206 research outputs found
Worst case tractability of -approximation for weighted Korobov spaces
We study -approximation problems in the worst case
setting in the weighted Korobov spaces H_{d,\a,{\bm \ga}} with parameter
sequences {\bm \ga}=\{\ga_j\} and \a=\{\az_j\} of positive real numbers
1\ge \ga_1\ge \ga_2\ge \cdots\ge 0 and \frac1 2<\az_1\le \az_2\le \cdots.
We consider the minimal worst case error of algorithms that
use arbitrary continuous linear functionals with variables. We study
polynomial convergence of the minimal worst case error, which means that
converges to zero polynomially fast with increasing . We
recall the notions of polynomial, strongly polynomial, weak and
-weak tractability. In particular, polynomial tractability means
that we need a polynomial number of arbitrary continuous linear functionals in
and \va^{-1} with the accuracy \va of the approximation. We obtain that
the matching necessary and sufficient condition on the sequences {\bm \ga}
and \a for strongly polynomial tractability or polynomial tractability is
\dz:=\liminf_{j\to\infty}\frac{\ln \ga_j^{-1}}{\ln j}>0, and the exponent
of strongly polynomial tractability is p^{\text{str}}=2\max\big\{\frac 1 \dz,
\frac 1 {2\az_1}\big\}.$
Tip induced unconventional superconductivity on Weyl semimetal TaAs
Weyl fermion is a massless Dirac fermion with definite chirality, which has
been long pursued since 1929. Though it has not been observed as a fundamental
particle in nature, Weyl fermion can be realized as low-energy excitation
around Weyl point in Weyl semimetal, which possesses Weyl fermion cones in the
bulk and nontrivial Fermi arc states on the surface. As a firstly discovered
Weyl semimetal, TaAs crystal possesses 12 pairs of Weyl points in the momentum
space, which are topologically protected against small perturbations. Here, we
report for the first time the tip induced superconductivity on TaAs crystal by
point contact spectroscopy. A conductance plateau and sharp double dips are
observed in the point contact spectra, indicating p-wave like unconventional
superconductivity. Furthermore, the zero bias conductance peak in low
temperature regime is detected, suggesting potentially the existence of
Majorana zero modes. The experimentally observed tunneling spectra can be
interpreted with a novel mirror-symmetry protected topological superconductor
induced in TaAs, which can exhibit zero bias and double finite bias peaks, and
double conductance dips in the measurements. Our work can open a broad avenue
in search for new topological superconducting phases from topological Weyl
materials and trigger intensive investigations for pursuing Majorana fermions
CO2 capture performance using biomass-templated cement-supported limestone pellets
Synthetic biomass-templated cement-supported CaO-based sorbents were produced by granulation
process for high-temperature post-combustion CO2 capture. Commercial flour was used as the biomass
and served as a templating agent. The investigation of porosity showed that the pellets with biomass or
cement resulted in enhancement of porosity. Four types of sorbents containing varying proportions of
biomass and cement were subject to 20 cycles in a TGA under different calcination conditions. After
first series of tests calcined at 850 °C in 100% N2, all composite sorbents clearly exhibited higher CO2
capture activity compared to untreated limestone with exception of sorbents doped by seawater. The
biomass-templated cement-supported pellets exhibited the highest CO2 capture level of 46.5% relative
to 20.8% for raw limestone after 20 cycles. However, the observed enhancement in performance was
substantially reduced under 950 °C calcination condition. Considering the fact that both sorbents
supported by cement exhibited relatively high conversion with a maximum value of 19.5%, cement
promoted sorbents appear to be better at resisting of harsh calcination conditions. Although flour as
biomass-templated material generated significantly enhancement in CO2 capture capacity, further
exploration must be carried out to find the way of maintaining outstanding performance for CaO-based
sorbents under severe reaction conditions
Spatiotemporal expression of histone acetyltransferases, p300 and CBP, in developing embryonic hearts
Histone acetyltransferases (HATs), p300 and cAMP response element binding protein (CREB)-binding protein (CBP) are two structurally related transcriptional co-activators that activate expression of many eukaryotic genes involved in cellular growth and signaling, muscle differentiation and embryogenesis. However, whether these proteins play important and different roles in mouse cardiogenesis is not clear. Here, we investigate the protein distributions and mRNA expression of the two HATs in embryonic and adult mouse heart during normal heart development by using immunohistochemical and RT-PCR techniques. The data from immunohistochemical experiments revealed that p300 was extensively present in nearly every region of the hearts from embryonic stages to the adulthood. However, no CBP expression was detected in embryonic hearts at day E7.5. CBP expression appeared at the later stages, and the distribution of CBP was less than that of p300. In the developmental hearts after E10.5, both for p300 and CBP, the mRNA expression levels reached a peak on day E10.5, and then were gradually decreased afterwards. These results reveal that both p300 and CBP are related to embryonic heart development. The dynamic expression patterns of these two enzymes during mouse heart development indicate that they may play an important role on heart development. However, there is a difference in spatiotemporal expression patterns between these two enzymes during heart development. The expression of p300 is earlier and more predominate, suggesting that p300 may play a more important role in embryonic heart development especially during cardiac precursor cell induction and interventricular septum formation
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Oral Cytokine Levels Are More Linked to Levels of Plasma and Oral HIV-1 RNA Than to CD4+ T-Cell Counts in People With HIV.
BackgroundWe determined the levels of 11 soluble immune mediators in oral washings of AIDS Clinical Trials Group A5254 participants with varying degrees of plasma viremia and CD4 T-cell counts to characterize the mucosal immune response at different stages of HIV-1 infection.MethodsA5254 was a multicenter, cross-sectional study in people with HIV (PWH) recruited into 4 strata based on CD4 count and levels of plasma viremia: stratum (St) A: CD4 ≤200 cells/mm3, HIV-1 RNA (viral load [VL]) >1000 cps/mL; St B: CD4 ≤200, VL ≤1000; St C: CD4 >200, VL >1000; St D: CD4 >200, VL ≤1000. Oral/throat washings were obtained from all participants. Soluble markers were tested in oral/throat washings using a multibead fluorescent platform and were compared across strata. Linear regression was used to determine the associations between cytokines and HIV-1 in plasma and oral fluid.ResultsSt A participants had higher levels of interleukin (IL)-1β, IL-6, IL-17, tumor necrosis factor alpha (TNFα), and interferon gamma (IFNγ) compared with St B and D (P = .02; P < .0001) but were not different from St C. IL-8, IL-10, and IL-12 were elevated in St A compared with the other 3 strata (P = .046; P < .0001). Linear regression demonstrated that oral HIV-1 levels were associated with IL-1β, IL-6, IL-8, and TNFα production (R > .40; P < .001) when controlling for CD4 count and opportunistic infections.ConclusionsOur results show that high levels of oral HIV-1, rather than low CD4 counts, were linked to the production of oral immune mediators. Participants with AIDS and uncontrolled viremia demonstrated higher levels of pro- and anti-inflammatory soluble immune mediators compared with participants with lower HIV-1 RNA. The interplay of HIV-1 and these immune mediators could be important in the oral health of PWH
Physics perspectives of heavy-ion collisions at very high energy
Heavy-ion collisions at very high colliding energies are expected to produce
a quark-gluon plasma (QGP) at the highest temperature obtainable in a
laboratory setting. Experimental studies of these reactions can provide an
unprecedented range of information on properties of the QGP at high
temperatures. We report theoretical investigations of the physics perspectives
of heavy-ion collisions at a future high-energy collider. These include initial
parton production, collective expansion of the dense medium, jet quenching,
heavy-quark transport, dissociation and regeneration of quarkonia, photon and
dilepton production. We illustrate the potential of future experimental studies
of the initial particle production and formation of QGP at the highest
temperature to provide constraints on properties of strongly interaction
matter.Comment: 35 pages in Latex, 29 figure
Optimal dispatch based on prediction of distributed electric heating storages in combined electricity and heat networks
The volatility of wind power generations could significantly challenge the economic and secure operation of combined electricity and heat networks. To tackle this challenge, this paper proposes a framework of optimal dispatch with distributed electric heating storage based on a correlation-based long short-term memory prediction model. The prediction model of distributed electric heating storage is developed to model its behavior characteristics which are obtained by the autocorrelation and correlation analysis with external factors including weather and time-of-use price. An optimal dispatch model of combined electricity and heat networks is then formulated and resolved by a constraint reduction technique with clustering and classification. Our method is verified through numerous simulations. The results show that, compared with the state-of-the-art techniques of support vector machine and recurrent neural networks, the mean absolute percentage error with the proposed correlation-based long short-term memory can be reduced by 1.009 and 0.481 respectively. Compared with conventional method, the peak wind power curtailment with dispatching distributed electric heating storage is reduced by nearly 30% and 50% in two cases respectively
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