693 research outputs found
Decoherence of two qubits in a non-Markovian reservoir without rotating-wave approximation
The decoherence of two initially entangled qubits in a non-Markovian
reservoir has been investigated exactly without Born Markovian approximation
and rotating-wave approximation(RWA). The non-perturbative quantum master
equation is derived and its exact solution is obtained. The decoherence
behaviors of two qubits, initially entangled in Bell states, has been
investigated in three different cases of parameters. The results show that the
counter-rotating wave terms have great influence on the decoherence behavior,
and there are differences between the exact solution of the Hamiltonian with
RWA and that of the exact Hamiltonian without RWA. It might be improper to take
RWA when the atom is in a non-markovian reservoir
Method of determining cosmological parameter ranges with samples of candles with an intrinsic distribution
In this paper, the effect of the intrinsic distribution of cosmological
candles is investigated. We find that, in the case of a narrow distribution,
the deviation of the observed modulus of sources from the expected central
value could be estimated within a ceratin range. We thus introduce a lower and
upper limits of , and , to
estimate cosmological parameters by applying the conventional minimizing method. We apply this method to a gamma-ray burst (GRB) sample as well as
to a combined sample including this GRB sample and an SN Ia sample. Our
analysis shows that: a) in the case of assuming an intrinsic distribution of
candles of the GRB sample, the effect of the distribution is obvious and should
not be neglected; b) taking into account this effect would lead to a poorer
constraint of the cosmological parameter ranges. The analysis suggests that in
the attempt of constraining the cosmological model with current GRB samples,
the results tend to be worse than what previously thought if the mentioned
intrinsic distribution does exist.Comment: 6 pages,4 figures,1 tables.Data updated. Main conclusion unchange
Futher Study of CP Violation and Branching Ratios for and in the Standard Model and Beyond
In this work we study the CP violation for and
up to leading and next-to-leading order QCD corrections
in the standard model, two-Higgs-doublet model and the minimal supersymmetric
extension of the standard model. We also study the effect of new physics on the
branching ratios of these two decay modes. We find that within the parameter
space constrained by the observation of the decay , new physics
does not affect the CP asymmetries greatly, and the prediction of new physics
to the branching ratios of and is the same as that of the standard model up to a minor discrepancy as far
as the Yukama couplying constants are perturbative.Comment: some figures being reduced, accepted by J. Physics
Antiarrhythmic effects of stimulating the left dorsal branch of the thoracic nerve in a canine model of paroxysmal atrial tachyarrhythmias
Background
Stellate ganglion nerve activity (SGNA) precedes paroxysmal atrial tachyarrhythmia (PAT) episodes in dogs with intermittent high-rate left atrial (LA) pacing. The left dorsal branch of the thoracic nerve (LDTN) contains sympathetic nerves originating from the stellate ganglia.
Objective
The purpose of this study was to test the hypothesis that high-frequency electrical stimulation of the LDTN can cause stellate ganglia damage and suppress PAT.
Methods
We performed chronic LDTN stimulation in 6 dogs with and 2 dogs without intermittent rapid LA pacing while monitoring SGNA.
Results
LDTN stimulation reduced average SGNA from 4.36 μV (95% confidence interval [CI] 4.10–4.62 μV) at baseline to 3.22 μV (95% CI 3.04–3.40 μV) after 2 weeks (P = .028) and completely suppressed all PAT episodes in all dogs studied. Tyrosine hydroxylase staining showed large damaged regions in both stellate ganglia, with increased percentages of tyrosine hydroxylase–negative cells. The terminal deoxynucleotidyl transferase dUTP nick end labeling assay showed that 23.36% (95% CI 18.74%–27.98%) of ganglion cells in the left stellate ganglia and 11.15% (95% CI 9.34%–12.96%) ganglion cells in the right stellate ganglia were positive, indicating extensive cell death. A reduction of both SGNA and heart rate was also observed in dogs with LDTN stimulation but without high-rate LA pacing. Histological studies in the latter 2 dogs confirmed the presence of extensive stellate ganglia damage, along with a high percentage of terminal deoxynucleotidyl transferase dUTP nick end labeling–positive cells.
Conclusion
LDTN stimulation damages both left stellate ganglia and right stellate ganglia, reduces left SGNA, and is antiarrhythmic in this canine model of PAT
Experimental demonstration of a free space cylindrical cloak without superluminal propagation
We experimentally demonstrated an alternative approach of invisibility
cloaking that can combine technical advantages of all current major cloaking
strategies in a unified manner and thus can solve bottlenecks of individual
strategies. A broadband cylindrical invisibility cloak in free space is
designed based on scattering cancellation (the approach of previous plasmonic
cloaking), and implemented with anisotropic metamaterials (a fundamental
property of singular-transformation cloaks). Particularly, non-superluminal
propagation of electromagnetic waves, a superior advantage of
non-Euclidian-transformation cloaks constructed with complex branch cuts, is
inherited in this design, and thus is the reason of its relatively broad
bandwidth. This demonstration provides the possibility for future practical
implementation of cloaking devices at large scales in free space.Comment: 16 pages, 3 figures, accepted by Physical Review Letter
Role of Apamin-Sensitive Calcium-Activated Small-Conductance Potassium Currents on the Mechanisms of Ventricular Fibrillation in Pacing-Induced Failing Rabbit Hearts
BACKGROUND:
Ventricular fibrillation (VF) during heart failure is characterized by stable reentrant spiral waves (rotors). Apamin-sensitive small-conductance calcium-activated potassium currents (IKAS) are heterogeneously upregulated in failing hearts. We hypothesized that IKAS influences the location and stability of rotors during VF.
METHODS AND RESULTS:
Optical mapping was performed on 9 rabbit hearts with pacing-induced heart failure. The epicardial right ventricular and left ventricular surfaces were simultaneously mapped in a Langendorff preparation. At baseline and after apamin (100 nmol/L) infusion, the action potential duration (APD80) was determined, and VF was induced. Areas with a >50% increase in the maximum action potential duration (ΔAPD) after apamin infusion were considered to have a high IKAS distribution. At baseline, the distribution density of phase singularities during VF in high IKAS distribution areas was higher than in other areas (0.0035±0.0011 versus 0.0014±0.0010 phase singularities/pixel; P=0.004). In addition, high dominant frequencies also colocalized to high IKAS distribution areas (26.0 versus 17.9 Hz; P=0.003). These correlations were eliminated during VF after apamin infusion, as the number of phase singularities (17.2 versus 11.0; P=0.009) and dominant frequencies (22.1 versus 16.2 Hz; P=0.022) were all significantly decreased. In addition, reentrant spiral waves became unstable after apamin infusion, and the duration of VF decreased.
CONCLUSIONS:
The IKAS current influences the mechanism of VF in failing hearts as phase singularities, high dominant frequencies, and reentrant spiral waves all correlated to areas of high IKAS. Apamin eliminated this relationship and reduced VF vulnerability
Elliptical Galaxies with Emission Lines from the Sloan Digital Sky Survey
We present the results of 11 elliptical galaxies with strong nebular emission
lines during our study of star formation history along the Hubble sequence.
After removing the dilution from the underlying old stellar populations by use
of stellar population synthesis model, we derive the accurate fluxes of all
emission lines for these objects, which are later classified with emission line
ratios into one Seyfert 2, six LINERs and four HII galaxies. We also identify
one HII galaxy (A1216+04) as a hitherto unknown Wolf-Rayet galaxy from the
presence of the Wolf-Rayet broad bump at 4650 \AA. We propose that the
star-forming activities in elliptical galaxies are triggered by either
galaxy-galaxy interaction or the merging of a small satellite/a massive star
cluster, as already suggested by recent numerical simulations
PmoB subunit of particulate methane monooxygenase (pMMO) in Methylococcus capsulatus (Bath): The Cu^I sponge and its function
In this study, we describe efforts to clarify the role of the copper cofactors associated with subunit B (PmoB) of the particulate methane monooxygenase (pMMO) from Methylococcus capsulatus (Bath) (M. capsulatus). This subunit exhibits strong affinity toward Cu^I ions. To elucidate the high copper affinity of the subunit, the full-length PmoB, and the N-terminal truncated mutants PmoB_(33–414) and PmoB_(55–414), each fused to the maltose-binding protein (MBP), are cloned and over-expressed into Escherichia coli (E. coli) K12 TB1 cells. The Y374F, Y374S and M300L mutants of these protein constructs are also studied. When this E. coli is grown with the pmoB gene in 1.0 mM Cu^(II), it behaves like M. capsulatus (Bath) cultured under high copper stresswith abundant membrane accumulation and high CuI content. The recombinantPmoB proteins are verified by Western blotting of antibodies directed against the MBP sub-domain in each of the copper-enriched PmoB proteins. Cu K-edge X-rayabsorption near edge spectroscopy (XANES) of the copper ions confirms that all the PmoB recombinants are Cu^I proteins. All the PmoB proteins show evidence of a “dicopper site” according to analysis of the Cu extended X-ray absorption edge fine structure (EXAFS) of the membranes. No specific activities toward methane and propene oxidation are observed with the recombinant membrane-bound PmoB proteins. However, significant production of hydrogen peroxide is observed in the case of the PmoB_(33–414) mutant. Reaction of the dicopper site with dioxygenproduces hydrogen peroxide and leads to oxidation of the CuI ions residing in the C-terminal sub-domain of the PmoB subunit
Observation of eight-photon entanglement
Using ultra-bright sources of pure-state entangled photons from parametric
down conversion, an eight-photon interferometer and post-selection detection,
we demonstrate the ability to experimentally manipulate eight individual
photons and report the creation of an eight-photon Schr\"odinger cat state with
an observed fidelity of .Comment: 6 pages, 4 figure
Complex in vitro 3D models of digestive system tumors to advance precision medicine and drug testing: Progress, challenges, and trends
Digestive system cancers account for nearly half of all cancers around the world and have a high mortality rate. Cell culture and animal models represent cornerstones of digestive cancer research. However, their ability to en- able cancer precision medicine is limited. Cell culture models cannot retain the genetic and phenotypic heteroge- neity of tumors and lack tumor microenvironment (TME). Patient-derived xenograft mouse models are not suitable for immune-oncology research. While humanized mouse models are time- and cost-consuming. Suitable preclinical models, which can facilitate the understanding of mechanisms of tumor progression and develop new therapeutic strategies, are in high demand. This review article summarizes the recent progress on the establish- ment of TME by using tumor organoid models and microfluidic systems. The main challenges regarding the translation of organoid models from bench to bedside are discussed. The integration of organoids and a microflu- idic platform is the emerging trend in drug screening and precision medicine. A future prospective on this field is also provided.This study was supported by the National Natural Science Foundation of China (Grant No.82073148), the Guangdong Provincial Key Laboratory of Digestive Cancer Research (No. 2021B1212040006), the Sanming Project of Medicine in Shenzhen (SZSM201911010), the Shenzhen Key Medical Discipline Construction Fund (SZXK016), the Shenzhen Sustainable Project (KCXFZ202002011010593), and the Shenzhen-Hong Kong-Macau Technology Research Programme (Type C) (Grant No. SGDX2020110309260100)
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