Strong and Broadband Pure Optical Activity in 3D Printed THz Chiral Metamaterials

Optical activity (polarization rotation of light) is one of the most desired features of chiral media, as it is important for many polarization related applications. However, in the THz region, chiral media with strong optical activity are not available in nature. Here, we study theoretically, and experimentally a chiral metamaterial structure composed of pairs of vertical U-shape resonators of "twisted" arms, and we reveal that it demonstrates large pure optical activity (i.e. optical activity associated with negligible transmitted wave ellipticity) in the low THz regime. The experimental data show polarization rotation up to 25 (deg) for an unmatched bandwidth of 1 THz (relative bandwidth 80 %), from a 130 um-thickness structure, while theoretical optimizations show that the rotation can reach 45 (deg). The enhanced chiral response of the structure is analyzed through an equivalent RLC circuit model, which provides also simple optimization rules for the enhancement of its chiral response. The proposed chiral structures allow easy fabrication via direct laser writing and electroless metal plating, making them suitable candidates for polarization control applications.Comment: 17 pages, 7 figure

The nematode enhanced susceptibility to Fusarium and Verticillium wilt of cotton

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN030049 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Enhancement of germination of spores of Verticillium dahliae and Fusarium oxysporum esp vasinfectum in vascular fluid from cotton plants infected with the root-knot nematode

Root-knot nematode [RKN] (Meloidogyne incognita) can increase the severity of Verticillium (V dahliae) and Fusarium (F oxysporum f.sp. vasinfectum) wilt diseases in cotton (Gossypium hirsutum). This study was conducted to determine some of the physiological responses caused by nematode invasion that might decrease resistance to vascular wilt diseases. The effect of RKN was investigated on spore germination and protein, carbohydrate and peroxidase content in the xylem fluids extracted from nematode-infected plants. Two cotton cultivars were used with different levels of resistance to both of the wilt pathogens. Spore germination was greater in the xylem fluids from nematode-infected plants than from nematode-free plants. The effect on spore germination was greater in the Fusarium-resistant cultivar (51%). Analysis of these fluids showed a decrease in total protein and carbohydrate levels for both wilt-resistant cultivars, and an increase in peroxidase concentration. Fluids from nematode-free plants of the Verticillium-resistant cultivar contained 46% more peroxidase than the Fusarium-resistant cultivar. The results provide further evidence that the effect of RKN on vascular wilt resistance is systemic and not only local. Changes in metabolites in the xylem pass from the root to the stem, accelerating disease development

Blast fungus inoculation reduces accumulation and remobilization of pre-anthesis assimilates to rice grains

The importance of stored assimilates for grain development in cereals has been widely recognized, particularly in cereals exposed to stress during the grain filling period. This study was conducted to investigate the effect of the blast fungus Magnaporthe grisea on dry matter accumulation, remobilization and utilization in rice (Oryza sativa L.) under field conditions. Four rice varieties with various levels of susceptibility to rice blast were grown in 2003 and 2004 under high and low disease intensity, caused by early inoculation and natural infection respectively. High disease intensity reduced plant height, dry matter accumulation, the harvest index and grain yield. Plants grown under high disease intensity translocated fewer stored assimilates to the grain than plants grown under low disease intensity. Dry matter translocation from the vegetative parts to the grain was significantly correlated with dry matter at anthesis (r=0.65, P&lt0.05;). High stress from early leaf blast caused by inoculation with the blast fungus affected overall plant growth and lowered the production of pre-anthesis assimilates, as well as causing severe levels of neck blast that resulted in a low translocation rate during the filling period, and therefore a lower grain yield than in naturally infected plants