On the beneficial effect of noise in vertex localization

A theoretical and experimental analysis related to the effect of noise in the task of vertex identication in unknown shapes is presented. Shapes are seen as real functions of their closed boundary. An alternative global perspective of curvature is examined providing insight into the process of noise- enabled vertex localization. The analysis reveals that noise facilitates in the localization of certain vertices. The concept of noising is thus considered and a relevant global method for localizing Global Vertices is investigated in relation to local methods under the presence of increasing noise. Theoretical analysis reveals that induced noise can indeed help localizing certain vertices if combined with global descriptors. Experiments with noise and a comparison to localized methods validate the theoretical results

Shape Representation, Indexing and Retrieval of Images

Η Διατριβή επικεντρώνεται σε θέματα αναπαράστασης, κωδικοποίησης, ταξινόμησης και ανάκτησης της οπτικής πληροφορίας είτε αυτή είναι σε μορφή σχήματος είτε σε μορφή εικόνας με μία προσέγγιση που είναι συμβατή με βιολογικά αλλά και λειτουργικά δεδομένα σε σχέση με την ανθρώπινη αντίληψη. Στην περίπτωση της αναπαράστασης και κωδικοποίησης σχημάτων εισάγονται έννοιες βιολογικής αλλά και αντιληπτικής συμβατότητας. Στην περίπτωση των εικόνων εισάγονται έννοιες γνωσιακής συμβατότητας που χρησιμοποιούνται για τον σκοπό της καλύτερης ταξινόμησης και ανάκτησης εικόνων.The dissertation is focused on issues of representation, classification, indexing and retrieval of visual information either in the form of shape or in the form of image in an approach that is compatible to biological but also functional data concerning human perception. In the case of shape representation and image classification, concepts of biological as well as perceptual compatibility to the human perceptual system are introduced. In the case of indexing and classification of images, concepts of adaptive knowledge representation through dynamic human interaction are introduced and implemented for better annotation based image retrieval.Κωνσταντίνος Α. Ραυτόπουλο

Infection probability score, APACHE II and KARNOFSKY scoring systems as predictors of bloodstream infection onset in hematology-oncology patients

Background: Bloodstream Infections (BSIs) in neutropenic patients often cause considerable morbidity and mortality. Therefore, the surveillance and early identification of patients at high risk for developing BSIs might be useful for the development of preventive measures. The aim of the current study was to assess the predictive power of three scoring systems: Infection Probability Score (IPS), APACHE II and KARNOFSKY score for the onset of Bloodstream Infections in hematology-oncology patients.Methods: A total of 102 patients who were hospitalized for more than 48 hours in a hematology-oncology department in Athens, Greece between April 1stand October 31st2007 were included in the study. Data were collected by using an anonymous standardized recording form. Source materials included medical records, temperature charts, information from nursing and medical staff, and results on microbiological testing. Patients were followed daily until hospital discharge or death.Results: Among the 102 patients, Bloodstream Infections occurred in 17 (16.6%) patients. The incidence density of Bloodstream Infections was 7.74 per 1,000 patient-days or 21.99 per 1,000 patient-days at risk. The patients who developed a Bloodstream Infection were mainly females (p = 0.004), with twofold time mean length of hospital stay (p <, 0.001), with fourfold time mean length of neutropenia (p <, 0.001), with neutropenia <, 500 (p <, 0.001), suffered mainly from acute myeloid leukemia (p <, 0.001), had been exposed to antibiotics (p = 0.045) and chemotherapy (p = 0.023), had a surgery (p = 0.048) and a Hickman catheter (p = 0.025) as compared to the patients without Bloodstream Infection. The best cut-off value of IPS for the prediction of a Bloodstream Infection was 10 with a sensitivity of 75% and specificity of 70.9%. Conclusion: Between the three different prognostic scoring systems, Infection Probability Score had the best sensitivity in predicting Bloodstream Infections. 2010 Apostolopoulou et al, licensee BioMed Central Ltd

Infection probability score : a predictor of clostridium difficile-associated disease onset in patients with haematological malignancy

Purpose: to assess the predictive power of three systems: Infection Probability Score, APACHE II and KARNOFSKY score for the onset of Clostridium difficile-associated disease (CDAD) in hematology-oncology patients. Methods and sample: A retrospective pilot surveillance survey was conducted in the hematology unit of a general hospital in Greece. Data were collected by using an anonymous standardised case-record form. The sample consisted of 102 hospitalized patients. Results: The majority of the patients (33.3%) suffered from acute myeloid leukemia. The cumulative incidence of CDAD was 10.8% and the incidence rate of C difficile associated diarrhea was 5 per 1000 patient-days (14.2 per 1000 patient-days at risk). Patients with CDAD had twofold higher time of mean length of hospital stay compared with patients without CDAD (38.82 ± 23.88 vs 19.45 ± 14.56 days). Additionally patients with CDAD had received a greater number of different antibiotics compared to those without CDAD (5.18 ± 1.99 vs 2.54 ± 2.13), suffered from diabetes, from non Hodgkin's lymphoma, had a statistically significant higher duration of neutropenia ≥3 days and had received antifungal treatment. The best cutoff value of IPS for the prediction of CDAD was 13 with a sensitivity of 45.5% and a specificity of 82.4%. Conclusions: IPS is an early diagnostic test for CDAD detection

PEG-POSS Star Molecules Blended in Polyurethane with Flexible Hard Segments: Morphology and Dynamics

A star polymer with a polyhedral oligomeric silsesquioxanne (POSS) core and poly(ethylene glycol) (PEG) vertex groups is incorporated in a polyurethane with flexible hard segments in-situ during the polymerization process. The blends are studied in terms of morphology, molecular dynamics, and charge mobility. The methods utilized for this purpose are scanning electron and atomic force microscopies (SEM, AFM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and to a larger extent dielectric relaxation spectroscopy (DRS). It is found that POSS reduces the degree of crystallinity of the hard segments. Contrary to what was observed in a similar system with POSS pendent along the main chain, soft phase calorimetric glass transition temperature drops as a result of plasticization, and homogenization of the soft phase by the star molecules. The dynamic glass transition though, remains practically unaffected, and a hypothesis is formed to resolve the discrepancy, based on the assumption of different thermal and dielectric responses of slow and fast modes of the system. A relaxation &alpha;&prime;, slower than the bulky segmental &alpha; and common in polyurethanes, appears here too. A detailed analysis of dielectric spectra provides some evidence that this relaxation has cooperative character. An additional relaxation g, which is not commonly observed, accompanies the Maxwell Wagner Sillars interfacial polarization process, and has dynamics similar to it. POSS is found to introduce conductivity and possibly alter its mechanism. The study points out that different architectures of incorporation of POSS in polyurethane affect its physical properties by different mechanisms

Effects of Segment Length and Crosslinking via POSS on the Calorimetric and Dynamic Glass Transition of Polyurethanes with Aliphatic Hard Segments

The glass transition in polyurethanes is a complicated phenomenon governed by a multitude of factors, including the microphase separation, which in turn depends strongly on the molar mass of the hard and soft segments, as well as the presence of additives. In this work, we study the effects of the segments’ length on the microphase separation and consequently on the calorimetric and dynamic glass transition of a polyurethane with aliphatic, “flexible” hard segments. It is found that the dependence of the calorimetric glass transition follows the same principles as those in systems with aromatic hard segments. Strikingly, however, the dynamic glass transition, as studied by dielectric spectroscopy, shows a slowing down of its dynamics despite a decrease in Tg. This discrepancy is discussed in terms of the strong dielectric response of the flexible segments, especially those close to the interface between the hard domains and soft phase, as opposed to a weak thermal one. In addition, polyhedral oligomeric silsesquioxanes (POSS) are introduced in the soft phase of the three matrices as crosslinking centres. This modification has no visible effect on the calorimetric glass transition; nevertheless, it affects the microphase separation and the dielectric response in a non-monotonic manner

Dual Orthogonal Switching of the “Schizophrenic” Self-Assembly of Diblock Copolymers

Based on diblock copolymers, a pair of “schizo-phrenic” micellar systems is designed by combining a nonionic andthermoresponsive block with a zwitterionic block, which isthermoresponsive and salt-sensitive. The nonionic block ispoly(N-isopropylacrylamide) (PNIPAM) or poly(N-isopropyl-methacrylamide) (PNIPMAM) and exhibits a lower criticalsolution temperature (LCST) behavior in aqueous solution. Thezwitterionic block is a polysulfobetaine, i.e., poly(4-((3-methacryl-amidopropyl)dimethylammonio)butane-1-sulfonate) (PSBP), andhas an upper critical solution temperature (UCST) behavior withthe clearing point decreasing with increasing salt concentration. The PSBP-b-PNIPAM and PSBP-b-PNIPMAM diblockcopolymers are prepared by successive reversible addition−fragmentation chain transfer (RAFT) polymerizations. The PSBPblock is chosen such that the clearing point of the homopolymer is significantly higher in pure water than the cloud point ofPNIPAM or PNIPMAM. Using turbidimetry, 1H NMR, and small-angle neutron scattering, we investigate the overall phasebehavior as well as the structure and interaction between the micelles and the intermediate phase, both in salt-free D2O and in0.004 M NaBr in D2O in a wide temperature range. We find that PSBP-b-PNIPAM at 50 g L−1 in salt-free D2O is turbid in theentire temperature range. It forms spherical micelles below the cloud point of PNIPAM and cylindrical micelles above. Similarbehavior is observed for PSBP-b-PNIPMAM at 50 g L−1 in salt-free D2O with a slight and smooth increase of the lighttransmission below the cloud point of PNIPMAM and an abrupt decrease above. Upon addition of 0.004 M NaBr, the UCST-type cloud point of the PSBP-block is notably decreased, and an intermediate regime is encountered below the cloud point ofPNIPMAM, where the light transmission is slightly enhanced. In this regime, the polymer solution exhibits behavior typical forpolyelectrolyte solutions. Thus, double thermosensitive and salt-sensitive behavior with “schizophrenic” micelle formation isfound, and the width of the intermediate regime, where both blocks are hydrophilic, can be tuned by the addition of electrolyte

pH Responsiveness of hydrogels formed by telechelic polyampholytes

We investigate the influence of pH on the rheological and structural properties of hydrogels formed by hydrophobic association of the sticky ends of the triblock terpolymer poly(methyl methacrylate)-b-poly(2-(diethylamino)ethyl methacrylate-co-methacrylic acid)-b-poly(methyl methacrylate) (PMMA-b-P(DEA-co-MAA)-b-PMMA). The middle block is a weak polyampholyte having a pH dependent charge density and sign, which enables tuning of the rheological and structural properties by pH variation. Small-angle neutron scattering (SANS) studies of solutions in D2O at 0.05 wt% and pH 3.0 reveal clusters of interconnected spherical micelles having PMMA cores, stabilized by repulsive ionic interactions in the middle polyampholyte block. With increasing pH, the degree of ionization of the DEA units decreases, whereas the one of the MAA units increases, resulting in a complete loss of the correlation between these micelles. At a concentration of 3 wt% at low pH values, the system forms a gel with charged fuzzy spheres from PMMA interacting via a screened Coulomb potential. With increasing pH, the gel disintegrates due to the decrease in the effective charge on the micelles. At both concentrations, the hydrophobic aggregation of micelles is observed near the isoelectric point. At pH 3.0–7.4, the autocorrelation functions measured by rotational dynamic light scattering at 3 wt% exhibit a decay steeper than single exponential, which confirms that the gels are frozen, presumably due to the glassy PMMA cores and hydrophobic interpolyelectrolyte complexes. At pH 11, the diffusion of single micelles is observed in addition to the frozen dynamics

Dual Orthogonal Switching of the “Schizophrenic” Self-Assembly of Diblock Copolymers

Based on diblock copolymers, a pair of “schizophrenic” micellar systems is designed by combining a nonionic and thermoresponsive block with a zwitterionic block, which is thermoresponsive and salt-sensitive. The nonionic block is poly­(<i>N</i>-isopropyl­acrylamide) (PNIPAM) or poly­(<i>N</i>-isopropyl­methacrylamide) (PNIPMAM) and exhibits a lower critical solution temperature (LCST) behavior in aqueous solution. The zwitterionic block is a polysulfobetaine, i.e., poly­(4-((3-methacryl­amidopropyl)­dimethyl­ammonio)­butane-1-sulfonate) (PSBP), and has an upper critical solution temperature (UCST) behavior with the clearing point decreasing with increasing salt concentration. The PSBP-<i>b</i>-PNIPAM and PSBP-<i>b</i>-PNIPMAM diblock copolymers are prepared by successive reversible addition–fragmentation chain transfer (RAFT) polymerizations. The PSBP block is chosen such that the clearing point of the homopolymer is significantly higher in pure water than the cloud point of PNIPAM or PNIPMAM. Using turbidimetry, ¹H NMR, and small-angle neutron scattering, we investigate the overall phase behavior as well as the structure and interaction between the micelles and the intermediate phase, both in salt-free D₂O and in 0.004 M NaBr in D₂O in a wide temperature range. We find that PSBP-<i>b</i>-PNIPAM at 50 g L^–1 in salt-free D₂O is turbid in the entire temperature range. It forms spherical micelles below the cloud point of PNIPAM and cylindrical micelles above. Similar behavior is observed for PSBP-<i>b</i>-PNIPMAM at 50 g L^–1 in salt-free D₂O with a slight and smooth increase of the light transmission below the cloud point of PNIPMAM and an abrupt decrease above. Upon addition of 0.004 M NaBr, the UCST-type cloud point of the PSBP-block is notably decreased, and an intermediate regime is encountered below the cloud point of PNIPMAM, where the light transmission is slightly enhanced. In this regime, the polymer solution exhibits behavior typical for polyelectrolyte solutions. Thus, double thermosensitive and salt-sensitive behavior with “schizophrenic” micelle formation is found, and the width of the intermediate regime, where both blocks are hydrophilic, can be tuned by the addition of electrolyte