Showing papers by "Leibniz University of Hanover published in 1993"
TL;DR: Roll vortices may be loosely defined as quasi-two-dimensional organized large eddies with their horizontal axis extending through the whole planetary boundary layer (PBL), and their indirect manifestation is most obvious in so-called cloud streets as can be seen in numerous satellite pictures as mentioned in this paper.
Abstract: Roll vortices may be loosely defined as quasi two-dimensional organized large eddies with their horizontal axis extending through the whole planetary boundary layer (PBL). Their indirect manifestation is most obvious in so-called cloud streets as can be seen in numerous satellite pictures. Although this phenomenon has been known for more than twenty years and has been treated in a review by one of us (R.A.Brown) in 1980, there has been a recent resurgence in interest and information. The interest in ocena/land-atmosphere interactions in the context of climate modeling has led to detailed observational and modeling efforts on this problem. The presence of rolls can have a large impact on flux modelling in the PBL. Hence, we shall review recent advances in our understanding of organized large eddies in the PBL and on their role in vertical transport of momentum, heat, moisture and chemical trace substances within the lowest part of the atmosphere.
477 citations
TL;DR: In this paper, a bending theory for thin shells undergoing finite rotations is presented, and its associated finite element model is described, and the kinematic assumption is based on a shear elastic Reissner-Mindlin theory.
Abstract: A bending theory for thin shells undergoing finite rotations is presented, and its associated finite element model is described. The kinematic assumption is based on a shear elastic Reissner-Mindlin theory. The starting point for the derivation of the strain measures are the resultant equilibrium equations and the associated principle of virtual work. Within this formulation the polar decomposition of the shell material deformation gradient leads to symmetric strain measures. The associated work-conjugate stress resultants and stress couples are integrals of the Biot stress tensor. This tensor is invariant with respect to rigid body motions and, therefore, appropriate for the formulation of constitutive equations. Finite rotations are introduced via Eulerian angles. The finite element discretization of arbitrary shells is based on the isoparametric concept formulated with respect to a plane reference configuration. The numerical model is applied to different non-linear plate and shell problems and compared with existing formulations. Due to a consistent linearization, the step size of a load increment is only limited by the local convergence behaviour of Newton's method.
85 citations
TL;DR: In a 2-year field experiment conducted on a Gleyic Luvisol in Stuttgart-Hohenheim one experimental and nine commercial maize cultivars were compared for their ability to utilize soil nitrate and to reduce related losses of nitrate through leaching as discussed by the authors.
Abstract: In a 2-year field experiment conducted on a Gleyic Luvisol in Stuttgart-Hohenheim one experimental and nine commercial maize cultivars were compared for their ability to utilize soil nitrate and to reduce related losses of nitrate through leaching. Soil nitrate was monitored periodically in CaCl2 extracts and in suction cup water. Nitrate concentrations in suction water were generally higher than in CaCl2 extracts. Both methods revealed that all cultivars examined were able to extract nitrate down to a soil depth of at least 120 cm (1988 season) or 150 cm (1987 season). Significant differences among the cultivars existed in nitrate depletion particularly in the subsoil. At harvest, residual nitrate in the upper 150 cm of the profile ranged from 73–110 kg N ha−1 in 1987 and from 59–119 kg N ha−1 in 1988. Residual nitrate was closely correlated with nitrate losses by leaching because water infiltration at 120 cm soil depth started 4 weeks after harvest (1987) or immediately after harvest (1988) and continued until early summer of the following year. The calculated amount of nitrate lost by leaching was strongly influenced by the method of calculation. During the winter of 1987/88 nitrate leaching ranged from 57–84 kg N ha−1 (suction cups) and 40–55 kg N ha−1 (CaCl2 extracts), respectively. The corresponding values for the winter of 1988/89 were 47–79 and 20–39 kg N ha−1, respectively. ei]Section editor: B E Clothier
85 citations
TL;DR: The Nco I restriction fragment length polymorphism of the tumor necrosis factor beta (TNFB) gene is investigated in 173 patients with systemic lupus erythematosus, 192 unrelated healthy controls, and eleven panel families of German origin to find positive linkage disequilibrium between TNFB*1 and the following alleles.
Abstract: We investigated the Nco I restriction fragment length polymorphism (RFLP) of the tumor necrosis factor beta (TNFB) gene in 173 patients with systemic lupus erythematosus (SLE), 192 unrelated healthy controls, and eleven panel families, all of German origin. The phenotype frequency of the TNFB*1 allele was significantly increased in patients compared to controls (63.6% vs 47.1%, RR = 1.96, p <0.002). The results of a two-point haplotype statistical analysis between TNFB and HLA alleles show that there is linkage disequilibrium between TNFB*1 and HLA-A1, Cw7, B8, DR3, DQ2, and C4A DE. The frequency of TNFB*1 was compared in SLE patients and controls in the presence or absence of each of these alleles. TNFB*1 is increased in patients over controls only in the presence of the mentioned alleles. Therefore, the whole haplotype A1, Cw7, B8, TNFB*1, C4A DE, DR3, DQ2 is increased in patients and it cannot be determined which of the genes carried by this haplotype is responsible for the susceptibility to SLE. In addition, two-locus associations were analyzed in 192 unrelated healthy controls for TNFB and class I alleles typed by serology, and for TNFB and class II alleles typed by polymerase chain reaction/oligonucleotide probes. We found positive linkage disequilibrium between TNFB*1 and the following alleles: HLA-A24, HLA-B8, DRB1*0301, DRB1*1104, DRB1*1302, DQA1*0501, DQB1*0201, DQB1*0604, and DPB1*0101. TNFB*2 is associated with HLA-B7, DRB1*1501, and DQB1*0602.
81 citations
TL;DR: Findings settle a recent discussion about whether there are deterministically chaotic features present in the dynamics of SBS in fibers by revealing that for the limiting case of vanishing external reflectivity, the dynamics is purely stochastic.
Abstract: We report on experimental investigations of stimulated Brillouin scattering (SBS) in single-mode optical fibers, taking fully into account the influence of external feedback from the fiber ends. A threshold condition for arbitrary external reflectivity is derived. Detailed time-series analysis reveals that for the limiting case of vanishing external reflectivity, the dynamics is purely stochastic. For finite reflectivities, the observed dynamics is periodic provided environmental perturbations are suppressed. These findings settle a recent discussion about whether there are deterministically chaotic features present in the dynamics of SBS in fibers.
78 citations
TL;DR: The activity of glyoxalase I is found to be modulated during the proliferation cycle, with a maximal activity between day 2 and day 4 of culture growth and both the enzyme activity and cell growth could be re-initiated with auxin.
Abstract: Using a strictly auxin-dependent soybean (Glycine max (L.) Merr.) cell suspension, we studied the correlation of auxin-dependent cell proliferation and the activity of glyoxalase I (S-lactoylglutathione-lyase EC 4.4.1.5.), an enzyme generally associated with cell proliferation in animal, microbial and, as reported recently, also plant systems. We found the activity of glyoxalase I to be modulated during the proliferation cycle, with a maximal activity between day 2 and day 4 of culture growth. After starving the culture of auxins for three subsequent periods, both the enzyme activity and cell growth could be re-initiated with auxin. Enzyme activity reached its maximum 1 d before cell number was at a maximum. The enzyme was purified to homogeneity and characterized.
76 citations
TL;DR: Analytical formulas for the frequency dependent complex line impedance and admittance are derived and the validity of these formulas is proved by comparison with results obtained from full-wave analyses using the Spectral-Domain-Approach and with experimental data gained from on-chip measurements.
72 citations
TL;DR: The main factors contributing to the higher P efficiency of the modern cultivar are efficient use of assimilates for root growth characteristics which enhance P acquisition: smaller root diameter, and longer root hairs, and efficient remobilization of P from vegetative plant organs to the grains.
Abstract: In an attempt to evaluate whether breeding and selection for high yielding capacity did change the P requirements of modern wheat cultivars, the response of two wheat cultivars to different levels of P supply was investigated. A traditional cultivar (“Peragis”) and a modern cultivar (“Cosir”) were cultivated in a C-loess low in available P and high in CaCO3 in 120 cm high PVC pots. Shoot and root growth at different developmental stages was compared. The grain yield of the modern cultivar Cosir was higher at limiting and non-limiting P supply and, therefore, this cultivar can be considered as more P-efficient than the traditional cultivar. From the results it can be concluded that the main factors contributing to the higher P efficiency of the modern cultivar are (i) efficient use of assimilates for root growth characteristics which enhance P acquisition: smaller root diameter, and longer root hairs, (ii) efficient remobilization of P from vegetative plant organs to the grains, and (iii) lower P requirement for grain yield formation because of lower ear number per plant but higher grain number per ear.
66 citations
TL;DR: In this paper, internal solid state reactions in nonmetallic systems (in particular in oxide systems) are reviewed, both in respect of theory and experiment, and internal reductions are treated.
61 citations
TL;DR: In this paper, the largest Lyapunov exponent from deterministically chaotic data is estimated from stochastic data, and a finite positive value is obtained from the same data set.
58 citations
TL;DR: C3d, and particularly the C3d/C3 ratio, provide sensitive markers for disease activity in SLE and reflects complement activation better than C3, C4 and CH50.
Abstract: In order to investigate, if complement levels can be used as an indicator of clinical activity in systemic lupus erythematosus (SLE), levels of C3, C4, CH50, and C3d were measured in 79 patients, 41 with inactive, 31 with moderately active and 7 with severely active disease. Our study shows that C3d, and particularly the C3d/C3 ratio, provide sensitive markers for disease activity in SLE. Since C3d is a direct measurement of complement turnover, it reflects complement activation better than C3, C4 and CH50.
TL;DR: In this article, the influence of shear forces on pellet formation and the productivity of Penicillium chrysogenum was investigated, and a narrow pellet size distribution with a mean pellet diameter of less than 300 μm was obtained.
TL;DR: In this article, a numerical model for layered composite structures based on a geometrical nonlinear shell theory is presented, where the in-plane displacements of each layer are described by independent director vectors.
Abstract: A numerical model for layered composite structures based on a geometrical nonlinear shell theory is presented. The kinematic is based on a multi-director theory, thus the in-plane displacements of each layer are described by independent director vectors. Using the isoparametric apporach a finite element formulation for quadrilaterals is developed. Continuity of the interlaminar shear stresses is obtained within the nonlinear solution process. Several examples are presented to illustrate the performance of the developed numerical model.
TL;DR: In this paper, the dependence of the ion abundances in the TSP mass spectra of several pesticides, including anilides, carbamates, N-heterocyclic and organophosphorus compounds and phenylureas under collision-activated dissociation conditions was investigated.
01 Jan 1993
TL;DR: In this article, a theoretical and numerical shakedown analysis of perfectly plastic and kinematic hardening materials in the framework of geometrical linear theory is presented, where the authors give an introduction to theoretical analysis of these materials.
Abstract: This course will give an introduction to theoretical and numerical shake-down analysis of perfectly plastic and kinematic hardening materials in the framework of geometrical linear theory.
TL;DR: In this paper, a two-stage anaerobic-aerobic treatment of potato starch wastewaters with high concentrations of COD, nitrogen and phosphorus has been studied and several tests have been carried out on nitrification/denitrification by means of the intermediate product nitrite.
TL;DR: In this article, potato pulp consisting of pectins, starch, cellulose and hemicellulose was separated by treatment with dilute sulphuric acid into pectin and starch on the one hand and cellulose, hemicelulose, and xylose on the other.
TL;DR: A vision–based 3‐D scene analysis system is described that is capable to model complex real–world scenes like streets and buildings automatically from stereoscopic image pairs, and realistic looking image sequences from arbitrary view points can be synthesized using computer graphics.
Abstract: A vision–based 3-D scene analysis system is described that is capable to model complex real–world scenes like streets and buildings automatically from stereoscopic image pairs. Input to the system is a sequence of stereoscopic images taken with two standard CCD Cameras and TV lenses. The relative orientation of both cameras to each other is known by calibration. The camerapair is then moved throughout the scene and a long sequence of closely spaced views is recorded. Each of the stereoscopic image pairs is rectified and a dense map of 3-D suface points is obtained by area correlation, object segmentation, interpolation, and triangulation. 3-D camera motion relative to the scene coordinate system is tracked directly from the image sequence which allows to fuse 3-D surface measurements from different viewpoints into a consistent 3-D model scene. The surface geometry of each scene object is approximated by a triangular surface mesh which stores the suface texture in a texture map. From the textured 3-D models, realistic looking image sequences from arbitrary view points can be synthesized using computer graphics.
TL;DR: In this article, the iridoid composition of four Liniria species has been investigated and two new iridoids along with known compounds were isolated and identified, and structure elucidations were carried out mainly by spectral methods and molecular mechanics calculations.
TL;DR: In this article, the Mossbauer spectra of magnetite, Fe 3−δ O 4, have been measured at high temperatures (up to 1400°C) as a function of oxygen partial pressure, p O 2.
TL;DR: Two different FIA-based biosensor systems are described for application to different biotechnologically relevant purposes and a calorimetric immunoassay based on the use of an enzyme thermistor is described.
TL;DR: The effect of long-term exposure of rats to a 50-Hz, 30-mT magnetic field (MF) on cell proliferation and frequencies of sister-chromatid exchanges (SCE) in peripheral lymphocytes of rats following exposure to MF for 7 or 28 days is investigated.
TL;DR: In this paper, the dependence of fractional conversions of NO, NH3 and CO was measured as a function of residence time, temperature, initial NH 3 NO molar ratio and concentrations of CO and O2.
TL;DR: In clinical specimens with a monoclonal lymphoid population, a clone-specific pattern of bands was identified representing conformational polymorphisms of cRNA molecules of rearranged T-cell receptor gamma genes of the predominant lymphoid clone.
TL;DR: It is demonstrated, on the molecular level, that these hypopigmented lesions contain tumour clone‐specific DNA and may represent early manifestations of mycosis fungoides.
Abstract: A specific molecular probe for the malignant lymphoid clone of lesions of a patient with mycosis fungoides was developed. As a clone-specific marker the junctional region of rearranged T-cell-receptor-gamma (TCR-gamma) genes was used. An oligonucleotide primer complementary to these sequences was designed. Using this primer and polymerase chain-reaction technology, early hypopigmented lesions of the patient, which were previously unclassifiable by conventional microscopy, were analysed. The study demonstrates, on the molecular level, that these hypopigmented lesions contain tumour clone-specific DNA and may represent early manifestations of mycosis fungoides.
TL;DR: Compared to the clinical findings, the results of an animal experiment demonstrate less complications by fixation of vascularized bone grafts to mandibular angle defects (guineapig) when THORP plates are used instead of miniplates.
Abstract: Summary In 24 patients, fixation of isolated or combined bone grafts has been performed exclusively with miniplates. Other than the lateral displacement of one osteomyocutaneous iliac crest graft, no complication occurred with regard to the fixation method chosen. In contrast to the clinical findings, our results of an animal experiment demonstrate less complications by fixation of vascularized bone grafts to mandibular angle defects (guineapig) when THORP plates are used instead of miniplates. Whereas we consider miniplate fixation of vascularized bone grafts to be the method of choice, selected patients may require more stable fixation systems, especially when a high postoperative mobility may be expected or large amounts of the mandible including the condyle have to be reconstructed.
TL;DR: Combining well-known immunoassays with the FIA technique, the heterogeneous and the turbidimetric immuno-FIA methods are presented to demonstrate the effectiveness and application of these immunoanalysis methods.
TL;DR: It was shown that isolated PCR amplification products can be used as RFLP probes to detect polymorphisms for a certain locus in progenies where the corresponding RAPD pattern is monomorphic or no amplification product is observed.
Abstract: Genetic and linkage analysis of marker loci were performed with 4 selfed progenies, derived from single plant (I0/1 lines) of carrot (Daucus carota L. sativus). The analysis of 58 markers included 1 morphological marker, 10 isozyme loci, 14 RFLPs, 28 RAPD markers, and 6 isolated PCR fragments used as RFLP probes. Linkage analysis was carried out with the MAPMAKER program and resulted in the construction of 8 linkage groups containing 55 markers with an average distance of 13.1 cM, 3 marker loci remained unlinked. 24% of the markers deviated significantly from the expected Mendelian ratios (1:2:1 or 3:1) due to gametic or zygotic selection. It was shown that isolated PCR amplification products can be used as RFLP probes to detect polymorphisms for a certain locus in progenies where the corresponding RAPD pattern is monomorphic or no amplification product is observed. Since carrot has a relative small genome the probability of amplifying repetitive DNA sequences is comparatively low. Thus PCR amplification products represent an additional useful source of RFLP probes.
TL;DR: In this article, a simplified analytic model is used to derive an upper limit for capture velocities, and the resulting scaling law agrees well with the observed number of atoms and with the density as a function of field gradient.
TL;DR: In this paper, the authors used 3/2-type fused-mullite single crystals to measure the thermal expansion of a, b, and c axes and found that the slopes of a and volume expansion curves are higher above the expansion discontinuity than below.
Abstract: Thermal expansion data of mullite were collected between 25° and 800°C with high accuracy by means of an X-ray high-temperature Guinier powder camera, and high-resolution single-crystal Bond techniques. 3/2-type mullites, synthesized from chemically coprecipitated precursors and 2/1-type fused-mullite single crystals, were used for the measurements. Mullite displays low and nonlinear thermal expansions along the crystallographic a, b, and c axes below about 200°C, and linear expansions between 200° and 400°C. Between about 400° and 500°C, expansion curves are discontinuous. Above 500°C, a, b, and c expansions are linear again. The temperature-induced expansion discontinuities are relatively strong parallel to a, but are much weaker parallel to b and c. The slopes of the a and volume expansion curves are higher above the expansion discontinuity than below, while there is no significant tendency for those of b and c. Thermal expansion coefficients and discontinuity effects are reversible without any hysteresis. The increase of the a and volume expansion curves above the expansion discontinuities may be due to possible deformations, rotations, and tiltings of the [AlO6] octahedra. Another factor responsible for the higher a and volume expansion coefficients at high temperatures may be a geometrical deformation of the [Al⋆O4] tetrahedra. At present, no conclusive model exists to explain the discontinuous change of thermal expansion coefficients between 400° and 500°C.