2,010 research outputs found

    An Evolutionary Approach to Adaptive Image Analysis for Retrieving and Long-term Monitoring Historical Land Use from Spatiotemporally Heterogeneous Map Sources

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    Land use changes have become a major contributor to the anthropogenic global change. The ongoing dispersion and concentration of the human species, being at their orders unprecedented, have indisputably altered Earth’s surface and atmosphere. The effects are so salient and irreversible that a new geological epoch, following the interglacial Holocene, has been announced: the Anthropocene. While its onset is by some scholars dated back to the Neolithic revolution, it is commonly referred to the late 18th century. The rapid development since the industrial revolution and its implications gave rise to an increasing awareness of the extensive anthropogenic land change and led to an urgent need for sustainable strategies for land use and land management. By preserving of landscape and settlement patterns at discrete points in time, archival geospatial data sources such as remote sensing imagery and historical geotopographic maps, in particular, could give evidence of the dynamic land use change during this crucial period. In this context, this thesis set out to explore the potentials of retrospective geoinformation for monitoring, communicating, modeling and eventually understanding the complex and gradually evolving processes of land cover and land use change. Currently, large amounts of geospatial data sources such as archival maps are being worldwide made online accessible by libraries and national mapping agencies. Despite their abundance and relevance, the usage of historical land use and land cover information in research is still often hindered by the laborious visual interpretation, limiting the temporal and spatial coverage of studies. Thus, the core of the thesis is dedicated to the computational acquisition of geoinformation from archival map sources by means of digital image analysis. Based on a comprehensive review of literature as well as the data and proposed algorithms, two major challenges for long-term retrospective information acquisition and change detection were identified: first, the diversity of geographical entity representations over space and time, and second, the uncertainty inherent to both the data source itself and its utilization for land change detection. To address the former challenge, image segmentation is considered a global non-linear optimization problem. The segmentation methods and parameters are adjusted using a metaheuristic, evolutionary approach. For preserving adaptability in high level image analysis, a hybrid model- and data-driven strategy, combining a knowledge-based and a neural net classifier, is recommended. To address the second challenge, a probabilistic object- and field-based change detection approach for modeling the positional, thematic, and temporal uncertainty adherent to both data and processing, is developed. Experimental results indicate the suitability of the methodology in support of land change monitoring. In conclusion, potentials of application and directions for further research are given

    Solid state NMR characterization of structural and motional parameter distributions in polyamidoammonium dendrimers

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    The characterization of narrow distributions of structural and motional parameters, and their evolution during the broad glass transition, is performed for deuterated PAMAM dendrimer salts using solid state NMR. The broadening of deuteron quadrupole echo (QE) lineshapes is consistent with the presence of narrow hydrogen bond length distribution (sigmar \u3c 0.25 A) at the spacer amide and branching tertiary amine sites. The temperature dependent averaging of the experimental lineshapes is explained on the basis of fast planar librations in the dendrimer interior, and fast rotation and intermediate regime libration (in an asymmetric cone) of the dendrimer termini. The amplitudes of libration are temperature dependent and higher for low generation dendrimers, while librational rates show Arrhenius behavior only within the glass transition region. In this region, the width of log-normal distribution of rates increases with temperature at sites associated with chlorine counterions. The largest distributions are still less than one order of magnitude wide, unlike the dendrimer in solution or the linear polymers. Interpenetrated low generations (G \u3c 3), uniform intermediate generations (G = 3--5) with surface network, and backfolded high generations (G \u3e 5), are distinguished by interior and termini dynamics.;In the regime of fast motion QE lineshapes are highly sensitive to the presence of narrow structural and motional parameter distributions, and provide constraints on motional geometry independent of rates. The precise characterization of narrow log-normal rate distributions in the intermediate regime can be done using 2H magic angle spinning (MAS). Deuteron inversion-recovery techniques provide quantitative information on the rates of fast motion. For PAMAM salts, the influence of narrow distributions of structural and motional parameters, and fast planar libration, is negligible for distance determination using Rotational Echo Double Resonance (REDOR). The discrimination between inter- and intra-molecular hydrogen bonding can be done through selective labeling of dendrimer core and termini and dilution in natural abundance samples according to developed strategies. The internuclear distances evaluated on the basis of QE results are 3.4--4.0 A. These fall within the sensitivity range of 13C-15N REDOR, as exemplified by the measurements on small amino acids according to analytically predicted optimum dephasing scheme

    Synthesis, Characterization and Crystal Growth of I2-II-IV-VI4 and I4-II-IV2-VI7 Diamond-Like Semiconductors with potential In IR-NLO Applications

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    In this dissertation, several new and existing diamond-like semiconductors (DLSs) were synthesized and investigated for their potential in infrared nonlinear optical (IR-NLO) applications. In Chapter 2 growth of large single crystals of Li2MnGeS4 was carried out using iodine vapor transport and a newly created graphite-tube containment system. This crystallization method produced sizable single crystals on the scale of 2x1x1 mm3, that were used to determine the material’s magnetic properties. Magnetization data indicate that the compound is antiferromagnetic with a NĂ©el temperature of 10 K and an effective magnetic moment of 5.6 /f.u.. The specific heat measurements show that as the field strength increases the NĂ©el temperature decreases; the low NĂ©el temperature confirms the weak magnetic coupling of the Mn2+ ions. Chapters 3, 4 and 5 report the new DLS Cu4MnGe2S7, Cu4CdSi2S7 and Li2ZnSiS4 for which detailed descriptions of their physical and electronic structures are given. Chapter 4 also reports the NLO properties of Cu4MnGe2S7 and Cu2MnGeS4. The chi(2) value for Cu4MnGe2S7 was determined to be 2.33 ± 0.86 pm/V. Due to the relatively weak SHG response, phase matching could only be tested up to 1600 nm, where the compound was found to be non-phase-matchable. On the other hand, Cu2MnGeS4 is phase matchable at 3100 nm and exhibits a significant chi(2) value of 16.9 ± 2.0 pm/V. Chapter 6 presents a study in which one polymorph of Cu2ZnSiS4 was targeted through alteration of the cooling rate. These products of these reactions were analyzed via neutron diffraction and solid-state MAS-NMR. While a single polymorph was not attained, a modified beta polymorph (gamma) was discovered

    Structural studies of lead-free piezoelectrics with the fresnoite structure type

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    The lead free piezoelectric fresnoite A2M3O8 (A = Ba, Sr, K, Cs; M = Ti, V, Si, Ge) modulated structure type has been investigated owing to its potential to exhibit excellent piezoelectric response coefficients. Ba2TiSi2O8, Sr2TiSi2O8, and Ba2TiGe2O8 end members in addition to members of the Ba2xSr2-2xTiSi2O8, Ba2xSr2 2xTiGe2O8, Ba2TiGe2ySi2 2yO8, and BaSrTiGe2ySi2 2yO8 series were synthesised and characterised using a combination of variable temperature diffraction techniques. The Ba2TiSi2O8 and Sr2TiSi2O8 modulated structures at ambient temperature were characterised using neutron powder diffraction for the first time. Variable temperature synchrotron X ray diffraction data showed a new means of identifying the incommensurate to prototypic structural phase transition at 433 K. Resonant ultrasound spectroscopy has shown coupling between the elastic moduli and structural changes in fresnoite samples. Polycrystalline Sr2TiSi2O8 samples were shown to undergo a first order phase transition from a two phase mixture of incommensurately modulated tetragonal and orthorhombic phases to a single incommensurately modulated orthorhombic phase that is complete by 567 K. The proportion of the orthorhombic phase Sr2TiSi2O8 samples was shown to slowly decrease on cooling to 125 K. The Sr2TiSi2O8 structure was also shown to undergo an additional phase transition from the incommensurately modulated orthorhombic phase to a tetragonal phase at 1323 K for the first time. The inclusion of barium or germanium into the Sr2TiSi2O8 structure was shown to suppress the formation of the orthorhombic phase at ambient temperature and elevated temperatures. New phase diagrams for the Ba2xSr2-2xTiSi2O8 and Sr2TiGe2ySi2 2yO8 systems summarise the phase transitions investigated. The intrinsic piezoelectric coefficients were calculated to be approximately 5 pm V 1 and 27 pm V 1 for polycrystalline samples of Ba2TiSi2O8 and Sr2TiSi2O8 respectively and compared to common piezoelectric materials

    Untersuchung von Magnetostriktiven und Piezotronischen Mikrostrukturen und Materialien fĂŒr biomagnetische Sensoren mittels Röntgenstrahlen

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    Detecting electric potential differences from the human physiology is an established technique in medical diagnosis, e.g., as electrocardiogram. It arises from a changing electrical polarization of living cells. Simultaneously, biomagnetism is induced and can be utilized for medical examinations, as well. Benefits in using magnetic signals are, no need for direct skin contact and an increased spatial resolution, e.g., for mapping brain activity, especially in combination with electrical examinations. But biomagnetic signals are very weak and, thus, highly sensitive devices are necessary. The development of small and easy to use biomagnetic sensors, with a sufficient sensitivity, is the goal of the Collaborative Research Centre 1261 - Magnetoelectric Sensors: From Composite Materials to Biomagnetic Diagnostics. This thesis was written as part of this collaboration, with the main focus on the investigation of crystalline structures and structure related properties of piezotronic and magnetostrictive materials by utilizing a selection of X-ray techniques, i.e., X-ray diffraction (XRD), X-ray reflectivity (XRR) and coherent X-ray diffraction imaging (CXDI). Piezotronics, realized by combining piezoelectricity and Schottky contacts in one structure, provides a promising path to enhance sensor sensitivity. A first study investigated the crystalline structure of three piezotronic ZnO rods, spatially resolved by scanning nano XRD and combined with electrical examinations of their Schottky contact properties. It is found that the crystalline quality has a clear impact on the electrical properties of the related Schottky contact, probably due to crystalline defects. A complementary transmission electron microscopy (TEM) and XRD study performed on hybride vapor phase epitaxy (HVPE) grown GaN showed a slight, photoelectrochemical etching related relaxion of strain originating from crystal growth. In a separate study, CXDI was utilized for three-dimensional visualization of strain in a gold coated ZnO rod, with spatial resolution below 30 nm. A distinct strain distribution was found inside the rod, denoted to depletion and screening effects occurring in bent piezotronic structures, and a high strain at the interface may be related to Schottky contact formation. This interface strain agrees with results obtained from TEM. A succeeding CXDI study was conducted on a ZnO rod coated with magnetostrictive FeCoSiB and the possibility for the investigation of the Schottky contacts electrical properties. It was found that FeCoSiB sputtered on ZnO results in an ohmic contact and that an external magnetic field causes a change of the electrical properties, probably due to a strain change, visualized by CXDI. In a fifth study, magnetostrictive FeCo/TiN multilayer structures were investigated by a combined TEM and XRD/XRR approach, showing a relaxation of the structure due to an annealing process and a cube-on-cube structure of the FeCo and TiN layers

    The SAR Handbook: Comprehensive Methodologies for Forest Monitoring and Biomass Estimation

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    This Synthetic Aperture Radar (SAR) handbook of applied methods for forest monitoring and biomass estimation has been developed by SERVIR in collaboration with SilvaCarbon to address pressing needs in the development of operational forest monitoring services. Despite the existence of SAR technology with all-weather capability for over 30 years, the applied use of this technology for operational purposes has proven difficult. This handbook seeks to provide understandable, easy-to-assimilate technical material to remote sensing specialists that may not have expertise on SAR but are interested in leveraging SAR technology in the forestry sector

    Tools for the economic evaluation of wastewater reclamation and reuse

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    The economic evaluation is basic for any reclaimed water reuse project. Nevertheless, the calculation tools for this evaluation have scarcely been developed due to the lack of application of the existing models and the need to consider more circumstances that the actually used for the evaluations. The authors develop a comprehensive tool, comprising several steps, as follows: analysis of the basics of any project; socioeconomic characterization; building, operation and maintenance of the facility; and evaluation of the positive and negative externalities

    INVESTIGATING THE ROLE OF POST-TRANSLATIONAL MODIFICATIONS IN THE CORE RAS GTPASE DOMAIN

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    Ras proteins are the most commonly mutated oncoproteins in cancer (~30%). Oncogenic, activating Ras mutations are known drivers of the deadliest human cancers, including lung, pancreatic and colorectal cancers. Ras proteins function as critical regulators of cellular growth by acting as molecular switches, cycling between active, GTP- and inactive, GDP-bound states. In their active form, Ras proteins signal through downstream pathways that regulate cellular growth, differentiation and apoptosis. Early attempts to target Ras proteins (farnesyltransferase inhibitors) were directed toward inhibiting key carboxyl (C)-terminal lipid post-translational modifications (PTMs), which are crucial for proper Ras localization and function at the cellular membrane. Despite their failure, FTIs represent the first direct targeting efforts of Ras proteins. Promising new classes of anti-cancer drugs directed at targeting the dysregulation of PTM status in cancers (kinase inhibitors, histone deacetylase inhibitors, HDACi and methyltransferase inhibitors) have demonstrated multiple clinical successes in recent years. PTMs have been demonstrated to alter protein stability and localization as well as protein-protein interactions in several non-histone cancer-related proteins. While PTMs have been extensively studied in the C-terminus of Ras proteins, their role remains poorly understood in the core Ras guanine nucleotide binding domain (GTPase domain). Monoubiquitylation and acetylation within the core Ras GTPase domain have been demonstrated to modulate Ras protein activity, signaling and tumorigenesis, suggesting that PTMs in this region are capable of regulating Ras behavior. Further, aberrant dysregulation in the balance of PTMs has been characterized in several cancer types, including the Ras-driven pancreatic cancer. It is therefore reasonable that Ras PTMs may present a novel avenue for therapeutic targeting in cancer. Despite more than three decades of research, Ras has remained an elusive target for cancer therapy. We have recently identified novel sites of PTMs in Ras proteins at highly conserved residues within the core GTPase domain. Herein, we present highly innovative and novel methods of generating both acetyl- and methyl-lysine in intact Ras proteins. With the combined use of biochemical, structural, cellular and computational data, we provide mechanistic insight into the regulation Ras proteins by PTMs and also provide rationale for novel therapeutic targeting approaches in Ras-driven cancers.Doctor of Philosoph

    Master of Science

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    thesisAn ever-present challenge at most active mining operations is controlling blastinduced damage beyond design limits. Implementing more effective wall control during blasting activities requires (1) understanding the damage mechanisms involved and (2) reasonably predicting the extent of blast-induced damage. While a common consensus on blast damage mechanisms in rock exists within the scientific community, there is much work to be done in the area of predicting overbreak. A new method was developed for observing near-field fracturing with a borescope. A field test was conducted in which a confined explosive charge was detonated in a body of competent rhyolite rock. Three instrumented monitoring holes filled with quick-setting cement were positioned in close proximity to the blasthole. Vibration transducers were secured downhole and on the surface to measure near-field vibrations. Clear acrylic tubing was positioned downhole and a borescope was lowered through it to view fractures in the grout. Thin, two-conductor, twisted wires were placed downhole and analyzed using a time-domain reflectometer (TDR) to assess rock displacement. Fracturing in the grout was easily observed with the borescope up to 3.78 m (12.4 ft) from the blasthole, with moderate fracturing visible up to 2.10 m (6.9 ft). Measured peak particle velocities (PPV) at these distances were 310 mm/s (12.2 in./s) and 1,490 mm/s (58.5 in./s), respectively, although no fracturing was observed near the depth of the vibration transducers located 3.78 m (12.4 ft) from the blasthole. TDR readings were difficult to interpret but indicated rock displacement in two of the monitoring holes. Three methods were used to predict the radial extent of tensile damage around the blasthole: a modified Holmberg-Persson (HP) model, a shockwave transfer (SWT) model, and a dynamic finite element simulation using ANSYS AutodynTM. The extent of damage predicted by the HP and SWT models is similar to field measurements when using static material properties of the rock, but is underestimated using dynamic material properties. The Autodynℱ model significantly overpredicted the region of damage but realistically simulated the zones of crushing and radial cracking. Calibration of material parameters for the AutodynTM model would be needed to yield more accurate results
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