bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface albedo observations at Gusev Crater and Meridiani Planum, Mars
Authors: Bell J. F. , Rice M. S. , Johnson J. R. , Hare T. M.
Published: May 2008

During the Mars Exploration Rover mission, the Pancam instrument has periodically acquired large‐scale panoramic images with its broadband (739 ± 338 nm) filter in order to estimate the Lambert bolometric albedo of the surface along each rover's traverse. In this work we present the full suite of such estimated albedo values measured to date by the Spirit and Opportunity rovers along their traverses in Gusev Crater and Meridiani Planum, respectively. We include estimated bolometric albedo values of individual surface features (e.g., outcrops, dusty plains, aeolian bed forms, wheel tracks, light‐toned soils, and crater walls) as well as overall surface averages of the 43 total panoramic albedo data sets acquired to date. We also present comparisons to estimated Lambert albedo values taken from the Mars Global Surveyor Mars Orbiter Camera (MOC) along the rovers' traverses, and to the large‐scale bolometric albedos of the sites from the Viking Orbiter Infrared Thermal Mapper (IRTM) and Mars Global Surveyor/Thermal Emission Spectrometer (TES). The ranges of Pancam‐derived albedos at Gusev Crater (0.14 to 0.25) and in Meridiani Planum (0.10 to 0.18) are in good agreement with IRTM, TES, and MOC orbital measurements. These data sets will be a useful tool and benchmark for future investigations of albedo variations with time, including measurements from orbital instruments like the Context Camera and High Resolution Imaging Science Experiment on Mars Reconnaissance Orbiter. Long‐term, accurate albedo measurements could also be important for future efforts in climate modeling as well as for studies of active surface processes.
Elevated primary productivity of calcareous nannoplankton associated with ocean anoxic event 1b during the Aptian/Albian transition (Early Cretaceous)
Authors: Browning Emily L. , Watkins David K.
Published: May 2008

Previous isotopic investigations of Aptian/Albian oceanic anoxic event (OAE) 1b from the western North Atlantic (Blake Nose) posited that increased sea surface temperatures and decreased salinity led to stratification of the upper water column, resulting in lowered dissolved oxygen and enhanced organic matter preservation. We examined calcareous nannofossils from the same site in the western North Atlantic (Blake Nose) to evaluate changes in surface water conditions prior to, during, and after the Aptian/Albian OAE1b. The results of our analysis conflict somewhat with the previous interpretation that OAE1b at Blake Nose was linked to water column stratification. The signal from calcareous nannofossils indicates that in the late Aptian, prior to OAE1b, oligotrophic conditions in the surface waters were replaced by mesotrophic conditions that persisted throughout the OAE event and into the early Albian. We speculate that increased surface water productivity facilitated to some degree the development of OAE1b at Blake Nose.
Unprecedented evidence for deep convection hydrating the tropical stratosphere
Authors: Corti T. , Luo B. P. , de Reus M. , Brunner D. , Cairo F. , Mahoney M. J. , Martucci G. , Matthey R. , Mitev V. , dos Santos F. H. , Schiller C. , Shur G. , Sitnikov N. M. , Spelten N. , Vössing H. J. , Borrmann S. , Peter T.
Published: May 2008

We report on in situ and remote sensing measurements of ice particles in the tropical stratosphere found during the Geophysica campaigns TROCCINOX and SCOUT‐O3. We show that the deep convective systems penetrated the stratosphere and deposited ice particles at altitudes reaching 420 K potential temperature. These convective events had a hydrating effect on the lower tropical stratosphere due to evaporation of the ice particles. In contrast, there were no signs of convectively induced dehydration in the stratosphere.
Debye‐length scaled structure of perpendicular electric field in collisionless magnetic reconnection
Authors: Huang J. , Ma Z. W. , Li D.
Published: May 2008

Generation of electric fields at the scale of the local electron Debye length in collisionless magnetic reconnection is studied through two‐dimensional Darwin particle‐in‐cell simulation. For asymmetric initial temperature and density profile across the Harris current sheet, intense perpendicular electrostatic structure with the local electron Debye‐length scaling (∼2.9 λDe) is observed near the edge of the magnetic island in the high‐temperature/low‐density region. It is also found that a weak electron jet with return electron flow on the high‐density side results in the formation of an electron current loop. However, in the low density region only a strong electron outflow is detected. Because of a single‐looped electric current on each side of the outflow region, the usual quadrupole structure appearing in the earlier symmetric‐profile simulations is replaced by a dipole‐like structure of the guiding magnetic field. Possible applications of the present results in the dayside magnetopause are discussed.
Electromagnetic induction of planar windings with cylindrical symmetry between two half-spaces
Authors: Acero J. , Alonso R. , Burdío J. M. , Barragán L. A. , Llorente S.
Published: May 2008

A closed-form solution is derived for the equivalent impedance of a planar winding with cylindrical symmetry placed between two half-spaces. This is basically the structure of a domestic induction heating appliance comprised of a planar winding, a metallic vessel, and a lossless magnetic substrate. The first matter addressed is the impedance of a sandwiched single-turn coil, obtained by using the vector potential Helmholtz equation solution, and the result is generalized to n-turn coils. The real part of this impedance represents power dissipated in the form of heat. The proposed model includes geometry dependence, frequency of excitation currents, and electromagnetic properties of both top and bottom media. Enhancement of power dissipation in the conducting media as a result of the inclusion of a magnetic substrate is also explored. Experimental results are presented in order to validate the theoretical model.
Excitation and photoluminescence of pure and Si-doped β-Ga2O3 single crystals
Authors: Shimamura Kiyoshi , Víllora Encarnación G. , Ujiie Takekazu , Aoki Kazuo
Published: May 2008

Excitation and photoluminescence spectra of high purity and Si-doped β-Ga2O3 single crystals are investigated. Emission peaks in the UV and blue wavelength regions are observed. These are excited at two bands, which can be differentiated by polarized light. The features of the spectra are independent of excitation and emission wavelengths in the case of an undoped sample. On the contrary, after Si doping, the blue emission becomes strongly dependent. A model to interpret the characteristics of blue luminescence is proposed.
Dynamics and reversibility of oxygen doping and de-doping for conjugated polymer
Authors: Liao Hua-Hsien , Yang Chia-Ming , Liu Chien-Cheng , Horng Sheng-Fu , Meng Hsin-Fei , Shy Jow-Tsong
Published: May 2008

We perform comprehensive long-time monitoring of the p-doping and de-doping of poly(3-hexyl thiophene) under changing external conditions of oxygen, light, and temperature. They are shown to be controlled by the complex adsorption and desorption process with time scales ranging from seconds to weeks. The oxygen doping at atmospheric pressure takes several hours in the dark. The doping is dramatically accelerated to be within seconds with light of wavelength of 500–700 nm. Even at low oxygen pressure of 10−4 torr doping occurs within minutes with light. The de-doping by oxygen desorption takes as long as weeks at room temperature and vacuum of 10−4 torr, but when the temperature is raised to near the polymer glass temperature of 370 K, the de-doping is accelerated to minutes as the enhanced chain motion releases the trapped oxygen. Even though visible and near infrared light causes very efficient doping within seconds or minutes depending on vacuum level, such light-induced doping is not a chemical reaction and is fully reversible by thermal annealing at the end without sacrificing the mobility. For the polymer field-effect transistors, only the carrier density is changed while the mobility remains roughly a constant for all the conditions.
O
⋆
-algebras and quantum dynamics: Some existence results
Authors: Bagarello F.
Published: May 2008

We discuss the possibility of defining an algebraic dynamics within the settings of O⋆-algebras. Compared to our previous results on this subject, the main improvement here is that we are not assuming the existence of some Hamiltonian for the full physical system. We will show that, under suitable conditions, the dynamics can still be defined via some limiting procedure starting from a given regularized sequence.
Roles of external noise correlation in optimal intracellular calcium signaling
Authors: Lang Xiufeng , Li Qianshu
Published: May 2008

The dynamics of a minimal calcium model, which is subjected to white noise or colored noise, was investigated. For white noise, coherence of noise-induced calcium oscillations reached a maximum at an optimal noise intensity, characterizing coherence resonance. Higher resonance peaks could be observed at lower noise intensity when a control parameter is tuned to approach a bifurcation point. For colored noise, a maximal coherence of the oscillations was found for suitable values of both the intensity and the correlation time. Moreover, the coherence of the oscillations exhibited two maxima at two values of noise intensity (correlation time) for appropriate noise correlation time (intensity). In addition, a quantitative description of the effects of noise correlation time on the resonance behavior was presented. The resonance behavior, which is induced either by white noise or colored noise, was interpreted by terms of height and relative width of a spectral peak.
A new class of solvable dynamical systems
Authors: Calogero Francesco
Published: May 2008

A new class of dynamical systems are presented, together with their solutions. Some of these models are isochronous, namely, their generic solutions are all completely periodic with the same period; others are characterized by friction, all solutions vanishing in the remote future; and still others are “asymptotically isochronous,” approaching an isochronous behavior in the remote future.
Measurement of derivative of ion temperature using high spatial resolution charge exchange spectroscopy with space modulation optics
Authors: Ida K. , Sakamoto Y. , Yoshinuma M. , Inagaki S. , Kobuchi T. , Matsunaga G. , Koide Y.
Published: May 2008

A new technique to measure the first and second derivatives of the ion temperature profile has been developed by using a charge exchange spectroscopy system with space modulation optics. The space observed is scanned up to ±3cm with a cosine wave modulation frequency up to 30Hz by shifting the object lens in front of the optical fiber bundle by 0.5mm with a piezoelement. The first and second derivatives of ion temperature are derived from the modulation component of the ion temperature measured by using Fourier series expansion.
Differential cross sections and product energy distributions for the C(P3)+OH(XΠ2)→CO(XΣ+1)+H(S2) reaction using a quasiclassical trajectory method
Authors: Zanchet Alexandre , Halvick Philippe , Bussery-Honvault Béatrice , Honvault Pascal
Published: May 2008

Quasiclassical trajectory calculations have been carried out for the C(P3)+OH(XΠ2)→CO(XΣ+1)+H(S2) reaction using a recent ab initio potential energy surface for the ground electronic state XA′2 of COH. Differential cross sections (DCSs), and product vibrational, rotational and translational distributions have been determined for a wide range of collision energies (0.001–1eV). The role of excitations (rotation or vibration) of the OH reactant on these quantities has been investigated. Product vibrational, rotational, and translational distributions are found to be almost independent on the rovibrational state of OH, whereas DCSs show a weak dependence on the initial rotational state of OH. We also analyze the results using a study based on the lifetime of the intermediate complex and on the kinematic constraint associated with the mass combination.
An application of the van der Waals density functional: Hydrogen bonding and stacking interactions between nucleobases
Authors: Cooper Valentino R. , Thonhauser T. , Langreth David C.
Published: May 2008

We apply the van der Waals density functional (vdW-DF) to study hydrogen bonding and stacking interactions between nucleobases. The excellent agreement of our results with high level quantum chemical calculations highlights the value of the vdW-DF for first-principles investigations of biologically important molecules. Our results suggest that, in the case of hydrogen-bonded nucleobase pairs, dispersion interactions reduce the cost of propeller twists while having a negligible effect on buckling. Furthermore, the efficient scaling of DFT methods allowed for the easy optimization of separation distance between nucleobase stacks, indicating enhancements in the interaction energy of up to 3kcal∕mol over previous fixed distance calculations. We anticipate that these results are significant for extending the vdW-DF method to model larger vdW complexes and biological molecules.
Ultrafast strong-field dissociative ionization dynamics of CH2Br2 probed by femtosecond soft x-ray transient absorption spectroscopy
Authors: Loh Zhi-Heng , Leone Stephen R.
Published: May 2008

Femtosecond time-resolved soft x-ray transient absorption spectroscopy based on a high-order harmonic generation source is used to investigate the dissociative ionization of CH2Br2 induced by 800nm strong-field irradiation. At moderate laser peak intensities (2.0×1014W∕cm2), strong-field ionization is accompanied by ultrafast C–Br bond dissociation, producing both neutral Br (P3∕22) and Br* (P1∕22) atoms together with the CH2Br+ fragment ion. The measured rise times for Br and Br* are 130±22fs and 74±10fs, respectively. The atomic bromine quantum state distribution shows that the Br∕Br* population ratio is 8.1±3.8 and that the Br P3∕22 state is not aligned. The observed product distribution and the time scales of the photofragment appearances suggest that multiple field-dressed potential energy surfaces are involved in the dissociative ionization process. At higher laser peak intensities (6.2×1014W∕cm2), CH2Br2+ undergoes sequential ionization to form the metastable CH2Br22+ dication. These results demonstrate the potential of core-level probing with high-order harmonic transient absorption spectroscopy for studying ultrafast molecular dynamics.
Near band-gap photoluminescence properties of hexagonal boron nitride
Authors: Museur Luc , Kanaev Andrei
Published: May 2008

Near band-gap luminescence (hν⩾5eV) of hexagonal boron nitride has been studied by means of the time- and energy-resolved photoluminescence spectroscopy method. Two emissions have been observed at 5.5 and 5.3eV. The high-energy emission at 5.5eV is composed of fixed subbands assigned to bound excitons at 5.47, 5.56, and 5.61eV. The nonstructured low-energy emission at 5.3eV undergoes a large blueshift (up to 120meV) with a linear slope ΔElum∕ΔEexc<1 with increasing excitation energy Eexc. At Eexc⩾5.7eV, the band position is fixed and marks the transition from the Raman to the photoluminescence regime. We assign the 5.3eV band to quasi-donor-acceptor pair (q-DAP) states due to electrostatic band fluctuations induced by charged defects. The shift is explained by photoinduced neutralization of charged defect states. The absence of contribution to the q-DAP luminescence from exciton suggests the existence of a large exciton binding energy, which is qualitatively consistent with theoretical predictions.
Effects of tensile and compressive in-plane stress fields on adhesion in laser induced delamination experiments
Authors: Fedorov A. , Vellinga W. P. , De Hosson J. Th. M.
Published: May 2008

In this work, the adhesion of a polymer coating on steel substrate subjected to uniaxial tensile plastic deformations was studied with the laser induced delamination technique. A decrease in the practical work of adhesion has been measured as the deformation of the substrate progressed. Moreover, it was observed that the deformation of the metal substrate introduced in-plane stresses in the polymer coating. Delamination was studied under compressive or tensile in-plane stresses. The model presented enabled to derive from the experimental data not only the practical work of adhesion but also the magnitude and the character (tensile or compressive) of the in-plane stress. The strain fields of the metal substrate during plastic deformation and after the elastic relaxation were monitored with a digital image correlation analysis system. The measured strain fields were confronted to the in-plane stresses obtained from the delamination experiments.
Heat-driven thermoacoustic cryocooler operating at liquid hydrogen temperature with a unique coupler
Authors: Hu J. Y. , Luo E. C. , Li S. F. , Yu B. , Dai W.
Published: May 2008

A heat-driven thermoacoustic cryocooler is constructed. A unique coupler composed of a tube, reservoir, and elastic diaphragm is introduced to couple a traveling-wave thermoacoustic engine (TE) and two-stage pulse tube refrigerator (PTR). The amplitude of the pressure wave generated in the engine is first amplified in the coupler and the wave then passes into the refrigerator to pump heat. The TE uses nitrogen as its working gas and the PTR still uses helium as its working gas. With this coupler, the efficiency of the system is doubled. The engine and coupler match at a much lower operating frequency, which is of great benefit for the PTR to obtain a lower cooling temperature. The coupling place between the coupler and engine is also optimized. The onset problem is effectively solved. With these improvements, the heat-driven thermoacoustic cryocooler reaches a lowest temperature of 18.1K, which is the demonstration of heat-driven thermoacoustic refrigeration technology used for cooling at liquid hydrogen temperatures.
A plastic phase of water from computer simulation
Authors: Takii Yoshio , Koga Kenichiro , Tanaka Hideki
Published: May 2008

We report a member of ices called plastic or rotator phase, in which individual water molecules make facile rotations as in liquid state but are held tightly in an ordered structure. Molecular dynamics simulations of three classical models of water show that a plastic ice phase appears at a temperature when ice VII is heated or liquid water is cooled at high pressures above several gigapascals. A large amount of latent heat is absorbed when ice VII is transformed to the rotator phase at 590K and 10GPa, which is a typical characteristic of the plastic transitions for nearly spherical molecules. In addition to the spontaneous formation of plastic phase in the simulations, its existence is supported by robustness of plastic phase for hypothetical water with varying degrees of Coulombic interactions.
A neutron scattering study of strong-symmetric hydrogen bonds in potassium and cesium hydrogen bistrifluoroacetates: Determination of the crystal structures and of the single-well potentials for protons
Authors: Fillaux François , Cousson Alain , Archilla Juan F. R. , Tomkinson John
Published: May 2008

The crystal structures of potassium and cesium bistrifluoroacetates, KH(CF3COO)2 and CsH(CF3COO)2, respectively, were determined at room and cryogenic temperatures with the single crystal neutron diffraction technique. The crystals belong to the monoclinic space groups, I2∕a and A2∕a, respectively, and there is no evidence of any structural phase transition. In both crystals, trifluoroacetate entities in centrosymmetric dimers are linked by very short hydrogen bonds lying across a center of inversion. The thermal parameters provide no evidence of any double minimum potential for hydrogen bond protons. Single-minimum potentials were determined via best fitting to the inelastic neutron scattering spectral profiles of the stretching vibrations. They comprise a narrow well for the ground state and a very broad quasiharmonic well for excited states. The spread out of the wave functions of these states shows that protons are no longer confined between the oxygens. Presumably, they are attracted by the lone pairs of oxygen atoms. These potentials emphasize the covalent nature of the OO bond and the ionic character of the hydrogen bond proton.
Kinetic Monte Carlo study of metal organic chemical vapor deposition growth dynamics of GaN thin film at microscopic level
Authors: Fu K. , Fu Y. , Han P. , Zhang Y. , Zhang R.
Published: May 2008

Group III nitrides, especially gallium nitride (GaN), have many applications. The materials are usually grown by metal organic chemical vapor deposition (MOCVD) technology. By combining the computational fluid dynamics and kinetic Monte Carlo method, we present a multiscale modeling of fluid dynamics, thermodynamics, and molecular dynamics to study the chemical and physical growth process of GaN in a standard MOCVD reactor, which shows a general agreement with experimental results. The theoretical model thus provides us with a fundamental guideline for optimizing GaN MOCVD growth at the microscopic level.
Burnout current density of bismuth nanowires
Authors: Cornelius T. W. , Picht O. , Müller S. , Neumann R. , Völklein F. , Karim S. , Duan J. L.
Published: May 2008

Single bismuth nanowires with diameters ranging from 100nmto1μm were electrochemically deposited in ion track-etched single-pore polycarbonate membranes. The maximum current density the wires are able to carry was investigated by ramping up the current until failure occurred. It increases by three to four orders of magnitude for nanowires embedded in the template compared to bulk bismuth and rises with diminishing diameter. Simulations show that the wires are heated up electrically to the melting temperature. Since the surface-to-volume ratio rises with diminishing diameter, thinner wires dissipate the heat more efficiently to the surrounding polymer matrix and, thus, can tolerate larger current densities.
Radiation transport in inhomogeneous media
Authors: Keiter Paul , Gunderson Mark , Foster John , Rosen Paula , Comley Andrew , Taylor Mark , Perry Ted
Published: May 2008

Calculations of radiation transport in heated materials are greatly complicated by the presence of regions in which two or more materials are inhomogeneously mixed. This phenomenon is important in many systems, such as astrophysical systems where density clumps can be found in star-forming regions and molecular clouds. Laboratory experiments have been designed to test the modeling of radiation transport through inhomogeneous plasmas. A laser-heated hohlraum is used as a thermal source to drive radiation through polymer foam containing randomly distributed gold particles. Experimental measurements of radiation transport in foams with gold particle sizes ranging from 5–9μm to submicrometer diameters as well as the homogeneous foam case are presented. The simulation results of the radiation transport are compared to the experiment and show that an inhomogeneous transport model must be applied to explain radiation transport in foams loaded with 5μm diameter gold particles.
Measuring distances between half-integer quadrupolar nuclei and detecting relative orientations of quadrupolar and dipolar tensors by double-quantum homonuclear dipolar recoupling nuclear magnetic resonance experiments
Authors: Mali Gregor , Kaučič Venčeslav , Taulelle Francis
Published: May 2008

We studied the possibility of using double-quantum homonuclear dipolar recoupling magic angle spinning nuclear magnetic resonance experiments for structural analysis of systems of half-integer quadrupolar nuclei. We investigated symmetry-based recoupling schemes R221 and R221R22−1 and showed that the obtained double-quantum filtered signals depend substantially on magnitudes and relative orientations of dipolar and quadrupolar tensors. Experimental results measured on aluminophosphate molecular sieve AlPO4-14, containing dipolar-coupled spin-5∕2 aluminum nuclei, were compared to results of time-consuming numerical simulations. The comparison for short mixing times allowed us to roughly measure internuclear Al–Al distances, if constraints about relative tensor orientations were available. Inspection of relative orientations of dipolar and quadrupolar tensors, using known distances between nuclei, required experimental and simulated data for long mixing times and yielded less accurate results. Two experimental protocols were employed for measuring double-quantum filtered curves, the symmetric protocol, in which excitation and reconversion periods are incremented simultaneously, and the asymmetric protocol, in which only the length of the excitation period is incremented and the length of the reconversion period is kept constant. The former experimental protocol was more convenient for the detection of internuclear distances, and the latter one was more appropriate for the inspection of relative orientations of interaction tensors.
A robust and reliable method for detecting signals of interest in multiexponential decays
Authors: Cover Keith S.
Published: May 2008

The concept of rejecting the null hypothesis for definitively detecting a signal was extended to relaxation spectrum space for multiexponential reconstruction. The novel test was applied to the problem of detecting the myelin signal, which is believed to have a time constant below 40ms, in T2 decays from magnetic resonance imagining of the human brain. It was demonstrated that the test allowed the detection of a signal in a relaxation spectrum by using only the information in the data, thus avoiding any potentially unreliable prior information. The test was implemented both explicitly and implicitly for simulated T2 measurements. For the explicit implementation, the null hypothesis was that a relaxation spectrum existed that had no signal below 40ms and that was consistent with the T2 decay. The confidence level by which the null hypothesis could be rejected gave the confidence level that there was signal below the 40ms time constant. The explicit implementation assessed the test’s performance with and without prior information where the prior information was the non-negative relaxation spectrum assumption. The test was also implemented implicitly with a data conserving multiexponential reconstruction algorithm that used left invertible matrices and that has been published previously. The implicit and explicit implementations demonstrated similar characteristics in detecting the myelin signal in both the simulated and experimental T2 decays, providing additional evidence to support the close link between the two tests. When the relaxation spectrum was assumed to be non-negative, the novel test required signal to noise ratios (SNRs) approaching 1000 in the T2 decays for detection of the myelin signal with high confidence. When the relaxation spectrum was not assumed to be non-negative, the SNR requirements for a detection with high confidence increased by a factor of 25. The application of the test to a T2 decay from human white matter, measured in vivo with a SNR of 650, demonstrated a solid detection of the signal below 40ms believed to be due to the myelin water. This study demonstrated the robustness and reliability of extending the concept of rejecting the null hypothesis to relaxation spectrum space. The study also raised serious questions about the susceptibility to false positive detection of the myelin signal of the multiexponential reconstruction algorithms currently in use.
High strength and utilizable ductility of bulk ultrafine-grained Cu–Al alloys
Authors: An X. H. , Han W. Z. , Huang C. X. , Zhang P. , Yang G. , Wu S. D. , Zhang Z. F.
Published: May 2008

Lack of plasticity is the main drawback for nearly all ultrafine-grained (UFG) materials, which restricts their practical applications. Bulk UFG Cu–Al alloys have been fabricated by using equal channel angular pressing technique. Its ductility was improved to exceed the criteria for structural utility while maintaining a high strength by designing the microstructure via alloying. Factors resulting in the simultaneously enhanced strength and ductility of UFG Cu–Al alloys are the formation of deformation twins and their extensive intersections facilitating accumulation of dislocations.
Measuring dopant concentrations in compensated p-type crystalline silicon via iron-acceptor pairing
Authors: Macdonald D. , Cuevas A. , Geerligs L. J.
Published: May 2008

We present a method for measuring the concentrations of ionized acceptors and donors in compensated p-type silicon at room temperature. Carrier lifetime measurements on silicon wafers that contain minute traces of iron allow the iron-acceptor pair formation rate to be determined, which in turn allows the acceptor concentration to be calculated. Coupled with an independent measurement of the resistivity and a mobility model that accounts for majority and minority impurity scatterings of charge carriers, it is then possible to also estimate the total concentration of ionized donors. The method is valid for combinations of different acceptor and donor species.
The Mn effect on the ferroelectric performance of the donor-substituted ABi4Ti4O15-based thin films
Authors: Kuo Dong-Hau , Kao Yi-Wen
Published: May 2008

Donor-substituted (K0.45Bi0.55)Bi4Ti4O15 thin films fabricated by a chemical solution deposition were modified by incorporating manganese into B lattice sites to change the type and concentration of the point defects. The ferroelectric hysteresis was related to the existence of Ti3+, oxygen vacancies, and Mn3+. The variations of dielectric properties were related to point defects. The conduction mechanisms of the leakage current involved a field-assisted ionic conduction and a space charge-limited conduction. The maximal polarization occurred for the (K0.45Bi0.55)Bi4(Ti4−yMny)O15 thin films at y=0.2 with the minimum amount of Ti3+.
Melt-dispersion mechanism for fast reaction of aluminum particles: Extension for micron scale particles and fluorination
Authors: Levitas Valery I. , Pantoya Michelle L. , Watson Kyle W.
Published: May 2008

The theoretically predicted relationship for the relative flame rate versus relative particle size based on the melt dispersion mechanism (MDM), which was previously confirmed for oxidation of 40–120nm diameter aluminum particles, is found to be in agreement with experiments for 1–3μm diameter Al particles and fluorination. The main physical parameters for MDM (pressure in molten particle, cavitation threshold, and nanoclusters’ velocity) have been estimated for micron scale particles. The results suggest parameters that could be controlled during particle synthesis that would enable micron scale Al particles to react and achieve the performance of nanoscale Al particles.
Magnéli phases TinO2n−1 nanowires: Formation, optical, and transport properties
Authors: Han Wei-Qiang , Zhang Yan
Published: May 2008

We have prepared triclinic Ti8O15 nanowires and Ti4O7 quasi-one-dimensional fibers by heat-treating thick H2Ti3O7 nanowires under hydrogen atmospheres at 850 and 1050°C, respectively. In contrast to wide-bandgap semiconducting tetragonal TiO2, both Ti8O15 and Ti4O7 exhibit high electrical conducting behavior at room temperature. The electrical conductivities of Ti8O15 and Ti4O7 are, respectively, 0.24 and 10.4S∕cm at 300K, and 2.4×10−5 and 4×10−3S∕cm at 77K. In both materials, the light absorption band covers the full visible-light spectrum region and extends into the near-infrared region.
Intermodal Freight Transportation and Regional Accessibility in the United States
Authors: Lim Hyunwoo , Thill Jean-Claude
Published: May 2008

The authors investigate how the intermodal freight-transportation network affects the ability of regions to position themselves more effectively in the national space economy. The case of domestic containerized freight traffic is examined because it is closely associated with contemporary forms of integration between rail shipping and trucking. With the help of a geographic information system, the potential impact of intermodalism in the United States is analyzed by mapping integral place accessibility measures of five-digit zip-code areas. The performance of the intermodal freight network is evaluated by comparing accessibility measures based on the highway network and on the intermodal network, respectively. Geographically weighted regressions are also performed to identify the variables that contribute to the improvement of accessibility due to intermodalism, while accounting for the spatial nonstationarity of relationships.
Simultaneous observations of aerosol–cloud–albedo interactions with three stacked unmanned aerial vehicles
Authors: Roberts G. C. , Ramana M. V. , Corrigan C. , Kim D. , Ramanathan V.
Published: May 2008

Aerosol impacts on climate change are still poorly understood, in part, because the few observations and methods for detecting their effects are not well established. For the first time, the enhancement in cloud albedo is directly measured on a cloud-by-cloud basis and linked to increasing aerosol concentrations by using multiple autonomous unmanned aerial vehicles to simultaneously observe the cloud microphysics, vertical aerosol distribution, and associated solar radiative fluxes. In the presence of long-range transport of dust and anthropogenic pollution, the trade cumuli have higher droplet concentrations and are on average brighter. Our observations suggest a higher sensitivity of radiative forcing by trade cumuli to increases in cloud droplet concentrations than previously reported owing to a constrained droplet radius such that increases in droplet concentrations also increase cloud liquid water content. This aerosol-cloud forcing efficiency is as much as −60 W m
−2
per 100% percent cloud fraction for a doubling of droplet concentrations and associated increase of liquid water content. Finally, we develop a strategy for detecting aerosol–cloud interactions based on a nondimensional scaling analysis that relates the contribution of single clouds to albedo measurements and illustrates the significance of characterizing cloud morphology in resolving radiometric measurements. This study demonstrates that aerosol–cloud–albedo interactions can be directly observed by simultaneous observations below, in, and above the clouds.
Neuronal avalanches organize as nested theta- and beta/gamma-oscillations during development of cortical layer 2/3
Authors: Gireesh Elakkat D. , Plenz Dietmar
Published: May 2008

Maturation of the cerebral cortex involves the spontaneous emergence of distinct patterns of neuronal synchronization, which regulate neuronal differentiation, synapse formation, and serve as a substrate for information processing. The intrinsic activity patterns that characterize the maturation of cortical layer 2/3 are poorly understood. By using microelectrode array recordings
in vivo
and
in vitro
, we show that this development is marked by the emergence of nested θ- and β/γ-oscillations that require NMDA- and GABA
A
-mediated synaptic transmission. The oscillations organized as neuronal avalanches, i.e., they were synchronized across cortical sites forming diverse and millisecond-precise spatiotemporal patterns that distributed in sizes according to a power law with a slope of −1.5. The correspondence between nested oscillations and neuronal avalanches required activation of the dopamine D
1
receptor. We suggest that the repetitive formation of neuronal avalanches provides an intrinsic template for the selective linking of external inputs to developing superficial layers.
Forward estimation of movement state in posterior parietal cortex
Authors: Mulliken Grant H. , Musallam Sam , Andersen Richard A.
Published: May 2008

During goal-directed movements, primates are able to rapidly and accurately control an online trajectory despite substantial delay times incurred in the sensorimotor control loop. To address the problem of large delays, it has been proposed that the brain uses an internal forward model of the arm to estimate current and upcoming states of a movement, which are more useful for rapid online control. To study online control mechanisms in the posterior parietal cortex (PPC), we recorded from single neurons while monkeys performed a joystick task. Neurons encoded the static target direction and the dynamic movement angle of the cursor. The dynamic encoding properties of many movement angle neurons reflected a forward estimate of the state of the cursor that is neither directly available from passive sensory feedback nor compatible with outgoing motor commands and is consistent with PPC serving as a forward model for online sensorimotor control. In addition, we found that the space–time tuning functions of these neurons were largely separable in the angle–time plane, suggesting that they mostly encode straight and approximately instantaneous trajectories.
The Sleipnir library for computational functional genomics
Authors: Huttenhower Curtis , Schroeder Mark , Chikina Maria D , Troyanskaya Olga G.
Published: May 2008

Motivation: Biological data generation has accelerated to the point where hundreds or thousands of whole-genome datasets of various types are available for many model organisms. This wealth of data can lead to valuable biological insights when analyzed in an integrated manner, but the computational challenge of managing such large data collections is substantial. In order to mine these data efficiently, it is necessary to develop methods that use storage, memory and processing resources carefully.

Results: The Sleipnir C++ library implements a variety of machine learning and data manipulation algorithms with a focus on heterogeneous data integration and efficiency for very large biological data collections. Sleipnir allows microarray processing, functional ontology mining, clustering, Bayesian learning and inference and support vector machine tasks to be performed for heterogeneous data on scales not previously practical. In addition to the library, which can easily be integrated into new computational systems, prebuilt tools are provided to perform a variety of common tasks. Many tools are multithreaded for parallelization in desktop or high-throughput computing environments, and most tasks can be performed in minutes for hundreds of datasets using a standard personal computer.

Availability: Source code (C++) and documentation are available at http://function.princeton.edu/sleipnir and compiled binaries are available from the authors on request.

Contact:  ogt@princeton.edu
Slavery
Authors: Einhorn Robin L.
Published: May 2008

The history of slavery cannot be separated from the history of business in the United States, especially in the context of the relationship between public power and individual property rights. This essay suggests that the American devotion to “sacred” property rights stemsmore from the vulnerability of slaveholding elites than to a political heritage of protection for the “common man.”
Airway epithelium‐derived transforming growth factor‐β is a regulator of fibroblast proliferation in both fibrotic and normal subjects
Authors: Hostettler K. E. , Roth M. , Burgess J. K. , Gencay M. M. , Gambazzi F. , Black J. L. , Tamm M. , Borger P.
Published: May 2008

Background
In the healthy lung, airway epithelial cells (AEC) regulate fibroblast proliferation through release of soluble factors, such as prostaglandins and proteins. Fibroproliferative diseases and airway remodelling may result from an inadequate generation of suppressive factors by AEC or the inability of fibroblasts to respond to them appropriately.

Objective
The aim of this study was to study the effect of primary human AEC on the proliferation of fibroblasts obtained from healthy and fibrotic lungs in an interactive cell culture model.

Results
Conditioned medium (CM) from 14 out of 16 AEC lines significantly inhibited proliferation of normal human lung fibroblasts by 51.2±6.0%. The proliferation of fibroblasts derived from patients with lung fibrosis was equally inhibited by CM of AEC. The inhibitory effect of AEC‐CM was completely reversed when fibroblasts were pre‐incubated with 2.5 μm indomethacin. Furthermore, primary human AEC, but not fibroblasts, secrete TGF‐β, and the inhibitory effect of the AEC‐CM was blocked by neutralizing anti‐TGF‐β antibodies.

Conclusion
These results demonstrate that AEC actively inhibit the proliferation of both normal and fibrotic fibroblasts via TGF‐β, which induces the prostaglandin E2 synthesis in fibroblasts. The data indicate that proliferative lung diseases may be treated using the epithelial cell as the target of medication.
Exercise training improves autonomic function and inflammatory pattern in women with polycystic ovary syndrome (PCOS)
Authors: Giallauria Francesco , Palomba Stefano , Maresca Luigi , Vuolo Laura , Tafuri Domenico , Lombardi Gaetano , Colao Annamaria , Vigorito Carlo ,   Francesco Orio
Published: May 2008

Background  Polycystic ovary syndrome (PCOS) is a common female reproductive‐age endocrine disease predominantly characterized by chronic anovulation, hyperandrogenism, insulin‐resistance and low‐grade inflammatory status. Exercise training (ET) favourably modulates cardiopulmonary function and insulin‐sensitivity markers in PCOS women. The present study investigated the effects of ET on autonomic function and inflammatory pattern in PCOS women.

Study design  Prospective baseline uncontrolled clinical study.

Methods  One‐hundred and eighty five PCOS women referred to our department were screened for the inclusion into the study protocol from March 2004 to July 2007. One‐hundred and twenty four PCOS women met the criteria for the inclusion into the study protocol and were subdivided into two groups each composed of 62 patients: PCOS‐T (trained) group underwent 3‐month ET program, whereas PCOS‐UnT (untrained) group did not. At baseline and at 3‐month follow‐up, hormonal and metabolic profile, cardiopulmonary parameters, autonomic function (as expressed by heart rate recovery, HRR) and inflammatory pattern [as expressed by C‐reactive protein (CRP) and white blood cells (WBCs) count] were evaluated.

Results  PCOS‐T showed a significant (P < 0·05) improvement in maximal oxygen consumption (VO2max) and in post‐exercise HRR, and a significant (P < 0·001) decrease in CRP and WBCs; whereas no statistically significant changes of the same parameters were observed in PCOS‐UnT. Multiple linear regression analysis showed that 3‐month HRR is linearly related to the inclusion in training group (β = 0·316, P < 0·001), VO2max (β = 0·151, P = 0·032) and the ratio between glucose and insulin area under curve (AUC) (β = 0·207, P = 0·003), and inversely related to body mass index (β = –0·146, P = 0·046), insulin AUC (β = –0·152, P = 0·032), CRP (β = –0·165, P < 0·021), and WBCs count (β = –0·175, P = 0·039).

Conclusions  Exercise training improves autonomic function and inflammatory pattern in PCOS women.
High plasma C‐reactive protein (CRP) is related to low paraoxonase‐I (PON‐I) activity independently of high leptin and low adiponectin in type 2 diabetes mellitus
Authors: Dullaart Robin P. F. , De Vries Rindert , Sluiter Wim J. , Voorbij Hieronymus A. M.
Published: May 2008

Objectives  In type 2 diabetes mellitus, circulating C‐reactive protein (CRP) is increased, whereas the high density lipoprotein (HDL)‐associated, anti‐oxidative and anti‐inflammatory enzyme, paraoxonase‐I, is decreased. Both high CRP and low paraoxonase‐I activity may predict cardiovascular disease. It is unknown whether lower paraoxonase‐I activity contributes to higher CRP levels in diabetes. In type 2 diabetic and control subjects, we determined the relationship of CRP with paraoxonase‐I when taking account of plasma levels of pro‐ and anti‐inflammatory adipokines.

Design and patients  In 81 type 2 diabetic patients and 89 control subjects, plasma high‐sensitive CRP, serum paraoxonase‐I activity (arylesterase activity, assayed as the rate of hydrolysis of phenyl acetate into phenol), plasma leptin, adiponectin, resistin and lipids were determined.

Results  Body mass index (BMI), waist, insulin resistance, triglycerides, CRP, leptin and resistin levels were higher (P < 0·05 to P < 0·001), whereas HDL cholesterol, paraoxonase‐I activity and adiponectin levels were lower (P = 0·02 to P < 0·001) in diabetic compared to control subjects. Multiple linear regression analysis demonstrated that, after controlling for age and gender, CRP was inversely related to paraoxonase‐I activity (β = –0·15, P = 0·028) and adiponectin (β = –0·18, P = 0·009), and positively to leptin (β = 0·33, P < 0·001) and BMI (β = 0·22, P = 0·007), independently of the diabetic state (or of fasting glucose or HbA1c), insulin resistance and lipids (P > 0·20 for all).

Conclusions  low paraoxonase‐I activity is related to higher CRP, independently of adipokines, as well as of obesity and lipids. Low paraoxonase‐I activity in type 2 diabetes mellitus may contribute to increased cardiovascular risk via an effect on enhanced systemic low‐grade inflammation.
Acid properties of fulvic and humic acids isolated from two acid forest soils under different vegetation cover and soil depth
Authors: López R. , Gondar D. , Iglesias A. , Fiol S. , Antelo J. , Arce F.
Published: May 2008

We studied the acid‐base properties of 16 fulvic acids and 16 humic acids isolated from the surface (3–15 cm) and subsurface (> 45 cm) horizons of two types of acid forest soils, derived respectively from amphibolite and granite rocks, under five different types of vegetation. The observed differences between the contents of humic substances in the two types of soils were related to the degree of Al‐saturation of the soil organic matter, as indicated by the molar ratio between pyrophosphate extractable Al and C. Humic fractions were characterized in terms of elemental composition, and CPMAS 13C NMR spectrometry. The contents of carboxylic and phenolic groups were estimated by potentiometric titrations conducted in 0.1 m KNO3 in a nitrogen atmosphere. The fulvic acids contained more carboxylic groups but less phenolic groups than the humic acids: the ratio of phenolic to carboxylic groups in the humic acids was 0.48 ± 0.10 and in the fulvic acids 0.23 ± 0.05. The mean values of the protonation constants of each of the humic substance fractions can be used as generic parameters for describing the proton binding properties. The fulvic acids isolated from the subsurface horizon of the soil contained between 2.6 and 23% more carboxylic groups, and the humic acids between 8 and 43% more carboxylic groups than those isolated from the surface horizon of the same soil.
Experimental study and modelling of the water phase change kinetics in soils
Authors: Lozano A.‐L. , Cherblanc F. , Cousin B. , Bénet J.‐C.
Published: May 2008

When dealing with porous media, the liquid‐gas phase‐change is generally considered instantaneous, while a retardation time is observed in the case of hygroscopic soils. So far, little research has been done to characterize the non‐equilibrium behaviour of water phase change. Therefore, we propose a macroscopic model of the liquid‐gas phase‐change rate in porous media, based on the difference of chemical potentials between the liquid and its vapour, which is taken as the driving force. It introduces a phenomenological coefficient that must be determined experimentally. An original experiment able to create a macroscopic non‐equilibrium between the liquid and its vapour is described. Analysing the return to equilibrium leads to the determination of the phenomenological phase‐change coefficient. Depending on the range of partial vapour pressure, two different behaviours are observed: a linear domain close to equilibrium and a non‐linear one far from equilibrium. The results emphasize the relation between water retention properties in hygroscopic porous media and these phase‐change characteristics.