THE FORMATION AND COEXISTENCE OF GIBBSITE, BOEHMITE, ALUMINA AND ALUNITE AT ROOM TEMPERATURE

1982 ◽  
Vol 62 (2) ◽  
pp. 327-332 ◽  
Author(s):  
S. SHAH SINGH
Keyword(s):  
Room Temperature ◽  
Thermal Conditions ◽  
Laboratory Conditions ◽  
Aluminum Sulphate ◽  
Aluminum Compounds ◽  
Solid Phases

The formation and coexistence of four aluminum compounds, namely, gibbsite (Al(OH)3), boehmite (AlOOH), alumina (Al2O3) and alunite (NaAl3(OH)6(SO4)2) is reported under laboratory conditions. These solid phases were formed as hydrolytic products of aluminum sulphate solutions at room temperature. These results provide evidence that thermal conditions are not essential and not the only conditions under which boehmite and alumina are formed.

scholarly journals Hetero-Diels–Alder reactions of hetaryl and aryl thioketones with acetylenic dienophiles

2015 ◽  
Vol 11 ◽  
pp. 576-582 ◽  
Author(s):  
Grzegorz Mlostoń ◽  
Paulina Grzelak ◽  
Maciej Mikina ◽  
Anthony Linden ◽  
Heinz Heimgartner
Keyword(s):  
High Pressure ◽  
Room Temperature ◽  
Thermal Conditions ◽  
Alder Reaction ◽  
Diels Alder ◽  
Hydrogen Shift ◽  
Diels Alder Reaction ◽  
Shift Sequence

Selected hetaryl and aryl thioketones react with acetylenecarboxylates under thermal conditions in the presence of LiClO4 or, alternatively, under high-pressure conditions (5 kbar) at room temperature yielding thiopyran derivatives. The hetero-Diels–Alder reaction occurs in a chemo- and regioselective manner. The initially formed [4 + 2] cycloadducts rearrange via a 1,3-hydrogen shift sequence to give the final products. The latter were smoothly oxidized by treatment with mCPBA to the corresponding sulfones.

scholarly journals Growth of immature Chironomus calligraphus (Diptera, Chironomidae) in laboratory conditions

2011 ◽  
Vol 83 (4) ◽  
pp. 1279-1286 ◽  
Author(s):  
Rita de Cássia S.A. Canteiro ◽  
Edélti F. Albertoni
Keyword(s):  
Native Species ◽  
Room Temperature ◽  
Average Length ◽  
Larval Growth ◽  
Time Duration ◽  
Constant Growth Rate ◽  
Fish Food ◽  
Laboratory Conditions ◽  
Spiral Form ◽  
Constant Growth

Chironomidae larvae are important macroinvertebrates in limnic environments, but little knowledge exists about their biometrics development characteristics. This study aims to describe the immature Chironomus calligraphus Goeldi, 1905 under laboratory conditions by the accomplishment of thirteen egg masses from eggs eclosion to adults emergency, at controlled room temperature (25ºC) and photoperiod (12-12h). Larvae were feed ad libitum with "Alcon Basic - MEP 200 Complex" fish food and commercial dehydrated Spirulina. The postures had a mean length of 9 ± 1 mm (n = 13) and 348 ± 66 eggs. The brownish colored eggs with elliptical shape had length of 160.3 ± 17.7 µm (n = 130), being arranged as an organized string in a pseudo spiral form. The time duration from the first to the four instars were three, four, four and eight days, and the average length of a cephalic capsule to each one of the instars (66.3 ± 12.3 µm, 102.9 ± 22.1 µm, 159 ± 24.6 µm, 249.2 ± 29.7 µm, n = 456) were significantly different (ANOVA, p < 0.001). The Dyar’s Rule showed a constant growth rate, r = 1.5. Our results demonstrated that C. calligraphus is a species with short life cycle, low mortality rate, food adaptability, fast larval growth and easily maintained at laboratory, factors that allowed the use of this native species as a tool for ecotoxicological tests.

Analysis and Interpretation of Microstructures after Liquid Oxide Corrosion

2010 ◽  
Vol 70 ◽  
pp. 114-129
Author(s):  
Jacques Poirier
Keyword(s):  
Experimental Data ◽  
High Temperature ◽  
Room Temperature ◽  
Local Thermodynamic Equilibrium ◽  
High Alumina ◽  
Essential Information ◽  
Phase Rule ◽  
Liquid Oxide ◽  
Chemical Profiles ◽  
Solid Phases

Corrosion by liquid oxides is one of the most severe modes of degradations which limit the lifetime of the refractory linings. The study of the microstructures of corroded refractories provides essential information. However, the interpretation of the microscopic observations is difficult : - The refractories are multi-component and heterogeneous ceramics, - The microscopic observations are carried out at room temperature. They are not representative of the mineral and vitreous phases existing at high temperature, - During cooling, new solid phases appear by crystallization of liquid oxides. The composition of the vitreous phases also evolves with the temperature. Consequently, the information obtained is often limited. In this paper , we will present a method to analyse and interpret the microstructures of refractories after use. The concept of local thermodynamic equilibrium and the use of the phase rule make it possible to interpret the microstructures of corroded refractories, to explain the observed mineral zonation and to quantify the composition of the liquid phase at high temperature from chemical profiles established by S.E.M. Experimental data from corrosion of MgO-C, Al2O3-MgO and high alumina refractories will illustrate and validate this theoretical approach.

Phase Transitions and Water Dynamics of [Mn(H2O)6](ClO4 )2 Studied by Differential Scanning Calorimetry and Neutron Scattering Methods

2000 ◽  
Vol 55 (9-10) ◽  
pp. 759-764 ◽  
Author(s):  
E. Mikuli ◽  
A. Migdał-Mikuli ◽  
I. Natkaniec ◽  
J. Mayer
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Neutron Scattering ◽  
Structural Phase Transition ◽  
Room Temperature ◽  
Structural Phase ◽  
Water Dynamics ◽  
Water Molecules ◽  
Temperature Phase ◽  
Solid Phases

Abstract DSC measurements performed at 95 -290 K have shown that [Mn(H 2 O) 6 ](CIO 4) 2 possesses, besides a high-temperature phase, existing above 323 K, four low-temperature solid phases. The inelastic incoherent neutron scattering (IINS) spectra and neutron powder diffraction (NPD) pat-terns registered at 20 -290 K have supported the DSC results and provided evidence that the investigated substance possesses even more than five solid phases. The IINS spectra have shown that in the room-temperature phase, water molecules perform fast stochastic reorientation at the picosecond scale. The orientational disorder characteristic for the room-temperature phase can be easily overcooled and frozen. Even by relatively slow cooling at ca. 40 K/hour a metastable, orientational (protonic) glass phase is formed below ca. 160 K. Below ca. 100 K, a structural phase transition was observed by the NPD, however the IINS spectra indicate existence of the pure ordered low-temperature phase only after annealing the sample for a few hours at 100 K. On heating, a structural phase transition takes place at ca. 120 K, and at ca. 225 K water molecules begin fast reorientation.

Formation Of Hydrogen Molecules In Crystalline Silicon Treated With Atomic Hydrogen

1996 ◽  
Vol 442 ◽  
Author(s):  
K. Murakami ◽  
N. Fukata ◽  
S. Sasaki ◽  
K. Ishioka ◽  
K. G. Nakamura ◽  
...  
Keyword(s):  
Raman Spectrum ◽  
Room Temperature ◽  
Crystalline Silicon ◽  
Molecular Gas ◽  
Frequency Shifts ◽  
Hydrogen Molecules ◽  
Solid Phases ◽  
Liquid And Solid Phases ◽  
Pressure Hydrogen ◽  
Rule Out

AbstractHydrogen molecules have been formed in crystalline silicon at various temperatures by a hydrogen-atom remote treatment. The Raman spectrum of the vibrational lines of hydrogen molecules in crystalline silicon is detected for silicon samples treated at temperatures between 250 and 500° C. The maximum production is obtained at 400° C. The Raman spectrum of hydrogen molecules in silicon observed at room temperature exhibits a frequency shift of around 4158 cm−1 and a very broad half-width of approximately 34 cm−1. Isotope shift also can be observed at around 2990 cm−1 in silicon treated with deuterium atoms at 400° C. The frequency shifts of the observed lines are in close agreement with those reported for molecular hydrogen and deuterium in gas, liquid, and solid phases. We discuss a model for the hydrogen molecule configuration and rule out the possibility of high-pressure hydrogen molecular gas in microvoids in crystalline silicon. These results indicate that hydrogen molecules exist at the tetrahedral interstitial sites in crystalline silicon.

Evidence of Radiolytic Oxidation of 241Am in Na+ / Cl− / HCO−3/ CO2−3 Media.

1992 ◽  
Vol 294 ◽  
Author(s):  
Eric Giffaut ◽  
Pierre Vitorge
Keyword(s):  
Aqueous Phase ◽  
Waste Disposal ◽  
Metallic Iron ◽  
Room Temperature ◽  
Extraction Methods ◽  
Slow Kinetics ◽  
Solid Phases ◽  
Radiolytic Oxidation ◽  
Chemical Conditions ◽  
Kinetics Of

ABSTRACTThis paper examines Americium behaviour in CI− media at room temperature in connection with environmental and waste disposal programs. Most published values on U, Np, Pu and Am complexation in chloride media have been determined using extraction methods. Spectrophotometric techniques are not sensitive enough to prove actinide complexation by chloride, which is confirmed in this paper for Am(III).Am(OH)3(s), AmOHCO3(s), Am2(CO3)3(s) or NaAm(CO3)2(s) solid phases can control the Am solubility, depending on the chemical conditions of the aqueous phase (usually PCO2). 241Am solubility is here found to be higher in NaCl 4M media than in NaCl 0.1 M (up to 3 orders of magnitude). Addition of a reducing agent (metallic iron) lowers the solubility. After a week, solubilities in NaCl 0.1 M and 4 M are similar. These results are consistent with Am(III) radiolytic oxidation to Am(V), due to cc radiations. Little evidence of Cl− or mixed Cl−-CO2−3 complexes is found in these conditions. In Na+-OH−-Cl− media, 241Am(III) oxidation had also been proposed. Slow kinetics of precipitation could induce experimental uncertainities.

scholarly journals Supramolecular Diversity of Oxabicyclo[2.2.2]octenes Formed between Substituted 2H-Pyran-2-ones and Vinyl-Moiety-Containing Dienophiles

Symmetry ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 1714
Author(s):  
Krištof Kranjc ◽  
Amadej Juranovič ◽  
Marijan Kočevar ◽  
Franc Perdih
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Thermal Conditions ◽  
Diels Alder ◽  
X Ray Diffraction ◽  
Secondary Product ◽  
X Ray ◽  
Primary Products ◽  
Stereogenic Centers ◽  
Pressure Synthesis

In Diels–Alder reactions, 2H-pyran-2-ones as dienes can yield a large variety of cycloadducts with up to four contiguous carbon stereogenic centers. Some of the potentially most useful, however difficult to prepare due to their low thermal stability, are the primary CO2-containing oxabicyclo[2.2.2]octenes, which could be formed as eight distinctive isomers (two sets of regioisomers, each of these composed of four different stereoisomers). A high-pressure synthesis of such products was recently described in a few cases where vinyl-moiety-containing dienophiles were used as synthetic equivalents of acetylene. However, structures of the primary products have been so far only rarely investigated in detail. Herein, we present seven novel single-crystal X-ray diffraction structures of such cycloadducts of both stereoisomeric forms, i.e., endo and exo. Additionally, we present a single-crystal structure of a rare case of a cyclohexadiene system stable at room temperature, obtained as a secondary product upon the retro-hetero-Diels–Alder elimination of CO2 under thermal conditions (microwave irradiation), during this elimination the symmetry is increased and out of eight initially possible isomers of the reactant, this number in the product is decreased to four. In oxabicyclo[2.2.2]octene compounds, centrosymmetric hydrogen bonding was found to be the predominant motif and diverse supramolecular patterns were observed due to rich variety of C–H⋯O and C–H⋯π interactions.

scholarly journals Lethal effect of a bait for Rhodnius prolixus (Hemiptera: Reduviidae), the vector of Chagas' disease, containing hexachlorocyclohexane (HCH), under laboratory conditions

1992 ◽  
Vol 34 (4) ◽  
pp. 295-301 ◽  
Author(s):  
Marli Maria Lima ◽  
Luis Rey ◽  
Rubens Pinto de Mello
Keyword(s):  
Mortality Rate ◽  
Chagas Disease ◽  
Room Temperature ◽  
Lethal Effect ◽  
Rhodnius Prolixus ◽  
Active Principle ◽  
Laboratory Conditions

The lethal effect of a bait containing an aqueous hexachlorocyclohexane (HCH) suspension at the concentration of 1g/l and maintained at room temperature was studied in the laboratory over a period of 12 weeks. The suspension was placed in a latex bag hanging inside a 1000-ml beaker tightly covered with nylon netting, and left there with no changes for 85 days. Sixteen groups of R. prolixas bugs, consisting on average of 30 specimens each, were successively exposed to the bait and observed at different intervals for one week each. The mortality rate was 100% for all groups, except for the 16th, whose mortality rate was 96.7%. As the groups succeeded one another, mortality started to occur more rapidly and was more marked at the 6- and 24-h intervals. Later tests respectively started at 6:00 a.m. and 6:00 p.m. showed that diurnal and nocturnal periodicity in the offer of food had no effect on mortality. First- and 2nd- instar nymphs and adults male were more sensitive and 5th- instar nymphs were more resistant to the active principle of the bait.

Factors influencing the emergence of a northern population of Eastern Ribbon Snakes (Thamnophis sauritus) from artificial hibernacula

2009 ◽  
Vol 87 (12) ◽  
pp. 1221-1226 ◽  
Author(s):  
J. Todd ◽  
J. Amiel ◽  
R. Wassersug
Keyword(s):  
Sample Size ◽  
Water Level ◽  
Water Table ◽  
Room Temperature ◽  
Thermal Conditions ◽  
Temperature Gradients ◽  
Northern Population ◽  
Water Level Rise ◽  
Factors Influencing

We investigated whether Eastern Ribbon Snakes ( Thamnophis sauritus (L., 1766)) use a rise in water level as a cue for emergence from hibernation. We also examined the hypotheses that snakes use temperature gradients or endogenous signals as emergence cues. Twelve artificial hibernacula were used to house 15 Ribbon Snakes. Water level and temperature were regulated. Four Ribbon Snakes emerged from hibernation without any manipulation of water level or temperature. Eight snakes emerged after thermal conditions in their hibernacula changed. Of these, one emerged after the hibernaculum was made warmer on the surface than at depth, four emerged after the room temperature was increased to 9 °C, and three emerged after incandescent lights were shone on the surface of each hibernaculum. Three snakes died during hibernation. Eight snakes chose to hibernate fully submerged in water. Although the sample size is too small to draw conclusions that are statistically significant at α = 0.05, our observations collectively suggest that Ribbon Snakes do not use a rise in water level as a cue to emerge. While water-level rise does not appear to be an emergence cue, hibernation below the water table may lead to increased survivorship by decreased metabolism and elimination of the risk of desiccation.

Conjugate Heat Transfer Scaling for Inconel 718

2017 ◽  
Author(s):  
William R. Stewart ◽  
Thomas E. Dyson
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Biot Number ◽  
Film Cooling ◽  
Inconel 718 ◽  
Conjugate Heat Transfer ◽  
Room Temperature ◽  
Internal Cooling ◽  
Laboratory Conditions ◽  
Transfer Testing

Over the last decade, conjugate heat transfer testing has been shown to be important because it replicates the sum of the hot gas path heat transfer coefficient, film cooling, film cooling heat transfer augmentation, bore cooling, conduction through the wall, internal cooling heat transfer coefficients, and the relative amounts of heat pick up in the cooling flow. Instead of measuring these boundary conditions in individual experiments, conjugate heat transfer testing measures the cumulative effect as well as each boundary condition’s effect on the others. Typically, matched Biot number heat transfer experiments are performed at near room temperature with a surrogate material; however, this study examines how the thermal conductivity of a nickel alloy sufficiently changes between room temperature and temperatures representative of turbine engines to allow matched Bi heat transfer tests using nickel at laboratory conditions. The ratio of the thermal conductivity of air to the thermal conductivity of Inconel 718 stays mostly constant between engine representative temperatures and room temperature. Over this range, the thermal conductivity of both air and Inconel 718 change ∼2.5X, and the change in thermal conductivity allows for conjugate heat transfer tests to match Reynolds number, Nusselt number, film effectiveness, Biot number, and Stanton number. Experimental results at two temperature conditions are shown confirming the theory. Finally, a method for scaling the thermal impact of dust accumulation at laboratory conditions to turbine conditions is proposed.

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