Convective heat transfer measured directly with a heat flux sensor

A heat flux disk has been developed that directly measures the convective heat transfer in W/m2. When the sensor is calibrated on an aluminum cylinder, the calibration constant obtained is greatest in still air. As air movement increases, the calibration constant is reduced with increasing convective heat transfer coefficient, 0.5%.W-1.m2.K. The influence of wind on the calibration value is greatly reduced when the sensor is attached to a surface with lower thermal conductivity. The local convective heat transfer coefficient (hc) of the human body was measured. The leg acts in a manner similar to that of a cylinder, with the highest hc value at the front facing the wind and the lowest approximately 90 degrees from the wind, and in the wake a value is obtained that is close to the average hc value of the leg. When hc is measured at several angles and positions all over the body, the results indicate that the body acts approximately as a cylinder with a hc value related to the wind speed as hc = 8.6.v0.6 W.m-2.K-1, where v is velocity.     

Attrition-free pyrolysis to produce bio-oil and char

Experiments are performed on a laboratory scale setup where beech wood chips are heated by gas convection and walls radiation. This study shows that it is possible to obtain high bio-oil and char yields with relatively low external heat transfer coefficients. The main advantage of this convection/radiation heat transfer mode compared to solid–solid collisions, applied in fluidized bed or twin screw reactors, is the reduction of solid attrition (char and sand). Thus tricky gas–solid separation through hot cyclones and/or hot filters could be avoided or reduced. It should be possible to recover directly bio-oil with less char particles and char free of sand dust. These qualities would allow easier use of these bio-products in different applications.     

Fourier's law of heat transfer and its implication to cell motility

Fourier's law of heat transfer addressing temperature differences is intrinsically selective in favoring the mitigation of the differences proceeding as fast as possible. We present an experimental demonstration of such selective behavior of material origin. When an actin filament equipped with nano-scale heat acceptors was placed under heat pulsation, it demonstrated a unidirectional movement without the presence of myosin or ATP. The prime factor for the unidirectional movement was the temperature differences between the locally heated portions on the actin filament and the cooler material bodies in the surroundings. The unidirectional movement could be enhanced in the process of mitigating the temperature differences as fast as possible.     

A simple method to predict body temperature of small reptiles from environmental temperature

To study behavioral thermoregulation, it is useful to use thermal sensors and physical models to collect environmental temperatures that are used to predict organism body temperature. Many techniques involve expensive or numerous types of sensors (cast copper models, or temperature, humidity, radiation, and wind speed sensors) to collect the microhabitat data necessary to predict body temperatures. Expense and diversity of requisite sensors can limit sampling resolution and accessibility of these methods. We compare body temperature predictions of small lizards from iButtons, DS18B20 sensors, and simple copper models, in both laboratory and natural conditions. Our aim was to develop an inexpensive yet accurate method for body temperature prediction. Either method was applicable given appropriate parameterization of the heat transfer equation used. The simplest and cheapest method was DS18B20 sensors attached to a small recording computer. There was little if any deficit in precision or accuracy compared to other published methods. We show how the heat transfer equation can be parameterized, and it can also be used to predict body temperature from historically collected data, allowing strong comparisons between current and previous environmental temperatures using the most modern techniques. Our simple method uses very cheap sensors and loggers to extensively sample habitat temperature, improving our understanding of microhabitat structure and thermal variability with respect to small ectotherms. While our method was quite precise, we feel any potential loss in accuracy is offset by the increase in sample resolution, important as it is increasingly apparent that, particularly for small ectotherms, habitat thermal heterogeneity is the strongest influence on transient body temperature.     

Multiplexed SOI BioFETs

Nanoscale Field Effect Transistors have emerged as a promising technology for ultrasensitive, unlabeled diagnostic applications. However, their use as quantitative sensors has been problematic because of the need for individual sensor calibration. In this work we demonstrate an internal calibration scheme for multiplexed nanoribbon field effect sensors by utilizing the initial current rates rather than end point detection. A linear response is observed consistent with initial binding kinetics. Moreover, we are able to show that top-down fabrication techniques yield reproducible device results with minimal fluctuations, enabling internal calibration.     

Impact of microwave heating on the physico-chemical properties of a starch–water model system

The objective of this work was to understand the physico-chemical changes induced in a wheat starch model system as a result of microwave heating. Wheat starch dispersions in water, with final solids content of 33%, 40% or 50%, were heated in a microwave oven. Following heating the samples were stored at 25 °C for up to 120 h and analyzed periodically. Microwave heated gels were significantly different from conduction heated gels in all parameters measured. The differences in properties are a reflection of the differences in the heat and mass transfer of the different modes of heating. The lack of granule swelling and the resulting soft gel are two key observations. The results of this study suggest a different mechanism of starch gelatinization compared to conduction heating. The vibrational motion and the rapid increase in temperature also result in granule rupture and formation of film polymers coating the granule surface.     

Modelling of pyrolysis of large wood particles

A fully transient mathematical model has been developed to describe the pyrolysis of large biomass particles. The kinetic model consists of both primary and secondary reactions. The heat transfer model includes conductive and internal convection within the particle and convective and radiative heat transfer between the external surface and the bulk. An implicit Finite Volume Method (FVM) with Tridiagonal Matrix Algorithm (TDMA) is employed to solve the energy conservation equation. Experimental investigations are carried out for wood fines and large wood cylinder and sphere in an electrically heated furnace under inert atmosphere. The model predictions for temperature and mass loss histories are in excellent agreement with experimental results. The effect of internal convection and particle shrinkage on pyrolysis behaviour is investigated and found to be significant. Finally, simulation studies are carried out to analyze the effect of bulk temperature and particle size on total pyrolysis time and the final yield of char.     

Heat transport mechanisms in vascular tissues: a model comparison

We have conducted a parametric comparison of three different vascular models for describing heat transport in tissue. Analytical and numerical methods were used to predict the gross temperature distribution throughout the tissue and the small-scale temperature gradients associated with thermally significant blood vessels. The models are: an array of unidirectional vessels, an array of countercurrent vessels, and a set of large vessels feeding small vessels which then drain into large vessels. We show that three continuum formulations of bioheat transfer (directed perfusion, effective conductivity, and a temperature-dependent heat sink) are limiting cases of the vascular models with respect to the thermal equilibration length of the vessels. When this length is comparable to the width of the heated region of tissue, the local temperature changes near the vessels can be comparable to the gross temperature elevation. These results are important to the use of thermal techniques used to measure the blood perfusion rate and in the treatment of cancer with local hyperthermia.     

A force plate based method for the calibration of force/torque sensors

This study describes a novel calibration method for six-degrees-of-freedom force/torque sensors (FTsensors) using a pre-calibrated force plate (FP) as a reference measuring device. In this calibration method, the FTsensor is rigidly connected to a FP and force/torque data are synchronously recorded while a dynamic functional loading procedure is applied by the researcher. Based on these data an accurate calibration matrix for the FTsensor can easily be obtained via least-squares optimization. Using this calibration method, this study further investigated what loading methods are appropriate for the calibration of FTsensors intended for ambulatory measurement of ground reaction forces (GRFs). Seven different loading methods were compared (e.g., walking, pushing while standing on the FTsensor). Calibration matrices were calculated based on the raw data from the seven loading methods individually and all loading methods combined. Performance of these calibration matrices was subsequently compared in an in situ trial. During the in situ trial, five common work tasks (e.g., walking, manual lifting, pushing) were performed by an experimenter, while standing on the FP wearing a "ForceShoe" with two calibrated FTsensors attached to its sole. Root-mean-square differences (RMSDs) between the FTsensor and FP outcomes were calculated over all tasks. Using the calibration matrices based on all loading methods combined resulted in small RMSDs (GRF: <8 N, center of pressure: <2 mm). Using the calibration matrices based on "pushing against manual resistance" resulted in similar RMSDs, proving it to be the best single loading method.     

The effect of media tonicity on Escherichia coli resistance to heating with different gradient

The influence of NaCl water solutions and glycerine hypertonic concentration on the survival of bacteria Escherichia coli B/r heated with different values of heat drop was investigated. It was shown that the transfer of cell suspensions from isotonic conditions to media with raised osmotic pressure, preliminarily heated up to 60 degrees C, and the following heating at this temperature inhibited differences in cell sensitivity to heating at different heat drop. Unlike, it was found that the transfer of cell suspensions from isotonic conditions to hypertonic media before and after heating at 60 degrees C increased differences in resistance of these microorganisms to heating at different heat drop. It is proposed that different resistance of bacteria to damaging action of hyperthermia at different heat drop, and a modified influence of hypertonic solutions on these differences may be due to heat induced destabilization of cell osmotic homeostasis. The extent of expression of this destabilization may be determined by a quantitative ratio of osmotic pressure values in the cell-suspension medium system in particular temperature and tonic environmental conditions.     

Optimal Homotopy Asymptotic Method for Flow and Heat Transfer of a Viscoelastic Fluid in an Axisymmetric Channel with a Porous Wall

In this article, an approximate analytical solution of flow and heat transfer for a viscoelastic fluid in an axisymmetric channel with porous wall is presented. The solution is obtained through the use of a powerful method known as Optimal Homotopy Asymptotic Method (OHAM). We obtained the approximate analytical solution for dimensionless velocity and temperature for various parameters. The influence and effect of different parameters on dimensionless velocity, temperature, friction factor, and rate of heat transfer are presented graphically. We also compared our solution with those obtained by other methods and it is found that OHAM solution is better than the other methods considered. This shows that OHAM is reliable for use to solve strongly nonlinear problems in heat transfer phenomena.     

Replica plating of mammalian cells using low melt agarose

We have developed a technique to replica plate mammalian cells grown on plastic dishes using low melt agarose. This method is simpler than previously described methods that use polyester membranes to grow and transfer cells. We have tested the effectiveness of this technique on normal and immortal cell lines and have found that we can transfer cells with an efficiency of 80–90%. We have used this technique to rapidly screen clones for insertion of a lentivirally encoded gene without a selectable marker.     

Heat transfer normal to paired arterioles and venules embedded in perfused tissue during hyperthermia

A numerical model of the heat transer normal to an arteriole-venule pair embedded in muscle tissue has been constructed. Anatomical data describing the blood vessel size, spacing, and density have been incorporated into the model. This model computes temperatures along the vessel walls as well as the temperature throughout the tissue which comprises an infinitely long Krogh cylinder around the vessel pair. Tissue temperatures were computed in the steady-state under resting conditions, while transient calculations were made under hyperthermic conditions. Results show that for both large- (1st generation) and medium-sized (5th generation) vessel pairs, the mean tissue temperature within the tissue cylinder is not equal to the mean of the arteriole and venule blood temperatures under both steady-state and transient conditions. The numerical data were reduced so that a comparison could be made with the predictions of a simple two-dimensional superposition of line sources and sinks presented by Baish et al. This comparison reveals that the superposition model accurately describes the heat transfer effects during hyperthermia, permitting subsequent incorporation of this theory into a realistic three-dimensional model of heat transfer in a whole limb during hyperthermia.     

Identification of Mre11 as a target for heat radiosensitization

Thermal radiosensitization is believed to be mediated by an inhibition of double-strand break (DSB) repair, but the exact mechanism of radiosensitization remains to be elucidated. Previously, we demonstrated that proteins of the Mre11/Rad50/Nbs1 complex (MRN) translocate from the nucleus to the cytoplasm in cells have that been heated or heated and then irradiated; this finding led us to propose that heat radiosensitization was due at least in part to translocation of MRN. In the current study, we used leptomycin B to inhibit MRN translocation in heated, irradiated cells, but we found that heat radiosensitization was not altered. Thus enhanced radiosensitivity was not attributed to translocation of MRN proteins. To determine which of the MRN subunits contributed to heat radiosensitization, we compared the extent of heat radiosensitization in wild-type cells with that of cells hypomorphic for Mre11 or Nbs1 or cells in which the level of Rad50 was suppressed. We found that neither Nbs1 nor Rad50 is involved in heat radiosensitization, because a similar amount of heat radiosensitization was observed in cells deficient in those proteins compared to cells expressing normal levels. However, heat radiosensitization was not observed in A-TLD1 cells deficient in Mre11. Measurement of exonuclease activity of purified Mre11 heated at 42.5°C or 45.5°C indicated that the protein is very heat-labile. Immunoprecipitation of Mre11 from heated HeLa cells also revealed that hsp70 associates with Mre11 and that this association is maintained long after heating. Taken together, these findings implicate Mre11 as a target for heat radiosensitization and suggest that heat radiosensitization and inhibition of DSB repair may be mediated by heat-induced conformational changes in Mre11.     

Cationic neutrophil proteins increase transendothelial albumin movement

Neutrophils play a role in the development of pulmonary edema in many models of the adult respiratory distress syndrome, but the mechanism of their action is not completely understood. We asked whether two neutrophil secretory products, human neutrophil cationic protein (NCP) and human neutrophil elastase (HNE), would nonenzymatically alter the movement of albumin across a cultured endothelial monolayer. Both enzymes were inactivated by heating before use. HNE was additionally enzymatically inactivated with a chloromethylketone oligopeptide (CMK) inhibitor and with alpha 1-proteinase inhibitor (alpha 1-PI). Heated NCP, heated HNE, and CMK-complexed HNE all increased transendothelial albumin transfer. The cation protamine also increased albumin transfer across the endothelium and this increase was blocked by heparin. Alpha 1-PI and fetal bovine serum also prevented the cationic proteins from increasing albumin transfer. Using the release of lactate dehydrogenase as a marker of cytotoxicity, heated HNE was toxic to endothelial cells, heated NCP had only minimal toxicity, and protamine had no toxicity. Changes in endothelial cell shape with gap formation was seen after exposure to both heated HNE and heated NCP. Both the cytotoxicity associated with heated HNE and the cell shape changes associated with heated NCP and heated HNE could be blocked by heparin. These results suggest that in addition to neutrophil proteases and reactive O2 molecules, neutrophil-derived cationic proteins can directly and nonenzymatically contribute to edema formation during acute inflammation.     

Respiratory heat loss in the sheep: a comprehensive model

A model is presented for the respiratory heat loss in sheep, considering both the sensible heat lost by convection ( C(R)) and the latent heat eliminated by evaporation ( E(R)). A practical method is described for the estimation of the tidal volume as a function of the respiratory rate. Equations for C(R) and E(R) are developed and the relative importance of both heat transfer mechanisms is discussed. At air temperatures up to 30 degrees C sheep have the least respiratory heat loss at air vapour pressures above 1.6 kPa. At an ambient temperature of 40 degrees C respiratory loss of sensible heat can be nil; for higher temperatures the transfer by convection is negative and thus heat is gained. Convection is a mechanism of minor importance for the respiratory heat transfer in sheep at environmental temperatures above 30 degrees C. These observations show the importance of respiratory latent heat loss for thermoregulation of sheep in hot climates.     

Learning and discrimination of colored papers in jumping spiders (Araneae, Salticidae)

Color discrimination in jumping spiders Hasarius adansoni was examined by heat-avoidance learning in association with colored papers. The arena for the experiment was divided into two halves by a pair of colored papers. The colored papers used in this study were blue, green, yellow, red, white, gray and black. In training sessions, one half of the arena was heated from the bottom by a hot plate, and freely walking spiders were individually trained to avoid the heated half. In subsequent memory tests without heat, they consistently avoided the heat-associated colored papers. We found that jumping spiders could learn blue-green, blue-yellow, blue-red, blue-gray, green-yellow, green-red, green-gray, yellow-red, yellow-gray and red-gray patterns. Moreover, spiders trained with a blue-white pattern, a green-white pattern, a yellow-white pattern or a red-white pattern could discriminate the blue, green, yellow or red from black. It seems that jumping spiders can discriminate the blue, green, yellow and red papers by their hue, although brightness may also be used together with the color cue to discriminate colored papers.     

Deep body and surface temperature responses to hot and cold environments in the zebra finch

Global warming increasingly challenges thermoregulation in endothermic animals, particularly in hot and dry environments where low water availability and high temperature increase the risk of hyperthermia. In birds, un-feathered body parts such as the head and bill work as ‘thermal windows’, because heat flux is higher compared to more insulated body regions. We studied how such structures were used in different thermal environments, and if heat flux properties change with time in a given temperature. We acclimated zebra finches (Taeniopygia guttata) to two different ambient temperatures, ‘cold’ (5 °C) and ‘hot’ (35 °C), and measured the response in core body temperature using a thermometer, and head surface temperature using thermal imaging. Birds in the hot treatment had 10.3 °C higher head temperature than those in the cold treatment. Thermal acclimation also resulted in heat storage in the hot group: core body temperature was 1.1 °C higher in the 35 °C group compared to the 5 °C group. Hence, the thermal gradient from core to shell was 9.03 °C smaller in the hot treatment. Dry heat transfer rate from the head was significantly lower in the hot compared to the cold treatment after four weeks of thermal acclimation. This reflects constraints on changes to peripheral circulation and maximum body temperature. Heat dissipation capacity from the head region increased with acclimation time in the hot treatment, perhaps because angiogenesis was required to reach peak heat transfer rate. We have shown that zebra finches meet high environmental temperature by heat storage, which saves water and energy, and by peripheral vasodilation in the head, which facilitates dry heat loss. These responses will not exclude the need for evaporative cooling, but will lessen the amount of energy expend on body temperature reduction in hot environments.     

Comparison of Sensor Selection Mechanisms for an ERP-Based Brain-Computer Interface

A major barrier for a broad applicability of brain-computer interfaces (BCIs) based on electroencephalography (EEG) is the large number of EEG sensor electrodes typically used. The necessity for this results from the fact that the relevant information for the BCI is often spread over the scalp in complex patterns that differ depending on subjects and application scenarios. Recently, a number of methods have been proposed to determine an individual optimal sensor selection. These methods have, however, rarely been compared against each other or against any type of baseline. In this paper, we review several selection approaches and propose one additional selection criterion based on the evaluation of the performance of a BCI system using a reduced set of sensors. We evaluate the methods in the context of a passive BCI system that is designed to detect a P300 event-related potential and compare the performance of the methods against randomly generated sensor constellations. For a realistic estimation of the reduced system''s performance we transfer sensor constellations found on one experimental session to a different session for evaluation. We identified notable (and unanticipated) differences among the methods and could demonstrate that the best method in our setup is able to reduce the required number of sensors considerably. Though our application focuses on EEG data, all presented algorithms and evaluation schemes can be transferred to any binary classification task on sensor arrays.     

Significance of sleeping plate as a thermal protection for farmed raccoon dogs (Nyctereutes procyonoides)

1. Both living and model animals were used to evaluate the significance of a sleeping plate as a thermal protection for the farmed raccoon dog (Nyctereutes procyonoides, Gray, 1834), its use by the animals and its cleanliness while used. 2. A dry sleeping plate effectively prevented heat loss from the model animal while a wet plate was less effective. The degree of heat transfer was highest when the plate was ice-covered. Heat loss in windy conditions was significantly higher than in calm conditions. 3. The use of a sleeping plate did not depend on ambient air temperature; in spite of the cold weather (about -25 degrees C) only one in four animals preferred to lie on plate. Animals which did not prefer to use sleeping plates most eagerly messed them up.