Quaternionic representation of electromagnetism for material media

In this study, the electromagnetic fields are developed in the presence of both the electric and magnetic induction fields by quaternion algebra. In this sense, the polarization and magnetization effects, which are valid in the material media, gain much importance. Quaternions are one of the most convenient tools for representing electromagnetism with regard to having non-commutative but associative algebraic division ring. By defining the quaternion induction field, the quaternion source term has been obtained in basic and elegant notation for the first time. In addition, one type of Poynting theorem, named as the Minkowski form, has been presented including the permittivity and permeability constants by quaternions.

Gravitational waves at their own gravitational speed

Gravitational waves propagate at the speed of light in general relativity, because of their special relativistic basis. However, light propagation is linked to the electromagnetic phenomena, with the permittivity and permeability constants as the determining factors. Is there a deeper reason why waves in a geometric theory of gravity propagate at a speed determined by electromagnetic constants? What is the relation between gravity’s own constants and the speed of gravitational waves? Our attempt to answer these fundamental questions takes us far and deep into the universe.

Effect of Oxygen Potential Gradient on Mass Transfer in Polycrystalline α-Alumina at High Temperature

The oxygen permeability of polycrystalline α-alumina wafers, which served as model alumina scales formed on heat-resistant alloys, was evaluated at a temperature of 1873 K. Mass transfer along grain boundaries (GBs) in an alumina wafer exposed to a large oxygen potential gradient (dμO), where both oxygen and aluminum mutually diffuse along GBs, was analyzed using 18O2 and SIMS. 18O was concentrated at GB ridges on the high oxygen partial pressure (PO2(hi)) surface and along the GBs near the PO2(hi) surface. 18O adsorbed on the surface diffused almost immediately to surface GBs, resulting in the formation of new alumina by reaction with aluminum diffusing outward along the GBs. Oxygen GB diffusion coefficients in the vicinity of the PO2(hi) surface were determined from the 18O depth profile along each GB for the 18O map of the cross section of the exposed alumina wafer. The oxygen GB diffusion coefficients were comparable to the values calculated from the oxygen permeability constants assuming an electronic conductivity and were obviously lower than those of oxygen GB self-diffusion without an oxygen potential gradient.

Steady State Thermal Behaviour of Ceramic Wick Structure for Application in Two Phase Heat Transfer Devices

This work reports on results from two phase heat transfer devices assembled with ceramic capillary structure. It is firstly presented the manufacturing of the ceramic wick structures and afterwards the characterization of the morphological-and fluid-dynamical properties of these ceramic wick structures. As closing results, it is presented the thermal behaviour of two different two phase heat transfer devices, i.e. a Capillary Pumped Loop and a Loop Heat Pipe. The properties of the ceramic wick structure are within the desirable range for a correct functioning of these devices, e.g. porosity, pore size and permeability constants ranging from 40 to 60%, from 5 to 30μm and from 10-10 to 10-13m2, respectively. The thermal behaviour tests of the heat transfer devices used power heat load input in range from 10 to 20W and for all devices the evaporator temperature reached steady state condition. Thus, as a result, it can be claimed these ceramic wick structures as successful alternative for assembling capillary evaporator of CPL and LHP.

A new method to determine open porosity and permeability constants of open-pore sintered glasses by photoacoustic technique

The Photoacoustic (PA) technique was used to investigate the structural properties (e.g. open porosity and permeability) of open-pore sintered glasses. This work demonstrates that the photoacoustic signal of open-pore sintered glasses, which are produced with different grain sizes and several degrees of open porosity, is sensitive to the morphology of the open-pore samples. The results obtained by the PA technique were related to results obtained by the Pressure Decay technique, and an excellent correlation was obtained. This demonstrates that PA technique, which is non-intrusive and non-destructive, is promising for application in analysis of porous ceramic structures, even if the sample is semi-transparent.

The Permeability of Human Oral Mucosa and Skin to Water

Specimens from fbur regions of oral mucosa (palate, buccal mucosa, lateral border of the tongue, and the floor of the mouth) and of abdominal skin were taken from 58 individuals at autopsy, for determination of permeability constants (Kp) to tritium-labeled water. Comparisons between fresh specimens and those stored at -80°C revealed no significant effect on Kp as a result of freezing; similar results were found with use of specimens from corresponding regions of the pig. Values for Kp were significantly different for all of the tissue regions examined and ranged from 44 ± 4 × 10-7 cm/min for skin to 973 ± 33 x 10-7 cmlmin for the floor of the mouth, which was the most penneable region. Similar differences were evident among corresponding regions of porcine oral mucosa and skin. Moreover, the Kp values obtained for human tissues were not significantly different from those of the pig, except for the floor of the mouth, which was more permeable in human than in pig tissue. The results reveal interesting differences in the permeability of human oral mucosa that might be related to susceptibility to mucosal disease in those conditions where local extrinsic etiological agents are implicated.

Resistance of Polymers to Permeation by Air Conditioning Refrigerants and Water

The permeability of several polymers to refrigerants and to water vapor has been determined. The investigation included refrigerant R-12 which is currently used in automotive air conditioning and refrigerants R-22 and R-134A which are considered as future candidates. For the different polymers investigated, the permeability constants for R-22 at 93°C ranged between 0 and cm/11×10−10 cm2 sec cm2 cm Hg for the plastics, 29×10−10 and 124×10−10 for thermoplastic elastomers and 135×10−10 and 276×10−10 for crosslinked elastomers. The permeability decreased with decrease in test temperature and with increase in molecular size of the refrigerants. Hence both R-12 and R-134A exhibited lower permeability constants than R-22 because of their bigger size. Trends in water permeability of the different polymers were mostly opposite to those of the refrigerant permeability. For example, polynorbornene has the lowest water permeability of the polymers tested, but has one of the highest permeability constants for refrigerants. Of the new polymers investigated, the lowest overall permeability to water and refrigerants was exhibited by PET polyester, polypropylene, Hytrel polyester, and plasticized Polyamide 12 (5% plasticizer).

Erythrocyte ghost – buffer partition coefficients of phenobarbital, pentobarbital, and thiopental support the pH-partition hypothesis

The partition coefficient (λ) between red cell ghosts and buffer has been determined for three barbiturates over a range of pH. Experimental partition coefficients were linearly proportional to the calculated degree of association of the barbiturates. λ was 9.5 ± 0.52 for phenobarbital, 12.7 ± 0.91 for pentobarbital, and 27 ± 4.9 for thiopental in their acid forms. λ for all three barbiturates in their anionic forms was zero. Our data support the assumption of the pH-partition hypothesis that the dependence of λ on pH in biological membranes behaves essentially like that in organic solvents. However, the relative magnitudes of the erythrocyte partition coefficients correlate much more closely with the physiological permeability constants than do those of organic solvents, which tend to overestimate the differences between these compounds.