54 research outputs found
Synthesis of as-grown superconducting MgB_2 thin films by molecular beam epitaxy in UHV conditions
As-grown superconducting MgB_2 thin films have been grown on SrTiO_3(001),
MgO(001), and Al_2O_3(0001) substrates by a molecular beam epitaxy (MBE) method
with novel co-evaporation conditions of low deposition rate in ultra-high
vacuum. The structural and physical properties of the films were studied by
RHEED, XRD, electrical resistivity measurements, and SQUID magnetometer. The
RHEED patterns indicate three-dimensional growth for MgB_2. The highest T_c
determined by resistivity measurement was about 36K in these samples. And a
clear Meissner effect below T_c was observed using magnetic susceptibility
measurement. We will discuss the influence of B buffer layer on the structural
and physical properties.Comment: 9 pages with 4 figures, ISS2003 proceedin
Higher harmonics of ac voltage response in narrow strips of YBa2Cu3O7 thin films: Evidence for strong thermal fluctuations
We report on measurements of higher harmonics of the ac voltage response in
strips of YBa2Cu3O7 thin films as a function of temperature, frequency and ac
current amplitude. The third (fifth) harmonic of the local voltage is found to
exhibit a negative (positive) peak at the superconducting transition
temperature and their amplitudes are closely related to the slope (derivative)
of the first (Ohmic) harmonic. The peaks practically do not depend on frequency
and no even (second or fourth) harmonics are detected. The observed data can be
interpreted in terms of ac current induced thermal modulation of the sample
temperature added to strong thermally activated fluctuations in the transition
region.Comment: 9 pages, 4 figures (PDF file
Observation of Individual Josephson Vortices in YBCO Bicrystal Grain-boundary Junctions
The response of YBCO bicrystal grain-boundary junctions to small dc magnetic
fields (0 - 10 Oe) has been probed with a low-power microwave (rf) signal of
4.4 GHz in a microwave-resonator setup. Peaks in the microwave loss at certain
dc magnetic fields are observed that result from individual Josephson vortices
penetrating into the grain-boundary junctions under study. The system is
modeled as a long Josephson junction described by the sine-Gordon equation with
the appropriate boundary conditions. Excellent quantitative agreement between
the experimental data and the model has been obtained. Hysteresis effect of dc
magnetic field is also studied and the results of measurement and calculation
are compared.Comment: 11 pages, 4 figure
Mycosis fungoides: is it a Borrelia burgdorferi-associated disease?
Mycosis fungoides (MF) is the most frequently found cutaneous T-cell lymphoma with an unknown aetiology. Several aetiopathogenetic mechanisms have been postulated, including persistent viral or bacterial infections. We looked for evidence of Borrelia burgdorferi (Bb), the aetiologic agent of Lyme disease (LD), in a case study of MF patients from Northeastern Italy, an area with endemic LD. Polymerase chain reaction for the flagellin gene of Bb was used to study formalin-fixed paraffin-embedded lesional skin biopsies from 83 patients with MF and 83 sex- and age-matched healthy controls with homolocalised cutaneous nevi. Borrelia burgdorferi-specific sequence was detected in 15 out of 83 skin samples of patients with MF (18.1%), but in none out of 83 matched healthy controls (P<0.0001). The Bb positivity rates detected in this study support a possible role for Bb in the aetiopathogenesis of MF in a population endemic for LD
Herpes-Virus Infection in Patients with Langerhans Cell Histiocytosis: A Case-Controlled Sero-Epidemiological Study, and In Situ Analysis
BACKGROUND: Langerhans cell histiocytosis (LCH) is a rare disease that affects mainly young children, and which features granulomas containing Langerhans-type dendritic cells. The role of several human herpesviruses (HHV) in the pathogenesis of LCH was suggested by numerous reports but remains debated. Epstein-barr virus (EBV, HHV-4), & Cytomegalovirus (CMV, HHV-5) can infect Langerhans cells, and EBV, CMV and HHV-6 have been proposed to be associated with LCH based on the detection of these viruses in clinical samples. METHODOLOGY: We have investigated the prevalence of EBV, CMV and HHV-6 infection, the characters of antibody response and the plasma viral load in a cohort of 83 patients and 236 age-matched controls, and the presence and cellular localization of the viruses in LCH tissue samples from 19 patients. PRINCIPAL FINDINGS: The results show that prevalence, serological titers, and viral load for EBV, CMV and HHV-6 did not differ between patients and controls. EBV was found by PCR in tumoral sample from 3/19 patients, however, EBV small RNAs EBERs -when positive-, were detected by in situ double staining in bystander B CD20+ CD79a+ lymphocytes and not in CD1a+ LC. HHV-6 genome was detected in the biopsies of 5/19 patients with low copy number and viral Ag could not be detected in biopsies. CMV was not detected by PCR in this series. CONCLUSIONS/SIGNIFICANCE: Therefore, our findings do not support the hypothesis of a role of EBV, CMV, or HHV-6 in the pathogenesis of LCH, and indicate that the frequent detection of Epstein-barr virus (EBV) in Langerhans cell histiocytosis is accounted for by the infection of bystander B lymphocytes in LCH granuloma. The latter observation can be attributed to the immunosuppressive micro environment found in LCH granuloma
Salivary Markers for Oral Cancer Detection
Oral cancer refers to all malignancies that arise in the oral cavity, lips and pharynx, with 90% of all oral cancers being oral squamous cell carcinoma. Despite the recent treatment advances, oral cancer is reported as having one of the highest mortality ratios amongst other malignancies and this can much be attributed to the late diagnosis of the disease. Saliva has long been tested as a valuable tool for drug monitoring and the diagnosis systemic diseases among which oral cancer. The new emerging technologies in molecular biology have enabled the discovery of new molecular markers (DNA, RNA and protein markers) for oral cancer diagnosis and surveillance which are discussed in the current review
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