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Results for “Optical Devices”

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At least 1,351 records · Page 75Linked to original sources
PubMed2005

Ultrarapid desalting of protein solutions for electrospray mass spectrometry in a microchannel laminar flow device.

The adverse effects of nonvolatile salts on the electrospray (ESI) mass spectra of proteins and other biological analytes are a major obstacle for a wide range of applications. Numerous sample cleanup approaches have been devised to facilitate ESI-MS analyses. Recently developed microdialysis techniques can shorten desalting times down to several minutes, the bottleneck being diffusion of the contaminant through a semipermeable membrane. This work introduces an approach that allows the on-line desalting of macromolecule solutions within tens of milliseconds. The device does not employ a membrane; instead, it uses a two-layered laminar flow geometry that exploits the differential diffusion of macromolecular analytes and low molecular weight contaminants. To maximize desalting efficiency, diffusive exchange between the flow layers is permitted only for such a time as to allow full exchange of salt, while incurring minimal macromolecule exchange. Computer simulations and optical studies show that the device can reduce the salt concentration by roughly 1 order of magnitude, while retaining approximately 70% of the original protein concentration. Application of this approach to the on-line purification of salt-contaminated protein solutions in ESI-MS results in dramatic improvements of both the signal-to-noise ratio and the absolute signal intensity. However, efficient desalting requires the diffusion coefficients of salt and analyte to differ by roughly 1 order of magnitude or more. This technique has potential to facilitate high-throughput analyses of biological macromolecules directly from complex matrixes. In addition, it may become a valuable tool for process monitoring and for on-line kinetic studies on biological systems.

Bradykinin↗
PubMed2003

Mode-order converter in a multimode waveguide.

A novel device that converts the order of modes in an integrated-optic multimode waveguide was proposed and fabricated. The device consists of two mode splitters and tapered waveguides. Its operation at a wavelength of 1.55 microm was confirmed by observation of the output mode profiles. The cross talk measured by an indirect method was >10.2 dB. The excess loss with reference to a straight multimode waveguide was 1.5 dB, compared with the propagation loss of a straight multimode waveguide.

Journal Article↗
PubMedDate not supplied

Microfabricated devices: A new sample introduction approach to mass spectrometry.

Instrument miniaturization is one way of addressing the issues of sensitivity, speed, throughput, and cost of analysis in DNA diagnostics, proteomics, and related biotechnology areas. Microfluidics is of special interest for handling very small sample amounts, with minimal concerns related to sample loss and cross-contamination, problems typical for standard fluidic manipulations. Furthermore, the small footprint of these microfabricated structures leads to instrument designs suitable for high-density, parallel sample processing, and high-throughput analyses. In addition to miniaturized systems designed with optical or electrochemical detection, microfluidic devices interfaced to mass spectrometry have also been demonstrated. Instruments for automated sample infusion analysis are now commercially available, and microdevices utilizing chromatographic or capillary electrophoresis separation techniques are under development. This review aims at documenting the technologies and applications of microfluidic mass spectrometry for the analysis of proteomic samples.

Biotechnology↗
PubMed1996

A small chamber for making optical measurements on single living cells at elevated hydrostatic pressure.

A 100-microliters chamber has been developed to facilitate the use of optical techniques for the study of living cells under conditions of high hydrostatic pressure and other environmental manipulations. The chamber attaches to the mechanical stage of an inverted microscope and is capable of sustaining cells under physiologic conditions over a range of hydrostatic pressure from 1 to 150 atmospheres (1 atm = 101.325 kPa). Cells are located directly on the pressure supporting window that forms the bottom of the chamber. This window is made from coverslip glass which is bonded to the chamber using an epoxy adhesive and is thin enough to permit ultraviolet epi-illumination using high magnification, high numerical aperture objectives. Electrodes for stimulating excitable cells are also located on this window. In operation, the chamber is installed in a custom stage mount which provides X, Y, Z, and rotational alignment of chamber contents with respect to the microscope's optical axis. This allows precise registration of the cell specimen with the image sensing devices attached to the microscope. Mechanical and optical alignment can be performed at any pressure over the working range of the chamber. The separate cover that seals the chamber is also fitted with a window to allow for simultaneous transillumination of the specimen. A high pressure liquid chromatography pump is used to continuously perfuse the chamber with a solution that is controlled for temperature, pressure, gas tension, and ionic composition.

Atmosphere Exposure Chambers↗
PubMed1995

[A semi-quantitative measurement of glycocalyx and an ATP bioluminescent assay for the analysis of Pseudomonas aeruginosa biofilm].

BACKGROUND: In order to analyze each element of a bacterial biofilm, a semi-quantitative measurement of glycocalyx using toluidine blue and an improved ATP bioluminescence assay were developed. RESULTS: In the toluidine blue assay, a linear correlation was obtained between optical density and the amount of gellan gum, which is an exopolysaccharide derived from Pseudomonas elodea. By using the improved ATP assay, ATP at concentration of 1 x 10(-4) mol/l or floating bacterial cells of 10(3) cfu could be detected. The applicability of these two methods was examined in evaluating a total amount of glycocalyx and ATP content of Pseudomonas aeruginosa biofilms, which were developed or treated with antimicrobial agents in a modified Robbins device. CONCLUSION: The changes in optical density and ATP luminescence were reasonable, and well correlated with those obtained by scanning electron microscopy. These results indicate that the toluidine blue assay and ATP assay are useful in analyzing bacterial biofilms.

Adenosine Triphosphate↗
PubMed1990

Image evaluation of ophthalmic devices.

Methods used in the ophthalmic industry to evaluate the optical image quality of correcting lenses have remained the same over many years. This is especially true for single-vision ophthalmic lenses. With the development of new optical designs and materials for correcting refractive errors and presbyopia, new procedures for evaluating lens performance are being explored. One such method is the measurement of the modulation transfer function. Over the last 2 years, we have been measuring modulation transfer functions on a variety of single-vision and bifocal contact lenses, progressive addition spectacle lenses, holographic-diffractive lenses, and intraocular lenses. In this article, the modulation transfer function procedure and its application and results from one study on safety goggles will be presented and discussed.

Eye Protective Devices↗
PubMed2003

Arrayed waveguide Sagnac interferometer.

We present a novel device, an arrayed waveguide Sagnac interferometer, that combines the flexibility of arrayed waveguides and the wide application range of fiber or integrated optics Sagnac loops. We form the device by closing an array of wavelength-selective light paths provided by two arrayed waveguides with a single 2 x 2 coupler in a Sagnac configuration. The equations that describe the device's operation in general conditions are derived. A preliminary experimental demonstration is provided of a fiber prototype in passive operation that shows good agreement with the expected theoretical performance. Potential applications of the device in nonlinear operation are outlined and discussed.

Journal Article↗
PubMed2006

Self-assembled one-dimensional nanostructure arrays.

A range of proposed devices relies on the electronic, optical or magnetic properties of one-dimensional (1D) chains of nanoparticles. Here, well-controlled 1D arrays have been formed by templating a spherical-morphology block copolymer within a narrow groove. Significantly, the domains are distorted into ellipses with aspect ratio and major axis orientation controlled by the groove width. This technique gives unprecedented control over the period, particle size, aspect ratio, and orientation of nanoparticles in 1D arrays, making it valuable for creating self-assembled masks for the fabrication of novel devices.

Computer Simulation↗
PubMed2005

A fiber-optic system for recording skin conductance in the MRI scanner.

The acquisition of the skin conductance response (SCR) during functional magnetic resonance imaging (fMRI) raises significant safety issues, as well as practical ones, which need to be addressed in order for these experiments to be conducted safely and successfully. Metallic and conductive wires in the presence of time-varying gradient magnetic fields such as those present in fMRI experiments may induce heating, as well as electric fields, in these components and, if in contact with the subject, could produce severe burns and electric shocks. Moreover, these metallic and conductive components can significantly distort the magnetic field, resulting in image artifacts. A system for recording the SCR in humans simultaneously with fMRI is presented. The device is a fiber-optic-based transducer, which records the SCR from two fingers of the same hand, using electrodes containing inline radio frequency (RF) suppression filters and protective resistive loads. The fiber-optic SCR transducer was tested using 1.5 and 3.0 Tesla MRI scanners running EPI sequences. This system was able to safely record SCRs free of RF interference during an fMRI experiment, and the fiber-optic design of the transducer eliminated any artifacts on the MRI scan.

Brain↗
PubMed1967

Cesar: cervical smear analyser and reader. A new approach to evaluating cells in cytological preparations.

Cesar presents an automated multiparameter approach to pattern recognition in the rapid detection of malignant cells from cervical and other cancers. Cells are cybernetically classified. They are collected into a container into which a nuclear stain may be incorporated and laid as a track on 35 mm. film using a disposable mapping pen device. The film track (Cytotrack) may be scanned using conventional optics and provision may be made for electronic sensing devices measuring a number of parameters, some of which are not normally used in conventional microscopy.

Cervix Uteri↗
PubMedDate not supplied

[Acute loss of vision in children].

The differential diagnosis of acute loss of vision in children includes acute loss of vision due to retinal or optic nerve disease, and cortical blindness. The retinal disorders which may be mis diagnosed as optic neuritis include Leber neuroretinitis, Leber hereditary optic neuropathy, and Stargardt macular dystrophy. Retinal changes which evolve in neuroretinitis, and the pseudopapilledema in Leber heredity optic neuropathy are helpful in differentiating these disorders from optic neuritis. Stargardt macular dystrophy, a disorder associated with a variety of mutations, may be mis diagnosed as psychogenic visual loss due to the early normal appearance of the retina, and the loss of vision over a period of weeks. The differentiation of optic neuritis from anterior ischemic optic neuropathy (AION), depends upon the initial appearance of the optic disc (in AION either hyperemia due to reperfusion, or swelling and pallor if total infarction has occurred). The authors have described children with abrupt loss of vision during renal dialysis, whose risk factors for AION included systemic hypotension and intra ocular hypertension. Children with vigorous treatment of accelerated hypertension, and children with migraine and pro thrombotic disorders have also incurred AION. Thus, AION should be suspected when acute loss of vision occurs in association with certain ocular and systemic risk factors. In children capable of cooperating for visual field examination, the typical change in AION is an altitudinal defect, while optic neuritis it is a central scotoma. The association of optic neuritis with multiple sclerosis, DeVic disease, and with acute demyelinating1 encephalomyelitis require special consideration in regard to treatment and prognosis. Acute loss of vision due to cerebral cortical insults involves a large differential diagnosis which includes vascular, metabolic and infective disease; as well as disorders causing transitory blindness such as seizures and migraine

Blindness, Cortical↗
PubMed2004

All-fiber narrowband polarization controller based on coherent acousto-optic mode coupling in single-mode fiber.

An all-fiber, narrowband, tunable polarization controller is proposed and demonstrated. The device is based on coherent acousto-optic mode coupling induced by two orthogonal acoustic waves on a dispersion-compensating fiber. The cooperative coupling between the two polarizations of the core mode and the TE01 cladding mode through the two gratings permits indirect coupling between the two polarizations of the core mode with nearly 100% efficiency, which makes the polarization-controlling function possible. Experimental results verify the operation of the polarization controller with an insertion loss of <1 dB.

Journal Article↗
PubMed2006

Recent developments in optical detection methods for microchip separations.

This paper summarizes the features and performances of optical detection systems currently applied in order to monitor separations on microchip devices. Fluorescence detection, which delivers very high sensitivity and selectivity, is still the most widely applied method of detection. Instruments utilizing laser-induced fluorescence (LIF) and lamp-based fluorescence along with recent applications of light-emitting diodes (LED) as excitation sources are also covered in this paper. Since chemiluminescence detection can be achieved using extremely simple devices which no longer require light sources and optical components for focusing and collimation, interesting approaches based on this technique are presented, too. Although UV/vis absorbance is a detection method that is commonly used in standard desktop electrophoresis and liquid chromatography instruments, it has not yet reached the same level of popularity for microchip applications. Current applications of UV/vis absorbance detection to microchip separations and innovative approaches that increase sensitivity are described. This article, which contains 85 references, focuses on developments and applications published within the last three years, points out exciting new approaches, and provides future perspectives on this field.

Journal Article↗
PubMed1993

A device for measuring mucociliary activity in the human bronchi during fibre-optic bronchoscopy.

An in vivo method for the study of mucociliary activity in the human trachea and bronchi is presented. The method is based on a two-way fibre-optic system whereby reflections of light emitted by one glass-fibre and reflected by the cilia are picked up by a second glass fibre and transmitted to a recording unit. The glass fibre system is designed to be used in conjunction with a regular fibre bronchoscope, and is convenient for routine use in daily clinical work. As reference material, 15 subjects aged 23-73 years without evidence of disease were examined in their right upper bronchus. The average cilial beat frequency was found to be 12.0 +/- 1.0 (SD) waves per second.

Adult↗
PubMed1998

Optical coherence tomography.

The optical coherence tomograph is a new, noninvasive technical device that can obtain cross-sectional, high-resolution images-optical coherence tomographs (OCT)-of the retina. This instrument permits an accurate evaluation of various macular and chorioretinal pathologies and the early detection of glaucomatous damage. Images of the retina are obtained similar to ultrasound B-scan, with 10-microm longitudinal resolution. Because the OCT operates with a near-infrared wavelength (about 840 nm), the examination is of minimal discomfort for the patient. OCT examination is indicated in cases of macular pathologies such as vitreoretinal interface syndrome, in the early detection and quantitative assessment of macular edema, and in the evaluation of a glaucomatous damage by measuring the retinal nerve fiber layer thickness. The future role of this instrument and its applications for clinical diagnosis depend on the future improvement and updating of the software.

Humans↗
PubMedDate not supplied

Pediatric Devic's neuromyelitis optica.

PURPOSE: Neuromyelitis optica (Devic's disease) is a rare clinical syndrome of unilateral or bilateral optic neuritis (ON) and transverse myelitis (TM) occurring within an 8-week time interval. All reports mainly involve adults and describe a poor neurologic and ophthalmic clinical course without specific attention to their few pediatric cases. The purpose of this study was to develop a clinical profile in the pediatric population. METHODS: A retrospective chart review over 15 years revealed nine cases of neuromyelitis optica. A literature search was undertaken and all cases of pediatric neuromyelitis optica were tabulated and analyzed separately. RESULTS: The average age of onset was 7 years with a preceding viral prodrome in all patients. The optic neuritis was bilateral in eight of nine patients (89%). Visual loss ranged from 20/30 to light perception. Moderate anterior disc edema was seen in all 17 affected eyes. The clinical course was characterized by a rapid visual and neurologic recovery. The average follow up was 5.3 years, with five patients followed for 6 years or longer. None of the nine patients had any visual or neurologic recurrence or other significant subsequent illness. Visual system follow up showed 20/20 in each eye of all patients with mild optic atrophy, identified in 47% of eyes. CONCLUSIONS: Devic's neuromyelitis optica occurs in the pediatric population as a distinct clinical entity with an excellent prognosis for visual and systemic recovery and no future recurrence or long-term sequelae.

Age of Onset↗