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At least 1,297 records · Page 72Linked to original sources
PubMed1992

Construction and performance of a rapid scan monochromator for multiwavelength fluorimetry.

A rapid scan monochromator was constructed for multiwavelength illumination of biological samples. A light weight holographic grating (2400 grooves/mm) was driven by a rapid stepper motor with 0.014 degrees angular resolution in an f/4 monochromator. Angular velocity and acceleration kinetics were optimized to minimize the time for grating rotation and stabilization. The times required for shifting output wavelengths by 20, 100, and 300 nm were 6, 7, and 9 ms, respectively. Wavelength selection and dwell times were software controlled and reproducible over extended data collections. Instrument utility was demonstrated by measurement of intracellular calcium in fura-2-labeled Chinese hamster lung fibroblasts at excitation wavelengths of 340, 360, and 380 nm. Compared to available filter wheel and chopper devices, the rapid scan monochromator has advantages of rapid and software-selectable wavelength control, excellent optical alignment, small size, and low cost. Applications of this device include illumination optics for multiwavelength microfluorimetry and scanning absorption spectroscopy, and detection optics for microspectroscopy.

Animals↗
PubMed2004

Chromatic dispersion characterization by direct instantaneous frequency measurement.

A new concept for the measurement of chromatic dispersion is presented. The group delay of the device under test is directly obtained from the instantaneous frequency of a short optical pulse after propagation in the device, itself obtained with temporal and spectral interferometry. Temporal and spectral fringe encoding provide excellent accuracy and resistance to noise, and a wide variety of dispersions can be characterized even at high insertion losses.

Journal Article↗
PubMed2005

Electro-optic modulation in hybrid solgel doped with Disperse Red chromophore.

An electro-optically active hybrid solgel doped with Disperse Red 13 has been developed by use of a simple solvent-assisted method. It permits a high loading concentration and has low optical loss at 1550 nm. A channel waveguide amplitude modulator has been fabricated by use of active and passive hybrid solgel materials. The device shows an electro-optic coefficient of 14 pm/V at 1550 nm and stable operation.

Journal Article↗
PubMed2001

Outpatient treatment with (131)I-anti-B1 antibody: radiation exposure to family members.

UNLABELLED: The Nuclear Regulatory Commission (NRC) regulations that govern release of patients administered radioactive material have been revised to include dose-based criteria in addition to the conventional activity-based criteria. A licensee may now release a patient if the total effective dose equivalent to another individual from exposure to the released patient is not likely to exceed 5 mSv (500 mrem). The result of this dose-based release limit is that now many patients given therapeutic amounts of radioactive material no longer require hospitalization. This article presents measured dose data for 26 family members exposed to 22 patients treated for non-Hodgkin's lymphoma with (131)I-anti-B1 antibody after their release according to the new NRC dose-based regulations. METHODS: The patients received administered activities ranging from 0.94 to 4.77 GBq (25--129 mCi). Family members were provided with radiation monitoring devices (film badges, thermoluminescent or optically stimulated luminescent dosimeters, or electronic digital dosimeters). Radiation safety personnel instructed the family members on the proper wearing and use of the devices. Instruction was also provided on actions recommended to maintain doses to potentially exposed individuals as low as is reasonably achievable. RESULTS: Family members wore the dosimeters for 2--17 d, with the range of measured dose values extending from 0.17 to 4.09 mSv (17--409 mrem). The average dose for infinite time based on dosimeter readings was 32% of the predicted doses projected to be received by the family members using the NRC method provided in regulatory guide 8.39. CONCLUSION: Therapy with (131)I-anti-B1 antibody can be conducted on an outpatient basis using the established recommended protocol. The patients can be released immediately with confidence that doses to other individuals will be below the 5-mSv (500 mrem) limit.

Ambulatory Care↗
PubMed2004

Sensing properties of asymmetric double-layer-covered tapered fibers.

A novel, to our knowledge, device based on a tapered optical fiber with a double-layer deposition including a metallic media is presented, and its properties are studied. The main novelty of the device consists of the introduction of a dielectric layer, whereas the systems depicted in the literature are simply metal-coated tapered fibers. The presence of the dielectric layer permits one to tune the response of the device to the refractive index of the surrounding medium. We have proved the suitability of this scheme for refractive-index sensing by depicting two measurement modes, namely, total power attenuation and spectral transmittance.

Journal Article↗
PubMedDate not supplied

Managing low vision patients.

1. The ophthalmologist and staff are ultimately responsible for identifying low vision patients. 2. Most low vision patients who have a professional low vision evaluation are able to use vision enhancing devices. 3. In addition to optical magnifyers, new computer and television technology enhances use of residual vision.

Communication Devices for People with Disabilities↗
PubMed1989

Biosensors.

Biosensors are analytical devices that respond selectively to analytes in an appropriate sample and convert their concentration into an electrical signal via a combination of a biological recognition system and an electrochemical, optical or other transducer. Such devices will find application in medicine, agriculture, environmental monitoring and the bioprocessing industries. The last few years have seen great advances in the design of sensor architectures, the marriage of biological systems with monolithic silicon and optical technologies, the development of effective electron-transfer systems and the configuration of direct immunosensors. Recent progress in these areas has already led to the introduction of new-generation biosensors into the competitive diagnostics market place.

Biosensing Techniques↗
PubMedDate not supplied

[Return signal processing and problems of laser angioplasty with optical detection of intravascular objects].

The paper deals with the development of devices for visualization on intravascular formations by using multifiber optical catheters, describes a scheme for a pilot testing unit based on periodical pulse-acting Nd:YAG laser that operates at the second harmonics (lambda = 532 nm). Analyzes errors while processing the return signal received by intravascular objects, proposes a statistical model which describes the received signal, which permits the development a of block diagram for an optimized device for initial processing of signals.

Angioplasty, Laser↗
PubMed2004

Optical sensor interrogation with a blazed fiber Bragg grating and a charge-coupled device linear array.

We present what is to our knowledge the first comprehensive investigation of the use of blazed fiber Bragg gratings (BFBGs) to interrogate wavelength division multiplexed (WDM) in-fiber optical sensor arrays. We show that the light outcoupled from the core of these BFBGs is radiated with sufficient optical power that it may be detected with a low-cost charge-coupled device (CCD) array. We present thorough system performance analysis that shows sufficient spectral-spatial resolution to decode sensors with a WDM separation of 75 rhom, signal-to-noise ratio greater than 45-dB bandwidth of 70 nm, and drift of only 0.1 rhom. We show the system to be polarization-state insensitive, making the BFBG-CCD spectral analysis technique a practical, extremely low-cost, alternative to traditional tunable filter approaches.

Journal Article↗
PubMedDate not supplied

Dual modality instrument for simultaneous optical coherence tomography imaging and fluorescence spectroscopy.

We develop a dual-modality device that combines the anatomical imaging capabilities of optical coherence tomography (OCT) with the functional capabilities of laser-induced fluorescence (LIF) spectroscopy. OCT provides cross-sectional images of tissue structure to a depth of up to 2 mm with approximately 10-microm resolution. LIF spectroscopy provides histochemical information in the form of emission spectra from a given tissue location. The OCT subsystem utilizes a superluminescent diode with a center wavelength of 1300 nm, whereas a helium cadmium laser provides the LIF excitation source at wavelengths of 325 and 442 nm. Preliminary data are obtained on eight postmortem aorta samples, each 10 mm in length. OCT images and LIF spectra give complementary information from normal and atherosclerotic portions of aorta wall. OCT images show structures such as intima, media, internal elastic lamina, and fibrotic regions. Emission spectra ratios of 520/490 (325-nm excitation) and 595/635 (442-nm excitation) could be used to identify normal and plaque regions with 97 and 91% correct classification rates, respectively. With miniaturization of the delivery probe and improvements in system speed, this dual-modality device could provide a valuable tool for identification and characterization of atherosclerotic plaques.

Aged↗
PubMed2005

Raman injection laser.

Stimulated Raman scattering is a nonlinear optical process that, in a broad variety of materials, enables the generation of optical gain at a frequency that is shifted from that of the incident radiation by an amount corresponding to the frequency of an internal oscillation of the material. This effect is the basis for a broad class of tunable sources known as Raman lasers. In general, these sources have only small gain (approximately 10(-9) cm W(-1)) and therefore require external pumping with powerful lasers, which limits their applications. Here we report the realization of a semiconductor injection Raman laser designed to circumvent these limitations. The physics underlying our device differs in a fundamental way from existing Raman lasers: it is based on triply resonant stimulated Raman scattering between quantum-confined states within the active region of a quantum cascade laser that serves as an internal optical pump--the device is driven electrically and no external laser pump is required. This leads to an enhancement of orders of magnitude in the Raman gain, high conversion efficiency and low threshold. Our lasers combine the advantages of nonlinear optical devices and of semiconductor injection lasers, and could lead to a new class of compact and wavelength-agile mid-and far-infrared light sources.

Journal Article↗
PubMed2005

Detection of subgingival calculus with a novel LED-based optical probe.

BACKGROUND: A recently introduced detection device is designed for objective subgingival calculus diagnosis. The aim of the present study was to assess the possibility of detecting subgingival calculus with this novel LED-based optical probe in vitro. METHODS: Twenty extracted human teeth with calculus on the root surface were fixed on a translation stage. Measurements on the root surface were carried out in increments of 0.25 mm with an angulation of 0 to 10 degrees , 45 degrees , or 90 degrees to the optical fiber. Teeth were covered either with sodium chloride (NaCl) or blood in order to determine the influence of ambient fluids. Successional areas of positive measurements were defined as "length of positive values" (LPV). The results were compared to the clinical and histological findings. RESULTS: Clinically and histologically apparent calculus on the root surface was accompanied by positive measurement values. A reduction of the angulation between probe and root surface resulted in shorter LPV when measurements were performed in blood (P <0.05) and longer LPV employing NaCl as the ambient fluid (P <0.05). For both blood and NaCl, sensitivity and/or specificity values decreased when using lower angulations. CONCLUSION: The optical probe offers the possibility of subgingival calculus detection and may, therefore, be suited to determine the endpoint of root surface instrumentation during non-surgical periodontal therapy.

Dental Calculus↗
PubMed2005

Semiconductor nanowires for subwavelength photonics integration.

This article focuses on one-dimensional (1D) semiconductor subwavelength optical elements and assesses their potential use as active and passive components in photonic devices. An updated overview of their optical properties, including spontaneous emission, ultrafast carrier dynamics, cavity resonance feedback (lasing), photodetection, and waveguiding, is provided. The ability to physically manipulate these structures on surfaces to form simple networks and assemblies is the first step toward integrating chemically synthesized nanomaterials into photonic circuitry. These high index semiconductor nanowires are capable of efficiently guiding light through liquid media, suggesting a role for such materials in microfluidics-based biosensing applications.

Journal Article↗
PubMed2003

The acoustic spectrophonometer: a novel bioanalytical technique based on multifrequency acoustic devices.

A measurement technique similar to optical absorption spectroscopy but based on evanescent acoustic waves is described in this paper. This format employs a planar spiral coil to vibrate a single crystal of quartz from 6 to 400 MHz, in order to measure multifrequency acoustic spectra. Consistency with the defined Sauerbrey and Kanazawa terms K1 and K2 when applied to multiple frequencies was found for these specific operating conditions in terms of a significant fit between the measured and calculated values: For an IgG surface density of 13.5 ng mm(-2) the measured value of K1 is 22.5 x 10(-6) and the calculated value is 20.4 x 10(-6), whilst for glycerol viscous loadings of 5.131 cP the measured value of K2 is 0.47 and the calculated value is 0.54. Thus for these specific surface loadings the multifrequency data fits to the predictions of the Sauerbrey model to within 10% and to Kanazawa model within 13%. However collective frequency shifts for 5.131 cP solutions of sucrose, dextran and glucose were found to exhibit an unanticipated additional variability (R2 < 0.4) with frequency, but retained a square root of frequency dependency within a factor 2 of the interpolated K2 values. The response to the 5.131 cP dextran solution was found to be significantly below the other isoviscous solutions, with a substantially reduced frequency shift and K2 value than would be expected from its bulk viscosity. In comparison with these viscous solutions, IgG protein films consistently produced linear frequency shifts with little scatter (R2 > 0.96) that were proportional to the operating frequency, and fully consistent with the Sauerbrey model under these specific conditions. A t-test value of 14.52 was calculated from the variance and mean of the two groups, and demonstrates that the acoustic spectrophonometer can be used to distinguish between the acoustic impedance characteristics of two chemical systems that are not clearly differentiable at a single operating frequency.

Acoustics↗
PubMed1994

Performance of glass fiber antiscatter devices at mammographic energies.

Using fiber optic manufacturing techniques, it is possible to produce a radiographic grid that discriminates against scattered radiation in two dimensions. Such grids consist of septa composed of glass with a high lead content; the interspace material is air, so that approximately 80% of the grid area is open. In this way, effective high ratio grids can be produced with relatively low Bucky factors. The performance of samples of such grid material is characterized in terms of both scatter rejection and dose efficiency for application in digital mammography in both slot-beam and area-beam geometry. For area beams, five- to tenfold improved scatter rejection relative to conventional grids was observed. In slot configurations, such grids could provide improved SNR/dose performance and more effective utilization of the heat loading capability of the x-ray source.

Fiber Optic Technology↗
PubMed2004

Experimental techniques using optically enabled ring oscillators.

We present a method for characterizing transceiver performance in parallel optical data links. By establishing a bidirectional link between two optically enabled chips, the conditions for a ring oscillator are made possible. We propose this technique as a means of measuring the sensitivity of transceiver latency to controlled variables such as temperature, optical output power, supply voltage, and device misalignment. This method is noninvasive and independent of the packaging, circuit topology, and optical medium used. The technique is demonstrated experimentally, and results are compared with a simulation.

Journal Article↗
PubMed2003

Light-emitting field-effect transistor based on a tetracene thin film.

We report the first organic light-emitting field-effect transistor. The device structure comprises interdigitated gold source and drain electrodes on a Si/SiO(2) substrate. A polycrystalline tetracene thin film is vacuum sublimated on the substrate forming the active layer of the device. Both holes and electrons are injected from the gold contacts into this layer leading to electroluminescence from the tetracene. The output characteristics, transfer characteristics, and the optical emission properties of the device are reported. A possible mechanism for electron injection is suggested.

Journal Article↗