Triangle Singularity as the Origin of the a_{1}(1420).

The COMPASS Collaboration experiment recently discovered a new isovector resonancelike signal with axial-vector quantum numbers, the a_{1}(1420), decaying to f_{0}(980)π. With a mass too close to and a width smaller than the axial-vector ground state a_{1}(1260), it was immediately interpreted as a new light exotic meson, similar to the X, Y, Z states in the hidden-charm sector. We show that a resonancelike signal fully matching the experimental data is produced by the decay of the a_{1}(1260) resonance into K^{*}(→Kπ)K[over ¯] and subsequent rescattering through a triangle singularity into the coupled f_{0}(980)π channel. The amplitude for this process is calculated using a new approach based on dispersion relations. The triangle-singularity model is fitted to the partial-wave data of the COMPASS experiment. Despite having fewer parameters, this fit shows a slightly better quality than the one using a resonance hypothesis and thus eliminates the need for an additional resonance in order to describe the data. We thereby demonstrate for the first time in the light-meson sector that a resonancelike structure in the experimental data can be described by rescattering through a triangle singularity, providing evidence for a genuine three-body effect.

Beam-Recoil Polarization Measurement of π

The helicity-dependent recoil proton polarizations P_{x}^{'} and P_{z}^{'} as well as the helicity-independent component P_{y} have been measured in the p(e[over →],e^{'}p[over →])π^{0} reaction at four-momentum transfer Q^{2}≃0.1 GeV^{2}, center-of-mass proton emission angle θ_{p}^{*}≃90°, and invariant mass W≃1440 MeV. This first precise measurement of double-polarization observables in the energy domain of the Roper resonance P_{11}(1440) by exploiting recoil polarimetry has allowed for the extraction of its scalar electroexcitation amplitude at an unprecedentedly low value of Q^{2}, establishing a powerful instrument for probing the interplay of quark and meson degrees of freedom in the nucleon.

High-precision determination of the electric and magnetic form factors of the proton.

New precise results of a measurement of the elastic electron-proton scattering cross section performed at the Mainz Microtron MAMI are presented. About 1400 cross sections were measured with negative four-momentum transfers squared up to Q² = 1 (GeV/c)² with statistical errors below 0.2%. The electric and magnetic form factors of the proton were extracted by fits of a large variety of form factor models directly to the cross sections. The form factors show some features at the scale of the pion cloud. The charge and magnetic radii are determined to be ½ = 0.879(5)stat(4)syst(2)model(4)group fm and ½ = 0.777(13)stat(9)syst(5)model(2)group fm.

The impact and recovery of asteroid 2008 TC(3).

In the absence of a firm link between individual meteorites and their asteroidal parent bodies, asteroids are typically characterized only by their light reflection properties, and grouped accordingly into classes. On 6 October 2008, a small asteroid was discovered with a flat reflectance spectrum in the 554-995 nm wavelength range, and designated 2008 TC(3) (refs 4-6). It subsequently hit the Earth. Because it exploded at 37 km altitude, no macroscopic fragments were expected to survive. Here we report that a dedicated search along the approach trajectory recovered 47 meteorites, fragments of a single body named Almahata Sitta, with a total mass of 3.95 kg. Analysis of one of these meteorites shows it to be an achondrite, a polymict ureilite, anomalous in its class: ultra-fine-grained and porous, with large carbonaceous grains. The combined asteroid and meteorite reflectance spectra identify the asteroid as F class, now firmly linked to dark carbon-rich anomalous ureilites, a material so fragile it was not previously represented in meteorite collections.

Measurement of the exclusive 3He(e,e'p) reaction below the quasielastic peak.

New, high-precision measurements of the 3He(e,e(')p) reaction using the A1 Collaboration spectrometers at the Mainz microtron MAMI are presented. These were performed in antiparallel kinematics at energy transfers below the quasielastic peak, and at a central momentum transfer of 685 MeV/c. Cross sections and distorted momentum distributions were extracted and compared to theoretical predictions and existing data. The longitudinal and transverse behavior of the cross section was also studied. Sizable differences in the cross-section behavior from theoretical predictions based on the plane wave impulse approximation were observed in both the two- and three-body breakup channels. Full Faddeev-type calculations account for some of the observed excess cross-section, but significant differences remain.

Measurement of the beam-helicity asymmetry in the p((-->)e,e'p)pi(0) reaction at the energy of the Delta(1232) resonance.

In a p((-->)e,e'p)pi(0) out-of-plane coincidence experiment at the three-spectrometer setup of the Mainz Microtron MAMI, the beam-helicity asymmetry has been precisely measured around the energy of the Delta(1232) resonance and Q(2) = 0.2(GeV/c)(2). The results are in disagreement with three up-to-date model calculations. This is interpreted as a lack of understanding of the nonresonant background, which in dynamical models is related to the pion cloud.

Neutral pion threshold production at Q(2) = 0.05 GeV(2)/c(2) and chiral perturbation theory.

New data are presented on the p(e,e'p)pi(0) reaction at threshold at a four-momentum transfer of Q(2) = 0.05 GeV(2)/c(2). The data were taken with the three-spectrometer setup of the A1 Collaboration at the Mainz Microtron MAMI. The complete center of mass solid angle was covered up to a center of mass energy of 4 MeV above threshold. Combined with measurements at three different values of the virtual photon polarization epsilon, the structure functions sigma(T), sigma(L), sigma(TT), and sigma(TL) are determined. The results are compared with calculations in heavy baryon chiral perturbation theory and with a phenomenological model. The measured cross section is significantly smaller than both predictions.

Measurement of the recoil polarization in the p(e-->, e'p-->)pi(0) reaction at the Delta(1232) resonance.

The recoil proton polarization has been measured in the p(e-->,e'p-->)pi(0) reaction in parallel kinematics around W = 1232 MeV, Q2 = 0.121 (GeV/c)2, and epsilon = 0.718 using the polarized cw electron beam of the Mainz Microtron. All three proton polarization components, Px/P(e) = (-11.4+/-1.3+/-1.4)%, P(y) = (-43.1+/-1.3+/-2.2)%, and P(z)/P(e) = (56.2+/-1.5+/-2.6)%, could be measured simultaneously. The Coulomb quadrupole to magnetic dipole ratio, CMR = (-6.4+/-0.7(stat)+/-0.8(syst))%, was determined from Px in the framework of the Mainz Unitary Isobar Model. The consistency among the reduced polarizations and the extraction of the ratio of longitudinal-to-transverse response is discussed.

Oral administration of iopentol (Imagopaque 300 mg I/ml) compared with amidotrizoate (Peritrast 300 mg I/ml), both diluted to 2% (v/v), in imaging of the gastrointestinal tract in abdominal contrast enhanced CT. A clinical trial assessing patient tolerance, distribution of contrast medium and Hounsfield unit measurements.

The aim of the trial was to evaluate and compare the safety and efficacy of iopentol (Imagopaque, Nycomed Imaging AS, Oslo, Norway) and amidotrizoate (Peritrast, Köhler Pharma, Alsbach, Germany), both 300 mg I/ml initially, but diluted to 2% (v/v) and administered orally. Sixty-four and 65 patients were included in the respective contrast medium groups. Portions of contrast medium, totally 1.51, were taken every 15 min during the hour before the examination. A standard radiological procedure for abdominal CT was followed. Nine percent of the patients in each group experienced adverse events which were possibly contrast medium related. Taste acceptance was comparable in the two groups. Except for the stomach, radiographic efficacy was satisfactory for all intestinal segments. The difference in density in the proximal small bowel (main parameter) achieved with the media was not significant (p = 0.33), nor was that as regards image homogeneity (contrast distribution). In conclusion, iopentol is well suited for oral contrast enhancement of the gastrointestinal tract in abdominal computed tomography.

[Therapeutic interventions in benign bile duct strictures]. / Therapeutische Interventionen bei benignen Gallengangsstrikturen.

Surgical treatment of benign bile duct strictures continues to be associated with significant lethality. Thus, radiological interventions become increasingly important. A total of 32 patients were treated. Their bile duct strictures had different origins. We performed percutaneous transhepatic cholangiographies in 32 patients, cholangioscopies in 7, and biopsies in 2 patients. Therapeutic interventions included percutaneous transhepatic drainages in 30 patients, laser lithotripsies in 5, and dilatations in 8 patients. As a total, 36 stents (mostly Palmaz stents) were implanted in 27 patients. Acuflex stents were implanted in 2 of these patients and were extracted after successful clearance of the bile ducts following stone fragmentation. No severe complications were observed. Five out of 8 dilatations were unsuccessful, so that stents were implanted. Five patients died. Three stent occlusions and 1 spontaneous stent migration occurred after an average of 29 months; the latter could be treated by means of radiological procedures. The remaining patients are living symptom-free, on average, since 18.6 months.

Reversible metastatic pulmonary calcification in a patient with multiple myeloma.

A-52-year-old patient presented with a 2-year history of multiple myeloma, recurrent episodes of hypercalcemia, and extensive bone involvement. She developed pulmonary infiltrates, initially misdiagnosed as interstitial pneumonia. High-resolution computed tomography and bone scintiscanning indicated pulmonary calcification, which was confirmed by a transbronchial biopsy. Cytostatic treatment of multiple myeloma in combination with repetitive i.v. administration of bisphosphonates over a period of 6 months led to a significant improvement of clinical symptoms. Regression of pulmonary infiltrates was demonstrated by chest radiograph and computed tomography. There are only a few reports on pulmonary calcification in patients with multiple myeloma; the condition was associated mostly with progressive disease, kidney failure, adult respiratory distress syndrome and bad prognosis. In our patient isolated calcification of the lungs without involvement of other organ systems was successfully treated. These findings suggest that interstitial pulmonary calcinosis in multiple myeloma can be reversed by normalization of serum calcium levels using bisphosphonates combined with cytostatic treatment.

[Percutaneous dynamic atherectomy with the aid of 12-F and 14-F transluminal atherectomy catheters (TEC): initial results]. / Perkutane dynamische Atherektomie mit Hilfe des 12-F- und 14-F-, transluminalen Atherektomiekatheters (TEC): erste Erfahrungen.

OBJECTIVE: The presented study reports on the first experience with the large diameter 12 F and 14 F TEC system for percutaneous dynamic atherectomy of peripheral vascular obstructions. METHODS AND PATIENTS: The 12 F and 14 F TEC-extraction catheter was used to recanalize peripheral vascular obstructions in 4 patients. The extracted material was continuously aspirated during the procedure. Three patients with intermittent claudication suffered from chronic arterial occlusion (two cases) or from stenosis of an implanted stent (one case) in the region of the superficial femoral artery. In another patient with long-term dialysis history an insufficient collier shunt was treated by atherectomy. RESULTS: Complete vascular recanalisation was achieved in all cases. Supplementary intervention was not necessary. There were no complications. CONCLUSION: Atherectomy with the large diameter 12 F and 14 F TEC allows a safe and complete recanalisation of complex peripheral vascular occlusions. Further studies must show whether the enlarged vascular intrusion is justified by more favourable results.

[Thrombectomy using a high-speed rotatable catheter--initial results]. / Thrombektomie mit Hilfe eines Hochgeschwindigkeits-Rotationskatheters--erste Erfahrungen.

Evaluation of the Amplatz rotational catheter for the recanalisation of acute thrombotic occlusions in various vascular regions. The Amplatz air-driven rotational catheter was used in 5 patients with acute vessel occlusion in various vascular regions: superficial and profundal femoral artery respectively and popliteal artery with tibiofibular trunk (case 1 and 2), a Collier-Shunt (case 3), the left main pulmonary artery (case 4) and the portal vein after TIPS procedure (case 5). A complete or partial recanalisation was achieved in all cases. Time accounted for recanalisation was between 40 and 90 seconds. No adjunctive intervention was necessary. No complications occurred. The Amplatz thrombectomy device allows a fast, safe and effective mechanical thrombectomy of peripheral arteries and haemodialysis shunts. Partial recanalisation of large caliber vessels is also possible.

[Experiences with an alternative distension medium in oral contrast imaging of the small intestine]. / Erfahrungen mit einem alternativen Distensionsmittel in der oralen Dünndarmkontrastierung.

PURPOSE: The image quality of oral small bowel imaging is often poor on account of the small bowel enema. A new contrast medium should increase the image quality due to better compliance of patient because of the better taste of substance. The loading of patient with radiation or time should not increase. METHODS AND PATIENTS: We investigated prospectively 40 patients, randomized in two groups of 20 patients each. Two different substances were used as contrast medium: barium-methylcellulose and Barium-Mucofalk, respectively. The quality of the double contrast, profile of the mucosa, duration of radiation, duration of examination, dose-area product, and taste of the substance were judged for significance. RESULTS: The taste of the new contrast medium was judged to be better: twice as often as "good" and five times less often as "bad", the difference was not significant due to the small number of patients. There is no significant difference in the other criterias. CONCLUSION: Mucofalk is an alternative contrast medium for oral small bowel radiology in cases of difficult placement of the tube for enema. The quality of double contrast and visualization of the profile of mucosa are the same while the taste is better.

[Results of catheter embolization of renal cell carcinoma]. / Ergebnisse nach Katheterembolisation bei Nierenzellkarzinom.

PURPOSE: We pointed out the value of catheter embolisation of kidney tumours. METHODS AND PATIENTS: We treated 42 patients with kidney tumours. For peripheral embolisation we placed Histoacryl or Ethibloc into the kidney artery via a transfemoral catheter. 33 patients had haematuria. 8 patients were lost for follow up. 26 patients were treated by embolisation alone and 8 patients were treated before nephrectomy. RESULTS: Haematuria was stopped in 98% and never reoccurred. The intraoperative blood-loss was 600 ml on average. 55% of patients treated by embolisation alone died within the first year. 51% of patients suffered from a slight postinfarction syndrome. One patient died of sepsis and one had pulmonary insufficiency due to AV shunt and pulmonary embolism. CONCLUSIONS: Peripheral embolisation of kidney tumours can be used successfully and is minimal invasive, in case of haematuria and pain. The perioperative risk is reduced due to limited blood loss.

[First clinical experience with a new nitinol stent in the biliary system]. / Erste klinische Erfahrung mit einem neuen Nitinolstent im biliären System.

PURPOSE: To evaluate the clinical usefulness of a new nitinol biliary stent (Memotherm) in patients with malignant biliary obstruction. 32 self expanding nitinol stents were applied in 17 patients. The following parameters were investigated: Difficulty of placement, lateral stability and patency over an observation time between 3 weeks and 11 months. RESULTS: In 29/32 stent application could be performed with high precision. In 3/32 we observed a displacement about 1 cm--according to the optimal stent position. Stent shortening was about 5 mm in 31/32 stents, secondary shortening only occurred in one patient with primarily distracted stent design. Lateral stability was sufficient in 21/25 stenoses with the consequence that dilatation was only performed in 4 cases. Average stent patency was 4.8 months, the average survival 5.1 months. Because of his special design, this stent may not be used for a stenosis with angulation higher than 90 degrees. CONCLUSION: Basing on a small calibre introducing system, easy placement, predictable minimal shortening and good lateral stability, the Memotherm seems an interesting alternative to other metal stents.

[Alveolar echinococcosis of the liver--computerized tomography findings]. / Alveoläre Leberechinokokkose--Computertomographische Befunde.

In order to ascertain the typical computed tomographic findings of hepatic alveolar echinococcosis, 24 computed tomograms of 19 patients were evaluated. The liver was involved in all cases whereas the diaphragma was infiltrated in 32%, and the retroperitoneal area in 42%. The right liver lobe was affected in 65%. Both before and after intravenous bolus contrast medium administration, the lesions were mainly inhomogeneous and of low density; a masking of the lesions due to the contrast medium administration was not observed; the enhancement pattern was irregular. Calcifications were detected in 96% of the cases, cystic structures in 50%, and cholestasis in 54%. On the basis of the crucial finding of calcifications in combination with the other typical observations, CT seems to be very suitable for the evaluation of hepatic alveolar echinococcosis.