Calorimetric investigations on As-Te-Se and Ge-As-Se glasses

Results of calorimetric investigations performed on two groups of glasses, viz. As-Te-Se and Ge-As-Se, are described. The glass transition temperatureT _g and specific heat at constant pressureC _p of these two families of glasses have been determined using a differential scanning calorimeter. The composition dependence of glass transition temperature and variation of heat capacity during transition are discussed.     

Calorimetric measurements of nuclear quadrupole interactions in tellurium-doped bismuth

By doping bismuth with tellurium to increase the charge carrier density and thus speed up the slow nuclear spin-lattice relaxation the nuclear quadrupole heat capacity becomes measurable in contrast to pure bismuth. The quadrupole heat capacity is greatly influenced by doping, increasing by 64% over the pure bismuth value on the addition of 0.23 at. % of tellurium. This results from a local asymmetric distortion of the valence electron states of the bismuth ions around the impurity site.     

Topographic measurements of precision-ground optical glasses

We studied the surfaces of six precision-ground optical glass samples of fused silica, BK-7, BaCD16, LaC14, NbF1, and LHG8 glass, using a mechanical profiler, a photon tunneling microscope, and a scanning force microscope. The measured roughnesses of the scanning force microscope varied from 3.5 A rms for BK-7 glass to 30 A rms for LHG8 laser glass. Good agreement was obtained among the roughness values measured with all three instruments.     

Calorimetric output power measurements on a CW 20 kW 7.16 GHzmicrowave transmitter

A calorimetric measurement technique developed for NASA's Deep Space Network (DSN) transmitters that does not require data on the coolant's thermal parameters is described. Calibration of the measurement system is achieved by measuring the DC input power to the klystron and relating coolant temperature increase to this known power dissipation. Agreement between calorimetric and electrical measurements of total system power was good, the difference being less than 2%. The operation of the system was not greatly affected by the composition of the coolant, which was varied from pure water to 40% ethylene glycol by mass. Good accuracy was also shown at output power levels, which varied over a 3.6:1 range     

Calorimetric bridge schemes for thermophysical measurements under steady-state thermal conditions

We consider the possibilities for using bridge measurement methods as applied to determination of the thermal resistance and thermal conductivity. We present thermometric bridge schemes for determination of the thermal resistance and thermal conductivity of materials and substances in different physical states.Translated from Izmeritel'naya Tekhnika, No. 9, pp. 40–44, September, 1995.     

Calorimetric Cv-V-T measurements and the equation of state for n-Propyl alcohol

Calorimeteric C_v-V-T measurements have given a new equation of state for n-propyl alcohol, which incorporates qualitative features of the critical point and the stability limit for the homogeneous phase (spinodal).Deceased.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 2, pp. 275–281, August, 1986.     

Calorimetric measurements of transformation thermodynamics and thermal efficiencies of NiTi helices

The latent heats and thermal efficiency of a NiTi helix as the driving element of a Shape Memory Effect (SME) heat engine was measured by an adiabatic calorimeter capable of simulating a heat engine cycle. The latent heat measurements were found to be highly variable. Thermal efficiencies between 2.6 and 4.5% were measured in the limit of low external stresses needed for reproducible cycling behaviour.     

Detection of strength limiting defects in cellular glasses by dielectric measurements

Cellular (foamed) glasses are a prime candidate for certain structural applications, such as support of the silvered glass concentrator mirrors in solar thermal energy systems. An economical nondestructive measurement of strength-limiting defects in these materials would permit development of designs in which the material is subjected to a higher working stress level and maintains the same probability of failure. This would result in weight and cost savings for any application. A method of measuring the capacitance of well-defined regions of a specimen was investigated. Large voids were found to produce significant localized changes in the capacitance of the specimen. The feasibility of locating the large, strength limiting defects in this porous material has been demonstrated for one type of cellular glass. Means of producing an image from this type of data and an implementation scheme for on-line production measurements are discussed.     

Calorimetric dissolution testing.

It is frequently desirable to obtain dissolution information about a new drug in the pre-formulation stage. This is difficult for two reasons. One is that there usually is not much drug available at this particular point in time (and e.g. a rotation disk dissolution (Levich, 1962) can hence, not be carried out). Another reason is that the assay methodology may not be completely worked out.

The article to follow deals with the possibility of using calorimetry for this purpose. With a sensitive calorimeter it may be possible to determine dissolution characteristics at the hydrodynamics prevalent in the calorimeter, and then to correlate them with what happens in a USP dissolution apparatus.

Sodium chloride has been used here as a hydrodynamic calibrator, and the system checked with ascorbic acid and propantheline bromide as model drug substances, cornstarch and microcrystalline cellulose as model excipients and salicylic acid acetylsalicylic acid tablets as model tablets.     

Calorimetric Detection of X-Rays

During the past 15 years a broad range of cryogenic particle detectors have been developed primarily for use in astro-particle physics, nuclear physics and material science. Among these, calorimetric detectors play an important role. In particular, micro calorimeters have proven to be a suitable tool for the detection of x-rays. We will discuss the concept of calorimetric particle detectors and the results for x-ray detection obtained with different types of calorimeters.     

Calorimetric Measurements of CuAlNi Alloys

The martensitic transformation of CuAlNi single crystals is measured by DSC (differential scanning calorimeter). An isothermal single interface DO3→2H transformation arises when the specimen is quenched at a slow rate, but 2H→DO3 transformation always proceeds with multiple interfaces due to the existence of stored elastic energy inside martensite. The elastic energy is essentially stored on the martensitic interfaces and results in As→Mf, which brings a separate spectrum of heat flow on the measured curve. The size of stored elastic energy affects the hysteresis     

Combustion Calorimetric Studies on C60 and C70

Combustion calorimetric studies on C₆₀ and C₇₀ were made using a new micro-bomb combustion calorimeter. Standard enthalpies of formation at 298.15 K were determined to be (2273±15) kJ·mol^-1 and (2375±18) kJ·mol^-1 for C₆₀ and C₇₀, respectively.