EXTRACTION OF TITANIUM(IV) BY MIXTURES OF MONO- AND DH(2-ETHYLHEXYL) PHOSPHORIC ACID ESTERS

ABSTRACT

Solvent extraction of titanium(IV) from hydrochloric acid solutions by mixtures of mono- and di-2-ethylhexyl phosphoric acid esters (MEHPA and DEHPA) has been investigated as a function of HC1 concentration in the aqueous phase and extractants concentration in the organic phase

It was found that MEHPA extracts Ti, 3 orders of magnitude more efficiently than DEHPA. Efficiency of extraction by MEHPA does not depend on acid concentration in the aqueous phase in the range of 0·1 – 8·8 mole/Kg. As a rule Ti/MEHPA ratio in the complex is 1/2. At low aqueous phase acidities (0·1–1·0 mole/Kg HCl) formation of six- (or eight-) coordinate bidentate hydrated Ti(IV)-2MEHPA complexes is suggested. At acidities above 7·0 mole/Kg HC1 titanium forms tridentate six- (or eight-) coordinate complexes. At medium acidities (2·0–6·0 mole/Kg HCl) mixtures of these complexes are formed. Prolonged mixing of the phases or aging of the organic phase leads to dehydration and to transformation of bidentate to tridentate Ti-2MEHPA complexes. Ti-2MEHPA complexes are colorless

At ratios Ti/MEHPA<0·5 formation of Ti-MEHPA hydrated or solvated complex ions is suggested which form emulsion in the aqueous phase. These species slowly react with DEHPA and formation of Ti:MEHPA:DEHPA=1:1:2 complex is realized. This complex is yellow.     

Encapsulation of RNA Molecules in BSA Microspheres and Internalization into Trypanosoma Brucei Parasites and Human U2OS Cancer Cells

RNA was encapsulated in bovine serum albumin (BSA) microspheres using a one‐step sonochemical process from an water–oil solvent biphasic system. Confocal microcoscopy and fluorescence‐activated cell sorting indicate that a CY3‐RNA (RNA labeled with red fluorescent indocarbocyanine Cy3 dye) sphere is encapsulated in the BSA outer sphere. The diameter of the sphere depends on the number of nucleotides of the RNA, ranging from 0.63 to 2.74 μm. Total RNA (t‐RNA) was used as a prototype for the future small interfering RNA (siRNA) delivery. A very broad size distribution characterizes the RNA spheres and therefore, among the loaded BSA spheres, there were sufficiently small spheres to be successfully introduced into trypanosoma brucei parasites and human osteosarcoma U2OS cancer cells.     

Robust formulations for clustering-based large-scale classification

Chebyshev-inequality-based convex relaxations of Chance-Constrained Programs (CCPs) are shown to be useful for learning classifiers on massive datasets. In particular, an algorithm that integrates efficient clustering procedures and CCP approaches for computing classifiers on large datasets is proposed. The key idea is to identify high density regions or clusters from individual class conditional densities and then use a CCP formulation to learn a classifier on the clusters. The CCP formulation ensures that most of the data points in a cluster are correctly classified by employing a Chebyshev-inequality-based convex relaxation. This relaxation is heavily dependent on the second-order statistics. However, this formulation and in general such relaxations that depend on the second-order moments are susceptible to moment estimation errors. One of the contributions of the paper is to propose several formulations that are robust to such errors. In particular a generic way of making such formulations robust to moment estimation errors is illustrated using two novel confidence sets. An important contribution is to show that when either of the confidence sets is employed, for the special case of a spherical normal distribution of clusters, the robust variant of the formulation can be posed as a second-order cone program. Empirical results show that the robust formulations achieve accuracies comparable to that with true moments, even when moment estimates are erroneous. Results also illustrate the benefits of employing the proposed methodology for robust classification of large-scale datasets.     

Sonochemically Prepared high Dispersed Ru/TiO2 Mesoporous Catalyst for Partial Oxidation of Methane to Syngas

Highly dispersed Ru nanoparticles on mesoporous TiO₂ have been synthesized by a one-step ultrasound assisted polyol reduction procedure. The catalysts have been characterized by XRD, TEM and HR-TEM, EDX, BET and TPR methods. It has been demonstrated that the sonochemical method reduces the Ru⁺³ ions creating a narrow size distribution of metallic nanoparticles deposited on the mesoporous support without damaging its pore structure. The nanoparticles of Ru are highly dispersed and stable because of their incorporation into the mesopores, and the strong metal-support interaction. The catalytic properties of Ru/TiO₂(MSP) have been tested in the partial oxidation of methane, and high activity and selectivity towards CO and H₂ have been demonstrated.     

Sensitive surface loop-gap microresonators for electron spin resonance

This work presents the design, construction, and experimental testing of unique sensitive surface loop-gap microresonators for electron spin resonance (ESR) measurements. These resonators are made of "U"-shaped gold structures with typical sizes of 50 and 150?μm that are deposited on a thin (220?μm) rutile substrate and fed from the rear by a microstrip line. This allows accommodating a large flat sample above the resonator in addition to having variable coupling properties. Such resonators have a very small volume which, compared to previous designs, improves their absolute spin sensitivity by a factor of more than 2 (based on experimental results). They also have a very high microwave field-power conversion ratio of up to 86?gauss/√Hz. This could facilitate the use of very short excitation pulses with relatively low microwave power. Following the presentation and the discussion of the experimental results, ways to further increase sensitivity significantly are outlined.     

Combining MoS<Subscript>2</Subscript> or MoSe<Subscript>2</Subscript> nanoflakes with carbon by reacting Mo(CO)<Subscript>6</Subscript> with S or Se under their autogenic pressure at elevated temperature

This paper describes a non-aqueous, solvent-free, environmentally friendly, one-pot facile reaction to synthesize inorganic materials inclusion with carbon (MoS₂ or MoSe₂/C) at low temperatures. Nanoflakes of MoS₂ and MoSe₂ inclusion with carbon are prepared by a thermal (750 °C) reaction between Mo(CO)₆ and S or Se at their autogenic pressure in a closed reactor under inert atmosphere. Elemental sulfur or selenium powders are chosen in order to avoid the use of highly toxic H₂S and H₂Se gases. Without further processing of the as-prepared MoS₂/C or MoSe₂/C products, their compositional, morphological and structural characterization are carried out. The possibility of hydrogen storage in as-synthesized MoS₂/C or MoSe₂/C products is examined. A probable reaction mechanism for the formation of MoS₂ or MoSe₂ nanoflakes inclusion with C is discussed.     

A Zn‐Doped CuO Nanocomposite Shows Enhanced Antibiofilm and Antibacterial Activities Against Streptococcus Mutans Compared to Nanosized CuO

Zinc‐doped copper oxide and copper oxide nanoparticles (NPs) are synthesized and deposited on artificial teeth by sonic irradiation, and the ability of these coatings to restrict biofilm formation by Streptococcus mutans is examined. The CuO and Zn:CuO NP‐coated teeth show significant reductions in biofilm formation of 70% and 88%, respectively, compared to uncoated teeth. The mechanism of the Zn:CuO nanoparticles is investigated, revealing that the nanoparticles attach to and penetrate the bacteria and generate intracellular reactive oxygen species (ROS) that enhance lipid peroxidation and cause cell death. Conversely, the CuO or ZnO NPs do not show this behavior and could not generate intracellular ROS. These results highlight the superior efficacy of Zn:CuO nanocomposites over CuO and ZnO NPs and the role of ROS in their antimicrobial effect.     

Creation of Shock-Abrasion Resistance Build-up Metal Using a Physicochemical Model of High-Temperature Processes

Build-up metal for shock-abrasion resistance was the focus of this work, where the mathematical model of physicochemical high-temperature processes developed by the authors in their previous works was used. A computer program based on the model permitted forecasting of the required chemical composition and structure of the build-up metal. Flux-cored wires were fabricated from a cold-rolled ribbon (1008 steel) and filled with a powder mixture. Low carbon steel (A 516) was used as the base metal. The specimens were prepared by 3-layered build-up. The prepared specimens were tested using light microscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), hardness measurements, and shock-abrasion resistance measurements. The results of the above-mentioned tests confirmed the correct calculation of the model and the good shock-abrasion resistance of the suggested build-up metal.     

Successful treatment of early secondary myelofibrosis in SLE with IVIG

With increasing demand for esthetics, dentists face the challenge of delivering definitive restorations that fulfill patients' expectations of esthetics, biocompatibility, and durability. Recent technical developments have encouraged fabrication of gold-reinforced porcelain inlays that meet these important criteria. This article describes a sequence to construct metal-reinforced porcelain inlay restorations.