947 research outputs found
Absence of Effective Vesicular-Arbuscular Mycorrhizae on Lecythidaceae in a Primary Forest Area of Central Amazonia.
Lecythidaceae comprise one of the four most common tree families in the Amazon forest, but there have been few studies of vesicular-arbuscular mycorrhizae in this taxon. In this study roots of 31 species in six genera of Lecythidaceae were collected in a primary forest on an acid oxisol. No vesicular-arbuscular mycorrhizae, as indicated by the presence of vesicles or arbuscules were detected. Only some hyfas were found on some species roots, but not enough for increasing the nutrient absorption from the soil. This indicated that under the edaphic condiction and the time which the samples were collected, these species worked as no mycor-rhizal plants. These informations confirm datas found for other researches, and may be important for exploring more efficiently and by a not predatory way, the species of Lecythidaceae on agroforestry systems in the Amazon.As Lecythidaceae compreendem uma das quatro famĂlias de ĂĄrvores mais abundantes na floresta amazĂŽnica, mas foram pouco estudadas no que sc refere Ă simbiose com fungos micorrĂzicos dos solos. Foram coletadas raĂzes de 31 espĂ©cies de seis gĂȘneros desta famĂlia numa floresta de terra firme da AmazĂŽnia Central, prĂłxima a Manaus, sob um latossolo amarelo. Em algumas espĂ©cies observou-se uma ausĂȘncia total de fungos nas raĂzes, enquanto que em outras, apenas algumas hifas de fungos, mas sem vesĂculas ou arbĂșsculos, estruturas que serviriam para confirmar a presença de micorrizas vesĂculo-arbusculares efetivas nas mesmas. As poucas bifas encontradas nĂŁo seriam suficientes para aumentar a absorção de nutrientes do solo, indicando que nas condiçÔes edĂĄficas e Ă©pocas de coletas do presente estudo, as plantas se comportaram como nĂŁo micorrizicas. Estas informaçÔes reforçam dados obtidos por outros autores e podem servir de embasamento para uma exploração mais eficiente e nĂŁo predatĂłria de espĂ©cies desta famĂlia em sistemas agroflorestais na AmazĂŽnia
Turning to God in the Face of Ostracism: Effects of Social Exclusion on Religiousness
The present research proposes that individuals who are socially excluded can turn to religion to cope with the experience. Empirical studies conducted to test this hypothesis consistently found that socially excluded persons reported (a) significantly higher levels of religious affiliation (Studies 1, 2, and 4) and (b) stronger intentions to engage in religious behaviors (Study 2) than comparable, nonexcluded individuals. Direct support for the stress-buffering function of religiousness was also found, with a religious prime reducing the aggression-eliciting effects of consequent social rejection (Study 5). These effects were observed in both Christian and Muslim samples, revealing that turning to religion can be a powerful coping response when dealing with social rejection. Theoretical and practical implications of these findings are discussed
Connectivity clues from short-term variability in settlement and geochemical tags of mytilid mussels
The use of geochemical tags in calcified structures of fish and invertebrates is an exciting tool for investigating larval population connectivity. Tag evaluation over relatively short intervals (weeks) may detect environmental and ecological variability at a temporal scale highly relevant to larval transport and settlement. We collected newly settled mussels (Mytilus californianus and M. galloprovincialis) weekly during winter/spring of 2002 along the coast of San Diego, CA, USA, at sites on the exposed coast (SIO) and in a protected coastal bay (HI), to investigate temporal patterns of geochemical tags in mussel shells. Analyses of post-settlement shell via LA-ICP-MS revealed statistically significant temporal variability for all elements we examined (Mg, Mn, Cu, Sr, Cd, Ba, Pb and U). Despite this, our ability to distinguish multielemental signatures between sites was largely conserved. Throughout our 13-week study, SIO and HI mussels could be chemically distinguished from one another in 78-87% of all cases. Settlement varied between 2 and 27 settlers gram-byssus-1week-1 at SIO and HI, and both sites were characterized by 2-3weeks with "high" settlement. Geochemical tags recorded in early larval shell of newly settled mussels differed between "high" and "low" settlement weeks at both sites (MANOVA), driven by Mg and Sr at SIO (p=0.013) and Sr, Cd, Ba and Pb at HI (p<0.001). These data imply that shifts in larval sources or transport corridors were responsible for observed settlement variation, rather than increased larval production. In particular, increased settlement at HI was observed concurrent with the appearance of geochemical tags (e.g., elevated Cd), suggesting that those larvae were retained in upwelled water near the mouth of the bay. Such shifts may reflect short-term changes in connectivity among sites due to altered transport corridors, and influence the demography of local populations
Classical Cepheids: Yet another version of the Baade-Becker-Wesselink method
We propose a new version of the Baade--Becker--Wesselink technique, which
allows one to independently determine the colour excess and the intrinsic
colour of a radially pulsating star, in addition to its radius, luminosity, and
distance. It is considered to be a generalization of the Balona approach. The
method also allows the function F(CI) = BC + 10 log (Teff) for the class of
pulsating stars considered to be calibrated. We apply this technique to a
number of classical Cepheids with very accurate light and radial-velocity
curves and with bona fide membership in open clusters (SZ Tau, CF Cas, U Sgr,
DL Cas, GY Sge), and find the results to agree well with the reddening
estimates of the host open clusters. The new technique can also be applied to
other pulsating variables, e.g. RR Lyrae and RV Tauri.Comment: 6 pages, 2 figures, 1 table; Submitted to Astrophysical Bulletin,
201
Sugars of pearl millet [Pennisetum americanum (L.) Leeke] grains
The sugars in the grains of nine pearl millet cultivars were fractionated through a Biogel column. Five different sugarsâ(stachyose, raffinose, sucrose, glucose, and fructose) were identified. Sucrose was predominant in all the cultivars. Raffinose content was high as compared to other cereals, and maltose was absen
Non-Kaehler Heterotic String Compactifications with non-zero fluxes and constant dilaton
We construct new explicit compact supersymmetric valid solutions with
non-zero field strength, non-flat instanton and constant dilaton to the
heterotic equations of motion in dimension six. We present balanced Hermitian
structures on compact nilmanifolds in dimension six satisfying the heterotic
supersymmetry equations with non-zero flux, non-flat instanton and constant
dilaton which obey the three-form Bianchi identity with curvature term taken
with respect to either the Levi-Civita, the (+)-connection or the Chern
connection. Among them, all our solutions with respect to the (+)-connection on
the compact nilmanifold satisfy the heterotic equations of motion.Comment: LaTeX, 16 pp., no figures, new Theorem 1.1, references adde
Quasars and their host galaxies
This review attempts to describe developments in the fields of quasar and
quasar host galaxies in the past five. In this time period, the Sloan and 2dF
quasar surveys have added several tens of thousands of quasars, with Sloan
quasars being found to z>6. Obscured, or partially obscured quasars have begun
to be found in significant numbers. Black hole mass estimates for quasars, and
our confidence in them, have improved significantly, allowing a start on
relating quasar properties such as radio jet power to fundamental parameters of
the quasar such as black hole mass and accretion rate. Quasar host galaxy
studies have allowed us to find and characterize the host galaxies of quasars
to z>2. Despite these developments, many questions remain unresolved, in
particular the origin of the close relationship between black hole mass and
galaxy bulge mass/velocity dispersion seen in local galaxies.Comment: Review article, to appear in Astrophysics Update
Homogeneous nucleation of quark-gluon plasma, finite size effects and long-lived metastable objects
The general formalism of homogeneous nucleation theory is applied to study
the hadronization pattern of the ultra-relativistic quark-gluon plasma (QGP)
undergoing a first order phase transition. A coalescence model is proposed to
describe the evolution dynamics of hadronic clusters produced in the nucleation
process. The size distribution of the nucleated clusters is important for the
description of the plasma conversion. The model is most sensitive to the
initial conditions of the QGP thermalization, time evolution of the energy
density, and the interfacial energy of the plasma-hadronic matter interface.
The rapidly expanding QGP is first supercooled by about . Then it reheats again up to the critical temperature T_c. Finally it
breaks up into hadronic clusters and small droplets of plasma. This fast
dynamics occurs within the first . The finite size effects and
fluctuations near the critical temperature are studied. It is shown that a drop
of longitudinally expanding QGP of the transverse radius below 4.5 fm can
display a long-lived metastability. However, both in the rapid and in the
delayed hadronization scenario, the bulk pion yield is emitted by sources as
large as 3-4.5 fm. This may be detected experimentally both by a HBT
interferometry signal and by the analysis of the rapidity distributions of
particles in narrow p_T-intervals at small p_T on an event-by-event basis.Comment: 29 pages, incl. 12 figures and 1 table; to be published in Phys. Rev.
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