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A portion of an insertion sequence present in a member of theRIRE3family of retrotransposons inOryza sativaL. cv. IR36 was found to have an LTR sequence followed by a PBS sequence complementary to the 3′-end region of tRNAMet, indicative of another rice retrotransposon (namedRIRE7). Cloning and sequencing of PCR-amplified fragments that made up all parts of theRIRE7sequence showed thatRIRE7is agypsy-type retrotransposon with partial homology in thepolregion to the ricegypsy-type retrotransposonsRIRE2andRIRE3identified in rice previously. Interestingly, various portions of theRIRE7sequence were homologous to several DNA segments present in the centromere regions of cereal chromosomes. Further cloning and nucleotide sequencing of fragments flankingRIRE7copies showed thatRIRE7was inserted into a site within a tandem repeat sequence that has a unit length of 155 bp. The tandem repeat sequence, named TrsD, was homologous to tandem repeat sequences RCS2 and CentC, previously identified in the centromeric regions of rice and maize chromosomes. Fluorescencein situhybridization (FISH) analysis of the metaphase chromosomes ofO. sativacv. Nipponbare showed that bothRIRE7and TrsD sequences were present in the centromere regions of the chromosomes. The presence ofRIRE7and the TrsD sequences in the centromere regions of several chromosomes was confirmed by the identification of several YAC clones whose chromosomal locations are known. Further FISH analysis of rice pachytene chromosomes showed that the TrsD sequences were located in a pericentromeric heterochromatin region. These findings strongly suggest thatRIRE7and TrsD are components of the pericentromeric heterochromatin of rice chromosomes.

Geothermal energy extraction from hot, dry rock requires the circulation of water under pressure through a crack with a small opening (several millimeters) and a large radius (several hundred meters) at several kilometers beneath ground surface. Here we present the basic two-dimensional field equations for the fluid flow and heat transfer, by systematically integrating over the crack thickness the fundamental mass, momentum, and energy equations. The importance of various terms on physical grounds is briefly discussed, and on this basis the corresponding equations are simplified. Finally, with the aid of a finite-element approximation, typical illustrative examples are worked out. These examples reveal that a more accurate estimate for the effective conductivity between fluid and the solid must be obtained in order to more realistically estimate the basic heat extraction process. In particular, the effect of secondary cracks must be carefully examined. This and related aspects of the problem are discussed, and certain areas in need of further research are pointed out.

This paper proposes a new finite element method for treating the stress analysis of a piping system under general loading conditions. This finite element method will be referred as the finite ring method, since its elements are ring-shaped. This finite ring treatment is based on the general thin shell theory incorporating shear and distributed deformations along the pipe length. In this paper, emphasis is given to the theoretical aspects of the method. A comparison with other experimental and theoretical results is presented to substantiate the validity of the present method.

In vivo recombination was found to occur between plasmid pHS1, a temperature-sensitive replication mutant of pSC101 carrying tetracycline resistance, and plasmid ColE1 after selection for tetracycline resistance at the restrictive temperature, 42 degrees C. Extensive analysis of the physical structures of three of these recombinant plasmids, using restriction endonucleases and the electron microscope heteroduplex method, revealed that the plasmid pHS1 was integrated into different sites on ColE1. The recombinant plasmids contained a duplication of a unique 1-kilobase (kb) sequence of pHS1 in a direct orientation at the junctions between the two parental plasmid sequences. This was confirmed by comparing the nucleotide sequence of the recombinants and their parental plasmids. Nucleotide sequence analysis further revealed that nine nucleotides at the site of recombination of ColE1 were duplicated at the junction of each of the 1-kb sequences. The formation of recombinants was independent of RecA function. Based on our previous finding that a plasmid containing a deoxyribonucleic acid insertion (IS) element can recombine with a second plasmid to generate a duplication of the IS element, we conclude that the 1-kb sequence is an insertion sequence, which we named IS102. For convenience, we have also denoted the IS102 sequence as eta theta to assign the orientation of the sequence. Eighteen nucleotides at one end (eta end) were found to be repeated in an inverted orientation at the other end (theta end) of IS102. The nucleotide sequence of the eta end of the sequence was found to be identical to the sequence at the ends of the transposon Tn903, which is responsible for transposition of the kanamycin resistance gene.

The present paper investigates the flexibility and stress factors for the pipe bends when they are connected with straight pipes and subjected to out-of-plane as well as in-plane bending moments, to which the conventional methods are not directly applicable. The stress analysis is carried out by the use of a new finite ring element method which is based on the general thin shell theory incorporating shear strain. The numerical results obtained for flexibility and stress factors are compared with the code formula. The influence of initial deflections and the variation of the pipe wall thickness is also studied.

A method is described for isolation of inverted repeat DNA sequences that occur in E. coli plasmids. The procedures of the isolation involved: (a) denaturation of intact plasmid DNA, (b) a rapid, 30 sec, renaturation of inverted-repeat sequences in the genome, (c) digestion of the single-stranded portion by S1 nuclease to recover duplex DNA, and (d) detection and purification of the duplexes using 1.4% agarose gel electrophoresis. If a plasmid DNA carried inverted repeats of either one type or two different types of special DNA sequences, these procedures enabled us to observe either one or two characteristic DNA bands, respectively, in the agarose gels. If a plasmid DNA did not carry any inverted repeats, or if the plasmid DNA only carried direct repeat sequences, no characteristic DNA bands were recovered. Cleavage of the spacer DNA between inverted repeat sequences generated no gel bands. This indicated that the inverted repeat sequences must be in the same strand. Using this method, we isolated and purified several repeated sequences, including IS1, IS2, and IS3, from derivatives of F and R plasmids.

PSM2, PSM1, and PSM15 are small plasmids derived from R100 by spontaneous deletions at either end of the insertion sequence IS1. These plasmids were used to identify regions neighboring IS1 as well as the IS1 DNA itself, by cleavage with EcoR1, HindIII, Hae III, Hpa II, Hha I, Hinf, and AIu I. The nucleotide sequencing results demonstrate that IS1 contains 768 bases. About 30 bases at the ends of IS1 were found to be repeated in an inverted order. The deletions occurring at the ends of IS1 were found to be due to illegitimate recombination. The hypothesis that RNA polymerase could play an important role in such recombination phenomena is discussed based on the nucleotide sequences surrounding the recombinational hot spots.

We studied in vivo recombination between the plasmid pHS1, a temperature-sensitive replication mutant carrying tetracycline resistance, and pSM1, a small plasmid carrying one copy of the insertion element IS1. Recombinant plasmids were found by selection for tetracycline resistance at 42 degrees C. Their formation was independent of recA function. Analysis of the physical structures of various recombinant DNA molecules with electron microscopy and restriction endonucleases revealed that pSMI was integrated at its IS1 into numerous sites on pHS1, giving rise to a duplication of IS1 in the same orientation at both junctions. Nucleotide sequence analysis of recombinant plasmids and their parental plasmid DNA revealed that nine nucleotides at a target site were duplicated at the junction of each IS1. This phenomenon implies that plasmids containing a translocatable DNA element can be potential transposons.

Electron scattering and charged pion photoproduction at 200 MeV on12C and13C have been studied by the nuclear shell model to investigateM1 andE2 nuclear form factors of the isovector type. Starting with the Op-shell model of Hauge-Maripuu, the effects of core polarization by theM 3Y force and the one-pion-exchange current are taken into account. The effect of core polarization is found to be essential in both electron scattering and pion photoproduction, while the meson-exchange current, which also improves the calculated results, gives contributions of about 10%–15%.

The present paper describes a simplified finite element method for analysis of behavior of complex piping systems under elevated temperature. Elastic-plastic-creep deformations of a piping system under a combined moment loading can be analyzed by the present method. The system is idealized by straight and curved beams, and derivation of the finite element equation is based on the force method. The unified constitutive relations are used for creep and plastic behavior, where plastic deformation is treated as a limiting case of creep. The numerical results are compared with previous experimental ones, which verifies the validity of the proposed method. Elastic follow-up problem of a piping system of actually complex configuration is also solved by the present method.