3,207 research outputs found
The diquark model: New Physics effects for charm and kaon decays
Motivated by diquark exchange, we construct a class of extensions of the
standard model. These models can generate large CP conserving and CP violating
contributions to the doubly Cabbibo suppressed decays D^0\to K^+\pi^- without
affecting D^0-\overline{D^0} mixing, contrary to what is usually believed in
the literature. We find an interesting specific realization of these models,
which has the LR chiral structure and can induce novel density \times density
operators. It is new for non-leptonic kaon decays, and particularly, may
provide a possible solution to the \Delta I=1/2 rule and direct CP violation,
without inducing large flavour changing neutral currents.Comment: LaTeX, 12 pages and 2 eps figures. Minor changes, paper accepted by
Physics Letters
Solute carriers involved in energy transfer of mitochondria form a homologous protein family
AbstractThe sequences of three mitochondrial carriers involved in energy transfer, the ADP/ATP carrier, phosphate carrier and uncoupling carrier, are analyzed. Similarly to what has been previously reported for the ADP/ATP carrier and the uncoupling protein, now also the phosphate carrier is found to have a tripartite structure comprising three similar repeats of approx. 100 residues each. The three sequences show a fair overall homology with each other. More significant homologies are found by comparing the repeats within and between the carriers in a scheme where the sequences are spliced into repeats, which are arranged for maximum homology by allowing possible insertions or deletions. A striking conservation of critical residues, glycine, proline, of charged and of aromatic residues is found throughout all nine repeats. This is indicative of a similar structural principle in the repeats. Hydropathy profiles of the three proteins and a search for amphipathic α-spans reveal six membrane-spanning segments for each carrier, providing further support for the basic structural identity of the repeats. The proposed folding pattern of the carriers in the membrane is exemplified with the phosphate carrier. A possible tertiary arrangement of the repeats and the membranespanning helices is shown. The emergence of a mitochondrial carrier family by triplication and by divergent evolution from a common gene of about 100 residues is discussed
A Simple Approach to Distinguish Classic and Formaldehyde-Free Tannin Based Rigid Foams by ATR FT-IR
Tannin based rigid foams (TBRFs) have been produced with formaldehyde since 1994. Only recently several methods have been
developed in order to produce these foams without using formaldehyde. TBRFs with and without formaldehyde are visually
indistinguishable; therefore a method for determining the differences between these foams had to be found. The attenuated total
reflectance infrared spectroscopy (ATR FT-IR) investigation of the TBRFs presented in this paper allowed discrimination between
the formaldehyde-containing (classic) and formaldehyde-free TBRFs.Thespectra of the formaldehyde-free TBRFs, indeed, present
decreased band intensity related to the C–O stretching vibration of (i) the methylol groups and (ii) the furanic rings. This evidence
served to prove the chemical difference between the two TBRFs and explained the slightly higher mechanical properties measured
for the classic TBRFs
Cell Shape and Forces in Elastic and Structured Environments: From Single Cells to Organoids
With the advent of mechanobiology, cell shape and forces have emerged as essential elements of cell behavior and fate, in addition to biochemical factors such as growth factors. Cell shape and forces are intrinsically linked to the physical properties of the environment. Extracellular stiffness guides migration of single cells and collectives as well as differentiation and developmental processes. In confined environments, cell division patterns are altered, cell death or extrusion might be initiated, and other modes of cell migration become possible. Tools from materials science such as adhesive micropatterning of soft elastic substrates or direct laser writing of 3D scaffolds have been established to control and quantify cell shape and forces in structured environments. Herein, a review is given on recent experimental and modeling advances in this field, which currently moves from single cells to cell collectives and tissue. A very exciting avenue is the combination of organoids with structured environments, because this will allow one to achieve organotypic function in a controlled setting well suited for long-term and high-throughput culture
Impact of differentiated macrophage-like cells on the transcriptional toxicity profile of cuo nanoparticles in co-cultured lung epithelial cells
To mimic more realistic lung tissue conditions, co-cultures of epithelial and immune cells are one comparatively easy-to-use option. To reveal the impact of immune cells on the mode of action (MoA) of CuO nanoparticles (NP) on epithelial cells, A549 cells as a model for epithelial cells have been cultured with or without differentiated THP-1 cells, as a model for macrophages. After 24 h of submerged incubation, cytotoxicity and transcriptional toxicity profiles were obtained and compared between the cell culture systems. Dose-dependent cytotoxicity was apparent starting from 8.0 µg/cm CuO NP. With regard to gene expression profiles, no differences between the cell models were observed concerning metal homeostasis, oxidative stress, and DNA damage, confirming the known MoA of CuO NP, i.e., endocytotic particle uptake, intracellular particle dissolution within lysosomes with subsequent metal ion deliberation, increased oxidative stress, and genotoxicity. However, applying a co-culture of epithelial and macrophage-like cells, CuO NP additionally provoked a pro-inflammatory response involving NLRP3 inflammasome and pro-inflammatory transcription factor activation. This study demonstrates that the application of this easy-to-use advanced in vitro model is able to extend the detection of cellular effects provoked by nanomaterials by an immunological response and emphasizes the use of such models to address a more comprehensive MoA
Phonon-pump XUV-photoemission-probe in graphene: evidence for non-adiabatic heating of Dirac carriers by lattice deformation
We modulate the atomic structure of bilayer graphene by driving its lattice
at resonance with the in-plane E1u lattice vibration at 6.3um. Using time- and
angle-resolved photoemission spectroscopy (tr-ARPES) with extreme ultra-violet
(XUV) pulses, we measure the response of the Dirac electrons near the K-point.
We observe that lattice modulation causes anomalous carrier dynamics, with the
Dirac electrons reaching lower peak temperatures and relaxing at faster rate
compared to when the excitation is applied away from the phonon resonance or in
monolayer samples. Frozen phonon calculations predict dramatic band structure
changes when the E1u vibration is driven, which we use to explain the anomalous
dynamics observed in the experiment.Comment: 16 pages, 8 figure
Assessment of a Serial Cooling Concept for HTPEM Fuel Cell Systems for Aviation Applications
The thermal management subsystem is a significant mass contributor to a fuel cell system. In this paper a serial cooling concept for high temperature proton exchange membrane fuel cell systems is introduced and analysed. For a liquid cooling system, the coolant mass has a high share of the overall thermal management system mass. A cooling concept where multiple fuel cell units are put in serial from a coolant flow perspective allows for an increase in total temperature difference over the coolant and therefore significant reduction of coolant mass. As the temperature difference over each fuel cell unit is kept constant at 10 K, the different fuel cell units operate at different temperatures. This results in slightly less efficient and heavier fuel cell units. Furthermore, the increased overall temperature difference of the coolant also has an impact on the heat exchanger design. These trade-offs are evaluated for a different number of fuel cell units in serial and different design parameter combinations. The studies indicate that the proposed serial cooling concept offers significant weight savings or efficiency improvements, which can be traded against each other
Melting and Equilibrium Shape of Icosahedral Gold Nanoparticles
We use molecular dynamics simulations to study the melting of gold
icosahedral clusters of a few thousand atoms. We pay particular attention to
the behavior of surface atoms, and to the equilibrium shape of the cluster. We
find that although the surface of the cluster remains ordered up to the melting
T_m, the increasing mobility of vertex and edge atoms significantly soften the
surface structure, leading to inter- and intra-layer diffusion, and shrinking
of the average facet size, so that the average shape of the cluster is nearly
spherical at melting.Comment: 4 pages, 4 figures - replaced with final published versio
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