Gauge Consistent Wilson Renormalization Group II: Non-Abelian Case

We give a wilsonian formulation of non-abelian gauge theories explicitly consistent with axial gauge Ward identitities. The issues of unitarity and dependence on the quantization direction are carefully investigated. A wilsonian computation of the one-loop QCD beta function is performed.Comment: 34 pages, 1 eps figure, latex2e. Minor changes, version to appear in Int. J. Mod. Phy

High-resolution video characterisation of vulcanian plumes at Sabancaya Volcano, Peru

Since November 2016, volcanic activity at Sabancaya volcano (Peru) has been characterized by multiple short-lived Vulcanian explosions per day. These Vulcanian-type explosions and related volcanic plumes were also recorded in visible light during July and August 2018. Specific objectives of this work are to: i) develop a new algorithm to identify and isolate the plume pixels; ii) extract the main geometrical parameters of the eruptive column, such as the height and width as a function of time; iii) determine quantitative information related to the plume motion (e.g. the rise velocity and air entrainment coefficient), based on the physical quantities obtained through the first-order analysis; iv) characterize the eruption dynamics of Vulcanian plumes at Sabancaya. The results show that the algorithm traces well the plume boundaries and is also capable of automatically calculating the geometrical parameters (height of the top, maximum width and rise velocity of the plume head). We focussed on 8 explosions that are characterized by optimal weather and plume rise conditions. The calculated height for these selected explosions ranges from 180 to 715 m within 30 seconds after ejection, while the exit velocities are up to 96.5 m/s. The air entrainment coefficients were also estimated, and lie around 0.15 ± 0.04. Moreover, we found that plumes at Sabancaya have a transient/thermal behaviour, dominated by an unsteady release of pyroclastic material that strongly controls its features and evolution. Thus, high resolution video analysis, quantitative measurements and numerical modelling are merged here to improve the understanding of volcanic explosions at Sabancaya volcano and of volcanic plumes in general

Exact Renormalization Group in Algebraic Noncovariant Gauges

I study a class of Wilsonian formulations of non-Abelian gauge theories in algebraic noncovariant gauges where the Wilsonian infrared cutoff $\Lambda$ is inserted as a mass term for the propagating fields. In this way the Ward-Takahashi identities are preserved to all scales. Nevertheless the BRS-invariance in broken and the theory is gauge-dependent and unphysical at $\Lambda\neq0$. Then I discuss the infrared limit $\Lambda\to0$. I show that the singularities of the axial gauge choice are avoided in planar gauge and in light-cone gauge. Finally the rectangular Wilson loop of size $2L\times 2T$ is evaluated at lowest order in perturbation theory and a noncommutativity between the limits $\Lambda\to0$ and $T\to\infty$ is pointed out.Comment: 6 pages, latex2e, Proceeding of the Second Conference on the Exact R

The situational library.

This paper introduces the ongoing series of itinerant participatory artworks called the Situational Library. Through the construction of a publicly accessible and open-source archive of physical and digital books, the Situational Library attempts to create a heightened sense of the exchange of something other, or external, which accompanies the exchange of the book itself

On the Consistency of the Exact Renormalization Group Approach Applied to Gauge Theories in Algebraic Non-Covariant Gauges

We study a class of Wilsonian formulations of non-Abelian gauge theories in algebraic non-covariant gauges where the Wilsonian infrared cutoff $\Lambda$ is inserted as a mass term for the propagating fields. In this way the Ward-Takahashi identities are preserved to all scales. Nevertheless BRST-invariance in broken and the theory is gauge-dependent and unphysical at $\Lambda\neq0$. Then we discuss the infrared limit $\Lambda\to0$. We show that the singularities of the axial gauge choice are avoided in planar gauge and light-cone gauge. In addition the issue of infrared divergences is addressed in some explicit example. Finally the rectangular Wilson loop of size $2L\times 2T$ is evaluated at lowest order in perturbation theory and a non commutativity between the limits $\Lambda\to0$ and $T\to\infty$ is pointed out.Comment: Latex2e, 49 pages, 2 EPS figures. Misprints corrected. Version to be published on IJMP

Dark matter and gravitational lensing as teaching tools for physics and astronomy

In this work, mainly aimed at teachers of physics, mathematics and astronomy, it is illustrated how two important topics of cosmology can be introduced as valuable teaching aids: the dark matter problem and gravitational lensing. These complex and articulated topics have been treated with appropriate elementarisation and the use of simplified models, that made them suitable for introduction into the classroom in the form of exercises and/or extracurricular projects for students in their final years of secondary school or first years of university. In the first part of this thesis, the concepts of radial and rotational velocity, together with those of spider diagram and rotation curve, are introduced and applied to the solar system and a spiral galaxy. The inclusion of the spider diagram in this educational context is innovative. All this is discussed while working with real data and using the dynamic mathematical software Geogebra. Finally, we estimate the amount of non-visible mass that apparently influences the motion of all matter in a spiral galaxy. This provides evidence for the possible existence of dark matter. In the second part, we discuss the phenomenon of strong gravitational lensing, which can produce optical illusions observable in the universe. This effect is investigated for several examples of mass distributions acting as lenses. By examining the geometry of the gravitational lens system, we deduce size, distances and alignment of the components. Using this information and thanks to the software Geogebra, visualisations and interactive simulations of the images resulting from the gravitational lensing effect are created. Finally, the form to be given to lenses made of glass, to recreate the same effects produced by gravitational lenses, is studied. We have designed and produced five models of plexiglass lenses, that add an experimental part to the teaching of this subject, as they reproduce the gravitational lens effect directly in the classroom

The influence of hypoxia in erythropoiesis and morphology of red blood cells in sickle cell disease and hereditary spherocytosis.

Die Lebensfahigkeit menschlicher Zellen h ¨ angt in hohem Maße vom Sauerstoff ab, der von den roten ¨ Blutkorperchen transportiert und zur Verf ¨ ugung gestellt wird. In dieser Arbeit wird untersucht, wie ¨ Sauerstoff die Physiologie und Pathophysiologie jener roten Blutkorperchen beeinflusst. Die Arbeit ¨ ist in zwei wesentliche Teile gegliedert. Zunachst werden Ergebnisse einer gr ¨ oßeren Studie mit Probanden vorgestellt, die in großer H ¨ ohe ¨ (3450 m) durchgefuhrt wurde. In dieser H ¨ ohe sorgt der reduzierte Luftdruck f ¨ ur eine Abnahme ¨ der Sauerstoffsattigung im Blut und f ¨ uhrt so zu einer erh ¨ ohten Produktion an roten Blutk ¨ orperchen ¨ (Erythropoese). Nach der Ruckkehr aus großer H ¨ ohe f ¨ allt die Zahl an roten Blutk ¨ orperchen nach ¨ kurzer Zeit wieder auf das vorherige Niveau Es ist bislang nicht verstanden, ob die neugebildeten roten Blutzellen dazu abgebaut werden. Der hyptothetische Mechanismus der Neozytolyse (engl. Neocytolisis) geht davon aus, dass ausgerechnet die neu gebildeten, roten Blutzellen als erste wieder abgebaut werden, wenn die Ruckkehr auf Meeresniveau erfolgt. Die wissenschaftliche Fragestellung, ¨ die im Rahmen dieser Studie beantwortet wurde, ist, ob und in welchem Maß Neocytolyse nach einem 3-wochigen Aufenthalt in großer H ¨ ohe stattfindet. Dazu wurden zun ¨ achst Untersuchungen an aller ¨ Probanden mittels in-vitro Zellkulturen durchgefuhrt, um sowohl die Erythropoese als auch (neu ent- ¨ standende) Retikulozyten zu charakterisieren. Die Ergebnisse zeigen eine beschleunigte Reifung der Vorlauferzellen in Zellkulturen bei niedrigerem Sauerstoffgehalt (3%) verglichen mit normaler Atmo- ¨ sphare (20%) und eine unerwartet verbesserte ¨ Uberlebensrate der Retikulozyten. Dies stimmt mit dem ¨ Ergebnis der Studie uberein, dass nach der R ¨ uckkehr von der gew ¨ ahlten H ¨ ohe keine Neozytolyse, d.h. ¨ kein bevorzugter Abbau von neu gebildeten roten Blutzellen, auftrat, was die Hypothese eines selektiven, vorzeitigen Abbaus von unreifen roten Blutzellen widerlegt. Weiterhin wurde in der Zellkultur unter verringerter Sauerstoffgabe eine erhohte Zahl bikonkaver Zellen beobachtet, was eine typische ¨ Gestalt fur einen fortgeschrittenen Reifegrad ist. Diese Beobachtung k ¨ onnte ein Anhaltspunkt daf ¨ ur¨ sein, dass der Reifeprozess von roten Blutzellen durch die Reduzierung des atmospharischen Sauer- ¨ stoffgehaltes begunstigt werden kann. Im Rahmen dieser Arbeit wurde zus ¨ atzlich ein Protokoll zur ¨ Isolation der Retikulozyten vom Vollblut der Probanden entwickelt, um die pure Zell-RNA jeweils vor und in großer Hohe zu sequenzieren. Jedoch muss die Ausbeute an RNA weiter optimiert werden, ¨ um einen detaillierten Vergleich der Gen-Expressions-Niveaus anstellen zu konnen. ¨ Der zweite Teil der Arbeit konzentriert sich auf die Untersuchung der Morphologie der roten Blutkor- ¨ perchen bei zwei Arten von Anamie. Aufgrund der hohen Empfindlichkeit der roten Blutk ¨ orperchen ¨ gegenuber Formvariationen, mussten die Proben vor jeder experimentellen Manipulation fixiert wer- ¨ den. Dazu musste ein angemessenes Verfahren entwicklelt werden, das im Rahmen dieser Arbeit vorgestellt wird. Zunachst wird auf die Sichelzellenan ¨ amie eingegangen, bei der es unter Desoxy- ¨ genierung des Hamoglobins zur starken Verformung der roten Blutk ¨ orperchen (Sichelzellen) kommt. ¨ Dies beintrachtigt sowohl deren Funktion als auch Lebensdauer. Eine quantitative Analyse von Zell- ¨ Projektionsbildern aus konfokalen Mikroskopieaufnahmen wurde mit Hilfe eines maßgeschneiderten Computerprogramms im Rahmen einer klinischen Pilotstudie der Phase II zur Therapie der Sichelzellanamie durchgef ¨ uhrt. Es konnte gezeigt werden, dass diese Methode in Kombination mit anderen ¨ experimentellen Verfahren ein wirkungsvolles Instrument zur Beurteilung des Zellhydratationszustands von Sichelzellenpatienten ist. Daher kann diese Technik zur Beurteilung der Wirksamkeit von Sichelzellen-Therapien oder zur Beurteilung des Zustands der roten Blutkorperchen eines Pa- ¨ tienten verwendet werden. Da die roten Blutkorperchen bei verschiedenen Arten von An ¨ amie auch ¨ verschiedene Formvariationen aufweisen, wurde eine weitere Blutkrankheit, die hereditare Sph ¨ arozy- ¨ tose, untersucht. In diesem Fall lag der Schwerpunkt auf der automatisierten Formerkennung der roten Blutkorperchen, die in der Regel manuell durchgef ¨ uhrt wird und daher einer Bewertungsinkonsistenz ¨ unterliegt. Die Untersuchung nutzt die 3D-Rekonstruktion der Zellen aus konfokalen Mikroskopieaufnahmen und die anschließende Formerkennung mittels kunstlicher neuronaler Netze. Die Beurteilung ¨ dieses Systems zeigte sowohl eine sehr gute Erkennungsrate, hohe Prazision, eine schnelle Prozesszeit, ¨ als auch ein objektives Ergebnis verglichen mit der manuellen Klassifikation. Verglichen mit der Analyse von 2D Mikroskopieaufnahmen von Blutabstrichen, konnten durch die Auswertung korrespondierender 3D Aufnahmen außerdem andere Formspektren abgeleitet werden. Dies legt die Empfehlung nahe, die manuelle Klassifizierung von Zellformen (Stand der Technik) im Kontext von hereditarer Sph ¨ arozytose zu ¨ uberdenken.Human cell viability highly depends on oxygen, which is carried and provided by red blood cells. This thesis aimed to investigate how oxygen influences physiology and pathophysiology of red blood cells and is divided in two main parts. The first one presents results that are part of a larger study performed at high altitude (3450 m). Here, the reduced air pressure causes a decrease in blood oxygenation, which is balanced by an increase in red blood cells production (erythropoiesis). Upon return from high altitude, the amount of red blood cells is restored to the original levels within a few days, which is in contrast with the average red blood cell lifespan of 120 days. The reasons leading to such red blood cells premature clearance are not well understood. A hypothetical mechanism previously proposed is defined as neocytolisis, i.e. the selective clearance of the red blood cells formed at high altitude upon return to sea level. The scientific question of the study was therefore to assess if and how neocytolisis occurs after a 3-week stay at high altitude. The investigations performed in this thesis involved in vitro culture of erythroid precursors of the donors participating in the study to characterize both erythropoiesis and the obtained immature red blood cells, namely reticulocytes. Results highlighted an accelerated maturation of erythroid precursors in cultures performed at lower oxygen (3%) compared to atmospheric oxygen (20%) ones and an unexpected improved cell survival of the obtained reticulocytes. This was in accordance with the finding that after the stay at the chosen altitude no neocytolisis occurred, denying the hypothesis of a higher fragility of cells formed at low oxygen causing their selective premature clearance upon return from high altitude. Moreover, cultures performed at low oxygen resulted in the formation of more biconcave cells, the typical shape of mature red blood cells. This suggests that reducing oxygen levels in cultures may contribute to advance their maturation in vitro. In addition to cell cultures, another objective was to perform RNA sequencing of isolated reticulocytes from whole blood of the donors to compare pre- and high altitude conditions. A protocol for the isolation of a pure fraction of reticulocytes and their RNA was developed. However, total RNA yield needs to be increased to perform an accurate comparison of gene expression levels. The second part of the thesis focused on studying red blood cell morphology in two types of anemia. Because of the high sensitivity of red blood cells to shape variation, samples were always fixed before any experimental manipulation. A thorough study describing how to perform red blood cell fixation is presented. The first blood disease of study was sickle cell anemia. In this pathology, deoxygenation of hemoglobin causes the deformation of red blood cells to the shape of a sickle that impairs their functions and lifespan. The quantitative analysis of cell projections from confocal images by means of a customized computer program was employed within a pilot phase II clinical trial for the therapy of sickle cell disease. The obtained results combined with other experimental evaluations showed that red blood cell shape analysis of sickle cell disease patients is a simple but powerful tool to evaluate cell hydration state. Therefore, this technique may be used for the assessment of the efficacy of sickle cell disease therapies or to evaluate the state of red blood cells of a patient. Since red blood cells display shape variations in different types of anemia, a second blood disease was investigated, namely hereditary spherocytosis. In this case, the focus was the automation of red blood cells shape recognition, which is usually performed manually and therefore subjected to evaluation inconsistency. The investigation made use of 3D cell reconstructions from confocal images and automated shape recognition by means of artificial neural networks. System benchmarks showed a good recognition performance, high accuracy, fast processing time as well unbiased results compared to the manual classification. Moreover, the application of 3D imaging in contrast to the traditional 2D-microscopy typically employed in blood smear analysis revealed a different red blood cell shapes spectrum. These results therefore suggest to revise the state-of-the art manual shape classification applied in hereditary spherocytosis