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In contrast to a two-stage hardening and tempering process, the definition of optimized cooling routes after hot working of low-alloy Cr steel allows the adjustments of high-strength microstructures with a sufficient degree of ductility at the same time without any additional heat-treatment. While compressed air cooling after hot forging of micro-alloyed steel grades leads to the formation of lower bainite with finedispersed cementite platelets, quenching by water spray down to the martensite start temperature results in the formation of martensite, that is self-tempered during the subsequent slow-cooling in air. The precipitation of nano-sized cementite precipitates result in superior mechanical properties with respect to impact and tensile testing. Cyclic deformation and crack propagation tests being carried out using resonance testing (100Hz) and ultrasonic fatigue testing (20kHz) systems revealed a pronounced increase in fatigue strength by about 150MPa of the self-tempered martensite condition as compared to the bainitic modification. For the latter one, a steady decrease of the fatigue strength is observed rather than the existence of a real fatigue limit.

The effect of the protein residues, taking human DNA polymerase [beta] as a model system, is studied for understanding of catalytic control, specifically on the transition state (TS) binding energy. It is seen that the protein reorganization between the open, unbound form and the closed from does not change the magnitude of the calculated mutational effects and the success of the PDLD/SLRA approach in computing that energy of the TS can help in rapid mutational screening of TS analogues.

A reference system for DNA replication fidelity was studied by free energy perturbation (FEP) and liner interaction energy (LIE) methods. The studied system included a hydrated duplex DNA with the 5'CG dangling end of the templating strand and [dCTP.sup.4+].[Mg.sup.2+] or [dTTP.sup.4-].[Mg.sup.2+] inserted opposite the dangling G to form a correct or incorrect base pair, respectively.

The free energy surface for the nucleotide transfer reaction of T7 polymerase is evaluated by free energy pertubation/empirical valence bond (FEP/EVB) calculations. A key aspect of the enzyme simulation is a comparison of enzymatic free energy profiles with the corresponding reference reactions in water using the same computational methodology, thereby enabling a quantitative estimate for the free energy of the nucleotide insertion reaction.

The relative stability of Watson-Crick and mismatched dNTP template base pairs in the active site of T7 DNA polymerase (pol T7) was examined using linear-response molecular dynamics simulations. It was found that pol T7 provides a larger binding contribution to the replication fidelity than pol beta by discriminating more effectively against mismatches that are most probable to occur in the neutral anti-anti configurations.

A theoretical study of the selection of right/wrong deoxy-ribonucleotide triphosphates substrates by DNA polymerases at the initial binding step, a major component of the DNA replication fidelity is presented. Calculations are performed to predict the effects of amino acid substitutions on the fidelity for mutant forms of pol beta, thus providing a deeper understanding of the role of the polymerase active site in ensuring replication accuracy.

Byline: Rene Hudec (1), Pavel Spurny (1), Jan Florian (1), Jaroslav Bocek (1), Milos Tichy (2), Jana Ticha (2), Libor Vyskocil (3), Wolfgang Wenzel (4), Scott Barthelmy (5), Thomas Cline (5), Niels Gehrels (5), Gerald Fishman (6), Chryssa Kouveliotou (6), Charles Meegan (6), Asen Mutafov (7) Abstract: We present first preliminary results obtained with the European Observation Network consisting of 9 observatories in the Czech Republic, Germany and Bulgaria. We also discuss related problems such as the background of unknown variable stars and suggest a strategy for work in this area. Author Affiliation: (1) Astronomical Institute, Czech Academy of Sciences, CZ-251 65, OndAejov, Czech Republic (2) Klet Observatory, Zatkovo nabAezi 4, CZ-370 01, Ceske BudAjovice, Czech Republic (3) Apice Observatory, CZ-542 32, Apice, Czech Republic (4) Sternwarte Sonneberg, D-96515, Sonneberg, Germany (5) NASA Goddard Space Flight Center, Greenbelt, MD, 20771, U.S.A. (6) NASA Marshall Space Flight Center, Huntsville, AL, 35812, U.S.A. (7) Astronomical Observatory, P.O.B. 36, BG-1504, Sofia, Bulgaria Article History: Registration Date: 15/10/2004

Context. Powerful active galactic nuclei (AGN) are supposed to play a key regulatory role on the evolution of their host galaxies by shaping the thermodynamic properties of their gas component. However, little is known as to the nature and the visibility timescale of the kinematical imprints of AGN-driven feedback. Gaining theoretical and observational insights into this subject is indispensable for a thorough understanding of the AGN-galaxy coevolution and could yield empirical diagnostics for the identification of galaxies that have experienced a major AGN episode in the past. Aims. We present an investigation of kinematical imprints of AGN feedback on the warm ionized gas medium (WIM) of massive early-type galaxies (ETGs). To this end, we take a two-fold approach that involves a comparative analysis of H velocity fields in 123 local ETGs from the CALIFA (Calar Alto Legacy Integral Field Area Survey) integral field spectroscopy survey with 20 simulated galaxies from high-resolution hydrodynamic cosmological SPHgal simulations. The latter were resimulated for two modeling setups, one with and another without AGN feedback. Methods. In order to quantify the effects of AGN feedback on gas kinematics, we measured three parameters that probe deviations from simple regular rotation by using the kinemetry package. These indicators trace the possible presence of distinct kinematic components in Fourier space (k3;5=k1), variations in the radial profile of the kinematic major axis (PA), and offsets between the stellar and gas velocity fields (). These quantities were monitored in the simulations from a redshift 3 to 0.2 to assess the connection between black hole accretion history, stellar mass growth, and the kinematical perturbation of the WIM. Results. Observed local massive galaxies show a broad range of irregularities, indicating disturbed warm gas motions, which is irrespective of being classified via diagnostic lines as AGN or not. Simulations of massive galaxies with AGN feedback generally exhibit higher irregularity parameters than without AGN feedback, which is more consistent with observations. Besides AGN feedback, other processes like major merger events or infalling gas clouds can lead to elevated irregularity parameters, but they are typically of shorter duration. More specifically, k3;5=k1 is most sensitive to AGN feedback, whereas is most strongly affected by gas infall. Conclusions. We conclude that even if the general disturbance of the WIM velocity is not a unique indicator for AGN feedback, irregularity parameters that are high enough to be consistent with observations can only be reproduced in simulations with AGN feedback. Specifically, an elevated value for the deviation from simple ordered motion is a strong sign for previous events of AGN activity and feedback. [ABSTRACT FROM AUTHOR]

The concept of a positive hydrogen entity, later called the hydrogen ion and proton, seems to have started with Theodor von Grotthuss in 1805. The conception proposed by von Grotthuss has evolved via the works of many scientists; especially the contributions of Justus Liebig, Svante Arrhenius, S. P. L. Sorensen, I. M. Kolthoff, and R. P. Bell. This process of evolution has at times led to confusion, yet even after more than two centuries of use, the earlier model (though dressed in different trappings) still is intact. (Contains 5 notes.)

An analysis of DNA polymerase [beta]-catalyzed nucleotidyl transfer mechanism that provides insight into the structural differences of transition states for correct and mispair incorporation of DNA polymerase [beta] system is reported.

The two-metal ion mechanism observed in the restriction endonuclease BamHI is discussed. The results show that the BamHI catalysis requires only one metal ion to stabilize the nucleophilic attack.

The structural and functional analogy between difluoromethylene bisphosphonate (C[F.sub.2]PP) and pyrophosphate (P[P.sub.i]) is examined in a reaction with V(V) in the form of vanadate. The results have shown that P[P.sub.i]'s affinity for a metal ion at neutral pH has decreased by a factor 4-5 when the bridging oxygen atoms is substituted with C[F.sub.2].

The dGTP analogues replacing the [beta],[gamma]-bridging O with C[H.sub.2], CHF, C[F.sub.2], or C[Cl.sub.2] was used to explore leaving-group effects on the nucleotidyl transfer mechanism and fidelity of DNA polymerase (pol) [beta]. The location of the breaks relative to p[K.sub.a]s of C[F.sub.2], O, and the sterically bulky C[Cl.sub.2]-bridging compounds suggests that the biphasic nature of the Bronsted correlations is due to a modification-induced change in the mechanism by stabilization of leaving-group elimination.

The structural and electronic similarities of both the ground state and the transition state (TS) are examined in the framework of the potential energy surfaces of the alkaline methanolysis of [(C[H.sub.3]O).sub.2]P[O.sub.2.sup.-] and [(C[H.sub.3]O).sub.2]V[O.sub.2.sup.-]. The atomic charges of the starting material and the pentavalent dianionic intermediate containing the vanadium(V) and phosphorus central atoms are calculated, which establishes a firm foundation for the design of vanadate-diester-based transition state analogues for nucleic acid synthesis and hydrolysis.

Free energy perturbation (FEP) calculations using the Amber 95 force field and the TIP3P water model were conducted to evaluate the solvation free energy of deoxyribonucleoside triphosphates in aqueous solution. Structural origins of the relative solvation free energies of deoxyrilbonuclcoside-phosphates are examined by calculating the contribution of the interaction of the base moiety with its surrounding.

A study is conducted to understand the quantitative relevant energetics of the catalytic reaction of cysteine proteases and the free energy surface for the corresponding reference solution reaction is determined. The calculations involve self-consistent evaluation of the solute charges in solution as \well as mapping the solution free energy surface.

A study is conducted to evaluate the solvation free energy cost associated with thymine (T) -> difluorotoluene (F), T -> cytosine (C) and C -> T transformation in aqueous solution and in a DNA duplex. The dependence of the calculated free energies on the DANA sequence, the simulation length, size of the water droplet and phosphate charges are examined.

About 50 years ago, one thousand ring‐like structures (called stellar‐rings) were discovered by Isserstedt (1968). They were believed to be groups of young stars formed by shell‐like triggered star formation, which would make them excellent tracers of spiral arms, for example. Neglected for 40 years, we used highly accurate kinematic, astrometric, and photometric data to investigate the four most prominent stellar rings. The aim is to investigate if those structures are indeed physically related groups of stars. We used proper motions and parallaxes from the Gaia DR2 to calculate distances and to search for common properties. Color‐magnitude diagrams using BVJHKs measurements were investigated and isochrones fitted. None of the four stellar rings consists of a physically related group of young stars. The location of stars in the line‐of‐sight mimics a ring‐like structure on the sky. The color‐magnitude diagrams are typical for an integrated field population and not for a young star cluster, for example. The currently available data are sufficient to analyze ring‐like structures with a high statistical significance. This allows a new search for such structures in the Milky Way. [ABSTRACT FROM AUTHOR]

The hybrid quantum mechanical/molecular mechanical (QM/MM) methods are considered as the only practical way of quantitative modeling of chemical reactions in macromolecules or solutions. Replacing the MC-MM name by the universal EVB trademark would be beneficial for the image of computational biochemistry.

Examines the base-catalyzed and general base/acid catalyzed methanolysis of formamide. Basis for the methanolysis; Calculation of nonlocal density functionals; Construction of free energy surfaces; Observation of free energy surface for water catalyzed reaction; Formation and basicity of tetrahedral intermediate; Relevance of nucleophilic attack in acetylation.

Ab-initio CCSD(T)/6-311G(3df, 2p) calculations of the molecular structure and the harmonic force field of methanol were carried out to obtain high-level benchmark data. These results are compared with calculations based on the second-order Moller-Plesset, the Hartree-Fock (HF) and the non-local density functional methods, and with experimental results. Special attention has been paid to evaluation of methanol Raman intensities and depolarization ratios. The CCSD(T) force field was combined with the Cartesian polarizability derivatives calculated using the HF and the density functional (B-LYP) methods. [ABSTRACT FROM AUTHOR]

Focuses on the structure of guanine.cytosine base pairs. Study of canonical base pair and rare base-pair tautomers; Determination of the stabilities and dissociation energies of the base pairs; Applicability of findings to DNA replication; Contrast to the adenine.thymine base pair; Significance of frequency from the fidelity of DNA replication viewpoint.

Studies whether point mutations in DNA bases could be formed simultaneously via tautomerism of free nucleotides in solution. Presence of double proton transfer in Watson-Crick type of adenosine-thymine (AT) base pair; Use of ab initio HF MINI-I full gradient optimization technique; Confirmation of stability of genetic code.

Presents a conformational analysis of the dimethyl phosphate anion, dimethyl phosphorothioate anion, dimethyl methylphosphonate, and methyl ethylphosphonate anion in the gas phase and in aqueous solution. Description of experiments conducted; Relative stabilities of various conformers of phosphate, phosphonate, and phosphorothioate methyl esters in gas phase and aqueous solution; Concluding remarks on the analysis conducted.

A series of systematically modified vanadyl-beta-diketone complexes, VO(beta-diketone)(2), bearing substituent groups with different electron inductive properties were synthesized and evaluated as inhibitors against calf-intestine alkaline phosphatase (APase). A combination of biochemical and quantum mechanical techniques were employed to identify structure-activity relationships relevant for rational design of phosphatase inhibitors. Kinetic parameters and activation free energy, enthalpy, and entropy for calf-intestine APase-catalyzed dephosphorylation of para-nitrophenylphosphate were also determined along with the inhibition constants (K(i)) for the VO(beta-diketone)(2) complexes. Increased positive charge on the vanadyl group increases the inhibition potency of the complex while the absence of an available coordination site on the complex decreases its inhibition potency. These findings correlate well with the results of ab initio electron density calculations for the complexes.