Fluctuations and Dissipation of Coherent Magnetization

A quantum mechanical model is used to derive a generalized Landau-Lifshitz equation for a magnetic moment, including fluctuations and dissipation. The model reproduces the Gilbert-Brown form of the equation in the classical limit. The magnetic moment is linearly coupled to a reservoir of bosonic degrees of freedom. Use of generalized coherent states makes the semiclassical limit more transparent within a path-integral formulation. A general fluctuation-dissipation theorem is derived. The magnitude of the magnetic moment also fluctuates beyond the Gaussian approximation. We discuss how the approximate stochastic description of the thermal field follows from our result. As an example, we go beyond the linear-response method and show how the thermal fluctuations become anisotropy-dependent even in the uniaxial case.Comment: 22 page

Gut morphology and nutrient retention responses of broiler chicks and White Pekin ducklings to dietary threonine deciency

Growth performance, villi length and width, nutrient digestibility, basal short-circuit current, and glutamine transport were investigated in male broilers and White Pekin ducklings offered diets containing 3.3, 5.8, or 8.2 g of threonine (Thr) kg-1 in four studies. Seventy-two birds of each species were fed a standard broiler starter diet from 1 to 14 d of age followed by assignment to three dietary treatments in a randomized complete block design for a 7-d feeding trial in exp. 1 (broilers) and exp. 2 (ducklings). The dietary treatments consisted of an isonitrogenous, corn-soybean-meal-based diet with the addition of crystalline amino acids and graded levels of Thr. Dietary formulation and experimental design for exp. 3 (broilers) and exp. 4 (ducklings) were similar to exps. 1 and 2 except that birds were fed 3.3 or 8.2 g Thr kg-1 for a duration of 14 d. Chromic oxide was added to the dietary treatments as an indigestible marker. Excreta were collected on day 19 to 21 of age for exps. 1 and 2, and from day 26 to 28 of age for exps. 3 and 4. For chicks, there was no effect of dietary treatment on gain for birds fed treatments for 7 d, whereas gain increased (P &lt; 0.001) as dietary Thr increased in birds fed dietary treatments for 14 d. Dry-matter retention increased (P &lt; 0.05) as dietary Thr increased in chicks fed for 7 and 14 d. Threonine increased P retention (P = 0.02), but not Ca or N retention in chicks fed dietary treatments for 14 d. Increasing dietary Thr increased gain (P &lt; 0.05) for ducklings fed dietary treatments for 7 and 14 d. Furthermore, DM retention increased (P &lt; 0.05) as dietary Thr increased for ducklings fed dietary treatments for 7 and 14 d. Nitrogen retention increased (P = 0.04) as dietary Thr increased in ducklings fed dietary treatments for 14 d, but there was no effect of dietary treatment on P or Ca retention. There was no effect of dietary treatment on villi characteristics, basal short-circuit current, or glutamine transport in chicks or ducklings. The data established a link between dietary Thr and nutrient retention in broiler chicks and ducklings, although villi characteristics and permeability measurements were not altered. </jats:p