bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of vibrationally excited nitrogen in the formation of the mid-latitude negative ionospheric storms
Authors: Pavlov A. V.
Published: April 2005

Abstract. Millstone Hill ionospheric storm time measurements of the electron density and temperature during the ionospheric storms (15-16 June 1965; 29-30 September 1969 and 17-18 August 1970) are compared with model results. The model of the Earth's ionosphere and plasmasphere includes interhemispheric coupling, the H+, O+(4S), O+(2D), O+(2P), NO+, O+2 and N+2 ions, electrons, photoelectrons, the electron and ion temperature, vibrationally excited N2 and the components of thermospheric wind. In order to model the electron temperature at the time of the 16 June 1965 negative storm, the heating rate of the electron gas by photoelectrons in the energy balance equation was multiplied by the factors 5-30 at he altitude above 700 km for the period 4.50-12.00 LT, 16 June 1965. The [O]/[N2] MSIS-86 decrease and vibrationally excited N2 effects are enough to account for the electron density depressions at Millstone Hill during the three storms. The factor of 2 (for 27-30 September 1969 magnetic storm) and the & actor 2.7 (for 16-18 August 1970 magnetic storm) reduction in the daytime peak density due to enhanced vibrationally excited N2 is brought about by the increase in the O++N2 rate factor.
Ring current and auroral electrojets in connection with interplanetary medium parameters during magnetic storm
Authors: Feldstein Y. I. , Levitin A. E. , Golyshev S. A. , Dremukhina L. A. , Vestchezerova U. B. , Valchuk T. E. , Grafe A.
Published: April 2005

Abstract. The relationship between the auroral electrojet indices (AE) and the ring current magnetic field (DR) was investigated by observations obtained during the magnetic storm on 1-3 April 1973. During the storm main phase the DR development is accompanied by a shift of the auroral electrojets toward the equator. As a result, the standard AE indices calculated on the basis of data from auroral observatories was substantially lower than the real values (AE'). To determine AE' during the course of a storm main phase data from subauroral magnetic observatories should be used. It is shown that the intensity of the indices (AE') which take into account the shift of the electrojets is increased substantially relative to the standard indices during the storm main phase. AE' values are closely correlated with geoeffective solar wind parameters. A high correlation was obtained between AE' and the energy flux into the ring current during the storm main phase. Analysis of magnetic field variations during intervals with intense southward IMF components demonstrates a decrease of the saturation effect of auroral electrojet currents if subauroral stations magnetic field variations are taken into account. This applies both to case studies and statistical data. The dynamics of the electrojets in connection with the development of the ring current and of magnetospheric substorms can be described by the presence (absence) of saturation for minimum (maximum) AE index values during a 1-h interval. The ring current magnetic field asymmetry (ASY) was calculated as the difference between the maximum and minimum field values along a parallel of latitude at low latitudes. The ASY value is closely correlated with geoeffective solar wind parameters and simultaneously is a more sensitive indicator of IMF Bz variations than the symmetric ring current. ASY increases (decreases) faster during the main phase (the recovery phase) than DR. The magnetic field decay at low latitudes in the recovery phase occurs faster in the afternoon sector than at dusk.
A superposed epoch analysis of geomagnetic storms
Authors: Taylor J. R. , Lester M. , Yeoman T. K.
Published: April 2005

Abstract. A superposed epoch analysis of geomagnetic storms has been undertaken. The storms are categorised via their intensity (as defined by the Dst index). Storms have also been classified here as either storm sudden commencements (SSCs) or storm gradual commencements (SGCs, that is all storms which did not begin with a sudden commencement). The prevailing solar wind conditions defined by the parameters solar wind speed (vsw), density (ρsw) and pressure (Psw) and the total field and the components of the interplanetary magnetic field (IMF) during the storms in each category have been investigated by a superposed epoch analysis. The southward component of the IMF, appears to be the controlling parameter for the generation of small SGCs (-100 nT< minimum Dst ≤ -50 nT for ≥ 4 h), but for SSCs of the same intensity solar wind pressure is dominant. However, for large SSCs (minimum Dst ≤ -100 nT for ≥ 4 h) the solar wind speed is the controlling parameter. It is also demonstrated that for larger storms magnetic activity is not solely driven by the accumulation of substorm activity, but substantial energy is directly input via the dayside. Furthermore, there is evidence that SSCs are caused by the passage of a coronal mass ejection, whereas SGCs result from the passage of a high speed/ slow speed coronal stream interface. Storms are also grouped by the sign of Bz during the first hour epoch after the onset. The sign of Bz at t = +1 h is the dominant sign of the Bz for ~24 h before the onset. The total energy released during storms for which Bz was initially positive is, however, of the same order as for storms where Bz was initially negative.
Observations of 50-MHz type-II coherent echoes from within the polar cap
Authors: Kustov A. V. , Koehler J. A. , Sofko G. J. , Danskin D. W. , McKibben M. J.
Published: April 2005

Abstract. 50-MHz type-II coherent echoes at geometrical aspect angles of 11.5° have been observed in the northern polar cap during pre-noon hours. The echoes had an unusually large Doppler width of 1200-1400 m s-1 and were well correlated with strong magnetic disturbances in the range 500-1000 nT. The dependence of intensity, spectral width and skewness versus radial velocity were similar to those known from previous experiments at lower latitudes and at small aspect angles. It is concluded that echo onset was due to the combination of several factors, including a highly conducting ionosphere, the presence of a very intense electric field, and strong radar wave refraction.
Development and evaluation of airborne microwave refractometer for studies on atmospheric tropical boundary layer radiorefractive index
Authors: Sarma S. B. S. S. , Reddy B. M.
Published: April 2005

Abstract. Observations of high-resolution data on radio refractivity were obtained by the airborne microwave refractometer over the Indian sub-continent (a tropical country) from 1971 to 1988. Detailed vertical and horizontal distributions of radio refractivity on a near-real-time basis in the atmospheric boundary layer were determined . Radiosonde observations cannot detect the thin refractivity gradients which characterize the propagation environment in this low-altitude region. This knowledge is required to design reliable and efficient communication systems for strategic, tactical and operational needs. However, the results demonstrate the layer structures and the variability of the boundary layer in time and space. The radio refractive effects on electromagnetic propagation and the future direction of radio refractivity fine-structure measurements are discussed.
South Atlantic circulation in a world ocean model
Authors: England Matthew H. , Garçon Véronique C.
Published: April 2005

Abstract. The circulation in the South Atlantic Ocean has been simulated within a global ocean general circulation model. Preliminary analysis of the modelled ocean circulation in the region indicates a rather close agreement of the simulated upper ocean flows with conventional notions of the large-scale geostrophic currents in the region. The modelled South Atlantic Ocean witnesses the return flow and export of North Atlantic Deep Water (NADW) at its northern boundary, the inflow of a rather barotropic Antarctic Circumpolar Current (ACC) through the Drake Passage, and the inflow of warm saline Agulhas water around the Cape of Good Hope. The Agulhas leakage amounts to 8.7 Sv, within recent estimates of the mass transport shed westward at the Agulhas retroflection. Topographic steering of the ACC dominates the structure of flow in the circumpolar ocean. The Benguela Current is seen to be fed by a mixture of saline Indian Ocean water (originating from the Agulhas Current) and fresher Subantarctic surface water (originating in the ACC). The Benguela Current is seen to modify its flow and fate with depth; near the surface it flows north-westwards bifurcating most of its transport northward into the North Atlantic Ocean (for ultimate replacement of North Atlantic surface waters lost to the NADW conveyor). Deeper in the water column, more of the Benguela Current is destined to return with the Brazil Current, though northward flows are still generated where the Benguela Current extension encounters the coast of South America. At intermediate levels, these northward currents trace the flow of Antarctic Intermediate Water (AAIW) equatorward, though even more AAIW is seen to recirculate poleward in the subtropical gyre. In spite of the model's rather coarse resolution, some subtle features of the Brazil-Malvinas Confluence are simulated rather well, including the latitude at which the two currents meet. Conceptual diagrams of the recirculation and interocean exchange of thermocline, intermediate and deep waters are constructed from an analysis of flows bound between isothermal and isobaric surfaces. This analysis shows how the return path of NADW is partitioned between a cold water route through the Drake Passage (6.5 Sv), a warm water route involving the Agulhas Current sheeding thermocline water westward (2.5 Sv), and a recirculation of intermediate water originating in the Indian Ocean (1.6 Sv).
South Atlantic sea surface temperature anomalies and air-sea interactions: stochastic models
Authors: Dobrovolski S. G.
Published: April 2005

Abstract. Data on the South Atlantic monthly sea surface temperature anomalies (SSTA) are analysed using the maximum-entropy method. It is shown that the Markov first-order process can describe, to a first approximation, SSTA series. The region of maximum SSTA values coincides with the zone of maximum residual white noise values (sub-Antarctic hydrological front). The theory of dynamic-stochastic climate models is applied to estimate the variability of South Atlantic SSTA and air-sea interactions. The Adem model is used as a deterministic block of the dynamic-stochastic model. Experiments show satisfactorily the SSTA intensification in the sub-Antarctic front zone, with appropriate standard deviations, and demonstrate the leading role of the abnormal drift currents in these processes.
Ground-based mobile scanning LIDAR for remote sensing of contrails
Authors: Freudenthaler V. , Homburg F. , Jäger H.
Published: April 2005

Abstract. Air traffic is a source of trace gases in the upper troposphere and lower stratosphere. Contrails readily form from water vapor exhausts under favorable meteorological conditions. Since contrails are ice crystal clouds like natural cirrus clouds, they bear a greenhouse potential which has to be investigated. The IFU has built a scanning lidar system employing a pulsed Nd:YAG laser as the emitter and a 52-cm diameter telescope as the receiver. Signals are processed in several channels to investigate depolarization and wavelength dependencies of the light backscattered from ice crystals. These investigations are aimed at the formation and life cycles of contrails, their optical properties, and their climatological consequences in areas of dense air traffic. The experimental lidar setup is described and a sample measurement is shown.
The transformation of magnetoacoustic waves into Alfvén waves inside the magnetosphere
Authors: Kozlovsky A. E. , Safargaleev V. V. , Lyatsky W. B.
Published: April 2005

Abstract. A mechanism for the transformation of a magnetoacoustic wave into an Alfvén wave is proposed. During the compression of the magnetosphere by the solar wind the inner edge of the plasma sheet and the contours of B=const move in different ways. In the case of asymmetrical compression, the contours of B=const will cross the inner edge of the plasma sheet. To close the drift currents - that flow in the plasma sheet along the contours of B=const - the appearance of the field-aligned currents is necessary. This appearance corresponds to the generation of the Alfvén wave.
Long-term variations in the geomagnetic activity level Part II: Ascending phases of sunspot cycles
Authors: Mussino V. , Borello Filisetti O. , Storini M. , Nevanlinna H.
Published: April 2005

Abstract. Monthly averages of the Helsinki Ak-values have been reduced to the equivalent aa-indices to extend the aa-data set back to 1844. A periodicity of about five cycles was found for the correlation coefficient (r) between geomagnetic indices and sunspot numbers for the ascending phases of sunspot cycles 9 to 22, confirming previous findings based on a minor number of sunspot cycles. The result is useful to researchers in topics related to solar-terrestrial physics, particularly for the interpretation of long-term trends in geomagnetic activity during the past, and to forecast geomagnetic activity levels in the future.
Particle-in-cell plasma simulations of the modified two-stream instability
Authors: Schlegel K. , Thiemann H.
Published: April 2005

Abstract. We model the modified two-stream plasma instability occurring in the ionospheric E-region using a 2.5-dimensional particle-in-cell code. Compared to previous similar work we concentrate on simulated quantities that can easily be measured in the real ionosphere by coherent radars or rockets, such as the Doppler velocity, the backscattered power, backscattered spectra, aspect angle behaviour and electron temperature enhancement. Despite using a relatively small simulation model, we obtain remarkably good agreement between actual observed and simulated plasma parameters. The advantage of such a small system is that we were able to perform (other than in previous related work) many simulation runs with different sets of input parameters, thus studying the unstable plasma under various conditions.
Evidence of a 50-year increase in tropospheric ozone in Upper Bavaria
Authors: Schmidt M.
Published: April 2005

Abstract. In a series of ozone-sonde soundings at the Hohenpeißenberg observatory, starting in 1967, the most striking features are increases of \\sim2.2% per year in all tropospheric heights up to 8 km during the past 24 years. These facts have recently been published and discussed by several authors. In this paper, we present some evidence for the increase of tropospheric ozone concentrations during the past 50 years 1940-1990 in the territory of the northern edge of the Bavarian Alps, including the Hohenpeißenberg data. In December 1940 and August 1942, probably the first exact wet-chemical vertical soundings of ozone up to 9 km height were made by an aircraft in the region mentioned. These results were published in the earlier literature. We have converted the results of the flights on 4 days in December 1940 and on 6 days in August 1942 to modern units and have compared them with the Hohenpeißenberg ozone-sonde data of the December and August months. We also compared the data at the ground with the August results of Paris-Montsouris 1886-1898. Our results show an increase of ozone concentration at all tropospheric heights in Upper Bavaria during the past 50 years, compared with the Montsouris data in August during the past 105 years. In the recently published papers, the increases since 1967 were approximated linearly.Our results, extended to the past, show non-linear trends, with steeper increases since 1975-1979. Possible reasons for these findings are discussed. Quite recently (in case of the December months since 1986/87, the August months since 1990), the ozone mixing ratios at and above Hohenpeißenberg seem to have decreased.
Disorders of intermediary metabolism: Toxic leukoencephalopathies
Authors: Hörster F. , Surtees R. , Hoffmann G. F.
Published: April 2005

Myelination starts in the latter half of gestation. It is initiated by oligodendrocyte progenitor cells. Three sequential steps can be distinguished: (1) initial ensheathment of axons by premyelin sheaths generated by oligodendrocyte progenitor cells; (2) initial insertion of myelin basic protein (MBP) into transitional sheaths; and (3) generation of mature MBP‐rich myelin. Different inborn errors of metabolism can interfere with different stages of these physiological processes, causing white‐matter diseases, i.e. toxic leukoencephalopathies. Some inborn errors of metabolism disturb the formation of myelin by being toxic to oligodendrocytes or by interference with the biosynthesis of cholesterol and lipids, e.g. globoid cell leukodystrophy and phenylketonuria. Remethylation defects, e.g. methylenetetrahydrofolate reductase deficiency, cobalamin C, D, E, F and G defects, interfere with the expression, processing and insertion of MBP. The concept of excitotoxicity, which has been developed in neurons, has recently been modified and has been extended to the oligodendroglial lineage. Mitochondriopathies and cerebral organic acid disorders may cause secondary excitotoxicity resulting in toxic encephalopathies, which may affect both neurons and oligodendrocytes. This review aims to present relevant diseases, summarizing recent knowledge on mechanisms and formulating testable hypotheses of pathophysiology leading to new and improved treatment strategies.
Gamma‐hydroxybutyric aciduria: A biochemist's education from a heritable disorder of GABA metabolism
Authors: Gibson K. M.
Published: April 2005

In keeping with the theme of the 41st Annual Symposium (Metabolic Encephalopathies), the current report provides an overview of a quarter century of research investigating a rare inborn error of GABA metabolism, succinic semialdehyde dehydrogenase (SSADH) deficiency (also referred to as gamma‐hydroxybutyric aciduria). The clinical phenotype, treatment challenges, pathomechanistic concepts, as well as metabolic, enzymatic and molecular characteristics, of the disorder are summarized. In addition, important features of a recently developed murine model are presented, with discussion of how this model has broadened thinking about, and treatment approaches to, the clinical disease. In addition, a brief scientific history of the author is provided, and an account of how serendipitous circumstances brought him together with other colleagues to begin delineating the aetiological mechanisms in SSADH deficiency. The evolution of research on SSADH deficiency re‐establishes the classical approach beginning at clinical characterization, evolving to enzyme and metabolite identification as well as molecular characterization, and eventually to model development and preclinical treatment approaches. This scientific evolution admirably supports the life and ideals of Dr George Komrower, in whose honour this lecture is named.
Microsite variation in light availability and photosynthesis in a cool‐temperate deciduous broadleaf forest in central Japan
Authors: Sakai Toru , Saigusa Nobuko , Yamamoto Susumu , Akiyama Tsuyoshi
Published: April 2005

An empirical light simulation model was applied to estimate stand scale photosynthesis in a deciduous broadleaved forest in central Japan. Based on diurnal courses of photosynthetically active photon flux density (PPFD), we characterized the components of incoming light within the forest canopy, and found that the instantaneous relative PPFD (PPFD under the canopy relative to that above the canopy) under diffuse light condition was a reliable estimator of the intensity and duration of PPFD. We calculated the daily photosynthesis (Aday) for each PPFD class using photosynthesis–light response curves. Model simulated Aday were corroborated with the estimates obtained from the nearby CO2 flux tower. The result demonstrated the potential of the light simulation model. The light use efficiency of two dominant species, Betula ermanii as overstory and Sasa senanensis as understory species, were then evaluated. At the forest understory, PPFD under 50 μmol m−2 s−1 contributed to 77% of the sunshine duration on a completely clear day. Therefore, a higher apparent quantum yield for S. senanensis enhanced the utilization of low PPFD for photosynthesis. On the other hand, at the upper forest canopies, B. ermanii with a higher light‐saturated photosynthetic rate used high PPFD efficiently. Consequently, potential of daily net photosynthesis for both B. ermanii and S. senanensis was high under each light condition. Such interspecific difference in the patterns of light utilization was suggested as one of factors allowing coexistence of the two species in the study forest.
High and low ionospheric conductivity standing guided Alfvén wave eigenfrequencies: A model for plasma density mapping
Authors: Ozeke L. G. , Mann I. R.
Published: April 2005

Numerical solutions to the guided toroidal Alfvén wave equation in a dipole field are presented with symmetric ionospheric Pedersen conductivities ΣPN,S, and using a range of field‐aligned plasma density profiles ∝ 1/rp, where p takes integer values from 0 to 6. We show that weakly damped fundamental guided toroidal Alfvén waves can occur when ΣPN,S are both less than or greater than a critical value. Our results show that for low p values the equatorial plasma density inferred from a measurement of a fundamental mode wave frequency using the high ΣPN,S (“fixed end”) solution can be up to a factor of 4 different from that determined from the low ΣPN,S (“free end”) solution. These results illustrate that in order to correctly invert wave frequency observations and to obtain accurate estimates of the equatorial plasma mass density in the nighttime sector where ΣPN,S may drop below a critical conductivity, the numerical solution of the guided toroidal Alfvén wave equation must be used. In addition, we present results which can be used to scale equatorial plasma densities derived from observed eigenperiods using the analytic WKBJ solutions, with p = 6, into the equatorial plasma densities derived from the solution of the toroidal wave equation for any integer value of p, from 0 to 6, in both the daytime (high ΣPN,S) sectors and nighttime (low ΣPN,S) sectors of the magnetosphere.
A novel site contributing to growth-arrest-specific gene 6 binding to its receptors as revealed by a human monoclonal antibody
Authors: FISHER Paul W. , BRIGHAM-BURKE Michael , WU Sheng-Jiun , LUO Jinquan , CARTON Jill , STAQUET Kim , GAO Wei , JACKSON Sheila , BETHEA Deidra , CHEN Cailin , HU Bing , GILES-KOMAR Jill , YANG Jing
Published: April 2005

Gas6 (growth-arrest-specific gene 6) is a vitamin K-dependent protein known to activate the Axl family of receptor tyrosine kinases. It is an important regulator of thrombosis and many other biological functions. The C-terminus of Gas6 binds to receptors and consists of two laminin-like globular domains LG1 and LG2. It has been reported that a Ca2+-binding site at the junction of LG1 and LG2 domains and a hydrophobic patch at the LG2 domain are important for receptor binding [Sasaki, Knyazev, Cheburkin, Gohring, Tisi, Ullrich, Timpl and Hohenester (2002) J. Biol. Chem. 277, 44164–44170]. In the present study, we developed a neutralizing human monoclonal antibody, named CNTO300, for Gas6. The antibody was generated by immunization of human IgG-expressing transgenic mice with recombinant human Gas6 protein and the anti-Gas6 IgG sequences were rescued from an unstable hybridoma clone. Binding of Gas6 to its receptors was partially inhibited by the CNTO300 antibody in a dose-dependent manner. To characterize further the interaction between Gas6 and this antibody, the binding kinetics of CNTO300 for recombinant Gas6 were compared with independently expressed LG1 and LG2. The CNTO300 antibody showed comparable binding affinity, yet different dependence on Ca2+, to Gas6 and LG1. No binding to LG2 was detected. In the presence of EDTA, binding of the antibody to Gas6 was disrupted, but no significant effect of EDTA on LG1 binding was evident. Further epitope mapping identified a Gas6 peptide sequence recognized by the CNTO300 antibody. This peptide sequence was found to be located at the LG1 domain distant from the Ca2+-binding site and the hydrophobic patch. Co-interaction of Gas6 with its receptor and CNTO300 antibody was detected by BIAcore analysis, suggesting a second receptor-binding site on the LG1 domain. This hypothesis was further supported by direct binding of Gas6 receptors to an independently expressed LG1 domain. Our results revealed, for the first time, a second binding site for Gas6–receptor interaction.
Aha1 competes with Hop, p50 and p23 for binding to the molecular chaperone Hsp90 and contributes to kinase and hormone receptor activation
Authors: HARST Anja , LIN Hongying , OBERMANN Wolfgang M. J.
Published: April 2005

The ATP-dependent molecular chaperone Hsp90 (heat-shock protein 90) is essential for the maturation of hormone receptors and protein kinases. During the process of client protein activation, Hsp90 co-operates with cofactors/co-chaperones of unique sequence, e.g. Aha1 (activator of Hsp90 ATPase 1), p23 or p50, and with cofactors containing TPR (tetratricopeptide repeat) domains, e.g. Hop, immunophilins or cyclophilins. Although the binding sites for these different types of cofactors are distributed along the three domains of Hsp90, sterical overlap and competition for binding sites restrict the combinations of cofactors that can bind to Hsp90 at the same time. The recently discovered cofactor Aha1 associates with the middle domain of Hsp90, but its relationship to other cofactors of the molecular chaperone is poorly understood. Therefore we analysed whether complexes of Aha1, p23, p50, Hop and a cyclophilin with Hsp90 are disrupted by the other four cofactors by gel permeation chromatography using purified proteins. It turned out that Aha1 competes with the early cofactors Hop and p50, but can bind to Hsp90 in the presence of cyclophilins, suggesting that Aha1 acts as a late cofactor of Hsp90. In contrast with p50, which can bind to Hop, Aha1 does not interact directly with any of the other four cofactors. In vivo studies in yeast and in mammalian cells revealed that Aha1 is not specific for kinase activation, but also contributes to maturation of hormone receptors, proposing a general role for this cofactor in the activation of Hsp90-dependent client proteins.
Oxalate-inducible AMBP gene and its regulatory mechanism in renal tubular epithelial cells
Authors: GREWAL Jasjit S. , TSAI Jeng Y. , KHAN Saeed R.
Published: April 2005

The AMBP [A1M (α1-microglobulin)/bikunin precursor] gene encodes two plasma glycoproteins: A1M, an immunosuppressive lipocalin, and bikunin, a member of plasma serine proteinase inhibitor family with prototypical Kunitz-type domain. Although previously believed to be constitutively expressed exclusively in liver, the present study demonstrates the induction of this gene by oxalate in porcine proximal tubular LLC-PK1 cells and rat kidney. In liver, the precursor protein is cleaved in the Golgi network by a furin-like enzyme to release constituent proteins, which undergo glycosylation before their export from the cell. In the renal tubular cells, A1M and bikunin co-precipitate, indicating lack of cleavage of the precursor protein. As the expression of the AMBP gene is regulated by A1M-specific cis elements and transcription factors, A1M protein was studied as a representative of AMBP gene expression in renal cells. Oxalate treatment (500 μM) resulted in a time- and dose-dependent induction of A1M protein in LLC-PK1 cells. Of the four transcription factors, HNF-4 (hepatocyte nuclear factor-4) has been reported previously to be a major regulator of AMBP gene expression in liver. Electrophoretic mobility-shift assay, supershift assay, immunoreactivity assay and transfection-based studies showed the presence of an HNF-4 or an HNF-4-like protein in the kidney, which can affect the expression of the AMBP gene. In situ hybridization and immunocytochemical studies showed that the expression of this gene in kidney was mainly restricted to cells lining the renal tubular system.
Endothelin-1 expression is strongly repressed by AU-rich elements in the 3′-untranslated region of the gene
Authors: REIMUNDE Francisco M. , CASTAÑARES Cristina , REDONDO-HORCAJO Mariano , LAMAS Santiago , RODRÍGUEZ-PASCUAL Fernando
Published: April 2005

The regulation of the synthesis of the endothelial-derived vasoconstrictor ET-1 (endothelin-1) is a complex process that occurs mainly at the mRNA level. Transcription of the gene accounts for an important part of the regulation of expression, as already described for different modulators such as the cytokine TGF-β (transforming growth factor-β). However, very little is known about mechanisms governing ET-1 expression at the post-transcriptional level. The aim of the present study was to investigate the regulation of the ET-1 expression at this level. Since the 3′-UTR (3′-untranslated region) of mRNAs commonly contains genetic determinants for the post-transcriptional control of gene expression, we focused on the potential role of the 3′-UTR of ET-1 mRNA. Experiments performed with luciferase reporter constructs containing the 3′-UTR showed that this region exerts a potent destabilizing effect. Deletional analyses allowed us to locate this activity within a region at positions 924–1127. Some (but not all) of the AREs (AU-rich elements) present in this region were found to be essential for this mRNA-destabilizing activity. We also present evidence that cytosolic proteins from endothelial cells interact specifically with these RNA elements, and that a close correlation exists between the ability of the AREs to destabilize ET-1 mRNA and the binding of proteins to these elements. Our results are compatible with the existence of a strong repressional control of ET-1 expression mediated by destabilization of the mRNA exerted through the interaction of specific cytosolic proteins with AREs present in the 3′-UTR of the gene.
Characterization of the promoters of Epsilon glutathione transferases in the mosquito Anopheles gambiae and their response to oxidative stress
Authors: DING Yunchuan , HAWKES Nicola , MEREDITH Janet , EGGLESTON Paul , HEMINGWAY Janet , RANSON Hilary
Published: April 2005

Epsilon class GSTs (glutathione transferases) are expressed at higher levels in Anopheles gambiae mosquitoes that are resistant to DDT [1,1,1-trichloro-2,2-bis-(p-chlorophenyl)ethane] than in insecticide-susceptible individuals. At least one of the eight Epsilon GSTs in this species, GSTe2, efficiently metabolizes DDT to DDE [1,1-dichloro-2,2-bis-(p-chlorophenyl)ethane]. In the present study, we investigated the factors regulating expression of this class of GSTs. The activity of the promoter regions of GSTe2 and GSTe3 were compared between resistant and susceptible strains by transfecting recombinant reporter constructs into an A. gambiae cell line. The GSTe2 promoter from the resistant strain exhibited 2.8-fold higher activity than that of the susceptible strain. Six polymorphic sites were identified in the 352 bp sequence immediately upstream of GSTe2. Among these, a 2 bp adenosine indel (insertion/deletion) was found to have the greatest effect on determining promoter activity. The activity of the GSTe3 promoter was elevated to a lesser degree in the DDT-resistant strain (1.3-fold). The role of putative transcription-factor-binding sites in controlling promoter activity was investigated by sequentially deleting the promoter constructs. Several putative transcription-factor-binding sites that are responsive to oxidative stress were present within the core promoters of these GSTs, hence the effect of H2O2 exposure on the transcription of the Epsilon GSTs was investigated. In the DDT-resistant strain, expression of GSTe1, GSTe2 and GSTe3 was significantly increased by a 1-h exposure to H2O2, whereas, in the susceptible strain, only GSTe3 expression responded to this treatment.
The optical properties of ZnO hexagonal prisms grown from poly (vinylpyrrolidone)-assisted electrochemical assembly onto Si (111) substrate
Authors: Liu Y. L. , Liu Y. C. , Feng W. , Zhang J. Y. , Lu Y. M. , Shen D. Z. , Fan X. W. , Wang D. J. , Zhao Q. D.
Published: April 2005

ZnO hexagonal prisms have been grown from poly (vinylpyrrolidone)-assisted electrochemical assembly onto p-type Si (111) substrate. These ZnO prisms arrays are highly (0002) orientated. The (0001) end facets and {101¯0} side facets of the hexagonal prisms are well defined. The photoluminescence (PL) spectrum of these ZnO prisms shows an intense ultraviolet near band-gap emission with a full width at half maximum of 86meV at room temperature. The low-temperature PL spectrum is split into well-resolved free and bound exciton emission lines. The temperature dependence of the exciton emission intensities shows a nonmonotonic decaying behavior, which can be explained by the existence of interfacial states.
Dynamo-free plasma in the reversed-field pinch: Advances in understanding the reversed-field pinch improved confinement mode
Authors: Anderson J. K. , Adney J. , Almagri A. , Blair A. , Brower D. L. , Cengher M. , Chapman B. E. , Choi S. , Craig D. , Demers D. R. , Hartog D. J. Den , Deng B. , Ding W. X. , Ebrahimi F. , Ennis D. , Fiksel G. , Forest C. B. , Franz P. , Goetz J. , Harvey R. W. , Holly D. , Hudson B. , Kaufman M. , Lovell T. , Marrelli L. , Martin P. , McCollam K. , Mirnov V. V. , Nonn P. , O’Connell R. , Oliva S. , Piovesan P. , Prager S. C. , Predebon I. , Sarff J. S. , Spizzo G. , Svidzinski V. , Thomas M. , Wyman M. D.
Published: April 2005

Generation and sustainment of the reversed field pinch (RFP) magnetic configuration normally relies on dynamo activity. The externally applied electric field tends to drive the equilibrium away from the relaxed, minimum energy state which is roughly described by a flat normalized parallel current density profile and is at marginal stability to tearing modes. Correlated fluctuations of magnetic field and velocity create a dynamo electric field which broadens the parallel current density profile, supplying the necessary edge current drive. These pervasive magnetic fluctuations are also responsible for destruction of flux surfaces, relegating the standard RFP to a stochastic-magnetic transport-limited device. Application of a tailored electric field profile (which matches the relaxed current density profile) allows sustainment of the RFP configuration without dynamo-driven edge current. The method used to ascertain that a dynamo-free RFP plasma has been created is reported here in detail. Several confinement improvements during the accompanying periods of low magnetic fluctuations are observed. Namely, the magnetic fluctuation level is reduced to the point where stochastic-magnetic transport is no longer the dominant process in the core and nested flux surfaces are restored in the core of the dynamo-free RFP.
Effect of reactive ion etching-induced defects on the surface band bending of heavily Mg-doped p-type GaN
Authors: Lin Yow-Jon , Chu Yow-Lin
Published: April 2005

The effect of reactive ion etching-induced defects on the surface band bending of heavily Mg-doped p-type GaN (p-GaN) was investigated in this study. According to the observed results from x-ray photoelectron spectroscopy and secondary-ion-mass spectroscopy (SIMS) measurements, we found that the formation of more nitrogen-vacancy-related defects created near the surface by reactive ion etching technique would lead to an increase in the surface band bending, a shift of the surface Fermi level toward the conduction-band edge, the reduction of the current flow at the metal∕etched p-GaN interface, and an increase in the barrier height at the metal∕etched p-GaN interface. In addition, from the SIMS measurements, it is suggested that the depth of the nitrogen-deficient near-surface region resulting from the dry-etch process is about 60nm.
Increased carrier lifetimes in GaN epitaxial films grown using SiN and TiN porous network layers
Authors: Özgür Ü. , Fu Y. , Moon Y. T. , Yun F. , Morkoç H. , Everitt H. O.
Published: April 2005

Improved structural quality and radiative efficiency were observed in GaN thin films grown by metalorganic chemical vapor deposition on SiN and TiN porous network templates. The room-temperature decay times obtained from biexponential fits to time-resolved photoluminescence data are increased with the inclusion of SiN and TiN layers. The carrier lifetime of 1.86ns measured for a TiN network sample is slightly longer than that for a 200μm-thick high-quality freestanding GaN. The linewidth of the asymmetric x-ray diffraction (XRD) (101¯2) peak decreases considerably with the use of SiN and TiN layers, indicating the reduction in threading dislocation density. However, no direct correlation is yet found between the decay times and the XRD linewidths, suggesting that point defect and impurity-related nonradiative centers are the main parameters affecting the lifetime.
Effective elastic constants in nonlinear elasticity
Authors: Bosher S. H. B. , Dunstan D. J.
Published: April 2005

The Lagrangian elastic constants cIJ and cIJK which are given in data-books are not stress-strain relationships. The relationships between them and any experimental observables are far from straightforward to evaluate under conditions of finite deformation when elasticity is nonlinear. We present effective second- and third-order elastic constants, which are thermodynamic stress-strain relationships and which express real material properties. They are derived by applying two and three independent strains to an elastic body and expressed in terms of the Lagrangian cIJ and cIJK. Experimental observables are readily calculated using the effective constants. Their application is demonstrated by deriving the Murnaghan equation of state, by calculating the stress-strain relationships of a pseudomorphic epitaxial strained layer, and by deriving the observable changes in acoustic velocities under stress.
Nusselt number scaling in tokamak plasma turbulence
Authors: Takeda K. , Benkadda S. , Hamaguchi S. , Wakatani M.
Published: April 2005

Anomalous heat transport caused by ion temperature gradient (ITG) driven turbulence in tokamak plasmas is evaluated from numerical simulations of the two-dimensional (2D) partial-differential equations of the ITG model and of a reduced 1D version derived from a quasilinear approximation. In the strongly turbulent state, intermittent bursts of thermal transport are observed in both cases. In the strongly turbulent regime, the reduced model as well as the direct numerical simulation show that the Nusselt number Nu (normalized heat flux) scales with the normalized ion pressure gradient Ki as Nu∝Ki1∕3. Since the Rayleigh number for ITG turbulence is proportional to Ki, the Nusselt number scaling for ITG turbulence is thus similar to the classical thermal transport scaling for Rayleigh–Bénard convections in neutral fluids.
Electrical doping of poly(9,9-dioctylfluorenyl-2,7-diyl) with tetrafluorotetracyanoquinodimethane by solution method
Authors: Hwang Jaehyung , Kahn Antoine
Published: April 2005

We investigate p-type doping of poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) films with tetrafluorotetracyanoquinodimethane (F4-TCNQ) introduced via cosolution. Doped and undoped films are compared using ultraviolet photoelectron spectroscopy (UPS) and current–voltage (I–V) measurement. In spite of the difference between the ionization energy of PFO (5.8 eV) and the electron affinity of F4-TCNQ (5.24 eV), p doping occurs, as seen from the movement of the Fermi level (EF) toward the polymer highest occupied molecular orbital (HOMO). Interface hole barriers are measured for undoped and doped PFO deposited on three substrates with different work functions, indium-tin-oxide (ITO), gold (Au), and poly-3,4-ethylenedioxythiophene∙polystyrenesulfonate (PEDOT∙PSS). Doping leads to the formation of a depletion region at the PFO/ITO and PFO∕Au interfaces. The depletion region is believed to be at the origin of the (hole) current enhancement observed on simple metal/PFO/substrate devices.
van der Waals force calculation between laminated media, pertinent to the magnetic storage head-disk interface
Authors: White Lee R. , Dagastine Raymond R. , Jones Paul M. , Hsia Yiao-Tee
Published: April 2005

Lifshitz theory of van der Waals interactions is applied to the geometry and materials of the head-disk interface (HDI). A simplified two-substrate model with intervening air gap is used to illustrate the effects of retardation. The calculation of the Hamaker functions for increasingly complex layered structures is then presented to illustrate the importance of the multilayered nature of the HDI on the van der Waals (vdW) interaction. The full Lifshitz-multilayer calculation is then compared to approximations of the vdW force and relative errors are displayed. The results indicate the necessity of performing the full Lifshitz calculation on a realistic layered model of the HDI for accurate force modeling.
Surface waves in anisotropic Maxwellian plasmas
Authors: Lee Myoung-Jae , Lee Hee J.
Published: April 2005

Dispersion relation of electromagnetic surface waves propagating on the interface between a vacuum and anisotropic Maxwellian plasmas is derived from Vlasov–Maxwell equations. By taking the limit of infinite speed of light in the electromagnetic dispersion relation, we derived dispersion relation of electrostatic surface waves, and we find that plasmas with equilibrium distribution f0α=(mα∕2πTα)exp{−[mα(vx2+vy2)]∕2Tα}δ(vz) (α=e,i; electrons and ions), where the z direction is normal to the interface, can be unstable to perturbations of ion-acoustic surface wave type.
Conversion of ordinary and extraordinary waves into upper hybrid waves in inhomogeneous plasmas
Authors: Kim Kyung-Sub , Kim Eun-Hwa , Lee Dong-Hun , Kim Kihong
Published: April 2005

Linear mode conversion of ordinary and extraordinary waves into upper hybrid waves has been investigated by adopting a time-dependent numerical model. In order to solve the wave equations as an initial-valued problem, the finite difference method is used in both time and space. It is examined how wave coupling occurs in a cold magnetized plasma, where inhomogeneity lies perpendicular to the ambient magnetic field, by analyzing time histories of both electric and magnetic field components. The results show that electromagnetic energy of ordinary and extraordinary waves is transferred into electrostatic energy when the resonant condition at upper hybrid resonances is satisfied.
Tuning and widening of stop bands of microstrip photonic band gap ring structures
Authors: Kee Chul-Sik , Jang Mi-Young , Kim Sung-II , Park Ikmo , Lim H.
Published: April 2005

We show that the characteristics of microstrip ring structures exhibiting stop bands can be varied by mounting reactive components on the gap of the ring. The presence of capacitor (inductor) on the gap decreases (increases) the center frequency and the frequency range of the stop band. We also show that the stop band can be widened by modifying the structure of the ring. These properties can be useful in the applications to the compact microwave circuits, tunable filters, and microwave switches.
High-field optically detected nuclear magnetic resonance in GaAs
Authors: Poggio M. , Awschalom D. D.
Published: April 2005

A method for high-field optically detected nuclear magnetic resonance (ODNMR) is developed sensitive to 108 nuclei. Nuclear spin transitions are induced using a radio frequency coil and detected through Faraday rotation spectroscopy. Unlike conventional ODNMR, which is limited to low fields and relies on the measurement of time-averaged luminescence polarization, this technique monitors nuclear polarization through time-resolved measurements of electron spin dynamics. Measurements in a (110) GaAs quantum well reveal Ga69, Ga71, and As75 resonances and their quadrupolar splittings while resolving changes in nuclear polarization of 0.02%.
Soil water extraction and biomass production by lucerne in the south of Western Australia
Authors: Dolling P. J. , Latta R. A. , Ward P. R. , Robertson M. J. , Asseng S.
Published: April 2005

To understand the factors involved in lucerne reducing drainage below the root-zone and influencing lucerne biomass production and water extraction were analysed in the south of Western Australia. The lucerne was grown for 3 years before removal. The factors investigated as part of the water extraction analysis included the rate of advance of the extraction front or extraction front velocity (EFV, mm/day), the soil plant-available water-holding capacity (PAWC, mm/m soil), and the temporal change in soil water deficit (drainage buffer, mm). The drainage buffer is related to the EFV and PAWC.
A site with deep sand had the highest EFV (mean of 9.2 mm/day) but the lowest PAWC (mean of 32 mm/m soil) to a depth of 4 m. In the duplex soils the EFV was 18–34% of the deep sand EFV and the PAWC was 60–222% higher than the deep sand PAWC to a depth of 1.6–2.1 m. The EFV was reduced by the higher clay content and sodicity in the B horizon of the duplex soils. The highest drainage buffer measurements occurred in the deep sand site and the better structured duplex soils and therefore these soils will have the greater effect on reducing drainage below the root-zone. However, lucerne was able to create a drainage buffer to at least a depth of 1.5 m over 3 years and therefore contribute to a reduced drainage even on the most sodic and saline sites. Low soil pH did not affect the drainage buffer as much as soil texture and structure.
Variation in biomass production of lucerne-based pastures was positively related to rainfall and water use (taking into account soil water storage and drainage losses) across sites, explaining approximately 50% of the biomass variation. Rainfall and water use could therefore be used for predicting lucerne biomass production in Western Australia. Biomass water use efficiency was highest in spring (15 kg/ha.mm) and least during autumn (4.5 kg/ha.mm).
Agrobacterium-mediated transformation and generation of male sterile lines of Australian canola
Authors: Zhang Yan , Singh Mohan B. , Swoboda Ines , Bhalla Prem L.
Published: April 2005

An efficient protocol for Agrobacterium-mediated transformation of Australian commercial canola cultivars using seedling explants is described. Seedling explants provide flexibility and reduction in labour and maintenance costs of explant sources. Five commercial genotypes of canola were successfully transformed using the developed protocol. A transformation efficiency of 67% was obtained for genotypes Oscar and RK7 from cotyledon explants, which was higher than the rate for the most commonly used cultivar Westar (33%). Comparison of different seedling explants showed that although transgenic plants could be regenerated from all explant types (cotyledons, hypocotyls, and roots) used, the number of plants regenerated per explant type varied among the cultivars. Cotyledons produced the maximum number of transgenic shoots (RK7, RI25, Oscar, and Westar cultivars), whereas root explants produced the lowest numbers of shoots. Therefore, cotyledons and hypocotyls can be considered as ideal explants for the Agrobacterium-mediated transformation of these Australian canola cultivars. Integration and expression of the introduced transgene were analysed by DNA gel blot, leaf disc test, and GUS expression assays. Analysis of progeny showed that the transgene was stably inherited. The possibility of producing male sterile lines using an antisense approach was also explored. For this, Bcp1, a gene shown to be vital for viable pollen development, was targetted. Pollen ablation and lack of seed set were observed in the transgenic plants. Histochemical tests showed an intact tapetum layer and well developed pollen in control plants, whereas degraded tapetum and ablated pollen were noted in the transgenic plants. These results indicate that it is possible to generate stable transgenic male-sterile lines of canola using this strategy.