236 research outputs found

    Optical Determination of Electron-Phonon Coupling in Carbon Nanotubes

    Full text link
    We report on an optical method to directly measure electron-phonon coupling in carbon nanotubes by correlating the first and second harmonic of the resonant Raman excitation profile. The method is applicable to 1D and 0D systems and is not limited to materials that exhibit photoluminescence. Experimental results for electron-phonon coupling with the radial breathing mode in 5 different nanotubes show coupling strengths from 3-11 meV, depending on chirality. The results are in good agreement with the chirality and diameter dependence calculated by Goupalov et al.Comment: Corrected a mistake in the reference

    An ultrasensitive SiO2-encapsulated alloyed CdZnSeS quantum dot-molecular beacon nanobiosensor for norovirus

    Get PDF
    AbstractUltrasensitive, rapid and selective diagnostic probes are urgently needed to overcome the limitations of traditional probes for norovirus (NV). Here, we report the detection of NV genogroup II via nucleic acid hybridization technology using a quantum dot (QD)-conjugated molecular beacon (MB) probe. To boost the sensitivity of the MB assay system, an ultrasensitive QD fluorophore with unique optical properties was synthesized, characterized and exploited as a fluorescence signal generator. Alloyed thioglycolic (TGA)-capped CdZnSeS QDs with a high photoluminescence (PL) quantum yield (QY) value of 92% were synthesized, and a modified silanization method was employed to encapsulate the thiol-capped QDs in a silica layer. The resulting highly luminescent alloyed SiO2-coated CdZnSeS QDs had a remarkable PL QY value of 98%. Transmission electron microscopy and dynamic light scattering confirmed the monodispersity of the alloyed nanocrystals, and zeta potential analysis confirmed their colloidal stability. Powder X-ray diffraction and PL lifetime measurements confirmed the surface modification of the QDs. The alloyed TGA-capped and SiO2-coated CdZnSeS QD-conjugated MB bioprobes detected extremely low concentrations of NV RNA. Ultrasensitive detection of low concentrations of NV RNA with a limit of detection (LOD) of 8.2copies/mL in human serum and a LOD of 9.3 copies/mL in buffer was achieved using the SiO2-coated CdZnSeS QD-MB probes, an increase in sensitivity of 3-fold compared with the detection limit for NV RNA using TGA-capped CdZnSeS QD-MBs. The additional merits of our detection system are rapidity, specificity and improved sensitivity over conventional molecular test probes

    Improving cluster recovery with feature rescaling factors

    Get PDF
    The data preprocessing stage is crucial in clustering. Features may describe entities using different scales. To rectify this, one usually applies feature normalisation aiming at rescaling features so that none of them overpowers the others in the objective function of the selected clustering algorithm. In this paper, we argue that the rescaling procedure should not treat all features identically. Instead, it should favour the features that are more meaningful for clustering. With this in mind, we introduce a feature rescaling method that takes into account the within-cluster degree of relevance of each feature. Our comprehensive simulation study, carried out on real and synthetic data, with and without noise features, clearly demonstrates that clustering methods that use the proposed data normalization strategy clearly outperform those that use traditional data normalization

    Diagnostic approach of tuberculous lymphadenitis in a multicenter study

    Get PDF
    Introduction: Tuberculous lymphadenitis (TBLN) is the most common infectious etiology of peripheral lymphadenopathy in adults, in Turkiye. This study aimed to identify the demographic, clinical, and laboratory variables that differentiate TBLN from non-tuberculous lymphadenitis (NTBLN), as well as the etiology of lymphadenopathy in adults. Methodology: Patients who were over 18 years old and were referred to the infectious disease outpatient clinics with complaints of swollen peripheral lymph nodes, and who underwent lymph node biopsy between 1 January 2010 and 1 March 2021, were included in this multicenter, nested case-control study. Results: A total of 812 patients at 17 tertiary teaching and research hospitals in Turkiye were included in the study. TBLN was the most frequent diagnosis (53.69%). The proportion of patients diagnosed with TBLN was higher among females; and among those who had a higher erythrocyte sedimentation rate, positive purified protein derivative test, and positive interferon-gamma release test result (p < 0.05). However, TBLN was less frequent among patients with generalized lymphadenopathy, bilateral lymphadenopathy, axillary lymphadenopathy, inguinal lymphadenopathy, hepatomegaly, splenomegaly, leukocytosis, and moderately increased C reactive protein levels (p < 0.05). Conclusions: Identifying the variables that predict TBLN or discriminate TBLN from NTBLN will help clinicians establish optimal clinical strategies for the diagnosis of adult lymphadenopathy
    corecore