Poly(L-lysine)-poly(ethylene glycol) layers with different structure and their influence on silica suspension stability

The effects of the structure of di- and triblock copolymers of poly(L-lysine) – LYS with poly(ethylene glycol) – PEG as well as the length of nonionic fragment in the LYS-PEG macromolecule on the copolymer chains conformation in the adsorption layer formed on the colloidal silica (SiO2) surface were examined. Spectrophotometry and turbidimetry were applied for the determination of copolymer adsorbed amounts and stability coefficients of silica aqueous suspensions. The electrokinetic parameters such as solid surface charge density and zeta potential were also estimated. The adsorption of LYS-PEG was proved to be the highest at pH 10 whereas the lowest adsorption on the solid surface was found for the triblock copolymer with long fragments of LYS at the same pH value.     

Shape design of internal cooling passages within a turbine blade

The article concerns the optimization of the shape and location of non-circular passages cooling the blade of a gas turbine. To model the shape, four Bezier curves which form a closed profile of the passage were used. In order to match the shape of the passage to the blade profile, a technique was put forward to copy and scale the profile fragments into the component, and build the outline of the passage on the basis of them. For so-defined cooling passages, optimization calculations were carried out with a view to finding their optimal shape and location in terms of the assumed objectives. The task was solved as a multi-objective problem with the use of the Pareto method, for a cooling system composed of four and five passages. The tool employed for the optimization was the evolutionary algorithm. The article presents the impact of the population on the task convergence, and discusses the impact of different optimization objectives on the Pareto optimal solutions obtained. Due to the problem of different impacts of individual objectives on the position of the solution front which was noticed during the calculations, a two-step optimization procedure was introduced. Also, comparative optimization calculations for the scalar objective function were carried out and set up against the non-dominated solutions obtained in the Pareto approach. The optimization process resulted in a configuration of the cooling system that allows a significant reduction in the temperature of the blade and its thermal stress.     

Recommendation of RILEM Technical Committee 250-CSM: Test method for Textile Reinforced Mortar to substrate bond characterization

Textile Reinforced Mortar (TRM), also known as Fabric Reinforced Mortar or Fabric Reinforced Cementitious Matrix, composites are an emerging technology for the external repair and strengthening of existing structures. For most applications, the effectiveness of the TRM reinforcement relies on its bond performance. This recommendation identifies the best practice to characterize the bond behaviour of TRM. A shear bond test method is proposed to determine the peak axial stress (associated with the maximum load that can be transferred from the structural member to the externally bonded TRM reinforcement), the stress–slip relationship and the failure mode that controls the TRM-to-substrate load transfer capacity. Guidelines on specimen manufacturing, experimental setup, test execution, and determination of test results are provided.     

Preparation and characterization of magnetic carbon nanomaterials bearing APTS–silica on their surface

The formation of metal-encapsulated carbon nanomaterials by using metallic catalysts (iron, cobalt, and nickel) has been studied. Moreover, these materials were coated with silica surface modified by (3-Aminopropyl)-trimethoxysilane (APTS). Each intermediate structure was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The surface morphology of silica-coated carbon nanomaterials was analyzed by scanning electron microscopy (SEM). The modified, APTS–silica surface was additionally characterized by Fourier transform infrared spectroscopy (FT-IR), elemental (EA), and thermogravimetric analysis (TGA).     

Uranium isotopes in public drinking water and dose assessment for man in Poland

238U, 234U and 235U were determined in tap water from municipal water pipes that drew their supply from surface water or ground water in various locations in Poland. Average activity concentrations of 238U, 234U and 235U in tap water from surface water were 9.6 +/- 7.1, 12.8 +/- 9.7 and 0.41 +/- 0.31 Bq m(-3), respectively, whereas from ground water they were 4.5 +/- 6.0, 5.7 +/- 6.9 and 0.19 +/- 0.27 Bq m(-3), respectively. Activity concentrations of 234U were higher than 238U. Ratios of 234U/238U ranged from 1.07 to 2.60, indicating the lack of equilibrium between these isotopes. The average 235U/238U ratio was 0.043 +/- 0.008, being close to 0.046 for natural uranium. Average annual intake with water and food was 7.6 +/- 5.1 Bq for 238U and 9.5 +/- 6.6 Bq for 234U. Annual committed effective doses calculated from these intakes for adults were 0.34 +/- 0.23 and 0.47 +/- 0.32 microSv, respectively; 235U contributed to the total dose from the uranium isotopes by about 2%.     

On-line coloring and cliques covering for KK s,t -free graphs

The problem of on-line coloring of an arbitrary graphs is known to be hard. Here we consider the problem of on-line coloring in the simplified situation where the input graph is KK_s,t-free. We show that the on-line coloring algorithm with the First Fit strategy of proposed by Capponi and Pilotto in [1] is the best one for KK_1,t-free graphs (t≥3). A.Capponi and C.Pilotto have shown that this algorithm achieves a competitive ratio of t−1 while we show that it is the best possible. However for the family of KK_s,t-free graphs (s≥2, t≥2) there exists no on-line coloring algorithm with a competitive function. The problem of an on-line cliques covering for these families is hard. There exists no on-line cliques covering algorithm with a competitive function for the family of KK_s,t-free graphs (s≥ 1, t≥3). The additional assumption that the input graph is given in a connected way does not help a lot and does not change our results described above.     

Continuous separation,with microfluidics,of the components of a ternary mixture: from vacuum to purge gas pervaporation

The general objective of this paper is to investigate the separation, with microfluidics, of the components of a ternary mixture, when using vacuum or purge gas pervaporation. The ternary mixture considered is a mixture of methanol (MeOH), water (H₂O) and hydrogen peroxide (H₂O₂). In a previous work (Ziemecka in Lab Chip 15:504–511, 2015), we presented the proof of concept of a microfluidic device, which was able to partially separate MeOH from the other components of such a mixture, by using vacuum pervaporation. Here, our goal is to optimize the operation of this device, by considering vacuum pervaporation, but also purge gas pervaporation. First, we provide a mathematical model of the device. This model is used to discuss the influence of the operating parameters on the device operation. To apply this model to the considered mixture, we determined the MeOH and H₂O permeability coefficients of PDMS membranes prepared from different concentrations of the curing agent. The model is then successfully compared to experimental data. The model and the experiments show that high efficiencies can be reached for both vacuum and purge gas pervaporation, provided a fine-tuning of the operating parameters. For instance, a good efficiency of the vacuum pervaporation is reached at high temperature and low pressure. For purge gas pervaporation, it is reached for low temperature and high pressure.     

A sensitivity analysis of powder forging processes

The purpose of this paper is to analyze the sensitivity problems in metal forming of rigid-visco-poroplastic materials. A repressing powder forging process is analyzed. Parameter sensitivity, material derivative, and control volume approaches to shape sensitivity analysis are presented, analyzed, and compared. Discretization of the continuum expressions is presented. The numerical solutions for parameter sensitivity in forging problems have been described. Numerical examples concerning simple compression test of cylindrical porous specimen are presented.     

Hydroxyalkylation of parabanic acid. I. Reactions with formaldehyde

The results of investigations into the reaction of parabanic acid with formaldehyde at different molar ratios of the reagents are presented. A fast and effective method of synthesis of N,N′‐bis(hydroxymethyl)parabanate was developed. The reaction of parabanic acid with an excess of formaldehyde was analyzed and the structure of the products proposed. Conditions at which the hydroxymethyl derivatives of parabanic acid undergo self‐condensation as well as prospects of using them in subsequent oxyalkylation with oxiranes are specified. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2858–2872, 2002; DOI 10.1002/app.10274     

ROS-Scavengers,Osmoprotectants and Violaxanthin De-Epoxidation in Salt-Stressed Arabidopsis thaliana with Different Tocopherol Composition

To determine the role of α- and γ-tocopherol (TC), this study compared the response to salt stress (200 mM NaCl) in wild type (WT) Arabidopsis thaliana (L.) Heynh. And its two mutants: (1) totally TC-deficient vte1; (2) vte4 accumulating γ-TC instead of α-TC; and (3) tmt transgenic line overaccumulating α-TC. Raman spectra revealed that salt-exposed α-TC accumulating plants were more flexible in regulating chlorophyll, carotenoid and polysaccharide levels than TC deficient mutants, while the plants overaccumulating γ-TC had the lowest levels of these biocompounds. Tocopherol composition and NaCl concentration affected xanthophyll cycle by changing the rate of violaxanthin de-epoxidation and zeaxanthin formation. NaCl treated plants with altered TC composition accumulated less oligosaccharides than WT plants. α-TC deficient plants increased their oligosaccharide levels and reduced maltose amount, while excessive accumulation of α-TC corresponded with enhanced amounts of maltose. Salt-stressed TC-deficient mutants and tmt transgenic line exhibited greater proline levels than WT plants, lower chlorogenic acid levels, and lower activity of catalase and peroxidases. α-TC accumulating plants produced more methylated proline- and glycine- betaines, and showed greater activity of superoxide dismutase than γ-TC deficient plants. Under salt stress, α-TC demonstrated a stronger regulatory effect on carbon- and nitrogen-related metabolites reorganization and modulation of antioxidant patterns than γ-TC. This suggested different links of α- and γ-TCs with various metabolic pathways via various functions and metabolic loops.