Arrays of horizontally-oriented mini-reservoirs generate steady microfluidic flows for continuous perfusion cell culture and gradient generation

This paper describes the use of arrays of horizontally-oriented reservoirs to deliver liquids through microchannels at a constant flow rate over extended periods of time (hours to days). The horizontal orientation maintains a constant hydraulic pressure drop across microfluidic channels even as the volumes of liquids within the reservoirs change over time. For a given channel-reservoir system, the magnitude of the flow velocity depends linearly on the height difference between reservoirs. The simple structure and operation mechanism make this pumping system versatile. A one-inlet-one-outlet system was used to continuously deliver media for perfusion cell culture, and an array of inlet reservoirs coupled to an outlet reservoir via microchannels was used to drive flows of multiple laminar streams. The parallel pumping scheme conveniently generated various smooth and step concentration gradients, and allowed evaluation of the effect of colchicine on myoblasts. Since the reservoir arrays are configured to be compatible with commercialized multichannel pipettors designed for 96 well plate handling, this simple pumping scheme is envisioned to be broadly useful for medium to high throughput microfluidic perfusion cell culture assays, cell migration assays, multiple laminar flow drug tests, and any other applications needing multiple microfluidic streams.     

Schur complement preconditioners for anisotropic problems

We present two new variants of Schur complement domain decompositionpreconditioners suitable for 2D anisotropic problems. Thesevariants are based on adaptations of the probing idea, describedby Chan et al (1992 Fifth Int. Symp. on Domain DecompositionMethods for Partial Differential Equations, Philadelphia: SIAM,pp 236-249), used in conjunction with a coarse grid approximationas introduced by Bramble et al (1986 Math. Comput. 47, 103-134).The new methods are specifically designed for situations wherethe coupling between neighbouring interfaces is stronger thanthe coupling within an interface. Taking into account this strongcoupling, one variant uses a multicolour probing technique toavoid distortion in the probe approximations that appear whenusing the method proposed by Chan et al. The second techniqueuses additional probe matrices to approximate not only the couplingwithin the interfaces but also the coupling between interfacepoints across the subdomains. This latter procedure looks somewhatlike an alternating line relaxation method for anisotropic problems,see Brandt (1977 Math. Comput.. 31, 333-390). To assess therelevance of the new preconditioners, we compare their numericalbehaviour with well known robust preconditioners such as thebalanced Neumann-Neumann method proposed by Mandel (1993 Commun.Numer. Methods Eng.. 9, 233-241).     

评《马氏决策过程》

（《马氏决策过程》,侯振挺、郭先平著,长沙,湖南科技出版社,1997,中文版,386页,定价：28元）马尔可夫决策过程是概率论的运筹学的理论研究和实际应用中极其重要的领域之一．随着中国和国际上对马尔可夫决策过程（MarkovDecisionProcesses,简记为MDP）研究的新进展,许     

Simulation model for anomalous precession of the perihelion of mercury's orbit

The ‘anomalous perihelion precession’ of Mercury, announced by Le Verrier in 1859, was a highly controversial topic for more than half a century and invoked many alternative theories until 1916, when Einstein presented his theory of general relativity as an alternative theory of gravitation and showed perihelion precession to be one of its potential manifestations. As perihelion precession was a directly derived result of the full General Theory and not just the Equivalence Principle, Einstein viewed it as the most critical test of his theory. This paper presents the computed value of the anomalous perihelion precession of Mercury's orbit using a new relativistic simulation model that employs a simple transformation factor for mass and time, proposed in an earlier paper. This computed value compares well with the prediction of general relativity and is, also, in complete agreement with the observed value within its range of uncertainty. No general relativistic equations have been used for computing the results presented in this paper.     

Locally Desarguesian spaces

In Riemannian spaces, locally Desarguesian spaces have constant curvature and are therefore locally symmetric. This does not hold for Finsler spaces, so that locally Desarguesian spaces represent a generalization other than the obvious one we studied previously of (certain) Riemannian symmetric spaces. In this paper we discuss them in detail; as an example of the results obtained we mention that a simply connected locally Desarguesian space without conjugate points is globally Desarguesian. Applications are then given to spaces which are locally symmetric in a wider sense. We also study (and in Minkowski spaces determine exactly) the properties of functions which measure the distance of a point from those on a line.     

Flatness of bisectors and the symmetry of distance

H. Busemann proved that the elementary spaces are characterized by the flatness of bisectors among all G-spaces with symmetric distance. In this paper we prove that in two dimensional straight G-spaces with a not necessarily symmetric distance the symmetry of distance is in fact implied by the flatness of bisectors. Thus Busemann's characterizations of the euclidean and hyperbolic planes are shown to hold among all straight two dimensional G-spaces with a not necessarily symmetric distance.     

Thermal behaviour of fibrous zeolites of the natrolite group

The western region of the Deccan Volcanic Province (DVP) is constituted of tholeiitic lava flows. They host numerous cavities, varying in size and shape, largely occupied by zeolites and a variety of secondary minerals, amongst which the fibrous zeolites (natrolite group), are particularly gorgeous and attractive. Scolecite and mesolite are the only two members commonly occurring in this region. Our data on their thermal behaviour significantly differs from that reported in previous literature. Scolecite, Ca₈(Al₁₆Si₂₄O₈₀)·24H₂O shows three distinct steps instead of two and water loss is observed even beyond 550°C. It is held that the first step corresponds to the expulsion of water from the site farthest away from Ca and the next two steps in succession correspond to the two sites nearer to Ca. Mesolite, Na₁₆Ca₁₆(Al₄₈Si₇₂O₂₄₀)· 64H₂O has much more complex behaviour with four or five steps of water expulsion and a major loss around 248–270°C in a double reaction attributed here to the expulsion of water from scolecite type channels. It is further held that the natrolite type channels are emptied in further steps. Loss of water in steps even beyond 400°C is particularly noted and such reactions are well reflected in the TG and the DTG. Peak temperature dependence on sample amounts is also evident. Successive phase transformations above 700°C, up to 1000°C are reflected in the DTA curves.