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1.
Stereoselective transformation of Baylis-Hillman acetates I into corresponding （Z）-allyl iodides 2 has been achieved by treatment of I with samarium triiodide in THF. Remarkable rate acceleration of samarium triiodide-mediated iodination of 1 was found when ionic liquid 1-n-butyl-3-methyl-imidazolium tetrafluroborate （[bmim]BF4） was used as reaction media in stead of THF. This novel approach proceeds readily at 50 ℃ within a few minutes to afford （Z）-allyl iodides 2 in excellent yields. A mechanism involving stereoselective iodination of the acetates of Baylis-Hillman adducts by samarium triiodide is described, in which a six-membered ring transition state played a key role in the stereoselective formation of 2.  相似文献   

2.
Due to the globalization and the spread of the Internet, distance learning （D-learning） has gained extraordinary impulse in recent years by classes broadcasted by Websites and assignments fulfilled by students in their own computers. D-learning facilitates the access to education to those people who are working or have low buying power due to its reduced cost and time convenience. Although D-learning has existed in the world for over 150 years, only in the last decades, it has become the focus of academic studies and researches in a systematic way. In this context, the objective of this research is to evaluate the impact of computer literacy on the academic performance of the D-learning students of Faculdade lnterativa COC--EAD （COC--D-learning Interactive College）, P61o Lafaiete （Lafaiete Branch）, Ribeirao Preto. The research consisted of a questionnaire with 21 qualitative dichotomous questions, concerning the level of knowledge and mastery of information techdologies, besides the gender and academic performance （weighted average and marks of the last module）. The data were tabulated, being considered two main variables： （a） academic performance, represented by the marks of the last module; and （b） computer literacy, represented by the sum of the questions concerning this matter. The data were analyzed statistically, and the correlation between the two variables considered was analyzed by Pearson＇s Correlation Test. The interviews of the 54 interviewees （24 males （44.45%） and 30 females （55.55%）） taking the business administration course were analyzed. The correlation coefficient r = 0.303 indicates that there is a meaningful correlation between the students＇ academic performance （marks） and their computer literacy, that is, the greater the computer literacy, the better the marks obtained by these students in the D-learning course. D-learning has computing as its main tool, theretbre, the students with less computer literacy find barriers in D-learning, which o ref  相似文献   

3.
In July 2009, the Obama administration lauched its $4.35 billion Race to the Top （RTT） Fund, providing states with competitive grants in an effort to reform education. One of the main conditions of this program was to award educational innovation. With this in mind, states enacted new legislation in the hopes of attracting more funding for their proposed programs. Although there were many levels of reform targeted by the RTT, of significance to this research is the emphasis placed on improving teacher effectiveness and measuring teacher performance via evaluation systems. The Teacher Effectiveness and Accountability for the Children of New Jersey （TEACHNJ） Act was adopted by the New Jersey legislature in August 2012 with the intent to raise student achievement by improving the quality of instruction. This research explores the impact the TEACHNJ Act has on teacher evaluations and professional development. A survey was administered to 1,235 public school teachers in New Jersey to ascertain teacher perceptions of the： （a） evaluation system in their school; （b） level of communication between teachers and administrators; and （c） availability, frequency, and effectiveness of professional development opportunities. The response rate was 21%. We found that formal evaluations are conducted infrequently with a varying degree of accuracy and impact. Nearly half of the teachers indicated that formal evaluations did not lead to improvements in their classroom. A majority of teachers questioned the administrative value of formal teacher evaluations, in particular the rewards and sanctions associated with the outcome of evaluations and a concem that poor performers were not sanctioned nor were effective teachers rewarded. We found that teachers perceive the greatest value to professional development, which is derived from peer mentoring and observations. We also found that professional development is the most effective when it is offered onsite, embedded in the classroom, continuous, and sustained over ti  相似文献   

4.
The effectiveness of vitamin C in treating Cr(Ⅵ)-contaminated water is being evaluated. Cr(Ⅵ) is an identified pollutant of some soils and groundwater. Vitamin C, an important biological reductant in humans and animals, can be used to transform Cr(Ⅵ) to essentially nontoxic Cr(Ⅲ). The removal efficiency was 89% when the mass concentration of vitamin C was 80 mg/L in 60 min, and nearly 100% Cr(Ⅵ) was removed when the mass concentration was 100 mg/L. Our data demonstrated that the removal efficiency was affected by vitamin C concentration, the reaction temperature and the dissolved oxygen concentration.The reaction mechanism of Cr(Ⅵ) by vitamin C was presented. Our study opens the way to use vitamin C to remediate Cr(Ⅵ)-contaminated soils and groundwater.  相似文献   

5.
A field demonstration of reduction of lead availability in a soil and cabbage （Brassica Chinensis L.） contaminated by mining tailings, located in Shaoxing, China was carried out to evaluate the effects of applications of phosphorus fertilizers on Pb fractionation and Pb phytoavailability in the soil. It was found that the addition of all three P fertilizers including single super phosphate （SSP）, phosphate rock （PR）, and calcium magnesium phosphate （CMP） significantly decreased the percentage of water-soluble and exchangeable （WE） soil Pb and then reduced the uptake of Pb, Cd, and Zn by the cabbage compared to the control （CK）. The results showed that the level of 300 g P/mE soil was the most cost-effective application rate of P fertilizers for reducing Pb availability at the first stage of remediation, and that at this P level, the effect of WE fraction of Pb in the soil decreased by three phosphorus fertilizers followed the order： CMP （79%）〉SSP （41%）〉PR （23%）; Effectiveness on the reduction of Pb uptake by cabbage was in the order： CMP （53%）〉SSP （41%）〉PR （30%）. Therefore our field trial demonstrated that it was effective and feasible to reduce Pb availability in soil and cabbage contaminated by mining tailings using P fertilizers in China and PR would be a most cost-effective amendment.  相似文献   

6.
In order to improve the efficiency in management of public work projects, screening and controlling influencing factors affecting the quality of a public work project is essential. This study synthesized 9 influential categories including 91 factors related to quality management of public works in Taiwan using a sequential analysis procedure. According to the Borda-values of influencing factors obtained from a first stage questionnaire, the number of primary factors selected by the responsible entities and the design-supervisory entities were 44 and 45 respectively. A Fuzzy Analytic Hierarchy Process （FAHP） was used to prioritize and rank these factors. The top five factors ranked by the responsible entities were （1） introduction of the earned value analysis, （2） working efficiency, （3） environmental laws and regulations, （4） price-index fluctuation, and （5） on-site safety management. The top five factors ranked by the design-supervisory entities were （1） man power, （2） laws and regulations, （3） price-index fluctuation, （4） traffic conditions, and （5） faulty design.  相似文献   

7.
Collaboration is becoming increasingly important in the realm of education （Novoa, 2004）. For instance, as soon as training is undertaken, the future teacher must develop an ability to cooperate in a pedagogical context. However, in order to learn to make a relevant contribution to a teaching team＇s undertakings and to provide innovative suggestions in pedagogical matters （Gouvernement du Quebec, 2001）, the student teacher needs solid backing from the cooperating teacher. A student teacher＇s willingness to reflect on and to question his own teaching practices will create a much more promising learning context （Portelance ＆ Durand, 2006）. Reciprocally, the cooperating teacher will make a positive contribution to the student teacher by accepting that his positions be questioned and even altered （Johnston, Wetherill ＆ Greenebaum, 2002）. It is the dynamics of sharing of knowledge and know-how in this partnership that retains our interest. From 2004 to 2007, the researchers carried out a study of the subject by examining four practicum sessions at high school level in a number of Quebec schools. To gather data, the researchers used written questionnaires, individual interviews, as well as recordings of conversations between student teachers and their cooperating teachers. These conversations pertain to the conception and to the execution, by the student teacher, of teaching-learning situations. These dialogues were integrally transcribed and processed by N＇vivo, software designed to analyze qualitative data. the researchers present a typology of the respective roles taken on by the two partners in their discussions. The cooperating teacher reveals himself to be an advisor, a transmitter of information and a teacher. The student teacher also takes on the role of transmitter of information, as well as that of reflective practitioner, among others, the researchers observed that the conversations are usually carried out in an egalitarian spirit and, in some cases, give rise to co-construction of practical knowledge.  相似文献   

8.
More recent motivational research focuses on the identification of effective techniques for enhancing instructional design and meeting the needs of diverse student populations （Wlodkowski R. J., 1981）. Learning-motivation researchers are applying some of the same theories and concepts found to be effective in industry to the development of motivational models that enhance the teaching-learning environment. One of such models is the Attention Relevance Confidence Satisfaction （ARCS） model of motivational design developed by John M. Keller （Small Ruth V., 2007）. The continuous improvement in handheld devices technologies has led to a new learning paradigm called mobile learning which involves the delivery of learning contents to learners utilizing mobile computing devices. Handheld devices, however, have constraints which limit their use for effective learning. Towards improving the effectiveness of mobile learning is a new mobile learning model proposed by Shih on which instructional designs for mobile learning can be based to facilitate mobile learning design and to achieve better mobile learning outcomes （Yushin E. Shih ＆ Dennis Mills, 2007）. Shih＇s model is based on Graphical User Interface （GUI）. This paper presents an enhanced Shih＇s model for effective mobile learning outcome in a university environment by making provision for instructional design to include online library search for both e-books and audio books using collaborative filtering algorithm to aid the search and posting and reading of testimonials about positive mobile learning outcomes so as to encourage other mobile learners. It also incorporates the use of Voice User Interface （VUI） to access the learning portal in order to overcome mobile devices interface limitations in addition to Graphical User Interface （GUI） proposed by Shih, so as to cater for the learning needs of the blind and the visually impaired.  相似文献   

9.
It is argued that the lack of consensus on what constitutes an inquiry-based approach makes the generalization about it difficult, because the concept is relatively unspecific and vague. This problem can partially be solved by constructing a set of activities promoted by inquiry, thus defining the inquiry objectives for classroom and laboratory teaching. Five high school and college Mexican teachers＇ PICK （pedagogical inquiry/content knowledge） was documented and assessed by means of Loughran, Mulhall and Berry＇s （2004） l-CoRe （inquiry content representation） developed by the authors through a proposal of a set of seven inquiry activities. They were also interviewed to construct the professional and pedagogical experience repertoires, a second tool by Loughran et al. （2004） to document PICK. It was observed that all teachers interviewed have used inquiry to modify their students＇ way of thinking, mainly through question posing. Some of them employed research as their main tool to promote scientific inquiry but others mentioned the lack of time to do it. It is interesting to notice that in spite of the fact that inquiry is out of the curriculum in M6xico, the teachers make use of it to improve their teaching practice. According to their answers, their actions in the classroom or the lab were classified within the three general approaches expressed by Lederman （2004）： implicit, historical and explicit. It is concluded that a given teacher cannot be classified exclusively in one of them, because in his/her activities one general approach overlaps the others. The authors conclude that Lederman＇s classification has to be taken into account as an orientation to characterize a given activity of one teacher, even though the same teacher may use another activity characterized by other general approach. That is, Lederman＇s classification applies to characterize activities, not persons  相似文献   

10.
This study compares the life events perceived as ＂rites of passage＂ from adolescence to adulthood by respondents between the ages of 14 and 23 in 3 countries and discusses the possible influences of culture and globalization on these perceptions. Participants include： （1） 250 adolescents from the US （125 males and 125 females）; （2） 191 adolescents from southeastern Brazil （70 males and 121 females）; and （3） 163 adolescents from Malaysia （76 males and 87 females）. These adolescents ranked a variety of life events which may be perceived as indicative of adult status by completing a questionnaire about perceived rites of passage. Although there were similarities among the 3 groups, several differences also emerged. The most commonly noted indicator of adult status for Malaysian youth was physical maturity, followed by completing one＇s education. Participants from the US cited financial independence as the major indicator of adult status, while those from Brazil cited the ability to make important decisions independently from family and to take responsibility for others, such as children, aging parents or a spouse. Brazilian youth were significantly more likely to cite a love affair and voting in major elections as rites of passage than were participants from the other 2 countries. Participants from the US were significantly more likely to cite military service, and Malaysian youth were significantly more likely to consider completion of education and achieving physical maturity as rites of passage. Gender and age differences within groups were evident on some items, but these were not consistent across groups. Possible explanations for the differences between countries and implications for educators working with adolescents in rapidly changing societies are discussed.  相似文献   

11.
Suppose {Xi,i≥1} and {Yi, i≥1} are two independent sequences with distribution functions and , respectively. Zi,n is the combination of Xi and Yi with a probability for each I with 1≤ i≤n. The extreme value distribution GZ(x) of this particular triangular array of the i.i.d. Random variables Z1,n,… Z2,n, Zn,n is discussed. We found a new form of the extreme value distributions i)ΦAα1(x)Φα2 and ii) ψAα(x)ψα2(x)α1<α2), which are not max-stable. It occurs if FX and FY belong to the same MDA(Φ) or MDA(Ψ).  相似文献   

12.
The sequences {Zi,n, l≤i≤n}, n≥l have multi-nomial distribution among i.i.d. random variables {X1,i, i≥1}, {X2,i,u≥l }, …, {Xm,i, i≥1 }. The extreme value distribution Gz(x) of this particular triangular array of i.i.d, random variables Z1,n, Z2Zn,n is discussed in this paper. We found a new type of not max-stable extreme value distributions, i) Gz(x) = r-1∏i=1ФAiαi(x) × Фαr (x);ii) Gz (x) = r-1∏i=1ψAiαi (x) × ψαr (x); iii) Gz (x) = r-1∏i=1 ∧Ai (λix) × A(x), r≥2, 0＜α1≤α2≤…≤αr and λi∈ (0,1] for i, l≤i≤r-1 which occur if Fj, …, Fm belong to the same MDA.  相似文献   

13.
INTRODUCTION Throughout this paper, we shall work with a filtered complete probability space (?,F,(Ft),P) sat-isfying the usual conditions. Let B=(Bt)t≥0 be a stan-dard Brownian motion with B0=0. Denote by ú the set of all non-negative real numbers. Recall that a diffusion process X starting at x≥0 is called the square of a Bessel process of dimension δ>0 if d X t = δd t 2 | X t |d Bt , X 0= x, (1) Clearly, this equation has a unique non-negative strong solution X, i.e., …  相似文献   

14.
The line persistence of a graph G, Pt （ G ） is the minimum number of lines which must be removed to increase the diameter of G. In Ref. [7] （J. Shanghai Univ., 2003,7（4）：352-357）, we gave a characterization of graphs of diameter five with ρ1 （ G ）≥2. In this paper we will show that each of the 8 special graphs Xi （ i = 1,2,3,4,5,6,7,8） listed in condition （2） of Theorem 1 in Ref. [7] can not be deleted. Therefore the results we obtained in Ref. [7] can not in general be improved.  相似文献   

15.
In this paper, the Tφ-convex functions were introduced as a generalizations of convex functions. Then the characteristics of the Tφ-convex functions were discussed. Furthermore, some new inequalities for the Tφ-convex functions were derived.  相似文献   

16.
The molecular cloning of the G1 genome segment of the Z10 strain of Hantaan virus and analysis of the first gene data on the currently widely used Hantavirus vaccine strain in China are presented. The G1 genome segment of Z10 virus was amplified by the method of RT-PCR, and the products were cloned into the pGEM-T vector after identification and purification. The clone was sequenced by Sanger’s dideoxy chain termination method. The 1449 bases of the Z10 G1 genome segment, and the coding for 483 amino acids were determined. The base compositions for the G1 segment RNA determined from cDNA sequence information, were 20.6% A, 21.6% G, 18.8% C and 30.0% U. These values are similar to those of the 76/118, Lee and SR virus. As compared to the Z10 G1 segment, the sequence homology at the nucleotide level is 87% (76/118, type I), 86% (Lee, type I), 86% (Hojo, type I), 67% (R22, type II), and 59% (K22, type III). The Z10 virus G1 protein amino acid sequence identity with other Hantaan viruses (94–95% homology) was higher than that with Seoul type viruses (77–80%). More amino acid sequence heterogeneity between the Z10 and 76/118 was observed in the N terminal, especially the diverging cluster of ten amino acids at position 84 to 93 of the Z10 virus G1 protein. Conclusion: (1) The Z10 strain is one of the Hantaan viruses. (2) The important region of the Z10 G1 segment was conservative. (3) Although substantial divergence of nucleotide sequences of the G1 genome segment was found between the Z10 strain and other type I Hantaviruses, relatively high amino acid sequence homology was shown among them. Thus, good immune protection could be obtained with the inactivated Meriones unguiculatus kidney cell vaccine against other strains of Hantaviruses.  相似文献   

17.
A meta‐analysis of the relationship between attitudes in reading and achievement in reading was conducted to provide a statistical summary to the observed variability in the magnitude of previously reported effect sizes. A total of 32 studies, with a total sample size of 224,615 were used, and included a total of 118 effect sizes. A multi‐level approach was used in meta‐analysis to determine if variance in the magnitude of effect sizes could be partitioned to study (level 1) and moderator (level 2) levels by using a mixed model approach. Results from the meta‐analysis indicated that the mean strength of the relationship between reading attitudes and achievement is moderate (Zr=.32), while stronger for students in elementary school (Zr=.44) when compared with middle school students (Zr=.24). Findings related to selected moderator variables are discussed, with suggestions for future research.  相似文献   

18.
The construction of multirate rearrangeable network has long been an interesting problem. Of many results published, all were achieved on 3-stage Clos network. The monotone routing algorithm proposed by Huet al. (2001) was also first applied to 3-stage Clos network. In this work, we adopt this algorithm and apply it to log d (N,m,p) networks. We first analyze the properties of log d (N,m,p) networks. Then we use monotone algorithm in log d (N,0,p) network. Furthermore we extend the result to construct multirate rearrangeable networks based on log d (N,m,p) network (1≤m≤n−1). Project (No. 10371028) supported by the National Natural Science Foundation of China  相似文献   

19.
This article reports first-principles band structure calculations forRMn6Sn6 (R=Tb, Dy). The calculation uses the linear muffin-tin orbitals (LMTO) method in the atomic-sphere-approximation (ASA), and yields results showing that both TbMn6Sn6 and DyMn6Sn6 are ferrimagnetic compounds with antiparallel aligned moments ofR and Mn atoms. In this research the 4f states ofR atoms are treated as localized states, i.e., the hybridization of 4f states with other valence electrons is neglected. The moments of Mn in both compounds were determined to be 2.43 μB and 2.38 μB, respectively. The considerably small additional moments for Mn from the spin-orbit coupling indicates that the spin-orbital coupling is not dominated for Mn atoms. The total moments of Tb and Dy atoms are 10.28 μB and 11.20 μB. All the calculation findings accorded well with experimental results. Project supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry of China.  相似文献   

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