Two dimensional pattern formation in a chemotactic system

Chemotaxis is known to be important in cell aggregation in a variety of contexts. We propose a simple partial differential equation model for a chemotactic system of two species, a population of cells and a chemoattractant to which cells respond. Linear analysis shows that there exists the possibility of spatially inhomogeneous solutions to the model equations for suitable choices of parameters. We solve the full nonlinear steady state equations numerically on a two dimensional rectangular domain. By using mode selection from the linear analysis we produce simple pattern elements such as stripes and regular spots. More complex patterns evolve from these simple solutions as parameter values or domain shape change continuously. An example bifurcation diagram is calculated using the chemotactic response of the cells as the bifurcation parameter. These numerical solutions suggest that a chemotactic mechanism can produce a rich variety of complex patterns

The COBE DIRBE Point Source Catalog

We present the COBE DIRBE Point Source Catalog, an all-sky catalog containing infrared photometry in 10 bands from 1.25 microns to 240 microns for 11,788 of the brightest near and mid-infrared point sources in the sky. Since DIRBE had excellent temporal coverage (100 - 1900 independent measurements per object during the 10 month cryogenic mission), the Catalog also contains information about variability at each wavelength, including amplitudes of variation observed during the mission. Since the DIRBE spatial resolution is relatively poor (0.7 degrees), we have carefully investigated the question of confusion, and have flagged sources with infrared-bright companions within the DIRBE beam. In addition, we filtered the DIRBE light curves for data points affected by companions outside of the main DIRBE beam but within the `sky' portion of the scan. At high Galactic latitudes (|b| > 5 degrees), the Catalog contains essentially all of the unconfused sources with flux densities greater than 90, 60, 60, 50, 90, and 165 Jy at 1.25, 2.2, 3.5, 4.9, 12, and 25 microns, respectively, corresponding to magnitude limits of approximately 3.1, 2.6, 1.7, 1.3, -1.3, and -3.5. At longer wavelengths and in the Galactic Plane, the completeness is less certain because of the large DIRBE beam and possible contributions from extended emission. The Catalog also contains the names of the sources in other catalogs, their spectral types, variability types, and whether or not the sources are known OH/IR stars. We discuss a few remarkable objects in the Catalog. [abridged]Comment: Accepted for publication in the Astrophysical Journal Supplement. The full tables are available at http://www.etsu.edu/physics/bsmith/dirbe

The core structure of presolar graphite onions

Of the ``presolar particles'' extracted from carbonaceous chondrite dissolution residues, i.e. of those particles which show isotopic evidence of solidification in the neighborhood of other stars prior to the origin of our solar system, one subset has an interesting concentric graphite-rim/graphene-core structure. We show here that single graphene sheet defects in the onion cores (e.g. cyclopentane loops) may be observable edge-on by HREM. This could allow a closer look at models for their formation, and in particular strengthen the possibility that growth of these assemblages proceeds atom-by-atom with the aid of such in-plane defects, under conditions of growth (e.g. radiation fluxes or grain temperature) which discourage the graphite layering that dominates subsequent formation of the rim.Comment: 4 pages, 7 figures, 11 refs, see also http://www.umsl.edu/~fraundor/isocore.htm

Testosterone Might Not Be Necessary To Support Female Aggression In Incubating Northern Cardinals

Testosterone\u27s (T) influence on male aggression has been well established in many vertebrate species, but the impact of T on female aggressive behaviour is poorly understood. Among birds, a link between T and female aggression is plausible, as females of many species exhibit a seasonal peak in T concentrations at the onset of breeding when social instability is greatest and they may have circulating T through much of the breeding season. However, investigations examining the relationship between T and female aggression are few and have yielded conflicting results, with experimentally or endogenously elevated T supporting aggressive behaviour in females of some species but not others, and T elevating with aggression at some points of the reproductive cycle but not others. We examined the relationship between endogenous levels of T and female aggression in the northern cardinal, Cardinalis cardinalis, a resident temperate species in which pairs exhibit prolonged territoriality and females have measurable levels of T year-round, including all stages of reproduction (incubation, nestling feeding, etc.). Using simulated nest intrusions, we assessed aggressive responses of incubating females to intrasexual \u27intruders\u27 at the nest and quantified T levels after each aggressive encounter. Displays of aggression towards \u27intruders\u27 varied among females; yet, individuals showing greater levels of aggression did not demonstrate higher levels of T. These results imply that T might not support maternal aggression in this species

The morpho-kinematics of the circumstellar envelope around the AGB star EP Aqr

ALMA observations of CO(1-0) and CO(2-1) emissions of the circumstellar envelope of EP Aqr, an oxygen-rich AGB star, are reported. A thorough analysis of their properties is presented using an original method based on the separation of the data-cube into a low velocity component associated with an equatorial outflow and a faster component associated with a bipolar outflow. A number of important and new results are obtained concerning the distribution in space of the effective emissivity, the temperature, the density and the flux of matter. A mass loss rate of (1.6$\pm$0.4)10$^{-7}$ solar masses per year is measured. The main parameters defining the morphology and kinematics of the envelope are evaluated and uncertainties inherent to de-projection are critically discussed. Detailed properties of the equatorial region of the envelope are presented including a measurement of the line width and a precise description of the observed inhomogeneity of both morphology and kinematics. In particular, in addition to the presence of a previously observed spiral enhancement of the morphology at very small Doppler velocities, a similarly significant but uncorrelated circular enhancement of the expansion velocity is revealed, both close to the limit of sensitivity. The results of the analysis place significant constraints on the parameters of models proposing descriptions of the mass loss mechanism, but cannot choose among them with confidence.Comment: 26 pages, 31 figures, accepted for publication in MNRA

12CO emission from EP Aqr: Another example of an axi-symmetric AGB wind?

The CO(1-0) and (2-1) emission of the circumstellar envelope of the AGB star EP Aqr has been observed using the IRAM PdBI and the IRAM 30-m telescope. The line profiles reveal the presence of two distinct components centered on the star velocity, a broad component extending up to ~10 km/s and a narrow component indicating an expansion velocity of ~2 km/s. An early analysis of these data was performed under the assumption of isotropic winds. The present study revisits this interpretation by assuming instead a bipolar outflow nearly aligned with the line of sight. A satisfactory description of the observed flux densities is obtained with a radial expansion velocity increasing from ~2 km/s at the equator to ~10 km/s near the poles. The angular aperture of the bipolar outflow is ~45 deg with respect to the star axis, which makes an angle of ~13 deg with the line of sight. A detailed study of the CO(1-0) to CO(2-1) flux ratio reveals a significant dependence of the temperature on the star latitude, smaller and steeper at the poles than at the equator at large distances from the star. Under the hypothesis of radial expansion and of rotation invariance about the star axis, the effective density has been evaluated in space as a function of star coordinates. Evidence is found for an enhancement of the effective density in the northern hemisphere of the star at angular distances in excess of ~3" and covering the whole longitudinal range. The peak velocity of the narrow component is observed to vary slightly with position on the sky, a variation consistent with the model and understood as the effect of the inclination of the star axis with respect to the line of sight. While the phenomenological model presented here reproduces well the general features of the observations, significant differences are also revealed, which would require a better spatial resolution to be properly described.Comment: accepted for publication in Astronomy & Astrophysic

Observation of narrow polar jets in the nascent wind of oxygen-rich AGB star EP Aqr

Using ALMA observations of $^{12}$CO(2-1), $^{28}$SiO(5-4) and $^{32}$SO$_2$(16$_{6,10}$-17$_{5,13}$) emissions of the circumstellar envelope of AGB star EP Aqr, we describe the morpho-kinematics governing the nascent wind. Main results are: 1) Two narrow polar structures, referred to as jets, launched from less than 25 au away from the star, build up between $\sim$ 20 au and $\sim$ 100 au to a velocity of $\sim$ 20 \kms. They fade away at larger distances and are barely visible in CO data. 2) SO$_2$, SiO and CO emissions explore radial ranges reaching respectively $\sim$30 au, 250 au and 1000 au from the star, preventing the jets to be detected in SO$_2$ data. 3) Close to the star photosphere, rotation (undetected in SiO and CO data) and isotropic radial expansion combine with probable turbulence to produce a broad SO$_2$ line profile ($\sim$ 7.5 \kms\ FWHM). 4) A same axis serves as axis of rotation close to the star, as jet axis and as axi-symmetry axis at large distances. 5) A radial wind builds up at distances up to $\sim$ 300 au from the star, with larger velocity near polar than equatorial latitudes. 6) A sharp depletion of SiO and CO emissions, starting near the star, rapidly broadens to cover the whole blue-western quadrant, introducing important asymmetry in the CO and particularly SiO observations. 7) The $^{12}$C/$^{13}$C abundance ratio is measured as 9$\pm$2. 8) Plausible interpretations are discussed, in particular assuming the presence of a companion.Comment: 18 pages, 16 figures, MNRAS accepte

Synthesis and biodistribution of immunoconjugates of a human IgM and polymeric drug carriers

The synthesis and purification of radiolabelled immunoconjugates, composed of a human IgM monoclonal antibody directed against an intracellular tumour-associated antigen and either poly (alpha-L-glutamic acid) (PGA) or poly[N5-(2-hydroxyethyl)-L-glutamine] (PHEG) is described. Coupling of polymers to the antibody was performed through disulfide bond formation involving a single thiol group at the C-terminus of the polymer chain and 2-pyridyldisulfide groups introduced onto the antibody. The antibody was iodinated with 131I before conjugation. The polymers contained tyrosinamide in a low degree of substitution and were radiolabelled with 125I. 125I-labelled PGA and PHEG were found to be stable for at least 3 days in murine and human plasma. The biodistribution in mice of the doubly labelled immunoconjugates was studied and was compared with the pharmacokinetics of the individual components.\ud \ud PHEG showed a relatively slow blood clearance, the half-life being approximately 10 h with low uptake in liver, kidneys and spleen. PGA was rapidly cleared from the circulation and was significantly taken up in liver, kidneys and spleen. The biodistribution of both immunoconjugates was indistinguishable from that of the IgM proper, with plasma half-lives of approximately 6 h, indicating that the pharmacokinetic properties of the immunoconjugates are largely determined by the antibody part

Integrative Review: Parent Perspectives on Care of Their Child at the End of Life

This integrative review aims to describe parents\u27 perspectives on end-of-life care for their children. Fifteen publications from a literature search of the Cochrane databases, CINAHL, MEDLINE, and PSYCHinfo were included in the review. Recurring themes included poor communication/lack of information, strained relationships/inadequate emotional support, parental need to maintain parent/child relationships in life and death, quality of care continues after the death of the child, influence of services/planning on parent/child impacts quality of life, and the difficult decision to terminate life support. No studies were identified that focused on parents\u27 perspectives on the care their child received at the end of life. Further research that focuses on the special needs of parents at this difficult time is needed