1,721,188 research outputs found
OPTICAL CONDUCTIVITY OF SINGLE CRYSTALS OF Na(0.57)CoO(2)
No full textThe optical conductivity of single crystals of NaxCoO2 for x=0.57) is reported between 295 and 30 K. In the far infrared, an ‘‘anomalous Drude’’ analysis leads to a carrier effective mass of 561 electron masses. This high value is attributed to strong electron-phonon coupling, as suggested by the Fano distortion of a phonon at 570 cm-1. A peak at 8800 cm-1 scales with the charge transfer band of high-Tc cuprates by simply replacing the in-plane Cu-O bond length with that for Co-O
Frequency-Dependent Thermal Response of the Charge System and the Restricted Sum Rules of La2xSrxCuO4
No full textIn La2xSrxCuO4 (LSCO) the spectral weight W obeys the same law W =W0 -BT^2 as in a conventional metal such as gold, for any frequency up to the plasma edge. However, in LSCO B points toward correlation effects and, unlike in gold, is related to an energy scale tT < 2000 cm1
Multifocal, concomitant and independent neoplasias of the large intestine
No full textThe Authors report the presence of two simultaneous neoplasms of the large bowel which are independent of each other from the histological point of view. The Authors point out the more interesting aspects of this particular neoplastic pathology, which creates different clinical syndromes; diagnosis and therapeutic possibilities were investigated. The frequency of these neoplasms is not exceptional, and, therefore, the possible existence even in subjects having a single tumor of the colon or rectum should not be neglected
Fourier transform far infrared spectroscopic ellipsometry for standoff material identification
No full textThe ellipsometry is an efficient method to determine the optical properties of matter. It has been largely employed with grating spectrometers in the visible, UV and near-infrared ranges for the characterization of thin films, surfaces and interfaces. In the mid- and far-infrared, where most substance-specific absorption lines are present, spectroscopic ellipsometry with Fourier-transform spectrometers is still not extended as a routine method. In particular, the lack of powerful sources in the far-infrared/terahertz range has prevented standoff application of this method. We will show that it is possible to measure the complex dielectric constant of a solid in the far-infrared and terahertz range by a reflection experiment with polarized light and ellipsometric analysis with a suitable calibration procedure. Extraction of terahertz synchrotron radiation from storage rings provides a suitable source for research-grade experiments. The optical constants determined by ellipsometry compare well with those obtained by KramersKronig procedures, a method which, however, requires broader frequency range and absolute reflectance standard. We will present the case of remote spectroscopic identification of explosive materials, which is relevant for forthcoming security applications
Plasmon-enhanced Ge-based metal-semiconductor-metal photodetector at near-IR wavelengths
Full text linkWe demonstrate the use of plasmonic effects to boost the near-infrared sensitivity of metal-semiconductor-metal detectors. Plasmon-enhanced photodetection is achieved by properly optimizing Au interdigitated electrodes, micro-fabricated on Ge, a semiconductor that features a strong near IR absorption. Finite-difference time-domain simulations, photocurrent experiments and Fourier-transform IR spectroscopy are performed to validate how a relatively simple tuning of the contact geometry allows for an enhancement of the response of the device adapting it to the specific detection needs. A 2-fold gain factor in the Ge absorption characteristics is experimentally demonstrated at 1.4 µm, highlighting the potential of this approach for optoelectronic and sensing applications.QCD/Scappucci La
Modeling of second harmonic generation in hole-doped silicon-germanium quantum wells for mid-infrared sensing
Full text linkThe development of Ge and SiGe chemical vapor deposition techniques on silicon wafers has enabled the integration of multi-quantum well structures in silicon photonics chips for nonlinear optics with potential applications to integrated nonlinear optics, however research has focused up to now on undoped quantum wells and interband optical excitations. In this work, we present model calculations for the giant nonlinear coefficients provided by intersubband transitions in hole-doped Ge/SiGe and Si/SiGe multi-quantum wells. We employ a valence band-structure model for Si1-xGex to calculate the confined hole states of asymmetric-coupled quantum wells for second-harmonic generation in the mid-infrared. We calculate the nonlinear emission spectra from the second-order susceptibility tensor, including the particular vertical emission spectra of valence-band quantum wells. Two possible nonlinear mid-infrared sensor architectures, one based on waveguides and another based on metasurfaces, are described as perspective application
Amoxycillin for the infectious pathology of the operated biliary passages
No full textThe authoirs discuss the use of amoxicillin in infectious pathology of the operated biliary trac
An analytical framework for the research on prehistoric weight systems. A case study from Nuragic Sardinia
No full textThe preliminary results of a research project on protohistoric metal economy are presented,
and an analytical framework is outlined, for the study of weight systems in pre-literate contexts. Past
research on weight systems acknowledged that weight values of prehistoric bronze objects and fragments
are not randomly distributed, but tend instead to cluster in relevant concentrations. However, although
promising in terms of research development, such studies have never been followed by a serious critical
debate. The potential of former research was hindered by an overemphasized focus on exactness, often
misconceiving the inherently approximate nature of real life measurements. In this article we introduce
an alternative approach to the study of protohistoric weight series, which makes use of both mathematical
tools and archaeological considerations. The method is tested on the sample of Sardinian Early
Iron Age bronze hoards
Bunch-to-bunch coherence of coherent synchrotron radiation from the electron storage ring BESSY II
No full textCoherent Synchrotron Radiation (CSR) has been proven to be a powerful spectroscopic source in the THz range at electron storage rings. However, CSR driven instabilities in the electron distribution within the bunch can cause fluctuations in the emitted THz radiation heavily disturbing the quality of Fourier transformed spectra. Here we discuss the interference of the coherent radiation emitted by two successive electron bunches as a possible tool for studying the longitudinal bunch coherence. © 2010 IEEE
Midinfrared surface plasmon sensor based on a substrateless metal mesh
No full textA midinfrared mass sensor based on high quality factor surface plasmon modes was designed, fabricated, and tested by infrared spectroscopy for the detection of nanometric layers of dielectric materials. Substrate removal below a metal mesh with period of 2 mu m results in the coupling between degenerate surface plasmon modes on the two surfaces, resulting in a quality factor up to 33 for the antisymmetric mode. The presented substrateless metal mesh integrates mass sensing capability together with midinfrared spectroscopy, and is therefore of potential interest for substance-selective environmental and biomedical sensing applications (C) 2011 American Institute of Physics. [doi:10.1063/1.3559616
- …
