Don't Panic! Closed String Tachyons in ALE Spacetimes

We consider closed string tachyons localized at the fixed points of noncompact nonsupersymmetric orbifolds. We argue that tachyon condensation drives these orbifolds to flat space or supersymmetric ALE spaces. The decay proceeds via an expanding shell of dilaton gradients and curvature which interpolates between two regions of distinct angular geometry. The string coupling remains weak throughout. For small tachyon VEVs, evidence comes from quiver theories on D-branes probes, in which deformations by twisted couplings smoothly connect non-supersymmetric orbifolds to supersymmetric orbifolds of reduced order. For large tachyon VEVs, evidence comes from worldsheet RG flow and spacetime gravity. For \IC^2/\IZ_n, we exhibit infinite sequences of transitions producing SUSY ALE spaces via twisted closed string condensation from non-supersymmetric ALE spaces. In a $T$-dual description this provides a mechanism for creating NS5-branes via {\it closed} string tachyon condensation similar to the creation of D-branes via {\it open} string tachyon condensation. We also apply our results to recent duality conjectures involving fluxbranes and the type 0 string.Comment: 48 pages, harvmac big; 13 figures. v2: added references; comment on gravity regime added to section 5.2. v3: added reference

The energy dependence of p_t angular correlations inferred from mean-p_t fluctuation scale dependence in heavy ion collisions at the SPS and RHIC

We present the first study of the energy dependence of pt angular correlations inferred from event-wisemean transverse momentum (pt) fluctuations in heavy ion collisions. We compare our large-acceptancemeasurements at CM energies √^sNN = 19.6, 62.4, 130 and 200 GeV to SPS measurements at 12.3 and 17.3 GeV. p_t angular correlation structure suggests that the principal source of p_t correlations and fluctuations is minijets (minimum-bias parton fragments). We observe a dramatic increase in correlations and fluctuations from SPS to RHIC energies, increasing linearly with ln √^sNN from the onset of observable jet-related (p_t) fluctuations near 10 GeV

Searching a biomedical bibliographic database from the Ukraine: the Panteleimon database

The Panteleimon database is available via the Internet and is a public access, database, capable of being searched in English, Russian and Ukrainian, covering medical, pharmaceutical, and chemical publications, published in he Ukraine and Russia from 1998. Describes the formulation of a search strategy for the Panteleimon database, for the identification of citations to randomized controlled trials (RCTs), and the comparison of the search results with records included in the Cochrane Library's Cochrane Central Register of Controlled Trials (CENTRAL) database, to evaluate how comprehensive the coverage of the CENTRAL database is for the literature of the Ukraine. The results indicated that Panteleimon is an easily accessible bibliographic database offering easy access to the Ukrainian biomedical literature. The English language retrieval functions picked up most of the reports of RCTs/CCTs (91 per cent precision but the lower recall of 55 per cent indicates the need to search using Russian and Ukrainian terms for completeness. The overall precision of 26 per cent compares favourably with a search for RCTs in EMBASE, carried out by the UK Cochrane Centre, where 70,000 reports of RCTs were identified from 300,000 records down-loaded (precision 23 per cent). (Quotes from original text

Two-particle correlations on transverse momentum and momentum dissipation in Au–Au collisions at √sNN = 130 GeV

Measurements of two-particle correlations on transverse momentum p_t for Au–Au collisions at √^sNN = 130 GeV are presented. Significant largemomentum-scale correlations are observed for charged primary hadrons with 0.15 ≤ p_t ≤ 2 GeV/c and pseudorapidity |η| ≤ 1.3. Such correlations were not observed in a similar study at lower energy and are not predicted by theoretical collision models. Their direct relation to mean-p_t fluctuations measured in the same angular acceptance is demonstrated. Positive correlations are observed for pairs of particles which have large pt values while negative correlations occur for pairs in which one particle has large p_t and the other has much lower p_t . The correlation amplitudes per final state particle increase with collision centrality. The observed correlations are consistent with a scenario in which the transverse momentum of hadrons associated with initial-stage semi-hard parton scattering is dissipated by the medium to lower p_t

Isospectral Flow and Liouville-Arnold Integration in Loop Algebras

A number of examples of Hamiltonian systems that are integrable by classical means are cast within the framework of isospectral flows in loop algebras. These include: the Neumann oscillator, the cubically nonlinear Schr\"odinger systems and the sine-Gordon equation. Each system has an associated invariant spectral curve and may be integrated via the Liouville-Arnold technique. The linearizing map is the Abel map to the associated Jacobi variety, which is deduced through separation of variables in hyperellipsoidal coordinates. More generally, a family of moment maps is derived, identifying certain finite dimensional symplectic manifolds with rational coadjoint orbits of loop algebras. Integrable Hamiltonians are obtained by restriction of elements of the ring of spectral invariants to the image of these moment maps. The isospectral property follows from the Adler-Kostant-Symes theorem, and gives rise to invariant spectral curves. {\it Spectral Darboux coordinates} are introduced on rational coadjoint orbits, generalizing the hyperellipsoidal coordinates to higher rank cases. Applying the Liouville-Arnold integration technique, the Liouville generating function is expressed in completely separated form as an abelian integral, implying the Abel map linearization in the general case.Comment: 42 pages, 2 Figures, 1 Table. Lectures presented at the VIIIth Scheveningen Conference, held at Wassenaar, the Netherlands, Aug. 16-21, 199

Tendon proper- and peritenon-derived progenitor cells have unique tenogenic properties.

IntroductionMultipotent progenitor populations exist within the tendon proper and peritenon of the Achilles tendon. Progenitor populations derived from the tendon proper and peritenon are enriched with distinct cell types that are distinguished by expression of markers of tendon and vascular or pericyte origins, respectively. The objective of this study was to discern the unique tenogenic properties of tendon proper- and peritenon-derived progenitors within an in vitro model. We hypothesized that progenitors from each region contribute differently to tendon formation; thus, when incorporated into a regenerative model, progenitors from each region will respond uniquely. Moreover, we hypothesized that cell populations like progenitors were capable of stimulating tenogenic differentiation, so we generated conditioned media from these cell types to analyze their stimulatory potentials.MethodsIsolated progenitors were seeded within fibrinogen/thrombin gel-based constructs with or without supplementation with recombinant growth/differentiation factor-5 (GDF5). Early and late in culture, gene expression of differentiation markers and matrix assembly genes was analyzed. Tendon construct ultrastructure was also compared after 45 days. Moreover, conditioned media from tendon proper-derived progenitors, peritenon-derived progenitors, or tenocytes was applied to each of the three cell types to determine paracrine stimulatory effects of the factors secreted from each of the respective cell types.ResultsThe cell orientation, extracellular domain and fibril organization of constructs were comparable to embryonic tendon. The tendon proper-derived progenitors produced a more tendon-like construct than the peritenon-derived progenitors. Seeded tendon proper-derived progenitors expressed greater levels of tenogenic markers and matrix assembly genes, relative to peritenon-derived progenitors. However, GDF5 supplementation improved expression of matrix assembly genes in peritenon progenitors and structurally led to increased mean fibril diameters. It also was found that peritenon-derived progenitors secrete factor(s) stimulatory to tenocytes and tendon proper progenitors.ConclusionsData demonstrate that, relative to peritenon-derived progenitors, tendon proper progenitors have greater potential for forming functional tendon-like tissue. Furthermore, factors secreted by peritenon-derived progenitors suggest a trophic role for this cell type as well. Thus, these findings highlight the synergistic potential of including these progenitor populations in restorative tendon engineering strategies

Forward Neutral Pion Production in p + p and d + Au Collisions at √s_(NN) = 200 GeV

Measurements of the production of forward π^0 mesons from p + p and d + Au collisions at √s_(NN) = 200  GeV are reported. The p + p yield generally agrees with next-to-leading order perturbative QCD calculations. The d + Au yield per binary collision is suppressed as η increases, decreasing to ~30% of the p + p yield at =4.00, well below shadowing expectations. Exploratory measurements of azimuthal correlations of the forward π^0 with charged hadrons at η ≈ 0 show a recoil peak in p + p that is suppressed in d + Au at low pion energy. These observations are qualitatively consistent with a saturation picture of the low-x gluon structure of heavy nuclei

Directed flow in Au + Au collisions at √s_(NN) = 62.4 GeV

We present the directed flow (v1) measured in Au+Au collisions at √s_(NN) = 62.4 GeV in the midpseudorapidity region |η| < 1.3 and in the forward pseudorapidity region 2.5 < |η| < 4.0. The results are obtained using the three-particle cumulant method, the event plane method with mixed harmonics, and for the first time at the Relativistic Heavy Ion Collider, the standard method with the event plane reconstructed from spectator neutrons. Results from all three methods are in good agreement. Over the pseudorapidity range studied, charged particle directed flow is in the direction opposite to that of fragmentation neutrons