julilili42/papers huggingface dataset:
CASIMIR EFFECTS IN RENORMALIZABLE QUANTUM FIELD THEORIES
2002-03-20

We present a framework for the study of one–loop quantum corrections to extended field configurations in renormalizable quantum field theories. We work in the continuum, transforming the standard Casimir sum over modes into a sum over bound states and an integral over scattering states weighted by the density of states. We express the density of states in terms of phase shifts, allowing us to extract divergences by identifying Born approximations to the phase shifts with low order Feynman diagrams. Once isolated in Feynman diagrams, the divergences are canceled against standard counterterms. Thus regulated, the Casimir sum is highly convergent and amenable to numerical computation. Our methods have numerous applications to the theory of solitons, membranes, and quantum field theories in strong external fields or subject to boundary conditions.
LOOPS AND LOOP CLOUDS — A NUMERICAL APPROACH TO THE WORLDLINE FORMALISM IN QED
2002-03-20

A numerical technique for calculating effective actions of electromagnetic backgrounds is proposed, which is based on the string-inspired worldline formalism. As examples, we consider scalar electrodynamics in three and four dimensions to one-loop order. Beyond the constant-magnetic-field case, we analyze a step-function-like magnetic field exhibiting a nonlocal and nonperturbative phenomenon: "magnetic-field diffusion". Finally, generalizations to fermionic loops and systems at finite temperature are discussed.
Taste bud development in the zebrafish, Danio rerio
2002-03-21

Abstract Taste buds are chemosensory endorgans consisting of modified epithelial cells. Fish and other vertebrates use their taste bud cells to sample potential food, either selecting or rejecting substances according to their edibility. The adult gustatory system in fish has been studied thoroughly, including regeneration experiments. Taste buds occur in the epithelia of the lips, the mouth cavity, the oropharyngeal cavity, and also in the skin of the barbels, the head, and sometimes even all over the body surface. Despite its importance for feeding, little is known about the ontogeny of the fish taste system. We examined the development of taste buds in the zebrafish on the light microscopical and the scanning and transmission electron microscopical levels. Taste buds develop later than the olfactory organ and the solitary chemosensory cells, two other chemosensory systems in aquatic vertebrates. The first few taste bud primordia are visible within the epithelia of lips and gill arches 3 to 4 days after fertilization, and the first few taste buds with open receptor areas appear on the lips and simultaneously on the gill arches 4–5 days after fertilization, which coincides with the onset of feeding. Taste buds in the mouth cavity, on the head, and on the barbels are formed later in development. As seen in other fish, zebrafish taste buds contain elongate dark and light cells, termed according to their electron density. Dark cells with a cell apex of many short microvilli appear first, followed by the light cells with one large microvillus. In addition, the zebrafish has a third fusiform cell type, which appears last. This cell type is low in electron density and has a brush‐like apical ending with several small microvilli. This cell type has not been described previously. Furthermore, in zebrafish, the ontogenetic processes of taste bud formation differ from regenerative processes described in the literature. © 2002 Wiley‐Liss, Inc.
Quadrupole moments of baryons
2002-03-21

Quadrupole moments of decuplet baryons and the octet-decuplet transition\\nquadrupole moments are calculated using Morpurgo's general QCD parameterization\\nmethod. Certain relations among the decuplet and the octet to decuplet\\ntransition quadrupole moments are derived. These can be used to predict the\\n quadrupole moments which are difficult to measure.\\n
A posteriori error estimation for elliptic eigenproblems
2002-03-25

Abstract An a posteriori error estimator is presented for a subspace implementation of preconditioned inverse iteration, which derives from the well‐known inverse iteration in such a way that the associated system of linear equations is solved approximately by using a preconditioner. The error estimator is integrated in an adaptive multigrid algorithm to compute approximations of a modest number of the smallest eigenvalues together with the eigenfunctions of an elliptic differential operator. Error estimation is applied both within the actual finite element space (in order to estimate the iteration error) as well as in its hierarchical refinement of higher‐order elements (to estimate the discretization error) which gives rise to a balanced reduction of the iteration error and of the discretization error in the adaptive multigrid algorithm. Copyright © 2002 John Wiley &amp; Sons, Ltd.
Interactions of some decuplet baryons in the quark cluster model
2002-03-25

In the framework of the resonating-group method, the interactions of decuplet baryon-baryon systems with strangeness numbers and are investigated by employing the chiral SU(3) quark model. The effective baryon-baryon interactions deduced from quark-quark interactions and scattering cross sections of the and systems are calculated.
Differentiation of promyelocytic leukaemia: alterations in Fas (CD95/Apo‐1) and Fas Ligand (CD178) expression
2002-03-25

Summary. The survival of leukaemic blasts contributes to the pathological mechanism of acute promyelocytic leukaemia (APL). While treatment of APL using retinoic acid (RA) is a model of differentiation therapy, little is known about possible effects of this treatment on the Fas/FasL system. Investigation of APL cells from patients undergoing differentiation therapy with RA and of promyelocytic HL‐60 and monoblastic U‐937 cells cultured with RA revealed a reduction of surface expression of both Fas and its ligand. Accordingly, the sensitivity of the cells to anti‐Fas‐induced apoptosis decreased proportionally and the reduced expression of FasL resulted in a decreased ability of the leukaemic cells to induce apoptosis in T cells. Our findings demonstrate that there are significant changes in Fas and FasL expression during RA treatment of APL, which probably have consequences for the interaction between host immune and leukaemia cells, and thus may be involved in the beneficial effects of differentiation therapy.
Intramolecular Diels−Alder Reactions Using α-Methylene Lactones as Dienophile
2002-03-26

Several dienals were prepared and reacted in the presence of zinc metal with ethyl 2-bromomethylacrylate to provide in a Reformatsky-like reaction alpha-methylene lactones carrying a dienyl side chain. Thermolysis of these compounds (11, 21, 29, and 37) gave in an intramolecular Diels-Alder reaction the corresponding tricyclic cycloadducts (51, 52, 53, and 54). The cycloadditions took place with good diastereoselectivity and yields. The stereochemistry of the major isomer is in accordance with an endo transition state for cycloadducts 51, 52, and 54. In one instance (compound 58), the structure was supported by X-ray crystallography. In contrast to the other substrates, the nonatriene 29 cyclized to the exo product 53exo. The stereochemical situation could also be proven by NOESY NMR. However, the intramolecular Diels-Alder reaction did not work with furan as dienophile (compound 41) and substrate 50 featuring a densely functionalized tether connecting diene and alpha-methylene lactone.
Synthesis and Characterization of Soluble Axially Substituted Tetra‐( tert ‐butyl)gallium(III)phthalocyanines
2002-03-26

The synthesis and characterization of the highly soluble tetra(tert-butyl)gallium(III) phthalocyanines (tBu)4PcGaCl (2) and (tBu)4PcGa(p-TMP) (3) is described. They were characterized by IR, UV/Vis, MS, and 1H, 13C, and 19F NMR spectroscopy. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)
ChemInform Abstract: Pharmaceutical Applications of Supercritical Carbon Dioxide
2002-03-26

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
MRI of muscular fat
2002-03-28

Abstract An MRI technique with high selectivity and sensitivity to the signal components in the chemical shift range of methylene and methyl protons of fatty acids has been developed for noninvasive assessment of muscular fat in vivo. A spoiled gradient‐echo sequence with spatial‐spectral excitation by six equidistant pulses with 2°‐(−9°)‐17°‐(−17°)‐9°‐(−2°) and a multi‐echo train (TE = 16, 36, 56, 76, 96, and 116 ms) allowed a series of images to be recorded with a receiver bandwidth of 78 Hz per pixel. SIs from phantoms with lipid contents between 0.1% and 100% were compared to those from pure water. Thirty healthy volunteers underwent fat‐selective imaging of their lower leg, and parallel localized proton spectroscopy of the tibialis anterior and the soleus muscle by a single‐voxel stimulated echo acquisition mode (STEAM) technique (TR = 2 s, TE = 10 ms, TM = 15 ms). Results show a high correlation (r = 0.91) between fat imaging and the spectroscopic approach in the soleus muscle, considering the percentage total fat content of musculature. The correlation coefficient was clearly lower (r = 0.55) in the tibialis anterior muscle due to signal contaminations from adjacent subcutaneous fat in the images, inhomogeneous fat distribution, and generally lower lipid content in this muscle. Applications of the new imaging technique showed marked intra‐ and interindividual variability in the spatial distribution of lipids in the musculature of the lower leg. No significant correlation of the muscular fat with the thickness of the subcutaneous fat layer was found. In addition, the body mass index does not appear to determine muscular fat content, except in very obese cases. Magn Reson Med 47:720–727, 2002. © 2002 Wiley‐Liss, Inc.
<title>Diagnosing the predisposition for diabetes mellitus by means of mid-IR spectroscopy</title>
2002-03-28

The vicious circle of insulin resistance and hyperinsulinemia is considered to precede the manifestation of diabetes type-2 by decades and the corresponding cluster of risk factors is described as the 'insulin resistance syndrome' or 'metabolic syndrome'. Since the present diagnosis of insulin resistance is expensive, time consuming and cumbersome, there is a need for diagnostic alternatives. We conducted a clinical study on 129 healthy volunteers and 99 patients suffering from the metabolic syndrome. We applied mid-infrared spectroscopy to dried serum samples from these donors and evaluated the spectra by means of disease pattern recognition (DPR). Substantial differences were found between the spectra originating from healthy volunteers and those spectra originating from patients with the metabolic syndrome. A linear discriminant analysis was performed using approximately one half of the sample set for teaching the classification algorithm. Within this teaching set, a classification sensitivity and specificity of 84 percent and 81 percent respectively can be derived. Furthermore, the resulting discriminant function was applied to an independent validation of the remaining half of the samples. For the discrimination between 'healthy' and 'metabolic syndrome' a sensitivity and a specificity of 80 percent and 82 percent respectively is obtained upon validating the algorithm with the independent validation set.
A metacaspase of Trypanosoma brucei causes loss of respiration competence and clonal death in the yeast Saccharomyces cerevisiae
2002-03-29

Metacaspases constitute a new group of cysteine proteases homologous to caspases. Heterologous expression of Trypanosoma brucei metacaspase TbMCA4 in the budding yeast Saccharomyces cerevisiae resulted in growth inhibition, mitochondrial dysfunction and clonal death. The metacaspase orthologue of yeast, ScMCA1 ( YOR197w ), exhibited genetic interaction with WWM1 ( YFL010c ), which encodes a small WW domain protein. WWM1 overexpression resulted in growth arrest and clonal death, which was suppressed by concomitant overexpression of ScMCA1 . GFP‐fusion reporters of WWM1 , ScMCA1 and TbMCA4 localized to the nucleus. Taken together, we suggest that metacaspases may play a role in nuclear function controlling cellular proliferation coupled to mitochondrial biogenesis.
Couplings to Classical and Non-Classical Squeezed White Noise as Stationary Markov Processes
2002-03-31

The squeezed white noise states of the quantum optics literature are identified with specific quasifree states on the bosonic C *-Weyl (resp. CCR) algebra, which are not gauge invariant. Their properties are discussed, and concrete realizations of their GNS-representations are given. The squeezed white noise states are obtained from the chaotic temperature (or white noise states) by the application of squeezing Bogoliubov transformations, which may lead to a noise reduction in selected modes. A squeezing strength is determined, below which the squeezed white noise states remain classical and above which they are rendered non-classical. We further couple additional systems to the squeezed white noise, the quantum character of which are leading to a large class of stationary quantum Markov processes with related quantum stochastic calculus. Their interactions are described in terms of unitary cocycles, which arise from adapted additive cocycles by means of solutions of stochastic differential equations resp. by stochastic Itô integrals. The restriction of the Markovian dynamics to the sub-system leads to a quantum semi-group, for which the Lindblad generator is of detailed balance type. Finally the stochastic Itô table for squeezed white noise is derived. From the latter non-classicality of the squeezed white noise process can now be checked by inspection.
Total Reconstruction, PF Movement, and Derivational Order
2002-04-01

Theories of total reconstruction have generally supposed that movement can be followed by an undoing operation like LF lowering (May 1977, 1985) or deletion of higher copies (Chomsky 1993). We argue that reconstruction effects can be derived only if the original movement is purely phonological. There are no undoing operations. We present three distinct arguments, based on an interaction between raising and wh-movement in English, facts from agreement with group terms in British English, and multiple scrambling in Japanese. The arguments imply that the T-model is correct in supposing that movement that affects both LF and PF must precede movement that affects only PF.
Nested-grid calculations of disk-planet interaction
2002-04-01

We study the evolution of embedded protoplanets in a protostellar disk using\\nvery high resolution nested-grid computations. This method allows us to perform\\nglobal simulations of planets orbiting in disks and, at the same time, to\\nresolve in detail the dynamics of the flow inside the Roche lobe of the planet.\\nThe primary interest of this work lies in the analysis of the gravitational\\ntorque balance acting on the planet. For this purpose we study planets of\\ndifferent masses, ranging from one Earth-mass up to one Jupiter-mass, assuming\\ntypical parameters of the protostellar disk. The high resolution of the method\\nallows a precise determination of the mass flow onto the planet and the\\nresulting torques. The obtained migration time scales are in the range from few\\ntimes 10^4 years, for intermediate mass planets, to 10^6 years, for very low\\nand high mass planets. Typical growth time scales depend strongly on the\\nplanetary mass, ranging from a few hundred years, in the case of Earth-type\\nplanets, to several ten thousand years, in the case of Jupiter-type planets.\\n
MR Imaging of the Heart with Cine True Fast Imaging with Steady-State Precession: Influence of Spatial and Temporal Resolutions on Left Ventricular Functional Parameters
2002-04-01

The influence of changes in spatial and temporal resolutions on functional parameters in the left ventricle (LV) were investigated with magnetic resonance (MR) imaging with a modified true fast imaging with steady-state precession, or FISP, two-dimensional sequence that provided temporal resolution of 21-90 msec and spatial resolution of 1-3 mm. MR imaging in the heart was performed in 15 healthy volunteers. A decrease in LV functional parameters was observed with reduced spatial and temporal resolutions. The influence of temporal resolution was more relevant.
Reversed lateralization of temporal activation during speech production in thought disordered patients with schizophrenia
2002-04-01

Background. Formal thought disorder is a core symptom of schizophrenia. It is associated with a reversed lateralization of the superior temporal cortex volume, an area that is implicated in lexical retrieval. We investigated the neural correlates of word retrieval during continuous speech in patients with formal thought disorder using functional magnetic resonance imaging (fMRI). Methods. Blood oxygenation level dependent (BOLD) contrast was measured with fMRI while six patients with schizophrenia and six healthy control subjects spoke about seven Rorschach inkblots for 3 min each. Subjects produced varying amounts of speech during each run. In a within subject design, the number of words produced was correlated with the BOLD contrast in the two runs in each participant who showed the highest variance of speech output. Results. In control subjects, the amount of speech produced was mainly correlated with activation in the left superior temporal gyrus. In the patient group, the main correlations were in the right superior temporal gyrus. Conclusions. During the production of continuous speech, patients with formal thought disorder showed a reversed laterality of activation in the superior temporal cortex. This is consistent with findings of perturbed hemispheric interaction in schizophrenia, particularly in patients with formal thought disorder.
X-ray Crystallographic Structures of the Escherichia coli Periplasmic Protein FhuD Bound to Hydroxamate-type Siderophores and the Antibiotic Albomycin
2002-04-01

Siderophore-binding proteins play an essential role in the uptake of iron in many Gram-positive and Gram-negative bacteria. FhuD is an ATP-binding cassette-type (ABC-type) binding protein involved in the uptake of hydroxamate-type siderophores in Escherichia coli. Structures of FhuD complexed with the antibiotic albomycin, the fungal siderophore coprogen and the drug Desferal have been determined at high resolution by x-ray crystallography. FhuD has an unusual bilobal structure for a periplasmic ligand binding protein, with two mixed beta/alpha domains connected by a long alpha-helix. The binding site for hydroxamate-type ligands is composed of a shallow pocket that lies between these two domains. Recognition of siderophores primarily occurs through interactions between the iron-hydroxamate centers of each siderophore and the side chains of several key residues in the binding pocket. Rearrangements of side chains within the binding pocket accommodate the unique structural features of each siderophore. The backbones of the siderophores are not involved in any direct interactions with the protein, demonstrating how siderophores with considerable chemical and structural diversity can be bound by FhuD. For albomycin, which consists of an antibiotic group attached to a hydroxamate siderophore, electron density for the antibiotic portion was not observed. Therefore, this study provides a basis for the rational design of novel bacteriostatic agents, in the form of siderophore-antibiotic conjugates that can act as "Trojan horses," using the hydroxamate-type siderophore uptake system to actively deliver antibiotics directly into targeted pathogens.
Seed‐specific overexpression of a potato sucrose transporter increases sucrose uptake and growth rates of developing pea cotyledons
2002-04-01

Summary During the storage phase, cotyledons of developing pea seeds are nourished by nutrients released to the seed apoplasm by their maternal seed coats. Sucrose is transported into pea cotyledons by sucrose/H + symport mediated by PsSUT1 and possibly other sucrose symporters. PsSUT1 is principally localised to plasma membranes of cotyledon epidermal and subepidermal transfer cells abutting the seed coat. We tested the hypothesis that endogenous sucrose/H + symporter(s) regulate sucrose import into developing pea cotyledons. This was done by supplementing their transport activity with a potato sucrose symporter (StSUT1), selectively expressed in cotyledon storage parenchyma cells under control of a vicilin promoter. In segregating transgenic lines, enhanced [ 14 C]sucrose influx into cotyledons above wild‐type levels was found to be dependent on StSUT1 expression. The transgene significantly increased (approximately 2‐fold) transport activity of cotyledon storage parenchyma tissues where it was selectively expressed. In contrast, sucrose influx into whole cotyledons through the endogenous epidermal transfer cell pathway was increased by only 23% in cotyledons expressing the transgene. A similar response was found for rates of biomass gain by intact cotyledons and by excised cotyledons cultured on a sucrose medium. These observations demonstrate that transport activities of sucrose symporters influence cotyledon growth rates. The attenuated effect of StSUT1 overexpression on sucrose and dry matter fluxes by whole cotyledons is consistent with a large proportion of sucrose being taken up at the cotyledonary surface. This indicates that the cellular location of sucrose transporter activity plays a key role in determining rates of sucrose import into cotyledons.
Nonribosomal biosynthesis of vancomycin-type antibiotics: a heptapeptide backbone and eight peptide synthetase modules The GenBank/EMBL/DDBJ accession number for the balhimycin biosynthetic gene sequence reported in this paper is Y16952.
2002-04-01

During analysis of the recently identified gene cluster for the glycopeptide antibiotic balhimycin, produced by Amycolatopsis mediterranei DSM 5908, novel genes were identified and characterized in detail. The gene products of four of the identified genes (bpsA, bpsB, bpsC and bpsD) are nonribosomal peptide synthetases (NRPSs); one (Orf1-protein) shows similarities to small proteins associated with several NRPSs without an assigned function. BpsA and BpsB are composed of three modules each (modules 1-6), BpsC of one module (module 7) and BpsD of a minimal module (module 8). Thus, the balhimycin gene cluster encodes eight modules, whereas its biosynthetic product is a heptapeptide. Non-producing mutants were created by a gene disruption of bpsB, an in-frame deletion of bpsC and a gene replacement of bpsD. After establishment of a gene complementation system for Amycolatopsis strains, the replacement mutant of bpsD was complemented, demonstrating for the first time that BpsD, encoding the eighth module, is indeed involved in balhimycin biosynthesis. After feeding with beta-hydroxytyrosine the capability of the bpsD mutant to produce balhimycin was restored, demonstrating the participation of BpsD in the biosynthesis of this amino acid. The specificity of four of the eight adenylation domains was determined by ATP/PP(i) exchange assays: modules 4 and 5 activated L-4-hydroxyphenylglycine, module 6 activated beta-hydroxytyrosine and module 7 activated L-3,5-dihydroxyphenylglycine, which is in accordance with the sequence of the non-proteogenic amino acids 4 to 7 of the balhimycin backbone.