Epidemiology of acute spinal cord injuries in the Groote Schuur Hospital Acute Spinal Cord Injury (GSH ASCI) Unit, Cape Town, South Africa, over the past 11 years

Background. Spinal cord injury (SCI) is devastating to both patient and society, with acute management and ongoing care being extremely expensive. Few epidemiological data are available on SCIs in South Africa (SA).Objectives. To identify the epidemiological profile of SCI patients at Groote Schuur Hospital (GSH), Cape Town, SA, and identify seasonal trends and peak periods. As the majority of the injuries are preventable, these data are important to develop prevention strategies. Methods. A retrospective review of prospectively collected data was conducted on all patients admitted to the Acute Spinal Cord Injury (ASCI) Unit at GSH from 1 April 2003 to 31 March 2014. All cases registered on a prospectively maintained database were included in the study.Results. The total number of patients admitted to the ASCI Unit was 2 042, with an average of 185 admissions per year. The male/female ratio was 5.25:1. The 21 - 30-year-old age category was the largest, comprising 33.5% of the patients. The most prevalent cause of injury was motor vehicle accidents (44.6%), followed by violence-related injuries (27.2%). Thirty-two point two percent of patients needed ventilatory support, and 91.5% of mechanically ventilated patients were successfully weaned. December was the busiest month in the unit. In patients in whom neurological deficit was incomplete, the average motor function improvement was 16.0%.Conclusions. Data capturing and analysis of SCIs should be encouraged in SA to guide management and prevention strategies, and to optimise outcomes. This study establishes the ASCI Unit at GSH to be one of the key role players in acute SCI management in SA

Influence of spin waves on transport through a quantum-dot spin valve

We study the influence of spin waves on transport through a single-level quantum dot weakly coupled to ferromagnetic electrodes with noncollinear magnetizations. Side peaks appear in the differential conductance due to emission and absorption of spin waves. We, furthermore, investigate the nonequilibrium magnon distributions generated in the source and drain lead. In addition, we show how magnon-assisted tunneling can generate a fullly spin-polarized current without an applied transport voltage. We discuss the influence of spin waves on the current noise. Finally, we show how the magnonic contributions to the exchange field can be detected in the finite-frequency Fano factor.Comment: published version, 15 pages, 10 figure

Probing the exchange field of a quantum-dot spin valve by a superconducting lead

Electrons in a quantum-dot spin valve, consisting of a single-level quantum dot coupled to two ferromagnetic leads with magnetizations pointing in arbitrary directions, experience an exchange field that is induced on the dot by the interplay of Coulomb interaction and quantum fluctuations. We show that a third, superconducting lead with large superconducting gap attached to the dot probes this exchange field very sensitively. In particular, we find striking signatures of the exchange field in the symmetric component of the supercurrent with respect to the bias voltage applied between the ferromagnets already for small values of the ferromagnets' spin polarization.Comment: published version, 10 pages, 7 figure

Spintronic magnetic anisotropy

An attractive feature of magnetic adatoms and molecules for nanoscale applications is their superparamagnetism, the preferred alignment of their spin along an easy axis preventing undesired spin reversal. The underlying magnetic anisotropy barrier --a quadrupolar energy splitting-- is internally generated by spin-orbit interaction and can nowadays be probed by electronic transport. Here we predict that in a much broader class of quantum-dot systems with spin larger than one-half, superparamagnetism may arise without spin-orbit interaction: by attaching ferromagnets a spintronic exchange field of quadrupolar nature is generated locally. It can be observed in conductance measurements and surprisingly leads to enhanced spin filtering even in a state with zero average spin. Analogously to the spintronic dipolar exchange field, responsible for a local spin torque, the effect is susceptible to electric control and increases with tunnel coupling as well as with spin polarization.Comment: 6 pages with 4 figures + 26 pages of Supplementary Informatio

Staircase Quantum Dots Configuration in Nanowires for Optimized Thermoelectric Power

The performance of thermoelectric energy harvesters can be improved by nanostructures that exploit inelastic transport processes. One prototype is the three-terminal hopping thermoelectric device where electron hopping between quantum-dots are driven by hot phonons. Such three-terminal hopping thermoelectric devices have potential in achieving high efficiency or power via inelastic transport and without relying on heavy-elements or toxic compounds. We show in this work how output power of the device can be optimized via tuning the number and energy configuration of the quantum-dots embedded in parallel nanowires. We find that the staircase energy configuration with constant energy-step can improve the power factor over a serial connection of a single pair of quantum-dots. Moreover, for a fixed energy-step, there is an optimal length for the nanowire. Similarly for a fixed number of quantum-dots there is an optimal energy-step for the output power. Our results are important for future developments of high-performance nanostructured thermoelectric devices

From thermal rectifiers to thermoelectric devices

We discuss thermal rectification and thermoelectric energy conversion from the perspective of nonequilibrium statistical mechanics and dynamical systems theory. After preliminary considerations on the dynamical foundations of the phenomenological Fourier law in classical and quantum mechanics, we illustrate ways to control the phononic heat flow and design thermal diodes. Finally, we consider the coupled transport of heat and charge and discuss several general mechanisms for optimizing the figure of merit of thermoelectric efficiency.Comment: 42 pages, 22 figures, review paper, to appear in the Springer Lecture Notes in Physics volume "Thermal transport in low dimensions: from statistical physics to nanoscale heat transfer" (S. Lepri ed.

Study Protocol: A Pilot Study to Determine the Safety and Efficacy of Induction-Therapy, De Novo MPA and Delayed mTOR-Inhibition in Liver Transplant Recipients with Impaired Renal Function. PATRON-Study

<p>Abstract</p> <p>Background</p> <p>Patients undergoing liver transplantation with preexisting renal dysfunction are prone to further renal impairment with the early postoperative use of Calcineurin-inhibitors. However, there is only little scientific evidence for the safety and efficacy of de novo CNI free "bottom-up" regimens in patients with impaired renal function undergoing liver transplantation. This is a single-center study pilot-study (<b>PATRON07</b>) investigating safety and efficacy of CNI-free, "bottom-up" immunosuppressive (IS) strategy in patients undergoing liver transplantation (LT) with renal impairment prior to LT.</p> <p>Methods/Design</p> <p>Patients older than 18 years with renal impairment at the time of liver transplantation eGFR < 50 ml/min and/or serum creatinine levels > 1.5 mg/dL will be included. Patients in will receive a CNI-free combination therapy (basiliximab, MMF, steroids and delayed Sirolimus). Primary endpoint is the incidence of steroid resistant acute rejection within the first 30 days after LT. The study is designed as prospective two-step trial requiring a maximum of 29 patients. In the first step, 9 patients will be included. If 8 or more patients show no signs of biopsy proven steroid resistant rejection, additional 20 patients will be included. If in the second step a total of 27 or more patients reach the primary endpoint the regimen is regarded to be safe and efficient.</p> <p>Discussion</p> <p>If a CNI-free-"bottom-up" IS strategy is safe and effective, this may be an innovative concept in contrast to classic top-down strategies that could improve the patient short and long-time renal function as well as overall complications and survival after LT. The results of <b>PATRON07 </b>may be the basis for a large multicenter RCT investigating the new "bottom-up" immunosuppressive strategy in patients with poor renal function prior to LT.</p> <p><url>http://www.clinicaltrials.gov</url>-identifier: NCT00604357</p

Detection of dicistroviruses RNA in blood of febrile Tanzanian children.

Fever is the leading cause of paediatric outpatient consultations in Sub-Saharan Africa. Although most are suspected to be of viral origin, a putative causative pathogen is not identified in over a quarter of these febrile episodes. Using a de novo assembly sequencing approach, we report the detection (15.4%) of dicistroviruses (DicV) RNA in sera collected from 692 febrile Tanzanian children. In contrast, DicV RNA was only detected in 1/77 (1.3%) plasma samples from febrile Tanzanian adults, suggesting that children could represent the primary susceptible population. Estimated viral load by specific quantitative real-time RT-PCR assay ranged from &lt; 1.32E3 to 1.44E7 viral RNA copies/mL serum. Three DicV full-length genomes were obtained, and a phylogenetic analyse on the capsid region showed the presence of two clusters representing tentative novel genus. Although DicV-positive cases were detected throughout the year, a significantly higher positivity rate was observed during the rainy season. This study reveals that novel DicV RNA is frequently detected in the blood of Tanzanian children, paving the way for further investigations to determine if DicV possibly represent a new agent in humans

Effect of wood smoke exposure on vascular function and thrombus formation in healthy fire fighters

Background: Myocardial infarction is the leading cause of death in fire fighters and has been linked with exposure to air pollution and fire suppression duties. We therefore investigated the effects of wood smoke exposure on vascular vasomotor and fibrinolytic function, and thrombus formation in healthy fire fighters. Methods: In a double-blind randomized cross-over study, 16 healthy male fire fighters were exposed to wood smoke (~1 mg/m3 particulate matter concentration) or filtered air for one hour during intermittent exercise. Arterial pressure and stiffness were measured before and immediately after exposure, and forearm blood flow was measured during intra-brachial infusion of endothelium-dependent and -independent vasodilators 4–6 hours after exposure. Thrombus formation was assessed using the ex vivo Badimon chamber at 2 hours, and platelet activation was measured using flow cytometry for up to 24 hours after the exposure. Results: Compared to filtered air, exposure to wood smoke increased blood carboxyhaemoglobin concentrations (1.3% versus 0.8%; P &lt; 0.001), but had no effect on arterial pressure, augmentation index or pulse wave velocity (P &gt; 0.05 for all). Whilst there was a dose-dependent increase in forearm blood flow with each vasodilator (P &lt; 0.01 for all), there were no differences in blood flow responses to acetylcholine, sodium nitroprusside or verapamil between exposures (P &gt; 0.05 for all). Following exposure to wood smoke, vasodilatation to bradykinin increased (P = 0.003), but there was no effect on bradykinin-induced tissue-plasminogen activator release, thrombus area or markers of platelet activation (P &gt; 0.05 for all). Conclusions: Wood smoke exposure does not impair vascular vasomotor or fibrinolytic function, or increase thrombus formation in fire fighters. Acute cardiovascular events following fire suppression may be precipitated by exposure to other air pollutants or through other mechanisms, such as strenuous physical exertion and dehydration.Originally included in thesis in manuscript form.</p