Strain-induced electronic band convergence: effect on the Seebeck coefficient of Mg2Si for thermoelectric applications.

The present theoretical study, performed using density-functional theory and Boltzmann transport theory formalisms, shows that under 2.246 % isotropic tensile strain, the two energy-lowest conduction bands of Mg2Si overlap. The two, threefold-degenerated orbitals become a unique, sixfold-degenerated orbital. It is demonstrated that such degeneracy implies an increase of the Seebeck coefficient, of the electrical conductivity, of the power factor, and in fine of the figure of merit.

Heterogeneous melting of methane confined in nano-pores.

The melting transition of methane adsorbed in nanopores has been studied and compared in two types of structures: carbon slits pores and square shaped channels. We show that the nano-confinement not only modifies the temperatures of phase transformation but also induces strong space heterogeneity of the adsorbate. We emphasize the role of the structural heterogeneity on the mechanism of melting: in nanometric pores, each adsorbed layer exhibits different mechanisms of structural transformation and the notion of a unique transition temperature is not well defined.

Magnetic properties of NpNiGa(5).

We have investigated a polycrystalline sample of NpNiGa(5) by magnetization, specific heat and (237)Np Mössbauer spectroscopy. We confirm that a ferromagnetic order sets in at T(C)≈30 K and that NpNiGa(5) undergoes a second transition at T(N)≈18 K. Mössbauer data indicate that the transition at T(N) is accompanied by a steep increase of the Np magnetic moment, which saturates to a value of 0.94 µ(B), in good agreement with the recently published neutron diffraction results. The Sommerfeld specific heat coefficient γ = 114 mJ mol(-1) K(-2) is the highest among the NpTGa(5) compounds. It compares to the ones observed in the PuTGa(5) superconductors. The trend of the isomer shift along the NpTGa(5) (T = Fe, Co, Ni, Rh) series points to a tendency towards localization of the 5f electrons when increasing the number of d electrons of the transition metal T. Neither fully localized nor fully itinerant models are able to reproduce the whole experimental data. Realistic models should include the dual nature of the 5f electrons, i.e. consider the difference in the degree of itinerancy among 5f electrons in the NpTGa(5) compounds.

[Breast MRI in invasive lobular carcinoma: diagnosis and staging]. / Apport de l'IRM dans le diagnostic et le bilan d'extension des cancers lobulaires infiltrants.

PURPOSE: To assess the use of breast MRI for the diagnosis and staging of invasive lobular carcinoma and its impact on surgical management. MATERIALS AND METHODS: Retrospective study of 35 invasive lobular carcinoma, histologically diagnosed in 34 patients who underwent clinical exam, mammography, ultrasonography and magnetic resonance imaging. RESULTS: Enhancement at MRI was seen for all 35 cancers. It was focal for 24 patients, regional for 10 and diffuse for 1. The kinetic of the enhancement was characteristic of malignancy for 33 patients. For 11 patients the MRI staging was positive, finding 8 news cancers. For 3 patients MRI lead to biopsy of benign lesions but improved the surgical management in the 8 cases of new cancers: wider excision for 3 cases, planned breast conservation converted to mastectomy in 3 cases and excision of contralateral lesion in 2 cases. CONCLUSION: Breast MRI is useful in diagnosis, staging and surgical management of invasive lobular breast carcinoma.

Structural tuning of unconventional superconductivity in PuMGa5 (M=Co,Rh).

The superconducting properties of the recently discovered PuMGa5 (M=Co,Rh) superconductors, including the power law behavior of the specific heat, the evolution of the superconducting transition T(c) temperature with pressure, and the linear relation between T(c) and ratio of tetragonal lattice parameters c/a, are compared to those of the heavy fermion CeMIn5 (M=Co,Rh,Ir) unconventional superconductors. The striking similarity of the properties between the two families of superconductors suggests a common physics and a common (magnetically mediated) mechanism of superconductivity.

Understanding the formation of new clusters of alkali and alkaline Earth metals: a new synthetic approach, single-crystal structures, and theoretical calculations.

A new synthetic approach, reacting alkaline earth metal iodides with butyllithium, lithium hydroxide, and/or lithium butoxide under salt elimination, is presented, giving access to some interesting clusters of calcium, strontium, and barium, partially in combination with lithium. The so far largest calcium cluster Li[[Ca(7)(mu(3)-OH)(8)I(6)(thf)(12)](2)(mu(2)-I)].3THF, 4, and the new strontium compound [Sr(3)I(3)(OH)(2)(thf)(9)]I, 5, are shown to feature common building blocks of OH-capped M(3) triangles. On the basis of mainly electrostatic interactions, these clusters are not volatile. By introducing LiO(t)Bu, the two clusters [IM(O(t)Bu)(4)[Li(thf)](4)(OH)] (6, M = Sr; 7, M = Ba) are prepared, 7 exhibiting volatility as an important physical property, which makes it a potential precursor for chemical vapor deposition. The structural relationship between 4, 5, 6, and 7 and their respective starting materials is shown, and possible reaction mechanisms are proposed. Exhibiting surprising and new structural motifs, the bonding modes of these clusters are investigated by the electron localization function as well as by ab initio calculations.

Plutonium-based superconductivity with a transition temperature above 18 K.

Plutonium is a metal of both technological relevance and fundamental scientific interest. Nevertheless, the electronic structure of plutonium, which directly influences its metallurgical properties, is poorly understood. For example, plutonium's 5f electrons are poised on the border between localized and itinerant, and their theoretical treatment pushes the limits of current electronic structure calculations. Here we extend the range of complexity exhibited by plutonium with the discovery of superconductivity in PuCoGa5. We argue that the observed superconductivity results directly from plutonium's anomalous electronic properties and as such serves as a bridge between two classes of spin-fluctuation-mediated superconductors: the known heavy-fermion superconductors and the high-T(c) copper oxides. We suggest that the mechanism of superconductivity is unconventional; seen in that context, the fact that the transition temperature, T(c) approximately 18.5 K, is an order of magnitude greater than the maximum seen in the U- and Ce-based heavy-fermion systems may be natural. The large critical current displayed by PuCoGa5, which comes from radiation-induced self damage that creates pinning centres, would be of technological importance for applied superconductivity if the hazardous material plutonium were not a constituent.

Photochemistry of the CpNiNO complex. A theoretical study using density functional theory.

The photochemistry of the CpNiNO complex has been investigated using density functional theory. The whole potential energy curve along the NiNO angle coordinate is presented for the first time with both ground and metastable states, and transition states connecting the minima. The excited states of the GS, MS(I), and MS(II) species have been calculated using time-dependent density functional theory. Furthermore, the structure of the excited states pertaining to the photochemistry of CpNiNO has been optimized. From these results it is shown that the backward GS <-- MS(II) <-- MS(I) reaction is more efficient than the forward GS --> MS(II) --> MS(I) scheme.

Essential drugs in the new international economic environment.

Recent global developments in the regulation of trade and intellectual property rights threaten to hinder the access of populations in developing countries to essential drugs. The authors argue for state intervention in the health and pharmaceutical markets in order to guarantee equitable access to these products.

[Mass screening for breast cancer in Herault county. First results in women between 40 and 70 years old]. / Dépistage de masse du cancer du sein dans l'Hérault. Premiers résultats chez la femme entre 40 et 70 ans.

A large scale mammography breast cancer screening has begun in Herault county on the first of july 1990. The aim of the project was to determine the impact of two-view mammography upon the size of the tumor and later upon mortality from breast cancer. The women aged 40-70 at entry were invited by mail to the first round of mobile breast screening. Between the start and the 8th of march 1991, 5098 (64%) attended the first round. The cancer detection rate was 5.9/1000, the positive detection rate was 7.75%, the benign malignant surgical biopsy ratio was 1:0.7 and the percentage of surgical biopsies positives for malignancy was 42.6%. Two months after this study, the screening specificity was 96.7% and the sensibility was 92.7%. The rate of tumor size less or equal to 1 cm was 72% (for 30 malignancies) and the rate of mastectomies was 43.3%. These friendly results were compared to those of others breast cancers screenings.

The use of iodolipids in hepatosplenic computed tomography.

Iodolipids have been used as a contrast medium for hepatosplenic computed tomography (CT) in 148 patients. In all but two of these cases, the contrast material was injected by the intravenous route. The method appears to be safe due to the marked reduction of dosage in CT compared with conventional radiographic iodolipid hepatography. This decreased dosage is made possible by the improved density and spatial resolution of CT. Pictorial and histographic densitometric analysis of normal and abnormal liver after iodolipid administration yields considerable diagnostic improvement.