Measuring methods for determination of gas transport parameters in soils

Measurement methods for gas transport parameters in soils have been developed to assess the geogenic radon potential. The methods are based on the determination of selected physical soil properties, e.g., diffusion coefficient, gas permeability and radon emanation of undisturbed soil samples. Additionally, a probe has been developed for determination of the in situ gas permeability of soils. The variation of emanation coefficients shows the influence of the natural texture of the soils

Evolution of E2 transition strength in deformed hafnium isotopes from new measurements on 172^{172}Hf, 174^{174}Hf, and 176^{176}Hf

The available data for E2 transition strengths in the region between neutron-deficient Hf and Pt isotopes are far from complete. More and precise data are needed to enhance the picture of structure evolution in this region and to test state-of-the-art nuclear models. In a simple model, the maximum collectivity is expected at the middle of the major shell. However, for actual nuclei, this picture may no longer be the case, and one should use a more realistic nuclear-structure model. We address this point by studying the spectroscopy of Hf. We remeasure the 2^+_1 half-lives of 172,174,176Hf, for which there is some disagreement in the literature. The main goal is to measure, for the first time, the half-lives of higher-lying states of the rotational band. The new results are compared to a theoretical calculation for absolute transition strengths. The half-lives were measured using \gamma-\gamma and conversion-electron-\gamma delayed coincidences with the fast timing method. For the determination of half-lives in the picosecond region, the generalized centroid difference method was applied. For the theoretical calculation of the spectroscopic properties, the interacting boson model is employed, whose Hamiltonian is determined based on microscopic energy-density functional calculations. The measured 2^+_1 half-lives disagree with results from earlier \gamma-\gamma fast timing measurements, but are in agreement with data from Coulomb excitation experiments and other methods. Half-lives of the 4^+_1 and 6^+_1 states were measured, as well as a lower limit for the 8^+_1 states. We show the importance of the mass-dependence of effective boson charge in the description of E2 transition rates in chains of nuclei. It encourages further studies of the microscopic origin of this mass dependence. New data on transition rates in nuclei from neighboring isotopic chains could support these studies.Comment: 16 pages, 16 figures, 7 tables; Abstract shortened due to character limi

Symmetry-breaking transitions in networks of nonlinear circuit elements

We investigate a nonlinear circuit consisting of N tunnel diodes in series, which shows close similarities to a semiconductor superlattice or to a neural network. Each tunnel diode is modeled by a three-variable FitzHugh-Nagumo-like system. The tunnel diodes are coupled globally through a load resistor. We find complex bifurcation scenarios with symmetry-breaking transitions that generate multiple fixed points off the synchronization manifold. We show that multiply degenerate zero-eigenvalue bifurcations occur, which lead to multistable current branches, and that these bifurcations are also degenerate with a Hopf bifurcation. These predicted scenarios of multiple branches and degenerate bifurcations are also found experimentally.Comment: 32 pages, 11 figures, 7 movies available as ancillary file

The Marco Gonzalez Maya site, Ambergris Caye, Belize: assessing the impact of human activities by examining diachronic processes at the local scale

Research at the Maya archaeological site of Marco Gonzalez on Ambergris Caye in Belize is socio-ecological because human activities have been a factor in the formation and fluctuation of the local marine and terrestrial environments over time. The site is one of many on Belize's coast and cayes that exhibit anomalous vegetation and dark-coloured soils. These soils, although sought for cultivation, are not typical 'Amazonian Dark Earths' but instead are distinctive to the weathering of carbonate-rich anthropogenic deposits. We tentatively term these location-specific soils as Maya Dark Earths. Our research seeks to quantify the role of human activities in long-term environmental change and to develop strategies, specifically Life Cycle Assessment (LCA), that can be applied to environmental impact modelling today

Use of Micro-Computed Tomography to Nondestructively Characterize Biomineral Coatings on Solid Freeform Fabricated Poly (L-Lactic Acid) and Poly (ɛ-Caprolactone) Scaffolds In Vitro and In Vivo

Biomineral coatings have been extensively used to enhance the osteoconductivity of polymeric scaffolds. Numerous porous scaffolds have previously been coated with a bone-like apatite mineral through incubation in simulated body fluid (SBF). However, characterization of the mineral layer formed on scaffolds, including the amount of mineral within the scaffolds, often requires destructive methods. We have developed a method using micro-computed tomography (?-CT) scanning to nondestructively quantify the amount of mineral in vitro and in vivo on biodegradable scaffolds made of poly (L-lactic acid) (PLLA) and poly (?-caprolactone) (PCL). PLLA and PCL scaffolds were fabricated using an indirect solid freeform fabrication (SFF) technique to achieve orthogonally interconnected pore architectures. Biomineral coatings were formed on the fabricated PLLA and PCL scaffolds after incubation in modified SBF (mSBF). Scanning electron microscopy and X-ray diffraction confirmed the formation of an apatite-like mineral. The scaffolds were implanted into mouse ectopic sites for 3 and 10 weeks. The presence of a biomineral coating within the porous scaffolds was confirmed through plastic embedding and ?-CT techniques. Tissue mineral content (TMC) and volume of mineral on the scaffold surfaces detected by ?-CT had a strong correlation with the amount of calcium measured by the orthocresolphthalein complex-one (OCPC) method before and after implantation. There was a strong correlation between OCPC pre- and postimplantation and ?-CT measured TMC (R2=0.96 preimplant; R2=0.90 postimplant) and mineral volume (R2=0.96 preimplant; R2=0.89 postimplant). The ?-CT technique showed increases in mineral following implantation, suggesting that ?-CT can be used to nondestructively determine the amount of calcium on coated scaffolds.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140242/1/ten.tec.2012.0495.pd

Erratum to: Design of pharmaceutical products to meet future patient needs requires modification of current development paradigms and business models

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