435 research outputs found
Wall-sheared thermal convection: heat transfer enhancement and turbulence relaminarization
We studied the flow organization and heat transfer properties in
two-dimensional and three-dimensional Rayleigh-B\'enard cells that are imposed
with different types of wall shear. The external wall shear is added with the
motivation of manipulating flow mode to control heat transfer efficiency. We
imposed three types of wall shear that may facilitate the single-roll, the
horizontally stacked double-roll, and the vertically stacked double-roll flow
modes, respectively. Direct numerical simulations are performed for fixed
Rayleigh number and fixed Prandtl number , while the
wall-shear Reynolds number () is in the range .
Generally, we found enhanced heat transfer efficiency and global flow strength
with the increase of . However, even with the same magnitude of global
flow strength, the heat transfer efficiency varies significantly when the cells
are under different types of wall shear. An interesting finding is that by
increasing the wall-shear strength, the thermal turbulence is relaminarized,
and more surprisingly, the heat transfer efficiency in the laminar state is
higher than that in the turbulent state. We found that the enhanced heat
transfer efficiency at the laminar regime is due to the formation of more
stable and stronger convection channels. We propose that the origin of thermal
turbulence laminarization is the reduced amount of thermal plumes. Because
plumes are mainly responsible for turbulent kinetic energy production, when the
detached plumes are swept away by the wall shear, the reduced number of plumes
leads to weaker turbulent kinetic energy production. We also quantify the
efficiency of facilitating heat transport via external shearing, and find that
for larger , the enhanced heat transfer efficiency comes at a price of
a larger expenditure of mechanical energy.Comment: 27 pages, 16 figure
Pore-scale statistics of temperature and thermal energy dissipation rate in turbulent porous convection
We report pore-scale statistical properties of temperature and thermal energy
dissipation rate in a two-dimensional porous Rayleigh-B\'enard (RB) cell.
High-resolution direct numerical simulations were carried out for the fixed
Rayleigh number () of and the Prandtl numbers () of 5.3 and
0.7. We consider sparse porous media where the solid porous matrix is
impermeable to both fluid and heat flux. The porosity () range , the corresponding Darcy number () range
and the porous Rayleigh number () range
. Our results indicate that the plume dynamics in
porous RB convection are less coherent when the solid porous matrix is
impermeable to heat flux, as compared to the case where it is permeable. The
averaged vertical temperature profiles remain almost a constant value in the
bulk, whilst the mean square fluctuations of temperature increases with
decreasing porosity. Furthermore, the absolute values of skewness and flatness
of the temperature are much smaller in the porous RB cell than in the canonical
RB cell. We found that intense thermal energy dissipation occurs near the top
and bottom walls, as well as in the bulk region of the porous RB cell. In
comparison with the canonical RB cell, the small-scale thermal energy
dissipation field is more intermittent in the porous cell, although both cells
exhibit a non-log-normal distribution of thermal energy dissipation rate. This
work highlights the impact of impermeable solid porous matrices on the
statistical properties of temperature and thermal energy dissipation rate, and
the findings may have practical applications in geophysics, energy and
environmental engineering, as well as other fields that involve the transport
of heat through porous media.Comment: 30 pages, 16 figure
Pressure-Driven Filling of Closed-End Microchannel: Realization of Comb-Shaped Transducers for Acoustofluidics
We demonstrate the complete filling of both deionized water (DI water) and liquid metal (eutectic
gallium-indium, EGaIn) into closed-end microchannels driven by a constant pressure at the inlet. A mathematical
model based on gas diffusion through a porous polydimethylsiloxane (PDMS) wall is developed
to unveil the physical mechanism in the filling process. The proposed theoretical analysis based on our
model agrees well with the experimental observations. We also successfully generate traveling surface
acoustic waves by actuating interdigitated microchannels filled with EGaIn. Our work provides significant
insights into the fabrication of liquid electrodes that can be used for various acustofluidics applicationsAustralian Research Council DE170100600National Natural Science Foundation of China Grants No. 11472094, No. 11772259, No. U1613227, No. B1703
Origin of the Temperature Oscillation in Turbulent Thermal Convection
We report an experimental study of the three-dimensional spatial structure of
the low frequency temperature oscillations in a cylindrical Rayleigh-B\'{e}nard
convection cell. It is found that thermal plumes are not emitted periodically,
but randomly and continuously, from the top and bottom plates. We further found
that the oscillation of the temperature field does not originate from the
boundary layers, but rather is a result of the horizontal motion of the hot
ascending and cold descending fluids being modulated by the twisting and
sloshing motion of the bulk flow field.Comment: 5 figure
The correlation between the plasma concentration of gemcitabine and short-term efficacy and adverse reactions in patients with advanced squamous cell carcinoma of the lung using liquid chromatography-mass spectrometry
AbstractBackground: Worldwide, non-small cell lung cancers have the highest incidence and mortality rates of all cancers. Gemcitabine (2’,2’-difluoro-2’-deoxycytidine or dFdC, C9H11F2N304) is widely used as the first-line chemo-reagent for lung cancer patients whose tumors have been diagnosed to be at an advanced stage and are therefore unresectable.
Objective: The objective of this systematic study was to establish the correlation between the plasma concentration of gemcitabine and short-term clinical efficacy and adverse reactions in patients with advanced squamous cell carcinoma of the lung using liquid chromatography-mass spectrometry.
Material and methods: In total, 53 patients were given the chemotherapy medications, gemcitabine and cisplatin, every 3 weeks. Plasma concentrations of gemcitabine were determined using liquid chromatography-mass spectrometry. A modified methodology of the liquid chromatography-mass spectrometry system was verified and performed to detect plasma concentrations of gemcitabine. The clinical endpoints – short-term clinical efficacy and adverse reactions – were evaluated after two cycles.
Results: The plasma concentration range of gemcitabine in 53 patients was 1.58-28.70μg/ml (mean 14.37±8.63μg/ml), with 28 patients in the >15μg/ml group (mean 21.76±3.45μg/ml), and 25 patients in the ≤15μg/ml group (mean 6.09±3.57μg/ml). The clinical benefit rate (CBR) of the >15μg/ml group was significantly higher than that of the 15μg/ml group (p<0.05). The incidences of leukopenia and neutropenia, thrombocytopenia and grade III-IV gastrointestinal reactions in the >15μg/ml group were significantly higher than in the ≤15μg/ml group (p<0.05). There was no statistical difference between the two groups in terms of the incidences of reduced hemoglobin, liver and kidney function damage, allergic reaction and rash (p>0.05). The analysis of the plasma concentration of gemcitabine and the percentage of reduction in neutrophil count (NEUT) (r2 = 0.3212; p<0.05) and platelet (PLT) (r2 = 0.6439; p<0.05) showed a significant positive correlation.
Conclusions: In patients with advanced non-small cell lung cancer, a high plasma concentration of gemcitabine can improve the short-term clinical efficacy of treatment, but increase the incidence of grade III-IV adverse reactions. [Ethiop. J. Health Dev. 2021; 35(1):72-82]
Key words: Non-small cell lung cancer, gemcitabine, plasma concentration, short-term efficacy, adverse reaction
The Mineral Nutrients Content and the Organic Manure Quality Appraisal for the \u3cem\u3eStylosanthes\u3c/em\u3e Green Manure
Stylo (Stylosanthes spp.) is a leguminous crop planted widely in the world tropics. In the past the stylo was commonly used as pasture with high quality, and was less used as a green manure. However, stylo is recently used more as a green manure in tropical plantations. As there is little relevant research on the organic manure quality for stylo, the purpose of this research was to evaluate the quality of stylo green manure. Selection of stylo green manure with the highest quality was based on the analysis of nutrients and organic matter content in stylo
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