Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 668
Filtrar
Filtros adicionais











País/Região como assunto
Intervalo de ano
1.
Phys Rev Lett ; 123(7): 070505, 2019 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-31491117

RESUMO

Quantum teleportation allows a "disembodied" transmission of unknown quantum states between distant quantum systems. Yet, all teleportation experiments to date were limited to a two-dimensional subspace of quantized multiple levels of the quantum systems. Here, we propose a scheme for teleportation of arbitrarily high-dimensional photonic quantum states and demonstrate an example of teleporting a qutrit. Measurements over a complete set of 12 qutrit states in mutually unbiased bases yield a teleportation fidelity of 0.75(1), which is well above both the optimal single-copy qutrit state-estimation limit of 1/2 and maximal qubit-qutrit overlap of 2/3, thus confirming a genuine and nonclassical three-dimensional teleportation. Our work will enable advanced quantum technologies in high dimensions, since teleportation plays a central role in quantum repeaters and quantum networks.

2.
Phys Rev Lett ; 123(8): 080401, 2019 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-31491194

RESUMO

We report an experiment to test quantum interference, entanglement, and nonlocality using two dissimilar photon sources, the Sun and a semiconductor quantum dot on the Earth, which are separated by ∼150 million kilometers. By making the otherwise vastly distinct photons indistinguishable in all degrees of freedom, we observe time-resolved two-photon quantum interference with a raw visibility of 0.796(17), well above the 0.5 classical limit, providing unambiguous evidence of the quantum nature of thermal light. Further, using the photons with no common history, we demonstrate postselected two-photon entanglement with a state fidelity of 0.826(24) and a violation of Bell inequality by 2.20(6). The experiment can be further extended to a larger scale using photons from distant stars and open a new route to quantum optics experiments at an astronomical scale.

3.
Phys Rev Lett ; 123(5): 050502, 2019 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-31491305

RESUMO

Superconducting circuits have emerged as a powerful platform of quantum simulation, especially for emulating the dynamics of quantum many-body systems, because of their tunable interaction, long coherence time, and high-precision control. Here in experiments, we construct a Bose-Hubbard ladder with a ladder array of 20 qubits on a 24-qubit superconducting processor. We investigate theoretically and demonstrate experimentally the dynamics of single- and double-excitation states with distinct behaviors, indicating the uniqueness of the Bose-Hubbard ladder. We observe the linear propagation of photons in the single-excitation case, satisfying the Lieb-Robinson bounds. The double-excitation state, initially placed at the edge, localizes; while placed in the bulk, it splits into two single-excitation modes spreading linearly toward two boundaries, respectively. Remarkably, these phenomena, studied both theoretically and numerically as unique properties of the Bose-Hubbard ladder, are represented coherently by pairs of controllable qubits in experiments. Our results show that collective excitations, as a single mode, are not free. This work paves the way to simulation of exotic logic particles by subtly encoding physical qubits and exploration of rich physics by superconducting circuits.

4.
Nature ; 573(7773): 281-286, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31485078

RESUMO

Enzymes that catalyse CpG methylation in DNA, including the DNA methyltransferases 1 (DNMT1), 3A (DNMT3A) and 3B (DNMT3B), are indispensable for mammalian tissue development and homeostasis1-4. They are also implicated in human developmental disorders and cancers5-8, supporting the critical role of DNA methylation in the specification and maintenance of cell fate. Previous studies have suggested that post-translational modifications of histones are involved in specifying patterns of DNA methyltransferase localization and DNA methylation at promoters and actively transcribed gene bodies9-11. However, the mechanisms that control the establishment and maintenance of intergenic DNA methylation remain poorly understood. Tatton-Brown-Rahman syndrome (TBRS) is a childhood overgrowth disorder that is defined by germline mutations in DNMT3A. TBRS shares clinical features with Sotos syndrome (which is caused by haploinsufficiency of NSD1, a histone methyltransferase that catalyses the dimethylation of histone H3 at K36 (H3K36me2)8,12,13), which suggests that there is a mechanistic link between these two diseases. Here we report that NSD1-mediated H3K36me2 is required for the recruitment of DNMT3A and maintenance of DNA methylation at intergenic regions. Genome-wide analysis shows that the binding and activity of DNMT3A colocalize with H3K36me2 at non-coding regions of euchromatin. Genetic ablation of Nsd1 and its paralogue Nsd2 in mouse cells results in a redistribution of DNMT3A to H3K36me3-modified gene bodies and a reduction in the methylation of intergenic DNA. Blood samples from patients with Sotos syndrome and NSD1-mutant tumours also exhibit hypomethylation of intergenic DNA. The PWWP domain of DNMT3A shows dual recognition of H3K36me2 and H3K36me3 in vitro, with a higher binding affinity towards H3K36me2 that is abrogated by TBRS-derived missense mutations. Together, our study reveals a trans-chromatin regulatory pathway that connects aberrant intergenic CpG methylation to human neoplastic and developmental overgrowth.

5.
J Zhejiang Univ Sci B ; 20(10): 861-864, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31489805

RESUMO

Rectal neuroendocrine neoplasms (NENs) are low-grade malignancies, which are slow-growing and usually become symptomatic late in the course of the disease (Basuroy et al., 2016). In recent years, rectal NENs are increasingly frequently detected, with the widespread availability and accessibility of endoscopy and cross-sectional imaging modalities (Kos-Kudla et al., 2017). Multiple studies have shown that endoscopic ultrasound (EUS) is an advanced endoscopic technique and is currently used in the diagnosis and preoperative assessment of NENs (Kim, 2012; Liu et al., 2013; Zhang et al., 2017). However, EUS imaging of rectal NEN and differential diagnosis with other submucosal tumors (SMTs) has not been adequately reported. In this study, we reviewed and summarized the EUS imaging and pathological features of rectal NENs of 38 cases to improve preoperative diagnosis rate and reduce unreasonable treatment.

6.
Opt Express ; 27(15): 20358-20372, 2019 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-31510131

RESUMO

Compared to glass walls with a positive curvature, those with a negative curvature have been proven to have stronger confinement of light. Therefore, we change the multi-layered air holes in a photonic crystal fiber into several negative curvature tubes. As a result, the confinement medium is shifted from a low-index cladding material into a special structure. The theoretical analysis shows that each vector eigenmode has a corresponding threshold value for the outer tube thickness. It means that we can confine the target modes and filter the unnecessary modes by shifting the outer tube thickness. After substantial investigation on this fiber, we obtain the appropriate values for each structural parameter and then fabricate this negative curvature ring-core fiber under the guidance of the simulation results. Firstly, we draw the central cane under vacuum condition, then stack the cane and six capillaries to form the preform, and finally draw the ring-core fiber by using vacuumization method. The fiber test experiment indicates that the fiber length should be at least 15 m∼20 m to form the donut facula, and the tested losses of OAM+1,1, OAM+2,1, OAM+3,1, and OAM+4,1 are 0.30 dB/m, 0.36 dB/m, 0.37 dB/m, and 0.42 dB/m, respectively.

7.
Opt Express ; 27(15): 21597-21607, 2019 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-31510233

RESUMO

In this paper, we present a novel accelerometer based on the Sagnac interferometer configuration using a polarization-maintaining photonic crystal fiber (PM-PCF), which has a sensitivity of ~8 pm/G, and a resonant frequency exceeding 2.5 kHz. The proposed accelerometer is capable of functioning with a constant sensitivity in a large frequency range from 0 to 1 kHz which is much wider than many FBG-based accelerometers. Experimental results obtained from a field test in railway monitoring, demonstrate a broader frequency range for the proposed accelerometer compared to that of the FBG based accelerometer and is comparable to the conventional piezoelectric sensor. The abrupt change in the acceleration measured by the sensor aids in locating any defect or crack present on the railway track. To the best of our knowledge, this is the first demonstration of an accelerometer based on a fiber interferometer aimed for the railway industry. The proposed accelerometer operating at high accelerations (>40 G) and capable of functioning at a broad frequency range, shows significant potential in being used in applications which require detection of strong and fast vibrations, especially in structural health monitoring of trains and railway tracks in real time.

8.
Opt Express ; 27(14): 19486-19502, 2019 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-31503707

RESUMO

We report a novel technique to detect dynamic strain variations simultaneously at multiple locations. Our technique is based on Brillouin optical correlation domain analysis implemented through external modulation to generate multiple independently-accessible correlation peaks within the sensing fiber. Experiments are carried out to demonstrate the precise determination of Brillouin frequency shift (BFS) from multiple locations independently. As a proof of principle, two correlation peaks are generated within a 1 km long fiber and their independent tunability is verified experimentally by mapping the spatial profile of the two correlations. We also experimentally demonstrate the detection of dynamic strain variations at two locations simultaneously, each with a spatial resolution of 60 cm over 100 m long fiber.

9.
Sensors (Basel) ; 19(16)2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31443271

RESUMO

A Pd-Ni alloy thin-film coated surface acoustic wave (SAW) device is proposed for sensing hydrogen. The Pd-Ni thin-film was sputtered onto the SAW propagation path of a SAW device with a delay line pattern to build the chip-sized hydrogen sensor. The prepared sensor chip was characterized by employing a differential oscillation loop. The effect of the Pd-Ni film thickness on sensing performance was also evaluated, and optimal parameters were determined, allowing for fast response and high sensitivity. Excellent working stability (detection error of 3.7% in half a year), high sensitivity (21.3 kHz/%), and fast response (less than 10 s) were achieved from the 40 nm Pd-Ni alloy thin-film coated sensing device.

11.
Sensors (Basel) ; 19(17)2019 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-31450826

RESUMO

As the main component of an autonomous driving system, the motion planner plays an essential role for safe and efficient driving. However, traditional motion planners cannot make full use of the on-board sensing information and lack the ability to efficiently adapt to different driving scenes and behaviors of different drivers. To overcome this limitation, a personalized behavior learning system (PBLS) is proposed in this paper to improve the performance of the traditional motion planner. This system is based on the neural reinforcement learning (NRL) technique, which can learn from human drivers online based on the on-board sensing information and realize human-like longitudinal speed control (LSC) through the learning from demonstration (LFD) paradigm. Under the LFD framework, the desired speed of human drivers can be learned by PBLS and converted to the low-level control commands by a proportion integration differentiation (PID) controller. Experiments using driving simulator and real driving data show that PBLS can adapt to different drivers by reproducing their driving behaviors for LSC in different scenes. Moreover, through a comparative experiment with the traditional adaptive cruise control (ACC) system, the proposed PBLS demonstrates a superior performance in maintaining driving comfort and smoothness.

12.
Kidney Blood Press Res ; : 1-8, 2019 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-31437854

RESUMO

BACKGROUND/AIMS: Liddle syndrome (LS) is a rare autosomal dominant disease caused by mutations in genes coding for epithelial sodium channel (ENaC) subunits. The aim of this study was to identify the mutation responsible for the LS in an extended Chinese family. METHODS: DNA samples from the proband with early-onset, treatment-resistant hypertension, and hypokalemia and 19 additional relatives were all sequenced for mutations in exon 13 of the ß-ENaC and γ-ENaC genes, using amplification by polymerase chain reaction and direct DNA sequencing. RESULTS: Genetic testing of exon 13 of SCNN1B revealed duplication of guanine into a string of 3 guanines located at codon 602. This frameshift mutation is predicted to generate a premature stop codon at position 607, resulting in truncated ß-ENaC lacking the remaining 34 amino acids, including the crucial PY motif. Among a total of 9 participants with the identical mutation, different phenotypes were identified. Tailored treatment with amiloride was safe and effective in alleviating disease symptoms in LS. No mutation of SCNN1G was identified in any of the examined participants. CONCLUSIONS: We report here a family affected by LS harboring a frameshift mutation (c.1806dupG) with a premature stop codon deleting the PY motif of ß-ENaC. Our study demonstrates that the earlier LS patients are diagnosed by genetic testing and treated with tailored medication, the greater the likelihood of preventing or minimizing complications in the vasculature and target organs.

13.
Environ Int ; 132: 105087, 2019 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-31430607

RESUMO

The persistence of extracellular DNA (eDNA) is crucial for ensuring species diversity and ecological function in aquatic systems. However, scarce information exists about the impact of pesticides on eDNA, although they often co-exist in the aquatic environment. Using a variety of spectroscopic analyses, eDNA degradation and the associated alterations in DNA secondary structure was investigated by exposing DNase I to tested DNA in the presence of chlorpyrifos, a commonly used organophosphate pesticide. Molecular dynamics simulation was used to explore the weak interactions between the tested DNA and chlorpyrifos. The results indicated that chlorpyrifos significantly enhanced DNA degradation without affecting the enzyme activity of DNase I in an aqueous system. Spectroscopic experiments confirmed that chlorpyrifos and the analog chlorpyrifos-methyl could bind with DNA to cause the bases noncovalent stacking interaction. Molecular simulations further demonstrated that pesticide binding with DNA molecules caused widening of the DNA grooves and destruction of the hydrated layer, which enhanced DNA degradation. The findings presented herein provide novel insight into the genotoxicity and ecotoxicity of chlorpyrifos and chlorpyrifos-methyl, as well as their impacts on DNA persistence in aquatic environments.

14.
GM Crops Food ; 10(3): 181-190, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31366287

RESUMO

Glyphosate tolerant soybeans represent a large portion of soybeans grown and fed to farm animals around the world. Despite their widespread use for many years, some have raised questions regarding their safety because the soybeans were genetically modified. The CP4 EPSPS gene which imparts resistance to topical application of the herbicide glyphosate was introduced into soybeans. Application of glyphosate to soybean fields will reduce weed pressure and increase soybean yield. To assess their safety on the rat reproduction system, male Sprague Dawley rats were fed either glyphosate-tolerant (GM) soybean (40-3-2) or near-isogenic, non-GM (A5403) (control) soybean meal. The processed soybean meal was added to formulated rodent diets at 20% (w/w) and fed to rats for 90 days. Some rats from the control group were separately administered mitomycin C for 40 days and served as positive controls in the sperm abnormality test. Body weights and behavior were monitored daily, serum enzymes and histologic and EM appearance of the testis, and sperm morphology were also examined. After 90 days of feeding, no adverse effects were observed in rats fed glyphosate-tolerant soybeans.

15.
Cancer Res ; 2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31409638

RESUMO

Heat shock transcription factor 1 (HSF1) is the master regulator of the proteotoxic stress response, which plays a key role in breast cancer tumorigenesis. However, the mechanisms underlying regulation of HSF1 protein stability are still unclear. Here, we showed that HSF1 protein stability is regulated by PIM2-mediated phosphorylation of HSF1 at Thr120, which disrupts the binding of HSF1 to the E3 ubiquitin ligase FBXW7. In addition, HSF1 Thr120 phosphorylation promoted proteostasis and carboplatin-induced autophagy. Interestingly, HSF1 Thr120 phosphorylation induced HSF1 binding to the PD-L1 promoter, and enhanced PD-L1 expression. Furthermore, HSF1 Thr120 phosphorylation promoted breast cancer tumorigenesis in vitro and in vivo. PIM2, pThr120-HSF1 and PD-L1 expression positively correlated with each other in breast cancer tissues. Collectively, these findings identify PIM2-mediated HSF1 phosphorylation at Thr120 as an essential mechanism that regulates breast tumor growth, and potential therapeutic target for breast cancer.

16.
Helicobacter ; : e12655, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31411799

RESUMO

BACKGROUND: Various studies reported the relationship between Helicobacter pylori (H pylori) and vitamin D, but there is some controversy around that. This study aimed to conduct a meta-analysis to clarify the relationship between vitamin D and H pylori infection, and vitamin D and H pylori eradication. METHODS: Articles published until June 1, 2019, in the PubMed, MEDLINE, and EMBASE databases with English-language medical studies were searched. According to the inclusion criteria, relevant statistical data were extracted to Microsoft Excel and analyzed by STATA15.1. RESULTS: Ten articles were finally included. It was demonstrated that average 25(OH)D level in H pylori-positive patients was lower than H pylori-negative (SMD = -0.53 ng/mL, 95% CI = (-0.91, -0.16 ng/mL)). For H pylori eradication individuals, the result showed that average 25(OH)D level in H pylori successful eradication individuals was higher than unsuccessful (SMD = 1.31 ng/mL, 95% CI = [0.60, 2.02 ng/mL]). In addition, individuals with vitamin D deficiency had lower H pylori eradicate rate (OR = 0.09, 95% CI = [0.02, 0.41]). Sensitivity analysis showed that the meta-analysis results were stable and reliable. CONCLUSIONS: Vitamin D was a protective factor to H pylori infection. Moreover, vitamin D can improve the success rate of H pylori eradication.

17.
Opt Lett ; 44(15): 3753-3756, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31368960

RESUMO

Frequency offset (FO) is an important impairment in coherent transmission systems induced by wavelength mismatch between a free-running local oscillator (LO) and the transmit laser. A fast-Fourier-transform-based FO estimation (FFT-FOE) scheme is commonly employed. The obtained FOE value can be used to compensate FO of a relatively long duration of the signal. On the other hand, the drift of the laser frequency leads to time-varying FO, and FOE should operate in intervals to track the FO drift (FOD) for the best system performance. However, the complexity of FFT is high, and continuous operation of FFT-FOE results in huge energy consumption since it is unclear when FO drifts to an intolerable value. This Letter aims to solve such a problem: How often should FFT-FOE be operated to guarantee system performance with the lowest complexity? Here, we propose a FOD monitoring scheme based on sparse fast Fourier transform, by which optimum performance and minimum cost of FOE are achieved simultaneously. A downsampling process is further proposed to reduce the complexity of subsequent FFT-FOE. The performance is experimentally verified with 28 Gbaud coherent systems.

18.
Zhongguo Zhen Jiu ; 39(7): 781-4, 2019 Jul 12.
Artigo em Chinês | MEDLINE | ID: mdl-31286743

RESUMO

Zhenjiu Dacheng (Compendium of Acupuncture and Moxibustion) contains a large number of acupuncture medical cases, involving a variety of illnesses, and more cases of the treatment of cancer. The medical cases in Compendium of Acupuncture and Moxibustion point out that the tumor is a tangible evil, and its pathological factors are often regarded as sputum. It should be diagnosed and treated early, and it is easy to be dangerous if delayed. Acupuncture treatment should be based on the treatment of tumor itself, in the consideration of consolidating the root and cultivating the primary, treatment should be clear about the condition of the disease, pay attention to the timing of acupuncture, selecting correctly the reinforcing or reducing technique, emphasizing the use of moxibustion. The academic characteristics of Compendium of Acupuncture and Moxibustion medical treatment of tumors have had a profound impact on later generations, and it is still of great significance for guiding clinical acupuncture treatment of tumor diseases today.


Assuntos
Terapia por Acupuntura , Moxibustão , Neoplasias , Humanos , Neoplasias/terapia
19.
Colloids Surf B Biointerfaces ; 182: 110384, 2019 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-31357126

RESUMO

Polymeric micelles with high thermodynamic stability and loading capacity are of tremendous significance for their potential applications in drug delivery. In the present study, super-amphiphiles in the form of poly(ethylene glycol)-crosslinked multi-armed polyethylenimine-g-poly(ε-benzyloxycarbonyl-L-lysine)s (PEZ-alt-PEG) were designed, synthesized, and optimized as nanocarriers for hydrophobic drugs. In an aqueous solution, the copolymer PEZ-alt-PEG self-assembled into sub-100-nm spherical shell crosslinked micelles with low toxicity in vitro and in vivo. The crosslinked super-amphiphilic structure of PEZ-alt-PEG could not only enhance the thermodynamic stability of polymeric micelles, but it could also significantly improve the loading capacity of hydrophobic drugs, such as curcumin (CUR). CUR-loaded PEZ-alt-PEG micelles could mediate effective drug delivery with sustained and complete CUR release. The use of PEZ-alt-PEG micellar nanocarriers remarkably improved the cellular uptake of CUR and therefore exhibited effective inhibitory activity on the growth of human hepatoma (HepG2) cells. Compared to free CUR, CUR-loaded polymeric micelles significantly accelerated the apoptosis rate of HepG2 cells. Therefore, PEZ-alt-PEG polymeric micelles, with their high thermodynamic stability, high drug-loading capacity, enhanced drug uptake and improved pharmacodynamic effects, could serve as efficient and promising nanocarriers for poorly water-soluble drugs.

20.
Artigo em Inglês | MEDLINE | ID: mdl-31347489

RESUMO

OBJECTIVE: This study was conducted to evaluate the pharmacokinetic properties and bioequivalence of two oral formulations of canagliflozin: a newly developed generic formulation (test) and a branded formulation (reference). MATERIALS AND METHODS: A randomized, open-label, two-way crossover study was conducted in 55 healthy Chinese subjects. They were randomized to receive a single oral dose of 100 mg of test or reference canagliflozin tablets according to an open crossover design under fasting and fed states. Plasma canagliflozin concentrations were determined by liquid chromatography-tandem mass spectrometry, and the pharmacokinetic parameters maximum concentration (Cmax) and area under the concentration-time curve (AUC0-t and AUC0-∞) were used to evaluate bioequivalence. RESULTS: The geometric mean ratio 90% confidence intervals for fasting Cmax, AUC0-t, and AUC0-∞ were 85.14 - 114.40%, 102.14 - 106.51%, and 102.21 - 106.85%, respectively, and fed Cmax, AUC0-t, and AUC0-∞ were 90.15 - 107.17%, 97.38 - 102.19%, and 96.78 - 101.92%, respectively. The mean values of tmax were prolonged in the test compared with the reference formulations. In addition, the mean values of tmax and Cmax for both formulations were significantly different under fed compared with fasting conditions, while there was no significant difference in AUC0-t or AUC0-∞ Conclusion: The two types of canagliflozin tablets were bioequivalent under both fasting and fed states, and both were generally well tolerated.
.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA