326 research outputs found
How to distinguish the Haldane/Large-D state and the intermediate-D state in an S=2 quantum spin chain with the XXZ and on-site anisotropies
We numerically investigate the ground-state phase diagram of an S=2 quantum
spin chain with the and on-site anisotropies described by , where denotes the XXZ anisotropy parameter of the
nearest-neighbor interactions and the on-site anisotropy parameter. We
restrict ourselves to the and case for simplicity. Our main
purpose is to obtain the definite conclusion whether there exists or not the
intermediate- (ID) phase, which was proposed by Oshikawa in 1992 and has
been believed to be absent since the DMRG studies in the latter half of 1990's.
In the phase diagram with and there appear the XY state, the
Haldane state, the ID state, the large- (LD) state and the N\'eel state. In
the analysis of the numerical data it is important to distinguish three gapped
states; the Haldane state, the ID state and the LD state. We give a physical
and intuitive explanation for our level spectroscopy method how to distinguish
these three phases.Comment: Proceedings of "International Conference on Frustration in Condensed
Matter (ICFCM)" (Jan. 11-14, 2011, Sendai, Japan
4D topology optimization: Integrated optimization of the structure and self-actuation of soft bodies for dynamic motions
Topology optimization is a powerful tool utilized in various fields for
structural design. However, its application has primarily been restricted to
static or passively moving objects, mainly focusing on hard materials with
limited deformations and contact capabilities. Designing soft and actively
moving objects, such as soft robots equipped with actuators, poses challenges
due to simulating dynamics problems involving large deformations and intricate
contact interactions. Moreover, the optimal structure depends on the object's
motion, necessitating a simultaneous design approach. To address these
challenges, we propose "4D topology optimization," an extension of
density-based topology optimization that incorporates the time dimension. This
enables the simultaneous optimization of both the structure and self-actuation
of soft bodies for specific dynamic tasks. Our method utilizes multi-indexed
and hierarchized density variables distributed over the spatiotemporal design
domain, representing the material layout, actuator layout, and time-varying
actuation. These variables are efficiently optimized using gradient-based
methods. Forward and backward simulations of soft bodies are done using the
material point method, a Lagrangian-Eulerian hybrid approach, implemented on a
recent automatic differentiation framework. We present several numerical
examples of self-actuating soft body designs aimed at achieving locomotion,
posture control, and rotation tasks. The results demonstrate the effectiveness
of our method in successfully designing soft bodies with complex structures and
biomimetic movements, benefiting from its high degree of design freedom.Comment: 36 pages, 27 figures; for supplementary video, see
https://youtu.be/sPY2jcAsNY
Bose-Einstein Condensation of Europium
We report the realization of a Bose-Einstein condensate of europium atoms,
which is a strongly dipolar species with unique properties, a highly symmetric
electronic ground state and a
hyperfine structure. By means of evaporative cooling in a crossed optical
dipole trap, we produced a condensate of Eu containing up to atoms. The scattering length of Eu was estimated to be by comparing the velocities of expansion of condensates
with different orientations of the atomic magnetic moments. We observed
deformation of the condensate in the vicinity of the Feshbach resonance at
with a width of .Comment: 5 pages, 4 figure
Dynamic Determinants of the Uncontrolled Manifold during Human Quiet Stance
Human postural sway during stance arises from coordinated multi-joint movements. Thus, a sway trajectory represented by a time-varying postural vector in the multiple-joint-angle-space tends to be constrained to a low-dimensional subspace. It has been proposed that the subspace corresponds to a manifold defined by a kinematic constraint, such that the position of the center of mass (CoM) of the whole body is constant in time, referred to as the kinematic uncontrolled manifold (kinematic-UCM). A control strategy related to this hypothesis (CoM-control-strategy) claims that the central nervous system (CNS) aims to keep the posture close to the kinematic-UCM using a continuous feedback controller, leading to sway patterns that mostly occur within the kinematic-UCM, where no corrective control is exerted. An alternative strategy proposed by the authors (intermittent control-strategy) claims that the CNS stabilizes posture by intermittently suspending the active feedback controller, in such a way to allow the CNS to exploit a stable manifold of the saddle-type upright equilibrium in the state-space of the system, referred to as the dynamic-UCM, when the state point is on or near the manifold. Although the mathematical definitions of the kinematic- and dynamic-UCM are completely different, both UCMs play similar roles in the stabilization of multi-joint upright posture. The purpose of this study was to compare the dynamic performance of the two control strategies. In particular, we considered a double-inverted-pendulum-model of postural control, and analyzed the two UCMs defined above. We first showed that the geometric configurations of the two UCMs are almost identical. We then investigated whether the UCM-component of experimental sway could be considered as passive dynamics with no active control, and showed that such UCM-component mainly consists of high frequency oscillations above 1 Hz, corresponding to anti-phase coordination between the ankle and hip. We also showed that this result can be better characterized by an eigenfrequency associated with the dynamic-UCM. In summary, our analysis highlights the close relationship between the two control strategies, namely their ability to simultaneously establish small CoM variations and postural stability, but also make it clear that the intermittent control hypothesis better explains the spectral characteristics of sway
Gadolinium silicide/silicon composite with excellent high-rate performance as lithium-ion battery anode
Novel composite materials consisted of elemental Si and rare-earth metal silicides, Sm–Si, Gd–Si, and Dy–Si, were synthesized and were evaluated for the first time as a high-performance anode material of Li-ion battery. Thick-film electrodes of the silicide/Si composites were prepared by an arc melting method and a successive gas-deposition method. Among them, the Gd–Si/Si composite electrode exhibited reversible Li-insertion/extraction reactions and the best cycling performance: the initial Coulombic efficiency was 80% and the discharge capacity at the 1000th cycle was 840 mA h g–1. In addition to this, the composite electrode delivered a superb high-rate performance with the capacity of 2100 mA h g–1 even at the high current rate of 12.0 A g–1 (4.8C). The remarkable performances demonstrated that the gadolinium silicide is favorable to significantly enhance anode properties of Si-based composite electrodes
A case of spontaneous parasitic myoma in a patient without a history of myomectomy treated laparoscopically
Parasitic myoma (PM) is a rare disease in which multiple leiomyomas are intraperitoneally formed. Recently, an increasing number of cases due to specimen morcellation during minimally invasive surgery has been reported. We present the first case of a PM identified intraoperatively during laparoscopic hysterectomy. A 40-year-old Japanese multiparous woman presented to our hospital with heavy menstrual bleeding. She had no history of previous surgery. Magnetic resonance imaging showed uterine myomas. As the patient did not wish for further pregnancy, she underwent oral gonadotropin-releasing hormone antagonist therapy followed by a total laparoscopic hysterectomy. Intraoperatively, we identified a thumb-sized tumor on the left side of the peritoneum. Histopathological examination showed evidence of benign leiomyoma
Accuracy management survey of nucleic acid amplification tests using inactivated SARS-CoV-2 in Hiroshima Prefecture
At the beginning of 2020, the number of laboratories performing SARS-CoV-2 testing increased with the rapid expansion of COVID-19 in Hiroshima Prefecture. Thus, it is necessary to compare and verify the validity of the test results among local laboratories. In this study, we distributed the same standard samples to laboratories that performed COVID-19 testing using the nucleic acid amplification method and confirmed the accuracy of the tests. The SARS-CoV-2 strain distributed by the National Institute of Infectious Diseases (NIID), Japan, was used for testing. As measured by RT-qPCR, a specific amount of the virus was inactivated by ethanol and dried as specimens for distribution. This study included 27 tests performed at 15 laboratories conducting or planning to conduct nucleic acid amplification tests (RT-qPCR and LAMP methods) for SARSCoV-2. The detection limit of each test method was set at the value provided by the NIID. The accuracy of the tests was examined to determine whether they met the required accuracy criteria. SARS-CoV-2 genomic RNA was reliably detected in all 27 tests. The inactivated specimens used in this study were safe to distribute and could be used as positive controls for all methods.This study was supported by a grant from the Government-Academia Collaboration of Hiroshima Prefecture and by a research grant for COVID-19 from AMED, Japan under Grant Number 20he0622011h0001(to J. T.)
Topology optimization of locomoting soft bodies using material point method
Topology optimization methods have widely been used in various industries,
owing to their potential for providing promising design candidates for
mechanical devices. However, their applications are usually limited to the
objects which do not move significantly due to the difficulty in
computationally efficient handling of the contact and interactions among
multiple structures or with boundaries by conventionally used simulation
techniques. In the present study, we propose a topology optimization method for
moving objects incorporating the material point method, which is often used to
simulate the motion of objects in the field of computer graphics. Several
numerical experiments demonstrate the effectiveness and the utility of the
proposed method
Activation of Stat1 and subsequent transcription of inducible nitric oxide synthase gene in C6 glioma cells is independent of interferon-γ-induced MAPK activation that is mediated by p21ras
AbstractRat C6 glioma cells have been used to characterize molecular events involved in the regulation of inducible nitric oxide synthase (iNOS) gene expression stimulated by interferon-γ (IFN-γ) plus lipopolysaccharide (LPS). IFNs induce a signaling event which involves activation of Stat1 transcription factor. Previous studies have shown that IFNs also induce extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) activation. However, the mechanisms by which IFNs stimulate MAPK activation remain elusive. Here we show that in C6 glioma cells, transiently expressing the dominant-negative form of c-Ha-Ras (Asn-17) abrogated IFN-γ-induced ERK1 and ERK2 activation. Furthermore, PD98059, a specific MEK1 inhibitor, also blocked this activation. These results indicate that p21ras and MEK1 are required for IFN-γ-induced ERK1 and ERK2 activation. Recent studies have reported that MAPK is responsible for serine phosphorylation of Stat1 which is required for Stat1's DNA binding and maximal transcriptional activity. Thus, we examined the role of the Ras-MAPK pathway in Stat1 activation and subsequent iNOS induction in C6 glioma cells. Further experiments showed that neither Asn-17 Ras expression nor concentrations of PD98059, which completely abrogated IFN-γ-induced ERK1 and ERK2 activation, affected Stat1 DNA binding activity or iNOS induction, indicating that the Ras-MAPK pathway does not appear to be involved in the activation of Stat1 and subsequent iNOS induction in C6 glioma cells
Biological responses according to the shape and size of carbon nanotubes in BEAS-2B and MESO-1 cells
This study aimed to investigate the influence of the shape and size of multi-walled carbon nanotubes (MWCNTs) and cup-stacked carbon nanotubes (CSCNTs) on biological responses in vitro. Three types of MWCNTs - VGCF (R)-X, VGCF (R)-S, and VGCF (R) (vapor grown carbon fibers; with diameters of 15, 80, and 150 nm, respectively) - and three CSCNTs of different lengths (CS-L, 20-80 mu m; CS-S, 0.5-20 mu m; and CS-M, of intermediate length) were tested. Human bronchial epithelial (BEAS-2B) and malignant pleural mesothelioma cells were exposed to the CNTs (1-50 mu g/mL), and cell viability, permeability, uptake, total reactive oxygen species/superoxide production, and intracellular acidity were measured. CSCNTs were less toxic than MWCNTs in both cell types over a 24-hour exposure period. The cytotoxicity of endocytosed MWCNTs varied according to cell type/size, while that of CSCNTs depended on tube length irrespective of cell type. CNT diameter and length influenced cell aggregation and injury extent. Intracellular acidity increased independently of lysosomal activity along with the number of vacuoles in BEAS-2B cells exposed for 24 hours to either CNT (concentration, 10 mu g/mL). However, total reactive oxygen species/superoxide generation did not contribute to cytotoxicity. The results demonstrate that CSCNTs could be suitable for biological applications and that CNT shape and size can have differential effects depending on cell type, which can be exploited in the development of highly specialized, biocompatible CNTs.ArticleINTERNATIONAL JOURNAL OF NANOMEDICINE. 9:1979-1990 (2014)journal articl
- …