Development of poly(urethane-ester)amide from corn oil and their anticorrosive studies

Corn oil-based poly(urethane-ester)amide was synthesized from corn oil-based fatty amide diol, camphoric acid, and tolylene 2,4-diisocyanate. The structure of corn polyesteramide and corn poly(urethane-ester)amide (CPEA) was confirmed by Fourier transform infrared, ¹H NMR, and ¹³C NMR spectroscopic techniques. CPUEA coatings were made on mild steel strips and their physicomechanical analysis (scratch hardness, impact test, conical mandrel test, and pencil hardness tests) was performed by standard methods. The surface morphology of coatings was observed by scanning electron microscopy and thermal stability was assessed by thermogravimetric analysis/differential scanning calorimetry. Anticorrosion properties of CPUEA were observed in acidic, saline, and tap water medium at room temperature using potentiodynamic polarization technique. The results of CPUEA coatings exhibit good physicomechanical and anticorrosive properties and can find application up to 175°C.     

Development of a multivariate model with desirability-based optimization for determination of atenolol and hydrochlorothiazide by eco-friendly HPLC method with fluorescence detection

Determination of a widely used antihypertensive combination of atenolol and hydrochlorothiazide was achieved by rapid and eco-friendly high-performance liquid chromatography method combined with fluorescence detection. The response surface methodology is conducive to the complete separation of the two drugs in a shorter analysis time. The separation of the mixture was achieved using an Inertsil C18 analytical column (150 × 4.6 mm, 5 µ). The mobile phase used was ethanol: potassium dihydrogen phosphate at pH 3 (65:35 v/v) and the flow rate was 0.7 mL/min. The fluorescence detector operated at excitation and emission wavelengths of 230 and 310 nm (atenolol) and 270 and 375 nm (hydrochlorothiazide). The linearity of the developed method covered a concentration of atenolol of 0.05–5 µg/mL and a concentration of hydrochlorothiazide of 0.02–1 µg/mL. The greenness of the developed method was evaluated by analytical eco-scale and the recently reported evaluation method, that is, green analytical procedure index, and it was found to be an excellent, sensitive, and green alternative to the reported methods. The developed method was validated according to the ICH guidelines and compared with the reference method. No significant difference was found in terms of accuracy.     

<Emphasis Type="Italic">G</Emphasis>-projectable and Λ-projectable binary linear block codes

The binary [24,12,8] Golay code has projection O onto the quaternary [6,3,4] hexacode [9] and the [32,16,8] Reed-Muller code has projection E onto the quaternary self-dual [8,4,4] code [6]. Projection E was extended to projection G in [8]. In this paper we introduce a projection, to be called projection Λ, that covers projections O, E and G. We characterise G-projectable self-dual codes and Λ-projectable codes. Explicit methods for constructing codes having G and Λ projections are given and several so constructed codes that have best known optimal parameters are introduced.      

Boosting COVID-19 Image Classification Using MobileNetV3 and Aquila Optimizer Algorithm

Currently, the world is still facing a COVID-19 (coronavirus disease 2019) classified as a highly infectious disease due to its rapid spreading. The shortage of X-ray machines may lead to critical situations and delay the diagnosis results, increasing the number of deaths. Therefore, the exploitation of deep learning (DL) and optimization algorithms can be advantageous in early diagnosis and COVID-19 detection. In this paper, we propose a framework for COVID-19 images classification using hybridization of DL and swarm-based algorithms. The MobileNetV3 is used as a backbone feature extraction to learn and extract relevant image representations as a DL model. As a swarm-based algorithm, the Aquila Optimizer (Aqu) is used as a feature selector to reduce the dimensionality of the image representations and improve the classification accuracy using only the most essential selected features. To validate the proposed framework, two datasets with X-ray and CT COVID-19 images are used. The obtained results from the experiments show a good performance of the proposed framework in terms of classification accuracy and dimensionality reduction during the feature extraction and selection phases. The Aqu feature selection algorithm achieves accuracy better than other methods in terms of performance metrics.     

Some boundary properties of holomorphic functions of several complex variables

A local uniqueness theorem and analogs of the theorem on removable singularities under the hypothesis of boundedness are proved for functions satisfying the tangential Cauchy-Riemann conditions on hypersurfaces in Cⁿ. The results can be interpreted as giving certain boundary properties of holomorphic functions of several complex variables.Translated from Matematicheskie Zametki, Vol. 23, No. 6, pp. 839–844, June, 1978.In conclusion I express my thanks to B. V. Shabat for his contant interest in this work.     

Simulating the equation of state of model globular proteins adsorbed at a surface

Monte Carlo computer simulation is used to follow the adsorption of a model globular and disordered protein at a hard surface and to simulate the surface equation of state for these molecules. The simulation utilizes the deformable globule model where the "protein" is treated as a collection of interacting subunits. Disordered globules are modeled as athermal molecules, whereas globular molecules have a strong attractive interaction between subunits. The surface equation of state is modeled by applying a known pressure to an adsorbed globule and following the changes in adsorbed conformation. Simulated equations of state for the disordered and globular molecules show features that are observed in experimental surface pressure versus area plots. In particular the simulated equations of state show "kinks" that correspond to regions where the adsorbed globules undergo conformational changes as they lift away from the surface in response to the increased pressure. The model proteins follow Bull's equation at low surface pressures in a way that is broadly in line with results from experiment, and the changes in conformation as a function of surface pressure are in line with predictions by DeFeijter and Benjamins made using a soft-particle model for adsorbed proteins.     

The use of dilute solution viscometry to characterize the network properties of carbopol microgels

We used dilute solution viscometry, specifically, measurements of intrinsic viscosity and overlap concentration to characterize two members of the carbopol family, carbopols 940 and 941. These measured quantities were then used to calculate the swollen-to-dry volume ratios for both resins over a range of ionic strengths. The variation in this ratio is representative of the swelling equilibria of the micronetwork and is modeled using standard network theory with modifications for non-Gaussian chain statistics and for fixed charges on the chains. By fitting to experimental data, the cross-link density is determined as 1450 monomer units between cross-link sites for carbopol 940 and 3300 units for carbopol 941. The shear modulus of the microgel domain is then predicted from the swelling data and found to be an order of magnitude greater than the elastic modulus measured on concentrated carbopol dispersions. We argue that this discrepancy is due to a large number of defects which reduce the cycle rank of the network. Current microgel technology specifies that their rheological behavior can be predicted once the domain cross-link density is known. Simple dilute solution viscometry appears capable of providing this prerequisite.     

Osmotic deswelling of microgels by linear polyelectrolytes

Polyacrylate microgels used as absorbers or viscosifiers in water are known to have these useful qualities reduced in the presence of linear poly-electrolytes. An osmotic deswelling mechanism is postulated whereby the counterions from linear chains sterically excluded from the gel act to draw solvent from the gel phase. This postulate is tested using intrinsic viscosity measurements of Carbopol microgels, made with the linear polyelectrolyte considered as parr of the solvent. The intrinsic viscosity is used to calculate the swollen-to-dry volume ratio for the microgel in the presence or absence of 0.1% linear sodium polyacrylate over a range in ionic strength. Simultaneously, a standard treatment for the free energy of a network of non-Gaussian chains containing fixed charges is modified to include the osmotic effect of the excluded counterions. In the absence of linear polymer, the theory is fit to the data, the fitting parameter being the 3100 monomer units between crosslink sites in the network. In the presence of high (350 000) molecular weight linear polymer, good agreement is found between the observed deswelling and that predicted if the linear chains are totally excluded. Lower molecular weight linear chains are found to give a reduced deswelling which is shown to be self-consistent with their partitioning into the network.Presented in part at the 64th Colloid and Surface Science Symposium, Lehigh University, June 1990     

Use of iridium oxide films as hydrogen gas evolution cathodes in aqueous media

Hydrous iridium oxide films are highly resistant to reduction under cathodic, hydrogen gas evolution, conditions in aqueous acid or base. Such behavior is not in agreement with simple thermodynamic (Pourbaix) data based on the assumption that the system behaves in a reversible manner. The barrier to reduction is attributed, as discussed earlier for RuO₂, to the involvement of high-energy intermediates (iridium atoms or microclusters of same) which can only be generated at unusually negative overpotential values evidently far into the hydrogen gas evolution region. Thermally prepared IrO₂/Ti electrodes are possible candidates for hydrogen gas evolution cathodes in water electrolysis cells; however, under extended operating conditions, the performance of these cathodes was found to deteriorate due to gradual shedding of the active oxide layer.