604 research outputs found
Preferential Syntheses of Semiconducting Vertically Aligned Single-Walled Carbon Nanotubes for Direct Use in FETs
Carbon nanotube electroactive polymer materials: opportunities and challenges
Carbon nanotubes (CNTs) with macroscopically ordered structures (e.g., aligned or patterned mats, fibers, and sheets) and associated large surface areas have proven promising as new CNT electroactive polymer materials (CNT-EAPs) for the development of advanced chemical and biological sensors. The functionalization of CNTs with many biological species to gain specific surface characteristics and to facilitate electron transfer to and from them for chemical- and bio-sensing applications is an area of intense research activity. Mechanical actuation generated by CNT-EAPs is another exciting electroactive function provided by these versatile materials. Controlled mechanical deformation for actuation has been demonstrated in CNT mats, fibers, sheets, and individual nanotubes. This article summarizes the current status and technological challenges for the development of electrochemical sensors and electromechanical actuators based on carbon nanotube electroactive materials
One-step coating of fluoro-containing silica nanoparticles for universal generation of surface superhydrophobicity
Stable superhydrophobic surfaces with water contact angles over 170 degrees and sliding angles below 7 degrees were produced by simply coating a particulate silica sol solution of co-hydrolysed TEOS/fluorinated alkyl silane with NH3.H2O on various substrates, including textile fabrics (e.g. polyester, wool and cotton), electrospun nanofibre mats, filter papers, glass slides, and silicon wafers.<br /
Orientin Ameliorates LPS-Induced Inflammatory Responses through the Inhibitory of the NF- κ
Inflammation is a complex response to diverse pathological conditions, resulting in negative rather than protective effects when uncontrolled. Orientin (Ori), a flavonoid component isolated from natural plants, possesses abundant properties. Thus, we aimed to discover the potential therapeutic effects of orientin on lipopolysaccharide- (LPS-) induced inflammation in RAW 264.7 cells and the underlying mechanisms. In our studies, we evaluated the effects of Ori on proinflammatory mediator production stimulated by LPS, including tumor necrosis factor- (TNF-) α, interleukin- (IL-) 6, IL-18, and IL-1β, along with prostaglandin E2 (PGE2) and NO. Our data indicated that orientin dramatically inhibited the levels of these mediators. Consistent with these results, the expression levels of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) were also reduced. Further study demonstrated that such inhibitory effects of Ori were due to suppression of the nuclear factor-kappa B (NF-κB) pathway and nucleotide-binding domain- (NOD-) like receptor protein 3 (NLRP3) inflammasome activation, which may contribute to its anti-inflammatory effects. Together, these findings show that Ori may be an effective candidate for ameliorating LPS-induced inflammatory responses
Burst phase distribution of SGR J1935+2154 based on Insight-HXMT
On April 27, 2020, the soft gamma ray repeater SGR J1935+2154 entered its
intense outburst episode again. Insight-HXMT carried out about one month
observation of the source. A total number of 75 bursts were detected during
this activity episode by Insight-HXMT, and persistent emission data were also
accumulated. We report on the spin period search result and the phase
distribution of burst start times and burst photon arrival times of the
Insight-HXMT high energy detectors and Fermi Gamma-ray Burst Monitor (GBM). We
find that the distribution of burst start times is uniform within its spin
phase for both Insight-HXMT and Fermi-GBM observations, whereas the phase
distribution of burst photons is related to the type of a burst's energy
spectrum. The bursts with the same spectrum have different distribution
characteristics in the initial and decay episodes for the activity of magnetar
SGR J1935+2154.Comment: 12 pages, 9 figure
A possible 250-second X-ray quasi-periodicity in the fast blue optical transient AT2018cow
The fast blue optical transients (FBOTs) are a new population of
extragalactic transients of unclear physical origin. A variety of mechanisms
have been proposed including failed supernova explosion, shock interaction with
a dense medium, young magnetar, accretion onto a compact object, and stellar
tidal disruption event, but none is conclusive. Here we report the discovery of
a possible X-ray quasi-periodicity signal with a period of 250 second (at
a significance level of 99.76%) in the brightest FBOT AT2018cow through the
analysis of XMM-Newton/PN data. The signal is independently detected at the
same frequency in the average power density spectrum from data taken from the
Swift telescope, with observations covering from 6 to 37 days after the optical
discovery, though the significance level is lower (94.26%). This suggests that
the QPO frequency may be stable over at least 1.1 10 cycles.
Assuming the 250 second QPO to be a scaled-down analogue of that
typically seen in stellar mass black holes, a black hole mass of
solar masses could be inferred. The overall X-ray
luminosity evolution could be modeled with the stellar tidal disruption by a
black hole of solar masses, providing a viable mechanism to produce
AT2018cow. Our findings suggest that other bright FBOTs may also harbor
intermediate-mass black holes.Comment: 18 pages, 10 figures. Accepted for publication in Research in
Astronomy and Astrophysic
The emission positions of kHz QPOs and Kerr spacetime influence
Based the Alfven wave oscillation model (AWOM) and relativistic precession
model (RPM) for twin kHz QPOs, we estimate the emission positions of most
detected kHz QPOs to be at r=18+-3 km (R/15km) except Cir X-1 at r = 30\+-5 km
(R/15km). For the proposed Keplerian frequency as an upper limit to kHz QPO,
the spin effects in Kerr Spacetime are discussed, which have about a 5% (2%)
modification for that of the Schwarzchild case for the spin frequency of 1000
(400) Hz.The application to the four typical QPO sources, Cir X-1, Sco X-1, SAX
J1808.4-3658 and XTE 1807-294, is mentioned.Comment: Science China, Physics, Mechanics & Astronomy, 2010, 53, NO.
Type-A quasi-periodic oscillation in the black hole transient MAXI J1348-630
We present a detailed analysis of the spectral and timing characteristics of
a 7-Hz type-A quasi-periodic oscillation (QPO) detected in NICER observations
of the black hole X-ray binary MAXI J1348-630 during its high-soft state. The
QPO is broad and weak, with an integrated fractional rms amplitude of 0.9 per
cent in the 0.5-10 keV band. Thanks to the large effective area of NICER,
combined with the high flux of the source and a relatively long accumulative
exposure time, we construct the first rms and phase-lag spectra for a type-A
QPO. Our analysis reveals that the fractional rms amplitude of the QPO
increases with energy from below 1 per cent at 1 keV to 3 per cent at 6 keV.
The shape of the QPO spectrum is similar to that of the Comptonised component,
suggesting that the Comptonised region is driving the variability. The phase
lags at the QPO frequency are always soft taking the lowest energy as
reference. By jointly fitting the time-averaged spectrum of the source and the
rms and phase-lag spectra of the QPO with the time-dependent Comptonisation
model vkompthdk, we find that the radiative properties of the type-A QPO can be
explained by a vertically extended Comptonised region with a size of 2300 km.Comment: 7 pages, 5 figures, accepted for publication in MNRA
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