Transcultural nursing and malaria: Identifying global health strategies through the lived experiences of nurses from the villages surrounding Bamenda, Cameroon

This study highlights the challenges faced by nurses working in the villages surrounding Bamenda, Cameroon. This is done as a necessary first step towards developing a culturally compelling intervention strategy fro Malaria prevention/treatment, through direct interaction of nurses in villages surrounding Bamenda in Cameroon. Malaria and other diseases pose significant health care problems in remote regions of Cameroon

Addressing flux suppression, radio frequency interference, and selection of optimal solution intervals during radio interferometric calibration

The forthcoming Square Kilometre Array is expected to provide answers to some of the most intriguing questions about our Universe. However, as it is already noticeable from MeerKAT and other precursors, the amounts of data produced by these new instruments are significantly challenging to calibrate and image. Calibration of radio interferometric data is usually biased by incomplete sky models and radio frequency interference (RFI) resulting in calibration artefacts that limit the dynamic range and image fidelity of the resulting images. One of the most noticeable of these artefacts is the formation of spurious sources which causes suppression of real emissions. Fortunately, it has been shown that calibration algorithms employing heavy-tailed likelihood functions are less susceptible to this due to their robustness against outliers. Leveraging on recent developments in the field of complex optimisation, we implement a robust calibration algorithm using a Student’s t likelihood function and Wirtinger derivatives. The new algorithm, dubbed the robust solver, is incorporated as a subroutine into the newly released calibration software package CubiCal. We perform statistical analysis on the distribution of visibilities and provide an insight into the functioning of the robust solver and describe different scenarios where it will improve calibration. We use simulations to show that the robust solver effectively reduces the amount of flux suppressed from unmodelled sources both in direction independent and direction dependent calibration. Furthermore, the robust solver is shown to successfully mitigate the effects of low-level RFI when applied to a simulated and a real VLA dataset. Finally, we demonstrate that there are close links between the amount of flux suppressed from sources, the effects of the RFI and the employed solution interval during radio interferometric calibration. Hence, we investigate the effects of solution intervals and the different factors to consider in order to select adequate solution intervals. Furthermore, we propose a practical brute force method for selecting optimal solution intervals. The proposed method is successfully applied to a VLA dataset

Calibration and imaging with variable radio sources

Calibration of radio interferometric data is one of the most important steps that are required to produce high dynamic range radio maps with high fidelity. However, naive calibration (inaccurate knowledge of the sky and instruments) leads to the formation of calibration artefacts: the generation of spurious sources and the deformations in the structure of extended sources. A particular class of calibration artefacts, called ghost sources, which results from calibration with incomplete sky models has been extensively studied by Grobler et al. (2014, 2016) and Wijnholds et al. (2016). They developed a framework which can be used to predict the fluxes and positions of ghost sources. This work uses the approach initiated by these authors to study the calibration artefacts and ghost sources that are produced when variable sources are not considered in sky models during calibration. This work investigates both long-term and short-term variability and uses the root mean square (rms) and power spectrum as metrics to evaluate the “quality” of the residual visibilities obtained through calibration. We show that the overestimation and underestimation of source flux density during calibration produces similar but symmetrically opposite results. We show that calibration artefacts from sky model errors are not normally distributed. This prevents them from being removed by employing advanced techniques, such as stacking. The power spectrums measured from the residuals with a variable source was significantly higher than those from residuals without a variable source. This implies advanced calibration techniques and sky model completeness will be required for studies such as probing the Epoch of Reoinization, where we seek to detect faint signals below thermal noise

Design of solar -powered grass trimmer

Common grass-cutter machines are operated by fuel and electrical energy, which are expensive, and need high maintenance. To keep environment clean and reduce use of fuel a solar powered grass trimmer has been designed in this research work. The purpose of this study is to design and fabricate a solar-powered grass trimmer which is affordable, easy to operate and environment friendly. The grass trimmer uses a 12V, - 100AH battery to power a 12V DC motor of 180W. A solar panel 1 000V system voltage is used to charge the battery. A solar charge controller of 20A is used to control the energy into the battery. The machine uses sheet metal blade to cut the grass. It can run for almost two hours when fully charged and there is no sun. It is easy to tell if the battery is fully charged or flat.Mechanical and Industrial Engineerin

First-principles calculation of positron lifetimes and affinities in perfect and imperfect transition-metal carbides and nitrides

First-principles electronic structure and positron-state calculations for transition-metal carbides and nitrides are performed. Perfect NaCl structures as well as structures with metal or carbon/nitrogen vacancies are considered. The positron affinities and lifetimes are determined. The trends are discussed and the results are compared with recent positron lifetime measurements for group-IV and -V refractory metal carbides. The present analysis suggests, contradictory to an earlier interpretation, that positrons are trapped and annihilated at both carbon and metal vacancies. The concentration of metal vacancies detected by positron annihilation methods is probably very low, below the sensitivity limit of other experimental methods.Peer reviewe

A study on Alvar Aalto and his experimentation in Villa Mairea.

Modem architecture has often been understood under one style or -ism, and therefore the pictures were inevitably oversimplified and sometimes distorted with prejudices. However, if we look into one building, we come to face many conflicting testimonies with the asserted manifesto. For this reason, it is essential to excavate each design project as deeply as possible in order to reveal the richness and diversity of modem architecture. Eventually, it will lay more steadfast foundation of architectural historiography. As one small step of the work, this thesis aims at exploring the Villa Mairea project (1937-39) by Alvar Aalto (1898-1976). The Villa Mairea, for the clients Maire and Harry Gullichsen, has been regarded as one of the most important house designs in modem architectural history. Through an extensive collaboration with the clients, Aalto considered the house as an experimental laboratory, in which he could re-examine his established architectural concepts and possibilities for his later career. Owing to the experimental spirit, the design had come through various early versions with a number of drawings that show numerous and complex ideas. By analYSing the drawings, I made a chronological order of each design stage and produced computer 3D models of them. This thesis also investigates Aalto's experiments in the design. I categorised them into three: experiment with typo-morphology; with space; and with reconciliation of polarities, and researched their meaning in architecture. Additionally, I dealt with Aalto's collective housing designs because he argued that the experimental spirit in the Villa Mairea could be applied to mass-produced housing. They show 'Existenz-Maximum' that illustrates 'new individualism', which is also the character of Hans Scharoun's housing projects. Through this study, the depth of (modem) architecture became for me better illuminated. 'By advancing from one work to the next', we need to continually excavate the treasure of meaning in architecture

Stochastic Effect of Grain Elongation on Nanocrystalline Materials Strain and Strain Rate Produced by Accumulative Roll-Bonding and Equal Channel Angular Pressing

Severe plastic deformation techniques are acknowledged to produce elongated grains during fabrication of nanostructured materials. Previous models relating grain size to mechanical properties considered only equivalent radius, thus ignoring other approaches of measuring grain sizes such as semiminor axis, semimajor axis, and major axis radii that determine true grain shape. In this paper, stochastic models of nanomaterials mechanical properties that include the ignored parameters have been proposed. The proposed models are tested with data from nanocrystalline aluminum samples. The following facts were experimentally observed and also revealed by the models. Grain elongates to a maximum value and then decreases with further grain refinement due to grain breakages. Materials yield stress increases with elongation to a maximum and then decreases continuously. The varying approaches of measuring grain radius reveal a common trend of Hall-Petch and Reverse Hall-Petch Relationship but with different critical grain sizes. Materials with high curvature grains have more enhanced yield stress. Reducing strain rates leads to materials with more enhanced yield stress, with critical strain rates values beyond which further reductions do not lead to yield stress enhancement. It can be concluded that, by considering different approaches of measuring grain sizes, reasons for different yield stress for nanomaterials that were observed but could not be explained have been dealt with

Thermoluminescence of natural quartz

The kinetic and dosimetric features of the main thermoluminescence peak of quartz have been investigated in unannealed as well in quartz annealed at 500˚C for 10 minutes. The main peak is found at 92 and 86˚C respectively for aliquots of unannealed and annealed samples irradiated to 10 Gy and heated at 5.0˚C/s. For each sample, the intensity of the main peak is enhanced with repetitive measurement whereas its maximum temperature is unaffected. The peak position of the main peak in each sample is independent of the irradiation dose and this, together with its fading characteristics are consistent with first-order kinetics. For low doses, typically between 2 and 10 Gy, the dose response of the main peak in each sample is linear. In the intermediate dose range from 10 to 60 Gy, the growth of the main peak in each sample is sub-linear and for greater doses, in the range from 60 Gy to 151 Gy, it is linear again. The half-life of the main peak of the unannealed sample is about 1.3 h whereas that of the annealed sample is about 1.2 h. The main peak in each sample can be approximated to a first-order glow peak. As the heating rate increases, the intensity of the main peak in each sample decreases. This is evidence of thermal quenching. The main peak in each sample is the only peak regenerated by phototransfer. The resulting phototransferred peak occurs at the same temperature as the original peak and has similar kinetic and dosimetric features. For a preheat temperature of 120˚C, the intensity of the phototransferred peak in each sample increases with illumination time up to a maximum and decreases afterwards. At longer illumination times (such as 30 min up to 1 h), no further decrease in the intensity of the phototransferred peak is observed. The traps associated with the 325˚C peak are the main source of the electrons responsible for the regenerated peak. Radioluminescence emission spectra were also measured for quartz annealed at various temperatures. Emission bands in quartz are affected by annealing and irradiation. A strong enhancement of the 3.4 eV (~366 nm) emission band is observed in quartz annealed at 500˚C. A new emission band which grows with annealing up to 1000˚C is observed at 3.7 eV (~330 nm) for quartz annealed at 600˚C. An attempt has been made to correlate the changes in radioluminescence emission spectra due to annealing with the influence of annealing on luminescence lifetimes in quartz

Ab-initio investigation of phonon dispersion and anomalies in palladium

In recent years, palladium has proven to be a crucial component for devices ranging from nanotube field effect transistors to advanced hydrogen storage devices. In this work, I examine the phonon dispersion of fcc Pd using first principle calculations based on density functional perturbation theory. While several groups in the past have studied the acoustic properties of palladium, this is the first study to reproduce the phonon dispersion and associated anomaly with high accuracy and no adjustable parameters. In particular, I focus on the Kohn anomaly in the [110] direction.Comment: 19 pages, preprint format, 7 figures, added new figures and discussio