B-Zerfälle aus QCD Summenregeln

<i>B</i>-Zerfälle aus QCD Summenregeln <br /> Das Standardmodell der Elementarteilchenphysik erklärt die <i>CP</i>-Verletzung genannte Materie-Antimaterie- Asymmetrie durch eine komplexe Phase in der Kopplung der Quarks an das <i>W</i>-Boson, die durch die <i>CKM</i>-Matrix beschrieben wird. Um diesen Ansatz zu überprüfen und seine fundamentalen Parameter, die Einträge der <i>CKM</i>-Matrix, zu bestimmen, müssen schwache Zerfallsprozesse von Hadronen untersucht werden. Wichtige Einblicke bieten zum Beispiel <i>B</i>-Meson-Zerfälle in zwei leichte Pseudoskalare (<font size=-1>&pi;</font>,<i>K</i>). Über sie können die <i>CKM</i>-Winkel &alpha; und &gamma; bestimmt werden. Allerdings wird die theoretische Behandlung der Zerfälle dadurch erschwert, dass gebundene Quarkzustände nicht mit der Störungstheorie beschrieben werden können. In der Literatur behilft man sich oft mit Berechnungen im Limes <i>m<font size=-1>_b</font></i> &#8594; _{<font size=+1>&infin;</font>} (schweres Beauty-Quark) und <i>m<font size=-1>_s</font></i> &#8594; 0 (leichtes Strange-Quark). In QCD Summenregeln können die Korrekturen zu dieser Näherung berechnet werden. In <i>B</i> &#8594; <font size=-1>&pi;&pi;</font>-Zerfällen zum Beispiel ist die theoretische Vorhersage im Grenzfall <i>m<font size=-1>_b</font></i> &#8594; _{<font size=+1>&infin;</font>} inkonsistent mit den Messdaten. In der vorliegenden Arbeit wurden zusätzlich zu bereits bekannten 1/<i>m<font size=-1>_b</font></i>-Korrekturen die Annihilations-Beiträge zu diesen Zerfällen mit Lichtkegel-Summenregeln berechnet. Sie sind allerdings zu klein, um die Diskrepanz zwischen Theorie und Experiment aufzuheben. Mit der gleichen Methode wurden auch perturbative Korrekturen zu Emissionsdiagrammen neu berechnet. Das Ergebnis ist vergleichbar mit dem anderer Methoden, schließt aber eine neue 1/<i>m<font size=-1>_b</font></i>-unterdrückte starke Phase ein und hängt nicht von der <i>B</i>-Meson-Verteilungsamplitude ab, die noch nicht gut bekannt ist. Darüberhinaus wurden die Effekte der Strange- Quark-Masse in <i>B</i>_{(<i><font size=-1>s</font></i>)} &#8594; <font size=-1>&pi;</font><i>K</i>- und <i>KK</i>-Zerfällen berechnet. Dazu wurden prozessunabhängige Größen, die Lichtkegel-Verteilungsamplituden beschreiben, in Zweipunkt-Summenregeln berechnet. Es stellte sich heraus, dass der Grenzwert <i>m<font size=-1>_s</font></i> &#8594; 0 keine besonders gute Näherung ist, die QCD Summenregeln aber bei endlichem <i>m<font size=-1>_s</font></i> eine gute Beschreibung liefern.<i>B</i>-Zerfälle aus QCD Summenregeln <br /> In the Standard Model of elementary particle physics, the asymmetry between matter and antimatter, called <i>CP</i>-violation, is explained by a complex phase in the <i>CKM</i>-matrix which governs the coupling of the quarks to the <i>W</i> boson mediating the weak interaction. In order to test this theoretical framework and to determine its fundamental parameters, the <i>CKM</i> matrix elements, weak decays of hadrons have to be investigated. One interesting class of such decays are those of <i>B</i> mesons to two light pseudoscalars (<font size=-1>&pi;</font>,<i>K</i>). They are sensitive to the weak <i>CP</i>-violating phases &alpha; and &gamma; of the <i>CKM</i> matrix. The theoretical treatment required to extract them from the measured data is however very difficult, as the bound states of quarks cannot be described by perturbation theory. In the literature, the limits <i>m<font size=-1>_b</font></i> &#8594; _{<font size=+1>&infin;</font>} (heavy beauty quark) and <i>m<font size=-1>_s</font></i> &#8594; 0 (light strange quark) are often used in the calculation of physical observables. With the help of QCD twopoint and light-cone sum rules, corrections to this limits can be calculated. In <i>B</i> &#8594; <font size=-1>&pi;&pi;</font> decays, for example, one observes a discrepancy between the theoretical description in the <i>m<font size=-1>_b</font></i> &#8594; _{<font size=+1>&infin;</font>} limit and the measured quantities. In this work, the contributions from the annihilation mechanism have been calculated using light-cone sum rules, in addition to several already known 1/<i>m<font size=-1>_b</font></i>-corrections. They were found to be too small to reconcile theory and experiment, however. The same method was also applied to perturbative corrections to the dominant emission diagrams. The latter ones have already been calculated in other methods and the results are consistent with each other. At the same time, the new result includes a new 1/<i>m<font size=-1>_b</font></i>-suppressed strong phase and does not depend on the poorly known distribution amplitude of the <i>B</i> meson. In <i>B</i>_{(<i><font size=-1>s</font></i>)} &#8594; <font size=-1>&pi;</font><i>K</i> and <i>KK</i>-decays, the effects of the strange quark mass were calculated. To this end, nonperturbative, process-independent quantities related to the light-cone distribution amplitudes have been computed in two-point sum rules. Using this values, it was found that the <i>m<font size=-1>_s</font></i> &#8594; 0 limit is not a very good approximation for the decay amplitudes, and that QCD sum rules successfully describe the amplitudes without relying on this limit

3D-Printed piezoelectric actuators

Usually smart piezoelectric actuators are driven far away from their resonances to avoid control and design efforts. Being in a sharp contrast to that we propose actuator designs, that consider the structural conformity of structurally integrated actuators. This strategy requires perfect impedance-matched actuators, whereas their transfer functions are matched to the structural system of interest. Consequently the actuator characteristics are not linear anymore. The main advantage of structurally conformed actuators is a perfect power transfer to the mechanical structures. But we have to innovate a paradigm shift: such low-energy concepts require a simultaneous design of all components from the very first beginning. Furthermore we found out, that such high-sophisticated actuators have extreme complex topologies, especially in three-dimensional cases. Additive manufacturing seems to be the most-promising fabrication method for impedance-matched actuators even against the background, that we have to develop a print technique for piezoelectric materials. In this presentation we will explain the concept of low-energy actuators that can be highly loaded, yielding in completely new actuator geometries. We will present 3D-printing techniques for piezoelectric materials and we will propose several new actuator types. Experimental results prove the performance of 3D-printed piezoelectric actuators

3D-Printed piezoelectric actuators

Usually smart piezoelectric actuators are driven far away from their resonances to avoid control and design efforts. Being in a sharp contrast to that we propose actuator designs, that consider the structural conformity of structurally integrated actuators. This strategy requires perfect impedance-matched actuators, whereas their transfer functions are matched to the structural system of interest. Consequently the actuator characteristics are not linear anymore. The main advantage of structurally conformed actuators is a perfect power transfer to the mechanical structures. But we have to innovate a paradigm shift: such low-energy concepts require a simultaneous design of all components from the very first beginning. Furthermore we found out, that such high-sophisticated actuators have extreme complex topologies, especially in three-dimensional cases. Additive manufacturing seems to be the most-promising fabrication method for impedance-matched actuators even against the background, that we have to develop a print technique for piezoelectric materials. In this presentation we will explain the concept of low-energy actuators that can be highly loaded, yielding in completely new actuator geometries. We will present 3D-printing techniques for piezoelectric materials and we will propose several new actuator types. Experimental results prove the performance of 3D-printed piezoelectric actuators

ETMR-05: Single-cell transcriptomics of ETMR reveals developmental cellular programs and tumor-pericyte communications in the microenvironment [Abstract]

BACKGROUND: Embryonal tumors with multilayered rosettes (ETMR) are pediatric brain tumors bearing a grim prognosis, despite intensive multimodal therapeutic approaches. Insights into cellular heterogeneity and cellular communication of tumor cells with cells of the tumor microenvironment (TME), by applying single-cell (sc) techniques, potentially identify mechanisms of therapy resistance and target-directed treatment approaches. MATERIAL AND METHODS: To explore ETMR cell diversity, we used single-cell RNA sequencing (scRNA-seq) in human (n=2) and murine ETMR (transgenic mode; n=4) samples, spatial transcriptomics, 2D and 3D cultures (including co-cultures with TME cells), multiplex immunohistochemistry and drug screens. RESULTS: ETMR microenvironment is composed of tumor and non-tumor cell types. The ETMR malignant compartment harbour cells representing distinct transcriptional metaprograms, (NSC-like, NProg-like and Neuroblast-like), mirroring embryonic neurogenic cell states and fuelled by neurogenic pathways (WNT, SHH, Hippo). The ETMR TME is composed of oligodendrocyte and neuronal progenitor cells, neuroblasts, microglia, and pericytes. Tumor-specific ligand-receptor interaction analysis showed enrichment of intercellular communication between NProg-like ETMR cells and pericytes (PC). Functional network analyses reveal ETMR-PC interactions related to stem-cell signalling and extracellular matrix (ECM) organization, involving factors of the WNT, BMP, and CxCl12 networks. Results from ETMR-PC co-culture and spatial transcriptomics pointed to a pivotal role of pericytes in keeping ETMR in a germinal neurogenic state, enriched in stem-cell signalling. Drug screening considering cellular heterogeneity and cellular communication suggested novel therapeutic approaches. CONCLUSION: ETMR demonstrated diversity in the microenvironment, with enrichment of cell-cell communications with pericytes, supporting stem-cell signalling and interfering in the organization of the tumor extracellular matrix. Targeting ETMR-PC interactions might bring new opportunities for target-directed therapy

Flavour SU(3) Symmetry in Charmless B Decays

QCD sum rules are used to estimate the flavour SU(3)-symmetry violation in two-body B decays to pions and kaons. In the factorizable amplitudes the SU(3)-violation manifests itself in the ratio of the decay constants f_K/f_pi and in the differences between the B->K, B_s->K and B->pi form factors. These effects are calculated from the QCD two-point and light-cone sum rules, respectively, in terms of the strange quark mass and the ratio of the strange and nonstrange quark-condensate densities. Importantly, QCD sum rules predict that SU(3) breaking in the heavy-to-light form factors can be substantial and does not vanish in the heavy-quark mass limit. Furthermore, we investigate the strange-quark mass dependence of nonfactorizable effects in the B->K pi decay amplitudes. Taking into account these effects we estimate the accuracy of several SU(3)-symmetry relations between charmless B-decay amplitudes.Comment: Two references added, version to be published in Phys.Rev.D, 21 pages, 12 postscript figure

Osmium isotope systematics of the Proterozoic and Phanerozoic ophiolitic chromitites : in situ ion probe analysis of primary Os-rich PGM

Author Posting. © Elsevier B.V., 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 245 (2006): 777-791, doi:10.1016/j.epsl.2006.03.021.In-situ 187Os/188Os ratios are determined on Os-rich platinum-group minerals in podiform chromitites both in the Proterozoic ophiolite, Eastern Desert, Egypt, and in the Phanerozoic Oman ophiolite. Because they have very low Re/Os, these primary minerals reflect the initial 187Os/188Os ratios of their parental magmas. The platinum-group minerals (PGM) in the central Eastern Desert chromitites exhibit sub-chondritic to chondritic 187Os/188Os ratios, 0.1226 on average, which is lower than the primitive upper mantle evolution trend of a comparable age. Those of the southern Eastern Desert chromitites have more radiogenic Os, with supra-chondritic 187Os/188Os ratio of about 0.1293 on average, which could be due to crustal contamination. The three chromitite types in the northern part of the Oman ophiolite are almost indistinguishable in terms of their 187Os/188Os ratios; they have overlapping values ranging from sub-chondritic to supra-chondritic ratios. The PGE-rich, mantle chromitite samples have a wide range of 187Os/188Os ratio from 0.1230 up to 0.1376, with an average of 0.1299. The values of the PGE-poor mantle chromitites overlap in their 187Os/188Os ratios with PGE-rich chromites, but are less variable and have a significantly higher average ratio. The Moho transition zone (MTZ) chromitites are highly variable in the 187Os/188Os ratio, ranging from 0.1208 up to 0.1459. The wide range of 187Os/188Os ratios, from 0.1192 to 0.1459, in platinum-group minerals in Egyptian and Oman ophiolites can be attributed to the diversity of origin of their podiform chromitites. The Os-isotope data combined with spinel chemistry indicate that the way involved in podiform chromitite formation was not substantially different between the Proterozoic ophiolite of Egypt and the Phanerozoic ophiolite in northern Oman. The Os-isotope compositions of the mantle chromitites in the Proterozoic ophiolite of Egypt clearly suggest crustal contamination. The heterogeneity of 187Os/188Os ratios combined with the spinel chemistry and high PGE contents of the PGE-rich chromitite in the Oman ophiolite may give reliable evidence for high degree partial melting at a supra-subduction zone setting. Crustal contamination from the subducted slab, and assimilation of previously altered, lower crustal gabbro, may have contributed to the high Cr# spinel and radiogenic Os characteristics in chromitite formed in the mantle section and along the Moho transition zone, respectively.Kelemen and Hanghøj were supported in this project by US National Science Foundation grants OCE-9819666 and OCE-0118572

Resolving Structure and Mechanical Properties at the Nanoscale of Viruses with Frequency Modulation Atomic Force Microscopy

Structural Biology (SB) techniques are particularly successful in solving virus structures. Taking advantage of the symmetries, a heavy averaging on the data of a large number of specimens, results in an accurate determination of the structure of the sample. However, these techniques do not provide true single molecule information of viruses in physiological conditions. To answer many fundamental questions about the quickly expanding physical virology it is important to develop techniques with the capability to reach nanometer scale resolution on both structure and physical properties of individual molecules in physiological conditions. Atomic force microscopy (AFM) fulfills these requirements providing images of individual virus particles under physiological conditions, along with the characterization of a variety of properties including local adhesion and elasticity. Using conventional AFM modes is easy to obtain molecular resolved images on flat samples, such as the purple membrane, or large viruses as the Giant Mimivirus. On the contrary, small virus particles (25–50 nm) cannot be easily imaged. In this work we present Frequency Modulation atomic force microscopy (FM-AFM) working in physiological conditions as an accurate and powerful technique to study virus particles. Our interpretation of the so called “dissipation channel” in terms of mechanical properties allows us to provide maps where the local stiffness of the virus particles are resolved with nanometer resolution. FM-AFM can be considered as a non invasive technique since, as we demonstrate in our experiments, we are able to sense forces down to 20 pN. The methodology reported here is of general interest since it can be applied to a large number of biological samples. In particular, the importance of mechanical interactions is a hot topic in different aspects of biotechnology ranging from protein folding to stem cells differentiation where conventional AFM modes are already being used

Crystal structure of rhodopsin bound to arrestin by femtosecond X-ray laser.

G-protein-coupled receptors (GPCRs) signal primarily through G proteins or arrestins. Arrestin binding to GPCRs blocks G protein interaction and redirects signalling to numerous G-protein-independent pathways. Here we report the crystal structure of a constitutively active form of human rhodopsin bound to a pre-activated form of the mouse visual arrestin, determined by serial femtosecond X-ray laser crystallography. Together with extensive biochemical and mutagenesis data, the structure reveals an overall architecture of the rhodopsin-arrestin assembly in which rhodopsin uses distinct structural elements, including transmembrane helix 7 and helix 8, to recruit arrestin. Correspondingly, arrestin adopts the pre-activated conformation, with a ∼20° rotation between the amino and carboxy domains, which opens up a cleft in arrestin to accommodate a short helix formed by the second intracellular loop of rhodopsin. This structure provides a basis for understanding GPCR-mediated arrestin-biased signalling and demonstrates the power of X-ray lasers for advancing the frontiers of structural biology

Needs, trends, and advances in scintillators for radiographic imaging and tomography

Scintillators are important materials for radiographic imaging and tomography (RadIT), when ionizing radiations are used to reveal internal structures of materials. Since its invention by R\"ontgen, RadIT now come in many modalities such as absorption-based X-ray radiography, phase contrast X-ray imaging, coherent X-ray diffractive imaging, high-energy X- and $\gamma-$ray radiography at above 1 MeV, X-ray computed tomography (CT), proton imaging and tomography (IT), neutron IT, positron emission tomography (PET), high-energy electron radiography, muon tomography, etc. Spatial, temporal resolution, sensitivity, and radiation hardness, among others, are common metrics for RadIT performance, which are enabled by, in addition to scintillators, advances in high-luminosity accelerators and high-power lasers, photodetectors especially CMOS pixelated sensor arrays, and lately data science. Medical imaging, nondestructive testing, nuclear safety and safeguards are traditional RadIT applications. Examples of growing or emerging applications include space, additive manufacturing, machine vision, and virtual reality or `metaverse'. Scintillator metrics such as light yield and decay time are correlated to RadIT metrics. More than 160 kinds of scintillators and applications are presented during the SCINT22 conference. New trends include inorganic and organic scintillator heterostructures, liquid phase synthesis of perovskites and $\mu$m-thick films, use of multiphysics models and data science to guide scintillator development, structural innovations such as photonic crystals, nanoscintillators enhanced by the Purcell effect, novel scintillator fibers, and multilayer configurations. Opportunities exist through optimization of RadIT with reduced radiation dose, data-driven measurements, photon/particle counting and tracking methods supplementing time-integrated measurements, and multimodal RadIT.Comment: 45 pages, 43 Figures, SCINT22 conference overvie