bluuebunny/crossref_metadata_2025 huggingface dataset:
Three New Alkaloids, Convolutamines F and G, and Convolutamydine E, from the Floridian Marine Bryozoan Amathia convoluta
Authors: Kamano Yoshiaki , Kotake Ayano , Hashima Hirofumi , Hayakawa Ichiro , Hiraide Hatsue , Zhang Hui-ping , Kizu Haruhisa , Komiyama Kanki , Hayashi Masahiko , Pettit George R.
Published: July 2002

Two new (2-phenylethyl)amine alkaloids, convolutamines F and G, and a dibromohydroxyoxindole alkaloid, convolutamydine E, have been isolated from the butan-1-ol soluble material of the Floridian marine bryozoan Amathia convoluta. Their structures were elucidated on the basis of spectroscopic data. Convolutamine F exhibited activity against KB, KB/VJ-300, and U937 cells. This compound also exhibited the inhibitory effects for cell division of fertilized sea urchin eggs.
Solvation Effects of Complex Anions in Cryolite Melt
Authors: Varga Štefan , Mach Pavel , Turi Nagy Ladislav
Published: July 2002

Equilibrium constants of the main dissociation scheme of cryolite complex anions and corresponding solvation energies are calculated using both the Hartree-Fock and density-functional schemes with direct inclusion of the reaction field into the Hamiltonian in a self-consistent way. The results are compared with previous a posteriori static-reaction-field calculations.
Cytochromes P450 Involved in Cyclophosphamide, Paclitaxel and Docetaxel Metabolism in Rats
Authors: Bořek-Dohalská Lucie , Gut Ivan , Souček Pavel , Roth Zdeněk , Hodek Petr
Published: July 2002

We investigated involvement of cytochromes P450 (CYPs) of rat liver microsomes in metabolism of two anticancer drugs, paclitaxel (PCT) and docetaxel (DTX), by an indirect method. This method is based on the presumption that the compound competitively inhibiting oxidation of the CYP-selective substrate should also be a substrate for the CYP enzyme. The validity of this approach was confirmed using the model drug, cyclophosphamide (CPA). Indeed, CPA competitively inhibited oxidation of substrates specific for CYP2B1 and CYP3A1/2, enzymes previously reported to be capable of metabolizing CPA. Using this method, we identified CYP enzymes participating in PCT and DTX metabolism. The CYP2D1/2/3 and CYP3A1/2 are enzymes oxidizing PCT while CYP3A1/2 and CYP2E1 are responsible for metabolism of DTX. Here, we report a suitable method serving for easy and fast estimation of CYP enzymes involved in drug metabolism.
Proteases of HIV-1 and MAV Hydrolyze Specifically Human Apo-Hemopexin
Authors: Kluh Ivan , Černá Věra , Pichová Iva , Voburka Zdeněk
Published: July 2002

The specificities of HIV-1 (Human Immunodeficiency Virus Type 1) and MAV (Myeloblastosis Associated Virus) proteases have been evaluated for their ability to split two-domain protein human apo-hemopexin. Both proteases hydrolyze only one peptidic bond Leu240-Ser241located in the connecting region between two domains. The ability of viral proteases to cleave Leu-Ser bond was confirmed by cleavage of synthetic octapeptide His-Leu-Val-Leu-Ser-Ala-Leu-Thr-NH2covering the susceptible area of human apo-hemopexin. The results demonstrate that the cleavage of Leu-Ser bond is not due to its location in the interdomain region of apo-hemopexin. The cleavable bond Leu-Ser has never been found either in viral or in non-viral proteins. According to the vector projection method this octapeptide was considered as non-hydrolyzable.
Calculation of Chemical Equilibrium in Complex Systems: System Restrictions
Authors: Voňka Petr , Leitner Jindřich
Published: July 2002

The set of positive solutions of the mass balance equations Ω must not be empty; otherwise, at least one species exists which has zero number of moles independently of the chemical changes in the system. If the set Ω is empty, then numerical problems can occur in the course of the calculation of chemical equilibrium. Two examples demonstrate the importance of this problem and the algorithm, allowing to prove emptiness or non-emptiness of the set Ω, is proposed.
Enzymological Characterization of Secreted Proteinases from Candida parapsilosis and Candida lusitaniae
Authors: Hrušková-Heidingsfeldová Olga , Dostál Jiří , Hamal Petr , Pazlarová Jarmila , Ruml Tomáš , Pichová Iva
Published: July 2002

Opportunistic pathogens of the genusCandidaproduce secreted aspartic proteinases (Saps) that are considered as one of the virulence factors. While Saps ofC. albicansandC. tropicalishave been studied extensively, information concerning proteinases secreted by other pathogenicCandidaspecies is scarce. To our knowledge, enzymologic characterizations of Sap ofC. parapsilosis(Sapp1p) andC. lusitaniae(Saplp) are limited. We have purified Saps ofC. parapsilosisandC. lusitaniaefrom yeast culture supernatants and detected only one gene product of both Sapp1p and Saplp using isoelectric focusing and N-terminal sequencing. Molecular weight of Saplp determined by SDS-PAGE is approximately 42 000. For the highest enzyme activity, both Sapp1p and Saplp require pH ranging from 3 to 4 and temperature between 27-40 °C for Saplp and 45 °C for Sapp1p, respectively. At physiological temperature, both the proteinases are stable. The characterization of Saps of clinical isolates ofC. parapsilosisandC. lusitaniaeshould contribute to design of novel drugs specifically targeted on proteinases.
Exercise and outdoor ambient air pollution
Authors: Carlisle A J , Sharp N C C
Published: July 2002

Objectives—To establish by literature survey: (a) levels at which air pollutants are considered damaging to human health and to exercisers in particular; (b) the current ambient levels experienced in the United Kingdom; (c) whether athletes are especially at risk.

Methods—Six major urban air pollutants were examined: carbon monoxide (CO); nitrogen oxides (NOX); ozone (O3); particulate matter (PM10); sulphur dioxide (SO2); volatile organic compounds (VOCs).

Results—CO is detrimental to athletic performance. NO2is of concern to human health, but outdoor levels are low. O3poses a potentially serious risk to exercising athletes. Decrements in lung function result from exposure, and there is evidence that athletic performance may be affected. Detrimental effects may occur at low ambient levels, but there is no scientific consensus on this matter. PM10is causing concern in the scientific community. Blood lead accumulation during exercise indicates that personal exposure to toxic compounds associated with PM10may be magnified. Generally, outdoor ambient levels of SO2are too low to cause a problem to the athlete, except the asthmatic athlete. The few studies on exposure of exercisers to VOCs are reviewed.

Conclusions—Athletes and exercisers should avoid exercising by the road side even though levels of the more noxious air pollutants have been controlled in the United Kingdom. O3is particularly damaging to athletes; it reaches its highest concentrations on hot bright days in rural areas.
Dramatic diurnal variation in the concentration of the human trefoil peptide TFF2 in gastric juice
Authors: Semple J I , Newton J L , Westley B R , May F E B
Published: July 2002

BACKGROUND

TFF2, a member of the trefoil factor family of proteins, is a glycosylated protein of 106 amino acids. It is secreted by gastric antral and pyloric glands and by Brunner's glands of the duodenum. TFF2 is found in high concentrations around sites of ulceration. It stimulates cell motility and is probably the principal cytoprotective trefoil peptide in the stomach.

AIMS

To determine if production of TFF2 follows a circadian rhythm and to measure changes in secretion of TFF2 in response to food intake and during sleep.

SUBJECTS

Young healthy adults were recruited. They were asymptomatic and were not receiving medication. The 24 hour regimen was designed to allow normal stimulation of gastric secretion in response to food intake and sleep. Gastric juice was collected two hourly via a nasogastric tube.

METHODS

Glycosylated and non-glycosylated TFF2 proteins were measured by quantitative western transfer analysis. The results were analysed statistically using SPSS software.

RESULTS

There was a dramatic diurnal variation in the concentration of TFF2. The mean concentration was lowest in the early evening (0.29 μg/ml), increased gradually during the evening, and then sharply during the night to reach 7.9 μg/ml. The ratio of glycosylated to non-glycosylated TFF2 varied and was higher during the night than in the afternoon. pH, total protein, and pepsin concentrations in gastric juice did not vary significantly over 24 hours.

CONCLUSION

The data suggest that diurnal variations in TFF2 secretion occur independently of pepsin and gastric acid secretion. The concentration of glycosylated TFF2 in the gastric lumen falls in response to food intake. TFF2 secretion increases during inactivity and sleep. These results suggest that secretion of TFF2 in the stomach is highest during the night and that the cytoprotective effects of TFF2 on the gastric mucosa occur mainly during sleep.
Parental duties and untreatable genetic conditions
Authors: Clarkeburn Henriikka
Published: July 2002

This paper considers parental duties of beneficence and non-maleficence to use prenatal genetic testing for non-treatable conditions. It is proposed that this can be a duty only if the testing is essential to protect the interests of the child ie only if there is a risk of the child being born to a life worse than non-existence. It is argued here that non-existence can be rationally preferred to a severely impaired life. Uncontrollable pain and a lack of any opportunity to develop a continuous self are considered to be sufficient criteria for such preference. When parents are at risk of having a child whose life would be worse than non-existence, the parents have a duty to use prenatal testing and a duty to terminate an affected pregnancy. Further, such duty does not apply to any conditions where the resulting life can be considered better than non-existence.
Exposure of Paris taxi drivers to automobile air pollutants within their vehicles
Authors: Zagury Emmanuelle , Le Moullec Yvon , Momas Isabelle
Published: July 2002

OBJECTIVES

To study the exposure of Parisian taxi drivers to automobile air pollutants during their professional activity.

METHODS

A cross sectional study was carried out from 27 January to 27 March 1997, with measurements performed in the vehicles of 29 randomly selected drivers. Carbon monoxide (CO) content was measured over an 8 hour period by a CO portable monitor. The fine suspended particles were measured according to the black smoke index (BS), with a flow controlled portable pump provided with a cellulose filter. The nitrogen oxides, NO and NO2were measured with a passive sampler.

RESULTS

These drivers are exposed during their professional activity to relatively high concentrations of pollutants (mean, median (SD) 3.8, 2 (1.7) ppm for CO, 168, 164 (53) μg/m3for BS, 625, 598 (224) μg/m3for NO, and 139, 131 (43) μg/m3for NO2.) For CO the concentrations were clearly lower than the threshold values recommended by the World Health Organisation. The situation is less satisfactory for the other pollutants, especially for the BS index. All concentrations of pollutants recorded were noticeably higher than concentrations in air recorded by the ambient Parisian air monitoring network and were close to, or slightly exceeded, the concentrations measured at the fixed stations close to automobile traffic. Pollutant concentrations were also influenced greatly by weather conditions.

CONCLUSION

This first French study conducted in taxi drivers shows that they are highly exposed to automobile pollutants. The results would justify a medical follow up of this occupational group.
Carbohydrate-deficient glycoprotein syndromes
Authors: Gordon Neil
Published: July 2002

Four types of carbohydrate-deficient glycoprotein syndrome have been described, and the cause of two of them has been found. The symptoms and signs of these syndromes are described, with variations that occur at different ages. The commonest is type Ia with an autosomal recessive form of inheritance, and the gene responsible has been mapped to 16p. The typical pathology is atrophy of the cerebellum and brainstem, sometimes also involving the cortex, although both the pathology and the biochemical deficiencies vary between different types of syndrome. The diagnosis depends firstly on recognising the clinical features, including the presence of complications such as thyroid disorders. Then biochemical tests can be carried out, especially chromatographic carbohydrate-deficient transferrin assay and isoelectric focusing of serum transferrin.

The prognosis depends on the complications, renal, hepatic, and cardiac, but affected children will be severely handicapped. Therefore treatment consists mainly of coping with the complications, and supporting the child and the family. Oral infusion of mannose can be effective in type Ib disease.
Acute hospital admissions from nursing homes: some may be avoidable
Authors: Bowman C E , Elford J , Dovey J , Campbell S , Barrowclough H
Published: July 2002

A retrospective survey of acute hospital admissions from nursing homes over a year to a district hospital revealed high overall hospital admission rates and wide variations of admission rates from similar homes. Medical admissions dominated, infections and poorly controlled heart failure being notably common. A significant proportion of admissions may have been avoided by active chronic disease management, together with better information for doctors responding to emergency calls and specialist support programmes facilitating in situ treatment.
Laparoscopic excision of splenic hydatid cyst
Authors: Gharaibeh K I A
Published: July 2002

Hydatid disease of the spleen is a rare condition. The standard treatment is open total or partial splenectomy. Recently hand assisted laparoscopic total splenectomy for splenic hydatid cyst has been reported. A case is described of splenic hydatid cyst in a 45 year old man that was excised laparoscopically; the related literature is reviewed.
Mutagen sensitivity and p53 expression in colorectal cancer in China
Authors: Shao L , Lai M , Huang Q
Published: July 2002

OBJECTIVE

This study was designed to investigate DNA damage and/or repair capability, non-random chromatid breakage, and p53 expression in patients with colorectal cancer.

METHODS

The bleomycin sensitivity assay was used in a case-control study to compare the DNA damage repair system between colorectal cancer patients and controls. G-banding was used to search for non-random chromatid breaks. Immunocytochemistry was used to investigate p53 expression in tumour tissues and adjacent normal tissues.

Results

It was found that cases typically had a higher number of chromosome breaks than controls (0.84v 0.69 breaks/cell, p<0.01). After correction by sex and age, the difference was still significant (F=4.38, p<0.05). The correlation coefficient between mutagen sensitivity and age was 0.31(p<0.05) in controls and 0.18 (p>0.05) in cases. The ratio of odds ratios among bleomycin resistant, sensitive, and hypersensitive classes was 1:2.31:3.85. Overexpression of p53 was detected in 25 of 47 tumour tissues independent of tumour stage. Cases who had a family history of cancer were susceptible to the p53 aberration (p<0.05). Chromosomes 1p, 5q, and 14q were susceptible to breakage in patients with colorectal cancer.

Conclusion

Patients with colorectal cancer show increased bleomycin induced chromatid breaks and may have minor DNA repair deficiencies. p53 aberration is an early event in the development of colorectal cancer, but no definite correlation is found between p53 overexpression and mutagen sensitivity.
Prognosis for fertility and ovarian function after treatment with radioiodine for thyroid cancer
Authors: Vini L , Hyer S , Al-Saadi A , Pratt B , Harmer C
Published: July 2002

The aim of this study was to review the outcome of ablative radioiodine treatment on ovarian function in young women treated for differentiated thyroid carcinoma. Of 1398 patients with differentiated thyroid cancer, 496 were women under the age of 40 at the time of diagnosis who had received radioiodine therapy. Of these, 322 received a single 3 GBq ablation dose of radioiodine while the remainder received subsequent treatment with 131I with a cumulative activity of 8.5–59 GBq for residual, recurrent, or metastatic disease. Transient amenorrhoea or menstrual irregularities lasting up to 10 months were experienced in 83 patients (17%). No cases of permanent ovarian failure were recorded. There were 427 children born to 276 women; only one patient wishing to achieve a successful pregnancy outcome has been unsuccessful. Four premature births and 14 miscarriages occurred but no congenital abnormalities were reported. The risk of permanent damage to the ovaries after ablative radioiodine treatment appears to be low and patients can be reassured they can have normal pregnancies after this treatment.
A prospective investigation of the impact of smoking bans on tobacco cessation and relapse
Authors: Longo Daniel R , Johnson Jane C , Kruse Robin L , Brownson Ross C , Hewett John E
Published: July 2002

BACKGROUND AND OBJECTIVES

To examine the long term impact of workplace smoking bans on employee smoking cessation and relapse. Over three years we studied a total of 1033 current or former smokers (intervention group) employed in smoke-free hospitals and 816 current or former smokers (comparison group) employed in non-smoke-free workplaces. The design of this natural experiment is a prospective cohort study. We randomly selected both hospitals and employees from 12 strata based on hospital size and state tobacco regulations, and sampled employees in the same communities. Main outcome measures were post-ban quit ratio and relapse rate.

RESEARCH DESIGN

Between groups comparisons were conducted using the Cochran-Mantel-Haenszel statistic for general association, stratified Cox proportional hazards models, and the CMH analysis of variance statistic based on ranks. McNemar's test and the sign test were used to test for changes over time within each group.

RESULTS

Differences in the post-ban quit ratio were observed between intervention and comparison groups (p ⩽ 0.02). For employees whose bans were implemented at least seven years before survey, the post-ban quit ratio was estimated at 0.256, compared with 0.142 for employees in non-smoke-free workplaces (p = 0.02). After controlling for a variety of factors, time to quit smoking was shorter for the hospital employees (p < 0.001), with an overall relative risk of quitting of 2.3. Contrary to expectations, relapse rates were similar between the groups.

CONCLUSION

Employees in workplaces with smoking bans have higher rates of smoking cessation than employees where smoking is permitted, but relapse is similar between these two groups of employees. The results of this investigation have international applicability for policy makers, clinicians, employers, and employees. Countries should review smoking policies in workplaces in light of their own smoking patterns and efforts to deal with environmental tobacco smoke.
Catalytic reduction of benzoate esters and lactones in the presence of PhMeSiH2and a titanocene-based catalyst
Authors: Shu Ronghua , Harrod John F , Lebuis Anne-Marie
Published: July 2002

PhMeSiH2reduces ethyl benzoate in the presence of a Cp2TiMe2(Cp = η5-cyclopentadienyl) catalyst to give PhMeSi(OEt)(OCH2Ph) (1). Small to moderate amounts of toluene are also produced, depending on the reaction conditions. Under 40 psi of H2the same reaction gives quantitative reduction of the ester to toluene. PhCHO is reduced, under the same conditions as the ester, to a mixture of PhMeSi(OCH2Ph)2and toluene in proportions similar to that observed with the ester. A stoichiometric reaction of PhMeSiH2, PhCOOEt, and Cp2TiMe2resulted in the formation of known [Cp2Ti(OEt)]2(2) in 75% isolated yield. A mechanism is proposed in which the C=O of the ester inserts into a TiH bond. A Ti-mediated transfer of the ethoxy group from the resulting (α-ethoxy)benzyloxytitanium intermediate to silicon produces PhMeSi(OEt)H and PhCHO. 1 is generated via hydrosilation of PhCHO by PhMeSi(OEt)H. Both β- and γ-butyrolactones react with PhMeSiH2in the presence of a catalytic amount of Cp2TiMe2to produce copolymers -[O-PhMeSi-O(CH2)3CHR]n- (R = H, 3; R = Me, 4) (Mw[Formula: see text] 1 × 103; Mw/Mn[Formula: see text] 1.3). A mechanism analogous to that proposed for the ethyl benzoate reduction is proposed. A reaction of PhMeSiH2and γ-butyrolactone with a stoichiometric amount of Cp2TiMe2in the presence of tetrahydofuran (THF) produces Cp2Ti(µ-H)(µ-η1,η5-C5H4)Ti(OC4H8)Cp(5) (65% isolated yield) whose structure is determined by X-ray crystallography.Key words: hydrosilation, esters, lactones, titanocene, catalysis.
Effect of landscape structure on the movement behaviour of a specialized goldenrod beetle, Trirhabda borealis
Authors: Goodwin Brett J , Fahrig Lenore
Published: July 2002

We hypothesize that the ability of an organism to move through a landscape is determined by the interaction between its movement behaviour and the landscape structure. In contrast, models predicting spatial distribution, local population stability, or metapopulation stability typically assume that movement ability is independent of landscape structure. These model predictions will be invalid if the assumption of constant movement ability is incorrect. To assess the influence of landscape structure on movement behaviour (and therefore movement ability), we tracked individual goldenrod beetles (Trirhabda borealis) through microlandscapes composed of three patch types (goldenrod, cut vegetation, and cut vegetation containing camouflage netting to a height of 50 cm) that differed in terms of available food resources and structural complexity. In goldenrod patches, beetles moved infrequently in brief bursts of slow meandering movements. In cut patches, beetles moved frequently in sustained bursts of slow directed movements. In netting patches, beetles moved frequently in brief bursts of fast meandering movements. Using mark-release experiments, we determined that T. borealis did not detect goldenrod from afar or respond to edge type. Since T. borealis movement behaviour differed between patch types, its movement ability must depend on landscape structure. If this general result applies to other species, it implies that predictions of local population and metapopulation responses to landscape alteration could be erroneous. Effects of landscape alteration on movement behaviour should be incorporated into models of population response to landscape alteration.
ADDITION OF INDEPENDENT VARIABLES IN QUANTUM GROUPS
Authors: LENCZEWSKI ROMUALD
Published: July 2002

A q-analog version of the quantum central limit theorem (qclt) for quantum groups [Formula: see text] with generators [Formula: see text] and associated bialgebras [Formula: see text] (subject to CR1 [Formula: see text], titj = tjti) and [Formula: see text] (subject to CR1 and CR2: tiej = qaij ejti, tifj = q-aijfjti) is presented. Our approach is based on the method of moments of Giri and von Waldenfels [6] and von Waldenfels [18] for tensor ungraded and graded algebras, respectively. Thus, it is shown that for certain functionals ϕ, one can evaluate the limit of moments [Formula: see text], where [Formula: see text] are generators subject to some CR with the normalization related to [N], the q-analog of N, ϕ*N = ϕ⊗N ◦ ∆N–1, where Δ is the coproduct in [Formula: see text] and ∆N its Nth iteration. This work is restricted to q ∈ R+.
Cluster Properties of One Particle Schrödinger Operators. II
Authors: Kostrykin V. , Schrader R.
Published: July 2002

We continue the study of cluster properties of spectral and scattering characteristics of Schrödinger operators with potentials given as a sum of two wells, begun in our preceding article [Rev. Math. Phys. 6 (1994) 833–853] and where we determined the leading behaviour of the spectral shift function and the scattering amplitude as the separation of the wells tends to infinity. In this article we determine the explicit form of the subleading contributions, which in particular show strong oscillatory behaviour. Also we apply our methods to the critical and subcritical double well problems.
SELF-DUAL YANG–MILLS: SYMMETRIES AND MODULI SPACE
Authors: POPOV A. D.
Published: July 2002

Geometry of the solution space of the self-dual Yang–Mills (SDYM) equations in Euclidean four-dimensional space is studied. Combining the twistor and group-theoretic approaches, we describe the full infinite-dimensional symmetry group of the SDYM equations and its action on the space of local solutions to the field equations. It is argued that owing to the relation to a holomorphic analogue of the Chern–Simons theory, the SDYM theory may be as solvable as 2D rational conformal field theories, and successful nonperturbative quantization may be developed. An algebra acting on the space of self-dual conformal structures on a 4-space (an analogue of the Virasoro algebra) and an algebra acting on the space of self-dual connections (an analogue of affine Lie algebras) are described. Relations to problems of topological and N=2 strings are briefly discussed.
THE BIANCHI–DARBOUX TRANSFORM OF L-ISOTHERMIC SURFACES
Authors: MUSSO EMILIO , NICOLODI LORENZO
Published: July 2002

We study an analogue of the classical Bäcklund transformation for L-isothermic surfaces in Laguerre geometry, the Bianchi–Darboux transformation. First we show how to construct the Bianchi–Darboux transforms of an L-isothermic surface by solving an integrable linear differential system, then we establish a permutability theorem for iterated Bianchi–Darboux transforms.
A LINEAR SYSTEM ON NARUKI'S MODULI SPACE OF MARKED CUBIC SURFACES
Authors: VAN GEEMEN BERT
Published: July 2002

Allcock and Freitag recently showed that the moduli space of marked cubic surfaces is a subvariety of a nine dimensional projective space which is defined by cubic equations. They used the theory of automorphic forms on ball quotients to obtain these results. Here we describe the same embedding using Naruki's toric model of the moduli space. We also give an explicit parametrization of the tritangent divisors, we discuss another way to find equations for the image and we show that the moduli space maps, with degree at least ten, onto the unique quintic hypersurface in a five dimensional projective space which is invariant under the action of the Weyl group of the root system E6.
SPIN TOPOLOGICAL QUANTUM FIELD THEORIES
Authors: BELIAKOVA ANNA
Published: July 2002

Starting from the quantum group [Formula: see text], we construct operator invariants of 3-cobordisms with spin structure, satisfying the requirements of a topological quantum field theory and refining the Reshetikhin–Turaev and Turaev–Viro models. We establish the relationship between these two refined theories.
NORMAL ALGEBRAIC SURFACES WITH TRIVIAL TWO OR FOUR TIMES OF THE CANONICAL DIVISOR
Authors: ZHANG D.-Q.
Published: July 2002

We prove that upto isomorphisms there are exactly, three rational log Enriques surface of index four and Type A17, and three rational log Enriques surfaces of index two and actual Type A17+ A1.
FRACTAL DIMENSIONALITY OF PORE AND GRAIN VOLUME OF A SILICICLASTIC MARINE SAND
Authors: REED A. H. , PANDEY R. B. , LAVOIE D. L.
Published: July 2002

Three-dimensional (3D) spatial distributions of pore and grain volumes were determined from high-resolution computer tomography (CT) images of resin-impregnated marine sands. Using a linear gradient extrapolation method, cubic three-dimensional samples were constructed from two-dimensional CT images. Image porosity (0.37) was found to be consistent with the estimate of porosity by water weight loss technique (0.36). Scaling of the pore volume (Vp) with the linear size (L), V ~ LD provides the fractal dimensionalities of the pore volume (D = 2.74 ± 0.02) and grain volume (D = 2.90 ± 0.02) typical for sedimentary materials.
INFLATION INDUCED BY VACUUM ENERGY AND GRACEFUL EXIT FROM IT
Authors: PAPANTONOPOULOS E. , PAPPA I.
Published: July 2002

Motivated by brane cosmology, we solve the Einstein equations with a time-dependent cosmological constant. Assuming that at an early epoch the vacuum energy scales as 1/log t, we show that the universe passes from a fast growing phase (inflation) to an expanding phase in a natural way.
μSR STUDY ON THE Cu-SPIN STATE IN La2-xSrxCu1-yZnyO4
Authors: WATANABE I. , AOYAMA M. , AKOSHIMA M. , NISHIMAKI K. , KAWAMATA T. , ADACHI T. , KOIKE Y. , OHIRA S. , HIGEMOTO W. , NAGAMINE K.
Published: July 2002

Static and dynamical properties of Cu spins in the overdoped single-crystals of La 2-x Sr x Cu 1-y Zn y O 4 have been investigated by the muon-spin-relaxation (μSR) method. In the Zn-substituted single-crystal with x=0.21 and y=0.01, where the high-T c superconductivity is anomalously suppressed, a coexisting state of statically ordered Cu-spins and localized holes has been found at low temperatures below about 2 K. The dynamical depolarization rate of the muon spin at 3.0 K has been found to be nearly proportional to minus-root-square of the external magnetic-field applied along the initial muon-spin polarization. This field-dependence can be explained by assuming the existence of an excited state of the Cu spins diffusing in a one-dimensional direction. The present study suggests a high possibility of the existence of a new one-dimensional stripe ordered state of the Cu spins and doped holes at x=0.21 in the overdoped region of La 2-x Sr x Cu 1-y Zn y O 4.
LOCAL LATTICE DISTORTIONS IN YBa2Cu3Oy PROBED BY XAS: CRITICAL FLUCTUATION, PSEUDOGAP OPENING AND STRIPE ORDERING
Authors: OYANAGI H. , SAINI N. L. , BIANCONI A.
Published: July 2002

Local lattice distortions in YBa 2 Cu 3 O y single crystals are studied by polarized x-ray absorption spectroscopy (XAS) for E//ab and E//c orientations between 300 K and 20 K. From the Fourier transform analysis of the Cu K-EXAFS oscillations, we find that the out-of-plane Cu-O correlation shows an anomalous temperature dependence of radial distribution below Tl=240-250 K , indicating an increase of lattice fluctuations, while no anomalies are found for the Cu-Ba correlation. On further lowering temperature, the Fourier transform shows that the lattice fluctuation are reduced below T2~ T*=140-150 K associated with pseudogap opening. Below T*, the radial distribution of oxygen atoms became asymmetric, indicating that the distorted domain is formed. A strong electron-lattice coupling is indicated by the anomalous local lattice distortions at the cross-over temperatures characterizing various electronic transitions in the title system.
ENTANGLEMENT BETWEEN BOSE–EINSTEIN CONDENSATES
Authors: SHI YU
Published: July 2002

For a Bose condensate in a double-well potential or with two Josephson-coupled internal states, the condensate wavefunction is a superposition. Here we consider coupling two such Bose condensates, and suggest the existence of a joint condensate wavefunction, which is in general a superposition of all products of the bases condensate wavefunctions of the two condensates. The corresponding many-body state is a product of such superposed wavefunctions, with appropriate symmetrization. These states may be potentially useful for quantum computation. There may be robustness and stability due to macroscopic occupation of a same single particle state. The nonlinearity of the condensate wavefunction due to particle–particle interaction may be utilized to realize nonlinear quantum computation, which was suggested to be capable of solving NP-complete problems.
SUPERCONDUCTIVITY AND TYPES OF GAP IN HIGH-Tc CUPRATES
Authors: LIU FU-SUI , CHEN WAN-FANG
Published: July 2002

This paper extends the two-local-spin-mediated interaction from three- to four-band model, gives two T c formulas using long-range phase coherence condition in quantum and classical XY-models, phase diagram, and types of the gap in Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212). This paper argues that the superconducting gap and the pseudogap are the same gap just at different temperature regions. This paper also argues that the values of T c versus x should be determined by the long-range phase coherence conditions in the classical and quantum XY-model for underdoped and overdoped regions, respectively.
QUANTUM TRANSPORT IN SEMICONDUCTOR SUPERLATTICES BEYOND THE KADANOFF–BAYM ANSATZ
Authors: KLEINERT P. , BRYKSIN V. V.
Published: July 2002

Quantum transport in semiconductor superlattices subject to quantizing parallel electric and magnetic fields is studied based on the Kadanoff–Baym–Keldysh double-time Green function approach. Exploiting the symmetry properties of the underlying Hamiltonian, coupled kinetic equations are derived and analytically solved for the density-of-states and the carrier distribution function. Scattering giving rise to collisional broadening plays an important role in our transport model, whose unperturbed eigenstates are completely discrete due to Wannier–Stark and Landau quantization. It is shown that a correct description of the stationary quantum transport in superlattices with field-induced localized eigenstates requires the determination of a time-dependent distribution function from a kinetic equation, which emerges beyond the Kadanoff–Baym Ansatz. Depending on the scattering strength, gaps are predicted to occur in the electric and magnetic field dependence of the current density. The rigorous quantum-mechanical approach reveals the hopping nature of the nonlinear transport in narrow miniband superlattices. This is compared with results obtained recently within the density-matrix approach.
THE EFFECTS OF HF/PdCl2 ACTIVATION ON ELECTROLESS COPPER FILM PROPERTIES
Authors: GOH W. L. , TAN K. T. , TSE M. S. , LIU K. Y.
Published: July 2002

A thin seed layer (usually deposited by PVD or CVD) is essential for the copper electroplating technology in ULSI metallizations. Electroless Cu deposition has been proposed as an alternative to the PVD or CVD Cu seed technology due to its conformal nature. The electroless (EL) Cu technology requires an activation or catalyzation (usually by HF/PdCl 2 solution) to initiate the deposition process. This paper reports on the effect of the HF/PdCl 2 activation on the electroless Cu film properties. The implications of the HF/PdCl2 activation method on electroless Cu role as seed layer for Cu electroplating are also discussed. Electroless Cu has a very conformal growth on the TiN/Ti substrate; with a deposition rate of 15 nm/min. Prolonged HF/PdCl 2 has a negative impact to the Cu (111) texture, roughness and resistivity. The RBS analysis show that only trace amount of Pd is incorporated into the electroless Cu film.
PZT THICK FILMS FABRICATION USING A SOL-GEL BASED 0-3 COMPOSITE PROCESSING
Authors: ZHAO CHANGLEI , WANG ZHIHONG , ZHU WEIGUANG , YAO XI , LIU WEIGUO
Published: July 2002

A sol-gel based 0-3 ceramic-ceramic composite processing has been applied to fabricate lead zirconate titanate thick films with a composition near the morphotropic phase boundary, PZT53/47. In order to eliminate the effects of humidity on the stability of the sols, solid PZT precursors are prepared from partially stabilized titanium isopropoxide, lead acetate trihydrate and zirconium acetylacetonate without any solvent. Then the solid precursors were dissolved in 2-methoxythanol to form sols. Certain quantum modified PZT ceramic powder was dispersed into this obtained solution. Crack-free thick films with series thickness of 5 ~ 20-μm were fabricated using spin-coating method. The surface morphology and structural properties of the films were studied with Field Emission-SEM and X-ray diffraction techniques respectively. Electrical properties were compared with those of thin films. Thick PZT films should have good perspective in the application of new piezoelectric devices that cannot be achieved using conventional thin film or bulk techniques.
A NEW METHOD FOR SUPERSATURATION MEASUREMENT: IDEA, IMPLEMENTATION AND RESULTS
Authors: LÖFFELMANN M. , MERSMANN A.
Published: July 2002

Up to now supersaturation measurement can be generalized as using physical properties that show a dependence on concentration as measurands for supersaturation. Impurities, foreign particles or ions influence the metastable zone width as well as the kinetics of nucleation and crystal growth, but most of the existing measurement methods are not able to incorporate those disturbances in the measured supersaturation. Therefore, a supersaturation sensor considering the actual crystallization process itself has been developed. The idea of the new supersaturation sensor is to induce crystallization on the sensor surface by generating an additional supersaturation by cooling and to observe the time-dependent development of the incrustation. Assuming a constant cooling rate and constant properties of the sensor surface the starting time of the incrustation on the sensor surface depends only on the prevailing supersaturation in the process solution. Experimental results obtained for inorganic ( KNO 3) and organic (Adipicacid) crystallizing solutes proved the applicability of the new sensor.
A STUDY OF ALUMINA THIN FILMS GROWN BY LOW PRESSURE MOCVD: XPS AND AES
Authors: SINGH M. P. , SHIVASHANKAR S. A. , SHRIPATHI T.
Published: July 2002

We have studied the chemical composition of alumina ( Al 2 O 3) films grown on Si(100) at different substrate temperatures by metalorganic chemical vapor deposition (MOCVD) using aluminium acetylactonate { Al(acac) 3} as the precursor. We have found that the resulting films of Al 2 O 3 contain substantial amounts of carbon. X-ray photoelectron spectroscopy (XPS) was employed to study the chemical state of carbon present in such films. The XPS spectrum reveals that the carbon present in Al 2 O 3 film is graphitic in nature. Auger electron spectroscopy (AES) was employed to study the distribution of carbon in the Al 2 O 3 films. The AES depth profile reveals that carbon is present throughout the film. The AES study on Al 2 O 3 films corroborates the XPS findings. An investigation of the Al 2 O 3/ Si (100) interface was carried out using cross-sectional transmission electron microscopy (XTEM). The TEM study reveals textured growth of alumina film on Si(100), with very fine grains of alumina embedded in an amorphous carbon-containing matrix.
ELECTRONIC STRUCTURE AND EXCHANGE IN Li2VOSiO4
Authors: ROSNER H. , SINGH R. R. P. , PICKETT W. E. , ZHENG W. H. , OITMAA J.
Published: July 2002

Exchange couplings are calculated for Li2VOSiO4 using local density approximation (LDA). From a two band tight-binding model fitted to the LDA band structure and mapped to a Heisenberg model, the in-plane and inter-plane exchange integrals are obtained. While the sum of in-plane couplings J1+J2=9.5±1.5  K and the inter-plane coupling J⊥ ~ 0.2-0.3  K agree with recent experimental data, the ratio J2/J1 ~ 12 exceeds the reported value by an order of magnitude. Using geometrical considerations, high temperature expansions and perturbative mean field theory, we show that the LDA derived exchange constants lead to a remarkably accurate description of the properties of these materials including specific heat, susceptibility and Neél temperatures.
X-RAY ABSORPTION STUDY OF Mg1-xAlxB2 AT B K-EDGE
Authors: TSUEI K.-D. , LIN H.-J. , LIN L.-C. , HOU T.-Y. , HSIEH H.-H. , CHEN C. T. , SAINI N. L. , BIANCONI A. , SACCONE A.
Published: July 2002

We have measured B K-edge X-ray absorption spectra of Mg 1-x Al x B 2 (x=0.0 ~ 0.4) using bulk-sensitive total fluorescence yield (TFY) at room temperature and 30 K. In contrast to previous reports no peaks near 192 eV and 194 eV could be observed after repeated scraping, indicating their origin being due to surface contamination. These clean spectra show a peak right above the absorption threshold, anticipated from transition to the unoccupied B 2p states. Except in the intermediate Al doping range of x ~ 0.1 to 0.28 the threshold peak intensity decreases, consistent with pσ-hole filling. The increase of peak intensity in the intermediate range is correlated with structural phase transition.
FERROMAGNETIC POTTS MODEL ON A HIERARCHICAL LATTICE WITH RANDOM LAYERED INTERACTIONS
Authors: MUZY P. T. , SALINAS S. R.
Published: July 2002

We analyze the critical behavior of a q-state Potts model with correlated disordered ferromagnetic exchange interactions along the layers of a diamond hierarchical lattice. For a special class of weakly disordered distributions, we use the topological properties of the lattice to write a set of recursion relations for the moments of the probability distribution of the interaction parameters. We identify a small parameter, q-q0, where q0=0.537…, to expand and decouple the recursion relations. For qq0 (that correponds, in a uniform case, to a specific heat critical exponent α>-2), the existence of a stable disordered fixed point indicates a change in the critical behavior. We make some remarks on the validity of the Harris criterion for hierarchical lattices.
A NEW APPROACH TO SHOT NOISE IN RESONANT TUNNELLING CURRENT
Authors: SUN H. B. , MILBURN G. J.
Published: July 2002

A quantum Markovian master equation is derived to describe the current noise in resonant tunnelling junctions. We calculate the noise spectrum for a double well device and predict sub-shot noise statistics for strong tunnelling between the wells. The method is an alternative to Greeen's functions methods.
Deposition of Borocarbides Thin Films by Pulsed Laser Ablation: Growth Parameters and Characterization
Authors: Ferdeghini C. , Cimberle M.R. , Grassano G. , Marre D. , Putti M. , Canepa F.
Published: July 2002

In this paper we report results on the growth of borocarbides ErNi 2 B 2C and DyNi 2 B 2 C thin films by an ultra high vacuum laser ablation technique. The dependence of the film structure and properties on the deposition parameters has been studied. Moreover the possibility to obtain superconducting films with a tungsten buffer layer on MgO substrates has been successfully checked. Here we present details on the deposition procedure as well as on the structural, morphological, and physical characterization.
DC-Squid Readout for STJ Astronomical Detectors
Authors: Torrioli G. , Castellano M. G. , Leoni R. , Greco F. V. , Buonanno R. , Pedichini F. , Carelli P.
Published: July 2002

The new generation of astronomical detectors based on Superconducting Tunnel Junctions (STJs) is capable of detecting photons in a wide range of wavelengths, and, in some cases, even of counting single photons. Since these detectors operate at very low temperature (down to 100 mK), a natural candidate for the readout electronics is the dc-SQUID, a superconducting device that can work as a current preamplifier, reaching very good noise performance. In this paper we present measurements on a homemade dc-SQUID, showing the response of the device to small current pulses, which simulate the real signals from an STJ. An optimal filtering processing of the data is performed, in order to extract from the noisy data the best estimate for the pulse height, which, in a real experiment with single optical photons, would be the parameter that carries the spectroscopic information.
The Interaction between Two Spheres in Silicone Oil under an Electric Field
Authors: Wang Y. R. , Men S. Q. , Xu X. Y. , Huang X. M. , Lan Y. C. , Zhao X. P. , Wang J. M. , Lu K. Q.
Published: July 2002

The attraction force between two spheres (single crystal SrTiO 3 spheres and SrTiO 3-coated metal spheres) in silicone oil under an electric field is measured and calculated. The dependence of the force on the field strength and interspherical distance is given. The interaction force of SrTiO 3-coated metal spheres is much larger than that of SrTiO 3 spheres at a small interspherical gap.
A NEW DEFINITION OF BOSONS
Authors: CELEGHINI ENRICO
Published: July 2002

A recipe is given to reproduce algebraically the Bose prescription in Quantum Statistics. Bosons are thus defined as coherent states of the [Formula: see text] representation of the Lie-Hopf algebra su(1, 1), while h(1) is shown to be related to Boltzmann statistics. The technical power of group theory is used to show that black-body radiation formula as well as all other experimental results obtained in continuum limit do not require Bose distribution but are compatible with many other less symmetric ones. This may have dramatical effects on the predictions on Bose condensation.
HOLON-PAIR CONDENSATION OF HIGH Tc CUPRATES: SUPERSYMMETRY CONDITIONS
Authors: LEE SUNG-SIK , SALK SUNG-HO SUCK
Published: July 2002

Based on the t–J Hamiltonian of U(1) slave-boson symmetry it is shown from our derived free energy that symmetry breaking can occur to allow holon-pair bose condensation. Supersymmetry conditions are proposed based on our derived quasiparticle Hamiltonian involving both spinons and holons.
OXYGEN-DOPING DEPENDENCE OF THERMOELECTRIC POWER AND THERMAL CONDUCTIVITY MEASUREMENTS IN EuBa2Cu3O7-δ
Authors: GONZALEZ G. M. , RODRIGUEZ-MIJANGOS R.
Published: July 2002

The temperature variation of thermoelectric power, S (T) , and thermal conductivity, k (T) , in EuBa 2 Cu 3 O 7-δ polycrystalline samples with various degrees of oxygenation is reported. The temperature dependence in the range of highly oxygenated to deoxygenated samples displays a gradual transformation from metallic-like to semiconductor-like features in the normal state. For δ values near zero; the critical temperature, indicated by S (T) , shows a lowering which is attributed to a possible raising in electron carriers due to oxygen overdoping. Above T c, thermal conductivity is found to decrease with increase in temperature, pointing towards a contribution to thermal resistivity from three-phonon Umklapp processes. Below T c, thermal conductivity increases rapidly before reaching a maximum, attributed this effect to electron-phonon enhancement combined with a temperature dependent defect scattering limitation in the lifetime of the phonons. A nonmonotonic doping dependence on k (T) is indicated in data, suggesting sensitivity to both oxygen content and oxygen order. The experimental set up is described and results discussed.
Bi-2223 PHASE DEVELOPMENT UNDER INFLUENCE OF ADDITIONS OF 5B METAL OXIDES
Authors: SÝKOROVÁ D. , SMRČKOVÁ O. , VAŠEK P.
Published: July 2002

Formation of the high temperature Bi-2223 phase has been studied for samples with nominal composition Bi 3,2-x Pb 0.8 M x Sr 4 Ca 5 Cu 7 O y. M represented V, Nb, Ta, their contents was altered from 0 to 0.6 mol %. The effect of the additives on the growth of the phase 2223, lattice parameters and the superconducting properties of the samples was detected. It was found that the additives enhanced the volume of the 2223 phase, improved the intergrain connection resp. the critical current density. The additives did not affect the lattice parameters and T c significantly.
COMPOSITION MIXTURE PROBABILISTIC MODEL IN THE FORMATION OF SEMICONDUCTOR MATERIALS OBTAINED BY RANDOM GROWTH TECHNIQUES
Authors: IRIBARREN A. , MENÉNDEZ-PROUPIN E. , CABALLERO-BRIONES F. , CASTRO-RODRÍGUEZ R. , PEÑA J. L.
Published: July 2002

During the obtaining of semiconductor materials by some growth techniques the film structure forms randomly according to how the species arrive to the subtract. If the film is a material with three or more elements they can organize in several compounds, which have only local order and even become amorphous. As a consequence the physico-chemical parameters manifest non-typical behaviors other than in pure materials. In the present work we develop a dynamical-probabilistic model, which describes quantitatively such composition mixture and was applied on the behavior of the absorption profiles of CdTeO films grown by radio frequency (rf) sputtering with different oxygen concentrations. The model can be applied to films obtained by other growth techniques.