275 research outputs found

    Confidence Bands for ROC Curves With Serially Dependent Data

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    <p>We propose serial correlation-robust asymptotic confidence bands for the receiver operating characteristic (ROC) curve and its functional, viz., the area under ROC curve (AUC), estimated by quasi-maximum likelihood in the binormal model. Our simulation experiments confirm that this new method performs fairly well in finite samples, and confers an additional measure of robustness to nonnormality. The conventional procedure is found to be markedly undersized in terms of yielding empirical coverage probabilities lower than the nominal level, especially when the serial correlation is strong. An example from macroeconomic forecasting demonstrates the importance of accounting for serial correlation when the probability forecasts for real GDP declines are evaluated using ROC. Supplementary materials for this article are available online.</p

    Table1_Noisy condition and three-point shot performance in skilled basketball players: the limited effect of self-talk.xlsx

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    In modern basketball, the three-point shot plays an important tactical role. Basketball players often face the distraction from audience and opponents, necessitating psychological skill to maintain their performance. The study examined the effects of self-talk interventions on the three-point shot performance under quiet and noisy conditions. It involved 42 national second-level basketball players and used a 2 (Condition: quiet condition, noisy condition) × 3 (Intervention: control group, motivational self-talk, instructional self-talk) mixed design to investigate the performance of the static and dynamic three-point shots tasks. The results revealed that the static three-point shot score was significantly lower in noisy condition compared to quiet condition (p = 0.016), while the main effect of Intervention and the interaction effect of Condition × Intervention were not significant. Post-hoc analysis indicated that only the control group showed significantly lower scores in the noisy condition (p = 0.043). For the dynamic three-point shots performance, there were no significant main effects of Intervention or Condition, nor any significant interaction effect between Condition and Intervention. In conclusion, noise distraction negatively affects the static three-point shots task, and although self-talk interventions can mitigate such negative effects, their effectiveness is limited for dynamic three-point shots task with high physical demands.</p

    Getting the ROC into Sync

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    Judging the conformity of binary events in macroeconomics and finance has often been done with indices that measure synchronization. In recent years, the use of Receiver Operating Characteristic (ROC) curve has become popular for this task. This paper shows that the ROC and synchronization approaches are closely related, and each can be derived from a decision-making framework. Furthermore, the resulting global measures of the degree of conformity can be identified and estimated using the standard method of moments estimators. The impact of serial dependence in the underlying series upon inferences can therefore be allowed for. Such serial correlation is common in macroeconomic and financial data.</p

    Nitrogen and Fluorine-Codoped Porous Carbons as Efficient Metal-Free Electrocatalysts for Oxygen Reduction Reaction in Fuel Cells

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    The severe dependence of oxygen reduction reaction (ORR) in fuel cells on platinum (Pt)-based catalysts greatly limits the process of their commercialization. Therefore, developing cost-reasonable non-precious-metal catalysts to replace Pt-based catalysts for ORR is an urgent task. Here, we use the composite of inexpensive polyaniline and superfine polytetrafluoroethylene powder as precursor to synthesize a metal-free N,F-codoped porous carbon catalyst (N,F-Carbon). Results indicate that the N,F-Carbon catalyst obtained at the optimized temperature 1000 °C exhibits almost the same onset (0.97 V vs RHE) and half-wave potential (0.84 V vs RHE) and better durability and higher crossover resistance in alkaline medium compared to commercial 20% Pt/C, which is attributed to the good dispersion of fluorine and nitrogen atoms in the carbon matrix, high specific surface area, and the synergistic effects of fluorine and nitrogen on the polarization of adjacent carbon atoms. This work provides a new strategy for in situ synthesis of N,F-codoped porous carbon as highly efficient metal-free electrocatalyst for ORR in fuel cells

    HNO Binding in a Heme Protein: Structures, Spectroscopic Properties, and Stabilities

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    HNO can interact with numerous heme proteins, but atomic level structures are largely unknown. In this work, various structural models for the first stable HNO heme protein complex, MbHNO (Mb, myoglobin), were examined by quantum chemical calculations. This investigation led to the discovery of two novel structural models that can excellently reproduce numerous experimental spectroscopic properties. They are also the first atomic level structures that can account for the experimentally observed high stabilities. These two models involve two distal His conformations as reported previously for MbCNR and MbNO. However, a unique dual hydrogen bonding feature of the HNO binding was not reported before in heme protein complexes with other small molecules such as CO, NO, and O<sub>2</sub>. These results shall facilitate investigations of HNO bindings in other heme proteins

    Density Functional Kinetic Monte Carlo Simulation of Water–Gas Shift Reaction on Cu/ZnO

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    We describe a density functional theory based kinetic Monte Carlo study of the water–gas shift (WGS) reaction catalyzed by Cu nanoparticles supported on a ZnO surface. DFT calculations were performed to obtain the energetics of the relevant atomistic processes. Subsequently, the DFT results were employed as an intrinsic database in kinetic Monte Carlo simulations that account for the spatial distribution, fluctuations, and evolution of chemical species under steady-state conditions. Our simulations show that, in agreement with experiments, the H<sub>2</sub> and CO<sub>2</sub> production rates strongly depend on the size and structure of the Cu nanoparticles, which are modeled by single-layer nano islands in the present work. The WGS activity varies linearly with the total number of edge sites of Cu nano islands. In addition, examination of different elementary processes has suggested competition between the carboxyl and the redox mechanisms, both of which contribute significantly to the WGS reactivity. Our results have also indicated that both edge sites and terrace sites are active and contribute to the observed H<sub>2</sub> and CO<sub>2</sub> productivity

    3D Printing-Assisted Supramalleolar Osteotomy for Ankle Osteoarthritis

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    Ankle osteoarthritis (OA) is an important factor that causes pain and dysfunction after ankle joint movement. In early and mid-term ankle OA, supramalleolar osteotomy can delay the progression of disease and maximize the preservation of ankle joint function. Three-dimensional printing (3DP) technology has brought us new hope, which can improve the accuracy of osteotomy, reduce the number of fluoroscopy, reduce the amount of blood loss, and achieve personalized and accurate treatment. The data of 16 patients with ankle OA in our center from January 2003 to July 2020 were retrospectively analyzed and divided into the 3DP group and the traditional group according to different treatment methods. Seven patients in the 3DP group used the 3DP personalized osteotomy guide; nine patients were treated by traditional osteotomy. All patients were followed up for 13.9 ± 3.1 months after the operation. The operation time in the 3DP group was 126.4 ± 11.1 min, its intraoperative blood loss was 85.7 ± 24.1 mL, and its intraoperative fluoroscopy time was 2.4 ± 0.2, which were all significantly less than 167.3 ± 12.2 min, 158.3 ± 22.8 mL, and 5.8 ± 0.2 times in the traditional group (P < 0.05), respectively. In the 3DP group, its postoperative tibial anterior surface (TAS) angle was 90.6 ± 0.3° and the talar tilt (TT) angle was 2.2 ± 0.6°, which were all significantly different compared with its preoperative data of 83.4 ± 1.7 and 8.0 ± 1.5°, respectively (P < 0.05). Compared with traditional osteotomy, 3DP-assisted supramalleolar osteotomy for varus and valgus ankle OA can significantly shorten the operation time and reduce intraoperative bleeding and the frequency of intraoperative fluoroscopy; personalized 3DP osteotomy guides and models can assist in the accurate correction of varus deformity during operation, restore the lower limb alignment, and improve the biomechanical status of the lower limbs. In addition, the 3DP of porous tantalum has good histocompatibility, and its interface structure and porosity are more conducive to bone ingrowth. For complex bone defects and revision prostheses, matching implants can be printed individually, which could realize the personalized precise treatment

    Improved antimelanogenesis and antioxidant effects of polysaccharide from Cuscuta chinensis Lam seeds after enzymatic hydrolysis

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    <div><p>Cuscuta chinensis polysaccharide (CPS) was extracted using hot water and enzymatically hydrolyzed C. chinensis polysaccharide (ECPS) was produced by the mannase enzymatic hydrolysis process. The purpose of this research was to investigate the antimelanogenic activity of ECPS and CPS in B16F10 melanoma cells. The in vitro antioxidant activity was assessed by their ferric iron reducing power and DPPH free radical scavenging activities. The molecular mass distribution of polysaccharides was determined using SEC-MALLS-RI. CPS was successfully enzymatically degraded using mannase and the weighted average molecular weights of CPS and ECPS were 434.6 kDa and 211.7 kDa. The results of biological activity assays suggested that the enzymatically hydrolyzed polysaccharide had superior antimelanogenic activity and antioxidant effect than the original polysaccharide. ECPS exhibited antimelanogenic activity by down-regulating the expression of tyrosinase, MITF, and TRP-1 without cytotoxic effects in B16F10 melanoma cells. In conclusion, ECPS have the potential to become a skin whitening product.</p></div

    Characteristics of all subjects.

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    <p>The data are presented as mean±S.E.</p><p>*<i>P</i> < 0.05</p><p>***<i>P</i> < 0.001 versus normal healthy controls.</p><p>BMI: body mass index; HbA1c: hemoglobin A1c; TG: triglyceride; Cr: creatinine; BUN: blood urea nitrogen; ACR, albumin to creatinine ratio; H-CRP: high-sensitive C-reactive protein. ACEI: angiotensin-converting enzyme inhibitor; ARB: angiotensin Ⅱ receptor antagonist</p><p>Characteristics of all subjects.</p

    Mechanism of Carbon Monoxide Induced N–N Bond Cleavage of Nitrous Oxide Mediated by Molybdenum Complexes: A DFT Study

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    The detailed mechanism of CO-induced N–N bond cleavage of N<sub>2</sub>O mediated by molybdenum complexes leading to the nitrosyl isocyanate complex has been investigated via density functional theory (DFT) calculations at the B3LYP level. On the basis of the calculations, we proposed a new reaction mechanism of CO-induced N–N bond cleavage of N<sub>2</sub>O with an overall free energy barrier of 23.6 kcal/mol, significantly lower than that of the reaction mechanism (42.2 kcal/mol) proposed by Sita et al. The calculations also indicated that CO-induced N–N bond cleavage of N<sub>2</sub>O is competitive with oxygen atom transfer (OAT) to carbon monoxide due to the comparable free energy barriers. The metal-bound carbonyl complex obtained from OAT can be recycled to give more nitrosyl isocyanate complexes. In addition, we demonstrated why the analogous tungsten complex cannot give the nitrosyl isocyanate complex via CO-induced N–N bond cleavage of N<sub>2</sub>O. The calculations are consistent with experimental observations
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