Supersymmetry on Graphs and Networks

We show that graphs, networks and other related discrete model systems carry a natural supersymmetric structure, which, apart from its conceptual importance as to possible physical applications, allows to derive a series of spectral properties for a class of graph operators which typically encode relevant graph characteristics.Comment: 11 pages, Latex, no figures, remark 4.1 added, slight alterations in lemma 5.3, a more detailed discussion at beginning of sect.6 (zero eigenspace

Triangulating Horizontal Inequality: Towards Improved Conflict Analysis.

Does economic inequality cause civil war? Deviating from individualist measures of inequality such as the Gini coefficient, recent studies have found a statistical link between group-level inequalities and conflict onset. Yet, this connection remains controversial, not least because of the difficulties associated with conceptualizing and measuring group-level differences in development. In an effort to overcome weaknesses afflicting specific methods of measurement, we introduce a new composite indicator that exploits the strengths of three sources of data. The first step of our method combines geocoded data from the G-Econ project with night lights emissions data from satellites. In a second step, we bring together the combined spatial values with survey estimates in order to arrive at an improved measure of group-level inequality that is both more accurate and robust than any one of the component measures. We evaluate the effect of the combined indicator and its components on the onset of civil violence. As expected, the combined index yields stronger results as more information becomes available, thus confirming the initial hypothesis that horizontal economic inequality does drive conflict in the case of groups that are relatively poorer compared to the country average. Furthermore, these findings appear to be considerably more robust than those relying on a single data source.Swiss National Science FoundationAlexander von Humboldt Foundatio

Quantitative analysis of particles, genomes and infectious particles in supernatants of haemorrhagic fever virus cell cultures

Information on the replication of viral haemorrhagic fever viruses is not readily available and has never been analysed in a comparative approach. Here, we compared the cell culture growth characteristics of haemorrhagic fever viruses (HFV), of the Arenaviridae, Filoviridae, Bunyaviridae, and Flavivridae virus families by performing quantitative analysis of cell culture supernatants by (i) electron microscopy for the quantification of virus particles, (ii) quantitative real time PCR for the quantification of genomes, and (iii) determination of focus forming units by coating fluorescent antibodies to infected cell monolayers for the quantification of virus infectivity

On the spectrum of a bent chain graph

We study Schr\"odinger operators on an infinite quantum graph of a chain form which consists of identical rings connected at the touching points by $\delta$-couplings with a parameter $\alpha\in\R$. If the graph is "straight", i.e. periodic with respect to ring shifts, its Hamiltonian has a band spectrum with all the gaps open whenever $\alpha\ne 0$. We consider a "bending" deformation of the chain consisting of changing one position at a single ring and show that it gives rise to eigenvalues in the open spectral gaps. We analyze dependence of these eigenvalues on the coupling $\alpha$ and the "bending angle" as well as resonances of the system coming from the bending. We also discuss the behaviour of the eigenvalues and resonances at the edges of the spectral bands.Comment: LaTeX, 23 pages with 7 figures; minor changes, references added; to appear in J. Phys. A: Math. Theo

Role of the long cytoplasmic domain of the SIV Env glycoprotein in early and late stages of infection

<p>Abstract</p> <p>Background</p> <p>The Env glycoproteins of retroviruses play an important role in the initial steps of infection involving the binding to cell surface receptors and entry by membrane fusion. The Env glycoprotein also plays an important role in viral assembly at a late step of infection. Although the Env glycoprotein interacts with viral matrix proteins and cellular proteins associated with lipid rafts, its possible role during the early replication events remains unclear. Truncation of the cytoplasmic tail (CT) of the Env glycoprotein is acquired by SIV in the course of adaptation to human cells, and is known to be a determinant of SIV pathogenicity.</p> <p>Results</p> <p>We compared SIV viruses with full length or truncated (T) Env glycoproteins to analyze possible differences in entry and post-entry events, and assembly of virions. We observed that early steps in replication of SIV with full length or T Env were similar in dividing and non-dividing cells. However, the proviral DNA of the pathogenic virus clone SIVmac239 with full length Env was imported to the nucleus about 20-fold more efficiently than proviral DNA of SIVmac239T with T Env, and 100-fold more efficiently than an SIVmac18T variant with a single mutation A239T in the SU subunit and with a truncated cytoplasmic tail (CT). In contrast, proviral DNA of SIVmac18 with a full length CT and with a single mutation A239T in the SU subunit was imported to the nucleus about 50-fold more efficiently than SIVmac18T. SIV particles with full length Env were released from rhesus monkey PBMC, whereas a restriction of release of virus particles was observed from human 293T, CEMx174, HUT78 or macrophages. In contrast, SIV with T Envs were able to overcome the inhibition of release in human HUT78, CEMx174, 293T or growth-arrested CEMx174 cells and macrophages resulting in production of infectious particles. We found that the long CT of the Env glycoprotein was required for association of Env with lipid rafts. An Env mutant C787S which eliminated palmitoylation did not abolish Env incorporation into lipid rafts, but prevented virus assembly.</p> <p>Conclusion</p> <p>The results indicate that the long cytoplasmic tail of the SIV Env glycoprotein may govern post-entry replication events and plays a role in the assembly process.</p

Inverse Eigenvalue Problems for Perturbed Spherical Schroedinger Operators

We investigate the eigenvalues of perturbed spherical Schr\"odinger operators under the assumption that the perturbation $q(x)$ satisfies $x q(x) \in L^1(0,1)$. We show that the square roots of eigenvalues are given by the square roots of the unperturbed eigenvalues up to an decaying error depending on the behavior of $q(x)$ near $x=0$. Furthermore, we provide sets of spectral data which uniquely determine $q(x)$.Comment: 14 page

Green's function for a Schroedinger operator and some related summation formulas

Summation formulas are obtained for products of associated Lagurre polynomials by means of the Green's function K for the Hamiltonian H = -{d^2\over dx^2} + x^2 + Ax^{-2}, A > 0. K is constructed by an application of a Mercer type theorem that arises in connection with integral equations. The new approach introduced in this paper may be useful for the construction of wider classes of generating function.Comment: 14 page

Relational time in generally covariant quantum systems: four models

We analize the relational quantum evolution of generally covariant systems in terms of Rovelli's evolving constants of motion and the generalized Heisenberg picture. In order to have a well defined evolution, and a consistent quantum theory, evolving constants must be self-adjoint operators. We show that this condition imposes strong restrictions to the choices of the clock variables. We analize four cases. The first one is non- relativistic quantum mechanics in parametrized form. We show that, for the free particle case, the standard choice of time is the only one leading to self-adjoint evolving constants. Secondly, we study the relativistic case. We show that the resulting quantum theory is the free particle representation of the Klein Gordon equation in which the position is a perfectly well defined quantum observable. The admissible choices of clock variables are the ones leading to space-like simultaneity surfaces. In order to mimic the structure of General Relativity we study the SL(2R) model with two Hamiltonian constraints. The evolving constants depend in this case on three independent variables. We show that it is possible to find clock variables and inner products leading to a consistent quantum theory. Finally, we discuss the quantization of a constrained model having a compact constraint surface. All the models considered may be consistently quantized, although some of them do not admit any time choice such that the equal time surfaces are transversal to the orbits.Comment: 18 pages, revtex fil

Quantum Effects for the Dirac Field in Reissner-Nordstrom-AdS Black Hole Background

The behavior of a charged massive Dirac field on a Reissner-Nordstrom-AdS black hole background is investigated. The essential self-adjointness of the Dirac Hamiltonian is studied. Then, an analysis of the discharge problem is carried out in analogy with the standard Reissner-Nordstrom black hole case.Comment: 18 pages, 5 figures, Iop styl