bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of chlorpyrifos and its metabolites in rat brain tissue using coupled‐column liquid chromatography/electrospray ionization tandem mass spectrometry
Authors: Williamson Leah N. , Terry Alvin V. , Bartlett Michael G.
Published: August 2006

A method has been developed to quantify chlorpyrifos (O,O‐diethyl‐O‐[3,5,6,‐trichloro‐2‐pyridyl] phosphorothionate) and its metabolites chlorpyrifos‐oxon (O,O‐diethyl‐O‐[3,5,6,trichloro‐2‐pyridinyl] phosphate) and TCP (3,5,6,‐trichloro‐2‐pyridinol) in rat brain tissue by coupled‐column liquid chromatography/electrospray ionization tandem mass spectrometry (LC/LC/ESI‐MS/MS). Rat brains were homogenized and treated by protein precipitation using ice‐cold acetonitrile. The supernatant was directly injected onto the coupled‐column system. Sample clean‐up was achieved on a Zorbax Extend‐C18 column (2.1 × 50 mm, 5 µm) using a mobile phase of acetonitrile/water with 0.0025% formic acid (40:60, v/v). The compounds were separated isocratically on a Zorbax Eclipse XDB C8 column (2.0 × 150 mm, 5 µm) using a mobile phase of acetonitrile/water with 0.0025% formic acid (75:25, v/v). Chlorpyrifos and chlorpyrifos‐oxon were detected in positive ion mode using multiple reaction monitoring (MRM). TCP was detected in negative ion mode using precursor‐to‐precursor transition monitoring. The method was validated and the specificity, linearity, limit of quantitation (LOQ), precision, accuracy, stability, and recoveries were determined. Calibration curves for all three analytes yielded correlation coefficients of 0.993 or greater. The LOQs were 25.3 ng/g for chlorpyrifos and 6.3 ng/g for chlorpyrifos‐oxon and TCP. All precision relative standard deviations (RSDs) were less than 16% for the LOQ and less than 11% for the other QC samples. This method was successfully applied to six rats that were injected subcutaneously with chlorpyrifos. Copyright © 2006 John Wiley & Sons, Ltd.
Desorption electrospray ionisation mass spectrometry and tandem mass spectrometry of low molecular weight synthetic polymers
Authors: Jackson Anthony T. , Williams Jonathan P. , Scrivens James H.
Published: August 2006

A range of low molecular weight synthetic polymers has been characterised by means of desorption electrospray ionisation (DESI) combined with both mass spectrometry (MS) and tandem mass spectrometry (MS/MS). Accurate mass experiments were used to aid the structural determination of some of the oligomeric materials. The polymers analysed were poly(ethylene glycol) (PEG), polypropylene glycol (PPG), poly(methyl methacrylate) (PMMA) and poly(α‐methyl styrene). An application of the technique for characterisation of a polymer used as part of an active ingredient in a pharmaceutical tablet is described. The mass spectra and tandem mass spectra of all of the polymers were obtained in seconds, indicating the sensitivity of the technique. Copyright © 2006 John Wiley & Sons, Ltd.
Physiological stress reactions in 6th and 9th graders during test performance
Authors: Lindblad Frank , Lindahl Mats , Theorell Töres , von Scheele Bo
Published: August 2006

Forty‐six randomly selected 6th and 9th graders volunteered for an extra‐curricular school test (relaxation–reading–relaxation–mathematics–relaxation) with simultaneous registration of heart rate, peripheral vasoconstriction, oxygen saturation, respiratory rate, exhalation carbon dioxide (CO2) and CO2 in residual expiratory air. Results were compared with previously reported saliva cortisol levels before and after test.

Oxygen saturation before test was higher than on all other occasions. A successive increase in peripheral vasoconstriction was observed. Comparisons were made between students, sensitive to test performance stress (worry group) and the others. The worry group showed a higher level of peripheral vasoconstriction through the whole test procedure. During reading the worry group showed decreased peripheral vasoconstriction.

There was a positive correlation between oxygen saturation during mathematics test and cortisol levels after test situation.

Oxygen saturation is not an easily interpreted stress indicator, since it reflects increased saturation due to anticipated demands as well as increased consumption due to increased efforts imposed by the stressors. At certain key points of time and at group comparisons, however, illustrative changes may be observed. Peripheral vasoconstriction, however, seems to reflect the on‐going demands in a more easily interpreted way as a response to continued sympathetic activation. Copyright © 2006 John Wiley & Sons, Ltd.
The association between peritraumatic dissociation and acute stress reactions among rescue personnel 36–48h after a gas pipe explosion in Tel‐Aviv: a preliminary report
Authors: Ben‐Ezra Menachem , Essar Nir , Saar Ronen
Published: August 2006

The association between peritraumatic dissociation and acute stress reactions were examined among rescue personnel 36–48h after exposure to a gas pipe explosion resulting in a collapsed building in Tel Aviv. The entire rescue personnel were examined for peritraumatic dissociation and acute stress reactions. The results showed that among men there was a negative association between peritraumatic dissociation and acute stress reactions. Among women, there was a positive association between peritraumatic dissociation and acute stress reactions. These results correspond with previous studies that found an association between peritraumatic dissociation and acute stress reactions. Explanations to these results are discussed. Copyright © 2006 John Wiley & Sons, Ltd.
Energetic and developmental costs of mounting an immune response in greenfinches (Carduelis chloris)
Authors: Amat Juan A. , Aguilera Eduardo , Visser G. Henk
Published: August 2006

It is assumed that there is a trade‐off between the costs allocated to mounting an immune defence and those allocated to costly functions such as breeding and moulting. The physiological basis for this is that mounting an immune response to pathogen challenge has energetic and/or nutrient costs which may interfere with metabolic processes of the challenged individual. If the energetic costs of mounting an immune response are not too high, animals may face such costs by increasing their acquisition of food energy, suggesting that limited nutrients may be responsible for the costs of immune defence. We assessed the energetic and developmental costs of mounting an immune response in an experiment in captivity with first‐year greenfinches (Carduelis chloris) challenged with sheep red blood cells and Brucella abortus. Antibody production against both antigens increased the daily energy expenditure (4.7%) of immune‐challenged birds relative to control birds, although the difference was non‐significant. We estimated that the maximum effect size supported by the data would be 9.9% higher in immune‐challenged birds relative to control birds. We plucked the two outermost rectrices of each bird to assess the effects of the immune challenge on growth of the regenerated feathers. The immune challenge had no significant effect on the length of the regenerated rectrices. However, these feathers were more asymmetric in length in immune‐challenged birds than in control birds. Although first‐year male greenfinches paid a relatively low energetic cost when mounting an immune response, we suggest that immune‐challenged individuals may have paid some costs over the long term based on the increased fluctuating asymmetry in the developing feathers.
The reaction of neuroglobin with potential redox protein partners cytochrome b5 and cytochrome c
Authors: Fago Angela , Mathews Antony J. , Moens Luc , Dewilde Sylvia , Brittain Thomas
Published: August 2006

Previously identified, potentially neuroprotective reactions of neuroglobin require the existence of yet unknown redox partners. We show here that the reduction of ferric neuroglobin by cytochrome b
5 is relatively slow (k
= 6 × 102
M−1
s−1 at pH 7.0) and thus is unlikely to be of physiological significance. In contrast, the reaction between ferrous neuroglobin and ferric cytochrome c is very rapid (k
= 2 × 107
M−1
s−1) with an apparent overall equilibrium constant of 1 μM. Based on this data we propose that ferrous neuroglobin may well play a role in preventing apoptosis.
Retracted: Selective modulation of the CAP/Cbl pathway in the adipose tissue of high fat diet treated rats
Authors: Prada Patrícia Oliveira , Pauli José Rodrigo , Ropelle Eduardo Rochete , Zecchin Henrique Gottardello , Carvalheira José Barreto Campello , Velloso Lício Augusto , Saad Mario José Abdalla
Published: August 2006

A high‐fat diet (HFD) is associated with reduced glucose uptake in muscle, but not in adipose tissue. In the present study, we investigated whether a HFD can modulate glucose uptake in adipose tissue by increasing signal transduction through the CAP/Cbl pathway, independently of the PI3‐K/Akt pathway. Our results suggest that, in HFD, the differential regulation of insulin‐induced glucose uptake between skeletal muscle and adipose tissue may, in part, be a consequence of the CAP/Cbl/C3G pathway, since the expression of CAP and Cbl, and also the activation of this pathway were increased in adipose tissue but not in muscle.
Human resources and access to maternal health care
Authors: ten Hoope‐Bender P. , Liljestrand J. , MacDonagh S.
Published: August 2006

The lack of human resources is one of the main bottlenecks to achieving the Millennium Development Goals on maternal and child health. A coherent national policy, recognized across government, needs to be in place to overcome this especially in countries severely affected by HIV/AIDS. Such a policy should cover selection of pre‐service students, the qualifications of trainers and training sites, supportive supervision, career path development, a package of carefully thought‐out incentives for the retention of staff, strategies for interaction with communities, and an agreed‐upon health staff HIV/AIDS policy. Without such coherent human resource planning, a large number of countries will fail to reduce maternal and newborn mortality.
Remission and relapse in psychosis: operational definitions based on case-note data
Authors: BEBBINGTON PAUL E. , CRAIG TOM , GARETY PHILIPPA , FOWLER DAVID , DUNN GRAHAM , COLBERT SUSANNAH , FORNELLS-AMBROJO MIRIAM , KUIPERS ELIZABETH
Published: August 2006

Background. In psychosis, the prime indicator of outcome has been relapse, but hospital readmission can no longer be used for this purpose. Researchers now require methods for assessing relapse that are objective, blind, reliable and valid. We describe the reliability and validity of such a technique using case-notes.

Method. Information from routine clinical notes of participants in the Lambeth Early Onset (LEO) study (less all references that would unblind the assessor) were recorded on a form divided into 1-month sections. Operational definitions of remission and relapse enabled clinicians to identify remissions and relapses blindly from the summary information. We calculated reliability regarding both the fact and the timing of remission and relapse. PANSS ratings at 6 and 18 months provided a measure of validity.

Results. The kappa value for the identification of remission by individuals ranged from 0·64 to 0·82, while that for consensus between paired raters was 0·56. The corresponding values for relapse were 0·57–0·59 and 0·71. Intra-class correlations for time to remission and to relapse were very high. Raters guessed correctly whether the participants came from the intervention or control group on 60–75% of occasions. Independent PANSS ratings were strongly related to the remission/relapse status of participants.

Conclusions. The reliability of the technique described here was moderate to good, its validity was good, and it provides a useful and timely addition to methods of evaluating remission and relapse in psychosis. On the basis of our experience, we recommend consensus rather than individual ratings.
Localization Effect on the Metal Biosorption Capability of Recombinant Mammalian and Fish Metallothioneins in Escherichia coli
Authors: Kao Wei‐Chen , Chiu Yao‐Pang , Chang Chia‐Che , Chang Jo‐Shu
Published: August 2006

In this study, we examined the expression of mammalian and fish metallothioneins (MTs) in Escherichia coli as a strategy to enhance metal biosorption efficiency of bacterial biosorbents for lead (Pb), copper (Cu), cadmium (Cd), and zinc (Zn). In addition, MT proteins were expressed in either the cytoplasmic or periplasmic compartment of host cells to explore the localization effect on metal biosorption. The results showed that MT expression led to a significant increase (5–210%) in overall biosorption efficiency (ηads), especially for biosorption of Cd. The MT‐driven improvement in metal biosorption relied more on the increase in the biosorption rates (r2, a kinetic property) than on the equilibrium biosorption capacities (qmax, a thermodynamic property), despite a 10–45% and 30–80% increase in qmax of Cd and Zn, respectively. Periplasmic expression of MTs appeared to be more effective in facilitating the metal‐binding ability than the cytoplasmlic MT expression. Notably, disparity of the impacts on biosorption ability was observed for the origin of MT proteins, as human MT (MT1A) was the most effective biosorption stimulator compared to MTs originating from mouse (MT1) and fish (OmMT). Moreover, the overall biosorption efficiency (ηads) of the MT‐expressing recombinant biosorbents was found to be adsorbate‐dependent: the ηads values decreased in the order of Cd > Cu > Zn > Pb.
Effect of Temperature and High Pressure on the Activity and Mode of Action of Fungal Pectin Methyl Esterase
Authors: Duvetter Thomas , Fraeye Ilse , Sila Daniel N. , Verlent Isabel , Smout Chantal , Clynen Elke , Schoofs Liliane , Schols Henk , Hendrickx Marc , Van Loey Ann
Published: August 2006

Pectin was de‐esterified with purified recombinantAspergillus aculeatuspectin methyl esterase (PME) during isothermal‐isobaric treatments. By measuring the release of methanol as a function of treatment time, the rate of enzymatic pectin conversion was determined. Elevated temperature and pressure were found to stimulate PME activity. The highest rate of PME‐catalyzed pectin de‐esterification was obtained when combining pressures in the range 200–300 MPa with temperatures in the range 50–55 °C. The mode of pectin de‐esterification was investigated by characterizing the pectin reaction products by enzymatic fingerprinting. No significant effect of increasing pressure (300 MPa) and/or temperature (50 °C) on the mode of pectin conversion was detected.
Recent sediment accumulation and carbon burial in the East China Sea
Authors: Deng Bing , Zhang Jing , Wu Ying
Published: August 2006

Sediment and carbon budgets were constructed for the East China Sea (ECS) Shelf based on up‐to‐date data. The total annual sediment flux in the ECS Shelf is approximately 96% of the terrestrial input. There is high retention of sediment on the ECS Shelf owing to the broad nature of the shelf edge (i.e., 500–600 km) and because of an along‐shore sediment dispersal path driven by the East China Sea Coastal Current (ECSCC) and the Taiwan Warm Current (TWC). Organic carbon (OC) burial was also observed, based on the results for sediment accumulation and the OC proportion in surface sediment. A total of 7.4 × 106 t of OC is preserved in shelf sediments. Source discrimination of sedimentary OC revealed that the percentage of OC burial for both terrigenous and marine OC sources was higher than the global mean value, at 10% and 5.5%, respectively, presumably owing to high sediment accumulation. High OC flux to sediment in the estuary and shelf break suggests that riverine discharge and upwelling of the Kuroshio intrusion are key factors regulating OC burial over the shelf. Estimated using a mass balance model, 15–20% of the carbon inventory is buried in the shelf sediment, while >80% of the carbon inventory must be transported out of shelf area in the form of dissolved carbon (organic and inorganic). The accumulation of carbon in sediments and the outflow of dissolved carbon sustain a high carbon sink in the ECS.
Structure and dynamics of a new class of thin current sheets
Authors: Sitnov M. I. , Swisdak M. , Guzdar P. N. , Runov A.
Published: August 2006

New results on a steady state Vlasov theory of current sheets, which generalizes the Harris (1962) model by assuming anisotropic and nongyrotropic plasmas and using the invariant of particle motion in regions of strong gradients, are presented with the aim to explain multiprobe observations of thin current sheets in the geomagnetotail and laboratory experiments, including the effects of current sheet embedding and bifurcation. The dynamics of these sheets is explored using a full particle code with more realistic mass ratio and anisotropy parameters than those used in our earlier works. The results relevant to 2001 CLUSTER observations, with the sheet thickness appreciably exceeding the thermal ion gyroradius, include ion distributions and pressure tensor components, which reveal the important role of nongyrotropic effects on the structure of these sheets. Their flapping motions are distinguished by north‐south asymmetry of current profiles, quasi‐rectangular shape of the flapping waves, and their small propagation speed, suggesting an explanation of their propagation toward the flanks of the tail sheet. The main effect of the ion anisotropy on the sheets with thickness less than the thermal ion gyroradius, relevant to 2003 CLUSTER observations and laboratory experiments, is their charging, which may limit their minimum thickness, while their structure can be modified by electron anisotropy. Other distinctive features of these sheets are three‐peaked current density profiles, found both in simulations and in the steady state theory, the north‐south asymmetry of flapping sheets, and the shape of flapping waves, which is drastically different from the case of thicker sheets.
The rise and fall of axial highs during ridge jumps
Authors: Shah Anjana K. , Buck W. Roger
Published: August 2006

We simulate jumps of ocean spreading centers with axial high topography using elastoplastic thin plate flexure models. Processes considered include ridge abandonment, the breaking of a stressed plate on the ridge flank, and renewed spreading at the site of this break. We compare model results to topography at the East Pacific Rise between 15°25′N and 16°N, where there is strong evidence of a recent ridge jump. At an apparently abandoned ridge, gravity data do not suggest buoyant support of topography. Model deflections during cooling and melt solidification stages of ridge abandonment are of small vertical amplitude because of plate strengthening, resulting in the preservation of a “frozen” fossil high. The present‐day high is bounded by slopes with up to a 40% grade, a scenario very difficult to achieve flexurally given generally accepted constraints on lithospheric strength. We model these slopes by assuming that the height at which magma is accreted increases rapidly after the ridge jumps. This increase is attributed to high overburden pressure on melt that resided in an initially deep magma chamber, followed by a rapid increase in temperature and melt supply to the region shortly after spreading began. The high is widest at the segment center, suggesting that magmatic activity began near the center of the segment, propagated south and then north. The mantle Bouguer anomaly exhibits a “bull's‐eye” pattern centered at the widest part of the high, but the depth of the axis is nearly constant along the length of the segment. We reconcile these observations by assigning different cross‐axis widths to a low‐density zone within the crust.
Modeling the isotopic composition of Antarctic snow using backward trajectories: Simulation of snow pit records
Authors: Helsen M. M. , van de Wal R. S. W. , van den Broeke M. R. , Masson‐Delmotte V. , Meijer H. A. J. , Scheele M. P. , Werner M.
Published: August 2006

The quantitative interpretation of isotope records (δ18O, δD, and d excess) in ice cores can benefit from a comparison of observed meteorology with associated isotope variability. For this reason we studied four isotope records from snow pits in western Dronning Maud Land (DML), Antarctica, covering the period 1998–2001. Timing and magnitude of snowfall events on these locations were monitored using sonic height rangers. For the distinguished snowfall events we evaluated the isotopic composition of the moisture during transport by combining backward trajectory calculations with isotopic modeling, using a Rayleigh‐type distillation model (MCIM). The initial isotope ratio of the moisture was determined from monthly mean isotope fields from a general circulation model (ECHAM4). The trajectory analysis showed that the southern Atlantic Ocean is the major moisture source for precipitation in DML. Modeling results along the trajectories revealed that most of the isotopic depletion occurred during the last day of the transport. Finally, a diffusion model was applied to describe the diffusion in the firn layer such that the modeled isotopes could be compared with the observed isotope records. The resulting modeled isotope profiles were mostly in good agreement with the observed seasonal variability in the snow. However, at low temperatures (especially on the Antarctic interior), magnitude of the total distillation was underestimated. Regarding the d excess parameter, our results show a large influence of advection height on the final value of d excess in precipitation. This in turn points to the importance of the vertical structure of d excess over the oceanic source region, which obscures the classical interpretation of this parameter in terms of temperature and relative humidity in the moisture source region.
Partitioning of HNO3 and particulate nitrate over Tokyo: Effect of vertical mixing
Authors: Morino Y. , Kondo Y. , Takegawa N. , Miyazaki Y. , Kita K. , Komazaki Y. , Fukuda M. , Miyakawa T. , Moteki N. , Worsnop D. R.
Published: August 2006

Ground‐based measurements of gas‐phase nitric acid (HNO3) and particulate nitrate (NO3−) were performed in Tokyo during 2003–2004. These measurements provide a comprehensive data set for investigating the diurnal and seasonal variations of gas‐phase HNO3 and particulate NO3− and the thermodynamic equilibrium of these compounds. HNO3 and NO3− have distinct diurnal and seasonal variations, especially in summer. This study shows that the thermodynamic equilibrium of HNO3 and NO3− and the production rate of total nitrate (TNO3 = HNO3 + NO3−) are the major controlling factors affecting these seasonal and diurnal variations. A thermodynamic equilibrium model (ISORROPIA) is newly coupled with a one‐dimensional (1‐D) model to take into account the effect of vertical mixing during daytime on the partitioning of HNO3 and NO3− by constraining the TNO3 concentrations to the observations. The 1‐D model reproduces the NO3−/TNO3 ratios observed during daytime, whereas the equilibrium model significantly underestimates these ratios. The agreement between the observed and calculated NO3−/TNO3 ratios is improved over the observed temperature range (1°–34°C) and relative humidity (18–95%) by the 1‐D model. These results suggest the importance of vertical mixing in determining HNO3‐NO3− partitioning in the boundary layer. It is also found that the mass accommodation coefficient for HNO3 needs to be approximately 0.1 to explain the observed HNO3‐NO3− partitioning at the surface.
Evidence of multidecadal salinity variability in the eastern tropical North Atlantic
Authors: Moses Christopher S. , Swart Peter K. , Rosenheim Brad E.
Published: August 2006

Ocean circulation and global climate are strongly influenced by seawater density, which is itself controlled by salinity and temperature. Although adequate instrumental sea surface temperature (SST) records exist for most of the surface oceans over the past 100–150 years, records of salinity really only exist for the last 40–50 years. Here we show that longer proxy records from corals (Siderastrea radians) in the eastern tropical North Atlantic are dominated by multidecadal variations in salinity which are correlated with the relationship between SST and the North Atlantic Oscillation (NAO) over the course of the 20th century. The data reveal an increase in eastern tropical North Atlantic salinity of +0.5 practical salinity units (psu) between about 1950 and 1990. Rather than a monotonic secular increase, as indicated by some instrumental records, the preinstrumental coral proxy records presented here suggest that salinity in the tropical North Atlantic is periodic on a decadal to multidecadal scale.
Real‐time HF ray tracing through a tilted ionosphere
Authors: Huang Xueqin , Reinisch Bodo W.
Published: August 2006

High‐frequency (HF) direction‐finding (DF) systems measure the angles of arrival of signals at selected frequencies. With this information, ray tracing can accurately determine the location of the HF transmitters if the three‐dimensional (3‐D) electron density (Ne) distribution between the DF site and the transmitters is known. The usual approach is to use an ionospheric model like the International Reference Ionosphere (IRI) as a proxy for the density distribution. We describe a more realistic approach developed in cooperation with Codem Systems in Merrimack, New Hampshire. A collocated digisonde at the DF site measures the vertical electron density profile and the local ionospheric tilt, providing, in real time, the inputs for the construction of the 3‐D Ne distribution. The vertical profile is automatically obtained from the Automated Real Time Ionogram Scaler with True Height (ARTIST)‐scaled ionogram and the local tilt from the sky maps recorded after each ionogram. The characteristics of each layer, for example, critical frequencies and peak heights, are expressed as a function of latitude λ and longitude Ψ. In the neighborhood of the DF site each characteristic, for example, foF2, is given as foF2(λ, Ψ) = foF2m (1 + C7Δλ + C8ΔΨ) (1 + CλΔλ + CΨΔΨ). The coefficients C7 and C8 for any given azimuth direction are determined with the use of the Union Radio Scientifique Internationale/CCIR coefficients (which are also used in IRI), and the calculation of Cλ and CΨ makes use of the measured ionospheric tilt data; foF2m is the local, measured foF2 value. When the measured density profile and tilt data are available, the derived 3‐D density distribution represents the instantaneous ionosphere structure near the site. The numerical ray tracing includes the effects of the magnetic field and properly treats the spitze effect, making the ray‐tracing program especially useful for small distances. Ray tracing through simulated tilts shows that the differences in ground distances for one‐hop high‐frequency (HF) propagation vary from about 1 to 100 km depending on the assumed tilts and distances. Operational tests for distances up to approximately 100 km have demonstrated good results in determining the transmitter location in real time and have illustrated the importance of using the actual ionospheric profiles and tilts in the ray tracing.
Polarization of elliptic E region plasma irregularities and implications for coherent radar backscatter from Farley‐Buneman waves
Authors: Hysell D. L. , Drexler J.
Published: August 2006

The problem of two‐dimensional, homogeneous, elliptical irregularities in an otherwise homogeneous plasma with anisotropic conductivity is considered. We find an analytic solution for the potential inside and outside the irregularities. In the special case of circular irregularities, the internal electric field is reduced from the background field in both depletions and enhancements. The internal field is rotated in different directions for depletion and enhancements, however. When the irregularity is elongated, the electric field inside can be larger or smaller than the background field in both depletions and enhancements, depending on the attack angle of the background field. The effects of ion inertia can further suppress the internal electric field in small‐scale circular irregularities. These electrodynamics considerations may help explain some aspects of radar observations of irregularities excited by Farley‐Buneman waves and instabilities in the electrojets, in particular, their tendency to exhibit Doppler shifts significantly smaller than the line‐of‐sight background electron convection speed and proportional to the cosine of the flow angle. The analysis generalizes that of St.‐Maurice and Hamza (2001), who introduced this avenue of investigation.
Front dynamics of supercritical non‐Boussinesq gravity currents
Authors: Ancey C. , Cochard S. , Wiederseiner S. , Rentschler M.
Published: August 2006

In this paper, we seek similarity solutions to the shallow water (Saint‐Venant) equations for describing the motion of a non‐Boussinesq, gravity‐driven current in an inertial regime. The current is supplied in fluid by a source placed at the inlet of a horizontal plane. Gratton and Vigo (1994) found similarity solutions to the Saint‐Venant equations when a Benjamin‐like boundary condition was imposed at the front (i.e., nonzero flow depth); the Benjamin condition represents the resisting effect of the ambient fluid for a Boussinesq current (i.e., a small‐density mismatch between the current and the surrounding fluid). In contrast, for non‐Boussinesq currents the flow depth is expected to be zero at the front in absence of friction. In this paper, we show that the Saint‐Venant equations also admit similarity solutions in the case of non‐Boussinesq regimes provided that there is no shear in the vertical profile of the streamwise velocity field. In that case, the front takes the form of an acute wedge with a straight free boundary and is separated from the body by a bore.
The influence of time domain reflectometry rod induced flow disruption on measured water content during steady state unit gradient flow
Authors: Hinnell Andrew C. , Ferré Ty P. A. , Warrick Art W.
Published: August 2006

Intrusive measurement techniques require placing a sensor within the sample, possibly changing the conditions under which the measurement is collected and thereby affecting the quality of the measurement. In this study we consider time domain reflectometry (TDR), which is an intrusive water content measurement method. TDR rods are impermeable, and thus water is forced to flow around the rods. In an unsaturated medium this changes the water content distribution in the vicinity of the rods, with the water content increased at the tops of the rods and decreased at the bottoms of the rods. TDR has nonuniform spatial sensitivity, with much higher sensitivity immediately adjacent to rods, in the regions that experience the greatest change in water content due to this flow disruption. Furthermore, the spatial sensitivity of TDR depends on the water content distribution within the sample volume. This raises the possibility that flow disruptions caused by TDR rods may affect the TDR‐measured water content. In this study we are specifically interested in the effects of flow disruption due to TDR rods. Therefore we consider steady state unit gradient unsaturated flow in a homogeneous medium to eliminate spatial heterogeneity of water content due to soil heterogeneity and transient flow conditions. For common TDR probe designs in the wide range of soils examined, flow disruption gives rise to a water content measurement error that is less than 0.005 cm3 cm−3. This is smaller than the reported accuracy of the TDR method of 0.02 cm3 cm−3. As a result, we conclude that it is appropriate to ignore flow disruption caused by commonly used TDR probes when assessing sources of TDR measurement error.
Carbon monoxide (CO) maximum over the Zagros mountains in the Middle East: Signature of mountain venting?
Authors: Kar Jayanta , Drummond James R. , Jones Dylan B. A. , Liu Jane , Nichitiu Florian , Zou Jason , Gille John C. , Edwards David P. , Deeter Merritt N.
Published: August 2006

We report an intriguing feature observed in daytime measurements of CO over the Middle East, in spring and summer, by the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument. Enhanced CO is observed over the Zagros mountains of Iran, following the local topography over this region (25–40N, 40–60E). The MOPITT averaging kernels do not seem to indicate any data artifacts in this area. We argue that this feature likely forms by the process of mountain venting by thermal winds caused by strong daytime differential heating. This is consistent with an analysis of vertical velocity in the NCEP reanalysis data in this region. The phenomenon was observed in all the years of available MOPITT measurements and may have implications for the pollution episodes in the region and the Middle East ozone maximum that has been observed earlier.
CLUSTER observation of collisionless transport at the magnetopause
Authors: Panov E. V. , Büchner J. , Fränz M. , Korth A. , Savin S. P. , Fornaçon K.‐H. , Dandouras I. , Rème H.
Published: August 2006

On May 10, 2002 the CLUSTER spacecraft (SC) encountered a ∼450 km (five magnetosheath thermal proton gyro‐radii) wide high‐latitude magnetopause (MP). Magnetic field observations indicate the crossing of a ∼130 km thick MP current sheet (CS) located inside a magnetic hole. Proton flux measurements diagnose a dense boundary layer (BL) directly attached to the MP and an additional rare BL located earthwards from the MP. Enhanced magnetic fluctuations are found near the local proton‐cyclotron frequency Ωcp (0.4–2 Hz). Applying the phase‐differencing technique we obtained a wavelength of 150–250 km and the propagating direction earthward perpendicular to the MP. Inside the MP the pitch‐angle proton distribution demonstrates the presence of a transverse population. The formation of the two BLs can be understood by enhanced collisionless diffusion of magnetosheath protons due to wave‐particle interaction, while higher‐energy protons (Wp > 300 eV) penetrate into the BLs also via finite gyro‐radius effect.
Formation of atmospheric H2SO4/H2O particles in the absence of organics: A laboratory study
Authors: Berndt Torsten , Böge Olaf , Stratmann Frank
Published: August 2006

The formation of H2SO4/H2O particles has been investigated in a laboratory study using a flow tube at atmospheric pressure. H2SO4 was produced in situ applying different formation pathways. Experiments performed in the absence of organics as well as those in the presence of selected organics with low concentration yielded nearly the same results indicating that organics are not implicitly needed in the formation process of atmospheric H2SO4/H2O particles. The number of newly formed particles increased with increasing humidity in the range r.h. = 11–60%. Measurements of particle size distributions at r.h. = 42% revealed a mean particle diameter of ∼2 nm for an H2SO4 concentration of ∼107 molecule cm−3 and for a residence time of 290 sec. From the measured fraction of positively and negatively charged particles it was concluded that ion‐mediated nucleation was negligible under the chosen experimental conditions.
A new numerical model of electrokinetic potential response during hydrocarbon recovery
Authors: Saunders J. H. , Jackson M. D. , Pain C. C.
Published: August 2006

We present results from a new numerical model capable of simulating two‐phase flow in a porous medium and the electrical potentials arising due to electrokinetic phenomena. We suggest that, during water‐flood of an initially oil‐filled reservoir, encroaching water causes changes in the electrokinetic potential at the production well which could be resolved above background electrical noise; indeed, water approaching the well could be detected several 10's to 100's of meters away. The magnitude of the measured potential depends upon the production rate, the coupling between fluid and electrical potentials, and the nature of the front between the displaced oil and the displacing water.
Reexamination of instrument change effects in the U.S. Historical Climatology Network
Authors: Hubbard K. G. , Lin X.
Published: August 2006

The homogenized U.S. Historical Climatology Network (HCN) data set contains several statistical adjustments. One of the adjustments directly reflects the effect of instrument changes that occurred in the 1980s. About sixty percent of the U.S. HCN stations were adjusted to reflect this instrument change by use of separate constants applied universally to the monthly average maximum and minimum temperatures regardless of month or location. To test this adjustment, this paper reexamines the effect of instrument change in HCN using available observations. Our results indicate that the magnitudes of bias due to the instrument change at individual stations range from less than −1.0°C to over +1.0°C and some stations show no statistical discontinuities associated with instrument changes while others show a discontinuity for either maximum or minimum but not for both. Therefore, the universal constants to adjust for instrument change in the HCN are not appropriate.
Simulatory effect of porcine insulin on noradrenaline secretion in guinea‐pig ileum myenteric nerve terminals
Authors: Cheng Juei‐Tang , Hung Chen‐Road , Lin Ming‐I
Published: August 2006

The effect of insulin on the release of noradrenaline (NA) from nerve terminals was investigated in isolated ileal synaptosomes of guinea‐pig. Release was determined as the amount of NA, quantified by h.p.l.c.‐electrochemical detection, from samples incubated with insulin minus that in parallel blanks treated with some volume of vehicle.

Porcine insulin stimulated the secretion of NA in a concentration‐dependent manner from 0.01 i.u. ml−1, while the value of lactate dehydrogenase in the incubated medium was not influenced by insulin.

The presence of insulin receptors in this preparation was illustrated by immunoblotting with insulin receptor monoclonal antibodies.

The release of NA by insulin was reduced by guanethidine and bretylium and it was markedly lowered in the samples obtained from guinea‐pigs that had received an intraperitoneal injection of DSP‐4, the noradrenergic neurotoxin.

Tetrodotoxin attenuated the action of insulin at concentrations sufficient to block sodium channels. The depolarizing effect of insulin on the membrane potential was also illustrated by a concentration‐dependent increase in the fluorescence of bisoxonol, a potential‐sensitive dye.

The action of insulin was attenuated by removal of calcium chloride from the bathing medium. The induction of calcium ion influx by insulin into the synaptosomes is supported by the inhibitory effects of the calcium channel blockers ω‐conotoxin GVIA (for the N‐type channels) and nifedipine (for the L‐type channels).

These findings suggest that insulin can stimulate NA release from noradrenergic terminals via activation of calcium influx.

British Journal of Pharmacology (1997) 121, 15–20; doi:10.1038/sj.bjp.0701091
Characterization of human recombinant somatostatin sst5 receptors mediating activation of phosphoinositide metabolism
Authors: Wilkinson Graeme F , Feniuk Wasyl , Humphrey Patrick P A
Published: August 2006

We have functionally characterized the human recombinant somatostatin (SRIF) sst5 receptor in Chinese hamster ovary‐K1 (CHOsst5) cells by measuring total [3H]‐inositol phosphate ([3H]‐InsPx) accumulation, in the presence of 10 mM LiCl, in cells labelled with [3H]‐myo‐inositol.

In CHOsst5 cells, SRIF, SRIF‐28 and the cyclic hexapeptide, L‐362,855, produced time‐ and concentration‐related increases in [3H]‐InsPx accumulation, with similar potency (pEC50 values of 6.5, 6.8 and 7.2, respectively). L‐362,855 behaved as a partial agonist, producing approximately 30% of the SRIF maximum response. The other peptide analogues of SRIF, BIM‐23027 and BIM‐23056, were inactive as agonists.

Increasing concentrations of L‐362,855 increased [3H]‐InsPx accumulation and simultaneously produced rightward shifts of SRIF concentration‐effect curves, with an estimated pKp value of 7.6, confirming that it was acting as a partial agonist.

BIM‐23056, but not BIM‐23027, potently antagonized SRIF‐induced [3H]‐InsPx accumulation, with an estimated pKB value of 7.4. BIM‐23056 did not antagonize [3H]‐InsPx accumulation induced by uridine 5′‐triphosphate (UTP).

SRIF‐ but not UTP‐induced [3H]‐InsPx accumulation was inhibited by increasing concentrations of pertussis toxin (0.01–100 ng ml−1), indicating the involvement of pertussis toxin‐sensitive G‐proteins.

These findings show that the human recombinant sst5 receptor, when stably expressed in CHO‐K1 cells, is able to mediate activation of phosphoinositide metabolism in a pertussis toxin‐sensitive manner. In this system L‐362,855 behaved as a partial agonist while BIM‐23056 was a specific antagonist. These agents should provide useful tools for functionally characterizing endogenous SRIF receptors.

British Journal of Pharmacology (1997) 121, 91–96; doi:10.1038/sj.bjp.0701116
Cytochrome c‐d regulates developmental apoptosis in the Drosophila retina
Authors: Mendes César S , Arama Eli , Brown Samara , Scherr Heather , Srivastava Mayank , Bergmann Andreas , Steller Hermann , Mollereau Bertrand
Published: August 2006

The role of cytochrome c (Cyt c) in caspase activation has largely been established from mammalian cell‐culture studies, but much remains to be learned about its physiological relevance in situ. The role of Cyt c in invertebrates has been subject to considerable controversy. The Drosophila genome contains distinct cyt c genes: cyt c‐p and cyt c‐d. Loss of cyt c‐p function causes embryonic lethality owing to a requirement of the gene for mitochondrial respiration. By contrast, cyt c‐d mutants are viable but male sterile. Here, we show that cyt c‐d regulates developmental apoptosis in the pupal eye. cyt c‐d mutant retinas show a profound delay in the apoptosis of superfluous interommatidial cells and perimeter ommatidial cells. Furthermore, there is no apoptosis in mutant retinal tissues for the Drosophila homologues of apoptotic protease‐activating factor 1 (Ark) and caspase 9 (Dronc). In addition, we found that cyt c‐d—as with ark and dronc—regulates scutellar bristle number, which is known to depend on caspase activity. Collectively, our results indicate a role of Cyt c in caspase regulation of Drosophila somatic cells.
The herpes simplex virus ICP27 protein: a multifunctional post-transcriptional regulator of gene expression
Authors: Smith R.W.P. , Malik P. , Clements J.B.
Published: August 2006

The herpes simplex virus 1 ICP27 is an essential, highly conserved protein involved in various steps of herpes simplex virus 1 gene regulation as well as in the shut-off of host gene expression during infection. It functions primarily at the post-transcriptional level in inhibiting precursor mRNA splicing and in promoting nuclear export of viral transcripts. These activities are discussed.
Systems biology: will it work?
Authors: Williamson M.P.
Published: August 2006

Systems biology describes the collection of a set of measurements on a system, integrated with a mathematical model of that system. The model and the measurements must be made together and refined iteratively, requiring close collaboration between biologists and modellers. A complete cell is probably too large and complicated to model yet, but simplified subsystems will probably produce valuable results. I consider various ways of simplifying the system and conclude that the biggest challenge is to get everyone working together productively.
A reexamination of the ice III/IX hydrogen bond ordering phase transition
Authors: Knight Chris , Singer Sherwin J.
Published: August 2006

Ice III is a hydrogen bond disordered crystal which when cooled 1K∕min or faster transforms to an antiferroelectric hydrogen bond ordered structure, ice IX. Throughout its region of stability, experiments indicate that the H bonds in ice III are, in fact, partially ordered, i.e., some proton arrangements are preferred. In addition, there has been evidence that the structure of ice IX retains some residual disorder after the transition. Diffraction experiments and calorimetry apparently conflict with regard to the degree of ordering at the ice III/IX transition. Mean field statistical mechanical theories have been used to link partial occupations from diffraction data with thermodynamics. In this work, we investigate the ice III/IX proton ordering phase transition using electronic density functional theory calculations for small unit cells, extended to simulate the phase transition in a large unit cell using graph invariants. In agreement with experiment, we observe partial ordering over a wide range of temperatures as ice III transforms to partially disordered ice IX, near 126K, which becomes fully ordered at lower temperatures. We compare our results from full statistical mechanical simulations with mean field models, finding small errors for the low-temperature ice IX phase and much larger errors for the high-temperature ice III phase. The failure of mean field theories may explain the apparent conflict between diffraction experiments and calorimetry.
Direct dynamics study on the hydrogen abstraction reactions N2H4+R→N2H3+RH (R=NH2,CH3)
Authors: Li Qian Shu , Zhang Xin
Published: August 2006

We present a direct ab initio dynamics study on the hydrogen abstraction reactions N2H4+R→N2H3+RH (R=NH2,CH3), which are predicted to have six possible reaction channels for NH2 abstraction and four for CH3 abstraction caused by the different N2H4 isomers and various attacking orientations of foreign radical to N2H4. The structures and frequencies at the stationary points and the points along the minimum energy paths (MEPs) of all reaction channels are obtained at the UMP2(full)∕6-31+G(d,p) level of theory. Energetic information of stationary points and the points along the MEPs is further refined by means of MC-QCISD method. The rate constants of these channels are calculated using the improved canonical variational transition-state theory with the small-curvature tunneling correction (ICVT/SCT) method. The calculated results show that the favorable reaction channels are channels (n1) and (n4) as well as (c1) and (c3) (refer to Scheme 1) in the whole temperature range. The total ICVT/SCT rate constants of all channels for the two reactions at the MC-QCISD∕∕UMP2(full)∕6-31+G(d,p) level are both in good agreement with the available experimental data, and corresponding three-parameter expressions of kICVT∕SCT in 220–3000K are fitted as 6.46×10−15(T∕298)3.60exp(−386∕T)cm3mol−1s−1 for NH2 abstraction and 1.04×10−14(T∕298)4.00exp(−2037∕T)cm3mol−1s−1 for CH3 abstraction. Additionally, the long range interaction between the H atom of X–H bond in foreign radicals and the lone pair on the nonreactive N atom of the transition states is further discussed to explain the various transition-state numbers of the two similar hydrogen abstraction reactions.
Contractivity of positive and trace-preserving maps under Lp norms
Authors: Pérez-García David , Wolf Michael M. , Petz Denes , Ruskai Mary Beth
Published: August 2006

We provide a complete picture of contractivity of trace preserving positive maps with respect to p-norms. We show that for p>1 contractivity holds in general if and only if the map is unital. When the domain is restricted to the traceless subspace of Hermitian matrices, then contractivity is shown to hold in the case of qubits for arbitrary p⩾1 and in the case of qutrits if and only if p=1, ∞. In all noncontractive cases best possible bounds on the p-norms are derived.
Straightforward biodegradable nanoparticle generation through megahertz-order ultrasonic atomization
Authors: Forde Gareth , Friend James , Williamson Tom
Published: August 2006

Simple and reliable formation of biodegradable nanoparticles formed from poly-ε-caprolactone was achieved using 1.645MHz piston atomization of a source fluid of 0.5% w/v of the polymer dissolved in acetone; the particles were allowed to descend under gravity in air 8cm into a 1mM solution of sodium dodecyl sulfate. After centrifugation to remove surface agglomerations, a symmetric monodisperse distribution of particles ϕ 186nm (SD=5.7, n=6) was obtained with a yield of 65.2%.