•Facile fabrication process to prepare photoswitchable visualized platform is developed.•Azo is blended with PAA brush with cationic surfactant groups to assign photoswitchable function.•Geometry of ...PAA grating changes reversible with Azo structure under UV-light irradiation.•Geometry of PAA grating changes result the visualized color changes under UV-light irradiation.•Color of Azo-PAA grating switches from yellow to red under irradiation of UV-light.
Line arrays of poly(methacrylic acid) brush gratings (PBGs) were prepared to hybridize azobenzene (Azo) cationic surfactants. The change in the free volume of the Azo unit between the cis-state and its trans counterpart under 365-nm irradiation resulted in geometrical-parameter variations of the PBGs. The effective refractive index (neff) of the PBGs changed from 1.202 to 1.245 under 365-nm irradiation. To observe the color change under 365-nm irradiation, the correlation between the reflection wavelength and the reflection angle at a diffraction order ranging from 1 to 5 was established to obtain the optimal observation angle. The PBG exhibited yellow light initially, which was observed at 60°–70° by the naked eye. This is consistent with our prediction. The yellow changed to red under irradiation at 365 nm and returned to yellow under irradiation at 460 nm. The photomechanical (contraction and expansion) color of the dry polymer brush was reversible with repeated irradiation cycles, indicating potential for applications in photomanipulable sensors or actuators.
The heat transfer properties of current liquids are specifically improved by suspending nanocrystalline solid elements smaller than 100 nm in diameter. These liquids are considered as potential ...working fluids for applications such as car radiators, solar collectors, electronic frost systems, nuclear reactors and heat pipes. Due to such uses, here we formulate CuO–H
2
O nanofluids in a two-dimensional circular geometry with a rhombus-shaped barrier maintaining the constant temperature of two adjacent high walls. The streamlines and isotherms have been plotted using the control volume finite element method and applying the KKL model for nanofluid simulation. The results were calculated for different concentrations of nanoparticles, Hartmann number and Rayleigh number. It was found that in a large number of volume fraction and Hartmann number, the isotherms near the outer margin are more prominent while the low-volume-concentration isotherms are concentrated near the adiabatic wall of the obstacle. It was also found that there is a temperature gradient in the radial direction at a higher volume fraction and Hartmann number (Ha). The temperature gradient was limited to adiabatic walls of the obstruction in lower volume fraction and Ha. Two similar shapes but differently directed eddies are formed for any value of Ra in streamlines. |
Ψ
max
|
nf
increases with an increase in the values of Ra from 10
3
to 10
5
.
Calcium lignosulfonate (CaLS) is an organic anionic surfactant, which has been used for the first time as a charged additive to improve the performance of Pebax membranes for CO2 separation. Owing to ...the abundant hydrophobic groups and low charge density of lignosulfonate ion (LS2−), CaLS was found to efficiently interrupt the chain packing of Pebax 1657 matrix via both metal-organic complexation and hydrophobic interaction, endowing membranes with tunable fractional free volume (FFV). For dry membranes, CaLS could slightly enlarge membrane FFV without forming highly crosslinked structures. For humidified membranes, water-induced swelling led to a remarkable enhancement of FFV, while the hydrophobic interaction between CaLS and Pebax avoided excessive swelling. With the coexistence of CaLS and water, optimal FFV and moderate salting-out effect were acquired, resulting in very high CO2 permeability (3585Barrer) and fairly good CO2/gas selectivity (29 for CO2/CH4 and 71 for CO2/N2). The separation mechanism was discussed by analyzing the relationship between salting-out effect and the well-known solution-diffusion mechanism. Based on the performance comparison of Pebax–CaLS membrane with the previously reported Pebax–salt membranes, the guideline about the design of polymer electrolyte membranes for CO2 capture was tentatively proposed.
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•Calcium lignosulfonate was added in Pebax membrane for CO2 separation.•Membrane free volume property was synergically tuned by water and salt.•Efficient CO2 capture was gained by optimal microstructure and salting-out effect.
Introducción. La patología biliar es una causa frecuente de intervención quirúrgica, Pero en Colombia no se cuenta con datos oficiales de mortalidad ni volumen quirúrgico asociados a este ...procedimiento.
El objetivo de este estudio fue determinar el volumen de colecistectomías y describir la tasa general de mortalidad perioperatoria en seis regiones geográficas del país, en el periodo de 2012 a 2016.
Métodos. Estudio de cohortes retrospectivo que incluyó pacientes mayores de 18 años, afiliados al régimen contributivo de salud, llevados a colecistectomía. Se utilizó la base de datos de suficiencia de la Unidad de Pago por Capitación (UPC), la base de estadísticas vitales del Departamento Administrativo Nacional de Estadística (DANE) y la del Sistema Integrado de Información de la Protección Social (SISPRO).
Resultados. Durante el periodo de estudio, se realizaron 192.080 colecistectomías, lo que corresponde a 206 colecistectomías por 100.000 habitantes. Se encontró mayor volumen quirúrgico en personas entre los 65 y 80 años, en el sexo femenino y en la ciudad de Bogotá. La mortalidad perioperatoria encontrada correspondió al 0,6 %, siendo mayor en los pacientes de sexo masculino, de edad avanzada, en aquellos en quienes se practicó laparotomía y en los pacientes operados en la ciudad de Bogotá.
Discusión. De acuerdo con los hallazgos, esta investigación puede servir de base para estudios posteriores, que muestren claramente las cifras oficiales de volumen quirúrgico y de mortalidad por colecistectomía en Colombia.
Elastomer is one of the important materials for vibration and noise reduction. However, its narrow effective damping temperature range (tanδ ≥ 0.3) remains to be a major issue that hinders its ...application as a damping material. Herein, we precisely design and synthesize a polyurethane structure where specific dangling chains with both electron‐donating group and electron‐absorbing group were introduced into prepolymers, generating more hydrogen bonding interaction with the main chain to hinder microphase separation. At the same time, hyperbranched polyester as a cross‐linking agent increases its free volume effectively. The synergy effect of enhancement of hydrogen bonding, decrease of microphase separation, and increase of free volume results in a higher damping polyurethane elastomer with a great wider effective damping temperature range up to 175°C (−60°C‐115°C), which provides a new idea for the preparation of damping elastomer.
Diamond nanothread (DNT), a novel carbon-based nanomaterial exhibiting ultra-light density and outstanding mechanical properties, has attracted intensive attentions in polymer composites. This study ...investigates the influences of DNT on the glass transition temperature (Tg) of poly (methyl methacrylate) (PMMA) composites and reveals the glass-rubber transition mechanism through molecular dynamics simulation. We demonstrates that DNT exhibits better improvement than other carbon-based nanomaterials in enhancing the Tg of PMMA composite, suggesting that DNT is a promising reinforcement for polymer nanocomposite with higher service temperature and better mechanical performances. Significantly, we find that interfacial interactions including van der Waals interaction and mechanical interlocking play an important part in glass transition of PMMA composite. The transition from glassy state to rubbery is induced through the interfacial debonding brought by the enlargement of free volume at the interface. According to the interfacial degrading mechanism, cross links between DNT reinforcement and PMMA chains are introduced to provide bidirectional hindrance for free motions of polymer chains, resulting in a 70 K enhancement of Tg of PMMA composites. These findings not only shed light to the prospective application of DNT in advanced nanocomposite, but also provide important guidance to improve the reinforcing efficiency of nanomaterials in engineering application, such as building and aerospace industry.
For binary systems containing 1-Hexyl-3-methylimidazolium nitrate (HmimNO3) ionic liquid and a homolog series of 2-alkanols, new data of density and viscosity at different temperatures and ...atmospheric pressure have been reported. Temperature range is 293.15–323.15 K, and the considered alcohols are 2-propanol, 2-butanol, and 2-pentanol. Regarding these data, values of thermal expansion coefficient, α excess thermal expansion coefficient, αE excess molar volume, VmE and deviation in viscosity, Δη were calculated. Both excess molar volumes and viscosity deviations are negative over the whole concentration range. The magnitude and type of interactions were interpreted versus the temperature and increase of carbon atom of alcohols. Findings show that strong interactions in the mixtures occur relative to the pure state, and intermolecular forces are weaker in the long-chain alcohols. For correlation and prediction of systems density, the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was applied and results obtained from this theory are consistent with experimental data. Outcome densities from this theory were implemented for free volume theory to correlate the binary viscosities. Results are satisfactory with the maximum of 1.75% deviation from experimental viscosities. The whole data reported for binary systems are novel, and so far no reports have been investigated in scientific papers.
The potential use of an ultrafine flour fraction obtained by jet milling pulverization of a commercial white wheat flour in breadmaking was explored in this study. Three bread formulations were made ...by mixing the commercial flour with different levels of the ultrafine fraction (0, JM0, control; 50% JM50; and 100%, JM100), having flour median particle size values, d50, 75, 24 and 21 μm, respectively. With decreasing flour particle size the loaf specific volume, crust lightness and pore size decreased, whereas crust and crumb hardness increased. Upon storage, starch retrogradation, crumb hardness and crust moisture increased, while crust hardness, and crumb elasticity, cohesiveness and moisture decreased due to the staling events. A trained panel detected the changes in sensorial attributes upon storage, but differences between JM0 and JM100 breads (fresh and staled) were not perceived.
•Jet milled flours decrease loaf volume, crust lightness and pore size of breads.•Jet milled flours increase crust and crumb hardness and decrease crumb elasticity.•Bread sensory attributes are not affected by inclusion of jet milled flour.
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•Numerical simulations in new design cyclones with 1, 2 and 3 inlets are investigated.•RANS equation with the RSM model using Eulerian-Lagrangian method is solved.•To calculate the ...cyclone collection efficiency the Rosin-Rammler method is used.•The effect of number of cyclone inlets on new cyclone performance is investigated.•The results show the cyclone with three inlets has more η and less ΔP.
Numerical study of the fluid flow and particle dynamics is presented by numerical techniques to characterize the performance of new design cyclone separators with one, two and three tangential inlets. The design of this cyclone is based on the idea of improving cyclone performance by increasing the vortex length. This cyclone differs from a conventional cyclone with the separation space. Instead of conical part, the separation space of this cyclone consists of an outer cylinder and a vortex limiter. The Reynolds averaged Navier–Stokes equations with Reynolds stress turbulence model (RSM) are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the computational domain. The Eulerian-Lagrangian computational procedure is used to predict particles tracking in the cyclones. The velocity fluctuations are simulated using the Discrete Random Walk (DRW). In the results the effects of number of inlets on the different important parameters such as pressure drop, collection efficiency, axial velocity and turbulence are investigated and deeply discussed. Contours of velocity, pressure and turbulent kinetic energy within these cyclones with different number of inlets are shown. The results show that the cyclone with three inlets has more collection efficiency, less pressure drop and less turbulence distribution with respect to cyclones with one and two inlets which is good in cyclones performance. Generally it is recommended to use the new cyclone designs with higher number of inlets.
In this research, second law and exergy analysis for nanofluid turbulent flow due to inserting modified turbulators has been studied. Nanofluid behavior is predicted via single phase model. Finite ...volume method is considered to model the governing equations. Exergy loss and second law performance were calculated for various values of revolution angle and Reynolds number. Also good correlations have been offered according to outputs. Results indicate that second law performance is an augmenting function of revolution angle. Exergy loss enhances with decrease of revolution angle and Reynolds number.
•Exergy analysis of nanofluid heat transfer improvement is studied.•FVM is utilized as a simulation tool.•Exergy loss decreases with rise β and Re.•Second law performance has direct relationship with revolution angle.
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