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The kinetics of the adsorption of Pb2+ and Cd2+ by sodium tetraborate (NTB)-modified kaolinite clay adsorbent was studied. A one-stage and two-stage optimization of equilibrium data were carried out using the Langmuir and time-dependent Langmuir models, respectively. Increasing temperature was found to increase the pseudo-second order kinetic rate constant and kinetic data for Pb2+ adsorption were found to fit well with the pseudo-second order kinetic model (PSOM) while that for Cd2+ were found to show very good fit to the modified pseudo-first order kinetic model (MPFOM). Binary solutions of Pb2+ and Cd2+ reduced the adsorption capacity of the modified adsorbent for either metal ion with increased initial sorption rate due to competition of metal ions for available adsorption sites. The use of NTB-modified kaolinite clay adsorbent reduces by approximately 72.2% and 96.3% the amount of kaolinite clay needed to adsorb Pb2+ and Cd2+ from wastewater solutions. From the two-stage batch adsorber design study, the minimum operating time to determine a specified amount of Pb2+ and Cd2+ removal was developed. The two-stage batch adsorption process predicted less than half the minimum contact time to reach equilibrium in the one-stage process for the adsorption of Pb2+ and Cd2+ by NTB-modified kaolinite clay adsorbent and requires 0.05 times the mass of the adsorbent for the single-stage batch adsorption at the same operating conditions.  相似文献   
2.
This study evaluated the effect of high or low digestible energy ratio of carbohydrate in a high or normal dietary energy density on performance, amino acid utilization and intestinal functions of weaned piglets. A total of 32 healthy weaners (9.60 ± 0.13 kg) were allocated to two dietary energy densities (3,400 and 3,800 kcal/kg) and two digestible energy ratio of carbohydrate to fat (9:1 and 3:1) in a 2 × 2 factorial arrangement. There were eight piglets per treatment. The feed intake of piglets was significantly increased by dietary high carbohydrate ratio (9:1) (p < 0.01); however, this did not result in improved body weight gain (p > 0.05). The piglets fed high carbohydrate energy ratio had a reduced villus height/crypt depth (VH/CD) ratio in the duodenum (p < 0.05), and dietary high energy density further decreased the VH/CD ratio in the ileum (p < 0.01). In the duodenum, the lymphocyte count was increased by dietary high energy density (p < 0.05), while dietary energy density and carbohydrate energy ratio interacted to increase lymphocyte count in the ileum (p < 0.05). The serum cholesterol, triglyceride and low‐density lipoprotein were not significantly affected (p > 0.05), but dietary energy density interacted with dietary energy ratio to increase high‐density lipoprotein concentration (p < 0.05) in piglets fed reduced carbohydrate energy ratio. Dietary high energy density reduced energy digestibility (p < 0.05), whereas high carbohydrate energy ratio increased crude protein digestibility in the piglets (p < 0.05). The intestinal sucrase, lactase activities and serum concentrations of histidine, leucine, lysine, methionine, phenylalanine, alanine, glycine, tyrosine and citrulline were higher in the piglets fed dietary increased carbohydrate energy ratio. Oxidative stress markers and volatile fatty acids concentrations were altered by the dietary treatments. It was concluded that dietary high energy density could be detrimental to piglets intestinal functions and that increased carbohydrate energy ratio could affect amino acid utilization and body weight gain in weaner pigs.  相似文献   
3.
The population structure of 302 randomly selected West African Dwarf (WAD) and Red Sokoto (RS) goats was examined using multivariate morphometric analyses. This was to make the case for conservation, rational management and genetic improvement of these two most important Nigerian goat breeds. Fifteen morphometric measurements were made on each individual animal. RS goats were superior (P < 0.05) to the WAD for the body size and skeletal proportions investigated. The phenotypic variability between the two breeds was revealed by their mutual responses in the principal components. While four principal components were extracted for WAD goats, three components were obtained for their RS counterparts with variation in the loading traits of each component for each breed. The Mahalanobis distance of 72.28 indicated a high degree of spatial racial separation in morphology between the genotypes. The Ward’s option of the cluster analysis consolidated the morphometric distinctness of the two breeds. Application of selective breeding to genetic improvement would benefit from the detected phenotypic differentiation. Other implications for management and conservation of the goats are highlighted.  相似文献   
4.
The structure of haplotype blocks in the human genome   总被引:1,自引:0,他引:1  
Haplotype-based methods offer a powerful approach to disease gene mapping, based on the association between causal mutations and the ancestral haplotypes on which they arose. As part of The SNP Consortium Allele Frequency Projects, we characterized haplotype patterns across 51 autosomal regions (spanning 13 megabases of the human genome) in samples from Africa, Europe, and Asia. We show that the human genome can be parsed objectively into haplotype blocks: sizable regions over which there is little evidence for historical recombination and within which only a few common haplotypes are observed. The boundaries of blocks and specific haplotypes they contain are highly correlated across populations. We demonstrate that such haplotype frameworks provide substantial statistical power in association studies of common genetic variation across each region. Our results provide a foundation for the construction of a haplotype map of the human genome, facilitating comprehensive genetic association studies of human disease.  相似文献   
5.
Veterinary Research Communications - Infections with divergent strains of astroviruses appear to be endemic in commercial poultry. In order to investigate enteric viruses associated with hatchery...  相似文献   
6.
The protein fractions in three different teff types were studied in comparison to sorghum to explain teff’s superior bread making quality. The proportion of aqueous alcohol-soluble teff protein was approx 40% and it was rich in glutamine and leucine. Hence, contrary to previous reports, prolamin is the major teff grain storage protein. With SDS-PAGE under non-reducing and reducing conditions, teff prolamins showed broad bands at approx. 20.3 and 22.8 kDa. Other bands were at approx. 36.1, 50.2, 66.2 and 90.0 kDa, respectively under non-reducing conditions, but were absent under reducing conditions, indicating that these polypeptides are disulphide bonded. The presence of broad monomeric prolamin bands in teff under non-reducing conditions indicates that teff prolamin is less polymerized than sorghum prolamin. Estimated free energy of hydration of teff prolamins was −161.3 kcal/mol compared to −139.8 kcal/mol for sorghum prolamin. By 2-D electrophoresis, teff protein contained more polypeptides than maize or sorghum. Teff contained a higher proportion of basic polypeptides than maize. With differential scanning calorimetry, teff prolamin exhibited a single endothermic peak at 69.85 °C, while no peak was detected for sorghum prolamin. The lower polymerization, hydrophobicity and denaturation temperature of teff prolamins probably make them somewhat functional in bread making.  相似文献   
7.
The aetiology of geophagia in periurban dairy cattle in Nigeria was assessed in relation to the mineral status of the serum, the herbage consumed, and the soil from where the herbage was consumed. The study was carried out using nine herds in the derived savannah zone during both the wet and dry seasons. Generally, the Na, Ca, Fe, Zn and Cu levels in the samples were adequate. However, the forages were low in Ca and the serum was deficient in P. Forage, soil and termite hill samples were also deficient in P. The low levels of P in the soil and termite hill samples showed that the consumption of sand by the cattle did not have any positive impact on their P intake. A seasonal effect was apparent (p<0.05) on the serum Na+, PO4 3–, Cu2+ and Fe2+ concentrations but not on Ca2+ and Zn2+ concentrations. A seasonal effect was also significant (p<0.05) on the minerals in the forage. There were also seasonal differences in most of the soil and termite hill minerals. Most samples had higher (p<0.05) mineral levels in the dry season. Herd size and farming activity had no apparent influence on the aetiology of geophagia as they did not affect (p>0.05) the concentration of P in the serum, the reported cause of geophagia. Geophagia is probably caused by a marginal level of P in the serum and low levels in the forage and soil. Experimental trials will be required to confirm these observations.  相似文献   
8.
Host defense in vertebrates depend on many secreted regulatory proteins such as major histocompatibility complex (MHC) class II which provide important regulatory and effector functions of T cells. Gene polymorphism in the second exon of Capra-DRB gene in three major Nigerian goat breeds [West African Dwarf (WAD), Red Sokoto (RS), and Sahel (SH)] was analyzed by restriction fragment length polymorphisms (RFLP). Four restriction enzymes, BsaHI, AluI, HaeIII, and SacII, were utilized. The association between the polymorphic sites and some heat tolerance traits were also investigated in a total of 70 WAD, 90 RS, and 50 SH goats. Fourteen different types of alleles identified in the Nigerian goats, four of which were found in the peptide coding region (A57G, Q89R, G104D, and T112I), indicate a high degree of polymorphism at the DRB locus in this species. An obvious excess (P?<?0.01) of non-synonymous substitutions than synonymous (dN/dS) in this locus is a reflection of adaptive evolution and positive selection. The phylogenetic trees revealed largely species-wise clustering in DRB gene. BsaHI, AluI, HaeIII, and SacII genotype frequencies were in Hardy-Weinberg equilibrium (P?>?0.05), except AluI in RS goats and HaeIII in WAD goats (P?<?0.05). The expected heterozygosity (H), which is a measure of gene diversity in the goat populations, ranged from 0.16 to 0.50. Genotypes AA (BsaHI), GG, GC and CC (AluI) and GG, GA, AA (HaeIII) appeared better in terms of heat tolerance. The heat-tolerant ability of SH and RS goats to the hot and humid tropical environment of Nigeria seemed better than that of the WAD goats. Sex effect (P?<?0.05) was mainly on pulse rate and heat stress index, while there were varying interaction effects on heat tolerance. Variation at the DRB locus may prove to be important in possible selection and breeding for genetic resistance to heat stress in the tropics.  相似文献   
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