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961.
Stewart JJ 《Journal of molecular modeling》2007,13(12):1173-1213
Several modifications that have been made to the NDDO core-core interaction term and to the method of parameter optimization
are described. These changes have resulted in a more complete parameter optimization, called PM6, which has, in turn, allowed
70 elements to be parameterized. The average unsigned error (AUE) between calculated and reference heats of formation for
4,492 species was 8.0 kcal mol−1. For the subset of 1,373 compounds involving only the elements H, C, N, O, F, P, S, Cl, and Br, the PM6 AUE was 4.4 kcal
mol−1. The equivalent AUE for other methods were: RM1: 5.0, B3LYP 6–31G*: 5.2, PM5: 5.7, PM3: 6.3, HF 6–31G*: 7.4, and AM1: 10.0 kcal
mol−1. Several long-standing faults in AM1 and PM3 have been corrected and significant improvements have been made in the prediction
of geometries.
Figure Calculated structure of the complex ion [Ta6Cl12]2+ (footnote): Reference value in parenthesis
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
962.
A three-dimensional model of the beta3-homopentamer of the gamma-aminobutyric acid (GABA) receptor/chloride ionophore complex was developed by homology modeling using the cyro-electron microscopy structure of nicotinic acetylcholine as a template. Interactions between the beta3-homopentamer and two classes of fipronil-related non-competitive antagonists were investigated using docking studies. The phenyl groups of these compounds were stabilized by strong hydrophobic and hydrophilic interactions with the rings formed by Thr256 and Ala252. Leu253 and Ile255 were involved mainly in hydrophobic contact with the pyrazole moiety. Different substitution at positions 15, 16 and 17 of the pyrazole ring of fipronil resulted in weakening of the hydrogen bonds and hydrophobic interactions between the beta3-receptor and fipronil-related heterocyclic compounds, which maybe the principal cause of the decreased affinities reported in vitro. Moreover, a good correlation between total binding energies calculated by AutoDock and experimentally determined IC(50) values proved our models to be reasonable in predicting the interaction mode of the antagonist with the GABA beta3-receptor. 相似文献
963.
Sonia Cristina Zapata Alejandro Travaini Pablo Ferreras Miguel Delibes 《European Journal of Wildlife Research》2007,53(4):276-286
We evaluated the existence of trophic guild structure, considering seasonal and annual variation, in two terrestrial carnivore assemblages: one from Santa Cruz province (Argentinean Patagonia, composed by six carnivore species), and the other from Doñana National Park (SW Spain, composed by five carnivore species). To identify trophic guilds, we first studied seasonal and annual diets of predators, calculated trophic overlap among species pairs, and then constructed overlap matrices (similarity matrices). We determined guild membership objectively by entering the similarity matrices into the clustering technique unweighted pair-group method with arithmetic averaging. Carnivores from both assemblages were grouped, respectively, into four feeding guilds. Lagomorphs and rodents promoted the formation of two feeding guilds in both study sites, although the taxonomic composition of predator species that composed them was different. The ungulates-edentates feeding guild was only present at Santa Cruz, whereas the birds and reptiles feeding guild was only present at Doñana. Invertebrates and fruits were the base for the formation of a guild composed by species of the same taxonomic origin both in Santa Cruz and Doñana. Guild structure of Santa Cruz and Doñana assemblages did not exhibit seasonal or annual variation, although the specific guild composition changed over the two studied periods for both assemblages. This structure probably responded to discontinuities in resource spectra in Santa Cruz and fluctuations in rabbit abundance in Doñana. Our results support the hypothesis that establishes that guilds are originated by opportunistic convergence of species on abundant and energetically rewarding resources. 相似文献
964.
Heather E. Johnson Vernon C. Bleich Paul R. Krausman John L. Koprowski 《European Journal of Wildlife Research》2007,53(1):9-15
Although antler size has been identified as a primary determinant of dominance, fighting success, and reproductive success
in male cervids, >80% of the male tule elk (Cervus elaphus nannodes) in the Owens Valley, California, experience antler breakage. To determine the effect of antler breakage on male mating success,
we recorded antler morphology, body size, and mating behavior of male elk throughout the rut. Antler breakage, regardless
of severity, had no effect on male–male assessment, fighting success, or harem-holding status. The factor consistently associated
with our indices of male mating success was not antler size but body size. Although antler size is frequently emphasized as
a key factor in male dominance and social rank, this association may reflect the correlation between antler size and body
size. In the Owens Valley, it appears that male elk are not assessing competitors based on antler morphology but on other
characteristics.
An erratum to this article can be found at 相似文献
965.
The addition of a carbon nutrient feed to a fed-batch cultivation is often not enough to obtain satisfactory growth and/or
production. In some cases, an additional feed with for example supplementary amino acids or complex media is required. This
work presents the development of feeding strategies where more than one feed is required and the knowledge of the growth requirements
is low. Simulations and cultivations with E. coli are shown using the proposed feed controllers which are based on a probing control concept. The strategies work well and
they can be used to shorten the process development phase considerably. 相似文献
966.
Flores A Nisola GM Cho E Gwon EM Kim H Lee C Park S Chung WJ 《Bioprocess and biosystems engineering》2007,30(3):197-205
The performance of enriched sludge augmented with the B21 strain of Alcaligenes defragrans was compared with that of enriched sludge, as well as with pure Alcaligenes defragrans B21, in the context of a sulfur-oxidizing denitrification (SOD) process. In synthetic wastewater treatment containing 100–1,000 mg
NO3−-N/L, the single strain-seeded system exhibited superior performance, featuring higher efficiency and a shorter startup period,
provided nitrate loading rate was less than 0.2 kg NO3−-N/m3 per day. At nitrate loading rate of more than 0.5 kg NO3−-N/m3 per day, the bioaugmented sludge system showed higher resistance to shock loading than two other systems. However, no advantage
of the bioaugmented system over the enriched sludge system without B21 strain was observed in overall efficiency of denitrification.
Both the bioaugmented sludge and enriched sludge systems obtained stable denitrification performance of more than 80% at nitrate
loading rate of up to 2 kg NO3−-N/m3 per day. 相似文献
967.
A bioactive foam reactor (BFR), a novel bioreactor operated using surfactant foams and suspended microorganisms for the treatment
of gaseous toluene, was investigated to characterize its performance with respect to the mass transfer and biodegradation
rates. The BFR system consisted of two reactors in series; a foam column for toluene mass transfer using fine bubbles and
a cell reservoir where suspended microorganisms actively biodegraded toluene. In this study, a series of short-term experiments
demonstrated that the BFR could achieve stable removal performance and a high elimination capacity (EC) for toluene at 100.3 g/m3/h. A numerical model, combining mass balance equations for the mass transfer and subsequent biodegradation, resulted in reasonable
agreement with the experimental findings. At an inlet toluene concentration of 100 ppmv, the toluene concentration in the liquid phase remained extremely low, indicating that the microbial activity was not hindered
in the BFR system. However, the experimental and model prediction results showed that the actual mass of toluene transferred
into the liquid phase was not closely balanced with the amount of toluene biodegraded in the BFR used in this study. Consequently,
methods, such as increasing the effective volume of the foam column or the mass transfer coefficient, need to be implemented
to achieve higher toluene EC and better BFR performance. 相似文献
968.
Fishmeal wastewater, a seafood processing waste, was utilized for production of lactic acid and fungal biomass by Rhizopus oryzae AS 3.254 with the addition of sugars. The 30 g/l exogenous glucose in fishmeal wastewater was superior to starch in view
of productivities of lactic acid and fungal biomass, and COD reduction. Fishmeal wastewater can be a replacement for peptone
which was the most suitable nitrogen source for lactic acid production among the tested organic or inorganic nitrogen sources.
Exogenous NaCl (12 g/l) completely inhibited the production of lactic acid and fungal growth. In the medium of COD 5,000 mg/l
fishmeal wastewater with the addition of 30 g/l glucose, the maximum productivity of lactic acid was 0.723 g/l h corresponding
to productivity of fungal biomass 0.0925 g/l h, COD reduction 84.9% and total nitrogen removal 50.3% at a fermentation time
of 30 h. 相似文献
969.
In these studies, butanol (acetone butanol ethanol or ABE) was produced from wheat straw hydrolysate (WSH) in batch cultures
using Clostridium beijerinckii P260. In control fermentation 48.9 g L−1 glucose (initial sugar 62.0 g L−1) was used to produce 20.1 g L−1 ABE with a productivity and yield of 0.28 g L−1 h−1 and 0.41, respectively. In a similar experiment where WSH (60.2 g L−1 total sugars obtained from hydrolysis of 86 g L−1 wheat straw) was used, the culture produced 25.0 g L−1 ABE with a productivity and yield of 0.60 g L−1 h−1 and 0.42, respectively. These results are superior to the control experiment and productivity was improved by 214%. When
WSH was supplemented with 35 g L−1 glucose, a reactor productivity was improved to 0.63 g L−1 h−1 with a yield of 0.42. In this case, ABE concentration in the broth was 28.2 g L−1. When WSH was supplemented with 60 g L−1 glucose, the resultant medium containing 128.3 g L−1 sugars was successfully fermented (due to product removal) to produce 47.6 g L−1 ABE, and the culture utilized all the sugars (glucose, xylose, arabinose, galactose, and mannose). These results demonstrate
that C. beijerinckii P260 has excellent capacity to convert biomass derived sugars to solvents and can produce over 28 g L−1 (in one case 41.7 g L−1 from glucose) ABE from WSH. Medium containing 250 g L−1 glucose resulted in no growth and no ABE production. Mixtures containing WSH + 140 g L−1 glucose (total sugar approximately 200 g L−1) showed poor growth and poor ABE production.
Mention of trade names or commercial products in this article is solely for the purpose of providing scientific information
and does not imply recommendation or endorsement by the United States Department of Agriculture. 相似文献