Author Correction: Universal mechanical exfoliation of large-area 2D crystals.

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Universal mechanical exfoliation of large-area 2D crystals.

Two-dimensional materials provide extraordinary opportunities for exploring phenomena arising in atomically thin crystals. Beginning with the first isolation of graphene, mechanical exfoliation has been a key to provide high-quality two-dimensional materials, but despite improvements it is still limited in yield, lateral size and contamination. Here we introduce a contamination-free, one-step and universal Au-assisted mechanical exfoliation method and demonstrate its effectiveness by isolating 40 types of single-crystalline monolayers, including elemental two-dimensional crystals, metal-dichalcogenides, magnets and superconductors. Most of them are of millimeter-size and high-quality, as shown by transfer-free measurements of electron microscopy, photo spectroscopies and electrical transport. Large suspended two-dimensional crystals and heterojunctions were also prepared with high-yield. Enhanced adhesion between the crystals and the substrates enables such efficient exfoliation, for which we identify a gold-assisted exfoliation method that underpins a universal route for producing large-area monolayers and thus supports studies of fundamental properties and potential application of two-dimensional materials.

Preparation and Optical Absorption Properties of Ternary Rare Earth Boride LaxPr1-xB6 Submicron Powders.

As multifunctional materials, rare-earth hexaborides (RB6) display many interesting physical properties such as optical absorption, magnetic and thermionic emission. With the wide application of rare earth hexaboride and the continuous extension of its research fields, researchers have studied the synthesis of multi-rare earth hexaboride nano-powders and their thermal emission and light absorption properties. In the present work, ternary Single-phase LaxPr1-xB6 submicron powders are successfully synthesized using a solid-state reaction, in which lanthanum chloride (LaCl3) and praseodymium chloride (PrCl3) are used as rare-earth source and NaBH4 as the boron source under continuous vacuum conditions. The reaction temperature is 1150 °C and the holding time is 2 h. The Pr doping effects on crystal structure, grain morphology, and optical absorption properties were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and ultraviolet-vis absorption measurements. The XRD patterns show that the diffraction peaks are sharp and well-defined, and no other extra impurity peaks were detected, indicating the characteristics of well-crystallized materials. It is found that all the LaxPr1-xB6 solid powders are of single phase. The SEM results demonstrate that the cubicshaped ternary LaxPr1-xB6 submicron crystals with a size of 50~200 nm are obtained. The TEM images reveal the cubic single-crystalline nature, and the FFT patterns implies the lattice fringe d = 0.416 nm which agrees well with the (100) crystal plane. The elements mapping results indicates that the Pr atoms occupied the lattice sites of LaB6. The optical absorption results show that the absorption valley of LaB6 are located at 591 nm. With the increase of Pr doping contents from 0.2 to 0.8, the absorption valley moves from 596.3 nm to 612.9 nm, indicating the characteristics of visible light high transparency. The first-principle calculation results manifest that the move of the absorption valley of LaB6 in the visible region after doping Pr is related to the decrease of kinetic energy of electrons near the Fermi plane. X-ray photoelectron spectroscopy (XPS) analysis shows that the La and Pr exist in the type of La3+ and Pr3+ in LaxPr1-xB6. Therefore, it exists as an efficient optical absorption material. The LaxPr1-xB6 should open up a new route to extend the optical applications of rare-earth hexaborides.

[Effect of total flavonoids of astragalus on endoplasmic reticulum chaperone, calumenin and connecxin 43 in suckling mouse myocardium with myocarditis caused by coxsackievirus B3].

OBJECTIVE: To investigate the effect of total flavonoids of astragalus on the expression of endoplasmic reticulum chaperone, calumenin and connecxin 43 (CX43) in suckling mouse myocardium with myocarditis caused by coxsackievirus B3 (CVB3). METHODS: The primary culture of suckling mouse myocardium cells were randomly divided into control group, CVB3 infected group and total flavonoids of astragalus group. Firstly, to confirm the identity of the suckling mouse myocardium, α-SMA was monitored by immunohistochemistry method. Then the protein expression changes of endoplasmic reticulum chaperone-glucose regulatory protein 78 ( GRP78), calumenin and CX43 were detected by Western blot. RESULTS: (1) Compared with that of the control group, the GRP78 expression level in CVB3 infected group was improved, the expression levels of calumenin and CX43 were all reduced. (2) Compared with that of CVB3 infected group, GRP78 expression level was decreased, and the expression levels of calumenin and CX43 were increased in total flavonoids of astragalus group. CONCLUSION: CVB3 infection may cause endoplasmic reticulum stress of rat myocardium cells by increasing the expression of GRP78 and decreasing the expression of calumenin and CX43. On the other hand, total flavonoids of astragalus can reduce the expression of GRP78 and increase the expression of calumenin and CX43.The results of this experiment may be closely related to the effects of anti-arrhythmia with viral myocarditis caused by CVB3.

Osteopontin in metastatic lesions as a prognostic marker in ovarian cancers.

Osteopontin (OPN) is expressed in various human cancers and associated with tumor progression, invasion and metastasis in many manners. The purpose of this study is to investigate the clinical significance of OPN expression in metastatic lesions of ovarian cancers, since the prognosis of the patients with peritoneal dissemination is extremely poor. In primary tumors and peritoneal metastatic lesions from 40 patients with stage III ovarian cancers, the protein levels of OPN and histoscores were determined by enzyme immunoassay and immunohistochemistry, respectively. Immunohistochemical staining revealed OPN was distributed in the cytoplasm and nuclear compartments of the cancer and stromal cells within and around the tumor. The OPN level was significantly (p < 0.05) increased in 32 of 40 metastatic lesions of ovarian cancers. The OPN increased cases identified by immunohistochemical staining were consistent with those identified by the sandwich immunoassay. The prognosis of the 32 patients with significant increase of OPN in ovarian cancers was extremely poor, whereas the 36-month survival rate of the 8 patients with no increase of OPN was 75%. Multivariate analysis revealed that the levels of OPN were independent predictors of prognosis from clinical characteristics (age, lesion size, histological types). OPN might be associated with peritoneal metastasis and its advancement, and that the OPN level in metastatic lesion may be a prognostic indicator in ovarian cancers.

Factors associated with the extent of care-seeking delay for patients with acute myocardial infarction in Beijing / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Prehospital delay remains one of the main causes of reduced benefit of reperfusion therapy for patients with acute myocardial infarction (AMI). The largest proportion of prehospital delay involves the interval between the onset of symptoms and the decision to seek medical treatment. The purpose of this study was to examine the factors associated with the extent of care-seeking delay in Beijing for patients with AMI.</p><p><b>METHODS</b>A structured interview was conducted in 102 patients with AMI in eight hospitals in Beijing.</p><p><b>RESULTS</b>The mean decision time in patients with AMI was (204 +/- 43) minutes, and prehospital delay time was (311 +/- 54) minutes. Only 34% of patients sought medical care within one hour and a further 36% of patients presented to one of the eight hospitals within two hours after onset. Educational level, atypical presentation of AMI, and family members at the site where AMI occurred were associated with longer delay time in seeking medical assistance (P < 0.05, respectively), whereas the intensity of chest pain was inversely related to patients' delay time (P < 0.01). Patients who perceived their family relationship as good, attributed their symptoms to AMI origin, knew the time-dependent nature of reperfusion therapy, or used emergency medical service tended to seek medical care in a more rapid manner (P < 0.05, respectively).</p><p><b>CONCLUSIONS</b>Patients with AMI in Beijing delay seeking medical care to a great extent. Health education to increase the level of awareness of the target population at increased risk of AMI, including patients and their family members, is probably beneficial to reduce patients' care-seeking delay.</p>