Sensible heat balance method to determine rates of soil freezing and thawing

Soil freezing and thawing can have a significant impact on the winter hydrology of soil, and soil ice content is an important component of the winter hydrological cycle. However, transient soil ice contents have been difficult to quantify under field conditions. A sensible heat balance (SHB) method using a sequence of heat pulse probes (HPP) has the potential to measure in-situ soil ice content. Therefore, the objectives of this dissertation are to develop, to test, and to improve the SHB method for determining soil ice content. A series of numerical, field, and laboratory studies were conducted. The SHB method for soil ice content determination contains two important assumptions; negligible convective soil heat fluxes, and non-concurrent water evaporation and water fusion. A numerical study shows that these assumptions are acceptable for soil layers deeper than 12 mm, and the SHB method in theory can accurately estimate soil ice contents. However, when applied to an actual winter field, the in-situ soil ice contents determined with the SHB method are inaccurate. The inaccurate soil ice contents are associated with errors in soil thermal conductivity measured with the HPP. A sensitivity analysis shows that at least 20% accuracy of soil thermal conductivity is required to accurately estimate soil ice contents with the SHB method. In addition, the use of short time steps in the SHB method (e.g., 15 min) can improve soil ice content estimation. A numerical study was performed to understand the sensitivity of HPP measurement needle temperature changes to properties of partially frozen soil. The measurement needle temperature changes were sensitive to soil thermal conductivity and freezing characteristics but not to volumetric heat capacity. The HPP may not be able to determine volumetric heat capacity accurately when soil temperature is between -2°C and 0°C. The sensitivity analysis suggests that soil thermal conductivity and soil freezing characteristics are the best candidate parameters for determination by inverse analysis. The inverse analysis may improve the accuracy of soil thermal conductivity and soil ice content determination with the SHB method. A laboratory study was performed to further evaluate the SHB method for determining soil ice contents with soil column freezing and thawing. The SHB method accurately described the latent heat associated with soil freezing and thawing and provided reasonable transient soil ice content values at soil temperatures between -3°C and 0°C. The SHB method was not sensitive enough to determine soil ice content at temperatures below -3°C. Latent heat values are relatively large at temperatures between -3°C and 0°C but latent heat values are small at temperatures below -3°C. The soil ice contents during extended freezing periods at temperature below -3°C could be accurately estimated with change in volumetric heat capacity determined with the HPP. Thus, a combination of the SHB method and HPP volumetric heat capacity determination can be used to determine soil ice contents for a wide range of temperatures. The SHB method is a new approach that has some advantages compared to other methods for estimating transient soil freezing and thawing. This dissertation presents fundamental information on the SHB approach and provides guidance for further development of the SHB method

Copper-mediated Trifluoromethylthiolation of Alkenyl Iodides with AgSCF₃

A copper-mediated trifluoromethylthiolation of alkenyl iodides with AgSCF₃ has been developed. CuSCF₃ species generated in-situ from a copper salt and AgSCF₃ can be coupled with alkenyl iodides to produce the corresponding trifluoromethylthioalkenes efficiently. The reaction conditions are compatible with various functional groups. Moreover, its scale-up synthesis is also possible to provide the desired trifluoromethylthiolated product even on a gram-scale

Copper-Catalyzed Regio- And Enantioselective Hydroallylation of 1-Trifluoromethylalkenes: Effect of Crown Ether

A Cu-catalyzed regio- and enantioselective hydroallylation of 1-trifluoromethylalkenes with hydrosilanes and allylic chlorides has been developed. Anin situgenerated CuH species undergoes the hydrocupration regio- and enantioselectively to form a chiral α-CF3alkylcopper intermediate, which then leads to the optically active hydroallylated product. The key to success is the use of not only an appropriate chiral bisphosphine ligand but also 18-crown-6 to suppress the otherwise predominant β-F elimination from the α-CF3alkylcopper intermediate. The asymmetric Cu catalysis successfully constructs the nonbenzylic and nonallylic CF3-substituted Csp3chiral center, which is difficult to operate by other means.Kojima Y., Miura M., Hirano K.. Copper-Catalyzed Regio- And Enantioselective Hydroallylation of 1-Trifluoromethylalkenes: Effect of Crown Ether. ACS Catalysis. 11(18), 11663-11670, (2021), 17 September 2021; © 2021 American Chemical Society. https://doi.org/10.1021/acscatal.1c02947

Wide frequency tuning of continuous terahertz wave generated by difference frequency mixing under exciton-excitation conditions in a GaAs/AlAs multiple quantum well

Continuous terahertz wave sources with narrow bandwidth and wide frequency tunability enable high-resolution terahertz spectroscopy and high-speed information communication. In this study, using the optical nonlinearity of excitons as the source of second-order nonlinear polarization, we realize a continuous terahertz electromagnetic wave demonstrating wide frequency tunability from 0.1 to 18 THz without a decrease in intensity due to phonon scattering. Because of excitation of two exciton states in a Ga As / Al As multiple quantum well using two continuous-wave lasers, terahertz waves are emitted as a result of difference-frequency mixing, where the intensity shows a square dependence on the excitation intensity. Using the inhomogeneous width of exciton lines, we achieve wide frequency tunability without phonon effects

Synthesis of gem-difluoroalkenes by copper-catalyzed regioselective hydrodefluorination of 1-trifluoromethylalkenes

A copper-catalyzed regioselective hydrodefluorination of 1-trifluoromethylalkenes with hydrosilanes has been developed. The copper catalysis is compatible with several functional groups, including alkyl chloride, ether, ester, nitrile, and imide moieties, to form the corresponding gem-difluoroalkenes in good yields. Additionally, asymmetric induction is also possible by using the chiral DTBM-SEGPHOS ligand, and gem-difluoroalkene with point chirality at the allylic position is obtained with high enantioselectivity

Pd-catalysed, Ag-assisted C2-H alkenylation of benzophospholes

A palladium-catalysed, silver-assisted regioselective C2-H alkenylation of benzophospholes with terminal alkenes has been developed. The palladium catalysis accommodates styrenes and electron-deficient alkenes including ester, ketone, nitrile, and phosphonate. Thus, this protocol enables the rapid construction of various benzophosphole-vinylene conjugations from the two simple C-H starting substrates. Optical properties of newly synthesized C2-alkenylated benzophospholes are also investigated.Tokura Y., Xu S., Kojima Y., et al. Pd-catalysed, Ag-assisted C2-H alkenylation of benzophospholes. Chemical Communications 58, 12208 (2022); https://doi.org/10.1039/D2CC04942B

Photochemical Characterization of a New Heliorhodopsin from the Gram-Negative Eubacterium Bellilinea caldifistulae (BcHeR) and Comparison with Heliorhodopsin-48C12

Many microorganisms express rhodopsins, pigmented membrane proteins capable of absorbing sunlight and harnessing that energy for important biological functions such as ATP synthesis and phototaxis. Microbial rhodopsins that have been discovered to date are categorized as type-1 rhodopsins. Interestingly, researchers have very recently unveiled a new microbial rhodopsin family named the heliorhodopsins, which are phylogenetically distant from type-1 rhodopsins. Among them, only heliorhodopsin-48C12 (HeR-48C12) from a Gram-positive eubacterium has been photochemically characterized [Pushkarev, A., et al. (2018) Nature 558, 595-599]. In this study, we photochemically characterize a purple-colored heliorhodopsin from Gram-negative eubacterium Bellilinea caldifistulae (BcHeR) as a second example and identify which properties are or are not conserved between BcHeR and HeR-48C12. A series of photochemical measurements revealed several conserved properties between them, including a visible absorption spectrum with a maximum at around 550 nm, the lack of ion-transport activity, and the existence of a second-order O-like intermediate during the photocycle that may activate an unidentified biological function. In contrast, as a property that is not conserved, although HeR-48C12 shows the light adaptation state of retinal, BcHeR showed the same retinal configuration under both dark- and light-adapted conditions. These comparisons of photochemical properties between BcHeR and HeR-48C12 are an important first step toward understanding the nature and functional role of heliorhodopsins

Development of light-induced disruptive liposomes (LiDL) as a photoswitchable carrier for intracellular substance delivery

Light-driven inward proton pump rhodopsin RmXeR was embedded in pH-sensitive liposomes. Substance release from the proteoliposomes was observed following light illumination both in vitro and in cells, indicating the successful production of light-induced disruptive liposomes (LiDL). Thus, LiDL is a photoswitchable carrier utilized for intracellular substance delivery

Bulk Density Effects on Soil Hydrologic and Thermal Characteristics: a Numerical Investigation

Soil bulk density (ρb) is commonly treated as static in studies of land surface dynamics. Magnitudes of errors associated with this assumption are largely unknown. Our objectives were to: i) quantify ρb effects on soil hydrologic and thermal properties, and ii) evaluate effects of ρb on surface energy balance and heat and water transfer. We evaluated six soil properties, volumetric heat capacity, thermal conductivity, soil thermal diffusivity, water retention characteristics, hydraulic conductivity, and vapor diffusivity, over a range of ρb, using a combination of six models. Thermal conductivity, water retention, hydraulic conductivity, and vapor diffusivity were most sensitive to ρb, each changing by fractions greater than the associated fractional changes in ρb. A 10% change in ρb led to 10-11% change in thermal conductivity, 6-11% change in saturated and residual water content, 49-54% change in saturated hydraulic conductivity, and 80% change in vapor diffusivity. Subsequently, three field seasons were simulated with a numerical model (HYDRUS-1D) for a range of ρb values. When ρb increased from 1.2 to 1.5 Mg m-3; 25% increase, soil temperature variation decreased by 2.1°C in shallow layers and increased by 1°C in subsurface layers. Surface water content differed by 0.02 m3 m-3 for various ρb values during drying events but differences mostly disappeared in the subsurface. Matric potential varied by \u3e100 m of water. Surface energy balance showed clear trends with ρb. Latent heat flux decreased 6%, sensible heat flux increased 9%, and magnitude of ground heat flux varied by 18% with a 25% ρb increase). Transient ρb impacted surface conditions and fluxes, and clearly it warrants consideration in field and modeling investigations