Pion Excess, Nuclear Correlations, and the Interpretation of (p⃗,n⃗\vec p, \vec n) Spin Transfer Experiments

Conventional theories of nuclear interactions predict a net increase in the distribution of virtual pions in nuclei relative to free nucleons. Analysis of data from several nuclear experiments has led to claims of evidence against such a pion excess. These conclusions are usually based on a collective theory (RPA) of the pions, which may be inadequate. The issue is the energy dependence of the nuclear response, which differs for theories with strong NN correlations from the RPA predictions. In the present paper, information about the energy dependence is extracted from sum rules, which are calculated for such a correlated, noncollective nuclear theory. The results lead to much reduced sensitivity of nuclear reactions to the correlations that are responsible for the pion excess. The primary example is $(\vec p,\vec n)$ spin transfer, for which the expected effects are found to be smaller than the experimental uncertainties. The analysis has consequences for Deep Inelastic Scattering (DIS) experiments as well.Comment: 16 pages, LaTeX, no figures, submitted to Phys. Rev.

Inhibition of StearoylCoA Desaturase Activity Blocks Cell Cycle Progression and Induces Programmed Cell Death in Lung Cancer Cells

Lung cancer is the most frequent form of cancer. The survival rate for patients with metastatic lung cancer is ∼5%, hence alternative therapeutic strategies to treat this disease are critically needed. Recent studies suggest that lipid biosynthetic pathways, particularly fatty acid synthesis and desaturation, are promising molecular targets for cancer therapy. We have previously reported that inhibition of stearoylCoA desaturase-1 (SCD1), the enzyme that produces monounsaturated fatty acids (MUFA), impairs lung cancer cell proliferation, survival and invasiveness, and dramatically reduces tumor formation in mice. In this report, we show that inhibition of SCD activity in human lung cancer cells with the small molecule SCD inhibitor CVT-11127 reduced lipid synthesis and impaired proliferation by blocking the progression of cell cycle through the G1/S boundary and by triggering programmed cell death. These alterations resulting from SCD blockade were fully reversed by either oleic (18:1n-9), palmitoleic acid (16:1n-7) or cis-vaccenic acid (18:1n-7) demonstrating that cis-MUFA are key molecules for cancer cell proliferation. Additionally, co-treatment of cells with CVT-11127 and CP-640186, a specific acetylCoA carboxylase (ACC) inhibitor, did not potentiate the growth inhibitory effect of these compounds, suggesting that inhibition of ACC or SCD1 affects a similar target critical for cell proliferation, likely MUFA, the common fatty acid product in the pathway. This hypothesis was further reinforced by the observation that exogenous oleic acid reverses the anti-growth effect of SCD and ACC inhibitors. Finally, exogenous oleic acid restored the globally decreased levels of cell lipids in cells undergoing a blockade of SCD activity, indicating that active lipid synthesis is required for the fatty acid-mediated restoration of proliferation in SCD1-inhibited cells. Altogether, these observations suggest that SCD1 controls cell cycle progression and apoptosis and, consequently, the overall rate of proliferation in cancer cells through MUFA-mediated activation of lipid synthesis

A Model for nuclear matter in terms of quark clusters

Thesis (Ph. D.)--University of Rochester. Dept. of Physics and Astronomy, 1986.We investigate the question of how a system of quarks can exhibit the dynamical properties of nuclear matter as a collection of bound clusters of quarks, based on the notion that each nucleon consists of three quarks coupled into a color neutral state. In our simple model, we consider non-relativistic quarks with three colors but no spin or flavor, interacting through a one-dimensional δ-function force in a box. The color confinement of the whole system is achieved by a boundary condition, but quarks are only dynamically confined to each nucleon as a result of the clustering mechanism generated by the quark-quark interaction. We use the variational method as an approximation because it is applicable to more general models including spin and flavor in three-dimensional space. The one-dimensional δ-function problem is particularly interesting because the exact method is available and we can examine the accuracy of our approximation by comparing the results. We develop a variational wave function which is analogous to the BCS wave function of the pairing problem, but is unique in dealing with three-quark (triplet) clusters rather than pairs. We show that the system consists of non-interacting nucleons in the zero density limit and becomes a Fermi (free) gas of quarks in the infinite density limit. At small but non-vanishing density, the BCS-type wave function gives us a systematic method of calculation of the dynamical properties of the system through density expansions. We show that the energy per particle of the system through the order [sic] is represented by that of a Fermi gas of nucleons whose internal structure is described by the Faddeev equation of a free triplet of a given total momentum. It is remarkable that the variational result through that order agrees with the exact low density expansion. The existence of the exact solution further supports the variational approach for higher orders in density. The possible extensions of the model to include spin and isospin, and to three-dimensional forces are also discussed as future work

Theory of meson interactions with nucleir

xii, 403 p.; 23 cm

Quantum mechanics of many degrees of freedom

xiv, 313 p.; 24 cm

Quantum mechanics of many degrees of freedom

xiv, 313 p.; 24 cm

Theory of meson interactions with nuclei

xii, 403 p.; 23 cm

Replica approach to directed Feynman paths with random phases

Directed Feynman paths in $1+1$ dimensions that acquire random phases, encountered in the study of electron and light propagation in disordered media, are examined by means of the replica trick. Two models are considered – one with short-range correlations, the other with very long-range correlations. The large and small (finite) $n$ behavior of the resulting $2n$-body quantum Hamiltonians with competing interactions is calculated. The difficulties that arise in extrapolating the results to $n \rightarrow 0$ and the possibility of replica symmetry breaking are discussed.Les chemins de Feynman dirigés qui accumulent des phases aléatoires font partie des études récentes de la propagation d'électrons ou d'ondes électromagnetiques en milieux désordonnés. Nous examinons leurs propriétés d'échelle en utilisant la théorie des répliques. Deux modèles avec corrélations de courte et de très longue portée en $1+1$ dimensions sont étudiés. Nous évaluons le comportement à grandes et petites valeurs (finies) de $n$ des modèles quantiques à $2n$ corps avec interactions attractives et répulsives qui en resultent. Nous soulignons les difficultés qui sugissent dans la limite $n \rightarrow 0$ et la possibilité de brisure de symétrie des répliques