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Inom elitfotboll utvärderas fysisk prestation på spelplanen med hjälp av global positioning systems (GPS:er). På lägre nivåer används istället tester av fysisk kapacitet, såsom Yo-Yo Intermittent Recovery Test Level 2 (YYIR2), som prediktor av fysisk matchprestation. Det är dock oklart om prestation på YYIR2 har något samband med fysisk prestation under fotbollsmatcher. Syftet med denna studie var att undersöka om det fanns korrelationer mellan prestation på YYIR2 och fysiska matchprestationsparametrar mot slutet av fotbollsmatcher. Nio manliga fotbollsspelare (medelvärde ± SD: ålder = 24.2 ± 3.8 år; längd = 184 ± 5.4 cm; vikt = 78.9 ± 4.6 kg) tillhörande ett elitlag på seniornivå i det svenska seriesystemet deltog i studien. Data från fem fysiska parametrar samlades in från 28 matcher under säsongen 2020 med STATSport Apex 10 Hz GPS-system. YYIR2 genomfördes av samtliga spelare under försäsongen. Korrelationer mellan prestation på YYIR2 och alla  matchparametrar undersöktes genom Spearman’s rho korrelationsanalys. En signifikant negativ korrelation observerades mellan YYIR2 och andelen accelerationer (r = -0.812, p = 0.008). Inga signifikanta korrelationer observerades mellan YYIR2 och total distans (r = 0.059, p = 0.881),höghastighetslöpningar (r = -0.437, p = 0.240), sprinter (r = -0.268, p = 0.486) eller decelerationer (r = -0.360, p = 0.342). Resultaten indikerar på att YYIR2 är en dålig prediktor på spelarnas förväntade fysiska prestation i slutet av fotbollsmatcher. Resultaten ska dock tolkas med försiktighet på grund av låg statistisk power. Framtida studier bör undersöka påverkan av spelares position på den här typen av korrelationer. / In elite football, physical performance during matches is evaluated using global positioning systems (GPSs). At lower levels, tests of physical capacity, such as the Yo-Yo Intermittent Recovery Test Level 2 (YYIR2), are used to predict physical match performance. It is however unclear whether YYIR2 performance is associated with physical match performance. This study investigated potential correlations between YYIR2 performance and physical match parameters towards the end of football matches.Nine male football players (mean ± SD: age = 24.2 ± 3.8 years; height = 184 ± 5.4 cm; weight = 78.9 ± 4.6 kg) of an elite Swedish football team participated. Data from five physical parameters were collected from 28 matches during the 2020 season with the STATSport Apex 10 Hz GPS system. YYIR2 was performed by all players during pre-season. Correlations between YYIR2 performance and each physical match parameter were analysed using Spearman's rho.A significant negative correlation was observed between YYIR2 and the proportion of accelerations (r = -0.812, p = 0.008). No significant correlations were observed between YYIR2 and total distance (r = 0.059, p = 0.881), high-speed runs (r = -0.437, p = 0.240), sprints (r = -0.268, p = 0.486) or decelerations (r = -0.360, p = 0.342).Results indicate that the YYIR2 is a poor predictor of physical performance towards the end of football matches. The results should however be interpreted with caution due to low statistical power. Future research should investigate the influence of playing position on such correlations.

We investigate nonlinear Thomson scattering generated by intense laser pulses focused in noble gases. Electrons are ionized from low-density helium or argon early during the laser pulse and scatter light out the side of the focus. We measure fundamental, second, and third harmonic light focus over nearly the entire emission sphere. We investigate the influence of electron bunching, when individual atoms ionize multiple electrons sequentially as the laser field increases early during the laser pulse. Simulations suggest that correlation between electron positions for the ten electrons ionized from argon should distort the spatial pattern of nonlinear Thomson scattering relative to the two-electron pattern observed for helium. Preliminary experimental measurements do not reveal a difference in emission patterns between helium and argon. However, our experimental efforts were hampered by prepulses in our laser system, which could cause electrons to ionize ahead of the main pulse and disrupt the coherence between electrons. In the future, we hope to improve the pulse temporal contrast of the laser system and revisit this experiment. We also explore observed distortions in the angular emission patterns of nonlinear Thomson scattering. These persistent distortions arise presumably from subtle defects in the laser field, which can imprint on the angular distribution of the scattered light. Possibilities include variations in laser focal shape, spatial chirp, and laser-field polarization. We set out on a systematic experimental course to identify laser beam characteristics that may contribute to such distortions in the angular emission patterns. We develop experimental tests which have implicated our wave plate, used to rotate linear laser polarization, as a likely source of distortion. Further tests on the wave plate are required to confirm and explain how it affects the angular distribution of nonlinear Thomson scattering.

Extremely high currents can be generated in relativistic short pulse laser interactions with matter. This raises the question if return currents can be used to drive a conventional fast Z-pinch process to produce high energy density (HED) matter. At the HZDR Draco Laser facility, cryogenic hydrogen jet targets are investigated for laser acceleration of protons, and Z-pinch phenomena may have been observed. This thesis addresses this possibility with a multi-timescale theoretical treatment of relativistic laser interactions with cylindrical hydrogen jets and metallic wire targets. To achieve this, the hydrodynamic ray-tracing (HD-RT) method is invented to determine the plasma temperature invhydrogen jets irradiated at laser intensity of 𝑎0 ≈ 1. The HD-RT fit reveals bulk-electron temperatures of 250 eV to 300 eV in experiments but the electron thermal temperature are overestimated invthe Particle-in-cell (PIC) simulations. The HD-RT method now provides a testbed platform which can be used to benchmark the PIC method. At higher laser intensity of 𝑎0 ≈ 15, the HD-RT method resolved the different temperature distributions within the hydrogen jets. The surface plasma exhibits a significantly higher temperature (∼ 300 eV), and bulk has a lower temperature ≲ 100 eV. Additionally, a jump in the shadow diameter of the expanding hydrogen jet plasma is observed with optical probing at 30 ps to 40 ps. These indicate that the surface return current is heating the target surface and induces a cylindrical shock. Two-dimensional and three-dimensional PIC simulations are conducted to study the generation mechanisms of the return current. The simulations reveal that the return current, concentrated in the ∼ 0.1 µm skin depth layer on the wire, has a duration of 100 femtosecond (fs) scale, and propagates along the wire due to surface wave propagation, for the 30 fs duration laser pulse. Based on those findings, the theory of generating convergent shock waves on wire targets initiated by the short pulse surface return current is developed. It is found that the compression shock wave arises from a prompt magnetic pressure, during the current pulse, plus a longer duration ablation pressure due to the surface heating. The corresponding simulations are consistent with the measured hydrogen jet shadow diameter, whose jump behavior is identified as evidence of the rebound shock, after the convergence of the initial shock to the axis. A return current scaling law is then developed to predict this behavior in targets of arbitrary atomic number (Z) and radii (≥ 1 µm). The relative magnitude of the magnetic and ablative pressures vary with target radius and atomic number. An experiment conducted at the HED-HiBEF Instrument of the European XFEL shows direct observation of the convergent shock wave on a 25 µm diameter copper wire, with peak pressure reaching ∼ 100 TPa at convergence. The rebound shock is also directly imaged. The scaling theory is validated with this experiment and exhibits good consistency. These experiments provide clear evidence that the short-pulse return current does not drive a conventional Z-pinch process, but a transient surface heating of the target instead, which causes the ablative pressure shock compression. Furthermore, the mechanisms causing the instabilities are studied under the assumptions of shortpulse and long-pulse return current. The results demonstrate that the filament structures observed in the hydrogen jets, and at late times in wires, can result from the thermal expansion of initial density perturbations caused by the transient hot electron dynamics, and from Weibel instabilities arising from the increasing plasma scale length. This conclusion further supports the theory of short pulse return current. The results of this thesis open a new regime to achieve extreme high pressure conditions (∼ 100 TPa) by using a J-level short pulse laser, and have established a robust theoretical framework for future applications of utilizing laser-driven return currents in the field of HED physics.:Contents 1 Introduction 1 2 Return current generation and propagation in high-intensity laser-solid interactions 6 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 Return current in 3D PIC simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.3 Return current in 2D PIC simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.4 Surface return current propagation in infinite plasma wire . . . . . . . . . . . . . . . . 14 2.4.1 Surface wave generation mechanism . . . . . . . . . . . . . . . . . . . . . . . . 14 2.4.2 Model description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.4.3 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.5 Bulk return current generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3 Bulk return current heating and bulk plasma temperature benchmark with the experiment 24 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.2 Testbed platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 3.2.1 Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.2.2 HD-RT fit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.2.2.1 Hydrodynamics simulation - HD . . . . . . . . . . . . . . . . . . . . . 27 3.2.2.2 Ray-tracing simulation - RT . . . . . . . . . . . . . . . . . . . . . . . 28 3.2.2.3 𝜒2 fit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.3 PIC simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 3.5 Future prospects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 4 Surface return current heating and convergent shock compression driven by the surface return current 35 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 4.2 Dynamic shock compression initiated by the surface return current . . . . . . . . . . . 36 4.2.1 The Z-pinch effect induced by the strong transient magnetic field . . . . . . . . 36 4.2.2 Heating mechanism of surface return current . . . . . . . . . . . . . . . . . . . 37 4.2.3 Hydrodynamic time scale of the convergent compression in hydrogen jets initi- ated by the Z-pinch and surface ablation . . . . . . . . . . . . . . . . . . . . . . 39 4.2.4 Scaling law of return current compression to high Z and large radius solid target 40 4.3 Convergent shock compression in hydrogen jets and probed with optical laser . . . . . 43 4.4 Convergent shock compression in copper wires and probed by X-ray free electron lasers (XFEL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 4.4.1 Experiment setup and results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 4.4.2 PIC simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 4.4.3 Hydrodynamic simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.4.4 Phase contrast image simulation . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.4.5 High-pressure physics experiment designation based on the return current heating 55 4.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 5 Plasma instabilities in high-intensity laser solid interactions 57 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 5.2 Thermal expansion dominated plasma instabilities . . . . . . . . . . . . . . . . . . . . 58 5.2.1 Obtained the plasma initial condition after laser irradiation . . . . . . . . . . . 58 5.2.2 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 5.3 MRT instabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 5.3.1 Initial conditions of the MRT instabilities . . . . . . . . . . . . . . . . . . . . . 60 5.3.2 Simulation data processing with FFT method . . . . . . . . . . . . . . . . . . . 62 5.3.3 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 5.4 Kinetic instabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.4.1 Weibel instabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 5.4.2 Biermann battery mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 5.4.3 Determination of the hydrogen plasma conditions . . . . . . . . . . . . . . . . . 65 5.4.4 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 5.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 6 Summary and outlook 71 7 Appendix 73 7.1 Single electron dynamics in a laser field . . . . . . . . . . . . . . . . . . . . . . . . . . 73 7.2 Pondermotive force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 7.3 Hot electron temperature scaling in laser-plasma interactions . . . . . . . . . . . . . . 77 7.4 X-ray transmission propagation simulations . . . . . . . . . . . . . . . . . . . . . . . . 77 7.5 FDTD method to solve the equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 7.6 Experimental details of the optical microscope . . . . . . . . . . . . . . . . . . . . . . 80 7.7 Measurement of the variation of the initial target diameter . . . . . . . . . . . . . . . 80 7.8 Discussion of the HD-RT fit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 7.9 Equation of state of hydrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 7.10 Ionization state of the target . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 7.11 Radiative cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 7.12 2D3V-PIC simulation versus 3D-PIC Simulation . . . . . . . . . . . . . . . . . . . . . 85 7.13 Low-temperature-collision correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 7.14 Effect of the Coulomb logarithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 7.15 Lateral heat transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 7.15.1 Hot-electron-pressure gradient in transverse direction . . . . . . . . . . . . . . . 89 7.15.2 Lateral heat transfer by diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . 91 7.16 Bulk electron temperature along the longitudinal direction of the wire . . . . . . . . . 91

Thesis (MScSportSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: There are extensive literature on the PEH response after acute and chronic aerobic and resistance exercise, as well as a few studies on concurrent and water exercise. However, there is comparatively little evidence that high intensity interval training (HIIT) elicits similar post exercise blood pressure reductions (PEH) compared to other types of exercise. Furthermore, it is difficult to quantify the magnitude of the hypotensive response following these exercises, due to variations in exercise protocols in terms of intensity and duration. Both these training variables are considered important determinants of the magnitude and duration of the PEH response. The current study determined the magnitude of the PEH response after an acute bout and six sessions of HIIT, and the effects after two weeks of detraining in overweight/obese young women. Twenty young women (aged 21 ± 2 years) volunteered for the study. All the subjects were normotensive (SBP: 119.2 ± 5.6 mmHg and DBP: 78.8 ± 4.1 mmHg). Subjects performed six sessions of HIIT within two weeks and detrained for two weeks. SBP, DBP, MAP and HR were monitored during seated recovery after exercise for 60 min to determine the change from resting values. The overall outcome showed that an acute HIIT session resulted in a reduction of 2.9 mmHg in SBP which approached near clinical significance, while six sessions of HIIT caused a clinically significant reduction of 5.3 mmHg; this response was almost totally reversed after detraining. There were no clinically significant reductions in DBP after the acute or six sessions of HIIT (1.7 and 2.7 mmHg, respectively). However, a clinically significant hypotensive response of 3.9 mmHg was sustained after detraining following the maximal exercise capacity test. MAP also reduced by a magnitude of 2.3 and 5.6 mmHg, respectively, after the acute bout and six sessions of HIIT, and detraining values were still 2.9 mmHg lower than resting values and approached near clinical significance. The results indicate that both an acute bout and six sessions of HIIT elicited a meaningful PEH response. However, the six sessions of HIIT caused a clinically significant reduction which was approximately twice the acute session. Likewise, detraining showed clinically significant effects in DBP and MAP, but SBP returned to near baseline values. This suggests that in only two weeks, the accumulated effects of six sessions of HIIT elicited a greater hypotensive response than after an acute session of HIIT. / AFRIKAANSE OPSOMMING: Daar is omvattende literatuur oor die post-oefening hipotensie (POH) na afloop van akute en kroniese aërobiese en weerstandsoefeninge, asook enkele studies oor gelyktydige krag- en uithouvermoë- en wateroefeninge. Daar is egter relatief min bewyse dat hoë intensiteit interval oefening (HIIO) soortgelyke post-oefening afnames in bloeddruk (POH) in vergelyking met ander tipes oefening veroorsaak. Voorts is dit moeilik om die omvang van die hipotensiewe respons na afloop van oefening te kwantifiseer, hoofsaaklik as gevolg van die variasies in oefeningprotokolle in terme van intensiteit en tydsduur. Beide hierdie inoefeningveranderlikes word as belangrike determinante van die omvang en die tydsduur van die POH respons beskou. Die huidige studie het die omvang van die POH respons na ʼn akute sessie en ses sessies HIIO, en die gevolge na afloop van twee weke se nie-inoefening (“detraining”) by oorgewig/vetsugtige jong dames, bepaal. Twintig jong dames (ouderdom 21 ± 2 jaar) het vrywillig ingestem om aan die studie deel te neem. Al die deelnemers was normotensief (SBD: 119.2 ± 5.6 mmHg en DBD: 78.8 ± 4.1 mmHg). Die deelnemers het ses sessies HIIO binne twee weke voltooi en het daarna vir twee weke geen inoefeningsessies gehad nie. SBD, DBD, GAD en HS is tydens ʼn sittende herstelfase vir 60 minute gemonitor om die verandering vanaf rustende waardes te bepaal. Die algehele uitkoms toon dat ʼn akute HIIO sessie ʼn afname van 2.9 mmHg in SBD tot gevolg gehad het wat aan kliniese betekenisvolheid grens, terwyl ses sessies van HIIO ʼn klinies betekenisvolle afname van 5.3 mmHg veroorsaak het; hierdie respons wat bykans volledige omgekeerd na die twee weke met geen inoefening. DBD het geen kliniese betekenisvolle afname na afloop van die akute of ses sessies van HIIO getoon nie (1.7 en 2.7 mmHg, respektiewelik). ʼn Klinies betekenisvolle hipotensiewe respons van 3.9 mmHg is egter gevind na die geen inoefeningsperiodes. GAD het ook met ʼn omvang van 2.3 en 5.6 mmHg, respektiewelik, verminder na afloop van die akute sessie en ses sessies van HIIO. Die geen inoefening waardes was steeds 2.9 mmHg laer as die rustende waardes en het aan kliniese betekenisvolheid gegrens. Die resultate toon dat beide ʼn akute sessie en ses sessies van HIIO ʼn betekenisvolle POH respons ontlok het. Ses sessies van HIIO het egter ʼn klinies betekenisvolle afname, wat ongeveer twee keer soveel as die afname van die akute sessie was, veroorsaak. In dieselde lig het ʼn twee weke geen inoefeningsperiode steeds klinies betekenisvolle veranderinge in DBD en GAD getoon, maar SBD het tot naby aan die basislyn waardes teruggekeer. Hierdie resultate suggereer dat in slegs twee weke die geakkumuleerde effekte van ses sessies van HIIO ʼn groter hipotensiewe respons as na ʼn akute sessie van HIIO ontlok het.

Thesis (MScSportSc)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: There is a growing concern in South Africa and worldwide about the global epidemic of obesity and overweightness among the general population. Obesity mediates the pathogenesis of pathological conditions and is associated with a poor quality of life, high morbidity and mortality rates and a huge burden on an individual’s and the health system’s infrastructure and finances. The answer to this rising epidemic is weight loss. Endurance training has been shown to induce weight loss however, people usually cite lack of time as a barrier to meaningful participation in exercise programmes. High intensity interval training (HIIT) therefore emerges as a potential solution to these barriers as it takes a relatively short period of time compared to endurance training. Despite the differences in exercise durations the most cogent advantage is that HIIT elicits not just similar, but even superior central and peripheral adaptations. The central and peripheral adaptations have been shown to enhance weight loss, improve blood lipids and glucose levels, as well as decreasing blood pressure. The challenge facing exercise physiologists is to find the optimal exercise intensity and duration of HIIT bouts which would be time efficient, safe and well tolerated by overweight and obese people. The shortcomings of literature are that most HIIT studies have focused on healthy, overweight and obese men and these studies cannot be extrapolated to women who have been shown to respond differently to training. Moreover, other interventions investigating the effects of HIIT in women and men have been longer term rather than short term interventions. In order to fill the gaps in the literature, the main aim of this study was to investigate the training and detraining effects of a short-term HIIT programme on selected health-related measures in young overweight and obese women. To this end, a non-random sample of 20 overweight and obese women (aged 18-25) volunteered to participate in this study. Selected health-related outcomes were measured prior to training. The pre-training testing was followed by the HIIT intervention which was two weeks and consisted of six sessions using the 10 – 15x1 minute running at 90% HRmax which was separated by one minute active recovery periods at 50-60% of HRmax. The HIIT intervention was followed by a post test in which baseline measurements were repeated. This was then followed by a two week detraining period and follow up testing. The main finding of this study was that a period of two weeks of HIIT can elicit adaptations that can lower the risk profiles of young overweight and obese women. The results showed a statistically significant decrease in body mass (1.6%, p = 0.001), fat mass (3.7%, p = 0.001) and waist circumference (4.8%, p = 0.001), and an increase in lean mass of 1.9% (p = 0.001). There was also a decrease in blood glucose (11%, p = 0.001), total cholesterol (10.4 %, p = 0.01), systolic (3.4%, p = 0.001) and diastolic blood pressure (5.8%, p = 0.001) levels. Finally there was a statistically significant increase in relative VO2max and exercise capacity after the HIIT The follow-up testing after two weeks of detraining shows that the metabolic adaptations that were achieved by the HIIT protocol are relatively lasting or are at least not completely reversed. The weight loss induced by HIIT is important in that it is the major target in lowering the prevalence of overweightness and obesity. The HIIT protocol in this study emerges as a time efficient strategy in eliciting positive adaptations in clinical populations and healthy people. Moreover these findings suggest that 10 minute and 15 minute HIIT work bouts at near-maximal intensities are possibly the minimum amount of training that is needed to induce significant weight loss and other positive health-related outcomes. / AFRIKAANSE OPSOMMING: Daar bestaan ʼn toenemende besorgdheid in Suid-Afrika en wêreldwyd oor die globale epidemie van obesiteit en oorgewig onder die algemene bevolking. Obesiteit fasiliteer die patogenese van verskeie siektetoestande en word met ʼn swak kwaliteit lewe, hoë morbiditeit en mortaliteit en ʼn geweldige las op ʼn individu en die gesondheidsowerhede se infrastruktuur en finansies geassosieer. Een van die antwoorde op hierdie stygende epidemie is gewigsverlies. Dit is reeds gewys dat uithouvermoë oefening saam met ʼn kalorie beperkende dieet gewigsverlies in die hand werk. Mense dui egter ʼn tekort aan tyd as ʼn hindernis tot betekenisvolle deelname aan ʼn oefenprogram aan. Hoë intensiteit interval inoefening (HIIO) is dus ʼn potensiële oplossing tot hierdie hindernis aangesien dit in vergelyking met uithouvermoë inoefening in ʼn relatiewe korter periode van tyd uitgevoer kan word. Afgesien van die verskille in inoefenperiodes is die mees logiese voordeel dat die HIIO nie net soortgelyke nie, maar self beter sentrale en periferale fisiologiese aanpassing voortbring. Die sentrale en periferale aanpassing verhoog gewigsverlies, verbeter bloedlipiedes en glukose vlakke, en veroorsaak ʼn afname in bloeddruk. Alhoewel ʼn aantal studies die voordele van HIIO by jonger en ouer populasies aandui, is baie min studies op vrouens uitgevoer. Bevindinge kan nie noodwendig na vrouens ekstrapoleer word nie omdat hulle dikwels verskillend op inoefening as mans reageer. Dit is ook nie bekend of ʼn kort HIIO intervensie ʼn betekenisvolle impak op oorgewig en vetsugtige vrouens sou hê nie, asook hoe blywend enige veranderinge sou wees nie. Die hoofdoel van hierdie studie was dus om die inoefening- en die geen-inoefening effekte van ʼn korttermyn HIIO program op geselekteerde gesondheidskenmerke in jong oorgewig en vetsugtige dames te bepaal. ʼn Nie-ewekansige steekproef van 20 oorgewig en vetsugtige vrouens (18-25 jaar) het vrywillig ingestem om aan hierdie studie deel te neem. Geselekteerde gesondheidskenmerke is voor die aanvang van die inoefening gemeet. Die HIIO intervensie het twee weke geduur en het uit ses sessies bestaan (10 – 15x1 minuut draf by 90% HSmaks en een minuut aktiewe herstel by 50-60% HSmaks). Die HIIO intervensie is deur ʼn na-toets gevolg waarin basislyn metings herhaal is. Dit is deur ʼn twee weke geen-inoefening periode en opvolgtoetse opgevolg. Die hoofbevinding van hierdie studie was dat ses sessies van HIIO fisiologiese aanpassings na vore gebring het wat die risiko profiele van jong oorgewig en vetsugtige vrouens verlaag het. Daar was statisties betekenisvolle afnames in liggaamsmassa (1.6%, p < 0.001), vetmassa (3.7%, p < 0.001) en heupomtrek (4.8%, p < 0.001) en ʼn toename in vetvrye liggaamsmassa van 1.9% (p < 0.001). Daar was ook ʼn afname in bloedglukose (11%, p < 0.001), totale cholesterol (10.4 %, p = 0.01), sistoliese (3.4%, p < 0.001) en diastoliese bloeddruk (5.8%, p < 0.001). Daar was ook statisties betekenisvolle verbeteringe in relatiewe VO2maks en oefeningtoleransie na inoefening. Die opvolgtoetse na twee weke van geen-inoefening het getoon dat metaboliese aanpassings wat deur die HIIO bereik is, relatief blywend van aard was of ten minste nie totaal omgekeerd was nie. Die gewigsverlies wat deur die HIIO veroorsaak was is belangrik in die sin dat dit die hoofdoelwit aanspreek om die voorkoms van oorgewig en vetsugtigheid te verminder. Die studie suggereer verder dat 10 – 15 minute HIIO werksessies, by naby maksimale intensiteite, moontlik die minimum hoeveelheid inoefening is wat benodig word om betekenisvolle gewigsverlies en ander positiewe gesondheidskenmerke te bereik.

High Intensity Focussed Ultrasound (HIFU) ablation is a promising technology for the non-invasive, targeted treatment of certain types of cancer. The technique functions by subjecting tumours to a cytotoxic level of intense, localised heating, while leaving the surrounding tissue unharmed. However, a number of limitations in the available HIFU treatment monitoring methods are currently hampering the effectiveness and clinical adoption of the therapy. This work aims to develop improved metrics of HIFU-induced biological damage that are specifically suited to monitoring and controlling HIFU ablation. Firstly, an optical method that enables straightforward quantification of thermal damage in protein-embedding hydrogels is developed. Secondly, hydrogels embedded with different cell lines are used to assess the performance of common temperature-based metrics of cell death across a range of HIFU-relevant conditions. Finally, a novel, passive acoustic detector designed for the real-time monitoring of HIFU-induced tissue damage is proposed. The detector is shown to predict lesioning with over 80% accuracy in regimes that are very likely to create lesions (60 J of acoustic energy or more), with an error rate of less than 6% for exposures that are too short to cause lesioning (up to 1 s long). The proposed detector could therefore provide a low-cost means of effectively monitoring clinical HIFU treatments passively and in real time.

Side effects of current chemotherapeutics limit their use in cancer therapy. Although many current drugs are highly toxic and potent, the effects they have on non-cancerous tissue are unbearable for patients. Targeting these drugs may provide a means to restrict their toxic effects to only cancer tissue while leaving healthy tissue unaffected. This approach requires that the drug is only available in cancer tissue, which has been achieved here by encapsulating drugs into liposomal nano-capsules which are capable of passively accumulating in cancerous tissue via the enhanced permeability and retention effect (EPR). In addition to localisation, a threshold dose must be achieved to deliver the desired toxic effect to the target tumour tissue. Previous strategies have relied on passive 'leaching' of the drug from liposomes, however this 'leaching' does not necessarily achieve the threshold dose required. In the present work, a new generation of liposomes has been developed whereby release is solely achieved in the presence of ultrasound triggered cavitation. Instigation of such cavitation events would normally require the target tissue be exposed to high and possibly damaging ultrasound pressures. To remove the need for these high pressures, cavitation nuclei have been developed to lower the cavitation threshold of surrounding media. To allow for improved co-localisation and treatment deeper into cancer tissue, cavitation nuclei were developed to be in the nanoscale size range. Two types of novel cavitation nuclei were produced, a rough surfaced carbon nanoparticle (CNP, ~180 nm) and smooth shaped polymeric nano-cup particle (NC, ~150, 470, or 770 nm). Both types of particle are solid nanoparticles with gas entrapped on their surface which was capable of cavitating in response to ultrasound without greatly affecting the particle itself. These particles are classified as cavicatalytic nanoparticles due to their ability to reduce the cavitation threshold of their surrounding media without being destroyed themselves. Finally, an entirely nanoscale release system was developed and tested in vitro and in vivo. The drug carrier (the liposome) and effector agent (the cavicatalytic nanoparticle) were used to demonstrate ultrasound triggered drug release, specifically in response to the generation of cavitation events. These cavitation events could be non-invasively monitored and characterised, adding to the potential clinical utility of the technologies developed and described here.