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Showing papers by "Karlsruhe Institute of Technology published in 1996"


Journal ArticleDOI
TL;DR: In this paper, the three-parameter Lee-Yang-Parr (B3LYP) functional was used to compute low-lying electronic excitations of N2, ethylene, formaldehyde, pyridine and porphin.

5,087 citations


Journal ArticleDOI
TL;DR: A new dimension in early stress detection in plants has been achieved by the novel high resolution fluorescence imaging analysis of plants, which not only senses the chlorophyll fluorescence, but also the bluegreen fluorescence emanating from epidermis cell walls which can change under stress induced strain.

742 citations


Journal ArticleDOI
01 Jan 1996-Carbon
TL;DR: In this paper, the surface structure and chemistry of various surface oxidized HT carbon fibers, an IM and a HM carbon fiber were studied by SEM, STM, CAM (contact angle measurement), XPS and TPD with special reference to adsorbed oxidized water.

707 citations


Journal ArticleDOI
TL;DR: In this article, Wu et al. developed a hypoplastic theory for granular materials developed by Gudehus and Bauer and discussed the suitability of the Matsuoka/Nakai criterion for critical states.
Abstract: A hypoplastic theory for granular materials developed by Gudehus and Bauer is discussed. The description of asymptotic states is of particular interest. Three forms of asymptotic states are defined. Useful criteria to describe the tensorial part of the constitutive relation is developed for one of them, namely for the critical states. The terms proposed by Wu are correlated to the well-known formulations of elastic plastic theory: the Drucker/Prager model and the yield condition by Matsuoka/Nakai. The suitability of the Matsuoka/Nakai criterion for critical states is discussed. Specification of tensorial functions follows in two steps. First the hypoplastic Drucker/Prager model is developed, and then the limit condition by Matsuoka/Nakai is implemented. The resulting tensorial functions require the critical friction angle as the only material constant. The limit condition in critical states obtained from the hypoplastic law coincide with the one by Matsuoka/Nakai. A more comprehensive hypoplastic constitutive relation based on these new tensorial functions is discussed and applied to simulations of element tests. These numerical results are compared with experimental results for sand.

669 citations



Journal ArticleDOI
TL;DR: It is concluded that RTKs exhibit significant spontaneous protein kinase activity; several adverse agents target (an) essential SH‐group carried by (a) membrane‐bound protein tyrosine phosphatase(s).
Abstract: Several non-physiologic agents such as radiation, oxidants and alkylating agents induce ligand-independent activation of numerous receptor tyrosine kinases (RTKs) and of protein tyrosine kinases at the inner side of the plasma membrane (e.g. Devary et al., 1992; Sachsenmaier et al., 1994; Schieven et al., 1994; Coffer et al., 1995). Here we show additional evidence for the activation of epidermal growth factor receptor (EGFR), and we show activation of v-ErbB, ErbB2 and platelet-derived growth factor receptor. As a common principle of action the inducing agents such as UVC, UVB, UVA, hydrogen peroxide and iodoacetamide inhibit receptor tyrosine dephosphorylation in a thiol-sensitive and, with the exception of the SH-alkylating agent, reversible manner. EGFR dephosphorylation can also be modulated by these non-physiologic agents in isolated plasma membranes in the presence of Triton X-100. Further, substrate (EGFR) and phosphatase have been separated: a membrane preparation of cells that have been treated with epidermal growth factor (EGF) and whose dephosphorylating enzymes have been permanently destroyed by iodoacetamide can be mixed with a membrane preparation from untreated cells which re-establishes EGFR dephosphorylation. This dephosphorylation can be modulated in vitro by UV and thiol agents. We conclude that RTKs exhibit significant spontaneous protein kinase activity; several adverse agents target (an) essential SH-group(s) carried by (a) membrane-bound protein tyrosine phosphatase(s).

517 citations


15 Mar 1996
TL;DR: In this paper, a constitutive equation for describing changes of states of granular materials which are sufficiently characterized by the void ratio and the stress tensor is proposed, which may be considered as an extension of the Critical State concept.
Abstract: A constitutive equation is proposed for describing changes of states of granular materials which are sufficiently characterized by the void ratio and the stress tensor. It may be considered as an extension of the Critical State concept. It is based on recently published hypoplastic equations and covers a wide range of densities, pressures and deformations. A factorial decomposition allows a rather easy separation and determination of material parameters. Two factors depend on a relative void ratio so that it remains within lower and upper bounds. The bounding void ratios decrease monotonously from maximal values to zero with increasing pressure. The same reduction of the void ratio is proposed for an isotropic compression starting from a suspension. Thus a granulate hardness is defined, and a stiffness factor can be determined. Four material parameters can be estimated from classification tests and determined from the asymptotic behaviour in element tests. Four further parameters are determined by calibration; they are rather constant for wide groups of materials. Strength and stiffness values can be derived and used for the analysis of deformations, stability, and flow. The viscous behaviour is modelled by a rate dependent factor with one further parameter. Limitations and possible extensions of this comprehensive approach are also outlined.

497 citations


Journal ArticleDOI
TL;DR: In this paper, a constitutive equation for describing changes of states of granular materials which are sufficiently characterized by the void ratio and the stress tensor is proposed, which may be considered as an extension of the Critical State concept.

495 citations


Journal ArticleDOI
TL;DR: In this paper, high spectral resolution reflectance measurements were acquired for spring, summer and autumn maple and chestnut leaves covering a wide range of chlorophyll content and consistent and diagnostic differences in the red edge range (680-750 nm) of the reflectance spectrum were obtained for the various leaf samples of both species studied.

447 citations


Journal ArticleDOI
01 Oct 1996-Fuel
TL;DR: In this article, the kinetics of the thermal conversion of aromatic hydrocarbons in the presence of hydrogen and steam were studied, using anphthalene, toluene and benzene as model compounds.

372 citations


Journal ArticleDOI
TL;DR: Based on the assumption that intensity and structure are the most important dimensions of a firm's technological network, the authors of as discussed by the authors identified seven different types of technology-oriented network configurations and showed that innovation success is significantly correlated with a firms technological network.

Journal ArticleDOI
TL;DR: The biosynthesis of all plastidic isoprenoids investigated, including the carotenoids beta-carotene and lutein, does not proceed via the classical acetate/mevalonate pathway, but via the novel glyceraldehyde 3-phosphate/pyruvate route recently detected in eubacteria.
Abstract: Isoprenoid biosynthesis was investigated in the green alga Scenedesmus obliquus grown heterotrophically on 13C-labelled glucose and acetate. Several isoprenoid compounds were isolated and investigated by 13C-NMR spectroscopy. According to the 13C-labelling pattern indicated by the 13C-NMR spectra, the biosynthesis of all plastidic isoprenoids investigated (prenyl side-chains of chlorophylls and plastoquinone-9, and the carotenoids beta-carotene and lutein), as well as of the non-plastidic cytoplasmic sterols, does not proceed via the classical acetate/mevalonate pathway (which leads from acetyl-CoA via mevalonate to isopentenyl diphosphate), but via the novel glyceraldehyde 3-phosphate/pyruvate route recently detected in eubacteria. Formation of isopentenyl diphosphate involves the condensation of a C2 unit derived from pyruvate decarboxylation with glyceraldehyde 3-phosphate and a transposition yielding the branched C5 skeleton of isoprenic units.

Journal ArticleDOI
TL;DR: In this article, a theory for the calculation of nuclear magnetic shielding constants at the coupled cluster singles and doubles level augmented by a perturbative correction for connected triple excitations (CCSD(T)) has been developed and implemented.
Abstract: A theory for the calculation of nuclear magnetic shielding constants at the coupled‐cluster singles and doubles level augmented by a perturbative correction for connected triple excitations (CCSD(T)) has been developed and implemented. The approach, which is based on the gauge‐including atomic orbital (GIAO) ansatz, is illustrated by several numerical examples. These include a comparison of CCSD(T) and other highly correlated methods with full configuration interaction for the BH molecule, and a systematic comparison with experiment for HF, H2O,NH3, CH4, N2, CO, HCN, and F2. The results demonstrate the importance of triple excitations in establishing quantitative accuracy. Finally, the ability of GIAO‐CCSD(T) to make accurate predictions for difficult cases is explored in calculations for formaldehyde (CH2O), diazomethane(CH2NN), and ozone (O3).

Journal ArticleDOI
TL;DR: In this article, the generalized Leveque equation was used to predict the heat transfer coefficient of a plate and frame heat exchanger with chevron corrugation pattern, which is the most important design parameter with respect to fluid friction and heat transfer.
Abstract: Manufacturers of plate and frame heat exchangers nowadays mainly offer plates with chevron (or herringbone) corrugation patterns. The inclination angleof the crests and furrows of that sinusoidal pattern relative to the main flow direction has been shown to be the most important design parameter with respect to fluid friction and heat transfer. Two kinds of flow may exist in the gap between two plates (pressed together with the chevron pattern of the second plate turned into the opposite direction): the crossing flow of small substreams following the furrows of the first and the second plate, respectively, over the whole width of the corrugation pattern, dominating at lower inclination angles (lower pressure drop); and the wavy longitudinal flow between two vertical rows of contact points, prevailing at highangles (high pressure drop). The combined effects of the longer flow paths along the furrows, the crossing of the substreams, flow reversal at the edges of the chevron pattern, and the competition between crossing and longitudinal flow are taken into account to derive a relatively simple but physically reasonable equation for the friction factor ξ as a function of the angleand the Reynolds number Re. Heat-transfer coefficients are then obtained from a theoretical equation for developing thermal boundary layers in fully developed laminar or turbulent channel flow — the generalized Leveque equation — predicting heat-transfer coefficients as being proportional to (ξ·Re2)1/3. It is shown, by comparison, that this prediction is in good agreement with experimental observations quoted in the literature.

Journal ArticleDOI
TL;DR: In this article, the spectral properties of the reflectance spectrum of leaves were investigated and two new vegetation indices, R750/R700 and R 750/R550, were proposed for chlorophyll determination.

Journal ArticleDOI
TL;DR: In this paper, the microwave vacuum drying of banana slices was investigated experimentally and the drying process was examined by introducing pulse generated microwave power in banana samples, and the material temperature was monitored.

Journal ArticleDOI
TL;DR: In this paper, a very short overview of the most commonly used protecting groups is given, in which they are classified according to their lability and not according to the functional group they protect.
Abstract: The choice of protecting groups is one of the decisive factors in the successful realization of a complex, demanding synthetic project. The protecting groups used influence the length and efficiency of the synthesis and are often responsible for its success or failure. A wide range of blocking groups are currently available for the different functional groups; however, an overall strategy combining these different masking techniques in an advantageous and reliable manner has never been proposed or at best only for individual cases. This review attempts to make a contribution to filling this gap. First a very short overview of the most commonly used protecting groups will be given, in which they are classified according to their lability and not according to the functional group they protect. This classification clarifies coherent concepts for the development of blocking strategies. On the basis of this brief summary reliable strategies will then be illustrated and developed with selected examples from the recent literature by which protecting groups may be combined successfully and advantageously in synthetic projects of differing degrees of complexity and difficulty.

Journal ArticleDOI
P. Abreu, Wolfgang Adam, Tim Adye1, E. Agasi  +548 moreInstitutions (36)
TL;DR: The DEtector with Lepton, Photon and Hadron Identification (DELPHI) is a detector for particle identification at the Large Electron-Positron (LEP) collider at CERN.
Abstract: DELPHI (DEtector with Lepton, Photon and Hadron Identification) is a detector for e^+e^- physics, designed to provide high granularity over a 4\pi solid angle, allowing an effective particle identification. It has been operating at the LEP (Large Electron-Positron) collider at CERN since 1989. This article reviews its performance.

Journal ArticleDOI
TL;DR: In this article, a high-resolution fluorescence imaging system was established, which allows a fast and large scale screening of fluorescence gradients and local disturbances in fluorescence emission over the whole leaf surface.

Journal ArticleDOI
TL;DR: This work studies resonant tunneling through a single-level quantum dot in the presence of strong Coulomb repulsion beyond the perturbative regime and predicts that the sign of the zero-bias anomaly depends on the level position relative to the Fermi level of the leads.
Abstract: We study resonant tunneling through a single-level quantum dot in the presence of strong Coulomb repulsion beyond the perturbative regime. The level is either spin degenerate or can be split by a magnetic field. Furthermore we discuss the influence of a bosonic environment. Using a real-time diagrammatic formulation, we calculate transition rates, the spectral density, and the nonlinear I-V characteristic. The spectral density shows a multiplet of Kondo peaks split by the transport voltage and the boson frequencies and shifted by the magnetic field. This leads to zero-bias anomalies in the differential conductance, which agree well with recent experimental results for the electron transport through single-charge traps. Furthermore, we predict that the sign of the zero-bias anomaly depends on the level position relative to the Fermi level of the leads. \textcopyright{} 1996 The American Physical Society.

Journal ArticleDOI
TL;DR: In this paper, the three-loop vacuum polarization function induced by a massive quark is calculated and a comprehensive description of the method is presented. But this method is not suitable for the case of large numbers of quarks.

Journal ArticleDOI
TL;DR: The bosonic two-loop electroweak radiative corrections to the muon’s anomalous magnetic moment, a (g 2)=2, are presented.
Abstract: Bosonic two-loop electroweak radiative corrections to the muon's anomalous magnetic moment, ${a}_{\ensuremath{\mu}}\ensuremath{\equiv}\frac{({g}_{\ensuremath{\mu}}\ensuremath{-}2)}{2}$, are presented. We find $\frac{\ensuremath{\Delta}{a}_{\ensuremath{\mu}}^{\mathrm{EW}}(2 \mathrm{loop}\mathrm{bosonic})}{{a}_{\ensuremath{\mu}}^{\mathrm{EW}}(1 \mathrm{loop})}\ensuremath{\approx}(\frac{\ensuremath{\alpha}}{\ensuremath{\pi}})\ifmmode\times\else\texttimes\fi{}[\ensuremath{-}3.6\mathrm{ln}(\frac{{M}_{W}^{2}}{{m}_{\ensuremath{\mu}}^{2}})+0.10]\ensuremath{\approx}\ensuremath{-}0.11$ for ${M}_{\mathrm{Higgs}}\ensuremath{\approx}250$ GeV. Combining that result with our previous two-loop fermionic calculation, we obtain an overall 22.6% reduction in ${a}_{\ensuremath{\mu}}^{\mathrm{EW}}$ from 195 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}11}$ to 151(4) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}11}$. Implications for the full standard model prediction and an upcoming high precision measurement of ${a}_{\ensuremath{\mu}}$ are briefly discussed. We also give the two-loop electroweak corrections to the anomalous magnetic moments of electron and tau lepton; they result in a reduction of the one-loop estimates by 35% and 15%, respectively.

Book ChapterDOI
01 Sep 1996
TL;DR: This contributions provides an introduction to the theory of place/transition Petri nets and some analysis techniques that are based on the structure of place and transition Petrinets.
Abstract: This contributions provides an introduction to the theory of place/transition Petri nets Topics include the sequential and the concurrent behavior of place/ transition Petri nets, marking graphs and coverability trees, and some analysis techniques that are based on the structure of place/transition Petri nets

Journal ArticleDOI
TL;DR: The MIPAS (Michelson interferometer for passive atmospheric sounding) balloon-borne and space-based experiments apply the Fourier-transform infrared spectrometers to limb-emission sounding by the use of cryogenic instrumentation to study ozone trends and periods of significant ozone depletion.
Abstract: A deeper understanding of long-term ozone trends and periods of significant ozone depletion as well as of the anthropogenic greenhouse effect requires the concerted actions of experimenters and modelers. With respect to observations, atmospheric constituents need to be measured simultaneously and on a global basis. Fourier-transform infrared spectrometers are especially suited for this measurement task. Apromising and challenging branch of Fourier-transform infrared spectroscopy is its application to limb-emission sounding by the use of cryogenic instrumentation. This method allows the measurements to be made independently of the time of the day. The MIPAS (Michelson interferometer for passive atmospheric sounding) balloon-borne (MIPAS-B) and space-based (MIPAS-S) experiments apply this technique. While the MIPAS-B instrument has already been used for several years for stratospheric process studies, the MIPAS-S instrument is in development for the European Space Agency's ENVISAT mission. Instrumental aspects of these MIPAS experiments are highlighted, the most important results in ozone research achieved with MIPAS-B are reviewed, and a brief overview of the scientific capabilities of the MIPAS space experiment is given.

Journal ArticleDOI
TL;DR: The results of the first geochemical and isotopic survey of basaltic glasses dredged along the spreading ridge of the southern Mariana Trough (SMT; 15-17°N) are reported in this paper.

Journal ArticleDOI
TL;DR: A crossover in flux dynamics from elastic to plastic creep is shown to be the origin of the fishtail in YBa 2Cu3O72x.
Abstract: Local magnetic relaxation measurements in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} crystals show evidence for plastic vortex creep associated with the motion of dislocations in the vortex lattice. This creep mechanism governs the vortex dynamics in a wide range of temperatures and fields below the melting line and above the field corresponding to the peak in the {open_quote}{open_quote}fishtail{close_quote}{close_quote} magnetization. In this range the activation energy {ital U}{sub pl}, which decreases with field, drops below the elastic (collective) creep activation energy, {ital U}{sub el}, which increases with field. A crossover in flux dynamics from elastic to plastic creep is shown to be the origin of the fishtail in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}}. {copyright} {ital 1996 The American Physical Society.}

Journal ArticleDOI
P. Abreu1, Wolfgang Adam2, Tim Adye3, I. V. Ajinenko  +578 moreInstitutions (46)
TL;DR: In this article, improved tunings of the JETSET, ARIADNE and HERWIG parton shower models were obtained by fitting the models to these DELPHI data as well as to identified particle distributions from all LEP experiments.
Abstract: Event shape and charged particle inclusive distributions are measured using 750000 decays of the Z to hadrons from the DELPHI detector at LEP. These precise data allow a decisive confrontation with models of the hadronization process. Improved tunings of the JETSET, ARIADNE and HERWIG parton shower models and the JETSET matrix element model are obtained by fitting the models to these DELPHI data as well as to identified particle distributions from all LEP experiments. The description of the data distributions by the models is critically reviewed with special importance attributed to identified particles.

Journal ArticleDOI
TL;DR: In this paper, the Tikhonov regularization method with the regularization parameter chosen by the so-called L-curve criterion is considered and an infinite dimensional example is constructed for which the selected regularisation parameter vanishes too rapidly as the noise to signal ratio in the data goes to zero.
Abstract: This paper considers the Tikhonov regularization method with the regularization parameter chosen by the so-called L-curve criterion. An infinite dimensional example is constructed for which the selected regularization parameter vanishes too rapidly as the noise to signal ratio in the data goes to zero. As a consequence the computed reconstructions do not converge to the true solution. Numerical examples are given to show that similar phenomena can be observed under more general assumptions in “discrete ill-posed problems” provided the exact solution of the problem is “smooth”.

Journal ArticleDOI
TL;DR: In this article, a new technique for interpretation of 3D seismic tomographic models in terms of temperature, degree of partial melt and rock composition is presented and tested, considering both anharmonic and anelastic temperature effects on seismic velocities as well as the effects of mineral reactions, composition and partial melt.

Proceedings ArticleDOI
TL;DR: In this article, a comparison of detailed flowfield measurements for three different single scaled-up hole geometries, all at a blowing ratio and density ratio of unity, is presented.
Abstract: One viable option to improve cooling methods used for gas turbine blades is to optimize the geometry of the film-cooling hole. To optimize that geometry, effects of the hole geometry on the complex jet-in-crossflow interaction need to be understood. This paper presents a comparison of detailed flowfield measurements for three different single, scaled-up hole geometries, all at a blowing ratio and density ratio of unity. The hole geometries include a round hole, a hole with a laterally expanded exit, and a hole with a forward-laterally expanded exit. In addition to the flowfield measurements for expanded cooling hole geometries being unique to the literature, the testing facility used for these measurements was also unique in that both the external mainstream Mach number (Ma{sub {infinity}} = 0.25) and internal coolant supply Mach number (Ma{sub c} = 0.3) were nearly matched. Results show that by expanding the exit of the cooling holes, both the penetration of the cooling jet and the intense shear regions are significantly reduced relative to a round hole. Although the peak turbulence level for all three hole geometries was nominally the same, the source of that turbulence was different. The peak turbulence level for both expanded holes was locatedmore » at the exit of the cooling hole resulting from the expansion angle being too large. The peak turbulence level for the round hole was located downstream of the hole exit where the velocity gradients were very large.« less