Structure and size-dependent vibrational and thermal properties of Ni clusters: A systematic ab initio approach

There is scarce information on the vibrational and thermal properties of small Ni clusters. Here, the outcomes of ab initio spin-polarized density functional theory calculations on the size and geometry effects upon the vibrational and thermal properties of Ni_n (n = 13 and 55) clusters, are discussed. For theses clusters a comparison is presented between the closed shell symmetric octahedral (O_h) and the icosahedral (I_h) geometries. The results indicate that the I_h isomers are lower in energy. Besides, ab initio molecular dynamics runs at T = 300K show that Ni₁₃ and Ni₅₅ clusters transform from their initial O_h geometries towards the corresponding I_h ones. For Ni₁₃, we also consider the lowest energy less symmetric layered 1-3-6-3 structure, and the cuboid, recently observed experimentally for Pt₁₃, which is competitive in energy but is unstable, as phonon analysis reveals. We calculate their vibrational density of states (νDOS) and heat capacity, and compare with the Ni FCC bulk counterpart. The characteristic features of the νDOS curves of these clusters are interpreted in terms of the clusters' sizes, the interatomic distance contractions, the bond order values as well as the internal pressure and strains of the clusters. We find that the softest possible frequency of the clusters is size and structure-dependent, being the smallest for the O_h ones. We identify mostly shear, tangential type displacements involving mainly surface atoms for the lowest frequency of the spectra of both I_h and O_h isomers. For the maximum frequencies of these clusters the central atom shows anti-phase movements against groups of nearest neighbor atoms. An excess of heat capacity at low temperatures with respect to the bulk is found, while at high temperatures a constant limiting value, close but lower to the Dulong and Petit value, is determined.

A single-cell transcriptional gradient in human cutaneous memory T cells restricts Th17/Tc17 identity

The homeostatic mechanisms that fail to restrain chronic tissue inflammation in diseases, such as psoriasis vulgaris, remain incompletely understood. We profiled transcriptomes and epitopes of single psoriatic and normal skin-resident T cells, revealing a gradated transcriptional program of coordinately regulated inflammation-suppressive genes. This program, which is sharply suppressed in lesional skin, strikingly restricts Th17/Tc17 cytokine and other inflammatory mediators on the single-cell level. CRISPR-based deactivation of two core components of this inflammation-suppressive program, ZFP36L2 and ZFP36, replicates the interleukin-17A (IL-17A), granulocyte macrophage-colony-stimulating factor (GM-CSF), and interferon gamma (IFNγ) elevation in psoriatic memory T cells deficient in these transcripts, functionally validating their influence. Combinatoric expression analysis indicates the suppression of specific inflammatory mediators by individual program members. Finally, we find that therapeutic IL-23 blockade reduces Th17/Tc17 cell frequency in lesional skin but fails to normalize this inflammatory-suppressive program, suggesting how treated lesions may be primed for recurrence after withdrawal of treatment.

Recovery and characterization of nickel particles by chemical reduction method from wastes generated in electroless industry

The discarded solutions by the chemical nickel industry have high amounts of nickel, this is why they are considered hazardous wastes for the health and the environment. On the other side, Ni particles can have potential applications in the developing of magnetorheological fluids currently being used to improve the performance of mechanical devices. The present study raises the treatment of a residual effluent from a chemical nickel industry by applying a chemical precipitation which uses sodium hypophosphite as a reducer, and varying the order of the reagents involved in the conditioning of the reaction with respect to the reducer. The recovered solids were studied using different material characterization techniques to recognize the chemical composition (X-Ray Fluorescence, Inductively Coupled Plasma Mass Spectrometry), crystallinity and morphology (X-Ray Diffraction, Scanning Electron Microscope), surface charge and size distribution (Dynamic Light Scattering). By the chemical reduction treatment it was possible to decrease the amount of nickel in the residual between 97.25% and 99.50%, obtaining Ni particles that were then tested to be used in magnetic fluids. To this purpose a suspension was prepared by mixing the Ni particles with silicone oil in a constant solid/liquid ratio, and the rheological behavior of this suspension was evaluated as a function of the magnetic field and the deformation applied, revealing an interesting magnetorheological behavior.

Estimation of genetic parameters for partial egg production periods by means of random regression models

We estimated genetic parameters for egg production in different periods by means of random regression models, aiming at selection based on partial egg production from a generation of layers. The production was evaluated for each individual by recording the number of eggs produced from 20 to 70 weeks of age, with partial records taken every three weeks for a total of 17 periods. The covariance functions were estimated with a random regression model by the restricted maximum likelihood method. A model composed of third-order polynomials for the additive effect, ninth-order polynomials for the permanent environment, and a residual variance structure with five distinct classes, was found to be most suitable for adjusting the egg production data for laying hens. The heritability estimates varied from 0.04 to 0.14. The genetic correlations were all positive, varying from 0.10 to 0.99. Selection applied in partial egg production periods will result in greater genetic profit for the adjacent periods. However, as the distance in time between periods increases, selection becomes less efficient. Selection based on the second period (23 to 25 weeks of age), where greater heritability was estimated, would note benefit the final egg-laying cycle periods.

Heritabilities and genetic correlations for reproductive traits in an F2 reciprocal cross chicken population

Studies estimating genetic parameters for reproductive traits in chickens can be useful for understanding and improvement of their genetic architecture. A total of 1276 observations of fertility (FERT), hatchability of fertile eggs (HFE) and hatchability of total eggs (HTE) were used to estimate the genetic and phenotypic parameters of 467 females from an F2 population generated by reciprocal crossing between a broiler line and a layer line, which were developed through a poultry genetics breeding program, maintained by Embrapa Swine and Poultry, Concordia, Santa Catarina, Brazil. Estimates of heritability and genetic and phenotypic correlations were obtained using restricted maximum likelihood calculations under the two-trait animal model, including the fixed effect of group (hatching of birds from the same genetic group) and the random additive genetic and residual effects. The mean percentages for FERT, HFE and HTE were 87.91 ± 19.77, 80.07 ± 26.81 and 70.67 ± 28.55%, respectively. The highest heritability estimate (h(2)) was 0.28 ± 0.04 for HTE. Genetic correlations for FERT with HFE (0.43 ± 0.17), HFE with HTE (0.98 ± 0.02) and FERT with HTE (0.69 ± 0.10) were positive and significant. Individuals with high breeding value for HTE would have high breeding values for HFE and FERT because of the high genetic association between them. These results suggest that HTE should be included as a selection criterion in genetic breeding programs to improve the reproductive performance of chickens, because HTE had the highest heritability estimate and high genetic correlation with FERT and HFE, and it is the easiest to measure.

The effects of short term recombinant human growth hormone (rhGH) on blood rheology in healthy young males

INTRODUCTION

It has been shown that growth hormone (GH) exerts regulatory effects on hemorheology and other metabolic functions. GH stimulates the production of insulin-like growth factor I (IGF-I) and GH-IGF-I system has profound effects on body fluid status. There are speculations that GH has become widely used as a performance enhancing drug among athletes of various sports. The present study evaluated the possible hemorheological effects of short term administration of human recombinant growth hormone (rhGH) in healthy young males.

METHODOLOGY

Thirty young healthy males (27 ± 9) participated in a 29 days study where it was administered either 0.9% sodium chloride or 1 mg of human rhGH from day 1 to day 7. The participants were randomly assigned into either placebo (C) n = 15 or rhGH 1 mg/day (rhGH) group n = 15. This study evaluated plasma fibrinogen levels, red blood cell (RBC) aggregation, deformability and serum IGF-I levels between and within the groups along 29 days.

RESULTS

There was a significant increase in erythrocytes aggregation index post injection (day 8), in accordance to an increase in serum IGF-I.

Phenotypic and functional evaluation of natural killer cells in thymectomized children

The purpose of this study was to determine the effect of thymectomy on the number and activity of NK cells in the peripheral blood of children submitted to thymus removal. Twenty-three children, aged 4 to 48 months at thymectomy, whose thymus was fully removed to permit access to the heart for corrective surgery, were studied. Only children thymectomized during the first year of life had a decreased number of CD2+/CD3+, CD4+/CD16- , and CD8+/CD16- T subsets and an increase in the CD16-/CD56bright+ NK subset. In addition, the CD57-/CD16+ and CD57-/D56+ subsets which are shared by T and NK cells were increased. These findings associated with a tendency to increased NK activity suggest that the human thymus is partially involved in the control of the release of circulating T cells and may negatively modulate some NK subsets, as well as NK activity, during the first year of life but not later.

The large septal arteries in normal hearts, in aortic valve disease, and in tetralogy of Fallot

BACKGROUND

Several surgical techniques such as the Ross operation or total correction of tetralogy of Fallot require incisions of the upper ventricular septum. Very few reports on the anatomy of the septal arteries of the pathologic heart can be found in the literature. To get a more precise knowledge of the large septal arteries in pathologic hearts, we have compared the anatomy of normal hearts with that of hearts with aortic valve disease and of tetralogy of Fallot.

METHODS

Twenty-six normal heart specimens (group A), 11 with aortic valve disease (group B), and 4 with tetralogy of Fallot (group C) were dissected.

RESULTS

In groups B and C a single large septal artery was always found. The large septal artery had the orientation previously described for normal hearts. Still, its course in the lower border of the anterior extension of the septomarginal trabecula was deeper. The anterior extension of the septomarginal trabecula was 4 +/- 3 mm deep in group A, 6 +/- 2 mm in group B, and 3 mm in group C. The interventricular septum was much thicker in groups B and C than in group A.

CONCLUSIONS

The position of the large septal artery can be predicted from coronary angiography and from the morphology of the anterior extension of the septomarginal trabecula. Knowledge of its position can improve the safety of operations performed on the outflow of the interventricular septum.