Inhomogeneous spin diffusion in traps with cold atoms

The spin diffusion and damped oscillations are studied in the collision of two spin polarized clouds of cold atoms with resonant interactions. The strong density dependence of the diffusion coefficient leads to inhomogeneous spin diffusion that changes from central to surface spin flow as the temperature increases. The inhomogeneity and the smaller finite trap size significantly reduce the spin diffusion rate at low temperatures. The resulting spin diffusion rates, spin drag and initial damped oscillations are compatible with measurements at low to high temperatures for resonant attractive interactions but are incompatible with a metastable ferromagnetic phase.Comment: 3 pages, 1 figure; Phys. Rev. Letters, 201

Itinerant ferromagnetism in a two-dimensional atomic gas

Motivated by the first experimental evidence of ferromagnetic behavior in a three-dimensional ultracold atomic gas, we explore the possibility of itinerant ferromagnetism in a trapped two-dimensional atomic gas. Firstly, we develop a formalism that demonstrates how quantum fluctuations drive the ferromagnetic reconstruction first order, and consider the consequences of an imposed population imbalance. Secondly, we adapt this formalism to elucidate the key experimental signatures of ferromagnetism in a realistic trapped geometry.Comment: Accepted for publication in Phys. Rev.

Measurements and mechanisms of localized aqueous corrosion in aluminum-lithium alloys

Like most heat treatable aluminum alloys, localized corrosion and stress corrosion of Al-Li-Cu alloys is strongly dependent on the nature and distribution of second phase particles. To develop a mechanistic understanding of the role of localized corrosion in the stress corrosion process, bulk samples of T(sub 1) (Al2CuLi) and a range of Al-Cu-Fe impurity phases were prepared for electrochemical experiments. Potentiodynamic polarization and galvanic couple experiments were performed in standard 0.6 M NaCl and in simulated crevice solutions to assess corrosion behavior of these particles with respect to the alpha-Al matrix. A comparison of time to failure versus applied potential using a constant load, smooth bar SCC test technique in Cl(-), Cl(-)/CrO4(2-), and Cl(-)/CO3(2-) environments shows that rapid failures are to be expected when applied potentials are more positive than the breakaway potential (E sub br) of T(sub 1) (crack tip) but less than E(sub br) of alpha-Al (crack walls). It is shown that this criterion is not satisfied in aerated Cl(-) solutions. Accordingly, SCC resistance is good. This criterion is satisfied, however, in an alkaline isolated fissure exposed to a CO2 containing atmosphere. Rapid failure induced by these fissures was recently termed preexposure embrittlement. Anodic polarization shows that the corrosion behavior of T(sub 1) is relatively unaffected in alkaline CO3(2-) environments but the alpha-Al phase is rapidly passivated. X ray diffraction of crevice walls from artificial crevices suggests that passivation of alpha-Al occurs as hydrotalcite-type compound (LiAl2(OH)6)2(+) - CO3(2-) - nH2O

The effect of season on response of growing-finishing pigs to dietary fat levels

This experiment was conducted to examine the influence of season on the response of finishing pigs to practical levels of fat addition. A total of 378 pigs (average initial weight per trial ranging from 83 to 98 pounds) were utilized in four finishing trials conducted during time frames approximating the 4 seasons of the year. Groups of pigs were taken off trial as they reached market weight (230 pounds). There was no season x fat level interaction for any of the criteria measured. Therefore, it is concluded that season has essentially no effect on fat level response. Fat addition influenced average daily gain (ADG), resulting in significant (P\u3c.05) linear and quadratic effects. Average daily feed intake (ADFI) and feed efficiency (F /G) responded linearly (P\u3c.05) to fat additions to the finishing diet. The ADG and ADFI responses to fat additions were not affected by season. However, F/G was influenced by season. The pigs were more feed efficient during the warmer seasons of the year.; Swine Day, Manhattan, KS, November 19, 198

Effect of a select menhaden fish meal in starter diets for pigs

A growth study was conducted to evaluate the effect of a select menhaden fish meal (SMFM) as a protein source in starter diets for pigs. A total of 150, 3-week old weaned pigs were utilized. Diets were formulated by replacing soy protein with protein from SMFM. The replacement of soy protein with SMFM elicited a quadratic response in average daily gain (ADG) and average daily feed intake (ADFI) by the end of week 5. Inclusion of SMFM at 8% yielded the maximum observed ADG, whereas ADFI was maximized with the 12% SMFM diet. Addition of SMFM did not affect feed conversion. These results suggest that SMFM may have potential as a protein source in starter diets for the early weaned pig.; Swine Day, Manhattan, KS, November 20, 198

Tricritical behavior in itinerant quantum ferromagnets

It is shown that the peculiar features observed in the low-temperature phase diagrams of ZrZn_2, UGe_2, and MnSi can be understood in terms of a simple mean-field theory. The nature of the ferromagnetic transition changes from second order to first order at a tricritical point, and in a small external magnetic field surfaces of first-order transitions emerge which terminate in quantum critical points. This field dependence of the phase diagram follows directly from the existence of the tricritical point. The quantum critical behavior in a nonzero field is calculated exactly.Comment: 4pp., 4 eps figure

Magnetic tight-binding and the iron-chromium enthalpy anomaly

We describe a self consistent magnetic tight-binding theory based in an expansion of the Hohenberg-Kohn density functional to second order, about a non spin polarised reference density. We show how a first order expansion about a density having a trial input magnetic moment leads to the Stoner--Slater rigid band model. We employ a simple set of tight-binding parameters that accurately describes electronic structure and energetics, and show these to be transferable between first row transition metals and their alloys. We make a number of calculations of the electronic structure of dilute Cr impurities in Fe which we compare with results using the local spin density approximation. The rigid band model provides a powerful means for interpreting complex magnetic configurations in alloys; using this approach we are able to advance a simple and readily understood explanation for the observed anomaly in the enthalpy of mixing.Comment: Submitted to Phys Rev

Discrete transverse superconducting modes in nano-cylinders

Spatial variation in the superconducting order parameter becomes significant when the system is confined at dimensions well below the typical superconducting coherence length. Motivated by recent experimental success in growing single-crystal metallic nanorods, we study quantum confinement effects on superconductivity in a cylindrical nanowire in the clean limit. For large diameters, where the transverse level spacing is smaller than superconducting order parameter, the usual approximations of Ginzburg-Landau theory are recovered. However, under external magnetic field the order parameter develops a spatial variation much stronger than that predicted by Ginzburg-Landau theory, and gapless superconductivity is obtained above a certain field strength. At small diameters, the discrete nature of the transverse modes produces significant spatial variations in the order parameter with increased average magnitude and multiple shoulders in the magnetic response.Comment: 10 pages, 8 figure

C/O white dwarfs of very low mass: 0.33-0.5 Mo

The standard lower limit for the mass of white dwarfs (WDs) with a C/O core is roughly 0.5 Mo. In the present work we investigated the possibility to form C/O WDs with mass as low as 0.33 Mo. Both the pre-WD and the cooling evolution of such nonstandard models will be described.Comment: Submitted to the "Proceedings of the 16th European White Dwarf Workshop" (to be published JPCS). 7 pages including 13 figure

Effects of ultra pig krave extra® on starter pig performance

A growth study and a preference study were conducted to evaluate the effect of a commercially available flavoring agent on starter pig performance. A total of 192, 3-wk old, weaned pigs were utilized. A 2-phase starter program was used in the growth study. Half the pigs received creep feed with added flavor and half without, beginning at 10 days of age. Pigs receiving flavored feed at 10 days of age had significantly better gains and feed intake the first 2 wk postweaning than pigs on nonflavored feed. The pigs in the preference study demonstrated a clear preference for flavored vs nonflavored feed. These results indicate addition of flavor to a creep diet beginning at 10 days of age will increase feed intake and gains in the nursery. However, when a creep feed is fed, addition of flavor to a nursery diet did not result in improved performance.; Swine Day, Manhattan, KS, November 17, 198