A Convex Formulation for Spectral Shrunk Clustering

Spectral clustering is a fundamental technique in the field of data mining and information processing. Most existing spectral clustering algorithms integrate dimensionality reduction into the clustering process assisted by manifold learning in the original space. However, the manifold in reduced-dimensional subspace is likely to exhibit altered properties in contrast with the original space. Thus, applying manifold information obtained from the original space to the clustering process in a low-dimensional subspace is prone to inferior performance. Aiming to address this issue, we propose a novel convex algorithm that mines the manifold structure in the low-dimensional subspace. In addition, our unified learning process makes the manifold learning particularly tailored for the clustering. Compared with other related methods, the proposed algorithm results in more structured clustering result. To validate the efficacy of the proposed algorithm, we perform extensive experiments on several benchmark datasets in comparison with some state-of-the-art clustering approaches. The experimental results demonstrate that the proposed algorithm has quite promising clustering performance.Comment: AAAI201

Effectiveness and influencing factors of online teaching among primary and secondary school teachers in China during the COVID-19: in depth interviews

During COVID-19, online teaching was adopted in many countries and online teaching effectiveness attracted widespread attention. This study used in-depth interviews to explore the factors affecting online teaching efficacy of primary and secondary school teachers from teachers’ perspectives, and used open coding, axial coding, and selective coding to analyze and organize the interview materials. Five thematic elements were finally derived, namely acceptance, professionalism, interactivity, instructional leadership and support, and home-school collaboration. From the teacher’s perspective, acceptance, professionalism, and interactivity are closely related to the individual teacher, while instructional leadership and support, and home-school collaboration are two important external elements. This study explored the influencing factors of teaching effectiveness in different contexts, enriched the theory of teaching effectiveness, and provided practical support for the future development of online teaching

Genetic dissection of plant-virus interactions

Résumé : Pour se propager dans les cellules de son hôte et évader les réponses immunitaires, les virus végétaux ont développé plusieurs stratégies de défense. Ici, nous avons investigué les structures génétiques du Apple stem pitting virus (ASPV). Nous avons aussi étudié la diversité moléculaire des isolats d’ASPV provenant des poires en regardant les séquences des gènes CP et TGB afin de mieux comprendre les mécanismes évolutionnaires utilisés par ASPV. Nos études ont démontré que les mutations, incluant les insertions et les délétions, la sélection purificatrice et la recombinaison furent des facteurs importants dans l’évolution du l’ASPV en Chine et possiblement mondialement. Comme tous les virus végétaux, l’ASPV se défend contre le RNA silencing de l’hôte grâce à un suppresseur de RNA silencing (VSR) et nous avons montré que le VSR de l’ASPV est la protéine de capside (CP) du virus. Nous avons aussi établi que la diversité moléculaire cause non seulement une variété de symptômes chez son hôte, Nicotiana occidentalis. Cependant elle cause aussi de la variabilité antigénique chez différents isolats, ce qui mène à des écarts de réactivité sérologique entre isolats. Les plantes ont développé plusieurs stratégies pour se défendre contre les virus. Ici, nous avons étudié comment la plante Arabidopsis se défend contre le Tobacco rattle virus (TRV) via le RNA silencing. Nous avons constaté que les phénomènes de susceptibilité, récupération et virus induced gene silencing (VIGS) sont des mécanismes séparables. Nous avons démontré que les protéines AGO2 et AGO4 sont nécessaires à la susceptibilité initiale au TRV, tandis qu’AGO1 est importante pour les VIGS, tandis que la récupération est médiée par d’autres acteurs qui n’ont pas encore été identifiés. Nos résultats suggèrent l’existence de complexes distincts ciblant différentes populations d’ARN viral et cellulaire. De plus, nous avons montré que la répression de la traduction est un mécanisme important durant la récupération de la plante suite à une infection virale, et que les complexes de décoiffage et de RNA processing jouent des rôles importants dans la dégradation des ARNs viraux. Finalement, nous avons montré que les plantes ayant une mutation dans le gène DCP2 présentent un niveaux de VIGS accrue, ainsi qu’une augmentation des niveaux d’ARN viral. Puisque DCP2 fait partie des complexes de décoiffage qui se trouvent dans des granules spécialisés nommés processing bodies (PBs), cela suggère que les PBs jouent un rôle important dans l’élimination les virus.Abstract : To live in host cells or to escape from host immunity, plant viruses involved a series of defense strategies. Here we investigated Apple stem pitting virus (ASPV) population structures and molecular diversity of ASPV pear isolates based on its function important gene CP and TGB in China, so as to infer the evolution mechanisms of ASPV. Our study showed that mutations (including insertions or deletions), purifying selection, and recombination were important factors driving ASPV evolutions in China or maybe even in the world. And also ASPV defends against it hosts by encoding a VSR. We also showed that ASPV molecular diversity not only induced different biological properties on its herbaceous host N. occidentails but also resulted in antigenic variation of different ASPV CP isolates, which leaded to differences in serological reactivity among rCPs of different ASPV isolates. Plants have developed a series of mechanisms to defend themselves against viruses. Here we how Arabidopsis defend against. We show that virus susceptibility, recovery, and virus induced gene silencing (VIGS) appear to be separable phenomena, with AGO2 and AGO4 playing important roles in the initial susceptibility to TRV, AGO1 playing an important role in VIGS, and as yet unidentifid players mediating recovery. These results suggest the existence of distinct RNA-induced silencing complexes that target different RNA populations within the cell and over time. Furthermore, we showed that translational repression of viral RNA is likely to play an important role in virus recovery and that decapping function plays an important role in clearing viral RNA from the cell. We also showed that a decapping mutant (DCP2) displayed an increased VIGS and virus RNA accumulation, an important role for PBs in eliminating viral RNA

Examining the Effects of Individual's Polychronicity and Supervisor's Management Style on Creative Self-Efficacy

This research focuses on the area of individuals' creative self-efficacy studies in the workplace. Creative self-efficacy is the self belief of whether one has the capacity to perform the job creatively. In the literature, it has been established as an important factor affecting individual's creative performance. However, studies on the variables which can affect creative self-efficacy are rare. The objectives of this research are to examine whether individual polychronicity can affect creative self-efficacy; whether supervisors' supportive and non-controlling management style can influence creative self-efficacy; and whether organisational environmental factors (organisational structure, interaction with co-workers, risk-taking orientation, and a trusting and caring atmosphere) can impact creative self-efficacy. This research argues that supervisory management style can affect organisational environmental factors. Paper questionnaires and web-based surveys were conducted among 123 post-experienced students from Victoria Management School, School of Government, School of Information Management, and Centre for Continuing Education in Victoria University of Wellington. The research findings suggest that individual polychronicity, supervisory management style, interaction with co-workers and risk-taking orientation are significantly associated with individuals' creative self-efficacy at workplace. As expected, supervisory management style is significantly correlated with organisational structure, interaction with co-workers, risk-taking orientation, and a trusting and caring atmosphere. The results also show that factors like individualistic/collectivistic culture and the appointment of people in the management/non-management position can affect creative self-efficacy. Theoretically, this research has contribution to the creative self-efficacy and creative performance studies, polychronicity studies and "fit" theory between employees and organisational environment. Practically, organisations that want employees to have high creative self-efficacy may recruit polychronic individuals, provide positive creative environment, and encourage supervisors to have supportive and non-controlling management styles

Analysis of Additives in Milk Powders with SPE-HPLC or 2D-HPLC Method

Dairy products are beneficial to human health, especially for formula-fed newborns. According to the regulation of FDA and China national food safety standard, food additives such as benzoic acid, sorbic acid, natamycin, lysozyme, saccharin sodium, and aspartame are not permitted to be added to milk powder. So, the establishment of accurate and convenient methods for the analysis of these food additives in milk powder is critical to people’s health. For the reason of the complex matrix of infant milk powders, we compared six sample pretreatment methods (liquid-liquid extraction, organic precipitation, heavy precipitation, and three different solid-phase extraction (SPE) methods (C18, HLB, MAX)) from recovery, easy operation, time cost, and organic solvent usage aspects. Finally, Poly-Sery HLB cartridge was confirmed as the most appropriate material for its high recovery and time cost merits. We are also introducing two-dimensional liquid chromatography (2DLC) method for the simultaneous determination of five major proteins and seven food additives in milk powders. Optimization of switching mode, choice of columns, mobile phase, and flow speed was discussed. We also compared limit of detection (LOD), recovery, and sample treatment with the results of high-performance liquid chromatography (HPLC). Results show that 2DLC is simpler, faster, and more accurate than the HPLC method

α-Mangostin Induces Apoptosis and Suppresses Differentiation of 3T3-L1 Cells via Inhibiting Fatty Acid Synthase

α-Mangostin, isolated from the hulls of Garcinia mangostana L., was found to have in vitro cytotoxicity against 3T3-L1 cells as well as inhibiting fatty acid synthase (FAS, EC 2.3.1.85). Our studies showed that the cytotoxicity of α-mangostin with IC50 value of 20 µM was incomplicated in apoptotic events including increase of cell membrane permeability, nuclear chromatin condensation and mitochondrial membrane potential (ΔΨm) loss. This cytotoxicity was accompanied by the reduction of FAS activity in cells and could be rescued by 50 µM or 100 µM exogenous palmitic acids, which suggested that the apoptosis of 3T3-L1 preadipocytes induced by α-mangostin was via inhibition of FAS. Futhermore, α-mangostin could suppress intracellular lipid accumulation in the differentiating adipocytes and stimulated lipolysis in mature adipocytes, which was also related to its inhibition of FAS. In addition, 3T3-L1 preadipocytes were more susceptible to the cytotoxic effect of α-mangostin than mature adipocytes. Further studies showed that α-mangostin inhibited FAS probably by stronger action on the ketoacyl synthase domain and weaker action on the acetyl/malonyl transferase domain. These findings suggested that α-mangostin might be useful for preventing or treating obesity

Long-Term Exposure to High Altitude Affects Voluntary Spatial Attention at Early and Late Processing Stages

The neurocognitive basis of the effect of long-term high altitude exposure on voluntary attention is unclear. Using event related potentials, the high altitude group (people born in low altitude but who had lived at high altitude for 3 years) and the low altitude group (living in low altitude only) were investigated using a voluntary spatial attention discrimination task under high and low perceptual load conditions. The high altitude group responded slower than the low altitude group, while bilateral N1 activity was found only in the high altitude group. The P3 amplitude was smaller in the high altitude compared to the low altitude group only under high perceptual load. These results suggest that long-term exposure to high altitudes causes hemispheric compensation during discrimination processes at early processing stages and reduces attentional resources at late processing stages. In addition, the effect of altitude during the late stage is affected by perceptual load

Effect of Carbon Particles on Aerodynamic Performance of a Radial Inflow Turbine in Closed Brayton Cycle

For the closed Brayton cycle using carbon heaters, working fluid contains some solid particles generally. These impurities will enter turbine along with gas, influence aerodynamic performance, and even make turbine work under off-design condition. Therefore, it is necessary to study the influence of particles on turbine. In this paper, a turbine using argon with carbon particles as working fluid is investigated. Particles are assumed to have no volume and are evenly divided into ten different sizes. Based on the discrete phase model (DPM), CFD method is adopted to simulate turbine flow field, and influences of carbon particle mass fraction, particle diameter and incident velocity on aerodynamic performance are analyzed. The results indicate that as particle mass fraction increases, total pressure, static pressure and Mach number decrease significantly, isentropic efficiency decreases slightly, while temperature increases. Collision and rebound of particles in flow field are more intense with a larger particle diameter, but flow field is less influenced under the same mass fraction due to decrease of particle number. Incident velocity has little effect on aerodynamic performance; however, with increase of incident velocity, diameter of particles on blade surface is larger and collision of particles is more intense especially in nozzle. These results will help understand the influence of solid particles on turbines