DEFECT MOBILITY AND REACTION: DIFFUSIONAL AND RATE THEORY FORMULATIONS IN ONE AND THREE DIMENSIONS.

The migration of defects, leading to eventual reaction, is analyzed on the basis of diffusion theory and compared with chemical rate theory. A diffusional treatment is carried out in detail and in special cases of particular interest. Correlations between interstitials and vacancies, typical of metals following electron irradiation, are examined. Trapping by impurities and dislocations, thermal conversion, and high temperature bombardment are also treated. In each case, formulations are developed along both one- and three-dimensional diffusion models. These alternative results are compared with experiments, particularly annealing in copper irradiated by electrons at low temperature. The results support the conclusion that the defect which migrates in Stage I diffuses in three dimensions

Novel magnetic phases in a Gd2Ti2O7 pyrochlore for a field applied along the [100] axis

We report on longitudinal and transverse magnetisation measurements performed on single crystal samples of Gd2Ti2O7 for a magnetic field applied along the [100] direction. The measurements reveal the presence of previously unreported phases in fields below 10 kOe in an addition to the higher-field-induced phases that are also seen for H//[111], [110], and [112]. The proposed H-T phase diagram for the [100] direction looks distinctly different from all the other directions studied previously.Comment: 4 pages, 5 figure

Accessibility for Line-Cutting in Freeform Surfaces

Manufacturing techniques such as hot-wire cutting, wire-EDM, wire-saw cutting, and flank CNC machining all belong to a class of processes called line-cutting where the cutting tool moves tangentially along the reference geometry. From a geometric point of view, line-cutting brings a unique set of challenges in guaranteeing that the process is collision-free. In this work, given a set of cut-paths on a freeform geometry as the input, we propose a conservative algorithm for finding collision-free tangential cutting directions. These directions, if they exist, are guaranteed to be globally accessible for fabricating the geometry by line-cutting. We then demonstrate how this information can be used to generate globally collision-free cut-paths. We apply our algorithm to freeform models of varying complexity.RYC-2017-2264

Magnetic excitations in dipolar pyrochlore antiferromagnet Gd2_2Sn2_2O7_7

The spin dynamics in the geometrically frustrated pyrochlore antiferromagnet $\rm Gd_2Sn_2O_7$ is studied by means of the electron spin resonance. In the ordered phase ($T_N = 1$ K), we have detected three gapped resonance modes. Their values agree well with the developed spin-wave theory which takes into account the Heisenberg nearest-neighbor exchange, the single-ion anisotropy and the long-range dipolar interactions. The theory also predicts a fourth lowest-frequency gap, which lies beyond the experimental range of frequencies, but determines the exponential decrease of the specific heat at low temperature.Comment: 8 pages, 5 figure

HST color-magnitude diagrams of 74 galactic globular clusters in the HST F439W and F555W bands

We present the complete photometric database and the color-magnitude diagrams for 74 Galactic globular clusters observed with the HST/WFPC2 camera in the F439W and F555W bands. A detailed discussion of the various reduction steps is also presented, and of the procedures to transform instrumental magnitudes into both the HST F439W and F555W flight system and the standard Johnson B and V systems. We also describe the artificial star experiments which have been performed to derive the star count completeness in all the relevant branches of the color magnitude diagram. The entire photometric database and the completeness function will be made available on the Web immediately after the publication of the present paper.Comment: 21 pages, 77 figures. High resolution version of this paper can be retrived at http://dipastro.pd.astro.it/globular

The Construction of Conforming-to-shape Truss Lattice Structures via 3D Sphere Packing

Truss lattices are common in a wide variety of engineering applications, due to their high ratio of strength versus relative density. They are used both as the interior support for other structures, and as structures on their own. Using 3D sphere packing, we propose a set of methods for generating truss lattices that fill the interior of B-rep models, polygonal or (trimmed) NURBS based, of arbitrary shape. Once the packing of the spheres has been established, beams between the centers of adjacent spheres are constructed, as spline based B-rep geometry. We also demonstrate additional capabilities of our methods, including connecting the truss lattice to (a shell of) the B-rep model, as well as constructing a tensor-product trivariate volumetric representation of the truss lattice - an important step towards direct compatibility for analysis.RYC-2017-2264

Effect of breed and aging time on physicochemical and organoleptic quality of beef and its oxidative stability

In this experiment we used the meat of 16 Polish Red-and-White and Simmental bulls slaughtered at the age of 24 months. Physicochemical and organoleptic analyses were carried out on meat aged for 2, 7, 14 and 21 days and subjected to heat treatment. In addition, the effect of aging on oxidative stability and fatty acid profile of meat lipids was examined after 21 days of aging. The meat aging process determined all the physicochemical characteristics except for heating loss, as well as most of the sensory properties of meat. During aging, lightening of muscle colour, increased redness and chroma, and improved tenderness were observed. High scores were given for aroma intensity and taste desirability. The highest scores were awarded to meat aged for 7 and 14 days. The evaluation showed that meat tenderness and delicate texture steadily improved until day 14, after which they remained at a similar level or slightly deteriorated after 21 days of aging. Meat from the conserved breed generally had better scores, which could be influenced by better component scores for delicate texture and juiciness, as well as taste intensity. This study revealed no significant effect of breed on the degree of lipid peroxidation expressed as thiobarbituric acid-reactive substances (TBARS). The amount of malondidehyde was higher in meat aged for 21 days than in fresh meat. Aging did have an effect on the fatty acid profile of longissimus dorsi muscle (MLD) intramuscular fat. Wet aging of meat for 21 days was found to alter the content of capric (C10 : 0), palmitoleic (C16 : 1) and stearic acids (C18 : 0)