Ενίσχυση σκέδασης Raman σε φωτονικούς κρυστάλλους TiO2 τροποποιημένους με νανοκολλοειδή οξειδίου γραφενίου

Το φαινόμενο επιφανειακής ενίσχυσης της σκέδασης Raman (Surface Enhanced Raman Scattering–SERS) αποτελεί μία ιδιαιτέρα ευαίσθητη αναλυτική μέθοδο που δίνει τη δυνατότητα ανίχνευσης και απεικόνισης οργανικών ουσιών έως το επίπεδο ενός απλού μορίου. Παρά τον υψηλό παράγοντα ενίσχυσης που επιτυγχάνεται μέσω του εντοπισμένου επιφανειακού πλασμονικού συντονισμού νανοδομημένων μετάλλων, τα αντίστοιχα υποστρώματα SERS χαρακτηρίζονται από υψηλό κόστος, μικρή σταθερότητα, χαμηλή βιοσυμβατότητα και αδυναμία επαναχρησιμοποίησης. Η ανάπτυξη διηλεκτρικών υποστρωμάτων SERS ημιαγωγών με κατάλληλα διαμορφωμένα μορφολογικά χαρακτηριστικά και ηλεκτρονικές ιδιότητες προσελκύει έντονο ερευνητικό ενδιαφέρον τα τελευταία χρόνια ως μια υποσχόμενη εναλλακτική προσέγγιση σε σχέση με τα συμβατικά μεταλλικά υποστρώματα, ιδιαίτερα σε εφαρμογές όπου δεν απαιτείται υψηλή ευαισθησία. Στόχος της παρούσας εργασίας ήταν η εφαρμογή επιφανειακά τροποποιημένων φωτονικών κρυστάλλων TiO2 με νανοκολλοειδή γραφενίου (nanoGO) ως αποδοτικά υποστρώματα SERS απουσία πλασμονικής ενίσχυσης. Μελετήθηκαν φωτονικοί κρύσταλλοι TiO2 με τη μορφολογία αντιστρόφου οπαλίου τριών διαφορετικών διαμέτρων με φωτονικά χάσματα 435, 502, και 646 nm για την ανίχνευση του πρότυπου αναλύτη κυανού του μεθυλενίου με διέγερση laser στα 488, 514, 633 και 785 nm. Την καλύτερη απόδοση παρουσίασε ο φωτονικός κρύσταλλος με χάσμα στα 435 mn για τα laser μήκους κύματος 488 και 514 nm λόγω του συντονισμού της συχνότητας διέγερσης με την περιοχή αργών φωτονίων, όπου η αργή διάδοση του προσπίπτοντος φωτός έχει ως αποτέλεσμα τη δημιουργία πολλαπλών ανακλάσεων στα νανοκρυσταλλικά τοιχώματα τιτανίας στα οποία βρίσκονται προσροφημένα τα μόρια αναλύτη και την αύξηση του σήματος Raman. Επιπρόσθετη συνεισφορά παρατηρήθηκε μέσω της χημικής αλληλεπίδρασης μεταξύ του αναλύτη και υποστρώματος TiO2. Επιφανειακή τροποποίηση των φωτονικών κρυστάλλων TiO2 με νανοφύλλα GO είχε ως αποτέλεσμα τη δραστική αύξηση της απόδοσης SERS κατά μια τάξη μεγέθους υποδεικνύοντας σημαντική συνέργεια μεταξύ GO και φωτονικών κρυστάλλων TiO2. Η ενίσχυση αυτή μπορεί να συσχετιστεί με την αυξημένη προσρόφηση μορίων του αναλύτη μέσω επιφανειακών ομάδων οξυγόνου και της σύζευξης π-π στην επιφάνεια του υποστρώματος αλλά και μέσω της διεπιφανειακής μεταφοράς φορτίου μεταξύ GO και του συστήματος χρωστική-TiO2. Συνδυάζοντας τους παραπάνω μηχανισμούς ενίσχυσης, η ελάχιστη συγκέντρωση MB που εντοπίστηκε ήταν 710-7 Μ στα 514 nm, από τις χαμηλότερες που έχουν αναφερθεί στη βιβλιογραφία στην ανίχνευση SERS του κυανού του μεθυλενίου με διηλεκτρικά υποστρώματα. Η τροποποίηση φωτονικών κρυστάλλων TiO2 με κατάλληλα νανοϋλικά, όπως το οξείδιο του γραφενίου, ανοίγει σημαντικές προοπτικές για την ανάπτυξη αποδοτικών, ανακυκλώσιμων, φιλικών προς το περιβάλλον υποστρωμάτων SERS χαμηλού κόστους, με δυνατότητα αυτό-καθαρισμού μέσω του μηχανισμού της φωτοκατάλυσης.Surface enhanced Raman scattering (SERS) has been established as a highly sensitive analytical technique with unprecedented resolution in the identification of minute amounts of analytes reaching the level of single molecule detection and imaging. Despite the marked progress in the field, fabrication of low cost, recyclable and biocompatible SERS substrates based on the local field and radiation enhancement generated by the localized surface plasmon resonance (LSPR) of coinage metals has been a key challenge for the implementation of practical SERS applications. The development of dielectric nanostructures with suitably modified morphology and electronic properties has been attracting particular research interest as a promising means to alleviate the major shortcomings of conventional metallic SERS substrates, especially in applications where ultrasensitive detection is not a prerequisite. In this work, surface modified TiO2 photonic crystals by graphene oxide nanocolloids (nanoGO) were explored as efficient, plasmon-free SERS substrates. TiO2 photonic crystals in the form of inverse opals for three different diameters with photonic gaps (stop bands) of 435, 502, και 646 nm were applied for the detection of methylene blue as model analyte at variable laser excitations of 488, 514, 633 και 785 nm. The best performance was observed for the photonic crystal with 435 stop band at 488 and 514 nm due to the close match of the laser excitation with the slow photon spectral region. In that case, slow light propagation results in multiple light scattering at the nanocrystalline titania walls, where the analyte molecues are adsorbed, leading to the effective extension of the path length of incident photons and the Raman amplification. Additional contribution was identified by the chemical interaction of the analyte molecules with the semiconducting substrate. Surface functionalization of the TiO2 photonic crystals with nanoGO sheets resulted in a marked increase of the SERS performance by one order of magnitude indicative of significant synergy. This enhancement can be related to the increased adsorption of the analyte molecules by means of surface oxygen groups and π-π interactions on the substrate and the interfacial charge transfer between GO and the analyte-TiO2 system. Optimal combination of these mechanisms resulted in a limit of detection reaching 710-7 Μ at 514 nm, one of the lowest reported in the literature for SERS detection of MB on dielectric substrates, paving the way for the development of efficient self-cleaning dielectric SERS by means of their photocatalytic properties

Signatures of X-ray reverberation in the power spectra of AGN

Aims: we study the effects of X-ray reprocessing in the power spectra (PSDs) of active galactic nuclei (AGNs).Methods: we compute fully relativistic disc response functions in the case of lamp-post geometry using the full observed reflection spectrum for various X-ray source heights, disc inclination, and spin values of the central black hole. Since the observed PSD is equal to the product of the intrinsic power spectrum with the transfer function (i.e. the Fourier transform of the disc response function), we are able to predict the observed PSDs in the case of X-ray illumination of the inner disc.Results: the observed PSD should show a prominent dip at high frequencies and an oscillatory behaviour with a decreasing amplitude at higher frequencies. The reverberation echo features should be more prominent in energy bands where the reflection component is more pronounced. The frequency of the dip is independent of energy, and it is mainly determined by the black hole mass and the X-ray source height. The amplitude of the dip increases with increasing black hole spin and inclination angle, as long as the height of the lamp is smaller than ~10 gravitational radii.Conclusions: the detection of the X-ray reverberation signals in the PSDs can provide further evidence for X-ray illumination of the inner disc in AGN. Our results are largely independent of the assumed geometry of the disc-corona system, as long as it does not change with time, and the disc response function is characterized by a sharp rise, a plateau, and a decline at longer times. Irrespective of the geometry, the frequency of the main dip should decrease with increasing mean time of the response function, and the amplitude of the dip should increase with increasing reflection fractio

Posterior Instrumentation for Occipitocervical Fusion

Since 1995, 29 consecutive patients with craniocervical spine instability due to several pathologies were managed with posterior occipitocervical instrumentation and fusion. Laminectomy was additionally performed in nineteen patients. The patients were divided in two groups: Group A which included patients managed with screw-rod instrumentation, and Group B which included patients managed with hook-and-screw-rod instrumentation. The patients were evaluated clinically and radiographically using the following parameters: spine anatomy and reconstruction, sagittal profile, neurologic status, functional level, pain relief, complications and status of arthrodesis. The follow-up was performed immediately postoperatively and at 2, 6, 12 months after surgery, and thereafter once a year. Fusion was achieved in all but one patient. One case of infection was the only surgery related complication. Neurological improvement and considerable pain relief occurred in the majority of patients postoperatively. There were neither intraoperative complications nor surgery related deaths. However, the overall death rate was 37.5% in group A, and 7.7% in group B. There were no instrument related failures. The reduction level was acceptable and was maintained until the latest follow-up in all of the patients. No statistical difference between the outcomes of screw-rod and hook-and-screw-rod instrumentation was detected. Laminectomy did not influence the outcome in either group. Screw-rod and hook-and-screw-rod occipitocervical fusion instrumentations are both considered as safe and effective methods of treatment of craniocervical instability

Suicide Attempts from Height and Injury Patterns: An Analysis of 64 Cases

Falls from height are a common cause of death and disability. A majority of free falls occur accidentally and only a minority result from suicidal behaviour. Adolescents in many countries show high rates of suicide attempts and their repetition is a common feature. We describe the demographic characteristics of these patients, their psychiatric diagnosis at the time of the attempt and the injury patterns. We present 64 patients who sustained injuries as a result of a fall from height. They were divided into those without mental disorders (n = 32, group I) and those with mental disorders (n = 32, group II). The mean height from which the fall occurred was 5.4 m (range, 3–25 m). The mean injury severity score was 19 (range, 6–58) for all fall victims. Upper extremity fractures were found in 37 patients, while pelvic and lower extremity fractures were found in 198 cases. Spinal fractures were noted in 32 patients. Head injuries were revealed by CT scan in 16 patients. Patients following a suicidal high fall mostly had lower limb fractures, pelvis fractures, spinal fractures and head injuries

Interfacility transfers in a non-trauma system setting: an assessment of the Greek reality

<p>Abstract</p> <p>Background</p> <p>Quality assessment of any trauma system involves the evaluation of the transferring patterns. This study aims to assess interfacility transfers in the absence of a formal trauma system setting and to estimate the benefits from implementing a more organized structure.</p> <p>Methods</p> <p>The 'Report of the Epidemiology and Management of Trauma in Greece' is a one year project of trauma patient reporting throughout the country. It provided data concerning the patterns of interfacility transfers. We compared the transferred patient group to the non transferred patient group. Information reviewed included patient and injury characteristics, need for an operation, Intensive Care Unit (ICU) admittance and mortality. Analysis employed descriptive statistics and Chi-square test. Interfacility transfers were then assessed according to each health care facility's availability of five requirements; Computed Tomography scanner, ICU, neurosurgeon, orthopedic and vascular surgeon.</p> <p>Results</p> <p>Data on 8,524 patients were analyzed; 86.3% were treated at the same facility, whereas 13.7% were transferred. Transferred patients tended to be younger, male, and more severely injured than non transferred patients. Moreover, they were admitted to ICU more often, had a higher mortality rate but were less operated on compared to non transferred patients. The 34.3% of transfers was from facilities with none of the five requirements, whereas the 12.4% was from those with one requirement. Low level facilities, with up to three requirements transferred 43.2% of their transfer volume to units of equal resources.</p> <p>Conclusion</p> <p>Trauma management in Greece results in a high number of transfers. Patients are frequently transferred between low level facilities. Better coordination could lead to improved outcomes and less cost.</p

PALANTIR demo: leveraging SecaaS model for managing threats in industrial environments

PALANTIR, an EU-funded Innovation Action project, delivers tailored and pervasive resource protection through the Security-as-a-Service paradigm. This demo presents the architecture and validates the prototype against three threat scenarios with botnet, data breach and tampering attacks

Satellite-assisted monitoring of water quality to support the implementation of the Water Framework Directive

The EU Water Framework Directive1 (WFD) is an ambitious legislation framework to achieve good ecological and chemical status for all surface waters and good quantitative and chemical status for groundwater by 2027. A total of 111,062 surface waterbodies are presently reported on under the Directive, 46% of which are actively monitored for ecological status. Of these waterbodies 80% are rivers, 16% are lakes, and 4% are coastal and transitional waters. In the last assessment, 4% (4,442) of waterbodies still had unknown ecological status, while in 23% monitoring did not include in situ water sampling to support ecological status assessment2. For individual (mainly biological) assessment criteria the proportion of waterbodies without observation data is much larger; the full scope of monitoring under the WFD is therefore still far from being realised. At the same time, 60% of surface waters did not achieve ‘good’ status in the second river basin management plan and waterbodies in Europe are considered to be at high risk of having poor water quality based on combined microbial, physical and physicochemical indicators3

Safety of intravenous ferric carboxymaltose versus oral iron in patients with nondialysis-dependent CKD: an analysis of the 1-year FIND-CKD trial.

Background: The evidence base regarding the safety of intravenous (IV) iron therapy in patients with chronic kidney disease (CKD) is incomplete and largely based on small studies of relatively short duration. Methods: FIND-CKD (ClinicalTrials.gov number NCT00994318) was a 1-year, open-label, multicenter, prospective study of patients with nondialysis-dependent CKD, anemia and iron deficiency randomized (1:1:2) to IV ferric carboxymaltose (FCM), targeting higher (400-600 µg/L) or lower (100-200 µg/L) ferritin, or oral iron. A post hoc analysis of adverse event rates per 100 patient-years was performed to assess the safety of FCM versus oral iron over an extended period. Results: The safety population included 616 patients. The incidence of one or more adverse events was 91.0, 100.0 and 105.0 per 100 patient-years in the high ferritin FCM, low ferritin FCM and oral iron groups, respectively. The incidence of adverse events with a suspected relation to study drug was 15.9, 17.8 and 36.7 per 100 patient-years in the three groups; for serious adverse events, the incidence was 28.2, 27.9 and 24.3 per 100 patient-years. The incidence of cardiac disorders and infections was similar between groups. At least one ferritin level ≥800 µg/L occurred in 26.6% of high ferritin FCM patients, with no associated increase in adverse events. No patient with ferritin ≥800 µg/L discontinued the study drug due to adverse events. Estimated glomerular filtration rate remained the stable in all groups. Conclusions: These results further support the conclusion that correction of iron deficiency anemia with IV FCM is safe in patients with nondialysis-dependent CKD