bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamics of thin polymer films: Recent insights from incoherent neutron scattering
Authors: Soles Christopher L. , Douglas Jack F. , Wu Wen‐Li
Published: July 2004

Incoherent neutron scattering is presented as a powerful tool for interpreting changes in molecular dynamics as a function of film thickness for a range of polymers. Motions on approximately nanosecond and faster timescales are quantified in terms of a mean‐square atomic displacement (〈u2〉) from the Debye–Waller factor. Thin‐film confinement generally leads to a reduction of 〈u2〉 in comparison with the bulk material, and this effect becomes especially pronounced when the film thickness approaches the unperturbed dimensions of the macromolecule. Generally, there is a suppression (never an enhancement) of 〈u2〉 at temperatures T above the bulk calorimetric glass‐transition temperature (Tg). Below Tg, the reduction in the magnitude of 〈u2〉 depends on the polymer and the length scales being probed. Polymers with extensive segmental or local mobility in the glass are particularly susceptible to reductions of 〈u2〉 with confinement, especially at the Q vectors probing these longer length scales, whereas materials lacking these sub‐Tg motions are relatively insensitive. Moreover, a reduced 〈u2〉 value correlates with reduced mobility at long time and spatial scales, as measured by diffusion in these thin polymer films. Finally, this reduced thin‐film mobility is not reliably predicted by thermodynamic assessments of an apparent Tg, as measured by discontinuities or kinks in the T dependence of the thermal expansion, specific volume, index of refraction, specific heat, and so forth. These measurements illustrate that 〈u2〉 is a powerful and predictive tool for understanding dynamic changes in thin polymer films. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3218–3234, 2004
Real‐time neutron reflectivity study of the early stages of diffusion into and dissolution of glassy polymers
Authors: Bucknall D. G. , Higgins J. S. , Butler S. A.
Published: July 2004

The early stages of the penetrant behavior of a series of phthalate plasticizers into thin films of glassy, high‐molecular‐weight deuterated poly(methyl methacrylate) (dPMMA) have been studied with in situ real‐time neutron reflectivity. After an initial induction phase, both dioctyl phthalate and diisononyl phthalate penetrate the dPMMA films, as indicated by an increase in the thickness. In both cases, a fast linear rate of swelling of the polymer is followed by another behavior that is much slower. The slowdown in the velocity of the plasticizers at or near the transition point is assumed to occur because of a balancing of the misfit‐induced pressure and the osmotic pressure, which is responsible for the initial plasticizer ingress. In contrast, and unexpectedly, lower molecular weight dibutyl phthalate does not swell dPMMA, but after an initial induction period, the polymer film begins to dissolve. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3267–3281, 2004
Small‐angle neutron scattering studies of dynamics and hierarchical pattern formation in binary mixtures of polymers and small molecules
Authors: Hashimoto Takeji
Published: July 2004

We present the dynamics of the composition fluctuations and pattern formation of two‐component systems in both single‐phase and two‐phase states as studied by time‐resolved small‐angle neutron scattering and light scattering. Two‐component systems to be covered here include not only dynamically symmetric systems, in which each component has nearly identical self‐diffusion coefficients, but also dynamically asymmetric systems, in which each component has different self‐diffusion coefficients. We compare the dynamic behaviors of the two systems and illuminate their important differences. The scattering studies presented for dynamically asymmetric systems highlight that stress–diffusion coupling and viscoelastic effects strongly affect the dynamics and pattern formation. For dynamically symmetric systems, we examine the universality existing in both polymer systems and small‐molecule systems as well as new features concerning the time evolution of hierarchical structures during phase separation via spinodal decomposition over a wide range of wave numbers (up to four orders of magnitude). For both systems, we emphasize that polymers provide good model systems for studying the dynamics and pattern formation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3027–3062, 2004
Polaron signatures in the line shape of semiconductor ;intersubband transitions: quantum kinetics of the electron–phonon interaction
Authors: Butscher S. , Förstner J. , Waldmüller I. , Knorr A.
Published: July 2004

We present a theory of the optical line shape of coherent intersubband transitions in a semiconductor quantum well, considering non‐Markovian LO‐phonon scattering as major broadening mechanism. We show that a quantum kinetic approach leads to additional polaron resonances and a resonance enhancement for gap energies close to the phonon energy. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Design evolution of the trinity college IGVC robot ALVIN
Authors: Bovard Michelle , Gillette Matthew , de Lanerolle Trishan , Marinkovic Bozidar , Trinh Nhon H. , Votto Peter , Ahlgren David J. , Nepal Kundan , Tamrakar Amir
Published: July 2004

In this paper we discuss the design and evolution of Trinity College's ALVIN robot, an autonomous ground vehicle that has participated in the Association for Unmanned Vehicle Systems International Intelligent Ground Vehicle Competition (IGVC) since 2000. The paper first discusses the Trinity Robot Study Team, which has been responsible for developing ALVIN. We then illustrate the four generations of ALVIN, focusing on improvements made as the result of performance shortcomings and outright failures. The discussion considers the robot's body design, drive system, sensors, navigation algorithms, and vision systems. We focus especially on the vision and navigation systems developed for Trinity's fourth‐generation IGVC robot, ALVIN IV. The paper concludes with a plan for future work on ALVIN and with a discussion of educational outcomes resulting from the ALVIN project. © 2004 Wiley Periodicals, Inc.
Vision based robotic control
Authors: Atkinson Brian , Duffy Michael C. , Klingensmith Thomas , Grabbe Robert
Published: July 2004

The University of Colorado at Denver robotics society is constructing an autonomous ground vehicle (AGV) capable of accomplishing the Association of Unmanned Vehicle Systems International (AUVSI) competition objectives. The design presented features an engineering focus on a statistical, vision based discrete‐time control system optimized for an exterior robotic vehicle. A simple robust strategy incorporates ultrasonic ranging to make this vehicle capable of negotiating the features presented in the autonomous challenge. © 2004 Wiley Periodicals, Inc.
Transport of dead infant mountain gorillas by mothers and unrelated females
Authors: Warren Ymke , Williamson Elizabeth A.
Published: July 2004

This report describes prolonged carriage of the corpses of two mountain gorilla infants by both related and unrelated adult females. Two hypotheses regarding this transport are considered: 1) that maternal behavior toward unrelated infants may be a by‐product of the hormonal condition of pregnancy, and 2) that the animals may be “learning to mother,” as nulliparous females could benefit from the experience of handling an infant that is no longer alive. Some factors pertinent to the event of infant deaths in captivity are considered. Zoo Biol 23:375–378, 2004. © 2004 Wiley‐Liss, Inc.
Survey of the reproductive cyclicity status of Asian and African elephants in North America
Authors: Brown Janine L. , Olson Deborah , Keele Mike , Freeman Elizabeth W.
Published: July 2004

The Asian and African elephant populations in North America are not self‐sustaining, and reproductive rates remain low. One problem identified from routine progestagen analyses is that some elephant females do not exhibit normal ovarian cycles. To better understand the extent of this problem, the Elephant TAG/SSP conducted a survey to determine the reproductive status of the captive population based on hormone and ultrasound evaluations. The survey response rates for facilities with Asian and African elephants were 81% and 71%, respectively, for the studbook populations, and nearly 100% for the SSP facilities. Of the elephants surveyed, 49% of Asian and 62% of African elephant females were being monitored for ovarian cyclicity via serum or urinary progestagen analyses on a weekly basis. Of these, 14% of Asian and 29% of African elephants either were not cycling at all or exhibited irregular cycles. For both species, ovarian inactivity was more prevalent in the older age categories (>30 years); however, acyclicity was found in all age groups of African elephants. Fewer elephant females (∼30%) had been examined by transrectal ultrasound to assess reproductive‐tract integrity, and corresponding hormonal data were available for about three‐quarters of these females. Within this subset, most (∼75%) cycling females had normal reproductive‐tract morphologies, whereas at least 70% of noncycling females exhibited some type of ovarian or uterine pathology. In summary, the survey results suggest that ovarian inactivity is a significant reproductive problem for elephants held in zoos, especially African elephants. To increase the fecundity of captive elephants, females should be bred at a young age, before reproductive pathologies occur. However, a significant number of older Asian elephants are still not being reproductively monitored. More significantly, many prime reproductive‐age (10–30 years) African females are not being monitored. This lack of information makes it difficult to determine what factors affect the reproductive health of elephants, and to develop mitigating treatments to reinitiate reproductive cyclicity. Zoo Biol 23:309–321, 2004. © 2004 Wiley‐Liss, Inc.
The effects of transport stress on tiger physiology and behavior
Authors: Dembiec Daniel P. , Snider Richard J. , Zanella Adroaldo J.
Published: July 2004

Tigers are often transported for education, conservation, and zoo enhancement purposes, however the effect of transfer on them has not yet been documented. Our objective was to evaluate how transport affects the behavior and physiology of tigers, taking into account previous experience with the transport procedure. We simulated transport by relocating five tigers in a small individual transfer cage. Two tigers had prior experience with the procedure, and three tigers were naïve to it. After 30 min, each tiger was released back into their original enclosure. Physiological measurements were recorded for four of the five tigers; these included respiration rate and immune‐reactive fecal cortisol response using radioimmunoassay. We also recorded the behavior of all five tigers before, during, and after transport. Our behavioral analysis included activity level, pacing behavior, time spent investigating, respiration rate, and ear position. Average respiration rates of all tigers increased from 56.1 breaths/min to 94.6 breaths/min during transport and to 132.3 breaths/min 10 min following release into their enclosures. Average immune‐reactive cortisol concentrations peaked 3–6 days after transport at 239% above baseline and returned to baseline levels 9–12 days afterward. During their peak time block, naïve tigers exhibited a higher average increase in cortisol levels (482% above baseline) than the experienced tigers (158% above baseline). The naïve tigers' average immune‐reactive cortisol concentration remained elevated for a longer period (9–12 days) than the experienced tigers' (3–6 days). In both groups, behavioral responses ranged from active to inactive, however naïve tigers performed these repertoires with greater intensity by pacing faster and performing fewer state changes. Results suggest that prior exposure to elements of the transport procedure may lead to some level of habituation, thus reducing the effects of transportation stress. Zoo Biol 23:335–346, 2004. © 2004 Wiley‐Liss, Inc.
Interactions between red‐billed oxpeckers and black rhinos in captivity
Authors: McElligott Alan G. , Maggini Ivan , Hunziker Lorenz , König Barbara
Published: July 2004

The relationship between oxpeckers and African ungulates has traditionally been considered mutualistic, because the birds were thought to reduce the tick loads of their hosts. However, recent field studies have questioned the validity of this assumption. Red‐billed oxpeckers were found to have no impact on the number of ticks living on domestic cattle and they also prolonged the healing time of wounds (Weeks [1999] Anim Behav 58:1253–9; Weeks [2000] Behav Ecol 11:154–60). One of the important limitations of these studies is the fact that the two species did not coevolve, and therefore the results may not be representative of the relationships between oxpeckers and their native African ungulate hosts in general. We carried out observations between red‐billed oxpeckers and one of their natural host species, the black rhino, in captivity, to investigate their relationship. We found that the rhinos had oxpeckers present on them for almost half (approximately 45%) the time that the two species were in the same enclosure. The oxpeckers spent a large proportion (approximately 40%) of their time on the rhinos foraging, and mostly at wounds. We observed oxpeckers opening wounds on their hosts for the first time; they created four new wounds on the female rhino and nine on the male. Although the rhinos were intolerant of the presence of the oxpeckers at wounds, only approximately 43% of their attempts at removal were successful. Therefore if oxpeckers are housed with any of their native hosts in captivity, observations should be carried out to determine the activities of the oxpeckers on those hosts. Zoo Biol 23:347–354, 2004. © 2004 Wiley‐Liss, Inc.
Photo‐acceleration of protein release from endosome in the protein transduction system
Authors: Matsushita Masayuki , Noguchi Hirofumi , Lu Yun-Fei , Tomizawa Kazuhito , Michiue Hiroyuki , Li Sheng-Tian , Hirose Kenzo , Bonner-Weir Susan , Matsui Hideki
Published: July 2004

The protein transduction system has been employed for delivery of bioactive proteins into cells via an endocytotic mechanism. However, trapping of endocytosed proteins in the endosome may significantly attenuate biological actions in cells. The present investigation demonstrated that endosomal release of transduced protein could be artificially accelerated by exposure to fluorescent light. Exposure to light at 480 nm stimulated endosomal release of transduced FITC‐11 arginine‐protein transduction domain (11R‐PTD), TAT‐PTD and Antennapedia‐PTD. Moreover, FITC‐11R‐p53 protein was released from endosomes following stimulation with light. These data suggest that photo‐acceleration is a more efficient strategy in terms of the protein transduction system.
Repression of the c‐fms gene in fibroblast cells by c‐Myc‐MM‐1‐TIF1β complex
Authors: Satou Akiko , Hagio Yuko , Taira Takahiro , Iguchi-Ariga Sanae M.M , Ariga Hiroyoshi
Published: July 2004

MM‐1 has been reported to repress the E‐box‐dependent transcription activity of c‐Myc by recruiting histone deacetylase 1 complex via TIF1β/KAP1. In this study, to identify target genes for c‐Myc‐MM‐1‐TIF1β, we established rat‐1 cells harboring the dominant‐negative form of TIF1β to abrogate the pathway from TIF1β to MM‐1‐c‐Myc. This cell line, in which transcription activity of c‐Myc was activated, was found to be tumorigenic. By DNA‐microarray analysis of this cell line, expression and promoter activity of the c‐fms oncogene were found to be upregulated. Of the two promoters, pE1 and pE2, in the c‐fms gene, pE1 promoter activity was found to be activated in an E‐box‐dependent manner.
A family of glycosyl hydrolase family 45 cellulases from the pine wood nematode Bursaphelenchus xylophilus
Authors: Kikuchi Taisei , Jones John T , Aikawa Takuya , Kosaka Hajime , Ogura Nobuo
Published: July 2004

We have characterized a family of GHF45 cellulases from the pine wood nematode Bursaphelenchus xylophilus. The absence of such genes from other nematodes and their similarity to fungal genes suggests that they may have been acquired by horizontal gene transfer (HGT) from fungi. The cell wall degrading enzymes of other plant parasitic nematodes may have been acquired by HGT from bacteria. B. xylophilus is not directly related to other plant parasites and our data therefore suggest that horizontal transfer of cell wall degrading enzymes has played a key role in evolution of plant parasitism by nematodes on more than one occasion.
Human apoA‐I/C‐III/A‐IV gene cluster transgenic rabbits: effects of a high‐cholesterol diet
Authors: Recalde Delia , Baroukh Nadine , Viglietta Celine , Prince Sonia , Verona Julián , Vergnes Laurent , Pidoux Josette , Nazeem Nanjee M , Brites Fernando , Ochoa Alberto , Castro Graciela , Zakin Mario M , Miller Norman E , Marie Houdebine Louis
Published: July 2004

We have generated transgenic rabbits that express the entire human apoA‐I/C‐III/A‐IV gene cluster. As in humans, h‐apoA‐I and h‐apoC‐III were expressed in liver and intestine, whereas h‐apoA‐IV mRNA was detected in intestine only. Transgenic rabbits had significantly higher plasma total cholesterol, HDL‐cholesterol and total phospholipid concentrations than non‐transgenic littermates. In contrast to similar transgenic mice previously generated, which have gross hypertriglyceridemia, triglyceride concentrations were only moderately raised in transgenic rabbits. Plasma and HDL from transgenic rabbits were more effective than those from controls in promoting cholesterol efflux from cultured hepatoma cells. They had lower LCAT, lower CETP and higher PLTP activities than non‐transgenic littermates. Cholesterol‐feeding produced major increases in plasma lipids. The qualitative response to the diet was not modified by cluster expression. Human apoA‐I concentration was halved by cholesterol‐feeding, whereas h‐apoC‐III and h‐apoA‐IV concentrations were not significantly altered. Cholesterol efflux from hepatoma cells to plasma and HDL was not altered by the diet. Since lipoprotein metabolism of rabbits closely resembles that of humans, human apoA‐I/C‐III/A‐IV transgenic rabbits may provide a reliable model for studies of the transcriptional regulation of the cluster, and for evaluating the effects of different agents on the expression of the three genes.
Dynamic properties of nuclear pore complex proteins in gp210 deficient cells
Authors: Eriksson Charlotta , Rustum Cecilia , Hallberg Einar
Published: July 2004

Gp210, an integral membrane protein of the nuclear pore complex (NPC), is believed to be involved in NPC biogenesis. To test this hypothesis, we have investigated dynamic properties of the NPC and distribution of NPC proteins in NIH/3T3 cells lacking gp210. POM121 (the other integral NPC protein) and NUP107 (of the NUP107/160 complex) were correctly distributed at the nuclear pores in the absence of gp210. Furthermore, fluorescence recovery after photobleaching experiments showed that POM121 and NUP107 remained stably associated at the NPCs. We conclude that gp210 cannot be required for incorporation of POM121 or NUP107 or be required for maintaining NPC stability.
Phosphorylated α‐synuclein in normal mouse brain
Authors: Hirai Yu , Fujita Shinobu C , Iwatsubo Takeshi , Hasegawa Masato
Published: July 2004

α‐Synuclein phosphorylated at Ser129 is the main component of Lewy bodies of Parkinson's and closely related diseases. We studied, by quantitative immunoblotting, changes in the phosphorylation level of α‐synuclein in the mouse brains subjected to cold water stress. Relative basal level of α‐synuclein phosphorylation at Ser129 was 40% higher in the striatum compared with the hippocampus. The phosphorylation level decreased to 57% in the striatum 20 min after 5 min of cold water stress, and also in the hippocampus and cortex to lesser degrees. Recovery to basal levels took place over several hours. The stress‐induced temporary dephosphorylation was of smaller magnitude in the striatum of aged (18 months) mice. These results show that α‐synuclein phosphorylation level at Ser129 in vivo responds to physiological stimuli. Relative prominence and age sensitivity of this phenomenon in the striatum may be relevant to the pathogenesis of Parkinson's disease.
In utero nicotine exposure causes persistent, gender‐dependant changes in locomotor activity and sensitivity to nicotine in C57Bl/6 mice
Authors: Pauly James R. , Sparks Jae A. , Hauser Kurt F. , Pauly Thomas H.
Published: July 2004

Maternal cigarette smoking during pregnancy can result in a wide variety of adverse fetal outcomes, ranging from preterm delivery and low birth weight, to sudden infant death syndrome. In addition, in utero tobacco smoke exposure is associated with delayed or impaired neuropsychological development. Although the causative agent in tobacco smoke that leads to these aberrations is not known, some studies have concluded that nicotine may play an important role. Many studies using animal models of prenatal nicotine exposure have supported the hypothesis that nicotine may directly and/or indirectly cause impairments in fetal and neonatal development. However, in many of the animal studies nicotine has been administered acutely to naive dams, which could lead to significant fetal hypoxia; some routes of drug administration are also very stressful to pregnant dams, and changes in stress hormones could also create an unfavorable fetal environment. In this study, pregnant mice were exposed to chronic nicotine via the drinking solution; locomotor activity and sensitivity to nicotine were evaluated in the offspring. We have previously shown that oral nicotine administration produces behavioral and physiological changes that resemble those seen following other routes of nicotine administration. Although oral nicotine exposure did not significantly alter any aspect of the pregnancy, dams drinking a nicotine‐containing solution consumed approximately 20% less volume, compared to saccharin controls. All animals were cross fostered to nicotine naı̈ve lactating dams, immediately after birth. On PN40 and PN60, male mice exposed to in utero nicotine demonstrated significant locomotor hyperactivity in an open filed arena. Although female animals did not show any signs of hyperactivity, they did have a significant attenuation of their hypothermic response to acute nicotine challenge. These results suggest that oral nicotine delivery to pregnant mice causes persistent, gender‐dependant changes in behavior and sensitivity to nicotine. This model may be very useful for future studies that try to more accurately define the windows of sensitivity for nicotine exposure and the possible underlying neurochemical mechanisms involved.
Enhanced concentration of COMP (cartilage oligomeric matrix protein) in osteochondral fractures from racing Thoroughbreds
Authors: Skiöldebrand E. , Heinegård D. , Eloranta M.‐L. , Nilsson G. , Dudhia J. , Sandgren B. , Ekman S.
Published: July 2004

The aim of the present study was to correlate the levels of COMP and aggrecan as indicators of tissue damage, in synovial fluid (sf) from carpal joints of acutely lame racehorses, with macroscopical lesions of articular cartilage (OA), osteochondral fractures and ligament tears found at arthroscopy.

Sixty‐three lame horses [49 Standardbred trotters (STB) and 14 Thoroughbreds (TB)] in conventional training and racing that underwent arthroscopy of their middle carpal or radiocarpal joints were included in the study. Intact as well as fragmented COMP and aggrecan released into the synovial fluid were quantified by western blot analyses and ELISA. The expression of COMP in tissues was estimated by mRNA in situ hybridisation and protein immunolocalisation in cartilage and osteochondral fractures.

The concentration of sf‐COMP was higher in TB with an osteochondral fracture than in STB with osteochondral fractures and TB and STB with OA. The chondrocytes in middle and deep zones of the articular cartilage of the osteochondral fragments (from a TB) expressed COMP mRNA, in contrast to the cartilage on the opposite side of the fracture where no expression was detected. In the synovial fluid from a joint (TB) with osteochondral fractures only intact COMP was present, whereas, fragmented COMP was more prominent in synovial fluid from a joint with OA. The concentration of sf‐aggrecan did not differ between the two breeds, or between different lesions. The increased concentration of sf‐COMP in TB with osteochondral fractures, but not in synovial fluid from equine joints with OA, is a novel finding. The results from this study indicate that elevated sf‐COMP concentration in the joints of Thoroughbreds may be a useful marker for carpal joint osteochondral fragments. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
Carbon dioxide uptake of a forested region in southwest France derived from airborne CO2 and CO measurements in a quasi‐Lagrangian experiment
Authors: Schmitgen Sandra , Geiß Heiner , Ciais Philippe , Neininger Bruno , Brunet Yves , Reichstein Markus , Kley Dieter , Volz‐Thomas Andreas
Published: July 2004

This paper presents a Lagrangian budgeting approach to quantify the uptake of CO2 by vegetation at horizontal scales of several tens of kilometers. For this purpose, CO2 and meteorological parameters were measured from a small aircraft during four flights in June 2001 over a flat homogeneous and productive temperate forest in the Landes region (southwestern France). Additional CO measurements were made in order to identify and quantify the potential influence of anthropogenic emissions on the net CO2 flux derived from the measurements. For one of four flights, Lagrangian conditions were nearly perfectly fulfilled. On average, the CO2 mixing ratio in the boundary layer decreased at a rate of 0.11 ppm km−1, yielding an average CO2 uptake by the forest of 16 ± 2.5 μmol m−2 s−1 between 1230 and 1430 UT. Our result is about 15% smaller than the local net ecosystem exchange measured by eddy covariance at a tower north of the flight domain and about 12% higher than a regional estimate based on remote sensing data for the whole experimental area. The contribution of anthropogenic emissions to the regional CO2 budget was estimated from the CO measurements to be to <0.5 μmol m−2 s−1.
An assessment of three alternatives to linear trends for characterizing global atmospheric temperature changes
Authors: Seidel Dian J. , Lanzante John R.
Published: July 2004

Historical changes in global atmospheric temperature are typically estimated using simple linear trends. This paper considers three alternative simple statistical models, each involving breakpoints (abrupt changes): a flat steps model, in which all changes occur abruptly; a piecewise linear model; and a sloped steps model, incorporating both abrupt changes and slopes during the periods between breakpoints. First‐ and second‐order autoregressive models are used in combination with each of the above. Goodness of fit of the models is evaluated using the Schwarz Bayesian Information Criterion. These models are applied to the instrumental record of global monthly temperature anomalies at the surface and to the radiosonde and satellite records for the troposphere and stratosphere. The alternative models often provide a better fit to the observations than the simple linear model. Typically the two top‐performing models have very close values of the Schwarz Bayesian Information Criterion. Usually the two models have the same basic form and the same net temperature change but with a different choice of autoregressive model. However, in some cases the best fits are from two different basic models, yielding different net temperature changes and suggesting different interpretations of the nature of those changes. For the surface data during 1900–2002 the sloped steps and piecewise linear models offer the best fits. Results for tropospheric data suggest that it is reasonable to consider most of the warming during 1958–2001 to have occurred at the time of the abrupt climate regime shift in 1977. Two fundamentally different, but equally valid, descriptions of stratospheric cooling were found: gradual linear change versus more abrupt ratcheting down of temperature concentrated in postvolcanic periods (∼2 years after eruption). Because models incorporating abrupt changes can be as explanatory as simple linear trends, we suggest consideration of these alternatives in climate change detection and attribution studies.
Site specificity of bed load measurement using an acoustic Doppler current profiler
Authors: Rennie Colin D. , Villard Paul V.
Published: July 2004

Concurrent measurements of bed load transport velocity (v) from the bottom tracking feature of an acoustic Doppler current profiler (aDcp) and bed load transport rate (gb) from conventional pressure difference samplers are presented. Data sets were collected from both gravel bed and sand bed reaches of the Fraser River, covering a bed material range of 0.25–25 mm. Strong relations, in which v explained >70% of the variability of measured gb, were observed in a gravel bed and a sand bed reach. Differences in correlation between v and gb among the contrasting environments are attributed to variations in both the bed load particle size and aDcp operating parameters. Similar values of v were associated with lower mass transport rates in a sand bed than in a gravel bed reach. A nondimensional data collapse, accounting for differences in bed load particle size, explained 42% of the observed variance of the combined data set. Longer averaging times were required in the gravel bed reach, likely due to the stochastic nature of bed load entrainment in gravels and the resulting heterogeneous bed load velocity field. Bed load transport was modeled using both shear stress models and a kinematic model that utilizes the estimated bed load velocity. The standard shear stress models provided poor matches to the measured bed load transport rates: the sand bed data were overpredicted, and the gravel bed predictions correlated poorly with the measured predictions. Use of the kinematic model yields an estimate for the product of bed load concentration and bed load layer depth. This work highlights the potential of acoustic techniques for estimating bed load.
Formal and informal water markets: Drivers of sustainable rural communities?
Authors: Bjornlund Henning
Published: July 2004

This paper analyzes irrigator behavior in formal and informal water markets within an irrigation region of southeastern Australia to identify the extent to which these markets have facilitated the development of sustainable rural communities. The analyses show clear evidence that both the formal and informal markets have assisted irrigators in managing the significant adjustment pressure within the irrigation industry and the increased risk management burden placed on them by changing allocation policies. There is also evidence that many irrigators are active as both buyers and sellers and within both the formal and informal market, shifting their risk position within and between seasons and adjusting the allocation of their capital assets. All of these functions are essential to develop sustainable rural communities and retain community cohesion.
Shock‐induced melting of MgSiO3 perovskite and implications for melts in Earth's lowermost mantle
Authors: Akins Joseph A. , Luo Sheng‐Nian , Asimow Paul D. , Ahrens Thomas J.
Published: July 2004

New shock wave equation of state (EOS) data for enstatite and MgSiO3 glass constrain the density change upon melting of Mg‐silicate perovskite up to 200 GPa. The melt becomes denser than perovskite near the base of Earth's lower mantle. This inference is confirmed by shock temperature data suggesting a negative pressure‐temperature slope along the melting curve at high pressure. Although melting of Earth's mantle involves multiple phases and chemical components, this implies that the partial melts invoked to explain anomalous seismic velocities in the lowermost mantle may be dynamically stable.
Application of Aerosondes to high‐resolution observations of sea surface temperature over Barrow Canyon
Authors: Inoue Jun , Curry Judith A.
Published: July 2004

Continuous observation of sea surface temperature (SST) were obtained for a period of 27 hours over Barrow Canyon on 20–21 September 2002 using a small robotic aircraft called the Aerosonde. These observations demonstrated significant spatial and temporal variations in the SST at scales that would be very difficult to measure using mooring and satellite observations. Over a region of 25 km2, SST values varied from 1–6°C. A sharp SST front with a temperature gradient of 3°C was observed over the northwestern shelf of Barrow Canyon, which moved northward during the observation period. Relatively cold water was transported from the southwest into the region. Current speeds were estimated using the time series of observations. This analysis demonstrates new technology for oceanographic observations and supports previous evidence that the flow through Barrow Canyon has a strongly sheared flow into the Arctic Ocean.
Shape changes of calcareous nannofossils upon aqueous dissolution as revealed by atomic force microscope measurements
Authors: Takahashi‐Shimase Kyoma , Nakashima Satoru
Published: July 2004

We measured three‐dimensional shape of a specimen of calcareous nannofossil by using an atomic force microscope (AFM), and traced its change during an aqueous dissolution experiment. Some numerical values are calculated to characterize the shape changes of the specimen upon dissolution; volume, surface area, and roughness of the specimen decreased by the dissolution. The present AFM method is expected to study quantitatively possible changes in calcareous nannofossil assemblage due to different dissolution rates for different fossil forms.
Emissions of ozone‐depleting substances in Russia during 2001
Authors: Hurst D. F. , Romashkin P. A. , Elkins J. W. , Oberländer E. A. , Elansky N. F. , Belikov I. B. , Granberg I. G. , Golitsyn G. S. , Grisenko A. M. , Brenninkmeijer C. A. M. , Crutzen P. J.
Published: July 2004

There is a long‐standing need for measurement‐based estimates of the emissions of ozone‐depleting substances (ODSs) in Russia. This need arises from >20 years of globally important ODS manufacture in Russia that reportedly ceased in December 2000, for which only aggregated, unaudited production figures are available. The integrity of these production figures is questionable because, for nearly the last decade, the global emissions of several important ODSs estimated from global production figures (production‐based estimates) have been insufficient to account for their measured atmospheric burdens. Are these shortfalls in worldwide production‐based estimates the result of Russian emissions that are inordinate relative to the reported production figures? We estimate Russian emissions of six ODSs (chlorofluorocarbon‐11 (CFC‐11, CCl3F), CFC‐12 (CCl2F2), CFC‐113 (CCl2FCClF2), carbon tetrachloride (CCl4), methyl chloroform (CH3CCl3), and halon‐1211 (CBrClF2)) from thousands of measurements of their mixing ratios along 8500 km of the Russian trans‐Siberian railway in June–July 2001. Our measurement‐based estimates indicate that Russian emissions in 2001, even if grossly underestimated because of underreported production, were insufficient in magnitude to play a major role in recent global emission shortfalls. The results also corroborate the reported termination of CFC production in Russia at the end of 2000. The large CFC‐12 emissions observed in Russia suggest that a recent estimate of the global CFC‐12 reserve is too small.
Remote sensing and geographic information systems methods for global spatiotemporal modeling of biomass burning emissions: Assessment in the African continent
Authors: Palacios‐Orueta Alicia , Parra Alexander , Chuvieco Emilio , Carmona‐Moreno César
Published: July 2004

A spatially explicit model for analysis of biomass burning emissions is presented. The model, based on that ofSeiler and Crutzen[1980], uses satellite images and geographic information systems (GIS) modeling tools to improve the estimation of biomass loads and burning efficiency. The model was assessed in the African continent using the Global Burned Area (GBA‐2000) maps derived from SPOT‐Vegetation by the Joint Research Center. A total amount of 5711.78 and 336.43 Tg CO was estimated from the model. The areas south of the equator were estimated to release 3579.22 and 218.21Tg CO, while 2132.56 and 118.22 Tg CO were estimated for the Northern Hemisphere. Most of these emissions were generated by two latitude strips: between 3.5° and 11°N, and between 5° and 13°S. Monthly variability shows a clear bimodal temporal behavior, with two maxima in November–February in the northern band and in June–September in the southern band. The effect of biomass loads distribution on gas emissions is clearly shown, with higher gas emissions in the Southern Hemisphere in spite of having lower burned extension.
Comment on “Stiffness in stochastic chemically reacting systems: The implicit tau-leaping method” [J. Chem. Phys. 119, 12784 (2003)]
Authors: De Cock Katrien , Zhang Xueying , Bugallo Mónica F. , Djurić Petar M.
Published: July 2004

We give an alternative derivation for the expected value and variance of the number of molecules in a first order reversible reaction. Our derivation is based on the master equation and the corresponding generating function. Moreover, we show that from the generating function, the time dependent distribution function for the number of molecules can be obtained when all parameters, i.e., the initial amount of molecules and the reaction rates, are given.
The onset of gas pull-through during dual discharge from a stratified two-phase region: Theoretical analysis
Authors: Ahmed M. , Hassan I. , Esmail N.
Published: July 2004

A theoretical analysis for the onset of gas pull-through (entrainment) during discharge from a stratified two-phase region through two vertically aligned side branches has been developed in this paper. Initially, a simplified point-sink model was developed, which was then followed by the acquisition of a more accurate finite-branch model. The prediction of the critical height at the onset of gas entrainment was found to be a function of the corresponding Froude number of each branch (Fr1 and Fr2), as well as the vertical distance between the centerlines of the two branches (L/d). The predicted values of the critical height were found to be consistent with the corresponding experimental data for different values of Fr1, Fr2 and L/d. From the basis of the present models, it was found that by increasing the flow through the lower branch, the critical height increases for all values of Fr1 and L/d. Furthermore, by increasing the vertical distance between the two branches, the effect of the lower branch on the determination of the critical height was decreased.
Revisiting infinite lattice sums with the periodic fast multipole method
Authors: Kudin Konstantin N. , Scuseria Gustavo E.
Published: July 2004

The evaluation of lattice sums as well as stress lattice sums encountered in the periodic fast multipole method is reinvestigated. Simple, accurate, and efficient recurrence expressions for such sums following the ideas of the renormalization method are derived. The first few nonzero lattice sum terms in a three-dimensional cubic lattice are computed and given in Tables. The practical considerations accompanying the computation of the sums such as convergence and accuracy are discussed.
Electric field effects on the shielding constants of noble gases: A four-component relativistic Hartree-Fock study
Authors: Pecul Magdalena , Saue Trond , Ruud Kenneth , Rizzo Antonio
Published: July 2004

Second derivatives of nuclear shielding constants with respect to an electric field, i.e., shielding polarizabilities, have been calculated for the noble gas atoms from helium to xenon. The calculations have been carried out using the four-component relativistic Hartree-Fock method. In order to assess the importance of the individual relativistic corrections, the shielding polarizabilities have also been calculated at the nonrelativistic Hartree-Fock level, with spin–orbit and scalar (Darwin and mass-velocity) effects having been established by perturbative methods. Electron correlation effects have been estimated using the second-order polarization propagator approach. The relativistic effects on the tensor components of the shielding polarizabilities are found to be larger and changing less regularly with the atomic number than for the shielding constant itself. However, there is a partial cancellation of the contributions to the parallel and perpendicular components of the shielding polarizability and as a consequence the mean shielding polarizability is far less affected than the individual components.
Quantum collective approach to the thermodynamic properties of degenerate plasma
Authors: Khalfaoui A. H. , Bennaceur-Doumaz D. , Saoudi L.
Published: July 2004

Thermodynamic functions of a system of partially degenerate electrons and strongly coupled ions are derived from first principles. A quantum collective approach is developed to analyze nonidealities inherent to very high density plasma. The model considers the electron oscillations (plasmons) and ion oscillations (ion sound waves) as quasiparticles sharing the energy of the system. Statistical thermodynamic calculations lead to simple, analytical expressions for internal energy as well as an equation of state. A dispersion relation for the high frequency branch is introduced to take into account the partial degeneracy state and thereby to quantify temperature finiteness effect on thermodynamic properties of very dense plasma. The present results are in good quantitative agreement with the existing models and represent a significant improvement over previous calculations which are based mainly on numerical experiments. More physical insight is explicitly stated presently which makes a contribution to the theoretical knowledge of coupled degenerate plasma for thermonuclear fusion as well as of astrophysical interests.
Characterization of the resonant electromagnetic mode in helicon discharges
Authors: Panevsky Martin I. , Bengtson Roger D.
Published: July 2004

This paper presents experimental evidence for the existence of a resonant electromagnetic mode in a helicon plasma, and characterizes its resonant frequency, energy absorption rate, and contribution to the overall power balance. An experimental method developed to detect and characterize the plasma impedance is introduced. Power flow analysis shows that the resonant electromagnetic mode is the dominant mechanism driving helicon plasma discharges in cylindrical geometry. The weakly damped wavefields are absorbed in a short distance, indicating that the wavefields may be trapped in a potential well created by a density gradient.
Contributions of short-range and excluded-volume interactions to unperturbed polymer chain dimensions
Authors: Yamakawa Hiromi , Yoshizaki Takenao
Published: July 2004

A Monte Carlo study is made of the mean-square radius of gyration 〈S2〉 for the freely rotating chain with such fictitious excluded-volume interactions that the Lennard-Jones 6-12 potentials at the Θ temperature act only between the fourth-through (3+Δ)th-neighbor beads (Δ⩾1) along the chain. The behavior of the asymptotic value (〈S2〉/n)∞ of the ratio 〈S2〉/n as a function of the number n of bonds in the chain in the limit of n→∞ is examined as a function of Δ. It is shown that the approach of (〈S2〉/n)∞ to its value for the real unperturbed chain with Δ=∞ is so slow that the interactions between even up to about 100th-neighbor beads should be taken into account in order to reproduce nearly its dimension. The result implies that the unperturbed polymer chain dimension as experimentally observed at the Θ temperature depends not only on short-range interactions but also to a considerable extent on the long-range excluded-volume interactions, and that the asymptotic value C∞ of the characteristic ratio Cn for the rotational isomeric state model in the limit of n→∞, which is determined only by the very local conformational energy, cannot be directly compared with the corresponding experimental value.
Absolute and convective instabilities of parallel propagating circularly polarized Alfvén waves: Decay instability
Authors: Ruderman M. S. , Simpson D.
Published: July 2004

The absolute and convective instabilities of circularly polarized Alfvén waves propagating along an ambient magnetic field are studied. The approximation of ideal magnetohydrodynamics is used. The analysis is restricted to the decay instability that occurs when the sound speed is smaller than the Alfvén speed. In addition, it is assumed that the amplitude a of an unstable Alfvén wave (pump wave) is small. This assumption allows us to study the problem analytically using expansions in power series with respect to a. It is shown that there are quantities, Ul<0 and Ur>0, such that the pump wave is absolutely unstable in a reference frame moving with velocity U with respect to the rest plasma if Ul<U<Ur. If either UUr, then the pump wave is convectively unstable. The expressions for Ul and Ur are found. The signaling problem is studied in a reference frame where the pump wave is convectively unstable. It is shown that spatially amplifying waves exist only when the signaling frequency is in two narrow symmetric frequency bands with the widths of the order of a. The implication of the obtained results on the interpretation of observational data obtained in space missions is discussed. It is shown that circularly polarized Alfvén waves propagating in the solar wind are convectively unstable in a reference frame of any spacecraft moving with the velocity not exceeding a few tens of km/s in the solar reference frame. The spatial amplification scale of these waves is very large, of the order of 1/6 a.u. In view of these results it is not surprising at all that evidence of the decay instability of Alfvén waves in the solar wind is sparse.
Recoil ion momentum spectroscopy using magneto-optically trapped atoms
Authors: Nguyen H. , Fléchard X. , Brédy R. , Camp H. A. , DePaola B. D.
Published: July 2004

A novel apparatus has been developed in which atoms in a magneto-optical trap are used as targets in ion-atom collision experiments. The apparatus is an extension of earlier methodology in which the momentum of the recoiling target is measured and used to deduce the collision Q value and projectile scattering angle. In the present work, the low temperature of the target atoms yields increased momentum resolution, which in turn leads to improved Q value and scattering angle resolution. In addition, because the trapping process leaves some fraction of the atoms in an excited state, the new methodology is ideal for the study of collisions with excited targets. The prototypical system presented is low energy charge transfer between singly charged alkali ions and trapped rubidium atoms in the ground and first excited state.
High energy asymptotics of the magnetic spectral shift function
Authors: Bruneau Vincent , Raikov Georgi D.
Published: July 2004

We consider the three-dimensional Schrödinger operators H0 and H where H0=(i∇+A)2−b, A is a magnetic potential generating a constant magnetic field of strength b>0, and H=H0+V where V∈L1(R3;R) satisfies certain regularity conditions. Then the spectral shift function ξ(E;H,H0) for the pair of operators H, H0 is well-defined for energies E≠2qb, q∈Z+. We study the asymptotic behavior of ξ(E;H,H0) as E→∞, E∈Or, r∈(0,b), where Or≔{E∈(0,∞)|dist(E,2bZ+)>r}. We obtain a Weyl-type formula limE→∞,E∈OrE−1/2ξ(E;H,H0)=(1/4π2) ∫ R3V(x)dx.