Production of antihydrogen via double charge exchange

Spectroscopy of the 1S-2S transition of antihydrogen confined in a neutral atom trap and comparison with the equivalent spectral line in hydrogen will provide an accurate test of CPT symmetry and the first one in a mixed baryon-lepton system. Also, with neutral antihydrogen atoms, the gravitational interaction between matter and antimatter can be tested unperturbed by the much stronger Coulomb forces.rnAntihydrogen is regularly produced at CERN's Antiproton Decelerator by three-body-recombination (TBR) of one antiproton and two positrons. The method requires injecting antiprotons into a cloud of positrons, which raises the average temperature of the antihydrogen atoms produced way above the typical 0.5 K trap depths of neutral atom traps. Therefore only very few antihydrogen atoms can be confined at a time. Precision measurements, like laser spectroscopy, will greatly benefit from larger numbers of simultaneously trapped antihydrogen atoms.rnTherefore, the ATRAP collaboration developed a different production method that has the potential to create much larger numbers of cold, trappable antihydrogen atoms. Positrons and antiprotons are stored and cooled in a Penning trap in close proximity. Laser excited cesium atoms collide with the positrons, forming Rydberg positronium, a bound state of an electron and a positron. The positronium atoms are no longer confined by the electric potentials of the Penning trap and some drift into the neighboring cloud of antiprotons where, in a second charge exchange collision, they form antihydrogen. The antiprotons remain at rest during the entire process, so much larger numbers of trappable antihydrogen atoms can be produced. Laser excitation is necessary to increase the efficiency of the process since the cross sections for charge-exchange collisions scale with the fourth power of the principal quantum number n.rnThis method, named double charge-exchange, was demonstrated by ATRAP in 2004. Since then, ATRAP constructed a new combined Penning Ioffe trap and a new laser system. The goal of this thesis was to implement the double charge-exchange method in this new apparatus and increase the number of antihydrogen atoms produced.rnCompared to our previous experiment, we could raise the numbers of positronium and antihydrogen atoms produced by two orders of magnitude. Most of this gain is due to the larger positron and antiproton plasmas available by now, but we could also achieve significant improvements in the efficiencies of the individual steps. We therefore showed that the double charge-exchange can produce comparable numbers of antihydrogen as the TBR method, but the fraction of cold, trappable atoms is expected to be much higher. Therefore this work is an important step towards precision measurements with trapped antihydrogen atoms.

Formation and surface exchange of nitrous acid

Die salpetrige Säure (HONO) ist eine der reaktiven Stickstoffkomponenten der Atmosphäre und Pedosphäre. Die genauen Bildungswege von HONO, sowie der gegenseitige Austausch von HONO zwischen Atmosphäre und Pedosphäre sind noch nicht vollständig aufgedeckt. Bei der HONO-Photolyse entsteht das Hydroxylradikal (OH) und Stickstoffmonooxid (NO), was die Bedeutsamkeit von HONO für die atmosphärische Photochemie widerspiegelt.rnUm die genannte Bildung von HONO im Boden und dessen anschließenden Austausch mit der Atmosphäre zu untersuchen, wurden Messungen von Bodenproben mit dynamischen Kammern durchgeführt. Im Labor gemessene Emissionsflüsse von Wasser, NO und HONO zeigen, dass die Emission von HONO in vergleichbarem Umfang und im gleichen Bodenfeuchtebereich wie die für NO (von 6.5 bis 56.0 % WHC) stattfindet. Die Höhe der HONO-Emissionsflüsse bei neutralen bis basischen pH-Werten und die Aktivierungsenergie der HONO-Emissionsflüsse führen zu der Annahme, dass die mikrobielle Nitrifikation die Hauptquelle für die HONO-Emission darstellt. Inhibierungsexperimente mit einer Bodenprobe und die Messung einer Reinkultur von Nitrosomonas europaea bestärkten diese Theorie. Als Schlussfolgerung wurde das konzeptionelle Model der Bodenemission verschiedener Stickstoffkomponenten in Abhängigkeit von dem Wasserhaushalt des Bodens für HONO erweitert.rnIn einem weiteren Versuch wurde zum Spülen der dynamischen Kammer Luft mit erhöhtem Mischungsverhältnis von HONO verwendet. Die Messung einer hervorragend charakterisierten Bodenprobe zeigte bidirektionale Flüsse von HONO. Somit können Böden nicht nur als HONO-Quelle, sondern auch je nach Bedingungen als effektive Senke dienen. rnAußerdem konnte gezeigt werden, dass das Verhältnis von HONO- zu NO-Emissionen mit dem pH-Wert des Bodens korreliert. Grund könnte die erhöhte Reaktivität von HONO bei niedrigem pH-Wert und die längere Aufenthaltsdauer von HONO verursacht durch reduzierte Gasdiffusion im Bodenporenraum sein, da ein niedriger pH-Wert mit erhöhter Bodenfeuchte am Maximum der Emission einhergeht. Es konnte gezeigt werden, dass die effektive Diffusion von Gasen im Bodenporenraum und die effektive Diffusion von Ionen in der Bodenlösung die HONO-Produktion und den Austausch von HONO mit der Atmosphäre begrenzen. rnErgänzend zu den Messungen im Labor wurde HONO während der Messkampagne HUMPPA-COPEC 2010 im borealen Nadelwald simultan in der Höhe von 1 m über dem Boden und 2 bis 3 m über dem Blätterdach gemessen. Die Budgetberechnungen für HONO zeigen, dass für HONO sämtliche bekannte Quellen und Senken in Bezug auf die übermächtige HONO-Photolyserate tagsüber vernachlässigbar sind (< 20%). Weder Bodenemissionen von HONO, noch die Photolyse von an Oberflächen adsorbierter Salpetersäure können die fehlende Quelle erklären. Die lichtinduzierte Reduktion von Stickstoffdioxid (NO2) an Oberflächen konnte nicht ausgeschlossen werden. Es zeigte sich jedoch, dass die fehlende Quelle stärker mit der HONO-Photolyserate korreliert als mit der entsprechenden Photolysefrequenz, die proportional zur Photolysefrequenz von NO2 ist. Somit lässt sich schlussfolgern, dass entweder die Photolyserate von HONO überschätzt wird oder dass immer noch eine unbekannte, HONO-Quelle existiert, die mit der Photolyserate sehr stark korreliert. rn rn

Volatile organic compounds at the air-sea interface : gas exchange rates, oceanic emissions and the effect of ocean acidification

Oceans are key sources and sinks in the global budgets of significant atmospheric trace gases, termed Volatile Organic Compounds (VOCs). Despite their low concentrations, these species have an important role in the atmosphere, influencing ozone photochemistry and aerosol physics. Surprisingly, little work has been done on assessing their emissions or transport mechanisms and rates between ocean and atmosphere, all of which are important when modelling the atmosphere accurately.rnA new Needle Trap Device (NTD) - GC-MS method was developed for the effective sampling and analysis of VOCs in seawater. Good repeatability (RSDs <16 %), linearity (R2 = 0.96 - 0.99) and limits of detection in the range of pM were obtained for DMS, isoprene, benzene, toluene, p-xylene, (+)-α-pinene and (-)-α-pinene. Laboratory evaluation and subsequent field application indicated that the proposed method can be used successfully in place of the more usually applied extraction techniques (P&T, SPME) to extend the suite of species typically measured in the ocean and improve detection limits. rnDuring a mesocosm CO2 enrichment study, DMS, isoprene and α-pinene were identified and quantified in seawater samples, using the above mentioned method. Based on correlations with available biological datasets, the effects of ocean acidification as well as possible ocean biological sources were investigated for all examined compounds. Future ocean's acidity was shown to decrease oceanic DMS production, possibly impact isoprene emissions but not affect the production of α-pinene. rnIn a separate activity, ocean - atmosphere interactions were simulated in a large scale wind-wave canal facility, in order to investigate the gas exchange process and its controlling mechanisms. Air-water exchange rates of 14 chemical species (of which 11 VOCs) spanning a wide range of solubility (dimensionless solubility, α = 0:4 to 5470) and diffusivity (Schmidt number in water, Scw = 594 to 1194) were obtained under various turbulent (wind speed at ten meters height, u10 = 0:8 to 15ms-1) and surfactant modulated (two different sized Triton X-100 layers) surface conditions. Reliable and reproducible total gas transfer velocities were obtained and the derived values and trends were comparable to previous investigations. Through this study, a much better and more comprehensive understanding of the gas exchange process was accomplished. The role of friction velocity, uw* and mean square slope, σs2 in defining phenomena such as waves and wave breaking, near surface turbulence, bubbles and surface films was recognized as very significant. uw* was determined as the ideal turbulent parameter while σs2 described best the related surface conditions. A combination of both uw* and σs2 variables, was found to reproduce faithfully the air-water gas exchange process. rnA Total Transfer Velocity (TTV) model provided by a compilation of 14 tracers and a combination of both uw* and σs2 parameters, is proposed for the first time. Through the proposed TTV parameterization, a new physical perspective is presented which provides an accurate TTV for any tracer within the examined solubility range. rnThe development of such a comprehensive air-sea gas exchange parameterization represents a highly useful tool for regional and global models, providing accurate total transfer velocity estimations for any tracer and any sea-surface status, simplifying the calculation process and eliminating inevitable calculation uncertainty connected with the selection or combination of different parameterizations.rnrn

Tuning of magnetic exchange interactions between organic radicals through bond and space

The dissertation entitled "Tuning of magnetic exchange interactions between organic radicals through bond and space" comprises eight chapters. In the initial part of chapter 1, an overview of organic radicals and their applications were discussed and in the latter part motivation and objective of thesis was described. As the EPR spectroscopy is a necessary tool to study organic radicals, the basic principles of EPR spectroscopy were discussed in chapter 2. rnAntiferromagnetically coupled species can be considered as a source of interacting bosons. Consequently, such biradicals can serve as molecular models of a gas of magnetic excitations which can be used for quantum computing or quantum information processing. Notably, initial small triplet state population in weakly AF coupled biradicals can be switched into larger in the presence of applied magnetic field. Such biradical systems are promising molecular models for studying the phenomena of magnetic field-induced Bose-Einstein condensation in the solid state. To observe such phenomena it is very important to control the intra- as well as inter-molecular magnetic exchange interactions. Chapters 3 to 5 deals with the tuning of intra- and inter-molecular exchange interactions utilizing different approaches. Some of which include changing the length of π-spacer, introduction of functional groups, metal complex formation with diamagnetic metal ion, variation of radical moieties etc. During this study I came across two very interesting molecules 2,7-TMPNO and BPNO, which exist in semi-quinoid form and exhibits characteristic of the biradical and quinoid form simultaneously. The 2,7-TMPNO possesses the singlet-triplet energy gap of ΔEST = –1185 K. So it is nearly unrealistic to observe the magnetic field induced spin switching. So we studied the spin switching of this molecule by photo-excitation which was discussed in chapter 6. The structural similarity of BPNO with Tschitschibabin’s HC allowed us to dig the discrepancies related to ground state of Tschitschibabin’s hydrocarbon(Discussed in chapter 7). Finally, in chapter 8 the synthesis and characterization of a neutral paramagnetic HBC derivative (HBCNO) is discussed. The magneto liquid crystalline properties of HBCNO were studied by DSC and EPR spectroscopy.rn

Microbial formation of nitrous acid and its exchange processes between soils and atmosphere

Salpetrige Säure (HONO) ist eine wichtige Form von reaktivem Stickstoff, die aufgrund ihrer Photolyse zu Stickstoffmonoxid (NO) und dem Hydroxylradikal (OH), sehr kurzlebig ist. Ein genaues Verständnis der Quellen und Senken von HONO ist eine grundlegende Voraussetzung, um dessen Einfluss auf die Umwelt zu beurteilen. Allerdings wird immer noch nach einer starken HONO-Quelle am Tag gesucht und nächtliche HONO-Deposition auf den Boden wurde bisher stets nur postuliert. Diese Dissertation folgt der Zielsetzung die Prozesse der HONO-Aufnahme und Freisetzung von Böden aufzudecken und die zugrunde liegenden Mechanismen zu verstehen.rnUm die Rolle von HONO-Bodenemissionen zu quantifizieren, wurden 17 Böden in einem dynamischen Kammersystem untersucht. Es konnten HONO-Emissionen derselben Größenordnung wie die bereits gut untersuchten NO-Emissionen festgestellt werden. Unerwarteter Weise wurden die stärksten Emissionen bei Böden mit neutralem pH aus ariden und landwirt¬schaftlichen Gebieten beobachtet. Die Temperaturabhängigkeit der Bodenemissionen von HONO und NO führten zu der Annahme einer mikrobiellen Freisetzung von HONO, welche durch Reinkulturexperimente mit dem ammoniumoxidierenden Bakterium Nitrosomonas europaea bestätigt werden konnte. Ein konzeptionelles Model für die Freisetzung reaktiver Stickstoffverbindungen aus Böden in Abhängigkeit des Bodenwassergehaltes wurde um HONO-Emissionen erweitert.rnDurch Nachweise mittels Reinkultur- und Inhibitionsexperimenten konnten weitere Untersuchungen der bakteriellen Freisetzung von HONO aus Böden zeigen, dass innerhalb der bakteriellen Nitrifikation nur ammoniumoxidierende Bakterien zur Emission von HONO fähig sind. Durch kontrolliert initiierte Zelllyse konnte gezeigt werden, dass intrazellulär akkumuliertes Hydroxylamin (NH2OH) für die HONO-Freisetzung verantwortlich sind. Zum ersten Mal wurde NH2OH in der Gasphase nachgewiesen und dass dieses über den gesamten Bodenfeuchtebereich von ammoniumoxidierenden Bakterien freigesetzt wird. Es wurde gezeigt, dass die heterogene Reaktion von NH2OH mit Wasserdampf auf einer Glasperlenoberfläche HONO bildet. Diese Reaktion erklärt die beobachtete Freisetzung von HONO bei niedrigen Bodenfeuchten, da nur dann die Oberfläche zur Reaktion zur Verfügung steht und nicht von Wasser bedeckt ist.rnEine 15N Isotopenmarkierungsmethode wurde entwickelt um isotopenmarkiertes gasförmiges HONO zu messen, was die Untersuchung der Bildungsprozesse von HONO und dessen Rolle in biogeochemischen Zyklen ermöglicht. Die Anwendung dieser neuen Methode auf eine Bodenprobe die mit 15N Harnstoff angereichert und in einem dynamischen Kammersystem untersucht wurde, bestätigt die obigen Ergebnisse einer starken mikrobiellen Beteiligung von Bodenbakterien zur HONO Freisetzung.rnBidirektionale Flüsse von HONO wurden für sechs untersuchte Bodenproben gefunden. Die Richtung der Flüsse hängt dabei vom Umgebungsmischungsverhältnis von HONO und dem Bodenwassergehalt ab. Eine wichtige Größe, die die bidirektionalen Flüsse von HONO beschreibt, ist das „Ökosystem spezifische Kompensationsmischungsverhältnis von HONO“, χcomp. Dieser neue Begriff wurde definiert und eingeführt, da die verschiedenen in den Bodenaustausch von HONO involvierten Prozesse nicht mit dem klassischen Kompensationspunktkonzept kompatibel sind. Die Untersuchungen bestätigen neueste Feldbeobachtungen, dass HONO, welches bei hohen Umgebungsmischungsverhältnissen vom Boden adsorbiert wird, bei niedrigen Mischungsverhält-nissen wieder vom Boden desorbiert wird. Folglich wird nächtlich akkumuliertes HONO tagsüber in eine Quelle für HONO umgewandelt. Vier Prozesse - Verteilung von HONO zwischen Gas- und Flüssigphase nach Henrys Gesetz, bakterielle HONO Bildung aus NH2OH, Adsorption und Desorption von HONO - und deren Dominanz in speziellen Bodenfeuchtebereichen wurden identifiziert. Dadurch wurde ein konzeptionelles Model für die Prozesse, die in Aufnahme und Freisetzung von HONO aus Böden involviert sind, als Funktion der Bodenfeuchte entwickelt.rnZusammenfassend hat diese Dissertation die entscheidenden Prozesse im Austausch von HONO zwischen Boden und Atmosphäre aufgeklärt und den der bakteriellen HONO Bildung zugrunde liegenden Mechanismus aufgedeckt. Es konnte gezeigt werden, dass Böden sowohl eine wichtige Quelle als auch eine Senke für HONO sind und sollten folglich in zukünftigen Feldmessungen stärker berücksichtigt werden.rn

Effect of site of lactate infusion on regional lactate exchange in pigs

The rate of extra-hepatic lactate production and the route of influx of lactate to the liver may influence both hepatic and extra-hepatic lactate exchange. We assessed the dose-response of hepatic and extra-hepatic lactate exchange during portal and central venous lactate infusion.

Macrophages and dendritic cells express tight junction proteins and exchange particles in an in vitro model of the human airway wall

The human airway epithelium serves as structural and functional barrier against inhaled particulate antigen. Previously, we demonstrated in an in vitro epithelial barrier model that monocyte derived dendritic cells (MDDC) and monocyte derived macrophages (MDM) take up particulate antigen by building a trans-epithelial interacting network. Although the epithelial tight junction (TJ) belt was penetrated by processes of MDDC and MDM, the integrity of the epithelium was not affected. These results brought up two main questions: (1) Do MDM and MDDC exchange particles? (2) Are those cells expressing TJ proteins, which are believed to interact with the TJ belt of the epithelium to preserve the epithelial integrity? The expression of TJ and adherens junction (AJ) mRNA and proteins in MDM and MDDC monocultures was determined by RT-PCR, and immunofluorescence, respectively. Particle uptake and exchange was quantified by flow cytometry and laser scanning microscopy in co-cultures of MDM and MDDC exposed to polystyrene particles (1 μm in diameter). MDM and MDDC constantly expressed TJ and AJ mRNA and proteins. Flow cytometry analysis of MDM and MDDC co-cultures showed increased particle uptake in MDDC while MDM lost particles over time. Quantitative analysis revealed significantly higher particle uptake by MDDC in co-cultures of epithelial cells with MDM and MDDC present, compared to co-cultures containing only epithelial cells and MDDC. We conclude from these findings that MDM and MDDC express TJ and AJ proteins which could help to preserve the epithelial integrity during particle uptake and exchange across the lung epithelium.

Magnetization exchange with water and T(1) relaxation of the downfield resonances in human brain spectra at 3.0 T

The use of water suppression for in vivo proton MR spectroscopy diminishes the signal intensities from resonances that undergo magnetization exchange with water, particularly those downfield of water. To investigate these exchangeable resonances, an inversion transfer experiment was performed using the metabolite cycling technique for non-water-suppressed MR spectroscopy from a large brain voxel in 11 healthy volunteers at 3.0 T. The exchange rates of the most prominent peaks downfield of water were found to range from 0.5 to 8.9 s(-1), while the T(1) relaxation times in absence of exchange were found to range from 175 to 525 ms. These findings may help toward the assignments of the downfield resonances and a better understanding of the sources of contrast in chemical exchange saturation transfer imaging.

Spatial and functional relationships between air conduits and blood capillaries in the pulmonary gas exchange tissue of adult and developing chickens

The documented data regarding the three-dimensional structure of the air capillaries (ACs), the ultimate sites of gas exchange in the avian lung is contradictory. Further, the mode of gas exchange, described as cross-current has not been clearly elucidated. We studied the temporal and spatial arrangement of the terminal air conduits of the chicken lung and their relationship with the blood capillaries (BCs) in embryos as well as the definitive architecture in adults. Several visualization techniques that included corrosion casting, light microscopy as well as scanning and transmission electron microscopy were used. Two to six infundibulae extend from each atrium and give rise to numerous ACs that spread centrifugally. Majority of the ACs are tubular structures that give off branches, which anastomose with their neighboring cognates. Some ACs have globular shapes and a few are blind-ending tapering tubes. During inauguration, the luminal aspects of the ACs are characterized by numerous microvillus-like microplicae, which are formed during the complex processes of cell attenuation and canalization of the ACs. The parabronchial exchange BCs, initially inaugurated as disorganized meshworks, are reoriented via pillar formation to lie predominantly orthogonal to the long axes of the ACs. The remodeling of the retiform meshworks by intussusceptive angiogenesis essentially accomplishes a cross-current system at the gas exchange interface in the adults, where BCs form ring-like patterns around the ACs, thus establishing a cross-current system. Our findings clarify the mode of gas exchange in the parabronchial mantle and illuminate the basis for the functional efficiency of the avian lung.

Differential effects of long and short carbon nanotubes on the gas-exchange region of the mouse lung

Abstract We hypothesise that inflammatory response and morphological characteristics of lung parenchyma differ after exposure to short or long multi-walled carbon nanotubes (MWCNT). Mice were subjected to a single dose of vehicle, short or long MWCNT by pharyngeal aspiration. Bronchoalveolar lavage fluid (BALF) obtained at 24 h was analysed for inflammatory reaction and lung tissue was analysed for morphological alterations using stereology. Short MWCNT had stronger potential to induce polymorphonuclear cells whereas long MWCNT increased interleukin-6 levels in BALF. Alveolar septal fibrosis was only observed with short MWCNT. Type II pneumocyte hypertrophy was only detected with long MWCNT. There was no reduction in total alveolar surface area and no sign of type II cell hyperplasia. We observed mild inflammatory and pathological responses to short and long MWCNT in the lung parenchyma depending on the size of the applied MWCNT.

Capuchin Monkeys Exercise Self-control by Choosing Token Exchange Over an Immediate Reward

Self-control is a prerequisite for complex cognitive processes such as cooperation and planning. As such, comparative studies of self-control may help elucidate the evolutionary origin of these capacities. A variety of methods have been developed to test for self-control in non-human primates that include some variation of foregoing an immediate reward in order to gain a more favorable reward. We used a token exchange paradigm to test for self-control in capuchin monkeys (Cebus apella). Animals were trained that particular tokens could be exchanged for food items worth different values. To test for self-control, a monkey was provided with a token that was associated with a lower-value food. When the monkey exchanged the token, the experimenter provided the monkey with a choice between the lower-value food item associated with the token or another token that was associated with a higher-value food. If the monkey chose the token, they could then exchange it for the higher-value food. Of seven monkeys trained to exchange tokens, five demonstrated that they attributed value to the tokens by differentially selecting tokens for higher-value foods over tokens for lower-value foods. When provided with a choice between a food item or a token for a higher-value food, two monkeys selected the token significantly more than expected by chance. The ability of capuchin monkeys to forego an immediate food reward and select a token that could then be traded for a more preferred food demonstrated some degree of self-control. Thus, results suggest a token exchange paradigm could be a successful technique for assessing self-control in this New World species.

Decreasing frequency of plasma exchange complications in patients treated for thrombotic thrombocytopenic purpura-hemolytic uremic syndrome, 1996 to 2011

Plasma exchange (PEX) treatment for patients with thrombotic thrombocytopenic purpura-hemolytic uremic syndrome (TTP-HUS) has risk for major complications.