Minichromosome formation in Chlorella cells irradiated with electron beams

Three minichromosomes, miniP7, miniB7, and miniK4 of 800 kbp, 450 kbp, and 550 kbp, respectively, were obtained from Chlorella vulgaris chromosome I by electron-beam irradiation. Two of them were structurally characterized: MiniP7 was formed by the deletion of an internal 180 kbp close to the right end of chromosome I. The 180-kbp region with a small interspersed nuclear element (SINE)-like element on its left terminus was translocated to another chromosome, leaving a footprint-like structure on miniP7. MiniB7 was a hybrid of chromosome I and another chromosome, retaining the left telomere and the centromere of chromosome I. The centromeric repetitive elements served as a rearrangement point in the miniB7 formation. These examples showed the complicated mechanisms involved in the minichromosome formation. The minichromosomes thus obtained can be useful for isolating the fundamental structural elements of a chromosome. Moreover, they may serve as starting materials or a vector to generate artificial chromosomes carrying useful genes.     

Isolation of an Acremonium sp. capable of liquefying cross-linked poly(gamma-glutamic acid) hydrogels and the fungal enzyme involved in the disruption of gamma-ray irradiation-mediated cross-linking

A microorganism capable of liquefying cross-linked poly(gamma-glutamic acid) (C-L PGA) was isolated and identified to be an Acremonium sp. The fungus produced an enzyme that can disrupt the cross-linkages of C-L PGA generated by gamma-ray irradiation. The enzyme can also liquefy C-L PGA prepared by chemical cross-linkage, suggesting the involvement of ester bonds in the gamma-ray irradiation-mediated cross-linking of PGA.     

Microlens fabricated by the planar process

A novel microlens that can be integrated on a laser-diode substrate by the planar process is proposed. It consists of two microcylindrical lenses fabricated by the planar process, and all of their dimensions are less than 100 μm. One lens is a horizontal focusing lens whose curved shape determines focusing. The other is a vertical focusing lens whose gradient refractive index determines focusing. The relationship between fabrication errors and lens characteristics is quantitatively established by comparing lenses with various fabrication errors. Also a laser diode integrated with the horizontal focusing lens is successfully fabricated without damage     

Determination of the flexural strength and elastic modulus of ice from in situ cantilever-beam tests

From the theory of cantilever beams on an elastic foundation, it is shown that the strength index and modulus index of ice can be determined from measurements of either the failure load or the tip deflection, or both, of in situ cantilever beams tested over a wide enough range of ratio of beam length to beam thickness. Four methods are proposed, two of which do not require the measurement of beam deflection during beam loading, an often difficult task to perform with sufficient reliability, especially in the field. The methods have been applied to available field and laboratory data. The initial results show reasonably consistent estimates of the strength index but a large variation in the predicted values of the modulus index. One preferred method is suggested but its validity and reliability need to be further evaluated by analyzing a sufficient number of field and laboratory tests.     

Novel method for measuring cutoff wavelength of HE21-, TE01-and TM01-modes

A new measurement method for the cutoff wavelength of HE21-, TE01-and TM01 modes using a polariser is described. The experimental results show that higher measurement accuracy and sensitivity are obtained compared with the previous method.