| 231. |
- Osadchii, E, et al.
(författare)
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Thermodynamic properties of dyscrasite (Ag3Sb) at isostatic pressures 4000-8000 bar
- 1998
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Ingår i: Physics and chemistry of minerals. - 0342-1791 .- 1432-2021. ; 25:4, s. 288-291
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Tidskriftsartikel (refereegranskat)abstract
- The objective of the present study was to demonstrate the possibility of application of high-pressure equipment in combination with the solid state EMF technique. The equilibrium reaction 3 Ag+Sb double left right arrow Ag3Sb was chosen for the studies. The experiments were carried out under argon gas pressure and the majority of data points were measured in the pressure range 4000-8000 bar at temperatures 550-725 K. The solid electrolyte consisted of AgI. Reproducible results were obtained along seven isotherms and one isobar at 7100 bar. The molar volume change for the reaction studied was calculated and compared with corresponding literature data at one bar.
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| 232. |
- Oscarson, Nils, et al.
(författare)
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Methods of evaluating dental care costs in the Swedish public dental health care sector
- 1998
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Ingår i: Community Dentistry and Oral Epidemiology. - : Wiley. - 0301-5661 .- 1600-0528. ; 26:3, s. 160-165
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Tidskriftsartikel (refereegranskat)abstract
- Twenty-six Swedish dental health care clinics participating in the intervention study "Evaluation of caries preventive measures" have been analysed with focus on costs, with the aim of demonstrating techniques suitable for evaluating direct dental care costs and also finding out whether charges are acceptable as a proxy for real costs. Three different approaches to calculating unit costs are discussed: average treatment time cost and two methods of different allocation of overhead cost. Average treatment time cost shows treatment time cost regardless of who (dentist, dental hygienist or nurse) provides the dental care. The other two methods reflect both the differences of treatment costs depending on practitioners' skill level and competence (salary) and the methods of handling overhead cost allocation. Our conclusions are that the proposed methods seem useful for evaluating costs in cost-effectiveness and cost-benefit analysis. The alternative to average treatment time cost or unit time cost depends on what data is available and the perspective of the analysis. This study also concludes that charges are not sufficient as an alternative to a more detailed cost evaluation, at least not in Swedish public dental health care, since charges do not cover costs.
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| 233. |
- Ozana, Marek, et al.
(författare)
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Squeezed states of a particle in magnetic field
- 1998
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Ingår i: Physics of the solid state. - : Pleiades Publishing Ltd. - 1063-7834 .- 1090-6460. ; 40:8, s. 1276-1282
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Tidskriftsartikel (refereegranskat)abstract
- For a charged particle in a homogeneous magnetic field, we construct stationary squeezed states which are eigenfunctions of the Hamiltonian and the non-Hermitian operator (X) over cap(Phi) = (X) over cap cos Phi + (Y) over cap sin Phi, (X) over cap and (Y) over cap being the coordinates of the Larmor circle center and Phi is a complex parameter. In the family of the squeezed states, the quantum uncertainty in the Larmor circle position is minimal. The wave functions of the squeezed states in the coordinate representation are found and their properties are discussed. Besides, for arbitrary gauge of the vector potential we derive the symmetry operators of translations and rotations.
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| 234. |
- Peagler, FD, et al.
(författare)
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Enzyme histochemical and immunohistochemical localization of carbonic anhydrase as a marker of ductal differentiation in the developing rat parotid gland.
- 1998
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Ingår i: Anatomical Record. - 0003-276X .- 1097-0185. ; 250:2, s. 190-8
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Carbonic anhydrase has been localized to the acini and ducts of mature rat parotid glands. This enzyme has been associated with ion transport, a prominent function of striated and excretory ducts in salivary glands, suggesting that it might be used as a marker of ductal differentiation. The purpose of this study was histochemically to document developmental changes in carbonic anhydrase in the ducts of the rat parotid gland. METHODS: Parotid glands were excised from rats at representative developmental ages. Enzyme histochemistry was done on frozen sections fixed in acetone, and immunohistochemistry was performed with antibodies to human carbonic anhydrase isoenzymes I, II, and VI on paraffin sections of glands fixed in Helly's fluid. RESULTS: Carbonic anhydrase activity was weak until age 21 days after birth, when it had increased slightly in the acini and intercalated ducts and moderately in striated and excretory ducts. The adult pattern was attained by 28 days, in which reactions were moderate to strong in the striated and excretory ducts and modest in the acini and intercalated ducts. Immunohistochemical reactions were weak until 14 days, then increased rapidly, and by 28 days approached the adult pattern of virtually none in the acini and modest to moderately strong in the striated and excretory ducts. The order of reaction intensity of the antibodies was II > I > VI. CONCLUSIONS: Carbonic anhydrase is a useful marker of the functional differentiation of the striated and excretory ducts of the developing rat parotid gland.
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| 235. |
- Pervozvanski, Anatoly A., et al.
(författare)
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On the astatism of nonlinear systems
- 1998
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Ingår i: Avtomatika i Telemekhanika. - : Plenum Publishing Corporation. ; 59:7, s. 35-43
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Tidskriftsartikel (refereegranskat)abstract
- Astatism, a traditional concept in linear theory, is extended to nonlinear systems. Astatism conditions are stated. The response of an astatic nonlinear system do varying perturbations increasing with a bounded rate is studied. The error in tracking a desirable varying stale is estimated. How integral feedback ensures astatism is examined. This result is applied to control Lagrange systems.
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| 236. |
- Pinto do Ó, Perpétua, et al.
(författare)
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Expression of the LIM-homeobox gene LH2 generates immortalized Steel factor-dependent multipotent hematopoietic precursors
- 1998
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Ingår i: EMBO Journal. - : Oxford University Press. - 0261-4189 .- 1460-2075. ; 17:19, s. 5744-5756
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Tidskriftsartikel (refereegranskat)abstract
- The genes controlling self-renewal and differentiation in the hematopoietic system are largely unknown. The LIM-homeobox genes are known to be important for asymmetric cell divisions and differentiation of specific cell types and organs. One member of this family, LH2, is expressed in fetal liver at the time of active hematopoiesis. Therefore, we have assessed the function of LH2 during the formation and initial expansion of the hematopoietic system by differentiating LH2-transduced embryonic stem (ES) cells in vitro. This procedure generated multipotent hematopoietic precursor cell (HPC) lines that required Steel factor for growth. HPC lines have been maintained in an undifferentiated state in culture for >7 months. Other growth factors tested efficiently induce terminal differentiation of HPCs into various mature myeloid lineages. Steel factor is also required and acts synergistically with the other growth factors to generate multilineage colonies from the HPCs. These HPC lines express transcription factors that are consistent with an immature progenitor, and the pattern of cell surface marker expression is similar to that of early fetal multipotent hematopoietic progenitors. Collectively, these data suggest that the HPC lines represent an early fetal multipotent hematopoietic progenitor, and suggest a role for LH2 in the control of cell fate decision and/or proliferation in the hematopoietic system.
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| 237. |
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| 238. |
- Porankiewicz, J, et al.
(författare)
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Membrane lipid composition and restoration of photosynthesis during low temperature acclimation in Synechococcus sp. strain PCC 7942
- 1998
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Ingår i: Physiologia Plantarum. - 0031-9317 .- 1399-3054. ; 104:3, s. 405-412
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Tidskriftsartikel (refereegranskat)abstract
- We compared temperature acclimation of the cyanobacterium Synechococcus sp. strain PCC 7942 and two psbA inactivation mutants, R2K1 and R2S2C3, following shifts from 37 to 25 degrees C. Wild-type cultures incubated in the dark at 25 degrees C showed no chill-induction of lipid desaturation, probably because the lipid acclimation is dependent on photosynthesis. Incubation in the light at 25 degrees C, however, induced considerable increases in membrane lipid desaturation, and within 24 h the monoenoic fatty acids increased from about 46 to about 57%. In parallel with this desaturation the ratio of monogalactosyldiacylglycerol to digalactosyldiacylglycerol (MGDG/DGDG) increased. Both of these lipid changes increase the repulsive forces of the hydrophobic chains of the membrane lipids and thereby alter the physical properties of the membrane. As expected, under irradiation this temperature shift also induced a reversible replacement of the constitutive photosystem II protein, D1:1, with an alternative stress form, D1:2. Photosynthesis decreased to 42% of the control level within the initial 2 h of cold incubation. but later recovered. The D1:2 protein accumulated to high levels between 2 and 4 h after the temperature shift, when desaturation of membrane lipids and MGDG/DGDG ratio had not yet increased significantly. Much of this accumulated D1:2 protein was in a higher molecular mass form, termed D1:2*, which is probably an unprocessed precursor form of the protein. In contrast to the wild-type cells the psbA inactivation mutants, R2K1 and R2S2C3 did not accumulate any precursor form of D1 protein either at the optimal or low growth temperature. The R2S2C3 mutant strain expresses only the constitutive D1:1 protein and suffered severe photoinhibition following the temperature shift. Nevertheless; R2S2C3 eventually recovered some photosynthetic activity, induced lipid desaturation and slowly resumed growth ar 25 degrees C, thus demonstrating acclimation to the lower growth temperature. The R2K1 mutant synthesizes only the D1:2 stress form of D1 protein and maintained oxygen evolution at a high level (ca 70% of a control rate) after the low temperature shift. Chill-induced lipid desaturation and increase in MGDG/DGDG ratio did proceed but, for unknown reasons the strain did nor resume growth at the lower temperature. The physical properties of the membrane lipids were not the limiting factor for growth resumption. Our results demonstrate that in the wild-type the chill-induced desaturation of membrane lipids follows after the exchange of the two forms of the D1 proteins, but the D1 exchange results in accumulation of unprocessed D1:2* polypeptides until the lipid composition later acclimates. We also show that the lipid desaturation process in Synechococcus sp. strain PCC 7942 is dependent upon photosynthetic activity.
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| 239. |
- Puu, Tönu, 1936-
(författare)
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The chaotic duopolists revisited
- 1998
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Ingår i: Journal of Economic Behavior and Organization. - 0167-2681 .- 1879-1751. ; 33:3-4, s. 385-394
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The adjustment process of three oligopolists is studied, under Cournot and Stackelberg action. It is demonstrated that with an iso-elastic demand function and constant marginal costs, the system can result in periodic or in chaotic behaviour. In particular, the case with two identical and one different oligopolists is focused, which turns into a virtual duopoly, though displaying a wider set of bifurcations than can occur in genuine duopoly.
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| 240. |
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