Fractions as Numbers and Extensions of the Number System: Developing Activities Based on Research

Existing studies have shown fractions present significant challenges for K-8 students and pre-service teachers. They suggest that students may fail to see fractions as numbers and have difficulty moving beyond the part-whole realization, and thus they often think of fractions as objects disconnected from the number system. To address this issue, the current study proposes several activities that can be used in mathematics courses for pre-service elementary/secondary teachers or students to help the mrecognize fractions as numbers with the same visual representations as whole numbers (e.g., the number line) and on which the same kinds of operations can be used. Along with a description of the activities,the paper also provides observations about what happened when we gave the activities to a group of 28 prospective elementary teachers, highlighting evidence of their understanding of fractions as numbers

Enzymatically active microspheres for self-propelled colloidal engines

Micro- and nano-motors have attracted numerous attentions from various scientific areas due to their potential applications. Most studies on self-propelled colloidal engines have exploited catalytic decomposition of hydrogen peroxide to drive the motor. Since the hydrogen peroxide is caustic, it is not suitable to use in biological applications, encouraging people to develop “greener” fuels. The aim of this research is to study a new transduction mechanism for self-propulsion not tied to hydrogen peroxide, and which can in particular be used with biological molecules as fuels. In this study, we focus on making particles with enzymatic activity which can effectively decompose biomolecules for self-propulsion. We select elastase as a catalyst and coat it on the surface of polystyrene (PS) particles, and use SucAla3-pNA as a substrate to examine the activity of the elastase-coated particles. We exploit biotin-streptavidin chemistry to couple the elastase on the surface of the PS particles. We confirm that SucAla3-pNA can be effectively decomposed by elastase and elastase-coated particles using spectrophotometric measurement. The results demonstrate that the elastase-coated PS particles are catalytically active, showing great potential to be used in biologically-friendly system

Recent Trends in Water Quality Management in Korea: An Introduction to Korea’s Total Maximum Daily Load (TMDL) Program

In 1999, the Korean Ministry of Environment adopted the Total Maximum Daily Load (TMDL) management system to resolve the problems of traditional water quality management policies represented by concentration regulations, land-use regulations, and environmental treatment facilities. A special act established in 1999 recommends the autonomous implementation of the program in the Han River watershed. Also, a series of special acts established in 2002 require the compulsory implementation for three other major river watersheds. Accordingly, as of 2007, four major river watersheds are implementing the first phase of the TMDLs as well as preparing for a second phase set to begin in 2011. Although the introduction of the TMDL program can be evaluated as a paradigm shift in water quality management, the current system addresses issues that originated specifically in Korea’s political and economic context

DPM: A Novel Training Method for Physics-Informed Neural Networks in Extrapolation

We present a method for learning dynamics of complex physical processes described by time-dependent nonlinear partial differential equations (PDEs). Our particular interest lies in extrapolating solutions in time beyond the range of temporal domain used in training. Our choice for a baseline method is physics-informed neural network (PINN) [Raissi et al., J. Comput. Phys., 378:686--707, 2019] because the method parameterizes not only the solutions but also the equations that describe the dynamics of physical processes. We demonstrate that PINN performs poorly on extrapolation tasks in many benchmark problems. To address this, we propose a novel method for better training PINN and demonstrate that our newly enhanced PINNs can accurately extrapolate solutions in time. Our method shows up to 72% smaller errors than existing methods in terms of the standard L2-norm metric.Comment: Accepted by AAAI 202

RIDESOURCING IN MANUFACTURING SITES: A FRAMEWORK AND CASE STUDY

With the recent innovations in transportation, ridesourcing services have been proliferating in many countries. There are increasing attempts to apply ridesourcing in the corporate context. Manufacturing companies now install the Industrial Internet of Things (IIOT) sensors to vehicles to obtain real-time data on the movement of goods and materials. Despite the massive amount of data accumulated, little attention has been paid to exploiting the data for vehicle fleet management (FM). This paper proposes an analytical framework to solve two FM problems: how to group organizational units for vehicle sharing and where to deploy the groups. The framework is then validated with a case study of a Korean shipbuilder. The results indicate that grouping departments with similar spatial patterns can reduce the current fleet

Left dominance of EEG abnormalities in patients with transient global amnesia

AbstractPurposeTransient global amnesia (TGA) is a syndrome of unknown etiology. Electroencephalographic (EEG) abnormalities in TGA have been reported previously. We analyzed the frequency and characteristics of EEG abnormalities in patients with TGA.MethodsWe collected EEGs of patients with a clinical diagnosis of TGA who had visited the emergency room or the outpatient clinic over a period of 8 years and compared clinical and demographic characteristics of the patients with normal EEGs with those with abnormal EEGs.ResultsEEG abnormalities were found in 35 (22.9%) out of 153 patients and epileptiform discharges were seen in 26 (74.3%) out of these 35 patients. Spikes or sharp waves were detected on the left side only (48.6%) or on both sides (25.7%), but none of the patients showed spikes or sharp waves on right side only. In six patients the EEG had normalized within three months of presentation, in ten within six months, and in twelve by one year. The EEG remained abnormal in eleven out of the 23 patients one year after presentation.ConclusionIn this largest consecutive EEG study at one center, the proportion of patients with TGA in whom epileptiform discharges were demonstrated within days of the episode of TGA was significantly higher than in the previous literature. EEG abnormalities such as spikes or sharp waves spontaneously disappeared in almost half of cases over one-year of follow-up. There was a clear left dominance of EEG abnormalities in patients with TGA

What Is It to Be Mentally Healthy from the North Korean Refugees' Perspective?:Qualitative Research on the Changes in Mental Health Awareness among the North Korean Refugees

Objective: We investigated how mental health awareness among North Korean refugees transformed depending on temporal-spatial context changes. Methods: In 2013, we conducted interviews with 10 refugees (eight women) who had been in South Korea for over a year and performed a qualitative analysis of the change in mental health awareness in the differences between living in North Korea, escape (a related period of forced sojourn in a third country), and settlement in South Korea. Results: We classified 39 concepts into five main categories. The first two categories (while living in North Korea) were "a mindset for the system, but not for individual mental health" and "being confined in a social environment that was indifferent to mental health." A third category appeared during escape: "focusing on survival amid continuity of intense suffering." The final two categories appeared when settling in South Korea: "recognition of mental health amid cultural shock" and "introspection and sorting oneself out". Conclusion: This qualitative study enabled a better multi-dimensional understanding of the social and cultural aspects involved in improving mental health awareness among North Korean refugees in South Korea. It is desirable to integrate mental health as a part of daily life and to expand training for North Korean settlers

Resveratrol induces autophagy by directly inhibiting mTOR through ATP competition

Resveratrol (RSV) is a natural polyphenol that has a beneficial effect on health, and resveratrol-induced autophagy has been suggested to be a key process in mediating many beneficial effects of resveratrol, such as reduction of inflammation and induction of cancer cell death. Although various resveratrol targets have been suggested, the molecule that mediates resveratrol-induced autophagy remains unknown. Here, we demonstrate that resveratrol induces autophagy by directly inhibiting the mTOR-ULK1 pathway. We found that inhibition of mTOR activity and presence of ULK1 are required for autophagy induction by resveratrol. In line with this mTOR dependency, we found that resveratrol suppresses the viability of MCF7 cells but not of SW620 cells, which are mTOR inhibitor sensitive and insensitive cancer cells, respectively. We also found that resveratrol-induced cancer cell suppression occurred ULK1 dependently. For the mechanism of action of resveratrol on mTOR inhibition, we demonstrate that resveratrol directly inhibits mTOR. We found that resveratrol inhibits mTOR by docking onto the ATP-binding pocket of mTOR (i.e., it competes with ATP). We propose mTOR as a novel direct target of resveratrol, and inhibition of mTOR is necessary for autophagy inductionopen

Identification and purification of a soluble region of BubR1: a critical component of the mitotic checkpoint complex

The mitotic checkpoint complex (MCC) ensures the fidelity of chromosomal segregation, by delaying the onset of anaphase until all sister chromatids have been properly attached to the mitotic spindle. In essence, this MCC-induced delay is achieved via the inhibition of the anaphase-promoting complex (APC). Among the components of the MCC, BubR1 plays two major roles in the functions of the mitotic checkpoint. First, BubR1 is able to inhibit APC activity, either by itself or as a component of the MCC, by sequestering a APC coactivator, known as Cdc20. Second, BubR1 activates mitotic checkpoint signaling cascades by binding to the centromere-associated protein E, a microtubule motor protein. Obtaining highly soluble BubR1 is a prerequisite for the study of its structure. BubR1 is a multi-domain protein, which includes a KEN box motif, a mad3-like region, a Bub3 binding domain, and a kinase domain. We obtained a soluble BubR1 construct using a three-step expression strategy. First, we obtained two constructs from BLAST sequence homology searches, both of which were expressed abundantly in the inclusion bodies. We then adjusted the lengths of the two constructs by secondary structure prediction, thereby generating partially soluble constructs. Third, we optimized the solubility of the two constructs by either chopping or adding a few residues at the C-terminus. Finally, we obtained a highly soluble BubR1 construct via the Escherichia coli expression system, which allowed for a yield of 10.8 mg/L culture. This report may provide insight into the design of highly soluble constructs of insoluble multi-domain proteins