170,248 research outputs found
Sir Charles Ballance : A pioneer surgeon in Malta
No full textCharles Ballance was arguably the most eminent surgeon stationed in Malta during the Great War. On the 16th February 1918 he removed a bullet from the heart of trooper Robert Martin who was shot in the chest in Salonika three months previously. Sadly the patient died of sepsis one month later, a fact that obscured the importance of this landmark operation, the third of its kind worldwide. This paper sets the background to this achievement and celebrates the impact that this surgical pioneer left on our shores.peer-reviewe
A nonlinear disturbance observer for robotic manipulators
No full textA new nonlinear disturbance observer (NDO) for robotic manipulators is derived in this paper. The global exponential stability of the proposed disturbance observer (DO) is guaranteed by selecting design parameters, which depend on the maximum velocity and physical parameters of robotic manipulators. This new observer overcomes the disadvantages of existing DOs, which are designed or analyzed by linear system techniques. It can be applied in robotic manipulators for various purposes such as friction compensation, independent joint control, sensorless torque control and fault diagnosis. The performance of the proposed observer is demonstrated by the friction estimation and compensation for a two-link robotic manipulator. Both simulation and experimental results show the NDO works well
Sir Charles Alfred Ballance (1856-1936) and the introduction of facial nerve crossover anastomosis in 1895
No full textSir Charles Ballance (1856-1936) was the first surgeon in history to perform a facial nerve crossover anastomosis in 1895. Although, recently, several papers on the history of facial nerve surgery have been published, little is known about this historically important operation, the theoretical reasoning behind the operation or the surgical perspective in which Ballance developed this method. An original document on the operation, dated in 1895, is not known. The earliest report of the operation is a paper by Ballance, published in 1903. Study of this 1903 paper reveals that Ballance stopped performing the operation after his first attempt in 1895 until he resumed in December 1901. What was the reason for this interruption? Why did Ballance start doing it again in 1901? Between 1895 and Ballance's 1903 paper, several other surgeons had published the results of their facial nerve crossovers. Were they inspired by Ballance's operation from 1895 to do the same or did they invent the method independently? To enhance our knowledge about the early history of facial nerve surgery, the original manuscripts by Ballance and his contemporaries have been studied. Ballance's first facial nerve crossover from 1895 is described in the surgical perspective of the end of the 19th century. The theoretical reasoning for the operation is discussed. It was discovered that Ballance's operation was first recorded in St. Thomas's Hospital Report of 1895, which was published in 1897. However, this report was probably hardly known by Ballance's contemporaries and consequently could not have stimulated them to perform the operation themselves. Jean Louis Faure (1863-1944), from France, appears to have been the first to have performed the operation until Ballance's 1903 paper was published. In 1903, after Ballance's paper had been published, many other accounts of this method were reported in the literature. At that moment facial nerve crossover seems to have been widely regarded as a potential successful technique, a technique which, a century later, is still part of our repertoire. (C) 2008 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved
Engineering tough, hygroscopic, and active hydrogels for surgical simulation and anti-biofouling
No full textHydrogels have emerged as a class of materials useful for a variety of contexts, including tissue engineering, anti-fouling, drug release, medical devices, and flexible electronics. The usefulness of hydrogels in these contexts stems from their structure, consisting of a 3D cross-linked polymer network containing mostly water. This structure leads to a material with tunable, tissue-like softness and water content, biocompatibility, resistance to biological fouling, high porosity, and transparency. However, the utility of these numerous properties is often offset by hydrogel brittleness and, if exposed directly to air, eventual drying. Therefore, hydrogels are difficult to use for applications involving puncture or high shear forces, such as surgical simulation, as well as open-air environments. The goal of my thesis research is to bridge this technological gap by engineering hydrogels that are both tough and non-drying so that new applications may be opened for this unique material. Chapter 2 discusses a general strategy to improve hydrogel toughness by forming a highly concentrated polyacrylamide hydrogel with a low number of cross-links, thereby increasing the polymer entanglements that may form between cross-linking junctions. Chapter 3 demonstrates that the drying of hydrogels exposed to air can be prevented by incorporating glycerol within the gel network, leading to a hygroscopic material that draws humidity from the surrounding ambient air. Both of these properties of toughness and non-drying are combined in Chapter 4 to demonstrate the 3D printing of suturable organ mimics for preoperative planning and surgical training. Further applications of the tough hydrogel in drug release are shown in Chapter 5. In this study, drug-binding cyclodextrin linked within the tough polyacrylamide hydrogel releases its molecular cargo in response to tensile stretching. The tough hydrogels also exhibited anti-fouling properties due to the high water content in the gel. Therefore, they were used for anti-fouling in contexts where physical forces are present. Chapter 6 demonstrates the anti-fouling capabilities of the tough hydrogel by layering it on top of a vibrating dielectric actuator to actively remove pre-formed biofilms. Finally, in Chapter 7, the anti-fouling property of the hydrogel is enhanced by interpenetrating the network with polyvinylpyrrolidone complexed with anti-bacterial iodine to prevent corrosion of stainless steel by sulfate-reducing bacteria. Overall, tough and non-drying hydrogels were successfully engineered and then used for a variety of applications, including model organs for surgical simulation, flexible electronics, drug release, and anti-biofouling.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-05-01The student, William Ballance, accepted the attached license on 2020-04-17 at 13:35.The student, William Ballance, submitted this Dissertation for approval on 2020-04-17 at 13:51.This Dissertation was approved for publication on 2020-04-20 at 09:55.DSpace SAF Submission Ingestion Package generated from Vireo submission #14995 on 2020-08-25 at 17:40:21Made available in DSpace on 2020-08-27T00:49:56Z (GMT). No. of bitstreams: 3
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Early cardiac surgery in Malta
No full textCardiac surgery in Malta started in 1918 with the removal of a bullet from the left ventricle. The second operation took place almost thirty years later with the ligation of a persistent ductus arteriosus. During the next thirty five years close ties with the UK were fostered and Maltese patients were sent there for specialist treatment and surgery. By the early 1980's patients were being investigated in Malta and visiting teams from the UK performed surgery both here and abroad. This expanding service was a prelude to the setting up of a permanent local service, which began operations in 1995.peer-reviewe
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Simulation of hot working of austenitic stainless steels.
No full textThe published literature on the strength and
structural changes occurring during and after hot working of
AI5I316 and 304 austenitic stainless steels are reviewed.
Isothermal plane strain compression tests have
been carried out with the purpose of determining
relationships to describe the kinetics of static
recrystallization, the recrystallized grain size, the
isothermal grain growth rate and the strength during hot
rolling of AISI316 steel. The kinetics of static
recrystallization were also studied in samples tested in
axisymmetric compression, or hot rolled. The effect on the
kinetics of static recrystallization of the strain
distribution in samples tested in plane strain compression
was analysed. The set of equations determined for 316 steel wasused in a computer model modified from the one developed by Leduc (1980) for simulation of hot rolling loads and
microstructural evolution. Partially recrystallized
microstructure was generated in a laboratory hot rolling
mill and was reasonably simulated by the use of the computer
programme. Non-isothermal plane strain compression tests were carried out for direct simulation of laboratory hot rolling results. Comparison between experimental hot rolling and plane strain compression data has shown reasonable levels of agreement in the microstructural simulations undertaken in the present work. The mean plane strain strengths from non-isothermal plane strain compression tests were higher than the ones from hot rolling. This may have been caused by thermal gradients inside the sample being tested
Intermediate-coupling R -matrix calculations of electron-impact excitation of Fe 5+
No full textFor applications to laboratory and astrophysical plasmas, there is a great need for accurate electron-impact excitation data between individual levels in the lower charge-state ions of iron. Recently, we have reported on the first intermediate-coupling R -matrix calculation of electron-impact excitation in Fe 4+ , in which the close-coupling expansion of the target included levels from both ground and excited configurations (Ballance et al 2007 J. Phys. B: At. Mol. Opt. Phys. [/0953-4075/40/23/f01] 40 F327 , 2008 Europhys. News 39 14). In this paper, we present the results of two large intermediate-coupling Dirac R -matrix calculations of electron-impact excitation of Fe 5+ . The results from the two calculations, which differ only in the configuration–interaction expansions of the target, are compared. These comparisons provide some indication of the accuracy of the calculations and the resulting data should be useful in modelling plasmas containing iron
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