Fast Drying Combined With Rapid Cooling Can Enhance The Survival of The Desiccation Sensitive Wheat Pollen After Ultra-Low Temperature Storage

Long-term storage of pollen is important for the fertilization of spatially or temporally isolated female parents, especially during hybrid breeding. Wheat pollen is dehydration-sensitive and rapidly loses viability after shedding. To preserve wheat pollen, we hypothesized that fast-(flash)-drying and fast cooling (150°C min-1) compared to slow-(air)-drying and slow cooling (1°C min-1) would increase the rate of intracellular water content (WC) removal, decrease intracellular ice crystal formation, and increase viability after exposure to ultra-low temperatures. High correlations were found between pollen WC and viability analyzed by impedance flow cytometry (IFC viability: r=0.92, P<0.001) and pollen germination (r=0.94, P<0.001). After 10 min of air-drying, 66% WC was lost and pollen germination was at 12.2±12.3%. After 10 min of flash-drying, WC of pollen reduced by 74%. IFC viability decreased from 90.2±6.7 to 39.4±17.9%, and pollen germination dropped from 33.7±16.9 to 1.9±3.9%. After 12 min of flash-drying, WCs decreased to <0.34 mg H2O mg-1 DW, ice crystal formation was completely prevented (ΔH=0 J mg-1 DW), and pollen germination reached 1.2±1.0%. After slow and fast cooling, flash-dried pollen (WC 0.91±0.11 mg H2O mg-1 DW) showed less ice crystal formation during cryomicroscopic-video-recordings and had IFC viability of 4.5±7.0% (slow) and 6.1±8.8% (fast), respectively, compared to air-dried pollen which lost all viability. Generally, fast-(flash)-drying and increased cooling rates may enable the survival of wheat pollen likely due to (1) a fast rate of intracellular WC loss that reduces deleterious biochemical changes associated with the drying process and (2) a delay and reduction in intracellular ice crystal formation.

Primer on Aircraft Induced Clouds and Their Global Warming Mitigation Options

Pressure is increasing on all industrial sectors to address climate sustainability, not only for the welfare of the planet, but also to preserve the customer base and manage operating costs. The aviation industry has a unique opportunity to halve its global radiative forcing (RF) contribution by minimizing the generation of aircraft induced clouds (AIC). These anthropogenic (human-made) condensation trails create a greenhouse effect by absorbing or directing back to Earth approximately 33% of emitted outgoing thermal longwave radiation. The effect of AIC accounts for 2% of the Earth's total anthropogenic RF. The effect of reducing AIC on global warming is immediate (unlike CO2 emissions which have a 2-decade delay in affecting global warming). This paper describes the physics of AIC formation and RF to identify candidate interventions to reduce AIC RF: 1) reduce the quantity of soot generated, 2) reduce or eliminate ice crystal formation, and 3) modify RF properties of AIC. The highest utility and lowest costs is to reduce ice crystal formation by avoiding cruise flight levels in the atmospheric conditions that are conducive to AIC generation. Reducing soot through drop-in biofuels, and synthetic fuels, require significant investment to scale production. Options that require the redesign of jet engines or use of alternative fuels such as liquid natural gas and liquid hydrogen, require significant research and turn-over of the existing fleets. Fuel additives to suppress ice crystal formation, change the RF properties of ice crystals, or both, are still nascent research topics. The implications and limitations are discussed.

Effects of Immersion Freezing on Ice Crystal Formation and the Protein Properties of Snakehead (Channa argus)

This study aimed to evaluate the effect of immersion freezing (IF) at different temperatures on ice crystal formation and protein properties in fish muscle. Snakehead blocks were frozen by IF at −20, −30, and −40 °C, and conventional air freezing (AF) at −20 °C. The size of ice crystals in the frozen samples was evaluated using Image J software. Changes in protein properties were analyzed by Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). Snakehead blocks frozen using IF contained smaller ice crystals and better microstructures, especially at lower temperatures. The mean cross-sectional areas of ice crystals formed in the frozen samples were 308.8, 142.4, and 86.5 μm2 for IF treatments at −20, −30, and −40 °C, respectively, and 939.6 μm2 for the AF treatment. The FT-IR results show that protein aggregation in the frozen fish blocks was manifested by a decrease in α-helices connected to the increased random coil fraction. The DSC results show that samples prepared by IF had a higher denaturation enthalpy (∆H) and denaturation maximum temperature (Tmax) than those prepared by AF. These results confirm that IF generated a larger number of smaller ice crystals, which is conducive to food preservation.

Trehalose as an alternative to glycerol as a glassing agent for in vivo DNP MRI

In dynamic nuclear polarization (DNP), the solutions of the hyperpolarizable molecule and the paramagnetic agent need to form a glass when frozen to attain significant levels of polarization in reasonable time periods. Molecules which do not form glasses by themselves are often mixed with excipients to form glasses. While glassing agents are often essential in DNP studies, they have the potential to perturb the metabolic measurements that are being studied. Glycerol, the glassing agent of choice for in vivo DNP studies, is effective at reducing ice crystal formation during freezing but is rapidly metabolized, potentially altering the redox and ATP balance of the system. As a biologically inert alternative to glycerol, we show here that 15–20 wt % trehalose yields a glass that polarizes samples more rapidly than the commonly used 60% wt formulation of glycerol and yields similar polarization levels within clinically relevant timeframes. Trehalose may be an attractive alternative to glycerol for situations where there may be concerns about glycerol’s glucogenic potential and possible alteration of the ATP/ADP and redox balance.

StudioAntarctica: Embedding Art in a Geophysics Sea Ice Expedition

Motivated by the potential for cross-disciplinary outcomes, an artist was embedded in a science expedition to the sea ice around Antarctica, as part of an art-science collaboration with marine physicist Craig Stevens. The scientist and the artist together focused on ice crystal formation. Most elements of the art process had three phases—before, during and after the science process. The environment largely dominated the progress and evolution of ideas. The results were multimaterial and multiscale and provided a way to engage a wide range of audiences while also making nondidactic connections around global climate—and producing art.