Output concepts for accelerated Turing machines

The accelerated Turing machine (ATM) is the work-horse of hypercomputation. In certain cases, a machine having run through a countably infinite number of steps is supposed to have decided some interesting question such as the Twin Prime conjecture. One is, however, careful to avoid unnecessary discussion of either the possible actual use by such a machine of an infinite amount of space, or the difficulty (even if only a finite amount of space is used) of defining an outcome for machines acting like Thomson’s lamp. It is the authors’ impression that insufficient attention has been paid to introducing a clearly defined counterpart for ATMs of the halting/non-halting dichotomy for classical Turing computation. This paper tackles the problem of defining the output, or final message, of a machine which has run for a countably infinite number of steps. Non-standard integers appear quite useful in this regard and we describe several models of computation using filters.     

Atom-transfer radical graft polymerization initiated directly from silica applied to functionalization of stationary phases for high-performance liquid chromatography in the hydrophilic interaction chromatography mode

Initiation of atom-transfer radical polymerization of a number of monomers (styrene, methyl acrylate, 3-[N,N-dimethyl-N-(methacryloyloxyethyl)ammonium] propanesulfonate, butyl methacrylate, 2,3-epoxypropyl methacrylate) directly from chlorinated porous silica particles has been performed. The grafting has been confirmed and evaluated by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. This initiation technique results in a hydrolytically stable initial Si-C bond, tethering the polymer to the silica substrate. The resulting grafted particles have been used as separation materials for both reversed-phase and hydrophilic interaction chromatography.     

Preparation and application of organo-modified zeolitic material in the removal of chromates and iodides

The removal of chromates and iodides from aqueous solutions by organo-modified tuffs from the Pentolofos area (Thrace, Greece) was investigated using (51)Cr- and (131)I-labelled solutions and gamma-ray spectroscopy. The zeolitic material was modified by hexadecyltrimethyl-ammonium bromide (HDTMA-Br) and octadecyltrimethyl-ammonium bromide (ODTMA-Br) and characterized by scanning electron microscopy, FT-IR spectrometry and zeta potential measurements. Both experimental study and modelling indicated that both organo-zeolitic sorbents have a bigger affinity for iodide than for chromate. The chromium uptake did not seem to be influenced by the type of modifier but showed, as expected, a dependence on the solution pH. The maximum sorption capacity (2.27 mg/g) of Cr(VI) was achieved for the solution of initial pH 4. On the other hand, the HDTMA-modified tuff showed a lower sorption affinity for iodides than did the ODTMA-modified one (3.37 and 4.02 mg/g, respectively).     

Study of diethyl dithiophosphate adsorption on chalcopyrite and tennantite at varied pHs

The kinetics of diethyl dithiophosphate adsorption on chalcopyrite and tennantite has been studied by UV-visible spectroscopy at pH values of 4, 6, and 9. The concentration of diethyl dithiophosphate in the solution has been monitored as a function of time and pH for both minerals. It was found that the adsorption tendency of diethyl dithiophosphate on both minerals decreased with the increasing pH treatments. This is due to the existence of metal hydroxide species onto the mineral surface in more alkaline condition inhibiting the adsorption of diethyl dithiophosphate species. In comparison to that of chalcopyrite, tennantite possessed slightly higher adsorption of diethyl dithiophosphate in acid condition, while vice versa correlation observed at other pH treatments at where the coverage of metal hydroxide species obtained higher than that of chalcopyrite showing that the rate oxidation of tennantite is higher. An adsorption mechanism has been proposed and tested against the experimental kinetic data. Both the kinetic data and flotation studies are consistent with the proposed mechanism.     

Distinct bioaccumulation profile of pesticides and dioxin-like compounds by mollusk bivalves reared in polluted and unpolluted tropical bays: Consumption risk and seasonal effect

Mariculture activity has increased its production along the Atlantic Coast of Brazil over the last years. This protein source for human consumption may also represent risks due to the exposure to bioaccumulated contaminants in the tissues of organisms reared in polluted shallow waters. This study evaluated the bioaccumulation of pesticides and dioxin-like compounds in two commercial marine bivalve species reared at different sites along the Rio de Janeiro State coast (SE-Brazil). We observed distinct contamination profiles in bivalve tissues reared at each sampling site, which may be related to human activities historically developed in those areas. A pronounced tendency for higher contamination levels in animals sampled in the last month of winter (September) is discussed as being likely due to environmental issues, rather than biological factors. Based on Minimal Risk Level, Maximum Residue, Acceptable Daily Intake and Toxic Equivalent, bivalves are classified as safe for human consumption.     

Fluorescent labelled thiourea-bridged glycodendrons

GlcNAc-coated glycodendrimers, which are polyvalent glycomimetics, display strong in vitro affinity for the rat natural killer cell protein-1A (NKR-P1A), a C-type lectin-like receptor of natural killer (NK) cells in rats, humans and some strains of mice. Administration of these compounds in vivo results in a substantial increase in the antitumour activity with involvement of the natural cell immunity. To clarify the in vitro and in vivo fate of these molecules, we synthesized labelled glycodendron analogues of the previously studied glycodendrimers. Labelling with fluorescent tags enabled the localization of the glycodendrons in white blood cells, tumours and other tissues by using different imaging techniques such as fluorescence and confocal microscopy. These studies are useful for probing the mechanism of action and fate of artificial ligands and the cell receptors involved.     

Assessment of refractive index gradients by standard rainbow thermometry

Up to now the application of rainbow thermometry has been limited to particle systems possessing a uniform refractive index. This is mostly due to the absence of an appropriate data inversion algorithm that takes into account the presence of a refractive index gradient. In this paper, for the first time to our knowledge, exploiting a generalization of the Airy theory, a data inversion algorithm for a single droplet, presenting a parabolic refractive index gradient, is proposed. This data inversion algorithm is used to compute the diameter and the refractive index at the core and at the surface of a simulated burning droplet. The results are compared to the analytical solutions showing a satisfactory agreement.     

Chemical transformations of polymers. XI. Mercuration of polystyrene

The mercuration of soluble polystyrene was investigated, and it was found that an addition of perchoric acid to the reaction mixture significantly accelerated the polymer transformation. The mercuration proceeds as a polymer analogous reaction, i.e., without any change in the degree of the polymerization. The mercurated product could be converted back to the original polystyrene by hydrolysis or to the corresponding bromopolystyrene by bromination. Ultracentrifuge measurements show that even at low conversion rates all macromolecules were mercurated and unreacted polystyrene could not be identified in the product. Calorimetry indicated the presence of styrene–mercuric acetate blocks in copolymers with high mercury contents.     

Transient Inclusion Evolution During Modification of Alumina Inclusions by Calcium in Liquid Steel: Part I. Background,Experimental Techniques and Analysis Methods

In aluminum-killed steels, modification of solid alumina inclusions is often carried out by calcium treatment, converting the alumina to liquid calcium aluminates. When calcium treatment is performed, calcium can either react with sulfur in the melt or with solid alumina. Calcium sulfide inclusions are solid at steel casting temperatures and thus would be detrimental to castability if they remained in the steel after calcium treatment. The aim was to study the transient evolution of inclusions after calcium treatment, testing the hypothesis that calcium sulfide may form as an intermediate reaction product, which can subsequently react with alumina to form modified calcium aluminates. The first part gives the project background and describes the experimental and quantification techniques adopted, including the effect of sampler size in laboratory melts. Results of the formation of intermediate calcium reaction products in laboratory and industrial heats are presented in the second part.     

Silicon carbide matrix composites reinforced with two-dimensional titanium carbide – Manufacturing and properties

Within this paper, it is explored how two-dimensional Ti₂C sheets addition affects silicon carbide matrix composites in terms of the microstructure and mechanical properties. In order to consolidate the powder mixtures, powder metallurgy processing followed by Spark Plasma Sintering was performed to prepare the sinters. According to our knowledge, this is the first attempt to apply delaminated MXene phases as a reinforcing phases of ceramic matrix composites. The delaminated MXene phases were characterized using a high-resolution transmission microscope (HRTEM) and X-ray photoelectron spectroscopy (XPS). Significant improvement of the fracture toughness and hardness for the composites reinforced with 1.5?wt% 2D Ti₂C compared to the reference sample were observed. It is expected that the applied reinforcing phase will have an influence on the fracture mechanism, and so this has also been investigated. Two of the main mechanisms of crack propagations (crack deflection and bridging) were observed.