Showing papers by "DSM published in 1997"

Reversible Polymers Formed from Self-Complementary Monomers Using Quadruple Hydrogen Bonding

Abstract: Units of 2-ureido-4-pyrimidone that dimerize strongly in a self-complementary array of four cooperative hydrogen bonds were used as the associating end group in reversible self-assembling polymer systems. The unidirectional design of the binding sites prevents uncontrolled multidirectional association or gelation. Linear polymers and reversible networks were formed from monomers with two and three binding sites, respectively. The thermal and environmental control over lifetime and bond strength makes many properties, such as viscosity, chain length, and composition, tunable in a way not accessible to traditional polymers. Hence, polymer networks with thermodynamically controlled architectures can be formed, for use in, for example, coatings and hot melts, where a reversible, strongly temperature-dependent rheology is highly advantageous.

Effect of orogeny, plate motion and land-sea distribution on Eurasian climate change over the past 30 million years

Abstract: The Eurasian climates of today, 10 million and 3O million years ago are simulated using an atmospheric general circulation model that incorporates realistic continental geography and epicontinental sea distributions. The resulting climates compare well with various palaeoclimate records. The retreat of the Paratethys–an epicontinental sea–shifts the central Asian climate from temperate to continental conditions, and plays as important a role as uplift of the Himalayan/Tibetan plateau in driving the Asian monsoon changes.

The H1 detector at HERA

Abstract: General aspects of the H1 detector at the electron-proton storage ring HERA as well as technical descriptions of the magnet, luminosity system, trigger, slow-control, data acquisition and off-line data handling are given. The three major components of the detector, the tracking, calorimeter and muon detectors, will be described in a forthcoming article. The present paper describes the detector that was used from 1992 to the end of 1994. After this a major upgrade of some components was undertaken. Some performance figures from luminosity runs at HERA during 1993 and 1994 are given.

Subpicosecond study of carrier trapping dynamics in wide-band-gap crystals

Abstract: Using a very sensitive time-resolved interferometric technique, we study the laser induced carrier trapping dynamics in wide band-gap crystals with 100 fs temporal resolution The fast trapping of electrons in the band-gap is associated with the formation of self-trapped excitons (STE's) The STE's formation kinetics does not depend on the pump laser intensity in ${\mathrm{SiO}}_{2}$, while the trapping rate increases in NaCl with the excitation density We interpret this result as a direct evidence of exciton trapping in the first case, and an electronic trapping following a hole trapping in the second This result is explained in terms of electron trajectories calculated with a simple Monte Carlo simulation: the electrons can explore a large volume before being trapped in NaCl, not in ${\mathrm{SiO}}_{2}$ A temperature influence on the initial trapping process is observed in KBr, not in NaCl and ${\mathrm{SiO}}_{2}$ Finally, we find no evidence of STE formation in diamond This result is in agreement with general consideration about the STE's formation in terms of lattice elasticity and deformation potentials

Galactic Cosmic Rays from Supernova Remnants. II. Shock Acceleration of Gas and Dust

Abstract: We present a quantitative model of Galactic cosmic-ray (GCR) origin and acceleration, wherein a mixture of interstellar and/or circumstellar gas and dust is accelerated by a supernova remnant blast wave. The gas and dust are accelerated simultaneously, but differences in how each component is treated by the shock leave a distinctive signature, which we believe exists in the cosmic-ray composition data. A reexamination of the detailed GCR elemental composition, presented in a companion paper, has led us to abandon the long-held assumption that GCR abundances are somehow determined by first ionization potential. Instead, volatility and mass (presumably mass-to-charge ratio) seem to better organize the data: among the volatile elements, the abundance enhancements relative to solar increase with mass (except for the slightly high H/He ratio); the more refractory elements seem systematically overabundant relative to the more volatile ones in a quasi-mass-independent fashion. If this is the case, material locked in grains in the interstellar medium must be accelerated to cosmic-ray energies more efficiently than interstellar gas-phase ions. Here we present results from a nonlinear shock model that includes (1) the direct acceleration of interstellar gas-phase ions, (2) a simplified model for the direct acceleration of weakly charged grains to ~100 keV amu-1 energies, simultaneously with the acceleration of the gas ions, (3) the energy losses of grains colliding with the ambient gas, (4) the sputtering of grains, and (5) the simultaneous acceleration of the sputtered ions to GeV and TeV energies. We show that the model produces GCR source abundance enhancements of the volatile, gas-phase elements that are an increasing function of mass, as well as a net, mass-independent enhancement of the refractory, grain elements over protons, consistent with cosmic-ray observations. We also investigate the implications of the slightly high H/He ratio. The GCR22Ne excess may also be accounted for in terms of the acceleration of 22Ne-enriched presupernova Wolf-Rayet star wind material surrounding the most massive supernovae. We also show that cosmic-ray source spectra, at least below ~1014 eV, are well matched by the model.

Galactic Cosmic Rays from Supernova Remnants. I. A Cosmic-Ray Composition Controlled by Volatility and Mass-to-Charge Ratio

Abstract: We show that the Galactic cosmic-ray source (GCRS) composition is best described in terms of (1) a general enhancement of the refractory elements relative to the volatile ones, and (2) among the volatile elements, an enhancement of the heavier elements relative to the lighter ones. This mass dependence most likely reflects a mass-to-charge (A/Q) dependence of the acceleration efficiency; among the refractory elements, there is no such enhancement of heavier species, or only a much weaker one. We regard as coincidental the similarity between the GCRS composition and that of the solar corona, which is biased according to first ionization potential. In a companion paper, this GCRS composition is interpreted in terms of an acceleration by supernova shock waves of interstellar and/or circumstellar (e.g.,22Ne-rich Wolf-Rayet wind) gas-phase and, especially, dust material.

Study of the spatial and temporal coherence of high order harmonics

Abstract: We apply the theory of high-order harmonic generation by low-frequency laser fields in the strong field approximation to the study of the spatial and temporal coherence properties of the harmonics. We discuss the role of dynamically induced phases of the atomic polarization in determining the optimal phase matching conditions and angular distributions of harmonics. We demonstrate that the phase matching and the spatial coherence can be controlled by changing the focusing parameters of the fundamental laser beam. Then we present a detailed study of the temporal and spectral properties of harmonics. We discuss how the focusing conditions influence the individual harmonic spectra and time profiles, and how the intensity dependence of the dynamically induced phase leads to a chirp of the harmonic frequency. This phase modulation can be used to control the temporal and spectral properties of the harmonic radiation. Temporally, the harmonic chirped pulse can be recompressed to very small durations. Spectrally, chirping of the fundamental beam may be employed to compensate for the dynamically induced chirp and to control the individual harmonic spectrum. Finally, we discuss the short pulse effects, in particular nonadiabatic phenomena and the possibility of generating attosecond pulses. Comment: Latex file with 37 pages, 25 postscript figures. to appear in Advances in Atomic, Molecular and Optical Physics

A SAXS study of the internal structure of dendritic polymer systems

Abstract: Small-angle x-ray scattering was used to characterize the single-particle scattering factors produced by poly(amidoamine) dendrimers, poly(propleneimine) dendrimers, and polyol hyperbranched polymers in dilute solutions with methanol as solvent. Fits from electron density modeling reveal similar overall densities of the dendrimers as a function of dendrimer generation. The seventh through tenth generation poly(amidoamine) dendrimers exhibit higher order scattering features that require nearly monodisperse, spherical particles with essentially uniform internal segment densities. Dilute hyperbranched polymer solutions exhibit scattering more indicative of the inherent irregularity of internal segment densities and overall sizes to be expected within these systems. Radii of gyration estimated from electron density modeling agree reasonably well with those estimated by standard Guinier methods used in previous studies.

Two acute monocytic leukemia (AML-M5a) cell lines (MOLM-13 and MOLM-14) with interclonal phenotypic heterogeneity showing MLL-AF9 fusion resulting from an occult chromosome insertion, ins(11;9)(q23;p22p23)

Abstract: We describe two new human leukemia cell lines, MOLM-13 and MOLM-14, established from the peripheral blood of a patient at relapse of acute monocytic leukemia, FAB M5a, which had evolved from myelodysplastic syndrome (MDS). Both cell lines express monocyte-specific esterase (MSE) and MLL-AF9 fusion mRNA. Gene fusion is associated with a minute chromosomal insertion, ins(11;9)(q23;p22p23). MOLM-13 and MOLM-14 are the first cell lines with, and represent the third reported case of, MLL gene rearrangement arising via chromosomal insertion. Both cell lines carry trisomy 8 which was also present during the MDS phase, as well as the most frequent trisomies associated with t(9;11), ie, +6, +13, +19 variously present in different subclones. Despite having these features in common, differences in antigen expression were noted between the two cell lines: that of MOLM-13 being CD34+, CD13-, CD14-, CD15+, CD33+; whereas MOLM-14 was CD4+, CD13+, CD14+, CD15+, CD33+. Differentiation to macrophage-like morphology could be induced in both cell lines after stimulation with INF-gamma alone, or in combination with TNF-alpha, which treatment also induced or upregulated, expression of certain myelomonocyte-associated antigens, including CD13, CD14, CD15, CD64, CD65 and CD87. Together, these data confirm that both cell lines are likely to be novel in vitro models for studying monocytic differentiation and leukemogenesis.

Preparation of microbial polyunsaturated fatty acid containing oil from pasteurised biomass

Abstract: The present invention discloses a microbial polyunsaturated fatty acid(PUFA)-containing oil with a high triglyceride content and a high oxidative stability. In addition, a method is described for the recovery of such oil from a microbial biomass derived from a pasteurised fermentation broth, wherein the microbial biomass is subjected to extrusion to form granular particles, dried and the oil then extracted from the dried granules using an appropriate solvent.

The tracking calorimeter and muon detectors of the H1 experiment at Hera

Abstract: Technical aspects of the three major components of the H1 detector at the electron-proton storage ring HERA are described. This paper covers the detector status up to the end of 1994 when a major upgrading of some of its elements was undertaken. A description of the other elements of the detector and some performance figures from luminosity runs at HERA during 1993 and 1994 are given in a paper previously published in this journal.

The H1 lead/scintillating-fibre calorimeter

Abstract: The backward region of the H1 detector has been upgraded in order to provide improved measurement of the scattered electron in deep inelastic scattering events. The centerpiece of the upgrade is a high-resolution lead/scintillating-fibre calorimeter. The main design goals of the calorimeter are: good coverage of the region close to the beam pipe, high angular resolution and energy resolution of better than 2% for 30 GeV electrons. The calorimeter should be capable of providing coarse hadronic energy measurement and precise time information to suppress out-of-time background events at the first trigger level. It must be compact due to space restrictions. These requirements were fulfilled by constructing two separate calorimeter sections. The inner electromagnetic section is made of 0.5 mm scintillating plastic fibres embedded in a lead matrix. Its lead-to-fibre ratio is 2.3:1 by volume. The outer hadronic section consists of 1.0 mm diameter fibres with a lead-to-fibre ratio of 3.4:1. The mechanical construction of the new calorimeter and its assembly in the H1 detector are described.

Southern ultraluminous infrared galaxies: An optical and infrared database

Abstract: We have carried out an optical and infrared study of 24 ultraluminous infrared galaxies in the southern hemisphere (SULIRGs). This flux limited, complete sample, has been extracted from the redshift survey of IRAS galaxies compiled by Strauss et al. (1992). It includes systems with a 60 IRAS flux greater than 3 Jy and a far-infrared luminosity greater than $6.5~ 10^{11}~\mbox{$L_{\odot}$}$ (). With the ESO New Technology Telescope, we have obtained high resolution optical images in the R band of all SULIRGs, and with the ESO/MPI 2.2-meter telescope, near infrared J , H and K images for most of them. Low and high resolution spectra have been taken with the 4-meter telescope of the Cerro Tololo Inter-American Observatory. The nature and morphology of all objects are consistent with the wide-spread idea that most, if not all, galaxies with an extreme far-infrared luminosity are close interacting or merging systems. The galaxies that appear as isolated and devoid of tidal features exhibit several isophotal distortions in their main body. However three cases are more ambiguous. They are indeed interacting systems, but their companions are at a distance greater than 40 kpc. We find in the SULIRG sample a significant proportion of objects having AGN like spectra: $55 \pm 6\%$, including one Seyfert 1 galaxy.

Radiation-curable resin composition

Abstract: The present invention provides a curable composition, comprising: a (meth)acrylate urethane compound derived from a polypropylene glycol or a propyleneoxide ethyleneoxide copolymer glycol having a molecular weight between 1,000 and 13,000 and an amount of unsaturation less than 0.01 meq/g. The liquid curable resin composition of the present invention has improved liquid stability and can produce cured products having superior mechanical characteristics by polymerization. The composition further comprises preferably a primary or secondary amine. The liquid curable resin composition can be used as a coating material for optical fibers, adhesives, and the like. The composition is particularly suitable as a coating material for optical fibers for which long-term stability is required.

Light Elements and Cosmic Rays in the Early Galaxy

Abstract: Observations of Be and B in low-metallicity halo stars formed during the first 109 yr of Galactic evolution show that cosmic-ray acceleration must have taken place in the early Galaxy. The observed abundances of these elements relative to Fe, which, in the early Galaxy, is almost exclusively produced in Type II supernovae, strongly suggest that the cosmic-ray acceleration is also related to such supernovae with the particles being accelerated out of freshly nucleosynthesized matter before it mixes into the ambient, essentially nonmetallic interstellar medium. The observed abundances require that about 3 × 1049 to 2 × 1050 ergs per Type II supernova be imparted to these metallic cosmic rays, depending on whether or not H and He are accelerated along with the metals. The current data, however, are not sufficient to decide whether these cosmic rays are predominantly low energy or high energy. But, in any case, arguments of energetics imply a hard-energy spectrum extending up in energy to at least 50 MeV nucleon-1. This rules out Be and B production by supernova ejecta without further acceleration. In addition to production by cosmic rays, there must also be significant 11B production by neutrinos. This argument is driven by the observed 11B/10B ratio in meteorites that is very difficult to reproduce by cosmic-ray interactions. Observations of 6Li and Li in the early Galaxy provide information on the acceleration of nonmetallic cosmic rays out of the interstellar medium.

Gender identity disorder: a review of the past 10 years.

Abstract: Objective To review the clinically relevant literature on gender identity disorder (GID) in children and adolescents over the past 10 years. Method All literature referring to gender identity and children or adolescents from 1985 on was reviewed. Results Changes in the DSM-IV nomenclature include (1) adoption of the single diagnosis of GID to apply to children, adolescents, and adults; (2) changes in the format of the criteria; and (3) placement in the section “Sexual and Gender Identity Disorders.” Rates of associated psychopathology in children with GID are comparable with those in children with other psychiatric disorders, particularly disorders that are intemalizing in form. Biological and psychosocial factors thought to be relevant in the development of GID are reviewed. Conclusions Research is required to elucidate the complicated interaction between biological and psychosocial factors in the development of GID and to evaluate treatment efficacy. J. Am. Acad. Child Adolesc. Psychiatry, 1997, 36(7):872–880.

Thiuram- and dithiocarbamate-accelerated sulfur vulcanization from the chemist's perspective; methods, materials and mechanisms reviewed

Abstract: This paper describes research methodologies for the investigation of the mechanism of vulcanization and discusses the reactivity of thiuram and dithiocarbamate chemicals. The combined knowledge is subsequently applied to thoroughly review the mechanism and chemistry of both thiuram- and dithiocarbamate-accelerated sulfur vulcanization. Integration of the original mechanistic ideas from the 1960s and the results obtained in the past three decades now have led to a more balanced appraisal of events during vulcanization. Questions have been answered, solutions for old problems are proposed, and remaining fields of endeavor are identified.

Discrimination of Streptomyces albidoflavus strains based on the size and number of 16S-23S ribosomal DNA intergenic spacers

Abstract: In an attempt to develop a rapid and accurate method for discrimination of streptomycetes at the strain level, 21 strains identified by fatty acid analysis as Streptomyces albidoflavus and the type strains of nine subjective synonyms of S. albidoflavus were selected for a full or partial 16S ribosomal DNA (rDNA) sequence analysis and an investigation of the 16S-23S rDNA intergenic spacer region. 16S rDNA sequence analysis showed that 27 of the strains exhibited 100% sequence similarity; these strains included the type strain of S. albidoflavus and the type strains of the subjective synonyms Streptomyces canescens, Streptomyces coelicolor, Streptomyces felleus, Streptomyces limosus, Streptomyces odorifer, and Streptomyces sampsonii. The type strains of the other subjective synonyms of S. albidoflavus (i.e., Streptomyces gougerotii, Streptomyces intermedius, and Streptomyces rutgersensis) were found to have levels of 16S rDNA sequence difference of 1.0 to 1.1% when they were compared to the type strain of S. albidoflavus. In order to discriminate between the strains which had identical 16S rDNA sequences, the 16S-23S rDNA intergenic spacer regions were amplified and cloned, and the sequences of the spacer regions were determined for four S. albidoflavus strains, including the type strain. The 16S-23S rDNA intergenic spacer region was found to vary in length and sequence composition among the strains and within each strain. The sizes and numbers of 16S-23S rDNA intergenic spacer regions for the 27 strains with identical 16S rDNA sequences were determined by high-resolution electrophoresis of FAM-labeled PCR products and a subsequent size analysis with GeneScan 672 software. This was shown to be a useful method for discrimination of S. albidoflavus strains. Strains with the same 16S-23S rDNA intergenic spacer band pattern, as determined by high-resolution electrophoresis of FAM-labeled PCR products, could be further discriminated on the basis of the sequence composition of the spacer region.

Deuterium and oxygen-18 in present-day precipitation: data and modelling

Abstract: The cycles of the water isotopic species (HDO and H2 18O) have been incorporated in three atmospheric General Circulation Models (GCMs) with the main objective of predicting the distribution of water stable isotopes in precipitation, The performances of those models are examined for present-day climate through a comparison with existing data available from the IAEA/WMO network established in 1961 and from other sources.

Four climate cycles in Vostok ice core

Abstract: Author(s): Petit, JR; Basile, I; Leruyuet, A; Raynaud, D; Lorius, C; Jouzel, J; Stievenard, M; Lipenkov, VY; Barkov, NI; Kudryashov, BB; Davis, M; Saltzman, E; Kotlyakov, V

Process for the preparation of a granular microbial biomass and isolation of valuable compounds therefrom

Abstract: A process for the isolation of desired compound(s) from a microbial biomass is diclosed, wherein the microbial biomass (which, if necessary, is pretreated to give a dry matter content of from 25 to 80 %) is granulated (e.g. by extrusion) and then dried to a dry matter content of at least 80 %. The granulation of the biomass to granules significantly eases subsequent drying of the biomass (which can be stored as dried granules) and gives higher yields on extraction of the compound(s).