Simulated acoustic emissions from coupled strings

We consider traveling transverse waves on two identical uniform taut strings that are elastically coupled through springs that gradually decrease their stiffness over a region of finite length. The wave system can be decomposed into two modes: an in-phase mode ( + ) that is transparent to the coupling springs, and an out-of-phase mode ( − ) that engages the coupling springs and can resonate at a particular location depending on the excitation frequency. The system exhibits linear mode conversion whereby an incoming ( + ) wave is reflected back from the resonance location both as a propagating ( + ) wave and an evanescent ( − ) wave, while both types emerge as propagating forward through the resonance location. We match a local transition layer expansion to the WKB expansion to obtain estimates of the reflection and transmission coefficients. The reflected waves may be an analog for stimulated emissions from the ear

Local-global compatibility for l=p, II

We prove the compatibility at places dividing l of the local and global Langlands correspondences for the l-adic Galois representations associated to regular algebraic essentially (conjugate) self-dual cuspidal automorphic representations of GL_n over an imaginary CM or totally real field. We prove this compatibility up to semisimplification in all cases, and up to Frobenius semisimplification in the case of Shin-regular weight.Comment: 13 page

Characterization of a Gene Expressed during Human Myeloid Cell Differentiation

Characterization of a gene expressed during human myeloid cell differentiation Previous work using differential screening of a cDNA library representing poly A+ RNA from the peripheral blood leukocytes of a chronic phase CGL patient had led to the isolation of cDNA clones representing mRNAs found at high abundance in this leukaemia compared to ANLL, CLL or normal peripheral blood leukocytes. The gene encoding one clone, pCG14, was also found to be expressed during normal human myelopoiesis in the neutrophilic myelocyte, a bone-marrow restricted neutrophil progenitor. In this work the pCG14 cDNA was completely sequenced and shown to encode HNP3, one of a group of three closely homologous peptides called defensins. These peptides are found in abundance in the granules of neutrophils and are involved in destruction of micro-organisms. The human defensin peptides HNP1 and HNP3 were shown to be encoded by two mRNAs differing at only one coding position that could be distinguished by PCR, and the regulation of the abundance of these mRNAs during myelopoiesis was investigated using induced differentiation of HL60 cells as a model system. Four different genes, two encoding HNP1 and two encoding HNP3, were isolated and one gene encoding HNP1 was characterized in detail. It was shown to be comprised of three exons and its 5'-regulatory region shown to contain two functional promoters. Using the presence of a single nucleotide change which distinguishes the coding regions of HNP1 and 3 genes, giving rise to a polymorphic Hae3 restriction enzyme site, individuals were shown to contain variable relative amounts of HNP1 and HNP3 genes. To explain these results it was hypothesized that individuals contain four defensin genes per diploid cell, one tandem pair on each chromosome 8. This model was tested using DNAs from a family where it was shown that defensin genes were inherited as a pair

Dynamical experiments on models of colliding disk galaxies

Collisions between galaxies can induce large morphological changes in the participants and, in the case of colliding disk galaxies, bridges and tails are often formed. Observations of such systems indicate a wide variation in color (see Larson and Tinsley, 1978) and that some of the particpants are experiencing enhanced rates of star formation, especially in their central regions (Bushouse 1986, 1987; Kennicutt et al., 1987, Bushouse, Lamb, and Werner, 1988). Here the authors describe progress made in understanding some of the dynamics of interacting galaxies using N-body stellar dynamical computer experiments, with the goal of extending these models to include a hydrodynamical treatment of the gas so that a better understanding of globally enhanced star formation will eventually be forthcoming. It was concluded that close interactions between galaxies can produce large perturbations in both density and velocity fields. The authors measured, via computational experiments that represent a galaxy's stars, average radial velocity flows as large as 100 km/sec and 400 percent density increases. These can occur in rings that move outwards through the disk of a galaxy, in roughly homologous inflows toward the nucleus, and in off center, non-axisymmetric regions. Here the authors illustrate where the gas is likely to flow during the early stages of interaction and in future work they plan to investigate the fate of the gas more realistically by using an N-body/Smoothed Particle Hydrodynamics code to model both the stellar and gaseous components of a disk galaxy during a collision. Specifically, they will determine the locations of enhanced gas density and the strength and location of shock fronts that form during the interaction

The morphology of and locations of star formation in impact induced ring galaxies

Observed ring galaxies appear to fall into two major types. The first tends to consist of isolated galaxies which display a smooth, apparently circular ring and a central nucleus. These have been variously classified as R(S) by de Vaucouleurs (1959) and as type O by Few and Madore (1986). The second class of ring galaxy nearly always has a close companion of comparable size (no less than about one tenth that of the ring galaxy). In these objects the ring is knotty in appearance, is usually elliptical, even when deprojected on the sky, and is often open on one side, having a 'horse shoe' or 'banana' shape. The nucleus does not usually appear at the center of the ring and is sometimes apparently absent, giving rise to an 'empty ring' galaxy. deVaucouleurs et al. (1976) designated this second type as RING, while Few and Madore (1986) have classified similar galaxies as P type. These galaxies have elevated far IR emission, bright HII regions, and blue spectral colors. The different environments of the two types or ring galaxy, together with their overall morphological and spectral differences suggest that the R(S)/O type are most probably the result of an instability that occurs in isolated galaxies, whereas the RING/P type appears to be the result of a recent collision between two roughly equal mass objects, at least one of which is a disk galaxy. Theys and Spiegel (1976) studied a sample of this latter type and identified three subclasses: RE: galaxies with crisp, empty rings; RN: galaxies like those of RE but with off-center nuclei; RK: galaxies having single dominant knots or condensations in the rings. A presentation of a preliminary understanding of the connections between these different observed forms in terms of parameters which are intrinsic to the galaxy system, such as time since collision and impact parameter, and in terms of our line of sight view is the purpose of this paper. Here we report results we have obtained from three dimensional computer simulations of collisions between equal mass galaxies, one of which is a rotating, disk galaxy containing both gas and stars and the other is an elliptical containing stars only. We have used a combined n-body/SPH program (see Balsara, 1990) to model fully self consistent models in which the halo mass is 2.5 times that of the disk and gas comprises ten percent of the disk mass