Search Results - (Author, Cooperation:M. Salvato)

2011-01-14

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

1089-7550

AIP Digital Archive

Physics

The superconducting properties of spin-glass superconducting multilayers made of Nb (superconducting) and CuMn (spin glass) have been studied. The superconducting critical temperature Tc of the multilayers was strongly dependent on the thickness of the spin-glass layers. The Radovic et al. theory [Phys. Rev. B 44, 759 (1991)], which foresees a phase difference 0≤φ≤π between neighboring superconducting layers, has given a qualitative description of these experimental data. The parallel and perpendicular critical magnetic-field measurements have shown many interesting effects related to the reduced dimensionality of the samples. © 1995 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The electrical transport properties of Bi2Sr2Ca1Cu2O8+x thin films have been measured in the temperature range from 20 to 50 K and in external magnetic fields up to 4 T. The dependence of the normalized pinning force f=Fp/Fp,max on the reduced magnetic field h=H/H* (H* is the irreversibility field) exhibits a scaling law behavior, indicating that a single pinning mechanism is present in the investigated temperature range. The Fp(H) curves were analyzed within the framework of the classical Anderson–Kim theory of flux creep, taking into consideration the nonlinear current dependence of the pinning energy U and its dependence on the temperature T, the magnetic field H, and the current density J. Under these assumptions a generalized formula for Fp was obtained which, assuming a suitable U(J) dependence, was able to explain the f(h) curve in the observed temperature range. © 1996 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

We developed an in situ micropatterning process for Bi2Sr2Ca1Cu2O8+x thin films using the large volumetric increase of refractory metals such as Nb, V, and Ta, during the hard regime of oxidation. After the lift-off procedure, our films showed nonreduced critical currents and temperatures. This technique is particularly suitable for multilayer in situ lithographic process. © 1995 American Institute of Physics.

Electronic Resource

1365-3083

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Presentation of cytosolic peptides in the context of major histocompatibility complex (MHC) class I antigen is crucial for immune recognition of virus-infected and malignant cells. This process, which is often defective in cancer cells, involves a series of cellular events which may be facilitated by heat shock proteins (molecular chaperones). To address the influence of chaperone function on the presentation of cytosolic peptides, we have utilized B16 melanoma cells (H-2b). These tumour cells are resistant to lysis by MHC class I-restricted cytotoxic T lymphocytes (CTL), due to a very low level of surface MHC expression. The authors found that stably transfected clones of B16 expressing a heterologous heat shock protein (Hsp65) exhibit significantly increased levels of MHC class I antigens on their surface, and are effectively lysed by alloreactive CTL. These MHC class I molecules can form functional MHC-peptide complexes which are recognized by virus-specific CTL. Moreover, mice immunized with Hsp65-expressing tumour cells, but not with control-transfected tumour cells, display a significantly increased resistance to a subsequent challenge with live, wild-type B16. Together, these results indicate that the suitable expression of a molecular chaperone can overcome a defect in MHC class I expression and antigen presentation, and suggest a novel approach to cancer immunotherapy.

Electronic Resource

1365-2559

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Aims:  To investigate CD27 expression in splenic marginal zone lymphoma (SMZL), an indolent low-grade B-cell lymphoma with constant involvement of the bone marrow, especially with an intrasinusoidal pattern. It is not clear if the neoplastic clone is composed of virgin or somatically mutated B cells. CD27 is reported to be a hallmark of memory B cells.Methods and results:  We evaluated 64 bone marrow biopsy specimens (BMBs) from 36 patients with SMZL for the expression of CD27. For comparison, splenectomy specimens of patients with traumatic splenic rupture or with SMZL were used. All BMBs showed lymphomatous infiltration. When located in the marrow sinusoids, neoplastic cells were CD27– in all cases and therefore corresponded to naive B cells. In nodular/interstitial infiltration, the cells were CD27+ and therefore corresponded to memory B cells. No difference in immunohistochemical expression of B and T antibodies was found between intrasinusoidal and interstitial/nodular infiltration. CD27 was constantly expressed in the splenic marginal zone of normal spleen, surgically removed for trauma, and in seven out of 10 spleens with SMZL.Conclusion:  We propose the existence of two different phases of neoplastic progression with, first, expansion of a virgin B clone in the bone marrow and, following exposure to antigen, a re-colonization of the bone marrow.

Electronic Resource

0392-6737

Superconducting films ; Conference proceedings

Springer Online Journal Archives 1860-2000

Physics

Summary We realized BSCCO thin films withT c(R=0)=88 K using the Molecular Beam Epitaxy (MBE) technique. The stoichiometric control is reached by a multilayer deposition technique in which Ca−Cu−Sr−Bi are sequentially deposited using the two effusive cells and the two e-guns present in the system. EDS and X-ray analyses are used to cross-check the obtained results, after theex situ in air annealing. The recent acquisition of an atomic oxygen source will allow in the close future the completelyin situ realization of BSCCO thin films.

Electronic Resource

1434-6036

Springer Online Journal Archives 1860-2000

Physics

Abstract. The influence of the finite dimensions of superconducting metallic multilayers on H-T phase diagram is studied. It is established that the geometrical symmetry of the samples determines crucially the $H_{c2\vert \vert}(T)$ dependencies. For samples where the symmetry plane is in the middle of the superconducting layer the $H_{c2\vert \vert}$ values are, for temperatures close to T c , larger than the $H_{c2\vert \vert}$ values of the samples for which the symmetry plane lies in the middle of the normal layer. The results are analysed on the basis of the Ginzburg-Landau approach and are explained by considering the different symmetry of the wave function describing the system. The experimental results are in good agreement with the elaborated model, which takes into account the actual symmetry of the samples.

Electronic Resource

1434-6036

Springer Online Journal Archives 1860-2000

Physics

Abstract. We have investigated, in the framework of proximity effect theory, the interface transparency ${\cal T}$ of superconducting/normal metal layered systems which consist of Nb and high paramagnetic Pd deposited by dc magnetron sputtering. The obtained ${\cal T}$ value is relatively high, as expected by theoretical arguments. This leads to a large value of the ratio $d_{s}^{cr}/ \xi_{s}$ although Pd does not exhibit any magnetic ordering.

Electronic Resource