21 research outputs found
Comparação entre microssatélites e o gene Ml MntH como alvos para a identificação do Mycobacterium leprae por PCR na hansenÃase
Evaluation of qPCR-Based Assays for Leprosy Diagnosis Directly in Clinical Specimens
The increased reliability and efficiency of the quantitative polymerase chain reaction (qPCR) makes it a promising tool for performing large-scale screening for infectious disease among high-risk individuals. To date, no study has evaluated the specificity and sensitivity of different qPCR assays for leprosy diagnosis using a range of clinical samples that could bias molecular results such as difficult-to-diagnose cases. In this study, qPCR assays amplifying different M. leprae gene targets, sodA, 16S rRNA, RLEP and Ag 85B were compared for leprosy differential diagnosis. qPCR assays were performed on frozen skin biopsy samples from a total of 62 patients: 21 untreated multibacillary (MB), 26 untreated paucibacillary (PB) leprosy patients, as well as 10 patients suffering from other dermatological diseases and 5 healthy donors. To develop standardized protocols and to overcome the bias resulted from using chromosome count cutoffs arbitrarily defined for different assays, decision tree classifiers were used to estimate optimum cutoffs and to evaluate the assays. As a result, we found a decreasing sensitivity for Ag 85B (66.1%), 16S rRNA (62.9%), and sodA (59.7%) optimized assay classifiers, but with similar maximum specificity for leprosy diagnosis. Conversely, the RLEP assay showed to be the most sensitive (87.1%). Moreover, RLEP assay was positive for 3 samples of patients originally not diagnosed as having leprosy, but these patients developed leprosy 5–10 years after the collection of the biopsy. In addition, 4 other samples of patients clinically classified as non-leprosy presented detectable chromosome counts in their samples by the RLEP assay suggesting that those patients either had leprosy that was misdiagnosed or a subclinical state of leprosy. Overall, these results are encouraging and suggest that RLEP assay could be useful as a sensitive diagnostic test to detect M. leprae infection before major clinical manifestations
f-electron hybridised Fermi surface in magnetic field-induced metallic YbB12
The nature of the Fermi surface observed in the recently discovered family of unconventional insulators starting with SmB6 is a subject of intense inquiry. Here we shed light on this question by accessing quantum oscillations in the high magnetic fieldinduced metallic regime above ≈47 T in YbB12, which we compare with the unconventional insulating regime. In the field-induced metallic regime, we find prominent quantum oscillations in the electrical resistivity characterised by multiple frequencies and heavy effective masses. The close similarity in Lifshitz-Kosevich low-temperature growth of quantum oscillation amplitude in insulating YbB12 to field-induced metallic YbB12, points to an origin of quantum oscillations in insulating YbB12 from in-gap neutral low energy excitations. Higher frequency Fermi surface sheets of heavy quasiparticle effective mass emerge in the field-induced metallic regime of YbB12 in addition to multiple heavy Fermi surface sheets observed in both insulating and metallic regimes. f-electron hybridisation is thus observed to persist from the unconventional insulating to the field-induced metallic regime of YbB12, in contrast to the unhybridised conduction electron Fermi surface observed in unconventional insulating SmB6. Our findings thus require an alternative model for YbB12, of neutral in-gap low energy excitations, wherein the f-electron hybridisation is retained
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f-electron hybridised Fermi surface in magnetic field-induced metallic YbB<inf>12</inf>
Funder: EC | EU Framework Programme for Research and Innovation H2020 | H2020 Priority Excellent Science | H2020 European Research Council (H2020 Excellent Science - European Research Council); doi: https://doi.org/10.13039/100010663Funder: Ministry of Education (Ministry of Education, Republic of China (Taiwan)); doi: https://doi.org/10.13039/100010002Funder: RCUK | Engineering and Physical Sciences Research Council (EPSRC); doi: https://doi.org/10.13039/501100000266Funder: RCUK | Economic and Social Research Council (ESRC); doi: https://doi.org/10.13039/501100000269Funder: Deutsche Forschungsgemeinschaft (German Research Foundation); doi: https://doi.org/10.13039/501100001659Funder: National Science Foundation (NSF); doi: https://doi.org/10.13039/100000001Funder: United States Department of Defense | United States Navy | Office of Naval Research (ONR); doi: https://doi.org/10.13039/100000006The nature of the Fermi surface observed in the recently discovered family of
unconventional insulators starting with SmB and subsequently YbB is
a subject of intense inquiry. Here we shed light on this question by comparing
quantum oscillations between the high magnetic field-induced metallic regime in
YbB and the unconventional insulating regime. In the field-induced
metallic regime beyond 47 T, we find prominent quantum oscillations in the
contactless resistivity characterised by multiple frequencies up to at least
3000 T and heavy effective masses up to at least 17 ,
characteristic of an -electron hybridised metallic Fermi surface. The growth
of quantum oscillation amplitude at low temperatures in electrical transport
and magnetic torque in insulating YbB is closely similar to the
Lifshitz-Kosevich low temperature growth of quantum oscillation amplitude in
field-induced metallic YbB, pointing to an origin of quantum
oscillations in insulating YbB from in-gap neutral low energy
excitations. The field-induced metallic regime of YbB is characterised
by more Fermi surface sheets of heavy quasiparticle effective mass that emerge
in addition to the heavy Fermi surface sheets yielding multiple quantum
oscillation frequencies below 1000 T observed in both insulating and metallic
regimes. We thus observe a heavy multi-component Fermi surface in which
-electron hybridisation persists from the unconventional insulating to the
field-induced metallic regime of YbB, which is in distinct contrast to
the unhybridised conduction electron Fermi surface observed in the case of the
unconventional insulator SmB. Our findings require a different theoretical
model of neutral in-gap low energy excitations in which the -electron
hybridisation is retained in the case of the unconventional insulator
YbB