Hua Zhang

Bio: Hua Zhang is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topics: Medicine & Graphene. The author has an hindex of 163, co-authored 1503 publications receiving 116769 citations. Previous affiliations of Hua Zhang include Shenzhen University & Zhengzhou University.

DPN-Generated Nanostructures Made of Gold, Silver, and Palladium

Abstract: Dip-pen nanolithography (DPN) has been used to generate resist layers on Au, Ag, and Pd that when combined with wet-chemical etching can lead to nanostructures with deliberately designed shapes and sizes. Monolayers of mercaptohexadecanoic acid (MHA) or octadecanethiol (ODT), patterned by DPN, were explored as etch resists. They work comparably well on Au and Ag, but ODT is the superior material for Pd. MHA seems to attract the FeCl3 etchant and results in nonuniform etching of the underlying Pd substrate. Dots, lines, triangles, and circles, ranging in size from sub-100 to several hundred nanometers have been fabricated on Si/SiOx substrates. These results show how one can use DPN as an alternative to more complex and costly procedures such as electron beam lithography to generate nanostructures from inorganic materials.

Hierarchical TiO2 nanobelts@MnO2 ultrathin nanoflakes core–shell array electrode materials for supercapacitors

Abstract: Hierarchical TiO2 nanobelts@MnO2 ultrathin nanoflakes core–shell arrays (TiO2@MnO2 NBAs) have been fabricated on a Ti foil substrate by hydrothermal approach and further investigated as the electrode for a supercapacitor. Their electrochemical properties were examined using cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) in a three-electrode cell. The experimental observations clearly show that the fabricated TiO2@MnO2 NBAs electrode possesses superior rate capability and outstanding cycling performance due to its rationally designed nanostructure. A specific capacitance as high as 557.6 F g−1 is obtained at a scan rate of 200 mV s−1 (454.2 F g−1 at a current density of 200 mA g−1) in 1 M Na2SO4 aqueous solution. The energy density and power density measured at 2 A g−1 are 7.5 Wh kg−1 and 1 kW kg−1 respectively, demonstrating its good rate capability. In addition, the composite TiO2@MnO2 NBAs electrode shows excellent long-term cyclic stability. The fabrication method presented here is facile, cost-effective and scalable, which may open a new pathway for real device applications.

Adult human and mouse ovaries lack DDX4-expressing functional oogonial stem cells.

Abstract: The generally accepted viewpoint for more than 50 years has been that the number of oocytes is fixed in fetal or neonatal ovaries, and therefore, oocytes cannot renew themselves in postnatal or adult life. Over the past decade, however, the traditional viewpoint has been challenged by a number of investigators who have presented evidence that postnatal follicular renewal occurs in mammals, and that mitotically active oogonial stem cells (OSCs) exist in postnatal mouse ovaries. Health, Inc. All rights reserved. 30 Obstetrical and Gynecological Survey This letter to the editor presents experimental evidence that disputes the existence of mitotically active OSC in postnatal mouse ovaries. The results presented here are the summary of research conducted independently in 4 laboratories. A previous study (White et al.Nat Med. 2012;18:413–421) reported that OSCs could be purified from adult human and mouse ovaries by use of DEAD box polypeptide 4 (DDX4) antibody–based fluorescence-activated cell sorting (FACS), and that after in vitro manipulation, these isolated OSCs could form oocytes. Based on the well-established cytoplasmic location of DDX4, the use of this protein as a cell surface marker is controversial. Using the same DDX4 antibody–based FACS approach as in the White et al study, the investigators isolated a population of cells from human ovarian cortical tissue biopsied from 16 fertile reproductive-age women who had had at least 1 previous live birth. No DDX4 messenger RNA (mRNA) expression was detected using quantitative polymerase chain reaction in these cells or by a more sensitive single-cell mRNA sequencing analysis that could detect low expression of DDX4. In additional experiments, the sorted human ovarian cells were cultured as described in the previous study. Although no DDX4 expression was detected in the cultured DDX4-positive cells (cultured-POS) or cultured DDX4-negative cells (cultured-NEG) by immunofluorescence staining, the cultured-POS cells and cultured-NEG cells both bound tightly to the DDX4-specific antibody in FACS and became DDX4-positive after culture. The previous study had reported that oocytes enclosed in follicles regenerated 1 week after the DDX4-positive human OSCs were injected into human ovarian cortical tissues that were subsequently xenografted into female severe combined immunodeficient mice. The investigators repeated this experiment and labeled the cultured-POS cells with stable enhanced green fluorescent protein (EGFP) expression. After culturing and expanding this cell population, EGFP-expressing cultured-POS cells were injected into human ovarian cortical tissue biopsies, and these cortical tissues were then xenografted into female severe combined immunodeficient mice for further growth. Grafts were analyzed 1 week, 2 weeks, and 4 weeks after transplantation of the EGFP–cultured-POS cells into the human cortical tissues. The results of this experiment showed that EGFP-positive cells could be observed in the vicinity of the injection sites, but the absence of any EGFP-positive oocytes demonstrated that the DDX4-positive human cells obtained with the DDX4 antibody are not functional stem cells and cannot regenerate oocytes. To confirm these findings that the DDX4-specific antibody–based FACS does not select for a specific cell population expressing DDX4, the same FACS was performed with mouse cells from several organs (including adult liver, spleen, and kidney) that do not express DDX4. DDX4-positive cell populations were obtained from cells of these organs, which provide additional evidence that use of the DDX4-specific antibody using the FACS protocol (critical in purifying the reported OSCs) does not select for DDX4-expressing cells. These findings provide evidence that supports the traditional view that no postnatal follicular renewal occurs in mammals, and no mitotically active DDX4-expressing female germline progenitors exist in postnatal mouse ovaries.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

Abstract: Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.