bluuebunny/crossref_metadata_2025 huggingface dataset:
Galileo ultraviolet spectrometer observations of Jupiter's auroral spectrum from 1600–3200 Å
Authors: Pryor Wayne R. , Ajello Joseph M. , Tobiska W. Kent , Shemansky Donald E. , James Geoffrey K. , Hord Charles W. , Stephens Stuart K. , West Robert A. , Stewart A. Ian F. , McClintock William E. , Simmons Karen E. , Hendrix Amanda R. , Miller Deborah A.
Published: September 2002

In 1996 and 1997 the Galileo Ultraviolet Spectrometer (UVS) obtained the first measurements of Jupiter's nightside midultraviolet (MUV) polar auroral spectrum from 1620 to 3231 Å at 13 Å resolution. The reduced polar spectra, after removal of off‐axis scattered radiation from the sunlit dayside of Jupiter, contain a spectrum that matches laboratory spectra of the H2 continuum in the a‐b dissociative emission transition. This is the first direct identification of the H2 a‐b transition in astronomy. The a‐b emission is excited by electron impact exchange reactions with H2 that peak in cross section near 15 eV. The emission threshold is at 1216 Å, and the continuum peaks in intensity in the 2000–2500 Å range. Jupiter's observed wavelength‐integrated MUV H2 a‐b emissions (1620–3231 Å) have a photon flux ∼8 times smaller than simultaneously observed wavelength‐integrated far‐ultraviolet (FUV) H2 band emissions (1230–1650 Å). Because the FUV H2 emissions have an emission cross section that peaks at higher energies near 50 eV, this FUV/MUV brightness ratio is diagnostic of the secondary electron energy distribution and is consistent with a “warm” distribution of electrons.
Hubble Space Telescope imaging of Jupiter's UV aurora during the Galileo orbiter mission
Authors: Clarke John T. , Ballester Gilda , Trauger John , Ajello Joe , Pryor Wayne , Tobiska Kent , Connerney J. E. P. , Gladstone G. Randall , Waite J. H. , Ben Jaffel Lotfi , Gérard Jean‐Claude
Published: September 2002

Hubble Space Telescope (HST) Wide‐Field Planetary Camera 2 (WFPC 2) images of Jupiter's aurora have been obtained close in time with Galileo ultraviolet spectrometer (UVS) spectra and in situ particles, fields, and plasma wave measurements between June 1996 and July 1997, overlapping Galileo orbits G1, G2, G7, G8, and C9. This paper presents HST images of Jupiter's aurora as a first step toward a comparative analysis of the auroral images with the in situ Galileo data. The WFPC 2 images appear similar to earlier auroral images, with the main ovals at similar locations to those observed over the preceding 2 years, and rapidly variable emissions poleward of the main ovals. Further examples have been observed of the equatorward surge of the auroral oval over 140–180° longitude as this region moves from local morning to afternoon. Comparison of the WFPC 2 reference auroral ovals north and south with the VIP4 planetary magnetic field model suggests that the main ovals map along magnetic field lines exceeding 15 RJ, and that the Io footprint locations have lead angles of 0–10° from the instantaneous magnetic projection. There was an apparent dawn auroral storm on June 23, 1996, and projections of the three dawn storms imaged with HST to date demonstrate that these appear consistently along the WFPC 2 reference oval. Auroral emissions have been consistently observed from Io's magnetic footprints on Jupiter. Possible systematic variations in brightness are explored, within factor of 6 variations in brightness with time. Images are also presented marked with expected locations of any auroral footprints associated with the satellites Europa and Ganymede, with localized emissions observed at some times but not at other times.
Auroral radio emissions at the outer planets: Observations and theories
Authors: Zarka Philippe
Published: September 2002

We review both observational and theoretical aspects of the generation of auroral radio emissions at the outer planets, trying to organize the former in a coherent frame set by the latter. Important results have been obtained in the past few years on these radio emissions at the five magnetized planets, from the observations of Ulysses at Jupiter and of Wind and other Global Geospace Science spacecraft in Earth orbit, from the reanalysis of Voyager data about Saturn, Uranus, and Neptune, from ground‐based high frequency‐time resolution and full polarization measurements, and from pioneering multispectral observations of the Jovian and Saturnian aurorae (radio/UV/IR). In parallel, considerable progress has been made in their generation theory (Cyclotron‐Maser operating in small‐scale, laminar, hot‐plasma‐dominated radio source structures), mostly on the basis of in situ observations of terrestrial radio sources. Particle acceleration and precipitation is also better documented, thanks to in situ measurements in the Earth auroral zones and to multispectral studies of Jupiter and Saturn. Finally, the modeling of the planetary magnetic field and magnetospheric plasma at these two planets has also been considerably improved. To organize the wealth of observational results within a coherent theoretical frame, we emphasize unresolved questions (e.g., planetary radio bursts generation) and contradictions and propose ways to answer them. Our ability, already significant, to perform remote sensing of magnetoplasmas at the giant planets and, hopefully, at other distant radio sources (solar, stellar) in the near future, depends on the good understanding of the physical processes underlying the generation of auroral electromagnetic emissions. The question of the existence of exoplanetary radio emissions and the possibility to detect and study them is briefly discussed.
Preliminary results on photometric properties of materials at the Sagan Memorial Station, Mars
Authors: Johnson Jeffrey R. , Kirk Randolph , Soderblom Laurence A. , Gaddis Lisa , Reid Robert J. , Britt Daniel T. , Smith Peter , Lemmon Mark , Thomas Nicolas , Bell James F. , Bridges Nathan T. , Anderson Robert , Herkenhoff Ken E. , Maki Justin , Murchie Scott , Dummel Andreas , Jaumann Ralf , Trauthan Frank , Arnold Gabriele
Published: September 2002

Reflectance measurements of selected rocks and soils over a wide range of illumination geometries obtained by the Imager for Mars Pathfinder (IMP) camera provide constraints on interpretations of the physical and mineralogical nature of geologic materials at the landing site. The data sets consist of (1) three small “photometric spot” subframed scenes, covering phase angles from 20° to 150°; (2) two image strips composed of three subframed images each, located along the antisunrise and antisunset lines (photometric equator), covering phase angles from ∼0° to 155°; and (3) full‐image scenes of the rock “Yogi,” covering phase angles from 48° to 100°. Phase functions extracted from calibrated data exhibit a dominantly backscattering photometric function, consistent with the results from the Viking lander cameras. However, forward scattering behavior does appear at phase angles >140°, particularly for the darker gray rock surfaces. Preliminary efforts using a Hapke scattering model are useful in comparing surface properties of different rock and soil types but are not well constrained, possibly due to the incomplete phase angle availability, uncertainties related to the photometric function of the calibration targets, and/or the competing effects of diffuse and direct lighting. Preliminary interpretations of the derived Hapke parameters suggest that (1) red rocks can be modeled as a mixture of gray rocks with a coating of bright and dark soil or dust, and (2) gray rocks have macroscopically smoother surfaces composed of microscopically homogeneous, clear materials with little internal scattering, which may imply a glass‐like or varnished surface.
Observations of Phobos, Deimos, and bright stars with the Imager for Mars Pathfinder
Authors: Thomas N. , Britt D. T. , Herkenhoff K. E. , Murchie S. L. , Semenov B. , Keller H. U. , Smith P. H.
Published: September 2002

The Imager for Mars Pathfinder (IMP) was used to observe several objects during the Martian night. The satellites, Phobos and Deimos, were observed on two occasions each, through the IMP geological filters covering the wavelength range 440 nm to 1 μm. The observations were converted to geometric albedo using triaxial ellipsoid models of the satellites and phase functions derived from Viking Orbiter images. The spectral slopes over the full wavelength range were 7.9(±0.5)% (100 nm)−1 and 9.6(±0.6)% (100 nm)−1, respectively, referenced to 600 nm. In the Deimos spectra, some evidence for decreased reddening toward the trailing hemisphere was found. The geometric albedoes of Phobos and Deimos were found to be 0.065 (±0.010) and 0.068 (±0.009), respectively, averaged over 440 and 600 nm, in good agreement with previous measurements. The nighttime optical depth was investigated using observations of stars. A mean value of 0.56 (±0.09) was determined from measurements at different airmass. A possible maximum in the optical depth near 0200 local time was found, which may result from condensation during the night. A measurement of the egress of Phobos from eclipse was made. Modeling of the light curve gave a scale height for the scatterers of 10–15 km. The exact time of the eclipse reappearance over the limb could be reconstructed from the measurements and was in reasonable accord with predictions, although a small modification to the predicted position of Phobos of 6.8 (±6.0) km would have produced better agreement.
The color of the Martian sky and its influence on the illumination of the Martian surface
Authors: Thomas N. , Markiewicz W. J. , Sablotny R. M. , Wuttke M. W. , Keller H. U. , Johnson J. R. , Reid R. J. , Smith P. H.
Published: September 2002

The dust in the atmosphere above the Mars Pathfinder landing site produced a bright, red sky that increases in redness toward the horizon at midday. There is also evidence for an absorption band in the scattered light from the sky at 860 nm. A model of the sky brightness has been developed [Markiewicz et al., this issue] and tested against Imager for Mars Pathfinder (IMP) observations of calibration targets on the lander. The resulting model has been used to quantify the total diffuse flux onto a surface parallel to the local level for several solar elevation angles and optical depths. The model shows that the diffuse illumination in shadowed areas is strongly reddened while areas illuminated directly by the Sun (and the blue forward scattering peak) see a more solar‐type spectrum, in agreement with Viking and IMP observations. Quantitative corrections for the reddening in shadowed areas are demonstrated. It is shown quantitatively that the unusual appearance of the rock Yogi (the east face of which appeared relatively blue in images taken during the morning but relatively red during the afternoon) can be explained purely by the changing illumination geometry. We conclude that any spectrophotometric analysis of surfaces on Mars must take into account the diffuse flux. Specifically, the reflectances of surfaces viewed under different illumination geometries cannot be investigated for spectral diversity unless a correction has been applied which removes the influence of the reddened diffuse flux.
Detecting electrical activity from Martian dust storms
Authors: Farrell W. M. , Kaiser M. L. , Desch M. D. , Houser J. G. , Cummer S. A. , Wilt D. M. , Landis G. A.
Published: September 2002

We present a model addressing the possible electrification of Martian dust storms based on the effective electrical charging of an individual dust grain. An upper charge bound on a grain can be determined based on the grain capacitance in the low‐pressure Martian atmosphere. It is assumed that treiboelectric and inductive processes, like that presumed operating in terrestrial dust storms, can electrify the grain to significant levels. A collection of such grains charged in a dust cloud of many tens of kilometers in size can yield a substantial electric field moment. Given various grain charge and dust storm sizes, the electric moment will be determined along with estimates of electrical discharge and emitted radio power based upon known models. We also suggest the possibility that remote detection of discharge‐related VLF emission propagating in the surface/ionosphere waveguide can be used to determine subsurface conductivity.
An evaluation of a new two‐dimensional analytic ionospheric ray‐tracing technique: Segmented method for analytic ray tracing (SMART)
Authors: Norman R. J. , Cannon P. S.
Published: September 2002

Analytic ray tracing is considerably less time consuming than numerical ray tracing. However, despite the advantage of speed, analytic ray tracing has a major limitation: the difficulty of including the effects on the ray path of horizontal gradients in electron density. In the past this difficulty has been addressed using ionospheric models whereby an effective tilt is introduced by displacing the center of the ionosphere from the center of the Earth. In this paper, ray equations for the ground range, phase path, group path, and divergent power loss are developed for a new two‐dimensional analytic ray tracing technique, known as the segmented method for analytic ray tracing (SMART), which is able to deal with horizontal gradients in electron density. Ray tracing using two tilting methods are compared with ray tracing using SMART. Further, these results are compared with a numerical ray tracing program known as homing‐in ray tracing (HIRT).
Statistical characterization of time variability in midlatitude single‐tone HF channel response
Authors: Arikan Feza , Erol Cemil B.
Published: September 2002

In this paper, a statistical analysis approach is proposed to characterize the variability of HF channel response to single‐tone signals by using only the amplitude information of the received signal. By the proposed methodology, robust estimates of the time varying mean and variance of the channel response can be obtained. For this purpose, we use sliding window statistics of the available data. On the basis of the estimated variance of the obtained results, a detailed justification of the proper window size is given. In order to obtain more reliable estimates, the data are median filtered prior to statistical analysis. A robust way of choosing the length of the median filter is presented. We applied the statistical analysis approach to a set of available data obtained from a measurement campaign between England and Turkey conducted from April 1992 to February 1993. The results of the statistical analysis confirmed the expectations of the physical behavior of the ionospheric channel. It was found that the midlatitude single‐frequency channel is slowly time varying and locally stationary in a sliding window of 22 s. Also, it was observed that the amplitude of the received signal exhibits a significant diurnal variation. In addition, during early morning hours and night hours, the channel is considerably more stable for communication purposes compared with day and early evening hours.
Synthetic ΔKprocessing method applied to multifrequency radar observations
Authors: Aarholt Eldar
Published: September 2002

Both the range resolution and the range ambiguity interval of a sensor system can be maintained using a very much reduced number of data carriers across the bandwidth. This is demonstrated using real data from internal sea waves collected with a multifrequency radar system. The described signal processing methods favor the use of small numbers of sensors, which, through synthesis of additional data channels, give rise to a very high signal processing gain. Large synthetic sensor arrays can be constructed using very few real sensors for applications such as phased antenna array systems, microphone arrays for seismic prospecting, or imaging multifrequency radar systems.
Effect of aperture averaging upon tropospheric phase fluctuations seen with a radio antenna
Authors: Linfield Roger P.
Published: September 2002

The spectrum of tropospheric phase fluctuations expected for a radio antenna at timescales <100 s on a space to ground link has been calculated. A new feature included in these calculations is the effect of aperture averaging, which causes a reduction in delay fluctuations on timescales less than the antenna wind speed crossing time, ∼D/(8 m/s) (D is the antenna diameter). On timescales less than a few seconds, the Allan deviation σy(Δt) ∝ (Δt)+1, rather than σy(Δt) ∝ (Δt)−1/6 without aperture averaging. Calibration of tropospheric phase fluctuations with water vapor radiometers will not be possible on timescales less than ∼10 s, due to thermal radiometer noise. However, the tropospheric fluctuation level will be small enough that phase measurements on timescales less than a few seconds will be limited by the stability of frequency standards and/or other nontropospheric effects.
Deterministic retrieval of ionospheric phase screen from amplitude scintillations
Authors: Bhattacharyya Archana
Published: September 2002

In the phase screen theory of ionospheric scintillations the ionospheric irregularities are considered as pure phase objects, and the diffraction pattern produced on the ground, by radio waves propagating through this phase screen, is obtained from conventional Fresnel diffraction theory. In the present paper the inverse problem of retrieving phase variations in the screen from the diffraction pattern on the ground is treated by using the transport‐of‐intensity equation (TIE), which is derived from the Fresnel diffraction theory result. An approximate version of the TIE is solved to obtain the phase variation in the screen from the intensity distribution on the ground. It is seen that when the phase variations involve spatial scale lengths ∼400 m, phase fluctuations of ∼5 rad can be recovered from intensity variations on the ground, for a 300‐MHz signal. For larger spatial scale lengths and higher frequencies this method can be used to retrieve larger phase variations in the screen.
Application of novel basis functions in a hybrid method simulation of the response of induction logging in axisymmetrical stratified media
Authors: Zhang Geng Ji , Wang Gong Li , Wang Han Ming
Published: September 2002

The hybrid method is employed in the numerical simulation of electromagnetic waves propagating in an axisymmetrical and longitudinally stratified medium. Two categories of basis functions are introduced, one of which sustains the amplitude and the other of which sustains the slope, of the function in question at nodal points. An interval extending to infinity is devised, whereby infinity is treated more reasonably than in previous works. The application of the above two contrivances makes possible the reduction of nodal points from 45, as necessitated by triangular basis functions, to 4 and also a two‐orders‐of‐magnitude improvement of the overall computational efficiency. Such a substantial improvement will facilitate the inversion of induction logging.
Determination of aircraft wake vortex radar cross section due to coherent Bragg scatter from mixed atmospheric water vapor
Authors: Myers Theodore J. , Scales Wayne A. , Marshall Robert E.
Published: September 2002

Remote detection and tracking of wing‐tip‐generated wake vortices are important for hazard avoidance, especially near airports. Aircraft that fly through these hazardous vortices experience sudden induced roll. Experiments have demonstrated that there is sufficient radar cross section for remote detection at frequencies ranging from VHF to C band (100 MHz to 5 GHz). The mechanism that yields this radar cross section is Bragg scattering from the index of refraction variations due to the atmospheric water vapor being mixed by the wake vortex system. Refractive index variations of the size that correspond to half the operating radar wavelength produce the observed radar return. Previous analysis has postulated turbulence within the wake vortex to be the generator of the index of refraction variations. In this work, a new mechanism is identified that does not assume turbulence within the wake vortex system. This “laminar flow mechanism” mixes the stratified atmosphere as the wake vortex system swirls and descends, which causes refractive index structure that stretches into successively smaller spirals over time. The results are quantitatively consistent with experimental data.
Biases of correlation dimension estimates of streamflow data in the Canadian prairies
Authors: Wang Qiang , Gan Thian Yew
Published: September 2002

The correlation dimension (D2) of the unregulated streamflow data of six rivers in the Canadian prairies were estimated using the Hill estimate and Grassberger‐Procaccia algorithms. From both procedures and using an embedding phase space up to 10 the D2 obtained for all cases are found to “saturate” at ∼3.0. However, the saturated D2 generally increased to between 4 and 6 when the data were first randomly resampled prior to estimating the correlation dimension. Since the highest embedding dimension d used in this study is 10, theoretically, randomly resampled data should have a D2 approximately equal to 10. Therefore there is a consistent underestimation of D2 by an amount of 4–6. By accounting for the combined clustering effect of the streamflow data's underlying distribution (which is Gamma), the effect of sample size and possibly the choice of time delay ∇, the D2 of the prairie streamflow data should be ∼7–9. The hypothesis that the clustering effect of unevenly distributed data contributed to the underestimation of D2 was confirmed from the different D2 obtained for random numbers of uniform, Gamma, and Poisson distributions. In addition, analysis of the uniformly distributed random numbers and streamflow data showed that increasing the sample size from, say 6500 to 17,000 marginally improved the estimated D2. However, for the range of time delay chosen for this study, 40–180 days, its effect on D2 is less obvious. This may be partly because all the streamflow data tested exhibit long‐term persistence.
Single‐phase flow regimes in a discrete fracture model
Authors: Weir Graham J.
Published: September 2002

Typical flow regimes occurring in a finite fractured reservoir, occupied by a single‐phase liquid, are quantified, using approximate analytical expressions. Estimates are provided for the time at the beginning and end of each regime and of the expected pressure drawdown within each regime. The central result is the derivation of an approximate r4/t self‐similarity for the bilinear flow regime, and new analytical expressions are obtained for the early and late development of this bilinear regime. The evolution of flow regimes is problem dependent, and examples of slope halving and slope doubling are provided for the transition between the first and second regimes. Examples discussed and quantified include radial and linear flows, fracture flows, bilinear flows, parallel flows, block drawdown, and finite fracture regimes.
Chandra provides new eye on the universe
Authors: Showstack Randy
Published: September 2002

When the sun shade door on the Chandra X‐Ray Observatory opened on August 12, it was “like an infant opening his eyes for the first time,” said Robert Kirshner, associate director of the Harvard‐Smithsonian Center for Astrophysics in Cambridge, Mass.

During that initial period with the door unlatched, scientists directed one of Chandra's instruments, the Advanced CCD Imaging Spectrometer (AGS), to snap several images. These exposures helped to test the calibration of the world's most powerful X‐ray telescope.The images—unexpectedly stunning pictures of the Cassiopeia A (Cas A) supernova remnant and distant quasar PKS 0637‐752—also are providing scientists with early examples of how the space observatory promises to help with the study of some of the hottest and most violent parts of the universe. These include exploding stars, collapsing galaxies, dark matter, and black holes.
Electron Acceleration in the Aurora and Beyond
Authors: Schulz Michael
Published: September 2002

Charged particles that populate Earth's space environment span an enormous range of kinetic energies, from less than 1 eV in the ionosphere to millions of GeV in the spectrum of cosmic rays. Duncan Bryant's ambitious new book, Electron Acceleration in the Aurora and Beyond, spans approximately this range as well. This is a delightful book, in which the author uses mainly words and diagrams to provide clear explanations of a large variety of space plasma topics, all related in some way to charged particles in space.

The scope of the book extends well beyond mechanisms of electron acceleration. It begins at a very elementary level by introducing the mass and charge of an electron, and it ends (apart from appendices) with careful discussions of first‐order and second‐order Fermi acceleration of galactic electrons to cosmic ray energies.
Position statement on climate change and greenhouse gases
Authors: Anonymous
Published: September 2002

Adopted by Council December 1998

Atmospheric concentrations of carbon dioxide and other greenhouse gases have substantially increased as a consequence of fossil fuel combustion and other human activities. These elevated concentrations of greenhouse gases are predicted to persist in the atmosphere for times ranging to thousands of years. Increasing concentrations of carbon dioxide and other greenhouse gases affect the Earth‐atmosphere energy balance, enhancing the natural greenhouse effect and thereby exerting a warming influence at the Earth's surface. Although greenhouse gas concentrations and their climatic influences are projected to increase, the detailed response of the system is uncertain. Principal sources of this uncertainty are the climate system's inherent complexity and natural variability.The increase in global mean surface temperatures over the past 150 years appears to be unusual in the context of the last few centuries, but it is not clearly outside the range of climate variability of the last few thousand years. The geologic record of the more distant past provides evidence of larger climate variations associated with changes in atmospheric carbon dioxide. These changes appear to be consistent with present understanding of the radiative properties of carbon dioxide and the influence of climate on the carbon cycle.There is no known geologic precedent for the transfer of carbon from the Earth's crust to atmospheric carbon dioxide, in quantities comparable to the burning of fossil fuels, without simultaneous changes in other parts of the carbon cycle and climate system.This close coupling between atmospheric carbon dioxide and climate suggests that a change in one would in all likelihood be accompanied by a change in the other.
Cellular immune responses in transplantation‐associated chronic viral infections
Authors: Addo M.M. , Rosenberg E.S. , Addo M.M. , Rosenberg E.S.
Published: September 2002

Abstract: Viral pathogens are important causes of morbidity following transplantation. Cytomegalovirus (CMV) and Epstein‐Barr virus (EBV) infections represent two major viral complications in transplant recipients. Recent advances in methodology have led to a better understanding of host immune responses directed against chronic viral infections. We review the nature of antiviral immunity involved in control of CMV and EBV. Viral mechanisms of immune evasion and immunotherapeutic strategies in the transplantation setting will also be addressed.
Rhodococcus equi pulmonary infection in a pancreas‐alone transplant recipient: consequence of intense immunosuppression
Authors: Lo A. , Stratta R.J. , Trofe J. , Norwood J. , Egidi F. , H. Shokouh‐Amiri M. , Grewal H.P. , Alloway R.R. , Gaber A.O.
Published: September 2002

Abstract We report the case of a pancreas‐alone transplant recipient who developed Rhodococcus equi pneumonia after receiving multiple courses of antilymphocyte therapy for the treatment of recurrent acute pancreas allograft rejection. We also review and discuss the diagnosis, clinical course, and treatment of 18 cases of R. equi infection reported in solid organ transplant recipients.

The lung is the most common primary site of infection, but R. equi infection is difficult to diagnose because of the pleomorphic, gram‐positive, and partially acid‐fast nature of the organism. Treatment usually involves a combination of antibiotics including rifampin, macrolides, vancomycin, and ciprofloxacin. The optimal duration of therapy is unknown, but relapse is common if the duration of treatment is less than 14 days. The duration of therapy should be guided by clinical recovery, culture results, and radiographic findings. Monitoring levels of immunosuppressive agents—such as tacrolimus and cyclosporine—is needed in order to avoid clinically significant drug interactions with rifampin or the macrolides when these agents are used in order to treat R. equi infection in the transplant population.
Regulation of the avidity of ternary complexes containing the human 5‐HT1A receptor by mutation of a receptor contact site on the interacting G protein α subunit
Authors: Welsby Philip J , Carr I Craig , Wilkinson Graeme , Milligan Graeme
Published: September 2002

Fusion proteins were constructed between the human 5‐HT1A receptor and pertussis toxin‐resistant forms of both Gi1α and Go1α mutated at residue351 from cysteine to either glycine or isoleucine. Each of these was expressed stably in HEK293 cells.

Increasing concentrations of GDP inhibited binding of the agonist [3H]‐8‐OH‐DPAT but not the antagonist [3H]‐MPPF to each construct.

The IC50 for GDP was greater for constructs containing isoleucine at residue351 of the G proteins compared to those with glycine at this position.

The G protein antagonist suramin had similar effects to GDP on the binding of [3H]‐8‐OH‐DPAT.

The proportion of 5‐HT1A receptor binding sites detected by [3H]‐MPPF that displayed high affinity for 8‐OH‐DPAT was significantly greater when the interacting G protein contained isoleucine rather than glycine at residue351.

The 5‐HT1A receptor displayed similar avidity of interaction with Gi1α and Go1α.

These results indicate that a higher avidity ternary complex is formed between 8‐OH‐DPAT, the 5‐HT1A receptor and G proteins when isoleucine rather than glycine is located at residue351 of the interacting G protein.

British Journal of Pharmacology (2002) 137, 345–352. doi:10.1038/sj.bjp.0704880
Pharmacological characterization of the novel nociceptin/orphanin FQ receptor ligand, ZP120: in vitro and in vivo studies in mice
Authors: Rizzi Anna , Rizzi Daniela , Marzola Giuliano , Regoli Domenico , Larsen Bjarne Due , Petersen Jorgen Soberg , Calo′ Girolamo
Published: September 2002

This study reports on the pharmacological characterization of ZP120, a novel ligand of the nociceptin/orphanin FQ (N/OFQ) peptide receptor, NOP. ZP120 is a structure inducing probes modified NOP ligand: Zealand Pharma proprietary SIP technology was used to increase the enzymatic stability and half‐life of peptide.

In vitro, ZP120 mimicked the inhibitory effects of N/OFQ in the electrically stimulated mouse vas deferens, showing however higher potency (pEC50 8.88 vs 7.74), lower maximal effects (Emax 69±5% vs 91±2%), and slower onset of action. Like N/OFQ, the effects of ZP120 were not modified by 1 μM naloxone, but they were antagonized by the NOP receptor selective antagonist J‐113397 (pA2 7.80 vs ZP120, 7.81 vs N/OFQ).

In vivo, ZP120 mimicked the effects of N/OFQ, producing pronociceptive effects in the tail withdrawal assay and decreased locomotor activity after i.c.v., but not after i.v. administration in mice. ZP120 elicited similar maximal effects as N/OFQ, but it was about 10 fold more potent and its effects lasted longer.

In conclusion, the novel NOP receptor ligand ZP120 is a highly potent and selective partial agonist of the NOP receptor with prolonged effects in vivo.

British Journal of Pharmacology (2002) 137, 369–374. doi:10.1038/sj.bjp.0704894
A new ligand for the urotensin II receptor
Authors: Camarda Valeria , Guerrini Remo , Kostenis Evi , Rizzi Anna , Calò Girolamo , Hattenberger Almut , Zucchini Marina , Salvadori Severo , Regoli Domenico
Published: September 2002

The cyclic peptide human urotensin II (U‐II) has been recently recognized as the endogenous ligand of an orphan GPCR, subsequently named the UT receptor. No synthetic ligands are available for investigating this novel peptide‐receptor system. A novel UT receptor ligand, [Orn8]U‐II, was synthesized and evaluated in calcium functional assays performed on HEK293 cells expressing the recombinant rat and human UT receptor and in the rat aorta bioassay. [Orn8]U‐II behaves as a full agonist (pEC50≈8) at both human and rat UT receptors in the FlipR calcium assay eliciting similar maximal effects as the natural ligand U‐II. On the contrary, in the rat aorta bioassay, [Orn8]U‐II behaves as a competitive and selective antagonist (pA2=6.56) showing however a small but consistent residual agonist activity. It is therefore proposed that [Orn8]U‐II is a partial agonist at UT receptors.

British Journal of Pharmacology (2002) 137, 311–314. doi:10.1038/sj.bjp.0704895
Regulation of V(D)J recombination: A dominant role for promoter positioning in gene segment accessibility
Authors: Sikes Michael L. , Meade Amber , Tripathi Rajkamal , Krangel Michael S. , Oltz Eugene M.
Published: September 2002

Antigen receptor gene assembly is regulated by transcriptional promoters and enhancers, which control the accessibility of gene segments to a lymphocyte-specific V(D)J recombinase. However, it remained unclear whether accessibility depends on the process of transcription itself or chromatin modifications that accompany transcription. By using T cell receptor β substrates that integrate stably into nuclear chromatin, we show that promoter location, rather than germ-line transcription or histone acetylation, is a primary determinant of recombination efficiency. These spatial constraints on promoter positioning may reflect an RNA polymerase-independent mechanism to target adjacent gene segments for chromatin remodeling events that facilitate rearrangement.
Role of the C-terminal propeptide in the activity and maturation of γ-interferon-inducible lysosomal thiol reductase (GILT)
Authors: Phan Uyen T. , Lackman Rebecca L. , Cresswell Peter
Published: September 2002

γ-Interferon-inducible lysosomal thiol reductase (GILT) is constitutively expressed in antigen-presenting cells. GILT facilitates unfolding of endocytosed antigens in MHC class II-containing compartments by enzymatically reducing disulfide bonds. The enzyme is synthesized as a 35-kDa precursor. Although a fraction of the precursor is secreted as a disulfide-linked dimer, the majority is directed via the mannose-6-phosphate receptor pathway to endocytic compartments where its N- and C-terminal propeptides are cleaved to generate the 30-kDa mature form. Both precursor and mature GILT reduce disulfide bonds with an acidic pH optimum. In this report, we show that the cysteine residues in the C-terminal propeptide, Cys-211 and Cys-222, serve key structural roles. Mutation of Cys-222 abolishes disulfide-linked dimerization of precursor GILT and decreases the efficiency of GILT maturation. Mutation of Cys-211 results in both impaired intracellular maturation and loss of enzymatic activity of the precursor form at an acidic pH. A similar phenotype was obtained upon mutation of Cys-200, which is retained in the mature form. Cys-200 and Cys-211 seem to form a disulfide bond that links the propeptide and the mature enzyme until reduction in the lysosome. This disulfide bridge is essential for stability of the enzyme at low pH and for its proper maturationin vivo.
Gβγ-independent constitutive association of Gαswith SHP-1 and angiotensin II receptor AT2is essential in AT2-mediated ITIM-independent activation of SHP-1
Authors: Feng Ying-Hong , Sun Yan , Douglas Janice G.
Published: September 2002

Conventional mode of activation of SH2 domain-containing phosphatase 1 (SHP-1) by a single transmembrane (TM) inhibitory receptor such as killer cell inhibitory receptor, Fcγ receptor type IIb1, and paired Ig-like receptors of inhibitory types requires tyrosine phosphorylation of immunoreceptor tyrosine-based inhibitory (ITIM) motifs in the cytoplasmic domains of the inhibitory receptors. Contrary to this paradigm, AT2, a G protein-coupled 7TM receptor that does not undergo tyrosine phosphorylation in response to angiotensin II (Ang II) stimulation, also activates SHP-1. Here we show that SHP-1 constitutively and physically associates with AT2receptor in transfected COS-7 cells. On stimulation by Ang II, SHP-1 becomes activated and dissociated from AT2receptor, independent of pertussis toxin. Cotransfection of transducin Gβγinhibits SHP-1/AT2association and the SHP-1 activation, whereas cotransfection of C-terminal of β-adrenergic receptor kinase, which abrogates Gβγsignaling, facilitates SHP-1 activation. Surprisingly, SHP-1/AT2association and the SHP-1 activation requires the presence of Gαsas shown by differential coimmunoprecipitation, dominant negative Gαs, constitutively active Gαs, and Gαpeptides. A mutant AT2receptor D141A–R142L that is inactive in Gαprotein activation constitutively associates with SHP-1 and activates it. Together, these results indicate that Gαsalone, rather than exclusively in the form of Gαβγheterotrimer may facilitate signal transduction for G protein-coupled receptors, suggesting a novel mechanism distinct from the classic paradigm of heterotrimeric G proteins. The AT2-mediated ITIM-independent activation of SHP-1 that is distinct from the conventional mode of activation, may represent a general paradigm for activation of SHP-1/2-class tyrosine phosphatases by G protein-coupled receptors.
Physical constraints and functional characteristics of transcription factor–DNA interaction
Authors: Gerland Ulrich , Moroz J. David , Hwa Terence
Published: September 2002

We study theoretical “design principles” for transcription factor (TF)–DNA interaction in bacteria, focusing particularly on the statistical interaction of the TFs with the genomic background (i.e., the genome without the target sites). We introduce and motivate the concept of programmability, i.e., the ability to set the threshold concentration for TF binding over a wide range merely by mutating the binding sequence of a target site. This functional demand, together with physical constraints arising from the thermodynamics and kinetics of TF–DNA interaction, leads us to a narrow range of “optimal” interaction parameters. We find that this parameter set agrees well with experimental data for the interaction parameters of a few exemplary prokaryotic TFs, which indicates that TF–DNA interaction is indeed programmable. We suggest further experiments to test whether this is a general feature for a large class of TFs.
FRACTALS IN FLUID MECHANICS
Authors: SREENIVASAN K. R.
Published: September 2002

The basic concepts of fractal geometry are relatively simple. Although they are not entirely new, the recognition that these simple notions form a unified language for a variety of disciplines in natural science is due to Mandelbrot.1 Our objective is to assess briefly the role of fractals and multifractal measures in fluid flows broadly, including turbulence and combustion. As applications have yet to mature, the report captures a snap-shot of the changing scene. We focus on activities that are common to both fluid dynamics and fractals and ignore some isolated aspects; we also omit comments on possible fractal structure obtained in chaotic mixing. Finally, we emphasize the question of how fractals enter physical problems, not the classical results. Much of the material to be covered below can be found in refererences cited in the bibliography2–7. Other references cited are not meant to be exhaustive.
ANOMALOUS RELAXATION IN NOISE-DRIVEN BISTABLE SYSTEMS
Authors: FRASER SIMON J. , KAPRAL RAYMOND
Published: September 2002

Relaxation dynamics for bistable oscillators driven by a periodic dichotomous noise process is described. The corresponding stochastic differential equation is a smooth flow between noise-switching events but the dynamics of the two-branched map induced by the transitions is a Markov process. Overdamped relaxation dynamics in harmonic and quartic bistable potentials are compared. Infrequent transitions produce cantor-set-like attractors. In the harmonic case the attractor is self-similar and the irreversible mass flow towards this attractor produces anomalous decay. However, for the quartic potential the map branches are sigmoidal functions and multiple transitions into the endpoints of the attractor also produce anomalous decay.
COMPLEXITY MAPS REVEAL CLUSTERS IN NEURONAL ARBORIZATIONS
Authors: DUBUC B. , ZUCKER S. W. , STRYKER M. P.
Published: September 2002

A central issue in characterizing neuronal growth patterns is whether their arbors form clusters. Formal definitions of clusters have been elusive, although intuitively they appear to be related to the complexity of branching. Standard notions of complexity have been developed for point sets, but neurons are specialized "curve-like" objects. Thus we consider the problem of characterizing the local complexity of a "curve-like" measurable set. We propose an index of complexity suitable for defining clusters in such objects, together with an algorithm that produces a complexity map which gives, at each point on the set, precisely this index of complexity. Our index is closely related to the classical notions of fractal dimension, since it consists in determining the rate of growth of the area of a dilated set at a given scale, but it differs in two significant ways. First, the dilation is done normal to the local structure of the set, instead of being done isotropically. Second, the rate of growth of the area of this new set, which we named "normal complexity", is taken at a fixed (given) scale instead instead of around zero. The results will be key in choosing the appropriate representation when integrating local information in low level computer vision. As an application, they lead to the quantification of axonal and dendritic tree growth in neurons.
ELASTO-PLASTIC BUCKLING OF PRESTRESSED ARCHES
Authors: MIRMIRAN AMIR , AMDE AMDE M. , XU ZEFANG
Published: September 2002

Intentional buckling as a fabrication technique for arch frameworks results in prestrains at every section of the arch, which in turn affect its strength and stability. A nonlinear corotational straight beam element with elastic, linear strain hardening material has been developed to study the elasto-plastic buckling of prestressed arches. The study indicates that for prestressed arches there is an interdependence between the slenderness and steepness ratios of the arch with the ratio of prestresses to the yield strength of the material, all of which control the magnitude and shape of buckling mode. While steeper arches are generally more stable in their elastic range, the effect of steepness ratio is reduced as the prestress exceeds 55% of the yield strength. Effects of loading and support conditions have also been considered. Although fixed supports result in more stable arches, their effectiveness depends on the steepness ratio and the level of prestresses. Finally, the effect of strain hardening on the plastic buckling of the arch is more pronounced for lower values of the plastic tangent modulus.
EFFECTS OF THE FOLLOWER FORCE ON THE STATIC BUCKLING OF BEAMS
Authors: WANG Q.
Published: September 2002

The paper discusses the effect of a follower force on the buckling capacities of a beam structure subjected to a non-follower force. The potential of the research is on the application of smart materials in the buckling enhancement of beams, since the follower force is always modeled at the interaction between the smart materials and the substrate. The buckling capacities of beams with different boundary conditions are obtained analytically. Trivial solutions are found for the simply supported beam, beam with two fixed ends, and propped cantilever beam. However, the result from the analysis of a cantilever beam shows that, when the value of follower force is small, the buckling load decreases with the increase of the follower force. Nevertheless, the buckling capacity of the cantilever beam "jumps" to a big value if the follower force on the beam is relative large and beyond a critical value. This observation indicates that by properly applying the follower force with smart materials, the buckling capacities of the beam can be enhanced dramatically for the cantilever beams.

It is hoped that this work will enable designers to capitalize on the effectiveness of using piezoelectric actuators or SMA in enhancing the buckling capacities of beams.
Chirality and Stereogenicity for Allene Derivatives. Observance and Violation of Chirality Fittingness
Authors: Fujita Shinsaku
Published: September 2002

Allene derivatives have been combinatorially enumerated under a point group D2d as well as under a permutation group S9[4], which is a subgroup of the symmetric group of degree 4 and is isomorphic to the point group D2d. These enumerations have been compared in terms of the observance and the vilolation of chirality fittingness, where two types of Young’s tableaus (point-group symmetry and permutation-group symmetry) have been used to clarify the relationship between stereochemistry and permutability of allene derivatives. The concept of chirality/achirality for stereochemistry has been compared with the concept of stereogenicity/astereogenicity for permutability. Enantiomers, which have been characterized by equivalency under point-group symmetry, have been classified into two classes according to whether or not they have been assigned to orbits (equivalence classes) under permutation-group symmetry. On the other hand, diastereomers have been related to equivalence classes (orbits) under permutation-group symmetry only. The terms enantiostereogenic and diastereogenic have been coined to discuss the behavior under permutaiton-group symmetry. The CIP (Cahn–Ingold–Prelog) system is examined in terms of stereogenicity/astereogenicity. A new combination of chirality and stereogenicity described in the present paper provides us with a tool for restructuring stereochemistry.
Photoreaction of Cinnamate with Nitrogen Monoxide Catalyzed by Metallosalen Complexes
Authors: Furusho Yoshio , Sohgawa Yow-hei , Kihara Nobuhiro , Takata Toshikazu
Published: September 2002

Ethyl cinnamate was allowed to react with nitrogen monoxide (NO) by photoirradiation in the presence of metallosalen complexes (4), oxygen, and axial ligands for 4 to yield furoxan derivatives (6). Oxygen and axial ligands are indispensable for this reaction. Photoirradiation enhanced the yield of 6. Lowering the reaction temperature increased the yield of 6 up to 55% (at −5 °C).
Studies on Confirming the Type of Dried Urushi Film and Its Formation Mechanism (Urushi Hardening Study Report II)
Authors: Shiihara Isao
Published: September 2002

In a previous report (Ref. 1), the author described the chemical structure of acetone powder (AP, the so-called laccase) of the Japan urushi sap, and dope obtained by the classic Kurome process is interpreted as urushiol orthosilicate. In this paper, the further discussion is given about flake pieces which were accidentally obtained from a broken Al tube containing raw urushi during the summer; also described is dope obtained under a special treatment (three ceramic rolls mill (TR) compounding) and hardening while keeping at room temperature and 80% humidity. Precise studies have shown that both have hexagonally and octahedrally oriented oxygen atoms around the center Si atom of the acetone powder. It has been found that three kinds of urushiol silicate and inorganic bond (peroxide) bridging formation, such as –H2C–O–OCaOH or –H2C–O–OMgOH, are the true hardening mechanisms, instead of a hitherto considered enzyme action.