Integration of a macro/micro architectured compartmentalised neuronal culture device using a rapid prototyping moulding process

The rapid prototyping of a reversible and one step moulded compartmentalised neuron glass/PDMS device with a thin wall barrier directly adjacent to the reservoirs is presented. A simple moulding technique to produce these devices results in a barrier of 560 μm where the 3 μm deep by 8 μm wide channels can be reversibly fabricated in either the glass base or PDMS compartmentalised mould depending on the type of application required. Using glass substrates with commercially laser engraved microchannels, both the PDMS planar and PDMS channelled device can be easily fabricated in a standard laboratory. The compartmentalised device has several advantages including good experimental accessibility and versatility with a variety of end user applications.     

Oxygen transfer processes in (La,Sr)MnO3/Y2O3-stabilized ZrO2 cathodes: an impedance spectroscopy study

Impedance spectroscopy was used to study the oxygen reaction kinetics of La_0.8Sr_0.2MnO₃ (LSM)-based electrodes on Y₂O₃-stabilized ZrO₂ (YSZ) electrolytes. Three types of electrodes were studied: pure LSM, LSM–YSZ composites, and LSM/LSM–YSZ bilayers. The electrodes were formed by spin coating and sintering on single-crystal YSZ substrates. Measurements were taken at temperatures ranging from 550 to 850°C and oxygen partial pressures from 1×10⁻³ to 1 atm. An arc whose resistance R_el had a high activation energy, E_a=1.61±0.05 eV, and a weak oxygen partial pressure dependence, (P_O2)^−1/6, was observed for the LSM electrodes. A similar arc was observed for LSM–YSZ electrodes, where R_el(P_O2)^−0.29 and the activation energy was 1.49±0.02 eV. The combination of a high activation energy and a weak P_O2 dependence was attributed to oxygen dissociation and adsorption rate-limiting steps for both types of electrodes. LSM–YSZ composite cathodes showed substantially lower overall interfacial resistance values than LSM, but exhibited an additional arc attributed to the resistance of YSZ grain boundaries within the LSM–YSZ. At 850°C and low P_O2, an additional arc was observed with size varying as (P_O2)^−0.80 for LSM and (P_O2)^−0.57 for LSM–YSZ, suggesting that diffusion had become an additional rate limiting step. Bilayer LSM/LSM–YSZ electrodes yielded results intermediate between LSM and LSM–YSZ. The results showed that most of the improvement in electrode performance was achieved for a LSM–YSZ layer only ≈2 μm thick. However, a decrease in the grain-boundary resistance would produce much better performance in thicker LSM–YSZ electrodes.     

A long-wavelength biolabeling reagent based on the oxonol fluorophore

A red fluorescent dye of the oxonol class, bis-[1-(carboxymethyl)barbituric acid-(5)]-pentamethinoxonol, has been synthesized and, in the form of the succinimidyl active ester, has been applied to antibody labeling for application to flow cytometry and to imaging of tissue sections. The new dye, named CMOX (for carboxymethyloxonol), shows maximum excitation at 583 nm and emission at 611 nm, with a quantum yield of 0.2 in aqueous buffer and methanol. Antibodies labeled with the new dye show favorable brightness, photostability, and low levels of nonspecific binding.     

Rate constants for the reaction of OH radicals with 2-methyl-2-butene over the temperature range 297–425 K

Absolute rate constants, k₂, for the reaction of OH radicals with 2-methyl-2-butene have been determined over the temperature range 297–425 K using a flash photolysis-resonance fluorescence technique. The Arrhenius expression obtained was k₂ = 3.6 × 10^?11 exp [(450 ± 400)/RT] cm³ molecule^?1 s^?1.     

Charge density waves effects on the phonon modes of 1T-TaS2

The effects of lattice distortion driven charge density waves on the 1T polytype of TaS₂ are reported. The results of a raman study of this transition metal dichalcogenide show features consistent with results previously reported using resistivity and electron diffraction techniques. The possibility of the presence of a phason mode in the raman spectra is suggested and the temperature dependence of this mode is fitted to the expected functional form.     

Luminescence of the hydrolysis products of Th(IV)

Raising the pH of an aqueous solution of thorium nitrate results in the precipitation of a hydrated thorium oxide. At room temperature this material does not exhibit any emissive properties, but upon cooling to 77 K a strong green luminescence can be observed. The emission spectrum is fairly broad, and is characterized by an emission lifetime of 125 μs. Calcination of the hydrolysis product produces an anhydrous thorium oxide which is not luminescent at any temperature. Through the production of a series of mixed lanthanide/thorium hydrolysis products, it was established that the luminescent species was a clustered thorium compound. Sensitization of Eu(III) emission by the thorium hydrolysis product was observed.     

Iterative solution of a non-linear boundary value problem for a rotating string

The problem of determining the motion of a rotating inextensible string of length l, free at one end and fixed at the other can, under certain assumptions, be treated by solving a non-linear boundary value problem. p]In this paper, two Picard-type iterative schemes are constructed and the sequences generated are proved to converge to a positive solution of that non-linear boundary value problem. Additionally, one sequence converges to the solution from above, the other from below. Moreover, the iterative scheme can be used to solve the inverse problem of determining the angular velocity of the rotating string, given two observations (at one point in time) of position of the string.     

Positive mass theorems for black holes

We extend Witten's proof of the positive mass theorem at spacelike infinity to show that the mass is positive for initial data on an asymptotically flat spatial hypersurface Σ which is regular outside an apparent horizonH. In addition, we prove that if a black hole has electromagnetic charge, then the mass is greater than the modulus of the charge. These results are also valid for the Bondi mass at null infinity. Finally, in the case of the Einstein equation with a negative cosmological constant, we show that a suitably defined mass is positive for data on an asymptotically anti-de Sitter surface Σ which is regular outside an apparent horizon.