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Search Results: 1 - 10 of 190014 matches for " G. Christodoulou "
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BrainNetVis: An Open-Access Tool to Effectively Quantify and Visualize Brain Networks
Eleni G. Christodoulou,Vangelis Sakkalis,Vassilis Tsiaras,Ioannis G. Tollis
Computational Intelligence and Neuroscience , 2011, DOI: 10.1155/2011/747290
Abstract: This paper presents BrainNetVis, a tool which serves brain network modelling and visualization, by providing both quantitative and qualitative network measures of brain interconnectivity. It emphasizes the needs that led to the creation of this tool by presenting similar works in the field and by describing how our tool contributes to the existing scenery. It also describes the methods used for the calculation of the graph metrics (global network metrics and vertex metrics), which carry the brain network information. To make the methods clear and understandable, we use an exemplar dataset throughout the paper, on which the calculations and the visualizations are performed. This dataset consists of an alcoholic and a control group of subjects. 1. Introduction One of the major issues in neuroscience is to describe how different brain areas communicate with each other during perception, cognition, and action as well as during spontaneous activity in the default or resting state. Mainly two different approaches for capturing and localizing brain activity motifs have been proposed; univariate spectrum based analysis and functional connectivity analysis [1]. Friston [2] defined functional connectivity as the statistical dependence between the activations of distinct and often well-separated neuronal populations. Network models and graph theory provide a common framework for describing brain functional connectivity [3–5]. The interdependence between brain areas is estimated using multivariate neurophysiological signals (EEG, MEG, ECoG) and/or haemodynamic response images (fMRI). Then, a network is formed by corresponding either brain areas or channels to vertices and by considering an edge between two vertices if and only if the estimated interdependence is above a threshold. Regarding threshold selection, it is important to notice that it is a rather tricky part and there is currently no established way of favouring a specific threshold value. In practice, a broad range of threshold values is used to characterize the network. However, the authors propose two alternative approaches in selecting a threshold value based either on group statistics between specific graph-theoretic measures of the populations under analysis [6] or utilizing a signal-based technique of selecting the optimal visualization threshold using surrogate (artificially generated ensemble of data aiming at revealing the most significantly coupled brain regions) datasets to correctly identify the most significant correlation patterns [7]. The next step in the analysis, after edge
Dynamic Mechanical Properties of Tissue after Long-Term Implantation of Collagen and Polypropylene Meshes in Animal Models  [PDF]
Michail G. Christodoulou, Apostolos Papalois, Dionysios Mouzakis, Stefanos Zaoutsos, Theodoros Kouranos, Miltiadis Seferlis, Charilaos Katsifotis, Angelos Liapis
Open Journal of Urology (OJU) , 2013, DOI: 10.4236/oju.2013.33029

Purpose: Pelvic floor reconstructive surgery has grown significantly in recent years. A wide variety of available types of meshes exist but the safety and success has not been adequately proven. We sought to evaluate the effects on dynamic biomechanical properties of tissue after long-term implantation of synthetic and biological grafts. Methods: A total of 96 New Zealand white female rabbits (approximately 3 kg) were used, 72 of which were surgically implanted with acellular, collagen mesh (n = 36) or nonabsorbable monofilament polypropylene mesh (n = 36). There was a no mesh-rupture of fascia group (n = 12) and a second, no-mesh, no-fascia rupture control group (n = 12). In the 59 rabbits, of 72 (13 died) tissue was harvested 3 months (n = 24), 6 months (n = 23) and 9 months (n = 12) later, while in the fascia rupture group, tissue was harvested 6 months later. Tissue samples (2 × 2 cm) underwent dynamic mechanical analysis (DMA) testing during which the dynamic rigidity and tissue damping capacities were measured. The statistical analysis was performed with General Linear Model with Tukeys post hoc testing (sPss v.17.0). Results: With respect to mesh type, the rabbit tissue in which polypropylene mesh was used showed the greatest dynamic rigidity. Those with biological mesh delivered the lowest rigidity results, while the two other groups had almost similar behavior. The meshes exhibited their highest relative

Isolated Crohn’s disease of the vermiform appendix or chronic granulomatous appendicis?
Tsianos E.,Katsanos K.,Mpaltayiannis G.,Christodoulou D.
Annals of Gastroenterology , 2007,
Abstract: SUMMARY The etiology of granulomatous appendicitis includes infectious diseases, foreign bodies and diseases of unknown etiology such as Crohn s disease and sarcoidosis. Pain in the right lower guardant is a common symptom of intestinal Crohn s disease but, pain in this area can also be the presenting symptom of acute appendicitis. Crohn s disease affects any part of the gastrointestinal tract including the vermiform appendix. Crohn s disease initially confined to the appendix is rare and there are less than 100 well-documented cases in the literature. A 28-years-old female patient was admitted to our hospital because of fever up to 39oC and abdominal pain in the right lower quadrant with bloating. Serology and faecal, urine and blood cultures for microbial infection including Yersinia proved negaive. Lower abdomen ultrasonography revealed no evidence of adnexae inflammation but suspected thickness of the bowel wall in the right lower quadrant. Because of no response to conservative treatment two months later surgery was performed. At laparotomy a long, thickened and distended appendix was found and removed. No other lesions were noted in the intestines or mesentery. Histological examination of the removed appendix showed signs compatible with Crohn s disease of the appendix. In case of Crohn s disease of the appendix two clinical possibilities may arise; the first is the presence of mild Crohn s disease in other intestinal parts and the second possibility is the risk of relapse which occurred in 7-14% of the published cases. Could this case be regarded as an isolated Crohn s disease of the appendix or as a granulomatous and follicular appendicitis of unknown etiology (idiopathic) and unrelated to a formal Crohn s disease according to the accepted definition. Key words: Crohn s disease, appendix, granuloma, appendicitis
Endoscopic resection of colonic polyps – A review
D. Christodoulou,G. Kandel,E.V. Tsianos,N. Marcon
Annals of Gastroenterology , 2007,
Abstract: Endoscopic polypectomy has become standard care for the treatment of colonic polyps. While about 90% of polyps are small in size and easy to resect, a small percentage of polyps are of large size (>2 cm) and broad base and endoscopic resection is a real challenge for the endoscopist. An appropriate technique for safe removal of these large colorectal polyps has been developed and includes submucosal injection of large amounts of normal saline with diluted epinephrine and piecemeal resection. We address the importance of adding a few drops of methylene blue in the submucosally injected fluid to enhance the margins of the lesion and increase the accuracy of resection. The success rate of polypectomy of large polyps is more than 90%, while up to 10% of patients may finally require surgical treatment due to malignancy or incomplete resection. Small pieces of the polyp that remain unresected at the margins during polypectomy can be destroyed by argon plasma coagulator. Immediate bleeding after polypectomy can usually be successfully treated with diluted epinephrine injection and placement of hemoclips or loops, while delayed bleeding is rare (1%). Perforation of the bowel using this technique is very rare (0.3%). In addition, all modern and new techniques for the resection of colorectal polyps are described. Colonoscopic polypectomy is considered among the high-risk procedures to induce significant bleeding, so, prior to polypectomy, adjustment in anticoagulation is necessary. For patients with high-risk conditions for a thromboembolic event, warfarin therapy should be discontinued 3 to 5 days before the procedure. The decision to administer heparin once INR falls below the therapeutic levels should be individualized For elective high-risk procedures, temporary discontinuation of newer antiplatelet medications (such as clopidogrel), particularly if the patient is on concomitant aspirin, is desirable, preferably for 7-10 days. In the absence of a pre-existing bleeding disorder, endoscopic procedures including polypectomy may be performed in patients taking aspirin and other NSAIDS in standard doses Antibiotic prophylaxis in patients undergoing polypectomy should be limited to patients with a prosthetic valve, history of endocarditis, presence of systemic-pulmonary shunt or a synthetic vascular graft less than 1 year old.
Prolonged benign intrahepatic cholestatic syndrome due to administration of fucidic acid with ticarcillin-clavulanic acid
. Katsanos K.H.,. Christodoulou D.,Tzambouras N.,Mpaltayiannis G.
Annals of Gastroenterology , 2007,
Abstract: We present the case of a 64-years-old man who was admitted because of 15 days jaundice, white stools, coloured urine, weakness and upper abdominal pain. He had a history of Billroth II operation 35 years ago and before 1 month he was admitted in the Department of Opthalmology because of a trauma in his eye. The laboratory exams revealed mixed hyperbilirubinemia with transaminasemia and elevation of GT and alkaline phosphatase. Because the imagine techniques including ERCP were implying the possibility of a bile duct malignancy a laparotomy was performed which proved negative for malignancy. The Liver biopsy revealed a cholestatic protype with no findings for neoplasia, cirrhosis or other kind of inflammation and the final diagnosis was prolonged delated benign intrahepatic cholestatic syndrome due to the possible synergic action of fucidic acid with ticarcillin-clavulanic acid. These drugs were administered 1 month before during his admission at he Department of Ophthalmology. The biochemical profile became normal 2 months later and the patient lives in excellent health. Key words: jaundice, bilirubin, cholestasis, fucidic acid, ticarcillin-clavulanic acid
Revisiting the Dynamical Case for a Massive Black Hole in IC10 X-1
Silas G. T. Laycock,Thomas J. Maccarone,Dimitris M. Christodoulou
Physics , 2015, DOI: 10.1093/mnrasl/slv082
Abstract: The relative phasing of the X-ray eclipse ephemeris and optical radial velocity (RV) curve for the X-ray binary IC10 X-1 suggests the He[$\lambda$4686] emission-line originates in a shadowed sector of the stellar wind that avoids ionization by X-rays from the compact object. The line attains maximum blueshift when the wind is directly toward us at mid X-ray eclipse, as is also seen in Cygnus X-3. If the RV curve is unrelated to stellar motion, evidence for a massive black hole evaporates because the mass function of the binary is unknown. The reported X-ray luminosity, spectrum, slow QPO, and broad eclipses caused by absorption/scattering in the WR wind are all consistent with either a low-stellar-mass BH or a NS. For a NS, the centre of mass lies inside the WR envelope whose motion is then far below the observed 370 km/s RV amplitude, while the velocity of the compact object is as high as 600 km/s. The resulting 0.4\% doppler variation of X-ray spectral lines could be confirmed by missions in development. These arguments also apply to other putative BH binaries whose RV and eclipse curves are not yet phase-connected. Theories of BH formation and predicted rates of gravitational wave sources may need revision.
The Magnetic Field of the Ultraluminous X-ray Pulsar M82 X-2
Dimitris M. Christodoulou,Silas G. T. Laycock,Demosthenes Kazanas
Physics , 2014,
Abstract: Pulsations were recently detected from the ultraluminous X-ray source X-2 in M82. The newly discovered pulsar has been described as a common neutron star with a 1 TG magnetic field that accretes above the Eddington rate and as a magnetar-like pulsar with a 100 TG magnetic field that is above the quantum limit. We show here that this X-ray source is not exotic in any sense. The standard equations of accretion along field lines predict that, for the measured spin period $P_S$ and spinup rate $\dot{P_S}$, the isotropic X-ray luminosity $L_X$ must be near the Eddington limit (i.e., $L_{X}\approx 3.5\times 10^{38}$~erg~s$^{-1}$); and that the surface magnetic field $B$, that does not depend on $P_S$, must be modest (i.e., $B_*\approx 1-10$ TG). The observed higher luminosity can be explained by a moderate amount of geometric beaming that occurs in our direction. Other ultraluminous X-ray sources may also turn out to be common pulsars with similar physical characteristics, but since the emission must occur at a favorable angle to the observer, we expect that very few such pulsars will be discovered in the future.
Olanzapine-associated neuroleptic malignant syndrome: Is there an overlap with the serotonin syndrome?
Vassilis P Kontaxakis, Beata J Havaki-kontaxaki, Nikolaos G Christodoulou, Konstantinos G Paplos, George N Christodoulou
Annals of General Psychiatry , 2003, DOI: 10.1186/1475-2832-2-10
Abstract: This retrospective phenomenological study aims to examine the seventeen reported olanzapine – induced neuroleptic malignant syndrome cases under the light of possible overlap between neuroleptic malignant syndrome and serotonin syndrome clinical features.The serotonin syndrome clinical features most often reported in cases initially diagnosed as neuroleptic malignant syndrome are: fever (82%), mental status changes (82%) and diaphoresis (47%). Three out of the ten classical serotonin syndrome clinical features were concurrently observed in eleven (65%) patients and four clinical features were observed in seven (41%) patients.The results of this study show that the clinical symptoms of olanzapine-induced neuroleptic malignant syndrome and serotonin syndrome are overlapping suggesting similarities in underlying pathophysiological mechanisms.The neuroleptic malignant syndrome (NMS) is a rare but potentially fatal condition associated with antipsychotic medication. It is mainly characterized by fever, extrapyramidal symptoms, autonomic instability and an altered state of consciousness. It is primarily caused by dopamine (D2) receptors blockage in the nigrostriatal tract, mesocortical pathway and hypothalamic nuclei [1]. Recently, many authors have expressed the view that NMS is not caused by dopamine block alone. Other aminergic systems have also been implicated such as serotonin, norepinephrine, GABA e.t.c. [1,2]. There are controversies as to whether atypical antipsychotics can cause "classical" forms of NMS [3-5].During the last years, a condition of serotoninergic hyperstimulation called "serotonin syndrome" (SS) has been described. It is mainly associated with administration of antidepressive medication. The most frequent clinical features of this syndrome are changes in mental status, restlessness, myoclonus and hyperreflexia [6].The difficulty of differentiating between NMS and SS has been well recognized [7,8].Olanzapine is an atypical antipsychotic, which exhib
Reliability and validity of the adapted Greek version of scoliosis research society – 22 (SRS-22) questionnaire
Petros D Antonarakos, Labrini Katranitsa, Lefteris Angelis, Aristofanis Paganas, Errikos M Koen, Evangelos A Christodoulou, Anastasios G Christodoulou
Scoliosis , 2009, DOI: 10.1186/1748-7161-4-14
Abstract: Following the steps of cross – cultural adaptation the adapted Greek version of the SRS-22 questionnaire and a validated Greek version of the SF-36 questionnaire were mailed to 68 patients treated surgically for Idiopathic Scoliosis. 51 out of the 68 patients returned the 1st set of questionnaires, while a second set was emailed to 30 randomly selected patients of the first time responders. 20 out of the 30 patients returned the 2nd set. The mean age at the time of operation was16,2 years and the mean age at the time of evaluation was 21,2 years. Descriptive statistics for content analysis were calculated. Reliability assessment was determined by estimating Cronbach's α and intraclass correlation coefficient (ICC) respectively. Concurrent validity was evaluated by comparing SRS-22 domains with relevant domains in the SF-36 questionnaire using Pearson's Correlation Coefficient (r).The calculated Cronbach's α of internal consistency for three of the corresponding domains (pain 0.85; mental health 0.87; self image 0.83) were very satisfactory and for two domains (function/activity 0.72 and satisfaction 0.67) were good. The ICC of all domains of SRS-22 questionnaire was high (ICC>0.70), demonstrating very satisfactory or excellent test/retest reproducibility. Considering concurrent validity all correlations were found to be statistically significant at the 0.01 level among related domains and generally demonstrated high correlation coefficient.The adapted Greek version of the SRS-22 questionnaire is valid and reliable and can be used for the assessment of the outcome of the treatment of the Greek speaking patients with idiopathic scoliosis.There is a strong interest of treating physicians in appropriate and valid measures that allow them to evaluate health-related quality of life (HRQL) outcomes associated with their treatments and to establish the efficacy, or lack thereof, of their interventions [1,2]. Idiopathic scoliosis is a type of deformity that usually does not
The Case against Dark Matter and Modified Gravity: Flat Rotation Curves Are a Rigorous Requirement in Rotating Self-Gravitating Newtonian Gaseous Discs  [PDF]
Dimitris M. Christodoulou, Demosthenes Kazanas
Journal of Modern Physics (JMP) , 2016, DOI: 10.4236/jmp.2016.77067
Abstract: By solving analytically the various types of Lane-Emden equations with rotation, we have discovered two new coupled fundamental properties of rotating, self-gravitating, gaseous discs in equilibrium: isothermal discs must, on average, exhibit strict power-law density profiles in radius x on their equatorial planes of the form \"\" , where A and k-1 are the integration constants; and “flat” rotation curves precisely such as those observed in spiral galaxy discs. Polytropic discs must, on average, exhibit strict density profiles of the form \"\" , where n is the polytropic index; and “flat” rotation curves described by square roots of upper incomplete gamma functions. By “on average”, we mean that, irrespective of the chosen boundary conditions, the actual profiles must oscillate around and remain close to the strict mean profiles of the analytic singular equilibrium solutions. We call such singular solutions the “intrinsic” solutions of the differential equations because they are demanded by the second-order equations themselves with no regard to the Cauchy problem. The results are directly applicable to gaseous galaxy discs that have long been known to be isothermal and to protoplanetary discs during the extended isothermal and adiabatic phases of their evolution. In galactic gas dynamics, they have the potential to resolve the dark matter—modified gravity controversy in a sweeping manner, as they render both of these hypotheses unnecessary. In protoplanetary disc research, they provide observers with a powerful new probing tool, as they predict a clear and simple connection between the radial density profiles and the rotation curves of self-gravitating discs in their very early (pre-Class 0) phases of evolution.
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