Showing papers by "DSM published in 1999"

Optimizing High Harmonic Generation in Absorbing Gases: Model and Experiment

Abstract: We study high-order harmonic generation in the general case of absorbing and dispersive atomic gas media. For ultrashort laser pulses, the harmonic conversion efficiency tends to a limit mainly imposed by the harmonic reabsorption in the gas. This limit, independent on the gas density, is the same for both the case of a loosely focused beam or a beam guided in a gas-filled hollow-core fiber. Under optimum conditions, we measured the highest conversion efficiency to date $(4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5})$ for the 15th harmonic generated in xenon using a 40 fs, 1.5 mJ, 800 nm pulse at a 1 kHz repetition rate.

The LX—T relation and intracluster gas fractions of X-ray clusters

Abstract: We re-examine the X-ray luminosity–temperature relation using a nearly homogeneous data set of 24 clusters selected for statistically accurate temperature measurements and absence of strong cooling flows. The data exhibit a remarkably tight power-law relation between bolometric luminosity and temperature with a slope 2.88 ± 0.15. With reasonable assumptions regarding cluster structure, we infer an upper limit on fractional variations in the intracluster gas fraction 〈(δ fgas fgas)2〉1/2≤ 15 per cent. A strictly homogeneous Ginga subset of 18 clusters places a more stringent limit of 9 per cent. Imaging data from the literature are employed to determine absolute values of fgas within spheres encompassing density contrasts δc=500 and 200 with respect to the critical density. Comparing binding mass estimates based on the virial theorem (VT) and the hydrostatic β-model (BM), we find a temperature-dependent discrepancy in fgas between the two methods caused by systematic variation of the outer slope parameter β with temperature. Mean values (for H0=50 km s−1 Mpc−1) range from f¯gas=0.10 for cool (T 4 keV) clusters using the BM at δc=200. There is evidence that cool clusters have a lower mean gas fraction than hot clusters, but it is not possible to assess the statistical significance of this effect in the present data set. The T dependence of the intracluster medium (ICM) density structure, coupled with the increase of the gas fraction with T in the VT approach, explains the steepening of the LX–T relation. The small variation about the mean gas fraction within this majority subpopulation of clusters presents an important constraint for theories of galaxy formation and supports arguments against an Einstein–de Sitter universe based on the population mean gas fraction and conventional, primordial nucleosynthesis. The apparent trend of lower gas fractions and more extended atmospheres in low-temperature systems is consistent with expectations of models incorporating the effects of galactic winds on the ICM.

Spectroscopic Classification of Late-M and L Field Dwarfs

Abstract: We present spectra for 12 new ultracool dwarfs found in the DENIS infrared survey. Seven of them have spectral types at the bottom of the M-class (M8–M9.5), and the other five belong to the cooler "L" class. We also present spectra for the two new L dwarfs found by the EROS 2 proper-motion survey. We introduce a scheme for L dwarf classification that is based on an extension to cooler spectra of a pseudocontinuum ratio previously defined for M dwarfs. For calibrating the spectral subclasses, we use a temperature scale for late-M and L dwarfs recently obtained by Basri et al. from synthetic spectrum fitting of high-resolution profiles of Cs I and Rb I resonance lines. We define that the subclass range from L0 to L6 corresponds to the temperature range from 2200 K to 1600 K. Our subclasses L0, L1, and L2 agree with recent findings by Kirkpatrick et al., but then they diverge such that our L6 is equivalent to their L8. We find that late-M and L dwarf subclasses can be assigned either in the optical with the PC3 index or in the near-infrared with the H2O H-band index. We discuss the main photospheric features present in L dwarf spectra, in particular in the region 400–650 nm, which has never been shown before. The TiO bands at 549.7, 559.7, 615.9, and 638.4 nm fade with decreasing temperature, but do not vanish until well inside the L domain (~L5). The Na I 589.0, 589.6 nm resonance doublet in our latest object (L6) becomes the broadest atomic feature ever seen in any cool dwarf. We do not detect Hα emission in our L dwarfs later than L3. We discuss the ages and masses of our objects using their temperatures and absence or presence of lithium. Finally, we compare two L1 dwarfs with different gravities (one with lithium and one without it) and discuss differences in spectral features.

Widespread intraspecies cross-contamination of human tumor cell lines arising at source.

Abstract: We present a panoptic survey of cell line cross-contamination (CLCC) among original stocks of human cell lines, investigated using molecular genetic methods. The survey comprised 252 consecutive human cell lines, almost exclusively tumor-derived, submitted by their originators to the DSMZ and 5 additional cell repositories (CRs), using a combination of DNA profiling (4-locus minisatellite and multilocus microsatellite probes) and molecular cytogenetics, exploiting an interactive database (http://www.dsmz.de/). Widespread high levels of cross-contaminants (CCs) were uncovered, affecting 45 cell lines (18%) supplied by 27 of 93 originators (29%). Unlike previous reports, most CCs (42/45) occurred intraspecies, a discrepancy attributable to improved detection of the more insidious intraspecies CCs afforded by molecular methods. The most prolific CCs were classic tumor cell lines, the numbers of CCs they caused being as follows: HeLa (n = 11), T-24 (n = 4), SK-HEP-1 (n = 4), U-937 (n = 4) and HT-29 (n = 3). All 5 supposed instances of spontaneous immortalization of normal cells were spurious, due to CLCC, including ECV304, the most cited human endothelial cell line. Although high, our figure for CCs at the source sets a lower limit only as (i) many older tumor cell lines were unavailable for comparison and (ii) circulating cell lines are often obtained indirectly, rather than via originators or CRs. The misidentified cell lines reported here have already been unwittingly used in several hundreds of potentially misleading reports, including use as inappropriate tumor models and subclones masquerading as independent replicates. We believe these findings indicate a grave and chronic problem demanding radical measures, to include extra controls over cell line authentication, provenance and availability. Int. J. Cancer 83:555–563, 1999. © 1999 Wiley-Liss, Inc.

The initial conditions of isolated star formation — III. Millimetre continuum mapping of pre-stellar cores

Abstract: We present the results of 1.3-mm continuum mapping observations of eight pre-stellar cores, taken with the IRAM 30-m telescope equipped with the 19-channel MPIfR bolometer array. The new 1.3-mm data, which were obtained in the `on-the-fly' mapping mode, have higher angular resolution and sensitivity than previous surveys, reaching an rms noise level of ∼ 3--9 mJy per 13-arcsec beam. The present study supports the conclusions of our previous James Clerk Maxwell Telescope (JCMT) survey and suggests that, in contrast with some theoretical predictions, most pre-stellar cores have flat inner density gradients that only approach ρ (r) ∝ r-2 beyond a few thousand au. Several of the cores have a filamentary-like morphology and are apparently fragmented in a small number (∼ 2--4) of subclumps. This implies that the initial conditions for protostellar collapse depart significantly from a singular isothermal sphere. We also note quantitative disagreement in time-scales with published ambipolar diffusion models for the quasi-static evolution of molecular cloud cores under the influence of a uniform magnetic field. We speculate that turbulent processes might help to explain our observations.

Hydrogen‐bonded supramolecular polymer networks

Abstract: The strong dimerizing, quadruple hydrogen-bonding ureido-pyrimidone unit is used to obtain reversible polymer networks. A new synthetic route from commercially available starting materials is described. The hydrogen-bonding ureido-pyrimidone network is prepared using 3(4)-isocyanatomethyl-1-methylcyclohexyl-isocyanate (IMCI) in the regioselective coupling reaction of multi-hydroxy functionalized polymers with isocytosines. 1H- and 13C-NMR, IR, MS, and ES-MS analysis, performed on a model reaction using butanol, demonstrated the formation of the hydrogen-bonding ureido-pyrimidone unit in a yield of more than 95%. The well-defined, strong hydrogen-bonding ureido-pyrimidone network is compared with a traditional covalently bonded polymer network, a multi-directional hydrogen-bonded polymer network based on urea units, and a reference compound. The advantage of the reversible, hydrogen-bonded polymer networks is the formation of the thermodynamically most favorable products, which show a higher “virtual” molecular weight and shear modulus, compared to the irreversible, covalently bonded polymer network. The properties of the ureido-pyrimidone network are unique; the well-defined and strong dimerization of the ureido-pyrimidone unit does not require any additional stabilization such as crystallization or other kinds of phase separation, and displays a well-defined viscoelastic transition. The ureido-pyrimidone network represents the first example of a truly reversible polymer network showing these features. Furthermore, the ureido-pyrimidone dimerization is strong enough to construct supramolecular materials possessing acceptable mechanical properties. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3657–3670, 1999

EPDM−Carbon Black Interactions and the Reinforcement Mechanisms, As Studied by Low-Resolution 1H NMR

Abstract: Proton, low-resolution T2 NMR relaxation experiments are used to study the adsorption of EPDM to the surface of carbon blacks and the structure of the physical EPDM/carbon black network in cured an...

Standard Solar Models in the Light of New Helioseismic Constraints. II. Mixing below the Convective Zone

Abstract: In previous work, we have shown that recent updated standard solar models cannot reproduce the radial profile of the sound speed at the base of the convective zone and fail to predict the photospheric lithium abundance. In parallel, helioseismology has shown that the transition from differential rotation in the convective zone to almost uniform rotation in the radiative solar interior occurs in a shallow layer called the tachocline. This layer is presumably the seat of a large-scale circulation and of turbulent motions. Here we introduce a macroscopic transport term in the structure equations that is based on a hydrodynamical description of the tachocline proposed by Spiegel & Zahn, and we calculate the mixing induced within this layer. We discuss the influence of different parameters that represent the tachocline thickness, the Brunt-Vaisala frequency at the base of the convective zone, and the time dependence of this mixing process along the Sun's evolution. We show that the introduction of such a process inhibits the microscopic diffusion by about 25%. Starting from models including a pre-main-sequence evolution, we obtain (1) a good agreement with observed photospheric chemical abundance of light elements such as 3He, 4He, 7Li, and 9Be; (2) a smooth composition gradient at the base of the convective zone; and (3) a significant improvement of the sound-speed square difference between the seismic Sun and the models in this transition region when we allow the photospheric heavy-element abundance to adjust, within the observational incertitude, as a result of the action of this mixing process. The impact on neutrino predictions is also discussed.

Discovery of an Extremely Young Accreting Protostar in Taurus

Abstract: We report the discovery of a new, very young accreting class 0 protostar in the southern part of the Taurus molecular cloud. This object, designated by IRAM 04191+1522, coincides with a cold (T~12 K) dust continuum condensation found at 1.3 mm with the IRAM 30 m telescope ~1' southwest of the class I infrared source IRAS 04191+1523. Although IRAM 04191+1522 was not seen by IRAS, it is associated with a weak 3.6 cm VLA radio continuum source, a highly collimated CO bipolar outflow, and 60-850 μm emission detected by ISOPHOT and SCUBA. Molecular line observations are consistent with the protostellar condensation currently undergoing gravitational collapse. The spectral energy distribution and low bolometric luminosity (Lbol~0.15 L☉) we derive suggest that the protostellar core at the center of IRAM 04191+1522 may still be dissociating molecular hydrogen. High-resolution snapshot 1.4 mm continuum observations with the IRAM interferometer fail to detect this protostar, implying it has not yet developed a large accretion disk.

Diamond Infrared Emission Bands in Circumstellar Media

Abstract: Since the discovery of small diamond grains in meteorites, the presence of such grains in the interstellar medium has been suspected. Here we report what we think to be the first unambiguous evidence of the presence of small crystallites of diamond in the dusty envelopes surrounding stars. Thanks to experimental results obtained in different laboratories on the diamond growth process, we identify two peculiar unidentified infrared emission bands at 3.43 and 3.53 μm as the vibrational modes of hydrogen-terminated crystalline facets of diamond. The intensities of these two strong features observed in the envelope of HD 97048 correspond to a mass of 10-10 to 10-9 M☉ of diamond dust at an equilibrium temperature of ~1000 K.

Polynucleotide Probes That Target a Hypervariable Region of 16S rRNA Genes To Identify Bacterial Isolates Corresponding to Bands of Community Fingerprints

Abstract: Temperature gradient gel electrophoresis (TGGE) is well suited for fingerprinting bacterial communities by separating PCR-amplified fragments of 16S rRNA genes (16S ribosomal DNA [rDNA]). A strategy was developed and was generally applicable for linking 16S rDNA from community fingerprints to pure culture isolates from the same habitat. For this, digoxigenin-labeled polynucleotide probes were generated by PCR, using bands excised from TGGE community fingerprints as a template, and applied in hybridizations with dot blotted 16S rDNA amplified from bacterial isolates. Within 16S rDNA, the hypervariable V6 region, corresponding to positions 984 to 1047 (Escherichia coli 16S rDNA sequence), which is a subset of the region used for TGGE (positions 968 to 1401), best met the criteria of high phylogenetic variability, required for sufficient probe specificity, and closely flanking conserved priming sites for amplification. Removal of flanking conserved bases was necessary to enable the differentiation of closely related species. This was achieved by 5′ exonuclease digestion, terminated by phosphorothioate bonds which were synthesized into the primers. The remaining complementary strand was removed by single-strand-specific digestion. Standard hybridization with truncated probes allowed differentiation of bacteria which differed by only two bases within the probe target site and 1.2% within the complete 16S rDNA. However, a truncated probe, derived from an excised TGGE band of a rhizosphere community, hybridized with three phylogenetically related isolates with identical V6 sequences. Only one of the isolates comigrated with the excised band in TGGE, which was shown to be due to identical sequences, demonstrating the utility of a combined TGGE and V6 probe approach.

Standard Solar models in the Light of New Helioseismic Constraints II. Mixing Below the Convective Zone

Abstract: In previous work, we have shown that recent updated standard solar models cannot reproduce the radial profile of the sound speed at the base of the convective zone (CZ) and fail to predict the Li7 depletion. In parallel, helioseismology has shown that the transition from differential rotation in the CZ to almost uniform rotation in the radiative solar interior occurs in a shallow layer called the tachocline. This layer is presumably the seat of large scale circulation and of turbulent motions. Here, we introduce a macroscopic transport term in the structure equations, which is based on a hydrodynamical description of the tachocline proposed by Spiegel and Zahn, and we calculate the mixing induced within this layer. We discuss the influence of different parameters that represent the tachocline thickness, the Brunt-Vaissala frequency at the base of the CZ, and the time dependence of this mixing process along the Sun's evolution. We show that the introduction of such a process inhibits the microscopic diffusion by about 25%. Starting from models including a pre-main sequence evolution, we obtain: a) a good agreement with the observed photospheric chemical abundance of light elements such as He3, He4, Li7 and Be9, b) a smooth composition gradient at the base of the CZ, and c) a significant improvement of the sound speed square difference between the seismic sun and the models in this transition region, when we allow the phostospheric heavy element abundance to adjust, within the observational incertitude, due to the action of this mixing process. The impact on neutrino predictions is also discussed.

The Converging Inflow Spectrum Is an Intrinsic Signature for a Black Hole: Monte Carlo Simulations of Comptonization on Free-falling Electrons

Abstract: An accreting black hole is, by definition, characterized by the drain. Namely, matter falls into a black hole much the same way as water disappears down a drain: matter goes in and nothing comes out. As this can only happen in a black hole, it provides a way to see "a black hole," a unique observational signature of black holes. The accretion proceeds almost in a free-fall manner close to the black hole horizon, where the strong gravitational field dominates the pressure forces. In this paper we calculate (by using Monte Carlo simulations) the specific features of X-ray spectra formed as a result of upscattering of the soft (disk) photons in the converging inflow (CI) within about 3 Schwarzschild radii of the black hole. The full relativistic treatment has been implemented to reproduce these spectra. We show that spectra in the soft state of black hole systems (BHS) can be described as the sum of a thermal (disk) component and the convolution of some fraction of this component with the CI upscattering spread (Green's) function. The latter boosted photon component is seen as an extended power law at energies much higher than the characteristic energy of the soft photons. We demonstrate the stability of the power spectral index (α=1.8±0.1) over a wide range of the plasma temperature, 0-10 keV, and mass accretion rates (higher than 2 in Eddington units). We also demonstrate that the sharp high-energy cutoff occurs at energies of 200-400 keV, which are related to the average energy of electrons mec2 impinging on the event horizon. The spectrum is practically identical to the standard thermal Comptonization spectrum (Hua & Titarchuk) when the CI plasma temperature is getting of order of 50 keV (the typical ones for the hard state of BHS). In this case one can see the effect of the bulk motion only at high energies, where there is an excess in the CI spectrum with respect to the pure thermal one. Furthermore, we demonstrate that the change of spectral shapes from the soft X-ray state to the hard X-ray state is clearly to be related to the temperature of the bulk flow. We derive a generic formula for the temperature of the emitting region (CI) that depends on the ratio of the energy release in this very region and in the disk. Using this formula, we demonstrate that the temperature of the emission region in the hard state of the BHS is approximately 2 times higher than the ones of neutron star systems (NSS) in the hard state, which is confirmed by recent RXTE and Beppo-SAX observations of the hard state of NSS. The effect of the bulk Comptonization compared with the thermal one is getting stronger when the plasma temperature drops below 10 keV. These Monte Carlo simulated CI spectra are an inevitable stamp of the BHS where the strong gravitational field dominates the pressure forces.

Atomic-oxygen-assisted MBE growth of α − F e 2 O 3 on α − A l 2 O 3 (0001): Metastable FeO(111)-like phase at subnanometer thicknesses

Abstract: The growth of $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ on $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}(0001)$ by atomic oxygen---molecular-beam epitaxy has been studied by real time reflection high-energy electron diffraction, low energy electron diffraction, and x-ray photoelectron spectroscopy. For equivalent thicknesses below 2 ML, epitaxial islands of an uncommon iron oxide are evidenced. This metastable FeO(111)-like phase exhibits a strongly expanded in-plane parameter, and contains ferric ${\mathrm{Fe}}^{3+}$ ions instead of ferrous ${\mathrm{Fe}}^{2+}$ ones. This phase seems to be specific to a given thickness (\ensuremath{\sim}2 ML), independently of the substrate. For higher equivalent thicknesses, epitaxial islands of hematite $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}(0001)$ begin to nucleate. The amount of the hematite phase increases whereas that of the FeO(111)-like phase decreases with deposition time. For a deposit equivalent to one hematite unit cell, islands coalesce and $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}(0001)$ grows in a two-dimensional mode, with the hematite bulk in-plane parameter.

Dust in an Extremely Metal-Poor Galaxy: Mid-infrared Observations ofSBS 0335-052

Abstract: The metal-deficient (Z=Z?/41) blue compact dwarf galaxy SBS 0335-052 was observed with ISOCAM between 5 and 17 ?m. With an L12?m/LB ratio of 2.15, the galaxy is unexpectedly bright in the mid-infrared for such a low-metallicity object. The mid-infrared spectrum shows no sign of the unidentified infrared bands, which we interpret as an effect of the destruction of their carriers by the very high UV energy density in SBS 0335-052. The spectral energy distribution (SED) is dominated by a very strong continuum, which makes the ionic lines of [S IV] and [Ne III] very weak. From 5 to 17 ?m, the SED can be fitted with a graybody spectrum, modified by an extinction law similar to that observed toward the Galactic center, with an optical depth of AV ~19-21 mag. Such a large optical depth implies that a large fraction (as much as ~75%) of the current star formation activity in SBS 0335-052 is hidden by dust with a mass between 3 ? 103 and 5 ? 105 M?. Silicate grains that are present as silicate extinction bands at 9.7 and 18 ?m can account for the unusual shape of the MIR spectrum of SBS 0335-052. It is remarkable that such a nearly primordial environment contains as much dust as galaxies that are 10 times more metal-rich. If the hidden star formation in SBS 0335-052 is typical of young galaxies at high redshifts, then the cosmic star formation rate derived from UV/optical fluxes would be underestimated.

Use of SAXS and linear correlation functions for the determination of the crystallinity and morphology of semi-crystalline polymers. Application to linear polyethylene

Abstract: The use of correlation functions to obtain the morphological parameters of crystalline-amorphous two-phase lamellar systems is critically reviewed and extended. It is shown that processing of the experimental SAXS-patterns only significantly affects the curvature of the autocorrelation triangle and that the parameters of the corresponding ideal two-phase structure can be determined independently of the data processing procedure. The methods to be used depend on the normalization of the correlation function. The validity of the formulation is illustrated for a sample of linear polyethylene, cooled and heated at 10°C per min. Crystallite thickening during crystallization and surface melting during heating are observed. The overall crystallinity and the fraction of semi-crystalline stacks during crystallization and melting are determined quantitatively as a function of temperature using the total scattering power of the corresponding ideal two-phase structure, correlation functions, and a scaling procedure. Absolute intensities are not required. The SAXS results are confirmed by independent techniques (DSC, WAXD, and SALLS). During crystallization, amorphous regions are present outside the semi-crystalline regions because growing spherulites do not fill space completely. During melting, larger amorphous regions develop in the spherulites because of the complete melting of stacks. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1715–1738, 1999

Attractive interactions between reverse aggregates and phase separation in concentrated malonamide extractant solutions

Abstract: Using small angle X-ray scattering, conductivity, and phase behavior determination, we show that concentrated solutions of molanamide extractants, dimethyldibutyltetradecylmalonamide (DMDBTDMA), are organized in reverse oligomeric aggregates which have many features in common with reverse micelles. The aggregation numbers of these reverse globular aggregates as well as their interaction potential are determined from absolute scattering curves. An attractive interaction is responsible for the demixing of the oil phase when in equilibrium with excess oil. Prediction of conductivity as well as the formation conditions for the third phase is possible using standard liquid theory applied to the extractant aggregates. The interactions, modeled with the sticky sphere model proposed by Baxter, are shown to be due to steric interactions resulting from the hydrophobic tails of the extractant molecule and van der Waals forces between the highly polarizable water core of the reverse micelles. The attractive interacti...

Kocuria palustris sp. nov. and Kocuria rhizophila sp. nov., isolated from the rhizoplane of the narrow-leaved cattail (Typha angustifolia)

Abstract: Two Gram-positive, aerobic spherical actinobacteria were isolated from the rhizoplane of narrow-leaved cattail (Typha angustifolia) collected from a floating mat in the Soroksar tributary of the Danube river, Hungary. Sequence comparisons of the 16S rDNA indicated these isolates to be phylogenetic neighbours of members of the genus Kocuria, family Micrococcaceae, in which they represent two novel lineages. The phylogenetic distinctness of the two organisms TA68T and TAGA27T was supported by DNA-DNA similarity values of less than 55% between each other and with the type strains of Kocuria rosea, Kocuria kristinae and Kocuria varians. Chemotaxonomic properties supported the placement of the two isolates in the genus Kocuria. The diagnostic diamino acid of the cell-wall peptidoglycan is lysine, the interpeptide bridge is composed of three alanine residues. Predominant menaquinone was MK-7(H2). The fatty acid pattern represents the straight-chain saturated iso-anteiso type. Main fatty acid was anteiso-C15:0. The phospholipids are diphosphatidylglycerol, phosphatidylglycerol and an unknown component. The DNA base composition of strains TA68T and TAGA27T is 69.4 and 69.6 mol% G+C, respectively. Genotypic, morphological and physiological characteristics are used to describe two new species of Kocuria, for which we propose the names Kocuria palustris, type strain DSM 11925T and Kocuria rhizophila, type strain DSM 11926T.

Must: a silicon strip detector array for radioactive beam experiments

Abstract: A new and innovative array, MUST, based on silicon strip technology and dedicated to the study of reactions induced by radioactive beams on light particles is described. The detector consists of 8 silicon strip – Si(Li) telescopes used to identify recoiling light charged particles through time of flight, energy loss and energy measurements and to determine precisely their scattering angle through X, Y position measurements. Each 60×60 mm 2 double sided silicon strip detector with 60 vertical and 60 horizontal strips yields an X – Y position resolution of 1 mm, an energy resolution of 50 keV, a time resolution of around 1 ns and a 500 keV energy threshold for protons. The backing Si(Li) detectors stop protons up to 25 MeV with a resolution of approximately 50 keV. CsI crystals read out by photo-diodes which stop protons up to 70 MeV are added to the telescopes for applications where higher energy particles need to be detected. The dedicated electronics in VXIbus standard allow us to house the 968 logic and analog channels of the array in one crate placed adjacent to the reaction chamber and fully remote controlled, including pulse visualization on oscilloscopes. A stand alone data acquisition system devoted to the MUST array has been developed. Isotope identification of light charged particles over the full energy range has been achieved, and the capability of the system to measure angular distributions of states populated in inverse kinematics reactions has been demonstrated.

Citromicrobium bathyomarinum, a Novel Aerobic Bacterium Isolated from Deep-Sea Hydrothermal Vent Plume Waters That Contains Photosynthetic Pigment-Protein Complexes

Abstract: We have taxonomically and phylogenetically characterized a new aerobic bacterial strain (JF-1) that contains photosynthetic pigment-protein complexes and which was recently isolated from black smoker plume waters of the Juan de Fuca Ridge. Strain JF-1 is a gram-negative, yellow-pigmented, motile bacterium that is salt-, pH-, and thermotolerant. These properties are consistent with an oligotrophic adaptation to varied environmental conditions thought to exist around deep-sea hydrothermal vents. The analysis of 16S rDNA sequences revealed that strain JF-1 forms a separate phylogenetic branch between the genus Erythromonas and the Erythromicrobium-Porphyrobacter-Erythrobacter cluster within the alpha subclass of the Proteobacteria. The taxonomic name Citromicrobium bathyomarinum (gen. nov., sp. nov.) is proposed for strain JF-1.

Repeated Relativistic Ejections in GRS 1915+105

Abstract: In 1994 February-August we observed with the VLA four ejection events of radio-emitting clouds from the high-energy source GRS 1915+105. These events are all consistent with antiparallel ejections of twin pairs of clouds moving away from the compact source at ~0.92 of the speed of light and angles of ~70° with respect to the line of sight. The flux ratios and time evolution of the expelled clouds are consistent with actual motions of the radiating matter rather than with the simple propagation of pulses in a medium moving at slower velocities. The large kinetic power of the sudden, short, and rather discontinuous ejections exceeds by more than an order of magnitude the maximum steady photon luminosity of the source, suggesting that in GRS 1915+105 a radiation acceleration mechanism of the ejecta is unlikely. As in other galactic and extragalactic radio sources, the decrease in flux density as a function of angular separation from the central source shows a steepening with distance. Additional ejection events have been observed in 1995 and 1997 and we compare them with the 1994 events.