Difference In Temperature Dependence Research Articles

Breakage of cyanobacterial filaments by small- and large-sized Daphnia: are there any temperature-dependent differences?

Filamentous cyanobacteria disturb food collection in Daphnia by mechanical interference with the filtering apparatus by the long trichomes. The intensity of this interference depends on the water temperature and the Daphnia body size. However, Daphnia are capable of breaking down the filaments, therefore improving the palatability of the cyanobacteria. The main objective of this study was to test whether the shortening of cyanobacterial filaments and the ensuing clearance rate of Daphnia would increase at higher temperatures to a greater degree in small-bodied Daphnia species than in large-bodied one. Laboratory feeding experiments were conducted in order to measure variation in the length of Cylindrospermopsis raciborskii trichomes and to calculate clearance rate. The filament length and the cyanobacteria clearance rate by Daphnia were calculated following their exposure to grazing by large-bodied D.pulicaria and small-bodied D. longispina in 20, 24, and 28°C. Rising temperature did not affect the intensity of breakage of C. raciborskii trichomes by D. pulicaria and caused decrease in clearance rate of this species, whereas for D. longispina, the temperature increase enhanced both filament breakage and clearance rate. We suggest that these temperature-related changes may affect relative competitive performance of Daphnia species in the presence of cyanobacteria.

Temperature-dependent differences in wettability and photocatalysis of TiO2 nanotube arrays thin films

TiO2 nanotubes arrays (TiO2-NTAs) layers were successfully formed by electrochemical anodization on a titanium (Ti) surface in fluorine-containing electrolytes under different processing voltages and annealing temperatures. The formed TiO2-NTAs layers annealed at different temperatures were compared in terms of their morphologies, structures and band gaps. Their wetting abilities, photo-induced hydrophilicities and photocatalytic performances were also evaluated. It was found the sample anodized at 40V for 2h have the most uniform surface morphology. The TiO2-NTAs structures annealed at 600°C for 2h in air show multiphase crystallinity and have the narrowest band gap (2.89eV). These structures have noticeable nanowires on the top of the nanotubes. Their photocatalytic activity, tested by degradation of aqueous methylene orange solutions under UV light illumination for 2h, is the highest among all samples (degradation efficiency was 89.05%). Specimens annealed at 200, 400 and 800°C show light-induced hydrophilicity. However, small contact angle change was observed when samples were annealed at 600°C.

The effect of water temperature on air entrainment, bubble plumes, and surface foam in a laboratory breaking-wave analog

Air-entraining breaking waves form oceanic whitecaps and play a key role in climate regulation through air-sea bubble-mediated gas transfer, and sea spray aerosol production. The effect of varying sea surface temperature on air entrainment, subsurface bubble plume dynamics, and surface foam evolution intrinsic to oceanic whitecaps has not been well studied. By using a breaking wave analog in the laboratory over a range of water temperatures (Tw = 5°C to Tw = 30°C) and different source waters, we have examined changes in air entrainment, subsurface bubble plumes, and surface foam evolution over the course of a breaking event. For filtered seawater, air entrainment was estimated to increase by 6% between Tw = 6°C and Tw = 30°C, driven by increases of about 43% in the measured surface roughness of the plunging water sheet. After active air entrainment, the rate of loss of air through bubble degassing was more rapid at colder water temperatures within the first 0.5 s of plume evolution. Thereafter, the trend reversed and bubbles degassed more quickly in warmer water. The largest observed temperature-dependent differences in subsurface bubble distributions occurred at radii greater than about 700 μm. Temperature-dependent trends observed in the subsurface bubble plume were mirrored in the temporal evolution of the surface whitecap foam area demonstrating the intrinsic link between surface whitecap foam and the subsurface bubble plume. Differences in foam and plume characteristics due to different water sources were greater than the temperature dependencies for the filtered seawater examined.

Larval development reflects biogeography in two formerly synonymised southern African coastal crabs

The southern African crab Hymenosoma orbiculare was recently split into five distinct species, of which three are estuarine/coastal and have peripatric distributions that are linked to temperature-defined marine bioregions. This suggests that the species’ ranges may be limited by physiological adaptations to their thermal environment. We explored this hypothesis by rearing the larvae of the warm-temperate lineage of H. orbiculare and the warm-temperate/subtropical H. longicrure at a range of water temperatures, and found clear temperature-dependent differences in the duration of larval development. Our study contributes to the growing body of evidence that stresses the importance of adaptation to regional environmental conditions, rather than physical dispersal barriers on their own, in limiting the mixing of marine species between temperature-defined biogeographic regions.

(Solid + liquid) solubility of organic compounds in organic solvents – Correlation and extrapolation

A semi-empirical model is developed for the regression of (solid+liquid) solubility data with temperature. The model fulfils the required boundary conditions, allowing for robust extrapolation to higher and lower temperatures. The model combines a representation of the solid-state activity which accommodates a temperature-dependent heat capacity difference contribution with a scaled three-parameter Weibull function representing the temperature dependence of the solution activity coefficient at equilibrium. Evaluation of the model is based on previously published experimental calorimetric and solubility data of four organic compounds, fenoxycarb, fenofibrate, risperidone and butyl paraben, in five common organic solvents, methanol, ethyl acetate, acetone, acetonitrile, and toluene. The temperature dependence of the van’t Hoff enthalpy of solution and its components is analysed and discussed. Among the four compounds the influence of temperature on the enthalpy of fusion varies from moderate to substantial. Based on the semi-empirical model, a new equation containing three adjustable parameters is proposed for regression and extrapolation of solubility data for cases when only melting data and solubility data is available. The equation is shown to provide good accuracy and robustness when evaluated against the full semi-empirical model as well as against commonly used, more simple empirical equations. It is shown how such a model can be used to obtain an estimate of the heat capacity difference for cases where accurate solubility data is available in multiple solvents.

Absolute MR thermometry using nanocarriers

Accurate time-resolved temperature mapping is crucial for the safe use of hyperthermia-mediated drug delivery. We here propose a magnetic resonance imaging temperature mapping method in which drug delivery systems serve not only to improve tumor targeting, but also as an accurate and absolute nano-thermometer. This method is based on the temperature-dependent chemical shift difference between water protons and the protons in different groups of drug delivery systems. We show that the chemical shift of the protons in the ethylene oxide group in polyethylene glycol (PEG) is temperature-independent, whereas the proton resonance of water decreases with increasing temperature. The frequency difference between both resonances is linear and does not depend on pH and physiological salt conditions. In addition, we show that the proton resonance of the methyl group in N-(2-hydroxypropyl)-methacrylamide (HPMA) is temperature-independent. Therefore, PEGylated liposomes, polymeric mPEG-b-pHPMAm-Lac2 micelles and HPMA copolymers can provide a temperature-independent reference frequency for absolute magnetic resonance (MR) thermometry. Subsequently, we show that multigradient echo MR imaging with PEGylated liposomes in situ allows accurate, time-resolved temperature mapping. In conclusion, nanocarrier materials may serve as highly versatile tools for tumor-targeted drug delivery, acting not only as hyperthermia-responsive drug delivery systems, but also as accurate and precise nano-thermometers.

Abstract 061: Interstitial Matrix Flow-Regulation:Myocardial Fibroblasts Respond to Colloidosmotic Pressure

Ischemia-reperfusion injury induces large differences in hydration potential between ischemic and nonischemic areas of the myocardium. They influence the rate and volume of fluid transfer in myocardial explants; temperature-dependent hydration-potential differences of approximately 100 mmHg in at-risk areas, as opposed to contiguous areas that are not at risk, suggest prompt interstitial fluid-transfer control mechanisms (Circ. Res . 2012;11:A235) . Aim: We adapted osmotic-stress techniques to determine whether myocardial fibroblasts, which are known to respond to mechanical and flow signals, also respond to hydration-potential changes. Methods: Fibroblasts were isolated from midwall regions of the left ventricles of healthy pigs using standard procedures. They were incorporated into 3-dimensional collagen gels of 500 mm 3 volume at 150 cells/mm 3 and equilibrated overnight in cultures using the nontoxic, inert polymer polyethylene glycol 8000 (molecular radius ~26.5 Å; concentration range 0-10% w/w) to adjust colloidosmotic pressure from approximately 5 to 205 mmHg . After the gels were detached from the dish, fluid flux was derived from any time-dependent changes in their dimensions. Results: The volume of gels without fibroblasts did not change significantly at any coloidosmotic pressure. In those with fibroblasts, the volume decreased, more slowly in those subjected to higher-than-plasma pressure levels. Progression curves conformed well to a two-exponential term model (R 2 >0.9) suggesting that two parallel processes contribute to matrix efflux, one relatively fast, with decay constant 0.274 ± 0.014 (n = 3) , and another ~50-fold slower. Initial rates were calculated from the fitted curves, and linear regression analysis used to examine their dependence on colloidosmotic pressure. Initial efflux rates decreased with pressure, mean slope, - 0.29 ± 0.08 µl/h/mmHg (R 2 = 0.7; P-value = 0.006). Conclusion: In vitro , fibroblasts in collagen matrices regulate fluid efflux in response to colloidosmotic stresses within the range of hydration-potential differences measured in myocardial explants after ischemia-reperfusion injury.

Temperature insensitive high-precision refractive-index sensor using two concatenated dual-resonance long-period gratings

In this Letter we report on fabricating and analyzing a temperature insensitive refractometer based on two concatenated dual-resonance long-period gratings (LPGs) with an appropriate inter-grating space (IGS) in between. The IGS provides a temperature-dependent extra phase difference between the core and cladding modes, making the refractometer similar to a Mach-Zehnder interferometer with its arms phase shifted. We demonstrate that an appropriate IGS can produce temperature-insensitive resonance wavelengths. The interferometer is highly stable over a wide range of temperature (20°C-100°C). The measured refractive index sensitivity for aqueous solutions (1.333-1.343) is ~2583 nm/RIU, which is the highest reported so far for biological samples. The interferometer can be used for various other temperature-immune sensing applications also.

High temperature low cycle fatigue properties of 24Cr ferritic stainless steel for SOFC applications

The low cycle fatigue (LCF) properties of 24Cr ferritic stainless steel for solid oxide fuel cell interconnects were investigated. The fatigue strength of 24Cr stainless steel decreased with increasing temperature, but the fatigue life increased at 600°C and 700°C. The fatigue behavior at room temperature (RT) was characterized as cyclic hardening followed by saturation and cyclic softening while marginal cyclic hardening was observed at 600°C and 700°C. The superior oxidation resistance of 24Cr stainless steel allows preventing the fatal impact of oxidation on the high-temperature fatigue life. Microstructural analysis showed that persistent slip bands (PSBs) developed prevalently at RT but not at 600°C and 700°C. Such temperature-dependent microstructural difference retarded the crack initiation and prolonged fatigue life at high temperatures.

Influence of fluid flow on the regional thermal field: results from 3D numerical modelling for the area of Brandenburg (North German Basin)

We analyse the effect of fluid flow on the recent thermal field for the Brandenburg region (North German Basin) which is strongly affected by salt structures. The basin fill is modified by a thick layer of mobilized salt (Zechstein, Upper Permian) that decouples the overburden from deeper parts of the lithosphere and is responsible for thermal anomalies since salt has a distinctly higher thermal conductivity than the surrounding sediments and is impermeable to fluid flow. Numerical simulations of coupled fluid flow and heat transfer are carried out to investigate the influence of fluid flow on the shallow temperature field above the Zechstein salt, based on the finite element method. A comparison of results from conductive and coupled modelling reveals that the temperature field down to the low-permeable Triassic Muschelkalk is influenced by fluids, where the shallow low-permeable Tertiary Rupelian-clay is absent. Overall cooling is induced by forced convective forces, the depth range of which is controlled by the communication pathways between the different aquifers. Moreover, buoyancy-induced effects are found in response to temperature-dependent differences in the fluid density where forced convective forces are weak. The range of influence is controlled by the thickness and the permeability of the permeable strata above the Triassic Muschelkalk. With increasing depth, thermal conduction mainly controls the short-wavelength pattern of the temperature distribution, whereas the long-wavelength pattern results from interaction between the highly conductive crust and low-conductive sediments. Our results provide generic implications for basins affected by salt tectonics.

Substrate Mediation in Vapor Deposition Growth of Layered Chalcogenide Nanoplates: A Case Study of SnSe2

The two-dimensional (2D) nanostructure of layered chalcogenide materials (LCMs) is very interesting, but to make it a useful material platform necessiates the development of sophisticated synthetic control. We present the synthesis of single-crystalline SnSe2 nanoplates by a noncatalytic vapor deposition process and demonstrate that the growth is subject to strong influences from substrates. The effect of substrates is evidenced by a temperature-dependent morphological difference in the nanoplates grown on mica and silicon substrates. At a growth temperature of 280 °C, the diameter of the nanoplates grown on mica is larger than those grown on silicon by a ratio of 6.2. This ratio substantially decreases to be unity (1.04) at a higher temperature of 420 °C. Additionally, different from the nanoplates grown on silicon, which always show a well-defined hexagonal shape, the nanoplates grown on mica exhibit an irregular shape at low temperature and can gradually evolve into the hexagonal shape with increasing temperature. Our dynamics analysis suggests that the observed temperature-dependent morphological difference can be specifically correlated to the migration of SnSe2 adatoms on the surface of substrates. SnSe2 adatoms may migrate on mica more easily than on silicon substrates because of the presence of dangling bonds at the surface of silicon. The role of the facile migration on mica in the nanoplate growth may be further confirmed by a correlation between the nanoplate diameter and the distance between neighboring nanoplates. While the focus is on SnSe2, we believe that this understanding can apply to the growth of two-dimensional (2D) nanostructures of other layered chalcogenide materials (LCMs). It may pave the way for the development of a general synthetic paradigm that leverages the effect of substrates to control the growth of 2D LCM nanostructures.

Esterase activity of lactic acid bacteria isolated from malolactic fermentation of red wines

The goal of this study was to examine the esterase activity of 243 lactic acid bacteria (LAB) strains from wines of different red grape varieties, belonging to the genera Oenococcus, Lactobacillus, Pediococcus and Enterococcus. p-Nitrophenyl octanoate was used as substrate. All strains presented esterase activity in the first screening, but only those showing higher activity were used in subsequent studies to determine the cellular location of this activity, the influence of pH, temperature and the presence of ethanol and the substrate specificity. For the thirteen selected strains, the highest activity was observed in the intracellular fraction. Responses to pH, temperature and ethanol were strain-dependent, but for all the strains, a marked decrease in activity in presence of ethanol was observed. When the influence of pH and ethanol acting together was studied at 25°C and 37°C, temperature-dependent differences were not observed for any of the strains except for Oen6. In the substrate specificity assay, the majority of strains of all genera displayed a trend to more readily hydrolyse ester substrates from C8 and longer.

Thermodynamic Measurements of Fe-Rh Alloys

FeRh undergoes an unusual antiferromagnetic-to-ferromagnetic (AFM-FM) transition just above room temperature (T(AFM>FM)) that can be tuned or even completely suppressed with small changes in composition. The underlying temperature-dependent entropy difference between the competing AFM and FM states that drives this transition is measured by specific heat as a function of temperature from 2 to 380 K on two nearly equiatomic epitaxial Fe-Rh films, one with a ferromagnetic ground state (Fe-rich) and the other with an antiferromagnetic ground state (Rh-rich). The FM state shows an excess heat capacity near 100 K associated with magnetic excitations that are not present in the AFM state. The integrated entropy and enthalpy differences between the two alloys up to T(AFM>FM) agree with the previously measured entropy of the transition (ΔS = 17 ± 3 J/kg/K) and yield a T=0 energy difference of 3.4 J/g, consistent with literature calculations and experimental data; this agreement supports the use of the Fe-rich FM sample as a proxy for the (unstable) FM state of the AFM Rh-rich sample. From the low-temperature specific heat, along with sound velocity and photoemission measurements, the lattice contribution to the difference (ΔS(latt) = -33 ± 9 J/kg/K) and electronic contribution (ΔS(el) = 8 ± 1 J/kg/K) to the difference in entropy are calculated, from which the excess heat capacity in the FM phase and the resulting entropy difference are shown to be dominated by magnetic fluctuations (ΔS(mag) = 43 ± 9 J/kg/K). The excess magnetic heat capacity is dominated by the magnetic heat capacity of the FM phase, which can be fit to a Schottky-like anomaly with an energy splitting of 16 ± 1 meV and a multiplicity of 1 per unit cell.

Comparative analysis of temperature-dependent transcriptome of Pseudomonas aeruginosa strains from rhizosphere and human habitats

In this study, we investigated the effects of a change in growth temperature on the transcriptome of two strains of Pseudomonas aeruginosa. The chosen P. aeruginosa strains were M18 and PAO1, which are adapted to two different niches, rhizosphere and human, respectively. To assess the changes induced by a change in temperature, we used a newly designed microarray covering the complete genome of four P. aeruginosa strains: PAO1, M18, PA14 and LESB58, which proved informative and reliable for the transcriptome study. Using the microarray, we analysed the transcriptome profile changes of two P. aeruginosa strains of M18 and PAO1 at their originating and non-originating temperatures: 28 °C for the rhizosphere and 37 °C for the human. The transcriptome profiles showed significant temperature-dependent differences (64.8 % in M18 and 66.8 % in PAO1) compared with the genome structure (6 % in M18 and 4.1 % in PAO1). Furthermore, we found that the specific induced genes at the non-originating growth temperature of the each strain (207 genes in M18 and 229 genes in PAO1) were evidently more than those induced at the originating growth temperature (158 genes in M18 and 169 genes in PAO1). The functional analysis of several newly found specific regulated operons (such as phh, liu, hmg) in the two strains indicated possible strategies implemented to respond to the non-originating temperature. This study provides new insight into how P. aeruginosa species responds to temperature change and a microarray platform covering the complete genomes of four widely studied P. aeruginosa strains.

Ultrafast Momentum-Dependent Response of Electrons in AntiferromagneticEuFe2As2Driven by Optical Excitation

Employing the momentum sensitivity of time- and angle-resolved photoemission spectroscopy we demonstrate the analysis of ultrafast single- and many-particle dynamics in antiferromagnetic EuFe(2)As(2). Their separation is based on a temperature-dependent difference of photoexcited hole and electron relaxation times probing the single-particle band and the spin density wave gap, respectively. Reformation of the magnetic order occurs at 800 fs, which is 4 times slower compared to electron-phonon equilibration due to a smaller spin-dependent relaxation phase space.

Temperature-Dependent Production of Various PlcR-Controlled Virulence Factors in Bacillus weihenstephanensis Strain KBAB4

The Bacillus cereus sensu lato complex has recently been divided into several phylogenetic groups with clear differences in growth temperature range. However, only a few studies have investigated the actual pathogenic potential of the psychrotolerant strains of the B. cereus group at low temperature, and little information is available concerning gene expression at low temperature. We found that vegetative cells of the psychrotolerant B. weihenstephanensis strain KBAB4 were pathogenic against the model insect Galleria mellonella at 15°C but not at 30°C. A similar temperature-dependent difference also was observed for the supernatant, which was cytotoxic to Vero epithelial cell lines and to murine macrophage J774 cells at 15°C but not at 30°C. We therefore determined the effect of low temperature on the production of various proteins putatively involved in virulence using two-dimensional protein gel electrophoresis, and we showed that the production of the Hbl enterotoxin and of two proteases, NprB and NprP2, was greater at a growth temperature of 15°C than at 30°C. The quantification of the mRNA levels for these virulence genes by real-time quantitative PCR at both temperatures showed that there was also more mRNA present at 15°C than at 30°C. We also found that at 15°C, hbl mRNA levels were maximal in the mid- to late exponential growth phase. In conclusion, we found that the higher virulence of the B. cereus KBAB4 strain at low temperature was accompanied by higher levels of the production of various known PlcR-controlled virulence factors and by a higher transcriptional activity of the corresponding genes.

Temperature-dependent behaviours are genetically variable in the nematode Caenorhabditis briggsae

Temperature-dependent behaviours in Caenorhabditis elegans, such as thermotaxis and isothermal tracking, are complex behavioural responses that integrate sensation, foraging and learning, and have driven investigations to discover many essential genetic and neural pathways. The ease of manipulation of the Caenorhabditis model system also has encouraged its application to comparative analyses of phenotypic evolution, particularly contrasts of the classic model C. elegans with C. briggsae. And yet few studies have investigated natural genetic variation in behaviour in any nematode. Here we measure thermotaxis and isothermal tracking behaviour in genetically distinct strains of C. briggsae, further motivated by the latitudinal differentiation in C. briggsae that is associated with temperature-dependent fitness differences in this species. We demonstrate that C. briggsae performs thermotaxis and isothermal tracking largely similar to that of C. elegans, with a tendency to prefer its rearing temperature. Comparisons of these behaviours among strains reveal substantial heritable natural variation within each species that corresponds to three general patterns of behavioural response. However, intraspecific genetic differences in thermal behaviour often exceed interspecific differences. These patterns of temperature-dependent behaviour motivate further development of C. briggsae as a model system for dissecting the genetic underpinnings of complex behavioural traits.

Abstract P350: Interstitial Volume Regulation in the Heart: Mechanistic Insights from ex Vivo Fluid Dynamics in Pig Myocardia

Developing and testing specific therapies for myocardial edema require understanding their mode and site of action. However, parsing determinants of interstitial volume/pressure relationships in vivo is difficult, particularly in the myocardium, where rhythmic contractions add to the confounding components of fluid-transfer driving pressures. Here, we describe a novel ex-vivo model system based on osmotic stress techniques and illustrate its application to analyses of local myocardial fluid dynamics that exclude systemic influences and systole/diastole compressive cycles. Freshly harvested ventricular explants were equilibrated in physiologic media at colloidosmotic pressures ranging from 3 to 219 mmHg, and fluid transfer in/out was measured gravimetrically as a function of time and pressure. The relationship between the change in explant volume and the imposed colloidosmotic pressure of the media was linear. The hydration potential , defined empirically as the pressure at which explant volume did not change, was calculated from the abscissa intercept at volume change = 0 , and the compliance from the slope of volume/pressure regression lines. Fluid-transfer rates and energies were derived from volume versus time trajectories measured at 4 and 37 °C. Hydration potential was 71.3 ± 10.6 and 23.0 ± 15.2 mmHg at 4 and 37°C (significant, P = 0.002), while compliance was 1.09 ± 0.3 and 1.22 ± 0.2 µl/g/ mmHg (not significant, P = 0.2, n = 5). Temperature-dependent differences between in/out flow rates were also significant, giving experimental activation energies of −5.9 ± 2.2 and 1.4 ± 0.7 kcal/mol for inflow and outflow, respectively. Results show that at physiologic temperatures, even without vascular hydrostatic pressure gradients and lymphatic drainage, the myocardial bias toward interstitial fluid efflux persists. These findings are consistent with local fluid-control mechanisms actuated by colloidosmotic and tensional forces rather than passive changes in flow resistance. This new approach allows quantitative evaluation of interstitial components of Starling’s forces and should help in mechanistic preclinical characterization of treatments to correct interstitial myocardial edema.

Proteomic analysis of the extremely thermoacidophilic archaeon Picrophilus torridus at pH and temperature values close to its growth limit

The thermoacidophilic archaeon Picrophilus torridus belongs to the Thermoplasmatales order and is the most acidophilic organism known to date, growing under extremely acidic conditions around pH 0 (pH(opt) 1) and simultaneously at high temperatures up to 65°C. Some genome features that may be responsible for survival under these harsh conditions have been concluded from the analysis of its 1.55 megabase genome sequence. A proteomic map was generated for P. torridus cells grown to the mid-exponential phase. The soluble fraction of the cells was separated by isoelectric focusing in the pH ranges 4-7 and 3-10, followed by a two dimension (2D) on SDS-PAGE gels. A total of 717 Coomassie collodial-stained protein spots from both pH ranges (pH 4-7 and 3-10) were excised and subjected to LC-MS/MS, leading to the identification of 665 soluble protein spots. Most of the enzymes of the central carbon metabolism were identified on the 2D gels, corroborating biochemically the metabolic pathways predicted from the P. torridus genome sequence. The 2D master gels elaborated in this study represent useful tools for physiological studies of this thermoacidophilic organism. Based on quantitative 2D gel electrophoresis, a proteome study was performed to find pH- or temperature-dependent differences in the proteome composition under changing growth conditions. The proteome expression patterns at two different temperatures (50 and 70°C) and two different pH conditions (pH 0.5 and 1.8) were compared. Several proteins were up-regulated under most stress stimuli tested, pointing to general roles in coping with stress.

Temperature-Dependent Differences in the Nonlinear Acoustic Behavior of Ultrasound Contrast Agents Revealed by High-Speed Imaging and Bulk Acoustics

Previous work by the authors has established that increasing the temperature of the suspending liquid from 20°C to body temperature has a significant impact on the bulk acoustic properties and stability of an ultrasound contrast agent suspension (SonoVue, Bracco Suisse SA, Manno, Lugano, Switzerland). In this paper the influence of temperature on the nonlinear behavior of microbubbles is investigated, because this is one of the most important parameters in the context of diagnostic imaging. High-speed imaging showed that raising the temperature significantly influences the dynamic behavior of individual microbubbles. At body temperature, microbubbles exhibit greater radial excursion and oscillate less spherically, with a greater incidence of jetting and gas expulsion, and therefore collapse, than they do at room temperature. Bulk acoustics revealed an associated increase in the harmonic content of the scattered signals. These findings emphasize the importance of conducting laboratory studies at body temperature if the results are to be interpreted for in vivo applications.