Analysis of a true time delay photonic beamformer for transmission of a linear frequency-modulated waveform

A generalized conversion matrix (GCM) and numerical analysis are used to study the distortions suffered by a linear frequency-modulated radio frequency (RF) pulse while propagating through photonic links to be used in wideband phased arrays. The analysis shows the effects of dispersion of all orders, coherent crosstalk and nonlinearity of the optical components on the RF pulse, and the high performance needed to achieve acceptable RF performance of the temporal (impulse) response. The effects of the electrical-to-optical (E/O) and optical-to-electrical (O/E) conversions are also considered. Using the GCM, the optical amplitude and phase fluctuations are converted into their RF counterparts, thereby reducing the optical problem into the well-understood RF domain. A photonic wavelength-controlled true delay device is experimentally shown to achieve good RF performance over a 4-GHz bandwidth, with predicted sidelobe levels below 30 dB.     

Wideband Antenna Patterns and Impulse Response of Broadband RF Phased Arrays With RF and Photonic Beamforming

The general expression for a monochromatic antenna pattern is extended to a two dimensional function with dependence on both space and time. Expressions for the wideband antenna pattern in space and the impulse response in time are developed. The effects of random errors in the spatial domain and errors common to all elements with fluctuations in the frequency domain are analyzed. Examples are given, including RF beamformers and elements in finite arrays, but with an emphasis on a photonic beamformer, which shows improved performance relative to its RF counterparts in both the spatial and time domains     

Regression of C6 rat brain tumors by cells expressing an antisense insulin-like growth factor I receptor RNA

The aim of the study was to measure incidence of oral impacts on daily performances and their related features in a low dental disease population. 501 people aged 35-44 years in 16 rural villages in Ban Phang district, Khon Kaen, Thailand, were interviewed about oral impacts on nine physical, psychological and social aspects of performance during the past 6 months, and then had an oral examination. The clinical and behavioural data showed that the sample had low caries (DMFT = 2.7) and a low utilization of dental services. 73.6% of all subjects had at least one daily performance affected by an oral impact. The highest incidence of performances affected were Eating (49.7%), Emotional stability (46.5%) and Smiling (26.1%). Eating, Emotional stability and Cleaning teeth performances had a high frequency or long duration of impacts, but a low severity. The low frequency performances; Physical activities, Major role activity and Sleeping were rated as high severity. Pain and discomfort were mainly perceived as the causes of impacts (40.1%) for almost every performance except Smiling. Toothache was the major causal oral condition (32.7%) of almost all aspects of performance. It was concluded that this low caries people have as high an incidence of oral impacts as industrialized, high dental disease populations. Frequency and severity presented the paradoxical effect on different performances and should both be taken into account for overall estimation of impacts.     

Concomitant infusion cisplatin and hyperfractionated radiotherapy for locally advanced nasopharyngeal and paranasal sinus tumors

PURPOSE: This is a prospective study to improve the therapeutic ratio in the treatment of patients with locally advanced nasopharyngeal and paranasal sinus tumors by using split-course concomitant infusion cisplatin chemotherapy and hyperfractionated radiotherapy. METHODS AND MATERIALS: From 1983 to 1993, 21 patients with locally advanced nasopharyngeal and paranasal sinus tumors (T3 and T4, or recurrent tumors involving the facial bones and/or the base of the skull) were treated with a regimen of split-course hyperfractioned radiotherapy (1.2 Gy/fraction/bid) and concomitant infusion cisplatin (5-10 mg/m2/24 h). The therapy was given in three separate 2-week sessions with 1 to 2 week breaks between sessions. Seventeen of 21 patients were treated with curative intent with cumulative radiation doses ranging from 64.8 to 70.8 Gy. Four patients were treated with palliative intent to a total dose of less than 60 Gy or to a limited field due to previous irradiation. RESULTS: Sixteen of 17 patients (94%) treated curatively achieved a complete response. Of the 16 patients who achieved complete response, 7 patients (50%) were alive at the time of analysis (36 to 126 months). One patient was alive at 4 years with no evidence of disease, and died in 10 years at the age of 80 of unknown cause. Two patients died of local recurrence at 21 and 45 months and one patient died of a cerebrovascular accident at 12 months with disease status unknown. Five patients died of distant metastases. The one patient who had a partial response died in 25 months with local disease and metastases to the bone and lung. Four patients that were previously irradiated received a reduced total dose or treated to a limited irradiation field. All had near complete responses, but died within a year of treatment, with the exception of one patient who died at 23 months. Acute reactions included intense erythema of the mucosa in all patients. Five of 21 (23%) developed punctate mucositis and 3 of 21 (14%) developed confluent mucositis. Hematologically, one patient developed neutropenia (1800 WBC/mm3) and one developed thrombocytopenia (38,000/mm3). A rising creatinine was observed in three patients (2.0, 1.7, 1.7) all of whom were treated with the higher 10 mg/m2/day dose of infusional cisplatin. In all three of these cases, the creatinine slowly returned to normal over a 6-month period. Hormonal evaluations were performed in three patients and all were within normal ranges. There was no evidence of neck fibrosis or trismus. One patient with gross recurrent disease of the orbit developed blindness of the involved eye due to corneal opacification. The orbital area had been reirradiated in this patient. CONCLUSIONS: Concomitant infusion cisplatinum with hyperfractionated radiation improved tumor control, but did not increase normal tissue injury. Acute reactions were minimized by splitting the treatment with a 1- to 2-week break after each 2 weeks of radiation treatment. Late complications were not increased by using a hyperfractionated radiation regimen. The local failure rate was only 18% (3 of 17 patients), but the distant failure rate was 35% (6 patients). Further investigation is needed to prove if adjuvant chemotherapy after concomitant chemoradiation improves survival by decreasing the distant failure in such advanced cases.     

Atheroma as a neoplastic disease

An hypothesis is proposed that atheroma may be classified as a leiomyosarcoma derived from the tunica media of an artery. The notion that atheroma is a neoplastic disease provides a simple explanation for a highly complex phenomenon; the pathogenesis of artherosclerosis. According to this hypothesis some smooth-muscle cells in the media undergo malignant transformation, which is manifested by excessive production of hyaluronidase and other glycosaminoglycan hydrolases. This enzymic system frees cells from their bonds and allows them to proliferate. The enzymes also evoke a fibroblast hyperplasia which is followed by a protective collagenization producing a local area of increased resistance to the hydrolases. This accounts for the sclerosing aspect of the disease. Several other features of atherosclerosis are a result of the neoplastic nature of the disease.     

Beam width and transmitter power adaptive to tracking system performance for free-space optical communication

The basic free-space optical communication system includes at least two satellites. To communicate between them, the transmitter satellite must track the beacon of the receiver satellite and point the information optical beam in its direction. Optical tracking and pointing systems for free space suffer during tracking from high-amplitude vibration because of background radiation from interstellar objects such as the Sun, Moon, Earth, and stars in the tracking field of view or the mechanical impact from satellite internal and external sources. The vibrations of beam pointing increase the bit error rate and jam communication between the two satellites. One way to overcome this problem is to increase the satellite receiver beacon power. However, this solution requires increased power consumption and weight, both of which are disadvantageous in satellite development. Considering these facts, we derive a mathematical model of a communication system that adapts optimally the transmitter beam width and the transmitted power to the tracking system performance. Based on this model, we investigate the performance of a communication system with discrete element optical phased array transmitter telescope gain. An example for a practical communication system between a Low Earth Orbit Satellite and a Geostationary Earth Orbit Satellite is presented. From the results of this research it can be seen that a four-element adaptive transmitter telescope is sufficient to compensate for vibration amplitude doubling. The benefits of the proposed model are less required transmitter power and improved communication system performance.