Performatiwiteit en die hedendaagse skool(hoof)

Performativity and the modern school (principal) Based on observations in the field of education management science, including the results of a recent empirical survey, we concluded that schools and their principals have become inundated with the demands for performativity, i.e. the demand to achieve in measurable terms as well as submit to the cult of efficiency and effectiveness. After briefly considering recent developments and changes in schools and in the work of school principals, we refer to the findings of the empirical survey. This is followed by a discussion of three key objections to performativity in schools and in the work of principals, namely the reductionism that it presupposes, its non-pedagogical tendencies and its negative effects on the school as a societal relationship. The discussion is conducted within a Christian-reformational frame of reference

A study on the function of some subcellular systems of the sheep myocardium during gousiekte. II. The contractile protein system

Two groups of Merino sheep were intoxicated separately and at different times with "gousiektebossie" (Pachystigma pygmaeum) until definite symptoms of heart failure were auscultated. Cardiectomy was carried out and some ventricular muscle from I group was stored in 50% glycerol at -20⁰C for about 4 months. Natural actomyosin (n-actomyosin) was subsequently extracted and tested for magnesium, calcium and adenosine triphosphate (ATP)-dependent adenosine triphosphatase (ATP-ase) activity as well as for superprecipitation characteristics. Muscle strips were taken from the other group and stored for 2 weeks in 50% glycerol at -20⁰C, where after it was analysed for an isometric tension-calcium response. The data showed no difference between gousiekte and control sheep in the sensitivity of the contractile system to the activating effect of calcium ions with respect to isometric tension development. A significant reduction of the magnesium dependent ATP-ase was found for gousiekte n-actomyosin in either the presence or absence of calcium ions. A depressed sensitivity for this enzyme to increasing concentrations of ATP in comparison to controls was also found ([ATP] < 1mM, [MgC1₂] = 1mM). No significant difference could be detected in the sensitivity of the n-actomyosin:ATP-ase system to magnesium. n-Actomyosin:ATP-ase of gousiekte hearts revealed a depressed sensitivity to calcium ions. Gousiekte n-actomyosin also showed a significant depression in the rate of superprecipitation with a concomitant increase in the duration of the clearing phase. We conclude from these observations that a definite biochemical lesion is induced in the contractile proteins of heart muscle obtained from sheep intoxicated with "gousiektebossie" at the stage of cardiac failure. This condition is characterized by abnormal superprecipitation characteristics and a depressed n-actomyosin:ATP-ase activity, showing a reduced sensitivity to the activating effect of calcium ions.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

A study on the function of some subcellular systems of the sheep myocardium during gousiekte. I. The energy production system

In order to determine the status of the energy production system of the heart during cardiac failure of sheep with gousiekte, observations were made of the heart tissue levels of adenosine triphosphate (ATP), creatine phosphate (CrP), inorganic phosphate, reduced nicotine adenine dinucleotide (NADH) and lactate. Some measurements on oxidative phosphorylation were also made. A significant decrease in ATP and CrP levels coincided with a simultaneous rise in the ATP:CrP ratio and lactate levels in gousiekte hearts. No significant deviations in inorganic phosphate and NADH levels could be demonstrated. These abnormalities were accompanied by a decreased uptake of oxygen by isolated mitochondria of gousiekte hearts. There was a marked increase in the anaerobic state of the hearts of dying gousiekte sheep, while the values of NADH and the ATP:CrP ratio at a presymptomatic stage indicated a possible early derangement in the energy metabolism of sheep fed the toxic material. No hypertrophy could be detected for the failing ventricles of gousiekte sheep after being corrected for a significant amount of oedema found in the heart tissue of these animals. It was concluded that the depressed ATP and CrP levels in the heart tissue of gousiekte sheep during cardiac failure could at least in part, be attributed to a depressed aerobic energy production. It is not possible, however, to state whether this is a primary or a secondary response due to intoxication and also whether it could be seen as a cause or effect of cardiac failure.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Cane Water Content and Yield Responses of Vitis vinifera L. cv. Sultanina to Overhead Irrigation During the Dormant Period

The possibility to increase grapevine cane water content during the dormant period by applying overhead irrigation, and thereby increasing yield, was investigated in a semi-arid summer rainfall climate. A field trial was carried out with Sultanina grapevines in the Lower Orange River region over two seasons. During the 2000/2001 season control grapevines (Tl) that received no overhead irrigation in winter were compared to ones receiving overhead irrigation applied over a ca. 30-day period, starting either in July (T2), mid-July (T3), August (T4) or mid-August (TS).  Overhead irrigation was applied as ten-minute pulses on the hour from 10:00 until 16:00. Due to the lack of winter rainfall, all treatments received normal, under-vine irrigation in winter to avoid severe water deficits. All treatments, except T2, were repeated during the 2001/2002 season. Two additional treatments which received no irrigation during winter were included during the second season. Of these two, T6 received overhead irrigation in August, whereas T7 received no overhead irrigation. Compared to the Tl control, overhead irrigation applied during August 2000 (T4) not only increased cane water content measured before bud break, i.e. early September, but also increased yield.  The other overhead irrigation treatments did not affect cane water content or yield. During the second season overhead irrigation started in mid-July (T3) or in the beginning of August (T4) induced higher yields compared to grapevines that received overhead irrigation in the period before bud break (TS). Where available soil water depletion of 90% occurred, overhead irrigation (T6) seemed to negate the adverse effects of dry soil on yield. In contrast, cane water content and yield were considerably lower where neither normal nor overhead irrigation was applied (T7), compared to T3 and T4. These results confirmed that overhead irrigation can increase cane water content and yield, and that soil water deficits during the dormant period should be avoided. Overhead irrigation and/or water deficits during winter did not affect cane mass, as measured at the end of the following growing season