603 research outputs found
HHSMT Observations of the Venusian Mesospheric Temperature, Winds, and CO abundance around the MESSENGER Flyby
We present submillimeter observations of 12CO J=3-2 and J=2-1, and 13CO J =
2-1 lines of the Venusian mesosphere and lower thermosphere with the Heinrich
Hertz Submillimeter Telescope (HHSMT) taken around the second MESSENGER flyby
of Venus on 5 June 2007. The observations cover a range of Venus solar
elongations with different fractional disk illuminations. Preliminary results
like temperature and CO abundance profiles are presented.These data are part of
a coordinated observational campaign in support of the ESA Venus Express
mission. Furthermore, this study attempts to contribute to cross-calibrate
space- and ground-based observations, to constrain radiative transfer and
retrieval algorithms for planetary atmospheres, and to a more thorough
understanding of the global patters of circulation of the Venusian atmosphere.Comment: 12 pages, 8 figures. Latex, uses elsart.cls (included). Higher
resolution figures in original article. Planetary and Space Science, in pres
Submillimetric spectroscopic observations of volatiles in comet C/2004 Q2 (Machholz)
We aim to determine the production rates of several parent and product
volatiles and the 12C/13C isotopic carbon ratio in the long-period comet C/2004
Q2 (Machholz), which is likely to originate from the Oort Cloud. The line
emission from several molecules in the coma was measured with high
signal-to-noise ratio in January 2005 at heliocentric distance of 1.2 AU by
means of high-resolution spectroscopic observations using the Submillimeter
Telescope (SMT). We have obtained production rates of several volatiles (CH3OH,
HCN, H13CN, HNC, H2CO, CO and CS) by comparing the observed and simulated
line-integrated intensities. Furthermore, multiline observations of the CH3OH
(7-6) series allow us to estimate the rotational temperature using the rotation
diagram technique. We find that the CH3OH population distribution of the levels
sampled by these lines can be described by a rotational temperature of 40 \pm 3
K. Derived mixing ratios relative to hydrogen cyanide are
CO/CH3OH/H2CO/CS/HNC/H13CN/HCN = 30.9/24.6/4.8/0.57/0.031/0.013/1 assuming a
pointing offset of 8" due to the uncertain ephemeris at the time of the
observations and the telescope pointing error. The measured relative molecular
abundances in C/2004 Q2 (Machholz) are between low- to typical values of those
obtained in Oort Cloud comets, suggesting that it has visited the inner solar
system previously and undergone thermal processing. The HNC/HCN abundance ratio
of ~3.1% is comparable to that found in other comets, accounting for the
dependence on the heliocentric distance, and could possibly be explained by
ion-molecule chemical processes in the low-temperature atmosphere. From a
tentative H13CN detection, the measured value of 97 \pm 30 for the H12CN/H13CN
isotopologue pair is consistent with a telluric value.Comment: 14 pages with 11 figures, abridged abstrac
Estratégia competitiva de uma multinacional estrangeira na avicultura de postura no Brasil.
Este estudo aborda a questão das estratégias envolvidas no processo de importação de gaiolas para aves de postura, direcionadas ao centro de distribuição de uma multinacional estrangeira localizada em Araraquara, São Paulo. Identifica as razões que levam uma empresa multinacional a aumentar seus investimentos no Brasil, onde está implantando um centro de distribuição (CD). Para estudar as estratégias envolvidas no processo, realizou-se pesquisa exploratória sobre o atual processo logÃstico da empresa, buscando identificar tais estratégias e as vantagens do novo processo. O trabalho apoia-se nas cinco forças competitivas de Porter, na análise SWOT, nas estratégias genéricas adotadas para obtenção de retorno sobre os investimentos e ainda, fundamenta-se em temas como, importação, logÃstica, armazenagem e centro de distribuição. A pesquisa demonstra que a implantação do CD envolve a estratégia de inserção do produto no mercado nacional, especificamente em São Paulo, onde está o maior mercado de aves de postura do PaÃs. Para obter vantagem competitiva, a multinacional adota ainda a estratégia genérica da diferenciação, com foco em tecnologia e qualidade do produto. Apesar dos altos custos da construção e manutenção do CD representarem uma barreira de entrada no mercado, o investimento não representa risco financeiro, já que aumentará a demanda pelo produto, resultando maior retorno sobre o capital investido
Synergism between feremycorrhizal symbiosis and free-living diazotrophs leads to improved growth and nutrition of wheat under nitrogen deficiency conditions
A controlled-environment study was conducted to explore possible synergistic interactions between the feremycorrhizal (FM) fungus Austroboletus occidentalis and soil free-living N2-fixing bacteria (diazotrophs). Wheat (Triticum aestivum) plants were grown under N deficiency conditions in a field soil without adding microbial inoculum (control: only containing soil indigenous microbes), or inoculated with a consortium containing four free-living diazotroph isolates (diazotrophs treatment), A. occidentalis inoculum (FM treatment), or both diazotrophs and A. occidentalis inoculums (dual treatment). After 7 weeks of growth, significantly greater shoot biomass was observed in plants inoculated with diazotrophs (by 25%), A. occidentalis (by 101%), and combined inoculums (by 106%), compared to the non-inoculated control treatment. All inoculated plants also had higher shoot nutrient contents (including N, P, K, Mg, Zn, Cu, and Mn) than the control treatment. Compared to the control and diazotrophs treatments, significantly greater shoot N content was observed in the FM treatment (i.e., synergism between the FM fungus and soil indigenous diazotrophs). Dually inoculated plants had the highest content of nutrients in shoots (e.g., N, P, K, S, Mg, Zn, Cu, and Mn) and soil total N (13–24% higher than the other treatments), i.e., synergism between the FM fungus and added diazotrophs. Root colonization by soil indigenous arbuscular mycorrhizal fungi declined in all inoculated plants compared to control. Non-metric multidimensional scaling (NMDS) analysis of the bacterial 16S rRNA gene amplicons revealed that the FM fungus modified the soil microbiome. Our in vitro study indicated that A. occidentalis could not grow on substrates containing lignocellulosic materials or sucrose, but grew on media supplemented with hexoses such as glucose and fructose, indicating that the FM fungus has limited saprotrophic capacity similar to ectomycorrhizal fungi. The results revealed synergistic interactions between A. occidentalis and soil free-living diazotrophs, indicating a potential to boost microbial N2 fixation for non-legume crops
Overexpression of toll-like receptors 3 and 4 in synovial tissue from patients with early rheumatoid arthritis: Toll-like receptor expression in early and longstanding arthritis
OBJECTIVE: To analyze the expression, regulation, and biologic relevance of Toll-like receptors (TLRs) 1-10 in synovial and skin fibroblasts and to determine the expression levels of TLRs 2, 3, and 4 in synovial tissues from patients with early rheumatoid arthritis (RA), longstanding RA, and osteoarthritis (OA). METHODS: Expression of TLRs 1-10 in RA synovial fibroblasts (RASFs), OASFs, and skin fibroblasts was analyzed by real-time polymerase chain reaction (PCR). Fibroblasts were stimulated with tumor necrosis factor alpha, interleukin-1beta (IL-1beta), bacterial lipopeptide, poly(I-C), lipopolysaccharide, and flagellin. Production of IL-6 was determined by enzyme-linked immunosorbent assay and induction of TLRs 2-5, matrix metalloproteinases (MMPs) 3 and 13 messenger RNA by real-time PCR. Expression of TLRs 2-4 in synovial tissues was analyzed by immunohistochemistry. RESULTS: Synovial fibroblasts expressed TLRs 1-6, but not TLRs 7-10. Among the expressed TLRs, TLR-3 and TLR-4 were the most abundant in synovial fibroblasts, and stimulation of synovial fibroblasts with the TLR-3 ligand poly(I-C) led to the most pronounced increase in IL-6, MMP-3, and MMP-13. In contrast, skin fibroblasts did not up-regulate MMP-3 or MMP-13 after stimulation with any of the tested stimuli. In synovial tissues from patients with early RA, TLR-3 and TLR-4 were highly expressed and were comparable to the levels of patients with longstanding RA. These expression levels were elevated as compared with those in OA. CONCLUSION: Our findings of high expression of TLRs, particularly TLRs 3 and 4, at an early stage of RA and the reactivity of synovial fibroblasts in vitro to TLR ligands suggest that TLR signaling pathways resulting in persistent inflammation and joint destruction are activated early in the disease process
Editorial: Frontiers in astronomy and space sciences: Rising stars
Editorial on the Research Topic Frontiers in astronomy and space sciences: Rising star
Inmigrants and education in Facultad de Ciencias Exactas, Universidad Nacional de La Plata. Considerations on the educational experience
El objetivo de este trabajo de investigación es compartir algunos datos, análisis y reflexiones sobre las experiencias universitarias de estudiantes extranjeros en la Facultad de Ciencias Exactas de la Universidad Nacional de La Plata. Conocer nuestros estudiantes y sus vidas durante el trayecto universitario se configura en un tema de interés para mejorar y actualizar nuestras prácticas docentes generándolas de forma inclusiva y democrática. En este estudio nos centramos en una población particular del estudiantado, los alumnos extranjeros. Sus experiencias en la educación superior se ven atravesadas transversalmente por la cuestión migrante de una manera particular. En esta publicación se analizarán datos poblacionales de los últimos años. Se presenta esta investigación desarrollada en dos partes principales. La primera, es un análisis cuantitativo de la presencia de estudiantes extranjeros en Exactas, incluimos datos de número de ingresantes, nacionalidad y carrera elegida. En la segunda parte del trabajo se analiza y discute una investigación exploratoria realizada con los estudiantes migrantes sobre los siguientes temas: motivaciones para la inmigración, representaciones de la Universidad argentina y anhelos personales, experiencias iniciales en la Facultad, relaciones sociales en La Plata, trabajo y vida económica y por último dificultades, situaciones de discriminación y violencia.The objective of this research work is to share some data, analysis and reflections on the university experiences of foreign students at the Faculty of Exact Sciences of the National University of La Plata. Knowing our students and their lives during the university journey becomes a topic of interest to improve and update our teaching practices, generating them in an inclusive and democratic way. In this study we focus on a particular population of the student body, foreign students. Their expe-riences in higher education are traversed by the migrant issue in a particular way.Especialización en Docencia Universitari
Searches for HCl and HF in comets 103P/Hartley 2 and C/2009 P1 (Garradd) with the Herschel space observatory
HCl and HF are expected to be the main reservoirs of fluorine and chlorine
wherever hydrogen is predominantly molecular. They are found to be strongly
depleted in dense molecular clouds, suggesting freeze-out onto grains in such
cold environments. We can then expect that HCl and HF were also the major
carriers of Cl and F in the gas and icy phases of the outer solar nebula, and
were incorporated into comets. We aimed to measure the HCl and HF abundances in
cometary ices as they can provide insights on the halogen chemistry in the
early solar nebula. We searched for the J(1-0) lines of HCl and HF at 626 and
1232 GHz, respectively, using the HIFI instrument on board the Herschel Space
Observatory. HCl was searched for in comets 103P/Hartley 2 and C/2009 P1
(Garradd), whereas observations of HF were conducted in comet C/2009 P1. In
addition, observations of HO and HO lines were performed in C/2009
P1 to measure the HO production rate. Three lines of CHOH were
serendipitously observed in the HCl receiver setting. HCl is not detected,
whereas a marginal (3.6-) detection of HF is obtained. The upper limits
for the HCl abundance relative to water are 0.011% and 0.022%, for 103P and
C/2009 P1, respectively, showing that HCl is depleted with respect to the solar
Cl/O abundance by a factor more than 6 in 103P, where the error is
related to the uncertainty in the chlorine solar abundance. The marginal HF
detection obtained in C/2009 P1 corresponds to an HF abundance relative to
water of (1.80.5) 10, which is approximately consistent
with a solar photospheric F/O abundance. The observed depletion of HCl suggests
that HCl was not the main reservoir of chlorine in the regions of the solar
nebula where these comets formed. HF was possibly the main fluorine compound in
the gas phase of the outer solar nebula.Comment: Accepted for publication in Astronomy & Astrophysic
"TNOs are Cool": A survey of the trans-Neptunian region VI. Herschel/PACS observations and thermal modeling of 19 classical Kuiper belt objects
Trans-Neptunian objects (TNO) represent the leftovers of the formation of the
Solar System. Their physical properties provide constraints to the models of
formation and evolution of the various dynamical classes of objects in the
outer Solar System. Based on a sample of 19 classical TNOs we determine
radiometric sizes, geometric albedos and beaming parameters. Our sample is
composed of both dynamically hot and cold classicals. We study the correlations
of diameter and albedo of these two subsamples with each other and with orbital
parameters, spectral slopes and colors. We have done three-band photometric
observations with Herschel/PACS and we use a consistent method for data
reduction and aperture photometry of this sample to obtain monochromatic flux
densities at 70.0, 100.0 and 160.0 \mu m. Additionally, we use Spitzer/MIPS
flux densities at 23.68 and 71.42 \mu m when available, and we present new
Spitzer flux densities of eight targets. We derive diameters and albedos with
the near-Earth asteroid thermal model (NEATM). As auxiliary data we use
reexamined absolute visual magnitudes from the literature and data bases, part
of which have been obtained by ground based programs in support of our Herschel
key program. We have determined for the first time radiometric sizes and
albedos of eight classical TNOs, and refined previous size and albedo estimates
or limits of 11 other classicals. The new size estimates of 2002 MS4 and 120347
Salacia indicate that they are among the 10 largest TNOs known. Our new results
confirm the recent findings that there are very diverse albedos among the
classical TNOs and that cold classicals possess a high average albedo (0.17 +/-
0.04). Diameters of classical TNOs strongly correlate with orbital inclination
in our sample. We also determine the bulk densities of six binary TNOs.Comment: 21 pages, 9 figures, accepted for publication in Astronomy and
Astrophysic
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