Incremental Temperature Increase Research Articles

The Atlantic salmon's (Salmo salar) incremental thermal maximum is a more relevant and sensitive indicator of family-based differences in upper temperature tolerance than its critical thermal maximum

Rising sea surface temperatures and heat waves are a challenge to salmon aquaculture, and the industry must endeavour to mitigate their impacts. To investigate genetic-based differences in upper thermal tolerance, 20 salmon families were exposed to an incremental temperature increase (+0.2 °C per day from 12 °C) to mimic the rise in temperatures experienced at sea-cages in Atlantic Canada during the summer, or held at 10 °C. Post-smolt Atlantic salmon exposed to the incremental temperature increase up to 20 °C gained more weight than fish reared at 10 °C over the same period, and there were family-specific differences (p < 0.05) in growth and body morphometrics. Significant differences were also detected between the families' incremental thermal maximum (ITMax), with average family ITMax values ranging from 23.3 to 25.0 °C. Fish weight and growth rate were not significantly related to ITMax, but a negative correlation (p < 0.01) was found between hepatosomatic index (HSI) and ITMax. In contrast, the critical thermal maximum (CTMax, measured using a temperature increase of 2 °C h−1 from 10 °C) of the bottom and top four temperature tolerant families (as determined by ITMax) did not differ (∼28.0 °C). A negative correlation (p < 0.01) between HSI and CTMax was also found. However, no relationship was evident between relative ventricular mass (RVM) and ITMax or CTMax. Our data show that ITMax is a more sensitive metric of a salmon's upper temperature tolerance than even an ‘environmentally relevant/realistic’ CTMax test, and suggest that it could be used in breeding programs that aim to enhance the salmon's tolerance to withstand rising ocean temperatures.

The thermal ecology of burying beetles: temperature influences reproduction and daily activity in Nicrophorus marginatus

1. Understanding how organisms respond to thermal stress can help predict long‐term population viability under projected climate change models. Behavioural plasticity can mediate the impact of thermal stress; however, some behavioural modifications in response to novel environments act maladaptively and could implicate population persistence.2. Burying beetles (Silphidae: Nicrophorus) have been found to modify traits related to individual fitness to be favourable in their perceived environments. To reproduce, breeding individuals of the nicrophorine genus work together to bury and prepare a suitable vertebrate carcass as food for their developing larvae.3. Here, we explore how sustained temperature treatments influence traits that closely tie to individual fitness in Nicrophorus marginatus. We measure carcass handling, reproductive output, and activity levels in controlled and elevated temperature treatments.4. At only 27.5 °C, we observed significantly reduced reproductive success rates, extended carcass handling time, and increased levels of activity when compared to the baseline temperature treatment of 26 °C. Additionally, at 26.5 °C, we document reduced brood size.5. These findings indicate that slight incremental increases in temperature could have profound effects on burying beetle fitness when experienced for extended periods.

The Atlantic salmon's stress- and immune-related transcriptional responses to moderate hypoxia, an incremental temperature increase, and these challenges combined.

The marine environment is predicted to become warmer, and more hypoxic, and these conditions may negatively impact the health and survival of coastal fish species, including wild and farmed Atlantic salmon (Salmo salar). Thus, we examined how: (1) moderate hypoxia (∼70% air saturation) at 12°C for 3 weeks; (2) an incremental temperature increase from 12°C to 20°C (at 1°C week−1) followed by 4 weeks at 20°C; and (3) treatment “2” combined with moderate hypoxia affected transcript expression in the liver of post-smolts as compared to control conditions (normoxia, 12°C). Specifically, we assessed the expression of 45 genes related to the heat shock response, oxidative stress, apoptosis, metabolism and immunity using a high-throughput qPCR approach (Fluidigm Biomark™ HD). The expression profiles of 27 “stress”-related genes indicated that: (i) moderate hypoxia affected the expression of several stress genes at 12°C; (ii) their expression was impacted by 16°C under normoxic conditions, and this effect increased until 20°C; (iii) the effects of moderate hypoxia were not additive to those at temperatures above 16°C; and (iv) long-term (4 weeks) exposure to 20°C, with or without hypoxia, resulted in a limited acclimatory response. In contrast, the expression of 15 immune-related genes was not greatly affected until temperatures reached 20°C, and this effect was particularly evident in fish exposed to the added challenge of hypoxia. These results provide valuable information on how these two important environmental factors affect the “stress” physiology and immunology of Atlantic salmon, and we identify genes that may be useful as hypoxia and/or temperature biomarkers in salmonids and other fishes.

Climate Change Impacts and Forecasts of Oil Palm Leaf Miner Populations

Agricultural production is very sensitive to climate change, and it suffers from periodic outbreaks of insect pests which cause considerable losses especially in the humid and sub-humid tropics which severely constrain the productivity potential of global agriculture under changing climate conditions. The oil palm leaf miner is a major pest of the oil palm. Mathematical relationships between the leaf miner insect stages and weather factors were developed for pest predictions and forecasting. Decadal variation in air temperature was characterized by wide differences between 1961 – 1970 and 2001 – 2010. The assessment of the sensitivity of leaf miner to variability in weather and climate conditions is important in view of evidence that show expansion of pest ranges as a result of climate variability impacts. The study has established an upward increase in temperature, attributed to climate change, with a concomitant increase in leaf miner abundance between 1980 and 2010. Larvae showed an increasing trend for the observed period. When this observation was correlated with the weather (temperature, rainfall, and relative humidity) during these periods, it could be inferred that there was proliferation as a result of weather changes. This was different from the decreasing trend observed during the 1976 – 1980 period. Pupae showed a decreasing trend for the observed period. Adults showed an increasing trend for the observed period. It could be inferred that adults were proliferating due to temperature increases and rainfall decreases. An incremental increase in temperature could help explain fluctuations in insect pest populations within and between years. Thus climatic conditions greatly influenced seasonal leaf miner populations. The climate forecast up to 2050 indicates an upward trend in temperature and a downward trend in rainfall and relative humidity. This followed the climate trend between 1961 and 2010. This study contributes to the understanding of the insect pest-weather relationship in broad agricultural and food security terms. A major advantage is the potential for limiting the spread of outbreaks through timely control of early pest infestations.

Real-Time Detection of Fouling-Layer with a Non-Intrusive Continuous Sensor (NICS) during Thermal Processing in Food Manufacturing

The fouling of indirect shell and coil heat exchanger by heavy whipping cream (HWC) and non-fat dry milk (NFDM) was studied at aseptic Ultra-High Temperature (UHT) processing conditions (140 °C) using a novel non-intrusive sensor. The sensor emitted a heat pulse intermittently throughout the duration of the process causing an incremental increase in temperature at the tube external surface. The temperature response of the sensor varied due to the radial growth of the fouling layer formed by certain components of the products. Each heating pulse and the temperature response was studied to estimate the thermal conductivity of the fouling layer using inverse problems and parameter estimation. The changes in thermal conductivity were used as an indication of the fouling layer development during food processing at UHT temperatures. The estimated parameters from experimental results showed a decreasing trend in the thermal conductivity of HWC and NFDM from 0.35 to 0.10 and 0.63 to 0.37, respectively. An image analysis tool was developed and used to measure the fouling layer thickness at the end of each trial. The measured thickness was found to be 0.58 ± 0.15 for HWC and 0.56 ± 0.07 mm for NFDM. The fouling layer resistance for HWC and NFDM was 5.95 × 10−3 ± 1.53 × 10−3 and 1.53 × 10−3 ± 2.0 × 10−4 (m2K)/W, respectively.

The impacts of increasing temperature and moderate hypoxia on the production characteristics, cardiac morphology and haematology of Atlantic Salmon (Salmo salar)

Given the predicted effects of climate change on seawater temperatures and water oxygen levels (i.e., the frequency and severity of hypoxia), it is important to understand the impact of these two environmental challenges on salmon used in the Atlantic Canada aquaculture industry (i.e., of Saint John River origin). Thus, we exposed salmon to: 1) control conditions (12 °C, 100% air sat.); 2) an incremental temperature increase (1 °C per week from 12 °C to 20 °C) and then held the fish at 20 °C for an additional 3 weeks (Experiment #1); and 3) an incremental increase in temperature until mortalities reached ~ 30% (Experiment #2). Further, we conducted the two temperature challenges under both normoxic and moderately hypoxic (~ 70% air sat.) conditions. Our experiments show that these salmon can be held at temperatures up to 20 °C, and 20 °C plus moderate hypoxia, for periods of up to a month without any mortalities. However, exposure to the incremental temperature regime resulted in a ~ 10% increase in feed conversion ratio, and the addition of hypoxia decreased feed intake, and thus, growth (15–20% depending on metric). In Experiment #2, specific growth rate and feed intake dropped dramatically after 19 - 20 °C, and mortalities were ~ 15% at 22 °C and ~ 30% by 23 °C. Interestingly, hypoxia did not affect survival at these temperatures, and high temperature + hypoxia enhanced blood oxygen carrying capacity (by 15%) whereas high temperature alone increased relative ventricular mass (by 21%). This research suggests that further increases (i.e., beyond 18 - 20 °C) in coastal temperatures in Atlantic Canada may negatively impact salmon production, especially if combined with hypoxia. In addition, it highlights the need for a better understanding of how these two environmental stressors interact to affect salmon biology/physiology (especially as increases in sea-cage water temperatures are incremental world-wide, and poorly investigated).

Enhanced chalcopyrite dissolution in stirred tank reactors by temperature increase during bioleaching

Primary copper sulfides, such as chalcopyrite, represent the most important copper resource and are currently mainly exploited by pyrometallurgy. Bioleaching is considered as environmental-friendly and economic alternative, and the technical feasibility of stirred tank reactor (STR) bioleaching of copper ore concentrates using acidophilic, iron- /sulfur-oxidizing microorganisms was proven. In case of copper concentrates from Kupferschiefer-type ore the copper recovery at temperatures suitable for moderately thermophilic acidophiles was, however, incomplete due to inefficient chalcopyrite dissolution.The presented study therefore aimed to enhance chalcopyrite dissolution by decoupling of growth and bioleaching activity of the acidophiles. This was achieved by a controlled temperature increase in laboratory bioreactor experiments with copper concentrate from Kupferschiefer-type ore. Total cell number and microbial activity monitoring allowed to define three stages of the bioleaching process: (i) growth phase, (ii) bioleaching phase and (iii) resting phase. The total residence time was close to seven days, according to copper recovery and iron oxidation activity. Experiments at constant temperatures (42 °C, 48 °C, 50 °C) and a controlled temperature increase at the end of the growth phase of 42/46 °C, 44/48 °C and 46/50 °C, showed that metal recovery was enhanced by incremental temperature increase and resulted in a lower redox potential. Copper recovery was improved from originally 86% to 97% by only 4–8 °C temperature increase. Mineralogical analysis confirmed an almost complete absence of chalcopyrite in the residues after the 46/50 °C bioleaching experiments. These results indicate a distinct temperature effect on copper recovery. The study defines parameters to make STR bioleaching of chalcopyrite-rich ores more efficient and economically feasible and ensures an optimal control of the process for upscaling.

Application of the thermofluor PaSTRy technique for improving foot-and-mouth disease virus vaccine formulation.

Foot-and-mouth disease (FMD) has a major economic impact throughout the world and is a considerable threat to food security. Current FMD virus (FMDV) vaccines are made from chemically inactivated virus and need to contain intact viral capsids to maximize efficacy. FMDV exists as seven serotypes, each made up by a number of constantly evolving subtypes. A lack of immunological cross-reactivity between serotypes and between some strains within a serotype greatly complicates efforts to control FMD by vaccination. Thus, vaccines for one serotype do not afford protection against the others, and multiple-serotype-specific vaccines are required for effective control. The FMDV serotypes exhibit variation in their thermostability, and the capsids of inactivated preparations of the O, C and SAT serotypes are particularly susceptible to dissociation at elevated temperature. Methods to quantify capsid stability are currently limited, lack sensitivity and cannot accurately reflect differences in thermostability. Thus, new, more sensitive approaches to quantify capsid stability would be of great value for the production of more stable vaccines and to assess the effect of production conditions on vaccine preparations. Here we have investigated the application of a novel methodology (termed PaSTRy) that utilizes an RNA-binding fluorescent dye and a quantitative (q)PCR machine to monitor viral genome release and hence dissociation of the FMDV capsid during a slow incremental increase in temperature. PaSTRy was used to characterize capsid stability of all FMDV serotypes. Furthermore, we have used this approach to identify stabilizing factors for the most labile FMDV serotypes.

The Effect of Temperature on Life History Traits ofCulexMosquitoes

Climatic changes forecasted in the coming years are likely to result in substantial alterations to the distributions and populations of vectors of arthropod-borne pathogens. Characterization of the effect of temperature shifts on the life history traits of specific vectors is needed to more accurately define how such changes could impact the epidemiological patterns of vector-borne disease. Here, we determined the effect of temperatures including 16, 20, 24, 28, and 32 degreeC on development time, immature survival, adult survival, mosquito size, blood feeding, and fecundity of both field and colonized populations of the Culex mosquitoes Culex pipiens L, Culex quinquefasciatus Say, and Culex restuans Theobald. Our results demonstrate that temperature significantly affects all of these traits, yet also that the extent of this effect is at times incongruent among temperatures, as well as being population and species-specific. Comparisons of colonized mosquitoes with field populations generally demonstrate decreased adult and immature survival, increased blood feeding and egg production, and significant variation in the effects of temperature, indicating that such colonies are not fully representative of natural populations. Results with field populations in general indicate that increases in temperature are likely to accelerate mosquito development, and that this effect is greater at temperatures below 24 degreeC, but also that temperature significantly increases mortality. Among field populations, Cx. restuans were most affected by temperature increases, with decreased longevity relative to other species and significant increases in adult and immature mortality measured with each incremental temperature increase. Despite the unique climates characteristic of the geographic ranges ofCx. quinquefasciatus and Cx. pipiens, evidence of significant species-specific adaptation to temperature ranges was not seen. Taken together, these results indicate that geographic region, as well as species and population differences, must be considered when measuring the effect of temperature on vector populations.

Cover Picture: Morphological Phase Diagram of Biocatalytically Active Ceria Nanostructures as a Function of Processing Variables and Their Properties (ChemPlusChem 12/2013)

The cover pictue shows a morphological phase diagram of CeO2 indicating regions of nanoparticle nanorod and nanocube formation after certain time periods of hydrothermal treatment. The phase boundaries are estimated by using experimental parameters (NaOH concentration (M), temperature (°C), and time (h)) of the hydrothermal process. The phase boundaries from nanoparticles to nanorods and nanocubes are observed to shift at higher temperature with low caustic concentration. The relative incremental increase in temperature suggests that nanorod and nanocube formation is more dependent on temperature than caustic concentration. Inset is the atomic simulation of nanostructured materials showing the growth direction. Details of this study are given in the Full Paper at page 1446 ff. by S. Seal and co-workers.

Effects of Fixed and Fluctuating Temperature on Hatch of Round Whitefish and Lake Whitefish Eggs

AbstractTemperature‐response information for use in evaluating thermal discharges is often over 30 years old and in the nonpeer‐reviewed literature, especially for Round Whitefish Prosopium cylindraceum and Lake Whitefish Coregonus clupeaformis exposed to nonlethal, elevated, and variable temperatures. Egg incubation experiments on Round Whitefish collected in Lake Ontario and Lake Whitefish collected in Lake Huron were carried out from December 13, 2011, to April 7, 2012. Experimental treatments included ambient baseline control conditions as well as fixed and fluctuating (variable) temperature increases of 1, 2, 3, and 5°C above ambient baseline conditions. For both species, the window for hatching for all experimental temperature treatments was variable (range, 10–38 d for Round Whitefish and 11–44 d for Lake Whitefish), and the hatching windows tended to be greater as temperatures increased. Our results indicated that both fixed and variable incremental increases in temperature above ambient baseline conditions have a statistically significant effect on 50% hatch, and hatch occurs earlier with higher incremental temperature increases. The ecological significance of advanced hatch, such as indirect mortality and food source availability, was evaluated.Received February 19, 2013; accepted July 8, 2013

Climate change impacts on agro-ecosystem sustainability across three climate regions in the maize belt of South Africa

The Highveld region in South Africa is an important area for its food production for the nation, as 70% of country's cereal crops and 90% of the commercially grown maize is cultivated there. The sustainability of these agro-ecosystems is, therefore, of vital importance for the nation's food security. The western part of the Highveld is characterised by relatively low mean annual precipitation (MAP) and highly variable yields, and while rainfall increases towards the east, inter-annual yield variability remains high. Variability of yields is already a concern for agro-ecosystems and it is hypothesised that it could be exacerbated by future climate changes. A sustainability framework was used to assess the sustainability agro-ecosystems under plausible future climate scenarios. Three Quaternary Catchments were assessed ranging from relatively dry (MAP 432 mm) to relatively moist (MAP 903 mm). A sensitivity analysis of plausible scenarios was performed with incremental increases in temperature by 1, 2 or 3 °C, increases/decreases of rainfall by 10% and a doubling of pre-industrial atmospheric CO 2 concentrations to 555 ppmv. From the present and nine plausible future climate scenarios which were modelled using CERES-Maize over a 44-year period, it is shown that climatic changes could have major negative effects on the already drier western, and therefore more vulnerable, areas of the South African Highveld. An increase in temperature increases the variability of yields in the relatively moist Piet Retief area (MAP 903 mm), while at the more sub-humid Bothaville, with a MAP of only 552 mm, the inter-annual variability remains the same but mean yield over 44 seasons is reduced by 30%. A simulated increase in temperature coupled with a doubling of CO 2 increases the rate of soil organic nitrogen depletion from the agro-ecosystem. Therefore, long-term perspectives in regard to human well-being and ecological integrity need to be applied to policies and actions for sustainability of both commercial and smallholder agro-ecosystems, particularly, in the western Highveld.

2004 Dr. Gary J. Becker Young Investigator Award: Relative Thermosensitivity of Cytotoxic Drugs Used in Transcatheter Arterial Chemoembolization

Large hepatocellular carcinoma tumors are being treated increasingly with a combination of transcatheter arterial chemoembolization (TACE) and radiofrequency (RF) ablation. However, the high temperatures reached during RF ablation may reduce the cytotoxic effects of antineoplastic agents, but this has not been studied. Therefore, in the present study, the relative thermosensitivity of cytotoxic drugs commonly used in TACE was studied. The relative cytotoxic effects of cisplatin, doxorubicin HCl, and mitomycin on the growth of human colon HT29 and lung A549 adenocarcinoma cells before and after heating each drug in solution was determined from the standpoints of different durations of exposure (15, 30, 60, 90, and 120 minutes) at a fixed temperature (120 degrees C) and exposure to different temperatures (60 degrees C, 80 degrees C, 100 degrees C, and 120 degrees C) for a fixed period of time (2 hours). After 72 hours of exposure of the cells to each drug, relative cell growth inhibition was assessed by MTT assay, and 50% inhibitory concentration (IC(50)) values were calculated for each cytotoxic agent. Finally, the heat-dependent degradation of mitomycin and doxorubicin was analyzed with use of tandem electrospray mass spectrometry. The relative cytotoxic activities (shown by cell growth inhibition and IC(50) values) of cisplatin, doxorubicin, and mitomycin heated to 120 degrees C for 2 hours decreased by factors of 1.35 (range, 1-1.75), 9.5 (range, 8.5-10.5), and 7.05 (range, 3.5-12), respectively. The cytotoxic activities of doxorubicin and mitomycin continued to decrease with incremental increases in temperature. Similarly, with incremental increases in the duration of exposure to heat, the cytotoxic activities of doxorubicin and mitomycin decreased. Mass spectrometric analysis of residual drug content showed that a 2-hour exposure to a temperature of 120 degrees C caused doxorubicin and mitomycin to degrade by 95% and 84%, respectively. The cytotoxicity of cisplatin is not affected by heat. The cytotoxicities of doxorubicin and mitomycin are reduced by high temperature and duration of exposure to heat. Although degradation of cytotoxicity starts at 60 degrees C and after 30 minutes of exposure to heat, statistically significant changes are encountered at 100 degrees C and after 90 minutes of exposure.

Nuclear microprobe analysis of artificial coal

An artificially coalified Taxodium peat was used to examine the behavior of inorganic constituents in terrestrial organic matter during the early coalification process. The artificial coal is produced by subjecting the peat to incremental increases in temperature up to 60 °C and pressures to 14.48 MPa over a four-week period in a partially open reactor. A standard polished thin section 30 μm thick is then cut from the resulting disk and examined using light microscopy to select and mark areas to be cut from the polished thin section. The distribution of inorganic constituents in these areas of the solid produced during the coalification process is then studied using nuclear microscopy. Results suggest that concentrations of inorganic constituents, including silicon, are lower in the newly produced solids than in the initial material. Distributions of other inorganic elements, including aluminum, sulfur, chlorine, potassium, calcium, barium and iron are also investigated.

Kinetic and equilibrium processes in the formation and melting of agarose gels

The formation and melting of agarose gels has been monitored by small-deformation oscillatory measurements of storage and loss moduli ( G' and G’). The onset of network formation on cooling at 1 °C min −1 moved to progressively higher temperature with increasing polymer concentration, from ~23 °C at 0.1 wt% to ~33 °C at 2.0 wt%. Isothermal measurements showed comparatively rapid gelation of concentrated (2.0 wt%) solutions at temperatures where the rate of gelation of more dilute samples (0.25 wt%) had dropped to zero. Both phenomena are interpreted in terms of kinetically determined helix-helix aggregation displacing the thermodynamic equilibrium between disordered coils and double helixes. Gel melting occurred as an equilibrium process, with moduli reaching constant, stable values after incremental increase in temperature. Rheological equilibration, however, was substantially slower than conformational disordering, as monitored by optical rotation, suggesting diffusion-controlled separation of strands after dissociation of ordered helices. Gels formed by rapid quenching to 5 °C melted at substantially (12–13 °C) lower temperature than those formed by cooling at 1 °C min −1. It is suggested that the helix-length required for stable association increases with increasing temperature, with slow cooling therefore giving longer helices than rapid quenching, and that increasing helix length promotes helix-helix aggregation. Consistent with this interpretation, the gels formed by slow cooling were stronger, and more turbid, than those obtained on quenching. Re-examination of a previous report that final melting of agarose gels occurs at a temperature well above completion of conformational disordering revealed a gross discrepancy in experimental evidence. Gel setting and melting temperatures obtained under identical conditions (1.0 wt% agarose in 50 wt% of dimethylsulphoxide) in both investigations were in close agreement, but the order-disorder transition temperature (from optical rotation) determined in the present work was ~25 °C higher, and indicated a finite residual helix-fraction on completion of gel melting.

Insitu incorporation of Al and N andp-n junction diode fabrication in alpha(6H)-SiC thin films

Aluminum and nitrogen have been introduced asp- andn-type dopants, respectively, during chemical vapor deposition (CVD) ofα(6H)-SiC films on 6H-SiC substrates. The atomic concentration of each dopant in the films showed a linear dependence on partial pressure of the dopant source gas. The Al species exhibited ideal behavior based on a dilute solution model. Thus elemental Al and/or a complex containing only one Al atom were the principal species which contributed to the incorporation of this constituent. The incorporation of N was greater than expected from the dilute solution theory which implied interaction between N and Si in the SiC. The relationship between ionized dopant concentration (carrier concentration) and the concentration in each dopant source gas was also linear and parallel to its atomic concentration. The ratios of the carrier concentration to the atomic concentration for Al and N were 0.02 and 0.06, respectively.P-n junction diodes were fabricated which exhibited rectification and reverse leakage currents at 100 V of 0.19, 0.75, and 1.3 ΜA at 298, 523, and 623 K, respectively. The turn-on voltage decreased from 2.2 to 2.1 and 1.9 V with each incremental increase in temperature.

Response of Oxypetalum caeruleum to Irradiance, Temperature, and Photoperiod

Incremental increases in temperature from 14 to 22 to 30C resulted in linear increases in stem length and node number and decreases in stem diameter and stem strength of Oxypetalum caeruleum (D. Don.) Decne. Higher temperatures also resulted in additional flower abortion, reduced time to flowering, and fewer flowering stems per inflorescence. Reduction in the photosynthetic photon flux (PPF) from 695 to 315 μmol·s-1·m-2 had similar effects as increasing the temperature on vegetative characteristics, but had little effect on reproductive ones. The rate of stem elongation was greatest at low PPF for all temperatures and at high temperature for all PPF treatments. Net photosynthesis rose between 14 and 22C and declined at 30C for all PPF treatments. Long photoperiods (12 or 14 hours) resulted in longer internodes, longer stems, and more flowers per cyme than short photoperiods (8 or 10 hours), but photoperiod had little effect on flowering time. Treatments to reduce latex coagulant and silver thiosulfate treatments had no significant effect on vase life.

Porcine muscle responses to carbachol, alpha- and beta-adrenoceptor agonists, halothane or hyperthermia.

1. Whole body trans-section at the level of the first or second lumbar vertebra of stress-susceptible or normal Poland China swine provided a preparation of isolated perfused caudal muscle that was without nervous or hormonal influences. Metabolic responses to halothane anaesthesia were exaggerated in the susceptible preparation. 2. Carbachol (10(-4) M) increased O2 consumption threefold and elevated blood lactate levels from 3 to 8 mumole/ml. in susceptible but not in normal muscle preparations. 3. Isoprenaline in a continuous infusion (2.5 micrograms/kg caudal wt. per min for 12 min, subsequently diminished to 1.2 microgram/kg per min) did not increase O2 consumption of susceptible or normal muscle but did increase blood lactate by 2 mumole/ml. in both. 4. Simultaneous administration of carbachol and isoprenaline resulted in additive increases in blood lactate. 5. Incremental increases in temperature above 41 degrees C initiated exaggerated increases in O2 consumption and blood lactate in susceptible but not normal muscle; these were similar to whole body responses. 6. Phenylephrine (0.2-25 micrograms/kg per min continuous) produced (i) hypertension, (ii) no observed effects upon aerobic or anaerobic metabolism and (iii) progressive tissue oedema; these effects were similar in susceptible and normal muscle. 7. Skeletal muscle from stress-susceptible swine is evidently inherently capable of metabolic responses to cholinergic agonists and increased temperature; these responses are greater than those in normal muscle. This suggests that initiation of stress responses in intact swine is related to somatic motor and sympathetic stimulation of abnormal skeletal muscle, and not to a disorder of the somatic or sympathetic nervous system.

Thermodynamics of a simple rubber-band heat engine

We analyze the thermodynamics of a simple heat engine. The engine’s efficiency is calculated for an idealized but reasonable model. The engine’s work cycle is compared with a Carnot cycle, and it is shown to be equivalent to the Carnot cycle as an extremely ideal limiting case. A working model of the engine is easily constructed for classroom demonstrations. We measured the force law parameters for a working model, and we estimate the efficiency of this model. The estimated efficiency of our demonstration engine is small compared with that of a Carnot engine operating at the same temperatures. We show that a Carnot engine could in principle be constructed based on the thermal expansion concept, but its efficiency would be intrinsically small when rubber is the working substance because of the inherently small incremental temperature increase possible in an adiabatic expansion.