ABSTRACT
We propose an efficient, robust, and broadband nonlinear optical frequency conversion technique, which uses segmented crystals constructed in analogy with the composite pulses in nuclear magnetic resonance and quantum optics. The composite crystals are made of several macroscopic segments of nonlinear susceptibilities of opposite signs and specific thicknesses, which are determined from the condition to maximize the conversion efficiency with respect to variations in the experimental parameters. These crystals deliver broadband operation for significantly lower pump intensities than single bulk crystals. We demonstrate this technique by numerical simulation of sum-frequency generation in MgO:LiNbO3 crystal.
ABSTRACT
A new design of a broadband optical isolator, composed as a sequence of ordinary Faraday rotators and achromatic quarter-wave plates (QWPs), is presented. In particular, we demonstrate that by using four Faraday rotators and six achromatic QWPs, rotated at specific angles, optical isolation better than 15 dB over the range from 700 to 1000 nm can be achieved. The measured transmittance (corrected for absorption and reflection) in the forward direction over the same wavelength range shows broadening of the transmission spectrum compared with the one of a single Faraday rotator.
ABSTRACT
INTRODUCTION: The effect of combined treatment (methylprednisolone and cyclophosphamide) of multiple sclerosis relapse within one year was investigated in an open clinical trial study of 70 patients. The sample comprised subjects shown to have clinically proven multiple sclerosis according to the criteria of C Poser and degree of neurological deficit according to EDSS rating from 2.5 to 6.0 points. MATERIAL AND METHODS: Methylprednisolone (200 mg, i.v., every other day, 10 doses, total course dose 2 g) was administered to 35 patients (mean age 31.34 +/- 1.53 years). Methylprednisolone using the same schedule and cyclophosphamide (200 mg, i.v.) given in the methylprednisolone-free day, 10 doses plus 200 mg i.v. once a month in the first three consecutive months (total course dose 2.6 g) were applied in another 35 patients (mean age 33.22 +/- 1.32 years). RESULTS AND DISCUSSION: The changes of EDSS ratings at the end of months 1 and 12, of the CD+ T-lymphocytes subpopulations and B-lymphocytes from peripheral blood--prior to treatment and between the 5th and 9th week of treatment were compared. The neurological deficit degree according to EDSS dropped significantly (P < 0.01; P < 0.001) after one month of treatment in both groups. At the end of month 12 this indicator reached its baseline value in the group treated only with methylprednisolone while remaining significantly lower in the combined therapy group (P < 0.01). After methylprednisolone and cyclophosphamide application the suppressor/inducer CD8+ T-cells increased significantly in percentage (P < 0.05), while the values of B-lymphocytes decrease significantly (P < 0.05), in contrast to the results from the methylprednisolone-only treatment. CONCLUSIONS: The results clearly indicate the greater efficaciousness of treatment by combining two immunosuppressive drugs.
