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At least 793 records · Page 44Linked to original sources
PubMed2003

Neuromyelitis optica: importance of cerebrospinal fluid examination during relapse.

Devic's neuromyelitis optica (NMO) is a clinical entity characterised by severe transverse myelitis, optic neuropathy and monophasic or recurrent course. We report the case of a woman affected by myelitis and optic neuritis suggesting Devic's disease. Diagnosis was supported by clinical, neuroradiological and biochemical findings. In 14 months, the patient developed 5 clinical exacerbations. Six cerebrospinal fluid (CSF) examinations were performed, 3 during relapses and 3 during remitting phases: all the CSF specimens obtained during relapses showed granulocyte pleocytosis and increased protein level, whereas CSF was normal during stationary phases. Oligoclonal banding was always absent. Spinal cord MRI showed altered signal at cervical and thoracic levels. We did not find any concomitant systemic disease. The case we report underlines the importance of CSF examination during clinical relapse in NMO diagnosis.

Disability Evaluation↗
PubMedDate not supplied

Dynamic versus static grip strength: how grip strength changes when the wrist is moved, and why dynamic grip strength may be a more functional measurement.

The synergistic relationship between wrist/forearm range of motion (ROM) and grip strength (GS) is arguably one of the most important aspects of hand function. Clinically, GS is measured with the wrist in a standardized static position, and the results of such tests have been deemed valid and reliable. The question remains, however, whether this static GS (SGS) measurement is an accurate indication of how an individual functionally grips objects--that is, most functional tasks require the fingers to grasp an object forcibly while moving the proximal joints such as the wrist and forearm. Therefore, further analysis of an individual's dynamic GS (DGS) during wrist/forearm movements may improve the clinician's understanding of hand function and provide more pertinent guidelines for assessing functional gripping, e.g., for vocational and avocational tasks and in designing workstations. The purpose of this study is twofold: to describe and assess a DGS testing device that utilizes optically encoded gyroscopes and a strain-gauge dynamometer to simultaneously measure GS and wrist/forearm position over real time; and to assess and compare grip force production differences in SGS and DGS in uninjured wrists, using this novel device. Twenty-nine uninjured wrists of men (n = 15) and women (n = 14)--age range, 21 to 43 years--were tested with the DGS device. Subjects were excluded if they had any previous wrist/forearm fracture, pain, or limitation of motion. The DGS device was designed and fabricated with two optically encoded gyroengines, a vertical gyroscope with two axes for measuring flexion/extension and radial/ulnar deviation, and a directional gyroscope with one axis for measuring supination/pronation, mounted on a strain-gauge dynamometer. The signals from the gyroscopes and dynamometer were processed by means of a data aquisition board and analog-to-digital circuitry and collected on a 486-MHz computer. The methods included repeated testing of each gyroscope axis to known angular measurements, and randomly assigned maximal gripping trials from the 29 subjects. The standard deviation of gyroengines is 1 degree to 2 degrees for each ROM axis. Maximal DGS is significantly less (mean 14%) than SGS, and SGS is 29% less than DGS at the same three-dimensional ROM positions. Gyroengines are feasible three-dimensional tracking devices that can be used to monitor wrist/forearm ROM in conjunction with GS.

Adult↗
PubMed2001

Responses of neurons in the medial column of the inferior olive in pigeons to translational and rotational optic flowfields.

The responses of neurons in the medial column of the inferior olive to translational and rotational optic flow were recorded from anaesthetized pigeons. Panoramic translational or rotational flowfields were produced by mechanical devices that projected optic flow patterns onto the walls, ceiling and floor of the room. The axis of rotation/translation could be positioned to any orientation in three-dimensional space such that axis tuning could be determined. Each neuron was assigned a vector representing the axis about/along which the animal would rotate/translate to produce the flowfield that elicited maximal modulation. Both translation-sensitive and rotation-sensitive neurons were found. For neurons responsive to translational optic flow, the preferred axis is described with reference to a standard right-handed coordinate system, where +x, +y and +z represent rightward, upward and forward translation of the animal, respectively (assuming that all recordings were from the right side of the brain). t(+y) neurons were maximally excited in response to a translational optic flowfield that results from self-translation upward along the vertical (y) axis. t(-y) neurons also responded best to translational optic flow along the vertical axis but showed the opposite direction preference. The two remaining groups, t(-x+z) and t(-x-z) neurons, responded best to translational optic flow along horizontal axes that were oriented 45 degrees to the midline. There were two types of neurons responsive to rotational optic flow: rVA neurons preferred rotation about the vertical axis, and rH135c neurons preferred rotation about a horizontal axis at 135 degrees contralateral azimuth. The locations of marking lesions indicated a clear topographical organization of the six response types. In summary, our results reinforce that the olivo-cerebellar system dedicated to the analysis of optic flow is organized according to a reference frame consisting of three approximately orthogonal axes: the vertical axis, and two horizontal axes oriented 45 degrees to either side the midline. Previous research has shown that the eye muscles, vestibular semicircular canals and postural control system all share a similar spatial frame of reference.

Animals↗
PubMedDate not supplied

[Reading device for the blind based on the transformation of the optical image into a vibrotactile one].

The article describes a device in which the printed text letters after their photo-transforming are presented as a matrix of bimorphous piezoelements in the vibrotactile form. The operation of a bimorph as an element of a tactile matrix has been studied experimentally and requirements to parameters of excitation signals were settled. Consideration is given to the phototactile transformation principle and to some circuits for its practical embodiment.

Blindness↗
PubMed2003

Soliton-based Y-branch in photorefractive crystals induced through dispersion-shifted optical fiber.

We experimentally demonstrate for what is believed to be the first time that a dispersion-shifted fiber can be used to electro-optically induce a soliton Y-branch structure in a photorefractive centrosymmetric paraelectric crystal (potassium lithium tantalate niobate). The application of a nonstationary external bias field enables us to stabilize the spatially partially coherent behavior of the optical beam at the fiber output. Furthermore, we show the switching capabilities of this soliton-based device in the optical communication field guiding a probe beam at a nonphotorefractive wavelength (1557 nm).

Journal Article↗
PubMed1995

Waking effectiveness of visual alerting signals.

People who are unable to hear acoustic alarm signals because they have a complete or partial hearing loss must rely on visual or tactile signals to warn them in the event of an emergency. However, consumers report that personal smoke detector devices which provide a visual alarm do not wake people reliably. We examined the ability of visual alerting devices to wake people from the deepest stages of sleep: slow wave sleep (SWS) and rapid-eye-movement sleep (REM). These results were related to the physical (optical) characteristics of devices currently on the market. In Experiment 1, a range of strobe intensities and locations were investigated. Experiment 2 confirmed the results of this pilot study on an independent set of subjects. On each trial, the strobe was allowed to run at a constant intensity until the subject awoke, or a maximum of 5 min had elapsed. Even though a diffuse light remained directly over the subject's face for each trial, subjects did not wake consistently. Under the favorable optical (smoke-free) conditions of the present study, the most intense of the devices presently offered for sale in Canada cannot be relied on to wake a sleeping person in the event of a fire. It remains unclear whether any visual alerting device can be expected to safely wake a sleeper in an emergency situation.

Adult↗
PubMed2006

Broadband diffuse optical spectroscopy measurement of hemoglobin concentration during hypovolemia in rabbits.

Serial blood draws for the assessment of trauma patients' hemoglobin (sHgb) and hematocrit (sHct) is standard practice. A device that would allow for continuous real-time, non-invasive monitoring of hemoglobin and tissue perfusion would potentially improve recognition, monitoring and resuscitation of blood loss. We developed a device utilizing diffuse optical spectroscopy (DOS) technology that simultaneously measures tissue scattering and near-infrared (NIR) absorption to obtain non-invasive measurements of oxy- (Hb-O(2)), deoxyhemoglobin (Hb-R) concentrations and tissue hemoglobin concentration (THC) in an animal model of hypovolemic shock induced by successive blood withdrawals. Intubated New Zealand White rabbits (N = 16) were hemorrhaged via a femoral arterial line every 20 min until a 20% blood loss (10-15 cc kg(-1)) was achieved to attain hypovolemia. A broadband DOS probe placed on the inner thigh was used to measure muscle concentrations of Hb-O(2) and Hb-R, during blood withdrawal. THC and tissue hemoglobin saturation (S(T)O(2)) were calculated from DOS [Hb-O(2)] and [Hb-R]. Broadband DOS-measured values were compared against traditional invasive measurements: systemic sHgb, arterial oxygen saturation (S(a)O(2)) and venous oxygen saturation (S(v)O(2)) drawn from arterial and central venous blood. DOS and traditional invasive measurements versus blood loss were closely correlated (r(2) = 0.96) showing a decline with removal of blood. S(T)O(2) and [Hb-O(2)] followed similar trends with hemorrhage, while [Hb-R] remained relatively constant. These measurements may be limited to some extent by the inability to distinguish between hemoglobin and myoglobin contributions to DOS signals in tissue at this time. Broadband DOS provides a potential platform for reliable non-invasive measurements of tissue oxygenated and deoxygenated hemoglobin and may accurately reflect the degree of systemic hypovolemia and compromised tissue perfusion.

Animals↗
PubMed2005

[In-vitro comparison of morphology of current microkeratomes for LASIK].

BACKGROUND: We have performed an in-vitro examination of the morphology of flap thickness and stromal bed after LASIK in porcine eyes. MATERIALS AND METHODS: Freshly enucleated porcine eyes and synthetic eye models were used for cutting flaps with the microkeratomes Hansatome-Excellus (Bausch&Lomb), M2 single use (Moria), Amadeus (AMO), MK-2000 (Nidek) and Carriazo-Pendular (Schwind). The flap thickness of porcine eyes was determined using a non-contact, confocal optical distance measuring device (CHR 150N, Jurca), in the eye models a mechanical thickness measuring device (Käfler) was used. The morphology of the stromal bed was examined by photography, histology, scanning electron microscopy and confocal optical distance measurements. RESULTS: The optical/mechanical flap thickness measurements showed an average difference compared to the adjusted thickness of - 3/+ 90 microm (Hansatome-Excellus), + 7/+ 100 microm (M2 single use), - 35/+ 40 microm (Amadeus), - 4/+ 80 microm (MK-2000) and + 11/+ 0 microm (Carriazo-Pendular). Histology showed no mechanical damage and smooth, slightly undulating surfaces with all microkeratomes. In the scanning electron microscopic examination, the stromal surface was found to be homogeneous and smooth for all of the microkeratomes. Average roughness of the ablation surface was 0.27 microm (Hansatome-Excellus), 0.23 microm (M2 single use), 0.21 microm (Amadeus), 0.23 microm (MK-2000) and 0.29 microm (Carriazo-Pendular). CONCLUSION: The stromal bed showed in all cases only a slightly roughness, which seems to be acceptable for the clinical outcome. However, the more critical point is the large variations in flap thickness compared to the intended thickness.

Animals↗
PubMed2003

In-line liquid-crystal microcell polarimeter for high-speed polarization analysis.

We report a type of high-speed microcell polarimeter that utilizes microelectrodes, liquid-crystal films, and ultrathin high-contrast polarizers, all integrated between the tips of two optical fibers. When combined with optimized nematic liquid-crystal materials, this compact (2.5 cm x 0.5 cm x 0.5 cm) device offers excellent optical properties and continuous, high-speed operation at > 2 kHz with moderately low operating voltages. It requires no bulk optical elements, and it shows excellent performance when implemented for the measurement of degree of polarization in 10-Gbit/s test systems. Polarimeters based on this design have promising potential applications in polarization analysis for high-speed optical communication systems.

Journal Article↗
PubMed2004

Diffraction of optical communication Gaussian beams by volume gratings: comparison of simulations and experimental results.

The diffraction effects induced by a thick holographic grating on the propagation of a finite Gaussian beam are theoretically analyzed by means of the coupled-wave theory and the beam propagation method. Distortion of the transmitted and diffracted beams is simulated as a function of the grating parameters. Theoretical results are verified by experimentation realized by use of LiNbO3 volume gratings read out by a 1550-nm Gaussian beam, typical of optical fiber communications. This analysis can be implemented as a useful tool to aid with the design of volume grating-based devices employed in optical communications.

Journal Article↗
PubMed2000

Piezoelectric Mass-Sensing Devices as Biosensors-An Alternative to Optical Biosensors?

In the early days of electronic communication-as a result of the limited number of quartz resonators available-frequency adjustment was accomplished by a pencil mark depositing a foreign mass layer on the crystal. In 1959, Sauerbrey showed that the shift in resonance frequency of thickness-shear-mode resonators is proportional to the deposited mass. This was the starting point for the development of a new generation of piezoelectric mass-sensitive devices. However, it was the development of new powerful oscillator circuits that were capable of operating thickness shear mode resonators in fluids that enabled this technique to be introduced into bioanalytic applications. In the last decade adsorption of biomolecules on functionalized surfaces turned in to one of the paramount applications of piezoelectric transducers. These applications include the study of the interaction of DNA and RNA with complementary strands, specific recognition of protein ligands by immobilized receptors, the detection of virus capsids, bacteria, mammalian cells, and last but not least the development of complete immunosensors. Piezoelectric transducers allow a label-free detection of molecules; they are more than mere mass sensors since the sensor response is also influenced by interfacial phenomena, viscoelastic properties of the adhered biomaterial, surface charges of adsorbed molecules, and surface roughness. These new insights have recently been used to investigate the adhesion of cells, liposomes, and proteins onto surfaces, thus allowing the determination of the morphological changes of cells as a response to pharmacological substances and changes in the water content of biopolymers without employing labor-intense techniques. However, the future will show whether the quartz-crystal microbalance will assert itself against established label-free sensor devices such as surface plasmon resonance spectroscopy and interferometry.

Journal Article↗
PubMed1986

Evaluation of light transmission characteristics of protective eyeglasses for visible light-curing units.

Eyeglasses with protective filters are recommended for users of visible light-curing units to decrease the intensity of blue light reaching the eyes. The transmission curves of 20 commercially available filter glasses are obtained. The irradiance from eight curing units through these glasses is measured. The reduction in irradiance through the filter glasses is related to the transmission curves.

Evaluation Studies as Topic↗
PubMed1975

[Special glasses].

Explore the source record for details and available documents.

Eye Protective Devices↗
PubMed2005

Optically fabricated three dimensional nanofluidic mixers for microfluidic devices.

This paper describes a simple technique for fabricating complex, but well defined, three-dimensional (3D) networks of nanoscale flow paths in the channels of microfluidic systems. Near field scanning optical measurements reveal the optics associated with the fabrication process and the key features that enable its application to the area of microfluidics. Confocal studies of microfluidic devices that incorporate 3D nanostructures formed using this approach show that they function as efficient passive mixing elements, particularly at low Reynolds numbers. This application and others such as separation and extraction inmicrofluidic total analysis systems or lab on a chip devices represent promising areas for 3D nanostructures of this general type.

Equipment Design↗
PubMed2003

Excitation dynamics in a three-quantum dot system driven by optical near-field interaction: towards a nanometric photonic device.

Using density operator formalism, we discuss interdot excitation energy transfer dynamics driven by the optical near-field and phonon bath reservoir, as well as coherent excitation dynamics of a quantum dot system. As an effective interaction between quantum dots induced by the optical near-field, the projection operator method gives a renormalized dipole interaction, which is expressed as a sum of the Yukawa functions and is used as the optical near-field coupling of quantum dots. We examine one- and two-exciton dynamics of a three-quantum dot system suggesting a nanometric photonic switch, and numerically obtain a transfer time comparable with the recent experimental results for CuCl quantum dots.

Journal Article↗
PubMed2005

[Low-vision rehabilitation of age-related macular degeneration patients with retrofoveal choroidal new-vessels treated with photodynamic therapy with verteporfin].

PURPOSE: To demonstrate the rehabilitation benefit and immediate optical magnification and electronic equipment advantage in an age-related macular degeneration population with retrofoveal choroidal new-vessels treated by photodynamic therapy using Visudyne. PATIENTS AND METHODS: Sixty seven consecutive patients with retrofoveal choroidal new-vessels treated by Photodynamic Therapy using Visudyne were referred to an orthoptist for low-vision rehabilitation. The criteria investigated for this study were: long distance visual acuity, reading ability, contrast sensitivity, (before treatment and during post-treatment examinations), and fixation localization and optical equipment model. RESULTS: This study showed and studied visual acuity variations, mostly for patients with good visual acuity at inclusion. Contrast sensitivity stayed more or less the same. Retinal fixation was foveolar most of the time (68.7%). Optical or electronic devices for low-vision patients are numerous and video systems were the most currently used among our population. 62.7% des patients had low-vision rehabilitation with optic aids. DISCUSSION AND CONCLUSION: This study threw light on patient optic aids which must be prescribed according to his needs and difficulties, without delay. This equipment will then be readapted at each stage of the patient evolution. PDT treatment gives an important role to low-vision rehabilitation associated with optic magnification aids.

Aged↗
PubMed1993

Jet ring cell: a tool for flow injection spectroscopy and microscopy on a renewable solid support.

A new flow cell design for spectroscopic measurements of suspensions, the jet ring cell, is introduced. This cell exploits radial flow through a narrow ring-shaped gap to retain suspended particles within the detection region. This ring constitutes a detection volume of well-defined area from which the trapped particles can be instantaneously removed at will. The bed of particles thus forms a renewable surface, which can be probed by reflectance, fluorescence, or chemiluminescence using a microscope or optical fiber. This device should prove useful for microscopic study of cells, for automated immunoassays, and for preconcentration of analytes on sorbents with in situ spectroscopic detection. In conjunction with a fiber optic detection system, the jet ring cell becomes a component of a renewable chemical sensor system.

Animals↗