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- Akselsson, Roland, et al.
(författare)
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Application of Proton Induced X-Ray Emission Analysis to the St. Louis Regional Air Pollution Study
- 1975
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Ingår i: Advances in X-Ray Analysis. ; 18, s. 588-597
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Tidskriftsartikel (refereegranskat)abstract
- The St Louis aerosol was sampled during the period 16-22 August 1973 simultaneously at two locations using cascade impactors for sequential 12-hour samples. The six particle size fractions of each sampling were individually analyzed using PIXE for elements from S to Br and beyond and for heavy elements including Pb which permitted time variations of concentrations and particle size distributions to be followed and related to meteorological changes during the sampling period. In addition, the data were compared with average levels of the elements in coastal north Florida and maritime Bermuda as well as at a third St. Louis site. From this it appeared that some of the concentrations in St. Louis were at natural levels whereas others appeared to be higher and linked to air pollution sources. These relationships and others in this study may lead to criteria for distinguishing between pollutants and natural background in urban aerosols.
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| 3. |
- Fetz, E. E., et al.
(författare)
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Autogenetic inhibition of motoneurones by impulses in group Ia muscle spindle afferents.
- 1979
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Ingår i: The Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 293, s. 173-195
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Tidskriftsartikel (refereegranskat)abstract
- 1. Inhibitory post‐synaptic potentials evoked by adequate stimulation of group Ia muscle spindle afferents of homonymous and synergistic muscles and by selective electrical stimulation of tendon organ afferents were analysed in motoneurones of triceps surae and plantaris. 2. Selective activation of Ia afferents was verified to occur with brief stretches of triceps surae and plantaris 35 micrometer or less in amplitude with an initial muscle tension of 5 N; stretches of 30‐‐35 micrometer were estimated to activate 80‐‐90% of Ia afferents in these muscles. Under the same conditions the lowest thresholds for group Ib tendon organ afferents were about 40 micrometer. 3. Stretches less than or equal to 30 micrometer evoked i.p.s.p.s in 80% of triceps surae and plantaris motoneurones; lowest thresholds for evoking i.p.s.p.s wef triceps surae and plantaris motoneurones; lowest thresholds for evoking i.p.s.p.s were 10 micrometer or less. However, such low thresholds for stretch‐evoked i.p.s.p.s, lower than the thresholds for activation of Ib afferents, were found mainly in spinalized, unanaesthetized (after decerebration) or lightly anaesthetized animals. The latencies of these i.p.s.p.s indicated disynaptic and trisynaptic coupling between Ia afferents and motoneurones. The i.p.s.p.s were evoked (i) from the homonymous and synergistic muscles stretched together, (ii) from the homonymous muscles alone and (iii) from the synergistic muscles alone. 4. Control experiments showed that i.p.s.p.s could be evoked by stretches sub‐threshold for discharging motoneurones, thus showing that those i.p.s.p.s were not mediated by Renshaw cells. The stretch‐evoked i.p.s.p.s disappeared after sectioning the nerves from the corresponding muscles, further excluding their mediation by afferents other than group Ia afferents from thf stretched muscle. 5. In order to selectively activate tendon organ afferents, thresholds for excitation of Ia afferents by electrical stimuli were increased to a level above the threshold for Ib afferents by prolonged muscle vibration (Coppin, Jack & MacLennan, 1970). I.p.s.p.s evoked by stimuli near threshold for Ib afferents appeared with latencies indicating disynaptic coupling. Later (trisynaptic) components of Ib i.p.s.p.s required somewhat stronger stimuli. 6. Amplitudes of Ia i.p.s.p.s evoked by muscle stretches activating about 80% of muscle spindle afferents were compared with amplitudes of Ib i.p.s.p.s due to less than 50% of tendon organ afferents of the same muscles. The Ia i.p.s.p.s were much smaller (16‐‐35%) than the Ib i.p.s.p.s. The amplitudes of such Ia and Ib i.p.s.p.s constituted about 10 and 25‐‐66%, respectively, of the maximal i.p.s.p.s evoked by electrical stimulation of all group I afferents. 7. We conclude that inhibition of motoneurones may be evoked from Ia muscle spindle afferents from homonymous and synergistic muscles as well as from Ib tendon organ afferents... © 1979 The Physiological Society
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| 4. |
- Hermansson, Kersti, et al.
(författare)
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Hydrogen bond studies. CXX. An X-ray determination of the crystal structure of LiNO 3.3H 2O
- 1977
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Ingår i: Acta Crystallogr. B, Struct. Crystallogr. Cryst. Chem. (Denmark). - 0567-7408. ; B33, s. 2857-2861
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Tidskriftsartikel (refereegranskat)abstract
- For pt.CXIX see Z. Naturforsch. a, vol.32, p.134 (1977). The crystal structure of lithium nitrate trihydrate, LiNO 3.3H 2O, has been determined by X-ray diffraction at 295K. The crystal is orthorhombic, space group Cmcm, a=6.8018 (4), b=12.7132 (9), c=5.9990 (4) Aring, V=518.75 Aring 3, Z=4. The nitrate ions, Li + ions and one of the two crystallographically non-equivalent water molecules lie in a mirror plane and are bonded to atoms in adjacent planes through the second water molecule. The Li + ion is octahedrally surrounded by six O atoms, four belonging to water molecules and two to nitrate ions. The two non-equivalent water molecules are present in the structure in distinctly different bonding situations. One is bonded to two Li + ions and is the donor of two hydrogen bonds. The other is involved in six hydrogen bonds: the O atom accepts two hydrogen bonds, and both protons are involved in bifurcated hydrogen bonds.
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| 7. |
- Van Grieken, René E., et al.
(författare)
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Geophysical Applicability of Aerosol Size Distribution Measurements Using Cascade Impactors and Proton Induced X-Ray Emission
- 1976
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 0004-6981. ; 10:8, s. 571-576
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Tidskriftsartikel (refereegranskat)abstract
- Proton Induced X-ray Emission, (PIXE), is capable of high precision analysis for trace element components of aerosol particle size fractions sampled by cascade impactor. A statistical evaluation of data quality has been carried out in order to distinguish between analytical uncertainties in the PIXE procedure, errors caused by cascade impactor performance and by other factors in the sampling procedure, and geophysical causes of differences in composition and particle size distributions of the elements in aerosols. Replicate analyses and simultaneous samplings taken in north Florida and St. Louis have been used for the data evaluation. In addition to the analytical error the sampling procedure contributes an error of ~ 10% to be added quadratically. The resulting precision is sufficient to evaluate the data in geophysical terms. This is illustrated by means of sample sets taken simultaneously in an urban, forest and coastal environment of the same region.
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