Experimental Study on Friction between Saline Ice and Steel

Understanding the interaction of sea ice with offshore structures is of primary importance for the development of technology in cold climate regions. The rheological properties of sea ice (strength, creep, viscosity) as well as the roughness of the contact surface are the main factors influencing the type of interaction with a structure. A device was developed and designed and small scale laboratory experiments were carried out to study sea ice frictional interaction with steel material by means of a uniaxial compression rig. Sea-ice was artificially grown between a stainless steel piston (of circular cross section) and a hollow cylinder of the same material, coaxial to the former and of the same surface roughness. Three different values for the roughness were tested: 1.2, 10 and 30 μm Ry (maximum asperities height), chosen as representative values for typical surface conditions, from smooth to normally corroded steel. Creep tests (0.2, 0.3, 0.4 and 0.6 kN) were conducted at T = -10 ºC. By pushing the piston head towards the cylinder base, three different types of relative movement were observed: 1) the piston slid through the ice, 2) the piston slid through the ice and the ice slid on the surface of the outer cylinder, 3) the ice slid only on the cylinder surface. A cyclic stick-slip motion of the piston was detected with a representative frequency of 0.1 Hz. The ratio of the mean rate of axial displacement to the frequency of the stick-slip oscillations was found to be comparable to the roughness length (Sm). The roughness is the most influential parameter affecting the amplitude of the oscillations, while the load has a relevant influence on the their frequency. Guidelines for further investigations were recommended. Marco Nanetti - seloselo@virgilio.it

PTA e stenting carotideo: valutazione morfologica ed evolutiva, a breve e medio termine

In un periodo di tre anni è stato svolto un lavoro mirato alla valutazione delle complicanze correlate all’utilizzo dello stenting carotideo. Dopo la preparazione di un protocollo con definizione di tutti i fattori di rischio sono stati individuati i criteri di inclusione ed esclusione attraverso i quali arruolare i pazienti. Da Luglio 2004 a Marzo 2007 sono stati inclusi 298 pazienti e sono state valutate le caratteristiche della placca carotidea, con particolare riferimento alla presenza di ulcerazione e/o di stenosi serrata, la tortuosità dei vasi e il tipo di arco aortico oltre a tutti i fattori di rischio demografici e metabolici. E’ stato valutato quanto e se questi fattori di rischio incrementino la percentuale di complicanze della procedura di stenting carotideo. I pazienti arruolati sono stati suddivisi in due gruppi a seconda della morfologia della placca: placca complicata (placca con ulcera del diametro > di 2 mm e placca con stenosi sub occlusiva 99%) e placca non complicata. I due gruppi sono stati comparati in termini di epidemiologia, sintomatologia neurologica preoperatoria, tipo di arco, presenza di stenosi o ostruzione della carotide controlaterale, tipo di stent e di protezione cerebrale utilizzati, evoluzione clinica e risultati tecnici. I dati sono stati valutati mediante analisi statistica di regressione logistica multipla per evidenziare le variabili correlate con l’insuccesso. Dei 298 pazienti consecutivi sottoposti a stenting, 77 hanno mostrato una placca complicata (25,8%) e 221 una placca non complicata (74,2%). I due gruppi non hanno avuto sostanziali differenze epidemiologiche o di sintomatologia preoperatoria. Il successo tecnico si è avuto in 272 casi (91,2%) e sintomi neurologici post-operatosi si sono verificati in 23 casi (23.3%). Tutti i sintomi sono stati temporanei. Non si sono avute differenze statisticamente significative tra i due gruppi in relazione alle complicanze neurologiche e ai fallimenti tecnici. L’età avanzata è correlata ad un incremento dei fallimenti tecnici. I risultati dello studio portano alla conclusione che la morfologia della placca non porta ad un incremento significativo dei rischi correlati alla procedura di stenting carotideo e che l’indicazione alla CAS può essere posta indipendentemente dalla caratteristica della placca.

Transformation von Schulsystemen am Beispiel des Freistaates Sachsen

Die vorliegende Arbeit beschäftigt sich mit dem Transformationsprozess von Schulsystemen, den die ostdeutschen Länder mit dem Erlangen der deutschen Vereinigung bewältigen mussten am Beispiel der Mittelschule im Freistaat Sachsen. Dieser Prozess wird mit Fokus auf die Sekundarstufe I und darin insbesondere auf die Mittelschule als „neue Schulform“ nachge-zeichnet und analysiert. Die skizzierten Entwicklungslinien werden aufgegriffen und am Beispiel dieses konkreten bildungspolitischen Vorhabens, des Aufbaus einer neuen Schulform und eines zweigliedrigen Schulsystems, vor dem Hintergrund der widersprüchlichen Aufgabe, ein Schulsystem zu reformieren und dabei weder Ausgangspunkt noch Ziel der Reform genau bestimmen zu können, diskutiert und in ihrer Wirkung bewertet. Dabei werden die Bedeutung der Einzelschule bei der Transformation des Schulsystems herausgearbeitet, die Wirkung von Modellversuchsergebnissen für die weitere Gestaltung des Schulsystems kritisch untersucht und schließlich danach gefragt, welche Form von Steuerung einzelne Schulen brauchen, um sich ansprechend der sich verschärfenden Anforderung an Bildung optimal entwickeln zu können und welche Art der bildungspolitischen Steuerung des Gesamtsystems erforderlich ist, um Qualitätssicherung und Qualitätsentwicklung im Kontext der internationalen Leistungsvergleichsstudien zu realisieren. Die Analysen des Transformationsprozesses stehen unter dem Einfluss der Ergebnisse der ersten PISA-Studie und der sich daran anschließenden bildungspolitischen Diskussionen über die Qualität von Schule in Deutschland im internationalen Vergleich. Damit wird die Perspektive über den Einigungsprozess hinaus geöffnet und an bestehende Forschungsergebnisse angeknüpft, wonach sich der deutsch-deutsche Einigungsprozess hinsichtlich der mit ihm vollzogenen Öffnung in der Gestaltung der Schulverhältnisse als ein Probestück der Bundesrepublik für den europäischen Einigungsprozess verstehen lässt und sich in diesem Sinne auch bewährt hat. Mit den Debatten um Bildung und vor allem um Qualität von Bildung in der Folge der länderübergreifenden Vergleichsstudien zeigt sich aber, dass die Themen auf der bildungspolitischen Agenda raschen Veränderungen unterworfen sind. Im Lichte dieser gesellschaftlichen Debatte um die Qualität und die Steuerung von Bildung werden abschließend die Herausforderungen für die Schulforschung vor dem Hintergrund globalisierter Leistungsanforderungen und erweiterter Selbstverantwortung der Einzelschulen skizziert.

Update on macrophage clearance of inhaled micro- and nanoparticles

Lung macrophages, that is, the intravascular, interstitial, pleural, and surface macrophages, are part of the mononuclear phagocyte system. They are derived from the hematopoietic stem cell in the bone marrow with the monocytes as their putative precursors. Macrophages residing on the inner surfaces of the lungs and immersed within the lung lining layer, that is, the alveolar and the airway macrophages, are constantly exposed to the environment; it is those cells that are recognized as first line of cellular host defense.

Safety, effectiveness and predictors for early reoperation in therapeutic and prophylactic vertebroplasty: short-term results of a prospective case series of patients with osteoporotic vertebral fractures

Abstract Introduction Vertebroplasty (VP) is a cost-efficient alternative to kyphoplasty; however, regarding safety and vertebral body (VB) height restoration, it is considered inferior. We assessed the safety and efficacy of VP in alleviating pain, improving quality of life (QoL) and restoring alignment. Methods In a prospective monocenter case series from May 2007 until July 2008, there were 1,408 vertebroplasties performed during 319 interventions in 306 patients with traumatic, lytic and osteoporotic fractures. The 249 interventions in 233 patients performed because of osteoporotic vertebral fractures were analyzed regarding demographics, treatment and radiographic details, pain alleviation (VAS), QoL improvement (NASS and EQ-5D), complications and predictors for new fractures requiring a reoperation. Results The osteoporotic patient sample consisted of 76.7% (179) females with a median age of 80 years. A total of 54 males had a median age of 77 years. On average, there were 1.8 VBs fractured and 5 VBs treated. The preoperative pain was assessed by the visual analog scale (VAS) and decreased from 54.9 to 40.4 pts after 2 months and 31.2 pts after 6 months. Accordingly, the QoL on the EQ-5D measure (−0.6 to 1) improved from 0.35 pts before surgery to 0.56 pts after 2 and to 0.68 pts after 6 months. The preoperative Beck Index (anterior height/posterior height) improved from a mean of 0.64 preoperative to 0.76 postoperative, remained stable at 2 months and slightly deteriorated to 0.72 at 6 months postoperatively. There were cement leakages in 26% of the fractured VBs and in 1.4% of the prophylactically cemented VBs; there were symptoms in 4.3%, and most of them were temporary hypotension and one pulmonary cement embolism that remained asymptomatic. The univariate regression model revealed a tendency for a reduced risk for new or refractures on radiographs (OR = 2.61, 95% CI 0.92–7.38, p = 0.12) and reoperations (OR = 2.9, 95% CI 0.94–8.949, p = 0.1) when prophylactic augmentation was performed. The final multivariate regression model revealed male patients to have an about three times higher refracture risk (radiographic) (OR = 2.78, p = 0.02) at 6 months after surgery. Patients with a lumbar index fracture had an about three to five times higher refracture/reoperation risk than patients with a thoracic (OR = 0.33/0.35, p = 0.009/0.01) or thoracolumbar (OR = 0.32/0.22, p = 0.099/0.01) index fracture. Conclusion If routinely used, VP is a safe and efficacious treatment option for osteoporotic vertebral fractures with regard to pain relief and improvement of the QoL. Even segmental realignment can be partially achieved with proper patient positioning. Certain patient or fracture characteristics increase the risk for early radiographic refractures or new fractures, or a reoperation; a consequent prophylactic augmentation showed protective tendencies, but the study was underpowered for a final conclusion.

Subsecond fluorine-19 MRI of the lung

Minimal scan times in rapid fluorine-19 MRI using sulfur hexafluoride (SF6) have been on the order of 10 s. Because of the very short T1 relaxation time of SF6 (T1 = 1.65 ms), high receiver bandwidths are necessary to allow for a high number of excitations. Since high bandwidths cause high levels of electronic noise, SNR per acquisition has been too low to further reduce scan time. The purpose of this study was to investigate whether scan times could be reduced using hexafluoroethane (C2F6), a gas with a longer T1 (T1 = 7.9 ms) at a relatively low bandwidth of 488 Hz/pixel. Gradient-echo images were acquired during and after completion of the wash-in of a 70% C2F6- 30% O2 mixture. Peak SNR values of 16 and 7.9 were observed for coronal projection images acquired within 2 s and 260 ms, respectively. These results demonstrate that subsecond imaging is feasible using C2F6.

Effect of a recombinant N-terminal fragment of bactericidal/permeability-increasing protein (rBPI23) on cerebrospinal fluid inflammation induced by endotoxin

Endotoxin triggers the subarachnoid inflammation of gram-negative meningitis. This study examined the ability of a recombinant N-terminal fragment of bactericidal/permeability-increasing protein (rBPI23) to block endotoxin-induced meningitis in rabbits. Intracisternal (ic) injection of 10-20 ng of meningococcal endotoxin induced high cerebrospinal fluid (CSF) concentrations of tumor necrosis factor (TNF) and CSF pleocytosis and increased CSF lactate concentrations. ic administration of rBPI23 significantly reduced meningococcal endotoxin-induced TNF release into CSF (P < .005), lactate concentrations (P < .001), and CSF white blood cell counts (P < .01). No such effect was observed in animals receiving intravenous rBPI23. Concentrations of rBPI23 in CSF were high after ic administration but low or undetectable after systemic administration. Thus, high concentrations of rBPI23 can effectively neutralize meningococcal endotoxin in CSF, but low CSF concentrations after systemic administration currently limit its potential usefulness as adjunctive drug treatment in gram-negative meningitis.

DENITRIFICATION IN SOILS: FROM GENES TO ENVIRONMENTAL OUTCOMES

Denitrification is an important process of global nitrogen cycle as it removes reactive nitrogen from the biosphere, and acts as the primary source of nitrous oxide (N2O). This thesis seeks to gain better understanding of the biogeochemistry of denitrification by investigating the process from four different aspects: genetic basis, enzymatic kinetics, environmental interactions, and environmental consequences. Laboratory and field experiments were combined with modeling efforts to unravel the complexity of denitrification process under microbiological and environmental controls. Dynamics of denitrification products observed in laboratory experiments revealed an important role of constitutive denitrification enzymes, whose presence were further confirmed with quantitative analysis of functional genes encoding nitrite reductase and nitrous oxide reductase. A metabolic model of denitrification developed with explicit denitrification enzyme kinetics and representation of constitutive enzymes successfully reproduced the dynamics of N2O and N2 accumulation observed in the incubation experiments, revealing important regulatory effect of denitrification enzyme kinetics on the accumulation of denitrification products. Field studies demonstrated complex interaction of belowground N2O production, consumption and transport, resulting in two pulse pattern in the surface flux. Coupled soil gas diffusion/denitrification model showed great potential in simulating the dynamics of N2O below ground, with explicit representation of the activity of constitutive denitrification enzymes. A complete survey of environmental variables showed distinct regulation regimes on the denitrification activity from constitutive enzymes and new synthesized enzymes. Uncertainties in N2O estimation with current biogeochemical models may be reduced as accurate simulation of the dynamics of N2O in soil and surface fluxes is possible with a coupled diffusion/denitrification model that includes explicit representation of denitrification enzyme kinetics. In conclusion, denitrification is a complex ecological function regulated at cellular level. To assess the environmental consequences of denitrification and develop useful tools to mitigate N2O emissions require a comprehensive understanding of the regulatory network of denitrification with respect to microbial physiology and environmental interactions.