Solving the Schroedinger Equation for a Coulomb Potential with Cut-Off

The problem of solving the Schroedinger equation for a cut off Coulomb potential, has some importance in certain calculations concerning the excited states of solids1. The problem has actually been solved numerically for a particular case by Tibbs2. Numerical methods are always very specialized and have to be repeated in every new case. It is the purpose of this note to call attention to the fact that such problems are often capable of analytic solution comprising most of the possible cases

Some properties of frustrated spin systems: extensions and applications of Lieb-Schupp approach

Lieb and Schupp have obtained, using certain version of ``spin-reflection positivity'' method, a number of ground-state properties for frustrated Heisenberg models. One group of these results is related to singlet nature of ground state and it needs an assumption of reflection symmetry present in the system. In this paper, it is shown that the result holds also for other symmetries (inversion etc.). The second Lieb-Schupp result is relation between ground-state energies of certain systems. In the paper, this relation is applied to multidimensional models on various lattices.Comment: 15 pages, 8 eps figures, revtex

The Microbiome And Pneumonia Disease Severity In Asthmatic Children

Background: Pnuemonia is a leading cause of morbidity and mortality worldwide and children diagnosed with asthma have been shown to be at greatly increased risk of recurrent Community-Acquired Pneumonia (CAP). CAP in asthmatic children can incur nearly double the healthcare costs and lead to poorer outcomes during the course of the pneumonia infection. Objective: This study seeks to determine if sputum (SP) samples may be used in the pediatric population to better understand the microbiome environment during severe pneumonia in place or in conjunction with the more commonly used nasopharyngeal (NP) samples. Additionally, this study seeks to identify features of the microbiome associated with pneumonia severity in asthmatic children. Methods: Sputum and nasopharyngeal/oropharyngeal (NP/OP) samples were collected from asthmatic children diagnosed with asthma upon admission to a hospital. Bacterial cultures for known CAP pathogens using sputum samples, and PCR detection for viral pneumonia pathogens on the NP/OP samples were performed. To study the microbiome, 16s rRNA analysis of sputum and nasopharyngeal samples was performed and analysis conducted using a variety of single and community-based analyses. Outcomes of interest were LOS \u3e 4 days and admission to the ICU. Results: High relative abundance of CAP pathogens, including Moraxella and Haemophilus, were associated with poorer CAP outcomes in both age groups for both ICU admission and longer LOS. Similarly, a positive sputum culture result for Staphylococcus aureus was found to be significantly associated with more severe pneumonia. Bacteroidetes was associated with shorter LOS and Rothia association with longer LOS in several of the analyses. Both conclusions are consistent with previous characterizations of the bacteria in the onset of pneumonia and asthma. Moraxella was consistently associated with longer LOS and increased risk of ICU admission, consistent with its characterization as a minor CAP pathogen, but was protective against longer LOS in the younger age group. Conclusions: First, our study demonstrates that sputum samples may be used in a pediatric population. Our findings demonstrate that many of the microbiome features previously identified as being predictive of, or associated with, CAP, also serve to predict severe pneumonia outcomes in this pediatric population, including longer Length of Stay (LOS) and Intensive Care Unit (ICU) admission. However, certain inconsistencies in the trends in our data highlight the need to perform microbiome analyses using many different approaches to fully understand the complex relationships between the diverse commensal and pathogenic bacteria that comprise the microbiome

Spin-charge-orbital ordering on triangle-based lattices

We investigate the ground-state property of an e_g-orbital Hubbard model at quarter filling on a zigzag chain by exploiting the density matrix renormalization group method. When two orbitals are degenerate, the zigzag chain is decoupled to a doble-chain spin system to suppress the spin frustration due to the spatial anisotropy of the occupied orbital. On the other hand, when the level splitting is increased and the orbital anisotropy disappears, a characteristic change in the spin incommnsurability is observed due to the revival of the spin frustration.Comment: 2 pages, 1 figure, Proceedings of SCES'05 (July 26-30, 2005, Vienna

EPA\u27s Impending Greenhouse Gas Regulations: Digging through the Morass of Litigation

As the U.S. Congress has failed to pass meaningful climate legislation, the EPA has initiated a series of regulations under the Clean Air Act designed to recognize greenhouse gases as endangering human health and welfare, and set greenhouse gas emission standards for vehicle fleets and for major stationary sources. Unsurprisingly these efforts have been challenged in the DC Circuit Court of Appeals. This paper discusses both the substantive and procedural issues surrounding the cases, all of which merit attention: in the absence of viable climate legislation these decisions will have important bearing on the extent to which the United States is able to address its greenhouse gas emissions

Virtual Desktop Sizing

This paper is intended to describe a process of choosing and building a demo of virtualization solution for a group of people in campus of EPFL located in a city of Sion, Valais Wallis. The aim of the paper is to compare different desktop virtualization solutions and choose the best one within the given customer’s requirements and infrastructure. The second goal of the paper is to provide a demo implementation of the selected virtualization solution with guidelines describing how it was created and notes on specific customizations required within the given internal computer structure of the campus

Bias driven coherent carrier dynamics in a two-dimensional aperiodic potential

We study the dynamics of an electron wave-packet in a two-dimensional square lattice with an aperiodic site potential in the presence of an external uniform electric field. The aperiodicity is described by $\epsilon_{\bf m} = V\cos{(\pi\alpha m_x^{\nu_x})}\cos{(\pi\alpha m_y^{\nu_y})}$ at lattice sites $(m_x, m_y)$, with $\pi \alpha$ being a rational number, and $\nu_x$ and $\nu_y$ tunable parameters, controlling the aperiodicity. Using an exact diagonalization procedure and a finite-size scaling analysis, we show that in the weakly aperiodic regime ($\nu_x,\nu_y < 1$), a phase of extended states emerges in the center of the band at zero field giving support to a macroscopic conductivity in the thermodynamic limit. Turning on the field gives rise to Bloch oscillations of the electron wave-packet. The spectral density of these oscillations may display a double peak structure signaling the spatial anisotropy of the potential landscape. The frequency of the oscillations can be understood using a semi-classical approach.Comment: 16 pages, to appear in Phys. Lett.

Dense packing on uniform lattices

We study the Hard Core Model on the graphs ${\rm {\bf \scriptstyle G}}$ obtained from Archimedean tilings i.e. configurations in $\scriptstyle \{0,1\}^{{\rm {\bf G}}}$ with the nearest neighbor 1's forbidden. Our particular aim in choosing these graphs is to obtain insight to the geometry of the densest packings in a uniform discrete set-up. We establish density bounds, optimal configurations reaching them in all cases, and introduce a probabilistic cellular automaton that generates the legal configurations. Its rule involves a parameter which can be naturally characterized as packing pressure. It can have a critical value but from packing point of view just as interesting are the noncritical cases. These phenomena are related to the exponential size of the set of densest packings and more specifically whether these packings are maximally symmetric, simple laminated or essentially random packings.Comment: 18 page

On the definition of temperature using time--averages

This paper is a natural continuation of a previous one by the author, which was concerned with the foundations of statistical thermodynamics far from equilibrium. One of the problems left open in that paper was the correct definition of temperature. In the literature, temperature is in general defined through the mean kinetic energy of the particles of a given system. In this paper, instead, temperature is defined "a la Caratheodory", the system being coupled to a heat bath, and temperature being singled out as the ``right'' integrating factor of the exchanged heat. As a byproduct, the ``right'' expression for the entropy is also obtained. In particular, in the case of a q-distributions the entropy turns out to be that of Tsallis, which we however show to be additive, at variance with what is usually maintained

The structure of a far-red fluorescent protein, AQ143, shows evidence in support of reported red-shifting chromophore interactions

Engineering fluorescent proteins (FPs) to emit light at longer wavelengths is a significant focus in the development of the next generation of fluorescent biomarkers, as far-red light penetrates tissue with minimal absorption, allowing better imaging inside of biological hosts. Structure-guided design and directed evolution have led to the discovery of red FPs with significant bathochromic shifts to their emission. Here, we present the crystal structure of one of the most bathochromically shifted FPs reported to date, AQ143, a nine-point mutant of aeCP597, a chromoprotein from Actinia equina. The 2.19 Å resolution structure reveals several important chromophore interactions that contribute to the protein's far-red emission and shows dual occupancy of the green and red chromophores