Atmospheric pressure as a natural climate regulator for a terrestrial planet with a biosphere

Lovelock and Whitfield suggested in 1982 that, as the luminosity of the Sun increases over its life cycle, biologically enhanced silicate weathering is able to reduce the concentration of atmospheric carbon dioxide (CO_2) so that the Earth's surface temperature is maintained within an inhabitable range. As this process continues, however, between 100 and 900 million years (Ma) from now the CO_2 concentration will reach levels too low for C_3 and C_4 photosynthesis, signaling the end of the solar-powered biosphere. Here, we show that atmospheric pressure is another factor that adjusts the global temperature by broadening infrared absorption lines of greenhouse gases. A simple model including the reduction of atmospheric pressure suggests that the life span of the biosphere can be extended at least 2.3 Ga into the future, more than doubling previous estimates. This has important implications for seeking extraterrestrial life in the Universe. Space observations in the infrared region could test the hypothesis that atmospheric pressure regulates the surface temperature on extrasolar planets

Arterial-Spin-Labeling-Sequenzentwicklung zur Optimierung der 3T- & 7T-Perfusionsbildgebung und zur Permeabilitätsmodellierung

Arterial spin labeling sequence development for optimization of 3T & 7T perfusion imaging and for permeability modeling Pseudo-continuous arterial spin labeling (pCASL) is a magnetic resonance technique for imaging and quantifying cerebral blood flow. Magnetically labeled arterial blood serves as an endogenous tracer. Special extensions of the fundamental method fascilitate a modeling of additional physiological parameters besides cerebral perfusion. Good quantifiability and non-invasiveness make pCASL of interest for clinical use and for scientific research, which is enhanced by a wide availability and technical development of magnetic resonance scanners. The first 7 Tesla ultra-high field scanner has been approved for clinical use in 2017. Stronger magnetic fields provide the advantages of a higher signal-to-noise ratio (SNR) and a longer persisting pCASL signal. However, magnetic field inhomogeneities and energy limitations make an application more difficult. This thesis contributes to pCASL-based perfusion measurements and a modeling of blood-brain barrier permeabilities at 3 Tesla and it addresses the challenges to further develop pCASL imaging at 7 Tesla. The first part focuses on the development and application of pCASL for the quantitative measurement of cerebral blood flow at 3 Tesla. An efficient pCASL encoding method using Hadamard matrices is implemented and its theoretical advantages are experimentally demonstrated. Application-optimized protocols and a data processing pipeline are obtained. In vivo measurements confirm a solid data quality. The applicability for clinical measurements is demonstrated in a single case. A test-retest measurement series reveals the suitability for longitudinal and multicenter studies. The second part considers the T2 relaxation of the pCASL signal at 3 Tesla. It focuses on a T2-based investigation of the tracer transition from the intravascular to the extravascular compartment and a potential inference on the blood-brain barrier integrity. Therefore, a sequence module is implemented for the acquisition of T2-weighted data and a study protocol implemented. Additionally, the reliability of quantitative T2 times is validated within a test-retest study. Then, a modeling approach is developed to compartmentalize the pCASL tracer into intra- and extravascularly localized fractions based on the T2 times. Additional supplementing measurements and highly simplified model assumptions stabilize the compartmentalization model, as demonstrated in vivo. As a result, pCASL-T2 times may be a relevant parameter for the investigation of physiological processes. The third part addresses the implementation of pCASL measurements at 7 Tesla. Parallel pulse transmission techniques adapt the magnetic labeling pulses to compensate for non-ideal magnetic field distributions. Multiple adjustment concepts are implemented in a 7 Tesla pCASL sequence. Simulations and first in vivo investigations, using some of these methods, demonstrate a feasibility also at ultra-high field and an improvement of the pCASL signal compared to non-adjusting approaches.Die pseudo-kontinuierliche arterielle Spinmarkierung (pCASL) ist ein Verfahren der Magnetresonanzperfusionsbildgebung zur Darstellung und Quantifizierung des zerebralen Blutflusses. Bei dieser Technik wird einströmendes, arterielles Blut magnetisch markiert und so als körpereigener Tracer verwendet. Durch spezielle Erweiterungen eröffnen sich Ansätze, neben der zerebralen Perfusion, zusätzliche physiologische Parameter zu modellieren. Die einfache Quantifizierbarkeit und die Nicht-Invasivität, sowie die Verfügbarkeit und technische Entwicklung von Magnetresonanztomographen machen dieses Verfahren interessant für klinische und für wissenschaftliche Anwendungen. Im Jahr 2017 wurde der erste 7 Tesla Ultrahochfeld-Scanner für die klinische Anwendung zugelassen. Stärkere Magnetfelder bieten die Vorteile eines höheren Signal-zu-Rausch-Verhältnisses und eines länger bestehenden pCASL-Signals. Gleichzeitig führen Magnetfeldinhomogenitäten und Energieeinschränkungen zu einer erschwerten Anwendbarkeit. Die vorliegende Arbeit befasst sich mit der pCASL-basierten Perfusionsmessung und einer Modellierung von Blut-Hirn-Schranken-Durchlässigkeiten bei 3 Tesla, sowie der Sequenzweiterentwicklung zur Messung perfusionsgewichteter Daten bei 7 Tesla. Der erste Teil konzentriert sich auf die Entwicklung und Anwendung von pCASL zur quantitativen Messung des zerebralen Blutflusses bei 3 Tesla. In diesem Rahmen wird ein effizientes pCASL-Kodierungsverfahren mittels Hadamard-Matrizen implementiert. Dessen theoretischen Vorteile werden experimentell gezeigt. Es resultieren anwendungsoptimierte Protokolle und eine Auswertungspipeline. In vivo Messungen bestätigen eine solide Datenqualität. Die Eignung für klinische Messungen wird an einem Einzelfall demonstriert. Die Ergebnisse einer Test-Retest-Messreihe lassen auf die Eignung für longitudinale und multizentrische Studien schließen. Der zweite Teil beschäftigt sich mit der T2-Relaxation des pCASL-Signals bei 3 Tesla. Dabei stehen die T2-basierte Untersuchung des Tracerübergangs aus dem intravaskulären in das extravaskuläre System und ein möglicher Schluss auf die Integrität der Blut-Hirn-Schranke im Fokus. Für die Aufnahme T2-gewichteter Daten wird ein geeigetes Sequenzmodul implementiert und ein Studienprotokoll entworfen. Innerhalb einer Test-Retest-Studie wird die Zuverlässigkeit quantitativer T2-Zeiten validiert. In einem zweiten Schritt wird ein Modellierungsverfahren erarbeitet, um den pCASL-Tracer, basierend auf den gemessenen T2-Zeiten, in intra- und extravaskuläre Anteile zu kompartmentalisieren. In vivo Messungen demonstrieren eine Stabilisierung des Kompartmentalisierungsmodells durch das Hinzuziehen von Hilfsmessungen und die Anwendung stark vereinfachter Modellannahmen. Es resultiert eine potenzielle Relevanz von pCASL-T2-Zeiten als Parameter für die Untersuchung physiologischer Prozesse. Der dritte Teil befasst sich mit der Realisierung von pCASL-Messungen bei 7 Tesla. Spezielle Techniken der parallelen Pulstransmission passen die Pulse, welche die magnetischen Markierung vornehmen, an nicht-idealen Magnetfeldverteilungen an. Es werden verschiedene Anpassungskonzepte in einer 7 Tesla pCASL-Sequenz implementiert. Simulationen und erste in vivo Messungen mit einem Teil dieser Verfahren zeigen neben der Realisierbarkeit im Ultrahochfeld eine Verbesserung des pCASL-Signals gegenüber bisherigen, nicht-anpassenden Ansätzen

A carbonate-banded iron formation transition in the Early Protorezoicum of South Africa

Seven new and two resurveyed stratigraphic sections through the important carbonate-BIF transition in Griqualand West are presented and compared with six published sections. Lateral correlation within this zone is attempted but the variability was found to be too great for meaningful subdivision. Substantial lithological irregularity is the only unifying character of this zone, for which the new name Finsch Member (Formation) is proposed. Vertical and lateral lithological variations as well as chemical changes across this zone are discussed with reference to environmental aspects. Local and regional considerations lead to the conclusion that fresh water-sea water mixing occurred in a shallowing basin

Palaeoproterozoic magnesite: lithological and isotopic evidence for playa/sabkha environments

Magnesite forms a series of 1- to 15-m-thick beds within the approximate to2.0 Ga (Palaeoproterozoic) Tulomozerskaya Formation, NW Fennoscandian Shield, Russia. Drillcore material together with natural exposures reveal that the 680-m-thick formation is composed of a stromatolite-dolomite-'red bed' sequence formed in a complex combination of shallow-marine and non-marine, evaporitic environments. Dolomite-collapse breccia, stromatolitic and micritic dolostones and sparry allochemical dolostones are the principal rocks hosting the magnesite beds. All dolomite lithologies are marked by delta C-13 values from +7.1 parts per thousand to +11.6 parts per thousand (V-PDB) and delta O-18 ranging from 17.4 parts per thousand to 26.3 parts per thousand (V-SMOW). Magnesite occurs in different forms: finely laminated micritic; stromatolitic magnesite; and structureless micritic, crystalline and coarsely crystalline magnesite. All varieties exhibit anomalously high delta C-13 values ranging from +9.0 parts per thousand to +11.6 parts per thousand and delta O-18 values of 20.0-25.7 parts per thousand. Laminated and structureless micritic magnesite forms as a secondary phase replacing dolomite during early diagenesis, and replaced dolomite before the major phase of burial. Crystalline and coarsely crystalline magnesite replacing micritic magnesite formed late in the diagenetic/metamorphic history. Magnesite apparently precipitated from sea water-derived brine, diluted by meteoric fluids. Magnesitization was accomplished under evaporitic conditions (sabkha to playa lake environment) proposed to be similar to the Coorong or Lake Walyungup coastal playa magnesite. Magnesite and host dolostones formed in evaporative and partly restricted environments; consequently, extremely high delta C-13 values reflect a combined contribution from both global and local carbon reservoirs. A C- 13-rich global carbon reservoir (delta C-13 at around +5 parts per thousand) is related to the perturbation of the carbon cycle at 2.0 Ga, whereas the local enhancement in C-13 (up to +12 parts per thousand) is associated with evaporative and restricted environments with high bioproductivity

An urban development center.

Massachusetts Institute of Technology. Dept. of Architecture. Thesis. 1967. M.Arch.Bibliography: leaf 21.M.Arch

Produtividade e qualidade industrial de trigo em diferentes anos e regiões de cultivo

The productivity and technological quality of wheat is influenced by genetic, environmental and management factors. The environmental contribution in the definition of component traits of yield and quality attributes of flour requires extensive evaluation of genotypes in multiple locations for years. The objective of this study was to evaluate the effect of years (2007-2011) and growing regions (Abelardo Luz- SC , Cascavel - PR, Castro - PR, Guarapuava - PR , Não-Me-Toque - RS and Palotina - PR) on the quality industrial and grain yield in sets of trials of wheat ( Triticum aestivum L.), with a view to recommending cultivars and identification of regions that maximize the quality of baking. Analyses of joint variance and calculated statistical comparison of means , association between character and adaptability and stability of genotypes to different growing regions, using graphical GGE Biplot analysis and AMMI analysis were performed. The results indicate that all traits were influenced by genotype (G), environment (E) interaction GxE. The determinants of quality characters of wheat bread have their phenotypic variation mainly controlled by genetic effects. The CD 150, CD 108 and IPR 85 cultivars showed excellent behavior in relation to baking quality. The test environment Não-Me-Toque is ideal for selection of genotypes with a focus on yield and hectoliter mass. Ideal environments for the selection of genotypes with a focus on quality of bread making, in order, Abelardo Luz, Cascavel and Guarapuava.A produtividade e a qualidade tecnológica do trigo são influenciadas por fatores genéticos, ambientais e de manejo. A participação do ambiente na definição de caracteres componentes do rendimento e atributos qualitativos de farinha requer extensiva avaliação de genótipos em vários locais durante anos. O objetivo deste trabalho foi avaliar o efeito de anos (2007 a 2011) e regiões de cultivo (Abelardo Luz- SC, Cascavel-PR, Castro-PR, Guarapuava-PR, Não Me Toque- RS e Palotina-PR) sobre a qualidade industrial e produtividade de grãos em conjuntos de ensaios de trigo (Triticum aestivum L.), com vistas a recomendação de cultivares e identificação de regiões que maximizem a qualidade de panificação. Foram realizadas as análises de variância conjunta e calculadas as estatísticas de comparação de médias, associação entre caracteres e adaptabilidade e estabilidade dos genótipos às diferentes regiões de cultivo, utilizando analises gráficas GGE Biplot e análises AMMI. Os resultados indicam que todos os caracteres avaliados foram influenciados pelo genótipo (G), ambiente (E) interação GxE. Os caracteres determinantes da qualidade de panificação de trigo têm sua variação fenotípica controlada principalmente pelo efeito genético. As cultivares CD 150, CD 108 e IPR 85 apresentaram excelente comportamento quanto à qualidade de panificação. O ambiente de teste Não-Me-Toque é ideal para seleção de genótipos com foco no rendimento de grãos e massa do hectolitro. Ambientes ideais para a seleção de genótipos com foco na qualidade de panificação incluem, em ordem, Abelardo Luz, Cascavel e Guarapuava

Reliability and Reproducibility of Hadamard Encoded Pseudo-Continuous Arterial Spin Labeling in Healthy Elderly

The perfusion parameters cerebral blood flow (CBF) and arterial transit time (ATT) measured with arterial spin labeling (ASL) magnetic resonance imaging (MRI) provide valuable essentials to assess the integrity of cerebral tissue. Brain perfusion changes, due to aging, an intervention, or neurodegenerative diseases for example, could be investigated in longitudinal ASL studies with reliable ASL sequences. Generally, pseudo-continuous ASL (pCASL) is preferred because of its larger signal-to-noise ratio (SNR) compared to pulsed ASL (PASL) techniques. Available pCASL versions differ regarding their feature details. To date only little is known about the reliability and reproducibility of CBF and ATT measures obtained with the innovative Hadamard encoded pCASL variant, especially if applied on participants in old age. Therefore, we investigated an in-house developed Hadamard encoded pCASL sequence on a group of healthy elderly at two different 3 Tesla Siemens MRI systems (Skyra and mMR Biograph) and evaluated CBF and ATT reliability and reproducibility for several regions-of-interests (ROI). Calculated within-subject coefficients of variation (wsCV) demonstrated an excellent reliability of perfusion measures, whereas ATT appeared to be even more reliable than CBF [e.g., wsCV(CBF) = 2.9% vs. wsCV(ATT) = 2.3% for a gray matter (GM) ROI on Skyra system]. Additionally, a substantial agreement of perfusion values acquired on both MRI systems with an inter-session interval of 78 ± 17.6 days was shown by high corresponding intra-class correlation (ICC) coefficients [e.g., ICC(CBF) = 0.704 and ICC(ATT) = 0.754 for a GM ROI]. The usability of this novel Hadamard encoded pCASL sequence might improve future follow-up perfusion studies of the aging and/or diseased brain

The bioenergetic role of dioxygen and the terminal oxidase(s) in cyanobacteria

AbstractOwing to the release of 13 largely or totally sequenced cyanobacterial genomes (see http://www.kazusa.or.jp/cyano and www.jgi.doe.gov/), it is now possible to critically assess and compare the most neglected aspect of cyanobacterial physiology, i.e., cyanobacterial respiration, also on the grounds of pure molecular biology (gene sequences). While there is little doubt that cyanobacteria (blue-green algae) do form the largest, most diversified and in both evolutionary and ecological respects most significant group of (micro)organisms on our earth, and that what renders our blue planet earth to what it is, viz. the O2-containing atmosphere, dates back to the oxygenic photosynthetic activity of primordial cyanobacteria about 3.2×109 years ago, there is still an amazing lack of knowledge on the second half of bioenergetic oxygen metabolism in cyanobacteria, on (aerobic) respiration. Thus, the purpose of this review is threefold: (1) to point out the unprecedented role of the cyanobacteria for maintaining the delicate steady state of our terrestrial biosphere and atmosphere through a major contribution to the poising of oxygenic photosynthesis against aerobic respiration (“the global biological oxygen cycle”); (2) to briefly highlight the membrane-bound electron-transport assemblies of respiration and photosynthesis in the unique two-membrane system of cyanobacteria (comprising cytoplasmic membrane and intracytoplasmic or thylakoid membranes, without obvious anastomoses between them); and (3) to critically compare the (deduced) amino acid sequences of the multitude of hypothetical terminal oxidases in the nine fully sequenced cyanobacterial species plus four additional species where at least the terminal oxidases were sequenced. These will then be compared with sequences of other proton-pumping haem–copper oxidases, with special emphasis on possible mechanisms of electron and proton transfer

Polimorfismo do gene da proteína prion celular (PrPC) e imunohistoquímica de tecido linfóide em ovinos

O objetivo deste trabalho foi avaliar o polimorfismo do gene da proteína prion celular (PRPN) de ovinos introduzidos numa propriedade onde ocorreu um surto de scrapie, e relacionar com a suscetibilidade à doença por meio da análise da presença da proteína prion celular alterada (PrPSc), utilizando imunohistoquímica (IHQ) de tecido linfóide associado à mucosa reto-anal. Foram avaliados 42 ovinos, mestiços Texel. Eram fêmeas entre um e oito anos de idade, sendo que sete (16,67%) ovelhas foram introduzidas adultas na propriedade em 2006. As demais, 83,33%, eram nascidas na fazenda. A genotipagem do PRPN foi feita pela análise do polimorfismo de comprimento de fragmento de restrição - RFLP ("Restriction Fragment Lenght Polimorphism"). O genótipo ARQ/ARQ foi o mais freqüente, encontrado em 73,81% dos animais, seguido do genótipo ARR/ARQ, com 16,67% e do ARQ/VRQ, com 9,52%. Os alelos ARH e AHQ não foram encontrados nestes animais. O resultado da IHQ foi negativo em todas as amostras. Não foi possível, portanto, estabelecer uma relação entre genótipo e maior susceptibilidade ao scrapie, devido à ausência de PrPSc na amostras examinadas. No Brasil, há poucos dados de genotipagem do gene da proteína prion celular (PRNP) em ovinos e, até o momento, nenhum tipo de controle baseado em cruzamentos direcionados foi implementado

Seizure-mediated iron accumulation and dysregulated iron metabolism after status epilepticus and in temporal lobe epilepsy

Neuronal dysfunction due to iron accumulation in conjunction with reactive oxygen species (ROS) could represent an important, yet underappreciated, component of the epileptogenic process. However, to date, alterations in iron metabolism in the epileptogenic brain have not been addressed in detail. Iron-related neuropathology and antioxidant metabolic processes were investigated in resected brain tissue from patients with temporal lobe epilepsy and hippocampal sclerosis (TLE-HS), post-mortem brain tissue from patients who died after status epilepticus (SE) as well as brain tissue from the electrically induced SE rat model of TLE. Magnetic susceptibility of the presumed seizure-onset zone from three patients with focal epilepsy was compared during and after seizure activity. Finally, the cellular effects of iron overload were studied in vitro using an acute mouse hippocampal slice preparation and cultured human fetal astrocytes. While iron-accumulating neurons had a pyknotic morphology, astrocytes appeared to acquire iron-sequestrating capacity as indicated by prominent ferritin expression and iron retention in the hippocampus of patients with SE or TLE. Interictal to postictal comparison revealed increased magnetic susceptibility in the seizure-onset zone of epilepsy patients. Post-SE rats had consistently higher hippocampal iron levels during the acute and chronic phase (when spontaneous recurrent seizures are evident). In vitro, in acute slices that were exposed to iron, neurons readily took up iron, which was exacerbated by induced epileptiform activity. Human astrocyte cultures challenged with iron and ROS increased their antioxidant and iron-binding capacity, but simultaneously developed a pro-inflammatory phenotype upon chronic exposure. These data suggest that seizure-mediated, chronic neuronal iron uptake might play a role in neuronal dysfunction/loss in TLE-HS. On the other hand, astrocytes sequester iron, specifically in chronic epilepsy. This function might transform astrocytes into a highly resistant, pro-inflammatory phenotype potentially contributing to pro-epileptogenic inflammatory processes