Hydrodynamic focusing—a versatile tool

The control of hydrodynamic focusing in a microchannel has inspired new approaches for microfluidic mixing, separations, sensors, cell analysis, and microfabrication. Achieving a flat interface between the focusing and focused fluids is dependent on Reynolds number and device geometry, and many hydrodynamic focusing systems can benefit from this understanding. For applications where a specific cross-sectional shape is desired for the focused flow, advection generated by grooved structures in the channel walls can be used to define the shape of the focused flow. Relative flow rates of the focused flow and focusing streams can be manipulated to control the cross-sectional area of the focused flows. This paper discusses the principles for defining the shape of the interface between the focused and focusing fluids and provides examples from our lab that use hydrodynamic focusing for impedance-based sensors, flow cytometry, and microfabrication to illustrate the breadth of opportunities for introducing new capabilities into microfluidic systems. We evaluate each example for the advantages and limitations integral to utilization of hydrodynamic focusing for that particular application.     

1,3,3a,5—四苯基—3a,4,5,11—四氢—3H,6H—1,2,4—三唑并（ …

通过２，４－二苯基－２，３－二氢－１Ｈ－１，５－苯并二氮杂Ｚｕｏ与苯甲酰氯苯腙的（２＋３）环加成反应制备了标题化合物，用Ｘ射线单晶衍射仪测定了其晶体结构，晶体属正交晶系，空间群为Ｆｄｄ２．晶胞参数；ａ＝１．７６２８（４）ｎｍ，ｂ＝５．７５１２（１２）ｎｍ，ｃ＝１．０２２７ｎｍ，Ｖ＝１０．３６８（５）ｎｍ＾３，Ｚ＝１６，Ｄｃ＝１．２６２ｇ．ｃｍ＾－３，μ＝０．０７５ｍｍ＾－１，Ｆ（０００）＝４１６０     

Solid-state potentiometric gas sensors—a supplement

Potentiometric in situ gas probes with solid electrolytes were described for the first time 50 years ago. It is the intention of the present communication to give some additions on oxygen sensors in reducing gases which have been neglected in a recent review (J Solid State Electrochem, 13:3, 2009). Today, the most frequently used solid electrolyte gas sensors are the lambda probes. In their electrodes is a very quick change between gas phases with excess of oxygen and excess of components of reducing gases. Changes in the interpretation of the mechanism of the interaction between gas and solid electrolyte in the gas sensors are discussed. At low temperatures, mixed potentials appear which have to be expected at oxygen electrodes also with air and technical oxygen, if these gases are not cleaned particularly. Among the CO₂ sensors, the system with the reference electrode SiO₂, Na₂Si₂O₅ on ß-alumina must be mentioned. This system has special advantages and in the commercially available device it reaches excellent long-term stability. A report about long-term measurements of SO₂ traces in air is worth mentioning. For measurements of SO₂ in industrial gases, Westinghouse has offered a complicated system in the 1980s.     

L-selectin — a signalling receptor for lipopolysaccharide

The activation of leukocytes by bacterial cell-wall lipopolysaccharide contributes to the pathogenesis of septic shock. We propose that in neutrophils, and possibly other leukocytes, L-selectin can act as a low-affinity lipopolysaccharide receptor. Inhibitors of L-selectin may therefore be of therapeutic value in treating this life-threatening condition.     

Anatase—a pigment in ancient artwork or a modern usurper?

Fragments of wall-paintings from Roman villas in Easton Maudit, which date from ca 150 AD have been studied by Raman spectroscopy. An intact ancient Roman paint pot discovered in the remains of a villa in Castor, Cambridgeshire, still containing a mixture of white and red pigment was also analysed and the pigments identified as haematite and anatase. The discovery of anatase in the intact artist’s paint pot, particularly, and also on fragments of broken paint pots from the Easton Maudit villa site, is a unique contribution to current knowledge of ancient European pigment history, because the presence of this mineral has not hitherto been recognised fully in an ancient artist’s palette. The relative spectral response of anatase and haematite in the Raman data is compared with that of anatase and other red pigments such as minium, cinnabar, and litharge.     

电子束蒸发a—Si1—xGdx薄膜的光吸收

研究了电子束蒸发的掺稀土非晶硅基薄膜材料a—Si_(1-x)Gd_x的光吸收特性。这类材料的组分变化对近红外长波吸收特性的影响灵敏,在0.1at％相似文献   

Dehydrodimers of arylaldoxime——a convenient source of iminoxy radicals

Arylaldoxime dehydrodimers 3a—1 have been prepared from the corresponding oximes 1a—1by using (HCrO_4)_2(Py)_4Co as oxidant.Their structures were assigned to be bisnitrone by XPS studies.ESR studies of 3a—1 in hot chloroform show that iminoxy radicals 2a—1 are formed.Therefore thedehydrodimers can provide a convenient source of these radicals.     

Poly-N-benzylaniline prepared in perchloric acid——a new soluble semiconducting polymer

Chemical or electrochemical oxidation of N-benzylaniline in perehloric acid solution yieldsa highly colored polymer——poly-N-benzylaniline (PBAn).The polymer has good solubility in a num-ber of organic solvents in either acid or base form.At room temperature,conductivity measurementson pressed pellets of the acid form PBAn give a conductivity of 9.3×10~(-6) S·cm~(-1).The soluble polymerwas analyzed using a variety of common experimental techniques including UV-vis,IR,NMR,ESRspectroscopy,elemental analysis and electrochemieal analysis.All experimental results showed thatPBAn has a structure similar to polyaniline with the elimination of some benzyl groups.