| 4971. |
- Yan, Yubin, 1965
(författare)
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Semidiscrete Galerkin approximation for a linear stochastic parabolic partial differential equation driven by an additive noise
- 2004
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Ingår i: BIT. - 0006-3835 .- 1572-9125. ; 44:4, s. 829-847
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Tidskriftsartikel (refereegranskat)abstract
- Abstract We study the semidiscrete Galerkin approximation of a stochastic parabolic partial differential equation forced by an additive space-time noise. The discretization in space is done by a piecewise linear finite element method. The space-time noise is approximated by using the generalized L2 projection operator. Optimal strong convergence error estimates in the L2 and norms with respect to the spatial variable are obtained. The proof is based on appropriate nonsmooth data error estimates for the corresponding deterministic parabolic problem. The error estimates are applicable in the multi-dimensional case.
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| 4972. |
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| 4973. |
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| 4974. |
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| 4975. |
- Yang, Xiao Lin, 1955, et al.
(författare)
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Evidence of impaired adipogenesis in insulin resistance
- 2004
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Ingår i: Biochem Biophys Res Commun. - : Elsevier BV. - 0006-291X. ; 317:4, s. 1045-51
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Tidskriftsartikel (refereegranskat)abstract
- To elucidate the roles of adipose tissue and skeletal muscle in the early development of insulin resistance, we characterized gene expression profiles of isolated adipose cells and skeletal muscle of non-diabetic insulin-resistant first-degree relatives of type 2 diabetic patients using oligonucleotide microarrays. About 600 genes and expressed sequence tags, which displayed a gene expression pattern of cell proliferation, were differentially expressed in the adipose cells. The differentially expressed genes in the skeletal muscle were mostly related to the cellular signal transduction and transcriptional regulation. To verify the microarray findings, we studied expression of genes participating in adipogenesis. The expression of Wnt signaling genes, WNT1, FZD1, DVL1, GSK3beta, beta-catenin, and TCF1, and adipogenic transcription factors, C/EBPalpha and beta and delta, PPARgamma, and SREBP-1, was reduced in the adipose tissue. The expression of adipose-specific proteins related to terminal differentiation, such as adiponectin and aP2, was reduced both in the adipose tissue and in the adipose cells isolated from portions of the biopsies. The adipose cells were enlarged in the insulin-resistant relatives and the cell size inversely correlated with the expression of the Wnt signaling genes, adiponectin, and aP2. Our findings suggest that insulin resistance is associated with an impaired adipogenesis.
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| 4976. |
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| 4977. |
- Yao, Yiming, 1957, et al.
(författare)
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Synthesis of carbon nanotube films by thermal CVD in the presence of supported catalyst particles. Part II: the nanotube film
- 2004
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Ingår i: Journal of Materials Science: Materials in Electronics. ; 15:9, s. 583-594
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Carbon nanotube films have been grown at 750° and 900 °C by thermal chemical vapor deposition (CVD) with acetylene (C2H2) and hydrogen on silicon (0 0 2) wafers supporting preformed (Fe,Si)3O4 particles. The reduction of the (Fe,Si)3O4 particles during CVD at 750 °C was accompanied by a disintegration leading to the formation of a high density of smaller (predominantly 5–15 nm) iron silicide (α1-Fe2Si) particles that catalyzed the growth of a dense and aligned multi-wall carbon nanotube film. The tubes did not contain any inclusions apart from the catalytic particles present in the bottom part of the film, and it was concluded that the nanotubes grew via a “base-growth” mechanism. CVD at 900 °C resulted in a random growth of predominantly multi-wall carbon nanotubes. The film contained an increased number of amorphous carbon, or graphite, clusters containing particles that had been carbonized, the larger ones to cementite, θ-Fe3C. Nanotubes were observed to grow from some of these clusters. Multi-wall carbon nanotube tips contained after CVD at 900 °C encapsulated θ-Fe3C, or in a few cases α- or γ-Fe, particles.
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| 4978. |
- Yazdanparast, P., et al.
(författare)
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A thyroid hormone analogue, triiodothyroacetic acid, corrects corticosteroid-downregulated collagen synthesis
- 2004
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Ingår i: Thyroid. ; 14:5, s. 345-53
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to compare the change in collagen synthesis between topical treatments with two doses of triiodothyroacetic acid (TRIAC), a thyroid hormone analogue, and placebo, after pretreatment with topical betamethasone 17-valerate (BM). Eighteen healthy volunteers were pretreated with BM on abdominal skin for 3 days, and were then treated for 14 days with a cream containing TRIAC (0.03% or 0.1%) or a placebo cream. Collagen production was assessed by quantifying the amino terminal propeptides of human type I and type III procollagen (PINP and PIIINP) in fluids from suction-induced blisters on the treated skin. Three days of treatment with BM led to an average reduction of PINP of 70% and of PIIINP of 50%. Seven days after treatment, the median increase in PINP was 230% (p = 0.03) in the Triac 0.03% group, 148% (p = 0.2) in the TRIAC 0.1% and 5% in the placebo group. The median increase in PINP in the skin area from the start of treatment to the end of treatment was 521% (p = 0.06) in the TRIAC 0.03% group, 339% (p = 0.2) in the TRIAC 0.1% group, and 55% in the placebo group (the p values are related to baseline). Seven days after treatment, the median increase in PIIINP was 24% (p = 0.6) in the Triac 0.03% group, 23% (p = 0.6) in the TRIAC 0.1% group, and -12% in the placebo group. The median increase in PIIINP in the skin area from the start of treatment to the end of treatment was 137% (p = 0.7) in the TRIAC 0.03% group, 230% (p = 0.9) in the TRIAC 0.1% group and 58% in the placebo group (the p values are related to baseline). Histologic examinations of sections from punch biopsies taken at the end of the treatment showed more thickened collagen fibers and increased density of PINP-producing dermal fibroblasts in the TRIAC groups compared to the placebo group. The result suggests a potential role for TRIAC-containing cream concomitant with anti-inflammatory topical treatment with potent glucocorticoids to prevent their suppressive activity on dermal collagen production.
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| 4979. |
- Yesuf, Mahmud, 1969
(författare)
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Risk, Time and Land Management under Market Imperfections: Applications to Ethiopia
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This Ph.D. thesis addresses both theoretical and empirical issues pertaining to land management decisions of farm households in developing countries working under an imperfect market and institutional setting (with case studies from Ethiopia). Using techniques in experimental economics, efforts are also made to assign some quantitative measures to the most important parameters (such as risk and time preferences) in the same decision making process. Paper I: A Dynamic Economic Model of Soil Conservation with Imperfect Markets and Institutions In this paper, we develop a dynamic soil conservation model that explicitly incorporates labor, capital and land market imperfections and their interactions to suit the problems of smallholders in many developing countries. We use the model to analyze the impact of these institutional and market imperfections on the optimal levels of labor allocations into cultivation and conservation efforts. Increased transaction cost in factor markets is found to have a direct impact on soil conservation effort by increasing its shadow prices and curtailing its demand. It also has an indirect impact on soil conservation by affecting the shadow price of the soil stock and hence enhancing or curtailing its demand depending on the initial factor endowments of farm households, the relative strength of conservation and cultivation inputs on the soil dynamics, the profit share of cultivation input, and the degree of interaction across the factor markets. The overall impact is thus inconclusive. Various possible scenarios are explored in the model. Paper II: Risk Preferences of Farm Households in Ethiopia This study measures farmersâ?? attitudes towards risk using an experimental approach for a sample of 262 farm households in the Ethiopian highlands. We find more than 50 percent of the households in the severe to extreme risk aversion category, with a constant partial risk aversion coefficient of more than 2.00. With careful construction of the experiment, the natures of absolute and partial risk aversion are examined, and our data supports the presence of Decreasing Absolute Risk Aversion (DARA) and Increasing Partial Risk Aversion (IPRA) behavior. The validity of some of the expected utility theory predictions is tested, and the predictions of risk neutrality for smaller stakes and predictions of similar preferences for gains and losses, which stem from the major tents of the theory (concavity and asset integration), are not supported by our experiment. Paper III: Time Preferences of Farm Households in Ethiopia This study measures
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| 4980. |
- Yilmaz, Aylin, 1974, et al.
(författare)
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Cerebrospinal fluid and plasma HIV-1 RNA levels and lopinavir concentrations following lopinavir/ritonavir regimen.
- 2004
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Ingår i: Scandinavian journal of infectious diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 36:11-12, s. 823-8
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Tidskriftsartikel (refereegranskat)abstract
- Our objective was to study the effect of lopinavir/ritonavir on cerebrospinal fluid (CSF) viral load as part of an antiretroviral combination treatment for HIV-1 infected individuals, and to determine the steady-state concentrations of lopinavir in CSF in relationship to plasma concentrations. Paired CSF and plasma samples from 12 antiretroviral-naïve HIV-1 infected patients starting combination therapy containing lopinavir/ritonavir were collected at baseline, and during treatment at a first follow-up at median 3.0 months (range 2.6-6.0 months), and at a second follow-up at median 12.1 months (range 6.0-16.5 months). Levels of HIV-1 RNA, CD4+ T-cell count, beta2-microglobulin, neopterin, and lopinavir concentration were analysed. In addition, CSF and plasma lopinavir concentrations in 4 patients already on combination therapy including lopinavir/ritonavir were analysed. Nine of 11 patients had undetectable viral load in CSF and 5/11 in plasma at the first follow-up. At the second follow-up 7/7 had undetectable viral load in CSF and 9/9 in plasma. Intrathecal immunoactivation, measured by neopterin and beta2-microglobulin, decreased significantly both in CSF and serum. The total CSF concentrations of lopinavir were of the same order of magnitude as the unbound concentrations in plasma. Lopinavir mean (+/-SD) concentrations were 42.1 (+/-31.5) nM in CSF and 52.7 (+/-25.2) nM unbound in plasma. We found that antiretroviral combination therapy including lopinavir/ritonavir substantially decreases the viral load, both in CSF and plasma, as well as the intrathecal immunoactivation, measured by beta2-microglobulin and neopterin. CSF concentrations of lopinavir were low, but probably sufficient to have a virological effect.
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