Design and Preliminary Experiment of W-Band Broadband TE02 Mode Gyro-TWT

The gyrotron travelling wave tube (gyro-TWT) is an ideal high-power, broadband vacuum electron amplifier in millimeter and sub-millimeter wave bands. It can be applied as the source of the imaging radar to improve the resolution and operating range. To satisfy the requirements of the W-band high-resolution imaging radar, the design and the experimentation of the W-band broadband TE02 mode gyro-TWT were carried out. In this paper, the designs of the key components of the vacuum tube are introduced, including the interaction area, electron optical system, and transmission system. The experimental results show that when the duty ratio is 1%, the output power is above 60 kW with a bandwidth of 8 GHz, and the saturated gain is above 32 dB. In addition, parasitic mode oscillations were observed in the experiment, which limited the increase in duty ratio and caused the measured gains to be much lower than the simulation results. For this phenomenon, the reasons and the suppression methods are under study.

A STUDY OF POTENTIAL LISTERIOSIS: AN EMERGING FOOD-BORNE DISEASE

The incidence of listeriosis has been rising 1980s. Epidemic outbreaks are becoming more widespread and are accompanied by high mortality. The most common cause of infectionis consumption of food contaminated with pathogenic Listeria species, in particular L. monocytogenes . Listeria bacteria are psychrophiles, live in all media of the environment, and easily move from saprotrophic to parasitic mode of life. All these qualities have provided them with adaptability and high survival capacity. The sources of food contamination with Listeria bacteria usually are contaminated raw materials or equipment of food production facilities. Deep frozen beef blocks were tested for contamination with Listeria bacteria that were detected and identified by bacteriological technique and enzyme immunoassayand immunochromatographic assay. Listeria bacteria were found in 35% of samples but there were no pathogenic species among them. The isolated species were identified as L. innocua, L. welshimeri, L. grayi and L. seeligeri . These species often colonisevarious media of the environment. The examined meat samples were found to be safe. Listeriosis can be prevented by systemic proactive measures including sanitary and epidemiological control of food raw materials and finished products, properly organized technological process, and hygienic education of the population.

Biochemical Studies on Cestode Parasites in Mastacembelus Armatus in Nasik District, M. S. (India)

Parasitic biochemistry is an arena which is emerging in parallel with the new surge of interest in tropical diseases. The previously known parasitologists have been known to adopt biochemical methodology in order to stay up-to-date of development. The main source of energy for cestode inhabiting the alimentary tract of vertebrates is glucose. Proteins and lipids are also crucial and play many important biological roles. The protein content of the parasites adapted to parasitic mode of life typically constitute 20 to 40 percent of their dry weight, while as older proglottids are known to contain higher contents of lipid. The present study deals with biochemical estimation of cestode parasites and its host (Normal and infected intestinal tissue of Mastacembelus armatus) from Nasik district. The result show higher concentration of lipid in parasites than its host.

Evolution of parasitism along convergent lines: from ecology to genomics

SUMMARYFrom hundreds of independent transitions from a free-living existence to a parasitic mode of life, separate parasite lineages have converged over evolutionary time to share traits and exploit their hosts in similar ways. Here, we first summarize the evidence that, at a phenotypic level, eukaryotic parasite lineages have all converged toward only six general parasitic strategies: parasitoid, parasitic castrator, directly transmitted parasite, trophically transmitted parasite, vector-transmitted parasite or micropredator. We argue that these strategies represent adaptive peaks, with the similarities among unrelated taxa within any strategy extending to all basic aspects of host exploitation and transmission among hosts and transcending phylogenetic boundaries. Then, we extend our examination of convergent patterns by looking at the evolution of parasite genomes. Despite the limited taxonomic coverage of sequenced parasite genomes currently available, we find some evidence of parallel evolution among unrelated parasite taxa with respect to genome reduction or compaction, and gene losses or gains. Matching such changes in parasite genomes with the broad phenotypic traits that define the convergence of parasites toward only six strategies of host exploitation is not possible at present. Nevertheless, as more parasite genomes become available, we may be able to detect clear trends in the evolution of parasitic genome architectures representing true convergent adaptive peaks, the genomic equivalents of the phenotypic strategies used by all parasites.