bluuebunny/crossref_metadata_2025 huggingface dataset:
1H magnetic resonance spectroscopy of invasive cervical cancer: an in vivo study with ex vivo corroboration
Authors: Mahon Marrita M. , Williams Andreanna D. , Soutter W. Patrick , Cox I. Jane , McIndoe G. Angus , Coutts Glyn A. , Dina Roberto , deSouza Nandita M.
Published: March 2004

The objective of this study was to establish in vivo 1H‐magnetic resonance (MR) spectroscopic appearances of cervical cancer using an endovaginal receiver coil and corroborate findings with magic angle spinning (MAS) MR spectroscopy of tissue samples. Fifty‐three women (14 controls and 39 with cervical cancer) underwent endovaginal coil MR imaging at 1.5 T with T1‐ and T2‐weighted scans sagittal and transverse to the cervix. Localized 1H MR spectra (PRESS technique, TR 1600 ms, TE 135 ms) were accumulated in all controls and 29 cancer patients whose tumour filled > 50% of a single 3.4 cm3 voxel. Peaks from triglyceride‐CH2 and ‐CH3 were defined as present and in‐phase (with the choline resonance), present but out‐of‐phase, or not present. Peak areas of choline‐containing compounds were standardized to the area of unsuppressed tissue water resonance. Comparisons in observed resonances between groups were made using Fisher's exact test (qualitative data) and a t‐test (quantitative data). Biopsies from these women analysed using MAS‐MR spectroscopy and normalized to the intensity of an external standard of silicone rubber were similarly compared. Adequate water suppression permitted spectral analysis in 11 controls and 27 cancer patients. In‐phase triglyceride‐CH2 resonances (1.3 ppm) were observed in 74% of tumours but in no control women (p < 0.001). No differences were observed in the presence of a 2 ppm resonance, choline‐containing compounds or creatine in cancer compared with control women. However, ex vivo analysis showed significant differences not only in CH2, but also in CH3, a 2 ppm resonance, choline‐containing compounds and creatine between tissues from control women and cancer tissue (p < 0.001, = 0.001, = 0.036, < 0.001 and = 0.004 respectively). On in vivo 1H‐MR spectroscopy, the presence of positive triglyceride‐CH2 resonances can be used to detect and confirm the presence of cervical cancer. However, technical improvements are required before routine clinical use. Copyright © 2004 John Wiley & Sons, Ltd.
MRI detects early hindlimb muscle atrophy in Gly93Ala superoxide dismutase‐1 (G93A SOD1) transgenic mice, an animal model of familial amyotrophic lateral sclerosis
Authors: Brooks Keith J. , Hill Mark D. W. , Hockings Paul D. , Reid David G.
Published: March 2004

MRI has been used to measure hindlimb muscle volume in female and male transgenic mice overexpressing the Gly93Ala (G93A) mutant human superoxide dismutase 1 (SOD1), a widely used model of familial amyotrophic lateral sclerosis (FALS), over the first 4 months of life. Significant decreases in the hindlimb muscle volume of the female G93A SOD1 mice were evident from 11 weeks of age, before other overt pathology appeared. By 15 weeks volume had decreased by 37% compared with 7 weeks, from 0.84±0.04 cm3 (mean±standard deviation, n = 6) to 0.54±0.07 cm3, (p < 0.05), despite an increase in body weight of ca. 12% (from 16.2 ± 1.4 to 18.1 ± 0.7 g). Female wild‐type volume increased by ca. 30% whilst the body weight increased by 15%. Muscle wasteage was less (0.82±0.1 to 0.65±0.02 cm3, p < 0.05, n = 6) in male G93A SOD1 mice between 8 and 16 weeks of age, against a body weight increase trend from 20.7 ± 0.4 to 21.6 ± 0.5 g, (p > 0.05). Wild‐type male muscle volume did not change significantly over this period, with an increase in body weight of 20%. Longitudinal MRI hindlimb muscle volume measurements may provide a straightforward, rapid, non‐invasive and sensitive, way of monitoring outcome of experimental ALS treatments. Copyright © 2004 John Wiley & Sons, Ltd.
How faith‐based social service organizations manage secular pressures associated with government funding
Authors: Vanderwoerd James R.
Published: March 2004

This article reports selected findings from a qualitative case study of two faith‐based social service
organizations to address two questions: (1) How does government funding influence the religious
characteristics of faith‐based social service organizations? (2) How do
government‐funded, faith‐based social service organizations manage the tensions arising from both
secular and religious contexts? The findings suggest that the adaptation of secular institutional practices
is not as inevitable as some have feared. Rather, the two organizations studied showed convincingly that their
faith traditions and values were alive and widely evident throughout their organizations. Three key strategies
emerged as means for maintaining religiousness in the face of secular pressures: (1) Religious
identities were perceived as given rather than chosen, and therefore were not negotiable; (2)
religious values provided strong justification for seeking relationships with others who do not share their
faith; (3) the religious worldview blurred religious and secular distinctions so that secular
technologies and practices could comfortably be utilized.
The role of religious networks and other factors in types of volunteer work
Authors: Grønbjerg Kirsten A. , Never Brent
Published: March 2004

In view of current efforts to strengthen volunteering and promote the faith‐based provision of social
services in the United States, we examine both the underlying complexity of volunteering and who performs
particular types of volunteer work. This paper, drawing on a telephone interview survey of 526 randomly selected
Indiana residents, considers whether religious involvement helps explain engagement in different types of
volunteer work independent of such other contributing factors as family status, socioeconomic status, and
community attachment. We find that religious involvement plays an independent role, but only for certain types of
volunteer work.
Mission, money, and merit: Strategic decision making by nonprofit managers
Authors: Krug Kersti , Weinberg Charles B.
Published: March 2004

Public and nonprofit organizations need to make strategic choices about where to invest their resources. They
also need to expose hidden managerial assumptions and lack of adequate knowledge that prevent the attainment of
consensus in strategic decision making. The approach we developed and tested in the field used a dynamic,
three‐dimensional model that tracks individual programs in an organization's portfolio on their
contribution to mission, money, and merit. The first dimension measures whether the organization is doing the right
things; the second, whether it is doing things right financially; and the third, whether it doing things
right in terms of quality. Senior managers provide their own evaluations of the organization's programs. Both
the consensus view and the variation in individual assessments contribute to an improved managerial understanding of
the organization's current situation and to richer discussions in strategic decision making. In field tests,
this visual model proved to be a useful and powerful tool for illuminating underlying assumptions and variations in
knowledge among managers facing the complex, multidimensional tradeoffs needed in strategic decision making.
Community organizing and managing
Authors: Netting F. Ellen
Published: March 2004

Analytical Skills for Community Organization Practice, by Donna Hardina. New York: Columbia
University Press, 2002. 390 pp., $52.00 cloth.
Self‐esteem and self‐certainty: a mediational analysis
Authors: Story Amber L.
Published: March 2004

Self‐esteem has been found to be related to the certainty with which specific self‐conceptions are held. This study tested a number of competing accounts for this relationship, using a more rigorous idiographic approach. Specifically, it was thought that the relationship between self‐esteem and self‐certainty might be mediated by self‐concept clarity, the positivity of specific self‐conceptions, and impression management concerns. However, none of these fully mediated the relationship between self‐esteem and self‐certainty. Participants with higher self‐esteem were more certain of their central self‐conceptions than were those with lower self‐esteem. This was true even though participants were allowed to generate their most relevant and central self‐conceptions themselves. Discussion focuses on the role of social information in the possibly direct relationship between self‐esteem and self‐certainty. Copyright © 2003 John Wiley & Sons, Ltd.
Next generation satellite systems for aeronautical communications
Authors: Ercetin Ozgur , Ball Michael O. , Tassiulas Leandros
Published: March 2004

U.S. airspace is reaching its capacity with the current air traffic control (ATC) system. The number of flights is constantly rising and it is estimated to be over 58 million per year by 2005. The FAA has undertaken several projects to modernize the National Airspace System (NAS) to ensure the safety of the increasing number of flights. Of special importance is the modernization of the air–ground communications infrastructure, which is the heart of the ATC. The current plan in the modernization of the air–ground communications is to migrate from analog voice only system to integrated digital voice and data system. The next generation satellite systems can be an alternative to the terrestrial air–ground systems by their low propagation and transmission delays, global coverage, high capacity and free flight suitable characteristics. In this paper, we give an overview of the current and the future ATC architectures, describe the systems and the communications issues in these systems and develop a framework in which next generation satellite systems can be integrated to the future ATC systems. Copyright © 2004 John Wiley & Sons, Ltd.
W‐band physical layer design issues in the context of the DAVID–DCE experiment
Authors: Sacchi Claudio , Gera Gianluca , Regazzoni Carlo S.
Published: March 2004

This paper aims at focusing on the aspects concerning the physical layer design for an innovative satellite communication experiment. Such an experiment, denoted by the acronym DAVID–DCE (Data and Video Interactive Distribution—Data Collection Experiment) is based on the exploitation of the W‐band (75–110 GHz) for high‐bit‐rate satellite transmission. The potential advantages of using of the W‐band are mainly related to the great bandwidth availability, and to the absence of interference. Moreover, an expected result of the experiment is a substantive improvement in the communication system's performances in the presence of meteorological phenomena (e.g. rain) as compared with the more conventional Ka‐band satellite transmission. On the other hand, problems to be faced concern the non‐ideal behaviours of hardware devices employed for high‐frequency digital transmission. In particular, carrier recovery and timing recovery are the most crucial signal‐processing tasks to be carefully considered in the design of the physical level of the system, because they considerably suffer from hardware impairments. The purpose of this work is to illustrate the proposed solutions in terms of the most critical modulation, demodulation and synchronization design issues, together with the effects of non‐ideal behaviours of hardware components on BER performances. Copyright © 2004 John Wiley & Sons, Ltd.
Integrating the scene length characteristics of MPEG video bitstreams into a direct broadcast satellite network with return channel system
Authors: Alagöz Fatih
Published: March 2004

In order to optimize the network resources, we should incorporate all the available information into the network design. However, incorporating irrelevant information may increase the design complexity and/or decrease the performance of the network. In this paper, we investigate the relevance of integrating the scene length characteristics of moving pictures expert group (MPEG) coded video bitstreams into a direct broadcast satellite (DBS) network with return channel system (DVB‐RCS). Due to the complexity of the studied system, unless disputable simplifications are made, it is hard to achieve a mathematical foundation for this integration. Our analysis relies on extensive set of simulations. Firstly, we achieve the scene length distributions for MPEG bitstreams based on the proposed scene change models and their subjective observations of the actual video. We show that these models may be used to estimate the scene length of MPEG bitstreams. We then integrate this estimation into a DBS network simulator. Finally, we show that the scene length characteristics may be used to improve the DBS network performance under certain conditions. Copyright © 2004 John Wiley & Sons, Ltd.
Satellite handover techniques for LEO networks
Authors: Papapetrou E. , Karapantazis S. , Dimitriadis G. , Pavlidou F.‐N.
Published: March 2004

Low earth orbit satellite constellations could play an important role in future mobile communication networks due to their characteristics, such as global coverage and low propagation delays. However, because of the non‐stationarity of the satellites, a call may be subjected to handovers, which can be cell or satellite handovers. Quite many techniques have been proposed in the literature dealing with the cell handover issue. In this paper, a satellite handover procedure is proposed, that investigates and exploits the partial satellite diversity (namely, the existing common coverage area between contiguous satellites) in order to provide an efficient handover strategy, based always on a tradeoff of blocking and forced termination probabilities for a fair treatment of new and handover calls. Three different criteria were examined for the selection of a satellite. Each one of them could be applied either to new or handover calls, therefore we investigated nine different service schemes. A simulation tool was implemented in order to compare the different service schemes and simulation results are presented at the end of the paper. Copyright © 2004 John Wiley & Sons, Ltd.
Polyvalency of Tn (GalNAcα1→Ser/Thr) glycotope as a critical factor for Vicia villosa B4 and glycoprotein interactions
Authors: Wu Albert M.
Published: March 2004

Vicia villosa B4 (VVL‐B4) is an important lectin for detecting exposed Tn (GalNAcα1‐Ser/Thr) determinants on cancer cells. In order to elucidate the binding factors involved in VVL‐B4 and glycotope interaction, the binding properties of this lectin were analyzed by enzyme‐linked lectinosorbent and inhibition assays. From the results, it is concluded that the most critical factor affecting VVL‐B4 binding is polyvalency at the α anomer of Gal with –NH CH3CO at carbon‐2 (Tn epitope), which enhances the reactivity by 3.3×105 times over monovalent Gal. The reactivities of glycotopes can be ranked as follows: high density Tn cluster≫Tn glycopeptides (MW<3.0×103)≫monomeric Tn to tri‐ Tn glycopeptides⋙other GalNAcα/β‐related structural units>Gal and Galα‐ or β‐linked ligands, demonstrating the essential role of the polyvalency of Tn glycotopes in the enhancement of the binding.
Cholesterol diet‐induced hyperlipidemia influences gene expression pattern of rat hearts: a DNA microarray study
Authors: Puskás László G. , Nagy Zsolt B. , Giricz Zoltán , Ónody Annamária , Csonka Csaba , Kitajka Klára , Hackler László , Zvara Ágnes , Ferdinandy Péter
Published: March 2004

To profile gene expression patterns involved in the direct myocardial effect of cholesterol‐enriched diet‐induced hyperlipidemia, we monitored global gene expression changes by DNA microarray analysis of 3200 genes in rat hearts. Twenty‐six genes exhibited significant up‐regulation and 25 showed down‐regulation in hearts of rats fed a 2% cholesterol‐enriched diet for 8 weeks as compared to age‐matched controls. The expression changes of 12 selected genes were also assessed by real‐time quantitative polymerase chain reaction. Genes with altered expression in the heart due to hyperlipidemia included procollagen type III, cofilin/destrin, tensin, transcription repressor p66, synaptic vesicle protein 2B, Hsp86, chaperonin subunit 5ϵ, metallothionein, glutathione S‐transferase, protein kinase C inhibitor, ATP synthase subunit c, creatine kinase, chloride intracellular channel 4, NADH oxidoreductase and dehydrogenase, fibronectin receptor β chain, CD81 antigen, farnesyltransferase, calreticulin, disintegrin, p120 catenin, Smad7, etc. Although some of these genes have been suspected to be related to cardiovascular diseases, none of the genes has been previously shown to be involved in the mechanism of the cardiac effect of hyperlipidemia.
The G protein‐coupled receptor rhodopsin in the native membrane
Authors: Fotiadis Dimitrios , Liang Yan , Filipek Slawomir , Saperstein David A , Engel Andreas , Palczewski Krzysztof
Published: March 2004

The higher‐order structure of G protein‐coupled receptors (GPCRs) in membranes may involve dimerization and formation of even larger oligomeric complexes. Here, we have investigated the organization of the prototypical GPCR rhodopsin in its native membrane by electron and atomic force microscopy (AFM). Disc membranes from mice were isolated and observed by AFM at room temperature. In all experimental conditions, rhodopsin forms structural dimers organized in paracrystalline arrays. A semi‐empirical molecular model for the rhodopsin paracrystal is presented validating our previously reported results. Finally, we compare our model with other currently available models describing the supramolecular structure of GPCRs in the membrane.
Automated large‐scale purification of a G protein‐coupled receptor for neurotensin
Authors: White Jim F , Trinh Loc B , Shiloach Joseph , Grisshammer Reinhard
Published: March 2004

Structure determination of integral membrane proteins requires milligram amounts of purified, functional protein on a regular basis. Here, we describe a protocol for the purification of a G protein‐coupled neurotensin receptor fusion protein at the 3‐mg or 10‐mg level using immobilized metal affinity chromatography and a neurotensin column in a fully automated mode. Fermentation at a 200‐l scale of Escherichia coli expressing functional receptors provides the material needed to feed into the purification routine. Constructs with tobacco etch virus protease recognition sites at either end of the receptor allow the isolation of neurotensin receptor devoid of its fusion partners. The presented expression and purification procedures are simple and robust, and provide the basis for crystallization experiments of receptors on a routine basis.
The plug domain of a neisserial TonB‐dependent transporter retains structural integrity in the absence of its transmembrane β‐barrel
Authors: Oke M , Sarra R , Ghirlando R , Farnaud S , Gorringe A.R , Evans R.W , Buchanan S.K
Published: March 2004

Transferrin binding protein A (TbpA) is a TonB‐dependent outer membrane protein expressed by pathogenic bacteria for iron acquisition from human transferrin. The N‐terminal 160 residues (plug domain) of TbpA were overexpressed in both the periplasm and cytoplasm of Escherichia coli. We found this domain to be soluble and monodisperse in solution, exhibiting secondary structure elements found in plug domains of structurally characterized TonB‐dependent transporters. Although the TbpA plug domain is apparently correctly folded, we were not able to observe an interaction with human transferrin by isothermal titration calorimetry or nitrocellulose binding assays. These experiments suggest that the plug domain may fold independently of the β‐barrel, but extracellular loops of the β‐barrel are required for ligand binding.
Back to the Future in Acadian French
Authors: KING RUTH , NADASDI TERRY
Published: March 2004

Our article presents a variationist analysis of future verb forms in Acadian French. The main variants considered are the inflected future (e.g. je partirai) and the periphrastic future (e.g. je vais partir). The purpose of this study is two-fold: a) it will determine the distribution of these variants and their linguistic correlates; b) it will compare the use of future verb forms with other varieties of French. Our results reveal that the inflected future is used with greater frequency in Acadian French than in other Canadian varieties and that the factors that condition the variable in Acadian are not the same as in other varieties.
Nutrient trapping in the equatorial Pacific: The ocean circulation solution
Authors: Aumont O. , Orr J. C. , Monfray P. , Madec G. , Maier‐Reimer E.
Published: March 2004

Nutrient trapping is a chronic problem found in global carbon cycle models with particle‐only remineralization schemes. It is defined as the excess of subsurface nutrient concentrations relative to observations and occurs principally in the eastern equatorial Pacific. Previous studies reduced excess simulated nutrients by increasing the complexity of modeled biogeochemistry, i.e., by adding pools for nutrients (and carbon) either in dissolved organic form or as plankton. Conversely, our study suggests that deficiencies in modeled circulation fields from global coarse‐resolution ocean models are mostly responsible. This new interpretation stems from our use of an ocean general circulation model with higher resolution, which offers a more realistic equatorial circulation. We used the same biogeochemical model Hamburg ocean carbon cycle model, version 3, as in some of the previous studies. Our model‐predicted distribution of PO43− in the equatorial Pacific agrees reasonably well with the observations both at the surface and in the subsurface. Subsurface PO43− concentrations in our model's eastern equatorial Pacific exceed observations by, at most, 15%, unlike coarser‐resolution models. Improvement is due to enhanced meridional resolution (0.5°) near the equator, which allows the model to simulate a vigorous equatorial undercurrent that brings in low‐nutrient water from the western basin. Furthermore, the model upwells no nutrient‐rich abyssal water into the surface equatorial Pacific. Our results suggest that dissolved organic carbon plays a minor role in the carbon budget of the equatorial Pacific.
Isotopic evolution of Mauna Loa and the chemical structure of the Hawaiian plume
Authors: DePaolo Donald J. , Bryce Julia G. , Dodson Allen , Shuster David L. , Kennedy B. Mack
Published: March 2004

New He isotopic data from the HSDP pilot hole core, lava accumulation rate models, and data from the literature are used to develop a 200,000 year isotopic record for the lava erupted from the Mauna Loa volcano. This record, coupled with an analogous record from Mauna Kea from the Hawaii Scientific Drilling Project (HSDP) pilot hole project and other literature data from the GEOROC database, are used to construct a “map” of lava isotopic compositions for the island of Hawaii. The isotopic map is converted to a map of the He and Nd isotopic compositions of melts from the mantle plume, which can be compared with a published melt supply map derived from geodynamic modeling. The resulting map of the plume indicates that values of helium 3He/4He > 20 Ra are confined to the core of the plume (radius ≈ 20–25 km) and correspond to potential temperatures >1565°C, suggesting the He isotopic signal is derived from deep in the mantle. The 3He/4He map has closed contours down to 10 Ra; the contours are teardrop‐shaped and elongated in the general direction of plate motion. The closed contours indicate that most of the plume He signal is lost during the early stages of melting, which is consistent with helium behaving as a strongly incompatible element (KHe ≤ 0.001). The εNd contours (and by inference the contours for Sr, Pb, Hf, and Os) do not all close on the scale of the island of Hawaii but instead partially follow material flow lines within the plume beneath the lithosphere. The plume signal for Nd extends circa 100 km in the direction of plate motion, which is consistent with the moderately incompatible behavior of Nd (KNd ≈ 0.02). Downstream from the plume core epicenter, plume Nd occurs with asthenospheric He; this could be mistaken for an additional plume component, whereas it may be only a manifestation of differing incompatibility. Data from Mauna Loa suggest the presence of a low‐3He/4He plume component that has low εNd and high 87Sr/86Sr. The plume map suggests that this component may be a blob (circa 20 km scale), located between Mauna Loa and Hualalai and separated from the main plume core by a zone of more asthenosphere‐like material. The HSDP data preclude a proposed model where this material represents a ring of entrained material from the lower mantle. The orientation of the elongation of contours on the plume He and Nd isotope maps (∼N45°W) does not match the modern plate motion as measured by GPS (N65°W) nor does it match the trend of the ridge axis between Maui and Loihi (N30°W). The geochemical evidence, as well as the locations and growth histories of the Hawaiian volcanoes, suggest that the plume, as well as the Pacific plate, has been moving at a velocity of several centimeters per year over the past 1 to 2 million years.
Seismic structure and magmatism of the Young Kyushu Subduction Zone
Authors: Zhao Dapeng , Asamori Koichi , Iwamori Hikaru
Published: March 2004

Seismic tomography shows that slow velocity anomalies exist in the mantle wedge and extend to the forearc region down to the subducting Philippine Sea slab under northern Kyushu. We also conducted numerical simulations with petrologic data to estimate the fluid distribution in the mantle wedge. The seismic and simulation results indicate that regimes of melting and magmatism in a subduction zone with a young slab are different from those with old slabs. Dehydration and melting occur beneath the arc and forearc above a young (and warm) slab such as in northern Kyushu (≤ 26 Ma), while fluids (aqueous solution and melt) occur mainly beneath the back arc above old slabs.
Topographic phase recovery from stacked ERS interferometry and a low‐resolution digital elevation model
Authors: Sandwell David T. , Sichoix Lydie
Published: March 2004

A hybrid approach to topographic recovery from ERS interferometry is developed and assessed. Tropospheric/ionospheric artifacts, imprecise orbital information, and layover are key issues in recovering topography and surface deformation from repeat‐pass interferometry. Previously, we developed a phase gradient approach to stacking interferograms to reduce these errors and also to reduce the short‐wavelength phase noise (see Sandwell and Price [1998] and Appendix A). Here the method is extended to use a low‐resolution digital elevation model to constrain long‐wavelength phase errors and an iteration scheme to minimize errors in the computation of phase gradient. We demonstrate the topographic phase recovery on 16‐m postings using 25 ERS synthetic aperture radar images from an area of southern California containing 2700 m of relief. On the basis of a comparison with 81 GPS monuments, the ERS‐ derived topography has a typical absolute accuracy of better than 10 m except in areas of layover. The resulting topographic phase enables accurate two‐pass, real‐time interferometry even in mountainous areas where traditional phase unwrapping schemes fail. As an example, we form a topography‐free (127‐m perpendicular baseline) interferogram spanning 7.5 years; fringes from two major earthquakes and aseismic slip on the San Andreas Fault are clearly isolated.
Experimental and theoretical fracture mechanics applied to fracture of the crust of Venus
Authors: Balme Matthew R. , Sammonds Peter R. , Vita‐Finzi Claudio , Couchman Jonathon P.
Published: March 2004

Mapping of closely spaced, parallel extensional fractures in the Guinevere and Sedna Planitia regions of Venus reveals a concentric pattern of fractures around the edge of the large topographic rise of Western Eistla Regio. We have constructed 13 transects through these closely spaced parallel fractures (CSPF) and find a mean spacing of between 0.8 and 1.2 km. A two‐dimensional, nonlayered, fracture mechanics computer model for the formation of CSPF is described. For cracks extended by a remote tensile stress the stress intensity factor controls the depth of penetration, which in turn, governs the spacing between adjacent cracks based upon the stress‐shadow principle. The stress required to initiate cracks depends upon the strength of the material; thus spacing of CSPF depends only on the physical properties of the preexisting rock mass. Using a new fracture mechanics apparatus designed to simulate Venusian conditions (90 bar CO2, 450°C) the fracture toughness of basalt was measured for confining pressures up to 20 MPa and for temperature up to 600°C. Fracture toughness was found to increase from ∼2.4 MPam1/2 at ambient pressure to ∼3.0 MPam1/2 at 10 MPa confining pressure. Fracture toughness showed no clear trend with temperature. The experimental results for fracture toughness suggest that the preexisting rock mass that fits best with observations contains an inverse square distribution of flaws with maximum sizes of only ∼20–80 cm and that a remote tensile stress of ∼3–6 MPa is required to form the observed CSPF.
Trajectory studies of large HNO3‐containing PSC particles in the Arctic: Evidence for the role of NAT
Authors: McKinney K. A. , Wennberg P. O. , Dhaniyala S. , Fahey D. W. , Northway M. J. , Künzi K. F. , Kleinböhl A. , Sinnhuber M. , Küllmann H. , Bremer H. , Mahoney M. J. , Bui T. P.
Published: March 2004

Large (5 to >20 μm diameter) nitric‐acid‐containing polar stratospheric cloud (PSC) particles were observed in the Arctic stratosphere during the winter of 1999–2000. We use a particle growth and sedimentation model to investigate the environment in which these particles grew and the likely phase of the largest particles. Particle trajectory calculations show that, while simulated nitric acid dihydrate (NAD) particle sizes are significantly smaller than the observed maximum particle sizes, nitric acid trihydrate (NAT) particle trajectories are consistent with the largest observed particle sizes.
NAO and solar radiation variability in the European North Atlantic region
Authors: Pozo‐Vázquez D. , Tovar‐Pescador J. , Gámiz‐Fortis S. R. , Esteban‐Parra M. J. , Castro‐Díez Y.
Published: March 2004

We explore the relationship between the NAO and the solar radiation spatio‐temporal variability in the European North Atlantic area during winter. Measured monthly sums of sunshine duration and short‐wave downward solar flux reanalysis data have been used. Correlation analysis between the NAO index and the measured sunshine duration shows a dipolar pattern, with maximum positive values (+0.75) over the Iberian Peninsula, and maximum negative values (−0.71) over Norway. Reanalysis results confirm these findings. Composite analysis shows, for northern Europe, negative anomalies (−10% to −20%) associated with NAO > 1 and positive anomalies (10% to 20%) associated with NAO < −1; while for southern Europe anomalies are, respectively, 10% to 20% and −10% to −20%. A stronger influence is found during the NAO negative phase; particularly, the northern British Isles, Norway and the Iberian Peninsula present a significant non‐linear response, with higher anomalies (10% to 20%) during this negative phase.
Barrier layer in the North Pacific subtropical gyre
Authors: Sato Kanako , Suga Toshio , Hanawa Kimio
Published: March 2004

By analyzing all the available temperature/salinity profiles obtained by Argo floats as of August 2003, we evaluate the barrier layers (BLs) in the North Pacific subtropical gyre. 20.5% of the profiles at 10°–25°N have BLs with thickness greater than 10 m. The relative frequency and typical thickness of the BLs are generally higher and greater, respectively, during January–May, which are consistent with the wider distribution of the previously reported climatological BL in winter and spring. Because evaporation dominates over precipitation in winter, we infer that the subduction of high saline water, known as North Pacific Tropical Water, is responsible for the BL formation in 10°–25°N, at least in winter. Patchy occurrence of the BLs detected by the floats, and locally confined intense salinity fronts in several synoptic sections, suggest that the BLs are formed by the subduction at those sharp salinity fronts.
Summer‐winter dependences of day‐night differences in the ion temperature in the polar upper F region
Authors: Oyama S. , Lathuillere C. , Maeda S. , Watkins B. J.
Published: March 2004

The daily variation of ion temperature observed with the European Incoherent Scatter (EISCAT) Tromsø UHF radar in the upper F region (from 300 to 500 km) has been found to be significantly dependent on season. Of particular interest is the statistics that the ion temperature at local night is higher than that at local daytime for near solar maximum summer conditions; by contrast no differences for winter. Using the ion energy equation estimates of the heat exchange with electrons suggest these local time and seasonal differences. A case study using summer‐time data from the Sondrestrom incoherent‐scatter radar (ISR) also shows local‐time dependences similar to that observed with the Tromsø ISR. The case study using a summer‐time data from the EISCAT Svalbard radar (ESR) shows the opposite sense. These seasonal characteristics of the ion temperature that depend on the observation site suggest that the day‐night difference of ion temperature in the polar upper F region has complicated magnetic‐latitudinal dependences.
Dissipation effects in North Atlantic Ocean modeling
Authors: Dietrich D. E. , Mehra A. , Haney R. L. , Bowman M. J. , Tseng Y. H.
Published: March 2004

Numerical experiments varying lateral viscosity and diffusivity between 20 and 150 m2/s in a North Atlantic Ocean (NAO) model having 4th‐order accurate numerics, in which the dense deep current system (DCS) from the northern seas and Arctic Ocean is simulated directly show that Gulf Stream (GS) separation is strongly affected by the dissipation of the DCS. This is true even though the separation is highly inertial with large Reynolds number for GS separation flow scales. We show that realistic NAO modeling requires less than 150 m2/s viscosity and diffusivity in order to maintain the DCS material current with enough intensity to get realistic GS separation near Cape Hatteras (CH). This also demands accurate, low dissipation numerics, because of the long transit time (1–10 years) of DCS material from its northern seas and Arctic Ocean source regions to the Cape Hatteras region and the small lateral and vertical scales of DCS.
Martian subsurface volatile concentrations as a function of time: Clues from layered ejecta craters
Authors: Barlow Nadine G.
Published: March 2004

Martian layered ejecta morphologies are characterized using a new preservation classification system and through measurement of ejecta mobility (EM) ratios. EM, the ratio of ejecta extent to crater radius, is believed to provide information about ejecta material fluidity during emplacement. This study compares EM and preservation classification to determine if subsurface volatile concentrations have changed measurably over time. Results from both regional and local analyses suggest that concentrations of subsurface volatiles have remained approximately constant at the depths and over the time periods recorded by these craters.
A coupled sheet‐conduit mechanism for jökulhlaup propagation
Authors: Flowers Gwenn E. , Björnsson Helgi , Pálsson Finnur , Clarke Garry K. C.
Published: March 2004

The largest glacier outburst flood (jökulhlaup) ever recorded in Iceland occurred in 1996 and came from subglacial lake Grímsvötn in Vatnajökull ice cap. Among other noteworthy features, this flood was characterized by an unprecedentedly high lake level prior to flood initiation, extremely rapid linear rise in lake discharge, delay between the onset of lake drainage and floodwater arrival at the glacier terminus, formation of short‐lived supraglacial fountains, and initially unchannelized outbursts of floodwater at the terminus. Observations suggest that the 1996 flood propagation mechanism was fundamentally different than that of previously observed floods from Grímsvötn. We advance a new model whereby floodwater initially propagates in a turbulent subglacial sheet, which feeds a nascent system of conduits. This model is able to explain key observations made of the 1996 jökulhlaup and may shed light on other outburst floods that do not conform to the standard model.
Orientation and propagation of current sheet oscillations
Authors: Sergeev V. , Runov A. , Baumjohann W. , Nakamura R. , Zhang T. L. , Balogh A. , Louarnd P. , Sauvaud J.‐A. , Reme H.
Published: March 2004

Using the four‐spacecraft Cluster system, we analyze rapid neutral sheet crossings near the Cluster apogee at about −18RE. In case studies of multiple oscillations of the locally quiet plasma sheet as well as in a statistical study of oscillations in dawn and dusk near‐flank plasma sheet portions we typically obtain that locally these dynamical current sheets are very corrugated and that subsequent crossings basically show portions of large‐scale kink‐like waves propagating from the tail center toward flanks. Propagation velocities are in the range of several tens km/s for the locally quiet sheets, and up to 200 km/s during fast flows. These results suggest that the flapping motions are of internal origin and that kink‐like waves are emitted in the central part of the tail by some impulsive source and propagate toward the tail flanks. The wave properties do not match any local excitation mechanism previously discussed so far in the literature.
Stimulated scattering of intense radio waves in partially ionized space dusty plasmas
Authors: Shukla P. K. , Eliasson B. , Stenflo L.
Published: March 2004

The nonlinear interaction between intense ordinary mode (O‐mode) radio waves and modified magnetoacoustic waves in partially ionized space dusty plasmas is considered, including the combined action of the radio wave pressure and the electron Joule heating caused by the O‐mode electric field. A set of equations containing the wave equation for the radio waves and the electron density and temperature fluctuations associated with the modified magnetoacoustic waves is derived. The set is then used to investigate decay and modulational instabilities of a constant amplitude O‐mode radio wave in the Earth's ionosphere and mesosphere.
Whole layer convection in a heterogeneous planetary mantle
Authors: Le Bars M. , Davaille A.
Published: March 2004

Geochemical observations demonstrate that Earth's mantle is heterogeneous, but the sizes, forms, and characteristics of its reservoirs are not constrained. Using laboratory experiments, we have systematically studied a simple nonhomogeneous system, where two layers of miscible fluids with different densities, depths, and viscosities are subjected to a destabilizing temperature contrast. When the buoyancy number B (i.e., the ratio of the stabilizing chemical density anomaly to the destabilizing thermal density anomaly) is lower than 0.3–0.5, the whole layer regime develops, with a deformed interface and convective patterns over the whole tank depth. The system systematically evolves toward one‐fluid Rayleigh‐Bénard convection because of stirring. However, the two isolated fluids can persist for very long time compared to the characteristic timescale of thermal convection and give rise to numerous transient behaviors. Of particular interest for planetary mantles are the pulsatory dynamics, where the interface between the two layers deforms in large domes moving up and down quasiperiodically: According to the scaling laws derived from the experiments, such a mechanism could indeed provide a simple and single physical explanation for the superswells observed at present on Earth and more generally for the long‐term episodicity in planetary interiors observed in geological records.
Shear and compaction band formation on an elliptic yield cap
Authors: Rudnicki John W.
Published: March 2004

Conditions for shear and compaction localization are examined for stress states on an elliptic yield cap in the space of Mises equivalent shear stress and mean normal compressive stress σ. Localization is predicted to occur when the slope of the hydrostatic stress versus inelastic volume strain curve falls to a critical value kcrit. When applied to the standard triaxial test, the analysis reveals a transition from compaction localization to shear localization as lateral confining stress σc decreases below a particular value. This value also corresponds to the largest value of kcrit, which is zero if normality is satisfied and slightly positive if not, for either shear or compaction bands. For σc larger than the transition value, compaction bands are the only mode of localized deformation predicted, and kcrit becomes increasingly negative with increasing σc. For σc smaller than the transition value, both shear bands and compaction bands are possible, but the value of kcrit is larger for shear bands. These results are consistent with experimental observations of compaction bands on relatively flat portions of the stress versus strain curve, corresponding to kcrit ≈ 0, and with their occurrence in a limited range of σc. As σc is decreased from the transition value, the predicted angle between the normal to the shear band and the maximum compression direction increases rapidly from 0° (for a compaction band) to 20°–30°. This rapid increase provides a possible explanation for the infrequent observation of very low angle shear bands.
Remote sensing oceanography of a harmful algal bloom off the coast of southeastern Vietnam
Authors: Tang Dan Ling , Kawamura Hiroshi , Doan‐Nhu Hai , Takahashi Wataru
Published: March 2004

Harmful algal blooms (HABs) in the southeastern Vietnamese coastal waters have caused large economic losses in aquacultured and wild fisheries in recent years; however, there have been few oceanographic studies on these HAB events. The present study reports an extensive HAB off southeastern Vietnamese waters during late June to July 2002 with in situ observations and analyzes the oceanographic conditions using satellite remote sensing data. The HAB had high chlorophyll a (Chl a) concentrations (up to 4.5 mg m−3) occurring ∼200 km off the coast and ∼200 km northeast of the Mekong River mouth for a period of ∼6 weeks. The bloom was dominated by the harmful algae haptophyte Phaeocystis cf. globosa and caused a very significant mortality of aquacultured fish and other marine life. In the same period, sea surface temperature (SST) imagery showed a cold water plume extending from the coast to the open sea, and QuikScat data showed strong southwesterly winds blowing parallel to the coastline. This study indicated that the HAB was induced and supported by offshore upwelling that brings nutrients from the deep ocean to the surface and from coastal water to offshore water and that the upwelling was driven by strong wind through Ekman transport when winds were parallel to the coastline. This study demonstrated the possibility of utilizing a combination of satellite data of Chl a, SST, and wind velocity together with coastal bathymetric information and in situ observations to give a better understanding of the biological oceanography of HABs.
Modeling of formation and distribution of secondary aerosols in the Milan area (Italy)
Authors: Andreani‐Aksoyoglu S. , Prévôt A. S. H. , Baltensperger U. , Keller J. , Dommen J.
Published: March 2004

The performance of an aerosol module of the three‐dimensional Eulerian model CAMx (Comprehensive Air Quality Model with Extensions) was evaluated in a domain covering the Po Basin in northern Italy. Concentrations of secondary aerosol species such as particulate NO3−, NH4+, SO42−, and SOC (secondary organic carbon) were calculated for the particle size below 2.5 μm and compared with the data available from a field experiment, which took place in May–June 1998. Model results for the inorganic aerosols were comparable to the measurements at an urban and a rural station. Sensitivity studies with reduced anthropogenic NOx and volatile organic carbon (VOC) emissions showed that SOC behaves in the same way as ozone, i.e., decreases with reduced VOC emissions and increases with reduced NOx emissions in the plume where ozone production is predicted to be VOC sensitive. Sensitivity of secondary aerosol formation to NH3 and NOx emissions was studied by reducing these emissions. Varying NH3 emissions led to an almost linear change in secondary aerosol mass at sites with low NH3. At ammonia‐rich sites, on the other hand, availability of nitrate became important for the further formation of secondary aerosols. Monoterpene emissions were predicted to contribute about 25% of the secondary organic aerosols produced in the northern part of the model domain, which is mostly a forested area.
Hydrological flow paths during snowmelt: Congruence between hydrometric measurements and oxygen 18 in meltwater, soil water, and runoff
Authors: Laudon Hjalmar , Seibert Jan , Köhler Stephan , Bishop Kevin
Published: March 2004

Streamflow generation in boreal catchments remains poorly understood. This is especially true for snowmelt episodes, which are the dominant hydrological event in many seasonally snow covered regions. We examined the spatial and temporal aspects of flow pathways by linking detailed oxygen 18 observations of stream, melt, soil, and groundwater with hydrometric measurements in a small catchment in northern Sweden during the snowmelt period. The results demonstrate that soil horizons below 90 cm were hardly affected by the approximately 200 mm of snowmelt water infiltrating into the soil during the spring. The approximately sixtyfold increase in runoff, from 0.13 mm d−1 to 8 mm d−1, was generated by a 30–40 cm rise of the groundwater level. The total runoff during the snowmelt period from late April to late May was 134 mm, of which 75% was preevent water. Mass balance calculations based on hydrometric and isotopic data independently, both using upscaling of a hillslope transect to the entire 13‐ha catchment, provided similar results of both water storage changes and the amount of event water that was left in the catchment after the snowmelt. In general, groundwater levels and runoff were strongly correlated, but different functional relationships were observed for frozen and unfrozen soil conditions. Although runoff generation in the catchment generally could be explained by the transmissivity feedback concept, the results suggest that there is a temporal variability in the flow pathways during the spring controlled by soil frost during early snowmelt.