Precursor Decomposition,Microstructure, and Porosity of Yttria Stabilized Zirconia Thin Films Prepared by Aerosol‐Assisted Chemical Vapor Deposition

Microstructures of yttria stabilized zirconia thin films deposited by aerosol assisted chemical vapor deposition (AA‐CVD) are correlated with the thermal decomposition behavior of the corresponding metal precursors, zirconium and yttrium 2,4‐pentanedionate. Process conditions of AA‐CVD are investigated with the aim of producing dense and compact YSZ thin films for applications as gas‐tight electrolyte. Based on systematic cross sectional scanning transmission electron microscopy (STEM) investigations and conductivity measurements, the development of percolating nanoporosity is observed in samples prepared at temperatures between 350 °C and 600 °C at standard solution throughput. Compact columnar thin films with bulk conductivity are obtained at 600 °C by reducing the metal content of the precursor solution and at 450 °C by reducing the solution throughput.     

Dielectric Properties of Normal and Metastatic Lymph Nodes Ex Vivo From Lung Cancer Surgeries

The dielectric properties of normal and tumor human tissues have been widely reported in recent years. However, the dielectric properties of intrathoracic lymph nodes (LNs) have not been reported. In this communication, we measured the dielectric properties (i.e., permittivity and conductivity) of ex vivo intrathoracic LNs obtained from lung cancer surgeries. Results show that the permittivity and conductivity of metastatic LNs are higher than those of normal LNs over the frequency range of 1 MHz–4 GHz. Statistically significant differences are observed at single specific frequencies (64, 128, 298, 433, and 915 MHz and 2.45 GHz). Our study provides the basic data to support future-related research and fills the research gap on the dielectric properties of LNs in the lungs. Bioelectromagnetics. 2020;41:148–155. © 2020 Bioelectromagnetics Society.     

Soybean leaf hydraulic conductance does not acclimate to growth at elevated [CO2] or temperature in growth chambers or in the field

Background and Aims

Leaf hydraulic properties are strongly linked with transpiration and photosynthesis in many species. However, it is not known if gas exchange and hydraulics will have co-ordinated responses to climate change. The objective of this study was to investigate the responses of leaf hydraulic conductance (K_leaf) in Glycine max (soybean) to growth at elevated [CO₂] and increased temperature compared with the responses of leaf gas exchange and leaf water status.

Methods

Two controlled-environment growth chamber experiments were conducted with soybean to measure K_leaf, stomatal conductance (g_s) and photosynthesis (A) during growth at elevated [CO₂] and temperature relative to ambient levels. These results were validated with field experiments on soybean grown under free-air elevated [CO₂] (FACE) and canopy warming.

Key results

In chamber studies, K_leaf did not acclimate to growth at elevated [CO₂], even though stomatal conductance decreased and photosynthesis increased. Growth at elevated temperature also did not affect K_leaf, although g_s and A showed significant but inconsistent decreases. The lack of response of K_leaf to growth at increased [CO₂] and temperature in chamber-grown plants was confirmed with field-grown soybean at a FACE facility.

Conclusions

Leaf hydraulic and leaf gas exchange responses to these two climate change factors were not strongly linked in soybean, although g_s responded to [CO₂] and increased temperature as previously reported. This differential behaviour could lead to an imbalance between hydraulic supply and transpiration demand under extreme environmental conditions likely to become more common as global climate continues to change.     

Molecular dynamics simulations of heat conduction in multi-walled carbon nanotubes

Heat conduction in multi-walled carbon nanotubes (MWNTs) was studied using non-equilibrium molecular dynamics simulations. This research focuses on the effects of the multi-wall structure of the MWNTs on the heat conduction. The results show that the thermal conductivity of a MWNT is almost the same as that of the corresponding single-walled carbon nanotubes (SWNTs) rather than much smaller as has been suggested. Thus, the multi-wall structure does not significantly affect the thermal conduction in the MWNTs. Analysis of the temperature profiles and the phonon density of states confirms that there is almost no heat transport between the MWNT layers and that each layer conducts heat nearly independently along parallel channels. This is physically reasonable since the weak inter-wall interactions and large interfacial thermal resistances make the MWNT layers behave like parallel thermal circuits.     

Aqueous pathways dominate permeation of solutes across Pisum sativum seed coats and mediate solute transport via diffusion and bulk flow of water

The permeability of seed coats to solutes either of biological or anthropogenic origin plays a major role in germination, seedling growth and seed treatment by pesticides. An experimental set‐up was designed for investigating the mechanisms of seed coat permeation, which allows steady‐state experiments with isolated seed coats of Pisum sativum. Permeances were measured for a set of organic model compounds with different physicochemical properties and sizes. The results show that narrow aqueous pathways dominate the diffusion of solutes across pea seed coats, as indicated by a correlation of permeances with the molecular sizes of the compounds instead of their lipophilicity. Further indicators for an aqueous pathway are small size selectivity and a small effect of temperature on permeation. The application of an osmotic water potential gradient across isolated seed coats leads to an increase in solute transfer, indicating that the aqueous pathways form a water‐filled continuum across the seed coat allowing the bulk flow of water. Thus, the uptake of organic solutes across pea testae has two components: (1) by diffusion and (2) by bulk water inflow, which, however, is relevant only during imbibition.     

Midday stomatal conductance is more related to stem rather than leaf water status in subtropical deciduous and evergreen broadleaf trees

Midday depressions in stomatal conductance (g_s) and photosynthesis are common in plants. The aim of this study was to understand the hydraulic determinants of midday g_s, the coordination between leaf and stem hydraulics and whether regulation of midday g_s differed between deciduous and evergreen broadleaf tree species in a subtropical cloud forest of Southwest (SW) China. We investigated leaf and stem hydraulics, midday leaf and stem water potentials, as well as midday g_s of co‐occurring deciduous and evergreen tree species. Midday g_s was correlated positively with midday stem water potential across both groups of species, but not with midday leaf water potential. Species with higher stem hydraulic conductivity and greater daily reliance on stem hydraulic capacitance were able to maintain higher stem water potential and higher g_s at midday. Deciduous species exhibited significantly higher stem hydraulic conductivity, greater reliance on stem capacitance, higher stem water potential and g_s at midday than evergreen species. Our results suggest that midday g_s is more associated with midday stem than with leaf water status, and that the functional significance of stomatal regulation in these broadleaf tree species is probably for preventing stem xylem dysfunction.     

Membrane phase behavior during cooling of stallion sperm and its correlation with freezability

Abstract

Stallion sperm exhibits great male-to-male variability in survival after cryopreservation. In this study, we have investigated if differences in sperm freezability can be attributed to membrane phase and permeability properties. Fourier transform infrared spectroscopy (FTIR) was used to determine supra and subzero membrane phase transitions and characteristic subzero membrane hydraulic permeability parameters. Sperm was obtained from stallions that show differences in sperm viability after cryopreservation. Stallion sperm undergoes a broad and gradual phase transition at suprazero temperatures, from 30–10°C, whereas freezing-induced dehydration of the cells causes a more severe phase transition to a highly ordered gel phase. Sperm from individual stallions showed significant differences in post-thaw progressive motility, percentages of sperm with abnormal cell morphology, and chromatin stability. The biophysical membrane properties evaluated in this study, however, did not show clear differences amongst stallions with differences in sperm freezability. Cyclodextrin treatment to remove cholesterol from the cellular membranes increased the cooperativity of the suprazero phase transition, but had little effects on the subzero membrane phase behavior. In contrast, freezing of sperm in the presence of protective agents decreased the rate of membrane dehydration and increased the total extent of dehydration. Cryoprotective agents such as glycerol decrease the amount of energy needed to transport water across cellular membranes during freezing.     

Outstanding Low Temperature Thermoelectric Power Factor from Completely Organic Thin Films Enabled by Multidimensional Conjugated Nanomaterials

In an effort to create a paintable/printable thermoelectric material, comprised exclusively of organic components, polyaniline (PANi), graphene, and double‐walled nanotube (DWNT) are alternately deposited from aqueous solutions using the layer‐by‐layer assembly technique. Graphene and DWNT are stabilized with an intrinsically conductive polymer, poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). An 80 quadlayer thin film (≈1 μm thick), comprised of a PANi/graphene‐PEDOT:PSS/PANi/DWNT‐PEDOT:PSS repeating sequence, exhibits unprecedented electrical conductivity (σ ≈ 1.9 × 10⁵ S m^?1) and Seebeck coefficient (S ≈ 120 μV K^?1) for a completely organic material. These two values yield a thermoelectric power factor (PF = S ² σ ^?1) of 2710 μW m^?1 K^?2, which is the highest value ever reported for a completely organic material and among the highest for any material measured at room temperature. These outstanding properties are attributed to the highly ordered structure in the multilayer assembly. This water‐based thermoelectric nanocomposite is competitive with the best inorganic semiconductors (e.g., bismuth telluride) at room temperature and can be applied as a coating to any flexible surface (e.g., fibers in clothing). For the first time, there is a real opportunity to harness waste heat from unconventional sources, such as body heat, to power devices in an environmentally‐friendly way.     

Hydraulic conductance and the maintenance of water balance in flowers

Flowers face desiccating conditions, yet little is known about their ability to transport water. We quantified variability in floral hydraulic conductance (K_flower) for 20 species from 10 families and related it to traits hypothesized to be associated with liquid and vapour phase water transport. Basal angiosperm flowers had trait values associated with higher water and carbon costs than monocot and eudicot flowers. K_flower was coordinated with water supply (vein length per area, VLA) and loss (minimum epidermal conductance, g_min) traits among the magnoliids, but was insensitive to variation in these traits among the monocots and eudicots. Phylogenetic independent contrast (PIC) correlations revealed that few traits had undergone coordinated evolution. However, VLA and the desiccation time (T_des), the quotient of water content and g_min, had significant trait and PIC correlations. The near absence of stomata from monocot and eudicot flowers may have been critical in minimizing water loss rates among these clades. Early divergent, basal angiosperm flowers maintain higher K_flower because of traits associated with high rates water loss and water supply, while monocot and eudicot flowers employ a more conservative strategy of limiting water loss and may rely on stored water to maintain turgor and delay desiccation.