390 research outputs found
False Vacuum in the Supersymmetric Mass Varying Neutrinos Model
We present detailed analyses of the vacuum structure of the scalar potential
in a supersymmetric Mass Varying Neutrinos model. The observed dark energy
density is identified with false vacuum energy and the dark energy scale of
order is understood by gravitationally suppressed supersymmetry
breaking scale, , in the model. The vacuum expectation
values of sneutrinos should be tiny in order that the model works. Some decay
processes of superparticles into acceleron and sterile neutrino are also
discussed in the model.Comment: 7 pages, 5 figures, revtex, typos correcte
When to Replan? An Adaptive Replanning Strategy for Autonomous Navigation using Deep Reinforcement Learning
The hierarchy of global and local planners is one of the most commonly
utilized system designs in autonomous robot navigation. While the global
planner generates a reference path from the current to goal locations based on
the pre-built static map, the local planner produces a kinodynamic trajectory
to follow the reference path while avoiding perceived obstacles. To account for
unforeseen or dynamic obstacles not present on the pre-built map, ``when to
replan'' the reference path is critical for the success of safe and efficient
navigation. However, determining the ideal timing to execute replanning in such
partially unknown environments still remains an open question. In this work, we
first conduct an extensive simulation experiment to compare several common
replanning strategies and confirm that effective strategies are highly
dependent on the environment as well as the global and local planners. Based on
this insight, we derive a new adaptive replanning strategy based on deep
reinforcement learning, which can learn from experience to decide appropriate
replanning timings in the given environment and planning setups. Our
experimental results demonstrate that the proposed replanner can perform on par
or even better than the current best-performing strategies in multiple
situations regarding navigation robustness and efficiency.Comment: 7 pages, 3 figure
Electrochemical and Mechanistic Study of Oxidative Degradation of Favipiravir by Electrogenerated Superoxide through Proton-Coupled Electron Transfer
Electrochemical analyses aided by density functional theory calculations were used to investigate the oxidative degradation of pyrazine antiviral drugs, 3-hydroxypyrazine-2-carboxamide (T-1105) and 6-fluoro-3-hydroxypyrazine-2-carboxamide (favipiravir, T-705), by the electrogenerated superoxide radical anion (O2•–). T-1105 and T-705 are antiviral RNA nucleobase analogues that selectively inhibit the RNA-dependent RNA polymerase. They are expected as a drug candidate against various viral infections, including COVID-19. The pyrazine moiety was decomposed by O2•– through proton-coupled electron transfer (PCET). Our results show that its active form, pyrazine-ribofuranosyl-5′-triphosphate, is easily oxidized under inflamed organs by overproduced O2•– through the PCET mechanism in the immune system. This mechanistic study implies that the oxidative degradation of pyrazine derivatives will be prevented by controlling the PCET through simple modification of the pyrazine structure
Effects of Nanosecond Laser Fabrication on Bioactivity of Pure Titanium
AbstractWe are developing surface modification techniques for dental implants with the aim of reducing the time required to realize good adhesion between bone and implant surfaces. A nanosecond Nd:YVO4 laser was used to modify the surfaces of commercially pure titanium (CP Ti) disks and their bioactivities were then evaluated. The surfaces of the CP Ti disks were covered by lines after laser treatment. This treatment created complex microasperities of titania with rutile and anatase crystal structures. This results in the formation of hydroxyapatite on surfaces immersed in 1.5-times concentrated simulated body fluid for 7 days, whereas no hydroxyapatite was observed on conventionally polished surfaces that were immersed under the same conditions. This indicates that laser treatment improves the bioactivity of CP Ti, which is a critical property for osseointegrated implants
広域重力地形補正計算の高精度化とReal Bouguer Anomaly算出の試み
取得学位:博士(理学),学位授与番号:博甲第699号,学位授与年月日:平成17年3月22日,学位授与年:200
Scattering polarization of 3-m water-ice feature by large icy grains
Water ice has a strong spectral feature at a wavelength of approximately
m, which plays a vital role in our understanding of the icy universe. In
this study, we investigate the scattering polarization of this water-ice
feature. The linear polarization degree of light scattered by m-sized icy
grains is known to be enhanced at the ice band; however, the dependence of this
polarization enhancement on various grain properties is unclear. We find that
the enhanced polarization at the ice band is sensitive to the presence of
m-sized grains as well as their ice abundance. We demonstrate that this
enhancement is caused by the high absorbency of the water-ice feature, which
attenuates internal scattering and renders the surface reflection dominant over
internal scattering. Additionally, we compare our models with polarimetric
observations of the low-mass protostar L1551 IRS 5. Our results show that
scattering by a maximum grain radius of a few microns with a low water-ice
abundance is consistent with observations. Thus, scattering polarization of the
water-ice feature is a useful tool for characterizing ice properties in various
astronomical environments.Comment: 19 pages, 17 figures, 1 table; Accepted for publication in Ap
In vitro production of L-cysteine using thermophilic enzymes
L-Cysteine (L-Cys) is a commercially important amino acid and widely used in food, pharmaceutical, and cosmetic industries. Commercial production of L-Cys has long been done by an acid-hydrolysis of human hair and animal feather, leading to the generation of a large quantity of hazardous wastes. Although several biotechnology companies have recently launched a fermentative production of L-Cys using engineered bacteria, these processes suffer from the low product titer mainly due to the cytotoxic effect of L-Cys. To provide an alternative approach for the commercial production of L-Cys, we aimed at the development of a non-fermentative, in vitro manufacturing system using thermophilic enzymes. In this system, enzymes from (hyper)thermophilic bacteria and archaea were assembled to construct an in vitro synthetic pathway for the one-pot conversion of glucose to L-Cys (Figure 1). By using experimentally optimized concentrations of enzymes, L-Cys could be produced at a rate of 0.9 g/L/h with a molar conversion yield of 25%.
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Propolis Components and Biological Activities from Stingless Bees Collected on South Sulawesi, Indonesia
Three new compounds, namely sulabiroins A (1) and B (2), and 2',3'-dihydro-3'-hydroxypapuanic acid (3), were isolated from the propolis of stingless bees (Tetragonula aff. biroi) collected on South Sulawesi, Indonesia. In addition, ten known compounds, (–)-papuanic acid (4), (–)-isocalolongic acid (5), isopapuanic acid (6), isocalopolyanic acid (7), glyasperin A (8), broussoflavonol F (9), (2S)-5,7-dihydroxy-4'-methoxy-8-prenylflavanone (10), isorhamnetin (11), (1'S)-2-trans,4-trans-abscisic acid (12), and (1'S)-2-cis,4-trans-abscisic acid (13) were identified. The structures of the new and known compounds were determined by spectroscopic analysis. The absolute configurations of sulabiroins A (1) and B (2) were determined by X-ray crystallography analysis and ECD calculation, respectively. The propolis from stingless bee (Tetragonula aff. biroi) collected on South Sulawesi contained compounds not present in propolis from other regions. Sulabiroin A (1) and isorhamnetin (11) were examined for xanthine oxidase (XO) inhibitory activity as one of biological activities; isorhamnetin (11) exhibited potent XO inhibitory activity, with an IC50 value of 3.9 µm
Speed of Sound in the Mass Varying Neutrinos Scenario
We discuss about the speed of sound squared in the Mass Varying Neutrinos
scenario (MaVaNs). Recently, it was argued that the MaVaNs has a catastrophic
instability which is the emergence of an imaginary speed of sound at the
non-relativistic limit of neutrinos. As the result of this instability, the
neutrino-acceleron fluid cannot act as the dark energy. However, it is found
that the speed of sound squared in the neutrino-acceleron fluid could be
positive in our model. We examine the speed of sound in two cases of the scalar
potential. One is the small fractional power-law potential and another is the
logarithmic one. The power-law potential model with the right-handed neutrinos
gives a stable one.Comment: 17 pages, References added, minor modification
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