Microscopic Structure of the Calcium Isotopes

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Microscopic Structure of the Calcium Isotopes

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

Proton Scattering from 206-Pb: Neutron Densities in the Nuclear Interior

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Charged hydrogenic problem in a magnetic field: Non-commutative translations, unitary transformations, and coherent states

An operator formalism is developed for a description of charged electron-hole complexes in magnetic fields. A novel unitary transformation of the Hamiltonian that allows one to partially separate the center-of-mass and internal motions is proposed. We study the operator algebra that leads to the appearance of new effective particles, electrons and holes with modified interparticle interactions, and their coherent states in magnetic fields. The developed formalism is used for studying a two-dimensional negatively charged magnetoexciton $X^-$. It is shown that Fano-resonances are present in the spectra of internal $X^-$ transitions, indicating the existence of three-particle quasi-bound states embedded in the continuum of higher Landau levels.Comment: 9 pages + 2 figures, accepted in PRB, a couple of typos correcte

The Coherent State Representation of Quantum Fluctuations in the Early Universe

Using the squeezed state formalism the coherent state representation of quantum fluctuations in an expanding universe is derived. It is shown that this provides a useful alternative to the Wigner function as a phase space representation of quantum fluctuations. The quantum to classical transition of fluctuations is naturally implemented by decohering the density matrix in this representation. The entropy of the decohered vacua is derived. It is shown that the decoherence process breaks the physical equivalence between vacua that differ by a coordinate dependent phase generated by a surface term in the Lagrangian. In particular, scale invariant power spectra are only obtained for a special choice of surface term.Comment: 25 pages in revtex 3. This version is completely revised with corrections and significant new calculation

Soluble triggering receptor expressed on myeloid cells in sputum of patients with community-acquired pneumonia or pulmonary tuberculosis : a pilot study

Soluble triggering receptor expressed on myeloid cells is upregulated on the surface of inflammatory cells in the presence of bacterial infections apparently excluding those due to Mycobacterium tuberculosis. Therefore, sputum concentrations of Soluble Triggering Receptor Expressed on Myeloid Cells (s-TREM-1) may be of value in distinguishing bacterial pneumonia from pulmonary tuberculosis (PTB) in patients with respiratory infections. The current pilot study was designed to evaluate whether s-TREM-1 concentrations measured in the sputum of patients with suspected community-acquired pneumonia (CAP) allowed differentiation of those patients with PTB from other causes of pneumonia and to correlate s-TREM-1 with the CURB-65, a marker of disease severity. Methods. Soluble s-TREM-1 concentrations were measured in sputum samples from patients admitted to a tertiary hospital with CAP or PTB by means of an ELISA procedure. Results. Soluble-TREM-1 was readily detectable and quantifiable in sputum samples from patients with both CAP and PTB, with concentrations of 234 ± 47 and 178 ± 36 pg/ml respectively, but did not differ significantly between the 2 groups. However, patients with PTB had significantly lower leukocyte counts, 9 ± 1.3 versus 15 ± 1.4 x 109/l compared to those without PTB. Interestingly, sputum s-TREM-1 concentrations correlated significantly with the CURB-65 pneumonia severity score calculated at the time of admission. Conclusions. Soluble-TREM-1 expression is upregulated in patients with both CAP and PTB, but does not differentiate these two conditions. Sputum concentrations of s-TREM-1 may predict the severity of disease in patients with CAP.http://www.springerlink.com/content/0934-9723

Chemical Fractionation and Abundances in Coronal Plasma

Much of modern astrophysics is grounded on the observed chemical compositions of stars and the diffuse plasma that pervades the space between stars, galaxies and clusters of galaxies. X-ray and EUV spectra of the hot plasma in the outer atmospheres of stars have demonstrated that these environments are subject to chemical fractionation in which the abundances of elements can be enhanced and depleted by an order of magnitude or more. These coronal abundance anomalies are discussed and some of the physical mechanisms that might be responsible for producing them are examined. It is argued that coronal abundances can provide important new diagnostics on physical processes at work in solar and stellar coronae. It seems likely that other hot astrophysical plasmas will be subject to similar effects.Comment: 10 pages, 4 figures, to appear in Adv.Sp.Re

A framework for the local information dynamics of distributed computation in complex systems

The nature of distributed computation has often been described in terms of the component operations of universal computation: information storage, transfer and modification. We review the first complete framework that quantifies each of these individual information dynamics on a local scale within a system, and describes the manner in which they interact to create non-trivial computation where "the whole is greater than the sum of the parts". We describe the application of the framework to cellular automata, a simple yet powerful model of distributed computation. This is an important application, because the framework is the first to provide quantitative evidence for several important conjectures about distributed computation in cellular automata: that blinkers embody information storage, particles are information transfer agents, and particle collisions are information modification events. The framework is also shown to contrast the computations conducted by several well-known cellular automata, highlighting the importance of information coherence in complex computation. The results reviewed here provide important quantitative insights into the fundamental nature of distributed computation and the dynamics of complex systems, as well as impetus for the framework to be applied to the analysis and design of other systems.Comment: 44 pages, 8 figure