Extruded colour-based plastic film for the measurement of dissolved CO2

Dissolved CO2 measurements are usually made using a Severinghaus electrode, which is bulky and can suffer from electrical interference. In contrast, optical sensors for gaseous CO2, whilst not suffering these problems, are mainly used for making gaseous (not dissolved) CO2 measurements, due to dye leaching and protonation, especially at high ionic strengths (>0.01 M) and acidity (<pH 4). This is usually prevented by coating the sensor with a gas-permeable, but ion-impermeable, membrane (GPM). Herein, we introduce a highly sensitive, colourimetric-based, plastic film sensor for the measurement of both gaseous and dissolved CO2, in which a pH-sensitive dye, thymol blue (TB) is coated onto particles of hydrophilic silica to create a CO2-sensitive, TB-based pigment, which is then extruded into low density polyethylene (LDPE) to create a GPM-free, i.e. naked, TB plastic sensor film for gaseous and dissolved CO2 measurements. When used for making dissolved CO2 measurements, the hydrophobic nature of the LDPE renders the film: (i) indifferent to ionic strength, (ii) highly resistant to acid attack and (iii) stable when stored under ambient (dark) conditions for >8 months, with no loss of colour or function. Here, the performance of the TB plastic film is primarily assessed as a dissolved CO2 sensor in highly saline (3.5 wt%) water. The TB film is blue in the absence of CO2 and yellow in its presence, exhibiting 50% transition in its colour at ca. 0.18% CO2. This new type of CO2 sensor has great potential in the monitoring of CO2 levels in the hydrosphere, as well as elsewhere, e.g. food packaging and possibly patient monitoring.

Banana and abaca fiber-reinforced plastic composites obtained by rotational molding process

Natural fibers can be used in rotational molding process to obtain parts with improved mechanical properties. Different approaches have been followed in order to produce formulations containing banana or abaca fiber at 5% weight, in two- and three-layer constructions. Chemically treated abaca fiber has also been studied, causing some problems in processability. Fibers used have been characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), optical microscopy, and single-fiber mechanical tests. Rotomolded parts have been tested for tensile, flexural, and impact properties, demonstrating that important increases in elastic modulus are achieved with these fibers, although impact properties are reduced. © 2013 Copyright Taylor and Francis Group, LLC.

Influence of loggerhead egg agregation on survival: why does single eggs buried into natural sand dye in few days?

[EN] The incubation is an essential life period for oviparous species that very often experiences a high mortality. In some reptile species the number of eggs that develop together in the incubation chamber affects survival and hatchling phenotype. Sea turtle eggs develop in underground locations on sandy beaches in large masses that usually have more than 80 eggs. Natural egg mortality seems to vary among species and for the sensitive leatherbacks, external eggs seems to survive better than internal ones within the nest.

Evaluation of Cross Correlation Technique to Measure Flow in Pipes of the Oil Industry

The present work is concerned with the use of the cross correlation technique to measure delay time between two simulated signals displaced with respect to time, in order to develop a cross correlator system that will be used to measure the water and oil pipes flowrate in which the detection system is composed by two external low intensity radiation sources located along the tube and two NaI(Tl) gamma-ray detectors. The final purpose of the correlator system is to use the natural disturbances, as the turbulence in the own flow rather than to inject radioactive tracers to the fluid flow as usually is carried out. In the design of this correlator is evaluated the point-by-point calculation method for the cross correlation function in order to produce a system accurate and fast. This method is divided at the same time in three modes of operation: direct, relay and polarity.

Hybrid formulation solution for stress analysis of curved pipes with welded bending joints

A method is presented for evaluating the stress intensity factor of part-through cracks in a thin pipe elbow. A hybrid formulation solution is used to evaluate the stress field close to the crack area. The stress field values are then inputted into a previously developed method published in the literature to evaluate the stress intensity factor in cylindrical shells. Results from cylindrical shells with part-through cracks are extended to double-curvature pipe configurations that contain the same kind of flaw.