Effect of molecular architecture on the crystalline structure and stiffness of iPP homopolymers: modeling based on annealing experiments

Five PP homopolymers were selected and their molecular structure was thoroughly characterized to determine the effect of molecular architecture on their annealing behavior and on the ultimate stiffness achieved by heat treatment. Molecular mass and its distribution were characterized by rheological measurements, while chain regularity was determined by calorimetry, by the stepwise isothermal segregation technique (SIST). The samples were annealed in two different ways. Tensile bars were treated in an oven at 165 °C for increasing times to determine changes in stiffness. Various defects developed during the annealing of tensile specimens that did not allow the reliable determination of modulus by direct measurement. On the other hand, the second approach, the annealing of small samples in a DSC cell clearly showed the changes occurring in crystalline structure and also the effect of nucleation and molecular architecture on them. The large molecular weight fraction used to facilitate nucleation hinders crystal perfection, while the presence of a heterogeneous nucleating agent increases overall crystallinity, but does not influence recrystallization during annealing. Melting traces were transformed into lamella thickness distributions, from which average lamella thickness was derived. Lamella thickness and crystallinity, the independent variables of the empirical equation used for the calculation of modulus, were extrapolated to infinite annealing time to predict maximum stiffness. The value obtained, 3.5 GPa, is very far from the theoretically predicted 40 GPa of oriented crystals, which cannot be achieved under practical conditions

Untersuchungen zur natürlichen Resistenz verschiedener Dinkelsorten gegen Zwergsteinbrand

In inoculated field trials with dwarf bunt (Tilletia controversa) spelt wheat cultivars appeared more resistant than bread wheat cultivars. Among 10 spelt wheat cultivars, Tauro showed the lowest infection rates. Early sowing of spelt wheat in the field resulted in significantly reduced dwarf bunt severity compared to normal sowing times

Improvement of the impact strength of ethylene-propylene random copolymers by nucleation

Five ethylene-propylene random copolymers were nucleated with two soluble nucleating agents. Ethylene content changed between 1.7 and 5.3 wt %, while nucleating agent content was adjusted according to the solubility of the additive. It changed from 0 to 5000 ppm for the sorbitol (1,2,3-tridesoxy-4,6:5,7-bis-O-[(4-propylphenyl) methylene]-nonitol) and from 0 to 500 ppm for the trisamide compound (1,3,5-benzene-trisamide) used. Crystalline structure was analyzed in detail by various methods (DSC, XRD, and SEM). Mechanical properties were characterized by tensile and instrumented impact measurements. The results showed that most properties changed moderately upon nucleation, but impact resistance increased considerably. Spherulitic structure was not detected, but instead in the presence of the soluble nucleating agents used a microcrystalline structure formed. The large increase of impact resistance could not be related directly to changes in crystalline morphology. On the other hand, local rearrangement of morphology was detected by XRD and SEM analysis including an increase of lamella thickness, crystal orientation, and the formation of shish-kebab structures in the core of the injection molded specimens. A small increase in the γ-phase content of PP was also observed. These changes increased crack propagation energy considerably leading to the large improvement observed in impact resistance. Although the phenomenon could be related to ethylene content, differences in molecular weight also helped to explain the changes observed

The role of solubility and critical temperatures for the efficiency of sorbitol clarifiers in polypropylene

The optical properties of polypropylene (PP) were modified by nine different sorbitol type clarifiers available commercially or synthesized in the study. The solubility of the clarifiers in PP was estimated by thermodynamic model calculations. The results showed that the solubility of these additives in PP is small, a few 1000 ppm at most. Solubility is determined by the chemical structure of the sorbitol and the heat of fusion of the latter changes solubility by at least one order of magnitude. Solubility can be estimated reasonably by the Flory-Huggins lattice theory. The morphology of most sorbitols transforms at a temperature much below their melting point upon heating. This transformation, which is accompanied by crystal perfection, seems to influence melting and solubility. A fibrillar structure forms upon the cooling of molten sorbitols, but the diameter of the fibrils is much larger than those forming in the polymer melt. The nucleating effect of the clarifier depends on solubility, but also on processing conditions. Nucleus density is related to the amount of dissolved clarifier. A close correlation was found between the Flory-Huggins interaction parameter of sorbitols and the minimum achievable haze, which can be explained with the effect of solubility and nucleus density

CHAIN REGULARITY OF ISOTACTIC POLYPROPYLENE DETERMINED BY DIFFERENT THERMAL FRACTIONATION METHODS

Abstract The chain regularity of isotactic polypropylene (iPP) homo- and random copolymers was characterized by different thermal fractionation methods in this study. Different stepwise temperature programs were applied in a calorimeter (DSC), in order to develop a method which is significantly faster than SIST and provides reliable information about the chain regularity of iPP. Our studies prove that self-seeding accelerates the crystallization process during annealing in SSA-DSC experiments (successive self-nucleation and annealing). Consequently, the time of isothermal steps can be shortened significantly in the SSA-DSC method. On the other hand we found that step time should not be too short if the goal of the measurement is the determination of average chain regularity. Our results clearly indicate that both the experimental conditions and the evaluation technique influence the obtained results. A standard experimental procedure is proposed for reliably determining the average chain regularity of iPP. The length of the SSA-DSC temperature program developed in this study is much shorter compared to that of the conventional SIST (stepwise isothermal segregation technique) measurements used recently for such experiments. The proposed SSA-DSC program makes the reliable characterization of a large number of samples on an acceptable timescale possible

Quantitative Comparison of Cone Beam Computed Tomography and Microradiography in the Evaluation of Bone Density after Maxillary Sinus Augmentation: A Preliminary Study

Purpose Cone beam computed tomography ( CBCT ) and microradiographic analyses were comparatively performed in maxillary sinus augmentation to preliminarily verify the diagnostic potential of CBCT on the evaluation of bone regeneration. Materials and Methods A two‐stage protocol was conducted in 19 consenting patients, all having the crestal bone ≤2 mm, in private dental office. Mineralized human bone allograft particles were used to augment sinus using lateral window approach. A succession of CBCT scans of the maxilla was taken before surgery, after sinus augmentation, and immediately after implant insertion. Using virtual probes, CBCT data were processed by medical imaging software and expressed as gray level ( GL ). A bone core biopsy was taken at implant placement, 6 months after surgery. Microradiography of transverse sections, taken 6, 8, and 10 mm from the crestal surface, of methacrylate‐embedded biopsies was performed to analyze and to evaluate the mineralized material amount ( MM %). Results A total of 21 sinus augmentations were performed. CBCT (mean GL : 646–693) data were not statistically different when comparing 6‐, 8‐, and 10‐mm sites to after grafting/implant‐insertion values. Furthermore, microradiographic (mean MM %: 45.3–48.3) data were not statistically different comparing 6‐, 8‐, and 10‐mm sites, due to variation of values among patients. A GL and MM % parallelism was identified considering each patient, instead. A significant correlation ( p  < .001) between GL and MM % was found after both W ilcoxon test for paired data and simple linear regression analysis. Conclusions The preliminary result clearly demonstrated the predictability of the CBCT analysis. Due to the limited sample and great variations of the MM % recorded in patients, further clinical and morphometric studies are needed to fulfill diagnostic expectations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108331/1/cid12016.pd

Cardio-Respiratory Sleep Studies at Home:Experience in Research and Clinical Cohorts

Objective To evaluate the success rates of home cardiorespiratory polygraphy in children under investigation for sleep-disordered breathing and parent perspectives on equipment use at home. Design Prospective observational study. Setting Sheffield, Evelina London and Southampton Children's Hospitals. Patients Data are reported for 194 research participants with Down syndrome, aged 0.5-5.9 years across the three centres and 61 clinical patients aged 0.4-19.5 years from one centre, all of whom had home cardiorespiratory polygraphy including respiratory movements, nasal pressure flow, pulse oximetry, body position and motion. Main outcome measures Percentage of home cardiorespiratory studies successfully acquiring ≥4 hours of artefact-free data at the first attempt. Parental report of ease of use of equipment and preparedness to repeat home diagnostics in the future. Results 143/194 (74%; 95% CI 67% to 79%) of research participants and 50/61 (82%; 95% CI 71% to 90%) of clinical patients had successful home cardiorespiratory polygraphy at the first attempt. Some children required multiple attempts to achieve a successful study. Overall, this equated to 1.3 studies per research participant and 1.2 studies per clinical child. The median artefact-free sleep time for successful research studies was 515 min (range 261-673) and for clinical studies 442 min (range 291-583). 84% of research and 87% of clinical parents expressed willingness to repeat home cardiorespiratory polygraphy in the future. 67% of research parents found the equipment 'easy or okay' to use, while 64% of clinical parents reported it as 'easy' or 'very easy'. Conclusions Home cardiorespiratory polygraphy offers an acceptable approach to the assessment of sleep-disordered breathing in children.</p

Effect of the molecular structure of the polymer and nucleation on the optical properties of polypropylene homo- and copolymers.

Two soluble nucleating agents were used to modify the optical properties of nine PP homo- and random copolymers. The ethylene content of the polymers changed between 0 and 5.3 wt%. Chain regularity was characterized by the stepwise isothermal segregation technique (SIST), while optical properties by the measurement of the haze of injection molded samples. Crystallization and melting characteristics were determined by differential scanning calorimetry (DSC). The analysis of the results proved that lamella thickness and change in crystallinity influence haze only slightly. A model was introduced which describes quantitatively the dependence of nucleation efficiency and haze on the concentration of the nucleating agent. The model assumes that the same factors influence the peak temperature of crystallization and optical properties. The analysis of the results proved that the assumption is valid under the same crystallization conditions. The parameters of the model depend on the molecular architecture of the polymer. Chain regularity determines supermolecular structure and thus the dependence of optical properties on nucleation

Approximate parametrization of plane algebraic curves by linear systems of curves

t is well known that an irreducible algebraic curve is rational (i.e. parametric) if and only if its genus is zero. In this paper, given a tolerance ϵ>0 and an ϵ-irreducible algebraic affine plane curve C of proper degree d, we introduce the notion of ϵ-rationality, and we provide an algorithm to parametrize approximately affine ϵ-rational plane curves by means of linear systems of (d−2)-degree curves. The algorithm outputs a rational parametrization of a rational curve of degree d which has the same points at infinity as C. Moreover, although we do not provide a theoretical analysis, our empirical analysis shows that and C are close in practice

"The Poles of the Western World"

Die vorliegende Diplomarbeit ist eine Medienanalyse, die sich mit der Darstellung osteuropäischer Einwanderer in drei irischen Zeitungen – Irish Times, Sunday Independent und Irish News - im Zeitraum zwischen Mai 2004 und Dezember 2006 befasst. Besondere Aufmerksamkeit ist auf die Darstellung historischer, politischer und religiöser Gemeinsamkeiten zwischen Irland und Osteuropa gerichtet. Diese Gemeinsamkeiten waren im 19. Jahrhunderte, zu einer Zeit als Irland und verschiedene osteuropäische Länder beträchtliche Parallelen aufwiesen, in irischen Medien vielfach hervorgestrichen worden. Der Analyseteil dieser Diplomarbeit gliedert sich in zwei Teile. Im ersten Teil wird der Frage nach der Darstellung historischer, kultureller und religiöser Gemeinsamkeiten zwischen Irland und Osteuropa nachgegangen. Es wird dabei klar, dass eine Art longue durée gegeben haben dürfte, da Verweise auf historische Parallelen zwischen den beiden Regionen zum wiederholten Male vorkamen. Schlussendlich wurde klar, dass besonders Irlands eigene Erfahrung von Emigration eine reichliche Quelle für Vergleiche bat. Es wurde von vielen Journalisten von der Tatsache, dass jahrhundertelang viel Iren nach Amerika und Großbritannien auswanderten, eine moralische Verpflichtung abgeleitet, Fremden gegenüber großzügig und mitfühlend zu sein Der zweite Teil der Inhaltsanalyse beschäftigt sich mit der Darstellung osteuropäischer Einwanderer als wirtschaftlicher Faktor. Dieser Diskurs beschränkte sich zumeist auf eine einfache Kosten-Nutzen Rechnung, die dem vorrangigen Ziel des anhaltenden Wirtschaftswachstums alles andere unterordnete. Einwanderer wurden daher nur als eine volkswirtschaftliche Variable gesehen, die unter den gegebenen Umständen positiv ist, bei veränderter Wirtschaftslage aber auch negativ sein könnte. Diese Konzentration auf ökonomische Aspekte wurde jedoch auch von verschiedenen Seiten in Frage gestellt.This thesis is a media analysis with evaluates the representation of Eastern European immigrants in three Irish Newspapers – The Irish Times, The Sunday Independent and The Irish News - in the period between May 2004 and December 2006. Particular attention is focused on the perception of historical, political and religious similarities between Ireland and Eastern Europe. These similarities were often highlighted in Irish media in the 19th century, at a time when Ireland and various Eastern European countries had significant parallels. The analysis part of this thesis is divided into two parts. In the first part the representation of historical, cultural and religious similarities between Ireland and Eastern Europe were investigated. It became clear that a longue durée must have happened because references to historical parallels between the two regions occurred frequently. Eventually Ireland's own experience of emigration was often the source of comparison. Many journalists derived from the fact that for centuries many Irish people emigrated to America and Great Britain a moral obligation to be generous and compassionate to contemporary immigrants. The second part of the content analysis focuses on the representation of Eastern European immigrants as an economic commodity. This discourse was limited mostly to a simple cost-benefit calculation, which subordinates everything else to continuing economic growth. Immigrants were therefore seen simply as an economic variable that was positive under the current economic circumstances, but could easily be negative if the economic situation changed. This concentration on economic aspects, however, was also criticised from various journalists