Directional linearly polarized terahertz emission from argon clusters irradiated by noncollinear double-pulse beams

It has been demonstrated that the interaction between argon clusters and intense femtosecond double laser pulses with appropriate intervals in time and space provides important properties for terahertz electromagnetic wave generation, namely, high forward directivity, power enhancement, and linear polarization with a variable direction. Irradiating argon clusters with double pulses (1 and 3 mJ, 40 fs, 810 nm) in 133-ps and 40-μm intervals results in terahertz wave emission in the forward direction that is 10 times greater than that for a single pulse. The polarization direction of terahertz electromagnetic waves can be varied by changing the relative focal positions of the first and second pulses

高強度レーザー駆動電子による金属ワイヤーへの高強度テラヘルツ表面波の発生

京都大学0048新制・課程博士博士(理学)甲第22244号理博第4558号新制||理||1655(附属図書館)京都大学大学院理学研究科物理学・宇宙物理学専攻(主査)教授 阪部 周二, 准教授 橋田 昌樹, 教授 鶴 剛学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDGA

Highly intensified emission of laser-accelerated electrons from a foil target through an additional rear laser plasma

Intensification of electrons escaping from an intense laser-produced plasma is demonstrated by using double femtosecond laser pulses. The electron density distribution at the rear surface of a laser-irradiated foil target is controlled by preirradiation to suppress sheath field growth and to expand the plasma into which the fast electrons are released. Consequently, the number of electrons escaping from the plasma that have an energy of 380 keV increases by a factor of 7. The experimental results are well explained by numerical simulations of a foil plasma with a preformed plasma and analytical evaluations considering the plasma expansion

Cognitive transitions based on functional status in older adults with heart failure: a population‐based study

Abstract Aims Cognitive impairment and functional status are both important determinants of poor outcomes in heart failure (HF). However, little is known about how functional status impacts the changes in cognitive status during the disease course. This study aimed to describe the cognitive transitions in patients with HF and assess the relationship of these transitions to functional status, which was assessed by the dependency of activities of daily living (ADL). Methods and results This retrospective cohort study included 1764 patients with an International Classification of Diseases‐10 code of HF (≥65 years, mean age 82.3 ± 7.9 years, 39% male) from a long‐term care and medical insurance database from Nobeoka city, a rural city of south‐western Japan. Cognitive status at baseline and 6, 12, 18, and 24 month time points was collected, and participants were stratified based on ADL status at baseline. Generalized estimating equations and multi‐state modelling were used to examine associations between ADL dependency and cognitive changes/mortality. Transition probabilities were estimated using multi‐state modelling. At baseline, there were 1279 (73%) and 485 (27%) patients with independent and dependent ADL, respectively. In overall patients, 1656 (93.9%) patients had normal/mild cognitive status and 108 (6%) patients had a moderate/severe cognitive status at baseline. The majority [104 (96%) patients] of patients with moderate/severe cognitive status at baseline had dependent ADL. In patients with moderate/severe cognitive status, the number of patients with dependent ADL always outnumbered that of the independent ADL throughout the follow‐up. Multi‐state modelling estimated that patients with dependent ADL and normal/mild cognitive status at baseline had 47% probability of maintaining the same cognitive status at 24 months, while the probability of maintaining the same cognitive status was 86% for those with independent ADL. Patients with normal/mild cognitive status in the dependent ADL group at baseline had a higher risk of experiencing a transition to moderate/severe cognitive status at any time point during 24 months compared with those with independent ADL [hazard ratio 5.24 (95% confidence interval 3.47–7.90)]. Conclusions In older patients with HF, the prevalence of cognitive impairment was always higher for those with reduced functional status. Despite having a normal/mild cognitive status at baseline, patients with dependent ADL are at high risk of experiencing cognitive decline over 24 months with substantially less chance of maintaining their cognitive status. ADL dependency was an important risk factor of cognitive decline in patients with HF

Impact of Jiggling Exercise as Conservative Treatment for Hip Osteoarthritis: A Report of Two Cases

Total hip arthroplasty has been recognized as a feasible treatment for hip osteoarthritis, especially in advanced and terminal stages, but whether it is the best treatment for patients who are younger, have comorbidities, and/or are likely to have low compliance to medical treatment is unknown. Jiggling exercise, which involves the continuous shaking of the foot and leg in small steps, has been reported to be the easiest and a less invasive exercise for patients with hip osteoarthritis. We herein report two patients who performed jiggling exercise as conservative treatment and had successful outcomes. The first case was a 28-year-old woman with advanced-stage hip osteoarthritis that could not be treated with hip preservation surgery; furthermore, the patient refused to undergo total hip arthroplasty because of her young age. The second case was a 74-year-old woman with terminal-stage hip osteoarthritis in whom total hip arthroplasty was deemed not feasible because of possible low compliance due to mental disorder. One year after the initiation of the jiggling exercise, both patients had remarkable clinical improvement. Three years later, remarkable joint remodelling was also revealed in plain radiographs. Jiggling exercise might be a feasible conservative treatment option for joint preservation

Increased energy of THz waves from a cluster plasma by optimizing laser pulse duration

We have investigated the generation of terahertz (THz) waves from an argon cluster plasma produced by laser pulses of various durations. THz energy depends on laser pulse duration and reaches a peak at a pulse duration of ∼250 fs. This dependence of THz energy on laser pulse duration is attributed to the plasma density produced by the rising edge of the pulse. By irradiating clusters with collinear double laser pulses, we demonstrate that the THz energy can be increased by controlling the plasma density. Optimizing the delay time of the collinear double laser pulses increases the THz energy by ∼2.5 times that with simultaneous irradiation of collinear double laser pulses

Photoelectron diffraction from laser-aligned molecules with X-ray free-electron laser pulses

We report on the measurement of deep inner-shell 2p X-ray photoelectron diffraction (XPD) patterns from laser-aligned I 2 molecules using X-ray free-electron laser (XFEL) pulses. The XPD patterns of the I 2 molecules, aligned parallel to the polarization vector of the XFEL, were well matched with our theoretical calculations. Further, we propose a criterion for applying our molecular-structure-determination methodology to the experimental XPD data. In turn, we have demonstrated that this approach is a significant step toward the time-resolved imaging of molecular structures