Monte Carlo study of Si(111) homoepitaxy

An attempt is made to simulate the homoepitaxial growth of a Si(111) surface by the kinetic Monte Carlo method in which the standard Solid-on-Solid model and the planar model of the (7x7) surface reconstruction are used in combination. By taking account of surface reconstructions as well as atomic deposition and migrations, it is shown that the effect of a coorparative stacking transformation is necessary for a layer growth.Comment: 4 pages, 5 figures. For Fig.1 of this article, please see Fig.2 of Phys.Rev. B56, 3583 (1997). To appear in Phys.Rev.B. (June 1998

An L∞ regularisation strategy to the inverse source identification problem for elliptic equations

In this paper we utilise new methods of Calculus of Variations in L ∞ to provide a regularisation strategy to the ill-posed inverse problem of identifying the source of a non-homogeneous linear elliptic equation, satisfying Dirichlet data on a domain. One of the advantages over the classical Tykhonov regularisation in L 2 is that the approximated solution of the PDE is uniformly close to the noisy measurements taken on a compact subset of the domain

Relationship between adiposity and admixture in African-American and Hispanic-American women.

ObjectiveThe objective of this study was to investigate whether differences in admixture in African-American (AFA) and Hispanic-American (HA) adult women are associated with adiposity and adipose distribution.DesignThe proportion of European, sub-Saharan African and Amerindian admixture was estimated for AFA and HA women in the Women's Heath Initiative using 92 ancestry informative markers. Analyses assessed the relationship between admixture and adiposity indices.SubjectsThe subjects included 11 712 AFA and 5088 HA self-identified post-menopausal women.ResultsThere was a significant positive association between body mass index (BMI) and African admixture when BMI was considered as a continuous variable, and age, education, physical activity, parity, family income and smoking were included covariates (P<10(-4)). A dichotomous model (upper and lower BMI quartiles) showed that African admixture was associated with a high odds ratio (OR=3.27 (for 100% admixture compared with 0% admixture), 95% confidence interval 2.08-5.15). For HA, there was no association between BMI and admixture. In contrast, when waist-to-hip ratio (WHR) was used as a measure of adipose distribution, there was no significant association between WHR and admixture in AFA but there was a strong association in HA (P<10(-4); OR Amerindian admixture=5.93, confidence interval=3.52-9.97).ConclusionThese studies show that: (1) African admixture is associated with BMI in AFA women; (2) Amerindian admixture is associated with WHR but not BMI in HA women; and (3) it may be important to consider different measurements of adiposity and adipose distribution in different ethnic population groups

The effect of octahedral distortions on the electronic properties and magnetic interactions in O3 NaTMO2 compounds (TM = Ti–Ni & Zr–Pd)

The interplay between the coordination environment and magnetic properties in O3 layered sodium transition metal oxides (NaTMO2) is a fascinating and complex problem. Through detailed and comprehensive density functional investigations on O3 NaTMO2 compounds, we demonstrate that the TM ions in O3 NaMnO2, NaFeO2 and NaCoO2 adopt a high spin state. Structurally, NaMnO2 and NaPdO2 undergo Jahn–Teller distortions while NaNbO2 undergoes puckering distortion. Furthermore, in addition to Jahn–Teller distortion, NaPdO2 exhibits charge disproportionation as it contains Pd2+, Pd3+ and Pd4+ species. These distortions stabilize the inter-plane ferromagnetism. Additionally, the inter-plane ferromagnetic coupling is stabilized by kinetic p–d exchange mechanism in undistorted NaCoO2, NaNiO2 and NaTcO2. The intra-plane coupling in this family of compounds on the other hand was found to be generally weak. Only NaMnO2, NaNiO2 and NaTcO2 are predicted to show bulk ferromagnetism with estimated Curie temperatures below ∼50 K

T cell clones specific for hybrid I-A molecules. Discrimination with monoclonal anti-I-A (k) antibodies

Alloreactive and soluble antigen-reactive, I-A-restricted T cell clones were examined for their ability to recognize hybrid I-A antigens. Several clones that recognized hybrid I-A(b)/I-A(k) molecules on (C57BL/6 x A/J)F(1) [(B6A)F(1)] spleen cells were studied. We were able to distinguish clones that recognized hybrid I-A molecules of the A(b)(a)A(k)(β) type from those that recognized A(k)(a)A(b)(β) molecules. We reached this conclusion by considering data from three independent types of experiments. (a) Monoclonal antibodies were used to inhibit T cell stimulation. Antibodies 10.2.16 and H116.32 distinguished two mutually exclusive “families” of T cell clones. One group of clones was inhibited by 10-2.16 and not H116.32, the other group exhibited reciprocal inhibition. (b) T cell proliferation was assayed using antigen-presenting cells from B6.C-H-2(bml2) (bml2) and [bml2 × B10.A(4R)]F(1) mice. Because the bml2 strain has a mutation that results in an altered A(b)(β) polypeptide chain (A(bm12)(β)), we reasoned that clones that could recognize the [bm12 × B 10.A(4R)]F(1) cells were recognizing A(b)(a)A(k)(β) molecules. Alternatively, clones not recognizing [bml2 × B10.A(4R)]F(1) cells had specificity for A(k)(a)A(b)(β) molecules. (c) I-A molecules immunoprecipitated from radiolabeled (B6A)F(1) splenocyte extracts were analyzed by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These experiments confirmed an earlier report that antibody 10.2.16 recognized determinants on the A(k)(β) chain (12). Antibody H116.32 immunoprecipitated products consistent with recognition of A(k)(a) determinants. Taken together, these three types of results offer conclusive evidence that T cell clones recognizing “hybrid” I-A molecules use either A(b(k)A(k)(β) or A(k)(a)A(b)(β) molecules as recognition or restriction sites. Clones whose proliferation was supported by [bm 12 x B10.A(4R)]F(1) cells and blocked by anti-I-A(k) antibody 10-2.16 recognized A(b)(a)A(k)(β) B molecules. Clones that were blocked by antibody H116.32 and did not recognize [bml2 X B10.A(4R)]F(1) cells use a recognition site(s) on A(b)(a)A(k)(β) molecules. Thus, we can demonstrate both functionally and biochemically that hybrid F(1) I-A molecules of the structure A(k)(a)A(b)(β) and A(b)(a)A(k)(β) both exist on (B6A)F(1) splenocytes and that both configurations are used in immune recognition phenomena

Involvement of Mhc Loci in immune responses that are not Ir-gene-controlled

Twenty-nine randomly chosen, soluble antigens, many of them highly complex, were used to immunize mice of two strains, C3H and B10.RIII. Lymphnode cells from the immunized mice were restimulated in vitro with the priming antigens and the proliferative response of the cells was determined. Both strains were responders to 28 of 29 antigens. Eight antigens were then used to immunize 11 congenic strains carrying different H-2 haplotypes, and the T-cell proliferative responses of these strains were determined. Again, all the strains responded to seven of the eight antigens. These experiments were then repeated, but this time -antibodies specific for the A (AA) or E (EE) molecules were added to the culture to block the in vitro responsiveness. In all but one of the responses, inhibition with both A-specific and E-specific antibodies was observed. The response to one antigen (Blastoinyces) was exceptional in that some strains were nonresponders to this antigen. Furthermore, the response in the responder strains was blocked with A-specific, but not with E-specific, antibodies. The study demonstrates that responses to antigens not controlled by Irr genes nevertheless require participation of class II Mhc molecules. In contrast to Ir gene-controlled responses involving either the A- or the E-molecule controlling loci (but never both), the responses not Ir-controlled involve participation of both A- and E-controlling loci. The lack of Ir-gene control is probably the result of complexity of the responses to multiple determinants. There is thus no principal difference between responses controlled and those not controlled by Ir genes: both types involve the recognition of the antigen, in the context of Mhc molecules