Amount Of Diluent Research Articles

Layered and double perovskites as methane coupling catalysts

Layered perovskites of the form A 2Ln 2Ti 3O 10 (A = K,Rb; Ln = La,Nd,Sm, Gd,Dy) and alkali carbonate promoted double perovskite LaCaMnCoO 6 were examined as methane oxidative coupling catalysts. The layered perovskites were of interest since they were reported to contain layers of alkali ions dispersed and sandwiched between lanthanide perovskite layers. The double perovskite, LaCaMnCoO 6, was of interest as a redox coupling catalyst due to its unique structure and redox properties. The material was reported to have an ordered perovskite structure showing multiple occupation of both A (La and Ca) and B (Mn and Co) sublattices. Layered perovskites of the form A 2Ln 2Ti 3O 10 gave coupling results comparable to many of the reported literature methane coupling catalysts. Trends observed upon changing temperature, CH 4/O 2 feed ratio or diluent amount in the feed were examined. Alkali carbonate doped LaCaMnCoO 6 were shown to be a unique class of sequential (redox) mode coupling catalysts. These catalysts showed very high initial C 2+ selectivities (>80%) and exhibited the unique characteristic that the CH 4 conversions and C 2 selectivities are at maximas during the early stages of the catalyst reduction. This characteristic has not been reported for any other sequential (redox) mode coupling catalysts.

Use of the Gravimetric Diluter in Microbiological Work

Manual dilutions of food samples (e.g., 1:10 dilution) for microbiological investigations are cumbersome. We tested an automatic diluter (Model GD-600 Gravimetric Diluter, Spiral System, Inc., Bethesda, MD) for accuracy and sterility for microbiological work and found that the system provided ±0.1 to +0.2g of accuracy in delivering a commanded amount of diluent. The delivered diluent was essentially sterile, with a few samples giving 1 to 4 colonies per ml after plating. With this system, weighing and dilution are fast, easy, and accurate.

Effect of gravity on flame instabilities in premixed gases

The effects of gravity on instabilities in laminar, premixed flames in dilute H 2 -O 2 -N 2 mixtures is investigated using detailed, time-dependent, two-dimensional numerical simulations. The physical processes included in the model are fluid convection, detailed hydrogen-oxygen chemistry, multispecies diffusion, thermal conduction, viscosity, and gravity. The results from the simulations show that the effects of gravity become more important as the burning velocity of a mixture is decreased by either decreasing the amount of fuel or increasing the amount of diluent

Influence of chain flexibility and crosslink density on mechanical properties of epoxy/amine networks

AbstractBlends of a bisphenol A diglycidyl ether prepolymer and an aliphatic diepoxy diluent crosslinked with a cycloaliphatic diamine were studied. These model networks have the characteristic that the crosslink density and the chain flexibility increase with the amount of diluent. These combined effects were studied by observing their mechanical properties. The decreases in the Young's modulus and the ultrasonic modulus were associated with the secondary thermomechanical relaxations that have been recorded and identified. Pre‐plastic and plastic behaviors were discussed in terms of flexibility and crosslink density. A linear relationship was established between pre‐plastic activation volume and crosslink density at temperatures lower than the activation of molecular chain motions responsible for the sub‐Tg relaxations. At 0°C, a temperature above these secondary transitions, the higher the flexibility, the more defect nucleation and propagation increased. The work hardening rate and the upper yield stress decreased as the amount of diluent was increased. Fracture toughness was improved as the amount of diluent was increased. Crack propagation was related to the ability of the networks to deform plastically.

High-Pressure Ignition of Oil Sands Samples in Oxygen Atmospheres Containing Various Concentrations of Diluents

In-situ recovery of oil from oil sands deposits by combustion requires the injection of vast quantities of oxygen into the bed of deposits. Accordingly, there is a need to establish the ignition characteristics of high-grade Athabasca oil sands in environments containing pure oxygen at high-pressure and including the role of the presence of various diluents with the oxygen. A high-pressure constant volume bomb with a water calorimeter was employed as the test apparatus over the pressure range of 0.1 MPa to 4.0 MPa at ambient temperature. The role of the presence of the diluents, helium, nitrogen and carbon dioxide, with the oxygen, was also considered. Controlled ignition was achieved by employing electrically fusable nickel-chromium wire looped around the sample. Moreover, the presence of an ignition promotor such as benzoic acid was also considered. The paper presents the results of an experimental program that examined the effects of changes in the pressure, amounts of diluents and ignition energy on the ignition limits and subsequent combustion processes at ambient initial temperature. Moreover, the morphological changes to the samples at various stages of the process were also examined and discussed.

Offshore Production of Heavy Oil

This paper presents methods developed to enable the lifting and producing of low-gravity, high-viscosity crude from offshore fields. Relative advantages and disadvantages of several lifting, treating, and transportation methods are discussed. The paper also reviews actual experiences with heavy-oil production offshore southern California, as well as plans for development of newly discovered heavy-oil fields in the Santa Maria basin offshore central California and offshore Sicily in the Mediterranean Sea.

ＮｂＮの自己燃焼合成と超伝導特性

An investigation has been made on the synthesis of superconducting NbN and (Nb, Mo)N powders by a combustion reaction of nitriding their metal elements under high nitrogen pressures up to 10MPa. Nearly stoichiometric B1-NbN powders were prepared by the combustion reaction of Nb powders with a proper amount of NbN addition under 1-10MPa nitrogen pressures. The characteristics of this combustion reaction were investigated by measuring the propagating velocity of combustion for the packed reactants with various amounts of diluent. The superconducting transition temperature of NbN powders obtained was 16.9K, which is very close to the highest value of 17.3K reported for NbN up to now. On the other hand, Nb powders with 5, 10, and 20wt% Mo were burned under 10MPa nitrogen pressure in order to synthesize (Nb, Mo)N solid solutions. The combustion product of Nb with 5wt% Mo consisted of B1 phase only, while those with 10 and 20wt% Mo contained a small amount of residual Mo. The transition temperatures in the Nb-Mo-N system were 12.7-15.9K, which were lower than that of pure NbN obtained in this study.

The study of modified poly(styrene‐co‐divinylbenzene) by inverse gaschromatographic analysis

AbstractFor modified poly(styrene‐co‐divinylbenzene) the changes in supermolecular structure resulting from diluting the monomers during copolymerization with various amounts of inert diluents were studied. It has been found that the copolymers, obtained in the presence of substantial amounts of diluent, have a looser structure than those obtained with less diluent, as suggested by both the swelling measurements and the results of the inverse gas chromatographic (IGC) analysis. By this latter method it was found that the looser the copolymer structure, the broader was the range of adsorption‐absorption nonequilibrium region and the lower was the heat of adsorption of normal aliphatic alcohols by the copolymers. Since the copolymers had the same crosslinking degree, no difference in their apparent glass transition temperatures were detected.

Screening for Barbiturates in Vitreous Humor by the EMIT®-st Serum Enzyme Immunoassay

In 16 medical examiner's cases, which were found to be barbiturate-positive by thin-layer chromatographic screening of the liver, blood barbiturate concentrations were determined by gas chromatography. The corresponding vitreous humor samples were screened by the enzyme multiplied immunoassay technique, the EMIT-st serum barbiturate assay. By using the recommended dilution for detecting serum barbiturates, it was possible to detect barbiturates in vitreous humor at a toxic concentration. By using one fourth the amount of diluent, the barbiturates could be detected also at a therapeutic concentration. The EMIT-st assay proved to be useful in the screening for barbiturates in vitreous humor, a material that is readily available in forensic toxicology.

Extraction and sorption studies using linear polymer chains and model networks

AbstractModel networks have been prepared by tetrafunctionally endlinking linear polydimethylsiloxane (PDMS) chains having molecular weights Mn in the range 2000–15,000 g mole−1. The first series of networks were prepared from mixtures containing known amounts of unreactive linear PDMS chains with molecular weights Md between 1000 and 16,000 g mole−1. Rates of extraction were used to estimate diffusion coefficients; as expected, they were found to increase with increase in molecular weight Mc = Mn between crosslinks, but to decrease with increase in Md. The ease with which all of such a diluent could be removed showed the same dependence on Mc and Md. A second series of networks was prepared from the same reactive PDMS chains without diluents. Sorption and extraction studies using the same diluents were then carried out. The diffusion coefficients for sorption were found to be in the range (1.7–15.0) × 10−12 m2 s−1 and depended on both Mc and Md. The amount of diluent absorbed at equilibrium was between 10 and 70%, which is in good agreement with predictions from the Flory equation for dilation in networks, with account of constraints on crosslink fluctuations.

Effects of varying dilutions of quality control sera onprecision of analytes

Precisions obtained during an “unknown” quality control program using lyophilized serum reconstituted with varying amounts of diluent were compared with precisions achieved with the manufacturer's recommended dilution for 23 commonly measured analytes, including enzymes and radioimmunoassays, for four laboratories over two years. Except for bilirubin and possibly calcium and alkaline phosphatase, no tendency to deterioration of precision was observed as a result of varying the volume of diluent. The range of dilutions was from 92% to 108% of the recommend volume.

Use of a nomogram to quantitate plasma dilutions for serological testing following blood collection in capillary tubes

A technique for the processing and quantitation of small volumes of plasma collected in heparinized capillary tubes is presented using a nomogram that determines the final amount of diluent needed for variable volumes of plasma.

Electrophysiologic effects of Tween 80 in the myocardium and specialized conduction system of the canine heart

Amiodarone, a wide spectrum antiarrhythmic agent, has been associated with hypotensive reactions in man as well as in dogs after intravenous use. This hypotensive effect has been attributed to Tween 80, the diluent in the commercially available form of amiodarone. We studied the electrophysiologic effects of Tween 80 in the cardiac conduction system of the dog. Electrophysiologic studies were conducted in anesthetized adult dogs before and after the administration of 10 and 20 mg/kg of Tween 80, equivalent to the amount of diluent in 5 and 10 mg/kg respectively of commercial intravenous amiodarone. In addition to a drop of 60% in systolic blood pressure and 66% in diastolic blood pressure (p less than 0.005), 10 mg/kg of Tween 80 induced a decrease in heart rate (sinus cycle length increased from 523 +/- 57 msec to 662 +/- 27 msec, p less than 0.025), prolongation of sinus node recovery time (652 +/- 77 msec to 804 +/- 45 msec, p less than 0.05), depression of AV nodal function manifested by induction of Wenckebach at longer cycle length (from 208 +/- 18 msec to 266 +/- 14 msec, p less than 0.005), and increase in atrial ERP (from 138 +/- 7 msec to 176 +/- 14 msec, p less than 0.025) and FRP (from 180 +/- 14 msec to 209 +/- 12 msec, p less than 0.025). No further significant changes were observed after the second Tween 80 dose. The ventricular ERP increased significantly (from 168 +/- 18 msec to 20 +/- 16 msec, p less than 0.025) following the 20 mg/kg dose. It is demonstrated that Tween 80 is a potent depressant of the cardiac conduction system in the dog, capable of causing electrophysiologic changes similar to those produced by amiodarone in humans and dogs.

The use of model networks with reptating chains to study extraction efficiencies

AbstractIt is possible to prepare “model” elastomeric networks having known values of the molecular weight Mc between crosslinks by endlinking functionally terminated polymer chains having number‐average molecular weights Mn equal to the desired values of Mc. If chains having chemically inert groups at both ends are intentionally included during the preparation of such a system, they will remain unattached, merely reptating through the subsequently formed network structure. This technique was used to prepare a series of tetrafunctional polydimethylsiloxane (PDMS) networks having essentially the same degree of crosslinking (10−3Mc = 11.3 g mol−1) and constant amount of diluent in the form of unattached PDMS chains having molecular weights of 10−3Md = 26.4, 18.6, 15.8, 9.8, 6.7, 1.2, and 0.70 g mol−1. Because of the very high mobility of PDMS, it was also possible to introduce essentially the same amount of the same diluents into already formed PDMS networks having the same Mc. Extractions carried out using tetrahydrofuran at room temperature showed that the diluent (“sol fraction”) introduced by swelling the network is more easily removed than that present during the endlinking, possibly because of less convoluted arrangements within the network structure. Chains with the largest values of Md which were present during the endlinking were found to be very difficult to remove entirely. It is therefore extremely important to carry out exhaustive extractions to obtain reliable values of network sol fractions, particularly when such data are to be used to estimate extents of reaction in the preparation of end‐linked elastomers.

Styrene‐divinylbenzene copolymers, IV. Structure and texture changes during synthesis

AbstractStyrene‐divinylbenzene macroporous resins were prepared with the same composition (13% DVB), but varying diluent amount of benzyl alcohol. From sample analysis, the copolymerization kinetics concerning both monomer consumption and residual double bond amount were determined. Porous texture and morphology analyses by BETBrunauer, Emmett, Teller. , BJHE. P. Barrett, L. G. Joyner, P. P. Halenda, J. Am. Chem. Soc. 73 (1951) 373. , Mercury porosimetry, and scanning electron microscopy were carried out, too. Depending on diluent amount, the final product is classified as inside or outside the macroporous domain. Texture evolution is clearly different for the two classes of products, although their chemical evolutions are almost the same. A qualitative discussion of porous texture formation is presented, based on occurrence of three critical events: gelation, phase separation and molecular overlap.

Swelling and collapse of polymer networks

The swelling of a polymer network in a good solvent and of the collapse of this sample in a poor solvent is discussed theoretically for networks prepared in the presence of a large amount of diluent. The notation used is convenient for comparison with the theory of the swelling and collapse of a single macromolecule. The reference state for the networks under consideration must be chosen near the θ temperature for the corresponding linear macromolecule. For a free network and a network with fixed dimensions along one or two axes we obtain asymptotic results for the swelling of the network in a good solvent; these do not coincide with the classical Flory results. Results for the collapse of the network, which takes place upon cooling below the θ-point are also obtained. The collapse can occur either as a discrete first order phase transition (if the network chains are stiff or if it is stretched along one or two axes), or as a continuous non-phase transition (located in a narrow temperature range).

The structure of low conversion polymers of ethylene dimethacrylate

Results of study of the pregel chain polymerization of ethylene dimethacrylate in the presence of various amounts of diluent suggest the formation of compact microgel-like particles even at the very beginning of polymerization, as a consequence of predominant cyclization. This view is based on following experimental findings. The fraction of units with pendant vinyls (70 mol %) is independent of conversion and depends only slightly on dilution; critical conversion at gelation is displaced by a factor of about 10 2; molecular weights at the beginning correspond approximately to molecular weights of poly(methyl methacrylate) obtained under the same conditions; intrinsic viscosities are very low and much lower than those of strongly branched poly(methyl methacrylates).

Styrene divinyl benzene copolymers. I. Texture of macroporous copolymers with ethyl‐2‐hexanoic acid in diluent

AbstractThe texture and the pore size distribution of a set of styrene divinylbenzene copolymers, prepared by suspension polymerization with various compositions and various amounts of ethyl‐2‐hexanoic acid as diluent, have been studied using nitrogen adsorption‐desorption isotherms, mercury porosimetry, and scanning‐electron microscopy. It appears that pore volume and surface area may be well predicted in a large range of conditions (divinylbenzene contents between 20 and 60%, ethyl‐2‐hexanoic acid contents between 35% and 60%). In this range of conditions there are three structures: the elementary nuclei are spherical particles of about 100–200 Å in diameter. They are organized in microspheres of about 500–1000 Å, and the microspheres form aggregates (2500–5000 Å) more or less separated by large holes. The smaller pores (<40 Å) are in the microspheres, between the nuclei; they are present only if the amount of divinylbenzene is high enough. Intermediate pores (40–500 Å) are, in the aggregates, between the microspheres, although the larger pores between the aggregates range from about 500 Å to more than 10,000 Å, depending on the amount of diluent.

Crystallization of poly(vinylidene fluoride): Equilibrium melting point and heat of fusion of the α‐polymorph

AbstractSamples of poly(vinylidene fluoride) were crystallized either (a) isothermally at a series of temperatures, or (b) in the presence of varying amounts of diluent (dimethylphthalate or dimethylacetamide). The α‐polymorph was the only crystalline form present in these samples. Melting points of the first series (a) were determined by DSC and of the second (b) by dilatometry. The same equilibrium melting point for the α‐polymorph (178°C) was obtained from analysis of the two sets of data. A value of 1425 cal mole−1 (5.96 kJ mole−1) for the heat of fusion of this polymorph was obtained from analysis of the polymer–diluent melting data. The heat of fusion and the entropy of fusion calculated therefrom correlated well with corresponding values for other fluoroethylene polymers. Thus, the equilibrium melting point and the heat of fusion could be predicted for a fluoropolymer for which data have not yet been reported–poly(trifluoroethylene). The melting point predicted, 222°C, agreed remarkably well with that determined here for an experimental sample, thereby lending support to the empirical correlations. The heat of fusion of poly(trifluoroethylene) is, therefore, expected to be approximately 1300 cal mole−1.

SO2 promoted oxidative dehydrogenation of ethylbenzene

AbstractIt has been demonstrated that SO2 acts as an efficient dehydrogenation agent in the conversion of ethylbenzene to styrene in the presence of alkali and alkaline earth metal oxide doped alumina and titania catalysts. Development of these catalysts, which give styrene yields of greater than 80% per pass, is described in the paper. The catalysts allow the use of close to stoichiometric amounts of sulphur dioxide, are active in the presence of steam diluent and show low deactivation with time. The effect of varying process conditions such as temperature, reactant concentration and diluent amount is also described.