Differential pH sensitivity of tissue superoxide dismutases

Superoxide dismutase (SOD) activities in the human and rat RBCs and rat liver, kidney, brain and heart mitochondria as well as cytosolic fractions were determined by the pyrogallol assay procedure with slight modifications. Measurements were carried out in 0.1 M potassium phosphate buffer pH 8.0 and 9.2 to assess the pH stability of the SODs from various systems. Under these conditions the SODs from different systems including RBCs exhibited differential pH stability i.e. they displayed differential susceptibility at pH 9.2. Even in a given tissue, the mitochondrial and cytosolic SODs contents show a tissue-specific pattern. Our results also suggest that measurements carried out at pH 8.0 may give more realistic estimates of SOD activities.     

Learner modelling: systematic review of the literature from the last 5 years

The field of adaptive e-learning is continuously developing. More research is being conducted in this area as adaptive e-learning aims to provide learners with adaptive learning paths and content, according to their individual characteristics and needs, which makes e-learning more efficient and effective. The learner model, which is a representation of different learner’s characteristics, plays a key role in this adaptation. This paper presents a systematic literature review about learner modelling during the last 5 years, describing the different modelled characteristics and the adopted modelling techniques and modeling types: automatic modeling and collaborative modeling. 107 publications were selected and analyzed, and six categories of the modelled characteristics were identified. This literature review contributes to the identification of the learners’ individual traits and presents the most used modelling techniques for each of them. It also identifies the latest research trends of Learner Modeling and generates future research directions in this field.

     

Not all reading disabilities are alike

In this article, reading disability is defined broadly to refer to below-average achievement in reading comprehension as assessed by a standardized test. With our research we tried to answer the question of whether all children with reading disability share a common etiology of deficient phonology, or constitute heterogeneous groups. The answer to this question was sought in four studies that examined reading disabilities from the perspective of componential skills of reading. In Part 1, the results of the first study are reported. A principal-components analysis of the performance of 139 children from Grades 3, 4, and 6 on reading-related tasks yielded two factors: decoding and comprehension. However, factor analyses conducted for each grade separately indicated that orthographic skill and processing speed could possibly constitute a third component. The orthography-speed factor emerged as a factor only in the 6th grade. Part 2 of this article reports the findings of three studies that analyzed the componential skills profiles of poor readers. It was found that the poor readers constituted heterogeneous groups and that four different types of poor readers could be identified with deficiency in any one of the following skills: (a) decoding only, (b) comprehension only, (c) a combination of decoding and comprehension, and (d) a combination of orthographic processing and reading speed. It was also found that the criteria used in selecting poor readers influenced the distribution of the ratio of the four types of poor readers within any given group.     

Effect of feeding Carica papaya (Papita) fruits on blood lipid profile of albino rabbits

Effect of feeding ripe and unripe papaya fruit pulps were investigated on blood lipid profile of normal male adult albino rabbits by giving them pulps separately at the dose of 15 and 30g per day along with standard diet over a period of six weeks. As compared to controls both fruit pulps resulted in highly significant (p<0.001) and consistent lowering of serum cholesterol, low density lipoprotein cholesterol and triglycerides and elevation in phospholipids and high density lipoprotein cholesterol levels at 1,3 and 6 weeks of fruit pulp feeding indicating a dose dependent effect. Observations clearly support medicinal value ofC. Papaya in the management of atherosclerosis, fatty liver, ischaemic changes and consequential myocardial infarction.     

Spelling performance of English consonants among students whose first language is Arabic

The purpose of the present study was to examine the influence of some aspects of the Arabic phonological system on spelling English words. In Study 1, the spelling performance of Arabic students from grades four and six was compared with English students in cognate phoneme pairs which exist across both languages (/d/ and /t/), and pairs in which only one of the phonemes exists in Arabic (/b/ and /p/, /f/ and /v/) using a spelling test which contained words with the target phonemes. The findings showed that the Arabic participants performed similarly to the English participants on the phonemes /t/ and /d/, but they tended to spell the phonemes /b/, /p/, /f/, and /v/ using their cognate pairs more often than the English participants did. In Study 2, the spelling performance of Arabic students was compared across grades 4, 6, 8, and 10 for the same target phonemes. The analyses showed no difference between the Arabic participants in how often they confused the target phonemes with their cognate pairs across the different grade levels, except for the phonemes /p/ and /v/, for which the effect size was small. The findings of this study demonstrate the importance of phonology in spelling, as well as the influence of the first language on spelling in a second language. They also indicate that Arabic students continue to be dependent on phonological processes when spelling English words even as they grow older.     

Hardy-weinberg equilibrium and the foundations of evolutionary genetics 3. Incorporating Mutation and Migration

The year 2008 marked the 150th anniversary of the debut of the concept of natural selection as a mechanism of adaptive evolution through the reading of papers by Darwin and Wallace to the Linnaean Society. It also marked the 100th anniversary of the enunciation of the principle defining the inertial state of populations from a genetic viewpoint through the independent publication of papers on the topic by G H Hardy and W Weinberg. In this series, we examine the significance of the Hardy-Weinberg Equilibrium as a basic model of population genetics that forms the foundation for evolutionary genetics. In Part 3 of this series, we begin to relax some of the assumptions of the basic model underlying the Hardy-Weinberg Equilibrium, and analyse the situations where either mutation or migration occur in an otherwise ideal large population.     

DNA chip

This article presents a brief overview of DNA chips, or microarrays. Microarrays are a very significant technological development in molecular biology, and are perhaps the most efficient tool available for functional genomics today.     

Vignettes of Haeckel’s Contributions to Biology

Ernst Haeckel was a very versatile and complete biologist, equally at home with imaginative leaps of conceptualization, serious natural history in the wild, and meticulous experimentation in embryology. His work shaped the development of a holistic evolutionary perspective that brought ecology, ontogeny, phylogeny, and biogeography together into a unified explanation of the patterns of diversity seen in the living world. He, along with Darwin and Mendel, was perhaps one of the three most consequential biologists of the nineteenthcentury, in many ways the golden age of biology.     

Event based estimation with correlated noises

For a linear system having event based measurements and correlated noises, a state estimation algorithm is proposed. A general event based sampling is employed to obtain the measurements, where in the case of unavailability of measurements, event based strategy itself is used to obtain approximate state and covariance estimates. To deal with correlated noises, a two-step ahead prediction approach is employed to obtain recursive equations for estimated state and covariance. The obtained results are illustrated using a simulation example.