Evaluation of Cognitive Complexity of Tasks for the Topic Hydrogen Exponent in the Solutions of Acids and Bases

The aim of this study was evaluation of cognitive complexity of tasks for the topic hydrogen exponent in the solutions of acids and bases and its validation. The created procedure included an assessment of the difficulty of concepts and an assessment of their interactivity. There were 48 freshmen students enrolled in the study program Basic academic studies in chemistry. As a research instrument for assessing performance, test of knowledge was specifically constructed for this research. Each task in the test was followed by a seven-point Likert scale for the evaluation of invested mental effort. The evaluation of cognitive complexity was confirmed by a series of linear regression analysis where high values of correlation coefficients are obtained among the examined variables: student’s performance and invested mental effort (dependent variables) and cognitive complexity (independent variable)

Functional Expression of Human Adenine Nucleotide Translocase 4 in Saccharomyces Cerevisiae

The adenine nucleotide translocase (ANT) mediates the exchange of ADP and ATP across the inner mitochondrial membrane. The human genome encodes multiple ANT isoforms that are expressed in a tissue-specific manner. Recently a novel germ cell-specific member of the ANT family, ANT4 (SLC25A31) was identified. Although it is known that targeted depletion of ANT4 in mice resulted in male infertility, the functional biochemical differences between ANT4 and other somatic ANT isoforms remain undetermined. To gain insight into ANT4, we expressed human ANT4 (hANT4) in yeast mitochondria. Unlike the somatic ANT proteins, expression of hANT4 failed to complement an AAC-deficient yeast strain for growth on media requiring mitochondrial respiration. Moreover, overexpression of hANT4 from a multi-copy plasmid interfered with optimal yeast growth. However, mutation of specific amino acids of hANT4 improved yeast mitochondrial expression and supported growth of the AAC-deficient yeast on non-fermentable carbon sources. The mutations affected amino acids predicted to interact with phospholipids, suggesting the importance of lipid interactions for function of this protein. Each mutant hANT4 and the somatic hANTs exhibited similar ADP/ATP exchange kinetics. These data define common and distinct biochemical characteristics of ANT4 in comparison to ANT1, 2 and 3 providing a basis for study of its unique adaptation to germ cells

Publisher: Institute for Animal Husbandry, Belgrade-Zemun UDC 637.4 DOI: 10.2298/BAH1002117R COMPETITIVENESS OF TABLE EGGS FROM NON- CAGE HOUSING SYSTEMS

Abstract: Experiences of developed countries show that production costs in non-cage housing systems for layer hens are from 8 to 59%, and in organic production over 200 % higher compared to production costs in the conventional cage system. Consequently, eggs deriving from non-cage systems can be competitive only provided that the consumers are willing to pay adequately higher price for eggs produced in said way. In this paper, 720 consumers were interviewed with aim to determine to what extent they are prepared to pay higher price for eggs deriving from non-cage systems. Obtained results show that over of consumers were willing to pay higher price for such eggs. This, however, was limited in majority of consumers (53%) to increase of price by up to 20%. This is enough to cover increased costs of production in the floor system, but not in case of free range system and organic production. Taking into consideration the fact that in EU, from year 2012, serious egg deficit can be expected due to the ban of housing of layers in battery cages, and that this deficit will probably be covered by supply from surrounding countries, it can be concluded that for certain number of producers transition to non-cage housing systems can be good business decision. For most of them, however, transition to so called enriched cages poses less risk, and in this production system they can expect premium price for egg with increase of production costs not exceeding 15%. Key words: table eggs, price, competitiveness, non-cage housing system