Production of (S)-β-Nitro Alcohols by Enantioselective C−C Bond Cleavage with an R-Selective Hydroxynitrile Lyase

Hydroxynitrile lyase (HNL)-catalysed stereoselective synthesis of β-nitro alcohols from aldehydes and nitroalkanes is considered an efficient biocatalytic approach. However, only one S-selective HNL—Hevea brasiliensis (HbHNL)—exists that is appropriate for the synthesis of (S)-β-nitro alcohols from the corresponding aldehydes. Further, synthesis catalysed by HbHNL is limited by low specific activity and moderate yields. We have prepared a number of (S)-β-nitro alcohols, by kinetic resolution with the aid of an R-selective HNL from Arabidopsis thaliana (AtHNL). Optimization of the reaction conditions for AtHNL-catalysed stereoselective C−C bond cleavage of racemic 2-nitro-1-phenylethanol (NPE) produced (S)-NPE (together with benzaldehyde and nitromethane, largely from the R enantiomer) in up to 99 % ee and with 47 % conversion. This is the fastest HNL-catalysed route known so far for the synthesis of a series of (S)-β-nitro alcohols. This approach widens the application of AtHNL for the synthesis not only of (R)- but also of (S)-β-nitro alcohols from the appropriate substrates. Without the need for the discovery of a new enzyme, but rather by use of a retro-Henry approach, it was used to generate a number of (S)-β-nitro alcohols by taking advantage of the substrate selectivity of AtHNL.     

网络环境下高职院校学生思想政治教育的创新刍议

本文将明确网络环境下高职院校学生思想政治教育进行创新的重要性和必要性，探究网络环境下高职院校学生思想政治教育面临的挑战，并提出一些在网络环境下高职院校学生思想政治教育进行创新的途径。     

Scalability of assessments of wiki-based learning experiences in higher education

In recent years, the focus on higher education learning has shifted from knowledge to skills, with interpersonal skills likely being the most difficult to assess and work with. Wikis ease open collaboration among peers. A number of these skills can be objectively assessed by using wikis in an educational environment: collaborative writing, conflict resolution, group management, leadership, etc. However, when the number of students increases, their interactions usually increase at a higher rate. Under these circumstances, traditional assessment procedures suffer from scalability problems: manually evaluating in detail the information stored in a wiki to retrieve objective metrics becomes a complex and time-consuming task. Thus, automated tools are required to support the assessment of such processes. In this paper we compare seven case studies conducted in Computer Science courses of two Spanish universities: Cádiz and Seville. We comment on their different settings: durations, milestones, contribution sizes, weights in the final grade and, most importantly, their assessment methods. We discuss and compare the different methodologies and tools used to assess the desired skills in the context of each case study.     

Microbubble generator excited by fluidic oscillator's third harmonic frequency

Efficient generation of sub-millimetre microbubbles was recently made possible by pulsating the flow of gas supplied into a parallel-exits aerator, using a fluidic oscillator for the purpose. Without moving parts, it can generate oscillation at high frequency, an important factor due to bubble natural frequency rapidly increasing with the desirable decrease of their size. This paper discusses development of an unusual oscillator – a part of an integral oscillator/aerator unit – capable of generating a particularly high driving frequency, in the kilohertz range, in a layout that promotes a strong third harmonic frequency of the basic oscillation.     

Teachers’ attitude regarding the use of ICT. A factor reliability and validity study

Current research examines the need for design and validation of a unifactorial scale to measure attitudes of university teachers with regard to ICT. The main goal of this study is to achieve a simple scale, composed of a single factor contributing a clearly reliable measure with acceptable content and factorial validity. A case study is presented, which has been developed with the teaching staff of the University of Salamanca (Spain). In this case study, an expert content validation was done at a first stage. After that, an attitude scale regarding the usage of ICT in teaching was applied with a representative sample of teachers (N = 2329; n = 161). An individual analysis of the items was made with the obtained results and then a Cronbach’s alpha based reliability test was carried out to show the internal consistency of the survey. Finally, an exploratory and confirmatory factor analysis was applied to prove its structural soundness and unifactoriality. The main conclusion of this paper is to offer to the scientific community a tool with adequate psychometric properties that gives added pedagogical value to the introduction of ICT in higher education teaching.     

Experimental study and empirical correlation development of fuel properties of waste cooking palm biodiesel and its diesel blends at elevated temperatures

In this experimental work, the density, dynamic viscosity and higher heating value of methyl ester based waste cooking palm-biodiesel oil (WMEPB) was investigated under varying temperature and blend ratio condition with No. 2 diesel fuel. The transesterified fatty acid methyl ester of palm vegetable oil collected from local food and beverage shops was used as neat biodiesel. Four different fuel blends (20%, 40%, 60% and 80% by volume mixing with base diesel) were studied along with base No. 2 diesel fuel and pure biodiesel. Tests for dynamic viscosity and density were performed in the temperature range 0–130 °C for each fuel sample whereas the higher heating values were determined at 25 °C room temperature condition. It is found that pure biodiesel has the highest density and dynamic viscosity at a given temperature whereas it exhibits lowest combustion heating value among the six fuels. Moreover, the density for each fuel sample decreases linearly with the increase in temperature. On the other hand, the dynamic viscosity decreases exponentially with the temperature for each fuel sample. In addition, based on the experimental results, regression correlations have been proposed for the density, dynamic viscosity, and higher heating value of the fuels. Subsequently, comprehensive error analyses of these proposed correlations were performed. In particular, the correlation for density and dynamic viscosity were respectively compared with Kay's mixing rule and Grunberg-Nissan mixing rule theory in order to validate their applicability. It is found that density correlations predicted within ±0.3% average error band. And, as high as 72.2% of the dynamic viscosity data were in the range of ±5% average error while the remaining data fell within ±10% error range. And finally, through a comparative study with the available fuel property results of fresh methyl ester palm biodiesel, it is found that available existing correlations derived from fresh palm biodiesel studies can not accurately predict the fuel properties of same waste biodiesel and its blends with diesel.     

中国高等教育大众化出现的问题及对策

随着高等教育大众化时代的到来,中国高等教育面临着学龄人口减少、教学质量下降、财政运行困难和毕业生就业难等问题。针对上述问题,提出了致力高等教育国际化、大力发展成人教育、加强校企合作、强化特色办学和严格执行教师资格认定制度等对策。     

导高职学生走进健身广场提升运动技能的探析

学校体育工作不仅是教育事业的有机组成部分,而且是全民健身事业的重要内容,还是全体公民终身体育的教育基础,为了使学生全面适应社会的发展,跟上时代的步伐,我们必须开发有效的学习手段来增强学生的学习能力,以适应现代教学需要和社会的需求。