Adding surfactant can improve the stability of hybrid nanofluids. However, positive or negative effects of the surfactant on the thermophysical properties of hybrid nanofluids should be further ...investigated. In the present study, effects of different surfactants, including SDS, PVP and CTAB, with various mass concentrations and temperatures on the stability of Al2O3-CuO/Water (W) and Al2O3-TiO2/Water (W) hybrid nanofluids are investigated. Results show that increment of surfactant concentration improves the stability and viscosity. Then obtained results from UV–Vis Spectrophotometer, TEM and sedimentation methods are compared, and PVP surfactant has the highest degree of stability, with the minimal sedimentation up to 25 days. At the optimum PVP surfactant concentrations of 0.005 wt% and 0.01 wt%, the maximum thermal conductivity enhancement is 12% and 14% at 60 °C for Al2O3-CuO/W and Al2O3-TiO2/W hybrid nanofluids. Therefore, adding even little amount of surfactant can improve the stability and thermal conductivity of hybrid nanofluids.
To understand the remarkable enhancements in viscosity and thermal conductivity of nanofluids, a molecular dynamics (MD) simulation approach was used to investigate the structure and thickness of the ...interfacial layer and obtain values for radial distribution function, g(r), viscosity, and thermal conductivity of Cu/water nanofluids with volume fractions and temperatures ranging from 0.5–2 vol% and 293–333 K, respectively. The results revealed that value of g(r) was much higher in the first molecular nanolayer compared to the second layer, indicating that greater numbers of water molecules are present in the first layer, which reduces contact thermal resistance and improves thermal conductivity of nanofluids. Moreover, while value of g(r) increased with increasing Cu volume fraction and decreased with temperature, nanolayer thickness was unchanged with temperature at each volume fraction, indicating that intermolecular forces intensify in the first nanolayer. Macroscopically, viscosity and thermal conductivity of the nanofluids increased at higher volume fractions, showing increases of 71.7% and 75% for viscosity, and 41.7% and 53.3% for thermal conductivity at 0.5 and 2 vol%, respectively, compared to water at 333 K. These results, although obtained for Cu/water systems, can provide useful insights into structural and transport properties of nanofluids in general.
The aim is to estimate the stability of Al2O3-ethylene glycol (EG) nanofluids using the particle size distribution and velocity ratio. The thermal conductivity and viscosity were measured under ...ultrasonic conditions for various time intervals, mass fraction (from 0 to 2.0 wt%), and temperature range (from 25 to 60 °C). Moreover, various criteria were presented to estimate the thermal performance in the convective heat transfer. Based on different sets of experimental data, new correlations and optimal artificial neural network models (ANN) were proposed. The results showed that Al2O3-EG nanofluids obtained by ultrasonation for 60 min exhibits the most encouraging properties. Moreover, the correlations for the experiment and ANN models can predict these two parameters. However, the ANN model is more precise. It is expected that the results to be useful for other studies of nanofluids stability especially since it recommends suitable selecting criteria based on heat transfer behavior before real applications.
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•The stability of Al2O3-EG nanofluids is estimated by size of nanoparticle and velocity ratio.•The heat transfer performance of nanofluids is estimated based on different criteria.•Correlations and ANN model are used to predict viscosity and thermal conductivity.
Iron-based MIL-88B and NH2-MIL-88B microcrystals with high dispersibility and uniform size were successfully synthesized by using a rapid microwave-assisted solvothermal method. By carefully ...controlling the reaction conditions, the microwave method provided superior quality MIL-88B crystals in high yields and excellent phase purity. Framework flexibility was observed for both MIL-88B-Fe and NH2-MIL-88B-Fe frameworks in various solvents, which however significantly differs between the two materials. MIL-88B-Fe shrinks reversibly by about 25% only when it is dispersed in the strongly hydrogen bonding solvents water or methanol. In contrast, NH2-MIL-88B-Fe shrinks up to 33% upon replacement of dimethylformamide (DMF) by any other solvent studied (benzene, chloroform, acetone, acetonitrile, methanol, water). The change in unit cell parameters (shortening of the a axis) can be seen macroscopically, although the overall integrity of the materials is maintained. We suggest that hydrogen bonding between the oxygen atoms of the MIL-88B-Fe framework and solvent molecules plays an important role in the framework shrinkage, while in the NH2-MIL-88B-Fe framework additional hydrogen bonds may form and thus a different breathing behavior is observed.
Crystals of MIL‐88B‐Fe and NH2‐MIL‐88B‐Fe were prepared by a new rapid microwave‐assisted solvothermal method. High‐purity, spindle‐shaped crystals of MIL‐88B‐Fe with a length of about 2 μm and a ...diameter of 1 μm and needle‐shaped crystals of NH2‐MIL‐88B‐Fe with a length of about 1.5 μm and a diameter of 300 nm were produced with uniform size and excellent crystallinity. The possibility to reduce the as‐prepared frameworks and the chemical capture of carbon monoxide in these materials was studied by in situ ultrahigh vacuum Fourier‐transform infrared (UHV‐FTIR) spectroscopy and Mössbauer spectroscopy. CO binding occurs to unsaturated coordination sites (CUS). The release of CO from the as‐prepared materials was studied by a myoglobin assay in physiological buffer. The release of CO from crystals of MIL‐88B‐Fe with t1/2=38 min and from crystals of NH2‐MIL‐88B‐Fe with t1/2=76 min were found to be controlled by the degradation of the MIL materials under physiological conditions. These MIL‐88B‐Fe and NH2‐MIL‐88B‐Fe materials show good biocompatibility and have the potential to be used in pharmacological and therapeutic applications as carriers and delivery vehicles for the gasotransmitter carbon monoxide.
Send and deliver: Spindle‐shaped crystals of MIL‐88B‐Fe with a length of about 2 μm and a diameter of 1 μm and needle‐shaped crystals of NH2‐MIL‐88B‐Fe with a length of about 1.5 μm and a diameter of 300 nm were produced with uniform size and excellent crystallinity (see picture). These materials show good biocompatibility and have potential pharmacological and therapeutic applications as carriers and delivery vehicles for the gasotransmitter CO.
In this paper, we describe a general method for the controlled synthesis of nanosized isoreticular metal−organic framework (IRMOF-n) crystals, which for the first time combine good monodispersity and ...crystallinity. Nano-IRMOF-1 and -3 crystals are produced as examples. TEM and SEM micrographs show nanocrystals with regular shape and uniform size of 200−300 nm. While powder X-ray diffraction data show a high degree of crystallinity, the BET surface area of the nano-IRMOF-1 crystals of ca. 3000 m2/g demonstrates the large internal pore volume. The nanocrystal growth mechanism under the assistance of hexadecyltrimethylammonium bromide (CTAB) as surfactant was studied by systematically changing the parameters of the preparation. The influence of each step in the preparation could be explained, and a rational synthesis protocol was thus obtained. Thereby, this work provides access to much-desired but difficult to obtain high-quality nano-MOF crystals through an optimized and rational synthesis. Moreover, the synthesis principles outlined herein should be transferable to other nanoporous materials with related growth mechanisms.
Two researchers independently identified and classified studies and the following data were extracted: (1) first author, year of publication, etc., and (2) primary outcomes, including left ...ventricular ejection fraction (LVEF, %), left ventricular end-diastolic volume (LVEDV, mL), left ventricular end-systolic volume (LVESV, mL), wall motion score index (WMSI, %), left ventricular end-diastolic internal diameter (LVDd, mm), infarct size (%), and the incidence of clinical events including death, recurrent myocardial infarction (MI), target vessel revascularization (TVR), and rehospitalization for heart failure (HF). In meta-analysis, BMCs transplantation can significantly increase LVEF (46 studies; MD: 1.84, 95% CI 1.19–2.48; I2: 30%, P = 0.03), and significantly reduced LVESV (35 studies; MD:–1.96, 95% CI –3.41 to –0.50; I2: 0%, P = 0.65), moreover LVDd (4 studies; MD = –1.59, 95% CI –3.08 to –0.11; I2: 1%, P = 0.39), WMSI (11 studies; MD: –0.08, 95% CI –0.14 to –0.01; I2: 44%, P = 0.06), and infarct size (16 studies; MD: –3.16, 95% CI –4.22 to –2.10; I2: 0%, P = 0.57), but no significant difference in LVEDV (37 studies; MD: –1.37, 95% CI –2.84 to 0.09; I2: 0%, P = 0.97) Supplementary Table 3, http://links.lww.com/CM9/B670. Transplantation of BMCs was associated with a significant reduction in the odds of rehospitalization for HF (14 studies; OR: 0.35, 95% CI 0.20–0.63; I2: 1%; P = 0.43), and demonstrated a trend toward decreased odds of recurrent MI (13 studies; OR: 0.59, 95% CI 0.33–1.06; I2: 0%, P = 0.86) that approached statistical significance (P = 0.08) Supplementary Table 3, http://links.lww.com/CM9/B670. ...over the medium term, BMCs transplantation was associated with a significant reduction in recurrent MI (4 studies; OR: 0.31, 95% CI 0.10–0.99; I2: 0%, P = 0.62), but not in death (5 studies; OR: 0.96, 95% CI 0.31–3.00; I2: 0%, P = 0.47), TVR (4 studies; OR: 0.74, 95% CI 0.42–1.32; I2: 0%, P = 0.66), and rehospitalization for HF (5 studies; OR: 0.36, 95% CI 0.10–1.27; I2: 0%, P = 0.90). Chin Med J 2023;136:2518–2520. doi: 10.1097/CM9.0000000000002799 References 1 Rizas, KD, McNitt, S, Hamm, W, Massberg, S, Kaab, S, Zareba, S, Prediction of sudden and non-sudden cardiac death in post-infarction patients with reduced left ventricular ejection fraction by periodic repolarization dynamics:
Layer-selective installation of functional groups at SURMOFs (surface-attached metal−organic framework multilayers) is reported. Multilayers of Cu(ndc)(dabco)0.5 grown in 001 orientation on ...pyridine-terminated organic self-assembled monolayers on Au substrates were functionalized with amino groups by step-by-step liquid-phase epitaxy. The method allows the growth of samples exhibiting one monolayer of functional groups at the external thin-film surface. In situ quartz crystal microbalance monitoring confirmed the presence of amino groups by turning the multilayer film from a non-reactive to a reactive material for covalent binding of fluoresceinisothiocyanate, and fluorescence microscopy displays the expected luminous property.
Nitrogen(N) addition can significantly improve the aboveground productivity of plants. The responses of reproductive strategies to N addition remain elusive for Leymus chinensis. Here, we examined ...the vegetative growth and clonal and sexual reproduction of a rhizome clonal grass, Leymus chinensis (Trin.) Tzvel, in response to N addition rates of 0, 2, 4, 8, 16, 32, and 64 g N m−2. N addition altered the reproductive strategy and allometric growth patterns of L. chinensis along the N addition gradient. N addition generally promoted higher investment in the biomass of vegetative and clonal organs, and a lower investment in sexual organs. N addition rates of 16 and 32 g N m−2 were key thresholds; 16 g N m−2 was the optimal rate for sexual reproduction and 32 g N m−2 was optimal for vegetative growth and clonal reproduction. At an addition rate of 16 g N m−2, the sexual reproductive capacity of L. chinensis was highest. Resource allocation to sexual reproduction increased with N addition, but decreased at rates>16 g N m−2. The growth and clonal reproduction of L. chinensis decreased at N concentrations>32 g N m−2. Our findings highlight that the reproductive strategy of L. chinensis varies with N addition rate, and the growth, sexual reproduction, and clonal reproduction strategies of L. chinensis are plastic, which has important implications for production.
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