Three-dimensional charge transport mapping by two-photon absorption edge transient-current technique in synthetic single-crystalline diamond

We demonstrate the application of two-photon absorption transient current technique to wide bandgap semiconductors. We utilize it to probe charge transport properties of single-crystal Chemical Vapor Deposition (scCVD) diamond. The charge carriers, inside the scCVD diamond sample, are excited by a femtosecond laser through simultaneous absorption of two photons. Due to the nature of two-photon absorption, the generation of charge carriers is confined in space (3-D) around the focal point of the laser. Such localized charge injection allows to probe the charge transport properties of the semiconductor bulk with a fine-grained 3-D resolution. Exploiting spatial confinement of the generated charge, the electrical field of the diamond bulk was mapped at different depths and compared to an X-ray diffraction topograph of the sample. Measurements utilizing this method provide a unique way of exploring spatial variations of charge transport properties in transparent wide-bandgap semiconductors.Comment: This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Applied Physics Letters and may be found at https://doi.org/10.1063/1.509085

Signaling from the plasma-membrane localized plant immune receptor RPM1 requires self-association of the full-length protein

Pathogen recognition first occurs at the plasma membrane, where receptor-like kinases perceive pathogen-derived molecules and initiate immune responses. To abrogate this immune response, pathogens evolved effector proteins that act as virulence factors, often following delivery to the host cell. Plants evolved intracellular receptors, known as NOD-like receptors (NLRs), to detect effectors, thereby ensuring activation of effector-triggered immunity. However, despite their importance in immunity, the molecular mechanisms underlying effector recognition and subsequent immune activation by membrane-localized NLRs remain to be fully elucidated. Our analyses reveal the importance of and need for self-association and the coordinated interplay of specific domains and conserved residues for NLR activity. This could provide strategies for crop improvement, contributing to effective, environmentally friendly, and sustainable solutions for future agriculture

TIR-only protein RBA1 recognizes a pathogen effector to regulate cell death in Arabidopsis

Multicellular organisms must have complex immune systems to detect and defeat pathogens. Plants rely on nucleotide binding site leucine rich repeat (NLR) intracellular receptors to detect pathogens. For hundreds of years, plant breeders have selected for disease-resistance traits derived from NLR genes. Despite the molecular cloning of the first NLRs more than 20 y ago, we still do not understand how these sensors function at a mechanistic level. Here, we identified a truncated NLR protein that activates cell death in response to a specific pathogen effector. Understanding how truncated NLRs function will provide a better mechanistic understanding of the plant immune system and an expanded toolkit with which to engineer disease resistance rationally in crops

Measurements of branching fraction ratios and CP-asymmetries in suppressed B^- -> D(-> K^+ pi^-)K^- and B^- -> D(-> K^+ pi^-)pi^- decays

We report the first reconstruction in hadron collisions of the suppressed decays B^- -> D(-> K^+ pi^-)K^- and B^- -> D(-> K^+ pi^-)pi^-, sensitive to the CKM phase gamma, using data from 7 fb^-1 of integrated luminosity collected by the CDF II detector at the Tevatron collider. We reconstruct a signal for the B^- -> D(-> K^+ pi^-)K^- suppressed mode with a significance of 3.2 standard deviations, and measure the ratios of the suppressed to favored branching fractions R(K) = [22.0 \pm 8.6(stat)\pm 2.6(syst)]\times 10^-3, R^+(K) = [42.6\pm 13.7(stat)\pm 2.8(syst)]\times 10^-3, R^-(K)= [3.8\pm 10.3(stat)\pm 2.7(syst]\times 10^-3, as well as the direct CP-violating asymmetry A(K) = -0.82\pm 0.44(stat)\pm 0.09(syst) of this mode. Corresponding quantities for B^- -> D(-> K^+ pi^-)pi^- decay are also reported.Comment: 8 pages, 1 figure, accepted by Phys.Rev.D Rapid Communications for Publicatio

Observation of Exclusive Gamma Gamma Production in p pbar Collisions at sqrt{s}=1.96 TeV

We have observed exclusive \gamma\gamma production in proton-antiproton collisions at \sqrt{s}=1.96 TeV, using data from 1.11 \pm 0.07 fb^{-1} integrated luminosity taken by the Run II Collider Detector at Fermilab. We selected events with two electromagnetic showers, each with transverse energy E_T > 2.5 GeV and pseudorapidity |\eta| < 1.0, with no other particles detected in -7.4 < \eta < +7.4. The two showers have similar E_T and azimuthal angle separation \Delta\phi \sim \pi; 34 events have two charged particle tracks, consistent with the QED process p \bar{p} to p + e^+e^- + \bar{p} by two-photon exchange, while 43 events have no charged tracks. The number of these events that are exclusive \pi^0\pi^0 is consistent with zero and is < 15 at 95% C.L. The cross section for p\bar{p} to p+\gamma\gamma+\bar{p} with |\eta(\gamma)| < 1.0 and E_T(\gamma) > 2.5$ GeV is 2.48^{+0.40}_{-0.35}(stat)^{+0.40}_{-0.51}(syst) pb.Comment: 7 pages, 4 figure