bluuebunny/crossref_metadata_2025 huggingface dataset:
Broccoli ‘Fiolaro’ (Brassica oleracea) an endangered typical Italian cultivar. A genetic analysis by SSR markers
Authors: Vischi M. , Fiori M. , De Paoli E. , Padovan S. , Guarda M. , Olivieri A.
Published: May 2008

‘Broccolo fiolaro’ (Brassica oleraceaL. convar. Italica) is a typical vegetable produced in a restricted hill country area around Creazzo (Vicenza) in north-eastern Italy. The cultivation of this vegetable dates back several centuries ago, but a very few farms are still involved in the production. ‘Broccolo fiolaro’ is a variety of broccoli highly valued for its agronomic and organoleptic features.

Four ‘Broccolo fiolaro’ selections were characterized by simple sequence repeats (SSRs) molecular markers and compared with other five cultivated varieties of broccoli of the Italica group in order to reconstruct their genetic structure and evaluate the degree of similarity among and within populations. The analysis of 12 SSR polymorphic loci pointed out a low genetic variability among the four ‘Broccolo fiolaro’ selections. Moreover, the whole ‘Fiolaro’ group showed significant differentiation from the other broccoli cultivars and could be easily distinguished by cluster analysis. An assignment test on ~30 genotyped plants randomly chosen from each broccoli population correctly recognized the proper accession 88% of the time, proving this method to be useful for cultivar identification.
Nutzen einer antihypertensiven Therapie bei über 80-Jährigen
Authors: Waeber B. , Burnier M. , Hess O. , Lüscher T.
Published: May 2008

Die HYVET-Studie hatte das Ziel zu prüfen, ob eine antihypertensive Therapie auch beim Patienten von 80 und mehr Jahren einen Nutzen hat. Die Patienten (n = 3 845) mit einem systolischen Blutdruck von 160 bis 190 mmHg und einem diastolischen Blutdruck unter 110 mmHg wurden zu Indapamid (1.5 mg/Tag), bei Bedarf in Kombination mit Perindopril (2–4 mg/Tag), oder einem Placebo randomisiert. Die Patienten wurden doppelblind während einer durchschnittlichen Beobachtungszeit von 2.1 Jahren verfolgt. Der Zielwert des Blutdrucks (<150/80 mmHg) wurde nach 2 Jahren von 48.0% der Patienten in der Behandlungsgruppe, versus 19.9% in der Placebogruppe (p < 0.001) erreicht. Das Risiko eines tödlichen zerebrovaskulären Ereignisses konnte dank der Therapie um 39% (p = 0.05), die Entwicklung einer Herzinsuffizienz (tödlich oder nicht tödlich) um 64%( p < 0.001) und die kardiovaskuläre Mortalität um 23% (p < 0.06) gesenkt werden. Die totale Mortalität konnte um 21% (p = 0.01) vermindert werden. Die medikamentöse Therapie war ebenso gut verträglich wie Placebo und war mit deutlich weniger schweren Nebenwirkungen behaftet als letzteres. Diese positiven Resultate mit einer Therapie mit Indapamid und Perindopril rechtfertigen ab jetzt eine Therapie der über 80-jährigen hypertonen Patienten.
A decadal‐scale Holocene sea surface temperature record from the subpolar North Atlantic constructed using diatoms and statistics and its relation to other climate parameters
Authors: Berner K. S. , Koç N. , Divine D. , Godtliebsen F. , Moros M.
Published: May 2008

A sediment core from Reykjanes Ridge has been studied at 10‐ to 50‐year time resolution to document variability of Holocene surface water conditions in the western North Atlantic and to evaluate effects of Holocene ice‐rafting episodes. Diatom assemblages are converted to quantitative sea surface temperatures (SST) using three different transfer functions. Spectral and scale‐space methods are also applied on the records to explore variability at different timescales. Diatom assemblage and SST records clearly show that decaying remnants of the Laurentide ice sheet strongly influenced early Holocene climate in the western North Atlantic. This overrode the predominance of Milankovitch forcing, which played a key role in the development of Holocene climate in the eastern North Atlantic and Nordic Seas. Superimposed on general Holocene climate change is high‐frequency SST variability on the order of 1°−3°C. The record also documents climatic oscillations with 600‐ to 1000‐, ∼1500‐, and 2500‐year periodicities, with a time‐dependent dominance of different periodicities through the Holocene; a clear change in variability occurred about 5 ka BP. The SST record also provides evidence for Holocene cooling events (HCE) that, in some cases, correlate to documented southward intrusions of ice into the North Atlantic.
Mass transfer process in a two‐region medium
Authors: Chastanet J. , Wood Brian D.
Published: May 2008

Two‐region mass transfer models have been widely considered for describing flow and transport in highly heterogeneous porous media. Previous studies have indicated that in two‐region systems the effective mass transfer coefficient is not a constant but depends upon a time convolution of the concentration history. Although such a representation does capture the mass transfer dynamics correctly, it can be difficult to apply because the convolution operation couples the effective mass transfer rate to the average concentration. In this work, we present the upscaling of a two‐region system complete with a method for predicting the time‐varying effective mass transfer coefficient that arises. We consider in detail the particular case that occurs when the convective flux in the low conductivity region can be neglected and the inclusions are spherical. This puts the problem in a classical context, and we develop explicit closed‐form expressions for the time‐varying effective mass transfer coefficient within the context of volume averaging. Our goals in this work are to (1) determine the general (convolution) form of the macroscale two‐equation model for transport in such a medium using volume averaging, (2) assess the influence of several simplifications to the convolution form of the two‐equation model, and (3) compare this result with existing classical results for the simplified geometry of spherical inclusions. A comparison of the results predicted by theory and experimental data from two macroscale, two‐region systems is made. Additional discussion about how the method can be extended to other geometries and to cases where the convective flux is not negligible is also presented.
Effect of heat transmission through melt ponds and ice on melting during summer in the Arctic Ocean
Authors: Inoue Jun , Kikuchi Takashi , Perovich Donald K.
Published: May 2008

To observe sea ice and ocean conditions in the Arctic in summer, a trans‐Arctic research cruise of the U.S. Coast Guard Cutter Healy was conducted from 5 August to 30 September 2005. The relationship between the ice concentration observed by the on‐board ice‐watch and the temperature above the freezing point (ΔT) measured by expendable conductivity‐temperature‐depth (XCTD) sensors had a negative correlation (CT‐relationship) before the onset of freezing. This means that as ice concentration decreases, ΔT increases due to the larger absorption of solar radiation. However, ΔT in high ice‐covered regions (>90%) remains more than 0.1 K during the melting season, suggesting that sea‐ice and melt‐pond areas work as heat source areas as well as leads. By separating the effects of heat input from open water, melt ponds, and ice on the heating of mixed layers, we found that the contribution of the transmitted heat through ponds and ice on the ΔT‐gain is large in highly ice‐covered regions. To examine the effect of such heating on ice melting, a simplified ice‐ocean‐coupled model was applied. By changing the heat input to obtain the analyzed ΔT‐gain for each surface category, the transmittances of ponds and ice were indirectly estimated as 55% and 9%, respectively. After including the effects of transmitted heat through ponds and ice, the modeled results agreed with the observed CT‐relationship. Comparisons between the results of turning on and off the effect of transmitted heat through ponds and ice showed that it amplified the open water‐albedo feedback mechanism in the highly ice‐covered region.
Pseudomonas aeruginosa uses type III secretion system to kill biofilm-associated amoebae
Authors: Matz Carsten , Moreno Ana Maria , Alhede Morten , Manefield Mike , Hauser Alan R , Givskov Michael , Kjelleberg Staffan
Published: May 2008

Bacteria and protozoa coexist in a wide range of biofilm communities of natural, technical and medical importance. Generally, this interaction is characterized by the extensive grazing activity of protozoa on bacterial prey populations. We hypothesized that the close spatial coexistence in biofilms should allow opportunistic pathogenic bacteria to utilize their eukaryote-targeting arsenal to attack and exploit protozoan host cells. Studying cocultures of the environmental pathogen Pseudomonas aeruginosa and the amoeba Acanthamoeba castellanii, we found that P. aeruginosa rapidly colonized and killed biofilm-associated amoebae by a quorum-sensing independent mechanism. Analysis of the amoeba-induced transcriptome indicated the involvement of the P. aeruginosa type III secretion system (T3SS) in this interaction. A comparison of mutants with specific defects in the T3SS demonstrated the use of the secretion apparatus and the effectors ExoU, ExoS and ExoT in the killing process, of which ExoU had the greatest impact. T3SS-mediated virulence towards A. castellanii was found to be controlled by the global regulators RpoN and RpoS and through modulation of cAMP and alginate biosynthesis. Our findings suggest that conserved virulence pathways and specifically the T3SS play a central role in bacteria–protozoa interactions in biofilms and may be instrumental for the environmental persistence and evolution of opportunistic bacterial pathogens.
“Infrared” singularities in the field theory of superfluidity and temperature corrections to the first and second sound velocities in helium II
Authors: Pashitskiĭ É. A. , Vilchinskiĭ S. I. , Chumachenko A. V.
Published: May 2008

Higher-order corrections to the self-energy parts of the field theory of superfluidity are obtained using V. N. Popov’s perturbation theory modified for a strongly interacting Bose system and free of infrared divergences. It is shown that the calculation of these corrections reduces to solving kinetic-type equations. Using these equations as a basis, the temperature corrections to the first and second sound velocities in the superfluid Bose liquid He4 are obtained. The temperature dependence of the density of the superfluid component of the Bose liquid He4 is calculated on the basis of a model of the superfluid component as a superposition of interaction-suppressed single-particle and intense pair condensates.
Defects and supersolidity: effects of annealing and stress on elastic behavior of solid He4
Authors: Syshchenko A. , Day J. , Beamish J.
Published: May 2008

Recent measurements have shown that solid He4 can decouple from a torsional oscillator below 200mK, and defects appear to be crucial to this behavior. Helium’s shear modulus increases in the same range, which can be understood in terms of dislocations pinned by He3 impurities at the lowest temperatures, but mobile above 100mK. We measure the pressure and shear modulus of helium to study the effects of annealing and stresses applied at low temperatures. Pressure gradients produced during crystal growth or plastic deformation are greatly reduced by annealing, but only at temperatures close to melting. Annealing does not change the low-temperature modulus but usually raises it at high temperature, as expected if annealing eliminates some dislocations. Large stresses also affect the modulus, but these changes are reversed by heating above 0.5K, suggesting that defects introduced by stress are easier to anneal than those produced during growth.
Growth of He3 crystals at different magnetic fields
Authors: Bueno J. , Blaauwgeers R. , Parshin A. Y. , Jochemsen R.
Published: May 2008

Experiments on He3 crystal growth are carried out in magnetic field up 9T. The data are analyzed and compared with the results found at zero magnetic field. It is found that the interface and the crystal lattice couple weakly in the presence of an external magnetic field, and we can set an upper limit of the step energy of the ⟨110⟩, ⟨100⟩ and ⟨211⟩ facets at different magnetic fields.
Complex-time velocity autocorrelation functions for Lennard-Jones fluids with quantum pair-product propagators
Authors: Kegerreis Jeb , Nakayama Akira , Makri Nancy
Published: May 2008

We use the pair-product approximation to the complex-time quantum mechanical propagator to obtain accurate quantum mechanical results for the symmetrized velocity autocorrelation function of a Lennard-Jones fluid at two points on the thermodynamic phase diagram. A variety of tests are performed to determine the accuracy of the method and understand its breakdown at longer times. We report quantitative results for the initial 0.3 ps of the dynamics, a time at which the correlation function has decayed to approximately one fifth of its initial value.
Analysis of charge transfer effects in molecular complexes based on absolutely localized molecular orbitals
Authors: Khaliullin Rustam Z. , Bell Alexis T. , Head-Gordon Martin
Published: May 2008

A new method based on absolutely localized molecular orbitals (ALMOs) is proposed to measure the degree of intermolecular electron density delocalization (charge transfer) in molecular complexes. ALMO charge transfer analysis (CTA) enables separation of the forward and backward charge transfer components for each pair of molecules in the system. The key feature of ALMO CTA is that all charge transfer terms have corresponding well defined energetic effects that measure the contribution of the given term to the overall energetic stabilization of the system. To simplify analysis of charge transfer effects, the concept of chemically significant complementary occupied-virtual orbital pairs (COVPs) is introduced. COVPs provide a simple description of intermolecular electron transfer effects in terms of just a few localized orbitals. ALMO CTA is applied to understand fundamental aspects of donor-acceptor interactions in borane adducts, synergic bonding in classical and nonclassical metal carbonyls, and multiple intermolecular hydrogen bonds in a complex of isocyanuric acid and melamine. These examples show that the ALMO CTA results are generally consistent with the existing conceptual description of intermolecular bonding. The results also show that charge transfer and the energy lowering due to charge transfer are not proportional to each other, and some interesting differences emerge which are discussed. Additionally, according to ALMO CTA, the amount of electron density transferred between molecules is significantly smaller than charge transfer estimated from various population analysis methods.
Deformation potentials of the direct band gap of n-Al0.25Ga0.75As from controlled microscopic stress fields
Authors: Porporati Alessandro Alan , Furukawa Naohide , Zhu Wenliang , Pezzotti Giuseppe
Published: May 2008

The deformation potentials have been experimentally determined for the direct gap of n-Al0.25Ga0.75As and compared to experimental and theoretical literature values. Highly localized spectroscopic stress assessments could be achieved using a field-emission electron gun as the energy source for stimulating cathodoluminescence (CL) emission from an epitaxial thin film sample. The three independent deformation potentials for the zinc-blende-type crystal structure could be obtained from a single set of CL measurements in small material volumes of the order of the μm3, while all previously published characterizations required samples of a relatively large size (i.e., of the order of mm3).
Density functional theory of inhomogeneous liquids. II. A fundamental measure approach
Authors: Lutsko James F.
Published: May 2008

Previously, it has been shown that the direct correlation function for a Lennard–Jones fluid could be modeled by a sum of that for hard-spheres, a mean-field tail, and a simple linear correction in the core region constructed so as to reproduce the (known) bulk equation of state of the fluid [Lutsko, J. Chem. Phys. 127, 054701 (2007)]. Here, this model is combined with ideas from the fundamental measure theory to construct a density functional theory for the free energy. The theory is shown to accurately describe a range of inhomogeneous conditions including the liquid vapor interface, the fluid in contact with a hard wall, and a fluid confined in a slit pore. The theory gives quantitatively accurate predictions for the surface tension, including its dependence on the potential cutoff. It also obeys two important exact conditions: That relating the direct correlation function to the functional derivative of the free energy with respect to density and the wall theorem.
Electrostatic resonances of a negative-permittivity hemisphere
Authors: Kettunen Henrik , Wallén Henrik , Sihvola Ari
Published: May 2008

This article studies the electric response of an electrically small hemispherical object with negative permittivity by computing its polarizability which is determined by two orthogonal components, the axial one and the transverse one. A certain range of negative permittivity values is found where the mathematical determination of the polarizability becomes impossible due to an unlimited number of singularities. These singularities are due to surface plasmons, also referred to as electrostatic resonances, caused by the sharp edge of the hemisphere. It is also found that the planar surface of the hemisphere may support resonant surface modes. Furthermore, there exists a dipolar resonance determined by the overall geometry. In addition, it is shown that the resonances can be smoothened by introducing losses and, even more importantly, rounding the edge.
Solution of the Percus-Yevick equation for hard disks
Authors: Adda-Bedia M. , Katzav E. , Vella D.
Published: May 2008

The authors solve the Percus-Yevick equation in two dimensions by reducing it to a set of simple integral equations. They numerically obtain both the pair correlation function and the equation of state for a hard disk fluid and find good agreement with available Monte Carlo results. The present method of resolution may be generalized to any even dimension.
Deuteron NMR relaxation, spectra, and evidence for the order-disorder phase transition in (ND4)2PtCl6
Authors: Birczyński A. , Ylinen E. E. , Punkkinen M. , Prager M. , Szymocha A. M. , Lalowicz Z. T.
Published: May 2008

Deuteron NMR relaxation and spectra were studied at the resonance frequency of 46MHz in polycrystalline (ND4)2PtCl6 between 300–5K. The relaxation rate maximum near 50K is about 53% smaller than the calculated maximum related to 120° rotations about the threefold symmetry axes of the ammonium ion. The difference is explained by assuming for a N–D vector a total of 24 equilibrium directions, which in groups of six deviate from the nearest Pt–N vector by a certain angle Θ. So-called limited jumps between the directions of each group take place much more frequently than the large-angle rotations, thus rendering a fraction of the deuteron quadrupole coupling ineffective in relaxation. A motional model is presented, which takes into account both these motions simultaneously. A comparison with experimental data leads to Θ=26.0°, in reasonable agreement with earlier neutron diffraction data. A sharp decrease found in the relaxation rate at the order-disorder phase transition temperature of 27.2K is related to the fact that one of the six equilibrium directions becomes preferred. This leads to a formation of ordered domains, in which the active motion driving the relaxation is 120° rotations. Two components in the spectra found below 55K are related to domains (broad) and transition regions between domains (narrow). Reasons for the nonexponentiality observed below 20K are discussed, the most likely explanation being that limited jumps dominate within transition regions and make the corresponding deuterons relax faster than those in domains.
Energy bandgap bowing of InAlN alloys studied by spectroscopic ellipsometry
Authors: Iliopoulos E. , Adikimenakis A. , Giesen C. , Heuken M. , Georgakilas A.
Published: May 2008

In x Al 1 − x N films were heteroepitaxially grown on AlN∕Al2O3 (0001) templates by molecular beam epitaxy. The compositions studied spanned the whole ternary range. The complex dielectric function of the films was investigated by variable angle spectroscopic ellipsometry in the energy range from 0.55to6eV. The energy bandgap bowing parameter was found to strongly depend on composition, monotonically increasing with decreasing InN mole fraction. This behavior is in agreement with theoretical predictions of large charge transfer contributions to bandgap bowing.
Polarization rotation transitions in anisotropically strained SrTiO3 thin films
Authors: Vasudevarao A. , Denev Sava , Biegalski Michael D. , Li Yulan , Chen Long-Qing , Trolier-McKinstry Susan , Schlom Darrell G. , Gopalan Venkatraman
Published: May 2008

Commensurately strained epitaxial SrTiO3 thin films on a GdScO3 substrate with anisotropic in-plane tensile strains of 1.46% and 1.59% were grown. By using optical second harmonic generation and polarization measurements, a ferroelectric transition from a tetragonal 4∕mmm phase to a ferroelectric mm2 phase at ∼400K and an antiferrodistortive transition to a multiferroic phase at 150–175K are observed, which are in agreement with thermodynamic calculations. In addition, a series of polarization rotation transitions between ⟨100⟩p to ⟨l00⟩p (0<l<1) is observed in the 4–400K temperature range.
Wedged multilayer Laue lens
Authors: Conley Ray , Liu Chian , Qian Jun , Kewish Cameron M. , Macrander Albert T. , Yan Hanfei , Kang Hyon Chol , Maser Jörg , Stephenson G. Brian
Published: May 2008

A multilayer Laue lens (MLL) is an x-ray focusing optic fabricated from a multilayer structure consisting of thousands of layers of two different materials produced by thin-film deposition. The sequence of layer thicknesses is controlled to satisfy the Fresnel zone plate law and the multilayer is sectioned to form the optic. An improved MLL geometry can be created by growing each layer with an in-plane thickness gradient to form a wedge, so that every interface makes the correct angle with the incident beam for symmetric Bragg diffraction. The ultimate hard x-ray focusing performance of a wedged MLL has been predicted to be significantly better than that of a nonwedged MLL, giving subnanometer resolution with high efficiency. Here, we describe a method to deposit the multilayer structure needed for an ideal wedged MLL and report our initial deposition results to produce these structures.
Double-layer porous TiO2 electrodes for solid-state dye-sensitized solar cells
Authors: Fan Xiaojuan , Demaree David P. , St. John Jessica M. , Tripathi Akhilesh , Oliver Scott R. J.
Published: May 2008

We report a rapid and inexpensive method to fabricate double-layer porous TiO2 electrodes for quasisolid dye-sensitized solar cells. Polymethylmethacrylate mixed with titanium alkoxide in methyl ethyl ketone was used as template precursor. Thermal removal of the polymer at 500°C leads to mesoporous double-layer TiO2 thin films of nanocrystalline anatase. The cells show a high open-circuit voltage of ∼1.18V and overall photoelectric conversion efficiency of 2.05% under an illumination of one sun (AM1.5 global, 100mW∕cm2).
Tuning the polarization state of enhanced transmission in gratings
Authors: Crouse David , Hibbins Alastair P. , Lockyear Matthew J.
Published: May 2008

The polarization characteristics of enhanced transmission of lamellar gratings with structural dimensions on the subwavelength scale were studied and experimental results were compared to numerical models. The ability to tune the polarization state of the transmitted beam by varying the grating’s structural parameters is discussed. Gratings were fabricated and tested in the microwave spectral region, and the results were compared to theoretically modeled results. Enhanced transmission produced by cavity modes was experimentally verified for both s-polarized and p-polarized incident beams of light. Applications of these results to photonic devices in the visible, infrared, and microwave spectral regions are discussed.
On the Kertész line: Some rigorous bounds
Authors: Ruiz Jean , Wouts Marc
Published: May 2008

We study the Kertész line of the q-state Potts model at (inverse) temperature β in the presence of an external magnetic field h. This line separates the two regions of the phase diagram according to the existence or not of an infinite cluster in the Fortuin–Kasteleyn representation of the model. It is known that the Kertész line hK(β) coincides with the line of first order phase transition for small fields when q is large enough. Here, we prove that the first order phase transition implies a jump in the density of the infinite cluster; hence, the Kertész line remains below the line of first order phase transition. We also analyze the region of large fields and prove, using techniques of stochastic comparisons, that hK(β) equals log(q−1)−log(β−βp) to the leading order, as β goes to βp=−log(1−pc), where pc is the threshold for bond percolation.
Joule heating in ferromagnetic nanowires: Prediction and observation
Authors: Kim Kab-Jin , Lee Jae-Chul , Choe Sug-Bong , Shin Kyung-Ho
Published: May 2008

We present an analytic theory of the Joule heating in metallic nanowires. The steady state is calculated for heat conduction through the insulation layer and then the transient state is considered from the thermodynamics law. The temperature is predicted to exhibit a quick exponential decay to a steady state within a few tens of nanoseconds. The decay time is linearly dependent on the temperature coefficient and both increase to saturation values with the increasing wire width. The validity of the theory is experimentally confirmed by the in situ measurement of the temperature-dependent electric resistance.
Polarity dependent breakdown of the high-κ∕SiOx gate stack: A phenomenological explanation by scanning tunneling microscopy
Authors: Ang D. S. , Ong Y. C. , O’Shea S. J. , Pey K. L. , Tung C. H. , Kawanago T. , Kakushima K. , Iwai H.
Published: May 2008

From scanning tunneling microscopy, we present unambiguous evidence of thermally induced localized conduction paths exhibiting an asymmetrical conduction property in the high-κ gate stack. The tunneling current under gate injection biasing is found to be much larger than that under substrate injection biasing after a 700°C postdeposition anneal, i.e., the localized paths exhibit a much lower resistance under gate injection biasing. This finding provides a phenomenological explanation for the polarity dependent breakdown of the high-κ gate stack as observed from electrical stressing of large-area metal-oxide-semiconductor capacitors.
Spectral dependence of the excited-state absorption of erbium in silica fiber within the 1.48–1.59μm range
Authors: Guzman-Chavez A. D. , Barmenkov Yu. O. , Kir’yanov A. V.
Published: May 2008

We report the study of the excited-state absorption (ESA) spectrum of Er3+ in erbium-doped silica fiber (EF) within the telecom band, 1.48–1.59μm. Two experimental techniques, the detection of up-conversion emission following the ESA process and the measurement of the EF nonlinear transmission coefficient, both supplied with a theoretical background, allow obtaining a mutually consistent spectral behavior of the ESA parameter, which is the ratio of ESA to ground-state absorption cross section, at 1.48–1.59μm excitation.
A tunable all-fiber filter based on microfiber loop resonator
Authors: Yu Wu , Xu Zeng , Changlun Hou , Jian Bai , Guoguang Yang
Published: May 2008

In this paper, a tunable high finesse microfilter is described, which is based on microfiber loop resonator (MLR). The length of microfiber loop could be controlled by a small cylindrical piezoelectric ceramic. As we calculated, this resonator has the maximum Q factor of 2400 and the finesse of 4.3. MLR filter was demonstrated that the maximum extinction ratio is about 10dB, and the free spectral range variation range could be more than 100GHz. This device could also be integrated into a smaller size due to the bigger radius of curvature of the microfiber.
Young’s modulus of VO2 thin films as a function of temperature including insulator-to-metal transition regime
Authors: Sepúlveda Nelson , Rúa Armando , Cabrera Rafmag , Fernández Félix
Published: May 2008

Young’s modulus of VO2 thin films has been measured for the first time through the material’s insulator-to-metal transition. The resonant frequency of silicon VO2 coated cantilevers was measured in the temperature range 30–90°C. It has been found that during the semiconductor to metallic transition of VO2 thin films, which occurs at a temperature of 68°C, Young’s modulus changes most dramatically with temperature, abruptly reversing its declining trend with increasing temperature. The film is stiffened through the transition and, as the temperature is further raised, the declining trend is reasserted at a similar rate.
First principles study of Ge∕Si exchange mechanisms at the Si(001) surface
Authors: Zipoli F. , Cereda S. , Ceriotti M. , Bernasconi M. , Miglio Leo , Montalenti F.
Published: May 2008

Based on density functional theory calculations, we show that an isolated Ge adatom on Si(001) triggers an exchange mechanism involving three atoms, which leads to the formation of a Si adatom and a mixed SiGe surface dimer. The activation energy calculated from first principles is sufficiently low (0.8eV) to make such a process viable down to the lowest temperature (330K) at which intermixing was reported. A second mechanism, with a higher barrier, is also proposed and shown to possibly contribute to the incorporation of Ge into deeper layers as experimentally observed at higher temperatures.
Fiber based organic photovoltaic devices
Authors: O’Connor Brendan , Pipe Kevin P. , Shtein Max
Published: May 2008

A fiber-shaped organic photovoltaic cell is demonstrated, utilizing concentric thin films of small molecular organic compounds. Illuminated at normal incidence to the fiber axis through a thin metal electrode, the cell exhibits 0.5% power conversion efficiency, compared to 0.76% for a planar control device. The fiber device efficiency is nearly independent of illumination angle, increasing its power generation over the planar counterpart for diffuse illumination. Losses due to partial shading of the fiber surface are minimal, while the coated fiber length is limited only by the experimental deposition chamber geometry—factors favoring scale-up to woven energy harvesting textiles.
Energy difference space random walk to achieve fast free energy calculations
Authors: Min Donghong , Yang Wei
Published: May 2008

A method is proposed to efficiently obtain free energy differences. In the present algorithm, free energy calculations proceed by the realization of an energy difference space random walk. Thereby, this algorithm can greatly improve the sampling of the regions in phase space where target states overlap.
Conductive atomic force microscopy of InAs∕GaAs quantum rings
Authors: Mlakar Tomaž , Biasiol Giorgio , Heun Stefan , Sorba Lucia , Vijaykumar T. , Kulkarni G. U. , Spreafico Vittorio , Prato Stefano
Published: May 2008

The properties of self-assembled InAs∕GaAs quantum rings are investigated by conductive atomic force microscopy. Our two-dimensional current maps and current-voltage curves show a lower conductivity of the central ring hole as compared to rim and surrounding planar region. This result is quite surprising if we take into account the compositional profile of quantum rings: being the region with the highest In concentration, one would expect the central hole to be the region with the highest conductivity. However, including the presence of a surface oxide into numerical simulations yields consistent results, which show the same qualitative behavior as the measured conductivities.
Experimental study of space-charge-limited flows in a nanogap
Authors: Bhattacharjee Sudeep , Vartak Adish , Mukherjee Victor
Published: May 2008

An experimental investigation of space-charge-limited flow of current in a nanogap is presented. Electrodes with gap size d∼70–110nm corresponding to d∕λ0∼(1−5)×103, where λ0 is the de Broglie wavelength of the space-charge electrons are experimented. Unlike classical Child–Langmuir’s (CL) law, the current density varies as square root of applied voltage (V1∕2), when d becomes comparable to λ0. Additionally, a transition regime has been found for the 90nm gap size where the CL law appears at voltages >45V. At d=110nm, the system is found to exhibit purely classical behavior.
Manipulating interfaces in a hybrid solar cell by in situ photosensitizer polymerization and sequential hydrophilicity/hydrophobicity control for enhanced conversion efficiency
Authors: Lee Wonjoo , Shin Seunghoon , Han Sung-Hwan , Cho Byung Won
Published: May 2008

The polyacetylene photosensitizer with quaternary pyridinium salts was layered on CdS nanoparticles films by in situ polymerization of 2-ethynylpyridine and 4-bromobutyric acid. The hydrophilic nature of the polyacetylene is shown to enhance the interfacial contact and electrical coupling between hydrophilic CdS and the polymer. The hydrophilicity of the polymer was modified toward hydrophobicity by anion exchange in order to adequately layer the hydrophobic poly(3-hexylthiophene) by spin coating, power-conversion efficiency 1.18% (AM1.5, I=100mW∕cm2).
Study on threading dislocations blocking mechanism of GaN∕AlxGa1−xN superlattices
Authors: Sang L. W. , Qin Z. X. , Fang H. , Zhou X. R. , Yang Z. J. , Shen B. , Zhang G. Y.
Published: May 2008

Ga N ∕ Al x Ga 1 − x N superlattices (SLs) with different period thicknesses tp were grown as interlayers between GaN and AlyGa1−yN epilayers. The effect of threading dislocations (TDs) blocking became more evident with increasing tp. Transmission electron microscopy analysis shows that TDs are inclined to be bended in SLs and terminated in GaN wells as a result of strain. X-ray diffraction measurement also validated that GaN wells played a more important role as a TDs filter. The blocking of TDs in SLs resulted in an abnormal decrease in relaxation factors R(SLs) with increasing tp.
Modification of the electronic structure in a carbon nanotube with the charge dopant encapsulation
Authors: Choi Woon Ih , Ihm Jisoon , Kim Gunn
Published: May 2008

We present the first-principles study of effects of the charge dopants such as cesium and iodine encapsulated on the electronic structure of carbon nanotubes (CNTs). An encapsulated cesium atom donates an electron to the nanotube and produces donorlike states below the conduction bands. In contrast, an iodine trimer (I3) accepts an electron from the nanotube and produces an acceptorlike state above the valence band maximum. We find that a Cs atom inside a metallic armchair CNT gives rise to spatial oscillations of the density of states near the Fermi level.
Observation of spin-glass behavior in antiperovskite Mn3GaN
Authors: Song Bo , Jian Jikang , Bao Huiqiang , Lei Ming , Li Hui , Wang Gang , Xu Yanping , Chen Xiaolong
Published: May 2008

The dc magnetization, ac susceptibility, and isothermal remanent magnetization measurements are carried out for antiperovskite Mn3GaN. Strong indication for a frozen state with freeing temperature of Tf at ∼133K is found, determined from the difference between field-cooled and zero-field-cooled magnetizations. The ac susceptibility measurements show a peak around Tf, with the peak position shifting as a function of the driving frequency f and magnetic field H, respectively. Relaxation effects are observed after switching the external magnetic field below Tf. These findings consistently demonstrate that Mn3GaN exhibits a canonical spin-glass state at low temperature.
Does salinity reduce the tolerance of two contrasting wetland plants, the submerged monocot Vallisneria australis and the woody shrub Melaleuca ericifolia, to wetting and drying?
Authors: Salter Jacqueline , Morris Kay , Boon Paul I.
Published: May 2008

Adverse hydrological regimes and secondary salinisation are ubiquitous stressors to wetland plants in south-eastern Australia. To test whether salinity stress interacts with hydrological stress to affect the growth and survival of aquatic plants, we examined the responses of Melaleuca ericifolia Smith, a shrub favouring drained sites, and the obligately submerged monocot Vallisneria australis (S.W.L. Jacobs & D.H. Les) to different hydrological regimes under freshwater and saline conditions. Under freshwater conditions both species recovered from water regimes that were considered prima facie unsuitable to their growth form: M. ericifolia from 5 and 10 weeks of submersion, and V. australis from a simulated water-level drawdown and exposure to air. Salinity, however, markedly compromised the survival of M. ericifolia after it was re-exposed following submersion. Salinity not only reduced the recovery of V. australis after its release from a period of drying that desiccated aboveground organs, but prohibited recovery when the soil dried out. We conclude that M. ericifolia and V. australis can tolerate short periods of submergence and drying, respectively, under freshwater conditions, but that salinity compromises the ability of both taxa to recover from water regimes that, based on the plant’s growth form, would be considered unsuitable for long-term survival and growth.
Variation in evacuation rates of different foods skew estimates of diet in the western rock lobster Panulirus cygnus
Authors: Waddington Kris
Published: May 2008

Knowledge regarding differences in evacuation rates of diet items from a consumer’s stomach is important when using gut content analysis to quantify consumer diet. Evacuation rates of three diet items (pilchards, crabs and coralline algae) from the foreguts of western rock lobsters (Panulirus cygnus) were compared in aquaria. To determine evacuation rates, lobsters were allowed to consume offered food over a 90-min feeding period before being killed at 4, 6, 8, 10 and 12 h after the feeding period concluded. Diet items differed in their rate of evacuation from lobster foreguts with coralline algae evacuated most rapidly, followed by crabs, then pilchards. The evacuation of crabs and pilchards was still not complete 12 h after the feeding period concluded. Food not evacuated after 12 h predominantly consisted of hard components of the lobster diet, indicating that it is these components that account for slower evacuation. Observed variation in evacuation rates between diet items may skew the results of studies that use gut content analysis to quantify the diet of western rock lobsters.
Neighbour and environmental influences on the growth patterns of two temperate Haliclonid sponges
Authors: Abdo D. A. , McDonald J. I. , Harvey E. S. , Fromont J. , Kendrick G. A.
Published: May 2008

Understanding the growth dynamics of an organism is central to understanding its ecology and biology. Sponges often dominate many subtidal habitats, however, determining their growth dynamics is often difficult owing to the plastic and amorphous morphologies that occur in many species. Two sympatric Haliclonid sponge species were examined using a novel photogrammetric technique to understand how environmental and competitive influences affect their growth. Sponges of both species were tagged and monitored over a 14-month period. Haliclona sp. 1 (green Haliclona) showed little variation in growth compared with Haliclona sp. 2 (brown Haliclona), which had a significant seasonal growth pattern. Both green and brown Haliclona grew a significant amount over the period of study (green Haliclona: 3.4% month–1; brown Haliclona: 6.0% month–1 (with neighbours) and 4.1% month–1 (without neighbours)). In both species, growth was not significantly influenced by competition from neighbours; rather, neighbouring organisms appeared to provide protection from adverse environmental conditions. The growth dynamics of both species have important implications for the maintenance of both species populations, particularly given the important habitat they provide for other organisms, and their potential exploitation for the supply of bioactive metabolites.
MLL protects CpG clusters from methylation within the
Hoxa9
gene, maintaining transcript expression
Authors: Erfurth Frank E. , Popovic Relja , Grembecka Jolanta , Cierpicki Tomasz , Theisler Catherine , Xia Zhen-Biao , Stuart Tara , Diaz Manuel O. , Bushweller John H. , Zeleznik-Le Nancy J.
Published: May 2008

Homeobox
(
HOX
) genes play a definitive role in determination of cell fate during embryogenesis and hematopoiesis.
MLL
-related leukemia is coincident with increased expression of a subset of
HOX
genes, including
HOXA9
. MLL functions to maintain, rather than initiate, expression of its target genes. However, the mechanism of MLL maintenance of target gene expression is not understood. Here, we demonstrate that Mll binds to specific clusters of CpG residues within the
Hoxa9
locus and regulates expression of multiple transcripts. The presence of Mll at these clusters provides protection from DNA methylation. shRNA knock-down of Mll reverses the methylation protection status at the previously protected CpG clusters; methylation at these CpG residues is similar to that observed in
Mll
null cells. Furthermore, reconstituting MLL expression in
Mll
null cells can reverse DNA methylation of the same CpG residues, demonstrating a dominant effect of MLL in protecting this specific region from DNA methylation. Intriguingly, an oncogenic MLL-AF4 fusion can also reverse DNA methylation, but only for a subset of these CpGs. This method of transcriptional regulation suggests a mechanism that explains the role of Mll in transcriptional maintenance, but it may extend to other CpG DNA binding proteins. Protection from methylation may be an important mechanism of epigenetic inheritance by regulating the function of both
de novo
and maintenance DNA methyltransferases.
Protein folding: Independent unrelated pathways or predetermined pathway with optional errors
Authors: Bédard Sabrina , Krishna Mallela M. G. , Mayne Leland , Englander S. Walter
Published: May 2008

The observation of heterogeneous protein folding kinetics has been widely interpreted in terms of multiple independent unrelated pathways (IUP model), both experimentally and in theoretical calculations. However, direct structural information on folding intermediates and their properties now indicates that all of a protein population folds through essentially the same stepwise pathway, determined by cooperative native-like foldon units and the way that the foldons fit together in the native protein. It is essential to decide between these fundamentally different folding mechanisms. This article shows, contrary to previous supposition, that the heterogeneous folding kinetics observed for the staphylococcal nuclease protein (SNase) does not require alternative parallel pathways. SNase folding kinetics can be fit equally well by a single predetermined pathway that allows for optional misfolding errors, which are known to occur ubiquitously in protein folding. Structural, kinetic, and thermodynamic information for the folding intermediates and pathways of many proteins is consistent with the predetermined pathway–optional error (PPOE) model but contrary to the properties implied in IUP models.
Chemicals that modulate stem cell differentiation
Authors: Hwang Ki-Chul , Kim Ji Young , Chang Woochul , Kim Dae-Sung , Lim Soyeon , Kang Sang-Moon , Song Byeong-Wook , Ha Hye-Yeong , Huh Yong Joon , Choi In-Geol , Hwang Dong-Youn , Song Heesang , Jang Yangsoo , Chung Namsik , Kim Sung-Hou , Kim Dong-Wook
Published: May 2008

Important cellular processes such as cell fate are likely to be controlled by an elaborate orchestration of multiple signaling pathways, many of which are still not well understood or known. Because protein kinases, the members of a large family of proteins involved in modulating many known signaling pathways, are likely to play important roles in balancing multiple signals to modulate cell fate, we focused our initial search for chemical reagents that regulate stem cell fate among known inhibitors of protein kinases. We have screened 41 characterized inhibitors of six major protein kinase subfamilies to alter the orchestration of multiple signaling pathways involved in differentiation of stem cells. We found that some of them cause recognizable changes in the differentiation rates of two types of stem cells, rat mesenchymal stem cells (MSCs) and mouse embryonic stem cells (ESCs). Among many, we describe the two most effective derivatives of the same scaffold compound, isoquinolinesulfonamide, on the stem cell differentiation: rat MSCs to chondrocytes and mouse ESCs to dopaminergic neurons.
Acute effect of dietary stanyl ester dose on post-absorptive α-tocopherol, β-carotene, retinol and retinyl palmitate concentrations
Authors: Relas Heikki , Gylling Helena , Miettinen Tatu A.
Published: May 2008

Stanyl esters dissolved in margarine inhibit cholesterol absorption, lower sterol absorption in general, and lower serum total cholesterol, LDL-cholesterol and plant sterol levels. To find out whether stanyl esters inhibit absorption of fat-soluble vitamins and β-carotene in acute experiments, we performed two fat-tolerance tests fortified with vitamins (retinol 0.9–3.7 mg, α-tocopherol 70–581 mg), β-carotene (25–150 mg) and squalene (0.5 g) with and without 1 g of stanyl ester added to the test meal in ten healthy men. The concentrations or areas under the curves (AUC) of cholesterol, triacylglycerols, squalene and α-tocopherol, β-carotene and retinyl palmitate showed typical postprandial changes in serum, chylomicrons, VLDL and VLDL infranatant (intermediate-density lipoproteins, LDL and HDL) over 24 h after the test meal without stanyl esters, and they were not affected by the addition of stanyl esters. The post-absorptive serum campesterol concentration and campesterol : cholesterol were significantly lowered at 6–9 h by stanyl ester supplementation, reflecting reduced sterol absorption efficiency. Changes in vitamin and β-carotene AUC did not correlate with the given doses. In conclusion, the present study shows that stanyl esters dissolved in margarine do not detectably interfere in a short-term study with the absorption of α-tocopherol, β-carotene or retinol measured by a 24 h oral fat-load test.
Association of the maternal experience and changes in adiposity measured by BMI, waist:hip ratio and percentage body fat in urban Brazilian women
Authors: Rodrigues Maria L.C.F. , Da Costa Teresa H.M.
Published: May 2008

The aim of the present study was to determine the association between the maternal experience and changes in adiposity measured by BMI, percentage body fat (PBF) and waist:hip ratio (WHR). In a cross-sectional study, 203 women were recruited at health care and educational facilities in Brasilia, Brazil. These women were divided into three groups: fifty-three nulliparous (no full-term pregnancy); sixty-three primiparous (one full-term pregnancy); eighty-seven multiparous (two or more full-term pregnancies). Socio-economic, behavioural, reproductive and dietary data were collected. All the women were measured for weight, height, skinfold thicknesses and waist and hip circumferences. Analysis of covariance was used to measure the differences among the three groups in relation to BMI, PBF and WHR, controlling for the following covariates: age; socio-economic status; use of oral contraceptives; smoking; energy intake level; cooking oil intake; physical activity level; lactation score; parity. The three groups of women differed significantly for BMI (P=0·04), PBF (P=0·0008) and WHR (P=0·0001). Multiparous women presented higher BMI (P=0·01) and PBF (P=0·03) compared with primi- and nulliparous groups. PBF was also associated with age and high socio-economic status. Primi- and multiparous women showed a higher WHR than nulliparous women (P<0·0001). Age and smoking habit were also factors associated with higher WHR.