454 research outputs found
Optical properties and local structures of Tm<sup>3+</sup> ions in F co-doped lead-germanate glasses
Rare-earth doped optical fibres have received considerable attention in recent years due to the enhanced performance that optically pumped fibre devices Carl give over bulk glass devices. For many years, however, fabrication of low loss rare-earth doped fibres has been confined to silica-related glasses (lately fluoride-based ZBLAN glass fibres have become available, but their weak mechanical strength and poor chemical durability are problematic in practice). This has caused considerable problem in developing future important fibre devices such as 1.3µm optical amplifiers and long or short wavelength fibre lasers. It is thus absolutely essential that the range of rare-earth doped glasses that can be made into fibre structures is extended, particularly into lower phonon-energy glasses, combining possibly the best properties of both silica (low-loss, high strength etc.) and fluoride-based glasses (low non-radiative relaxation rate, etc.
Electronic and Structural Properties of a 4d-Perovskite: Cubic Phase of SrZrO
First-principles density functional calculations are performed within the
local density approximation to study the electronic properties of SrZrO, an
insulating 4d-perovskite, in its high-temperature cubic phase, above 1400 K, as
well as the generic 3d-perovskite SrTiO, which is also a d^0-insulator and
cubic above 105 K, for comparison reasons. The energy bands, density of states
and charge density distributions are obtained and a detailed comparison between
their band structures is presented. The results are discussed also in terms of
the existing data in the literature for both oxides.Comment: 5 pages, 2 figure
Fabrication and optical properties of lead-germanate glasses and a new class of optical fibres doped with Tm<sup>3+</sup>
In this article we present a study of a new class of optical fibers based on lead germanate glass. The maximum vibrational frequency of this glass is intermediate between silica and zirconium barium lanthanum aluminum fluoride glass, causing a beneficial change in nonradiative decay and therefore quantum efficiency for particular laser transitions. Fabrication of high-strength, low-loss fibers of this glass has been achieved by modification of the composition to produce optimal physical properties for fiber drawing, while retaining the useful vibrational properties of the original PbGeO2 glass. Measurements of both the thermal and optical properties are described. The fibers produced are ideal for many applications in fiber devices
On complex-valued 2D eikonals. Part four: continuation past a caustic
Theories of monochromatic high-frequency electromagnetic fields have been
designed by Felsen, Kravtsov, Ludwig and others with a view to portraying
features that are ignored by geometrical optics. These theories have recourse
to eikonals that encode information on both phase and amplitude -- in other
words, are complex-valued. The following mathematical principle is ultimately
behind the scenes: any geometric optical eikonal, which conventional rays
engender in some light region, can be consistently continued in the shadow
region beyond the relevant caustic, provided an alternative eikonal, endowed
with a non-zero imaginary part, comes on stage. In the present paper we explore
such a principle in dimension We investigate a partial differential system
that governs the real and the imaginary parts of complex-valued two-dimensional
eikonals, and an initial value problem germane to it. In physical terms, the
problem in hand amounts to detecting waves that rise beside, but on the dark
side of, a given caustic. In mathematical terms, such a problem shows two main
peculiarities: on the one hand, degeneracy near the initial curve; on the other
hand, ill-posedness in the sense of Hadamard. We benefit from using a number of
technical devices: hodograph transforms, artificial viscosity, and a suitable
discretization. Approximate differentiation and a parody of the
quasi-reversibility method are also involved. We offer an algorithm that
restrains instability and produces effective approximate solutions.Comment: 48 pages, 15 figure
Measurement of the branching fraction for
We have studied the leptonic decay of the resonance into tau
pairs using the CLEO II detector. A clean sample of tau pair events is
identified via events containing two charged particles where exactly one of the
particles is an identified electron. We find . The result is consistent with
expectations from lepton universality.Comment: 9 pages, RevTeX, two Postscript figures available upon request, CLNS
94/1297, CLEO 94-20 (submitted to Physics Letters B
Measurement of the B0-anti-B0-Oscillation Frequency with Inclusive Dilepton Events
The - oscillation frequency has been measured with a sample of
23 million \B\bar B pairs collected with the BABAR detector at the PEP-II
asymmetric B Factory at SLAC. In this sample, we select events in which both B
mesons decay semileptonically and use the charge of the leptons to identify the
flavor of each B meson. A simultaneous fit to the decay time difference
distributions for opposite- and same-sign dilepton events gives ps.Comment: 7 pages, 1 figure, submitted to Physical Review Letter
Autoimmune and infectious skin diseases that target desmogleins
Desmosomes are intercellular adhesive junctions of epithelial cells that contain two major transmembrane components, the desmogleins (Dsg) and desmocollins (Dsc), which are cadherin-type cell–cell adhesion molecules and are anchored to intermediate filaments of keratin through interactions with plakoglobin and desmoplakin. Desmosomes play an important role in maintaining the proper structure and barrier function of the epidermis and mucous epithelia. Four Dsg isoforms have been identified to date, Dsg1–Dsg4, and are involved in several skin and heart diseases. Dsg1 and Dsg3 are the two major Dsg isoforms in the skin and mucous membranes, and are targeted by IgG autoantibodies in pemphigus, an autoimmune disease of the skin and mucous membranes. Dsg1 is also targeted by exfoliative toxin (ET) released by Staphylococcus aureus in the infectious skin diseases bullous impetigo and staphylococcal scalded skin syndrome (SSSS). ET is a unique serine protease that shows lock and key specificity to Dsg1. Dsg2 is expressed in all tissues possessing desmosomes, including simple epithelia and myocardia, and mutations in this gene are responsible for arrhythmogenic right ventricular cardiomyopathy/dysplasia. Dsg4 plays an important adhesive role mainly in hair follicles, and Dsg4 mutations cause abnormal hair development. Recently, an active disease model for pemphigus was generated by a unique approach using autoantigen-deficient mice that do not acquire tolerance against the defective autoantigen. Adoptive transfer of Dsg3−/− lymphocytes into mice expressing Dsg3 induces stable anti-Dsg3 IgG production with development of the pemphigus phenotype. This mouse model is a valuable tool with which to investigate immunological mechanisms of harmful IgG autoantibody production in pemphigus. Further investigation of desmoglein molecules will continue to provide insight into the unsolved pathophysiological mechanisms of diseases and aid in the development of novel therapeutic strategies with minimal side effects
A Historiometric Examination of Machiavellianism and a New Taxonomy of Leadership
Although researchers have extensively examined the relationship between charismatic leadership and Machiavellianism (Deluga, 2001; Gardner & Avolio, 1995; House & Howell, 1992), there has been a lack of investigation of Machiavellianism in relation to alternative forms of outstanding leadership. Thus, the purpose of this investigation was to examine the relationship between Machiavellianism and a new taxonomy of outstanding leadership comprised of charismatic, ideological, and pragmatic leaders. Using an historiometric approach, raters assessed Machiavellianism via the communications of 120 outstanding leaders in organizations across the domains of business, political, military, and religious institutions. Academic biographies were used to assess twelve general performance measures as well as twelve general controls and five communication specific controls. The results indicated that differing levels of Machiavellianism is evidenced across the differing leader types as well as differing leader orientation. Additionally, Machiavellianism appears negatively related to performance, though less so when type and orientation are taken into account.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
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