The radio luminosity distribution of pulsars in 47 Tucanae

We have used the Australia Telescope Compact Array to seek the integrated radio flux from all the pulsars in the core of the globular cluster 47 Tucanae. We have detected an extended region of radio emission and have calibrated its flux against the flux distribution of the known pulsars in the cluster. We find the total 20-cm radio flux from the cluster's pulsars to be S = 2.0 +/- 0.3 mJy. This implies the lower limit to the radio luminosity distribution to be L_1400 = 0.4 mJy kpc^2 and the size of the observable pulsar population to be N < 30.Comment: 7 pages, 4 figures, MNRAS in pres

Increased apoptosis and DNA double-strand breaks in the embryonic mouse brain in response to very low-dose X-rays but not 50 Hz magnetic fields

The use of X-rays for medical diagnosis is enhancing exposure to low radiation doses. Exposure to extremely low-frequency electromagnetic or magnetic fields is also increasing. Epidemiological studies show consistent associations of childhood leukaemia with exposure to magnetic fields but any causal relationship is unclear. A limitation in assessing the consequence of such exposure is the availability of sensitive assays. The embryonic neuronal stem and progenitor cell compartments are radiosensitive tissues. Using sensitive assays, we report a statistically significant increase in DNA double-strand break (DSB) formation and apoptosis in the embryonic neuronal stem cell compartment following in utero exposure to 10–200 mGy X-rays. Both endpoints show a linear response. We also show that DSB repair is delayed following exposure to doses below 50 mGy compared with 100 mGy. Thus, we demonstrate in vivo consequences of low-dose radiation. In contrast to these impacts, we did not observe any significant induction of DSBs or apoptosis following exposure to 50 Hz magnetic fields (100 or 300 µT). We conclude that any DSB induction by treatment with magnetic fields is lower than following exposure to 10 mGy X-rays. For comparison, certain procedures involving computed tomography scanning are equivalent to 1–5 mGy X-rays

Long-term variability of radio-bright BL Lacertae objects

Radio-bright BL Lacertae objects (BLOs) are typically variable and exhibit prominent flaring. We use a sample of 24 BLOs to get a clear idea of their flaring behavior and to find possible commonalities in their variability patterns. Our goal was to compare the results given by computational time scales and the observed variability parameters determined directly from the flux curves. Also, we wanted to find out if the BLO flares adhere to the generalized shock model. We use long-term monitoring data from 4.8, 8, 14.5, 22, 37, 90 and 230 GHz. The structure function, discrete correlation function and Lomb-Scargle periodogram time scales, calculated in a previous study, are analyzed in more detail. We determine flare durations, rise and decay times, absolute and relative peak fluxes from the monitoring data. We find that BLOs demonstrate a wide range of variability behavior. BLOs include sources with fast and strong variability, such as OJ 287, PKS 1749+096 and BL Lac, but also sources with more rolling fluctuations like PKS 0735+178. The most extreme flares can last for up to 13 years or have peak fluxes of approximately 12 Jy in the observer's frame. When the Doppler boosting effect is taken into account, the peak flux of a flare does not depend on the duration of the flare. A rough analysis of the time lags and peak flux evolution indicates that BLO flares in the mm - cm wavelengths are high-peaking, i.e., are in the adiabatic stage. Thus, the results concur with the generalized shock model.Comment: Published in the Astronomical Journa

Low-speed aerodynamic characteristics of a 1/8-scale X-29A airplane model at high angles of attack and sideslip

A 1/8-scale model of the X-29A airplane was tested in the Ames 12-Foot Pressure Wind Tunnel at a Mach number of 0.20 and Reynolds numbers of 0.13 x 10 to the 6th power to 2.00 x 10 to the 6th power based on a fuselage forebody depth of 0.4 ft, For the test series presented herein, the angle of attack ranged from 40 deg. to 90 deg. and the angle of sideslip ranged from -10 deg. to 30 deg. for the erect attitude. Tests with the model inverted covered angles of attack from -40 deg. to -90 deg. and angles of sideslip from -30 deg. to 10 deg. Data were obtained for the basic design and for several forebody strakes. An alternate forebody design was also tested. The results provided information for selection of forebody strakes for compensation of Reynolds number effect on the 1/25-scale free-spinning model tested in the Langley Spin Tunnel

State of charge and state of health estimation for lithium iron phosphate batteries

Thesis (MEng)--Stellenbosch University, 2023.ENGLISH ABSTRACT: Accurate state of charge (SOC) and state of health (SOH) is important for safe and optimal operation of lithium batteries. This study investigates multiple existing SOC and SOH estimation methods. These methods are analyzed for their advantages and disad- vantages. There is speci_cally focused on the practicality of these methods to implement them in a typical energy storage system with variable operating conditions. The relationship between the saturation charged energy (energy that is charged dur- ing the saturation charge phase) and the SOH of a lithium iron phosphate (LFP) cell is investigated. A SOH estimation method is proposed based on this relationship that is found. This estimation method only requires partial charging data and does not need data of a full charge or discharge cycle. A hardware system is developed to perform charge and discharge cycles on a single LFP cell while monitoring the vital parameters of the cell. This system is used to perform all testing that is required to develop and evaluate the proposed SOH estimation method. The coulomb counting SOC estimation method is investigated to be improved. Various enhancements are made to the existing method to increase its accuracy and practicality. There is speci_cally focused on considering the charge and discharge e_ciencies of a LFP cell while performing coulomb counting. The OCV (open-circuit voltage) SOC estima- tion method is also combined with the coulomb counting method to form a hybrid SOC estimation method. It was found that the improved hybrid SOC estimation method and the newly found SOH estimation method showed similar accuracy when compared to existing methods. But the main bene_t of these new found methods is their practicality for typical LFP energy storage systems. The improved methods proved to be insensitive to their operating conditions as they do not require a very controlled charge or discharge cycle to obtain accurate estimation values for the SOC and SOH.AFRIKAANS OPSOMMING: Akkurate laaitoestand (LT Eng:SOC) en gesondheidstoestand (GT Eng:SOH) is be-langrik vir veilige en optimale gebruik van litium batterye. Hierdie studie ondersoek verskeie bestaande LT en GT beramingsmetodes. Hierdie metodes word ontleed vir hul voor- en nadele. Daar word spesi ek gefokus op die praktiese toepassing van hierdie metodes om dit in 'n tipiese energiebergingstelsel met veranderlike bedryfstoestande te implementeer. Die verwantskap tussen die energie wat tydens die versadigingsladingfase van 'n LFP- sel gelaai word en die GT van die sel word ondersoek. 'n GT beramingsmetode word voorgestel op grond van hierdie verwantskap wat gevind word. Hierdie beramingsmetode vereis slegs gedeeltelike laai data en benodig nie data van 'n volle laai- of ontlaai-siklus nie. 'n Hardewarestelsel word ontwikkel om laai- en ontlaai-siklusse op 'n enkele litium- ysterfosfaat (LFP)-sel uit te voer terwyl die kritiese parameters van die sel gemonitor word. Hierdie stelsel word gebruik om alle toetse uit te voer wat nodig is om die voorge- stelde GT beramingsmetode te ontwikkel en te evalueer. Die coulomb telling LT beramingsmetode word ondersoek om verbeter te word. Ver- skeie verbeterings word aan die bestaande metode aangebring om die akkuraatheid en bruikbaarheid daarvan te verhoog. Daar is spesi ek gefokus op die oorweging van die laai- en ontlaai doeltre endheid van 'n LFP-sel terwyl coulomb-telling uitgevoer word. Die oop kring spanning LT beramingsmetode word ook gekombineer met die coulomb- telmetode om 'n hibriede SOC-beramingsmetode te vorm. Daar is gevind dat die verbeterde hibriede LT beramingsmetode en die nuutgevonde GT beramingsmetode soortgelyke akkuraatheid getoon het in vergelyking met bestaande metodes. Maar die grootste voordeel van hierdie nuutgevonde metodes is hul praktiese toepassing vir tipiese LFP-energiebergingstelsels. Die verbeterde metodes toon om on- sesitief te wees vir hul bedryfstoestande aangesien dit nie 'n baie beheerde volle laai of ontlaai-siklus benodig om akkurate beramingswaardes vir die LT en GT te verkry nie.Master

Teaching Land as an Extension of Self: The Role of Ecopsychology in Disrupting Capitalist Narratives of Land and Resource Exploitation

Ecopsychology, which investigates the human-nature relationship, draws on marginalized ways of knowing such as Native American Shamanism, “whole earth thinking,” and the dynamic feminine (Gomez &amp; Kanner, 1995). Impediments of literal classroom walls and systemic bias against unquantifiable course outcomes limits traditional pedagogy. Traditional pedagogical approaches to environmental curriculum reinforce perceived helplessness in the face of capitalist forces which identify land only as explotiable “other” (hooks, 2011). This paper describes a university English classroom's radical Ecopedagogy without spatial impedences and state policed “standards” that no longer enforce normative identity constructs. In this Ecopedagogy, students explore Biophilia, which awakens a powerful, dormant identity, expanding the self to include the entire biosphere. </jats:p

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This teaching notes describes an experience which leads to important questions about the nature of inquiry and social justice pedegogy