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We report on experimental observation of non-laminar proton acceleration modulated by a strong magnetic field in laser irradiating micrometer aluminum targets. The results illustrate the coexistence of ring-like and filamentation structures. We implement the knife edge method into the radiochromic film detector to map the accelerated beams, measuring a source size of 30–110 μm for protons of more than 5 MeV. The diagnosis reveals that the ring-like profile originates from low-energy protons far off the axis whereas the filamentation is from the near-axis high-energy protons, exhibiting non-laminar features. Particle-in-cell simulations reproduced the experimental results, showing that the short-term magnetic turbulence via Weibel instability and the long-term quasi-static annular magnetic field by the streaming electric current account for the measured beam profile. Our work provides direct mapping of laser-driven proton sources in the space-energy domain and reveals the non-laminar beam evolution at featured time scales.
Early life adversity (ELA) has been linked with increased arousal responses to threat, including increased amygdala reactivity. Effects of ELA on brain function are well recognized, and emerging evidence suggests that caregivers may influence how environmental stressors impact children’s brain function. We investigated the hypothesis that positive interaction between mother and child can buffer against ELA effects on children’s neural responses to threat, and related symptoms. N = 53 mother–child pairs (children ages 8–14 years) were recruited from an urban population at high risk for violence exposure. Maternal caregiving was measured using the Parenting Questionnaire and in a cooperation challenge task. Children viewed fearful and neutral face stimuli during functional magnetic resonance imaging. Children who experienced greater violence at home showed amygdala sensitization, whereas children experiencing more school and community violence showed amygdala habituation. Sensitization was in turn linked with externalizing symptoms. However, maternal warmth was associated with a normalization of amygdala sensitization in children, and fewer externalizing behaviors prospectively up to 1 year later. Findings suggested that the effects of violence exposure on threat-related neural circuitry depend on trauma context (inside or outside the home) and that primary caregivers can increase resilience.
To examine associations between serum micronutrients and neurobehavioural function and the mediating role of sleep quality in early adolescents.
In this cross-sectional study, peripheral blood samples were analysed for Fe and Zn levels. The Pittsburgh Sleep Quality Index and Penn Computerized Neurocognitive Battery were used to assess sleep quality and neurobehavioural function, respectively. The logistic/linear regressions and generalised structural equation modelling were performed to estimate the associations.
In total, 226 adolescents (106 females) from the Jintan Child Cohort study.
Adolescents with low Fe (<75 μg/dl) (OR = 1·29, P = 0·04) and low Zn (<70 μg/dl) (OR = 1·58, P < 0·001) were associated with increased odds for poor sleep quality. Adolescents with low Fe and Zn were associated with fast (Fe: β = –1353·71, P = 0·002, Zn: β = –2262·01, P = 0·02) but less-accurate (Fe: β = –0·97, P = 0·04; Zn: β = –1·76, P = 0·04) performance on non-verbal reasoning task and poor sleep quality partially mediated the associations between low Fe/Zn and non-verbal reasoning (P < 0·05). Additionally, low Fe was associated with a slower reaction on spatial processing task (β = 276·94, P = 0·04), and low Zn was associated with fast (β = –1781·83, P = 0·03), but error-prone performance (β = –1·79, P = 0·04) on spatial processing ability and slower reaction speed (β = 12·82, P = 0·03) on the attention task. We observed similar trends using a cut-off point of 75 μg/dl for low serum Zn, except for the association with attention task speed (P > 0·05).
Fe and Zn deficiencies may possibly be associated with poor sleep and neurobehavioural function among early adolescents. Poor sleep may partially mediate the relationship between micronutrients and neurobehavioural function.
The onset of magnetic reconnection in space, astrophysical and laboratory plasmas is reviewed discussing results from theory, numerical simulations and observations. After a brief introduction on magnetic reconnection and approach to the question of onset, we first discuss recent theoretical models and numerical simulations, followed by observations of reconnection and its effects in space and astrophysical plasmas from satellites and ground-based detectors, as well as measurements of reconnection in laboratory plasma experiments. Mechanisms allowing reconnection spanning from collisional resistivity to kinetic effects as well as partial ionization are described, providing a description valid over a wide range of plasma parameters, and therefore applicable in principle to many different astrophysical and laboratory environments. Finally, we summarize the implications of reconnection onset physics for plasma dynamics throughout the Universe and illustrate how capturing the dynamics correctly is important to understanding particle acceleration. The goal of this review is to give a view on the present status of this topic and future interesting investigations, offering a unified approach.
Flexibility is one of the important mechanical performance parameters of stent. The flexibility of tapered stents, especially self-expanding tapered stents, remains unknown. In this study, we developed a new selfexpanding tapered stent for tapered arteries and performed a numerical investigation of stent flexibility by using finite element method. The effect of stent design parameters, including taper and link space width, on stent flexibility was studied. The flexibility of the proposed stent was also compared with that of traditional cylindrical stents. Results show that the tapered stent is more flexible than the traditional cylindrical stent. Furthermore, the flexibility of the tapered stent increases with increasing stent taper and stent link space width. The increase in the stent link space width can contribute to the reduction in the peak stress. Therefore, tapered stents with high link space width will improve the stent flexibility. This work provides useful information for improvement of stent design and clinical selection.
Financial crisis could play a key role in changing the policy equilibrium concerning financial markets and institutions. Using a recent comprehensive dataset on financial liberalization across ninety-four countries for the period between 1973 and 2015, we formally test the validity of this prediction for the member states of the European Union as well as a global sample. We contribute by (a) using a new up-to-date dataset of reforms and crises and (b) subjecting it to a combination of difference-in-differences and local projection estimations. In the global sample, our findings on the causal relationship between crises and liberal reforms consistently point out a negative direction between the two, suggesting that governments react to crises by intervening in financial markets. However, in a dynamic setting with impulse responses, we also illustrate that such interventions are only temporary and liberalization process restarts after a financial crisis. In the EU sample, however, we do not find sufficient evidence to support either of these observations.
The financial crisis of 2007–2008, which led to the Great Recession of 2008–2009 and triggered the sovereign debt crisis in the euro area in 2010, has led to a lot of soul searching among professional economists. With the benefit of hindsight, it can now be said that these crises were misdiagnosed in two ways. First, many economists interpreted these crises to have increased the need for more flexibility in labour and product markets. Structural reforms aimed at making both labour and product markets more flexible were seen as the tools to boost economic activity and to launch countries into a higher growth path. Thus, although the initial shocks were understood to have originated from a financial and banking implosion, which led to a collapse of aggregate demand in 2009, many economists surprisingly advised to fix the supply side.
It has long been argued that structural reforms constitute a remedy for getting countries out of the low-growth environment that Europe has experienced in the last decade. Many recent studies show long-term benefits of such reforms in cross-country settings, but ignore the heterogeneity across different country experiences. To address this gap in the context of the European Union, we focus on the largest early reforms that its four members (Denmark, France, Greece and Portugal) adopted in financial and labour markets. By using a Synthetic Control Method, we find that many of these early reform episodes do not seem to have been as fruitful as their advocates claimed at the time. Our results indicate a rather mixed relationship between reforms and several macro measures, including economic growth and inequality. Reforms, especially when introduced all at once as a big-bang, do not seem to always produce the intended results.
One reason the effects of individual structural reforms are notoriously difficult to capture is the possibility that they depend upon other reforms and institutions. This chapter studies whether and to what extent reforms in labour market regulation are complementary to tax changes in increasing employment in the European Union (EU). We use a dynamic model of employment growth to estimate and try to disentangle the individual effects from the combined effects of these reforms using a yearly panel of EU countries from 1990 to 2015. Our estimates suggest that reform complementarity between labour market policy and taxation, through substantial and significant interaction effects, seems key to foster employment growth and enhance the effectiveness of both reforms.