Temperature-induced Morphological Changes Research Articles

Elevated developmental temperatures impact the size and allometry of morphological traits of the bumblebee Bombus terrestris.

The impact of global warming on wild bee decline threatens the pollination services they provide. Exposure to temperatures above optimal during development is known to reduce adult body size but how it affects the development and scaling of body parts remains unclear. In bees, a reduction in body size and/or a reduction in body parts, such as the antennae, tongue and wings, and how they scale with body size (i.e. their allometry) could severely affect their fitness. To date, it remains unclear how temperature affects body size and the scaling of morphological traits in bees. To address this knowledge gap, we exposed both males and workers of Bombus terrestris to elevated temperature during development and assessed the effects on (i) the size of morphological traits and (ii) the allometry between these traits. Colonies were exposed to optimal (25°C) or stressful (33°C) temperatures. We then measured the body size, wing size, antenna and tongue length, as well as the allometry between these traits. We found that workers were smaller and the antennae of both castes were reduced at the higher temperature. However, tongue length and wing size were not affected by developmental temperature. The allometric scaling of the tongue was also affected by developmental temperature. Smaller body size and antennae could impair both individual and colony fitness, by affecting foraging efficiency and, consequently, colony development. Our results encourage further exploration of how the temperature-induced changes in morphology affect functional traits and pollination efficiency.

Heat dissipation in graphene foams

Graphene foam (GF)—a three-dimensional network of hollow graphene branches—is a highly attractive material for diverse applications. However, to date, the heat dissipation characteristics of GFs have not been characterized. To fill this gap, we synthesized GF devices, subjected them to high temperatures, and investigated their thermal behavior by using infrared microthermography. We find that while the convective area of GF devices is comparable to that of bulk materials (such as metals), the coefficient of convection of these devices is several orders of magnitude higher than that of metals. In addition, the GF devices showed a reproducible thermal behavior, which we attribute to negligible temperature-induced morphological changes (as confirmed by Raman analysis). Taken together, our findings suggest GF as a promising candidate material for advanced cooling applications where efficient heat dissipation is needed, e.g., in electrical circuits.

Thermally Induced Switch of Coupling Reaction Using the Morphological Change of a Thermoresponsive Polymer on a Reactive Heteroarmed Nanoparticle.

Control of the cross-linking reaction is imperative when developing a sophisticated in situ forming hydrogel in the body. In this study, a heteroarmed thermoresponsive (TR) nanoparticle was designed to investigate the mechanism of controlling reactivity of the functional groups introduced into the nanoparticles. The coupling reaction was suppressed/proceeded by utilizing temperature-induced morphological changes of the TR polymer. The heteroarmed TR nanoparticle was prepared by the coassembly of amphiphilic block copolymers possessing both a TR segment and hydrophilic segment with reactive functional groups of succinimide. The longer TR chain on the nanoparticle covered the succinimide group and suppressed the reaction with the primary amine on the external nanoparticle. In contrast, the coupling reaction was promoted at a high temperature to create the chemical cross-linking structure between the nanoparticles because of the exposure of the succinimide group on the surface of the particle as a consequence of the morphological change of the TR polymer. In addition, the thermally controlled chemical reaction modulated initiation of the gelation using a highly concentrated nanoparticle solution. The heteroarmed TR nanoparticle offers great practical advantages for clinical uses, such as embolization agents, through precise control of the reaction.

Crystal Morphology Prediction and Anisotropic Evolution of 1,1-Diamino-2,2-dinitroethylene (FOX-7) by Temperature Tuning

Temperature-induced morphological changes are one of the strategies for designing crystal shapes, but the role of temperature in enhancing or inhibiting crystal growth is not well understood yet. To meet the requirements of high density and low sensitivity, we need to control the crystal morphology of the energetic materials. We studied the crystal morphology of 1,1-diamino-2,2-dinitroethylene (FOX-7) in dimethyl sulfoxide/water mixed solvent by using the modified Hartman-Perdok theorem. Molecular dynamics simulations were used to determine the interaction of FOX-7 and solvents. The results showed that the crystal shape of FOX-7 is hexagonal, the (101) face is the largest exposed face and is adjacent to six crystal faces at 354 K. As the temperature goes down, the area of the (001) face is significantly reduced. The crystal morphology of FOX-7 at 324 K has a smaller aspect ratio of 4.72, and this temperature is suitable for tuning the morphology from slender hexagon into diamond. The prediction results are in remarkable agreement with the experiments. Moreover, we predicted the evolution path of FOX-7 morphology by Gibbs-Curie-Wulff theorem and explained the variation of crystal shape caused by different external conditions in the actual crystallization process.

3D characterization of heat-induced morphological changes of Au nanostars by fast in situ electron tomography.

A thorough understanding of the thermal stability and potential reshaping of anisotropic gold nanostars is required for various potential applications. Combination of a tomographic heating holder with fast tilt series acquisition has been used to monitor temperature-induced morphological changes of Au nanostars. The outcome of our 3D investigations can be used as an input for boundary element method simulations, enabling us to investigate the influence of reshaping on the nanostars' plasmonic properties. Our work leads to a better understanding of the mechanism behind thermal reshaping. In addition, the approach presented here is generic and can hence be applied to a wide variety of nanoparticles made of different materials and with arbitrary morphology.

Temperature-induced changes in morphology and microstructure of electrospun mullite nanofibers fabricated from a hybrid mullite sol

Mullite nanofibers with small diameter and high surface area are an ideal candidate as the reinforcements in composite materials, and have promising applications in the fields of catalysis, filtration, thermal storage and so forth. In this work, electrospun mullite nanofibers were successfully synthesized using a hybrid mullite sol. The morphology and microstructure of fibers calcined at different temperatures were investigated. The morphology of fibers synthesized at 900°C is porous with coarse surface, and after crystallization it becomes compact with smooth surface. The densities of fibers increase with the increasing temperatures. At 1200°C the surface of fibers becomes coarse again, as a result of the grain growth of mullite. The crystallization path of fibers was revealed that the Al-rich mullite (4Al2O3·SiO2) together with amorphous silica formed at 1000°C, changed into mullite with higher silica contents as temperature further increased, and finally transformed into a stable 3Al2O3·2SiO2 phase at 1200°C. During this crystallization process, the flow of amorphous silica phase and the formation of mullite crystal structure benefit the densification of fibers, leading to the resultant fibers with fine and compact microstructure. The present findings can provide a guideline for the preparation of the promising high-mechanical mullite nanofibers and the synthesized nanofibers display great potential as reinforcements in structural ceramic composites.

Electrochemical properties and structure of ion-exchange membranes upon thermochemical treatment

The effect of temperature-induced morphological changes on the electrochemical and physicochemical properties of the heterogeneous sulfo cation-exchange membrane MK-40 in aqueous, alkaline, and acidic media is subjected to comparative analysis. The deviation between the surface and volume microstructure of swollen membrane samples after their chemical conditioning and thermochemical treatment are visualized by a scanning electron microscope. The porosity and the fraction of the ion-exchange component in membranes subjected to heating in water and aggressive media are observed to increase more noticeably in their surface layer as compared with their volume. The maximum effect thus modified structural characteristics on the transport (conductivity, diffusion permeability, selectivity) and physicochemical (exchange capacity, water content, density, linear sizes) properties is observed for MK-40 membrane samples when heated in a sulfuric acid solution. The effect of thermal destruction of inert polymers (divinylbenzene, caprone) involved in the membrane composition on the transport characteristics is revealed.

Temperature-induced changes in morphology and structure of TiO2–Al2O3 fibers

Electrospinning of a sol-gel and polymer mixture is used to produce titania-alumina (TiO2–Al2O3) fibers with diameters ranging from 200 to 800 nm. These composite metal-oxide fibers were calcined at various temperatures and their morphology is studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The decrease in the average diameter of the fibers with increasing temperature is observed. Powder X-ray diffraction (XRD) reveals that up to 800 °C the composite fibers have anatase titania structure whereas at 900 °C the fibers exhibit mixture of anatase and rutile phases. It is found that specific surface area decreases as a function of temperature in the 700–900 °C range. The change in phase (anatase-to-rutile) and the increase in crystallite size occur simultaneously. The presence of smaller amount of amorphous alumina in the primarily titania-based structure seems to play the role in stabilizing the anatase phase.

High temperature-induced changes in morphology in imaginal disc cells of a temperature sensitive lethal mutant of Drosophila melanogaster

A temperature sensitive lethal allele of suppressor forked in D. melanogaster, I(I)su(f)ts67g (1–65.9), was used to study the relation between the imaginal disc ability to evaginate and the temperature sensitivity of the mutant. The imaginal leg discs of larvae shifted up to 30°C early in development are unable to evaginate at this temperature either in vivo or in vitro. Furthermore, after four days at 30°C, the discs are unable to evaginate when the larvae are shifted back to 25°C. On the bases of gynandromorph analysis and the in vitro evagination experiments we conclude that the absence of evagination is autonomous. No abnormal cell death is found in the discs, indicating that the failure to evaginate is not a direct result of cell degeneration. After four days at 30°C some morphological abnormalities were found in imaginal disc cells. Annulate lamellae appear in the cytoplasm, the ribosomal packing and the microtubular character of the imaginal disc cells are also altered. We suggest that a defective proliferation is involved in the formation of this phenotype since mitotic cells were also found after the prolonged heat treatment.

Portable dynamic light scattering instrument and method for the measurement of blood platelet suspensions

No routine test exists to determine the quality of blood platelet transfusions although every year millions of patients require platelet transfusions to survive cancer chemotherapy, surgery or trauma. A new, portable dynamic light scattering instrument is described that is suitable for the measurement of turbid solutions of large particles under temperature-controlled conditions. The challenges of small sample size, short light path through the sample and accurate temperature control have been solved with a specially designed temperature-controlled sample holder for small diameter, disposable capillaries. Efficient heating and cooling is achieved with Peltier elements in direct contact with the sample capillary. Focusing optical fibres are used for light delivery and collection of scattered light. The practical use of this new technique was shown by the reproducible measurement of latex microspheres and the temperature-induced morphological changes of human blood platelets. The measured parameters for platelet transfusions are platelet size, number of platelet-derived microparticles and the response of platelets to temperature changes. This three-dimensional analysis provides a high degree of confidence for the determination of platelet quality. The experimental data are compared to a matrix and facilitate automated, unbiased quality testing.

Temperature-induced morphological changes of ZnO grown by metalorganic chemical vapor deposition

Changes of morphology during the growth of ZnO on Al 2O 3 (0 0 0 1) substrates by metalorganic chemical vapor deposition (MOCVD) were investigated as a function of growth temperature ( T g). The morphology of ZnO changes dramatically with T g. At very low growth temperatures of T g⩽200 °C, no meaningful ZnO forms. At 200 °C< T g⩽260 °C, columnar grained, textured ZnO films having a large amount of crystalline defects grow. At higher growth temperatures of 260 °C< T g⩽320 °C, arrays of vertically well-aligned ZnO nanorods grow. The nanorods are aligned epitaxially with a 30° rotation of ZnO basal planes with respect to Al 2O 3 basal planes. At further higher growth temperatures of 320 °C< T g⩽380 °C, ZnO of nanoneedle type grows. However, at T g>380 °C, ZnO nanowires start to grow on top of a continuous ZnO layer. Both the nanoneedles and the nanowires are not only well aligned both in the out-of- and in the in-plane direction, but also show a very low density of crystalline defects. Our results suggest that T g is one of the key processing parameters and need to be optimized in a narrow regime in order to grow a desired type of ZnO in MOCVD process.