A Class of N=1 Dual String Pairs and its Modular Superpotential

We compare the N=1 F-theory compactification of Donagi, Grassi and Witten with modular superpotential - and some closely related models - to dual heterotic models. We read of the F-theory spectrum from the cohomology of the fourfold and discuss on the heterotic side the gauge bundle moduli sector (including the spectral surface) and the necessary fivebranes. Then we consider the N=1 superpotential and show how a heterotic superpotential matching the F-theory computation is built up by worldsheet instantons. Finally we discuss how the original modular superpotential should be corrected by an additional modular correction factor, which on the F-theory side matches nicely with a `curve counting function' for the del Pezzo surface. On the heterotic side we derive the same factor demanding correct T-duality transformation properties of the superpotential.Comment: 18 pages, Late

Correlates of Access to Business Research Databases

This study examines potential correlates of business research database access through academic libraries serving top business programs in the United States. Results indicate that greater access to research databases is related to enrollment in graduate business programs, but not to overall enrollment or status as a public or private institution

The Role of Microglia in the Effects of Steroid Hormones on Brain Inflammation

The conditions defining whether microglial activation is detrimental or beneficial to neuronal survival are still poorly understood. Better understanding of the factors regulating microglia activation may lead to improved therapies for neurodegenerative diseases. Clinical and animal studies point to the neuroprotective and anti-inflammatory effects of steroid hormones. However, our comprehension of the cellular targets and mechanisms of action of these hormones in the CNS is still unresolved. In view of these limitations, the main question addressed in this dissertation was the role that microglia play in the anti-inflammatory effects of steroid hormones in the brain, with particular emphasis on the neuroprotective hormone 17β-estradiol (E2), and the anti-inflammatory steroid, corticosterone. To address this problem, microglia culture models were established using a microglia cell line and primary cultures from transgenic mice that facilitate the identification of microglia by EGFP expression. Collaborative studies were also done in mice in vivo. The expression of steroid hormone receptors was studied as well as their function. This dissertation shows that microglia cells are not direct targets of estrogen actions, but respond profoundly to glucocorticoids, which exert anti-inflammatory effects on the production of cytokines like TNFα, IL-6 and NO. Steroid hormones can be produced within the brain. In this dissertation, microglia cells are shown to participate in the metabolism of steroids through expression of steroidconverting enzymes. Expression of 11βHSD1 in microglia mediated an autocrine re-activation of glucocorticoids, whereas, expression of enzymes like 17βHSD1 and 5αR catalyzed the conversion of active androgens and estrogens from steroid hormone precursors AD and DHEA. These microglia-derived hormones had estrogenic effects on neuronal cells, as described in the last section of this dissertation where the characterization and responsiveness of a neural progenitor cell line are presented. In summary, microglia cells are highly susceptible to the action of glucocorticoids, but not estrogens. This specificity is dictated by the abundant expression of glucocorticoid receptors, and a minimal expression of estrogen receptors. A novel role of microglia is also presented. Microglia express steroid-metabolizing enzymes, which mediate the autocrine reactivation of glucocorticoids, or the production of active androgens and estrogens from steroid hormone precursors

Recent tests for the statistical parton distributions

We compare some recent experimental results obtained at DESY, SLAC and Jefferson Lab., with the predictions of the statistical model, we have previously proposed. The result of this comparison is very satisfactory.Comment: 12 pages, 6 eps figures, version to appear in Mod. Phys. Lett.

Proton recoil polarization in exclusive (e,e'pp) reactions

The general formalism of nucleon recoil polarization in the (${\vec e},e'{\vec N}N$) reaction is given. Numerical predictions are presented for the components of the outgoing proton polarization and of the polarization transfer coefficient in the specific case of the exclusive $^{16}$O(${\vec e},e'{\vec p}p$)$^{14}$C knockout reaction leading to discrete states in the residual nucleus. Reaction calculations are performed in a direct knockout framework where final-state interactions and one-body and two-body currents are included. The two-nucleon overlap integrals are obtained from a calculation of the two-proton spectral function of $^{16}$O where long-range and short-range correlations are consistently included. The comparison of results obtained in different kinematics confirms that resolution of different final states in the $^{16}$O(${\vec e},e'{\vec p}p$)$^{14}$C reaction may act as a filter to disentangle and separately investigate the reaction processes due to short-range correlations and two-body currents and indicates that measurements of the components of the outgoing proton polarization may offer good opportunities to study short-range correlations.Comment: 12 pages, 6 figure

Cantilever-based Resonant Gas Sensors with Integrated Recesses for Localized Sensing Layer Deposition

This work presents mass-sensitive hammerhead resonators with integrated recesses as a gas-phase chemical microsensor platform. Recesses are etched into the head region of the resonator to locally deposit chemically sensitive polymers by ink-jet printing. This permits the sensing films to be confined to areas that (a) are most effective in detecting mass loading and (b) are not strained during the in-plane vibrations of the resonator. As a result of the second point, even 5-μm thick polymer coatings on resonators with a 9-12 μm silicon thickness barely affect the Q-factor in air. This translates into higher frequency stability and ultimately higher sensor resolution compared to uniformly coated devices

Structural Projections on JBW*-Triples

A linear projection R on a Jordan*-triple A is said to be structural provided that, for all elements a, b and c in A, the equality {Rab Rc} = R{a Rbc} holds. A subtriple B of A is said to be complemented if A = B + Ker(B), where Ker(B) = {a∈A: {B a B} = 0}. It is shown that a subtriple of a JBW*-triple is complemented if and only if it is the range of a structural projection. A weak* closed subspace B of the dual E* of a Banach space E is said to be an N*-ideal if every weak* continuous linear functional on B has a norm preserving extension to a weak* continuous linear functional on E* and the set of elements in E which attain their norm on the unit ball in B is a subspace of E. It is shown that a subtriple of a JBW*-triple A is complemented if and only if it is an N*-ideal, from which it follows that complemented subtriples of A are weak* closed, and structural projections on A are weak* continuous and norm non-increasing. It is also shown that every N*-ideal in A possesses a triple product with respect to which it is a JBW*-triple which is isomorphic to a complemented subtriple of

Compact tripotents in bi-dual JB*-triples

The set consisting of the partially ordered set of tripotents in a JBW*-triple C with a greatest element adjoined forms a complete lattice. This paper is mainly concerned with the situation in which C is the second dual A** of a complex Banach space A and, more particularly, when A is itself a JB*-triple. A subset of consisting of the set of tripotents compact relative to A (denned in Section 4) with a greatest element adjoined is studied. It is shown to be an atomic complete lattice with the properties that the infimum of an arbitrary family of elements of is the same whether taken in or in and that every decreasing net of non-zero elements of has a non-zero infimum. The relationship between the complete lattice and the complete lattice where B is a Banach space such that B** is a weak*-closed subtriple of A** is also investigated. When applied to the special case in which A is a C*-algebra the results provide information about the set of compact partial isometries relative to A and are closely related to those recently obtained by Akemann and Pedersen. In particular it is shown that a partial isometry is compact relative to A if and only if, in their terminology, it belongs locally to A. The main results are applied to this and other example

Smoothness Properties of the Unit Ball in a JB*-Triple

An element a of norm one in a JB*-triple A is said to be smooth if there exists a unique element x in the unit ball A1* of the dual A* of A at which a attains its norm, and is said to be Fréchet-smooth if, in addition, any sequence (xn) of elements in A1* for which (xn(a)) converges to one necessarily converges in norm to x. The sequence (a2n+1) of odd powers of a converges in the weak*-topology to a tripotent u(a) in the JBW*-envelope A** of A. It is shown that a is smooth if and only if u(a) is a minimal tripotent in A** and a is Fréchet-smooth if and only if, in addition, u(a) lies in