Progressive lowering temperature

The experimental value of Tg appears at progressively lower temperatures the more slowly the experiment is conducted. 

Live attenuated vaccines for RSV are also being developed. Most of these vaccine candidates are derived from cold adaptation, by passing the vims at progressingly lower temperatures than human body temperatures. However, other means of mutagenesis have been used to generate vaccine candidates (72). Several clinical trials of these vaccines are also in progress (73,74). 

The first rhodium-catalyzed reductive cyclization of enynes was reported in I992.61,61a As demonstrated by the cyclization of 1,6-enyne 37a to vinylsilane 37b, the rhodium-catalyzed reaction is a hydrosilylative transformation and, hence, complements its palladium-catalyzed counterpart, which is a formal hydrogenative process mediated by silane. Following this seminal report, improved catalyst systems were developed enabling cyclization at progressively lower temperatures and shorter reaction times. For example, it was found that A-heterocyclic carbene complexes of rhodium catalyze the reaction at 40°C,62 and through the use of immobilized cobalt-rhodium bimetallic nanoparticle catalysts, the hydrosilylative cyclization proceeds at ambient temperature.6... 

However, further milling for 10 and 20 h does not measurably shift the peak maximum to progressively lower temperatures (Fig. 2.29b). Second, a smooth and symmetrical DSC peak of the as-received powder transforms after milling into an asymmetrical peak having a pronounced low-temperature shoulder (Fig. 2.29a,b). The appearance of this shoulder on a DSC pattern can be assigned to the decomposition of mostly y-MgH being formed. 

An aqueous solution contains 50.0 wt% KNO3 at 80 0. To what temperature would this solution have to be cooled before solid crystals begin to form What happens as the solution is cooled to progressively lower temperatures ... 

The eroded channels on Mars s surface show that the planet once had running water. Water boils at progressively lower temperatures as one goes to higher altitudes because the atmospheric pressure is lower. (At lower pressures it is easier for molecules to escape the surface of a liquid.) On Mars today, water would boil immediately even at the low Martian temperatures, because the atmospheric pressure is so low. This suggests that the Martian atmosphere was once much denser than it is now. Otherwise, water could never have flowed on the planet s surface. 

HF behaves quite differently from the other halogen acids, and nothing is yet known of the structures of its hydrates. The hydrates of HCl melt at progressively lower temperatures (-154°, -174°, and -24-9°C) and the crystal structures of all three are known. The i.r. spectrum of the monohydrate (at —195°C) indicates the presence of pyramidal H30 ions structurally similar to the isoelectronic NH3 molecule. This has been confirmed by the determination of the crystal structure. In corrugated 3-connected layers of the simplest possible type (Fig. 15.25(a)) each 0 or Cl atom has three pyramidal neighbours, so that the units are Cl and H30 ions, (i). The distance 0—H--C1 is 2-95 A and the interbond angle 0—H—0 is 117°. 

Metal nitrites and nitrito compounds. Until recently the only stable simple metal nitrites known were those of the alkali and alkaline-earth metals, Zn, Cd, Ag(i), and Hg(i). The alkali nitrites decompose at red heat, the others at progressively lower temperatures. The ionic nitrites of the more electropositive metals contain the NOJ ion which in NaN02 has the following configuration ONO, 1154°, and N-0, 1-236 A. It may be of interest to summarize here the structural data for the unique series NOj, NO2, and NO2 with respectively 16,17, and 18 valence electrons ... 

Recovery of ethylene (b.p. —103.7°C) from the mixed hydrocarbon product vapors is accomplished by compression, condensation, and then fractionation at progressively lower temperatures. Ethane (b.p. —88.6°C) is the most difficult constituent to separate from ethylene, but even this is technically feasible. 

As the size of the ester alkyl group increases in a series of poly(n-alkyl methacrylate)s, the polymer molecules become spaced further apart and the intermolecular attraction is reduced. Thus, as the length of the side chain increases, the softening point decreases, and the polymers become rubbery at progressively lower temperatures (Figure 4.9). However, when the number of carbon atoms in the side chain exceeds 12, the polymers become less rubbery, and the softening point, brittle point, and other... 

Sequential traps at progressively lower temperatures, with the first designed for water vapor, can overcome this difficulty. To avoid combustion hazards. 

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