bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic and disturbance energy analysis of a flow with heat communication
Authors: KARIMI NADER , BREAR MICHAEL J. , MOASE WILLIAM H.
Published: February 2008

This paper presents a comparative analysis of the budgets of acoustic energy and Myers' second-order ‘disturbance energy’ in a simple inhomogeneous flow with heat communication. The flow considered is non-diffusive and one-dimensional, with excitation by downstream-travelling acoustic and entropic disturbances. Two forms of heat communication are examined: a case with only steady heat communication and another in which unsteady heat addition cancels the generation of entropy disturbances throughout the inhomogeneous region.

It is shown that significant entropic disturbances are usually generated at low frequency when a flow with steady heat communication is excited either acoustically or entropically. However, for acoustic excitation and regardless of the form of heat communication, entropic disturbances are not created at high frequency, inferring that all source terms create mainly sound in this limit. A general method is therefore proposed for determining an approximate frequency beyond which the generation of entropy disturbances can be ignored, and the disturbance energy flux then approximates the acoustic energy flux. This frequency is shown to depend strongly on the problem under investigation, which is expected to have practical significance when studying sound generation and propagation in combusting flows in particular. Further, sound is shown to be generated by fluid motion experiencing only steady heat communication, which is consistent with the known mechanism of sound generation by the acceleration of density disturbances.
Steady rimming flows with surface tension
Authors: BENILOV E. S. , BENILOV M. S. , KOPTEVA N.
Published: February 2008

We examine steady flows of a thin film of viscous fluid on the inside of a cylinder with horizontal axis, rotating about this axis. If the amount of fluid in the cylinder is sufficiently small, all of it is entrained by rotation and the film is distributed more or less evenly. For medium amounts, the fluid accumulates on the ‘rising’ side of the cylinder and, for large ones, pools at the cylinder's bottom. The paper examines rimming flows with a pool affected by weak surface tension. Using the lubrication approximation and the method of matched asymptotics, we find a solution describing the pool, the ‘outer’ region, and two transitional regions, one of which includes a variable (depending on the small parameter) number of asymptotic zones.
Competition and bistability of ordered undulations and undulation chaos in inclined layer convection
Authors: DANIELS KAREN E. , BRAUSCH OLIVER , PESCH WERNER , BODENSCHATZ EBERHARD
Published: February 2008

Experimental and theoretical investigations of undulation patterns in high-pressure inclined layer gas convection at a Prandtl number near unity are reported. Particular focus is given to the competition between the spatiotemporal chaotic state of undulation chaos and stationary patterns of ordered undulations. In experiments, a competition and bistability between the two states is observed, with ordered undulations most prevalent at higher Rayleigh number. The spectral pattern entropy, spatial correlation lengths and defect statistics are used to characterize the competing states. The experiments are complemented by a theoretical analysis of the Oberbeck–Boussinesq equations. The stability region of the ordered undulations as a function of their wave vectors and the Rayleigh number is obtained with Galerkin techniques. In addition, direct numerical simulations are used to investigate the spatiotemporal dynamics. In the simulations, both ordered undulations and undulation chaos were observed dependent on initial conditions. Experiment and theory are found to agree well.
Streamwise development of turbulent boundary-layer drag reduction with polymer injection
Authors: HOU Y. X. , SOMANDEPALLI V. S. R. , MUNGAL M. G.
Published: February 2008

Zero-pressure-gradient turbulent boundary-layer drag reduction by polymer injection has been studied with particle image velocimetry. Flow fields ranging from low to maximum drag reduction have been investigated. A previously developed technique – the (1 −y/δ) fit to the total shear stress profile – has been used to evaluate the skin friction, drag reduction and polymer stress. Current results agree well with the semi-log plot of drag reductionvs. normalized polymer flux which has been used by previous workers and can be used as a guide to optimize the use of polymer from a single injector. Detailed flow-field statistics show many special features that pertain to polymer flow. It is shown that the mean velocity responds quickly to the suddenly reduced wall shear stress associated with polymer injection. However, it takes a much longer time for the entire Reynolds shear stress profile to adjust to the same change. The Reynolds shear stress profiles in wall units can be higher than unity and this unique feature can be used to further judge whether the flow is in equilibrium. The streamwise evolution of drag reduction magnitude is used to divide the flow into three regions: development region; steady-state region; and depletion region. The polymer stress is estimated and found to be proportional to drag reduction in the depletion region, but not necessarily so in the other regions. The interaction between injected polymer and turbulent activity in a developing boundary-layer flow is dependent upon the flow history and it produces an equally complex relationship between polymer stress and drag reduction. The stress balance in the boundary layer and the dynamical contribution of the various stresses to the total stress are evaluated and it is seen that the polymer stresses can account for up to 25% of the total stress. This finding is in contrast to channel flows with homogeneous polymer injection where the polymer stress is found to account for up to 60% of the total stress.
Inviscid waves on a Lamb–Oseen vortex in a rotating stratified fluid: consequences for the elliptic instability
Authors: LE DIZÈS STÉPHANE
Published: February 2008

The inviscid waves propagating on a Lamb–Oseen vortex in a rotating medium for an unstratified fluid and for a strongly stratified fluid are analysed using numerical and asymptotic approaches. By a local Lagrangian description, we first provide the characteristics of the local plane waves (inertia–gravity waves) as well as the local growth rate associated with the centrifugal instability when the vortex is unstable. A global WKBJ approach is then used to determine the frequencies of neutral core modes and neutral ring modes. We show that these global Kelvin modes only exist in restricted domains of the parameters. The consequences of these domain limitations for the occurrence of the elliptic instability are discussed. We argue that in an unstratified fluid the elliptic instability should be active in a small range of the Coriolis parameter which could not have been predicted from a local approach. The wavenumbers of the sinuous modes of the elliptic instability are provided as a function of the Coriolis parameter for both an unstratified fluid and a strongly stratified fluid.
The effect of gravity and cavitation on a hydrofoil near the free surface
Authors: FALTINSEN ODD M. , SEMENOV YURIY A.
Published: February 2008

A nonlinear analysis has been made to determine the effects of the free surface and transverse gravity field on the steady cavity flow past a shaped hydrofoil beneath the free surface. A closed cavity wake model has been proposed, and a method for the determination of an analytical function from its modulus and argument on the region boundary has been employed to derive the complex flow potential in a parameter plane. The boundary-value problem is reduced to a system of integral and integro-differential equations in the velocity modulus along the free boundaries and the velocity angle along the hydrofoil surface, both written as a function of parametric variables. The system of equations is solved through a numerical procedure, which is validated in the cases of a cavitating flat plate and non-cavitating shaped hydrofoils by comparison with data available in the literature. The results are presented in a wide range of Froude numbers and depths of submergence in terms of the cavity and free-surface shapes and force coefficients. The influences of the free surface and gravity on the aforementioned quantities are discussed. The limiting cavity size corresponding to zero cavitation number in the presence of gravity is found for various initial flow parameters.
Collective diffusion in sheared colloidal suspensions
Authors: LESHANSKY ALEXANDER M. , MORRIS JEFFREY F. , BRADY JOHN F.
Published: February 2008

Collective diffusivity in a suspension of rigid particles in steady linear viscous flows is evaluated by investigating the dynamics of the time correlation of long-wavelength density fluctuations. In the absence of hydrodynamic interactions between suspended particles in a dilute suspension of identical hard spheres, closed-form asymptotic expressions for the collective diffusivity are derived in the limits of low and high Péclet numbers, where the Péclet number ${\it Pe}\,{=}\,\gamdot a^2/D_0$ with $\gamdot$ being the shear rate and D0 = kBT/6πη a is the Stokes–Einstein diffusion coefficient of an isolated sphere of radius a in a fluid of viscosity η. The effect of hydrodynamic interactions is studied in the analytically tractable case of weakly sheared (Pe ≪ 1) suspensions.

For strongly sheared suspensions, i.e. at high Pe, in the absence of hydrodynamics the collective diffusivity Dc = 6 Ds∞, where Ds∞ is the long-time self-diffusivity and both scale as $\phi \gamdot a^2$, where φ is the particle volume fraction. For weakly sheared suspensions it is shown that the leading dependence of collective diffusivity on the imposed flow is proportional to D0 φPeÊ, where Ê is the rate-of-strain tensor scaled by $\gamdot$, regardless of whether particles interact hydrodynamically. When hydrodynamic interactions are considered, however, correlations of hydrodynamic velocity fluctuations yield a weakly singular logarithmic dependence of the cross-gradient-diffusivity on k at leading order as ak → 0 with k being the wavenumber of the density fluctuation. The diagonal components of the collective diffusivity tensor, both with and without hydrodynamic interactions, are of O(φPe2), quadratic in the imposed flow, and finite at k = 0.

At moderate particle volume fractions, 0.10 ≤ φ ≤ 0.35, Brownian Dynamics (BD) numerical simulations in which there are no hydrodynamic interactions are performed and the transverse collective diffusivity in simple shear flow is determined via time evolution of the dynamic structure factor. The BD simulation results compare well with the derived asymptotic estimates. A comparison of the high-Pe BD simulation results with available experimental data on collective diffusivity in non-Brownian sheared suspensions shows a good qualitative agreement, though hydrodynamic interactions prove to be important at moderate concentrations.
Viscous effects on wave generation by strong winds
Authors: ZEISEL A. , STIASSNIE M. , AGNON Y.
Published: February 2008

This paper deals with the stability of water waves in a shear flow. Both temporal and spatial growth rates are derived. A carefully designed numerical solver enables us to extend the range of previous calculations, and to obtain results for larger wavelengths (up to 20 cm) and stronger winds (up to a friction-velocity of 1 m s−1). The main finding is the appearance of a second unstable mode which often turns out to be the dominant one. A comparison between results from the viscous model (Orr–Sommerfeld equations) and those of the inviscid model (Rayleigh equations), for 18 cm long waves, reveals some similarity in the structure of the eigenfunctions, but a significant difference in the imaginary part of the eigenvalues (i.e. the growth rate). It is found that the growth rate for the viscous model is 10 fold larger than that of the inviscid one.
Electrified viscous thin film flow over topography
Authors: TSELUIKO D. , BLYTH M. G. , PAPAGEORGIOU D. T. , VANDEN-BROECK J.-M.
Published: February 2008

The gravity-driven flow of a liquid film down an inclined wall with periodic indentations in the presence of a normal electric field is investigated. The film is assumed to be a perfect conductor, and the bounding region of air above the film is taken to be a perfect dielectric. In particular, the interaction between the electric field and the topography is examined by predicting the shape of the film surface under steady conditions. A nonlinear, non-local evolution equation for the thickness of the liquid film is derived using a long-wave asymptotic analysis. Steady solutions are computed for flow into a rectangular trench and over a rectangular mound, whose shapes are approximated with smooth functions. The limiting behaviour of the film profile as the steepness of the wall geometry is increased is discussed. Using substantial numerical evidence, it is established that as the topography steepness increases towards rectangular steps, trenches, or mounds, the interfacial slope remains bounded, and the film does not touch the wall. In the absence of an electric field, the film develops a capillary ridge above a downward step and a slight depression in front of an upward step. It is demonstrated how an electric field may be used to completely eliminate the capillary ridge at a downward step. In contrast, imposing an electric field leads to the creation of a free-surface ridge at an upward step. The effect of the electric field on film flow into relatively narrow trenches, over relatively narrow mounds, and down slightly inclined substrates is also considered.
Accountability in Hostile Times: the Case of the Peruvian Human Rights Ombudsman 1996–2001
Authors: PEGRAM THOMAS
Published: February 2008

This article examines the record of the Peruvian human rights ombudsman between 1996 and 2001, seeking to explain its relative effectiveness under conditions of semi-authoritarian government. It suggests that this can be attributed to three factors: (1) the robustness of the institution's foundations; (2) the capacity of the first appointee and personnel, and; (3) the ability of the institution to build alliances which were able to enhance accountability. Drawing on O'Donnell's theory of a new generation of horizontal accountability mechanisms – that is, appointed, as opposed to elected, institutions – it argues that the human rights ombudsman occupied a distinct position in the Peruvian political system during this period that allowed it to interconnect different actors and arenas of accountability.
Radiation forces between dust grains in a plasma
Authors: MENDONÇA J. T. , STENFLO L.
Published: February 2008

In this work we show that a repulsive force between nearby dust grains in a plasma can exist, due to scattering of the incident radiation. Two types of forces are discussed, one of them being formally identical to electrostatic repulsion. This leads to the definition of an effective dust charge of the dust grain, which only depends on the scattering process. Our discussion shows that such a repulsive interaction occurs in quite general physical conditions.
New taxa of foliicolous lichens from eastern India
Authors: SINGH Krishna Pal , PINOKIYO Athokpam
Published: February 2008

Two new species, Mazosia lueckingii Kr. P. Singh & Pinokiyo and Sporopodium awasthianum Kr. P. Singh & Pinokiyo and a new variety, Aspidothelium scutellicarpum R. Lücking var. indicum Kr. P. Singh & Pinokiyo, are described.
Diversity and distribution of lichens in relation to altitude within a protected biodiversity hot spot, north-east India
Authors: PINOKIYO Athokpam , SINGH Krishna Pal , SINGH Jamuna Sharan
Published: February 2008

A study of the diversity and distribution of lichens at 10 sites within the Mehao Wildlife Sanctuary in Arunachal Pradesh, India, revealed 177 species, belonging to 71 genera and 35 families. The Sanctuary exhibited almost all the habit and habitat groups of lichens within its climatically heterogenous and altitudinally (400–2700 m) varied landscape. Among the different habitat groups, obligately corticolous lichens were dominant (133 species), followed by facultatively corticolous lichens (occurring on both rock and bark; 25 species), saxicolous lichens (17 species) and terricolous lichens (2 species). The corticolous habitat group was dominated by crustose species while saxicolous and terricolous groups were made up of mostly fruticose species. A substantial number of species (77) occurred at single sites only, and each of the 10 sites supported a distinct lichen assemblage. Altitude and humidity were the putative key factors controlling the diversity and distribution of lichens within the Sanctuary. The mid altitude range 1400–1600 m had the greatest lichen diversity, which showed a unimodal pattern in relation to altitude.
Conservation of the rare British lichen Vulpicida pinastri: changing climate, habitat loss and strategies for mitigation
Authors: BINDER Mark D. , ELLIS Christopher J.
Published: February 2008

Autecological information targeted towards rare and threatened lichen species is severely lacking. This study adopts the rare British lichen Vulpicida pinastri as a case study species and examines its ecological response to emerging threats: climate change and the recurrent loss of its primary habitat (juniper scrub). We used predictive niche modelling to examine the response of V. pinastri to a range of present-day climatic variables. A successful model was projected for a period during the 2050s based on IPCC climate change scenarios (UKCIP02 data), and threat was estimated as the proportional change in bioclimatic space. To estimate the potential range now and during the 2050s, projected bioclimatic space was masked by a habitat map equivalent to (i) the present-day distribution of juniper and (ii) theoretical juniper distribution based on existing rates of decline. Our results point to potential range loss of V. pinastri with climate warming, exacerbated by the recurrent decline in juniper habitat. This predictive modelling approach was complemented by an assessment of local stand-scale effects. At four sites in north-east Scotland we examined the occurrence and abundance of V. pinastri thalli, in response to juniper spatial distribution, and the life-stage and structure of individual shrubs. Vulpicida pinastri appeared to be dispersal limited at small-scales, and was significantly more abundant on old and degenerate juniper shrubs. Our results evidence a close relationship between management for habitat quality and effective lichen conservation. Effective conservation of V. pinastri must ensure cohorts of older and degenerate juniper shrubs are maintained at sites where the species is expected to be most resistant to long-term climate warming, i.e. in the uplands of north-east Scotland.
Physical mechanisms for the offshore detachment of the Changjiang Diluted Water in the East China Sea
Authors: Chen Changsheng , Xue Pengfei , Ding Pingxing , Beardsley R. C. , Xu Qichun , Mao Xianmou , Gao Guoping , Qi Jiahua , Li Chunyan , Lin Huichan , Cowles Geoffrey , Shi Maochong
Published: February 2008

Physical mechanisms for the summertime offshore detachment of the Changjiang Diluted Water (CDW) into the East China Sea are examined using the high‐resolution, unstructured‐grid, Finite‐Volume Coastal Ocean Model (FVCOM). The model results suggest that isolated low salinity water lens detected west of Cheju Island can be formed by (1) a large‐scale adjustment of the flow field to the Changjiang discharge and (2) the detachment of anticyclonic eddies as a result of baroclinic instability of the CDW front. Adding the Changjiang discharge intensifies the clockwise vorticity of the subsurface current (originating from the Taiwan Warm Current) flowing along the 50‐m isobath and thus drives the low‐salinity water in the northern coastal area of the Changjiang mouth offshore over a submerged plateau that extends toward Cheju Island. Given a model horizontal resolution of less than 1.0 km, the CDW front becomes baroclinically unstable and forms a chain of anticyclonic and cyclonic eddies. The offshore detachment of anticyclonic eddies can carry the CDW offshore. This process is enhanced under northward winds as a result of the spatially nonuniform interaction of wind‐induced Ekman flow and eddy‐generated frontal density currents. Characteristics of the model‐predicted eddy field are consistent with previous theoretical studies of baroclinic instability of buoyancy‐driven coastal density currents and existing satellite imagery. The plume stability is controlled by the horizontal Ekman number. In the Changjiang, this number is much smaller than the criterion suggested by a theoretical analysis.
Terrigenous organic matter in sediments from the Fly River delta‐clinoform system (Papua New Guinea)
Authors: Goni Miguel A. , Monacci Natalie , Gisewhite Rachel , Crockett John , Nittrouer Charles , Ogston Andrea , Alin Simone R. , Aalto Rolf
Published: February 2008

Although an inordinate fraction of the global sediment flux to the ocean occurs in tropical mountainous river margins, little is known regarding the sources and fate of organic matter in these systems. To address these knowledge gaps, the distribution and composition of organic matter in sediments from the Fly River delta‐clinoform were examined in the context of the source‐to‐sink study of the Papuan Continuum. The significant contrasts in the texture of seabed sediments measured across the study area coincided with stark contrasts in concentration and composition of the sedimentary organic matter. Coarser sediments displayed significantly lower organic carbon and nitrogen contents, more enriched stable carbon and nitrogen compositions, lower lignin product yields, and distinctly different lignin and nonlignin product compositions than their fine‐textured counterparts. Compositional differences were also measured between high‐ and low‐density fractions of selected sediment samples. Subsurface sediments showed marked compositional variations that were predominantly associated with changes in the texture of the deposits. Most sediments were characterized by moderate carbon loadings (0.5–1.0 mg C m−2), although several samples from the outer topset region, an area of sediment bypass, were characterized by lower carbon loadings indicative of enhanced carbon losses. Overall, the organic matter in both surface and subsurface sediments appeared to have predominantly a terrigenous origin, with no evidence for dilution and/or replacement by marine carbon. The measured compositions were consistent with contributions from modern vascular plant detritus, aged soil organic matter, and very old or fossil organic matter devoid of recognizable biochemicals.
Imaging the sources and full extent of the sodium tail of the planet Mercury
Authors: Baumgardner Jeffrey , Wilson Jody , Mendillo Michael
Published: February 2008

Observations of sodium emission from Mercury can be used to describe the spatial and temporal patterns of sources and sinks in the planet's surface‐boundary‐exosphere. We report on new data sets that provide the highest spatial resolution of source regions at polar latitudes, as well as the extraordinary length of a tail of escaping Na atoms. The tail's extent of ∼1.5 degrees (nearly 1400 Mercury radii) is driven by radiation pressure effects upon Na atoms sputtered from the surface in the previous ∼15 hours. Wide‐angle filtered‐imaging instruments are thus capable of studying the time history of sputtering processes of sodium and other species at Mercury from ground‐based observatories in concert with upcoming satellite missions to the planet. Plasma tails produced by photo‐ionization of Na and other gases in Mercury's neutral tails may be observable by in‐situ instruments.
Sharpness of the D″ discontinuity beneath the Cocos Plate: Implications for the perovskite to post‐perovskite phase transition
Authors: Lay T.
Published: February 2008

The depth extent, or sharpness, of the D″ seismic velocity discontinuity is determined by modeling distance‐dependence of reflected S‐wave signals sampling the lowermost mantle beneath the Cocos Plate. The data, spanning distances from 64° to 83° and grouped in two small turning‐point bins from 5° to 10°N and 10° to 15°N, are compatible with a sharp 1 to 2% shear velocity increase near 300 km above the core‐mantle boundary, but not with reflection from a transition zone extending more than ∼30 km in depth. Interpretation of the velocity structure as the result of magnesium‐silicate perovskite undergoing a phase transition to post‐perovskite requires limited presence of Al and Fe, which will broaden the phase transition. Current experiments indicate that the phase transition may occur over ∼5 GPa (90 km) in pyrolitic material, requiring either distinct chemistry or dynamical mechanisms to sharpen the phase transition for this high‐velocity sub‐circum‐Pacific region.
Spatial variability in annual sea level variations around the Korean peninsula
Authors: Kang Sok Kuh , Cherniawsky Josef Y. , Foreman Michael G. G. , So Jae‐Kwi , Lee Sang Ryong
Published: February 2008

Analyses of annual sea level variations (Sa) around the Korean peninsula reveal systematic spatial patterns in the phase lags and amplitudes. Sa amplitudes in this region vary between 10 and 20 cm, with atmospheric pressure accounting for only 7.7 to 9.4 cm. These patterns are dominated by annual changes in thermosteric sea levels in the Yellow Sea (YS) and East/Japan Sea (EJS), with only minor contributions from seasonal wind‐driven set up.
The relationship between sea‐level and bottom pressure variability in an eddy permitting ocean model
Authors: Bingham Rory J. , Hughes Chris W.
Published: February 2008

We investigate the relationship between sea‐level (after application of an inverse‐barometer correction) and ocean bottom pressure, in an eddy‐permitting ocean model. We find the presence of eddies can disrupt this relationship even on timescales as short as 10–20 days, but only in the regions of most energetic eddy variability. Away from eddies, the relationship is similar to that seen in a coarser‐resolution model, with a tight relationship between sea‐level and bottom pressure at high frequencies, but with significant correlations between sea‐level and bottom pressure at interannual timescales seen only in shelf sea regions. In the deep ocean, regions where sea‐level and bottom pressure remain related out to the longest timescales are in the Arctic Ocean and regions of the Southern Ocean, where particularly large amplitude barotropic fluctuations are found but where the mesoscale signal is weak.
Energization of radiation belt electrons by ring current ion driven ULF waves
Authors: Ozeke L. G. , Mann I. R.
Published: February 2008

In this paper we examine the hypothesis that MeV energy radiation belt electrons can be energized by ULF waves, the ULF waves themselves being excited by drift‐bounce resonance with energetic ring current ions. We show that this energization is most likely to occur during depleted plasmatrough conditions and when the plasmapause lies on a low L‐shell. For example, when the plasmasphere has been eroded so that the plasmapause lies at L = 3, then efficient energization for electrons with energies >1 MeV at L ≃ 3–4 can be caused by ULF waves generated by the N = 2 drift‐bounce resonance with either ≃ 10–15 keV H+, or ≃ 100–300 keV O+, ring current ions respectively. We illustrate this transfer of energy from the ring current to the radiation belt by considering a radiation belt electron drift resonance with fundamental field‐aligned mode m ≃ +20 guided poloidal Alfvén waves, the waves being excited by westward drifting ring current ions. Our results are significant in that they offer a new paradigm for the ULF wave energization of MeV radiation belt electrons, suggesting that ring current ion driven ULF waves may play an important role in radiation belt energization by ULF waves. Given the prevalence of ∼100 keV O+ ions in the ring current at L ∼ 3–4 during storm‐times, and the storm‐time erosion of the plasmapause, the conditions required for efficient ULF wave energy transfer from the ring current to >1 MeV electrons in the radiation belt will be satisfied during storm‐times.
Spectral morphology of the X‐ray emission from Jupiter's aurorae
Authors: Branduardi‐Raymont G. , Elsner R. F. , Galand M. , Grodent D. , Cravens T. E. , Ford P. , Gladstone G. R. , Waite J. H.
Published: February 2008

Simultaneous Chandra X‐ray and Hubble Space Telescope FUV observations of Jupiter's aurorae carried out in February 2003 have been re‐examined to investigate the spatial morphology of the X‐ray events in different energy bands. The data clearly show that in the Northern auroral region (in the main auroral oval and the polar cap) events with energy > 2 keV are located at the periphery of those with energy < 2 keV and coincide with FUV bright features. In addition, X‐ray spectra extracted from the areas where the two event distributions are concentrated possess different shapes. We associate the > 2 keV events (∼45 MW emitted power) with the electron bremsstrahlung component recently revealed by XMM‐Newton in the spectra of Jupiter's aurorae, and the < 2 keV emission (∼230 MW) with the product of ion charge exchange, now established as the likely mechanism responsible for the soft X‐ray Jovian aurora. We suggest that the same population of energetic electrons may be responsible for both, the X‐ray bremsstrahlung and the FUV emission of Jupiter's aurorae. Comparison of the > 2 keV X‐ray and FUV (340 GW) powers measured during the observations shows that they are broadly consistent with the predicted emissions from a population of energetic electrons precipitating in the planet's atmosphere, thus supporting our interpretation.
Determination of magnetic properties of rocks by analysis of demagnetization curves: Hematite‐ilmenite bearing rocks from SW Sweden
Authors: Eneroth Erik , Johansson Leif
Published: February 2008

Granulites from the high‐grade Sveconorwegian (corresponding to Grenvillian) gneiss terrane of SW Sweden were investigated in order to relate magnetic properties to the granulite facies mineralogy and the amphibolite facies retrograde mineralogy. We used standard paleomagnetic techniques, susceptibility measurements, electron and optical microscopy, and a new way to analyze demagnetization curves based on vector difference sums. The new technique allowed quantitation of the relative contributions of partial natural remanent magnetization (NRM) components as well as numerical extraction of thermal and coercive force (alternating field, AF) unblocking data. Two major components were identified, one stable which is carried by hematite‐ilmenite, and one less stable carried by multidomain (MD) magnetite. The age of the hematite‐ilmenite component is circa 930 Ma, and it has steep negative inclination, coercivities in excess of 150 mT, and unblocking temperatures between 540°C and 640°C. Two corresponding poles are reported (1) paleolatitude/paleolongitude (plat/plong) (218°/−24.3°) with Dp/Dm (9.4°/9.9°) (paleopole) and (2) plat/plong (203°/−51°) with Dp/Dm (4.4°/5.6°) (VGP). The MD magnetite component is a recent or Cretaceous‐Paleogene, steeply positive inclined NRM component associated with strong induced magnetization (plat/plong 2°/−74° and Dp/Dm 11°/14°) (VGP). The MD magnetite was unblocked at conditions of 6–40 mT and 60–400°C. Our new analysis method was successful in showing that retrograde amphibole formation strongly decreases the importance of the hematite‐ilmenite component on behalf of the MD magnetite. It has a diminishing effect on a negative aeromagnetic anomaly in the area. The 930 Ma components constitute 80–0% of the vector difference sums depending on rock composition. However, as this fraction goes down to 60%, the induced magnetization seems to outweigh the hematite‐ilmenite influence on aeromagnetic anomalies due to its opposite direction. These rocks still have a strong and stable hematite‐ilmenite dominated NRM.
Detection of migrating diurnal tide in the tropical upper troposphere and lower stratosphere using the Challenging Minisatellite Payload radio occultation data
Authors: Zeng Zhen , Randel William , Sokolovskiy Sergey , Deser Clara , Kuo Ying‐Hwa , Hagan Maura , Du Jian , Ward William
Published: February 2008

The atmospheric limb sounding technique making use of radio signals transmitted by the Global Positioning System (GPS) has already proven to be a promising approach for global atmospheric measurements. In this study, we assess for the first time the potential of GPS radio occultation soundings for detecting the migrating diurnal tide. Retrieved temperatures between 10 and 30 km in the tropics from the Challenging Minisatellite Payload (CHAMP) occultation observations during May 2001 to August 2005 are analyzed using space‐time spectrum analysis to isolate diurnal waves. Because of incomplete local time (LT) coverage of the monthly CHAMP occultation data in any given year, data from all available years are merged to obtain complete 24‐h LT coverage. The effects of aliasing associated with uneven data sampling and measurement noise are estimated using synthetic data. The results show the feasibility of determining tidal structures from the composite CHAMP occultation data, and the vertical, seasonal, and latitudinal structures of the diurnal tide are presented. The estimated diurnal amplitude generally increases with altitude, exhibiting a maximum of order 1 K at 30 km. The estimated phase indicates an upward propagating mode above 14 km with a vertical wavelength about 20 km. The observed diurnal tide at 30 km exhibits a distinct seasonal‐latitudinal variation. Comparison of the observed diurnal tide to the simulated tide in the extended Canadian Middle Atmosphere Model (CMAM) and Global‐Scale Wave Model Version 2 (GSWM02) indicates that CMAM overestimates the amplitude but reproduces the seasonal‐latitudinal variation of the diurnal tide while GSWM02 simulates well the annual mean amplitude but lacks the seasonal‐latitudinal variation of the diurnal tide.
Composition and origin of the Dewar geochemical anomaly
Authors: Lawrence Samuel J. , Hawke B. Ray , Gillis‐Davis Jeffrey J. , Taylor G. Jeffrey , Lawrence David J. , Cahill Joshua T. , Hagerty Justin J. , Lucey Paul G. , Smith Gregory A. , Keil Klaus
Published: February 2008

Dewar crater is a 50‐km diameter impact structure located in the highlands northwest of the South Pole–Aitken basin on the lunar farside. A low‐albedo area with enhanced Th and Sm values is centered east‐northeast of Dewar crater. This area also exhibits elevated FeO abundances (9.0–16.6 wt %) and TiO2 values (0.6–2 wt %). The range of FeO and TiO2 abundances determined for the darkest portions of the geochemical anomaly overlap the range of FeO and TiO2 values determined for nearside mare basalt deposits. Analysis of Clementine spectra obtained from the darkest portions of the Dewar geochemical anomaly indicates that the low‐albedo materials contain large amounts of high‐Ca clinopyroxene consistent with the presence of major amounts of mare basalt. Cryptomare deposits have played an important role in the formation of the Dewar geochemical anomaly. The evidence indicates that buried basalt, or cryptomare, was excavated from depth during impact events that formed dark‐haloed craters in the region. We show that an early Imbrian‐ or Nectarian‐age, low‐TiO2 mare basalt deposit with enhanced Th concentrations (6–7 μg/g) exists in the Dewar region. This ancient mare unit was buried by ejecta from Dewar crater, creating a cryptomare. Although most mare units on the central farside of the Moon exhibit low Th abundances, the enhanced Th values associated with the Dewar cryptomare deposit indicate that at least some portions of the underlying lunar interior (mantle and crust) on the farside of the Moon were not Th poor.
Capturing the influence of groundwater dynamics on land surface processes using an integrated, distributed watershed model
Authors: Kollet Stefan J. , Maxwell Reed M.
Published: February 2008

The influence of groundwater dynamics on the energy balance at the land surface is studied using an integrated, distributed watershed modeling platform. This model includes the mass and energy balance at the land surface; three‐dimensional variably saturated subsurface flow; explicit representation of the water table; and overland flow. The model is applied to the Little Washita watershed in Central Oklahoma, USA and compared to runoff, soil moisture and energy flux observations. The connection between groundwater dynamics and the land surface energy balance is studied using a variety of conventional and spatial statistical measures. For a number of energy variables a strong interconnection is demonstrated with water table depth. This connection varies seasonally and spatially depending on the spatial composition of water table depth. A theoretical critical water table depth range is presented where a strong sensitivity between groundwater and land‐surface processes may be observed. For this particular watershed, a critical depth range is established between 1 and 5 m in which the land surface energy budget is most sensitive to groundwater storage. Finally, concrete recommendations are put forth to characterize this interconnection in the field.
Allicin from garlic suppresses TNF-α and augments IFN-γ expressions in monocyte cultures from patients with Vaginitis
Authors: Islam Najmul , Iqbal Jawed , Hasan Nazarul , Fatima Zeeshan , Thakur Hamida , Hasan Nazia , Mahdi Abbas Ali , Khan Tamkin , Bano Farzana , Ansari Irfan Ahmad
Published: February 2008

Objective:

We tried to explore beneficial effects of allicin- a natural antioxidant from garlic in the possible management of vaginitis. Methods: Peripheral blood mononuclear cells (PBMC’s) were isolated from blood of patients having vaginal infections as well as normal healthy subjects as per our published protocol. Monocytes (MN’s) from above PBMC’s were adhered, rested overnight and cultured without or with varying doses of allicin (0-500 ng/ml). Some cultures received SN50 and SN50M (100 ug/ml). After 24 hrs cultures, the cells were harvested and the supernatants subjected to secreted TNF-α and sIFN-γ assays by ELISA. Treated/untreated harvested cells were subjected to glutathione peroxidase (GPx) activity assay.

Results:

We show involvement of inflammatory cytokines and reactive oxygen species (ROS) in vaginitis. Augmented secreted TNF-α and decreased sIFN-γ levels were observed in monocyte cultures of vaginal patients. Relative to healthy controls, a decrease by 2.5-fold in glutathione peroxidase (GPx) activity in cultures of vaginal patients was observed. Treatment with allicin from garlic appreciably decreased secreted TNF-α with simultaneous amelioration in sIFN-γ and GPx activity. Allicin (500 ng/ml) ameliorated GPx activity by ~ 2.16-folds in patient monocyte cultures. The anti-oxidant and anti-inflammatory actions of allicin induced in monocyte cultures of vaginal infection patients were mediated via NF-κB.

Conclusion:

Thus, the above results may help in understanding the use of allicin as an adjunct in vaginal infection therapy, and in turn, may address the globally female health.
Azadirachta indica induced suppression of Mycobacterium tuberculosis secreted proteins in human monocyte
Authors: Iqbal Jawed , Kumar Ajay , Islam Najmul
Published: February 2008

The H37Rv strain of MTB was grown in modified Sauton’s medium till mid-log phase. Peripheral blood mononuclear cells (PBMC) were isolated by density gradient sedimentation on Ficoll-Paque separation medium. Adherent monocytes obtained from PBMC’s were infected with H37Rv for 90 min. in the ratio of 1:1 (1 bug: 1 cell). Thereafter, after washing, infected cells were co-cultured with varying doses of neem extract for 24 hrs, and harvested subsequently. Modulation of secreted TNF-[alpha], iNOS and MTB Ag85 complex expressions in culture supernatants was estimated by ELISA.We report the high basal expression of secreted tumor necrosis factor-[alpha] (TNF-[alpha]), inducible nitric oxide synthase (iNOS) and MTB Ag85 complex in MTB-infected monocytes was suppressed by neem extract in a dose-dependent manner (P<0.001 for all). A concentration of 1ug/ml of neem extract showed a suppression by ~ 2.5-fold (P<0.001), 1.7-fold (P<0.001) and 1.8-fold (P<0.001) in the expressions ofsecreted TNF-[alpha], iNOS and MTB Ag85 respectively in 24 hr culture supernatants of MTB-infected monocytes.Thus, neem extract seems to be a potential future adjunct for in-depth studies in the management of tuberculosis.
Vascular effects of adiponectin: molecular mechanisms and potential therapeutic intervention
Authors: Zhu Weidong , Cheng Kenneth K. Y. , Vanhoutte Paul M. , Lam Karen S. L. , Xu Aimin
Published: February 2008

Adiponectin is a major adipocyte-secreted adipokine abundantly present in the circulation as three distinct oligomeric complexes. In addition to its role as an insulin sensitizer, mounting evidence suggests that adiponectin is an important player in maintaining vascular homoeostasis. Numerous epidemiological studies based on different ethnic groups have identified adiponectin deficiency (hypoadiponectinaemia) as an independent risk factor for endothelial dysfunction, hypertension, coronary heart disease, myocardial infarction and other cardiovascular complications. Conversely, elevation of circulating adiponectin concentrations by either genetic or pharmacological approaches can alleviate various vascular dysfunctions in animal models. Adiponectin exerts its vasculoprotective effects through its direct actions in the vascular system, such as increasing endothelial NO production, inhibiting endothelial cell activation and endothelium–leucocyte interaction, enhancing phagocytosis, and suppressing macrophage activation, macrophage-to-foam cell transformation and platelet aggregation. In addition, adiponectin reduces neointima formation through an oligomerization-dependent inhibition of smooth muscle proliferation. The present review highlights recent research advances in unveiling the molecular mechanisms that underpin the vascular actions of adiponectin and discusses the potential strategies of using adiponectin or its signalling pathways as therapeutic targets to combat obesity-related metabolic and vascular diseases.
Theoretical investigation of C56 fullerene isomers and related compounds
Authors: Chen De-Li , Tian Wei Quan , Feng Ji-Kang , Sun Chia-Chung
Published: February 2008

All the 924 classical isomers of fullerene C56 have been investigated by PM3, and some most stable isomers are refined with HCTH/3-21G and B3LYP∕6-31G(d) methods. D2:003 with the least number of adjacent pentagons is predicted to be the most stable isomer at B3LYP∕6-31G(d) level, while Cs:022 and C2:049 possess nearly degenerate energies with relative energies of 0.03 and 3.90kcal∕mol, respectively. However, as to dianionic C562− fullerene, C2v:011 is predicted to be the most stable isomer. Investigations also show that the encapsulation of Ca atom in C56 fullerene is exothermic and the metallofullerenes Ca@C56 can be described as Ca2+@C562−. The computed relative stabilities show that the D2:003 behaves more thermodynamically stable than other isomers in a wide temperature interval, and C2v:011 should also be an important component. The electronic isomerization of C56 (C2v:011) and C50 (D5h:002) indicates that this phenomenon might be rather general in fullerenes and causes different properties, thus bringing about new possible applications of fullerenes. The static second-order hyperpolarizabilities of the three most stable isomers are slightly larger than that of C60.
MPSA effects on copper electrodeposition investigated by molecular dynamics simulations
Authors: Guymon Clint G. , Harb John N. , Rowley Richard L. , Wheeler Dean R.
Published: February 2008

In superconformal filling of copper-chip interconnects, organic additives are used to fill high-aspect-ratio trenches or vias from the bottom up. In this study we report on the development of intermolecular potentials and use molecular dynamics simulations to provide insight into the molecular function of an organic additive (3-mercaptopropanesulfonic acid or MPSA) important in superconformal electrodeposition. We also investigate how the presence of sodium chloride affects the surface adsorption and surface action of MPSA as well as the charge distribution in the system. We find that NaCl addition decreases the adsorption strength of MPSA at a simulated copper surface and attenuates the copper-ion association with MPSA. The model also was used to simulate induced-charge effects and adsorption on a nonplanar electrode surface.
Electric quadrupole polarizabilities of nuclear magnetic shielding in some small molecules
Authors: Ferraro M. B. , Caputo M. C. , Pagola G. I. , Lazzeretti P.
Published: February 2008

Computational procedures, based on (i) the Ramsey common origin approach and (ii) the continuous transformation of the origin of the quantum mechanical current density-diamagnetic zero (CTOCD-DZ), were applied at the Hartree-Fock level to determine electric quadrupole polarizabilities of nuclear magnetic shielding for molecules in the presence of a nonuniform electric field with a uniform gradient. The quadrupole polarizabilities depend on the origin of the coordinate system, but values of the magnetic field induced at a reference nucleus, determined via the CTOCD-DZ approach, are origin independent for any calculations relying on the algebraic approximation, irrespective of size and quality of the (gaugeless) basis set employed. On the other hand, theoretical estimates of the induced magnetic field obtained by single-origin methods are translationally invariant only in the limit of complete basis sets. Calculations of electric quadrupole polarizabilities of nuclear magnetic shielding are reported for H2, HF, H2O, NH3, and CH4 molecules.
A method to reduce the size of the vibronic basis employed in the simulation of spectra using the multimode vibronic coupling approximation
Authors: Schuurman Michael S. , Yarkony David R.
Published: February 2008

In the time-independent multimode approach for the determination of vibronic spectra involving strongly coupled electronic states, the equilibrium geometry and normal modes of the reference or precursor state are usually employed as the basis for the multimode expansion. This basis, while easily constructed, is generally ill-suited for determining the eigenstates of the observed species. Employing a more computationally effective basis requires the evaluation of Franck-Condon overlap integrals. Using established generalized Hermite polynomial generating function formalisms, an algorithm is developed that can efficiently determine the enormous requisite number of these overlap integrals. It is found that this flexibility in the choice of multimode basis can significantly reduce the size of the basis needed to obtain converged spectral simulations. The previously reported spectrum of the ethoxy (C2H5O) radical serves as an example of the efficacy of the new technique.