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V Milman

Publications and source records attributed to V Milman.

17 recordsLinked to original sources
PubMed2001

Systematic ab initio study of the compressibility of silicate garnets.

The structural properties of the silicate garnets andradite, Ca(3)Fe(2)Si(3)O(12), uvarovite, Ca(3)Cr(2)Si(3)O(12), knorringite, Mg(3)Cr(2)Si(3)O(12), goldmanite, Ca(3)V(2)Si(3)O(12), blythite, Mn(2+)(3)Mn(3+)(2)Si(3)O(12), skiagite, Fe(2+)(3)Fe(3+)(2)Si(3)O(12), calderite, Mn(2+)(3)Fe(3+)(2)Si(3)O(12), and khoharite, Mg(3)Fe(3+)(2)Si(3)O(12), have been investigated with a quantum-mechanical model as a function of applied pressure. The study has been performed with the density functional theory code CASTEP, which uses pseudopotentials and a plane-wave basis set. All structural parameters have been optimized. The calculated static geometries (cell parameters, internal coordinates of atoms and bond lengths), bulk moduli and their pressure derivatives are in good agreement with the experimental data available. Predictions are made for those cases where no experimental data have been reported. The data clearly indicate that the elastic properties of all silicate garnets are dominated by the compressibility of the dodecahedral site. The compression mechanism is found to be based on a bending of the angle between the centers of the SiO(4) tetrahedra and the adjacent octahedra, as in the aluminosilicate garnets. An analysis of the relationship between ionic radii of the cations and the compressibility of silicate garnets is presented.

Journal Article↗
PubMed2000

Use of sunscreen is linked with elevated naevi counts in Israeli school children and adolescents.

Epidemiological evidence indicates that a fair complexion and exposure to solar radiation in early years contribute to the proliferation of naevi and subsequent melanoma risk. To determine whether protection from sunlight is associated with lower naevi counts, we examined the prevalence and risk factors of naevi in a sample of Israeli school pupils. Whole body counts of naevi were recorded in 974 out of 1312 (74.2%) recruited pupils (7 and 12 year olds) from Ramat-Gan and Jerusalem. Host characteristics and habits of sun exposure were obtained using questionnaires. In each age group and geographic area, the mean whole body naevi counts, adjusted for confounders, were higher among males, pupils of European-American descent, and those susceptible to sunburn. The contributions to naevi risk of fair skin colour and frequent recreational sun exposure were higher among 7 year olds. Regular sunscreen use contributed to the naevi risk for both age strata in Ramat-Gan (at age 7, rate ratio [RR] = 1.7, 95% confidence interval [CI] = 1.3-2.2; at age 12, RR = 1.5, 95% CI = 1.1-2.1). Among the younger age group in Ramat-Gan, even seldom compared with no use of sunscreen was associated with higher naevi counts (RR= 1.5, 95% CI = 1.2-2.0). Similar patterns were noted with the pupils from Jerusalem. In conclusion, the elevated naevi count with increased sunscreen use indicates that sunscreens apparently do not modify the genetic predisposition to naevi proliferation. For better protection of children and adolescents, including those who use sunscreens, from the naevogenic effect of solar radiation, they should be encouraged to limit their exposure and wear protective clothing when in the sun.

Adolescent↗
PubMed2000

Aplanarity of CO3 groups: a theoretical investigation.

Density functional theory-based calculations have been used to demonstrate that the aplanarity of CO3 groups in some carbonates such as dolomite, CaMg(CO3)2, aragonite, CaCO3, and norsethite, BaMg(CO3)2, is a ground-state property. This distortion stabilizes dolomite by approximately 500 J mol(-1). Up to at least 6 GPa, the aplanarity of CO3 groups in dolomite is independent of pressure. In aragonite the aplanarity increases slightly on increasing pressure, while a significant tilting of the CO3 groups occurs. The calculations do not support previous findings of anomalously low values for the pressure derivative of the bulk moduli, B', of aragonite and dolomite. Instead, the computed pressure dependences of the unit-cell volumes correspond to B' = 5.0 (5) for aragonite and B' = 4(1) for dolomite, when fitted with a third-order Birch-Murnaghan equation-of-state.

Journal Article↗
PubMed2000

Structure of Cu6PbO8

First-principles quantum mechanical calculations based on density functional theory were performed for Cu6PbO8, hexacopper lead octaoxide, murdochite. The computed lattice parameter, density and bond lengths at ambient pressure are in good agreement with experimental data for murdochite. At about 18 GPa a phase transition is predicted, when a polymorph with a Suzuki-type structure, i.e. a close-packed structure with ordered vacancies, is proposed to become stable. The pressure dependence of the structural parameters has been calculated for the two polymorphs and their bulk moduli have been predicted. It is argued that the incorporation of halogen atoms is not a precondition for the stability of murdochite.

Journal Article↗