bluuebunny/crossref_metadata_2025 huggingface dataset:
Proceedings of the Thirty-ninth Meeting of the Agricultural Research Modellers' Group
Authors: CROMPTON L. A. , WHEELER T. R.
Published: October 2007

This group, which is concerned with the applications of mathematics to agricultural science, was formed in 1970 and has since met at approximately yearly intervals in London for one-day meetings. The thirty-ninth meeting of the group, chaired by Professor N. Crout of the University of Nottingham, was held in the Kohn Centre at the Royal Society, 6 Carlton House Terrace, London on Friday, 30 March 2007 when the following papers were read.
IS CONSANGUINEOUS MARRIAGE RELIGIOUSLY ENCOURAGED? A REPLY TO SAADAT
Authors: AKRAMI SEYED MOHAMMAD
Published: October 2007

I thank Dr M. Saadat for taking the time to carefully read this article (Akrami & Osati, J. biosoc. Sci.39, 313–316) and for making helpful comments. After studying his input, I believe he is in agreement with our conclusion that there is no encouragement of consanguineous marriage in the Islamic context. As he stated, it highlights the importance of the historical background of such practice in some parts of Iran. However, I believe this statement may not be applicable to the entire country. He is right with his second comment regarding Imam Ali and the Fatima family relationship.
The Emergence of Emphatic ‘ne’ in Conversational Swiss French
Authors: FONSECA-GREBER BONNIBETH BEALE
Published: October 2007

This study explores ne use in a previously unexamined variety of French: Swiss French. Based on a corpus of conversation among friends and family recorded at home, the results of this study show the lowest ne use reported for adult, middle-class speakers of European French, 2.5%. It also shows that ne functions micro-stylistically to effect micro-shifts in register allowing speakers to enact the institutional talk of public discourse. Finally, a new function appears to emerge: the use of ne as an emphatic, where it tends to appear in foregrounded clauses often with other emphatics, functioning as speaker evaluation or involvement.
Evolution et diversification des emplois de la locution en fait de
Authors: LAGAE VERONIQUE
Published: October 2007

Dans cette étude diachronique, il est démontré que les trois types d'emplois de la locution en fait de qui coexistent dans la langue actuelle, représentent différentes étapes dans l'évolution de la locution, déjà attestée en moyen français avec des emplois du premier type. Une étude de corpus permet de situer l'apparition des deux autres types respectivement au milieu du XIXe siècle et dans la deuxième moitié du XXe siècle Il apparaît en outre que la diversification des valeurs sémantiques de en fait de va de pair avec deux tendances opposées dans sa distribution: d'une part, une extension de son usage à d'autres catégories grammaticales que celle du nom et, d'autre part, une restriction progressive quant aux positions et fonctions syntaxiques qu'il peut occuper. Ces données confirment l'idée que l'innovation linguistique peut favoriser le passage d'une fonction syntaxique (complément plus ou moins lié au verbe) à une fonction discursive (constituant périphérique marqueur de thématisation, de cadrage etc.)
Transpressional tectonics and stream terraces of the Gobi‐Altay, Mongolia
Authors: Vassallo R. , Ritz J.‐F. , Braucher R. , Jolivet M. , Carretier S. , Larroque C. , Chauvet A. , Sue C. , Todbileg M. , Bourlès D. , Arzhannikova A. , Arzhannikov S.
Published: October 2007

We studied the patterns, rates and evolution of fluvial terraces and fault system during the building process of an intracontinental transpressional mountain in the Gobi‐Altay (Mongolia). By analyzing incisions and offsets of fluvial terraces and alluvial fans, we show that the massif has grown by outward migration of thrust faults through time. On the northern flank, the present bounding thrust fault began its activity ∼600 ka ago, while a more internal sub‐parallel fault was still active until ∼200‐100 ka. Vertical offset of an alluvial fan abandoned ∼100 ka ago allows an estimate of 0.1 mm/yr Upper Pleistocene ‐ Holocene uplift rate. The morphology of the catchment‐piedmont system strongly suggests a periodical formation of the alluvial surfaces, controlled by the climatic pulses, at the beginning of the wet interglacial periods. The abandonment of the alluvial terraces lags by several thousand years the abandonment of the alluvial fans, showing a diachronous incision propagating upstream. The incision rate deduced from the different elevations of straths exceeds of one order of magnitude the rock uplift rate. This excess is mostly due to ongoing drainage network growth at the core of the massif, and incision due to alluvial apron entrenchment near the outlet. This implies that fluvial response is mainly controlled by drainage growth, interaction with piedmont and cyclic climatic variations, rather than by rock uplift.
Ecohydrology of a seasonal cloud forest in Dhofar: 1. Field experiment
Authors: Hildebrandt Anke , Al Aufi Mohammed , Amerjeed Mansoor , Shammas Mahaad , Eltahir Elfatih A. B.
Published: October 2007

We describe the ecohydrology of a unique semiarid broadleaf deciduous forest in Dhofar (Oman). The forest is surrounded by desert and is confined to a coastal area, where the summer wet season is characterized by a persistent dense cloud immersion. Using field observations, we show how clouds render the ecosystem particularly water conserving and therefore create a niche for a moist forest biome in a semiarid area in three ways. First, horizontal precipitation (collection of cloud droplets on tree canopies) added valuable water, such that about two times as much water was received below the canopy (net precipitation) compared to above (rainfall). Second, high stemflow, of about 30% to net precipitation, led to concentrated water input around the stems. Third, transpiration was suppressed during the cloudy summer season, which allowed for storage of the received water. It was only used after the end of the wet season and lasted for the following 3 months, which roughly doubled the length of the growing season. Our results demonstrate that cloud immersion may shape ecosystem hydrology in significant ways, particularly in semiarid environments.
Effect of fluid velocity on model‐estimated rates of radial solute diffusion in a cylindrical macropore column
Authors: Haws Nathan W. , Paraskewich Michael R. , Hilpert Markus , Ball William P.
Published: October 2007

Solute transfer between regions of high and low permeability will limit rates of aquifer remediation in the field and can also affect solute transport through laboratory columns. Transport in systems with such rate limitations is often modeled by assuming that advective transport occurs only in the high‐permeability region (mobile domain) and that solute movement within the lower‐permeability region (immobile domain) is via diffusion only. The validity of such models was explored by experimentally observing the influence of pore water velocity on the apparent rates of transfer within a geometrically well defined, two‐domain system. Tritiated water tracer (3H2O) experiments were conducted in a 7‐cm soil column with a central cylindrical zone of highly permeable material surrounded by an annulus of relatively impermeable finer‐grained sediment. Experimental pore water velocities spanned over two orders of magnitude and included “long” and “short” solute input pulse lengths. The breakthrough data were interpreted using a first‐order mass transfer model (FOM) and a Fickian pore‐diffusion model (PDM). As expected, the rate parameters fitted to the PDM were less sensitive to pore water velocity than those estimated using the FOM. Nonetheless, parameters for the PDM exhibited a negative correlation with pore water velocity. Reestimated parameters from experiments of Young and Ball (1998) showed similar scaling. The velocity dependency indicates deficiencies in inherent model assumptions of both the FOM and the PDM. For the PDM, reasons for the velocity dependency may include mass transfer limitations in the mobile domain and/or heterogeneity of diffusion rates within the immobile domain.
Centennial‐scale compound‐specific hydrogen isotope record of Pleistocene–Holocene climate transition from southern New England
Authors: Hou Juzhi , Huang Yongsong , Oswald W. Wyatt , Foster David R. , Shuman Bryan
Published: October 2007

Northeastern North America experienced major climate shifts during the Pleistocene–Holocene transition. However, there have been no high‐resolution isotopic records of climate change from this region. Here, we present a centennial‐scale record of climate change during the transition based on D/H ratios of behenic acid (C22n‐acid) or δDBA from a sediment core in Blood Pond, Massachusetts. Surface calibrations from a transect of 19 lakes in eastern North America show that δDBA values track mean annual atmospheric temperature variations. The abrupt climate events observed in Blood Pond records show remarkable similarity with Greenland ice core δ18O records during the Pleistocene. During the early Holocene, the northeastern North America δDBA record was more variable than Greenland, possibly due to the close proximity of the Laurentide ice sheet, and impact of freshwater outbursts as the ice sheet rapidly retreated.
A missing sink for gas‐phase glyoxal in Mexico City: Formation of secondary organic aerosol
Authors: Volkamer Rainer , San Martini Federico , Molina Luisa T. , Salcedo Dara , Jimenez Jose L. , Molina Mario J.
Published: October 2007

The sources of secondary organic aerosol (SOA) are highly uncertain. Direct measurements of gas‐phase glyoxal in Mexico City are compared to experimentally constrained model predictions. Observed glyoxal concentrations are found significantly below those predicted. Additional glyoxal sources are likely and would increase these differences; an additional glyoxal sink must be operative. The model‐measurement differences are fully resolved by a sink parameterized from aerosol parameters as either (1) irreversible uptake to aerosol surface area (uptake coefficientγ≈ 0.0037); reversible partitioning to (2) aerosol liquid water (effective Henry's law coefficientHeff≈ 4 × 109M atm−1), or (3) the oxygenated organic aerosol phase (activity coefficientζ≈ 6 × 10−9); (4) a combination of the above. The missing sink has the potential to determine 70–95% of the atmospheric lifetime of glyoxal. The glyoxal imbalance corresponds to severalμg m−3of equivalent SOA mass, and can explain at least 15% of the SOA formation in Mexico City.
Enhancement mechanisms of magnetic susceptibility in the Chinese red‐clay sequence
Authors: Nie Junsheng , King John W. , Fang Xiaomin
Published: October 2007

Little is known about the mechanisms of magnetic susceptibility (χ) enhancement for the red‐clay sequence on the Chinese Loess Plateau (CLP), in comparison to the overlying loess‐paleosol sequence. Here we present a rock magnetic study of the red‐clay sediments from the central CLP. Our results show that frequency dependence of χ (χfd = χlf − χhf, where χlf and χhf are χ measured at 470 Hz and 4700 Hz, respectively), χlf, and susceptibility of anhysteretic‐remanent‐magnetization (χARM) are linearly correlated within the red‐clay sequence. This linear correlation indicates that the pedogenic magnetic minerals of the red‐clay have a rather uniform grain size distribution as in the loess‐paleosol sequence, and the grain size is independent of the degree of pedogenesis. Nevertheless, red‐clay sediments are slightly more enriched in superparamagnetic magnetic particles than the overlying loess‐paleosol sediments as indicated by the higher slope of the regression line between χfd and χlf.
Intraseasonal variability in the summer South China Sea: Wind jet, cold filament, and recirculations
Authors: Xie Shang‐Ping , Chang Chueh‐Hsin , Xie Qiang , Wang Dongxiao
Published: October 2007

A recent study shows that the blockage of the southwest monsoon by the mountain range on the east coast of Indochina triggers a chain of ocean‐atmospheric response, including a wind jet and cold filament in the South China Sea (SCS). We extend this climatological analysis by using higher temporal resolution (weekly) to study intraseasonal variability in summer. Our analysis shows that the development of the wind jet and cold filament is not a smooth seasonal process but consists of several intraseasonal events each year at about 45‐day intervals. In a typical intraseasonal event, the wind jet intensifies to above 12 m/s, followed in a week by the development of a cold filament advected by an offshore jet east of South Vietnam on the boundary of a double gyre circulation in the ocean. The double gyre circulation itself also strengthens in response to the intraseasonal wind event via Rossby wave adjustment, reaching the maximum strength in 2 to 3 weeks. The intraseasonal cold filaments appear to influence the surface wind, reducing the local wind speed because of the increased static stability in the near‐surface atmosphere. To first order, the above sequence of events may be viewed as the SCS response to atmospheric intraseasonal wind pulses, which are part of the planetary‐scale boreal summer intraseasonal oscillation characterized by the northeastward propagation of atmospheric deep convection. The intraseasonal anomalies of sea surface temperature and precipitation are in phase over the SCS, suggesting an oceanic feedback onto the atmosphere. As wind variations are now being routinely monitored by satellite, the lags of 1–3 weeks in oceanic response offer useful predictability that may be exploited.
In‐stream biotic control on nutrient biogeochemistry in a forested stream, West Fork of Walker Branch
Authors: Roberts Brian J. , Mulholland Patrick J.
Published: October 2007

A growing body of evidence demonstrates the importance of in‐stream processing in regulating nutrient export, yet the influence of temporal variability in stream metabolism on net nutrient uptake has not been explicitly addressed. Stream water DIN and SRP concentrations in Walker Branch, a first‐order deciduous forest stream in eastern Tennessee, show a repeated pattern of annual maxima in summer and biannual minima in spring and autumn. Temporal variations in catchment hydrologic flow paths result in lower winter and higher summer nutrient concentrations, but do not explain the spring and autumn nutrient minima. Ambient nutrient uptake rates were measured 2–3 times per week over an 18‐month period and compared to daily rates of gross primary production (GPP) and ecosystem respiration (ER) to examine the influence of in‐stream biotic activity on nutrient export. GPP and ER rates explained 81% of the variation in net DIN retention with high net NO3− uptake (and lower net NH4+ release) rates occurring during spring and autumn and net DIN release in summer. Diel nutrient concentration patterns were examined several times throughout the year to determine the relative importance of autotrophic and heterotrophic activity on net nutrient uptake. High spring GPP corresponded to daily decreases in NO3− over the illuminated hours resulting in high diel NO3− amplitude which dampened as the canopy closed. GPP explained 91% of the variance in diel NO3− amplitude. In contrast, the autumn nutrient minima was largely explained by heterotrophic respiration since GPP remained low and little diel NO3− variation was observed during the autumn.
Angiotensin AT1 receptor antagonists exert anti‐inflammatory effects in spontaneously hypertensive rats
Authors: Dai Q , Xu M , Yao M , Sun B
Published: October 2007

Background and purpose:

Although the main therapeutic effect of angiotensin AT1 receptor antagonists is to decrease blood pressure, they also exert anti‐inflammatory effects in the cardiovascular system. However, the underlying mechanisms remain unclear. We investigated the inhibitory effect of AT1 antagonists on the chemokine monocyte chemoattractant protein 1 (MCP‐1) and its receptor C‐C chemokine receptor 2 (CCR2) in rat monocytes and aortas.

Experimental approach:

Spontaneous hypertensive rats (SHRs) were treated with the AT1 antagonists losartan or telmisartan for 4 weeks, and Wistar‐Kyoto rats (WKYs) were used as normotensive controls. Systolic arterial pressure was measured, and the number of macrophages in the aortic vessel wall was assessed by anti‐ED‐1 antibody immunolabelling.

Key results:

Compared with WKYs, SHRs showed significantly increased ED‐1 positive macrophages in the aortic wall, which were decreased after high doses of losartan or telmisartan. Low doses of losartan did not improve blood pressure significantly as did the high doses, but markedly decreased macrophage infiltration in the vessel wall. AT1 antagonists, particularly at high doses, improved aortic remodeling in SHR. At the molecular level, AT1 antagonists attenuated the expression of MCP‐1 and CCR2 in the aorta and peripheral blood monocytes and lowered the serum level of MCP‐1. In addition, Western blotting showed that AT1 antagonists inhibited the phosphorylation of Akt in mouse monocytes.

Conclusions and implications:

AT1 antagonism inhibited vessel wall inflammation and inhibition of PI3K/Akt may be involved in the modulation of the MCP‐1/CCR2 system by AT1 antagonists in SHRs.

British Journal of Pharmacology (2007) 152, 1042–1048; doi:10.1038/sj.bjp.0707454; published online 8 October 2007
Direct suppression of autoreactive lymphocytes in the central nervous system via the CB2 receptor
Authors: Dittel B N
Published: October 2007

The cannabinoid system is now recognized as a regulator of both the nervous and immune systems. Although marijuana has been used for centuries for the treatment of a variety of disorders, its therapeutic mechanisms are only now being understood. The best‐studied plant cannabinoid, Δ9‐tetrahydrocannabinol (THC), produced by Cannabis sativa and found in marijuana, has shown evidence of being immunosuppressive in both in vivo and in vitro. Since THC binds to at least two receptors that are differentially expressed by the immune and nervous systems, it has not been possible to clearly discriminate the biological effects it exerts in the two systems. In addition, endogenous cannabinoids have also been described that bind to both receptors and exert both neuronal and immune modulatory activity. The generation of mice deficient in specific cannabinoid receptors has facilitated studies to discriminate cannabinoid‐specific functions. This review focuses on the function of the cannabinoid receptor 2 (CB2), primarily expressed in the immune system, in regulating T cell effector functions associated with autoimmune inflammation in the central nervous system (CNS).

British Journal of Pharmacology (2008) 153, 271–276; doi:10.1038/sj.bjp.0707493; published online 8 October 2007
PTEN: a promising pharmacological target to enhance epithelial wound healing
Authors: Zhao M
Published: October 2007

PI3Ks (phosphoinositide‐3 kinases) produce PIP3 (phosphatidylinositol(3,4,5)‐trisphosphate) which mediates signals for cell survival and proliferation. The tumour suppressor PTEN (phosphatase and tensin homologue) dephosphorylates PIP3 and is a key negative regulator of PI3K signalling. Recent research highlighted important roles for PI3K/PTEN in cell polarization and directional cell migration, pointing to a significant role for PTEN in wound healing where spatially organized tissue growth is essential. Lai et al. (in this issue of British Journal of Pharmacology) have moved a step closer in utilizing PTEN for wound healing through pharmacological inhibition. Two vanadium derivative inhibitors targeting PTEN significantly elevated the level of phosphorylated Akt (protein kinase B) and nearly doubled the wound healing rate in monolayer cultures of lung and airway epithelial cells. Damage to airway and lung epithelia underlies a wide spectrum of significant clinical conditions. With further experiments, this promising approach may find potential clinical use in situations where enhanced wound healing of pulmonary and other epithelia is important.

British Journal of Pharmacology (2007) 152, 1141–1144; doi:10.1038/sj.bjp.0707503; published online 8 October 2007
Photocatalytic generation of dissolved oxygen and oxyhemoglobin in whole blood based on the indirect interaction of ultraviolet light with a semiconducting titanium dioxide thin film
Authors: Gilbert Richard J. , Carleton Linda M. , Dasse Kurt A. , Martin Peter M. , Williford Ralph E. , Monzyk Bruce F.
Published: October 2007

Most current artificial lung technologies require the delivery of oxygen to the blood via permeable hollow fibers, depending on membrane diffusivity and differential partial pressure to drive gas exchange. We have identified an alternative approach in which dissolved oxygen (DO) is generated directly from the water content of blood through the indirect interaction of ultraviolet (UV) light with a semiconducting titanium dioxide thin film. This reaction is promoted by photon absorption and displacement of electrons from the photoactive film and yields a cascading displacement of electron “holes” to the aqueous interface resulting in the oxidation of water molecules to form DO. Anatase TiO2 (photocatalyst) and indium tin oxide (ITO) (electrically conductive and light transparent) coatings were deposited onto quartz flow-cell plates by direct current reactive magnetron sputtering. The crystal structure of the films was evaluated by grazing incidence x-ray diffraction, which confirmed that the primary crystal phase of the TiO2 thin film was anatase with a probable rutile secondary phase. Surface topology and roughness were determined by atomic force microscopy, demonstrating a stochastically uniform array of nanocrystallites. UV illumination of the titanium dioxide thin film through the quartz/ITO surface resulted in the rapid increase of DO and oxyhemoglobin in adjacent flowing blood on the opposite TiO2 surface at a rate of 1.0×10−5 mmol O2∕s. The rate of oxyhemoglobin generation was linearly proportional to residence time adjacent to the photoactive surface in a flow-through test cell under steady-state conditions. Preliminary biocompatibility for the proposed photocatalytic effect on whole blood demonstrated no increase in the rate of hemolysis or generation of toxic byproducts of photo-oxidation. These results demonstrate the feasibility and safety of employing optoelectronic mechanisms to promote oxygenation of hemoglobin in whole blood and provide substantiation for the use of this technology as a mechanism for artificial respiratory support.
Evolution of an initially turbulent stratified shear layer
Authors: Brucker Kyle A. , Sarkar Sutanu
Published: October 2007

Direct numerical simulations of a stratified shear layer are performed for several different values of Reynolds, bulk Richardson, and Prandtl numbers. Unlike previous numerical studies, the initial perturbations are turbulent. These initial broadband perturbations do not allow the formation of distinct coherent structures such as Kelvin-Helmholtz rollers and streamwise vortices found in previous studies. In the absence of stratification, the shear layer thickness grows linearly and fully developed turbulence is achieved with mean velocities, turbulence intensities, and turbulent kinetic energy budgets that agree well with previous experimental and numerical data. When buoyancy is included, the shear layer grows to an asymptotic thickness, and the corresponding bulk Richardson number, Rib, is within the range, 0.32±0.06, found in previous studies. The apparent scatter in the evolution of Rib is shown to have a systematic dependence on Reynolds and Prandtl numbers. A detailed description of buoyancy effects on turbulence energetics, transport, and mixing is presented. The Reynolds shear stress, ⟨u1′u3′⟩, is significantly reduced by buoyancy, thus decreasing the shear production of turbulence. Owing to buoyancy, gradients in the vertical direction tend to be larger than other gradients in the fluctuating velocity and density fields. However, this anisotropy of the gradients is lower when the Reynolds number increases. Coherent finger-like structures are identified in the density field at late time and their vertical extent obtained by a scaling analysis.
Quantum study of HIV-1 protease-bridge water interaction
Authors: Duan Li L. , Tong Yan , Mei Ye , Zhang Qing G. , Zhang John Z. H.
Published: October 2007

We present a fully quantum mechanical calculation for binding interaction between HIV-1 protease (PR) and the water molecule W301 which bridges the flaps of the protease with the inhibitors of PR. The quantum calculation is made possible by applying a recently developed molecular fractionation with conjugate caps (MFCC) method which divides a protein molecule into capped amino acid-based fragments and their conjugate caps. These individual fragments are properly treated to preserve the chemical property of bonds that are cut. Ab initio methods at HF, B3LYP, and MP2 levels with a fixed basis set 6-31+G* have been employed in the present calculation. The MFCC calculation produces a quantum mechanical interaction “map” representing interactions between individual residues of PR and W301. This enables a detailed quantitative analysis on binding of W301 to specific residues of PR at quantum mechanical level.
Infrared multiphoton induced isomerization and dissociation of FCN, ClCN, and BrCN in liquid Ar: A classical simulation study
Authors: Zhang Ming , Gong Jiangbin , Ma Ao , Rice Stuart A.
Published: October 2007

We report the results of classical mechanics simulations of infrared multiphoton induced control of isomerization of FCN, ClCN, and BrCN in liquid Ar, using ab initio potential energy and dipole moment surfaces for the XCN molecules. The field induced isomerization and fragmentation dynamics of these molecules are found to be different from that of HCN in liquid Ar. In particular, the scheme that provides complete controlled conversion of HCN to CNH in liquid Ar fails to generate complete conversion of XCN to CNX in liquid Ar for X=F,Cl,Br. It is suggested that the sources of the differences in behavior arise from differences in the spectra of vibrational nonlinear resonances in HCN and XCN and to the occurrence of monodromy in the dynamics of the XCN molecules.
Electrostatic potential fluctuation induced by charge discreteness in a nanoscale trench
Authors: Lee Taesang , Kim S. S. , Jho Y. S. , Park Gunyoung , Chang C. S.
Published: October 2007

A simplified two-dimensional Monte Carlo simulation is performed to estimate the charging potential fluctuations caused by strong binary Coulomb interactions between discrete charged particles in nanometer scale trenches. It is found that the discrete charge effect can be an important part of the nanoscale trench research, inducing scattering of ion trajectories in a nanoscale trench by a fluctuating electric field. The effect can enhance the ion deposition on the side walls and disperse the material contact energy of the incident ions, among others.
Dust trajectories and diagnostic applications beyond strongly coupled dusty plasmas
Authors: Wang Zhehui , Ticoş Cătălin M. , Wurden Glen A.
Published: October 2007

Plasma interaction with dust is of growing interest for a number of reasons. On the one hand, dusty plasma research has become one of the most vibrant branches of plasma science. On the other hand, substantially less is known about dust dynamics outside the laboratory strongly coupled dusty-plasma regime, which typically corresponds to 1015m−3 electron density with ions at room temperature. Dust dynamics is also important to magnetic fusion because of concerns about safety and potential dust contamination of the fusion core. Dust trajectories are measured under two plasma conditions, both of which have larger densities and hotter ions than in typical dusty plasmas. Plasma-flow drag force, dominating over other forces in flowing plasmas, can explain the dust motion. In addition, quantitative understanding of dust trajectories is the basis for diagnostic applications using dust. Observation of hypervelocity dust in laboratory enables dust as diagnostic tool (hypervelocity dust injection) in magnetic fusion. In colder plasmas (∼10eV or less), dust with known physical and chemical properties can be used as microparticle tracers to measure both the magnitude and directions of flows in plasmas with good spatial resolution as the microparticle tracer velocimetry.
Kinetic theory of hydromagnetic turbulence. I. Formal results for parallel propagation
Authors: Yoon Peter H.
Published: October 2007

Formal weak turbulence kinetic equations for magnetized collisionless plasmas are derived. The kinetic theory of plasma turbulence found in the literature is largely applicable for unmagnetized plasmas, and most of the available literature only deal with electrostatic Langmuir turbulence problem. However, real plasmas in nature and laboratory are usually immersed in magnetic fields. At present there is no practical kinetic theory for turbulence in magnetized plasmas. The present paper and a companion article [P. H. Yoon and T.-M. Fang, Phys. Plasmas 14, 102303 (2007)] constitute a first step in the formulation of general kinetic theory for magnetized plasmas. For the sake of simplicity, it is assumed that turbulent fluctuations predominantly propagate along the direction of ambient magnetic field vector, and that the characteristic frequency associated with the fluctuations is much lower than the electron gyrofrequency, i.e., hydromagnetic turbulence. The effects of spontaneous thermal fluctuation and spatial inhomogeneity are also ignored.
Kinetic theory of hydromagnetic turbulence. II. Susceptibilities
Authors: Yoon Peter H. , Fang Ta-Ming
Published: October 2007

The present paper augments the previous paper [P. H. Yoon, Phys. Plasmas 14, 102302 (2007)] in which a formal kinetic theory of hydromagnetic turbulence propagating back-and-forth along the ambient magnetic field was developed. In the present paper, linear wave properties are discussed in detail, various symmetry properties associated with response functions are derived, alternative forms of the response functions are presented, and limiting and approximate forms of nonlinear susceptibilities are discussed.
Plane waves in a rotating micropolar porous elastic solid
Authors: Singh Jaswant , Tomar S. K.
Published: October 2007

Propagation of plane waves in a linear, homogeneous, and isotropic micropolar porous elastic solid rotating with a uniform angular velocity has been investigated. It has been found that there can exist three longitudinal waves and two sets of coupled transverse waves in a linear homogeneous micropolar porous elastic solid rotating with uniform angular velocity. Out of the three longitudinal waves, one is a longitudinal microrotational wave, second is a longitudinal displacement wave already encountered in the theory of micropolar elasticity, and the third one is a longitudinal void volume fractional wave carrying a change in void volume fraction. The phase speeds of each set of coupled transverse waves are found to be affected by the rotation of the body. However, the presence of voids does not affect the phase speeds of coupled transverse waves. The phase speed of longitudinal microrotational waves is found to be independent of the rotation of the body and the presence of the voids. In general, the phase speed, energy loss, and decay coefficient of the remaining two longitudinal waves are found to be influenced by the micropolarity, the presence of voids, and the rotation of the body. At high and low frequencies, the rotation of the body has a significant effect on the longitudinal displacement wave speed, while the phase speed of the wave carrying a change in void volume fraction remains unaffected. The results of some earlier workers have also been reduced from the present formulation.
Electron mobility in InN and III-N alloys
Authors: Hsu L. , Jones R. E. , Li S. X. , Yu K. M. , Walukiewicz W.
Published: October 2007

We have calculated electron mobilities in InN and its III-nitride alloys using a variational procedure and taking into account the standard scattering mechanisms of Coulomb scattering, alloy disorder, and optical and acoustic phonons. The effects of the nonparabolicity of the conduction band and resulting energy-dependent effective mass have also been included. Scattering from charged Coulombic centers and alloy disorder are the dominant scattering mechanisms that limit the mobilities in currently available materials. Phonons play a role only in relatively pure (n<1018 cm−3) samples or at very high temperatures (T>400 K). In addition, our calculations are in good agreement with experimental Hall mobilities obtained through controlled doping studies performed on InN, InGaN, and InAlN by high energy irradiation.
Observation of room temperature magnetoelectric coupling in a Ni substituted Pb1−xNixTiO3 system
Authors: Kumar Manoj , Yadav K. L.
Published: October 2007

We report magnetoelectric coupling at room temperature between ferroelectric and magnetic order parameters in a Pb1−xNixTiO3 (x=0.1, 0.3, and 0.5) system. These samples exhibited magnetism and ferroelectricity simultaneously at room temperature. The Ni substitution reduced the lattice distortion, i.e., c∕a ratio and, hence, the ferroelectric Curie temperature decreased. An anomaly in dielectric constant was observed in the vicinity of ferromagnetic Curie temperature. The magnetoelectric coupling at room temperature was evidence by the increase in saturation polarization after poling the samples in the magnetic field. For the Pb0.5Ni0.5TiO3 sample poled at 1.2 T of magnetic field, the increase in saturation polarization is about ∼11%.
Contact resistance study of noble metals and alloy films using a scanning probe microscope test station
Authors: Chen L. , Lee H. , Guo Z. J. , McGruer N. E. , Gilbert K. W. , Mall S. , Leedy K. D. , Adams G. G.
Published: October 2007

The proper selection of electrical contact materials is one of the critical steps in designing a metal contact microelectromechanical system (MEMS) switch. Ideally, the contact should have both very low contact resistance and high wear resistance. Unfortunately this combination cannot be easily achieved with the contact materials currently used in macroswitches because the available contact force in microswitches is generally insufficient (less than 1mN) to break through nonconductive surface layers. As a step in the materials selection process, three noble metals, platinum (Pt), rhodium (Rh), ruthenium (Ru), and their alloys with gold (Au) were deposited as thin films on silicon (Si) substrates. The contact resistances of these materials and their evolution with cycling were measured using a specially developed scanning probe microscope test station. These results were then compared to measurements of material hardness and resistivity. The initial contact resistances of the noble metals alloyed with Au are roughly proportional to their resistivities. Measurements of contact resistance during cycling of different metal films were made under a contact force of 200–250μN in a room air environment. It was found that the contact resistance increases with cycling for alloy films with a low concentration of gold due to the buildup of contamination on the contact. However, for alloy films with a high gold content, the contact resistance increase due to contamination is insignificant up to 108cycles. These observations suggest that Rh, Ru, and Pt and their gold alloys of low gold content are prone to contamination failure as contact materials in MEMS switches.
Charge-transfer doping by fullerenes on oxidized Si surfaces
Authors: Tada Tetsuya , Uchida Noriyuki , Kanayama Toshihiko , Hiura Hidefumi , Kimoto Kenji
Published: October 2007

We have studied the charge transfer between various fullerenes (C60, C78, C84, C60F36, and C60F48) and oxidized Si surfaces in order to evaluate their capability of charge-transfer doping to form ultrashallow junctions in Si. Although the lowest unoccupied molecular orbitals of these fullerene molecules in isolated states are higher in energy than the valence band maximum (VBM) of Si, the fullerenes C60F36 and C60F48, which were deposited on oxidized Si substrates, captured electrons from the Si surfaces; this generated hole inversion layers. C60, C78, and C84 did not induce such electron transfer. From the densities of the generated holes, we estimated the acceptor levels of C60F36 and C60F48, which were condensed on the oxidized Si surface, to be 5.6–5.7 and 5.2eV below the vacuum level, respectively; these values are lower than the VBM of Si.
Temperature and wavelength dependence of the thermo-optical properties of tellurite and chalcogenide glasses
Authors: Silva K. C. , Sakai O. A. , Steimacher A. , Pedrochi F. , Baesso M. L. , Bento A. C. , Medina A. N. , Lima S. M. , Oliveira R. C. , Moraes J. C. S. , Yukimitu K. , Araújo E. B. , Petrovich M. , Hewak D. W.
Published: October 2007

The refractive index and the temperature coefficient of the optical path length change of tellurite (80TeO2:20Li2O) and chalcogenide glasses (72.5Ga2S3:27.5La2O3) were determined as a function of temperature (up to 150°C) and wavelength (in the range between 454 and 632.8nm). The tellurite glass exhibits the usual refractive index dispersion in the wavelength range analyzed, while anomalous refractive index dispersion was observed for the chalcogenide glass between 454 and 530nm. The dispersion parameters were determined by means of the single-effective oscillator model. In addition, a strong dependence of the temperature coefficient of the optical path length on the photon energy and temperature was found for the chalcogenide glass. The latter was correlated to the shift of the optical band gap (or electronic edge) with temperature, which was interpreted by the electron-phonon interaction model.
Pressure drop enhancement in a concentrated suspension flowing through an abrupt axisymmetric contraction-expansion
Authors: Moraczewski Tracey , Shapley Nina C.
Published: October 2007

In this work, we investigate the pressure drop of concentrated suspensions flowing through a 4:1:4 axisymmetric contraction-expansion at low Reynolds number. Pressure drop measurements across the narrow tube show an enhanced pressure drop relative to a Newtonian fluid at the same flow rate. A linear increase in pressure drop as a function of flow rate is observed for the suspensions, with a steeper slope at higher particle volume fraction. However, due to shear-induced particle migration, the pressure drop at each concentration is lower than would be expected for a uniform Newtonian fluid of the same viscosity as the bulk suspension viscosity. The Krieger [I. M. Krieger, Adv. Colloid Interface Sci. 3, 111 (1972)] expression for the relative viscosity provides an accurate estimate of the dependence of the normalized suspension pressure drop on particle volume fraction, although the bulk suspension viscosity follows the more rapidly increasing curve of Zarraga [I. E. Zarraga, D. A. Hill, and D. T. Leighton, J. Rheol. 44, 185 (2000)]. As the particle volume fraction increases, the normalized pressure drop rises in a similar manner to the area of the recirculation regions in the corner of the expansion and also to the ratio of suspension viscosities in the tube center and recirculation regions. The pressure measurements, along with nuclear magnetic resonance imaging results, suggest that the viscosity ratio between the center and recirculation regions of the suspension, recirculation region size, and pressure drop are all related in contraction-expansion flows of suspensions.
Terahertz characteristics of electrolytes in aqueous Luria-Bertani media
Authors: Oh Seung Jae , Son Joo-Hiuk , Yoo Ocki , Lee Dong-Hee
Published: October 2007

We measured the optical constants of aqueous biomaterial mixtures with various electrolyte concentrations using terahertz time-domain spectroscopy. The mixtures were divided into water and other electrolyte parts in mass fractions for analysis. The optical constants of the electrolyte, excluding water, were obtained by applying the ideal mixture equation, and the power absorption of the electrolyte was observed to be larger than that of water above 1THz. Data from the measurement were fitted with the modified double Debye model, and the reorientation and hydrogen-bond formation decomposition times were found to decrease as the electrolyte concentration increased.
Effect of transition from slip to free molecular flow on gas transport in porous media
Authors: Bravo Maria Cecilia
Published: October 2007

Traditional models, such as the advection-diffusion and the dusty gas models, overlook the contribution of the transition flow regime between the slip and the free molecular flow, on the gas transport in porous media. In this work we demonstrate that, due to the existence of this intermediate regime, the Klinkenberg [Drill. & Prod. Prac. 1941, 200 (1941)] parameter b depends on the pressure. Reported experiments were used to corroborate such an effect and a formulation that extends the Klinkenberg equation—to include the effect of a region at pore scale where both molecule-molecule and molecule-wall interactions are important—was developed. The mathematical form of the extended Klinkenberg equation remains the same, but the slippage Klinkenberg’s parameter b is now a generalized parameter that is a function of Knudsen’s number. It was demonstrated that the widely accepted relation between the parameter b and the Knudsen diffusion coefficient is a good approximation just for Knudsen numbers corresponding to the free molecular flow regime. The model proposed in this paper reproduces the experimental data and predicts practical situations where important errors on total flow rate can be expected if the transition flow regime is neglected in the formalism.
Comment on “Two pathways for photon upconversion in model organic compound systems” [J. Appl. Phys. 101, 023101 (2007)]
Authors: Steer R. P.
Published: October 2007

This Comment notes that Baluschev et al. [J. Appl. Phys. 101, 023101 (2007)] have used an inappropriate model to describe photon upconversion by triplet-triplet annihilation and electronic energy transfer in metalloporphyrin-organic electronic energy acceptor systems. Models that account for aggregation of the metalloporphyrins and coaggregation of the metalloporphyrins with the organic energy acceptors must be employed. Several additional pathways for photon upconversion involving excitons in aggregates are proposed. Heterospecies triplet-triplet annihilation must be considered in the coaggregated metalloporphyrin-diphenylanthracene system.
Response to “Comment on ‘Two pathways for photon upconversion in model organic compound systems’ [J. Appl. Phys. 101, 023101 (2007)]”
Authors: Baluschev S. , Yakutkin V. , Wegner G. , Minch B. , Miteva T. , Nelles G. , Yasuda A.
Published: October 2007

We have studied the phenomenon of photon upconversion in systems of two model compounds as highly efficient blue emitters sensitized with metallated macrocycle molecules in thin films. Aggregation between the active molecules (metallated porphyrins and anthracene derivatives) indeed plays a very important role in the triplet-triplet annihilation supported photon upconversion process. Contrary to the suggestions of Steer [J. Appl. Phys. 102, 076102 (2007)] aggregation (followed from phase separation) is a highly undesired effect: external quantum yields of the level of 1%–3% are observed only in systems with a low degree of aggregation (solutions), whereas the solid state films exhibit at least order of magnitude lower upconversion quantum yield than solutions. Additionally, the “only excitons in aggregates model” cannot explain the increase of the linear absorption of the sensitizer at the presence of the emitter. Furthermore, this hypothesis cannot explain why the upconversion quantum yield increases when decreasing the total molecular concentration. Finally, the only excitons in aggregates model needs to assume equal aggregation properties of molecules with different solubilities, sizes, and decorations, as the case of PdPh4TBP and PdPh4OMe8TNP.
Investigation of guanidine hydrochloride induced chlorophyll protein 43 and 47 denaturation in the terahertz frequency range
Authors: Chen Hua , Wang Li , Qu Yuangang , Kuang Tingyun , Li Liangbi , Peng Weixian
Published: October 2007

In investigating guanidine (Gu)HCl-denatured chlorophyll protein 43 (CP43) and CP47 using the terahertz time-domain spectroscopy, we explored the feasibility and sensitivity of the terahertz technology in sensing protein denaturation and associated conformation changes. It was found that the conformation change was induced by the CO group of chlorophyll a, interacting with the N–H group of GuHCl to form hydrogen bonds. According to the fluorescence emission spectra of the CPs treated by GuHCl with different concentrations, we found that CP47 is more sensitive to GuHCl treatment than CP43.
Higher order first integrals in classical mechanics
Authors: Horwood Joshua T.
Published: October 2007

We present a practical algorithm for computing first integrals of motion which are polynomial in the momenta for natural Hamiltonian systems defined in a flat pseudo-Riemannian space of arbitrary dimension and signature. We then apply our algorithm to explore the integrability of two physical systems. First, we study the Holt potential in two dimensions and derive analogous potentials which admit an additional first integral quartic in the momenta. Second, we analyze a class of cylindrically symmetric potentials in three-dimensional Euclidean space and recover known families of second-order maximally superintegrable systems.
Lateral force microscope calibration using a modified atomic force microscope cantilever
Authors: Reitsma M. G.
Published: October 2007

A proof-of-concept study is presented for a prototype atomic force microscope (AFM) cantilever and associated calibration procedure that provide a path for quantitative friction measurement using a lateral force microscope (LFM). The calibration procedure is based on the method proposed by Feiler et al. [Rev. Sci. Instrum. 71, 2746 (2000)] but allows for calibration and friction measurements to be carried out in situ and with greater precision. The modified AFM cantilever is equipped with lateral lever arms that facilitate the application of normal and lateral forces, comparable to those acting in a typical LFM friction experiment. The technique allows the user to select acceptable precision via a potentially unlimited number of calibration measurements across the full working range of the LFM photodetector. A microfabricated version of the cantilever would be compatible with typical commercial AFM instrumentation and allow for common AFM techniques such as topography imaging and other surface force measurements to be performed.
The photodissociation dynamics of ozone at 226 and 248nm: O(PJ3) atomic angular momentum polarization
Authors: Brouard M. , Goman A. , Horrocks S. J. , Johnsen A. J. , Quadrini F. , Yuen W.-H.
Published: October 2007

Speed distributions, and spatial anisotropy and atomic angular momentum polarization parameters have been determined for the O(PJ3) products following the photodissociation of ozone at 248 and 226nm using velocity map ion imaging. The data have been interpreted in terms of two dissociation mechanisms that give rise to fast and slow products. In both cases, excitation is believed to occur to the B̃ state. Consistent with previous interpretations, the speed distributions, translational anisotropy parameters, and angular momentum polarization moments support the assignment of the major pathway to curve crossing from the B̃ to the repulsive R̃ surface, generating fast fragments in a wide range of vibrational states. For the slow fragments, it is proposed that following excitation to the B̃ state, the system crosses onto the Ã state. The crossing seam is only accessible to molecules that are highly vibrationally excited and therefore possess modest recoil speeds. Once on the Ã state, the wavepacket is thought to funnel through a conical intersection to the ground state. The velocity distributions, spatial anisotropy parameters, spin-orbit populations and polarization data each lend support to this mechanism.