Mobility Edge in Aperiodic Kronig-Penney Potentials with Correlated Disorder: Perturbative Approach

It is shown that a non-periodic Kronig-Penney model exhibits mobility edges if the positions of the scatterers are correlated at long distances. An analytical expression for the energy-dependent localization length is derived for weak disorder in terms of the real-space correlators defining the structural disorder in these systems. We also present an algorithm to construct a non-periodic but correlated sequence exhibiting desired mobility edges. This result could be used to construct window filters in electronic, acoustic, or photonic non-periodic structures.Comment: RevTex, 4 pages including 2 Postscript figure

Rootstock resistance to Fusarium wilt and effect on watermelon fruit yield and quality

The potential of grafted watermelon for resistance to Fusarium oxysporum f.sp. niveum on some Curcurbitaceae, Lagenaria, Luffa, Benincasa and commercial rootstocks was evaluated. Effects of grafting on yield and quality of diseased plants were evaluated. All grafted plants and rootstocks were resistant to the three known races (0, 1, and 2) of F oxysporum f.sp. niveum except watermelon cv. 'Crimson Tide', which was susceptible to race 2. Fruit yield was positively (21-112%) affected by Lagenaria rootstocks but negatively affected (200-267%) by Cucurbita rootstocks when compared with the control. While only minor differences in fruit quality were determined in control and grafted plants on Lagenaria rootstocks, the quality parameters for watermelon grafted onto Cucurbita rootstocks were lower than in the control. The reasons for low yield and quality might be due to an incompatibility between Cucurbita rootstocks and watermelon. These results showed that rootstock influence on disease resistance as well as yield and quality of scion fruit is important in determining the potential use of grafting applications in watermelon