An all fiber source of frequency entangled photon pairs

We present an all fiber source of frequency entangled photon pairs by using four wave mixing in a Sagnac fiber loop. Special care is taken to suppress the impurity of the frequency entanglement by cooling the fiber and by matching the polarization modes of the photon pairs counter-propagating in the fiber loop. Coincidence detection of signal and idler photons, which are created in pair and in different spatial modes of the fiber loop, shows the quantum interference in the form of spatial beating, while the single counts of the individual signal (idler) photons keep constant. When the production rate of photon pairs is about 0.013 pairs/pulse, the envelope of the quantum interference reveals a visibility of $(95\pm 2)$, which is close to the calculated theoretical limit 97.4%Comment: 11 pages, 6 figures, to appear in Phys. Rev.

Generalized retarded integral inequalities

We prove some new retarded integral inequalities. The results generalize those in [J. Math. Anal. Appl. 301 (2005), no. 2, 265--275].Comment: Changes suggested by the referee don

Numerical Investigation of Hypersonic Unsteady Flow Around a Spiked Blunt-body

AbstractThe obvious unsteady flow characteristics of the flow field around the spiked blunt-body have negative effect on the drag reduction of vehicle and the thermo-protection of the head. The hypersonic self-sustained oscillatory flow was numerical simulated, and the flow structure and mechanism of the three process of one cycle: collapse, inflation and withhold, were discussed in detail. The correspondence between the drag coefficient curve and the different flow structure was obtained, which will provide basis to the drag reduction and thermo-protection of hypersonic blunt-body vehicle through flow control in the future

Couching Techniques for Cataract Treatment in Osogbo, South West Nigeria

Background: Couching is still being practised in developing countries including Nigeria despite its adverse effects on vision.Objectives: To find out the different techniques of couching, highlight the unacceptable poor visual sequelae and assess knowledge, attitudes, and practices of subjects.Settings and Design: Clinic based and prospective observational study.Methods and Material: Structured interview and clinical examination of consecutive patients was used to obtain information.Results: Fifteen subjects and 20 eyes of 9(60%) males and 6(40%) females were studied. Age range 60 -90 years and mean 72.4±8.0. Commonest presenting complaints were “I cannot see properly/clearly” 4(26.7%) and “I want to do my second eye so I can see better” 3(20%). Presenting Versus (vs.) Corrected visual acuity (VA) was75% vs 60% blind, 55% vs 45% low vision, and 0% vs 10% normal vision, p= 0.032. Friends and neighbours mostly introduced subjects tocouching (26.7% each). Commonest methods involved using sharp objects/needling 45% and blunt/grooving/rocking methods (30%). Subjects assumed “supine” position 75% of time. Eighty five percent of eyes were done at the coucher’s. Procedure was painful in 73.3%. Only 5 eyes (25%) maintained vision for >10years. Thirteen (86.7%) said “no” to a repeat procedure and 93.4% would advice against couching.Conclusions: Couching methods used were very crude and archaic with attendant poor quality of vision and dissatisfaction. Public education, affordable and accessible cataract surgical services taken to the rural communities could gradually phase out couching.Keywords: Couching, Methods, Visual sequelae, Nigeri