1,448 research outputs found
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 CrFeO ({}=La, Sr
The nearly well-ordered double perovskite LaCrFeO has been
synthesized recently. Contrary to previous theoretical predictions, but in
agreement with experimental observations, our first principle calculations
indicate an insulating ferrimagnet LaCrFeO with antialigned S=3/2
Cr and S=5/2 Fe 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
SrCrFeO, which is as yet unsynthesized. In LSDA calculations, this
system shows formally tetravalent Cr and Fe ions both having antialigned =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 SrCrFeO.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) 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 SrPtP 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
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