Isotensor Dibaryon in the pp→ppπ^{+}π^{-} Reaction?

Exclusive measurements of the quasifree pp→ppπ^{+}π^{-} reaction have been carried out at WASA@COSY by means of pd collisions at T_{p}=1.2  GeV. Total and differential cross sections have been extracted covering the energy region T_{p}=1.08-1.36  GeV, which is the region of N^{*}(1440) and Δ(1232)Δ(1232) resonance excitations. Calculations describing these excitations by t-channel meson exchange are at variance with the measured differential cross sections and underpredict substantially the experimental total cross section. An isotensor ΔN dibaryon resonance with I(J^{P})=2(1^{+}) produced associatedly with a pion is able to overcome these deficiencies.

Spin Dependence of η Meson Production in Proton-Proton Collisions Close to Threshold

Taking advantage of the high acceptance and axial symmetry of the WASA-at-COSY detector, and the high polarization degree of the proton beam of COSY, the reaction p[over →]p→ppη has been measured close to threshold to explore the analyzing power A_{y}. The angular distribution of A_{y} is determined with the precision improved by more than 1 order of magnitude with respect to previous results, allowing a first accurate comparison with theoretical predictions. The determined analyzing power is consistent with zero for an excess energy of Q=15  MeV, signaling s-wave production with no evidence for higher partial waves. At Q=72  MeV the data reveal strong interference of Ps and Pp partial waves and cancellation of (Pp)^{2} and Ss^{*}Sd contributions. These results rule out the presently available theoretical predictions for the production mechanism of the η meson.

Abashian-Booth-Crowe effect in basic double-pionic fusion: a new resonance?

We report on an exclusive and kinematically complete high-statistics measurement of the basic double-pionic fusion reaction pn→dπ(0)π(0) over the full energy region of the ABC effect, a pronounced low-mass enhancement in the ππ-invariant mass spectrum. The measurements, which cover also the transition region to the conventional t-channel ΔΔ process, were performed with the upgraded WASA detector setup at COSY. The data reveal the Abashian-Booth-Crowe effect to be uniquely correlated with a Lorentzian energy dependence in the integral cross section. The observables are consistent with a narrow resonance with m=2.37  GeV, Γ≈70  MeV and I(J(P))=0(3(+)) in both pn and ΔΔ systems. Necessary further tests of the resonance interpretation are discussed.

Mechanism of near-threshold production of the eta meson

Measurements of the analyzing power for the pp-->pp eta reaction have been performed at excess energies of Q=10 and 36 MeV. The determined analyzing power is essentially consistent with zero, implying dominance of the s wave at both excess energies. The angular dependence of the analyzing power, combined with the isospin dependence of the total cross section for the eta meson production in nucleon-nucleon collisions, reveal that the excitation of the nucleon to the S11(1535) resonance is predominantly due to the exchange of the pi meson between the colliding nucleons.

Muon decay: measurement of the transverse polarization of the decay positrons and its implications for the fermi coupling constant and time reversal invariance

The two transverse polarization components P(T1) and P(T2) of the e(+) from the decay of polarized mu(+) have been measured as a function of the e(+) energy. Their energy averaged values are P(T1)=(6.3+/-7.7+/-3.4) x 10(-3) and P(T2)=(-3.7+/-7.7+/-3.4) x 10(-3). From the energy dependence of P(T1) and P(T2) the decay parameters eta,eta('') and alpha(')/A,beta(')/A are derived, respectively. Assuming only one additional coupling besides the dominant V-A interaction one gets improved limits on eta, beta(')/A, and the scalar coupling constant g(S)(RR): eta=(-2.1+/-7.0+/-1.0) x 10(-3), beta(')/A=(-1.3+/-3.5+/-0.6) x 10(-3), Re{g(S)(RR)}=(-4.2+/-14.0+/-2.0) x 10(-3), and Im{g(S)(RR)}=(5.2+/-14.0+/-2.4) x 10(-3).

Calcification of the aortic wall in hypercalcemic rabbits

The mineralization process was investigated in the aortic wall of hypercalcemic rabbits. The elevated calcium level in serum was induced by intramuscular injection of vitamin D3. The animals were killed at different times of the experiment (max. 246 d). The freeze-dried tissue homogenates were used for elemental composition studies by means of proton induced X-ray emission (PIXE) and atomic absorption spectroscopy. The structural information was obtained from infrared (IR) and X-ray diffraction (XRD) spectra. Moreover, the ascending part of the aortic arch was separated and used for micro-PIXE (PIXE in combination with proton microprobe) and histochemical examinations. It was found that hypercalcemia (blood serum Ca content elevated by about 20%) induced calcification of the aortic wall. The mineral phase within the aortic wall consisted of Ca-P salts. The Ca/P ratio continuously increased during the experiment and approached 2 after 246 d of the vitamin D3 treatment. The IR and XRD studies made possible the identification of the complex phase composition of the samples. The hydroxyapatite crystals were detected after 196 days, however, in earlier phases of the experiment, amorphous calcium phosphate, dicalcium phosphate dihydrate and octacalcium phosphate were also observed. On the basis of the data obtained, the mechanism of the precipitation and growth of inorganic deposits in the tunica media of the aortic wall was discussed.

Physicochemical characterization of the inorganic phases in the aortic wall of young individuals

The autopsy samples of human aortic wall were investigated to determine the structure of the inorganic deposits formed at the onset of the mineralization process. The studies were concentrated on the material for which histochemical staining of randomly selected sections did not reveal the presence of minerals. The highly mineralized human media samples as well as broad spectrum of model compounds were investigated for comparative purposes. It was found that the inorganic phase at the onset of tunica media mineralization is composed of a few compounds including octacalcium phosphate as the predominant Ca-P compound, and a Mg-compound, probably magnesium carbonate or double/triple salts containing magnesium carbonate.

Calcification of aortic wall in cholesterol-fed rabbits

Development of the mineralization process in the course of atherogenesis was studied using the cholesterol-fed rabbit model. The aorta samples were investigated by means of proton and electron microprobes, infrared spectroscopy and X-ray diffraction as well as selected histochemical staining. Blood serum was analysed every 2 weeks to determine the content of cholesterol, triglycerides, inorganic phosphorus, ionized calcium, elemental composition as well as activity of alkaline phosphatase. It was found that the administered diet did not disturb the calcium and phosphorus homeostasis. Histochemical findings confirmed the formation of lipid-rich lesions blocking the lumen of the vessel. The dystrophic calcification was observed only in the atheroma, while in the tunica media a slight mineralization similar to that found in controls was observed after 210 days of the diet. In the atheroma the only phase detected was a defective hydroxyapatite. The perfection of the crystals, as well as the diameter of the deposits, increased during the course of the diet reaching about 2 microns after 210 days. The crystals were not contaminated with carbonate groups regardless of the duration of the diet.

[Effects of acute nicotine administration on the function of the human parotid gland]

The effect of acute administration of nicotine on the secretory function of the human parotid gland was investigated in 4 male volunteers. After intravenous infusion of 20 micrograms nicotine/kg b.w. within 10 min in all subjects an increased salivary amylase activity and protein concentration was observed. This phenomenon is believed to be caused by a stimulation of parotid beta-adrenoceptors secondary to a nicotine-induced release of catecholamines from the adrenals.

Intramembranaceous ossification analyses by a proton microprobe

The proton induced X-ray emission method in combination with a proton microprobe was applied to study the intramembranaceous ossification. As material sections of mouse embryo skulls from the 17th and 19th day of gestation were used. The morphology of the sample was examined by routine histochemical procedure performed on the sections adjacent to that irradiated by the proton microprobe. The measurements were made in line scan and raster scan mode. The concentrations of P, S, Cl, K, Ca, Fe and Zn were determined at each irradiated point. The average element concentrations were calculated for four parts of each section (bone, cartilage, mesenchymal tissue close to the bone and mesenchymal tissue in other places). The distributions of Ca and P (less markedly than Ca) concentrations almost exclusively correlate with localization of the bone while S, Cl and K concentrations show preference to the cartilage. The amount of inorganic material in flat bones of the 17-day embryo amounts to 14% of the dry mass. The material is characterized by a Ca/P ratio of about 1.6. In the embryo 2 days older the amount of the inorganic phase is practically the same (15%) while the Ca/P ratio approaches 2. This suggests the presence of the precursor phase in the flat bone calcification. It is possible that octacalcium phosphate (Ca/P ratio equals to 1.72) is formed at the onset of the flat bone mineralization which transforms rapidly (in 2 days) to a more stable mineral (defective hydroxyapatite).

Artery wall calcification: correlation of atherosclerosis with mineralization

Popliteal arteries from 14 individuals (17-85 y old) were investigated. The concentrations and localizations of P, S, Cl, K, Ca, Fe, Cu, Zn and Br were measured by means of PIXE and micro-PIXE methods. The presence of PO4(3-) and CO3(2-) groups was assessed using the IR technique. The amount of P and Ca increased with age approaching at places 9% and 20% and mineral deposits were detected in tunica media. At the same time an increase in the Ca/P ratio and in the crystallinity of deposits was observed. The samples from old individuals also contained more CO3(2-) groups. The concentrations and localization of Zn and Br showed artery wall layer-dependent changes. In some places of the artery wall, minerals were also found in young persons. They were not correlated with places of blood vessel branching.

The analysis of mineral deposits and proteoglycans content in the cartilage of mouse trachea using PIXE in combination with proton microprobe

The tracheal cartilage of mature mice have been investigated using PIXE (proton induced X-ray emission) in combination with a proton microprobe on snap frozen cryosectioned material. The localization and quantitative measurements of P, S, Cl, K, Ca, Fe, and Zn concentrations as well as direct and indirect assessment of glycosaminoglycans by measurement of S content and measurement of bound colloidal iron at pH = 1.8 has been performed. Adjacent sections were stained with the Hale method in Müller modifications and the v. Koss method for sulphated mucins and inorganic deposits respectively. It has been found that hyaline cartilage in trachea contains mineral deposits and that P + Ca amounts up to 22% of cartilage dry mass. The Ca/P ratio approaches 2 what indicates hydroxyapatite type crystals. The cartilage contains substantial amounts of S reflecting the presence of sulphate groups. It was found that the cartilage binds also colloidal iron at low pH. There is a good correlation between places with high amount of bound colloidal iron assessed by PIXE and places showing strong Prussian Blue staining. The Fe/S ratio was, however, much lower in the cartilage than in other tissues what indicates that the colloidal iron method does not give quantitative results. There were no regions showing substantial decrease in Fe/S ratio which we found previously as typical for degenerating and calcifying growth plate cartilage. This may be connected with a relatively low degree of calcification degree of the tracheal cartilage.

Measurement of colloidal iron binding at low pH in cartilage using the proton microprobe

Quantitative micro-PIXE analysis was performed on mouse embryo epiphyseal cartilage and on the rib cartilage of mature animals after incubation of sections with colloidal iron at pH 1.8. The iron content as well as that of sulphur and phosphorus and Fe/S, Fe/P ratios were determined. It was found that colloidal iron content was higher in the cartilage than in other tissues. The cartilage also displayed the highest content of sulphur. The Fe/S ratio was however not constant, being highest in the degeneration zone close to the mineralization front, where the binding of iron was strongest while the amount of sulphur decreased. This indicates that factors other than number of sulphate groups influence the binding of positively charged molecules to glycosaminoglycans. This is confirmed by differences in the results obtained for embryonic and mature rib cartilage.

Measurements of mineralization process in the femur growth plate and rib cartilage of the mouse using pixe in combination with a proton microprobe

The femoral bone from the 18-day pregnancy embryo and an rib cartilage of mature mice have been investigated using PIXE (proton induced X-ray emission) in combination with a proton microprobe on snap frozen cryosectioned material. The localization and the results of quantitative measurement of P, S, Cl, K, Ca, Fe and Zn have been correlated with the histochemical localization of inorganic deposits. It has been found that in calcifying and degenerating cartilage of the growth plate there is substantial loss of S; this element being indicative for sulphate groups of glycosaminoglycans. This change seems to be an important factor conditioning the process of mineralization. Zn is found in higher concentration in mineralized tissues, both in embryonal and mature cartilage as well as in the bone, and this suggests that Zn is also involved in the mineralization process. The mineralization of rib cartilage exceeds that of embryonal bone, and the Ca/P ratio is higher in the former than in the hydroxyapatite of the latter. The method described is a useful analytical tool especially for such types of studies in which elements are not easily redistributed by freezing, cutting and drying; e.g. in investigations of mineral deposits.

Distribution of elements in rabbit liver lobule

The elemental composition of rabbit liver was determined by the PIXE and micro-PIXE methods. The mean concentrations of P, S, Cl, K, Fe, Cu, Zn, and Rb measured by both methods were similar. The latter method also allowed for localization of elements within lobule territory. It has been found that some elements are more prevalent in the veins (Cl, Fe) and others in the liver parenchyma (P, Cu, Zn). Moreover, Zn showed the characteristic intralobular distribution. Some methodological aspects of microbeam application to biological materials were also discussed.

Elemental composition of the human atherosclerotic artery wall

The elemental composition of the human atherosclerotic popliteal artery was examined using the proton-induced X-ray-emission (PIXE) method. The application of a narrow proton beam (3 X 10 micron 2) enabled us to determine not only the concentrations of Cl, K, Ca, Fe, Cu, Zn, Br and Pb, but also their localization in different artery-wall regions. The highest mean concentrations of Cl, K, Zn and Br were found in the tunica media. In the investigated sections the distribution of Ca and Fe varied: sometimes, these elements were prevalent in the tunica intima, whereas in other cases, the highest concentrations were observed in the tunica media or tunica adventitia. The concentration profiles of each element were characterized by many sharp, narrow peaks. The highest concentrations of Ca and Fe showed such high levels that only one explanation is possible, i.e. the presence of crystals. The correlation of Ca peaks with those of Zn and Fe is discussed. The usefulness of the micro-PIXE method for the investigation of biomedical materials is also considered.