bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of an Androgen-Dependent Enhancer within the Prostate Stem Cell Antigen Gene
Authors: Jain Anjali , Lam Amanda , Vivanco Igor , Carey Michael F. , Reiter Robert E.
Published: September 2002

Prostate stem cell antigen (PSCA) is emerging as an important diagnostic marker and therapeutic target in prostate cancer. Previous studies indicated that PSCA was directly regulated by androgens, but the mechanism has not been elucidated. Here we describe the identification of a compact cell-specific and androgen-responsive enhancer between 2.7 and 3 kb upstream of the transcription start site. The enhancer functions autonomously when positioned immediately adjacent to a minimal promoter. Deoxyribonuclease I footprinting analysis with recombinant androgen receptor (AR) reveals that the enhancer contains two AR binding sites at one end. Mutational analysis of the AR binding sites revealed the importance of the higher affinity one. The dissociation constant of the high affinity binding site (androgen response element I) was determined to be approximately 87 nm. The remainder of the enhancer contains elements that function synergistically with the AR. We discuss the structural organization of the PSCA enhancer and compare it with that found in other AR-regulated genes.
The Roles of Androgen Receptors and Androgen-Binding Proteins in Nongenomic Androgen Actions
Authors: Heinlein Cynthia A. , Chang Chawnshang
Published: September 2002

The biological activity of testosterone and dihydrotestosterone is thought to occur predominantly through binding to the androgen receptor (AR), a member of the nuclear receptor superfamily that functions as a ligand-activated transcription factor. However, androgens have also been reported to induce the rapid activation of kinase-signaling cascades and modulate intracellular calcium levels. These effects are considered to be nongenomic because they occur in cell types that lack a functional AR, in the presence of inhibitors of transcription and translation, or are observed to occur too rapidly to involve changes in gene transcription. Such nongenomic effects of androgens may occur through AR functioning in the cytoplasm to induce the MAPK signal cascade. In addition, androgens may function through the sex hormone binding globulin receptor and possibly a distinct G protein-coupled receptor to activate second messenger signaling mechanisms. The physiological effect of nongenomic androgen action has yet to be determined. However, it may ultimately contribute to regulation of transcription factor activity, including mediation of the transcriptional activity of AR.
Colocalization and Ligand-Dependent Discrete Distribution of the Estrogen Receptor (ER)α and ERβ
Authors: Matsuda Ken-ichi , Ochiai Ikuo , Nishi Mayumi , Kawata Mitsuhiro
Published: September 2002

To investigate the relationships between the loci expressing functions of estrogen receptor (ER)α and that of ERβ, we analyzed the subnuclear distribution of ERα and ERβ in response to ligand in single living cells using fusion proteins labeled with different spectral variants of green fluorescent protein. Upon activation with ligand treatment, fluorescent protein-tagged (FP)-ERβ redistributed from a diffuse to discrete pattern within the nucleus, showing a similar time course as FP-ERα, and colocalized with FP-ERα in the same discrete cluster. Analysis using deletion mutants of ERα suggested that the ligand-dependent redistribution of ERα might occur through a large part of the receptor including at least the latter part of activation function (AF)-1, the DNA binding domain, nuclear matrix binding domain, and AF-2/ligand binding domain. In addition, a single AF-1 region within ERα homodimer, or a single DNA binding domain as well as AF-1 region within the ERα/ERβ heterodimer, could be sufficient for the cluster formation. More than half of the discrete clusters of FP-ERα and FP-ERβ were colocalized with hyperacetylated histone H4 and a component of the chromatin remodeling complex, Brg-1, indicating that ERs clusters might be involved in structural changes of chromatin.
Cloning and Characterization of a Novel Endothelial Promoter of the Human CYP19 (Aromatase P450) Gene that Is Up-Regulated in Breast Cancer Tissue
Authors: Sebastian Siby , Takayama Kazuto , Shozu Makio , Bulun Serdar E.
Published: September 2002

Intratumoral expression of aromatase P450 (P450arom) promotes the growth of breast tumors via increased local estrogen concentration. We cloned a novel 101-bp untranslated first exon (I.7) that comprises the 5′-end of 29–54% of P450arom transcripts isolated from breast cancer tissues (n = 7). The levels of P450arom transcripts with exon I.7 were significantly increased in breast tumor tissues and adipose tissue adjacent to tumors. We identified a promoter immediately upstream of exon I.7 and mapped this to about 36 kb upstream of ATG translation start site of the CYP19 (aromatase cytochrome P450) gene. Sequence analysis of I.7 revealed a TATA-less promoter containing an initiator, two consensus GATA sites, and cis-regulatory elements found in megakaryocytes and endothelial type promoters. Luciferase activity directed by the promoter I.7 sequence (−299/+81 bp) was 4-fold greater than a minimum length promoter sequence (−35/+81 bp) in human microvascular endothelial cells (HMEC-1), but only 2-fold greater in MCF-7 breast malignant epithelial cells. There was no promoter activity in primary breast adipose fibroblasts. Site-directed mutations demonstrated that maximal basal promoter activity required two GATA motifs at −146/−141 bp and −196/−191 bp. Gel shift and deoxyribonuclease I footprinting assays demonstrated the binding of GATA-2 transcription factor but not GATA-1 to the −196/−191-bp region. Overexpression of GATA-2 in HMEC-1 cells increases promoter I.7 activity by 5-fold. In conclusion, promoter I.7 is a GATA-2-regulated endothelial promoter of the human CYP19 gene and may increase estrogen biosynthesis in vascular endothelial cells of breast cancer. The activity of this promoter may also be important for intracrine and paracrine effects of estrogen on blood vessels.
Nuclear Export of Glucocorticoid Receptor is Enhanced by c-Jun N-Terminal Kinase-Mediated Phosphorylation
Authors: Itoh M. , Adachi M. , Yasui H. , Takekawa M. , Tanaka H. , Imai K.
Published: September 2002

The c-Jun N-terminal kinase (JNK) phosphorylates the glucocorticoid receptor (GR) and inhibits GR-mediated transcription. However, the biological effect of the GR phosphorylation remains unknown. Here we demonstrate that activated JNK phosphorylates human GR at Ser226 and enhances its nuclear export after withdrawal of a ligand for GR, dexamethasone. At 1 h after dexamethasone withdrawal, green fluorescent protein-GR molecules were mostly retained at the nucleus, whereas UV exposure enhanced its nuclear export, and approximately 30–40% of cells revealed distinct nuclear export. JNK overexpression alone mimics UV exposure and enhanced GR export accompanied by inhibition of GR-mediated transcription. However, mutation of the Ser226 JNK phosphorylation site in GR abrogated UV-mediated enhancement of GR nuclear export. Furthermore, overexpression of a dominant negative SEK1 mutant also abrogated the effects of UV exposure on GR export. Taken together, these findings suggest that JNK-mediated phosphorylation of the GR-Ser226 enhances GR nuclear export and may contribute to termination of GR-mediated transcription.
Downward Migration of Coastal Conifers as a Response to Recent Land Emergence in Eastern Hudson Bay, Québec
Authors: Bégin Yves , Bérubé Dominique , Grégoire Martin
Published: October 2002

Postglacial uplift in the eastern Hudson Bay area is among the most rapid in the world (300 m during the last 8000 yr). Although emergence curves based on 14 C-dated raised shorelines give a consistent basis for modeling relative sea-level changes, such a low-resolution dating method is inappropriate for estimating trends over recent decades. A major downward displacement of white spruce (Picea glauca (Moench) Voss) and tamarack (Larix laricina (DuRoi) K. Koch) occurred on protected shores as a response to shoreline retreat during this century. Analysis of the age distribution of trees indicates a progradation of white spruce and tamarack on gently sloping terrain ranging from 1.3 and 2.6 cm/yr, respectively, toward the sea. Improvement of climatic conditions during the 20th century favored such expansion which was probably faster than the real land emergence rates, but recent episodes of high water levels caused regression of forest margins over the highly exposed shores. Nevertheless, the downward trend of the treeline over this century substantiates the projections of 14C-dated coastal emergence curves during the modern period (1.0 to 1.3 cm/yr) by providing an estimate of the maximum rates of shoreline retreat.
Radiocarbon-Dated Pollen and Sediment Records From Near the Boylston Street Fishweir Site in Boston, Massachusetts
Authors: Newby Paige E. , Webb Thompson
Published: October 2002

A radiocarbon-dated pollen record near the Boylston Street Fishweir site in Boston; Massachusetts, provides a regional and local record of vegetation changes from the middle Holocene to present. The stratigraphy begins about 5630 ± 90 yr B.P. with a marine transgression and is continuous up to the historic backfilling of the Back Bay area about 100 yr B.P. When pollen began accumulating at the site, the immediate area resembled the swamp forests growing today in southern New England. Fresh- and brackish-water vegetation was present before the area near the site was submerged. While these vegetation changes occurred locally, oak forest grew in the region. Correlation of this stratigraphy with archaeological data collected from 500 Boylston Street indicates that between 4700 and 3700 yr B.P., a number of fence-like alignments ("weirs"), were probably placed within existing channels and/or along shorelines to capture fish and other marine animals as they moved with the tidal flow.
Groundwater Isotopic Evidence for Paleorecharge in U.S. High Plains Aquifers
Authors: Dutton Alan R.
Published: October 2002

Compositions of δD, δ18O,14C, and3H are distinct in unconfined and confined groundwaters beneath the nonglaciated U.S. High Plains and reflect differences in average paleoclimatic conditions between the Holocene and the Middle to Late Wisconsinan. δD and δ18O are more depleted in confined groundwaters than in unconfined groundwaters beneath the southern and central Plains but are more enriched in confined than in unconfined groundwaters beneath the northern Plains. The range in stable isotopic composition of meteoric water north-to-south across the High Plains was apparently smaller during the Middle to Late Wisconsinan than it has been during the Holocene. The greater δD and δ18O depletion of confined groundwater beneath the southern and central Plains agrees with isotopic and noble gas data on other paleowaters that suggest Middle to Late Wisconsinan recharge temperatures were cooler than average Holocene temperatures by 5 to 8°C. The greater δD and δ18O enrichment of confined groundwater beneath the northern High Plains adds to previously reported evidence for stable isotope enrichment in glacial age precipitation across the northern Plains to the eastern United States. Additional research is needed to evaluate how patterns and mechanisms of moisture transport and other climatic variables might explain isotopic composition of paleorecharge during the last glacial period.
Early Holocene Vegetation Record from the Salton Basin, California
Authors: Rinehart Roberta B. , McFarlane Donald A.
Published: October 2002

Plant and vertebrate macrofossils in an early Holocene fossil packrat (Neotomasp.) midden with a radiocarbon age of 8640 ± 10014C yr B.P. are reported from the Chocolate Mountains, near the Salton Sea, Riverside County, California. An inventory of the midden has permitted a comparison of the modern flora and fauna of the site with that extant during the early Holocene. Whereas the biota had assumed most aspects of its modern Sonoran desert aspect by this date, statistically significant evidence of differences is attributed to an increased flow of surface water in Salt Creek, a high-standing, low-salinity Lake LeConte, and the late arrival of some characteristic Sonoran desert plants. These observations are consistent with models of significant fall-winter precipitation in the Sonoran Desert, although we cannot exclude alternative explanations.
Paleoevaporation and Paleoprecipitation in the Tanganyika Basin at 18,000 Years B.P. Inferred from Hydrologic and Vegetation Proxies
Authors: Bergonzini Laurent , Chalié Francoise , Gasse Francoise
Published: October 2002

Paleo-hydrologic and -vegetation proxy data from the Tanganyika basin are integrated in energy and water balance equations to infer past evaporation and precipitation during the last glacial maximum (LGM). Our approach is first validated on the modern system. Large variations are assigned to input variables to simulate the interannual precipitation variability. Equations are then applied to the LGM. We first change those input parameters inferred from proxies (basin and lake surfaces, temperature, and land albedo). Our LGM simulation suggests (in percent of modern mean values) decreases in evaporation from the lake [El: −5% (between −13% and +3%)] and land [Ec: −8% (−19/+5)] bodies, in precipitation [P: −11% (−21/0)] and (P − Ec): −42% (−44/−40). Decreases in P and E are amplified [El: −8% (−16/0); Ec: −14% (−24/−2); P: −17% (−26/−6)] when including empirical changes in atmospheric transmission coefficient and Bowen ratio. Sensitivity runs suggest that even large changes in cloud cover and air humidity should not modify these trends. The results suggest that the Earth's glacial/interglacial boundary conditions play a significant role on climate of subequatorial southern Africa.
Holocene History of the Chocó Rain Forest from Laguna Piusbi, Southern Pacific Lowlands of Colombia
Authors: Behling Hermann , Hooghiemstra Henry , Negret Alvaro José
Published: October 2002

A high-resolution pollen record from a 5-m-long sediment core from the closed-lake basin Laguna Piusbi in the southern Colombian Pacific lowlands of Chocó, dated by 11 AMS14C dates that range from ca. 7670 to 22014C yr B.P., represents the first Holocene record from the Chocó rain forest area. The interval between 7600 and 610014C yr B.P. (500–265 cm), composed of sandy clays that accumulated during the initial phase of lake formation, is almost barren of pollen. Fungal spores and the presence of herbs and disturbance taxa suggest the basin was at least temporarily inundated and the vegetation was open. The closed lake basin might have formed during an earthquake, probably about 440014C yr B.P. From the interval of about 600014C yr B.P. onwards, 200 different pollen and spore types were identified in the core, illustrating a diverse floristic composition of the local rain forest. Main taxa are Moraceae/Urticaceae, Cecropia,Melastomataceae/Combretaceae, Acalypha, Alchornea,Fabaceae, Mimosa, Piper, Protium, Sloanea, Euterpe/Geonoma, Socratea,and Wettinia.Little change took place during that time interval. Compared to the pollen records from the rain forests of the Colombian Amazon basin and adjacent savannas, the Chocó rain forest ecosystem has been very stable during the late Holocene. Paleoindians probably lived there at least since 346014C yr B.P. Evidence of agricultural activity, shown by cultivation of Zea maissurrounding the lake, spans the last 1710 yr. Past and present very moist climate and little human influence are important factors in maintaining the stable ecosystem and high biodiversity of the Chocó rain forest.
A Continuous Holocene Glacial Record Inferred from Proglacial Lake Sediments in Banff National Park, Alberta, Canada
Authors: Leonard Eric M. , Reasoner Mel A.
Published: October 2002

Sediment cores from three proglacial lakes in northern Banff National Park, Alberta, preserve a record of Holocene glacial activity upvalley which is more continuous and better dated than available surficial records. Dating of the cores is based on tephrochronology and 16 AMS14C ages of terrestrial macrofossils. All cores contain a threefold sequence of lacustrine sediments overlying a late Pleistocene diamicton. Basal lacustrine sediments >10,10014C yr old contain little organic matter. Sediment composition indicates a large glacigenic contribution. A sharp increase in organic content marks the beginning of the Altithermal interval at all three lakes. This transition occurred abruptly at about 10,10014C yr B.P. at Crowfoot Lake and possibly more gradually at the other lakes. Altithermal sediments contain relatively little glacigenic material, and during most of the Altithermal, glaciers may have been absent above Crowfoot and Bow Lakes. Glaciers draining into Hector Lake appear to have persisted through the Altithermal. A subsequent decrease in organic content in each lake, reflecting increased clastic sedimentation, marks the end of the Altithermal and the onset of Neoglacial ice advances. The transition took place between about 5800 and 400014C yr B.P. and may be time-transgressive, beginning earlier in Hector Lake than in Crowfoot Lake. Changing Neoglacial clastic sedimentation rates through the Neoglacial interval indicate two main periods of increased glacier extent, between ca. 3000 and 1800 varve yr ago (ca. 2900–190014C yr B.P.) and during the last several hundred years. During the intervening period glaciers were less extensive, but much more extensive than during the recessions of the Altithermal interval.
Human Responses to Middle Holocene (Altithermal) Climates on the North American Great Plains
Authors: Meltzer David J.
Published: October 2002

The climate of the Great Plains during the middle Holocene varied considerably, but overall it was marked by a north–south gradient of increasingly warmer and drier conditions, with a reduction in effective moisture, surface water, and resource abundance, and an increase in resource patchiness, sediment weathering, erosion, and aeolian activity. Pronounced drought conditions were most evident on the Southern High Plains. Understanding the human responses to middle Holocene climates is complicated by a lack of archaeological data, which is partly a result of geomorphic processes that removed or deeply buried sites of this age, and by the varying adaptive responses of hunter-gatherers during this period. On the Southern High Plains, where drought was most severe, surface and groundwater sources dried and bison populations were diminished, prompting substantial adaptive changes, including local abandonment, well-digging to tap underground water, and a widening of the diet breadth to incorporate higher-cost, lower-return seed and plant resources. Sites of this age on the Central and Northern Plains also show a possible increase in diet breadth (with the incorporation of plant foods in the diet), and perhaps changes in settlement mobility (including possible shift into higher elevation areas, or mapping-on to extant rivers and springs). But linking those changes to middle Holocene drought is less straightforward.
Federal‐funds‐rate volatility and the reserve‐maintenance period
Authors: Eagle David
Published: October 2002

The day‐to‐day changes in the federal funds rate affects all banks, in particular those banks who execute their single federal funds transaction through larger correspondent banks. This paper's stochastic equilibrium model discusses how a major determinant of that behavior—the bank's reserve‐maintenance period—molds the interday pattern of federal‐funds‐rate volatility. In particular, the model explains why the volatility of the federal funds rate increases from the beginning to the end of that period. While Spindt and Hoffmeister (1988) tried to explain that increases in terms of transaction‐cost avoidance, this paper's model demonstrates that rational expectations alone will generate this effect. It also shows that lengthening the reserve‐maintenance period increases federal‐funds rate volatility on the last day of the period.
Abnormal profits and relative strength in mutual fund returns
Authors: Volkman David A. , Wohar Mark E.
Published: October 2002

This study investigates the relative strength in mutual fund performance by employing three different empirical methods to analyze the profitability of twenty trading strategies, based on varying evaluation horizons and investment periods. Specifically, we test for positive persistence in fund performance by focusing on the optimal weighting of past performance information. Counter to an earlier study on relative strength of fund performance, this study's results do not support the decay of performance persistence after one year. Rather, we find persistent abnormal fund returns over a one to three year investment period based on a three to four year evaluation horizon. In addition, results show that relative strength in fund performance is directly related to persistence in superior performing funds rather than a function of persistence in inferior performing funds.
The policy content of the yield curve slope
Authors: Gamber Edward N.
Published: October 2002

The slope of the yield curve, defined as the difference between 10 year and 3 month government bond yields, has been shown to predict both inflation and real economic activity. This paper investigates whether the forecasting ability of the yield curve slope is solely due to its relationship to monetary policy or whether it contains independent information about the future course of inflation and output growth. The predictive content of the yield curve slope is measured over three separate monetary policy regimes. The empirical results suggest that the yield curve slope contains independent predictive information about a variable only when the Federal Reserve does not react to changes in that variable.
Effects of soyabean leaflet inclination on some factors related to photosynthesis
Authors: IKEDA T. , MATSUDA R.
Published: October 2002

Leaflet movement in soyabean (Glycine max (L.) Merr.) is considered to be an important physiological adaptation for intercepting sunlight for photosynthesis. Solar tracking may serve to increase plant production by maximizing light interception. The objective of this study was to determine the response of A (leaflet net assimilation rate), τ (stomatal conductance) and Ci (internal leaf carbon dioxide concentration) when penultimate fully expanded leaflet angles were changed. Soyabean (cv. Enrei, Maturity group VI) was planted at Niigata University, Japan, at two densities (25 and 16 plants/m2) in mid-May of 1992 and 1993. PFD (photon flux density), A, τ, and Ci were measured with a portable leaf photosynthesis instrument. The more towards vertical the leaflets were moved, the lower the PFD and A were. A measured at R5 showed no light saturation, but did show this at V13 and R3. While A measured at 09.00 h showed no saturation point, there was saturation at 12.00 h and 15.00 h at or less than 1500 μmol/m2/s. At R3 a high correlation (r = 0.89, P < 0.01) was found between PFD and A for naturally oriented leaflets, but not for horizontal ones. These results suggest that leaflet movement is an adaptation to optimize A.
Determination of the casein content in bovine milk by 31P-NMR
Authors: BELLOQUE JOSEFINA , RAMOS MERCEDES
Published: October 2002

The relative proportion of caseins to total protein is a parameter that can be used to control the protein quality in standardised milk, an increasing tendency in dairy industries. 31P-NMR was used to analyse the casein content of milk, by the quantitation of the area under the resonances belonging to SerP, and using methylenediphosphonic acid as internal standard. This procedure yielded good results, as similar values of caseins were obtained from N Kjeldahl and NMR analysis for slightly heated milk samples. Heating at 95 °C for 15 min did not alter the casein content results. Casein content of raw, pasteurised and UHT milks (25·6±1·4, 26·4±1·8, 25·5±1·6 g casein/l milk, respectively), obtained by NMR, were not significantly different, giving an average of 25·8±1·6 g casein/l for bulk liquid milk. This work concluded that 31P-NMR could be used as an alternative method to determine casein in raw, pasteurised, dry and UHT milks.
Influence of enrichment with vitamins and minerals on the bioavailability of iron in cows' milk
Authors: PÉREZ ANTONIO , LORENZO M. LUISA , CABRERA CARMEN , LÓPEZ M. CARMEN
Published: October 2002

Iron is an essential element for humans and physiological needs are determined
by obligatory loss, growth, menstruation and pregnancy. Although iron metabolism
occurs in a ‘closed circuit’, physiological losses occur and they must be made good.
Three factors are important in the study of iron needs: the total amount of iron in
the diet; the nature of the iron compound; and other components of the diet
(Hallberg et al. 1998). Although iron de®ciency ensues if insu¾cient iron is absorbed
to meet requirement, the total iron absorbed normally exceeds requirement (Hallberg
et al. 1997; Jackson, 1997).
Genetic differences between two sibling sympatric Dipolydora species (Polychaeta: Spionidae) from the Sea of Japan, and a new species description
Authors: Manchenko Gennady P. , Radashevsky Vasily I.
Published: October 2002

A Dipolydora species (Polychaeta: Spionidae) was found in mud tubes attached to the larger tubes of the chaetopterid polychaete Chaetopterus cautus in Peter the Great Bay of the Sea of Japan. The worms were close in morphology to D. carunculata, a borer of various calcareous substrata and sponges described earlier from the same area. The chaetopterid-associated tube-building individuals usually differed from shell-boring individuals by the presence of black pigmentation on palps. However, some of them were not pigmented and appeared almost identical to D. carunculata. Isozymes of the tube-building and shell-boring individuals were compared using starch gel electrophoresis. Two of 16 studied isozyme loci proved diagnostic and unequivocally demonstrated the presence of two distinct species. The chaetopterid-associated individuals are described here as a new species, D. melanopalpa. Unbiased Nei's genetic distance between D. melanopalpa and D. carunculata (D=0·949) as well as the level of intraspecific genetic variation in either of them (D. melanopalpa, He=0·206±0·054; D. carunculata, He=0·239±0·044) are high and comparable to those of other electrophoretically studied polydorids. In contrast to other examined polydorids, D. carunculata and D. melanopalpa have the same numbers of expressed isozyme loci.
Corbula gibba (Mollusca: Bivalvia) death assemblages in Augusta harbour, Mediterranean Sea
Authors: Giacobbe Salvatore , Rinelli Paola
Published: October 2002

Death assemblages found in the Augusta Roadstead harbour (Mediterranean Sea) reflected some modifications in benthic environment that occurred since the 1960s, when the construction of dams closed the commercial harbour. In particular, evidence of a drop in the hydrodynamic levels were found, together with a mud sedimentation increasing. Furthermore, a turbidity phase characterized by a dominant Corbula gibba was identified as due to extensive dredging. Such temporary communities, distributed in accordance to the degree of instability and pollution, preceded the present day, very poor and destructured benthic assemblages.
Relationship between body size and population growth rate in two opportunistic polychaetes
Authors: Prevedelli D. , Simonini R.
Published: October 2002

The relationship between body size and population growth rate λ has been studied in two species of opportunistic polychaetes, Dinophilus gyrociliatus and Ophryotrocha labronica, which colonize harbour environments. These species exhibit a semi-continuous iteroparous reproductive strategy, are phylogenetically closely-related but differ in body size and in some aspects of their sexuality. Ophryotrocha labronica is about 4 mm in body length, displays only slight sexual dimorphism and its sex ratio is biased towards the female sex in the ratio 2:1. Dinophilus gyrociliatus is about 1 mm in length, the males are extremely small and the sex ratio is strongly biased (3:1) in favour of the females. In spite of the considerable differences in all traits of their life histories and in many demographic parameters, the growth rates of the two populations are very similar. The analyses carried out have shown that the rapid attainment of sexual maturity of D. gyrociliatus gives it an advantage that offsets the greater fecundity of O. labronica. It is very likely that the reproductive peculiarities of D. gyrociliatus help to raise the population growth rates. The ‘saving’ on the male sex achieved both by the shift of the sex ratio in favour of the females and by the reduction in the males' body size would appear to enable D. gyrociliatus to grow at the same rate as O. labronica, a larger and more fecund species.
Sulphur signature in the hydrothermal vent mussel Bathymodiolus azoricus from the Mid-Atlantic Ridge
Authors: Pruski Audrey Margareth , Rousse Nathalie , Fiala-Médioni Aline , Boulègue Jacques
Published: October 2002

The sulphur compound composition of the hydrothermal vent mussel Bathymodiolus azoricus (Bivalvia: Mytilidae) was analysed in order to determine the specific biochemical characteristics of a thiotrophic mode of nutrition. In specimens collected from two contrasting vent fields on the Mid-Atlantic Ridge (Menez Gwen and Lucky Strike), substantial differences in the sulphur composition were observed between tissues and sampling sites. Total sulphur content was higher for samples from Lucky Strike than for those from Menez Gwen. The amount of elemental sulphur in the gill of B. azoricus was in the same range as values previously reported for the vesicomyid clam Calyptogena phaseoliformis and the lucinid clam Lucinoma annulata. Rings of orthorhombic sulphur or compounds such as polythionates or organopolysulphides excreted in the cytoplasm by the symbionts may account for the large amounts of elemental sulphur evidenced for the first time in an hydrothermal vent mussel. A large proportion of the tissue-sulphur was incorporated into free amino compounds such as taurine, hypotaurine, thiotaurine and cysteine, and in a lesser extent to the tripeptide glutathione. In mantles, sulphur seems to be contained mainly in organic compounds such as proteins, mucopolysaccharides and lipids. However, the occurrence of specific compounds such as thiotaurine and elemental sulphur in gills indicate that in this tissue a large proportion of the sulphur might be involved in specific pathways related to transport, storage and detoxification of sulphide. Moreover, our results suggest a greater reliance on thiotrophy of mussels from Lucky Strike as compared to specimens from Menez Gwen.
Variations in the feeding intensity and diet composition of red mullet (Mullus barbatus) during 24-h period in the summertime in Hisarönü Bay
Authors: Ünlüoğlu A. , Cihangir B. , Kaya M. , Benli H.A. , Katağan T.
Published: October 2002

Diel feeding pattern of red mullet in the Hisarönü Bay was studied from samples collected by bottom trawl during a 24-h period in the summer of 1997. Feeding activity of red mullet commenced at dawn and reached its maximum value at noon. During the period between noon to early evening, feeding intensity slowed down and then showed a small increase towards sunset. After sunset, the feeding activity nearly stopped and fish with empty stomachs increased. At night almost all stomachs were empty. Polychaetes, decapods, bivalves and amphipods were the major prey groups in the diet of red mullet and no significant diel variations were observed in the relative importance of these groups.
Compact groups with large abelian subgroups
Authors: HOFMANN KARL H. , MORRIS SIDNEY A.
Published: October 2002

In this paper we formulate a new conjecture and introduce methods to verify it in
many cases.
Quillen model structures for relative homological algebra
Authors: CHRISTENSEN J. DANIEL , HOVEY MARK
Published: October 2002

An important example of a model category is the category of unbounded chain
complexes of R-modules, which has as its homotopy category the derived category
of the ring R. This example shows that traditional homological algebra is encompassed by Quillen's homotopical algebra. The goal of this paper is to show that more
general forms of homological algebra also fit into Quillen's framework. Specifically,
a projective class on a complete and cocomplete abelian category [Ascr ] is exactly the
information needed to do homological algebra in [Ascr ]. The main result is that, under
weak hypotheses, the category of chain complexes of objects of [Ascr ] has a model category structure that reflects the homological algebra of the projective class in the
sense that it encodes the Ext groups and more general derived functors. Examples
include the ‘pure derived category’ of a ring R, and derived categories capturing
relative situations, including the projective class for Hochschild homology and co-homology.
We characterize the model structures that are cofibrantly generated, and
show that this fails for many interesting examples. Finally, we explain how the category of simplicial objects in a possibly non-abelian category can be equipped with a
model category structure reflecting a given projective class, and give examples that
include equivariant homotopy theory and bounded below derived categories.
Growth in the Sumatran elephant (Elephas maximus sumatranus) and age estimation based on dung diameter
Authors: Reilly Joanne
Published: October 2002

The aim of this study was to investigate age‐related growth in the Sumatran elephantElephas maximus sumatranusand to use the derived relationship to determine the age structure of the wild elephant population in Way Kambas National Park (WKNP), Sumatra. Shoulder height, forefoot circumference and diameter of dung bolus were found to be related to age of captive Sumatran elephants using the Von Bertalanffy growth function. All length measurements were highly correlated with age in the Sumatran elephant and provide growth models for determining the age structure of wild populations. Female captive elephants reached their growth plateau earlier than male elephants who continued growing throughout the ages observed. There was no clear evidence of a secondary growth spurt in male elephants. The growth model relating dung diameter to age was used to predict the age structure of the wild elephant population in WKNP from dung measured along random line transects. The wild elephant population in WKNP is young and dominated by sub‐adults (between 5 and 15 years of age). There are marked differences between the age structure of the population as revealed in the current survey and that reported from previous studies, suggesting that changes have occurred within the population in the intervening period. The use of dung diameter to predict age offers a robust field technique for use in situations where direct observations are limited, and the use of other age estimation methods is impractical. It is easily coupled with dung counts for estimating the size, age structure and biomass of elephant populations, and has considerable potential for investigating the effects of poaching on age structure and identifying where priority action should be directed in human–elephant conflict situations.
Seasonal patterns of reproduction and abundance of leaf litter frogs in a Central American rainforest
Authors: Watling James I. , Donnelly Maureen A.
Published: October 2002

Patterns of reproductive phenology and temporal variation in species composition and age structure were investigated for a sample of terrestrial leaf litter frogs from a lowland tropical rainforest in north‐eastern Costa Rica. Recruitment of most species showed a seasonal pattern in which the growth of juveniles occurred during the dry season. The phenology of the assemblage was also seasonal, with a peak in abundance during the dry season. Variation in abundance was driven by seasonal patterns of juvenile recruitment in one species, Eleutherodactylus brandsfordii. We suggest that the timing of reproduction and patterns of frog phenology may be tied to the availability of arthropod prey items. A comparison of our data with data collected at other rainforest sites in Central America and the Amazon basin of South America indicates that patterns of recruitment and abundance, while correlated with arthropod abundance on both continents, show divergent seasonal patterns. This and other studies indicate that peaks in abundance and recruitment of juvenile frogs are concentrated in the dry season in Central America, whereas in South American rainforests, the wet season is the period of highest abundance and juvenile recruitment. We suggest that the length and severity of dry periods in the Amazon basin limits the ability of terrestrial frogs to reproduce successfully, while in Central America a more benign dry season, while strong enough to create distinct seasonal trends in the phenology of rainforest animals, is not strong enough to prohibit frogs from recruiting juveniles during the dry season.
Drug treatment of Alzheimer’s disease
Authors: Jones Roy W
Published: October 2002

Alzheimer’s disease (AD) is an international problem of enormous significance. The human and financial cost to the sufferers, their families and friends is huge, matched by the costs to health and social services in all developed countries and, increasingly, elsewhere.
Quasiclassical Rate Coefficients for the H2+H2 Reaction and Dissociation
Authors: Ceballos A. , Garcia E. , Laganà A.
Published: September 2002

Vibrational state-to-state quasiclassical rate coefficients of the H2+H2 reaction summed over product rotational states for thermalized reactants’ rotations and translations are given at various values of the temperature in the range 1000–4000 K. Values are given for both reactive and nonreactive processes. Separate values are also given for processes involving dissociation.
Hamiltonian Feynman path integrals via the Chernoff formula
Authors: Smolyanov O. G. , Tokarev A. G. , Truman A.
Published: September 2002

The main aim of the present paper is using a Chernoff theorem (i.e., the Chernoff formula) to formulate and to prove some rigorous results on representations for solutions of Schrödinger equations by the Hamiltonian Feynman path integrals (=Feynman integrals over trajectories in the phase space). The corresponding theorem is related to the original (Feynman) approach to Feynman path integrals over trajectories in the phase space in much the same way as the famous theorem of Nelson is related to the Feynman approach to the Feynman path integral over trajectories in the configuration space. We also give a representation for solutions of some Schrödinger equations by a series which represents an integral with respect to the complex Poisson measure on trajectories in the phase space.
Behavior of the survival probability in some one-dimensional problems
Authors: Astaburuaga M. Angélica , Covian Pablo , Fernández Claudio
Published: September 2002

We study the behavior of the survival probability Pφ(t) in potential barrier problems on the half-line. We consider two cases: when the initial state φ is a truncated outgoing solution corresponding to a scattering frequency and when it is an approximate bound state. Using techniques and methods from Spectral Theory, Fourier Analysis, and from Ordinary Differential Equations, we obtain approximate exponential decay in both cases.
Additivity for unital qubit channels
Authors: King Christopher
Published: September 2002

Additivity of the Holevo capacity is proved for product channels, under the condition that one of the channels is a unital qubit channel, with the other completely arbitrary. As a byproduct this proves that the Holevo bound is the classical information capacity of such qubit channels, and provides an explicit formula for this classical capacity. Additivity of minimal entropy and multiplicativity of p-norms are also proved under the same assumptions. The proof relies on a new bound for the p-norm of an output state from the half-noisy phase-damping channel.
A family of solutions with radiation reaction and retarded interactions for two charges in classical electrodynamics
Authors: Rivera R. , Villarroel D.
Published: September 2002

A family of solutions of the Lorentz–Dirac equation is constructed. It consists in the motion of two charges e1 and e2 of masses m1 and m2 in two coplanar and concentric circles of radii a and b. The charges rotate with constant angular velocity, and have an angular separation ψ. The radiation reaction forces and the retarded interactions between the charges are taken into account. The external electromagnetic field that allows the motion consists of a tangential time-independent electric field that takes a fixed value on each orbit, and a homogeneous time-independent magnetic field perpendicular to the plane of the motion. For all the solutions energy conservation is rigorously demonstrated by evaluating the energy radiated, with independence of the equation of motion, through the calculation of the instantaneous energy flux across a sphere of an infinitely large radius.
A family of new integrable couplings with two arbitrary functions of TC hierarchy
Authors: Yan Zhenya , Zhang Hongqing
Published: September 2002

Seeking new integrable couplings of the known integrable hierarchies of evolution equations is a quite new interesting aspect and is of great significance in soliton theory. In this paper, a loop algebra P̃ and its basis are first presented. Second, a new isospectral problem with four potentials in the loop algebra P̃ is considered to construct integrable couplings of the well-known TC hierarchy by the zero-curvature equation such that a family of new integrable couplings including two arbitrary functions are obtained. In particular, when we set two arbitrary functions to be zero, a special integrable couplings of the generalized Korteweg–de Vries equation is also given.
Chiral superconducting strings and Nambu–Goto strings in arbitrary dimensions
Authors: Siemens Xavier , Olum Ken D.
Published: September 2002

We present general solutions to the equations of motion for a superconducting relativistic chiral string that satisfy the unit magnitude constraint in terms of products of rotations. From this result we show how to construct a general family of odd harmonic superconducting chiral loops. We further generalize the product of rotations to an arbitrary number of dimensions.
Liouville integrability of the finite dimensional Hamiltonian systems derived from principal chiral field
Authors: Zhou Zixiang
Published: September 2002

For finite dimensional Hamiltonian systems derived from 1+1 dimensional integrable systems, if they have Lax representations, then the Lax operator creates a set of conserved integrals. When these conserved integrals are in involution, it is believed quite popularly that there will be enough functionally independent ones among them to guarantee the Liouville integrability of the Hamiltonian systems, at least for those derived from physical problems. In this article, we give a counterexample based on the U(2) principal chiral field. It is proved that the finite dimensional Hamiltonian systems derived from the U(2) principal chiral field are Liouville integrable. Moreover, their Lax operator gives a set of involutive conserved integrals, but they are not enough to guarantee the integrability of the Hamiltonian systems.
Multiple splitting of G-band modes from individual multiwalled carbon nanotubes
Authors: Zhao Xinluo , Ando Yoshinori , Qin Lu-Chang , Kataura Hiromichi , Maniwa Yutaka , Saito Riichiro
Published: September 2002

Surface-enhanced Raman scattering spectra of an individual multiwalled carbon nanotube (MWNT) with the innermost diameter ∼1 nm, prepared by hydrogen arc discharge, show a single peak of radial breathing mode and multiple splitting of the tangential stretching G-band modes. Based on Lorentzian line shape analysis and related theoretical calculations, the G-band modes of MWNT are confirmed to be composed of both G-band modes (linewidth 4 cm−1) from the innermost tube and graphite-like mode (linewidth ∼20 cm−1) from the outer cylinders in MWNT. This observation indicates that MWNTs are unique and possess characteristic Raman spectra different from other sp2 carbon allotropes.
Hamiltonian guiding center equations in a toroidal system
Authors: Abdullaev S. S. , Finken K. H.
Published: September 2002

A Hamiltonian method to study the guiding center motion of charged particles in a toroidal magnetic system has been developed. It uses a cylindrical coordinate system instead of a magnetic coordinate system on which many conventional standard methods are based. The six-dimensional (6D) Hamiltonian equations for the guiding center motion are derived by a canonical transformation of fast-oscillating variables to slowly varying ones which are guiding center coordinates. It is shown that one of these slowly varying variables, i.e., the action variable conjugated to the fast-oscillating gyrophase is an adiabatic invariant for the tokamak equilibrium magnetic field perturbed by the external time-dependent magnetic field. This allows to reduce the 6D Hamiltonian system to the 4D one. The method is valid for the study of the guiding center motion of particles in time-dependent magnetic and electric fields, especially, ergodic magnetic fields, where spatial and temporal scales of variation are much larger than the gyroradius and the gyroperiod.
On the invariance of residues of Feynman graphs
Authors: Bierenbaum Isabella , Kreckel Richard , Kreimer Dirk
Published: September 2002

We use simple iterated one-loop graphs in massless Yukawa theory and QED to pose the following question: what are the symmetries of the residues of a graph under a permutation of places to insert subdivergences. The investigation confirms partial invariance of the residue under such permutations: the highest weight transcendental is invariant under such a permutation. For QED this result is gauge invariant, i.e., the permutation invariance holds for any gauge. Computations are done making use of the Hopf algebra structure of graphs and employing GiNaC to automate the calculations.
Measurement and modeling of molecular ion concentrations in a hydrogen reflex-arc discharge
Authors: Hollmann E. M. , Pigarov A. Yu.
Published: September 2002

The concentrations of the ions H+, H2+, and H3+ are measured in a weakly-ionized hydrogen plasma with electron temperatures Te=3–7 eV, electron densities Ne=1011–1012 cm−3, and background gas densities NH2=5×1013–1015 cm−3. The relative ion concentrations are measured using an omegatron-type mass spectrometer, while the electron density and temperature are measured using a Langmuir probe together with absolutely-calibrated Hα emission spectroscopy. The mean lifetime of ions in the plasma is estimated from fixed wall probe measurements. From the measured parameters, the expected steady-state molecular ion concentrations are modeled using the relevant rate balance equations. It is found that the observed molecular ion concentrations can be predicted within the experimental accuracy using currently available collision cross sections.
Acoustic modes in dense dusty plasmas
Authors: Avinash K. , Bhattacharjee A. , Hu S.
Published: September 2002

Properties of acoustic modes in high dust density dusty plasmas are studied. The solutions of fluid equations for electrons, ions, and dust grains with collisional and ionization effects are solved along with an equation for grain charging. The high dust density effects on the acoustic modes are interpreted in terms of a change in the screening properties of the grain charge. At low dust density, the grain charge is screened due to electrons and ions. However, at high dust density, the screening of the grain charge due to other grains also becomes important. This leads to a reduction of the phase-velocity, which in turn is shown to make the plasma more unstable at high dust density. In this regime the role of the ion acoustic mode is replaced by the charging mode. The relevance of these results to earlier theoretical studies and experimental results are discussed.