Showing papers by "Karlsruhe Institute of Technology published in 1995"

Auxiliary basis sets to approximate Coulomb potentials

Abstract: We demonstrate accuracy and computational efficiency resulting from an approximate treatment of Coulomb operators which is based on the expansion of molecular electron densities in atom-centered auxiliary basis sets. This is of special importance in density functional methods which separate the treatment of Coulomb and exchange-correlation terms. Auxiliary basis sets are optimized as much as possible for isolated atoms and then augmented for use in molecular electronic structure calculations. For molecules involving atoms up to Br this typically affects energies by only 10−4 au per atom, and computed structure constants by less than 0.1 pm in bond distances and 0.1° in bond angles.

A laser-Doppler velocimetry study of ensemble-averaged characteristics of the turbulent near wake of a square cylinder

Abstract: Ensemble-averaged statistics at constant phase of the turbulent near-wake flow (Reynolds number ≈ 21400 around a square cylinder have been obtained from two-component laser-Doppler measurements. Phase was defined with reference to a signal taken from a pressure sensor located at the midpoint of a cylinder sidewall. The distinction is drawn between the near wake where the shed vortices are ‘mature’ and distinct and a base region where the vortices grow to maturity and are then shed. Differences in length and velocity scales and vortex celerities between the flow around a square cylinder and the more frequently studied flow around a circular cylinder are discussed. Scaling arguments based on the circulation discharged into the near wake are proposed to explain the differences. The relationship between flow topology and turbulence is also considered with vorticity saddles and streamline saddles being distinguished. While general agreement with previous studies of flow around a circular cylinder is found with regard to essential flow features in the near wake, some previously overlooked details are highlighted, e.g. the possibility of high Reynolds shear stresses in regions of peak vorticity, or asymmetries near the streamline saddle. The base region is examined in more detail than in previous studies, and vorticity saddles, zero-vorticity points, and streamline saddles are observed to differ in importance at different stages of the shedding process.

Stimulation of c-Jun activity by CBP: c-Jun residues Ser63/73 are required for CBP induced stimulation in vivo and CBP binding in vitro.

Abstract: The CBP protein mediates PKA induced transcription by binding to the PKA phosphorylated activation domain of CREB. Here we show that CBP also stimulates the activity of both c-Jun and v-Jun in vivo. The CREB binding domain of CBP is sufficient to contact to c-Jun in vitro. When this domain of CBP is linked to the activation domain of VP16 and expressed in vivo it stimulates c-Jun dependent transcription. Deletion analysis of c-Jun indicate that the CBP binding site is within the N-terminal activation domain. Loss of binding to CBP in vitro correlates with severely reduced transactivation capacity in vivo. Mutation of Ser63/73 in c-Jun, or the corresponding position in v-Jun (Ser36/46) leads to reduced binding to CBP in vitro and abolishes augmentation of transcription in vivo. These data are consistent with a mechanism by which CBP acts as a co-activator protein for Jun dependent transcription by interacting with the Jun N-terminal activation domain.

Optical investigations of defects in Cd1-xZnxTe.

Abstract: We investigated the optical properties of defects in CdTe and ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Zn}}_{\mathit{x}}$Te (0x1). Residual impurities give rise to specific far infrared absorptions, while metal vacancy-donor complexes (A centers), identified by optically detected magnetic resonance, are characterized by their near infrared (1.4 eV) photoluminescence (PL) properties. The specific zero-phonon-line positions and phonon couplings are worked out for these complexes involving different group-VII (F, Cl, Br, In) or group-III (In, Al) donors. In addition to the A center PL two emission bands are found at 1.135 and at 1.145 eV. The temperature dependences of the PL show that the 1.145 eV luminescence follows the temperature dependence of the band gap, while the energy position of the 1.135 eV band emission shifts to higher energies with increasing temperature. The A-center PL and the luminescence bands at 1.1 eV are investigated throughout the complete alloy composition range form x=0 to 1. The A center and the 1.135 eV band were found to follow the band-gap shift from CdTe to ZnTe, whereas the 1.145 eV luminescence keeps its emission energy constant.

A call-by-need lambda calculus

Abstract: The mismatch between the operational semantics of the lambda calculus and the actual behavior of implementations is a major obstacle for compiler writers. They cannot explain the behavior of their evaluator in terms of source level syntax, and they cannot easily compare distinct implementations of different lazy strategies. In this paper we derive an equational characterization of call-by-need and prove it correct with respect to the original lambda calculus. The theory is a strictly smaller theory than the lambda calculus. Immediate applications of the theory concern the correctness proofs of a number of implementation strategies, e.g., the call-by-need continuation passing transformation and the realization of sharing via assignments.

Developments in the continuous mechanical production of oil-in-water macro-emulsions

Abstract: Emulsification processes are determined both by droplet disruption and droplet re-coalescence. This paper explains the fundamentals of droplet disruption in laminar and turbulent flow. Emulsification results from different continuous emulsification machines are compared with respect to the energy density (specific volumetric energy input) achieved. This is the first time that such a comparison has been made for both droplet disruption itself and droplet disruption superimposed by re-coalescence.

Coupled-cluster calculations of nuclear magnetic resonance chemical shifts

Abstract: Theory and implementation of the gauge‐including atomic orbital (GIAO) ansatz for the gauge‐invariant calculation of nuclear magnetic resonance chemical shifts are described for the coupled‐cluster singles and doubles (CCSD) approach. Results for the shielding constants of the hydrides HF, H2O, NH3, and CH4 as well as for a few multiply bonded systems such as CO, N2, and HCN demonstrate the importance of higher‐order correlation corrections, as good agreement with experiment is only obtained at the CCSD level and to some extent at partial fourth‐order many‐body perturbation theory [SDQ‐MBPT(4)] with the latter slightly overestimating correlation effects due to single and double excitations. For relative chemical shifts, GIAO‐CCSD calculations provide in difficult cases (e.g., CO and CF4) more accurate results than previous GIAO‐MBPT(2) calculations. But, it seems that it is often more important to include rovibrational effects (as well as possible molecule–solvent interactions) than higher‐order correlation corrections. Despite that, GIAO‐CCSD proves to be a powerful tool for the accurate calculation of NMR chemical shifts. Its capabilities as well as its limitations are demonstrated in shielding calculations for formaldehyde, diazomethane, and ozone. At least for the latter, the description provided by the CCSD ansatz is not sufficient and even higher excitations need to be considered.

Perturbative treatment of the similarity transformed Hamiltonian in equation‐of‐motion coupled‐cluster approximations

Abstract: A series of size‐consistent approximations to the equation‐of‐motion coupled cluster method in the singles and doubles approximation (EOM‐CCSD) are developed by subjecting the similarity transformed Hamiltonian H=exp(−T)H exp(T) to a perturbation expansion Attention is directed to N and N−1 electron final state realizations of the method defined by truncation of H at second order Explicit spin–orbital equations for the energy and its first derivative are documented for both approaches [EOMEE‐CCSD(2) and EOMIP‐CCSD(2), respectively], and have been implemented in a large‐scale quantum chemistry program Vertical ionization potentials calculated by EOMIP‐CCSD(2) are shown to be equivalent to those of an approach presented recently by Nooijen and Snijders [J Chem Phys 102, 1681 (1995)] Applications of both EOMIP‐CCSD(2) and EOMEE‐CCSD(2) provide results for final state properties that compare favorably with those obtained in full EOM‐CCSD calculations Analysis of the computational aspects of the approximate and full EOM‐CCSD methods shows that the cost of EOMIP‐CCSD(2) energy and gradient calculations scales in proportion to the fifth power of the basis set size, a significant savings over the sixth power dependence of EOMIP‐CCSD This feature is of great practical importance, as it shows that this N−1 electron final state approach has a large domain of applicability and is therefore likely to become a valuable tool for application calculations On the other hand, the same cannot be said for EOMEE‐CCSD(2) since its asymptotic computational dependence and storage requirements are the same as the full EOMEE‐CCSD method

The HW95 tidal potential catalogue

Abstract: The catalogue named HW95 of the harmonic development of the Earth tide generating potential due to the Moon, the Sun and the planets Venus, Jupiter, Mars, Mercury and Saturn is presented here. This catalogue of the fully normalized potential coefficients contains 12935 waves, including 1483 waves due to the direct planetary effects (Hartmann and Wenzel 1994a,b). It is based on the DE200 numerical ephemerides of the planets and the Moon between the years 1850 and 2150. The error of gravity tides computed from the catalogue HW95 at mid-latitude stations between the years 1850 and 2150 is estimated to about 1.4 (12.3) pm/s² rms (at maximum) in time domain and 0.002 (0.11) pm/s² rms (at maximum) in frequency domain (1 pm/s²=10−12 m/s²=0.1 ngal) using a new bench-mark tidal gravity series (Wenzel 1996). An improvement in accuracy of a factor of 50 over the catalogues of Tamura (1987) and Xi (1989) has been achieved.

The one-loop renormalization of the MSSM Higgs sector and its application to the neutral scalar Higgs masses

Abstract: The structure of the Higgs sector in the minimal supersymmetric standard model is reviewed at the oneloop level. An on-shell renormalization scheme of the MSSM Higgs sector is presented in detail together with the complete list of formulae for the neutral Higgs masses at the one-loop level. The results of a complete one-loop calculation for the mass spectrum of the neutral MSSM Higgs bosons and the quality of simpler Born-like approximations are discussed for sfermion and gaugino masses in the range of the electroweak scale.

A comparison of single reference methods for characterizing stationary points of excited state potential energy surfaces

Abstract: The accuracy of geometries, vibrational frequencies and dipole moments of stationary points on excited state potential energy surfaces is assessed for three single reference excited state theories—configuration interaction (CIS), a perturbative doubles correlation correction to CIS, termed CIS(D), and equation‐of‐motion coupled cluster theory with single and double substitutions (EOM‐CCSD). Two groups of systems are studied: the diatomic molecules H2, BH, BF, C2, CO, and N2; and the lowest singlet excited states of ammonia, formaldehyde and acetylene. The calculations demonstrate that CIS systematically underestimates bond lengths and overestimates frequencies and dipole moments, a pattern often associated with the Hartree–Fock method for ground states. CIS(D) fails to provide a systematic improvement to CIS for all geometries and frequencies, often overestimating correlation corrections. EOM‐CCSD, by contrast, performs significantly better than CIS for all properties considered.

leanTAP: Lean tableau-based deduction

Abstract: “prove ((E, F), A, B, C, D) : - !, prove (E, [F ∣ A], B, C, D). prove ((E; F), A, B, C, D) : - !, prove (E, A, B, C, D), prove (F, A, B, C, D). prove (all(H, I), A, B, C, D) : - !, ∖+ length (C, D), copy_term ((H, I, C), (G, F, C)), append (A, [all (H, I)], E), prove(F, E, B, [G ∣ C], D). prove (A,_, [C ∣ D] ,_, _) :-((A= − (B); − (A) = B)) -> (unify(B, C); prove (A, [], D,_,_)). prove (A, [E ∣ F], B, C, D): - prove (E, F, [A∣B], C,D).” implements a first-order theorem prover based on free-variable semantic tableaux. It is complete, sound, and efficient.

Voluntary Contributions to a Public Good When Partial Contribution is a Dominant Strategy

Abstract: We present an experiment on voluntary contributions to a public good. The game has a dominant strategy solution in the interior of the strategy space. In the experiment we observe significant over-contribution. This result is similar to those of the typical corner solution experiments.

Röntgenographische Untersuchung von Spannungszuständen in Werkstoffen

Abstract: X-Ray Investigation of Stress States in Materials X-ray stress analyses on crystalline or partially crystalline materials are based on the determination of elastic lattice strains which are converted to stresses by means of theory of elasticity. The development of the sin2 ψ-method of X-ray stress analysis and of diffractometers substituting film chambers during the 1960s initiated an enormous progress in X-ray stress analysis during the following three decades both in respect of the knowledge of the underlying principles and in respect of the practical application. This report sketches the historical development of X-ray stress analyses and describes the actual state of the art of this important tool for materials science and engineering. Besides some important elements of X-ray physics and theory of elasticity, experimental aspects of practical applications are outlined. Standard measuring procedures and special measuring problems are described, and hints for practical solutions are given. In particular, examples of destructive and non-destructive depth profiling of residual stresses, of residual stress analysis in thin coatings, in multilayer structures of thin coatings and in chemically graded coatings, of residual stress analyses in presence of textures, of residual and loading stress analyses in heterogeneous materials, in coarse grained, and in single crystalline materials are presented. The methods established up to now are explained and possible future developments are pointed out.

Electroweak fermion-loop contributions to the muon anomalous magnetic moment.

Abstract: The two-loop electroweak corrections to the anomalous magnetic moment of the muon, generated by fermionic loops, are calculated. An interesting role of the top quark in the anomaly cancellation is observed. New corrections, including terms of order ${\mathit{G}}_{\mathrm{\ensuremath{\mu}}}$\ensuremath{\alpha}${\mathit{m}}_{\mathrm{\ensuremath{\mu}}}^{2}$${\mathit{m}}_{\mathit{t}}^{2}$/${\mathit{M}}_{\mathit{W}}^{2}$, are computed and a class of diagrams previously thought to vanish are found to be important. The total fermionic correction is -(23\ifmmode\pm\else\textpm\fi{}3)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}11}$ which decreases the electroweak effects on g-2, predicted from one-loop calculations, by 12%. We give an updated theoretical prediction for g-2 of the muon.

Expression of interstitial collagenase during skeletal development of the mouse is restricted to osteoblast-like cells and hypertrophic chondrocytes.

Abstract: We determined the expression pattern of the matrix metalloproteinase interstitial collagenase (MMP-1) during mouse embryo development using in situ hybridization and immunohistochemistry. Localized MMP-1 mRNA was first detected at 14.5 days postconceptus. The spatial and temporal expression was restricted to areas of endochondral and intramembranous bone formation, such as in the mandibula, maxilla, clavicle, scapula, in the vertebrae, and in the dorsal, but not the ventral part of the ribs. The highest levels of MMP-1 transcripts and MMP-1 protein were found in the metaphyses and diaphyses of the long bones. MMP-1 was expressed by hypertrophic chondrocytes and by osteoblastic cells localized along the newly formed bone trabeculae. No expression was detected in osteoclasts. Two other related members of the MMP family, stromelysin-1 (MMP-3) and stromelysin-2 (MMP-10), were not expressed during days 7.5 and 16.5 of mouse embryogenesis. The tissue-specific expression of MMP-1 and the exclusive ability of interstitial collagenase to digest native collagen of types I, II, III, and X, the major components of bone, cartilage, and tendon, strongly suggests an important and specific function of this enzyme in bone development and remodeling.

Accurate Calculation of NMR Chemical Shifts

Abstract: An overview over currently available methods for the calculation of NMR chemical shifts is given. After a brief discussion of the basis aspects, i.e. definition of the shielding tensor and gauge-origin problem in the calculation of magnetic properties, recently developed methods for calculating NMR chemical shifts based on electron-correlated quantum chemical approaches will be discussed. The importance of electron correlation effects for the accurate determination of absolute shielding constants and relative shifts is demonstrated and the accuracy of various approaches assessed by a careful comparison with experiment, before a few representative applications will be presented. In case of the carboranes C2B3H5 and C2B3H7, electron-correlated calculations were essential to resolve discrepancies between SCF calculations and experiment, while for the vinyl-substituted vinyl cations CH2 = C+ –CH = CHCH3 correlated NMR chemical shift calculations – but not the SCF calculations – allow the unequivocal assignment of the measured 13C signals to the Z and E isomers formed in superacid solutions. Finally, an outlook with respect to pending problems in the area of NMR chemical shift calculations is given.

On noise reduction in vertical seismic records below 2 mHz using local barometric pressure

Abstract: We propose a simple method for the reduction of noise in vertical seismic recordings at frequencies below 2 mHz. The method consists in subtracting the locally recorded, scaled, atmospheric pressure signal from the gravity record. The scale factor is frequency independent and can be linearly estimated from the data. While such a pressure correction was previously only used in the analysis of tidal records, it is equally efficient at the low-frequency end of the normal mode band and we use gravity recordings of the big 1994 Shikotan and Bolivian quakes to demonstrate this point. Our examples also show that this correction permits to achieve noise levels well below the New Low Noise Model (NLNM) [Peterson, 1993]. The success of the correction also sheds some light on the physical processes responsible for the generation of low-frequency seismic noise at quiet observatories.

Generalized Planck's radiation law for luminescence via indirect transitions

Abstract: Based on microscopic transition probabilities and on the principle of detailed balance, absorption and emission rates are calculated for indirect transitions. It is found that the emission rate at a photon energy ħω can be expressed by the absorption coefficient for the same photon energy in the same way as for direct transitions. This relation is quite generally valid including cases where the electrons in the exited state (conduction band) and the electrons in the ground state (valence band) are distributed according to two different quasi-Fermi distributions. A generalized Planck's law is formulated for luminescence which contains a nonzero chemical potential of the emitted photons as the only difference to the description of thermal radiation.

The mechanism of action of phenylalanine ammonia-lyase: the role of prosthetic dehydroalanine.

Abstract: Phenylalanine ammonia-lyase (EC 4.3.1.5) from parsley is posttranslationally modified by dehydrating its Ser-202 to the catalytically essential dehydroalanine prosthetic group. The codon of Ser-202 was changed to those of alanine and threonine by site-directed mutagenesis. These mutants and the recombinant wild-type enzyme, after treatment with sodium borohydride, were virtually inactive with L-phenylalanine as substrate but catalyzed the deamination of L-4-nitrophenylalanine, which is also a substrate for the wild-type enzyme. Although the mutants reacted about 20 times slower with L-4-nitrophenylalanine than the wild-type enzyme, their Vmax for L-4-nitrophenylalanine was two orders of magnitude higher than for L-phenylalanine. In contrast to L-tyrosine, which was a poor substrate, DL-3-hydroxyphenylalanine (DL-m-tyrosine) was converted by phenylalanine ammonia-lyase at a rate comparable to that of L-phenylalanine. These results suggest a mechanism in which the crucial step is an electrophilic attack of the prosthetic group at position 2 or 6 of the phenyl group. In the resulting carbenium ion, the beta-HSi atom is activated in a similar way as it is in the nitro analogue. Subsequent elimination of ammonia, concomitant with restoration of both the aromatic ring and the prosthetic group, completes the catalytic cycle.

The knowledge acquisition and representation language, KARL

Abstract: The Knowledge Acquisition and Representation Language (KARL) combines a description of a knowledge based system at the conceptual level (a so called model of expertise) with a description at a formal and executable level. Thus, KARL allows the precise and unique specification of the functionality of a knowledge based system independent of any implementation details. A KARL model of expertise contains the description of domain knowledge, inference knowledge, and procedural control knowledge. For capturing these different types of knowledge, KARL provides corresponding modeling primitives based on Frame Logic and Dynamic Logic. A declarative semantics for a complete KARL model of expertise is given by a combination of these two types of logic. In addition, an operational definition of this semantics, which relies on a fixpoint approach, is given. This operational semantics defines the basis for the implementation of the KARL interpreter, which includes appropriate algorithms for efficiently executing KARL specifications. This enables the evaluation of KARL specifications by means of testing.

VUV photolysis of aqueous solutions of nitrate and nitrite

Abstract: Water homolyses upon vacuum-uv excitation into HO* radicals, hydrogen atoms and with lower efficiency, hydrated electrons. These primary species induce a series of reactions partially depleting nitrate and nitrite from aqueous solutions. Depletion rates depend on the presence of dissolved oxygen and temperature. Nitrate, nitrite, peroxynitrite and N2O were identified as reaction products after irradiation of, either, nitrite and nitrate in aqueous solutions. A reaction mechanism is proposed in accord with the experimental facts and with the evidence given in the literature, where NO2 * and NO* are key intermediates. NO3 −, NO2 −, NO2 *, NO* O2NO2 −, ONO2 − and N2O, seem to be interrelated by many redox reactions and reaction equilibria where pH and the availability of electrons determine their occurrence. The proposed mechanism is supported by a computer program with which the observed experimental behavior could be simulated.