Quark-Gluon Plasma/Black Hole duality from Gauge/Gravity Correspondence

The Quark-Gluon Plasma (QGP) is the QCD phase of matter expected to be formed at small proper-times in the collision of heavy-ions at high energy. Experimental observations seem to favor a strongly coupled QCD plasma with the hydrodynamic properties of a quasi-perfect fluid, i.e. rapid thermalization (or isotropization) and small viscosity. The theoretical investigation of such properties is not obvious, due to the the strong coupling. The Gauge/Gravity correspondence provides a stimulating framework to explore the strong coupling regime of gauge theories using the dual string description. After a brief introduction to Gauge/Gravity duality, and among various existing studies, we focus on challenging problems of QGP hydrodynamics, such as viscosity and thermalization, in terms of gravitational duals of both the static and relativistically evolving plasma. We show how a Black Hole geometry arises naturally from the dual properties of a nearly perfect fluid and explore the lessons and prospects one may draw for actual heavy ion collisions from the Gauge/Gravity duality approach.Comment: 6 pages, 4 figures, invited talk at the EPS HEP 2007 Conference, Manchester (UK), and at the ``Deuxiemes rencontres PQG-France'', Etretat (2007); reference adde

Pseudoheterodyne near-field imaging at kHz repetition rates via quadrature-assisted discrete demodulation

Scattering-type scanning near-field optical microscopy enables the measurement of optical constants of a surface beyond the diffraction limit. Its compatibility with pulsed sources is hampered by the requirement of a high-repetition rate imposed by lock-in detection. We describe a sampling method, called quadrature-assisted discrete (quad) demodulation, which circumvents this constraint. Quad demodulation operates by measuring the optical signal and the modulation phases for each individual light pulse. This method retrieves the near-field signal in the pseudoheterodyne mode, as proven by retraction curves and near-field images. Measurement of the near-field using a pulsed femtosecond amplifier and quad demodulation is in agreement with results obtained using a CW laser and the standard lock-in detection method

Fostering modeling competencies: benefits of worked examples, problems to be solved, and fading procedures

The application of mathematics to real-world problems is moving more and more in the focus of attention of mathematics education; however, many learners experience huge difficulties in relating "pure" mathematics to everyday contents. In order to solve "modeling problems", it is first necessary to find a transition from a real-world description to a mathematical model; second, intra-mathematical calculations have to be performed; and third, the result has to be interpreted with respect to the described real situation. In the present work, the effectivity of learning with worked examples and with fading procedures was tested experimentally. A design with 4 groups was implemented: "forward fading", "backward fading", "example-problem pairs", and "problem-example pairs". The results show that translation competencies were fostered best by way of example-problem pairs, whereas intramathematical skills were fostered most effectively by a backward fading procedure. Subjective assessments were especially positive when fading procedures or example-problem pairs were implemented

Death receptor-based enrichment of Cas9-expressing cells

Background: The CRISPR/Cas9 genome editing system has greatly facilitated and expanded our capacity to engineer mammalian genomes, including targeted gene knock-outs. However, the phenotyping of the knock-out effect requires a high DNA editing efficiency. Results: Here, we report a user-friendly strategy based on the extrinsic apoptosis pathway that allows enrichment of a polyclonal gene-edited cell population, by selecting Cas9-transfected cells that co-express dominant-negative mutants of death receptors. The extrinsic apoptosis pathway can be triggered in many mammalian cell types, and ligands are easy to produce, do not require purification and kill much faster than the state-of-the-art selection drug puromycin. Stringent assessment of our advanced selection strategy via Sanger sequencing, T7 endonuclease I (T7E1) assay and direct phenotyping confirmed a strong and rapid enrichment of Cas9-expressing cell populations, in some cases reaching up to 100 % within one hour. Notably, the efficiency of target DNA cleavage in these enriched cells reached high levels that exceeded the reliable range of the T7E1 assay, a conclusion that can be generalized for editing efficiencies above 30 %. Moreover, our data emphasize that the insertion and deletion pattern induced by a specific gRNA is reproducible across different cell lines. Conclusions: The workflow and the findings reported here should streamline a wide array of future low- or high-throughput gene knock-out screens, and should largely improve data interpretation from CRISPR experiments

Tackling the Root Cause of Surface-Induced Coagulation: Inhibition of FXII Activation to Mitigate Coagulation Propagation and Prevent Clotting

Factor XII (FXII) is a zymogen present in blood that tends to adsorb onto the surfaces of blood-contacting medical devices. Once adsorbed, it becomes activated, initiating a cascade of enzymatic reactions that lead to surface-induced coagulation. This process is characterized by multiple redundancies, making it extremely challenging to prevent clot formation and preserve the properties of the surface. In this study, a novel modulatory coating system based on C1-esterase inhibitor (C1INH) functionalized polymer brushes, which effectively regulates the activation of FXII is proposed. Using surface plasmon resonance it is demonstrated that this coating system effectively repels blood plasma proteins, including FXII, while exhibiting high activity against activated FXII and plasma kallikrein under physiological conditions. This unique property enables the modulation of FXII activation without interfering with the overall hemostasis process. Furthermore, through dynamic Chandler loop studies, it is shown that this coating significantly improves the hemocompatibility of polymeric surfaces commonly used in medical devices. By addressing the root cause of contact activation, the synergistic interplay between the antifouling polymer brushes and the modulatory C1INH is expected to lay the foundation to enhance the hemocompatibility of medical device surfaces.© 2023 The Authors. Macromolecular Bioscience published by Wiley-VCH GmbH

Stability of bicontinuous cubic phases in ternary amphiphilic systems with spontaneous curvature

We study the phase behavior of ternary amphiphilic systems in the framework of a curvature model with non-vanishing spontaneous curvature. The amphiphilic monolayers can arrange in different ways to form micellar, hexagonal, lamellar and various bicontinuous cubic phases. For the latter case we consider both single structures (one monolayer) and double structures (two monolayers). Their interfaces are modeled by the triply periodic surfaces of constant mean curvature of the families G, D, P, C(P), I-WP and F-RD. The stability of the different bicontinuous cubic phases can be explained by the way in which their universal geometrical properties conspire with the concentration constraints. For vanishing saddle-splay modulus $\bar \kappa$, almost every phase considered has some region of stability in the Gibbs triangle. Although bicontinuous cubic phases are suppressed by sufficiently negative values of the saddle-splay modulus $\bar \kappa$, we find that they can exist for considerably lower values than obtained previously. The most stable bicontinuous cubic phases with decreasing $\bar \kappa < 0$ are the single and double gyroid structures since they combine favorable topological properties with extreme volume fractions.Comment: Revtex, 23 pages with 10 Postscript files included, to appear in J. Chem. Phys. 112 (6) (February 2000

Deductive synthesis of recursive plans in linear logic

Linear logic has previously been shown to be suitable for describing and deductively solving planning problems involving conjunction and disjunction. We introduce a recursively defined datatype and a corresponding induction rule, thereby allowing recursive plans to be synthesised. In order to make explicit the relationship between proofs and plans, we enhance the linear logic deduction rules to handle plans as a form of proof term

Results of the QUENCH-20 experiment with BWR test bundle [in press]

The experiment QUENCH-20 with BWR geometry simulation bundle was successfully conducted at KIT on 9th October 2019 in the framework of the international SAFEST project. The test bundle mock-up represented one quarter of a BWR fuel assembly with 24 electrically heated fuel rod simulators and two B4C control blades. The rod simulators were filled with Kr to an inner pressure of 5.5 bar. The pre-oxidation stage in a flowing gas mixture of steam and argon (each 3 g/s) and system pressure of 2 bar lasted 4 hours at the peak cladding temperature of 1250 K. The Zry-4 corner rod, withdrawn at the end of this stage, showed the maximal oxidation at elevations between 930 and 1020 mm with signs of breakaway. During the transient stage, the bundle was heated to a maximum temperature of 2000 K. The coolability of the bundle was decreased by its squeezing due to the shroud ductile deformation caused by an overpressure outside the shroud. The cladding radial strain and failures due to inner overpressure (about 4 bar) were observed at temperature about 1700 K and lasted about 200 s. During the period of rod failures also the first absorber melt relocation accompanied by shroud failure were registered. The interaction of B4C with the steel blade and the ZIRLO channel box were observed at elevations 650…950 mm with the formation of eutectic melt. The typical components of this melt are (Fe, Cr) borides and ZrB2 precipitated in steel or in Zr-steel eutectic melt. Massive absorber melt relocation was observed 50 s before the end of transition stage. Small fragments of the absorber melt moved down to the elevation of 50 mm. The melting point of Inconel spacer grids at 500 and 1050 mm was also reached at the end of the transition stage. The Inconel melt from the elevation 1050 mm relocated downwards through hot bundle regions to the Inconel grid spacer at 550 mm and later (during the escalation caused by quench) to 450 mm. This melt penetrated also under the damaged cladding oxide layer and formed molten eutectic mixtures between elevations 450 and 550 mm. The test was terminated by quench water injection with a flow rate of 50 g/s from the bundle bottom. Fast temperature escalation from 2000 to 2300 K during 20 s was observed due to the strongly exothermic oxidation reactions. As result, the metal part (prior β-Zr) of the claddings between 550 and 950 mm was melted, partially released into space between rods and partially relocated in the gap between pellet and outer oxide layer to 450 mm. In this case, the positive role of the oxide layer should be noted, which does not allow the melt to completely escape into the inter-rod space. It is thereby limiting the possibility of interactions of a large amount of melt with steam, which could significantly increase the exothermic oxidation processes and the escalation of temperatures. The distribution of the oxidation rate within each bundle cross section is very inhomogeneous: whereas the average outer ZrO2 layer thickness for the central rod (#1) at the elevation of 750 mm is 465 µm, the same parameter for the peripheral rod #24 is only 108 µm. The average oxidation rate of the inner cladding surface (due to interaction with steam and with ZrO2 pellets) is about 20% in comparison to the outer cladding oxidation. The bundle elevations 850 and 750 mm are mostly oxidized with average cladding ECR 33%. The oxidation of the melt relocated inside the rods was observed at elevations 550…950 mm. The mass spectrometer measured release of CO (12.6 g), CO2 (9.7 g) and CH4 (0.4 g) during the reflood as products of absorber oxidation; the corresponding B4C reacted mass was 41 g or 4.6% of the total B4C inventory. It is significantly lower than in the PWR bundle tests QUENCH-07 and QUENCH-09 containing central absorber rod with B4C pellets inserted into a thin stainless steel cladding and Zry-4 guide tubes (20% and 50% reacted B4C correspondingly). Hydrogen production during the reflood amounted to 32 g during the reflood (57.4 g during the whole test) including 10 g from B4C oxidation

Spectral Flow on the Higgs Branch and AdS/CFT Duality

We use AdS/CFT duality to study the large N_c limit of the meson spectrum on the Higgs branch of a strongly coupled, N=2 supersymmetric SU(N_c) gauge theory with N_f =2 fundamental hypermultiplets. In the dual supergravity description, the Higgs branch is described by SU(2) instanton configurations on D7-branes in an AdS background. We compute the spectral flow parameterized by the size of a single instanton. In the large N_c limit, there is a sense in which the flow from zero to infinite instanton size, or Higgs VEV, can be viewed as a closed loop. We show that this flow leads to a non-trivial rearrangement of the spectrum.Comment: v2; 16 pages, 3 figures, LaTeX + JHEP class, 3 refs added, accepted for publication by JHE