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Determining efficient temperature sets for the simulated tempering method
In statistical physics, the efficiency of tempering approaches strongly
depends on ingredients such as the number of replicas , reliable
determination of weight factors and the set of used temperatures, . For the simulated tempering (SP) in
particular -- useful due to its generality and conceptual simplicity -- the
latter aspect (closely related to the actual ) may be a key issue in
problems displaying metastability and trapping in certain regions of the phase
space. To determine 's leading to accurate thermodynamics
estimates and still trying to minimize the simulation computational time, here
it is considered a fixed exchange frequency scheme for the ST. From the
temperature of interest , successive 's are chosen so that the exchange
frequency between any adjacent pair and has a same value .
By varying the 's and analyzing the 's through relatively
inexpensive tests (e.g., time decay toward the steady regime), an optimal
situation in which the simulations visit much faster and more uniformly the
relevant portions of the phase space is determined. As illustrations, the
proposal is applied to three lattice models, BEG, Bell-Lavis, and Potts, in the
hard case of extreme first-order phase transitions, always giving very good
results, even for . Also, comparisons with other protocols (constant
entropy and arithmetic progression) to choose the set are
undertaken. The fixed exchange frequency method is found to be consistently
superior, specially for small 's. Finally, distinct instances where the
prescription could be helpful (in second-order transitions and for the parallel
tempering approach) are briefly discussed.Comment: 10 pages, 14 figure
Comparative Studies of Phytophthora Palmivora from Cocoa and Durian and Their Control
Phytophthora palmivora (But 1.) Butler is known to be a
variable or ganism and is considered to be one of the most
destructive pathogens of cocoa and durian which are being
inter cropped in Malaysia. Studies were under taken to compare the
cultural characteristics, sexuality, and pathogenicity of six
Phytophthora isolates from these crops as well as the in-vitro and
in-vivo efficacy of fungicide s against the pathogen. Preliminary
studies on the use of a bio-control agent against the organism
were also looked into.
Cultural studies established that the Phytophthora isolates
belonged to MFI P. palmivora. They produced stellate and striate colonies on carrot, cornmeal, and V-8 juice agar media. Mycelial
growth was opt imum at 28 + 1.5C. No growth occurred at 36C.
Sporangia were caducous, with length: breadth ratios from 1.22 to
1.8 and possessed short, occluded pedicels. Abundant
chlamydospores were produced in culture
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