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Search Results: 1 - 10 of 189829 matches for " G. Tsagarakis "
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On the Kinematic Motion Primitives (kMPs) - Theory and Application
Federico L. Moro,Nikos G. Tsagarakis
Frontiers in Neurorobotics , 2012, DOI: 10.3389/fnbot.2012.00010
Abstract: Human neuromotor capabilities guarantee a wide variety of motions. A full understanding of human motion can be beneficial for rehabilitation or performance enhancement purposes, or for its reproduction on artificial systems like robots. This work aims at describing the complexity of human motion in a reduced dimensionality, by means of kinematic Motion Primitives (kMPs). A set of five invariant kMPs are identified for periodic motions, and a set of two kMPs for discrete motions. It is shown how these two sets of kMPs can be combined to synthesize more complex motion as the simultaneous execution of the periodic and the discrete motions. The results reported are an evidence of the theory of Central Pattern Generators (CPG), showing its effects on the kinematics, and are related to what presented in the literature on the Motor Primitives extracted from EMG signals. Experimental tests with the COmpliant huMANoid (COMAN) were performed to show that the kMPs extracted from human subjects can be used to transfer the features of human locomotion to the gait of a robot.
Sampled Data Control of a Compliant Actuated Joint Using On/Off Solenoid Valves
V. A. Tsachouridis,N. G. Tsagarakis,D. G. Caldwell
Journal of Engineering Science and Technology Review , 2011,
Abstract: This paper proposes a new control system design method for a compliant actuated joint using on/off solenoid valves. Themathematical modelling and the system’s hardware are described in detail. The control design method is presented in ageneral manner so it could be applied for any other similar system. For the present system, the designed controller is implementedvia a digital computer and it is characterised by very good performance and simplicity. The success of the proposedmethod is validated via simulations and experiment.
Statistical Review of UK Residential Sector Electrical Loads
G. Tsagarakis,A. J. Collin,A. E. Kiprakis
Physics , 2013, DOI: 10.1515/ijeeps-2013-0078
Abstract: This paper presents a comprehensive statistical review of data obtained from a wide range of literature on the most widely used electrical appliances in the UK residential load sector. It focuses on individual appliances and begins by consideration of the electrical operations performed by the load. This approach allows for the loads to be categorised based on the electrical characteristics, and also provides information on the reactive power characteristics of the load, which is often neglected from standard consumption statistics. This data is particularly important for power system analysis. In addition to this, device ownership statistics and probability distribution functions of power demand are presented for the main residential loads. Although the data presented is primarily intended as a resource for the development of load profiles for power system analysis, it contains a large volume of information which provides a useful database for the wider research community.
Cortisol reserve in head trauma victims: evaluation with the low-dose (1 μg) corticotropin (ACTH) stimulation test
I Dimopoulou, A Kouyialis, S Tsagarakis, M Theodorakopoulou, G Assithianakis, M Christoforaki, N Thalassinos, C Roussos
Critical Care , 2003, DOI: 10.1186/cc1891
Abstract: In conclusion, adrenal cortisol secretion following dynamic stimulation is deficient in a subset of head injury patients; this condition is associated with vasopressor dependency.
Octreotide induces caspase activation and apoptosis in human hepatoma HepG2 cells
Nikos J Tsagarakis, Ioannis Drygiannakis, Antonis G Batistakis, George Kolios, Elias A Kouroumalis
World Journal of Gastroenterology , 2011,
Abstract: AIM: To investigate the role of octreotide on cellular proliferation and apoptosis of human hepatoma (HepG2) cells.METHODS: We studied cellular proliferation, apoptosis and the possible internal caspase-mediated apoptosis pathway involved, after treatment of HepG2 carcinoma cells with octreotide in comparison with the apoptosis caused by tumor necrosis factor-α (TNF-α). Activities of caspase-3, caspase-9, caspase-8 and caspase-2 were studied, while apoptosis was investigated through detection of DNA fragmentation and through identification of apoptotic cells with the annexin-V/propidium iodide flow cytometric method.RESULTS: After an initial increase in HepG2 cellular proliferation, a significant inhibition was observed with 10-8 mol/L octreotide, while TNF-α dose-dependently decreased proliferation. Early and late apoptosis was significantly increased with both substances. Octreotide significantly increased caspase-3, caspase-8 and caspase-2 activity. TNF-α significantly increased only caspase-2. Cellular proliferation was decreased after treatment with octreotide or TNF-α alone but, in contrast to TNF-α, octreotide decreased proliferation only at concentrations of 10-8 mol/L, while lower concentrations increased proliferation.CONCLUSION: Our findings are suggestive of caspase-mediated signaling pathways of octreotide antitumor activity in HepG2 cells, and indicate that measurements of serum octreotide levels may be important, at least in clinical trials, to verify optimal therapeutic drug concentrations.
Unusual causes of Cushing's syndrome
Vassiliadi, Dimitra;Tsagarakis, Stylianos;
Arquivos Brasileiros de Endocrinologia & Metabologia , 2007, DOI: 10.1590/S0004-27302007000800010
Abstract: although in the majority of the patients with cushing's syndrome (cs), hypercortisolism is due to acth hypersecretion by a pituitary tumour or to ectopic acth secretion from an extrapituitary neoplastic lesion or to autonomous cortisol secretion by an adrenal tumour, in occasional patients a much rarer entity may be the cause of the syndrome. herein, we attempted to summarise and categorise these unusual causes according to their presumed aetiology. to this end, we performed a comprehensive computer-based search for unusual or rare causes of cs. the following unusual forms of cs were identified: (i) acth hyperesecretion due to ectopic corticotroph adenomas in the parasellar region or the neurohypophysis, or as part of double adenomas, or gangliocytomas; (ii) acth hypersecretion due to ectopic crh or crh-like peptide secretion by various neoplasms; (iii) acth-independent cortisol hypersecretion from ectopic or bilateral adrenal adenomas; (iv) glucocorticoid hypersensitivity; (v) iatrogenic, due to megestrol administration or to ritonavir and fluticasone co-administration. such unusual presentations of cs illustrate why cushing's syndrome represents one of the most puzzling endocrine syndromes.
Endocrine dysfunction in the immediate period following traumatic brain injury
I Dimopoulou, S Tsagarakis, G Assithianakis, M Christoforaki, M Theodorakopoulou, A Kouyialis, S Korfias, N Thalassinos, C Roussos
Critical Care , 2003, DOI: 10.1186/cc1890
Abstract: These preliminary results suggest that a certain degree of hypopituitarism occurs in more than 50% of patients with moderate or severe head injury in the immediate post-trauma period, with cortisol hyporesponsiveness and hypogonadism being most common. Further studies are required to elucidate the pathogenesis of these abnormalities and to investigate whether they affect long-term morbidity.
Unification of Archaeological Sites in Greece: A Design Approach Based on Public Participation and Sustainability Criteria  [PDF]
Kiriaki M. Keramitsoglou, Efthymia M. Mylonopoulou, Vasiliki I. Georgiou, Angelos L. Protopapas, Konstantinos P. Tsagarakis
Current Urban Studies (CUS) , 2017, DOI: 10.4236/cus.2017.52014
Abstract: The simultaneous involvement of aesthetic variables and economic, social and environmental objectives in urban design and planning is quite rare, and difficult to be implemented and interpreted within a local context. The top-down approach has been the most common strategy employed in urban planning, whereas sustainability principles call for more participatory methods. This study presents a design approach to the unification of archaeological sites in the town of Didimoticho, Greece, based on public participation and sustainability criteria. A fully structured questionnaire was used to define aesthetic parameters. Six options were designed and then evaluated by the local community. Thus, taking into account the local conditions, a list of Must and a list of Wants were established according to selected sustainability criteria, which are significant tools for the Kepner-Tregoe model application. The proposed methodology revealed the optimal design solution. This systemic participatory approach applicable to urban design and planning can be implemented in other cases as well.
Treatment of Olive Mill Wastewater with Constructed Wetlands
Iosif E. Kapellakis,Nikolaos V. Paranychianakis,Konstantinos P. Tsagarakis,Andreas N. Angelakis
Water , 2012, DOI: 10.3390/w4010260
Abstract: The objective of this study was to investigate the application of constructed wetlands as a mean to manage olive mill wastewater (OMW). Two free water surface (FWS) constructed wetlands, one without (CW1) and one with effluent recirculation (CW2), were operated for a two-year period with diluted OMW (1:10) and evaluated in terms of the removal of COD, TSS, TKN, NH4+-N, NO3?-N, TP and total phenols. The organic loading rate of CWs was adjusted to 925 kg BOD/ha·d. In CW1 the removal efficiency averaged 80%, 83%, 78%, 80%, and 74% for COD, TSS, TKN, TP, and total phenols, respectively, during the operation period. Effluent recirculation further improved the treatment efficiency which approached 90%, 98%, 87%, 85%, and 87% for COD, TSS, TKN, TP, and total phenols, respectively. Constructed wetlands also showed high removal efficiency for NH4+-N. Nitrate concentration maintained low in both CWs basins, probably due to the prevalence of high denitrification rates that efficiently removed the NO3--N produced by NH4+-N oxidation. Despite the increased removal percentages, pollutant concentration in effluent exceeded the allowable limits for discharge in water bodies, suggesting that additional practices, including enhanced pre-application treatment and/or higher dilution rates, are required to make this practice effective for OMW management.
Beta-Thalassemia Major and Female Fertility: The Role of Iron and Iron-Induced Oxidative Stress
Paraskevi Roussou,Nikolaos J. Tsagarakis,Dimitrios Kountouras,Sarantis Livadas,Evanthia Diamanti-Kandarakis
Anemia , 2013, DOI: 10.1155/2013/617204
Abstract: Endocrine complications due to haemosiderosis are present in a significant number of patients with beta-thalassemia major (BTM) worldwide and often become barriers in their desire for parenthood. Thus, although spontaneous fertility can occur, the majority of females with BTM is infertile due to hypogonadotropic hypogonadism (HH) and need assisted reproductive techniques. Infertility in these women seems to be attributed to iron deposition and iron-induced oxidative stress (OS) in various endocrine organs, such as hypothalamus, pituitary, and female reproductive system, but also through the iron effect on other organs, such as liver and pancreas, contributing to the impaired metabolism of hormones and serum antioxidants. Nevertheless, the gonadal function of these patients is usually intact and fertility is usually retrievable. Meanwhile, a significant prooxidants/antioxidants imbalance with subsequent increased (OS) exists in patients with BTM, which is mainly caused by tissue injury due to overproduction of free radicals by secondary iron overload, but also due to alteration in serum trace elements and antioxidant enzymes. Not only using the appropriate antioxidants, essential trace elements, and minerals, but also regulating the advanced glycation end products, could probably reduce the extent of oxidative damage and related complications and retrieve BTM women’s infertility. 1. Introduction In beta-thalassemia major (BTM), iron overload is the joint outcome of multiple blood transfusions and an inappropriately increased iron absorption associated with ineffective erythropoiesis [1]. The outpouring of catabolic iron that exceeds the iron-carrying capacity of transferrin results in the emergence of nontransferrin-bound iron (NTBI), which catalyzes the formation of free radicals, resulting in oxidative stress (OS) and damage to mitochondria, lysosomes, lipid membranes, proteins, and DNA [1]. Thus, thalassemics are in a state of enhanced OS [2]. Meanwhile, recent advances in the management of BTM have significantly improved life expectancy and quality of life of BTM patients, with a consequent increase in their reproductive potential and desire to have children [3]. However, endocrine complications due to haemosiderosis are still present in a significant number of patients worldwide and often become a barrier in their desire for parenthood [4]. Female patients with BTM usually suffer from hypogonadotropic hypogonadism (HH) associated with amenorrhea, anovulation, and infertility, attributed to the iron effect on the pituitary gland as well as on the
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