7,664 research outputs found
On the effect of dispersion on nonlinear phase noise
The variance of nonlinear phase noise is analyzed by including the effect of
intrachannel cross-phase modulation (IXPM)-induced nonlinear phase noise.
Consistent with Ho and Wang [1] but in contrary to the conclusion of both Kumar
[2] and Green et al. [3], the variance of nonlinear phase noise does not
decrease much with the increase of chromatic dispersion. The results are
consistent with a careful reexamination of both Kumar [2] and Green et al. [3].Comment: 3 pages, 1 figure, submitted to Optics Letter
Transient complete heart block following catheter ablation of a left lateral accessory pathway.
A 16-year-old female with symptomatic Wolff-Parkinson-White (WPW) syndrome underwent catheter ablation of a left-sided lateral accessory pathway. The accessory pathway was eliminated with the first ablation lesion; however, the patient immediately developed complete heart block (CHB). At first, complete heart block was thought to be due to ablation of left atrial extension of the AV node, and pacemaker therapy was considered. However, careful ECG analysis revealed that the development of CHB was in fact due to bump injury to the AV node during transseptal catheterization. Conservative management allowed resolution of AV nodal conduction without need for a permanent pacemaker
Lagrangian of Self-dual Gauge Fields in Various Formulations
The Lagrangian of self-dual gauge theory in various formulations are
reviewed. From these results we see a simple rule and use it to present some
new non-covariant Lagrangian based on the decomposition of spacetime into
. Our prescription could be easily extended to more complex
decomposition of spacetime and some more examples are presented therefore. The
self-dual property of the new Lagrangian is proved in detail. We also show that
the new non-covariant actions give field equations with 6d Lorentz invariance.Comment: Latex, 27 pages,9 tables. V4: Modify Lagrangian (3.1) and prove its
self-dualit
D-Instanton in AdS_5 and Instanton in SYM_4
Following the observation of Banks and Green that the D-instantons in AdS_5
correspond to the instantons in 4-dimensional supersymmetric Yang-Mills theory,
we study in more detail this correspondence for individual instantons. The
supergravity solution for a D-instanton in AdS_5 is found using the ansatz used
previously for D-instantons in flat space. We check that the actions and
supersymmetries match between the D-instanton solution and the Yang-Mills
instanton. Generalizing this result, we propose that any supergravity solution
satisfying the ansatz corresponds to a (anti-)self-dual Yang-Mills
configuration. Using this ansatz a family of identities for correlation
functions in the supersymmetric Yang-Mills theory are derived.Comment: LaTeX, 19 pages, no figure, some typos correcte
High-energy zero-norm states and symmetries of string theory
High-energy limit of zero-norm states (HZNS) in the old covariant first
quantized (OCFQ) spectrum of the 26D open bosonic string, together with the
assumption of a smooth behavior of string theory in this limit, are used to
derive infinitely many linear relations among the leading high-energy, fixed
angle behavior of four point functions of different string states. As a result,
ratios among all high-energy scattering amplitudes of four arbitrary string
states can be calculated algebraically and the leading order amplitudes can be
expressed in terms of that of four tachyons as conjectured by Gross in 1988. A
dual calculation can also be performed and equivalent results are obtained by
taking the high-energy limit of Virasoro constraints. Finally, as a consistent
sample calculation, we compute all high-energy scattering amplitudes of three
tachyons and one massive state at the leading order by saddle-point
approximation to justify our results.Comment: 10 pages, no figure, modifications of text and reference
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Induction of Paralysis and Visual System Injury in Mice by T Cells Specific for Neuromyelitis Optica Autoantigen Aquaporin-4.
While it is recognized that aquaporin-4 (AQP4)-specific T cells and antibodies participate in the pathogenesis of neuromyelitis optica (NMO), a human central nervous system (CNS) autoimmune demyelinating disease, creation of an AQP4-targeted model with both clinical and histologic manifestations of CNS autoimmunity has proven challenging. Immunization of wild-type (WT) mice with AQP4 peptides elicited T cell proliferation, although those T cells could not transfer disease to naĂŻve recipient mice. Recently, two novel AQP4 T cell epitopes, peptide (p) 135-153 and p201-220, were identified when studying immune responses to AQP4 in AQP4-deficient (AQP4-/-) mice, suggesting T cell reactivity to these epitopes is normally controlled by thymic negative selection. AQP4-/- Th17 polarized T cells primed to either p135-153 or p201-220 induced paralysis in recipient WT mice, that was associated with predominantly leptomeningeal inflammation of the spinal cord and optic nerves. Inflammation surrounding optic nerves and involvement of the inner retinal layers (IRL) were manifested by changes in serial optical coherence tomography (OCT). Here, we illustrate the approaches used to create this new in vivo model of AQP4-targeted CNS autoimmunity (ATCA), which can now be employed to study mechanisms that permit development of pathogenic AQP4-specific T cells and how they may cooperate with B cells in NMO pathogenesis
Probing the Balance of AGN and Star-Forming Activity in the Local Universe with ChaMP
The combination of the SDSS and the Chandra Multiwavelength Project (ChaMP)
currently offers the largest and most homogeneously selected sample of nearby
galaxies for investigating the relation between X-ray nuclear emission, nebular
line-emission, black hole masses, and properties of the associated stellar
populations. We present here novel constraints that both X-ray luminosity Lx
and X-ray spectral energy distribution bring to the galaxy evolutionary
sequence H II -> Seyfert/Transition Object -> LINER -> Passive suggested by
optical data. In particular, we show that both Lx and Gamma, the slope of the
power-law that best fits the 0.5 - 8 keV spectra, are consistent with a clear
decline in the accretion power along the sequence, corresponding to a softening
of their spectra. This implies that, at z ~ 0, or at low luminosity AGN levels,
there is an anti-correlation between Gamma and L/Ledd, opposite to the trend
exhibited by high z AGN (quasars). The turning point in the Gamma -L/Ledd LLAGN
+ quasars relation occurs near Gamma ~ 1.5 and L/Ledd ~ 0.01. Interestingly,
this is identical to what stellar mass X-ray binaries exhibit, indicating that
we have probably found the first empirical evidence for an intrinsic switch in
the accretion mode, from advection-dominated flows to standard (disk/corona)
accretion modes in supermassive black hole accretors, similar to what has been
seen and proposed to happen in stellar mass black hole systems. The
anti-correlation we find between Gamma and L/Ledd may instead indicate that
stronger accretion correlates with greater absorption. Therefore the trend for
softer spectra toward more luminous, high redshift, and strongly accreting
AGN/quasars could simply be the result of strong selection biases reflected in
the dearth of type 2 quasar detections.Comment: 23 pages, 8 figures, 1 long (3 page) table, to appear in Ap
Epitaxial Growth of Ge on Si by Magnetron Sputtering
Epitaxial growth of Ge on Si has received considerable attention for its compatibility with Si process flow and the scarcity of Ge compared with Si. Applications that drive the efforts for integrating Ge with Si include high mobility channel in metal-oxide-semiconductor field-effect transistors, infrared photodetector in Si-based optical devices, and template for III-V growth to fabricate high-efficiency solar cells. Epitaxy Ge on Si can be used as a virtual Ge substrate for fabrication of III-V solar cells, which has advantages of superior mechanical properties and low cost over Ge wafers. This work investigates the epitaxial growth of Ge on Si using magnetron sputtering, which is an environment-friendly, inexpensive, high throughput, and simple deposition technique. The effects of substrate temperature on the properties of Ge are analyzed. A novel method to epitaxially grow Ge on Si by magnetron sputtering at low temperature is developed using one-step aluminum-assisted crystallization. By applying an in-situ low temperature (50–150°C) heat treatment in between Al and Ge sputter depositions, the epitaxial growth of Ge on Si is achieved. This method significantly lowers the required temperature for and therefore the cost of epitaxial growth of Ge on Si
Ramond-Ramond (boundary) states
The description of D-branes as boundary states for type II string theories
(in the covariant formulation) requires particular care in the R-R sector. Also
the vertices for R-R potentials that can couple to D-branes need a careful
handling. As an illustration of this, the example of the D0-D8 system is
reviewed, where a ``microscopic'' description of the interaction via exchange
of R-R potentials becomes possible.Comment: 8 pages, LaTeX, no figures. Talk presented at the 2nd Conference on
Quantum aspects of Gauge Theories, Supersymmetry and Unification, Corfu,
Greece, 21-26 September 199
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