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Fragile X syndrome (FXS), the leading cause of inherited intellectual disability and autism spectrum disorder, is associated with multiple neurobehavioral abnormalities including sleep difficulties. Nonetheless, frequency, severity, and consequences of sleep problems are still unclear. The Fragile X Online Registry with Accessible Research Database (FORWARD-version-3), including Clinician Report and Parent Report forms, was analyzed for frequency, severity, relationship with behavioral problems, and impact of sleep difficulties in a mainly pediatric cohort. A focused evaluation of sleep apnea was also conducted. Six surveyed sleep difficulties were moderately frequent (~23%-46%), relatively mild, affected predominantly younger males, and considered a problem for 7%-20% of families. Snoring was more prevalent in older individuals. All sleep difficulties were associated with irritability/aggression and most also to hyperactivity. Only severe snoring was correlated with sleep apnea (loud snoring: 30%; sleep apnea: 2%-3%). Sleep difficulties are prevalent in children with FXS and, although they tend to be mild, they are associated with behavioral problems and negative impact to families. Because of its cross-sectional nature, clinic-origin, use of ad hoc data collection forms, and lack of treatment data, the present study should be considered foundational for future research aiming at better recognition and management of sleep problems in FXS.

Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by the full mutation as well as highly localized methylation of the fragile X mental retardation 1 (FMR1) gene on the long arm of the X chromosome. Children with FXS are commonly co-diagnosed with Autism Spectrum Disorder, attention and learning problems, anxiety, aggressive behavior and sleep disorder, and early interventions have improved many behavior symptoms associated with FXS. In this review, we performed a literature search of original and review articles data of clinical trials and book chapters using MEDLINE (1990–2021) and ClinicalTrials.gov. While we have reviewed the biological importance of the fragile X mental retardation protein (FMRP), the FXS phenotype, and current diagnosis techniques, the emphasis of this review is on clinical interventions. Early non-pharmacological interventions in combination with pharmacotherapy and targeted treatments aiming to reverse dysregulated brain pathways are the mainstream of treatment in FXS. Overall, early diagnosis and interventions are fundamental to achieve optimal clinical outcomes in FXS.

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Multi-element germanium detectors for X-ray fluorescence are widely used in synchrotron experiments and in particular in XAFS experiments. This paper presents the construction and characterization of a demonstrator built to investigate the viability of multi-element monolithic germanium detectors equipped with CMOS front-end electronics. Semikon Detector GmbH fabricated a germanium sensor segmented with a pad pattern with pad size $1\times 1~\hbox{mm}^2$ . 16 channels were instrumented with the CUBE preamplifiers developed at XGLab Srl. The detector was tested with radioactive sources and with the synchrotron X-ray beam of Diamond. The results showed spectra with energy resolution satisfactory for XAFS experiments but with a considerable tail. The low energy tail was proved to be due to charge sharing. In addition the spectra showed the peak stability as a function of counting rate better than 1% for rate up to 838 kcps. The non-linearity of the peak position vs. energy was estimated to be a maximum of 0.13% No evidence of charge loss in the crystal was identified. This work proved that this technology is a viable option to improve the throughput of germanium fluorescence detectors as long as methods to reduce events leading to charge sharing are in place.

We have constructed a pixelated germanium detector using a technique which has been shown to provide good isolation between adjacent pixels. In this work we present initial tests of the application of a low-noise CMOS ASIC to read out this detector. The detector has 64 pixels, each 0.5mm × 5mm, arranged as a series of strips. It is connected by wire-bonds to two 32-channel ASICs (Application-Specific Integrated Circuit) which provide a complete photon-counting chain for every channel. Since the size of the pixel array is no longer restricted by the difficulties of instrumenting large channel-count conventional electronics, this development will open up the possibility of even larger arrays, similar to those offered by silicon detectors.

The General AntiParticle Spectrometer (GAPS) is a novel approach for indirect dark matter searches that exploits cosmic antideuterons. The GAPS detection method involves capturing antiparticles into a target material with the subsequent formation of an excited exotic atom. The exotic atom decays with the emission of atomic X-rays and charged particles from nuclear annihilation, which uniquely identifies the captured antiparticle. We are currently developing the lithium-drifted silicon (Si(Li)) detector for the GAPS flight experiment. In this paper, we describe the diagnostic tests conducted on three prototype Si(Li) detectors and the noise model to characterize each detector. The GAPS prototype flight, preparatory for a long duration balloon flight from Antarctica in 2016–2017, is scheduled for launch from Japan in summer 2012.

We have measured inclusive data on K + -meson production in pp collisions at COSY Julich close to the hyperon production threshold and determined the hyperon–nucleon invariant mass spectra. The spectra were decomposed into three parts: Λp, Σ 0 p and Σ + n . The cross section for the Σ + n channel was found to be much smaller than a previous measurement in that excess energy region. The data together with previous results at higher energies are compatible with a phase space dependence.

The angular distributions of the unpolarised differential cross section and tensor analysing power $A_{xx}$ of the $\vec{d}d\to\alpha \eta$ reaction have been measured at an excess energy of 16.6 MeV. The ambiguities in the partial-wave description of these data are made explicit by using the invariant amplitude decomposition. This allows the magnitude of the s-wave amplitude to be extracted and compared with results published at lower energies. In this way, firmer bounds could be obtained on the scattering length of the $\eta \alpha$ system. The results do not, however, unambiguously prove the existence of a quasi-bound $\eta \alpha$ state.

The extracted s-wave scattering amplitude from both the polarized and unpolarized d + d → 4He + η reaction at 2385.5 MeV/c allowed to determine the scattering length which fulfills the requirements for bound η. In the p + 27Al → 3He + p + π- + X reaction studied at recoil free kinematics the η meson is produced almost at rest and so it can be bound with enhanced probability. This state proceeds via N*(1535) resonance and the decay products proton and pion emitted into opposite direction are detected in concidence with 3He produced at zero degree. Under these conditions some hints for bound state can be observed with an upper limit of the cross section of ≈ 0.5 nb.

þ ðLpÞ K þ =pþ separation abstract A new threshold Cherenkov detector has been built for the detection of charged pions in the focal plane of a magnetic spectrograph. Silica aerogel with refractive index of n ¼ 1:05 is applied as a radiator. The detector exhibits a very high detection efficiency for pions with momenta X900 MeV=c. Using two Cherenkov detectors in series a very high pion suppression factor of 10 5 was achieved.

The measurement of the η meson production in [Formula: see text] reaction has been performed at the Big Karl magnetic spectograph at COSY synchrotron in Jülich. The vector and tensor polarized deuetron beam at the excess energy of Q=16 MeV was used. The preliminary results for the unpolarized cross section are presented here.

An experiment to search for the bound state of η meson in nuclei has been performed at COSY, Juelich using the ENSTAR detector and Big Karl magnetic spectrometer. Reaction (p,3 He ) on 27 Al target has been used to search for the η-mesic nucleus 25 Mg η in the missing mass distribution from the measured 3 He particles. A preliminary figure of 1.5 nb for the upper limit of the formation cross section of η-nucleus bound state has been determined.

New possibilities are opened up utilizing position-sensitive germanium detectors in the X-ray spectroscopy of highly charged heavy ions at GSI-Darmstadt. The recent experiments revealed the need for two-dimensional strip detectors with their inherent advantages concerning spectroscopy and imaging capabilities as well as polarization sensitivity. For the first prototype a germanium diode (70 mmtimes41 mm, 11 mm thick) with a boron implanted contact and an amorphous Ge contact was prepared. A 128-strip structure on an area of 32 mmtimes56 mm with a pitch of 250 mum on the front contact (implanted) and a 48-strip structure with a pitch of 1167 mum on the rear contact (amorphous Ge) are realized with the help of plasma etching. The detector is mounted in a cryostat which will enable any orientation of the detector with respect to a photon source. The results of laboratory tests and planned applications at the ESR storage ring in Darmstadt are presented

Recent developments of large-area Si(Li) orthogonal-strip detectors have revealed their capability for applications in Compton-effect-based instruments. Some inherent advantages of silicon such as the dominance of Compton scattering in photon interactions and operation at room or somewhat lower temperature combined with the availability of large-volume Si(Li) detectors could stimulate the development of powerful Compton instruments. Several diodes 10 mm in thickness with a diameter of 102 mm were fabricated. Two 10 mm thick diodes were cut to form a 74 mmtimes74 mm square with slightly rounded corners. The same position-sensitive structure, 32 strips with a pitch of 2 mm, was produced on the thin Li-diffused n-contact and boron-implanted p+-contact by means of photolithography and plasma etched grooves. The position-sensitive area of 64 mmtimes64 mm is surrounded by a 5 mm wide guard-ring. One of these 10 mm thick Si(Li) orthogonal-strip detectors has been mounted in a cryostat prepared at Lawrence Livermore National Laboratory (LLNL). The detector will be extensively tested there with the goal of being integrated into the Compact Si+Ge Compton camera system consisting of this Si(Li) and a HPGe orthogonal-strip detector

The positively charged pions produced in proton–proton collisions at a beam momentum of 1640 MeV/c were measured in the forward direction with a high resolution magnetic spectrograph. The missing mass distribution shows the bound state (deuteron) clearly separated from the pn continuum. Despite the very good resolution, there is no evidence for any significant

A crystal spectrometer has been constructed in the Focusing Compensated Asymmetric Laue geometry covering the energy range between 30 and 120 keV. We summarize the crystal optics and show the usefulness of the instrument for spectroscopy of stationary and fast moving X-ray sources. Results are reported from several tests employing a 169 Yb gamma-ray source and the Lyman radiation of one-electron Au 78+ ions travelling at a velocity corresponding to β = v / c o ≈0.44.

The established technique for producing position-sensitive structures by means of photolithography and subsequent plasma etching of grooves through detector contacts was applied for amorphous germanium contacts (a-Ge contacts). A simple 50-strip structure with a pitch of 615 /spl mu/m was produced. Charge sharing between two adjacent strips (33 mm length) was investigated with the aid of 60-keV photons and 5.8-MeV /spl alpha/-particles. No charge losses were detected when irradiating the structured a-Ge contact of the 16-mm-thick detector with 60-keV photons. The same was concluded for /spl alpha/-particles hitting the unstructured p/sup +/-contact made by boron implantation. Moreover, excellent position information for /spl alpha/-particles, with an accuracy of about 30 /spl mu/m, could be extracted in this case. Surprising results were obtained for /spl alpha/-particles impinging on the structured a-Ge contact. No coincident signals from the two adjacent strips caused by /spl alpha/-particles were observed. But a normally positive signal from one of the strips occasionally coincided with a negative signal from the other strip and vice versa. Using a cooled FET assembly mounted near a strip, an energy resolution of 0.78 keV [FWHM] for 60-keV photons was achieved and a slightly better resolution for lower energies. Even better energy resolutions will probably be possible, because the measuring setup was far from being optimized.

The spectroscopy of atomic transitions in the hard X-ray regime above 15 keV utilizing position-sensitive solid state detectors is discussed. Special emphasis is given to the current detector developments for X-ray spectroscopy of heavy ions at the ESR storage ring where applications for precision spectroscopy as well as for polarization studies are of particular interest. For both cases, the advantages and new possibilities which are opened up by position and energy resolving solid state detectors are illustrated by the presentation of first experiments.

A stack of annular detectors made of high purity germanium was used to measure p + d → 3 He + π 0 and p + d → 3 H + π + differential and total cross sections at beam momenta from 900 to 1050 MeV/c. The total cross sections are consistent with ∆-excitation. The differential data consist of two components. One corresponds to large momentum transfer from the projectile to the pion, the other to small momentum transfer. The former shows an independence of the slope as function of the momentum transfer t (scaling). The scale parameter is different for π + and π 0 emission which violates isospin symmetry. The second component which is almost isotropic is in agreement with isospin symmetry. It is approximately a quarter of the total yield in the ∆ resonance region.  2002 Elsevier Science B.V. All rights reserved.

We performed a series of experiments employing the two pion production reactions p + d → 3 He + π 0 and p + d → 3 H + π + . The two isopin related reactions differ by a Clebsch Gordan coefficient of 2. We searched for deviations in this ratio in complete angular distributions in the range of the Δ excitation as well as in the vicinity of the η production threshold.

The paper describes modifications of the Julich magnetic spectrometer Big Karl needed to study meson production and especially to investigate charge symmetry breaking effects—an experiment that requires a high-precision measurement. New elements that have been added to Big Karl have extended the spectrometer capabilities to a much wider momentum range. The new features also facilitate simultaneous detection of particles with very different rigidities. The experimental methods for improving background and determining relative acceptance of the spectrometer at various rigidities are presented.

Rich sets of high precision cross sections, vector and tensor analyzing powers for the [Formula: see text] breakup reaction were measured at 130 and 100 MeV beam energy with the use of detection systems covering large parts of the phase space. The cross section data allowed to establish evidences for three-nucleon force contributions and to confirm predictions of sizable effect of the Coulomb force in the breakup reaction. Analyzing power data are generally quite well described by theoretical predictions even with pure nucleon-nucleon interactions. However, in some regions discrepancies has been observed for tensor analyzing powers at 130 MeV.

Total and differential cross sections for the reactions p + d → 3He + m 0 with m=π, η and p + d → 3H+π+ were measured with the GEM detector at COSY for beam momenta between threshold and the maximum of the corresponding baryon resonance. For both reactions a strong forward-backward asymmetry was found. The data were compared with model calculations. The aspect of isospin symmetry breaking is studied.

For the current X-ray spectroscopy program at the ESR storage ring (GSI-Darmstadt) a position sensitive germanium detector system has been completed. The position sensitive structure of the detector has been realized on an area of 47/spl times/23.4 mm/sup 2/ by an array of 200 strips (200 /spl mu/m wide and 23.4 mm long) separated by 35 /spl mu/m wide grooves etched through a boron implanted contact. The thickness of the detector inclusive of a 0.6 mm thick Li-diffused rear contact amounts to 4.1 mm. Each strip has been joined to a preamplifier placed outside the cryostat with printed leads inside the flexible Kapton foil. The energy resolution of the strips has been about 1.8 keV [FWHM] for 60 keV photons. Coincidences between neighbouring strips were measured whereby a time resolution of 70 ns [FWHM] was obtained. First preliminary results obtained with the detector mounted at the transmission X-ray spectrometer FOCAL demonstrated that an energy resolution better than 100 eV is achievable together with high detection efficiency. Along with a new kind of X-ray spectrometer this detector may play a key role for the next step of high precision X-ray experiments, aiming for a precise test of quantum electrodynamics in the heaviest one-electron systems such as a hydrogenlike uranium.

The production of neutral and charged pions as well as eta mesons is studied in the Delta and N* resonance region, respectively. Heavy A=3 recoils were measured with the GEM detector. The differential cross sections covering the full angular range are compared with model calculations., Comment: 4 pages, latex, 4 figures, talk presented at the XVIIth European Conference on Few-Body Problems in Physics, Evora, Portugal, September 2000; to be published in Nucl. Phys. A

In addition to their far greater X-ray detection efficiency, germanium strip detectors offer superior energy and position resolution as compared to those fabricated of silicon for energies in the range of 15 to 100 keV. We have characterized 200-/spl mu/m strip pitch detectors fabricated by two different processes. By scanning a 10-/spl mu/m-wide monochromatic synchrotron X-ray beam across these detectors, measurements were made on both spectral energy response and spatial resolution. X-rays absorbed between neighboring diode strips suffer from charge diffusion splitting of their signals which seriously degrades the detector performance, but by reconstructing events using an energy-sum coincidence algorithm we succeeded in producing artifact-free spectra with energy resolution 1000, and count uniformities across the detector surface

We present a method to determine precisely the absolute momentum of the external proton beam from the Julich Cooler Synchrotron COSY near 1930 MeV /c . In the pp → d π + reaction at 1930.477 MeV /c incident beam momentum, the forward going pions ( θ c.m. =0° ) and the backward going deuterons ( θ c.m. =180° ) have the same laboratory momentum. Such coincident pion–deuteron events are detected in the focal plane of the magnetic spectrometer BIG KARL located at θ lab =0° . Using the nearly linear dependence of the difference between the measured pion and deuteron momenta as a function of the proton beam momentum, the absolute momentum of the external proton beam from COSY near 1930 MeV /c was determined with a precision of 5.2×10 −5 .

A stack of annular detectors made of high-purity germanium was developed. The detectors are position sensitive with radial structures. The first one (“Quirl”) is double-sided position sensitive defining 40 000 pixels, the following three (E1, E2 and E3) have 32 wedges each. The Quirl acts as tracker while the other three act as calorimeter. The stack was successfully operated in meson production reactions close to threshold.

In near-threshold reactions the heavy reaction products are emitted within a narrow cone in the forward direction. To detect these a small-size charged-particle telescope has been built that is operated inside the vacuum chamber within the dipole magnets of the CELSIUS storage ring. The first aim has been to study two-pion production close to threshold. By measuring the d(d,2π) 4 He reaction at a beam energy of 569 MeV, corresponding to 29 MeV above the production threshold for two neutral pions in the c.m., we add a low-energy end point to the previous experiments concerning this reaction. The two pions are produced in a T=0 channel which is the signature of the so called ABC-effect.

The GEM detector, a hybrid system consisting of the Germanium Wall and the magnetic spectrometer BIG KARL, was developed to investigate meson production and meson-nucleus interaction with cooled external proton beams from the COSY accelerator at Julich. The Germanium Wall is a stack of up to four annular position-sensitive semiconductor detectors made from high-purity germanium. Its special structure allows experiments with high counting rates. Design features and results from first test runs with the uncooled COSY beam are presented.

Germanium diode microstrip arrays offer position-sensitive detection of X-rays combined with energy resolution over the range 5–100 keV. As part of a programme to develop a 300 strip photon-counting detector for Compton scattering experiments at the ESRF, we describe the design of a system permitting multiple high-density connections to cryogenically cooled detectors. We report on measurements made on two germanium microstrip strip detectors with ≈200 μm pitch fabricated using different process technologies. The position resolution and spectral energy response of these detectors has been characterised using a 15 μm wide scanning beam of monochromatic synchrotron X-rays at energies 15–100 keV. The raw data is dramatically improved by reconstruction of split-charge events arising from X-rays absorbed between contact strips, and energy spectra are obtained with peak/valley ratios >2000.

A small size spectrometer for detecting heavy reaction products emitted at small angles has been developed. It is installed at the synchrotron storage ring CELSIUS in Uppsala. It uses the focussing and bending magnetic elements of the storage ring itself in combination with a detector telescope, made of high-purity germanium, inserted into the ring vacuum. The spectrometer has been used for studies of pion production reactions close to threshold. The spectrometer is described together with results of ray-trace calculations and experimental tests.

The momentum spectrum of 4 He particles from d + d reactions at E lab = 569 MeV has been measured at zero degrees in the laboratory. The missing-mass spectrum is consistent with a pure phase space behaviour for the isospin zero channel of two pions, corresponding to a total cross section of 43 ± 5 nb.

Radiation detectors consisting of MBE-, LPE-, and MOCVD-grown gallium arsenide layers were fabricated by employing standard photolithography techniques. The active region of the devices varied between 5 and 60 μm thickness. Hall and CV measurements confirm the high quality of the material with unintended residual doping densities of the order 1014/cm3 and mobilities typical for GaAs. Dark current densities as low as j d = 0.2..2.0 μA/cm2 were achieved for all devices. The energy resolution (FWHM) at room temperature for 60 keV γ-photons was 1.8 keV, while for 5.8 MeVα-particles (244Cm ) an energy resolution of 18.3 keV (FWHM) has been determined. The detectors exhibit a charge collection efficiency of approximately 100% within the experimental error.

An AlGaAs/GaAs avalanche photodiode with separate absorption- and multiplication regions (SAM-APD) has been realized as an X-ray detector. We report on the growth (MBE) and the processing of the detector as well as on results obtained by measurements with radioactive sources. Gains higher than 20 could be achieved with a staircaselike multiplication region. Typical dark currents of 100 pA at 90% of the breakdown voltage were measured for devices with an active area of A = 320 × 450 μ m 2 . Tests with X-rays of an 241 Am source showed an energy resolution of 1.95 keV (FWHM) at 13.96 keV without avalanche gain. At an optimal working point the detector reached an energy resolution of 0.9 keV (FWHM) for the same energy with an internal gain of M = 4.1. This corresponds to a relative energy resolution of ΔE E = 6.5% at room temperature. The calculated efficiency was approximately η = 23%. Additionally three X-ray escape peak doublets related to the 13.96 keV, 17.8 keV and 20.8 keV peaks of 241 Am could be resolved.

The 3α (triple-alpha) process leading to the formation of stable carbon in the Universe is one of the most important nuclear astrophysical processes. The radiative width of the so called Hoyle-state, involving the 7.654 MeV E0 and the 3.215 MeV E2 transitions, is known with 12.5% accuracy. We report on the development of a Si(Li)-detector array for a new magnetic pair spectrometer, which will be used for the measurement of the pair conversion of the E0 and E2 transitions from the Hoyle-state. The results of the final detector tests will be presented.

Results of the first measurements on HPGe- and Si(Li)-detectors with an one dimensional fine pitch strip structure are presented. The position-sensitive structures were fabricated on implanted boron contacts by means of photolithography with a subsequent plasma etching. A group of 5 neighbouring strips of both detector types was examinated concerning the reverse current, resistance between a position-element and the neighbourhood and the response to the photons up to 60 keV.

The reaction pp -> K^+ + (Lambda p) has been measured at T_p = 1.953 GeV and \Theta = 0 deg with a high missing mass resolution in order to study the Lambda p final state interaction. Narrow S = -1 resonances predicted by bag model calculations are not visible in the missing mass spectrum. Small structures observed in a previous experiment are not confirmed. Upper limits for the production cross section of a narrow resonance are deduced for missing masses between 2058 and 2105 MeV/c^2.

The motivation for the experiment is shortly discussed. In contrast to the classical method of π− absorption we will produce a π− directly in a bound state employing the COSY Julich proton beam. A special choice of the underlying kinematics favors the cross section. The considerations from these constraints for the detector will be given together with its status. An outlook is given on further possible activities.

The cross section for the reaction p+{sup 6}Li{yields}{eta}+{sup 7}Be was measured at an excess energy of 11.28 MeV above threshold by detecting the recoiling {sup 7}Be nuclei. A dedicated set of focal plane detectors was built for the magnetic spectrograph Big Karl and was used for identification and four-momentum measurement of {sup 7}Be. A differential cross section of nb/(d{sigma}/d{Omega})=[0.69{+-}0.20(stat.){+-}0.20(syst.)] sr for the ground state plus 1/2{sup -} was measured. The result is compared to model calculations.

Fabriction and test of a position-sensitive Ge detector with 200 strips arepresented. The detector was designed for the energy analysis of Compton scattered photons dispersed on the Rowland circle of a Cauchois-type cylindrically bent crystal. Each strip of the liquid nitrgen cooled detector, 200 μm wide and separated by a 34 μm wide grooves, is read out by an individual amplification channel. Encoding of discriminator signals enables the rejection of pulse orinating simultaneously in more than one strip. The detector combines high efficiency for 30–50 keV photons with good reproducibility of this figure for each strip. The energy resolution of about 10% is only moderate, but it may be improved by a special preamplifier design with a cooled input stage.

The distribution of nuclei resulting from the annihilation of stopped antiprotons on238U has been studied by an off-line measurement of the residual radioactivity. It was found that the probability of fission exceeds 84% (68% c.l.). The charge and mass distributions of the fission products can be separated into two parts, a more frequent symmetric component originating from high energy fission (excitation energy between 100 MeV and 1 GeV) and an asymmetric component from low energy fission (excitation energy less than 40 MeV).

Using 98% linearly polarized radiation at the European Synchrotron Radiation Facility in Grenoble, the performance of a prototype two-dimensional microstrip Ge(i) detector for x-ray imaging and as a Compton polarimeter has been evaluated. Using the energy and position sensitivity of the detector, the ability to obtain a complete reconstruction of the Compton event has been demonstrated. The modulation coefficient of the polarimeter is in good agreement with the theoretical limit of a perfect detector.

Inclusive measurements of pion production in proton-proton collisions in the forward direction were undertaken at 400 and 600 MeV at the cooler synchrotron (COSY) at Forschungszentrum Julich using the Big Karl spectrograph. The high resolution in the pi(+) momentum ensured that there was an unambiguous separation of the pp ->pi(+)d/pi(+)pn channels. Using these and earlier data, the ratio of the production cross sections could be followed through the Delta region and compared with the predictions of final state interaction theory. Deviations are strongly influenced by long-range terms in the production operator and the tensor force in the final pn system. These have been investigated in a realistic pp ->pi(+)d/pi(+)pn calculation that includes S reversible arrow D channel coupling between the final nucleons. A semiquantitative understanding of the observed effects is achieved. .

International audience; Recent advances in the development of 2D microstrip detectors open up new possibilities for hard x-ray spectroscopy, in particular for polarization studies. These detectors make ideal Compton polarimeters, which enable us to study precisely the polarization of hard x-rays. Here, we present recent results from measurements of Radiative Electron Capture into the K-shell of highly-charged uranium ions. The experiments were performed with a novel 2D Si(Li) Compton polarimeter at the Experimental Storage Ring at GSI. Stored and cooled beams of U91+ and U92+ ions, with kinetic energies of 43 MeV/u and 96 MeV/u respectively, were crossed with a hydrogen gasjet. The preliminary data analysis shows x-rays from the K-REC process, emitted perpendicularly to the ion beam, to be strongly linearly polarized.