SURF -A simulation model for the behaviour of oil slicks at sea

This report describes the SURF model, one of the basic models of the OPERA software package, which predicts the fate of oil spilled at sea. SURF is a fully operational computer model for describing the behaviour of oil slicks at sea. With necessary information, it may be used to simulate or to forecast the transport, the spreading and the aging of oil slicks. The model aims mainly at forecasting the behaviour of a pollution in case of an accident at sea. The information provided by the model (position and extent of the polluted area, oil characteristics) can efficiently help the authorities and the combating teams in making decisions on how to wrestle the pollution. But other model applications can be faced. For instance, knowing the zones where oil is extracted, carried or trans-shiped, the model can be used to investigate, a priori, the high risk areas

Anesthetic Neurotoxicity in Pediatric Patients

In recent years, an increasing number of publications have shown the negative effects of anesthetics on the developing brain and have made inquiries about anesthesia for pediatric patients in practice. Anesthesia is applied to millions of children for surgery, imaging, and other invasive procedures; the issue is very serious and concerns. In this chapter, experimental and clinical studies about the issue have been summarized. As a result, anesthetic drugs except alpha-2 adrenergic agonist anesthetic (NMDA antagonist or a GABA agonist) used in pediatric patients (especially if there is no painful situation) have potential neurotoxicity. Particularly, if anesthesia exposure was applied in the fragile period (the first 4 years) and if used at higher concentrations or repeated anesthesia application, adverse effects of anesthesia exposure on the developing brain have been claimed. But, the issue is not fully clarified yet

Fate of the Universe, Age of the Universe, Dark Matter, and the Decaying Vacuum Energy

It is shown that in the cosmological models based on a vacuum energy decaying as a^{-2}, where a is the scale factor of the universe, the fate of the universe in regard to whether it will collapse in future or expand forever is determined not by the curvature constant k but by an effective curvature constant k_{eff}. It is argued that a closed universe with k=1 may expand forever, in other words simulate the expansion dynamics of a flat or an open universe because of the possibility that k_{eff}=0 or -1, respectively. Two such models, in one of which the vacuum does not interact with matter and in another of which it does, are studied. It is shown that the vacuum equation of state p_{vac}= -\rho_{vac} may be realized in a decaying vacuum cosmology provided the vacuum interacts wuth matter. The optical depths for gravitational lensing as a function of the matter density and other parameters in the models are calculated at a source redshift of 2. The age of the universe is discussed and shown to be compatible with the new Hipparcos lower limit of 11Gyr. The possibility that a time-varying vacuum energy may serve as dark matter is suggested.Comment: AAS LaTex, 29 pages, published in the Astrophysical Journal, 520, 45, 199

Clinical Evaluation of Small Diameter Straumann Implants in Partially Edentulous Patients: A 5-Year Retrospective Study

Objective: The aim of the present study was to retrospectively evaluate small-diameter (3.3 mm) Straumann® dental implants placed in the maxilla or the mandible over a period of 5 years in function.Materials and Methods: Twenty- eight partially edentulous patients received a total of 48 implants over a 5-year period. After the standard healing period (3 to 6 months), the implants were restored with single-tooth prostheses or fixed partial dentures. All patients were followed according to a strict maintenance program with regular recalls. The cumulative survival rates of implants were analyzed and prosthetic complications were assessed.Results: After 5 years of function, one single 10-mm-long implant in the maxillary premolar region was lost because of recurrent peri-implant infection in a female patient. Two single 10-mm-long maxillary implants placed in the posterior region were lost due to body fracture. The cumulative 5-year survival rate of the implants was 93.75 %. The most common prosthetic complication was loosening of the occlusal screw.Conclusion: Within the limited observation period and the number of patients included in this study, it may be concluded that the use of small-diameter implants appears to be predictable if clinical guidelines are followed and appropriate prosthetic restorations are provided. However, it should be noted that fatigue fracture may occur

Relationship Between Air-Blowing Duration and Bond Strengths of Three Adhesive Systems to Dentin After Thermal Aging

The purpose was to evaluate the effect of air-blowing duration of three different adhesive systems on immediate or thermal aged resin-dentin shear bond strength (SBS). Human dentin surfaces were bonded with: one-step (Bond Force, BF), two-step (FL-Bond II, FLB) and three-step (Scotch Bond Multi-Purpose, SBMP) adhesive systems. Bonded surfaces from each group were air-blown for 0, 5, or 10 s and cured. Composite cylinders were built on the treated surfaces and cured. Half of the specimens from each group were tested immediately and the other halves were tested after thermal aging. Statistical analysis showed signifcant decrease in SBS after thermal aging compared to immediate testing in all groups, except BF after 5 s air-blowing or FLB and SBMP with no air-blowing (p\u3e0.05). The results suggested that 5 s air-blowing is necessary to obtain a stable SBS for BF. However, extended airblowing duration of FLB and SBMP decreased the SBS significantly after thermal aging

High-sensitivity noncontact atomic force microscope/scanning tunneling microscope (nc AFM/STM) operating at subangstrom oscillation amplitudes for atomic resolution imaging and force spectroscopy

Cataloged from PDF version of article.We describe a new, highly sensitive noncontact atomic force microscope/scanning tunneling microscope (STM) operating in ultrahigh vacuum (UHV) with subangstrom oscillation amplitudes for atomic resolution imaging and force-distance spectroscopy. A novel fiber interferometer with similar to4x10(-4) A/rootHz noise level is employed to detect cantilever displacements. Subangstrom oscillation amplitude is applied to the lever at a frequency well below the resonance and changes in the oscillation amplitude due to tip-sample force interactions are measured with a lock-in amplifier. Quantitative force gradient images can be obtained simultaneously with the STM topography. Employment of subangstrom oscillation amplitudes lets us perform force-distance measurements, which reveal very short-range force interactions, consistent with the theory. Performance of the microscope is demonstrated with quantitative atomic resolution images of Si(111)(7x7) and force-distance curves showing short interaction range, all obtained with <0.25 Angstrom lever oscillation amplitude. Our technique is not limited to UHV only and operation under liquids and air is feasible. (C) 2003 American Institute of Physics

Investigating of Mechanical Properties of Mortars Based on Fly Ash and Blast Furnace Slag Activated with Alkali

Alkali activated mortars obtained from granulated blast furnace slag and fly ash were used instead of Portland cement by activating with alkali. Sodium silicate and sodium hydroxide were activated blast furnace slag and fly ash. Mortar samples were prepared 40x40x160 mm as prismatic samples according to TS EN 196-1 and they were cured at room temperature. Compressive and flexural strength of the mortar samples including blast furnace slag and fly ash were investigated by experimenting