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The dimensional characterization of capillary tubes is a recurring issue in microfluidic applications, since they are often used to connect microfluidic devices to injection and monitoring systems. In this work three experimental methods were applied and discussed for measuring the inner diameter of thin tubes, allowing the comparison and determination of the most accurate procedure, taking into account the application and involved measurement uncertainty. The methods analysed are based on (i) sizing by stereo microscope software, (ii) image analysis (binarization) and (iii) internal fluid mass. The results show that the three methods applied can provide accurate values, but the best choice in terms of simplicity and efficiency is that one based on image analysis.

Fluid blobs in an immiscible Newtonian fluid flowing in a capillary tube with varying radius show highly nonlinear behavior. We consider here a generalization of previously obtained results to blobs of non-Newtonian fluids. We compute here the yield pressure drop and the mean flow rate in two cases: (i) When a single blob is injected, (ii) When many blobs are randomly injected into the tube. We find that the capillary effects emerge from the non-uniformity of the tube radius and contribute to the threshold pressure for flow to occur. Furthermore, in the presence of many blobs the threshold value depends on the number of blobs and their relative distances which are randomly distributed. For a capillary fiber bundle of identical parallel tubes, we calculate the probability distribution of the threshold pressure and the mean flow rate. We consider two geometries: tubes of sinusoidal shape, for which we derive explicit expressions, and triangular-shaped tubes, for which we find that essential singularities are developed. We perform numerical simulations confirming our analytical results.

Evaporation-induced salt crystallization in complex porous structures is highly important for diverse scientific and industrial fields. Individual capillary tubes are elementary components used for investigating flow and transport in the interparticle interstices of porous media. In this study, the effects of the angularity and size of capillary tubes on water evaporation and salt crystallization were investigated through monitoring the receding meniscus, salt crystal morphology and growth process in capillary tubes with different cross sections. The Stefan diffusive and two-regional models were used to simulate evaporation from capillaries of different cross-sectional shapes in the absence and in the presence of salt, respectively. The evaporation process of deionized water in round tubes could be divided into two stages: the falling rate and the receding front stages. However, the evaporation process of deionized water for the square tubes, where a liquid film was formed, could be divided into three stages: a constant rate, receding front and falling rate stages. The salt evaporation rate was lower than that of deionized water owing to the lower water activity and obstruction from the salt crystals. The evaporation rate was proportional to the tube diameter for the round capillaries and inversely proportional to the inner side length of the square capillaries for both deionized water and the salt solution. Owing to the effect of thick liquid films on both the drying rate and ion transport, crystallization occurred in the bulk meniscus within a round tube, while crystallization preferentially occurred at the tube entrance for the square tubes. The agreement between the experimental observations and model simulations revealed that the two-region model was capable of describing the evaporation-induced salt crystallization in the square tubes.

DNA hydrogels have received considerable attention in analytical science, however, some limitations still exist in the applications of intelligent hydrogels. In this paper, we describe a way to prepare gel film in a capillary tube based on the thermal reversible principle of DNA hydrogel and the principle of capillary action. Because of the slight change in the internal structure of gel, its permeability can be increased by the addition of some specific targets. The capillary behavior is thus changed due to the different permeability of the hydrogel film. The duration time of the target solution flowing through the capillary tube with a specified length is used to quantify this change. With this proposed method, ultra-trace DNA hydrogel (0.01 μL) is sufficient to realize the sensitive detection of cocaine without the aid of other instruments, which has a low detection limit (1.17 nM) and good selectivity. DNA hydrogels have received considerable attention in analytical science but limitations still exist in the applications of intelligent hydrogels. Here, the authors describe a DNA hydrogel sensor for quantitative detection of cocaine based on the permeability change in a DNA hydrogel film.

Based on thermodynamic considerations, we derive a set of equations relating the seepage velocities of the fluid components in immiscible and incompressible two-phase flow in porous media. They necessitate the introduction of a new velocity function, the co-moving velocity. This velocity function is a characteristic of the porous medium. Together with a constitutive relation between the velocities and the driving forces, such as the pressure gradient, these equations form a closed set. We solve four versions of the capillary tube model analytically using this theory. We test the theory numerically on a network model.

In this paper, the performance of R600a was investigated in a household refrigerator originally designed to work with R134a using varied capillary tube length (1.0, 1.15, 1.30 and 1.45 m). The refrigerator was instrumented with four thermocouples at the inlet and outlet of the major components. Also, two pressure gauges were connected to the compressor to measure the suction and discharge of the compressor. The experimental results were used to evaluate the performance of the system. The results showed that at optimal capillary tube length the COP and cooling capacity of R600a in the system increased with 45% and 4.2% respectively and the power consumption reduced with 25% using 1.30 m varied capillary tube length compared to R134a. Conclusively, R600a can serve as a retrofit in the household refrigerator systems originally designed to work with R134a refrigerant.

In this research, the primary emphasis is placed on conducting experimental viscosity measurements of CF 3 I and subsequently developing empirical models using the obtained data to facilitate engineering system design calculations. Recognized for its non-explosive, low toxicity characteristics, and negligible contributions to ozone depletion and global warming, CF 3 I is identified as a promising candidate of a component for next-generation refrigerant mixtures. This potential arises from its advantageous thermodynamic properties, including a low boiling point and high critical temperature, making it a noteworthy component in refrigerant mixtures. The research employs the tandem capillary tube method to measure the viscosity of CF 3 I in both liquid and vapor phases. This approach, involving the series arrangement of two capillary tubes, is designed to neutralize the effects of the tubes, facilitating accurate viscosity measurement. Experimental data were collected at temperatures between 333 K and 374 K for the liquid phase and 333 K to 394 K for the vapor phase, under pressures ranging from 1.0 MPa to 4.0 MPa. Expanded uncertainties associated with these measurements were 2.22 % and 2.32 % for the liquid and vapor phases, respectively. Furthermore, the collected data were used to develop viscosity models for CF 3 I using the Extended Corresponding States and the modified Residual Entropy Scaling methods, effectively encapsulating the experimental findings within the calculated uncertainty limits. These models will also be useful for predicting the viscosity of any mixture refrigerant where CF 3 I is a constituent component.

With recent advances in molecular techniques, collecting blood from birds has become a common practice among field ornithologists. There are a variety of techniques for collecting blood samples and numerous caveats for how samples should be processed, depending on the research question being asked. Currently, few resources are available for individuals learning how to collect blood from birds or needing more information about how to process blood samples. Here, I describe commonly used methods for collecting, processing, and storing blood for particular research objectives, and provide answers to frequently asked questions about blood collection. The information provided is intended primarily for investigators working with passerines, but many techniques and suggestions are applicable to other avian taxa. Con los recientes avances en las técnicas moleculares, la colecta de sangre de las aves se ha convertido en una práctica común entre los ornitólogos de campo. Hay una variedad de técnicas para colectar muestras de sangre y numerosas advertencias de cómo deberán ser procesadas, en función a la pregunta de investigación. En la actualidad, hay pocos recursos disponibles para personas que están aprendiendo como colectar sangre de las aves, o para los que necesitan más información acerca de cómo procesar las muestras de sangre. Aquí, describo los métodos comúnmente utilizados para colectar, procesar y almacenar la sangre, dependiendo de los objetivos de la investigación en particular, y proveo respuestas a las preguntas más frecuentes acerca de la colecta de sangre. La información proporcionada está dirigida principalmente a los investigadores que trabajan con aves paseriformes, pero muchas técnicas y sugerencias son aplicables a otros grupos taxonómicos de aves.

By using clear vapor–liquid interface line images of the liquid inside the capillary, the measurement coordinate points of the vapor–liquid interface line were measured. A new method for measuring liquid contact angle has been proposed, which was used to calculate the actual coordinate points and fit the actual vapor–liquid interface line of the liquid. Finally, an angle measurement tool is used to measure the angle of the actual vapor–liquid interface line and obtain the actual contact angle of the liquid. Effectively reducing the influence of refraction on the contact angle by correcting the errors caused by the refractive index of different materials, it can be used for the precise measurement of the static contact angle of liquids. By measuring the static contact angle of the upper and lower liquid surfaces of the liquid column, it was found that the presence of refraction caused a difference of [1.84°, 5.61°] between the actual and measured values of the static contact angle.

Pore geometrical models are widely used to study transport in porous media, permeability, internal stability, and filter compatibility. Transport of fine grains through the voids between the skeleton of the coarser fraction is mainly controlled by the pore throats or constriction sizes. This study compares various constriction size distribution criteria and capillary tube models, which elucidate the limitations of the Kovacs capillary tube model, and this model is explained and developed. The new proposed threshold boundaries ( d 0 = 2 . 3 d 85 f and d 0 = 2 . 8 d 85 f ) categorized soil samples as internally stable, transient zone, or unstable. The model also incorporates the precise shape coefficient of particles. This improved model was validated based on a database from the literature, as well as performing 10 new experimental tests on two ideal gradation curves that identified the threshold boundary of Kenney and Lau criteria. This proposed model, which is dependent on grading, porosity, and grain shape, provides accurate predictions using a precise shape factor. This finding may enhance our knowledge about transport in porous media and contribute toward internal stability assessing for practical applications.