Einfluss van-der-Waals-artiger Wechselwirkungen auf den thermodynamischen Casimir-Effekt

Wird ein makroskopisches System, das im thermodynamischen Limes einen Phasenübergang zweiter Ordnung aufweist, in seiner räumlichen Ausdehnung beschränkt, so kann dies — wenn sich das System am oder in der Umgebung seines kritischen Punktes befindet — langreichweitige effektive Kräfte hervorrufen. Der Mechanismus, der der Entstehung dieser Kräfte zugrunde liegt, wird als thermodynamischer Casimir-Effekt bezeichnet, dessen experimenteller Nachweis erst Ende der 1990er Jahre gelang. Bei seiner experimentellen Realisierung spielen Flüssigkeiten und die darin auftretenden Phasenübergänge zweiter Ordnung eine wichtige Rolle, wie zum Beispiel der Übergang zur Suprafluidität in 4He und auch der flüssig-gasförmig Übergang in einfachen Flüssigkeiten. Bereits in früheren theoretischen Arbeiten konnte dabei qualitativ gezeigt werden, dass die in Flüssigkeiten vorhandenen langreichweitigen van der Waals-Wechselwirkungen Auswirkungen auf den thermodynamischen Casimir-Effekt haben, obgleich sie das führende kritische Verhalten des Systems nicht beeinflussen. Aus ihnen gehen lediglich Korrekturen hervor, die jedoch in Abhängigkeit von Parametern wie der Temperatur und auch den Längenskalen, die die räumliche Beschränkung des Systems charakterisieren, in einem gewissen Regime das Verhalten der thermodynamischen Casimir-Kraft in führender Ordnung bestimmen. Die qualitativen und quantitativen Unterschiede, die sich daraus im Vergleich zu Systemen mit rein kurzreichweitigen Wechselwirkungen ergeben, werden in dieser Arbeit untersucht. Dazu werden d-dimensionale O(n)-symmetrische Modelle mit L×∞^(d−1) Filmgeometrie und periodischen Randbedingungen betrachtet, und unter Beschränkung auf den Temperaturbereich bei und oberhalb der Übergangstemperatur (T ≥ T_{c,∞}) die thermodynamische Casimir-Kraft und ihre führenden Korrekturen hergeleitet. Zugrunde gelegt wird dabei eine isotrope langreichweitige Wechselwirkung, die für große Abstände x asymptotisch proportional zu x^{−(d+σ)} abfällt, wobei der Wert des Parameters σ auf das Intervall 2 < σ < 4 beschränkt ist. Um den Limes n → ∞ zu behandeln, wird ein hierzu äquivalentes exakt lösbares sphärisches Modell aufgestellt und unter Beschränkung auf 2 < d < 4 Dimensionen exakte Ergebnisse für die thermodynamische Casimir-Kraft und ihre führenden Korrekturen hergeleitet. Der Fall n < ∞, der in 2 < d < 4 Dimensionen keine exakten Lösungen gestattet, wird mit Hilfe eines feldtheoretischen φ^4-Modells beschrieben. Die freie Energie dieses Modells wird dabei im Rahmen der renormierungsgruppenverbesserten Störungstheorie in Zweischleifenordnung berechnet, und hieraus die thermodynamische Casimir-Kraft und ihre führenden Korrekturen abgeleitet. Anhand beider Modelle wird heraus gestellt, dass die thermodynamische Casimir-Kraft in Anwesenheit der langreichweitigen Wechselwirkung im Temperaturbereich T > Tc,∞ auf großen Längenskalen durch einen algebraischen Abfall ∼ L^{−(d+σ)} gekennzeichnet ist, während sie im rein kurzreichweitigen Fall auf der Skala der Korrelationslänge exponentiell abfällt. Ein Vergleich der störungstheoretischen Resultate für den rein kurzreichweitigen Fall mit Monte Carlo-Ergebnissen für das dreidimensionale Ising- und XY-Modell ergibt eine gute Übereinstimmung

ANALYSIS, DESIGN AND IMPLEMENTATION OF AN EMBEDDED REALTIME SOUND SOURCE LOCALIZATION SYSTEM BASED ON BEAMFORMING THEORY

This project is intended to analyze, design and implement a realtime sound source localization system by using a mobile robot as the media. The implementated system uses 2 microphones as the sensors, Arduino Duemilanove microcontroller system with ATMega328p as the microprocessor, two permanent magnet DC motors as the actuators for the mobile robot and a servo motor as the actuator to rotate the webcam directing to the location of the sound source, and a laptop/PC as the simulation and display media. In order to achieve the objective of finding the position of a specific sound source, beamforming theory is applied to the system. Once the location of the sound source is detected and determined, the choice is either the mobile robot will adjust its position according to the direction of the sound source or only webcam will rotate in the direction of the incoming sound simulating the use of this system in a video conference. The integrated system has been tested and the results show the system could localize in realtime a sound source placed randomly on a half circle area (0 - 1800) with a radius of 0.3m - 3m, assuming the system is the center point of the circle. Due to low ADC and processor speed, achievable best angular resolution is still limited to 25o

4-(3,5-Dimethyl-1H-pyrazol-1-yl)benzene­sulfonamide

The two aromatic rings of the title compound, C11H13N3O2S, are inclined at an angle of 47.81 (4)°. The N atom of the amino unit is pyramidally coordinated; one H atom inter­acts with the sulfamyl O atom of an adjacent mol­ecule, forming a centrosymmetric hydrogen-bonded dimer. The dimers are linked by N—H⋯N hydrogen bonds, generating a three-dimensional network

Distinct roles of Akt1 and Akt2 in regulating cell migration and epithelial–mesenchymal transition

The Akt family of kinases are activated by growth factors and regulate pleiotropic cellular activities. In this study, we provide evidence for isoform-specific positive and negative roles for Akt1 and -2 in regulating growth factor–stimulated phenotypes in breast epithelial cells. Insulin-like growth factor-I receptor (IGF-IR) hyperstimulation induced hyperproliferation and antiapoptotic activities that were reversed by Akt2 down-regulation. In contrast, Akt1 down-regulation in IGF-IR–stimulated cells promoted dramatic neomorphic effects characteristic of an epithelial–mesenchymal transition (EMT) and enhanced cell migration induced by IGF-I or EGF stimulation. The phenotypic effects of Akt1 down-regulation were accompanied by enhanced extracellular signal–related kinase (ERK) activation, which contributed to the induction of migration and EMT. Interestingly, down-regulation of Akt2 suppressed the EMT-like morphological conversion induced by Akt1 down-regulation in IGF-IR–overexpressing cells and inhibited migration in EGF-stimulated cells. These results highlight the distinct functions of Akt isoforms in regulating growth factor–stimulated EMT and cell migration, as well as the importance of Akt1 in cross-regulating the ERK signaling pathway

Macroalgal–bacterial interactions: identification and role of thallusin in morphogenesis of the seaweed Ulva (Chlorophyta)

Macroalgal microbiomes have core functions related to biofilm formation, growth, and morphogenesis of seaweeds. In particular, the growth and development of the sea lettuce Ulva spp. (Chlorophyta) depend on bacteria releasing morphogenetic compounds. Under axenic conditions, the macroalga Ulva mutabilis develops a callus-like phenotype with cell wall protrusions. However, co-culturing with Roseovarius sp. (MS2) and Maribacter sp. (MS6), which produce various stimulatory chemical mediators, completely recovers morphogenesis. This ecological reconstruction forms a tripartite community which can be further studied for its role in cross-kingdom interactions. Hence, our study sought to identify algal growth- and morphogenesis-promoting factors (AGMPFs) capable of phenocopying the activity of Maribacter spp. We performed bioassay-guided solid-phase extraction in water samples collected from U. mutabilis aquaculture systems. We uncovered novel ecophysiological functions of thallusin, a sesquiterpenoid morphogen, identified for the first time in algal aquaculture. Thallusin, released by Maribacter sp., induced rhizoid and cell wall formation at a concentration of 11 pmol l-1. We demonstrated that gametes acquired the iron complex of thallusin, thereby linking morphogenetic processes with intracellular iron homeostasis. Understanding macroalgae-bacteria interactions permits further elucidation of the evolution of multicellularity and cellular differentiation, and development of new applications in microbiome-mediated aquaculture systems.FCT: UID/Multi/04326/2019; UIDB/04326/2020; CCMAR/ID/16/2018; CEECINST/00114/2018. German Research Foundation (DFG) CRC1127; European Union (EU) 642575; ASSEMBLE 227799; COST Action 'Phycomorph' FA1406.info:eu-repo/semantics/publishedVersio

An Improved Neutron Electric Dipole Moment Experiment

A new measurement of the neutron EDM, using Ramsey's method of separated oscillatory fields, is in preparation at the new high intensity source of ultra-cold neutrons (UCN) at the Paul Scherrer Institute, Villigen, Switzerland (PSI). The existence of a non-zero nEDM would violate both parity and time reversal symmetry and, given the CPT theorem, might lead to a discovery of new CP violating mechanisms. Already the current upper limit for the nEDM (|d_n|<2.9E-26 e.cm) constrains some extensions of the Standard Model. The new experiment aims at a two orders of magnitude reduction of the experimental uncertainty, to be achieved mainly by (1) the higher UCN flux provided by the new PSI source, (2) better magnetic field control with improved magnetometry and (3) a double chamber configuration with opposite electric field directions. The first stage of the experiment will use an upgrade of the RAL/Sussex/ILL group's apparatus (which has produced the current best result) moved from Institut Laue-Langevin to PSI. The final accuracy will be achieved in a further step with a new spectrometer, presently in the design phase.Comment: Flavor Physics & CP Violation Conference, Taipei, 200

Anthropogenic reaction parameters - the missing link between chemical intuition and the available chemical space

How do skilled synthetic chemists develop such a good intuitive expertise ? Why can we only access such a small amount of the available chemical space — both in terms of the re actions used and the chemical scaffolds we make? We argue here that these seemingly unrelated questions have a common root and are strongly interdependent . We performed a comprehensive analysis of organic reaction parameters dating back to 1771 and discove red that there are several anthropogenic factors that limit the reaction parameters and thus the scop e of synthetic chemistry. Nevertheless, many of the anthropogenic limitations such as the narrow parameter space and the opportunity of the rapid and clear feedback on the progress of reactions appear to be crucial for the acquisition of valid and reliable chemical intuition. In parallel, however, all of these same factors represent limitations for the exploration of available chemistry space and we argue th at these are thus at least partly responsible for limited access to new chemistries. We advocate, therefore, that the present anthropogenic boundaries can be expanded by a more conscious expl oration of “off - road” chemistry that would also extend the intuit ive knowledge of trained chemists

Integrative genomic analysis of human ribosomal DNA

The transcription of ribosomal RNA (rRNA) is critical to life. Despite its importance, ribosomal DNA (rDNA) is not included in current genome assemblies and, consequently, genomic analyses to date have excluded rDNA. Here, we show that short sequence reads can be aligned to a genome assembly containing a single rDNA repeat. Integrated analysis of ChIP-seq, DNase-seq, MNase-seq and RNA-seq data reveals several novel findings. First, the coding region of active rDNA is contained within nucleosome-depleted open chromatin that is highly transcriptionally active. Second, histone modifications are located not only at the rDNA promoter but also at novel sites within the intergenic spacer. Third, the distributions of active modifications are more similar within and between different cell types than repressive modifications. Fourth, UBF, a positive regulator of rRNA transcription, binds to sites throughout the genome. Lastly, the insulator binding protein CTCF associates with the spacer promoter of rDNA, suggesting that transcriptional insulation plays a role in regulating the transcription of rRNA. Taken together, these analyses confirm and expand the results of previous ChIP studies of rDNA and provide novel avenues for exploration of chromatin-mediated regulation of rDNA