青海省埃坑德勒斯特地区水系沉积物地球化学特征及找矿远景

埃坑德勒斯特地区位于柴东缘,东昆南复合拼接带内,是东昆仑多金属成矿带的重要组成部分。通过在区内开展1∶2. 5万水系沉积物测量,获得了较为丰富的地球化学测量成果,完成了对成矿元素含量特征、分布特征、变化特征、相关性和异常区特征的分析。结果表明,该研究区成矿元素的富集、贫化受地层、侵入岩及构造控制较为明显,Au、Ag、Cu、Pb、Zn、Mo是区内重要的目标矿种。结合区内地质、物化探及矿产信息,圈定出6处找矿远景区。其中,达特乌拉—哈拉郭勒金银铅多金属找矿远景区和埃坑德勒斯特—乌兰托来托钼银多金属找矿远景区可作为进一步的找矿靶区,为下一步找矿勘查提供理论基础。

小学毕业班学生数学运算能力的培养

数学是人类文化重要的组成部分,数学离不开计算,而计算能力是学生学习数学的基本能力之一,教师要采用多种形式进行教学,重视学生计算兴趣的培养,开展多种多样的计算训练,从而提高学生的计算能力。对于小学毕业班的学生来说,数学运算能力的提高显得尤为重要,需要教师格外加以关注。

Superlubricity enabled dry transfer of non-encapsulated graphene

Transferring high-quality exfoliated graphene flakes onto different substrates while keeping the graphene free of polymer residues is of great importance, but at the same time very challenging. Currently, the only feasible way is the so-called all-dry "pick-and-lift" method, in which a hexagonal boron nitride(hBN) flake is employed to serve as a stamp to pick up graphene from one substrate and to lift it down onto another substrate. The transferred graphene samples, however,are always covered or encapsulated by hBN flakes, which leads to difficulties in further characterizations. Here, we report an improved "pick-and-lift" method, which allows ultra-clean graphene flakes to be transferred onto a variety of substrates without hBN coverage. Basically, by exploiting the superlubricity at the graphene/hBN stack interface, we are able to remove the top-layer hBN stamp by applying a tangential force and expose the underneath graphene.

Near-Field Optical Identification of Metallic and Semiconducting Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes(SWCNTs),due to their outstanding electrical and optical properties,are expected to have extensive applications,such as in transparent conductive fims and ultra-small field-effect transistors(FETs).However,those applications can only be best realized with pure metallic or pure semiconducting SWCNTs.Hence,identifying and separating metallic from semiconducting SWCNTs in as-grown samples are crucial.In addition,knowledge of the type of an SWCNT is also important for further exploring its new properties in fundamental science.Here we report employing scanning near-field optical microscopy(SNOM)as a direct and simple method to identify metallic and semiconducting SWCNTs on SiO2/Si substrates.Metallic and semiconducting SWCNTs show distinct near-field optical responses because the metallic tubes support plasmons whereas the semiconducting tubes do not.The reliability of this method is verified using FET testing and Rayleigh scattering spectroscopy.Our result demonstrates that the SNOM technique provides a reliable,simple,noninvasive and in situ method to distinguish between metallic and semiconducting SWCNTs.

Enhanced Mechanical Properties of Multi-layer Graphene Filled Poly(vinyl chloride) Composite Films

In order to improve mechanical properties of soft poly(vinyl chloride)(PVC) films,we used commercial multi-layer graphene(MLG) with large size and high structural integrity as reinforcing fillers,and prepared MLG/PVC composite films by using conventional melt-mixing methods.Microstructures,static and dynamic mechanical properties of the MLG/PVC composite films were investigated.The results showed that a small amount of MLG loading could greatly increase the mechanical properties of the MLG/PVC composites.The tensile modulus of the 0.96 wt%MLG/PVC composites was up to 40 MPa,increasing by31.3%in comparison to the neat PVC.Such a significant mechanical reinforcement was mainly attributed to uniform dispersion of the large-size MLG,good compatibility and strong interactions among MLG and plasticizers and PVC.

A graphene-laminated electrode with high glucose oxidase loading for highly-sensitive glucose detection

Graphene oxide(GO) has received considerable attention for glucose detection because of high surface area, abundant functional groups, and good biocompatibility. Defects and functional groups of the GO are beneficial to immobilization of glucose oxidase(GOD), but sacrificing electron-transfer capability for highly-sensitive detection. In order to obtain high GOD loading and highly-sensitive detection of biosensors, we first designed and fabricated a graphene-laminated electrode by combining GO and edgefunctionalized graphene(FG) layers together onto glassy-carbon electrode. The graphene-laminated electrodes exhibited faster electron transfer rate, higher GOD loading of 3.80 × 10^(-9) mol·cm^(-2), and higher detection sensitivity of 46.71 μA·mM^(-1)·cm^(-2) than other graphene-based biosensors reported in literature. Such high performance is mainly attributed to the abundant functional groups of GO, high electrical conductivity of FG, and strong interactions between components in the graphene-laminated electrodes.By virtue of their high enzyme loading and highly-sensitive detection, the graphene-laminated electrodes show great potential to be widely used as high-performance biosensors in the field of medical diagnosis.

Transfer-free CVD graphene for highly sensitive glucose sensors

Chemical vapor deposition(CVD)graphene film is a promising electrode-modifying material for fabricating high-performance glucose sensor due to its high electrical conductivity and two-dimensional structure over large area.However,the use of typical metal-based CVD graphene suffers from the residue contamination of polymer transfer-support and heavy metal ions.In this work,we directly grew fewlayer graphene on the SiO2/Si substrate without transfer process and then fabricated graphene-based glucose sensors by sequentially immobilizing glucose oxidase and depositing Nafion layer on its surface that was functionalized by oxygen-plasma treatment.Our transfer-and metal-free process shows distinct advantage over the common metal-CVD method in improving the electrochemical performance by eliminating the contamination of transfer-residue.Thus-obtained glucose sensor shows a high sensitivity(16.16μA mM-1cm-2)with a detection limit of 124.19μM.This method is simple and promising for the development of highly sensitive glucose sensors.

Up-regulation of miR-1245 by c-myc targets BRCA2 and impairs DNA repair

BRCA2,a clinical prognostic factor,is significantly up-regulated in mRNA level,while its protein expression is often decreased in sporadic breast cancer.However,how BRCA2 protein expressions are suppressed in these tumors remains unknown.In this study,we demonstrated that miR-1245 directly suppressed BRCA23′-UTR and translation,impaired homologous recombination(HR)-mediated repair,reduced DNA damage-induced Rad51 nuclear foci,and rendered cells hypersensitive to g-irradiation(IR),ul-timately inducing high chromosomal abnormalities in normal breast cells and breast cancer cells.Conversely,inhibiting miR-1245 in breast cancer cells enhanced BRCA2 levels and induced resistance to IR.Furthermore,we demonstrated that c-myc up-regulated miR-1245 expression via direct binding to the miR-1245 promoter,which led to down-regulation of BRCA2 and reduction in HR efficiency.Significantly,miR-1245 levels in primary breast tumors correlated with c-myc overexpression and BRCA2 suppression.These findings uncover a BRCA2 regulatory and signaling pathway in sporadic breast cancer and support a functionally and clinically relevant epigenetic mechanism in cancer pathogenesis.