bluuebunny/crossref_metadata_2025 huggingface dataset:
Association between serum concentrations of hexachlorobenzene and polychlorobiphenyls with thyroid hormone and liver enzymes in a sample of the general population
Authors: Sala M , Sunyer J , Herrero C , To-Figueras J , Grimalt J
Published: July 2002

OBJECTIVES

Hexachlorobenzene (HCB) is a highly lipophilic organochlorine compound of widespread environmental occurrence, that accumulates in the biological system. It affects the porphyrine metabolism, thyroid hormones, and the liver function in animals. Although HCB is one of the most common organochlorine compound in humans, little investigation on its health effects has been done. Polychlorobiphenyls (PCBs) are also widespread toxic environmental contaminants. The aim of the present study was to investigate the association of serum HCB and PCB concentrations with thyroid hormone status and liver enzymes in human.

METHODS

Thyroid stimulating hormone (TSH), total and free thyroxine (T4), aspartate aminotransferase (AST), alanine aminotransferase (ALT) and γ-glutamyltransferase (GGT) were measured as biological markers of thyroid and liver function in a rural population sample older than 14 years (n=192, except for TSH with n=608) highly exposed to HCB. Serum concentrations of HCB were measured by gas chromatography coupled to electron capture detection.

RESULTS

After adjustment for confounding variables, there was a significant negative association between serum HCB concentrations and total T4 (a decrease of 0.32 μg/dl per each unit, ln ng/ml, of increase of HCB) and a positive association with GGT (a relative increase of 10 % per each ln unit of increase of HCB), although most subjects (92%) were within the normal range for both T4 and GGT. These associations were not modified after adjustment for total lipid content or for other organochlorine compounds. The association of T4 and GGT with PCB was smaller although significant. No association was found with the other biochemical markers.

CONCLUSIONS

These results suggest that the internal dose of HCB of this population may reflect a subtle metabolic effect on thyroid function and an enzymatic induction activity. Further studies are needed to evaluate the health impact of these effects in more susceptible populations, such as infants.
Foetal growth and duration of gestation relative to water chlorination
Authors: Jaakkola J J K , Magnus P , Skrondal A , Hwang B-F , Becher G , Dybing E
Published: July 2002

OBJECTIVE

To assess the effect of exposure to chlorination byproducts during pregnancy on foetal growth and duration of pregnancy.

METHODS

A population based study was conducted of 137 145 Norwegian children born alive in 1993–5. Information was obtained from the Norwegian medical birth registry, waterwork registry, and social science data service. The outcomes of interest were birth weight, low birth weight (<2500 g), small for gestational age, and preterm delivery (gestational age <37 weeks). The exposure assessment was based on quality of drinking water in the municipality where the mother lived during pregnancy. Municipal exposure was calculated with information on chlorination and the amount of natural organic matter in raw water measured as colour in mg precipitate/l. The main exposure category was high colour and chlorination, which was contrasted with the reference category of low colour and no chlorination.

RESULTS

In logistic regression analysis adjusting for confounding, the risks of low birth weight (odds ratio (OR) 0.97, 95% confidence interval (95% CI) 0.89 to 1.06) and small for gestational age (OR 1.00, 95% CI 0.91 to 1.10) were not related to exposure. Contrary to the hypothesis, the risk of preterm delivery was slightly lower among the exposed than the reference category (OR 0.91, 95% CI 0.84 to 0.99). The risks of the studied outcomes were similar in newborn infants exposed to high colour drinking water without chlorination and chlorinated drinking water with low colour compared with the reference category.

CONCLUSIONS

The present study did not provide evidence that prenatal exposure to chlorination byproducts at the relatively low concentrations encountered in Norwegian drinking water increases the risk of the studied outcomes.
Role of the vascular endothelium in patients with angina pectoris or acute myocardial infarction with normal coronary arteries
Authors: Sztajzel Juan , Mach François , Righetti Alberto
Published: July 2002

Chest pain with normal coronary angiograms is a relatively common syndrome. The mode of presentation of this syndrome includes patients with syndrome X and patients with an acute myocardial infarction and angiographically normal coronary arteries. Different mechanisms have been proposed to elucidate the exact cause and to explain the various clinical presentations in these patients. Abnormalities of pain perception and the presence of oesophageal dysmotility have all been reported in patients with syndrome X. In situ thrombosis or embolization with subsequent clot lysis and recanalization, coronary artery spasm, cocaine abuse, and viral myocarditis have been described as potential mechanisms responsible for an acute myocardial infarction in patients with angiographically normal coronary arteries. Recent data suggest that both microvascular and epicardial endothelial dysfunction may play an important role in the pathophysiological mechanism of the syndrome of stable angina or acute myocardial infarction with normal coronary arteries.
Otorhinolaryngology
Authors: Weir Neil
Published: July 2002

Otorhinolaryngology, a product of the early 20th century, developed from the joining together of the separate departments of otology, whose practitioners were surgeons, and laryngology which was managed by physicians who also treated diseases of the nose and chest. The 20th century opened with brave attempts to perform skilful surgery under conditions of primitive anaesthesia and no antibiotics. The stimulus of two world wars led to significant advances in technology and greater opportunities to explore new and resurrect old surgical procedures. The discovery of antibiotics saw an end to acute mastoiditis and the complications of otitis media and sinusitis, as well as a decline in the number of tonsillectomy and adenoidectomy operations.

Over the last 30 years the specialty has undergone dramatic development and has taken advantage of new advances in endoscopy, microsurgery, the use of lasers, cytotoxic drugs, flap reconstruction and microchip technology. During the same period, although still calling themselves otorinolaryngologists, individual surgeons have subspecialised in otology, otoneurosurgery and skull-base surgery, head and neck surgery, phonosurgery, rhinology and facioplastic surgery, and paediatric otothinolaryngology. Each of these subspecialties has its own societies and specialist journals.
Sporophyte production and spore dispersal phenology in Sphagnum: the importance of summer moisture and patch characteristics
Authors: Sundberg Sebastian
Published: July 2002

Sporophyte production in Sphagnum was followed annually in 80 permanent 1-m2 plots at the bog expanse of a pristine mire during 19931999 and in 60 plots in peat pits abandoned 50 years ago during 19961999 in east central Sweden. The nine most abundant Sphagnum species produced sporophytes, with mean annual production ranging from 0.64 to 20 sporophytes/dm2 of cover among species. An estimated mean of 16 million Sphagnum spores/m2 mire area was produced annually at both mires. At the pristine mire, sporophyte production was positively related to the amount of precipitation the previous summer, suggesting that gametangium formation is especially sensitive to summer droughts. At the wetter peat pits, the amount of precipitation during spring in the year of sporophyte formation appeared more important, probably by positively affecting male gamete dispersal and fertilization. Larger patches had a higher probability of producing sporophytes at least once, showing areas with both sexes present among dioecious species, and thus giving an indication of clone size. Only slight differences in sporophyte production were found between the two mires, apart from effects of hydrological conditions and patch size. This indicates numerous colonizations at the peat pits. Summer droughts affected sporophyte maturation negatively by drying out sporophytes prematurely. Spore release phenology differed among species by up to a month and lasted from the beginning of July until the end of August. The early timing of spore dispersal in the most drought-sensitive, lawn-inhabiting sphagna should reduce the risk of sporophytes drying out prematurely during summer droughts.Key words: bryophyte, long-term study, mire, model, sexual reproduction, strategy.
A new bird from the Upper Cretaceous Two Medicine Formation of Montana
Authors: Varricchio David J
Published: July 2002

A partial humerus, ulna, and radius compose the type specimen of a new bird, Piksi barbarulna, new genus and species, from the Late Cretaceous (Campanian) Two Medicine Formation of western Montana. This ornithothoracine taxon differs from all other birds in having an enlarged dorsal epicondyle and a reduced ventral condyle on the humerus with corresponding modifications on the articular surface of the ulna. Among modern birds, Piksi is most similar to galliforms, but the paucity of unambiguous characters and its unusual morphology defy placement within any extant "order" and strongly questions any neornithine affinities. Instead, Piksi appears to have a fairly basal position within Ornithothoraces. Several morphologic features of Piksi occur in phylogenetically diverse but morphologically similar birds, such as galliforms, tinamous, and some columbiforms. The new bird comes from an inland, relatively dry paleo-environment. Atypical for a Cretaceous avian record dominated by waterfowl, Piksi appears to represents a heavy-bodied ground bird. Searching of inland depositional environments may yield new and ecologically distinct avian varieties.
Shifting gears: enzymatic evidence for the energetic advantage of switching diet in wild-living fish
Authors: Sherwood Graham D , Pazzia Ivano , Moeser Andrew , Hontela Alice , Rasmussen Joseph B
Published: July 2002

Large variations in the activity and scaling patterns of enzymes involved in anaerobic metabolism exist and appear to be related to species differences in the locomotory habits of fish. Here, we show how the scaling of muscle lactate dehydrogenase (LDH) activity is highly variable in fish, not only among species, but also among populations of yellow perch (Perca flavescens) and lake trout (Salvelinus namaycush) exhibiting large differences in the scaling of fish activity costs. These differences in LDH scaling properties were significantly related to differences in diet ontogeny. Scaling coefficients and adjusted R2 values of LDH versus body size relationships were both threefold higher in fish that do not make important diet shifts among planktivory, benthivory, and piscivory than in those that do. We argue that fish activity and related glycolytic potential are reset to lower values whenever fish are able to switch diet to larger prey while growing; we implicate the burst component of foraging (mostly attacks) as being responsible for changes in activity costs. Our results suggest that anaerobic power requirements in fish are highly plastic and adapted to local and recent food web conditions. We discuss these findings in relation to optimal foraging theory and the energetic basis of prey-size selection.
Phylogenetic analysis revealsStowaway-like elements may represent a fourth family of the IS630-Tc1-marinersuperfamily
Authors: Turcotte Kime , Bureau Thomas
Published: July 2002

The genomes of plants, like virtually all other eukaryotic organisms, harbor a diverse array of mobile elements, or transposons. In terms of numbers, the predominant type of transposons in many plants is the miniature inverted-repeat transposable element (MITE). There are three archetypal MITEs, known as Tourist, Stowaway, and Emigrant, each of which can be defined by a specific terminal inverted-repeat (TIR) sequence signature. Although their presence was known for over a decade, only recently have open reading frames (ORFs) been identified that correspond to putative transposases for each of the archetypes. We have identified two Stowaway elements that encode a putative transposase and are similar to members of the previously characterized IS630Tc1-mariner superfamily. In this report, we provide a high-resolution phylogenetic analysis of the evolutionary relationship between Stowaway, Emigrant, and members of the IS630Tc1-mariner superfamily. We show that although Emigrant is closely related to the pogo-like family of elements, Stowaway may represent a novel family. Integration of our results with previously published data leads to the conclusion that the three main types of MITEs have different evolutionary histories despite similarity in structure.Key words: Stowaway, Emigrant, MITE, mariner, transposon.
Comparison of orthologous and paralogous DNA flanking the wheat high molecular weight glutenin genes: sequence conservation and divergence, transposon distribution, and matrix-attachment regions
Authors: Anderson O D , Larka L , Christoffers M J , McCue K F , Gustafson J P
Published: July 2002

Extended flanking DNA sequences were characterized for five members of the wheat high molecular weight (HMW) glutenin gene family to understand more of the structure, control, and evolution of these genes. Analysis revealed more sequence conservation among orthologous regions than between paralogous regions, with differences mainly owing to transposition events involving putative retrotransposons and several miniature inverted transposable elements (MITEs). Both gyspy-like long terminal repeat (LTR) and non-LTR retrotransposon sequences are represented in the flanking DNAs. One of the MITEs is a novel class, but another MITE is related to the maize Stowaway family and is widely represented in Triticeae express sequence tags (ESTs). Flanking DNA of the longest sequence, a 20 425-bp fragment including and surrounding the HMW-glutenin Bx7 gene, showed additional cereal gene-like sequences both immediately 5' and 3' to the HMW-glutenin coding region. The transcriptional activities of sequences related to these flanking putative genes and the retrotransposon-related regions were indicated by matches to wheat and other Triticeae ESTs. Predictive analysis of matrix-attachment regions (MARs) of the HMW glutenin and several α-, γ-, and ω-gliadin flanking DNAs indicate potential MARs immediately flanking each of the genes. Matrix binding activity in the predicted regions was confirmed for two of the HMW-glutenin genes.Key words: wheat, glutenins, evolution, matrix-attachment regions, transposable elements.
AFLP markers and cytotaxonomic analysis reveal hybridisation in the genus Schoenus (Cyperaceae)
Authors: Scotti Ivan , Mariani Anna , Verona Valentino , Candolini Alberto , Cenci Carlo A , Olivieri Angelo M
Published: July 2002

Molecular, cytological, and morphological data support the existence of a hybrid population between Schoenus nigricans and Schoenus ferrugineus. This population was found in northeastern Italy, where S. nigricans is central with respect to its natural range and S. ferrugineus is marginal, being most common in the Alps and in central and northern Europe. Molecular marker data show that the putative hybrid population is genetically intermediate between nearby populations of the parent species. Cytological evidence confirmed the hybrid nature of this population, as does the almost complete sterility of plants within the population. Although no seeds were produced by the hybrid population, some possibly fertile pollen grains were produced; this suggests that the possibility of introgression between the two species through the hybrids cannot completely be excluded.Key words: Schoenus, AFLP markers, chromosome behaviour, introgression.
AFLPs mark different genomic regions compared with RFLPs: a case study in tomato
Authors: Bonnema Guusje , Berg Petra van den , Lindhout Pim
Published: July 2002

A set of three tomato chromosome 7 introgression lines (ILs) containing overlapping segments of Lycopersicon pennellii DNA was screened with a set of 10 EcoRIMseI and 10 PstIMseI AFLP primer combinations. A large number of markers were identified that mapped to one of the four regions of chromosome 7 defined by the set of three ILs. Because many of the identified markers have known map positions in three tomato reference maps, their location on the tomato genome could be verified. It was demonstrated that the three chromosome 7 ILs carried a chromosome 10 region harbouring a cluster of six AFLP markers that had not been detected before using RFLPs. The causes and implications of this observation are discussed.Key words: introgression lines, tomato, marker distribution, AFLP, RFLP, genetic linkage.
A non-destructive crack detection method for steel jacket offshore platforms based on global and local responses
Authors: Alam Md. Rabiul , Swamidas A SJ
Published: July 2002

A crack detection method for steel jacket offshore platforms based on global (displacement) and local (strain) responses is presented in this paper. One side panel of an idealized three-dimensional space frame structure was used in the numerical analysis; substructuring technique in finite element method was utilized as the numerical analysis procedure. Isoparametric thin shell elements, with reduced Gaussian integration, were used to discretize the whole structure. ABAQUS finite element software was used to solve the problem and process all information relating to the above-mentioned global and local responses. Numerical results obtained in the analysis have been compared with those obtained using other types of elements available in ABAQUS. The global and local parameters (displacements and strains) have been normalized using those obtained from the uncracked structure. It has been observed that the largest changes (in strain and stress) occur around the crack, but significant changes occur even away from the cracking weld toe. For cracks occurring at "one or both" saddle point(s), significant differences in strain exist to identify whether the cracking is on one side or on both sides. Significant change in slope of normalized global displacements, obtained around the crack, indicates the location of crack.Key words: crack detection, global and local responses, substructuring.
A case record of tailings dam construction using residual soils
Authors: Bedell Philip R , Firlotte Frederick W , Atherton Kevin
Published: July 2002

For cost effective construction, it is often necessary to optimize the use of on-site materials. At the Omai Gold Mine in Guyana, South America, tropical residual soils are used for construction of the tailings storage facility. At present, the geotechnical characteristics of residual soils have not been investigated or reported to the extent that transported soils have been. Geotechnical design and construction with these tropical residual soils can present unique challenges and problems. This case record outlines the investigation and construction procedures for the facility and provides a sample of the typical geotechnical engineering properties exhibited by the native tropical soils. In addition, data on observed behaviour and experience obtained handling and placing the materials as well as the performance of the structures during construction are provided.Key words: tropical residual soils, geotechnical design, tailings storage facility.
Estimation of hydraulic conductivity of unsaturated soils using a geotechnical centrifuge
Authors: Singh D N , Kuriyan Sneha J
Published: July 2002

A saturated silty soil sample is centrifuged in a geotechnical centrifuge to create an unsaturated state. The change in water content of the soil sample is recorded at different points along the length of the sample to obtain the water-content profile, which is then used to obtain the unsaturated hydraulic conductivity of the soil sample. These hydraulic conductivity values are compared with those obtained and reported by previous researchers by conducting accelerated falling-head tests on this soil sample in a centrifuge. The study demonstrates the use of centrifugation techniques to obtain hydraulic conductivities of unsaturated soils.Key words: silty soil, saturated soil, unsaturated soil, hydraulic conductivity, centrifuge testing.
Mechanical behavior of Tien-Liao mudstone in hollow cylinder tests
Authors: Lee Der-Her , Juang C Hsein , Lin Hung-Ming , Yeh Shing-Hung
Published: July 2002

A series of hollow cylinder tests were conducted to study the stressstrain characteristics and the yield surface of Tein-Liao mudstone, a soft rock widely distributed in southwestern Taiwan. These tests were carried out under different stress paths designed to utilize the versatility of the hollow cylinder testing system. The test results were used to establish the yield surface of the mudstone in the principal stress space. The experimental results were used to examine the accuracy of existing yield criteria, such as the Coulomb criterion, the extended Hoek-Brown model, and the Kim-Lade model. Among the three yield criteria examined, the Kim-Lade model provided the best agreement with the experimental results, although both the extended Hoek-Brown model and the Kim-Lade model are adequate for modeling the yield surface of the mudstone.Key words: rock, yield surface, stress path, hollow cylinder test.
Development of near infrared reflectance analysis calibrations for estimating genetic parameters for cellulose content in Eucalyptus globulus
Authors: Raymond C A , Schimleck L R
Published: July 2002

Determining kraft pulp yield in the traditional way is slow and expensive, limiting the numbers of samples that may be processed. An alternative is to use a secondary standard, such as cellulose content of the wood, which is strongly correlated with kraft pulp yield. The feasibility and efficiency of predicting cellulose content using near infrared reflectance (NIR) analysis was examined for Eucalyptus globulus Labill. Calibrations for NIR prediction of cellulose content indicated that NIR analysis could be used as a reliable predictor. Standard errors of calibration were 1% or lower, and there was excellent agreement between laboratory and predicted cellulose values. Cellulose content was under moderate genetic control (h2 ranging from 0.32 to 0.57), and genetic correlations with tree diameter and basic density were variable (ranging from 0.11 to 0.51 and 0.33 to 0.67, respectively). The advantages, disadvantages, and potential applications of NIR analysis for predicting cellulose content are examined.
Predator classification by the sea pen Ptilosarcus gurneyi (Cnidaria): role of waterborne chemical cues and physical contact with predatory sea stars
Authors: Weightman Janice O , Arsenault David J
Published: July 2002

Using laboratory and field experiments we examined the defensive behaviour of the sea pen Ptilosarcus gurneyi (Gray) towards three species of sea stars representing three levels of predatory threat. In the laboratory we first quantified the behaviour of P. gurneyi following physical contact with the sea stars Dermasterias imbricata (specialist predator), Pycnopodia helianthoides (generalist predator), and Pisaster ochraceus (nonpredator). Whereas the majority (73%) of the sea pens rapidly burrowed into the sediment following contact with D. imbricata, their response to P. helianthoides was highly variable and only 23% exhibited burrowing. In contrast, the response of P. gurneyi to P. ochraceus was weak and similar to that elicited by contact with a glass rod (control). Also, whereas the majority of sea pens displayed colony-wide bioluminescent flashes towards D. imbricata and P. helianthoides, their responses to P. ochraceus and the control were weaker and more localized. We subsequently examined whether waterborne predator chemical cues alone could trigger the defensive responses of P. gurneyi to D. imbricata and P. helianthoides, using laboratory bioassays of varying stimulus intensity. Interestingly, although exposure to chemical cues from predatory sea stars did not elicit any defensive response in P. gurneyi, subsequent physical contact with these predators triggered complete burrowing. Field bioassays using SCUBA yielded similar results, as P. gurneyi did not respond to the proximity of predators but rather delayed its response until physical contact occurred. Our study thus provides the first experimental evidence of predator-classification abilities in cnidarians and suggests that physical contact with predatory sea stars is required to trigger defensive behaviours in P. gurneyi.
A NEW LOOK AT GOLDSTONE’S THEOREM
Authors: BUCHHOLZ DETLEV , DOPLICHER SERGIO , LONGO ROBERTO , ROBERTS JOHN E.
Published: July 2002

The appearance of spontaneously broken symmetries and its bearing on the physical mass spectrum are analyzed in the algebraic setting of local quantum field theory. Within this setting, a generalization of Goldstone’s Theorem is established which does not rely on the existence of conserved currents. Continuous symmetries not satisfying the premises of the theorem can be spontaneously broken even in the presence of a mass gap.
GAP-LABELLING THEOREMS FOR SCHRÖDINGER OPERATORS ON THE SQUARE AND CUBIC LATTICE
Authors: VAN ELST ANDREAS
Published: July 2002

The spectra of Schrödinger operators on the square and cubic lattice are investigated by means of non-commutative topological K-theory. Using a general gap-labelling theorem, it is shown how to calculate the possible values of the integrated density of states on the gaps of the spectrum, provided some additional conditions hold. If the potential takes on only finitely many values, this reduces to the calculation of frequencies of patterns in the potential sequence. As an example, products of one-dimensional systems and potentials generated by higher-dimensional substitutions are considered.
LOCALIZATION AT WEAK DISORDER: SOME ELEMENTARY BOUNDS
Authors: AIZENMAN MICHAEL
Published: July 2002

An elementary proof is given of localization for linear operators H = Ho + λV, with Ho translation invariant, or periodic, and V (·) a random potential, in energy regimes which for weak disorder (λ → 0) are close to the unperturbed spectrum σ (Ho). The analysis is within the approach introduced in the recent study of localization at high disorder by Aizenman and Molchanov [4]; the localization regimes discussed in the two works being supplementary. Included also are some general auxiliary results enhancing the method, which now yields uniform exponential decay for the matrix elements <0|P[a,b] exp (−itH)|x> of the spectrally filtered unitary time evolution operators, with [a, b] in the relevant range.
HYBRID ENSEMBLE METHOD FOR THE UU COLLISION TERM
Authors: GIGLIO E. , REINHARD P.-G. , SURAUD E.
Published: July 2002

We present an efficient way to evaluate the Ühling–Uhlenbeck (UU) collision term in the case of semi-classical dynamics. We focus on finite fermionic systems such as small metal clusters, which we recently pointed out the importance of the UU collision term for the electronic dynamics. We show, how far the hybrid method, which lies between the full and the parallel ensemble methods, allows an efficient and accurate treatment of a Boltzmann–like collision term. We finally give a guideline to define the best parameter of the hybrid ensemble method for a given cluster size.
A SIMPLE MODEL OF PRICE FORMATION
Authors: SZNAJD-WERON K. , WERON R.
Published: July 2002

A simple Ising spin model, which can describe the mechanism of price formation in financial markets is proposed. In contrast to other agent-based models, the influence does not flow inward from the surrounding neighbors to the center site, but spreads outward from the center to the neighbors. The model thus describes the spread of opinions among traders. It is shown via standard Monte Carlo simulations that very simple rules lead to dynamics that duplicate those of asset prices.
The Effects of Long-Term Herbal Treatment for Pediatric AIDS
Authors: Tani Michio , Nagase Mahiko , Nishiyama Tadao , Yamamoto Tatsutaka , Matusa Rodica
Published: July 2002

This paper presents our long-term (1992–2000) treatment of pediatric Acquired Immune Deficiency Syndrome (AIDS) patients (maximum 100 children, last three years 65) using native herbal remedies in a voluntary medical assistance program in Constanta, Romania. We primarily report the progress of 10 children at a facility called the "House of Tomorrow" and three other facilities. The long-term (8 years and 8 months) treatment contributed to a drop of the amount of Human Immunodeficiency Virus Ribonucleic Acids (HIV-RNA) below the measurable level for 9 out of 10 patients at the "House of Tomorrow." Furthermore, the treatment led to preservation and increase of the cluster of differentiation (CD4) count, a remarkable decrease in mortality rate, as well as the maintenance of a good quality of life. It took one to three years for the beneficial effects of the treatment to emerge. No side-effects were recognized either clinically or biochemically, nor was there any emergence of drug-resistant strains of HIV as seen with anti-HIV chemical treatments.

This paper also refers to which herbal remedies were used and their general mechanism of action.
ON THE "UNIVERSAL" N=2 SUPERSYMMETRY OF CLASSICAL MECHANICS
Authors: DEOTTO E. , GOZZI E.
Published: July 2002

In this paper we continue the study of the geometrical features of a functional approach to classical mechanics proposed some time ago. In particular, we try to shed some light on a N = 2 "universal" supersymmetry which seems to have an interesting interplay with the concept of ergodicity of the system. To study the geometry better we make this susy local and clarify pedagogically several issues present in the literature. Secondly, in order to prepare the ground for a better understanding of its relation to ergodicity, we study the system on constant energy surfaces. We find that the procedure of constraining the system on these surfaces injects in it some local Grassmannian invariances and reduces the N = 2 global susy to an N = 1.
HAMILTONIAN FORMULATION OF OPEN WZW STRINGS
Authors: GIUSTO S. , HALPERN M. B.
Published: July 2002

Using a Hamiltonian approach, we construct the classical and quantum theory of open WZW strings on a strip. (These are the strings which end on WZW branes.) The development involves non-Abelian generalized Dirichlet images in an essential way. At the classical level, we find a new non-commutative geometry in which the equal-time coordinate brackets are non-zero at the world-sheet boundary, and the result is an intrinsically non-Abelian effect which vanishes in the Abelian limit. Using the classical theory as a guide to the quantum theory, we also find the operator algebra and the analogue of the Knizhnik–Zamolodchikov equations for the conformal field theory of open WZW strings.
GAUGE INVARIANCE, BACKGROUND FIELDS AND MODIFIED WARD IDENTITIES
Authors: FREIRE F. , LITIM D. F. , PAWLOWSKI J. M.
Published: July 2002

In this talk the gauge symmetry for Wilsonian flows in pure Yang-Mills theories is discussed. The background field formalism is used for the construction of a gauge invariant effective action. The symmetries of the effective action under gauge transformations for both the gauge field and the auxiliary background field are separately evaluated. Modified Ward-Takahashi and background field identities are used in my study. Finally it is shown how the symmetry properties of the full theory are restored in the limit where the cut-off is removed.
ExTRAPOLATION OF K→ππ DECAY AMPLITUDE
Authors: SUZUKI MAHIKO
Published: July 2002

We examine the uncertainties involved in the off-mass-shell extrapolation of the K→ππ decay amplitude with emphasis on those aspects that have so far been overlooked or ignored. Among them are initial-state interactions, choice of the extrapolated kaon field, and the relation between the asymptotic behavior and the zeros of the decay amplitude. In the inelastic region the phase of the decay amplitude cannot be determined by strong interaction alone and even its asymptotic value cannot be deduced from experiment. More a fundamental issue is intrinsic nonuniqueness of off-shell values of hadronic matrix elements in general. Though we are hampered with the complexity of intermediate-energy meson interactions, we attempt to obtain a quantitative idea of the uncertainties due to the inelastic region and find that they can be much larger than more optimistic views portray. If large uncertainties exist, they have unfortunate implications in the numerical accuracy of the computation of the direct CP violation parameter ∊′.
CHIRAL SUPERCONDUCTING MEMBRANES
Authors: CORDERO RUBÉN , ROJAS EFRAÍN
Published: July 2002

We develop the dynamics of the chiral superconducting membranes (with null current) in an alternative geometrical approach either making a Lagrangian description and a Hamiltonian point of view. Besides this, we show the equivalence of the resulting descriptions to the one known Dirac–Nambu–Goto (DNG) case. Integrability for chiral string model is obtained using a proposed light-cone gauge. In a similar way, domain walls are integrated by means of a simple ansatz. We compare the results with recent works that appeared in the literature.
FUZZY INSTANTONS
Authors: GROSSE HARALD , MACEDA MARCO , MADORE JOHN , STEINACKER HAROLD
Published: July 2002

We present a series of instanton-like solutions to a matrix model which satisfy a self-duality condition and possess an action whose value is, to within a fixed constant factor, an integer l2. For small values of the dimension n2 of the matrix algebra the integer resembles the result of a quantization condition but as n → ∞ the ratio l/n can tend to an arbitrary real number between zero and one.
EXCITATIONS OF A DROPLET OF ELECTRONS IN HALF-FILLED LANDAU LEVEL
Authors: YANG S.-R. ERIC , LYUE W. S.
Published: July 2002

We have investigated low energy excitations of a disk of electrons in half-filled Landau level using trial wave function and small-size exact diagonalization approaches. We have constructed a set of many-body basis states that describe correctly the low energy excitations. They suggest that a droplet can support an edge magnetoplasmon and low energy droplet excitations. A possibility of measuring these excitations in a quantum dot is discussed.
NONLOCAL KINETIC THEORY
Authors: MORAWETZ KLAUS , ŠPIČKA VÁCLAV , LIPAVSKÝ PAVEL
Published: July 2002

The short time behavior of a disturbed system is influenced by off-shell motion and characterized by the reduced density matrix possessing high energetic tails. After this short time regime the time evolution is controlled by small gradients. This leads to a nonlocal Boltzmann equation for the quasiparticle distribution and a functional relating the latter one to the reduced density matrix. The nonlocalities are presented as time and space shifts arising from gradient expansion and are leading to virial corrections in the thermodynamical limit.
REALISTIC MODELING OF STRONGLY CORRELATED ELECTRON SYSTEMS: AN INTRODUCTION TO THE LDA+DMFT APPROACH
Authors: HELD K. , NEKRASOV I. A. , BLÜMER N. , ANISIMOV V. I. , VOLLHARDT D.
Published: July 2002

The LDA+DMFT approach merges conventional band structure theory in the local density approximation (LDA) with a state-of-the-art many-body technique, the dynamical mean-field theory (DMFT). This new computational scheme has recently become a powerful tool for ab initio investigations of real materials with strong electronic correlations. In this paper an introduction to the basic ideas and the set-up of the LDA+DMFT approach is given. Results for the photoemission spectra of the transition metal oxide La 1-x Sr x TiO 3, obtained by solving the DMFT equations by quantum Monte Carlo (QMC) simulations, are presented and are found to be in very good agreement with experiment. The numerically exact DMFT(QMC) solution is compared with results obtained by two approximative solutions, i.e. the iterative perturbation theory and the non-crossing approximation.
MICROSCOPIC APPROACH TO ELECTRON–PHONON INTERACTION PHYSICS IN HALF-DOPED MANGANITES
Authors: YARLAGADDA SUDHAKAR
Published: July 2002

We present a microscopic picture of charge, orbital, and spin ordering in manganites at 50% doping by considering Jahn–Teller interaction. For spinless fermions, in two-dimensions and at 50% doping, we show that Jahn–Teller distortion and charge-orbital ordering occur simultaneously with the system in an essentially orbitally polarized state of dx2-y2 orbitals. Upon including spin degree of freedom, for small antiferromagnetic coupling, we obtain CE-type ordering.
IN-SITU PHOTOELECTRON SPECTROSCOPY OF MAGNETIC DOTS AND MAGNETIC SEMICONDUCTOR NANOSTRUCTURES
Authors: OSHIMA M. , ONO K. , MIZUGUCHI M. , YAMADA M. , OKABAYASHI J. , FUJIMORI A. , AKINAGA H. , SHIRAI M.
Published: July 2002

High resolution angle-resolved photoelectron spectroscopy (ARPES) has been performed on magnetic nanostructures which were in-situ grown hetero-epitaxially on GaAs substrates by low temperature molecular beam epitaxy. Sulfur termination of GaAs surfaces enabled the formation of NiAs-type MnSb dots and zinc-blende (zb) type MnAs dots, showing huge magnetoresistance at RT and half-metallic behavior, respectively. ARPES analysis revealed that the zb-MnAs dots show unique valence band feature with Mn 3d-related peak at about 4 eV of binding energy which is quite similar to (Ga,Mn)As DMS films. Zb-CrAs thin films on GaAs with T c higher than RT are found to show the band dispersion within 2 eV near the Fermi edge, which is in good agreement with the FLAPW calculation. We have also found that (Ga,Cr)As DMS thin films have the similar valence band features to zb-CrAs
DENSITY MATRIX RENORMALIZATION GROUP: INTRODUCTION FROM A VARIATIONAL POINT OF VIEW
Authors: NISHINO T. , HIKIHARA T. , OKUNISHI K. , HIEIDA Y.
Published: July 2002

The density matrix renormalization group theory is reviewed as a numerical variational method. The variational state, expressed as a product of local tensors, is improved through locally tuning each tensor. The first section is a tutorial with simplified discussions. Details are discussed in the subsequent sections. The review concludes with some recent developments and future directions.
EFFECTS OF DIMENSIONALITY IN THE RARE-EARTH MANGANATES
Authors: GUNDAKARAM R. , HUANG C. Y.
Published: July 2002

We report measurements of magnetization, magnetoresistance and ESR on systems with the 3-D and layered structures, to study the effect of reduced dimensionality. Compositions of the systems Pr 0.7 Sr 0.3- x Ca x MnO 3 and La 2-2 y Sr 1+2 y Mn 2- z Cr z O 7 were synthesized, which have the 3D and quasi-2D structures, respectively. The magnetic and transport properties are markedly affected by the reduction in dimensionality. Large values of magnetoresistance have been observed in the layered materials even at low temperature, in contrast with the behavior of the 3D compositions. ESR measurements on the Pr 0.7 Sr 0.3- x Ca x MnO 3 system show a single resonance line in the temperature range of our study. However, compositions of the La 2-2 y Sr 1+2 y Mn 2 O 7 system with y =0.3, 0.4 and 0.5 show a complex behavior. As the samples are cooled, a single resonance line is first observed, which can be described by a Lorentzian. Below ~2 T c, for compositions with y =0.3 and 0.4, a complex lineshape evolves, which can be resolved into two Gaussian lines. This crossover in the lineshape indicates a transition from a homogeneous to an inhomogeneous spin system, which can be attributed to the nature of the ferromagnetic ordering between the bilayers. The composition with y =0.5 shows a different behavior, which might be due to the antiferroma.gnetic ordering exhibited by this composition. A detailed analysis of the experiments is presented.
SOME NEW RELATIONS BETWEEN TARGET STATE AND QUANTUM TELEPORTED STATE GAINED BY VIRTUE OF THE |η> REPRESENTATION
Authors: FAN HONGYI , FAN YUE
Published: July 2002

Based on the entangled state representation <η| in two-mode Fock space (Fan and Klauder, Phys. Rev.A49, 704 (1994)), we provide an alternative approach for analyzing quantum teleportation of continuous variables and go a step further by deriving some relations between input (target) states and teleported states. The natural representation of the two-mode squeezing operator in the |η> representation greatly simplifies our calculations.
ARE SURFACES PERTINENT FOR DESCRIBING SOME THERMOTROPIC LIQUID CRYSTAL PHASES?
Authors: PANSU BRIGITTE
Published: July 2002

Surfaces, like minimal surfaces, are commonly used to describe intricate thermotropic liquid crystalline phase structures: cubic phases, TGB phases, quadratic phases, blue phases, and smectic blue phases. Such geometrical models are good tools to visualize the competition between the various molecular interactions generating these phases although they often cannot lead to the prediction of the thermodynamic phase diagrams.
GENERALIZED SYMMETRIC NONEXTENSIVE THERMOSTATISTICS AND q-MODIFIED STRUCTURES
Authors: LAVAGNO A. , SWAMY P. NARAYANA
Published: July 2002

We formulate a convenient generalization of the q-expectation value, based on the analogy of the symmetric quantum groups and q-calculus, and show that the q↔ q-1 symmetric nonextensive entropy preserves all of the mathematical structure of thermodynamics just as in the case of nonsymmetric. Tsallis statistics. Basic propreties and analogies with quantum groups are discussed.
ON THE RELIABILITY OF THE SURROGATE DATA TEST FOR NONLINEARITY IN THE ANALYSIS OF NOISY TIME SERIES
Authors: KUGIUMTZIS D.
Published: July 2002

In the analysis of real world data, the surrogate data test is often performed in order to investigate nonlinearity in the data. The null hypothesis of the test is that the original time series is generated from a linear stochastic process possibly undergoing a nonlinear static transform. We argue against reported rejection of the null hypothesis and claims of evidence of nonlinearity based on a single nonlinear statistic. In particular, two schemes for the generation of surrogate data are examined, the amplitude adjusted Fourier transform (AAFT) and the iterated AAFT (IAFFT) and many nonlinear discriminating statistics are used for testing, i.e. the fit with the Volterra series of polynomials and the fit with local average mappings, the mutual information, the correlation dimension, the false nearest neighbors, the largest Lyapunov exponent and simple nonlinear averages (the three point autocorrelation and the time reversal asymmetry). The results on simulated data and real data (EEG and exchange rates) suggest that the test depends on the method and its parameters, the algorithm generating the surrogate data and the observational data of the examined process.
NOVEL STABILITY CONDITIONS FOR CELLULAR NEURAL NETWORKS WITH TIME DELAY
Authors: LIAO XIAOFENG , WONG KWOK-WO , YU JUEBANG
Published: July 2002

In this paper, the global asymptotic stability of cellular neural networks with time delay is discussed using some novel Lyapunov functionals. Novel sufficient conditions for this type of stability are derived. They are less restrictive and more practical than those currently used. As a result, the design of cellular neural networks with time delay is refined. Our work can also be generalized to cellular neural networks with time-varying delay, a topic on which little research work has been done. By means of several different Lyapunov functionals, some sufficient conditions related to the global asymptotic stability for cellular neural networks with perturbations of time-varying delays are derived.
ON STICK–SLIP HOMOCLINIC CHAOS AND BIFURCATIONS IN A MECHANICAL SYSTEM WITH DRY FRICTION
Authors: PONTES B. R. , OLIVEIRA V. A. , BALTHAZAR J. M.
Published: July 2002

In this paper we consider a self-excited mechanical system by dry friction in order to study the bifurcational behavior of the arisen vibrations. The oscillating system consists of a mass block-belt-system which is self-excited by static and Coulomb friction. We analyze the system behavior numerically through bifurcation diagrams, phase portraits, frequency spectra and Poincaré maps, which show the existence of nonhomoclinic and homoclinic chaos and a route to homoclinic chaos. The homoclinic chaos is also analyzed analytically via the Melnikov prediction method. The system dynamic is characterized by the existence of two potential wells in the phase plane which exhibit rich bifurcational and chaotic behavior.
THREE-DIMENSIONAL STRATIFICATIONS, KNOTS AND BIFURCATIONS OF TWO-DIMENSIONAL DYNAMICAL SYSTEMS
Authors: BANKS S. P.
Published: July 2002

In this paper we consider dynamical systems in ℝ3 which are invariant on "concentric" surfaces of genus p and show that they are equivalent to systems invariant on spheres, and introduce a rotation group invariant for these systems to distinguish the different systems which they represent.
CHAOTIC INTERSPIKE INTERVALS WITH MULTIPEAKED HISTOGRAM IN NEURONS
Authors: GONG PULIN , XU JIANXUE , LONG KAIPING , HU SANJUE
Published: July 2002

In our paper, we report the findings that the interspike intervals of the injured dorsal root ganglion neurons have multipeaked histograms and the interspike intervals are chaotic. First, the symbolic analysis method presented in the paper and the nonlinear forecasting method are used to study the dynamic differences between the interspike intervals with a multipeaked histogram generated by chaos and those induced by noise in some neuron models. Then based on the dynamic differences, the interspike intervals recorded in our experiment are analyzed by the nonlinear forecasting and the symbolic analysis method. We obtain that the dynamics of our experimental interspike intervals are greatly different from those of the interspike intervals with a multipeaked histogram induced by noise, while they are similar to the dynamics of this kind of interspike intervals generated by chaos. The results show that the experimental interspike intervals with a multipeaked histogram are chaotic.
HOPF BIFURCATIONS AND DEGENERACIES IN CHUA'S CIRCUIT — A PERSPECTIVE FROM A FREQUENCY DOMAIN APPROACH
Authors: MOIOLA JORGE L. , CHUA LEON O.
Published: July 2002

In the present work explicit formulas for analyzing the birth of limit cycles arising in the Chua's circuit through a Hopf bifurcation is provided. A local amplitude equation is derived using a frequency domain approach and harmonic balance approximations. Furthermore, the first Lyapunov index used to detect degenerate Hopf bifurcations is derived in terms of the parameters of the nonlinear circuit. A perspective for analyzing other bifurcations using this frequency domain approach is discussed.
FUZZY PREDICTIVE CONTROL OF UNCERTAIN CHAOTIC SYSTEMS USING TIME SERIES
Authors: CHEN LIANG , CHEN GUANRONG
Published: July 2002

In this paper, a simple fuzzy logic based intelligent mechanism is developed for predicting and controlling a chaotic system to a desired target, using only input–output data obtained from the unknown (or uncertain) underlying chaotic system. In the chaos prediction phase, a fuzzy system approach incorporating with Gaussian type of fuzzy membership functions is used. Only system input–output data are needed for prediction, and a recursive least-squares computational algorithm is employed for the calculation. In the controller design phase, the Lyapunov stability criterion is used, which forms the basis of the main design principle. Some simulation results on the chaotic Sin map and Hénon map are given, for both prediction and control, to illustrate the effectiveness and control performance of the proposed method.