Emission features of microstructures fabricated by two-photon polymerization containing three organic dyes

Fabrication of microstructures containing active compounds, such as fluorescent dyes and nanoparticles have been exploited in the last few years, aiming at applications from photonics to biology. Here we fabricate, using two-photon polymerization, microstructures containing the fluorescent dyes Stilbene 420, Disodium Fluorescein and Rhodamine B. The produced microstructures, containing dyes at specific sites, present good structural integrity and a broad fluorescence spectrum, from about 350 nm until 700 nm. Such spectrum can be tuned by using different excitation wavelengths and selecting the excitation position in the microstructure. These results are interesting for designing multi-doped structures, presenting tunable and broad fluorescence spectrum. (C)2012 Optical Society of America

FINITE ELEMENT ANALYSIS OF MAXILLARY BONE STRESS CAUSED BY ARAMANY CLASS IV OBTURATOR PROSTHESES

Statement of problem. The retention of an Aramany Class IV removable partial dental prosthesis can be compromised by a lack of support. The biomechanics of this obturator prosthesis result in an unusual stress distribution on the residual maxillary bone. Purpose. This study evaluated the biomechanics of an Aramany Class IV obturator prosthesis with finite element analysis and a digital 3-dimensional (3-D) model developed from a computed tomography scan; bone stress was evaluated according to the load placed on the prosthesis. Material and methods. A 3-D model of an Aramany Class IV maxillary resection and prosthesis was constructed. This model was used to develop a finite element mesh. A 120 N load was applied to the occlusal and incisal platforms corresponding to the prosthetic teeth. Qualitative analysis was based on the scale of maximum principal stress; values obtained through quantitative analysis were expressed in MPa. Results. Under posterior load, tensile and compressive stresses were observed; the tensile stress was greater than the compressive stress, regardless of the bone region, and the greatest compressive stress was observed on the anterior palate near the midline. Under an anterior load, tensile stress was observed in all of the evaluated bone regions; the tensile stress was greater than the compressive stress, regardless of the bone region. Conclusions. The Aramany Class IV obturator prosthesis tended to rotate toward the surgical resection when subjected to posterior or anterior loads. The amount of tensile and compressive stress caused by the Aramany Class IV obturator prosthesis did not exceed the physiological limits of the maxillary bone tissue. (J Prosthet Dent 2012;107:336-342)

Root and Root Canal Morphology of Four-rooted Maxillary Second Molars: A Micro-Computed Tomography Study

Introduction: This study examined the anatomy of 4-rooted maxillary second molars by using micro computed tomography. Methods: Twenty-five 4-rooted maxillary second molars were scanned to evaluate the size and curvature of the roots; the distance and spatial configuration between some anatomical landmarks; the number of root canals and the position of apical foramina; the occurrence of fusion of roots and enamel pearls; the configuration of the canal at the apical third; the cross-sectional appearance, the volume, and surface area of the root canals. Data were compared by using analysis of variance post hoc Tukey test (alpha = 0.05). Results: The specimens were classified as types I (n = 16), II (n = 7), and III (n = 2). The size of the roots was similar (P > .05), and most of them presented straight with 1 canal, except the mesiobuccal that showed 2 canals in 24% of the samples. The configuration of the pulp chamber was mostly irregular quadrilateral-shaped. The lowest mean distance of the orifices was observed between the buccal roots (P < .05). Accessory canals were present mostly in the apical third. Location of the apical foramina varied considerably. Fusion of roots and enamel pearls occurred in 44% and 8% of the samples, respectively. Mean distance from the pulp chamber floor to the furcation was 2.15 +/- 0.57 mm. No statistical differences were found in the bi-dimensional and 3-dimensional analyses (P > .05). Conclusions: All analyzed parameters showed differences between roots, except for the length of the roots, the configuration of the canals at the apical third, cross-sectional appearance, volume, and surface area of the canals. (J Endod 2012;38:977-982)

New Equation for Prediction of Reverse Remodeling after Cardiac Resynchronization Therapy

Objectives: To integrate data from two-dimensional echocardiography (2D ECHO), three-dimensional echocardiography (3D ECHO), and tissue Doppler imaging (TDI) for prediction of left ventricular (LV) reverse remodeling (LVRR) after cardiac resynchronization therapy (CRT). It was also compared the evaluation of cardiac dyssynchrony by TDI and 3D ECHO. Methods: Twenty-four consecutive patients with heart failure, sinus rhythm, QRS = 120 msec, functional class III or IV and LV ejection fraction (LVEF) = 0.35 underwent CRT. 2D ECHO, 3D ECHO with systolic dyssynchrony index (SDI) analysis, and TDI were performed before, 3 and 6 months after CRT. Cardiac dyssynchrony analyses by TDI and SDI were compared with the Pearson's correlation test. Before CRT, a univariate analysis of baseline characteristics was performed for the construction of a logistic regression model to identify the best predictors of LVRR. Results: After 3 months of CRT, there was a moderate correlation between TDI and SDI (r = 0.52). At other time points, there was no strong correlation. Nine of twenty-four (38%) patients presented with LVRR 6 months after CRT. After logistic regression analysis, SDI (SDI > 11%) was the only independent factor in the prediction of LVRR 6 months of CRT (sensitivity = 0.89 and specificity = 0.73). After construction of receiver operator characteristic (ROC) curves, an equation was established to predict LVRR: LVRR =-0.4LVDD (mm) + 0.5LVEF (%) + 1.1SDI (%), with responders presenting values >0 (sensitivity = 0.67 and specificity = 0.87). Conclusions: In this study, there was no strong correlation between TDI and SDI. An equation is proposed for the prediction of LVRR after CRT. Although larger trials are needed to validate these findings, this equation may be useful to candidates for CRT. (Echocardiography 2012;29:678-687)

Prediction and probability of neonatal outcome in isolated congenital diaphragmatic hernia using multiple ultrasound parameters

Objectives To evaluate the accuracy and probabilities of different fetal ultrasound parameters to predict neonatal outcome in isolated congenital diaphragmatic hernia (CDH). Methods Between January 2004 and December 2010, we evaluated prospectively 108 fetuses with isolated CDH (82 left-sided and 26 right-sided). The following parameters were evaluated: gestational age at diagnosis, side of the diaphragmatic defect, presence of polyhydramnios, presence of liver herniated into the fetal thorax (liver-up), lung-to-head ratio (LHR) and observed/expected LHR (o/e-LHR), observed/expected contralateral and total fetal lung volume (o/e-ContFLV and o/e-TotFLV) ratios, ultrasonographic fetal lung volume/fetal weight ratio (US-FLW), observed/expected contralateral and main pulmonary artery diameter (o/e-ContPA and o/eMPA) ratios and the contralateral vascularization index (Cont-VI). The outcomes were neonatal death and severe postnatal pulmonary arterial hypertension (PAH). Results Neonatal mortality was 64.8% (70/108). Severe PAH was diagnosed in 68 (63.0%) cases, of which 63 died neonatally (92.6%) (P < 0.001). Gestational age at diagnosis, side of the defect and polyhydramnios were not associated with poor outcome (P > 0.05). LHR, o/eLHR, liver-up, o/e-ContFLV, o/e-TotFLV, US-FLW, o/eContPA, o/e-MPA and Cont-VI were associated with both neonatal death and severe postnatal PAH (P < 0.001). Receiver-operating characteristics curves indicated that measuring total lung volumes (o/e-TotFLV and US-FLW) was more accurate than was considering only the contralateral lung sizes (LHR, o/e-LHR and o/e-ContFLV; P < 0.05), and Cont-VI was the most accurate ultrasound parameter to predict neonatal death and severe PAH (P < 0.001). Conclusions Evaluating total lung volumes is more accurate than is measuring only the contralateral lung size. Evaluating pulmonary vascularization (Cont-VI) is the most accurate predictor of neonatal outcome. Estimating the probability of survival and severe PAH allows classification of cases according to prognosis. Copyright (C) 2011 ISUOG. Published by John Wiley & Sons, Ltd.

SAG2A protein from Toxoplasma gondii interacts with both innate and adaptive immune compartments of infected hosts

Abstract Background Toxoplasma gondii is an intracellular parasite that causes relevant clinical disease in humans and animals. Several studies have been performed in order to understand the interactions between proteins of the parasite and host cells. SAG2A is a 22 kDa protein that is mainly found in the surface of tachyzoites. In the present work, our aim was to correlate the predicted three-dimensional structure of this protein with the immune system of infected hosts. Methods To accomplish our goals, we performed in silico analysis of the amino acid sequence of SAG2A, correlating the predictions with in vitro stimulation of antigen presenting cells and serological assays. Results Structure modeling predicts that SAG2A protein possesses an unfolded C-terminal end, which varies its conformation within distinct strain types of T. gondii. This structure within the protein shelters a known B-cell immunodominant epitope, which presents low identity with its closest phyllogenetically related protein, an orthologue predicted in Neospora caninum. In agreement with the in silico observations, sera of known T. gondii infected mice and goats recognized recombinant SAG2A, whereas no serological cross-reactivity was observed with samples from N. caninum animals. Additionally, the C-terminal end of the protein was able to down-modulate pro-inflammatory responses of activated macrophages and dendritic cells. Conclusions Altogether, we demonstrate herein that recombinant SAG2A protein from T. gondii is immunologically relevant in the host-parasite interface and may be targeted in therapeutic and diagnostic procedures designed against the infection.

Morphologic micro–computed tomography analysis of mandibular premolars with three root canals

Introduction: This study aimed to describe the anatomy of mandibular premolars with type IX canal configuration by using micro–computed tomography. Methods: Mandibular premolars with radicular grooves (n = 105) were scanned, and 16 teeth with type IX configuration were selected. Number and location of canals, distances between anatomic landmarks, occurrence of apical delta, root canal fusion, and furcation canals, as well as 2-dimensional (area, perimeter, roundness, major and minor diameters) and 3-dimensional (volume, surface area, and structuremodel index) analysis were performed. Data were statistically compared by using analysis of variance and Kruskal-Wallis tests (a = 0.05). Results: Overall, specimens had 1 root with a main canal that divided into mesiobuccal, distobuccal, and lingual canals at the furcation level. Mean length of the teeth was 22.9 2.06 mm, and the configuration of the pulp chamber was mostly triangle-shaped. Mean distances from the furcation to the apex and cementoenamel junction were 9.14 2.07 and 5.59 2.19 mm, respectively. Apical delta, root canal fusion, and furcation canals were present in 4, 5, and 10 specimens, respectively. No statistical differences were found in the 2-dimensional and 3-dimensional analyses between root canals (P > .05). Conclusions: Type IX configuration of the root canal system was found in 16 of 105 mandibular premolars with radicular grooves. Most of the specimens had a triangle-shaped pulp chamber. Within this anatomic configuration, complexities of the root canal systems such as the presence of furcation canals, fusion of canals, oval-shaped canals in the apical third, small orifices at the pulp chamber level, and apical delta were also observed

PepT1 mRNA expression levels in sea bream (Sparus aurata) fed different plant protein sources

[EN] The expression and regulation of intestinal oligopeptide transporter (PepT)-1 when vegetable sources are used as a substitute for fish meal in the diet of marine fish has not yet been explored. In the present study, as part of our ongoing work on elucidating PepT1 gene expression in relation to different dietary treatments, we have now isolated and deposited in Genbank database (accession no. GU733710) a cDNA sequence representing the PepT1 in the sea bream (Sparus aurata). The ?de novo? prediction of the three-dimensional structure of PepT1 protein is presented. We also analyzed diet-induced changes in the expression of PepT1 mRNA via real-time RT-PCR using the standard curve method. Sea bream were fed for 140 days with one of the following four diet formulations (43% protein/21% lipid): a control fast growth-promoting diet (C), and three diets with the same formulation but in which 15% of the fish meal was substituted by protein concentrates either from lupine (LPC), chick pea (CPC), or green pea (PPC). Fish fed PPC had significantly (p < 0.05) lower levels of PepT1 transcripts in the proximal intestine than the controls, whereas PepT1 transcript levels in fish fed LPC or CPC were not significantly different from the controls. Although growth was similar between fish fed with different diets during the first 72 days of feeding, growth of the fish fed with PPC was reduced during the second part of the trial and was significantly (p < 0.05) lower than fish fed LPC and CPC diets by the end of the experiment. Correlation between these results and fish growth performances highlights that the intestinal PepT1 mRNA level may serve as a useful marker of the dietary protein quality and absorption efficiency.

Stem Cells as a therapy for myocardial infarction in animal models

Advances in stem cell biology have challenged the notion that infarcted myocardium is irreparable. The pluripotent ability of stem cells to differentiate into specialized cell lines began to garner intense interest within cardiology when it was shown in animal models that intramyocardial injection of bone marrow stem cells (MSCs), or the mobilization of bone marrow stem cells with spontaneous homing to myocardium, could improve cardiac function and survival after induced myocardial infarction (MI) [1, 2]. Furthermore, the existence of stem cells in myocardium has been identified in animal heart [3, 4], and intense research is under way in an attempt to clarify their potential clinical application for patients with myocardial infarction. To date, in order to identify the best one, different kinds of stem cells have been studied; these have been derived from embryo or adult tissues (i.e. bone marrow, heart, peripheral blood etc.). Currently, three different biologic therapies for cardiovascular diseases are under investigation: cell therapy, gene therapy and the more recent “tissue-engineering” therapy . During my Ph.D. course, first I focalised my study on the isolation and characterization of Cardiac Stem Cells (CSCs) in wild-type and transgenic mice and for this purpose I attended, for more than one year, the Cardiovascular Research Institute of the New York Medical College, in Valhalla (NY, USA) under the direction of Doctor Piero Anversa. During this period I learnt different Immunohistochemical and Biomolecular techniques, useful for investigating the regenerative potential of stem cells. Then, during the next two years, I studied the new approach of cardiac regenerative medicine based on “tissue-engineering” in order to investigate a new strategy to regenerate the infracted myocardium. Tissue-engineering is a promising approach that makes possible the creation of new functional tissue to replace lost or failing tissue. This new discipline combines isolated functioning cells and biodegradable 3-dimensional (3D) polymeric scaffolds. The scaffold temporarily provides the biomechanical support for the cells until they produce their own extracellular matrix. Because tissue-engineering constructs contain living cells, they may have the potential for growth and cellular self-repair and remodeling. In the present study, I examined whether the tissue-engineering strategy within hyaluron-based scaffolds would result in the formation of alternative cardiac tissue that could replace the scar and improve cardiac function after MI in syngeneic heterotopic rat hearts. Rat hearts were explanted, subjected to left coronary descending artery occlusion, and then grafted into the abdomen (aorta-aorta anastomosis) of receiving syngeneic rat. After 2 weeks, a pouch of 3 mm2 was made in the thickness of the ventricular wall at the level of the post-infarction scar. The hyaluronic scaffold, previously engineered for 3 weeks with rat MSCs, was introduced into the pouch and the myocardial edges sutured with few stitches. Two weeks later we evaluated the cardiac function by M-Mode echocardiography and the myocardial morphology by microscope analysis. We chose bone marrow-derived mensenchymal stem cells (MSCs) because they have shown great signaling and regenerative properties when delivered to heart tissue following a myocardial infarction (MI). However, while the object of cell transplantation is to improve ventricular function, cardiac cell transplantation has had limited success because of poor graft viability and low cell retention, that’s why we decided to combine MSCs with a biopolimeric scaffold. At the end of the experiments we observed that the hyaluronan fibres had not been substantially degraded 2 weeks after heart-transplantation. Most MSCs had migrated to the surrounding infarcted area where they were especially found close to small-sized vessels. Scar tissue was moderated in the engrafted region and the thickness of the corresponding ventricular wall was comparable to that of the non-infarcted remote area. Also, the left ventricular shortening fraction, evaluated by M-Mode echocardiography, was found a little bit increased when compared to that measured just before construct transplantation. Therefore, this study suggests that post-infarction myocardial remodelling can be favourably affected by the grafting of MSCs delivered through a hyaluron-based scaffold

Studio di biomateriali usati come scaffold per Tissue Engineering e loro caratterizzazione con tecniche spettroscopiche vibrazionali e di analisi termica

This research investigated someone of the main problems connected to the application of Tissue Engineering in the prosthetic field, in particular about the characterization of the scaffolding materials and biomimetic strategies adopted in order to promote the implant integration. The spectroscopic and thermal analysis techniques were usefully applied to characterize the chemico-physical properties of the materials such as – crystallinity; – relative composition in case of composite materials; – Structure and conformation of polymeric and peptidic chains; – mechanism and degradation rate; – Intramolecular and intermolecular interactions (hydrogen bonds, aliphatic interactions). This kind of information are of great importance in the comprehension of the interactions that scaffold undergoes when it is in contact with biological tissues; this information are fundamental to predict biodegradation mechanisms and to understand how chemico-physical properties change during the degradation process. In order to fully characterize biomaterials, this findings must be integrated by information relative to mechanical aspects and in vitro and in vivo behavior thanks to collaborations with biomedical engineers and biologists. This study was focussed on three different systems that correspond to three different strategies adopted in Tissue Engineering: biomimetic replica of fibrous 3-D structure of extracellular matrix (PCL-PLLA), incorporation of an apatitic phase similar to bone inorganic phase to promote biomineralization (PCL-HA), surface modification with synthetic oligopeptides that elicit the interaction with osteoblasts. The characterization of the PCL-PLLA composite underlined that the degradation started along PLLA fibres, which are more hydrophylic, and they serve as a guide for tissue regeneration. Moreover it was found that some cellular lines are more active in the colonization of the scaffold. In the PCL-HA composite, the weight ratio between the polymeric and the inorganic phase plays an essential role both in the degradation process and in the biomineralization of the material. The study of self-assembling peptides allowed to clarify the influence of primary structure on intermolecular and intermolecular interactions, that lead to the formation of the secondary structure and it was possible to find a new class of oligopeptides useful to functionalize materials surface. Among the analytical techniques used in this study, Raman vibrational spectroscopy played a major role, being non-destructive and non-invasive, two properties that make it suitable to degradation studies and to morphological characterization. Also micro-IR spectroscopy was useful in the comprehension of peptide structure on oxidized titanium: up to date this study was one of the first to employ this relatively new technique in the biomedical field.

Anwendung der konfokalen Laser-Scanning-Mikroskopie zur Charakterisierung der Struktur von Zähnen und von oberflächenmodifiziertem Titan für Knochenimplantate

Zusammenfassung Mittels Fluoreszenzfarbstoffen können Strukturen sichtbar gemacht werden, die auf kon-ventionellem Weg nicht, oder nur schwer darzustellen sind. Besonders in Kombination mit der Konfokalen Laser Scanning Mikroskopie eröffnen sich neue Wege zum spezifischen Nachweis unterschiedlichster Komponenten biologischer Proben und gegebenenfalls deren dreidimensionale Widergabe.Die Visualisierung des Proteinanteils des Zahnhartgewebes kann mit Hilfe chemisch kopplungsfähiger Fluorochrome durchgeführt werden. Um zu zeigen, daß es sich bei dieser Markierung nicht um unspezifische Adsorption des Farbstoffes handelt, wurde zur Kontrolle die Proteinkomponente der Zahnproben durch enzymatischen Verdau beseitigt. Derartig behandelte Präparate wiesen eine sehr geringe Anfärbbarkeit auf.Weiterführend diente diese enzymatische Methode als Negativkontrolle zum Nachweis der Odontoblastenfortsätze im Dentin bzw. im Bereich der Schmelz-Dentin-Grenze. Hiermit konnte differenziert werden zwischen reinen Reflexionsbildern der Dentinkanäle und den Zellausläufern deren Membranen gezielt durch lipophile Fluoreszenzfarbstoffe markiert wurden.In einem weiteren Ansatz konnte gezeigt werden, daß reduzierte und daher nichtfluoreszente Fluoresceinabkömmlinge geeignet sind, die Penetration von Oxidationsmitteln (hier H2O2) in den Zahn nachzuweisen. Durch Oxidation dieser Verbindungen werden fluoreszierende Produkte generiert, die den Nachweis lieferten, daß die als Zahnbleichmittel eingesetzten Mittel rasch durch Schmelz und Dentin bis in die Pulpahöhle gelangen können.Die Abhängigkeit der Fluoreszenz bestimmter Fluorochrome von deren chemischer Um-gebung, im vorliegenden Fall dem pH-Wert, sollte eingesetzt werden, um den Säuregrad im Zahninneren fluoreszenzmikroskopisch darzustellen. Hierbei wurde versucht, ein ratio-metrisches Verfahren zu entwickeln, mit dem die pH-Bestimmung unter Verwendung eines pH-abhängigen und eines pH-unabhängigen Fluorochroms erfolgt. Diese Methode konnte nicht für diese spezielle Anwendung verifiziert werden, da Neutralisationseffekte der mineralischen Zahnsubstanz (Hydroxylapatit) die pH-Verteilung innerhalb der Probe beeinflußen. Fluoreszenztechniken wurden ebenfalls ergänzend eingesetzt zur Charakterisierung von kovalent modifizierten Implantatoberflächen. Die, durch Silanisierung von Titantestkörpern mit Triethoxyaminopropylsilan eingeführten freien Aminogruppen konnten qualitativ durch den Einsatz eines aminspezifischen Farbstoffes identifiziert werden. Diese Art der Funktionalisierung dient dem Zweck, Implantatoberflächen durch chemische Kopplung adhäsionsvermittelnder Proteine bzw. Peptide dem Einheilungsprozeß von Implantaten in den Knochen zugänglicher zu machen, indem knochenbildende Zellen zu verbessertem Anwachsverhalten stimuliert werden. Die Zellzahlbestimmung im Adhäsionstest wurde ebenfalls mittels Fluoreszenzfarbstoffen durchgeführt und lieferte Ergebnisse, die belegen, daß die durchgeführte Modifizierung einen günstigen Einfluß auf die Zelladhäsion besitzt.

Untersuchung der Strukturdynamik arbeitender F1-ATPase und ATP-Synthase aus Micrococcus luteus in Einzelschußexperimenten mit Synchrotronstrahlung

ZusammenfassungDie ATP-Synthase koppelt im Energiestoffwechsel der Zellen den Protonentransport über die biologische Membran mit der Synthese des energiespeichernden Moleküls ATP aus ADP und Phosphat. ATP-Synthasen bestehen aus 2 Subkomplexen, wobei der katalytische F1-Teil von der membranständigen Domäne abgelöst werden kann und nur zur ATP-Hydrolyse fähig ist. Der hochkooperative Reaktionsmechanismus der dreizentrigen ATP-Synthasen ist weitgehend unklar.Im Rahmen dieser Arbeit wurde der ATP-Synthasekomplex und ihr wasserlösliches katalytisches F1-Fragment aus Micrococcus luteus in präparativem Maßstab mittels chromatographischer Trennmethoden isoliert. Die Überprüfung der Funktionalität beider Enzyme erfolgte mit enzymatischen Methoden. Durch zeitaufgelöste Röntgenkleinwinkelstreuung wurde die Strukturdynamik der arbeitenden ATP-Synthase und ihres F1-Fragmentes aus Micrococcus luteus im Laufe des ATP-Hydrolysezyklus untersucht. Diese Methode diente zum Nachweis weiträumiger Konformationsänderungen innerhalb der arbeitenden Enzyme unter nativen physiologischen Bedingungen. Die zeitaufgelösten Streuexperimente fanden an der ESRF (Europäische Synchrotronstrahlungsquelle) in Grenoble (F) statt. Dort wurden für beide Enzyme im Laufe des ATP-Hydrolysezykus molekulare Bewegungen nachgewiesen. Als Referenz zu den zeitaufgelösten Messungen dienten statische Messungen zur Strukturuntersuchung der Proteine am schwächeren DESY. Anhand dieser Strukturdaten wurden Molekülmodelle der F1-ATPase und ATP-Synthase aus Micrococcus luteus konstruiert. Das Molekülmodell der F1-ATPase war die Grundlage zur Modellierung einzelner Teilschritte des ATP-Hydrolysezyklus bei 20°C. Die experimentellen Daten wurden mit einer Kippbewegung der membranseitigen Domäne der katalytischen b-Untereinheiten der F1-ATPase während des ATP-Hydrolysezyklus interpretiert.

Tropospheric photochemistry of ozone, its precursors and the hydroxyl radical

Zusammenfassung Ein 3-dimensionales globales Modell der unterenAtmosphäre wurde für die Untersuchung derOzonchemie, sowie der Chemie des Hydroxylradikals (OH) undwichtiger Vorläufersubstanzen, wie reaktiverStickstoffverbindungen und Kohlenwasserstoffe, verwendet.Hierfür wurde die Behandlung vonNicht-Methan-Kohlenwasserstoffen (NMKW) hinzugefügt,was auch die Entwicklung einer vereinfachten Beschreibungihrer Chemie, sowie die Erfassung von Depositionsprozessenund Emissionen erforderte. Zur Lösung der steifengewöhnlichen Differentialgleichungen der Chemie wurdeeine schnelles Rosenbrock-Verfahren eingesetzt, das soimplementiert wurde, dass die Modell-Chemie fürzukünftige Studien leicht abgeändert werden kann. Zur Evaluierung des Modells wurde ein umfangreicherVergleich der Modellergebnisse mit Bodenmessungen, sowieFlugzeug-, Sonden- und Satelliten-Daten durchgeführt.Das Modell kann viele Aspekte der Beobachtungen derverschieden Substanzen realistisch wiedergeben. Es wurdenjedoch auch einige Diskrepanzen festgestellt, die Hinweiseauf fehlerhafte Emissionsfelder oder auf die Modell-Dynamikund auch auf fehlende Modell-Chemie liefern. Zur weiteren Untersuchung des Einflusses verschiedenerStoffgruppen wurden drei Läufe mit unterschiedlichkomplexer Chemie analysiert. Durch das Berücksichtigender NMKW wird die Verteilung mehrerer wichtiger Substanzensignifikant beeinflusst, darunter z.B. ein Anstieg desglobalen Ozons. Es wurde gezeigt, dass die biogene SubstanzIsopren etwa die Hälfte des Gesamteffekts der NMKWausmachte (mehr in den Tropen, weniger anderswo). In einer Sensitivitätsstudie wurden die Unsicherheitenbei der Modellierung von Isopren weitergehend untersucht.Dabei konnte gezeigt werden, dass die Unsicherheit beiphysikalischen Aspekten (Deposition und heterogene Prozesse)ebenso groß sein kann, wie die aus dem chemischenGasphasen-Mechanismus stammende, welche zu globalbedeutsamen Abweichungen führte. Lokal können sichnoch größere Abweichungen ergeben. Zusammenfassend kann gesagt werden, dass die numerischenStudien dieser Arbeit neue Einblicke in wichtige Aspekte derPhotochemieder Troposphäre ergaben und in Vorschläge fürweiter Studien mündeten, die die wichtigsten gefundenenUnsicherheiten weiter verringern könnten.

Polyelectrolytes and their counterions studied by EPR spectroscopy

In this thesis methods of EPR spectroscopy were used to investigate polyion-counterion interactions in polyelectrolyte solutions. The fact that EPR techniques are local methods is exploited and by employing spin-carrying (i.e., EPR-active) probe ions it is possible to examine polyelectrolytes from the counterions’ point of view. It was possible to gain insight into i) the dynamics and local geometry of counterion attachment, ii) conformations and dynamics of local segments of the polyion in an indirect manner, and iii) the spatial distribution of spin probe ions that surround polyions in solution. Analysis of CW EPR spectra of dianion nitroxide spin probe Fremy’s salt (FS, potassium nitrosodisulfonate) in solutions of cationic PDADMAC polyelectrolyte revealed that FS ions and PDADMAC form transient ion pairs with a lifetime of less than 1 ns. This effect was termed as dynamic electrostatic attachment (DEA). By spectral simulation taking into account the rotational dynamics as a uniaxial Brownian reorientation, also the geometry of the attached state could be characterized. By variation of solvent, the effect of solvent viscosity and permittivity were investigated and indirect information of the polyelectrolyte chain motion was obtained. Furthermore, analysis of CW EPR data also indicates that in mixtures of organic solvent/water PDADMAC chains are preferentially solvated by the organic solvent molecules, while in purely aqueous mixtures the PDADMAC chain segments were found in different conformations depending on the concentration ratio R of FS counterions to PDADMAC repeat units.Broadenings in CW EPR spectra of FS ions were assigned to spin-exchange interaction and hence contain information on the local concentrations and distributions of the counterions. From analysis of these broadenings in terms of a modified cylindrical cell approach of polyelectrolyte theory, radial distribution functions for the FS ions in the different solvents were obtained. This approach breaks down in water above a threshold value of R, which again indicates that PDADMAC chain conformations are altered as a function of R. Double electron-electron resonance (DEER) measurements of FS ions were carried out to probe the distribution of attached counterions along polyelectrolyte chains. For a significant fraction of FS spin probes in solution with a rigid-rod model polyelectrolyte containing charged Ru2+-centers, a bimodal distance distribution was found that nicely reproduced the spacings of direct and next-neighbor Ru2+-centers along the polyelectrolyte: 2.35 and 4.7 nm. For the system of FS/PDADMAC, DEER data could be simulated by assuming a two-state distribution of spin probes, one state corresponding to a homogeneous (3-dimensional) distribution of spin probes in the polyelectrolyte bulk and the other to a linear (1-dimensional) distribution of spin probes that are electrostatically condensed along locally extended PDADMAC chain segments. From this analysis it is suggested that the PDADMAC chains form locally elongated structures of a size of at least ~5 nm.

Sistemi strutturali cellulari a pareti portanti in cemento armato gettato in opera realizzate con la tecnologia del pannello di supporto in polistirene

In questa Tesi di Dottorato di Ricerca sono state studiate le caratteristiche strutturali e le relative prestazioni dei sistemi strutturali cellulari a pareti tozze di tipo sandwich in c. a. gettato in opera realizzate con la tecnologia del pannello di supporto in polistirene. Tali sistemi strutturali sono caratterizzati da numerose peculiarità; infatti, (i) il comportamento globale delle strutture risulta essere di tipo cellulare, e, le pareti che costituiscono il sistema resistente alle azioni sia orizzontali che verticali risultano essere: (ii) tozze, (iii) di tipo sandwich e caratterizzate da: (iv) basse percentuali di armatura, (v) ridotti tassi di lavoro a sforzo assiale e (vi) stesso quantitativo di armatura orizzontale e verticale. Date le specificità dei sistemi strutturali in esame, si è, in primo luogo, cercato di inquadrare le peculiarità strutturali sopra elencate nell’ambito scientifico. Ciò ha consentito di riscontrare una profonda carenza nella conoscenza relativa al comportamento di tali strutture specialmente nei confronti delle azioni orizzontali di tipo sismico. Pertanto i due principali obiettivi di questa Tesi di Dottorato sono stati: (1) la sistematizzazione scientifica e la relativa interpretazione di 10 anni di prove sperimentali condotte sul sistema strutturale in esame; e (2) la progettazione, la realizzazione e l’interpretazione preliminare dei risultati di una prova su tavola vibrante di una struttura a tre piani con pianta rettangolare, realizzata con la tecnologia del pannello di supporto in polistirene (la prova è stata effettuata nell’ambito del progetto di ricerca Europeo SERIES). Questa ricerca ha dunque consentito di far luce sul comportamento (in particolar modo, nei confronti delle azioni orizzontali di tipo sismico) dei sistemi strutturali composti da pareti tozze di tipo sandwich in c. a. gettato in opera realizzati con la tecnologia del pannello di supporto in polistirene.