An approach to reduce energy consumption and performance losses on heterogeneous servers using power capping

Journal of Scheduling - Rapid growth of demand for remote computational power, along with high energy costs and infrastructure limits, has led to treating power usage as a primary constraint in...     

Effect of lanthanum-modified magnesium silicate on isotactic polypropylene crystallization in composite materials during shear flow

The activity of isotactic polypropylene (iPP) nucleating additives during shear flow of composite materials is still not entirely explained. In current work the sol-gel method was employed to synthesize MgO·SiO₂ filler, surface-modified with trivalent lanthanum. The crystallization of commercial iPP in the presence of 0.5% by weight La³⁺ modified or unmodified silicates was analyzed. The wide angle X-ray scattering analysis proved that the presence of even small amount of filler influences significantly on supermolecular structure of iPP. The results of microscope observations confirmed that the lanthanum-modified filler shows the nucleating ability for iPP. In that case a significant reduction of crystallization induction time was noticed. The investigation of iPP crystallization in composites after shear treatment confirmed that the increase of shear rate reduces the nucleating ability of additives. Moreover, the flow of filler particles during shearing may impede the shear-induced crystallization phenomenon.     

Influence of selected alkoxysilanes on dispersive properties and surface chemistry of spherical silica precipitated in emulsion media

The process of silicas formation in emulsion system in the reaction of precipitation from water solutions of sodium silicate and hydrochloric acid has been studied. The effects of silica surface modifications with silane coupling agents from the group of alkoxysilanes with different functional groups have been determined. Both unmodified and modified silicas have been thoroughly characterised by scanning electron microscopy (SEM) and dynamic light scattering (DLS) and other methods.The effect of alkoxysilanes on the diameter distribution of the modified silica is insignificant; the presence of silane coupling agents causes a small increase in the particle diameter and a small increase in the tendency towards agglomeration, moreover the particles of silicon dioxide precipitated are characterised by spherical shape. The course of the electrokinetic curves depends mainly on the proton affinity of the modifiers. Significant changes in the stability of silica dispersions have been found as a result of modification with N-2-(aminoethyl)-3-aminopropyltrimethoxysilane. This compound causes the greatest increase in the tendency towards agglomeration of the primary particles. The modification mechanism has been established to be chemisorption, as indicated by the ¹³C and ²⁹Si CP MAS NMR spectra. The products have been shown to have typical mesoporous structure. The surface area of the unmodified silica is 133 m²/g, while those for the modified silicas vary from 115 to 182 m²/g.     

Removal of Persistent Sulfamethoxazole and Carbamazepine from Water by Horseradish Peroxidase Encapsulated into Poly(Vinyl Chloride) Electrospun Fibers

Enzymatic conversion of pharmaceutically active ingredients (API), using immobilized enzymes should be considered as a promising industrial tool due to improved reusability and stability of the biocatalysts at harsh process conditions. Therefore, in this study horseradish peroxidase was immobilized into sodium alginate capsules and then trapped into poly(vinyl chloride) electrospun fibers to provide additional enzyme stabilization and protection against the negative effect of harsh process conditions. Due to encapsulation immobilization, 100% of immobilization yield was achieved leading to loading of 25 μg of enzyme in 1 mg of the support. Immobilized in such a way, enzyme showed over 80% activity retention. Further, only slight changes in kinetic parameters of free (K_m = 1.54 mM) and immobilized horseradish peroxidase (K_m = 1.83 mM) were noticed, indicating retention of high catalytic properties and high substrate affinity by encapsulated biocatalyst. Encapsulated horseradish peroxidase was tested in biodegradation of two frequently occurring in wastewater API, sulfamethoxazole (antibiotic) and carbamazepine (anticonvulsant). Over 80% of both pharmaceutics was removed by immobilized enzyme after 24 h of the process from the solution at a concentration of 1 mg/L, under optimal conditions, which were found to be pH 7, temperature 25 °C and 2 mM of H₂O₂. However, even from 10 mg/L solutions, it was possible to remove over 40% of both pharmaceuticals. Finally, the reusability and storage stability study of immobilized horseradish peroxidase showed retention of over 60% of initial activity after 20 days of storage at 4 °C and after 10 repeated catalytic cycles, indicating great practical application potential. By contrast, the free enzyme showed less than 20% of its initial activity after 20 days of storage and exhibited no recycling potential.     

Analysis of Fluidized Bed Drying Kinetics on the Basis of Interphase Mass Transfer Coefficient

A particular way to define fluidized bed drying kinetics on the basis of interphase mass transfer coefficient and the conception of general kinetic curve has been described. The presented method, which allows for minimization of laboratory tests, has been checked experimentally. The method for calculating of mass transfer interphase coefficient in the constant rate period of fluidized bed drying based on Kunii and Levenspiel bubbling bed model is shown.     

Analysis of Fluidized Bed Drying Kinetics on the Basis of Interphase Mass Transfer Coefficient

A particular way to define fluidized bed drying kinetics on the basis of interphase mass transfer coefficient and the conception of general kinetic curve has been described. The presented method, which allows for minimization of laboratory tests, has been checked experimentally. The method for calculating of mass transfer interphase coefficient in the constant rate period of fluidized bed drying based on Kunii and Levenspiel bubbling bed model is shown.     

The Influence of Spray Drying on the Dispersive and Physicochemical Properties of Magnesium Oxide

Magnesium hydroxide was obtained in a precipitation reaction with the use of magnesium nitrate or magnesium sulphate and sodium hydroxide. The influence of the temperature of the process, the mode and rate of substrate supply, as well as the concentration and ratio of the substrates on the product's properties, were tested. The intermediate product Mg(OH)₂ was subjected to drying by static and spray techniques followed by calcination to obtain magnesium oxide. To establish the effect of the synthesis conditions and drying techniques on the dispersive and physicochemical properties of the magnesium oxide obtained, this product was characterized using a number of experimental methods to obtain the bulk density, polydispersity index, and particle size distribution in the nano- and micrometric ranges. Moreover, the wettability profiles in water system were examined. For selected magnesium oxide samples the crystalline structure was determined by the WAXS method, and adsorptive properties (surface area, volume, and size of pores) as well as electrical properties (dielectric permittivity and electrical conductivity) were measured. Application of all the above-mentioned methods enabled a comprehensive characterization of the products and revealed a significant effect of spray drying on their properties, in particular on their dispersion and morphology.     

Batch Drying Kinetics in a Two-Zone Bubbling Fluidized Bed

This article deals with investigation and modeling of batch drying process of solids in fluidized bed apparatus. There has been used model of fluidized bed drying, which consists two zones: emulsion zone and bubbling zone with taking into consideration the presence of solid particles in the bubbles. The results of theoretical expectations that arise from simulation calculations have been verified with experimental data obtained with the use of fluidized bed dryer 0.225 m in diameter. A drying process of silica gel, sand, and ammonium sulfate has been tested. To verify the model, the concept of a generalized drying curve has also been employed.     

Determination of composition and structure of spongy bone tissue in human head of femur by Raman spectral mapping

Biomechanical properties of bone depend on the composition and organization of collagen fibers. In this study, Raman microspectroscopy was employed to determine the content of mineral and organic constituents and orientation of collagen fibers in spongy bone in the human head of femur at the microstructural level. Changes in composition and structure of trabecula were illustrated using Raman spectral mapping. The polarized Raman spectra permit separate analysis of local variations in orientation and composition. The ratios of ν₂PO₄ ³⁻/Amide III, ν₄PO₄ ³⁻/Amide III and ν₁CO₃ ²⁻/ν₂PO₄ ³⁻ are used to describe relative amounts of spongy bone components. The ν₁PO₄ ³⁻/Amide I ratio is quite susceptible to orientation effect and brings information on collagen fibers orientation. The results presented illustrate the versatility of the Raman method in the study of bone tissue. The study permits better understanding of bone physiology and evaluation of the biomechanical properties of bone.     

Physicochemical studies on precipitated magnesium silicates

In this study, an attempt was made to obtain highly dispersed magnesium silicates which could be employed as polymer fillers or active adsorbents. Due to numerous applications of magnesium silicates and silicates of other metals, three procedures were suggested for production of their synthetic equivalents. The precipitation processes were optimized in respect to temperature, reagent dosing rate, rate of mixing them, substrate concentration, etc. In the process of magnesium silicate precipitation 5% solutions of sodium metasilicate (water glass) and magnesium sulphate(VI) were used. In order to broaden application range of synthetic magnesium silicates they were subjected to surface hydrophobization (for the purpose non-ionic surfactants were used) and surface modification (using silane pro-adhesive compounds). All the unmodified and modified samples were subjected to a broad physicochemical analysis. Chemical composition of unmodified magnesium silicates was determined using atomic adsorption spectrometry. In addition particle diameters were estimated in all the samples. Effective particle diameter, polydispersity were defined, particle size distributions were estimated using dynamic light scattering (DLS technique). Principal adsorptive properties were established to check up whether the obtained in laboratory synthetic magnesium silicates can be applied as adsorbents. This was executed by determination of nitrogen adsorption/desorption isotherms on the surface of magnesium silicates. Moreover, taking advantage of the isotherms, specific surface area, diameter and volume of pores were estimated.