Eccentric Contraction-Induced Muscle Fibre Adaptation

Hard-strength training induces strength increasing and muscle damage, especially after eccentric contractions. Eccentric contractions also lead to muscle adaptation. Symptoms of damage after repeated bout of the same or similar eccentrically biased exercises are markedly reduced. The mechanism of this repeated bout effect is unknown. Since electromyographic (EMG) power spectra scale to lower frequencies, the adaptation is related to neural adaptation of the central nervous system (CNS) presuming activation of slow-non-fatigable motor units or synchronization of motor unit firing. However, the repeated bout effect is also observed under repeated stimulation, i.e. without participation of the CNS. The aim of this study was to compare the possible effects of changes in intracellular action potential shape and in synchronization of motor units firing on EMG power spectra. To estimate possible degree of the effects of central and peripheral changes, interferent EMG was simulated under different intracellular action potential shapes and different degrees of synchronization of motor unit firing. It was shown that the effect of changes in intracellular action potential shape and muscle fibre propagation velocity (i.e. peripheral factors) on spectral characteristics of EMG signals could be stronger than the effect of synchronization of firing of different motor units (i.e. central factors)

Assessment of the Subjective Visual Dysfunction of Patients With Multiple Sclerosis Using Specialized Questionnaires

Recently, the questions of the limited opportunities for measurement of the subjective and often subclinical visual dysfunction are very topical. NEI-VFQ, the questionnaire of the National Eye Institute in the USA and VFQ-25, its short version (25-item Vision Function Questionnaire) are validated for visual-specific assessment of the quality of life of multiple sclerosis (MS) patients. MSVQ-7, a specific 7-item MS Vision Questionnaire is proposed, too. The authors used the VFQ-25 translated into Bulgarian, the MSVQ-7 and their correlation with the binocular visual acuity. These questionnaires were administered to 108 MS patients without history of optic neuritis and after optic neuritis as well registered in the MS Centre in Varna and to 30 healthy subjects. There was a statistically significant difference (p<0,0001) between MS patients and controls in all sub-scales and in the overall results from VFQ-25. The analysis of MSVQ-7 showed a statistically significant difference between the answers of question Nos 1, 2, 3 and 5  p<0,001 to p=0,015). The correlation of the results from VFQ-25 and the binocular visual acuity was moderate (Spearman's r=0,6;  <0,01). The application of questionnaires for assessment of visual function may contribute to the identification of less known and sought subclinical visual dysfunctions that appear in normal visual acuity. Our data confirm the possible usage of VFQ-25 and MSVQ-7 for effective measurement of the subjective visual deficit in MS diagnosis

Clinical, Instrumental and Immunological Follow-Up of Patients with Brain Tumors

Dynamic assessment of 66 patients with different brain tumours was carried out. The clinical, immunological and instrumental (electrophysiological and neuroimaging) follow-up included three groups of cases with stable clinical course, tumour progression and recurrence. Our results confirm that the changes in the functional and immune status of the patients with cerebral neoplasms as well as the alterations in the cerebral function and structure reflect the tumour development and the corresponding therapeutic behaviour. Monitoring of patients status and tumour growth provides opportunity for better disease control and prognosis

INVESTIGATION OF VISUAL ASSESSMENT OF ALTERNATING LUMINOUS AREAS IN NEUROOPHTHALMOLOGICAL DIAGNOSIS OF PATIENTS WITH INTRA - AND PARASELLAR TUMORS

The method for investigation of visual assessment of alternating luminous areas (VAALA) enables to establish visual disorders in different diffusive and local brain lesions including brain tumours. In this study the applicability of VAALA in the complex neuroophtalmological investigations in patients with intra- and pa nisei I ar tumours was analyzed. VAALA, peripheral vision, and visual acuity were assessed in 9 patients with extrasellar tumours and in 5 patients with intrasellar ones. VAALA showed changes in all the patients without any significant difference between both patients' groups. Routine neuroophthalmological examination even in patients with extrasellar tumours indicated some typical abnormalities in a part of the cases only while in single cases of intrasellar tumours only initial changes could be detected. Perimetria and especially visual acuity and VEP possessed a lower diagnostic value in perichiasmatic lesions than contemporary psychophysical tests, VAALA inclusive. The high sensitivity of VAALA concerning the visual disturbances in pathological processes in these areas enables its integration into the complex neuroophthalmological examination

Advances in surface EMG signal simulation with analytical and numerical descriptions of the volume conductor

Surface electromyographic (EMG) signal modeling is important for signal interpretation, testing of processing algorithms, detection system design, and didactic purposes. Various surface EMG signal models have been proposed in the literature. In this study we focus on 1) the proposal of a method for modeling surface EMG signals by either analytical or numerical descriptions of the volume conductor for space-invariant systems, and 2) the development of advanced models of the volume conductor by numerical approaches, accurately describing not only the volume conductor geometry, as mainly done in the past, but also the conductivity tensor of the muscle tissue. For volume conductors that are space-invariant in the direction of source propagation, the surface potentials generated by any source can be computed by one-dimensional convolutions, once the volume conductor transfer function is derived (analytically or numerically). Conversely, more complex volume conductors require a complete numerical approach. In a numerical approach, the conductivity tensor of the muscle tissue should be matched with the fiber orientation. In some cases (e.g., multi-pinnate muscles) accurate description of the conductivity tensor may be very complex. A method for relating the conductivity tensor of the muscle tissue, to be used in a numerical approach, to the curve describing the muscle fibers is presented and applied to representatively investigate a bi-pinnate muscle with rectilinear and curvilinear fibers. The study thus propose an approach for surface EMG signal simulation in space invariant systems as well as new models of the volume conductor using numerical methods

Manufacturing of custom-made medical implants for cranio / maxillofacial and orthopaedic surgery - an overview of the current state of the industry

Published ArticleExtensive work has been done in the area of manufacturing implants for medical purposes, and more recently the development of customised implants. Areas of application include cranio/maxillo-facial implants, dental drill guides, hip, knee and shoulder replacements, as well as different implants for the spine. Due to their high prevalence and complex anatomical geometry the purpose of this study is to investigate the current state of the industry regarding customised medical implants for cranio/maxillofacial and orthopaedic surgery. Implant customisation has far-reaching benefits, and a collective approach to solving current difficulties will require an in-depth study of successes already achieved. Several issues in this regard are examined, including what defines customisation, regulatory issues that govern customisation and design constraints, trends in different areas of application, suitable materials, and finally which manufacturing techniques are being employed, with a focus on the use of Layer Manufacturing technologies and their role in custom-made medical implants

Advances on Matroid Secretary Problems: Free Order Model and Laminar Case

The most well-known conjecture in the context of matroid secretary problems claims the existence of a constant-factor approximation applicable to any matroid. Whereas this conjecture remains open, modified forms of it were shown to be true, when assuming that the assignment of weights to the secretaries is not adversarial but uniformly random (Soto [SODA 2011], Oveis Gharan and Vondr\'ak [ESA 2011]). However, so far, there was no variant of the matroid secretary problem with adversarial weight assignment for which a constant-factor approximation was found. We address this point by presenting a 9-approximation for the \emph{free order model}, a model suggested shortly after the introduction of the matroid secretary problem, and for which no constant-factor approximation was known so far. The free order model is a relaxed version of the original matroid secretary problem, with the only difference that one can choose the order in which secretaries are interviewed. Furthermore, we consider the classical matroid secretary problem for the special case of laminar matroids. Only recently, a constant-factor approximation has been found for this case, using a clever but rather involved method and analysis (Im and Wang, [SODA 2011]) that leads to a 16000/3-approximation. This is arguably the most involved special case of the matroid secretary problem for which a constant-factor approximation is known. We present a considerably simpler and stronger $3\sqrt{3}e\approx 14.12$-approximation, based on reducing the problem to a matroid secretary problem on a partition matroid

Polymer Brushes in Cylindrical Pores: Simulation versus Scaling Theory

The structure of flexible polymers endgrafted in cylindrical pores of diameter D is studied as a function of chain length N and grafting density \sigma, assuming good solvent conditions. A phenomenological scaling theory, describing the variation of the linear dimensions of the chains with \sigma, is developed and tested by Molecular Dynamics simulations of a bead-spring model.Comment: 35 pages, 38 figure