Spelling suggestions: "subject:"anenrichment"" "subject:"nenrichment""
831 |
Soukromoprávní důsledky porušení soutěžního práva a jejich prosazování v ČR / Private-law consequences of a breach of competition law and their enforcement in the Czech RepublicMikulíková, Lucie January 2019 (has links)
V ANGLICKÉM JAZYCE Private-law consequences of a breach of competition law and their enforcement in the Czech Republic The private-law consequences of a breach of competition law, Articles 101 and 102 of the Treaty on the Functioning of the EU and Sections 3 and 11 of the Czech Competition Act, may affect many entities, irrespective of whether they are competitors or consumers. Recently, emphasis has been placed on private enforcement of competition law that is intended to serve as an important complement to public law enforcement. The first part of the dissertation defines basic concepts and principles of competition law including "public rules on restriction of competition". The history of the enforcement of competition law in the Czech Republic and the dynamic development in this area at the EU level are outlined in the second part. The third crucial part of this work deals with the right to damages caused by a breach of competition law in the Czech Republic. In 2014, the EU adopted Directive 2014/104 on certain rules in damages actions with the view, inter alia, to increase the effectiveness of private enforcement of competition rules by civil courts of EU Member States. On August 18, 2017, new Act No. 262/2017 Coll. which implements the Directive into Czech law was adopted. The dissertation...
|
832 |
Investigation of multicomponent catalyst systems for type-selective growth of SWCNTs by CVDMotaragheb Jafarpour, Saeed 25 February 2020 (has links)
Excellent electronic properties of semiconducting single-walled carbon nanotubes (sc-SWCNTs) motivated the investigation for using them in different application areas such as microelectronics, sensorics, MEMS and MOEMS. However, challenges arise from the lack of selectivity with respect to electronic type and chirality as well as ensuring high quality, high purity and well-aligned SWCNTs during fabrication process. Catalytic chemical vapour deposition (CCVD) has shown great potential in direct synthesis of high quality SWCNTs with chiral or type selectivity.
This thesis addresses three important aspects for growth of sc-SWCNT covering method development for fast screening for complex catalyst systems, process development for type-selective growth of SWCNTs and transfer of processes to a specific CVD reactor capable to scale the processes up to 8-inches wafer embedded in the microtechnologic process line. Multi-wavelengths Raman spectroscopy is applied to analyze type and chiral compositions of SWCNTs. In addition, different microscopic techniques of SEM, TEM and AFM are utilized to analyze surface morphology of catalyst layers and size of the nanoparticles as well as structure-related properties of SWCNTs. Initially, systematic studies on monometallic Co and bimetallic Co-Mo systems with different bilayer thickness configurations and their influences on the properties of grown SWCNTs are conducted on chip level. It is shown by adjusting the catalyst deposition conditions of bilayer catalyst as well as optimization of gas environments in CCVD process, structure-related properties of SWCNTs are dramatically enhanced. Furthermore, by utilizing shutter-assisted sputter deposition of gradient layer catalyst, a fast and efficient method for screening different bilayer configurations of Co-Mo, Co-Ru and Ni-Ru has been developed. By utilizing gradient layer deposition with finely resolved catalyst thicknesses, random network SWCNT is grown on bimetallic Co-Mo system under certain process condition with 45% (at 633 nm) and 75% (at 785 nm) semiconducting enrichment of long and high quality SWCNT. In contrast, bimetallic Co-Ru system under certain process condition is developed to grow in-plane SWCNT with 85% (at 633 nm) and 75% (at 785 nm) semiconducting enrichment of short and low quality SWCNT. In addition, different configurations of the bimetallic Co-Ru system are prepared from salt precursors by spin-coating technique. For a mixture of cobalt (II) chloride and ruthenium (III) nitrosylacetate, random network SWCNT with 70% (at 633 nm) and 95% (at 785 nm) semiconducting enrichment of long SWCNTs with high quality is obtained on wafer level. Random network SWCNT with high degree of semiconducting enrichment is used as channel material for thin-film transistors fabrication that results in CNTFET with on/off ratio in the order of 10*3:Bibliographic description 3
Vorwort 9
List of abbreviations and symbols 11
1 Introduction 15
2 Fundamentals of carbon nanotubes 21
2.1 Chemical bonds in carbon structures 21
2.2 Different allotropes of carbon 22
2.3 History of carbon nanotubes research 23
2.4 Structure of carbon nanotubes 24
2.5 Electronic properties of carbon nanotubes 26
2.6 Synthesis of carbon nanotubes 27
2.7 Growth mechanism of carbon nanotubes by CCVD 29
2.8 Catalyst for CCVD synthesis of SWCNTs 31
2.8.1 Catalyst nanoparticle formation from thin film 32
2.8.2 Mechanism of solid state dewetting 33
2.9 CCVD synthesis of SWCNT 35
2.10 Selective synthesis of SWCNT 37
3 Experimental 39
3.1 Preparation of different catalyst/support systems 39
3.1.1 Homogenous layer of catalyst prepared by PVD 39
3.1.2 Gradient layer deposition of catalyst by IBSD 41
3.1.3 Homogenous layer of catalyst prepared by spin coating 45
3.2 CVD reactors for synthesis of SWCNT 46
3.2.1 R&D vertical flow CVD reactor with showerhead 46
3.2.2 Industrial vertical flow CVD reactor with showerhead 47
3.2.3 Horizontal flow tube CVD reactor 49
3.3 Methods for characterization 50
3.3.1 Atomic force microscopy 50
3.3.2 Raman spectroscopy 50
3.3.3 Spectroscopic ellipsometry 56
3.3.4 X-ray reflection 56
3.3.5 Scanning electron microscopy 56
3.3.6 Transmission electron microscopy 56
4 Growth of SWCNT using PVD catalyst layer in vertical CVD reactor A 57
4.1 Monometallic Co catalyst supported on SiO2 57
4.1.1 Surface and morphological analysis of SiO2/Co 57
4.1.2 Analysis of CCVD grown SWCNT on SiO2/Co 59
4.1.3 Chirality and diameter analysis of SWCNTs on SiO2/Co 61
4.2 Monometallic Co catalyst supported on Al2O3 62
4.2.1 Surface and morphological analysis of Al2O3/Co 62
4.2.2 Analysis of CCVD grown SWCNT on Al2O3/Co 63
4.2.3 Chirality and diameter analysis of SWCNTs on Al2O3/Co 67
4.3 Bimetallic Co-Mo catalyst supported on Al2O3 68
4.3.1 Surface and Morphological analysis of Al2O3/Co-Mo 68
4.3.2 Effect of IBSD deposition parameters on NP formation 71
4.3.3 Analysis of CCVD grown SWCNT on Al2O3/Co-Mo 72
4.3.4 Chirality and diameter analysis of SWCNTs on Al2O3/Co-Mo 76
4.4 Comparison of SWCNT from different catalyst configurations 77
5 Growth of SWCNT using gradient layer of catalyst 79
5.1 Analysis of grown SWCNT on Co-Mo using step gradient A 79
5.2 Analysis of grown SWCNT on Co-Mo using step gradient B 80
5.2.1 Growth of SWCNT by utilizing shutter at position I 80
5.2.2 Growth of SWCNT by utilizing shutter at position II 82
5.2.3 Effect of vacuum breaking on CCVD growth of SWCNT 83
6 Growth of SWCNT using gradient layer catalyst in vertical CVD reactor B 87
6.1 SWCNT growth on gradient layer of monometallic catalyst 87
6.1.1 Analysis of CCVD grown SWCNT on gradient layer of Co 87
6.1.2 Analysis of CCVD grown SWCNT on gradient layer of Ni 89
6.1.3 Comparison of SWCNT properties for monometallic of Ni and Co 90
6.2 SWCNT growth on gradient layer of bimetallic catalyst 92
6.2.1 Analysis of CCVD grown SWCNT on gradient layer of Co-Mo 92
6.2.2 Analysis of CCVD grown SWCNT on gradient layer of Co-Ru 95
6.2.3 Comparison of SWCNTs on Co-Mo and Co-Ru catalyst systems 98
6.2.4 Analysis of CCVD grown SWCNTs on gradient layer of Ni-Ru 100
7 Growth of SWCNT using spin-coated catalyst precursor in horizontal CVD reactor 103
7.1 Effect of CCVD growth temperature on SWCNT properties 103
7.2 Effect of catalyst calcination temperature on SWCNT properties 103
7.3 Analysis of CCVD grown SWCNT on Co and Co-Ru 105
7.3.1 Monolayer configuration of different Co precursors 105
7.3.2 Bilayer configuration of Co and Ru precursors 106
7.3.3 Trilayer configuration of Co and Ru precursors 107
7.3.4 Monolayer configuration of Mixture Co and Ru precursors 109
7.3.5 Comparison of SWCNTs on different catalyst configurations 110
8 Growth of SWCNT using spin-coated catalyst precursor in vertical CVD reactor B 113
8.1 Growth of SWCNT on Mixture of Co and Ru precursors 113
8.2 Effect of CVD reactor geometry on SWCNT properties 115
8.3 Effect of catalyst preparation technique on SWCNT properties 116
8.4 Wafer-level growth of SWCNT on bimetallic Co-Ru 117
9 SWCNT-based device fabrication 119
9.1 Different approaches for SWCNT-based device fabrication 119
9.2 Growth-based technique for SWCNT-based device fabrication 121
9.2.1 FET fabrication on in-plane random network SWCNT 121
9.2.2 FET fabrication on out-of-plane random network SWCNT 123
10 Summary and outlook 127
Appendix 131
Bibliography 171
List of tables 183
List of figures 185
Versicherung 197
Theses 199
Curriculum vitae 201
List of publications 203 / Die hervorragenden elektronischen Eigenschaften von halbleitenden, einwandigen Kohlenstoff-Nanoröhren (sc-SWCNTs haben die Untersuchung dazu veranlasst, sie in verschiedenen Anwendungsbereichen wie der Mikroelektronik, Sensorik, MEMS und MOEMS einzusetzen. Herausforderungen ergeben sich jedoch aus dem Mangel an Selektivität bezüglich elektronischer Bauart und Chiralität sowie der Sicherstellung hoher Qualität, hoher Reinheit und gut aufeinander abgestimmter SWCNTs während des Herstellungsprozesses. Die Katalytische chemische Gasphasenabscheidung (CCVD) zeigt ein großes Potenzial bei der direkten Synthese von hochqualitativen SWCNTs mit Chiraler- oder Typenselektivität.
Diese Dissertation behandelt drei wichtige Aspekte für das Wachstum von sc-SWCNT und deckt die Methodenentwicklung des schnellen Screenings für komplexe Katalysatorsysteme, die Prozessentwicklung für das typselektive Wachstum von SWCNTs und die Übertragung von Prozessen in einen spezifischen CVD-Reaktor ab. Der Reaktor, welcher eingebettet in die mikrotechnologische Prozesslinie ist, kann Wafer bis zu 8- Zoll verarbeiten. Raman-Spektroskopie mit mehreren Wellenlängen wird verwendet, um die Zusammensetzung von SWCNTs zu analysieren. Darüber hinaus werden verschiedene mikroskopische Techniken von REM, TEM und AFM verwendet, um die Oberflächenmorphologie von Katalysatorschichten und die Größe der Nanopartikel sowie die strukturbezogenen Eigenschaften von SWCNTs zu analysieren. Zunächst werden systematische Untersuchungen an monometallischen Co- und Bimetall-Co-Mo-Systemen mit unterschiedlichen Doppelschichtdickenkonfigurationen durchgeführt und deren Einfluss auf die Eigenschaften gewachsener SWCNTs auf Chipebene untersucht. Es wird gezeigt, dass durch Einstellung der Katalysatorabscheidungsbedingungen des Doppelschichtkatalysators sowie durch Optimierung der Gasumgebung im CCVD-Prozess die strukturbezogenen Eigenschaften von SWCNTs drastisch verbessert werden können. Darüber hinaus wurde durch die Verwendung eines Gradientenschichtkatalysators, welcher mittels einer Shutter-unterstützten Zerstäubungsabscheidung hergestellt wurde, ein schnelles und effizientes Verfahren zum Untersuchen verschiedener Doppelschichtkonfigurationen von Co-Mo, Co-Ru und Ni-Ru entwickelt. Unter Verwendung der Abscheidung einer Gradientenschicht mit einer fein aufgelösten Katalysatordicke wurden ungerichtete SWCNTs auf einem bimetallischen Co-Mo-System unter definierten Prozessbedingungen mit 45% (bei 633 nm) und 75% (bei 785 nm) halbleitender Anreicherung von langem und hochwertigem SWCNT gezüchtet. Im Gegensatz dazu wird das bimetallische Co-Ru-System unter definierten Prozessbedingungen entwickelt, um SWCNT in der Ebene mit 85% (bei 633 nm) und 75% (bei 785 nm) halbleitender Anreicherung von kurzer und geringer Qualität von SWCNT zu wachsen. Außerdem werden verschiedene Konfigurationen des Bimetall-Co-Ru-Systems aus Salzvorläufern durch Spin-Coating-Technik hergestellt. Es zeigt sich für die Bimetallkonfiguration, die durch Mischung von Cobalt (II) -chlorid und Ruthenium (III) -nitrosylacetat, ein zufälliges Netzwerk SWCNT zu 70% (bei 633 nm) und 95% (bei 785 nm) halbleitender Anreicherung langer SWCNTs mit hohem Anteil hergestellt wurde Qualität wird auf Waferebene gewachsen. Ein zufälliges Netzwerk-SWCNT mit einem hohen Grad an halbleitender Anreicherung wird als Kanalmaterial für die Herstellung von Dünnschichttransistoren verwendet, was zu einem CNTFET mit einem Ein / Aus-Verhältnis um 10*3 führte.:Bibliographic description 3
Vorwort 9
List of abbreviations and symbols 11
1 Introduction 15
2 Fundamentals of carbon nanotubes 21
2.1 Chemical bonds in carbon structures 21
2.2 Different allotropes of carbon 22
2.3 History of carbon nanotubes research 23
2.4 Structure of carbon nanotubes 24
2.5 Electronic properties of carbon nanotubes 26
2.6 Synthesis of carbon nanotubes 27
2.7 Growth mechanism of carbon nanotubes by CCVD 29
2.8 Catalyst for CCVD synthesis of SWCNTs 31
2.8.1 Catalyst nanoparticle formation from thin film 32
2.8.2 Mechanism of solid state dewetting 33
2.9 CCVD synthesis of SWCNT 35
2.10 Selective synthesis of SWCNT 37
3 Experimental 39
3.1 Preparation of different catalyst/support systems 39
3.1.1 Homogenous layer of catalyst prepared by PVD 39
3.1.2 Gradient layer deposition of catalyst by IBSD 41
3.1.3 Homogenous layer of catalyst prepared by spin coating 45
3.2 CVD reactors for synthesis of SWCNT 46
3.2.1 R&D vertical flow CVD reactor with showerhead 46
3.2.2 Industrial vertical flow CVD reactor with showerhead 47
3.2.3 Horizontal flow tube CVD reactor 49
3.3 Methods for characterization 50
3.3.1 Atomic force microscopy 50
3.3.2 Raman spectroscopy 50
3.3.3 Spectroscopic ellipsometry 56
3.3.4 X-ray reflection 56
3.3.5 Scanning electron microscopy 56
3.3.6 Transmission electron microscopy 56
4 Growth of SWCNT using PVD catalyst layer in vertical CVD reactor A 57
4.1 Monometallic Co catalyst supported on SiO2 57
4.1.1 Surface and morphological analysis of SiO2/Co 57
4.1.2 Analysis of CCVD grown SWCNT on SiO2/Co 59
4.1.3 Chirality and diameter analysis of SWCNTs on SiO2/Co 61
4.2 Monometallic Co catalyst supported on Al2O3 62
4.2.1 Surface and morphological analysis of Al2O3/Co 62
4.2.2 Analysis of CCVD grown SWCNT on Al2O3/Co 63
4.2.3 Chirality and diameter analysis of SWCNTs on Al2O3/Co 67
4.3 Bimetallic Co-Mo catalyst supported on Al2O3 68
4.3.1 Surface and Morphological analysis of Al2O3/Co-Mo 68
4.3.2 Effect of IBSD deposition parameters on NP formation 71
4.3.3 Analysis of CCVD grown SWCNT on Al2O3/Co-Mo 72
4.3.4 Chirality and diameter analysis of SWCNTs on Al2O3/Co-Mo 76
4.4 Comparison of SWCNT from different catalyst configurations 77
5 Growth of SWCNT using gradient layer of catalyst 79
5.1 Analysis of grown SWCNT on Co-Mo using step gradient A 79
5.2 Analysis of grown SWCNT on Co-Mo using step gradient B 80
5.2.1 Growth of SWCNT by utilizing shutter at position I 80
5.2.2 Growth of SWCNT by utilizing shutter at position II 82
5.2.3 Effect of vacuum breaking on CCVD growth of SWCNT 83
6 Growth of SWCNT using gradient layer catalyst in vertical CVD reactor B 87
6.1 SWCNT growth on gradient layer of monometallic catalyst 87
6.1.1 Analysis of CCVD grown SWCNT on gradient layer of Co 87
6.1.2 Analysis of CCVD grown SWCNT on gradient layer of Ni 89
6.1.3 Comparison of SWCNT properties for monometallic of Ni and Co 90
6.2 SWCNT growth on gradient layer of bimetallic catalyst 92
6.2.1 Analysis of CCVD grown SWCNT on gradient layer of Co-Mo 92
6.2.2 Analysis of CCVD grown SWCNT on gradient layer of Co-Ru 95
6.2.3 Comparison of SWCNTs on Co-Mo and Co-Ru catalyst systems 98
6.2.4 Analysis of CCVD grown SWCNTs on gradient layer of Ni-Ru 100
7 Growth of SWCNT using spin-coated catalyst precursor in horizontal CVD reactor 103
7.1 Effect of CCVD growth temperature on SWCNT properties 103
7.2 Effect of catalyst calcination temperature on SWCNT properties 103
7.3 Analysis of CCVD grown SWCNT on Co and Co-Ru 105
7.3.1 Monolayer configuration of different Co precursors 105
7.3.2 Bilayer configuration of Co and Ru precursors 106
7.3.3 Trilayer configuration of Co and Ru precursors 107
7.3.4 Monolayer configuration of Mixture Co and Ru precursors 109
7.3.5 Comparison of SWCNTs on different catalyst configurations 110
8 Growth of SWCNT using spin-coated catalyst precursor in vertical CVD reactor B 113
8.1 Growth of SWCNT on Mixture of Co and Ru precursors 113
8.2 Effect of CVD reactor geometry on SWCNT properties 115
8.3 Effect of catalyst preparation technique on SWCNT properties 116
8.4 Wafer-level growth of SWCNT on bimetallic Co-Ru 117
9 SWCNT-based device fabrication 119
9.1 Different approaches for SWCNT-based device fabrication 119
9.2 Growth-based technique for SWCNT-based device fabrication 121
9.2.1 FET fabrication on in-plane random network SWCNT 121
9.2.2 FET fabrication on out-of-plane random network SWCNT 123
10 Summary and outlook 127
Appendix 131
Bibliography 171
List of tables 183
List of figures 185
Versicherung 197
Theses 199
Curriculum vitae 201
List of publications 203
|
833 |
Soukromoprávní důsledky porušení soutěžního práva a jejich prosazování v ČR / Private-law consequences of a breach of competition law and their enforcement in the Czech RepublicMikulíková, Lucie January 2019 (has links)
V ANGLICKÉM JAZYCE Private-law consequences of a breach of competition law and their enforcement in the Czech Republic The private-law consequences of a breach of competition law, Articles 101 and 102 of the Treaty on the Functioning of the EU and Sections 3 and 11 of the Czech Competition Act, may affect many entities, irrespective of whether they are competitors or consumers. Recently, emphasis has been placed on private enforcement of competition law that is intended to serve as an important complement to public law enforcement. The first part of the dissertation defines basic concepts and principles of competition law including "public rules on restriction of competition". The history of the enforcement of competition law in the Czech Republic and the dynamic development in this area at the EU level are outlined in the second part. The third crucial part of this work deals with the right to damages caused by a breach of competition law in the Czech Republic. In 2014, the EU adopted Directive 2014/104 on certain rules in damages actions with the view, inter alia, to increase the effectiveness of private enforcement of competition rules by civil courts of EU Member States. On August 18, 2017, new Act No. 262/2017 Coll. which implements the Directive into Czech law was adopted. The dissertation...
|
834 |
Využití zprostředkovaného učení ve školní výuce / Mediated Learning experience and its application in school educationRázgová, Lenka January 2017 (has links)
The dissertation thesis presents the results of a research project which focused on the application of mediated learning experience theory to teaching with respect to cognitive development of pupils. The first chapter introduces cognitive education, which concentrates on the process of learning. It also compares this approach with traditional methods aimed at the content of learning. The following parts of the thesis deal with selected theories postulated by Reuven Feuerstein which are important for understanding the context in which his other theory was developed: the theory of mediated learning experience. This theory is the central theme of the theoretical part of the thesis. Apart from its definition and parameters, the thesis presents specific recommendations for teachers about how to develop cognitive functions of their pupils by applying this theory directly in class. Afterwards, attention is paid to Feuerstein's well-known worldwide intervention program called The Feuerstein Instrumental Enrichment. This program is used in the Czech school system, too. The essential part of this chapter introduces a number of studies which focused on the verification of benefits of Feuerstein's approaches to cognitive development in children and adolescents. The last chapter of the theoretical part...
|
835 |
Role učitele a vychovatele ve Věznici Stráž pod Ralskem / Role of teacher and educator in prison Stráž pod RalskemPňačková, Tereza January 2020 (has links)
The thesis deals with the role of teachers and educators working in Stráž pod Ralskem Prison. The theoretical part of the thesis, therefore, focuses not only on the description of the Prison Service of the Czech Republic, but it also contains the characteristics of the Stráž pod Ralskem Prison and the Stráž pod Ralskem School Educational Center. It describes the educational system of convicts and mentions basic information about the Academy of Prison Service of the Czech Republic. Moreover, it briefly describes the activities of teachers and educators working in the prison environment. The diploma thesis aims to find out, what kind of roles teachers and educators play in the prison, what approaches, methods and forms are suitable and effective for working with convicts from the perspective of both workers and convicts, and what pitfalls limit the work of teachers and educators in this prison. A qualitative method was chosen for the research, and data were collected based on the questionnaire and the personal interview with a teacher, who used to work as an educator. The research was conducted in Stráž pod Ralskem Prison, the research sample consists of three groups: educators, teachers, and pupils - convicted in Stráž pod Ralskem Prison. The research survey shows that the role of the educator is...
|
836 |
Managing Invisible Boundaries: How "Smart" is Smartphone Use in the Work and Home Domains?Chatfield, Sarah E. January 2014 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / The present study sought to examine the impact of technology in permeating the boundaries between individuals’ work and family domains, testing and extending the current theoretical model of boundary management. The first goal, to explore predictors of the boundary management styles (BMS) people use with respect to communication technology (CT), was accomplished by demonstrating that three factors predicted BMS for CT use: preferences for integration, identity centrality, and work/family norms. The second goal, to examine outcomes that could result from varying CT use boundary management styles, was also supported in that BMS for CT use was a predictor of work-family conflict and enrichment. However, one key component of the model was not supported in that perceived control over BMS did not moderate the relationship between BMS and outcomes. Theoretical and practical implications of these findings are discussed, as well as suggestions for future research on boundary theory and CT use. By exploring tangible boundary management behaviors, the present study offers interesting implications that could ultimately assist organizations in developing policies regarding CT use both at home and at work.
|
837 |
Strukturelle Merkmale N-modifizierter Braunkohlen unter besonderer Berücksichtigung der HuminstoffeNinnemann, Horst 20 November 2007 (has links)
Motiviert durch die Zunahme der weltweiten Nachfrage nach hochwertigen Humusstoffen wurde am Institut für Holz- und Pflanzenchemie ein neuartiger Humusersatzstoff entwickelt. Dieses N-modifizierte Produkt wird auf Basis eines patentierten Normaldruckverfahrens der oxidativen Ammonolyse (OA) aus ligninhaltigen Ausgangssubstanzen, im vorliegenden Fall Lausitzer Braunkohle, hergestellt. Ziel war, die bisher vorliegenden Erkenntnisse der strukturellen Eigenschaften solcher Humusstoffe zu erweitern. Im Fokus standen die Gehalte und Charakteristik der Huminstofffraktionen (Humine, Humin- und Fulvosäuren). Der Stickstoff und die Art seines Einbaus in die organische Substanz spielt hierbei eine besondere Rolle. Für die Huminstoffisolierung kam die hinsichtlich der Ausbeuten und des Zeitaufwandes optimierte IHSS-Methode zum Einsatz. Wesentliche Merkmale N-modifizierter Substanzen sind erhöhte Huminsäurengehalte, zeitlich differenziert wirksame N-Bindungsformen und damit eine Diversifizierung der Funktionalität. Zusätzlich mit dem geringen Aschegehalt unterscheidet dies N-modifizierte Lausitzer Braunkohle von anderen auf Braunkohlebasis erzeugten Bodenverbesserungsmitteln des Marktes. Es konnte gezeigt werden, dass Huminsäuren hinsichtlich der Bereitstellung von Stickstoff und Funktionalität (z.B. Austauscherplätze) eine Schlüsselrolle einnehmen. Die Veränderungen durch die OA basieren stofflich auf der Bildung regenerierter Huminsäuren und chemisch u.a. auf der oxidativen Ringspaltung von Aromaten an nicht veretherten phenolischer OH-Gruppen von Methoxyphenolstrukturen. Dabei ist diese Reaktion entgegen früherer Annahmen nicht an eine Demethoxylierung gebunden und erfordert auch keine verschärften Reaktionsbedingungen (z.B. erhöhter Druck). Diese und weitere Reaktionsmechanismen führen zu ammoniumartig, amidartig und fest organisch gebundenen N-Bindungsformen. 15N-NMR-Spektroskopische Untersuchungen an einem 15N-angereicherten Produkt, Py-GC/MS-Untersuchungen und nasschemische Experimente zeigen, dass in der Vergangenheit die Bedeutung heterocyclischer, insbesondere heteroaromatischer N-Bindungsformen überschätzt wurde. Amidartiger Stickstoff präsentiert sich dabei als außerordentlich heterogen hinsichtlich seiner Hydrolysestabilität bzw. Pflanzenverfügbarkeit. Für die effektive Beurteilung möglicher Ausgangssubstanzen hinsichtlich ihrer Eignung für die Herstellung von Humusdüngestoffen nach dem Prinzip der OA kann der Huminsäurengehalt herangezogen werden. Er wird mit Hilfe eines degradativen Verfahrens ermittelt. Die mit dem Huminsäurengehalt in Verbindung stehenden Stoffeigenschaften von Kohlen korrelieren gut mit dem N-Einbau. Aus Sicht der Verfahrensführung hängt die Intensität des N-Einbaus eng mit dem Oxidationsregime zusammen. Durch Anwendung von reinem Sauerstoff anstelle von Luft als sehr einfach und günstig zu realisierende Maßnahme kann die Reaktionszeit halbiert werden. / The development of a novel artificial humus material at the Institute of Wood- and Plant Chemistry was accounted by the increasing demand for high grade humic matter. This N-modified product base on a patented ambient pressure technology of the oxidative ammonolysis. of lignin containing substances, in particular Lusitian lignite. Objective of the work was to broadening the current knowledge of structural properties with focus on the contents and characteristics of humic substances fractions (humins, humic acids, fulvic acids). Especially attention was given to nitrogen and its way of incorporation into organic matter. For isolating humic substances the IHSS method was used. The procedure was adapted in order to increase the yield of humic acids and decrease time needed. Main characteristics of N-modified substances are higher contents of humic acids and subtly differenciateted effective N-binding forms with leads to higher diversity of the chemical functionality. This and the low ash content makes the differences to other brown coal based soil improving agents available on the marked. It has been shown that humic acids give the main part providing nitrogen and functionality (e.g. cation exchange capacity). The oxidative ammonolysis leads to regenerated humic acids as well as e.g. the clevage of aromatic structures by reactions of free phenolic groups. In contrast to former assumptions the cleavage is not strongly related to demethoxylation or strong reaction conditions like high pressure. This and other reactions lead to short, middle, and long lasting N-binding forms. 15N-NMR-spectroscopic investigations on a 15N-enriched product, Py-GC/MS-investigations and conventional investigations show an overestimation of heterocyclic, in particular heteroaromatic N-binding forms up to now. Consequently amide like nitrogen reveals as extraordinary according to its persistent behaviour to hydrolysis and plant availability respectively. Corresponding the correlation of the N-incorporation and humic acid content of raw materials the latter can be used for evaluating possible raw material for its usage for N-modification. It can be easy obtained in a degratadive way. From the process engineering point of view the success of N-incorporating is strongly correlated to the oxidation conditions during processing. Using pure oxygen instead of air shorts the needed reaction at 50%.
|
838 |
Ancient environmental DNA as a means of understanding ecological restructuring during the Pleistocene-Holocene transition in Yukon, CanadaMurchie, Tyler James January 2021 (has links)
Humans evolved in a world of giant creatures. Current evidence suggests that most ice age megafauna went extinct around the transition to our current Holocene epoch. The ecological reverberations associated with the loss of over 65% of Earth’s largest terrestrial animals transformed ecosystems and human lifeways forever thereafter. However, there is still substantial debate as to the cause of this mass extinction. Evidence variously supports climate change and anthropogenic factors as primary drivers in the restructuring of the terrestrial biosphere. Much of the ongoing debate is driven by the insufficient resolution accessible via macro-remains. To help fill in the gaps in our understandings of the Pleistocene-Holocene transition, I utilized the growing power of sedimentary ancient DNA (sedaDNA) to reconstruct shifting signals of plants and animals in central Yukon. To date, sedaDNA has typically been analyzed by amplifying small, taxonomically informative regions. However, this approach is not ideally suited to the degraded characteristics of sedaDNA and ignores most of the potential data. Means of isolating sedaDNA have also suffered from the use of overly aggressive purification techniques resulting in substantial loss. To address these limitations, I first experimentally developed a novel means of releasing and isolating sedaDNA. Secondly, I developed a novel environmental bait-set designed to simultaneously capture DNA informative of macro-scale ecosystems. When combined, we identify a substantial improvement in the quantity and breadth of biomolecules recovered. These optimizations facilitated the unexpected discovery of horse and mammoth surviving thousands of years after their supposed extirpation. I followed up these results by extracting DNA from multiple permafrost cores where we confirm the late survival signal and identify a far more complex and high-resolution dataset beyond those identifiable by complementary methods. I was also able to reconstruct mitochondrial genomes from multiple megafauna simultaneously solely from sediment, demonstrating the information potential of sedaDNA. / Dissertation / Doctor of Philosophy (PhD) / A new addition to the rapidly growing field of palaeogenetics is environmental DNA (eDNA) with its immense wealth of biomolecules preserved over millennia outside of biological tissues. Organisms are constantly shedding cells, and while most of this DNA is metabolized or otherwise degraded, some small fraction is preserved through sedimentary mineral-binding. I experimentally developed new ancient eDNA methods for recovery, isolation, and analysis to maximize our access to these biomolecules and demonstrate that this novel approach outperforms alternative protocols. Thereafter, I used these methods to extract DNA from ice age permafrost samples dating between 30,000–6,000 years before present. These data demonstrate the power of ancient eDNA for reconstructing ecosystem change through time, as well as identifying evidence for the Holocene survival of caballine horse and woolly mammoth in continental North America. This late persistence of Pleistocene fauna has implications for understanding the human ecological and climatological factors involved in the Late Pleistocene mass extinction event. This effort is paralleled with megafaunal mitogenomic assembly and phylogenetics solely from sediment. This thesis demonstrates that environmental DNA can significantly augment macro-scale buried records in palaeoecology.
|
839 |
Determining the effects of elevated carbon dioxide on soil acidification, cation depletion, and soil inorganic carbon and mapping soil carbons using artificial intelligenceFerdush, Jannatul 09 August 2022 (has links) (PDF)
Soil carbon is the largest sink and source of the global carbon cycle and is disturbed by several natural, anthropogenic, and environmental factors. The global increase of atmospheric CO2 affects soil carbon cycling through varied biogeochemical processes. The first chapter is a compilation of current information on potential factors triggering soil acidification and weathering mechanisms under elevated CO2 and their consequences on soil inorganic carbon (SIC) pool and quality. Soil water content and precipitation were critical factors influencing elevated CO2 effects on the SIC pool. The second chapter examines a detailed column experiment in which six soils from the state of Mississippi, USA, representing acidic, neutral, and alkaline pH, were exposed to different CO2 enrichments (100%, 10%, and 1%) for 30 days. The leachates’ pH tended to attain an equilibrium state (neutral) with time under CO2 saturation. SIC increased under CO2 saturation, whereas cation exchange capacity (CEC) showed a decreasing pattern in all soils. In the third chapter, an eXplainable artificial intelligence (XAI) was performed to visualize the different forms of soil carbon variability across the Mississippi River Basin area. This model explains key insights and local discrepancies, suggesting a solution to the “Black-Box” issue. The best performing model, stack ensemble, showed improved RMSE (3 to 8%) and spatial variability for soil carbons than other ML models, especially after adding the residuals from regression analyses. Land cover type > soil pH > total nitrogen, > NDVI were identified as the top four crucial factors for predicting SOC when bulk density > precipitation, soil pH > mean annual temperature described SIC. The proposed automatic machine learning (AutoML) model with model agnostic interpolations might be a hallmark to mitigate the C loss under adverse climate change conditions and allow diverse knowledge groups to adopt a new interpretable ML algorithm more confidently. Findings from this study help predict the impact of elevated atmospheric CO2 on soil pH, acidification, and nutrient availability and develop strategies for sustainable land management practices under a changing climate.
|
840 |
A physics-based muon trajectory estimation algorithm for muon tomographic applicationsReshma Sanjay Ughade (16625865) 04 August 2023 (has links)
<p>Recently, the use of cosmic ray muons in critical national security applications, e.g., nuclear nonproliferation and safeguards verification, has gained attention due to unique muon properties such as high energy and low attenuation even in very dense materials. Applications where muon tomography has been demonstrated include cargo screening for detection of special nuclear materials smuggling, source localization, material identification, determination of nuclear fuel debris location in nuclear reactors, etc. However, muon image reconstruction techniques are still limited in resolution mostly due to multiple Coulombscattering (MCS) within the target object. Improving and expanding muon tomography would require development of efficient & flexible physics-based algorithms to model the MCS process and accurately estimate the most probable trajectory of a muon as it traverses the target object. The present study introduces a novel algorithmic approach that utilizes Bayesian probability theory and a Gaussian approximation of MCS to estimate the most probable path of cosmic ray muons as they traverse uniform media.</p>
<p>Using GEANT4, an investigation was conducted involving the trajectory of 10,000 muon particles that underwent bombardment from a point source parallel to the x-axis. The proposed algorithm was assessed through four types of simulations. In the first type, muons with energies of 1 GeV, 3 GeV, 10 GeV, and 100 GeV were utilized to evaluate the algorithms’ performance and accuracy. The second type of simulation involved the use of target cubes composed of different materials, including aluminum, iron, lead, and uranium. These simulations specifically focused on muons with an energy of 3 GeV. Next, the third type of simulation entailed employing target cubes with varying lengths, such as 10 cm, 20 cm, 40 cm, and 80 cm, specifically using muons with an energy of 3 GeV and a uranium target. Lastly, all the previous simulations were revised to accommodate a source of poly-energetic muons. This revision was undertaken to create a more realistic source scenario that aligns with the distribution of muon energies encountered in real-world situations.</p>
<p>The results demonstrate significant improvements in precision and muon flux utilization when comparing different algorithms. The Generalized Muon Trajectory Estimation (GMTE) algorithm shows around 50% improvement in precision compared to currently used Straight Line Path (SLP) algorithm across all test scenarios. Additionally, GMTE algorithm exhibits around 38% improvement in precision compared to the extensively used Point of Closest Approach (PoCA) algorithm. Similarly for both mono and poly energetic source of muons, the GMTE algorithm shows 10%-35% increase in muon flux utilization for high Z materials and a 10%-15% increase for medium Z materials compared to the PoCA algorithm. Similarly, it demonstrates 6%-9% increase in muon flux utilization for both medium and high Z materials compared to the SLP algorithm across all test scenarios. These results highlight the enhanced performance and efficiency of GMTE algorithm in comparison to SLP and PoCA algorithms.</p>
<p>Through these extensive simulations, our objective was to comprehensively evaluate the performance and effectiveness of the proposed algorithm across a range of variables, including energy levels, materials, and target geometries. The findings of our study demonstrate that the utilization of these algorithm enables improved resolution and reduced measurement time for cosmic ray muons when compared with current SLP and PoCA algorithm.</p>
|
Page generated in 0.165 seconds