151 research outputs found
Application of fullerenes-extracted soot modified with ethylenediamine as a novel adsorbent of hexavalent chromium in water
Fullerenes-extracted soot, the by-product of fullerene synthesis, is a carbon composite. The application of this material for water treatment has not yet been developed. Herein, fullerenes-extracted soot in the form of powder containing amino groups was prepared by reacting the soot with ethylenediamine, and was used as an adsorbent of hexavalent chromium [Cr(VI)] for removing Cr(VI) from aqueous solutions; this removal was studied by batch adsorption experiments. The effect of experimental parameters such as the pH, initial Cr(VI) concentration, and agitation time on the adsorption process was investigated. The adsorption of Cr(VI) was highly pH-dependent and the optimal pH for the adsorption process was 3.0. The data of Cr(VI) adsorption by fullerenes-extracted soot modified with ethylenediamine (FES-ED) fit the Langmuir isotherm equation well. The maximum Cr(VI)-uptake capacity of FES-ED was 93 mg g−1. The desorption of Cr(VI) from the adsorbent was also studied. The adsorbed Cr(VI) was eluted with 20 mL of an aqueous solution with pH 12 and the percentage recovery of Cr(VI) was determined as 75%. The adsorption and desorption test using the same FES-ED powder was repeated in triplicate to examine the reusability of the adsorbent. The adsorption was 97% and the desorption was >70% through the adsorption–desorption cycles. The adsorption of methyl orange onto the FES-ED was also examined. The dye was almost quantitatively removed from the aqueous solution by the adsorbent (the initial concentration of methyl orange: 40 μg mL−1; the adsorbent added: 10 mg/40 mL). Thus, we concluded that the FES-ED can be used as a novel adsorbent for removing pollutants from water.ArticleJournal of Environmental Chemical Engineering. 2(2):1191-1198 (2014)journal articl
Shock-induced star cluster formation in colliding galaxies
We studied the formation process of star clusters using high-resolution
N-body/smoothed particle hydrodynamcs simulations of colliding galaxies. The
total number of particles is 1.2x10^8 for our high resolution run. The
gravitational softening is 5 pc and we allow gas to cool down to \sim 10 K.
During the first encounter of the collision, a giant filament consists of cold
and dense gas found between the progenitors by shock compression. A vigorous
starburst took place in the filament, resulting in the formation of star
clusters. The mass of these star clusters ranges from 10^{5-8} Msun. These star
clusters formed hierarchically: at first small star clusters formed, and then
they merged via gravity, resulting in larger star clusters.Comment: 4 pages, 3 figures, Proceedings of IAU Symposium 270, Computational
Star Formatio
Toward first-principle simulations of galaxy formation: I. How should we choose star formation criteria in high-resolution simulations of disk galaxies?
We performed 3-dimensional N-body/SPH simulations to study how mass
resolution and other model parameters such as the star formation efficiency
parameter, C* and the threshold density, nth affect structures of the galactic
gaseous/stellar disk in a static galactic potential. We employ 10^6 - 10^7
particles to resolve a cold and dense (T 100 cm^{-3}) phase. We
found that structures of the ISM and the distribution of young stars are
sensitive to the assumed nth. High-nth models with nth = 100 cm^{-3} yield
clumpy multi-phase features in the ISM. Young stars are distributed in a thin
disk of which half-mass scale height is 10 - 30 pc. In low-nth models with nth
= 0.1 cm^{-3}, the stellar disk is found to be several times thicker, and the
gas disk appears smoother than the high-nth models. A high-resolution
simulation with high-nth is necessary to reproduce the complex structure of the
gas disk. The global properties of the model galaxies in low-nth models, such
as star formation histories, are similar to those in the high-nth models when
we tune the value of C* so that they reproduce the observed relation between
surface gas density and surface star formation rate density. We however
emphasize that high-nth models automatically reproduce the relation, regardless
of the values of C*. The ISM structure, phase distribution, and distributions
of young star forming region are quite similar between two runs with values of
C* which differ by a factor of 15. We also found that the timescale of the flow
from n_H ~1 cm^{-3} to n_H > 100 cm^{-3} is about 5 times as long as the local
dynamical time and is independent of the value of C*. The use of a high-nth
criterion for star formation in high-resolution simulations makes numerical
models fairy insensitive to the modelling of star formation. (Abridged)Comment: 15 pages, 14 figures, accepted for publication in PASJ. Abridged
abstract. For high resolution figures, see
http://www.cfca.nao.ac.jp/~saitoh/Papers/2008/Saitoh+2008a.pd
Toward First-Principle Simulations of Galaxy Formation: II. Shock-Induced Starburst at a Collision Interface During the First Encounter of Interacting Galaxies
We investigated the evolution of interacting disk galaxies using
high-resolution -body/SPH simulations, taking into account the multiphase
nature of the interstellar medium (ISM). In our high-resolution simulations, a
large-scale starburst occurred naturally at the collision interface between two
gas disks at the first encounter, resulting in the formation of star clusters.
This is consistent with observations of interacting galaxies. The probability
distribution function (PDF) of gas density showed clear change during the
galaxy-galaxy encounter. The compression of gas at the collision interface
between the gas disks first appears as an excess at in the PDF, and then the excess moves to higher densities () in a few times years where starburst takes
place. After the starburst, the PDF goes back to the quasi-steady state. These
results give a simple picture of starburst phenomena in galaxy-galaxy
encounters.Comment: 6 pages, 6 figures, accepted to PASJ. For high resolution figures,
see http://www.cfca.nao.ac.jp/~saitoh/Papers/2009/Saitoh+2009a.pd
Planetary Growth with Collisional Fragmentation and Gas Drag
As planetary embryos grow, gravitational stirring of planetesimals by embryos
strongly enhances random velocities of planetesimals and makes collisions
between planetesimals destructive. The resulting fragments are ground down by
successive collisions. Eventually the smallest fragments are removed by the
inward drift due to gas drag. Therefore, the collisional disruption depletes
the planetesimal disk and inhibits embryo growth. We provide analytical
formulae for the final masses of planetary embryos, taking into account
planetesimal depletion due to collisional disruption. Furthermore, we perform
the statistical simulations for embryo growth (which excellently reproduce
results of direct -body simulations if disruption is neglected). These
analytical formulae are consistent with the outcome of our statistical
simulations. Our results indicate that the final embryo mass at several AU in
the minimum-mass solar nebula can reach about Earth mass within
years. This brings another difficulty in formation of gas giant planets,
which requires cores with Earth masses for gas accretion. However, if
the nebular disk is 10 times more massive than the minimum-mass solar nebula
and the initial planetesimal size is larger than 100 km, as suggested by some
models of planetesimal formation, the final embryo mass reaches about 10 Earth
masses at 3-4 AU. The enhancement of embryos' collisional cross sections by
their atmosphere could further increase their final mass to form gas giant
planets at 5-10 AU in the solar system.Comment: Accepted for publication in Icaru
Planetary Core Formation with Collisional Fragmentation and Atmosphere to Form Gas Giant Planets
Massive planetary cores ( Earth masses) trigger rapid gas accretion
to form gas giant planets \rev{such as} Jupiter and Saturn. We investigate the
core growth and the possibilities for cores to reach such a critical core mass.
At the late stage, planetary cores grow through collisions with small
planetesimals. Collisional fragmentation of planetesimals, which is induced by
gravitational interaction with planetary cores, reduces the amount of
planetesimals surrounding them, and thus the final core masses. Starting from
small planetesimals that the fragmentation rapidly removes, less massive cores
are formed. However, planetary cores acquire atmospheres that enlarge their
collisional cross section before rapid gas accretion. Once planetary cores
exceed about Mars mass, atmospheres significantly accelerate the growth of
cores. We show that, taking into account the effects of fragmentation and
atmosphere, initially large planetesimals enable formation of sufficiently
massive cores. On the other hand, because the growth of cores is slow for large
planetesimals, a massive disk is necessary for cores to grow enough within a
disk lifetime. If the disk with 100\,km-sized initial planetesimals is 10 times
as massive as the minimum mass solar nebula, planetary cores can exceed 10
Earth masses in the Jovian planet region (AU).Comment: accepted for publication in Ap
Epigenetic Silencing of HOPX Promotes Cancer Progression in Colorectal Cancer
AbstractHomeodomain-only protein X (HOPX)-β promoter methylation was recently shown to be frequent in human cancers and was suggested as tumor suppressor gene in esophageal and gastric cancer. The aim of this study was to investigate the mechanistic roles of HOPX-β promoter methylation and its clinical relevance in colorectal cancer (CRC). HOPX-β promoter methylation was assessed in human CRC cell lines and 294 CRC tissues. HOPX mRNA and protein levels were measured in relation to HOPX-β promoter methylation. The effects of forced HOPX expression on tumorigenesis were studied using in vitro and in vivo assays. The association between HOPX-β promoter methylation and clinical relevance of CRC patients was determined. HOPX-β promoter methylation is cancer-specific and frequently found in CRC cell lines and tissues, resulting in the down-regulation of HOPX mRNA and protein levels. In CRC cell lines, forced expression of HOPX suppressed proliferation, invasion, and anchorage-independent growth. DNA microarray analyses suggested critical downstream genes that are associated with cancer cell proliferation, invasion or angiogenesis. In a mouse xenograft model, HOPX inhibited tumorigenesis and angiogenesis. Finally, HOPX-β promoter methylation was associated with worse prognosis of stage III CRC patients (hazard ratio= 1.40, P = .035) and also with poor differentiation (P = .014). In conclusion, HOPX-β promoter methylation is a frequent and cancer-specific event in CRC progression. This epigenetic alteration may have clinical ramifications in the diagnosis and treatment of CRC patients
Systematic Evaluation and Mechanistic Investigation of Antioxidant Activity of Fullerenols Using -Carotene Bleaching Assay
Antioxidant activity of hydroxylated fullerenes, so-called fullerenols, against lipid peroxyl radical was evaluated by -carotene bleaching assay. All samples showed moderate to high antioxidant activity (%AOA), especially for C 60 (OH) 12 (70.1) and C 60 (OH) 44 (66.0) as compared with 8, 24, 26, and 36 hydroxylated ones (31.7-62.8). The detection of the possible products was conducted in the model reaction of both fullerenols and C 60 with methyl linoleate by MALDI-TOF-MS. These results suggested that the two possible mechanisms, such as C-addition to double bonds and H-abstraction from -OH groups, are involved in the present radical scavenging reaction
Possible activation by the green tea amino acid theanine of mammalian target of rapamycin signaling in undifferentiated neural progenitor cells in vitro
AbstractWe have shown marked promotion of both proliferation and neuronal differentiation in pluripotent P19 cells exposed to the green tea amino acid theanine, which is a good substrate for SLC38A1 responsible for glutamine transport. In this study, we evaluated the activity of the mammalian target of rapamycin (mTOR) kinase pathway, which participates in protein translation, cell growth and autophagy in a manner relevant to intracellular glutamine levels, in murine neural progenitor cells exposed to theanine. Exposure to theanine promoted the phosphorylation of mTOR and downstream proteins in neurospheres from embryonic mouse neocortex. Although stable overexpression of SLC38A1 similarly facilitated phosphorylation of mTOR-relevant proteins in undifferentiated P19 cells, theanine failed to additionally accelerate the increased phosphorylation in these stable transfectants. Theanine accelerated the formation of neurospheres from murine embryonic neocortex and adult hippocampus, along with facilitation of both 5-bromo-2’-deoxyuridine incorporation and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide reduction in embryonic neurospheres. In embryonic neurospheres previously exposed to theanine, a significant increase was seen in the number of cells immunoreactive for a neuronal marker protein after spontaneous differentiation. These results suggest that theanine activates the mTOR signaling pathway for proliferation together with accelerated neurogenesis in murine undifferentiated neural progenitor cells
Body Mass Index and Risks of Incident Ischemic Stroke Subtypes: The Japan Public Health Center-Based Prospective (JPHC) Study
Background: The association of body mass index (BMI) with risks of ischemic stroke subtypes have not been established.Methods: Cumulative average BMI was calculated using self-reported body weight and height obtained from baseline (Cohort I in 1990, and Cohort II from 1993–1994) and 5- and 10-year questionnaire surveys of Japan Public Health Center-based prospective (JPHC) study. A total of 42,343 men and 46,413 women aged 40–69 years were followed-up for the incidence of lacunar, large-artery occlusive, and cardioembolic strokes. A sub-distribution hazard model was used to estimate sub-distribution hazard ratios (SHRs) and the 95% confidence intervals (CIs).Results: During a median of 20.0 years of follow-up, we documented 809 and 481 lacunar, 395 and 218 large-artery occlusive, and 568 and 298 cardioembolic strokes in men and women, respectively. After adjustment for baseline age, updated smoking, alcohol consumption, leisure-time physical activity, and histories of hypertension, dyslipidemia, and diabetes mellitus, cumulative average BMI was positively linearly associated with lacunar (trend P = 0.007), large-artery occlusive (trend P = 0.002), and cardioembolic (trend P < 0.001) strokes in men, and with lacunar (trend P < 0.001) and large-artery occlusive (trend P = 0.003) strokes in women. There were approximately two-fold excess risk of cardioembolic stroke in both sexes and of lacunar and large-artery occlusive strokes in women for cumulative average BMI ≥30 kg/m2 compared to BMI 23–<25 kg/m2.Conclusion: Cumulative average BMI showed a positive linear effect on sub-distribution hazards of lacunar, large-artery occlusive, and cardioembolic strokes in both sexes, except for cardioembolic stroke in women
- …