Construction and Expected Performance of the Hadron Blind Detector for the PHENIX Experiment at RHIC

A new Hadron Blind Detector (HBD) for electron identification in high density hadron environment has been installed in the PHENIX detector at RHIC in the fall of 2006. The HBD will identify low momentum electron-positron pairs to reduce the combinatorial background in the $e^{+}e^{-}$ mass spectrum, mainly in the low-mass region below 1 GeV/c$^{2}$. The HBD is a windowless proximity-focusing Cherenkov detector with a radiator length of 50 cm, a CsI photocathode and three layers of Gas Electron Multipliers (GEM). The HBD uses pure CF$_{4}$ as a radiator and a detector gas. Construction details and the expected performance of the detector are described.Comment: QM2006 proceedings, 4 pages 3 figure

Design, Construction, Operation and Performance of a Hadron Blind Detector for the PHENIX Experiment

A Hadron Blind Detector (HBD) has been developed, constructed and successfully operated within the PHENIX detector at RHIC. The HBD is a Cherenkov detector operated with pure CF4. It has a 50 cm long radiator directly coupled in a window- less configuration to a readout element consisting of a triple GEM stack, with a CsI photocathode evaporated on the top surface of the top GEM and pad readout at the bottom of the stack. This paper gives a comprehensive account of the construction, operation and in-beam performance of the detector.Comment: 51 pages, 39 Figures, submitted to Nuclear Instruments and Method

Periodic and Quasiperiodic Motion of an Elongated Microswimmer in Poiseuille Flow

We study the dynamics of a prolate spheroidal microswimmer in Poiseuille flow for different flow geometries. When moving between two parallel plates or in a cylindrical microchannel, the swimmer performs either periodic swinging or periodic tumbling motion. Although the trajectories of spherical and elongated swimmers are qualitatively similar, the swinging and tumbling frequency strongly depends on the aspect ratio of the swimmer. In channels with reduced symmetry the swimmers perform quasiperiodic motion which we demonstrate explicitely for swimming in a channel with elliptical cross section

Allergen-specific IgG+ memory B cells are temporally linked to IgE memory responses

BACKGROUND: Immunoglobulin E (IgE) are least abundant, tightly regulated and IgE producing B cells are rare. The cellular origin and evolution of IgE responses are poorly understood. OBJECTIVE: To investigate the cellular and clonal origin of IgE memory responses following mucosal allergen exposure by sublingual immunotherapy (SLIT). METHODS: In a randomized double-blind, placebo-controlled, time-course SLIT study, peripheral blood mononuclear cells (PBMCs) and nasal biopsies were collected from forty adults with seasonal allergic rhinitis at baseline, 4, 8, 16, 28 and 52 weeks. RNA was extracted from PBMCs, sorted B cells and nasal biopsies for VH repertoire sequencing. Moreover, monoclonal antibodies were derived from single B cell transcriptomes. RESULTS: Combining VH repertoire sequencing and single cell transcriptomics yielded direct evidence of a parallel boost of two clonally and functionally related B cell subsets of short-lived IgE+ plasmablasts and IgG+ memory B cells (termed IgGE). Mucosal grass pollen allergen exposure by SLIT resulted in highly diverse IgE and IgGE repertoires. These were extensively mutated and appeared relative stable as per heavy chain isotype, somatic hypermutations and clonal composition. Single IgGE + memory B cell and IgE+ pre-plasmablast transcriptomes encoded antibodies that were specific for major grass pollen allergens and were able to elicit basophil activation at very low allergen concentrations. CONCLUSION: For the first time, we have shown that upon mucosal allergen exposure, human IgE memory resides in allergen-specific IgG+ memory B cells. These rapidly switch isotype and expand into short-lived IgE+ plasmablasts and serve as a potential target for therapeutic intervention