969 research outputs found
G Electronics and Data Acquisition (Forward-Angle Measurements)
The G parity-violation experiment at Jefferson Lab (Newport News, VA) is
designed to determine the contribution of strange/anti-strange quark pairs to
the intrinsic properties of the proton. In the forward-angle part of the
experiment, the asymmetry in the cross section was measured for
elastic scattering by counting the recoil protons corresponding to the two
beam-helicity states. Due to the high accuracy required on the asymmetry, the
G experiment was based on a custom experimental setup with its own
associated electronics and data acquisition (DAQ) system. Highly specialized
time-encoding electronics provided time-of-flight spectra for each detector for
each helicity state. More conventional electronics was used for monitoring
(mainly FastBus). The time-encoding electronics and the DAQ system have been
designed to handle events at a mean rate of 2 MHz per detector with low
deadtime and to minimize helicity-correlated systematic errors. In this paper,
we outline the general architecture and the main features of the electronics
and the DAQ system dedicated to G forward-angle measurements.Comment: 35 pages. 17 figures. This article is to be submitted to NIM section
A. It has been written with Latex using \documentclass{elsart}. Nuclear
Instruments and Methods in Physics Research Section A: Accelerators,
Spectrometers, Detectors and Associated Equipment In Press (2007
Comparison of Forward and Backward \u3ci\u3epp\u3c/i\u3e Pair Knockout in \u3csup\u3e3\u3c/sup\u3eHe(e,e\u27pp)n
Measuring nucleon-nucleon short range correlations (SRCs) has been a goal of the nuclear physics community for many years. They are an important part of the nuclear wave function, accounting for almost all of the high-momentum strength. They are closely related to the EMC effect. While their overall probability has been measured, measuring their momentum distributions is more difficult. In order to determine the best configuration for studying SRC momentum distributions, we measured the 3He(e,e\u27pp)n reaction, looking at events with high-momentum protons (pp \u3e 0.35 GeV/c) and a low-momentum neutron (pn \u3c 0.2 GeV/c). We examined two angular configurations: either both protons emitted forward or one proton emitted forward and one backward (with respect to the momentum transfer, q). The measured relative momentum distribution of the events with one forward and one backward proton was much closer to the calculated initial-state pp relative momentum distribution, indicating that this is the preferred configuration for measuring SRC. ©2012 American Physical Societ
Single and Double Spin Asymmetries for Deeply Virtual Compton Scattering Measured with CLAS and a Longitudinally Polarized Proton Target
Single-beam, single-target, and double spin asymmetries for hard exclusive electroproduction of a photon on the proton âeâp~ â e\u27p\u27Îł are presented. The data were taken at Jefferson Lab using the CEBAF large acceptance spectrometer and a longitudinally polarized 14NH3 target. The three asymmetries were measured in 165 four-dimensional kinematic bins, covering the widest kinematic range ever explored simultaneously for beam and target-polarization observables in the valence quark region. The kinematic dependences of the obtained asymmetries are discussed and compared to the predictions of models of generalized parton distributions. The measurement of three DVCS spin observables at the same kinematic points allows a quasi-model-independent extraction of the imaginary parts of the H and ~H Compton form factors, which give insight into the electric and axial charge distributions of valence quarks in the proton
Relationship between Fusobacterium nucleatum, inflammatory mediators and microRNAs in colorectal carcinogenesis
AIM To examine the effect of Fusobacterium nucleatum (F. nucleatum) on the microenvironment of colonic neoplasms and the expression of inflammatory mediators and microRNAs (miRNAs). METHODS Levels of F. nucleatum DNA, cytokine gene mRNA (TLR2, TLR4, NFKB1, TNF, IL1B, IL6 and IL8), and potentially interacting miRNAs (miR-21-3p, miR-22-3p, miR-28-5p, miR-34a-5p, miR-135b-5p) were measured by quantitative polymerase chain reaction (qPCR) TaqManÂź assays in DNA and/or RNA extracted from the disease and adjacent normal fresh tissues of 27 colorectal adenoma (CRA) and 43 colorectal cancer (CRC) patients. KRAS mutations were detected by direct sequencing and microsatellite instability (MSI) status by multiplex PCR. Cytoscape v3.1.1 was used to construct the postulated miRNA:mRNA interaction network. RESULTS Overabundance of F. nucleatum in neoplastic tissue compared to matched normal tissue was detected in CRA (51.8%) and more markedly in CRC (72.1%). We observed significantly greater expression of TLR4, IL1B, IL8, and miR-135b in CRA lesions and TLR2, IL1B, IL6, IL8, miR-34a and miR-135b in CRC tumours compared to their respective normal tissues. Only two transcripts for miR-22 and miR-28 were exclusively downregulated in CRC tumour samples. The mRNA expression of IL1B, IL6, IL8 and miR-22 was positively correlated with F. nucleatum quantification in CRC tumours. The mRNA expression of miR-135b and TNF was inversely correlated. The miRNA:mRNA interaction network suggested that the upregulation of miR-34a in CRC proceeds via a TLR2/TLR4-dependent response to F. nucleatum. Finally, KRAS mutations were more frequently observed in CRC samples infected with F. nucleatum and were associated with greater expression of miR-21 in CRA, while IL8 was upregulated in MSI-high CRC. CONCLUSION Our findings indicate that F. nucleatum is a risk factor for CRC by increasing the expression of inflammatory mediators through a possible miRNA-mediated activation of TLR2/TLR4We thank Lucas Trevizani Rasmussen for kindly donating
some miRNA probes. We are grateful to the SĂŁo Paulo
Research Foundation (FAPESP, NO. 2015/21464-0) for
the support for English revision, the Coordination for the
Improvement of Higher Education Personnel (CAPES)
for the doctoral scholarship, and the National Council for
Scientific and Technological Development (CNPq, NO.
310120/2015-2) for the productivity research scholarship.info:eu-repo/semantics/publishedVersio
Marker-Assisted Pyramiding of Blast-Resistance Genes in a japonica Elite Rice Cultivar through Forward and Background Selection
Rice blast, caused by Pyricularia oryzae, is one of the main rice diseases worldwide. The
pyramiding of blast-resistance (Pi) genes, coupled to Marker-Assisted BackCrossing (MABC), provides
broad-spectrum and potentially durable resistance while limiting the donor genome in the
background of an elite cultivar. In this work, MABC coupled to foreground and background selections
based on KASP marker assays has been applied to introgress four Pi genes (Piz, Pib, Pita, and
Pik) in a renowned japonica Italian rice variety, highly susceptible to blast. Molecular analyses on the
backcross (BC) lines highlighted the presence of an additional blast-resistance gene, the Pita-linked
Pita2/Ptr gene, therefore increasing the number of blast-resistance introgressed genes to five. The
recurrent genome was recovered up to 95.65%. Several lines carrying four (including Pita2) Pi genes
with high recovery percentage levels were also obtained. Phenotypic evaluations confirmed the
effectiveness of the pyramided lines against multivirulent strains, which also had broad patterns
of resistance in comparison to those expected based on the pyramided Pi genes. The developed
blast-resistant japonica lines represent useful donors of multiple blast-resistance genes for future
rice-breeding programs related to the japonica group
The e p -> e' p eta reaction at and above the S11(1535) baryon resonance
New cross sections for the reaction e p -> ep eta are reported for total
center of mass energy W = 1.5--1.86 GeV and invariant momentum transfer Q^2 =
0.25--1.5 GeV^2. This large kinematic range allows extraction of important new
information about response functions, photocouplings, and eta N coupling
strengths of baryon resonances. Expanded W coverage shows sharp structure at W
\~ 1.7 GeV; this is shown to come from interference between S and P waves and
can be interpreted in terms of known resonances. Improved values are derived
for the photon coupling amplitude for the S11(1535) resonance.Comment: 11 pages, RevTeX, 5 figures, submitted to Phys. Rev. Let
Photoproduction of phi(1020) mesons on the proton at large momentum transfer
The cross section for meson photoproduction on the proton has been
measured for the first time up to a four-momentum transfer -t = 4 GeV^2, using
the CLAS detector at the Thomas Jefferson National Accelerator Facility. At low
four-momentum transfer, the differential cross section is well described by
Pomeron exchange. At large four-momentum transfer, above -t = 1.8 GeV^2, the
data support a model where the Pomeron is resolved into its simplest component,
two gluons, which may couple to any quark in the proton and in the .Comment: 5 pages; 7 figure
Q^2 Dependence of the S_{11}(1535) Photocoupling and Evidence for a P-wave resonance in eta electroproduction
New cross sections for the reaction are reported for total
center of mass energy =1.5--2.3 GeV and invariant squared momentum transfer
=0.13--3.3 GeV. This large kinematic range allows extraction of new
information about response functions, photocouplings, and coupling
strengths of baryon resonances. A sharp structure is seen at 1.7 GeV.
The shape of the differential cross section is indicative of the presence of a
-wave resonance that persists to high . Improved values are derived for
the photon coupling amplitude for the (1535) resonance. The new data
greatly expands the range covered and an interpretation of all data with
a consistent parameterization is provided.Comment: 31 pages, 9 figure
Measurement of Inclusive Spin Structure Functions of the Deuteron
We report the results of a new measurement of spin structure functions of the
deuteron in the region of moderate momentum transfer ( = 0.27 -- 1.3
(GeV/c)) and final hadronic state mass in the nucleon resonance region (
= 1.08 -- 2.0 GeV). We scattered a 2.5 GeV polarized continuous electron beam
at Jefferson Lab off a dynamically polarized cryogenic solid state target
(ND) and detected the scattered electrons with the CEBAF Large
Acceptance Spectrometer (CLAS). From our data, we extract the longitudinal
double spin asymmetry and the spin structure function . Our
data are generally in reasonable agreement with existing data from SLAC where
they overlap, and they represent a substantial improvement in statistical
precision. We compare our results with expectations for resonance asymmetries
and extrapolated deep inelastic scaling results. Finally, we evaluate the first
moment of the structure function and study its approach to both the
deep inelastic limit at large and to the Gerasimov-Drell-Hearn sum rule
at the real photon limit (). We find that the first moment varies
rapidly in the range of our experiment and crosses zero at between
0.5 and 0.8 (GeV/c), indicating the importance of the resonance at
these momentum transfers.Comment: 13 pages, 8 figures, ReVTeX 4, final version as accepted by Phys.
Rev.
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