Order G2 Research Articles

Vibrational analysis and ionization potentials of XCH 3 (X=Be,Mg,Ca) calculated by hybrid density functional theory and high order ab initio methods

The amount of attention dedicated to the theoretical and experimental investigation of small cationic organometallic systems in the literature is very limited. In this Letter we use the B3LYP method with a variety of basis sets as well as the very advanced CBS-Q, CBS-QB3, G1, G2MP2, G2, G3, and G3B3 ab initio methods in order to analyze the vibrational spectra as well as ionization potentials of BeCH 3,MgCH 3 and CaCH 3. The need for further addition of experimental data to the archives for these systems is discussed, as well as recommendations for which theoretical methods are optimum for a particular result.

Large “dipolar” vacuum fluctuations in quantum gravity

We study a novel set of gravitational field configurations, called “dipolar zero modes”, which give an exactly null contribution to the Einstein action and are thus candidates to become large fluctuations in the quantized theory. They are generated by static unphysical sources satisfying (up to terms of order G2 ) the simple condition ∫d3xT00(x)=0 . We give two explicit examples of virtual sources: (i) a “mass dipole” consisting of two separated mass distributions with different signs; (ii) two concentric “ +/− shells”. The field fluctuations can be large even at macroscopic scale. There are some, for instance, which last ∼1 s or more and correspond to the field generated by a virtual source with size ∼1 cm and mass ∼106 g. This appears paradoxical, for several reasons, both theoretical and phenomenological. We also give an estimate of possible suppression effects following the addition to the pure Einstein action of cosmological or R2 terms.

Nonlinear Poiseuille flow in a gas

The nonlinear Boltzmann equation for the steady planar Poiseuille flow generated by an external field g is exactly solved through order g2. It is shown that the pressure and temperature profiles, as well as the momentum and heat fluxes, are in qualitative disagreement with the Navier–Stokes predictions. For instance, the temperature has a local minimum at the middle layer instead of a maximum. Also, a longitudinal component of the heat flux exists in the absence of gradients along that direction and normal stress differences appear although the flow is incompressible. To account for these g2-order effects, which are relevant when the hydrodynamic quantities change over a characteristic length of the order of the mean free path, it is shown that the Chapman–Enskog expansion should be carried out three steps beyond the Navier–Stokes level.

Characterization of RAD9 of Saccharomyces cerevisiae and Evidence that Its Function Acts Posttranslationally in Cell Cycle Arrest after DNA Damage

In eucaryotic cells, incompletely replicated or damaged chromosomes induce cell cycle arrest in G2 before mitosis, and in the yeast Saccharomyces cerevisiae the RAD9 gene is essential for the cell cycle arrest (T.A. Weinert and L. H. Hartwell, Science 241:317-322, 1988). In this report, we extend the analysis of RAD9-dependent cell cycle control. We found that both induction of RAD9-dependent arrest in G2 and recovery from arrest could occur in the presence of the protein synthesis inhibitor cycloheximide, showing that the mechanism of RAD9-dependent control involves a posttranslational mechanism(s). We have isolated and determined the DNA sequence of the RAD9 gene, confirming the DNA sequence reported previously (R. H. Schiestl, P. Reynolds, S. Prakash, and L. Prakash, Mol. Cell. Biol. 9:1882-1886, 1989). The predicted protein sequence for the Rad9 protein bears no similarity to sequences of known proteins. We also found that synthesis of the RAD9 transcript in the cell cycle was constitutive and not induced by X-irradiation. We constructed yeast cells containing a complete deletion of the RAD9 gene; the rad9 null mutants were viable, sensitive to X- and UV irradiation, and defective for cell cycle arrest after DNA damage. Although Rad+ and rad9 delta cells had similar growth rates and cell cycle kinetics in unirradiated cells, the spontaneous rate of chromosome loss (in unirradiated cells) was elevated 7- to 21-fold in rad9 delta cells. These studies show that in the presence of induced or endogenous DNA damage, RAD9 is a negative regulator that inhibits progression from G2 in order to preserve cell viability and to maintain the fidelity of chromosome transmission.

Characterization of RAD9 of Saccharomyces cerevisiae and evidence that its function acts posttranslationally in cell cycle arrest after DNA damage.

In eucaryotic cells, incompletely replicated or damaged chromosomes induce cell cycle arrest in G2 before mitosis, and in the yeast Saccharomyces cerevisiae the RAD9 gene is essential for the cell cycle arrest (T.A. Weinert and L. H. Hartwell, Science 241:317-322, 1988). In this report, we extend the analysis of RAD9-dependent cell cycle control. We found that both induction of RAD9-dependent arrest in G2 and recovery from arrest could occur in the presence of the protein synthesis inhibitor cycloheximide, showing that the mechanism of RAD9-dependent control involves a posttranslational mechanism(s). We have isolated and determined the DNA sequence of the RAD9 gene, confirming the DNA sequence reported previously (R. H. Schiestl, P. Reynolds, S. Prakash, and L. Prakash, Mol. Cell. Biol. 9:1882-1886, 1989). The predicted protein sequence for the Rad9 protein bears no similarity to sequences of known proteins. We also found that synthesis of the RAD9 transcript in the cell cycle was constitutive and not induced by X-irradiation. We constructed yeast cells containing a complete deletion of the RAD9 gene; the rad9 null mutants were viable, sensitive to X- and UV irradiation, and defective for cell cycle arrest after DNA damage. Although Rad+ and rad9 delta cells had similar growth rates and cell cycle kinetics in unirradiated cells, the spontaneous rate of chromosome loss (in unirradiated cells) was elevated 7- to 21-fold in rad9 delta cells. These studies show that in the presence of induced or endogenous DNA damage, RAD9 is a negative regulator that inhibits progression from G2 in order to preserve cell viability and to maintain the fidelity of chromosome transmission.

β-Cyclodextrin Post-Column Fluorescence Enhancement of Aflatoxins for Reverse-Phase Liquid Chromatographic Determination in Corn

beta-Cyclodextrin enhances the fluorescence of aflatoxins B1 and G1 in aqueous systems. This effect was utilized in developing a unique reverse-phase liquid chromatographic (LC) method for determination of aflatoxins B1, B2, G1, and G2 (B1 detection limit 1 ppb), without preparing derivatives of B1 and G1. The aflatoxins are dissolved in methanol or the mobile phase for injection onto the LC system. Using a mobile phase of methanol-beta-cyclodextrin (1 + 1), the aflatoxins are resolved on a C18 column. Fluorescence of the aflatoxins is enhanced by post-column introduction of an aqueous concentrated beta-cyclodextrin solution. All 4 aflatoxins elute within 10 min in the order G2, G1, B2, B1. Fluorescence responses for B1 and G1 standards were linear over the concentration range 0.5-10 ng, yielding correlation coefficients (r) of 0.9989 and 1.000, respectively. The average peak response ratio for G1:B1 for the mobile phase-enhancement solution described was 0.765 with a coefficient of variation (CV) of 0.98%. CVs were 6.2, 9.0, and 7.5% for multiple assays of aflatoxin B1 in 3 samples of naturally contaminated corn. For samples of corn spiked to a total B1 content of 8.3 ng/g, average B1 recovery was 90% (CV 11.7%).

Improved likelihood ratio test for multinomial goodness of fit

For testing goodness-of-fit in a k cell multinomial distribution having very small frequencies, the usual chi-square approximation to the upper tail of the likelihood ratio statistic, G2 is not satisfactory. A new adjustment to G2 is determined on the basis of analytical investigation in terms of asymptotic bias and variance of the adjusted G2 A Monte Carlo simulation is performed for several one-way tables to assess the adjustment of G2 in order to obtain a closer approximation to the nomial level of significance.

Improved likelihood ratio tests and pearson chi-square tests for independence in two dimensional contingency tables

When an I×J contingency table has many cells having very small frequencies, the usual chi-square approximation to the upper tail of the likelihood ratio goodness-of-fit statistic, G2 and Pearson chi-square statistic, X2, for testing independence, are not satisfactory. In this paper we consider the problem of adjusting G2 and X2. Suitable adjustments are suggested on the basis of analytical investigation of asymptotic bias terms for G2 and X2. A Monte Carlo simulation is performed for several tables to assess the adjustments of G2 and X2 in order to obtain a closer approximation to the nominal level of significance.

Itô calculus for σ-models and Yang-Mills theories

It is pointed out that the effective continuum action for σ-models and Yang-Mills theories may differ from the naive continuum action by terms of order g 2 or higher, which are nonsymmetric. The modifications are produced by a generalization of the Ito calculus to dimensions higher than one.

Finite-temperature SU(2) lattice gauge theory with dynamical fermions

We study the influence of dynamical quarks on the deconfinement and chiral phase transitions of SU(2) lattice gauge theory using staggered fermions. The pseudo-fermion algorithm is used to include the effects of two flavours of light quarks in a Monte Carlo simulation on lattices of size 83 × 2 and 83 × 4. The systematic errors resulting from a truncation of the algorithm after a finite number of iterations are analyzed. In addition, we perform a weak coupling expansion of thermodynamic observables up to one-loop (order g2) to study the high-temperature limit of the quark-gluon plasma.

Field Theoretic Renormalization Group and the Scaling Behaviour in Polymer Solutions

AbstractQuantum field theoretic regularization methods are used to regularize the set of end‐to‐end chain correlation functions. The renormalization group invariance of the polymer theory allows to calculate the parameters g and S which in the regularized theory take on the role of z and Nl2 of the two parameter theory accordingly. The second virial coefficient A2 and the mean‐square end‐to‐end polymer distance R2 of a polymer solution are represented in powers of g. g and S are evaluated up to order ϵ2 (ϵ = 4 ‐ d, where d is the space dimension). A2 and R2 are calculated up to order g2 and g, respectively, and compared with results obtained by ELDERFIELD and des CLOIZEAUX.

Pion Exchange Mechanism for ( +, 2p) Reactions

Motivated by static s- and p-wave pion-nucleon interactions, general expressions for the amplitudes and cross sections for the processes A(π+, 2p)A - 2 are obtained for arbitrary states with correlated and uncorrelated nucleons. The treatment is based on field theory and presented to order g2 in the usual pion-nucleon coupling constant. As such, the analysis prescribes an off-mass-shell behavior of the pion in lowest order. Distortion of the protons is also considered.