N\'eel-Dimer Transition in Antiferromagnetic Heisenberg Model and Deconfinement of Spinons at the Critical Point

Quantum phase transition from the N\'eel to the dimer states in an antiferromagnetic(AF) Heisenberg model on square lattice is studied. We introduce a control parameter $\alpha$ for the exchange coupling which connects the N\'eel ($\alpha=0$) and the dimer ($\alpha=1$) states. We employ the $CP^1$ (the Schwinger boson) representation of the $s={1\over 2}$ spin operator and integrate out the half of the $CP^1$ variables at odd sites and we obtain a $CP^1$ nonlinear $\sigma$ model. The effective coupling constant is a function of $\alpha$ and at $\alpha=0$ the $CP^1$ model is in the ordered phase which corresponds to the N\'eel state of the AF Heisenberg model. A phase transition to the dimer state occurs at a certain critical value of $\alpha_C$ as $\alpha$ increases. In the N\'eel state, the dynamical composite U(1) gauge field in the $CP^1$ model is in a Higgs phase and low-energy excitations are gapless spin wave. In the dimer phase, a confinement phase of the gauge theory is realized and low-energy excitations are $s=1$ magnons. For the critical point, we argue that a deconfinement phase, which is similar to the Coulomb phase in 3 spatial dimensions, is realized and $s={1\over 2}$ spinons appear as low-energy excitations

How Do Agricultural Markets Respond to Radiation Risk?: Evidence from the 2011 Disaster in Japan

Since the explosion of the Fukushima Daiichi Nuclear Power Plant in March 2011, public anxiety surrounding the radioactive contamination of food and the environment has become widespread. This article examines how the price of vegetables in the Tokyo Metropolitan Central Wholesale Market was impacted in the wake of the nuclear accident. This study exploits the quasi-experimental condition generated by this accident to test the market price change using monthly panel data on the price of six types of fresh vegetable from each of the 47 prefectures in Japan. Our estimation results show that the price of vegetables grown in Fukushima Prefecture was discounted by 10 - 38 % after the disaster compared to the counter-factual estimates in the absence of a perceived radiation risk. This effect has persisted even after radioactive detection tests showed negative results in subsequent years. Consumer behavior of avoiding purchasing vegetables from Fukushima and instead buying vegetables grown in other areas may explain the price gap

Does Unit-Based Pricing Really Reduce Waste? A Causal Inference Approach with Panel Data

Preventing waste generation is the first priority of waste management policies in many countries. In this paper, we examine the effect of unit-based pricing policy using a causal inference approach. Although previous research has examined the impact of unit-based pricing, few studies implement a causal inference framework. We apply the approach called "Weighted Fixed Effects Regression Models for Causal Inference" developed by Imai and Kim (2016, 2019) and find that the effect of unit-based pricing is overestimated by standard linear fixed effects models. We also find evidence that the effect of unit-based pricing is not strictly increasing in the price of waste collection

The relationship between quite sleep and neurobehavioral development in preterm infants

[Background and aims] Recent experimental data suggest sleep plays a role in brain development. Behavioral and physiologic assessments of neonatal sleep might lead to more developmentally appropriate state regulation for infants in intensive care and assist in daily medical care and predicting the neurodevelopmental outcome. Analysis of sleep patterns using amplitude-integrated electroencephalography (aEEG) might predict further neurobehavioral developmental states in premature infants. The study aimed to evaluate the relationship between sleep states, investigated by aEEG, and short-term neurobehavioral developments in preterm infants. [Study design and subjects] 　aEEG and neurobehavioral assessments (Neonatal behavioral assessment scale ; NBAS) were performed at 37-39 weeks of post-conceptional age for 10 infants (median gestational age and birth weight were 35 weeks and 2175g. Quiet sleep (QS) data were collected by aEEG over 12 consecutive night hours. QS as the duration of QS intervals and the variation of QS duration periods were analyzed. NBAS were scored by six cluster scores (Habituation, Orientation, Motor, State Range, State Regulation and Autonomic Stability). Correlations analyses examined the relationship between the QS measurement items and NBAS cluster scores. [Results] There were significant negative correlations between the variation of QS duration periods and state range (ρ=-0.71, p<0.05), and the variation of QS duration periods and state regulation scores (ρ=-0.77, p<0.55). [Conclusions] 　Stable QS periods appear to have some short-term effects on neurobehavioral development in premature infants and therefore protected sleep during premature care is potentially advantageous in improving an infant’s neurobehavioral status

Spatially resolved metabolic distribution for unraveling the physiological change and responses in tomato fruit using matrix-assisted laser desorption/ionization–mass spectrometry imaging (MALDI–MSI)

Information on spatiotemporal metabolic behavior is indispensable for a precise understanding of physiological changes and responses, including those of ripening processes and wounding stress, in fruit, but such information is still limited. Here, we visualized the spatial distribution of metabolites within tissue sections of tomato (Solanum lycopersicum L.) fruit using a matrix-assisted laser desorption/ionization–mass spectrometry imaging (MALDI–MSI) technique combined with a matrix sublimation/recrystallization method. This technique elucidated the unique distribution patterns of more than 30 metabolite-derived ions, including primary and secondary metabolites, simultaneously. To investigate spatiotemporal metabolic alterations during physiological changes at the whole-tissue level, MALDI–MSI was performed using the different ripening phenotypes of mature green and mature red tomato fruits. Although apparent alterations in the localization and intensity of many detected metabolites were not observed between the two tomatoes, the amounts of glutamate and adenosine monophosphate, umami compounds, increased in both mesocarp and locule regions during the ripening process. In contrast, malate, a sour compound, decreased in both regions. MALDI–MSI was also applied to evaluate more local metabolic responses to wounding stress. Accumulations of a glycoalkaloid, tomatine, and a low level of its glycosylated metabolite, esculeoside A, were found in the wound region where cell death had been induced. Their inverse levels were observed in non-wounded regions. Furthermore, the amounts of both compounds differed in the developmental stages. Thus, our MALDI–MSI technique increased the understanding of the physiological changes and responses of tomato fruit through the determination of spatiotemporally resolved metabolic alterations

Mohawk promotes the maintenance and regeneration of the outer annulus fibrosus of intervertebral discs.

The main pathogenesis of intervertebral disc (IVD) herniation involves disruption of the annulus fibrosus (AF) caused by ageing or excessive mechanical stress and the resulting prolapse of the nucleus pulposus. Owing to the avascular nature of the IVD and lack of understanding the mechanisms that maintain the IVD, current therapies do not lead to tissue regeneration. Here we show that homeobox protein Mohawk (Mkx) is a key transcription factor that regulates AF development, maintenance and regeneration. Mkx is mainly expressed in the outer AF (OAF) of humans and mice. In Mkx(-/-) mice, the OAF displays a deficiency of multiple tendon/ligament-related genes, a smaller OAF collagen fibril diameter and a more rapid progression of IVD degeneration compared with the wild type. Mesenchymal stem cells overexpressing Mkx promote functional AF regeneration in a mouse AF defect model, with abundant collagen fibril formation. Our results indicate a therapeutic strategy for AF regeneration

The Decoupling of Affluence and Waste Discharge under Spatial Correlation: Do Richer Communities Discharge More Waste?

経済学 / EconomicsAlthough there are many studies on the environmental Kuznets curve, very few of them address municipal solid waste cases, and there is still controversy concerning the validity of the waste Kuznets curve hypothesis. In this paper, we provide empirical evidence for the waste Kuznets curve hypothesis by applying spatial econometrics methods to municipal-level data in Japan. To our knowledge, this is the first study that finds valid evidence for the waste Kuznets curve hypothesis in the absolute decoupling manner. The successful result owes in part to our highly disaggregated data and also to the use of a spatial econometric model that takes into account the mimicking behavior among neighboring municipalities. The former indicates that distinguishing between household and business waste is the key to revealing the waste–income relationship, while the latter implies the importance of peer effects when municipal governments formulate waste-reduction policies.http://www.grips.ac.jp/list/jp/facultyinfo/yoshida_yuichiro