Symmetry Reduction in the Quantum Kagome Antiferromagnet Herbertsmithite.

Employing complementary torque magnetometry and electron spin resonance on single crystals of herbertsmithite, the closest realization to date of a quantum kagome antiferromagnet featuring a spin-liquid ground state, we provide novel insight into different contributions to its magnetism. At low temperatures, two distinct types of defects with different magnetic couplings to the kagome spins are found. Surprisingly, their magnetic response contradicts the threefold symmetry of the ideal kagome lattice, suggesting the presence of a global structural distortion that may be related to the establishment of the spin-liquid ground state.

A comparison of rectal palpation and ultrasonography for the evaluation of superovulatory response in beef heifers.

The superovulatory response was followed up in 14 beef heifers by rectal palpation and by ultrasonographic examinations of the 28 ovaries, on day 7 after superovulation induced with PMSG (ovulation = day 0). Using a B-mode ultrasound instrument (Aloka Echo Camera SSD-210-DX II) equipped with a 5 MHz linear transrectal transducer, ultrasonography was found to be more reliable than rectal palpation. A significantly higher number of follicles (P < or = 0.049) was identified by ultrasound scanning than by rectal palpation of the ovaries: follicles were more easily differentiated from cysts using ultrasonography, since each fluid-filled vesicle was accurately measured on the screen and presented on the echogram.

[Role of sodium ions in gastric absorption of calcium in ruminants (author's transl)]. / Röle des ions sodium dans l'absorption gastrique du calcium chez les ruminants.

The influence of sodium ions on gastric absorption of calcium in ruminants was studied with regard to the accompanying anions. Bags made of the surviving mucous membrane of different compartments of bovine stomach were used for this purpose. The epithelial side of the mucous membrane always faced towards the inside of the bags. The bags were filled with a combined solution of a calcium salt (chloride, carbonate or phosphate) and sodium chloride. The concentration of calcium was always the same (10 mg/100 ml) while the concentration of sodium varied, amounting to 102.5, 205 and 1025 mg/100 ml. The external face of the bags was placed in Tyrode's solution. In general, calcium absorption became more and more intensive when the concentration of sodium in the contents increased, regardless of the solubility and dissociability of the calcium salt used. When chloride was the accompanying anion, this effect appeared in the rumen and omasum at a physiological concentration of sodium (205 mg/100 ml), and in the abomasum it appeared only at a concentration which widely exceeded the limits of the normal (1025 mg/100 ml). When either carbonate or phosphate were used for this purpose, this effect generally appeared at the highest concentration of sodium, and only in the abomasum, with phosphate as the accompanying anion, at a concentration of 205 mg/100 ml. On the basis of these results, it was concluded that the presence of sodium ions in the contents stimulates gastric absorption of calcium, but the concentration of sodium at which this stimulative effect appears depends, at least to a certain degree, on the accompanying anion of calcium. The possibility of improving the absorption of calcium in the digestive tract of ruminants is discussed in view of the results obtained.

The influence of 1 alpha,25- and 24(R),25-dihydroxyvitamin D3 on bone constituents during early mineralization in the rat.

The influence of vitamin D metabolites on intramuscular implants of bone matrix in rachitic rats was investigated. Recipient rats with rickets were injected daily with 1 alpha,25(OH)2D3,24(R),25(OH)2D3 or a combination of both metabolites. The presence of 1 alpha,25(OH)2D3 increased significantly the alkaline phosphatase activity, and slightly increased the activity of acid phosphatase. 24(R),25(OH)2D3 had no effect on the activity of the measured enzymes. The results of inductively coupled plasma emission spectrometric determination of bone elements revealed that: (a) 1 alpha,25(OH)2D3 stimulated the incorporation of magnesium and decreased the phosphorus content of bone implants when compared with rats given both vitamin D metabolites; (b) 1 alpha,25(OH)2D3 as well as 24(R),25(OH)2D3 had antagonistic effects on bone carbonate content. The values for 1 alpha,25(OH)2D3 treated animals were significantly higher, and 24(R),25(OH)2D3 treated rats had a significantly lower carbonate content of implants when compared to the controls. Time-dependent CO2-liberation diagrams indicated a differently bound bone carbonate in 1 alpha,25(OH)2D3 treated rats; (c) when plotted against time, the diagrams for both the values for zinc and the activity distribution of the measured enzymes had a similar appearance, indicating zinc incorporation into bone enzymes during early mineralization. It is concluded that 24(R),25(OH)2D3 should not be compared to 1,25(OH)2D3 on the basis of the same effects, since other effects of 24(R),25(OH)2D3 on the developing bone exist, opposite to those of 1,25(OH)2D3; and these could be important for protecting bone from different agents and in determining the nature of early mineral deposited.