bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrophoretic and functional properties of mustard seed meals and protein concentrates
Authors: Aluko Rotimi E. , McIntosh Tara
Published: November 2006

Defatted meals and protein concentrates from five varieties of mustard seeds (four Brassica spp. and one Sinapis alba) were analyzed for polypeptide composition and functional properties. Nonreducing gel electrophoresis showed that Brassica seeds lacked the 135‐ and 50‐kDa polypeptides that were present in the seeds of the S. alba variety. On the other hand, the 29‐kDa polypeptide found in the Brassica seeds was absent from the seed of the S. alba variety. Under reducing conditions, the 135 kDa was not detected in the S. alba variety and the intensity of the 50‐kDa polypeptide was severely reduced; in contrast, the intensity of the 29‐kDa polypeptide in the Brassica seeds was not affected. Meals from yellow seeds had significantly higher (P≤0.05) protein contents than meals from the brown seeds. The emulsifying activity indexes (EAI) of meals and protein concentrates from the Brassica seeds were significantly higher (P≤0.05) than those obtained for similar products from S. alba sees. It was concluded that the disulfide‐bonded 50‐ and 135‐kDa polypeptides may have contributed to increased rigidity of S. alba meal proteins, which resulted in poor EAI when compared to the Brassica meals, which do not contain these polypeptides.
Titans/Planners, Bohemians/Revolutionaries: Male Empowerment in the 1930S
Authors: ABBOTT PHILIP
Published: November 2006

While William Leuchtenburg is certainly correct in concluding that the shadow of both FDR and the New Deal is receding, the decade of the 1930s is still regarded as the acme of progressive reform in America. Although the memories of the 1930s are fading and the reforms of the decade have been contested, in this narrative the achievements of the New Deal are still heroic.
William S. Burroughs's Cities of the Red Night Trilogy: Writing Outer Space
Authors: HOUEN ALEX
Published: November 2006

In August 1962 the American novelist Mary McCarthy surprised everyone by extolling the virtues of William S. Burroughs's Naked Lunch (1959), thereby raising the public profile of both the novel and novelist. The occasion was an Edinburgh conference on writing and censorship organized by the publisher John Calder, and attended by literary luminaries such as Norman Mailer and Henry Miller. For McCarthy the virtue of Naked Lunch was its timeliness, the way it appeared “sort of speeded up like jet travel”; “it has that somewhat supersonic quality.” Addressing the conference audience, Burroughs went a step further, heralding a new epoch of space writing:
I feel that a new mythology is now possible in the space age and that we can again have heroes and villains, with respect to the planet, and in closing I would say that the future of writing is in space and not in time.
The socio-legal context of privacy
Authors: Leith Philip
Published: November 2006

Privacy rights are growing apace, as can be seen from a continuing stream of judgments from UK and European courts, the rise of special interest privacy groups and other institutions tasked to protect privacy. Privacy has – its proponents suggest – at last arrived as a fully fledged legal right. However, despite these advancements, I suggest that privacy is becoming less prevalent in society; primarily because of technological and cultural changes, but also because the technical legal implementation of privacy is highly problematic. In this article it is argued that this seeming paradox should be more critically examined by socio-legal researchers who, to date, have done little to test the assertions and assumptions of the privacy lobby. This article maintains that there is a need for more investigation of the basis and assumptions behind data protection and privacy law and that a more robust analysis of the claims and rhetoric for these rights will change our attitudes towards privacy developments. The sociological conception that ‘underlying all social interaction there seems to be a fundamental dialectic’ will be used to undermine the legal notion of privacy as an individualistic ‘fundamental right’.
Effect of He++ ions on the propagation of low‐frequency magnetohydrodynamic waves in the magnetosheath
Authors: Kalra G. L. , Kumar S.
Published: November 2006

The paper investigates the role of suprathermal particles (He++) in the propagation of low‐frequency waves in average magnetosheath plasma by utilizing a model which is a concatenation of two magnetohydrodynamic (MHD) fluids. The suprathermal component is described by a relativistic, collisionless anisotropic fluid while the background plasma is assumed to be a nonrelativistic, anisotropic MHD fluid. The pressure components of both the fluids are described by heuristic double‐polytropic laws which are fairly well supported by observational data. The linearized analysis is carried out and dispersion relation is derived using normal mode technique. It is found that inclusion of the suprathermal component causes the excitation of an additional mode of propagation, besides reducing the phase speeds of slow, fast, and Alfvén modes. The additional mode, which can be characterized as a hybrid of the suprathermal and the fast modes in the direction perpendicular to the magnetic field, is the only mode which transports energy in the direction perpendicular to the magnetic field. Using appropriate polytropic indices obtained from AMPTE/IRM measurements in the magnetosheath leads to a new ordering of phase speeds and density‐magnetic field correlation of the fast mode. The new suprathermal mode shows positive density‐magnetic field correlation.
Influence of North Atlantic Oscillation on anthropogenic transport recorded in northwest Greenland ice cores
Authors: Burkhart John F. , Bales Roger C. , McConnell Joseph R. , Hutterli Manuel A.
Published: November 2006

Nitrate records from six Greenland ice cores covering the period 1789 to 1995 show a significant correlation in concentration for averaging periods greater than 10 years, as well as an approximately 60% increase in average concentration during the last 75 years. Annual nitrate fluxes contain low‐frequency trends driven primarily by changes in concentration, while higher‐frequency variability is driven by changes in snow accumulation. Increases in concentration yield nearly 30% higher nitrate flux (2.5 to 3.2 μg m−2 yr−1) and an 11% increase in variability during the 1895 to 1994 period versus the prior 100 years. Nitrate trends in the cores during the last 100 years are also correlated with global nitrate emissions, with a highly significant average r value of 0.93 for the six cores. During the period of anthropogenic influence, nitrate is positively correlated with the North Atlantic Oscillation, while prior to that the correlation is negative, and less significant, suggesting a link between transport of anthropogenic emissions and the North Atlantic Oscillation. Significant preanthropogenic periodicities identified through singular spectrum analysis show decadal variability in the nitrate record leading to shifts as great as 30% from the mean state but none as great as the anthropogenic‐driven deviation.
Surface dust redistribution on Mars as observed by the Mars Global Surveyor and Viking orbiters
Authors: Szwast Mark A. , Richardson Mark I. , Vasavada Ashwin R.
Published: November 2006

The variation of surface dust coverage on Mars is mapped using Mars Global Surveyor (MGS) and Viking albedo data. Albedo is shown to correlate well with spectrally derived measurements of surface dust abundance and is subsequently used to gauge dust coverage. Atmospheric aerosols modify the albedo observed from orbit, complicating this analysis. However, opacity cycles are highly repeatable, and simultaneous, independent records of aerosol opacities are available to isolate their impact. The MGS albedo and imaging data contain global coverage on a daily basis, allowing the relationship between dust cover and specific meteorological events to be elucidated. The 2001 global dust storm produced the largest changes in surface dust coverage during the MGS mission. Other processes yielding significant changes include seasonal cap‐edge winds, seasonally varying regional winds, local/regional dust storms, and extratropical cyclones. Dust devils and ongoing, small‐scale dust lifting do not appear to significantly modify the global patterns of dust cover. Finally, we show that the apparent long‐term darkening of the southern mid and high latitudes between the Viking and MGS eras is largely a consequence of the timing of image acquisition relative to global dust storms and surface dust “cleaning” by the seasonal ice cap; it does not represent a steady decadal‐scale, secular change. In fact, following the 2001 global dust storm, in late southern spring, the southern hemisphere was brighter in MGS than in Viking data. This study reveals albedo to be a dynamic, climatological variable for Mars, similar to sea‐surface temperature for terrestrial meteorology and climate.
Origin and distribution of terrestrial organic matter in the NW Mediterranean (Gulf of Lions): Exploring the newly developed BIT index
Authors: Kim Jung‐Hyun , Schouten Stefan , Buscail Roselyne , Ludwig Wolfgang , Bonnin Jérôme , Sinninghe Damsté Jaap S. , Bourrin François
Published: November 2006

The Branched and Isoprenoid Tetraether (BIT) index is based on the relative abundance of nonisoprenoidal glycerol dialkyl glycerol tetraethers (GDGTs) derived from organisms living in terrestrial environments versus a structurally related isoprenoid GDGT “crenarchaeol” produced by marine Crenarchaeota. The BIT index varies between 0 and 1, representing marine and terrestrial organic matter (OM) end‐members, respectively (Hopmans et al.,Earth Planet. Sci. Lett., 224, 107–116, 2004). In this study, the applicability of the BIT index to trace terrestrial OM is tested in combination with other organic parameters (TOC, C/N ratio, δ13Corg, total lipid, and n‐alkane) in the Gulf of Lions, a river‐dominated continental margin of the western Mediterranean. We analyzed a variety of soils and riverbed sediments from the continent as well as surface sediments from the shelf and canyons. The BIT index in soils and riverbed sediments shows high values (>0.9), while it varies between 0.02 and 0.83 in marine sediments, decreasing seaward from the inner shelf to the slope. For marine surface sediments, high BIT values are associated with lower δ13Corg values as well as higher TOC contents and higher n‐alkane concentrations. Our results confirm that the BIT index can be applied in coastal marine environments in order to characterize terrestrial OM as proposed by Hopmans et al. (2004). Therefore the BIT index is a useful addition to the proxies presently available for studying the origin and distribution of OM in continental margins and especially valuable in multiproxy studies.
Cassini radio occultations of Saturn's ionosphere: Model comparisons using a constant water flux
Authors: Moore Luke , Nagy Andrew F. , Kliore Arvydas J. , Müller‐Wodarg Ingo , Richardson John D. , Mendillo Michael
Published: November 2006

Recent radio occultations of Saturn's equatorial ionosphere by the Cassini spacecraft provide important insight into this poorly constrained region. Twelve new electron density profiles identify a clear dawn/dusk asymmetry as well as two apparently separate electron density peaks. This study uses a 3D general circulation model along with 1D water diffusion calculations to examine the possibility that a topside flux of neutral water into Saturn's atmosphere may provide a loss mechanism—via charge exchange with protons—that is sufficient to reproduce the ionosphere observed by Cassini. Results indicate that a constant influx of water of (0.5–1.0) × 107 H2O cm−2 sec−1 is adequate for reproducing Cassini measurements, providing a good match to the main electron density peak at dawn and dusk. In addition, these calculations use a reduced rate for the reaction H+ + H2(ν ≥ 4) → H2+ + H, significantly diminishing its importance in Saturn's ionospheric photochemistry.
Parameter dependence of quick magnetic reconnection triggering: A survey study using two‐dimensional simulations
Authors: Tanaka K. G. , Shinohara I. , Fujimoto M.
Published: November 2006

The current sheet structure modification by lower‐hybrid drift instability (LHDI) has been shown to lead to quick magnetic reconnection triggering (QMRT) even in a thick current sheet (Tanaka et al., 2005). The three‐dimensional simulations, however, have been limited to certain sets of parameters. Having learned which effects of LHDI are crucial for QMRT in these three‐dimensional results, we perform a series of two‐dimensional simulations of LHDI (reconnection itself not included) with various current sheet thickness D, guide field intensity B0y, and the frequency ratio τ (τ = ωpe/Ωe, where ωpe is the electron plasma frequency and Ωe is the electron gyrofrequency) and inspect how these parameters affect the QMRT process. While QMRT looked promising in the three‐dimensional studies with B0y = 0 and τ = 1, the two realistic factors, nonzero guide field and τ larger than 1, requires rather small current sheet thickness for QMRT to be operative in the magnetospheric situations.
Source and propagation of internal solitary waves in the northeastern South China Sea
Authors: Zhao Zhongxiang , Alford Matthew H.
Published: November 2006

Large‐amplitude internal solitary waves (ISWs) observed near Dongsha Island in the South China Sea originate in tide‐topography interactions at Luzon Strait. Their arrival times at two moorings (S7 at 117°17′E, 21°37′N, and Y at 117°13.2′E, 21°2.8′N) are investigated, with respect to model‐predicted barotropic tidal currents over Lan‐Yu ridge at Luzon Strait. Each ISW packet can be associated with a westward tidal current peak. The time lags between the ISWs and the barotropic tidal currents are 57.6 ± 0.9 hours at S7 and 55.1 ± 1.0 hours at Y, consistent with the mode‐one internal waves propagating nondispersively through the region's bathymetry and climatological stratification. Larger ISWs usually arrive earlier than smaller ones, consistent with the theoretical relation between nonlinear wave speed and wave amplitude. The observation that the ISWs are associated with westward tidal currents, with/without the presence of earlier eastward tidal currents, suggests that they are generated by nonlinear steepening of internal tides, rather than by the lee‐wave mechanism. An idealized nonlinearization distance, over which the ISWs are generated in internal tide troughs, is estimated to be 260 ± 40 km from Luzon Strait.
Assessment of temperature, trace species, and ozone in chemistry‐climate model simulations of the recent past
Authors: Eyring V. , Butchart N. , Waugh D. W. , Akiyoshi H. , Austin J. , Bekki S. , Bodeker G. E. , Boville B. A. , Brühl C. , Chipperfield M. P. , Cordero E. , Dameris M. , Deushi M. , Fioletov V. E. , Frith S. M. , Garcia R. R. , Gettelman A. , Giorgetta M. A. , Grewe V. , Jourdain L. , Kinnison D. E. , Mancini E. , Manzini E. , Marchand M. , Marsh D. R. , Nagashima T. , Newman P. A. , Nielsen J. E. , Pawson S. , Pitari G. , Plummer D. A. , Rozanov E. , Schraner M. , Shepherd T. G. , Shibata K. , Stolarski R. S. , Struthers H. , Tian W. , Yoshiki M.
Published: November 2006

Simulations of the stratosphere from thirteen coupled chemistry‐climate models (CCMs) are evaluated to provide guidance for the interpretation of ozone predictions made by the same CCMs. The focus of the evaluation is on how well the fields and processes that are important for determining the ozone distribution are represented in the simulations of the recent past. The core period of the evaluation is from 1980 to 1999 but long‐term trends are compared for an extended period (1960–2004). Comparisons of polar high‐latitude temperatures show that most CCMs have only small biases in the Northern Hemisphere in winter and spring, but still have cold biases in the Southern Hemisphere spring below 10 hPa. Most CCMs display the correct stratospheric response of polar temperatures to wave forcing in the Northern, but not in the Southern Hemisphere. Global long‐term stratospheric temperature trends are in reasonable agreement with satellite and radiosonde observations. Comparisons of simulations of methane, mean age of air, and propagation of the annual cycle in water vapor show a wide spread in the results, indicating differences in transport. However, for around half the models there is reasonable agreement with observations. In these models the mean age of air and the water vapor tape recorder signal are generally better than reported in previous model intercomparisons. Comparisons of the water vapor and inorganic chlorine (Cly) fields also show a large intermodel spread. Differences in tropical water vapor mixing ratios in the lower stratosphere are primarily related to biases in the simulated tropical tropopause temperatures and not transport. The spread in Cly, which is largest in the polar lower stratosphere, appears to be primarily related to transport differences. In general the amplitude and phase of the annual cycle in total ozone is well simulated apart from the southern high latitudes. Most CCMs show reasonable agreement with observed total ozone trends and variability on a global scale, but a greater spread in the ozone trends in polar regions in spring, especially in the Arctic. In conclusion, despite the wide range of skills in representing different processes assessed here, there is sufficient agreement between the majority of the CCMs and the observations that some confidence can be placed in their predictions.
Using the modified Gaussian model to extract quantitative data from lunar soils
Authors: Noble Sarah K. , Pieters Carlé M. , Hiroi Takahiro , Taylor Lawrence A.
Published: November 2006

The Lunar Soil Characterization Consortium (LSCC) has examined and characterized a suite of lunar soils with a wide range of compositions and maturities. The purpose of this study is to compare the Vis/NIR spectral properties of these lunar soils with their petrologic and chemical compositions using the modified Gaussian model (MGM) to obtain quantitative data about the character of relatively weak near‐infrared absorption bands. Useful compositional information can be extracted from high‐quality soil spectra using the MGM. The model had some difficulty fitting absorption bands in the 2 μm region of the lunar spectrum, but bands in the 1 and 1.2 μm regions provided physically realistic results. The model was able to distinguish high‐Ca and low‐Ca pyroxenes in the LSCC suite of lunar soils in the appropriate relative abundance. In addition, unexpected insights into the nature and causes of absorption bands in lunar soils were identified. For example, at least two distinct absorption bands are required in the 1.2 μm region of the spectrum, and neither of these bands can be attributed to plagioclase or agglutinates, but are found instead to be largely due to pyroxene.
Microstructural and magnetic properties of ZnO:TM (TM=Co,Mn) diluted magnetic semiconducting nanoparticles
Authors: Mandal S. K. , Das A. K. , Nath T. K. , Karmakar Debjani , Satpati B.
Published: November 2006

We have investigated the structural and the magnetic properties of 3d transition metal (TM) doped Zn1−xTMxO (TM=Co,Mn) diluted magnetic semiconducting nanoparticles for different doping concentrations (0⩽x⩽0.4) synthesized by chemical “pyrophoric reaction process.” From x-ray diffraction measurements the solubility limits of Co and Mn in ZnO nanoparticles are found to be strongly dependent on growth (calcinations) temperature (Tg). The highest solubility limit of both Co2+ and Mn2+ in ZnO at Tg∼300°C is found to be ∼30%. High resolution transmission electron microscopy studies show that Zn1−xTMxO particles are single crystalline of high quality with a wide particle size distribution in nanometric regime. The non-mean-field-like very strong concave nature of temperature dependent magnetization curves is observed at very low temperature in both the systems without showing any distinct magnetic transition. The magnetic behaviors of those Mn2+ and Co2+ doped ZnO semiconducting nanoparticles are observed to be quite different. The magnitude of net magnetization at a field of 5000Oe for Zn1−xMnxO system is found to grow with the dopant concentration (x) in sharp contrast to the case for Zn1−xCoxO where it is found to decrease. From mean field the Curie-Weiss fit as well as from the calculated values of effective exchange interaction constants (Jex), which is found to be negative, we can assert that the ground states of both of these systems are antiferromagnetic for the entire series. In the case of Zn1−xMnxO samples the magnitude of Jex is found to decrease with the increase in Mn+2 ion concentration, whereas for Zn1−xCoxO samples the magnitude of Jex is found to increase. These typical variations of Jex with antiferromagnetic interaction have been best explained through the magnetic polaron-polaron interaction model [P. A. Wolf et al., J. Appl. Phys. 79, 5196 (1996)].
Protein folding using fragment assembly and physical energy function
Authors: Kim Seung-Yeon , Lee Weontae , Lee Julian
Published: November 2006

We perform a systematic study of the effects of sequence-independent backbone interactions and sequence-dependent side-chain interactions on protein folding using fragment assembly and physical energy function. Structures for ten proteins belonging to various structural classes are predicted only with Lennard-Jones interaction between backbone atoms. We find nativelike structures for β proteins, suggesting that for proteins in this class, the global tertiary structures can be determined mainly by sequence-independent backbone interactions. On the other hand, for α proteins, nonlocal hydrophobic side-chain interaction is also required to obtain nativelike structures.
An alternative model for elastic bending deformation of multilayered beams
Authors: Zhang Neng-Hui , Xing Jing-Jing
Published: November 2006

An exact closed-form solution for elastic deformation of multilayered beams due to residual stresses and external bending is derived in terms of the normal strain at the centroidal principal axis and the curvature radius of the neutral axis for zero normal strain. Two approximate models for the case of multilayered films on a thick substrate are obtained. For a bilayered beam, the exact solution can be expressed in terms of the mismatch stress between the film and the substrate, the thickness ratio, and the modulus ratio. The reduction error analysis for the two approximations is applied.
Optical properties of 92%Pb(Mg1∕3Nb2∕3)O3–8%PbTiO3 thin films prepared by chemical solution deposition
Authors: Xue J. Q. , Huang Z. M. , Liu A. Y. , Hou Y. , Meng X. J. , Chu J. H.
Published: November 2006

92 % Pb ( Mg 1 ∕ 3 Nb 2 ∕ 3 ) O 3 – 8 % Pb Ti O 3 (PMNT) thin films have been prepared on Pt∕Ti∕SiO2∕Si substrate with a LaNiO3 buffer layer and on sapphire substrate by a chemical solution deposition method. X-ray diffraction analysis shows that the PMNT thin films on Pt∕Ti∕SiO2∕Si substrate are polycrystalline with (110)-preferential orientation. The optical properties of PMNT thin film in 2.5–12.5μm and 200–1100nm ranges have been investigated using infrared spectroscopic ellipsometry and ultravisible transmission spectra, respectively. The optical constants and thickness of the thin films have been obtained by fitting the measured ellipsometric parameter (Δ and Ψ) data and transmission spectrum with classical infrared and Tauc-Lorentz models. The optical band gap energy of the PMNT thin films on sapphire substrate is derived to be about 4.02eV.
Prompt toroidal momentum balance with collisionless neutral beam injected torque in DIII-D
Authors: deGrassie J. S. , Groebner R. J. , Burrell K. H.
Published: November 2006

In electron cyclotron heated (ECH) H-mode discharges with neutral beam injection (NBI) pulses that are short compared with the fast ion scattering or slowing times, and it is observed that the plasma stores all the angular momentum delivered by the NBI torque impulse. The pulse length is also much shorter than the momentum confinement time of the plasma. Source computations with the Monte Carlo code TRANSP [R. J. Goldston, D. C. McCune, H. H. Towner et al., J. Comput. Phys. 43, 61 (1981)] show that during a pulse approximately 90% of this torque impulse is delivered via the collisionless fast radial current injection process, so that the plasma acquires the balancing toroidal acceleration through ion drift motion in the increasing ∂E∕∂t where E is the electric field normal to the flux surfaces. The measured radial profile of the toroidal momentum increase matches the source, i.e., the computed torque impulse profile. We measure the bulk ion toroidal acceleration in helium discharges, as well as that of the primary impurity, carbon. These two species show a common acceleration, consistent with an incremental velocity due to an electric drift. This process is mediated by the dielectric response of the ions. The acceleration measurements are consistent with this being the neoclassical value of the dielectric constant, as computed from measured quantities.
Retardation effect on energy losses of electrons moving parallel to solid surfaces
Authors: Li Y. C. , Tu Y. H. , Kwei C. M. , Tung C. J.
Published: November 2006

When a charged particle moves parallel and close to a solid surface, it suffers an energy loss arising from the induced potentials caused by the interactions between the charged particle and the surface. For the fast moving charged particle, the induced potentials could be affected by the electromagnetic retardation effect. In the present work, the retardation effect on the induced potentials was studied using a dielectric function with spatial dispersion for an electron of high energy moving parallel to the solid surface. Appropriate boundary conditions and the Lorentz gauge were employed to calculate the induced potentials by solving Maxwell equations in the Fourier space using the dielectric response theory. Analytical formulas of the differential inverse inelastic mean free path (DIIMFP), inelastic mean free path (IMFP), and stopping power (SP) were derived by considering the retardation effect using relativistic energy and momentum conservation relations and applying the extended Drude dielectric function with spatial dispersion. The DIIMFP, IMFP, and SP were calculated for electron moving parallel to the Cu surface with different electron energies. Results calculated with the retardation effect were compared to corresponding data without the retardation effect.
Multidimensional infrared spectroscopy of water. I. Vibrational dynamics in two-dimensional IR line shapes
Authors: Loparo Joseph J. , Roberts Sean T. , Tokmakoff Andrei
Published: November 2006

In this and the following paper, we describe the ultrafast structural fluctuations and rearrangements of the hydrogen bonding network of water using two-dimensional (2D) infrared spectroscopy. 2D IR spectra covering all the relevant time scales of molecular dynamics of the hydrogen bonding network of water were studied for the OH stretching absorption of HOD in D2O. Time-dependent evolution of the 2D IR line shape serves as a spectroscopic observable that tracks how different hydrogen bonding environments interconvert while changes in spectral intensity result from vibrational relaxation and molecular reorientation of the OH dipole. For waiting times up to the vibrational lifetime of 700fs, changes in the 2D line shape reflect the spectral evolution of OH oscillators induced by hydrogen bond dynamics. These dynamics, characterized through a set of 2D line shape analysis metrics, show a rapid 60fs decay, an underdamped oscillation on a 130fs time scale induced by hydrogen bond stretching, and a long time decay constant of 1.4ps. 2D surfaces for waiting times larger than 700fs are dominated by the effects of vibrational relaxation and the thermalization of this excess energy by the solvent bath. Our modeling based on fluctuations with Gaussian statistics is able to reproduce the changes in dispersed pump-probe and 2D IR spectra induced by these relaxation processes, but misses the asymmetry resulting from frequency-dependent spectral diffusion. The dynamical origin of this asymmetry is discussed in the companion paper.
Temperature dependence of the photoluminescence properties of self-assembled InGaAs∕GaAs single quantum dot
Authors: Bafna Manish K. , Sen P. , Sen P. K.
Published: November 2006

Based on the semiclassical density matrix approach, a detailed theoretical investigation is made to analyze the effect of temperature and strain on photoluminescence (PL) spectra of an InxGa1−xAs∕GaAs single quantum dot. The temperature effects have been incorporated via temperature dependent (i) dephasing mechanism, (ii) band gap energy, and (iii) population density. A redshift of the PL peak is found to occur with increasing temperature. In our case, the full width at half maximum of the PL spectrum exhibits anomalous behavior at low temperature. The present analysis further reveals the disappearance of biexciton peaks at higher temperatures due to the quenching effect.
Reduction of laser power threshold for melting tungsten due to subsurface helium holes
Authors: Kajita Shin , Nishijima Dai , Ohno Noriyasu , Takamura Shuichi
Published: November 2006

Interactions between nanosecond laser pulses and a tungsten substrate having submicron holes near the surface formed by exposure to helium plasmas are investigated experimentally and numerically. After tungsten surface having helium holes was irradiated by nanosecond laser pulses in helium plasmas, scanning electron microscope micrographs of the tungsten surface show that the roughness of the surface is significantly enhanced under certain experimental conditions. For an understanding of the physical mechanisms to arise the phenomena, heat conduction in the substrate having holes is modeled by solving a three-dimensional heat conduction equation. The model calculations show that the surface reaches a melting point locally even if the pulse energy is low enough to lead to the melting of a virgin substrate. On the basis of surface temperature calculations and from an evaluation of the tensile stress put on the lid of the hole, repetitive explosions of the helium holes caused by heating the lids are considered to be the mechanism enhancing the surface roughness. Simultaneous irradiation of laser pulses and the helium ions may have a drilling effect on tungsten with repetitive formation and explosions of the subsurface helium holes.
Electrical and photoconductive properties of vertical ZnO nanowires in high density arrays
Authors: Fan Zhiyong , Dutta Deepanshu , Chien Chung-Jen , Chen Hsiang-Yu , Brown Evan C. , Chang Pai-Chun , Lu Jia G.
Published: November 2006

High density vertical zinc oxide nanowire arrays were fabricated using highly ordered channels in anodic alumina membranes via chemical vapor deposition assisted by electrochemical deposition methods. Using conductive atomic force microscopy, the electrical transport and photoconduction of individual vertical nanowires were investigated. A negative photoconductivity was observed as a result of electron trapping in the alumina membrane. In contrast, positive photoconductivity was observed using a thermally annealed anodic alumina membrane as the nanowire growth template. These studies provide a pathway for constructing highly integrated nanoscale electronic and optoelectronic circuits, such as logic circuits, light emitting diodes, solar cells, and ultrahigh resolution imaging sensors.
Thermal calibration of photodiode sensitivity for atomic force microscopy
Authors: Attard Phil , Pettersson Torbjörn , Rutland Mark W.
Published: November 2006

The photodiode sensitivity in the atomic force microscope is calibrated by relating the voltage noise to the thermal fluctuations of the cantilever angle. The method accounts for the ratio of the thermal fluctuations measured in the fundamental vibration mode to the total, and also for the tilt and extended tip of the cantilever. The method is noncontact and is suitable for soft or deformable surfaces where the constant compliance method cannot be used. For hard surfaces, the method can also be used to calibrate the cantilever spring constant.
Quantum decoherence of nanodevices under convective and radiative boundary conditions
Authors: Garrity Patrick L.
Published: November 2006

Low dimensional nanostructures under thermal transport conditions have been traditionally treated as closed quantum systems. Many emerging operational nanodevices, however, will interact with their environment through convection and radiation processes. The realistic treatment of boundary conditions apart from internal conduction must now be quantified. Starting with a nanostructure operating in the ballistic or quasiballistic transport regime, the behavior of coherent carrier transport is investigated with the onset of convection and radiation interactions. Quantum decoherence is found to occur due to nanostructure heat carrier correlations to the fluid molecules or photons. Diagonalization of the quantum density matrix follows and serves as a mechanism to induce classicality on the heat carrier transport regime. Numerical experimentation has been performed with a silicon nanowire modeled under convective and radiative boundary conditions. Decoherence time scales of the nanowire are characterized for varying gaseous flow speeds, temperatures, and radiation environments. The magnitude of environmental coupling is also investigated to determine the decoherence behavior. Decoherence time scales are found to range from 300nsto7ms with gaseous convection producing the shortest temporal evolution. The loss of coherence has been found in every case analyzed, thus suggesting the transport regime to lie in classical phase space for this type of open quantum system. The transformation of heat carrier coherent quantum transport to the classical structure of phase space with the onset of environmental thermal interactions such as gas/liquid molecules or photons represents the major result of this work. The predictable outcome of preferred pointer states is discussed with the possibility of fabricating nanostructures that exhibit predetermined engineered thermal transport behavior under a specific set of boundary conditions.
Ion channeling investigation of proton-irradiation-induced In–Ga atomic intermixing in self-assembled InAs∕GaAs quantum dot structures
Authors: Zhu J. , Oktyabrsky S. , Huang M. B.
Published: November 2006

We have applied ion channeling techniques to investigate effects of proton irradiation combined with thermal annealing on In–Ga atomic intermixing in a self-assembled InAs∕GaAs quantum dot (QD) system. A molecular-beam-epitaxy grown InAs∕GaAs QD sample was first irradiated with 1.0MeV protons to a dose of 1014cm−2 and subsequently annealed at temperatures between 300–700°C. Ion channeling measurements indicate that such postgrowth processing leads to an enhanced amount of In atoms registering along the ⟨100⟩ growth direction. This observation yields direct evidence for the occurrence of In–Ga atomic intermixing in the QD structure during postirradiation annealing. The effective activation energy for such intermixing process is determined to be ∼0.2eV. Furthermore, ion channeling data suggest three distinct stages for In–Ga atomic intermixing processes in the QD system, with In–Ga interdiffusion proceeding vertically along the growth direction or laterally in the QD layer, depending on postirradiation annealing temperatures.
Bent Marshak waves
Authors: Hurricane O. A. , Hammer J. H.
Published: November 2006

Radiation-driven heat waves (Marshak waves) are ubiquitous in astrophysics and terrestrial laser-driven high-energy density plasma physics experiments. Generally, the equations describing Marshak waves are so nonlinear, that solutions involving more than one spatial dimension require simulation. However, in this paper it is shown that one may analytically solve the problem of the two-dimensional nonlinear evolution of a Marshak wave, bounded by lossy walls, using an asymptotic expansion in a parameter related to the wall albedo and a simplification of the heat front equation of motion. Three parameters determine the nonlinear evolution: a modified Markshak diffusion constant, a smallness parameter related to the wall albedo, and the spacing of the walls. The final nonlinear solution shows that the Marshak wave will be both slowed and bent by the nonideal boundary. In the limit of a perfect boundary, the solution recovers the original diffusion-like solution of Marshak. The analytic solution will be compared to a limited set of simulation results and experimental data.
Solid-state nanocluster formation of praseodymium compounds in silicon and silicon dioxide
Authors: Kögler R. , Mücklich A. , Eichhorn F. , Posselt M. , Reuther H. , Skorupa W.
Published: November 2006

Nanoclusters of Pr compounds were formed in a silicon-on-insulator structure by ion beam synthesis in order to identify the most stable Pr compounds in contact with Si and SiO2. The processes of ion-induced atomic mixing, phase segregation, texturing, and nanocluster formation were investigated by transmission electron microscopy, Auger electron spectroscopy, and x-ray diffraction. After annealing at 900°C an array of Si precipitates is formed in SiO2. The size distribution of Si precipitates corresponds to the concentration profile of excess Si atoms in SiO2. Implanted Pr atoms are accumulated at the periphery around the Si precipitates decorating them. During annealing at 1100°C two types of crystalline silicate nanoclusters are formed, Pr2Si2O7 and Pr9.33Si6O26. In the top Si layer a narrow layer of Pr silicate nanoclusters is formed by self-organization rather equidistant to the Si∕SiO2 interface. Pr oxide (Pr2O3), the most desired high-k material, was not definitely verified. The predominant process in the solid-state synthesis of Pr compounds is the Pr silicate formation that provides both high atomic package density and low reordering energy.
Compression and neutron and ion beams emission mechanisms within a plasma focus device
Authors: Yousefi H. R. , Mohanty S. R. , Nakada Y. , Ito H. , Masugata K.
Published: November 2006

This paper reports some results of investigations of the neutron emission from middle energy Mather-type plasma focus. Multiple compressions were observed, and it seems that multiple compression regimes can occur at low pressure, while single compression appeared at higher pressure, which is favorable for neutron production. The multiple compression mechanism can be attributed to the (m=0 type) instability. The m=0 type instability is a necessary condition for fusion activity and x-ray production, but is not sufficient by itself. Accompanying the multiple compressions, multiple deuteron and neutron pulses were detected, which implies that there are different kinds of acceleration mechanisms.
Vibration analysis with pinhole confocal technique
Authors: Vagh Hardik , Chhaniwal Vani K. , Chakrabarty B. S. , Anand Arun
Published: November 2006

A pinhole confocal imaging system is developed to measure both frequency and amplitude of harmonic vibrations. The optical depth discrimination capability of confocal imaging is utilized to detect and measure vibrations. The beam is focused on to the vibrating surface and the change in intensity resulting from defocusing due to vibration is used to determine the vibration amplitude. The frequency is determined from temporal change in intensity. The instrument could be extended to measure nonharmonic vibrations by incorporating Fourier analysis algorithm. A vibrating speaker was used as the object and tests were carried out with the present setup and vibration amplitudes were measured with an accuracy of 0.014mm.
Effects of multivalent salt addition on effective charge of dilute colloidal solutions
Authors: Wang Tzu-Yu , Sheng Yu-Jane , Tsao Heng-Kwong
Published: November 2006

The effective charge Z* is often invoked to account for the accumulation of counterions near the colloid with intrinsic charge Z. Although the ion concentrations ci are not uniform in the solution due to the presence of the charged particle, their chemical potentials are uniform everywhere. Thus, on the basis of ion chemical potential, effective ion concentrations ci*, which can be experimentally measured by potentiometry, are defined with the pure salt solution as the reference state. The effective charge associated with the charged particle can then be determined by the global electroneutrality condition. Monte Carlo simulations are performed in a spherical Wigner-Seitz cell to obtain the effective charge of the colloid. In terms of the charge ratio α=Z*∕Z, the effects of added salt concentration, counterion valency, and particle charge are examined. The effective charge declines with increasing salt concentration and the multivalent salt is much more efficient in reducing the effective charge of the colloidal solution. Moreover, the extent of effective charge reduction is decreased with increasing intrinsic charge for a given concentration of added salt. Those results are qualitatively consistent with experimental observations by electrophoresis.
Magnetoencephalography with an atomic magnetometer
Authors: Xia H. , Ben-Amar Baranga A. , Hoffman D. , Romalis M. V.
Published: November 2006

The authors demonstrate detection and mapping of brain magnetic fields evoked by auditory stimulation with a noncryogenic magnetometer based on spin precession of potassium atoms in spin-exchange-relaxation-free regime. Optical readout using a photodiode array allows flexibility in detector placement while using common elements for most components of the multichannel system. Absence of a cryogenic dewar eliminates magnetic Johnson noise from radiation shields and allows the use of a compact magnetic shield with a high shielding factor. The magnetometer sensitivity is currently equal to 3.5fT∕Hz1∕2 at 10Hz, similar to superconducting quantum interference device magnetoencephalography systems.
Generation of arbitrary terahertz wave forms in fanned-out periodically poled lithium niobate
Authors: Danielson J. R. , Amer N. , Lee Yun-Shik
Published: November 2006

The authors demonstrate a flexible terahertz pulse-shaping technique, manipulating spatially dispersed multifrequency components generated by optical rectification in a fanned-out periodically poled lithium niobate crystal. Spatial masks of low pass, high pass, and double slit in front of the crystal manipulate the spatial pattern of the optical excitation beam on the crystal, which is mapped onto the intensity profile of the terahertz spectrum. The spatial dispersion of the terahertz spectrum is removed by the line-to-point imaging of a spherical mirror.
Plasmon-enhanced erbium luminescence
Authors: Mertens H. , Polman A.
Published: November 2006

It is demonstrated that the photoluminescence intensity of optically active erbium ions positioned in close proximity of anisotropic Ag nanoparticles is significantly enhanced if the nanoparticles support plasmon modes that are resonant with the erbium emission. In addition, the photoluminescence intensity enhancement is found to be polarized corresponding to polarization of these plasmon modes. Both observations demonstrate that the photoluminescence enhancement is due to coupling of the Er3+ I13∕24−I15∕24 transition dipoles with plasmon modes in the Ag nanoparticles. As this coupling mechanism is known to affect the emission rate, metal nanoparticles provide an opportunity to reduce the effect of temperature or concentration quench processes that are known to occur in a wide range of erbium-doped materials.
Observation of nanosecond laser-induced phase explosion in aluminum
Authors: Porneala Cristian , Willis David A.
Published: November 2006

The transition from normal vaporization to phase explosion during laser ablation of aluminum was investigated using a nanosecond Nd:YAG laser. The threshold nature of phase explosion was observed by a discontinuous jump in the ablation depth at approximately 5.2J∕cm2. Ablation was imaged using a shadowgraph technique that was capable of probing ablation with nanosecond exposure time and nanosecond time delay resolution with respect to laser heating. Images above the threshold captured a mixture of vapor and droplets generated by phase explosion, which began near the end of the laser pulse without a significant time lag.
Quartz crystal microbalance sample stage for in situ characterization of thickness and surface morphology of spin coated polymer films
Authors: Rao Nanxia , Xie Xin , Wielizcka David , Zhu Da-Ming
Published: November 2006

A miniature spin coating stage is developed for in situ characterization of the thickness and the surface morphology of spin coated polymer films using quartz crystal microbalance (QCM) and atomic force microscopy. The spin coated polystyrene films deposited on gold surfaces from solutions using the stage were found to be uniform; the thickness of the films varied linearly with the polystyrene concentration in solution. The film thickness determined by the QCM agree with that from ellipsometry measurements.
Modeling the water related trap state created in pentacene transistors
Authors: Pernstich K. P. , Oberhoff D. , Goldmann C. , Batlogg B.
Published: November 2006

The authors report on the modeling of the water related trap state in pentacene single crystal field-effect transistors that is created by a prolonged application of a gate voltage [C. Goldmann et al., Appl. Phys. Lett. 88, 063501 (2006)]. The authors find a trap state narrow in energy to be appropriate to explain the steplike feature measured in the subthreshold region of the transfer characteristic. The trap state forms in an interface layer next to the gate insulator and is centered at 430±50meV above the valence band edge. The density increases from (2to10.5)×1018∕cm3 during gate bias stress. The knowledge of the details of this defect state can help to identify the physical and chemical origin of the created trap state.
Blue luminescent silicon nanocrystals prepared by ns pulsed laser ablation in water
Authors: Švrček Vladimir , Sasaki Takeshi , Shimizu Yoshiki , Koshizaki Naoto
Published: November 2006

Here the authors report on a simple and cost-effective procedure to prepare blue luminescent colloidal silicon nanocrystals (Si-ncs) in de-ionized water at room temperature and atmospheric pressure by nanosecond pulsed laser ablation. At low laser fluences well-separated and spherical Si-ncs aggregates are formed. The fluence increase leads to fragmentation of spherical aggregates and the generation of finer Si-ncs with quantum confinement size effect. After aging in de-ionized water, such irregular Si-ncs fragments get stabilized into quite regular spheres and ovals. During the aging process the increase of blue room temperature photoluminescence centered around 2.9eV is recorded.
Short-wavelength (λ≈3.3μm) InP-based strain-compensated quantum-cascade laser
Authors: Semtsiv M. P. , Wienold M. , Dressler S. , Masselink W. T.
Published: November 2006

The authors describe the design and implementation of a short-wavelength quantum-cascade laser emitting at approximately 3.3μm at 80K. The active region is based on the strain-compensated In0.73Ga0.27As–In0.55Al0.45As–AlAs heterosystem on InP. The band structure and the strain are controlled through the use of both composite barriers as well as composite wells. The structure is designed so the transition resulting in laser emission is very spatially diagonal; the upper laser state is primarily located in a thick In0.55Al0.45As layer in the injector while the lower laser state is in an In0.73Ga0.27As well. This design allows the lasing transition to bypass (in energy–growth-coordinate space) the lowest indirect X and L valleys of In0.73Ga0.27As, and population inversion is achieved in spite of the upper laser state reaching the energy of the indirect X- and L-valley edges of the adjacent In0.73Ga0.27As well.