At sufficiently low temperatures, condensed-matter systems tend to develop order. A notable exception to this behaviour is the case of quantum spin liquids, in which quantum fluctuations prevent a ...transition to an ordered state down to the lowest temperatures. There have now been tentative observations of such states in some two-dimensional organic compounds, yet quantum spin liquids remain elusive in microscopic two-dimensional models that are relevant to experiments. Here we show, by means of large-scale quantum Monte Carlo simulations of correlated fermions on a honeycomb lattice (a structure realized in, for example, graphene), that a quantum spin liquid emerges between the state described by massless Dirac fermions and an antiferromagnetically ordered Mott insulator. This unexpected quantum-disordered state is found to be a short-range resonating valence-bond liquid, akin to the one proposed for high-temperature superconductors: the possibility of unconventional superconductivity through doping therefore arises in our system. We foresee the experimental realization of this model system using ultra-cold atoms, or group IV elements arranged in honeycomb lattices.
Previous studies of geometric and morphologic parameters of intracranial aneurysms have been conducted to determine rupture risk, which remains incompletely defined due to patient-specific risk ...factors, such as sex, hypertension, and age. To this end, we compared characteristics of ruptured and unruptured aneurysms in the same patients with symmetric bilateral intracranial aneurysms.
Between January 2008 and March 2014, 2361 patients with 2674 aneurysms were diagnosed by CT angiography or surgical findings at 4 medical centers. Geometric and morphologic parameters examined for symmetric bilateral intracranial aneurysms comprised aneurysm wall regularity, size, neck width, aspect ratio, size ratio, neck-to-parent artery ratio, and area ratio. Univariate and multivariate statistical analyses were performed to determine independent risk factors for rupture.
Sixty-three patients (48 women, 15 men; mean age, 62.5 ± 9.8 years) with symmetric bilateral aneurysms were eligible for the study and were included. The most frequent aneurysm location was the posterior communicating artery. Univariate analysis disclosed that aneurysm size, aspect ratio, size ratio, area ratio, and irregular wall differed between patients with ruptured and unruptured aneurysms. Multivariate analysis indicated that aspect ratio of ≥1.6 (adjusted OR, 9.521; 95% CI, 2.182-41.535), area ratio of ≥1.5 (adjusted OR, 4.089; 95% CI, 1.247-13.406), and irregular shape (adjusted OR, 10.443; 95% CI 3.394-32.135) were significant predictive factors for aneurysm rupture after adjustment for aneurysm size.
An aspect ratio of ≥1.6, area ratio of ≥1.5, and irregular wall are associated with aneurysm rupture independent of aneurysm size and patient characteristics. These characteristics alone can help in distinguishing ruptured bilateral intracranial aneurysms from unruptured ones.
Previous studies have demonstrated that microRNA (miRNA) expression is altered in human cancer. However, the molecular mechanism underlying these changes in miRNA expression remains unclear. In this ...study, we investigated the epigenetic modification of miR-124 genes and the potential function of miR-124 in pancreatic cancer. Using pyrosequencing analysis, we found that miR-124 genes (including miR-124-1, miR-124-2 and miR-124-3) are highly methylated in pancreatic cancer tissues compared with in non-cancerous tissues. Hypermethylation mediated the silencing of miR-124, which was a frequent event in pancreatic duct adenocarcinoma (PDAC). Furthermore, miR-124 downregulation was significantly associated with worse survival of PDAC patients. Functional studies showed that miR-124 inhibited cell proliferation, invasion and metastasis. Furthermore, we characterized Rac1 as a direct target of miR-124, and miR-124 interacted with the 3'-untranslated region of Rac1, which we showed to be a putative tumor promoter in pancreatic cancer. Thus, the miR-124-mediated downregulation of Rac1 led to the inactivation of the MKK4-JNK-c-Jun pathway. Therefore, our study demonstrates that miR-124 is a tumor suppressor miRNA that is epigenetically silenced in pancreatic cancer. Our findings suggest a previously unidentified molecular mechanism involved in the progression and metastasis of pancreatic cancer.
•Heat storage and retrieval tests in a LTES unit were studied.•Molten salt and metal foam/salt composites were used as the PCMs comparatively.•Thermal non-equilibrium model was established to ...describe the heat transfer characteristics.•Time-duration with composite PCM during heat retrieval process was reduced more.•Slight temperature difference existed between the metal skeleton and PCM.
Eutectic molten salt can be used as the latent thermal energy storage (LTES) medium in solar energy applications. In the present study, eutectic salt (50wt% NaNO3, 50wt% KNO3) with a melting temperature of about 220°C was employed as the PCM for the middle-temperature solar energy application, which can be powered by the parabolic-trough solar collector using oil as the heat transfer fluid. There are many LTES units in which the molten salt is encapsulated in the thermal energy storage tank, where the heat transfer characteristic of the LTES unit is very important for the overall performance of the entire thermal energy storage tank. We experimentally and numerically investigated the heat transfer characteristics of the molten-salt in a LTES unit with and without heat transfer enhancement. Various heating temperatures of 240°C, 250°C, and 260°C and cooling temperatures of 30°C, 70°C, and 110°C were employed in the study, so as to extensively reveal the heat transfer characteristics during heat storage and retrieval. It was found that natural convection was very dominant during heat storage in the case of pure molten-salt, especially when the heating temperature was higher, and it was weakened in the case of molten-salt with metal foam; while the heat retrieval process was enhanced by the presence of the metal foam. The numerical results were compared with the experimental results, showing reasonable agreement, which indicated that such numerical model could be used for the further study of the performance of the LTES system.
Clinical prognostic parameters of liver metastasis from pancreatic adenocarcinoma have not been specifically identified.This study is to explore the risk factors of liver metastasis in advanced ...pancreatic adenocarcinoma (PDAC) patients in China.
A multicenter cohort study was conducted to explore whether liver metastasis in locally advanced and metastatic PDAC could be reflected by some common laboratory indexes. We collected 1787 advanced PDAC patients from three participating hospitals between 2004 and 2014. The associations between some laboratory indexes and risks of liver metastases were analyzed.
Results have shown that 87% of stage IV patients developed synchronous liver metastasis. Primary tumor location (body/tail vs. head/neck, OR 0.55, 95% CI 0.36-0.83), primary tumor diameter (≥20 mm vs. <20 mm, OR 1.77, 95% CI 1.16-2.70), elevated ALT and AST (OR 1.62, 95% CI 0.92-2.83), and elevated CA19-9 (OR 2.72, 95% CI 1.85-3.99) upon diagnosis are significantly associated with risk of synchronous liver metastasis. Among stage III patients, 30.1% developed metachronous liver metastasis. However, no risk factors were identified among these patients.
Primary tumor location, diameter, elevated ALT and AST, and increased CA19-9 are independent risk factors of synchronous liver metastasis in PDAC patients.
Summary
This paper presents a hybrid element‐free Galerkin (HEFG) method for solving wave propagation problems. By introducing the dimension split method, the three‐dimensional wave propagation ...problems are transformed into a series of two‐dimensional ones in other one‐dimensional directions. The two‐dimensional problems are solved using the improved element‐free Galerkin (IEFG) method, and the finite difference method is used in the one‐dimensional splitting direction and the time space. Then, the formulas of the HEFG method for three‐dimensional wave propagation problems are obtained. Numerical examples are selected to show the effectiveness and the advantage of the HEFG method. The convergence and error analysis of the HEFG method are discussed according to the numerical results under different splitting directions, weight functions, node distributions, scale parameters of the influence domain, penalty factors, and time steps. The numerical results are given to show the convergence and advantages of the HEFG method over the IEFG method. Comparing with the IEFG method, the HEFG method has greater computational precision and speed for three‐dimensional wave propagation problems.
Laccase, a member of a group of proteins collectively known as multicopper oxidases, is hypothesized to play an important role in insect cuticle sclerotization by oxidizing catechols in the cuticle ...to their corresponding quinones, which then catalyze protein cross-linking reactions. Laccase 2 has been proved as the gene required for beetle cuticle tanning through RNA interference (RNAi) experiments on red flour beetle Tribolium castaneum. The pine sawyer beetle, Monochamus alternatus (Coleoptero: Cerambycidae) is the insect serving as a major vector of the pinewood nematode, Bursaphelenchus xylophilus, which is the causative agent for pine wilt disease. The cDNA of MaLac2 was cloned from the insect in this study. The conceptual amino-acid sequence deduced was much conserved with other known insect laccases, particularly with the enzyme of Tribolium castaneum. Injection in hemolymph of pine sawyer larva of dsRNA targeting the laccase 2 mRNA leads to important alterations of the tanning, hardening and sclerotization of the pupal and adult cuticles. Defaults appear in a dose-dependent manner and high loads of dsRNA are lethal. The decrease of the endogenous laccase 2 mRNA affects the procuticle which is thinner and without the characteristic piling up of successive layers. The observations reinforce the role of laccase 2 as an essential phenoloxidase for making cuticle.
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