184,044 research outputs found
Slow degrading Mg-based materials induce tumor cell dormancy on an osteosarcoma-fibroblast coculture model
No full textOsteosarcoma is one of the most common cancers in young adults and is commonly treated using surgery and chemotherapy. During the past years, these therapy approaches improved but failed to ameliorate the outcomes. Therefore, novel, targeted therapeutic approaches should be established to enhance treatment success while preserving patient's quality of life. Recent studies suggest the application of degradable magnesium (Mg) alloys as orthopedic implants bearing a potential antitumor activity. Here, we examined the influence of Mg-based materials on an osteosarcoma-fibroblast coculture. Both, Mg and Mg–6Ag did not lead to tumor cell apoptosis at low degradation rates. Instead, the Mg-based materials induced cellular dormancy in the cancer cells indicated by a lower number of Ki-67 positive cancer cells and a higher p38 expression. This dormancy-like state could be reversed by reseeding on non-degrading glass slides but could not be provoked by inhibition of the protein kinase R-like endoplasmic reticulum kinase. By investigating the influence of the disjunct surface-near effects of the Mg degradation on cell proliferation, an increased pH was found to be a main initiator of Mg degradation-dependent tumor cell proliferation inhibition
Optimizing an osteosarcoma-fibroblast coculture model to study antitumoral activity of magnesium-based biomaterials
No full textOsteosarcoma is among the most common cancers in young patients and is responsible for one-tenth of all cancer-related deaths in children. Surgery often leads to bone defects in excised tissue, while residual cancer cells may remain. Degradable magnesium alloys get increasing attention as orthopedic implants, and some studies have reported potential antitumor activity. However, most of the studies do not take the complex interaction between malignant cells and their surrounding stroma into account. Here, we applied a coculture model consisting of green fluorescent osteosarcoma cells and red fluorescent fibroblasts on extruded Mg and Mg–6Ag with a tailored degradation rate. In contrast to non-degrading Ti-based material, both Mg-based materials reduced relative tumor cell numbers. Comparing the influence of the material on a sparse and dense coculture, relative cell numbers were found to be statistically different, thus relevant, while magnesium alloy degradations were observed as cell density-independent. We concluded that the sparse coculture model is a suitable mechanistic system to further study the antitumor effects of Mg-based material
Teaching Undergraduate Macroeconomics with the Taylor-Romer Model
Get PDFThis paper sets out a version of the Taylor-Romer model of short-run macroeconomic equilibrium which can be used for teaching undergraduate economics principles courses. The aim is to generate a model with the proven advantages of the IS-LM framework but with a more realistic description of central bank behaviour. The paper then provides a dynamic analysis of longer-term adjustment using a phase diagram but without the need for a formal mathematical derivation.
The Dynamics of the Romer R&D Growth Model with Quality Upgrading
Get PDFThis paper replaces increasing product variety with quality upgrading in the Romer (1990) model. We show that the range of parameters for which a steady state exists can be divided into two subspaces with well-behaved comparative statics and saddle-point dynamics in one subspace, but with “perverse” comparative-statics properties and either equilibrium indeterminacy or instability in the other subspace. In the latter subspace, a parameter change possibly leads to a Hopf bifurcation. Using a theorem in Arnold (in press), these results for the closed economy can also be used to characterize the dynamics of the M-country open-economy version of the model
Growth in OECD countries and elsewhere: how much do education and R&D explain?
Get PDFWe find that the Nonneman and Vanhoudt (1996) extension to include R&D in the Mankiw, Romer and Weil (1992) growth model with human capital performs well also outside of OECD countries. It explains 61 to 86 percent of cross-country variation in income and growth over 40 years, explanatory variables being of expected sign for all country groups and significant in most cases. We test for the role of adding control variables and excluding outliers.augmented Solow model
Dynamic Scoring in a Romer-style Economy
Get PDFThis paper explores the dynamic behavior of a Romer-style endogenous growth model, analyzing how changes in tax rates affect government revenue in the short run and the long run. I show that in this environment lowering taxes on financial income is unlikely to stimulate tax revenue in the long run and has modest effects on the tax base, contrary to some other studies of the dynamic response of revenue to tax rates. Calibrations of the model that suggest Laffer curve effects can be substantial require implausibly low values for the elasticity of substitution between varieties of intermediate goods. For more plausible parameter values, I find that around 20% of a tax cut would be self-financing due to an expansion in the tax base.
Technology Trade, Productivity and Growth
Get PDFInternational trade is a major channel for technology diffusion. However regressing trade in R&D intensive goods to evaluate the effect of technology imports on productivity in a cross section of countries may be misleading because of simultaneity bias. I identify the effect of technology trade on productivity using geographical instruments for the trade variable as in Frankel and Romer (1999). I make several contributions. First, I provide evidence that OLS estimates are downward biased. Second, the effect is robust to the exclusion of outliers, the inclusion of latitude, and to different subsamples. Finally, I document the channels throughout technology imports affect productivity.Growth, Technology Diffusion, Instrumental Variables, R&D Spillovers, Capital Goods.
How large are the effects of tax changes?
Get PDFWe use the time series of shifts in U.S. Federal tax liabilities constructed by Romer and Romer to estimate tax multipliers. Differently from the single-equation approach adopted by Romer and Romer, our estimation strategy (a Var that includes output, government spending and revenues, inflation and the nominal interest rate) does not rely upon the assumption that tax shocks are orthogonal to each other as well as to lagged values of other macro variables. Our estimated multiplier is much smaller: one, rather than three at a three-year horizon. When we split the sample in two sub-samples (before and after 1980) we find, before 1980, a multiplier whose size is never greater than one, after 1980 a multiplier not significantly different from zero. Following the findings in Bohn (1998), we also experiment with a model that includes debt and the non-linear government budget constraint. We find that, while in general not very important, the non-linearity that arises from the budget constraint makes a difference after 1980, when the response of fiscal variables to the level of the debt becomes stronger.
Economic Integration and Endogenous Growth Revisited: Pro-Competitive Gains from Trade in Goods and the Long Run Benefits to the Exchange of Ideas
Get PDFThis paper re-examines the Romer [1990] “knowledge driven” endogenous growth model in an open economy setting. As an alternative to Rivera-Batiz and Romer [1991], we consider trade between two absolutely identical countries that are characterized by imperfect competition in one of the trade goods. Contrary to Rivera- Batiz and Romer [1991], we find that trade in goods without trade in ideas is detrimental to long run growth while trade in goods in conjunction with trade in ideas is good for long run growth. We further demonstrate that the pro-competitive gains from trade in goods is analogous to the analysis of imperfect competition by standard international trade theory.Knowledge Driven, Endogenous Growth, International Trade, Imperfect Competition
Venyukovioidea WATSON & ROMER 1956
No full textVENYUKOVIOIDEA WATSON & ROMER, 1956 Revised diagnosis Basal anomodonts characterized by four unambiguous autapomorphies: (1) maxillary alveolar region long, occupying 72% or more of the length of the bone; (2) fused vomers; (3) mid-ventral plate of vomers without expanded area posterior to junction with premaxilla; (4) premaxilla–palatine contact present. In addition, four ambiguous autapomorphies need to be confirmed by more complete material of Otsheria or Ulemica: (5) coarse serrations on marginal teeth present; (6) denticulated cingulum on marginal teeth present; (7) squared-off profile of occiput in posterior view present; (8) olecranon process poorly ossified and presumably cartilaginous.Published as part of Fröbisch, Jörg & Reisz, Robert R., 2011, The postcranial anatomy of Suminia getmanovi (Synapsida: Anomodontia), the earliest known arboreal tetrapod, pp. 661-698 in Zoological Journal of the Linnean Society 162 (3) on page 664, DOI: 10.1111/j.1096-3642.2010.00685.x, http://zenodo.org/record/544055
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