bluuebunny/crossref_metadata_2025 huggingface dataset:
Distribution of the αGal‐ and the non‐αGal T‐antigens in the pig kidney: potential targets for rejection in pig‐to‐man xenotransplantation
Authors: Kirkeby Svend , Mikkelsen Hanne B
Published: February 2008

Carbohydrate antigens, present on pig vascular endothelial cells, seem to be the prime agents responsible for graft rejection, and although genetically modified animals that express less amounts of carbohydrate antigen are available, it is still useful to decide the localization of the reactive xenoantigens in organs contemplated for xenotransplantation. Here we compare the distribution in pig kidney of antigens important in xenograft destruction, namely the Galα1–3Gal (αGal) glycans, with the localization of the T‐antigen (Galβ1–3GalNAc). The α‐galactose‐specific lectin Griffonia simplicifolia isolectin 1B4 was used to detect the Galα1–3Gal glycans, whereas Arachis hypogaea (PNA) lectin and a monoclonal antibody (3C9) detected T‐antigen. In addition, two vascular markers (anti‐caveolin‐1 and anti‐von Willebrand factor) served to identify vascular structures of the kidney. Both conventional fluorescence and confocal microscopy were used to distinguish lectin and immunohistochemical staining. On the basis of fluorescence signals, the results indicate that the carbohydrate antigens are heterogeneously distributed in the pig kidney. αGal epitopes were sparse in the capillary loops forming the glomeruli and in the capillaries surrounding the convoluted tubules, but showed stronger staining in capillaries surrounding the limbs of Henle. In addition, the brush border and basement membranes of the convoluted tubules strongly reacted with the GS1‐B4‐lectin. Finally, the Galα1–3Gal glycans were also present on epithelial cells of the large collecting tubules. Regarding the T‐antigen, PNA and 3C9 reacted with different glomerular cells, whereas both reacted strongly with the endothelial cells lining the large kidney vessels. Human serum incubation of pig kidney sections, in which the αGal epitopes were blocked by unconjugated GS1‐B4, showed staining of the same vascular structures as were obtained after incubation with the T‐antigen‐detecting agents. The study thus proves a complex spatial distribution of carbohydrate antigens relevant for xenotransplantation of pig kidney.
How to Make the Most of IP Due Diligence in Deals Involving Generics
Authors: Lubit Beverly W
Published: February 2008

Due diligence is a necessary component of any transaction. One way or another — before the deal or during litigation involving the circumstances of the deal — a company involved in a transaction is going to have to do its due diligence. The objectives of due diligence are: (1) to identify risk to an appropriate level of detail in a due diligence report by understanding the assets of the target, issues relating to the target and how those issues may affect its ability to continue to operate its business and (2) to ensure informed drafting of the transaction documents so that they both shield the parties from liability and ensure the worth/value of a proposed transaction. Risk is identified by recognising hidden or unexpected liabilities and/or major regulatory obstacles to the acquisition. Intellectual property (IP) due diligence is a key component of technology-driven deals. Its purpose is to assess the scope, validity and enforceability of the target company's IP. A due diligence investigation involving generic medicines has specialised requirements. This paper will serve as a guide on how to make the most of IP due diligence in such deals.
Inductive coupled radio frequency plasma bridge neutralizer
Authors: Scholze F. , Tartz M. , Neumann H.
Published: February 2008

A 13.56MHz radio frequency plasma bridge neutralizer (rf-PBN) for ion thruster applications as well as ion beam surface processing of insulating materials is presented. The energy for the plasma excitation is inductively coupled into the plasma chamber. Because no components are located inside the plasma, the lifetime of the rf-PBN is expected to be very long. A compact tuning system adapts the input power to the plasma impedance. The electron current may be controlled over a wide range by the rf input power. An electron current of up to 1.6A has been extracted.
Numerical analysis of H− ion transport processes in Cs-seeded negative ion sources
Authors: Matsushita D. , Takado N. , Hatayama A. , Inoue T.
Published: February 2008

The H− ion transport processes are numerically simulated to understand the extraction process of surface-produced H− ions. The three-dimensional transport code using Monte Carlo method has been applied to calculate the H− ion extraction probabilities in the model geometry of the JAEA 10 ampere negative ion source. The roles of (1) filter magnetic field and (2) collisions with neutrals (H0 atoms and H2 molecules) on the H− ion extraction are systematically studied. The results show that H− ions are extracted mainly by the filter magnetic field under the low gas pressure condition. The simulation results of extracted H− ion beam intensity in the JAEA 10 ampere negative ion source without the magnetic filter tend to be smaller than the experimental results, especially under the low pressure condition. Further model improvements, e.g., modeling and implementation of the effects of the electric field near the extraction aperture, will be required to understand the extraction process of the H− ions under the low gas pressure condition.
A status report of the multipurpose superconducting electron cyclotron resonance ion source (invited)
Authors: Ciavola G. , Gammino S. , Barbarino S. , Celona L. , Consoli F. , Gallo G. , Maimone F. , Mascali D. , Passarello S. , Galatà A. , Tinschert K. , Spaedtke P. , Lang R. , Maeder J. , Rossbach J. , Koivisto H. , Savonen M. , Koponen T. , Suominen P. , Ropponen T. , Baruè C. , Lechartier M. , Beijers J. P. M. , Brandenburg S. , Kremers H. R. , Vanrooyen D. , Kuchler D. , Scrivens R. , Schachter L. , Dobrescu S. , Stiebing K.
Published: February 2008

Intense heavy ion beam production with electron cyclotron resonance (ECR) ion sources is a common requirement for many of the accelerators under construction in Europe and elsewhere. An average increase of about one order of magnitude per decade in the performance of ECR ion sources was obtained up to now since the time of pioneering experiment of R. Geller at CEA, Grenoble, and this trend is not deemed to get the saturation at least in the next decade, according to the increased availability of powerful magnets and microwave generators. Electron density above 1013cm−3 and very high current of multiply charged ions are expected with the use of 28GHz microwave heating and of an adequate plasma trap, with a B-minimum shape, according to the high B mode concept [S. Gammino and G. Ciavola, Plasma Sources Sci. Technol. 5, 19 (1996)]. The MS-ECRIS ion source has been designed following this concept and its construction is underway at GSI, Darmstadt. The project is the result of the cooperation of nine European institutions with the partial funding of EU through the sixth Framework Programme. The contribution of different institutions has permitted to build in 2006–2007 each component at high level of expertise. The description of the major components will be given in the following with a view on the planning of the assembly and commissioning phase to be carried out in fall 2007. An outline of the experiments to be done with the MS-ECRIS source in the next two years will be presented.
Measurements and analysis of bremsstrahlung x-ray spectrum obtained in NANOGAN electron cyclotron resonance ion source
Authors: Baskaran R. , Selvakumaran T. S. , Rodrigues G. , Kanjilal D. , Roy A.
Published: February 2008

From the ECR plasma, hot electrons leak across the magnetic lines of force and by striking the plasma chamber produce bremsstrahlung x-rays. The wall bremsstrahlung gives information on the confinement status of hot electron. In our studies, experimental measurements are carried out in NANOGAN electron cyclotron resonance (ECR) ion source for the wall bremsstrahlung x-rays and the results are presented. While optimizing a particular charge state in ECR ion source, experimental parameters are adjusted to get a maximum current. The wall bremsstrahlung components are studied in these cases for understanding the hot electron confinement conditions.
Design of a proton microbeam of the PEFP
Authors: Kim Kye Ryung , Kim Yong Hwan , Chang Ji Ho , Kim Kui Young
Published: February 2008

The PEFP has been developing a 100MeV proton linear accelerator and user facilities for 20 and 100MeV proton beams. At one end of the five 20MeV proton beam lines, a proton microbeam construction was considered for an application in the fields of material, biological, and medical sciences. To develop the proton microbeam, realization of a few MeV proton beam with a few tens of microamperes in diameter of a beam spot was essentially required. In this report, the basic descriptions of the proton microbeam which is composed of an energy degrader, slits, magnetic lens, a target chamber, and detectors are presented including a consideration of unfavorable aspects concerning some specific characteristics of a linear accelerator, such as pulse mode operation and fixed energy. Some calculation results from a Monte Carlo simulation by using the SRIM2006 and the TURTLE codes are also included.
Beamlet deflection due to beamlet-beamlet interaction in a large-area multiaperture negative ion source for JT-60U
Authors: Kamada M. , Hanada M. , Ikeda Y. , Grisham L. R. , Jiang W.
Published: February 2008

The JT-60U negative ion source has been designed to produce high current beams of 22A through grids of 1080 apertures (five segments with nine rows of 24 apertures). One of the key issues is to steer such a high current beam through the multiaperture grids in order to focus the overall beam envelope because the beamlet-beamlet interaction may deflect the outer beamlets outward due to unbalanced space charge repulsion. To clarify the beam deflection in the JT-60U negative ion source, the beamlet trajectory in a multiaperture ion source was calculated by a three-dimensional simulation code. The measured angles of the outmost beamlets were in agreement with the calculated results where space charge of the beamlets was taken into account. It is noticed that the deflection of the outermost beamlet due to the beamlet-beamlet interaction is saturated at 5.2mrad outward for beamlets more than ten.
Accelerating the convergence of the total energy evaluation in density functional theory calculations
Authors: Zhou Baojing , Wang Yan Alexander
Published: February 2008

A special feature of the Strutinsky shell correction method (SCM) [D. Ullmo et al., Phys. Rev. B 63, 125339 (2001)] and the recently proposed orbital-corrected orbital-free density functional theory (OO-DFT) [B. Zhou and Y. A. Wang, J. Chem. Phys. 124, 081107 (2006)] is that the second-order corrections are incorporated in the total energy evaluation. In the SCM, the series expansion of the total electronic energy is essentially the Harris functional with its second-order correction. Unfortunately, a serious technical problem for the SCM is the lack of the exact Kohn-Sham (KS) density ρKS(r) required for the evaluation of the second-order correction. To overcome this obstacle, we design a scheme that utilizes the optimal density from a high-quality density mixing scheme to approximate ρKS(r). Recently, we proposed two total energy density functionals, i.e., the Zhou-Wang-λ (ZWλ) and the Wang-Zhou-α (WZα) functionals, for use in the OO-DFT method. If the two interpolation parameters, λ and α, are chosen to allow the second-order errors of the ZWλ and the WZα functionals to vanish, these two functionals reduce to the Hohenberg-Kohn-Sham functional with its second-order correction. Again, the optimal density from a high-quality density mixing scheme is used to approximate ρKS(r) in the evaluation of λ and α. This approach is tested in iterative KS-DFT calculations on systems with different chemical environments and can also be generalized for use in other iterative first-principles quantum chemistry methods.
Direct plasma injection scheme in accelerators (invited)
Authors: Okamura M. , Takeuchi T. , Jameson R. A. , Kondrashev S. , Kashiwagi H. , Sakakibara K. , Kanesue T. , Tamura J. , Hattori T.
Published: February 2008

The idea of direct plasma injection scheme (DPIS) was proposed in 2000. This new technique has been studied and proven to accelerate intense ion beams. To provide medium mass ions with highly charged states, small tabletop solid lasers were used for plasma production. Based on the measured plasma properties, aluminum and carbon ions were accelerated with more than 60mA of current. The next experiments will use an radio frequency quadrupole designed for q∕m=1∕6 and explore beam productions using targets up to silver, and future work will explore production up to uranium. The DPIS has been established and is ready to be used with various accelerators which require pulsed high current, high charge state ion beams.
Measurement of the high energy component of the x-ray spectra in the VENUS electron cyclotron resonance ion source (abstract only)
Authors: Leitner D. , Benitez J. Y. , Lyneis C. M. , Todd D. S. , Ropponen T. , Ropponen J. , Koivisto H. , Gammino S.
Published: February 2008

High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (versatile ECR for nuclear science), produce large amounts of x rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different than for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates in dependence of various ion source parameters such as confinement fields, minimum B-field, rf power, and heating frequency.
Direct plasma injection scheme with beam extraction in a radio frequency quadrupole linac cavity
Authors: Kashiwagi Hirotsugu , Okamura Masahiro , Tamura Jun , Takano Junpei
Published: February 2008

Direct plasma injection scheme (DPIS) is a recently developed idea about beam injection into a radio frequency quadrupole (RFQ) linac to obtain high current pulsed heavy ion beam. Since a laser ion source is directly connected to an RFQ linac, a low energy beam transport is not needed. An ion beam is extracted at the edge of the cavity. We shifted the extraction position in the RFQ cavity to improve the beam loss problem due to beam diverging before arriving at the entrance of the RFQ electrode region. In this scheme, ion beam is extracted at the entrance of the RFQ electrode region and the extracted beam is immediately captured by a rf quadrupole electric field. A plasma electrode is inserted in the accelerator resonant cavity. It is required to avoid serious effect on the acceleration characteristics of the RFQ linac. The rf properties were measured using a network analyzer to verify the effect. The shifts of resonant frequency were negligibly small by inserting the electrode. The measurements of the electric field distribution along the beam axis in the RFQ linac showed that the plasma electrode had little effect on it. The result of beam acceleration experiment showed that the beam current was increased by about 20%. It was confirmed that the beam loss was reduced by this scheme.
Spectroscopy of the UO2+ cation and the delayed ionization of UO2
Authors: Merritt Jeremy M. , Han Jiande , Heaven Michael C.
Published: February 2008

Vibronically resolved spectra for the UO2+ cation have been recorded using the pulsed field ionization zero electron kinetic energy (PFI-ZEKE) technique. For the ground state, long progressions in both the bending and symmetric stretch vibrations were observed. Bend and stretch progressions of the first electronically excited state were also observed, and the origin was found at an energy of 2678cm−1 above the ground state zero-point level. This observation is consistent with a recent theoretical prediction [Infante et al., J. Chem. Phys. 127, 124308 (2007)]. The ionization energy for UO2, derived from the PFI-ZEKE spectrum, namely, 6.127(1)eV, is in excellent agreement with the value obtained from an earlier photoionization efficiency measurement. Delayed ionization of UO2 in the gas phase has been reported previously [Han et al., J. Chem. Phys. 120, 5155 (2004)]. Here, we extend the characterization of the delayed ionization process by performing a quantitative study of the ionization rate as a function of the energy above the ionization threshold. The ionization rate was found to be 5×106s−1 at threshold, and increased linearly with increasing energy in the range investigated (0–1200cm−1).
EPR and IR spectra of the FSO3 radical revisited: Strong vibronic interactions in the A22 electronic ground state
Authors: Beckers H. , Willner H. , Grote D. , Sander W.
Published: February 2008

The previous controversy about the ground-state symmetry and contradictory vibrational analyses of FSO3 has been solved by a reinvestigation of its EPR and IR matrix spectra. The anisotropic EPR spectrum of FSO3 isolated in an argon matrix at 5K is in agreement with an axial symmetry and an A22 electronic ground state. While the obtained hyperfine-coupling constants agree quite well to previous measurements in different environments, the g values may be affected by the large motion of the low-lying (162cm−1) rocking mode of FSO3. For the first time measurements of the IR matrix spectra were extended to the far infrared region and to all O16∕18 isotopomers of FSO3. A new fundamental at 161.6cm−1 in Ar matrix and, for the nine strongest bands of FSO3, the isotopic O16∕18 pattern have been observed and analyzed. The four line pattern of the a1-type fundamental modes at 1052.7, 832.5, and 531.0cm−1 confirmed the C3v symmetry of FSO3 in the electronic ground state. The e-type fundamental modes at 931.6, 426.2, and 161.6cm−1 are unusually low in energy and in intensity due to vibronic interaction to the low-lying electronic excited E2 states. On the other hand, several combinations and overtones of e-type fundamentals are strongly enhanced due to vibronic interactions.
The effect of hydrodynamic interactions on the dynamics of DNA translocation through pores
Authors: Izmitli Aslin , Schwartz David C. , Graham Michael D. , de Pablo Juan J.
Published: February 2008

In this work, we investigate the effect of hydrodynamic interactions on the dynamics of DNA translocation through micropores. We simulate DNA as a bead-spring chain and use a lattice Boltzmann method to simulate the flow field that arises from the motion of the molecule. We investigate the free-draining entrance of DNA to the pore by diffusion and find that, consistent with experiments, molecules have a higher probability of entering the pore from one end. We then consider the electric-field driven translocation of 21–210μm DNA with and without hydrodynamic interactions. Consistent with experiments, we study translocation events that are much shorter than the relaxation time of DNA. We find that the effect of hydrodynamic interactions on this process is to cause different regions of a molecule, other than the ones pulled by voltage or chain connectivity into the pore, to move toward the pore. We quantify this effect and show that it is smaller than the difference in the translocation dynamics of chains that arises from different initial configurations of the molecules. A power-law scaling of translocation time with chain length is observed, with exponents of 1.28±0.03 and 1.31±0.03 in simulations with and without hydrodynamic interactions, respectively. Our results are in good agreement with recent translocation experiments conducted in small pores and show that, for the regime considered in this work, hydrodynamic interactions play a minor role in the relation of the translocation time to chain length. For fast translocation processes, the effect of hydrodynamic interactions is local and the main factor determining the dynamics of DNA is the initial configuration of the molecules.
Effect of interactions on molecular fluxes and fluctuations in the transport across membrane channels
Authors: Kolomeisky Anatoly B. , Kotsev Stanislav
Published: February 2008

Transport of molecules across membrane channels is investigated theoretically using exactly solvable one-dimensional discrete-state stochastic models. An interaction between molecules and membrane pores is modeled via a set of binding sites with different energies. It is shown that the interaction potential strongly influences the particle currents as well as fluctuations in the number of translocated molecules. For small concentration gradients, the attractive sites lead to largest currents and fluctuations, while the repulsive interactions yield the largest fluxes and dispersions for large concentration gradients. Interaction energies that lead to maximal currents and maximal fluctuations are the same only for locally symmetric potentials, where transition states are equally distant from the neighboring binding sites, while they differ for the locally asymmetric potentials. The conditions for the most optimal translocation transport with maximal current and minimal dispersion are discussed. It is argued that, in this case, the interaction strength is independent of local symmetry of the potential of mean forces. In addition, the effect of the global asymmetry of the interaction potential is investigated, and it is shown that it also strongly affects the particle translocation dynamics. These phenomena can be explained by analyzing the details of the particle entering and leaving the binding sites in the channel.
Study of the local environment diversity between Co- and Mn-doped ZnO single crystal film by multilayer growth technique
Authors: Huang J. C. A. , Hsu H. S. , Sun J. H. , Chiu S. L. , Lee C. H. , Liao Y. F. , Chou H.
Published: February 2008

We investigated the room temperature ferromagnetism and their local coordination environment of Co and Mn doped in ZnO single crystal films. Both films show room temperature ferromagnetism and the saturated magnetization of the Mn-doped ZnO film is stronger than that of the Co-doped films. From the analysis on the local structures of Zn, Co, and Mn, we verify that the lattice distortions mainly surround the Co and Mn dopants. Due likely to the relatively large cation size, the Mn dopant would induce a greater local lattice distortion. We suggest that the local environment disorder between the Co and Mn dopants may play a role to the origin of ZnO based diluted magnetic semiconductor films.
Mean field kinetic theory for a lattice gas model of fluids confined in porous materials
Authors: Monson Peter A.
Published: February 2008

We consider the mean field kinetic equations describing the relaxation dynamics of a lattice model of a fluid confined in a porous material. The dynamical theory embodied in these equations can be viewed as a mean field approximation to a Kawasaki dynamics Monte Carlo simulation of the system, as a theory of diffusion, or as a dynamical density functional theory. The solutions of the kinetic equations for long times coincide with the solutions of the static mean field equations for the inhomogeneous lattice gas. The approach is applied to a lattice gas model of a fluid confined in a finite length slit pore open at both ends and is in contact with the bulk fluid at a temperature where capillary condensation and hysteresis occur. The states emerging dynamically during irreversible changes in the chemical potential are compared with those obtained from the static mean field equations for states associated with a quasistatic progression up and down the adsorption/desorption isotherm. In the capillary transition region, the dynamics involves the appearance of undulates (adsorption) and liquid bridges (adsorption and desorption) which are unstable in the static mean field theory in the grand ensemble for the open pore but which are stable in the static mean field theory in the canonical ensemble for an infinite pore.
Momentum transport from tearing modes with shear flow
Authors: Ebrahimi F. , Mirnov V. V. , Prager S. C.
Published: February 2008

A theoretical and computational study of momentum transport from reconnection from tearing modes in the presence of sheared flow in a reversed field pinch has been performed. Momentum transport from single tearing modes in the linear and nonlinear regimes and transport from multiple tearing modes is studied. It is found that, whereas a single mode produces transport, a strong enhancement in transport arises from the nonlinear coupling of multiple modes. A single tearing mode, in the presence of equilibrium flow, produces momentum transport in the vicinity of the reconnection layer. This is demonstrated from quasilinear calculation of Maxwell and Reynolds stresses. However, nonlinear, resistive magnetohydrodynamics computation of the full, multimode nonlinear dynamics reveals an additional effect. In the presence of multiple tearing modes, nonlinear coupling strongly enhances the torques and broadens their radial width. The resulting transport from current-driven instability is much more rapid than classical viscous forces.
Study of magnetic configuration effects on plasma boundary and measurement of edge electron density in the spherical tokamak compact plasma wall interaction experimental device using Li sheet beam
Authors: Bhattacharyay R. , Zushi H. , Morisaki T. , Inada Y. , Kikukawa T. , Watanabe S. , Sasaki K. , Ryoukai T. , Hasegawa M. , Hanada K. , Sato K. N. , Nakamura K. , Sakamoto M. , Idei H. , Yoshinaga T. , Kawasaki S. , Nakashima H. , Higashijima A.
Published: February 2008

Two-dimensional lithium beam imaging technique has been applied in the spherical tokamak CPD (compact plasma wall interaction experimental device) to study the effects of magnetic field configurations on rf plasma boundary in the absence of any plasma current, and also for the measurement of a two-dimensional edge electron density profile. With the present working condition of the diagnostics, the minimum measured electron density can be ∼1.0×1016m−3; this is considered to be the definition for the plasma boundary. The performance of the lithium sheet beam is absolutely calibrated using a quartz crystal monitor. Experimental results reveal that magnetic field configuration, either mirror or so-called null, critically affects the rf plasma boundary. A sharp lower boundary is found to exist in magnetic null configuration, which is quite different from that in the weak mirror configuration. Theoretical calculations of particle drift orbit and magnetic connection length (wall-to-wall) suggest that only mirror trapped particles are confined within a region where the magnetic connection length is ∼4.0m or more. A two-dimensional edge electron density profile is obtained from the observed LiI intensity profile. Overdense plasma formation is discussed from the viewpoint of mode conversion of rf wave into electron Bernstein wave and its dependence on the electron density profile.
Laser-induced breakdown spectroscopy in reactive flows of hydrocarbon-air mixtures
Authors: Michalakou Amalia , Stavropoulos Polychronis , Couris Stelios
Published: February 2008

Laser-induced breakdown spectroscopy is used for the determination of the local equivalence ratio (i.e., the ratio of the actual fuel-to-oxidizer mass over the ratio of the fuel-to-oxidizer mass at stoichiometry) in different methane-, ethylene-, and propane-air mixtures. In particular, it is shown that the ratio of the intensities of the atomic spectral lines of H, C, and O, emitted from a laser-induced spark in the gaseous mixture, can be used for the rapid and accurate determination of the local equivalence ratio.
Room-temperature magnetocaloric effect in La0.7Sr0.3Mn1−xMx′O3 (M′=Al,Ti)
Authors: Nam D. N. H. , Dai N. V. , Hong L. V. , Phuc N. X. , Yu S. C. , Tachibana M. , Takayama-Muromachi E.
Published: February 2008

Magnetic entropy and adiabatic temperature changes in and above the room-temperature region have been measured for La0.7Sr0.3Mn1−xMx′O3 (M′=Al,Ti) by means of magnetization and heat capacity measurements in magnetic fields up to 6 T. The magnetocaloric effect becomes largest at the ferromagnetic ordering temperature Tc that is tuned (from 364.5 K for x=0) to ∼300 K by the substitution of Al or Ti for Mn. While the substitution of Al for Mn drastically reduces the maximum magnetic entropy (−ΔSm) and adiabatic temperature (ΔTa) changes, it extends considerably the working temperature span and therefore improves the relative cooling power (RCP). Under a magnetic field change ΔH=2 T, −ΔSm (or ΔTa) of La0.7Sr0.3Mn1−xAlxO3 decreases from 2.66 J/kg K (or 1.65 K) for x=0 to 1.18 J/kg K (or 0.69 K) for x=0.1, while RCP increases from 80.3 to 108.8 J/kg, respectively. While Tc is largely suppressed, the magnetocaloric effect is only lightly affected by the Ti substitution. With ΔH=2 T, the La0.7Sr0.3Mn0.95Ti0.05O3 sample exhibits −ΔSm (or ΔTa) =2.44 J/kg K (or 1.38 K) with RCP=89.9 J/kg. The decrease of magnetic moment is found to be one possible reason behind the suppression of the MCE. The magnetocaloric effect in manganite materials seems to be inhibited by the existence of short-range ferromagnetic correlations above Tc.
Effective area reduction in directly coupled superconducting quantum interference device based micromagnetometers
Authors: Prigiobbo A. , Sarnelli E.
Published: February 2008

We have designed and tested a set of YBa2Cu3O7−δ (YBCO) directly coupled superconducting quantum interference devices (SQUIDs). The proposed layout introduces a reduction of the device effective area that leads to high design flexibility for micromagnetometer sensors. SQUID magnetometers have been realized using YBCO grain boundary junctions fabricated on symmetric 30° [001] bicrystal substrates. Sensors have been characterized in a highly shielded environment confirming theoretical predictions.
Electron dephasing in nanocrystalline silicon thin films
Authors: Zhang K. , Shen W. Z.
Published: February 2008

In combination with dephasing and weak localization theories, we have presented a detailed magnetotransport investigation for the electron dephasing characteristics in hydrogenated nanocrystalline silicon thin films. It is found that the experimental magnetoconductivity can be well fitted by an integration of diffusive Fermi surface and scaling models, taking into account both the two-dimensional quasielastic small energy transfer via scattering of localized electrons on potential barriers of several different dots (Nyquist mechanism) and three-dimensional inelastic phonon scattering contribution. The dephasing time and length have also been extracted with a temperature exponent p≈1.2 for the natural semiconductor quantum dot system.
Asymptotic analysis of the selective dip coating of power-law fluids
Authors: Tiwari Naveen , Davis Jeffrey M.
Published: February 2008

The dip coating of a chemically micropatterned surface bearing alternating wetting and nonwetting vertical strips is analyzed for a non-Newtonian power-law fluid. Asymptotic matching is used to determine the thickness of liquid films deposited on the O(10μm) strips at small capillary and Bond numbers. The chemical patterning that confines the fluid laterally induces a significant transverse curvature of the free-surface. The streamwise variation in this transverse curvature along the strip provides an additional contribution to the capillary pressure gradient that is not present for uniform surfaces. Consequently, the difference in the thickness of the deposited liquid film relative to a Newtonian fluid is significantly less than for homogeneous plates or fibers.
Identification of the atomic-scale defects involved in the negative bias temperature instability in plasma-nitrided p-channel metal-oxide-silicon field-effect transistors
Authors: Campbell J. P. , Lenahan P. M. , Krishnan A. T. , Krishnan S.
Published: February 2008

We utilize a combination of DC gate-controlled diode recombination current measurements as well as two very sensitive electrically detected magnetic resonance techniques, spin-dependent recombination and spin-dependent tunneling, to identify atomic-scale defects involved in the negative bias temperature instability (NBTI) in 2.3nm plasma-nitrided SiO2-based p-channel metal-oxide-silicon field-effect transistors. We demonstrate that the dominating NBTI-induced defect in the plasma-nitrided devices is fundamentally different than those observed in pure SiO2-based devices. (In pure SiO2 devices, we observe NBTI-induced Pb0 and Pb1 defects.) Our measurements indicate that the NBTI-induced defect in the plasma-nitrided devices extends into the gate dielectric. The defect participates in both spin-dependent recombination and spin-dependent tunneling. The defect also has a density of states which is more narrowly peaked than that of Pb centers near the middle of the band gap. The high sensitivity of our spin-dependent tunneling measurements allow for an identification of the physical and chemical nature of this defect through observations of Si29 hyperfine interactions. We identify these defects as silicon dangling bond defects in which the central silicon is back bonded to nitrogen atoms. We assign these NBTI-induced defects as KN centers because of their similarity to K centers observed in silicon nitride. (The silicon nitride K centers are also silicon dangling bond defects in which the silicon atom is back-bonded to nitrogen atoms.) The defect identification in plasma-nitrided devices helps to explain (1) why NBTI is exacerbated in nitrided devices, (2) conflicting reports of NBTI-induced interface states and/or bulk traps, and (3) fluorine’s ineffectiveness in reducing NBTI in nitrided devices.
Effects of molecular diffusion on the subgrid-scale modeling of passive scalars
Authors: Brun C. , Balarac G. , da Silva C. B. , Métais O.
Published: February 2008

The spectral eddy-viscosity and eddy-diffusivity closures derived from the eddy-damped quasinormal Markovian (EDQNM) theory, and one of its physical space counterparts, i.e., the structure function model [Métais and Lesieur, J. Fluid Mech. 239, 157 (1992)], are revisited to account for molecular viscosity and diffusivity effects. The subgrid-scale Schmidt number (usually set to Sct≈0.6) is analytically derived from the EDQNM theory and shown to be Reynolds number dependent, a property of utmost importance for flows involving scalar transport at moderate Reynolds numbers or during the transition to turbulence. A priori tests in direct numerical simulation of homogeneous isotropic turbulence [da Silva and Pereira, Phys. Fluids 19, 035106 (2007)] and in spatially evolving turbulent plane jets [da Silva and Métais, J. Fluid Mech. 473, 103 (2002)], as well as a posteriori (large eddy simulation) tests in a round jet are carried out and show that the present viscous structure function model improves the results from the classical approaches and at a comparatively small computational cost.
Tougher ultrafine grain Cu via high-angle grain boundaries and low dislocation density
Authors: Zhao Y. H. , Bingert J. F. , Zhu Y. T. , Liao X. Z. , Valiev R. Z. , Horita Z. , Langdon T. G. , Zhou Y. Z. , Lavernia E. J.
Published: February 2008

Although there are a few isolated examples of excellent strength and ductility in single-phase metals with ultrafine grained (UFG) structures, the precise role of different microstructural features responsible for these results is not fully understood. Here, we demonstrate that a large fraction of high-angle grain boundaries and a low dislocation density may significantly improve the toughness and uniform elongation of UFG Cu by increasing its strain-hardening rate without any concomitant sacrifice in its yield strength. Our study provides a strategy for synthesizing tough UFG materials.
In-plane microelectromechanical resonator with integrated Fabry–Pérot cavity
Authors: Pruessner Marcel W. , Stievater Todd H. , Rabinovich William S.
Published: February 2008

A silicon-on-insulator in-plane microelectromechanical resonator coupled to a high-Q (Q≈4,200), high finesse (FMax=265) optical Fabry–Pérot microcavity is presented. The cavity utilizes high reflectance dry-etched silicon/air distributed Bragg reflectors. By suspending one of the Bragg mirrors to a microbridge resonator, the mirror can be displaced and the cavity is tuned. Using electrostatic actuation, bidirectional cavity tuning from −12.1to+17.0nm (29.1nm total range) is demonstrated near 1601nm wavelength. The device also enables measurement of thermal-mechanical noise with sensitivity better than 10fm∕Hz1∕2 and may find application in high resolution sensors.
Maskless electrodeposited contact for conducting polymer nanowires
Authors: Hangarter Carlos M. , Bangar Mangesh , Hernandez Sandra C. , Chen Wilfred , Deshusses Marc A. , Mulchandani Ashok , Myung Nosang V.
Published: February 2008

This letter reports a simple and scalable method to create mechanical joints and electrical contacts of conducting polymer nanowires to electrodes by selective maskless metal electrodeposition on electrodes. This is an attractive route for contacting nanowires as it bypasses harsh processing conditions of conventional methods. The electrodeposition conditions and initial resistance of the nanowires were found to have a significant impact on the selective maskless deposition. Different dopants were also investigated to understand the polymer reduction during cathodic deposition of metal. A single dodecyl sulfate doped polypyrrole nanowire with maskless electrodeposited nickel contacts was shown to have improved sensitivity toward ammonia gas.
Plugging of porous media and filters: Maximum clogged porosity
Authors: Kampel Guido , Goldsztein Guillermo H. , Santamarina Juan C.
Published: February 2008

We model porous media as two-dimensional networks of channels. As suspension flows through the network, particles clog channels. Assuming no flow through clogged channels, we determine an upper bound on the number of channels that clog and leave the network impervious. More precisely, the number of channels that clog does not exceed the number of faces of the multigraph associated with the network. In terms of d, the average coordination number of the network, the number of channels that clog does not exceed (1−2∕d) of the total number of channels.
First-principles calculations of elastic properties of Cu3Sn superstructure
Authors: Chen Jiunn , Lai Yi-Shao , Ren Chung-Yuan , Huang Di-Jing
Published: February 2008

We report the elastic properties of Cu3Sn superstructure based on first-principles calculations. Polycrystalline Young’s modulus and Poisson’s ratio are deduced from the calculated elastic stiffness. The calculations of electronic structures with the principal strains along different directions unravel the electronic nature of anisotropic elasticity of Cu3Sn. Weak Sn–Cu bonding in Cu3Sn suggests that Sn atoms are the dominant diffusion species, revealing the mechanism of vacancy formation within the Cu3Sn superstructure.
Influence of an ultrathin GaAs interlayer on the structural properties of InAs∕InGaAsP∕InP (001) quantum dots investigated by cross-sectional scanning tunneling microscopy
Authors: Ulloa J. M. , Anantathanasarn S. , van Veldhoven P. J. , Koenraad P. M. , Nötzel R.
Published: February 2008

Cross-sectional scanning tunneling microscopy is used to study at the atomic scale how the structural properties of InAs∕InGaAsP∕InP quantum dots (QDs) are modified when an ultrathin (0–1.5 ML) GaAs interlayer is inserted underneath the QDs. Deposition of the GaAs interlayer suppresses the influence of the As∕P exchange reaction on QD formation and leads to a planarized QD growth surface. A shape transition from quantum dashes, which are strongly dissolved during capping, to well defined QDs takes place when increasing the GaAs interlayer thickness between 0 and 1.0 ML. Moreover, the GaAs interlayer allows the control of the As∕P exchange reaction, reducing the QD height for increased GaAs thicknesses above 1.0 ML, and decreases the QD composition intermixing, producing almost pure InAs QDs.
Photoemission and x-ray absorption studies of valence states in (Ni,Zn,Fe,Ti)3O4 thin films exhibiting photoinduced magnetization
Authors: Kobayashi M. , Ooki Y. , Takizawa M. , Song G. S. , Fujimori A. , Takeda Y. , Terai K. , Okane T. , Fujimori S.-I. , Saitoh Y. , Yamagami H. , Seki M. , Kawai T. , Tabata H.
Published: February 2008

By means of photoemission and x-ray absorption spectroscopy, we have studied the electronic structure of (Ni,Zn,Fe,Ti)3O4 thin films, which exhibits a cluster glass behavior with a spin-freezing temperature Tf of ∼230K and photoinduced magnetization (PIM) below Tf. The Ni and Zn ions were found to be in the divalent states. Most of the Fe and Ti ions in the thin films were trivalent (Fe3+) and tetravalent (Ti4+), respectively. While Ti doping did not affect the valence states of the Ni and Zn ions, a small amount of Fe2+ ions increased with Ti concentration, consistent with the proposed charge-transfer mechanism of PIM.
Impacts of prior mis-specification on Bayesian fisheries stock assessment
Authors: Chen Yong , Sun Chi-Lu , Kanaiwa Minoru
Published: February 2008

One of the key features of a Bayesian stock assessment is that the modeller needs to provide knowledge on model parameters. Priors summarise modellers’ understanding of model parameters and are often defined by a probability distribution function. Priors are often mis-specified with arbitrary and unrealistic accuracy and precision in perceiving the state of nature for the parameters as a result of our limited understanding of fisheries ecosystems. Commonly used probability functions such as normal distribution functions tend to be sensitive to prior mis-specification, resulting in large uncertainty and/or errors in Bayesian stock assessment. Fat-tailed functions such as the Cauchy distribution function have been found to be robust to prior mis-specification. Using the Maine sea urchin fishery as an example, we evaluated the impacts of mis-specification in defining the prior distributions on Bayesian stock assessment. The present study suggests that the quantification of priors with a Cauchy distribution tends to be robust to the prior mis-specification. Given our limited understanding of fisheries a function such as the Cauchy distribution function that is robust to prior mis-specification tends to be more desirable. Future studies should explore the use of other fat-tailed distribution functions for quantifying priors in fisheries stock assessment.
Seasonal flooding, instream habitat structure and fish assemblages in the Mulgrave River, north-east Queensland: towards a new conceptual framework for understanding fish-habitat dynamics in small tropical rivers
Authors: Rayner Thomas S. , Pusey Bradley J. , Pearson Richard G.
Published: February 2008

Strong relationships between seasonal flooding, instream habitat structure and fish assemblages have been well documented in large tropical rivers (e.g. the flood pulse concept). However, the mechanics of these relationships are likely to differ substantially in smaller coastal rivers, such as those in Costa Rica, south-east Brazil and Australia’s Wet Tropics. These systems typically feature steep upland streams with short, deeply incised lowland channels and poorly connected floodplains. This hypothesis was investigated by documenting spatial and temporal variation in fish-habitat relationships in the Mulgrave River, north-east Queensland. Sampling was conducted at four lowland sites under a range of flow conditions, from dry-season baseflows to a one-in-ten-year flood. Longitudinal environmental gradients and fine-scale habitat patches were important in regulating fish assemblage structure during the dry season. However, high wet-season flows, constrained by the deep channel, acted as disturbances rather than gentle flood-pulses. In particular, the mobilisation of bed sediments led to scouring of aquatic vegetation and a dramatic reduction in habitat heterogeneity. Seasonal movements of fish led to significant changes in assemblage structure – from a community dominated by Neosilurus ater, Hypseleotris compressa, Awaous acritosus and Redigobius bikolanus during the dry season, to one dominated by Nematalosa erebi, Ambassis agrammus and Glossamia aprion during the wet season. Based on these observations, together with information from the literature, a conceptual model of fish-habitat dynamics is presented that is better suited to small tropical rivers than those developed in larger systems with expansive floodplains.
Human single-neuron responses at the threshold of conscious recognition
Authors: Quiroga R. Quian , Mukamel R. , Isham E. A. , Malach R. , Fried I.
Published: February 2008

We studied the responses of single neurons in the human medial temporal lobe while subjects viewed familiar faces, animals, and landmarks. By progressively shortening the duration of stimulus presentation, coupled with backward masking, we show two striking properties of these neurons. (
i
) Their responses are not statistically different for the 33-ms, 66-ms, and 132-ms stimulus durations, and only for the 264-ms presentations there is a significantly higher firing. (
ii
) These responses follow conscious perception, as indicated by the subjects' recognition report. Remarkably, when recognized, a single snapshot as brief as 33 ms was sufficient to trigger strong single-unit responses far outlasting stimulus presentation. These results suggest that neurons in the medial temporal lobe can reflect conscious recognition by “all-or-none” responses.
Vacancy-mediated dehydrogenation of sodium alanate
Authors: Gunaydin Hakan , Houk Kendall N. , Ozoliņš Vidvuds
Published: February 2008

Clarification of the mechanisms of hydrogen release and uptake in transition-metal-doped sodium alanate, NaAlH
4
, a prototypical high-density complex hydride, has fundamental importance for the development of improved hydrogen-storage materials. In this and most other modern hydrogen-storage materials, H
2
release and uptake are accompanied by long-range diffusion of metal species. Using first-principles density-functional theory calculations, we have determined that the activation energy for Al mass transport via AlH
3
vacancies is
Q
= 85 kJ/mol·H
2
, which is in excellent agreement with experimentally measured activation energies in Ti-catalyzed NaAlH
4
. The activation energy for an alternate decomposition mechanism via NaH vacancies is found to be significantly higher:
Q
= 112 kJ/mol·H
2
. Our results suggest that bulk diffusion of Al species is the rate-limiting step in the dehydrogenation of Ti-doped samples of NaAlH
4
and that the much higher activation energies measured for uncatalyzed samples are controlled by other processes, such as breaking up of AlH
4
−
complexes, formation/dissociation of H
2
molecules, and/or nucleation of the product phases.