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Search Results: 1 - 10 of 2298 matches for " Axel; "
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Green’s Function Approach to the Bose-Hubbard Model  [PDF]
Matthias Ohliger, Axel Pelster
World Journal of Condensed Matter Physics (WJCMP) , 2013, DOI: 10.4236/wjcmp.2013.32020
Abstract:

We use a diagrammatic hopping expansion to calculate finite-temperature Green functions of the Bose-Hubbard model which describes bosons in an optical lattice. This technique allows for a summation of subsets of diagrams, so the divergence of the Green function leads to non-perturbative results for the boundary between the superfluid and the Mott phase for finite temperatures. Whereas the first-order calculation reproduces the seminal mean-field result, the second order goes beyond and shifts the phase boundary in the immediate vicinity of the critical parameters determined by high-precision Monte-Carlo simulations of the Bose-Hubbard model. In addition, our Greens function approach allows for calculating the excitation spectrum both for zero and finite temperature and for determining the effective masses of particles and holes.

In-Situ Hydroelectrothermal Deposition of Silicate Layers on Stainless Steel Surfaces  [PDF]
Jaybalan Tamahrajah, Axel Brehm
Advances in Materials Physics and Chemistry (AMPC) , 2015, DOI: 10.4236/ampc.2015.59038
Abstract: The deposition of zeolites on solid support materials is possible by means of electrochemical methods, impregnation processes, as well as in-situ syntheses. Electrochemical deposition of zeolites has been reported as well, however with readily synthesized zeolite structures. Adhesive deposition of zeolites on stainless steel (S316) has been reported. This report investigates the feasibility of the deposition of silicates by in-situ hydroelectrothermal means. The investigation was done in aqueous solutions of pH = 7 to 13 at different temperatures (25°C to 70°C) by linear sweep method. Deposition was done at a saturated H2 atmosphere to ensure prior deposition of thin iron oxide film on the surface and formation of Fe-O-Si-linkages. This was proven by Raman measurement of the samples. Further linear sweep experiments in the presence of silica show monodentate and bidentate Fe-O-Si linkages on the surface, proven by IR-measurements. Presence of dissolved silica was done by UV-Vis with the molybdate yellow method. The best results are achieved at 70°C at pH 13 and ﹣4 mV (vs Ag/AgCl) or 200 mV (vs SHE). Discontinuous homogeneous layers are found on the stainless steel surface observed by SEM, EDX measurements and electrochemical measurements. Layer discontinuties are caused due to low silica concentration at equilibrium hydrothermal conditions, especially in the absence of silicic acid. All results shown are for the best results achieved except for linear sweep measurements and solubility constants of dissolved silica.
Nuclear Power and Radioactive Contamination  [PDF]
Nils-Axel M?rner
Journal of Environmental Protection (JEP) , 2014, DOI: 10.4236/jep.2014.53021
Abstract:

Nuclear power was designed to produce electric power. Each part of the chain from uranium mining to handling of the waste is linked to serious contamination risks, however. Uranium mining is generally linked to local to regional contamination. The fuel production also produces depleted uranium at a ratio of 1:7. The reactors are operating under danger of accidents. Numerous minor accidents and endless temporary shut-downs are occasionally mixed with disastrous accidents. The Chernobyl (1986) and Fukushima (2011) accidents are notorious. The radioactive contamination from those accidents is still incomprehensible and will keep serious destructions of the environment for centuries to come. The handling of the high-level nuclear waste remains unsolved. Methods proposed in Sweden, Finland and France seem likely to lead to disastrous radioactive contaminations in the future. The only way out of this dilemma seems to be a disposal where the waste, though effectively sealed-off in the bedrock, remains accessible and controllable. At present, the “cost & benefit” balance seems strongly tilted over to the “far too costly side”, however.

An M > 6 Earthquake ~750 BC in SE Sweden  [PDF]
Nils-Axel M?rner
Open Journal of Earthquake Research (OJER) , 2014, DOI: 10.4236/ojer.2014.32008
Abstract:

At about 780-750 BC, a major earthquake struck southeast Sweden. At Brantetrask, the bedrock of quartzite was heavily fractured into big, flat blocks. Local people turned the site into a quarry for flat blocks to be placed around the Late Bronze Age graves at Brantevik, the big flat blocks of the sarcophagus, and two 5 tons monoliths transported 30 km to the SSW and erected as the bow and stern stones in the huge ship monument of Ales Stones. Rock carvings from the Bronze Age at Jarrestad became traversed by numerous fractures. Similar rock carving fracturing was observed at six other sites within a radius of 5 km from Brantetrask. In the shore cliff at Ales Stones a seismite was recorded and dated at 780-750 BC. At Glimme hallar, 4 km WSW of Brantevik, the bedrock shows signs of young tectonization. At Lillehem, 40 km to the NNW of Brantetrask, seismically disturbed beds were recorded and dated at the Late Holocene. The seismic event is concluded to have occurred around 780-750 cal.yrs BC and to have had a magnitude in the order of 6.3 to 6.8 and an intensity of about IX on the IES scale.

The Flooding of Ur in Mesopotamia in New Perspectives  [PDF]
Nils-Axel M?rner
Archaeological Discovery (AD) , 2015, DOI: 10.4236/ad.2015.31003
Abstract: At around 5000 years BP sea level peaked in the Persian Gulf region at a level of +0.3 m as now determined in Qatar. This coincides with the famous flooding of the ancient city of Ur, originally interpreted as due to local changes in the fluvial system. We can now propose that, in fact, it was the sea level rise that triggered the fluvial reorganization and rise in ground water level that ultimately led to “the flooding of Ur”.
Glacial Isostasy: Regional—Not Global  [PDF]
Nils-Axel M?rner
International Journal of Geosciences (IJG) , 2015, DOI: 10.4236/ijg.2015.66045
Abstract: The load of the continental ice caps of the Ice Ages deformed the bedrock, and when the ice melted in postglacial time, land rose. This process is known as glacial isostasy. The deformations are compensated either regionally or globally. Fennoscandian data indicate a regional compensation. Global sea level data support a regional, not global, compensation. Subtracting GIA corrections from satellite altimetry records brings—for the first time—different sea level indications into harmony of a present mean global sea level rise of 0.0 to 1.0 mm/yr.
Origin of the Amazonian Rainforest  [PDF]
Nils-Axel M?rner
International Journal of Geosciences (IJG) , 2016, DOI: 10.4236/ijg.2016.74036
Abstract: In the last 30 ma, the passive continental margin of South America and the Amazonian basin experienced three periods of major sea level inundation; viz. at around 20 ma, at around 10 ma and at around 3 ma. The establishment of the immense Amazonian rainforest ecosystem covering some 6 million square km can neither have occurred during the periods of high sea level nor at the intermediate periods of arid or semi-arid climatic conditions. Therefore, the origin of the Amazonian rainforest of present-day dimensions must be set at the Late Miocene. The establishment of the Amazonian rainforest implied the withdrawal of enormous quantities of water from the global hydrological cycle. The drastic increase in evaporation leading to the Messinian salinity crisis in the Mediterranean occurred at the same time as the Amazonian rainforest (sensu hodierno) establishment suggesting a causal linkage.
Rates of Sea Level Changes—A Clarifying Note  [PDF]
Nils-Axel M?rner
International Journal of Geosciences (IJG) , 2016, DOI: 10.4236/ijg.2016.711096
Abstract: The values of present to future rates in sea level changes vary in an almost chaotic way. In view of the urgent need to handle this question in a constructive way, we must anchor the issue in observational facts, physical laws and long-term scientific experience. Doing so, we can put a solid ultimate frame of any possible rise in sea level in the next centuries: viz. 10.0 mm/yr or 1.0 m per century. If this is the ultimate possible rate, the expected rate in the 21st century must be far less. The author’s proposition is +5 cm ± 15 cm by year 2100.
Converting Tsunami Wave Heights to Earthquake Magnitudes  [PDF]
Nils-Axel M?rner
Open Journal of Earthquake Research (OJER) , 2017, DOI: 10.4236/ojer.2017.62005
Abstract: There is a fairly strict relation between maximum tsunami wave heights and causation earthquake magnitudes. This provides a new tool for estimating the magnitude of past earthquakes from the observed wave heights of related paleo-tsunami events. The method is subjected to a test versus two paleoseismic events with multiple independent estimates of corresponding earthquake magnitude. The agreement to the tsunami wave height conversion is good, confirming very high magnitudes of M 8.5 - 9.0 and M 8.4 - 8.5. Applying the same method to two Late Holocene events of methane venting tectonics indicates a ground shaking of forces equivalent to a M 8.0 earthquake, seriously changing previous long-term crustal hazard assessments.
The Reef Woman of the Maldives  [PDF]
Nils-Axel M?rner
Archaeological Discovery (AD) , 2017, DOI: 10.4236/ad.2017.54014
Abstract: A human skeleton was found embedded in beachrock in the Maldives. It was identified as the remains of a woman, died, killed or washed ashore at a former shore at about AD 1150. The shore was at the same elevation as today’s shore. Sea rose to about +60 cm, covering the skeleton with coral rubble. Sea fell again to its present position, cementing the shore deposits into beachrock including the skeleton. In sub-recent time, the beachrock was trimmed into a rock-cut platform at sea level of about +20 cm. In the 1970s, sea level fell to its present position, starting to erode a new rock-cut platform at about present high-tide level, by that exposing the old skeleton. The skeleton has come to be known as “the Reef Woman” of the Maldives or of Lhosfushi. The skeleton lacks its feet, suggesting that the woman was killed on the beach and the feet cut-off. The age of the bones is calAD 1135 ± 70. Therefore, it seems highly likely that the killing took place at the invasion and takeover of the Maldives by the Muslims in AD 1153. It seems we have cleared up an 864-year old murder.
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