The effect of radio-frequency heating on vacuum-packed saury (Cololabis saira) in water

We characterized vacuum-packed whole saury (Cololabis saira) treated using radio-frequency (RF) heating and compared it with that treated using conventional retort heating. RF heating is electrical heating based on dielectric heating. In this study, the effect of RF heating on softening and collagen in backbone was analyzed. RF heating heated the center of fish faster than water. The backbone was softened to a chewable level, and the heating time was shortened to one-third. The amount of crude protein and collagen in backbone decreased with decreasing elasticity, although that heated using RF (131°C) still contained a higher amount than conventional heating. However, β and γ collagen, and then α1 and α2 collagen chain in backbone disappeared with heating; therefore, collagen was degraded to collagen peptide. Results confirmed that RF heating provided wholly eatable fish containing low-molecular collagen peptide in a short heating time.     

Time-temperature relationships for L1A2 cells step-down heated from 38 to 45 degrees C in vitro

The in vitro response of L1A2 cells to a single exposure to one temperature and to step-down heating was investigated. Single heating consisted of heating for a specified time at a constant temperature in the range 38.0-45.0 degrees C, whereas step-down heating involved a pretreatment of either 45.0 degrees C for 10 min or 42.0 degrees C for 90 min. The pretreatments were adjusted to give the same survival level. The survival curves for single heating had an initial shoulder followed by an exponential region, whereas for step-down heating they were strictly exponential and had no shoulder. The time-temperature relationship for cells exposed to single heating showed a biphasic Arrhenius curve with a downward inflection at 40.5 degrees C. Biphasic Arrhenius curves were also observed for step-down heating, but both the 45 degrees C/10 min and the 42 degrees C/90 min pretreatment showed an upward inflection that broke at 42.5 degrees C and 40.5 degrees C, respectively. The downward inflection on the Arrhenius curve for single heating has been attributed to thermotolerance development and the effect of step-down heating to a temporary inhibition of thermotolerance development. However, the present shape of the Arrhenius curves for step-down heating cannot be explained by inhibition of thermotolerance. It is therefore reasonable to assume that step-down heating is more than just the inhibition of thermotolerance, and that step-down heating and thermotolerance are distinct phenomena which act independently.     

Heating of cardiovascular stents in intense radiofrequency magnetic fields

We consider the heating of a metal stent in an alternating magnetic field from an induction heating furnace. An approximate theoretical analysis is conducted to estimate the magnetic field strength needed to produce substantial temperature increases. Experiments of stent heating in industrial furnaces are reported, which confirm the model. The results show that magnetic fields inside inductance furnaces are capable of significantly heating stents. However, the fields fall off very quickly with distance and in most locations outside the heating coil, field levels are far too small to produce significant heating. The ANSI/IEEE C95.1-1992 limits for human exposure to alternating magnetic fields provide adequate protection against potential excessive heating of the stents.     

Thermal Hardening: A New Seed Vigor Enhancement Tool in Rice

In a laboratory study, indica and japonica rice (Oryza sativa L.) seeds were exposed to thermal hardening (heating followed by chilling followed by heating; chilling followed by heating followed by chilling; heating followed by chilling or chilling followed by heating). In indica rice, heating followed by chilling followed by heating resulted in decreased mean germination time, time to start germination, electrical conductivity of seed leachates, and time to 50% germination, as well as increased germination index, energy of germination, radicle and plumule length, root length, root/shoot ratio, root fresh and dry weight, radicle and plumule growth rate, and shoot fresh weight. In japonica rice, chilling followed by heating followed by chilling performed better than all other treatments, including control.     

Kinetics of inactivation of Bacillus subtilis spores by continuous or intermittent ohmic and conventional heating

Bacillus subtilis spores were suspended in 0.1% NaCl solution (ca. 10(7) CFU/mL) and treated by conventional or ohmic heating under identical temperature histories. Temperatures tested were in the range of 88 to 99 degrees C. Survival curves and calculated D values showed significantly higher lethality for spores by ohmic than conventional heating. The z or Ea values corresponding to the two heating methods, however, were not significantly different. Spores of B. subtilis were suspended in nutrient broth and treated with conventional and ohmic heating through a single- or a double-stage treatment. In case of double-stage treatment, heating was interrupted by a 20 min of incubation at 37 degrees C to induce a Tyndallization effect. Spore inactivation during double-stage treatment was greater for ohmic than conventional heating. The enhanced spore inactivation by ohmic, compared with conventional, heating resulted from a greater rate of spore death during the first stage of heating and greater decrease in count of viable spores immediately after the incubation period that intervened the heating process. Thus it is concluded that spore inactivation during ohmic heating was primarily due to the thermal effect but there was an additional killing effect caused by the electric current.     

Thermal Hardening： A New Seed Vigor Enhancement Tool in Rice

In a laboratory study, indica and japonica rice (Oryza sativa L.) seeds were exposed to thermal hardening (heating followed by chilling followed by heating; chilling followed by heating followed by chilling; heating followed by chilling or chilling followed by heating). In indica rice, heating followed by chilling followed by heating resulted in decreased mean germination time, time to start germination, electrical conductivity of seed leachates, and time to 50% germination, as well as increased germination index, energy of germination, radicle and plumule length, root length, root/shoot ratio, root fresh and dry weight, radicle and plumule growth rate, and shoot fresh weight. In japonica rice, chilling followed by heating followed by chilling performed better than all other treatments, including control.     

Effect of heat on endotoxin in plasma and in pyrogen-free water, as measured in the Limulus amoebocyte lysate assay

Four modes of heating endotoxin in plasma and two different times of heating endotoxin in pyrogen-free water were compared. There were no significant differences in standard curves after heating endotoxin in plasma at 100 degrees C for 1 and for 10 min. However, the standard curve after heating for 10 min at 75 degrees C had a significantly less steep slope, and after heating for 10 min at 56 degrees C, it was completely flat. Heating of endotoxin in pyrogen-free water for 1 min also resulted in the flattening of the standard curve, which was even more pronounced after 10 min of heating.     

Heat-induced changes in the mechanics of a collagenous tissue: isothermal, isotonic shrinkage.

We present data from isothermal, isotonic-shrinkage tests wherein bovine chordae tendineae were subjected to well-defined constant temperatures (from 65 to 90 degrees C), durations of heating (from 180 to 3600 s), and isotonic uniaxial stresses during heating (from 100 to 650 kPa). Tissue response during heating and "recovery" at 37 degrees C following heating was evaluated in terms of the axial shrinkage, a gross indicator of underlying heat-induced denaturation. There were three key findings. First, scaling the heating time via temperature and load-dependent characteristic times for the denaturation process collapsed all shrinkage data to a single curve, and thereby revealed a time-temperature-load equivalency. Second, the characteristic times exhibited an Arrhenius-type behavior with temperature wherein the slopes were nearly independent of applied load--this suggested that applied loads during heating affect the activation entropy, not energy. Third, all specimens exhibited a time-dependent, partial recovery when returned to 37 degrees C following heating, but the degree of recovery decreased with increases in the load imposed during heating. These new findings on heat-induced changes in tissue behavior will aid in the design of improved clinical heating protocols and provide guidance for the requisite constitutive formulations.     

Effect of step-down heating on brachytherapy in a murine tumor system

The effects of step-down heating combined with low-dose-rate irradiation (brachytherapy) were studied using a murine mammary adenocarcinoma (MTG-B) grown in the flanks of C3H mice. Treatment was initiated when tumors reached 0.9 to 1.1 cm in diameter. Step-down heating consisted of 7.5 min at 45 degrees C immediately followed by 7.5 min at 42 degrees C. Step-up heating consisted of 7.5 min at 42 degrees C immediately followed by 7.5 min at 45 degrees C. Step-down heating and step-up heating were compared to a single 45 degrees C, 15-min hyperthermia treatment. These hyperthermia protocols were combined before, in the middle of, or after brachytherapy. There were 4 untreated controls, 6 sham controls, and 11 treated animals in each of the brachytherapy-alone and combined treatment groups. The entire experiment was repeated at brachytherapy doses of 988, 1273, and 1603 cGy. In addition, the effects of step-down heating, step-up heating, and single-temperature hyperthermia were tested alone and in combination with sham treatment for each sequence. Based on daily measurements of tumor diameter, the growth delay to doubling volume was used as the biological end point. To compare the various treatment protocols, an isoeffect thermal enhancement ratio (TERiso) was calculated. Step-down heating after 988 cGy brachytherapy had a TERiso of 2.0 +/- 0.04, while step-up heating after 988 cGy brachytherapy had a TERiso of 1.7 +/- 0.05. Overall, the thermal enhancement ratios calculated from these growth delays indicate that step-down heating caused significantly greater hyperthermic radiosensitization than step-up heating when combined with brachytherapy.     

Comparative Study of Antigen Retrieval Heating Methods: Microwave, Microwave and Pressure Cooker, Autoclave, and Steamer

We present a study comparing the most popular beating methods currently used for antigen retrieval (AR) immunostaining: the microwave oven, microwave with pressure cooker, autoclave, and steamer heating. A panel of 21 antibodies was tested on formalin fixed, paraffin embedded sections using these heating methods and Tris-HC1 buffer, pH 9.5, plus 5% urea as the AR solution. Three observers independently evaluated the intensity of AR immunostaining. All heating methods yielded good results for AR immunostaining. There were only minor differences among the heating methods for AR when the optimal concentration of primary antibody for normal immunostaining was used; however, background staining may occasionally be troublesome if antibodies are not retitrated and diluted further for use on tissues after AR. Significant differences were observed only after further dilution of the primary antibodies; the microwave pressure cooker, extended microwave heating (5 min × 4) and autoclave heating then showed a similar intensity of staining that was stronger than results obtained with the steamer (20 min) or regular microwave heating (5 min × 2 J. Extension of the steamer heating time, however, yielded equivalent results. This study indicates that different heating methods can yield similar intensities of AR immunostaining if the heating times are adjusted appropriately. It is noteworthy that, in general, the adjusted conditions for maximal retrieval differ from those most widely cited in the literature, or recommended by manufacturers. That several heating devices may provide similar results permits the use of different AR heating methods according to the equipment available. This study also is an early step in standardizing the AR immunostaining protocol by providing uniform conditions for “maximal retrieval” as a common end point for all laboratories.     

Effect of heating temperature and time on pharmaceutical characteristics of albumin microspheres containing 5-fluorouracil

Conclusion  In this study, we found that both heating temperature and heating time affect mean particle size, particle size distribution, and drug entrapment efficiency of albumin microspheres. The change in heating temperature may affect the particle size of the product, especially when heating is carried out at a lower temperature (90°C–120°C). Hence the temperature should be selected on the basis of desired size range. Given that it is desirable for a maximum amount of the drug used in the preparation to become entrapped in microspheres, heating temperature and heating time for denaturation of albumin should be selected cautiously, as both have a significant effect on drug entrapment efficiency. In the present case, the highest entrapment was found in batches prepared by heating at 90°C for 5 minutes. However, the extent of stabilization at the selected temperature and the time of heating should also be taken into consideration, as they may affect the release of drugs to target tissue.     

Altered mechanical behavior of epicardium under isothermal biaxial loading

Most soft tissues that are treated clinically via heating experience multiaxial states of stress and strain in vivo and are subject to complex constraints during treatment. Remarkably, however, there are no prior data on changes in the multiaxial mechanical behavior of a collagenous tissue subjected to isometric constraints during heating. This paper presents the first biaxial stress-stretch data on a collagenous membrane (epicardium) before and after heating while subjected to various biaxial isometric constraints. It was found that isometric heating does not allow the increase in stiffness at low strains that occurs following isotonic heating. Moreover increasing the degree of stretch prior to heating increased the thermal stability of the tissue consistent with the concept that mechanical loading primarily affects the activation entropy, not the activation energy.     

Alternatives for natural‐gas‐based heating systems: A quantitative GIS‐based analysis of climate impacts and financial feasibility

The heating of buildings currently produces 6% of global greenhouse gas emissions. Sustainable heating technologies can reduce heating‐related CO₂ emissions by up to 90%. We present a Python‐based GIS model to analyze the environmental and financial impact of strategies to reduce heating‐related CO₂ emissions of residential buildings. The city‐wide implementation of three alternatives to natural gas are evaluated: high‐temperature heating networks, low‐temperature heating networks, and heat pumps. We find that both lowering the demand for heat and providing more sustainable sources of heat will be necessary to achieve significant CO₂‐emission reductions. Of the studied alternatives, only low‐temperature heating networks and heat pumps have the potential to reduce CO₂ emissions by 90%. A CO₂ tax and an increase in tax on the use of natural gas are potent policy tools to accelerate the adoption of low‐carbon heating technologies.     

Effects of electroconductive heat treatment and electrical pretreatment on thermal death kinetics of selected microorganisms

Suspensions of yeast cell (zygo Saccharomyces bailii) in a phosphate buffer solution were subjected to conventional (hot water) and ohmic (electric current) heating under identical temperature histories. Experiments were also conducted with cells of Escherichia coli to compare the lethal effect of combination of sublethal electrical preteatment and conventional heating with conventional heating. The kinetic parameters (D,Z,K and E(a)) were determined for both organisms during different treatments. There was no significant difference in the death rate of yeast cells during conventional and ohmic heating at the voltage range used in this study. Results of electrical pretreatment and conventional heating on E. coli indicated differences under certain conditions when compared with pure conventional heating. Thus it is concluded that microbial death during ohmic heating was due primarily to thermal effects with no significant effect of electric current per se. Sublethal electrical pretreatment appears to offer potential for increased bacterial inactivation in certain cases.     

Influence of heat transmission mode on heating rates and on the selection of patches for heating in a mediterranean lizard

Heliothermy (heat gain by radiation) has been given a prominent role in basking lizards. However, thigmothermy (heat gain by conduction) could be relevant for heating in small lizards. To ascertain the importance of the different heat transmission modes to the thermoregulatory processes, we conducted an experimental study where we analyzed the role of heat transmission modes on heating rates and on the selection of sites for heating in the Mediterranean lizard Acanthodactylus erythrurus (Lacertidae). The study was conducted under laboratory conditions, where two situations of different operative temperatures (38 degrees and 50 degrees C) were simulated in a terrarium. In a first experiment, individuals were allowed to heat up during 2 min at both temperatures and under both heat transmission modes. In a second experiment, individuals were allowed to select between patches differing in the main transmission mode, at both temperatures, to heat up. Experiences were conducted with live, nontethered lizards with a starting body temperature of 27 degrees C. Temperature had a significant effect on the heating rate, with heat gain per unit of time being faster at the higher operative temperature (50 degrees C). The effect of the mode of heat transmission on the heating rate was also significant: at 50 degrees C, heating rate was greater when the main heat transmission mode was conduction from the substrate (thigmothermy) than when heating was mainly due to heat gain by radiation (heliothermy); at 38 degrees C, heating rates did not significantly differ between transmission modes. At 38 degrees C, selection of the site for heating was not significantly different from that expected by chance. However, at 50 degrees C, the heating site offering the slowest heating rate (heliothermic patch) was selected. These results show that heating rates vary not only with environmental temperature but also with different predominant heat transmission modes. Lizards are able to identify and exploit this heterogeneity, selecting the source of heat gain (radiation) that minimizes the risk of overheating when temperature is high.     

Formation of alcohols during sucrose heating with amino acids]

The formation of alcohols during sucrose heating with amino acids was investigated. The sucrose heating to 180-190 degrees C resulted in the formation of methanol and ethanol and its heating with alanine--propanol and isobutanol. The sucrose heating with phenylalanine led to the formation of beta-phenylethanol as well. Alcohols were identified as benzoates by paper chromatography. They were also identified by infrared spectra.     

Skin blood flow influences near-infrared spectroscopy-derived measurements of tissue oxygenation during heat stress.

Near-infrared (NIR) spectroscopy is a noninvasive optical technique that is increasingly used to assess muscle oxygenation during exercise with the assumption that the contribution of skin blood flow to the NIR signal is minor or nonexistent. We tested this assumption in humans by monitoring forearm tissue oxygenation during selective cutaneous vasodilation induced by locally applied heat (n = 6) or indirect whole body heating (i.e., heating subject but not area surrounding NIR probes; n = 8). Neither perturbation has been shown to cause a measurable change in muscle blood flow or metabolism. Local heating (approximately 41 degrees C) caused large increases in the NIR-derived tissue oxygenation signal [before heating = 0.82 +/- 0.89 optical density (OD), after heating = 18.21 +/- 2.44 OD; P < 0.001]. Similarly, whole body heating (increase internal temperature 0.9 degrees C) also caused large increases in the tissue oxygenation signal (before heating = -0.31 +/- 1.47 OD, after heating = 12.48 +/- 1.82 OD; P < 0.001). These increases in the tissue oxygenation signal were closely correlated with increases in skin blood flow during both local heating (mean r = 0.95 +/- 0.02) and whole body heating (mean r = 0.89 +/- 0.04). These data suggest that the contribution of skin blood flow to NIR measurements of tissue oxygenation can be significant, potentially confounding interpretation of the NIR-derived signal during conditions where both skin and muscle blood flows are elevated concomitantly (e.g., high-intensity and/or prolonged exercise).     

A possible way to reverse the impurity influx by alfvén heating in a tokamak plasma

A study is made of the effect of local heating on impurity fluxes in the Pfirsch-Schlüter regime. When the effect of the thermoforce on impurity ions is taken into consideration, the impurity flux can be reversed by heating the impurities. This concept may be implemented in experiments on Alfvén heating of plasmas in tokamaks. The RF heating power required to reverse the impurity influx is estimated.     

Radiosensitizing and damaging effect of hyperthermia on different biological systems. Radiosensitizing and damaging effect of hyperthermia on cells of mouse La leukemia

When mouse leukosis cell suspensions were subjected to heating the survival rate of animals decreased exponentially with increasing time of heating. It is shown that the increase of temperature for 1 degree C in the range 40-45 degrees C is equivalent to a decrease in the heating time by a factor of approximately 2. The hyperthermia-induced increase in the radiosensitivity of leukosis cells was dependent upon a medium in which heating was performed.