bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic self‐field effects on current collection by an ionospheric bare tether
Authors: Sanmartín J. R. , Estes R. D.
Published: December 2002

It was recently suggested that the magnetic field created by the current of a bare tether strongly reduces its own electron‐collection capability when a magnetic separatrix disconnecting ambient magnetized plasma from tether extends beyond its electric sheath. It is here shown that current reduction by the self‐field depends on the ratio L*/Lt parameterizing bias and current profiles along the tether (Lt ≡ tether length, L* ≡ characteristic length gauging ohmic effects) and on a new dimensionless number Ks involving ambient and tether parameters. Current reduction is weaker the lower Ks and L*/Lt, which depend critically on the type of cross section: Ks varies as R5/3, h2/3R, and h2/3 × 1/4 width for wires, round tethers conductive only in a thin layer, and thin tapes, respectively; L* varies as R2/3 for wires and as h2/3 for tapes and round tethers conductive in a layer (R ≡ radius, h ≡ thickness). Self‐field effects are fully negligible for the last two types of cross sections whatever the mode of operation. In practical efficient tether systems having L*/Lt low, maximum current reduction in case of wires is again negligible for power generation; for deorbiting, reduction is <1% for a 10 km tether and ∼15% for a 20 km tether. In the reboost mode there are no effects for Ks below some threshold; moderate effects may occur in practical but heavy reboost‐wire systems that need no dedicated solar power.
Field‐aligned currents in the outermost plasma sheet boundary layer with Geotail observation
Authors: Ueno Genta , Ohtani Shin‐ichi , Saito Yoshifumi , Mukai Toshifumi
Published: December 2002

We have studied the outermost field‐aligned currents (FACs) in the plasma sheet boundary layer (PSBL) with the Geotail observations. The trajectory and plasma data of Geotail enable us to conduct a more comprehensive and systematic survey than former work based on the ISEE 1 and 2 data. We identified the FACs with the variation of the dawn‐dusk magnetic field component and calculated their intensities on the assumption of the sheet geometry. A case study indicated that the FACs flow earthward on the earthward side of the reconnection site while the FACs are directed tailward on the tailward side. This tendency was confirmed statistically for PSBL crossings by Geotail inside XGSM = −40 RE. This FAC distribution can be reasonably interpreted in terms of the Hall current system generated by the magnetic reconnection process. The statistical study also showed a dawn‐dusk asymmetry of the polarity of the outermost FACs on the earthward side of the reconnection site. That is, while the FACs flow mainly earthward, tailward‐flowing FACs frequently appear in the dusk sector. In the tailward side of the reconnection site, however, we did not find such a dawn‐dusk dependence about the polarity of the outermost FACs.
Solar activity prediction: Timing predictors and cycle 24
Authors: Schatten Kenneth
Published: December 2002

Solar activity forecasting uses numerous methods. Some methods employed are purely numerological, whereas others utilize readily available, well‐established mathematical techniques. There often is, however, no physical basis for some of these methods. Within this arena, however, there is a small subset, called “precursors,” which does have a physical basis. We briefly describe the physical basis of these methods and relate them to solar dynamo physics. Further, we develop techniques to reduce one major source of uncertainty or “error” in these solar activity predictions. This uncertainty is in the timing of the solar cycle. The importance of solar activity timing is apparent when one considers that past solar cycles have periods varying from 8 to 17 years. This makes the timing of the solar cycle only second in importance in solar activity prediction to obtaining the amplitude of any cycle. Two solar phenomena are utilized to obtain a “time mark” for each solar cycle. These are the “polar field reversal” and the march of activity centers towards the equator. This latter phenomenon is often referred to as the “butterfly diagram.” These timings essentially provide a “phasing” of the cycle. With this, we provide a preliminary prospective on solar cycle 24.
A simple concept for modeling cosmic ray modulation in the inner heliosphere during solar cycles 20–23
Authors: Wibberenz G. , Richardson I. G. , Cane H. V.
Published: December 2002

Recent observations suggest a close relationship between the evolution of the solar magnetic field and high‐energy cosmic ray modulations at 1 AU on timescales of ≳1 year. We investigate this relationship using the simple concept that changes in the solar magnetic field propagate from the Sun and cause a change in the radial diffusion coefficient, assumed to scale as some inverse power of the interplanetary magnetic field (IMF) magnitude (K ∝ B−n). Increases in the IMF cause a reduction in the cosmic ray density in the inner heliosphere. A continuous recovery process is also assumed to operate, represented by a timescale τ which physically is related to particle entry into the depleted regions of the heliosphere by drift and diffusion processes. We integrate numerically the spherically symmetric equation representing this process, and incorporate the observed variations of the parameters included in the equation. The concept is able to account for the variations in cosmic ray intensity at 1 AU during solar cycles 20–23 remarkably successfully using physically plausible values of n ∼ 1–2. An important requirement is that recovery times are shorter (τ ∼ 30 days for >2 GV cosmic rays observed by neutron monitors) during epochs when the polarity of the solar global magnetic field A > 0, than when A < 0 (τ ∼ 100 days). This dependence has a simple physical interpretation, since particle inflows into the inner heliosphere are expected to be faster from over the poles in A > 0 epochs than along the heliospheric current sheet when A < 0. We also identify a period around solar maximum when recovery times are long, consistent with the disappearance of latitudinal intensity gradients observed by Ulysses approaching the maximum of solar cycle 23. This period commences when the axisymmetric component of the solar open flux reaches a minimum, essentially corresponding to the disappearance of the polar coronal holes, prior to solar maximum. Part of the energy dependence of the size of cosmic ray intensity variations can be accounted for by recovery times that decrease with increasing particle energy. Despite the simplicity of the concept, we suggest that it provides important insight into the relationships between variations of the solar magnetic field, interplanetary parameters, and cosmic ray modulation.
A traveling convection vortex event study: Instantaneous ionospheric equivalent currents, estimation of field‐aligned currents, and the role of induced currents
Authors: Amm O. , Engebretson M. J. , Hughes T. , Newitt L. , Viljanen A. , Watermann J.
Published: December 2002

We analyze a traveling convection vortex (TCV) event on 31 January 1997 using ground magnetometer data of the CANOPUS, MACCS, Geological Survey of Canada, Greenland, and IMAGE networks. For the first time, spatial and instantaneous distributions of the mesoscale ionospheric equivalent currents associated with a TCV are obtained. We apply the method of spherical elementary currents (SECS) to calculate these currents, as well as to infer the part of the ground magnetic signatures that is caused by internal currents induced in the Earth. The resulting ionospheric equivalent currents consist of a leading clockwise vortex centered at 71° CGM latitude which moves westward with ∼7.3 km s−1 and a trailing anticlockwise vortex at 77 ° latitude which moves southwestward away from noon at ∼3.0 km s−1. In an area of ∼200 km around the center of the twin vortices the derived equivalent current densities are less than 70 mA m−1 but reach 100–160 mA m−1 in a broad channel of equatorward currents between the vortices. Using the assumption of a uniform Hall to Pedersen conductance ratio and the assumption that conductance gradients perpendicular to the ionospheric electric field are vanishing, we can estimate the field‐aligned current (FAC) associated with the TCV. The maxima of ∼1 μA m−2 of downward FAC in the leading western vortex, and of ∼0.4 μA m−2 of upward FAC in the trailing eastern vortex occur along the perimeter of the vortices, not in their centers, in contrast to the prediction of ionosphere‐magnetosphere coupling theories for TCVs. The integrated FAC are not fully balanced between the two vortices but show an excess of downward FAC. While the ratio between the internally generated and the total horizontal ground magnetic field for most magnetometer sites in the TCV area amounts to around 20–40%, at some stations it can reach values of 50% and larger.
Tracking transient events through geosynchronous orbit and in the high‐latitude ionosphere
Authors: Korotova G. I. , Sibeck D. G. , Singer H. J. , Rosenberg T. J.
Published: December 2002

We combine observations from seven satellites and more than 50 ground magnetometers to study a series of impulsive ground magnetometer events that originated in response to sudden solar wind plasma and interplanetary magnetic field variations on an otherwise quiet day. We demonstrate that the events were global and conjugate. We use high time resolution geosynchronous magnetometer data to determine the origin, velocity, and direction of propagation of the transient events in the magnetosphere. We show that the transient events propagated antisunward but that the IMF orientation controlled the direction of their propagation near local noon in the sense predicted by the dynamic pressure pulse model.
On the interaction between nitrogen and halogen species in the Arctic polar vortex during THESEO and THESEO 2000
Authors: Rivière E. D. , Pirre M. , Berthet G. , Renard J.‐B. , Taupin F. G. , Huret N. , Chartier M. , Knudsen B. , Lefèvre F.
Published: December 2002

Large disagreements between measured and simulated NO2 have been observed several times in the Arctic polar vortex. Here we report on the comparison of two sets of nighttime balloonborne measurements of the couple (OClO, NO2) with Lagrangian model outputs in order to study the interactions between halogen and nitrogen species. Those measurements were characterized by the simultaneous presence of significant amounts of both species. Large disagreements are observed between modeled and measured NO2. Very surprisingly, good agreement can be achieved for OClO in spite of the supposed strong coupling between these two species. The only simultaneous agreement between model and measurements for both species occurs in the case of denoxified conditions, i.e., when there is no interaction between halogen and nitrogen compounds. Furthermore, agreement for OClO cannot be obtained if a source for NO2 is assumed to fit the measurements of this specie. This result shows that some uncertainties still exist in the interaction between nitrogen and halogen species.
Aircraft observations of the creation of lower positive charges in thunderstorms
Authors: Mo Qixu , Helsdon John H. , Winn William P.
Published: December 2002

The existence of lower positive charges in the so‐called tripole thundercloud model has been confirmed by in situ measurements from balloons and by remote measurements from ground‐based electric field meters. However, the source of these charges is still not well understood. In this paper, we report on in situ measurements of some distinct lower positive charges using a different platform: instrumented aircraft. Results obtained by interpreting airborne electric field data recorded by two aircraft flying in close formation below, but very near, the estimated 3.4 km mean sea level (msl) cloud base in New Mexico show that, at least in some instances, localized lower positive charge may be the result of deposition by lightning. In one case studied, the deduced charge magnitude of about 1.25 C near 4 km msl is comparable to that obtained by balloons and ground‐based electric field meters. A simulation involving aircraft‐sampled electric fields in the vicinity of an idealized charge dipole with the instantaneous introduction of a lower positive charge shows good agreement with the observations. The data also show that during the mature stage the horizontal charge distribution in the lower portion of the cloud near cloud base may be quite complex, including side‐by‐side regions of opposite charge.
Retrieval of vertical profiles of NO3 from zenith sky measurements using an optimal estimation method
Authors: Coe Hugh , Allan Beverley J. , Plane John M. C.
Published: December 2002

The generic optimal estimation method (OEM) developed by Rodgers [1976, 1990, 2000] for solving atmospheric data inversion problems has been successfully developed to retrieve vertical profile information of NO3 from zenith sky spectroscopic measurements of column abundance made through sunrise. The technique has been shown to be robust and yields profile information to an altitude of 20 km. The rapid photolysis of NO3 at dawn ensures that a time series of column density measurements provides significant vertical information. The method has been extensively tested and a thorough error analysis was performed. The largest source of error arises from the undersampling of the column density through sunrise, the so‐called smoothing error. The measurement errors and uncertainties in the forward model are also significant. Although a simple forward model involving only photolysis of NO3 during sunrise is able to successfully map the retrieved profile onto the column density measurements on some days, on other days systematic errors arise in the retrieval. These can be accounted for by either increased cloudiness or thermal decomposition of N2O5 in polluted boundary layer air, both effects extending the lifetime of NO3 through sunrise. The technique allows NO3 profile information to be retrieved in a variety of conditions over an extended period of time in a reliable and consistent manner.
Observations of NO3 concentration profiles in the troposphere
Authors: Allan B. J. , Plane J. M. C. , Coe H. , Shillito J.
Published: December 2002

A zenith sky spectrometer has been deployed at a number of remote locations in the Northern and Southern Hemispheres. The technique of differential optical absorption spectroscopy was used to determine the column density of the nitrate radical (NO3) as a function of solar zenith angle (SZA) during sunrise. The tropospheric column densities show a large degree of day‐to‐day variability and indicate that a significant fraction of tropospheric NO3 exists in the free troposphere (FT). The change in the NO3 column density with SZA was then used to retrieve the vertical concentration profile of NO3, by applying an optimal estimation method [see Coe et al., 2002]. This analysis indicates that there is often substantially more NO3 in the upper boundary layer and lower FT than at the surface. Back‐trajectory calculations and a simple box model are used to account for the observations.
Maritime cloud‐to‐ground lightning: The western Mediterranean Sea
Authors: Rivas Soriano Luis , de Pablo Fernando
Published: December 2002

For the first time, the temporal and spatial distribution of cloud‐to‐ground lightning over the western Mediterranean Sea have been studied. The monthly variation shows a single peak in September and October while minimum values are observed in January to March. The diurnal cycle shows a maximum on 0600–0700 LT and a minimum around 1600–1700 LT. The percentage of positive flashes is 8%, although it is higher in the winter than in the summer. The average multiplicity is 2.1 for the negative flashes and 1.1 for the positive flashes, and the percentage of single‐stroke flashes is 48% and 91%, respectively. The annual distribution of multiplicity reveals a maximum in the summer and a minimum in the winter for the negative flashes. The median intensity was found to be 27.5 kA for the negative flashes. Positive flashes show maximum intensities in April and minima in August. The average maximum flash density is 1.5 flashes km−2 yr−1. The geographical distribution of density shows that the highest values are associated with the coastline and decrease eastward. The lightning activity over the island of Mallorca shows characteristics associated with both the land and the sea. The results are discussed in the context of the measurements taken for the land area of the Iberian Peninsula and for other oceanic areas.
Fast airborne sulfur dioxide measurements by Atmospheric Pressure Ionization Mass Spectrometry (APIMS)
Authors: Thornton Donald C. , Bandy Alan R. , Tu Fang H. , Blomquist Byron W. , Mitchell Glenn M. , Nadler Wolfgang , Lenschow Donald H.
Published: December 2002

An atmospheric pressure ionization mass spectrometer (APIMS) was developed to determine atmospheric sulfur dioxide (SO2). High precision and immunity to sample loss, fluctuations in instrument sensitivity, etc., were achieved by adding isotopically labeled SO2 (34S16O2) continuously to the manifold as an internal standard. During the NASA Transport And Chemical Evolution Over The Pacific (TRACE P) program and the National Science Foundation (NSF) Passing Efficiency of the Low Turbulence Inlet (PELTI) program, 32S16O2 and 34S16O2 were each determined with integration times of 20 ms. From these data the ambient SO2 level was computed every 40 ms. In the PELTI studies at SO2 levels of approximately 60 parts per trillion by volume (pptv), vertical fluxes were determined with a precision better than 10%. When the data were averaged to 1 s, the lower limit of detection was <1 pptv at the 2σ level. Isotopomer ratios observed during the Aerosol Characterization Experiment—Asia (ACE Asia), intercomparisons of APIMS and gas chromatography/mass spectrometry with isotopically labeled internal standard on the same aircraft in test flights and PELTI, and the intercomparison of two APIMS instruments on different aircraft during ACE Asia and TRACE P, are presented to support the high sensitivity, accuracy, specificity, and high time response of the instrument.
Fine particulate matter source attribution for Southeast Texas using 14C/13C ratios
Authors: Lemire Kenneth R. , Allen David T. , Klouda George A. , Lewis Charles W.
Published: December 2002

Radiocarbon analyses of fine particulate matter samples collected during the summer of 2000 in southeast Texas indicate that a substantial fraction of the aerosol carbon at an urban/suburban site (27–73%) and at a rural, forested site (44–77%) was modern carbon. Data from emission inventories and additional ambient measurements indicate that the most likely sources of this modern carbon are biomass burning fires and biogenic secondary organic aerosol.
Electrical discharge source for tropospheric “ozone‐rich transients”
Authors: Zahn A. , Brenninkmeijer C. A. M. , Crutzen P. J. , Parrish D. D. , Sueper D. , Heinrich G. , Güsten H. , Fischer H. , Hermann M. , Heintzenberg J.
Published: December 2002

In situ trace gas (O3, NO, NO2, NOy) and ultrafine aerosol particle data from a passenger aircraft (project CARIBIC) and the NOAA WP‐3D research aircraft are used to identify the origin of “ozone‐rich transients” that occasionally appear in aircraft ozone data sets along flight distances of 5–80 km. Evidence of ozone import from the stratosphere, once suggested as the most likely cause, cannot be found. Our data rather reveal that the majority of the recorded ozone transients are artifacts caused by electrical discharges on the aircraft fuselage and the sample air inlet system. These discharges produce not solely O3 but also nitric oxide (NO) which rapidly reacts with O3 to form nitrogen dioxide (NO2). Further evidence is, however, provided showing that some of the less pronounced and broader O3‐NO‐NO2‐rich transients are of atmospheric origin. We hypothesize that they are formed in an early (i.e., prelightning) phase of thunderstorms due to cold electrical discharges on the surface of charged hydrometeors. Simple considerations suggest that the amount of O3 and NO produced through these mechanisms is negligible with regard to the global tropospheric budget for the two gases.
A new energy source for organic synthesis in Europa's surface ice
Authors: Borucki Jerome G. , Khare Bishun , Cruikshank Dale P.
Published: December 2002

Colored regions on Jupiter's satellite Europa and other icy bodies in the outer solar system may be contaminated by organic macromolecular solid material that is produced when surface ices are exposed to electrical energy. Hypervelocity meteorite impacts and fracture may release tidal and tectonic stresses in icy crusts in the form of electrical discharges, which provide the energy for in situ synthesis of the organic solids. We report for the first time here on measurements of electrical discharge, light emission, and magnetic phenomena in hypervelocity impacts into ice with small iron projectiles having velocities ∼5 km s−1. In these experiments, part of the impacting projectile's kinetic energy is converted into electrical potential, while the mechanical disruption of the impact also causes the release of stress energy as light, heat, and electrical and magnetic fields as secondary emissions. These new energy sources described here suggest that the dark material in the area of impact craters may be solid phase, complex organic material called tholin, generated from the energy of the impacts. The morphology of Europa's impact craters is suggestive of fluidized colored material welling up from the fracture zone, probably during crater formation, but possibly later. Large pools of liquid water might persist under the meteorite crater for thousands of years [Thomson and Sagan, 1992], with the potential for prebiotic chemistry to take place at an accelerated rate due to energy pumped in from the secondary emissions.
Contact charging of lunar and Martian dust simulants
Authors: Sternovsky Zoltán , Robertson Scott , Sickafoose Amanda , Colwell Joshua , Horányi Mihály
Published: December 2002

Dusty regolith particles accumulate charge through grain‐grain contact and contact with various surfaces. These processes affect vertical and horizontal transport and may cause electrical discharges in dust storms. We report the results of a simple experimental setup used to investigate the contact charging properties of two planetary analog dust samples: lunar (JSC‐1) and Martian (JSC‐Mars‐1) regolith simulants. In these experiments, dust particles are brought into contact with various surfaces of known work functions (metals: Co, Ni, Au, Pt, and silica glass), and the resulting contact charges on the dust particles are measured. The surfaces are in the form of a thin disc mounted horizontally in a vacuum chamber. Agitation causes the dust grains to drop through a small hole into a Faraday cup, where their charge is measured. The charge on a ∼100 micron dust grain is typically more than 105 elementary charges and varies linearly with dust size. The measured contact charge of a dust particle increases with repeated agitation of the surface. The average contact charge also varies linearly with the work function of the contacting surface. The contact charging with oxidized metal surfaces is found to be independent of the metal's work function. The effective work functions of the planetary analogs are determined by extrapolation to be 5.8 eV and 5.6 eV for the lunar and Martian dust simulants, respectively.
Measurement of snow interception and canopy effects on snow accumulation and melt in a mountainous maritime climate, Oregon, United States
Authors: Storck Pascal , Lettenmaier Dennis P. , Bolton Susan M.
Published: December 2002

The results of a 3 year field study to observe the processes controlling snow interception by forest canopies and under canopy snow accumulation and ablation in mountain maritime climates are reported. The field study was further intended to provide data to develop and test models of forest canopy effects on beneath‐canopy snowpack accumulation and melt and the plot and stand scales. Weighing lysimeters, cut‐tree experiments, and manual snow surveys were deployed at a site in the Umpqua National Forest, Oregon (elevation 1200 m). A unique design for a weighing lysimeter was employed that allowed continuous measurements of snowpack evolution beneath a forest canopy to be taken at a scale unaffected by variability in canopy throughfall. Continuous observations of snowpack evolution in large clearings were made coincidentally with the canopy measurements. Large differences in snow accumulation and ablation were observed at sites beneath the forest canopy and in large clearings. These differences were not well described by simple relationships between the sites. Over the study period, approximately 60% of snowfall was intercepted by the canopy (up to a maximum of about 40 mm water equivalent). Instantaneous sublimation rates exceeded 0.5 mm per hour for short periods. However, apparent average sublimation from the intercepted snow was less than 1 mm per day and totaled approximately 100 mm per winter season. Approximately 72 and 28% of the remaining intercepted snow was removed as meltwater drip and large snow masses, respectively. Observed differences in snow interception rate and maximum snow interception capacity between Douglas fir (Pseudotsuga menziesii), white fir (Abies concolor), ponderosa pine (Pinus ponderosa), and lodgepole pine (Pinus contorta) were minimal.
Usefulness of three-dimensional computed tomography in a living-donor extended right lobe liver transplantation
Authors: Kanazawa Akishige , Hirohashi Kazuhiro , Tanaka Hiromu , Kubo Shoji , Yamamoto Takatugu , Hai Seikan , Kinoshita Hiroaki , Nishida Norifumi , Tanaka Koichi
Published: December 2002

Although living-donor liver transplantation (LDLT) of right lobe graft is becoming a popular option for adult patients, management of venous outflow remains controversial. We report a successful extended-right lobe liver transplantation using a recipient’s left portal vein as a graft from the middle hepatic vein. Preoperative three-dimensional computed tomography (3D-CT) of the donor revealed a small right hepatic vein (RHV) without inferior RHV and a large middle hepatic vein (MHV) draining segments 5 and 8. During the donor operation, right lobe graft was harvested with the MHV, preserving the drainage vein from segment 4. The donor recovered uneventfully except for mild transient hyperbilirubinemia. The recipient’s condition rapidly improved, and was discharged from hospital 49 days postoperation. A 3D-CT after LDLT also clearly revealed successful vascular anastomosis. Preoperative and postoperative 3D-CT was useful for determination of the vascular anatomy and the decision about the line of transection in the donor hepatectomy, as well as for evaluation of the vascular anastomoses after transplantation.
Ischemic preconditioning attenuates the oxidant-dependent mechanisms of reperfusion cell damage and death in rat liver
Authors: Cavalieri Barbara , Perrelli Maria-Giulia , Aragno Manuela , Mastrocola Raffaella , Corvetti Giovanna , Durazzo Marilena , Poli Giuseppe , Cutrìn Juan C.
Published: December 2002

In an in vivo rat model of liver ischemia followed by reperfusion a consistent appearance of necrosis and activation of biochemical pathways of apoptosis was reproduced and monitored after 30 minutes reperfusion. Preconditioning by application of a short cycle of ischemia-reperfusion (10 minutes + 10 minutes) positively conditioned recovery of the organ at reperfusion, attenuating both necrotic and apoptotic events. Preconditioning at least halved cell oxidative damage occurring early at reperfusion, and as a major consequence, the increase of cytolysis and apoptosis occurring at reperfusion was about 50% less. The attenuation of both pathways of cell death by preconditioning appeared at least partly related to its modulate action on H2O2 and 4-hydroxy-2,3-trans-nonenal production. The overall data point to a marked diminished oxidant generation and oxidative reactions as one major possible mechanism through which ischemic preconditioning exerts protection against necrotic and apoptotic insult to the postischemic liver.
Fulminant hepatic failure: Outcome after listing for highly urgent liver transplantation—12 years experience in the nordic countries
Authors: Brandsæter Bjørn , Höckerstedt Krister , Friman Styrbjörn , Ericzon Bo-Göran , Kirkegaard Preben , Isoniemi Helena , Olausson Michael , Broome Ulrika , Schmidt Lars , Foss Aksel , Bjøro Kristian
Published: December 2002

Fulminant hepatic failure is a common indication for liver transplantation. Outcomes of patients listed for a highly urgent liver transplantation have been studied, with special emphasis on etiology of the liver disease, clinical condition, and ABO blood type. Data have been collected from the Nordic Liver Transplantation Registry. All Nordic patients listed for a highly urgent primary liver transplantation during a 12-year period have been included. Of the 315 patients listed for a highly urgent liver transplantation, 229 (73%) received a first liver allograft, 50 patients (16%) died without transplantation, and 36 patients (11%) were permanently withdrawn and survived. In 43% of the patients, no definite etiology of the liver failure could be established. Paracetamol intoxication was the most frequent specific indication for listing. Patients with blood type A had no significant shorter waiting time (3.8 v 6.6 days; P = .1) but a higher rate of transplantation (82% v 66%, P = .006) as compared with blood type O patients. In a multivariate analysis, paracetamol intoxication remained the single independent predictor of an outcome without transplantation. In conclusion, a high transplantation rate was observed among patients listed for a highly urgent liver transplantation because of fulminant hepatic failure. Blood type O patients had a lower chance of receiving a liver allograft. Patients with paracetamol intoxication had both a higher mortality without transplantation and a higher withdrawal rate attributable to improved condition.
Brain edema in liver failure: Basic physiologic principles and management
Authors: Larsen Fin Stolze , Wendon Julia
Published: December 2002

In patients with severe liver failure, brain edema is a frequent and serious complication that may result in high intracranial pressure and brain damage. This short article focuses on basic physiologic principles that determine water flux across the blood-brain barrier. Using the Starling equation, it is evident that both the osmotic and hydrostatic pressure gradients are imbalanced across the blood-brain barrier in patients with acute liver failure. This combination will tend to favor cerebral capillary water influx to the brain. In contrast, the disequilibration of the Starling forces seems to be less pronounced in patients with cirrhosis because the regulation of cerebral blood flow is preserved and the arterial ammonia concentration is lower compared with that of patients with acute liver failure. Treatments that are known to reverse high intracranial pressure tend to decrease the osmotic pressure gradients across the blood-brain barrier. Recent studies indicate that interventions that restrict cerebral blood flow, such as hyperventilation, hypothermia, and indomethacin, are also efficient in preventing edema and high intracranial pressure, probably by decreasing the transcapillary hydrostatic pressure gradient. In our opinion, it is important to recall that rational fluid therapy, adequate ventilation, and temperature control are of direct importance to controlling cerebral capillary water flux in patients with acute liver failure. These simple interventions should be secured before more advanced experimental technologies are instituted to treat these patients.
Combination of HBIG and lamivudine-resistant mutations: A formula for trouble?
Authors: Fontana Robert J. , Lok Anna S.F.
Published: December 2002

Abstract

Background & Aims:

Lamivudine has become a main therapeutic option for treating hepatitis B virus (HBV) infection. Although drug resistance develops, the clinical course after selection of antiviral-resistant HBV mutants seems to be benign. However, we observed a severe clinical course of hepatitis B infection in several liver transplant recipients after the emergence of lamivudine resistance. This was associated with high viral load in the blood.

Methods:

In this report, we characterize the molecular mechanisms underlying drug-dependent enhanced replication of particular lamivudine-resistant HBV mutants selected in these patients, which were associated with sudden onset of liver failure.

Results:

The clinical course was characterized by a sudden rise in serum bilirubin, prothrombin time, and transaminase. HBV sequence analysis of these patients revealed both mutations in the “a-determinant” of the envelope and the YMDD (tyrosine, methionine, aspartate, aspartate) motif (domain C) of the polymerase protein. Transfection experiments with replication competent vectors indicated that the “a-determinant” changes were not associated with resistance, whereas mutations in the YMDD motif conferred resistance to lamivudine. More importantly, combinations of mutations in the “a-determinant” and the YMDD motif in patients with a severe hepatitis were not only resistant to lamivudine treatment, but showed enhanced replication in vitro in the presence of lamivudine. This observation was confirmed in separate laboratories.

Conclusions:

Severe and fatal hepatitis B infection can occur during lamivudine therapy and may be associated with certain HBV mutants selected during sequential nucleoside and HBIg treatment. The lamivudine-enhanced replication shown by these mutants suggests that continuation of therapy with lamivudine could be deleterious in some patients.
Targeting in dissipative chaotic systems: A survey
Authors: Iplikci Serdar , Denizhan Yagmur
Published: December 2002

The large number of unstable equilibrium modes embedded in the strange attractor of dissipative chaotic systems usually presents a sufficiently rich repertoire for the choice of the desirable motion as a target. Once the system is close enough to the chosen target local stabilization techniques can be employed to capture the system within the desired motion. The ergodic behavior of chaotic systems on their strange attractors guarantees that the system will eventually visit a close neighborhood of the target. However, for arbitrary initial conditions within the basin of attraction of the strange attractor the waiting time for such a visit may be intolerably long. In order to reduce the long waiting time it usually becomes indispensable to employ an appropriate method of targeting, which refers to the task of steering the system toward the close neighborhood of the target. This paper provides a survey of targeting methods proposed in the literature for dissipative chaotic systems.
Multifractal chaotic attractors in a system of delay-differential equations modeling road traffic
Authors: Safonov Leonid A. , Tomer Elad , Strygin Vadim V. , Ashkenazy Yosef , Havlin Shlomo
Published: December 2002

We study a system of delay-differential equations modeling single-lane road traffic. The cars move in a closed circuit and the system’s variables are each car’s velocity and the distance to the car ahead. For low and high values of traffic density the system has a stable equilibrium solution, corresponding to the uniform flow. Gradually decreasing the density from high to intermediate values we observe a sequence of supercritical Hopf bifurcations forming multistable limit cycles, corresponding to flow regimes with periodically moving traffic jams. Using an asymptotic technique we find approximately small limit cycles born at Hopf bifurcations and numerically preform their global continuations with decreasing density. For sufficiently large delay the system passes to chaos following the Ruelle–Takens–Newhouse scenario (limit cycles–two-tori–three-tori–chaotic attractors). We find that chaotic and nonchaotic attractors coexist for the same parameter values and that chaotic attractors have a broad multifractal spectrum.
Four-particle decay of the Bethe–Salpeter kernel in the high-temperature Ising model
Authors: Auil F.
Published: December 2002

In this article we study the four-particle decay of the Bethe–Salpeter (B-S) kernel for the high-temperature Ising model. We use the hyperplane decoupling method [T. Spencer, Commun. Math. Phys. 44, 143 (1975); R. S. Schor, Nucl. Phys. B 222, 71 (1983)] to prove exponential decay in a set of variables particularly adapted to the methods of Spencer and Zirilli [Commun. Math. Phys. 49, 1 (1976)] for the analysis of scattering and bound states in QFT, transcribed to lattice theories by Auil and Barata [Ann. Henri Poincare 2, 1065 (2001)]. We study arbitrary derivatives of the general n-point correlation functions with respect to the interpolating variables, and we are able to obtain, in some cases, information about the third derivatives of the B-S kernel. As a later consequence, we have two-body asymptotic completeness for the (massive) Euclidean lattice field theory implemented by this model. This allows us to analyze the Ornstein–Zernike behavior of four-point functions, related to the specific heat of the model.
Josephson tunneling properties in MgB2/AlN/NbN tunnel junctions
Authors: Saito A. , Kawakami A. , Shimakage H. , Terai H. , Wang Z.
Published: December 2002

We report on the fabrication of Josephson tunnel junctions with as-grown MgB2 thin films and on the Josephson tunneling properties of the junctions. MgB2/AlN/NbN trilayers were continuously deposited on sapphire (0001) substrates in the same vacuum run. The as-grown MgB2 thin films were fabricated using the conventional sputtering method at the low-substrate temperature of 250 °C, and the AlN tunnel barrier and the NbN counter electrode were deposited by reactive sputtering at the ambient substrate temperature. The Tc of the MgB2 thin films was 28 K. The junctions demonstrated clear Josephson tunneling characteristics with evident supercurrents, gap voltages, and small subgap leakage currents. The normal resistance of these junctions had an ideal dependence on the junction areas and on the AlN-barrier thickness. The temperature dependence of the gap voltages and the external dc magnetic-field dependence of the supercurrents were measured to investigate the Josephson tunneling behaviors in the MgB2/AlN/NbN junctions. The junctions showed BCS-like temperature dependence of the gap voltage and ideal Fraunhofer patterns.
On the nonlocal equations and nonlocal charges associated with the Harry Dym hierarchy
Authors: Brunelli J. C. , da Costa G. A. T. F.
Published: December 2002

A large class of nonlocal equations and nonlocal charges for the Harry Dym hierarchy is exhibited. They are obtained from nonlocal Casimirs associated with its bi-Hamiltonian structure. The Lax representation for some of these equations is also given.
Modeling of laser cleaning of metallic particulate contaminants from silicon surfaces
Authors: Arronte M. , Neves P. , Vilar R.
Published: December 2002

A model for laser-assisted particle removal was developed. The model was applied to micrometer-sized particles of gold, copper, and tungsten on silicon substrates. A two-dimensional heat transfer model is used to calculate the temperature profiles and the thermal expansion for the metallic particles and the silicon substrate irradiated with ultraviolet nanosecond laser pulses. The particle/substrate system was modeled as a simple spring oscillator under the sudden thermal expansion excitation pulse and a concept of degree of coupling between the laser induced thermal expansion associated frequency and the particle/substrate system is introduced. In terms of this degree of coupling a simple method to determine the most appropriate laser pulse duration is proposed. The theoretical results were compared with previously reported experimental observations. The experimental cleaning efficiency for the different particle materials and size distributions, as well as the possibility of substrate contamination due to metal evaporation are well accounted by the theoretical model.
Superintegrability with third-order integrals in quantum and classical mechanics
Authors: Gravel Simon , Winternitz Pavel
Published: December 2002

We consider here the coexistence of first- and third-order integrals of motion in two-dimensional classical and quantum mechanics. We find explicitly all potentials that admit such integrals, and all their integrals. Quantum superintegrable systems are found that have no classical analog, i.e., the potentials are proportional to ℏ2, so their classical limit is free motion.
Soliton-like solutions of higher order wave equations of the Korteweg–de Vries type
Authors: Tzirtzilakis E. , Marinakis V. , Apokis C. , Bountis T.
Published: December 2002

In this work we study second and third order approximations of water wave equations of the Korteweg–de Vries (KdV) type. First we derive analytical expressions for solitary wave solutions for some special sets of parameters of the equations. Remarkably enough, in all these approximations, the form of the solitary wave and its amplitude-velocity dependence are identical to the sech2 formula of the one-soliton solution of the KdV. Next we carry out a detailed numerical study of these solutions using a Fourier pseudospectral method combined with a finite-difference scheme, in parameter regions where soliton-like behavior is observed. In these regions, we find solitary waves which are stable and behave like solitons in the sense that they remain virtually unchanged under time evolution and mutual interaction. In general, these solutions sustain small oscillations in the form of radiation waves (trailing the solitary wave) and may still be regarded as stable, provided these radiation waves do not exceed a numerical stability threshold. Instability occurs at high enough wave speeds, when these oscillations exceed the stability threshold already at the outset, and manifests itself as a sudden increase of these oscillations followed by a blowup of the wave after relatively short time intervals.
De Rham–Wu decomposition of holomorphic Riemannian manifolds
Authors: Law Peter R.
Published: December 2002

It is shown that a de Rham–Wu decomposition for holomorphic Riemannian manifolds is obtained easily from the underlying real geometry of holomorphic Riemannian manifolds by appealing to H. Wu’s extension to pseudo-Riemannian manifolds of de Rham’s decomposition theorem.
A single-photon detector for the measurement of optical activity in the deep sea
Authors: Ameli F. , Bonori M. , Coluzza C. , Masullo R. , Petruccetti M. , Massa F. , Pappalardo L.
Published: December 2002

A module was constructed for the measurement of deep sea optical activity at a sensitivity level of a single photoelectron. We describe the features of the module and a method for calibrating it. The average sensitivity in the interval from 350 to 500 nm is 0.89 Hz/(photons cm−2 s−1), where Hz is the rate detected by the module.
Thomson scattering diagnostic of solid density plasmas using x-ray lasers
Authors: Baldis H. A. , Dunn J. , Foord M. E. , Rozmus W.
Published: December 2002

In this article, we demonstrate through calculations and theoretical analysis the first application of an x-ray laser for probing hot, high-density plasmas (ne⩾1023 cm−3) using a Ni-like transient collisional excitation x-ray laser as a probe. Theoretical predictions are used to diagnose the electron temperature in short-pulse (500 fs) laser-produced plasmas. The threshold power of the x-ray probe is estimated by comparing theoretical scattering levels with plasma thermal emission. The necessary spectral resolution of the instrument sufficient for resolving electron temperature is given. Effects of the electron heat flow on the ion-acoustic fluctuation spectra are presented. The outlook for these and next generation experiments are discussed.
Epitaxial growth of n-type SiC using phosphine and nitrogen as the precursors
Authors: Wang Rongjun , Bhat Ishwara B. , Chow T. Paul
Published: December 2002

Epitaxial growth of n-type SiC was carried out using PH3 and N2 as the dopant precursors in a chemical vapor deposition system. Thermodynamic simulations were performed to analyze the gas phase composition at the growth conditions. It was shown that the incorporation behaviors of these two dopants are quite different. Compared to nitrogen, phosphorous incorporation has a weaker dependence on flow rate and has a limited site competition effect. Also, phosphorus incorporation for a given precursor flow decreases with temperature while that of nitrogen increases. It was also observed that phosphorous incorporation increases with decreasing C/Si when the ratio is between 0.8 and 3, which suggests phosphorous might incorporate into C site when C/Si is low. Variable temperature Hall measurements were used to characterize the doped layers. Two donor levels at 82–83 and 105–114 meV for phosphorous in 6H–SiC, 50–52 meV, and 78–80 meV for phosphorous in 4H–SiC were resolved. These results were compared to those from ion-implanted samples.
Relaxation kinetics of photoinduced surface relief grating on azopolymer films
Authors: Matsui Tatsunosuke , Yamamoto Shin-ichiro , Ozaki Masanori , Yoshino Katsumi , Kajzar Francois
Published: December 2002

The relaxation kinetics of the photoinduced surface relief grating (SRG) formed on an azopolymer film after stopping laser beam writing has been systematically investigated. In addition to a photoinduced increase of the diffraction efficiency in the SRG, an anomalous further enhancement of the efficiency was observed even without light irradiation, after the recording light beam was switched off. This anomalous relaxation process consists of two components with short and long relaxation times, and strongly depends on the temperature and polarization of the probe beam used for the diffraction measurement. At lower temperatures the anomalous growth is more effective and the fast component is dominant. From the results of the polarization dependence of the diffraction efficiency and optical absorption, it has been manifested that the fast component of the relaxation originates from the cis-trans thermal isomerization of azobenzene in the side chain. The origin of the slow decay is also discussed in terms of the order parameter change of the azomolecules caused by the reorientational relaxation.
Imaging system for low-density plasma by heterodyne interferometer with fan beam microwave
Authors: Ito H. , Yugami N. , Nishida Y. , Sakai W.
Published: December 2002

A microwave imaging system based on a heterodyne interferometer has been developed to measure the spatial distribution of the plasma density without introducing any direct disturbance to the plasma by employing a diode array scattering technique. The imaging system with the use of a fan beam microwave for a radar system demonstrates the principle of the technique by placing finite-size dielectric phantoms instead of the plasma between the horn antenna and the diode antenna array. Experimental results show that very good image of the objects can be reconstructed and the system is equivalent to popularly known multichannel imaging system. As a result, it is possible to make simple, low-cost, and compact microwave interferometer for measuring the spatial distribution of the plasma density.
Duality and representations for new exotic bialgebras
Authors: Arnaudon D. , Chakrabarti A. , Dobrev V. K. , Mihov S. G.
Published: December 2002

We find the exotic matrix bialgebras which correspond to the two nontriangular nonsingular 4×4 R-matrices in the classification of Hietarinta, namely, RS0,3 and RS1,4. We find two new exotic bialgebras S03 and S14 which are not deformations of the classical algebras of functions on GL(2) or GL(1|1). With this we finalize the classification of the matrix bialgebras which unital associative algebras generated by four elements. We also find the corresponding dual bialgebras of these new exotic bialgebras and study their representation theory in detail. We also discuss in detail a special case of RS1,4 in which the corresponding algebra turns out to be a special case of the two-parameter quantum group deformation GLp,q(2).