Speaker-wire vortices in stratified anabatic Prandtl slope flows and their secondary instabilities

Stationary longitudinal vortical rolls emerge in katabatic and anabatic Prandtl slope flows due to the dominance of the normal component of the buoyancy force over flow shear. Here, we further identify self pairing of these longitudinal rolls as a unique flow structure. The topology of the counter-rotating vortex pair bears a striking resemblance to speaker-wires and their interaction with each other is a precursor to further destabilization and breakdown of the flow field into smaller structures. On its own, a speaker-wire vortex retains its unique topology without any vortex reconnection or breakup. For a fixed slope angle $\alpha=3^{\circ}$ and at a constant Prandtl number, we analyse the saturated state of speaker-wire vortices and perform a bi-global linear stability analysis based on their stationary state. We establish the existence of both fundamental and subharmonic secondary instabilities depending on the circulation and transverse wavelength of the base state of speaker-wire vortices. The dominance of subharmonic modes relative to the fundamental mode helps explain the relative stability of a single vortex pair compared to the vortex dynamics in presence of two or an even number of pairs.These instability modes are essential for the bending and merging of multiple speaker-wire vortices, which break up and lead to more dynamically unstable states, eventually paving the way for transition towards turbulence. This process is demonstrated via direct numerical simulations with which we are able to track the nonlinear temporal evolution of these instabilities

Impact of stratification mechanisms on turbulent characteristics of stable flows over flat surfaces

Flow over a surface can be stratified by imposing a fixed mean vertical temperature (density) gradient profile throughout or via cooling at the surface. These two distinct mechanisms can act simultaneously as well to establish a stable stratification in a flow. Here, we perform a series of direct numerical simulations of open channel flows to study adaptation of a neutrally stratified turbulent flow under the combined or independent action of the aforementioned stratification mechanisms. When both stratification mechanisms are active, the dimensionless stratification perturbation number enters the picture as an external flow control parameter, in addition to the Reynolds, Froude, and Prandtl numbers. Additionally, we force the fully developed flow with constant mass flow rate. This alternative way of forcing the flow enables us to keep the bulk Reynolds number constant throughout our investigation and avoid complications arising from the acceleration of the bulk flow when a constant pressure gradient approach to drive the flow were to be adopted instead. We demonstrate that significant deviations from the original Monin-Obukhov similarity formulation are possible when both stratification mechanisms are active within an otherwise weakly stable flow with contiguous turbulence, even when the flux Richardson number is well below 0.2.Independent of active stratification mechanisms, the degree of deviation from neutral dimensionless shear as a function of the vertical coordinate emerges as a good measure for the strength of stable stratification for the six different cases investigated in this study. An extended version of the Monin-Obukhov similarity also shows promise.Comment: submitted to the Journal of the Atmospheric Science

Asymmetric nested pitchfork bifurcation in stratified anabatic flows in idealized valleys

We characterize the full structure of steady laminar anabatic flows in a stably stratified V-shaped valley using a dynamical systems approach. Our approach is based on the discovery of a quiescent conduction state from which a unique asymmetric nested pitchfork bifurcation emerges. We characterize the flow via the stratification perturbation parameter, $\Pi_s$, which is a measure of the surface heat flux relative to the strength of the background stable stratification. At very low $\Pi_s$ values, the pure conduction state remains stable. Beyond a threshold $\Pi_s$ value, it bifurcates into asymmetric and symmetric circulation patterns, with the critical value for the asymmetric state being slightly lower than that of the symmetric state. The asymmetric instability manifests as a perfect mirror image of a clockwise and counterclockwise circulation in the valley. The symmetric instability gives rise to an upslope and a downslope convection patterns which are not mirror images of each other. Linear modal analysis and numerical simulations show that these two symmetric states are linearly unstable and will transition to the asymmetric state under the slightest perturbation.Comment: 10 pages, 6 figure

Design and Testing of an Online Fertilizing Amount Detection Device Based on the Moment Balance Principle

Based on the principle of moment balance, this paper designs a fertilizer application amount online detection device, which is mainly composed of two major parts: the fertilizer guide mechanism and the fertilizer metering and discharging mechanism.Under the electromagnetic reversing and buffering of the fertilizer guide mechanism, the fertilizer discharged into the device falls alternately into the storage box of the two metering units of the metering and discharging mechanism. Once the gravity of the fertilizer in the storage box is greater than the suction of the electromagnetic sucker, the fertilizer discharging board is automatically opened for fertilizer discharge, and the metering pulse signal is accumulated once. Meanwhile, the fertilizer guide plate is driven by the electromagnetic commutator to reverse the material, and then another storage box is started for fertilizer storage and metering. In this approach, online detection of fertilizer flow can be realized by repeatedly guiding and reversing and metering the incoming fertilizer. According to the single metering fertilizer quality and the number of metering pulse signals, the fertilization amount can be calculated in real-time.The performance of the device was verified by bench test. The test results indicated that: The established fertilizer application detection model is a quadratic function (R2>0.98), and the verification error was less than 3.73% in the detection of alternating cycle fertilizer discharge; the coefficient of determination (R2) and the root mean square error (RMSE) reached 0.992 and 9.858 respectively, indicating high detection accuracy of the device is

DCQA: Document-Level Chart Question Answering towards Complex Reasoning and Common-Sense Understanding

Visually-situated languages such as charts and plots are omnipresent in real-world documents. These graphical depictions are human-readable and are often analyzed in visually-rich documents to address a variety of questions that necessitate complex reasoning and common-sense responses. Despite the growing number of datasets that aim to answer questions over charts, most only address this task in isolation, without considering the broader context of document-level question answering. Moreover, such datasets lack adequate common-sense reasoning information in their questions. In this work, we introduce a novel task named document-level chart question answering (DCQA). The goal of this task is to conduct document-level question answering, extracting charts or plots in the document via document layout analysis (DLA) first and subsequently performing chart question answering (CQA). The newly developed benchmark dataset comprises 50,010 synthetic documents integrating charts in a wide range of styles (6 styles in contrast to 3 for PlotQA and ChartQA) and includes 699,051 questions that demand a high degree of reasoning ability and common-sense understanding. Besides, we present the development of a potent question-answer generation engine that employs table data, a rich color set, and basic question templates to produce a vast array of reasoning question-answer pairs automatically. Based on DCQA, we devise an OCR-free transformer for document-level chart-oriented understanding, capable of DLA and answering complex reasoning and common-sense questions over charts in an OCR-free manner. Our DCQA dataset is expected to foster research on understanding visualizations in documents, especially for scenarios that require complex reasoning for charts in the visually-rich document. We implement and evaluate a set of baselines, and our proposed method achieves comparable results

The changes of CD4+CD25+/CD4+ proportion in spleen of tumor-bearing BALB/c mice

CD4+CD25+ regulatory T lymphocytes (T(R)) constitute 5–10% of peripheral CD4+ T cells in naive mice and humans, and play an important role in controlling immune responses. Accumulating evidences show that T(R )cells are involved in some physiological processes and pathologic conditions such as autoimmune diseases, transplantation tolerance and cancer, and might be a promising therapeutic target for these diseases. To evaluate the change of CD4+CD25+ T(R )cells in mouse tumor models, CD4+CD25+ subset in peripheral blood and spleen lymphocytes from normal or C26 colon-carcinoma-bearing BABL/c mice were analyzed by flow cytometry using double staining with CD4 and CD25 antibodies. The proportion of CD4+CD25+/CD4+ in spleen lymphocytes was found to be higher than that in peripheral blood lymphocytes in normal mice. No difference was observed in the proportion in peripheral blood lymphocytes between tumor bearing mice and normal mice, while there was a significant increase in the proportion in spleen lymphocytes in tumor bearing mice as compared with normal mice. Moreover, the proportion increased in accordance with the increase in the tumor sizes. The increase in the proportion was due to the decrease in CD4+ in lymphocytes, which is resulted from decreased CD4+CD25- subset in lymphocytes. Our observation suggests the CD4+CD25+/CD4+ proportion in spleen lymphocytes might be a sensitive index to evaluate the T(R )in tumor mouse models, and our results provide some information on strategies of antitumor immunotherapy targeting CD4+CD25+ regulatory T lymphocytes

The effect of experimental warming on leaf functional traits, leaf structure and leaf biochemistry in Arabidopsis thaliana

<p>Abstract</p> <p>Background</p> <p>The leaf is an important plant organ, and how it will respond to future global warming is a question that remains unanswered. The effects of experimental warming on leaf photosynthesis and respiration acclimation has been well studied so far, but relatively little information exists on the structural and biochemical responses to warming. However, such information is very important to better understand the plant responses to global warming. Therefore, we grew <it>Arabidopsis thaliana </it>at the three day/night temperatures of 23/18°C (ambient temperature), 25.5/20.5°C (elevated by 2.5°C) and 28/23°C (elevated by 5°C) to simulate the middle and the upper projected warming expected within the 21st century for this purpose.</p> <p>Results</p> <p>The 28/23°C treatment significantly reduced the life span, total biomass and total weight of seeds compared with the other two temperatures. Among the three temperature regimes, the concentrations of starch, chlorophyll, and proline were the lowest at 28/23°C, whereas the total weight of seeds, concentrations of chlorophyll and proline, stomatal density (SD), stomatal conductance (g_s), net CO₂assimilation rate (A) and transpiration rate (E) were the highest at 25.5/20.5°C. Furthermore, the number of chloroplasts per cell and mitochondrial size were highest at 25.5/20.5°C and lowest at 28/23°C.</p> <p>Conclusions</p> <p>The conditions whereby the temperature was increased by 2.5°C were advantageous for <it>Arabidopsis</it>. However, a rise of 5°C produced negative effects, suggesting that lower levels of warming may benefit plants, especially those which belong to the same functional group as <it>Arabidopsis</it>, whereas higher levels of warming may produce negative affects. In addition, the increase in A under moderately warm conditions may be attributed to the increase in SD, chlorophyll content, and number of chloroplasts. Furthermore, starch accumulation in chloroplasts may be the main factor influencing chloroplast ultrastructure, and elevated temperature regulates plant respiration by probably affecting mitochondrial size. Finally, high SOD and CAT activities may enable plants grown at elevated temperatures to exhibit relatively high tolerance to temperature stress, thus alleviating the harmful effects of superoxide anion radicals and hydrogen peroxide.</p

Effects of Chinese Formula Jueyin Granules on Psoriasis in an Animal Model

Although Traditional Chinese medicine (TCM) is known to be effective for psoriasis patients, the responsible mechanisms still remain poorly understood. In this study, we aimed to evaluate the effect of one formula, named Jueyin granules (JYG) in the mouse model of the vaginal epithelium and tail epidermis. Additionally, we also determined the anti-inflammatory effects of JYG in an imiquimod- (IMQ-) induced psoriasis-like skin mouse model. Our results show that JYG can attenuate the IMQ-induced psoriasis-like inflammation, accompanied with increased epidermal hyperplasia. We also measured estrogenic stage mitosis of vaginal epithelial cells and the formation of granular cell layers in male mouse tails per 100 scales, as well as the tissue nitric oxide (NO) and malondialdehyde (MDA) levels using the ELISA method. The results suggest that JYG significantly inhibited mitosis in mouse vaginal epithelial cells, promoted the formation of the squamous epidermal granular layer in mice tails, and reduced the levels of NO and MDA in an imiquimod-induced psoriasis-like skin mouse model after 14 d (P<0.05). These results demonstrate that JYG might be an effective clinical treatment for psoriasis and the effects may be related to inhibited keratinocytes proliferation, improved parakeratotic epidermal cells, and reduced expression of NO and MDA

A novel index for the study of synergistic effects during the co-processing of coal and biomass

In this study, synergistic interaction between coal and biomass and its intensity were investigated systematically using a low rank coal and its blends with different biomass samples at various blending ratios. The catalytic effects of minerals originated from biomass were also studied. It was found that some of the minerals existing in the ash derived from oat straw catalysed the combustions process and contributed to synergistic interactions. However, for the coal and rice husk blends, minimal improvements were recorded even when the biomass and coal blending ratio was as high as 30 wt%. Biomass volatile also influenced the overall combustion performance of the blends and contributed to synergistic interactions between the two fuels in the blends. Based on these findings, a novel index was formulated to quantify the degree of synergistic interactions. This index was also validated using data extracted from literature and showed satisfactory correlation coefficients. It was found that at a blending ratio of 30 wt% oat straw in the blend, the degree of synergistic interaction between coal and oat straw showed an additional SF value of 0.25 with non-catalytic and catalytic synergistic effect contributing 0.16 (64%) and 0.09 (36%) respectively. This index could be used in the selection of proper biomass and proper blending ratio for co-firing at coal-fired power stations aiming at improving the combustion performance of poor quality coals via enhancing synergistic interactions during co-processing