184 research outputs found
Persian Gardens: Meanings, Symbolism, and Design
Culture and identity in a society can be represented in the architecture and the meanings intertwined with it. In this sense, the architecture and design are the interface for transferring meaning and identity to the nation and future generations. Persian gardens have been evolved through the history of Persian Empire in regard to the culture and beliefs of the society. This paper aims to investigate the patterns of design and architecture in Persian gardens and the meanings intertwined with their patterns and significant elements such as water and trees. Persian gardens are not only about geometries and shapes; but also manifest different design elements, each representing a specific symbol and its significance among the society. This paper seeks to explore Persian gardens in terms of their geometric structure, irrigation system, network construction and pavilions alongside design qualities such as hierarchy, symmetry, centrality, rhythm and harmony. In the second stage, the paper investigates the fundamental symbols and their philosophy in the creation of Persian gardens and in relation to the architecture and design
Finite difference schemes for second order systems describing black holes
In the harmonic description of general relativity, the principle part of
Einstein's equations reduces to 10 curved space wave equations for the
componenets of the space-time metric. We present theorems regarding the
stability of several evolution-boundary algorithms for such equations when
treated in second order differential form. The theorems apply to a model black
hole space-time consisting of a spacelike inner boundary excising the
singularity, a timelike outer boundary and a horizon in between. These
algorithms are implemented as stable, convergent numerical codes and their
performance is compared in a 2-dimensional excision problem.Comment: 19 pages, 9 figure
Concept note : a democratisation programme in Georgia
A technical report identifying optimal ways of engagement with the Georgian civil society to promote democracy and human rights as part of development programmes funded by DANIDA - the development arm of the Ministry of Foreign Affairs of Denmark
Concept note : a democratisation programme in Ukraine
A technical report on field research in Ukraine identifying the most promising areas in the sphere of the media and civil society for deployment of DANIDA resources in future development and democratisaton programmes funded by the Danish Foreign Ministry
Elimination of Transcoarctation Pressure Gradients Has No Impact on Left Ventricular Function or Aortic Shear Stress After Intervention in Patients With Mild Coarctation
Objectives: This study sought to investigate the impact of transcatheter intervention on left ventricular function and aortic hemodynamics in patients with mild coarctation of the aorta (COA). Background: The optimal method and timing of transcatheter intervention for COA remains unclear, especially when the severity of COA is mild (peak-to-peak transcoarctation pressure gradient < 20 mm Hg). Debate rages regarding the risk/benefit ratio of intervention versus long-term effects of persistent minimal gradient in this heterogeneous population with differing blood pressures, ventricular function, and peripheral perfusion. Methods: We developed a unique computational fluid dynamics and lumped parameter modeling framework based on patient-specific hemodynamic input parameters and validated it against patient-specific clinical outcomes (before and after intervention). We used clinically measured hemodynamic metrics and imaging of the aorta and the left ventricle in 34 patients with mild COA to make these correlations. Results: Despite dramatic reduction in the transcoarctation pressure gradient (catheter and Doppler echocardiography pressure gradients reduced by 75% and 47.3%, respectively), there was only modest effect on aortic flow and no significant impact on aortic shear stress (the maximum time-averaged wall shear stress in descending aorta was reduced 5.1%). In no patient did transcatheter intervention improve left ventricular function (e.g., stroke work and normalized stroke work were reduced by only 4.48% and 3.9%, respectively). Conclusions: Transcatheter intervention that successfully relieves mild COA pressure gradients does not translate to decreased myocardial strain. The effects of the intervention were determined to the greatest degree by ventricular–vascular coupling hemodynamics and provide a novel valuable mechanism to evaluate patients with COA that may influence clinical practice. Key Words: aortic hemodynamics, left ventricle function, mild coarctation, peak-to-peak pressure gradient, transcatheter interventionNational Institute of Mental Health (U.S.) (R01 GM 49039)American Heart Association (Postdoctoral Fellowship 16POST26420039
Evaluation of the efficacy of two doses of vitamin D supplementation on glycemic, lipidemic and oxidative stress biomarkers during pregnancy: a randomized clinical trial
Background: Vitamin D deficiency during pregnancy is common and is likely to be associated with metabolic complications in the mother. The aim of this study was to assess the efficacy of two doses of vitamin D supplementation during pregnancy on maternal and cord blood vitamin D status and metabolic and oxidative stress biomarkers. Methods: The eligible pregnant women (n = 84) invited to participate in the study and randomly allocated to one of the two supplementation groups (1000 IU/d vitamin D and 2000 IU/d). Biochemical assessments of mothers including serum concentrations of 25(OH)D, calcium, phosphate, iPTH, fasting serum sugar (FBS), insulin, triglyceride, total cholesterol, LDL-C, HDL-C, malondialdehyde (MDA) and total antioxidant capacity (TAC) were done at the beginning and 34 weeks of gestation. Cord blood serum concentrations of 25(OH)D, iPTH, MDA and TAC were assessed at delivery as well. To determine the effects of vitamin D supplementation on metabolic markers 1-factor repeated-measures analysis of variance (ANOVA) was used. Between groups comparisons was done by using Independent-samples Student�s t-test or Mann-Whitney test. P < 0.05 was considered as significant. Results: Supplementation with 1000 IU/d and 2000 IU/d vitamin D resulted in significant changes in vitamin D status over pregnancy (24.01 ± 21.7, P < 0.001 in 1000 IU/d group and 46.7 ± 30.6 nmol/L, P < 0.001 in 2000 IU/d group). Daily intake of 2000 compared with 1000 IU/d tended to increase the serum concentration of HDL-C (10 ± 8.37, P < 0.001 in 1000 IU/d group and 9.52 ± 11.39 mg/dL, P < 0.001 in 2000 IU/d group). A significant decrement in serum concentration of iPTH observed in both groups (� 4.18 ± 7.5, P = 0.002 in 1000 IU/d group and � 8.36 ± 14.17, P = 0.002 in 2000 IU/d group). Conclusions: Supplementation with 2000 IU/d vitamin D as compared with 1000 IU/d, is more effective in promoting vitamin D status and HDL-C serum concentration and in decreasing iPTH over pregnancy. Trial registration: This trial is registered at clinicaltrials.gov (NCT03308487). Registered 12 October 2017 �retrospectively registered�. © 2020, The Author(s)
A posteriori error analysis and adaptive non-intrusive numerical schemes for systems of random conservation laws
In this article we consider one-dimensional random systems of hyperbolic
conservation laws. We first establish existence and uniqueness of random
entropy admissible solutions for initial value problems of conservation laws
which involve random initial data and random flux functions. Based on these
results we present an a posteriori error analysis for a numerical approximation
of the random entropy admissible solution. For the stochastic discretization,
we consider a non-intrusive approach, the Stochastic Collocation method. The
spatio-temporal discretization relies on the Runge--Kutta Discontinuous
Galerkin method. We derive the a posteriori estimator using continuous
reconstructions of the discrete solution. Combined with the relative entropy
stability framework this yields computable error bounds for the entire
space-stochastic discretization error. The estimator admits a splitting into a
stochastic and a deterministic (space-time) part, allowing for a novel
residual-based space-stochastic adaptive mesh refinement algorithm. We conclude
with various numerical examples investigating the scaling properties of the
residuals and illustrating the efficiency of the proposed adaptive algorithm
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