Precise Measurement of Differential Cross Sections of the Σ^{-}p→Λn Reaction in Momentum Range 470-650 MeV/c

The differential cross sections of the Σ^{-}p→Λn reaction were measured accurately for the Σ^{-} momentum (p_{Σ}) ranging from 470 to 650  MeV/c at the J-PARC Hadron Experimental Facility. Precise angular information about the Σ^{-}p→Λn reaction was obtained for the first time by detecting approximately 100 reaction events at each angular step of Δcosθ=0.1. The obtained differential cross sections show a slightly forward-peaking structure in the measured momentum regions. The cross sections integrated for -0.7≤cosθ≤1.0 were obtained as 22.5±0.68 [statistical error(stat.)] ±0.65 [systematic error(syst.)] mb and 15.8±0.83(stat)±0.52(syst)  mb for 470<p_{Σ}(MeV/c)<550 and 550<p_{Σ}(MeV/c)<650, respectively. These results show a drastic improvement compared with past measurements of the hyperon-proton scattering experiments. They will play essential roles in updating the theoretical models of the baryon-baryon interactions.

Recent progress and future prospects of hyperon nucleon scattering experiment

A new hyperon-proton scattering experiment, dubbed J-PARC E40, was performed to measure differential cross sections of the Σ+p, Σ−p elastic scatterings and the Σ−p → Λn scattering by identifying a lot of Σ particles in the momentum ranging from 0.4 to 0.8 GeV/c produced by the π±p → K+Σ± reactions. We successfully measured the differential cross sections of these three channels with a drastically improved accuracy with a fine angular step. These new data will become important experimental constraints to improve the theories of the two-body baryon-baryon interactions. Following this success, we proposed a new experiment to measure the differential cross sections and spin observables by using a highly polarized Λ beam for providing quantitative information on the ΛN interaction. The results of three Σp channels and future prospects of the Λp scattering experiment are described.

Gender differences in self-perceived changes among Japanese workers with depression

BACKGROUND

The number of patients living with depression continues to increase in Japan. The economic effects of depression include loss of productivity due to both absenteeism and presenteeism. Gender differences have been reported in prevalence, onset pathways and subjective symptoms of depression.

AIMS

To understand how workers with major depressive disorder (MDD) perceive problems in the workplace and examine gender differences in their self-perceived levels of functioning at work, noticed during the initial stages of depression.

METHODS

This is a cross-sectional study of Japanese workers with MDD. Participants' self-perceived changes in the level of functioning at work were surveyed after the diagnosis during the first visit. The relationship between gender and changes in the level of functioning at work as initially perceived by the participants themselves was analysed using the chi-square test, supplemented by a residual analysis.

RESULTS

We administered the survey to 147 workers with MDD. In terms of gender differences in initial self-perceived changes in the level of functioning at work, the proportion of men reporting reduced work efficiency was significantly higher than that of women, while the proportion of women reporting deterioration in relationships with colleagues and superiors was significantly higher than that of men.

CONCLUSIONS

The findings suggest that greater attention to reduced work efficiency by men and to deterioration in work relationships by women with MDD should be essential components of self-care. Managers need to pay attention to the level of functioning and provide adequate social support for employees.

First Determination of the Level Structure of an sd-Shell Hypernucleus, _{Λ}^{19}F

We report on the first observation of γ rays emitted from an sd-shell hypernucleus, _{Λ}^{19}F. The energy spacing between the ground state doublet, 1/2^{+} and 3/2^{+} states, of _{Λ}^{19}F is determined to be 315.5±0.4(stat)_{-0.5}^{+0.6}(syst)  keV by measuring the γ-ray energy of the M1(3/2^{+}→1/2^{+}) transition. In addition, three γ-ray peaks are observed and assigned as E2(5/2^{+}→1/2^{+}), E1(1/2^{-}→1/2^{+}), and E1(1/2^{-}→3/2^{+}) transitions. The excitation energies of the 5/2^{+} and 1/2^{-} states are determined to be 895.2±0.3(stat)±0.5(syst) and 1265.6±1.2(stat)_{-0.5}^{+0.7}(syst)  keV, respectively. It is found that the ground state doublet spacing is well described by theoretical models based on existing s- and p-shell hypernuclear data.

Oral administration of milk-derived phospholipids inhibits penetration of cutaneous nerve fibres into epidermis in a mouse model of acute dry skin

The density of intraepidermal nerve fibres has been shown to be higher in itchy dry skin than in healthy skin, suggesting that epidermal hyperinnervation is at least partly involved in peripheral itch sensitization. We investigated whether oral administration of milk-derived phospholipids (MPLs) would inhibit epidermal hyperinnervation in a mouse model of dry skin. We found that the number of intraepidermal nerve fibres was significantly lower in the MPL group than in the control group. Expression of nerve growth factor (NGF) levels in the epidermis was significantly decreased by oral administration of MPLs, whereas expression of semaphorin (Sema)3A, a nerve repulsion factor, was increased in the MPL group. These results suggest that dietary MPLs attenuate the penetration of nerve fibres into the epidermis by reducing epidermal NGF levels and increasing Sema3A level. Thus, dietary MPLs may have beneficial effects in the prevention and/or alleviation of dry skin-induced itch by reducing intraepidermal nerve fibre density.

Vertical distribution of 236U in the North Pacific Ocean

The first extensive study on ²³⁶U in the North Pacific Ocean has been conducted. The vertical distribution of ²³⁶U/²³⁸U isotopic ratios and the ²³⁶U concentrations were analysed on seven depth profiles, and large variations with depth were found. The range of ²³⁶U/²³⁸U isotopic ratios was from (0.09 ± 0.03) × 10^-10 to (14.1 ± 2.2) × 10^-10, which corresponds to ²³⁶U concentrations of (0.69 ± 0.24) × 10⁵ atoms/kg and (119 ± 21) × 10⁵ atoms/kg, respectively. The variations in ²³⁶U concentrations could mainly be attributed to the different water masses in the North Pacific Ocean and their formation processes. Uranium-236 inventories on the water column of each sampling station were calculated and varied between (3.89 ± 0.08) × 10¹² atoms/m² and (7.03 ± 0.50) × 10¹² atoms/m², which is lower than in former studies on comparable latitudes in the North Atlantic Ocean and the Sea of Japan. The low inventories of ²³⁶U found for the North Pacific Ocean in this study can be explained by the lack of additional input sources of artificial radionuclides, apart from global and regional/local fallout. This study expands the use of ²³⁶U as oceanographic circulation tracer to yet another ocean basin and shows that this isotope can be used for tracing circulation patterns of water masses in the Pacific Ocean.

First study on 236U in the Northeast Pacific Ocean using a new target preparation procedure for AMS measurements

We succeeded in obtaining the depth profile of ²³⁶U for a sampling station in the Northeast Pacific Ocean using only one litre of seawater sample from each depth. For this purpose, a new procedure was developed that allowed for the preparation of accelerator mass spectrometry targets for trace uranium using only 100 μg of iron carrier material. The ²³⁶U concentrations in water samples from the Northeast Pacific Ocean showed large variations from (9.26 ± 0.42) × 10⁶ atoms/kg at 60 m depth to (0.08 ± 0.02) × 10⁶ atoms/kg at a depth of 3000 m. The high ²³⁶U concentrations in surface water reflect the input of ²³⁶U by global and local fallout from nuclear weapons tests. The low ²³⁶U concentrations in seawater from 1500 m and below are an indicator for the low vertical diffusion of surface water to deeper layers in the North Pacific Ocean. The total inventory of ²³⁶U on the water column was (8.35 ± 0.23) × 10¹² atoms/m², which is lower compared to those of other ocean regions solely affected by global fallout on comparable latitudes. This study represents the first dataset for ²³⁶U in the Pacific Ocean and shows the possibility of downsizing sample volumes which may help in future applications of ²³⁶U as tracer for large ocean areas.

Interference Effect between ϕ and Λ(1520) Production Channels in the γp→K^{+}K^{-}p Reaction near Threshold

The ϕ-Λ(1520) interference effect in the γp→K^{+}K^{-}p reaction has been measured for the first time in the energy range from 1.673 to 2.173 GeV. The relative phases between ϕ and Λ(1520) production amplitudes were obtained in the kinematic region where the two resonances overlap. The measurement results support strong constructive interference when K^{+}K^{-} pairs are observed at forward angles but destructive interference for proton emission at forward angles. Furthermore, the observed interference effect does not account for the sqrt[s]=2.1  GeV bump structure in forward differential cross sections for ϕ photoproduction. This fact suggests possible exotic structures such as a hidden-strangeness pentaquark state, a new Pomeron exchange, or rescattering processes via other hyperon states.

Observation of Spin-Dependent Charge Symmetry Breaking in ΛN Interaction: Gamma-Ray Spectroscopy of _{Λ}^{4}He

The energy spacing between the spin-doublet bound state of _{Λ}^{4}He(1^{+},0^{+}) was determined to be 1406±2±2  keV, by measuring γ rays for the 1^{+}→0^{+} transition with a high efficiency germanium detector array in coincidence with the ^{4}He(K^{-},π^{-})_{Λ}^{4}He reaction at J-PARC. In comparison to the corresponding energy spacing in the mirror hypernucleus _{Λ}^{4}H, the present result clearly indicates the existence of charge symmetry breaking (CSB) in ΛN interaction. By combining the energy spacings with the known ground-state binding energies, it is also found that the CSB effect is large in the 0^{+} ground state but is vanishingly small in the 1^{+} excited state, demonstrating that the ΛN CSB interaction has spin dependence.

Isotopic Pu, Am and Cm signatures in environmental samples contaminated by the Fukushima Dai-ichi Nuclear Power Plant accident

Dust samples from the sides of roads (black substances) have been collected together with litter and soil samples at more than 100 sites contaminated heavily in the 20-km exclusion zones around Fukushima Dai-ichi Nuclear Power Plant (FDNPP) (Minamisoma City, and Namie, Futaba and Okuma Towns), in Iitate Village located from 25 to 45 km northwest of the plant and in southern areas from the plant. Isotopes of Pu, Am and Cm have been measured in the samples to evaluate their total releases into the environment from the FDNPP and to get the isotopic compositions among these nuclides. For black substances and litter samples, in addition to Pu isotopes, (241)Am, (242)Cm and (243,244)Cm were determined for most of samples examined, while for soil samples, only Pu isotopes were determined. The results provided a coherent data set on (239,240)Pu inventories and isotopic composition among these transuranic nuclides. When these activity ratios were compared with those for fuel core inventories in the FDNPP accident estimated by a group at JAEA, except (239,240)Pu/(137)Cs activity ratios, fairly good agreements were found, indicating that transuranic nuclides, probably in the forms of fine particles, were released into the environment without their large fractionations. The obtained data may lead to more accurate information about the on-site situation (e.g., burn-up, conditions of fuel during the release phase, etc.), which would be difficult to get otherwise, and more detailed information on the dispersion and deposition processes of transuranic nuclides and the behavior of these nuclides in the environment.

Search for the Θ+ pentaquark via the π(-)p→K(-)X reaction at 1.92 GeV/c

The Θ(+) pentaquark baryon was searched for via the π(-)p→K(-)X reaction with a missing mass resolution of 1.4 MeV/c(2) (FWHM) at the Japan Proton Accelerator Research Complex (J-PARC). π(-) meson beams were incident on the liquid hydrogen target with a beam momentum of 1.92 GeV/c. No peak structure corresponding to the Θ(+) mass was observed. The upper limit of the production cross section averaged over the scattering angle of 2° to 15° in the laboratory frame is obtained to be 0.26 μb/sr in the mass region of 1.51-1.55 GeV/c(2). The upper limit of the Θ(+) decay width is obtained to be 0.72 and 3.1 MeV for J(Θ)(P)=1/2(+) and J(Θ)(P)=1/2(-), respectively, using the effective Lagrangian approach.

The histone H4 lysine 20 monomethyl mark, set by PR-Set7 and stabilized by L(3)mbt, is necessary for proper interphase chromatin organization

Drosophila PR-Set7 or SET8 is a histone methyltransferase that specifically monomethylates histone H4 lysine 20 (H4K20). L(3)MBT has been identified as a reader of methylated H4K20. It contains several conserved domains including three MBT repeats binding mono- and dimethylated H4K20 peptides. We find that the depletion of PR-Set7 blocks de novo H4K20me1 resulting in the immediate activation of the DNA damage checkpoint, an increase in the size of interphase nuclei, and drastic reduction of cell viability. L(3)mbt on the other hand stabilizes the monomethyl mark, as L(3)mbt-depleted S2 cells show a reduction of more than 60% of bulk monomethylated H4K20 (H4K20me1) while viability is barely affected. Ploidy and basic chromatin structure show only small changes in PR-Set7-depleted cells, but higher order interphase chromatin organization is significantly affected presumably resulting in the activation of the DNA damage checkpoint. In the absence of any other known functions of PR-Set7, the setting of the de novo monomethyl mark appears essential for cell viability in the presence or absence of the DNA damage checkpoint, but once newly assembled chromatin is established the monomethyl mark, protected by L(3)mbt, is dispensable.

Feasibility of using 236U to reconstruct close-in fallout deposition from the Hiroshima atomic bomb

The first results on the feasibility of using (236)U to reconstruct the level and spatial distribution of close-in fallout deposition from the Hiroshima A-bomb are reported, coupled with the use of global fallout (137)Cs and (239+240)Pu. The results for global fallout (236)U in soil samples (0-30cm) from Ishikawa prefecture showed that the deposition density of (236)U from the global fallout can be accurately evaluated using AMS. All deposited (236)U, (137)Cs and (239+240)Pu appeared to have been recovered using 30-cm cores. It was also noted from the depth profiles for (236)U/(239+240)Pu and (236)U/(137)Cs ratios that the downward behavior of (236)U in the soil was apparently similar to that of (239+240)Pu, while the (137)Cs was liable to be retained in upper layers compared with (236)U and (239+240)Pu. The accumulated levels were 1.78×10(13)atomsm(-2) for (236)U, 4340Bqm(-2) for (137)Cs and 141Bqm(-2) for (239+240)Pu. The ratios of (236)U/(137)Cs and (236)U/(239+240)Pu were (4.10±0.12)×10(9) and (1.26±0.04)×10(11)atomsBq(-1), respectively. Results of (236)U, (137)Cs and (239+240)Pu measurements for the seven soil cores (0-30cm) from Hiroshima were discussed on the basis of ratios of (236)U/(137)Cs and (236)U/(239+240)Pu by comparing with those from the background area in Ishikawa, indicating that the global fallout dominates the current level of (236)U accumulation in soil in the Black-rain area around Hiroshima after the Hiroshima bomb, and the contribution of the close-in fallout (236)U produced by the Hiroshima A-bomb seems difficult to observe.

Near-threshold Lambda(1520) production by the gamma(p)-->K{+}Lambda(1520) reaction at forward K+ angles

Differential cross sections and photon-beam asymmetries for the gamma(p)-->K{+}Lambda(1520) reaction have been measured with linearly polarized photon beams at energies from the threshold to 2.4 GeV at 0.6<cos(theta){c.m.}{K}<1. A new bump structure was found at W approximately 2.11 GeV in the cross sections. The bump is not well reproduced by theoretical calculations introducing a nucleon resonance with J<or=3/2. This result suggests that the bump might be produced by a nucleon resonance possibly with J>or=5/2 or by a new reaction process, for example, an interference effect with the phi photoproduction having a similar bump structure in the cross sections.

Near-threshold photoproduction of Lambda(1520) from protons and deuterons

Photoproduction of Lambda(1520) with liquid hydrogen and deuterium targets was examined at photon energies below 2.4 GeV in the SPring-8 LEPS experiment. For the first time, the differential cross sections were measured at low energies and with a deuterium target. A large asymmetry of the production cross sections from protons and neutrons was observed at backward K+/0 angles. This suggests the importance of the contact term, which coexists with t-channel K exchange under gauge invariance. This interpretation was compatible with the differential cross sections, decay asymmetry, and photon beam asymmetry measured in the production from protons at forward K+ angles.

First results on 236U levels in global fallout

The global fallout (236)U level in soil was deduced from measurements of (236)U, (239+240)Pu and (137)Cs in surface soils which are solely influenced by global fallout. A total of 12 soil cores from the depths of 0-10, 0-20 and 0-30 cm were collected at a flat forest area in Japan. Concentrations of (239+240)Pu and (238)U were determined by alpha-particle spectrometry, while the (236)U/(238)U ratio was measured with accelerator mass spectrometry (AMS). Consistent (236)U/(239)Pu ratios between 0.212 and 0.253 were found. Using this ratio, the total global fallout of (236)U on the earth is estimated to be as much as ca. 900 kg. This knowledge will contribute to the promotion of research on U isotopes, including (236)U, for the fields of geo-resources, waste management and geochemistry.

Cross sections and beam asymmetry for K;{+}Sigma;{*-} photoproduction from the deuteron at E_{gamma}=1.5-2.4 GeV

The Sigma(1385) resonance, or Sigma;{*}, is well known as part of the standard baryon decuplet with spin J=3/2. Measurements of the reaction gammap-->K;{+}Sigma;{*0} are difficult to extract due to overlap with the nearby Lambda(1405) resonance. However, the reaction gamman-->K;{+}Sigma;{*-} has no overlap with the Lambda(1405) due to its charge. Here we report the first measurement of cross sections and beam asymmetries for photoproduction of the Sigma;{*-} from a deuteron target. The cross sections at forward angles range from 0.4 to 1.2 mub, with a broad maximum near E_{gamma} approximately 1.8 GeV. The beam asymmetries are negative, in contrast with positive values for the gamman-->K;{+}Sigma;{-} reaction.

Determination of 240Pu/239Pu isotopic ratios in human tissues collected from areas around the Semipalatinsk Nuclear Test Site by sector-field high resolution ICP-MS

Information on the 240Pu/239Pu isotope ratios in human tissues for people living around the Semipalatinsk Nuclear Test Site (SNTS) was deduced from 9 sets of soft tissues and bones, and 23 other bone samples obtained by autopsy. Plutonium was radiochemically separated and purified, and plutonium isotopes (239Pu and 240Pu) were determined by sector-field high resolution inductively coupled plasma-mass spectrometry. For most of the tissue samples from the former nine subjects, low 240Pu/239Pu isotope ratios were determined: bone, 0.125 +/- 0.018 (0.113-0.145, n = 4); lungs, 0.063 +/- 0.010 (0.051-0.078, n = 5); and liver, 0.148 +/- 0.026 (0.104-0.189, n = 9). Only 239Pu was detected in the kidney samples; the amount of 240Pu was too small to be measured, probably due to the small size of samples analyzed. The mean 240Pu/239Pu isotope ratio for bone samples from the latter 23 subjects was 0.152 +/- 0.034, ranging from 0.088 to 0.207. A significant difference (a two-tailed Student's t test; 95% significant level, alpha = 0.05) between mean 240Pu/239Pu isotope ratios for the tissue samples and for the global fallout value (0.178 +/- 0.014) indicated that weapons-grade plutonium from the atomic bombs has been incorporated into the human tissues, especially lungs, in the residents living around the SNTS. The present 239,240Pu concentrations in bone, lung, and liver samples were, however, not much different from ranges found for human tissues from other countries that were due solely to global fallout during the 1970's-1980's.

Spatial distribution of soil contamination by 137Cs and 239,240Pu in the village of Dolon near the Semipalatinsk nuclear test site: new information on traces of the radioactive plume from the 29 August 1949 nuclear test

The village of Dolon located about 60 km northeast from the border of the Semipalatinsk Nuclear Test Site in Kazakhstan is one of the most affected inhabited settlements as a result of nuclear tests by the former USSR. Radioactive contamination in Dolon was mainly caused by the first USSR nuclear test on 29 August 1949. As part of the efforts to reconstruct the radiation dose in Dolon, Cs and Pu in soil samples collected from 26 locations in the vicinity of and within the village were measured to determine the width and position of the center-axis of the radioactive plume that passed over the village from the 29 August 1949 nuclear test. Measured soil inventories of Cs and Pu were plotted as a function of the distance from the supposed center-axis of the plume. A clear shape similar to a Gaussian function was observed in their spatial distributions with each maximum around a center-axis. It was suggested that the plume width that contaminated Dolon was at most 10 km and the real center-axis of the radioactive plume passed 0.7-0.9 km north of the supposed centerline. A peak-like shape with the maximum near the center-axis was also observed in the spatial distribution of the Pu/Cs activity ratio, which may reflect the fractionation effect between Pu and Cs during the deposition process. These results support the recently reported results. The data obtained here will provide useful information on the efforts to estimate radiation dose in Dolon as reliably as possible. Health Phys. 94(4):328-337; 2008.

Aberrant monomethylation of histone H4 lysine 20 activates the DNA damage checkpoint in Drosophila melanogaster

PR-Set7 is a histone methyltransferase that specifically monomethylates histone H4 lysine 20 (K20) and is essential for cell proliferation. Our results show that in PR-Set7 mutants, the DNA damage checkpoint is activated. This phenotype is manifested by reduction in both the mitotic and the S phase indexes, a delay in the progression through early mitosis, and strong reduction of cyclin B. Furthermore, in a double mutant of PR-Set7 and mei-41 (the fly ATR orthologue), the abnormalities of mitotic progression and the cyclin B protein level were rescued. PR-Set7 also showed a defect in chromosome condensation that was enhanced in the double mutant. We therefore propose that monomethylated H4K20 is involved in the maintenance of proper higher order structure of DNA and is consequently essential for chromosome condensation.

Differential cross section and photon-beam asymmetry for the gamma n --> K+ Sigma- reaction at E gamma = 1.5-2.4 GeV

Differential cross sections and photon-beam asymmetries have been measured for the gamma n --> K+ Sigma- and gamma p --> K+Sigma0 reactions separately using liquid deuterium and hydrogen targets with incident linearly polarized photon beams of E gamma = 1.5-2.4 GeV at 0.6 < cos ThetacmK< 1. The cross section ratio of sigma K+ Sigma-/sigma K+ Sigma0, expected to be 2 on the basis of the isospin 1/2 exchange, is found to be close to 1. For the K+ Sigma- reaction, large positive asymmetries are observed, indicating the dominance of K* exchange. The large difference between the asymmetries for the K+ Sigma- and K+ Sigma0 reactions cannot be explained by simple theoretical considerations based on Regge model calculations.

Stress-induced transcription of the endoplasmic reticulum oxidoreductin gene ERO1 in the yeast Saccharomyces cerevisiae

Gene transcription changes dramatically in response to various stresses. This event is an obligatory step for adaptation of cells to certain environments. Endoplasmic reticulum (ER) oxidoreductin encoded by the ERO1 gene of the yeast Saccharomyces cerevisiae is essential for the formation of protein disulfide bonds in the ER and for cell viability. We show that transcription of ERO1 is regulated by two transcriptional activators in response to different stresses. In the unfolded protein response induced by the reductant dithiothreitol, transcription factor Hac1 activates ERO1 transcription through a sequence that diverges from the consensus Hac1-binding sequence. Heat shock transcription factor Hsf1 activates ERO1 in response to heat, ethanol, and oxidative stresses. Using cells containing mutations in the Hac1- and Hsf1-binding sequences of the chromosomal ERO1 promoter, we demonstrate that Hac1-regulated transcription of ERO1 confers resistance to dithiothreitol. Although mutations in the Hsf1-binding sequences do not affect the sensitivity of cells to heat, ethanol, or oxidative stresses, both the Hac1- and Hsf1-regulated pathways are critical for normal growth under complex stress conditions.

Near-threshold diffractive psi-meson photoproduction from the proton

Photoproduction of a phi meson on protons was studied by means of linearly polarized photons at forward angles in the low-energy region from threshold to Egamma = 2.37 GeV. The differential cross sections at t = -|t|min do not increase smoothly as Egamma increases but show a local maximum at around 2.0 GeV. The angular distributions demonstrate that phi mesons are photoproduced predominantly by helicity-conserving processes, and the local maximum is not likely due to unnatural-parity processes.

Production of the neutron-rich hypernucleus 10LambdaLi in the (pi-,K+) double charge-exchange reaction

In order to produce a neutron-rich Lambda hypernucleus for the first time, we carried out an experiment by utilizing the (pi-,K+) double charge-exchange reaction on a 10B target. We observed the production of a 10LambdaLi hypernucleus. The cross section for the Lambda bound region was found to be 11.3+/-1.9 nb/sr with the 1.2 GeV/c incident momentum, which is compared with the 10LambdaB hypernucleus production cross section, 7.8+/-0.3 microb/sr, in the (pi+,K+) reaction with a 1.05 GeV/c incident momentum beam.

Functional compatibility between isoform alpha and beta of type II DNA topoisomerase

DNA topoisomerase II (topo II) plays a crucial role in controlling the conformation of both DNA and whole chromosomes. This activity is essential for several cellular events such as DNA replication, transcription, chromosome condensation and segregation. In mammals, two genes code for isoforms of topo II, termed alpha and beta. They are similar in primary structure and have almost identical catalytic properties in vitro. We transfected HeLa cells with small interfering RNAs (siRNAs) targeted against either topo IIalpha or IIbeta, and succeeded in knocking down the expression of the corresponding protein. Chromosomes were condensed and aligned at metaphase in topo IIalpha-knockdown cells. Although some lagging chromosomes were observed, they were still segregated at anaphase despite the absence of topo IIalpha. When both topo IIalpha and topo IIbeta were removed, the segregation of chromosomes was severely arrested, suggesting that topo IIbeta could partially substitute for topo IIalpha. Double-knockdown experiments also revealed that topo II was required for shortening of the chromosome axis.

Beam-polarization asymmetries for the p(gamma-->, K+)Lambda and p(gamma-->, K+)Sigma(0) reactions for E(gamma)=1.5-2.4 GeV

Beam polarization asymmetries for the p(gamma-->,K+)Lambda and p(gamma-->,K+)Sigma(0) reactions are measured for the first time for E(gamma)=1.5-2.4 GeV and 0.6<cos((theta(c.m.)(K+))<1.0 by using linearly polarized photons at the Laser-Electron-Photon facility at SPring-8 (LEPS). The observed asymmetries are positive and gradually increase with rising photon energy. The data are not consistent with theoretical predictions based on tree-level effective-Lagrangian approaches. Including the new results in the development of the models is, therefore, crucial for understanding the reaction mechanism and to test the presence of baryon resonances which are predicted in quark models but are thus far undiscovered.

Induction of apoptosis by depletion of DNA topoisomerase IIalpha in mammalian cells

Inactivation of topoisomerase (topo) IIalpha arrests murine embryonic development. In topo IIalpha-depleted embryos, nuclei were partitioned to daughter cells without complete separation and formed an interconnecting droplet-like structure. The present study examined the fates of topo IIalpha-depleted cells with the droplet-like nuclear structure. When the embryos with abnormal nuclei were further incubated, apoptosis was induced along with the formation of fragmented and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling positive nuclei. ICRF-193 treatment of embryos activated caspases. Apoptosis induced by ICRF-193 was suppressed by z-VAD-fmk, a caspase inhibitor, and pifithrin-alpha, a p53 inhibitor. Moreover, when mitosis was blocked by nocodazole, ICRF-193-induced nuclear abnormalities and apoptosis were abolished. These data suggest that cycling through the M-phase is essential for ICRF-193-induced apoptosis. Nuclear abnormalities similar to those of topo IIalpha-depleted embryos were induced in HeLa cells in which topo IIalpha was knocked down by transfection with short interfering RNA (siRNA) against topo IIalpha, followed by induction of apoptosis. Our results suggest that topo IIalpha-depleted cells with the droplet-like nuclear structure induce apoptosis, which is dependent on caspase and p53 activity during the G1 phase in mammalian cells.

Evidence for a narrow S = +1 baryon resonance in photoproduction from the neutron

The gamman-->K(+)K(-)n reaction on 12C has been studied by measuring both K+ and K- at forward angles. A sharp baryon resonance peak was observed at 1.54+/-0.01 GeV/c(2) with a width smaller than 25 MeV/c(2) and a Gaussian significance of 4.6sigma. The strangeness quantum number (S) of the baryon resonance is +1. It can be interpreted as a molecular meson-baryon resonance or alternatively as an exotic five-quark state (uuddsmacr;) that decays into a K+ and a neutron. The resonance is consistent with the lowest member of an antidecuplet of baryons predicted by the chiral soliton model.

Flow measurements via two-particle azimuthal correlations in Au + Au collisions at sqrt [s(NN)]=130 GeV

Two-particle azimuthal correlation functions are presented for charged hadrons produced in Au+Au collisions at the Relativistic Heavy Ion Collider (sqrt [s(NN)]=130 GeV). The measurements permit determination of elliptic flow without event-by-event estimation of the reaction plane. The extracted elliptic flow values (v2) show significant sensitivity to both the collision centrality and the transverse momenta of emitted hadrons, suggesting rapid thermalization and relatively strong velocity fields. When scaled by the eccentricity of the collision zone epsilon, the scaled elliptic flow shows little or no dependence on centrality for charged hadrons with relatively low p(T). A breakdown of this epsilon scaling is observed for charged hadrons with pT >1.0 GeV/c.

Epitope distribution of randomly established monoclonal antibodies against human type II DNA topoisomerases

The epitopes of about 100 monoclonal antibodies against human type II DNA topoisomerase were mapped along the enzyme molecules. Although they were randomly and independently established, epitope sites were unevenly distributed the toward N-terminal or C-terminal region. We suggest that the central catalytic domain is hidden inside the molecule and inaccessible to the antigen recognition sites. Using antibodies, we demonstrate the distinct localization of isoforms of Topo II in cultured cells. Some particularly useful antibodies are listed.

Measurement of Lambda and Lambda(macro) particles in Au+Au collisions at the square root of S(NN) = 130 GeV

We present results on the measurement of Lambda and Lambda(macro) production in Au+Au collisions at square root of (S (NN) = 130 GeV with the PHENIX detector at the Relativistic Heavy Ion Collider. The transverse momentum spectra were measured for minimum bias and for the 5% most central events. The Lambda;/Lambda ratios are constant as a function of p(T) and the number of participants. The measured net Lambda density is significantly larger than predicted by models based on hadronic strings (e.g., HIJING) but in approximate agreement with models which include the gluon-junction mechanism.

Net charge fluctuations in Au + Au interactions at sqrt[s(NN)]=130 GeV

Data from Au + Au interactions at sqrt[s(NN)]=130 GeV, obtained with the PHENIX detector at the Relativistic Heavy-Ion Collider, are used to investigate local net charge fluctuations among particles produced near midrapidity. According to recent suggestions, such fluctuations may carry information from the quark-gluon plasma. This analysis shows that the fluctuations are dominated by a stochastic distribution of particles, but are also sensitive to other effects, like global charge conservation and resonance decays.