Characterization of Carbon-Contaminated B4C-Coated Optics after Chemically Selective Cleaning with Low-Pressure RF Plasma.

Boron carbide (B4C) is one of the few materials that is expected to be most resilient with respect to the extremely high brilliance of the photon beam generated by free electron lasers (FELs) and is thus of considerable interest for optical applications in this field. However, as in the case of many other optics operated at light source facilities, B4C-coated optics are subject to ubiquitous carbon contaminations. Carbon contaminations represent a serious issue for the operation of FEL beamlines due to severe reduction of photon flux, beam coherence, creation of destructive interference, and scattering losses. A variety of B4C cleaning technologies were developed at different laboratories with varying success. We present a study regarding the low-pressure RF plasma cleaning of carbon contaminated B4C test samples via inductively coupled O2/Ar, H2/Ar, and pure O2 RF plasma produced following previous studies using the same ibss GV10x downstream plasma source. Results regarding the chemistry, morphology as well as other aspects of the B4C optical coating before and after the plasma cleaning are reported. We conclude that among the above plasma processes only plasma based on pure O2 feedstock gas exhibits the required chemical selectivity for maintaining the integrity of the B4C optical coatings.

k=0 magnetic structure and absence of ferroelectricity in SmFeO3.

SmFeO3 has attracted considerable attention very recently due to its reported multiferroic properties above room temperature. We have performed powder and single crystal neutron diffraction as well as complementary polarization dependent soft X-ray absorption spectroscopy measurements on floating-zone grown SmFeO3 single crystals in order to determine its magnetic structure. We found a k=0 G-type collinear antiferromagnetic structure that is not compatible with inverse Dzyaloshinskii-Moriya interaction driven ferroelectricity. While the structural data reveal a clear sign for magneto-elastic coupling at the Néel-temperature of ∼675 K, the dielectric measurements remain silent as far as ferroelectricity is concerned.

Two-dimensional electron gases at LaAlO3/SrTiO3 interfaces: orbital symmetry and hierarchy engineered by crystal orientation.

Recent findings show the emergence of two-dimensional electron gases (2DEGs) at LaAlO(3)/SrTiO(3) interfaces along different orientations; yet details on band reconstructions have remained so far unknown. Via x-ray linear dichroism spectroscopy, we demonstrate that crystal symmetry imposes distinctive 2DEG orbital hierarchies on (001)-and (110)-oriented quantum wells, allowing selective occupancy of states of different symmetry. Such orientational tuning expands the possibilities for electronic engineering of 2DEGs and opens up enticing opportunities to understand the link between orbital symmetry and complex correlated states at LaAlO(3)/SrTiO(3) quantum wells.

Surface symmetry-breaking and strain effects on orbital occupancy in transition metal perovskite epitaxial films.

The electron occupancy of 3d-orbitals determines the properties of transition metal oxides. This can be achieved, for example, through thin-film heterostructure engineering of ABO(3) oxides, enabling emerging properties at interfaces. Interestingly, epitaxial strain may break the degeneracy of 3d-e(g) and t(2g) orbitals, thus favoring a particular orbital filling with consequences for functional properties. Here we disclose the effects of symmetry breaking at free surfaces of ABO(3) perovskite epitaxial films and show that it can be combined with substrate-induced epitaxial strain to tailor at will the electron occupancy of in-plane and out-of-plane surface electronic orbitals. We use X-ray linear dichroism to monitor the relative contributions of surface, strain and atomic terminations to the occupancy of 3z(2)-r(2) and x(2)-y(2) orbitals in La(2/3)Sr(1/3)MnO(3) films. These findings open the possibility of an active tuning of surface electronic and magnetic properties as well as chemical properties (catalytic reactivity, wettability and so on).

[Departmental compilation of histoprognostic data in senology. Apropos of campaign screening in Bouches-du-Rhône]. / Recueil départemental des données histopronostiques en sénologie. A propos de la campagne de dépistage des Bouches-du-Rhône.

In January 1990 a registry for cases of breast cancer occurring in the Bouches-du-Rhone area was set up in conjunction with a screening programme for women over 50 years of age. The aim of this study was to compare histoprognostic findings of unscreened patients (A) with a palpable lesion, screened patients (B) with or without a palpable lesion and self screened patients (C) registered for clinically occult mammary carcinoma. The histoprognostic criteria studied were: histological type, tumor size, prognostic grade and axillary lymph node involvement. Of the 2,478 surgical procedures registered, 1,125 involved women over 50 years of age including 47% with malignant disease. Only 3.7% of screened patients presented intraductal carcinoma compared with 1.17% to 18.2% of unscreened A or self-screened C patients. The incidence of minimal infiltrating breast cancer smaller than 10 mm varied widely from 17.3% in A patients to 33.7% in B patients and 51.4% in C patients (P < 0.001). The incidence of histoprognostic grade III tumors ranged from 17.9% in A patients to 10% in B patients and 4.3% in C patients (P < 0.007). Lymph node involvement decreases from 41% in A to 28% in B patients and 23% in C patients (P = 0.01). Based on our data, 41.9% of screened patients were in the most favorable prognostic category, ie intraductal carcinoma or infiltrating carcinoma less than 10 mm or grade I and no lymph node involvement, versus only 26.1% of A patients and 60.9% of C patients (P < 0.0001). Information of the incidence, pathology of interval tumors in previously screened women will be evaluated in the future. This first study underscores the necessity for this kind of registry to evaluate the histoprognostic profile year by year of a breast cancer screening campaign.

Alteration in prostacyclin and prostaglandin E2 production. Correlation with changes in human aortic atherosclerotic disease.

Prostacyclin (PGI2) and prostaglandin E2 (PGE2) production was investigated in human aortas (five controls and 27 with atherosclerotic lesions). The specific activities of PGI2 and PGE2 synthetase were studied using radioimmunoassays of PGE2 and 6-keto-PGE1 alpha of aortic microsomes incubated in the presence of additional substrate and cofactors. The atherosclerotic lesions were examined under the light microscope and were classified as Stage 1 when the disease was restricted to the intima and as Stages 2 and 3 when there were moderate or advanced lesions. Prostaglandin production for the control group (n = 5), Stage 1 (n = 7), Stage 2 (n = 10), and Stage 3 (n = 10) were as follows: 454 +/- 15, 162 +/- 81, 92 +/- 90, and 65 +/- 61 pmol 6-K-PGF1 alpha/50 mg protein/10 minutes; and 15 +/- 12, 399 +/- 406, 227 +/- 174, and 366 +/- 362 pmol PGE2/50 mg protein/10 minutes (mean +/- SD) respectively. We conclude that: 1) In normal aortas, PGE2 production was low, while PGI2 synthesis activity was elevated. The reverse situation was observed in aortas with atherosclerosis lesions (p less than 0.05). 2) There was an inverse relationship between PGE2 and PGI1 production (p less than 0.05). 3) There was a direct histologic relationship between lower PGI2 production and atherosclerosis progression. A decided decline in 6-K-PGF1 alpha production was detected in aortas in the early stages (65% of control values). 4) By contrast, a progressive increase in PGE2 production was found in Stage 2 and Stage 3 groups (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

[Plasma thromboxane B2 and capacity of the aorta to produce prostacyclin in arteriopathies of the lower extremities]. / Thromboxane B2 plasmatique et capacité de production de prostacycline par l'aorte dans les artériopathies des membres inférieurs.

Plasma levels of thromboxane B2, and 6-Keto-PGF1 alpha, stable metabolites of thromboxane and of prostacyclin were determined by radioimmunoassay in 17 patients with arterial disease and 10 control subjects. The production of prostacyclin from incubates of aortic microsomal fractions of patients was also studied. There was a significant elevation of thromboxane B2 in the peripheral venous blood of patients with arterial lesions (142 +/- 152 pg/ml vs 22 +/- 2 pg/ml, p less than 0.005); levels of 6-KetoPGF1 alpha were equally low in controls and patients. Rate of production of prostacyclin, which was 450 +/- 24 pmol/50 mg of proteins in 10 minutes in controls, was reduced to 97 +/- 86 pmol/50 mg prot. 10 min (p less than 0.01) in patients. Co-existence of raised plasma thromboxane levels and a reduced capacity for prostacyclin synthesis in the same patients is supportive evidence of the thrombogenic theory of arterial disease.

Ultrastructural study of osteosarcomas.

The ultrastructural examination of four osteosarcomas (osteogenic, undifferentiated, and pleomorphic) is described. There are three types of tumor cells. Most of the cells are held in contact by desmosome-like tight junctions; they are atypical osteoblasts with cytoplasmic processes, dilated rough endoplasmic reticulum, mitochondria carrying calcific inclusions, lipid droplets surrounded by glycogen, and intracellular fine filamentous fibers. Other cells exhibiting varying degrees of osteoblastic maturity are also seen with multilobed nuclei, a clear cytoplasm, and straight bordered membranes. The last type is chondroid with abundant deposits of glycogen, lipid droplets, and undilated rough endoplasmic reticulum. The matrix is composed of fibrils without periodicity, scattered and deteriorated collagen fibers, and focal calcium deposits of hydroxyapatite crystals as in embryonal bone, dentine, or callus bone.