The mobility impairment caused by a paralysis like a spinal cord injury or a stroke has, beside many other impacts, an influence on the transfer of signals between the muscles of the lower ...extremities and the brain. In a paraplegic person, this means that she or he can not stand without holding onto a support or standing in a standing frame while the impact on the ability to balance in a hemiplegic person can be less severe. Although the connection between the muscles and the brain is impaired by the injury, the muscles still retain the ability to contract if innervated. This thesis describes control approaches which combine the remaining voluntary control of the paraplegic and stroke patients with the artificially controlled stimulation of the muscles of the paralysed limbs to aid the subject in balancing. The aim was to develop new control approaches which would assist balance in paraplegic subjects and in stroke. To support standing in paraplegic subjects, the moment generated at the ankle using electrical stimulation of the shank muscles was integrated with the voluntary control of the upper body, resulting in the concept of Integrated Voluntary Control (IVC). In the outer loop the ankle moment produced by the paraplegic subject due to his voluntary upper body movement was estimated using a mathematical model based on the inclination angles of upper and lower body. This estimated ankle moment was then compared with the actual moment applied at the force plates the subject was standing on, and an appropriate stimulation signal was applied to the paralysed shank muscles. Experimental evaluation initially involved four able bodied volunteers in which base line results with stiffness and stiffness-viscosity controllers using a rotating standing platform were obtained. This was extended to the paraplegic subject, where electrical muscle stimulation was used to generate the required ankle moment. The IVC concept was then evaluated with the paraplegic subject and compared to the base line results. Due to the nature of the system and implied perturbation onto the control system controlling the posture of the paraplegic subject the known evaluation values (e.g. rise time, steady state value, overshoot value etc.) are not suitable. Therefore, the variance of a time signal around its mean value was used as an evaluation value which allowed to compare the achieved performance of the paraplegic subject employing the new control approach with the stiffness and stiffness-viscosity controllers directly. To assist balance in stroke patients, a new training approach was introduced based on the concept of integrating the voluntary abilities of the patient with mechanical balance support and sensory electrical stimulation. This concept was evaluated in a training program with one stroke subject which demonstrated the feasibility and potential balance improvement resulting from this approach.
BACKGROUND: Aggression can have a wide range of damaging consequences for both perpetrators and victims. Theoretical and empirical studies into problems of aggression increasingly show the importance ...of social and cognitive factors in aggressive behaviour. Such research has commonly been approached through the framework of the Social-Information Processing (SIP) model. SIP explains social behaviours by the sequence of cognitive processes that occur between encountering a social stimulus and enacting a response to it. Crucially, it is apparent that particular processing styles, such as the way in which people interpret others’ behaviour, play important roles in aggression. However, while SIP has long been used to explain aggression in the non-disabled population, it is only in more recent years that this approach has been applied to people with intellectual disabilities (IDs). This is important because a significant minority of people with IDs demonstrate frequent aggressive behaviour. Although several studies have already indicated that particular cognitive processing tendencies and aptitudes contribute to aggression in adults with ID, no research has considered younger people in the transition to adulthood. To this end, the present thesis sought to investigate the possible influences of certain psychosocial factors on this group of young people with mild to moderate IDs. OBJECTIVES: To identify which specific factors to investigate, a systematic review was conducted of existing research into SIP and aggression with people who have IDs. On the basis of these findings, the thesis examined 1) the social interactions that typically elicit anger, 2) experiences of parental aggression 3) ability to discern affect from dynamic social cues and 4) beliefs about the consequences of aggressive and submissive behaviour. With the review also stressing the importance of examining aggression at specific developmental stages, the studies focused on individuals in the transition from adolescence to adulthood (between 16 and 20 years). Although this stage is thought to be important in the development of cognitive factors associated with aggression, there is little or no research in this area with young adults with IDs. METHODS: The thesis comprised four distinct research studies. Each adopted a group-comparison design, comparing aggressive and non-aggressive young people with IDs. To evaluate the extent to which findings were specific to people with IDs, additional comparisons were conducted between aggressive and non-aggressive individuals without IDs. For Study 1, 26 young adults with IDs and 20 non-disabled young adults completed a semi-structured interview about a recent experience of interpersonal conflict. Participants were asked to describe their beliefs and feelings about the event and their subsequent response. Studies 2, 3 and 4 used data from a second phase of data collection involving 46 young people with and 48 people without IDs. Study 2 used a task in which participants were asked to rank different types of social conflict in order of provocativeness. The author developed these scenarios to reflect the experiences of conflict reported by participants in Study 1. Participants also indicated how recently they had encountered each type of scenario. Study 3 used motion-capture stimuli of people walking in different emotional states to examine whether groups differed in how they encode dynamic social cues. Study 4 used provocative vignettes to examine whether aggressive young people with IDs expect different outcomes from aggressive and submissive responses to such scenarios. RESULTS: Study 1 found that participants with IDs were more likely to encounter conflict with strangers or peers outside their friendship group. They were also more likely to describe incidents of aggression and to characterise people with whom they were in conflict globally as “bad” and to perceive their actions as being personally directed at them. Study 2 did not suggest that experiences of being victimised by peers were more common for people with IDs, but did show that aggressive individuals were more likely to encounter incidents of physical aggression from peers. Parental conflict was the most recently encountered, but was perceived to be the least provocative form of conflict for all groups. In Study 3, no group differences were found in accuracy or response tendencies for the emotion recognition task. Aggressive and non-aggressive participants with IDs in Study 4 did not predict different outcomes form aggression and submission. However, the aggressive participants without IDs predicted more positive outcomes from aggression and more negative outcomes for submission. While aggressive participants with IDs were more likely to give aggressive responses, they were just as likely as the non-aggressive group to respond actively (assertively or aggressively) rather than passively. CONCLUSION: The findings of this thesis, viewed from the perspective of the SIP model, suggest that there are key cognitive and contextual differences between individuals who show frequent aggression, both with and without IDs. Although, somewhat surprisingly, emotion recognition skills did not appear to be associated with a tendency toward aggressive behaviour, the non-ID aggressive and non-aggressive groups differed in their anticipated outcomes for aggressive and submissive behaviour. The context in which conflict occurred also appeared to differ between those young people with and without IDs. However, the absence of some predicted findings from these studies may be related to methodological shortcomings; these possible limitations are considered, and directions for future work are suggested. Applications for clinical practice and policy are also discussed and recommendations for future research are given.
Effect of the carrier shape in the ultra high dense wavelength division multiplexing (WDM) return to zero differential phase shift keying (RZ-DPSK) transmission has been examined through numerical ...optimization of the pulse form, duty cycle and narrow multiplex/de-multiplex (MUX/DEMUX) filtering parameters.
Purpose: To investigate the subretinal toxicity profile of the ribozyme to the proliferating cell nuclear antigen (PCNA-Rz) and 5-fluorouracil (5-FU), as well as the highest nontoxic subretinal dose ...of the mixture of the two agents in rat eyes. Methods: Brown-Norway rats received subretinal injections of 1 μ g, 10 μ g, and 100 μ g/μ l PCNA-Rz and 0.06 μ g/μ l, 0.3 μ g/μ l, and 1.5 μ g/μ l 5-FU in the right eyes, and the left eyes were injected with H-BSS as control. Each dose was tested on 5 eyes in a 5 μ l volume. In a second study, a combination of 5-FU (1.5 μ g/μ L) with varying 10-30-50 μ g/μ l doses of PCNA-Rz was tested in a regimen of four sequential subretinal injections. Toxicity was monitored by biomicroscopy, indirect ophthalmoscopy, electroretinography (ERG), and histology. Results: The highest nontoxic dose for subretinal PCNA-Rz was 10 μ g/μ l, whereas 100 μ g/μ l showed disturbance of pigmentation with corresponding histological changes of retinal photoreceptor loss and retinal pigment epithelium proliferation or irregularities. Subretinal injection of all three doses of 5-FU did not show any toxicity. Serial injections of a mixture of 1.5 μ g/μ l 5-FU with 10 μ g/μ l of PCNA-Rz was found to be safe in rat eyes. Conclusions: Subretinal injections of the combination of PCNA-Rz (10 μ g/μ l) and 5-FU (1.5 μ g/μ l) demonstrated to be safe in rat eyes during the course of this study, even with a multiple administration of four injections.
Current hypernova models for γ-ray bursts (GRBs) associated with supernovae suffer from the baryon contamination problem, which prevents formation of relativistic shocks and emission of γ-rays. Here ...we present a possible solution to this difficulty. Our model can be divided into two steps. In the first step, the core collapse of a star with mass⩾19
M
⊙ leads to a massive neutron star and a supernova (SN), and subsequently, one jet produced via neutrino annihilation during hypercritical accretion of the neutron star will push out of its front matter, resulting in a small cone relatively free of baryons. In the second step, once the mass of the neutron star reaches the maximum value, it will promptly implode to a rapidly rotating black hole surrounded by a torus. The gravitational binding energy of the torus will convert to the expansion energy of the SN ejecta, thus yielding a hypernova, while the rotational energy of the black hole will be extracted via the Blandford–Znajek process to generate another jet responsible for a GRB. We show that the mass of baryons loading with the second jet is smaller than 10
−3
M
⊙ and the Lorentz factor of this jet is larger than 100. Thus our model can avoid the baryon contamination problem suffered from in the hypernova models.
This study aimed to investigate any difference between the attributions parents made about their child’s sleep problem, in parents of children with an Autism Spectrum Disorder and parents of children ...with Down Syndrome. Seventy-six parents of children with an Autism Spectrum Disorder and fifty-two parents of children with Down Syndrome completed a series of questionnaires on-line, regarding their child’s sleep problem, their beliefs about their child’s sleep problem and the parent’s level of anxiety and depression. A significant difference was found between the groups on four of the causal items; other health problem, child’s emotional state, child’s personality and diet. Parents of children with Down Syndrome showed a higher level of agreement that their child’s sleep problem could be attributed to another health problem compared to parents of children with an Autism Spectrum Disorder. Parents of children with an Autism Spectrum Disorder showed a higher level of agreement that their child’s sleep problem could be attributed to their child’s personality, their child’s emotional state and their child’s diet compared to parents of children with DS. There was a high level of agreement across all parents that their child’s disability was a causal factor to their sleep problem and differences in attributions may reflect characteristics of the child’s diagnosis. The results are consistent with previous findings that parents view disability as an important causal factor to their child’s sleep problem and suggest a possible overlap in parent’s views of their child’s sleep problem and views of their disability.
Digital imaging has long been available in radiology in the form of computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound. Initially the transition to general radiography was slow ...and fragmented but in the last 10-15 years in particular, huge investment by the manufacturers, greater and cheaper computing power, inexpensive digital storage and high bandwidth data transfer networks have lead to an enormous increase in the number of digital radiography systems in the UK. There are a number of competing digital radiography (DR) technologies, the most common are computer radiography (CR) systems followed by indirect digital radiography (IDR) systems. To ensure and maintain diagnostic quality and effectiveness in the radiology department appropriate methods are required to evaluate and optimise the performance of DR systems. Current semi-quantitative test object based methods routinely used to examine DR performance suffer known short comings, mainly due to the subjective nature of the test results and difficulty in maintaining a constant decision threshold among observers with time. Objective image quality based measurements of noise power spectra (NPS) and modulation transfer function (MTF) are the ‘gold standard’ for assessing image quality. Advantages these metrics afford are due to their objective nature, the comprehensive noise analysis they permit and in the fact that they have been reported to be relatively more sensitive to changes in detector performance. The advent of DR systems and access to digital image data has opened up new opportunities in applying such measurements to routine quality control and this project initially focuses on obtaining NPS and MTF results for 12 IDR systems in routine clinical use. Appropriate automatic exposure control (AEC) device calibration and a reproducible measurement method are key to optimising X-ray equipment for digital radiography. The uses of various parameters to calibrate AEC devices specifically for DR were explored in the next part of the project and calibration methods recommended. Practical advice on dosemeter selection, measurement technique and phantoms were also given. A model was developed as part of the project to simulate CNR to optimise beam quality for chest radiography with an IDR system. The values were simulated for a chest phantom and adjusted to describe the performance of the system by inputting data on phosphor sensitivity, the signal transfer function (STF), the scatter removal method and the automatic exposure control (AEC) responses. The simulated values showed good agreement with empirical data measured from images of the phantom and so provide validation of the calculation methodology. It was then possible to apply the calculation technique to imaging of tissues to investigate optimisation of exposure parameters. The behaviour of a range of imaging phosphors in terms of energy response and variation in CNR with tube potential and various filtration options were investigated. Optimum exposure factors were presented in terms of kV-mAs regulation curves and the large dose savings achieved using additional metal filters were emphasised. Optimum tube potentials for imaging a simulated lesion in patient equivalent thicknesses of water ranging from 5-40 cm thick for example were: 90-110kVp for CsI (IDR); 80-100kVp for Gd2O2S (screen /film); and 65-85kVp for BaFBrI. Plots of CNR values allowed useful conclusions regarding the expected clinical operation of the various DR phosphors. For example 80-90 kVp was appropriate for maintaining image quality over an entire chest radiograph in CR whereas higher tube potentials of 100-110 kVp were indicated for the CsI IDR system. Better image quality is achievable for pelvic radiographs at lower tube potentials for the majority of detectors however, for gadolinium oxysulphide 70-80 kVp gives the best image quality. The relative phosphor sensitivity and energy response with tube potential were also calculated for a range of DR phosphors. Caesium iodide image receptors were significantly more sensitive than the other systems. The percentage relative sensitivities of the image receptors averaged over the diagnostic kV range were used to provide a method of indicating what the likely clinically operational dose levels would be, for example results suggested 1.8 µGy for CsI (IDR); 2.8 µGy for Gd2O2S (Screen/film); and 3.8 µGy for BaFBrI (CR). The efficiency of scatter reduction methods for DR using a range of grids and air gaps were also reviewed. The performance of various scatter reduction methods: 17/70; 15/80; 8/40 Pb grids and 15 cm and 20 cm air gaps were evaluated in terms of the improvement in CNR they afford, using two different models. The first, simpler model assumed quantum noise only and a photon counting detector. The second model incorporated quantum noise and system noise for a specific CsI detector and assumed the detector was energy integrating. Both models allowed the same general conclusions and suggest improved performance for air gaps over grids for medium to low scatter factors and both models suggest the best choice of grid for digital systems is the 15/80 grid, achieving comparable or better performance than air gaps for high scatter factors. The development, analysis and discussion of AEC calibration, CNR value, phosphor energy response, and scatter reduction methods are then brought together to form a practical step by step recipe that may be followed to optimise digital technology for clinical use. Finally, CNR results suggest the addition of 0.2 mm of copper filtration will have a negligible effect on image quality in DR. A comprehensive study examining the effect of copper filtration on image quality was performed using receiver operator characteristic (ROC) methodology to include observer performance in the analysis. A total of 3,600 observations from 80 radiographs and 3 observers were analysed to provide a confidence interval of 95% in detecting differences in image quality. There was no statistical difference found when 0.2 mm copper filtration was used and the benefit of the dose saving promote it as a valuable optimisation tool.
In the work, the intensity and phase modulation methods are compared for different versions of the wavelength division multiplexing (WDM) system. Binary and multilevel code formats are evaluated ...numerically, with OptSim simulation software at the bit rate of 10 and 40 Gbit/s, using long-fiber spans and dispersion compensation technique. The problems to be overcome at exploitation of multiterabit WDM systems based on 40 Gbit/s optical transmissions are: chromatic dispersion (CD), polarization-mode dispersion (PMD), dispersion slope, and nonlinear effects of the transmission line. We have investigated the potentialities of modulation formats for 40 Gbit/s WDM networks where most of the listed problems are avoided. It is shown that Duobinary and differential phase shift keying (DPSK) modulation formats are perfectly suitable for ultra-high spectral efficient WDM systems and possess high resistance to dispersion and nonlinear optical effects (NOE).
Darbā pētītas un salīdzinātas intensitātes un fāzes modulācijas metodes optiskajās spektrālās blīvēšanas (WDM) sistēmās. Binārie un daudzlīmeņu kodēšanas formāti ir skaitliski novērtēti ar simulācijas programmatūras OptSim palīdzību pie 10 Gbit/s un 40 Gbit/s pārraides ātrumiem, izmantojot garas optiskās šķiedras līnijas un dispersijas kompensēšanas tehniku. Galvenās problēmas, kas ekspluatācijas laikā ir jāņem vērā sistēmās ar pārraides ātrumu līdz 40 Gbit/s, ir hromatiskā dispersija (CD), polarizācijas - modu dispersija (PMD), dispersijas slīpums un pārraides līnijas nelineārie efekti. Novērtēti perspektīvākie modulācijas formāti 40 Gbit/s WDM sistēmām. Pētījumā uzskatāmi demonstrēts, ka daudzlīmeņu modulācijas un diferenciālās fāzes manipulācijas (DPSK) formāti ir atbilstošākie liela ātruma spektrāli efektīvām sistēmām. Tos var raksturot ar augstu noturības līmeni pret dispersiju un nelineārajiem optiskajiem efektiem (NOE).
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