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PubMed1977

Interaction of air temperature and core temperatures in thermoregulation of the goat.

1. The interaction between air temperature, hypothalamus temperature, and spinal cord temperature in driving heat production and respiratory evaporative heat loss has been studied in conscious goats with chronically implanted thermodes. 2. Thermoregulatory heat production could be described as being approximately proportional to the sum of two linear drives determined by hypothalamus temperature and spinal cord temperature. This was found also for respiratory evaporative heat loss except that it was not influenced by spinal cord cooling. 3. Thermoregulatory heat production could be further described as being approximately proportional to a product of linear drives determined by hypothalamus and spinal cord temperature on one hand and air temperature on the other. Respiratory evaporative heat loss was approximately proportional to the sum of drives determined by spinal cord, hypothalamus and air temperatures. 4. Sensitivity to central cooling was found to undergo long-lasting but temporary changes which interfered with the immediate effects of air temperature on thermoregulation. 5. Central threshold temperatures for heat production and respiratory evaporative heat loss were found to be differently affected by air temperature. This indicates that integrating mechanisms for heat production and respiratory evaporative heat loss are to some extent functionally independent.

Animals↗
PubMed2002

Effect of environmental temperature on body temperature and metabolic heat production in a heterothermic rodent, Spermophilus tereticaudus.

This study quantifies the thermoregulatory ability and energetics of a mammal, the round-tailed ground squirrel Spermophilus tereticaudus, that can relax thermoregulatory limits without becoming inactive. We measured body temperature and metabolic rate in animals exposed for short periods (1 h) to air temperatures ranging from 10 to 45 degrees C and for long periods (8 h) to air temperatures ranging from 10 to 30 degrees C. Within 45 min of exposure to air temperatures ranging from 10 to 45 degrees C, the mean body temperatures of alert and responsive animals ranged from 32.1 degrees C (T(air)=10 degrees C) to 40.4 degrees C (T(air)=45 degrees C). This thermolability provided significant energetic savings below the thermoneutral zone, ranging from 0.63 W (18 %) at 10 degrees C to 0.43 W (43 %) at 30 degrees C. When exposed for 8 h to air temperatures between 10 and 30 degrees C, animals varied their body temperature significantly over time. At all air temperatures, the lowest body temperature (maintained for at least 1 h) was 31.2 degrees C. The highest body temperatures (maintained for at least 1 h) were 33.6 degrees C at 10 degrees C, 35.3 degrees C at 20 degrees C and 36.3 degrees C at 30 degrees C. The energetic savings realized by maintaining the minimum rather than the maximum body temperature was 0.80 W (25 %) at 10 degrees C, 0.71 W (33 %) at 20 degrees C and 0.40 W (47 %) at 30 degrees C. This study demonstrates in several ways the ability of this species to adjust energy expenditure through heterothermy.

Animals↗
PubMed1981

Autoregulation of skin temperature with feedback-assisted relaxation of the target limb, and controlled variation in local air temperature.

The primary aim of this study was to determine whether feed-back-assisted skin temperature regulation can be demonstrated when skeletomuscular mediation, in the form of altered local EMG activity, is prevented. A second aim was to determine whether the success of such regulation is affected by the basal temperature of the skin. 30 adult subjects were asked to increase or decrease the temperature of the index finger of the dominant hand, while the local musculature was kept in a relaxed state using EMG feedback. The local ambient air temperature surrounding the limb was set at either 10 degrees C, 24 degrees C, or 38 degrees C, resulting in large differences in basal skin temperature. Subjects were successful at both increasing and decreasing skin temperature while maintaining an integrated EMG output below 75 muV in the target limb. The magnitude of change, much smaller than those commonly reported in this field, did not vary across the air temperature levels, indicating that skin temperature autoregulation under these conditions does not conform to the law of initial value. It was concluded that autoregulation of skin temperature can be demonstrated in a virtually flaccid limb, and that the amount of temperature change achieved is not a function of basal skin temperature.

Adolescent↗
PubMed1970

Temperature and transpiration resistances of xanthium leaves as affected by air temperature, humidity, and wind speed.

Transpiration and temperatures of single, attached leaves of Xanthium strumarium L. were measured in high intensity white light (1.2 calories per square centimeter per minute on a surface normal to the radiation), with abundant water supply, at wind speeds of 90, 225, and 450 centimeters per second, and during exposure to moist and dry air. Partitioning of absorbed radiation between transpiration and convection was determined, and transpiration resistances were computed.Leaf resistances decreased with increasing temperature (down to a minimum of 0.36 seconds per centimeter). Silicone rubber replicas of leaf surfaces proved that the decrease was due to increased stomatal apertures. At constant air temperature, leaf resistances were higher in dry than in moist air with the result that transpiration varied less than would have been predicted on the basis of the water-vapor pressure difference between leaf and air.The dependence of stomatal conductance on temperature and moisture content of the air caused the following effects. At air temperatures below 35 C, average leaf temperatures were above air temperature by an amount dependent on wind velocity; increasing wind diminished transpiration. At air temperatures above 35 C, leaf temperatures were below air temperatures, and increasing wind markedly increased transpiration. Leaf temperatures equaled air temperature near 35 C at all wind speeds and in moist as well as in dry air.

Journal Article↗
PubMed1986

Body temperature and temperature gradients: changes during the estrous cycle and in response to ovarian steroids.

Rectal temperature, body weight, and vaginal membrane condition were monitored in female guinea pigs in order to determine the pattern and magnitude of changes in these variables across the estrous cycle and as a result of treatment with ovarian hormones. A thermistor probe was used to measure rectal temperatures at depths of 4 and 8 cm and to determine the temperature gradient between these two sites. Data collected across the estrous cycles of 18 intact females were aligned by day of vaginal membrane rupture, the estimated time of ovulation. Compared to measurements during the midluteal phase of the estrous cycle, rectal temperatures increased significantly one to three days prior to vaginal membrane rupture. In addition, a significant periovular decline was observed in the temperature gradient and in body weight. Treatment of ovariectomized females with 3 micrograms estradiol benzoate for 3 days (EB) followed by a single injection of 0.4 mg progesterone on the 4th day (P) led to biphasic changes in temperature. Compared to a control group which received injections of 0.2 ml corn oil vehicle for 4 consecutive days (OIL), EB significantly increased rectal temperature measured at the depth of 4 cm, but had no significant effect on measurements taken at a depth of 8 cm. The temperature difference between these two sites also decreased significantly. Rectal temperatures at both 4 cm and 8 cm sites dropped significantly following injection of progesterone. Ovarian hormones therefore have significant effects on body temperature of guinea pigs, effects which, in combination with other evidence, lead us to suggest that some of the observed temperature variations may be related to estrogen-induced changes in peripheral vasodilation or other mechanisms of heat loss.

Animals↗
PubMed2001

Effects of irrigation fluid temperature on core body temperature during transurethral resection of the prostate.

OBJECTIVES: To determine the effect irrigation fluid temperature has on core body temperature changes in patients undergoing transurethral resection of the prostate (TURP). METHODS: Fifty-six male patients (mean age 71.2 +/- 8.2 years) scheduled for TURP were enrolled in the study. Patients were randomized to one of two groups. Group 1 consisted of 27 patients who received room temperature irrigation fluid (70 degrees F) throughout TURP; group 2 consisted of 29 patients whose procedure was performed with warmed irrigation fluid (91.5 degrees F). The irrigation fluid used for both groups was glycine. The baseline temperature, final temperature, total time in the operating room, and amount of irrigation fluid used during the procedure were recorded for each patient. RESULTS: No significant difference in the average time spent in the operating room or in the total irrigation fluid used between the two groups was observed. Of the 27 patients who received room temperature irrigation fluid, 15 (55.6%) had a decrease in body temperature. A decrease in temperature was observed in 21 (72.4%) of the 29 patients who received warm irrigation fluid. Groups 1 and 2 had 12 (44.4%) of 27 and 8 (27.6%) of 29 patients, respectively, who demonstrated an elevation in their core body temperature. CONCLUSIONS: The results of our study suggest that irrigation fluid temperature is not a factor responsible for altering the core body temperature in patients undergoing TURP.

Aged↗
PubMed1986

Rise in lens temperature on exposure to sunlight or high ambient temperature.

The effect of increase ambient temperature and sunlight on the temperatures of the rabbit lens and posterior chamber (PC) aqueous humour was measured by needle thermistor probes while the rectal temperature was monitored. Exposure of rabbits to sunlight (35 degrees-42 degrees C), in New Haven, Connecticut, USA, resulted in significant temperature increases in PC (4.3 degrees C), lens (3.2 degrees C), and rectum (2.3 degrees C). Returning animals to the shade resulted in a progressive decrease in the temperatures of the PC or lens in the tested eye, but repeating exposure to sunlight resulted in significant increases of the baseline (PC) temperature (increase 2.68 degrees C) of the second eye. Exposure of rabbits to sunlight at 49 degrees C in Chandigarh, India, resulted in increased PC temperature of 4.48 degrees C after 9 minutes. Increased PC and lens temperatures after exposure to sunlight are due both to an ambient temperature effect through the cornea and to increased body temperature. In dry and hot tropical areas of the world temperature increases in the lens after exposure to sunlight may initiate or accelerate the formation of senile cataracts.

Animals↗
PubMed1993

Cocaine and body temperature: effect of exercise at high ambient temperature.

The laboratory rat has been used as an animal model to investigate the effects of cocaine on body temperature and to determine if abuse of the drug is a risk factor in the pathogenesis of exercise-induced heat stroke. Animals were trained to run on a treadmill which was enclosed so that the ambient temperature could be regulated. Exercise at ambient temperatures of 20 and 30 degrees C led to a similar rise in core temperature of approximately 1 degrees C, although the starting core temperature was higher in the rats at 30 degrees C (38.5 +/- 0.10 degrees C compared to 37.9 +/- 0.06 degrees C). Cocaine (20 mg/kg) led to a transient fall in core temperature in the 20 degrees C group; the temperature then rapidly recovered, so that after 60 min exercise there was no significant difference between these and the control animals. At the higher ambient temperature cocaine augmented the rise in core temperature during running, although the animals had regained thermal balance by 30 min and core temperature was maintained at 40.2 +/- 0.13 degrees C until the end of the exercise period. The dopamine D1 receptor antagonist SCH 23390 (0.1, 0.3 or 1.0 mg/kg) led to suppression of spontaneous motor activity so that the rats could be persuaded to exercise for only 30-45 min after treatment. Pretreatment with the antagonist did not affect the rise in core temperature induced by cocaine at 30 degrees C which again stabilized by 30 min at 40.0 +/- 0.12 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1975

[Influences of the complex of environmental temperature, relative humidity and air velocity on the body temperature of restrained mice (author's transl)].

Effects of the complexes of environmental factors, such as ambient-temperature, relative humidity and air velocity, on the body temperature were investigated in restrained mice. Observations were carried out before and after 60 min-exposure to various triple combinations among environmental temperatures of 15, 25 and 35 degreesC, relative humidities of 40, 65 and 90%, and air velocities of 0.2, 1.0 and 2.0 m/sec. The analysis of variance about the differences of body temperature revealed significant effects of the environmental temperature and the air velocity levels, while no significant effects were recognized of the relative humidity. Effects of the double factors, either the environmental temperature plus the relative humidity or the environmental temperature plus the air velocity, were significant at 5 or 1% level respectively. However, effects of the double factors the relative humidity plus the air velosity, as well as the triple factors were not significant. Under the environments consisted of triple factors, the environmental temperature of 20 and 25 degreesC, the relative humidities of 40 and 70% and the air velocities of 0.1 and 0.5 m/sec, significant effects at 1% level were recognized only in the environmental temperature levels. In the relative humidty or the air velocity levels, and the double or triple factor levels, no significant effects were recognized. From the results obtained, the effective temperature (Te) was indicated by the formula, Te=t+100x-v square root 38-t, in which were given the environmental temperature in t degrees C, the absolute humidity in x kg/kg and the air velocity in v m/sec.

Air Movements↗
PubMed1992

Research note: broiler acclimation to heat distress and feed intake effects on body temperature in birds exposed to thermoneutral and high ambient temperatures.

Relationships between ambient temperature, bird acclimation to cycling temperature, heat distress, and feed consumption were evaluated in two experiments. In the first experiment, birds previously acclimated to cycling temperature heat distress (24 to 35 C) for two 24-h cycles were observed to have 24% lower (P less than .01) feed consumption than birds previously housed at 24 C and experiencing their first heat distress exposure. A significant (P less than .01) acclimation history by ambient temperature interaction was detected, with acclimated birds having a higher rectal temperature (42.3 versus 41.2 C) when housed at 24 C and a lower rectal temperature (44.2 versus 44.6 C) when exposed to 35 C than did the unacclimated controls. In the second experiment, feed intake and acclimation effects were separated by precision-feeding birds 0, 5, and 10% of body weight. Rectal temperature in the 24 C and 35 C environments increased linearly (P less than .01) as feeding level increased for both acclimated and unacclimated birds. Similar to the first experiment, an ambient temperature by acclimation history interaction was detected (P less than .01), with acclimated birds exhibiting increased body temperature when housed in thermoneutral environments and lower body temperature when exposed to high ambient temperature distress.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1989

Intraoperative temperature monitoring sites in infants and children and the effect of inspired gas warming on esophageal temperature.

This study tested the hypotheses that 1) temperatures of "central" sites are similar in infants and children undergoing noncardiac surgery and 2) airway heating and humidification increases distal esophageal temperature. Twenty children were randomly assigned to receive 1) active airway humidification using an airway heater and humidifier set at 37 degrees C (N = 8), 2) passive airway humidification using a heat and moisture exchanger (N = 6), or 3) no airway humidification and/or heating (control, N = 6). There were no statistically significant differences between tympanic membrane, esophageal, rectal, and axillary temperatures. The temperatures of the peripheral skin surface (forearm and fingertip) were significantly lower than tympanic membrane temperature and significantly different from each other. Although esophageal and tympanic membrane temperatures in the entire group were similar, esophageal temperatures in patients receiving active and passive airway humidification were about 0.35 degrees C above tympanic temperatures after induction of anesthesia. In contrast, esophageal temperatures in patients without airway humidification were 0.25 degrees C below tympanic temperatures after induction of anesthesia. Esophageal-tympanic membrane temperature differences in the patients given active and passive humidification differed significantly from the corresponding sum in the control group at all times, but not from each other.

Anesthesia, Inhalation↗
PubMed1997

Activity, blood temperature and brain temperature of free-ranging springbok.

We used miniature data loggers to record temperature and activity in free-ranging springbok (Antidorcas marsupialis) naturally exposed to severe nocturnal cold and moderate diurnal heat. The animals were active throughout the day and night, with short rests; the intensity of activity increased during daylight. Arterial blood temperature, averaged over many days, exhibited a circadian rhythm with amplitude < 1 degree C, but with a wide range which resulted from sporadic rapid deviations of body temperature. Peak blood temperature occurred after sunset. Environmental thermal loads had no detectable effect on blood temperature, even though globe temperature varied by > 10 degrees from day to day and > 20 degrees C within a day. Brain temperature increased approximately linearly with blood temperature but with a slope < 1, so that selective brain cooling tended to be activated at high body temperature, but without a precise threshold for the onset of brain cooling. Low activity attenuated selective brain cooling and high activity abolished it, even at high brain temperature. Our results support the concept that selective brain cooling serves to modulate thermoregulation rather than to protect the brain against heat injury.

Animals↗
PubMed2000

Effect of ambient temperature on human pain and temperature perception.

BACKGROUND: Animal studies show reduced nociceptive responses to noxious heat stimuli and increases in endogenous beta-endorphin levels in cold environments, suggesting that human pain perception may be dependent on ambient temperature. However, studies of changes in local skin temperature on human pain perception have yielded variable results. This study examines the effect of both warm and cool ambient temperature on the perception of noxious and innocuous mechanical and thermal stimuli. METHODS: Ten subjects (7 men and 3 women, aged 20-23 yr) used visual analog scales to rate the stimulus intensity, pain intensity, and unpleasantness of thermal (0-50 degrees C) and mechanical (1.2-28.9 g) stimuli applied on the volar forearm with a 1-cm2 contact thermode and von Frey filaments, respectively. Mean skin temperatures were measured throughout the experiment by infrared pyrometer. Each subject was tested in ambient temperatures of 15 degrees C (cool), 25 degrees C (neutral), and 35 degrees C (warm) on separate days, after a 30-min acclimation to the environment. Studies began in the morning after an 8-h fast. RESULTS: Mean skin temperature was altered by ambient temperature (cool room: 30.1 degrees C; neutral room: 33.4 degrees C; warm room: 34.5 degrees C; P < 0.0001). Ambient temperature affected both heat (44-50 degrees C) and cold (25-0 degrees C) perception (P < 0.01). Stimulus intensity ratings tended to be lower in the cool than in the neutral environment (P < 0.07) but were not different between the neutral and warm environments. Unpleasantness ratings revealed that cold stimuli were more unpleasant than hot stimuli in the cool room and that noxious heat stimuli were more unpleasant in a warm environment. Environmental temperature did not alter ratings of warm (37 and 40 degrees C) or mechanical stimuli. CONCLUSIONS: These results indicate that, in humans, a decrease in skin temperature following exposure to cool environments reduces thermal pain. Suppression of Adelta primary afferent cold fiber activity has been shown to increase cold pain produced by skin cooling. Our current findings may represent the reverse phenomenon, i.e., a reduction in thermal nociceptive transmission by the activation of Adelta cutaneous cold fibers.

Adult↗
PubMed2001

Methodological investigation of measuring nasopharyngeal temperature as noninvasive brain temperature analogue in the neonate.

OBJECTIVES: (a) To investigate in a newborn animal model whether nasopharyngeal temperature is more closely related to epidural brain temperature than rectal temperature and (b) to investigate in human neonates whether measurement of nasopharyngeal temperature is dependent on the measurement site and other conditions. DESIGN AND SETTING: (a) Animal experiment in newborn piglets, at an institute for surgical research. (b) Prospective study in human neonates, at a neonatal intensive care unit of a tertiary care university hospital. ANIMALS AND PATIENTS: (a) Nineteen tracheostomized ventilated newborn piglets. (b) Twenty-two spontaneously breathing human newborns nursed either in an incubator or a cot. MEASUREMENTS AND RESULTS: (a) In the piglets nasopharyngeal temperature (Tnasoph) measured at the nose-ear distance, defined as distance from the inner brim of the nostril to the tragus and inner rim of the meatus accusticus, most closely reflected epidural temperature (Tepidur) at the epidural surface (r2 = 0.89), followed by skin temperature at the temple, rectal temperature (Trectum) at 2 cm depth, and esophageal temperature (Tesoph) in the middle esophagus. Tnasoph did not significantly differ before and after tracheostomy. (b) In the newborns Tnasoph was significantly lower than Trectum. Measurements of Tnasoph at nose-ear distance within a feeding tube had a high precision and were unaffected by breathing or head turning. A nasopharyngeal probe was imaged by magnetic resonance imaging in four newborns of various body weight; its tip when inserted to a depth equal to nose-ear distance was anatomically closest to the brain base but separated from it by tissue layer 2.2 cm thick. CONCLUSIONS: Tnasoph measured at a position anatomically closest to the brain reflects epidural brain temperature more closely than Trectum. When measured at nose-ear distance it is unaffected by breathing or head turning. Measuring Tnasoph within a feeding tube and standardizing the measuring position is crucial for its use as brain temperature analogue.

Animals↗
PubMed1995

Intracerebral temperature in neurosurgical patients: intracerebral temperature gradients and relationships to consciousness level.

Information regarding human brain temperature is still rather sparse, which is surprising giving the no longer recent findings that the mammalian brain is very sensitive to minor variations in temperature. We therefore report the results of intracranial temperature monitoring in thirty neurosurgical patients. Intraventricular temperature was monitored with a thermocouple specifically designed for the purpose, and introduced through a plastic catheter used for monitoring of intracranial pressure, with simultaneous measurements of rectal and epidural temperature with commercially available thermocouples. Human intraventricular temperature is higher than central core temperature, and there is also a temperature gradient within the brain, with the central parts being warmer than the surface. The presence of an intracerebral temperature gradient was confirmed in two patients undergoing stereotactic thalatomy. We found no clear evidence for a correlation between consciousness level and brain temperature. Observations of brain temperature changes after clinical diagnosis of brain death are also reported.

Adolescent↗
PubMed1979

Cells transformed by temperature-sensitive mutants of avian sarcoma virus cause tumors in vivo at permissive and nonpermissive temperatures.

Chick embryo (CE) fibroblasts and normal rat kidney (NRK) cells transformed by temperature-sensitive (ts) mutants of avian sarcoma virus (NY68, LA23, LA24, LA25, LA29, LA31, GI201, GI202, GI251, GI253 induce tumors on the chorioallantoic membrane (CAM) of chick eggs at temperatures that correspond to the permissive and nonpermissive temperatures used to induce conditional expression of the "transformed" phenotype in these cells when cultured in vitro. Chick embryo cells infected with transformation-defective mutants of ASV (td101, td108) or RAV-50 were nontumorigenic under the same conditions, as were nontransformed CE and NRK cells. This indicates that the CAM is not an unusually susceptible substrate for cell growth and that the ability of tsASV-transformed cells to form tumors at nonpermissive temperatures reflects their true tumorigenicity. In contrast, a ts mutant chemically transformed rat liver cell line, ts-223, only formed tumors on the CAM under permissive conditions. The wild-type parent cells (W-8) of this mutant produced tumors at both permissive and nonpermissive temperatures. Direct implantation of microprobe thermometers into tumors caused by ts-ASV-transformed cells at nonpermissive temperatures confirmed that tumor formation occurred in a stable temperature environment and was not due to temperature fluctuations which might have created semi-permissive conditions for tumor growth. Cells isolated from tumors formed at nonpermissive temperatures and recultured in vitro displayed temperature-dependent hexose transport and colony formation in agar similar to the orginal parent cell inoculum. Similarly, virus recovered from tumors at nonpermissive temperatures retained the ts mutation.

Alpharetrovirus↗
PubMed1997

Effect of burnout temperatures on strength of phosphate-bonded investments--Part II: Effect of metal temperature.

OBJECTIVES: It had previously been found that the strength of phosphate-bonded investments is temperature sensitive. However, while the effect of heat from the cast metal is expected to have some effect on continued reactions and melting, there is no published report dealing with this. It was the purpose of this study to consider further the effects of burnout temperature on strength and the contribution of metal casting temperature and investment composition. METHODS: The disc-rupture test (Luk, H. W.-K. and Darvell, B. W., Strength of phosphate-bonded investments at high temperature. Dental Materials 1991, 7, 99-102) was employed to determine the effect of burnout temperature (ranging from 400 to 1000 degrees C) on the 'actual' strength of six phosphate-bonded investments; the cast metal temperature was controlled to be the same as that of the mould. Atomic absorption was employed to investigate aspects of the composition of the investments. RESULTS: The 'actual' strength obtained in this test was always higher than the 'service' strength observed in similar testing with the metal at a fixed temperature (1460 degrees C). The 'actual' strength was also temperature sensitive, but with a different pattern of variation compared with the 'service' values. All investments tested were found to behave plastically at high temperatures. Calcium, sodium, zinc and iron were found in appreciable quantities in the investments. CONCLUSION: Heat from the high-temperature casting metal has a material effect in decreasing the strength of phosphate-bonded investments. Such heating increases the plastic behaviour of the investment and this, together with the casting pressure, may result in a distorted mould and thus inaccurate castings, a hitherto unrecognized source of error. 'Actual' strength gives no guide to the 'service' strength, emphasizing the need for tests under service conditions. Composition affects investment high-temperature strength substantially.

Calcium↗
PubMed1997

Effect of compaction temperature on consolidation of amorphous copolymers with different glass transition temperatures.

PURPOSE: The purpose of this study was to relate the combination of glass transition temperature (Tg) and temperature of measurement with the mechanical and compaction properties of some test materials. METHODS: Copolymers with different Tg'S were synthesised by free radical copolymerisation of methyl methacrylate with lauryl methacrylate. Elastic moduli were measured by dynamic mechanical analysis at different strain rates and temperatures. Compaction experiments were performed at different compaction speeds and temperatures. RESULTS: The difference between temperature of measurement and Tg appears to determine both elastic modulus and yield strength completely. They both decrease with decreasing difference between temperature of measurement and Tg and increase with strain rate. At temperatures of measurement higher than the Tg the elastic modulus is extremely low because the materials behave as rubbers. Consequently, the amount of energy stored during compaction decreases when the compaction temperature approaches the Tg and increases with strain rate. When the compaction temperature is higher than the Tg, the amount of stored energy is extremely large. The compaction experiments show that the final tablet porosity is completely determined by stress relaxation phenomena. Consequently, the final tablet porosity follows exactly the same relation as that of stored energy. CONCLUSIONS: The final tablet porosity is unequivocally determined by the amount of stored energy. This implies that tablet production at a temperature of about 20 K under the glass transition temperature of the material yields tablets with minimum porosity.

Glass↗