Food meanings in HIV and AIDS caregiving trajectories: Ritual, optimism and anguish among caregivers in Lesotho

The article describes the caregiving responsibility to provide food for chronically ill family members and the meanings attached to food and eating when ill created stress for family caregivers. The results come from a qualitative phenomenological study using in-depth interviews with 21 family caregivers of chronically ill HIV and AIDS patients in one district in Lesotho. Analysis of the interview data showed that the caregivers attached profound meanings to food and feeding care recipients. Their perceptions about food as part of family life and caring, the role of food and eating in curbing disease progression, the link between food and medical efficacy and the link between food and life led to ritualised behaviour around food, and moments of optimism and anguish in caregiving. Patients’ behaviour in relation to food was in most instances inconsistent with the caregivers’ goals, thus leading this aspect of caregiving to induce stress. Services intended to support home-based caregivers and patients could contribute to the reduction of stress associated with food through suitably tailored food assistance and professional support to caregivers to enhance their competences and understanding of the dynamics of food intake as AIDS progressed

Radiowave propagation measurements and prediction in bushfires

Australian vegetation is fire-prone. Every year, wet and dry sclerophyll forests of Western\ud Australia, southeastern Australia and grassland ecosystems of the northern part of the continent\ud are subject to high intensity fires. The sclerophyll vegetation contains up to 2.71 % of the\ud element potassium. The element exists in plants’ organic matrix: attached to the oxygen containing and carboxyl functional groups; in aqueous form such as potassium (K+) ions\ud surrounded by water; and as discrete particles in dried plant parts. Theoretically, temperature in\ud the conflagrations can be as high as 2000ºC. During the high intensity bushfires, potassium\ud atoms and salts are released from the plant structure as it crumbles into the combustion zone\ud where the species are ionized. Up to 20 % of the potassium present in plants is ionized in a\ud bushfire environment.\ud \ud During suppression of the threat, high frequency (HF) - ultra high frequency (UHF) radio\ud communications systems are in constant use by suppression crews in firegrounds. Despite their\ud use, HF and very high frequency (VHF) radio communications are reported to be failing in\ud extreme bushfire conditions. The reports of radio communication failure tend to be anecdotal and\ud therefore warrant an investigation. This study aims at carrying out field and laboratory radio wave\ud attenuation and phase shift measurements at HF to X-band frequencies in moderate intensity fires.\ud Very high intensity bushfires often spread very fast and change direction rapidly therefore it is\ud unsafe to set up equipment for measuring attenuation and phase shift in the fires. Consequently,\ud numerical experiments were used to study radio wave propagation in very high intensity fires.\ud \ud Propagation measurement data at radio wave (HF-VHF) frequencies through fire are scarce and\ud that which is available lacks precision. It is also the purpose of the study to produce attenuation\ud and phase measurement data at these frequencies. The field and laboratory measurements were\ud carried out using a Radio Wave Interferometer (RWI) and Vector Network Analyzer (VNA - HP\ud 8277C). RWI uses the same principles as Microwave interferometer (MWI) except that RWI\ud works at radio frequencies. Electron density and momentum transfer collision frequency in\ud moderate intensity bushfire plumes were estimated from the attenuation and phase shift\ud measurements.\ud \ud Laboratory and field measurements using a VNA - HP 8277C and RWI respectively in moderate\ud intensity fires (700-1000 K) have revealed that electron density in the plume could range from\ud 1014-1016 m-3. Theoretical calculations based on local thermal equilibrium in grassfires flames\ud with temperatures up to 1200 K suggest that electron density could be up to 1017 m-3 if up to 20 %\ud of the inherent potassium atoms are ionized.\ud \ud There are at least two possible mechanisms that could lead to a significant signal strength\ud reduction (attenuation) in bushfire environments. They are signal refraction due to thermal bubble\ud and ionization-induced signal absorption in the plume. Electrons, which result from thermal\ud ionization of potassium in the fire, transfer energy from the incident radio wave to the fire plume\ud through collision with inherent neutral particles. The transfer of energy can significantly attenuate\ud and induce a phase shift on radio wave signals. Experimental work carried out in the project\ud suggest that radio wave attenuation is significantly higher at UHF and X-Band frequencies than at\ud HF. Field radio wave propagation measurements at 1.50 m above the seat of a moderate intensity\ud grassfire revealed that 30 MHz signals can be attenuated by up to 0.03 dB/m while 151.3 MHz\ud signals were attenuated by up to 0.05 dB/m. An intense cane fire attenuated 151.3 MHz signals\ud by 0.05 dB/m. The attenuation effect was observed to increase when X-band (10.0 -12.5 GHz)\ud signals were considered. Attenuation coefficients up to 4.45 dB/m were measured.\ud \ud Phase shift induced on the signals was also observed to increase with the increase in frequency\ud band (low for HF and high for X-band). A 30 MHz signal suffered a 3.08º phase shift in the\ud moderate intensity grassfire whereas in the X-band frequencies, a phase shift of up to 29.31º was\ud observed in a fire of about the same intensity.\ud \ud Numerical experiments have shown that signal loss due to refraction is frequency dependent in\ud very hot regions of bushfire plumes. X-band waves are more affected than VHF waves.\ud Numerical experiments predicted maximum attenuation coefficients of 0.11 dBm-1 for 150 MHz\ud and 0.31 dBm-1 for 3 GHz radio waves when they propagate about a meter above fuel-flame\ud interface of a 90 MWm-1 bushfire with fuel potassium content of 0.50 %. Theoretical studies also\ud revealed that; for potassium content of about 0.20 %, a collimated beam of radio signals (10 cm\ud wide) propagating at grazing angles to the fuel-flame interface of a very high intensity bushfire\ud (1600 K) could suffer attenuation coefficients of about 1.45 dBm-1. This effect is calculated to\ud decrease with the increase in height above the combustion zone. For very high intensity bushfires\ud in fuels with high potassium content (e.g., up to 3.00 %), attenuation by refraction is likely to be\ud the most significant form of radio wave energy loss for collimated beams propagating at grazing\ud angles to the fuel-flame interface.\ud \ud The Line-Of-Sight (LOS) radio wave propagation measurements in moderate intensity vegetation\ud fires (700-1000 K) have shown that signal attenuation is plume temperature and frequency\ud dependent. Transmission through hottest region of the fire (combustion zone) suffers significant\ud signal strength loss whereas low attenuation has been observed at cooler regions of the plume.\ud This could be explained by the fact that “collisional plasma effect” on radio waves is more\ud pronounced at combustion zone than at the thermal plume region of the fire as the effect is\ud temperature dependent.\ud \ud Bcontinent with a potential combustion zone temperature of 2000ºC. These bushfires have a\ud potential to adversely affect LOS radio wave communications when transmission is through the\ud hottest part of the fire. It must be noted that radio wave communication blackout could even\ud occur at temperatures as low as 1300 K provided that the fire is sufficiently ionized

Ray Tracing Radio Waves in Wildfire Environments

Wildfires are uncontrolled exothermic oxidation of vegetation. Flame combustion temperatures could be in excess of 1600 K. Under the high temperature environment, plants' organic structure crumbles to release omnipresent alkali nutrients into the combustion zone. The alkali based compounds thermally decomposed to constituent atoms which ultimately ionised to give ions and electrons. The presence of electrons in the flame lowers its refractive index, thereby creating a medium of spatially varying refractive index. In the medium, incident radio waves change speed and are consequently deflected from their original path. The refraction has an effect of decreasing signal intensity at a targeted receiver which is at the same height as a collimated beam transmitter which is at a considerable distance away from the former. A numerical experiment was set to investigate the sub refractive behaviour of a very high intensity eucalyptus wildfire (90 MWm−1) plume using two dimensional (2D) ray tracing scheme. The scheme traces radio rays as they traverse the plume. The ratio of number rays in a collimated beam reaching the targeted receiver to number of rays leaving the transmitter is used to calculate signal intensity loss in decibels (dB) at the receiver. Assuming an average natural plant alkali (potassium) content of 0.5%, attenuation (dB) was observed to be factor of both propagation frequency and temperature at the seat of the fire plume; and only of temperature at cooler parts of the plume. The 2D ray tracing scheme predicted a maximum attenuations of 14.84 and 5.47 dB for 3000 and 150 MHz respectively at 0.8 m above canopy-flame interface over propagation path of 48.25 m. An attenuation of 0.85 dB was predicted for frequencies from 150-3000 MHz over the same propagation distance at plume height of 52.8 m above ground

Nonintrusive measurement of ionisation in vegetation fire plasma

Vegetation fires are slightly ionised gaseous medium. Omnipresent alkali metal species in plant's organic structure are the main source of thermally produced electrons in the fires. In the flames, electron-neutral particle collisions dominate other modes of particle interaction. The collision regime absorbs some of the incident energy when the fire is illuminated with electromagnetic waves. The rate of electromagnetic wave absorption in the vegetation fires has implications on the safety of fire-fighters. During wildfire suppression, radio communication blackout at vhf/uhf has been experienced. This may be partly due to thermal ionisation in the fire. In the experiment, the extent of ionisation in vegetation fires is measured using a 2-port vector network analyser. X-band microwaves are caused to propagate combustion zones of eucalyptus bark and guinea grass fires with maximum temperatures of 1114 and 1054 K respectively. Alkali content in the vegetation fuel was different. Measurements show maximum ionisation in flames produced from guinea grass, which had almost twice much potassium as that of eucalyptus bark, to be 2.63 × 1016 m−3 while that produced in eucalyptus bark flame was 1.46 × 1016 m−3

Analysis of Population Growth and Land Use in Pelaneng Bokong: Implications for Resource Management and Sustainable Agriculture

The question of whether population growth can contribute to environmental degradation and undermine efforts to manage resources sustainably and ultimately impairing agricultural development is a long-standing concern. This paper uses a three-tier methodology consisting of analysis of population dynamics, mapping of land use and changes, and superimposition of the two data sets to analyse the consequences of population pressure on the environment, especially on land resources. It draws implications for natural resource management and sustainable agriculture in the Pelaneng Bokong area. The analysis of population-land use relationship confirms a positive correlation between population growth and settlement expansion. Similarly, the rate at which settlements are growing seem to correlate with the rate at which rangelands are decreasing. However, the situation is different with cropland whereby fluctuations in the size of cropland have been observed despite significant population increases, thus indicating lack of correlation between population growth and size of cropland. Population growth in the Pelaneng Bokong area has also resulted into decrease of rangelands that are being converted into other uses namely settlements and cropland. Interestingly, the decrease in the availability of rangeland has not been accompanied by proportional reduction in livestock numbers thus resulting in overgrazing, decline in productivity as well as livelihoods and food security. The conversion of rangelands to other uses in most cases has meant clearing of grass cover, which has exposed soil to erosional forces, consequently reducing prospects for sustainable resource management and agriculture production

Effect of Wildfire-induced Thermal Bubble on Radio Communication

Horizontal roll vortex pairs are dynamical structures that\ud transfer energy and emissions from wildfires into the atmosphere. The vortices form at the edges of an intense line wildfire and emulate two cylinders, which form two curvatures of a biconcave thermal lens.\ud Wildfire plume provides a dielectric material for the dielectric lens, whose permittivity is influenced by the nature, quantity of constituents (e.g., potassium and graphitic carbon) and variation of temperature with height in the plume. The environment created by the plume is\ud radio sub-refractive with an effect of spreading radio wave beams. A numerical experiment was carried out to quantify loss of Ultra High Frequency (UHF) radio signal intensity when high intensity wildfireinduced horizontal roll vortices intercept UHF propagation path. In the numerical experiment, a collimated radio wave beam was caused to propagate along fuel-fire interface of a very high intensity wildfire in\ud which up to two roll vortex pairs are formed. Maximum temperature of the simulated wildfire was 1200 K. Flame potassium content was varied from 0.5–3.0%. At 3.0% potassium content, a vortex pair imposed a maximum radio ray divergence of 2.1 arcmins while two vortex pairs imposed a maximum divergence of 4.3 arcmins at the fuel-fire interface. The ray divergences caused maximum signal strength loss (in decibels (dB)) per unit path length of 0.154dBm−1 and 1.65dBm−1 respectively

Nondestructive Measurement of Momentum Transfer Collision Frequency for Low Temperature Combustion Plasma

Accurately measured momentum transfer collision frequency and electron density for fire plasma enable correct simulation of electromagnetic wave propagation in the medium. The simulation is essential for designing high-performance systems suitable for the environment. Despite this, momentum transfer collision frequency for fire plumes has always been an estimated quantity and/or crudely determined. There are anecdotal reports of severe line-of-sight (LOS) radio frequency signal degradation on firegrounds. The problem has implications on safety of fire-fighters during wildfire suppression hence the need of high performance communication systems. In the experiment, a nonintrusive and direct method for measuring momentum transfer collision frequency in a fire plume was carried out. Using an automatic network analyser, x-band microwaves were caused to propagate combustion zones of eucalyptus and grass litter fires to measure the flames, scattering parameters. The parameters were then used to determine average collision frequencies for the plumes. The average collision frequencies for the eucalyptus and grass fire plumes were measured to be 5.84×1010 and 5.92×1010 rad/s, respectively

Radio Wave Propagation Ex-periment in Sugarcane Fire Environments

Abstract Large fires have an effect of suppressing Very or Ultra High Frequency (VHF/UHF) radio wave signals strength which consequently impact negatively on the efficiency of radio communications at the frequency ranges. Mobile hand-held radio operating at the frequency ranges is a major communication tool during fire suppression; therefore inefficient radio communication systems put lives of fire fighters at risk. One of the causes of signal attenuation in fire environment is plume ionization. Plume species which include graphitic carbon, alkalis and thermally excited radicals such as methyl are responsible for ionization. As atmospheric pressure ionized medium (combustion plasma), sugarcane fire has momentum transfer electron-neutral collision frequency much higher than plasma frequency, hence propagation of VHF/UHF radio waves through such a medium is predicted to suffer a significant attenuation and phase shift. Radiowave propagation measurements were carried out in a moderate intensity prescribed sugarcane fire at 151 MHz frequency over a 590 m path using a radiowave interferometer. The radio wave interferometer measured signal attenuation of 0.43 dB through the fire with maximum temperature and flame depth of 1154 K and 8.7 m, respectively

Interferometric measurement of ionization in a grassfire

Grassfire plumes are weakly ionized gas. The ionization in the fire plume is due to thermal and chemi-ionization of incumbent species, which may include graphitic carbon, alkalis and thermally excited radicals, e.g., methyl. The presence of alkalis (e.g., potassium and sodium) in the fires makes thermal ionization a predominant electron producing mechanism in the combustion zone. Alkalis have low dissociation and ionization potentials and therefore require little energy to thermally decompose and give electrons. Assuming a Maxwellian velocity distribution of flame particles and electron-neutral collision frequency much higher than plasma frequency, the propagation of radio waves through a grassfire is predicted to have attenuation and phase shift. Radio wave propagation measurements were performed in a moderate intensity (554 kW m^−1) controlled grassfire at 30- and 151-MHz frequencies on a 44 m path using a radio wave interferometer. The maximum temperature measured in the controlled burn was 1071 K and the observed fire depth was 0.9 m. The radio wave interferometer measured attenuation coefficients of 0.033 and 0.054 dB m^−1 for 30- and 151-MHz, respectively. At collision frequency of 1.0 × 10^11 s^−1, maximum electron density was determined to be 5.061 × 10^15 m^−3

Prediction and measurement of electron density and collision frequency in a weakly ionised pine fire

Pine litter flame is a weakly ionised medium. Electron-neutral collisions are a dominant form of particle interaction in the flame. Assuming flame electrons to be in thermal equilibrium with neutrals and average electron-neutral collision frequency to be much higher than the plasma frequency, the propagation of microwaves through the flame is predicted to suffer signal intensity loss. A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The burner was equipped with thermocouples and used as a cavity for microwaves with a laboratory quality network analyzer to measure wave attenuation. Electron density and collision frequency were then calculated from the measured attenuation. The parameters are important for numerical prediction of electromagnetic wave propagation in wildfire environments. A controlled pine litter fire with a maximum flame temperature of 1080 K was set in the burner and microwaves (8–10.5 GHz) were caused to propagate through the flame. A microwave signal loss of 1.6–5.8 dB was measured within the frequency range. Based on the measured attenuation, electron density and electron-neutral collision frequency in pine fire were calculated to range from 0.51–1.35 × 1016 m−3 and 3.43–5.97 × 1010 s−1 respectively