A study of the structure of jet turbulence producing jet noise

Characteristics of turbulent structure of mixing region near outlet of circular subsonic jet and production of jet nois

Cigarette Smoking and Retinal Carotenoids: Implications for Age-related Macular Degeneration

AbstractThe foveal region of the retina has a yellow pigmentation composed primarily of the carotenoids lutein and zeaxanthin. Past studies have shown that cigarette smoking depresses carotenoid concentrations in the blood. This is the first report on the effects of cigarette smoking on carotenoids in the retina. Macular pigment optical density (MP) was measured psychophysically by comparing foveal and parafoveal sensitivities to light of 460 and 550 nm. General dietary patterns, smoking frequency (cigarettes/day) and personal data were collected by questionnaire. Thirty-four smokers and 34 nonsmokers were compared. Subjects were matched with respect to age, sex, dietary patterns and overall pigmentation (i.e., eye, skin and hair color). The smoking group had a mean MP of 0.16 (SD = 0.12) compared to a mean MP of 0.34 (SD = 0.15) for nonsmokers (P < 0.0001). MP density and smoking frequency were inversely related (r = −0.498 P < 0.001) in a dose-response relationship. A variety of evidence suggests that MP protects the macula from actinic damage both passively (by screening potentially harmful short-wave light) and actively as an antioxidant (e.g., by quenching reactive oxygen species). If smoking causes a reduction in MP density, then smokers may be at risk. Epidemiologic data identifying smoking as a risk factor for the neovascular form of age-related macular degeneration are consistent with this hypothesis. Copyright © 1996 Elsevier Science Ltd

Binary continuous random networks

Many properties of disordered materials can be understood by looking at idealized structural models, in which the strain is as small as is possible in the absence of long-range order. For covalent amorphous semiconductors and glasses, such an idealized structural model, the continuous-random network, was introduced 70 years ago by Zachariasen. In this model, each atom is placed in a crystal-like local environment, with perfect coordination and chemical ordering, yet longer-range order is nonexistent. Defects, such as missing or added bonds, or chemical mismatches, however, are not accounted for. In this paper we explore under which conditions the idealized CRN model without defects captures the properties of the material, and under which conditions defects are an inherent part of the idealized model. We find that the density of defects in tetrahedral networks does not vary smoothly with variations in the interaction strengths, but jumps from close-to-zero to a finite density. Consequently, in certain materials, defects do not play a role except for being thermodynamical excitations, whereas in others they are a fundamental ingredient of the ideal structure.Comment: Article in honor of Mike Thorpe's 60th birthday (to appear in J. Phys: Cond Matt.

I might be your once-in-a-while

https://digitalcommons.ithaca.edu/sheetmusic/1083/thumbnail.jp

Infrared phonon dynamics of multiferroic BiFeO3 single crystal

We discuss the first infrared reflectivity measurement on a BiFeO3 single crystal between 5 K and room temperature. The 9 predicted ab-plane E phonon modes are fully and unambiguously determined. The frequencies of the 4 A1 c-axis phonons are found. These results settle issues between theory and data on ceramics. Our findings show that the softening of the lowest frequency E mode is responsible for the temperature dependence of the dielectric constant, indicating that the ferroelectric transition in BiFeO3 is soft-mode driven.Comment: 5 pages (figures included