The Effect of Carboxylates on the Mg Content of Calcites that Transform from ACC

AbstractIn some skeletal-forming and sedimentary environments, calcite and other CaCO3 polymorphs are produced from an amorphous calcium carbonate (ACC) phase. This experimental study determined the Mg content of calcites that grew in the presence of ACC with/without carboxylated biomolecules. The Mg content of the initial ACC obeys a simple fractionation for all conditions except in the presence of oxydiacetate. For all solution compositions, this ACC transforms into calcite crystallites that contain zero to 38 mole %MgCO3, without evidence of secondary polymorphs (Mg/Ca = 0-15). Mg is in the calcite structure within the resolution of the XRD method. The biomolecules slow the ACC to calcite transformation in proportion to their selectivity for Ca over Mg. Citrate, tartarate, and oxydiacetate increase the amount of Mg in both ACC and the resulting calcite. When the Mg2+/Ca2+ ratios of initial solutions are less than ∼5-8, the Mg content of the ACC and calcite products are similar

Effect of different levels of copper on growth performance and cecal ecosystem of newly weaned piglets

The current study aimed to investigate the effects of different levels of copper sulfate on the growth performance and cecal ecosystem in newly weaned piglets. One hundred piglets weaned at 28±2 d were randomly allocated to 4 treatments with 5 replicates of 5 piglets each. Piglets received for 28 d the base diet with i) no addition (control) or with copper addition (from copper sulfate) at ii) 100, iii) 175, and iv) 250 mg/kg-1. On day 21, twenty piglets were randomly selected (one from each replicate) to slaughter and investigate the population and diversity of cecal microorganisms. The results showed that the diets containing 175 and 250 mg/kg-1 copper improved the average daily gain (ADG) by 51% and 60% and decreased the feed to gain ratio (F/G) by 21% and 16%, respectively. Adding 175 or 250 mg/kg-1 copper improved crude protein, ether extract, calcium and phosphorus digestibility. Viable counts of Enterobacteriaceae and Lactobacilli in cecum tended to be reduced, while the concentrations of cecal volatile fatty acids (VFA) were increased in pigs fed diet supplemented as copper level increased. Polymerase chain reaction (PCR) results showed that adding 175 or 250 mg/kg-1 copper reduced the lactobacilli in cecum. Denaturing gradient gel electrophoresis (DGGE) maps showed that band numbers and intensity of cecal bacterial 16S rDNA decreased as the copper levels increased. The results suggested that the effects of high dietary copper on microflora and their activities and metabolic products might contribute to the intestinal health and result in improved growth performance

Static and simulated seismic testing of the TRG-7 through -16 shear wall structures

Results from the static, simulated seismic base excitation, and experimental modal analysis tests performed on the TRG-7 through -16 structures are reported. These results were used to establish the scalability of static and dynamic response measured on small structural models to the dynamic response of conventional concrete structures. In addition, these tests provided information concerning cumulative damage effects that occur in concrete structures when they are subjected to different dynamic load sequences. In contrast to previous results obtained in the early part of this program, TRG-7 through -16 responded to simulated seismic excitations with theoretical stiffness values until peak nominal base shear stress levels of 150 psi were reached. A summary of all experimental data obtained during this program is provided. 23 refs., 47 figs., 22 tabs