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101.
Calculation of dietary intake for beef cattle using the equation outlined by the NRC (1984) is confounded by the need to know the net energy for maintenance content of the diet (NEmkg). Intake cannot be calculated until NEmkg is specified, but intake must be indicated before performance can be predicted. To calculate NEmkg, dietary intake must be known or estimated, or it can be calculated using a complicated quartic equation. This quartic equation, when solved, gives the percentages of selected feedstuffs necessary to balance a diet. Placing the resulting percentages of feedstuffs necessary back into the generalized net energy equation solves for NEmkg. The quartic equation may be simplified by inserting imaginary nutrient values that optimize the equation for simplicity. It remains a quartic equation, but the coefficients for the first three factors of the equation are fixed, with only the unary X term and the coefficient containing variables. A modified version of Newton's method of approximating roots of equations estimates the percentage of feed necessary and when incorporated into the generalized net energy equation solves for NEmkg. The final reduced form results in simplified equations for NEmkg for each of the classes of beef cattle that are easily solved by the hand-held calculator. 相似文献
102.
猪流感病毒可单独引起疾病,但更常见与其它病原混合感染,并在猪呼吸道疾病复合症中起着重要作用。 相似文献
103.
L Bernard C F R Backwell D Rémond D Wilson L A Bruce V Buchan J C MacRae 《Archives of Animal Nutrition》2002,56(1):13-21
Two methodologies for the measurement of peptide amino acids (PAA) in blood were compared to evaluate their effects on the measurement of the net flux of peptides across the gastrointestinal tract of sheep. These methods consisted of a chemical deproteinization of blood samples with sulfosalicylic acid (1.6 M, 0.1 ml for 1 ml of sample) or perchloric acid (1 M, 1 ml for 1 ml of sample) followed by ultrafiltration through a 3,000-Da cut-off filter (SSA + UF3 kD) or gel filtration through a Sephadex G-15 column (1,500-Da cut-off filter; PCA + G-15), respectively, prior to PAA analysis. Peptide concentrations as determined by amino acid concentrations before and after hydrolysis of samples were slightly greater with the SSA + UF3 kD (991 microM) than with the PCA + G-15 (605 microM) methodology. However, both methodologies gave similar net portal-drained viscera flux data in sheep fed on alfalfa pellets with histidine as the only significant uptake of peptide amino acid. 相似文献
104.
105.
Halpin K Mungall BA 《Comparative immunology, microbiology and infectious diseases》2007,30(5-6):287-307
Following the discovery of two new paramyxoviruses in the 1990s, much effort has been placed on rapidly finding the reservoir hosts, characterising the genomes, identifying the viral receptors and formulating potential vaccines and therapeutic options for these viruses, Hendra and Nipah viruses caused zoonotic disease on a scale not seen before with other paramyxoviruses. Nipah virus particularly caused high morbidity and mortality in humans and high morbidity in pig populations in the first outbreak in Malaysia. Both viruses continue to pose a threat with sporadic outbreaks continuing into the 21st century. Experimental and surveillance studies identified that pteropus bats are the reservoir hosts. Research continues in an attempt to understand events that precipitated spillover of these viruses. Discovered on the cusp of the molecular technology revolution, much progress has been made in understanding these new viruses. This review endeavours to capture the depth and breadth of these recent advances. 相似文献
106.
K. Bruce Newbold 《Growth and change》2002,33(3):370-389
Discussions of immigration, settlement and adjustment within the U.S. do not typically refer to immigrant status (i.e., refugee versus family preference), and instead refer to the foreign–born population as an aggregate. Distinguishing between refugees and other immigrant arrivals likely means differences with respect to their geographic distribution and embodied human capital owing to differences associated with the reasons for immigration (forced versus voluntary), period of arrival, and immigration policy. The lack of differentiation by group within the existing literature is typically due to a shortfall of detailed information relating to admission status within publicly released data files. Yet concrete knowledge of differences by admission category is important in understanding overall patterns of settlement and adjustment within the foreign–born population. This paper therefore explores potential differences with respect to settlement and endowed human capital between immigrants and refugees. Identification of the major sources of refugees within Immigration and Naturalization Service data files allows the refugee population to be identified within the 1990 Public Use Microdata Sample (PUMS), therefore increasing the range of variables and measures associated with the refugee population available to researchers, and points to the diversity of the refugee population. 相似文献
107.
108.
Robert P. Griffiths Bruce A. Caldwell Phillip Sollins 《Biology and Fertility of Soils》1993,16(3):157-162
Effects of vegetation and nutrient availability on potentail denitrification rates were studied in two volcanic, alluvial-terrace soils in lowland Costa Rica that differ greatly in weathering stage and thus in availability of P and base cations. Potential denitrification rates were significantly higher in plots where vegetation had been left undisturbed than in plots where all vegetation had been removed continuously, and were higher on the less fertile of the two soils. The potential denitrification rates were correlated strongly with respiration rates, levels of mineralizable N, microbial biomass, and moisture content, and moderately well with concentrations of extractable NH
inf4
sup+
, Kjeldahl N, and total C. In all plots, denitrification rates were stimulated by the removal of O2 and by the addition of glucose but not by the addition of water or NO
inf3
sup-
.This is Paper 2772 of the Forest Research Laboratory, Oregon State University 相似文献
109.
Steven W. Effler Carol M. Brooks Jeffrey M. Addess Susan M. Doerr Michelle L. Storey Bruce A. Wagner 《Water, air, and soil pollution》1991,55(3-4):427-444
Concentrations of Cl, total ammonia (TNH3), NO3 plus NO2, total P (TP), and soluble reactive P (SRP) were measured at two sites, located 5 km apart, on Ninemile Creek, New York, for a period of more than 8 mo. The sites bound the most recently formed Solvay waste beds, associated with the production of soda ash, that adjoin the creek. Concentrations of Cl and T-NH3 increased on average by factors of 16.1 and 7.6, respectively, over the monitored stream reach. The estimated average loadings of these materials to the stream over this reach were 2.3 × 105 and 1.2 × 102 kg d?1, respectively. These inputs are attributable to the Solvay waste beds. The loading of Cl from this source has not changed significantly over a 4 yr period since the closure of the soda ash manufacturing facility. This is the single largest source of Cl, and the second largest source of T-NH3, to polluted Onondaga Lake. Profiles of Cl in the lake indicated that at times the creek inflow plunges to subsurface layers as a result of its elevated density. This is at least in part a result of the creek's ionic enrichment. The concentration of SRP decreased by a factor of 2.0 on average over the study reach, probably due to adsorption to the CaCO3 deposits that cover the stream bed in this area. However, the TP load from the creek to the lake is not significantly affected by this phenomenon. 相似文献
110.
Smith BD 《Science (New York, N.Y.)》2007,315(5820):1797-1798