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

A closed manifold is a fat CW complex

In this paper, we introduce a notion of a fat CW complex to show that a closed manifold is a regular CW complex, while it is not always the case if we discuss about a smooth CW structure, introduced by the first author, instead of a fat CW structure. We also verify that de Rham theorem holds for a fat CW complex and that a regular CW complex is reflexive in the sense of Y.~Karshon, J.~Watts and P.~I-Zemmour. Further, any topological CW complex is topologically homotopy equivalent to a fat CW complex. It implies that there are lots of non-manifold examples supporting de Rham theorem.Comment: 17 page

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

Ligand-Enabled Copper-Catalyzed Regio- and Stereoselective Allylboration of 1-Trifluoromethylalkenes

A copper-catalyzed regio- and stereoselective allylboration of 1-trifluoromethylalkenes with bis(pinacolato)diboron (pinB-Bpin) and allylic chlorides has been developed to form functionalized trifluoromethylated products with high diastereoselectivity. The key to success is the judicious choice of Cs2CO3 base and t-Bu-modified dppe-type ligand, which enables the otherwise challenging high catalyst turnover and suppression of the competing defluorination side reaction from an alkylcopper intermediate. The product derivatization of the resulting Bpin moiety can deliver diverse CF3-containing molecules with high stereochemical fidelity.Kojima Y., Nishii Y., Hirano K.. Ligand-Enabled Copper-Catalyzed Regio- and Stereoselective Allylboration of 1-Trifluoromethylalkenes. Organic Letters. 24(40), 7450-7454, 14 October 2022; https://doi.org/10.1021/acs.orglett.2c03024

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

Proton transfer pathway in anion channelrhodopsin-1

Anion channelrhodopsin from Guillardia theta (GtACR1) has Asp234 (3.2 angstrom) and Glu68 (5.3 angstrom) near the protonated Schiff base. Here, we investigate mutant GtACR1s (e.g., E68Q/D234N) expressed in HEK293 cells. The influence of the acidic residues on the absorption wavelengths was also analyzed using a quantum mechanical/molecular mechanical approach. The calculated protonation pattern indicates that Asp234 is deprotonated and Glu68 is protonated in the original crystal structures. The D234E mutation and the E68Q/D234N mutation shorten and lengthen the measured and calculated absorption wavelengths, respectively, which suggests that Asp234 is deprotonated in the wild-type GtACR1. Molecular dynamics simulations show that upon mutation of deprotonated Asp234 to asparagine, deprotonated Glu68 reorients toward the Schiff base and the calculated absorption wavelength remains unchanged. The formation of the proton transfer pathway via Asp234 toward Glu68 and the disconnection of the anion conducting channel are likely a basis of the gating mechanism

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