Next generation of low global warming potential refrigerants: Thermodynamic properties molecular modeling

The recent global agreement signed in Kigali to limit the use of hydrofluorocarbons (HFCs) as refrigerants, starting by 2019, has promoted an active area of research toward the development of low global warming potential (GWP) new refrigerants. Hydrofluoroolefins (HFOs) have been proposed as a low GWP alternative to third generation HFC refrigerants, but further work on fully characterizing them and their blends with other compounds is still required to fully assess their performance to replace the ones in current use. In this work, the polar and perturbed chain statistical associating fluid theory coupled with the density gradient theory is used to predict the vapor–liquid equilibrium, isobaric heat capacity, speed of sound, and surface tension of selected HFC and HFO‐based commercial azeotropic blends as fourth generation low GWP refrigerants, seeking for a predictive tool for these properties. © 2017 American Institute of Chemical Engineers AIChE J, 63: 250–262, 2018     

Dielectric properties of thin films of Babassu‐based polymer and polyaniline blends

In the present work, we describe the preparation and subsequent characterization of polymeric blends consisting of a monoglyceride (MG) synthesized from the Babassu's oil and the already commonly employed polyaniline (PAni). By following changes in the complex impedance of capacitor‐like devices we observe that the presence of MG in the PAni/MG blends decreases electrical conductivity and that this decrease is a function of the content of MG in the blend, i.e., the blend with 30% of MG shows Z′ about seven times greater than the one with 10% of MG. Fourier transform infrared measurements prove the formation of MG and the presence of secondary amine groups (N? H bonds) in the blends, which allow for the chemical doping of PAni by protonation, further studies are necessary to access the viability of employing this new material as active layer in electronic organic devices. Atomic force microscopy images show the formation of agglomerates due to the presence of MG. In addition, the polymeric mixture acts only as a blend, providing a physical interaction between different components. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46198.     

Reaction of ozone with polybenzimidazole (PBI)

Ozone reacted with the polybenzimidazole (PBI) film surface and X-ray photoelectron spectroscopy (XPS) detected a rapid increase in O atom concentration up to a saturation level of 27 ± 1 atomic %. Atomic force microscopy measurements showed little change in surface roughness. The water contact angle of the treated film decreased by ca. 60% compared to untreated PBI film indicating an increase in hydrophilicity and hydrogen bonding due the formation of the polar oxygenated functional groups. With treatment, the curve fitting of the XPS chemical states showed a decrease in the C–C sp², C–C sp³, and C=N functional groups, and an increase in C–N, C=O, O–C=O, O–(C=O)–O, and N–C=O moieties which were explained using mechanisms associated with the dissociation of the primary ozonide formed from the addition of ozone to the C=C and C=N bonds and reaction with the amine groups in PBI. Washing the treated surface with water partially washed away the O concentration which indicated the formation of a weak boundary layer due to the breakage of bonds in the decomposition of the primary ozonide.     

Expression of TRPV4 in the zebrafish retina during development

The transient receptor potential (TRP) channels are involved in sensing mechanical/physical stimuli such as temperature, light, pressure, as well as chemical stimuli. Some TRP channels are present in the vertebrate retina, and the occurrence of the multifunctional channel TRP vanilloid 4 (TRPV4) has been reported in adult zebrafish. Here, we investigate the expression and distribution of TRPV4 in the retina of zebrafish during development using polymerase chain reaction (PCR), Western blot, and immunohistochemistry from 3 days post fertilization (dpf) until 100 dpf. TRPV4 was detected at the mRNA and protein levels in the eye of zebrafish at all ages sampled. Immunohistochemistry revealed the presence of TRPV4 in a population of the retinal cells identified as amacrine cells on the basis of their morphology and localization within the retina, as well as the co-localization of TRPV4 with calretinin. TRPV4 was first (3 dpf) found in the soma of cells localized in the inner nuclear and ganglion cell layers, and thereafter (10 dpf) also in the inner plexiform layer. The adult pattern of TRPV4 expression was achieved by 40 dpf the expression being restricted to the soma of some cells in the inner nuclear layer and ganglion cell layers. These data demonstrate the occurrence and developmental changes in the expression and localization of TRPV4 in the retina of zebrafish, and suggest a role of TRPV4 in the visual processing.     

Cyclic beta-(1,2)-glucan synthesis in Rhizobiaceae: roles of the 319-kilodalton protein intermediate

Cyclic beta-(1,2)-glucans are synthesized by members of the Rhizobiaceae family through protein-linked oligosaccharides as intermediates. The protein moiety is a large inner membrane molecule of about 319 kDa. In Agrobacterium tumefaciens and in Rhizobium meliloti the protein is termed ChvB and NdvB, respectively. Inner membranes of R. meliloti 102F34 and A. tumefaciens A348 were first incubated with UDP-[14C]Glc and then solubilized with Triton X-100 and analyzed by polyacrylamide gel electrophoresis under native conditions. A radioactive band corresponding to the 319-kDa protein was detected in both bacteria. Triton-solubilized inner membranes of A. tumefaciens were submitted to native electrophoresis and then assayed for oligosaccharide-protein intermediate formation in situ by incubating the gel with UDP-[14C]Glc. A [14C]glucose-labeled protein with an electrophoretic mobility identical to that corresponding to the 319-kDa [14C]glucan protein intermediate was detected. In addition, protein-linked radioactivity was partially chased when the gel was incubated with unlabeled UDP-Glc. A heterogeneous family of cyclic beta-(1,2)-glucans was formed upon incubation of the gel portion containing the 319-kDa protein intermediate with UDP-[14C]Glc. A protein with an electrophoretic behavior similar to the 319-kDa protein intermediate was "in gel" labeled by using Triton-solubilized inner membranes of an A. tumefaciens exoC mutant, which contains a protein intermediate without nascent glucan. These results indicate that initiation (protein glucosylation), elongation, and cyclization were catalyzed in situ. Therefore, the three enzymatic activities detected in situ reside in a unique protein component (i.e., cyclic beta-(1,2)-glucan synthase). It is suggested that the protein component is the 319-kDa protein intermediate, which might catalyze the overall cyclic beta-(1,2)-glucan synthesis.     

Robust control of wind turbines based on fractional nonlinear disturbance observer

In order to assure maximum energy conversion, the angular velocity of the wind turbine rotor tracks a nominal profile depending on the wind speed. However, conventionally, wind flows present non‐differentiable components due to turbulence and gust winds, which affect the wind energy management. Thus, a fast and robust controller is required to induce such nominal regime for maximum energy transfer. A fractional‐order nonlinear disturbance‐observer (FNDOB) is proposed in this paper to cancel the non‐differentiable components of the wind speed, as well as dynamic uncertainties and other aerodynamic disturbances. The proposed FNDOB is based on continuous fractional sliding modes, assuring that disturbances and uncertainties are exactly compensated in finite‐time. A representative simulation study for a variable‐speed wind turbine is presented to show the reliability of the proposed scheme, and a comparative analysis with respect to a conventional linear disturbance observer based control is presented.     

Continuous Fractional‐Order Sliding PI Control for Nonlinear Systems Subject to Non‐Differentiable Disturbances

Aiming at designing a robust controller to withstand a class of continuous, but not necessarily differentiable, disturbances, such as Hölder type, a continuous and chattering‐free sliding mode control is proposed. The key idea is a judicious synthesis of a resetting memory principle for the differintegral operators to show that a sliding mode is induced, and sustained, in finite‐time, to guarantee asymptotic tracking. The closed‐loop system achieves exact rejection of Hölder disturbances even in case of uncertain flow, but assuming certain knowledge of the input matrix. Furthermore, it is shown that our methodology generalizes continuous high‐oder sliding mode schemes by using an integral action of fractional‐order. A representative simulation study is discussed to show the feasibility of the proposal.     

Kinetic and Mass Transfer Model for Separation of Protein Using Ceramic Monoliths as a Stationary Phase

Rigid adsorbents used as matrix skeleton have advantages over soft gel media for downstream processing of proteins. The adsorption of bovine serum albumin (BSA) has been investigated on a rigid ceramic monolith coated with cross-linked microporous agarose (D5). The physical properties of the adsorbent and the adsorption equilibria, adsorption kinetics, and mass transfer behavior have been studied for five different flow rates, with a pH value ranging from pH 4.5 to 7.0. The optimal working flow rate was 14.0?cm³/min, and using this flow rate, increasing the pH does not generate a significant improvement in the adsorption capacity. The rates of BSA adsorption have been measured and it was possible to describe a theoretical model, in which the mass transfer involves a dispersion coefficient (k_disp), which describes the mass transfer in the adsorbent surface, from the volume of the protein solution to the agarose surface. This parameter presents an exponential tendency by increasing the flow rate from 2.37?×?10^?6 to 87.40?×?10^?6?cm/s for n?=?1. Values obtained for the adsorption kinetic constant (k_ads) followed the trend of the mass transfer parameter, increasing with the flow rate from 1.94?×?10⁴ to 117.39?×?10⁴?cm²/mol?s. The theoretical model predicts the protein concentration in equilibrium for successive column reuses and it can be readily used to determine the optimal reuse of column. Likewise, for a maximum flow rate of 14?cm³/min, pressure drop was 0.04?MPa, being an advantage in front of packed columns that have higher pressure drop.     

Potential for carrying dyes derived from spalting fungi in natural oils

Wood colored internally by fungi has long been used by woodcrafters and artisans as a substitute for synthetic dyes. Recent advances in the field of spalted wood have led to methods by which the fungal dyes can be extracted from either a fungal solution or colonized wood and then reapplied to clear wood. This takes the “guess work” out of spalting, as well as the time necessary for fungal colonization; however, it requires organic solvents like dichloromethane, which are toxic and not readily available to consumers. Herein, the authors show that the dyes can be successfully carried and blended together (to increase the range of colors) in a range of natural oils. The blue–green dye of Chlorociboria species, called xylindein, carried best in raw linseed oil, the red dye of Scytalidium cuboideum performed best in Danish oil, although more dye could be carried in raw linseed oil, and the yellow dye of Scytalidium ganodermophthorum performed best in walnut oil. The ability to carry and mix these dyes in easily purchased, nontoxic oils opens up their use to woodworkers who seek to follow the traditions of spalted wood, but do not have the skills or time to work with live fungal cultures or fungal dyes suspended in toxic organic solvents.     

Preparation and characterization of poly(vinyl chloride)/virgin and treated sisal fiber composites

Mechanical property changes, thermal stability, and water absorption capacity of poly(vinyl chloride) (PVC)/sisal fiber composites were assessed with respect to the effect of maleic anhydride chemical treatments of the sisal fiber, for five different sisal fiber contents, varying from 0 to 30% by weight in the composite. The composites prepared with the untreated sisal exhibited higher tensile modulus and hardness than the unloaded resin, while elongation and tensile strength were reduced. The deterioration in the mechanical properties of PVC blended with sisal fiber is attributed to the presence of moisture, interfacial defects at the fiber and polymer interface, and fiber dispersion in the PVC matrix. The amount of absorbed water is a function of the amount of fiber in the composite (F0 = 0 phr, F5 = 0.77 phr, and F20 = 4.83 phr). The comparison of the results of characterization of F5, F20, and F30 formulations prepared with the untreated fibers and the treated ones showed a reduction in absorbed water after the chemical treatment of fiber with maleic anhydride (F0 = 0 phr, F5 = 0.28 phr, and F20 = 2.99 phr), thus improving the mechanical properties of composites prepared with the treated sisal. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3630–3636, 2007