bluuebunny/crossref_metadata_2025 huggingface dataset:
Radical copolymerization of 2‐trifluoromethylacrylic monomers. III. Kinetics and monomer reactivities in the copolymerization of t‐butyl 2‐trifluoromethylacrylate and methacrylate with styrene bearing hexafluoroisopropanol
Authors: Ito Hiroshi , Okazaki Masaki , Miller Dolores C.
Published: February 2004

Radical copolymerizations of t‐butyl 2‐trifluoromethylacrylate (TBTFMA) and styrene‐bearing hexafluoroisopropanol [4‐(1,1,1,3,3,3‐hexafluoro‐2‐hydroxypropyl)styrene (STHFA)] with 2,2′‐azobisisobutyronitrile were investigated in detail through the analysis of the kinetics in situ with 1H NMR and through the determination of the monomer reactivity ratios. TBTFMA incorporation was less than 50 mol % unless its concentration in the feed was greater than 90 mol %. Furthermore, the penultimate model provided a better description of the TBTFMA–STHFA copolymerization. In contrast, t‐butyl methacrylate copolymerized with STHFA according to the terminal model. The copolymerizations were simulated on the basis of the monomer reactivity ratios to calculate the feed and copolymer composition changes, sequence distributions, and so forth as a function of the initial feed ratio and conversion. The simulation results showed excellent agreement with the kinetic data. The copolymers described in this article were evaluated as chemical amplification resist polymers for the emerging field of 157‐nm lithography. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1506–1527, 2004
Synthesis and cationic photopolymerization of new silicon‐containing oxetane monomers
Authors: Sangermano M. , Bongiovanni R. , Malucelli G. , Priola A. , Olbrych J , Harden A. , Rehnberg N.
Published: February 2004

The cationic photopolymerization of oxetane‐based systems containing silicon monomers was investigated. For this purpose, three new silicon‐containing oxetane monomers were synthesized through a simple and straightforward synthetic method. The silicon‐containing monomers were added to a typical oxetane resin, 3,3′‐[oxydi(methylene)]bis(3‐ethyloxetane), in concentrations of 1–5 wt %. They exploited a certain surface tension effect without affecting the rate of polymerization. Enrichment only on the air side was achieved, which induced hydrophobicity in the photocured films, depending on the monomer structure and concentration. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1415–1420, 2004
Transport properties of uniaxially oriented aliphatic polyketone
Authors: Backman A. , Lange J. , Hedenqvist M. S.
Published: February 2004

The oxygen, carbon dioxide, and water‐transport properties of a uniaxially oriented aliphatic polyketone were determined. The polyketone was drawn to 5–10 times its original length. The transport properties were related to changes in crystallinity estimated by differential scanning calorimetry and density measurements and by changes in the molecular and crystal orientation assessed by, respectively, infrared and X‐ray spectroscopy. The film structures were characterized by confocal scanning laser microscopy and scanning electron microscopy. Stress‐strain tests on the drawn specimens enabled the impacts of orientation on the transport and mechanical properties to be compared. A draw‐induced increase in crystallinity and molecular orientation yielded permeabilities at a draw ratio of 10 that were 30–40% of the original value, and the percentage decrease was basically independent of the type of gas/vapor molecule. Also, the diffusivities of oxygen and carbon dioxide decreased by an order of magnitude. The fact that the amorphous permeability was peaking at a draw ratio of about 5 was a consequence of a peak in amorphous solubility, which was very high for oxygen and absent for water. It was suggested that the peak in solubility was mainly caused by the destruction of the polymer hydrogen‐bond network during drawing and crystal reorientation. The impact of structural reorganization within the polymer and presence of surface valleys seemed to have less impact on the mechanical properties than on the transport properties. This suggested that transport data are more sensitive than mechanical data in probing material defects and changes in molecular packing and morphology. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 947–955, 2004
Unusual relaxation process in polybutadiene: Resolving the controversy
Authors: Ding Y. , Novikov V. N. , Sokolov A. P.
Published: February 2004

We report the observation of an unusual relaxation process in depolarized light scattering spectra of polybutadiene (PBD) with two different vinyl contents. The process showed up in the gigahertz frequency range with relatively mild temperature dependence and was similar to a secondary relaxation process. The most surprising observation was that the process exists even at high temperatures and does not merge with the segmental relaxation up to a temperature of 400 K (T > 2Tg). Possible mechanisms of this particular relaxation in PBD are discussed. The process is compared to the so‐called E process, double‐bond hopping process, and dielectric β process. We emphasize that this process differs from the dielectric β process, is unique for 1,4‐PBD, and has not been observed in other polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 994–999, 2004
Polypropylene modified with elastomeric metallocene‐catalyzed polyolefin blends: Fracture behavior and development of damage mechanisms
Authors: Fasce Laura A. , Frontini Patricia M. , Wong Shing‐Chung , Mai Yiu‐Wing
Published: February 2004

The fracture behavior and deformation mechanisms of polypropylene modified by elastomeric metallocene‐catalyzed polyolefin blends were investigated under both static and dynamic loading conditions. The fracture toughness was evaluated with the J integral approach. The development of damage mechanisms was studied by the examination of fracture surfaces with scanning electron microscopy and by the examination of single‐edge, double‐notch, four‐point‐bending or low‐impact‐energy fractured samples with optical microscopy. In addition, tensile dilatometry measurements were carried out to determine the nature of the deformation micromechanisms. The fracture behavior and the size and shape of the damage zones were drastically influenced by the elastomeric particles and the imposed constraint. The role of the elastomeric particles was different, depending on the strain rate. Under impact loading, particle pullout and crazing were responsible for the increased fracture toughness of polypropylene. Under quasistatic loading, stable fracture growth was caused by particle cavitation, which promoted ductile tearing of polypropylene before failure continued in an unstable fashion via crazing. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1075–1089, 2004
Complex formation and degradation in poly(acrylonitrile‐co‐vinyl acetate) containing copper nitrate
Authors: Silverstein Michael S. , Najary Youval , Grader Gideon S. , Shter Gennady E.
Published: February 2004

The pyrolysis of polymers containing metal nitrates may provide a relatively simple, rapid, and advantageous method of producing high‐temperature superconductors (HTSCs). The advantage lies in the ability to use conventional polymer processing or microlithographic patterning before pyrolysis. A copolymer of acrylonitrile and vinyl acetate [P(AN‐VA)], a well‐known fiber‐forming polymer, was investigated as a potential HTSC precursor. Complex formation with the highly polar acrylonitrile groups was expected to enhance atomic‐level mixing and hinder nitrate recrystallization. The metal nitrates were found to have a profound effect on P(AN‐VA) pyrolysis. P(AN‐VA) containing copper nitrate (CuN) exhibited complex formation and an exothermic decomposition that began at about 170 °C (reaction 1‐CuN). Reaction 1‐CuN had a heat of about 3.5 kJ/gNO3 and a mass loss of about 0.99 g/gNO3. As reaction 1‐CuN also involved the nitrile groups, it disrupted the nitrile cyclization reaction at about 290 °C. For a P(AN‐VA)/CuN ratio of 2/1, there was no nitrile cyclization, and the thermooxidative degradation temperature was reduced by approximately 200 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1023–1032, 2004
Chondrocyte viability in press‐fit cryopreserved osteochondral allografts
Authors: Gole Madhura D. , Poulsen Dan , Marzo John M. , Ko Seung‐Hee , Ziv Israel
Published: February 2004

The viability of chondrocytes in press‐fit glycerol‐preserved osteochondral allografts was compared to that in fresh autografts, after transplantation into load‐bearing and non‐load‐bearing sites in mature sheep stifle joints. We used macroscopic grading, tonometer pen indentation testing, histology, sulfate uptake and viability as determined by confocal‐microscopy to assess cartilage condition. Despite there being no statistical differences between macroscopic appearance and tonometer testing of all grafts, confocal microscopy and histology demonstrated a positive effect of load‐bearing placement on cryopreserved osteochondral allografts. Allografts transplanted into load‐bearing sites demonstrated superior confocal microscopy‐measured chondrocyte viability (77% ± 17%SD) than those transplanted into non‐load‐bearing sites (25%±2%). Load‐bearing effect was not seen in autografts (78%±15%), and was comparable in adjacent cartilage (83%±9%). Similarly, load‐bearing allografts demonstrated histological scoring closer to that of autografts and adjacent cartilage, all of which fared significantly better than non‐load‐bearing allografts. Load‐bearing allografts had a greater amount of fibrocartilage than autografts or adjacent cartilage but less fibrocartilage than non‐load‐bearing allografts. Both autografts and allografts had non‐significant increases in metabolism compared to adjacent cartilage as measured by sulfate‐uptake. Load‐bearing placement improved chondrocyte viability of glycerol cryopreserved osteochondral allograft following a press‐fit implantation. Published by Elsevier Ltd. All on behalf of orthopaedic Research Society.
Chasing Rainbow Notions: Enacting Community Psychology in the Classroom and Beyond in Post‐1994 South Africa
Authors: Sigogo Thabani Ngonyama ka , Hooper Megan , Long Carol , Lykes M. Brinton , Wilson Kenneth , Zietkiewicz Estelle
Published: February 2004

This paper discusses tensions and contradictions experienced by a group of psychologists in post‐1994 South Africa as we struggled to develop an MA program in community psychology. Situating our work within the history of the subdiscipline and the historical context confronting South Africans in the “wake of apartheid,” we explore models of community psychology that informed praxis under apartheid and contemporary challenges confronting a country in transition. We discuss three tensions that inform the ongoing program development. These include (1) the construction and deconstruction of Western and indigenous knowledge systems; (2) assessment and intervention at multiple levels and from differing value perspectives; and (3) paradoxes experienced by a team of university‐educated, primarily White academic staff committed to challenging oppression. We conclude our discussion by suggesting that, within these shifting sands of economic, political, cultural, and institutional change community psychology must, of necessity, resist rigid self‐definition and seek to position itself as a “work‐in‐progress.” We suggest that this seemingly anomalous self‐description may be suggestive for other community psychologists‐in‐the‐making facing similar challenges within the majority world.
Konstanz im Wandel?
Authors: Leutner Detlev
Published: February 2004

Zusammenfassung. Aus der Perspektive des geschäftsführenden Herausgebers der Diagnostica in den Jahren 1995 bis 2002 wird über herausgeberische Maßnahmen zur Sicherung und zur Verbesserung der Qualität der Zeitschrift berichtet. Die Maßnahmen betreffen die Anpassung an internationale Standards wissenschaftlicher Veröffentlichungspraxis bei Beibehaltung von Deutsch als Veröffentlichungssprache, die Fokussierung auf empirische Originalarbeiten und den Erhalt der Konkurrenz im Verhältnis zur Zeitschrift für Differentielle und Diagnostische Psychologie. Bei allem Wandel zeigt sich jedoch ein hohes Ausmaß an Konstanz, so dass die Diagnostica auch heute noch weitgehend den von ihrem Gründer im Jahr 1955 formulierten Zielvorgaben entspricht.
Die Diagnostica als Publikationsorgan deutschsprachiger Arbeiten zur psychologischen Diagnostik: Rückblick und Ausblick
Authors: Eid Michael
Published: February 2004

Zusammenfassung. Die Beiträge zum 50jährigen Jubiläum der Diagnostica werden zusammenfassend reflektiert. Insbesondere werden die Vorschläge zur Weiterentwicklung der Diagnostica zusammengeführt und durch eigene Überlegungen ergänzt. Probleme, die sich aus der zunehmenden Adaptation englischsprachiger Verfahren ergeben, werden behandelt. Zur weiteren Qualitätssicherung der Diagnostica und Psychodiagnostik im allgemeinen werden Arbeiten als erfolgsversprechend angesehen, die vermehrt auf neueren methodologischen Entwicklungen aufbauen, sich der gesamten Palette psychodiagnostischer Erfassungsmethoden widmen, die verschiedenen Facetten der Standards für pädagogisches und psychologisches Testen berücksichtigen, den Mut haben, amerikanischen Verfahren mit qualitativ besseren Erfassungsmethoden die Stirn zu bieten (sofern dies notwendig ist). Darüber hinaus sollte das Faktum nicht aus den Augen verloren werden, dass psychodiagnostische Erfassungsmethoden in einen psychodiagnostischen Prozess eingebettet sind, der nicht nur auf den individuellen Entscheidungsprozess fokussiert, sondern auch von gesellschaftlichen Einflüssen abhängt, und der ebenfalls beforscht werden sollte.
Direct observation of lunar pick‐up ions near the Moon
Authors: Mall U. , Kirsch E. , Cierpka K. , Wilken B. , Söding A. , Neubauer F. , Gloeckler G. , Galvin A.
Published: February 2004

Measurements made with the Suprathermal Ion Spectrometer (STICS) on the WIND spacecraft during 17 lunar fly‐bys which took place between 1995 and 1997 allow the direct observations of lunar pick‐up ions (PUI's) on the earthwards side of the Moon as close as 17 lunar radii. The composition measurements reveal an O+, an Al+, Si+ and possibly a P+ component.
A fast and simple diagnostic method for identifying tsunamigenic earthquakes
Authors: Shapiro N. M. , Singh S. K. , Pacheco J.
Published: February 2004

An analysis of regional broadband seismograms of moderate and large subduction‐zone earthquakes in Mexico shows that earthquakes which occur near the trench are abnormally depleted in high‐frequency radiation. This observation leads to a simple and fast method to assess regional tsunami potential from earthquakes which occur along the Pacific coast of Mexico. A significant advantage of the method is that a single broadband seismograph is sufficient for the purpose. The method is based on the ratio of the total energy to the high‐ frequency energy (between 1 and 5 Hz),ER, computed from the seismograms. For earthquakes with the same seismic moment,ERis an order of magnitude greater for a source area near the trench as compared to those near the coast. The same seismograms are used to compute energy magnitude,ME, which is tied to the moment magnitude,MW. A regional tsunami may be expected along the coast ifME≥ 6.5 andERcorresponds to a source near the trench. If, however,ERcorresponds to a near‐coast source, thenMEmay have to be greater than about 7.3 for a tsunami of similar size to occur along the coast. The method holds promise for a fast regional tsunami warning in many Pacific basin countries which lack an adequate seismic network.
Source process of the 21 April, 1997 Santa Cruz Island Earthquake (Mw 7.8)
Authors: Kaverina A. , Dreger D. , Antolik M.
Published: February 2004

We apply an Empirical Green's function method to recordings of teleseismic body waves from the April 21, 1997 Santa Cruz Island earthquake. The far‐field moment rate functions reveal that rupture occured on a shallow dipping fault plane (dip 17°). The main rupture consists of 6 large subevents and covers a total area of about 5000 km². While the hypocenter is fixed at 33 km depth, the main slip is located above 20 km depth within the accretionary wedge. The source duration is about 70 sec and the average rupture velocity is found to be 1.9 km/sec. This event caused a local tsunami and although it is not possible to determine whether it was caused by tectonic faulting or submarine shaking the fact that most of the moment release occured at shallow depths is consistent with either of these possibilities, and points to the utility of the procedure outlined here in possible rapid characterization of tsunami potential.
Stratospheric BrO profiles measured at different latitudes and seasons: Atmospheric observations
Authors: Harder H. , Camy‐Peyret C. , Ferlemann F. , Fitzenberger R. , Hawat T. , Osterkamp H. , Schneider M. , Perner D. , Platt U. , Vradelis P. , Pfeilsticker K.
Published: February 2004

Stratospheric BrO profiles were measured at different latitudes and in different seasons in 1996/97 during three flights of the LPMA/DOAS balloon gondola (LPMA/Laboratoire Physique Moléculaire et Application and DOAS/Differential Optical Absorption Spectrometry). Using direct sunlight DOAS spectrometry the following BrO mixing ratios were measured; (1) 9 to 14 ppt in the height range from 20 to 30 km (at solar zenith angles, SZA < 88°) during ascent, (2) about (14±2) ppt for altitudes above the balloon float altitude at 30.6 km, 30.0 km, and 39.8 km, and (3) 5 to 10 ppt in the 20–30 km region during sunset. The lower BrO concentrations during sunset than those observed prior at daytime indicate a conversion of BrO into nighttime reservoir species (BrONO2, HOBr, and BrCl). The overall agreement of our UV spectroscopic BrO profiles with recent measurements using the chemical conversion/resonance fluorescence technique is good. Our BrO profiles are also in reasonable agreement with the present stratospheric Bry burden and chemistry. Conversily collocated ground‐based and satellite column measurements, however, show significantly more total atmospheric BrO (50–100%) than the integrated stratospheric BrO balloon profiles can account for. This indicates a global tropospheric BrO background, estimated at 1–2 ppt.
Traveling ionospheric disturbances associated with the tropospheric vortexes around Qinghai‐Tibet Plateau
Authors: Wan Weixing , Yuan Hong , Ning Baiqi , Liang Jun , Ding Feng
Published: February 2004

To show the relationship between the traveling ionospheric disturbances (TIDs) observed in Central China and the vortexes corresponding to the topography of Qinghai‐Tibet Plateau, the wave parameters (frequency, wavenumber and propagation azimuth) and the exciting sources of the TIDs are statistically analyzed under the base of observation of an HF Doppler array. It is found that the observed TIDs propagate mainly in the northeastward (NE) and southeastward (SE) directions. The backward ray tracing shows that the sources of NE and SE TIDs are respectively located in the southeastern and northeastern edges of Qinghai‐Tibet Plateau, i.e., in the lee sides of the bulging terrain of the plateau where the vortexes are more probably produced. The geographical distributions as well as their seasonal variations of the occurrence rate of both the TID sources and the vortexes are very coincident with each other, this leads us to suggest that the observed TIDs be excited by the tropospheric vortexes which in turn are related to the topography of the plateau.
FTIR studies on lifetime prolongation of stratospheric ice particles due to NAT coating
Authors: Biermann U. M. , Crowley J. N. , Huthwelker T. , Moortgat G. K. , Crutzen P. J. , Peter Th.
Published: February 2004

Fourier Transform Infra‐Red (FTIR) analysis of thin ice films was performed in order to investigate the influence of Nitric Acid Trihydrate (NAT) coating on the lifetime of stratospheric ice particles in air subsaturated with respect to ice. Two sorts of experiments were performed in which NAT was either condensed from the gas phase onto preexisting ice films or was incorporated into growing ice films, which subsequently were subject to slow evaporation under controlled vapor pressure conditions. Neither a thermodynamically efficient sealing of the ice nor a significant kinetic slowing of its evaporation was observed. A possible alternative mechanism leading to a more efficient NAT coating is proposed.
Delineation of sediments below flood basalts by joint inversion of seismic and magnetotelluric data
Authors: Manglik A. , Verma Saurabh K.
Published: February 2004

A one‐dimensional joint‐inversion (JI) scheme considering seismic reflection and refraction, and MT data is developed. Its efficacy to resolve low velocity conducting sediments below high velocity resistive flood basalts is tested for a representative geological model considering noisy, incomplete data. The JI is found to provide improved results in comparison to those obtained by individual seismic and MT inversions.
Deep water formation and poleward ocean heat transport in the warm climate extreme of the Cretaceous (80 Ma)
Authors: Brady Esther C. , DeConto Robert M. , Thompson Starley L.
Published: February 2004

An ocean simulation of the “greenhouse” climate of the Late Cretaceous, about 80 million years ago (Ma), demonstrates that warm salty deep water, consistent with proxy climate data, can be formed by cooling in the high latitude Southern Hemisphere. This is contrary to the long standing hypothesis of deep water formation due to evaporation over low latitude marginal seas. A reduced equator to pole temperature gradient is maintained with a poleward ocean heat transport that is not larger than today's.
First observation of meteoritic charged dust in the tropical mesosphere
Authors: Gelinas L. J. , Lynch K. A. , Kelley M. C. , Collins S. , Baker S. , Zhou Q. , Friedman J. S.
Published: February 2004

We discuss a recent sounding rocket experiment which found charged dust in the Earth's tropical mesosphere. The dust detector was designed to measure small (5000–10000 amu) charged dust particles, most likely of meteoric origin. A 5 km thick layer of positively charged dust was found at an altitude of 90 km, in the vicinity of an observed sporadic sodium layer and sporadic E layer. The observed dust was positively charged in the bulk of the dust layer, but was negatively charged near the bottom.
The seasonal variation of auroral ion beams
Authors: Collin H. L. , Peterson W. K. , Lennartsson O. W. , Drake J. F.
Published: February 2004

We present observations of a seasonal variation in the occurrence frequency of upflowing ions beams near 1 RE altitude in the 1800–2400 local time sector. These observations were obtained from the Toroidal Imaging Mass‐Angle Spectrograph (TIMAS) instrument during POLAR satellite perigee passes from March 1996 to September 1997. We show that the observed variation is most simply interpreted as a variation in the magnitude of the auroral acceleration process responsible for creating upflowing ion beams and precipitating energetic electrons. These observations, the first to find a seasonal effect in the occurence of ion beams, also confirm previous reports which examined related phenomena and provide further evidence that changes in ionospheric conductivity have a measurable effect in the strength of the interaction between the Earth's magnetosphere and ionosphere.
Kinetic ballooning instability for substorm onset and current disruption observed by AMPTE/CCE
Authors: Cheng C. Z. , Lui A. T. Y.
Published: February 2004

A new interpretation of AMPTE/CCE observation of substorm onset and current disruption and the corresponding physical processes are presented. Toward the end of late growth phase the plasma β increases to ≥50 and a low frequency instability with a wave period of 50–75 sec is excited and grows to a large amplitude at the current disruption onset. At the onset, higher frequency instabilities are excited so that the plasma and electromagnetic field form a turbulent state. Plasma transport takes place to modify the ambient pressure profile so that the ambient magnetic field recovers from a tail‐like geometry to a more dipole‐like geometry. A new theory of kinetic ballooning instability (KBI) is proposed to explain the low frequency instability and the high β threshold (βc≥50) observed by AMPTE/CCE. The stabilizing effect is mainly due to kinetic effects of trapped electrons and finite ion Larmor radii which give rise to a large parallel electric field and hence a parallel current that greatly enhances the stabilizing effect of field line tension. As a result βc is greatly increased over the ideal MHD ballooning instability threshold by ≥ O(10² ‐ 10³). The wave‐ion magnetic drift resonance effect produces a perturbed resonant ion velocity distribution centered at a duskward velocity roughly equal to the average ion magnetic drift velocity. This perturbed ion distribution explains the enhanced duskward ion flux during the explosive growth phase and can excite higher frequency instabilities (such as the cross‐field current instability).
Shape of the northern hemisphere of Mars from the Mars Orbiter Laser Altimeter (MOLA)
Authors: Zuber Maria T. , Smith David E. , Phillips Roger J. , Solomon Sean C. , Banerdt W. Bruce , Neumann Gregory A. , Aharonson Oded
Published: February 2004

Eighteen profiles of ∼N‐S‐trending topography from the Mars Orbiter Laser Altimeter (MOLA) are used to analyze the shape of Mars' northern hemisphere. MOLA observations show smaller northern hemisphere flattening than previously thought. The hypsometric distribution is narrowly peaked with >20% of the surface lying within 200 m of the mean elevation. Low elevation correlates with low surface roughness, but the elevation and roughness may reflect different mechanisms. Bouguer gravity indicates less variability in crustal thickness and/or lateral density structure than previously expected. The 3.1‐km offset between centers of mass and figure along the polar axis results in a pole‐to‐equator slope at all longitudes. The N‐S slope distribution also shows a subtle longitude‐dependent variation that may represent the antipodal effect of the formation of Tharsis.
Quasi‐biennial and longer‐term changes in clear sky UV‐B solar irradiance
Authors: Zerefos C. , Meleti C. , Balis D. , Tourpali K. , Bais A. F.
Published: February 2004

Using the longest available clear sky time series of spectral UV‐B data (from November 1990 to present) at Thessaloniki, Greece (40°N), estimates are provided on the variability of UV‐B on annual and longer time scales. Solar irradiance at two distinct wavelengths are used: the strongly ozone dependent 305nm and the weakly dependent on ozone 325nm. The results are based on Brewer measurements of spectral and erythemally weighted irradiances at 63° and 50° solar zenith angles. The long‐term change in UV‐B solar irradiance, which can be attributed solely to the observed ozone change of 4.5% per decade, is the order of 10% per decade at 305 nm, 63° SZA‥ These long‐term change is checked against model calculations and changes imposed by the variability in air quality at Thessaloniki and is statistically significant. The peak‐to‐peak amplitude of the QBO in total ozone is 8% and its found to be associated with a 21% peak‐to‐peak amplitude relative to the mean for the solar irradiance at 305nm. Similar results are obtained with the erythemally weighted irradiance and are in agreement with results obtained from model calculations. The observed QBO in solar UV‐B has many implications not only because of the QBO biorhythm imposed to many species but also because of its importance in atmospheric chemistry.
Surface displacement of the March 26, 1997 Kagoshima‐Ken‐Hokuseibu Earthquake in Japan from synthetic aperture radar interferometry
Authors: Fujiwara Satoshi , Yarai Hiroshi , Ozawa Shinzaburo , Tobita Mikio , Murakami Masaki , Nakagawa Hiroyuki , Nitta Koh , Rosen Paul A. , Werner Charles L.
Published: February 2004

A JERS 1 differential L‐band synthetic aperture radar (SAR) interferogram of the March 26,1997 Kagoshima‐ken‐hokuseibu earthquake (Mw=6.1) in southwestern Japan shows about 9 cm peak‐to‐peak coseismic surface displacement in the radar line‐of‐sight (LOS) direction. A permanent GPS array detected 1 to 2 cm horizontal displacements from this earthquake. By inverting the SAR and GPS data together, we estimated a fault mechanism without any seismological data. A theoretical radar LOS displacement pattern from a single fault model of the earthquake motion matches the SAR and GPS observations closely. The model assumes left lateral slip of 0.46 cm with rake angle of 19° on a rectangular fault plane of dimensions 11 km (width) by 12 km (length). We demonstrate that L‐band SAR interferometry can describe several cm surface displacement in detail and construct a fault model. However, despite the acquisitions being during the cold season, there are apparent water vapor signatures in the interferogram with equivalent path delays of up to 1.5 cm.
Annual variation of airglow heights derived from wind measurements
Authors: Plagmann M. , Marsh S. H. , Baggaley W. J. , Bennett R. G. T. , Deutsch K. A. , Fraser G. J. , Hernandez G. , Lawrence B. N. , Plank G. E. , Smith R. W.
Published: February 2004

Three independent techniques for measuring wind in the mesosphere and lower thermosphere region were compared using simultaneous measurements during the period May 1997 to April 1998. The three instruments used, a Fabry‐Perot spectrometer, a medium frequency radar, and a meteor radar, are located on New Zealand's South Island. The results obtained during this investigation show reasonable agreement amongst the three methods, in particular between the Fabry‐Perot and the meteor radar. Correlation analysis of the meteor radar height‐resolved winds and the Fabry‐Perot spectrometer winds provides a valuable method for determining airglow heights. The results from the height determinations show a yearly variation of the OH emission layer, with its lowest height during summer, while the OI emission layer is found to remain at a relatively constant height.
Eddy‐mean flow decomposition and eddy‐diffusivity estimates in the tropical Pacific Ocean: 1. Methodology
Authors: Bauer Sonia , Swenson Mark S. , Griffa Annalisa , Mariano Arthur J. , Owens Ken
Published: February 2004

The tropical Pacific Ocean surface current system can be characterized by a strong degree of nonstationarity due to the fast response time of equatorial and near‐equatorial dynamics. The ocean‐atmospheric dynamics create longitudinally coherent zonal flow (zonal length scales lx ∼ 60°) with strong meridional shear (ly ∼ 1° in latitude) in the large‐scale mean and an energetic mesoscale (O(100 km)) component. Parameterization of the effects of the mesoscale field depends on the separation of the large‐scale mean from the observed velocity. In this paper the focus is placed on the key issue: separating the flow into large‐scale mean and mesoscale eddy components in order to compute meaningful eddy diffusivity estimates in flow regimes that demonstrate strong currents and strong shear. Large gradients in the large‐scale mean have precluded diffusivity estimation by traditional binning techniques. In this first of two publications, a method is developed for using Lagrangian data to estimate the diffusivity addressing the inhomogeneity of the mean flow. The spatially dependent estimate of the mean field is computed with a least squares bicubic smoothing spline interpolation scheme with an optimized roughness parameter which guarantees minimum energy in the fluctuation field at low frequencies. Numerical simulations based on a stochastic model of a turbulent shear flow are used to validate our approach in a conceptually simple but realistic scenario. The technique is applied to near‐surface drifter observations obtained from 1979–1996 from two dynamically distinct time‐space regions of the tropical Pacific Ocean. The first region, in the South Equatorial Current, is characterized by a linear zonal shear mean flow and an approximately exponential autocovariance structure in the residuals. The velocity residuals have velocity variance of ŝ2 = 130 cm2 s−2 for both components, and horizontal diffusivities are
and
. No significant interannual variations of the estimates are detected, but residual trends in the estimators arise from intraseasonal variations in the velocity field during the 3‐month season. The second region, in the North Equatorial Countercurrent and the North Equatorial Current, has a mean flow with a strong zonal shear and a weak northward velocity. The autocovariance is approximately exponential for the zonal component, while the meridional component has a negative lobe at about 10 days, probably due to the presence of instability waves. The variance is 380 cm2 s−2 for the zonal component and 360 cm2 s−2 for the meridional component, while the horizontal diffusivities are
and
. Strong intraseasonal variability requires a maximum time window of 2 months for approximate stationarity to hold for the covariance calculations.
Mesospheric momentum fluxes over Adelaide during the 2‐day wave: Results and interpretation
Authors: Murphy D. J. , Vincent R. A.
Published: February 2004

Estimates of the vertical flux of meridional momentum due to waves of periods between 8 min and 1 hour were obtained over a height range of approximately 80 to 94 km while the 2‐day wave was active during January 1987. Between 0600 and 1100 LT on the days of the northward phase of the 2‐day wave, pulses of momentum‐flux density, somewhat larger than the values present at other times, were found. The interpretation of momentum‐flux density profiles is considered and the concepts developed are applied to the data presented. It is found that the data are generally not consistent with the expected scenario of breaking upgoing gravity waves. An alternative explanation involving downgoing waves is tendered.
A GCM assessment of atmospheric seasonal predictability associated with soil moisture anomalies over North America
Authors: Wang Wanqiu , Kumar Arun
Published: February 2004

The impact of soil moisture anomalies on the seasonal mean atmospheric predictability over North America is investigated on the basis of a 100‐year simulation by an atmospheric general circulation model (AGCM). It is shown that soil moisture anomalies have the smallest persistence during the late spring and summer months, yet the associated near‐surface atmospheric climate anomalies are the largest. The causes for this seasonality are traced to the seasonal variation of the surface evaporation and the modulating control of the atmospheric dynamic variability. It is also shown that the dominant spatial modes of interannual soil moisture variability in late spring can have different degrees of interaction with the surface climate. To what extent do initial soil moisture anomalies and their subsequent evolution impact the atmospheric variability? This question is of relevance if the soil moisture anomalies are to be observed and are used as one of the initial conditions in seasonal climate forecast. To investigate this, we carried out additional AGCM experiments for which soil moisture anomalies are initialized as the extreme states from the control simulation. It is found that the relationship between the soil moisture and the near‐surface atmospheric anomalies in these additional experiments is similar to those obtained in the control simulation. This leads us to the conclusions that (1) there is a certain potential for seasonal predictability of the atmospheric surface climate anomalies due to interannual variations in the soil moisture, and (2) the effect of the soil moisture anomalies, however, is mostly confined to the near‐surface climate variability with little impact on the dynamic variability in the atmosphere, for example, in the upper troposphere. We conclude that atmospheric potential predictability associated with soil moisture anomalies is modest and confined to summer months. Any realization of this predictability depends on correctly observing and initializing large‐scale soil moisture anomalies. These conclusions are based on a particular AGCM and its land surface parameterization scheme. More thorough investigations with more sophisticated land surface schemes are certainly warranted.
A global signature of enhanced shortwave absorption by clouds
Authors: Collins William D.
Published: February 2004

Satellite observations of visible and near‐infrared radiation reflected by the ocean and atmosphere are compared to fluxes calculated with a general circulation model. The satellite data and model simulation are global and extend from 1979 to 1987. Under clear‐sky conditions, the observed and modeled spectral albedos are nearly identical. The observations and simulations diverge with increasing cloud albedo and cloud amount, regardless of cloud type or cloud phase. The differences between the model and the satellite data occur for all tropical and midlatitude ocean regions and exhibit minimal seasonal and interannual variability. These results are consistent with enhanced absorption of shortwave radiation by clouds relative to models of radiative transfer.
Oxygen and carbon isotopic record of climatic variability in tree ring cellulose (Picea abies): An example from central Switzerland (1913–1995)
Authors: Anderson W. T. , Bernasconi S. M. , McKenzie J. A. , Saurer M.
Published: February 2004

Stable isotopic data from terrestrial records spanning the last century provide an unique opportunity to test and calibrate how these systems respond to recent climatic change. Here we present an annual oxygen and carbon isotope record covering the period from 1913 to 1995 measured in tree ring cellulose of spruce trees (Picea abies) from central Switzerland. We compare these results with historical low‐ and high‐frequency instrumental data. The isotopic data show high‐frequency and spectral correlations, although long‐term trends appear to be dissimilar. Our approach also uses constructed time series of these isotopic data with the different climate variables and demonstrates that not all parameters affect the record in the same manner. Additionally, we tested the trees' ability to record the isotopic composition of precipitation and thus changes in temperature and atmospheric circulation. Over the last 23 years, changes of up to 2‰ in the δ 18O value of precipitation have been recorded in the nearby Bern Global Network for Isotopes in Precipitation station, and our tree ring isotopic record shows similar changes as a result of moisture uptake during the growing season. Naturally, all biologic systems react differently to environmental perturbations, and correlation with other records will provide a means to validate how well these systems reflect actual climatic changes.
Multispectral near‐IR imaging of Venus nightside cloud features
Authors: Chanover Nancy J. , Glenar David A. , Hillman John J.
Published: February 2004

Near‐infrared imaging observations of the Venus nightside were made on May 17–23, 1996, at the Apache Point Observatory. The data were taken with an acousto‐optic tunable filter camera (AOTF), which is a newly developed, RF‐tunable imager with a spectral resolution of λ/Δλ = 422 at 2.3 μm. The observations were made at several discrete wavelengths in the 2.3 μm spectral window in the Venus atmosphere that correspond to molecular absorption minima and maxima of several species. These data are sensitive to properties of the lower cloud deck of Venus; we examined the zonal wind speeds near an altitude of 50 km and studied the implications of the brightness contrasts seen in the images. We confirmed the ∼ 5‐day rotational period of the cloud features previously seen at this altitude level. We also confirmed previously reported contrast ratios between the brightest and darkest regions of 20:1 and found that this contrast ratio corresponds to a variation in optical depth of at least 8. We demonstrated the new technology of the near‐IR AOTF camera by illustrating one of its many applications for planetary science.
Auroral emissions of the giant planets
Authors: Bhardwaj Anil , Gladstone G. Randall
Published: February 2004

Auroras are (generally) high‐latitude atmospheric emissions that result from the precipitation of energetic charged particles from a planet's magnetosphere. Auroral emissions from the giant planets have been observed from ground‐based observatories, Earth‐orbiting satellites (e.g., International Ultraviolet Explorer (IUE), Hubble Space Telescope (HST), and Röentgensatellit (ROSAT)), flyby spacecraft (e.g., Voyager 1 and 2), and orbiting spacecraft platforms (e.g., Galileo) at X‐ray, ultraviolet (UV), visible, infrared (IR), and radio wavelengths. UV, visible, and IR auroras are atmospheric emissions, produced or initiated when ambient atmospheric species are excited through collisions with the precipitating particles, while radio and X‐ray auroras are beam emissions, produced by the precipitating species themselves. The emissions at different wavelengths provide unique and complementary information, accessible to remote sensing, about the key physical processes operating in the atmospheric and magnetospheric regions where they originate. This paper reviews the development of our current understanding of auroral emissions from Jupiter, Saturn, Uranus, and Neptune, as revealed through multispectral observations and supplemented by plasma measurements.
Pattern of mantle thinning from subsidence and heat flow measurements in the Gulf of Suez: Evidence for the rotation of Sinai and along‐strike flow from the Red Sea
Authors: Steckler Michael S. , Feinstein Shimon , Kohn Barry P. , Lavier Luc L. , Eyal M.
Published: February 2004

We have undertaken a combined analysis of tectonic subsidence, heat flow and uplift data for the Gulf of Suez. Results show significant differences along the length of the rift. The heat flow and subsidence in the northern Gulf of Suez can be fitted by close to uniform extension in the early Miocene with minimal extension since the middle Miocene. In contrast, the southern Gulf of Suez requires that the early Miocene extension is followed by both continuous slow (∼1 mm/yr) extension and mantle thinning greatly in excess of the crustal thinning. The continued extension of the southern Gulf of Suez is interpreted as indicating a counterclockwise rotation of the Sinai Peninsula that allows the southern Gulf of Suez to accommodate 10–15% of the motion of the Dead Sea transform. Our best estimate of the net crustal and mantle extension factors for southern Suez are δ=1.4–1.5 and β=2.2–2.6, respectively. While these values are approximate, they indicate a significant input of heat into the southern Gulf of Suez rift that is in excess of that directly advected by extension. Modeling indicates that while ∼1/2 of the extension occurred in the early Miocene, most of the lithospheric thinning, and virtually all of the excess thinning of the mantle lithosphere, developed since then. In addition, the Gulf of Suez is bordered by large and growing rift flank uplifts, particularly on the Sinai Peninsula. The geometry of the motions at the Sinai triple junction region has created a large contrast in extension between the Red Sea and Gulf of Suez‐Sinai since the middle Miocene. These lateral temperature gradients drove the flow of hot material that is responsible for the extra heating beneath southern Suez and Sinai. The rift flank uplift along most of the Gulf of Suez is interpreted as resulting from a combination of secondary convection and flexure. The much greater uplift in southern Sinai is produced by the additional convective flow from the Red Sea.
Mechanical modeling of compressional basins: Origin and interaction of faults, erosion, and subsidence in the Ventura basin, California
Authors: Niño Fernando , Chéry Jean , Gratier Jean‐Pierre
Published: February 2004

Using geophysical observations and some basic geological ideas on the present structure of the Ventura basin, we model its possible mechanical evolution during the last 4 million years. We use a two‐dimensional finite element model with frictional and elastoviscoplastic rheologies that allow strain localization. This allows us to study the mechanical origin of the San Cayetano thrust fault (SCF) and its interaction with the Oak Ridge fault (ORF). The results of our modeling indicate that the geometry and activity of a shear zone which mimics the San Cayetano fault are conditioned both by the preexistence of the Oak Ridge fault and by the shape of the brittle‐ductile transition. Furthermore, the presence of a décollement level is shown to favor the development of the San Cayetano fault shear zone as a low‐angle structure. The value of the effective friction on the Oak Ridge fault is evaluated from this model. Possible values of the viscosity of the sediments are also estimated; it is shown that low sediment viscosity may completely hinder the activity of such a fault at the surface, while slip at depth continues. The stratigraphic profile of the basin is also shown to depend on the relative strengths of the ORF and SCF, which also provide an explanation for the shortening and rapid subsidence of the basin.
Integration of soil moisture remote sensing and hydrologic modeling using data assimilation
Authors: Houser Paul R. , Shuttleworth W. James , Famiglietti James S. , Gupta Hoshin V. , Syed Kamran H. , Goodrich David C.
Published: February 2004

The feasibility of synthesizing distributed fields of soil moisture by the novel application of four‐dimensional data assimilation (4DDA) applied in a hydrological model is explored. Six 160‐km2 push broom microwave radiometer (PBMR) images gathered over the Walnut Gulch experimental watershed in southeast Arizona were assimilated into the Topmodel‐based Land‐Atmosphere Transfer Scheme (TOPLATS) using several alternative assimilation procedures. Modification of traditional assimilation methods was required to use these high‐density PBMR observations. The images were found to contain horizontal correlations that imply length scales of several tens of kilometers, thus allowing information to be advected beyond the area of the image. Information on surface soil moisture also was assimilated into the subsurface using knowledge of the surface‐ subsurface correlation. Newtonian nudging assimilation procedures are preferable to other techniques because they nearly preserve the observed patterns within the sampled region but also yield plausible patterns in unmeasured regions and allow information to be advected in time.
Trace gas exchange in a high‐Arctic valley: 2. Landscape CH4 fluxes measured and modeled using eddy correlation data
Authors: Friborg T. , Christensen T. R. , Hansen B. U. , Nordstroem C. , Soegaard H.
Published: February 2004

Eddy correlation measurements of methane exchange were conducted during a period of 43 days covering the summer season in high‐arctic, NE Greenland. Measurements were carried out over a fen area and showed fluxes ranging from no exchange in the early part of the campaign to 120 mg m−2 d−1 during midsummer. The emission showed a clear variation related to soil temperatures and water table level in the late part of the summer, whereas the thickness of the active soil layer was a main controlling parameter in the thaw period, in the early part of the season. A model to assess methane emission dependency on physical parameters is found to give a realistic estimate for the seasonal variations in flux. The proportion of C returned to the atmosphere as CH4 relative to the total C cycling was around 2%, which is similar to ratios often reported in literature. On the basis of these findings, an estimate is given for the total summer season emission of CH4, in which a simple model including both physical parameters and net primary production (NPP) is adapted to reproduce CH4 exchange rates for periods when no measurements were undertaken. In this way the total emission of CH4 during the period June 1 to September 1 1997, is found to equal 3.7 ± 0.57 g m−2, which is a relatively high rate given the harsh climate in which the measurements were made.