Waveguiding through a two-dimensional metallic photonic crystal.

We present a two-dimensional (2D) finite-difference time domain simulation of the propagation of light through linear and bent channels in metallic photonic crystals. We took as a starting point the Bozhevolnyi experiment, consisting of the scattering of surface plasmons by a 2D structure of finitely sized periodic gold dots arranged in a triangular lattice of 400-nm period. We model injection and propagation of light through linear channels of different widths. We also study the behaviour of light in the presence of a 90 degrees bent line defect made in the structure. We show that the confinement depends on the orientation of the input and output line defects. The two cases of GammaM and GammaK orientations are considered and a spectral study for five different wavelengths is carried out.

HTLV-I and HTLV-II infections in volunteer blood donors and high-risk groups in Lebanon.

A serosurvey for Human T-cell Lymphotropic virus type 1 (HTLV-I)/HTLV-II was conducted in 1,900 blood donors, 120 pregnant women and 436 high-risk group patients in Beirut, Lebanon. One of the 1,900 blood donors was anti-HTLV-I/II-seroreactive on screening by enzyme immunoassay (EIA) but was indeterminate by Western blot and negative by polymerase chain reaction. None of the other 556 subjects studied was seroreactive by EIA. The credibility of the zero prevalence of HTLV-I/II infection among the Lebanese blood donors is supported by the absence of seroreactivity of antibodies in the multiply transfused patients. It seems therefore that the prevalence of HTLV-I/II appears to be less than 1 in 2,456 in the Lebanese population and hence, HTLV-I/II infection does not appear to require routine screening in Lebanon.

[Evaluation of the Widal test for diagnosing typhoid fever in Lebanon]. / Evaluation du test de Widal pour le diagnostic de la fièvre typhoïde au Liban.

Typhoid fever is a major public health problem in developing countries. In Lebanon, where the sanitary infrastructure was severely damaged during the civil war, the high prevalence of typhoid fever creates a pressing need for a rapid and reliable diagnostic tool. To evaluate the diagnostic usefulness of the Widal test, patients with a positive blood culture for Salmonella typhi (n = 78) were compared to controls with fever due to another infection (n = 65) and with blood donors (n = 96). Discrimination between the patient group and the two control groups was best when an agglutinin O titer of 1/160 or more was used. With this cutoff, sensitivity was 67.9%; specificity was 93.8% versus the febrile controls and 100% versus the blood donors. These results suggest that despite its well-known limitations the Widal test remains a valuable tool for typhoid fever control in many developing countries.

Prevalence and etiology of intestinal parasites in Lebanon.

As there are no studies done on the prevalence of intestinal parasites in Lebanon since 1967, this study was undertaken to reveal the current patterns of intestinal parasitic infestations in Lebanese patients from two geographic regions: Beirut and Tripoli. Analysis was based on 33,253 stool specimens examined at the American University of Beirut Medical Center (AUH) and 11,611 specimens examined at the Islamic Hospital (IH) in Tripoli over five and three years, respectively. The prevalence of intestinal parasites at AUH and IH were 8.47% and 45.35%, respectively (overall 18%). The prevalence in males vs females was almost the same; being 8.23% vs 8.74%, and 44.67% vs 45.88%, at AUH and IH, respectively. Multiple infections were noted in 8.8% and 3.5% of stool specimens at AUH and IH, respectively. Although 18 different types of parasites were encountered, the most common pathogenic parasites found at AUH vs IH were: Giardia lamblia (20.7% vs 10.5% of parasites found), Entamoeba histolytica (19.41% vs 1.25%), Taenia spp. (6.03% vs 4.08%) and Ascaris lumbricoides (2.09% vs 46.97%). The overall yearly or monthly prevalence of parasites recovered from both hospitals did not show clear seasonal patterns. Compared to developed countries, Lebanon still suffers from a high prevalence and a wide spectrum of intestinal parasites.