Characterisation of flow dynamics within and around an isolated forest, through measurements and numerical simulations

The case study of ‘Bosco Fontana’, a densely-vegetated forest located in the north of Italy, is analysed both experimentally and numerically to characterise the internal ventilation of a finite forest with a vertically non-homogeneous canopy. Measurements allow for the evaluation of the turbulent exchange across the forest canopy. The case study is then reproduced numerically via a two-dimensional RANS simulation, successfully validated against experimental data. The analysis of the internal ventilation leads to the identification of seven regions of motion along the predominate-wind direction, for whose definition a new in-canopy stability parameter was introduced. In the vertical direction, the non-homogeneity of the canopy leads to the separation of the canopy layer into an upper foliage layer and a lower bush layer, characterised respectively by an increasing streamwise velocity and turbulence intensity, and a weak backflow. The conclusions report an improved description of the dynamic layer and regions of motion presented in the literature

Modulation of Hydrogen Peroxide Production in Cellular Systems by Low Level Magnetic Fields

Increased generation of reactive oxygen species (ROS) and an altered redox status have long been observed in cancer cells, suggesting that ROS might be involved in the development of these cells. However, recent studies suggest that inducing an excess of ROS in cancer cells can be exploited for therapeutic benefits. Cancer cells in advanced stage tumors frequently exhibit multiple genetic alterations and high oxidative stress, suggesting that it might be possible to preferentially modulate the development of these cells by controlling their ROS production. Low levels of ROS are also important for the development and survival of normal cells. In this manuscript, we present data on the influence of the suppression of the Earth's magnetic field (low level magnetic fields or LLF) which magnitudes range from 0.2 µT to 2 µT on the modulation of hydrogen peroxide (H2O2) in human fibrosarcoma cancer cell line HT1080, pancreatic AsPC-1 cancer cell line, and bovine pulmonary artery endothelial cells (PAEC) exposed to geomagnetic field (control; 45 µT–60 µT). Reduction of the Earth's magnetic field suppressed H2O2 production in cancer cells and PAEC. The addition of catalase and superoxide dismutase (SOD) mimetic MnTBAP inhibited the magnetic field effect. Modulating ROS production by magnetic fields may open new venues of biomedical research and therapeutic strategies

Chemical Magnetoreception: Bird Cryptochrome 1a Is Excited by Blue Light and Forms Long-Lived Radical-Pairs

Cryptochromes (Cry) have been suggested to form the basis of light-dependent magnetic compass orientation in birds. However, to function as magnetic compass sensors, the cryptochromes of migratory birds must possess a number of key biophysical characteristics. Most importantly, absorption of blue light must produce radical pairs with lifetimes longer than about a microsecond. Cryptochrome 1a (gwCry1a) and the photolyase-homology-region of Cry1 (gwCry1-PHR) from the migratory garden warbler were recombinantly expressed and purified from a baculovirus/Sf9 cell expression system. Transient absorption measurements show that these flavoproteins are indeed excited by light in the blue spectral range leading to the formation of radicals with millisecond lifetimes. These biophysical characteristics suggest that gwCry1a is ideally suited as a primary light-mediated, radical-pair-based magnetic compass receptor

Model calculations of magnetic field effects on the recombination reactions of radicals with anisotropic hyperfine interactions

The effects of anisotropic hyperfine interactions on the recombination reactions of spin correlated radical pairs in a weak applied magnetic field are discussed in the context of the radical pair mechanism (RPM). Model calculations are presented for radical pairs containing a single spin-1/2 nucleus with an axial or rhombic coupling to one of the unpaired electrons. The so-called low field effect (LFE) and various resonances in the magnetic field effect (MFE) are calculated. Approximate analytical expressions are given for the field positions of the resonances which are shown to arise from energy level crossings. © 2001 Elsevier Science B.V

A μSR study of spin dynamics in the n-type superconductor Nd1.85Ce0.15CuO4+δ

Because of the low number of chemical degrees of freedom and the unique band at the Fermi level, the copper oxide n-type superconductor Nd1.85Ce0.15CuO4+d\uf020 can be considered as a model system for the study of the physical properties related to the charge carrier density. Resistivity , thermopower and magnetic susceptibility in samples of Nd1.85Ce0.15CuO4+d\uf020 with well-known charge carrier density n , controlled by varying the oxygen content from d=0 to d=0.06 ( n=(4.075-d)*2-8 ) , suggested a possible interaction between carriers well above Tc [1]. Here we present a mu+SR investigation performed with the aim of adding important information on the mechanism at the basis of such an interaction. ZF-mu+SR measurements were made as a function of temperature in the range 10-100K in 5 samples prepared under a total pressure of 1 atmosphere and at different oxygen partial pressures: 1 (sample A), 10-2 (sample B), 10-3 (sample C), 10-4 (sample D), 10-6 (sample E) atmospheres, and extended in the range 0.08-10K for samples A and E. LF-mu+SR measurements were done on sample A at H=100, 150, 250 G and on sample E (d=0.014, n=0.12) at H=30, 60, 100G. The samples D and E are superconducting with Tc=18K and Tc=25K (onset); the other samples are non superconducting. We observed that in all the samples except the sample E, the asymmetry curve in ZF at low T (T<20K) has a form very similar to the one expected in systems where a spin freezing sets in (like for example in spin glasses, SG). In a recent paper [2] the SG phase in sample A was confirmed experimentally by a clear maximum in the ZFC susceptibility curve (blocking temperature Tg=5K), the associated irreversible ZFC-FC behaviour and the time behaviour of the relaxation. By current mu+SR measurements, the magnetic phase diagram was more clearly established. Moreover, we suggest that an antiferromagnetic disordered phase could co-exist with the superconducting phase, at least in sample