bluuebunny/crossref_metadata_2025 huggingface dataset:
Composition influence on the physical and electrical properties of SrxTi1−xOy-based metal-insulator-metal capacitors prepared by atomic layer deposition using TiN bottom electrodes
Authors: Menou N. , Popovici M. , Clima S. , Opsomer K. , Polspoel W. , Kaczer B. , Rampelberg G. , Tomida K. , Pawlak M. A. , Detavernier C. , Pierreux D. , Swerts J. , Maes J. W. , Manger D. , Badylevich M. , Afanasiev V. , Conard T. , Favia P. , Bender H. , Brijs B. , Vandervorst W. , Van Elshocht S. , Pourtois G. , Wouters D. J. , Biesemans S. , Kittl J. A.
Published: November 2009

In this work, the physical and electrical properties of SrxTi1−xOy (STO)-based metal-insulator-metal capacitors (MIMcaps) with various compositions are studied in detail. While most recent studies on STO were done on noblelike metal electrodes (Ru, Pt), this work focuses on a low temperature (250 °C) atomic layer deposition (ALD) process, using an alternative precursor set and carefully optimized processing conditions, enabling the use of low-cost, manufacturable-friendly TiN electrodes. Physical analyses show that the film crystallization temperature, its texture and morphology strongly depends on the Sr/Ti ratio. Such physical variations have a direct impact on the electric properties of SrxTi1−xOy based capacitors. It is found that Sr-enrichment result in a monotonous decrease in the dielectric constant and leakage current as predicted by ab initio calculations. The intercept of the EOT vs physical thickness plot further indicates that increasing the Sr-content at the film interface with the bottom TiN would result in lower interfacial equivalent-oxide thickness.
Broadband mid-infrared generation by difference-frequency generation in strongly dispersive Bragg reflection waveguides
Authors: Das Ritwick , Thyagarajan K.
Published: November 2009

We present a novel scheme for generation of broadband mid-infrared (mid-IR) radiation using a quasiphase-matched difference-frequency-generation (DFG) process in a planar high index core symmetric Bragg reflection waveguide (BRW) geometry based on GaN/AlxGa1−xN system. By suitably tailoring the dispersion properties of the BRW so as to maintain the phase-matching condition over a broad range of pump wavelengths, we show that the pump acceptance bandwidth could be enhanced by nine to ten times for a DFG process. This manifests into a broadband mid-IR difference-frequency idler with greater than 280 nm bandwidth close to 4.35 μm wavelength. Since the design presented here exploits the dispersive features of the BRW; we can shift the broadband characteristics to any desired region of the mid-IR spectrum within the constraints imposed by transparency and nonlinearity of the constituent materials. The design also facilitates pumping by standard high-power solid-state laser sources.
Temperature dependence of buried channel ion sensitive field effect transistors
Authors: Novitski Roman , Einati Hila , Shacham-Diamand Yosi
Published: November 2009

In this paper we describe the temperature dependence of buried channel (BC) ion sensitive field effect transistor (ISFET). The device response depends on the temperature; hence, temperature variations can cause erroneous readings. A theoretical model describing the temperature dependence of BC-ISFET and a theoretical solution to eliminate the signal variations due to temperature changes are presented here. The suggested solution is based on an inverter containing n-BC-ISFET and p-BC-ISFET. The influence of various parameters on the operation of the inverter and its sensitivity are investigated. We discuss the influence of self-assembled monolayers on the operation of the inverter.
Optimal measurement strategies for effective suppression of drift errors
Authors: Yashchuk Valeriy V.
Published: November 2009

Drifting of experimental setups with change in temperature or other environmental conditions is the limiting factor of many, if not all, precision measurements. The measurement error due to a drift is, in some sense, in-between random noise and systematic error. In the general case, the error contribution of a drift cannot be averaged out using a number of measurements identically carried out over a reasonable time. In contrast to systematic errors, drifts are usually not stable enough for a precise calibration. Here a rather general method for effective suppression of the spurious effects caused by slow drifts in a large variety of instruments and experimental setups is described. An analytical derivation of an identity, describing the optimal measurement strategies suitable for suppressing the contribution of a slow drift described with a certain order polynomial function, is presented. A recursion rule as well as a general mathematical proof of the identity is given. The effectiveness of the discussed method is illustrated with an application of the derived optimal scanning strategies to precise surface slope measurements with a surface profiler.
Measuring temperature-dependent water vapor and gas permeation through high barrier films
Authors: Hülsmann Philip , Philipp Daniel , Köhl Michael
Published: November 2009

A new test device for temperature-dependent permeation measurement, existing of a mass spectrometer and sample holders inside a climatic chamber was developed. The front face of a sample is loaded with the atmosphere in the cabinet or a test gas mixture, respectively. The permeated species are accumulated in a cell behind the sample. The increasing partial pressures of the permeants are measured by the mass spectrometer and than transferred into a transmission rate. The time-lag technique enables the determination of the diffusion coefficient. Results are given for atmospheric components as O2, N2, and water vapor permeated through different barrier films and laminates at temperatures from 23 to 80 °C. The limits of the detection of the transmission rates are in the range of 10−6 g/m2 d.
A threshold photoelectron-photoion coincidence spectrometer with double velocity imaging using synchrotron radiation
Authors: Tang Xiaofeng , Zhou Xiaoguo , Niu Mingli , Liu Shilin , Sun Jinda , Shan Xiaobin , Liu Fuyi , Sheng Liusi
Published: November 2009

A novel threshold photoelectron-photoion coincidence (TPEPICO) imaging spectrometer at the U14-A beamline of the Hefei National Synchrotron Radiation Laboratory is presented. A set of open electron and ion lenses are utilized to map velocity imaging of photoelectrons and photoions simultaneously, in which a repelling electric field using an extra lens is applied to magnify images of photoelectrons instead of traditional accelerating electric field in order to suppress the contribution of energetic electrons in the threshold photoelectron spectroscopy (TPES) and the mass-selected TPEPICO spectroscopy. The typical energy resolution of TPES is measured to be 9 meV (full width at half maximum), as shown on the P21/2 ionization of argon. The measured mass resolving power for the present TPEPICO imaging spectrometer is above 900 of M/ΔM. Subsequently as a benchmark, oxygen molecule is photoionized by monochromatic synchrotron radiation at 20.298 eV and dissociates to an oxygen atomic ion and a neutral oxygen atom, and the translation energy distribution of oxygen atomic ion is measured by the time-sliced imaging based on mass-selected TPEPICO experiment. The kinetic energy resolution of the present ion velocity imaging is better than 3% of ΔE/E.
Coadsorption of CO and NO on the Cu2O(111) surface: A periodic density functional theory study
Authors: Sun Bao-Zhen , Chen Wen-Kai , Xu Yi-Jun
Published: November 2009

Coadsorption of carbon monoxide (CO) and nitric oxide (NO) on the Cu2O(111) surface was studied using periodic density functional theory calculations. It is interesting to find that CO+NO on Cu2O(111) could react to form adsorbed NCO surface species. Coadsorption of CO and NO could give rise to the formation of a O–C⋯N–O complex well bound to the Cu2O(111) surface, in which both the C–O and N–O bonds are greatly activated and the C–N bond is formed. Consequently, the reaction of CO with NO to form adsorbed NCO and CNO species may occur, for which it is disclosed that NCO formation is more possible than CNO formation both thermodynamically and kinetically. In addition, our calculations of searching transition states reveal that it is facile for NCO formation both kinetically and thermodynamically when CO+NO reaction takes place at CuCUS site, and is impossible when this reaction takes places at Ovac site. Moreover, CO2 species cannot form when CO+NO reaction occurs at Ovac site. Therefore, oxygen vacancy on Cu2O(111) does not play a positive role on CO+NO reaction to forming NCO, CNO, or CO2 species.
Development of a surface conductivity measurement system for ultrahigh vacuum transmission electron microscope
Authors: Minoda H. , Hatano K. , Yazawa H.
Published: November 2009

The surface conductivity measurement system using a micro-four-point probe (M4PP) had been developed for the ultrahigh vacuum transmission electron microscope (UHV-TEM). Since the current distribution in the sample crystals during the current voltage measurement by the M4PP is localized within the depth of several micrometers from the surface, the system is sensitive to the surface conductivity, which is related with the surface superstructure. It was installed in the main chamber of the TEM and the surface conductivity can be measured in situ. The surface structures were observed by reflection electron microscopy and diffraction (REM-RHEED). REM-RHEED enables us to observe the surface superstructures and their structure defects such as surface atomic steps and domain boundaries of the surface superstructure. Thus the effects of the defects on the surface conductivity can be investigated. In the present paper we present the surface conductivity measurement system and its application to the Si(111)-3×3-Ag surface prepared on the Si(111) vicinal surfaces. The result clearly showed that the surface conductivity was affected by step configuration.
Spray and microjets produced by focusing a laser pulse into a hemispherical drop
Authors: Thoroddsen S. T. , Takehara K. , Etoh T. G. , Ohl C.-D.
Published: November 2009

We use high-speed video imaging to study laser disruption of the free surface of a hemispheric drop. The drop sits on a glass surface and the Nd:YAG (yttrium aluminum garnet) laser pulse propagates through the drop and is focused near the free surface from below. We focus on the evolution of the cylindrical liquid sheet and spray which emerges out of the drop and resembles typical impact crowns. The tip of the sheet emerges at velocities over 1 km/s. The tip of the crown breaks up into fine spray some of which is sucked back into the growing cavity at about 100 m/s. We measure the size of the typical spray droplets to be about 3 μm. We also show the formation of fine microjets, which are produced when the laser is focused inside the drop and the shock front hits small bubbles sitting under the free surface. For water these microjets are 5–50 μm in diameter and exit at 100–250 m/s. For higher viscosity drops, these jets can emerge at over 500 m/s.
Spectral representation of infimum of bounded quantum observables
Authors: Jun Shen , Junde Wu
Published: November 2009

In 2006, Gudder [Math. Slovaca 56, 573 (2006)] introduced a logic order ≼ on bounded quantum observable set S(H). In 2007, Pulmannova and Vincekova [Math Slovaca 57, 589 (2007)] proved that for each subset D of S(H), the infimum of D exists with respect to the logic order ≼. In 2008, Liu and Wu [J. Math. Phys. 49, 073521 (2008)] found a representation of the infimum A∧B for A,B∊S(H), and by using the limit methods, they gave out a representation for the infimum of D. But, that representation is complicated. In this paper, we present a simpler spectral representation for the infimum of D with respect to the logic order ≼.
A least-constraint principle for population dynamics and reaction kinetics: Modeling entropy-controlled chemical hypercycles
Authors: Horváth Denis , Kneller Gerald R.
Published: November 2009

In this paper, we investigate the treatment of constraints in rate equations describing the temporal evolution of biological populations or chemical reactions. We present a formulation for arbitrary holonomic and linear nonholonomic constraints which ensures the positivity of the dynamical variables and which is an analog of Gauss’ principle of least constraint in classical mechanics. The approach is illustrated for the replication of molecular species in the Schuster–Eigen hypercycle model, imposing the conservation of the total number of molecules and the entropy production as constraints. The latter is used to model the behavior of an isolated system tending toward equilibrium and, for comparison, a stationary nonequilibrium state of an open system, which is characterized by undamped oscillations.
Negatively buoyant starting jets
Authors: Marugán-Cruz C. , Rodríguez-Rodríguez J. , Martínez-Bazán C.
Published: November 2009

The initial development of negatively buoyant jets has been investigated experimentally and numerically, focusing on the role played by gravity in the evolution of the leading vortex ring. Under the experimental conditions considered in this work, the densimetric Froude number, Fr=ρjUj2/[(ρ0−ρj)gD], which represents the ratio between the jet momentum and the buoyancy forces, emerges as the most relevant parameter characterizing the dynamics of the flow. Two different flow regimes have been observed depending on the Froude number: for sufficiently small Fr, the vortex ring generated initially is pushed radially away by gravity forces before it has time to detach from the shear layer originating at the orifice. On the other hand, when the Froude number is larger than a critical value, Fr>Frc∼1, the vortex ring detaches from the injection orifice and propagates downstream into the stagnant ambient followed by a trailing jet until it eventually reaches a maximum penetration depth. In order to clarify the mechanisms leading to the transition between the two regimes, and to gain physical understanding of the formation dynamics of negatively buoyant starting jets, the total and the vortex circulation, as well as the trajectory of the vortex center, have been measured and compared to the case of neutrally buoyant jets. Finally, based on the experimental measurements and on the results of the numerical computations, a kinematic model that successfully describes the evolution of both total circulation and vortex trajectory is proposed.
The isotropic-nematic interface with an oblique anchoring condition
Authors: Kamil S. M. , Bhattacharjee A. K. , Adhikari R. , Menon Gautam I.
Published: November 2009

We present numerical and analytic results for uniaxial and biaxial orders at the isotropic-nematic interface within Ginzburg–Landau–de Gennes theory. We study the case where an oblique anchoring condition is imposed asymptotically on the nematic side of the interface, reproducing results of previous work when this condition reduces to planar or homeotropic anchoring. We construct physically motivated and computationally flexible variational profiles for uniaxial and biaxial orders, comparing our variational results to numerical results obtained from a minimization of the Ginzburg–Landau–de Gennes free energy. While spatial variations of the scalar uniaxial and biaxial order parameters are confined to the neighborhood of the interface, nematic elasticity requires that the director orientation interpolate linearly between either planar or homeotropic anchoring at the location of the interface and the imposed boundary condition at infinity. The selection of planar or homeotropic anchoring at the interface is governed by the sign of the Ginzburg–Landau–de Gennes elastic coefficient L2. Our variational calculations are in close agreement with our numerics and agree qualitatively with results from density functional theory and molecular simulations.
Characteristics of a micro dielectric barrier discharge ignited by a cold cathode with high ion-induced secondary electron emission for plasma display panel
Authors: Uchida Giichiro , Uchida Satoshi , Kajiyama Hiroshi , Shinoda Tsutae
Published: November 2009

We present here measurements of plasma display panel (PDP) ignited by SrO and SrCaO cold cathodes with high yield of ion-induced secondary electron emission (high γi). SrO- and SrCaO-cathode PDPs attain high luminous efficacy at low applied voltage, where the breakdown voltage is 30% lower than that of ordinary MgO-cathode PDP. Current and emission measurement clearly demonstrates that SrO- and SrCaO-cathode PDPs operated at low voltage realize a discharge with smaller current flow and lower electron energy, which are considerably appropriate for high luminous efficacy of PDP. Simulation analysis shows the effect of the high-γi cathode on the luminous efficacy of PDP. A discharge ignited by the high-γi cathode realizes high electron heating efficiency due to the abundant seed electrons from the high-γi cathode, resulting in high luminous efficacy of PDP.
Flux pinning of stress-induced magnetic inhomogeneity in the bilayers of YBa2Cu3O7−δ/La0.67Sr0.33MnO3−δ
Authors: Chen C. Z. , Cai C. B. , Peng L. , Gao B. , Fan F. , Liu Z. Y. , Lu Y. M. , Zeng R. , Dou S. X.
Published: November 2009

Elaborately designed bilayers consisting of epitaxial YBa2Cu3O7−δ (YBCO) and La0.67Sr0.33MnO3−δ (LSMO) films were fabricated by pulsed laser deposition with respect to the investigation into magnetic-dependent vortex pinning effect. The improvement in the critical current density and a pronounced upward shift in the superconducting irreversibility line based on magnetotransport measurements are observed when compared to the pure YBCO film, suggesting the enhancement in flux pinning in the studied bilayer. It is believed that the improved flux pinning for YBCO arises from the magnetic inhomogeneity of the underlying LSMO. Magnetization measurements show a nonuniform magnetic state in the LSMO film, most probably being macroscopically phase-separated clusters with ferromagnetic (FM) and anti-FM domains, which can be caused by the epitaxial strain due to the lattice mismatch. Such a magnetic disorder is hardly affected by the external magnetic field, unlike the magnetic disorder induced by the domain structures of FM materials where the magnetic domains naturally disappear as the applied field exceeds the coercive field. Hence, the present magnetic flux pinning may be stiff in the large magnetic fields, showing good prospects for artificial flux pinning enhancements.
Optimal excitation of N23a nuclear spins in the presence of residual quadrupolar coupling and quadrupolar relaxation
Authors: Lee Jae-Seung , Regatte Ravinder R. , Jerschow Alexej
Published: November 2009

Optimal control theory is applied for designing pulse sequences to optimally excite a spin-3/2 system with residual quadrupolar coupling in the presence of quadrupolar relaxation. A homogeneous form of the master equation is constructed to simulate the dynamics of the spin system, and a general optimization procedure with a homogeneous form of the equation of motion is described. The optimized pulses are tested with N23a NMR, and their performance is compared with that of pulses optimized in the absence of relaxation.
Measurement of effective electron mass in biaxial tensile strained silicon on insulator
Authors: Feste S. F. , Schäpers Th. , Buca D. , Zhao Q. T. , Knoch J. , Bouhassoune M. , Schindlmayr Arno , Mantl S.
Published: November 2009

We present measurements of the effective electron mass in biaxial tensile strained silicon on insulator (SSOI) material with 1.2 GPa stress and in unstrained SOI. Hall-bar metal oxide semiconductor field effect transistors on 60 nm SSOI and SOI were fabricated and Shubnikov–de Haas oscillations in the temperature range of T=0.4–4 K for magnetic fields of B=0–10 T were measured. The effective electron mass in SSOI and SOI samples was determined as mt=(0.20±0.01)m0. This result is in excellent agreement with first-principles calculations of the effective electron mass in the presence of strain.
On the difference between the transition properties calculated with linear response- and equation of motion-CCSD approaches
Authors: Caricato Marco , Trucks Gary W. , Frisch Michael J.
Published: November 2009

In this work, we quantitatively investigate the difference between the linear response (LR) and the equation of motion (EOM) coupled cluster (CC) approaches in the calculation of transition properties, namely, dipole and oscillator strengths, for the most widely used truncated CC wave function, which includes single and double excitation operators. We compare systems of increasing size, where the size-extensivity may be important. Our results suggest that, for small molecules, the difference is small even with large basis sets. The difference increases with the size of the system, but it is numerically small until hundreds of electron pairs are correlated. Although these calculations may be possible in a few years, at present the EOM approach is more advantageous, albeit more approximate, because it is computationally less demanding.
Block correlated coupled cluster method with the complete active-space self-consistent-field reference function: Applications for low-lying electronic excited states
Authors: Shen Jun , Li Shuhua
Published: November 2009

Block correlated coupled cluster (BCCC) method with the complete active-space (CAS) self-consistent-field reference function (CAS-BCCC) has been applied to investigate the vertical excitation energies of low-lying valence excited states in a number of medium-sized organic molecules, including unsaturated aliphatic hydrocarbons (ethene, E-butadiene, cyclopropene, and cyclopentadiene), aromatic heterocycles (furan and pyrrole), and carbonyl compounds (formaldehyde, acetone, and formamide). An approximate CAS-BCCC with the cluster operator truncated up to the four-block correlation level, CAS-BCCC4, is employed in the calculations. The results are compared with those from the multireference configuration interaction with singles and doubles (MR-CISD and its corrected version, MR-CISD+Q), the complete active space with second-order perturbation theory (CASPT2), and CC3. Our results show that the overall performance of CAS-BCCC4 is competitive with that of the multistate CASPT2 (slightly inferior to MR-CISD+Q), better than that of the single-state CASPT2 and MR-CISD approaches. For triplet excited states, various methods tend to give relatively consistent predictions. However, for singlet excited states, various methods lead to quite different excitation energies in some cases.
On the kinetics of the Al13−+Cl2 reaction: Cluster degradation in consecutive steps
Authors: Olzmann Matthias , Burgert Ralf , Schnöckel Hansgeorg
Published: November 2009

The kinetics of the reaction system initiated by the Al13−+Cl2 reaction was experimentally studied in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The Al13− clusters were produced by laser desorption/ionization of LiAlH4, then transferred into the ICR cell, cooled by collisions with Ar, and exposed to an excess of Cl2 with a concentration of ∼108 cm−3. Relative concentration-time profiles of Aln− clusters with n=13, 11, 9, and 7 as well as profiles of Cl− ions have been recorded. Other ionic species, besides traces of Al12Cl−, were not found, which indicates a double-step degradation mechanism via the odd-numbered Aln− clusters. From a kinetic analysis of the experimental results, a rate coefficient of (5±2)×10−10 cm3 s−1 for the Al13−+Cl2 reaction was obtained. Furthermore, it is inferred from a simultaneous fit of all concentration-time profiles that the Aln−+Cl2 reactions for n=13, 11, 9, and 7 occur with rate coefficients near the Langevin limit in the range kbim∼(5±4)×10−10 cm3 s−1. The branching ratios between the Aln−2−-producing and Cl−-producing channels of a given cluster AlnCl2− indicate an increasing contribution of the Cl−-producing channels with decreasing cluster size. Statistical rate theory calculations on the basis of molecular data from quantum chemical calculations show that the experimental Aln− profiles are compatible with a sequence of association-elimination reactions proceeding via the formation of highly excited AlnCl2− adducts followed by a sequential elimination of two AlCl molecules. Rate coefficients for these reactions were calculated, and the production of Cl− was shown probably not to proceed via these AlnCl2− intermediates.
Calculation of hydrogen storage capacity of metal-organic and covalent-organic frameworks by spillover
Authors: Suri Mayur , Dornfeld Matthew , Ganz Eric
Published: November 2009

We have used accurate ab initio quantum chemistry calculations together with a simple model to study the hydrogen storage capacity of metal-organic and covalent-organic frameworks by spillover. Recent experiments by Tsao et al. [J. Am. Chem. Soc. 131, 1404 (2009)] {based on an earlier work by Li and Yang [J. Am. Chem. Soc. 128, 8136 (2006)]} have found that IRMOF-8 with bridged Pt catalysts can reversibly store up to 4.7 wt % of hydrogen at room temperature and 100 bar. We have calculated the binding energy for multiple H atoms on model molecules. By counting active storage sites, we predict a saturation excess storage density at room temperature of 5.0 wt % for IRMOF-8. We also predict storage densities of 4.5 wt % for IRMOF-1, 5.4 wt % for MOF-177, 4.5 wt % for COF-1, and 5.7 wt % for IRMOF-15 and IRMOF-16. This suggests that the current experimental H storage results for IRMOF-8 are well optimized. However, for other materials such as MOF-177 and COF-1, the experimental results are not yet optimized, and significantly more H can be stored on these materials. We also find that significant strain will result from shrinkage of the linker molecules as H atoms are loaded onto the crystals.
Geometry and stability of CunN (n=1–6) and Cu3nNn (n=1–5) clusters
Authors: Ding Jian-Ning , Yuan Ning-Yi , Li Feng , Ding Gu-Qiao , Chen Zhi-Gang , Chen Xiao-Shuang , Lu Wei
Published: November 2009

The gradient-corrected density functional calculation is applied to search the lowest-energy configurations of CunN (n=1–6) clusters and the calculation indicated that Cu3N cluster is the most stable one. Based on the result, we further investigate the equilibrium geometries and stabilities of the Cu3nNn (n=2–5) clusters. We found that in Cu6N2 cluster, N atoms formed a separate N2 molecule away from the other part of the cluster. Furthermore, it was shown that the lowest-energy configurations of Cu3nNn (n=3–5) are stable with the nitrogen atoms well separated by the copper atoms. Therefore, it can be concluded that the Cu3N cluster can be used as a building block for the construction of the cluster-assembled compounds.
Structure and optical properties of core-shell bimetallic AgnNin clusters: Comparison with pure silver and nickel clusters
Authors: Harb M. , Rabilloud F. , Simon D.
Published: November 2009

We present the structural, electronic, and optical properties of bimetallic AgnNin (n≤7) clusters investigated in the framework of the density functional theory (DFT) (DFT and time-dependent DFT). The structure of AgnNin clusters is found to be governed essentially by the formation of a Ni-core surrounded by silver atoms. The cohesive energies and the ionization potentials are calculated. The UV-visible absorption spectra of bimetallic clusters are compared to those of pure silver and nickel clusters. An interpretation of spectroscopic patterns in terms of contribution from s- and d-type excitations is also given. In particular the d electrons of nickel atoms are found to play a crucial role in the optical transitions in Ni-rich systems.
Valence ionization spectra of group six metal hexacarbonyls studied by the symmetry-adapted cluster-configuration interaction method
Authors: Fukuda Ryoichi , Hayaki Seigo , Nakatsuji Hiroshi
Published: November 2009

The valence ionization spectra up to 20 eV of group six metal carbonyls, chromium hexacarbonyl, molybdenum hexacarbonyl, and tungsten hexacarbonyl were studied by the symmetry-adapted cluster-configuration interaction (SAC-CI) method. The assignments of the spectra are given based on reliable SAC-CI calculations. The relativistic effects including the spin-orbit effects are important for the ionization spectrum of W(CO)6. The relation between the metal-CO distance and ionization energies was examined. The lowest ionization energies of the three metal carbonyls are approximately the same because of the energy dependence of the metal-CO length and relativistic effects. In Cr(CO)6, the Cr–CO interaction significantly increases the lowest ionization energy in comparison with Mo(CO)6 and W(CO)6 because of the relatively short metal-CO bond length. The relativistic effect reduces the lowest ionization energy of W(CO)6 because the effective core potential of 5d electrons is more efficiently screened as a result of the relativistic contraction of the inner electrons.
Bulk viscosity universality and scaling function near the binary liquid consolute point
Authors: Bhattacharjee Jayanta K. , Iwanowski Ireneusz , Kaatze Udo
Published: November 2009

The hydrodynamical equations and the notion of a frequency dependent complex specific heat near the critical point of binary liquids are used to obtain an expression for the low-frequency bulk viscosity. In this way the interrelations between different theoretical models, treating the critical sound attenuation from either a specific heat or a bulk viscosity approach, are made evident. The general structure of the bulk viscosity relation agrees with that of Onuki [Phys. Rev. E 55, 403 (1997)] but a universal number emerges only if a normalization to the critical point value is done.
Optical spectroscopy gains a third dimension
Authors: Miller Johanna
Published: November 2009

An extension of a difficult optical technique provides unprecedented information about a semiconductor system.
International research university opens in Saudi Arabia
Authors: Feder Toni
Published: November 2009

The well-funded, strategically executed yet isolated experiment could fly or flop.
LLNL touts gamma-ray source for nuclear detection
Authors: Kramer David
Published: November 2009

Lab also sees applications in monitoring isotopic content of reactor fuel and assaying nuclear waste.
Materials in extreme environments
Authors: Hemley Russell J. , Crabtree George W. , Buchanan Michelle V.
Published: November 2009

The study of materials under harsh conditions is essential to meet a range of energy challenges—from creating better turbines, reactors, and batteries to developing future energy systems in dense plasmas.
Human-generated sound and marine mammals
Authors: Tyack Peter L.
Published: November 2009

Loud anthropogenic noises can alter the behavior of whales and other marine mammals, sometimes with fatal consequences.
Paul Dirac, a man apart
Authors: Farmelo Graham
Published: November 2009

Dirac practiced theoretical physics for almost 60 years with a unique style: a sometimes baffling combination of intuition, imagination, rectilinear logic, and steam-hammer mathematical power.
The surprising motion of ski moguls
Authors: Bahr David B. , Pfeffer W. Tad , Browning Raymond C.
Published: November 2009

Regularly spaced bumps that arise on ski slopes defy intuition by migrating uphill, even though skiers and snow move downhill.
Survey of Andromeda’s environs reveals relics of galactic cannibalism
Authors: Schwarzschild Bertram
Published: November 2009

The Milky Way’s nearest full-grown neighbor–almost its twin–offers a unique opportunity for studying how galaxies grow.
Irving Weissman: Working for regenerative medicine
Authors: LeBrasseur Nicole
Published: November 2009

A force behind both the science and politics of stem cell biology, Weissman now strives to translate his successes to the clinic.
Ase1/Prc1-dependent spindle elongation corrects merotely during anaphase in fission yeast
Authors: Courtheoux Thibault , Gay Guillaume , Gachet Yannick , Tournier Sylvie
Published: November 2009

Faithful segregation of sister chromatids requires the attachment of each kinetochore (Kt) to microtubules (MTs) that extend from opposite spindle poles. Merotelic Kt orientation is a Kt–MT misattachment in which a single Kt binds MTs from both spindle poles rather than just one. Genetic induction of merotelic Kt attachment during anaphase in fission yeast resulted in intra-Kt stretching followed by either correction or Kt disruption. Laser ablation of spindle MTs revealed that intra-Kt stretching and merotelic correction were dependent on MT forces. The presence of multiple merotelic chromosomes linearly antagonized the spindle elongation rate, and this phenomenon could be solved numerically using a simple force balance model. Based on the predictions of our mechanical model, we provide in vivo evidence that correction of merotelic attachment in anaphase is tension dependent and requires an Ase1/Prc1-dependent mechanism that prevents spindle collapse and thus asymmetric division and/or the appearance of the cut phenotype.
Membrane proteins Bqt3 and -4 anchor telomeres to the nuclear envelope to ensure chromosomal bouquet formation
Authors: Chikashige Yuji , Yamane Miho , Okamasa Kasumi , Tsutsumi Chihiro , Kojidani Tomoko , Sato Mamiko , Haraguchi Tokuko , Hiraoka Yasushi
Published: November 2009

In many organisms, telomeres cluster to form a bouquet arrangement of chromosomes during meiotic prophase. Previously, we reported that two meiotic proteins, Bqt1 and -2, are required for tethering telomeres to the spindle pole body (SPB) during meiotic prophase in fission yeast. This study has further identified two novel, ubiquitously expressed inner nuclear membrane (INM) proteins, Bqt3 and -4, which are required for bouquet formation. We found that in the absence of Bqt4, telomeres failed to associate with the nuclear membranes in vegetative cells and consequently failed to cluster to the SPB in meiotic prophase. In the absence of Bqt3, Bqt4 protein was degraded during meiosis, leading to a phenotype similar to that of the bqt4-null mutant. Collectively, these results show that Bqt4 anchors telomeres to the INM and that Bqt3 protects Bqt4 from protein degradation. Interestingly, the functional integrity of telomeres is maintained even when they are separated from the nuclear envelope in vegetative cells.
Enhancement of Notch receptor maturation and signaling sensitivity by Cripto-1
Authors: Watanabe Kazuhide , Nagaoka Tadahiro , Lee Joseph M. , Bianco Caterina , Gonzales Monica , Castro Nadia P. , Rangel Maria Cristina , Sakamoto Kei , Sun Youping , Callahan Robert , Salomon David S.
Published: November 2009

Nodal and Notch signaling pathways play essential roles in vertebrate development. Through a yeast two-hybrid screening, we identified Notch3 as a candidate binding partner of the Nodal coreceptor Cripto-1. Coimmunoprecipitation analysis confirmed the binding of Cripto-1 with all four mammalian Notch receptors. Deletion analyses revealed that the binding of Cripto-1 and Notch1 is mediated by the Cripto-1/FRL-1/Cryptic domain of Cripto-1 and the C-terminal region of epidermal growth factor–like repeats of Notch1. Binding of Cripto-1 to Notch1 occurred mainly in the endoplasmic reticulum–Golgi network. Cripto-1 expression resulted in the recruitment of Notch1 protein into lipid raft microdomains and enhancement of the furin-like protein convertase-mediated proteolytic maturation of Notch1 (S1 cleavage). Enhanced S1 cleavage resulted in the sensitization to ligand-induced activation of Notch signaling. In addition, knockdown of Cripto-1 expression in human and mouse embryonal carcinoma cells desensitized the ligand-induced Notch signaling activation. These results suggest a novel role of Cripto-1 in facilitating the posttranslational maturation of Notch receptors.
Quantitative Characterization of Polar Lipids from Wheat Whole Meal, Flour, and Starch
Authors: Finnie S. M. , Jeannotte R. , Faubion J. M.
Published: November 2009

Lipids constitute only a minor proportion of total flour components but the composition and structure of wheat flour polar lipids influence the end‐use quality of bread. So it is important to determine which specific lipid class and molecular species are present in wheat. Lipid profiling is the targeted, systematic characterization and analysis of lipids. The use of lipid profiling techniques to analyze grain‐based food has the potential to provide new insight into the functional relationships between a specific lipid species and its functionality. The objective of this study was to utilize lipid profiling techniques to quantitatively determine the polar lipid species present in whole wheat meal, flour, and starch. Two commonly grown wheat cultivars, Alpowa and Overley, were used in this study. Direct infusion electrospray ionization tandem mass spectrometry was used to identify and quantitatively determine 146 polar lipid species in wheat. The predominant polar lipid classes were digalactosyldiglycerols, monogalactosyldiglycerols, phosphatidylcholine, and lysophosphatidylcholine. ANOVA results concluded that the wheat fraction contributed a greater source of variation than did cultivar on total polar, total phospholipid, and total galactolipid contents. Wheat whole meal, flour, and surface starch contained greater concentrations of total galactolipids, whereas internal starch lipids contained greater concentrations of monoacyl phospholipids. This research provides evidence that lipid profiling will provide the ability to determine the functional relationships between specific lipid species and the impact on end‐use quality.
Quantitative and Qualitative Role of Added Gluten on White Salted Noodles
Authors: Park Sei Joon , Baik Byung‐Kee
Published: November 2009

A commercial gluten and glutens isolated from four soft and four hard wheat flours were incorporated into a hard and a soft white flour by replacement to directly determine the quantitative and qualitative role of gluten proteins in making noodles. Gluten incorporation (6%) decreased water absorption of noodle dough by 3%, shortened the length of the dough sheet by 15 and 18%, and increased the thickness of the dough sheet by 18 and 20% in soft and hard wheat flour, respectively. Noodles imbibed less water and imbibed water more slowly during cooking with gluten incorporation, which resulted in a 3‐min increase in cooking time for both soft and hard wheat noodles. Despite the extended cooking time of 3 min, noodles incorporated with 6% gluten exhibited decreases in cooking loss by 15% in soft wheat. In hard wheat flour, cooking loss of noodles was lowest with 2% incorporation of gluten. Tensile strength of fresh and cooked noodles, as well as hardness of cooked noodles, increased linearly with increase in gluten incorporation, regardless of cooking time and storage time after cooking. While hardness of cooked noodles either increased or showed no changes during storage for 4 hr, tensile strength of noodles decreased. There were large variations in hardness and tensile strength of cooked noodles incorporated with glutens isolated from eight different flours. Noodles incorporated with soft wheat glutens exhibited greater hardness and tensile strength than noodles with hard wheat glutens. Tensile strength of cooked noodles incorporated with eight different glutens negatively correlated with SDS sedimentation volume of wheat flours from which the glutens were isolated.
Total Phenolics and Antioxidant Activity of Water and Ethanolic Extracts from Distillers Dried Grains with Solubles With or Without Microwave Irradiation
Authors: Inglett George E. , Rose Devin J. , Stevenson David G. , Chen Diejun , Biswas Atanu
Published: November 2009

The purpose of this study was to determine the efficacy of extracting phenolic compounds with antioxidant activity from distillers' dried grains with solubles (DDGS) with water, 50% aqueous ethanol, and absolute ethanol, using microwave irradiation or a water bath at various temperatures. DDGS was extracted for 15 min with each solvent while heating at 23, 50, 100, and 150°C by microwave irradiation or in a water bath at 23, 50, and 100°C. Phenolic content of extracts increased with increasing temperature to a maximum of 12.02 mg/g in DDGS extracts that were microwave irradiated in water or with 50% aqueous ethanol at 150°C. Antioxidant activity range was 1.49–6.53 μmol of Trolox equivalents/g of DDGS. Highest antioxidant activities were obtained from 50% aqueous ethanol extracts at all temperatures, and water extracts that were heated at 100 and 150°C. These data indicate that DDGS extracts with high phenolic content and antioxidant activity can be obtained from DDGS, particularly with the use of water or 50% ethanol and high temperature (100 or 150°C). This may be valuable to ethanol manufacturers, livestock producers, and food and nutraceutical companies.
Study of a virus–bacteria interaction model in a chemostat: application of geometrical singular perturbation theory
Authors: Poggiale J.-C. , Auger P. , Cordoleani F. , Nguyen-Huu T.
Published: November 2009

This paper provides a mathematical analysis of a virus–marine bacteria interaction model. The model is a simplified case of the model published and used by Middelboe (Middelboe, M. 2000
Microb. Ecol
.
40
, 114–124). It takes account of the virus, the susceptible bacteria, the infected bacteria and the substrate in a chemostat. We show that the numerical values of the parameters given by Middelboe allow two different time scales to be considered. We then use the geometrical singular perturbation theory to study the model. We show that there are two invariant submanifolds of dimension two in the four-dimensional phase space and that these manifolds cross themselves on the boundary of the domain of biological relevance. We then perform a rescaling to understand the dynamics in the vicinity of the intersection of the manifolds. Our results are discussed in the marine ecological context.
A model of mechanical interactions between heart and lungs
Authors: Fontecave Jallon Julie , Abdulhay Enas , Calabrese Pascale , Baconnier Pierre , Gumery Pierre-Yves
Published: November 2009

To study the mechanical interactions between heart, lungs and thorax, we propose a mathematical model combining a ventilatory neuromuscular model and a model of the cardiovascular system, as described by Smith
et al.
(Smith, Chase, Nokes, Shaw & Wake 2004
Med. Eng. Phys.
26
, 131–139. (
doi:10.1016/j.medengphy.2003.10.001
)). The respiratory model has been adapted from Thibault
et al
. (Thibault, Heyer, Benchetrit & Baconnier 2002
Acta Biotheor
.
50
, 269–279. (
doi:10.1023/A:1022616701863
)); using a Liénard oscillator, it allows the activity of the respiratory centres, the respiratory muscles and rib cage internal mechanics to be simulated. The minimal haemodynamic system model of Smith includes the heart, as well as the pulmonary and systemic circulation systems. These two modules interact mechanically by means of the pleural pressure, calculated in the mechanical respiratory system, and the intrathoracic blood volume, calculated in the cardiovascular model. The simulation by the proposed model provides results, first, close to experimental data, second, in agreement with the literature results and, finally, highlighting the presence of mechanical cardiorespiratory interactions.
Distance-driven adaptive trees in biological metric spaces: uninformed accretion does not prevent convergence
Authors: Kergosien Yannick Louis
Published: November 2009

We present several variants of a stochastic algorithm which all evolve tree-structured sets adapted to the geometry of general target subsets in metric spaces, and we briefly discuss their relevance to biological modelling. In all variants, one repeatedly draws random points from the target (step 1), each time selecting from the tree to be grown the point which is closest to the point just randomly drawn (step 2), then adding to the tree a new point in the vicinity of that closest point (step 3 or accretion step). The algorithms differ in their accretion rule, which can use the position of the target point drawn, or not. The informed case relates to the early behaviour of self-organizing maps that mimic somatotopy. It is simple enough to be studied analytically near its branching points, which generally follow some unsuccessful bifurcations. Further modifying step 2 leads to a fast version of the algorithm that builds oblique binary search trees, and we show how to use it in high-dimensional spaces to address a problem relevant to interventional medical imaging and artificial vision. In the case of an uninformed accretion rule, some adaptation also takes place, the behaviour near branching points is computationally very similar to the informed case, and we discuss its interpretations within the Darwinian paradigm.
A model of a fishery with fish stock involving delay equations
Authors: Auger P. , Ducrot Arnaud
Published: November 2009

The aim of this paper is to provide a new mathematical model for a fishery by including a stock variable for the resource. This model takes the form of an infinite delay differential equation. It is mathematically studied and a bifurcation analysis of the steady states is fulfilled. Depending on the different parameters of the problem, we show that Hopf bifurcation may occur leading to oscillating behaviours of the system. The mathematical results are finally discussed.
An integrated formulation of anisotropic force–calcium relations driving spatio-temporal contractions of cardiac myocytes
Authors: Tracqui Philippe , Ohayon Jacques
Published: November 2009

Isolated cardiac myocytes exhibit spontaneous patterns of rhythmic contraction, driven by intracellular calcium waves. In order to study the coupling between spatio-temporal calcium dynamics and cell contraction in large deformation regimes, a new strain-energy function, describing the influence of sarcomere length on the calcium-dependent generation of active intracellular stresses, is proposed. This strain-energy function includes anisotropic passive and active contributions that were first validated separately from experimental stress–strain curves and stress–sarcomere length curves, respectively. An extended validation of this formulation was then conducted by considering this strain-energy function as the core of an integrated mechano-chemical three-dimensional model of cardiac myocyte contraction, where autocatalytic intracellular calcium dynamics were described by a representative two-variable model able to generate realistic intracellular calcium waves similar to those observed experimentally. Finite-element simulations of the three-dimensional cell model, conducted for different intracellular locations of triggering calcium sparks, explained very satisfactorily, both qualitatively and quantitatively, the contraction patterns of cardiac myocytes observed by time-lapse videomicroscopy. This integrative approach of the mechano-chemical couplings driving cardiac myocyte contraction provides a comprehensive framework for analysing active stress regulation and associated mechano-transduction processes that contribute to the efficiency of cardiac cell contractility in both physiological and pathological contexts.
A note on semi-discrete modelling in the life sciences
Authors: Mailleret Ludovic , Lemesle Valérie
Published: November 2009

Semi-discrete models are a particular class of hybrid dynamical systems that undergo continuous dynamics most of the time but repeatedly experience discrete changes at some given moments. In the life sciences, since the first semi-discrete model was derived to describe population dynamics by Beverton & Holt (Beverton & Holt 1957 InFisheries investigations, series 2, vol. 19), a large body of literature has been concerned with such modelling approaches. The aim of the present contribution is twofold. On the one hand, it provides a comprehensive introduction to semi-discrete modelling through two illustrative examples: the classical work by Beverton and Holt is recalled and an original example on immigration in a population model affected by a strong Allee effect is worked out. On the other hand, a short overview of the different applications of semi-discrete models in the life sciences is proposed.