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INTRODUCTIONCucumbermosaicvirus (CMV) ,thetypespeciesofthegenusCucumovirusoffamilyBro moviridae,isanisometricviruswithatripartitesingle strandedRNAgenomeofpositivepolari ty.CMVhasaparticularlywidehostrange ,in fectingmorethan 80 0speciesinover 70familieso… 相似文献
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The cucumber mosaic virus (CMV) isolate P1 caused very mild symptoms on many plant species After serial passages by mechanical
inoculation over five years, CMV P1 caused severe symptoms on several tobacco cultivars and tomato. A specific band of approximately
0.3 kb in length was amplified by RT-PCR with primers synthesized based on reported CMV satellite RNA (satRNA) sequences.
Sequence analysis showed there were two satRNAs (Sat-P1-1 and Sat-P1-2). Sat-P1-1 contained 335 nucleotides, and Sat-P1-2
contained 394 nucleotides. These two satRNAs shared 64% overall nucleotide sequence homology, and differences between the
two satRNAs included mutations as well as deletions. Sat-P1-1 was identical to a satRNA (Z96099) reported in 1995 in CMV P1.
Based on differences in the sequence and secondary structure between these two satRNAs, we conclude that Sat-P1-2 represents
the emergence of a new satellite (necrotic satellite) from attenuated satRNA populations. The possible effect of the emergence
of this new satRNA is discussed.
Project supported by research grants from the Teaching and Research Award Program for Outstanding Teachers in Higher Education
Institutes of the Ministry of Education of China and by the National Outstanding Youth Foundations of National Natural Science
Foundation of China (No. 30125032).
PhD student in Zhejiang University, from Agrarian University of Havana, Cuba. 相似文献
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Han Jeongyun Huh Sun Young Cho Young Hoan Park SoHyun Choi Jinhan Suh Bongwon Rhee Wonjong 《Educational technology research and development : ETR & D》2020,68(5):2055-2071
This study investigates the possibility of utilizing online learning data to design face-to-face activities in a flipped classroom. We focus on heterogeneous group formation for effective collaborative learning. Fifty-three undergraduate students (18 males, 35 females) participated in this study, and 8 students (3 males, 5 females) among them joined post-study interviews. For this study, a total of 6 student characteristics were used: three demographic characteristics obtained from a simple survey and three academic characteristics captured from online learning data. We define three demographic group heterogeneity variables and three academic group heterogeneity variables, where each variable is calculated using the corresponding student characteristic. In this way, each heterogeneity variables represents a degree of diversity within the group. Then, a two-stage hierarchical regression analysis was conducted to identify the significant group heterogeneity variables that influence face-to-face group achievement. The results show that the academic group heterogeneity variables, which were derived from the online learning data, accounted for a significant proportion of the variance in the group achievement when the demographic group heterogeneity variables were controlled. The interviews also reveal that the academic group heterogeneity indeed affected group interaction and learning outcome. These findings highlight that online learning data can be utilized to obtain relevant information for effective face-to-face activity design in a flipped classroom. Based on the results, we discuss the advantages of this data utilization approach and other implications for face-to-face activity design.
相似文献4.
Zi Yan 《Educational Research and Evaluation》2013,19(2):83-97
The theory of planned behaviour (TPB) was used to explore the Hong Kong teachers' intentions to implement school-based assessment (SBA) and the predictors of those intentions. A total of 280 teachers from Hong Kong secondary schools who had been involved in SBA were surveyed. Rasch-calibrated teacher measures were calculated for each of the 6 variables – affective and instrumental attitude, subjective norm, self-efficacy, knowledge, and intention – regarding SBA. The results of hierarchical multiple regression analysis revealed that instrumental attitude and self-efficacy made significant contributions to predicting intentions to implement SBA. These 2 predictors explained 55.2% of the variance in intentions. The other 3 variables, that is, affective attitude, subject norm, and knowledge, did not have significant predictive power on the formation of intentions to implement SBA. Possible explanations and implications of the findings are discussed. 相似文献
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Newborn status, ratings of temperament, and heretofore neglected experiential (parenting) antecedents of hyperactivity were evaluated in a prospective, longitudinal investigation. The experiential variables were derived from a developmental theory of arousal modulation in the early years. Patterns of maternal intrusive care, seductive behavior, and overstimulation were assessed at 6 months, 2 years, and 3 1/2 years, respectively. 2 of these 3 variables significantly predicted hyperactivity in kindergarten at age 5 or 6, as determined by clinically validated ratings made by teachers. Of the 38 early child variables, which included neonatal behavioral assessments and ratings of activity level by parents and observers on many occasions during the first 2 1/2 years, only the motor maturity factor from 2 composited Brazelton exams yielded a significant relation. In addition, a measure of distractibility at 42 months was predictive of hyperactivity. Although other child measures may prove to be more powerful than those we tested, it will remain the case that prospective data are a critical arbiter of etiological factors in hyperactivity. Such data have important implications for both diagnosis and treatment. 相似文献
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College cheating: Ten years later 总被引：3，自引：1，他引：3
George M. Diekhoff Emily E. LaBeff Robert E. Clark Larry E. Williams Billy Francis Valerie J. Haines 《Research in higher education》1996,37(4):487-502
In this 10-year follow-up study of student cheating, we surveyed 474 university students to (1) evaluate the extent of cheating; (2) assess attitudes toward cheating; (3) identify variables that discriminate between cheaters and noncheaters; (4) assess the relative effectiveness of various deterrents to cheating; and (5) examine changes in cheating attitudes and behaviors from 1984 to 1994. Most students (61.2%) reported cheating in 1994, up significantly from 54.1% in 1984 (Haines et al., 1986). Despite this increased cheating, students in 1994 were significantly less likely than in 1984 to neutralize (rationalize) their cheating. Ten variables that discriminated between cheaters and noncheaters in 1984 did so again in 1994, and 12 additional discriminating variables were identified. A principal components analysis of these 22 variables indicated that, compared to noncheaters, cheaters are (1) less mature; (2) less reactive to observed cheating; (3) less deterred by social stigma and guilt and more likely to neutralize cheating; (4) less personally invested in their education; and (5) more likely to be receiving scholarships, but doing less well in school. Both cheaters and noncheaters rated embarrassment and fear of punishment as the strongest deterrents to cheating; disapproval of one's friends was ranked as the least effective deterrent by both groups. 相似文献
9.
4 different procedures are commonly employed with sample data to reduce a set of predictor variables. In the present study these procedures were repeatedly applied to computer-simulated samples to provide comparative data pertaining to two questions: (a) Which procedure can be expected to produce an equation that yields the most accurate predictions for the population? (b) Which procedure is most likely to identify the optimal set of independent variables? The samples were drawn from 12, mathematically defined, multivariate normal populations. Each population consisted of 1 criterion and 10 predictor variables. Five or fewer independent variables constituted the optimal set in each case. With respect to both questions small differences among the procedures were observed. However, the forward selection and stepwise procedures consistently produced more favorable results than the 2 backward elimination procedures. The question of the number of sampling units to use is discussed. 相似文献
10.
The current study searched for continuities in mother-infant interaction observed at home, maternally perceived infant difficultness, and infant developmental competency. Also assessed were the possible moderator variables of maternal report of satisfaction with adjustment to the infant and background characteristics, for example, SES, presence of other young children, and infant gender. 128 dyads were assessed at ages 6 and 13 months. Many of the variables used to evaluate continuity were composites based on factor analysis. Bivariate correlations between 6- and 13-month variables produced a complex picture. In broad overview, as predicted by the prior literature, they indicated some degree of stability for mother variables and markedly less for the infant variables. Canonical correlation analysis yielded 3 significant canonical variates, producing a more integrated picture. The dimensions of continuity revealed by these variates were (1) Affectionate, Intellectually Stimulating Mothering, which had modest-to-moderate links to the indexes of infant competence; (2) Infant Temperamental Difficultness, which was determined mainly by consistency in mother report on 2 age-adjusted versions of the Infant Characteristics Questionnaire but which also contained loadings for objectively observed infant fussing, crying, and social demandingness; and (3) an unnamed dimension which resembles a pattern of intense involvement, both positive and negative, seen in older, clinically referred families. 相似文献
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Income Level, Gender, Ethnicity, and Household Composition as Predictors of Children''s School-based Competence 总被引：5，自引：0，他引：5
In the United States, being black, male, or growing up in a low-income and/or single-parent household have all been identified as risk factors for maladjustment during childhood. Interpretation of these findings is, however, often difficult because of the well-known associations among these variables. In the present study, we compared predictions of 3 different forms of children's competence from each of these 4 variables. In a sample of 868 black and white elementary school children from 2-parent and mother-headed 1-parent homes, we studied 3 aspects of school-based competence: conduct, peer relations, and academic achievement. Results showed that although the independent variables accounted for different amounts of variance in each domain of competence, income level and gender were better overall predictors of children's competence in conduct and peer relations than were ethnicity or household composition. Income level and ethnicity were better overall predictors of academic achievement than were gender or household composition, although each of the 4 variables made a significant contribution. Overall, income level and gender were thus the strongest predictors of children's competence. Black children were, however, more likely than white children to live in low-income homes. Our results thus highlighted some correlates of the unequal distribution of economic resources among black and white children growing up in the United States today. 相似文献
12.
John R. Staver 《科学教学研究杂志》1986,23(6):533-542
This study was designed to investigate the effects of problem format and the number of independent variables in the problem on the responses of students to a control of variables reasoning task. The Bending Rods problem was used. A four times two factorial research design with four levels (2-, 3-, 4-, 5-variables) of the number of independent variables and two formats (essay and multiple choice) was set up for the investigation. 548 eighth graders in 24 science classes in a suburban public school district northwest of Chicago participated in the study. Students were administered the Bending Rods problem in groups in their science classes. Each classroom was randomly assigned to a cell in the research design. Initial analysis of the data indicated four separate levels (2-, 3-, 4-, 5-variables) of the independent variable number of independent variables in the problem' were unnecessary. The 2- and 3-variable levels were pooled as were the 4- and 5-variable levels to give two distinct levels of this variable. Analysis of variance indicated that: (1) task format had no effect on subject's scores; but (2) the differences between subjects' mean scores on the 2-, 3-variable essay versions and the 4-, 5-variable essay versions are significantly greater than the mean scores of corresponding multiple choice versions of the task, which exhibit rather uniform scores; and (3) the 2-, 3-variable forms together were significantly less difficult for students than were the 4-, 5-variable forms together. Discussion focuses on interpretations that include: (1) task demands on working memory; (2) Pascual-Leone's M-energy; and (3) the use of testwiseness strategies in solving essay and multiple choice tasks, respectively. Implications for science teachers are set forth in view of these discussion points and their relevance to test construction and classroom assessment of learning objectives in science. 相似文献
13.
Computer Conferencing: An Environment for Collaborative Project-Based Learning in Distance Education
In this experimental study two independent variables were manipulated. Each was associated with online collaborative learning in a distance education context. One of these (group formation strategy) addresses one of the early decisions that must be made in forming groups for collaborative project work. The second (levels of tutor intervention) relates to the on-going process of group management in a computer-mediated environment. An additional independent variable (type of collaborative project) served as a within-group factor in the design. Two measures of individual achievement (final exam scores and idea units) and a measure of group dynamics served as dependent variables. Prior academic achievement (current grade point average) served as a covariate in the analysis of the achievement data. There were no differences across the two types of projects, but two slightly different interaction patterns emerged from the analysis of the achievement data. In general, however, these results favored the random assignment of students to collaborative groups (as contrasted with allowing students to pick their own partners) and the introduction of low tutor intervention during the course of project work. Two main effects emerged from an analysis of the group dynamics data, one of which supports the random assignment strategy. Because of these findings, it is difficult to suggest a totally unambiguous strategy for formulating and managing online collaborative project work. However, some tentative suggestions are advanced. Some guidelines for online collaborative learning are provided. 相似文献
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Myreille St-Onge Alexandre Lemyre 《International Journal of Disability, Development & Education》2018,65(4):459-474
The number of students with mental health disorders (MHDs) in postsecondary institutions is increasing. Teachers’ attitudes are among the main factors that influence these students’ academic success. Unfortunately, their attitudes are little studied, in part because of lack of validated scales. Therefore, this article has two purposes: (1) analyse the construct validity of new scales assessing teachers’ attitudes, as well as existing scales without an established construct validity; and (2) report the correlations between the variables assessed in these scales, with a special focus on two variables: (a) teachers’ negative attitudes; and (b) the measures offered to students by teachers. The participants are 232 teachers from 16 French and English CEGEPS in Quebec, Canada. The questionnaire includes three scales created by the research team and three scales from the Mental Illness Awareness Survey. Correlational and factor analyses were conducted. The scales present good construct validity. Four variables were associated with the two variables of interest: confidence in one’s ability to convince a student to seek help; familiarity with MHDs; knowledge and understanding of MHDs; favourable perception of the accommodations offered by adapted and psychosocial services. Based on these results, strategies are proposed to improve teachers’ attitudes. 相似文献
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《学习科学杂志》2013,22(1):61-94
Although it is common to see extreme case reasoning included in lists of expert heuristics for problem solving, little work has been reported on the role that extreme cases can play in learning that leads to conceptual change. Evidence is presented from video tapes of think-aloud tutoring sessions to document the learning from extreme cases in a unit about levers for seventh graders. The observations support the view that one role of extreme cases is to provide a firm data point or comparison that helps students to establish an ordinal relation between two given variables. Two new additional roles for extreme cases in fostering learning are also identified: (a) their role in activating an intuition, often in the form of a perceptual motor schema, that is used in constructing an imageable, intuitively, grounded, explanatory model as opposed to an empirical role; and (b) their role in facilitating the formation of new causal variables. Pending confirmation of similar effects in other subject areas, these roles are candidates for being included in a set of general learning strategies for science instruction. This illustrates the function that "learning-aloud" studies can play in documenting new types of learning processes and instructional strategies. The study highlights the importance for instructional design of research that uncovers students' existing knowledge structures and natural reasoning processes. The study suggests that explanatory model construction, causal relation construction, and concept formation can result from such instructional designs. The extent to which these three outcomes are evidence for strong conceptual change is also discussed. 相似文献
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OBJECTIVE: This study examines the relationship between two explanatory factors connected to the phenomena of runaways and the homeless among adolescents: behavioral problems of youths and parental violence to which they are subjected. The study demonstrates that these two factors are independently related to the different categories of homeless and runaway adolescents. METHODOLOGY: The data was collected from 130 adolescents (12 to 17 years of age) who were runaways for short periods on a recurring basis. Two subgroups were formed: Group A consisted of 79 adolescents who did not exhibit behavioral problems; Group B consisted of the other 51 who did exhibit them. The two groups had certain similar family characteristics (income levels, parents' occupations, structure and stability of the family). RESULTS: The bivariate analyses reveal significant differences between the two groups of runaways relating to: (1) gender, (2) a diagnosed conduct disorder, (3) affiliations with deviant peers, and (4) experiences of parental violence. The discriminant analysis demonstrates that these four variables clearly differentiate the two groups of runaways and predict the appropriate group membership for 84% of the cases. Therefore, the members of Group B have a higher probability of being diagnosed as having a conduct disorder, being male, and associating with delinquent peers. This group had not experienced a higher level of parental violence. The opposite is true for the members of Group A. CONCLUSION: Our study demonstrates that parental violence and behavioral problems are variables that are independently related to the defined categories of runaways. Therefore, these variables do not constitute, as some thinkers have claimed, the components of a unique dynamic able to explain the phenomenon of the runaway. Our results vitiate the doubts sometimes expressed by researchers about the importance of parental violence to the phenomenon of adolescent runaways. 相似文献
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What constitutes quality in graduate education? The most widely accepted definition has been proposed by Cartter who asked recognized scholars to rate departmental excellence in 30 disciplines. Cartter's instructions to the raters could have allowed the influence of a “halo effect” to operate. This is an error in rating which is produced when the particular characteristics being rated are contaminated by the rater's notion of the general worthiness of the object being rated. This study demonstrated that the halo effect related to size variables occurred in the Cartter study. Data were collected from public sources for each department of mathematics, physics, chemistry, and geology rated in the Cartter study as “extremely attractive,” “attractive,” “acceptable plus” and for a random sample of “less than acceptable plus” departments. These data consisted of the following size variables: (1) number of areas of specialization within a department; (2) number of faculty; (3) number of Ph.D. degrees awarded between 1960–64; (4) number of full-time students; (5) number of first year students; and (6) ratio of part-time to full-time students. Tests of statistical significance indicated that these variables differentiated the departmental ratings beyond chance expectation. A graphic illustration is provided for each discipline showing the relationships between the size measures and the mean departmental ratings. Implications of these findings are that measures of size ought not to be confused with measures of quality and that the development of measures of quality is a matter of urgent priority. 相似文献
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Karen Pine David Messer Kate St. John 《Research in Science & Technological Education》2013,31(1):79-96
The study examines the effects of Piagetian‐like tasks' characteristics on the performance of these tasks by different age group students. The tasks were taken from a developed and validated test (Shemesh, 1983) which measures students' reasoning skills in six cognitive operations: conservation, proportions, control of variables, probability, combinations and correlations. Subjects were seventh, ninth and twelfth grade students, enrolled in two urban schools. Three different 3X2 factorial research design experiments, with three levels of students age and two versions of the test in each experiment, were set up for this study. Experiment 1 tested the effect of the method of task presentation (video‐taped demonstrations versus paper‐and‐pencil tasks with illustrations). Experiment 2 tested the effect of questionnaire format (multiple‐choice versus short essay questions) and experiment 3 tested the effect of the numerical content (integer ratio like 1:2, 1:3 versus noninteger ratio like 2:3, 3:5) on different age group students' responses. 相似文献
19.
In this study, we examine children’s National Assessment Program—Literacy and Numeracy (NAPLAN) achievement predictors, which may enable or limit their numeracy performance and assess the relative importance of the predictor variables. Our data source was the NAPLAN numeracy results of Queensland schools from 2014 to 2017. Years 3 and 5 children’s NAPLAN numeracy scores were analysed using a hierarchical multiple regression model. We examined eight variables grouped into four themes to determine their predictive value for children’s numeracy performance in NAPLAN. Findings from this study indicate that parent’s educational level, parent’s occupation and indigenous status variables accounted for 10–11% of the total variance, while geolocation and sector type contributed an additional 0.2–0.4% of the variance. Gender and language background other than English (LBOTE) contributed 0.1–0.4% of the variance. These results were consistent across levels (Years 3 and 5) and test years (2014–2017). When these predictors were controlled, the influence of parent’s post-school education and LBOTE status were less and non-significant. Previous NAPLAN numeracy results for Year 5 children were found to be very large in its predictive value (R2?=?0.50). The implications of these results for teachers, parents and researchers are described.
相似文献20.
John R. Lyne 《Communication quarterly》2013,61(3):202-208
The performance of speech acts requires interpretive conditions that are best conceived within a semiotic frame. Three variables within these interpretive conditions are considered: (1) the options permitted or suggested by the structure of the discourse, (2) the degree to which illocutionary force is made explicit, and (3) the definition of the situation. Each of these suggests promising lines of confluence for the speech‐acts perspective and the rhetorical tradition, both of which focus on the pragmatic uses of codes. 相似文献