Transverse voltage in zero external magnetic fields, its scaling and violation of the time reversal symmetry in MgB2

The longitudinal and transverse voltages (resistances) have been measured for MgB$_2$ in zero external magnetic fields. Samples were prepared in the form of thin film and patterned into the usual Hall bar shape. In close vicinity of the critical temperature T$_c$ non-zero transverse resistance has been observed. Its dependence on the transport current has been also studied. New scaling between transverse and longitudinal resistivities has been observed in the form $\rho{_{xy}}\sim d\rho{_{xx}}/dT$. Several models for explanation of the observed transverse resistances and breaking of reciprocity theorem are discussed. One of the most promising explanation is based on the idea of time-reversal symmetry violation

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

Ultrathin MgB2 films fabricated on Al2O3 substrate by hybrid physical-chemical vapor deposition with high Tc and Jc

Ultrathin MgB2 superconducting films with a thickness down to 7.5 nm are epitaxially grown on (0001) Al2O3 substrate by hybrid physical-chemical vapor deposition method. The films are phase-pure, oxidation-free and continuous. The 7.5 nm thin film shows a Tc(0) of 34 K, which is so far the highest Tc(0) reported in MgB2 with the same thickness. The critical current density of ultrathin MgB2 films below 10 nm is demonstrated for the first time as Jc ~ 10^6 A cm^{-2} for the above 7.5 nm sample at 16 K. Our results reveal the excellent superconducting properties of ultrathin MgB2 films with thicknesses between 7.5 and 40 nm on Al2O3 substrate.Comment: 7 pages, 4 figures, 2 table

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

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