Characterization of micron-size hydrogen clusters using Mie scattering

Hydrogen clusters with diameters of a few micrometer range, composed of 10^8-10 hydrogen molecules, have been produced for the first time in an expansion of supercooled, high-pressure hydrogen gas into a vacuum through a conical nozzle connected to a cryogenic pulsed solenoid valve. The size distribution of the clusters has been evaluated by measuring the angular distribution of laser light scattered from the clusters. The data were analyzed based on the Mie scattering theory combined with the Tikhonov regularization method including the instrumental functions, the validity of which was assessed by performing a calibration study using a reference target consisting of standard micro-particles with two different sizes. The size distribution of the clusters was found discrete peaked at 0.33 ± 0.03, 0.65 ± 0.05, 0.81 ± 0.06, 1.40 ± 0.06 and 2.00 ± 0.13 µm in diameter. The highly reproducible and impurity-free nature of the micron-size hydrogen clusters can be a promising target for laser-driven multi-MeV proton sources with the currently available high power lasers.

Clonal structure in Ichthyobacterium seriolicida, the causative agent of bacterial haemolytic jaundice in yellowtail, Seriola quinqueradiata, inferred from molecular epidemiological analysis

Bacterial haemolytic jaundice caused by Ichthyobacterium seriolicida has been responsible for mortality in farmed yellowtail, Seriola quinqueradiata, in western Japan since the 1980s. In this study, polymorphic analysis of I. seriolicida was performed using three molecular methods: amplified fragment length polymorphism (AFLP) analysis, multilocus sequence typing (MLST) and multiple-locus variable-number tandem repeat analysis (MLVA). Twenty-eight isolates were analysed using AFLP, while 31 isolates were examined by MLST and MLVA. No polymorphisms were identified by AFLP analysis using EcoRI and MseI, or by MLST of internal fragments of eight housekeeping genes. However, MLVA revealed variation in repeat numbers of three elements, allowing separation of the isolates into 16 sequence types. The unweighted pair group method using arithmetic averages cluster analysis of the MLVA data identified four major clusters, and all isolates belonged to clonal complexes. It is likely that I. seriolicida populations share a common ancestor, which may be a recently introduced strain.

Ion pinhole imaging diagnostics on fast ion source in femtosecond laser plasma of cluster targets

The spatial configuration of the ion source generated under femtosecond laser interaction with clusters is investigated. While intense laser pulses (36 fs, 60 mJ, intensity of 4 × 10¹⁷ W/cm²) propagated in CO₂ cluster (~0.22 μm in diameter) media, the shape of the obtained plasma ion source was registered for the first time by means of pinhole imaging method. The remarkable decrease in fast ion yield in the vicinity of the assumed best laser focus near the gas cluster jet axis is observed. Such observed anisotropy of the ion source is suggested to originate from the influence of the laser prepulse destroying clusters in advance to the arrival of the main pulse. The assumption is confirmed by optical shadowgraphy images of the plasma channel and is important for further development of an efficient laser-plasma-based fast ion source. Following the observed geometry of the ion source, the laser intensity limit allowing to accelerate ions to ~100 keV energy range was estimated.

Scintillator-based transverse proton beam profiler for laser-plasma ion sources

A high repetition rate scintillator-based transverse beam profile diagnostic for laser-plasma accelerated proton beams has been designed and commissioned. The proton beam profiler uses differential filtering to provide coarse energy resolution and a flexible design to allow optimisation for expected beam energy range and trade-off between spatial and energy resolution depending on the application. A plastic scintillator detector, imaged with a standard 12-bit scientific camera, allows data to be taken at a high repetition rate. An algorithm encompassing the scintillator non-linearity is described to estimate the proton spectrum at different spatial locations.

Combined Analysis of Neutrino and Antineutrino Oscillations at T2K

T2K reports its first results in the search for CP violation in neutrino oscillations using appearance and disappearance channels for neutrino- and antineutrino-mode beams. The data include all runs from January 2010 to May 2016 and comprise 7.482×10^{20} protons on target in neutrino mode, which yielded in the far detector 32 e-like and 135  μ-like events, and 7.471×10^{20} protons on target in antineutrino mode, which yielded 4 e-like and 66  μ-like events. Reactor measurements of sin^{2}2θ_{13} have been used as an additional constraint. The one-dimensional confidence interval at 90% for the phase δ_{CP} spans the range (-3.13, -0.39) for normal mass ordering. The CP conservation hypothesis (δ_{CP}=0, π) is excluded at 90% C.L.

Association between Satisfaction with State of Health and Meals, Physical Condition and Food Diversity, Health Behavior, and Perceptions of Shopping Difficulty among Older People Living Alone in Japan

OBJECTIVE

This study aimed to examine perceptions of shopping difficulty, and the relationships with satisfaction with state of health and meals, physical condition, food diversity and health behavior in older people living alone in Japan.

DESIGN

A cross-sectional, multilevel survey was designed. The questionnaire was distributed by mail and self-completed by participants.

SETTING

The sample was drawn from seven towns and cities across Japan.

PARTICIPANTS

A geographic information system was used to select the sample of older people living alone, by proximity to a supermarket. In total, 2,346 older people (827 men and 1,519 women) completed the questionnaire.

MEASUREMENTS

The dependent variable was whether shopping was easy or difficult. A logistic regression analysis was performed, adjusting for age, socioeconomic status and proximity of residence to a supermarket using stepwise variable analyses.

RESULTS

The response rate was 67.8%. Overall, 14.5% of men and 21.7% of women considered shopping difficult. The stepwise logistic analysis showed that the factors most strongly related to shopping difficulty were a subjective feeling of poor health (men: OR = 3.01, women: OR = 2.16) and lack of satisfaction with meals (men: OR = 2.82, women: OR = 3.69). Other related physical condition and dietary factors were requiring nursing care (men: OR = 3.69, women: OR = 1.54), a high level of frailty, measured using the frailty index score (women: OR = 0.36) and low food diversity score (men: OR = 1.84, women: OR = 1.36).

CONCLUSION

The study found that older people's assessment of their shopping difficulty was related to satisfaction aspects, including a subjective feeling of poor health, and lack of satisfaction with meals, as well as physical condition. These have a greater influence on shopping difficulty than income in both sexes, and proximity to a supermarket in women.

"Eating Together" Is Associated with Food Behaviors and Demographic Factors of Older Japanese People Who Live Alone

OBJECTIVE

This study aimed to examine the relationships between eating together and subjective health, frailty, food behaviors, food accessibility, food production, meal preparation, alcohol intake, socioeconomic factors and geography among older Japanese people who live alone.

DESIGN

A cross-sectional, multilevel survey was designed. The questionnaire was distributed by post and self-completed by participants.

SETTING

The sample was drawn from seven towns and cities across Japan.

PARTICIPANTS

A geographic information system was used to select a representative sample of older people who lived alone based on their proximity to a supermarket. Recruitment for the study was conducted with municipal assistance.

MEASUREMENTS

A logistic regression analysis was performed that adjusted for the respondent's age, socioeconomic status and proximity to a supermarket using stepwise variable analyses. The dependent variable was whether the respondent ate together more or less than once a month.

RESULTS

In total, 2,196 older people (752 men and 1,444 women) completed the questionnaire (63.5% response rate). It was found that 47.1% of men and 23.9% of women ate together less than once a month. Those who ate together less than once a month had a significantly lower rate of subjective health, food diversity and food intake frequency than those who ate together more often. A stepwise logistic analysis showed that the factors most strongly related to eating together less than once a month were not having any food shopping assistance (men: OR = 3.06, women: OR = 2.71), not receiving any food from neighbors or relatives (men: OR = 1.74, women: OR = 1.82), daily alcohol intake (women: OR = 1.83), frailty (men: OR = 0.48) and income (men: OR = 2.16, women: OR = 1.32).

CONCLUSION

Eating together is associated with subjective health and food intake. Factors that affect how often older Japanese people who live alone eat together include food accessibility, daily alcohol intake, frailty and a low income.

Measurement of Coherent π^{+} Production in Low Energy Neutrino-Carbon Scattering

We report the first measurement of the flux-averaged cross section for charged current coherent π^{+} production on carbon for neutrino energies less than 1.5 GeV, and with a restriction on the final state phase space volume in the T2K near detector, ND280. Comparisons are made with predictions from the Rein-Sehgal coherent production model and the model by Alvarez-Ruso et al., the latter representing the first implementation of an instance of the new class of microscopic coherent models in a neutrino interaction Monte Carlo event generator. We observe a clear event excess above background, disagreeing with the null results reported by K2K and SciBooNE in a similar neutrino energy region. The measured flux-averaged cross sections are below those predicted by both the Rein-Sehgal and Alvarez-Ruso et al.

Measurement of Muon Antineutrino Oscillations with an Accelerator-Produced Off-Axis Beam

T2K reports its first measurements of the parameters governing the disappearance of ν[over ¯]_{μ} in an off-axis beam due to flavor change induced by neutrino oscillations. The quasimonochromatic ν[over ¯]_{μ} beam, produced with a peak energy of 0.6 GeV at J-PARC, is observed at the far detector Super-Kamiokande, 295 km away, where the ν[over ¯]_{μ} survival probability is expected to be minimal. Using a data set corresponding to 4.01×10^{20} protons on target, 34 fully contained μ-like events were observed. The best-fit oscillation parameters are sin^{2}(θ[over ¯]_{23})=0.45 and |Δm[over ¯]_{32}^{2}|=2.51×10^{-3}  eV^{2} with 68% confidence intervals of 0.38-0.64 and 2.26-2.80×10^{-3}  eV^{2}, respectively. These results are in agreement with existing antineutrino parameter measurements and also with the ν_{μ} disappearance parameters measured by T2K.

Food Accessibility and Perceptions of Shopping Difficulty among Elderly People Living Alone in Japan

OBJECTIVES

This aim of this study was to describe the association between shopping difficulty and food accessibility for elderly people living alone in Japan.

DESIGN

A cross-sectoral, multilevel survey was designed to measure shopping difficulty from a food accessibility perspective. The questionnaire was distributed by mail.

SETTING

The sample was drawn from seven towns and cities across Japan.

PARTICIPANTS

A geographic information system was used to select the sample: it identified the proximity of elderly people living alone to a supermarket. In total, 2,028 elderly people (725 men and 1,303 women) responded to the questionnaire.

MEASUREMENTS

The binary dependent variables were shopping is easy/shopping is difficult. A logistic regression analysis adjusting for age and area of residence and using stepwise variable analyses was performed.

RESULTS

The response rate was 58.6%. Overall, 14.6% of elderly men and 21.7% of elderly women consider shopping difficult. The stepwise logistic analysis showed that the food accessibility factors strongly related to shopping difficulty are infrequent car use (women: OR = 6.97), walking difficulties (men: OR = 2.81, women: OR = 3.48), poor eyesight (men: OR = 2.26, women: OR = 1.75), not cooking lunch by oneself (men: OR = 1.63, women: OR = 1.72), not having anyone to help with food shopping (women: OR = 1.45) and living over 1 km away from a supermarket (men: OR = 2.30, women: OR = 2.97).

CONCLUSION

The study concludes that elderly people's assessment of shopping difficulty is related to their food accessibility. Important food accessibility aspects include car or motorbike ownership, walking continuously for 1 km, poor eyesight, and having cooking skills and having someone to help with shopping. These physical activity restrictions have a greater influence on shopping difficulty than do either income or proximity to a supermarket.

Revealing the second harmonic generation in a femtosecond laser-driven cluster-based plasma by analyzing shapes of Ar XVII spectral lines

We present experiments dealing with a femtosecond laser-driven cluster-based plasma, where by analyzing the nonlinear phenomenon of satellites of spectral lines of Ar XVII, we revealed the nonlinear phenomenon of the generation of the second harmonic of the laser frequency. For performing this analysis we developed new results in the theory of satellites of spectral lines. From such lineshape analysis we found, in particular, that the efficiency of converting the short (40 fs) intense (3x10¹⁸ W/cm²) incident laser light into the second harmonic was 2%. This result is in the excellent agreement with the 2-Dimensional Particle-In-Cell (2D PIC) simulation that we also performed. There is also an order of magnitude agreement between the thresholds for the SHG found from the line shape analysis and from the 2D PIC simulations.

Search for Nucleon and Dinucleon Decays with an Invisible Particle and a Charged Lepton in the Final State at the Super-Kamiokande Experiment

Search results for nucleon decays p→e^{+}X, p→μ^{+}X, n→νγ (where X is an invisible, massless particle) as well as dinucleon decays np→e^{+}ν, np→μ^{+}ν, and np→τ^{+}ν in the Super-Kamiokande experiment are presented. Using single-ring data from an exposure of  273.4  kton·yr, a search for these decays yields a result consistent with no signal. Accordingly, lower limits on the partial lifetimes of τ_{p→e^{+}X}>7.9×10^{32} yr, τ_{p→μ^{+}X}>4.1×10^{32} yr, τ_{n→νγ}>5.5×10^{32} yr, τ_{np→e^{+}ν}>2.6×10^{32}  yr, τ_{np→μ^{+}ν}>2.2×10^{32} yr, and τ_{np→τ^{+}ν}>2.9×10^{31} yr at a 90% confidence level are obtained. Some of these searches are novel.

Nonlinear increase of X-ray intensities from thin foils irradiated with a 200 TW femtosecond laser

We report, for the first time, that the energy of femtosecond optical laser pulses, E, with relativistic intensities I > 10(21)  W/cm(2) is efficiently converted to X-ray radiation, which is emitted by "hot" electron component in collision-less processes and heats the solid density plasma periphery. As shown by direct high-resolution spectroscopic measurements X-ray radiation from plasma periphery exhibits unusual non-linear growth ~E(4-5) of its power. The non-linear power growth occurs far earlier than the known regime when the radiation reaction dominates particle motion (RDR). Nevertheless, the radiation is shown to dominate the kinetics of the plasma periphery, changing in this regime (now labeled RDKR) the physical picture of the laser plasma interaction. Although in the experiments reported here we demonstrated by observation of KK hollow ions that X-ray intensities in the keV range exceeds ~10(17)  W/cm(2), there is no theoretical limit of the radiation power. Therefore, such powerful X-ray sources can produce and probe exotic material states with high densities and multiple inner-shell electron excitations even for higher Z elements. Femtosecond laser-produced plasmas may thus provide unique ultra-bright X-ray sources, for future studies of matter in extreme conditions, material science studies, and radiography of biological systems.