Drought effects on carbon and nutrient dynamics in Scots pine : homeostasis, thresholds and tipping points

Species of the tree genus Pine (Pinus L.) exist all over the world and no other group contains so many attractive forms (Curtis & Bausor, 1943) . Scots pine (Pinus sylvestris L.) is currently the most widely distributed pine and occurs throughout all of Eurasia. In the central alpine valleys, Scots pine is growing at the dry border of its distribution range, which involves overcoming periods with extreme low water availability. Although the species is known for its ability to grow on dry and nutrient poor soils, several extreme droughts during the last two decades have caused a 50% dieback of Scots pine in the dry valleys of the Central Alps in Switzerland. The ability of trees to survive drought is determined by their initial health and their resilience to drought, as well as on the characteristics of a drought event – i.e. timing, duration and intensity. The mechanisms underlying drought-induced mortality are still unclear, as well as the recovery process after soil rewetting. Furthermore, possible mitigation or aggravation of drought effects by elevated nutrient availability in the soil has not been studied before. The carbon (C) balance in trees is used as an indicator for C assimilation, growth, defense and storage processes. When trees are exposed to drought, to changes in soil nutrition or sudden defoliation, the C balance may change. In this thesis, the main objective was thus to combine effects of drought and fertilization to study the C and nitrogen (N) dynamics in Scots pine trees. In the first chapter, I give an overview of the state-of-the-art in research on drought-affected C and N dynamics in trees. The aim of the second chapter was to assess the effects of long-term drought release on growth and non-structural carbohydrate (NSC) concentrations of adult P. sylvestris trees. A long-term (13 years) irrigation experiment was conducted in the Pfynwald, a Scots pine dominated forest located at the dry distribution margin of the species in southern Switzerland. I measured growth, NSC, N and phosphorus (P) concentrations, as well as the natural abundance of 13C isotopes on trees with different leaf area in control and irrigation plots. Irrigation resulted in higher growth rates and carbon isotope discrimination, but did not alter NSC levels. Growth and NSC decreased with lower leaf area in both control and irrigated trees, but NSC did not correlate with leaf-level gas exchange indices such as foliar δ13C, which is an indicator for water use efficiency, N or P, which are both stimulants of photosynthesis. Trees with initially low leaf area had limited ability to respond to the long-term irrigation, indicating a legacy effect of previously low crown condition. The NSC constancy across treatments suggests that carbohydrate storage may stay constant when changes in climate are slow enough to allow acclimation. Moreover, total leaf area, rather than leaf gas exchange per unit leaf area, drives variation in whole-tree carbohydrate dynamics in this system. The main focus of the third chapter was the mitigation or aggravation of drought effects by nutrient availability in the soil. Three year-old P. sylvestris saplings were exposed to drought during two subsequent years, using four different water and two soil nutrient regimes, and drought was released thereafter. In addition, partial and full needle removal was performed in order to assess effects of changes in source:sink ratio. Biomass, leaf gas exchange and tissue NSC were measured during and after the first and second growing season. Extreme drought reduced stomatal conductance, photosynthesis, biomass and NSC, whereas intermediate drought only slightly affected biomass and NSC. Defoliation stimulated photosynthesis and fertilization increased growth and root biomass fraction, but mainly in the two intermediate drought levels. Only extreme drought pushed P. sylvestris trees to mortality. The third chapter concludes that tree mortality under severe drought periods will not be mitigated, but that the effects of low intensity drought stress could be compensated by increased nutrient availability and decreased source:sink ratio. The aim of the fourth chapter was to assess the C and N allocation underlying the biomass changes that were found in chapter 3. I hypothesized that, during drought, increased soil nutrient availability stimulates root metabolism and carbon allocation to belowground tissues under drought stress. I therefore conducted a 15N and 13C labelling experiment in July and August 2016 respectively, on the saplings described above. 15N labelling was conducted with fertilized saplings from all water regimes, while 13C labelling was only conducted with saplings (both nutrient regimes) from two out of four water regimes (well-watered and mild drought). I assessed the abundance of 15N and 13C in the roots, stem and needles after the first growing season and during the second year. C uptake was slightly lower in drought stressed trees, and extreme drought inhibited largely the N uptake and transport. Carbon allocation to belowground tissues was decreased under drought, but not in combination with fertilization. The results indicate a potential positive feedback loop, where fertilization improved the metabolism and functioning of the roots, stimulating source activity and hence C allocation to belowground tissues. We can thus conclude that soil nutrients might play an important role in mitigating drought stress of trees. Overall this thesis shows that the impairment of tree functioning and mortality can be explained with thresholds: long-term drought causes a reduction in tree vigor and leaf area, and if a threshold of approximately 60 – 70% loss of leaf area is reached, trees may follow a trajectory towards mortality, even if drought is released in the soil. In the controlled experiment, soil moisture thresholds were visualized. The impairment of C allocation belowground under mild drought, the reduction of NSC in and impairment of 15N uptake by the roots under extreme drought indicate that roots might be the first tissue to lose function and eventually die off during drought stress. Additional nutrient supply can sustain root functioning under drought, indicating that soil moisture tipping points are not fixed, but can be modified. In general, trees have a strongly coordinated supply – demand regulation for C and N, enabling homeostatic C balances as long as changes in climate are slow or mild enough for trees to acclimate

Winning and losing in the creative industries: an analysis of creative graduates' career opportunities across creative disciplines

Following earlier work looking at overall career difficulties and low economic rewards faced by graduates in creative disciplines, the paper takes a closer look into the different career patterns and economic performance of “Bohemian” graduates across different creative disciplines. While it is widely acknowledged in the literature that careers in the creative field tend to be unstructured, often relying on part-time work and low wages, our knowledge of how these characteristics differ across the creative industries and occupational sectors is very limited. The paper explores the different trajectory and career patterns experienced by graduates in different creative disciplinary fields and their ability to enter creative occupations. Data from the Higher Education Statistical Agency (HESA) are presented, articulating a complex picture of the reality of finding a creative occupation for creative graduates. While students of some disciplines struggle to find full-time work in the creative economy, for others full-time occupation is the norm. Geography plays a crucial role also in offering graduates opportunities in creative occupations and higher salaries. The findings are contextualised in the New Labour cultural policy framework and conclusions are drawn on whether the creative industries policy construct has hidden a very problematic reality of winners and losers in the creative economy

Discriminative Appearance Models for Face Alignment

The proposed face alignment algorithm uses local gradient features as the appearance representation. These features are obtained by pixel value comparison, which provide robustness against changes in illumination, as well as partial occlusion and local deformation due to the locality. The adopted features are modeled in three discriminative methods, which correspond to different alignment cost functions. The discriminative appearance modeling alleviate the generalization problem to some extent

Combinatorial Discovery of Irradiation Damage Tolerant Nano-structured W-based alloys

One of the challenges in fusion reactors is the discovery of plasma facing materials capable of withstanding extreme conditions, such as radiation damage and high heat flux. Development of fusion materials can be a daunting task since vast combinations of microstructures and compositions need to be explored, each of which requires trial-and-error based irradiation experiments and materials characterizations. Here, we utilize combinatorial experiments that allow rapid and systematic characterizations of composition-microstructure dependent irradiation damage behaviors of nanostructured tungsten alloys. The combinatorial materials library of W-Re-Ta alloys was synthesized, followed by the high-throughput experiments for probing irradiation damages to the mechanical, thermal, and structural properties of the alloys. This highly efficient technique allows rapid identification of composition ranges with excellent damage tolerance. We find that the distribution of implanted He clusters can be significantly altered by the addition of Ta and Re, which play a critical role in determining property changes upon irradiation

Exponential Machines

Modeling interactions between features improves the performance of machine learning solutions in many domains (e.g. recommender systems or sentiment analysis). In this paper, we introduce Exponential Machines (ExM), a predictor that models all interactions of every order. The key idea is to represent an exponentially large tensor of parameters in a factorized format called Tensor Train (TT). The Tensor Train format regularizes the model and lets you control the number of underlying parameters. To train the model, we develop a stochastic Riemannian optimization procedure, which allows us to fit tensors with 2^160 entries. We show that the model achieves state-of-the-art performance on synthetic data with high-order interactions and that it works on par with high-order factorization machines on a recommender system dataset MovieLens 100K.Comment: ICLR-2017 workshop track pape

Study of comfort properties of natural and synthetic knitted fabrics in different blend ratios for winter active sportswear

The objective of the present study is to produce base layer winter active sportswear fabrics using natural and synthetic fibres and their blends which will deliver good comfort properties. Polyester, wool and bamboo fibres were selected for this study. Polyester is the most common fibre used in sportswear, wool is increasingly being used in sportswear and bamboo is a relatively new fibre that offers properties suitable for base layer sportswear. Bamboo is also regarded as a "green" and eco-sustainable fibre. Preliminary experiments were carried out to find the liquid moisture transfer performance of knitted fabrics made from each selected 100% fibre blend. Preliminary experimental sample fabrics were produced as single jerseys with different cover factors. It was concluded that cover factor was influenced by loop length; whereas cover factor, physical and structural fabrics properties influenced its performance, depending on the fibre type that was used. Experimental single jersey sample fabrics were also produced from different fibre blends including wool, polyester and bamboo. The physical and structural properties selected for testing were weight/m2, thickness, stitch density (courses/cm and wales/cm), porosity and optical porosity. The comfort properties selected for testing and analysis were liquid moisture transfer and a fabric classification with respect to the following properties: thermal conductivity, warm/cool feeling, stiffness and number of contact points. These parameters were assessed to determine the comfort properties of commercial and a range of experimental sample fabrics. It was concluded that fibre blending influenced comfort properties of experimental sample fabrics and that the most suitable for base layer winter active sportswear sample fabrics are P100, W43P57, W35B65, W52B48, W60b40 (experimental sample fabrics and MRWB (Commercial sample fabric

Plastische Verformungsmechanismen in hochgradig kaltgewalzten, ultrafeinkörnigen Wolframblechen

Der zentrale Forschungsschwerpunkt der Dissertation ist die Aufklärung der Mechanismen der plastischen Verformung in kaltgewalzten, ultrafeinkörnigen (UFG) Wolframblechen. Ein Verständnis dieser Mechanismen ist entscheidend für die Ertüchtigung des Werkstoffs als Konstruktionswerkstoff, womit sich die herausragenden thermomechanischen Eigenschaften des Wolframs in zukunftsweisenden Hoch-temperaturanwendungen wie der Fusionstechnologie nutzen ließen. Bisher beschränkt der spröde Charakter des konventionellen Wolframs bei niedrigen Temperaturen die Verwendung von Wolfram auf den Einsatz als Funktionswerkstoff, wie beispielsweise als Lampenfilament. Zur Lösung dieses Problems mittels der Duktilisierung des Wolframs lieferten Laminate aus Wolframblechen bereits vielversprechende Ergebnisse. Diese Laminate profitieren dabei vom duktilen Charakter der verwendeten Wolframfolien, welche sich selbst bei Raumtemperatur plastisch verformen lassen. Die Wolframfolien erhalten ihre besonderen Eigenschaften durch das Kaltwalzen zu hohen Umformgraden und der damit einhergehenden Veränderung der Mikrostruktur in den ultrafeinkörnigen Bereich. Hier setzt diese Arbeit an und soll als zentrale Fragestellung klären: Wie verändern sich die temperaturabhängigen mechanischen Eigenschaften unter uniaxialer Zugbelastung sowie die zugrundeliegenden Verformungsmechanismen bei kaltgewalzten Wolframblechen durch die Kornfeinung in den UFG Bereich? Diese Frage soll mit einer systematischen Studie an fünf Blechen mit verschiedenen Umformgraden beantwortet werden, welche aus einem einzigen Sinterling mittels Kaltwalzen hergestellt wurden. Zur Diskussion der Verformungsmechanismen werden die Erkenntnisse zweier sich ergänzender Ansätze kombiniert: (i) Durch die Charakterisierung des Gefüges und der Versetzungsstrukturen mittels Elektronenmikroskopie und Röntgendiffraktometrie werden direkte Hinweise zu den Verformungsmechanismen gewonnen. (ii) Mechanische Prüfverfahren bei Temperaturen bis 800 °C und die Untersuchung des dehnratensensitiven Verhaltens dienen zum indirekten Nachweis der Verformungsmechanismen. Dabei finden sowohl etablierte als auch im Rahmen dieser Arbeit eigens entwickelte oder speziell angepasste Methoden wie Dehnraten-wechselversuche und hochauflösende Mikroskopieverfahren Verwendung. Die Mikrostrukturanalyse zeigte mit zunehmendem Umformgrad eine erfolgreiche Kornfeinung in den UFG Bereich, wobei sich eine pfannkuchenartige Kornform und eine ausgeprägte (001) Textur entwickelte. Die Versetzungsdichte zeigt dabei eine starke Abhängigkeit von der verwendeten Kaltwalz Temperatur und weniger vom Umformgrad. Die Abbildungen einzelner Versetzungen wiesen außerdem für die am stärksten umgeformten Bleche mit Korngrößen kleiner 300 nm ungewöhnliche Versetzungsstrukturen anstelle der üblichen Versetzungsnetzwerke nach. Diese Abbildungen einzelner Versetzungen in der UFG Struktur gelangen durch die Weiterentwicklung einer speziellen Methode der Elektropolitur. Mittels uniaxialen Zugversuchen und eigens entwickelten Dehnratenwechselversuchen wurden die Bleche bis 800 °C elastisch plastisch verformt und in Kombination mit der Mikrostrukturanalyse Rückschlüsse auf die geschwindigkeitsbestimmenden Mecha-nismen der plastischen Verformung gezogen. Mit zunehmendem Umformgrad kam es im Zugversuch zur erwarteten höheren Fließspannung und schnelleren Verfestigung. Bei niedrigen homologen Temperaturen wies dabei sowohl die Fließspannung als auch die Dehnratensensitivität für alle kaltgewalzten Blechen eine starke Temperaturabhängigkeit auf, wie sie von konventionellem Wolfram bekannt ist. Dies führt zu der Erkenntnis, dass die plastische Verformung auch im UFG Wolfram von der Bewegung der Schrauben-versetzung dominiert wird. Daneben zeigten die kaltverformten Bleche aber auch plastische Verformbarkeit in Form einer Gleichmaßdehnung von rund einem Prozent bei Raumtemperatur und nicht mehr das spröde Verhalten des grobkörnigen Wolframs. Auf Grundlage der Mikrostrukturanalyse wurden dazu zwei mögliche Hypothesen für das Verformungsverhalten bei niedrigen homologen Temperaturen aufgestellt. Zum einen können die zahlreicheren Korngrenzen als Versetzungsquellen dienen und zum anderen ist in den pfannkuchenartigen Körnern ein selteneres Schneiden der Versetzungen untereinander denkbar, wodurch die Versetzungen sich weitestgehend ungestört im Korn bewegen können. Bei hohen homologen Temperaturen wurde ein Anstieg der Dehnratensensitivität mit der Temperatur beobachtet, der bei konventionellem Wolfram nicht auftritt. Dies deutet für hohe Temperaturen auf einen Wechsel des dominierenden Deformationsmechanismus in den UFG Blechen hin. Als Arbeitshypothese dient in diesem Temperaturbereich ein Modell der korngrenzenunterstützten Plastizität von Ahmed und Hartmaier, was einen absorbierenden Charakter der Korngrenzen als Basis nimmt. Die Ergebnisse beweisen, dass eine durch Kaltwalzen hergestellte pfannkuchenartigen Kornform mit einer Korngröße von unter 300 nm (UFG) sowohl zu einer Festigkeits-steigerung als auch zu einer Duktilisierung des technisch reinen Wolframs bei Raumtemperatur führt. Die Ergebnisse zeigten die besten Eigenschaften für die Bleche mit dem höchsten Umformgrad. Dabei wurde das volle Verbesserungspotential durch das Kaltwalzen noch nicht ausgereizt. Insbesondere das Kaltwalzen in einem Temperatur-bereich, in welchem die dynamische Erholung während dem Walzen reduziert ist, wird auf Grundlage der Ergebnisse dieser Arbeit als vielversprechend bewertet. Vergleichbare Experimente an UFG Chrom (ebenfalls kubisch raumzentriert) aus der Literatur zeigen ähnliche Ergebnisse und lassen hoffen, dass sich diese Verbesserungen auch auf andere technisch relevante, kubisch raumzentrierte Metalle wie Eisen und Molybdän übertragen lassen

The Difficulty Of Practising Fine Artists In Making A Living: Why Arts Entrepreneurship Education Is Important

This study identifies six key reasons explaining the social phenomenon that many practising fine artists find it so difficult to make a living in the arts. Due to a marked paucity of research explaining this social phenomenon, the study at hand investigates the internal factors related to artists’ personality, motivation, and skills as well as various external factors influencing artists’ working and business environment by applying two acknowledged analysis tools in strategic business management. The literature findings highlight four external threat factors mainly responsible for a very challenging working and business environment affecting practising fine artists’ chances of professional success. Consequently, two internal factors – notably artists’ motivation and ambition to conduct business and a living in the arts as well as their developed skills – turn out to be key factors to successfully deal with these external threat factors. In this context, three research aims related to practising artists’ professional education and preparation arise: the identification of crucial skills to successfully make a living in the arts as practising artists, the status of their professional education at higher education institutions (HEIs), and the capability of arts incubators as alternative education programmes to prepare large numbers of practising fine artists for professional success. The approach to investigation is exploratory and inductive with a cross-sectional survey strategy. To identify the crucial skills for professional success in the arts, surveys of up to 219 fine art lecturers, 168 fine art undergraduates, and 149 commercial galleries are conducted. To report on the status of fine artists’ educational preparation, 87 undergraduate degree programmes, 55 post-graduate programmes, and 46 extracurricular training offerings at HEIs are investigated. The study focuses mainly on the UK and Germany. These countries are selected due to their significantly different market sizes and reputation for the purpose of identifying differences in market challenges and professional preparations faced by fine artists. To analyse arts incubators’ capability in preparing large numbers of practising fine artists for a professional career, 92 arts incubation programmes around the globe are analysed and nine structured interviews with practising fine artists are conducted. The investigation of the crucial skills for fine artists’ professional success highlights in particular the development of an entrepreneurial mindset as well as of seven skills. Research on arts education shows evidence that fine art graduates are hardly equipped with this skillset and mindset due to HEIs’ lack of focus on the professional careers of practising artists. The analysis of arts incubation programmes illustrates serious limitations in supporting larger numbers of practising fine artists in their professional endeavours. The research findings stimulate the discussion in, and contribute to, knowledge in the fields of artists’ professional preparation, arts entrepreneurship, and the redesigning of fine art curriculum to purposefully prepare fine art graduates for an entrepreneurial and professional career as practising artists

Archaeological and Historical Investigations at the West End of the Martin and Bowie Streets Connections, San Antonio, Bexar County, Texas

Test excavations were conducted in November 1987 by the Center for Archaeological Research, The University of Texas at San Antonio at the site of a planned relocation of the eastbound lanes of Martin Street in downtown San Antonio. The lots in question were located on the north side of the early town site, and were known to have contained the residence of Thaddeus Smith, the county clerk for Bexar County in the last half of the 19th century. Testing was done by backhoe and by controlled hand excavations. Testing was done in relation to each of the three structures that were known to have existed in the area. The foundations of a house at 409 North Flores Street, built in 1868, were examined to record methods of construction, the structural evolution of the house, and its conversion into a commercial establishment ca. 1927. Part of the foundations were uncovered and recorded of Smith\u27s elaborate 1898 home at 403 North Flores Street. In search for the source of the late 18th-century artifacts from the levels beneath an 1868 house, test units were excavated at 401 North Flores Street in what appeared to be on the 1873 Koch map the back yard of a one-story adobe house. Artifacts recovered there, however, indicated post-1800 occupation. A jacal wall trench was located and recorded at this address. As a result of the comparatively undisturbed nature of the archaeological deposits at 401 North Flores Street, it is recommended that the area bounded by Flores, Salinas, and Rossy Streets and the new location of Martin Street be made a State Archeological Landmark. A number of structures were located in this area in 1873 that undoubtedly represent the first expansion of the town to the north of the plazas