandra O.
Published: April 2007

TorsinA is an AAA
+
protein located predominantly in the lumen of the endoplasmic reticulum (ER) and nuclear envelope responsible for early onset torsion dystonia (DYT1). Most cases of this dominantly inherited movement disorder are caused by deletion of a glutamic acid in the carboxyl terminal region of torsinA. We used a sensitive reporter,
Gaussia
luciferase (Gluc) to evaluate the role of torsinA in processing proteins through the ER. In primary fibroblasts from controls and DYT1 patients most Gluc activity (95%) was released into the media and processed through the secretory pathway, as confirmed by inhibition with brefeldinA and nocodazole. Fusion of Gluc to a fluorescent protein revealed coalignment and fractionation with ER proteins and association of Gluc with torsinA. Notably, fibroblasts from DYT1 patients were found to secrete markedly less Gluc activity as compared with control fibroblasts. This decrease in processing of Gluc in DYT1 cells appear to arise, at least in part, from a loss of torsinA activity, because mouse embryonic fibroblasts lacking torsinA also had reduced secretion as compared with control cells. These studies demonstrate the exquisite sensitivity of this reporter system for quantitation of processing through the secretory pathway and support a role for torsinA as an ER chaperone protein.
Intranuclear targeting and nuclear export of the adenovirus E1B-55K protein are regulated by SUMO1 conjugation
Authors: Kindsmüller Kathrin , Groitl Peter , Härtl Barbara , Blanchette Paola , Hauber Joachim , Dobner Thomas
Published: April 2007

We have investigated the requirements for CRM1-mediated nuclear export and SUMO1 conjugation of the adenovirus E1B-55K protein during productive infection. Our data show that CRM1 is the major export receptor for E1B-55K in infected cells. Functional inactivation of the E1B-55K CRM1-dependent nuclear export signal (NES) or leptomycin B treatment causes an almost complete redistribution of the viral protein from the cytoplasm to the nucleus and its accumulation at the periphery of the viral replication centers. Interestingly, however, this nuclear restriction imposed on the wild type and the NES mutant protein is fully compensated by concurrent inactivation of the adjacent SUMO1 conjugation site. Moreover, the same mutation fully reverses defects of the NES mutant in the nucleocytoplasmic transport of Mre11 and proteasomal degradation of p53. These results show that nuclear export of E1B-55K in infected cells occurs via CRM1-dependent and -independent pathways and suggest that SUMO1 conjugation and deconjugation provide a molecular switch that commits E1B-55K to a CRM1-independent export pathway.
RKIKK Motif in the Intracellular Domain Is Critical for Spatial and Dynamic Organization of ICAM-1: Functional Implication for the Leukocyte Adhesion and Transmigration
Authors: Oh Hyun-Mee , Lee SungGa , Na Bo-Ra , Wee Hyun , Kim Sang-Hyun , Choi Suck-Chei , Lee Kang-Min , Jun Chang-Duk
Published: April 2007

No direct evidence has been reported whether the spatial organization of ICAM-1 on the cell surface is linked to its physiological function in terms of leukocyte adhesion and transendothelial migration (TEM). Here we observed that ICAM-1 by itself directly regulates the de novo elongation of microvilli and is thereby clustered on the microvilli. However, truncation of the intracellular domain resulted in uniform cell surface distribution of ICAM-1. Mutation analysis revealed that the C-terminal 21 amino acids are dispensable, whereas a segment of 5 amino acids (507RKIKK511) in the NH-terminal third of intracellular domain, is required for the proper localization and dynamic distribution of ICAM-1 and the association of ICAM-1 with F-actin, ezrin, and moesin. Importantly, deletion of the507RKIKK511significantly delayed the LFA-1–dependent membrane projection and decreased leukocyte adhesion and subsequent TEM. Endothelial cells treated with cell-permeant penetratin-ICAM-1 peptides comprising ICAM-1 RKIKK sequences inhibited leukocyte TEM. Collectively, these findings demonstrate that507RKIKK511is an essential motif for the microvillus ICAM-1 presentation and further suggest a novel regulatory role for ICAM-1 topography in leukocyte TEM.
Direct Observation of Regulated Ribonucleoprotein Transport Across the Nurse Cell/Oocyte Boundary
Authors: Mische Sarah , Li Mingang , Serr Madeline , Hays Thomas S.
Published: April 2007

In Drosophila, the asymmetric localization of specific mRNAs to discrete regions within the developing oocyte determines the embryonic axes. The microtubule motors dynein and kinesin are required for the proper localization of the determinant ribonucleoprotein (RNP) complexes, but the mechanisms that account for RNP transport to and within the oocyte are not well understood. In this work, we focus on the transport of RNA complexes containing bicoid (bcd), an anterior determinant. We show in live egg chambers that, within the nurse cell compartment, dynein actively transports green fluorescent protein-tagged Exuperantia, a cofactor required for bcd RNP localization. Surprisingly, the loss of kinesin I activity elevates RNP motility in nurse cells, whereas disruption of dynein activity inhibits RNP transport. Once RNPs are transferred through the ring canal to the oocyte, they no longer display rapid, linear movements, but they are distributed by cytoplasmic streaming and gradually disassemble. By contrast, bcd mRNA injected into oocytes assembles de novo into RNP particles that exhibit rapid, dynein-dependent transport. We speculate that after delivery to the oocyte, RNP complexes may disassemble and be remodeled with appropriate accessory factors to ensure proper localization.
Increased Apoptosis and Skewed Differentiation in Mouse Embryonic Stem Cells Lacking the Histone Methyltransferase Mll2
Authors: Lubitz Sandra , Glaser Stefan , Schaft Julia , Stewart A. Francis , Anastassiadis Konstantinos
Published: April 2007

Epigenetic regulation by histone methyltransferases provides transcriptional memory and inheritable propagation of gene expression patterns. Potentially, the transition from a pluripotent state to lineage commitment also includes epigenetic instructions. The histone 3 lysine 4 methyltransferase Mll2/Wbp7 is essential for embryonic development. Here, we used embryonic stem (ES) cell lines deficient for Mll2 to examine its function more accurately. Mll2−/− ES cells are viable and retain pluripotency, but they display cell proliferation defects due to an enhanced rate of apoptosis. Apoptosis was not relieved by caspase inhibition and correlated with decreased Bcl2 expression. Concordantly, Mll2 binds to the Bcl2 gene and H3K4me3levels are reduced at the binding site when Mll2 is absent. In vitro differentiation showed delays along representative pathways for all three germ layers. Although ectodermal delays were severe and mesodermal delays persisted at about three days, endodermal differentiation seemed to recover and overshoot, concomitant with prolonged Oct4 gene expression. Hence, Mll2 is not required for ES cell self-renewal or the complex changes in gene expression involved in lineage commitment, but it contributes to the coordination and timing of early differentiation decisions.
Cx43 Mediates TGF-β Signaling through Competitive Smads Binding to Microtubules
Authors: Dai Ping , Nakagami Takuo , Tanaka Hideo , Hitomi Toshiaki , Takamatsu Tetsuro
Published: April 2007

Transforming growth factor-β (TGF-β) superfamily members play an important role in growth, differentiation, adhesion, apoptosis, and development in many species from insects and worms to vertebrates. Recently, TGF-β signaling has been demonstrated to be negatively regulated by microtubules (MTs), which anchor endogenous Smad2/3 to cytosol and also directly interact with connexin43 (Cx43), and the activity of TGF-β is mediated by Cx43. However, the mechanism underlying the intracellular regulation of TGF-β activity by Cx43 remains unknown. Here, we found that the functional link between TGF-β activation and Cx43 is mediated by interactions among Smad2/3, MTs, and Cx43. We confirmed that Cx43 competes with Smad2/3 for binding to MTs, which Cx43 specifically induces release of Smad2/3 from MTs and increases phospho-Smad2 and which, as a result, Smad2/3 and Smad4 are accumulated in the nucleus, leading to activation of the transcription of target genes. Consistently, knockdown of the endogenous Cx43 activity with double-strand RNA (dsRNA) in HL1 cardiomyocytes and Cx43 knockout mice cardiomyocytes consistently show the opposite effect. Our findings demonstrate a novel mechanism for Cx43 positive regulation of TGF-β function.
Fission Yeast Taz1 and RPA Are Synergistically Required to Prevent Rapid Telomere Loss
Authors: Kibe Tatsuya , Ono Yuuki , Sato Koichiro , Ueno Masaru
Published: April 2007

The telomere complex must allow nucleases and helicases to process chromosome ends to make them substrates for telomerase, while preventing these same activities from disrupting chromosome end-protection. Replication protein A (RPA) binds to single-stranded DNA and is required for DNA replication, recombination, repair, and telomere maintenance. In fission yeast, the telomere binding protein Taz1 protects telomeres and negatively regulates telomerase. Here, we show that taz1-d rad11-D223Y double mutants lose their telomeric DNA, indicating that RPA (Rad11) and Taz1 are synergistically required to prevent telomere loss. Telomere loss in the taz1-d rad11-D223Y double mutants was suppressed by additional mutation of the helicase domain in a RecQ helicase (Rqh1), or by overexpression of Pot1, a single-strand telomere binding protein that is essential for protection of chromosome ends. From our results, we propose that in the absence of Taz1 and functional RPA, Pot1 cannot function properly and the helicase activity of Rqh1 promotes telomere loss. Our results suggest that controlling the activity of Rqh1 at telomeres is critical for the prevention of genomic instability.
Functional Interaction between Phosducin-like Protein 2 and Cytosolic Chaperonin Is Essential for Cytoskeletal Protein Function and Cell Cycle Progression
Authors: Stirling Peter C. , Srayko Martin , Takhar Karam S. , Pozniakovsky Andrei , Hyman Anthony A. , Leroux Michel R.
Published: April 2007

The C haperonin Containing Tcp1 (CCT) maintains cellular protein folding homeostasis in the eukaryotic cytosol by assisting the biogenesis of many proteins, including actins, tubulins, and regulators of the cell cycle. Here, we demonstrate that the essential and conserved eukaryotic phosducin-like protein 2 (PhLP2/PLP2) physically interacts with CCT and modulates its folding activity. Consistent with this functional interaction, temperature-sensitive alleles of Saccharomyces cerevisiae PLP2 exhibit cytoskeletal and cell cycle defects. We uncovered several high-copy suppressors of the plp2 alleles, all of which are associated with G1/S cell cycle progression but which do not appreciably affect cytoskeletal protein function or fully rescue the growth defects. Our data support a model in which Plp2p modulates the biogenesis of several CCT substrates relating to cell cycle and cytoskeletal function, which together contribute to the essential function of PLP2.
The Nucleolar Channel System of Human Endometrium Is Related to Endoplasmic Reticulum and R-Rings
Authors: Kittur Nupur , Zapantis Gregory , Aubuchon Mira , Santoro Nanette , Bazett-Jones David P. , Meier U. Thomas
Published: April 2007

The nucleolar channel system (NCS) is a well-established ultrastructural hallmark of the postovulation endometrium. Its transient presence has been associated with human fertility. Nevertheless, the biogenesis, composition, and function of these intranuclear membrane cisternae are unknown. Membrane systems with a striking ultrastructural resemblance to the NCS, termed R-rings, are induced in nuclei of tissue culture cells by overexpression of the central repeat domain of the nucleolar protein Nopp140. Here we provide a first molecular characterization of the NCS and compare the biogenesis of these two enigmatic organelles. Like the R-rings, the NCS consists of endoplasmic reticulum harboring the marker glucose-6-phosphatase. R-ring formation initiates at the nuclear envelope, apparently by a calcium-mediated Nopp140-membrane interaction, as supported by the calcium-binding ability of Nopp140, the inhibition of R-ring formation by calcium chelators, and the concentration of Nopp140 and complexed calcium in R-rings. Although biogenesis of the NCS may initiate similarly, the reduced presence of complexed calcium and Nopp140 suggests the involvement of additional factors.
Phellinus linteus Extract Augments the Immune Response in Mitomycin C‐Induced Immunodeficient Mice
Authors: Matsuba Shintaro , Matsuno Hideo , Sakuma Masahiro , Komatsu Yasuhiro
Published: April 2007

Phellinus linteus is a fungus distributed throughout Japan, Korea and China. Boiled water‐soluble extracts from P. linteus (PLW) have shown anti‐tumor and immunomodulatory properties in experiments done by intraperitoneal treatment, or in in vitro cell cultures. This is the first investigation on how oral administration of PLW influences immune responses. Here, we established immunodeficient mice by mitomycin C (MMC) and then researched how PLW influenced plaque‐forming cell (PFC) production and populations of cytokine [interferon‐ (IFNγ‐) and interleukin‐4 (IL‐4)]‐producing T lymphocytes. PLW samples were administered orally for 19 days (1, 2 or 4 g/kg/day). PFC assay was followed using Jerne′s method. IFN‐ and IL‐4‐producing T lymphocyte populations were measured by flow‐activated cell sorter (FACS). These assays were conducted the day after the last oral administration. MMC groups were given MMC (1 mg/kg/day) intraperitoneally for 6 days with PLW administration. The number of PFC per 106 spleen cells increased significantly in the PLW (2 g/kg/day) group when compared with the MMC‐control (P < 0.05) while populations of IFNγ‐ and IL‐4‐producing T lymphocytes decreased by MMC treatment. However, the PLW group tended to increase more than the MMC‐control. Our results indicated that PLW augments the immune response of the spleen in MMC‐induced immunodeficient mice.
Chinese Medicine: A Cognitive and Epistemological Review
Authors: Kavoussi Ben
Published: April 2007

In spite of the common belief that Chinese natural philosophy and medicine have a unique frame of reference completely foreign to the West, this article argues that they in fact have significant cognitive and epistemic similarities with certain esoteric health beliefs of pre‐Christian Europe. From the standpoint of Cognitive Science, Chinese Medicine appears as a proto‐scientific system of health observances and practices based on a symptomological classification of disease using two elementary dynamical‐processes pattern categorization schemas: a hierarchical and combinatorial inhibiting–activating model (Yin‐Yang), and a non‐hierarchical and associative five‐parameter semantic network (5‐Elements/Agents). The concept‐map of the five‐parameter model amounts to a pentagram, a commonly found geomantic and spell casting sigil in a number of pre‐Christian health and safety beliefs in Europe, to include the Pythagorean cult of Hygieia, and the Old Religion of Northern Europe. This non‐hierarchical pattern‐recognition archetype/prototype was hypothetically added to the pre‐existing hierarchical one to form a hybrid nosology that can accommodate for a change in disease perceptions. The selection of five parameters rather than another number might be due to a numerological association between the integer five, the golden ratio, the geometry of the pentagram and the belief in health and wholeness arising from cosmic or divine harmony. In any case, this body of purely empirical knowledge is nowadays widely flourishing in the US and in Europe as an alternative to Western Medicine and with the claim of being a unique, independent and comprehensive medical system, when in reality it is structurally—and perhaps historically—related to the health and safety beliefs of pre‐Christian Europe; and without the prospect for an epistemological rupture, it will remain built upon rudimentary cognitive modalities, ancient metaphysics, and a symptomological view of disease.
What determines the mobility of charge carriers in conjugated polymers?
Authors: Laquai Frédéric , Wegner Gerhard , Bässler Heinz
Published: April 2007

In a conjugated polymer, the mobility of charge carriers is not a well-defined coefficient of a particular material as it is in an inorganic crystalline semiconductor but depends on the time domain of detection. On a time-scale of typically 100 fs, the on-chain mobility is ultra-high and controlled by the electronic band width of the polymer chain. When a carrier hits a chain imperfection, subsequent mesoscopic on-chain motion is retarded and controlled by intrachain disorder to which the chain environment contributes. Macroscopic transport commences after a time when interchain carrier jumps become rate limiting. It is routinely probed by time-of-flight experiments and can be rationalized in terms of random walk within a rough energy landscape. Experimental signatures of the various modes of transport are discussed.