| 1. |
- Crenshaw, D. M., et al.
(författare)
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Multiwavelength observations of short-timescale variability in NGC 4151. I. Ultraviolet observations
- 1996
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 470:1, s. 322-335335
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Tidskriftsartikel (refereegranskat)abstract
- Presents the results of an intensive ultraviolet monitoring campaign on the Seyfert 1 galaxy NGC 4151, as part of an effort to study its short-timescale variability over a broad range in wavelength. The nucleus of NGC 4151 was observed continuously with the International Ultraviolet Explorer for 9.3 days, yielding a pair of LWP and SWP spectra every ~70 minutes, and during 4 hr periods for 4 days prior to and 5 days after the continuous-monitoring period. The sampling frequency of the observations is an order of magnitude higher than that of any previous UV monitoring campaign on a Seyfert galaxy. The continuum fluxes in bands from 1275 to 2688 Aring went through four significant and well-defined ldquoeventsrdquo of duration 2-3 days during the continuous-monitoring period. The authors find that the amplitudes of the continuum variations decrease with increasing wavelength, which extends a general trend for this and other Seyfert galaxies to smaller timescales (i.e., a few days). The continuum variations in all the UV bands are simultaneous to within an accuracy of ~0.15 days, providing a strict constraint on continuum models. The emission-line light curves show only one major event during the continuous monitoring (a slow rise followed by a shallow dip) and do not correlate well with continuum light curves over the short duration of the campaign, because the timescale for continuum variations is apparently smaller than the response times of the emission lines
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| 2. |
- Edelson, R. A., et al.
(författare)
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Multiwavelength observations of short-timescale variability in NGC 4151. IV. Analysis of multiwavelength continuum variability
- 1996
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 470:1, s. 364-377377
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Tidskriftsartikel (refereegranskat)abstract
- For pt.III see ibid., vol.470, no.1, p.349-63 (1996). Combines data from the three preceding papers in order to analyze the multi wave-band variability and spectral energy distribution of the Seyfert 1 galaxy NGC 4151 during the 1993 December monitoring campaign. The source, which was near its peak historical brightness, showed strong, correlated variability at X-ray, ultraviolet, and optical wavelengths. The strongest variations were seen in medium-energy (~1.5 keV) X-rays, with a normalized variability amplitude (NVA) of 24%. Weaker (NVA=6%) variations (uncorrelated with those at lower energies) were seen at soft gamma-ray energies of ~100 keV. No significant variability was seen in softer (0.1-1 keV) X-ray bands. In the ultraviolet/optical regime, the NVA decreased from 9% to 1% as the wavelength increased from 1275 to 6900 Aring. These data do not probe extreme ultraviolet (1200 Aring to 0.1 keV) or hard X-ray (250 keV) variability. The phase differences between variations in different bands were consistent with zero lag, with upper limits of lsim0.15 day between 1275 Aring and the other ultraviolet bands, lsim0.3 day between 1275 Aring and 1.5 keV, and lsim1 day between 1275 and 5125 Aring. These tight limits represent more than an order of magnitude improvement over those determined in previous multi-wave-band AGN monitoring campaigns. The ultraviolet fluctuation power spectra showed no evidence for periodicity, but were instead well fitted with a very steep, red power law (ales-2.5)
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| 3. |
- Hansson, Lars, et al.
(författare)
-
Eye and Body Movements Characterized by Synchronized Sampling
- 1998
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An example of a result from a long-term cooperation with Lund University (together with professor Roland Akselsson at the Department of Ergonomics and Aerosol Technology) there some of the authors. (Engström) gained extensive grants (EU-financing and Wallenberg Stifelsen regarding equipment as well as other founding from e.g. the Swedish Work Environment Found). This publication was a result of the just mentioned EU-financing.
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| 4. |
- Hansson, Lars, et al.
(författare)
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Mannequin Properties Desired for Ergonomic Evaluation of Car Interiors
- 1998
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An example of a result from a long-term cooperation with Lund University (together with professor Roland Akselsson at the Department of Ergonomics and Aerosol Technology) there some of the authors. (Engström) gained extensive grants (EU-financing and Wallenberg Stifelsen regarding equipment as well as other founding from e.g. the Swedish Work Environment Found). This publication has emanated from an EU-financed research project.
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| 5. |
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| 6. |
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| 7. |
- Bohgard, Mats, et al.
(författare)
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Air Pollutants
- 1997
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Ingår i: The Workplace. - 8291833001 ; 1, s. 433-457
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Abstract in UndeterminedPollutants in the air can be in gaseous and particle (solid and liquid) phases. Interactions between these phases occur. The components are emitted to the air by different source mechanisms such as evaporation, disintegration of bulk material and chemical reactions. The significance of different transport mechanisms is, for airborne particles, dependent on the aerodynamic properties. Water solubility (for gases) and the aerodynamic properties (for particles) determine the site of deposition in the human airways. In work environments species with different physical, chemical and biological features can be abundant. A variety of methods are used to identify and quantify the pollutants. Remedial actions against health hazards include the substitution of materials and processes; preventing the airborne constituents reaching the environment (enclosures, hoods); local ventilation; general ventilation and respiratory protection.
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| 8. |
- Hansson, Lars, et al.
(författare)
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Annie, a Tool for Integrating Ergonomics in the Design of Car Interiors
- 1999
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An example of a result from a long-term cooperation with Lund University (together with professor Roland Axelsson at the Department for Work Environment) there some of the authors. (Engström) gained extensive grants (Wallenberg Stifelsen regarding equipment as well as other founding from e.g. the Swedish Work Environment Found).
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| 9. |
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| 10. |
- Macefield, Vaughan G, et al.
(författare)
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Control of grip force during restraint of an object held between finger and thumb : responses of cutaneous afferents from the digits
- 1996
-
Ingår i: Experimental Brain Research. - 0014-4819 .- 1432-1106. ; 108:1, s. 155-171
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Tidskriftsartikel (refereegranskat)abstract
- Unexpected pulling and pushing loads exerted by an object held with a precision grip evoke automatic and graded increases in the grip force (normal to the grip surfaces) that prevent escape of the object; unloading elicits a decrease in grip force. Anesthesia of the digital nerves has shown that these grip reactions depend on sensory signals from the digits. In the present study we assessed the capacity of tactile afferents from the digits to trigger and scale the evoked grip responses. Using tungsten microelectrodes inserted percutaneously into the median nerve of awake human subjects, unitary recordings were made from ten FA I and 13 FA II rapidly adapting afferents, and 12 SA I and 18 SA II slowly adapting afferents. While the subject held a manipulandum between a finger and the thumb, tangential load forces were applied to the receptor-bearing digit (index, middle, or ring finger or thumb) as trapezoidal load-force profiles with a plateau amplitude of 0.5-2.0 N and rates of loading and unloading at 2-8 N/s, or as "step-loads" of 0.5 N delivered at 32 N/s. Such load trials were delivered in both the distal (pulling) and proximal (pushing) direction. FA I afferents responded consistently to the load forces, being recruited during the loading and unloading phases. During the loading ramp the ensemble discharge of the FA I afferents reflected the first time-derivative of the load force (i.e., the load-force rate). These afferents were relatively insensitive to the subject's grip force responses. However, high static finger forces appeared to suppress excitation of these afferents during the unloading phase. The FA II afferents were largely insensitive to the load trials: only with the step-loads did some afferents respond. Both classes of SA afferents were sensitive to load force and grip force, and discharge rates were graded by the rate of loading. The firing of the SA I afferents appeared to be relatively more influenced by the subject's grip-force response than the discharge of the SA II afferents, which were more influenced by the load-force stimulus. The direction in which the tangential load force was applied to the skin influenced the firing of most afferents and in particular the SA II afferents. Individual afferents within each class (except for the FA IIs) responded to the loading ramp before the onset of the subject's grip response and may thus be responsible for initiating the automatic increase in grip force. However, nearly half of the FA I afferents recruited by the load trials responded to the loading phase early enough to trigger the subject's grip-force response, whereas only ca. one-fifth of the SA Is and SA IIs did so. These observations, together with the high density of FA I receptors in the digits, might place the FA I afferents in a unique position to convey the information required to initiate and scale the reactive grip-force responses to the imposed load forces.
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