Cell culture chip using low-shear mass transport

We have developed a flow cell that allows culturing adherent cells as well as suspended cells in a stable, homogeneous, and low-shear force environment. The device features continuous medium supply and waste exchange. In this paper, a simple and fast protocol for device design, fabrication, and assembly (sealing) based on a poly(dimethylsiloxane) (PMDS)/glass slide hybrid structure is described. The cell culture system performance was monitored, and the effective shear force inside the culture well was also determined. By manipulating the device dimensions and volumetric flow rate, shear stress was controlled during experiments. Cell adhesion, growth, proliferation, and death over long-term culture periods were observed by microscopy. The growth of both endothelial and suspension cells in this device exhibited comparable characteristics to those of traditional approaches. The low-shear culture device significantly reduced shear stress encountered in microfluidic systems, allowing both adherent and suspended cells to be grown in a simple device.     

Reference spectra of important adsorbed organic and inorganic phosphate binding forms for soil P speciation using synchrotron‐based K‐edge XANES spectroscopy

Direct speciation of soil phosphorus (P) by linear combination fitting (LCF) of P K‐edge XANES spectra requires a standard set of spectra representing all major P species supposed to be present in the investigated soil. Here, available spectra of free‐ and cation‐bound inositol hexakisphosphate (IHP), representing organic P, and of Fe, Al and Ca phosphate minerals are supplemented with spectra of adsorbed P binding forms. First, various soil constituents assumed to be potentially relevant for P sorption were compared with respect to their retention efficiency for orthophosphate and IHP at P levels typical for soils. Then, P K‐edge XANES spectra for orthophosphate and IHP retained by the most relevant constituents were acquired. The spectra were compared with each other as well as with spectra of Ca, Al or Fe orthophosphate and IHP precipitates. Orthophosphate and IHP were retained particularly efficiently by ferrihydrite, boehmite, Al‐saturated montmorillonite and Al‐saturated soil organic matter (SOM), but far less efficiently by hematite, Ca‐saturated montmorillonite and Ca‐saturated SOM. P retention by dolomite was negligible. Calcite retained a large portion of the applied IHP, but no orthophosphate. The respective P K‐edge XANES spectra of orthophosphate and IHP adsorbed to ferrihydrite, boehmite, Al‐saturated montmorillonite and Al‐saturated SOM differ from each other. They also are different from the spectra of amorphous FePO₄, amorphous or crystalline AlPO₄, Ca phosphates and free IHP. Inclusion of reference spectra of orthophosphate as well as IHP adsorbed to P‐retaining soil minerals in addition to spectra of free or cation‐bound IHP, AlPO₄, FePO₄ and Ca phosphate minerals in linear combination fitting exercises results in improved fit quality and a more realistic soil P speciation. A standard set of P K‐edge XANES spectra of the most relevant adsorbed P binding forms in soils is presented.     

Synthesis and crystal structure of the dinuclear copper(II) Schiff base complex μ‐hydroxido‐μ‐chlorido‐bis{[bis(trans‐2‐nitrocinnamaldehyde)ethylenediamine]chloridocopper(II)} dichloromethane sesquisolvate

Transition metal complexes of Schiff base ligands have been shown to have particular application in catalysis and magnetism. The chemistry of copper complexes is of interest owing to their importance in biological and industrial processes. The reaction of copper(I) chloride with the bidentate Schiff base N,N′‐bis(trans‐2‐nitrocinnamaldehyde)ethylenediamine {Nca₂en, systematic name: (1E,1′E,2E,2′E)‐N,N′‐(ethane‐1,2‐diyl)bis[3‐(2‐nitrophenyl)prop‐2‐en‐1‐imine]} in a 1:1 molar ratio in dichloromethane without exclusion of air or moisture resulted in the formation of the title complex μ‐chlorido‐μ‐hydroxido‐bis(chlorido{(1E,1′E,2E,2′E)‐N,N′‐(ethane‐1,2‐diyl)bis[3‐(2‐nitrophenyl)prop‐2‐en‐1‐imine]‐κ²N,N′}copper(II)) dichloromethane sesquisolvate, [Cu₂Cl₃(OH)(C₂₀H₁₈N₄O₄)₂]·1.5CH₂Cl₂. The dinuclear complex has a folded four‐membered ring in an unsymmetrical Cu₂OCl₃ core in which the approximate trigonal bipyramidal coordination displays different angular distortions in the equatorial planes of the two Cu^II atoms; the chloride bridge is asymmetric, but the hydroxide bridge is symmetric. The chelate rings of the two Nca₂en ligands have different conformations, leading to a more marked bowing of one of the ligands compared with the other. This is the first reported dinuclear complex, and the first five‐coordinate complex, of the Nca₂en Schiff base ligand. Molecules of the dimer are associated in pairs by ring‐stacking interactions supported by C—H…Cl interactions with solvent molecules; a further ring‐stacking interaction exists between the two Schiff base ligands of each molecule.     

Compact and subelliptic estimates for the $${\overline{\partial}}$$-Neumann operator on C2 pseudoconvex domains

In this paper, we will show that Catlin’s property (P) implies regularity for the -Neumann operator in W ¹ on C ² domains. We will also look at the subelliptic case and derive the natural generalization to C ^k domains when k ≥  2.     

Structural variations in bimetallic sodium-magnesium and sodium-zinc ketimides, and a sodium-zinc alkide-alkoxide-amide: connections to ring-stacking, ring-laddering, and inverse crown concepts

The first sodium-magnesium and sodium-zinc ketimido complexes display contrasting inverse crown ring and pseudo-cubane structures respectively, while a sodium-zinc heterotrianionic alkide-alkoxide-amide adopts a third type of structure with a stepped ladder motif.     

Non-aqueous synthetic methodology for TiW(5) polyoxometalates: protonolysis of [(MeO)TiW(5)O(18)](3-) with alcohols, water and phenols

The tetra-n-butylammonium (TBA) salt of [(MeO)TiW(5)O(18)](3-) 1 was reacted with alcohols ROH to give primary, secondary and tertiary alkoxide derivatives [(RO)TiW(5)O(18)](3-) (R = Et 2, (i)Pr 3 and (t)Bu 4), whilst hydrolysis afforded [(mu-O)(TiW(5)O(18))(2)](6-) 5 rather than the hydroxo derivative (R = H). In reactions with (i)PrOH and (t)BuOH, impurity peaks observed at 1015 and 1020 ppm in the (17)O NMR spectra indicate alkoxide degradation and Ti=O bond formation via reactions analogous to those occurring at the surfaces of solid heteropolyacids. Aryloxides [(ArO)TiW(5)O(18)](3-) were prepared by reacting 1 with phenols ArOH (Ar = C(6)H(5) 6, C(6)H(4)Me-4 7, C(6)H(4)(t)Bu-4 8, C(6)H(4)OH-4 9, C(6)H(4)OH-3 10, C(6)H(3)(OH)(2)-3,5 11 and C(6)H(4)CHO-2 13). TiW(5)O(18) units were linked by reacting 1 with 9 to give [(mu-1,4-OC(6)H(4)O)(TiW(5)O(18))(2)](6-) 12. (17)O and (183)W NMR spectra are reported and X-ray crystal structures were obtained for TBA salts of anions 3-10 and 13, which showed that the titanium is six-coordinate in all cases. Reactions were monitored by (1)H NMR, including a 2D-EXSY study of methoxo exchange, and the slow rates observed are probably associated with the reluctance of titanium in these anions to achieve seven-coordination.     

Luminescent Pt(II)(bipyridyl)(diacetylide) chromophores with pendant binding sites as energy donors for sensitised near-infrared emission from lanthanides: structures and photophysics of Pt(II)/Ln(III) assemblies

The complexes [Pt(bipy){CC-(4-pyridyl)}(2)] (1) and [Pt(tBu(2)bipy){CC-(4-pyridyl)}(2)] (2) and [Pt(tBu(2)-bipy)(CC-phen)(2)] (3) all contain a Pt(bipy)(diacetylide) core with pendant 4-pyridyl (1 and 2) or phenanthroline (3) units which can be coordinated to {Ln(diketonate)(3)} fragments (Ln = a lanthanide) to make covalently-linked Pt(II)/Ln(III) polynuclear assemblies in which the Pt(II) chromophore, absorbing in the visible region, can be used to sensitise near-infrared luminescence from the Ln(III) centres. For 1 and 2 one-dimensional coordination polymers [1Ln(tta)(3)](infinity) and [2Ln(hfac)(3)](infinity) are formed, whereas 3 forms trinuclear adducts [3{Ln(hfac)(3)}(2)] (tta=anion of thenoyl-trifluoroacetone; hfac=anion of hexafluoroacetylacetone). Complexes 1-3 show typical Pt(II)-based (3)MLCT luminescence in solution at approximately 510 nm, but in the coordination polymers [1Ln(tta)(3)](infinity) and [2Ln(hfac)(3)](infinity) the presence of stacked pairs of Pt(II) units with short PtPt distances means that the chromophores have (3)MMLCT character and emit at lower energy ( approximately 630 nm). Photophysical studies in solution and in the solid state show that the (3)MMLCT luminescence in [1Ln(tta)(3)](infinity) and [2Ln(hfac)(3)](infinity) in the solid state, and the (3)MLCT emission of [3{Ln(hfac)(3)}(2)] in solution and the solid state, is quenched by Pt-->Ln energy transfer when the lanthanide has low-energy f-f excited states which can act as energy acceptors (Ln=Yb, Nd, Er, Pr). This results in sensitised near-infrared luminescence from the Ln(III) units. The extent of quenching of the Pt(II)-based emission, and the Pt-->Ln energy-transfer rates, can vary over a wide range according to how effective each Ln(III) ion is at acting as an energy acceptor, with Yb(III) usually providing the least quenching (slowest Pt-->Ln energy transfer) and either Nd(III) or Er(III) providing the most (fastest Pt-->Ln energy transfer) according to which one has the best overlap of its f-f absorption manifold with the Pt(II)-based luminescence.     

Geometry and combinatorics of Julia sets of real quadratic maps

For real a correspondence is made between the Julia setB forz(z–)², in the hyperbolic case, and the set of-chains±(±(±..., with the aid of Cremer's theorem. It is shown how a number of features ofB can be understood in terms of-chains. The structure ofB is determined by certain equivalence classes of-chains, fixed by orders of visitation of certain real cycles; and the bifurcation history of a given cycle can be conveniently computed via the combinatorics of-chains. The functional equations obeyed by attractive cycles are investigated, and their relation to-chains is given. The first cascade of period-doubling bifurcations is described from the point of view of the associated Julia sets and-chains. Certain Julia sets associated with the Feigenbaum function and some theorems of Lanford are discussed.Supported by NSF grant No. MCS-8104862.Supported by NSF grant No. MCS-8203325.     

Laser-induced fluorescence of seeded nitric oxide as a flame thermometer

Received: 10 June 1997/Revised version: 25 November 1997