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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
581

X-ray And Timing Properties Of Anomalous X-ray Pulsar 1e 2259+586

Sasmaz Mus, Sinem 01 August 2007 (has links) (PDF)
In this thesis, we present the spectral and timing variabilities of anomalous X-ray pulsar 1E 2259+586 observed with European Photon Imaging PN Camera (EPIC PN) on board X-ray Multi Mirror Mission (XMM), Proportional Counter Array (PCA) on board Rossi X-ray Timing Explorer (RXTE) and Advanced CCD Imaging Spectrometer (ACIS) on board Chandra X-ray Observatory. We presented the results of spectral analysis of 2000 January 11 ACIS observation. Pulse phase spectroscopy was performed on two XMM observations before and after the outburst. Pulse profiles of two XMM observations before the outburst and three XMM observations after the outburst were studied. Results are consistent with the those presented by Patel et al. (2001) and Woods et al. (2004). We searched for the spectral variations versus spin rate during the outburst. Long-term spectral, frequency and spin-down rate variations are presented between 1996 and 2006 including 98 RXTE and 4 XMM observations. However, except outburst region (Woods et al. 2004) no significant spectral and spin rate variabilities were seen. Around the outburst region we confirmed the spectral hardening with increasing spin rate and flux.
582

Simulation and modeling of the powder diffraction pattern from nanoparticles: studying the influence of surface strain

Beyerlein, Kenneth Roy 07 July 2011 (has links)
Accurate statistical characterization of nanomaterials is crucial for their use in emerging technologies. This work investigates how different structural characteristics of metal nanoparticles influence the line profiles of the corresponding powder diffraction pattern. The effects of crystallite size, shape, lattice dynamics, and surface strain are all systematically studied in terms of their impact on the line profiles. The studied patterns are simulated from atomistic models of nanoparticles via the Debye function. This approach allows for the existing theories of diffraction to be tested, and extended, in an effort to improve the characterization of small crystallites. It also begins to allow for the incorporation of atomistic simulations into the field of diffraction. Molecular dynamics simulations are shown to be effective in generating realistic structural models and dynamics of an atomic system, and are then used to study the observed features in the powder diffraction pattern. Furthermore, the characterization of a sample of shape controlled Pt nanoparticles is carried out through the use of a developed Debye function analysis routine in an effort to determine the predominant particle shape. The results of this modeling are shown to be in good agreement with complementary characterization methods, like transmission electron microscopy and cyclic voltammetry.
583

Establishment of the Physical and Technical Prerequisites for the Determination of the Relative Biological Effectiveness of Low-energy Monochromatic X-rays / Etablierung der physikalischen und technischen Voraussetzungen für die Bestimmung der relativen biologischen Wirksamkeit niederenergetischer, monochromatischer Röntgenstrahlung

Lehnert, Anna 15 February 2006 (has links) (PDF)
Low-energy X-rays in the range 10 - 50 keV have a wide application. One important application in radiological diagnostics is mammography, whereas, in radiotherapy, they are used for irradiation of superficial tumours, in brachytherapy and photon activation therapy. The importance of soft X-rays for fundamental radiobiological research is based on the fact, that all species of ionizing radiation produce a wide spectrum of secondary electrons, mainly responsible for the primary damage to be transformed into an observable radiobiological effect. By variation of the primary soft X-ray energy, a variation in the secondary electron spectra and therefore in the local energy deposition is provided. However, up to now no definitive conclusions about the relative biological effectiveness (RBE) of soft X-rays can be made due to its dependence on the photon energy, biological endpoint and dose range and the consequent large spread of the published data. The superconducting electron linear accelerator of high brilliance and low emittance (ELBE) at the Forschungszentrum Rossendorf with an electron energy up to about 40 MeV is used, among all, to generate X-rays in a wide energy range. One method for production of intensive, quasi-monochromatic X-rays in the energy range 10 - 100 keV tunable in energy, is by channeling of electrons in a perfect crystal. This X-ray source has many advantages over the most widespread X-ray source, which is the X-ray tube. Although the physical basis of the channeling effect has been previously investigated, the feasibility of an X-ray source based on channeling radiation (CR) for radiobiological studies has been for the first time theoretically and experimentally studied and a dedicated CR source built and optimised in the frame of this thesis. CR has been theoretically characterised in order to estimate its applicability for radiobiological studies. A good agreement between the theoretical predictions and the measured data has been found. The intrinsic properties of the CR source have led to the conclusion that monochromatisation is necessary. A monochromator based on HOPG mosaic crystals, was designed and manufactured. The dosimetrical methods have been investigated at the CR source as well as at an X-ray tube. Absolute dose measurements using an ionisation chamber and spectral dose distribution determination using semiconductor detectors have been performed. In addition, an unconventional system based on thermally stimulated exoelectron emission (TSEE) detectors, allowing to measure dose in a small volume and in the real cell environment has been tested and has proven itself appropriate in a variable dose range and in a liquid environment, in cases where reproducible laboratory conditions are provided. The biological endpoints clonogenic cell survival and micronucleus induction have been optimised for two established cell lines. The human mammary epithelial cells MCF-12A have been chosen due to the importance of RBE of soft X-rays for determination of risk from mammography. On the other hand, the use of the widespread mouse fibroblast cell line NIH/3T3 allows to compare the results with previously published data. The influence of the specific irradiation procedure at ELBE on the control level of cell survival and micronucleus induction has been tested and an irradiation system was developed and constructed. In addition, the RBE for soft X-rays was determined by X-ray tube irradiation at the Medical Department of Technische Universität Dresden. The RBE of 10 kV and 25 kV X-rays relative to 200 kV X-rays was determined. The RBE was found to be in the range from 1.0 to 1.4, depending on the used radiation quality, cell line and the biological endpoint, in agreement with previously published data for the same radiation qualities. These results confirm that systematical studies of RBE dependence on photon energy at the ELBE CR source are necessary and feasible.
584

Η εξελικτική ακολουθία των ενεργών γαλαξιακών πυρήνων ως αποτέλεσμα των εγγύς γαλαξιακών αλληλεπιδράσεων

Κουλουρίδης, Ηλίας 03 August 2009 (has links)
Σκοπός του διδακτορικού αυτού είναι να αναδείξει τις ομοιότητες και τις διαφορές των ενεργών πυρήνων, μελετώντας το περιβάλλον γαλαξιών τύπου Sy1, Sy2, αλλά και λαμπρών υπέρυθρων γαλαξιών (BIRG, οι οποίοι ως επί το πλείστον είναι τύπου Starburst και Sy2) και συγκρίνοντας το με το περιβάλλον κανονικών μη ενεργών γαλαξιών. Διερευνάται επίσης εις βάθος, η σχέση Starburst και AGN γαλαξιών και περιλαμβάνεται η αναλυτική φασματοσκοπική μελέτη και κατηγοριοποίηση των γειτόνων των Seyfert και BIRG, σε μία προσπάθεια να βρεθεί η αναμενόμενη αμφίδρομη σχέση μεταξύ των αλληλεπιδρώντων γαλαξιών. Εν κατακλείδι, προτείνεται ένα συνολικό εξελικτικό σενάριο, που περιλαμβάνει όλους τους τύπους των ενεργών γαλαξιών που παρατηρούνται στο τοπικό σύμπαν. Το τελευταίο τμήμα της διατριβής προσεγγίζει το πρόβλημα του περιβάλλοντος των ενεργών γαλαξιών από μία διαφορετική πλευρά, αυτή των σμηνών γαλαξιών. Η ανεύρεση των ενεργών πυρήνων σε αυτή την περίπτωση γίνεται με χρήση δεδομένων ακτινών-Χ από το δορυφόρο XMM-Newton. Η ορθή ερμηνεία των αποτελεσμάτων προϋποθέτει την σύγκριση των αποτελεσμάτων με οπτικά δεδομένα, η οποία ακολουθεί σε δεύτερη φάση. / The purpose of the present thesis is to bring out the similarities and the differences of the Active Galactic Nuclei (AGN), by studying the environment of Seyfert and of Bright IRAS galaxies (BIRG, which in their majority are Starburst and Sy2 galaxies) and compare it with the environment of normal (non-active) galaxies. The Starburst/AGN connection is also studied and the spectroscopic analysis and classification of all the neighboring galaxies of Seyferts and BIRGs is included, in an attempt to find the expected bidirectional relation between interacting galaxies. We propose an evolutionary scenario, which includes all types of active galaxies present in the local universe. The last part approaches the problem from a different angle, that of the galaxy clusters. In this case the selection of the AGNs is based on their X-ray emmision, using data from the XMM-Newton satellite. Finally, we compare our findings with optical data from the Sloan Digital Sky Survey.
585

Ortsdosimetrie in gepulsten Strahlungsfeldern

Gotz, Malte, Karsch, Leonhard, Pawelke, Jörg 28 April 2015 (has links) (PDF)
In dem Bericht werden Methoden und Ergebnisse experimenteller Untersuchungen an verfügbaren Ortsdosisleistungsmessgeräten in Feldern gepulster, ionisierender Strahlung beschrieben. Es zeigte sich, dass die meisten Messgeräte nur erheblich eingeschränkt für die Messung dieser Art Strahlung geeignet sind. Ionisationskammern, soweit einsetzbar, stellen das geeignetste der untersuchten Messprinzipien dar. Felder gepulster Strahlung treten bei einer Vielzahl industrieller, medizinischer und wissenschaftlicher Anwendungen auf. Die Veröffentlichung richtet sich an die in diesen Bereichen tätigen Strahlenschützer.
586

Biological effects of high energy radiation and ultra high dose rates

Zackrisson, Björn January 1991 (has links)
Recently a powerful electron accelerator, 50 MeV race-track microtron, has been taken into clinical use. This gives the opportunity to treat patients with higher x-ray and electron energies than before. Furthermore, treatments can be performed were the entire fractional dose can be delivered in parts of a second. The relative biological effectiveness (RBE) of high energy photons (up to 50 MV) was studied in vitro and in vivo. Oxygen enhancement ratio (OER) of 50 MV photons and RBE of 50 MeV electrons were investigated in vitro. Single-fraction experiments, in vitro, using V-79 Chinese hamster fibroblasts showed an RBE for 50 MV x-rays of approximately 1.1 at surviving fraction 0.01, with reference to the response to 4 MV x- rays. No significant difference in OER could be demonstrated. Fractionation experiments were carried out to establish the RBE at the clinically relevant dose level, 2 Gy. The RBE calculated for the 2 Gy/fraction experiments was 1.17. The RBEs for 20 MV x-rays and 50 MeV electrons were equal to one. In order to investigate the validity of these results, the jejunal crypt microcolony assay in mice was used to determine the RBE of 50 MV x-rays. The RBE for 50 MV x-rays in this case was estimated to be 1.06 at crypt surviving fraction 0.1. Photonuclear processes are proposed as one possible explanation to the higher RBE for 50 MV x-rays. Several studies of biological response to ionizing radiation of high absorbed dose rates have been performed, often with conflicting results. With the aim of investigating whether a difference in effect between irradiation at high dose rates and at conventional dose rates could be verified, pulsed 50 MeV electrons from a clinical accelerator were used for experiments with ultra high dose rates (mean dose rate: 3.8 x 10^ Gy/s) in comparison to conventional (mean dose rate: 9.6 x 10"^ Gy/s). V-79 cells were irradiated in vitro under both oxic and anoxic conditions. No significant difference in relative biological effectiveness (RBE) or oxygen enhancement ratio (OER) was observed for ultra high dose rates compared to conventional dose rates. A central issue in clinical radiobiological research is the prediction of responses to different radiation qualities. The choice of cell survival and dose response model greatly influences the results. In this context the relationship between theory and model is emphasized. Generally, the interpretations of experimental data are dependent on the model. Cell survival models are systematized with respect to their relations to radiobiological theories of cell kill. The growing knowledge of biological, physical, and chemical mechanisms is reflected in the formulation of new models. This study shows that recent modelling has been more oriented towards the stochastic fluctuations connected to radiation energy deposition. This implies that the traditional cell survival models ought to be complemented by models of stochastic energy deposition processes at the intracellular level. / <p>S. 1-44: sammanfattning, s. 47-130: 5 uppsatser</p> / digitalisering@umu
587

Pulsed Laser Injected Enhancement Cavity for Laser-electron Interaction

You, Yan 03 June 2014 (has links) (PDF)
X-ray diffraction and scattering, X-ray spectroscopy, and X-ray crystallography are widely used in the life sciences, material science, and medical diagnosis. High-quality and high-brightness X-rays are a strong requirement to improve applications. Inverse Compton scattering (ICS) X-ray source has attracted great interests worldwide lately. To significantly enhance the average X-ray photon flux, a compact electron storage-ring combined with a high finesse optical enhancement cavity (OEC) can be utilized. In such a system, the collision rate between the electron beam and the laser pulse is greatly increased to the MHz range, enabling a photon flux up to 10¹³ph/s.In the first chapter, I describe the motivation behind the development of OEC based on ICS X-ray source. The characteristics of this kind of X-ray source are summarized, compared to those of the conventional low-repetition-rate Terawatt laser system based on ICS X-ray source. The latest progress and research status of OEC based on ICS X-ray source are presented. Pulsed-laser injected high-finesse OEC stacking theory and properties are discussed in Chapter 2. Not only does the OEC based on ICS X-ray source require the laser pulse repetition rate to be matched to the free spectral range (FSR) of the cavity, where both also have to match the electron storage-ring circulation frequency. In addition, we have to match the phase shift of the laser repetition rate to the phase offset introduced by the dispersion of the cavity mirrors, since our cavity finesse design value is quite high. The stacking theory is analyzed in the frequency domain. Cavity properties, including cavity mirror dispersion, finesse, and FSR, are discussed in detail. A laser frequency comb and OEC coupling is analyzed also. The laser source development is presented in Chapter 3. We constructed a mode-locked fiber laser based on nonlinear polarization rotation. The locking model, locking techniques, and the theory, simulations and experimental tests of tilt locking (TL) in the pulsed laser injected high-finesse OEC are discussed in Chapter 4. We succeeded in locking a pulsed laser to a high-finesse cavity with the TL technique. The experimental results show that the TL and the Pound-Drever-Hall techniques have the same performance: stable locking, high sensitivity, and the same power coupling rate for picosecond laser pulse case, while the test results for full spectrum TL locking show that it is uneasy to align the split-photodiode to the beam waist.Based on the above experimental study and tests, we design the OEC system for Tsinghua University X-ray project in Chapter 5. The expected X-ray flux is 10¹º to 10¹³ ph/s. We detail every subsystem requirement.
588

Pulsed Laser Injected Enhancement Cavity for Laser-electron Interaction

You, Yan 03 June 2014 (has links) (PDF)
X-ray diffraction and scattering, X-ray spectroscopy, and X-ray crystallography are widely used in the life sciences, material science, and medical diagnosis. High-quality and high-brightness X-rays are a strong requirement to improve applications. Inverse Compton scattering (ICS) X-ray source has attracted great interests worldwide lately. To significantly enhance the average X-ray photon flux, a compact electron storage-ring combined with a high finesse optical enhancement cavity (OEC) can be utilized. In such a system, the collision rate between the electron beam and the laser pulse is greatly increased to the MHz range, enabling a photon flux up to 10¹³ph/s.In the first chapter, I describe the motivation behind the development of OEC based on ICS X-ray source. The characteristics of this kind of X-ray source are summarized, compared to those of the conventional low-repetition-rate Terawatt laser system based on ICS X-ray source. The latest progress and research status of OEC based on ICS X-ray source are presented. Pulsed-laser injected high-finesse OEC stacking theory and properties are discussed in Chapter 2. Not only does the OEC based on ICS X-ray source require the laser pulse repetition rate to be matched to the free spectral range (FSR) of the cavity, where both also have to match the electron storage-ring circulation frequency. In addition, we have to match the phase shift of the laser repetition rate to the phase offset introduced by the dispersion of the cavity mirrors, since our cavity finesse design value is quite high. The stacking theory is analyzed in the frequency domain. Cavity properties, including cavity mirror dispersion, finesse, and FSR, are discussed in detail. A laser frequency comb and OEC coupling is analyzed also. The laser source development is presented in Chapter 3. We constructed a mode-locked fiber laser based on nonlinear polarization rotation. The locking model, locking techniques, and the theory, simulations and experimental tests of tilt locking (TL) in the pulsed laser injected high-finesse OEC are discussed in Chapter 4. We succeeded in locking a pulsed laser to a high-finesse cavity with the TL technique. The experimental results show that the TL and the Pound-Drever-Hall techniques have the same performance: stable locking, high sensitivity, and the same power coupling rate for picosecond laser pulse case, while the test results for full spectrum TL locking show that it is uneasy to align the split-photodiode to the beam waist.Based on the above experimental study and tests, we design the OEC system for Tsinghua University X-ray project in Chapter 5. The expected X-ray flux is 10¹º to 10¹³ ph/s. We detail every subsystem requirement.
589

Creating and Probing Extreme States of Materials : From Gases and Clusters to Biosamples and Solids

Iwan, Bianca January 2012 (has links)
Free-electron lasers provide high intensity pulses with femtosecond duration and are ideal tools in the investigation of ultrafast processes in materials. Illumination of any material with such pulses creates extreme conditions that drive the sample far from equilibrium and rapidly convert it into high temperature plasma. The dynamics of this transition is not fully understood and the main goal of this thesis is to further our knowledge in this area. We exposed a variety of materials to X-ray pulses of intensities from 1013 to above 1017 W/cm2. We found that the temporal evolution of the resulting plasmas depends strongly on the wavelength and pulse intensity, as well as on material related parameters, such as size, density, and composition. In experiments on atomic and molecular clusters, we find that cluster size and sample composition influence the destruction pathway. In small clusters a rapid Coulomb explosion takes place while larger clusters undergo a hydrodynamic expansion. We have characterized this transition in methane clusters and discovered a strong isotope effect that promotes the acceleration of deuterium ions relative to hydrogen. Our results also show that ions escaping from exploding xenon clusters are accelerated to several keV energies. Virus particles represent a transition between hetero-nuclear clusters and complex biological materials. We injected single mimivirus particles into the pulse train of an X-ray laser, and recorded coherent diffraction images simultaneously with the fragmentation patterns of the individual particles. We used these results to test theoretical damage models. Correlation between the diffraction patterns and sample fragmentation shows how damage develops after the intense pulse has left the sample. Moving from sub-micron objects to bulk materials gave rise to new phenomena. Our experiments with high-intensity X-ray pulses on bulk, metallic samples show the development of a transient X-ray transparency. We also describe the saturation of photoabsorption during ablation of vanadium and niobium samples. Photon science with extremely strong X-ray pulses is in its infancy today and will require much more effort to gain more knowledge. The work described in this thesis represents some of the first results in this area.
590

Ανίχνευση και μελέτη εξωγαλαξιακών υπολειμμάτων υπερκαινοφανών σε πολλαπλά μήκη κύματος / Detection and study of extragalactic multi-wavelength supernova remnants

Λεωνιδάκη, Ιωάννα 28 February 2013 (has links)
Η παρούσα διατριβή παρουσιάζει τα αποτελέσματα μιας συστηματικής έρευνας των πληθυσμών Υπολειμμάτων Υπερκαινοφανών (Υ/Υ) σε έξι κοντινούς γαλαξίες (NGC 2403, NGC 3077, NGC 4214, NGC 4395, NGC 4449 και NGC 5204) βασισμένη σε αρχειακά δεδομένα του δορυφόρου ακτίνων-Χ Chandra, και σε βαθειές οπτικές παρατηρήσεις με τα στενά φίλτρα Hα (λ 6563) και [SΙΙ] (λλ 6716, 6731) καθώς και φασματοσκοπικές παρατηρήσεις. Η ταξινόμηση των Υ/Υ επιλεγμένων στις ακτίνες-Χ βασίστηκε στα μαλακά, θερμικά φάσματα (kT < 3 keV) των πηγών στις ακτίνες-Χ ή στα χρώματά τους στις ακτίνες-Χ. Αντίστοιχα, η ταξινόμηση των οπτικών Υ/Υ βασίστηκε στο καθιερωμένο κριτήριο του λόγου των γραμμών εκπομπής [SΙΙ](λλ 6716, 6731)/Hα > 0.4. Εντοπίστηκαν 37 θερμικά Υ/Υ στις ακτίνες-Χ, 30 εκ των οποίων είναι νέες ανακαλύψεις και ~400 (~350 από αυτά είναι νέες ανιχνεύσεις) φωτομετρικά Υ/Υ, για 67 από τα οποία πιστοποιήθηκε φασματοσκοπικά η φύση τους ως Υ/Υ. Πολλοί από τους γαλαξίες στο δείγμα μας μελετώνται για πρώτη φορά στις ακτίνες-Χ (NGC 4214, NGC 4395 και NGC 5204) ή στο οπτικό μέρος του φάσματος (NGC 4395, NGC 3077) με συστηματικό τρόπο, καταλήγοντας στην ανακάλυψη αρκετών νέων Υ/Υ. Σε πολλές περιπτώσεις, η ταξινόμηση των πηγών ως Υ/Υ στις ακτίνες-Χ ή στο οπτικό μέρος του φάσματος επιβεβαιώνεται από ομόλογα Υ/Υ που έχουν ανιχνευθεί σε άλλα μήκη κύματος, δείχνοντας ότι οι μέθοδοι ανίχνευσης που χρησιμοποιούμε είναι αξιόπιστες. Συζητάμε τις ιδιότητες (π.χ. φωτεινότητα, θερμοκρασία, πυκνότητα, ταχύτητα σοκ) των Υ/Υ σε διάφορους τύπους γαλαξιών και ως εκ τούτου διαφορετικά περιβάλλοντα, προκειμένου να δούμε την εξάρτησή τους από το μεοσαστρικό μέσο. Συσχετίζουμε παραμέτρους των ανιχνευμένων οπτικών Υ/Υ (λόγος [SΙΙ]/Hα, φωτεινότητα) με τις παραμέτρους των αντίστοιχων Υ/Υ στις ακτίνες-Χ (θερμοκρασία, φωτεινότητα, πυκνότητα) προκειμένου να κατανοήσουμε την εξέλιξή τους. Μερικά από τα πιο ενδιαφέροντα αποτελέσματα αυτής της έρευνας είναι τα ακόλουθα: α) Βρίσκουμε ότι τα Υ/Υ που είναι ανιχνευμένα στις ακτίνες-Χ και βρίσκονται σε άμορφους γαλαξίες φαίνεται να είναι πιο λαμπρά από εκείνα στους σπειροειδείς γαλαξίες. Αποδίδουμε αυτό το γεγονός στη χαμηλότερη μεταλλικότητα των άμορφων γαλαξιών από αυτή των σπειροειδών (η χαμηλότερη μεταλλικότητα δημιουργεί πρόγονους αστέρες μεγαλύτερης μάζας) ή στις υψηλότερες τοπικές πυκνότητες που παρατηρούνται στο μεσοαστρικό μέσο των άμορφων γαλαξιών, β) Η σύγκριση του αριθμού των παρατηρούμενων λαμπρών Υ/Υ στις ακτίνες-Χ με τον αριθμό αυτών που αναμένονται με βάση τις κατανομές φωτεινότητας των Υ/Υ στις ακτίνες-Χ στα Νέφη του Μαγγελάνου και στον M33, δείχνουν ότι κατανομές φωτεινότητας των Υ/Υ μεταξύ σπειροειδών και άμορφων γαλαξιών είναι διαφορετικές, από αυτές που αφορούν τα Υ/Υ στους άμορφους γαλαξίες και τείνουν να είναι πιο επίπεδες, γ) Βρίσκουμε ότι υπάρχει διαφορά στους λόγους [NΙΙ]/Hα των Υ/Υ μεταξύ διαφορετικών τύπων γαλαξιών, το οποίο κατά πάσα πιθανότητα οφείλεται σε διαφορές στη μεταλλικότητά τους και δ) Υπάρχουν ισχυρές ενδείξεις για μια γραμμική σχέση μεταξύ του αριθμού των λαμπρών Υ/Υ στο οπτικό και στις ακτίνες-Χ και του ρυθμού αστρογένεσης των γαλαξιών του δείγματος. / This thesis presents the results of a comprehensive investigation of the Supernova Remnant (SNR) populations in six nearby galaxies (NGC 2403, NGC 3077, NGC 4214, NGC 4395, NGC 4449 and NGC 5204) based on Chandra archival data and deep optical narrow-band Hα and [SΙΙ] images, as well as spectroscopic observations. The classification of X-ray emitting SNRs was based on their soft thermal spectra (kT < 3 keV) or their X-ray colors and for optically-emitting SNRs on the well-established emission-line flux criterion of [SΙΙ](λλ 6716, 6731)/Hα(λ 6563) > 0.4. We have identified 37 X-ray selected thermal SNRs, 30 of which are new discoveries and ~400 optical SNRs (~350 are new detections), for 67 of which we spectroscopically verified their shock-excited nature. Many of the galaxies in our sample are studied for the first time in the X-ray (NGC 4214, NGC 4395, and NGC 5204) or optical (NGC 4395, NGC 3077) band in a self-consistent way, resulting in the discovery of many new SNRs. In many cases, the X-ray and optical classifications are confirmed based on the identification of SNR counterparts in other wavelengths, giving us confidence that the detection methods we use are robust. We discuss the properties (e.g. luminosity, temperature, density, shock velocity) of the X-ray/optically detected SNRs in different types of galaxies and hence different environments, in order to address their dependence on their interstellar medium. We compare optical ([SΙΙ]/Hα ratio, luminosity) and X-ray parameters (temperature, luminosity, density) of the detected SNRs, in order to understand their evolution and investigate possible selection effects. The most intriguing results of this survey are the following: a) We find that X-ray selected SNRs in irregular galaxies appear to be more luminous than those in spirals. We attribute this either to the lower metallicities and therefore more massive progenitor stars of irregular galaxies or to the higher local densities of the interstellar medium, b) A comparison of the numbers of observed luminous X-ray selected SNRs with those expected from the luminosity functions of X-ray SNRs in the Magellanic Clouds and M33 suggest different luminosity distributions between the SNRs in spiral and irregular galaxies, with the latter tending to have flatter distributions, c) We find that there is a difference in [NΙΙ]/Hα line ratios of the SNR populations between different types of galaxies which is the result of the low metalicity of irregular galaxies, and d) We find evidence for a linear relation between the number of luminous optical or X-ray SNRs and Star Formation Rate in our sample of galaxies.

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