对影响学生的体育运动心理原因的探讨

通过对学生体育运动时的心理状况,对学生产生这些心理的因素进行分析和总结,总结出学生在运动中应该怎样调节自己的情绪和心理,从而有利于其身心发展。     

基于非物质文化遗产视角的农村传统体育发展研究

发展农村体育是推动农村文化发展和农村人力资本跃迁的重要途径,但发展农村体育不等于农村体育设施的“硬件化”。本文立足既有的调研资料,采用文献资料法认为农村体育硬件化的思想根源在于原有研究视野比较重视物质层面的研究,而忽视了非物质层面的研究,忽视了农村体育发展的乡土性和非现代性的“土壤”。在进一步解析农村体育的乡土性和现代体育“竞技性”冲突的基础上,认为农民需要才是农村体育发展的基础,充分发挥以非物质文化遗产形式广泛存在的农村民间体育形式是较好实现农村体育发展的重要路径。     

A microfluidic manifold with a single pump system to generate highly mono-disperse alginate beads for cell encapsulation

Cell encapsulation technology is a promising strategy applicable to tissue engineering and cell therapy. Many advanced microencapsulation chips that function via multiple syringe pumps have been developed to generate mono-disperse hydrogel beads encapsulating cells. However, their operation is difficult and only trained microfluidic engineers can use them with dexterity. Hence, we propose a microfluidic manifold system, driven by a single syringe pump, which can enable the setup of automated flow sequences and generate highly mono-disperse alginate beads by minimizing disturbances to the pump pressure. The encapsulation of P19 mouse embryonic carcinoma cells and embryonic body formation are demonstrated to prove the efficiency of the proposed system.     

Label-free density difference amplification-based cell sorting

The selective cell separation is a critical step in fundamental life sciences, translational medicine, biotechnology, and energy harvesting. Conventional cell separation methods are fluorescent activated cell sorting and magnetic-activated cell sorting based on fluorescent probes and magnetic particles on cell surfaces. Label-free cell separation methods such as Raman-activated cell sorting, electro-physiologically activated cell sorting, dielectric-activated cell sorting, or inertial microfluidic cell sorting are, however, limited when separating cells of the same kind or cells with similar sizes and dielectric properties, as well as similar electrophysiological phenotypes. Here we report a label-free density difference amplification-based cell sorting (dDACS) without using any external optical, magnetic, electrical forces, or fluidic activations. The conceptual microfluidic design consists of an inlet, hydraulic jump cavity, and multiple outlets. Incoming particles experience gravity, buoyancy, and drag forces in the separation chamber. The height and distance that each particle can reach in the chamber are different and depend on its density, thus allowing for the separation of particles into multiple outlets. The separation behavior of the particles, based on the ratio of the channel heights of the inlet and chamber and Reynolds number has been systematically studied. Numerical simulation reveals that the difference between the heights of only lighter particles with densities close to that of water increases with increasing the ratio of the channel heights, while decreasing Reynolds number can amplify the difference in the heights between the particles considered irrespective of their densities.Separating specific cells from heterogeneous or homogeneous mixtures has been considered as a key step in a wide variety of applications ranging from biomedicine to energy harvesting. For example, the separation and sorting of rare circulating tumor cells (CTCs) from whole blood has gained significant importance in the potential diagnosis and treatment of metastatic cancers.^1,2 Similarly, malaria detection relies on the collection of infected red blood cells (RBCs) from whole blood.^3,4 In addition, the selective separation of lipid-rich microalgae from homogeneous mixtures of microalgae is a promising technique in biomass conversion.⁵To date, conventional cell separation can be done by labelling cells with biomolecules to induce differences in physical properties. For instance, in a fluorescence-activated cell sorter (FACS), cells to be separated are labelled with antibodies or aptamers with fluorescent molecules, and then sorted by applying an electrical potential.^6,7 Similarly, magnetic-activated cell sorter (MACS) uses magnetic.^8,9 Alternatively, label-free cell separation methods have exploited inherent differences in the physical properties (e.g., size and dielectric properties) of different kinds of cells. For example, acoustophoresis forces particles larger than a desired size to move into the center of a fluidic channel by using ultrasonic standing waves.^10–12 Inertial microfluidics takes advantage of curved fluidic channels in order to amplify the size differences between particles.^13,14 Mass-dependent separation of particles based on gravity and hydrodynamic flow was also reported.¹⁵ Particles with different dielectric properties can also be sorted by dielectrophoresis which induces the movement of polarizable particles.^16–18The disadvantage of these methods, however, is that they require external forces and labels that may cause unexpected damage to biological cells.^19–21 More importantly, most methods are limited in separating cells of the same kind or cells with similar sizes and dielectric properties.Here we designed a novel, label-free density difference amplification-based cell sorting (dDACS) that allows the separation of particles with the same size and charge by exploiting subtle differences in density without the use of external forces. Figure 1(a) illustrates the proposed microfluidic model and its underlying mechanism. The conceptual microfluidic system consists of an inlet, a separation chamber (hydraulic jump cavity), and multiple outlets. Particles entering through the inlet experience gravity (F_G), buoyancy (F_B), and drag (F_D) forces in the separation chamber. The net force acting on the particles can be described as F = F_G + F_B + F_D.(1)As particles enter the separation chamber (i.e., hydraulic jump cavity), F_D acting on the particles changes its direction along the streamline. The particles experience additional forces in the y direction due to large tangential angle (Fig. 1(b)). For lighter particles, whose densities are close to that of the surrounding water, F_D becomes comparable to F_G (i.e., in the y direction), while the net force for heavier particles is less affected by this additional contribution of F_D due to a large F_G. As a result, the height (H) and distance (D) that each particle can travel are different depending on its density. The difference in the maximum height (ΔH_max) between two particles with different density (ρ_p1 and ρ_p2) can be further approximated as ΔHmax∝(vyp0)2(vyf−vyp0), (ρp1−ρp2) ,(2)where v_yp0 and v_yf represent the velocity of particle and fluid along the y direction at the entrance of hydraulic jump cavity, respectively.Open in a separate windowFIG. 1.Schematic illustration of label-free density difference amplification-based cell sorting (dDACS), which exploits differences in the densities (ρ₁ > ρ₂) of particles with similar diameters (d) and charge. (a) The conceptual microfluidic design consists of an inlet, a separation chamber (hydraulic jump cavity), and multiple outlets. Incoming particles experience gravity (F_G), buoyancy (F_B), and drag (F_D) forces in the separation chamber, and depending on their densities, the height (H) and distance (D) that each particle is able to reach will be different, allowing the particles to be separated into multiple outlets. (b) Possible microfluidic channel configurations for density-based separation: Uniform channel height (left), gradual channel expansion (middle), and hydraulic jump cavity with sudden channel expansion (right). The height difference between particles with different densities can be amplified by the sudden channel expansion compared to the other two cases due to the relatively large tangential angle, θ of F_D. (|θ₁|≪ |θ₂|) (see Fig. S1 in the supplementary material²²).In comparison with the other two cases (Fig. 1(b) uniform channel height and gradual channel expansion), the height difference between the particles with different densities can be amplified by the sudden channel expansion in the hydraulic jump cavity due to relatively large tangential angle (see supplementary material²²). Therefore, the particles can be separated through the multiple outlets, depending on their height and distance.In order to analyze the separation behavior of particles in the chamber according to differences in their densities, H and D are systematically investigated. The numerical simulations are performed using a commercial CFD software (CFX 14.0; ANSYS 14.0; ANSYS, Inc.). Particles with the same density may have different trajectories in the separation chamber depending on their inlet positions (Fig. 2(a)). Prior to this investigation, the maximum height (H_max) and distance (D_max) for each particle are compared by examining H and D of 100 identical particles at different inlet positions since the inlet position of particles could be controlled.²⁰ Fig. 2(b) shows H_max and D_max of particles with respect to density at a fixed Reynolds number (Re = 0.1). Note that Reynolds number is defined as Re = ρ_fv_fD_h/μ, where ρ_f, v_f, D_h, μ are density of fluid, velocity of the fluid, hydraulic diameter of a channel, and dynamic viscosity of the fluid, respectively. The hydraulic diameter in the Reynolds number is determined with the inlet channel. Particle densities in the range of 1.1 to 2.0 g/cm³ are chosen with the increase of 0.1 g/cm³. These values are quite reasonable in that the densities of many microorganisms such as microalgae are typically within this range and their densities can be varied by 0.2 g/m³ depending on their cellular context.²³ The lighter particles travel with a higher H_max, and longer D_max. With the separation chamber, the height difference between particles with densities of 1.1 and 1.2 g/cm³ can be amplified by about 10 times as compared to that in a channel without the chamber, judging from the position where the 1.1 g/cm³ particle reaches its H_max.Open in a separate windowFIG. 2.Microfluidic particle separation with respect to Reynolds number (Re). (a) Trajectories in the separation chamber of a hundred particles with the same density starting from inlet positions chosen arbitrarily in order to investigate the effect of the inlet positions on the maxima of the height (H_max) and distance (D_max) prior to further simulation. (b) Representative trajectories of particles having different densities from 1.1 to 2.0 g/cm³. (c) The maximum height (H_max) of each particle with respect to Re. (d) Representative maximum distance (D_max) of each particle at Re = 0.1. (Left) Streamline of fluid and representative trajectories of particles with densities of 1.1 and 2.0 g/cm³ in the separation chamber at Re = 0.1 (right).In Fig. 2(c), the values for H_max of particles with respect to Reynolds number (Re) are presented. Since in our study, the maximum height (H_max) and distance (D_max) for each particle were compared by examining H and D of 100 identical particles that are randomly distributed in the channel (throughout all figures), there is little variation in H_max and D_max between each simulation. However, the standard deviation between each simulation is quite small and can be negligible. The H_max values particles at Re = 0.5 with densities of 1.1 g/cm³ and 1.2 g/cm³ are 2.21 × 10³μm and 2.17 × 10³μm, respectively. The difference between H_max of different particles, ΔH_max, increases with decreasing Re. For example, ΔH_max between particles with densities of 1.1 and 2.0 g/cm³ becomes 0.26 × 10³μm at Re = 1.0, but increases to 1.38 × 10³μm as Re decreases to 0.1. As Re increases (velocity of fluid increases), the relative velocity in the y direction between the fluid and the particle increases resulting in increasing of F_D in the y direction since the velocity of particle in the y direction is very small at the entrance of the separation chamber. Thus, contribution of F_D becomes comparable to the net force in the y direction. As a result, most of the particles even in the case of heavier ones travel quite similarly with the streamline, and ΔH_max subsequently decreases. On the other hand, as Re decreases, the contribution of F_G becomes dominant due to the decrease of F_D in the y direction. Consequently, the particles start to cross downwards streamlines as the density of the particles increases and H_max gradually decreases. In addition, irrespective of their densities, ΔH_max of the particles increases with decreasing Re.Fig. 2(d) shows D_max with respect to the density of the particles (left). Different densities of particles show different trajectories due to the relative contribution of F_D to the net force in the y direction depending on the particle density (right). At Re = 0.1, D_max of particles with densities of 1.1 cm³ and 1.2 g/cm³ are 2.91 × 10⁴μm and 1.43 × 10⁴μm, respectively. As the density of a particle increases, its D_max dramatically decreases. The difference in D_max between particles with densities of 1.1 and 1.2 g/cm³ is 1.48 × 10⁴μm, and 0.0037 × 10⁴μm for particles with densities of 1.9 and 2.0 g/cm³. The effect of F_D is stronger compared to that of F_G on lighter particles. Thus, lighter particles travel quite similarly with the streamline and finally have a large D_max. On the other hand, heavier particles where effect of F_G is stronger compared to that of F_D cross downwards streamlines and finally have a small D_max.Next, in order to investigate the separation behavior of particles with respect to the geometry of the microfluidic device, the effect of the ratio of the height of the separation chamber (h_c) to the inlet (h_i) on H_max is investigated as shown in Fig. ​Fig.3.3. Interestingly, H_max of particles with density of 1.1 g/cm³ increases from 1.93 × 10³μm to 6.48 × 10³μm while that of particles with density of 1.9 g/cm³ slightly changes from 0.70 × 10³μm to 0.73 × 10³μm as h_c/h_i increases from 5 to 20.Open in a separate windowFIG. 3.Microfluidic particle separation with respect to the ratio of the height of the inlet (h_i) to the separation chamber (h_c).This result can be attributed to two effects: (1) the change in the streamline and (2) the relative contribution of drag force to the net force depending on the density. With increasing h_c/h_i, dramatic increase in H_max for lighter particles is because the streamline for the lighter ones experiences more vertical displacement in the separation chamber and the contribution of F_D to the net force acting on the lighter one is more significant (see Fig. S2 in the supplementary material²²).Based on this approach, we propose a microfluidic device for the selective separation of the lightest particle. Fig. 4(a) shows one unit (with three outlets) of the proposed microfluidic device that can be connected in series. The ratio of channel heights (h_c/h_i) is set to 20, and the particle densities are in the range of 1.1 ∼ 1.5 g/m³. Fig. 4(b) shows the representative separation behavior of the particles. A portion of the lightest particles (1.1 g/cm³) is selectively separated into the upper and middle outlets, while remaining light particles together with four other heavier particles with densities in the range of 1.2 to 1.5 g/cm³ leave through the lowest outlet. With a single operation of this unit, 40% of the lightest particles are recovered. In addition, the yield increases with increasing number of cycles (Fig. 4(c)).Open in a separate windowFIG. 4.(a) One unit of the proposed microfluidic device for the selective separation of the lightest particle based on the simulation results. Particles are separated into two outlets based on differences in both the height and distance travelled stemming from differences in density. (b) Representative separation behavior of particles observed in the device. (c) The yield of the lightest particle (1.1 g/cm³) with the proposed microfluidic device according to the number of cycles (i.e., this unit is assumed to be connected in series).In summary, we have demonstrated a label-free microfluidic system for the separation of particles according to subtle differences in their densities without external forces. Our microfluidic design consists simply of an inlet, a separation chamber, and multiple outlets. When entering the separation chamber, the particles experience an additional drag force in the y direction, amplifying the difference in both the height and the distance that the particles with different densities can travel within the chamber. At a fixed Reynolds number, with increasing particle density, H_max decreases monotonously, and D_max decreases dramatically. On the other hand, as Reynolds number increases, the difference between the heights of particles with different densities is attenuated. In addition, the simulation reveals that increasing the ratio of the channel heights increases the difference between the heights of particles only when their densities are close to that of the surrounding water. Based on this approach, a microfluidic device for the separation of the lightest particles has been proposed. We expect that our density-based separation design can be beneficial to the selective separation of specific microorganisms such as lipid-rich microalgae for energy harvesting application.     

从陶行知的教育考试观审视现行高校考试制度改革

现代教育先驱陶行知先生对考试的基本观点以及对考试目的、内容和形式的独到见解为高校考试评价制度的改革提供了启示。社会对创新性人才的需求与高校现行考试制度现状的矛盾与反差,凸显了高校考试制度改革的必要性和紧迫性。因此,在新的教育思想指导下,只有从考试目标、考试内容、考试形式、考试制度等方面全面推进传统的应试教育考试制度改革,才能构建科学合理的高校考试体系。     

THE SOCIOCULTURALLY CONSTRUCTED MULTIVOICED SELF AS A FRAMEWORK FOR CHRISTIAN EDUCATION OF SECOND-GENERATION KOREAN AMERICAN YOUNG ADULTS

This article proposes a new framework for theory and practice of Christian education for second-generation Korean American young adults using the literature of sociocultural constructionism and the multivoiced self. This framework can provide holistic nurture and future trajectories in which to encourage a reflexive, praxis-generating faith. The author calls for a fostering of authentic community in which young adults can engage in self construction and self integration through their narrative.     

学前教育专业学生语言素质提升构想

学前教育专业学生的语言技能是其能力素质中重要的组成部分,事关未来幼儿教育的成败。要提升学前教育专业学生的语言素质,必须从基础抓起,加强实践能力的培养,设计细致全面的讲课内容,构建科学合理的评价体系。     

图书馆馆员专业知识、专业能力提升浅析

图书馆馆员队伍在性别和年龄结构、专业知识和专业能力结构等方面存在较严重的失衡,在服务理念和意识方面存在不足。本文认为,通过多种形式培训、专业进修、举办学术研讨会、参加科研等途径可以达到图书馆馆员专业知识与专业能力提升的目的。     

Korean-Immigrant Parents’ Support of Their American-Born Children’s Development and Maintenance of the Home Language

This study explores Korean-immigrant parents’ language ideologies and practices with respect to their American-born children’s language development. Participants were seven ethnic Korean families composed of immigrant parents and their American-born children, aged between five and seven, in Midwestern America. Interviews in the medium of Korean with the parents, and naturally-occurring family conversations during a meal time, reading time, and play time were audio-recorded and analyzed. The findings suggest that Korean-immigrant parents have a strong desire to pass on their mother tongue to their American-born children, largely derived from their language barrier, and perception of language as an identity marker and socio-economic capital in case they return to Korea for familial obligations and economic opportunities, which represent the context-specific nature of family language policy. Language strategies, such as parental feedback and language-mixing, serve as a catalyst for the implementation of family language policy on the levels of functions, forms, and teaching of the Korean language for Korean-American children’s bilingual development.     

有价值的审察 不应有的隔膜——论余光中对朱自清散文的批评

朱自清散文传世数十年以来,誉之者众,毁之者寡,在历代师生的教学对流中几成经典。然而,学者余光中专门撰文对朱自清的散文作出至为严厉的批评,认为其语言浅白累赘,好用女性意象,伤感滥情。细读余氏文章,他是带着对现代中国散文发展的更高期待所作出的清醒而富有价值的深刻审察,但因两位作家之间存在时空暌隔和个体、个性差异以及由此而来的不同艺术追求,其创作心理和审美追求上的隔膜也是显而易见的。