Design,Construction, and Installation of Movable Electrode Biasing System on Tokamak

The first results of the movable electrode biasing experiments performed on the IR-T1 tokamak are presented. For this purpose, a movable electrode biasing system was designed, constructed, and installed on the IR-T1 tokamak, and then the positive voltage applied to an electrode inserted inside the tokamak limiter and the plasma current, poloidal and radial components of the magnetic fields, loop voltage, and diamagnetic flux in the absence and presence of the biased electrode were measured. Results compared and discussed.     

Resorcinol formaldehyde xerogels modified with mercapto functional groups as mercury adsorbent

Resorcinol formaldehyde xerogels are modified by mercaptopropyl‐trimethoxysilane during the sol–gel process used to produce the xerogel. The chemical modification is confirmed by Fourier‐transform infrared spectroscopy. The xerogel is then used to adsorb mercury ions from aqueous solutions. The effects of the molar ratios of the precursors as well as the catalyst and the modifier are studied on the textural properties of the xerogel and the adsorption efficiency. It is shown that the chemical modification of the resorcinol formaldehyde xerogels creates the chemical sites on the structure of the xerogel to adsorb more mercury ions and increase the adsorption efficiency. At the same time, chemical modification decreases the xerogel surface area which results in a reduction of the mercury adsorption. Therefore, there exists an optimum value for the chemical modification of the xerogel to achieve the highest adsorption efficiency. Adsorption kinetics as well as equilibrium isotherm of xerogels were examined using pseudo‐first‐ and second‐order kinetic equations, and Freundlich and Langmuir isotherm models. The adsorption kinetics was found to follow the pseudo‐second‐order kinetic equations. The experimental data was also fitted into the Longmuir model more precisely comparing the Freundlich model. Finally, a series of mercury adsorption–desorption tests proved that the optimized mercapto‐modified resorcinol formaldehyde xerogel was an efficient reusable adsorbent for mercury ions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42543.     

Modification of poly(propylene) by grafted polyester‐amide‐based dendritic nanostructures with the aim of improving its dyeability

Fiber‐graded poly(propylene) was modified by polyester‐amide‐based dendritic nanostructures with the aim of improving its dyeability. Two different dendritic polymers were used and the dendritic nanostructures were formed in situ via reactive blending with maleic anhydride‐modified poly(propylene). Samples were chosen exploiting a 4‐component mixture design. Thermal, morphological, and rheological characterizations showed domains with different size and distribution were formed and primary properties of the dendritics determined the characteristics of the resulted domains. Morphological parameters were quantified by digital analysis of scanning electron microscope images. Thermal and rheological behavior also demonstrated good agreements with the inferred morphology of the formed dendritic domains. The modified samples were then dyed with dispersed dyestuffs. A variety of substantivities were obtained, and some of the modified samples showed a significant enhancement in dyeing properties. A predictive model was developed for K/S ratio, where K and S are absorption and scattering coefficients of the Kubelka‐Munk one constant theory, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Fabricating Janus membranes via physicochemical selective chemical vapor deposition

Membranes with asymmetric wettability-Janus membranes-have recently received considerable attention for a variety of critical applications. Here, we report on a simple approach to introduce asymmetric wettability into hydrophilic porous domains. Our approach is based on the physicochemical-selective deposition of polytetrafluoroethylene (PTFE) on hydrophilic polymeric substrates. To achieve selective deposition of PTFE, we inhibit the polymerization reaction within the porous domain. We prefill the substrates with glycerol, containing a known amount of free radical inhibitor, and utilize initiated chemical vapor deposition (iCVD) for the polymerization of PTFE. We show that the glycerol/inhibitor mixture hinders the deposition of PTFE within the membrane pores. As a result, the surface of the substrates remains open and porous. The fabricated Janus membranes show stable wetting-resistant properties, evaluated through sessile drop contact angle measurements and direct contact membrane distillation (DCMD).     

Ketonization of Proline Residues in the Peptide Chains of Actinomycins by a 4‐Oxoproline Synthase

X‐type actinomycins (Acms) contain 4‐hydroxyproline (Acm X₀) or 4‐oxoproline (Acm X₂) in their β‐pentapeptide lactone rings, whereas their α ring contains proline. We demonstrate that these Acms are formed through asymmetric condensation of Acm half molecules (Acm halves) containing proline with 4‐hydroxyproline‐ or 4‐oxoproline‐containing Acm halves. In turn, we show—using an artificial Acm half analogue (PPL 1) with proline in its peptide chain—their conversion into the 4‐hydroxyproline‐ and 4‐oxoproline‐containing Acm halves, PPL 0 and PPL 2, in mycelial suspensions of Streptomyces antibioticus. Two responsible genes of the Acm X biosynthetic gene cluster of S. antibioticus, saacmM and saacmN, encoding a cytochrome P450 monooxygenase (Cyp) and a ferredoxin were identified. After coexpression in Escherichia coli, their gene products converted PPL 1 into PPL 0 and PPL 2 in vivo as well as in situ in permeabilized cell of the transformed E. coli strain in conjunction with the host‐encoded ferredoxin reductase in a NADH (NADPH)‐dependent manner. saAcmM has high sequence similarity to the Cyp107Z (Ema) family of Cyps, which can convert avermectin B1 into its keto derivative, 4′′‐oxoavermectin B1. Determination of the structure of saAcmM reveals high similarity to the Ema structure but with significant differences in residues decorating their active sites, which defines saAcmM and its orthologues as a distinct new family of peptidylprolineketonizing Cyp.     

Thermal,mechanical, and acoustic properties of silica‐aerogel/UPVC composites

The properties of silica‐aerogel/UPVC composites have been investigated with emphasis on sound and heat insulation. UPVC is a material of construction for window profiles and drainage pipes. Hydrophobic silica aerogels were synthesized using silicate sodium as a precursor through a two‐step sol–gel process. The physical and textural properties of the synthesized silica aerogels such as density, surface area, and particle size were analyzed using SEM and BET analysis. Then, the synthesized aerogels were mixed with Unplastisized Polyvinyl Chloride (UPVC) compound at five different weight ratios in an internal mixer to find out the effects of silica aerogels on the thermal, mechanical, and acoustical characteristics. The prepared UPVC/aerogel composites were characterized for tensile properties, impact strength, hardness, Vicat softening temperature, thermal conductivity, sound absorption, and sound transmission loss. The results revealed that adding silica aerogel in to the matrix of UPVC increases its hardness and softening temperature while decreases impact strength. The thermal conductivity of UPVC was decreased by up to 50% using silica aerogel. The sound absorption property of UPVC was increased up to three times by using silica aerogels due to its high porosity. Silica aerogel increased the maximum sound transmission loss of UPVC in the low frequency range. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44685.     

Investigating the effect of nano-silica on efficiency of the foam in enhanced oil recovery

Due to the vast production of crude oil and consequent pressure drops through the reservoirs, secondary and tertiary oil recovery processes are highly necessary to recover the trapped oil. Among the different tertiary oil recovery processes, foam injection is one of the most newly proposed methods. In this regard, in the current investigation, foam solution is prepared using formation brine, C₁₉TAB surfactant and air concomitant with nano-silica (SiO₂) as foam stabilizer and mobility controller. The measurements revealed that using the surfactant-nano SiO₂ foam solution not only leads to formation of stable foam, but also can reduce the interfacial tension mostly considered as an effective parameter for higher oil recovery. Finally, the results demonstrate that there is a good chance of reducing the mobility ratio from 1.12 for formation brine and reservoir oil to 0.845 for foam solution prepared by nanoparticles.     

Remote sensing of salinity in the San Francisco Bay Delta

Salinity of the San Francisco Bay Delta has been studied for the past seven decades. There is a significant gradient in salinity within this estuarine system that influences the growth and distribution of phytoplankton as well as the abundance and migration of shrimp and fish population. Several government agencies which have jurisdictions over this area are attempting to gather extensive data for effectively monitoring of this estuary. Repetitive remotely sensed data acquired from Landsat may be considered by these agencies as having the potential to provide a cost-effective method for gathering and processing water quality related data. In this study, Landsat multispectral scanner (MSS) data and color and color infrared photographs acquired from a U-2 aircraft were combined with surface measurements for salinity mapping of the San Francisco Bay Delta. The salinity measurements and U-2 photography were obtained simultaneously and coincident with landsat overpass. A regression model was developed between the surface truth data and Landsat digital data for 29 preselected sample sites and was then extended to the entire study area. The results included a salinity map of the study area and the statistical summaries. The results were in general agreement with the reported distribution of salinity values in the literature for the same time of the year. Based on the results and the associated analyses of natural color and color infrared photographs and Landsat color composite imagery, it was concluded that: (1) it was virtually impossible, at least within this test site, to establish any quantitative judgement regarding the salinity values by visual interpretation of the imagery; and (2) the present study constitutes the first effort to successfully use Landsat digital data for salinity mapping, by means of digital processing, for this geographic area.     

A Taguchi analysis on structural properties of polypropylene microcellular nanocomposite foams containing Fe2O3 nanoparticles in batch process

Polypropylene (PP) as a thermoplastic polymer has been foamed using batch foaming process. CO₂ is used as the blowing agent of the foaming. Ferrous oxide nanoparticles (nano Fe₂O₃) are also added as reinforcement. Effect of different parameters including nanoparticle weight percentage, foaming temperature and time on the structural properties of PP/nano Fe₂O₃ nanocomposites is investigated using Taguchi approach. Scanning electron microscope results depict that an appropriate microcellular structure is obtained with the cell density of 10⁹ cells/cm³ and almost 1 μm of cell size. Analysis of variance results indicated that foaming temperature is the most significant parameter on the structural properties. Cell density and expansion ratio are decreased by increasing foaming temperature. This phenomenon could be due to the reducing melt strength of polymer/gas mixture. It was also inferred that adding 2 wt% of nanoparticles leads to 80% improvement in cell density while cell size and expansion ratio was decreased.     

On the hierarchy of conservation laws in a cellular automaton

Conservation laws in cellular automata (CA) are studied as an abstraction of the conservation laws observed in nature. In addition to the usual real-valued conservation laws we also consider more general group-valued and semigroup-valued conservation laws. The (algebraic) conservation laws in a CA form a hierarchy, based on the range of the interactions they take into account. The conservation laws with smaller interaction ranges are the homomorphic images of those with larger interaction ranges, and for each specific range there is a most general law that incorporates all those with that range. For one-dimensional CA, such a most general conservation law has—even in the semigroup-valued case—an effectively constructible finite presentation, while for higher-dimensional CA such effective construction exists only in the group-valued case. It is even undecidable whether a given two-dimensional CA conserves a given semigroup-valued energy assignment. Although the local properties of this hierarchy are tractable in the one-dimensional case, its global properties turn out to be undecidable. In particular, we prove that it is undecidable whether this hierarchy is trivial or unbounded. We point out some interconnections between the structure of this hierarchy and the dynamical properties of the CA. In particular, we show that positively expansive CA do not have non-trivial real-valued conservation laws.