Copper-constantan Thermocouples Research Articles

Effects of Temperature on the Development of Asiatic Lilies

Temperature effects the rate of development of Lilium (Asiatic hybrid). The long-term objective is to evaluate thermal units as a tool for crop timing. The objective of this work was to determine Lilium base temperature (Tb). One-hundred-ninety plants of two cultivars (`Butter Pixie' and `Horizon') were used. Phenological observations were made on plants during six plantings over a 2-year period. Developmental stages observed were: shoot visible out of the soil (SV), visible flower bud (BV), and open flower (OF). The two cultivars were grown in four different greenhouse compartments with settings at 13, 18, 24 and 27°C, respectively. During periods of extreme outdoor temperatures, actual temperature deviated from the settings. Actual temperatures were constantly monitored with copper-constantan thermocouples and stored in a datalogger. Rates of development were calculated as the inverse of the numbers of days to complete a given phenological phase. Tb values were obtained by calculating the x-interception of the linear regression describing rate of development as a function of mean air temperatures. Tb for `Butter Pixie' and `Horizon' for the entire growth cycle (SV through OF) were 0.4°C and 2.0°C respectively. The production cycle can be divided into two phases: SV–BV and BV–OF. For `Horizon', Tb for these phases were 1.4 and 1.9°C respectively. For `Butter Pixie', these Tb were 2.4 and –1.0, respectively. More observations of development at mean temperatures higher than 27°C and lower than 13°C are necessary in order to increase confidence on the obtained Tbs.

Seasonal Variations in the Turbulence Spectra Above and Within a Deciduous Forest

The seasonal variations in turbulence above and within a deciduous forest were studied in the Experimental Forest, in Hokkaido, in the northernmost temperate forest zone. Two three-dimensional sonic anemometer/thermometers were used to measure fluctuations in temperature and wind velocity from the period of leaf development to leaf-shedding. Variations in specific humidity above the canopy were determined with fine wire copper-constantan thermocouples placed near the sonic anemometer/thermometer. The sensible and latent heat fluxes were obtained using the WT and Wq covariance.

A chamber for laboratory studies of atmospheric aerosols and clouds

A stainless-steel chamber has been constructed and interfaced to a Fourier transform infrared spectrometer for the purpose of studying laboratory simulated atmospheric aerosols and clouds. The chamber is cylindrical in design and is comprised of a double-walled inner assembly that resides within an outer vacuum jacket. The volume of the aerosol sample region is 28 L. By circulating refrigerated methanol between the double walls of the inner assembly, constant temperature control of the sample region can be maintained between 187 and 300 K. A study of temperature uniformity within the chamber at 291, 240, and 187 K revealed a standard deviation in temperature of 1.6 K as determined from measurements made using five copper–constantan thermocouples. Good agreement is obtained between thermocouple measured temperatures and rotational temperatures computed from infrared absorption spectra of methane gas. The chamber described here has been used to examine heterogeneous chemistry of solid powder samples. A technique of generating an aerosol sample by rapidly dispersing a solid powder in a gas is presented. The half-life of a γ-alumina aerosol sample was measured to be 25 min.

Experimental studies on thermoacoustic refrigeration

Thermoacoustic refrigeration phenomena in a resonance tube were studied experimentally. A horizontal brass tube of 400 mm in length and 40 mm in diameter was closed at one end and attached to the acoustic driver (audio speaker) at the other end. Atmospheric air was enclosed in the tube as a working fluid. Stacks which were made of a bundle of ceramic tubes, a rolled abrasive paper with garnet, or a rolled copper metal netting, were set in the tube. Driven acoustic frequency was varied from 100 to 300 Hz, and electric power to the driver was varied from 0 to 7.8 W. Pressure and temperature distributions in the tube were measured by an axially movable pressure transducer and a Copper–Constantan thermocouple. The relation of refrigeration capacity and refrigeration temperature was also measured. It was found that the maximum cooling temperature was obtained when the stack was located near the closed end equivalent to the pressure antinode. Maximum refrigeration capacity was found to be made by the ceramic tubes stack composed of a bundle of ceramic tubes 0.8 mm in hydraulic diameter. A maximum temperature difference of 12 °C was achieved in this experiment.

Energy requirement of sodium reabsorption in the thick ascending limb of Henle's loop in the dog kidney: effects of bumetanide and ouabain.

To examine whether sodium reabsorption in the thick ascending limb of Henle's loop (TALH) in the dog kidney has a passive component, the ratios between reductions in sodium reabsorption and oxygen consumption (delta Na/delta Qo2 ratio) were measured by inhibiting tubular transport with bumetanide (30 micrograms kg-1) and ouabain (120 ng kg-1 intrarenally). Clearance studies were performed in volume expanded dogs treated with acetazolamide (100 mg kg-1) or maleate (400 mg kg-1). In five acetazolamide-treated dogs, bumetanide gave a delta Na/delta Qo2 ratio of 29.9 +/- 2.5, whereas the combination of bumetanide and ouabain gave 19.0 +/- 0.6. When ouabain was given before bumetanide, ouabain gave a delta Na/delta Qo2 ratio of 19.2 +/- 1.1 and the combination gave 19.9 +/- 1.2. In the maleate-treated dogs, bumetanide gave a delta Na/Qo2 ratio 30.3 +/- 1.7, and the combination of bumetanide and ouabain gave 27.1 +/- 1.5. To localize the metabolic effect of bumetanide and ouabain, local heat production was measured at 18 places in four kidneys with copper-constantan thermocouples. Bumetanide reduced metabolic rate in the outer medulla by 51 +/- 4%, and in the cortex by 16 +/- 6%. Subsequent infusion of ouabain reduced metabolic rate in the outer medulla by only 9 +/- 3%, whereas cortical metabolism was reduced by 33 +/- 4%. The results show that bumetanide mainly acts in the outer medullar where TALH is located, whereas the additional effect of ouabain is mainly located in cortical segment of the nephron including the proximal tubules. Bumetanide inhibits the reabsorption of 30 mol sodium for each mole oxygen consumed, which show that for each 18 mol sodium that are transported through the cells in the TALH in dog kidneys. 12 mol (40%) are transported along the paracellular route without additional requirement of energy.

Leaf Temperature Kinetics Measure Plant Adaptation to Extreme High Temperatures

Leaf temperature kinetics were studied as a function of the rate of change of ambient temperature (Vt), light conditions, plant age, and genotypic and species diversity for Zea mays, Cucumis sativus, Lycopersicon esculentum, Phaseolus vulgaris, Beta vulgaris, Cucurbita pepo and Raphanus sativus. Ambient temperature was varied from 26 to 60�C at rates from 0.5 to 8�C/min. Leaf-air temperature differences (LATD) were registered with differential copper-constantan thermocouples. As the ambient temperature rose LATD increased because stomata had been closed in darkness. Still in the darkness, at some critical ambient temperature stomata opened and the leaf temperature reduced dramatically as result of stomatal transpiration. The critical temperature is strongly dependent upon Vt. Simple equations for the calculation of a threshold of plant temperature sensitivity and of a time constant for stomatal signal transduction have been obtained. These parameters show a high correlation with plant heat tolerance both in genotypic and species aspects. This is consistent with the idea that temporal organisation of plant regulatory systems plays a leading role in evolution and in adaptation to extreme environmental conditions. Both characteristics measured tend to change with plant age. It is concluded that the measurement of leaf temperature kinetics is a very convenient procedure for estimating plant adaptive ability to high temperatures.

Influence of Shade Level, Wind Velocity, and Wind Direction on Interior Air Temperatures of Model Shade Structures

The effect of four shade levels (47%, 63%, 80%, and 91%) on air temperature was evaluated using twenty-four arch-shaped, open-ended shade structures oriented with their longitudinal axis north-south. Each model shade structure was 0.8 m wide, 1.85 m long, and 0.8 m high. Six replicates per treatment (shade level) were randomly assigned within the experimental area. Light levels were measured using PAR sensors. Temperatures were measured using copper-constantan thermocouples installed 0.6 m above ground level and 0.2 m from the north entrance. Data from twenty consecutive days in August, 1994 were analyzed. The highest air temperatures were measured under 80% shade. However, the average difference between 63% and 91% shade was less than 1C and the average difference between 47% and 80% shade was 1.4C. Wind direction and wind speed affected air temperature. Analysis of the data showed averaged air temperatures differed by 1.4C or less for all shade levels.

Thermal measurement of sap flow applied to the study of the water withdrawal from trees: literature review and method improvement

In this work various thermal methods now available for estimating xylem sap flow are reviewed. A cheap measuring devie involving two thermal sensors (copper-constantan thermocouples), one of which is conected to a constantan heat source, was performed. Sensors are inserted into the xylem to measure temperatura changes into the sap. Subsequent estimation of the volumetric sap flow rate by this method requires no calibration since empirical coefficients are available form the literature. The improved device was tested for estimating the hourly and daily transpiration rate of a birch tree in a field situation. Results show that the thermal sensor provides satisfactory transpiration estimates for individual trees under high and medium flow rate conditions.

Triple electrical channels on a triple fluid swivel and its use to monitor intracranial temperature with a thermocouple

A low-torque, bubble-free and multiple-channel fluid swivel of easy construction was recently described. This paper describes the design, construction and testing of 3 electrical channels added to the original fluid swivel. The new channels were tested monitoring intrahypothalamic temperature ( T hy) by means of a copper-constantan thermocouple in freely moving rats, before and after a single intraperitoneal (i.p.) amphetamine injection (3 mg/kg). This test showed an increase in T hy after the injection and the maintainance of the electrical continuity along the whole testing period, even when the animals were hyperactive. With this improvement the original swivel was transformed in a more versatile device for experiments requiring fluid handlings and electrophysiological manipulations. Electrical stimulation as in kindling or brain self-stimulation, and electrophysiological recordings as in electroencephalography, electromiography, electrocardiography, in vivo voltammetry and even neuronal unit recording, are just examples of the electrophysiological methods that can be combined with drug self-administration and microdialysis using the present device.

Shade Levels, Wind Speed, and Wind Direction Influence Air Temperature in Mini-shadehouses

The effect of four shade levels (47%, 63%, 80%, and 91%) on air temperature was evaluated using 24 arch-shaped, open-ended shadestructures oriented with their longitudinal axis in north–south direction. The mini-shadehouses were 80 × 185 × 80 cm (width × length × height). Six replicates per treatment (shade level) were randomly assigned within the experimental plot. Light levels were measured using Sunceram solar cells. Copper-Constantan thermocouples were installed 60 cm from ground level and 20 cm from the north entrance. The experiment was initiated in July 1994 and terminated in Oct. 1994. Data from 20 consecutive days in August were analyzed. Eighty percent shade had the highest air temperature; however, the average difference between 47%, 63%, and 91% shade was less than 1C. Wind direction and speed affected air temperature with north or south winds correlated with highest temperatures. Analysis of the data shows averaged air temperatures differed by ≤1C for all shade levels. Consequently, these structures may be used for replicated research studies involving plant growth.

Shade Levels, Wind Speed, and Wind Direction Influence Air Temperature in Mini-shadehouses

The effect of four shade levels (47%, 63%, 80%, and 91%) on air temperature was evaluated using 24 arch-shaped, open-ended shadestructures oriented with their longitudinal axis in north–south direction. The mini-shadehouses were 80 × 185 × 80 cm (width × length × height). Six replicates per treatment (shade level) were randomly assigned within the experimental plot. Light levels were measured using Sunceram solar cells. Copper-Constantan thermocouples were installed 60 cm from ground level and 20 cm from the north entrance. The experiment was initiated in July 1994 and terminated in Oct. 1994. Data from 20 consecutive days in August were analyzed. Eighty percent shade had the highest air temperature; however, the average difference between 47%, 63%, and 91% shade was less than 1C. Wind direction and speed affected air temperature with north or south winds correlated with highest temperatures. Analysis of the data shows averaged air temperatures differed by ≤1C for all shade levels. Consequently, these structures may be used for replicated research studies involving plant growth.

Thermoregulation of the intra-abdominal testes of the bottlenose dolphin (Tursiops truncatus) during exercise.

Dolphins possess a vascular countercurrent heat exchanger (CCHE) that functions to cool their intra-abdominal testes. Spermatic arteries in the posterior abdomen are juxtaposed to veins returning cooled blood from the surfaces of the dorsal fin and tail flukes. In this study, we investigated the effect of exercise on CCHE function in the bottlenose dolphin. The CCHE flanks a region of the bowel in the posterior abdomen and influences colonic temperatures. A rectal probe housing a linear array of seven copper-constantan thermocouples was designed to measure colonic temperatures simultaneously at positions anterior to, within and posterior to the region of the colon flanked by the CCHE. Immediately after vigorous swimming, temperatures at the CCHE decreased relative to resting and pre-swim values: post-swim temperatures at the CCHE were maximally 0.5 degrees C cooler than pre-swim temperatures. These data suggest that the CCHE has an increased ability to cool the arterial blood supply to the testes when the dolphin is swimming. This ability could offset the increased thermal load on the testes is an exercising dolphin. To the best of our knowledge, this is the first report of deep body cooling in an exercising mammal that is not undertaking a dive.

A recommended revision in the RTOG thermometry guidelines for hyperthermia administered by ultrasound.

RTOG thermometry guidelines for clinical trials of hyperthermia using planar ultrasound recommended that temperatures be mapped in polyurethane catheters by use of single-junction copper-constantan thermocouples. These guidelines were based on an assumption that the error in temperature measurement due to thermal conduction would generally not exceed +/- 0.3 degrees C. The validity of this assumption was tested with a commercially available single-junction copper-constantan thermocouple. The width of the point spread function, an indicator of the relative magnitude of the conduction error, was five times greater than expected. As a result, the conduction error is projected to exceed 0.3 degrees C in a temperature gradient of only 1.5 degrees C/cm. This projection was confirmed by mapping a thermal peak which simulates a typical clinical temperature profile. This peak had an amplitude of 6 degrees C, a full-width at half-maximum of 3.5 cm, and a maximum gradient of approximately 3 degrees C/cm. Temperatures measured at 0.5-cm intervals over the span of this peak were in error by a mean of +/- 0.6 degrees C. It is strongly recommended that the RTOG guidelines be revised to replace copper-constantan thermocouples with manganin-constantan single- or multi-junction thermocouples which will assure that the conduction error will be < +/- 0.3 degrees C.

Use of manganin-constantan thermocouples in thermometry units designed for copper-constantan thermocouples.

Commercial ultrasound hyperthermia systems typically include thermometry units designed for copper-constantan thermocouples. Replacing these copper-constantan thermocouples with manganin-constantan thermocouples is advantageous in reducing the measurement error caused by the conduction of heat along the copper wire, but their performance in these thermometry units is uncertain. The accuracy of manganin-constantan thermocouples in the Labthermics LT-100, Clini-Therm TS1200/TM100, and Physitemp TM-12 thermometry units was investigated using a temperature controlled circulating water bath monitored by a mercury thermometer having a calibration traceable to NIST. The results demonstrate that an accuracy of +/- 0.2 degrees C can be achieved with manganin-constantan thermocouples over the range 35-55 degrees C without hardware modification provided specific calibration procedures are followed. With the Labthermics LT-100, a double point calibration should be carried out at 35 and 55 degrees C. With the Clini-Therm TS1200/TM100, a self-calibration of the unit using its internal calibration well plus a single point calibration using an external temperature standard provides sufficient accuracy. The Physitemp TM-12 requires an external computer for read out and the user must provide additional software to correct for the error by either a single or multiple point calibration.

Temperature regulation of the testes of the bottlenose dolphin (Tursiops truncatus): evidence from colonic temperatures.

Dolphins possess a countercurrent heat exchanger that functions to cool their intra-abdominal testes. Spermatic arteries in the posterior abdomen are juxtaposed to veins returning cooled blood from the surfaces of the dorsal fin and flukes. A rectal probe housing a linear array of five copper-constantan thermocouples was designed to measure colonic temperatures simultaneously at positions anterior to, within, and posterior to the region of the colon flanked by the countercurrent heat exchanger. Colonic temperatures adjacent to the countercurrent heat exchanger were maximally 1.3 degrees C cooler than temperatures measured outside this region. Temporary heating and cooling of the dorsal fin and flukes affected temperatures at the countercurrent heat exchanger, but had little or no effect on temperatures posterior to its position. These measurements support the hypothesis that cooled blood is introduced into the deep abdominal cavity and functions specifically to regulate the temperature of arterial blood flow to the dolphin testes.

Intrapulpal temperatures during pulsed Nd:YAG laser treatment of dentin, in vitro.

Lasers are being used for soft tissue removal, caries removal, and treatment of root surface sensitivity. One concern for laser safety is that the heat produced at the irradiated root surface may diffuse to the pulp causing irreversible pulpal damage. To test this heat diffusion, copper-constantan thermocouples were inserted into the radicular pulp canals of extracted teeth. Simulating direct exposure which might occur during gingival excision, superficial caries removal, and modification of the dentin surface for treatment of root surface sensitivity, a 2 mm2 area of the external root surface was uniformly irradiated with a pulsed Nd:YAG laser using a 320 microns diameter fiber optic contact probe. Power was varied from 0.3 to 3.0 W with frequencies of 10 and 20 Hz. Temperature changes during cavity preparations using a high speed handpiece with air coolant were also recorded. Repeated measures ANOVA (P < or = 0.05) indicated that intrapulpal temperatures increased as a function of power, frequency, and time. Intrapulpal temperatures decreased as remaining dentin thickness (0.2 to 2.0 mm) increased for each laser parameter. Irradiation of dentin using a Nd:YAG pulsed laser, within the treatment times, powers, and frequencies with adequate remaining dentin thickness, as outlined in this paper, should not cause devitalizing intrapulpal temperature rises.

Thermoacoustic sensor for ultrasound power measurements and ultrasonic equipment calibration

This paper describes a thermoacoustic sensor developed for measurements of the acoustic power and calibration of ultrasonic transducers in the medical imaging and nondestructive testing frequency range. It is shown that the equilibrium temperature produced by ultrasound absorption in an absorbing material and detected by a copper-constantan thermocouple is proportional to the square of the current applied to the acoustic source. It is also demonstrated that the simultaneous measurement of this current and the corresponding equilibrium temperature at a given frequency allow the transmitting current sensitivity of the acoustic source to be calculated. The sensor thus provides a useful and low-cost alternative to the expensive calibration methods such as those based on the reciprocity technique, the planar scanning technique and the radiation force balance. The principles of the sensor's operation are outlined and its construction and characteristics are described. Experimental data in the frequency range of 1–8 MHz are presented and the advantages and disadvantages of the sensor are discussed.

Ultrasound heating in a tissue-bone phantom

Temperature rise generated by focused ultrasound beams was tested on semipermanent tissue-bone phantoms. The phantoms were capped (sealed) plastic hollow cylindrical containers filled with tissue-mimicking material (TMM), in which were imbedded 25μm diameter copper-constantan thermocouples (TC) and a piece of compact human or cow bone. The acoustic frequency specific attenuation coefficient of TMM was adjusted to be 0.3 dB cm −1 MHz −1 as specified by the FDA for a frequency range of 1–5 MHz. A high density 0.318 cm thick polyethylene sheet was chosen as the material to make caps of the phantoms. A formula developed to estimate the upper limit of temperature rises at tissue-bone interfaces generated by focused ultrasound has been proved to be appropriate experimentally using the semipermanent phantoms.

The recent warming in eastern Minnesota shown by ground temperatures

Soil and ground (here defined as beyond the depth of weathering or soil) temperatures can be superior to surface temperatures as indicators of climatic trends, because the “noise” common to the latter has been effectively reduced or removed. As a result, the 12.8 m ground temperatures recorded routinely at the University of Minnesota St. Paul campus climatological observatory since 1963 can provide valuable information on climatic trends.The observatory, located in the midst of land that has been in agricultural test plots since 1885, was instrumented with copper‐constantan thermocouples buried at various depths in the soil and ground. The two air temperature measurements, with which the 12.8 m ground temperature is compared, are made with maximum and minimum glass thermometers housed in standard temperature shelters.The mean air temperature increases of 0.049°C and 0.035°C per year, 1963–1990, at the observatory and the nearby Eastern Minnesota station, respectively, compare favorably with the 12.8 m ground temperature mean increase of 0.041°C per year. Due to the brevity of the record and to its approximate coincidence with the most recent northern hemisphere warming period, the extrapolation of these rates beyond the record period must be done with care.

Variation of 222Rn Concentration in Outdoor Air due to Variation of the Atmospheric Boundary Layer

Variation of 222Rn concentration in outdoor air, returns of a monostatic acoustic sounder and sensible heat flux are simultaneously observed at Okayama-shi in Japan. The sensible heat flux is measured with an eddy correlation method using a sonic anemometer and a copper-constantan thermocouple thermometer. Using height of a surface-based inversion layer obtained by the acoustic sounder returns and two 222Rn concentrations during the presence of the surface-based inversion layer, the exhalation rate of 222Rn at this site is estimated to be about 0.01 Bq.m-2.s-1, which agrees well with the exhalation rate of 222Rn estimated at Nagoya-shi in Japan. Using the estimated exhalation rates of 222Rn and the variation of the 222Rn concentration in the daytime, heights of mixing layers are estimated. These heights of the mixing layers are larger than the height of the mixing layer estimated using the sensible heat flux and the representative vertical profile of the autumnal night time air temperature in this area.