Trapping cells on a stretchable microwell array for single-cell analysis

There is a need for a technology that can be incorporated into routine laboratory procedures to obtain a continuous, quantitative, fluorescence-based measurement of the dynamic behaviors of numerous individual living cells in parallel, while allowing other manipulations, such as staining, rinsing, and even retrieval of targeted cells. Here, we report a simple, low-cost microarray platform that can trap cells for dynamic single-cell analysis of mammalian cells. The elasticity of polydimethylsiloxane (PDMS) was utilized to trap tens of thousands of cells on an array. The PDMS microwell array was stretched by a tube through which cells were loaded on the array. Cells were trapped on the array by removal of the tube and relaxation of the PDMS. Once that was accomplished, the cells remained trapped on the array without continuous application of an external force and permitted subsequent manipulations, such as staining, rinsing, imaging, and even isolation of targeted cells. We demonstrate the utility of this platform by multicolor analysis of trapped cells and monitoring in individual cells real-time calcium flux after exposure to the calcium ionophore ionomycin. Additionally, a proof of concept for target cell isolation was demonstrated by using a microneedle to locally deform the PDMS membrane in order to retrieve a particular cell from the array.     

Alternating projections in CAT(0) spaces

By using recently developed theory which extends the idea of weak convergence into CAT(0) space we prove the convergence of the alternating projection method for convex closed subsets of a CAT(0) space. Given the right notion of weak convergence it turns out that the generalization of the well-known results in Hilbert spaces is straightforward and allows the use of the method in a nonlinear setting. As an application, we use the alternating projection method to minimize convex functionals on a CAT(0) space.     

Experimental investigation of two-phase discharge from a stratified region through a small branch mounted on an inclined wall

Experimental data are presented for the mass flow rate and quality of two-phase discharge through a small branch of diameter d (=6.35 mm) attached normally to an inclined flat plane. The flat plane was situated in a large tank containing a stratified mixture of air and water under pressure (316 kPa) and at room temperature. The plane was inclined through various angles (θ) in increments of 30°, from the outlet-branch orientation being vertically upward through the horizontal to vertically downward. The bulk of the data correspond to seven inclination angles and two test-section-to-separator pressure differences (ΔP) of 11.0 and 115.5 kPa, and for each combination of θ and ΔP, the mass flow rate and quality were measured at different values of the interface level (h) between the onsets of gas and liquid entrainment. Four additional data sets were generated for other values of ΔP in order to confirm certain trends. Influences of these independent variables on the mass flow rate and quality are discussed and normalized plots are presented showing that the data can be collapsed for a wide range of conditions. Comparisons are made between the present data and previous correlations/models and new empirical correlations are formulated and shown to be capable of predicting the present data with good accuracy.     

Synthesis of 3-oxo-δ-lactones via hetero-Diels-Alder reactions

The hetero-Diels-Alder reaction between aldehydes, 2, and bis-1,1-dimethoxy-3-trimethyl-1-siloxy-1,3-butadiene, 1, produces 2-methoxy-5,6-dihydro-γ-pyrones, 4, which are subsequently hydrolyzed to afford substituted 3-oxo-δ-lactones, 5, in high yields, providing a new and efficient approach to these synthetically useful intermediates.     

On the electric current from electrodes in a magnetized semiconductor film

The problem on the electric current from electrodes in a magnetizedsemiconductor film is reduced to the skew derivative problemfor the Laplace equation outside cuts in a plane. The problemfor the Laplace equation is studied under different conditionsat infinity, which have a certain physical meaning. With thehelp of potential theory, the skew derivative problem is reducedto a Fredholm integral equation of the second kind, which isuniquely solvable. The Neumann problem for the Laplace equationin the exterior of cuts in a plane is a particular case of ourproblem.     

Heliuim-3 mass spectrometry for low-level tritium analysis of environmental samples

Helium-3 (³He) mass spectrometry for the analysis of low-level tritium (³H) concentrations (0.5 to 5 Bq·l^–1) in environmental sample matrices was compared with conventional low-level -decay counting methods. The mass-spectrometry method compared favorably, equalling or surpassing conventional decay-counting methods with respect to most criteria. Additional research and method refinements may make³He mass spectrometry the method of choice for routine, low-level to very-low-level (L<0.5 Bq·l^–1)³H measurements in a wide variety of environmental samples in the future.     

Seperation of neptunium from irradiated uranium targets

A new chemical method based in two separation steps was developed to isolate²³⁵Np from uranium targets irradiated with charged particles. Neptunium and plutonium are separated from uranium and most of the fission products by ion exchange. Then, neptunium is isolated from plutonium and remaining contaminants by extraction chromatography with tributyl phosphate in hydrochloric acid solution. High decontamination was achieved.     

Relaxation of H2O from its /04>- vibrational state in collisions with H2O, Ar, H2, N2, and O2

We report rate coefficients at 293 K for the collisional relaxation of H2O molecules from the highly excited /04>(+/-) vibrational states in collisions with H2O, Ar, H2, N2, and O2. In our experiments, the mid R:04(-) state is populated by direct absorption of radiation from a pulsed dye laser tuned to approximately 719 nm. Evolution of the population in the (/04>(+/-)) levels is observed using the combination of a frequency-quadrupled Nd:YAG laser, which selectively photolyses H2O(/04>(+/-)), and a frequency-doubled dye laser, which observes the OH(v=0) produced by photodissociation via laser-induced fluorescence. The delay between the pulse from the pump laser and those from the photolysis and probe lasers was systematically varied to generate kinetic decays. The rate coefficients for relaxation of H2O(/04>(+/-)) obtained from these experiments, in units of cm3 molecule(-1) s(-1), are: k(H2O)=(4.1+/-1.2) x 10(-10), k(Ar)=(4.9+/-1.1) x 10(-12), k(H2)=(6.8+/-1.1) x 10(-12), k(N2)=(7.7+/-1.5) x 10(-12), k(O2)=(6.7+/-1.4) x 10(-12). The implications of these results for our previous reports of rate constants for the removal of H2O molecules in selected vibrational states by collisions with H atoms (P. W. Barnes et al., Faraday Discuss. Chem. Soc. 113, 167 (1999) and P. W. Barnes et al., J. Chem. Phys. 115, 4586 (2001).) are fully discussed.     

Dyes in Liquid Crystals: Experimental and Computational Studies of a Guest–Host System Based on a Combined DFT and MD Approach

Practical applications of guest–host liquid crystal systems are critically dependent on the alignment of the guest species within the liquid crystal host. UV/Vis absorption spectroscopy shows that the 1,5‐dihydroxy‐2,6‐bis‐(4‐propylphenyl)‐9,10‐anthraquinone dye aligns within the E7 nematic host, giving an experimental dichroic ratio of 9.40 and dye order parameter of 0.74. This alignment was modelled by using a combination of density functional theory (DFT) and molecular dynamics (MD) computational approaches that do not require the input of experimental data. Time‐dependent DFT calculations show that the electronic transition dipole moment is highly aligned with the long molecular axis of the dye. Fully atomistic MD simulations show that the long axis of the dye is less highly aligned within the E7 host, indicating that this contribution limits the overall dye alignment and, thereby, the potential practical applications of this particular system. Importantly, this study demonstrates an experimental and combined DFT and MD computational approach that may be applied generally to guest–host systems, providing a potential route to their rational design.