Terahertz quantum plasmonics at nanoscales and angstrom scales

Through the manipulation of metallic structures, light-matter interaction can enter into the realm of quantum mechanics. For example, intense terahertz pulses illuminating a metallic nanotip can promote terahertz field-driven electron tunneling to generate enormous electron emission currents in a subpicosecond time scale. By decreasing the dimension of the metallic structures down to the nanoscale and angstrom scale, one can obtain a strong field enhancement of the incoming terahertz field to achieve atomic field strength of the order of V/nm, driving electrons in the metal into tunneling regime by overcoming the potential barrier. Therefore, designing and optimizing the metal structure for high field enhancement are an essential step for studying the quantum phenomena with terahertz light. In this review, we present several types of metallic structures that can enhance the coupling of incoming terahertz pulses with the metals, leading to a strong modification of the potential barriers by the terahertz electric fields. Extreme nonlinear responses are expected, providing opportunities for the terahertz light for the strong light-matter interaction. Starting from a brief review about the terahertz field enhancement on the metallic structures, a few examples including metallic tips, dipole antenna, and metal nanogaps are introduced for boosting the quantum phenomena. The emerging techniques to control the electron tunneling driven by the terahertz pulse have a direct impact on the ultrafast science and on the realization of next-generation quantum devices

Reexamining the Role of Cognitive Conflict in Science Concept Learning

Abstract In this study, we defined and quantified the degree of cognitive conflict induced by a discrepant event from a cognitive perspective. Based on the scheme developed, we investigated the relationship between cognitive conflict and conceptual change, and the influences of students’ cognitive characteristics on conflict in learning the concept of density. Subjects were 171 seventh-grade girls from two city middle schools in Korea. Tests regarding logical thinking ability, field dependence/independence, and meaningful learning approach were administered. A preconception test and a test of responses to a discrepant event were also administered. Computer-assisted instruction was then provided to students as a conceptual change intervention. A conception test was administered as a posttest. In analyzing students’ responses to the discrepant event, seven types of responses were identified: Rejection, reinterpretation, exclusion, uncertainty, peripheral belief change, belief decrease, and belief change. These types were then ordered into four levels. The results indicated that there existed a significant correlation between cognitive conflict and conceptual change. t -test results revealed that there were statistically significant differences in the degree of cognitive conflict by the levels of students’ logical thinking ability and field dependence/independence. Meaningful learning approach, however, was found to have no statistically significant effect on cognitive conflict. Educational implications are discussed

Perceived professional needs of Korean science teachers majoring in chemical education and their preferences for online and on-site training

In this study, we investigated the perceived professional needs of Korean science teachers majoring in chemical education, and examined their preferences for online and on-site inservice teacher training programs. The results were also compared with those of preservice teachers. Participants were 120 secondary school teachers and 67 preservice teachers, whose majors were either chemical education or science education with emphasis in chemistry. A questionnaire consisting of a modified Science Teacher Inventory of Need and a section concerning respondents’ demographic information and their use of the Internet was administered. In contrast to previous studies, the perceived needs of Korean inservice and preservice teachers were found to be very strong in all 30 needs assessment items, and their prominent needs were from all seven categories. Preservice teachers indicated significantly greater needs than inservice teachers on several items. Korean teachers generally tended to prefer online inservice to traditional on-site training programs, although they still preferred on-site types of programs in areas such as conducting laboratory sessions and demonstrating manipulative skills. Preferences for online programs tended to be stronger among preservice teachers than inservice teachers, and among non-veteran teachers than in veteran teachers. Educational implications are discussed

SPON1 Can Reduce Amyloid Beta and Reverse Cognitive Impairment and Memory Dysfunction in Alzheimer's Disease Mouse Model

Alzheimer's disease (AD) is a complex, age-related neurodegenerative disease that is the most common form of dementia. However, the cure for AD has not yet been founded. The accumulation of amyloid beta (A beta) is considered to be a hallmark of AD. Beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), also known as beta secretase is the initiating enzyme in the amyloidogenic pathway. Blocking BACE1 could reduce the amount of A beta, but this would also prohibit the other functions of BACE1 in brain physiological activity. SPONDIN1 (SPON1) is known to bind to the BACE1 binding site of the amyloid precursor protein (APP) and blocks the initiating amyloidogenesis. Here, we show the effect of SPON1 in A beta reduction in vitro in neural cells and in an in vivo AD mouse model. We engineered mouse induced neural stem cells (iNSCs) to express Spon1. iNSCs harboring mouse Spon1 secreted SPON1 protein and reduced the quantity of A beta when co-cultured with A beta -secreting Neuro 2a cells. The human SPON1 gene itself also reduced A beta in HEK 293T cells expressing the human APP transgene with AD-linked mutations through lentiviral-mediated delivery. We also demonstrated that injecting SPON1 reduced the amount of A beta and ameliorated cognitive dysfunction and memory impairment in 5xFAD mice expressing human APP and PSEN1 transgenes with five AD-linked mutations

Establishment of feeder-free culture system for human induced pluripotent stem cell on DAS nanocrystalline graphene

The maintenance of undifferentiated human pluripotent stem cells (hPSC) under xeno-free condition requires the use of human feeder cells or extracellular matrix (ECM) coating. However, human-derived sources may cause human pathogen contamination by viral or non-viral agents to the patients. Here we demonstrate feeder-free and xeno-free culture system for hPSC expansion using diffusion assisted synthesis-grown nanocrystalline graphene (DAS-NG), a synthetic non-biological nanomaterial which completely rule out the concern of human pathogen contamination. DAS-NG exhibited advanced biocompatibilities including surface nanoroughness, oxygen containing functional groups and hydrophilicity. hPSC cultured on DAS-NG could maintain pluripotency in vitro and in vivo, and especially cell adhesion-related gene expression profile was comparable to those of cultured on feeders, while hPSC cultured without DAS-NG differentiated spontaneously with high expression of somatic cell-enriched adhesion genes. This feeder-free and xeno-free culture method using DAS-NG will facilitate the generation of clinical-grade hPSC.ope

Cognitive conflict and situational interest as factors influencing conceptual change

In this study, we investigated the relationships among cognitive conflict and situational interest induced by a discrepant event, attention and effort allocated to learning, and conceptual change in learning the concept of density. Subjects were 183 seventh graders from six middle schools in Seoul, Korea. A preconception test, a test of responses to a dis-crepant event, and a questionnaire of situational interest were administered as pretests. Computer-assisted instruction was then provided to the students as a conceptual change in-tervention. Questionnaires regarding attention and effort, and a conception test were admin-istered as posttests. The conception test was administered once more as a retention test four weeks later. The results of path analysis indicated that both cognitive conflict and situational interest induced by a discrepant event respectively had an indirect effect on students‘ conceptual understanding, which were mediated by attention and effort allocated to concept learning. Situational interest, however, was found to exert a stronger influence on conceptual change than cognitive conflict. It was also found that attention, either directly or indirectly through effort, influenced students‘ conceptual understanding

A Study on the Elementary School Teachers’ Awareness of Students’ Alternative Conceptions about Change of States and Dissolution

Knowledge about students’ conceptions is one of the requisite components of pedagogical content knowledge. A keen awareness of students’ alternative conceptions provides teachers with information about prospective difficulties students may incur as they make attempts to learn more accurate scientific representations of critical concepts. In this study, we investigated elementary school teachers’ understanding of their students’ alternative conceptions about change of states and dissolution. The subjects were 152 elementary school teachers and 529 sixth graders in Korea. A conceptions test and the test of the understanding about students’ conceptions were administered in order to examine students’ alternative conceptions and the teachers’ awareness of their students’ alternative conceptions, respectively. The effects of teachers’ characteristics such as teaching experience, highest academic degree, science teaching efficacy, and views about teaching and learning (i.e., constructivist and traditional) in relation to their awareness of students’ alternative conceptions were also investigated. The results indicated that the teachers tended to overestimate the number of students with scientifically accepted conceptions. The teachers also did not possess adequate knowledge about the existence and the distribution of their students’ alternative conceptions. It was found that teaching experience, highest academic degree, science teaching efficacy, and the level of teachers’ adoption of a constructivist view about teaching and learning were not significantly related to the their awareness of students’ alternative conceptions. It was found, however, that there is a significant relationship between the level of teachers’ traditional view about teaching and learning and their awareness of students’ alternative conceptions. Educational implications are discussed