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At least 307 records · Page 17Linked to original sources
PubMed1997

Modeling of cometary X-rays caused by solar wind minor ions.

X-ray emission was discovered in comet Hyakutake (C/1996 B2) by the Röntgen satellite in 1996, and these emissions were attributed to the excitation of high charge state solar wind ions due to electron capture from cometary molecules or atoms. Using the plasma flow in the coma of Hyakutake calculated by a three-dimensional adaptive magnetohydrodynamic model, the density distribution of solar wind ions in the coma and the resulting x-ray emission were computed. The calculated High Resolution Imager count rate of 4.4 per second and the spatial distribution of the x-ray emission agree with the observations. A detailed energy spectrum of cometary x-rays is predicted in the 80 to 2000 electronvolt energy range. Cometary x-rays present a sensitive tool to monitor cometary activity and solar wind ion composition.

Carbon↗
PubMed1997

Behavior and ecological genetics of wind-borne migration by insects.

Wind-borne migration, in which migrants ascend to altitudes at which they are transported downwind, has evolved independently in several insect orders. The use of a range of observational techniques, including ground and air-borne radars, has provided new insights into how the migrants' behavior can influence the distance traveled and the degree of dispersal during migration. Simultaneously in recent years, advances in our knowledge of the genetics of migratory potential have provided a basis for understanding how the stochastic effects of the winds on destinations and the pattern of habitat distribution in space and time maintain variation in these traits in populations of wind-borne migrants. This variation, in turn, is an essential factor in the ability of these insects, many of which are important pests, to track often unpredictable changes in the spatial distribution of suitable habitats.

Journal Article↗
PubMed1990

Sensation of inspired volumes and pressures in professional wind instrument players.

Previous studies have failed to show consistent differences in pulmonary function between wind instrument musicians and normal controls. In this study, respiratory sensation was assessed in 13 professional wind instrument players and 13 age-matched controls. Psychophysical techniques were used to assess magnitude estimation and reproduction of lung volumes and inspiratory pressures. The exponent for volume magnitude estimation was not different in musicians and controls (1.17 +/- 0.11 vs. 1.16 +/- 0.11), but volume reproduction was more accurate in musicians. The mean exponent for pressure magnitude estimation was 1.34 +/- 0.14 and 1.06 +/- 0.09 (P = 0.057) in musicians and controls, respectively. There was no difference between groups for absolute or constant error for pressure reproduction. Professional wind instrument players appear to have some inherent or acquired differences in respiratory perception and ventilatory neuromuscular control compared with other normal subjects.

Adult↗
PubMed1995

The wind-evoked escape behavior of the cricket Gryllus bimaculatus: integration of behavioral elements

The wind-evoked escape behavior of freely ranging crickets (Gryllus bimaculatus) was studied using high-speed video and film analysis. The escape response can be of three types: a turn, a jump or a turn + jump. Any of these can be followed by running. The turn is similar to that of the cockroach, in terms of the details of body and leg movements. A jump occurs only when the cricket has its back to the wind, either because the stimulus came approximately from behind or because the cricket had first turned away from the wind and then jumped. The jump, like that of locust, requires some form of energy storage and quick release to obtain the necessary power. Locusts use long-term co-activation of antagonistic leg motor neurons to produce mechanical energy storage. By contrast, crickets do not appear to co-activate antagonistic leg motor neurons. Possible alternative energy storage and release mechanisms are discussed.

Journal Article↗
PubMed2002

Assessment of a multibeam Fizeau wedge interferometer for Doppler wind lidar.

The Fabry-Perot interferometer is the standard instrument for the direct detection Doppler lidar measurement of atmospheric wind speeds. The multibeam Fizeau wedge has some practical advantages over the Fabry-Perot, such as the linear fringe pattern, and is evaluated for this application. The optimal Fizeau must have a resolving power of 10(6) or more. As the multibeam Fizeau wedge is pushed to such high resolving power, the interference fringes of the device become complicated by asymmetry and secondary maxima. A simple condition for the interferometer plate reflectance, optical gap, and wedge angle reveals whether a set of parameters will yield simple, Airy-like fringes or complex Fizeau fringes. Tilting of the Fizeau wedge improves the fringe shape and permits an extension of the regime of Airy-like fringes to higher resolving power. Sufficient resolving power for the wind lidar application is shown to be possible with a large-gap, low-finesse multibeam Fizeau wedge. Liabilities of the multibeam Fizeau wedge in the wind lidar application include a smaller acceptance solid angle and calibration sensitivity to localized deviations of the plates from the ideal.

Journal Article↗
PubMed2002

Wind-induced deformations in a segmented mirror.

A Zernike expansion of wind-induced deformations in a segmented mirror is described. The wind model is a frozen turbulent field with a Kolmogorov spectrum for scales smaller than the outer scale and a flat spectrum for scales larger than the outer scale. The approach allows a mode-by-mode comparison of the wave-front error contributions from atmospheric phase distortions, wind-induced deformations, and the mirror control system noise. This is used to design a controller that minimizes the mirror surface errors by application of corrections based on edge sensor measurements and wave-front measurements on a guide star.

Journal Article↗
PubMed2003

Simultaneous measurements of particle backscattering and extinction coefficients and wind velocity by lidar with a Mach-Zehnder interferometer: principle of operation and performance assessment.

The development of remote-sensing instruments that can be used to monitor several parameters at the same time is important for the study of complex processes such as those that control climate and environment. In this paper the performance of a new concept of lidar receiver that allows for the direct measurement of aerosol and cloud optical properties simultaneously with wind velocity is investigated. This receiver uses a Mach-Zehnder interferometer. Two different configurations, either with four photometric output channels or with fringe imaging on a multichannel detector, are studied. Analytical expressions of the statistical errors are given under the assumption of Gaussian signal spectra. It is shown that similar accuracies can be achieved for both configurations. Performance modeling of the retrieval of semitransparent cloud optical scattering properties and wind velocity was done at different operation wavelengths for a Nd:YAG laser source. Results for such a lidar system onboard an aircraft flying at an altitude of 12 km show that for semitransparent clouds the best results were obtained at 355 nm, with relative standard deviations of 0.5% and 5% for the backscatter and extinction coefficients, respectively, together with a velocity accuracy of 0.2 ms(-1). The accuracy of optical properties retrieved for boundary layer aerosols are comparable, whereas the velocity accuracy is decreased to 1 ms(-1). Finally, an extrapolation to a large 355-nm spaceborne lidar shows accuracies in the range from 2.5% to 5% for the backscatter coefficient and from 10% to 15% for the extinction coefficient together with a vertical wind speed accuracy of better than 0.5 ms(-1) for semitransparent clouds and boundary layer, with a vertical resolution of 500 m and a 100 shot averaging.

Journal Article↗
PubMed2001

Sensitization of dorsal horn neurons in a two-compartment cell culture model: wind-up and long-term potentiation-like responses.

One of the main characteristics of central sensitization associated with postinjury pain and chronic pain is increased excitability of the dorsal horn neurons in the spinal cord. Two electrophysiological features associated with the origin and modulation of central sensitization are wind-up of action potential frequency and long-term potentiation (LTP), which have been demonstrated previously in the intact dorsal horn. Here we present evidence for electrically evoked sensitization of dorsal horn neurons in a two-compartment cell culture system of rat dorsal root ganglia (DRGs) and dorsal horn neurons. Whole-cell recordings of dorsal horn neurons showed that repetitive low-frequency stimulation of DRG axons induced a frequency-dependent cumulative depolarization of the membrane potential with a concomitant increase in action potential frequency in a subset of neurons (41%). The characteristics presented here for dissociated cells are in accordance with those ascribed to classical wind-up in the intact dorsal horn. In addition, tetanic stimulation of DRG axons resulted in a significant increase in the number of action potentials in response to test stimuli in 42% of the cells tested. This prolonged potentiation of neuronal excitability in the dorsal horn lasted throughout the recording period (>1 hr) and tended to be voltage dependent in an LTP-like manner. To our knowledge, this is the first time that wind-up and LTP-like responses are reported for dorsal horn neurons in cell culture.

Action Potentials↗
PubMed2006

[Clinical observation on needle-sticking method for treatment of rheumatoid arthritis of wind-cold-damp retention type].

OBJECTIVE: To observe clinical therapeutic effect of needle-sticking method on rheumatoid arthritis (RA) of wind-cold-damp retention type. METHODS: Fifty cases of such disease were divided into 2 groups in order of visiting. The treatment group (n = 30) were treated with needle-sticking method, and the control group (n = 20) with routine filiform needle therapy for 2 therapeutic courses. Total cumulative scores, numbers of both the pressure-pain joint and the swollen-distention joint, erythrocyte sedimentation rate (ESR), rheumatoid factor (RF), C reaction protein (CRP) before and after treatment were investigated. RESULTS: Both the needle-sticking method and the filiform needle therapy had an apparent therapeutic effect on RA of wind-cold-damp retention type, and the therapeutic effect for the clinical indexes in the treatment group was better than the control group, with a very significant difference in improvement of RF, the number of pressure-pain joints and the total cumulative scores as the treatment group compared with the control group (P < 0.01). CONCLUSION: Needle-sticking method has definite therapeutic effect on RA of wind-cold-damp retention type with obvious superiority.

Acupuncture Points↗
PubMed2006

An observation on the acupuncture treatment of ischemic wind-stroke with different lengths of needle-retaining time.

OBJECTIVE: To observe the effects of different lengths of needle-retaining time on the therapeutic results of acupuncture treatment for ischemic wind-stroke. METHODS: According to the severity of disease, 251 cases of ischemic wind-stroke were randomly divided into 3 groups and treated by acupuncture, with the needle-retaining time lasting 20, 40, and 60 minutes respectively. Observation was mainly focused on the scores of nervous dysfunction and the clinical therapeutic results. RESULTS: The comparison of the scores of nervous dysfunction in the 3 groups before and after the treatment showed that under Wilcoxon's pair-match symbol rank test, except for horizontal gaze, other indexes all showed significant differences (P < 0.01). In the between-group comparison before and after the treatment, there showed significant or very significant differences in the indexes of myodynamia of the upper limb, myodynamia of hand and the total scores (P < 0.05, P < 0.01). In the between-group comparison by Mann-Whitney rank test of the indexes of myodynamia of upper limb, myodynamia of hand and the total scores, the 20-min. group and the 60-min. group showed significant differences (P < 0.05); and 40-min. group and 60-min. group showed significant differences in myodynamia of upper limb (P < 0.05). In comparison of the therapeutic effects of the 3 groups by Kruskal-wallis rank test, there showed very significant differences (P < 0.01). In the between-group comparison by Mann-Whitney rank test, the 40-min.group and 60-min. group showed significant differences (P = 0.013); while the 20-min. group and 60-min. group showed very significant differences (P = 0.000). CONCLUSION: There is a time-effect relationship between the length of needle-retaining time and the therapeutic effects of acupuncture for ischemic wind-stroke.

Acupuncture Therapy↗
PubMed1984

"Second wind" during inspiratory loading.

Five human volunteers breathed through an inspiratory register to achieve a transdiaphragmatic pressure (Pdi) of 42-45% of the maximum, until fatigue. During the period of resistive breathing all subjects experienced at least one episode of a sudden feeling of relaxation and relief from dyspnea, i.e., "second wind." These episodes were accompanied by a sudden decrease in the neural stimulation to the diaphragm as reflected in the electromyogram (EMG). Changes in lung volume or chest configuration were eliminated as was recruitment of accessory muscles of inspiration during the "second wind"; thus, there appeared to be a change in the contractile function of the diaphragm such that the same force (Pdi) was achieved with less neural input. These results indicate that the phenomenon of "second wind" has physiologic correlates and may be subject to experimental verification and manipulation.

Adult↗
PubMed2002

Directional sensitivity of wind-sensitive giant interneurons in the cave cricket Troglophilus neglectus.

Unlike the situation in most cockroach and cricket species studied so far, the wind-sensitive cerci of the cave cricket Troglophilus neglectus Krauss (Rhaphidophoridae, Orthoptera) are not oriented parallel to the body axis but perpendicular to it. The effects of this difference on the morphology, and directional sensitivity of cercal giant interneurons (GIs), were investigated. In order to test the hypothesis that the 90 degrees change in cercal orientation causes a corresponding shift in directional sensitivity of GIs, their responses in both the horizontal and vertical planes were tested. One ventral and four dorsal GIs (corresponding to GIs 9-1a and 9-2a, 9-3a, 10-2a, 10-3a of gryllid crickets) were identified. The ventral GI 9-1a of Troglophilus differed somewhat from its cricket homologue in its dendritic arborisation and its directional sensitivity in the horizontal plane. The morphology and horizontal directionality of the dorsal GIs closely resembled that of their counterparts in gryllids. In the vertical plane, the directionality of all GIs tested was similar. They were all excited mainly by wind puffs from the axon-ipsilateral quadrant. The results suggest that directional sensitivity to air currents in the horizontal plane is maintained despite the altered orientation of the cerci. This is presumably due to compensatory modifications in the directional pReferences of the filiform hairs.

Animals↗
PubMed2005

Succession after stand replacing disturbances by fire, wind throw, and insects in the dark Taiga of Central Siberia.

The dark taiga of Siberia is a boreal vegetation dominated by Picea obovata, Abies sibirica, and Pinus sibirica during the late succession. This paper investigates the population and age structure of 18 stands representing different stages after fire, wind throw, and insect damage. To our knowledge, this is the first time that the forest dynamics of the Siberian dark taiga is described quantitatively in terms of succession, and age after disturbance, stand density, and basal area. The basis for the curve-linear age/diameter relation of trees is being analyzed. (1) After a stand-replacing fire Betula dominates (4,000 trees) for about 70 years. Although tree density of Betula decreases rapidly, basal area (BA) reached >30 m2/ha after 40 years. (2) After fire, Abies, Picea, and Pinus establish at the same time as Betula, but grow slower, continue to gain height and eventually replace Betula. Abies has the highest seedling number (about 1,000 trees/ha) and the highest mortality. Picea establishes with 100-400 trees/ha, it has less mortality, but reached the highest age (>350 years, DBH 51 cm). Picea is the most important indicator for successional age after disturbance. Pinus sibirica is an accompanying species. The widely distributed "mixed boreal forest" is a stage about 120 years after fire reaching a BA of >40 m2/ha. (3) Wind throw and insect damage occur in old conifer stands. Betula does not establish. Abies initially dominates (2,000-6,000 trees/ha), but Picea becomes dominant after 150-200 years since Abies is shorter lived. (4) Without disturbance the forest develops into a pure coniferous canopy (BA 40-50 m2/ha) with a self-regenerating density of 1,000 coniferous canopy trees/ha. There is no collapse of old-growth stands. The dark taiga may serve as an example in which a limited set to tree species may gain dominance under certain disturbance conditions without ever getting monotypic.

Animals↗
PubMed2006

Mechanistic models for wind dispersal.

The growing need for ecological forecasts of, for example, species migration, has increased interest in developing mechanistic models for wind dispersal of seeds, pollen and spores. Analytical models are only able to predict mean dispersal distances, whereas sophisticated trajectory simulation models are able to incorporate rare wind conditions causing long-distance dispersal and are therefore preferable. Despite the rapid development of mechanistic dispersal models, only a few studies have focused on comparing the performance of the models. To assess the level of model complexity needed, attention should be paid to model comparisons and the sensitivity of the predictions to model complexity. In addition to studying the movement of airborne particles, future modelling work should also focus on the processes of particle release and deposition.

Models, Biological↗
PubMed1999

Dendritic Ca2+ transient increase evoked by wind stimulus in the cricket giant interneuron.

In vivo Ca2+ imaging was applied to the cricket median giant interneuron (MGI), to visualize the dendritic processing of mechanosensory signals. Wind stimulation (air-puff) to the cerci induced a transient increase in the cytosolic Ca2+ concentration ([Ca2+]i) in the MGI with a latency of a few seconds, suggesting the release of Ca2+ from the intracellular store site in the MGI. The amplitude of the transient increase in [Ca2+]i in the dendrites depended on the direction of the air-puff, and the increase in [Ca2+]i evoked by the air-puff was suppressed by the hyperpolarizing current injection which blocked the generation of action potentials. These results indicate that the action potential is necessary to the direction-sensitive increase in [Ca2+]i induced by wind stimulation.

Animals↗
PubMed1997

Thermoregulatory responses of the North American porcupine (Erethizon dorsatum bruneri) to decreasing ambient temperature and increasing wind speed.

Average resting metabolic rate of five adult male porcupines (Erethizon dorsatum bruneri) was 0.23 ml O2/g.h +/- 0.007 SEM, between 10 degrees C (Tlc) and 25 degrees C, which is 70% of the value predicted by body mass. A Tb of 37.1 degrees C +/- 0.1 SEM was maintained between -10 degrees C and 25 degrees C. Calculated thermal conductance (between 6 degrees C and -10 degrees C) was 87% of the predicted value. There was no significant change in mean metabolic rate as a function of wind (up 4.3 m/s) at ambient temperatures (1 degree C and -5 degrees C) below their Tlc. Under these same ambient conditions, with and without wind, the skin surface and subcutaneous areas of the porcupine's rosette region exhibited marked temperature lability.

Animals↗
PubMed1990

Trajectory analysis of winds and vesicular stomatitis in North America, 1982-5.

Outbreaks of vesicular stomatitis, serotype New Jersey, during epidemics in the United States and northern Mexico, 1982-5, were examined by backward trajectories of winds to investigate spread and possible sources. The outbreaks selected for analysis did not involve introduction of disease by infected animals. The findings indicate that wind could have been responsible for carrying infection from northern Mexico to Arizona and New Mexico and thence to Colorado and Utah and on to Wyoming, Idaho and Montana. The results of these analyses are consistent with the findings from T1 RNAse fingerprinting of virus isolates from outbreaks during the epidemics. The arrival of the trajectories was associated with the passage of a front and rain or passage of a front alone or rain alone. At the time of the trajectories temperatures of 10 degrees C and higher were recorded at heights up to 2500-3500 m. Introduction by airborne particles would appear unlikely as it would have required a source of at least 10(5) infectious units per minute per animal. Vesicular stomatitis virus had been isolated from Simulium and Culicoides during the epidemic with amounts of virus from Simulium sufficient to suggest biological transmission. The possibility of Simulium infected with vesicular stomatitis virus being carried downwind to introduce disease is discussed in relation to the behaviour of Simulium and the pathogenesis of vesicular stomatitis in large animals.

Air Movements↗
PubMed2005

Emissions and energy efficiency assessment of baseload wind energy systems.

The combination of wind energy generation and energy storage can produce a source of electricity that is functionally equivalent to a baseload coal or nuclear power plant. A model was developed to assess the technical and environmental performance of baseload wind energy systems using compressed air energy storage. The analysis examined several systems that could be operated in the midwestern United States under a variety of operating conditions. The systems can produce substantially more energy than is required from fossil or other primary sources to construct and operate them. By operation at a capacity factor of 80%, each evaluated system achieves an effective primary energy efficiency of at least five times greater than the most efficient fossil combustion technology, with greenhouse gas emission rates less than 20% of the least emitting fossil technology currently available. Life-cycle emission rates of NOx and SO2 are also significantly lower than fossil-based systems.

Air Pollution↗