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Showing papers by "University of Kiel published in 1997"


Journal ArticleDOI
26 Jun 1997-Nature
TL;DR: It is reported that human skin is protected in a similar way by an inducible, transcriptionally regulated, antibiotic peptide, which resembles those in other mammals.
Abstract: To avoid opportunistic infections, plants and animals have developed antimicrobial peptides in their epithelia that can form pores in the cytoplasmic membrane of microorganisms1. After contact with microorganisms, vertebrate skin2, trachea and tongue epithelia3 are rich sources of peptide antibiotics1, which may explain the unexpected resistance of these tissues to infection. Here we report that human skin is protected in a similar way by an inducible, transcriptionally regulated, antibiotic peptide, which resembles those in other mammals.

1,336 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a set of benchmark instances for the evaluation of solution procedures for single and multi-mode resource-constrained project scheduling problems, which are systematically generated by the standard project generator ProGen.

1,096 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the structure of magnetic clouds (MCs) in the inner heliosphere and found that they can best be described as large-scale quasi-cylindrical magnetic flux tubes.
Abstract: . Plasma and magnetic field data from the Helios 1/2 spacecraft have been used to investigate the structure of magnetic clouds (MCs) in the inner heliosphere. 46 MCs were identified in the Helios data for the period 1974–1981 between 0.3 and 1 AU. 85% of the MCs were associated with fast-forward interplanetary shock waves, supporting the close association between MCs and SMEs (solar mass ejections). Seven MCs were identified as direct consequences of Helios-directed SMEs, and the passage of MCs agreed with that of interplanetary plasma clouds (IPCs) identified as white-light brightness enhancements in the Helios photometer data. The total (plasma and magnetic field) pressure in MCs was higher and the plasma-β lower than in the surrounding solar wind. Minimum variance analysis (MVA) showed that MCs can best be described as large-scale quasi-cylindrical magnetic flux tubes. The axes of the flux tubes usually had a small inclination to the ecliptic plane, with their azimuthal direction close to the east-west direction. The large-scale flux tube model for MCs was validated by the analysis of multi-spacecraft observations. MCs were observed over a range of up to ~60° in solar longitude in the ecliptic having the same magnetic configuration. The Helios observations further showed that over-expansion is a common feature of MCs. From a combined study of Helios, Voyager and IMP data we found that the radial diameter of MCs increases between 0.3 and 4.2 AU proportional to the distance, R, from the Sun as R0.8 (R in AU). The density decrease inside MCs was found to be proportional to R–2.4, thus being stronger compared to the average solar wind. Four different magnetic configurations, as expected from the flux-tube concept, for MCs have been observed in situ by the Helios probes. MCs with left- and right-handed magnetic helicity occurred with about equal frequencies during 1974–1981, but surprisingly, the majority (74%) of the MCs had a south to north (SN) rotation of the magnetic field vector relative to the ecliptic. In contrast, an investigation of solar wind data obtained near Earth's orbit during 1984–1991 showed a preference for NS-clouds. A direct correlation was found between MCs and large quiescent filament disappearances (disparition brusques, DBs). The magnetic configurations of the filaments, as inferred from the orientation of the prominence axis, the polarity of the overlying field lines and the hemispheric helicity pattern observed for filaments, agreed well with the in situ observed magnetic structure of the associated MCs. The results support the model of MCs as large-scale expanding quasi-cylindrical magnetic flux tubes in the solar wind, most likely caused by SMEs associated with eruptions of large quiescent filaments. We suggest that the hemispheric dependence of the magnetic helicity structure observed for solar filaments can explain the preferred orientation of MCs in interplanetary space as well as their solar cycle behavior. However, the white-light features of SMEs and the measured volumes of their interplanetary counterparts suggest that MCs may not simply be just Hα-prominences, but that SMEs likely convect large-scale coronal loops overlying the prominence axis out of the solar atmosphere.

643 citations


Journal ArticleDOI
TL;DR: It is proved that, in two and more space dimensions, it is impossible to eliminate the so-called pollution effect of the Galerkin FEM.
Abstract: The development of numerical methods for solving the Helmholtz equation, which behaves robustly with respect to the wave number, is a topic of vivid research. It was observed that the solution of the Galerkin finite element method (FEM) differs significantly from the best approximation with increasing wave number. Many attempts have been presented in the literature to eliminate this lack of robustness by various modifications of the classical Galerkin FEM. However, we will prove that, in two and more space dimensions, it is impossible to eliminate this so-called pollution effect. Furthermore, we will present a generalized FEM in one dimension which behaves robustly with respect to the wave number.

631 citations


Journal ArticleDOI
TL;DR: This contribution summarizes recent work in the field of lot sizing and scheduling and explains differences of formal models and provides some first readings recommendations on capacitated, dynamic, and deterministic cases.

606 citations


Journal ArticleDOI
TL;DR: The pooled ABP records of 1141 healthy children and adolescents with a body height between 115 and 185 cm provided well-based limits of normal ABP in mid-European children.

601 citations


Journal ArticleDOI
TL;DR: This paper reviewed empirical estimates of temporal slopes in polar regions and relevant information that can be inferred from isotope models: simple, Rayleigh-type distillation models and (particularly over Greenland) general circulation models (GCMs) fitted with isotope tracer diagnostics.
Abstract: Well-documented present-day distributions of stable water isotopes (HDO and H218O) show the existence, in middle and high latitudes, of a linear relationship between the mean annual isotope content of precipitation (δD and δ18O) and the mean annual temperature at the precipitation site. Paleoclimatologists have used this relationship, which is particularly well obeyed over Greenland and Antarctica, to infer paleotemperatures from ice core data. There is, however, growing evidence that spatial and temporal isotope/surface temperature slopes differ, thus complicating the use of stable water isotopes as paleothermometers. In this paper we review empirical estimates of temporal slopes in polar regions and relevant information that can be inferred from isotope models: simple, Rayleigh-type distillation models and (particularly over Greenland) general circulation models (GCMs) fitted with isotope tracer diagnostics. Empirical estimates of temporal slopes appear consistently lower than present-day spatial slopes and are dependent on the timescale considered. This difference is most probably due to changes in the evaporative origins of moisture, changes in the seasonality of the precipitation, changes in the strength of the inversion layer, or some combination of these changes. Isotope models have not yet been used to evaluate the relative influences of these different factors. The apparent disagreement in the temporal and spatial slopes clearly makes calibrating the isotope paleothermometer difficult. Nevertheless, the use of a (calibrated) isotope paleothermometer appears justified; empirical estimates and most (though not all) GCM results support the practice of interpreting ice core isotope records in terms of local temperature changes.

562 citations


Journal ArticleDOI
TL;DR: In patients with acute biliary pancreatis but without obstructive jaundice, early ERCP and sphincterotomy were not beneficial and patients in the invasive-treatment group had more severe complications.
Abstract: Background The role of early endoscopic retrograde cholangiopancreatography (ERCP) and papillotomy in the treatment of patients who have acute biliary pancreatitis without obstructive jaundice is uncertain. Methods We conducted a prospective, multicenter study in which 126 patients were randomly assigned to early ERCP (within 72 hours after the onset of symptoms) and endoscopic papillotomy for the removal of stones in the common bile duct, when appropriate, and 112 patients were assigned to conservative treatment. In the conservative-treatment group, ERCP was performed within three weeks if signs of biliary obstruction or sepsis developed. Overall mortality, mortality due to pancreatitis, and complications were compared in the two groups. Results Early ERCP was successful in 121 of the 126 patients in the invasive-treatment group. Endoscopic papillotomy was performed to remove bile-duct stones in 58 patients; stones were successfully extracted in 57. ERCP was performed in 22 of the 112 patients in the con...

545 citations


Journal ArticleDOI
01 Jan 1997-Nature
TL;DR: The contribution of Southern Ocean surface-water stratification to low atmospheric CO 2 concentrations during the last glacial period has been investigated in this article, showing that surface water stratification is correlated with CO 2 concentration.
Abstract: Contribution of Southern Ocean surface-water stratification to low atmospheric CO 2 concentrations during the last glacial period

523 citations


Journal ArticleDOI
TL;DR: The functional characteristics of c-Jun offer a model for the ability of a single molecule to serve as pivotal regulator for death or survival, not only in the response of the cell body to axonal lesions but also following neurodegenerative disorders.

521 citations


Journal ArticleDOI
TL;DR: The Greenland Ice Sheet Project 2 (GISP2) depth-age scale is presented based on a multiparameter continuous count approach to a depth of 2800 m, using a systematic combination of parameters that have never been used to this extent before as mentioned in this paper.
Abstract: The Greenland Ice Sheet Project 2 (GISP2) depth-age scale is presented based on a multiparameter continuous count approach, to a depth of 2800 m, using a systematic combination of parameters that have never been used to this extent before. The ice at 2800 m is dated at 110,000 years B.P. with an estimated error ranging from 1 to 10% in the top 2500 m of the core and averaging 20% between 2500 and 2800 m. Parameters used to date the core include visual stratigraphy, oxygen isotopic ratios of the ice, electrical conductivity measurements, laser-light scattering from dust, volcanic signals, and major ion chemistry. GISP2 ages for major climatic events agree with independent ages based on varve chronologies, calibrated radiocarbon dates, and other techniques within the combined uncertainties. Good agreement also is obtained with Greenland Ice Core Project ice core dates and with the SPECMAP marine timescale after correlation through the δ 18 O of O 2 . Although the core is deformed below 2800 m and the continuity of the record is unclear, we attempted to date this section of the core on the basis of the laser-light scattering of dust in the ice.

Journal ArticleDOI
TL;DR: It is suggested that age, sex, ethnicity and the physiologic effects of poverty may represent biologic modifiers of the EBV association and confirmed that this association is strongly but variably linked to histologic subtype.
Abstract: Hodgkin's disease (HD) has long been suspected to have an infectious precursor, and indirect evidence has implicated Epstein-Barr virus (EBV), a ubiquitous herpesvirus, as a causal agent. Recent molecular studies using EBER in situ hybridization or latency membrane protein-I (LMP-I) immunohistochemistry have identified EBV latent infection in up to 50% of HD tumors. However, the epidemiologic features of these cases have not been examined in detail. To explore the epidemiology of EBV-positive HD so as to understand the role of EBV in HD etiology more clearly, this project accumulated patient data from 14 studies that had applied these EBV assays to HD tumors. With information on age at diagnosis, sex, ethnicity, histologic subtype, country of residence, clinical stage and EBV tumor status from 1,546 HD patients, we examined risk for EBV-positive disease using logistic regression. Forty percent of subjects had EBV-positive tumors, and EBV prevalence varied significantly across groups defined by the study variables. Odds ratios (OR) for EBV-associated HD were significantly elevated for Hispanics vs. whites (OR = 4.1), mixed cellularity vs. nodular sclerosis histologic subtypes (OR = 7.3, 13.4, 4.9 for ages 0-14, 15-49, 50+ years), children from economically less-developed vs. more-developed regions and young adult males vs. females (OR = 2.5). These findings suggest that age, sex, ethnicity and the physiologic effects of poverty may represent biologic modifiers of the EBV association and confirm that this association is strongly but variably linked to histologic subtype. The data augment biologic evidence that EBV is actively involved in HD pathogenesis in some cases but describe epidemiologic complexity in this process.

Journal ArticleDOI
TL;DR: SPECTRUM as mentioned in this paper is a menu-driven PC program that allows the analysis of unevenly spaced time series in the frequency domain, which is based on the Lomb-Scargle Fourier transform and the Welch-Overlapped-Segment-Averaging procedure.

Book ChapterDOI
TL;DR: The aim of this chapter is to summarize the knowledge about Sias in masking, for example, galactose residues, and to review the progress made during the past few years with respect to Sias as recognition determinants in the adhesion of pathogenic viruses, bacteria, and protozoa, and particularly as binding sites for endogenous cellular interaction molecules.
Abstract: Sialic acids (Sias) are terminal components of many glycoproteins and glycolipids especially of higher animals. In this exposed position they contribute significantly to the structural properties of these molecules, both in solution and on cell surfaces. Therefore, it is not surprising that Sias are important regulators of cellular and molecular interactions, in which they play a dual role. They can either mask recognition sites or serve as recognition determinants. Whereas the role of Sias in masking and in binding of pathogens to host cells has been documented over many years, their role in nonpathological cellular interaction has only been shown recently. The aim of this chapter is to summarize our knowledge about Sias in masking, for example, galactose residues, and to review the progress made during the past few years with respect to Sias as recognition determinants in the adhesion of pathogenic viruses, bacteria, and protozoa, and particularly as binding sites for endogenous cellular interaction molecules. Finally, perspectives for future research on these topics are discussed.

Journal ArticleDOI
07 Feb 1997-Science
TL;DR: The Hs1pro-1 locus confers resistance to the beet cyst nematode (Heterodera schachtii Schmidt), a major pest in the cultivation of sugar beet, which was cloned with the use of genome-specific satellite markers and chromosomal break-point analysis.
Abstract: The Hs1pro-1 locus confers resistance to the beet cyst nematode (Heterodera schachtii Schmidt), a major pest in the cultivation of sugar beet (Beta vulgaris L.). The Hs1pro-1 gene was cloned with the use of genome-specific satellite markers and chromosomal break-point analysis. Expression of the corresponding complementary DNA in a susceptible sugar beet conferred resistance to infection with the beet cyst nematode. The native Hs1pro-1 gene, expressed in roots, encodes a 282-amino acid protein with imperfect leucine-rich repeats and a putative membrane-spanning segment, features similar to those of disease resistance genes previously cloned from higher plants.

Journal ArticleDOI
28 Feb 1997-Science
TL;DR: Analysis by in situ hybridization showed that SUT1 mRNA localizes mainly to the SE and is preferentially associated with plasmodesmata, providing evidence for targeting of plant endogenous mRNA and potentially S UT1 protein through phloem plasmidsmata and for sucrose loading at the plasma membrane of SE.
Abstract: The leaf sucrose transporter SUT1 is essential for phloem loading and long-distance transport of assimilates. Both SUT1 messenger RNA (mRNA) and protein were shown to be diurnally regulated and to have high turnover rates. SUT1 protein was detected by immunolocalization in plasma membranes of enucleate sieve elements (SEs) in tobacco, potato, and tomato. Analysis by in situ hybridization showed that SUT1 mRNA localizes mainly to the SE and is preferentially associated with plasmodesmata. Antisense inhibition of SUT1 expression under control of a companion cell (CC)-specific promoter indicated synthesis of SUT1 mRNA in the CC. These results provide evidence for targeting of plant endogenous mRNA and potentially SUT1 protein through phloem plasmodesmata and for sucrose loading at the plasma membrane of SE.

Journal ArticleDOI
TL;DR: This genome-wide scan identifies a psoriasis susceptibility locus at HLA, confirms linkage to 17q, and recommends two novel genomic regions for further scrutiny, one of these regions (16q) overlaps with a recently-identified susceptibility loci for Crohn's disease.
Abstract: In a 12.5 cM genome-wide scan for psoriasis susceptibility loci, recombination-based tests revealed linkage to the HLA region (Zmax = 3.52), as well as suggestive linkage to two novel regions: chromosome 16q (60-83.1 cM from pter, Zmax = 2.50), and chromosome 20p (7.5-25 cM from pter, Zmax = 2.62). All three regions yielded P values < or = 0.01 by non-parametric analysis. Recombination-based and allele sharing methods also confirmed a previous report of a dominant susceptibility locus on distal chromosome 17q (108.2 cM from pter, Zmax = 2.09, GENEHUNTER P = 0.0056). We could not confirm a previously reported locus on distal chromosome 4q; however, a broad region of unclear significance was identified proximal to this proposed locus (153.6-178.4 cM from pter, Zmax = 1.01). Taken together with our recent results demonstrating linkage to HLA-B and -C, this genome-wide scan identifies a psoriasis susceptibility locus at HLA, confirms linkage to 17q, and recommends two novel genomic regions for further scrutiny. One of these regions (16q) overlaps with a recently-identified susceptibility locus for Crohn's disease. Psoriasis is much more common in patients with Crohn's disease than in controls, suggesting that an immunomodulatory locus capable of influencing both diseases may reside in this region.

Journal ArticleDOI
TL;DR: Before concentrations of dissolved CO2 can be estimated from isotopic fractionations, some means of accounting for variations in growth rate must be found, perhaps by drawing on relationships between [PO4] and Cd/Ca ratios in shells of planktonic foraminifera.
Abstract: The carbon isotopic fractionation accompanying formation of biomass by alkenone-producing algae in natural marine environments varies systematically with the concentration of dissolved phosphate Specifically, if the fractionation is expressed by epsilon p approximately delta e - delta p, where delta e and delta p are the delta 13C values for dissolved CO2 and for algal biomass (determined by isotopic analysis of C37 alkadienones), respectively, and if Ce is the concentration of dissolved CO2, micromole kg-1, then b = 38 + 160*[PO4], where [PO4] is the concentration of dissolved phosphate, microM, and b = (25 - epsilon p)Ce The correlation found between b and [PO4] is due to effects linking nutrient levels to growth rates and cellular carbon budgets for alkenone-containing algae, most likely by trace-metal limitations on algal growth The relationship reported here is characteristic of 39 samples (r2 = 095) from the Santa Monica Basin (six different times during the annual cycle), the equatorial Pacific (boreal spring and fall cruises as well as during an iron-enrichment experiment), and the Peru upwelling zone Points representative of samples from the Sargasso Sea ([PO4] < or = 01 microM) fall above the b = f[PO4] line Analysis of correlations expected between mu (growth rate), epsilon p, and Ce shows that, for our entire data set, most variations in epsilon p result from variations in mu rather than Ce Accordingly, before concentrations of dissolved CO2 can be estimated from isotopic fractionations, some means of accounting for variations in growth rate must be found, perhaps by drawing on relationships between [PO4] and Cd/Ca ratios in shells of planktonic foraminifera

Journal ArticleDOI
TL;DR: In this paper, the authors explore the mid-Pleistocene climate transition in the time and frequency domains by new methods of time series analysis and find that the ice volume-related increase in δ18O mean (amplitude: 0.29 ± 0.05 (1 − σμ) ) significantly preceded the abrupt increase in the amplitude of the ∼ 100 ka cycle at 641 ± 9 ka.

Journal ArticleDOI
TL;DR: In this paper, the authors reviewed the available literature and experimental evidence from own experiments and concluded that no mechanism on its own provides an adequate explanation of the available data, and that ammonium toxicity is the result of one or more of the following effects: ammonium-induced mineral nutrient deficiency, arising from the impaired uptake of metal ions; secondary growth inhibition arising from acidification of the rooting medium; alterations in intracellular pH and osmotic balance; uncoupling of photophosphorylation from electron transport, following the accumulation of ammonium in leaves; and altered
Abstract: Nitrate and ammonium have different effects on many biochemical and physiological processes in plants, and at high concentrations this can lead to markedly different growth responses. Most plant species show reduced growth, smaller leaves and a stunted root system when exposed to high ammonium concentrations, and in severe cases this leads to chlorosis. Although well known, ammonium toxicity is poorly understood and is generally considered to be the result of one or more of the following effects; (i) ammonium-induced mineral nutrient deficiency, arising from the impaired uptake of metal ions; (ii) secondary growth inhibition arising from the acidification of the rooting medium; (iii) alterations in intracellular pH and osmotic balance; (iv) uncoupling of photophosphorylation from electron transport, following the accumulation of ammonium in leaves; and (v) altered polyamine and phytohormone metabolism. These hypotheses are reviewed in the light of the available literature and experimental evidence from own experiments. It is concluded that no mechanism on its own provides an adequate explanation of the available data.

Journal ArticleDOI
I. Abt1, T. Ahmed2, S. Aid3, Vladimir Andreev4  +564 moreInstitutions (28)
TL;DR: The H1 detector at the electron-proton storage ring HERA as mentioned in this paper was used from 1992 to the end of 1994, and a major upgrade of some components was undertaken.
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.

Journal ArticleDOI
Holger Ernst1
TL;DR: In this paper, the suitability of patent data for forecasting technological developments, based on the experience in the case of CNC-technology, is assessed, and patent data analysis provides a technological forecasting instrument with high potential benefits and relatively low cost.
Abstract: In the 1980s, a dramatic change in the competitive structure of the machine tool industry through the development and implementation of CNC-technology occurred. For the individual company, the timely anticipation and forecast of these technological challenges has been of vital importance in order to incorporate these technological changes into its strategic planning process. This paper assesses the suitability of patent data for forecasting technological developments, based on the experience in the case of CNC-technology. Following a general description of the technological life cycle concept and the discussion of possible benefits of patent data as a technological forecasting tool, actual patenting activity in CNC-technology is analysed. It is found that the diffusion of CNC-technology can be appropriately described by means of patent data. Different development stages in the life cycle of CNC-technology can be distinguished, where for each stage strategic R&D investment decisions can be derived. Analysing the impact of CNC-technology on the trade pattern between Japan and Germany clearly reveals that patenting activity causes subsequent and immediate market changes. The strong Japanese patent position in CNC-technology is closely associated with favourable trade changes. Consequently, it is recommended to incorporate the systematic and continuous monitoring of patenting activity into a company's overall competitor monitoring intelligence. Especially for small and medium-sized enterprises, patent data analysis provides a technological forecasting instrument with high potential benefits and relatively low cost.

Journal ArticleDOI
TL;DR: Mutations in the gene encoding the facilitative glucose transporter 2 (GLUT2) in three FBS families, including the original patient described in 1949, are reported, indicating that GLUT2 mutations are probably the cause of FBS.
Abstract: Fanconi-Bickel syndrome (FBS) is a rare autosomal-recessive inborn error of metabolism characterized by hepatorenal glycogen accumulation, Fanconi nephropathy and impaired utilization of glucose and galactose. To date, no underlying enzymatic defect in carbohydrate metabolism has been identified. Therefore, and because of the impairment of both glucose and galactose metabolism, a primary defect of monosaccharide transport across membranes has been suggested. Here we report mutations in the gene encoding the facilitative glucose transporter 2 (GLUT2) in three FBS families, including the original patient described in 1949 by Fanconi and Bickel. Homozygous mutations were found in affected individuals, whereas all parents tested were heterozygous for the respective mutation. Because all detected mutations (delta T446-449, C1251T and C1405T) predict truncated translation products that cannot be expected to have functional monosaccharide transport activity, GLUT2 mutations are probably the cause of FBS.

Journal ArticleDOI
TL;DR: The differences between overground and treadmill locomotion in children are investigated and whether the systems generating and integrating different modulations of locomotion into a stable movement pattern have reached full capacity in 6-7 year old children is discussed.
Abstract: Gait analysis on the treadmill and in the overground condition is used both in scientific approaches for investigating the neuronal organisation and ontogenetic development of locomotion and in a variety of clinical applications. We investigated the differences between overground and treadmill locomotion (at identical gait velocity) in 12 adults and 14 children (6-7 years old). During treadmill locomotion the step frequency increased by 7% in adults and 10% in children compared to overground walking, whereas the stride length and the stance phase of the walking cycle decreased. The swing phase, however, increased significantly by 5% in adults and remained unchanged in children. Balance-related gait parameters such as the step width and foot rotation angles increased during treadmill locomotion. The reduction of the step length was found to be stable after 10 min of treadmill walking in most subjects. With regard to the shifted phases of the walking cycle and the changed balance related gait parameters in the treadmill condition, we assume a different modulation of the central pattern generator in treadmill walking, due to a changed afferent input. Regarding the pronounced differences between overground and treadmill walking in children, it is discussed whether the systems generating and integrating different modulations of locomotion into a stable movement pattern have reached full capacity in 6-7 year old children.

Journal ArticleDOI
TL;DR: A computable error bound for mixed finite element methods is established in the model case of the Poisson-problem to control the error in the H(div,Ω) x L 2 (Ω)-norm.
Abstract: A computable error bound for mixed finite element methods is established in the model case of the Poisson-problem to control the error in the H(div,Ω) x L 2 (Ω)-norm. The reliable and efficient a posteriori error estimate applies, e.g., to Raviart-Thomas, Brezzi-Douglas-Marini, and Brezzi-Douglas-Fortin-Marini elements.

Journal ArticleDOI
TL;DR: In this article, a comprehensive spectroscopic survey of DA white dwarfs hotter than 25,000 K is presented, with the majority of the spectra covering the wavelength range of 3500-7500 A, allowing the detection of a number of cool companions.
Abstract: Results are presented from a comprehensive spectroscopic survey of DA white dwarfs hotter than ~25,000 K. The observations consisted of CCD spectra with signal-to-noise ratios of ~100 in the blue, with ~5 A resolution. The majority of the spectra covered the wavelength range of 3500-7500 A, allowing the detection of a number of cool companions. To date, spectra have been obtained and analyzed for 174 DA stars. The spectra were analyzed using our model atmospheres, which are described in detail here, resulting in temperatures and gravities with average internal errors of 1% and 0.04 dex, respectively. Comparisons with previously published results showed that temperature determinations for Teff 1.1 M☉. The ultramassive DA's comprise a much larger fraction of the total than was the case for cooler samples. Calculations based on white dwarf evolutionary models showed that a higher proportion of massive white dwarfs is expected to be found in samples with Teff 30,000 K as a result of differential cooling effects. Within the range Teff > 40,000 K, the EUV-selected subsample did have proportionately more massive stars than the optically selected subsample. However, a detailed comparison showed that EUV and optical surveys were equally capable of detecting relatively nearby massive white dwarfs. On the other hand, interstellar EUV absorption eliminated from the EUV sample many of the more distant stars that were detectable optically. Therefore, the apparent excess of massive DA white dwarfs in the EUV sample is largely due to a relative deficit of stars with more typical masses. Results are presented for individual stars, including a number of subdwarf identifications and reports of detections of cool companions. Properties of some of the more interesting binaries are discussed. We also report on some stars in the sample that evidently have varying He abundances. WD 0612+177 (G104-27) had been observed, at one point, to have photospheric He I; we confirm that He has remained absent since then. WD 0718-316 (RE 0720-314) is in a post-common-envelope binary and has photospheric He II, the abundance of which appears to vary by more than an order of magnitude over timescales of months.

Journal ArticleDOI
TL;DR: Investigations showed that lipid analyses can give important hints on trophic relationships of benthic species and may serve as means to establish the intensity of pelagic-benthic coupling.
Abstract: Arctic benthic organisms of various taxa (Anthozoa, Polychaeta, Pantopoda, Crustacea, Echinodermata) were collected on the shelves off northeast Greenland, Spitsbergen and the western Barents Sea. Their fatty acid compositions were generally characterised by the predominance of the polyunsaturated fatty acids 20:5(n-3) and 22:6(n-3) together with the saturated fatty acid 16:0, which reflect the dominance of phospholipids. The fatty acid compositions of most benthic specimens were influenced by fatty acids of dietary origin. High amounts of the fatty acid 16:1(n-7), typical of diatoms, were found in different taxa from the northeast Greenland shelf. The 18:4(n-3) fatty acid, often typical of non-diatom input, was only dominant in Ophiopholis aculeata from the Spitsbergen shelf. In some taxa small amounts of wax esters were detected with alcohol moieties similar to those of the dominant Arctic copepods. The occurrence of intact wax esters, as well as the wax ester typical fatty acids 20:1(n-9) and 22:1(n-11), also suggested ingestion of large herbivorous copepods. An unusual fatty acid composition was found for most brittle stars, due to a ratio of the 18:1(n-9) and (n-7) fatty acid isomers below 1 with lowest ratios of 0.1. A similar low ratio was also detected in the polychaete Onuphis conchylega. The extremely low portions of the 18:1(n-9) fatty acid are striking, since carnivores are generally characterised by high levels of this fatty acid. A clear gradient from low 18:1(n-9) to (n-7) ratios in suspension feeders, via predatory decapods, to higher ratios in the scavenging amphipods was a major characteristic of the benthic species. Our investigations showed that lipid analyses can give important hints on trophic relationships of benthic species and may serve as means to establish the intensity of pelagic-benthic coupling.

Journal ArticleDOI
TL;DR: In this paper, the screening of dust particles immersed in the sheath of a parallel plate rf discharge in helium is studied by excitation of waves in a linear chain arrangement, where the waves are excited by the radiation pressure of a modulated laser beam.
Abstract: The screening of dust particles immersed in the sheath of a parallel plate rf discharge in helium is studied by excitation of waves in a linear chain arrangement. The waves are excited by the radiation pressure of a modulated laser beam. The measured dispersion relation is compared with a one-dimensional dust lattice wave to obtain the shielding length. Dust acoustic waves are not compatible with the measured dispersion relation. {copyright} {ital 1997} {ital The American Physical Society}

Journal ArticleDOI
TL;DR: For example, the Greenland Ice Sheet Project 2 (GIP2) as mentioned in this paper has been used to date the Greenland ice core from central Greenland, allowing rapid dating of the core, and it has been observed that changes in bubble and grain structure caused by near-surface, primarily summertime formation of hoar complexes provide the main visible annual marker in the Holocene, and changes in “cloudiness of the ice correlated with dustiness mark Wisconsinan annual cycles; both markers are evident and have been intercalibrated in early Holocene ice.
Abstract: Annual layers are visible in the Greenland Ice Sheet Project 2 ice core from central Greenland, allowing rapid dating of the core. Changes in bubble and grain structure caused by near-surface, primarily summertime formation of hoar complexes provide the main visible annual marker in the Holocene, and changes in “cloudiness” of the ice correlated with dustiness mark Wisconsinan annual cycles; both markers are evident and have been intercalibrated in early Holocene ice. Layer counts are reproducible between different workers and for one worker at different times, with 1% error over century-length times in the Holocene. Reproducibility is typically 5% in Wisconsinan ice-age ice and decreases with increasing age and depth. Cumulative ages from visible stratigraphy are not significantly different from independent ages of prominent events for ice older than the historical record and younger than approximately 50,000 years. Visible observations are not greatly degraded by “brittle ice” or many other core-quality problems, allowing construction of long, consistently sampled time series. High accuracy requires careful study of the core by dedicated observers.

Journal ArticleDOI
TL;DR: Patch–clamp analysis shows that heterologously expressed, purified and reconstituted OEP75 constitutes a voltage‐gated ion channel with a unit conductance of Λ = 145pS, which implies that the environment of the polypeptide during the transit is mainly hydrophilic and that protein translocation requires almost complete unfolding of the precursor.
Abstract: The chloroplastic outer envelope protein OEP75 with a molecular weight of 75 kDa probably forms the central pore of the protein import machinery of the outer chloroplastic membrane. Patch-clamp analysis shows that heterologously expressed, purified and reconstituted OEP75 constitutes a voltage-gated ion channel with a unit conductance of Lambda = 145pS. Activation of the OEP75 channel in vitro is completely dependent on the magnitude and direction of the voltage gradient. Therefore, movements of protein charges of parts of OEP75 in the membrane electric field are required either for pore formation or its opening. In the presence of precursor protein from only one side of the bilayer, strong flickering and partial closing of the channel was observed, indicating a specific interaction of the precursor with OEP75. The comparatively low ionic conductance of OEP75 is compatible with a rather narrow aqueous pore (dporeapproximately equal to 8-9 A). Provided that protein and ion translocation occur through the same pore, this implies that the environment of the polypeptide during the transit is mainly hydrophilic and that protein translocation requires almost complete unfolding of the precursor.