Results For Temperature Change Research Articles

Low temperature phase transitions of [(NH 4) 1−xRb x] 3H(SO 4) 2 studied by XRD and Raman spectroscopy

Detailed temperature XRD and Raman studies were performed at successive low temperature phase transitions to determine the role of cation ions at low temperature phase transitions of [(NH 4) 1− x Rb x ] 3H(SO 4) 2 mixed crystals. Mixed crystals with low concentration of Rb ( x = 0; 0.03; 0.05) were chosen for the studies. Temperature XRD studies of [(NH 4) 0.97Rb 0.03] 3H(SO 4) 2 revealed a conspicuous jump of lattice parameters at the phase transition from P2/ n to P 1 ¯ at T 4 ≈ 125 K and insignificant changes at T 2 ≈ 260 K and T 3 ≈ 140 K. The crystal structure of [(NH 4) 0.97Rb 0.03] 3H(SO 4) 2 for all low temperature phases was also determined. The results of temperature changes of Raman spectra showed conspicuous changes of the frequencies related to internal vibrations of the constituents of the SO 4 H…SO 4 dimers at temperature T 4. Significant changes were also observed for the external vibration related to NH 4 + groups. It was shown that all low temperature phases exhibit ferroelastic properties. The ferroelastic domain structure undergoes a change at T 4. The results of our studies indicate a fundamental role of NH 4 + groups at low temperature phase transitions. A small amount of Rb added to the (NH 4) 3H(SO 4) 2 leads to disappearance of these phases.

Badenian discoasters from the section in Lenart (Northeast Slovenia, Central Paratethys)

In Slovenske gorice, south of Lenart, a 20 m profile of Middle Miocene strata has been exposed. During previous research numerous discoasters have been found among other coccoliths. In Slovenia Miocene discoasters have only been found in Badenian sediments in Slovenske gorice and they are particularly useful for paleoecological reconstructions. Additional samples were taken from three selected sections in the middle part of the profile, targeting strata with the greatest abundance of discoasters. In two of the three examined sections 9 species of discoasters were identified, the most abundant being D. exilis and D. variabilis. Even though warm water species were found in samples from all three sections, discoasters only occured in two short intervals. This pattern is not a result of temperature changes and is in our opinion connected with the changes in nutrient levels of seawater.

Transient piezothermoelastic problem for a laminated composite strip composed of angle-ply and piezoelectric laminae

This paper is concerned with the theoretical treatment of transient piezothermoelastic problem which is developed for a laminated composite strip composed of angle-ply laminae and a piezoelectric material of crystal class mm2, subject to nonuniform heat supply in the width direction. We obtain the exact solution for the two-dimensional temperature change in a transient state and the transient piezothermoelastic response of a simple supported composite strip under the state of generalized plane deformation. As an example, numerical calculations are carried out for a angle-ply laminated composite strip made of an alumina fiber reinforced aluminum composite, associated with a piezoelectric layer of a cadmium selenide solid. Some numerical results for temperature change, displacement, stress and electric potential distributions in a transient state are shown in figures. Furthermore, the influence of the thickness of the piezoelectric layer on the thermal stress or electric field is investigated.

Transient piezothermoelasticity for a cylindrical composite panel composed of angle-ply and piezoelectric laminae

This paper is concerned with the theoretical treatment of transient piezothermoelastic problem is developed for a cylindrical composite panel composed of angle-ply laminae and piezoelectric material of crystal class mm2, subject to non-uniform heat supply in the circumferential direction. We obtain the exact solution for the two-dimensional temperature change in a transient state, and transient piezothermoelastic response of a simple supported cylindrical composite panel under the state of generalized plane deformation. As an example, numerical calculations are carried out for an angle-ply laminated composite panel made of alumina fiber reinforced aluminum composite, associated with a piezoelectric layer of a cadmium selenide solid. Some numerical results for temperature change, displacement, stress and electric potential distributions in a transient state are shown in figures. Furthermore, the influence of thickness of the angle-ply laminate is investigated.

FT NIR Raman Studies of Ferroic Phase Transitions in β-LiNH 4 SO 4 and Pyridinium Periodate

The results of temperature changes of Raman spectra in the vicinity of ferroelectric-paraelectric phase transitions of g -LiNH 4 SO 4 and pyridinium periodate are presented. Conspicuous broadening of Raman lines with increasing temperature pointing to disordering of molecular groups is observed in both crystals. The changes in the vicinity of paraelectric-ferroelectric phase transition in g -LiNH 4 SO 4 may show on first order near second order type. In pyridinium periodate temperature changes of frequencies of some lines indicate pseudo-spin - phonon interaction in ferroelectric phases.

Effects of Temperature on Mortality of Fingerling Channel Catfish (Ictalurus punctatus) Experimentally Infected with Channel Catfish Virus

When water temperature was reduced from 28 to 19 C for channel catfish (Ictalurus punctatus) fingerlings 24 hr after injection with channel catfish virus (CCV), 24% mortality occurred. In comparison, fish held at a constant temperature of 28 C had a mortality of 94% and those held in 19 C water had 14% mortality. Reducing the temperature to 19 C when the first deaths occurred at 28 C (64–72 hr after injection) resulted in 78% mortality. Insignificant mortality occurred in fish injected with Hanks’ balanced salt solution. Results of temperature change are discussed as to their potential value in reducing the effects of CCV disease under cultural conditions.

Hypothalamic temperature and the regulation of respiration of the ox exposed to severe heat.

1. Thermodes have been chronically implanted in the hypothalamus of the ox.2. During exposure of the ox to severe heat stress, rapid shallow panting changed to slower deeper panting when hypothalamic temperature (T(hy)) was approximately 40.5 degrees C. With subsequent rapid ambient cooling, hypothalamic temperature declined rapidly, and there was a reversion to rapid shallow panting before respiration slowly returned to normal.3. When hypothalamic temperature and rectal temperature (T(R)) had reached about 40 degrees C, raising hypothalamic temperature to about 41.4 degrees C did not cause the onset of slower deeper panting.4. When hypothalamic temperature and rectal temperature had exceeded about 41 degrees C and slower deeper panting was well established, lowering hypothalamic temperature to about 40 degrees C did not cause any reversion to rapid shallow panting.5. When hypothalamic temperature and rectal temperature had reached about 40 degrees C, holding hypothalamic temperature at 40 degrees C did not prevent the onset of the slower deeper phase of panting.6. Under moderate heat stress when hypothalamic temperature was approximately 39.9 degrees C and rectal temperature was approximately 40.4 degrees C, raising hypothalamic temperature at the same rate as that which was associated with the onset of slower deeper panting during severe heat stress, resulted in a parallel increase in the respiratory frequency and fall in rectal temperature; there was no change to the slower deeper form of panting.7. Holding hypothalamic temperature at 41.7-42 degrees C during post-heat cooling did not prevent the reversion to rapid shallow panting.8. It was concluded that the change from rapid shallow to slower deeper panting during severe heat stress, and the reversion to rapid shallow panting during subsequent cooling, were not the result of changes in temperature of the hypothalamic thermoregulatory centres.

Origin of the Salina Salt of Michigan

The purpose of this study was to determine the manner of deposition of the Salina salt, including the approximate temperature of deposition and the origin of the dolomite-anhydrite laminae. Specimens were obtained from drill cores from the Michigan basin and from the Detroit mine of the International Salt Company. The bulk of the data was obtained through thin section study and this was supplemented by the examination of polished slabs, water-insoluble residues, and sections of core from which the salt had been dissolved. Pyramidal shaped hopper crystals of halite, comparable to those crystals produced in the manufacture of grainer salt and those formed in the manufacture of solar salt, were identified in the Salina salt. The pyramidal forms were outlined by liquid inclusions, and from these inclusions the temperatures of formation were determined as being between 32.0 and 48.4 degrees C. The salt was deposited in layers or bands of three distinct types: (1) cloudy layers of inclusion-rich pyramidal shaped hopper crystals of halite, (2) clear layers of inclusion-free halite, and (3) laminae of anhydrite and dolomite. These units are in part obscured in the recrystallized salt. The alternation of bands of clear and cloudy halite was the result of temperature changes probably related to the seasons. The salt crystals, initially formed on the surface, grew as pyramidal shaped hoppers. Until the brine became saturated, settling hopper crystals were dissolved. After the saturation point had been reached pyramidal shaped hopper crystals accumulated on the bottom of the basin to form a layer of cloudy salt. With subsequent cooling the brine passed into the supersaturated state and settling hopper crystals provided nuclei for clear overgrowths. These crystals which grew on the bottom of the basin are inclusion-free and form the layers of clear salt. The return of higher temperatures followed again by lower temperatures would cause a repetition of this sequence. This cycle could have been interrupted at any time by the addition of brine to the basin or by periods of unusual climatic conditions. The deposition of the anhydrite-dolomite laminae may be considered to have been the result of the influx of normal sea water. The addition of brine to the basin as a surface layer would have permitted the maintenance of life in this brine until the concentration reached the point at which mass extermination took place. Subsequent decomposition of the remains caused reducing conditions to develop in the basin and iron precipitated as pyrite. Indicative of this influx is the association with the laminae of carbonaceous material, pyrite, and a petroliferous odor and the lack of a recognizable relationship between the clear or cloudy salt and the anhydrite-dolomite laminae. Iron associated with the halite layers is in the form of hematite, indicating that oxidizing conditions were normal for the basin.