Cardiac hypertrophy was induced in adult female Wistar rats following 12 days of daily subcutaneous injections of isoproterenol (ISO). The left atria responded with a 13-14% increase in tissue ...growth, while the ventricles achieved a 34-39% increased tissue mass. Maximum force generation and twitch characteristics in 1.0 mM external Ca2+ for the left atria or the right papillary muscle were unchanged in the ISO-treated animals. The force-interval relation was determined at 26 degrees C between 0.5 and 120 s. The development of maximum force clearly passed through two phases identified as alpha and beta. To characterize these two processes the data were fitted to a two-term linear combination of exponentials (two-compartment model). The time constant and capacity of each process to contribute to the whole force-interval curve was determined by a four-parameter least square fit method. In control atrial muscle the time constants for the alpha and beta processes were 0.47 and 11.23 s, respectively. The contribution of each process to the total force curve in control atrial muscle was approximately 50% alpha and 50% beta. Following ISO-induced growth the time constants were 0.38 and 13.33 s with a shift of contributions towards 60% alpha and 40% beta. Control papillary muscle from the right ventricle had a similar alpha time constant of 0.49 s compared with atrial muscle but possessed a considerably slower beta time constant of 26.17 s. The contribution of each process to interval-dependent force development was 44.5 and 55.5%, respectively.
Using the South Pole Acoustic Test Setup (SPATS) and a retrievable transmitter deployed in holes drilled for the IceCube experiment, we have measured the attenuation of acoustic signals by South Pole ...ice at depths between 190 m and 500 m. Three data sets, using different acoustic sources, have been analyzed and give consistent results. The method with the smallest systematic uncertainties yields an amplitude attenuation coefficient α = 3.20 ± 0.57 km-1 between 10 and 30 kHz, considerably larger than previous theoretical estimates. Expressed as an attenuation length, the analyses give a consistent result for λ ≡ 1/α of ˜300 m with 20% uncertainty. No significant depth or frequency dependence has been found.
We report on the search for electromagnetic and hadronic showers ("cascades") produced by a diffuse flux of extraterrestrial neutrinos in the AMANDA neutrino telescope. Data for this analysis were ...recorded during 1001 days of detector livetime in the years 2000-2004. The observed event rates are consistent with the background expectation from atmospheric neutrinos and muons. An upper limit is derived for the diffuse flux of neutrinos of all flavors assuming a flavor ratio of νe:νμ:ντ = 1:1:1 at the detection site. The all-flavor flux of neutrinos with an energy spectrum Φ ∝ E-2 is less than 5.0 × 10-7 GeV s-1 sr-1 cm-2 at a 90% C.L. Here, 90% of the simulated signal would fall within the energy range 40 TeV to 9 PeV. We discuss flux limits in the context of several specific models of extraterrestrial and prompt atmospheric neutrino production.
The muon and anti-muon neutrino energy spectrum is determined from 2000-2003 AMANDA telescope data using regularised unfolding. This is the first measurement of atmospheric neutrinos in the energy ...range 2-200 TeV. The result is compared to different atmospheric neutrino models and it is compatible with the atmospheric neutrinos from pion and kaon decays. No significant contribution from charm hadron decays or extraterrestrial neutrinos is detected. The capabilities to improve the measurement of the neutrino spectrum with the successor experiment IceCube are discussed.
The \textit{KArlsruhe TRItium Neutrino} (KATRIN) experiment aims to measure the neutrino mass with a sensitivity of \SI{0.2}{\electronvolt} (\SI{90}{\percent} CL). This will be achieved by a ...precision measurement of the endpoint region of the \(\upbeta\)-electron spectrum of tritium decay. The \(\upbeta\)-electrons are produced in the \textit{Windowless Gaseous Tritium Source} (WGTS) and guided magnetically through the beamline. In order to accurately extract the neutrino mass the source activity is required to be stable and known to a high precision. The WGTS therefore undergoes constant extensive monitoring from several measurement systems. The \textit{Forward Beam Monitor} (FBM) is one such monitoring system. The FBM system comprises a complex mechanical setup capable of inserting a detector board into the KATRIN beamline with a positioning precision of better than \SI{0.3}{\milli\metre}. The electron flux density at that position is on the order of \SI{e6}{\per\second\per\milli\metre\squared}. The detector board contains two silicon detector chips of \pin diode type which can measure the \(\upbeta\)-electron flux from the source with a precision of \SI{0.1}{\percent} within \SI{60}{\second} with an energy resolution of FWHM \(=\) \SI{2}{\kilo\electronvolt}. The unique challenge in developing the FBM arise from its designated operating environment inside the Cryogenic Pumping Section which is a potentially tritium contaminated ultra-high vacuum chamber at cryogenic temperatures in the presence of a \SI{1}{\tesla} strong magnetic field. Each of theses parameters do strongly limit the choice of possible materials which e.g. caused difficulties in detector noise reduction, heat dissipation and lubrication. In order to completely remove the FBM from the beam tube a \SI{2}{\meter} long traveling distance into the beamline is needed demanding a robust as well as highly precise moving mechanism.
The fact that neutrinos carry a non-vanishing rest mass is evidence of physics beyond the Standard Model of elementary particles. Their absolute mass bears important relevance from particle physics ...to cosmology. In this work, we report on the search for the effective electron antineutrino mass with the KATRIN experiment. KATRIN performs precision spectroscopy of the tritium \(\beta\)-decay close to the kinematic endpoint. Based on the first five neutrino-mass measurement campaigns, we derive a best-fit value of \(m_\nu^{2} = {-0.14^{+0.13}_{-0.15}}~\mathrm{eV^2}\), resulting in an upper limit of \(m_\nu < {0.45}~\mathrm{eV}\) at 90 % confidence level. With six times the statistics of previous data sets, amounting to 36 million electrons collected in 259 measurement days, a substantial reduction of the background level and improved systematic uncertainties, this result tightens KATRIN's previous bound by a factor of almost two.
The GDH-M øller-Polarimeter at ELSA Speckner, T.; Anton, G.; von Drachenfels, W. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2004, Volume:
519, Issue:
3
Journal Article
Peer reviewed
The design, setup and performance of a new two-arm coincidence, large acceptance and variable energy M
øller-Polarimeter used within the GDH-Experiment at the Electron Stretcher Accelerator Facility ...(ELSA) in Bonn is described. The polarimeter employs a dipole magnetic spectrometer and lead glass detectors to detect both M
øller scattered electrons in coincidence. A target system consisting of three different pairs of coils provides the magnetic field to magnetize Vacoflux foils in three different space orientations. This allows to measure all beam polarization components. The variable geometry of the detector system enables adjustments to the kinematic conditions between 0.8 and
3.5
GeV
electron beam energy. A large center of mass acceptance of
θ
̄
=65°;115°
provides the measurement of the longitudinal electron beam polarization, for example at
1.9
GeV
with a statistical precision of 1% within
10
min
(
I
e
≈500
pA
). Unprecedented systematic studies of M
øller polarimetry as well as direct measurements of the transversal beam polarization components have been performed with this device.
In this work we present a keV-scale sterile-neutrino search with the first
tritium data of the KATRIN experiment, acquired in the commissioning run in
2018. KATRIN performs a spectroscopic ...measurement of the tritium $\beta$-decay
spectrum with the main goal of directly determining the effective electron
anti-neutrino mass. During this commissioning phase a lower tritium activity
facilitated the search for sterile neutrinos with a mass of up to $1.6\,
\mathrm{keV}$. We do not find a signal and set an exclusion limit on the
sterile-to-active mixing amplitude of down to $\sin^2\theta < 5\cdot10^{-4}$
($95\,\%$ C.L.), improving current laboratory-based bounds in the
sterile-neutrino mass range between 0.1 and $1.0\, \mathrm{keV}$.
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