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Parth Prashant Karnawat 《Resonance》2018,23(5):591-596
As an easy application of the intermediate value theorem, one can show that for any continuous function f: [0, 1] → ? with f (0) = f (1), there are points a, a + 1/2 both in [0, 1] such that f (a) = f (a + 1/2). In this note, we show that this property holds with 1/2 replaced by any number of the form 1/n for a positive integer n. More interestingly, we show that this is false for every number not of the form 1/n. 相似文献
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Alejandro S. González-Martín Elena Nardi Irene Biza 《Educational Studies in Mathematics》2018,98(3):231-252
We examine teachers’ use of resources as they prepare to teach the topic of numerical series of real numbers, in order to identify how their personal relationship with mathematical content—and its teaching—interacts with their use of a commonly used textbook. We describe this interplay between textbook and personal relationship, a term coined in the Anthropological Theory of the Didactic (ATD, Chevallard, 2003), in terms of documentation work (resources, aims, rules of action, operational invariants), a key construct from the documentational approach (DA, Gueudet & Trouche, in Educational Studies in Mathematics, 71, 199–218, 2009). We do so in the case of five post-secondary teachers who use the same textbook as a main resource for teaching the topic. Documentational analysis of interviews with the teachers led to the identification of their aims and rules of action (the what and how of their resource use as they organise their teaching of the topic) as well as the operational invariants (the why for this organisation of their teaching). We describe the teachers’ documentation work in two sets of aims/rules of action: scaffolding mathematical content (series as a stepping stone to learning about Taylor polynomials and Maclaurin series), and organising student learning about series through drill exercises, visualisation, examples, and applications. Our bridging (networking) of theoretical constructs originating in one theoretical framework (personal relationship, ATD) with the constructs of a different, yet compatible, framework (documentation work, DA) aims to enrich the latter (teachers’ documentation work) with the individual agency (teachers’ personal relationships with the topic) provided by the former. 相似文献
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Stelios Xinogalos 《Education and Information Technologies》2016,21(3):559-588
Designing and deploying programming courses is undoubtedly a challenging task. In this paper, an attempt to analyze important aspects of a sequence of two courses on imperative-procedural and object-oriented programming in a non-CS majors Department is made. This analysis is based on a questionnaire filled in by fifty students in a voluntary basis. The issues of the programming courses that are investigated refer to: the strategy selected for the introduction to programming; the sequence of the programming techniques and languages taught and the transition from the one to the other; students’ difficulties with programming in general and with imperative-procedural and object-oriented programming in specific; the teaching and learning design of both courses; and the material that students rely on for learning programming. Based on the analysis of students’ replies on the questionnaire, related work and the instructor’s experience on teaching the courses, conclusions are drawn regarding all the aforementioned aspects of designing and deploying programming courses. The main contribution of the paper is the fact that all the important and interrelated aspects of a sequence of two programming courses are investigated in conjunction, providing realistic implications and guidelines for improving the quality and effectiveness of existing programming courses and designing and deploying new courses. The main results refer to the usage of a pseudo-language for an introduction to programming, the transition from procedural to object-oriented programming, the intrinsic difficulties of learning programming, and practices for a more successful teaching and learning design of programming courses. 相似文献
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A circular jet has broad and important applications in practical engineering. Most research in this area has focused on a free jet, a wall jet or a vertical jet in a bounded domain. In this study, the mean velocities of circular offset jets were studied for four jet exit Froude numbers (Fr), three offset heights (S) (S/d=1, 2, 3) and three submergence ratios (ht/S) (surface jet, mixed jet, and submerged jet) in a bounded basin. Based on the results, we propose a velocity decay formula for a circular jet. The lateral velocity spread was more consistent with Gaussian and Cauchy–Lorentz distributions than the vertical velocity. Moreover, Fr had little effect on the decay of the mean velocity for a circular jet when Re>1×104. The lateral and vertical spreads showed a quadratic relationship with the streamwise distance for different values of Fr at X/d<10. The positions of maximum mean velocity decay were independent of Fr and S/d when X/d<10. The spread rate was more uniform in the lateral direction than that in the vertical direction in a certain region for different S/d and ht/S. Therefore, the decay, spread, and maximum velocity position of the mean velocity for a circular offset jet can remain stable under different values of Fr, offset height, and submergence ratio. 相似文献
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Starting with an elementary problem that appeared in the Putnam mathematics competition, we proceed to discuss some techniques of transcendental number theory and prove the following result. If p, q, r are distinct primes and if c is a real number with the property that pc, qc, rc are integers, then c must be a non-negative integer. The tools used are some linear algebra and complex analysis. The zero-density estimate method discussed here was used by Alan Baker to prove his celebrated theorem on linear forms in logarithms. The question as to whether we can replace three primes by two primes is an open question. 相似文献
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1 Introduction AmatrixA∈Cn×missaidtobecentrohermitianifA =Jn AJm,andskewcentrohermitianifA =-Jn AJm,where Adenotetheconjugateofthema trixAandJlisthepermutationmatrixoforderlwithonesonthecrossdiagonal(bottomlefttotopright)andzeroselsewhere .ThehermitianToeplitzmatricesformanimportantsubclassofcentrohermi tianmatriceswhichoccurnaturallyindigitalsignalprocessingandotherareas ,seeforinstance[1] andreferencetherein .Thecentrohermitianandrelatedmatricesrecentlyplayanimportantroleinthesolu… 相似文献
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Mariska Okkinga Roel van Steensel Amos J. S. van Gelderen Erik van Schooten Peter J. C. Sleegers Lidia R. Arends 《Educational Psychology Review》2018,30(4):1215-1239
Research has demonstrated that in controlled experiments in which small groups are being tutored by researchers, reading-strategy instruction is highly effective in fostering reading comprehension (Palincsar & Brown, Cognition and Instruction, 1(2), 117–175, 1984). It is unclear, however, whether reading-strategy interventions are equally effective in whole-classroom situations in which the teacher is the sole instructor for the whole class. This meta-analysis focuses on the effects of reading-strategy interventions in whole-classroom settings. Results of studies on the effectiveness of reading-strategy interventions in whole-classroom settings were summarized (Nstudies?=?52, K?=?125) to determine the overall effects on reading comprehension and strategic ability. In addition, moderator effects of intervention, study, and student characteristics were explored. The analysis demonstrated a very small effect on reading comprehension (Cohen’s d?=?.186) for standardized tests and a small effect (Cohen’s d?=?.431) on researcher-developed reading comprehension tests. A medium overall effect was found for strategic ability (Cohen’s d?=?.786). Intervention effects tended to be lower for studies that did not control for the hierarchical structure of the data (i.e. multilevel analyses).For interventions in which “setting reading goals” was part of the reading-strategy package, effects tended to be larger. In addition, effects were larger for interventions in which the trainer was the researcher as opposed to teachers and effect sizes tended to be larger for studies conducted in grades 6–8. Implications of these findings for future research and educational practice are discussed. 相似文献
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In the twenty-first century, the Gothic has experienced a cultural resurgence in literature, film, and television for young adult audiences. Young adult readers, poised between childhood and adulthood, have proven especially receptive to the Gothic’s themes of liminality, monstrosity, transgression, romance, and sexuality (James, 2009, p. 116). As part of the Gothic’s incorporation into a broad range of texts for young people, the school story—a conventionally realist genre—has begun to include supernatural gothic characters including vampires, witches, angels, and zombies, and has once again become a popular genre for young readers. In the past decade, in particular, a large number of Gothic young adult series with female protagonists set in boarding schools have been published (These include Shadow Falls (2011–2013) by C.C. Hunter, Covenant (2011–2013) by Jennifer L. Armentrout, House of Night (2007–2014) by P.C. Cast, Mythos Academy (2011–2014) by Jennifer Estep, The Dragonian (2013–2015) by Adrienne Woods, The Morganville Vampires (2006–2014) by Rachel Caine, Blue Bloods (2006–2013) by Melissa de la Cruz, and Fallen (2009–2012) by Lauren Kate). In this article, we will consider the first books in three such supernatural Gothic series that feature vampires and witches: Richelle Mead’s Vampire Academy (2007), Claudia Gray’s vampire romance Evernight (2008) and Rachel Hawkins’ Hex Hall (2010). These books are significant for the ways in which the traditional school story is adapted and transformed by the Gothic to define models of contemporary girlhood. Although Diane Long Hoeveler suggests that “the ‘body’ that emerges from female gothic textuality is a highly gendered one” (1998, p. 18), what we see in these texts is how the school story setting enables Gothic female protagonists who are unique, disruptive, and potentially transformative, despite the limitations enforced by the heterosexual romance plot. We argue that these novels, while conservative in some respects, rework the school story genre in that they foreground the sexual and romantic desires of girl protagonists regardless of the threat they constitute to the institution and the safety of others. 相似文献
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Colby Hall Garrett J. Roberts Eunsoo Cho Lisa V. McCulley Megan Carroll Sharon Vaughn 《Educational Psychology Review》2017,29(4):763-794
This meta-analysis synthesizes the last two decades of experimental and quasi-experimental research on reading instruction across academic contexts (e.g., social studies, science, mathematics, English language arts) for English learners (ELs) in grades 4 through 8, to determine (a) the overall effectiveness of reading instruction for upper elementary and middle school students who are ELs and (b) how the magnitude of the effect varies based on student, instructional, and study characteristics. The analysis included a total of 11 studies with 46 individual effect sizes and yielded a mean effect size of g?=?0.35 across all (i.e., standardized and unstandardized) reading measures, g?=?0.01 across standardized reading measures, and g?=?0.43 across unstandardized reading measures. For all reading, unstandardized reading, all vocabulary, and unstandardized vocabulary measures, results suggest that higher quality studies tended to have smaller effects, and these effects were even more evident for unstandardized measures (i.e., one unit increase in study quality was associated with decreased effects: g?=?0.21, g?=?0.30, g?=?0.24, g?=?0.30, respectively). For all comprehension measures, effects were larger for instruction that included both vocabulary and comprehension (g?=?0.39) than for instruction that focused on vocabulary alone (g?=?0.08). Results suggest the benefit of developing and refining high-impact approaches to reading instruction for ELs that can be delivered across content areas and grades. 相似文献
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Chen Zhi-guo 《浙江大学学报(A卷英文版)》2006,7(2):198-202
In this paper we give a short survey on a problem on extremal quasiconformal extensions. It had been a conjecture for a long time that the dilatations K0(h) and K1(h) are equal before Anderson and Hinkkanen disproved this by constructing concrete examples of a family of affine mappings of some parallelograms. The problem also engendered many interesting results. At the end of the current paper, we discuss relationships among K0(h), H(h) and K1(h) as a concluding remark. 相似文献
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The objective of this study was to describe the fecal microbiota succession of piglets from birth to post-weaning by pyrosequencing. The dominant bacterial phyla were Bacteroidetes, Firmicutes, Proteobacteria, and Fusobacteria, although the composition of the fecal microbiota changed as the piglets grew. Bacteroides, Parabacteroides, Prevotella, Lactobacillus, unclassified Lachnospiraceae, Ruminococcus, Oscillospira, Phascolarctobacterium, and Desulfovibrio were the core genera in the feces of piglets and existed from birth to post-weaning. Bacteroides was the most abundant at birth; however, the proportion of Bacteroides decreased as the piglets aged, while the proportion of Prevotella increased until it became the most abundant genus at the post-weaning stage. Principal coordinate analysis indicated that the microbial communities of piglet fecal samples from birth to post-weaning could be separated into four groups according to the similarity of community composition. These corresponded to time points on day 0 (birth); day 7; days 14, 21, and 28 (pre-weaning); and day 35 (post-weaning). This study suggests that the development of the intestinal microbiota in the piglet is a gradual and sequential process. This methodology establishes a basis for broader studies to investigate the microbiota of the piglet intestinal tract. 相似文献
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Adela Baird Janet Laugharne Eva Maagerø Elise Seip Tønnessen 《Children‘s Literature in Education》2016,47(1):1-17
Children as readers of picture books and the ways they respond to, and make meaning from, such texts are the focus of this article, which reports on a small-scale study undertaken in Norway and Wales, UK. The theoretical framing of the research draws on concepts of the multimodal ensemble in picture books and of the reading event as part of a social practice. The research design was developed from the team’s analysis of two texts, Pappa by Svein Nyhus (1998) and What does Daddy Do? by Rachel Bright (2009). Twenty-four children, who were 7 and 8 years old, took part in the study. This was built around two reading events for each book, staged as an immediate response and as a guided response. The data subsequently collected were analysed according to three overarching organisational principles, as book world, real world and play world. For both Daddy and Pappa, the first reading event showed the children’s responses were mainly directed towards exploring the book world. On the second reading event, references to the real world predominated for Daddy, while for Pappa the book world was again dominant. Across both reading events and for both books, the playworld revealed those occasions when the children expanded the meaning of the story, demonstrating an inventive ability to play with the text. Overall, the children’s responses moved fluidly across the three worlds, showing them to be energetically making connections between the reading, their experience of books and their own lives. 相似文献
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Dong-Yi Jin Cong-Lin Liu Jun-Nan Tang Zhao-Zhong Zhu Xue-Xi Xuan Xiao-Dan Zhu Yun-Zhe Wang Tian-Xia Zhang De-Liang Shen Xiao-Fang Wang Guo-Ping Shi Jin-Ying Zhang 《Journal of Zhejiang University. Science. B》2017,18(8):685-695
Background
Coronary heart disease (CHD) is characterized by arterial wall inflammation and matrix degradation. Matrix metalloproteinase (MMP)-22 and -29 and pro-inflammatory cytokine interleukin-18 (IL18) are present in human hearts. IL18 may regulate MMP-22 and -29 expression, which may correlate with CHD progression.Methods and results
Immunoblot analysis showed that IL18 induced MMP-22 expression in human aortic smooth muscle cells. The Mann Whitney test from a prospective study of 194 CHD patients and 68 non-CHD controls demonstrated higher plasma levels of IL18, MMP-22 and -29 in CHD patients than in the controls. A logistic regression test suggested that plasma IL18 (odds ratio (OR)=1.131, P=0.007), MMP-22 (OR=1.213, P=0.040), and MMP-29 (OR=1.198, P=0.033) were independent risk factors of CHD. Pearson’s correlation test showed that IL18 (coefficient (r)=0.214, P=0.045; r=0.246, P=0.031) and MMP-22 (r=0.273, P=0.006; r=0.286, P=0.012) were associated with the Gensini score before and after adjusting for potential confounding factors. The multivariate Pearson’s correlation test showed that plasma MMP-22 levels correlated positively with high-sensitive-C-reactive protein (hs-CRP) (r=0.167, P=0.023), and MMP-29 levels correlated negatively with triglyceride (r=?0.169, P=0.018). Spearman’s correlation test indicated that plasma IL18 levels associated positively with plasma MMP-22 (r=0.845, P<0.001) and MMP-29 (r=0.548, P<0.001).Conclusions
Our observations suggest that IL18, MMP-22 and -29 serve as biomarkers and independent risk factors of CHD. Increased systemic IL18 in CHD patients may contribute to elevated plasma MMP-22 and -29 levels in these patients.17.
We recently developed the Framework of Achievement Bests to explain the importance of effective functioning, personal growth, and enrichment of well-being experiences. This framework postulates a concept known as optimal achievement best, which stipulates the idea that individuals may, in general, strive to achieve personal outcomes, reflecting their maximum capabilities. Realistic achievement best, in contrast, indicates personal functioning that may show moderate capability without any aspiration, motivation, and/or effort expenditure. Furthermore, our conceptualization indicates the process of optimization, which involves the optimization of achievement of optimal best from realistic best.In this article, we explore the Framework of Achievement Bests by situating it within the context of student motivation. In our discussion of this theoretical orientation, we explore in detail the impact of instructional designs for effective mathematics learning as an optimizer of optimal achievement best. Our focus of examination of instructional designs is based, to a large extent, on cognitive load paradigm, theorized by Sweller and his colleagues. We contend that, in this case, cognitive load imposition plays a central role in the structure of instructional designs for effective learning, which could in turn influence individuals’ achievements of optimal best. This article, conceptual in nature, explores varying efficiencies of different instructional approaches, taking into consideration the potency of cognitive load imposition. Focusing on mathematical problem solving, we discuss the potentials for instructional approaches to influence individuals’ striving of optimal best from realistic best. 相似文献
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In this study, we aimed to examine the inhibitory effect of PA003, a Pediococcus acidilactici that produces lactic acid and antimicrobial peptides pediocin, on pathogenic biofilm formation on abiotic surfaces. PA003 and pathogens (Escherichia coli, Salmonella enterica serovar Typhimurium, Staphylococcus aureus and Listeria monocytogenes) were used to evaluate auto-aggregation, hydrophobicity, biofilm formation and biofilm formation inhibition on stainless steel, polyvinyl chloride and glass slides in terms of exclusion, displacement and competition. The results showed the highest auto-aggregation abilities were observed for one of the E. coli strains EAggEC (E58595) and the highest hydrophobic strain was observed with EPEC (E2348/69) (51.9%). The numbers of biofilm cells of E. coli, S. Typhimurium, S. aureus and L. monocytogenes on stainless steel, polyvinyl chloride and glass slide coupons were effectively reduced by approximately 4 log CFU/coupon. These results demonstrate that lactic acid bacteria can be used as an alternative to effectively control the formation of biofilms by food-borne pathogens. 相似文献
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C. O. Oladoye I. F. Connerton R. M. O. Kayode P. F. Omojasola I. B. Kayode 《Journal of Zhejiang University. Science. B》2016,17(4):317-332
Microbial attacks during storage are one of the primary causes of product deterioration, and can limit the process of prolonging the shelf-life of harvested food. In this study, sweet potatoes were stored at temperatures of 13, 21, and 29 °C for 4 weeks. Samples were collected during storage and plated on potato dextrose agar, from which axenic mold cultures were obtained and identified using 26S rRNA gene sequences. Physiological changes of potato tubers were assessed with respect to pathogenicity, enzyme activity, and atmospheric storage conditions. Six fungal species were identified, namely Penicillium chrysogenum (P. rubens), P. brevicompactum, Mucor circinelloides, Cladosporium cladosporiodes, P. expansum, and P. crustosum. The following fungal isolates, namely P. expansum, P. brevicompactum, and Rhizopus oryzae, were recovered from the re-infected samples and selected according to their levels of enzyme activity. This study revealed high levels of activity for cellulase and pectinase, which were most notable during the initial three days of testing, and were followed by a steady decrease (P<0.05). Polygalacturonase activity was prominent with values ranging from 12.64 to 56.79 U/mg (P. expansum) and 18.36 to 79.01 U/mg (P. brevicompactum). Spoilage was obvious in the control group, which had a 100% decay at the end of the experimental period compared with samples treated with iprodione and sodium hypochlorite, in which the decay rates were 5% and 55%, respectively. The data for the iprodione- and sodium hypochlorite-treated samples at the end of the 3-month storage period showed that they were significantly different (P=0.041), with the sodium hypochlorite-treated samples producing twice the rate of infection compared to the iprodione-treated samples. The comparative rate of the progression of decay in the treated samples can be expressed as iprodione<sodium hypochlorite<control. This study demonstrates that sweet potato tissue damage is due to the activities of microbial enzymes and, in particular, the pectinases of the organisms isolated from the infected potato tissues, and suggests the advantages of utilizing iprodione as a curing agent for potato tubers before storage. 相似文献
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Bai-kui Wang Yu-long Mao Li Gong Xin Xu Shou-qun Jiang Yi-bing Wang Wei-fen Li 《Journal of Zhejiang University. Science. B》2018,19(10):785-795