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- Berntsson, Thore, 1947, et al.
(författare)
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Research activities on heat transformers at Chalmers University of Technology
- 1988
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Ingår i: Commission of the European Communities, Absorption heat pumps, Proceedings of a workshop held in London 12 - 14 April 1988.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Ongoing and planned research work in the absorption field at Chalmers University of Technology can be divided into four areas:- System studies and optimization;A computer program has been developed with which a heat transformer can be simulated and its parts can be technically and/or economically optimized. Technical optimizations include optimal area distribution between the five heat exchangers to achieve a certain COP or a certain temperature lift and minimum total area needed for a certain heat output. Economic optimizations include optimal size of the heat transformer and its components at various conditions.- Desorption heat transfer; An experimental plant for studies of heat transfer coefficients of LiBr-H20 in a falling-film type desorber has been constructed. No results are yet available. -An activity-coefficient model for electrolyte systems; An activity-coefficient has been proposed to represent the properties over a wide electrolyte concentration range, i.e. high dilution to the solubility limit. It is well suited both for single-electrolyte and multi-electrolyte solutions.-Transport properties for electrolyte systems;The aim with this project is to develop methods and equations for correlation and prediction of transport properties, mainly viscosity, for single- and multicomponent electrolyte systems. An equation for correlation of viscosity data has been proposed and an equation for prediction of the viscosity based on activity coefficients is under development.
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| 2. |
- Hsueh, A J, et al.
(författare)
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Gonadotropin-releasing hormone induces ovulation in hypophysectomized rats : studies on ovarian tissue-type plasminogen activator activity, messenger ribonucleic acid content, and cellular localization.
- 1988
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Ingår i: Endocrinology. - 0013-7227 .- 1945-7170. ; 122:4, s. 1486-95
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Tidskriftsartikel (refereegranskat)abstract
- GnRH and its agonists are known to induce ovulation in hypophysectomized rats by acting directly at the ovary. Because tissue-type plasminogen activator (tPA) has been implicated in the gonadotropin induction of ovulation, we examined the effect of an ovulatory dose of GnRH on ovarian tPA activity, mRNA content, and cellular localization. Hypophysectomized immature rats were injected sc with 20 IU PMSG and a single dose of a GnRH agonist (GnRHa; des-Gly10,DLeu6(N alpha Me)Leu7,Pro9NHEt-GnRH) 58 h later. At different times after treatment, ovaries were prepared for morphological analysis. Using a fibrin overlay method, tPA activities were measured in ovarian homogenates and cumulus-oocyte complexes, whereas granulosa cells were cultured for 24 h to estimate tPA secretion. Total ovarian RNA was prepared for hybridization analysis of tPA message levels, and tPA localization was studied by immunohistochemistry of ovarian sections. GnRHa induced ovulation in PMSG-primed hypophysectomized rats 14-16 h after injection in a dose-dependent manner, and the GnRHa action was blocked by concomitant treatment with a GnRH antagonist. GnRHa stimulated the induction of tPA, but not urokinase-type PA, activity in ovarian homogenates and granulosa cell-conditioned medium in a time-dependent manner, reaching a maximum before ovulation. tPA activity in cumulus-oocyte complexes was also increased before ovulation, but this increase was sustained. Hybridization analysis of steady state tPA mRNA levels was performed using a rat cRNA probe. Northern blot analysis of total ovarian RNA demonstrated that GnRHa stimulated tPA mRNA levels 12 h after treatment, with a subsequent decrease 24 h after treatment. Immunohistochemistry indicated substantial increases in tPA staining in granulosa cells and oocytes of preovulatory follicles before ovulation. Thus, GnRHa acts through specific receptors to increase ovarian tPA enzyme activity, mRNA content, as well as immunostaining in granulosa cells and oocytes. Like gonadotropins, GnRH may induce ovulation by directly stimulating tPA levels in the ovary.
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| 5. |
- Liu, Tong
(författare)
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Fuktdiffusion i träbaserade skivor några data
- 1989
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Diffusiviteten för några olika träbaserade skivor har uppmätts med den s k sorptionsmetoden. Resultaten jämförs med litteraturdata och visar god överensstämmelse. Sorptionsmetoden kan därför vara ett alternativ till den vanligare s k koppmetoden.
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| 6. |
- Liu, Tong
(författare)
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Moisture transport in wood and wood-based panels
- 1988
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Rapporten presenterar en matematisk modell för fuktdiffusion i barrved, baserad på tidigare arbeten om olika diffusionsprocesser i kombination med kunskap om den mikroskopiska cellstrukturen hos barrved. Rapporten är på engelska med svensk sammanfattning och utgiven i samarbete med KTHs institution för byggmateriallära.
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| 7. |
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| 8. |
- Liu, Tong
(författare)
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Moisture transport in wood and wood-based panels a pre-study of sorption methods
- 1987
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- För att kunna beräkna fukttillstånd i byggnader behövs materialdata. Genom Träteks grundliga studie av fuktvandring i trä och träbaserade skivor vet vi nu mer. Fukt vandrar i trä och träbaserade material genom diffusion och massflöde (permeabilitet). Diffusiviteten av fukt kan bestämmas genom s k sorptionsmätningar. Denna förstudie konkretiserar och preciserar det praktiska tillvägagångssättet vid sorptionsmätningar. Diffusiviteten för några träbaserade skivor har bestämts, både vinkelrätt mot skivans plan och parallellt, i ett fåtal klimat. Skivdensiteten är den parameter som verkar ha störst betydelse. Resultaten visar att sorptionsmetoden kan användas för att bestämma diffusiviteten som funktion av materialets fuktkvot (eller av luftfuktigheten vid jämvikt). Rapporten är på engelska.
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| 10. |
- Liu, Yunda, et al.
(författare)
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A systematic comparison of nine models formed by various combinations of three Debye-Hückel expressions and three local-composition expressions for representation of nonideality in electrolyte solutions
- 1989
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Ingår i: Fluid Phase Equilibria. - : Elsevier BV. - 0378-3812. ; 53:December 1989, s. 269-277
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Tidskriftsartikel (refereegranskat)abstract
- The thermodynamic properties of electrolyte solutions are considered to be the sum of two contributions, one long-range and one short-range. Three Debye-Hückel expressions (Fowler and Guggenheim, 1949; Pitzer, 1973; Liu, Harvey and Prausnitz, 1989) have been applied to account for long-range contributions, and three local-composition expressions (NRTL type; Wilson type; Modified Wilson type) have been applied to account for short-range contributions. The nine models formed by various combinations of the three Debye-Hückel expressions and the three local-composition expressions have been systematically compared based on the same data and the same regression program. The Debye-Hückel expressions of Fowler-Guggenheim and Pitzer affect the results identically. The Debye-Hückel expression of Liu et al. can greatly improve the results. When using the Debye-Hückel expression of Liu et al., the deviations are generally less than one-tenth of those when using two other Debye-Hückel expressions. The local-composition expressions of NRTL type and Wilson type give qualitatively identical effects on deviation. The results when using the local-composition expression of the modified Wilson type, due to its more adjustable parameters, are better than those when using the other two local-composition expressions.
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