bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical Analysis of the Collaborative Study in Support of the Official Method AOCS Ce 1i‐07: Determination of Saturated, cis‐Monounsaturated and cis‐Polyunsaturated Fatty Acids in Marine and Other Oils Containing Long Chain Polyunsaturated Fatty Acids by Capillary GLC
Authors: Smith Sean A. , Hansen Steven L.
Published: August 2008

Analysis was done of the statistical results obtained by following recommended AOCS Collaborative Study Procedure M‐86 to evaluate the performance of Official Method AOCS Ce 1i‐07, which provides a gas–liquid chromatography (GLC) procedure for the determination of the fatty acid composition of oils containing long chain polyunsaturated fatty acids (PUFAs). The method obtains relative between‐lab reproducibility (%RSDR) values on the order of 5% or less for most fatty acids that are present above ~0.5% w/w; however, the reproducibility worsens dramatically for analytes below this threshold. Apparently, several participating labs had problems identifying small peaks in the sample chromatograms. They also had problems correctly identifying certain larger peaks that occurred in a congested area of the sample chromatograms, including the 9c‐16:1, 9c‐11c‐22:1, and 6c,9c,12c,15c‐16:4 fatty acids. Finally, several analytes with chain lengths between 16 and 18 and between 21 and 22 carbons that were present at moderate concentrations had worse than expected reproducibilities due to severe overlap of these analytes’ peaks. A detailed inspection of the contributed data shows that the relatively poor between‐lab reproducibility for analytes in this region is due to differences in the labs’ chromatographic efficiencies and perhaps in their methods of quantifying highly overlapped peaks.
Garnets of crustal parageneses in alluvial deposits of the eastern Siberian Platform: genesis and search significance
Authors: Nikolenko E.I. , Afanas’ev V.P. , Pokhilenko N.P.
Published: August 2008

We present results of study of the specific composition and parageneses of pyrope-almandine garnets from alluvial deposits of the Muna-Markha interfluve drainage in the Yakutian diamondiferous province. The data are correlated with the specific features of garnets (tentatively crustal) from Yakutian and Guinean kimberlites and their crustal xenoliths and from metamorphic rocks of the Anabar Shield. The conclusion is drawn that most of orange pyrope-almandine garnets from the alluvial deposits were generated from kimberlites with varying contents of disintegrated crustal material. This gives grounds to include the studied garnets into a complex of indicator minerals of kimberlites and use them in search for diamonds in the Yakutian diamondiferous province.
Diurnal and vertical variability of pH, [O2], and Eh in the Novosibirsk water reservoir
Authors: Belevantsev V.I. , Ryzhikh A.P. , Smolyakov B.S.
Published: August 2008

In situ data on the daily dynamics of pH, [O2], and Eh values at five water layer depths were obtained. Some regularities have been established: All these parameters are characterized by significant diurnal fluctuations and their daily cyclic recurrence; the diurnal cycles of pH and [O2] nearly coincide (they show close extreme points on the time scale); the Eh cycles are less distinct and antisymbatic to the pH and [O2] cycles, but typical Eh extremes sometimes lag by 2–3 h. These data were analyzed using the principle of equilibrium locality and partiality. The main flows of O2 and CO2 in the system have been revealed with regard to the water layer–atmosphere gas exchange, absorption of CO2 by phytoplankton in the photic layer, breathing of phyto- and zooplankton, birth and die-off of biota, settling of mortomass, and redistribution of detailed components within the water layer as well as between it and the bottom sediments. On the basis of the results obtained, the known technique for estimating the content of primary photosynthesis products (Bruevich’s method) was corrected. The used generalized algorithm of chemical thermodynamic analysis of the substance state in aqueous systems can be applied to waters of different classes as well as any surficial waters if Eh, pH, and [O2] are taken into account.
Stratotypes of Quaternary deposits of the Yaloman-Katun’ zone (Gorny Altai)
Authors: Zol’nikov I.D.
Published: August 2008

We revised geological data substantiating the unified 1983 Regional Stratigraphic Chart of Gorny Altai Quaternary deposits. Based on our own and literature data, we showed that Lower and Middle Quaternary glacial horizons are erroneously distinguished in the Yaloman-Katun’ zone of southeastern Altai. A new correlation is proposed, according to which the glacial complex of the maximum glaciation (MIS-6) corresponds to the Inya catafluvial series and the glacial complex of the first postmaximum glaciation (MIS-4 unit), to the Sal’dzhar catafluvial series. The lectostratotypes of both series are described. The event history of the second half of the Late Neopleistocene in Gorny Altai (MIS-3 and MIS-2) was less catastrophic for ancient biota and Paleolithic man than it was believed earlier.
Ordovician sea-level change and rapid change in crustal subsidence rates in East Siberia and Baltoscandia
Authors: Artyushkov E.V. , Tesakov Yu.I. , Chekhovich P.A.
Published: August 2008

Sea-level change has been commonly interpreted to be of eustatic origin, and many eustatic events were hypothesized for the Phanerozoic, including several 1–3 Myr long cycles in the Ordovician with magnitudes up to 100 or 200 m. However, sea-level change modeling using stratigraphic data from Northern Estonia, which was an area of slow shallow-marine (<10 m) deposition through most of the Ordovician, indicates fluctuations of no more than 20 m. In the Late Ordovician the sea level fell only twice for ∼100 m within 1 Myr during the Gondwanian glaciation. Although the sea level remained relatively stable, there were frequent 100–200 m changes of sea depths we inferred with reference to the time spans of stratigraphic units and intervals between tectonic events estimated reliably against stable durations of East Siberian chronozones (biochrons) of the Ordovician. In the absence of eustatic events, the sea-depth changes most likely resulted from rapid crustal uplift and subsidence. According to correlated well-documented Ordovician sections from East Siberia, the rate of crustal subsidence changed rapidly in different periods and in different places of the area, thus being of a regional scale. The controversy between the sea-level stability and the regional-scale variations in sea depths controlled by rates of crustal uplift and subsidence can be resolved assuming a model of variable eclogitization rates in the lower crust caused by lithospheric stress change. Our inferences undermine the traditional petroleum prediction approach implying formation of depositional traps due to rapid eustatic sea-level change.
Hilbert-semblance method for acoustic logging data processing
Authors: Akhmetsafin R.D. , Dubinskii V. , Patterson D.
Published: August 2008

We suggest a method of multi-element low-frequency acoustic logging data processing which combines advantages of the semblance and phase velocity processing (PVP) techniques, namely, the interference resistance in the former and better accuracy in the latter. The new method is based on point (windowless) semblance by the Hilbert transformation. The introduced concept of phase semblance makes it possible to estimate the signal distribution semblance and the phase. Also suggested are an algorithm for preliminary estimation of formation S-wave slowness from signal group power variations and improved forms of processed data imaging.
Historical seismicity on the southern margin of the Siberian craton: new data
Authors: Radziminovich Ya.B. , Shchetnikov A.A.
Published: August 2008

We discuss historical evidence for seismicity on the southern margin of the Siberian craton collected from old local newspapers. The reported earthquakes vary in magnitude from M = 2.5 to 4.5, and their macroseismic locations agree well with the regional tectonic framework. The new data prove seismic activity in the area and can be used in seismic risk assessment.
Mesozoic-Cenozoic tectonics and geodynamics of Altai, Tien Shan, and Northern Kazakhstan, from apatite fission-track data
Authors: Buslov M.M. , Kokh D.A. , De Grave J.
Published: August 2008

Apatite fission-track (AFT) thermochronological modeling as a diagnostic tool for periods of stability (peneplanation) and tectonic activity (orogeny) has been broadly used in tectonic studies of Central Asia in recent years. We discuss more than 100 AFT ages of samples from the Kyrgyz Tien Shan and Altai and compare them with AFT data from northern Kazakhstan. Geological, geomorphological, and AFT data indicate intense activity in the Late Cenozoic Eurasian continental interior. The impact from the India-Eurasia collision on the northern Tien Shan, Altai, and northern Kazakhstan regions showed up at 11, 5, and 3 Ma, respectively, as a result of stress propagation into the continent, with the ensuing reactivation and mountain growth. We hypothesize that a distant effect of the Late Cenozoic India-Eurasia collision was to rejuvenate Paleozoic fault zones and to deform the Mesozoic sedimentary cover north of the collision front as far as the West Siberian Plate. The reactivation facilitated formation of tectonic oil and gas traps. The activity in northern Central Asia under the effect of the Indian indentation into Eurasia appears to continue and may evolve to include uplift of southern West Siberian plate with uplift.
Contact coal transformation under the influence of dolerite dike (Kaierkan deposit, Noril’sk district)
Authors: Melenevsky V.N. , Fomin A.N. , Konyshev A.S. , Talibova O.G.
Published: August 2008

The influence of 6.75 m thick dolerite dike on the sheet coal of the Kaierkan deposit (northwestern Siberian Platform) was studied by organogeochemical methods. It is shown that initial bituminous coal was transformed into anthracite in the immediate vicinity of the dike. Chemical kinetic modeling of the dike-induced cracking of coal’s organic matter was performed, and the maximum paleotemperatures were estimated.
Carbon‐cycle feedbacks of changes in the Atlantic meridional overturning circulation under future atmospheric CO2
Authors: Zickfeld Kirsten , Eby Michael , Weaver Andrew J.
Published: August 2008

An Earth System model of intermediate complexity is used to quantify the effects of potential reorganizations of the Atlantic meridional overturning circulation, ranging from a weakening to a complete shutdown, on future uptake of excess CO2 by the ocean and the terrestrial biosphere. Circulation changes significantly reduce oceanic CO2 uptake, with the largest effects occurring under a complete shutdown. The reduction in uptake is caused to a large extent by a decline in marine export of organic particulate matter. On land, soil carbon increases because of reduced soil respiration in the mid‐latitudes of the Northern Hemisphere. This gain is partially compensated by loss of vegetation carbon associated with reduced primary production in the northern high latitudes due to a cooler and dryer climate. Altogether, these processes act to modestly enhance CO2 concentration levels in the atmosphere, thereby leading to a small positive feedback. The rise in atmospheric CO2 ranges from 13 ppm to 34 ppm in 2500, depending on the amount of AMOC weakening, the magnitude of the anthropogenic CO2 perturbation, and the future CO2 fertilization effect.
Aeolian dust dynamics in central Asia during the Pleistocene: Driven by the long‐term migration, seasonality, and permanency of the Asiatic polar front
Authors: Machalett Björn , Oches Eric A. , Frechen Manfred , Zöller Ludwig , Hambach Ulrich , Mavlyanova Nadira G. , Marković Slobodan B. , Endlicher Wilfried
Published: August 2008

Loess‐paleosol sequences preserve detailed archives of climate change, reflecting the dynamics of aeolian dust sedimentation and the paleodust content of the atmosphere. The detailed investigation of particle size distributions (PSDs) of windblown sediments is an increasingly used approach to assess the paleorecord of aeolian dust dynamics. The central Asian loess belt offers the potential to reconstruct Pleistocene atmospheric circulation patterns along an adjacent west‐east transect within interior Eurasia through granulometric studies. In this study we present the aeolian dust record of the loess sequence at Remisowka (SE Kazakhstan), which reflects a detailed signal of glacial‐interglacial climate and atmospheric dynamics in central Asia. On the basis of radiocarbon and amino acid geochronologic data, long‐term semicontinuous trends in the aeolian dust record of the Last Glacial Cycle are observed and interpreted to reveal their paleoclimate signal. In consideration of the modern synoptical atmospheric circulation patterns and aeolian dust transport in central Asia, it is likely that the observed trends reflect the long‐term migration, seasonal duration, and permanency of the polar front during the late Pleistocene. Previously published models, which focused on the reciprocal glacial‐interglacial influence of the zonal Westerlies and the Asiatic high on the aeolian dust transport in central Asia, were overly simplified and should be modified to include the major influence of the Asiatic polar front. As the polar front activity is intimately connected with the development and position of the interhemispherically active, high‐level planetary frontal zone (HPFZ), the presented data give insight to long‐term aeolian dust dynamics and climate variability of interior Eurasia, which are linked with interhemispheric climates.
Using measurements of Energetic Neutral Atoms from low Earth orbit to infer global magnetospheric ion distributions
Authors: DeMajistre R. , Brandt P. C. , Roelof E. C. , Mitchell D. G.
Published: August 2008

We show here that ENA observations from low Earth orbit (LEO) are worthy of consideration for remote sensing of the inner magnetosphere. We present simulations of energetic ion distributions retrieved from energetic neutral atom (ENA) images obtained from LEO. These simulations show that a large portion of the inner magnetosphere can be observed from a single spacecraft and that quantitative results can be extracted from such observations. We also demonstrate that even in a case where the assumed magnetic field topology is in error, useful results can still be obtained.
Modeling ice shelf cavities in a z coordinate ocean general circulation model
Authors: Losch M.
Published: August 2008

Processes at the ice shelf‐ocean interface and in particular in ice shelf cavities around Antarctica have an observable effect on the solutions of basin scale to global coupled ice‐ocean models. Despite this, these processes are not routinely represented in global ocean and climate models. It is shown that a new ice shelf cavity model for z coordinate models can reproduce results from an intercomparison project of earlier approaches with vertical σ or isopycnic coordinates. As a proof of concept, ice shelves are incorporated in a 100‐year global integration of a z coordinate model. In this simulation, glacial meltwater can be traced as far as north as 15°S. The observed effects of processes in the ice shelf cavities agree with previous results from a σ coordinate model, notably the increase in sea ice thickness. However, melt rates are overestimated probably because the parameterization of basal melting does not suit the low resolution of this configuration.
Boundary wave communication of bottom pressure and overturning changes for the North Atlantic
Authors: Roussenov Vassil M. , Williams Richard G. , Hughes Chris W. , Bingham Rory J.
Published: August 2008

The relationship between changes in sea‐surface height, bottom pressure, and overturning is explored using isopycnal model experiments for the North Atlantic. Changes in high‐latitude forcing are communicated rapidly over the basin through boundary wave propagation along the continental slope, involving a hybrid mixture of Kelvin and topographic Rossby waves, as well as spreading more slowly through advection along the western boundary. This wave communication leads to coherent signals in sea‐surface height and bottom pressure variability extending for several thousand kilometers along the continental slope. The model results are in broad agreement with altimetric diagnostics, and the patterns only alter in detail with the realism of the topography. The adjustment in bottom pressure is directly linked to a change in overturning since west‐east contrasts in bottom pressure are associated with a zonal integral in the meridional geostrophic flow. Correlation patterns reveal that temporal changes in overturning are primarily connected to the vertical contrast in bottom pressure, across the shelf and continental slope, along the western boundary.
An automatic cloud mask algorithm based on time series of MODIS measurements
Authors: Lyapustin A. , Wang Y. , Frey R.
Published: August 2008

Quality of aerosol retrievals and atmospheric correction over land depends strongly on accuracy of the cloud mask (CM) algorithm. The heritage CM algorithms developed for AVHRR and MODIS use the latest sensor measurements of spectral reflectance and brightness temperature and perform processing at the pixel level. The algorithms are threshold‐based and empirically tuned. They do not explicitly address the classical problem of cloud search, wherein the baseline clear‐skies scene is defined for comparison. Here we report on a new land CM algorithm, which explicitly builds and maintains a reference clear‐skies image of the surface (refcm) using a time series of MODIS measurements. The new algorithm, developed as part of the multiangle implementation of atmospheric correction (MAIAC) algorithm for MODIS, relies on the fact that clear‐skies images of the same surface area have a common textural pattern, defined by the surface topography, boundaries of rivers and lakes, distribution of soils and vegetation, etc. This pattern changes slowly given the daily rate of global Earth observations, whereas clouds introduce high‐frequency random disturbances. Under clear skies, consecutive gridded images of the same surface area have a high covariance, whereas in presence of clouds covariance is usually low. This idea is central to initialization of refcm, which is used to derive cloud mask in combination with spectral and brightness temperature tests. The refcm is continuously updated with the latest clear‐skies MODIS measurements, thus adapting to seasonal and rapid surface changes. The algorithm is enhanced by an internal dynamic land–water–snow classification coupled with a surface change mask. An initial comparison shows that the new algorithm offers the potential to perform better than the MODIS MOD35 cloud mask in situations where the land surface is changing rapidly and over Earth regions covered by snow and ice.
Mg/Ca and Sr/Ca ratios in planktonic foraminifera: Proxies for upper water column temperature reconstruction
Authors: Cléroux Caroline , Cortijo Elsa , Anand Pallavi , Labeyrie Laurent , Bassinot Franck , Caillon Nicolas , Duplessy Jean‐Claude
Published: August 2008

Reliable temperature estimates from both surface and subsurface ocean waters are needed to reconstruct past upper water column temperature gradients and past oceanic heat content. This work examines the relationships between trace element ratios in fossil shells and seawater temperature for surface‐dwelling foraminifera species, Globigerinoides ruber (white) and Globigerina bulloides, and deep‐dwelling species, Globorotalia inflata, Globorotalia truncatulinoides (dextral and sinistral) and Pulleniatina obliquiloculata. Mg/Ca and Sr/Ca ratios in shells picked in 29 modern core tops from the North Atlantic Ocean are calibrated using calculated isotopic temperatures. Mg/Ca ratios on G. ruber and G. bulloides agree with published data and relationships. For deep‐dwelling species, Mg/Ca calibration follows the equation Mg/Ca = 0.78 (±0.04) × exp (0.051 (±0.003) × T) with a significant correlation coefficient of R2 = 0.74. Moreover, there is no significant difference between the different deep‐dwellers analyzed. For the Sr/Ca ratio, the surface dwellers and P. obliquiloculata do not record any temperature dependence. For the Globorotalia species, the thermo dependence of Sr/Ca ratio can be described by a single linear relationship: Sr/Ca = (0.0182 (±0.001) × T) + 1.097 (±0.018), R2 = 0.85. Temperature estimates with a 1 sigma error of ±2.0°C and ±1.3°C can be derived from the Mg/Ca and Sr/Ca ratios, respectively, as long as the Sr geochemistry in the ocean has been constant through time.
Frequency‐and‐angular sounding of traveling ionospheric disturbances in the model of three‐dimensional electron density waves
Authors: Galushko V. G. , Kascheev A. S. , Paznukhov V. V. , Yampolski Yu. M. , Reinisch B. W.
Published: August 2008

A new technique for diagnostics of traveling ionospheric disturbances (TIDs) uses measurements of arrival angles and Doppler frequency shift variations of HF radio signals reflected from the ionosphere. This technique is a further improvement of a frequency‐and‐angular sounding method previously suggested. Here we solve the respective inverse problem of reconstructing TID parameters by using a physically realistic three‐dimensional model of electron density waves propagating through an ionospheric layer. The developed diagnostic algorithms were tested through computer simulations demonstrating the high efficiency of the proposed method. We also reprocessed the data collected in an earlier experiment carried out at the Millstone Hill Observatory in March 2001 using the new algorithms. In that campaign, HF signal trajectory parameters were recorded using the Digisonde instrument as a receiver monitoring continuous transmission from the CHU station. Comparison of the TID parameters determined with the frequency‐and‐angular sounding method and simultaneous incoherent scatter radar observations showed good agreement between the two diagnostic techniques with the differences of no greater than 10%.
A model for two‐phase flow in porous media including fluid‐fluid interfacial area
Authors: Niessner J. , Hassanizadeh S. M.
Published: August 2008

We present a new numerical model for macroscale two‐phase flow in porous media which is based on a physically consistent theory of multi‐phase flow. The standard approach for modeling the flow of two fluid phases in a porous medium consists of a continuity equation for each phase, an extended form of Darcy's law as well as constitutive relationships for relative permeability and capillary pressure. This approach is known to have a number of important shortcomings and, in particular, it does not account for the presence and role of fluid‐fluid interfaces. The alternative is to use an extended model, which is founded on thermodynamic principles and is physically consistent. In addition to the standard equations, the model uses a balance equation for specific interfacial area. The constitutive relationship for capillary pressure involves not only saturation, but also specific interfacial area. We present results of a numerical modeling study based on this extended model. We show that the extended model can capture additional physical processes compared to the standard model, such as hysteresis.
Significant enhancement of aerosol optical depth in marine air under high wind conditions
Authors: Mulcahy J. P. , O'Dowd C. D. , Jennings S. G. , Ceburnis D.
Published: August 2008

The relationship between the AOD and wind speed (U), obtained at the Mace Head atmospheric research station, is determined for clean marine (Northeast Atlantic) conditions under steady‐state wind speed scenarios. AOD measurements were made under much higher wind speed conditions (up to 18 m s−1) than hitherto measured. The AOD is found to be approximately dependent on U2, with a high correlation (r2 = 0.97) determined at all measured wavelengths of 862 nm, 500 nm, 412 nm and 368 nm. A corresponding anti‐correlation was observed between the Ångström exponent and wind speed (r2 = 0.93). The results illustrate that under moderate‐to‐high wind conditions, sea‐spray AOD can rival or even exceed that associated with pollution plumes over oceanic regions and can potentially contribute to radiative, dynamical and biogeochemical feedback processes associated with future climate change.
Seasonal variation of the longitudinal structure of the equatorial ionosphere: Does it reflect tidal influences from below?
Authors: Liu Huixin , Watanabe Shigeto
Published: August 2008

We have examined the longitudinal structure of the equatorial ionosphere at 400‐km altitude in the noon and postsunset local time sectors in different seasons using 6 years of F‐region plasma density observations from the CHAMP satellite. A four‐peak wave structure is observed in both local time sectors. In the noon sector at a fixed solar flux level, this structure is observed to be most prominent around September equinox and weakest around December solstice. This seasonal dependence agrees well with that of the nonmigrating diurnal tides DE3, hence supporting a close coupling between the ionosphere and the mesosphere‐lower thermosphere possibly via the DE3 tidal modulation of the E‐layer dynamo. In the postsunset sector, however, such agreement cannot be claimed. In this sector, although the four‐peak structure can be observed in all seasons at moderate and high solar flux levels, its seasonal dependence does not follow that of the DE3 tides. This structure becomes indiscernible near solstices at low solar flux levels. Furthermore, the postsunset four‐peak wave structure exhibits larger amplitude than that during daytime, hence indicating that it is more likely an amplified feature rather than a remnant of the daytime structure. The prereversal enhancement is speculated to be a possible candidate to cause this amplification.
Are changes of the geomagnetic field intensity related to changes of the tropical Pacific sea‐level pressure during the last 50 years?
Authors: Vieira Luis Eduardo Antunes , da Silva Ligia Alves , Guarnieri Fernando Luís
Published: August 2008

The influence of solar variability into the lower atmospheric regions has been suggested on different atmospheric parameters in different time scales. However, a plausible mechanism to explain these observations remains unclear. Although it is widely accepted that the climate change over the past 50 years is attributed to human influence, we present the case that local climate change in the tropical Pacific may be due to changes in the Earth's magnetic field strength. The changes in the tropical Pacific circulation have been observed during the last 50 years, and they are attributed to the increase of the global surface temperature. However, a geomagnetic modulation of the net radiative flux in the southern tropical Pacific was recently suggested. Moreover, comparisons of long‐term reconstructions of the Northern Hemisphere surface temperature and solar activity proxies indicated that the existence of a geomagnetic signal in climate data would support a direct link between solar variability and their effects on climate. Here we show that in the tropical Pacific the sea‐level pressure, which is a component of the Walker circulation, could be related to the magnetospheric, ionospheric, and upper‐atmosphere processes which may propagate downward to the lower atmosphere. Furthermore, we show that the changes in sea‐level pressure and the Walker circulation are correlated to the westward drift of the magnetic anomaly. We compare the region averaged monthly values of the sea‐level pressure in the tropical Pacific with those of the magnetic field intensity near the surface for the last 50 years. We find that the sea‐level pressure in the tropical Pacific is increasing as the magnetic field intensity is decreasing. The correlation coefficient of the sea‐level pressure 36‐month running means versus the magnetic field intensity is 0.96. We anticipate our investigation to be a starting point for a more sophisticated investigation of the coupling between the space weather processes and lower atmosphere and ocean dynamics.
Ice iron/sodium film as cause for high noctilucent cloud radar reflectivity
Authors: Bellan P. M.
Published: August 2008

Noctilucent clouds, tiny cold electrically charged ice grains located at about 85 km altitude, exhibit anomalously high radar reflectivity. It is shown that this observed high radar reflectivity can be explained by assuming the ice grains are coated by a thin metal film; substantial evidence exists indicating that such a film exists and is caused by the deposition of iron and sodium atoms on the ice grain from iron and sodium layers located immediately above the noctilucent cloud layer. The number of conduction electrons in the thin metal film coating an ice grain is very large. When averaged over the volume occupied by a large number of ice grains, the quivering of these metal film electrons provides a much larger contribution to radar reflectivity than does the much smaller number of dusty plasma electrons or electron holes. Using observations indicating that noctilucent clouds are the dominant sink for the summer‐time iron and sodium layers, it is shown that a sufficiently thick metal layer should form on a typical ice grain in a few hours to a few days.
Optical properties and sulfate scattering efficiency of boundary layer aerosol at coastal Neumayer Station, Antarctica
Authors: Weller Rolf , Lampert Astrid
Published: August 2008

We measured optical properties and ionic composition of the aerosol at Neumayer Station from 2004 through 2006 by an integrating nephelometer and chemical analysis of daily aerosol samples, respectively. From this unique data set, we discussed the seasonality of optical parameters along with the chemical composition of the aerosol. Austral summer (November through March) was characterized by mean particle number concentrations of 472 ± 260 cm−3 compared to 168 ± 160 cm−3 during winter (April through October), mean scattering Ångström exponents of 1.5 ± 0.6 compared to 1.2 ± 0.5 during winter, and mean hemispheric backscattering ratios at 700 nm of 0.21 ± 0.13 compared to 0.17 ± 0.08 during winter. In contrast, light scattering coefficients (σsp) showed a broad maximum during winter (4.8 ± 5.3 Mm−1 for σsp(550)). The mean single scattering albedo was 0.99 ± 0.020.01 at 550 nm. We further derived mass scattering and mass backscattering efficiencies for biogenic sulfate aerosol (BSA) at 450 nm, 550 nm, and 700 nm for relative humidities between 5% and 11%. At 550 nm, the scattering efficiency for biogenic sulfate aerosol αBSAS(550) was 8.9 ± 0.7 m2 g−1 with a corresponding backscattering efficiency αBSAbs(550) of 1.0 ± 0.08 m2 g−1. From the seasonality of the aerosol composition, we inferred a dominant contribution of sulfate aerosol regarding radiative forcing in the lower troposphere from December through January, while the impact of sea salt aerosol prevailed for the rest of the year at Neumayer.
Total hydrocarbon flux dynamics at a subarctic mire in northern Sweden
Authors: Bäckstrand Kristina , Crill Patrick M. , Mastepanov Mikhail , Christensen Torben R. , Bastviken David
Published: August 2008

This is a study of the spatial and temporal variability of total hydrocarbon (THC) emissions from vegetation and soil at a subarctic mire, northern Sweden. THCs include methane (CH4) and nonmethane volatile organic compounds (NMVOCs), both of which are atmospherically important trace gases and constitute a significant proportion of the carbon exchange between biosphere and atmosphere. Reliable characterization of the magnitude and the dynamics of the THC fluxes from high latitude peatlands are important when considering to what extent trace gas emissions from such ecosystems may change and feed back on climate regulation as a result of warmer climate and melting permafrost. High frequency measurements of THC and carbon dioxide (CO2) were conducted during four sequential growing seasons in three localities representing the trophic range of plant communities at the mire. The magnitude of the THC flux followed the moisture gradient with increasing emissions from a dry Palsa site (2.2 ± 0.1 mgC m−2 d−1), to a wet intermediate melt feature with Sphagnum spp. (28 ± 0.3 mgC m−2 d−1) and highest emissions from a wet Eriophorum spp. site (122 ± 1.4 mgC m−2 d−1) (overall mean ±1 SE, n = 2254, 2231 and 2137). At the Palsa site, daytime THC flux was most strongly related to air temperature while daytime THC emissions at the Sphagnum site had a stronger relation to ground temperature. THC emissions at both the wet sites were correlated to net ecosystem exchange of CO2. An overall spatial correlation indicated that areas with highly productive vegetation communities also had high THC emission potential.
Differential enhancement of leukaemia cell differentiation without elevation of intracellular calcium by plant‐derived sesquiterpene lactone compounds
Authors: Kim S H , Danilenko M , Kim T S
Published: August 2008

Background and purpose:

All‐trans retinoic acid (ATRA) induces complete remission in a majority of acute promyelocytic leukaemia patients, but resistance of leukaemic cells to ATRA and its toxicity, such as hypercalcaemia, lead to a limitation of treatment. Therefore, combination therapies with differentiation‐enhancing agents at non‐toxic concentrations of ATRA may overcome its side effects. Here, we investigated the effect of plant‐derived sesquiterpene lactone compounds and their underlying mechanisms in ATRA‐induced differentiation of human leukaemia HL‐60 cells.

Experimental approach:

HL‐60 cells were treated with four sesquiterpene lactones (helenalin, costunolide, parthenolide and sclareolide) and cell differentiation was determined by NBT reduction, Giemsa and cytofluorometric analyses. Signalling pathways were assessed by western blotting, gel‐shift assay and kinase activity determinations and intracellular calcium levels were determined using a calcium‐specific fluorescent probe.

Key results:

Helenalin, costunolide and parthenolide, but not sclareolide, increased ATRA‐induced HL‐60 cell differentiation into a granulocytic lineage. Signalling kinases PKC and ERK were involved in the ATRA‐induced differentiation enhanced by all of the effective sesquiterpene lactones, but JNK and PI3‐K were involved in the ATRA‐induced differentiation enhanced by costunolide and parthenolide. Enhancement of cell differentiation closely correlated with inhibition of NF‐κB DNA‐binding activity by all three effective compounds. Importantly, enhancement of differentiation induced by 50 nM ATRA by the sesquiterpene lactones was not accompanied by elevation of basal intracellular calcium concentrations.

Conclusions and implications:

These results indicate that plant‐derived sesquiterpene lactones may enhance ATRA‐mediated cell differentiation through distinct pathways.

British Journal of Pharmacology (2008) 155, 814–825; doi:10.1038/bjp.2008.319; published online 25 August 2008
H2S‐donating sildenafil (ACS6) inhibits superoxide formation and gp91phox expression in arterial endothelial cells: role of protein kinases A and G
Authors: Muzaffar S , Jeremy J Y , Sparatore A , Del Soldato P , Angelini G D , Shukla N
Published: August 2008

Background and purpose:

Superoxide (O2•−), derived from nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, is associated with acute respiratory distress syndrome (ARDS). NADPH oxidase activity and expression are blocked by nitric oxide (NO) and sildenafil. As another gas, hydrogen sulphide (H2S) is formed by blood vessels, the effect of sodium hydrosulphide (NaHS) and the H2S‐donating derivative of sildenafil, ACS6, on O2•− formation and the expression of gp91phox (a catalytic subunit of NADPH oxidase) in porcine pulmonary arterial endothelial cells (PAECs) was investigated.

Experimental approach:

PAECs were incubated with 10 ng mL−1 tumour necrosis factor‐α (TNFα) (±NaHS or ACS6), both of which released H2S, for 2 h or 16 h. O2•− was measured. Expression of gp91phox was measured by western blotting and the role of cyclic AMP (cAMP) and/or cyclic GMP was assessed using protein kinase inhibitors.

Key results:

After either 2‐ or 16‐h incubations, O2•− formation by PAECs was inhibited by NaHS or ACS6, with IC50 values of about 10 nM and less than 1 nM, respectively. Both 100 nM NaHS and 1 nM ACS6 completely inhibited gp91phox expression induced by TNFα. The effects of NaHS were blocked by the inhibition of protein kinase A (PKA), but not PKG, and not by the inhibition of guanylyl cyclase. Effects of ACS6 were blocked by inhibition of both PKA and PKG. Both NaHS and ACS6 augmented cAMP formation.

Conclusion and implications:

H2S inhibited O2•− formation and upregulation of NADPH oxidase in PAECs through the adenylyl cyclase‐PKA pathway. ACS6 may be effective in treating ARDS through both elevation of cAMP and inhibition of phosphodiesterase type 5 activity.

British Journal of Pharmacology (2008) 155, 984–994; doi:10.1038/bjp.2008.326; published online 1 September 2008
Effects of levo‐ and dextrosimendan on NF‐κB‐mediated transcription, iNOS expression and NO production in response to inflammatory stimuli
Authors: Sareila O , Korhonen R , Auvinen H , Hämäläinen M , Kankaanranta H , Nissinen E , Moilanen E
Published: August 2008

Background and purpose:

Levosimendan is used in the treatment of decompensated heart failure. It increases the contractility of the myocardium by sensitizing troponin C to calcium. In addition, levosimendan has been reported to have beneficial effects in experimental models of septic shock. Because heart failure and sepsis have been associated with excessive nitric oxide (NO) production through inducible NOS (iNOS), we investigated the effects of the simendans on NO production and iNOS expression and on generation of pro‐inflammatory cytokines.

Experimental approach:

Macrophages and fibroblasts were exposed to inflammatory stimuli to induce iNOS expression. Proteins were measured by western blot and mRNA expression was determined by quantitative RT‐PCR. Promoter activity and nuclear factor‐κB (NF‐κB) and the γ‐activated site (GAS; binding site for signal transducer and activator of transcription 1; STAT1)‐mediated transcription were investigated using luciferase reporter constructs. Cytokines tumour necrosis factor‐α (TNF‐α) and interleukin‐6 (IL‐6) were measured by ELISA.

Key results:

Levosimendan and dextrosimendan decreased NO production in a dose‐dependent manner in cells exposed to inflammatory stimuli. The simendans decreased iNOS protein and mRNA expression but did not affect iNOS mRNA decay. These compounds decreased iNOS promoter activity and inhibited NF‐κB‐mediated transcription but not that mediated by STAT1/GAS. The simendans reduced IL‐6 production slightly but they had no effect on TNF‐α synthesis.

Conclusions and implications:

The simendans downregulated NF‐κB‐dependent transcription and decreased iNOS promoter activity, iNOS expression and NO production. These mechanisms may contribute to their beneficial clinical effects.

British Journal of Pharmacology(2008)155, 884–895; doi:10.1038/bjp.2008.328; published online 18 August 2008
Activation of peroxisome proliferator‐activated receptor‐α in mice induces expression of the hepatic low‐density lipoprotein receptor
Authors: Huang Z , Zhou X , Nicholson A C , Gotto A M , Hajjar D P , Han J
Published: August 2008

Background and purpose:

Mutations in the low‐density lipoprotein receptor (LDLR) gene cause familial hypercholesterolaemia in humans and deletion of the LDLR induces lesion development in mice fed a high‐fat diet. LDLR expression is predominantly regulated by sterol regulatory element‐binding protein 2 (SREBP2). Fenofibrate, a peroxisome proliferator‐activated receptor α (PPARα) ligand, belongs to a drug class used to treat dyslipidaemic patients. We have investigated the effects of fenofibrate on hepatic LDLR expression.

Experimental approach:

The effects of fenofibrate on hepatic LDLR expression (mRNA and protein) and function were evaluated by both in vitro (with AML12 cells) and in vivo experiments in mice.

Key results:

Fenofibrate increased LDLR expression and LDL binding in a mouse hepatoma cell line, AML12 cells. Fenofibrate restored sterol‐inhibited hepatocyte LDLR expression. Mechanistic studies demonstrated that induction of LDLR expression by fenofibrate was dependent on PPARα and sterol regulatory elements (SRE). Specifically, fenofibrate induced LDLR expression by increasing maturation of SREBP2 and phosphorylation of protein kinase B (Akt) but had no effect on SREBP cleavage‐activating protein. In vivo, a high‐fat diet suppressed LDLR expression in mouse liver while elevating total and LDL cholesterol levels in plasma. However, fenofibrate restored LDLR expression inhibited by high‐fat diets in the liver and reduced LDL cholesterol levels in plasma.

Conclusions and implications:

Our data suggest that fenofibrate increased hepatic LDLR expression in mice by a mechanism involving Akt phosphorylation and LDLR gene transcription mediated by SREBP2.

British Journal of Pharmacology (2008) 155, 596–605; doi:10.1038/bjp.2008.331; published online 18 August 2008
Human embryonic stem cells and lung regeneration
Authors: Varanou A , Page C P , Minger S L
Published: August 2008

Human embryonic stem cells are pluripotent cells derived from the inner cell mass of preimplantation stage embryos. Their unique potential to give rise to all differentiated cell types has generated great interest in stem cell research and the potential that it may have in developmental biology, medicine and pharmacology. The main focus of stem cell research has been on cell therapy for pathological conditions with no current methods of treatment, such as neurodegenerative diseases, cardiac pathology, retinal dysfunction and lung and liver disease. The overall aim is to develop methods of application either of pure cell populations or of whole tissue parts to the diseased organ under investigation. In the field of pulmonary research, studies using human embryonic stem cells have succeeded in generating enriched cultures of type II pneumocytes in vitro. On account of their potential of indefinite proliferation in vitro, embryonic stem cells could be a source of an unlimited supply of cells available for transplantation and for use in gene therapy. Uncovering the ability to generate such cell types will expand our understanding of biological processes to such a degree that disease understanding and management could change dramatically.

British Journal of Pharmacology (2008) 155, 316–325; doi:10.1038/bjp.2008.333; published online 25 August 2008
Inhibition of fatty acid amide hydrolase produces PPAR‐α‐mediated analgesia in a rat model of inflammatory pain
Authors: Sagar D R , Kendall D A , Chapman V
Published: August 2008

Background and purpose:

We have previously demonstrated antinociceptive effects of fatty acid amide hydrolase (FAAH) inhibition that were accompanied by increases in the levels of endocannabinoids (ECs) in the hind paw. Here, the effects of the FAAH inhibitor URB597 (3′‐carbamoyl‐biphenyl‐3‐yl‐cyclohexylcarbamate) on responses of spinal neurons were studied.

Experimental approach:

Extracellular single‐unit recordings of dorsal horn neurons were made in anaesthetized rats with hind paw inflammation induced by λ‐carrageenan. Effects of intraplantar pre‐administration of URB597, or vehicle, on carrageenan‐evoked expansion of peripheral receptive fields of spinal neurons and mechanically evoked responses of neurons were studied. The cannabinoid receptor type 1 (CB1) antagonist AM251 (N‐(piperidin‐1‐yl)‐5‐(4‐iodophenyl)‐1‐(2,4‐dichlorophenyl)‐4‐ methyl‐1H‐pyrazole‐3‐carboxamide) and the peroxisome proliferator‐ activated receptor (PPAR)‐α antagonist GW6471 ([(2S)‐2‐[[(1Z)‐1‐ methyl‐3‐oxo‐3‐[4‐(trifluoromethyl)phenyl]‐1‐propenyl]amino]‐3‐[4‐[2‐ (5‐methyl‐2‐phenyl‐4‐oxa zolyl)ethoxy]phenyl]propyl]‐carbamic acid ethyl ester) were used to investigate the roles of these receptors in mediating the effects of URB597.

Key results:

URB597 (25 μg in 50 μL) pretreatment significantly inhibited carrageenan‐evoked receptive field expansion and this was significantly reversed by co‐administration of the PPAR‐α antagonist but not the CB1 antagonist. Pretreatment with the PPAR‐α receptor agonist WY14643 ([[4‐chloro‐6‐[(2,3‐dimethylphenyl)amino]‐2‐pyrimidinyl]thio]acetic acid) also significantly inhibited receptive field expansion. URB597 (25 or 100 μg in 50 μL) had no significant effect on mechanically evoked responses of spinal neurons.

Conclusions and implications:

URB597 inhibited receptive field expansions but not mechanically evoked responses of spinal neurons in rats with hind paw inflammation. These effects were blocked by PPAR‐α receptor antagonism. These data support the contention that URB597 exerts its antinociceptive effects by indirect inhibition of sensitization of neuronal responses at least partly through PPAR‐α activation due to enhanced EC levels.

British Journal of Pharmacology (2008) 155, 1297–1306; doi:10.1038/bjp.2008.335; published online 25 August 2008
Endogenous and synthetic agonists of GPR119 differ in signalling pathways and their effects on insulin secretion in MIN6c4 insulinoma cells
Authors: Ning Y , O'Neill K , Lan H , Pang L , Shan L X , Hawes B E , Hedrick J A
Published: August 2008

Background and purpose:

GPR119 is a G protein‐coupled receptor that is preferentially expressed in islet cells and mediates insulin secretion. Oleoyl‐lysophosphatidylcholine and oleoylethanolamide (OEA) act as endogenous ligands for this receptor, whereas PSN375963 and PSN632408 are two recently reported synthetic agonists. In this study, we explored mechanisms underlying GPR119‐induced insulin secretion. In addition, we assessed the potential utility of the synthetic agonists as tools for exploring GPR119 biology.

Experimental approach:

We examined natural and synthetic GPR119 agonist activity at GPR119 in MIN6c4 and RINm5f insulinoma cells. We evaluated insulin secretion, intracellular calcium [Ca2+]i, ion channel involvement and levels of cAMP.

Key results:

We report that increases in insulin secretion induced by OEA were associated with increased cAMP and a potentiation of glucose‐stimulated increases in [Ca2+]i. We also demonstrate that ATP‐sensitive K+ and voltage‐dependent calcium channels were required for GPR119‐mediated increases in glucose‐stimulated insulin secretion. In contrast to OEA, the synthetic GPR119 agonist PSN375963 and PSN632408 have divergent effects on insulin secretion, cAMP and intracellular calcium in MIN6c4 cells.

Conclusions and implications:

The endogenous ligand OEA signals through GPR119 in a manner similar to glucagon‐like peptide‐1 (GLP‐1) and its receptor with respect to insulin secretion, [Ca2+]i and cAMP. In addition, PSN375963 and PSN632408 substantially differ from OEA and from one another. These studies suggest that the commercially available synthetic agonists, although they do activate GPR119, may also activate GPR119‐independent pathways and are thus unsuitable as GPR119‐specific pharmacological tools.

British Journal of Pharmacology (2008) 155, 1056–1065; doi:10.1038/bjp.2008.337; published online 25 August 2008