Purification and Characterisation of Endopeptidase Produced by Lactococcus Lactis Subsp. Lactis RI 11

In the this study, 10 isolates of Lactic Acid Bacteria (LAB) were isolated from ikan rebus (steam fish) purchased from a local market, was characterised by phenotypical and biochemical characteristics. Eight isolates were identified as Lactococcus lactis subsp. lactis and were evaluated for endopeptidase activity. As the endopeptidase activity of the crude cell extracts varied among isolates, only Lc. lactis subsp. lactis RI 11 was selected for further study. The optimum endopeptidase activity was at pH 7.5 and 45°C. The crude enzyme preparation was purified to apparent homogeneity by ammonium sulphate fractionation, muon and cation exchange chromatography and gel filtration chromatography. The purification procedure has resulted 1.55% yield and 2.36 purification fold. As the purified endopeptidase has 3 optimum temperatures (10°C, 50°C and 90°C) and pH (3.5, 6.5 and 9.5), it was likely that the endopeptidase consist more than one isoenzymes. The molecular mass of purified endopeptidase was approximately 14.15 kDa estimated with Sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis. However, a lower molecular mass of 3.9 kDa was obtained from gel filtration chromatography. In terms of substrate specificity, the purified endopeptidase showed higher substrate affinity towards bradykinin with a K.m value of 0.029 mM, whilst, oxidised insulin B chain demonstrated the highest production rate with the Vmax value of 10.52

Developing Quality Learning Materials for Effective Teaching and Learning in an ODL environment: Making the jump from print modules to online modules

This paper highlights the need to develop quality learning materials for effective teaching and learning in an online and distance learning (ODL) environment. This is especially important today as ODL institutions mushroom and compete on an increasingly global platform. While this has helped to widen access to education, it also means that more attention needs to be paid to the quality of teaching and learning materials if ODL institutions wish to continue attracting learners, reduce attrition rate and stay relevant. Attempts must be made to come up with good learning material which can offer ODL learners a fulfilling and enriching learning experience. At Open University Malaysia, a number of e-learning initiatives have been launched towards this end. One of these is the online, hypertext-linked or html modules. The first phase of this project has already been implemented. The rationale for this latest e-learning initiative is outlined. The paper also comes up with a taxonomy of best practice beliefs which identify the characteristics html modules should have if they are to be truly effective. It is hoped that this will provide some sort of benchmark, or standards, for html modules to strive for, as well as a set of criteria for a formative evaluation of the modules. Ultimately, this may provide guidelines for improving html modules and useful pointers for fine tuning this e-learning initiative in the future. (Author's abstract

Evaluation of Half-metallic Antiferromagnetism in A2{\cal A}_2CrFeO6_6 ({A\cal A}=La, Sr

The nearly well-ordered double perovskite La$_2$CrFeO$_6$ has been synthesized recently. Contrary to previous theoretical predictions, but in agreement with experimental observations, our first principle calculations indicate an insulating ferrimagnet La$_2$CrFeO$_6$ with antialigned S=3/2 Cr$^{3+}$ and S=5/2 Fe$^{3+}$ ions,using the local spin density approximation (LSDA), a correlated band theory LDA+U, and a semilocal functional modified Becke-Johnson method. Additionally, we investigated the double perovskite Sr$_2$CrFeO$_6$, which is as yet unsynthesized. In LSDA calculations, this system shows formally tetravalent Cr and Fe ions both having antialigned $S$=1 moments, but is a simple metal. Once applying on-site Coulomb repulsion U on both Cr and Fe ions, this system becomes half-metallic and the moment of Fe is substantially reduced, resulting in zero net moment. These results are consistent with our fixed spin moment studies. Our results suggest a precisely compensated half-metallic Sr$_2$CrFeO$_6$.Comment: 7 page

Sobolev spaces and trace theorems for time-fractional evolution equations

We establish trace and extension theorems for evolutionary equations with the Caputo fractional derivatives in (weighted) $L_p$ spaces. To achieve this, we identify weighted Sobolev and Besov spaces with mixed norms that accommodate solution spaces and their initial values well-suited for equations involving time-fractional derivatives. Our analysis encompasses both time-fractional sub-diffusion and super-diffusion equations. We also provide observations on the initial behavior of solutions to time-fractional equations

Electron and phonon band-structure calculations for the antipolar SrPt3_{3}P antiperovskite superconductor: Evidence of low-energy two-dimensional phonons

SrPt3P has recently been reported to exhibit superconductivity with Tc = 8.4 K. To explore its superconducting mechanism, we have performed electron and phonon band calculations based on the density functional theory, and found that the superconductivity in SrPt3P is well described by the strong coupling phonon-mediated mechanism. We have demonstrated that superconducting charge carriers come from pd\pi-hybridized bands between Pt and P ions, which couple to low energy (~ 5 meV) phonon modes confined on the ab in-plane. These in-plane phonon modes, which do not break antipolar nature of SrPt3P, enhance both the electron-phonon coupling constant \lambda and the critical temperature Tc. There is no hint of a specific phonon softening feature in the phonon dispersion, and the effect of the spin-orbit coupling on the superconductivity is found to be negligible.Comment: 5 pages, 5 figures, 1 tabl

Teaching and Learning in an ODL University: Bridging the Gap between the Learning Environment, Learners and Instructors

Many researchers have commented that educators need to use different techniques and methodologies in an online, distance learning (ODL) environment. The constructivist perspective is said to be especially relevant to the ODL environment as it emphasizes independent learning and the active construction of knowledge, which suits ODL learners as they are usually self-motivated and more mature. However, two questions come to mind – do instructors and learners in the ODL environment really embrace constructivist principles in teaching and learning, or is there a gap between the learning environment, learners and instructors? This paper attempts to answer these questions by determining the preferred teaching and learning styles of instructors and learners in an ODL university, to gauge if they are more behaviourist or constructivist in their teaching beliefs and practices. It also attempts to identify the constructivist elements present in an ODL university and come up with conceptual framework for nurturing constructivist practices.(Authors' abstract

Low-bias Negative Differential Resistance effect in armchair graphene nanoribbon junctions

Graphene nanoribbons with armchair edges (AGNRs) have bandgaps that can be flexibly tuned via the ribbon width. A junction made of a narrower AGNR sandwiched between two wider AGNR leads was recently reported to possess two perfect transmission channels close to the Fermi level. Here, we report that by using a bias voltage to drive these transmission channels into the gap of the wider AGNR lead, we can obtain a negative differential resistance (NDR) effect. Owing to the intrinsic properties of the AGNR junctions, the on-set bias reaches as low as ~ 0.2 V and the valley current almost vanishes. We further show that such NDR effect is robust against details of the atomic structure of the junction, substrate and whether the junction is made by etching or by hydrogenation.Comment: The following article has been submitted to Applied Physics Letters (http://scitation.aip.org/content/aip/journal/apl). Copyright (2014) Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported Licens