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

Los proyectos de vivienda de promoción oficial para la población civil en la ciudad de Las Palmas de Gran Canaria : 1939-1954

Programa de doctorado: Restauración y rehabilitación arquitectónica

Oral mucosal findings related to tobacco use and alcohol consumption: a study on Swiss army recruits involving self-reported and clinical data

PURPOSE: The aim of the present study was to assess the oral mucosal health status of young male adults (aged 18 to 24 years) in Switzerland and to correlate their clinical findings with self-reported risk factors such as tobacco use and alcohol consumption. MATERIALS AND METHODS: Data on the oral health status of 615 Swiss Army recruits were collected using a standardised self-reported questionnaire, followed by an intraoral examination. Positive clinical findings were classified as (1) common conditions and anatomical variants, (2) reactive lesions, (3) benign tumour lesions and (4) premalignant lesions. The main locations of the oral mucosal findings were recorded on a topographical classification chart. Using correlational statistics, the findings were further associated with the known risk factors such as tobacco use and alcohol consumption. RESULTS: A total of 468 findings were diagnosed in 327 (53.17%) of the 615 subjects. In total, 445 findings (95.09%) were classified as common conditions, anatomical variants and reactive soft-tissue lesions. In the group of reactive soft-tissue lesions, there was a significantly higher percentage of smokers (P < 0.001) and subjects with a combination of smoking and alcohol consumption (P < 0.001). Eight lesions were clinically diagnosed as oral leukoplakias associated with smokeless tobacco. The prevalence of precursor lesions in the population examined was over 1%. CONCLUSIONS: Among young male adults in Switzerland, a significant number of oral mucosal lesions can be identified, which strongly correlate with tobacco use. To improve primary and secondary prevention, young adults should therefore be informed more extensively about the negative effects of tobacco use on oral health.

Evidence, lack of evidence, controversy, and debate in the provision and performance of the surgery of acute type A aortic dissection

Acute type A aortic dissection is a lethal condition requiring emergency surgery. It has diverse presentations, and the diagnosis can be missed or delayed. Once diagnosed, decisions with regard to initial management, transfer, appropriateness of surgery, timing of operation, and intervention for malperfusion complications are necessary. The goals of surgery are to save life by prevention of pericardial tamponade or intra-pericardial aortic rupture, to resect the primary entry tear, to correct or prevent any malperfusion and aortic valve regurgitation, and if possible to prevent late dissection-related complications in the proximal and downstream aorta. No randomized trials of treatment or techniques have ever been performed, and novel therapies-particularly with regard to extent of surgery-are being devised and implemented, but their role needs to be defined. Overall, except in highly specialized centers, surgical outcomes might be static, and there is abundant room for improvement. By highlighting difficulties and controversies in diagnosis, patient selection, and surgical therapy, our over-arching goal should be to enfranchise more patients for treatment and improve surgical outcomes.

From Unsuitable Ally to Vital Parter: The Case of US-Korean Relations and The Vietnam War, 1954-1966

This is the history of the decade prior to the entrance of Korean troops into the Vietnam War, roughly covering the years 1953-1965.