On Vacuum Fluctuations and Particle Masses

The idea that the mass m of an elementary particle is explained in the semi-classical approximation by quantum-mechanical zero-point vacuum fluctuations has been applied previously to spin-1/2 fermions to yield a real and positive constant value for m, expressed through the spinorial connection Γ _i in the curved-space Dirac equation for the wave function ψ due to Fock. This conjecture is extended here to bosonic particles of spin 0 and spin 1, starting from the basic assumption that all fundamental fields must be conformally invariant. As a result, in curved space-time there is an effective scalar mass-squared term , where R is the Ricci scalar and Λ _b is the cosmological constant, corresponding to the bosonic zero-point energy-density, which is positive, implying a real and positive constant value for m ₀, through the positive-energy theorem. The Maxwell Lagrangian density for the Abelian vector field F _ij ≡A _j,i −A _i,j is conformally invariant without modification, however, and the equation of motion for the four-vector potential A _i contains no mass-like term in curved space. Therefore, according to our hypothesis, the free photon field A _i must be massless, in agreement with both terrestrial experiment and the notion of gauge invariance.     

Pareto efficiency,simple game stability,and social structure in finitely repeated games

Simple game (sensu Brown and Vincent, 1987) evolutionary theory, when coupled with social structure measured as non‐random encounter of strategy “clones”, often permits equilibrium refinement leading to Pareto superior outcomes (e.g., Axelrod, 1981; Myerson et al., 1991), a foundational goal of economic game theory (Myerson, 1991: 370–375). This conclusion, derived from analyses of one‐shot and infinitely repeated games, fails for finitely repeated games. While mutant cluster invasion enhances Pareto efficiency of equilibria in the former, it can depress Pareto efficiency in the latter. Cooperative equilibria of finitely repeated games (under economic analysis) can be susceptible to cluster‐invasion by even more Pareto efficient strategies which are not themselves evolutionarily stable. Evolutionary (simple) game theory's ability to eliminate Pareto inferior Nash equilibrium strategies induces vulnerabilities foreign to economic analysis. Simple game analysis of finitely repeated games suggests that social structure, modeled as perennial invasion by mutant‐clusters, can induce cyclic invasion, saturation, and loss of cooperation.     

Syrian hamster embryo (SHE) assay (pH 6.7) coupled with infrared spectroscopy and chemometrics towards toxicological assessment

The Syrian hamster embryo (SHE) assay (pH 6.7) is an in vitro candidate to replace in vivo carcinogenicity tests. However, the conventional method of visual scoring of foci (non-transformed vs. transformed colonies) can be time-consuming and is open to subjectivity. Infrared (IR) spectroscopy has the potential to provide objective assessment of such SHE colonies with the added advantage of potentially providing mechanistic information. In this study, SHE cells were treated with one of eight different chemical regimens, allowed in culture to attach and form foci on IR-reflective glass slides; these were subsequently interrogated by attenuated total reflection (ATR) Fourier-transform IR (FTIR) spectroscopy. Derived mid-IR spectra (n = 13,406) were subjected to chemometric analysis focusing primarily on the extraction of biochemical information related to test agent treatment and/or morphological transformation. The use of ATR-FTIR spectroscopy with chemometrics to analyze the SHE assay is a novel approach to toxicological assessment.     

Determination of cerium in minerals with sulphanilic acid

Cerium can be determined colorimetrically in minerals with sulphanilic acid. Cerium(III) ions are oxidized with silver(II) in 1-7% sulphuric acid. Sulphanilic acid is oxidized by cerium(IV) ions in 20% sulphuric acid. The absorbance is determined at 540 nm. In the presence of maganese or chromium, cerium can be separated by precipitation as the oxalate. Lanthanum can be used as a gathering agent if necessary.     

Spin and lifetime of the ω− hyperon

A total of 101 ω^? decays have been found in K^?p interactions at 10 and $\text{16 GeV}\text{c}$. The decay angular distribution has been fitted under the assumptions that the ω^? has spin either $\text{1}\text{2}\text{or}\text{3}\text{2}$. It has been found that the probability of isotropy (spin$\text{1}\text{2}\text{)}$ is less than one in a thousand, whereas the probability for spin $\text{3}\text{2}$ is about 70%. Thus, we exclude the spin $\text{1}\text{2}$ assignment. The lifetime of the ω^? is found to be (1.41_?0.24^+0.15) × 10^?10s, in agreement with our earlier result based on about $\text{1}\text{5}$ of the present sample.     

The effect of a non-minimally coupled scalar field upon classical thermodynamics

It is known that a scalar field that is non-minimally coupled to the geometry implies a varying gravitational “constant” G_eff, and hence a violation of the continuity equations, $\text{T}\text{?}{}^{\mathrm{ik}}{}_{\mathrm{;k}}\text{≠ 0}$, where $\text{T}\text{?}{}_{\mathrm{ij}}$ is the uncorrected energy-momentum tensor. This in turn upsets classical thermodynamics. 3he simplest resolution of this difficulty is to multiply all energetic quantities by $\text{G}{}_{\mathrm{<mtext>eff</mtext>}}\text{G}{}_{\mathrm{<mtext>N</mtext>}}$, where G_N is the newtonian gravitational constant. This modified thermodynamics is applied to the scalar-field version of the cosmological model of Zee, for which it is shown to cause restoration of the symmetry above some critical temperature T_c close to the Planck temperature. We also illustrate how the second law of thermodynamics is always obeyed, correcting a recent discussion by Davies.     

Depth-profiling study of a thermal barrier coated superalloy using femtosecond laser-induced breakdown spectroscopy

Depth-profiling of a thermal barrier coating (TBC) system was carried out using femtosecond laser-induced breakdown spectroscopy (fs-LIBS). The TBC system consisted of an outer 7% yttria stabilized zirconia (7YSZ) ceramic coating and an inner Pt-modified bond coat on a Ni-based superalloy single crystal substrate. In the absence of the ceramic layer, it was possible to qualitatively differentiate between the bond coat and the substrate, and also between the two layers of the bond coat. The spatial location of the interface between the two bond coat layers could also be obtained accurately from the spectral profile of W. In presence of the ceramic coating, it was also possible to easily and accurately determine the ceramic/bond coat interface from the spectral profile of Al. Potential use of fs-LIBS in combination with fs laser machining to produce superior quality cooling holes on thermal barrier coated superalloy components is discussed.     

Scaffold topologies. 1. Exhaustive enumeration up to eight rings

Mapping the chemical space of small organic molecules is approached from a theoretical graph theory viewpoint, in an effort to begin the systematic exploration of molecular topologies. We present an algorithm for exhaustive generation of scaffold topologies with up to eight rings and an efficient comparison method for graphs within this class. This method uses the return index, a topological invariant derived from the adjacency matrix of the graph. Furthermore, we describe an algorithm that verifies the adequacy of the comparison method. Applications of this method for chemical space exploration in the context of drug discovery are discussed. The key result is a unique characterization of scaffold topologies, which may lead to more efficient ways to query large chemical databases.     

An investigation into the origin of the dramatically reduced reactivity of peptide-prolyl-thioesters in native chemical ligation

The low reactivity of peptide-prolyl-thioesters in native chemical ligation is not due to steric effects at the β-carbon, but rather to the presence of a carbonyl moiety on the nitrogen atom of the proline.