Showing papers by "University of Bremen published in 1999"
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4,478 citations
TL;DR: SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) is a spectrometer designed to measure sunlight transmitted, reflected, and scattered by the earth's atmosphere or surface in the ultraviolet, visible, and near-infrared wavelength region (240-2380 nm) at moderate spectral resolution (0.2-1.5 nm, λ/Δλ ≈ 1000-10
Abstract: SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) is a spectrometer designed to measure sunlight transmitted, reflected, and scattered by the earth’s atmosphere or surface in the ultraviolet, visible, and near-infrared wavelength region (240–2380 nm) at moderate spectral resolution (0.2–1.5 nm, λ/Δλ ≈ 1000–10 000). SCIAMACHY will measure the earthshine radiance in limb and nadir viewing geometries and solar or lunar light transmitted through the atmosphere observed in occultation. The extraterrestrial solar irradiance and lunar radiance will be determined from observations of the sun and the moon above the atmosphere. The absorption, reflection, and scattering behavior of the atmosphere and the earth’s surface is determined from comparison of earthshine radiance and solar irradiance. Inversion of the ratio of earthshine radiance and solar irradiance yields information about the amounts and distribution of important atmospheric constituents and the spectral reflecta...
1,762 citations
TL;DR: The Global Ozone Monitoring Experiment (GOME) is a new instrument aboard the European Space Agency's (ESA) Second European Remote Sensing Satellite (ERS-2), which was launched in April 1995 as mentioned in this paper.
Abstract: The Global Ozone Monitoring Experiment (GOME) is a new instrument aboard the European Space Agency’s (ESA) Second European Remote Sensing Satellite (ERS-2), which was launched in April 1995. The main scientific objective of the GOME mission is to determine the global distribution of ozone and several other trace gases, which play an important role in the ozone chemistry of the earth’s stratosphere and troposphere. GOME measures the sunlight scattered from the earth’s atmosphere and/or reflected by the surface in nadir viewing mode in the spectral region 240–790 nm at a moderate spectral resolution of between 0.2 and 0.4 nm. Using the maximum 960-km across-track swath width, the spatial resolution of a GOME ground pixel is 40 × 320 km2 for the majority of the orbit and global coverage is achieved in three days after 43 orbits. Operational data products of GOME as generated by DLR-DFD, the German Data Processing and Archiving Facility (D-PAF) for GOME, comprise absolute radiometrically calibrated e...
1,125 citations
01 Dec 1999
575 citations
TL;DR: Findings on the frequency, comorbidity and psychosocial impairment of social phobia and social fears among 1035 adolescents, aged 12-17 years, in the province of Bremen, Germany are presented.
422 citations
Lawrence Livermore National Laboratory1, University of Wisconsin System2, Lund University3, Max Planck Society4, Geophysical Fluid Dynamics Laboratory5, University of Oregon6, Centre national de la recherche scientifique7, University of Bremen8, Yonsei University9, Bureau of Meteorology10, University of Toronto11, Pennsylvania State University12, Goddard Institute for Space Studies13, University of Illinois at Urbana–Champaign14, Commonwealth Scientific and Industrial Research Organisation15, National Center for Atmospheric Research16, National Oceanic and Atmospheric Administration17
TL;DR: This article showed that the magnitude of the monsoon increases over northern Africa are underestimated by all the models, despite qualitative agreement with paleoecological estimates of biome shifts, despite quantitative evidence that biome shifts are correlated with changes in the distribution of monsoon rainfall.
Abstract: Amplification of the northern hemisphere seasonal cycle of insolation during the mid-Holocene causes a northward shift of the main regions of monsoon precipitation over Africa and India in all 18 simulations conducted for the Paleoclimate Modeling Intercomparison Project (PMIP). Differences among simulations are related to differences in model formulation. Despite qualitative agreement with paleoecological estimates of biome shifts, the magnitude of the monsoon increases over northern Africa are underestimated by all the models.
396 citations
TL;DR: In this paper, Malanotte-Rizzoli et al. used a 3D primitive equation numerical model to simulate the observed changes and understand the basic mechanisms which caused them.
382 citations
01 Mar 1999
TL;DR: The Cretan Sea Overflow Water (CSOW) as mentioned in this paper was proposed for the new deep water mass, which is warmer and more saline than the previously dominating Eastern Mediterranean Deep Water (EMDW), causing temperatures and salinities to rise towards the bottom.
Abstract: The recent changes in the thermohaline circulation of the Eastern Mediteranean caused by a transition from a system with a single source of deep water in the Adriatic to one with an additional source in the Aegean are described and assessed in detail. The name Cretan Sea Overflow Water (CSOW) is proposed for the new deep water mass. CSOW is warmer (θ>13.6°C) and more saline (S>38.80) than the previously dominating Eastern Mediterranean Deep Water (EMDW), causing temperatures and salinities to rise towards the bottom. All major water masses of the Eastern Mediterranean, including the Levantine Intermediate Water (LIW), have been strongly affected by the change. The stronger inflow into the bottom layer caused by the discharge of CSOW into the Ionian and Levantine Basins induced compensatory flows further up in the water column, affecting the circulation at intermediate depth. In the northeastern Ionian Sea the saline intermediate layer consisting of Levantine Intermediate Water and Cretan Intermediate Water (CIW) is found to be less pronounced. The layer thickness has been reduced by factor of about two, concurrently with a reduction of the maximum salinity, reducing advection of saline waters into the Adriatic. As a consequence, a salinity decrease is observed in the Adriatic Deep Water. Outside the Aegean the upwelling of mid-depth waters reaches depths shallow enough so that these waters are advected into the Aegean and form a mid-depth salinity-minimum layer. Notable changes have been found in the nutrient distributions. On the basin-scale the nutrient levels in the upper water column have been elevated by the uplifting of nutrient-rich deeper waters. Nutrient-rich water is now found closer to the euphotic zone than previously, which might induce enhanced biological activity. The observed salinity redistribution, i.e. decreasing values in the upper 500–1400 m and increasing values in the bottom layer, suggests that at least part of the transition is due to an internal redistribution of salt. An initiation of the event by a local enhancement of salinity in the Aegean through a strong change in the fresh water flux is conceivable and is supported by observations.
365 citations
TL;DR: In this paper, a high-temporal-resolution record of sea surface temperatures from the western tropical North Atlantic Ocean which spans the past 29,000 years, derived from measurements of temperature-sensitive alkenone unsaturation in sedimentary organic matter.
Abstract: Evidence for abrupt climate changes on millennial and shorter timescales is widespread in marine and terrestrial climate records1,2,3,4. Rapid reorganization of ocean circulation is considered to exert some control over these changes5, as are shifts in the concentrations of atmospheric greenhouse gases6. The response of the climate system to these two influences is fundamentally different: slowing of thermohaline overturn in the North Atlantic Ocean is expected to decrease northward heat transport by the ocean and to induce warming of the tropical Atlantic7,8, whereas atmospheric greenhouse forcing should cause roughly synchronous global temperature changes9. So these two mechanisms of climate change should be distinguishable by the timing of surface-water temperature variations relative to changes in deep-water circulation. Here we present a high-temporal-resolution record of sea surface temperatures from the western tropical North Atlantic Ocean which spans the past 29,000 years, derived from measurements of temperature-sensitive alkenone unsaturation in sedimentary organic matter. We find significant warming is documented for Heinrich event H1 (16,900–15,400 calendar years bp) and the Younger Dryas event (12,900–11,600 cal. yr bp), which were periods of intense cooling in the northern North Atlantic. Temperature changes in the tropical and high-latitude North Atlantic are out of phase, suggesting that the thermohaline circulation was the important trigger for these rapid climate changes.
353 citations
TL;DR: This paper used a sediment core from the western North Atlantic Ocean to show that two-thirds of the carbon-isotope anomaly occurred within no more than a few thousand years, indicating that carbon was catastrophically released into the ocean and atmosphere.
Abstract: Current models of the global carbon cycle lack natural mechanisms to explain known large, transient shifts in past records of the stable carbon-isotope ratio (δ13C) of carbon reservoirs1,2. The injection into the atmosphere of ∼1,200–2,000 gigatons of carbon, as methane from the decomposition of sedimentary methane hydrates, has been proposed to explain a δ13C anomaly3,4 associated with high-latitude warming1 and changes in marine5,6,7 and terrestrial8 biota near the Palaeocene–Eocene boundary, about 55 million years ago. These events may thus be considered as a natural ‘experiment’ on the effects of transient greenhouse warming. Here we use physical, chemical and spectral analyses of a sediment core from the western North Atlantic Ocean to show that two-thirds of the carbon-isotope anomaly occurred within no more than a few thousand years, indicating that carbon was catastrophically released into the ocean and atmosphere. Both the δ13C anomaly and biotic changes began between 54.93 and 54.98 million years ago, and are synchronous in oceans and on land. The longevity of the δ13C anomaly suggests that the residence time of carbon in the Palaeocene global carbon cycle was ∼120 thousand years, which is similar to the modelled response after a massive input of methane3,4. Our results suggest that large natural perturbations to the global carbon cycle have occurred in the past—probably by abrupt failure of sedimentary carbon reservoirs—at rates that are similar to those induced today by human activity.
340 citations
TL;DR: In this paper, the influence of electron-hole exchange on the emission of single three-dimensionalally confined biexcitons in II-VI semiconductor nanostructures has been studied by magnetophotoluminescence spectroscopy.
Abstract: The influence of quantum dot (QD) asymmetry on the emission of single three-dimensionally confined biexcitons in II-VI semiconductor nanostructures has been studied by magnetophotoluminescence spectroscopy. Investigating both the biexciton and the single-exciton transition in the same single QD, we obtain a unified picture of the impact of electron-hole exchange interaction on the fine structure and the polarization properties of optical transitions in QDs. The exchange splitting is demonstrated to have a strong influence on the derivation of the biexciton binding energy, which we determine to be about 17 meV, much less than the separation between exciton and biexciton lines ( $\ensuremath{\approx}24$ meV) in the spectra.
TL;DR: In this article, the effect of cooling and lubrication during the grinding process of a machined part has been investigated in the field of fluid dynamic processes in supply nozzles and in the grinding zone, thus offering the chance to minimize the amount of coolant in circulation.
01 Jan 1999
TL;DR: Lea et al. as mentioned in this paper showed that shell calcite values decrease with increasing sea water pH and/or carbonate ion concentration, which is independent of symbiont activity and temperature.
Abstract: Laboratory experiments with living planktic foraminifers show that the δ13C and δ18O values of shell calcite decrease with increasing sea water pH and/or carbonate ion concentration The effect has been quantified in symbiotic (Orbulina universa) and non-symbiotic (Globigerina bulloides) species and is independent of symbiont activity and temperature It is concluded that a kinetic fractionation process affects both the carbon and oxygen isotopic composition of the shell simultaneously At present it cannot be determined definitively whether the relationship is controlled by the pH dependent balance between hydration and hydroxylation of CO2 or by [CO3 2-] related variations in the calcification rate However, independent of which factor ultimately controls the relationship between the carbonate chemistry and isotopic fractionation, in the real ocean [CO3 2-] and pH covary linearly across the relevant pH range The true relationship between shell isotopic composition and the bulk carbonate chemistry is masked by the fact that host respiration and symbiont activity locally modify the carbonate system Respiration lowers and photosynthesis increases ambient pH and [CO3 2-] This translates into modified absolute shell values but leaves the slope between the shell isotopic composition and the bulk carbonate chemistry unaffected A second level of shell isotopic modification is introduced by the incorporation of respired carbon, enriched in 12C, which depletes the shell δ13C value In symbiont bearing species this depletion is partially negated by a shell δ13C enrichment in the light As an alternative to the RUBISCO hypothesis (enrichment via preferential removal of 12CO2), we propose that scavenging of respired CO2 during photosynthesis, raises the shell δ13C value Our results have partly been documented before (Spero et al 1997) and demonstrate that the carbonate chemistry is undoubtedly a major control on temporal geochemical variability in the fossil record For instance, the sea water carbonate system of the pre-Phanerozoic world (Berner 1994; Grotzinger and Kasting 1993) or during glacials (Sanyal et al 1995) was significantly different from today confounding direct interpretation of foraminiferal stable isotope data using existing relationships (see companion paper in this volume by Lea et al)
TL;DR: A Genetic Algorithm is presented which solves the job shop scheduling problem and a highly efficient decoding procedure is proposed which strongly improves the quality of schedules.
Abstract: A general model for job shop scheduling is described which applies to static, dynamic and non-deterministic production environments. Next, a Genetic Algorithm is presented which solves the job shop scheduling problem. This algorithm is tested in a dynamic environment under different workload situations. Thereby, a highly efficient decoding procedure is proposed which strongly improves the quality of schedules. Finally, this technique is tested for scheduling and rescheduling in a non-deterministic environment. It is shown by experiment that conventional methods of production control are clearly outperformed atreasonable runtime costs.
École Polytechnique1, University of Paris-Sud2, Rutherford Appleton Laboratory3, Centre national de la recherche scientifique4, Goddard Space Flight Center5, California Institute of Technology6, Pierre-and-Marie-Curie University7, University of Burgundy8, Université libre de Bruxelles9, University of Strathclyde10, Université catholique de Louvain11, University of Massachusetts Lowell12, University of Denver13, Stony Brook University14, University of Bremen15, Langley Research Center16, École Centrale Paris17, Technische Universität München18, University of Alabama19
TL;DR: The current version of the GEISA-97 database is described in this paper, which contains 1,346,266 entries and includes a catalog of absorption cross-sections of molecules such as chlorofluorocarbons which exhibit unresolvable spectra.
Abstract: The current version GEISA-97 of the computer-accessible database system GEISA (Gestion et Etude des Informations Spectroscopiques Atmospheriques: Management and Study of Atmospheric Spectroscopic Information) is described. This catalogue contains 1,346,266 entries. These are spectroscopic parameters required to describe adequately the individual spectral lines belonging to 42 molecules (96 isotopic species) and located between 0 and 22,656 cm-1. The featured molecules are of interest in studies of the terrestrial as well as the other planetary atmospheres, especially those of the Giant Planets. GEISA-97 contains also a catalog of absorption cross-sections of molecules such as chlorofluorocarbons which exhibit unresolvable spectra. The modifications and improvements made to the earlier edition (GEISA-92) and the data management software are described. GEISA-97 and the associated management software are accessible from the ARA/LMD (Laboratoire de Meteorologie Dynamique du CNRS, France) web site: http://ara01.polytechnique.fr/registration.
01 Jan 1999
TL;DR: This chapter describes the subroutine library SLICOT that provides Fortran 77 implementations of numerical algorithms for computations in systems and control theory and builds methods for the design and analysis of linear control systems.
Abstract: This chapter describes the subroutine library SLICOT that provides Fortran 77 implementations of numerical algorithms for computations in systems and control theory. Around a nucleus of basic numerical linear algebra subroutines, this library builds methods for the design and analysis of linear control systems. A brief history of the library is given together with a description of the current version of the library and the ongoing activities to complete and improve the library in several aspects.
TL;DR: The hypothesis that objects representations in visual short-term memory consist of oscillating synchronized cell assemblies is supported, as it is shown that sustained activities are more likely to reflect the continuous rehearsing process in memory than transient activities.
Abstract: In a visual delayed matching-to-sample task, compared to a control condition, we had previously identified different components of the human EEG that could reflect the rehearsal of an object representation in short-term memory (Tallon-Baudry et al., 1998). These components were induced oscillatory activities in the gamma (24-60 Hz) and beta (15-20 Hz) bands, peaking during the delay at occipital and frontal electrodes, and two negativities in the evoked potentials. Sustained activities (lasting until the end of the delay) are more likely to reflect the continuous rehearsing process in memory than transient (ending before the end of the delay) activities. Nevertheless, since the delay duration we used in our previous experiment was fixed and rather short, it was difficult to discriminate between sustained and transient components. Here we used the same delayed matching-to-sample task, but with variable delay durations. The same oscillatory components in the gamma and beta bands were observed again during the delay. The only components that showed a sustained time course compatible with a memory rehearsing process were the occipital gamma and frontal beta induced activities. These two activities slowly decreased with increasing delay duration, while the performance of the subjects decreased in parallel. No sustained response could be found in the evoked potentials. These results support the hypothesis that objects representations in visual short-term memory consist of oscillating synchronized cell assemblies.
TL;DR: In this article, a deterministic H∞-theory for linear stochastic systems with random state and input matrices is presented. But the authors do not consider the nonlinear matrix inequalities.
Abstract: In this paper we consider discrete-time, linear stochastic systems with random state and input matrices which are subjected to stochastic disturbances and controlled by dynamic output feedback. The aim is to develop an H∞-type theory for such systems. For this class of systems a stochastic bounded real lemma is derived which provides the basis for a linear matrix inequality (LMI) approach similar to, but more general than the one presented in Reference 1 for stochastic differential systems. Necessary and sufficient conditions are derived for the existence of a stabilizing controller which reduces the norm of the closed-loop perturbation operator to a level below a given threshold γ. These conditions take the form of coupled nonlinear matrix inequalities. In the absence of the stochastic terms they get reduced to the linear matrix inequalities of deterministic H∞-theory for discrete time systems. Copyright © 1999 John Wiley & Sons, Ltd.
TL;DR: Marine sediment cores from the continental slope off mid-latitude Chile (33°S) were studied with regard to grain-size distributions and clay mineral composition as discussed by the authors, providing a 28,000-yr14C accelerator mass spectrometry-dated record of variations in the terrigenous sediment supply reflecting modifications of weathering conditions and sediment source areas in the continental hinterland.
TL;DR: Both pure and also antibody-modified DNA-STV oligomers were used as reagents in immuno-PCR (IPCR), a highly sensitive detection method for proteins and other antigens, and it was demonstrated that the oligomers can further be functionalized, for instance by the coupling of biotinylated immunoglobulins.
Abstract: The self-assembly of bis-biotinylated double-stranded DNA and the tetravalent biotin-binding protein streptavidin (STV) have been studied by non-denaturing gel electrophoresis and atomic force microscopy (AFM). The rapid self-assembly reproducibly generated populations of individual oligomeric complexes. Most strikingly, the oligomers predominantly contained bivalent STV molecules bridging two adjacent DNA fragments to form linear nanostructures. Trivalent STV branch points occurred with a lower frequency and the presence of tetravalent STV was scarce. However, valency distribution, size and the exchange dynamics of the supramolecular aggregates were highly sensitive to stoichiometric variations in the relative molar coupling ratio of bis-biotinylated DNA and STV. The largest aggregates were obtained from equimolar amounts while excess STV led to the formation of smaller oligomers appearing as fingerprint-like band patterns in electrophoresis. Excess DNA, however, induces a complete breakdown of the oligomers, likely a consequence of the instability of STV conjugates containing more than two biotinylated DNA fragments. It was demonstrated that the oligomers can further be functionalized, for instance by the coupling of biotinylated immunoglobulins. Both pure and also antibody-modified DNA-STV oligomers were used as reagents in immuno-PCR (IPCR), a highly sensitive detection method for proteins and other antigens. Employment of the supramolecular reagents led to an approximately 100-fold enhanced sensitivity compared to the conventional IPCR procedure.
TL;DR: Results of the author’s studies on the effect of the pesticide Aldicarb on the Gamasina are summarized, which document various patterns of population development following pesticide application.
TL;DR: Quantitative measurements on microplates indicate that DDI proceeds with a higher immobilization efficiency than conventional immobilization techniques, such as the binding of the biotinylated proteins to streptavidin-coated surfaces or direct physisorption, and simultaneous immobilization of different compounds using microstructured oligonucleotide arrays as immobilization matrices demonstrate that D DI proceeds with site selectivity due to the unique specificity of Watson-Crick base pairing.
TL;DR: In this article, the photovoltaic behavior of the electrodes containing LiI/LiI3/propylene carbonate electrolyte was measured by irradiation with visible light and it was shown that electron injection into TiO2 occurs from the excited singlet state of the phthalocyanine derivatives.
Abstract: Several zinc(II) and aluminum(III) phthalocyanines substituted by carboxylic acid and sulfonic acid groups were anchored to nanocrystalline TiO2 films. By irradiation with visible light the photovoltaic behavior of the electrodes containing LiI/LiI3/propylene carbonate electrolyte was measured. Most efficient results were found using zinc(II) 2,9,16,23-tetracarboxyphthalocyanine, with a current conversion efficiency at 700 nm approaching 45%. It is shown that electron injection into TiO2 occurs from the excited singlet state of the phthalocyanine derivatives. High stability of the cell performance under continuous irradiation was found.
01 Jan 1999
TL;DR: A number of methods have been proposed to reconstruct ocean history using a large variety of methods with origins in the biological, chemical, and physical sciences, and uses modern statistical techniques for the interpretation of extensive and complex data sets as discussed by the authors.
Abstract: The reconstruction of ocean history employs a large variety of methods with origins in the biological, chemical, and physical sciences, and uses modern statistical techniques for the interpretation of extensive and complex data sets. Various sediment properties deliver useful information for reconstructing environmental parameters. Those properties that have a close relationship to environmental parameters are called “proxy variables” (“proxies” for short). Proxies are measurable descriptors for desired (but unobservable) variables. Surface water temperature is probably the most important parameter for describing the conditions of past oceans and is crucial for climate modelling. Proxies for temperature are: abundance of microfossils dwelling in surface waters, oxygen isotope composition of planktic foraminifera, the ratio of magnesium or strontium to calcium in calcareous shells or the ratio of certain organic molecules (e.g. alkenones produced by coccolithophorids). Surface water salinity, which is important in modelling of ocean circulation, is much more difficult to reconstruct. At present there is no established method for a direct determination of this parameter. Measurements associated with the paleochemistry of bottom waters to reconstruct bottom water age and flow are made on benthic foraminifera, ostracodes, and deep-sea corals. Important geochemical tracers are δ13C and Cd/Ca ratios. When using benthic foraminifera, knowledge of the sediment depth habitat of species is crucial. Reconstructions of productivity patterns are of great interest because of important links to current patterns, mixing of water masses, wind, the global carbon cycle, and biogeography. Productivity is reflected in the flux of carbon into the sediment. There are a number of fluxes other than those of organic carbon that can be useful in assessing productivity fluctuations. Among others, carbonate and opal flux have been used, as well as particulate barite. Furthermore, microfossil assemblages contain clues to the intensity of production as some species occur preferentially in high-productivity regions while others avoid these. One marker for the fertility of sub-surface waters (that is, nutrient availability) is the carbon isotope ratio within that water (I3C/12C, expressed as δ13C). Carbon isotope ratios in today’s ocean are negatively correlated with nitrate and phosphate contents. Another tracer of phosphate content in ocean waters is the Cd/Ca ratio. The correlation between this ratio and phosphate concentrations is quite well documented. A rather new development to obtain clues on ocean fertility (nitrate utilization) is the analysis of the 15N/14N ratio in organic matter. The fractionation dynamics are analogous to those of carbon isotopes. These various ratios are captured within the organisms growing within the tagged water. A number of reconstructions of the partial pressure of CO2 have been attempted using δ13C differences between planktic and benthic foraminifera and δ13C values of bulk organic material or individual organic components. To define the carbon system in sea water, two elements of the system have to be known in addition to temperature. These can be any combination of total CO2, alkalinity, or pH. To reconstruct pH, the boron isotope composition of carbonates has been used. Ba patterns have been used to infer the distribution of alkalinity in past oceans. Information relating to atmospheric circulation and climate is transported to the ocean by wind or rivers, in the form of minerals or as plant and animal remains. The most useful tracers in this respect are silt-sized particles and pollen.
TL;DR: In this article, it was found that the adsorption of tetrasulfonated metallophthalocyanines onto the growing surface of ZnO strongly affects the crystal growth and the orientation of the zinc oxide crystallites, creating a film looking like stacking disks aligned perpendicular to the substrate.
Abstract: Cathodic electrodeposition in an aqueous mixed solution of zinc nitrate and water-soluble tetrasulfonated metallophthalocyanines (TSPcMs), in which M = Zn(II) (TSPcZn), Al(III)[OH] (TSPcAl), or Si(IV)[OH]2 (TSPcSi), resulted in a self-assembled growth of zinc oxide (ZnO) thin films whose surface is modified by TSPcMs. It has been found that the adsorption of TSPcM onto the growing surface of ZnO strongly affects the crystal growth and the orientation of the ZnO crystallites. The effect was most prominently seen with TSPcSi, creating a film looking like stacking disks aligned perpendicular to the substrate. Crystallographic studies by X-ray diffraction and TEM observation coupled with the selected area electron beam diffraction have revealed that thin platelike crystals, whose planes and edges correspond to the (002) and (100) crystal faces, respectively, are aligned in the same orientation around the c-axis within the stacks. The evolution of this unique structure is interpreted as arising from the prefer...
TL;DR: It is directly demonstrated that the dorsal telencephalic proliferation zone (i.e. the pallium) extends – consistent with the process of eversion – some distance laterally on top of theTelencephalon.
Abstract: Large gaps of knowledge exist regarding postembryonic brain morphogenesis of the zebrafish Danio rerio (Cyprinidae, Teleostei). The zebrafish represents – together with the frog (Xenopus), chick and mouse – one of four major models for the genetic study of early brain development. Here, we used normal silver-stained Bodian material and immunohistochemical material stained with a monoclonal antibody against the proliferating cell nuclear antigen (PCNA, cyclin) to study the morphogenetic appearance and location of proliferation zones of the zebrafish brain between day 1 and day 10, focussing on the forebrain at day 5 postfertilization. Our results directly demonstrate that the dorsal telencephalic proliferation zone (i.e. the pallium) extends – consistent with the process of eversion – some distance laterally on top of the telencephalon. The subpallial telencephalic proliferation consists of dorsal and ventral zones. The preoptic region also includes dorsal and ventral proliferation zones. In the diencephalon proper, separate proliferation zones are present in the habenula, and in the periventricular cell masses of the dorsal thalamus, the ventral thalamus, and the pretectum. More ventrocaudally, the latter three massive proliferation zones appear to be replaced each by thinner, but distinct proliferation zones. Two of them represent ventrocaudal continuations of the dorsal and ventral thalamus and lie in the region referred to as the posterior tubercular area in adult teleostean neuroanatomy. The third lies in the region of the nucleus of the medial longitudinal fascicle. In addition, several hypothalamic proliferation zones are present. The data for the diencephalon are largely in agreement with the neuromeric model of brain organization of Puelles and Rubenstein (1993), which is mostly based on amniote data. Generally, the understanding of the prosomeric origin of teleostean prosencephalic cell masses may be regarded as pivotal for their comparative interpretation.
TL;DR: The concept of a transformation unit is presented, which allows systematic and structured specification and programming based on graph transformation, and a selection of applications are discussed, including the evaluation of functional expressions and the specification of an interactive graphical tool.
TL;DR: The Telecommunication Sector of the International Telecommunication Union ITU-T has developed a series of recommendations together comprising the H.323 system that provides for multimedia communications in packet-based .inter networks that has been accepted as being the standard for IP telephony.
TL;DR: Bismuth chemistry has received much less attention in comparison with that of N, P, As, and Sb, but the last years have revealed an increasing interest in the investigation of both the inorganic and the organometallic chemistry of the heaviest element of the group 15 elements.
Abstract: Bismuth chemistry has received much less attention in comparison with that of N, P, As, and Sb, but the last years have revealed an increasing interest in the investigation of both the inorganic and the organometallic chemistry of the heaviest element of the group 15 elements.1 There are several fields Cristian Silvestru (left) was born in Baia-Mare, Romania, in 1955 and graduated in chemistry at the Babes-Bolyai University, Cluj-Napoca, in 1979. He obtained his M.Sc. degree 1 year later. After 2 years as Chemist in a mining company, he was a Research Chemist at the Institute of Chemical and Biochemical Energetics from 1982 to 1989. He received his Ph.D. degree in the group of Professor Ionel Haiduc in Cluj in 1990, with his dissertation research on organometallic compounds with potential biologic activity. In 1990, he joined the Chemistry Department of the BabesBolyai University in Cluj-Napoca. Since 1995 he has been a Full Professor of Inorganic Chemistry and since 1996 Vice-Dean of the Faculty of Chemistry and Engineering Chemistry. He published a book, Organometallics in Cancer Chemotherapy (with I. Haiduc, 2 volumes, CRC Press: Boca Raton, FL, 1989, 1990), and in 1992 received the “Petre Spacu” award of the Romanian Academy for his contributions on the antitumor properties of organometallic compounds (with Dr. Carmen Socaciu and Dr. Adela Bara). Professor Silvestru spent several research stays in Germany (Bremen University 1993sVisiting Professor, 1996sDAAD Grant), Belgium (Vrije Universiteit Brussel 1993sEuropean Community Grant), and Mexico (Instituto de Quimica, Universidad Nacional Autonoma de Mexico 1993−95sVisiting Research Professor, CONACYT Grant). His research interests include organometallic chemistry of main group elements, coordination chemistry of thioligands (mainly organophosphorus compounds), and biological (antitumor) properties of main group organometallics.
TL;DR: In this article, the decay characteristics of excitons and biexcitons in one single semiconductor quantum dot (QD) are directly monitored using time and spatially resolved photoluminescence spectroscopy.
Abstract: The decay characteristics of excitons and biexcitons in one single semiconductor quantum dot (QD) are directly monitored using time- and spatially resolved photoluminescence spectroscopy. The experiments are performed on a CdSe/ZnSe QD, occupied by either one or two excitons at a time, allowing a direct comparison between the radiative lifetime of a biexciton and an exciton confined in the same QD. The rather surprising result of comparable recombination rates for both states is related to the spatial wave function distribution and the spin structure of the particles and their coupling to the photon field, i.e., the superradiance effect.