bluuebunny/crossref_metadata_2025 huggingface dataset:
United States Department of Agriculture—Agricultural Research Service: advances in the molecular genetic analysis of insects and their application to pest management
Authors: Handler Alfred M , Beeman Richard W
Published: May 2003

USDA‐ARS scientists have made important contributions to the molecular genetic analysis of agriculturally important insects, and have been in the forefront of using this information for the development of new pest management strategies. Advances have been made in the identification and analysis of genetic systems involved in insect development, reproduction and behavior which enable the identification of new targets for control, as well as the development of highly specific insecticidal products. Other studies have been on the leading edge of developing gene transfer technology to better elucidate these biological processes though functional genomics and to develop new transgenic strains for biological control. Important contributions have also been made to the development and use of molecular markers and methodologies to identify and track insect populations. The use of molecular genetic technology and strategies will become increasingly important to pest management as genomic sequencing information becomes available from important pest insects, their targets and other associated organisms. Published in 2003 for SCI by John Wiley & Sons, Ltd.
Current United States Department of Agriculture—Agricultural Research Service research on understanding agrochemical fate and transport to prevent and mitigate adverse environmental impacts
Authors: Hapeman Cathleen J , McConnell Laura L , Rice Clifford P , Sadeghi Ali M , Schmidt Walter F , McCarty Gregory W , Starr James L , Rice Pamela J , Angier Jonathan T , Harman‐Fetcho JA
Published: May 2003

Environmentally and economically viable agriculture requires a variety of cultivation practices and pest management options as no one system will be appropriate for every situation. Agrochemicals are some of the many pest control tools used in an integrated approach to pest management. They are applied with the intent of maximizing efficacy while minimizing off‐site movement; however, their judicious use demands a practical knowledge of their fate and effects in agricultural and natural ecosystems. Agrochemical distribution into environmental compartments is influenced by the physical and chemical properties of the agrochemical and environmental conditions, ie soil type and structure, and meteorological conditions. Agricultural Research Service (ARS) researchers working in the area of agrochemical fate have focused on accurately describing those processes that govern the transport, degradation and bioavailability of these chemicals under conditions reflecting actual agronomic practices. Results from ARS research concerning the environmental fate and effects of agrochemicals have led to the development of science‐based management practices that will protect vulnerable areas of the ecosystem. The new challenge is to identify these vulnerable areas and the temporal and spatial variations prior to use of the chemical by predicting how it will behave in environmental matrices, and using that information, predict its transport and transformation within an air‐ or watershed. With the development of better predictive tools and GIS (Geographic Information System)‐based modeling, the risks of agricultural management systems can be assessed at the watershed and basin levels, and management strategies can be identified that minimize negative environmental impacts. Published in 2003 for SCI by John Wiley & Sons, Ltd.
United States Department of Agriculture—Agriculture Research Service research on targeted management of the Formosan subterranean termite Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae)
Authors: Lax Alan R , Osbrink Weste LA
Published: May 2003

The Formosan subterranean termite, Coptotermes formosanus Shiraki is currently one of the most destructive pests in the USA. It is estimated to cost consumers over US $1 billion annually for preventative and remedial treatment and to repair damage caused by this insect. The mission of the Formosan Subterranean Termite Research Unit of the Agricultural Research Service is to demonstrate the most effective existing termite management technologies, integrate them into effective management systems, and provide fundamental problem‐solving research for long‐term, safe, effective and environmentally friendly new technologies. This article describes the epidemiology of the pest and highlights the research accomplished by the Agricultural Research Service on area‐wide management of the termite and fundamental research on its biology that might provide the basis for future management technologies. Fundamental areas that are receiving attention are termite detection, termite colony development, nutrition and foraging, and the search for biological control agents. Other fertile areas include understanding termite symbionts that may provide an additional target for control. Area‐wide management of the termite by using population suppression rather than protection of individual structures has been successful; however, much remains to be done to provide long‐term sustainable population control. An educational component of the program has provided reliable information to homeowners and pest‐control operators that should help slow the spread of this organism and allow rapid intervention in those areas which it infests. Published in 2003 for SCI by John Wiley & Sons, Ltd.
United States Department of Agriculture—Agricultural Research Service research on pre‐harvest prevention of mycotoxins and mycotoxigenic fungi in US crops
Authors: Cleveland Thomas E , Dowd Patrick F , Desjardins Anne E , Bhatnagar Deepak , Cotty Peter J
Published: May 2003

Mycotoxins (ie toxins produced by molds) are fungal metabolites that can contaminate foods and feeds and cause toxic effects in higher organisms that consume the contaminated commodities. Therefore, mycotoxin contamination of foods and feeds results is a serious food safety issue and affects the competitiveness of US agriculture in both domestic and export markets. This article highlights research accomplished by Agricultural Research Service (ARS) laboratories on control of pre‐harvest toxin contamination by using biocontrol, host‐plant resistance enhancement and integrated management systems. Emphasis is placed on the most economically relevant mycotoxins, namely aflatoxins produced by Aspergillus flavus, Link, trichothecenes produced by various Fusarium spp and fumonisins produced by F verticillioides. Significant inroads have been made in establishing various control strategies such as development of atoxigenic biocontrol fungi that can outcompete their closely related, toxigenic cousins in field environments, thus reducing levels of mycotoxins in the crops. Potential biochemical and genetic resistance markers have been identified in crops, particularly in corn, which are being utilized as selectable markers in breeding for resistance to aflatoxin contamination. Prototypes of genetically engineered crops have been developed which: (1) contain genes for resistance to the phytotoxic effects of certain trichothecenes, thereby helping reduce fungal virulence, or (2) contain genes encoding fungal growth inhibitors for reducing fungal infection. Gene clusters housing the genes governing formation of trichothecenes, fumonisins and aflatoxins have been elucidated and are being targeted in strategies to interrupt the biosynthesis of these mycotoxins. Ultimately, a combination of strategies using biocompetitive fungi and enhancement of host‐plant resistance may be needed to adequately prevent mycotoxin contamination in the field. To achieve this, plants may be developed that resist fungal infection and/or reduce the toxic effects of the mycotoxins themselves, or interrupt mycotoxin biosynthesis. This research effort could potentially save affected agricultural industries hundreds of millions of dollars during years of serious mycotoxin outbreaks. Published in 2003 for SCI by John Wiley & Sons, Ltd.
A review of aquatic weed biology and management research conducted by the United States Department of Agriculture—Agricultural Research Service
Authors: Anderson Lars WJ
Published: May 2003

Ever‐increasing demand for water to irrigate crops, support aquaculture, provide domestic water needs and to protect natural aquatic and riparian habitats has necessitated research to reduce impacts from a parallel increase in invasive aquatic weeds. This paper reviews the past 4–5 years of research by USDA‐ARS covering such areas as weed biology, ecology, physiology and management strategies, including herbicides, biological control and potential for use of natural products. Research approaches range from field‐level studies to highly specific molecular and biochemical work, spanning several disciplines and encompassing the most problematic weeds in these systems. This research has led to new insights into plant competition, host‐specificity, and the fate of aquatic herbicides, their modes of action and effects on the environment. Another hallmark of USDA‐ARS research has been its many collaborations with other federal, state action and regulatory agencies and private industry to develop new solutions to aquatic weed problems that affect our public natural resources and commercial enterprises. Published in 2003 for SCI by John Wiley & Sons, Ltd.
United States Department of Agriculture—Agricultural Research Service research on alternatives to methyl bromide: pre‐plant and post‐harvest
Authors: Schneider Sally M , Rosskopf Erin N , Leesch James G , Chellemi Daniel O , Bull Carolee T , Mazzola Mark
Published: May 2003

Methyl bromide is a widely used fumigant for both pre‐plant and post‐harvest pest and pathogen control. The Montreal Protocol and the US Clean Air Act mandate a phase‐out of the import and manufacture of methyl bromide, beginning in 2001 and culminating with a complete ban, except for quarantine and certain pre‐shipment uses and exempted critical uses, in January 2005. In 1995, ARS built on its existing programs in soil‐borne plant pathology and post‐harvest entomology and plant pathology to initiate a national research program to develop alternatives to methyl bromide. The focus has been on strawberry, pepper, tomato, perennial and nursery cropping systems for pre‐plant methyl bromide use and fresh and durable commodities for post‐harvest use. Recently the program has been expanded to include research on alternatives for the ornamental and cut flower cropping systems. An overview of the national research program is presented. Results from four specific research trials are presented, ranging from organic to conventional systems. Good progress on short‐term alternatives is being made. These will be used as the foundation of integrated management systems which begin with pre‐plant management decisions and continue through post‐harvest processing. Published in 2003 for SCI by John Wiley & Sons, Ltd.
High glucose potentiates palmitate‐induced NO‐mediated cytotoxicity through generation of superoxide in clonal β‐cell HIT‐T15
Authors: Okuyama Ryo , Fujiwara Toshihiko , Ohsumi Jun
Published: June 2003

Prolonged exposure to free fatty acids induces β‐cell cytotoxicity. We investigated whether this fatty‐acid‐induced cytotoxicity is affected by high glucose levels. In clonal β‐cell HIT‐T15, palmitate‐induced cytotoxicity was potentiated depending on elevated glucose concentrations due to increased apoptosis without cytotoxic effects of high glucose per se. This palmitate cytotoxicity was blocked by NO synthase inhibitors, and palmitate actually increased cellular NO production. The potentiation of palmitate cytotoxicity under high glucose was reversed by decreasing superoxide production, suggesting that superoxide overproduction under high glucose enhances NO‐mediated cytotoxicity in β‐cells, which may explain the mechanism of synergistic deterioration of pancreatic β‐cells by free fatty acids and high glucose.
pH dependence studies provide insight into the structure and mechanism of thimet oligopeptidase (EC 3.4.24.15)
Authors: Sigman Jeffrey A , Edwards Sarah R , Pabon Amanda , Glucksman Marc J , Wolfson Adele J
Published: June 2003

Thimet oligopeptidase (EC 3.4.24.15; TOP) is a Zn(II) endopeptidase implicated in physiological regulation of processes involving neuropeptides. The present study clarifies the active site structure and mechanism of catalysis of TOP. The enzyme exhibited a bell‐shaped pH dependence of activity having an acidic limb due to a protonation event with a pK
a of 5.7 and a basic limb with pK
a of 8.8. The acidic limb can be attributed to protonation of a residue affecting k
cat while the alkaline limb may be due to conformational change. Mutation of Tyr612 to Phe resulted in more than 400‐fold decrease in activity. This result, supported by modeling studies, implicates Tyr612 in transition state stabilization analogous to the role of His231 of thermolysin.
Differential signaling through NFκB does not ameliorate skeletal myoblast apoptosis during differentiation
Authors: Dee Keith , DeChant Anne , Weyman Crystal M.
Published: June 2003

During 23A2 skeletal myoblast differentiation, roughly 30% of the population undergoes apoptosis. Further, constitutive signaling by G12V:H‐Ras or Raf:CAAX abrogates this apoptosis. In this study, we demonstrate an increase in NFκB activity in myoblasts that have survived and are expressing muscle‐specific genes. NFκB activity is also elevated in myoblasts expressing constitutively active G12V:H‐Ras but not Raf:CAAX. Expression of a dominant negative IκB (IκB‐SR) sufficient to eliminate this elevated level of NFκB activity, in either the 23A2 myoblasts or their G12V:H‐Ras‐expressing counterparts, however, does not affect survival. Furthermore, expression of a constitutively active IκB kinase in 23A2 myoblasts does not protect these cells from the apoptosis associated with differentiation. Since signaling by IκB kinase can abrogate differentiation, this result demonstrates that abrogated differentiation and abrogated apoptosis are separable phenotypes.
Phasing of RecA monomers on quasi‐random DNA sequences
Authors: Volodin Alexander A. , Smirnova Elena A. , Bocharova Tatjana N. , Camerini-Otero R.Daniel
Published: June 2003

We show that some arbitrarily chosen DNA sequences have the ability to influence the positioning of RecA monomers in RecA–DNA complexes. The preferential phase of binding of RecA monomers is shown to depend on the DNA sequence and its nucleotide composition. A simple rearrangement of bases in a limited DNA stretch influences the phasing of RecA monomers. On the other hand, that some features of DNA sequences interfere with the phasing on specific DNA sites demonstrates the existence of mechanisms for both positive and negative regulation of phasing on natural DNAs. The possible role of phasing of RecA monomers on DNA is discussed.
Stepping motion of the organelle in a perfused characean cell
Authors: Kagawa Yuki , Tsuchiya Yoshimi
Published: June 2003

The sliding motion of organelles in a perfused characean internodal cell has been investigated. A small number of myosin molecules attached to the organelle are known to slide along actin bundles lying on the inner surface of the cell. The stepping motion of the organelles was first observed using a high‐speed camera with a time resolution of 1 ms. The spatial frequency of all pairwise differences in displacement of the stepping motion has been estimated to be 0.012–0.014 nm−1, which implies that the organelle moves with large steps of 71–83 nm along the actin bundles in a perfused characean cell.
Protein kinase CK2 phosphorylates the Fas‐associated factor FAF1 in vivo and influences its transport into the nucleus
Authors: Olsen Birgitte B. , Jessen Vibeke , Højrup Peter , Issinger Olaf-Georg , Boldyreff Brigitte
Published: June 2003

We previously identified the Fas‐associated factor FAF1 as an in vitro substrate of protein kinase CK2 and determined Ser289 and Ser291 as phosphorylation sites. Here we demonstrate that these two serine residues are the only sites phosphorylated by CK2 in vitro, and that at least one site is phosphorylated in vivo. Furthermore, we analyzed putative physiological functions of FAF1 phosphorylation. The ability of FAF1 to potentiate Fas‐induced apoptosis is not influenced by the FAF1 phosphorylation status; however, the nuclear import of a phosphorylation‐deficient FAF1 mutant was delayed in comparison to wild‐type FAF1.
Mutational analysis of the Mycobacterium tuberculosis Rv1625c adenylyl cyclase: residues that confer nucleotide specificity contribute to dimerization
Authors: Shenoy Avinash R , Srinivasan N , Subramaniam M , Visweswariah Sandhya S
Published: June 2003

The mycobacterial Rv1625c gene product is an adenylyl cyclase with sequence similarity to the mammalian enzymes. The catalytic domain of the enzyme forms a homodimer and residues specifying adenosine triphosphate (ATP) specificity lie at the dimer interface. Mutation of these residues to those present in guanylyl cyclases failed to convert the enzyme to a guanylyl cyclase, but dramatically reduced its adenylyl cyclase activity and altered its oligomeric state. Computational modeling revealed subtle differences in the dimer interface that could explain the biochemical data, suggesting that the structural and catalytic features of this homodimeric adenylyl cyclase are in contrast to those of the heterodimeric mammalian enzymes.
The progression of anterior translation after anterior cruciate ligament reconstruction in a caprine model
Authors: Cummings J. F. , Grood E. S.
Published: June 2003

Large post‐operative anterior–posterior translations are frequently reported after quadruped anterior cruciate ligament (ACL) reconstructions. To determine when the translation increases occur and the mechanism responsible, we followed the anterior and posterior translation limits in 18 goat knees for six months. Reconstructions were performed using grafts 4 or 7 mm wide placed in initially tight or lax positions. The anterior and posterior translation limits at 50 N were monitored using Roentgen stereophotogrammetric analysis. Graft bone block stability and soft tissue segment lengths were also assessed. Large (>2 mm) increases in anterior translation were noted in 71% of the subjects at two weeks, and in 88% at eight weeks. The translations in the lax and tight groups were indistinguishable after two weeks. Joints with wide grafts had less anterior translation compared to narrow grafts at all time periods, but were significant different only at 26 weeks. The posterior translation limit moved anteriorly over the 26 weeks. Eight of nine joints had stable graft bone markers and/or increases in graft soft tissue lengths. In conclusion, increased anterior translation occurred soon after ACL reconstruction, was associated with graft soft tissue changes, and appeared to be reduced by larger grafts. A post‐surgical decrease in posterior translation limit was also observed.

© 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.
Gender differences in the histamine and serotonin content of blood, peritoneal and thymic cells: a comparison with mast cells
Authors: Csaba György , Kovács Péter , Pállinger Éva
Published: June 2003

The serotonin and histamine content of mast cells and white blood cells in adult male and female rats was compared, using a flow cytometric immunological method. Serotonin was significantly higher in female peritoneal mast cells, peritoneal monocyte—ganulocyte—macrophage cells, blood lymphocytes and blood thymocytes. Histamine was significantly higher in female peritoneal monocyte—granulocyte—macrophage cells, and blood lymphocytes, monocytes and granulocytes, but was significantly less in thymocytes. Peritoneal lymphocytes and the monocyte—granulocyte—macrophage group contained significantly more histamine than mast cells. These experiments call attention to gender differences in the levels of biogenic amines in cells participating in defence reactions, and to the possible non‐unique role of mast cells in serotonin and histamine supply.
Bedingungen der Erhaltung und Förderung von Selbständigkeit im höheren Lebensalter (SIMA) Teil XIV: Verlaufsanalyse des psychomotorischen Status *Das interdisziplinäre Forschungsprojekt Bedingungen der Erhaltung und Förderung von Selbständigkeit im höheren Lebensalter (SIMA) des Instituts für Psychogerontologie der Friedrich-Alexander Universität Erlangen-Nürnberg wird geleitet von Prof. Dr. W. D. Oswald und Dr. R. Rupprecht, in Zusammenarbeit mit Prof. Dr. E. Lang (Carl Korth Institut), Prof. Dr. H. Baumann (Institut für Sportwissenschaft), Prof. Dr. M. Stosberg (Sozialwissenschaftliches Forschungszentrum), Dr. K. C. Steinwachs (Klinikum am Europakanal und IPG) und der Interdisziplinären Arbeitsgemeinschaft für Angewandte Gerontologie e. V. Das SIMA-Projekt wird mit Mitteln des Bundesministeriums für Familie, Senioren, Frauen und Jugend (GZ 303-1722-102/23) gefördert. Die Verantwortung für den Inhalt dieser Veröffentlichung liegt bei den Autoren.
Authors: Baumann Hartmut , Oswald Wolf D. , Hagen Bernd , Rupprecht Roland
Published: May 2003

Zusammenfassung: Zwischen 1991 und 1995 wurden die langfristigen Effekte der SIMA-Trainings auf den psychomotorischen Status der Teilnehmer (1991 N = 87) im Alter zwischen 75 und 89 Jahren (mittleres Alter 79.2 Jahre) untersucht. Der psychomotorische Status wurde aus den Leistungen in insgesamt sieben verschiedenen Funktionsbereichen aggregiert. Die Auswertung erfolgte mit der Stichprobe jeweils aller zu einem Zeitpunkt untersuchten Teilnehmer und mit der Stichprobe der 1995 verbliebenen Teilnehmer. Ein kombiniertes Gedächtnis- und Psychomotoriktrainingsprogramm zeigte vor allem kurzfristig bedeutsame Effekte auf den psychomotorischen Status, insbesondere die Umstellungs- und Rhythmisierungsfähigkeit. Langfristig zeigte sich in allen Treatmentgruppen und der Kontrollgruppe ein sinkender psychomotorischer Status. Die Ergebnisse lassen vermuten, daß die Kombination aus einer psychomotorischen Aktivierung und einem Gedächtnistraining zumindest kurzfristig verschiedene psychomotorische Funktionsbereiche der über 75jährigen Teilnehmer fördern und damit auch einen positiven Teilbeitrag zum Erhalt der Selbständigkeit und der Lebensqualität der Teilnehmer leisten konnte.
Psychisch krank und alt: Keine Daseinsberechtigung?
Authors: Kortus Rainer
Published: May 2003

Zusammenfassung: 25 bis 30 Prozent der Bevölkerung über 60 Jahren leiden an einer psychischen Erkrankung. Dies ist keine Randgruppe sondern ein erheblicher Teil der Bevölkerung. Sind diese Menschen wirklich bedroht? - Die Entwicklung der letzten Jahre zeigt zumindest große Gefahren der Unterversorgung und der Ausgrenzung auf: Gesundheitsreformgesetze mit der klaren Absicht zu Einsparungen, Zuzahlungen an auch für chronisch Kranke, Rationierung von Leistungen und Medikamenten durch feste Budgets, Leistungsverweigerung nach dem Pflegeversicherungsgesetz für psychisch Kranke und Behinderte. Die derzeitigen Folgen des gesellschaftlichen Umbruches bestehen in Triage und Selektion, ungenügender und falscher Behandlung bis hin zu sozial erwünschtem Suizid und Wiederaufleben einer fehlgeleiteten Euthanasiediskussion. Die demographische Entwicklung unserer Bevölkerung erfordert zwingend eine Berücksichtigung und Akzeptanz der Altersproblematik. Bei aktivem Herangehen ließen sich Lösungsmöglichkeiten finden: Solidaritätsnetze älterer Menschen untereinander sowie lebendige Hilfebeziehungen innerhalb der Generationen, z.B. als Patenschaften. Ohne einen gesellschaftlichen Wertewandel werden bei dem erkennbaren Sozialdarwinismus die Alten und Kranken einen schweren Stand haben.
Geropsychology and Psychology in the German- Speaking and Anglo-American Research Community
Authors: Wahl Hans-Werner , Krampen Günter
Published: May 2003

Summary: This paper is aimed to add to the understanding of the recent history of geropsychology by use of an underutilized tool, i.e., bibliometrical analysis. First, we employ an “external perspective” by focusing the development of geropsychology against the background of psychology as a whole as well as other selected psychology subfields. Second, from an “internal perspective,” we were interested in how major subfields of geropsychology have developed. In both of these issues, we compare the Anglo-American to the German-speaking research community. Third and finally, we explore the relative contribution of geropsychology work coming from German-speaking countries to the international literature. Regarding the external perspective, the major finding is that geropsychology has become a well-established subfield of psychology over the last quarter of the 20th century both in the Anglo-America and German-speaking research community. In particular, geropsychology has become a very prominent part of developmental psychology in German-speaking countries. From an “internal perspective,” research on cognitive functioning was the most frequent and consistent contributor to the geropsychology literature in both regions. Different between regions was the diverging interest in research on life experiences and coping (which was much higher in German-speaking countries). Finally, recent geropsychology research from German-speaking countries has contributed - in relative terms - more to the international literature than the psychology literature as a whole has done.
A theoretical, two‐layer, reduced‐gravity model for descending dense water flow on continental shelves/slopes
Authors: Wang Jia , Ikeda Moto , Saucier Francois J.
Published: May 2003

A theoretical, two‐layer, reduced‐gravity model for descending dense water flow on continental shelves/slopes has been developed to investigate the dynamics of bottom dense water plumes. The model is nonsteady state and includes vertical viscosity, the Coriolis force, and bottom friction. An integral solution rather than a perfect analytical expression is derived and, thus, the Simpson's 1/3 rule to approximate the integral is applied. At the very bottom, the dense water plume moves about 45° to the right (left) in the Northern (Southern) Hemisphere, looking downslope. From the bottom, the velocity vector rotates anticyclonically upward, indicating a bottom Ekman spiral that mimics the atmospheric Ekman boundary layer. The dense water within the bottom Ekman layer obeys a three‐force balance, while the dense water above the bottom Ekman layer is governed by a two‐force balance, which is a geostrophic flow with superimposed cycloidal inertial oscillations oriented from about 25° to 140° to the right (left) of the downslope direction in the Northern (Southern) Hemisphere. The transport within the bottom Ekman layer is directed about 60–70° to the right (left) of the downslope direction in the Northern (Southern) Hemisphere, forming an offshore (cross‐isobath) transport in the absence of eddy flux and wind‐forcing. The ratio of offshore transport to alongshore transport within the bottom Ekman layer is about 0.19 (19%), while the ratio above the bottom Ekman layer (i.e., geostrophic layer of the dense water) is only 3% (negligible compared to its alongshore transport), which, however, is equivalent in magnitude to its counterpart in the bottom Ekman layer if O(DE/h) ∼ 0.1 (where DE is the bottom Ekman layer thickness and h is the dense water layer thickness). In other words, the bottom Ekman layer and the geostrophic (dense) layer contribute equivalent dense water offshore (each contributes 50%). The magnitude of the descending dense water velocity depends linearly on reduced gravity and sin(θ) (slope angle).
From rifting to active spreading in the Lau Basin – Havre Trough backarc system (SW Pacific): Locking/unlocking induced by seamount chain subduction
Authors: Ruellan E. , Delteil J. , Wright I. , Matsumoto T.
Published: June 2003

Associated with Pacific‐Australia plate convergence, the Lau Basin – Havre Trough is an active back‐arc basin that has been opened since ∼5.5 Ma by rifting and southward propagating oceanic spreading. Current back‐arc opening rates decrease from 159 mm yr−1 in the northern Lau Basin to 15 mm y−1 in the southern Havre Trough. Major tectonic changes occur at the transition between Havre Trough rifting and full oceanic spreading of the Eastern Lau Spreading Center (ELSC), where the oblique‐to‐trench, westward subducting Louisville Seamount Chain (LSC) sweeps southwards along the Tonga trench. New swath bathymetry, seismic reflection data, and limited rock sampling in this area constrain a tectonic and kinematic back‐arc model that incorporates the effects of LSC subduction. The ELSC, which extends southward to 24°55′S, forms a deep rift valley propagating southward through older, rifted arc basement. Present‐day seismicity and fresh and fractured pillow lavas at 23°42′S are consistent with rift valley neovolcanism. Conversely, the northern Havre Trough has low seismicity and rifted volcanic basement ridges trending 25–45° oblique to the basin axis consistent with low levels of extensional tectonism and volcanism. This latter structural fabric is interpreted as an early stage of rifting that is now “locked” due to compression on the arc exerted by LSC subduction, while in the Lau Basin such effects have passed as the LSC swept along the Tonga Trench. It is proposed that the Lau‐Havre back‐arc opening is controlled by tectonic constraints exerted at the limits of the system by the LSC subduction, which determines the southward migration of the Tonga Arc pole of rotation and associated Lau Basin opening. A discrete three‐stage back‐arc opening evolution is proposed, comprising: (1) an initial phase of back‐arc rifting along the whole length of the plate boundary, beginning at ∼6–5 Ma; (2) a subsequent phase, mostly present in the southern part of the back‐arc domain and still active in the Havre Trough, of transpression and transtension, starting at ∼4 Ma in the north, as the LSC starts to subduct and sweeps southward along the Tonga trench; and (3) a renewed opening phase in the northern segment of the back‐arc domain, with rifting and spreading, starting at ∼3.5 Ma, as subduction of the LSC along the northern Tonga trench is progressively completed.
Assimilation of ice motion observations and comparisons with submarine ice thickness data
Authors: Zhang Jinlun , Thomas D. R. , Rothrock D. A. , Lindsay R. W. , Yu Y. , Kwok R.
Published: June 2003

Aided by submarine observations of ice thickness for model evaluation, we investigate the effects of assimilating buoy motion data and satellite SSM/I (85 Ghz) ice motion data on simulation of Arctic sea ice. The sea‐ice model is a thickness and enthalpy distribution model and is coupled to an ocean model. Ice motion data are assimilated by means of optimal interpolation. Assimilating motion data, particularly from drifting buoys, significantly improves the modeled ice motion, reducing the error to 0.04 m s−1 from 0.07 m s−1 and increasing the correlation with observations to 0.90 from 0.66. Without data assimilation, the modeled ice moves too slowly with excessive stoppage. Assimilation leads to more robust ice motion with substantially reduced stoppage, which in turn leads to strengthened ice outflow at Fram Strait and enhanced ice deformation everywhere. Enhanced deformation doubles the production of ridged ice to an Arctic Ocean average of 0.77 m yr−1, and raises the amount of ridged ice to half the total ice volume per unit area of 2.58 m. Assimilation also significantly alters the spatial distribution of ice mass and brings the modeled ice thickness into better agreement with the thickness observed in four recent submarine cruises, reducing the error to 0.66 m from 0.76 m, and increasing the correlation with observations to 0.65 from 0.45. Buoy data are most effective in reducing model errors because of their small measurement error. SSM/I data, because of their more complete spatial coverage, are helpful in regions with few buoys, particularly in coastal areas. Assimilating both SSM/I and buoy data combines their individual advantages and brings about the best overall model performance in simulating both ice motion and ice thickness.
A nonlinear model study on the long‐term behavior of shore face–connected sand ridges
Authors: Calvete D. , de Swart H. E.
Published: June 2003

A morphodynamic model is analyzed to gain further knowledge about the finite amplitude behavior of shore face–connected sand ridges observed on storm‐dominated inner shelves. The present work elaborates on previous studies in which it was demonstrated that ridge formation may be due to an instability of a storm‐driven current moving over a sandy inner shelf with a transverse slope. Here, the long‐term evolution of the ridges is studied by performing a nonlinear stability analysis in which the physical variables are expanded in eigenmodes of the linear stability problem. New physical aspects are that the longshore pressure gradient in the momentum equations and settling lag in the suspended load sediment transport are incorporated. Furthermore, along‐shelf uniform shelf modes and subharmonic eigenmodes are accounted for. The model shows that after the transient stage the competition between the modes results in saturation behavior that is dominated by a few modes only. The characteristic height of the final bed forms increases with increasing transverse slopes of the shelf, while the timescale of transient behavior decreases. The longshore uniform modes, pressure gradient, and settling lag effects only have a minor effect on the dynamics. A process analysis reveals that the mechanism responsible for the saturation behavior is the sediment transport related to the bottom slope and the effect of small‐scale bed forms. Subharmonic modes significantly affect the transient behavior of the ridges and cause the final bed forms to have larger amplitudes and longer wavelengths.
Transport and variability of the Antarctic Circumpolar Current in Drake Passage
Authors: Cunningham S. A. , Alderson S. G. , King B. A. , Brandon M. A.
Published: June 2003

The baroclinic transport of the Antarctic Circumpolar Current (ACC) above 3000 m through Drake Passage is 107.3 ± 10.4 Sv and has been steady between 1975 and 2000. For six hydrographic sections (1993–2000) along the World Ocean Circulation Experiment (WOCE) line SR1b, the baroclinic transport relative to the deepest common level is 136.7 ± 7.8 Sv. The ACC transport is carried in two jets, the Subantarctic Front 53 ± 10 Sv and the Polar Front (PF) 57.5 ± 5.7 Sv. Southward of the ACC the Southern Antarctic Circumpolar Current transports 9.3 ± 2.4 Sv. We observe the PF at two latitudes separated by 90 km. This bimodal distribution is related to changes in the circulation and properties of Antarctic Bottom Water. Three realizations of the instantaneous velocity field were obtained with lowered ADCPs. From these observations we obtain near‐bottom reference velocities for transport calculations. Net transport due to these reference velocities ranges from −28 to 43 Sv, consistent with previous estimates of variability. The transport in density layers shows systematic variations due to seasonal heating in near‐surface layers. Volume transport‐weighted mean temperatures vary by 0.40°C from spring to summer; a seasonal variation in heat flux of about 0.22 PW. Finally, we review a series of papers from the International Southern Ocean Studies Program. The average yearlong absolute transport is 134 Sv, and the standard deviation of the average is 11.2 Sv; the error of the average transport is 15 to 27 Sv. We emphasize that baroclinic variability is an important contribution to net variability in the ACC.
Southern ACC Front to the northeast of South Georgia: Pathways, characteristics, and fluxes
Authors: Meredith Michael P. , Watkins Jon L. , Murphy Eugene J. , Ward Peter , Bone Douglas G. , Thorpe Sally E. , Grant Sharon A. , Ladkin Russell S.
Published: May 2003

In December 2000 we conducted high‐resolution hydrographic and towed undulator transects across the South Georgia shelf and into the deep waters of the Georgia Basin. The Southern Antarctic Circumpolar Current Front (SACCF) was observed flowing northwestward close to the base of the slope at 53.7°S, with a second manifestation around 53.4°S having flow in the reverse direction. Both crossings had a significant barotropic component aligned with the flow. The region of the SACCF was characterized by large‐scale undulations of properties on horizontal scales of 5–10 km, similar to the local internal Rossby radius. We observe a distinct surface temperature gradient associated with the SACCF in the vicinity of South Georgia and demonstrate the usefulness of this by tracing the course of the front around the island with advanced very high resolution radiometer data. A distinct northward deflection of the front to the north of South Georgia is probably due to topographic steering by the North Georgia Rise. The signature of the SACCF is pronounced in the Circumpolar Deep Water, with strong isopycnal interleaving indicative of cross‐frontal mixing. The salinity of the Weddell Sea Deep Water is marginally higher between the two manifestations of the SACCF, reflecting the different pathways from its source regions in the Weddell Sea. Remarkably strong vertical gradients of potential temperature and salinity exist in the bottom 100 m of the water column (at depths of around 3500 m) because of the vertical juxtaposition of waters that have taken different routes around the Northeast Georgia Rise.
Identification of the property of a moving medium by the reflected electromagnetic wave
Authors: Huang Yao Xiong
Published: June 2003

The method of obtaining the information about the properties of a moving medium by the electromagnetic wave reflected from it has been derived. Based on this method, one can identify the moving medium to be a dielectric medium, a perfect conductor, or plasma, and even determine the dielectric constants of dielectric moving media, or the magnitude of np and hence the electron density of a plasma from the polarization state and the magnitude of the reflected field vectors.
Turbulent particle flux and momentum flux statistics in suspension flow
Authors: Hurther D. , Lemmin U.
Published: June 2003

The particle entrainment ability of coherent flow structures is investigated by comparing statistical properties of momentum flux u′w′ and of turbulent mass fluxes c′u′ and c′w′ in suspension, open‐channel flow under capacity charge conditions. The quadrant repartitions of these quantities as a function of the corresponding threshold levels are estimated. A cumulant discard probability density distribution is used to calculate the theoretical quadrant dynamics. Good agreement between the third‐order model and the experimental results is found for all investigated quantities in the wall and intermediate flow regions. In the free surface domain, the increase of intermittency of the momentum and mass transport processes leads to small discrepancies between the model and the experimental results. The quadrant distributions of the horizontal and vertical turbulent mass fluxes are dominated by the same two quadrants as the momentum flux u′w′. Ascendent mass flux events are found to correlate with ejections over the entire water depth. A dynamical equilibrium between the shear stress production term and the turbulent energy dissipation term is found in the intermediate flow region where the value of the normalized vertical flux of turbulent kinetic energy in suspension flow corresponds well with the one observed in clear water flows. This points toward a universality of the normalized vertical flux of turbulent kinetic in highly turbulent boundary layers. The suspended particle transport capacity of coherent structures is directly quantified from the estimation of the conditionally sampled terms of the particle diffusion equation. Coherent structures are found to play a dominant role in the mass transport mechanism under highly turbulent flow conditions in open‐channel flows.
Strong Lg wave attenuation in the Northern and Eastern Tibetan Plateau measured by a two‐station/two‐event stacking method
Authors: Fan Guang‐Wei , Lay Thorne
Published: May 2003

The regional seismic phase, Lg, which involves shear wave reverberations in the crust, is strongly attenuated along propagation paths in northern and eastern Tibet. Robust estimates of the attenuation quality factor, QLg, in these regions are obtained using a two‐station, two‐event stacking method for broadband, vertical component Lg data in the passband 0.2–1.0 Hz. We find average 1 Hz QLg values, Qo, of 79 ± 4 in northern central Tibet and 119 ± 17 in eastern Tibet for the 0.2–0.5 Hz passband. Localized regions of eastern Tibet have Qo estimates ranging from 66 to 121. These results confirm and augment the spatial coverage of recent estimates of low Qo values in north central and south central Tibet, and support the notion of widespread partial melting of the crust throughout the Plateau.
Upper mantle P wave velocity structure and transition zone thickness beneath the Arabian Shield
Authors: Benoit Margaret H. , Nyblade Andrew A. , VanDecar John C. , Gurrola Harold
Published: May 2003

We use P wave tomography and receiver function analysis to place new constraints on the nature of the thermal anomaly in the upper mantle beneath the Arabian Shield. A broad, low velocity anomaly is found in the upper mantle characterized by a strong lateral velocity gradient, with a peak to peak anomaly of at least 4–6% extending from the Red Sea eastward into the interior of the shield. The lowest velocities are found under the region adjacent to the Red Sea where elevations are more than 1 km higher than elsewhere in the Arabian Shield. We infer that large lateral temperature variations exist beneath the Arabian Shield associated with the higher elevations near the Red Sea. Receiver function stacks of P to S conversions from the 410 and 660 km discontinuities do not indicate thinning of the transition zone, suggesting that the broad, low velocity anomaly is likely confined to depths shallower than 410 km.
Acceleration and loss of relativistic electrons during geomagnetic storms
Authors: Reeves G. D. , McAdams K. L. , Friedel R. H. W. , O'Brien T. P.
Published: May 2003

We analyze the response of relativistic electrons to the 276 moderate and intense geomagnetic storms spanning the 11 years from 1989 through 2000. We find that geomagnetic storms can either increase or decrease the fluxes of relativistic electrons in the radiation belts. Surprisingly, only about half of all storms increased the fluxes of relativistic electrons, one quarter decreased the fluxes, and one quarter produced little or no change in the fluxes. We also found that the pre‐storm and post‐storm fluxes were highly uncorrelated suggesting that storms do not simply “pump up” the radiation belts. We found that these conclusions were independent of the strength of the storm (minimum Dst) and independent of L‐shell. In contrast, we found that higher solar wind velocities increase the probability of a large flux increase. However, for all solar wind velocities both increases and decreases were still observed. Our analysis suggests that the effect of geomagnetic storms on radiation belt fluxes are a delicate and complicated balance between the effects of particle acceleration and loss.
Indonesian smoke aerosols from peat fires and the contribution from volcanic sulfur emissions
Authors: Langmann Bärbel , Graf Hans F.
Published: June 2003

The island arc volcanoes in and around Indonesia have been permanently degassing for thousands of years, thereby contributing significantly to the total emissions of sulfur species in that region. The hot and wet tropical weather conditions with high solar irradiation and regular daily precipitation during the wet season lead to efficient removal of oxidised sulfate by wet deposition. This is accumulated in the Indonesian peat areas, which serve as natural sponges, soaking up rain during the wet season and slowly releasing moisture into the atmosphere during the dry season. When peat forests are drained for land clearing purposes, the peat quickly dries out and becomes extremely flammable. When ignited, the composition of the burning peat mainly determines the fire aerosol chemical composition and microphysical properties. In this paper we investigate the contribution of volcanic sulfur emissions to wet deposition of sulfur in Indonesian peat swamp areas based on numerical simulations carried out with a global atmospheric circulation model including the tropospheric sulfur cycle. Our study suggests that the observed hygroscopicity and elevated sulfur content of the Indonesian peat fire aerosols is due to accumulated volcanic sulfur.
Diamagnetic suppression of component magnetic reconnection at the magnetopause
Authors: Swisdak M. , Rogers B. N. , Drake J. F. , Shay M. A.
Published: June 2003

We present particle‐in‐cell simulations of collisionless magnetic reconnection in a system (like the magnetopause) with a large density asymmetry across the current layer. In the presence of an ambient component of the magnetic field perpendicular to the reconnection plane the gradient creates a diamagnetic drift that advects the X‐line with the electron diamagnetic velocity. When the relative drift between the ions and electrons is of the order the Alfvén speed the large scale outflows from the X‐line necessary for fast reconnection cannot develop and the reconnection is suppressed. We discuss how these effects vary with both the plasma β and the shear angle of the reconnecting field and discuss observational evidence for diamagnetic stabilization at the magnetopause.
A near‐bottom magnetic survey of the Mid‐Atlantic Ridge axis at 26°N: Implications for the tectonic evolution of the TAG segment
Authors: Tivey Maurice A. , Schouten Hans , Kleinrock Martin C.
Published: May 2003

An extensive deep‐tow magnetic survey of the TAG ridge segment on the Mid‐Atlantic Ridge reveals new information about the relationship between the magnetic anomaly field and the TAG hydrothermal deposits. Results show the strongest magnetization is located over the neovolcanic axis and asymmetrically toward the western side of the central Brunhes anomaly. A well‐defined linear magnetization low is located over the eastern rift valley wall of the TAG segment. The near‐bottom data show no direct correlation between this crustal magnetization low and the hydrothermal deposits. The magnetization low is explained by crustal thinning caused by 4 km of horizontal extension along a normal fault. Previous observations and sampling indicate exposures of gabbros and dikes in the eastern rift valley wall, suggesting slip along a normal fault has revealed this crust. Modeling suggests the fault has been active since 0.35 ± 0.1 Ma at a horizontal slip rate of roughly half the spreading rate of 22 km/Myr. The TAG hydrothermal system is located on the hanging wall of this fault within 3 km of its termination. Over the past several hundred thousand years, movement on the detachment fault may have episodically increased the permeability of the hanging wall reactivating the overlying hydrothermal systems. Significant vents like TAG may be typically associated with hanging walls of long‐term detachment faults near seafloor spreading centers. This would imply that it is the reactivation of permeability in the hanging wall related to repeated fault movement that controls the longevity of these hydrothermal systems.