4,282 research outputs found
Viscous Cosmology
We discuss the possibility to implement a viscous cosmological model,
attributing to the dark matter component a behaviour described by bulk
viscosity. Since bulk viscosity implies negative pressure, this rises the
possibility to unify the dark sector. At the same time, the presence of
dissipative effects may alleviate the so called small scale problems in the
CDM model. While the unified viscous description for the dark sector
does not lead to consistent results, the non-linear behaviour indeed improves
the situation with respect to the standard cosmological model.Comment: Latex file, 7 pages, 6 figures. To appear in the proceedings of the
XIIth International Conference on Gravitation, Astrophysics and Cosmology,
June 28-July 5, 2015, PFUR, Moscow, Russi
Accretion Signatures from Massive Young Stellar Objects
High resolution (lambda / Delta-lambda = 50,000) K-band spectra of massive,
embedded, young stellar objects are presented. The present sample consists of
four massive young stars located in nascent clusters powering Galactic giant H
II regions. Emission in the 2.3 micron 2--0 vibrational--rotational bandhead of
CO is observed. A range of velocity broadened profiles seen in three of the
objects is consistent with the emission arising from a circumstellar disk seen
at various inclination angles. Br gamma spectra of the same spectral and
spatial resolution are also presented which support an accretion disk or torus
model for massive stars. In the fourth object, Br emission suggesting a
rotating torus is observed, but the CO profile is narrow, indicating that there
may be different CO emission mechanisms in massive stars and this is consistent
with earlier observations of the BN object and MWC 349. To--date, only young
massive stars of late O or early B types have been identified with clear
accretion disk signatures in such embedded clusters. Often such stars are found
in the presence of other more massive stars which are revealed by their
photospheric spectra but which exhibit no disk signatures. This suggests the
timescale for dissipating their disks is much faster than the less massive OB
stars or that the most massive stars do not form with accretion disks.Comment: 28 pages, 10 Figures, accepted for publication in the Astrophysical
Journa
Seleção de rizóbios nativos de solos de Mato Grosso do Sul para inoculação em espécies de adubo verde.
bitstream/item/68485/1/091-Selecao-de-rizobios-nativos-de-solos-de-Mato-Grosso-do-Sul.pdfPublicado também no Cadernos de Agroecologia, v. 7, n. 2, 2012
Diagnose e perdas na cadeia produtiva da manga causadas por Neofusicoccum parvum.
Considerada uma das principais culturas do poloagrícola Petrolina, PE/Juazeiro, BA, a mangueira éresponsável por grande parte da absorção de mão-de-obra e de geração de divisas para a região. Este polocontribui com mais de 90% da exportação nacional demanga (ARAÚJO; CORREIA, 2004; PINTOet al.,2004). Entretanto, diferentes patógenos têm colocadoem risco o agronegócio da manga, a exemplo daspodridões causadas por fungos. Agentes de doençasque possuem a fase quiescente podem comprometer acredibilidade de produtores e fornecedores da fruta emrelação ao mercado consumidor. Podridões podemafetar a cultura da manga, e dentre os agentes causaispodem-se destacar os fungos Colletotrichumgloeosporioides, Alternariaalternata, Lasiodiplodiatheobromae(CHOUDHURY; COSTA, 2004) e o maisrecente, Neofusicoccum parvum (COSTA, 2008). Alémde podridão mole e/ou peduncular em manga, oNeofusicoccum parvum pode causar morte descendentee queima de inflorescência (SAAIMAN, 1997; PLOETZ;FREEMAN, 2009), ocasionando grandes perdas naprodução de manga.bitstream/item/17590/1/Comunicado-Neofusicoccum.pd
Comportamento de pomeleiros e laranjeiras doce da Embrapa Mandioca e Fruticultura em relação ao Citrus Tristeza virus e ao descamamento eruptivo.
O Citrus tristeza virus (CTV) é uma das principais viroses que ameaçam as plantas cítricas no Brasil. O descamamento eruptivo dos citros (Bahia Bark Scaling, BBS) é uma doença restrita à citricultura da Bahia e de Sergipe, que afeta pomeleiros (C. paradisi Macfadyen), tangerineiras (C. reticulata Blanco) e laranjeiras doce (C. sinensis L.), e ainda tem sua etiologia e método diagnóstico não estabelecidos.PDF. 160_11
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