Search

A hybrid-emulsion experiment has been carried out at KEK-PS to study S = −2 nuclei. With the analysis of about 35% of total emulsion, we have successfully found three events of sequential weak decay of a double-hypernucleus. The results of these E373 events are summarized together with those of past experiments. The first experimental study of the branching ratios of weak decay modes of double-hypernuclei has been performed.

Reliable techniques for extracting the gate dielectric layer thickness from capacitance-voltage (C-V) characteristics are essential for manufacturing process quality control. Continued reduction of the dielectric layer thickness has brought about a need for new measurement procedures which can account for the direct tunneling currents through the gate insulator. We present a guideline for performing two-frequency C-V analysis of sub-2 nm gate oxides and show that it is possible to extract the dielectric layer thickness with an error of less than 4%. We show that in order to achieve this level of accuracy, it is necessary to choose the measurement frequencies and the test device size so that the dissipation remains below 1.1 at least at one of the two measurement frequencies.

We examined the association between green tea consumption and mortality due to all causes, cancer, heart disease, cerebrovascular disease, respiratory disease, injuries, and other causes of death in a large-scale population-based cohort study in Japan.We studied 90,914 Japanese (aged between 40 and 69 years) recruited between 1990 and 1994. After 18.7 years of follow-up, 12,874 deaths were reported. The association between green tea consumption and risk of all causes and major causes of mortality was assessed using the Cox proportional hazards regression model with adjustment for potential confounders.Hazard ratios for all-cause mortality among men who consumed green tea compared with those who drank less than 1 cup/day were 0.96 (0.89-1.03) for 1-2 cups/day, 0.88 (0.82-0.95) for 3-4 cups/day, and 0.87 (0.81-0.94) for more than 5 cups/day (P for trend.001). Corresponding hazard ratios for women were 0.90 (0.81-1.00), 0.87 (0.79-0.96), and 0.83 (0.75-0.91; P for trend.001). Green tea was inversely associated with mortality from heart disease in both men and women and mortality from cerebrovascular disease and respiratory disease in men. No association was found between green tea and total cancer mortality.This prospective study suggests that the consumption of green tea may reduce the risk of all-cause mortality and the three leading causes of death in Japan.

Since the 1985 discovery of the phase transition at THO=17.5 K in the heavy-fermion metal URu2Si2, neither symmetry change in the crystal structure nor large magnetic moment that can account for the entropy change has been observed, which makes this hidden order enigmatic. Recent high-field experiments have suggested electronic nematicity that breaks fourfold rotational symmetry, but direct evidence has been lacking for its ground state in the absence of magnetic field. Here we report on the observation of lattice symmetry breaking from the fourfold tetragonal to twofold orthorhombic structure by high-resolution synchrotron X-ray diffraction measurements at zero field, which pins down the space symmetry of the order. Small orthorhombic symmetry-breaking distortion sets in at THO with a jump, uncovering the weakly first-order nature of the hidden-order transition. This distortion is observed only in ultrapure samples, implying a highly unusual coupling nature between the electronic nematicity and underlying lattice., 直接観測された物質物理学の謎「隠れた秩序」. 京都大学プレスリリース. 2014-06-19.

The purpose of this study was to determine the relationship between urinary 8-hydroxy-2’-deoxyguanosine (8-OHdG) and urine specific gravity (USG) following two hours of cycling exercise over the follicular and luteal phases. Twelve recreationally active eumenorrheic women served as the subjects [age: 20.9±0.3 year; height: 160.1±5.6 cm; body weight: 54.7±5.8 kg; body mass index: 21.3±1.8 kg/m2; body fat: 21.9±3.1 %; peak oxygen uptake (VO2peak): 44.4±5.0 ml/kg/min (mean±SD)]. Before and after 2 hours of cycling exercise performed at 60%VO2peak, 8-OHdG and USG were determined with high performance liquid chromatography and a handheld refractometer, respectively. All subjects performed the same exercise protocol during the follicular (F: 5~8 days after the onset of the menses) and luteal (L: 22~25 days after the onset of the menses) phase. In order to delay fatigue and prevent hypoglycemia and dehydration, carbohydrate-electrolyte solution were consumed every twenty minutes (2 ml/kg body mass) during each e...

We have been investigating the basic characteristics of an imaging plate JP) to develop a new type of ultra-heavy-particle detector. To acquire the information on the deposited energy, photostimulated luminescence (PSL) from the injection position is usually utilized, which occurs upon scanning the surface of the IP with a laser beam after the exposure of particles. However, in the use of PSL, there is the disadvantage that it fades with time. On the other hand, when heavy particles are injected to the IP, prompt luminescence (PL) also occurs from the injection position. We have succeeded in detecting the prompt luminescence from each heavy particle with the energy of several hundred MeV/n. Since the PL is useful for quick detection of the injection position, the PSL data can be read within a few seconds by scanning the determined position before any serious fading effect occurs.

An experiment to search for double-strangeness nuclei in nuclear emulsion is now being carried on as KEK-PS E373. Preliminary results of the data analysis for the K + spectrometer and the scintillating fiber detectors are presented. Status of the automatic track finding method for the emulsion is reported.

As a frame work of the study for the latent track size measurement using atomic force microscope, we have measured the minute etch pits and the extremely small amount of bulk etch of CR-39 at the beginning of chemical etching, and obtained its growth curves in nanometer dimensions. The pieces of CR-39 were exposed to 6 MeV / n C and Fe ions with normal incidence angle and were etched in 70°C 7 N NaOH solution for 0.5,1,2,3,5 min . The diameters of latent track were estimated to be ∼17 nm for Fe ions and ∼8 nm for C ions, respectively. These values are comparable to the experimental data on the average ‘track core diameters’ that have been obtained by various experimental techniques.

Two types of polymeric track detectors CR-39 and SR-90 were irradiated with protons, alpha particles, heavy ions and gamma-rays at different energies and fluences. After irradiation these detectors were analyzed with an FT-IR spectrometer of Jasco type 5300 in transmission and ATR modes. We have found that CO2 is produced not only by irradiation but also by polymerization. The amount of CO2 in the detector material is closely related to the latent track formation.

A hybrid emulsion experiment was carried out to study double-strangeness nuclei produced via Ξ− hyperon capture at rest with the expectation of ten times larger statistics than previous experiments. We have analyzed 5% of the total emulsion and found one “twin-hypernuclei” event involving the emission of two single-Λ hypernuclei and a nuclear fragment from a Ξ− hyperon stopping point. The event is interpreted as the decay of a Ξ − + 14 N atomic system to 5 Λ He + 5 Λ He + 4 He + neutron . The species of the Ξ−-atom and the fragmentation products are uniquely identified for the first time for twin-hypernuclei events. Combined with the results from a past hybrid-emulsion experiment, one double-Λ hypernucleus and three twin-hypernuclei events have been found from Ξ− captures on light emulsion nuclei. The ratio of the detected rate of double-Λ hypernuclei to that of twin-hypernuclei is compared with theoretical estimates.

We summarize some recent work on the formation mechanisms, structure and composition of oxynitride and high-K films, as investigated by high-resolution medium-energy ion scattering (MEIS). We show that nitridation of a silicon oxide thin film takes place through transport of NO molecules to the oxide/silicon interface. Ta2O5 films on Si have a compositionally graded oxide, breaking up at high annealing temperatures. A thin buffer layer of Si3N4 can prevent this.

In order to clarify the effects of medical education on attitudes towards mental illness among medical students, a follow-up study was conducted. All 100 students entering Kochi Medical School in 1988 were subjects. The initial questionnaire survey was conducted in 1988, and followed up in 1993. Response rate was 69% in the initial survey, and 83% in the follow-up study. By the time of the follow-up, all of the students had completed their medical education, including courses in psychiatry and mental health. Results were as follows: At the follow-up study, 1) a significantly higher percentage of students replied that they accepted the mentally ill as co-workers; 2) significantly favorable changes were observed in attitudes towards psychiatric services; 3) optimism about the effectiveness of treatment for mental illness at an early stage and prevention of mental illness had decreased; and 4) no change was observed in attitudes toward human rights of the mentally ill, except in the case of one item stating that the mentally ill should not have children in order to avoid hereditary handicaps, with which a lower percentage agreed. Conclusively, medical education can play an important role in attitudes towards mental illness.

We are investigating the basic characteristics of an Imaging Plate (IP) as a detector for ultra-heavy cosmic rays. Irradiating the IPs with argon and iron particles from several incident angles, the images on the IP were measured. We confirmed that the images due to particles extend along the incident direction and that the information is useful for the determination of the incident angle. Moreover, we found a certain relation between the incident angle and the Photo-Stimulated Luminescence (PSL) value on the IP due to the deposited energy. Using the relation, we can find out the PSL value at which the particle would be injected perpendicular to the IP. From the normalized PSL value, the dE/dx of the particle can be determined. As the relation is held independently of the nuclide and the energy of the incident particle, it is useful to measure the dE/dx.

The prolactin (PRL)-releasing activity (PRA) in the bovine hypothalamic extract (BHE) was compared to that of known substances with PRA and further characterized by gel filtration and reversed-phase high performance liquid chromatography (RP-HPLC). Crude BHE produced marked dose-dependent stimulation of PRL secretion from the cultured rat adenohypophysial cells. Among the synthetic substances examined, vasoactive intestinal peptide (VIP), thyrotropin-releasing hormone (TRH) and beta-endorphin (END) showed significant PRA. However, the flatter dose-response slope for TRH compared with BHE or the small amounts of VIP and END in BHE suggested that these peptides could not account for the major active elements of BHE. Oxytocin and interleukin-1beta were also tested, but they exhibited no PRA in our assay system. Gel filtration of BHE on the Sephadex G-100 column yielded two peaks of PRA distinct from TRH, VIP and END. One eluted in the void and the other in more retarded fractions. The latter fractions were pooled and subjected to the two-step RP-HPLC. The PRA was separated into three peaks designated peaks I, II and III in the first RP-HPLC experiment. Furthermore, the second RP-HPLCs with finer resolution revealed that peak II as well as peak III consisted of three peaks, while peak I eluted as a single peak. Most of these seven PRA peaks exhibited different RP-HPLC profiles from those of the newly characterized PRL-releasing peptides. These findings again provide confirmatory evidence that BHE contained unique factors different from the above known substances.

We have used Medium Energy Ion Scattering (MEIS) and other techniques to investigate the structure and formation mechanisms of ultrathin (less than 10 nm) layers of Ta 2 O 5 on Si. We find that a compositionally graded oxide with < 2 nm effective thickness can be formed. The film degenerates at high annealing temperatures both by roughening at the outer surface, and reacting at the interface, but a buffer layer of Si 3 N 4 can prevent the latter effect to a certain extent. Introducing a TiN/Ti layer between Ta 2 O 5 and Si (which may be desirable for DRAM applications) has an adverse effect on the thermal stability of the Ta 2 O 5 overlayer due to migration and subsequent reaction of oxygen with titanium.

During the summer of 1995, about 20 spot-billed ducks died unnaturally in a pond (Shin-ike) in Nishinomiya, Hyogo Prefecture, Japan. The suspected cause was the sudden appearance of toxic freshwater bloom of cyanobacteria. However, no birds died in a nearby pond (Oo-ike) in which the cyanobacteria was also present. Morphological observation of these cyanobacteria by microscope revealed that they were almost unialgal and were both Microcystis aeruginosa. The lyophilized algal cell powder from Shin-ike contained large amounts of microcystins which showed acute toxicity for mouse, while that from Oo-ike had only a very small amount of microcystin-RR which did not show acute toxicity. Autopsy of one of the birds revealed that the liver was necrotic and severely jaundiced with a dark green color, suggesting the toxicity of the microcystins. These results point to the cause of the unnatural death of spot-billed ducks in Shin-ike as being the sudden appearance of toxic Microcystis aeruginosa. This was due to eutrophication of the pond, following the influx of untreated sewage related to damage from the Great Hanshinn Earthquake of January 1995. This is the first experimental report of toxic cyanobacteria being implicated in the mass death of wild birds in Japan.

PURPOSE. To report a case in which optical coherence tomography (OCT) showed needle-shaped deposits on the retinal surface oriented toward the vitreous cavity and immunohistochemical findings suggested light chain-related amyloidosis. METHODS. A 59-year-old man with no systemic complications had bilateral neovascular glaucoma and vitreous opacities in the right eye. Vitrectomy was conducted on the right eye and the excised vitreous was examined histopathologically. RESULTS. Glass wool-like opacities were observed during vitrectomy. Postoperative fundus examination of the right eye showed retinal hemorrhage and white deposits around blood vessels and on retinal surface. Fluorescein angiography revealed hyperfluorescence of the optic disc, non-perfusion areas, and vascular focal staining. OCT depicted needle-shaped deposits perpendicular to the retinal surface oriented toward the vitreous. Histologic examination of deposits revealed positive reaction for Congo red stain, and immunohistochemical examination demonstrated positive reactivities for anti-lambda and anti-kappa light chains (precursors of amyloid protein), suggesting a diagnosis of light chain-related amyloidosis. C ONCLUSIONS. In this case, OCT showed needle-shaped deposits perpendicular to the retinal surface. Special staining with Congo red revealed the deposit to be amyloid deposition. Immunohistochemical staining suggested light chain-related amyloidosis. Vascular obstructive lesions and neovascular glaucoma secondary to retinal vascular damage in amyloidosis warrant particular attention. (Eur J Ophthalmol 2008; 18: 473-5)

We propose a new experimental technique to study the transport properties of stress-induced leakage current (SILC). Based on the carrier separation measurement for p-channel MOSFETs, the quantum yield of impact ionization for electrons involved in the SILC process is evaluated directly from the change in the source and gate currents of p-MOSFETs before and after stressing. Since the relationship between the electron energy and the quantum yield is established for direct and FN tunneling currents, the electron energy of electrons involved in the SILC process can be determined from the quantum yield. The results reveal that the measured energy of electrons in the SILC process is lower roughly by 1.5 eV than the energy expected in the elastic tunneling process. Trap-assisted inelastic tunneling model is proposed as a conduction mechanism of SILC accompanied by energy relaxation. It is shown, through the evaluation of the substrate hole current in n-channel MOSFETs, that the contribution of trap-assisted valence electron tunneling, another possible mechanism to explain the energy relaxation, to SILC is small.

A new I-V model to quantitatively represent stress-induced leakage current (SILC) is presented and compared with the experimental I-V characteristics. The trap-assisted tunneling model is modified so as to include the energy relaxation of tunneling electrons, which has been experimentally verified by applying the carrier separation technique to MOSFETs with the SILC component. The energy relaxation is treated in the new model as the change in the energy level of traps before and after the capture of electrons during two-step tunneling. It is demonstrated that this model successfully represents the experimental I-V characteristics of the SILC component and, particularly, the low apparent barrier height in the Fowler-Nordheim (FN) plot of the SILC component. The calculated low barrier height is attributed to the dominance of direct tunneling mechanism on both tunneling into traps and out of traps. The impact of the energy relaxation during tunneling, used in the present model, on the I-V characteristics is discussed in terms of the trap distribution inside the gate oxide, compared with conventional elastic tunneling model.

A study of 1.66 GeV c K − beam induced ( K − ,K + ) reactions in the nuclear emulsion target is presented and 796 ( K − , K + ) reaction vertices ( p K + ⩾ 1 GeV /c ) containing 18 single hyperfragments are identified. There is no clear(spatially separated) double hyperfragment nor twin single hyperfragment in the identified 796 ( K − ,K + ) reactions. These events are classified and their characteristics are described in detail. In the region p K + ⩾ 1 GeV /c where the quasifree K − (p) → K + Ξ − is the dominant process, the probability of Ξ − emission from the reaction vertex is determined to be 73.9 −4.6 +4.5 %. From this value, the mean free path of Ξ − in a nucleus is estimated to be 4.7 −1.0 +1.5 fm for 〈p Ξ − 〉 ∼ 0.6 GeV /c by assuming a simple model of uniform nuclear matter.

Multifactorial diseases, which include the common congenital abnormalities (incidence: 6%) and chronic diseases with onset predominantly in adults (population prevalence: 65%), contribute substantially to human morbidity and mortality. Their transmission patterns do not conform to Mendelian expectations. The model most frequently used to explain their inheritance and to estimate risks to relatives is a Multifactorial Threshold Model (MTM) of disease liability. The MTM assumes that: (i) the disease is due to the joint action of a large number of genetic and environmental factors, each of which contributing a small amount of liability, (ii) the distribution of liability in the population is Gaussian and (iii) individuals whose liability exceeds a certain threshold value are affected by the disease. For most of these diseases, the number of genes involved or the environmental factors are not fully known. In the context of radiation exposures of the population, the question of the extent to which induced mutations will cause an increase in the frequencies of these diseases has remained unanswered. In this paper, we address this problem by using a modified version of MTM which incorporates mutation and selection as two additional parameters. The model assumes a finite number of gene loci and threshold of liability (hence, the designation, Finite-Locus Threshold Model or FLTM). The FLTM permits one to examine the relationship between broad-sense heritability of disease liability and mutation component (MC), the responsiveness of the disease to a change in mutation rate. Through the use of a computer program (in which mutation rate, selection, threshold, recombination rate and environmental variance are input parameters and MC and heritability of liability are output estimates), we studied the MC-heritability relationship for (i) a permanent increase in mutation rate (e.g., when the population sustains radiation exposure in every generation) and (ii) a one-time increase in mutation rate. Our investigation shows that, for a permanent increase in mutation rate of 15%, MC in the first few generations is of the order of 1-2%. This conclusion holds over a broad range of heritability values above about 30%. At equilibrium, however, MC reaches 100%. For a one-time increase in mutation rate, MC reaches its maximum value (of 1-2%) in the first generation, followed by a decline to zero in subsequent generations. These conclusions hold for so many combinations of parameter values (i.e., threshold, selection coefficient, number of loci, environmental variance, spontaneous mutation rate, increases in mutation rate, levels of 'interaction' between genes and recombination rates) that it can be considered to be relatively robust. We also investigated the biological validity of the FLTM in terms of the minimum number of loci, their mutation rates and selection coefficients needed to explain the incidence of multifactorial diseases using the theory of genetic loads. We argue that for common multifactorial diseases, selection coefficients are small in present-day human populations. Consequently, with mutation rates of the order known for Mendelian genes, the FLTM with a few loci and weak selection provides a good approximation for studying the responsiveness of multifactorial diseases to radiation exposures.

At present, the photometric data for clusters at z ≲ 0.2 mainly come from photographic photometry. The lack of CCD data for such clusters is simply due to the fact that no CCD camera had been available until recently that covers the wide extension of clusters within a reasonable amount of observing time. We have developed a large mosaic CCD camera and conducted multicolor imaging observations of z ≲ 0.2 clusters using the 40-inch Swope telescope at Las Campanas Observatory.

Les caracteristiques de puissance des specimens inchanges mesures par un essai triaxial a grande echelle ont ete comparees a celles des specimens reconstitutes afin d'evaluer la puissance du sol naturel. Les specimens inchanges ont ete echantillonnes a partir du fond en graviers du lit de la riviere d'un barrage en remblai, en employant une methode de congelation des specimens par nitrogene liquide. On a constate que les caracteristiques de puissance dynamique des specimens inchanges sont plus importantes que celles des specimens reconstitutes.

Aino virus (JaNAr 28 strain), a possible agent of a congenital anomaly of calves, was inoculated into the yolk sac of chick embryos at a dose of 10(2), 10(3), 10(4) or 10(5) TCID50 0.2 ml-1 at four, six or eight days of incubation. At 21 days of incubation all the unhatched embryos or hatched chickens in the experimental and control groups were sacrificed for pathological examination. The incidence of hydranencephaly, cerebellar hypoplasia or agenesis and arthrogryposis or scoliosis was highest (85 per cent in the chicks inoculated with 10(3) TCID50 0.2 ml-1 at eight days of incubation. The lesions were very similar to those found in congenital abnormalities in calves suspected of a natural infection with Aino virus.

This revised version was published online in November 2006 with corrections to the Cover Date.

National Regulatory Authorities (NRAs) establish deferral criteria for donors with risk factors for transfusion transmissible infections (TTI). In most jurisdictions, epidemiological data show that men who have sex with men (MSM) have a significantly higher rate of TTI than the general population. Nevertheless, changes from an indefinite donor deferral for MSM have been considered in many countries in response to concerns over a perceived discrimination and questioning of the scientific need. Changes to MSM donor deferral criteria should be based on sound scientific evidence. Safety of transfusion recipients should be the first priority, and stakeholder input should be sought.

A hybrid experiment with nuclear emulsion and scintillating-fiber detectors (KEK-E373) has been performed to search for double-strangeness systems. Among about 10${}^{3}$ events of ${\ensuremath{\Xi}}^{\ensuremath{-}}$ hyperons captured at rest by emulsion nuclei, we have observed four events which clearly show the topology of cascade weak decays of double-$\ensuremath{\Lambda}$ hypernuclei including the ``Nagara'' event. Regarding the Nagara event, values of the two-$\ensuremath{\Lambda}$ binding energy (${B}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}$) and the $\ensuremath{\Lambda}$-$\ensuremath{\Lambda}$ interaction energy ($\ensuremath{\Delta}{B}_{\ensuremath{\Lambda}\ensuremath{\Lambda}}$) of ${}_{\ensuremath{\Lambda}}^{}{}_{\ensuremath{\Lambda}}^{6}\mathrm{He}$ have been revised to 6.91 $\ifmmode\pm\else\textpm\fi{}$ 0.16 and 0.67 $\ifmmode\pm\else\textpm\fi{}$ 0.17 MeV, respectively, due to the recent change of the ${\ensuremath{\Xi}}^{\ensuremath{-}}$ mass value (Particle Data Group). For another three events, we have determined possible species of double-$\ensuremath{\Lambda}$ hypernuclei together with their binding energies.

Pathogenesis of Aino virus (AIV), a suspected causative agent of congenital abnormalities of calves, has not yet been established by experimental infection of dams. To investigate the pathogenesis, 103 median tissue culture infective doses per 0.2 ml of AIV strain JaNAr 28 was inoculated into the yolk sac of 8-day-old chick embryos. At 4, 7, 10, and 13 days post-inoculation (PI) 20 eggs were opened and macro- and microscopic studies combined with virus recovery and immunohistochemical detection of the virus antigen were performed. At 7 to 13 days PI chick embryos manifested marked hydranencephaly, cerebellar hypoplasia, arthrogryposis, and scoliosis, with the highest incidences of 86.7%, 73.3%, 80,0%, and 20,0%, respectively. At 4 days PI the viral antigen was found in nerve cells, gitter cells in mild necrotic foci of the central nervous system (CNS), degenerative myotubules, and macrophages in the interstitium, which was associated with the early phase of AIV-induced encephalitis and polymyositis, with occasional accompanying hemorrhage and clumping of myotubular fragments. From 7 to 10 days PI, AIV antigen increased markedly in the liquefactive necrosis and in both degenerative and normal-looking myotubules in conjunction with developing hydranencephaly and arthrogryposis. The encephalitis and myositis had a tendency to mitigate by 10 days PI, coincident with a slight decrease in amount of AIV antigen. At 13 days PI there was almost no detectable AIV antigen in CNS and skeletal muscles, probably due to depletion of cells having affinity to AIV.

Twenty-seven feline parvovirus (FPV) isolates were recovered from cats clinically diagnosed with feline panleukopenia (FPL) for assessing antigenic and genomic properties of FPL viruses (FPLV) recently prevalent among cats in Japan. All isolates, with the exception of one novel isolate, FPV-314, possessed homologous properties, and their subgroups in FPVs were identified as FPLV. The FPV-314 isolate, which was from a 1.5-year-old cat which manifested clinical signs of FPL and died on the 13th day after the first medical examination, was finally identified as canine parvovirus (CPV) because it lacked a specific antigenic epitope commonly detected in FPLV and mink enteritis virus and because the nucleotide sequence of the capsid protein gene was almost identical to those of CPV-2a and -2b antigenic type strains recently prevalent among dogs in Japan. The present result together with our previous findings (M. Mochizuki, R. Harasawa, and H. Nakatani. Vet. Microbiol. 38:1-10, 1993) indicates the possibility that CPV and FPLV undergo mutual interspecies transmission between dogs and cats, and it is postulated that they may cause disease in some adventitious hosts.

We have observed $23.2 \pm 6.0_{-0.9}^{+1.0}$ purely-leptonic decays of $D_s^+ -> \mu^+ \nu_\mu$ from a sample of muonic one prong decay events detected in the emulsion target of Fermilab experiment E653. Using the $D_s^+ -> \phi \mu^+ \nu_\mu$ yield measured previously in this experiment, we obtain $B(D_s^+ --> \mu^+ \nu_\mu) / B(D_s^+ --> \phi \mu^+ \nu_\mu) =0.16 \pm 0.06 \pm 0.03$. In addition, we extract the decay constant $f_{D_s}=194 \pm 35 \pm 20 \pm 14 MeV$.

The strength and deformation characteristics of undisturbed specimens measured by large-scale triaxial tests were compared with those of reconstituted specimens to evaluate the stiffness of natural ground. The undisturbed specimens were sampled from the riverbed gravel foundation of an embankment dam using the freezing sampling method with liquid nitrogen. The validity of the results from the undisturbed specimens was evaluated by comparing the stiffness of the natural ground using P- and S-wave logging (PS logging). The dynamic deformation characteristics (stiffness) of undisturbed specimens are larger than those of reconstitued specimens. Key words: shear modulus, damping ratio, gravel, laboratory test.

Computer code calculations based on biophysical models are commonly used to evaluate the effectiveness of shielding in reducing the biological damage caused by cosmic radiation in space flights. Biological measurements are urgently needed to benchmark the codes. We have measured the induction of chromosomal aberrations in human peripheral blood lymphocytes exposed in vitro to 56Fe-ion beams accelerated at the HIMAC synchrotron in Chiba. Isolated lymphocytes were exposed to the 500 MeV/n iron beam (dose range 0.1-1 Gy) after traversal of 0 to 8 g/cm2 of either PMMA (lucite, a common plastic material) or aluminum. Three PMMA shield thickness and one Al shield thickness were used. For comparison, cells were exposed to 200 MeV/n iron ions and to X-rays. Chromosomes were prematurely condensed by a phosphatase inhibitor (calyculin A) to avoid cell-cycle selection produced by the exposure to high-LET heavy ion beams. Aberrations were scored in chromosomes 1, 2, and 4 following fluorescence in situ hybridization. The yield of chromosomal aberrations per unit dose at the sample position was poorly dependent on the shield thickness and material. However, the yield of aberrations per unit ion incident on the shield was increased by the shielding. This increase is associated to the increased dose-rate measured behind the shield as compared to the direct beam. These preliminary results prove that shielding can increase the effectiveness of heavy ions, and the damage is dependent upon shield thickness and material, and heavy ion energy and charge.

An event accompanied by two single hyperfragments emitted from a Ξ− nuclear capture at rest was found in a nuclear emulsion. It is interpreted as a Ξ−-12C bound system decaying into either a) Λ4H + Λ9Be, b) Λ 4 H + Λ 9 Be ∗ or c) Λ 4 H ∗ + Λ 9 Be . The binding energy of the Ξ-12C system is obtained as a) 3.70−0.19+0.18 MeV, b) 0.62−0.19+0.18 MeV and c) 2.66−0.19+0.18 MeV, respectively. The system is considered as a Ξ− hypernucleus in the cases a) and c). In case b), this event and another event of the same type (Yokohama event) can both be interpreted as a decay from the Ξ-12C system in 2P state when a shallow Ξ−-nuclear potential is assumed.

A search for charm hadron decays into two muons plus one or more hadrons has been carried out using a hybrid emulsion spectrometer. This technique is sensitive to modes with missing neutrals, e.g. π0μ+μ− and ϱ±μ+μ−, as well as to constrained modes having visible invariant masses equal to those of charm states. No evidence for any such decays has been found, which allows upper limits at the 90% confidence level as low as 1.8 × 10−4 to be placed on the branching fractions for charm-changing neutral-current and lepton-number violating decay modes.

The properties of a plasma in a parallel-plate radio frequency (rf) symmetric discharge of 13.56 MHz in oxygen have been investigated. The plasma contains negative ions. The temperature and density of the negative ions have been determined from the slope and height of the semilog-plotted second derivative of the probe characteristics. The laser photodetachment technique is applied, and data indicating the existence of negative ions are obtained. The negative ion densities deduced by both methods are comparable. The negative ion temperature is found to be from 0.1 to 0.6 eV, depending on the pressure and rf power density. The electron energy distribution f(E) deviates from Maxwellian and has a depletion of low-energy parts, which may be due to the loss of low-energy electrons in attachments. A shifted annular-shaped distribution is fitted to the measured f(E), and the data analysis is made according to this form of f(E).

The relative branching fraction RK = Γ(D0 → K−μ+v)/Γ(D0 → μ−X) has been measured by Fermilab experiment E653, using D0 mesons produced by 600 GeV π−. The semimuonic decay sample of 232 events was identified by the decay chain D ∗+ → D 0 π + , D 0 → μ + h − X , where h is a hadron. The Kμv component was extracted from the joint distribution of these events in the D0 decay variables Mmin and pTh. We find RK = 0.472 ± 0.051 (stat) ± 0.040 (sys), and use a world average of the D0 → Klv branching fraction to obtain the D0 inclusive semimuonic branching fraction B(D0 → μ+X) = (7.67 ± 1.13)%.