6,555 research outputs found
The Nimbus 7 LIMS (Limb Infrared Monitor of the Stratosphere) water vapor measurements
Earth orbital instruments, designed to measure the vertical and spatial distribution of atmospheric water vapor is discussed. Specifically, the operation of the Limb Infrared Monitor of the Stratosphere (LIMS) experiment is examined. The LIMS is a six channel limb scanning radiometer that was launched aboard Nimbus 7 in 1978. Profiles of stratospheric and mesospheric temperature, water vapor, and various other constituents were obtained by inverting the LIMS radiance measurements. This same technique was used in 1981 to analyze the data returned from another limb scanning radiometer aboard the Solar Mesosphere Explorer
Host and symbiont genetic contributions to fitness in a Trichogramma-Wolbachia symbiosis.
The fitness effects associated with Wolbachia infection have wide-ranging ecological and evolutionary consequences for host species. How these effects are modulated by the relative influence of host and Wolbachia genomes has been described as a balancing act of genomic cooperation and conflict. For vertically transmitted symbionts, like cytoplasmic Wolbachia, concordant host-symbiont fitness interests would seem to select for genomic cooperation. However, Wolbachia's ability to manipulate host reproductive systems and distort offspring sex ratios presents an evolutionary conflict of interest with infected hosts. In the parthenogenesis-inducing (PI) form of Wolbachia found in many haplodiploid insects, Wolbachia fitness is realized through females and is enhanced by their feminization of male embryos and subsequent parthenogenetic reproduction. In contrast, as long as Wolbachia is not fixed in a population and sexual reproduction persists, fitness for the host species is realized through both male and female offspring production. How these cooperating and competing interests interact and the relative influence of host and Wolbachia genomes were investigated in the egg parasitoid Trichogramma kaykai, where Wolbachia infection has remained at a low frequency in the field. A factorial design in which laboratory cultures of Wolbachia-infected T. kaykai were cured and re-infected with alternative Wolbachia strains was used to determine the relative influence of host and Wolbachia genomes on host fitness values. Our results suggest fitness variation is largely a function of host genetic background, except in the case of offspring sex ratio where a significant interaction between host and Wolbachia genomes was found. We also find a significant effect associated with the horizontal transfer of Wolbachia strains, which we discuss in terms of the potential for coadaptation in PI-Wolbachia symbioses
Acrylamide Production Using Encapsulated Nitrile Hydratase from \u3cem\u3ePseudonocardia thermophila\u3c/em\u3e in a Sol–gel Matrix
The cobalt-type nitrile hydratase from Pseudonocardia thermophila JCM 3095 (PtNHase) was successfully encapsulated in tetramethyl orthosilicate sol–gel matrices to produce a PtNHase:sol–gel biomaterial. The PtNHase:sol–gel biomaterial catalyzed the conversion of 600 mM acrylonitrile to acrylamide in 60 min at 35 °C with a yields of \u3e90%. Treatment of the biomaterial with proteases confirmed that the catalytic activity is due to the encapsulated enzyme and not surface bound NHase. The biomaterial retained 50% of its activity after being used for a total of 13 consecutive reactions for the conversion of acrylonitrile to acrylamide. The thermostability and long-term storage of the PtNHase:sol–gel are substantially improved compared to the soluble NHase. Additionally, the biomaterial is significantly more stable at high concentrations of methanol (50% and 70%, v/v) as a co-solvent for the hydration of acrylonitrile than native PtNHase. These data indicate that PtNHase:sol–gel biomaterials can be used to develop new synthetic avenues involving nitriles as starting materials given that the conversion of the nitrile moiety to the corresponding amide occurs under mild temperature and pH conditions
A Sampling Study of the Blue Point Woods, Poweshiek, Co., Iowa
During the fall of 1953 a study was made of the Blue Point Woods, an area located approximately nine miles southeast of Grinnell, in Section 14 of Washing ton Township, Poweshiek County, Iowa. The Blue Point forest is clearly divided into three stands, two of which are approximately the same age and older than the last. These stands are oriented in a north-south direction. From north to south, respectively, we find an old, grazed stand; a younger, cut-over stand; and a very old, undisturbed stand. The old, grazed stand is fairly open with little in the way of herbaceous and frutescent layers other than blue grass (Poa pratensis) and Ribes spp. The younger, cut-over stand is densely populated with trees, shrubs, and herbs. The undisturbed stand is made up of many large trees forming a dense canopy. The herbaceous and frutescent layers are also well developed and include many transgressives and tree seedlings. The investigation occurred so late in the year that no attempt was made to sample the herbaceous flora
Elevated Substitution Rates Among Wolbachia-infected Mosquito Species Results in Apparent Phylogenetic Discordance.
As one of the most widely distributed bacterial cytoplasmic symbionts on earth, Wolbachia pipientis Hertig serves as a model organism for the understanding of host-symbiont interactions. Many mosquito species are infected with Wolbachia strains that induce a form of reproductive manipulation called cytoplasmic incompatibility, in which infected females gain a reproductive advantage over uninfected females in mixed infection populations. The selective advantage of cytoplasmic incompatibility often results in a population sweep of Wolbachia and co-transmitted mitochondrial genomes. Mitochondrial evolution and phylogenetic inferences drawn from mitochondrial gene sequences are thus potentially compromised by reproductive manipulating symbionts, like Wolbachia. Our initial analyses of phylogenetic patterns among collected Wolbachia-infected and uninfected mosquito species suggested significant Wolbachia-induced effects on mitochondrial evolutionary patterns. Discordant mitochondrial and nuclear phylogenies among Aedes and Culex species were associated with infections status, with a distinct mitochondrial clade of infected Aedes and Culex species, separate from uninfected species of the genera. Statistical analyses of molecular substitution among infected and uninfected sequence samples revealed elevated rates of substitution for the mitochondrial sequences of the discordant infected Aedes/Culex clade. Subsequent phylogenetic analyses suggested that the observed discordance could be attributed to long-branch attraction effects associated with elevated rates of substitution. Our results highlight the impact cytoplasmic selection can have on phylogenetic inference in limited sample sets with Wolbachia-infected and uninfected species
Infections Associated with Bartonella Species in Persons Infected with Human Immunodeficiency Virus
Two members of the genus Bartonella, Bartonella quintana (formerly Rochalimaea quintana) and Bartonella henselae (formerly Rochalimaea henselae), have recently been recognized as agents of severe or fatal disease in patients infected with human immunodeficiencyv irus (HIV). The development of infection with B. henselae in HIV-infected individuals has been associated with traumatic contact with cats (scratches or bites), and domestic cats have been identified as a major reservoir for this organism. Specific information regarding the transmission of B. henselae to humans is not yet available, but common-sense precautions that minimize exposure to cat-associated organisms are appropriate. Preliminary accounts suggest that B. quintana infections are more common than B. henselae infections among HIV-infected individuals in San Francisco. The source of infection with B. quintana and the mechanism of its transmission remain unknown
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