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  • 1
    facet.materialart.
    Unknown
    Univ. Hamburg
    Publication Date: 2020-10-07
    Description: The main topic of this work is the introduction of time dependence into PHOENIX. This has been achieved for both the radiation field and the matter in the SN Ia model atmosphere. First, time dependence in the radiative transfer equation has been implemented. Two discretization schemes have been used for the implementation of the time derivative. Test calculations have been performed to confirm the correctness of the implementations. The radiation time scale computed with the time dependent radiative transfer is comparable to a simple analytic approach. Perturbations of the inner boundary condition of the atmosphere move through the whole atmosphere. For instance, an atmosphere with a sinusoidally varying inner light bulb leads to an atmosphere where the luminosity varies sinusoidally everywhere. For the next extension of time dependence for the matter, a simple hydrodynamical solver has been implemented. It computes the changes in the energy of an SN Ia atmosphere by considering the homologous expansion, energy transport and the deposition of energy by g -ray emission due to the radioactive decay of 56Ni and 56Co. Test calculations verified that each part of the solver works correctly. The energy deposition heats the atmosphere and increases the observed luminosity, whereas the adiabatic e expansion cools the atmosphere. The energy transport always pushes the temperature structure of the atmosphere towards the radiative equilibrium state ...
    Description: thesis
    Keywords: 523 ; THI 000 ; THU 162 ; Helligkeit von Sternen {Astronomie} ; Supernovae {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 107 S.
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  • 2
    facet.materialart.
    Unknown
    Univ. Potsdam
    Publication Date: 2020-10-07
    Description: Central stars of planetary nebulae are low-mass stars on the brink of their final evolution towards white dwarfs. Because of their surface temperature of above 25,000 K their UV radiation ionizes the surrounding material, which was ejected in an earlier phase of their evolution. Such fluorescent circumstellar gas is called a "Planetary Nebula". About one-tenth of the Galactic central stars are hydrogen-deficient. Generally, the surface of these central stars is a mixture of helium, carbon, and oxygen resulting from partial helium burning. Moreover, most of them have a strong stellar wind, similar to massive Pop-I Wolf-Rayet stars, and are in analogy classified as [WC]. The brackets distinguish the special type from the massive WC stars.
    Description: thesis
    Keywords: 523 ; TEG 000 ; Kosmogonie {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 102 S.
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  • 3
    Publication Date: 2021-03-29
    Description: Spectro-astrometry is a technique to obtain information about the structure of an astronomical source on sub-diffraction limited spatial scales down to milli- or micro-arcseconds. The method exploits the shift of the photocentre of a structured source over emission/absorption lines in its spectral energy distribution. Sub-diffraction limited resolution can be achieved because the method only uses wavelength-differential information of longslit spectra. Although spectro-astrometry has already been devised by Bailey (1998) and some studies have been performed to date on different astronomic targets, so far, no systematic analysis of the potential of this technique has been undertaken. The aim of this work was to analyse the potential of the method, develop the tools to exploit this potential and write the software which is needed to perform the analysis procedure. To verify the practical feasibility, observations were done with the VLT/CRIRES facility to demonstrate the capabilities of the method with respect to detecting structures on giant star surfaces. All steps of data reduction were analysed with respect to their influence on the spectro-astrometric quantities and a new method for bad pixel detection was devised and implemented ...
    Description: thesis
    Keywords: 523 ; THT 600 ; THK 000 ; THT 400 ; Riesensterne {Astronomie} ; Spektren und Spektroskopie von Sternen {Astronomie} ; Kalte Sterne {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 109 S.
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  • 4
    facet.materialart.
    Unknown
    Univ. Hamburg
    Publication Date: 2021-03-29
    Description: This thesis deals with the high-energy emission from young stellar objects, which are on the one hand still actively accreting from their disk, and on the other hand are no longer deeply obscured by their natal cloud. Stars of spectral type B and A are called Herbig Ae/Be (HAeBe) stars in this stage, all stars of later spectral type are termed classical T Tauri stars (CTTS); strictly speaking both types are defined by spectroscopic signatures, which are equivalent to the evolutionary stage described above. In this thesis CTTS and HAeBes are studied through high-resolution X-ray and UV spectroscopy and through detailed physical simulations. Spectroscopic X-ray data is reduced and presented for two targets: The CTTS V4046 Sgr was observed with Chandra for 100 ks, using a high-resolution grating spectrometer. The lightcurve contains one flare and the He-like triplets of Si XIII, Ne IX and O VII indicate high densities in the X-ray emitting regions. The second target is the HAeBe HD 163296, which was observed with XMM-Newton for 130 ks. The lightcurve shows only moderate variability, the elemental abundance follows a pattern, that is usual for active stars. The He-like triplet of O VII exhibits line ratios similar to coronal sources, indicating that neither a high density nor a strong UV-field is present in the region of the X-ray emission ...
    Description: thesis
    Keywords: 523 ; THP 000 ; Thermodynamische Vorgänge in Sternen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 84 S.
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  • 5
    Publication Date: 2021-03-29
    Description: Many stars evolve not alone but along one or more companions. While the evolution of single isolated stars is well predicted by theoretical calculations, close binary systems with their interactions are on the one hand far more difficult to handle, but on the other hand well constrained in their masses and sizes. One mechanism thought to produce such close binaries is the Common Envelope Evolution (CEE). Especially young post CEE binaries show great temperature differences between both components of about a factor 10 at a separation of just a few solar radii. This work focuses on close binary systems with a hot primary component (e.g. a subdwarf O-type star (sdO)) and a much cooler secondary component (e.g. a main-sequence star), which is heavily influenced by external radiation originating from the first. The technique to include external radiation into the stellar atmosphere code PHOENIX, i.e., the deviation of the outer boundary condition and the change in the temperature correction method, is described in detail. To concentrate on the irradiation effect, other difficulties such as asymmetric effects due to tear-drop shaped stars, ongoing mass accretion or shadows of a circumbinary disc, are avoided by selecting pre-cataclysmic variables (pre CVs) out of the class of close binaries as laboratory. The total eclipsing binary system UU~Sagittae is used as an example for massive irradiation and observed spectral features in the optical are fitted ...
    Description: thesis
    Keywords: 523 ; THK 000 ; THT 900 ; Spektren und Spektroskopie von Sternen {Astronomie} ; Doppelsterne {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 100 S.
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  • 6
    Publication Date: 2021-03-29
    Description: Supernovae are known to be the dominant energy source for driving turbulence in the interstellar medium. Yet, their effect on magnetic field amplification in spiral galaxies is still poorly understood. Analytical models based on the uncorrelated-ensemble approach predicted that any created field will be expelled from the disk before a significant amplification can occur. By means of direct simulations of supernova-driven turbulence, we demonstrate that this is not the case. Accounting for vertical stratification and galactic differential rotation, we find an exponential amplification of the mean field on timescales of 100Myr. The self-consistent numerical verification of such a fast dynamo is highly beneficial in explaining the observed strong magnetic fields in young galaxies. We, furthermore, highlight the importance of rotation in the generation of helicity by showing that a similar mechanism based on Cartesian shear does not lead to a sustained amplification of the mean magnetic field. This finding impressively confirms the classical picture of a dynamo based on cyclonic turbulence ...
    Description: thesis
    Keywords: 523 ; THR 000 ; THU 162 ; Elektrische und magnetische Felder {Sterne} ; Supernovae {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 109 S.
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  • 7
    Publication Date: 2021-03-29
    Description: The Sun is a star, which due to its proximity has a tremendous influence on Earth. Since its very first days mankind tried to "understand the Sun", and especially in the 20th century science has uncovered many of the Sun's secrets by using high resolution observations and describing the Sun by means of models. As an active star the Sun's activity, as expressed in its magnetic cycle, is closely related to the sunspot numbers. Flares play a special role, because they release large energies on very short time scales. They are correlated with enhanced electromagnetic emissions all over the spectrum. Furthermore, flares are sources of energetic particles. Hard X-ray observations (e.g., by NASA's RHESSI spacecraft) reveal that a large fraction of the energy released during a flare is transferred into the kinetic energy of electrons. However the mechanism that accelerates a large number of electrons to high energies (beyond 20 keV) within fractions of a second is not understood yet.
    Description: thesis
    Keywords: 523 ; TGC 560 ; TGC 440 ; Eruptionen, Flares {Astronomie: Sonne} ; Korpuskelstrahlung {Sonne}
    Language: English
    Type: monograph , publishedVersion
    Format: 122 S.
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  • 8
    Publication Date: 2021-03-29
    Description: The term "stellar activity" summarizes a number of phenomena on the stellar surface and in the stellar atmosphere. The origin of many of these phenomena are changes in the structure of the stellar magnetic field. While it is possible to directly observe different forms of activity on the Sun in great detail, this remains impossible for other stars. However, by analyzing the spectra of these stars, information about their activity can be obtained. This thesis addresses two aspects of activity: First, the X-ray emission from the positions of A-type stars and a possible mechanism to produce these X-rays and second, the chromospheric activity in the spectral range from late A- to late K-type stars. Since the dynamo, which is responsible for the activity of solar-like stars, emerges in the range of late A- to early F-type stars, this spectral range is of special interest for the understanding of the activity phenomena. To study the X-ray activity of A-type stars, their optical positions as given in the Bright Star Catalogue were compared with the positions of the X-ray sources listed in the ROSAT catalogs. The matching criteria for the ROSAT All-Sky Survey data were 90 arcseconds, 36 arcseconds for the pointing observations with the PSPC and 18 arcseconds for HRI data. Those stars which could be associated with X-ray sources were tested for indications of hidden late-type companions. Variations in the radial velocity, the proper motion, and the light curve were interpreted as signs for binarity...
    Description: thesis
    Keywords: 523 ; THP 000 ; THN 400 ; Thermodynamische Vorgänge in Sternen {Astronomie} ; Sternatmosphären {Astronomie}
    Language: English
    Type: monograph , publishedVersion
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  • 9
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    Unknown
    Univ. Potsdam
    Publication Date: 2021-03-29
    Description: The intergalactic medium is kept highly photoionised by the intergalactic UV background radiation field generated by the overall population of quasars and galaxies. In the vicinity of sources of UV photons, such as luminous high-redshift quasars, the UV radiation field is enhanced due to the local source contribution. The higher degree of ionisation is visible as a reduced line density or generally as a decreased level of absorption in the Lyman alpha forest of neutral hydrogen. This so-called proximity effect has been detected with high statistical significance towards luminous quasars. If quasars radiate rather isotropically, background quasar sightlines located near foreground quasars should show a region of decreased Lyman alpha absorption close to the foreground quasar. Despite considerable effort, such a transverse proximity effect has only been detected in a few cases...
    Description: thesis
    Keywords: 523 ; 550 ; TIE 400 ; TIE 900 ; Sonstige Sternensysteme {Astronomie} ; Spektren und Leuchtkraft von Sternsystemen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 144 S.
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  • 10
    Publication Date: 2021-03-29
    Description: In this work, nonanalytical line profiles for both cool and hot, dense atmospheres are added to the opacity calculations of the multipurpose stellar atmosphere code PHOENIX. Their influence on model atmospheres and synthetic spectra is studied. Model atmospheres are necessary in order to calculate synthetic spectra and to derive reliable stellar parameters. For cool, dense atmospheres, i.e., of objects of spectral type similar to and lower than latetype M, vanderWaals broadening is the most important pressure broadening mechanism. The spectra of these objects below ~1 micro-meter are dominated by alkali resonance lines. The profiles of the alkali resonance lines, especially of Na ID and KI, determine mostly the pseudo continuum in this wavelength range. Up to this work, classical analytical impact approximated alkali near line wing profiles perturbed by H2, He, and HI, which are the dominant perturbing particles, have been applied. In this work, various nonanalytical alkali line profiles, including far line wing and near line wing profiles, for Na I D, Li I, KI, and Rb I are included in order to describe the strong alkali absorption features which are characteristic for latetype dwarfs. For the alkali resonance line profiles, different theoretical approaches were used describing the far and near line wings. Non analytical alkali profiles for the far and near line wings perturbed by H2 and He are provided in the unified semiclassical theory...
    Description: thesis
    Keywords: 523 ; 550 ; THN 400 ; THK 000 ; Sternatmosphären {Astronomie} ; Spektren und Spektroskopie von Sternen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 156 S.
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  • 11
    Publication Date: 2021-03-29
    Description: Giacconi et al. (1962) discovered a diffuse cosmic X-ray background with rocket experiments when they searched for lunar X-ray emission. Later satellite missions found a spectral peak in the cosmic X-ray background at ~30 keV. Imaging X-ray satellites such as ROSAT (1990-1999) were able to resolve up to 80% of the background below 2 keV into single point sources, mainly active galaxies. The cosmic X-ray background is the integration of all accreting super-massive (several million solar masses) black holes in the centre of active galaxies over cosmic time. Synthesis models need further populations of X-ray absorbed active galaxy nuclei (AGN) in order to explain the cosmic X-ray background peak at ~30 keV. Current X-ray missions such as XMM-Newton and Chandra offer the possibility of studying these additional populations...
    Description: thesis
    Keywords: 523 ; 550 ; TBK 000 ; TIE 900 ; Hochenergieastronomie ; Sonstige Sternensysteme {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 226 S.
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  • 12
    Publication Date: 2021-03-29
    Description: This thesis describes two main projects; the first one is the optimization of a hierarchical search strategy to search for unknown pulsars. This project is divided into two parts; the first part (and the main part) is the semi-coherent hierarchical optimization strategy. The second part is a coherent hierarchical optimization strategy which can be used in a project like Einstein@Home. In both strategies we have found that the 3-stages search is the optimum strategy to search for unknown pulsars. For the second project we have developed a computer software for a coherent Multi-IFO (Interferometer Observatory) search. To validate our software, we have worked on simulated data as well as hardware injected signals of pulsars in the fourth LIGO science run (S4). While with the current sensitivity of our detectors we do not expect to detect any true Gravitational Wave signals in our data, we can still set upper limits on the strength of the gravitational waves signals...
    Description: thesis
    Keywords: 523 ; 550 ; TFA 000 ; Relativistische Astrophysik, Gravitation
    Language: English
    Type: monograph , publishedVersion
    Format: 135 S.
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  • 13
    Publication Date: 2021-03-29
    Description: Our dynamic Sun manifests its activity by different phenomena: from the 11-year cyclic sunspot pattern to the unpredictable and violent explosions in the case of solar flares. During flares, a huge amount of the stored magnetic energy is suddenly released and a substantial part of this energy is carried by the energetic electrons, considered to be the source of the nonthermal radio and X-ray radiation. One of the most important and still open question in solar physics is how the electrons are accelerated up to high energies within (the observed in the radio emission) short time scales. Because the acceleration site is extremely small in spatial extent as well (compared to the solar radius), the electron acceleration is regarded as a local process. The search for localized wave structures in the solar corona that are able to accelerate electrons together with the theoretical and numerical description of the conditions and requirements for this process, is the aim of the dissertation...
    Description: thesis
    Keywords: 523 ; TGC 765 ; Korona {Astronomie: Sonne}
    Language: English
    Type: monograph , publishedVersion
    Format: 109 S.
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  • 14
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    Unknown
    Univ. Potsdam
    Publication Date: 2021-03-29
    Description: Our Solar system contains a large amount of dust, containing valuable information about our close cosmic environment. If created in a planet's system, the particles stay predominantly in its vicinity and can form extended dust envelopes, tori or rings around them. A fascinating example of these complexes are Saturnian rings containing a wide range of particles sizes from house-size objects in the main rings up to micron-sized grains constituting the E ring. Other example are ring systems in general, containing a large fraction of dust or also the putative dust-tori surrounding the planet Mars. The dynamical life'' of such circumplanetary dust populations is the main subject of our study...
    Description: thesis
    Keywords: 523 ; TGL 800 ; Interplanetarer Staub {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 115, 10 Bl.
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  • 15
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 523 ; TGC 800 ; TGC 800 ; Magnetfelder {Astronomie: Sonne}
    Language: English
    Type: monograph , publishedVersion
    Format: 88 Bl.
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  • 16
    Publication Date: 2021-03-29
    Description: I perform and analyse the first ever calculations of rotating stellar iron core collapse in {3+1} general relativity that start out with presupernova models from stellar evolutionary calculations and include a microphysical finite-temperature nuclear equation of state, an approximate scheme for electron capture during collapse and neutrino pressure effects. Based on the results of these calculations, I obtain the to-date most realistic estimates for the gravitational wave signal from collapse, bounce and the early postbounce phase of core collapse supernovae.
    Description: thesis
    Keywords: 523 ; THU 162 ; TFA 000 ; Supernovae {Astronomie} ; Relativistische Astrophysik, Gravitation
    Language: English
    Type: monograph , publishedVersion
    Format: 291 S
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  • 17
    Publication Date: 2021-03-29
    Description: Die H.E.S.S. Kollaboration betreibt ein stereoskopisches System aus vier großen abbildenden Cherenkov-Teleskopen für den Nachweis sehr hochenergetischer Gamma-Strahlung (VHE; 〉 100 GeV). In dieser Arbeit wird über den Nachweis zweier neuer Quellen sehr hochenergetischer Gamma-Strahlung mit den H.E.S.S.-Teleskopen berichtet. Die extragalaktische Quelle 1ES0347-121 gehört zur Klasse der BL Lac Objekte und ist der aktive Kern einer entfernten Galaxie. Detektiert mit einer Signifikanz von mehr als 10 Standard-Abweichungen, ist es die bisher am weitesten entfernte Quelle sehr hochenergetischer Gamma-Strahlung (Rotverschiebung z = 0.1880). Ihr Energiespektrum läßt sich gut durch ein Potenzgesetz mit Photonindex Gamma = 3.08 +/- 0.23_stat +/- 0.1_sys beschreiben. Der integrale Fluss I(E 〉250GeV) entspricht ~2% des Flusses des Krebsnebels. Mit Hilfe des hochenergetische Gamma-Strahlungsspektrum von 1ES 0347-121 werden Einschränkungen auf die Dichte des extragalaktischen diffusen Photonfeldes bestimmt (s. unten). Bei der zweiten Quelle handelt es sich um die ausgehnte Quelle HESS J1023-577, die mit dem jungen, massiven Sternenhaufen Westerlund 2 und dessen Umgebung assoziert wird. Junge und massereichen Sterne strahlen starke Sternenwinde ab, die durch Schockbeschleunigung hochenergetische Teilchen produzieren können. Zum erstenmal konnte eine Quelle sehr hochenergetischer Gamma-Strahlung mit einer solchen Umgebung sicher identifiziert werden. Das Energiespekrum reicht von ~400GeV bis ~20TeV und läßt sich gut durch eine Potenzgesetz mit Photonindex Gamma=2.53 +/- 0.16_stat +/- 0.1_syst beschreiben.
    Description: thesis
    Keywords: 523 ; TIE 400 ; TBK 000 ; TCE 240 ; Spektren und Leuchtkraft von Sternsystemen {Astronomie} ; Hochenergieastronomie ; Röntgen- und Gammateleskope {Astronomische Instrumente}
    Language: English
    Type: monograph , publishedVersion
    Format: 123 S.
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  • 18
    Publication Date: 2021-03-29
    Description: Bei von Sternen verursachten Mikrolinsen-Ereignissen beobachtet man meist symmetrische Lichtkurven einer einzelnen Linse oder asymmetrische Lichtkurven (oftmals mit Kaustik-Crossing), die durch Doppel-Linsen hervorgerufen werden. Im Prinzip kann aus der Zahl der gemessenen unsymmetrischen Ereignisse der Anteil der Doppelstern-Systeme in Abhängigkeit vom Winkelabstand abgeschätzt werden. Allerdings kann auch ein Doppelsystem Lichtkurven erzeugen, die gut mit einer Einzellinsen-Lichtkurve gefittet werden können. Die gilt insbesondere bei lückenhafter Messung oder grossen Messfehlern. In dieser Arbeit wird für verschiedene Beobachtungsbedingungen untersucht, wie häufig Lichtkurven, die von Doppellinsen mit unterschiedlichen Abständen erzeugt werden, gut mit Einzellinsen-Lichtkurven gefittet werden können und damit fehlinterpretiert werden. Es wurde herausgefunden, dass der Anteil fehlinterpretierter Lichtkurven stark von der Separation der Komponenten abhängig ist: das Minimum liegt zwischen 2 A.E. and 5 A.E. , wobei der Anteil immer noch 5% beträgt...
    Description: thesis
    Keywords: 523 ; THX 100 ; TDC 000 ; Detektionsmethoden {Astronomie: Extrasolare Planetensysteme} ; Astrometrie
    Language: English
    Type: monograph , publishedVersion
    Format: 153 S.
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  • 19
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    Unknown
    Univ. Potsdam
    Publication Date: 2021-03-29
    Description: Seit ihrer Entdeckung im Jahre 1610 durch Galileo Galilei faszinieren die Ringe des Saturn sowohl Laien als auch Experten. Planetare Ringe finden sich in der Äquatorialebene aller vier Riesenplaneten unseres Sonnensystems und sind eines der eindruckvollsten Beispiele granularer Gase. Darunter gehören die Saturnringe zu den Bekanntesten. Sie bergen eine Vielzahl von Strukturen und erstrecken sich über mehr als 240 000 Kilometer, wobei sie weit weniger als 100 Meter dick sind. Unzählige kleinerer Körper bewegen sich auf leicht exzentrischen Kepler-ähnlichen Bahnen um den Zentralplaneten und bestehen dabei vorwiegend aus Eis. Die seit Juli 2004 im Orbit um den Saturn befindliche Raumsonde Cassini liefert atemberaubende Bilder und Daten, die nicht nur neue Erkenntnisse liefern, sondern auch alte Fragestellungen neu aufleben lassen. Dazu gehört z.B. die Frage nach dem Ursprung und den Entwicklungsstufen planetarer Ringe. Kürzlich, im äusseren A-Ring entdeckte Kleinmonde, deren Existenz schon viel früher postuliert wurde, weisen auf eventuell stattfindende Wachstumsprozesse hin. Da sich planetare Ringe jedoch hauptsächlich innerhalb der sogenannten Roche-Zone des jeweiligen Planeten befinden, ist ein effektives, allein auf gravitativen Wechselwirkungen beruhendes Größenwachstum nicht zu erwarten. Der Einfluß von Teilchenadhäsion auf diese Prozesse ist bis dato fraglich.
    Description: thesis
    Keywords: 523 ; TGE 590 ; TGG 650 ; Planetenringe {Astronomie} ; Saturn {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 106 S.
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  • 20
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    Unknown
    Univ. Hamburg
    Publication Date: 2021-03-29
    Description: Unter stellarer Aktivität werden eine Reihe von Phänomenen in den unterschiedlichen Atmosphärenschichten zusammengefasst, die eng mit dem Magnetfeld des einzelnen Sterns verbunden sind. Da eine direkte Auflösung der Sternoberfläche, wie uns dies bei der Sonne möglich ist, für aktive Sterne noch in ferner Zukunft liegt, können diese Phänomene im Normalfall nicht direkt beobachtet werden. Es können aber aus der Spektralanalyse indirekt Informationen über die Aktivität eines Sterns gewonnen werden. Die vorliegende Arbeit beschäftigt sich mit koronaler und chromosphärischer Aktivität von mittleren und späten M Sternen und deren Nachweis und Analyse in UVES Echelle-Spektren von 3030 bis 3880 und 4580 bis 6680 A. Dabei widmet sich der erste Teil der Arbeit dem Nachweis der verbotenen koronalen Fe XIII Linie bei 3388 A. Das mehrere Millionen Kelvin heiße koronale Gas wird normalerweise - und am leichtesten - im Röntgenbereich beobachtet...
    Description: thesis
    Keywords: 523 ; THK 000 ; THN 400 ; Spektren und Spektroskopie von Sternen {Astronomie} ; Sternatmosphären {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 101 S.
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  • 21
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    Univ. Hamburg
    Publication Date: 2021-03-29
    Description: The high ionization state of the intergalactic medium (IGM) is maintained by the metagalactic UV background radiation. This ionizing radiation field is supposed to be the integrated radiation of quasars and young star-forming galaxies, which is reprocessed and attenuated by the intergalactic gas. Since the UV background is inaccessible to direct observations, it is impossible to test theoretical predictions of its spectral energy distribution in great detail. However, constraints can be derived from studies of metal absorption systems, the HI Lyman alpha opacity, or the HeII Lyman alpha forest, respectively. Observations of the HeII/HI column density ratio eta particularly probe the variations of the UV background. Since unobscured quasars permitting observation of HeII absorption are rare, there are only two lines of sight, towards the quasars HE2347-4342 and HS1700+6416, where the HeII Lyman alpha forest can be resolved. This work presents a study of the UV background at redshifts z 〈 3 investigating the HeII absorption towards the quasars HS1700+6416 (z = 2.72), which provides the second line of sight where the HeII Lyman alpha forest is resolved. The numerous metal line systems detected in the spectra of this QSO are studied in order to avoid biases due to unrecognized metal line absorption in the HeII forest. In this connection, several shapes of the ionizing radiation are tested for each system. The majority of the considered systems, in particular those at z 〉 2, is best reproduced with an ionizing radiation similar to the UV background of Haardt & Madau (2001), where the HeII break, formally located at 4 Ryd, is shifted to lower energies (~ 3 Ryd), probably due to the opacity of the higher HeII Lyman series lines ...
    Description: thesis
    Keywords: 523 ; TIE 400 ; TBI 000 ; Spektren und Leuchtkraft von Sternsystemen {Astronomie} ; Ultraviolett-Astronomie
    Language: English
    Type: monograph , publishedVersion
    Format: 131 S.
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  • 22
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 523 ; TIE 900 ; TBG 000 ; TC 200 ; Sonstige Sternensysteme {Astronomie} ; Infrarot-Astronomie ; Astronomische Beobachtungen vom Weltraum aus
    Language: English
    Type: monograph , publishedVersion
    Format: 181 S.
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  • 23
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    Unknown
    Univ. Potsdam
    Publication Date: 2021-03-29
    Description: Sterne entstehen im Inneren von turbulenten Molekülwolken, die unter dem Einfluss ihrer eigenen Gravitation fragmentieren und kollabieren. So entsteht ein Sternhaufen aus hundert oder mehr Objekten. Der Sternentstehungsprozess wird durch das Wechselspiel von Überschallturbulenz und Gravitation reguliert. In dieser Arbeit werden verschiedene Eigenschaften solcher Sternhaufen, die mit Hilfe von numerischen Simulationen modelliert wurden, untersucht und mit Beobachtungsdaten verglichen. Dabei handelt es sich sowohl um Eigenschaften einzelner Protosterne, als auch um statistische Parameter des Sternhaufens als Ganzes...
    Description: thesis
    Keywords: 523 ; TIC 000 ; TEG 000 ; Sternhaufen {Astronomie} ; Kosmogonie {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 138 S.
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  • 24
    facet.materialart.
    Unknown
    Univ. Potsdam
    Publication Date: 2021-03-29
    Description: In dieser Dissertation nutze ich den Gravitationslinseneffekt, um eine Reihe von kosmologischen Fragen zu untersuchen. Der Laufzeitunterschied des Gravitationslinsensystems HE1104-1805 wurde mit unterschiedlichen Methoden bestimmt. Zwischen den beiden Komponenten erhalte ich einen Unterschied von Delta_t(A-B) = -310 +-20 Tagen (2 sigma Konfidenzintervall). Außerdem nutze ich eine dreijährige Beobachtungskampagne, um den Doppelquasar Q0957+561 zu untersuchen. Die beobachteten Fluktuationen in den Differenzlichtkurven lassen sich durch Rauschen erklären, ein Mikrogravitationslinseneffekt wird zur Erklärung nicht benötigt...
    Description: thesis
    Keywords: 523 ; TEG 400 ; TFA 000 ; Endstadien von Sternen {Astronomie: Kosmogonie} ; Relativistische Astrophysik, Gravitation
    Language: English
    Type: monograph , publishedVersion
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  • 25
    facet.materialart.
    Unknown
    Univ. Hamburg
    Publication Date: 2021-03-29
    Description: The Levantine Basin - a seismic investigation of the crustal structure and the evolution of the Messinian evaporites ABSTRACT This work presents an analysis of the crustal structure of the Levantine Basin, based on refraction seismic and gravity data, and an analysis of the evolution of the Messinian evaporites, based on reflection seismic data. Forward and inverse modelling of refraction seismic traveltimes along two profiles yielded 2-D velocity-depth-profiles. Gravity modelling along these profiles provided further information on the crustal structure. A great number of reflection seismic profiles was used for the analysis of the Messinian evaporites, which allowed an exhaustive investigation of the geometry of the evaporite layers, depositional phases of the evaporites and of their structural evolution. The Levantine Basin is located in the Southeastern Mediterranean Sea. The basin and its margin are key areas for the understanding of the geodynamic evolution of the Eastern Mediterranean. The opening of the Levantine Basin is closely related to the opening of the Neo-Tethys. Many geodynamic reconstructions of this area have been developed, but the key question, the origin of the crust, remained open. The Levantine Basin is also a world class site for studying the initial stages of salt tectonics driven by differential sediment load. The Messinian evaporites are comparatively young (deposited during the Messinian Salinity Crisis 5.9 - 5.3 Ma ago), the sediment load varies along the basin margin, they are hardly tectonically overprinted, and the geometry of the basin and the overburden is well-defined...
    Description: thesis
    Keywords: 550 ; TSF 000 ; VAE 820 ; VEF 000 ; Südeuropa und Mittelmeergebiet {Geophysik} ; Sedimentationsbecken als Erdkrustentypen {Geologie} ; Südeuropa und Mittelmeergebiet {Geologie}
    Language: English
    Type: monograph , publishedVersion
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  • 26
    Publication Date: 2021-03-29
    Description: Eine der entscheidenden Hauptquellen für Unsicherheiten von Klimaprojektionen ist, wie sensitiv das Klimasystem auf Änderungen der Strahlungsbilanz der Erde reagiert. Angesichts des kontinuierlichen Anstiegs der atmosphärischen Treibhausgaskonzentrationen ist die Einschränkung des Unsicherheitsbereichs dieser Sensitivität von entscheidender Bedeutung. Ein häufig verwendetes Maß zur Beschreibung dieser charakteristischen Kenngröße von Klimamodellen ist die sogenannte Klimasensitivität, definiert als die Gleichgewichtsänderung der simulierten globalen Mitteltemperatur, welche sich aus einer Verdoppelung des atmosphärischen CO2-Gehalts ergibt...
    Description: thesis
    Keywords: 551.6 ; TWC 100 ; TVH 100
    Language: English
    Type: monograph , publishedVersion
    Format: 107 S.
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  • 27
    Publication Date: 2021-03-29
    Description: Central Asia is characterized by a number of spectacular tectonic units such as the Tibetan Plateau, the Tien Shan intra-continental mountain belt and the Altyn Tagh strike-slip fault. Deformation of the lithosphere of these units is not well understood. In this dissertation, an attempt is made to answer the following tectonic questions: To what extent do the tectonic units formed in the upper crust in the course of the convergence between India and Eurasia weaken the underlying lithosphere? How is the Tibetan Plateau gravita-tionally compensated along its northern boundary? Do the Altyn Tagh and/or West Kunlun faults persist as vertical strike-slips throughout the crust and mantle lithosphere, thus representing a fundamental plate boundary? Which dynamic processes in the crust and mantle of the Tien Shan are responsible for intra-continental mountain building? What characterizes the local stress field in the Tien Shan and what causes the deformation of these mountains? To answer these questions, the elastic plate theory is used to interpret gravity and topography data, and in turn to derive specific characteristics of the lithospheric structure in Central Asia. Theoretical deflection of the elastic plate or plates were calculated using the 3D and 2D finite-difference methods. Variable-rigidity elastic plates are subjected to vertical and horizontal loads, shear forces, and terminal bending moments. Surface topo-graphic data from the Topo30 dataset is used as vertical surface loading to calculate the flexure of the elastic lithosphere...
    Description: thesis
    Keywords: 551.8 ; 622.15 ; 551 ; 550 ; VAE 400 ; VEK 000 ; TQA 000 ; TSK 000 ; VAE 400 ; VEK 000 ; TQA 000 ; TSK 000 ; Tektogenese {Geologie} ; Zentralasien {Geologie} ; Gravimetrische Verfahren {Geophysik} ; Zentralasien {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 136 Bl.
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  • 28
    Publication Date: 2021-03-29
    Description: Mit der Annahme schwacher Anisotropie vereinfachen sich die Lösungen der Modellierung und Inversion anisotroper Medien. Üblicherweise werden Perturbation-Methoden zur Beschreibung der Wellen-Ausbreitung in schwach anisotropen Medien verwendet, ein anisotropes Medium wird ersetzt durch ein isotropes Hintergrundmodell. Hier lässt sich die Wellenausbreitung leicht behandeln und die anisotropen Effekte werden mit Hilfe der Perturbations-Methode berechnet. Um die jeder Perturbations-Methode anhaftenden Fehler zu minimieren, sollte das gewählte isotrope Hintergrundmedium dem korrektem anisotropen Medium so ähnlich wie möglich sein. Zur Bestimmung des optimalen isotropen Mediums wurden Formeln für sektoriell best angepasste isotrope Medien entwickelt. Deren Anwendung wurde anhand von Modellen mit transversal isotropen und orthorombischen Symmetrien gezeigt...
    Description: thesis
    Keywords: 551.22 ; 550 ; Seismische Wellen {Geophysik} ; Übertragungsmedien {Seismologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 134 S.
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  • 29
    Publication Date: 2021-03-29
    Description: Die stärksten Erdbeben treten an Subduktionszonen auf, so z.B. das stärkste instrumentell jemals gemessene Erdbeben vom 22. Mai 1960 mit einer Magnitude von 9,5 Mw in Süd Chile. In dieser Arbeit werden lokal gewonnene seismologische Daten aus dem zentralen Bereich des 1960er-Bebens vorgestellt. Das seismologische Netzwerk umfasste den chilenischen Forearc zwischen Tiefseegraben und den vulkanischen Bogen zwischen 41,5ʿ-43,5ʿS und überdeckte sowohl die Insel Chiloé als auch die Nord-Süd-streichende Liquiñe-Ofqui Störungszone (LOFZ). Zwischen November 2004 und Oktober 2005 konnten 364 lokale Ereignisse registriert werden. Die gewonnen Aufzeichnungen erlauben Aussagen sowohl über das aktuelle Spannungsfeld im Forearc als auch über das lokale Geschwindigkeitsmodell und die Geometrie der subduzierten Benioff-Zone.
    Description: thesis
    Keywords: 551.22 ; 551.136 ; 550 ; TSX 500 ; VAE 700 ; Chile {Geophysik} ; Bau der Erdkruste großer Regionen der Erde {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 134 S.
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  • 30
    Publication Date: 2021-03-29
    Description: The Aggregated Carbon Cycle, Atmospheric Chemistry, and Climate model (ACC2) (Tanaka and Kriegler et al., 2007a) describes physical-biogeochemical processes in the Earth system at a global-annual-mean level. Compared to its predecessors NICCS (Hooss, 2001) and ICM (Bruckner et al., 2003), ACC2 adopts more detailed parameterizations of atmospheric chemistry involving a set of agents (CO2, CH4, N2O, O3, SF6, 29 species of halocarbons, sulfate aerosols (direct effect), carbonaceous aerosols (direct effect), all aerosols (indirect effect), stratospheric H2O, OH, and pollutants NOx, CO, and VOC). In contrast to the Impulse Response Function (IRF) approaches in the predecessor models, ACC2 uses DOECLIM (Kriegler, 2005), a land-ocean Energy Balance Model (EBM), to calculate temperature change. The carbon cycle is described by box models based on the IRF approach. A temperature feedback is newly implemented to ocean and land CO2 uptake. The most novel aspect of ACC2 is its inverse estimation, the first attempt to estimate uncertain parameters simultaneously for the carbon cycle, atmospheric chemistry, and climate system by taking their interactions into account. Theoretical underpinning of the ACC2 inversion is the probabilistic inverse estimation theory (Tarantola, 2005), which characterizes the ACC2 inversion as an integration of the existing Earth system knowledge. This includes parameter estimates, observational databases, reconstructions, and physical-biogeochemical laws...
    Description: thesis
    Keywords: 551.5 ; TUA 500 ; TOY 000 ; TVA 200 ; VJD 000 ; Meteorologische Modelle ; Energiebilanzen in der Geodynamik {Geophysik} ; Zusammensetzung der Atmosphäre {Meteorologie} ; Geochemie der Atmosphäre
    Language: English
    Type: monograph , publishedVersion
    Format: 300 S.
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  • 31
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551.22 ; 550 ; TOH 510 ; Charakteristik seismischer Störungen {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 157 S.
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  • 32
    Publication Date: 2021-03-29
    Description: In this thesis the thermo-hydraulic conditions of a seismically active zone have been investigated by means of surface and subsurface investigations, borehole studies and numerical modeling. European research activities in the Gulf of Corinth have been targeted for obtaining data on earthquake sources and fault mechanics and for investigating the role of faults on fluid flow in this seismically active area. In this context, the DFG funded a project aimed at the exploration of the thermo-hydraulic conditions in the area near Aigion and the southern graben shoulder of the northern Peloponnesus including the determination of surface heat flow in a 1000 m deep borehole, which is the scope of this work. First, due to a lack of geological information, a detailed investigation of the geological and tectonical situation was made. Secondly, the hydraulic parameters of the different lithological formations and of the hydraulic behavior of normal faults were determined...
    Description: thesis
    Keywords: 551.14 ; 550 ; TOH 400 ; TOH 510 ; TSF 300 ; Übertragungsmedien {Seismologie} ; Charakteristik seismischer Störungen {Geophysik} ; Griechenland und griechische Inseln {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 162 S.
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  • 33
    facet.materialart.
    Unknown
    Univ. Potsdam
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551.22 ; 550 ; TOH 200 ; Seismische Vorhersagen {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 230 S.
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  • 34
    Publication Date: 2021-03-29
    Description: Aim of the study was to test the capability of multiple trace gas analyses for the assessment of regional carbon budgets. Therefore, air samples were taken by airborne and ground level activities during several field campaigns within Europe. Basic elements for the data acquisition were the development of an adapted sampling system and of an enhanced investigation strategy. By the study important processes like insufficient mixing and advection were identified which could seriously effect the measurements and thus the calculated budgets. The concluding results prompt for improvements regarding appropriate flux estimation techniques and application of the enhanced investigation strategy within a frame of combined measurement activities.
    Description: thesis
    Keywords: 551.5 ; 550 ; TUA 700 ; VJI 000 ; VJD 100 ; TVA 210 ; Verfahren zur Untersuchung der freien Atmosphäre {Meteorologie} ; Geochemische Kreislaufmodelle ; Geochemie der Ungestörten Atmosphäre ; Chemische Zusammensetzung der Atmosphäre {Meteorologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 344 S.
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  • 35
    Publication Date: 2021-03-29
    Description: The southeastern Mediterranean Sea and the northern section of Egypt constitutes one of the most complex tectonic areas in the Mediterranean. This study is an attempt to achieve a better understanding of tectonics, and geodynamical processes along a complex tectonization region. These include crustal structure, thickness of sediments, transition between oceanic and continental crust and regional integrated model of the gravity field observed. A wide range of field work from the geophysical data has been acquired and used in this study with respect to the gravity and magnetic data as well as the results of deep seismic soundings. A comparison between the marine gravity data and the gravity data derived from satellite altimetry was made to ensure that the marine gravity data compiled from different marine surveys were compatible...
    Description: thesis
    Keywords: 622.15 ; 551.1 ; 550 ; TSZ 100 ; VAE 880 ; TSZ 100 ; VAE 880 ; Atlantischer Ozean {Geophysik} ; Passive und aktive Kontinentalränder {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 184 Bl.
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  • 36
    Publication Date: 2021-03-29
    Description: Die P- und S-Wellen-Geschwindigkeitsstruktur der D Schicht unter dem südwestlichen Pazifik wurde mittels kurzperiodischer Daten von 12 Tiefbeben in der Tonga-Fiji-Region untersucht, die vom J-Array und Hi-net-Array in Japan registriert wurden. Es wurde für Punktstreuer und ebene Schichten migriert, um schwache Signale zu extrahieren, die an relativ kleinräumigen Heterogenitäten des unteren Mantels entstehen. Um eine höhere Auflösung zu erzielen, wurde die Double Array-Methode (DAM) verwendet, die Empfängerarray und Quellarray gleichzeitig nutzt. Hierbei ist auch das Phase-Weighted Stack-Verfahren angewendet worden, um inkohärentes Rauschen zu reduzieren und somit schwache kohärente Signale aus dem unteren Mantel aufzulösen. Das Ergebnis der Ebenen-Schichten-Methode (RWB) zeigt, dass sich in der D-Schicht negative Geschwindigkeitsdiskontinuitäten mit P-Wellen Geschwindigkeitskontrasten von höchstens 1 % in den Tiefen von 2520 km und 2650 km befinden. Zusätzlich befindet sich eine positive Geschwindigkeitsdiskontinuitäten in der Tiefe von 2800 km. Bei den S Wellen treten Geschwindigkeitsdiskontinuitäten in einer Tiefe von etwa 2550 km und 2850 km auf. Die scheinbare Verschiebung (50 km) der S-Wellen-Geschwindigkeitsdiskontinuität in der Tiefe von 2850 km deutet darauf hin, daß die S-Wellen-Geschwindigkeitsreduktion im unteren Mantel 2-3 mal stärker ist als die P- Wellen-Geschwindigkeitsreduktion...
    Description: thesis
    Keywords: 551.22 ; 550
    Language: English
    Type: monograph , publishedVersion
    Format: 145 S.
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  • 37
    Publication Date: 2021-03-29
    Description: Collisions of black holes and neutron stars, named mixed binaries in the following, are interesting because of at least two reasons. Firstly, it is expected that they emit a large amount of energy as gravitational waves, which could be measured by new detectors. The form of those waves is expected to carry information about the internal structure of such systems. Secondly, collisions of such objects are the prime suspects of short gamma ray bursts. The exact mechanism for the energy emission is unknown so far...
    Description: thesis
    Keywords: 523 ; TEG 400 ; Endstadien von Sternen {Astronomie: Kosmogonie}
    Language: English
    Type: monograph , publishedVersion
    Format: 205 S.
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  • 38
    facet.materialart.
    Unknown
    Univ. Potsdam
    Publication Date: 2021-03-29
    Description: Strong damped Lyman alpha absorption (DLA) lines seen spectra of distant quasar are believed to arise when the sight line to the quasar goes trough the disc of a galaxy or a proto galaxy. Most of the neutral matter in the universe is contained in these clouds of neutral hydrogen that cause the absorption lines. Hence these DLAs are reservoirs for the formation of stars and galaxies throughout the universe. Despite intensive efforts over more than two decades only few galaxies responsible for the DLAs have been found. The problem is that the galaxies that harbour the neutral clouds are not necessarily bright, and selecting galaxies based on absorption lines could well select different types of galaxies than found in large surveys. If we are to understand how galaxies form out of neutral gas clouds it is essential to locate the galaxies in which DLAs reside ...
    Description: thesis
    Keywords: 523 ; TIE 900 ; TIE 400 ; Sonstige Sternensysteme {Astronomie} ; Spektren und Leuchtkraft von Sternsystemen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 187 S.
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  • 39
    Publication Date: 2021-03-29
    Description: Context Extragalactic absorbers with column densities exceeding NH I 〉 2 × 1020 hydrogen atoms cm-2 are generally termed damped Ly alpha (DLA) systems. The absorbers are basically comprised of predominantly neutral gas, which is an essential prerequisite for the formation of stars. The spectroscopy of absorbers offers the best possibility to study the chemical composition of the supposed equivalents of the interstellar medium of local galaxies at an earlier stage of cosmic evolution. Absorbers in the sub-DLA range with NH I 〉 1019 cm-2 may consist of predominantly neutral gas, if the cosmic UV background is reduced...
    Description: thesis
    Keywords: 523 ; TII 040 ; Physikalische Eigenschaften {Astronomie: Interstellare Materie}
    Language: English
    Type: monograph , publishedVersion
    Format: 68 S.
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  • 40
    Publication Date: 2021-03-29
    Description: With the last generation of X-ray satellites, such as XMM-Newton and Chandra, our knowledge about the X-ray properties of Active Galactic Nuclei (AGN) has greatly improved. Detailed spectroscopy and long-term observations of hundreds of kilo-seconds have provided new insights into the mechanisms of X-ray production, its modification by intervening matter, and X-ray variability. In this thesis I present radiative transfer modeling of AGN in the Far-UV and X-ray range. The modeling considers several aspects of the observed X-ray properties: the Compton reflection/reprocessed component, X-ray variability and flares, and the effects of the warm absorber. For the X-ray reprocessing, I investigate in detail the magnetic flare model assuming solar-like magnetic reconnections above the accretion disk
    Description: thesis
    Keywords: 523 ; TEG 440 ; TBK 000 ; Schwarze Löcher {Astronomie: Kosmogonie} ; Hochenergieastronomie
    Language: English
    Type: monograph , publishedVersion
    Format: 151 S.
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  • 41
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    Unknown
    Univ. Potsdam
    Publication Date: 2021-03-29
    Description: We investigate the rotational and thermal properties of star-forming molecular clouds using hydrodynamic simulations. Stars form from molecular cloud cores by gravoturbulent fragmentation. Understanding the angular momentum and the thermal evolution of cloud cores thus plays a fundamental role in completing the theoretical picture of star formation. This is true not only for current star formation as observed in regions like the Orion nebula or the ?-Ophiuchi molecular cloud but also for the formation of stars of the first or second generation in the universe...
    Description: thesis
    Keywords: 523 ; TEG 000 ; Kosmogonie {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 149 S.
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  • 42
    Publication Date: 2021-03-29
    Description: PHOENIX has been used to calculate model atmospheres of classical novae in the X-ray spectral range. The models account for an expanding, one-dimensional spherically symmetric medium in full non-local thermodynamic equilibrium. Nova atmospheres have been modeled with PHOENIX since the early 90's to fit the early nova spectra in the ultraviolet and infrared spectral ranges. In this work the PHOENIX-code has been enhanced to also model X-ray spectra. This was accomplished by accounting for atomic data and physical processes. The synthetic spectra were compared to observations from the LETGS onboard the CHANDRA X-ray satellite. The template is the observation of nova V4743 Sagittarii in March 2003. The spectrum is very spectacular because of the nova brightness and CHANDRA's spectral resolution. Further observations from July2003, September 2003, and February 2004 were taken. Models with solar and non-solar abundances have been calculated and the synthetic spectra have been fitted to the four observations. The fits were used to discuss discrepancies between models and observations. The effective temperature of the atmosphere, the hydrogen column density, and the abundances ofhelium, carbon, nitrogen, oxygen, and iron in the shell were determined by the fits. It was examined how the parameters evolve with time. With the models the atmosphere structure and NLTE effects were determined. The models were compared to the previous nova model atmospheres from PHOENIX ...
    Description: thesis
    Keywords: 523 ; THU 155 ; THN 400 ; Eruptionsveränderliche {Astronomie: Sterne} ; Sternatmosphären {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 196 S.
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  • 43
    Publication Date: 2021-03-29
    Description: The Sun shows a variety of transient surface features which are summarized as solar activity. Activity phenomena, apparently similar to the solar case, are also observed on stars other than the Sun. Stellar activity is closely related to magneto-hydrodynamic processes in a stars̉ convection zone. A dynamo is believed to operate in the outer convection zone of solar-like stars, generating magnetic fields by complex motions of the convecting plasma under the influence of rotation. Differential (i.e. non-rigid) rotation of the stellar surface is an important indicator of the overall dynamics of a stars̉ outer convection zone. Sunspots are a conspicuous token of solar activity; dark spots can also be observed on the surface of stars other than the Sun. To which degree starspots are analogues of sunspots is presently only poorly known; the processes governing their lifetime and structure are largely unexplored. Doppler imaging overcomes the diffraction-limitations of direct and interferometric imaging techniques by making use of information that is modulated into a star’s spectrum due to its rotation. Doppler imaging is currently the only method to produce well-resolved images of solar-like stars. After a selective review of the observational and theoretical foundation,
    Description: thesis
    Keywords: 523 ; THN 400 ; THE 400 ; Sternatmosphären {Astronomie} ; Rotation, Eigenbewegung {Astronomie: Sterne}
    Language: English
    Type: monograph , publishedVersion
    Format: 187 S.
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  • 44
    facet.materialart.
    Unknown
    Univ. Potsdam
    Publication Date: 2021-03-29
    Description: Der Aralsee ist ein intrakontinental gelegenes endorheisches Gewässer fernab von ozeanischen Einflüssen, welches ein exzellentes sedimentäres Archiv für hochauflösende Paläoklimastudien in Zentralasien darstellt. In der vorliegenden Studie wurden umfangreiche palynologische, mikrofazielle und geochemische Analysen anhand von mehreren Bohrkernen aus der Chernyshov-Bucht im NW des heutigen Großen Aralsees durchgeführt. Die vollständigste der erbohrten Sequenzen weist dabei eine Länge von 11 m auf und beinhaltet näherungsweise die letzten 2000 Jahre des Holozän. 〈br〉〈br〉 Die hochauflösenden palynologischen Analysen der Studie, welche sowohl die Untersuchung von Dinoflagellatenzysten als auch Pollen beinhaltet, zeugen von einschneidenden Umweltveränderungen im Aralsee und seinem Einzugsgebiet. Die Untersuchung von Diversität und räumlicher Verbreitung der fossilen Dinoflagellatenzysten vermittelt dabei ein genaues Bild von den Salinitäts- und Seespiegeländerungen der letzten 2000 Jahre. Aufgrund der weitgehenden Abhängigkeit der hydrologischen Verhältnisse des Aralsees von der Wasserführung seinen tributären Flüsse, hängt sein Seespiegel unmittelbar von den Schmelzwasserzuflüssen im Frühjahr ab. Da der Schmelzwasserzufluss seinerseits mit den Temperaturveränderungen im Tien Shan und Pamir während der Schneeschmelze in Verbindung steht, spiegeln die Paläo-Salinität und der Paläo-Seespiegel des Aralsees folglich die Temperaturveränderungen im hochgelegenen Einzugsgebiet des Aralsees wider...
    Description: thesis
    Keywords: 551 ; VKB 380 ; VDI 220 ; TWC 500 ; Sedimente bestimmter Regionen ; Holozän ; Klimaschwankungen und Klimaänderungen im Quartär
    Language: English
    Type: monograph , publishedVersion
    Format: 138 S.
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  • 45
    Publication Date: 2021-03-29
    Description: Reflection seismic is one of the most commonly used geophysical method for the oil and gas exploration. In this thesis I show the application of the Common Reflection Surface (CRS) stack technique to improve the quality of reflection seismic images. Conventional seismic imaging method based on the CMP stacking does not use the full potential of the dataset due to reflection point dispersal in the presence of dipping reflectors or laterally inhomogeneous media. Application of the CRS stack technique is advantageous in complex areas, since it involves information about the shape of seismic reflectors, i.e., dip and curvature, into processing. Moreover, a multiparameter formula allows to sum up more traces during the stack. All together, this leads to better imaging results, especially to an improvement of the signal-to-noise (S/N) ratio. Reflection events in the CRS stack sections appear clearer and more continuous compared to conventional CMP stack sections...
    Description: thesis
    Keywords: 622.15 ; TQC 220 ; VRE 110 ; Reflexionsseismik {Geophysik} ; Geophysikalische Verfahren
    Language: English
    Type: monograph , publishedVersion
    Format: 129 S.
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  • 46
    Publication Date: 2021-03-29
    Description: Interpretation of high and very high resolution reflection seismic data from the western Black Sea shelf yielded a seismic stratigraphic model of the Late Quaternary deposits on the southwestern Black Sea shelf. This model was combined with borehole information to carry out a regional subsidence analysis, so that the influence of tectonics and sediment compaction could be ruled out in the estimation of sea-level changes in the Black Sea. Mio-Pliocene sediments form the baseline of the interpretation. On top of it four Quaternary seismic stratigraphic units were identified on the western Black Sea shelf; they are named in chronological order Unit 4 to Unit 1 (U4 U1). Pliocene deposits are built up by gently basinward dipping layers of relatively high and approximately uniform thickness. Buried graben structures attest to the influence of extensional tectonics until the Upper Pliocene. Later, strong erosion left a rugged surface on the inner and middle shelf that was later overlain by a thin layer of Quaternary to Holocene sediments. The Pliocene is followed by the oldest observed Quaternary seismic sequence (Unit 4, U4); it comprises layers of Lower Quaternary age that dip towards the basin at a steeper angle than those of the Pliocene. Within U4 the oldest of three Quaternary shelfedge delta systems in the study area was found, that supposedly marks an Early Quaternary sea-level lowstand...
    Description: thesis
    Keywords: 551 ; 551 ; 550 ; VDI 200 ; VEZ 120 ; TSZ 100 ; Quartär ; Randmeere {Geologie} ; Atlantischer Ozean {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 170 S.
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  • 47
    Publication Date: 2021-03-29
    Description: The separation of natural and anthropogenically caused climatic changes is an important task of contemporary climate research. For this purpose, a detailed knowledge of the natural variability of the climate during warm stages is a necessary prerequisite. Beside model simulations and historical documents, this knowledge is mostly derived from analyses of so-called climatic proxy data like tree rings or sediment as well as ice cores. In order to be able to appropriately interpret such sources of palaeoclimatic information, suitable approaches of statistical modelling as well as methods of time series analysis are necessary, which are applicable to short, noisy, and non-stationary uni- and multivariate data sets. Correlations between different climatic proxy data within one or more climatological archives contain significant information about the climatic change on longer time scales. Based on an appropriate statistical decomposition of such multivariate time series, one may estimate dimensions in terms of the number of significant, linear independent components of the considered data set. In the presented work, a corresponding approach is introduced, critically discussed, and extended with respect to the analysis of palaeoclimatic time series. Temporal variations of the resulting measures allow to derive information about climatic changes ...
    Description: thesis
    Keywords: 551.6 ; VBE 000 ; TWC 100 ; Modellierung von Prozessen in der Geosphäre ; Instr. Ergebn. zu Klimaänderungen und Klimaschwankungen
    Language: English
    Type: monograph , publishedVersion
    Format: 169 S.
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  • 48
    Publication Date: 2021-03-29
    Description: The Andean orogen is the most outstanding example of mountain building caused by the subduction of oceanic below continental lithosphere. The Andes formed by the subduction of the Nazca and Antarctic oceanic plates under the South American continent over at least ~200 million years. Tectonic and climatic conditions vary markedly along this north-southoriented plate boundary, which thus represents an ideal natural laboratory to study tectonic and climatic segmentation processes and their possible feedbacks. Most of the seismic energy on Earth is released by earthquakes in subduction zones, like the giant 1960, Mw 9.5 event in south-central Chile.
    Description: thesis
    Keywords: 551.22 ; 551 ; 550 ; TSX 500 ; VEX 100 ; VEX 500 ; VAE 500 ; TOH 800 ; Chile {Geophysik} ; Anden {Geologie} ; Chile {Geologie} ; Geotektonische Entwicklung der Erdkruste {Tektonik} ; Paläoerdbeben {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 120 S.
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  • 49
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551.872 ; 550 ; TOO 000 ; VAE 130 ; Geothermik {Geophysik} ; Geomechanik
    Language: English
    Type: monograph , publishedVersion
    Format: 132 S.
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  • 50
    Publication Date: 2021-03-29
    Description: For seismic imaging of complex 3-D structures by e.g. prestack Kirchhoff depth migration large amounts of traveltime tables are required. This work provides a wavefront-oriented ray tracing technique for multi-valued traveltimes in smooth 3-D heterogeneous anisotropic media. In this method, wavefronts are propagated stepwise through the model and output quantities are interpolate (e.g., traveltimes, slowness) from rays to gridpoints. In contrast to isotropic media, where the input is a velocity model, the model for an anisotropic medium is defined by 21 elastic parameters at each gridpoint. To provide an efficient, accurate and fast algorithm for the interpolation of the elastic parameters to arbitrary points, the Cardinal Spline interpolation has been used, which produces an interpolated function that is continuous through the second derivative. The insertion of a new ray is performed by tracing it directly from the source. To calculate traveltimes at gridpoints a distance-weighted averaging method is used. To demonstrate the accuracy of the method the traveltimes computed for a homogeneous anisotropic model with elliptical symmetry are compared to exact traveltimes available for this medium. Since it exists no analytical solution for an inhomogeneous anisotropic model, I compare the results with an alternative method for traveltime computation, the FD perturbation method...
    Description: thesis
    Keywords: 622.1592 ; 550 ; TQC 200 ; Prospektionsseismik {Geophysik}
    Language: English
    Type: monograph , publishedVersion
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  • 51
    Publication Date: 2021-03-29
    Description: Merapi volcano in Central Java, Indonesia, is considered one of the most dangerous volcanoes worldwide. Due to the high viscosity of its magma, the lava emerging at the top the volcano cannot flow silently down the flanks of the volcano but builds a lava dome. An indicator for the stability of the lava dome are rockfalls and block and ash flows, which are caused by local instabilities at the dome. When the lava dome reaches a critical size, it collapses. This results in dangerous block and ash flows, which can reach several kilometers into the proximity of the volcano. In the past rockfall and block and ash flow activity has been observed visually or by seismic networks. However, visual observations are often impossible due to bad visibility conditions and until now seismic measurements allow only few insights into the dynamic processes that are involved in instability events, i.e. events of material breaks off the lava dome. In order to enhance monitoring of lava dome activity, a first prototype Doppler radar system has been installed at the western of the Merapi in October 2001. This system consists of a frequency modulated continuous wave (FMCW) 24GHz Doppler radar. The Doppler spectra recorded by the system give a relative measure of the amount of material moving through the beam as well as information about its velocities. Because the radar system is insensitive for clouds, the system provides first continuous "quasi-visual" observations of dome instabilities...
    Description: thesis
    Keywords: 551.21 ; TQD 800 ; TSJ 300 ; VAD 700 ; VAD 100 ; TSJ 300 ; VAD 700 ; VAD 100 ; Indonesien {Geophysik} ; Regionaler Vulkanismus {Geologie} ; Methodik in der Vulkanologie {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 156 S.
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  • 52
    facet.materialart.
    Unknown
    Univ. Hamburg
    Publication Date: 2021-03-29
    Description: In this thesis, the 1997 Vogtland/NW-Bohemia swarm has been selected for the analysis of inhomogeneities in the stress field because two predominant nearly perpendicular flat zones of seismicity are visible in the hypocentre distribution implying inhomogeneities in the stress field. This is unusual compared to other swarms originating from this area. An existing dataset of waveform data, P- and S-phase picks, and master event locations has been analysed regarding similarity of waveforms, location refinement, and estimation of relative moment tensors. The latter are used together with a regional dataset of 50 single focal mechanisms and 125 focal mechanisms from the 2000 hydraulic fracturing experiment at the KTB for an estimate of the regional homogeneous and the locally inhomogeneous stress field. An automated processing procedure consisting of coherence analysis,precise relocation, relative moment tensor inversion, and stress trajectory determination has been set up. The coherence analysis has been successfully applied using a new method that uses three component seismograms. 457 events are separated into 13 multiplets of similar waveforms of at least size 8. Another result are precise relative arrival time measurements which are fed into the precise relocation program "hypoDD". Two nearly perpendicular structures are found in the hypocentre distribution. 352 moment tensors are estimated using a relative moment tensor inversion. Three different algorithms to distinguish between fault plane and auxiliary plane are successfully applied to them...
    Description: thesis
    Keywords: 551.22 ; 550 ; VAE 130 ; TOH 400 ; Geomechanik ; Übertragungsmedien {Seismologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 184 S.
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  • 53
    Publication Date: 2021-03-29
    Description: Mittelozeanische Rücken finden sich in allen größeren Ozeanbecken der Erde. Sie besitzen die weltweit höchste Produktionsrate an Extrusiv- und Intrusivgesteinen. Bildung ozeanischer Kruste und Vulkanismus an divergenten Plattengrenzen sind fundamentale Prozesse, deren Grundverständnis wichtig ist. Magmatische Dykes bauen einen Großteil ozeanischer Kruste auf. Ihr Vorkommen ist besonders augenfällig im sogenannten Sheeted-Dyke-Komplex der oberen Kruste. In dieser Arbeit wird die Wechselwirkung zwischen Magmakammern und Dykes aufgrund von Spannungsfeldern untersucht. Die Ergebnisse werden zur Analyse ozeanischer Krustenbildung im allgemeinen und des Sheeted-Dyke-Komplexes im besonderen benutzt. Da nur wenig Daten über die Geologie mittelozeanischer Rücken und den Verlauf magmatischer Prozesse verfügbar sind und analytische Modelle zumeist an der Berücksichtigung inhomogener Medien und heterogener Spannungsfelder scheitern, stellen numerische Modelle ein wichtiges Werkzeug zur weiteren Erforschung dieser Abläufe dar. Um den Aufstieg von Dykes als Fortbewegung fluidgefüllter Risse zu berechnen, wurde eine Randelementmethode verwendet. Modelle für den Magmaaufstieg im Mantel müssen sowohl die hohen Transportgeschwindigkeiten als auch die Trennung von Schmelze und Mantelgestein zur Verhinderung chemischer Ausgleichsreaktionen und die Fokussierung des Magmas von der breiten Schmelzzone in der Tiefe zur schmalen Austrittszone an der Rückenachse leisten...
    Description: thesis
    Keywords: 551.1 ; 550.28 ; 550 ; VAE 130 ; VAE 890 ; TSZ 000 ; Geomechanik ; Ozeanische Kruste {Tektonik} ; Meeresräume {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 178 S.
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  • 54
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 622.15 ; 553.28 ; 550 ; TSI 000 ; VRE 160 ; VSI 000 ; TSI 000 ; VRE 160 ; VSI 000 ; Vorderasien {Geophysik} ; Regionale Exploration und Prospektion {Kohlenwasserstofflagerstätten} ; Vorderasien {Fossile Energieträger}
    Language: English
    Type: monograph , publishedVersion
    Format: 93 Bl.
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  • 55
    facet.materialart.
    Unknown
    Univ. Hamburg
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551.22 ; 550 ; TQC 100 ; Physikalische und mathematische Grundlagen {Geophysik: Seismik}
    Language: English
    Type: monograph , publishedVersion
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  • 56
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551.22 ; 550
    Language: English
    Type: monograph , publishedVersion
    Format: 188 S.
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  • 57
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 539.76 ; 550 ; TVB 420 ; Aeronomie
    Language: English
    Type: monograph , publishedVersion
    Format: 166 S.
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  • 58
    Publication Date: 2021-03-29
    Description: Diese Dissertation beschäftigt sich mit der Entwicklung eines automatisierten, datenorientierten Abbildungsverfahrens, das auf der sogenannten Common-Reflection-Surface (CRS) Stapelung basiert. Durch die Miteinbeziehung von benachbarten Experimenten bei der Rekonstruktion eines Einzelexperiments ergibt sich ein verbessertes Signal-zu-Rauschen Verhältnis und eine starke Bereinigung von Mehrdeutigkeiten. Hauptaugenmerk liegt auf der Adaption der Methode für Bohrloch- und Mehrkomponentendaten.
    Description: thesis
    Keywords: 622.15 ; 550 ; TQG 000 ; TQC 100 ; Geophysikalische Bohrlochmessungen ; Physikalische und mathematische Grundlagen {Geophysik: Seismik}
    Language: English
    Type: monograph , publishedVersion
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  • 59
    Publication Date: 2021-03-29
    Description: Land data acquisition often suffers from rough top-surface topography and complicated near-surface conditions. The resulting poor data quality makes conventional data processing very difficult. Under such circumstances, where simple model assumptions may fail, it is of particular importance to extract as much information as possible directly from the measured data. Fortunately, the ongoing increase in available computing power makes advanced data-driven imaging approaches feasible; thus, these have increasingly gained in relevance during the past few years. The common-reflection-surface (CRS) stack, a generalized high-density velocity analysis and stacking process, is one of these promising methods. It is applied in a non-interactive manner and provides, besides an improved zero-offset simulation, an entire set of physically interpretable stacking parameters that include and complement the conventional stacking velocity. For every zero-offset sample, these so-called kinematic wavefield attributes are obtained as a by-product of the data-driven stacking process. As will be shown, they can be applied both to improve the stack itself and to support subsequent processing steps...
    Description: thesis
    Keywords: 622.1592 ; 550 ; TQC 100 ; Physikalische und mathematische Grundlagen {Geophysik: Seismik}
    Language: English
    Type: monograph , publishedVersion
    Format: 191 S.
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  • 60
    Publication Date: 2021-03-29
    Description: For successful assessment and mitigation of earthquake hazards, it is necessary to be able to reliably predict the level of ground shaking which has to be expected from future large earthquakes. This prediction of ground motion can be done either by using empirical relations (derived from past earthquakes) between some ground motion parameter and the source and observer location, so-called attenuation relations, or by performing numerical simulations of future earthquakes based on models of the earthquake source and the propagation medium (i.e. the Earth). The capacity of the first option is at times rather limited, for instance if only very few large earthquakes occurred in the region of interest in instrumental times. Numerical simulations, on the other hand, cannot provide reliable results without a detailed description of the underlying source process and a thorough understanding of path and site effects. This thesis aims at a better understanding of the source process and the spectral characteristics of the intermediate-depth Vrancea (Romania) earthquakes...
    Description: thesis
    Keywords: 551.22 ; 550 ; TSE 000 ; TOH 400 ; Südosteuropa {Geophysik} ; Übertragungsmedien {Seismologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 205 S.
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  • 61
    Publication Date: 2021-03-29
    Description: During several marine geophysical data acquisition cruises in the western Baltic Sea, for the Baltseis and NeoBaltic projects, a dense grid of 2D high-resolution multichannel seismics and to some extend gravity and magnetic data were acquired in the German and Danish territorial waters of the region. The western Baltic Sea comprises the northern part of the Northeast German Basin on the southern flank of the Ringkøbing-Fyn High. Furthermore, parts of the suture zone between the Avalonia and Baltica plates (the Caledonian Deformation Front) and the Sorgenfrei Tornquist Zone were investigated during these research cruises. Adjacent to the study area two structures are located, which are important for the structural evolution in the region. To the west the N-S trending Glückstadt Graben and in the eastern part the E-W running Grimmen High...
    Description: thesis
    Keywords: 550 ; VBM 000 ; VAE 820 ; TSB 000 ; VEB 110 ; TQC 200 ; Geologische Interpretation geophysikalischer Beobachtungen ; Sedimentationsbecken als Erdkrustentypen {Geologie} ; Mitteleuropa {Geophysik} ; Norddeutsche Senke {Geologie} ; Prospektionsseismik {Geophysik}
    Language: English
    Type: monograph , publishedVersion
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  • 62
    Publication Date: 2021-03-29
    Description: In this study different full waveform techniques was developed for the investigation of seismic ocean bottom single station data. These techniques were applied to data obtained in a pilot ocean bottom experiment in the Tyrrhenian Sea/Italy (TySea experiment) from December 2000 to May 2001. A network of broadband seven ocean bottom seismometers and seven ocean bottom hydrophones was installed above the subducting Ionian plate which descends from Southeast to Northwest. Local and teleseismic earthquakes were recorded by the stations. The newly developed techniques produce very promising results in reconstructing the sea floor structure beneath the stations and in attenuating waveform effects generated by water layer multiples. Additionally the techniques offer a possibility to determine the orientation of free fall ocean bottom seismometers. The main results are: 1. The waveform recorded at the seafloor differs from waveforms recorded at land stations. This is primarily due to multiple reflections in the water layer. These multiple reflections show different patterns on seismometer and hydrophone recordings depending on the seafloor structure. This opens the possibility to constrain the P-wave velocity structure beneath the station by means of a full waveform inversion...
    Description: thesis
    Keywords: 550 ; TSZ 100 ; VAE 890 ; TQC 700 ; Atlantischer Ozean {Geophysik} ; Ozeanische Kruste {Tektonik} ; Seismische Verfahren zur Feststellung von Atomexplosionen {Geophysik}
    Language: English
    Type: monograph , publishedVersion
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  • 63
    facet.materialart.
    Unknown
    Univ. Potsdam
    Publication Date: 2021-03-29
    Description: Various types of uncertainty plague climate change simulation, which is, in turn, a crucialelement of Earth System modelling. This fact was recognized for example in the Third Assessment Report (TAR) of the Intergovernmental Panel on Climate Change (IPCC, Houghton et al. (2001)), where the authors indicate that for the period between 1990 and 2100 an increase of the global mean temperature around 1.4-5.8°C is to be expected (Houghton et al. 2001). The width of this span as well as the fact that the authors did not give a number concerning the most probable value or a probability distribution shows clearly the large uncertainty. This uncertainty does not only arise due to the different scenarios of future development concerning greenhouse gas emissions for example, but follows to large degree from the wide range of results from different models as well. The chain of these uncertainties of imponderables in the analysis of the Earth System (Schellnhuber and Wenzel 1998), which includes the climate system as well as the anthroposphere, reaches from uncertainties about the existence of critical thresholds, to ignorance of the exact state of today's climate, and ultimately to a lack of knowledge concerning climate-relevant processes, some of which are visible as uncertainties in climate models. Many attempts have been made to reduce these uncertainties by gaining a conceptual understanding of processes, e.g. of El Ni~no / Southern Oscillation (ENSO) (Jin 1997, e.g.) or of the Atlantic overturning (Stommel 1961; Rahmstorf 1996, e.g.), by developing methods to identify critical thresholds in the climate system (Alley et al. 2003; Rial et al. 2004, e.g.), or by implementing an increasing number of processes in a model, resulting in high resolution general circulation models (GCMs), e.g. ECHAM5/MPI-OM (Jungclaus et al. 2006) or HadCM3 (Gordon et al. 2000) and many more. Nevertheless, the much larger part of uncertainties is inevitable in the process of modelling as well as in our understanding of the Earth System. In this thesis we will structure this conglomeration of uncertainties climate research is confronted with. We will address several types of uncertainty and apply methods of dynamical systems theory on a trendsetting field of climate research, i.e. the Indian monsoon ...
    Description: thesis
    Keywords: 551.6 ; TWB 000 ; Statistische Klimatologie und Klimatologische Modelle
    Language: English
    Type: monograph , publishedVersion
    Format: 131 S.
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  • 64
    Publication Date: 2021-03-29
    Description: This work presents multichannel seismic and hydroacoustic data of four survey areas along the Red Sea Rift and the Dead Sea Transform Fault. Sedimentary Basins that developed due to the rifting of the Red Sea and the strike-slip displacement of the Dead Sea Transform Fault were investigated and models for their evolution were derived. The Red Sea Rift and the Dead Sea Transform Fault are the main tectonic features in the Middle East. The rifting process of the Red Sea that initiated in the late Oligocene and early Miocene separated the African Plate from the Arabian Plate. In the Middle Miocene, the extension was compensated in the northern part of the Red Sea with the initiation of the left lateral Dead Sea Transform Fault. Along the Red Sea, different stages of evolution can be observed. Whereas the southern part comprises already seafloor spreading, the northern part is assumed to be in the late stage of continental rifting. Because of huge evaporitic sediment layers within the entire Red Sea, direct basement observations are sparse. Surficial features like ocean deeps along the axis of the Red Sea are interpreted as first seafloor spreading cells in the transition process between seafloor spreading and continental rifting. Along the Dead Sea Transform Fault, 105 km of left lateral displacement are observed within the last 20 Ma. The displacement is most likely not continuous since its onset. The Dead Sea Transform Fault may have experienced a break in its history before 5 Ma...
    Description: thesis
    Keywords: 622.15 ; 551.8 ; 550 ; TSI 000 ; VAE 840 ; TSI 000 ; VAE 840 ; Vorderasien {Geophysik} ; Rifts {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 127 S.
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  • 65
    facet.materialart.
    Unknown
    Univ. Hamburg
    Publication Date: 2021-03-29
    Description: The purpose of the first part of this dissertation was to develop a migration algorithm for converted waves, and a tomographic method for estimating an interval shear wave velocity model. The developed algorithm is based on the Kirchhoff formalism. The elastic Kirchhoff integral and its implementation were discussed and summarised in Chapter 2. The derived migration integral was generalised for all types of multicomponent data. For practical reasons, multicomponent data are decomposed into their corresponding components (z,x, and y components), and the migration is performed separately for each component. Normally it is assumed that the decomposed wave components are free from other wave types. The migration result of each component shows particular characteristics of the subsurface. For example, PS data give the shear wave characteristics of the subsurface...
    Description: thesis
    Keywords: Reflexionsseismik {Geophysik} ; 622.15 ; 550 ; TQC 220
    Language: English
    Type: monograph , publishedVersion
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  • 66
    Publication Date: 2021-03-29
    Description: This work presents the first three-dimensional gravity and magnetic investigation along the convergent Peruvian margin. Three-dimensional magnetic modelling is still a relatively untried and challenging technique. The gravity and magnetic models image nearly the whole margin which has been only partly resolved with geophysical methods up to now. The gravity and magnetic models are constructed for three areas between 7.25ʿS and 16.75ʿS and are based on the available wide-angle seismic velocity models (Hampel et al., 2002a; Broser et al., 2002). The continental margin is characterised by positive free-air anomalies of varying amplitudes, indicating that the margin has been shaped by the subduction of different features on the Nazca Plate...
    Description: thesis
    Keywords: 551.1 ; 622.15 ; 550 ; TSX 800 ; TQA 000 ; TQB 000 ; VAE 880 ; VEX 800 ; Peru und Ecuador {Geophysik} ; Gravimetrische Verfahren {Geophysik} ; Erdmagnetische Verfahren {Geophysik} ; Passive und aktive Kontinentalränder {Geologie} ; Peru und Ecuador {Geologie}
    Language: English
    Type: monograph , publishedVersion
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