SOME COMPLICATING FACTORS IN THE PHOTOLYSIS OF ACETONE

1955 ◽  
Vol 33 (1) ◽  
pp. 47-55 ◽  
Author(s):  
P. Ausloos ◽  
E. W. R. Steacie
Keyword(s):  
Low Temperatures ◽  
Room Temperature ◽  
Disproportionation Reaction ◽  
Methyl Radicals ◽  
Wall Effects ◽  
Arrhenius Plots ◽  
Complicating Factors ◽  
Low Pressures

The photolysis of acetone has been investigated at room temperature using low pressures and high intensities. In addition an investigation was made of the photolysis of azomethane–acetone mixtures. The results indicate that the curvature at low temperatures of Arrhenius plots of[Formula: see text][Acetone] is due to two causes (a) a reaction between methyl radicals and adsorbed acetone and (b) to the occurrence of the disproportionation reaction [Formula: see text]Confirmatory evidence for wall effects was obtained from experiments at low pressures and higher temperatures.

THE PHOTOLYSIS OF BIACETYL

1955 ◽  
Vol 33 (1) ◽  
pp. 39-46 ◽  
Author(s):  
P. Ausloos ◽  
E. W. R. Steacie
Keyword(s):  
Activation Energy ◽  
Excellent Agreement ◽  
Low Temperatures ◽  
Arrhenius Plot ◽  
Disproportionation Reaction ◽  
Methyl Radicals

The photolysis of biacetyl has been reinvestigated. The results are, in general, in excellent agreement with those of Blacet and Bell. Curvature occurs at low temperatures in the Arrhenius plot of [Formula: see text][Biacetyl], and this is attributed to wall reactions, and to the disproportionation reaction[Formula: see text]Azomethane–biacetyl mixtures have been photolyzed to give further information on these points. An activation energy of 8.5 kcal. has been found for the reaction of methyl radicals with biacetyl.

scholarly journals Review of Multi-Physics Modeling on the Active Magnetic Regenerative Refrigeration

2021 ◽  
Vol 26 (2) ◽  
pp. 47
Author(s):  
Julien Eustache ◽  
Antony Plait ◽  
Frédéric Dubas ◽  
Raynal Glises
Keyword(s):  
Magnetic Field ◽  
Low Temperatures ◽  
Room Temperature ◽  
State Of The Art ◽  
Vapor Compression ◽  
Crucial Step ◽  
Potential Alternative ◽  
Vapor Compression Refrigeration ◽  
Preliminary Study ◽  
Physics Modeling

Compared to conventional vapor-compression refrigeration systems, magnetic refrigeration is a promising and potential alternative technology. The magnetocaloric effect (MCE) is used to produce heat and cold sources through a magnetocaloric material (MCM). The material is submitted to a magnetic field with active magnetic regenerative refrigeration (AMRR) cycles. Initially, this effect was widely used for cryogenic applications to achieve very low temperatures. However, this technology must be improved to replace vapor-compression devices operating around room temperature. Therefore, over the last 30 years, a lot of studies have been done to obtain more efficient devices. Thus, the modeling is a crucial step to perform a preliminary study and optimization. In this paper, after a large introduction on MCE research, a state-of-the-art of multi-physics modeling on the AMRR cycle modeling is made. To end this paper, a suggestion of innovative and advanced modeling solutions to study magnetocaloric regenerator is described.

scholarly journals On the measurement of the ratio of the specific heats using small volumes of gas.—The ratios of the specific heat of air and of hydrogen at atmospheric pressure and a temperatures between 20°C. and —183°C

1925 ◽  
Vol 107 (743) ◽  
pp. 510-543 ◽  
Keyword(s):  
Systematic Error ◽  
Low Temperatures ◽  
Room Temperature ◽  
Expansion Chamber ◽  
Small Vessels ◽  
Specific Heats ◽  
Large Expansion ◽  
Before And After ◽  
The One ◽  
Chamber Capacity

Introduction .—In nearly all the previous determinations of the ratio of the specific heats of gases, from measurements of the pressures and temperature before and after an adiabatic expansion, large expansion chambers of fror 50 to 130 litres capacity have been used. Professor Callendar first suggests the use of smaller vessels, and in 1914, Mercer (‘Proc. Phys. Soc.,’ vol. 26 p. 155) made some measurements with several gases, but at room temperature only, using volumes of about 300 and 2000 c. c. respectively. He obtained values which indicated that small vessels could be used, and that, with proper corrections, a considerable degree of accuracy might be obtained. The one other experimenter who has used a small expansion chamber, capacity about 1 litre, is M. C. Shields (‘Phys. Rev.,’ 1917), who measured this ratio for air and for hydrogen at room temperature, about 18° C., and its value for hydroger at — 190° C. The chief advantage gained by the use of large expansion chambers is that no correction, or at the most, a very small one, has to be made for any systematic error due to the size of the containing vessels, but it is clear that, in the determinations of the ratio of the specific heats of gases at low temperatures, the use of small vessels becomes a practical necessity in order that uniform and steady temperature conditions may be obtained. Owing, however, to the presence of a systematic error depending upon the dimensions of the expansion chamber, the magnitude of which had not been definitely settled by experiment, the following work was undertaken with the object of investigating the method more fully, especially with regard to it? applicability to the determination of this ratio at low temperatures.

scholarly journals The behaviour of visual purple at low temperature

1941 ◽  
Vol 179 (977) ◽  
pp. 151-159 ◽  
Keyword(s):  
Aqueous Solution ◽  
Low Temperature ◽  
Low Temperatures ◽  
Room Temperature ◽  
Absorption Curve ◽  
Quantum Yields

Visual purple is soluble and stable in a mixture of glycerol and water (3:1). At room temperature the spectrum of such a solution is identical with that of the aqueous solution. At — 73° C the peak of the absorption curve is higher and narrower than at room temperature, and it is shifted towards longer waves. The product of photodecomposition at — 73° C has a spectrum in ­ dependent of pH and is at low temperatures thermostable and photostable, but at room temperature it decomposes therm ally to indicator yellow. The primary product appears to be identical with transient orange. The quantum yields of the photoreaction at low and at room temperature are of the same order.

Magnetic Properties of Sputtered Fe-O and Co-O Thin Films

1995 ◽  
Vol 403 ◽  
Author(s):  
D. V. Dimitrov ◽  
A. S. Murthy ◽  
G. C. Hadjipanayis ◽  
C. P. SWANN
Keyword(s):  
Grain Size ◽  
Low Temperatures ◽  
Room Temperature ◽  
Oxide Films ◽  
X Ray Diffraction ◽  
Dc Magnetron Sputtering ◽  
Large Shift ◽  
X Ray ◽  
Grain Size And Shape ◽  
Spherical Grains

AbstractFe-O and Co-O films were prepared by DC magnetron sputtering in a mixture of Ar and O2 gases. By varying the oxygen to argon ratio, oxide films with stoichiometry FeO, Fe3O4, α-Fe2O3, CoO and Co3O4 were produced. TEM studies showed that the Fe – oxide films were polycrystalline consisting of small almost spherical grains, about 10 nm in size. Co-O films had different microstructure with grain size and shape dependent on the amount of oxygen. X-ray diffraction studies showed that the grains in Fe-O films were randomly oriented in contrast to Co-O films in which a <111> texture was observed. Pure FeO and α-Fe2O3 films were found to be superparamagnetic at room temperature but strongly ferromagnetic at low temperatures in contrast to the antiferromagnetic nature of bulk samples. A very large shift in the hysteresis loop, about 3800 Oe, was observed in field cooled Co-CoO films indicating the presence of a large unidirectional exchange anisotropy.

scholarly journals Comparison of preservation methods of Atta spp. (Hymenoptera: Formicidae) for RAPD analysis

2000 ◽  
Vol 29 (3) ◽  
pp. 489-496 ◽  
Author(s):  
Alfredo O. R. Carvalho ◽  
Luiz G. E. Vieira
Keyword(s):  
Silica Gel ◽  
Low Temperatures ◽  
Room Temperature ◽  
Rapd Analysis ◽  
Limiting Factors ◽  
Dna Yield ◽  
Remote Locations ◽  
Leaf Cutting ◽  
Storage Methods ◽  
Plot Design

High quality DNA for molecular studies can be easily extracted from fresh specimens. However, live samples are difficult to keep for long periods thus making their preservation a serious problem, specially when they are collected and transported from remote locations. In order to establish an efficient method to preserve Atta spp. (leaf-cutting ants) for RAPD analysis, six different storage methods were examined: 1) -70°C; 2) 95% ethanol at -20°C; 3) 95% ethanol at 4°C; 4) 95% ethanol at room temperature; 5) silica gel at room temperature; and 6) buffer (0.25 M EDTA, 2.5% SDS, 0.5 M Tris-HCl, pH 9.2) at room temperature. DNA was extracted (Cheung et al., 1993 - modified) and examined after 90, 210 and 360 days of storage. Freshly killed specimens were used as control. DNA yield was measured with a minifluorometer. DNA quality was determined by scanning photographs with a densitometer and the integral of the scan was calculated for DNA of size > 9.4 kb. Data were analyzed using a completely randomized split-plot design with four replicates. All methods were efficient to preserve Atta spp. DNA up to 210 days. At 360 days, DNA was degraded only in 95% ethanol at room temperature, which resulted in RAPD profiles with missing bands. Although preservation at low temperatures is recommended for long periods, methods using silica gel and buffer can be considered satisfactory alternatives when refrigeration and transportation are limiting factors.

Dolomite Decomposition to (Ca,Mg)O Solid Solutions: An X-Ray Diffraction Study.Part II.

1984 ◽  
Vol 39 (10) ◽  
pp. 981-985 ◽  
Author(s):  
G. Spinolo ◽  
U. Anselmi Tamburini
Keyword(s):  
Free Energy ◽  
Low Temperatures ◽  
Particle Sizes ◽  
Diffusional Process ◽  
X Ray Diffraction ◽  
High Iron Content ◽  
X Ray ◽  
Energy Of Mixing ◽  
Free Energy Of Mixing ◽  
Low Pressures

Abstract The full decomposition of dolomites with low and high iron content at low temperatures and low pressures is discussed with reference to the free energy of mixing of the ternary system Ca. Fe, Mg/O. The actual products of the primary step are a couple of rock salt structured oxides close to the spinodal compositions and with very small particle sizes. A subsequent diffusional process can produce large crystallites with equilibrium compositions, but it is effective only when either a low-iron dolomite is used as starting material or higher temperatures are employed.

scholarly journals The catalytic combination of hydrogen and oxygen at the surface of platinum

1936 ◽  
Vol 156 (888) ◽  
pp. 284-306 ◽  
Keyword(s):  
Room Temperature ◽  
Quantitative Measurement ◽  
Silver Oxide ◽  
Catalytic Properties ◽  
Metallic Surface ◽  
Metallic Silver ◽  
Mercury Vapour ◽  
Platinum Surface ◽  
Gaseous Oxygen ◽  
Low Pressures

Research on the catalysis by metals of the combination of hydrogen and oxygen at low pressures was commenced in these laboratories by Cooper in 1923. Investigating the catalytic properties of a short platinum filament subjected to various pre-treatments by heating it electrically in hydrogen or oxygen or in vacuo , he found that the metallic surface thus cleaned became so active at room temperature as to render the quantitative measurement of the catalysed reaction impossible. It was discovered also that mercury vapour is a very potent poison of the surface, the enormously active clean platinum surface being rendered completely inactive by exposure to mercury vapour for a few minutes: a fact noted but apparently insufficiently emphasized in a paper published by Chapman and Hall in 1929. Owing to the difficulties involved in wording with a catalyst of such high activity, the research was discontinued in favour of an investigation of the same reaction using silver instead of platinum, a clean surface of this metal having been found to catalyse the reaction at a convenient rate at room temperature. The following facts were established:— (1) At the temperature of the laboratory a surface of metallic silver adsorbs completely a quantity of gaseous oxygen sufficient to form a complete unimolecular layer of silver oxide. This adsorbed oxygen cannot, of course, be removed by evacuation.

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