Measurement of polarization observables T, P, and H in π0 and η photoproduction off quasi-free nucleons

The target asymmetry T, recoil asymmetry P, and beam-target double polarization observable H were determined in exclusive π 0 and η photoproduction off quasi-free protons and, for the first time, off quasi-free neutrons. The experiment was performed at the electron stretcher accelerator ELSA in Bonn, Germany, with the Crystal Barrel/TAPS detector setup, using a linearly polarized photon beam and a transversely polarized deuterated butanol target. Effects from the Fermi motion of the nucleons within deuterium were removed by a full kinematic reconstruction of the final state invariant mass. A comparison of the data obtained on the proton and on the neutron provides new insight into the isospin structure of the electromagnetic excitation of the nucleon. Earlier measurements of polarization observables in the γ p → π 0 p and γ p → η p reactions are confirmed. The data obtained on the neutron are of particular relevance for clarifying the origin of the narrow structure in the η n system at W = 1.68 GeV . A comparison with recent partial wave analyses favors the interpretation of this structure as arising from interference of the S 11 ( 1535 ) and S 11 ( 1650 ) resonances within the S 11 -partial wave.

Measurement of the helicity asymmetry E for the reaction γ p → π 0 p : The CBELSA/TAPS Collaboration

A measurement of the double-polarization observable E for the reaction γ p → π 0 p is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn frozen-spin butanol (C4 H9 OH) target, which provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range fromE γ = 600 to 2310 MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses.

Observation of the pη^{'} Cusp in the New Precise Beam Asymmetry Σ Data for γp→pη

Data on the beam asymmetry Σ in the photoproduction of η mesons off protons are reported for tagged photon energies from 1130 to 1790 MeV (mass range from W=1748  MeV to W=2045  MeV). The data cover the full solid angle that allows for a precise moment analysis. For the first time, a strong cusp effect in a polarization observable has been observed that is an effect of a branch-point singularity at the pη^{'} threshold [E_{γ}=1447  MeV (W=1896  MeV)]. The latest BnGa partial wave analysis includes the new beam asymmetry data and yields a strong indication for the N(1895)1/2^{-} nucleon resonance, demonstrating the importance of including all singularities for a correct determination of partial waves and resonance parameters.

N(1520) 3/2(-) helicity amplitudes from an energy-independent multipole analysis based on new polarization data on photoproduction of neutral pions

New data on the polarization observables T, P, and H for the reaction γp→pπ(0) are reported. The results are extracted from azimuthal asymmetries when a transversely polarized butanol target and a linearly polarized photon beam are used. The data were taken at the Bonn electron stretcher accelerator ELSA using the CBELSA/TAPS detector. These and earlier data are used to perform a truncated energy-independent partial wave analysis in sliced-energy bins. This energy-independent analysis is compared to the results from energy-dependent partial wave analyses.

First measurement of the helicity asymmetry for γp → pπ0 in the resonance region

The first measurement of the helicity dependence of the photoproduction cross section of single neutral pions off protons is reported for photon energies from 600 to 2300 MeV, covering nearly the full solid angle. The data are compared to predictions from the SAID, MAID, and BnGa partial wave analyses. Strikingly large differences between data and predictions are observed, which are traced to differences in the helicity amplitudes of well-known and established resonances. Precise values for the helicity amplitudes of several resonances are reported.

Well-established nucleon resonances revisited by double-polarization measurements

The first measurement is reported of the double-polarization observable G in the photoproduction of neutral pions off protons, covering the photon energy range from 620 to 1120 MeV and the full solid angle. G describes the correlation between the photon polarization plane and the scattering plane for protons polarized along the direction of the incoming photon. The observable is highly sensitive to contributions from baryon resonances. The new results are compared to the predictions from SAID, MAID, and BnGa partial wave analyses. In spite of the long-lasting efforts to understand γp→pπ(0) as the simplest photoproduction reaction, surprisingly large differences between the new data and the latest predictions are observed which are traced to different contributions of the N(1535) resonance with spin parity J(P)=1/2(-) and N(1520) with J(P)=3/2(-). In the third resonance region, where N(1680) with J(P)=5/2(+) production dominates, the new data are reasonably close to the predictions.

The lateral leeway in the habitual intercuspation: experimental studies and literature review

The habitual intercuspation is used ubiquitous for manufacturing small dental restorations. However, a little is known on its precision. The aim of the present study was therefore to investigate the unambiguity and accuracy of the habitual occlusion in mounted plaster casts from fully dentate persons. Eighty-one fully dentate volunteers, 36 women and 45 men aged 26.8 +/- 6.2 years (18-55 years), with minor fillings and no signs or symptoms of TMD took part in the experiments. Silicone impressions were taken, poured with stone plaster and the obtained casts mounted into Dentatus ARL(R)- articulators using an individual face bow transfer. Subsequently, the models were transferred to a custom-made measuring articulator where the lateral leeway and the accuracy of the hand-held habitual intercuspation were quantified in the condylar area. Measurements were repeated seven times with the upper cast pushed either to the maximum right or the maximum left intercuspation. The hand-held habitual intercuspation of upper and lower cast proved ambiguous in 57% of pairs of casts. The average lateral leeway of the habitual intercuspation in the condylar area was 0.10 +/- 0.05 mm (0-0.51 mm; median 0.07 mm) between the maximum right and left occlusal positions. The average accuracy of three repeated measurements was 0.22 +/- 0.09 mm (0.02-1.17 mm; median 0.16 mm). Natural occlusal surfaces in a full dentition do not guarantee an unambiguous habitual intercuspation of the plaster casts. The described leeway and technical limits might be possible causes for occlusal adjustments that are sometimes necessary when inserting restorations manufactured in habitual intercuspation.

Aufbau und Erprobung eines neuartigen Meßsystems für die dentale Biomechanik – Meßprinzip und Beispielmessungen des Hexapod-Meß-Systems / Design and Testing of a Novel Measuring Set-up for Use in Dental Biomechanics – Measuring Principle and Exemplary Measurements with the Hexapod Measuring System

A novel measuring set-up based on a hexapod system for use in dental biomechanics is described. It was specially developed to measure force/deflection characteristics of different dental materials and devices. The functionability and suitability of the system for use in experimental biomechanics were investigated in two different studies. In a first study the micro mobility of prosthetic telescopic crowns prior to and after simulated wear was determined to investigate the influence of wear processes on the stability of the anchorage elements and thus of prostheses. This study investigated the ability of the setup to load a specimen with high forces or torques of up to 100 Newton. The second study looked at the force/deflection characteristics of orthodontic anchorage pins used in orthodontics to additionally stabilize the anchorage unit, for example during molar movement. In this study specimens were loaded with small forces of less than 10 Newton, as are typically used in orthodontics. Using the setup, the deflection behaviour of these devices under high and low loading was measured at a resolution of approximately one micrometer or one angular second.

[Development of a periodontium-approximated specimen holder for attrition studies of telescopic crowns]

To enable attritional studies on telescopic crowns, a specimen holder has been constructed that is intended to simulate, in zero approximation, the biomechanical properties of abutments bearing telescopic crowns. The specimen holder consists essentially of a system with two metal "concertinas" with different elasticity constants reflecting the different biomechanical parameters for periodontium and bone. The biomechanical processes in the periodontium are too complex to be simulated accurately in vitro. Nevertheless, the specimen holder described here enables the forces acting during insertion and removal of a partial denture to be accommodated elastically in the angular and axial directions, to simulate the possible degrees of freedom of the abutments in situ. In this way, the unavoidable errors of specimen fixation are rendered tolerable, so that local preferential wear is decisively reduced.

The relevance of extracorporeal septoplasty in cleft nose correction

The aim of this paper is to delineate the importance of the correction of the nasal septum when attempting to improve the nasal shape and function in patients with cleft lip and palate (CLP) deformity. The particular problems of the nasal shape in CLP patients are assessed. Various approaches for adequate correction are reviewed and discussed. The method of extracorporeal septoplasty is presented in detail. This method was used between 1982 and 1997 in 141 out of 332 CLP patients who required septoplasties and appears particularly suited for this purpose since it offers the possibility of reconstructing an almost normal septum. This is necessary in order to achieve both a functionally and an aesthetically good result. Our experience over the past 16 years confirms the advantages of this approach.

[The effect of gamma radiation on the methionine and tryptophan content of soy protein products]

Effect of gamma irradiation on the content of methionine and tryptophan in soya protein products were investigated. Irradiation with doses of 1, 3 and 5 kGy caused significant (p = 0.05) decrease of methionine contents. Parallel with the decrease in methionine also the relative quality of proteins is lowered. Tryptophan content were significantly reduced (p = 0.05) at irradiation doses of 3 and 5 kGy. The relative decrease of methionine and tryptophan contents are significantly correlated (p = 0.05) with relative increase in amount of products by the irradiation induced oxidation of lipids; correlation coefficients were 0.576 and 0.715.

[Content of available lysine in gamma-irradiated soybean products]

The content in available lysine of soya protein products irradiated in a 60Co-gamma cell were investigated. The results indicate that available lysine content and crude protein content at irradiation doses of 1, 3 and 5 kGy were unaffected at the 95% significance level. During 3-month storage the irradiated samples showed no significant (p = 0,05) changes of available lysine content. In samples with high content of lecithin, which were irradiated at 1 kGy as well as non-irradiated the content of available lysine was significantly (p = 0,05) reduced after 8-month storage; the other products as well as the at 3 and 5 kGy irradiated samples showed no significant decrease. Immediately after irradiation the microflora was significantly (p = 0,05) reduced. Under the effect of radiation treatment at 3 and 5 kGy the microflora was reduced to nearly 100% after 3-month storage.

[Anterior guidance compared with curvatures of sagittal TMJ excursions]

The sagittal condylar paths of 17 healthy persons with class I occlusion were recorded by electronic axiography. Based on the radius values established for the geometry of each condylar path these could be compared with the protrusive facets of the incisors and the first premolar teeth. The results are important for our understanding of the movement profiles of the masticatory system. Correlations between the TMJ and the anterior teeth in terms of functional morphology were observed.

[Adhesive strengths of cast crowns with various types of cements]

In an in vitro study the adhesive strength of sand-blasted castings (gold alloy) was tested on human teeth prepared and finished in different ways. For cementation we used two glass ionomer and one phosphate cement. On the surfaces treated with carbide finishing instruments the force required for separating the crown from the tooth was about 1.9 N/mm2 for Ketac-cem, about 2 N/mm2 for Fuji Ionomer, and about 1.8 N/mm2 for Harvard (a zinc oxide phosphate cement). Compared with this, the values obtained for dentin surfaces pretreated with fine diamonds (red ring) were 1.5 N/mm2 for Ketac-cem, 1.6 N/mm2 for Fuji Ionomer, and 1.9 N/mm2 for Harvard. The measured differences between the various types of cement were statistically not significant.

[Pre- and post-eruption effects on the functional morphology of the articulating structures]

Profile traces of latero- and protrusive facets of subjects with class-I-occlusion showed characteristic regular patterns in curvature and angle to the occlusal plane. There was no significant correlation between the laterotrusive surface profiles and the corresponding transversal movement of the condyle which was recorded electronically in 3 dimensions. Curvature morphology was plotted as a function of tooth eruption, development of the dental hard tissues, and tooth wear. In conclusion the results were applied to comprehensive occlusal restorations.

[Changes in the tryptophan content during the technological manufacturing processes of several wheat flour products]

The change of tryptophan contents in proteins of bread and cookies under technological processing conditions were investigated. Tryptophan contents in all cookie samples were noted to be significantly (p = 0.05) reduced in relation to corresponding dough. The relative decreases are significantly correlated with fat content and the degree of unsaturation of fats in the dough of cookies (r = 0.802 and r = 0.777, p = 0.01), independently of various physical parameters during different cookie samples' processing. Tryptophan decrease in proteins of bread during baking was not significant.

[Comparative studies on the morphology of the curvature of the protrusive paths in anterior and posterior teeth]

The occlusal surfaces of 20 class I probands were recorded during protrusion with an electronic profilograph. Using a circular template, a definite radius could be attributed to each of the recorded curvatures. The radii and angles determined relative to the occlusal plane showed characteristic regularities. Thus, the radii of the anterior teeth are longer than those of the posterior teeth. The longest radius was generally found for the canines. The same tendency, although less pronounced, was observed with the angles. These phenomena can be explained by the fact that the masticatory system involves both "biting" and "grinding". Evolutionary and embryological theories have also been included in the discussion.

[Cervical discrepancies and closeness of marginal fit of full cast crowns in correlation with the luting agent used]

In an in-vitro study 75 extracted teeth were prepared with a chamfer and a 12 degree convergence angle. After corrective impression taking and preparation of the dies accurately fitting caps were made of "Stabilor G" alloy. The marginal defects were measured at 4 points on each tooth under the light-microscope before and after cementing with three different luting agents. Before cementation the mean values and standard deviation of the cervical discrepancies were 105 +/- 43 microns. The crowns fixed by means of zinc oxyphosphate cement (Harvard) exhibited marginal defects of 142 +/- 33 microns, those fixed with Fuji-Ionomer type I glass polyalkenoate cement had 159 +/- 20 microns, and the crowns cemented with Ketac-Cem had 127 +/- 6 microns. After exposing the specimens to thermal cycling, additional data on the sealing capacity of these cements could be obtained which showed zinc oxyphosphate cement to have the most favorable properties.

[Changes in the biological protein value of wheat grain caused by manufacture into flour and gluten]

The authors determined the amino-acid composition of the proteins of whole wheat grain, flour and gluten, and calculated the biological protein values of these products from the data obtained. The decrease in the contents of the single amino acids was as follows: flour, 8--13% (as compared to whole grain); and gluten, 2--5% (as compared to flour). The decrease in the biological protein value according to Mitchell was: wheat flour, 5% (as compared to whole grain); and gluten, 8% (as compared to flour). The decrease in the biological protein value according to Oser was: flour, 9% (as compared to whole grain); and gluten, 26% (as compared to flour).