bluuebunny/crossref_metadata_2025 huggingface dataset:
Pyrroloquinoline‐quinone: a reactive oxygen species scavenger in bacteria
Authors: Misra Hari S. , Khairnar Nivedita P. , Barik Atanu , Indira Priyadarsini K. , Mohan Hari , Apte Shree K.
Published: November 2004

Transgenic Escherichia coli expressing pyrroloquinoline‐quinone (PQQ) synthase gene from Deinococcus radiodurans showed superior survival during Rose Bengal induced oxidative stress. Such cells showed significantly low levels of protein carbonylation as compared to non‐transgenic control. In vitro, PQQ reacted with reactive oxygen species with rate constants comparable to other well known antioxidants, producing non‐reactive molecular products. PQQ also protected plasmid DNA and proteins from the oxidative damage caused by γ‐irradiation in solution. The data suggest that radioprotective/oxidative stress protective ability of PQQ in bacteria may be consequent to scavenging of reactive oxygen species per se and induction of other free radical scavenging mechanism.
Suppression of human Mnk1 by small interfering RNA increases the eukaryotic initiation factor 4F activity in HEK293T cells
Authors: O'Loghlen Ana , González Vı́ctor M. , Salinas Matilde , Elena Martı́n M.
Published: November 2004

Short‐interfering RNAs (siRNAs) have proved to be a useful tool in studying gene function in plants, invertebrates and mammalian systems. Herein, we report the use of siRNAs for targeting the human MAP kinase‐interacting kinase Mnk1 gene. This study demonstrates the efficacy of the designed siRNA in silencing Mnk1 in the human cell line HEK293T and shows that Mnk1 suppression decreases eukaryotic initiation factor 4E phosphorylation without causing any change in global protein synthesis rate and cell proliferation. Interestingly, suppression of Mnk1 results in a significant increase in eukaryotic initiation factor 4F complex formation after 72 h of transfection.
A new NF‐κB inhibitor attenuates a TH1 type immune response in a murine model
Authors: Kabashima Kenji , Honda Tetsuya , Nunokawa Youichi , Miyachi Yoshiki
Published: November 2004

Nuclear factor kappa B (NF‐κB) plays a wide variety of pathophysiological roles and modulation of its pathway can be a good novel drug target. Here, we found that our recently synthesized NF‐κB inhibitor attenuated an ovalbumin‐specific delayed‐type hypersensitivity response in vivo and suppressed production of IL‐12 by dendritic cells and TH1 cytokines by T cells in vitro. These findings suggest that the activation of NF‐κB mounts TH1 type immune responses, and that this new NF‐κB inhibitor has a therapeutic potential in this context.
The role of bestrophin in airway epithelial ion transport
Authors: Duta Valentin , Szkotak Artur J. , Nahirney Drew , Duszyk Marek
Published: November 2004

The purpose of this study was to identify Cl− channels in the basolateral membrane of airway epithelial cells at the molecular level. We have focused on a new family of Cl− channels, bestrophins, which have previously been identified in retinal pigment epithelium. RT‐PCR, Western blot and confocal microscopy studies revealed the presence of bestrophin in airway epithelial cells. Decreasing bestrophin expression using siRNA resulted in diminished 36Cl− flux. These studies also showed that bestrophin regulation is similar to that of native basolateral Cl− channels. The data indicate that the presence of a functional bestrophin may contribute to the basolateral cell conductance in airway epithelial cells.
The Ppz protein phosphatases regulate Trk‐independent potassium influx in yeast
Authors: Ruiz Amparo , del Carmen Ruiz Marı́a , Sánchez-Garrido Miguel Angel , Ariño Joaquı́n , Ramos José
Published: November 2004

The Ppz protein phosphatases have been recently shown to negatively regulate the major potassium transport system in the yeast Saccharomyces cerevisiae, encoded by the TRK1 and TRK2 genes. We have found that, in the absence of the Trk system, Ppz mutants require abnormally high concentrations of potassium to proliferate. This can be explained by the observation that trk1 trk2 ppz1 or trk1 trk2 ppz1 ppz2 strains display a very poor rubidium uptake, with markedly increased K
m values. These cells are very sensitive to the presence of several toxic cations in the medium, such as hygromicyn B or spermine, but not to lithium or sodium cations. At limiting potassium concentrations, addition of EGTA to the medium improves growth of these mutants. Therefore, our results indicate that, in addition to their role in regulating Trk potassium transporters, Ppz phosphatases (essentially Ppz1), positively affect the residual low affinity potassium transport mechanisms in yeast. These findings may provide a new way to elucidate the molecular nature of the low affinity potassium uptake system in yeast as well as a useful model to analyze the function of plant or mammalian potassium channels through heterologous expression in yeast.
Hepatocyte nuclear factors 1α and 4α control expression of proline oxidase in adult liver
Authors: Kamiya Akihide , Inoue Yusuke , Kodama Tatsuhiko , Gonzalez Frank J.
Published: November 2004

Adult liver functions are regulated by several hepatocyte nuclear factors (HNFs). HNF4α and HNF1α are involved in metabolic functions in the liver. The expression of proline oxidase (PO) and proline dehydrogenase was downregulated in the HNF4α liver‐specific null mice. In addition, the expression of PO was also diminished in the liver derived from HNF1α‐null mice. The −160 bp proximal promoter region of the PO gene has two HNF4α‐ and HNF1α‐binding consensus sites. Transactivation, electrophoretic mobility shift and chromatin immunoprecipitation studies revealed that these regions are important for PO promoter activity. These results suggested that HNF4α and HNF1α regulate proline metabolism in adult liver.
Infectious mononucleosis and Epstein-Barr virus
Authors: Vetsika Eleni-Kyriaki , Callan Margaret
Published: November 2004

Epstein-Barr virus (EBV) is a γ-herpesvirus that infects over 90% of the human population worldwide. It is usually transmitted between individuals in saliva, and establishes replicative infection within the oropharynx as well as life-long latent infection of B cells. Primary EBV infection generally occurs during early childhood and is asymptomatic. If delayed until adolescence or later, it can be associated with the clinical syndrome of infectious mononucleosis (also known as glandular fever or ‘mono%rsquo;), an illness characterised by fevers, pharyngitis, lymphadenopathy and malaise. EBV infection is also associated with the development of EBV-associated lymphoid or epithelial cell malignancies in a small proportion of individuals. This review focuses on primary EBV infection in individuals suffering from infectious mononucleosis. It discusses the mechanism by which EBV establishes infection within its human host and the primary immune response that it elicits. It describes the spectrum of clinical disease that can accompany primary infection and summarises studies that are leading to the development of a vaccine designed to prevent infectious mononucleosis.
Neodymium isotopic composition and rare earth element concentrations in the deep and intermediate Nordic Seas: Constraints on the Iceland Scotland Overflow Water signature
Authors: Lacan François , Jeandel Catherine
Published: November 2004

Neodymium isotopic composition and rare earth element concentrations were measured in seawater samples from eleven stations in the Nordic Seas. These data allow us to study how the Iceland Scotland Overflow Water (ISOW) acquires its neodymium signature in the modern ocean. The waters overflowing the Faroe Shetland channel are characterized by ɛNd = −8.2 ± 0.6, in good agreement with the only other data point, published 19 years ago. In the Greenland and Iceland Seas the water masses leading to the formation of the ISOW display lower neodymium isotopic composition, with ɛNd around −11 and −9, respectively. Since no water masses in the Nordic Seas are characterized by ɛNd > −8, the radiogenic signature of the ISOW likely reflects inputs from the highly radiogenic Norwegian Basin basaltic margins (Jan‐Mayen, Iceland, Faroe, with ɛNd ≈ +7). In addition to the neodymium isotopic composition, the rare earth element patterns suggest that these inputs occur via the remobilization (which includes resuspension and dissolution) of sediments deposited on the margins. Whereas the neodymium isotopic composition behaves conservatively in the oceans in the absence of lithogenic inputs, and can be used as a water mass tracer, these results emphasize the role of interactions, between sediments deposited on margins and seawater, in the acquisition of the neodymium isotopic composition of water masses. These results should allow a better use of this parameter to trace the present and the past circulation in the North Atlantic.
Validating AIRS upper atmosphere water vapor retrievals using aircraft and balloon in situ measurements
Authors: Hagan D. E. , Webster C. R. , Farmer C. B. , May R. D. , Herman R. L. , Weinstock E. M. , Christensen L. E. , Lait L. R. , Newman P. A.
Published: November 2004

This paper provides an initial assessment of the accuracy of the Atmospheric Infrared Sounder (AIRS) water vapor retrievals from 500 to 100 mbar. AIRS satellite measurements are compared with accurate aircraft (NASA WB57) and balloon in situ water vapor measurements obtained during the NASA Pre‐Aura Validation Experiment (Pre‐AVE) in Costa Rica during Jan. 2004. AIRS retrieval (each pressure level of a single footprint) of water vapor amount agrees with the in situ measurements to ∼25% or better if matched closely in time (1 hr) and space (50–100 km). Both AIRS and in situ measurements observe similar significant variation in moisture amount over a two‐day period, associated with large‐scale changes in weather patterns.
The strength of El Niño and the spatial extent of tropical drought
Authors: Lyon Bradfield
Published: November 2004

During El Niño events, several spatially coherent, nearly synchronous droughts typically develop in teleconnected tropical land areas. These droughts, reflected in below‐average tropical mean land area precipitation, are frequently accompanied by multiple and wide ranging impacts. Here it is shown, based on precipitation observations for the past half‐century, that there is a remarkably robust relationship between El Niño strength and the spatial extent of drought in the global tropics. Not reported previously, drought covers more than twice the land area in strong versus weak El Niños and in many areas severe drought is shown to be more likely during El Niño than for all other times. The results provide insight into large‐scale tropical rainfall variability and have implications for future droughts under global warming scenarios.
Tracing sources of nitrate in snowmelt runoff using a high‐resolution isotopic technique
Authors: Ohte N. , Sebestyen S. D. , Shanley J. B. , Doctor D. H. , Kendall C. , Wankel S. D. , Boyer E. W.
Published: November 2004

The denitrifier method to determine the dual isotopic composition (δ15N and δ18O) of nitrate is well suited for studies of nitrogen contributions to streams during runoff events. This method requires only 70 nmol of NO3− and enables high throughput of samples. We studied nitrate sources to a headwater stream during snowmelt by generating a high‐temporal resolution dataset at the Sleepers River Research Watershed in Vermont, USA. In the earliest phase of runoff, stream NO3− concentrations were highest and stream discharge, NO3− concentrations, and δ18O of NO3− generally tracked one another during diurnal melting. The isotopic composition of stream NO3− varied in‐between atmospheric and groundwater NO3− end members indicating a direct contribution of atmospherically‐derived NO3− from the snow pack to the stream. During the middle to late phases of snowmelt, the source shifted toward soil NO3− entering the stream via shallow subsurface flow paths.
Changes in the ocean transport through Drake Passage during the 1980s and 1990s, forced by changes in the Southern Annular Mode
Authors: Meredith Michael P. , Woodworth Philip L. , Hughes Chris W. , Stepanov Vladimir
Published: November 2004

We present the first direct evidence that interannual changes in ocean transport through Drake Passage are forced by variability in the Southern Annular Mode (SAM). This evidence is derived from two decades (1980s and 1990s) of subsurface pressure measurements from the tide gauge at Faraday station (western Antarctic Peninsula), combined with the output of an ocean general circulation model. In recent decades, the SAM has moved toward a higher‐index state (stronger circumpolar winds); this trend is not simply monotonic, but is the product of a long‐term change in the seasonality of the SAM. Whilst we cannot address directly the effect of the long‐term trend on circumpolar transport, bottom pressure data from Drake Passage during the 1990s demonstrate that ocean transport showed the same changes in seasonality as did the SAM. This offers a mechanism for atmospheric climate change to influence directly the large‐scale ocean circulation.
Impacts of the eruption of Miyakejima Volcano on air quality over far east Asia
Authors: Kajino Mizuo , Ueda Hiromasa , Satsumabayashi Hikaru , An Junling
Published: November 2004

A regional‐scale Eulerian Model System for Soluble Particles (MSSP) was constructed to simulate environmental changes caused by a SO42− increase as the result of the eruption of Miyakejima Volcano in the northwest Pacific Ocean. The measured volcanic SO2 emission was 9 Tg yr−1 for a year from the beginning of the eruption, July 2000. It is equivalent to 70% of global volcanic emission and 6.9% of global anthropogenic emission. Seasonal variations of the volcanic sulfate increase, and change of gas‐aerosol partitioning of NH3 and pH decrease of precipitation were studied using the MSSP model for 1 year from September 2000 to August 2001, together with observations performed at Happo Ridge observatory in the mountainous area in central Japan. In winter, northwesterly wind prevails, and volcanic SO42− was mainly transported southeastward to the Pacific Ocean while volcanic SO42− was transported southwestward to Japan, Korea, and Taiwan, owing to the subtropical high‐pressure system over the Pacific Ocean in summer. Temporal variations of SO42− concentrations and gas‐aerosol equilibrium of NH3 at Happo Ridge were well‐simulated. In the plume from the Asian continent, 98.7% of total SO42− was anthropogenic, and 63.5% of NH3 existed in aerosol phase as (NH4)2SO4. In the volcanic plume, 95.5% was volcanic, excessive sulfate fixed 100% of NH3 into aerosol phase, and aerosol was strongly acidified. Modeled annual mean pH of precipitation in Japan decreased by 0.3–1.0, which is equivalent to neutralization by yellow sand.
Turbulent exchange of heat, water vapor, and momentum over a Tibetan prairie by eddy covariance and flux variance measurements
Authors: Choi Taejin , Hong Jinkyu , Kim Joon , Lee Heechoon , Asanuma Jun , Ishikawa Hirohiko , Tsukamoto Osamu , Zhiqiu Gao , Ma Yaoming , Ueno Kenichi , Wang Jiemin , Koike Toshio , Yasunari Tetsuo
Published: November 2004

Land‐atmosphere interactions on the Tibetan Plateau are important because of their influence on energy and water cycles on both regional and global scales. Flux variance and eddy covariance methods were used to measure turbulent fluxes of heat, water vapor, and momentum over a Tibetan shortgrass prairie during the Global Energy and Water Cycle Experiment (GEWEX) Asian Monsoon Experiment (GAME) in 1998. Under unstable conditions during the monsoon period (July–September), the observed standard deviations of temperature and specific humidity (normalized by appropriate scaling parameters) followed the Monin‐Obukhov theory. The similarity constants for heat CT and water vapor Cq in their dimensionless functions of stability under a free convection limit were both 1.1, unlike the differences (i.e., CT ≤ Cq) reported in other studies. While the transfer efficiency of heat and water vapor exchange generally agreed with the prediction from the Monin‐Obukhov theory, momentum exchange was less efficient than predicted. In comparison with the eddy covariance data, the flux variance method (with CT = Cq = 1.1) underestimated both heat and water vapor fluxes by <5%. When the eddy covariance data were absent, the flux variance method was used for gap filling the seasonal flux database. To estimate latent heat flux during the premonsoon period in June, CT/Cq was approximated as rTq (where rTq is a correlation coefficient for the fluctuations of temperature and water vapor) because of the sensitivity of Cq to changes in soil moisture conditions. The dramatic changes in the Bowen ratio from 9.0 to 0.4 indicate the shift of energy sources for atmospheric heating over the plateau, which, in turn, resulted in the shift of turbulent exchange mechanisms for heat and water vapor.
Eleven‐year solar cycle signal throughout the lower atmosphere
Authors: Coughlin K. , Tung K. K.
Published: November 2004

A statistically significant atmospheric signal, which represents the influence of solar radiation changes on our climate, is found in global data (1958–2003). Using a nonlinear, nonstationary time series analysis, called empirical mode decomposition, it is shown that atmospheric temperatures and geopotential heights are composed of five global oscillations and a trend. The fourth mode is synchronized with the 11‐year solar flux almost everywhere in the lower atmosphere. Statistical tests show that this signal is different from noise, indicating that there is enhanced warming in the troposphere during times of increased solar radiation.
Climate response of fossil fuel and biofuel soot, accounting for soot's feedback to snow and sea ice albedo and emissivity
Authors: Jacobson Mark Z.
Published: November 2004

The first three‐dimensional global model in which time‐dependent spectral albedos and emissivities over snow and sea ice are predicted with a radiative transfer solution, rather than prescribed, is applied to study the climate response of fossil fuel plus biofuel black carbon plus organic matter (ff+bf BC+OM) when BC absorption in snow and sea ice is accounted for. The model treats the cycling of size‐resolved BC+OM between emission and removal by dry deposition and precipitation from first principles. Particles produce and enter size‐resolved clouds and precipitation by nucleation scavenging and aerosol‐hydrometeor coagulation. Removal brings BC to the surface, where internally and externally mixed BC in snow and sea ice affects albedo and emissivity through radiative transfer. Climate response simulations were run with a ff+bf BC+OC emission inventory lower than that used in a previous study. The 10‐year, globally averaged ff+bf BC+OM near‐surface temperature response due to all feedbacks was about +0.27 K (+0.32 in the last 3 years), close to those from the previous study (5‐year average of +0.3 K and fifth‐year warming of +0.35 K) and its modeled range (+0.15 to +0.5 K) because warming due to soot absorption in snow and sea ice here (10‐year average of +0.06 K with a modeled range of +0.03 to +0.11 K) offset reduced warming due to lower emission. BC was calculated to reduce snow and sea ice albedo by ∼0.4% in the global average and 1% in the Northern Hemisphere. The globally averaged modeled BC concentration in snow and sea ice was ∼5 ng/g; that in rainfall was ∼22 ng/g. About 98% of BC removal from the atmosphere was due to precipitation; the rest was due to dry deposition. The results here support previous findings that controlling ff+bf BC+OM and CO2 emission may slow global warming.
Convective generation of cirrus near the tropopause
Authors: Garrett T. J. , Heymsfield A. J. , McGill M. J. , Ridley B. A. , Baumgardner D. G. , Bui T. P. , Webster C. R.
Published: November 2004

During the July 2002 CRYSTAL‐FACE field program based from Key West, Florida, aircraft measurements showed that long‐lived thin tropopause cirrus (TTC) layers were often present above thunderstorm anvils. This paper describes these clouds and explores their possible origins. Measurements showed that the horizontal dimensions of TTC layers were nearly identical to convectively formed anvils beneath, but that TTC did not appear to have originated from convective detrainment. Rather, they appeared to have formed in stably stratified air derived from high altitudes near the tropopause. TTC were separated vertically from the top of the anvil by ∼1 km, they lacked precipitation particles, and they were strongly depleted in HDO, all of which indicate in situ formation. However, compared to surrounding clear air near the tropopause, TTC were enriched in moisture and trace gases. The degree of enrichment was consistent with mixing of air near the tropopause with the same convective air mass that produced the anvil. Unlike surrounding air, TTC had embedded a monochromatic gravity wave with a wavelength of 2 km and an amplitude of several hundred meters. This evidence, supported by a photograph from CRYSTAL‐FACE, leads to the conjecture that TTC originate as stratiform pileus clouds that form near the tropopause ahead of vigorous convective uplift. We hypothesize that the pileus are penetrated by the convection, moistened through turbulent mixing, and once the convection subsides, they are sustained by radiative cooling due to the presence of the anvil layer beneath.
Hygroscopic properties of levoglucosan and related organic compounds characteristic to biomass burning aerosol particles
Authors: Mochida Michihiro , Kawamura Kimitaka
Published: November 2004

Biomass burning, which is characterized by pyrolysis as well as vaporization and condensation of biomass constituents, is a significant source of atmospheric organic aerosols. In this study, hygroscopic properties of five organic compounds (levoglucosan, D‐glucose, and vanillic, syringic, and 4‐hydroxybenozoic acids), which are major pyrolysis products of wood, were measured using a tandem differential mobility analyzer. Levoglucosan, which is typically the most abundant species in wood burning aerosols, showed a significant hygroscopic growth for particles with a diameter of 100 nm. No efflorescence was observed under the measured relative humidity, and a supersaturated condition of levoglucosan‐water particles was observed. The growth factors of levoglucosan are 1.08, 1.18, 1.23, and 1.38 at relative humidity (RH) of 60, 80, 85, and 90%, respectively. The measured hygroscopic curves are in general consistent with those estimated from ideal solution theory and Uniquac Functional‐Group Activity Coefficient (UNIFAC) and Conductor‐Like Screening Model for Real Solvent (COSMO‐RS) methods. Significant hygroscopic growth was also observed for D‐glucose, whose growth factor is quite similar to that of levoglucosan. However, three model pyrolysis products of lignin (i.e., vanillic‐, syringic‐, and 4‐hydroxybenzoic acids) did not show any hygroscopic growth under the RH conditions up to 95%. On the basis of the organic composition of wood burning aerosols, the water absorption attributed to levoglucosan in wood burning aerosols is calculated to be up to 30% of the organic mass at 90% RH. This study demonstrates that oxygenated organics emitted from biomass burning could significantly enhance the hygroscopic properties of atmospheric aerosols.
What do accumulation records of single ice cores in Greenland represent?
Authors: Crüger Traute , Fischer Hubertus , von Storch Hans
Published: November 2004

It is investigated to what extent multiannual accumulation time series from Greenland reflect dynamic and thermodynamic processes and how representative single accumulation series are for the entire ice sheet. Furthermore, it is examined whether accumulation is related to low‐level atmospheric temperatures. For this purpose, two kinds of regression models are developed which linearly relate multiannual accumulation records to meteorological mean fields. Seven ice cores from north to central Greenland and the NCEP Reanalysis data are used for the period from 1948 to 1992. In order to reduce noise, the data are smoothed with a weighted 5‐year running mean. The downscaling technique is based on a stepwise multiple linear regression. One group of regression models distinguishes between dynamic and thermodynamic atmospheric effects. For that reason, stream functions are used in a first step to describe the dynamically controlled accumulation, whereas the thermodynamically controlled accumulation is determined by temperature in a second step. For six of the ice cores, these regression models describe more than 56% of the variability of the smoothed accumulation series, confirming that they represent to a large extent atmospheric states. Multiannual accumulation variability is found to dominantly represent circulation variability. However, the circulation fields that are linked with accumulation show marked differences among the cores concerning the represented seasons, areas, and structures. Thus local accumulation generally represents only regional‐scale climate features, which are probably to a great extent influenced by orography. Furthermore, regression models using only 700 hPa temperature as predictor show that a general linear relationship between accumulation and temperature does not exist over this 45‐year time interval. Therefore paleoaccumulation rates derived from isotopic temperatures should be interpreted with caution. Moreover, it is not reasonable to describe accumulation by means of temperature in mass balance models for the Greenland ice sheet in decadal timescales.
Air‐ground temperature coupling and subsurface propagation of annual temperature signals
Authors: Smerdon Jason E. , Pollack Henry N. , Cermak Vladimir , Enz John W. , Kresl Milan , Safanda Jan , Wehmiller John F.
Published: November 2004

Borehole‐based reconstructions of ground surface temperature (GST) have been widely used as indicators of paleoclimate. These reconstructions assume that heat transport within the subsurface is conductive. Climatic interpretations of GST reconstructions also assume that GST is strongly coupled to surface air temperature (SAT) on timescales of decades and longer. We examine these two assumptions using records of SAT and subsurface temperature time series from Fargo, North Dakota; Prague, Czech Republic; Cape Henlopen State Park, Delaware; and Cape Hatteras National Seashore, North Carolina. The characteristics of downward propagating annual temperature signals at each site clearly indicate that heat transport can be described as one‐dimensional conduction in a homogeneous medium. Extrapolations of subsurface observations to the ground surface yield estimates of annual GST signals and allow comparisons to annual SAT signals. All annual GST signals are modestly attenuated and negligibly phase shifted relative to SAT. The four sites collectively demonstrate that differences between annual GST and SAT signals arise in both summer and winter seasons, in amounts dependent on the climatic setting of each site.
Localization of individual lightning discharges via directional and temporal triangulation of sferic measurements at two distant sites
Authors: Wood T. G. , Inan U. S.
Published: November 2004

Lightning discharges generate electromagnetic pulses, known as sferics, that propagate through the waveguide formed by the Earth and the ionosphere. The energy in the VLF band can propagate over great distances (∼10,000 km) with low loss (3 dB/Mm) and can therefore be detected far from the source lightning location. Using sferic measurements from VLF receivers at Palmer Station, Antarctica, and Vieques Island, Puerto Rico, the locations of lightning discharges from regions such as South America, North America, and Africa are triangulated. Both sferic arrival azimuth at the two receivers and the time of arrival difference between the receivers are used to find the best estimate of the lightning discharge location. Owing to the extremely wide separation of the two receivers, ambiguities sometimes result in pairing sferics detected at one site to their matching sferics detected at the other site. In these cases a best‐best estimate scheme is used. Simulation results indicate that for the two receivers considered here the most accurate location performance is in South America with an expected median location error of ∼75 km. The system has the worst performance due north of the Vieques Island site, with an expected median location error of ∼2000 km. Triangulation results for South America are shown for the period 7–10 September 2001. Results for 8 September 2001 are compared to cloud‐to‐ground lightning flashes detected by the National Lightning Detection Network. For this day, 49% of flashes were detected with a median error of about 200 km. Results are also compared to lightning discharges detected by the Lightning Imaging Sensor (LIS) aboard the Tropical Rainfall Measuring Mission (TRMM) satellite. For a particular TRMM pass over South America, 20% of flashes detected by LIS were correctly located using the described technique, with a median error of 187 km. The event rate for a localized South American storm is also monitored and documented for the same 4‐day period.
Synergy between 1‐D and 3‐D radiation transfer models to retrieve vegetation canopy properties from remote sensing data
Authors: Pinty B. , Gobron N. , Widlowski J.‐L. , Lavergne T. , Verstraete M. M.
Published: November 2004

We devise a computer efficient and flexible inversion technique to retrieve vegetation canopy parameters, in particular the Leaf Area Index, from the radiance field emerging at the top of a structurally heterogeneous systems overlying an anisotropic spatially uniform surface background. The proposed inversion strategy focuses on a reanalysis of multiangle and multispectral measurements unhindered by the many specific constraints imposed by the operational application of the current algorithms and their associated limitations on data staging. This technique capitalizes on the decoupling between contributions due to the canopy only and those invoking the background reflectance properties. These contributions are decomposed into the wavelength dependent and independent contributions. A quasi‐linear relationship is thus obtained between the radiance/reflectance emerging from the top of the canopy layer and the background reflectance. Although all individual contributions can be estimated from accurate three‐dimensional radiation transfer models, we propose appropriate approximations in order to estimate the minor terms. These approximations exploit the relatively limited dependency exhibited by these relatively smaller contributions with respect to the azimuthal coordinate. Moreover, additional mathematical developments are proposed to further approximate these terms by their corresponding solutions obtained in the limit case of a plane‐parallel turbid medium scenario. They require defining effective values of the state variables entering the plane‐parallel turbid medium model. The resulting reflectance of a three‐dimensional spatially heterogeneous vegetation layer is driven by a sum of contributions that can be precomputed offline on the basis of the three‐dimensional and plane‐parallel homogeneous turbid medium model capabilities. The decoupling of the intrinsic vegetation and the background contributions allows many of the contributions to be precomputed and stored in look‐up tables. This development yields a simple and computer efficient inversion scheme that allows us to jointly retrieve the values of the main vegetation layer attributes and the underlying background radiative properties. Demonstration tests based on actual multiangular and multispectral data set are currently being investigated.
Inhibition of bacterial translocation by chronic ethanol consumption in the rat
Authors: BRAULIO VALERIA BENDER , DE QUEIROZ CÔRTES MAURO , BORGES‐NETO ARMANDO A. , BASTOS MARCO AURÉLIO , CRUZ MARCELO SOUZA , FRACALANZA SÉRGIO EDUARDO
Published: November 2004

Chronic ethanol ingestion has been associated with small intestine morphological changes, disrupted host mucosal defenses and bacterial overgrowth. Since bacterial translocation (BT) may result from such alterations, we have investigated the potential effect of chronic ethanol consumption on BT. For this purpose, male Wistar rats were fed a liquid diet containing 5% v/v ethanol for 4 weeks (EG, n=16), and a pair‐fed group received equal daily amounts of calories in a similar diet without ethanol (PFG, n=16). On experimental day 29, distal ileum ligature and small intestine inoculation of a tetracycline‐resistant E. coli strain (Tc®E. coli R6) followed by duodenal ligature was performed. After 1 or 5 h post inoculation, mesenteric lymph nodes, liver, spleen and kidney were excised. Unexpectedly, rats of the EG presented markedly less BT to the mesenteric lymph nodes (p<0.001) and to the other organs examined compared to rats of the PFG. This BT inhibition was observed at 1 and 5 h after bacterial inoculation, and may be attributed exclusively to chronic ethanol ingestion. Since alcoholism is well known to decrease host immunity, these results suggest that other factors, independent of the immune function, may be involved in the BT inhibition observed in this study.
Application of molecular biology techniques to the diagnosis of nontuberculous mycobacterial infections
Authors: RUÍZ M. , RODRÍGUEZ J. C. , ESCRIBANO I. , GARCÍA‐MARTÍNEZ J. , RODRÍGUEZ‐VALERA F. , ROYO G.
Published: November 2004

A total of 19,723 clinical samples were cultivated for the detection of mycobacteria from January 1995 to March 2001. The 203 strains of nontuberculous mycobacteria isolated were identified with the use of molecular techniques in combination with traditional biochemical tests. The molecular methods applied were PCR‐restriction fragment length polymorphism analysis (PRA) alone or in combination with 16S rRNA and 16S‐23S spacer sequencing. The patient records of those with specimens positive for mycobacteria were analysed to evaluate the clinical significance of the culture results. Twenty‐five of the 124 patients analysed (20%) were regarded as having clinical mycobacteriosis. The main species associated with mycobacteriosis were: Mycobacterium avium (13 cases), M. intracellulare (2 cases), M. kansasii (5 cases), M. chelonae (2 cases), M. malmoense (1 case), M. scrofulaceum (1 case) and M. marinum (1 case). The use of PRA alone or in combination with gene sequencing provided valuable help in discerning mycobacteria at both the intra‐ and interspecies level, thus contributing to a faster and more efficient diagnosis and epidemiological follow‐up.
EGFR and p53 expression and proliferative activity in parathyroid adenomas; an immunohistochemical study
Authors: GÜLKESEN KEMAL HAKAN , KILIÇARSLAN BAHAR , ALTUNBAŞ HASAN ALI , KARPUZOGˇLU GÜLTEN
Published: November 2004

EGFR (epidermal growth factor receptor), p53, and proliferative markers provide some clues as to the formation of several tumours. In this study the mechanism of the genesis of parathyroid adenomas was investigated using immunohistochemistry. Sections of parathyroid adenomas from 12 cases were stained using PCNA (proliferating cell nuclear antigen), EGFR, and p53 immunohistochemistry. Correlations between PCNA LI (labelling index), EGFR expression, p53 expression, age, serum parathormone, Ca and P levels, and tumour diameter were investigated. PCNA LI was 45.8±33.1 (mean±standard deviation) and all the cases were somewhat positive. Five cases (41.67 %) were EGFR positive. Maximum 10 % of the cells were positive in these cases. All the cases were p53 negative. There was a correlation between PCNA LI and serum parathormone level (r=0.607, p=0.036). According to these results, parathormone synthesis is high when the proliferative activity of parathyroid adenoma is high. Four of the five EGFR‐positive patients were below 35 years of age. These data may indicate that formation of parathyroid adenoma in young patients is related to a mechanism involving EGFR. Absence of p53 expression suggests that p53 mutation is not a common component of parathyroid adenomas.
Intranodal benign thyroid tissue: Significance of HBME‐1 in differentiation from metastatic papillary thyroid carcinoma
Authors: HIROKAWA MITSUYOSHI , HORIGUCHI HIDEHISA , WAKATSUKI SHINGO , MIKI HITOSHI , SONOO HIROSHI , MANABE TOSHIAKI , SANO TOSHIAKI
Published: November 2004

The aim of this study was to determine the significance of HBME‐1 immunostaining in the differentiation between intranodal benign thyroid tissue and metastatic papillary thyroid carcinoma in the lymph node. Immunohistochemically we examined normal‐appearing intranodal thyroid tissue in four patients who did not show evidence of papillary carcinoma histologically or clinically. We also examined follicular‐pattern‐predominant papillary carcinoma with metastatic foci in the lymph nodes. Normal‐appearing intranodal thyroid tissue and normal thyroid showed no immunopositivity for HBME‐1. In contrast, all papillary carcinomas in both the lymph nodes and thyroid demonstrated strong positivity for HBME‐1. HBME‐1 was predominantly positive for the luminal surface of the tumor cells. The immunopositivity of the cuboidal and low columnar carcinoma cells was more intensive than that of the flat‐shaped cells in the lymph nodes and thyroid. The results probably indicate that HBME‐1 immunostaining is helpful in distinguishing between intranodal benign thyroid tissue and metastatic papillary carcinoma in lymph nodes. We emphasize that the HBME‐1 reactivity should be evaluated in connection with the histological findings, and that positive and negative controls stained in parallel are necessary.
Evolution equation for a thin epitaxial film on a deformable substrate
Authors: Tekalign W. T. , Spencer B. J.
Published: November 2004

We consider a continuum model for the evolution of an epitaxially strained dislocation-free thin solid film on a deformable substrate in the absence of vapor deposition. By using a thin-film approximation we derived a nonlinear evolution equation. We examined the nonlinear evolution equation and found that there is a critical film thickness below which every film thickness is stable and a critical wave number above which every film thickness is stable. Preliminary numerical results indicate that the equation possesses island-like steady state solutions.
The effect of interlevel dielectric on the critical tensile stress to void nucleation for the reliability of Cu interconnects
Authors: Hau-Riege Christine S. , Hau-Riege Stefan P. , Marathe Amit P.
Published: November 2004

We have conducted electromigration experiments and modeling on Cu Damascene structures surrounded by different interlevel dielectric ILD and Cu-cap materials. We have determined the mechanical properties of the surrounding ILD and Cu cap to play a key role in the critical stress change to void nucleation (Δσcrit), which is one of the critical parameters in determining electromigration lifetime or any other void-limited lifetime. Specifically, we found that Δσcrit decreases as the Young’s modulus of the interlevel dielectric decreases, which is the case with low-k materials. In order to compensate for the lower threshold to void nucleation in low-k materials, a stronger emphasis needs to be placed on the quality or adhesion of the Cu∕cap interface, which is currently the preferred site for void nucleation, so that interconnects fabricated in low-k materials continue to meet the ever-increasing electromigration reliability requirements. Finally, the methodology developed in this study, which is based on experiment and modeling, can be used to determine Δσcrit, and therefore the critical jL product, for any combination of ILD and Cu-cap materials.
Nonvolatile two-step, two-color holography with continuous-wave lights for both congruent and near-stoichiometric LiNbO3:Fe
Authors: Shen Yan , Zhang Guoquan , Fu Bo , Xu Qingjun , Xu Jingjun
Published: November 2004

We have studied theoretically the steady-state nonvolatile two-step, two-color holographic recording performance for both the congruent and the near-stoichiometric LiNbO3:Fe based on the two-center model (the deep-trap and the shallow-trap centers are Fe2+∕Fe3+ and NbLi4+∕NbLi5+, respectively). The results show that the direct electron exchange between the Fe2+∕Fe3+ centers and the NbLi4+∕NbLi5+ centers due to the tunneling effect dominates the charge-transfer process during the nonvolatile two-step, two-color holography and determines the two-step, two-color holography performance in LiNbO3:Fe. We have further studied the effects of the crystal stoichiometry on the performance of the two-step, two-color holography. It is shown that, as far as the total space-charge field is considered, the nonvolatile two-step, two-color holography performance in the near-stoichiometric LiNbO3:Fe is much better than that in the congruent LiNbO3:Fe within the intensity range reachable by the continuous-wave lights.
Biexcitonic effect on optical nutation in semiconductor quantum wires
Authors: Sen Pranay K. , Bafna Manish K. , Gupta Saral K.
Published: November 2004

We have proposed a simplified theoretical model to examine the optical nutation in one-dimensional semiconductor quantum wires. We explored the role of excitons, biexcitons, and the effect of confinement in enhancing transient optical processes in such semiconductor nanostructures. We apply the time dependent perturbation technique to the coherent radiation-semiconductor interaction for a three-level system in the near band gap resonant excitation regime. We have incorporated the relaxation and dephasing mechanisms phenomenologically. The induced polarization is calculated theoretically and the role of biexciton density on the polarization is analyzed. Numerical estimations of refractive and absorptive optical nutation have been made for a GaAs∕AlxGa1−xAs quantum wire duly shined by femtosecond pulse Ti: sapphire laser. Our results agree qualitatively with available experimental observations.
Intersubband-coupling and screening effects on the electron subband mobility in a GaAs∕InxGa1−xAs delta-doped double quantum well system
Authors: Sahu T.
Published: November 2004

We study low temperature electron transport mobility μn in a GaAs∕InxGa1−xAs double quantum well structure. Both the extreme barriers are δ doped with Si so that the electrons diffuse into the adjacent wells (InGaAs layers) forming two sheets of two-dimensional electron gas separated by a thin central barrier. The subband electron wave functions and energy levels of the coupled quantum well system are obtained numerically as a function of well width and barrier width. We have considered the effect of alloy disorder scattering and impurity scattering on μn. The screening of the scattering potentials by the 2D-electrons is obtained in terms of the static dielectric response function within the random phase approximation. The effect of screening on the alloy disorder potential, which has been normally neglected due to short range nature of the potential, has been analyzed. We have also studied the effects of the intersubband scattering and coupling of wave functions through the barrier on μn for the multisubband system.
Accurate determination of optical constants of textured SnO2 using low incidence angle spectroscopic ellipsometry
Authors: Paulson P. D. , Hegedus Steven S.
Published: November 2004

Accurate optical constants (n and k) of textured SnO2 films were obtained in the range of 0.85–4.6eV using spectroscopic ellipsometry. The angular dependence of the spectroscopic ellipsometer measurement was determined at incident angles 30°, 50°, and 70° from normal to the sample surface. Depolarization components due to texturing and substrate backside reflection were separately analyzed using the measurement on polished and unpolished samples. Depolarization due to substrate backside reflection was modeled accurately. By performing the measurements at a low angle of incidence (30°), where the depolarization due to texturing is at a minimum and therefore can be neglected in the optical model, one can obtain the accurate values of n and k.
Enhanced ordinary magnetoresistance in Co∕Si systems
Authors: Honda S. , Ishikawa T. , Takai K. , Mitarai Y. , Harada H.
Published: November 2004

The enhancement of the ordinary magnetoresistance (OMR) in Si has been attempted by constructing two type of Co∕Si systems; one is the sputter-deposited current perpendicular to plane-type Co∕Si multilayers and the other is the sputtered-Co∕anodized-porous-Si system. The Co∕Si multilayers show the sharp OMR at a low field and the negative granular-type giant magnetoresistance at higher fields. At 50K, however, only the OMR appears with the ratio of about 3.0% for an in-plane field of 10kOe. In the Co∕anodized-Si system, a very large OMR of about 60% is observed at 50K for perpendicular field of 10kOe.
Structural, optical, and electrical characterization of gadolinium oxide films deposited by low-pressure metalorganic chemical vapor deposition
Authors: Singh M. P. , Thakur C. S. , Shalini K. , Banerjee S. , Bhat N. , Shivashankar S. A.
Published: November 2004

We report the growth and characterization of gadolinium oxide films deposited on Si(100) and fused quartz in the temperature range of 450–800°C by a low-pressure metalorganic chemical vapor deposition technique using a β-diketonate complex of gadolinium as the precursor. The x-ray diffractometry study of the films reveals that, irrespective of the growth temperature, the films grown on fused quartz (i.e., an amorphous substrate) and silicon (i.e., a single-crystal substrate) comprise the cubic Gd2O3 phase with a (111) texture. However, the films grown on fused quartz at higher temperatures also show the presence of the monoclinic phase of Gd2O3. The growth of strongly oriented films on fused quartz has been understood on the basis of minimization of the surface energy. The scanning electron microscopy and atomic force microscopy studies reveal that the films grown at or above 525°C are densely packed and grainy. Optical properties of the films, as studied by ultraviolet (UV)-visible spectrophotometry and Fourier transform infrared spectroscopy, are found to depend strongly on the chemical vapor deposition condition. The analyses reveal further that the films grown at or above 500°C are free of heteroatoms, i.e., C, N, and H. The optical band gap of the films is in the range of 5.0–5.4eV. Electrical characterization was carried out on Al∕Gd2O3∕Si metal-insulator-semiconductor structures by capacitance–voltage (C–V) and current–voltage analyses. The effective dielectric constant of the films was in the range of 7–23. The bidirectional C–V characteristics show a counterclockwise hysteresis due to the presence of slow interface traps. A minimum leakage current of 4.6×10–5A∕cm2 at the 1-MV∕cm field was demonstrated.
Improved contact resistance and linearity in optoelectronic devices with an intermediate quaternary layer
Authors: Przybylek G. J. , Reynolds, C. L. , Walters F. S.
Published: November 2004

The importance of the heterojunction between the contact and cladding layers in the contact resistance of optoelectronic devices is investigated. The incorporation of a quaternary layer, intermediate in composition, between these layers is shown to provide specific contact resistances at least 60% lower with some Rc values <10−7Ωcm2 and high-speed tandem modulators with an improved linearity and reduced series resistance. The lowering of the potential barrier for hole transport is most likely responsible for these observations. The thermal stability is quite good.