Latin American applied research

Dynamic manipulation of spherical yeast cells based on atomic force microscopy

Nowadays the importance of biological cells in life activities is not hidden to anyone. There is an increasing need to understand the biological processes and since the experiments which consider a group of cells to be analyzed can only give average biological results, research on single cell could be really beneficial. So single cell analysis has become an interesting topic in recent years. In such an analysis, one of the most important steps could be the ability to transport the single cell to exact locations. In this paper, the process of manipulation of spherical yeast cells based on atomic force microscopy (AFM) has been investigated. The dynamic governing equations have been considered and a simulation based on them gave the results of the analysis. In order to verify the obtaining results, a comparison has been made with an experimental work of another group. The simulation results show that the critical sliding force in manipulation process of yeast cell is 5.648 micro N and in the experiment this force was 6.661 micro N. So it seems that there is a negligible difference between these two amounts and the results of the simulation are correct. The biological liquid is ethanol in all the parts, but a comparison has been made between three liquids (ethanol, methanol and blood) in order to investigate the effect of environment on the results. The results show that the viscosity of the environmental liquid has more effect rather than its surface tension. The comparison between three important contact theories (JKR, DMT and Hertz) shows that there is a small difference between the critical times and forces of them. Also the contact depth and contact radius of the three models are compared to each other and they also confirmed the small differences between these three models

Washcoating of MnO_x on FeCralloy monoliths

Two MnOx catalyst as powder, prepared by decomposition of two different MnCO3, have been deposited on a FeCrAlloy® metallic monolith by means of washcoating using slurry concentration of 25 and 40 wt(%) (PM25, PM40 and AM25). When increase slurry concentration increase the amount of deposited material, but lower adhesion of solid retained is observed. The obtained monoliths showed excellent catalytic activity in the combustion of ethyl acetate and toluene, being the monoliths activity order: PM40 > AM25 > PM25. Nevertheless, the conversion g-1 and conversion m-2 show that PM25 is the more active monolith

Necessary condition on the onset of double-diffusive convection in couple-stress fluid in hydromagnetics saturated by a porous medium

In this paper, the effect of magnetic field on double-diffusive convection in couple-stress fluid saturating a porous medium is considered. By applying linear stability theory and normal mode analysis method, a necessary condition is derived which states that the viscoelastic double-diffusive convection at marginal state, cannot manifest as stationary convection if the thermal Rayleigh number R, the medium permeability parameter Pl the couple-stress parameter F, the stable solute gradient S, medium porosity e and the Chandrasekhar number Q, satisfy the inequality the result clearly established the stabilizing character of couple-stress parameter, stable solute gradient and magnetic field whereas destabilizing character of medium permeability and porosity

Application of nano-contact mechanics models in manipulation of biological nano-particle

Contact mechanics is related to the study of the deformation of solids that meet each other at one or more points. The physical and mathematical formulation of the problem is established upon the mechanics of materials and continuum mechanics. Contact mechanics gives essential information for the safe and energy efficient design of various systems. During manipulation process, contact forces cause deformation in contact region which is significant at nano-scale and affects the nano-manipulation process. Several nano-contact mechanics models such as Hertz, DMT (Derjaguin, Muller and Toporov), JKR (Johnson, Kendall, Roberts), BCP (Burnham, Colton, Pollock), MD (Maugis, Dugdale), COS (Carpick, Ogletree, Salmeron M ), PT (Pietrement, Troyon), and Sun have been applied as the continuum mechanics approaches at nano-scale. Recent studies show interests in manipulation of biological cells which have different mechanical properties. Low young modulus and consequently large deformation makes their manipulation so sensitive. In this article contact mechanics models are used for biological cell, in air and liquid environment, then results will be compared with Tatara contact mechanics model. Since biological cells are mostly modeled as visco- or hyper-elastic materials, this model will be more compatible with their condition

The utilization of wheat hull ash for the production of barium and calcium silicates

Wheat is the world's second most produced grain because of its high consumption rate, easy growth, multipurpose use and important role in the human diet. Every year, abundant amounts of wheat hull are obtained after shell process of the wheat as a waste material. Wheat hull, a by-product of the food industry, has low economic value. The utilization of wheat hull ash in various areas of industry can contribute to both financial and waste management strategies. In the present study, wheat hull ash that contains a high proportion of silica (43.22%), was utilized for barium and calcium silicate production. The wheat hull ash based barium and calcium silicate had a BET surface area of 30 and 54 m²/g, respectively. There has been no research on barium and calcium silicate production from wheat hull. So, this study will present originality on this area

Photocatalytic degradation of 2-chlorophenol by tio₂: kinetic studies

Kinetic studies of 2-chlorophenol photocatalytic degradation are carried out in a batch stirred built in quartz laboratory scale, using TiO2 as catalyst photoactived with ultraviolet light. Experimental design is performed using as independent variables or factors: catalyst concentration, catalyst calcinations temperature and initial concentration of 2-chlorophenol, to establish the best conditions of the degradation process. The experimental data were fitted with the Langmuir-Hinshelwood model. A kinetic constant k of 0.24 mg L-1min-1 was obtained

Photo-induced curing of thymine-based bioinspired polymers. a chemometric analysis

The curing process of new materials based on styrene monomers functionalized with thymine and charged ionic groups was studied using UV-vis spectroscopy in combination with chemometric models. The effect of the copolymer molecular weight on the immobilization point was analyzed. The evolution of the curing process of the copolymer (4-vinylbenzyl) thymine (VBT) -vinylbenzyl triethyl ammonium chloride (VBA) involved three species, which absorb in the spectral region analyzed. The contributions of each species to the total signal at each irradiation time were determined, and the kinetic constant of the crosslinking reaction was estimated. The study allowed evaluating the consistency of the chemometric decomposition, obtaining a reasonable correlation between the frequency spectra and the time evolution calculated with the algorithm. The chemometric analysis showed to be a powerful tool to provide complementary information on photo-induced immobilization of VBT-VBA films, which is crucial for developing new environmentally benign materials and new energy-saving methods

Copolymerization of Styrene and n-Butyl Acrylate with Itaconic Acid: Influence OF Carboxylic Groups Distribution on Performance of Decorative Paints

The main aim of this study is to understand the influence of itaconic acid (IA) on the colloidal properties of the latexes made by semi-batch emulsion copolymerization of styrene (St) with n-butyl acrylate (BA). A series of copolymerization were carried out with different IA concentrations to produce latexes for decorative paints. The effect of functional monomer on the conversion, colloidal properties of the latexes and the distribution of the carboxylic groups (buried, particle surface and serum) were investigated. The behavior of IA on wet scrub resistance of highly pigmented paints for architectural coatings was examined. The results obtained showed that the number of particles and polymerization rate both decreased with increase of the amount of IA. The properties of decorative paints are greatly dependent on the amount and carboxylic acid distribution. The carboxylic acid distributed in the aqueous phase has a strong influence on the characteristics of the final products

Cancelable biometrics for bimodal cryptosystems

Biometric-based techniques have recently emerged as a trustworthy and effective approach of user authentication; however, unlike conventional authentication methods such as passwords and tokens, if an enrolled biometric template is compromised, usually it cannot be revoked or re-issued. In this paper, four naive cancelable techniques, namely, shifting, password-dependent shifting, XOR and adding, for a bimodal biometric cryptosystem are presented. The proposed cancelable techniques are designed to be embedded into any bimodal biometric cryptosystem. The bimodal biometric cryptosystem uses speech and electrocardiogram signals as biometric information. The biometric cryptosystem implements an error-correction layer using the Hadamard code. The performance of the four cancelable techniques is assessed using ECG signals from MIT-BIH database and speech signals from a speech database created for testing purposes. The results show that the best performance in terms of FAR and FRR metrics is achieved with XOR and adding techniques

Numerical study of heat transfer by convection and thermal radiation in a ventilated room with human heat generation and co₂ production

The purpose of this work is to study the combined effect of heat generation produced by a human being and the mixed turbulent convection with thermal radiation, as well as the CO2 production from respiration. These factors are important to achieve healthy and pleasant indoor comfort conditions and to optimize the energy use in buildings. Numerical results in a rectangular ventilated room (3.0 m x 2.5 m) were carried out considering temperatures on the vertical walls of 298 and 308 K (25 and 35 °C) and the remaining walls were considered as adiabatic. The temperature surface of the human being was maintained at 307 K (34 °C). The inlet velocities were 0.05 m/s and 0.5 m/s, whereas the assumed emissivity values of the walls were 0.0 and 0.8. The mathematical model was solved numerically with software of Computational Fluid Dynamics. The flow patterns (streamlines), the temperature fields (isotherms) and CO2 concentration distributions are presented and discussed. Besides the heat transfer coefficients are reported. The results show that the natural ventilation reduces the average temperatures in the room between 4°C and 5.5°C, while the thermal radiation increases the average temperature between 0.2°C and 0.4°C

The yield zone concept and its application on a 4:1 abrupt contraction for an apparent-yield-stress fluid

The yield surface, a concept widely used in the literature that was born together with the Bingham model is discussed from the perspective of other models that are more related to apparent-yield-stress materials. As a consequence, it is necessary to define a yield zone, an intermediate transition region in the flow domain where plasticity manifests itself. A Galerkin Finite Element Method is used to investigate the performance of a SMD viscoplastic material through a 4:1 abrupt contraction. The influence of dimensionless parameters, like the Jump number and an equivalent to the Bingham number, on the size of the yield zone and on the pressure loss of the contraction are investigated

Tuantum chemical investigations of new conjugated compounds based on dithiobithiophene as solar cells materials

Thanks to their specific properties, The research in the organic p-conjugated molecules and polymers has become one of the most interesting topics in the fields of chemistry physics and materials science., these compounds have become the most promising materials for the optoelectronic device technology such as solar cells. In this work, The theoretical ground-state geometry and electronic structure of the studied molecules were investigated by the DFT method at B3LYP level with 6-31G(d) basis set has been performed to explore the optical and electronic properties of a series of different compounds based on bithiophene. Different electron side groups were introduced to investigate their effects on the electronic structure. The effects of the ring structure and the substituents on the geometries and electronic properties of these materials were discussed with the aim to evidence the relationship between molecular structure and optoelectronic properties. The theoretical knowledge of the HOMO and LUMO energy levels of the components is basic in studying organic solar cells so the HOMO, LUMO, Gap energy and Voc (open circuit voltage) of the studied compounds have been calculated and reported. These properties suggest these materials as a good candidate for organic dye-sensitized solar cells

Tuantum chemical investigations of new conjugated compounds based on dithiobithiophene as solar cells materials

Mathematical modelling of momentum, heat and mass transfer in grains stored in silos: Part I: model development and validation

A bidimensional finite element model that predicts temperature distribution, moisture migration and natural convection currents in stored grain is described. Validation was performed by comparing predicted and measured variables under laboratory conditions in corn and wheat. On average, standard errors were at most 1.7oC for temperature and 0.69 %w.b for moisture content. The sensitivity of the solution to variations in grain hygroscopic properties and to election of a sorption isotherm equation was examined. For a given temperature gradient, moisture migration was higher in soybean than in corn and wheat. As result of hygroscopic properties and permeability of grain, wheat exhibited the highest resistance to moisture migration

Mathematical modelling of momentum, heat and mass transfer in grains stored in silos: part II: Model application

A 2D finite element momentum, heat and mass transfer model was applied to predict natural convection flows, temperature distribution and moisture migration in soybean stored in a cylindrical bin without aeration from autumn to spring for the weather conditions of Rosario, Argentina. The effect of the initial moisture content and temperature of the grain (13%w.b and 25, 20 and 15°C) on storability conditions was evaluated. During winter, stronger natural convection flows developed for 25°C, promoting an average moisture migration of 0.4%w.b and average grain temperature decrease of 5°C at the bin bottom. For 20°C, these values reduced to 0.15%w.b and 3°C. For 15°C, safe conditions remained and moisture migration was negligible during winter, but in spring, solar radiation and natural convection increased the temperature of a boundary layer of 1.5 m width above 18°C. Interstitial equilibrium relative humidity remained below the threshold for mold development (ERH > 75%). During spring, natural convection increased as the initial grain storage temperature decreased. Permeability has the strongest effect on natural convection and a five fold increase of this parameter resulted in the development of spoilage areas in the upper part of the bin. Soybean and corn showed comparable moisture migration while for wheat was not significant

Speed of sound as a source of accurate thermodynamic properties of gases

A procedure for deriving thermodynamic properties of gases (the compression factor, the specific heat capacity at constant volume, and the specific heat capacity at constant pressure) from the speed of sound is presented. It is based on numerical integration of differential equations connecting the speed of sound with other thermodynamic properties. The set of differential equations is solved as the initial-boundary-value problem. The initial values of the compression factor and the specific heat capacity at constant volume are specified along the isochore in the perfect-gas limit, while the boundary values of the compression factor are specified along two isotherms at the lowest temperatures of the range. The procedure is tested on methane, ethane, and carbon dioxide. The average absolute deviations of the compression factor, the specific heat capacity at constant volume, and the specific heat capacity at constant pressure, from respective reference values, are 0.0001%, 0.004%, and 0.008%, respectively

Reduction of ethanol emissions using manganese oxides supported metallic monoliths: A pilot-scale plant study

Metallic monoliths were prepared by anodized aluminum-scale pilot plant, using sulfuric acid as electrolyte. Anodisation tests were conducted at different times and different temperatures of the electrolytic bath. Aluminum monolith anodized at 40°C for 30 min was selected for catalysts support. The monoliths were impregnated by two methods: i) impregnation in two stages using two Mn salts in an aqueous medium, and ii) impregnation using a KMnO4 solution in acetone. The last monolith presented a higher and a more homogeneous deposit of manganese oxide layer. The catalytic activity was tested in the total oxidation reaction of ethanol in a pilot-scale reactor at 50 L min-1, and ethanol concentrations of 900, 1800 and 3600 ppm. Monolith impregnated using acetone solution was more active that prepared in aqueous solution in all the experiments carried out

Latin American applied research

Dynamic manipulation of spherical yeast cells based on atomic force microscopy

Washcoating of MnOx on FeCralloy monoliths

Necessary condition on the onset of double-diffusive convection in couple-stress fluid in hydromagnetics saturated by a porous medium

Application of nano-contact mechanics models in manipulation of biological nano-particle

The utilization of wheat hull ash for the production of barium and calcium silicates

Photocatalytic degradation of 2-chlorophenol by tio2: kinetic studies

Photo-induced curing of thymine-based bioinspired polymers. a chemometric analysis

Copolymerization of Styrene and n-Butyl Acrylate with Itaconic Acid: Influence OF Carboxylic Groups Distribution on Performance of Decorative Paints

Cancelable biometrics for bimodal cryptosystems

Numerical study of heat transfer by convection and thermal radiation in a ventilated room with human heat generation and co2 production

The yield zone concept and its application on a 4:1 abrupt contraction for an apparent-yield-stress fluid

Tuantum chemical investigations of new conjugated compounds based on dithiobithiophene as solar cells materials

Tuantum chemical investigations of new conjugated compounds based on dithiobithiophene as solar cells materials

Mathematical modelling of momentum, heat and mass transfer in grains stored in silos: Part I: model development and validation

Mathematical modelling of momentum, heat and mass transfer in grains stored in silos: part II: Model application

Speed of sound as a source of accurate thermodynamic properties of gases

Reduction of ethanol emissions using manganese oxides supported metallic monoliths: A pilot-scale plant study

Washcoating of MnO_x on FeCralloy monoliths

Photocatalytic degradation of 2-chlorophenol by tio₂: kinetic studies

Numerical study of heat transfer by convection and thermal radiation in a ventilated room with human heat generation and co₂ production