Stamp collapse in soft lithography

We have studied the so-called roof collapse in soft lithography. Roof collapse is due to the adhesion between the PDMS stamp and substrate, and it may affect the quality of soft lithography. Our analysis accounts for the interactions of multiple punches and the effect of elastic mismatch between the PDMS stamp and substrate. A scaling law among the stamp modulus, punch height and spacing, and work of adhesion between the stamp and substrate is established. Such a scaling law leads to a simple criterion against the unwanted roof collapse. The present study agrees well with the experimental data.     

提升教学魅力,打造一门好课——《材料表面与界面》教学改革探索

《材料表面与界面》为高分子材料与工程专业复合材料方向的限选课。本课程对于学生奠定学科基础、培养学生对复合材料方向的兴趣具有重要的先导作用。笔者以"提升教学魅力,打造一门好课"为改革目标,充分贯彻了"教学内容是教学魅力的根本,教学方法与教学手段是将教学内容高效转化为教学魅力的催化剂"这一指导思想,从教学内容与教学方式两方面进行改革。从教学反馈看,这些改革措施能够改善教学效果,提高学生学习效率,得到了学生的认可。     

Synthesis of silk-like FeS2/NiS2 hybrid nanocrystals with improved reversible oxygen catalytic performance in a Zn-air battery

The development of highly active and stable reversible oxygen electrocatalysts is crucial for improving the efficiency of metal-air battery devices. Herein, an efficient liquid exfoliation strategy was designed for producing silk-like FeS₂/NiS₂ hybrid nanocrystals with enhanced reversible oxygen catalytic performance that displayed excellent properties for Zn-air batteries. Because of the unique silk-like morphology and interface nanocrystal structure, they can catalyze the oxygen evolution reaction (OER) efficiently with a low overpotential of 233 mV at j = 10 mA cm^?2. This is an improvement from the recently reported catalysts in 1.0 M KOH. Meanwhile, the oxygen reduction reaction (ORR) activity of the silk-like FeS₂/NiS₂ hybrid nanocrystals showed an onset potential of 911 mV and a half-wave potential of 640 mV. In addition, the reversible oxygen electrode activity of the silk-like FeS₂/NiS₂ hybrid nanocrystals was calculated to be 0.823 V, based on the potential of the OER and ORR. Further, the homemade rechargeable Zn-air batteries using FeS₂/NiS₂ hybrid nanocrystals as the air-cathode displayed a high open-circuit voltage of 1.25 V for more than 17 h and an excellent rechargeable performance for 25 h. The solid Zn-air batteries exhibited an excellent rechargeable performance for 15 h. This study provided a new method for designing interface nanocrystals with a unique morphology for efficient multifunctional electrocatalysts in electrochemical reactions and renewable energy devices.     

Characterization of the Phosphoryl-Nitrogen Linkages in Histone H4

In earlier work we nave described and partially characterized two histone kinases from regenerating rat liver and other tissues which catalyze the transfer of the γ-phosphoryl group from ATP to histones. The histone phosphates thus formed were observed to be acid-labile and base-stable. In the present study we report on the specificity of one of these enzymes, namely, the kinase which is optimally active at pH 9. This enzyme appears to be relatively specific for the two histidine residues of histone H4. These histidines occur at positions 18 and 75, and both are phosphorylated. However, when regenerating rat liver was the source of enzyme, the product was 1-phosphohistidine, whereas the enzyme from Walker-256 carcinosarcoma catalyzed the formation of 3-phosphohistidine.     

Etude cristallographique de l'arsénotellurure de zirconium quadratique

Single crystals of zirconium arsenotelluride (PbFCl type) have been prepared by direct synthesis from the elements. Chemical analysis gives: $\text{As}\text{Zr}\text{= 1.43 ± 0.02}$ and $\text{Te}\text{Zr}\text{= 0.46 ± 0.01}$, in atoms. Lattice constants are: a = 3.82 ± 0.01 Å and c = 8.17 ± 0.02Å. Experimental density is equal to 7.14 ± 0.05. Unit cell thus contains Zr_2.00As_2.86Te_0.92. The structure has been solved with 227 reflections of a single crystal recorded at room temperature. The final R factor is 0.081, excluding zero reflections. Part of the arsenic atoms fills a site and the remainder is located in a second site, the occupation of which is completed by a part of zirconium atoms. The third site is occupied, but not filled, by the tellurium atoms and the remainder of zirconium atoms.     

Half-sandwich titanium(IV) complexes with Kläui's tripod ligand

Treatment of [Ti(O-i-Pr)(2)Cl(2)] with NaL(OEt) (L(OEt)(-) = [CpCo[P(O)(OEt)(2)](3)](-), Cp = eta(5)-C(5)H(5)) afforded [L(OEt)Ti(O-i-Pr)(2)Cl] that reacted with HCl in ether to give [L(OEt)TiCl(3)] (1). The average Ti-O and Ti-Cl distances in 1 are 1.975 and 2.293 A, respectively. Reaction of titanyl sulfate with NaL(OEt) in water followed by addition of HBF(4) afforded [L(OEt)TiF(3)] (2), the Ti-O and Ti-F distances of which are 2.020(2) and 1.792(2) A, respectively. The Zr(IV) analogue [L(OEt)ZrF(3)] (3) was prepared similarly from zirconyl nitrate, NaL(Oet), and HBF(4) in water. The Zr-O and average Zr-F distances in 3 are 2.139(2) and 1.938(2) A, respectively. Treatment of 1 with tetrachlorocatechol (H(2)Cl(4)cat) afforded [L(OEt)Ti(Cl(4)cat)Cl] (4). The average Ti-O(P), Ti-O(C), and Ti-Cl distances in 4 are 1.972, 1.926, and 2.334 A, respectively. Hydrolysis of 4 in the presence of Et(3)N yielded the mu-oxo dimer [(L(OEt))(2)Ti(2)(Cl(4)cat)(2)(mu-O)] (5). The average Ti-O(P), Ti-O(C), and Ti-O(Ti) distances in 5 are 2.027, 1.926, and 1.7977(9) A. Treatment of 1 with 1,1'-binaphthol (BINOLH(2)) in the presence of Et(3)N afforded [(L(OEt))(2)Ti(2)(mu-O)(2)(mu-BINOL)] x 2BINOLH(2) (6.2BINOLH(2)). Complex 1 is capable of catalyzing ring opening of epoxides with Me(3)SiN(3) under solvent-free conditions presumably via a Ti-azide intermediate.     

Solid- and solution-phase synthesis of vancomycin and vancomycin analogues with activity against vancomycin-resistant bacteria

Vancomycin, the prototypical member of the glycopeptide family of antibiotics, is a clinically used antibiotic employed against a variety of drug-resistant bacterial strains including methicillin-resistant Staphylococcus aureus (MRSA). The recent emergence of vancomycin resistance, viewed as a growing threat to public health, prompted us to initiate a program aimed at restoring the potency of this important antibiotic through chemical manipulation of the vancomycin structure. Herein, we describe the development of synthetic technology based on the design of a novel selenium safety catch linker, application of this technology to a solid-phase semisynthesis of vancomycin, and the solid- and solution-phase synthesis of vancomycin libraries. Biological evaluation of these compound libraries led to the identification of a number of in vitro highly potent antibacterial agents effective against vancomycin-resistant bacteria. In addition to aiding these investigations, the solid-phase chemistry described herein is expected to enhance the power of combinatorial chemistry and facilitate chemical biology and medicinal chemistry studies.     

Stable isotope dilution mass spectrometry for the simultaneous determination of cortisol, cortisone, prednisolone and prednisone in plasma.

A capillary gas chromatographic-mass spectrometric method for the simultaneous determination of cortisol, cortisone, prednisolone and prednisone in human plasma is described. [1,1,19,19,19-2H5]Cortisol, [1,1,19,19,19-2H5]cortisone, [1,19,19,19-2H4]prednisolone and [1,19,19,19-2H4]prednisone were used as internal standards. Formation of the bismethylenedioxy-3-heptafluoro-n-butyryl (BMD-HFB) derivatives made possible the separation of the four corticosteroids with good gas chromatographic behaviour. The new double derivatization has been demonstrated to be of value for sensitive and selective quantification by this technique. Detection was performed by monitoring the molecular ion (M+) of the BMD-HFB derivatives for cortisone and prednisolone, the [M - 18]+ ion for cortisol, and the [M - 30]+ ion for prednisone. The method requires no complex corrections for contributions and provides good accuracy and precision.     

Rapid determination of sulphonamides in milk using liquid chromatographic separation and fluorescamine derivatization.

A simple and selective method is presented for the multiple residue determination of eight sulphonamides in consumers' milk. The drugs are sulphisomidine (ID), sulphadiazine (DZ), sulphamerazine, sulphadimidine, sulphamonomethoxine, sulphamethoxazole, sulphadimethoxine and sulphaquinoxaline (SQ). The milk sample was deproteinized with the same volume of 2 M hydrochloric acid and filtered. A 1-ml volume of the filtrate was mixed with 1 ml each of 1.25 M sodium acetate solution and a buffer (pH 3.0) for derivatization with 0.6 ml of 0.02% fluorescamine solution in acetone. A high-performance liquid chromatographic analysis was carried out on a C18 column with a mobile phase of acetonitrile-2% acetic acid (3:5) at 55 degrees C using a fluorescence detector at an excitation wavelength of 405 nm and an emission wavelength of 495 nm. Average recoveries at fortification levels of 2, 5 and 10 ng/ml were 114%, 109% and 106%, respectively. Relative standard deviations were 1-4% at 10 ng/ml for ID, 5 ng/ml for DZ and SQ and 2.5 ng/ml for the other five sulphonamides. The method was applied to 25 milk samples and all appeared to be free from the drugs.     

Partial purification and characterization of a factor for the enhancement of colony formation in vitro by myeloid progenitor cells.

We have purified a factor, hematopoietic promoting factor (HPF), from porcine kidney extract (PKE), which exhibits a promoting activity on granulocyte/macrophage (GM) colony and burst-forming-unit-erythroid (BFU-E)-derived colony formation by progenitors from murine bone marrow cells in vitro. The addition of HPF resulted in an enhancement of the GM colonies as well as BFU-E-derived colonies, but did not enhance the colony-forming-unit-erythroid (CFU-E)-derived colony formation. HPF was added to the BFU-E cultures together with cytokines, such as recombinant murine interleukin-3 (IL-3), recombinant murine GM colony-stimulating-factor (GM-CSF) and recombinant human G-CSF, which have all been shown to enhance BFU-E growth. The combination of HPF plus these cytokines resulted in an enhancement of benzidine negative colony formation in comparison to the case of each cytokine alone; however, no increase was found on BFU-E colony formation. HPF is able to enhance the granulopoiesis and erythropoiesis in vitro. And the synergistic activity of HPF is significantly affected by the presence of cytokines in the cultures.