Thermal Distribution Pattern Research Articles

Thermographic mapping of the skin surface of the head in bald-headed male subjects

Thermal patterns on the skin are related to skin blood perfusion. While knowledge concerning thermal distribution patterns of the face are well established, the thermal distribution patterns of the skin surface of other aspects of the head has only been investigated once previously in a study employing low resolution thermographic equipment [van Dulken, H., van Voss, S.F.C.H, 1971. The normal thermographic patterns of the human head. Acta Neurochir. 23, 247–58.] The purpose of the study was to re-examine the thermal distribution patterns of the surface of the entire head in 12 healthy bald headed male subjects (mean age 39±7.8 (SD) years) using a high definition infrared (IR) thermographic camera. The thermal distribution patterns were monitored using dynamic infrared thermography (DIRT) before, during and after a 2min local skin cooling procedure with a pair of fans. Infrared thermal images (thermograms) were taken of the superior, anterior, lateral and posterior aspects of the head. The thermal patterns in general followed the anatomical location of the main superficial arteries and veins of the head as described in anatomy books although there were some variations, especially with regard to the forehead and top of the head (superior aspect), ranging from an asymmetrical distribution pattern to a lack of a clear thermal pattern. The thermal patterns in the left and right lateral thermograms in each individual were relatively symmetrical. During the rewarming period the helix, auricular lobule of the auricles and the nose were relatively cold. The frontal thermograms were characterized by cool nasal and cheek areas and a clear warm area surrounding the eyes, especially around the inner canthus.

Neural Thermal Performance in Porcelain Crabs, GenusPetrolisthes

Neurons are highly temperature sensitive. Temperature-induced nerve failure may play an important role in determining organismal thermal tolerance limits and distribution patterns. To expand our understanding of the role of neuronal thermal performance in setting thermal limits, we compared the thermal performance of neurons from five porcelain crab (genus Petrolisthes) congeners that differ in thermal habitat. In experiment 1, neuronal performance of sensory neurons was determined by extracellular recording of spontaneous action potentials during thermal ramps. Arrhenius break temperatures of action potential generation were used to calculate maximum critical temperature (CT(max)) and minimum critical temperature (CT(min)) for neuronal performance. CT(max) and CT(min) were related to habitat temperature across the five species and were found to respond to acclimation temperature. In experiment 2, we assessed the performance of neurons from Petrolisthes cinctipes acclimated at 8°, 18°, and 25°C when placed at 30°C (near the whole-organism CT(max) of this species) and demonstrated that neural performance near whole-organism CT(max) increases with increasing acclimation temperature. In experiment 3, we compared the thermal limits of sensory afferents and pacemaker efferents and found that they were correlated, although pacemaker efferents tended to have a higher CT(max) and reduced plasticity. Our final analysis, which was of transcriptomic data in cardiac tissue, leads us to hypothesize that nerve membrane K(+) conductance may underlie variation in nerve thermal tolerance.

Visualization of Thermal Distribution Caused by Focused Ultrasound Field in an Agar Phantom

Ultrasound waves have been widely used not only in medical diagnostic systems but also in medical treatment. There has been increasing interest in the thermal distribution caused by ultrasound waves. In this study, using thermochromic particles, a visualization method was suggested in a mimic phantom for organic materials. By blending various thermochromic particles with different critical temperatures, the thermal field distribution in the phantom could be observed. The effect of a concave-type ultrasound transducer on the temperature distribution in an agar phantom mixed with thermochromic particles was observed. The temperature distribution corresponded to changes in the brightness distribution of gray. It was confirmed that the thermal distribution pattern in the vicinity of the focal area varies with the time exposure to ultrasound waves.

Heat Source Analysis of Hard Disk Drives with Different Wall Conditions using Infrared System

Increasing performance parameters of hard disk drive (HDD) such as higher capacity and faster data access speed with decreasing physical size make HDD more susceptible to thermal effects. Contact temperature measurement using thermocouple is not suitable for the rotating platter of HDD. Heat analysis using simulation software requires accurate initial parameter setting such as thermal (initial & boundary) conditions of certain regions. Temperature measurement using infrared (IR) system avoids these limitations; it is non-contact, responsive and does not require initial parameter setting. Thermal pattern distribution can be studied from the thermal images. However, emissivity of the target has to be known and calibration of the system is essential for accurate temperature reading. This paper showed that temperature within the HDD increases with ambient temperature and time, but the thermal distribution pattern in the HDD was not affected by different ambient temperatures. Three wall boundary conditions were conducted to study the thermal distribution pattern in the HDD. A solution was then proposed based on the results obtained from the experiments to improve the heat transfer rate and steady state temperature, and reduce the detrimental effects from high thermal generation in future prototypes. Another important finding was that the averaged temperature of the head cap was generally higher compared to that of the disk, as the spindle motor is the primary heat source within the HDD. Heat source analysis of HDD with IR system allows designers to have better visibility of the temperature generated in different components of the HDD. Proper cooling may enhance disk life as well as ensure the stability and integrity of the system.

Monitoring and Characterizing of Hard Disk Drive Thermal Sources

The growth of the hard disk drive's (HDD) capacity and its high performance have been instrumental in meeting the demands of a diverse spectrum of applications. However, thermal effects in HDD may cause several problems, such as thermal expansion, which causes read/write error due to misalignment, and thermal protrusion, which may cause contact between the magnetic head and disk, resulting in a HDD crash. To study the effects of temperature generated within an HDD, a Hitachi HDD (operating at 15000 rpm) was subjected to 12 different ambient temperatures, while thermal distributions of its head cap and disk were obtained using an infrared thermography system. The results show that the temperature within the HDD increases with the ambient temperature and time. However, the different ambient temperatures did not affect the thermal distribution pattern within the HDD. By comparing the results with ANSYS simulation, it was noted that the simulated result lacks details on some thermal conditions of certain regions, and the results of the simulated temperatures of the components within the HDD were also observed to be overpredicted.

Nickel membrane temperature sensor in micro-flow measurement

According to the principle of the thermal distribution pattern, a microfluidic sensor based on silicon was fabricated with the microelectronic technique and the micro electro-mechanical systems (MEMS) process, including a micro-heater and two temperature sensors. NiCr and Ni thin films were chosen as the materials of the micro-heater and the temperature sensors, respectively. The Ni membranes were deposited on different substrates, and the adhesion between Ni thin film and different substrates was investigated by electron probe micro analyzer (EPMA). The thermal characteristics of the nickel thin film fabricated on different substrates were measured. The results indicate that Si 3N 4 and SiO 2 are more suitable than Si to be used as the substrate for fabricating the temperature sensor. The temperature sensors satisfied the requisition of fast response and high sensitivity, and the microfluidic sensor fabricated in this paper will have much hope of using in biochemical analytical system.

Thermal distribution microfluidic sensor based on silicon

During the measurement and analysis of micro-total analysis system (μ-TAS), the bulk of the sample injected is about nano-liter, so that the study of microfluidic sensor has been becoming an important aspect of the analytical instrument. According to the principle of the thermal distribution pattern, a microfluidic sensor based on silicon is fabricated with the microelectronic technique and micromechanical process in this paper, including a micro-heater and two temperature sensors. Under the operational mode of the constant heating power, the characteristics of the microfluidic sensor are analyzed. The experimental results indicate that the measurement range of the microfluidic sensor is from 10 to 700 μl/min.

Classifying Regional Variation in Thermal Regime Based on Stream Fish Community Patterns

Although the importance of water temperature to the ecology of stream fishes is well documented, relatively little information is available on the extent of regional variation in thermal regime and its influence on stream fish distribution and abundance patterns. In streams draining the heterogeneous glacial landscape of Michigan's Lower Peninsula, regional variation in summer mean temperature and temperature fluctuation is among the highest reported in the literature. We developed a habitat classification to simplify the description of thermal regimes and to describe the relationships between available thermal regimes and distribution patterns of stream fishes. Changes in community composition, species richness, and standing stocks of key fish species occurred across gradients in mean temperature and temperature fluctuation. These changes were used to identify three mean temperature categories (cold, <19°C; cool, 19–<22°C; and warm, ≥22°C) and three temperature fluctuation categories (stable, <5°C; moderate, 5–<10°C; and extreme, ≥10°C). The combination of these categories resulted in a 3 × 3 matrix with nine discrete thermal regimes. The classification developed in this study provides a framework for descriptions of the realized thermal niche of stream fishes, and can be used as a baseline for measurement of changes in distribution patterns associated with future climate warming. Our results suggest that observed differences in community structure among sites are largely attributable to spatial variation in mean temperature and temperature fluctuation. Thus, accounting for the linkage between regional variation in thermal regime and fish community structure should improve our ability to effectively assess and manage stream resources.

PYROELECTRIC VIDICON THERMOGRAPHY AND COLD CHALLENGE QUANTIFY THE SEVERITY OF RAYNAUD'S PHENOMENON

Thermographic images of the hands of patients with primary and secondary Raynaud's phenomenon and of a group of normal subjects, recorded before and after cold provocation using a pyroelectric vidicon thermal imaging system, showed differences in thermal distribution patterns that were characteristic of primary Raynaud's phenomenon (RP), scleroderma (RS) and normal, and were exaggerated by cold provocation. The responses to cold challenge, assessed by computing the mean temperature of the hand as it recovered from cold challenge and plotting these values against time to produce a rewarming curve, were also characteristic of the patient and the normal groups, and gave an indication of the severity of circulatory impairment. Methods are described for the simple numerical characterization of these parameters.

The distribution of power and heat produced by interstitial microwave antenna arrays: I. Comparative phantom and canine studies

To adequately plan and administer localized hyperthermia with interstitial microwave antennas, the thermal distribution patterns generated by such antennas must be characterized. This study evaluated the performance of single node 915 MHz antennas operating either alone or as a 2 cm square array of four parallel antennas using both muscle-equivalent phantoms and canine thigh muscle. Two types of measurements were compared. Specific absorption rate (SAR), where temperature increases resulting from short duration microwave pulses were used to define power distribution, and temperature gradients during simulated hyperthermia treatments. SAR measurements in phantoms were comparable to those obtained in non-perfused canine muscle demonstrating the usefulness of the phantom for these measurements. For a single antenna there was a rapid decrease in power radially which resulted in a steep thermal gradient at distances within 0.5 cm. However, the power generated by a four-antenna array was highest along its central axis and declined to approximately 50% near the antennas at the array periphery. Along the central axis of the array power decreased most rapidly distal to the antenna nodes. The distribution of temperature measured during simulated hyperthermia treatments in phantoms paralleled the SAR distribution and was comparable to the temperature gradient observed in perfused canine muscle, suggesting that phantoms could be used to predict temperature distributions in resting muscle tissue.

Thermal distribution of magnetic-loop induction hyperthermia in phantoms and animals: Effect of the living state and velocity of heating

Hyperthermia has shown promise for the treatment of cancer. The magnetrode radio-frequency magnetic-loop induction applicator was recently introduced and is being evaluated at many centers with encouraging initial results. This investigation was undertaken to delineate the thermal distribution patterns of magnetrode hyperthermia in both normal tissue phantoms and healthy dogs. Temperatures on homogeneous and heterogeneous tissue equivalents and animal tissue phantoms, a dead animal extremity, a dead dog and a live dog subjected to rapid high-dose heating showed preferential and potentially injurious peripheral heating with a central “cold spot”. However, sequential moderate-dose heating in live dogs showed virtually uniform (<1°C) and potentially tumoricidal temperatures ≥42°C in both peripheral and central internal organs without injury to surface tissues. These data indicate that magnetic-loop induction can produce potentially safe and effective deep central heat in living, normal animals, but that safety and effectiveness are significantly influenced by the velocity of heat deposition. Furthermore, normal tissue phantom models and dead animals are unreliable predictors of magnetrode heat patterns in living systems.

The Performance and Selection of Domestic Heaters

The thermal performance of a wide range of domestic heaters has been assessed from detailed measurements of the thermal distribution patterns from the heaters installed in typical houses. Heated floors and ducted systems provide satisfactory temperature distributions but convection “space” heaters distribute the heat relatively poorly. Comparison of the cost of operating heaters in Melbourne, Australia with various fuels shows that gas, resistive storage heating with off-peak electricity, and heat pumps using electricity at normal tariffs, may be operated at comparable rates. The operating costs are more than double if the fuel is oil, bottled gas or electricity at normal tariffs for systems other than heat pumps. The factors to be considered when selecting a heating system for a particular dwelling are discussed.

Symposium on Thermal Waters: Papers solicited

A call for papers has been issued for the International Symposium on Thermal and Chemical Problems of Thermal Waters, to be held during the Sixteenth General Assembly of the International Union of Geodesy and Geophysics (IUGG) on the campus of the University of Grenoble, France, August 29–September 1, 1975. Sponsors of the symposium are the International Association of Hydrological Sciences (IAHS) and the International Association of Volcano logy and Chemistry of the Earth's Interior (IAVCEI).The program will consist of invited and offered papers on thermal water distribution patterns, geothermal zones of the earth's crust, geochemistry of thermal waters in various regions, utilization of the heat components of thermal waters, and thermal pollution.