Active 3-D microscaffold system with fluid perfusion for culturing in vitro neuronal networks

This work demonstrated the design, fabrication, packaging, and characterization of an active microscaffold system with fluid perfusion/nutrient delivery functionalities for culturing in vitro neuronal networks from dissociated hippocampal rat pup neurons. The active microscaffold consisted of an 8 x 8 array of hollow, microfabricated, SU-8 towers (1.0 mm or 1.5 mm in height), with integrated, horizontal, SU-8 cross-members that connect adjacent towers, thus forming a 3-D grid that is conducive to branching, growth, and increased network formation of dissociated hippocampal neurons. Each microtower in the microscaffold system contained a hollow channel and multiple fluid ports for media delivery and perfusion of nutrients to the in vitro neuronal network growing within the microscaffold system. Additionally, there were two exposed Au electrodes on the outer wall of each microtower at varying heights (with insulated leads running within the microtower walls), which will later allow for integration of electrical stimulation/recording functionalities into the active microscaffold system. However, characterization of the stimulation/recording electrodes was not included in the scope of this paper. Design, fabrication, fluid packaging, and characterization of the active microscaffold system were performed. Furthermore, use of the active microscaffold system was demonstrated by culturing primary hippocampal embryonic rat pup neurons, and characterizing cell viability within the microscaffold system.     

Quantitative analysis of arterial spin labeling FMRI data using a general linear model

Arterial spin labeling techniques can yield quantitative measures of perfusion by fitting a kinetic model to difference images (tagged-control). Because of the noisy nature of the difference images investigators typically average a large number of tagged versus control difference measurements over long periods of time. This averaging requires that the perfusion signal be at a steady state and not at the transitions between active and baseline states in order to quantitatively estimate activation induced perfusion. This can be an impediment for functional magnetic resonance imaging task experiments. In this work, we introduce a general linear model (GLM) that specifies Blood Oxygenation Level Dependent (BOLD) effects and arterial spin labeling modulation effects and translate them into meaningful, quantitative measures of perfusion by using standard tracer kinetic models. We show that there is a strong association between the perfusion values using our GLM method and the traditional subtraction method, but that our GLM method is more robust to noise.     

Energy and angular momentum transfer in atom-diatom collisions from polarized laser fluorescence

We report a study of collisional reorientation of diatomic lithium molecules by rare gas atoms using high resolution circularly polarized laser fluorescence. As in the case of I₂ we find that elastic collisions are very inefficient at reorienting Li₂ molecules and a selection rule ΔM′ _J = 0 appears to be in operation. Rotationally inelastic collisions, particularly those with argon, cause some degree of reorientation and are the result of relatively long range intermolecular interactions. Vibrational transfer features are more strongly depolarized. Optical pumping studies of oriented ¹Σ _g Li₂ molecules have yielded a cross section for inelastic transfer of 35 ± 15 Ų.     

A continuous-flow crushing device for on-line delta2H analysis of fluid inclusion water in speleothems

A method for the isotope analysis of fluid inclusion water in speleothem calcite is presented. The technique is based on a commercially available continuous-flow pyrolysis furnace (ThermoFinnigan TC-EA). The main adaptation made to the standard TC-EA configuration is the addition of a crusher and cold trap unit, which is connected to the carrier gas inlet at the top of the TC-EA reactor tube. A series of tests conducted with this device shows that: (1) standard waters, injected in the crusher, and passed through a cryogenic trapping routine, yield accurate delta(2)H values; (2) crushed cubes of speleothem calcite from two Peruvian caves with rather dissimilar seepage water delta(2)H values yield fluid inclusion delta(2)H values in good accordance with these drip waters. The clear advantage of this continuous-flow technique for fluid inclusion isotope analysis is that it is relatively quick compared with other techniques. Since the conditions of water sample introduction into the TC-EA are identical for delta(2)H and delta(18)O analysis, we expect that only limited adaptations to the extraction procedure are required to provide delta(18)O analysis of fluid inclusion samples with the same device.     

Reaction of anthracene with CH radicals: an experimental study of the kinetics between 58 and 470 K

The rate coefficient of the reaction of the methylidine radical CH with anthracene has been studied over a wide temperature range (58-470 K) in a dedicated "Cinétique de Réaction en Ecoulement Supersonique Uniforme" (Reaction Kinetics in Uniform Supersonic Flow) apparatus. The reaction exhibits a slight positive temperature dependence, which can be fitted to the expression k(T) = (3.32 +/- 1.00) x 10(-10)(T/298)((0.46+/-0.14)) cm3 molecule(-1) s(-1). Even at the lowest temperature, the reaction remains very fast indicating that the kinetics are probably driven by a capture process.     

Emmy Noether and Her Theorems

Today Noether's principal theorem occupies a prominent place in theoretical physics, though for a long time its significance was largely overlooked. Even now, relatively few physicists realize that Emmy Noether's original paper from 1918 contains two fundamental theorems. Moreover, both theorems are essential for understanding her original motivation, namely to distinguish between proper and improper conservation laws in physics.     

Application of infinite oscillator shell model calculations to the description of nuclear reactions

A simple R-matrix procedure is proposed to provide a means of using nuclear structure information, from calculations in an infinite oscillator well, to describe reaction cross sections. The procedure uses values for the channel radius parameters of the R-matrix theory that are extracted from knowledge of the structure and reaction properties of the neighbouring closed shell nucleus answering one of the main criticisms expressed concerning the dependence of the R-matrix on unphysical parameters. Application of the model to the scattering of neutrons from ¹⁵N and comparison to previous theoretical predictions are considered.     

Four-centre skeletal rearrangements in the mass spectra of thioanilides

Abundant peaks in the mass spectra of thioanilides involve loss of a substituted thiophenoxy radical by a process involving aryl migration from nitrogen to sulfur (a four-centre skeletal rearrangement). The effects of substituents on this process have been studied. Substituents in the amide ring, in the acid part of the molecule and on the nitrogen atom were studied. Four-centre aryl migrations seem to be favoured if the aryl group migrates from one atom to either a more polarizable or a more electronegative atom, and in the case of thioanilides this migration is more important in tertiary compounds than in secondary compounds.     

A current operator for the rotational model

A current operator for the rotational model is given. This operator is then used to calculate experimentally observable transition current multipoles.     

Isovector M6 excitations in the open-shell random phase approximation

OSRPA predictions are made for the excitation energies and transition amplitudes of J^π = 6^?, T = 1 excited states in the even N = Z sd shell nuclei. The results are employed in the calculation of electron scattering form factors. New expressions are given for the double commutators appearing in the OSRPA equations, which greatly facilitate their evaluation.