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At least 919 records · Page 51Linked to original sources
PubMed1990

The increase of oxygen consumption after a flash of light is tightly coupled to sodium pumping in the lateral ocellus of barnacle.

In the lateral ocellus of the barnacle, we have tested the hypothesis that the transient increase of oxygen consumption (delta QO2) induced by light results from an increase in the rate of Na+ pumping. With a Na(+)-sensitive microelectrode, we measured the intracellular concentration of Na+ (Nai) in the photoreceptor cells. Nai was 17.6 +/- 1.2 mM (SE; n = 18) in darkness and it increased transiently by 10-20 mM after an 80-ms flash of intense light. The increase of Nai recovered in about the same time as the delta QO2, and the Na+/O2 ratio was 19.2 +/- 3.8 (SE; n = 6). Removing Na+ from the bath caused the delta QO2 to decrease by 79 +/- 3% (SE; n = 5). Exposure to 25 microM ouabain inhibited Na+ pumping and abolished the delta QO2. Removal of K+ from the bathing solution inhibited Na+ pumping in darkness, but mostly shortened the duration of the delta QO2; with a K(+)-sensitive microelectrode, we measured pericellular [K+] and found that it increased after the flash for about the same time as the delta QO2. Increasing Na+ pumping in darkness by reintroducing K+ in the bath or by injecting Na+ into one of the photoreceptor cells induced a delta QO2. Finally, intracellular injection of adenosine diphosphate and inorganic phosphate (ADP + Pi), the metabolic products of ATP splitting by the Na+ pump, also induced a delta QO2 in darkness. We conclude that all the results obtained are consistent with the formulated hypothesis.

Adenosine Diphosphate↗
PubMed1977

Carboxyhemoglobin concentrations in flash fire victims: report of six simultaneous fire fatalities without elevated carboxyhemoglobin.

Eight people died in a traffic accident involving a tractor-trailer and ten autos. The accident caused a series of flash fires from ruptured gas tanks. Complete autopsies established that six of the victims died exclusively from thermal trauma; none showed an elevated blood carboxyhemoglobin concentration. Flash fire victims are exceptions to the axiom that elevation of blood carboxyhemoglobin is a sine qua non for concluding that a decedent recovered from the scene of a conflagration was alive in the fire.

Accidents, Traffic↗
PubMed1996

The dynamics of flash fires involving flammable hydrocarbon liquids.

Victims of fires are sometimes discovered to have less-than-lethal levels of carbon monoxide (CO) in the blood and no significant antemortem fire damage. Such occurrences are often linked to flash fires involving volatile hydrocarbon fuels. In this study, the dynamics of hydrocarbon fuel fires are examined, and the results of fullscale room tests ignited with small (< 2 L) quantities of flammable liquid are found to confirm the theoretical predictions. These tests showed that flame plumes with temperatures of 500-975 degrees C were produced above flammable liquids. Ignition of their vapors in a carpeted room produced a very short-lived flash of fire throughout the room, followed by intense flames in a layer above the floor approximately 1 m deep, which quickly degenerated to isolated pools of low flames. Combustion of hydrocarbon vapors in a room caused oxygen levels to drop below 8.5% in < 100 s, while causing carbon dioxide (CO2) levels to increase to 12-16% whether the door to the room was open or closed. Production of CO trailed maximum CO2 production by 15-30 s. A victim exposed to such a fire may collapse from extreme heat (aided by the water vapor created by the combustion of hydrocarbons), weakened by oxygen deprivation, before CO inhalation becomes a significant factor.

Carbon Dioxide↗
PubMed1997

Complications following butane inhalation and flash fire.

Solvent inhalation is a well-documented form of drug abuse that can cause euphoria and hallucinations. Sudden death involving a volatile substance is most commonly caused by cardiac arrythmias, asphyxia, direct drug effects, and trauma. The victim in this paper suffered superficial partial thickness (12% total body surface area) burns from a flash fire that occurred when lighting a match after inhaling butane in an enclosed vehicle. The victim was admitted to the hospital for 2 days of observation but did not develop any respiratory symptoms under 2 days following her release. The victim died during her readmission, 9 days after the flash fire. Postmortem examination showed extensive epithelial injury from the upper airway and trachea to the terminal bronchioles, most likely due in part to both the initial inhalation injury and the resulting adult respiratory distress syndrome (ARDS) and staphylococcal infection. Many victims with superficial burn injuries may not seek medical attention owing to either embarrassment or fear of legal prosecution. Even those who do seek medical assistance may not reveal solvent abuse as the cause of their injuries. It is possible that delayed death may occur at home following volatile substance abuse but may remain unrecognized even with a thorough scene investigation.

Adolescent↗
PubMed1991

Evaluation of ocular hazards due to electric arc flash at an in-line switch.

We investigated the ocular damage resulting from operation of a solid blade pole-mounted in-line electrical switch at between 16 and 17 kV with current loads between 38 A and 340 A. Spectroradiometric data for the electric arcs produced as the switch was opened were obtained over the waveband 200 to 1500 nm. The eyes of adult pigmented rabbits were exposed to the arc flash at a distance of 2 m. The ocular tissues were assessed clinically and histologically up to 48 h postexposure. Threshold damage was clinically detectable only in eyes exposed to a 340 A arc. We conclude that at the normal current loads on a 17-kV electric power transmission line, the principal oculovisual hazards are due to molten metal fulminated from the switch by the arc, and after-images due to the bright visible light flash. At a working distance of 2 m, the ultraviolet ocular hazard is negligible. Adequate eye protection is provided by clear polycarbonate safety lenses.

Animals↗
PubMedDate not supplied

Differentiation between hepatoma and hemangioma with inversion-recovery snapshot FLASH MRI and Gd-DTPA.

Thirty-eight patients with focal liver tumors (20 hepatomas, 18 hemangiomas) were studied by dynamic sequential inversion recovery (IR) snapshot fast low angle shot (FLASH) MR imaging with Gd-DTPA. Immediately after 0.05 mmol/kg Gd-DTPA was administered intravenously for 2-3 s followed by flushing with normal saline for 4-5 s, 10 images were obtained in the first 20 s (time zero is the end of flush, early phase). Then, one image every 30 s from 1 to 3 min (late phase) and images at 5 min and 7 min (delayed phase) were obtained serially. Hepatomas showed total enhancement in 18 of 20 patients in the early phase, and isointense or low intensity enhancement with respect to the surrounding liver parenchyma in 18 patients in the late to delayed phases. Hemangiomas showed peripheral enhancement in 14 patients in the early phase, but did not show total enhancement (except for two hemangiomas less than 3 cm in size) in the early phase, and showed high intensity enhancement in 15 patients in the late phase. Ninety percent of hepatomas and 82% of hemangiomas showed their characteristic enhancement patterns in the early to delayed phases. We conclude that dynamic sequential IR snapshot FLASH MR images enhanced with Gd-DTPA can facilitate differentiation between hepatomas and hemangiomas.

Aged↗
PubMedDate not supplied

Detection of renal ischemic lesions using Gd-DTPA enhanced turbo FLASH MRI: experimental and clinical results.

PURPOSE: Our goal was to investigate the role of Gd-DTPA-enhanced dynamic MRI in the evaluation of renal ischemic lesions. METHOD: With a turbo FLASH sequence before and after injection of Gd-DTPA, nine foxhound dogs after 60-120 min of renal ischemia underwent MR examination. In addition, five patients with a tumor in a solitary kidney were examined before and after nephron-sparing renal surgery to evaluate renal perfusion and function. The experimental and clinical findings were correlated with conventional measurements of kidney function and with histological findings. RESULTS: Complete renal ischemia leads to a poor corticomedullary differentiation in Gd-DTPA-enhanced turbo FLASH MRI. The signal-intensity-versus-time plots of kidneys with significant postischemic changes show a less steep increase of signal intensity in the cortex and a steeper increase of signal intensity in the medulla than those of normal kidneys. CONCLUSION: Dynamic MRI demonstrate renal morphology and reflect the functional status of renal vasculature.

Aged↗
PubMed1978

The effect of light flashing at 9 Hertz on rivalry suppression.

The translid binocular interactor (TBI), which presents binocularly out-of-phase lights flashing at 9 Hz, was designed to reduce suppression of amblyopes. To determine the effect of such flashing lights on rivalry suppression, subjects who showed strong suppression during binocular rivalry were exposed to a modified form of the TBI for a total of 2 2/3 hr over 4 days. A similar group of subjects was exposed to steady binocular light. The modified TBI had no effect on rivalry suppression; the changes in suppression that did occur were equivalent in the two groups.

Amblyopia↗
PubMed1979

An accessory fill-in flash for the Nikon photo-slit lamp.

High-quality slit lamp photographs require a balance between slit beam exposure and exposure of surrounding ocular structures. Proper exposure of surrounding ocular structure is difficult to obtain with the Nikon photo-slit lamp. The purpose of this research was to design an accessory fill-in flash for this slit lamp, which would provide proper exposure of over all ocular structures. In addition, this paper describes the procedures used to obtain proper exposure values and provides an exposure table for this accessory flash unit.

Eye↗
PubMed1988

Quantitative photorefraction using an off-center flash source.

When an eye is refracted by "eccentric photorefraction" with a flash source off-centered from a camera lens, a crescent of light is formed in the margin of the pupil. The size of the crescent varies directly with the eye's refractive error. This photographic method has been used in vision screening studies of young children where the appearance of a crescent indicated that the refractive error was above a certain threshold. Usually quantification of the refraction could not be achieved by the photorefractor but relied upon subsequent testing using retinoscopy. My research aimed to expand eccentric photorefraction so as to enable it to provide quantification of the eye's refractive error. This was achieved by varying the eccentricity of the flash source from the camera lens and then calibrating the instrument over a large range of refractive errors. The calibration modified a previously derived optical relation which defined the eye's refractive error in terms of the eccentricity of the source for a given pupil size. Eccentric photorefraction of 26 infants and children aged 7 to 48 months showed a good correlation with retinoscopy (r = 0.82). It is concluded that this method would be complementary to other photorefractive methods (e.g., isotropic) particularly as it is able to measure a large range of refractive errors once the astigmatic meridians of the eye are known.

Calibration↗
PubMed1988

Hot flash epilepsy.

A woman had episodes of bilateral thermal sensation, initially thought to be hot flashes related to menopause. EEG telemetry documented the epileptic nature of the attacks with an electrographic seizure emanating from the right temporal area coincident with the hot flashes.

Adult↗
PubMed2004

Flash visual evoked potentials predict visual outcome in traumatic optic neuropathy.

PURPOSE: To determine the significance of flash visual evoked potentials (FVEP) in the evaluation of patients with traumatic optic neuropathy (TON). METHODS: Eleven head-injured patients admitted to our center were diagnosed with unilateral TON. For every patient, FVEPs were obtained in both the affected eye and the unaffected eye. The normal eye thus functioned as each subject's internal control. We determined the amplitudes of FVEP waveforms for each eye and calculated an amplitude ratio of the affected/normal side for all individuals. The best-corrected visual acuity was obtained for each eye 2 weeks after acute hospitalization. We then determined the relation between best-corrected visual acuity in TON and the FVEP amplitude ratio. RESULTS: In 4 patients in whom the amplitude ratio was at least 0.5, visual acuity in the affected eye was 20/30 or better. In 7 patients, the amplitude ratio was less than 0.5, and visual acuity in the eye with TON did not exceed 20/300 (Pearson r = -0.93, p = 0.0001). CONCLUSIONS: Flash visual evoked potentials are highly predictive of the degree of visual function in unilateral TON. Finding FVEP amplitudes that are at least 50% of the normal eye appears to be critical in anticipating good, long-term visual outcome.

Adolescent↗
PubMed2005

Flash x-ray observations of cavitation in cadaver thighs caused by high-velocity bullets.

BACKGROUND: The purpose of this study was to record flash x-ray images of cavitation in human cadaver thighs caused by the passage of high-velocity bullets. The images are an initial step for understanding the cavitation process in human tissue and for implementing a better definition of extensive tissue injury. METHODS: Bullets were fired through the mid-thighs of 13 cadaver legs. The bullets were of two calibers, 7.62-mm full metal jacket boat tail with strike velocities in the range of 794 m/s to 880 m/s (10 thighs) and 5.70 mm full metal jacket with velocities in the range of 973 m/s to 992 m/s (3 thighs). Short duration (35 ns) x-ray images were recorded at various selected times after the bullets passed near the femurs. This study was carried out at the Armed Forces Institute of Pathology under approved human subject protocols. RESULTS: The cavity sizes and shapes were observed for the two types of bullets and at a number of times during the expansion and collapse of the cavities. As the bullets passed through the thighs, narrow cavities behind the bullets were observed. At later times, large expanded cavities were observed that encompassed the entire mid-thigh region. The observed cavities are at variance with those which were reported previously in gelatin tissue simulants. CONCLUSION: Flash x-ray radiography is an effective technique for the observation of internal cavitation in cadaver thighs caused by high-velocity bullets. These observations suggest that gelatin is not a proven simulant for human cadaver tissue in the study of cavitation subsequent to high-velocity missile impact.

Cadaver↗
PubMed2004

Feedback control in a collective flashing ratchet.

An ensemble of Brownian particles in a feedback controlled flashing ratchet is studied. The ratchet potential is switched on and off depending on the position of the particles, with the aim of maximizing the current. We study in detail a protocol which maximizes the instant velocity of the center of mass of the ensemble at any time. This protocol is optimal for one particle and performs better than any periodic flashing for ensembles of moderate size, but is defeated by a random or periodic switching for large ensembles.

Journal Article↗
PubMed1971

The photosynthetic unit in chlorella measured by repetitive short flashes.

Apparent size of the photosynthetic unit in Chlorella pyrenoidosa was estimated by the method of Emerson and Arnold: rate of oxygen evolution was measured under repetitive saturating flashes of about 10-microsecond duration separated by dark periods of 0.033 to 0.100 second. Cells used were taken from six steady state cultures maintained at different light intensities. Cell characteristics included a variation in chlorophyll content from 1 to 5%. Apparent size of the photosynthetic unit varied systematically with chlorophyll content in the range of 1560 to 2350 chlorophylls per O(2) per flash. Values for unit size showed no unusual statistical distribution and were not changed significantly by addition of low level background light at 645 or 705 nanometers. Maximal rate of unit turnover, calculated from light-saturated rate and unit size, varied inversely with chlorophyll content in the range of 70 to 180 per second.

Journal Article↗
PubMed1982

Growth, Pigment Synthesis, and Ultrastructural Responses of Phaseolus vulgaris L. cv. Blue Lake to Intermittent and Flashing Light.

Growing bean plants (Phaseolus vulgaris L. cv. Blue Lake) on cycles of 1 minute light-1 minute dark or 5 minutes light-5 minutes dark, providing an integrated 12 hours light-12 hours dark per day for each set of plants, led to production after 21 days of new leaves low or lacking in chloroplast pigments. Subsequently, dry weight increase was sharply cut. Leaf area was affected by the light regimes after the second week of growth. By the fourth week, plants on the 1 minute light-1 minute dark cycle showed about one-half the leaf area of the controls. Shoot growth was favored over root growth to the greatest degree on the 1 minute light-1 minute dark regimes. Chlorophyll a/b ratios were close to 3.0 in all of the intermittent light regimes, but the total amounts of chlorophyll in milligrams per primary leaf were higher from day 9 to day 23 for the 12 hour light-12 hours dark controls than for other plants.Although they produced chlorophyll, the plants receiving 1 or 2 milliseconds per second of light continued to lose weight at the same rate as the dark controls; thus, it is assumed there was no net photosynthesis. Plants receiving flashing light allocated significantly more food reserves from the seed to roots than did dark controls. Total chlorophyll formation was significantly accelerated by 2 milliseconds per second light. With 1 millisecond per second light, it took 5 days longer to achieve the same level of chlorophyll. After the 18th day, there was a steady decline in chlorophyll, b degrading more rapidly than a.It is thought that several light-driven reactions are involved in the observed pigment synthesis, photosynthesis, food allocation, and growth of bean. Some of these reactions may be cyclic and others linear. Collectively, they must reach a harmonic point for normal metabolism and development to occur. Because time courses for each of these reactions are different, the intermittent and flashing light technique offers the possibility of individually studying some of the key light-driven reactions.

Journal Article↗
PubMed1986

Oxygen exchange in ulva using a bare platinum electrode with 4 microsecond saturating light flashes.

Illuminating algae (Ulva species) on a bare platinum electrode with 4 microseconds of saturating light flashes leads to the familiar four-step oscillatory pattern of O(2) exchange. However, it appears that this O(2) exchange is a composite of O(2) evolution and endogenous O(2) uptake in the algae. We have added the O(2) uptake component to the O(2) exchange curve in order to obtain the corrected O(2) evolution flash sequence which shows a similar four-step oscillation as reported previously, but with negligible damping over the first three oscillations.

Journal Article↗
PubMed2000

Improving the X-ray resolution by reversible flash-cooling combined with concentration screening, as exemplified with PPase.

A significant improvement in the X-ray resolution of crystals of Escherichia coli inorganic pyrophosphatase at cryotemperature was obtained as a result of studying the relationship between the crystal order and cryosolution component concentrations. To perform the experiments, the ability to reverse the flash-cooling process and to return a crystal to ambient temperature was used. In each cycle, the crystal was transferred from a cold nitrogen-gas stream to a cryosolution with modified concentrations of the components. The crystal was then flash-cooled again and the diffraction quality checked. Such a technique allows the screening of a wide concentration range rather quickly without using a large number of crystals and allows the determination of optimal cryosolution component concentrations. The resolution limit for crystals of pyrophosphatase increased by almost 0.7 A, from 1.8 to 1.15 A.

Crystallography, X-Ray↗