559 research outputs found
Capicua deficiency induces autoimmunity and promotes follicular helper T cell differentiation via derepression of ETV5
High-affinity antibody production through the germinal centre (GC) response is a pivotal process in adaptive immunity. Abnormal development of follicular helper T (T(FH)) cells can induce the GC response to self-antigens, subsequently leading to autoimmunity. Here we show the transcriptional repressor Capicua/CIC maintains peripheral immune tolerance by suppressing aberrant activation of adaptive immunity. CIC deficiency induces excessive development of T(FH) cells and GC responses in a T-cell-intrinsic manner. ETV5 expression is derepressed in Cic null T(FH) cells and knockdown of Etv5 suppresses the enhanced T(FH) cell differentiation in Cic-deficient CD4+ T cells, suggesting that Etv5 is a critical CIC target gene in T(FH) cell differentiation. Furthermore, we identify Maf as a downstream target of the CIC-ETV5 axis in this process. These data demonstrate that CIC maintains T-cell homeostasis and negatively regulates T(FH) cell development and autoimmunity. ? The Author(s) 2017.117Nsciescopu
Kinetic modeling of H-mode pedestal with effects from anomalous transport and MHD stability
Scaling of the H-mode pedestal in tokamak plasmas with type I ELMs and dependence of the pedestal properties and the resulting divertor head load width with the plasma elongation and plasma current are investigated using the kinetic neoclassical XGC0 code for DIII-D and Alcator C-Mod tokamaks. The simulations in this study use realistic diverted geometry and are self-consistent with the inclusion of kinetic neoclassical physics, theory-based anomalous transport models with the E×B flow shearing effects, as well as an MHD ELM triggering criterion. Scalings for the pedestal width and height are developed as a function of the scanned plasma parameters. The nonlinear interplay between anomalous and neoclassical effects motivates the development of a self-consistent simulation model that includes neoclassical and anomalous effects simultaneously. It is demonstrated that the divertor heat load width depend on the plasma currents. In the development of this dependence, effects of neutral collisions and anomalous transport are taken into account. Changes in the neoclassical divertor heat load fluxes associated with the introduction of the neutral collision and anomalous transport effects are described.За допомогою кінетичного неокласичного коду XGC0 для розрядів в токамаках DIII-D і Alcator C-Mod досліджено скейлінг п’єдесталу в плазмі, що перебуває в режимі поліпшеного утримання, з прикордонними локалізованими модами (ПЛМ) першого типу, властивості п’єдесталу і потоку тепла на дивертор в залежності від витягнутості плазми та струму плазми. У розрахунках використовуються: реалістична геометрія дивертора, кінетична модель для неокласичних ефектів, модель аномального транспорту, яка враховує ефекти шира (ExB)-потоків, і умови збудження ПЛМ-нестійкостей. У результаті розрахунків отримані скейлінгі для ширини і висоти п’єдесталу як функції параметрів плазми. Нелінійна взаємодія неокласичних ефектів і ефектів, пов'язаних з аномальним транспортом, є мотивацією для розробки самоузгодженої чисельної моделі, яка одночасно включає ефекти аномального і неокласичного транспорту. Показано, що потоки тепла на дивертор залежать від плазмових струмів. Також представлено результати дослідження залежності напівширини профілів тепла на дивертор від ефектів, пов'язаних з аномальним транспортом і зіткненнями з нейтральними частинками.С помощью кинетического неоклассического кода XGC0 для разрядов в токамаках DIII-D и Alcator C-Mod исследованы скэйлинг пьедестала в плазме, находящейся в режиме улучшенного удержания, с приграничными локализованными модами (ПЛМ) первого типа, и зависимость свойств пьедестала и потока тепла на дивертор от вытянутости плазмы и тока плазмы. В расчетах используются: реалистичная геометрия дивертора, кинетическая модель для неоклассических эффектов, модель аномального транспорта, которая учитывает эффекты шира (ExB)-потоков, и условия возбуждения ПЛМ-неустойчивостей. В результате расчетов получены скэйлинги для ширины и высоты пьедестала как функции параметров плазмы. Нелинейное взаимодействие неоклассических эффектов и эффектов, связанных с аномальным транспортом, является мотивацией разработки самосогласованной численной модели, которая одновременно включает эффекты аномального и неоклассического транспорта. Показано, что потоки тепла на дивертор зависят от плазменных токов. Также представлены результаты исследования зависимости полуширины профилей тепла на дивертор от эффектов, связанных с аномальным транспортом и столкновениями с нейтральными частицами
A Study of Cosmic Ray Secondaries Induced by the Mir Space Station Using AMS-01
The Alpha Magnetic Spectrometer (AMS-02) is a high energy particle physics
experiment that will study cosmic rays in the to range and will be installed on the International Space Station
(ISS) for at least 3 years. A first version of AMS-02, AMS-01, flew aboard the
space shuttle \emph{Discovery} from June 2 to June 12, 1998, and collected
cosmic ray triggers. Part of the \emph{Mir} space station was within the
AMS-01 field of view during the four day \emph{Mir} docking phase of this
flight. We have reconstructed an image of this part of the \emph{Mir} space
station using secondary and emissions from primary cosmic rays
interacting with \emph{Mir}. This is the first time this reconstruction was
performed in AMS-01, and it is important for understanding potential
backgrounds during the 3 year AMS-02 mission.Comment: To be submitted to NIM B Added material requested by referee. Minor
stylistic and grammer change
Protons in near earth orbit
The proton spectrum in the kinetic energy range 0.1 to 200 GeV was measured
by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at
an altitude of 380 km. Above the geomagnetic cutoff the observed spectrum is
parameterized by a power law. Below the geomagnetic cutoff a substantial second
spectrum was observed concentrated at equatorial latitudes with a flux ~ 70
m^-2 sec^-1 sr^-1. Most of these second spectrum protons follow a complicated
trajectory and originate from a restricted geographic region.Comment: 19 pages, Latex, 7 .eps figure
Search for antihelium in cosmic rays
The Alpha Magnetic Spectrometer (AMS) was flown on the space shuttle
Discovery during flight STS-91 in a 51.7 degree orbit at altitudes between 320
and 390 km. A total of 2.86 * 10^6 helium nuclei were observed in the rigidity
range 1 to 140 GV. No antihelium nuclei were detected at any rigidity. An upper
limit on the flux ratio of antihelium to helium of < 1.1 * 10^-6 is obtained.Comment: 18 pages, Latex, 9 .eps figure
Measurement of the W+W-gamma Cross Section and Direct Limits on Anomalous Quartic Gauge Boson Couplings at LEP
The process e+e- -> W+W-gamma is analysed using the data collected with the
L3 detector at LEP at a centre-of-mass energy of 188.6GeV, corresponding to an
integrated luminosity of 176.8pb^-1. Based on a sample of 42 selected W+W-
candidates containing an isolated hard photon, the W+W-gamma cross section,
defined within phase-space cuts, is measured to be: sigma_WWgamma = 290 +/- 80
+/- 16 fb, consistent with the Standard Model expectation. Including the
process e+e- -> nu nu gamma gamma, limits are derived on anomalous
contributions to the Standard Model quartic vertices W+W- gamma gamma and W+W-Z
gamma at 95% CL: -0.043 GeV^-2 < a_0/Lambda^2 < 0.043 GeV^-2 0.08 GeV^-2 <
a_c/Lambda^2 < 0.13 GeV^-2 0.41 GeV^-2 < a_n/Lambda^2 < 0.37 GeV^-2
Production of Single W Bosons at \sqrt{s}=189 GeV and Measurement of WWgamma Gauge Couplings
Single W boson production in electron-positron collisions is studied with the
L3 detector at LEP. The data sample collected at a centre-of-mass energy of
\sqrt{s} = 188.7GeV corresponds to an integrated luminosity of 176.4pb^-1.
Events with a single energetic lepton or two acoplanar hadronic jets are
selected. Within phase-space cuts, the total cross-section is measured to be
0.53 +/- 0.12 +/- 0.03 pb, consistent with the Standard Model expectation.
Including our single W boson results obtained at lower \sqrt{s}, the WWgamma
gauge couplings kappa_gamma and lambda_gamma are determined to be kappa_gamma =
0.93 +/- 0.16 +/- 0.09 and lambda_gamma = -0.31 +0.68 -0.19 +/- 0.13
Search for an invisibly decaying Higgs boson in e^+e^- collisions at \sqrt{s} = 183 - 189 GeV
A search for a Higgs boson decaying into invisible particles is performed
using the data collected at LEP by the L3 experiment at centre-of-mass energies
of 183 GeV and 189 GeV. The integrated luminosities are respectively 55.3 pb^-1
and 176.4 pb^-1. The observed candidates are consistent with the expectations
from Standard Model processes. In the hypothesis that the production cross
section of this Higgs boson equals the Standard Model one and the branching
ratio into invisible particles is 100%, a lower mass limit of 89.2 GeV is set
at 95% confidence level
Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in e+e- Interactions at \sqrt{s} = 189 GeV
A search for the lightest neutral scalar and neutral pseudoscalar Higgs
bosons in the Minimal Supersymmetric Standard Model is performed using 176.4
pb^-1 of integrated luminosity collected by L3 at a center-of-mass energy of
189 GeV. No signal is observed, and the data are consistent with the expected
Standard Model background. Lower limits on the masses of the lightest neutral
scalar and pseudoscalar Higgs bosons are given as a function of tan(beta).
Lower mass limits for tan(beta)>1 are set at the 95% confidence level to be m_h
> 77.1 GeV and m_A > 77.1 GeV
Measurement of Bose-Einstein Correlations in e+e- -> W+W- at root(s)=189GeV
We investigate Bose-Einstein correlations (BEC) in W-pair production at
root(s)=189GeV using the L3 detector at LEP. We observe BEC between particles
from a single W decay in good agreement with those from a light-quark Z decay
sample. We investigate their possible existence between particles coming from
different W's. No evidence for such inter-W BEC is found
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