Through energy conservation and transformation perspectives, we numerically investigated the physical mechanism of cavitation generation surrounding the two-dimensional NACA 0015 hydrofoil using the ...mass-transfer cavitation model and modified-RNG k-epsilon model. Cavitation generation is triggered by strong turbulent kinetic energy (TKE) with pressure below the saturation pressure. However, cavitation development absorbs TKE as phase-change energy and decreases kinetic energy in near-wall flow fields, thereby increasing pressure according to the energy conservation law. The increased pressure closes the cavity and generates an attached vortex or re-entrant jet, which causes cavitation collapse, conversely decreasing the pressure to the saturation pressure in the leading edge. Simultaneously, the cavitation collapse releases phase-change energy that increases TKE to a maximum so that a new period begins. Cavitation evolution is an interaction between the vapor and liquid flow fields associated with energy conservation and transformation among TKE, pressure, and phase-change energy. Beyond 50% of the chord length, the TKE and pressure-energy in the near-wall flow fields decrease, resulting in the cavitation instability. Within the cavity, the relationship between the local TKE intensity and the volume fraction of water vapor is quantitatively defined as a linear function. Two designs are proposed for the verification of the mechanism and cavitation inhibition, namely, grooves on the hydrofoil surface and bilateral wings in the tail. Grooves do not affect TKE intensity significantly and hence cannot change the cavitating flows. Bilateral tail-wings transfer TKEs from the leading edge to the wake flows and inhibit the cavitation remarkably. The TKE distribution is the dominant mechanism for cavitation generation and stability.
A photoinduced and palladium-catalyzed remote desaturation of O-acyl hydroxamides to unsaturated amides under mild conditions has been achieved. The formation of the alkyl Pd(II) intermediate by the ...recombination of alkyl radical and Pd(I) species is critical to achieve this efficient and selective desaturation of alkanes. This reaction features good site-selectivity, is terminal oxidant-free, and produces moderate to excellent yields for a variety of unsaturated amides. Remarkably, this approach enables late-stage desaturation of complex and biologically important molecules.
The cloud-cavitation shedding mechanism was numerically investigated around the NACA 0015 hydrofoil of α = 7° and σ = 0.7, 0.67 under the identical computational conditions as in Paper I W. Jin, AIP ...Adv. 11, 065028 (2021). We discovered the invisible tail wing and self-inhibition effects of cloud cavitation. As the invisible tail wing of cloud cavitation swings up, the generated re-entrant jet causes cavitation shedding or collapse by the “sweeping and ejection” processes and simultaneously moves away turbulence kinetic energy (TKE) from the near-wall flow fields of the leeward hydrofoil surface, stopping the cavitation generation. In low pressure regions, non-uniform TKE intensity distributions cause different water-vapor volume fractions, resulting in discontinuity of cavitation generation. The attached vortex accompanying an individual cavity is defined, which causes fluctuations and cavitation instability on the bottom of the cavity. The cavity-bubble truncation and stretching are two primary transition mechanisms from the sheet to cloud cavitation. Compared with the invisible tail wing of cloud cavitation, the fixed unilateral wing can more effectively inhibit the cloud shedding because it can redistribute energies to two hydrofoil surfaces and transfer the strong TKE intensity from the minimum to the high-pressure region, which inhibits flow boundary layer separation and achieves non-cavitation control of the hydrofoil. Energy transfer and balance are the most effective mechanisms for inhibiting cloud cavitation. Larger unilateral wing sizes result in weaker TKE intensity along the leeward hydrofoil surface as well as more significant cloud-cavitation inhibition. The TKE intensity in the leading edge of the leeward hydrofoil surface determines the fluid boundary layer separation and cloud-cavitation stability.
In landscape appreciation, what tourists directly perceive is the atmosphere of the landscape. This paper introduces the concept of "Ecological Structure" from Gernot Böhme's theory of atmospheric ...aesthetics into the assessment of landscapes, utilizing atmosphere as a bridge between horticultural ecology, aesthetics, and culture. It examines the relationship between the objective environment and subjective perception. This study conducted a field survey of Xingqing Palace Park and selected the waterside plant landscape that directly reflects the atmosphere of the royal garden as the research object. In the first stage of this study, Scenic Beauty Estimation was used to evaluate the overall beauty of 32 landscape units; in the second stage, the Delphi method and Analytic Hierarchy Process were used to evaluate the ecological structures that affect the garden landscape atmosphere; in the third stage, the two evaluation results of the Kendall's W concord coefficient test Analytic Hierarchy Process and Scenic Beauty Estimation have high consistency, which shows that the atmosphere is great value to the beauty of the landscape. This study provides designers with a means to create a garden atmosphere using ecological structures and provides new ideas for landscape design.
Asymmetric hydrogenation plays an important role in organic synthesis, but that of the challenging substrates such as N‐unprotected imines, enamines, and N‐heteroaromatic compounds (1H‐indoles, ...1H‐pyrroles, pyridines, quinolines, and quinoxalines) has only received increased attention in the past three years. Considering the interaction modes of a Brønsted acid with a Lewis base, Brønsted acids may be used as the ideal activators of CN bonds. This Minireview summarizes the recent advances in transition‐metal‐catalyzed, Brønsted acid activated asymmetric hydrogenation of these challenging substrates, thus offering a promising substrate activation strategy for transformations involving CN bonds.
Protection free: Asymmetric hydrogenation of the title compounds has been realized under transition‐metal catalysis by means of Brønsted acid activators (see scheme). Activation of the Lewis‐basic substrates by protonation or hydrogen bonding with a Brønsted acid leads to highly enantioselective hydrogenation, thus providing efficient and atom‐economical access to the corresponding chiral amines.
One of the European gold standard measurement of vascular ageing, a risk factor for cardiovascular disease, is the carotid-femoral pulse wave velocity (cfPWV), which requires an experienced operator ...to measure pulse waves at two sites. In this work, two machine learning pipelines were proposed to estimate cfPWV from the peripheral pulse wave measured at a single site, the radial pressure wave measured by applanation tonometry. The study populations were the Twins UK cohort containing 3,082 subjects aged from 18 to 110 years, and a database containing 4,374 virtual subjects aged from 25 to 75 years. The first pipeline uses Gaussian process regression to estimate cfPWV from features extracted from the radial pressure wave using pulse wave analysis. The mean difference and upper and lower limits of agreement (LOA) of the estimation on the 924 hold-out test subjects from the Twins UK cohort were 0.2 m/s, and 3.75 m/s & -3.34 m/s, respectively. The second pipeline uses a recurrent neural network (RNN) to estimate cfPWV from the entire radial pressure wave. The mean difference and upper and lower LOA of the estimation on the 924 hold-out test subjects from the Twins UK cohort were 0.05 m/s, and 3.21 m/s & -3.11m/s, respectively. The percentage error of the RNN estimates on the virtual subjects increased by less than 2% when adding 20% of random noise to the pressure waveform. These results show the possibility of assessing the vascular ageing using a single peripheral pulse wave (e.g. the radial pressure wave), instead of cfPWV. The proposed code for the machine learning pipelines is available from the following online depository (https://github.com/WeiweiJin/Estimate-Cardiovascular-Risk-from-Pulse-Wave-Signal).
Maize (
subsp
) was domesticated from its wild ancestor, teosinte (
subsp
). Maize's distinct morphology and adaptation to diverse environments required coordinated changes in various metabolic ...pathways. However, how the metabolome was reshaped since domestication remains poorly understood. Here, we report a comprehensive assessment of divergence in the seedling metabolome between maize and teosinte. In total, 461 metabolites exhibited significant divergence due to selection. Interestingly, teosinte and tropical and temperate maize, representing major stages of maize evolution, targeted distinct sets of metabolites. Alkaloids, terpenoids, and lipids were specifically targeted in the divergence between teosinte and tropical maize, while benzoxazinoids were specifically targeted in the divergence between tropical and temperate maize. To identify genetic factors controlling metabolic divergence, we assayed the seedling metabolome of a large maize-by-teosinte cross population. We show that the recent metabolic divergence between tropical and temperate maize tended to have simpler genetic architecture than the divergence between teosinte and tropical maize. Through integrating transcriptome data, we identified candidate genes contributing to metabolic divergence, many of which were under selection at the nucleotide and transcript levels. Through overexpression or mutant analysis, we verified the roles of
,
, and maize
in the divergence of their related biosynthesis pathways. Our findings not only provide important insights into domestication-associated changes in the metabolism but also highlight the power of combining omics data for trait dissection.
Production of maternal haploids using a conspecific haploid inducer is routine and highly efficient in maize. However, the underlying mechanism of haploid induction (HI) is unclear. We develop a ...method to isolate three nuclei from a pollen grain and four microspores from a tetrad for whole-genome sequencing. A high rate of aneuploidy is observed at the three-nucleus stage (6/22 pollens) rather than at the tetrad stage (1/72 microspores) in one HI line CAU5. Frequent aneuploidy is also observed in another two inducer lines, but not in two regular lines, which implies that HI may be associated with pollen aneuploidy. We further sequence the individual embryos and endosperms of 88 maize kernels crossing between regular and inducer lines. Genome-wide elimination of the CAU5-derived chromosome is identified in eight of 81 embryos. Together, these results suggest that continuous chromosome fragmentation occurring post meiosis in the gametophyte may cause haploidy of the embryo.
Summary
The physical map of the hexaploid wheat chromosome 3B was screened using centromeric DNA probes. A 1.1‐Mb region showing the highest number of positive bacterial artificial chromosome (BAC) ...clones was fully sequenced and annotated, revealing that 96% of the DNA consisted of transposable elements, mainly long terminal repeat (LTR) retrotransposons (88%). Estimation of the insertion time of the transposable elements revealed that CRW (also called Cereba) and Quinta are the youngest elements at the centromeres of common wheat (Triticum spp.) and its diploid ancestors, with Quinta being younger than CRW in both diploid and hexaploid wheats. Chromatin immunoprecipitation experiments revealed that both CRW and Quinta families are targeted by the centromere‐specific histone H3 variant CENH3. Immuno colocalization of retroelements and CENH3 antibody indicated that a higher proportion of Quinta than CRWs was associated with CENH3, although CRWs were more abundant. Long arrays of satellite repeats were also identified in the wheat centromere regions, but they lost the ability to bind with CENH3. In addition to transposons, two functional genes and one pseudogene were identified. The gene density in the centromere appeared to be between three and four times lower than the average gene density of chromosome 3B. Comparisons with related grasses also indicated a loss of microcollinearity in this region. Finally, comparison of centromeric sequences of Aegilops tauschii (DD), Triticum boeoticum (AA) and hexaploid wheat revealed that the centromeres in both the polyploids and diploids are still undergoing dynamic changes, and that the new CRWs and Quintas may have undertaken the core role in kinetochore formation.
Hybrids between divergent populations commonly show hybrid sterility; this reproductive barrier hinders hybrid breeding of the japonica and indica rice (Oryza sativa L.) subspecies. Here we show that ...structural changes and copy number variation at the Sc locus confer japonica-indica hybrid male sterility. The japonica allele, Sc-j, contains a pollen-essential gene encoding a DUF1618-domain protein; the indica allele, Sc-i, contains two or three tandem-duplicated ~ 28-kb segments, each carrying an Sc-j-homolog with a distinct promoter. In Sc-j/Sc-i hybrids, the high-expression of Sc-i in sporophytic cells causes suppression of Sc-j expression in pollen and selective abortion of Sc-j-pollen, leading to transmission ratio distortion. Knocking out one or two of the three Sc-i copies by CRISPR/Cas9 rescues Sc-j expression and male fertility. Our results reveal the gene dosage-dependent allelic suppression as a mechanism of hybrid incompatibility, and provide an effective approach to overcome the reproductive barrier for hybrid breeding.
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