bluuebunny/crossref_metadata_2025 huggingface dataset:
Lesch‐Nyhan syndrome and its pathogenesis: Normal nicotinamide‐adenine dinucleotide but reduced ATP concentrations that correlate with reduced poly (ADP‐ribose) synthetase activity in HPRT‐deficient lymphoblasts
Authors: McCreanor G. M. , Harkness R. A.
Published: July 2006

In hypoxanthine (guanine) phosphoribosyltransferase‐ (HPRT; EC 2.4.2.8) deficient lymphoblasts, ATP but not nicotinamide‐adenine dinucleotide coenzyme concentrations are reduced by limited nutrition. Such reduced ATP concentrations are correlated with reduced poly(ADP‐ribose) synthetase (polyADPRT; EC 2.4.2.30) activity; this reduces the breakdown of nicotinamide‐adenine dinucleotide coenzymes and thus explains their normal intracellular concentrations. Since reductions in poly(ADP‐ribose) synthetase activity reduce DNA repair, alterations in DNA could accumulate even in non‐multiplying cells such as neurons, especially in the continuously active ‘respiratory centre’. Our Lesch‐Nyhan patients suffered respiratory deaths between 15 and 20 years of age.
Biliary Ascariasis: A Review
Authors: Shah Omar Javed , Zargar Showkat Ali , Robbani Irfan
Published: July 2006

Ascariasis, a helminthic infection of humans, is the most common parasitic infestation of the gastrointestinal tract. It infects about 25% of the world’s population; around 20 thousand deaths occur per year from an adverse clinical course of the disease. This review is focused on biliary ascariasis, examining in some detail the pathogenesis of the disease with special reference to postcholecystectomy ascariasis and related issues. Although an endemic disease of tropical and subtropical countries, increasing population migration facilitated by fast improving communication facilities demands that clinicians everywhere be familiar with the clinical profile and management of biliary ascariasis.
Adaptations in the lipid metabolism of the protozoan parasite Trypanosoma brucei
Authors: van Hellemond Jaap J. , Tielens Aloysius G.M.
Published: July 2006

Trypanosomes are unicellular parasites and like all decent parasites, they try to obtain from the host as much material as possible, including lipids. However, the needs of a parasite are not always the same as those of the host, and therefore, mostly, some biosynthetic work still has to be done by the parasite itself. Very often at least modifications of the lipid components that are acquired from the host have to be made. Furthermore, next to the lipids Trypanosoma brucei indeed obtains from the host, some other lipid components have to be synthesized de novo. Especially the processes where the metabolism of T. brucei differs from that of the host, will be discussed, as at least some of them are excellent targets for the development of urgently needed new chemotherapeutics.
Interfering polysialyltransferase ST8SiaII/STX mRNA inhibits neurite growth during early hippocampal development
Authors: Brocco Marcela A. , Frasch Alberto C.C.
Published: July 2006

Polysialic acid (PSA) attached to NCAM is involved in cell–cell interactions participating in structural and functional plasticity of neuronal circuits. Two polysialyltransferases, ST8SiaII/STX and ST8SiaIV/PST, polysialylate NCAM. We previously suggested that ST8SiaII/STX is the key enzyme for polysialylation in hippocampus. Here, polysialyltransferase mRNA interference experiments showed that, knock down of ST8SiaIV/PST transcripts did not affect PSA expression, but PSA was almost absent from neuronal surfaces when ST8SiaII/STX mRNA was interfered. Non‐polysialylated neurons bore a similar number of neurites per cell than polysialylated neurons. However, non‐polysialylated processes were shorter and a lower density of synaptophysin clusters accompanied this reduced neuritic growth. Therefore, ST8SiaII/STX expression is essential to allow a correct neuritic development at initial stages of hippocampus ontogeny.
Feedback Inhibition of High TGF-β1 Concentrations on Myofibroblast Induction and Contraction by Dupuytren’s Fibroblasts
Authors: WONG M. , MUDERA V.
Published: July 2006

Myofibroblasts and TGF-β1 are implicated in Dupuytren’s contracture. Transforming growth factor β1(TGF-β1) (1–10 ng/ml) increases myofibroblast induction in Dupuytren’s fibroblasts and contraction in a collagen model. However, higher doses (20–30 ng/ml) inhibit contraction in dermal fibroblasts. We hypothesized higher doses of TGF-β1 would inhibit induction of myofibroblasts and contraction by Dupuytren’s fibroblasts. Increasing doses of TGF-β1 (0–30 ng/ml) were tested on Dupuytren’s fibroblasts using immunofluorescence to determine myofibroblast upregulation and a 3D collagen model used to determine contractile forces. Flexor retinaculum fibroblasts were used as controls. TGF-β1 induced myofibroblasts in Dupuytren’s fibroblasts ( n = 3) from 12% (0 ng/ml) to 23% (12.5 ng/ml) at 24 hours but dropped to 13% at 30 ng/ml ( P < 0.05). This response was mirrored in the contraction profiles. These trends were similar for flexor retinaculum fibroblasts ( n = 3), but contractile forces and myofibroblast induction were significantly less ( P < 0.001). This is the first report of negative feedback inhibition of TGF-β1 at higher concentrations in Dupuytren’s fibroblasts.
Last glacial megafaunal death assemblage and early human occupation at Lake Menindee, southeastern Australia
Authors: Cupper Matthew L. , Duncan Jacqui
Published: July 2006

The Tedford subfossil locality at Lake Menindee preserves a diverse assemblage of marsupials, monotremes and placental rodents. Of the 38 mammal taxa recorded at the site, almost a third are of extinct megafauna. Some of the bones are articulated or semi-articulated and include almost complete skeletons, indicating that aeolian sediments rapidly buried the animals following death. New optical ages show the site dates to the early part of the last glacial (55,700 ± 1300 yr weighted mean age). This is close to the 51,200–39,800 yr Australia-wide extinction age for megafauna suggested by Roberts et al. [2001, Science 292:1888–1892], but like all previous researchers, we cannot conclusively determine whether humans were implicated in the deaths of the animals. Although an intrusive hearth at the site dating to 45,100 ± 1400 yr ago is the oldest evidence of human occupation of the Darling River, no artifacts were identified in situ within the sub-fossil-bearing unit. Non-anthropogenic causes, such as natural senescence or ecosystem stress due to climatic aridity, probably explain the mortality of the faunal assemblage at Lake Menindee.
Acquiring “Knowledge of Our Own Continent”: Geopolitics, Science, and Jeffersonian Geography, 1783–1803
Authors: ALLEN DEBORAH
Published: July 2006

In his role as a promoter of scientific exploration of North America, Thomas Jefferson shared with Jedidiah Morse, considered by many to be the father of American geography, the patriotic desire to counteract misinformation furnished by “imperfect and erroneous sketches” describing the continent's geography by European writers. Yet his interest in the science of geography was also motivated by a concern with America's self-image in the realm of international politics, learning, and commerce. In the summer of 1802 Jefferson was prompted to send an exploring party to North America's westernmost territories in response to reading Voyages from Montreal, Alexander Mackenzie's account of his voyages across the continent to its northwest coast. At the end of his narrative, the Scottish explorer had encouraged Britain's control of a region that, if certain natural obstacles were overcome, might supply fur and fish to “the markets of the four quarters of the globe,” and proposed a line of fortified posts to be established to maintain the British Empire's presence from Lake Winnipeg to the Pacific. Jefferson understood that such action would obstruct America's westward expansion, block Russian advances from Alaska, and thus make possible a British dominion linking two great oceans. Edward Thornton, the British minister to the United States, would later observe that Mackenzie's discoveries had provoked the American President, who in 1803 was also the president of the American Philosophical Society, to concretize his dream “to set on foot an expedition entirely of a scientific nature for exploring the Western continent of America,” and that he was, furthermore, “ambitious in his character of a man of letters and science, of distinguishing his Presidency by a discovery” of a route to the Pacific Ocean by way of the Missouri, “now the only one left to his enterprise, the Northern Communication having been so ably explored and ascertained by Sir Alexander Mackenzie's journeys.
“Latent color” and “exaggerated snow”: whiteness and race in Harriet Prescott Spofford's “The Amber Gods”
Authors: ELLIS R. J.
Published: July 2006

“We've some splendid old point-lace in our family, yellow and fragrant … all tags and tangles and fibrous and bewildering” (7). This is the way that Giorgione (Yone) Willoughby opens her tale, “The Amber Gods”; instead of “beginn[ing] at the beginning” (7) she offers a luxuriant description of a type of old lace, rich in sense impressions. Bewilderingly, like her point lace, her story's introductory proprieties are delayed until the second paragraph. Such improper sensuality disconcerted many of her Protestant New England readers when her story appeared in the Atlantic in 1860. Yet also, hypocritically, at this time, a rising bourgeoisie, secure in its socioeconomic position, was increasingly embracing a phase of conspicuous leisure and consumption. It is with this embrace, and its dark origins and dark legacies, that “The Amber Gods” engages.
From Toscanini to Tennessee: Robert Riskin, the OWI and the Construction of American Propaganda in World War II
Authors: SCOTT IAN
Published: July 2006

Hollywood screenwriter Robert Riskin was the head of the Overseas Branch of the Office of War Information during World War II. His role not only helped to shape the administrative and managerial strategy of the agency but also created a body of documentary film work that was arguably the most incisive of the entire war. And yet in most accounts of American propaganda production during the last sixty years, as well as specifically OWI conduct and development, Riskin's role has been confined to that of a functionary, a name that is only mentioned in cursory anecdotes. The aim of this article, therefore, is not only to foreground Riskin's contribution to the OWI, neglected though that is, but to argue that Riskin's documentary programme, Projections of America, was actually one of the most important, influential and substantive collections of propaganda made during the war.
The American Southwest Audrey Goodman, Translating Southwestern Landscapes: The Making of an Anglo Literary Region (Tucson: University of Arizona Press, 2002, $40.00). Pp. 250. ISBN 0 1865 2187 5. Molly H. Mullin, Culture in the Marketplace: Gender, Art, and Value in the Amerian Southwest (Durham: Duke University Press, 2001, $64.95 cloth, $19.95 paper). Pp. 248. ISBN 0 822 32610 8, 0 8223 2168 3. Curtis M. Hinsley and David R. Wilcox, The Lost Itinerary of Frank Hamilton Cushing (Tucson: University of Arizona Press, 2002, $50.00). Pp. 450. ISBN 0 8165 2269 3. Hal K. Rothman (ed.), The Culture of Tourism, the Tourism of Culture: Selling the Past to the Present in the American Southwest (Albuquerque: University of New Mexico Press, 2003, $34.95). Pp. 250. ISBN 0 826 32928 4.
Authors: PADGET MARTIN
Published: July 2006

Scholars have been debating what constitutes “the Southwest” for decades. Thirty years ago, geographer D. W. Meinig began his landmark study Southwest: Three Peoples in Geographical Change, 1600–1970 by stating: “The Southwest is a distinct place to the American mind but a somewhat blurred place on American maps.” For Meinig, the crucial determining factor in constituting the geographical parameters of his own study was the coincidence of Native American and Mexican American settlement patterns in Arizona, New Mexico and around El Paso, Texas. The watersheds of the Gila River in Arizona and the Rio Grande in New Mexico provide the focus of his study of the historical interaction of Indians, Mexican Americans and Anglos through the successive periods of Spanish colonialism, Mexican independence and American rule. The historical geographer Richard Francaviglia has challenged the relatively narrow focus of Meinig's study by calling for a more expansive consideration of the Greater Southwest, which, in addition to the core of Arizona and New Mexico, also includes parts of Colorado, Utah, Texas and the northern states of Mexico. He rationalizes, “The southwestern quadrant of North America is, above all, characterized by phenomenal physical and cultural diversity that regionalization tends to abstract or simplify. The more one tries to reduce this complexity, the smaller the Southwest becomes on one's mental map.”2
Writing American Literary History Sacvan Bercovitch (ed.), The Cambridge History of American Literature (Cambridge: Cambridge University Press, 1994–2005, £495.00). Volume One: 1590–1820 (1994, £70.00). Pp. xiii+829. ISBN 0 521 30105 [squf ]. Volume Two: Prose Writing, 1820–1865 (1995, £75.00). Pp. xviii+887. ISBN 0 521 30106 8. Volume Three: Prose Writing, 1860–1920 (2005, £80.00). Pp. xi+813. ISBN 0 521 30107 6. Volume Four: Nineteenth-Century Poetry, 1800–1910 (2004, £75.00). Pp. x+562. ISBN 0 521 30108 4. Volume Five: Poetry and Criticism, 1900–1950 (2003, £75.00). Pp. xi+624. ISBN 0 521 30109 2. Volume Six: Prose Writing, 1910–1950 (2002, £70.00). Pp. xx+620. ISBN 0 521 49731 0. Volume Seven: Prose Writing, 1940–1990 (1999, £75.00). Pp. xxiii+795. ISBN 0 521 49732 9. Volume Eight: Poetry and Criticism, 1940–1995 (1996, £75.00). Pp. viii+545. ISBN 0 521 49733 7.
Authors: GRAY RICHARD
Published: July 2006

Each generation needs to rewrite literary history. And it may be that this generation needs to do it more than most, if only because the proliferation of schools and theories has turned what was once common critical ground into a battlefield. American books, among others, have become a site of struggle, and American writers have been among those caught in the criss-crossing searchlights of ethnic and gender studies, interdisciplinary investigations and studies of popular culture, language and communication. Just how far things have gone can be measured by the fact that every term in the phrase “history of American literature,” is now open to debate. The textuality of history and the historicity of the text have become the most contentious issues in contemporary criticism, while the question of nationhood, in particular, is under scrutiny. In a famous phrase, Walt Whitman described his work as a language experiment, an attempt to summon a nation into being through words. The slippery, plural nature of American identity and the bewildering contingencies of American history that drove Whitman to say this feed into the more challenging of the recent accounts of American writing.
The Common European Framework of Reference for Languages: Content, purpose, origin, reception and impact
Authors: Little David
Published: July 2006

Since its circulation in two draft versions in 1996, and especially since its commercial publication in English and French in 2001, the Common European Framework of Reference for Languages (CEFR) has come to dominate discussion of L2 curricula, the assessment of L2 proficiency, and L2 teaching and learning in Europe. Although it is widely referred to, however, the CEFR remains relatively little known beyond the summaries of its six proficiency levels presented in the so-called ‘global scale’ and ‘self-assessment grid’. This article summarises the CEFR's content, purpose, and origins; describes its reception, paying particular attention to its impact on L2 teaching and learning (especially via its companion piece, the European Language Portfolio) and on the assessment of L2 proficiency; and concludes with a brief consideration of present challenges and future prospects.
Suppression, release and canopy recruitment in five tree species from a seasonal tropical forest in western Thailand
Authors: Baker Patrick J. , Bunyavejchewin Sarayudh
Published: July 2006

We used tree-rings to reconstruct long-term patterns of suppression, release and growth among five sympatric canopy tree species representing the full range of shade tolerance in a seasonal tropical forest in western Thailand. We expected that the frequency and duration of suppression and release events would be positively correlated with shade tolerance. All five species showed evidence of major and moderate growth releases. As expected, Melia azederach, an extreme heliophile, had the fewest releases. However, among the other species the number of major releases was consistent across the range of shade tolerance. The most significant difference among the species was the number of moderate releases recorded. There was a general positive correlation between the number of moderate releases and shade tolerance; however, Chukrasia tabularis, a relatively shade-intolerant species, had an anomalously high number of moderate releases. The study species also showed considerable variation in canopy accession strategies. The least common canopy accession strategy was establishment in the understorey and growth into the canopy in the absence of any gaps. However, with the exception of Melia, all four study species had one or more individuals that successfully reached the canopy using each of the four canopy accession strategies. These results highlight the importance of periodic or episodic bouts of gap formation on canopy tree recruitment and the utility of tree-rings for reconstructing long-term growth patterns in tropical trees.
The relative roles of environment, history and local dispersal in controlling the distributions of common tree and shrub species in a tropical forest landscape, Panama
Authors: Svenning Jens-Christian , Engelbrecht Bettina M. J. , Kinner David A. , Kursar Thomas A. , Stallard Robert F. , Wright S. Joseph
Published: July 2006

We used regression models and information-theoretic model selection to assess the relative importance of environment, local dispersal and historical contingency as controls of the distributions of 26 common plant species in tropical forest on Barro Colorado Island (BCI), Panama. We censused eighty-eight 0.09-ha plots scattered across the landscape. Environmental control, local dispersal and historical contingency were represented by environmental variables (soil moisture, slope, soil type, distance to shore, old-forest presence), a spatial autoregressive parameter (ρ), and four spatial trend variables, respectively. We built regression models, representing all combinations of the three hypotheses, for each species. The probability that the best model included the environmental variables, spatial trend variables and ρ averaged 33%, 64% and 50% across the study species, respectively. The environmental variables, spatial trend variables, ρ, and a simple intercept model received the strongest support for 4, 15, 5 and 2 species, respectively. Comparing the model results to information on species traits showed that species with strong spatial trends produced few and heavy diaspores, while species with strong soil moisture relationships were particularly drought-sensitive. In conclusion, history and local dispersal appeared to be the dominant controls of the distributions of common plant species on BCI.
Seedling species determines rates of leaf herbivory in a Malaysian rain forest
Authors: Eichhorn Markus P. , Compton Stephen G. , Hartley Sue E.
Published: July 2006

Seedlings of five species in the Dipterocarpaceae were grown in experimental plots in Sabah, Malaysia. These were sited both in gaps and understorey and on alluvial and sandstone soils. Half of all seedlings were provided with a complete fertilizer. Herbivore damage levels were recorded on over 25 000 individual leaves in four surveys over the course of 2 y. Rates of herbivory were lower on mature leaves (0.07–0.8% leaf area mo−1 among species) than new leaves (2.1–4.4% leaf area mo−1). There were no overall effects of light conditions, soil type, fertilizer treatment or time on rates of herbivory. The only consistent source of variation was that between species, with the three alluvial-specialist species suffering higher rates of damage than the two sandstone-specialists. Mature leaves of alluvial species received greater damage in sandstone soils, whereas sandstone species were damaged at equivalent rates on both soil types. New leaves were more damaged on their native soil type. Published herbivory rates vary in the timescales and methods of measurement. Nevertheless, the few comparable studies confirm that herbivory rates on seedlings in tropical rain forests are remarkably constant over time and across experimental treatments.
Site occupancy and density of sympatric Gaboon viper (Bitis gabonica) and nose-horned viper (Bitis nasicornis)
Authors: Luiselli Luca
Published: July 2006

The presence and density of two sympatric, large-sized vipers (the Gaboon viper, Bitis gabonica and the nose-horned viper, Bitis nasicornis) were studied along several transects, during both dry and wet seasons, and at different times of day, in southern Nigeria (West Africa). Three habitat types were found along the various transects (mature rain forest (MF), secondary rain forest (SF), swamp forest (SW)). The detection probabilities for these vipers were modelled with a set of competing models, and the various models were ordered by Akaike Information Criterion procedures. Two classes of models were used: the single-season model, and the multi-species model. The best models (single-season model) suggested that: for the Gaboon viper, habitat types SF and SW were particularly important in detecting this species, especially during the rainy season at 08h00–16h00. For nose-horned vipers, the best models had SW and MF as site-covariates. Application of the multi-species model revealed that there were different detection functions if both species are present at a site, with a ‘negative’ interaction of occupancy between the species. Females and males were similarly detectable in a logistic regression model, but feeding status and pregnancy slightly increased detection probability in a logistic regression model. Viper density was modelled by a DISTANCE sampling procedure. The density of one species tended to be inversely correlated to the density of the other, suggesting that (1) the rain-forest environment does not support abundant populations of both vipers when sympatric, and (2) the two Bitis species subtly partition the habitat resources.
Spatial variation of soil respiration across a topographic gradient in a tropical rain forest in French Guiana
Authors: Epron Daniel , Bosc Alexandre , Bonal Damien , Freycon Vincent
Published: July 2006

The objective of this study was to analyse the factors explaining spatial variation in soil respiration over topographic transects in a tropical rain forest of French Guiana. The soil of 30 plots along six transects was characterized. The appearance of the ‘dry to the touch’ character at a depth of less than 1.2 m was used to discriminate soils exhibiting vertical drainage from soils exhibiting superficial lateral drainage and along with colour and texture, to define five classes from well-drained to strongly hydromorphic soils. Spatial variation in soil respiration was closely related to topographic position and soil type. Increasing soil water content and bulk density and decreasing root biomass and soil carbon content explained most of the decrease in soil respiration from the plateaux (vertically drained hypoferralic acrisol) to the bottomlands (haplic gleysol). These results will help to stratify further field experiments and to identify the underlying determinants of spatial variation in soil respiration to develop mechanistic models of soil respiration.
Seedling survival and growth of three ectomycorrhizal caesalpiniaceous tree species in a Central African rain forest
Authors: Newbery D. M. , Chuyong G. B. , Zimmermann L. , Praz C.
Published: July 2006

Tree recruitment is determined in part by the survivorship and growth of seedlings. Two seedling cohorts of the three most abundant caesalpiniaceous species forming groves at Korup, Cameroon, were followed from 1995/1997 to 2002, to investigate why Microberlinia bisulcata, the most abundant species, currently has very few recruits compared with Tetraberlinia korupensis and T. bifoliolata. Numbers of seedlings dying, and the heights and leaf numbers of survivors, were recorded on 30 occasions. Survivorship after 2.5 y was 30% for M. bisulcata and 59% for the similar Tetraberlinia spp. together. After 7 y the corresponding values were 4 and 21%. Growth of all species was slow for the first 4 y; but survivors of T. korupensis became 63% taller, as the other species stagnated, by 7 y. The poor recruitment of M. bisulcata was the result of its very low seedling survival. Within species, the tallest seedlings of M. bisulcata and T. bifoliolata, but medium-height ones of T. korupensis, survived longest. This was likely due to higher root allocation in T. korupensis. Seedling dynamics of M. bisulcata and T. korupensis over 7 y accorded well with relative abundances of adult trees; T. bifoliolata is predicted to recruit later.
Spatial associations of humus, nutrients and soils in mixed dipterocarp forest at Lambir, Sarawak, Malaysian Borneo
Authors: Baillie I. C. , Ashton P. S. , Chin S. P. , Davies S. J. , Palmiotto P. A. , Russo S. E. , Tan S.
Published: July 2006

Discrete humus layers are common on podzols under temperate coniferous and tropical heath forests, and patchy layers also occur under some temperate broadleaved forests on non-podzolic soils. We used multiple data sets to test the reported association of humus with oligotrophic but non-podzolic soils under non-heath dipterocarp forest at Lambir, Sarawak. We examined the distribution, morphology and nutrient dynamics of necromass on soils derived from sandstone and shale. Concentrations of the main mineral nutrients were lower in fresh litter on the very oligotrophic sandstone soils than on shale. The rates of litterfall were similar, so that annual litterfall fluxes of all nutrients were lower on sandstone. The lower nutrient concentrations and fluxes in the litter on sandstone resulted in slower decomposition, longer residence times and larger standing crops of forest-floor necromass, with lower concentrations of nutrients. The necromass on sandstone sequestered significantly more N, K and Mg but less Ca and Mn than on shale, with no significant difference for P. The variations in necromass nutrient dynamics were associated with morphological differences. There were mats of densely rooted humus under the litter on sandstone, whereas litter lay directly over the mineral topsoil on shale. Spatial associations with soil nutrients were weak for necromass thickness, but clear for humus. The proportions of nutrients in the litterfall and necromass reflected the stoichiometric profiles of the soils. We attribute the differences in necromass nutrient dynamics and their association with soil reserve nutrients to lower rates of nutrient replenishment from the weathering of sandstone than from shale. Necromass characteristics are robust field indicators of multivariate edaphic differences in these and other tropical forests on Acrisols/Ultisols derived from Tertiary clastic sediments.
Observation of three‐dimensional structures of quasi‐periodic echoes associated with mid‐latitude sporadic‐E layers by MU radar ultra‐multi‐channel system
Authors: Saito S. , Yamamoto M. , Hashiguchi H. , Maegawa A.
Published: July 2006

Quasi‐periodic (QP) backscatter observed by VHF radars associated with the mid‐latitude Sporadic‐E (Es) layers is characterized by distinct striations on range‐time‐intensity (RTI) plots. Two competing models claim to explain the structure of unstable regions that scatter the radar waves: horizontally drifting patches at an almost constant altitude and unstable regions elongated in altitude along the geomagnetic field line. We have conducted interferometric imaging observations of QP radar echoes to investigate spatial structures of QP echoes, precisely. Kyoto University's newly developed ultra‐multi‐channel receiving system of middle and upper atmosphere (MU) radar was used. We used 19 independent channels for the radar imaging, and determined the three‐dimensional structure and the motion of the QP echoes. During the observation from 30 May to 02 June 2005, well‐defined QP echoes were observed on the nights of 31 May, 01 June, and 02 June 2005. Some of QP echoes were found at altitudes higher than 120 km and appeared to descend in altitude as they approached the radar. This result suggests that backscatter regions are developed along the geomagnetic field line from Es layer altitudes to as high as 130 km and that the fluctuations in plasma density and electric field observed by Pfaff et al. (2005) using in‐situ measurements form a part of QP echoes.
Recent trends in anthropogenic mercury emission in the northeast United States
Authors: Sigler J. M. , Lee X.
Published: July 2006

We combine wintertime measurements of total gaseous mercury (TGM) with a combustion tracer (carbon dioxide) at a background site in Connecticut to investigate changes in regional Hg emission from 1999/2000 through 2003/2004. This method allows timelier flux estimates than inventory approaches. We find a 20% decrease in emission between 1999/2000 and 2003/2004, although the rate has increased since 2001/2002. Air trajectory analysis reveals a source region of Hg influencing the site that encompasses most of the mid‐Atlantic and New England states, and Maryland and Delaware, with small interannual variation. The significant interannual changes in Hg emission therefore cannot be fully explained by climatological changes. Inventory calculations of Hg flux from the regional electric power sector show significant correlation with the emission trend derived from the atmospheric measurements, suggesting that the power sector strongly influences the regional Hg flux to the atmosphere. However, averaged over the five winters, the Hg flux from the power sector was 47–75% of the atmospheric flux, which is assumed to be >95% elemental Hg. If 50% or more of Hg emitted by power sources is speciated and deposits locally, the power sector can account for only 23–40% of the observed elemental Hg flux to the atmosphere. Possible explanations include conversion of some reactive Hg emitted by power plants to elemental Hg, underestimation of inventory emissions from sources outside the power sector, the possibility that emissions from municipal and medical waste combustion have not been curbed to the EPA targeted level, or that a combination of these factors exists.
On the ecohydrology of structurally heterogeneous semiarid landscapes
Authors: Caylor Kelly K. , D'Odorico Paolo , Rodriguez‐Iturbe Ignacio
Published: July 2006

Clarification of the coupled ecohydrological mechanisms that determine the spatial pattern and structural characteristics of vegetation in water‐limited landscapes remains a vexing problem in both hydrological and vegetation sciences. A particular challenge is the fact that the spatial pattern of vegetation is both a cause and effect of variation in water availability in semiarid ecosystems. Here we develop a methodology to derive the landscape‐scale distribution of water balance and soil moisture in a patchy vegetation mosaic based on the statistics of an underlying poisson distribution of individual tree canopies and their accompanying root systems. We consider the dynamics of water balance at a point to be dependent on the number of intersecting tree root systems and overlapping tree canopies. The coupling of individual pattern to landscape‐scale distribution of soil water balance allows for investigations into the role of tree density, average canopy size, and the lateral extension of tree root systems on the spatiotemporal patterns of soil moisture dynamics, plant water uptake, and plant stress in a wide range of open woodland ecosystems. Our model is applied to southern African savannas, and we find that locations in the landscape that contain average vegetation structure correspond to conditions of minimum stress across a wide range of annual rainfall and vegetation densities. Furthermore, observed vegetation structural parameters are consistent with an optimization that simultaneously maximizes plant water uptake while minimizing plant water stress. Finally, the model predicts adaptive changes in the optimal lateral extent of plant roots which decreases with increasing rainfall along a regional gradient in mean annual precipitation.
On the numerical simulation of dust devil–like vortices in terrestrial and Martian convective boundary layers
Authors: Kanak Katharine M.
Published: July 2006

This paper presents an overview of the numerical simulation studies to date, of vertical vortices, or dust devil–like vortices, which arise in atmospheric convective boundary layers (CBLs). The similarities and differences between these studies are highlighted. In addition, the accuracy of the simulated vortices as compared with observed physical characteristics is discussed. It is notable that vertical vortices formed in all of the studies considered for both Mars and Earth simulations, despite the fact that they have not often been pointed out in laboratory and numerical simulations of CBLs. A possible implication of this finding is that non‐visible vertical vortices may even be ubiquitous and thus may play an important role in boundary layer transports. If this is so, they may have implications for pollution and hazardous waste transports, as well as on impacts on descent and landing of spacecraft on Mars.
Measurement and modeling of background aerosols in remote marine atmospheres: Implications for sea salt flux
Authors: Halthore Rangasayi N. , Caffrey Peter F.
Published: July 2006

Aerosol optical thickness (AOT) measurements at two remote Pacific Ocean locations in the northern hemisphere reveal an absolute minimum in the solar spectrum of magnitude ∼0.02 at 550 nm and an Ångström exponent of about 1. Along with similar results from measurements at continental sites reported previously, this minimum indicates the presence of background aerosol at both continental and marine sites. A measure of marine boundary layer AOT is obtained by taking the difference between values measured at sea‐level and at altitude on Mauna Loa, Hawaii. This then is compared with AOT calculated by a Lagrangian boundary‐layer microphysical aerosol model using sea‐salt and sulfate aerosols and with meteorology input from a mesoscale model to provide estimates of the sea salt flux that are within a factor of 7 of a hybrid Monahan‐Smith formulation.
Hydraulic‐fracturing controlled dynamics of microseismic clouds
Authors: Shapiro S. A. , Dinske C. , Rothert E.
Published: July 2006

Several dynamic processes related to propagation of hydraulic fracture modify the stress state in rocks and, therefore, they are relevant for triggering of microseismicity. For instance, these are the creation of a new fracture volume, fracturing fluid loss and its infiltration into reservoir rocks as well as diffusion of the injection pressure into the pore space of surrounding rocks and inside the fracture. Using real data, we show that some of these processes can be seen from features of spatio‐temporal distributions of the induced microseismicity. Especially, the initial stage of fracture volume opening as well as the back front of the induced seismicity starting to propagate after termination of the fluid injection can be well identified and used for reservoir engineering.
Weak influences of the Earth's magnetic field on ocean circulation
Authors: Tyler R. H.
Published: July 2006

In this work, models for the Earth's magnetic field and global ocean circulation are combined to produce the first quantitative estimates of the electromagnetic Lorentz forces which couple abyssal ocean layers with the energetic surface layers. Under present conditions these coupling forces are very weak: typical time scales for the transfer of momentum to the lower layers are about three thousand years. But they are worth describing quantitatively because of the following: 1) The coupling rapidly increases in proportion with the square of the Earth's magnetic field strength; 2) This process is intrinsically efficient at accelerating slow or stagnant abyssal ocean layers; 3) These time scales, while long, are similar to those of rapid climate variability which are expected to be associated with past variability in ocean circulation, overturning and heat transport.
Nature of Pi1B pulsations as inferred from ground and satellite observations
Authors: Lessard M. R. , Lund E. J. , Jones S. L. , Arnoldy R. L. , Posch J. L. , Engebretson M. J. , Hayashi K.
Published: July 2006

The occurrence of Pi1B pulsations is well‐documented, including the fact that these pulsations can be observed both on the ground and at geosynchronous orbit at substorm onset, although information about their propagation characteristics has been lacking. In this paper, data are presented from FAST, GOES 9 and various ground stations that show the simultaneous observations of Pi1B pulsations in association with an onset. While the data at GOES 9 show that the pulsations are compressional in nature, data from FAST show the presence of shear mode waves, implying that Pi1B mode conversion of some type must take place in the region between geosynchronous orbit and FAST altitudes. An additional point is that Pi1B pulsations apparently propagate through auroral phenomena routinely, begging the question of what role they may play.
Advective transport of CO2in permeable media induced by atmospheric pressure fluctuations: 1. An analytical model
Authors: Massman W. J.
Published: July 2006

Advective flows within soils and snowpacks caused by pressure fluctuations at the upper surface of either medium can significantly influence the exchange rate of many trace gases from the underlying substrate to the atmosphere. Given the importance of many of these trace gases in understanding biogeochemical cycling and global change, it is crucial to quantify (as much as possible) any impact these flows can have on the transport of these gases. This study (part 1 of 2) details a new model describing the influence that naturally occurring, pressure‐driven, oscillatory advective flows have on CO2profiles within soils and snowpacks and on the associated CO2fluxes emanating from the underlying source. This model, which consists of two layers with differing permeability and CO2source strength, is developed for both a dispersive and a nondispersive medium. The pressure forcing and the CO2response, modeled as plane waves in time and the horizontal direction, have amplitudes that vary in the vertical direction as described by analytical solutions to the diffusion equation (for pressure) and the advective‐diffusive and dispersive‐diffusive equations (for CO2). In the case of a dispersive medium, the dispersion coefficient is derived in terms of the horizontal wave number and amplitude of the pressure forcing at the upper surface and the vertical structure and dispersivity of the medium. Diffusive flux enhancement factors, developed for the dispersive and nondispersive models, are expressed as functions of the surface amplitude of the pressure forcing, the permeability and cross‐sectional shape and dimension of the pore tubes of the medium, and the vertical structure of the medium. Results indicate that advective flows induced by naturally occurring atmospheric pressure fluctuations are likely to enhance diffusive fluxes more in a dispersive medium than a nondispersive medium. However, such pressure forcing can significantly enhance diffusive fluxes in either medium.
Advective transport of CO2 in permeable media induced by atmospheric pressure fluctuations: 2. Observational evidence under snowpacks
Authors: Massman W. J. , Frank J. M.
Published: July 2006

Meadow and forest CO2 amounts sampled beneath an approximately meter deep (steady state) snowpack at a subalpine site in southern Rocky Mountains of Wyoming are observed to vary by nearly 200 ppm over periods ranging from 4 to 15 days. This work employs the model of periodic, pressure‐induced, advective transport in permeable media developed in part 1 of this study to investigate these CO2 fluctuations. With the aid of this physically based model, inferences are made about the nature of the physical properties of both the forcing mechanism and the snowpack that contribute to these periodic variations in undersnow CO2. Results are consistent with the hypothesis that the undersnow CO2 is being driven by advective flows induced by pressure fields created when the wind interacts with the local aerodynamic roughness elements (nearby mountain peaks, forest edges, snowdrifts). Nonharmonic spectral and cospectral techniques indicate that the wind modulates the low‐frequency temporal dynamics of the undersnow CO2, whereas comparisons of the modeled and observed time lag between the surface forcing and the response of the undersnow CO2 suggest that site topography determines the horizontal structure of the wind (surface pressure) forcing. It is also suggested here that the snowpack is at most a weakly dispersive medium. Finally, because the model includes a CO2 source term in the soil underlying the snowpack, other findings suggest that both the wintertime CO2 fluxes emanating from the snowpack and the soil respiration rates may vary significantly between a meadow soil and a forest soil at this site.
Fast thermal desorption spectroscopy study of morphology and vaporization kinetics of polycrystalline ice films
Authors: Lu Haiping , McCartney Stephanie A. , Chonde M. , Smyla D. , Sadtchenko Vlad
Published: July 2006

Fast thermal desorption spectroscopy was used to investigate the vaporization kinetics of thin (50–100nm) H2O18 and HDO tracer layers from 2–5μm thick polycrystalline H2O16 ice films at temperatures ranging from −15to−2°C. The isothermal desorption spectra of tracer species demonstrate two distinct peaks, α and β, which we attribute to the vaporization of H2O18 initially trapped at or near the grain boundaries and in the crystallites of the polycrystalline ice, respectively. We show that the diffusive transport of the H2O18 and HDO tracer molecules in the bulk of the H2O16 film is slow as compared to the film vaporization. Thus, the two peaks in the isothermal spectra are due to unequal vaporization rates of H2O18 from grain boundary grooves and from the crystallites and, therefore, can be used to determine independently the vaporization rate of the single crystal part of the film and rate of thermal etching of the film. Our analysis of the tracer vaporization kinetics demonstrates that the vaporization coefficient of single crystal ice is significantly greater than those predicted by the classical vaporization mechanism at temperatures near ice melting point. We discuss surface morphological dynamics and the bulk transport phenomena in single crystal and polycrystalline ice near 0°C.
Shape memory surfaces
Authors: Zhang Yijun , Cheng Yang-Tse , Grummon David S.
Published: July 2006

Temperature-controlled reversible surface protrusions can be made on NiTi shape memory alloys and thin films as a result of indentation induced two-way shape memory effect. First, spherical indents or scratches are made on the surface of a NiTi alloy in its martensite phase. Second, the indented or scratched surface is planarized to restore a flat surface. Reversible circular and line protrusions are produced by altering the temperature to drive the martensite to austenite phase transformation. This phenomenon can be exploited for a wide range of optical, tribological, and microelectromechanical device applications.
Electronic structure of the GdF molecule by frozen-core four-component relativistic configuration interaction calculations
Authors: Tatewaki Hiroshi , Watanabe Yoshihiro , Yamamoto Shigeyoshi , Miyoshi Eisaku
Published: July 2006

The electronic structure of GdF is calculated based on frozen-core four-component relativistic configuration interactions. The resulting excitation energies are fairly close to experiment and correctly designate the excited states. For instance, the existence of the experimentally inferred state at 0.55eV above the ground state is confirmed, having Ω=13∕2 with (4f75d+16s+1); it is 0.58eV above the ground state according to the present calculation.
Giant tunnel magnetoresistance and high annealing stability in CoFeB∕MgO∕CoFeB magnetic tunnel junctions with synthetic pinned layer
Authors: Lee Y. M. , Hayakawa J. , Ikeda S. , Matsukura F. , Ohno H.
Published: July 2006

We investigated the relationship between tunnel magnetoresistance (TMR) ratio and the crystallization of CoFeB layers through annealing in magnetic tunnel junctions (MTJs) with MgO barriers that had CoFe∕Ru∕CoFeB synthetic ferrimagnet pinned layers with varying Ru spacer thickness (tRu). The TMR ratio increased with increasing annealing temperature (Ta) and tRu, reaching 361% at Ta=425°C, whereas the TMR ratio of the MTJs with pinned layers without Ru spacers decreased at Ta over 325°C. Ruthenium spacers play an important role in forming a (001)-oriented bcc CoFeB pinned layer, resulting in a high TMR ratio through annealing at high temperatures.
Preparation of ferromagnetic (In,Mn)As with a high Curie temperature of 90K
Authors: Schallenberg T. , Munekata H.
Published: July 2006

The authors found high Curie temperatures of up to 90K in annealed (In,Mn)As epilayers grown by molecular beam epitaxy using a relatively high V/III beam flux ratio. Magnetization data suggest that increasing the As beam flux results in an increase in the effective Mn content, and the carrier transport data indicate an increase in the hole concentration from a 1019to1020cm−3 range with low-temperature annealing after growth. The highest Curie temperature was obtained in lattice matched (In,Mn)As∕Al(As,Sb) samples. Both Hall effect and magneto-optical polar Kerr rotation measurements confirm that the high Curie temperature is due to hole-mediated ferromagnetism.
Efficient dye-sensitized solar cells based on a 2-thiophen-2-yl-vinyl-conjugated ruthenium photosensitizer and a conjugated polymer hole conductor
Authors: Mozer A. J. , Wada Y. , Jiang K.-J. , Masaki N. , Yanagida S. , Mori S. N.
Published: July 2006

Efficient dye-sensitized TiO2 solar cells based on a 2-thiophen-2-yl-vinyl-conjugated ruthenium photosensitizer and a conjugated polymer poly(3,4-ethylenedioxythiophene) have been fabricated. A maximum power conversion efficiency of 2.6% is achieved when the mesoporous TiO2 layer is 5–6μm. The high fill factor (0.74), the open circuit voltage (0.78V), and the linear light intensity dependence of the short circuit current density (4.5mAcm−2 at 100mWcm−2) make these devices promising for solid state photovoltaic applications.
Ultralow surface recombination of c-Si substrates passivated by plasma-assisted atomic layer deposited Al2O3
Authors: Hoex B. , Heil S. B. S. , Langereis E. , van de Sanden M. C. M. , Kessels W. M. M.
Published: July 2006

Excellent surface passivation of c-Si has been achieved by Al2O3 films prepared by plasma-assisted atomic layer deposition, yielding effective surface recombination velocities of 2 and 13cm∕s on low resistivity n- and p-type c-Si, respectively. These results obtained for ∼30nm thick Al2O3 films are comparable to state-of-the-art results when employing thermal oxide as used in record-efficiency c-Si solar cells. A 7nm thin Al2O3 film still yields an effective surface recombination velocity of 5cm∕s on n-type silicon.