13,637 research outputs found
Theoretical study of loss compensation in long-range dielectric loaded surface plasmon polariton waveguides
In this paper, a theoretical study of loss compensation in long-range dielectric loaded surface plasmon waveguides (LR-DLSPPs) is presented. Although extendable to other gain materials, rare-earth doped double tungstates are used as gain material in this work. Two different structures are studied and the effect of the different waveguide geometrical parameters on the material gain required to fully compensate the propagation losses are reported. The simulations were performed at 1.55 micrometer wavelength. A material gain as low as 12.5 dB/cm was determined as sufficient to obtain complete loss compensation in one of the proposed waveguide structures supporting sub-micron lateral mode dimension
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Relationship between thoracic kyphosis and neural axis abnormalities in patients with adolescent idiopathic scoliosis.
Purpose:Previous studies have suggested an association between increased thoracic kyphosis and neural axis abnormalities in patients with adolescent idiopathic scoliosis (AIS). However, the basis for this finding is unclear, and this association has been mainly noted in retrospective studies on a non-consecutive series of patients. The purpose of this study was to assess the relationship between thoracic kyphosis and neural axis abnormalities in patients with AIS. Methods:We studied a consecutive series of AIS patients treated with spinal fusion. Thoracic kyphosis (T2 to T12) was measured from preoperative lateral radiographs. All patients underwent a spine magnetic resonance imaging (MRI) prior to surgery, and MRI reports were reviewed to determine the presence of neural axis abnormalities. Statistical analyses included descriptive statistics and chi-squared analysis. Results:This study included 210 patients with AIS. There were no significant differences in age or gender between patients with thoracic hypokyphosis (kyphosis < 20°), normal thoracic kyphosis (kyphosis 20° to 40°) and thoracic hyperkyphosis (kyphosis > 40°) (p > 0.05). Neural axis abnormalities were present in 17.9% of patients with thoracic hypokyphosis, 9.8% of patients with normal thoracic kyphosis and 13.6% of patients with thoracic hyperkyphosis (p = 0.60). There were no significant differences in rates of Chiari malformation, syrinx, intra-spinal masses and other central nervous system abnormalities between groups (p > 0.05). Conclusions:Thoracic kyphosis was not associated with neural axis abnormalities in our consecutive series of patients with AIS. Increased thoracic kyphosis may not be a reliable indicator for the presence of neural axis abnormalities in patients with AIS. Level of Evidence:IV
Diffusion of Hydrogen in Pd Assisted by Inelastic Ballistic Hot Electrons
Sykes {\it et al.} [Proc. Natl. Acad. Sci. {\bf 102}, 17907 (2005)] have
reported how electrons injected from a scanning tunneling microscope modify the
diffusion rates of H buried beneath Pd(111). A key point in that experiment is
the symmetry between positive and negative voltages for H extraction, which is
difficult to explain in view of the large asymmetry in Pd between the electron
and hole densities of states. Combining concepts from the theory of ballistic
electron microscopy and electron-phonon scattering we show that H diffusion is
driven by the -band electrons only, which explains the observed symmetry.Comment: 5 pages and 4 figure
Total electron scattering cross sections from thiophene for the (1-300 eV) impact energy range
Experimental electron scattering cross sections for thiophene in the impact energy range from 1 to 300 eV have been measured with a magnetically confined electron transmission-beam apparatus. Random uncertainty limits have been estimated to be less than 5%, and systematic errors derived from acceptance angle limitations have also been identified and evaluated. Experimental values are compared with our previous low energy (1-15 eV) R-matrix and intermediate/high energy (15-300 eV) IAM-SCAR+I calculations finding reasonable agreement, within the combined uncertainty limits. Some of the low energy shape and core-excited resonances predicted by previous calculations are experimentally confirmed in this study
Bubbles from Nothing
Within the framework of flux compactifications, we construct an instanton
describing the quantum creation of an open universe from nothing. The solution
has many features in common with the smooth 6d bubble of nothing solutions
discussed recently, where the spacetime is described by a 4d compactification
of a 6d Einstein-Maxwell theory on S^2 stabilized by flux. The four-dimensional
description of this instanton reduces to that of Hawking and Turok. The choice
of parameters uniquely determines all future evolution, which we additionally
find to be stable against bubble of nothing instabilities.Comment: 19 pages, 6 figure
L'Arxiu de Simancas i la Universitat de Cervera: aspectes biogrĂ fics dels primers metges
En aquesta comunicació al XVII Congrés d’HMC, exposarem la investigació històrica dels aspectes biogrà fics particulars dels catedrà tics, metges i estudiants de la Facultat de Medicina en els primers anys de la Universitat de Cervera. Seguim la tecnologia de l’anà lisi ergonòmica i dels fons documentals del Archivo General de Simancas, però aquà utilitzarem també com a fonts documentals bibliogrà fiques, els estudis i aportacions que tenen com a font documental el “Archivo Universitario de Cervera”, ubicat a la Biblioteca Università ria de Barcelona. S’exposa la descripció en quatre apartats: 1r. Cà tedres i catedrà tics de Medicina; 2n. Les primeres oposicions; 3r. Cà tedres d’anatomia i cirurgia; 4rt. Comentaris històrics i valoració
"Diario de Barcelona" any 1935. Notes mèdiques.
Es transcriu el comentari que s’exposa en una carta al Sr. Editor del “Diario de Barcelona”, de 20 de juliol de 1835, sobre la situació el primer terç del segle XIX entre les distincions de les ciències i el contrast que presenten la formació als Col·legis i l’exercici dels profesionals de la Medicina, amb la varietat i catà leg de les seves denominacions i funcions, els possibles perjudicis que aquesta situació ocasionava, particularment al món rural, degut a la ignorà ncia i a l’abús de no complir les lleis que no concedien l’exercici professional a totes les parts de la Medicina
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