266 research outputs found
Confocal Ellipsoidal Reflector System for a Mechanically Scanned Active Terahertz Imager
We present the design of a reflector system that can rapidly scan and refocus a terahertz beam for high-resolution standoff imaging applications. The proposed optical system utilizes a confocal Gregorian geometry with a small mechanical rotating mirror and an axial displacement of the feed. For operation at submillimeter wavelengths and standoff ranges of many meters, the imaging targets are electrically very close to the antenna aperture. Therefore the main reflector surface must be an ellipse, instead of a parabola, in order to achieve the best imaging performance. Here we demonstrate how a simple design equivalence can be used to generalize the design of a Gregorian reflector system based on a paraboloidal main reflector to one with an ellipsoidal main reflector. The system parameters are determined by minimizing the optical path length error, and the results are validated with numerical simulations from the commercial antenna software package GRASP. The system is able to scan the beam over 0.5 m in cross-range at a 25 m standoff range with less than 1% increase of the half-power beam-width
Time-Delay Multiplexing of Two Beams in a Terahertz Imaging Radar
We demonstrate a time-delay multiplexing technique
that doubles the frame rate of a 660–690-GHz imaging radar
with minimal additional instrument complexity. This is done by
simultaneously projecting two offset, orthogonally polarized radar
beams generated and detected by a common source and receiver.
Beam splitting and polarization rotation is accomplished with a
custom designed waveguide hybrid coupler and twist. A relative
time lag of approximately 2 ns between the beams’ waveforms is
introduced using a quasi-optical delay line, followed by spatial
recombination using a selectively reflective wire grid. This delay is
much longer than the approximately 20-ps time-of-flight resolution
of the 30-GHz bandwidth radar, permitting the two beams’
reflected signals from a compact target to be easily distinguished
in digital post-processing of the single receiver channel
Penetrating 3-D Imaging at 4- and 25-m Range Using a Submillimeter-Wave Radar
We show experimentally that a high-resolution imaging radar operating at 576–605 GHz is capable of detecting weapons concealed by clothing at standoff ranges of 4–25 m. We also demonstrate the critical advantage of 3-D image reconstruction for visualizing hidden objects using active-illumination coherent terahertz imaging. The present system can image a torso with <1 cm resolution at 4 m standoff in about five minutes. Greater standoff distances and much higher frame rates should be achievable by capitalizing on the bandwidth, output power, and compactness of solid state Schottky-diode based terahertz mixers and multiplied sources
Revisión de los factores de riesgo de afectación pulpar con la utilización del instrumental rotatorio
En esta comunicación se efectúa una revisión de la bibliografía acerca de los factores que influyen en la respuesta pulpar en los tratamientos odontológicos que conllevan la utilización de instrumental rotatorio diamantado así como una experiencia de laboratorio comparando la eficacia del refrigerante de spray aire-agua y el de aire solo
Multi-pixel high-resolution three-dimensional imaging radar
A three-dimensional imaging radar operating at high frequency e.g., 670 GHz radar using low phase-noise synthesizers and a fast chirper to generate a frequency-modulated continuous-wave (FMCW) waveform, is disclosed that operates with a multiplexed beam to obtain range information simultaneously on multiple pixels of a target. A source transmit beam may be divided by a hybrid coupler into multiple transmit beams multiplexed together and directed to be reflected off a target and return as a single receive beam which is demultiplexed and processed to reveal range information of separate pixels of the target associated with each transmit beam simultaneously. The multiple transmit beams may be developed with appropriate optics to be temporally and spatially differentiated before being directed to the target. Temporal differentiation corresponds to a different intermediate frequencies separating the range information of the multiple pixels. Collinear transmit beams having differentiated polarizations may also be implemented
Equity, barriers and cancer disparities: study of the Spanish Society of Medical Oncology on the access to oncologic drugs in the Spanish Regions
[Purpose] The Spanish Society of Medical Oncology (SEOM) has conducted a study on the access to oncologic drugs across the 17 Spanish Regions with the aim of identifying potential heterogeneities and making proposals for eliminating the barriers identified at the different levels.[Methods] An Expert Panel made up of medical oncologists designed a survey on certain indications approved for 11 drugs in the approach of breast cancer, melanoma, lung cancer, prostate cancer and support treatment. This survey was sent to 144 National Health System (NHS) hospitals.
[Results] 77 hospitals answered the survey. The information modules analysed were: scope of the Commission that establishes binding decisions related to drug access; conditions, stages and periods of drug application, approval and administration processes; barriers to accessing drugs.
[Conclusions] The study shows variability in drug access. The SEOM makes proposals addressed to reducing the differences identified and homogenizing drug access conditions.This study was funded by SEOM
BICEP2 II: Experiment and Three-Year Data Set
We report on the design and performance of the BICEP2 instrument and on its
three-year data set. BICEP2 was designed to measure the polarization of the
cosmic microwave background (CMB) on angular scales of 1 to 5 degrees
(=40-200), near the expected peak of the B-mode polarization signature of
primordial gravitational waves from cosmic inflation. Measuring B-modes
requires dramatic improvements in sensitivity combined with exquisite control
of systematics. The BICEP2 telescope observed from the South Pole with a 26~cm
aperture and cold, on-axis, refractive optics. BICEP2 also adopted a new
detector design in which beam-defining slot antenna arrays couple to
transition-edge sensor (TES) bolometers, all fabricated on a common substrate.
The antenna-coupled TES detectors supported scalable fabrication and
multiplexed readout that allowed BICEP2 to achieve a high detector count of 500
bolometers at 150 GHz, giving unprecedented sensitivity to B-modes at degree
angular scales. After optimization of detector and readout parameters, BICEP2
achieved an instrument noise-equivalent temperature of 15.8 K sqrt(s). The
full data set reached Stokes Q and U map depths of 87.2 nK in square-degree
pixels (5.2 K arcmin) over an effective area of 384 square degrees within
a 1000 square degree field. These are the deepest CMB polarization maps at
degree angular scales to date. The power spectrum analysis presented in a
companion paper has resulted in a significant detection of B-mode polarization
at degree scales.Comment: 30 pages, 24 figure
Equity, barriers and cancer disparities: study of the Spanish Society of Medical Oncology on the access to oncologic drugs in the Spanish Regions
The Spanish Society of Medical Oncology (SEOM) has conducted a study on the access to oncologic drugs across the 17 Spanish Regions with the aim of identifying potential heterogeneities and making proposals for eliminating the barriers identified at the different levels. An Expert Panel made up of medical oncologists designed a survey on certain indications approved for 11 drugs in the approach of breast cancer, melanoma, lung cancer, prostate cancer and support treatment. This survey was sent to 144 National Health System (NHS) hospitals. 77 hospitals answered the survey. The information modules analysed were: scope of the Commission that establishes binding decisions related to drug access; conditions, stages and periods of drug application, approval and administration processes; barriers to accessing drugs. The study shows variability in drug access. The SEOM makes proposals addressed to reducing the differences identified and homogenizing drug access conditions
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