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Search Results: 1 - 10 of 39 matches for " Vana Sypsa "
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Assessing the impact of biomedical research in academic institutions of disparate sizes
Vana Sypsa, Angelos Hatzakis
BMC Medical Research Methodology , 2009, DOI: 10.1186/1471-2288-9-33
Abstract: The Modified Impact Index (MII) was defined as the ratio of the observed h-index (h) of an institution over the h-index anticipated for that institution on average, given the number of publications (N) it produces i.e. (α and β denote the intercept and the slope, respectively, of the line describing the dependence of the h-index on the number of publications in log10 scale). MII values higher than 1 indicate that an institution performs better than the average, in terms of its h-index. Data on scientific papers published during 2002–2006 and within 36 medical fields for 219 Academic Medical Institutions from 16 European countries were used to estimate α and β and to calculate the MII of their total and field-specific production.From our biomedical research data, the slope β governing the dependence of h-index on the number of publications in biomedical research was found to be similar to that estimated in other disciplines (≈0.4). The MII was positively associated with the average number of citations/publication (r = 0.653, p < 0.001), the h-index (r = 0.213, p = 0.002), the number of publications with ≥ 100 citations (r = 0.211, p = 0.004) but not with the number of publications (r = -0.020, p = 0.765). It was the most highly associated indicator with the share of country-specific government budget appropriations or outlays for research and development as % of GDP in 2004 (r = 0.229) followed by the average number of citations/publication (r = 0.153) whereas the corresponding correlation coefficient for the h-index was close to 0 (r = 0.029). MII was calculated for first 10 top-ranked European universities in life sciences and biomedicine, as provided by Times Higher Education ranking system, and their total and field-specific performance was compared.The MII should complement the use of h-index when comparing the research output of institutions of disparate sizes. It has a conceptual interpretation and, with the data provided here, can be computed for the total re
Transmission Dynamics of Carbapenemase-Producing Klebsiella Pneumoniae and Anticipated Impact of Infection Control Strategies in a Surgical Unit
Vana Sypsa,Mina Psichogiou,Georgia-Aikaterina Bouzala,Linos Hadjihannas,Angelos Hatzakis,Georgios L. Daikos
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0041068
Abstract: Carbapenemase-producing Klebsiella pneumoniae (CPKP) has been established as important nosocomial pathogen in many geographic regions. Transmission from patient to patient via the hands of healthcare workers is the main route of spread in the acute-care setting.
Estimating the Disease Burden of 2009 Pandemic Influenza A(H1N1) from Surveillance and Household Surveys in Greece
Vana Sypsa,Stefanos Bonovas,Sotirios Tsiodras,Agoritsa Baka,Panos Efstathiou,Meni Malliori,Takis Panagiotopoulos,Ilias Nikolakopoulos,Angelos Hatzakis
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0020593
Abstract: The aim of this study was to assess the disease burden of the 2009 pandemic influenza A(H1N1) in Greece.
Development of a new ultra sensitive real-time PCR assay (ultra sensitive RTQ-PCR) for the quantification of HBV-DNA
Dimitrios Paraskevis, Apostolos Beloukas, Catherine Haida, Antigoni Katsoulidou, Zisis Moschidis, Helen Hatzitheodorou, Agoritsa Varaklioti, Vana Sypsa, Angelos Hatzakis
Virology Journal , 2010, DOI: 10.1186/1743-422x-7-57
Abstract: Previously used HBV-DNA standards were calibrated against the WHO 1st International Standard for HBV-DNA (OptiQuant? HBV-DNA Quantification Panel, Accrometrix Europe B.V.). The 95% and 50% HBV-DNA detection end-point of the assay were 22.2 and 8.4 IU/mL. According to the calibration results, 1 IU/mL equals 2.8 copies/mL. Importantly the clinical performance of the ultra sensitive real-time PCR was tested similar (67%) to the Procleix Ultrio discriminatory HBV test (dHBV) (70%) in low-titer samples from patients with occult Hepatitis B. Finally, in the comparison of ultra sensitive RTQ-PCR with the commercially available COBAS TaqMan HBV Test, the in-house assay identified 94.7% of the 94 specimens as positive versus 90.4% identified by TaqMan, while the quantitative results that were positive by both assay were strongly correlated (r = 0.979).We report a new ultra sensitive real time PCR molecular beacon based assay with remarkable analytical and clinical sensitivity, calibrated against the WHO 1st International standard.Chronic hepatitis B virus (HBV) infection can be assessed by evaluating clinical features and biochemical, virologic, and histologic parameters. Knowledge of HBV-DNA viral load is useful for predicting disease prognosis, determining infectivity, evaluating indications for treatment, assessing response to treatment identifying emergence of resistance, and diagnosing occult HBV infection [1-5].There are several commercially available HBV-DNA tests. The oldest versions suffered from poor sensitivity (approximately 5·105 copies/mL) and a narrow dynamic range of HBV-DNA quantification (~3-4 log10), while the current limit of detection of the newer assays is lower than 50 IU/mL with a dynamic range of approximately 8 log10 [6-13]. Additionally several in-house quantitative assays for HBV-DNA have been developed, based mostly on real-time PCR methodology, showing a remarkable sensitivity and a wide linear range for quantification [6,7,11-14].Importantly, i
Comparative evaluation of the performance of the Abbott RealTime HIV-1 assay for measurement of HIV-1 plasma viral load on genetically diverse samples from Greece
Antigoni Katsoulidou, Chrysoula Rokka, Catherine Issaris, Catherine Haida, Kimon Tzannis, Vana Sypsa, Maria Detsika, Dimitrios Paraskevis, Angelos Hatzakis
Virology Journal , 2011, DOI: 10.1186/1743-422x-8-10
Abstract: In this study, the Abbott RealTime HIV-1 (Abbott RealTime) assay was compared to the Roche Cobas TaqMan HIV-1 (Cobas TaqMan) and the Siemens Versant HIV-1 RNA 3.0 (bDNA 3.0) assays, using clinical samples of various viral load levels and subtypes from Greece, where the recent epidemiology of HIV-1 infection has been characterized by increasing genetic diversity and a marked increase in subtype A genetic strains among newly diagnosed infections.A high correlation was observed between the quantitative results obtained by the Abbott RealTime and the Cobas TaqMan assays. Viral load values quantified by the Abbott RealTime were on average lower than those obtained by the Cobas TaqMan, with a mean (SD) difference of -0.206 (0.298) log10 copies/ml. The mean differences according to HIV-1 subtypes between the two techniques for samples of subtype A, B, and non-A/non-B were 0.089, -0.262, and -0.298 log10 copies/ml, respectively. Overall, differences were less than 0.5 log10 for 85% of the samples, and >1 log10 in only one subtype B sample. Similarly, Abbott RealTime and bDNA 3.0 assays yielded a very good correlation of quantitative results, whereas viral load values assessed by the Abbott RealTime were on average higher (mean (SD) difference: 0.160 (0.287) log10 copies/ml). The mean differences according to HIV-1 subtypes between the two techniques for subtype A, B and non-A/non-B samples were 0.438, 0.105 and 0.191 log10 copies/ml, respectively. Overall, the majority of samples (86%) differed by less than 0.5 log10, while none of the samples showed a deviation of more than 1.0 log10.In an area of changing HIV-1 subtype pattern, the Abbott RealTime assay showed a high correlation and good agreement of results when compared both to the Cobas TaqMan and bDNA 3.0 assays, for all HIV-1 subtypes tested. All three assays could determine viral load from samples of different HIV-1 subtypes adequately. However, assay variation should be taken into account when viral load monitoring
Integrating Phylodynamics and Epidemiology to Estimate Transmission Diversity in Viral Epidemics
Gkikas Magiorkinis ,Vana Sypsa,Emmanouil Magiorkinis,Dimitrios Paraskevis,Antigoni Katsoulidou,Robert Belshaw,Christophe Fraser,Oliver George Pybus,Angelos Hatzakis
PLOS Computational Biology , 2013, DOI: 10.1371/journal.pcbi.1002876
Abstract: The epidemiology of chronic viral infections, such as those caused by Hepatitis C Virus (HCV) and Human Immunodeficiency Virus (HIV), is affected by the risk group structure of the infected population. Risk groups are defined by each of their members having acquired infection through a specific behavior. However, risk group definitions say little about the transmission potential of each infected individual. Variation in the number of secondary infections is extremely difficult to estimate for HCV and HIV but crucial in the design of efficient control interventions. Here we describe a novel method that combines epidemiological and population genetic approaches to estimate the variation in transmissibility of rapidly-evolving viral epidemics. We evaluate this method using a nationwide HCV epidemic and for the first time co-estimate viral generation times and superspreading events from a combination of molecular and epidemiological data. We anticipate that this integrated approach will form the basis of powerful tools for describing the transmission dynamics of chronic viral diseases, and for evaluating control strategies directed against them.
Early hCG addition to rFSH for ovarian stimulation in IVF provides better results and the cDNA copies of the hCG receptor may be an indicator of successful stimulation
Peter Drakakis, Dimitris Loutradis, Apostolos Beloukas, Vana Sypsa, Vasiliki Anastasiadou, George Kalofolias, Helen Arabatzi, Erasmia Kiapekou, Konstantinos Stefanidis, Dimitris Paraskevis, Antonis Makrigiannakis, Angelos Hatzakis, Aris Antsaklis
Reproductive Biology and Endocrinology , 2009, DOI: 10.1186/1477-7827-7-110
Abstract: The achievement of a simple, safe and cost-effective treatment protocol in controlled ovarian hyperstimulation (COH) is of paramount importance to improve the quality of care in assisted reproduction. It is particularly important in the case of previous unsuccessful attempts. The midcycle gonadotrophin surge is a major event in the dynamics of ovulation. Rapidly increasing levels of luteinising hormone (LH) induce a number of key changes in both oocytes and follicular cells, which further modify the steroid and protein micro- and macroenvironment. These physiologic changes have a prominent role in the normal maturation of oocytes, the process of ovulation, and in subsequent fertilization and implantation [1].Human chorionic gonadotrophin (hCG) has been used as a substitute for the LH surge because of the degree of homology between the two hormones [2]. hCG has a slower plasma metabolic clearance, which consists of a rapid phase in the first 5-9 h following intramuscular (IM) administration and a slower phase in the first 1-1.3 days after administration. Both LH and hCG are complex heterodimeric glycoproteins with a molecular weight of ~30 K for recombinant human LH (rLH) and 40 K for hCG. Their carbohydrate molecule is, though, different, thus leading possibly to a different affinity to the LH/hCG receptor and therefore to a differentiated function between LH and hCG. These two hormones have identical α-subunits and a high cysteine content. Most importantly, they have the same natural function--to cause ovulation and support lutein cells. The major differences between the two hormones include the sequence of the β-subunit, the regulation of the secretion of the two hormones, the carbohydrate component and the pharmacokinetics of clearance of hCG as opposed to LH [3,4].The LH/hCG receptor has an almost ubiquitous distribution in reproductive organs, thus suggesting that the actions of hCG might be more extensive than previously thought. Independently of follicular st
Economic Recession and Emergence of an HIV-1 Outbreak among Drug Injectors in Athens Metropolitan Area: A Longitudinal Study
Dimitrios Paraskevis, Georgios Nikolopoulos, Anastasios Fotiou, Chrissa Tsiara, Dimitra Paraskeva, Vana Sypsa, Marios Lazanas, Panagiotis Gargalianos, Mina Psichogiou, Athanasios Skoutelis, Lucas Wiessing, Samuel R. Friedman, Don C. d. e. s. Jarlais, Manina Terzidou, Jenny Kremastinou, Meni Malliori, Angelos Hatzakis
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0078941
Abstract: Background During 2011, a dramatic increase (1600%) of reported HIV-1 infections among injecting drug users (IDUs) was noted in Athens, Greece. We herein assess the potential causal pathways associated with this outbreak. Methods Our study employed high resolution HIV-1 phylogenetic and phylogeographic analyses. We examined also longitudinal data of ecological variables such as the annual growth of gross domestic product (GDP) of Greece in association with HIV-1 and HCV sentinel prevalence in IDUs, unemployment and homelessness rates and HIV transmission networks in Athens IDUs before and during economic recession (2008–2012). Results IDU isolates sampled in 2011 and 2012 suggested transmission networks in 94.6% and 92.7% of the cases in striking contrast with the sporadic networking (5%) during 1998–2009. The geographic origin of most HIV-1 isolates was consistent with the recently documented migratory waves in Greece. The decline in GDP was inversely correlated with annual prevalence rates of HIV and HCV and with unemployment and homelessness rates in IDUs (all p<0.001). The slope of anti-HCV prevalence in the sentinel populations of IDUs and in “new” drug injectors was found 120 and 1.9-fold (p = 0.007, p = 0.08 respectively) higher in 2008–2012 (economic recession) compared with 2002–2006. The median (25th, 75th) size of transmission networks were 34 (12, 58) and 2 (2, 2) (p = 0.057) in 2008–2012 and 1998–2007, respectively. The coverage of harm reduction services was low throughout the study period. Conclusions Scaling-up harm reduction services and addressing social and structural factors related to the current economic crisis should be urgently considered in environments where HIV-1 outbreaks may occur.
The Thom Class and Localization of SUSY QM Generating Functional
O. Vana
Physics , 2001,
Abstract: We demonstrate the usage of explicit form of the Thom class found by Mathai and Quillen for the definition of generating functional of a simple supersymmetric quantum mechanical model.
Multiblock Copolymers of Styrene and Butyl Acrylate via Polytrithiocarbonate-Mediated RAFT Polymerization
Bastian Ebeling,Philipp Vana
Polymers , 2011, DOI: 10.3390/polym3020719
Abstract: When linear polytrithiocarbonates as Reversible Addition-Fragmentation chain Transfer (RAFT) agents are employed in a radical polymerization, the resulting macromolecules consist of several homogeneous polymer blocks, interconnected by the functional groups of the respective RAFT agent. Via a second polymerization with another monomer, multiblock copolymers—polymers with alternating segments of both monomers—can be prepared. This strategy was examined mechanistically in detail based on subsequent RAFT polymerizations of styrene and butyl acrylate. Size-exclusion chromatography (SEC) of these polymers showed that the examined method yields low-disperse products. In some cases, resolved peaks for molecules with different numbers of blocks (polymer chains separated by the trithiocarbonate groups) could be observed. Cleavage of the polymers at the trithiocarbonate groups and SEC analysis of the products showed that the blocks in the middle of the polymers are longer than those at the ends and that the number of blocks corresponds to the number of functional groups in the initial RAFT agent. Furthermore, the produced multiblock copolymers were analyzed via differential scanning calorimetry (DSC). This work underlines that the examined methodology is very well suited for the synthesis of well-defined multiblock copolymers.
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