Total magnetic fields and read characteristics of infinite length pole piece magnetic recording heads

Magnetic recording head fields generated by current distributions of zero total current flux are calculated considering the two topological possibilities for the current elements being either external to infinite permeability pole pieces or contained entirely within the pole pieces. The frequency response for each of these field configurations is determined by application of the fast Fourier transform.     

Enterotoxin formation by Clostridium perfringens during sporulation and vegetative growth

Growth, sporulation and enterotoxin production have been followed for three different strains of Clostridium perfringens on a vegetative (FTG) medium and a sporulation (DS) medium. Enterotoxin production was followed by use of enzyme-linked immunosorbent assay (ELISA). All strains produced enterotoxin under both vegetative growth and sporulation in spite of the fact that one strain is known to be enterotoxin negative. The presumed negative strain produced about the same amount of enterotoxin on both media (1 ng/ml). The two other strains produced about 1000–2000 times more enterotoxin during sporulation than during vegetative growth.     

Biogeo-optics: particle optical properties and the partitioning of the spectral scattering coefficient of ocean waters

We propose a direct method of partitioning the particulate spectral scattering coefficient of the marine hydrosol based on the concurrent determination of the concentrations of particulate mineral and organic matter (the total mass of optically active scattering material exclusive of water) with the particulate spectral scattering coefficient. For this we derive a Model II multiple linear regression model. The multiple linear regression of the particulate spectral scattering coefficient against the independent variables, the concentrations of particulate inorganic matter and particulate organic matter, yields their mass-specific spectral scattering cross sections. The mass-specific spectral scattering cross section is simply the particle scattering cross section normalized to the particle mass, a fundamental optical efficiency parameter for the attenuation of electromagnetic radiation [Absorption and Scattering of Light by Small Particles, (Wiley-Interscience, 1983), pp. 80-81, 289]. It is possible to infer the optical properties of the suspended matter from the mass-specific spectral scattering cross sections. From these cross sections we partition the particulate spectral scattering coefficient into its major components.     

The reading characteristics of a finite length pole piece recording head

The frequency response of a finite-length pole piece recording head is calculated numerically for various gap-to-pole-length ratios as well as for differing head-to-medium separations for an idealized sinusoidal magnetization distribution by application of the Cooley-Tukey fast Fourier transform.     

Extracting mineral effects on ultraviolet penetration and its effects in coastal and inland waters: a Monte Carlo study

A factor significantly affecting the ultraviolet (UV) radiation's interactions with the aquatic environment is the concentration of suspended sediment. We utilize data on UV penetration, absorption, and scattering in Lake Biwa, Japan, reported by Belzile et al. [Limnol. Oceanogr. 47, 95 (2002)], to drive Monte Carlo simulations of UV penetration. We generated Monte Carlo models (2 billion photons per simulation) of four stations reported by Belzile et al.: two low sediment stations and two high sediment stations. New modes are proposed for analyzing UV penetration and dosage factors for aquatic organisms in sediment dominated aquatic environments.     

Magnetization of a two-component Stoner-Wohlfarth particle

The free energy of an arbitrary two-component Stoner-Wohlfarth particle is derived and general criteria for stable states of magnetization are established. Hysteretic properties of coaxial prolate spheroids composed of γ-Fe2O3coated iron particles are calculated numerically and the specific extension to epitaxial cobalt ferrite γ-Fe2O3particles amongst other two-component systems is indicated.     

Frequency response function of a gapped infinite length pole piece recording head

The frequency (wavelength) response function of a gapped infinite length, infinite permeability magnetic reproduce head is calculated analytically.     

Optical scattering and backscattering by organic and inorganic particulates in U.S. coastal waters

We present the results of a study of optical scattering and backscattering of particulates for three coastal sites that represent a wide range of optical properties that are found in U.S. near-shore waters. The 6000 scattering and backscattering spectra collected for this study can be well approximated by a power-law function of wavelength. The power-law exponent for particulate scattering changes dramatically from site to site (and within each site) compared with particulate backscattering where all the spectra, except possibly the very clearest waters, cluster around a single wavelength power-law exponent of -0.94. The particulate backscattering-to-scattering ratio (the backscattering ratio) displays a wide range in wavelength dependence. This result is not consistent with scattering models that describe the bulk composition of water as a uniform mix of homogeneous spherical particles with a Junge-like power-law distribution over all particle sizes. Simultaneous particulate organic matter (POM) and particulate inorganic matter (PIM) measurements are available for some of our optical measurements, and site-averaged POM and PIM mass-specific cross sections for scattering and backscattering can be derived. Cross sections for organic and inorganic material differ at each site, and the relative contribution of organic and inorganic material to scattering and backscattering depends differently at each site on the relative amount of material that is present.