bluuebunny/crossref_metadata_2025 huggingface dataset:
Multispacecraft study on the dynamics of the dusk‐flank magnetosphere under northward IMF: 10–11 January 1997
Authors: Stenuit H. , Fujimoto M. , Fuselier S. A. , Sauvaud J.‐A. , Wing S. , Fedorov A. , Budnik E. , Savin S. P. , Trattner K. J. , Angelopoulos V. , Bonnell J. , Phan T. D. , Mukai T. , Pedersen A.
Published: November 2002

The latter half of the magnetic cloud event on 10–11 January 1997 is studied in the context of the cold‐dense plasma sheet. A fortuitous distribution of spacecraft in key regions allows us to relate the plasma sheet status transition with the boundary layer process. When the interplanetary magnetic field (IMF) was strongly northward and the solar wind density returned to a nominal value from an anomalously large one, two spacecraft, Geotail and Interball‐Tail, were in the dusk‐flank region and detected a change in the plasma sheet status from hot and tenuous to cold and dense. The change seen by these spacecraft making in situ observations is confirmed to be a global feature by DMSP observations at low altitude. Just around this time, Interball‐Aurora and Polar were crossing the dusk‐auroral oval, monitoring globally the dynamics of the dusk‐flank magnetopause at its footpoint. Injection of magnetosheath‐like ions was detected by these spacecraft. We try to relate these observations with the processes that transport the magnetosheath plasma onto the magnetospheric field lines. Three candidate processes are discussed, but none of them turn out to be convincing, indicating the need for further study on this issue.
Scattering characteristics of high‐resolution meteor head echoes detected at multiple frequencies
Authors: Close S. , Oppenheim M. , Hunt S. , Dyrud L.
Published: November 2002

Meteor data collected at the Kwajalein Missile Range (KMR) during the peak of the 1998 Leonid storm comprise the only simultaneous observations of meteor head echoes and trails using seven frequencies (very high frequency (VHF), ultrahigh frequency (UHF), L‐, S‐, C‐, Ka‐, and W‐band spanning 160 MHz to 95 GHz). The primary sensor was the ARPA Long‐Range Tracking and Instrumentation Radar (ALTAIR) radar operating at 160 MHz with 30 m range resolution and 422 MHz with 7.5 m range resolution, including both interferometric and polarization capabilities. This paper presents an analysis of this high‐resolution data set with the following results: First, these observations support the theory that head echo scattering arises from an ionized region with a density sufficiently high that its plasma frequency exceeds the radar frequency (overdense reflection). Second, radar cross section (RCS) decreases rapidly with decreasing wavelength because higher frequencies must penetrate further into the increasing density of the plasma surrounding the meteoroid to reach its reflection point. Third, head echo angle measurements indicate that most of the observed meteors are sporadics not originating from the Leonid radiant. Fourth, polarization ratios showed that head echo reflections result from plasmas with a circular cross section. Fifth, the highest RCS values are detected near 105 km altitude, where the meteoroid gives up the most kinetic energy during its decent. This paper presents the first analyses of a three‐frequency head echo as well as the polarization ratios and RCS characteristics from numerous two‐frequency head echoes, which will allow us to develop a better understanding of meteor physics.
Evidence for Langmuir wave tunneling in the inhomogeneous solar wind
Authors: Willes A. J. , Bale S. D. , Cairns Iver H.
Published: November 2002

Spacecraft observations of beat‐like Langmuir waveforms on two orthogonal antennas in Earth's foreshock and the solar wind have been interpreted as beating associated with large‐angle reflection of Langmuir waves from density inhomogeneities or nonlinear decay processes. However, the waveforms are often irregular, with uncorrelated waveform envelopes on orthogonal antennas. One interpretation is that irregular waveforms are a manifestation of the electromagnetic nature of Langmuir waves scattered to low wave numbers in the inhomogeneous solar wind. An alternative interpretation, investigated here, is that the shape of the waveform envelopes on orthogonal antennas becomes substantially different as Langmuir waves tunnel through evanescent regions, where the local plasma frequency in the inhomogeneous plasma exceeds the Langmuir wave frequency. We demonstrate that observations of uncorrelated waveform envelopes on orthogonal antennas are consistent with theoretical predictions for Langmuir wave tunneling in evanescent regions in the inhomogeneous solar wind. Incident Langmuir waves which are nearly aligned with the density gradient are also partially converted to transverse electromagnetic waves at the plasma frequency. The characteristic dual‐antenna waveform signature of mode conversion is difficult to detect for typical solar wind parameters.
Formation of the proton beam distribution in high‐speed solar wind
Authors: Tu C.‐Y. , Wang L.‐H. , Marsch E.
Published: November 2002

A new mechanism is suggested to explain the formation of proton beam velocity distributions in high‐speed streams of the solar wind. The proton beam is a well‐known kinetic phenomenon, which was already found in the early days of solar wind in situ measurements [Feldman et al., 1973; Marsch et al., 1982a; Rosenbauer et al., 1981]. Observationally, proton beams move faster than the core part of the proton distribution by more than the Alfvén speed. The beam has a higher temperature than the core, but the thermal anisotropy is usually smaller. Until today none of the major properties of the observed beams have been adequately explained. The basic difficulty faced by previous investigations is that in a proton‐electron plasma, hardly any cyclotron waves are found to be in resonance with the beam protons. However, when considering a proton‐alpha‐electron plasma, we find a second dispersion branch of outward propagating RHP and LHP waves. This branch is mainly determined by the alpha particles drifting at the Alfvén speed. The associated waves can resonate with the beam protons, and the resulting cyclotron‐resonance‐induced diffusion produces a beam velocity distribution. The time‐dependent two‐dimensional diffusion equation, as determined from the quasi‐linear theory of ion cyclotron‐wave resonance, is solved numerically. A proton beam distribution is shown to form, by diffusion in the wave field, out of an initial shuttle‐like bi‐Maxwellian velocity distribution function. The drift velocity of the model beam is about the Alfvén speed. The perpendicular thermal speed is about 44 km/s, and the thermal anisotropy of the beam is much less than the core anisotropy. Limitations of the present model and work to be done in the future are also discussed.
Simulations of plasma clouds in the midlatitude E region ionosphere with implications for type I and type II quasiperiodic echoes
Authors: Hysell D. L. , Yamamoto M. , Fukao S.
Published: November 2002

The electrodynamics of clouds of enhanced plasma density in the postsunset midlatitude E region ionosphere are simulated in three dimensions. Such clouds become polarized in the presence of a background electric field, as would be imposed by the F region dynamo. If the clouds are elongated so that their major and minor axes in the horizontal plane are much larger and smaller than about 1 km, respectively, the polarization electric field can become an order of magnitude larger than the applied field. Elongated depressions or ripples in planar layers also become polarized but to a lesser degree. Electric fields and Hall drifts sufficiently large to excite Farley Buneman instabilities can be produced, particularly when neutral wind forcing is considered in addition to background electric fields. The plasma clouds are also unstable to a collisional drift instability capable of generating large‐scale primary waves. A linear, local dispersion relation for this instability is derived. The primary waves are presumed to be capable of generating small‐scale irregularities through mode coupling and plasma turbulence. Polarized plasma clouds drifting through the radar‐scattering volume may account for many of the characteristics of type I and type II quasiperiodic echoes.
Acceleration of dust grains by means of electromagnetic cyclotron waves
Authors: Shukla P. K. , Stenflo L. , Mamun A. A. , Resendes D. P. , Sorasio G.
Published: November 2002

It is shown that charged dust grains can be accelerated by the nonuniform space charge electric fields that are created by the ponderomotive force of circularly polarized electromagnetic cyclotron waves. The relevance of our investigation to dust energization in the Earth's mesospheric plasma is stressed.
Speed fluctuations near 60 AU on scales from 1 day to 1 year: Observations and model
Authors: Burlaga L. F. , Richardson J. D. , Wang C.
Published: November 2002

This paper describes the multiscale, statistical state of the speed observed near 60 AU from mid‐1999 to mid‐2000 by Voyager 2 (V2), and it shows that a multifluid MHD model can explain the basic features of these observations. The probability distribution functions (PDFs) of the running speed differences (dVn) on scales from 1 day to 256 days provide a relatively complete description of some important properties of the large‐scale speed fluctuations. On a scale of 1 or 2 days the PDFs of the positive and negative speed differences observed by V2 are approximately exponential, which is related to jump‐ramp structures but might include a contribution from intermittent turbulence. On scales greater than 26 days (the solar rotation period) the PDFs of the speed differences are approximately Gaussian, i.e., quadratic on a semilog scale. On a scale of the order of several days, on which one sees jump‐ramp structures in the speed profile, the PDF of the speed differences is cubic on a semilog scale. The standard deviation of dVn increases with increasing scale. The skewness and kurtosis of dVn are relatively large at small scales and decrease to Gaussian values at scales ≥16 days. The PDFs of speed differences and their lower moments versus scale near 60 AU were also derived from a speed profile predicted by the deterministic, spherically symmetric, multifluid, MHD model of Chi Wang, using ACE observations at 1 AU as the inner boundary conditions. Although the projected speed profile is not the same as the observed speed profile because ACE and Voyager are not radially aligned throughout the 1‐year interval, the statistical properties of the observed profiles are essentially the same as the projected speed profiles. Significant evolution of the multiscale statistical properties of the solar wind speed fluctuations occurs between 1 and 60 AU; this evolution can be explained by a deterministic model.
The dayside reconnection X line
Authors: Moore T. E. , Fok M.‐C. , Chandler M. O.
Published: November 2002

The antiparallel reconnection hypothesis states that reconnection occurs at or near the locus along which magnetosheath and magnetospheric fields are antiparallel and the reconnecting component of the magnetic field is maximal. Recent observations have pointed toward significant reconnection rates in locales with much less than antiparallel field shear. We explore the alternative component reconnection hypothesis that reconnection occurs along a locus determined by integrating the local X line (XL) direction away from that region with the largest reconnecting field magnitude. We develop a description of the magnetospheric and magnetosheath magnetic fields at the magnetopause, compute the angle between the sheath and boundary layer fields, and the reconnecting component, everywhere on the magnetopause. We then integrate the XL across the magnetopause from a starting point or points where the reconnecting component is maximal. The resultant XL lies across the equatorial subsolar magnetopause for southerly Bz, as expected. For typical interplanetary magnetic field (IMF) conditions dominated by By, the XL tilts poleward and loops around the cusps into the high‐latitude regions, consistent with throat‐like cusp region flows. For northerly Bz, the XL bifurcates into high‐latitude and low‐latitude segments with subsolar reconnection disappearing only for mainly northward Bz. We argue that the component reconnection XL represents the mean location of quasi‐steady reconnection on the magnetopause, subject to of course to nonuniformities and variations of the interplanetary magnetic field and plasma. We conclude that reconnection should have appreciable rates across the subsolar magnetopause for most IMF clock angles, with higher rates at high latitudes for northward Bz.
Hydrogen wall and heliosheath Ly α absorption toward nearby stars: Possible constraints on the heliospheric interface plasma flow
Authors: Izmodenov Vlad , Wood Brian E. , Lallement Rosine
Published: November 2002

In this paper, we study heliospheric Ly α absorption toward nearby stars in different lines of sight. We use the Baranov–Malama model of the solar wind interaction with a two‐component (charged component and H atoms) interstellar medium. Interstellar atoms are described kinetically in the model. The code allows us to separate the heliospheric absorption into two components, produced by H atoms originating in the hydrogen wall and heliosheath regions, respectively. We study the sensitivity of the heliospheric absorption to the assumed interstellar proton and H atom number densities. These theoretical results are compared with interstellar absorption toward six nearby stars observed by the Hubble Space Telescope (HST).
Dynamics of Farley‐Buneman fluctuations in the presence of radar beams
Authors: Shukla P. K. , Stenflo L. , Rosenberg M. , Resendes D. P.
Published: November 2002

The nonlinear interaction between intense radar beams and the Farley‐Buneman modes in the Earth's atmosphere is considered. The interaction is governed by a pair of equations consisting of the radar beam equation and an equation for the Farley‐Buneman modes in the presence of the radar ponderomotive force. Our dynamical equations are used to study the effect of radar beams on the Farley‐Buneman instability. It is found that the latter can be stabilized in the presence of radar beams. Implications of our investigation to the suppression of plasma turbulence in dusty meteor trails and polar mesospheric clouds are discussed.
On the origin of radial magnetic fields in the heliosphere
Authors: Gosling J. T. , Skoug R. M.
Published: November 2002

Numerous examples of events wherein the heliospheric magnetic field (HMF) measured at a fixed point in space remains nearly radial for many hours have been reported in the literature. Such events are observed both in the normal solar wind and within disturbances driven by coronal mass ejections (CMEs). A very large fraction of these extended, nearly radial HMF intervals, whose average duration increases with increasing distance from the Sun, occur at times when the solar wind flow speed is declining gradually. Typically, when mapped back to the Sun using a constant speed‐with‐distance approximation, all portions of a given radial field event appear to have left the Sun at approximately the same time. Here we propose that these nearly radial HMF events result from temporally abrupt and semipermanent decreases in solar wind flow speed on these same field lines close to the Sun. The abrupt flow speed changes may be the result of an interchange reconnection of field lines that extend into the heliosphere with closed coronal loops. In our kinematic model a radially directed kink in the magnetic field connects the different spirals associated with the faster and slower flows immediately preceding and following the temporal flow speed discontinuity. With increasing heliocentric distance the length of the kink grows while the temporal flow speed discontinuity that produces it evolves into a gradual spatial flow speed decline.
Conjugate observations of traveling convection vortices: The field‐aligned current system
Authors: Murr D. L. , Hughes W. J. , Rodger A. S. , Zesta E. , Frey H. U. , Weatherwax A. T.
Published: November 2002

Analysis of a single traveling convection vortex (TCV) event that combines magnetometer, auroral imager, and riometer observations from conjugate hemispheres provides a complete view of the field‐aligned current (FAC) system associated with the TCV. Conjugate observations clearly show that the TCV is a pair of FACs that flow alternatively out of and then into both ionospheres. Imaging observations at 427.8 nm indicate that the upward FAC region is associated with a narrow arc 50–100 km wide and at least 600 km long. Mapping the imaging observations made in the Southern Hemisphere to the Northern Hemisphere shows excellent collocation of the precipitation with the flow vortex associated with the upward FAC as inferred from a large two‐dimensional network of magnetometers. Also consistent with the flows inferred from the magnetometers, the arc is found to be skewed with respect to the direction of motion of the transient. Low‐altitude spacecraft passes near the time of the event suggest that the FAC is coincident with, and possibly confined to, a relatively narrow region (less than 3° in latitude) in which 1–10 keV electrons characteristic of the central plasma sheet are present.
A Lagrangian numerical investigation of the origins and fates of the salinity maximum water in the Atlantic
Authors: Blanke Bruno , Arhan Michel , Lazar Alban , Prévost Gwenaëlle
Published: November 2002

The origins and fates of the Atlantic salinity maximum water (SMW), formed through excess evaporation in the tropics and subtropics of both hemispheres, are studied using monthly mean outputs of a numerical simulation of the world ocean climatological circulation. After defining formation domains from the surface salinity field and the vertical stratification, a Lagrangian technique is used to estimate the formation rates and main pathways in each hemisphere and the role of this water in the framework of the warm water return flow of the meridional overturning cell. Formation rates around 9 and 11 Sv are found in the Southern and Northern Hemispheres, respectively. While the export of the southern SMW from its formation area is realized by the western boundary currents, that of the northern SMW mainly results from interior subduction. Equatorward of the formation regions, a fraction of each SMW variety is entrained in the subtropical cells that connect the subtropics to the equatorial region. Poleward of them, both varieties are seen to feed the regions of subtropical mode water (STMW) formation around 35° of latitude in both hemispheres. The bulk of the transport associated with each variety eventually turns northward: This amounts to ∼6 Sv of southern SMW gathered in the North Brazil Undercurrent (NBUC), and ∼10 Sv of northern SMW found in the Gulf Stream at 35°N, of which 8 Sv have gone through the Caribbean Sea. Of the 13.4‐Sv northward transport of the meridional overturning cell estimated by the model at 47°N, more than 50% (6.9 Sv) is found to have transited through at least one of the SMW regions. This gives an indication of the likely important role of SMW formation in the observed northward salinity increase of the upper Atlantic Ocean.
Model studies on ion‐induced nucleation in the atmosphere
Authors: Laakso L. , Mäkelä J. M. , Pirjola L. , Kulmala M.
Published: November 2002

A new model for ion‐induced nucleation and charged aerosol dynamics is presented in this paper. It was found that ion‐induced nucleation is able to produce a considerable amount of new particles if the preexisting particle concentration is sufficiently low. Also, when only positive or negative ions nucleate a large amount of particles in observable sizes was produced. It was also found that there can be continuous nucleation in particle sizes below the detection limit of most commonly used aerosol instruments at low temperatures and high preexisting particle concentrations. In some simulated conditions, fair agreement with observed particle formation events in boreal forest environment was achieved. According to the results, in certain situations ion‐induced nucleation changes the charge distribution of the particles, which may allow the observation of ion‐induced nucleation in the atmospheric conditions.
Influence of planetary wave transport on Arctic ozone as observed by Polar Ozone and Aerosol Measurement (POAM) III
Authors: Strahan Susan
Published: November 2002

Interannual differences in Arctic ozone are investigated using data from the Polar Ozone and Aerosol Measurement (POAM) III instrument obtained between May 1998 and April 2001. These three winters were unusually warm or cold relative to the 1979–2001 mean, resulting in years with either a warm, disturbed vortex or a cold, quiet vortex. Contours of probability distribution functions (PDFs) of the POAM data are used to identify seasonal and interannual variations in the transport processes controlling ozone. A major warming in December, 1998, displaced the middle stratospheric vortex from the pole for nearly a month, dissipating it. The vortex reformed in January, 1999, filled with high O3 air from lower latitudes, which then cooled and descended. By the end of winter 1999, ozone at 500 K in the vortex was 0.5–1.0 ppm higher than in the subsequent cold winter. The winter of 2000–2001 had frequent wave disturbances, beginning with a fairly large event in November. However, at the end of this event, the high potential vorticity (PV) core of the vortex was intact, and by February, O3 in the vortex looked the same as in 2000. Transport in these winters is inferred from the PDFs and supported by potential vorticity analyses. This study demonstrates that variability in the O3‐PV relationship can be caused by transport, independent of loss by polar stratospheric clouds (PSCs). Ozone in the vortex in a very disturbed winter can be unusually high due to transport and will not represent O3 levels expected in the absence of PSCs in other years.
Synthesis inverse mapping: A robust method applicable to atmospheric remote sounding
Authors: Fussen Didier , Vanhellemont Filip , Bingen Christine
Published: November 2002

We develop a new inversion method that may be advantageously applied to remote sounding in atmospheric physics. The technique is based on the synthesis of the inversion operator which can be used in noisy measurements where the success of classical regularization and optimal estimation methods strongly depends on the accurate knowledge of the a priori atmospheric state. We outline the benefits of the method: robustness, full control of validity range as well as easy assessment of the smoothing error. An example of spectral inversion is extensively analyzed in the context of aerosol retrievals from limb occultation experiments.
The Large‐Scale Biosphere‐Atmosphere Experiment in Amazonia (LBA): Insights and future research needs
Authors: Avissar Roni , Silva Dias Pedro L. , Silva Dias Maria A. F. , Nobre Carlos
Published: November 2002

This overview summarizes general Large‐Scale Atmosphere‐Biosphere Experiment in Amazonia (LBA) papers and highlights some of the insights gained from these investigations and needs for future research. It complements the overview of Silva Dias et al. [2002a], which summarizes the papers published on the joint major atmospheric mesoscale campaign in the wet season (WetAMC), which was held jointly in Rondonia with the Tropical Rainfall Measuring Mission (TRMM) validation campaign known as TRMM‐LBA. It also complements the overview of Andreae et al. [2002], which summarizes the papers describing the biogeochemical cycling of carbon, water, energy, aerosols, and trace gases resulting from the European Studies on Trace Gases and Atmospheric Chemistry, known as LBA‐EUSTACH Project. The 17 papers summarized under this part of the special issue are regrouped into three main categories: (1) measurements and data sets, (2) remote sensing, and (3) modeling.
Amazonis Planitia: The role of geologically recent volcanism and sedimentation in the formation of the smoothest plains on Mars
Authors: Fuller Elizabeth R. , Head James W.
Published: November 2002

Amazonis Planitia, located between the two main volcanic provinces on Mars (Tharsis and Elysium), is characterized by extremely smooth topography at several scale lengths, as smooth as oceanic abyssal plains topography on Earth. We use Mars Global Surveyor (MGS) data (primarily very high resolution Mars Orbiter Laser Altimeter (MOLA) topography and derivative slope maps, gradient maps, and detrended maps) to examine the surface morphology of Amazonis Planitia and the stratigraphic relationships among previously mapped and newly defined units. These new data reveal the presence of a 1300 km diameter Noachian impact basin in northwest Amazonis Planitia and an extensive Late Hesperian lava flow unit that appears to have originated from the Olympus Mons source area prior to aureole formation. The presence of this previously unrecognized flow unit strongly suggests that Olympus Mons activity dates back to at least the Hesperian, as did activity on the Tharsis Montes. Emplacement of this ∼100 meter thick flow unit formed a barrier along the northern margin of Amazonis Planitia which had a profound influence on the subsequent geologic history of the region. Formation of Olympus Mons aureole deposits created an eastern topographic barrier, and subsequent Tharsis Montes lava flows entered the basin from the south, flowing around the aureole. These three barriers (degraded Noachian crater rim, proto‐Olympus Mons flow unit, and Olympus Mons aureole) caused subsequent lava flows and outflow channel effluents, primarily from the Elysium region to the west, to pond on the floor of Amazonis Planitia, preferentially smoothing the terrain there. Mars Orbiter Camera (MOC) images substantiate that at least two very fluid lava flows alternated with fluvial episodes from Elysium Planitia, flowing through Marte Valles onto the floor of the Amazonis Planitia basin. Within Amazonis Planitia, MOC images show flow‐like textures heavily mantled by sediments, and radar data reveal the presence of rough lava flow surfaces underlying the sedimentary debris. These data thus suggest that the unique smoothness of Amazonis Planitia is the result of deposition of thin fluid lava flows and fluvial sediments in an enclosed basin. Crater counts suggest that the most recent resurfacing may have occurred in the latest Amazonian Period, in the last 1% of the history of Mars. In light of its unique history, it is somewhat ironic to note that Amazonis Planitia was originally thought to be a typical young Martian surface and therefore used to name the Amazonian era.
Geologic setting and origin of Terra Meridiani hematite deposit on Mars
Authors: Hynek Brian M. , Arvidson Raymond E. , Phillips Roger J.
Published: November 2002

We have completed a regional analysis of the hematite deposit in Terra Meridiani and conclude that the unit is in the midst of a 600‐m‐thick stack of friable layered materials superposed on Middle and Late Noachian cratered terrain. The deposits resemble terrestrial pyroclastics in the fact that they are: (1) thin, parallel bedded deposits that conform to preexisting topography, (2) often extremely friable, and (3) composed of fine particles. Some of the lowermost layered units exhibit possible lava flow textures and features. Abundant outliers indicate that the deposits were once far more extensive and that erosion (primarily aeolian) has removed vast portions of the stratigraphic sequence. The hematite may have formed from thermal oxidation of the volcanic ash during eruption or have been precipitated from the circulation of fluids within the layered materials at a later time. Temporal and spatial association with outflow channels and evidence for cementation along joints and bedding planes within the layered deposits suggest the latter scenario.
Hierarchical geostatistics and multifacies systems: Boise Hydrogeophysical Research Site, Boise, Idaho
Authors: Barrash Warren , Clemo Tom
Published: November 2002

The geostatistical structure of a heterogeneous coarse fluvial aquifer is investigated with porosity data derived from neutron logs at a research well field (Boise Hydrogeophysical Research Site, or BHRS) that was designed, in part, to support three‐dimensional geostatistical analysis of hydrologic and geophysical parameters. Recognizing that the coarse fluvial deposits include subdivisions (units between bounding surfaces), we adopt a hierarchical approach and examine the porosity geostatistics of the aquifer at three scales. At the BHRS, the saturated fluvial deposits as a whole (maximum interwell spacing ∼80 m, thickness ∼16–18 m) are at hierarchical level 1; five subhorizontal units within these deposits (four cobble‐dominated units and a channel sand) can be traced across the central area of the BHRS and are at hierarchical level 2; and subunits (patches or lenses) in one of the level 2 units (Unit 4), are at hierarchical level 3. We use variography and porosity statistics to recognize nonstationarity at hierarchical level 1 and in one of the level 2 units (Unit 4) where the means and variances of porosity differences as a function of lag are not constant between distinct units and subunits, respectively. The geostatistical structure at level 1 is modeled with different horizontal and vertical structures that have different sills (vertical sill greater than horizontal sill). The difference in sills can be explained quantitatively by the summing of weighted sills from all individual units and combined units (i.e., a given pair of different units), where the weights are the proportions of data pairs contributing to the sills at each lag from the individual and combined units. Extension of this analysis leads to a weighted, multistructure form of the variogram function whereby a global experimental variogram in a hierarchical system can be decomposed quantitatively into weighted component individual‐ and combined‐unit (or facies) structures for any number of units or hierarchical levels. Such decomposition of the global horizontal variogram from the BHRS indicates that short‐range periodicity in that structure is due to both (1) combined‐unit structures associated with patches or lenses at hierarchical level 3 in Unit 4 and (2) variations in thickness of Unit 2. For hierarchical multifacies systems, structure models fit to global horizontal and vertical experimental variograms may not be useful for subsequent stochastic modeling if the system on which the structure models are based is nonstationary.
Spinning Toronto's Golden Age: The Making of a ‘City that Worked’
Authors: Donald Betsy
Published: December 2002

In this paper I explore the key elements of the mode of regulation operating at the urban scale in Toronto's postwar period to learn what it was that inspired an entire generation of scholars to call Toronto the ‘city that works' in this period. Despite the significant amount of literature discussing the general character of regulation operating at the city-region scale in the Fordist or managerial period of urban development, it is argued that surprisingly little empirical research has actually documented what allegedly made these Fordist metropolitan regions ‘work‘. Drawing on archival research in addition to insights from Canadian applied regulation theory and from an analysis of Canada's changing fiscal federalism, I argue that, although Toronto did develop within the context of a Fordist regime of accumulation, the particular elements of the mode of regulation it developed at the urban scale were distinctive and important in providing the conditions underlying the economic success of the region. Toronto may have benefited disproportionately from national regulatory policies. However, its economic dynamism also constituted one of the cornerstones of the nation's economic and social viability. Further, its more localized regulatory structures and social context had a specific institutional and cultural richness, which, in concert with its highly developed economic structure, served to stave off many of the crisis tendencies being felt by other industrial regions in the 1970s and 1980s. One of the principal and unique institutional innovations was the Municipality of Metropolitan Toronto (’Metro'), which can be regarded as a key (although hitherto underemphasized) component of the Canadian Fordist regime of accumulation. More than just a conduit through which nationally driven Keynesian welfare programs were delivered, Metro was also an innovator of unique urban-based postwar development policies. I conclude by demonstrating what this story of postwar Toronto can tell us more generally about urban government and governance under Fordism, and about the managerial paradigm and the regulation approach.
Microsimulation of Neighborhood Evacuations in the Urban–Wildland Interface
Authors: Cova Thomas J , Johnson Justin P
Published: December 2002

Residential development in fire-prone wildlands is occurring at an unprecedented rate. Community-based evacuation planning in many areas is an emerging need. In this paper we present a method for using microscopic traffic simulation to develop and test neighborhood evacuation plans in the urban–wildland interface. The method allows an analyst to map the subneighborhood variation in household evacuation travel times under various scenarios. A custom scenario generator manages household trip generation, departure timing, and destination choice. Traffic simulation, route choice, and dynamic visualization are handled by a commercial system. We present a case study for a controversial fire-prone canyon community east of Salt Lake City, Utah. GIS was used to map the spatial effects of a proposed second access road on household evacuation times. Our results indicate that the second road will reduce some household travel times much more than others, but all evacuation travel times will become more consistent.
Rethinking the Development of Economic Geography in Mainland China
Authors: Liu Weidong , Lu Dadao
Published: December 2002

Economic geography is a discipline encompassing diverse scopes and approaches. As such, it is not easy to achieve well-founded dialogues between economic geographers from different countries, though such dialogues are necessary for establishing a well-developed platform of discussion. The authors attempt to help scholars from other countries understand the development of economic geography in China by showing how such development has been affected by the country's institutional and economic conditions. They first introduce the context in which economic geography has developed in China and discuss changes in the definition of economic geography in the country. They then examine post-1949 development of economic geography in China in terms of research orientations or tasks, funding, and organization. The authors argue that the development of economic geography is embedded in a broad socioeconomic and institutional context and that this context is key to understanding the development of economic geography in different countries.
The Moral Commodity: Production, Consumption, and Governance in the Australasian Breakfast Cereal Industry
Authors: Le Heron Kiri , Hayward David
Published: December 2002

This paper examines the Australasian breakfast cereal commodity chain and the processes of value creation in the industry. The paper has two points of entry to the commodity chain; first, a productionist perspective aimed at revealing how the material commodity is constituted, and, second, a consumptionist viewpoint, intended to show the construction of symbolic elements of the commodity. The value of the breakfast cereal commodity includes both its utility (food) value, and the semiotic and moral narratives associated with it—its symbolic value. To maintain these value dimensions the breakfast cereal companies have fashioned relationships with other organisations to legitimise prod-ucts in the eyes of the consumers. Both governmental and nongovernmental organisations are drawn into the commodity chain, and along with consumers, they actively participate in the recreation and redescription of the commodity's value. Through adhering to the analytical strategy of delineating both production and consumption dimensions the case study was able to establish the multiple layering of meanings that are associated with breakfast cereals—meanings that continue to be aligned with the industry's founding principles.
Risk, Responsibility, and Blame: An Analysis of Vocabularies of Motive in Air-Pollution(ing) Discourses
Authors: Bickerstaff Karen , Walker Gordon
Published: December 2002

In this paper we analyse the reasonings that people deploy in explaining and rationalising their behaviour in relation to the collective environmental and health-risk problem of urban air quality. We draw on an empirical study of public perceptions of air pollution to identify a range of ‘vocabularies of motive’ or discourses that serve to move responsibility to act away from the individual and onto other groups. We consider how far each of these ‘vocabularies' can be interpreted as a mode of blaming, and draw conclusions linking our analysis to wider relational and moral tensions. Our analysis suggests that blame, although conceptually powerful, falters under empirical scrutiny. On this basis we argue for a more sensitive reading of responsibility discourses in academic debate and enquiry. Conclusions and policy implications are developed, linking our interpretation to the (confrontation of) wider relational and moral tensions, which characterise collective-risk situations.
Regional Cycles of Learning: Foreign Multinationals as Agents of Technological Upgrading in Less Developed Countries
Authors: Fromhold-Eisebith Martina
Published: December 2002

Within the debate about positive effects of foreign multinational branch plants on host regions in less developed countries questions of technological learning and upgrading rank at the top. This paper describes forces and mechanisms which, under favourable conditions, promote dissemination of know-how through the dynamics of regional cycles of learning. Enriching earlier insights into the local embedding of subsidiaries and processes of cumulative causation, it emphasises why and how agglom-erating branches of globally operating technology companies engage in upgrading their less developed locality: effects are triggered by a combination of increasing regional labour-cost pressure and corresponding reactions of firms which relate to their branch activities and affect the institutional framework. Two models of regional cycles of learning are introduced which depict crucial distinctions between spatial clusters of technology firms with and without foreign affiliates. Empirical evidence is provided by comparing two technology regions in developing Asia: Bangalore, India, and Bandung, Indonesia. Both are well endowed with universities, research institutions, and firms in technology sectors, but differ with regard to the presence of foreign firms, and accordingly, display divergent qualitative developments.
Technology Asymmetries, Group Algebra, and Multiplant Cost Minimization
Authors: Hennessy David A. , Lapan Harvey E.
Published: November 2002

For a homogeneous good, this article studies firm‐level production activities when the firm controls a plural number of plants. Through careful construction of cost function technology asymmetries, we inquire into the ordinal structure of the production vector for multiplant cost minimizers. When Schur‐convexity of a reference pseudo‐cost technology is the principal functional assumption, then ordinal concepts of technical asymmetries map into rank order on the equilibrium production vector. Under a more generalized characterization of the technical asymmetries a multiplant firm encounters, group theory is used to map a cardinal concept of asymmetries into cardinal bounds on the optimum allocation.
Conserved homeodomain proteins interact with MADS box protein Mcm1 to restrict ECB-dependent transcription to the M/G1 phase of the cell cycle
Authors: Pramila Tata , Miles Shawna , GuhaThakurta Debraj , Jemiolo Dave , Breeden Linda L.
Published: December 2002

Two homeodomain proteins, Yox1 and Yhp1, act as repressors at early cell cycle boxes (ECBs) to restrict their activity to the M/G1 phase of the cell cycle in budding yeast. These proteins bind to Mcm1 and to a typical homeodomain binding site. The expression of Yox1 is periodic and directly correlated with its binding to, and repression of, ECB activity. The absence of Yox1 and Yhp1 or the constitutive expression of Yox1 leads to the loss of cell-cycle regulation of ECB activity. Therefore, the cell-cycle-regulated expression of these repressors defines the interval of ECB-dependent transcription. Twenty-eight genes, including MCM2-7, CDC6, SWI4,CLN3, and a number of genes required during late M phase have been identified that are coordinately regulated by this pathway.
Complex transcriptional circuitry at the G1/S transition in Saccharomyces cerevisiae
Authors: Horak Christine E. , Luscombe Nicholas M. , Qian Jiang , Bertone Paul , Piccirrillo Stacy , Gerstein Mark , Snyder Michael
Published: December 2002

In the yeast Saccharomyces cerevisiae, SBF (Swi4–Swi6 cell cycle box bindingfactor) and MBF (MluIbinding factor) are the major transcription factors regulating the START of the cell cycle, a time just before DNA replication, bud growth initiation, and spindle pole body (SPB) duplication. These two factors bind to the promoters of 235 genes, but bind less than a quarter of the promoters upstream of genes with peak transcript levels at the G1 phase of the cell cycle. Several functional categories, which are known to be crucial for G1/S events, such as SPB duplication/migration and DNA synthesis, are under-represented in the list of SBF and MBF gene targets. SBF binds the promoters of several other transcription factors, includingHCM1, PLM2, POG1, TOS4, TOS8,TYE7, YAP5, YHP1, and YOX1. Here, we demonstrate that these factors are targets of SBF using an independent assay. To further elucidate the transcriptional circuitry that regulates the G1-to-S-phase progression, these factors were epitope-tagged and their binding targets were identified by chIp–chip analysis. These factors bind the promoters of genes with roles in G1/S events including DNA replication, bud growth, and spindle pole complex formation, as well as the general activities of mitochondrial function, transcription, and protein synthesis. Although functional overlap exists between these factors and MBF and SBF, each of these factors has distinct functional roles. Most of these factors bind the promoters of other transcription factors known to be cell cycle regulated or known to be important for cell cycle progression and differentiation processes indicating that a complex network of transcription factors coordinates the diverse activities that initiate a new cell cycle.
A common mechanism for mitotic inactivation of C2H2 zinc finger DNA-binding domains
Authors: Dovat Sinisa , Ronni Tapani , Russell Dana , Ferrini Roger , Cobb Bradley S. , Smale Stephen T.
Published: December 2002

Many nuclear proteins are inactivated during mitotic entry, presumably as a prerequisite to chromatin condensation and cell division. C2H2 zinc fingers define the largest transcription factor family in the human proteome. The linker separating finger motifs is highly conserved and resembles TGEKP in more than 5000 occurrences. However, the reason for this conservation is not fully understood. We demonstrate that all three linkers in the DNA-binding domain of Ikaros are phosphorylated during mitosis. Phosphomimetic substitutions abolished DNA-binding and pericentromeric localization. A linker within Sp1 was also phosphorylated, suggesting that linker phosphorylation provides a global mechanism for inactivation of the C2H2 family.
Cell identity and sexual development in Cryptococcus neoformans are controlled by the mating-type-specific homeodomain protein Sxi1α
Authors: Hull Christina M. , Davidson Robert C. , Heitman Joseph
Published: December 2002

Virulence in the human fungal pathogen Cryptococcus neoformans is associated with the α mating type. Studies to identify the properties of α cells that enhance pathogenesis have led to the identification of a mating-type locus of unusually large size and distinct architecture. Here, we demonstrate that the previously identified MATα components are insufficient to regulate sexual differentiation, and we identify a novel α-specific regulator,SXI1α. Our data show that SXI1α establishes α cell identity and controls progression through the sexual cycle, and we discover that ectopic expression of SXI1α in a cells is sufficient to drive a/α sexual development. SXI1α is the first example of a key regulator of cell identity and sexual differentiation in C. neoformans, and its identification and characterization lead to a new model of how cell fate and the sexual cycle are controlled in C. neoformans.
CD44 is required for two consecutive steps in HGF/c-Met signaling
Authors: Orian-Rousseau Véronique , Chen Linfeng , Sleeman Jonathan P. , Herrlich Peter , Ponta Helmut
Published: December 2002

The tyrosine kinase receptor c-Met and its ligand HGF/SF, ezrin, and splice variants of CD44 have independently been identified as tumor metastasis-associated proteins. We now show that these proteins cooperate. A CD44 isoform containing variant exon v6 sequences is strictly required for c-Met activation by HGF/SF in rat and human carcinoma cells, in established cell lines as well as in primary keratinocytes. CD44v6-deficient tumor cells were unable to activate c-Met unless they were transfected with a CD44v6-bearing isoform. Antibodies to two v6-encoded epitopes inhibited autophosphorylation of c-Met by interfering with the formation of a complex formed by c-Met, CD44v6, and HGF/SF. In addition, signal transduction from activated c-Met to MEK and Erk required the presence of the cytoplasmic tail of CD44 including a binding motif for ERM proteins. This suggests a role for ERM proteins and possibly their link to the cortical actin cytoskeleton in signal transfer.
A nucleolar mechanism controlling cell proliferation in stem cells and cancer cells
Authors: Tsai Robert Y.L. , McKay Ronald D.G.
Published: December 2002

The unique property of stem cells to self-renew suggests specific mechanisms that regulate their cell-cycle progression. In the present study, we identify a novel protein, nucleostemin, found in the nucleoli of CNS stem cells, embryonic stem cells, and several cancer cell lines and preferentially expressed by other stem cell-enriched populations. It contains an N-terminal basic domain and two GTP-binding motifs. When stem cells differentiate, nucleostemin expression decreases rapidly prior to cell-cycle exit both in vitro and in vivo. Depletion or overexpression of nucleostemin reduces cell proliferation in CNS stem cells and transformed cells. Mutation analysis indicates that excessive nucleostemin, particularly mutants that lack the GTP-regulatory domain, prevents cells from entering mitosis and causes apoptosis in a p53-dependent manner. The N-terminal basic domain specifies nucleolar localization, the p53 interaction, and is required for the cell death caused by overexpression. This work describes a novel nucleolar mechanism that controls the cell-cycle progression in CNS stem cells and cancer cells.