The analysis of thermoplastic characteristics of special polymer sulfur composite

Specific chemical environments step out in the industry objects. Portland cement composites (concrete and mortar) were impregnated by using the special polymerized sulfur and technical soot as a filler (polymer sulfur composite). Sulfur and technical soot was applied as the industrial waste. Portland cement composites were made of the same aggregate, cement and water. The process of special polymer sulfur composite applied as the industrial waste is a thermal treatment process in the temperature of about 150–155 \(^{\circ }\hbox {C}\). The result of such treatment is special polymer sulfur composite in a liquid state. This paper presents the plastic constants and coefficients of thermal expansion of special polymer sulfur composites, with isotropic porous matrix, reinforced by disoriented ellipsoidal inclusions with orthotropic symmetry of the thermoplastic properties. The investigations are based on the stochastic differential equations of solid mechanics. A model and algorithm for calculating the effective characteristics of special polymer sulfur composites are suggested. The effective thermoplastic characteristics of special polymer sulfur composites, with disoriented ellipsoidal inclusions, are calculated in two stages: First, the properties of materials with oriented inclusions are determined, and then effective constants of a composite with disoriented inclusions are determined on the basis of the Voigt or Rice scheme. A brief summary of new products related to special polymer sulfur composites is given as follows: Impregnation, repair, overlays and precast polymer concrete will be presented. Special polymer sulfur as polymer coating impregnation, which has received little attention in recent years, currently has some very interesting applications.     

Variations of Rate Coefficients and Termination Mechanism During the After‐Effects of a Light‐ Induced Polymerization of a Dimethacrylate Monomer

This work was aimed at studying variations in the termination mechanism occurring during the after‐effects of a light‐induced polymerization of a dimethacrylate monomer after the irradiation had been discontinued. The experimental method was based on differential scanning calorimetry. The initiation was stopped at various moments of the reaction corresponding to different degrees of double‐bond conversion (starting conversions). Three termination models: monomolecular, bimolecular, and mixed were used to calculate the ratio of the bimolecular termination and propagation rate coefficients k_t^b/k_p and/or the monomolecular termination rate coefficient k_t^m. The models were determined over short time intervals (conversion increments) of the dark reaction giving different values of rate coefficients for each time interval (interval approximation method). Two‐stage statistical analysis was used to find the model that best reproduced the experimental data obtained for each conversion increment. This enabled variations in the termination mechanism during the after‐effects to be followed. It was found that the termination mechanism changed with the time of the dark reaction from the bimolecular reaction to the mixed reaction when the light was cut off at low and medium double‐bond conversions. At higher starting conversions a monomolecular termination mechanism dominated from the beginning of the dark reaction. The mixed termination model was the only model to describe correctly the variations of rate coefficients in the dark, i. e., the increase in k_t^m and the decreasein the k_t^b/k_p ratio.     

Laser-Induced Generation of Hydrogen in Water by Using Graphene Target

A new method of hydrogen generation from water, by irradiation with CW infrared laser diode of graphene scaffold immersed in solution, is reported. Hydrogen production was extremely efficient upon admixing NaCl into water. The efficiency of hydrogen production increased exponentially with laser power. It was shown that hydrogen production was highly efficient when the intense white light emission induced by laser irradiation of graphene foam was occurring. The mechanism of laser-induced dissociation of water is discussed. It was found that hydrogen production was extremely high, at about 80%, and assisted by a small emission of O₂, CO and CO₂ gases.     

Conformal iterated function systems with applications to the geometry of continued fractions

In this paper we obtain some results about general conformal iterated function systems. We obtain a simple characterization of the packing dimension of the limit set of such systems and introduce some special systems which exhibit some interesting behavior. We then apply these results to the set of values of real continued fractions with restricted entries. We pay special attention to the Hausdorff and packing measures of these sets. We also give direct interpretations of these measure theoretic results in terms of the arithmetic density properties of the set of allowed entries.

     

Analytical Evaluation of an Integrated Ultrasonic Nebulizer-hydride Generator System for Simultaneous Determination of Hydride and Non-hydride Forming Elements by Microwave Induced Plasma Spectrometry

ABSTRACT

The commercial ultrasonic nebulizer NOVA-DUO (ultrasonic nebulizer dual capillary system USN/DCS) has been evaluated for the simultaneous determination of classical hydride forming (As, Bi, Ge, Sb, Se, Sn) and conventional non-hydride forming (Ba, Ca, Fe, Li, Mg, Sr) elements by microwave induced plasma-optical emission spectrometry (MIP-OES). Simultaneous mixing and nebulization of the two solutions (acidified sample and reductant) on the piezoelectric transducer, with the possibility of flow rate adjustment, permits a wide variation of sensitivity. The hydrides and aerosols were rapidly transported via a stream of Ar carrier to a MIP for simultaneous multi-element determination by OES. A univariate approach and simplex optimization procedure was used to achieve optimized conditions and derive analytical figures of merit. Analytical performance of the ultrasonic nebulization system was characterized by determination of the limits of detection (LODs) and precision (RSDs) with the USN/DCS observed at 11 µL min^?1 flow rate. The experimental concentration detection limits for simultaneous determination, calculated as the concentration giving a signal equal to three times of standard deviation of the blank (LOD, 3σ_blank criterion, peak height) were 1.3, 5.9, 6.6, 1.8, 3.6, 2.6, 41, 8.1, 11, 7.5, 9.2, and 12 ng mL^?1 for As, Bi, Ge, Sb, Se Sn, Ba, Ca, Fe, Li, Mg, and Sr, respectively. The method offers relatively good precision (RSD ranged from 9 to 13%) for liquid analysis and microsampling capability. Interference effects by transition metals have been shown to be corrected by the addition of thiourea, as a pre-reducing agent and masking agent. The accuracy of the method was verified by the use of certified reference materials (NRCC DOLT-2, NRC GBW 07302, NIST SRM 2710, NIST SRM 1643e) and by aqueous standard calibration technique. All results obtained for reference materials were in agreement with certified values at 95% confidence level by Student t-test.     

Prokinetic and Laxative Effects of Chrozophora tinctoria Whole Plant Extract

Chrozophora tinctoria (Euphorbiaceae) has been used as an emetic, anthelminthic, and cathartic agent in traditional medicine. We used gas chromatography-mass spectrometry (GC-MS) to characterize the composition of ethyl acetate (EAC) and dichloromethane (DCMC) fractions from the whole Chrozophora tinctoria plant. EAC and DCMC fractions were evaluated for acetylcholinesterase (AChE) inhibitory activity and acute toxicity. Their effects on intestinal propulsive movement and spasmogenic activity of the gastrointestinal tract (GIT) muscle were also assessed. The compounds detected in both fractions were mostly fatty acids, with about seven compounds in EAC and 10 in DCMC. These included pharmacologically active compounds such as imipramine, used to treat depression, or hexadecanoic acid methyl ester, an antioxidant. Both EAC and DCMC fractions inhibited acetylcholinesterase (AChE) activity with IC₅₀ values of 10 µg and 130 µg, respectively. Both the fractions were found to be toxic in a dose-dependent manner, inducing emesis at 0.5 g or higher and lethargy and mortality from 3–5 g upwards. Similarly, both of the fractions showed laxative activity in metronidazole- and loperamide-induced constipation models. EAC relaxed the intestinal muscle at a lower dose (1 mg/mL) than DCMC. Similarly, the EAC extract showed a significant relaxation effect (EC₅₀ = 0.67 ± 0.15 mg/mL) on KCL-induced contraction in rabbit jejunum as compared to DCMC (EC₅₀ = 5.04 ± 0.05 mg/kg). The present study strongly supports the folklore that this valuable plant is a cathartic agent. Further work is required to isolate and validate the bioactive compounds that act as diarrheal agents in Chrozophora tinctoria.     

Synthesis of silylene–propenylene oligomers via catalytic polycondensation of diallyldiorganosilanes

Acyclic diene polycondensation (ADP) of diallyldiorganosilanes (CH₂CHCH₂)₂SiR₂ (where R = Me, Ph), in the presence of various ruthenium and rhodium complexes, led predominantly to linear silylene–propenylene oligomers. Ruthenium catalysts (e.g. RuCl₂(PPh₃)₃, RuHCl(CO)(PPh₃)₃, and RuCl(SiMe₃)(CO)(PPh₃)₂) were found to be more efficient than the rhodium ones. The reaction proceeds via preliminary catalytic isomerization of allylsilane to silyl-1-propenes followed by their oligococondensation. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3299–3304, 1997     

Nonnegative Minimum Biased Quadratic Estimation in Mixed Linear Models

The problem of nonnegative quadratic estimation of a parametric function γ(β, σ)=β′Fβ+∑^r_i=1 f_iσ²_i in a general mixed linear model {y, Xβ, V(σ)=∑^r_i=1 σ²_iV_i} is discussed. Necessary and sufficient conditions are given for y′A₀y to be a minimum biased estimator for γ. It is shown how to formulate the problem of finding a nonnegative minimium biased estimator of γ as a conic optimization problem, which can be efficiently solved using convex optimization techniques. Models with two variance components are considered in detail. Some applications to one-way classification mixed models are given. For these models minimum biased estimators with minimum norms for square of expectation β² and for σ²₁ are presented in explicit forms.     

Isometric embeddings of polar Grassmannians and metric characterizations of their apartments

We describe isometric embeddings of polar Grassmann graphs formed by non-maximal singular subspaces. In almost all cases, they are induced by collinearity-preserving injections of polar spaces. As a simple consequence of this result, we get a metric characterization of apartments in polar Grassmannians.