julilili42/papers huggingface dataset:
Zur Alkylierung von 2,3-Dihydro-1,3-diisopropyl-4,5- dimethylimidazol-2-yliden [1] / On the Alkylation of 2,3-Dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene [1]
2002-06-01

Abstract The reaction of 2,3-dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (7, Im) and alkyl iodides has been investigated. With MeI, 7 forms a 1/1 mixture of [ImH]I (10) and [ImEt]I (11a) while from the reaction of 7 with EtI an 1/1/1 mixture of 10, 11a and [ImCH(Me)Et]I (11b) is obtained. The mechanism of the reactions is discussed, and the crystal structures of 10 and 11a are reported.
Analytical Solution to the Zero-Inertia Problem for Surge Flow Phenomena in Nonprismatic Channels
2002-06-01

Surge flow phenomena, e.g., as a consequence of a dam failure or a flash flood, represent free boundary problems. The extending computational domain together with the discontinuities involved renders their numerical solution a cumbersome procedure. This contribution proposes an analytical solution to the problem. It is based on the slightly modified zero-inertia (ZI) differential equations for nonprismatic channels and uses exclusively physical parameters. Employing the concept of a momentum-representative cross section of the moving water body together with a specific relationship for describing the cross sectional geometry leads, after considerable mathematical calculus, to the analytical solution. The hydrodynamic analytical model is free of numerical troubles, easy to run, computationally efficient, and fully satisfies the law of volume conservation. In a first test series, the hydrodynamic analytical ZI model compares very favorably with a full hydrodynamic numerical model in respect to published results of surge flow simulations in different types of prismatic channels. In order to extend these considerations to natural rivers, the accuracy of the analytical model in describing an irregular cross section is investigated and tested successfully. A sensitivity and error analysis reveals the important impact of the hydraulic radius on the velocity of the surge, and this underlines the importance of an adequate description of the topography. The new approach is finally applied to simulate a surge propagating down the irregularly shaped Isar Valley in the Bavarian Alps after a hypothetical dam failure. The straightforward and fully stable computation of the flood hydrograph along the Isar Valley clearly reflects the impact of the strongly varying topographic characteristics on the flow phenomenon. Apart from treating surge flow phenomena as a whole, the analytical solution also offers a rigorous alternative to both (a) the approximate Whitham solution, for generating initial values, and (b) the rough volume balance techniques used to model the wave tip in numerical surge flow computations.
Molecular Characterization of the Arabidopsis thaliana Flavoprotein AtHAL3a Reveals the General Reaction Mechanism of 4′-Phosphopantothenoylcysteine Decarboxylases
2002-06-01

The Arabidopsis thaliana flavoprotein AtHAL3a, which is linked to plant growth and salt and osmotic tolerance, catalyzes the decarboxylation of 4'-phosphopantothenoylcysteine to 4'-phosphopantetheine, a key step in coenzyme A biosynthesis. AtHAL3a is similar in sequence and structure to the LanD enzymes EpiD and MrsD, which catalyze the oxidative decarboxylation of peptidylcysteines. Therefore, we hypothesized that the decarboxylation of 4'-phosphopantothenoylcysteine also occurs via an oxidatively decarboxylated intermediate containing an aminoenethiol group. A set of AtHAL3a mutants were analyzed to detect such an intermediate. By exchanging Lys(34), we found that AtHAL3a is not only able to decarboxylate 4'-phosphopantothenoylcysteine but also pantothenoylcysteine to pantothenoylcysteamine. Exchanging residues within the substrate binding clamp of AtHAL3a (for example of Gly(179)) enabled the detection of the proposed aminoenethiol intermediate when pantothenoylcysteine was used as substrate. This intermediate was characterized by its high absorbance at 260 and 280 nm, and the removal of two hydrogen atoms and one molecule of CO(2) was confirmed by ultrahigh resolution mass spectrometry. Using the mutant AtHAL3a C175S enzyme, the product pantothenoylcysteamine was not detectable; however, oxidatively decarboxylated pantothenoylcysteine could be identified. This result indicates that reduction of the aminoenethiol intermediate depends on a redox-active cysteine residue in AtHAL3a.
Influences of pelvic floor structures and sacral innervation on the response to distension of the cat rectum
2002-06-01

Abstract The contributions to the rectal response to distension of the pelvic floor structures surrounding the rectum and of the sacral spinal innervation have never been studied. Using paralysed intercollicularly decerebrate, anaesthesia‐free cats, we studied pressure–volume relationships during slow ramp distensions of the rectum. Results obtained from animals with intact pelvic cavities were compared with those following mobilization of the rectum from the pelvic floor musculature. To assess the influences of spinal outflow and afferent input, rectal pressure–volume relationships were measured in the mobilized rectum following bilateral sequential transection of the spinal roots S1 to S3, first dorsal, then ventral. Isolation of the rectum from the pelvic floor structures resulted in a decrease in balloon volume in the lower range of distension pressure but did not affect volumes at higher pressures. The only afferent effect was seen after sectioning of dorsal roots S1, which resulted in a decrease in balloon volume. The only efferent effect was seen after sectioning of ventral roots S3, which decreased balloon volume further. In conclusion, the rectal response to distension depends on the properties of the rectal wall. It may be influenced by somatic inputs, inputs from the myenteric nervous plexus, and from the parasympathetic and sympathetic nervous systems. Afferent inputs and spinal autonomic reflexes may decrease the tone of the rectal musculature during distension.
Resolution and the Origins of Structural Reasoning: Early Proof-Theoretic Ideas of Hertz and Gentzen
2002-06-01

In the 1920s, Paul Hertz (1881–1940) developed certain calculi based on structural rules only and established normal form results for proofs. It is shown that he anticipated important techniques and results of general proof theory as well as of resolution theory, if the latter is regarded as a part of structural proof theory. Furthermore, it is shown that Gentzen, in his first paper of 1933, which heavily draws on Hertz, proves a normal form result which corresponds to the completeness of propositional SLD-resolution in logic programming.
Mobility Studies on Siloxane-Based Inorganic-Organic Hybrid Polymers by Dynamic Solid State, Suspended State, and Deuterium NMR Spectroscopy: Supported Organometallic Complexes. XXVI [1]Dedicated to Professor Joachim Strähle on the Occasion of his 65th Birthday
2002-06-01

Organic modified siloxanes of the type RSi(OMe2)2(CH2)3C6D4(CH2)3(OMe2)2SiR [R = Me (4), R = OMe (5)] were sol-gel processed employing solvents of different polarity (MeOH and THF) to yield the corresponding inorganic-organic hybrid polymers X4a — X5b with different physical properties. These polymers were investigated by multinuclear (2H, 13C, and 29Si) solid state and 1H suspension state NMR spectroscopy, including dynamic NMR techniques, in order to correlate the mobilities of these xerogels with physical properties, especially with the cross-linkage. Mobilitätsstudien an siloxan-basierten anorganisch-organischen Hybridpolymeren mittels dynamischer Festkörper-, Suspensions- und Deuterium-NMR-Spektroskopie Organisch modifizierte Siloxane des Typs RSi(OMe2)2(CH2)3C6D4(CH2)3(OMe2)2SiR [R = Me (4), R = OMe (5)] wurden mit Hilfe von Lösungsmitteln unterschiedlicher Polarität (MeOH und THF) Sol-gel prozessiert. Sie ergaben die entsprechenden anorganisch-organischen Hybridpolymere X4a — X5b mit unterschiedlichen physikalischen Eigenschaften. Diese Polymere wurden mit Multikern (2H, 13C, 29Si) Festkörper- und 1H Suspensions-NMR-Spektroskopie untersucht. Dabei wurden auch dynamische NMR-Methoden verwendet, um die Beweglichkeiten mit den physikalischen Eigenschaften der Xerogele — insbesondere deren Vernetzung — zu korrelieren.
Interaction induced deformation of the momentum distribution of spin polarized nuclear matter
2002-06-04

Effects of spin polarization on the structure of symmetric nuclear matter and\\npure neutron matter are investigated. We show that the spin polarization\\ninduces a deformation of the Fermi spheres for nucleons with spin parallel and\\nopposite to the polarization axes. This feature can be related to the structure\\nof the one pion exchange contribution to a realistic nucleon-nucleon\\ninteraction. While the anisotropies in the momentum distribution lower the\\nenergy of the system by small amount, the associated variations of the single\\nparticle energies with the angle between the polarization axis and the particle\\nmomentum are significant.\\n
Catascopia, a new genus for three Nearctic and one Palaearctic stagnicoline species (Gastropoda: Lymnaeidae)
2002-06-10

1. Lymnaea palustris and Lymnaea fuscus are potential but uncommon intermediate hosts of Fasciola hepatica in Sweden Adam Novobilský, Martin Kašný, Luboš Beran, Daniel Rondelaud, Johan Höglund Parasites & Vectors CrossRef
The nuclear equation of state probed by K$plus$ production in heavy ion collisions
2002-06-10

The dependence of production on the nuclear equation of state is investigated in heavy ion collisions. An increase of the excitation function of multiplicities obtained in heavy ( ) over light ( ) systems when going far below threshold which has been observed by the KaoS Collaboration strongly favours a soft equation of state. This observation holds despite of the influence of an in-medium kaon potential predicted by effective chiral models which is necessary to reproduce the experimental yields. Phase space effects are discussed with respect to the excitation function.
Spontaneous Breaking of Rotational Symmetry in Superconductors
2002-06-11

We show that homogeneous superconductors with broken spin/isospin symmetry lower their energy via a transition to a novel superconducting state where the Fermi surfaces are deformed to a quasiellipsoidal form at zero total momentum of Cooper pairs. In this state, the gain in the condensation energy of the pairs dominates over the loss in the kinetic energy caused by the lowest order (quadrupole) deformation of Fermi surfaces from the spherically symmetric form. The phase transition from the spherically symmetric state to the superconducting state with broken rotational symmetry is first order.
Unified description of three positive and three negative parity interacting bands
2002-06-11

The coherent state model (CSM) is extended so that three negative parity bands are treated on equal footing with three positive parity bands. The six rotational bands are generated by projecting out angular momenta and parities from three intrisic orthogonal states which exhibit both quadrupole and octupole deformations. The projected states are, by construction, mutually orthogonal. In the space of projected states, a sub-space of a quadrupole and octupole multi-boson states, an effective quadrupole and octupole boson Hamiltonian is solved. The eigenstates of the model Hamiltonian are linked by multipole transition operators for which lowest order boson expressions are considered. The calculations involve 6 structure coefficients and two deformation parameters. All of them are fixed by a least square fit of the known experimental energies. Applications are made to Gd158, Yb172, Ra218, Ra226, Th232, U238, Pu238. Very good agreement is obtained for both excitation energies and transition probabilities. New signatures for octupole deformation, manifested in excited bands, are pointed out.
Glutathione release from cultured brain cells: Multidrug resistance protein 1 mediates the release of GSH from rat astroglial cells
2002-06-12

Abstract To investigate the release of glutathione (GSH) from brain cells, cultures enriched for astroglial cells, neurons, oligodendroglial cells, and microglial cells derived from rat brain were studied. During incubation of astroglial cultures, GSH accumulated in the medium with a rate of 3.1 ± 0.6 nmol × h −1 × mg protein −1 . In contrast, only marginal amounts of extracellular GSH were detectable in the media of the other brain cell cultures investigated. The mechanism of GSH release from astroglial cells, as yet, has not been reported. Multidrug resistance protein 1 (Mrp1), a transport protein known to mediate cellular export of glutathione disulfide and glutathione conjugates, is expressed in astroglial cultures. Inhibitors of Mrp1 were used to test for a function of this transporter in mediating GSH release from astroglial cells. The presence of the competitive Mrp1 inhibitor MK571 at a concentration of 50 μM inhibited the rate of GSH release by 63%. In contrast, the low concentration of 1 μM of MK571 increased the rate of GSH release by 83%. This bimodal concentration‐dependent effect of MK571 is in accord with literature data for the effects of Mrp1 substrates on GSH release from cells. In addition, the presence of cyclosporin A (10 μM) reduced the GSH release rate significantly and completely blocked the stimulating effect of 1 μM MK571 on the release of GSH from astroglial cells. In conclusion, the data presented are a strong indication that Mrp1 participates in the release of GSH from astroglial cells. © 2002 Wiley‐Liss, Inc.
Bose-Einstein condensation of correlated atoms in a trap
2002-06-13

The Bose-Einstein condensation of correlated atoms in a trap is studied by\\nexamining the effect of inter-particle correlations to one-body properties of\\natomic systems at zero temperature using a simplified formula for the\\ncorrelated two body density distribution. Analytical expressions for the\\ndensity distribution and rms radius of the atomic systems are derived using\\nfour different expressions of Jastrow type correlation function. In one case,\\nin addition, the one-body density matrix, momentum distribution and kinetic\\nenergy are calculated analytically, while the natural orbitals and natural\\noccupation numbers are also predicted in this case. Simple approximate\\nexpressions for the mean square radius and kinetic energy are also given.\\n
GPI anchor transamidase ofTrypanosoma brucei: in vitro assay of the recombinant protein and VSG anchor exchange
2002-06-15

GPI8 from Trypanosoma brucei was cloned and expressed in Escherichia coli. TbGPI8 encodes a 37 kDa protein (35 kDa after removal of the putative signal sequence) with a pI of 5.5. It contains one potential N-glycosylation site near the N-terminus but no C-terminal hydrophobic region. Enzyme activity assays using trypanosomal lysates or recombinant TbGpi8 exhibited cleavage of the synthetic peptide acetyl-S-V-L-N-aminomethyl-coumarine, indicating that TbGpi8 is indeed directly involved in the proteolytic processing of the GPI anchoring signal. Intracellular localization of TbGpi8 within tubular structures, such as the endoplasmic reticulum, was observed by using specific anti-TbGpi8 antibodies. The transamidase mechanism of GPI anchoring was studied in bloodstream forms of Trypanosoma brucei using media containing hydrazine or biotinylated hydrazine. In the presence of the latter nucleophile, part of the newly formed VSG was linked to this instead of the GPI anchor and was not transferred to the cell surface. VSG-hydrazine-biotin was detected by streptavidin in western blots and intracellularly in Golgi-like compartments.
<title>Multiwavelength TCSPC lifetime imaging</title>
2002-06-17

We present a novel time-correlated single photon counting (TCPSC) imaging technique that allows time-resolved multi-wavelength imaging in conjunction with a laser scanning microscope and a pulsed excitation source. The technique is based on a four-dimensional histogramming process that records the photon density over time, the x-y coordinates of the scanning area and the detector channel number. The histogramming process avoids any time gating or wavelength scanning and therefore yields a near-perfect counting efficiency. Applied to resonance energy transfer (RET) measurements, the setup is capable to record time-resolved fluorescence decays for the donor and the acceptor simultaneously.
Mutation of the RGD sequence does not affect plasma membrane association and growth inhibitory effects of elevated IGFBP‐2 in vivo
2002-06-17

Using insulin‐like growth factor‐binding protein‐2 (IGFBP‐2) transgenic mice (D mice) as a model of elevated IGFBP‐2 expression, which is often found in unphysiological conditions, we found association of IGFBP‐2 to purified plasma membranes of many organs. To determine whether the RGD (Arg‐Gly‐Asp) motif of IGFBP‐2 mediates cell surface binding in vivo, we mutated the RGD motif of IGFBP‐2 into an RGE (Arg‐Gly‐Glu) sequence and produced transgenic mice (E mice) which express elevated amounts of mutated IGFBP‐2. Our data demonstrate that in vivo IGFBP‐2 cell surface association is not dependent on the RGD motif and that mutation of this sequence does not alter growth inhibitory effects of IGFBP‐2.
Basal hymenomycetes belonging to the Sebacinaceae are ectomycorrhizal on temperate deciduous trees
2002-06-18

Summary • Heterobasidiomycetous species of the Sebacinaceae family, previously considered as saprophytes or parasites, are shown here to form ectomycorrhizas on temperate forest trees. • Ectomycorrhizas were collected under sebacinoid sporophores and near root systems of Neottia nidus‐avis , an orchid symbiotic with sebacinoids. To identify the partners each ectomycorrhiza was submitted to amplification and sequencing of the plant and fungal internal transcribed spacer (ITS), and further investigated by light and electron microscopy whenever a sebacinoid ITS was found. • Molecular and microscopic analyses correlated well. Two sebacinoids of divergent rDNA sequences were demonstrated to form similar ectomycorrhizas, with a well‐developed Hartig net and a hyphal mantle having thick‐walled outer mantle hyphae. The ultrastructure of the septal pore (dolipore with imperforate caps) was typical for sebacinoids. In one case, intracellular colonization was seen. The ectomycorrhizal host range of these sebacinoids was not specific and included Betulaceae, Fagaceae and Tiliaceae. • Sebacinoids probably represent an overlooked ectomycorrhizal group and ectomycorrhizal symbiosis may be common among basal lineages of hymenomycetes.
Anisotropic flow of strange particles in heavy-ion collisions at RHIC energies
2002-06-19

Anisotropic flow of K's, anti-K's, and lambdas is studied in heavy ion collisions at SPS and RHIC energies within the microscopic quark-gluon string model. At SPS energy the directed flow of kaons differs considerably at midrapidity from that of antikaons, while at RHIC energy kaon and antikaon flows coincide. The change is attributed to formation of dense meson-dominated matter at RHIC, where the differences in interaction cross-sections of hadrons become unimportant. The directed flows of strange particles, , have universal negative slope at at RHIC. The elliptic flow of strange hadrons is developed at midrapidity at times 3<t<10 fm/c. It increases almost linearly with rising p_t and stops to rise at p_t < 1.5 GeV/c reaching the same saturation value in accord with experimental results.
Strangeness production in heavy ion collisions at SPS and RHIC within two-source statistical model
2002-06-19

The experimental data on hadron yields and ratios in central Pb+Pb and Au+Au collisions at SPS and RHIC energies, respectively, are analysed within a two-source statistical model of an ideal hadron gas. These two sources represent the expanding system of colliding heavy ions, where the hot central fireball is embedded in a larger but cooler fireball. The volume of the central source increases with rising bombarding energy. Results of the two-source model fit to RHIC experimental data at midrapidity coincide with the results of the one-source thermal model fit, indicating the formation of an extended fireball, which is three times larger than the corresponding core at SPS.
Is RX J1856.5−3754 a Quark Star?
2002-06-20

Deep Chandra LETG+HRC-S observations of the isolated neutron star candidate RX J1856.5-3754 have been analysed to search for metallic and resonance cyclotron spectral features and for pulsation behaviour. As found from earlier observations, the X-ray spectrum is well-represented by a ~ 60 eV (7e5 K) blackbody. No unequivocal evidence of spectral line or edge features has been found, arguing against metal-dominated models. The data contain no evidence for pulsation and we place a 99% confidence upper limit of 2.7% on the unaccelerated pulse fraction over a wide frequency range from 1e-4 to 100 Hz. We argue that the derived interstellar medium neutral hydrogen column density of 8e19 <= N_H <= 1.1e20 per sq. cm favours the larger distance from two recent HST parallax analyses, placing RX J1856.5-3754 at ~ 140 pc instead of ~ 60 pc, and in the outskirts of the R CrA dark molecular cloud. That such a comparatively rare region of high ISM density is precisely where an isolated neutron star re-heated by accretion of interstellar matter would be expected is either entirely coincidental, or current theoretical arguments excluding this scenario for RX J1856.5-3754 are premature. Taken at face value, the combined observational evidence -- a lack of spectral and temporal features and an implied radius at infinity of 3.8-8.2 km that is too small for current neutron star models -- points to a more compact object, such as allowed for quark matter equations of state.