Effect of a static non-uniform magnetic field on the surface properties of acrylic resin

INTRODUCTION: The acrylic resin is a polymeric material with several applications in different scientific and technological fields, especially in medicine and biotechnology. Its physical characteristics or their possible modifications can imply new ways of utilization and applicability. OBJECTIVE: To study the effect of a magnetic field on the surface physico-chemical properties usually implied in bacterial adhesion, especially surface hydrophobicity. METHODS: the hydrophobicity of the resin surface was determined by sessile drop contact angle measurements, using van Oss (1994) methodology. Accordingly, a substance (i) is considered hydrophobic when the variation of the free energy of interaction between two entities of substance (i) immersed in water is negative (DGiwi<0). That is to say, the two entities of substance (i) interact preferentially between them then with water. On the contrary, if DGiwi>0, substance (i) is hydrophilic. Two types of resin samples were used: hydrated and non-hydrated ones. The hydrated samples were obtained by autoclaving at 121ºC. Before contact angle measurements, the samples submitted to the magnetic field were exposed during 24 hours to a field of 500gauss generated between to parallel magnetite plates. RESULTS AND DISCUSSION: The principal results are summarized in Table 1. As could be expected the hydrated resin is hydrophilic, while the dehydrated is hydrophobic. However, when the hydrated resin is submitted to the magnetic field it becomes even more hydrophobic than when dehydrated. This can be explained by the effect of the magnetic field on the orientation of the water molecules of hydration. Consequently, there is an evident alteration of surface properties promoted by the magnetic field

Sea level variability in the Arctic Ocean from AOMIP models

Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 112 (2007): C04S08, doi:10.1029/2006JC003916.Monthly sea levels from five Arctic Ocean Model Intercomparison Project (AOMIP) models are analyzed and validated against observations in the Arctic Ocean. The AOMIP models are able to simulate variability of sea level reasonably well, but several improvements are needed to reduce model errors. It is suggested that the models will improve if their domains have a minimum depth less than 10 m. It is also recommended to take into account forcing associated with atmospheric loading, fast ice, and volume water fluxes representing Bering Strait inflow and river runoff. Several aspects of sea level variability in the Arctic Ocean are investigated based on updated observed sea level time series. The observed rate of sea level rise corrected for the glacial isostatic adjustment at 9 stations in the Kara, Laptev, and East Siberian seas for 1954–2006 is estimated as 0.250 cm/yr. There is a well pronounced decadal variability in the observed sea level time series. The 5-year running mean sea level signal correlates well with the annual Arctic Oscillation (AO) index and the sea level atmospheric pressure (SLP) at coastal stations and the North Pole. For 1954–2000 all model results reflect this correlation very well, indicating that the long-term model forcing and model reaction to the forcing are correct. Consistent with the influences of AO-driven processes, the sea level in the Arctic Ocean dropped significantly after 1990 and increased after the circulation regime changed from cyclonic to anticyclonic in 1997. In contrast, from 2000 to 2006 the sea level rose despite the stabilization of the AO index at its lowest values after 2000.This research is supported by the National Science Foundation Office of Polar Programs (under cooperative agreements OPP- 0002239 and OPP- 0327664) with the International Arctic Research Center, University of Alaska Fairbanks, and by the Climate Change Prediction Program of the Department of Energy’s Office of Biological and Environmental Research. The development of the UW model is also supported by NASA grants NNG04GB03G and NNG04GH52G and NSF grants OPP-0240916 and OPP-0229429

No association of vitamin D metabolism-related polymorphisms and melanoma risk as well as melanoma prognosis: a case–control study

Melanoma is one of the most aggressive human cancers. The vitamin D system contributes to the pathogenesis and prognosis of malignancies including cutaneous melanoma. An expression of the vitamin D receptor (VDR) and an anti-proliferative effect of vitamin D in melanocytes and melanoma cells have been shown in vitro. Studies examining associations of polymorphisms in genes coding for vitamin D metabolism-related proteins (1α-hydroxylase [CYP27B1], 1,25(OH)2D-24hydroxylase [CYP24A1], vitamin D-binding protein [VDBP]) and cancer risk are scarce, especially with respect to melanoma. Mainly VDR polymorphisms regarding melanoma risk and prognosis were examined although other vitamin D metabolism-related genes may also be crucial. In our hospital-based case–control study including 305 melanoma patients and 370 healthy controls single nucleotide polymorphisms in the genes CYP27B1 (rs4646536), CYP24A1 (rs927650), VDBP (rs1155563, rs7041), and VDR (rs757343, rs731236, rs2107301, rs7975232) were analyzed for their association with melanoma risk and prognosis. Except VDR rs731236 and VDR rs2107301, the other six polymorphisms have not been analyzed regarding melanoma before. To further improve the prevention as well as the treatment of melanoma, it is important to identify further genetic markers for melanoma risk as well as prognosis in addition to the crude phenotypic, demographic, and environmental markers used in the clinic today. A panel of genetic risk markers could help to better identify individuals at risk for melanoma development or worse prognosis. We, however, found that none of the polymorphisms tested was associated with melanoma risk as well as prognosis in logistic and linear regression models in our study population

Kara Sea freshwater dispersion and export in the late 1990s

A regional coupled ice-ocean model for the Kara Sea, forced with boundaryconditions from a large-scale North Atlantic/Arctic Ocean Model, is used to studydispersion and export of freshwater from Ob and Yenisei rivers toward the Arctic Oceanand the Laptev Sea, for the period 19962001. The years 1998 and 1999 werecharacterized by a strong positive sea level pressure (SLP) anomaly in the Siberian part ofthe Arctic Ocean. Owing to prevailing northeasterly winds, the SLP anomaly caused ablocking situation, which suppressed the otherwise eastward freshwater export to theArctic Ocean and Laptev Sea. This reversal of the prevailing circulation scheme led to adramatic freshening of the Kara Sea through accumulation of low-saline river water in thecentral and western parts. Additionally, the Kara Strait inflow from the Barents Sea,which presents the main source for saline Atlantic derived water, was reduced and partlyeven reversed. The suppressed freshwater export during winter 1998/1999 recovered inthe following winter 1999/2000 when a significant pulse of low-saline surface waterleft toward the Laptev Sea. The variability of the river discharge plays a minor role forthe investigated period because the interannual variability of runoff rates is generallytoo low to explain the observed hydrographic changes. The results underline theimportance of local shelf sea processes for the variability of the freshwater export from theArctic Shelves to the central Arctic Ocean

Validating satellite derived and modelled sea-ice drift in the Laptev Sea with in situ measurements from the winter of 2007/2008

A correct representation of the ice movement in an Arctic sea-ice-ocean coupled model is essential for a realistic sea-ice and ocean simulation. The aim of this study is to validate the observational and simulated sea-ice drift for the Laptev Sea Shelf region with in situ measurements from the winter of 2007/08. Several satellite remote-sensing data sets are first compared to mooring measurements and afterwards to the sea-ice drift simulated by the coupled sea-ice-ocean model. The different satellite products have a correlation to the in situ data ranging from 0.56 to 0.86. The correlations of sea-ice direction or individual drift vector components between the in situ data and the observations are high, about 0.8. Similar correlations are achieved by the model simulations. The sea-ice drift speed derived from the model and from some satellite products have only moderate correlations of about 0.6 to the in situ record. The standard errors for the satellite products and model simulations drift components are similar to the errors of the satellite products in the central Arctic and are about 0.03 m/s. The fast-ice parameterization implementation in the model was also successfully tested for its influence on the sea-ice drift. In contrast to the satellite products, the model drift simulations have a full temporal and spatial coverage and results are reliable enough to use as sea-ice drift estimates on the Laptev Sea Shelf

Multiple sea-ice states and abrupt MOC transitions in a general circulation ocean model

Sea ice has been suggested, based on simple models, to play an important role in past glacial–interglacial oscillations via the so-called “sea-ice switch” mechanism. An important requirement for this mechanism is that multiple sea-ice extents exist under the same land ice configuration. This hypothesis of multiple sea-ice extents is tested with a state-of-the-art ocean general circulation model coupled to an atmospheric energy–moisture-balance model. The model includes a dynamic-thermodynamic sea-ice module, has a realistic ocean configuration and bathymetry, and is forced by annual mean forcing. Several runs with two different land ice distributions represent present-day and cold-climate conditions. In each case the ocean model is initiated with both ice-free and fully ice-covered states. We find that the present-day runs converge approximately to the same sea-ice state for the northern hemisphere while for the southern hemisphere a difference in sea-ice extent of about three degrees in latitude between the different runs is observed. The cold climate runs lead to meridional sea-ice extents that are different by up to four degrees in latitude in both hemispheres. While approaching the final states, the model exhibits abrupt transitions from extended sea-ice states and weak meridional overturning circulation, to less extended sea ice and stronger meridional overturning circulation, and vice versa. These transitions are linked to temperature changes in the North Atlantic high-latitude deep water. Such abrupt changes may be associated with Dansgaard–Oeschger events, as proposed by previous studies. Although multiple sea ice states have been observed, the difference between these states is not large enough to provide a strong support for the sea-ice-switch mechanism