Investigation of Scalar Mixing in Turbulent Jets and Flames

The scalar-scalar-gradient filtered joint density function (FJDF) and its transport equation for large eddy simulation (LES) of turbulent combustion is studied experimentally. Measurements are made in the fully developed region of an axisymmetric turbulent jet (with jet Reynolds number UjDj/ν = 40000) using an array consisting of three X-wires and three resistance-wire temperature probes. Filtering in the cross-stream and streamwise directions are realized by using the array and by invoking Taylor’s hypothesis, respectively. The FJDF and the terms in the transport equation are analyzed using their means conditional on the filtered scalar and the subgrid-scale (SGS) scalar variance. The FJDF is unimodal when the SGS scalar variance is small compared to its mean value. The scalar gradient depends weakly on the SGS scalar. For large SGS variance the FJDF is bimodal and the gradient depends strongly on the SGS scalar; therefore the often-invoked independence assumption is not valid. The SGS scalar under such a condition contains a diffusion layer structure and the SGS mixing is similar to the early stages of binary mixing. The iso-scalar surface in the diffusion layer has a lower surface-to-volume ratio than those in a well mixed scalar. The conditionally filtered diffusion of the scalar gradient has a S- shaped dependence on the scalar gradient, which is expected to be qualitatively different from that of a reactive scalar under fast chemistry conditions. However, because modeling is performed at a higher level and because the scalar-scalar- gradient FJDF contains the information about the scalar dissipation and the surface-to-volume ratio, the FJDF approach is expected to be more accurate than scalar filtered density function approaches and has the potential to model turbulent combustion over a wide range of Damköhler numbers. An alternative for LES, the self-conditioned fields approach, is studied experimentally using the three-scalar mixing setup. This flow approximates the mixing process in turbulent non-premixed flames as mixing between the center jet scalar and the co-flow air must involve the annulus scalar. The physical-space scalar structures are investigated using the self-conditioned JPDF and the terms in the self-conditioned JPDF transport equation. The self-conditioned JPDF conditioning on the filtered fields (the filtered scalar and SGS variance) is studied first. The results are consistent with the FJDF results with additional spatial structures obtained. The transition of the peaks in the self-conditioned JPDF directly indicates a ramp-cliff structure in the physical space. The self-conditioned JPDF conditioning on the proper orthogonal decomposition (POD) coefficients is also studied. Unlike the locally filtered scalars, POD can best capture scalar structures and is a full-field parameter. The conditioning variables in the self-conditioned JPDF and their values are the same. Therefore the spatial variations of self-conditioned JPDF can be investigated in the entire field. Similar to conditioning on the locally filtered scalar and SGS variance, POD coefficients of scalar field and scalar square field are used as the conditioning variables. Our analysis shows the mixing process depends on the POD coefficient of the scalar square field. For small POD coefficient of the scalar square field, the scalars are well mixed with unimodal self-conditioned JPDF and the initial three-scalar mixing configuration is lost. For large POD coefficient of the scalar square field, the scalars are highly segregated with bimodal self-conditioned JPDF at radial locations near the peak of the variance of the center jet scalar. For the higher velocity ratio cases, the peak value of variance is larger and also the variance value is larger close to the centerline, hence resulting in stronger bimodality and appearance of the bimodal self-conditioned JPDF closer to the jet centerline. For the lower velocity ratios cases, the bimodal range extends further towards the jet edge due to a wider variance profile and larger values of variance. For the self-conditioned diffusion, the streamlines first converge to a manifold in the scalar space and continue along with the manifold to a stagnation point. The manifold is well defined at locations with bimodal self-conditioned JPDF, providing a mixing path between the center jet scalar and co-flow air. The initial three-scalar mixing configuration is maintained. The self-conditioned dissipation result further reveals the scalar structures in the flow. For the bimodal self-conditioned JPDF, the ramp-cliff structure is less steep at location with the strongest bimodality, i.e., smaller dissipation rate of the center jet scalar. The center jet scalar is similar to the mixture fraction in the non-premixed flames. The spatial structures obtained in the self-conditioned approach provides a better understanding of the mixing process in the turbulent reactive flows. Calculation of the self-conditioned field generally requires 2-D images due to its spatial dependence. However, 2-D measurements of mixture fraction in flames remain a challenge due to the limitations of existing measurement techniques, such as weak signals, requiring quenching corrections or limited to certain flames. A new technique that overcomes these limitations is developed to obtain 2-D images in piloted methane/air flames by utilizing the much stronger two-photon laser-induced fluorescence (TPLIF) of iodine atoms. Photodissociation characteristics of iodine are analyzed with 532nm and 266 nm lasers

Vitamin D and suicidality: a Chinese early adolescent cohort and Mendelian randomization study

Abstract Aims Previous cross-sectional and case–control studies have proposed that decreased vitamin D levels are positively correlated with the risk of suicidality in adults. However, limited studies have examined the association between vitamin D and suicidality in adolescents. This study aimed to investigate the relationship between serum vitamin D and suicidality risk among early adolescents. Methods Data were obtained from a Chinese early adolescent cohort. In this cohort, seventh-grade students from a middle school in Anhui Province were invited to voluntarily participate in the baseline assessments and provide peripheral blood samples (in September 2019). The participants were followed up annually (in September 2020 and September 2021). Serum 25-hydroxyvitamin D [25(OH)D] and vitamin D–related single-nucleotide polymorphisms at baseline were measured in November 2021. Traditional observational and Mendelian randomization (MR) analyses were performed to examine the relationship between serum 25(OH)D at baseline and the risk of baseline and incident suicidality (i.e., suicidal ideation [SI], plans and attempts). Results Traditional observational analysis did not reveal a significant linear or non-linear association of serum 25(OH)D concentration with the risks of baseline and 2-year incident suicidality in the total sample (P > .05 for all). Sex-stratified analysis revealed a non-linear association between the 25(OH)D concentration and the risk of baseline SI in women (Poverall = .002; Pnon-linear = .001). Moreover, the risk of baseline SI in the 25(OH) insufficiency group was lower than that in the 25(OH) deficiency group in the total sample (odds ratio [OR] = 0.69, 95% confidence interval [CI] = 0.51–0.92, P = .012). This difference remained significant in women (OR = 0.59, 95% CI = 0.40–0.87, P = .008) but not in men (OR = 0.78, 95% CI = 0.53–1.15, P = .205). Additionally, both linear and non-linear MR analyses did not support the causal effect of serum 25(OH)D concentration on the risk of baseline, 1-year and 2-year incident suicidality (P > .05 for all). Conclusions This study could not confirm the causal effect of vitamin D on suicidality risk among Chinese early adolescents. Future studies must confirm these findings with a large sample size

Anti-embolism devices therapy to improve the ICU mortality rate of patients with acute myocardial infarction and type II diabetes mellitus

BackgroundAnti-Embolism (AE) devices therapy is an additional antithrombotic treatment that is effective in many venous diseases, but the correlations between this medical compression therapy and cardiovascular arterial disease or comorbid diabetes mellitus (DM) are still controversial. In this study we investigated the association between compression therapy and intensive care unit (ICU) mortality in patients with a first acute myocardial infarction (AMI) diagnosis complicated with type II DM.MethodsThis retrospective cohort study analyzed all patients with AMI and type II DM in the Medical Information Mart for Intensive Care-IV database. We extracted the demographics, vital signs, laboratory test results, comorbidities, and scoring system results of patients from the first 24 h after ICU admission. The outcomes of this study were 28-day mortality and ICU mortality. Analyses included Kaplan–Meier survival analysis, Cox proportional-hazards regression, and subgroup analysis.ResultsThe study included 985 eligible patients with AMI and type II DM, of who 293 and 692 were enrolled into the no-AE device therapy and AE device therapy groups, respectively. In the multivariate analysis, compared with no-AE device therapy, AE device therapy was a significant predictor of 28-day mortality (OR = 0.48, 95% CI = 0.24–0.96, P = 0.039) and ICU mortality (OR = 0.50, 95% CI = 0.27–0.90, P = 0.021). In addition to age, gender and coronary artery bypass grafting surgery, there were no significant interactions of AE device therapy and other related risk factors with ICU mortality and 28-day mortality in the subgroup analysis.ConclusionsSimple-AE-device therapy was associated with reduced risks of ICU mortality and 28-day mortality, as well as an improvement in the benefit on in-hospital survival in patients with AMI complicated with type II DM

Monetary incentives and peer referral in promoting secondary distribution of HIV self-testing among men who have sex with men in China: A randomized controlled trial

Background Digital network–based methods may enhance peer distribution of HIV self-testing (HIVST) kits, but interventions that can optimize this approach are needed. We aimed to assess whether monetary incentives and peer referral could improve a secondary distribution program for HIVST among men who have sex with men (MSM) in China. Methods and findings Between October 21, 2019 and September 14, 2020, a 3-arm randomized controlled, single-blinded trial was conducted online among 309 individuals (defined as index participants) who were assigned male at birth, aged 18 years or older, ever had male-to-male sex, willing to order HIVST kits online, and consented to take surveys online. We randomly assigned index participants into one of the 3 arms: (1) standard secondary distribution (control) group (n = 102); (2) secondary distribution with monetary incentives (SD-M) group (n = 103); and (3) secondary distribution with monetary incentives plus peer referral (SD-M-PR) group (n = 104). Index participants in 3 groups were encouraged to order HIVST kits online and distribute to members within their social networks. Members who received kits directly from index participants or through peer referral links from index MSM were defined as alters. Index participants in the 2 intervention groups could receive a fixed incentive ($3 USD) online for the verified test result uploaded to the digital platform by each unique alter. Index participants in the SD-M-PR group could additionally have a personalized peer referral link for alters to order kits online. Both index participants and alters needed to pay a refundable deposit ($15 USD) for ordering a kit. All index participants were assigned an online 3-month follow-up survey after ordering kits. The primary outcomes were the mean number of alters motivated by index participants in each arm and the mean number of newly tested alters motivated by index participants in each arm. These were assessed using zero-inflated negative binomial regression to determine the group differences in the mean number of alters and the mean number of newly tested alters motivated by index participants. Analyses were performed on an intention-to-treat basis. We also conducted an economic evaluation using microcosting from a health provider perspective with a 3-month time horizon. The mean number of unique tested alters motivated by index participants was 0.57 ± 0.96 (mean ± standard deviation [SD]) in the control group, compared with 0.98 ± 1.38 in the SD-M group (mean difference [MD] = 0.41),and 1.78 ± 2.05 in the SD-M-PR group (MD = 1.21). The mean number of newly tested alters motivated by index participants was 0.16 ± 0.39 (mean ± SD) in the control group, compared with 0.41 ± 0.73 in the SD-M group (MD = 0.25) and 0.57 ± 0.91 in the SD-M-PR group (MD = 0.41), respectively. Results indicated that index participants in intervention arms were more likely to motivate unique tested alters (control versus SD-M: incidence rate ratio [IRR = 2.98, 95% CI = 1.82 to 4.89, p-value < 0.001; control versus SD-M-PR: IRR = 3.26, 95% CI = 2.29 to 4.63, p-value < 0.001) and newly tested alters (control versus SD-M: IRR = 4.22, 95% CI = 1.93 to 9.23, p-value < 0.001; control versus SD-M-PR: IRR = 3.49, 95% CI = 1.92 to 6.37, p-value < 0.001) to conduct HIVST. The proportion of newly tested testers among alters was 28% in the control group, 42% in the SD-M group, and 32% in the SD-M-PR group. A total of 18 testers (3 index participants and 15 alters) tested as HIV positive, and the HIV reactive rates for alters were similar between the 3 groups. The total costs were $19,485.97 for 794 testers, including 450 index participants and 344 alter testers. Overall, the average cost per tester was$24.54, and the average cost per alter tester was $56.65. Monetary incentives alone (SD-M group) were more cost-effective than monetary incentives with peer referral (SD-M-PR group) on average in terms of alters tested and newly tested alters, despite SD-M-PR having larger effects. Compared to the control group, the cost for one more alter tester in the SD-M group was$14.90 and $16.61 in the SD-M-PR group. For newly tested alters, the cost of one more alter in the SD-M group was$24.65 and $49.07 in the SD-M-PR group. No study-related adverse events were reported during the study. Limitations include the digital network approach might neglect individuals who lack internet access. Conclusions Monetary incentives alone and the combined intervention of monetary incentives and peer referral can promote the secondary distribution of HIVST among MSM. Monetary incentives can also expand HIV testing by encouraging first-time testing through secondary distribution by MSM. This social network–based digital approach can be expanded to other public health research, especially in the era of the Coronavirus Disease 2019 (COVID-19). Trial registration Chinese Clinical Trial Registry (ChiCTR) ChiCTR190002543

Recognizing human actions as the evolution of pose estimation maps

Most video-based action recognition approaches choose to extract features from the whole video to recognize actions. The cluttered background and non-action motions limit the performances of these methods, since they lack the explicit modeling of human body movements. With recent advances of human pose estimation, this work presents a novel method to recognize human action as the evolution of pose estimation maps. Instead of relying on the inaccurate human poses estimated from videos, we observe that pose estimation maps, the byproduct of pose estimation, preserve richer cues of human body to benefit action recognition. Specifically, the evolution of pose estimation maps can be decomposed as an evolution of heatmaps, e.g., probabilistic maps, and an evolution of estimated 2D human poses, which denote the changes of body shape and body pose, respectively. Considering the sparse property of heatmap, we develop spatial rank pooling to aggregate the evolution of heatmaps as a body shape evolution image. As body shape evolution image does not differentiate body parts, we design body guided sampling to aggregate the evolution of poses as a body pose evolution image. The complementary properties between both types of images are explored by deep convolutional neural networks to predict action label. Experiments on NTU RGB+D, UTD-MHAD and PennAction datasets verify the effectiveness of our method, which outperforms most state-of-the-art methods.Ministry of Education (MOE)Accepted versionThis work is supported in part by Singapore Ministry of Education Academic Research Fund Tier 2 MOE2015-T2-2-114 and start-up funds of University at Buffalo

Mesenchymal Stem Cell-Based Immunomodulation: Properties and Clinical Application

Mesenchymal stem cells (MSCs) are multipotent stem cells characterized by self-renewal, production of clonal cell populations, and multilineage differentiation. They exist in nearly all tissues and play a significant role in tissue repair and regeneration. Additionally, MSCs possess wide immunoregulatory properties via interaction with immune cells in both innate and adaptive immune systems, leading to immunosuppression of various effector functions. Numerous bioactive molecules secreted by MSCs, particularly cytokines, growth factors, and chemokines, exert autocrine/paracrine effects that modulate the physiological processes of MSCs. These invaluable virtues of MSCs provide new insight into potential treatments for tissue damage and inflammation. In particular, their extensive immunosuppressive properties are being explored for promising therapeutic application in immune disorders. Recently, clinical trials for MSC-mediated therapies have rapidly developed for immune-related diseases following reports from preclinical studies declaring their therapeutic safety and efficacy. Though immunotherapy of MSCs remains controversial, these clinical trials pave the way for their widespread therapeutic application in immune-based diseases. In this review, we will summarize and update the latest research findings and clinical trials on MSC-based immunomodulation