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Prognostic significance of 25‐hydroxivitamin D entirely explained by a higher comorbidity burden: Experience from a South‐Eastern European Dialysis Cohort
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Adalbert Schiller Mugurel Apetrii Mihai Onofriescu Dimitrie Siriopol Gabriel Veisa Oana Schiller Flaviu Bob Romulus Timar Adelina Mihaescu Mehmet Kanbay Adrian Covic 《Hemodialysis international. International Symposium on Home Hemodialysis》2015,19(2):249-255
Vitamin D deficiency is still a common problem particularly in the elderly and in individuals with various degrees of renal impairment. The present study aimed to evaluate the association between plasma concentrations of 25(OH)D and death in a large cohort of prevalent patients on hemodialysis (HD) from south‐east Romania, a typical Balkan region. This is an observational prospective study that included a total of 570 patients on maintenance HD. Study patients were classified into three groups by baseline 25(OH)D levels: (1) sufficient 25(OH)D—i.e., >30 ng/mL; (2) insufficient 25(OH)D—i.e., between 10 and 29 ng/mL; and (3) deficient 25(OH)D—i.e., <10 ng/mL. During the follow‐up period of 14 months, 68 patients (11.9%) died, the Kaplan–Meier analysis showing significant differences in all‐cause mortality for chronic kidney disease patients in different 25(OH)D groups (P = 0.002). Unadjusted Cox regression analysis also showed significant differences in survival. The multivariate Cox regression model showed no significant differences in survival according to vitamin D levels. Hazard ratio for death in the “<10 ng/mL” group was 1.619 (P = 0.190) and in the “10–30 ng/mL” group was 0.837 (P = 0.609). In our dialysis population with a high comorbidity burden, low 25(OH)D concentration was not associated with mortality in the adjusted Cox model, suggesting that vitamin D deficiency could represent only a non‐specific marker for a poor health status, with less impact on mortality. 相似文献
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A method is proposed to generate Earth‐bound artificial microgravity in a controlled facility capable of emulating lunar/Martian gravity or microgravity for experiments on passive/reactive catalytic multiphase flows. Its applicability was illustrated for trickle beds where flowing gas and liquid experience artificial microgravity inside the bore of a superconducting magnet generating large gradient magnetic fields to compensate for gravity. Artificial gravity is realized by commuting into apparent gravity acceleration the magnetization force at work on common “chemical engineering” non‐magnetic fluids. The scaling property to be matched and maintained invariant in multiphase systems to achieve magnetic mimicry is phasic mass magnetic susceptibility. Hydrodynamic (liquid holdup, wetting efficiency, pressure drop) as well as catalytic reaction (conversion and selectivity) measurements were obtained. The main finding is a proof that magnetic fields affect reactor outcomes exclusively via hydrodynamic phenomena making them appealing proxies for emulating non‐terrene reactor applications. © 2009 American Institute of Chemical Engineers AIChE J, 2009 相似文献
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Jia-Liang Le Rebecca Hendrickson Mihai O. Marasteanu Mugurel Turos 《Materials and Structures》2018,51(6):152
In this study, a discrete element computational model is applied to simulate the fracture behavior of asphalt mixtures at low temperatures. In this model, coarse aggregates are explicitly represented by rigid spherical particles. The bonds that connect these particles represent the fine aggregate matrix (FAM), which is defined as the combination of asphalt binder and fine aggregates. The bending beam rheometer (BBR) tests are performed to determine the strength and Young’s modulus of FAM at low temperatures. The model is then used to simulate the semi-circular bend (SCB) tests on the mixtures. The model is verified by a series of BBR and SCB tests on both conventional and graphite nano-platelet modified asphalt materials. The comparison between the experimental and simulated results indicates that the peak load capacity of the SCB specimens is primarily governed by the tensile strength of the FAM. However, in order to capture the entire load–displacement curve of the SCB specimens, one needs to employ a softening constitutive model of the FAM, which requires the information on its fracture energy. Several experimental methods for measuring the fracture energy of FAM are discussed for future prediction of the complete load–displacement response of asphalt mixtures at low temperatures. 相似文献
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Raul Velasquez Mugurel Turos Ki Hoon Moon Larry Zanko Mihai Marasteanu 《Construction and Building Materials》2009,23(9):3070-3078
Current demand from transportation agencies for construction and maintenance of their pavement network requires the use of large amounts of aggregate. Diminishing reserves of aggregate and environmental regulations for new aggregate extraction sites restricts the use of standard aggregates and encourages the use of recycled materials. This paper investigates the suitability of using taconite aggregates, a byproduct of taconite mining industries, for construction of asphalt pavements by evaluating the mechanical performance of asphalt mixtures prepared with taconite aggregates. The experimental work is performed by means of the semi-circular bending test (SCB), the indirect tensile test (IDT), dynamic modulus (E1) test, and the thermal stress restrained specimen test (TSRST) with acoustic emission monitoring. The results indicate that, in general, the mixtures prepared with taconite aggregates perform slightly better than the mixtures prepared with standard aggregates. 相似文献
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Mugurel Catalin Munteanu 《Chemical engineering science》2009,64(2):391-11759
Strong inhomogeneous magnetic fields in atmospheric-bore superconducting solenoid magnets were used to investigate the hydrodynamics in bore-fitted trickle beds which undergo emulated earth-bound artificial micro/macrogravity. This environment was able to modify the apparent gravity for both diamagnetic and paramagnetic materials by means of magnetization body force densities. Body force vectors can be co-linear or antiparallel to the cocurrent two-phase downflow in trickle beds depending on material magnetic susceptibilities, magnetic field gradient and direction of magnetic field. Trickle-to-pulse flow transition was experimentally studied in microgravity, macrogravity and beyond-levitation conditions for the air-water and the phenylacetylene-kerosene/hydrogen systems. Magnetic fields were found to displace the transition boundary from trickle to pulse flow. This was rationalized in terms of an equivalent artificial gravity effect by formally commuting magnetization forces into an equivalent gravitational acceleration. A theoretical analysis, using a modified Grosser et al. [1988. Onset of pulsing in two-phase cocurrent downflow through a packed bed. A.I.Ch.E. Journal 34, 1850-1860] “artificial gravity” transition model, was carried out and model predictions were found to follow qualitatively the experimental findings. 相似文献
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Augusto Cannone Falchetto Jia-Liang Le Mugurel I. Turos Mihai O. Marasteanu 《Materials and Structures》2014,47(1-2):157-169
Low temperature cracking of asphalt pavements is a major distress in cold regions. Accurate assessment of strength of asphalt mixtures at low temperatures is of great importance for ensuring the structural integrity of asphalt pavements. It has been shown that asphalt mixtures behave in a quasibrittle manner at low temperatures and consequently its nominal strength strongly depends on the structure size. The size effect on the strength of asphalt mixtures can be directly measured by testing geometrically similar specimens with a sufficiently large size range. Recent studies have shown in theory that for quasibrittle structures, which fail at the macrocrack initiation from one representative volume element, the mean size effect curve can also be derived from the scaling of strength statistics based on the finite weakest link model. This paper presents a comprehensive experimental investigation on the strength statistics as well as the size effect on the mean strength of asphalt mixtures at ?24 °C. It is shown that the size effect on mean structural strength can be obtained by strength histogram testing on specimens of a single size. The present study also indicates that the three-parameter Weibull distribution is not applicable for asphalt mixtures. 相似文献
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Yan Tianhao Marasteanu Mihai Turos Mugurel 《Mechanics of Time-Dependent Materials》2021,25(4):617-630
Mechanics of Time-Dependent Materials - Selecting asphalt binders that have good cracking resistance at low temperatures is the first step in designing asphalt mixtures for durable asphalt... 相似文献
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Salvadore Mugurel Burciu 《Journal of Mechanical Science and Technology》2014,28(10):4339-4344
The paper deals with computer simulation that allows the calculus of operating regimes with minimum fuel consumption for road vehicles, using engine’s mechanical characteristics for power and consumption, characteristics which are known from experimental determinations and are indicated by engine manufacturer. For the case considered, are establish the minimum fuel consumption for different car speeds, speeds according to engine rotations for minimum fuel consumption regimes and transmission ratios that ensure the minimum fuel consumption for the automotive speeds. 相似文献
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