Project description:Many ideas have been put forward for the adaptive value of the cassowary casque; and yet, its purpose remains speculative. Homeothermic animals elevate body temperature through metabolic heat production. Heat gain must be offset by heat loss to maintain internal temperatures within a range for optimal performance. Living in a tropical climate, cassowaries, being large bodied, dark feathered birds, are under thermal pressure to offload heat. We tested the original hypothesis that the casque acts as a thermal window. With infrared thermographic analyses of living cassowaries over an expansive range of ambient temperatures, we provide evidence that the casque acts as a thermal radiator, offloading heat at high temperatures and restricting heat loss at low temperatures. Interestingly, at intermediate temperatures, the casque appears thermally heterogeneous, with the posterior of the casque heating up before the front half. These findings might have implications for the function of similar structures in avian and non-avian dinosaurs.
Project description:Thermal ramp rate is a major limiting factor in using real-time polymerase chain reaction (PCR) for routine diagnostics. We explored the limits of speed by using liquid for thermal exchange rather than metal as in traditional devices, and by testing different polymerases. In a clinical setting, our system equaled or surpassed state-of-the-art devices for accuracy in amplifying DNA?RNA of avian influenza, cytomegalovirus, and human immunodeficiency virus. Using Thermococcus kodakaraensis polymerase and optimizing both electrical and chemical systems, we obtained an accurate, 35 cycle amplification of an 85-base pair fragment of E. coli O157:H7 Shiga toxin gene in as little as 94.1 s, a significant improvement over a typical 1 h PCR amplification.
Project description:Adaptive control of solar and thermal radiation through windows is of pivotal importance for building energy saving. However, such synchronous passive regulations are challenging to be integrated into one thermochromic window. Here, we develop a solar and thermal regulatory (STR) window by integrating poly(N-isopropylacrylamide) (pNIPAm) and silver nanowires (AgNWs) into pNIPAm/AgNW composites. A hitherto unexplored mechanism, originating from the temperature-triggered water capture and release due to pNIPAm phase transition, is exploited to achieve simultaneous regulations of solar transmission and thermal emission. The STR window shows excellent solar modulation (58.4%) and thermal modulation (57.1%) and demonstrates effective regulation of indoor temperatures during both daytime and nighttime. Compared to other thermochromic technologies, the STR window reduces heat loss in cold environment while promotes heat dissipation in hot conditions, achieving efficient energy saving in all weathers. This dual solar and thermal regulation mechanism may provide unidentified insights into the advancement of smart window technology.
Project description:The Brazilian free-tailed bat (Tadarida brasiliensis) experiences challenging thermal conditions while roosting in hot caves, flying during warm daylight conditions, and foraging at cool high altitudes. Using thermal infrared cameras, we identified hot spots along the flanks of free-ranging Brazilian free-tailed bats, ventral to the extended wings. These hot spots are absent in syntopic cave myotis (Myotis velifer), a species that forages over relatively short distances, and does not engage in long-distance migration. We hypothesized that the hot spots, or "radiators," on Brazilian free-tailed bats may be adaptations for migration, particularly in this long-distance, high-flying species. We examined the vasculature of radiators on Brazilian free-tailed bats with transillumination to characterize the unique arrangements of arteries and veins that are positioned perpendicular to the body in the proximal region of the wing. We hypothesized that these radiators aid in maintaining heat balance by flushing the uninsulated thermal window with warm blood, thereby dissipating heat while bats are flying under warm conditions, but shunting blood away and conserving heat when they are flying in cooler air at high altitudes. We also examined fluid-preserved specimens representing 122 species from 15 of 18 chiropteran families and radiators appeared present only in species in the family Molossidae, including both sedentary and migratory species and subspecies. Thus, the radiator appears to be a unique trait that may facilitate energy balance and water balance during sustained dispersal, foraging, and long-distance migration.
Project description:Nicotinic acetylcholine receptors (AChRs) are synaptic ion channels that spontaneously isomerize (i.e., gate) between resting and active conformations. We used single-molecule electrophysiology to measure the temperature dependencies of mouse neuromuscular AChR gating rate and equilibrium constants. From these we estimated free energy, enthalpy, and entropy changes caused by mutations of amino acids located between the transmitter binding sites and the middle of the membrane domain. The range of equilibrium enthalpy change (13.4 kcal/mol) was larger than for free energy change (5.5 kcal/mol at 25°C). For two residues, the slope of the rate-equilibrium free energy relationship (Φ) was approximately constant with temperature. Mutant cycle analysis showed that both free energies and enthalpies are additive for energetically independent mutations. We hypothesize that changes in energy associated with changes in structure mainly occur close to the site of the mutation, and, hence, that it is possible to make a residue-by-residue map of heat exchange in the AChR gating isomerization. The structural correlates of enthalpy changes are discussed for 12 different mutations in the protein.
Project description:There are a broad range of applications for narrowband long-wave infrared (LWIR) sources, especially within the 8-12 ?m atmospheric window. These include infrared beacons, free-space communications, spectroscopy, and potentially on-chip photonics. Unfortunately, commercial light-emitting diode (LED) sources are not available within the LWIR, leaving only gas-phase and quantum cascade lasers, which exhibit low wall-plug efficiencies and in many cases require large footprints, precluding their use for many applications. Recent advances in nanophotonics have demonstrated the potential for tailoring thermal emission into an LED-like response, featuring narrowband, polarized thermal emitters. In this work, we demonstrate that such nanophotonic IR emitting metamaterials (NIREMs), featuring near-unity absorption, can serve as LWIR sources with effectively no net power consumption, enabling their operation entirely by waste heat from conventional electronics. Using experimental emissivity spectra from a SiC NIREM device in concert with a thermodynamic compact model, we verify this feasibility for two test cases: a NIREM device driven by waste heat from a CPU heat sink and one operating using a low-power resistive heater for elevated temperature operation. To validate these calculations, we experimentally determine the temperature-dependent NIREM irradiance and the angular radiation pattern. We purport that these results provide a first proof-of-concept for waste heat-driven thermal emitters potentially employable in a variety of infrared application spaces.
Project description:Improving thermal insulation is vital for addressing thermal protection and energy efficiency challenges. Though silica aerogel has a record-low thermal conductivity at ambient pressure, its high production cost, due to its nanoscale porous structure, has hindered its widespread use. In this study, we introduce a cost-effective and mild method that enhances insulation by incorporating phase change materials (PCMs) into a micron-porous framework. With a thermal conductivity at 0.041 W m-1K-1 on par with conventional insulation materials, this PCMs aerogel presents additional advantages for thermal protection from transient high-temperature loads by effectively delaying heat propagation through heat absorption. Moreover, the PCMs aerogel remains stable under cyclic deformation and heating up to 300 °C and is self-extinguishing in the presence of fire. Our approach offers a promising alternative for affordable insulation materials with potential wide applications in thermal protection and energy conservation areas.
Project description:Here we use a transcriptomic approach to investigate the molecular underpinnings of thermal stress in the model cyanobacteria species Synechocystis. We impose gradual heat stress by increasing the temperature in a stepwise fashion (1.5 °C h-1) from their optimal growth temperature of 30 °C to a maximum temperature of 46.5 °C over a period of 12h.
Project description:The 'thermal grill illusion' (TGI) is a unique cutaneous sensation of unpleasantness, induced through the application of interlacing warm and cool stimuli. While previous studies have investigated optimal parameters and subject characteristics to evoke the illusion, our aim was to examine the modulating effect as a conditioning stimulus. A total of 28 healthy control individuals underwent three testing sessions on separate days. Briefly, 15 contact heat stimuli were delivered to the right hand dorsum, while the left palmar side of the hand was being conditioned with either neutral (32?°C), cool (20?°C), warm (40?°C), or TGI (20/40?°C). Rating of perception (numeric rating scale: 0-10) and evoked potentials (i.e., N1 and N2P2 potentials) to noxious contact heat stimuli were assessed. While cool and warm conditioning decreased cortical responses to noxious heat, TGI conditioning increased evoked potential amplitude (N1 and N2P2). In line with other modalities of unpleasant conditioning (e.g., sound, visual, and olfactory stimulation), cortical and possibly sub-cortical modulation may underlie the facilitation of contact heat evoked potentials.