717 research outputs found
Hadronic shift in pionic hydrogen
The hadronic shift in pionic hydrogen has been redetermined to be
\,eV by X-ray
spectroscopy of ground state transitions applying various energy calibration
schemes. The experiment was performed at the high-intensity low-energy pion
beam of the Paul Scherrer Institut by using the cyclotron trap and an
ultimate-resolution Bragg spectrometer with bent crystals.Comment: 10 pages, 6 figure
Highly charged ion X-rays from Electron-Cyclotron Resonance Ion Sources
Radiation from the highly-charged ions contained in the plasma of
Electron-Cyclotron Resonance Ion Sources constitutes a very bright source of
X-rays. Because the ions have a relatively low kinetic energy ( eV)
transitions can be very narrow, containing only small Doppler broadening. We
describe preliminary accurate measurements of two and three-electron ions with
Z=16--18. We show how these measurement can test sensitively many-body
relativistic calculations or can be used as X-ray standards for precise
measurements of X-ray transitions in exotic atoms
Determination of pulsation periods and other parameters of 2875 stars classified as MIRA in the All Sky Automated Survey (ASAS)
We have developed an interactive PYTHON code and derived crucial ephemeris
data of 99.4% of all stars classified as 'Mira' in the ASAS data base,
referring to pulsation periods, mean maximum magnitudes and, whenever possible,
the amplitudes among others. We present a statistical comparison between our
results and those given by the AAVSO International Variable Star Index (VSX),
as well as those determined with the machine learning automatic procedure of
Richards et al. 2012. Our periods are in good agreement with those of the VSX
in more than 95% of the stars. However, when comparing our periods with those
of Richards et al, the coincidence rate is only 76% and most of the remaining
cases refer to aliases. We conclude that automatic codes require still more
refinements in order to provide reliable period values. Period distributions of
the target stars show three local maxima around 215, 275 and 330 d, apparently
of universal validity, their relative strength seems to depend on galactic
longitude. Our visual amplitude distribution turns out to be bimodal, however
1/3 of the targets have rather small amplitudes (A 2.5) and could
refer to semi-regular variables (SR). We estimate that about 20% of our targets
belong to the SR class. We also provide a list of 63 candidates for period
variations and a sample of 35 multiperiodic stars which seem to confirm the
universal validity of typical sequences in the double period and in the
Petersen diagramsComment: 14 pages, 14 figures, and 8 tables. Accepted to The Astrophysical
Journal Supplement Series, September 201
Characterization of a CCD array for Bragg spectroscopy
The average pixel distance as well as the relative orientation of an array of
6 CCD detectors have been measured with accuracies of about 0.5 nm and 50
rad, respectively. Such a precision satisfies the needs of modern crystal
spectroscopy experiments in the field of exotic atoms and highly charged ions.
Two different measurements have been performed by illuminating masks in front
of the detector array by remote sources of radiation. In one case, an aluminum
mask was irradiated with X-rays and in a second attempt, a nanometric quartz
wafer was illuminated by a light bulb. Both methods gave consistent results
with a smaller error for the optical method. In addition, the thermal expansion
of the CCD detectors was characterized between -105 C and -40 C.Comment: Submitted to Review of Scientific Instrument
Precision determination of the dpi -> NN transition strength at threshold
An unusual but effective way to determine at threshold the dpi -> NN
transition strength is to exploit the hadronic ground-state broadening in
pionic deuterium, accessible by x-ray spectroscopy. The broadening is dominated
by the true absorption channel dpi- -> nn, which is related to s-wave pion
production pp -> dpi+ by charge symmetry and detailed balance. Using the exotic
atom circumvents the problem of Coulomb corrections to the cross section as
necessary in the production experiments. Our dedicated measurement finds
(1171+23/-49) meV for the broadening yielding (252+5/-11) \mub.Comment: 4 pages, 2 figures, 1 tabl
Suivi thérapeutique de l'imatinib
* Le monitoring (suivi) joue un rôle important pour un traitement et son évaluation - pour autant qu'il se base sur la mesure de marqueurs cliniques adéquats ou de substituts validés.
* Pour ce qui est du traitement d'imatinib, le «therapeutic drug monitoring» (TDM) semble être une option utile pour le contrôle du traitement de la LMC. Il utilise la concentration plasmatique de ce médicament comme marqueur.
* Les concentrations plasmatiques d'imatinib varient considérablement d'un patient à l'autre sous un même schéma posologique, en raison de la variabilité interindividuelle de sa pharmacocinétique. Il a été démontré que l'exposition plasmatique était en corrélation avec le résultat clinique des patients LMC - aussi bien pour la réponse au traitement que pour le profil d'effets indésirables.
* Il n'est pas encore établi si le TDM de l'imatinib doit être utilisé que dans le cas de problèmes cliniques ou si les patients LMC peuvent déjà profiter d'un contrôle préventif systématique «de routine» - de manière à garder la concentration plasmatique dans des marges thérapeutiques. Cela est toujours plus recommandé ces derniers temps.
* Pour répondre à cette question, une étude suisse prospective, randomisée et contrôlée recrute des patients LMC traités par imatinib depuis moins de 5 ans et propose en outre le TDM pour tous les patients en cas de problèmes cliniques.
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* Monitoring spielt eine wichtige Rolle zur Therapieevaluierung und Behandlungsentscheidung - solange es auf der Basis der Messung von entsprechenden klinischen oder validierten Surrogat-Markern stattfindet.
* Im Hinblick auf die Imatinib-Therapie scheint das «Therapeutische Drug-Monitoring» (TDM) ein nützlicher Ansatz zum Therapie-Monitoring der CML-Behandlung zu sein, welches die Plasmakonzentration des Arzneimittels als Marker zur Therapieüberwachung verwendet.
* Imatinib-Plasmakonzentrationen variieren beträchtlich von Patient zu Patient unter dem gleichen Dosierungsschema, aufgrund der interindividuell unterschiedlichen Pharmakokinetik des Arzneimittels. Für die Plasmaexposition wurde gezeigt, dass sie mit dem klinischen Outcome von CML-Patienten korreliert - sowohl im Bezug auf das Therapieansprechen als auch auf das Nebenwirkungsprofil.
* Es ist noch unklar, ob das TDM von Imatinib nur im Falle von klinischen Problemen Verwendung finden sollte oder ob CML-Patienten bereits von einem systematischen, präventiven «Routine»-Monitoring zur Therapieindividualisierung - zur Steuerung der Plasmakonzentration in einen therapeutischen Bereich - profitieren könnten, welches in letzter Zeit immer häufiger empfohlen wird.
* Um diese Fragestellung zu beantworten, nimmt eine prospektive, randomisiert kontrollierte Schweizer Studie CML-Patienten auf, die seit weniger als 5 Jahren mit Imatinib behandelt werden, und bietet das TDM zudem für alle Patienten im Falle von klinischen Problemen an
On radiative np -> 1s + gamma transitions, induced by strong low-energy interactions,in kaonic atoms
We calculate the rates of the radiative transitions np -> 1s + gamma in
kaonic hydrogen and kaonic deuterium, induced by strong low-energy interactions
and enhanced by Coulomb interactions. The obtained results should be taken into
account for the theoretical analysis of the experimental data on the X-ray
spectra and yields in kaonic atoms.Comment: 10 pages, 1 figur
Line shape of the muH(3p - 1s) hyperfine transitions
The (3p - 1s) X-ray transition to the muonic hydrogen ground state was
measured with a high resolution crystal spectrometer. A Doppler effect
broadening of the X-ray line was established which could be attributed to
different Coulomb de-excitation steps preceding the measured transition. The
assumption of a statistical population of the hyperfine levels of the muonic
hydrogen ground state was directly confirmed by the experiment and measured
values for the hyperfine splitting can be reported. The results allow a
decisive test of advanced cascade model calculations and establish a method to
extract fundamental strong-interaction parameters from pionic hydrogen
experiments.Comment: Submitted to Physical Review Letter
High Resolution He-like Argon And Sulfur Spectra From The PSI ECRIT
We present new results on the X-ray spectroscopy of multicharged argon,
sulfur and chlorine obtained with the Electron Cyclotron Resonance Ion Trap
(ECRIT) in operation at the Paul Scherrer Institut (Villigen, Switzerland). We
used a Johann-type Bragg spectrometer with a spherically-bent crystal, with an
energy resolution of about 0.4 eV. The ECRIT itself is of a hybrid type, with a
superconducting split coil magnet, special iron inserts which provides the
mirror field, and a permanent magnetic hexapole. The high frequency was
provided by a 6.4 GHz microwave emitter. We obtained high intensity X-ray
spectra of multicharged F-like to He-like argon, sulfur and chlorine with one
1s hole. In particular, we observed the 1s2s^{3}S_1 \to 1s^2^{1}S_0 M1 and
1s2p^{3}P_2 \to 1s^2^{1}S_0 M2 transitions in He-like argon, sulfur and
chlorine with unprecedented statistics and resolution. The energies of the
observed lines are being determined with good accuracy using the He-like M1
line as a reference
Line shape analysis of the K transition in muonic hydrogen
The K transition in muonic hydrogen was measured with a
high-resolution crystal spectrometer. The spectrum is shown to be sensitive to
the ground-state hyperfine splitting, the corresponding triplet-to-singlet
ratio, and the kinetic energy distribution in the state. The hyperfine
splitting and triplet-to-singlet ratio are found to be consistent with the
values expected from theoretical and experimental investigations and,
therefore, were fixed accordingly in order to reduce the uncertainties in the
further reconstruction of the kinetic energy distribution. The presence of
high-energetic components was established and quantified in both a
phenomenological, i.e. cascade-model-free fit, and in a direct deconvolution of
the Doppler broadening based on the Bayesian approach.Comment: 22 pages, 21 figure
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