A generic hierarchical model of organic matter degradation and preservation in aquatic systems

10 pagesOrganic matter degradation and preservation are crucial components of Earth’s carbon cycle. Empirical and phenomenological models usually contain parameters determined by site-specific data and focus on different aspects of the decay and accretion characteristics. To investigate more fundamental mechanisms, this study suggests a hierarchical model that links microscopic physical quantities to macroscopic degradation and preservation patterns. This mechanistic model predicts several commonly observed phenomena, including the lognormal distribution of degradation rate constants, the recalcitrance-dependent sensitivity to temperature, the dependence of a heterogeneous organic-matter system’s persistence on its complexity, logarithmic-time decay, and power-law degradation behavior. The theoretical predictions of this model are consistent with the observational data from marine and lake environments. This hierarchical model may provide a step towards a fundamental theory of organic matter degradation and preservation in aquatic and other ecosystems

Dynamics of Quadratic Families

Honors Project Paper, Department of Mathematics and Statistics, University of Minnesota Duluth, July 8, 2015This paper is based on the readings in the author's independent study on "advanced dynamical systems", and the author's mathematics honors project. It is a combination of the survey of some classical papers and the results from the research project. In the review part, none of the results are new and even less of them are due to the author; in the research part, we mainly focus the dynamics of the quadratic family along the real line. More specifically, in this paper we review and summarize the dynamics of one- and two- dimensional real quadratic maps from both topological and statistical viewpoints, and provide global pictures for their dynamics. Meanwhile, we briefly review the main results of the dynamics of one-dimensional complex quadratic maps under holomorphic singular perturbations, and provide recent research results about its dynamics under a nonholomorphic singular perturbation.Department of Mathematics and Statistics, University of Minnesota Dulut

Associations of lipids and lipid-lowering drugs with risk of stroke: a Mendelian randomization study

BackgroundStroke is a leading cause of death worldwide, but it is unclear whether circulating lipids and lipid-lowering drugs are causally associated with stroke and its subtypes.MethodsWe used two-sample Mendelian randomization (MR) to examine the effects of blood lipids and lipid-lowering drugs on stroke and its subtypes.ResultsThe inverse variance weighted Mendelian randomization (IVW-MR) revealed the low-density lipoprotein cholesterol (LDL-C) (OR, 1.46; 95% CI, 1.17–1.83; p = 0.0008) and apolipoprotein B (apoB) (OR, 1.46; 95% CI, 1.21–1.77; p = 0.0001) was positively correlated with large artery stroke (LAS). However, no causal effect was found in LDL-C and apoB on LAS risk when we conducted mvMR. The IVW-MR also found a suggestive evidence that decreased LDL-C levels mediated by the PCSK9 (proprotein convertase subtilisin-kexin type 9) gene were associated with a reduced risk of any stroke (AS) (OR, 1.31; 95% CI, 1.13–1.52; p = 0.0003), any ischemic stroke (AIS) (OR, 1.29; 95% CI, 1.10–1.51; p = 0.001), and LAS (OR, 1.73; 95% CI, 1.15–2.59; p = 0.008), while NPC1L1 (Niemann-Pick C1-like protein)-mediated LDL-C levels were associated with a higher risk of small vessel stroke (SVS) (OR, 6.10; 95% CI, 2.13–17.43; p = 0.0008). The SMR revealed that expression of PCSK9 was associated with risk of AS (OR, 1.15; 95% CI, 1.03–1.28; p = 0.01), AIS (OR, 1.02; 95% CI, 1.14–1.29; p = 0.03), cardioembolic stroke (CES) (OR, 1.28; 95% CI, 1.01–1.61; p = 0.04). And, a significant association was found between the expression of NPC1L1 and the risk of SVS (OR, 1.15; 95% CI, 1.00–1.32; p = 0.04).ConclusionWe cautiously find that LDL-C and apoB was positively correlated with LAS. These findings suggest that the reducing LDL-C levels could be an effective prevention strategy for reducing the risk of stroke

Treatment of avulsion fracture of posterior cruciate ligament tibial insertion by minimally invasive approach in posterior medial knee

ObjectiveThe study aims to explore the feasibility and clinical effect of posterior minimally invasive treatment of cruciate ligament tibial avulsion fracture.MethodsPosterior knee minimally invasive approach was used to treat avulsion fracture of posterior cruciate ligament (PCL) tibia in 15 males and 11 females. The length of the incision, intraoperative blood loss, operation time, postoperative hospital stay, residual relaxation, and fracture healing time were analyzed to evaluate the curative effect, learning curve, and advantages of the new technology. Neurovascular complications were recorded. During the postoperative follow-up, the International Knee Joint Documentation Committee (IKDC), Lysholm knee joint score, and knee joint range of motion were recorded to evaluate the function.ResultsAll 26 patients were followed up for 18–24 months, with an average of 24.42 ± 5.00 months. The incision length was 3–6 cm, with an average of 4.04 ± 0.82 cm. The intraoperative blood loss was about 45–60 ml, with an average of 48.85 ± 5.88 ml. The operation time was 39–64 min, with an average of 52.46 ± 7.64 min. The postoperative hospital stay was 2–5 days, with an average of 2.73 ± 0.87 days. All incisions healed grade I without neurovascular injury. All fractures healed well with an average healing time of 9.46 ± 1.33 weeks (range, 8–12 weeks). The Lysholm score of the affected knee was 89–98 (mean, 94.12 ± 2.49) at 12-month follow-up. The IKDC score was 87–95 with an average of 91.85 ± 2.19, and the knee range of motion was 129–148° with an average of 137.08 ± 5.59°. The residual relaxation was 1–3 mm, with an average of 1.46 ± 0.65 mm.ConclusionThis minimally invasive method provides sufficient exposure for internal fixation of PCL tibial avulsion fractures without the surgical complications associated with traditional open surgical methods. The process is safe, less invasive, and does not require a long learning curve

Inhibition mechanism of SARS-CoV-2 main protease by ebselen and its derivatives

The SARS-CoV-2 pandemic has triggered global efforts to develop therapeutics. The main protease of SARS-CoV-2 (M(pro)), critical for viral replication, is a key target for therapeutic development. An organoselenium drug called ebselen has been demonstrated to have potent M(pro) inhibition and antiviral activity. We have examined the binding modes of ebselen and its derivative in M(pro) via high resolution co-crystallography and investigated their chemical reactivity via mass spectrometry. Stronger M(pro) inhibition than ebselen and potent ability to rescue infected cells were observed for a number of derivatives. A free selenium atom bound with cysteine of catalytic dyad has been revealed in crystallographic structures of M(pro) with ebselen and MR6-31-2 suggesting hydrolysis of the enzyme bound organoselenium covalent adduct and formation of a phenolic by-product, confirmed by mass spectrometry. The target engagement with selenation mechanism of inhibition suggests wider therapeutic applications of these compounds against SARS-CoV-2 and other zoonotic beta-corona viruses

The Ninth Visual Object Tracking VOT2021 Challenge Results

acceptedVersionPeer reviewe

Scaling laws in the evolutionary processes of marine animals over the last 540 million years

Scaling laws are ubiquitous in modern biological systems. However, whether such patterns existed in deep-time biological systems is less investigated; the best-known example is the scaling law between the frequency and size of extinction events. Here, I show that the variation rates of biodiversity, origination intensity, extinction intensity, and body size of marine animals during the last 540 million years exhibited scaling laws. I then derive a general form of these scaling laws from a conceptual model with some principles of thermodynamics and assumptions about the global biological system. The results in this study suggest that the scaling laws systematically appearing in the biological metrics characterizing different aspects of the evolutionary processes of marine animals likely belong to the same universality class and probably derived from a set of common factors