Asymmetric arylation of secondary phosphine oxides (SPOs) has been rapidly developed, while there are few theoretical studies reported. DFT computations were carried out to study the whole catalytic ...cycle of Pd/Xiao‐Phos‐catalyzed asymmetric arylation of SPOs, and a modified mechanism including tautomerization and arylation was presented. Some new tautomerization mechanisms have been traversed, including base‐assisted and Pd/Xiao‐Phos‐catalyzed tautomerization. These are different from the existing report, where base‐assisted tautomerization is the most favored. The resulting intermediate enters the downstream arylation directly. Furthermore, oxidative addition is identified as the enantioselectivity‐determining step. IGMH analysis results indicate that the different non‐bonding interactions between Xiao‐Phos and SPO parts determine the enantioselectivity. This work not only provides deeper insights into the self‐adaptive property of SadPhos ligands but also offers valuable guidance for ligand design. Newly proposed tautomerization mechanisms will also bring some inspiration to subsequent related research.
DFT computations were carried out on Pd/Xiao‐Phos‐catalyzed asymmetric arylation of SPOs, and a modified mechanism including tautomerization and arylation was presented. Various tautomerization mechanisms have been investigated, and the results highlight the catalytic effect of base on this process. Further computations indicate that oxidative addition is the enantioselectivity‐determining step, and the origin of selectivity was thought to be the difference in non‐bonding interactions.
An optical fiber ultrashort polymer micro-nano waveguide Bragg grating (PMWG) for contact liquid temperature sensor was fabricated on the single-mode fiber tip by the femtosecond laser induced ...two-photon polymerization. This structure is composed of a conical waveguide, a micro-nano waveguide Bragg gating and a pair of tripods. The overall length of the structure is about 160 μm and the cross-sectional dimension of micro-nano waveguide is only 1.6 * 1.5 μm. The length of polymer micro-nano waveguide Bragg grating is less than 125 μm, which is about one fiftieth of the traditional FBG. The micro-nano waveguide grating was placed in deionized water. The surrounding liquid acts as the cladding of the micro-nano waveguide grating. The direct contact of the grating structure with the external liquid will result in faster and more sensitive liquid temperature response. In the liquid temperature corresponding experiment, the sensitivity of the micro-nano waveguide grating is up to 0.3385 nm/°C with deionized water temperature changing from 27.7 °C to 49.2 °C. It has a good application prospect in the field of optical fiber biochemical micro-nano detection, microfluidics, etc.
The accurate location of radiated passive intermodulation (R-PIM) source activated by antennas has become a tough problem in modern multicarrier wireless communication systems. In order to precisely ...locate multiple harmful R-PIM sources, we develop a novel imaging method called the cascaded time-reversal multiple signals classification (CTR-MUSIC). This method multiplies a group of time-reversal multiple signals classification (TR-MUSIC) pseudo-spectra together to form the new pseudo-spectrum. The cascaded multiplication highly brightens the pseudo-spectrum peaks to easily identify the positions of the R-PIM sources and suppresses the remained pseudo-spectrum approximately to 0. By combining the multiple-static data matrices (MDMs) optimized by the weak-correlation filter (WCF), the proposed method exhibits a good ability in removing the redundant frequency information. The imaging computational complexity, positioning error, and positioning resolution of CTR-MUSIC are analyzed by numerical simulations. Compared with the existing ultra-wideband TR-MUSIC (UWB-TR-MUSIC), the results show that the proposed method improves the positioning accuracy, reduces computation consumption several times, and decreases the number of detecting antennas required for the same positioning accuracy. Experimentally, the R-PIM source is located with the positioning error of 0.04 wavelength at the signal central frequency of 1.7 GHz that proves the feasibility of positioning R-PIM source using the proposed method.
Cyclic quantum teleportation Chen, Ying-Xuan; Du, Jing; Liu, Si-Yuan ...
Quantum information processing,
08/2017, Letnik:
16, Številka:
8
Journal Article
Recenzirano
We propose a scheme of cyclic quantum teleportation for three unknown qubits using six-qubit maximally entangled state as the quantum channel. Suppose there are three observers Alice, Bob and ...Charlie, each of them has been given a quantum system such as a photon or spin-
1
2
particle, prepared in state unknown to them. We show how to implement the cyclic quantum teleportation where Alice can transfer her single-qubit state of qubit
a
to Bob, Bob can transfer his single-qubit state of qubit
b
to Charlie and Charlie can also transfer his single-qubit state of qubit
c
to Alice. We can also implement the cyclic quantum teleportation with
N
⩾
3
observers by constructing a 2
N
-qubit maximally entangled state as the quantum channel. By changing the quantum channel, we can change the direction of teleportation. Therefore, our scheme can realize teleportation in quantum information networks with
N
observers in different directions, and the security of our scheme is also investigated at the end of the paper.
Link prediction can discover missing information and evolution mechanism of complex networks, so a huge number of novel algorithms have been proposed recently. However, the existing link prediction ...algorithms for directed signed networks only depend on motifs that satisfy status theory, and other types of motifs are rarely taken into account. In this study, first we propose a link prediction method based on the number of edge-dependent motifs, and explain it by a naive Bayes model. Furthermore, we put forward a Signed Local Naive Bayes (SLNB) model based on two kinds of different motifs, which has higher prediction performance than only considering a single motif. Finally, we combine all the 3-node motifs to form a motif family, and use a machine learning framework for link prediction. The results show that motif families can greatly improve the performance of link prediction. Moreover, according to the correlation between these predictors, the intrinsic relationship between different motifs can be discovered, and the computational complexity of link prediction can be reduced after feature selection. Our research can not only improve the performance of link prediction, but also be helpful to uncover the evolutionary mechanism of signed social networks.
Alzheimer's disease (AD) is a fatal neurodegenerative disease for which currently no cure is available. Electroacupuncture (EA) has been widely used in China as an alternative therapeutic approach ...for neurological diseases. The cognitive decline in patients with AD has been reported to be closely related to the deposition of amyloid‐β (Aβ) in the hippocampus of the brain, and the Morris water maze (MWM) test is a widely used method for assessing the behavior of animal models. In this study, the MWM test was performed to evaluate the effects of EA treatment on cognitive function and memory, and the micro‐positron emission tomography scan was used to assess the hippocampal Aβ deposition. The results showed that the cognitive function of APP/PS1 mice was significantly improved and the rate of 18FAV‐45 uptake was reduced in the EA group, compared with the AD group. Our study suggested that EA can exert a therapeutic effect in AD by improving spatial learning and memory and inhibiting the hippocampal Aβ deposition.
电针对APP/PS1转基因小鼠行为学的改善可能与减少海马Aβ沉积有关
摘要:老年痴呆症疾病(AD)是一种致命的神经退行性疾病，目前没有治愈方法。电针作为神经疾病的替代治疗手段，在我国已得到广泛应用。据报道，阿尔茨海默病患者的认知功能下降与β‐淀粉样蛋白沉积于大脑海马区关系密切，Morris水迷宫(MWM)试验是一种广泛应用的动物模型行为评估方法，本研究采用Morris水迷宫试验评估电针治疗对阿尔茨海默病模型动物认知功能和记忆的影响，并用微型正电子断层扫面技术评估海马区β‐淀粉样蛋白沉积，结果表明电针组与模型组相比，APP/PS1小鼠认知功能明显改善，18FAV‐45摄取率降低，我们的研究提示电针可通过改善模型动物小鼠空间学习记忆和抑制海马区β‐淀粉样蛋白沉积，对阿尔茨海默病起到一定的治疗作用。.
In order to improve the ability of denitrification and phosphorus removal from reclaimed water, a novel composite filler was prepared using sulfur powder and sponge iron powder, and a comparative ...experiment was constructed at different HRT(hydraulic retention time) and C/N(carbon-nitrogen ratio) conditions between the novel filler and the composite filler. The results showed that the efficiency of nitrogen and phosphorus removal on the novel filler was higher than that on the grain filler (more than 30% higher at HRT=4 h and C/N=1). Moreover, based on the 16S rRNA gene clone library, the denitrification system in the two reactors included sulfur autotrophic denitrification bacteria and heterotrophic denitrification bacteria, while the proportion of sulfur autotrophic denitrification bacteria in the novel filler system was higher. The dominant bacteria in the novel filler and composite filler were
and
, respectively.
Astaxanthin (AST) is a powerful antioxidant that occurs naturally in a wide variety of living organisms. Much experimental evidence has proved that AST has the function of eliminating oxygen free ...radicals and can protect organisms from oxidative damage. The present study was carried out to further investigate the neuroprotective effect of AST on oxidative stress induced toxicity in primary culture of cortical neurons and on focal cerebral ischemia-reperfusion induced brain damage in rats. AST, over a concentration range of 250-1000nM, attenuated 50I14M H2O2-induced cell viability loss. 500nM AST pretreatment significantly inhibited H2O2-induced apoptosis measured by Hoechst 33342 staining and restored the mitochondrial membrane potential (MMP) measured by a fluorescent dye, Rhodamine 123. In vivo, AST prevented cerebral ischemic injury induced by 2h middle cerebral artery occlusion (MCAO) and 24h reperfusion in rats. Pretreatment of AST intragastrically twice at 5h and 1h prior to ischemia dramatically diminished infarct volume and improved neurological deficit in a dose-dependent manner. Nissl staining showed that the neuronal injury was significantly improved by pretreatment of AST at 80mg/kg. Taken together, these results suggest that pretreatment with AST exhibits noticeable neuroprotection against brain damage induced by ischemia-reperfusion and the antioxidant activity of AST maybe partly responsible for it. a-ordmAST exhibits noticeable neuroprotection against brain damage induced by ischemia-reperfusion. a-ordmAST can protect cortical neurons from oxidative stress induced toxicity. a-ordmAST might be a promising neuroprotective agent.
We investigate the behavior of coherence in scattering quantum walk search on complete graph under the condition that the total number of vertices of the graph is significantly larger than the marked ...number of vertices we are searching, N ≫ v. We find that the consumption of coherence represents the increase of the success probability for the searching, also it is related to the efficiency of the algorithm in oracle queries. If no coherence is consumed or an incoherent state is utilized, the algorithm will behave as the classical blind search, implying that coherence is responsible for the speed-up in this quantum algorithm over its classical counterpart. The effect of noises, in particular of photon loss and random phase shifts, on the performance of algorithm is studied. Two types of noise are considered because they arise in the optical network used for experimental realization of scattering quantum walk. It is found that photon loss will reduce the coherence and random phase shifts will hinder the interference between the edge states, both leading to lower success probability compared with the noise-free case. We then conclude that coherence plays an essential role and is responsible for the speed-up in this quantum algorithm.
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