Measurement of thermal resistance of polymer sheets and fibrous layers is important in various applications including those within the engineering, ergonomics, clothing design and personal protective equipment fields. Standard methods for measurement of thermal resistance of plain materials are generally time consuming, expensive and often require the sample to be cut. Moreover, the temperature difference between the surfaces of both plates surrounding the sample must be known, as well as the sample thickness. This article describes a new measuring device named the Thermoscope. The Thermoscope is not limited by the aforementioned requirements and is able to evaluate the thermal resistance of polymer sheets and textiles by touching the sample on one surface alone. Simultaneously, the other surface is kept in thermal contact with the supporting base. The accuracy of this device was compared with the Alambeta thermal insulation tester. Effects of various base materials on measurement precision were also studied.
- MeSH
- polymery MeSH
- tepelná vodivost MeSH
- testování materiálů přístrojové vybavení metody MeSH
- textilie MeSH
- Publikační typ
- časopisecké články MeSH
This paper deals with the development and characteristics of the properties of a permeable water-resistant heat insulation panel based on recycled materials. The insulation panel consists of a thermal insulation core of recycled soft polyurethane foam and winter wheat husk, a layer of geopolymer that gives the entire sandwich composite strength and fire resistance, and a nanofibrous membrane that permits water vapor permeability, but not water in liquid form. The observed properties are the thermal conductivity coefficient, volumetric heat capacity, fire resistance, resistance to long-term exposure of a water column, and the tensile strength perpendicular to the plane of the board. The results showed that while the addition of husk to the thermal insulation core does not significantly impair its thermal insulation properties, the tensile strength perpendicular to the plane of these boards was impaired by the addition of husk. The geopolymer layer increased the fire resistance of the panel for up to 13 min, and the implementation of the nanofibrous membrane resulted in a water flow of 154 cm2 in the amount of 486 g of water per 24 h at a water column height of 0.8 m.
Heat tolerance of plants related to cell membrane thermostability is commonly estimated via the measurement of ion leakage from plant segments after defined heat treatment. To compare heat tolerance of various plants, it is crucial to select suitable heating conditions. This selection is time-consuming and optimizing the conditions for all investigated plants may even be impossible. Another problem of the method is its tendency to overestimate basal heat tolerance. Here we present an improved ion leakage method, which does not suffer from these drawbacks. It is based on gradual heating of plant segments in a water bath or algal suspensions from room temperature up to 70-75°C. The electrical conductivity of the bath/suspension, which is measured continuously during heating, abruptly increases at a certain temperature TCOND (within 55-70°C). The TCOND value can be taken as a measure of cell membrane thermostability, representing the heat tolerance of plants/organisms. Higher TCOND corresponds to higher heat tolerance (basal or acquired) connected to higher thermostability of the cell membrane, as evidenced by the common ion leakage method. The new method also enables determination of the thermostability of photochemical reactions in photosynthetic samples via the simultaneous measurement of Chl fluorescence.
Hypothermia is an effective neuroprotective strategy for acute stroke. However, in clinical practice, the induction of hypothermia is achieved through the systemic reduction of body temperature (using thermal covers or endovascular cooling devices) which results in a complex system associated in many cases to side effects. Therefore, the aim of this study was to test the magnetocaloric effect as a potential new therapeutic strategy for stroke by means of an adiabatic magnetic refrigerator device. As a first approach, we have developed a simple device to evaluate in vitro the thermodynamic behavior of different concentrations of commercial gadolinium powder as a reference magnetocaloric material. The samples, properly thermally insulated, were cyclically magnetized and demagnetized at room temperature by 1 T permanent magnets in order to induce an adiabatic magnetic effect. Under the experimental conditions tested, results showed a maximun non-accumulative temperature variation of 0.2 °C, insufficient to carry out an effective hypothermia. This study allowed us to discuss about the use of new materials and strategies for further in vivo experiments.
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- biokompatibilní materiály MeSH
- cévní mozková příhoda terapie MeSH
- gadolinium MeSH
- magnetické pole MeSH
- magnetismus metody přístrojové vybavení MeSH
- techniky in vitro MeSH
- tepelná vodivost MeSH
- terapeutická hypotermie * metody přístrojové vybavení MeSH
- Publikační typ
- práce podpořená grantem MeSH
PURPOSE: In 2010, approximately 14.9 million babies (11.1%) were born preterm. Because preterm infants suffer from an immature thermoregulatory system they have difficulty maintaining their core body temperature at a constant level. Therefore, it is essential to maintain their temperature at, ideally, around 37°C. For this, mathematical models can provide detailed insight into heat transfer processes and body-environment interactions for clinical applications. METHODS: A new multi-node mathematical model of the thermoregulatory system of newborn infants is presented. It comprises seven compartments, one spherical and six cylindrical, which represent the head, thorax, abdomen, arms and legs, respectively. The model is customizable, i.e. it meets individual characteristics of the neonate (e.g. gestational age, postnatal age, weight and length) which play an important role in heat transfer mechanisms. The model was validated during thermal neutrality and in a transient thermal environment. RESULTS: During thermal neutrality the model accurately predicted skin and core temperatures. The difference in mean core temperature between measurements and simulations averaged 0.25±0.21°C and that of skin temperature averaged 0.36±0.36°C. During transient thermal conditions, our approach simulated the thermoregulatory dynamics/responses. Here, for all infants, the mean absolute error between core temperatures averaged 0.12±0.11°C and that of skin temperatures hovered around 0.30°C. CONCLUSIONS: The mathematical model appears able to predict core and skin temperatures during thermal neutrality and in case of a transient thermal conditions.
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- biologické modely * MeSH
- gestační stáří MeSH
- lidé MeSH
- novorozenec fyziologie MeSH
- počítačová simulace MeSH
- předčasný porod patofyziologie MeSH
- tepelná vodivost MeSH
- teplota kůže MeSH
- teplota MeSH
- termoregulace * MeSH
- vysoká teplota MeSH
- životní prostředí MeSH
- Check Tag
- lidé MeSH
- novorozenec fyziologie MeSH
- Publikační typ
- časopisecké články MeSH
The effect of ionic surfactants and manufacturing methods on the separation and distribution of multi-wall carbon nanotubes (CNTs) in a silicone matrix are investigated. The CNTs are dispersed in an aqueous solution of the anionic surfactant dodecylbenzene sulfonic acid (DBSA), the cationic surfactant cetyltrimethylammonium bromide (CTAB), and in a DBSA/CTAB surfactant mixture. Four types of CNT-based composites of various concentrations from 0 to 6 vol.% are prepared by simple mechanical mixing and sonication. The morphology, electrical and thermal conductivity of the CNT-based composites are analyzed. The incorporation of both neat and modified CNTs leads to an increase in electrical and thermal conductivity. The dependence of DC conductivity versus CNT concentration shows percolation behaviour with a percolation threshold of about 2 vol.% in composites with neat CNT. The modification of CNTs by DBSA increases the percolation threshold to 4 vol.% due to the isolation/separation of individual CNTs. This, in turn, results in a significant decrease in the complex permittivity of CNT–DBSA-based composites. In contrast to the percolation behaviour of DC conductivity, the concentration dependence of thermal conductivity exhibits a linear dependence, the thermal conductivity of composites with modified CNTs being lower than that of composites with neat CNTs. All these results provide evidence that the modification of CNTs by DBSA followed by sonication allows one to produce composites with high homogeneity.
- MeSH
- benzensulfonáty chemie MeSH
- cetrimoniové sloučeniny chemie MeSH
- elektrická vodivost * MeSH
- impedanční spektroskopie MeSH
- nanokompozity chemie ultrastruktura MeSH
- nanotrubičky uhlíkové chemie ultrastruktura MeSH
- povrchově aktivní látky chemie MeSH
- silikonové elastomery chemie MeSH
- tepelná vodivost * MeSH
- termogravimetrie MeSH
- vibrace ultrazvukové MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
