1,046 research outputs found
Nutrição mineral de hortaliças: XXIV - carência de macronutrientes em berinjela (Solanum melongena L.)
Plantas de berinjela (Solanum melongena L. var. Híbrida F1, Piracicaba nº 100) foram cultivadas em vasos contendo sílica lavada. As plantas foram irrigadas com solução nutritiva purificada e submetidas aos seguintes tratamentos: completo, omissão de B, Cu, Fe, Mn, Mo e Zn. Os sintomas de carência desses elementos foram identificados e descritos. Aquilatou-se a possibilidade de recuperação de plantas deficientes fornecendo-se o elemento. Finalmente, as plantas foram separadas em: raiz, caule superior e inferior, folhas velhas e novas, frutos, e analisadas para B, Cu, Fe, Mn e Zn. A análise química das folhas afetadas pelas carências apresentou os seguintes valores (ppm): B- 48-71; Cu- 1-2; Fe- 169-204; Mn- .42-80; Zn- 37-38. Nas folhas sadias os valores foram (ppm): B- 70-82; Cu- 8; Fe- 192-283; Mn- 54-118; Zn- 52-54.Eggplants were grown in pots containing 7 kg of pure quartz sand. Twice a day they were irrigated by percolation with nutrient solutions. The treatments were: complete, -B, -Cu, -Fe, -Mn, -Zn. The deficiencies symptoms are described. The deficiencies were comproved by chemical analysis of the different parts of the plants. The following concentration, expressed in ppm in dry matter are
Determining the density of states for classical statistical models: A random walk algorithm to produce a flat histogram
We describe an efficient Monte Carlo algorithm using a random walk in energy
space to obtain a very accurate estimate of the density of states for classical
statistical models. The density of states is modified at each step when the
energy level is visited to produce a flat histogram. By carefully controlling
the modification factor, we allow the density of states to converge to the true
value very quickly, even for large systems. This algorithm is especially useful
for complex systems with a rough landscape since all possible energy levels are
visited with the same probability. In this paper, we apply our algorithm to
both 1st and 2nd order phase transitions to demonstrate its efficiency and
accuracy. We obtained direct simulational estimates for the density of states
for two-dimensional ten-state Potts models on lattices up to
and Ising models on lattices up to . Applying this approach to
a 3D spin glass model we estimate the internal energy and entropy at
zero temperature; and, using a two-dimensional random walk in energy and
order-parameter space, we obtain the (rough) canonical distribution and energy
landscape in order-parameter space. Preliminary data suggest that the glass
transition temperature is about 1.2 and that better estimates can be obtained
with more extensive application of the method.Comment: 22 pages (figures included
Measuring CMB Polarization with BOOMERANG
BOOMERANG is a balloon-borne telescope designed for long duration (LDB)
flights around Antarctica. The second LDB Flight of BOOMERANG took place in
January 2003. The primary goal of this flight was to measure the polarization
of the CMB. The receiver uses polarization sensitive bolometers at 145 GHz.
Polarizing grids provide polarization sensitivity at 245 and 345 GHz. We
describe the BOOMERANG telescope noting changes made for 2003 LDB flight, and
discuss some of the issues involved in the measurement of polarization with
bolometers. Lastly, we report on the 2003 flight and provide an estimate of the
expected results.Comment: 12 pages, 8 figures, To be published in the proceedings of "The
Cosmic Microwave Background and its Polarization", New Astronomy Reviews,
(eds. S. Hanany and K.A. Olive). Fixed typos, and reformatted citation
Spanning forests and the q-state Potts model in the limit q \to 0
We study the q-state Potts model with nearest-neighbor coupling v=e^{\beta
J}-1 in the limit q,v \to 0 with the ratio w = v/q held fixed. Combinatorially,
this limit gives rise to the generating polynomial of spanning forests;
physically, it provides information about the Potts-model phase diagram in the
neighborhood of (q,v) = (0,0). We have studied this model on the square and
triangular lattices, using a transfer-matrix approach at both real and complex
values of w. For both lattices, we have computed the symbolic transfer matrices
for cylindrical strips of widths 2 \le L \le 10, as well as the limiting curves
of partition-function zeros in the complex w-plane. For real w, we find two
distinct phases separated by a transition point w=w_0, where w_0 = -1/4 (resp.
w_0 = -0.1753 \pm 0.0002) for the square (resp. triangular) lattice. For w >
w_0 we find a non-critical disordered phase, while for w < w_0 our results are
compatible with a massless Berker-Kadanoff phase with conformal charge c = -2
and leading thermal scaling dimension x_{T,1} = 2 (marginal operator). At w =
w_0 we find a "first-order critical point": the first derivative of the free
energy is discontinuous at w_0, while the correlation length diverges as w
\downarrow w_0 (and is infinite at w = w_0). The critical behavior at w = w_0
seems to be the same for both lattices and it differs from that of the
Berker-Kadanoff phase: our results suggest that the conformal charge is c = -1,
the leading thermal scaling dimension is x_{T,1} = 0, and the critical
exponents are \nu = 1/d = 1/2 and \alpha = 1.Comment: 131 pages (LaTeX2e). Includes tex file, three sty files, and 65
Postscript figures. Also included are Mathematica files forests_sq_2-9P.m and
forests_tri_2-9P.m. Final journal versio
Influence of edapho-climatic factors on the sporulation and colonization of arbuscular mycorrhizal fungi in two Amazonian native fruit species
Arbuscular mycorrhizal fungi (AMF) colonization and spore numbers in the rhizosphere of two fruit species, Paullinia cupana Mart. and Theobroma grandiflorum Schum., growing in a terra firme ecosystem in Central Amazonia were studied from August 1998 to May 2000. Climatic and edaphic factors were also determined to investigate their influence on mycorrhizal variables. Soil pH, Al, Mn and effective cation exchange capacity exhibited seasonal variations during the investigation period. Temporal variations in mycorrhizal colonization levels and spore numbers occurred, indicating seasonality. Moreover, the patterns of mycorrhizal colonization levels and spore numbers for both host species were similar during the studied period. Mycorrhizal variables were related to climatic and edaphic factors, however, the intensity and type of influence of climatic and soil characteristics on AMF development tended to vary with the season and host plant species in Central Amazonia conditions
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