Realistic semiconductor heterostructures design using inverse scattering

We discuss the construction of optimized electronic filters using inverse scattering methods. We study a wide range of densities and temperatures, room temperature included. Discretization methods of the potential (including the self-consistent potential of the conduction electrons) are worked out that retain all its properties.     

The water purification system for the low background counting test facility of the Borexino experiment at Gran Sasso

The Borexino experiment, for the study of solar neutrino physics, requires radiopurity at the level of 5 × 10⁻¹⁶ g/g ²³⁸U equivalent (or 6 × 10⁻⁹ Bq/kg) on a detector mass of many tons of scintillator. Feasibility studies are performed in a counting test facility now operating at LNGS, which consists of 4 t of liquid scintillator viewed by 100 photomultipliers and shielded by 100 t of water. The accomplishment of this goal requires the shielding liquid, water, to be at the 10⁻¹³ g/g contamination level (1.2 × 10⁻⁶ Bq/kg) or better. This paper describes the water purification system; it consists of a combination of several purification processes to remove particulate, radioactive ions, dissolved gases and other impurities. Residual contaminations are measured by analytical or direct-counting techniques. For radon measurement, particularly challenging at this low activity levels, a low background counting method has been developed.     

A new upper bound on the minimum distance of turbo codes

In this paper, a new upper bound on the minimum distance of turbo codes is derived. The new bound is obtained by construction of an undirected graph which reflects the characteristics of the constituent codes and the interleaver. The resulting expression shows that the minimum distance of a turbo code grows approximately with the base-3 logarithm of the information word length. The new bound is easy to compute, applies to rate k/sub 0//n/sub 0/ constituent encoders, and often improves over existing results.     

Lipoprotein(a) and other lipids after oophorectomy and estrogen replacement therapy

We present a case report of uretero-acetabular fistula in a female complicating orthopaedic surgery of congenital coxal difformity. An ileal pedicle graft was used to replace the terminal ureter. The difficulty of such complication is to choose the best the rapeutic strategy between surgical and non surgical techniques. We review here the various urological armamentarium to affront such a rare and multifactorial complication.     

Effect of Regiochemistry and Methylation on the Anticancer Activity of a Ferrocene-Containing Organometallic Nucleoside Analogue

Four new bis-substituted ferrocene derivatives containing either a hydroxyalkyl or methoxyalkyl group and either a thyminyl or methylthyminyl group have been synthesised and characterised by a range of spectroscopic and analytical techniques. They were included in a structure-activity-relationship (SAR) study probing anticancer activities in osteosarcoma (bone cancer) cell lines and were compared with a known lead compound, 1 -(S,R_p), a nucleoside analogue that is highly toxic to cancer cells. Biological studies using the MTT assay revealed that a regioisomer of ferronucleoside 1 -(S,R_p), which only differs from the lead compound in being substituted on two cyclopentadienyl rings rather than one, was over 20 times less cytotoxic. On the other hand, methylated derivatives of 1 -(S,R_p) showed comparable cytotoxicities to the lead compound. Overall these studies indicate that a mechanism of action for 1 -(S,R_p) cannot proceed through alcohol phosphorylation and that its geometry and size, rather than any particular functional group, are crucial factors in explaining its high anticancer activity.     

A role for cell migration in the sexual transmission of HIV-1?

The issue of how human immunodeficiency virus-1 (HIV-1) enters the body following sexual contact has been the subject of considerable controversy. Several possible routes for the initial infection have been suggested [1-6], including the possibility that the transmission is mediated by HIV-1-infected lymphocytes or macrophages in serum and female genital tract secretions, rather than by free virus. We recently reported that HIV-1-infected, activated primary monocytes can migrate between epithelial cells grown in confluent monolayer cultures in vitro [7]. We report here on experiments carried out in mice to test the hypothesis that mononuclear blood cells are capable of migrating through intact epithelia, and thus of carrying a virus into an animal. We placed double-stained, activated mononuclear blood cells into the vaginas of mice; four hours later, numerous double-stained cells were observed in the connective tissue beneath the vaginal epithelium and the iliac lymph nodes of the experimental mice. We speculate that such migration may be involved in the sexual transmission of HIV-1.     

Nickel(III) and Copper(III) Complexes with 13- and 14-membered Tetra-aza Macrocycles. Ring-size and Medium Effects on the MIII/MII Redox Couple Potentials

The one-electron oxidation of the Ni^II and Cu^II complexes with 13- and 14-membered macrocycles 1 and 2 to produce authentic Ni^III and Cu^III species has been electrochemically investigated and the E_1/2 values associated to the reversible M^III/M^II redox couple have been determined by means of the Differential Pulse Voltammetry technique. The 13-membered ring favours the attainment of the Cu^III state, whereas the 14-membered ring favours the formation of the Ni^III complex. This opposite behaviour is satisfactorily interpreted in terms of size of the metal ions and aperture of the macrocyclic cave. Moreover the effect of the concentration of the inert electrolyte (NaClO₄, 0.1–7.0 M) on the E_1/2(M^III/M^II) values has been investigated: the increase of the NaClO₄ concentration favours the formation of the Cu^III complexes and disfavours the formation of the Ni^III species. This behaviour is ascribed to the destabilization of Ni^III and Cu^II complexes induced by perchlorate ion through the formation of hydrogen bonds with water molecules axially coordinated to the metal ions.     

A diffusive light collection system for hard X-ray astronomical scintillation detectors

A novel design of a detector system for hard X-ray astronomy is described which permits large sensitive areas to be constructed on a modular basis. The system also incorporates high quality active shielding without the use of the phoswich system. The development and performance of the diffusive light collection optics are discussed.     

Determination of radial growth rate of colonies of Sclerotium rolfsii F-6656 for the evaluation of culture medium, optimum incubation temperature, osmo- and halotolerance

The measurement of the colony radial growth rate (Kr) on solid medium of colonies of Sclerotium rolfsii Proimi F-6656 for the evaluation of scleroglucan production medium and other different media, incubation temperature and tolerance to diverse concentrations of sucrose and NaCl were studied. The optimum growth temperature observed was 30 degrees C. The Kr value reached on the Production Medium used (0.66 mm.h-1) showed no differences compared with those of the other media tested, indicating that all the requirements for growth were provided. Poor growth was only observed on Soil Extract Agar. The fungus tolerated concentrations of sucrose from 0.15 to 1.17 M, on both Czapek and production medium. Growth was limited by the highest concentrations of sucrose tested (0.88 and 1.17 M), as indicated by a slower increase in colony size. Addition of 0.86 M NaCl to the production medium and YM agar did not inhibit growth completely, but decreased the radial growth rate considerably (80 and 70% respectively).