Circular Kinks on the Surface of Granular Material Rotated in a Tilted Spinning Bucket

We find that circular kinks form on the surface of granular material when the axis of rotation is tilted more than the angle of internal friction of the material. Radius of the kinks is measured as a function of the spinning speed and the tilting angle. Stability consideration of the surface results in an explanation that the kink is a boundary between the inner unstable and outer stable regions. A simple cellular automata model also displays kinks at the stability boundary

Electrical contact resistance of a thin oxide layer with a low mechanical load

The electrical contact resistance of a vertical binary contact between stainless steel balls with a low mechanical load was investigated. Using a statistical approach, we measured the voltage at which the dielectric breakdown occurs within a thin surface oxide layer and the distribution of the contact resistance. Electrical load-bearing conduction through a thin insulating layer was found to occur through two possible sequential processes. In both cases, once a conduction path is formed, the melting of bridges as in conventional contact theory is involved. This suggests that conduction through an oxide layer with a low mechanical load depends mainly on breakdown-induced bridges. Furthermore, the distribution of such path’s resistance shows the log-normal distribution with a long tail toward high resistance

Time dependence in adsorption of N 2 on porous materials

Time dependence in the standard Brunauer-Emmett-Teller (BET) adsorption isotherm measurement was studied for porous adsorbents (Vycor glass and aerogel) with large surface area. At low coverages, very slow decrease in the adsorption cell pressure P which showed a long time power law dependence dP/dt # -P # was observed. The exponents were independent of the coverages (< 1/3 monolayer) and # = 2.0 ± 0.2 for Vycor glass, the same for two sample sizes, and 3.4 ± 0.2 for aerogel. We explain the long time dependence by the pressure dependent adsorption, pressure gradient and the resulting Knudsen flow of gas through the constricted paths of porous material. 47.55.Mh, 68.45.Da Typeset using REVT E X Porous materials have vast applications in the adsorption and separation of materials, material storage, and for the support of heterogeneous catalysts. However, there remain some practical problems related to the porous materials, e.g. the ones in the oil recovery industry. Many experiment..

Identification of Spinel Iron Oxide Nanoparticles by 57Fe NMR

We have synthesized and studied monodisperse iron oxide nanoparticles of smaller than 10 nm to identify between the two spinel phases, magnetite and maghemite. It is shown that 57Fe NMR spectroscopy is a promising tool for distinguishing between the two phases

Persistent Erectile Dysfunction after Discontinuation of 5-Alpha Reductase Inhibitor Therapy in Rats Depending on the Duration of Treatment

Purpose: The current study is aimed to assess whether a longer duration of 5α-reductase inhibitor (5α-RI) exposure was asso-ciated with higher rate of permanent erectile dysfunction (ED) in a rat model. Materials and Methods: Male Sprague-Dawley rats (n=76) were assigned to five groups: (i) normal control group; (ii) dutaste-ride (0.5 mg/rat/d) for 4-weeks group; (iii) dutasteride for 4-weeks plus 2-weeks of resting group; (iv) dutasteride for 8-weeks group; and (v) dutasteride for 8-weeks plus 2-weeks of resting group. In vivo erectile responses to electrical stimulation, and changes of fibrotic factors and smooth muscle/collagen contents in the corpus cavernosum were evaluated in each group. Results: Dutasteride administration for 4 and 8 weeks significantly decreased erectile parameters compared with the control group. Reduced erectile responses were recovered during 2 weeks of drug-free time in the 4-week treatment group, but were not in the 8-week group. Protein levels of fibrosis-related factors transforming growth factor (TGF)-β1, TGF-β2, and p-Smad/Smad (Smad 2/3) in the corpus cavernosum showed no significant change after 4 weeks of dutasteride oral administration, but were enhanced after 8 weeks. Dutasteride markedly decreased smooth muscle content and increased collagen after 4 and 8 weeks of use, but no nuclear size changes; however, neither group showed significant improvement in the smooth muscle to collagen ratio after the rest period. Conclusions: Our study showed that recovery from ED depended on the duration of medication, and administration of dutas-teride for more than 8-weeks in rats could result in irreversible ED even after discontinuation of medication