Problems With the Vortex-Boson Mapping in 1+1 Dimensions

Using the well known boson mapping, we relate the transverse magnetic susceptibility of a system of flux vortices in 1+1 dimensions to an appropriately defined conductivity of a one-dimensional boson system. The tilt response for a system free of disorder is calculated directly, and it is found that a subtle order of limits is required to avoid deceptive results.Comment: 4 Pages (REVTeX 3.0). Postscript file for this paper is available on the World Wide Web at http://cmtw.harvard.edu/~simon/

Vortex-line liquid phases: Longitudinal superconductivity in the lattice London model

We study the vortex-line lattice and liquid phases of a clean type-II superconductor by means of Monte Carlo simulations of the lattice London model. Motivated by a recent controversy regarding the presence, within this model, of a vortex-liquid regime with longitudinal superconducting coherence over long length scales, we directly compare two different ways to calculate the longitudinal coherence. For an isotropic superconductor, we interpret our results in terms of a temperature regime within the liquid phase in which longitudinal superconducting coherence extends over length scales larger than the system thickness studied. We note that this regime disappears in the moderately anisotropic case due to a proliferation, close to the flux-line lattice melting temperature, of vortex loops between the layers.Comment: 8 pages, Revtex, with eps figures. To appear in Phys. Rev.

Measurement properties of the Minimal Insomnia Symptom Scale (MISS) in an elderly population in Sweden

<p>Abstract</p> <p>Background</p> <p>Insomnia is common among elderly people and associated with poor health. The Minimal Insomnia Symptom Scale (MISS) is a three item screening instrument that has been found to be psychometrically sound and capable of identifying insomnia in the general population (20-64 years). However, its measurement properties have not been studied in an elderly population. Our aim was to test the measurement properties of the MISS among people aged 65 + in Sweden, by replicating the original study in an elderly sample.</p> <p>Methods</p> <p>Data from a cross-sectional survey of 548 elderly individuals were analysed in terms of assumptions of summation of items, floor/ceiling effects, reliability and optimal cut-off score by means of ROC-curve analysis and compared with self-reported insomnia criteria.</p> <p>Results</p> <p>Corrected item-total correlations ranged between 0.64-0.70, floor/ceiling effects were 6.6/0.6% and reliability was 0.81. ROC analysis identified the optimal cut-off score as ≥7 (sensitivity, 0.93; specificity, 0.84; positive/negative predictive values, 0.256/0.995). Using this cut-off score, the prevalence of insomnia in the study sample was 21.7% and most frequent among women and the oldest old.</p> <p>Conclusions</p> <p>Data support the measurement properties of the MISS as a possible insomnia screening instrument for elderly persons. This study make evident that the MISS is useful for identifying elderly people with insomnia-like sleep problems. Further studies are needed to assess its usefulness in identifying clinically defined insomnia.</p

Evolutionary Changes in the Complexity of the Tectum of Nontetrapods: A Cladistic Approach

Background: The tectum is a structure localized in the roof of the midbrain in vertebrates, and is taken to be highly conserved in evolution. The present article assessed three hypotheses concerning the evolution of lamination and citoarchitecture of the tectum of nontetrapod animals: 1) There is a significant degree of phylogenetic inertia in both traits studied (number of cellular layers and number of cell classes in tectum); 2) Both traits are positively correlated accross evolution after correction for phylogeny; and 3) Different developmental pathways should generate different patterns of lamination and cytoarchitecture. Methodology/Principal Findings: The hypotheses were tested using analytical-computational tools for phylogenetic hypothesis testing. Both traits presented a considerably large phylogenetic signal and were positively associated. However, no difference was found between two clades classified as per the general developmental pathways of their brains. Conclusions/Significance: The evidence amassed points to more variation in the tectum than would be expected by phylogeny in three species from the taxa analysed; this variation is not better explained by differences in the main course of development, as would be predicted by the developmental clade hypothesis. Those findings shed new light on th

The Flux-Line Lattice in Superconductors

Magnetic flux can penetrate a type-II superconductor in form of Abrikosov vortices. These tend to arrange in a triangular flux-line lattice (FLL) which is more or less perturbed by material inhomogeneities that pin the flux lines, and in high-$T_c$ supercon- ductors (HTSC's) also by thermal fluctuations. Many properties of the FLL are well described by the phenomenological Ginzburg-Landau theory or by the electromagnetic London theory, which treats the vortex core as a singularity. In Nb alloys and HTSC's the FLL is very soft mainly because of the large magnetic penetration depth: The shear modulus of the FLL is thus small and the tilt modulus is dispersive and becomes very small for short distortion wavelength. This softness of the FLL is enhanced further by the pronounced anisotropy and layered structure of HTSC's, which strongly increases the penetration depth for currents along the c-axis of these uniaxial crystals and may even cause a decoupling of two-dimensional vortex lattices in the Cu-O layers. Thermal fluctuations and softening may melt the FLL and cause thermally activated depinning of the flux lines or of the 2D pancake vortices in the layers. Various phase transitions are predicted for the FLL in layered HTSC's. The linear and nonlinear magnetic response of HTSC's gives rise to interesting effects which strongly depend on the geometry of the experiment.Comment: Review paper for Rep.Prog.Phys., 124 narrow pages. The 30 figures do not exist as postscript file

Analisi comparativa di materiali diversi utilizzati in GBR associata all’implantologia

L'uso della rigenerazione ossea guidata (GBR), associata all'implantologia, è diventato patrimonio della moderna chinirgia odontoiatrica. Molte ricerche istologiche e la comprovata evidenza clinica sono concordi nel dimostrare la validità di questa procedura. La capacità rigenerativa dipende dalla presenza delle cellule totipotenti, provenienti dal coagulo di origine ossea, in grado di maturare, differenziarsi e moltiplicarsi apponendo nuovo osso fino al riempimento del difetto stesso. Tale guarigione può avvenire solo a condizione che lo spazio sia mantenuto nel tempo, permettendo così alla membrana semipermeabile di svolgere appieno il ruolo di «tenda» isolante degli stipiti cellulari indesiderati (epitelio). Le attenzioni dei ricercatori si sono oggi concentrate sui problemi di perfezionamento della metodica, cercando di capire se e quanto il grado di rigenerazione ossea può essere influenzata dai materiali che si utilizzano. Vi sono differenze impiegando membrane riassorbibili o non riassorbibili? Quali tipi di membrana? Quale riempitivo? Sintetico, di derivazione naturale o nulla? Con questo lavoro gli autori cercano di dare un contributo alla soluzione di questi quesiti, analizzando sul piano clinico e istologico otto siti chirurgici trattati con le metodiche della GBR associata all'implantologia

Effetto della rimozione precoce delle membrane per una rigenerazione ossea soddisfacente

L’effetto sulla rigenerazione ossea della rimozione precoce, dopo 4 settimane, di membrane in PTFE nella GBR (Bio-Oss® + Fisiograft®) di 8 pazienti, è stato valutato istomorfometricamente (TBV) su biopsie effettuate 4/5 mesi dopo l’inserzione degli impianti. L’istologia ha evidenziato una buona rigenerazione ossea senza segni infiammatori, L’ammontare medio di osso rigenerato era 81,3%, statisticamente non diverso (test di Mann-Whitney) da quello (P<0,24) rilevato in un precedente lavoro (con rimozione della membrana dopo 5 mesi), mentre il TBV era statisticamente inferiore (P<0,01). La rimozione precoce delle membrane sembra pertanto produrre soddisfacenti risultati nella riparazione di difetti ossei, anche se conferme su casistiche più ampie sono necessarie

GBR in chirurgia implantare immediata post-estrattiva.

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