On Cowania and its intergeneric hybrids in Arizona

Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} The putative intergeneric hybridization between Stansbury Cliffrose ( Cowania ) and Apache Plume ( Fallugia ) is found to be undocumented. Chromosome counts support reported base numbers for Cowania and Fallugia to be n = 9 and n = 14 respectively.     

Localization of the human GM-CSF receptor gene to the X-Y pseudoautosomal region

Mammalian sex chromosomes share a small terminal region of homologous DNA sequences, which pair and recombine during male meiosis. Alleles in this region can be exchanged between X and Y chromosomes and are therefore inherited as if autosomal. Genes from this so-called pseudoautosomal region (PAR) are present in two doses in both males and females, and escape inactivation of the X chromosome in females. Indirect evidence suggests that there must be several pseudoautosomal genes, and several candidates have been proposed. Until now, the only gene that has been unequivocally located in the PAR is MIC2, which encodes a cell-surface antigen of unknown function. We now report the localization of a gene of known function to this region--the gene for the receptor of the haemopoietic regulator, granulocyte-macrophage colony stimulating factor. The chromosomal localization of this gene may be important in understanding the generation of M2 acute myeloid leukaemia.     

Re-evaluation of the phylogenetic position of the genus Dexiotrichides (Protozoa, Ciliophora, Scuticociliatida) inferred from stomatogenetic and molecular information for Dexiotrichides pangi

The divisional process and systematic position of the marine scuticociliate Dexiotrichides pangi are studied. Based on both stomatogenetic data and 18S rDNA gene sequences, the phylogeny and morphogenetic characteristics of this taxon, and of other related genera, are analyzed and discussed. Both the divisionary events and the molecular biological data indicate that this speciesgenus, together with certain other genera in the Dexiotricha-complex, occupies an intermediate position between the tetrahymenids and the “typical” scuticociliate, which suggests that the Dexiotricha-like taxa should be excluded from the “true” scuticociliates. As a further contribution, the process of stomatogenesis in D. pangi can be summarized as follows: (1) The oral primordia in the opisthe are formed only by the proliferation of basal bodies in the scutica field, which subsequently develop into three membranelles, while the new paroral membrane seems to be generated by the sub-anterior portion of somatic kinety 1 (the 1st postoral intercalary kinety). The latter character exhibits a mode similar to Tetrahymena. (2) In the proter the parental membranelles are retained and remain unchanged throughout the entire division process; only the old paroral membrane is disassembled and differentiated into the anlage, which then gives rise to the new paroral membrane and the scutica of the proter. The 18S rRNA gene sequence reported here is the first one for a ciliate in the Dexiotricha-complex.     

A kernel-driven model of effective directional emissivity fornon-isothermal surfaces

Land surface temperature (LST) is a key geophysical parameter that reflects the combined effects of land surface energy and radiation balance. Remote sensing of LST, however, requires understanding the directional patterns of thermal emission from heterogeneous land surfaces. Recently, semi-empirical, linear, kernel-driven models have been successfully used to describe observed directional patterns of land surface reflectance. Following a similar methodology and based on a recent model of the physics of directional thermal emission from heterogeneous land surfaces, a kernel-driven semi-empirical model for thermal emission is developed using three kernels: (i) an isotropic kernel, corresponding to the gray-body component in a heterogeneous pixel; (ii) a two-layer canopy kernel, derived from a previous conceptual model; and (iii) a geometric optical kernel that accounts for the fact that sunlit parts are hotter than shaded parts in a pixel. The three-kernel model fits 1997 airborne directional thermal brightness data over Avignon, France, very well.     

The star-formation history of the Universe from the stellar populations of nearby galaxies

The determination of the star-formation history of the Universe is a key goal of modern cosmology, as it is crucial to our understanding of how galactic structures form and evolve. Observations of young stars in distant galaxies at different times in the past have indicated that the stellar birthrate peaked some eight billion years ago before declining by a factor of around ten to its present value. Here we report an analysis of the 'fossil record' of the current stellar populations of 96,545 nearby galaxies, from which we obtained a complete star-formation history. Our results broadly support those derived from high-redshift galaxies. We find, however, that the peak of star formation was more recent--around five billion years ago. We also show that the bigger the stellar mass of the galaxy, the earlier the stars were formed, which indicates that high- and low-mass galaxies have very different histories.