Agulhas retroflection rings in the South Atlantic Ocean

The western boundary current rings shed from the Agulhas retroflection may be responsible for a considerable transfer of heat, salt and energy from the South Indian into the South Atlantic Ocean. Few hydrographic measurements have been collected from Agulhas rings in the South Atlantic Ocean and their characteristics and influence on the waters of the Cape Basin through which they pass are thus little known. The temperature, salinity, and nutrient data presented in the thesis were collected from three Agulhas rings on a number of recent hydrographic cruises in the South Atlantic Ocean. Temperature profiles, conductivity-temperature-depth measurements, nutrient data, GEOSAT altimeter data, and NOAA-11 satellite imagery were used to investigate one of the rings in May 1989. It had previously been postulated that the rings could have an important effect on the Benguela upwelling system and this thesis demonstrates the interaction of the ring with a filament from the upwelling system. An adverse influence of this interaction on the anchovy larval population is postulated, and cited as a possible cause of the very poor anchovy yearclass of 1989. The other two rings were encountered during winter (August 1990 and June 1992), closer to the retroflection, and only hydrographic observations were possible. One of the rings showed a very deep isothermal surface layer and evidence of a deep pycnostad at its centre. The deep stad is shown to be likely due to vortex stretching and possible sources for the water in the stad are suggested. Comparative hydrographic characteristics, water mass structure, velocity fields, and the potential for contribution to interbasin transfer of the three rings are presented and discussed in the thesis

Measured dose distributions of iodine-125 sources and the computerised optimisation of their positions in brachytherapy planning

Includes bibliographies.The use of 1-125 seeds in brachytherapy is widespread and becoming increasingly varied. The spatial dose distributions around two types of 1-125 seeds in general use, were measured using a Geiger-Muller chamber. Seeds with the 1-125 adsorbed onto resin spheres had a 10% less anisotropic dose distribution than seeds containing a silver wire with the 1-125 adsorbed onto it. An interpolative method was developed for fast dose calculations taking this anisotropy into account

Anaesthesia in the MRI suite

Anaesthesia in the magnetic resonance imaging (MRI) suite, or when performing surgery that requires MRI guidance, is becoming a more frequent and complex procedure for anaesthetists, as the study modality is increasing in application. MRI is not inert in its ability to do harm and may interfere with the anaesthetist’s ability to assess the patient and intervene in the event of emergencies. Strong superconducting magnets can affect the physical environment and present unseen yet pertinent dangers, which may be avoided through awareness and vigilance. A culture of safety and collaboration in the radiology department, an area that is often remote from the usual milieu that anaesthetic providers are comfortable with, is essential to preventing serious injury or death to both patients and staff. It is therefore an important domain of knowledge and expertise for an anaesthetist. This article also describes some of the difficulties occasionally apparent only to the anaesthetic provider, which warrants anaesthetists’ involvement in the planning and layout of MRI suites.Keywords: anaesthesia, emergencies in MRI, magnetic resonance imaging (MRI), MRI safety, radiolog

Northwest Tropical Atlantic Station (NTAS) : velocity data report for deployments 1 to 5

This report presents velocity data from the Northwest Tropical Atlantic Station (NTAS) deployments 1 through 5, from March 30, 2001, to February 28, 2006. The NTAS project has maintained a series of moorings near 14°50'N, 51°00'W in the northwest tropical Atlantic for air-sea flux measurement. The moorings include a surface buoy outfitted with Air- Sea Interaction Meteorology (ASIMET) systems for determination of bulk air-sea fluxes and oceanographic sensors along the upper 120 m of the mooring line. This report describes and presents the velocity data recovered from current meters and Acoustic Doppler Current Profilers (ADCPs) during the first five years of the NTAS project.Funding was provided by the National Oceanic and Atmospheric Administration under Grant No. NA09OAR432012

UNUSUAL BREEDING BY SEABIRDS AT MARION ISLAND DURING 1997/98

In 1997/98, breeding at subantarctic Marion Island was exceptionally good for five species of seabirds capable of foraging over wide areas and for a tern. The number of king penguin Aptenodytes patagonicus chicks surviving to the start of spring in 1997 was considerably more than previously recorded. Greater numbers of wandering Diomedea exulans and grey-headed Thalassarche chrysostoma albatrosses, northern giant petrels Macronectes halli and Kerguelen terns Sterna virgata bred than previously recorded, and more southern giant petrels M. giganteus did so than in any other year since 1994. For southern giant petrels, reproductive success was higher than in any other year, as was survival of chicks of northern giant petrels. Conversely, for two seabirds that feed close to the island, gentoo penguin Pygoscelis papua and Crozet shag Phalacrocorax [atriceps] melanogenis, 1997/98 was a particularly poor breeding season. Gentoo penguins initiated breeding later than usual and fledged few chicks. The number of Crozet shags that bred decreased; probably about 25% of the adult population did not breed. For two species with an intermediate foraging range that eat mainly crustaceans, macaroni Eudyptes chrysolophus and eastern rockhopper E. chrysocome filholi penguins, breeding was not noticeably different from normal except that chicks of rockhopper penguins fledged with a slightly heavier mass than in other years. However, for both these penguins, the mass of adults on arrival at colonies decreased substantially in the following (1998/99) breeding season. The unusual breeding by most of the seabirds coincided with the El Niño Southern Oscillation (ENSO) event of 1997/98. This synchrony contrasts with lagged responses to ENSO events of seabirds that breed farther south in the Southern Ocean. Continued monitoring of seabirds over well-separated sites in the Southern Ocean may elucidate how climatic perturbations operating at a global scale impact seabirds in the region.Afr. J. mar. Sci. 25: 453–46

Variability and sources of the southeastern Atlantic circulation

The 1992–1993 Benguela Sources and Transport (BEST) time series provide a quantitative view of the Benguela Current transport and the eddy field crossing 30S, as well as an estimate of the relation between its barotropic and baroclinic components. This is done by a simultaneous analysis of the BEST data derived from inverted echo sounders, pressure sensors, current meter moorings, CTD, and ADCP stations. The analysis of the time series indicates that the annual mean baroclinic transport of the Benguela Current is 13 Sv with a total transport of 16 Sv. Through the combination of instruments the total baroclinic plus barotropic transport of the upper 2600 m was obtained without making any assumption about the level of no motion. Results from this calculation corroborated the assumption that 1000 m as a level of no motion could be used as a fairly good approximation. The stationary flow of the Benguela Current is mostly confined near the African Continent while a transient flow, composed by large eddies shed from the Agulhas retroflection, dominates the western portion of the Benguela Current. In the stationary part of the Benguela Current, both barotropic and baroclinic components are equally important while in the transient part, the barotropic is more substantial. Several rings were observed during the experiment that migrated toward the west. An initial speed of 12 km/day diminished to 6 to 7 km/day at the Walvis Ridge. The water mass source of the Benguela Current includes Indian and South Atlantic subtropical thermocline water; relatively saline, low oxygen tropical Atlantic water; and the cooler, fresher subantarctic water. Changes in thermocline salinity correlate with transport: in general when the northward transport is increasing the thermocline salinity also increases, without a decrease in oxygen. This indicates that the Benguela Current increases in strength by bringing in more subtropical thermocline water. As the Agulhas input is most effective in boosting the salinity of the upper thermocline (the South Atlantic Current water being deficit in salinity relative to the Indian Ocean source) we suggest that the spatial variations in transport are tied to Agulhas water influx, presumably associated with the eddy field

Interaction of Agulhas filaments with mesoscale turbulence: a case study

The inter-ocean leakage of heat and salt from the South Indian Ocean to the South Atlantic has important consequences for the global thermohaline circulation and in particular for the strength of overturning of the Atlantic Ocean as a whole. This leakage between these two subtropical gyres takes place south of Africa. The main mechanisms are the intermittent shedding of Agulhas rings from the retroflection of the Agulhas Current and the advection of Agulhas filaments from the border of the Agulhas Current, both of which move northwestward into the South Atlantic. The subsequent behaviour and mixing of Agulhas rings has been much studied over the past years, that of Agulhas filaments not at all. We report here on fortuitous hydrographic observations of the behaviour of an Agulhas filament that interacted with a number of mesoscale features shortly after formation. This suggests that Agulhas filaments may be involved in many other circulation elements and not only the Benguela upwelling front, as was surmised previously, and may mix out in a very site-specific region

Pulmonary tuberculosis diagnosis, differentiation and disease management : a review of radiomics applications

Pulmonary tuberculosis is a worldwide epidemic that can only be fought effectively with early and accurate diagnosis and proper disease management. The means of diagnosis and disease management should be easily accessible, cost effective and be readily available in the high tuberculosis burdened countries where it is most needed. Fortunately, the fast development of computer science in recent years has ensured that medical images can accurately be quantified. Radiomics is one such tool that can be used to quantify medical images. This review article focuses on the literature currently available on the application of radiomics explicitly for the purpose of diagnosis, differentiation from other pulmonary diseases and disease management of pulmonary tuberculosis. Despite using a formal search strategy, only five articles could be found on the application of radiomics to pulmonary tuberculosis. In all five articles reviewed, radiomic feature extraction was successfully used to quantify digital medical images for the purpose of comparing, or differentiating, pulmonary tuberculosis from other pulmonary diseases. This demonstrates that the use of radiomics for the purpose of tuberculosis disease management and diagnosis remains a valuable data mining opportunity not yet realised.https://sciendo.com/journal/PJMPEam2022Nuclear Medicin

The importance of monitoring the Greater Agulhas Current and its inter-ocean exchanges using large mooring arrays

The 2013 Intergovernmental Panel on Climate Change report, using CMIP5 and EMIC model outputs suggests that the Atlantic Meridional Overturning Circulation (MOC) is very likely to weaken by 11–34% over the next century, with consequences for global rainfall and temperature patterns. However, these coupled, global climate models cannot resolve important oceanic features such as the Agulhas Current and its leakage around South Africa, which a number of studies have suggested may act to balance MOC weakening in the future. To properly understand oceanic changes and feedbacks on anthropogenic climate change we need to substantially improve global ocean observations, particularly within boundary current regions such as the Agulhas Current, which represent the fastest warming regions across the world’s oceans. The South African science community, in collaboration with governing bodies and international partners, has recently established one of the world’s most comprehensive observational networks of a western boundary current system, measuring the Greater Agulhas Current System and its inter-ocean exchanges south of Africa. This observational network, through its design for long-term monitoring, collaborative coordination of resources and skills sharing, represents a model for the international community. We highlight progress of the new Agulhas System Climate Array, as well as the South African Meridional Overturning Circulation programme, which includes the Crossroads and GoodHope hydrographic transects, and the South Atlantic MOC Basin-wide Array. We also highlight some of the ongoing challenges that the programmes still face

WHOI Hawaii Ocean Timeseries Station (WHOTS) : WHOTS-8 2011 mooring turnaround cruise report

Note: author "Ludovic Bariteau" is incorrectly listed as "Bariteau Ludovic" on the Cover and Title Page.The Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Timeseries (HOT) Site (WHOTS), 100 km north of Oahu, Hawaii, is intended to provide long-term, high-quality air-sea fluxes as a part of the NOAA Climate Observation Program. The WHOTS mooring also serves as a coordinated part of the HOT program, contributing to the goals of observing heat, fresh water and chemical fluxes at a site representative of the oligotrophic North Pacific Ocean. The approach is to maintain a surface mooring outfitted for meteorological and oceanographic measurements at a site near 22.75°N, 158°W by successive mooring turnarounds. These observations will be used to investigate air–sea interaction processes related to climate variability. This report documents recovery of the seventh WHOTS mooring (WHOTS-7) and deployment of the eighth mooring (WHOTS-8). Both moorings used Surlyn foam buoys as the surface element and were outfitted with two Air–Sea Interaction Meteorology (ASIMET) systems. Each ASIMET system measures, records, and transmits via Argos satellite the surface meteorological variables necessary to compute air–sea fluxes of heat, moisture and momentum. The upper 155 m of the moorings were outfitted with oceanographic sensors for the measurement of temperature, conductivity and velocity in a cooperative effort with R. Lukas of the University of Hawaii. A pCO2 system was installed on the WHOTS-8 buoy in a cooperative effort with Chris Sabine at the Pacific Marine Environmental Laboratory. A set of radiometers were installed in cooperation with Sam Laney at WHOI. The WHOTS mooring turnaround was done on the NOAA ship Hi’ialakai by the Upper Ocean Processes Group of the Woods Hole Oceanographic Institution. The cruise took place between 5 July and 13 July 2011. Operations began with deployment of the WHOTS-8 mooring on 6 July. This was followed by meteorological intercomparisons and CTDs. Recovery of WHOTS-7 took place on 11 July 2011. This report describes these cruise operations, as well as some of the in-port operations and pre-cruise buoy preparations.Funding was provided by the National Oceanic and Atmospheric Administration under Grant No. NA090AR4320129 and the Cooperative Institute for the North Atlantic Region (CINAR)