Pulse-width-dependent critical power for self-focusing of ultrashort laser pulses in bulk dielectrics.

Microscale filamentation of 0.25 NA-focused, linearly and circularly polarized 1030 nm and 515 nm ultrashort laser pulses of variable pulse widths in fused silica, fluorite, and natural and synthetic diamonds demonstrates the Raman-Kerr effect in the form of critical pulse power magnitudes, proportional to squared wavelength and inversely proportional to laser pulse width of 0.3-10 ps. The first trend represents the common spectral relationship between the quantities, while the second indicates its time-integrated inertial contribution of Raman-active lattice polarization, appearing in transmission spectra via ultrafast optical-phonon Raman scattering. The optical-phonon contribution to the nonlinear polarization could come from laser field-induced spontaneous/stimulated Raman scattering and coherent optical phonons generated by electron-hole plasma with its clamped density in the nonlinear focus. Almost constant product value of the (sub)picosecond laser pulse widths and corresponding critical pulse powers for self-focusing and filamentation in the dielectrics ("critical pulse energy") apparently implies constant magnitude of the nonlinear polarization and other "clamped" filamentation parameters at the given wavelength.

Structure of 10He low-lying states uncovered by correlations.

The 0+ ground state of the 10He nucleus produced in the 3H(8He,p)10He reaction was found at about 2.1±0.2 MeV (Γ∼2 MeV) above the three-body ^{8}He+n+n breakup threshold. Angular correlations observed for ^{10}He decay products show prominent interference patterns allowing us to draw conclusions about the structure of low-energy excited states. We interpret the observed correlations as a coherent superposition of a broad 1- state having a maximum at energy 4-6 MeV and a 2+ state above 6 MeV, setting both on top of the 0+ state "tail." This anomalous level ordering indicates that the breakdown of the N=8 shell known in 12Be thus extends also to the ^{10}He system.

Search for a light pseudoscalar particle in the decay K_{L};{0}-->pi;{0}pi;{0}X.

We performed a search for a light pseudoscalar particle X in the decay K_{L};{0}-->pi;{0}pi;{0}X, X-->gammagamma with the E391a detector at KEK. Such a particle with a mass of 214.3 MeV/c;{2} was suggested by the HyperCP experiment. We found no evidence for X and set an upper limit on the product branching ratio for K_{L};{0}-->pi;{0}pi;{0}X, X-->gammagamma of 2.4x10;{-7} at the 90% confidence level. Upper limits on the branching ratios in the mass region of X from 194.3 to 219.3 MeV/c;{2} are also presented.

Search for the Decay K L0-->pi0nu nu[over].

We performed a search for the K L0-->pi0nu nu[over] decay at the KEK 12-GeV proton synchrotron. No candidate events were observed. An upper limit on the branching ratio for the decay was set to be 6.7 x 10(-8) at the 90% confidence level.

Experimental evidence for the existence of 7H and for a specific structure of 8He.

Experimental search for the superheavy 7H isotope was performed in the reaction p(8He,pp)7H with the 8He beam at 61.3A MeV. The evidence for existence of the 7H state near the t+4n threshold was obtained. In the same experiment, the p(8He,t) reaction populating the ground and excited 2(+) state of 6He was investigated. The obtained results argue on a specific structure of the 8He ground state containing the 6He subsystem in the excited 2(+) state with a large weight.

Superheavy hydrogen (5)H.

Experimental search for (5)H using a secondary beam of (6)He has been performed. The transfer reaction (1)H((6)He,(2)He)(5)H was studied by detecting two protons emitted from the decay of (2)He. A peak consistent with a (5)H resonance at 1.7+/-0.3 MeV above the n+n+t threshold was observed, with a width of 1.9+/-0.4 MeV. The angular distribution of the (1)H((6)He,(2)He)(5)H reaction was measured as well as the energy correlation of the two protons.

Involvement of S2 episomal sequences in the generation of NCS4 deletion mutation in maize mitochondria.

Cytoplasmic male sterility (CMS) and the abnormal-growth, nochromosomal stripe (NCS) phenotypes are cytoplasmically determined traits in plants. Mitochondrial DNA rearrangements involving short repeats appear to be responsible for the production of CMS reversions to fertility and NCS mutations. NCS4, a new mutant of maize CMS-S, exhibits both abnormal growth and male fertility. This mutant is unique because both mutations occurred within the same plant. Free S1 and S2 episomes normally found in CMS-S mitochondria have been lost from NCS4 plants. An S2 sequence has recombined aberrantly with a ribosomal protein coding region, rps3/rpl16. One end of the S2 sequence and the 5' end of the rps3/rpl16 transcription unit are absent from the NCS4 recombinant genome. Loss of mitochondrial ribosomal protein function is lethal; therefore, NCS4 plants are heteroplasmic for the rps3 deletion. Loss of S sequences from CMS-S mitochondria is not lethal and plants regain pollen function. Thus, although NCS4 plants have very abnormal plant phenotypes, they are male-fertile.

Repeated sequences with unusual properties from the divergent region of Crithidia oncopelti maxicircle kinetoplast DNA.

The occurrence of bacterial promoter-like sequences was shown in the divergent region of Crithidia oncopelti maxicircular kinetoplast DNA. A promoter-cloning vector based on the neomycin phosphotransferase II (NPT II) gene was used to localize promoters in three homologous blocks of repeated sequences. The elements found displayed greater promoter strength in Escherichia coli than the normal promoter of the NPT II gene. Sequences of three promoter-containing inserts from different blocks were determined and typical prokaryotic promoter sequences were localized.

Kinetoplast DNA segments function as promoters in Escherichia coli cells.

By means of coupled transcription-translation in Escherichia coli cell-free system, an open reading frame was found in the Crithidia oncopelti maxi-circle kDNA segment cloned in the hybrid plasmid pCo1. Subfragments from this region were tested for their ability to function as promoters in E. coli cells. For this purpose the vector pVE8 was constructed using the aminoglycoside phosphotransferase II (APTII) gene from the Tn5 transposon, and the pHC79 cosmid. After cloning of Sau3A fragments of pCo1 by insertion into pVE8 three types of plasmids containing promoter sequences were obtained. Two of these plasmids displayed promoter strength in E. coli cells greater than that of the normal promoter of the APTII gene. However the promoters found are not necessary for the coupled transcription-translation of kDNA in the E. coli cell-free system.