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We report on the direct comparison of single-crystal and ceramic Yb3+:Lu203 gain media with respect to emission spectra, fluorescence lifetime, depolarization, and laser performance in a continuous-wave thin-disk laser oscillator. The most efficient laser operation was achieved with a single-crystal disk in multimode operation with a slope efficiency of 72.1% and an average output power of 997 W. At the same temperature level, a ceramic disk delivered 861 W with a slope efficiency of 68.6%. In fundamental-mode operation, the highest average power of 360 W and highest optical efficiency of 41.3% were obtained with a ceramic disk. For the single-crystal disk, the fundamental-mode output power was limited to 113 W at an optical efficiency of 29%, potentially due to stress within the crystal. [ABSTRACT FROM AUTHOR]

We report on the characterization and first laser operation of ceramic Yb:LuScO3 in a thin-disk oscillator. The optical performance achieved with a ceramic Yb:LuScO3 disk is compared to the one obtained with an existing ceramic Yb:Lu2O3 disk for reference. The characterization covers the measurement of the fluorescence spectra, the fluorescence lifetimes, and nomarsky imaging. The investigation on the laser operation covers the measurement of resonator losses, output powers, and thermal behavior during continuous-wave operation in a multimode thin-disk oscillator. An average output power of 149 W and a slope efficiency of 51.8% were achieved with the ceramic Yb:LuScO3 disk which reached a maximum surface temperature of about 150 °C. At the same temperature level, a disk made of the already established ceramic Yb:Lu2O3 delivered 957 W of output power with a slope efficiency of 75.7%. [ABSTRACT FROM AUTHOR]

Purpose: In this study, we investigated the effects of different concentration of propofol on cell viability of hippocampal neurons and explored the possible mechanism. Patients and methods: Primary hippocampal neurons were cultured in vitro and treated with different concentration of propofol. MTT was used to examine the survival of neurons. Flow cytometry was used to detect the neuronal apoptosis. Western-blot analysis was used to examine the expression level of p-p38MAPK and p38MAPK. Results: We found that low concentration propofol (0.5 μM and 1 μM) promoted the cell survival rate; however, high concentration of propofol (10 μM,50 μM,100 μM,150 μM, and 200 μM) decreased the cell survival rate (P < 0.05). Flow cytometry showed that the neuronal apoptosis rate was decreased in 1 μM propofol group (P < 0.05), but was significantly higher in10μM, 100 μM and 200 μM groups in a concentration-dependent manner (P < 0.05 or P < 0.01). Western blot revealed that the propofol induced the phosphorylation of p38MAPK concentration-dependently and time-dependently. SB203580, one inhibitor of p38MAPK, increased the cell survival rate and decreased the cell apoptosis induced by high concentration of propofol. Conclusion: Low concentration of propofol improved the survival rate of neurons, while high concentration of propofol promoted the cell apoptosis and decreased the cell viability. p38MAPK pathway is involved the effect of high concentration of propofol promoted on primary hippocampal neurons viability and apoptosis. [ABSTRACT FROM AUTHOR]

For an undirected simple graph G, we write G→(H1,H2)v if and only if for everyred-blue coloring of its vertices there exists a red H1 or a blue H2. Thegeneralized vertex Folkman number Fv(H1,H2;H) is defined as the smallest integer n for which there exists an H-free graph G of order n such that G→(H1,H2)v. The generalized edge Folkman numbers Fe(H1,H2;H) are defined similarly, when colorings of the edges are considered. We show that Fe(Kk+1,Kk+1;Kk+2-e) and Fv(Kk,Kk;Kk+1-e) are well defined for k≥3. We prove the nonexistence of Fe(K3,K3;H) for some H, in particular for H=B3, where Bk is the book graph of k triangular pages, and for H=K1+P4. We pose three problems ongeneralized Folkman numbers, including the existence question of edge Folkmannumbers Fe(K3,K3;B4), Fe(K3,K3;K1+C4) and Fe(K3,K3;P2∪P3¯). Our results lead to some general inequalities involving two-color and multicolor Folkmannumbers. [ABSTRACT FROM AUTHOR]

In order to fully explore the merits of the multi-tier heterogeneous network (HetNet) and ultra-dense small cell deployments, the evolution of the cellular network architecture is on the way. Based on the frameless network architecture, this paper proposes the control plane (CP) and user plane (UP) adaptation strategy to improve the system energy efficiency (EE). In this paper, we give a three-step system EE optimization with constraints on the CP/UP adaptation. We optimize the system EE via CP and UP construction and adaptation while guaranteeing the user quality of service (QoS). In the first step, the CP construction and adaptation scheme is proposed through the Voronoi Diagram with EE improvements. In the second step, by jointly allocating the AE and subchannel resources, we construct the on-demand user-centric UP. In the last step, based on the UP construction from the second step, we adjust each UP to optimize the EE performance. This is achieved by employing game theory. Furthermore, we verify the existence and uniqueness of the Nash Equilibrium for the non-cooperative game model with pricing. Finally, the system-level simulation results show that, with constraints on the QoS of the users, the system EE performances are improved. [ABSTRACT FROM AUTHOR]

The recent emergence of two-dimensional layered materials - in particular the transition metal dichalcogenides - provides a new laboratory for exploring the internal quantum degrees of freedom of electrons and their potential for new electronics. These degrees of freedom are the real electron spin, the layer pseudospin, and the valley pseudospin. New methods for the quantum control of the spin and these pseudospins arise from the existence of Berry phase-related physical properties and strong spin-orbit coupling. The former leads to the versatile control of the valley pseudospin, whereas the latter gives rise to an interplay between the spin and the pseudospins. Here, we provide a brief review of both theoretical and experimental advances in this field. [ABSTRACT FROM AUTHOR]

Studies the effects of extracellular calmodulin on pollen germination and tube growth of the plant Forsythia suspensa. Experimental procedure; Speed of pollen germination resulting from W7-agarose; Length of the tube.

A review of the article discussing broken symmetry for giant spin polarization in a semiconductor by Jonathon Riley and colleague, which appeared in the periodical “Nature Physics" in November, 2014, is presented.

For a graph G and integers a i ≥ 1 , the expression G → (a 1 , ... , a r) v means that for any r-coloring of the vertices of G there exists a monochromatic a i -clique in G for some color i ∈ { 1 , ... , r } . The vertex Folkman numbers are defined as F v (a 1 , ... , a r ; H) = min { | V (G) | : G is H-free and G → (a 1 , ... , a r) v } , where H is a graph. Such vertex Folkman numbers have been extensively studied for H = K s with s > max { a i } 1 ≤ i ≤ r . If a i = a for all i, then we use notation F v (a r ; H) = F v (a 1 , ... , a r ; H) . Let J k be the complete graph K k missing one edge, i.e. J k = K k - e . In this work we focus on vertex Folkman numbers with H = J k , in particular for k = 4 and a i ≤ 3 . A result by Nešetřil and Rödl from 1976 implies that F v (3 r ; J 4) is well defined for any r ≥ 2 . We present a new and more direct proof of this fact. The simplest but already intriguing case is that of F v (3 , 3 ; J 4) , for which we establish the upper bound of 135 by using the J 4 -free process. We obtain the exact values and bounds for a few other small cases of F v (a 1 , ... , a r ; J 4) when a i ≤ 3 for all 1 ≤ i ≤ r , including F v (2 , 3 ; J 4) = 14 , F v (2 4 ; J 4) = 15 , and 22 ≤ F v (2 5 ; J 4) ≤ 25 . Note that F v (2 r ; J 4) is the smallest number of vertices in any J 4 -free graph with chromatic number r + 1 . Most of the results were obtained with the help of computations, but some of the upper bound graphs we found are interesting by themselves. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate a SESAM mode-locked Tm:CaYLuAlO4 (a-cut) laser in the 2-μm spectral range. A birefringent filter (BF) is employed to shift the emission wavelength above 2 μm to support the stable mode locking through avoiding the structured water vapor absorption. Pulses as short as 288 fs are generated with a central wavelength of 2037 nm and an average power of 166 mW at a repetition rate of ~ 77.6 MHz. Moreover, wavelength tunable femtosecond laser with a tuning range from 2031.8 to 2081.1 nm is realized simply by rotating the birefringent filter around its surface normal. This work experimentally shows that birefringent filter is a simple and low-cost way to support the stable mode locking of Tm-bulk femtosecond lasers with an emission peak in the water vapor absorption region. [ABSTRACT FROM AUTHOR]

Provides information on a study which examined the role of heterotrimeric G proteins in pollen germination, tube growth and signal transduction of extracellular calmodulin. Background on related studies; Experimental procedures; Conclusion.

Fe1+yTe1−xSex is characterized by its complex magnetic phase diagram and highly orbital-dependent band renormalization. Despite this, the behavior of nematicity and nematic fluctuations, especially for high tellurium concentrations, remains largely unknown. Here we present a study of both B1g and B2g nematic fluctuations in Fe1+yTe1−xSex (0 ≤ x ≤ 0.53) using the technique of elastoresistivity measurement. We discovered that the nematic fluctuations in two symmetry channels are closely linked to the corresponding spin fluctuations, confirming the intertwined nature of these two degrees of freedom. We also revealed an unusual temperature dependence of the nematic susceptibility, which we attributed to a loss of coherence of the dxy orbital. Our results highlight the importance of orbital differentiation on the nematic properties of iron-based materials. Despite a significant amount of research, there are still many unknowns about the underlying mechanisms of the superconductivity in Fe-based superconductors, in particular the roles of magnetism and nematicity. Here, the authors investigate the compositional dependence of the nematic susceptibility in Fe1+yTe1−xSex and the interplay between nematic and spin fluctuations, as well as the effect of orbital differentiation on nematic instability. [ABSTRACT FROM AUTHOR]

The study investigates the role of digital-government (DG), government utilization, and regional integration on public health services (PHS) by considering E-government and globalization. This study takes public services fragility as a proxy for public health services. In contrast, E-government development as a DG globalization index (GI) has been taken as a proxy of regional integration, and government expenditures (GE) as a fiscal state capacity. The study employed a two-step system generalized method of moments estimation for the sample of 45-panel Asian economies from 2006-to-2022. The results reveal that DG substantially impacted and improved the PHS in Asian economies in the past decade. Moreover, regional integration added fuel to this progression and substantially influenced the PHS. However, GE adversely affects the PHS due to lousy governance and leakage of target spending. Furthermore, the novel DG integration with GE and GI promoted PHS and reduced health fragility through better resource utilization and technology deployment. It also reveals that DG helps in reducing the loopholes of GE and makes the resource implementation transparent and effective, which impacts the PHS. It concludes that these interactions with public policies play a prominent role in comprehensive coverage and healthcare accessibility in Asia through technology deployment with prudent administration strategies. It’s a novel study that integrates digitalization with regional integration and government expenditures from an Asian perspective by considering PHS, which made this study helpful for policy drafting during the COVID-19 pandemic and proposed a better framework to deal with future calamities. [ABSTRACT FROM AUTHOR]

Let G and H be finite undirected graphs. The Ramsey number R(G, H) is the smallest integer n such that for every graph F of order n, either F contains a subgraph isomorphic to G or its complement F ¯ contains a subgraph isomorphic to H. An (s, t)-graph is a graph that contains neither a clique of order s nor an independent set of order t. In this paper we obtain some inequalities involving Ramsey numbers of the form R (K 4 - e , K t) . In particular, a constructive proof implies that if G is a (k , s + 1) -graph, H is a (k , t + 1) -graph, and both G and H contain a (K k - e) -free graph M as an induced subgraph, then we have R (K k + 1 - e , K s + t + 1) > | V (G) | + | V (H) | + | V (M) |. Furthermore, if s ≤ t , then R (K 4 - e , K s + t + 1) ≥ R (3 , s + 1) + R (3 , t + 1) + s . In the experimental part, we use the (K 4 - e) -free graph generation process to construct graphs witnessing lower bounds for R (K 4 - e , K t) , and compare the results obtained by this approach to the results obtained by analogous triangle-free process. Finally, some open problems involving Ramsey numbers of the form R (K 4 - e , K t) and their asymptotics are posed. [ABSTRACT FROM AUTHOR]

Key message: CCA1α and CCA1β protein variants respond to environmental light and temperature cues, and higher temperature promotes CCA1β protein production and causes its retention detectable in the cytoplasm. CIRCADIAN CLOCK ASSOCIATED1 (CCA1), as the core transcription factor of circadian clock, is involved in the regulation of endogenous circadian rhythm in Arabidopsis. Previous studies have shown that CCA1 consists of two abundant splice variants, fully spliced CCA1α and intron-retaining CCA1β. CCA1β is believed to form a nonfunctional heterodimer with CCA1α and its closed-related homolog LHY. Many studies have established that CCA1β is a transcription product, while how CCA1β protein is produced and how two CCA1 isoforms respond to environmental cues have not been elucidated. In this study, we identified CCA1α and CCA1β protein variants under different photoperiods with warm or cold temperature cycles, respectively. Our results showed that CCA1 protein production is regulated by prolonged light exposure and warm temperature. The protein levels of CCA1α and CCA1β peak in the morning, but the detection of CCA1β is dependent on immunoprecipitation enrichment at 22 °C. Higher temperature of 37 °C promotes CCA1β protein production and causes its retention to be detectable in the cytoplasm. Overall, our results indicate that two splice variants of the CCA1 protein respond to environmental light and temperature signals and may, therefore, maintain the circadian rhythms and give individuals the ability to adapt to environment. [ABSTRACT FROM AUTHOR]

A diode-end-pumped continuous-wave and passively Q-switched mode-locked Nd:(Gd0.3Y0.7)2SiO5 laser was designed. At a pump power of 0.8W, we achieve dual-wavelength continuous-wave (CW) laser generation at wavelengths around 1,073.26 and 1,076.62 nm. Using a semiconductor saturable absorber mirror (SESAM), we obtain passively Q-switched mode-locked (QML) operation. A maximum average output power of 171 mW is obtained under a pump power of 5 W. The optical conversion efficiency for the QML laser is 3.4%. The duration of the mode-locked pulse is estimated to be about 649 ps at a repetition rate of 101.34 MHz. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated that when contextual diversity is controlled token word frequency has minimal effects on visual word recognition. With the exception of a single experiment by Plummer, Perea, & Rayner (2014, Journal of Experimental Psychology: Learning, Memory, and Cognition, 40, 275-283), those studies have examined words in isolation. The current studies address two potential limitations of the Plummer et al. experiment. First, because Plummer et al. used different sentence frames for words in different conditions, the effects might be due to uncontrolled differences on the sentences. Second, the absence of a frequency effect might be attributed to comparing higher and lower frequency words within a limited range. Three eye-tracking experiments examined effects of contextual diversity and frequency on Mandarin Chinese, a logographic language, for words embedded in the normal sentences. In Experiment 1, yoked words were rotated through the same sentence frame. Experiments 2a and 2b used a design similar to Plummer et al., which allows use of a larger sample of words to compare results between experiments with a smaller and larger difference in log frequency (0.41 and 1.06, respectively). In all three experiments, first-pass and later eye movement measures were significantly shorter for targets with higher contextual diversity than for targets with lower contextual diversity, with no effects of frequency. [ABSTRACT FROM AUTHOR]

The conserved polarity complex, which comprises partitioning-defective proteins Par3, Par6, and the atypical protein kinase C, affects various cell-polarization events, including assembly of tight junctions. Control of tight junction assembly is closely related to invasion and migration potential. However, as the importance of conserved polarity complexes in regulating pancreatic cancer invasion and metastasis is unclear, we investigated their role and mechanism in pancreatic cancers. We first detect that the key protein of the conserved polarity complex finds that only Par3 is down-regulated in pancreatic cancer tissues while Par6 and aPKC show no difference. What is more, Par3 tissues level was significantly and positively associated with patient overall survival. Knocking-down Par3 promotes pancreatic cancer cells invasion and migration. And Par3 requires interaction with Tiam1 to affect tight junction assembly, and then affect invasion and migration of pancreatic cancer cells. Then, we find that tight junction marker protein ZO-1 and claudin-1 are down-regulated in pancreatic cancer tissues. And the relationship of the expression of Par3 and ZO-1 in pancreatic cancer tissue is linear correlation. We establish liver metastasis model of human pancreatic cancer cells in Balb/c nude mice and find that knocking down Par3 promotes invasion and metastasis and disturbs tight junction assembly in vivo. Taken together, these results suggest that the Par3 regulates invasion and metastasis in pancreatic cancers by controlling tight junction assembly. [ABSTRACT FROM AUTHOR]

Laparoscopic bariatric surgery has become the gold standard for the treatment of morbidly obese patients. This experimental study aimed to develop a new, anatomically relevant, high-fidelity simulator to train advanced laparoscopic Roux-en-Y gastric bypass (LRYGB). An anatomical model similar to human abdominal organs was established using ex vivo porcine organs as materials. A three-dimensional (3D) printer was applied to print the laparoscopic simulation training box, including the placement of the model base, diaphragm fixators, and training box–height adjustment device. A total of six experts simulated LRYGB surgery and evaluated the model’s face, content validity, and realism of surgical technique through a questionnaire. The simulator was highly realistic in appearance, anatomy, touch, instrumentation, and core surgical procedures. All participants recommended the application of this model in bariatric surgery training. Compared with the actual operation, this model has enough fidelity and is easy to reproduce, which provides effective support for future surgical applications. [ABSTRACT FROM AUTHOR]

In this paper, multiple device-to-device (D2D) communication underlaying cellular multiuser multiple inputs multiple outputs (MU-MIMO) systems is investigated. This type of communication can improve spectral efficiency to address future demand, but interference management, user clustering, and resource allocation are three key problems related to resource sharing. Interference alignment (IA) is proposed to better mitigate in-cluster interference compared with a multiplex scheme, and user clustering and resource allocation are jointly investigated using binary-integer programming. In addition to an exhaustive search for a maximum throughput, we propose a two-step suboptimal algorithm by reducing the search space and applying branch-and-bound searching (BBS). To further obtain a good trade-off between performance and complexity, we propose a novel algorithm based on distance-constrained criteria for user clustering. The simulation results show that the IA and multiplex schemes acquiring user clustering gains outperform the orthogonal scheme without user clustering. Besides, the proposed two-step and location-based algorithms achieve little losses compared with the optimal algorithm under low complexities. [ABSTRACT FROM AUTHOR]

Single quantum emitters (SQEs) are at the heart of quantum optics and photonic quantum-information technologies. To date, all the demonstrated solid-state single-photon sources are confined to one-dimensional (1D; ref. 3) or 3D materials. Here, we report a new class of SQEs based on excitons that are spatially localized by defects in 2D tungsten-diselenide (WSe2) monolayers. The optical emission from these SQEs shows narrow linewidths of ∼130 μeV, about two orders of magnitude smaller than those of delocalized valley excitons. Second-order correlation measurements revealed a strong photon antibunching, which unambiguously established the single-photon nature of the emission. The SQE emission shows two non-degenerate transitions, which are cross-linearly polarized. We assign this fine structure to two excitonic eigenmodes whose degeneracy is lifted by a large ∼0.71 meV coupling, probably because of the electron-hole exchange interaction in the presence of anisotropy. Magneto-optical measurements also reveal an exciton g factor of ∼8.7, several times larger than those of delocalized valley excitons. In addition to their fundamental importance, establishing new SQEs in 2D quantum materials could give rise to practical advantages in quantum-information processing, such as an efficient photon extraction and a high integratability and scalability. [ABSTRACT FROM AUTHOR]

Semi-metallic graphene and semiconducting monolayer transition-metal dichalcogenides are the most intensively studied two-dimensional materials of recent years. Lately, black phosphorus has emerged as a promising new two-dimensional material due to its widely tunable and direct bandgap, high carrier mobility and remarkable in-plane anisotropic electrical, optical and phonon properties. However, current progress is primarily limited to its thin-film form. Here, we reveal highly anisotropic and strongly bound excitons in monolayer black phosphorus using polarization-resolved photoluminescence measurements at room temperature. We show that, regardless of the excitation laser polarization, the emitted light from the monolayer is linearly polarized along the light effective mass direction and centres around 1.3 eV, a clear signature of emission from highly anisotropic bright excitons. Moreover, photoluminescence excitation spectroscopy suggests a quasiparticle bandgap of 2.2 eV, from which we estimate an exciton binding energy of ∼0.9 eV, consistent with theoretical results based on first principles. The experimental observation of highly anisotropic, bright excitons with large binding energy not only opens avenues for the future explorations of many-electron physics in this unusual two-dimensional material, but also suggests its promising future in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Nonlinear optical frequency conversion, in which optical fields interact with a nonlinear medium to produce new field frequencies, is ubiquitous in modern photonic systems. However, the nonlinear electric susceptibilities that give rise to such phenomena are often challenging to tune in a given material and, so far, dynamical control of optical nonlinearities remains confined to research laboratories as a spectroscopic tool. Here, we report a mechanism to electrically control second-order optical nonlinearities in monolayer WSe2, an atomically thin semiconductor. We show that the intensity of second-harmonic generation at the A-exciton resonance is tunable by over an order of magnitude at low temperature and nearly a factor of four at room temperature through electrostatic doping in a field-effect transistor. Such tunability arises from the strong exciton charging effects in monolayer semiconductors, which allow for exceptional control over the oscillator strengths at the exciton and trion resonances. The exciton-enhanced second-harmonic generation is counter-circularly polarized to the excitation laser due to the combination of the two-photon and one-photon valley selection rules, which have opposite helicity in the monolayer. Our study paves the way towards a new platform for chip-scale, electrically tunable nonlinear optical devices based on two-dimensional semiconductors. [ABSTRACT FROM AUTHOR]

Engineering the electromagnetic environment of a nanometre-scale light emitter by use of a photonic cavity can significantly enhance its spontaneous emission rate, through cavity quantum electrodynamics in the Purcell regime. This effect can greatly reduce the lasing threshold of the emitter, providing a low-threshold laser system with small footprint, low power consumption and ultrafast modulation. An ultralow-threshold nanoscale laser has been successfully developed by embedding quantum dots into a photonic crystal cavity (PCC). However, several challenges impede the practical application of this architecture, including the random positions and compositional fluctuations of the dots, extreme difficulty in current injection, and lack of compatibility with electronic circuits. Here we report a new lasing strategy: an atomically thin crystalline semiconductor-that is, a tungsten diselenide monolayer-is non-destructively and deterministically introduced as a gain medium at the surface of a pre-fabricated PCC. A continuous-wave nanolaser operating in the visible regime is thereby achieved with an optical pumping threshold as low as 27 nanowatts at 130 kelvin, similar to the value achieved in quantum-dot PCC lasers. The key to the lasing action lies in the monolayer nature of the gain medium, which confines direct-gap excitons to within one nanometre of the PCC surface. The surface-gain geometry gives unprecedented accessibility and hence the ability to tailor gain properties via external controls such as electrostatic gating and current injection, enabling electrically pumped operation. Our scheme is scalable and compatible with integrated photonics for on-chip optical communication technologies. [ABSTRACT FROM AUTHOR]

Heterojunctions between three-dimensional (3D) semiconductors with different bandgaps are the basis of modern light-emitting diodes, diode lasers and high-speed transistors. Creating analogous heterojunctions between different 2D semiconductors would enable band engineering within the 2D plane and open up new realms in materials science, device physics and engineering. Here we demonstrate that seamless high-quality in-plane heterojunctions can be grown between the 2D monolayer semiconductors MoSe2 and WSe2. The junctions, grown by lateral heteroepitaxy using physical vapour transport, are visible in an optical microscope and show enhanced photoluminescence. Atomically resolved transmission electron microscopy reveals that their structure is an undistorted honeycomb lattice in which substitution of one transition metal by another occurs across the interface. The growth of such lateral junctions will allow new device functionalities, such as in-plane transistors and diodes, to be integrated within a single atomically thin layer. [ABSTRACT FROM AUTHOR]

Background: Colonoscopic perforation (CP) has a low incidence rate. However, with the extensive use of colonoscopy, even low incidence rates should be evaluated to identify and address risks. Information on CP is quite limited in China. Objective: Our study aimed to determine the frequency of CP in colonoscopies performed by surgeons at a large teaching hospital in China over a 12-year period. Methods: A retrospective review of medical records was performed for all patients who had CPs from 1 January 2000 to 31 December 2012. Iatrogenic perforations were identified mainly by abdominal X-ray or computed tomography scan. Follow-up information of adverse events post-colonoscopy was identified from the colorectal surgery database of our hospital. Patients' demographic data, colonoscopy procedure information, location of perforation, treatment, and outcome were recorded. Results: A total of 110,785 diagnostic and therapeutic colonoscopy procedures were performed (86,800 diagnostic cases and 23,985 therapeutic cases) within the 12-year study period. A total of 14 incidents (0.012 %) of CP were reported (seven males and seven females), of which nine cases occurred during diagnostic colonoscopy (0.01 %) and five after therapeutic colonoscopy (three polypectomy cases, one endoscopic mucosal resection, and one endoscopic mucosal dissection). Mean patient age was 67.14 years. One case of CP (7.14 %) after colonoscopy polypectomy was treated using curative colonoscopy endoclips. Other patients underwent operations: six cases (46.15 %) of primary repair, four cases (28.57 %) of resection with anastomosis, and two cases (15.38 %) of resection without anastomosis. No obvious perforation was found in one patient (7.69 %). Surgeons attempted to treat one case laparoscopically but eventually resorted to open surgery. The postoperative course was uncomplicated in eight cases (57.14 %) and complicated in six cases (42.86 %) but without mortality. Conclusion: CP is a serious but rare complication of colonoscopy. A perforation risk of 0.012 % was found in our study. The optimal management of CP remains controversial. Treatment for CP should be individualized according to the patient's condition, related devices, and surgical skills of endoscopists or surgeons. Selective measures such as colonoscopy without intravenous sedation and decrease of loop formation can effectively reduce rates of perforation. [ABSTRACT FROM AUTHOR]

The development of light-emitting diodes with improved efficiency, spectral properties, compactness and integrability is important for lighting, display, optical interconnect, logic and sensor applications. Monolayer transition-metal dichalcogenides have recently emerged as interesting candidates for optoelectronic applications due to their unique optical properties. Electroluminescence has already been observed from monolayer MoS2 devices. However, the electroluminescence efficiency was low and the linewidth broad due both to the poor optical quality of the MoS2 and to ineffective contacts. Here, we report electroluminescence from lateral p-n junctions in monolayer WSe2 induced electrostatically using a thin boron nitride support as a dielectric layer with multiple metal gates beneath. This structure allows effective injection of electrons and holes, and, combined with the high optical quality of WSe2, yields bright electroluminescence with 1,000 times smaller injection current and 10 times smaller linewidth than in MoS2 (refs 17,18). Furthermore, by increasing the injection bias we can tune the electroluminescence between regimes of impurity-bound, charged and neutral excitons. This system has the required ingredients for new types of optoelectronic device, such as spin- and valley-polarized light-emitting diodes, on-chip lasers and two-dimensional electro-optic modulators. [ABSTRACT FROM AUTHOR]

Coupling degrees of freedom of distinct nature plays a critical role in numerous physical phenomena. The recent emergence of layered materials provides a laboratory for studying the interplay between internal quantum degrees of freedom of electrons. Here we report new coupling phenomena connecting real spin with layer pseudospins in bilayer WSe2. In polarization-resolved photoluminescence measurements, we observe large spin orientation of neutral and charged excitons by both circularly and linearly polarized excitation, with the trion spectrum splitting into a doublet at large vertical electrical field. These observations can be explained as a locking of spin and layer pseudospin in a given valley, where the doublet implies an electrically induced spin splitting. The observed distinctive behaviour of the trion doublet under polarized excitation further provides spectroscopic evidence of interlayer and intralayer trion species, a promising step towards optical manipulation in van der Waals heterostructures through interlayer excitons. [ABSTRACT FROM AUTHOR]

A novel protodioscin-(steroidal saponin)-glycoside hydrolase, named protodioscin-glycosidase-1 (PGase-1), was purified and characterized from the Aspergillus oryzae strain. The molecular mass of this enzyme was determined to be about 55 kDa based on SDS-polyacrylamide gel electrophoresis. PGase-1 was able to hydrolyze the terminal 26- O-β- d-glucopyranoside of protodioscin (furostanoside) to produce dioscin (spirostanoside), and then further hydrolyze the terminal 3- O-(1 → 4)-α- l-rhamnopyranoside of dioscin to form progenin III. However, PGase-1 could hardly hydrolyze the 3- O-(1 → 2)-α- l-rhamnopyranoside of progenin III, 3- O-β- d-glucoside of trillin, and the 1- O-glycosides of ophiopogonin D (steroidal saponin). In addition, PGase-1 also could hydrolyze the α- d-galactopyranoside, β- d-glucopyranoside, and β- d-galactopyranoside of p-nitrophenyl-glycosides, but the enzyme could not hydrolyze the α- d-mannopyranoside, α- l-arabinopyranoside, α- d-glucopyranoside, β- d-xylopyranoside, and α- l-rhamnopyranoside of p-nitrophenyl-glycosides. These new properties of PGase-1 were significantly different from those of previously described steroidal saponin-glycosidases and the glycosidases currently described in Enzyme Nomenclature by the NC-IUBMB. The gene (termed as pgase- 1) encoding PGase-1 was cloned, sequenced, and expressed in Pichia pastoris GS115. The complete nucleotide sequence of pgase- 1 consists of 1,725 bp. The recombinant PGase-1 from recombinant P. pastoris GS115 strain also showed the activity hydrolyzing glycosides of steroidal saponins which was similar to that of the wild-type PGase-1 from A. oryzae. The PGase-1 gene is highly similar to Aspergilli α-amylase (EC 3.2.1.1), and PGase-1 should be classified as glycoside hydrolase family 13 by the method of gene sequence-based classification. But the enzyme properties of PGase-1 are different from those of α-amylase in this family. [ABSTRACT FROM AUTHOR]

Transition-metal dichalcogenides such as WSe2 and MoS2 have electronic band structures that are ideal for hosting many exotic spin-orbit phenomena. Here we investigate the possibility to generate and modulate a giant Zeeman-type spin polarization in WSe2 under an external electric field. By tuning the perpendicular electric field applied to the WSe2 channel with an electric-double-layer transistor, we observe a systematic crossover from weak localization to weak anti-localization in magnetotransport. Our optical reflection measurements also reveal an electrically tunable exciton splitting. Using first-principles calculations, we propose that these are probably due to the emergence of a merely out-of-plane and momentum-independent spin splitting at and in the vicinity of the vertices of the WSe2 Brillouin zone under electric field. The non-magnetic approach for creating such an intriguing spin splitting keeps the system time-reversally invariant, thereby suggesting a new method for manipulating the spin degrees of freedom of electrons. [ABSTRACT FROM AUTHOR]

As a consequence of degeneracies arising from crystal symmetries, it is possible for electron states at band-edges ('valleys') to have additional spin-like quantum numbers. An important question is whether coherent manipulation can be performed on such valley pseudospins, analogous to that implemented using true spin, in the quest for quantum technologies. Here, we show that valley coherence can be generated and detected. Because excitons in a single valley emit circularly polarized photons, linear polarization can only be generated through recombination of an exciton in a coherent superposition of the two valley states. Using monolayer semiconductor WSe2 devices, we first establish the circularly polarized optical selection rules for addressing individual valley excitons and trions. We then demonstrate coherence between valley excitons through the observation of linearly polarized luminescence, whose orientation coincides with that of the linearly polarized excitation, for any given polarization angle. In contrast, the corresponding photoluminescence from trions is not observed to be linearly polarized, consistent with the expectation that the emitted photon polarization is entangled with valley pseudospin. The ability to address coherence, in addition to valley polarization, is a step forward towards achieving quantum manipulation of the valley index necessary for coherent valleytronics. [ABSTRACT FROM AUTHOR]

Crystal symmetry governs the nature of electronic Bloch states. For example, in the presence of time-reversal symmetry, the orbital magnetic moment and Berry curvature of the Bloch states must vanish unless inversion symmetry is broken. In certain two-dimensional electron systems such as bilayer graphene, the intrinsic inversion symmetry can be broken simply by applying a perpendicular electric field. In principle, this offers the possibility of switching on/off and continuously tuning the magnetic moment and Berry curvature near the Dirac valleys by reversible electrical control. Here we investigate this possibility using polarization-resolved photoluminescence of bilayer MoS2, which has the same symmetry as bilayer graphene but has a bandgap in the visible spectrum allowing direct optical probing. We find that in bilayer MoS2 the circularly polarized photoluminescence can be continuously tuned from −15% to 15% as a function of gate voltage, whereas in structurally non-centrosymmetric monolayer MoS2 the photoluminescence polarization is gate independent. The observations are well explained as resulting from the continuous variation of orbital magnetic moments between positive and negative values through symmetry control. [ABSTRACT FROM AUTHOR]

The generation of a current by light is a key process in optoelectronic and photovoltaic devices. In band semiconductors, depletion fields associated with interfaces separate long-lived photo-induced carriers. However, in systems with strong electron-electron and electron-phonon correlations it is unclear what physics will dominate the photoresponse. Here, we investigate photocurrent in VO2, an exemplary strongly correlated material known for its dramatic metal-insulator transition at Tc ? 68 °C, which could be useful for optoelectronic detection and switching up to ultraviolet wavelengths. Using scanning photocurrent microscopy on individual suspended VO2 nanobeams we observe a photoresponse peaked at the metal-insulator boundary but extending throughout both insulating and metallic phases. We determine that the response is photothermal, implying efficient carrier relaxation to a local equilibrium in a manner consistent with strong correlations. Temperature-dependent measurements reveal subtle phase changes within the insulating state. We further demonstrate switching of the photocurrent by optical control of the metal-insulator boundary arrangement. Our work shows the value of applying scanning photocurrent microscopy to nanoscale crystals in the investigation of strongly correlated materials, and the results are relevant for designing and controlling optoelectronic devices employing such materials. [ABSTRACT FROM AUTHOR]

The combination of its high electron mobility, broadband absorption and ultrafast luminescence make graphene attractive for optoelectronic and photonic applications, including transparent electrodes, mode-locked lasers and high-speed optical modulators. Photo-excited carriers that have not cooled to the temperature of the graphene lattice are known as hot carriers, and may limit device speed and energy efficiency. However, their roles in charge and energy transport are not fully understood. Here, we use time-resolved scanning photocurrent microscopy to demonstrate that hot carriers, rather than phonons, dominate energy transport across a tunable graphene p-n junction excited by ultrafast laser pulses. The photocurrent response time varies from 1.5 ps at room temperature to 4 ps at 20 K, implying a fundamental bandwidth of ?500 GHz (refs 12, 13, 21). Gate-dependent pump-probe measurements demonstrate that both thermoelectric and built-in electric field effects contribute to the photocurrent, with the contribution from each depending on the junction configuration. The photocurrent produced by a single pulsed laser also displays multiple polarity reversals as a function of carrier density, which is a possible signature of impact ionization. [ABSTRACT FROM AUTHOR]

By first-principles calculations, we investigate the geometric stability, electronic and optical properties of the type-II PN-WSe2 and type-I PAs-WSe2 van der Waals heterostructures(vdWH). They are p-type semiconductors with indirect band gaps of 1.09 eV and 1.08 eV based on PBE functional respectively. By applying the external gate field, the PAs-WSe2 heterostructure would transform to the type-II band alignment from the type-I. With the increasing of magnitude of the electric field, two heterostructures turn into the n-type semiconductors and eventually into metal. Especially, PN/PAs-WSe2 vdWH are both high refractive index materials at low frequencies and show negative refractive index at high frequencies. Because of the steady absorption in ultraviolet region, the PAs-WSe2 heterostructure is a highly sensitive UV detector material with wide spectrum. The type-II PN-WSe2 heterostructure possesses giant and broadband absorption in the near-infrared and visible regions, and its solar power conversion efficiency of 13.8% is higher than the reported GaTe–InSe (9.1%), MoS2/p-Si (5.23%) and organic solar cells (11.7%). It does project PN-WSe2 heterostructure a potential for application in excitons-based solar cells. [ABSTRACT FROM AUTHOR]

We report a fully stabilized self-referenced all-solid-state-laser frequency comb based on a home-built Kerr-lens mode-locked Yb:CaYAlO4 oscillator, which delivers ultrafast pulses with a pulse duration of 54 fs and an average power of 1.5 W. Free running carrier-envelope phase offset frequency (fceo) is observed with a signal to noise ratio of 40 dB at 100 kHz resolution bandwidth, which is phase-locked to a microwave frequency synthesizer with a residual phase jitter of 370 mrad [1 Hz–1 MHz] and with a standard frequency deviation of 0.8 mHz at 1-s gate time within 3-h, corresponding to the relative frequency instability of 2.9 × 10−18 at 1-s average time. It is the lowest phase noise and the highest frequency stability of fceo obtained in a watt-level all-solid-state bulk laser frequency comb to the best of our knowledge. A 13th repetition rate is simultaneously phase-locked to the same microwave standard with a frequency instability level of 10−12 at 1 s average time. Such fully stabilized power scaling Yb: CaYAlO4 laser frequency combs have great potential for applications in broadband dual comb spectroscopy as well as high loss cases such as long-distance time and frequency transfer. [ABSTRACT FROM AUTHOR]

Pyrrolidines and piperidines are important building blocks in organic synthesis. Numerous methods exist for constructing substituted pyrrolidines and piperidines. However, efficient syntheses of pyrrolidines and piperidines bearing chiral tertiary alcohols are limited. Here we report an efficient enantioselective nickel-catalyzed intramolecular reductive cyclization of N-alkynones. A P-chiral bisphosphorus ligand DI-BIDIME is designed and applied in the synthesis of tertiary allylic siloxanes bearing pyrrolidine and piperidine rings in high yields and excellent enantioselectivities, with triethylsilane as reducing reagent. The highest turn over number achieved is 1000 (0.1 mol% catalyst loading) with > 99:1 er. This reaction provides a practical way to synthesize pyrrolidine and piperidine derivatives with chiral tertiary alcohols from easily accessible starting materials under mild conditions. The products can be scaled up and transformed to various useful chiral intermediates. The P-chiral bisphosphorus ligand developed in this study represents one of the few ligands for highly enantioselective cyclization of alkynones. Transition metal-catalyzed cyclization of alkynes and carbonyls offers a useful route to cyclic allylic alcohols, but typically uses precious metal catalysts. Here, enantioselective nickel-catalyzed reductive cyclization of N-alkynones gives tertiary allylic alcohols in up to 99:1 er with catalyst loadings of 0.1 mol% [ABSTRACT FROM AUTHOR]