Measurement of Ventricular Volume by Intracardiac Impedance: Theoretical and Empinrcal Approaches

The most widely used equation, V = pL2/R, is developed for the computation of ventricular volume from catheter based impedance measurements. The assumptions implicit in this derivation are examined and found to be generally invalid. An empirical discrete resistor model is described which includes the impedance of the myocardial tissue and the adjoining ventricular blood volume. Once the parameters of this model are determined for individual canine hearts, the model predicts stroke volume from measured impedances. Due to the difficulty involved in determining the parameters of the empirical model, a numerical model is developed which solves the equation V ?a V U + F = 0 in a three-dimensional volume. This model is then used to determine the effect of parallel tissue resistance, catheter position, and contraction of the other ventricle on volumes computed by intracardiac impedance. Parallel tissue resistance is found to have the greatest impact on absolute volume measurements. However, stroke volume computations are relatively unaffected by any of the three factors.     

Nanochannel electroporation delivers precise amounts of biomolecules into living cells

Many transfection techniques can deliver biomolecules into cells, but the dose cannot be controlled precisely. Delivering well-defined amounts of materials into cells is important for various biological studies and therapeutic applications. Here, we show that nanochannel electroporation can deliver precise amounts of a variety of transfection agents into living cells. The device consists of two microchannels connected by a nanochannel. The cell to be transfected is positioned in one microchannel using optical tweezers, and the transfection agent is located in the second microchannel. Delivering a voltage pulse between the microchannels produces an intense electric field over a very small area on the cell membrane, allowing a precise amount of transfection agent to be electrophoretically driven through the nanochannel, the cell membrane and into the cell cytoplasm, without affecting cell viability. Dose control is achieved by adjusting the duration and number of pulses. The nanochannel electroporation device is expected to have high-throughput delivery applications.     

On the malleability of ideology: Motivated construals of color blindness.

The authors propose that the content of certain sociopolitical ideologies can be shaped by individuals in ways that satisfy their social motivations. This notion was tested in the context of color-blind ideology. Color blindness, when construed as a principle of distributive justice, is an egalitarian stance concerned with reducing discrepancies between groups' outcomes; as a principle of procedural justice, however, color blindness can function as a legitimizing ideology that entrenches existing inequalities. In Study 1, White people high in antiegalitarian sentiment were found to shift their construal of color blindness from a distributive to a procedural principle when exposed to intergroup threat. In Studies 2, 3A, and 3B, the authors used manipulations and a measure of threat to show that antiegalitarian White people endorse color blindness to legitimize the racial status quo. In Study 3B, participants' endorsement of color-blind ideology was mediated by increases in their preference for equal treatment (i.e., procedural justice) as a response to threat. In the Discussion section, the authors examine implications of the present perspective for understanding the manner in which individuals compete over the meaning of crucial ideologies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cinemetrics: Embodying architectural representation in the digital age

How can architecture emerge from the prison of its current forms of representation? Grahame Shane1 1 D.G. Shane, “Balkanization and the Postmodern City,” in Peter Lang (ed.), Mortal City, New York: Princeton Architectural Press, 1995, pp. 55-69. interprets the concluding diagram of Robin Evans' Projective Cast: Architecture and its Three Geometries2 2 Robin Evans, The Projective Cast: Architecture and Its Three Geometries, Cambridge, MA: MIT Press, 1995. as a critique of postmodern architecture's self-reflection and lack of engagement with the world. Shane argues that Evan's diagram depicts architectural representation as a self-reinforcing, closed, conceptual triangle of mirrored reflections between the human observer, the scopic regime of perspective, orthographic architectural drawing conventions, and designed objects. Shane draws his interpretation from Evans's early work on Victorian prison architecture as well as one of Evan's last public lectures. Shane characterized Evans' critical view of postmodern architectural practice and representation as a “self-correcting means of stabilization and pacification of the physical, built environment.”3 3 Shane, “Balkanization and the Postmodern City,” p. 68 This essay develops a theory of Cinemetrics that demonstrates how contemporary architectural production, with the aid of digital tools, has the capacity to break this closed system with open-ended, embodied cybernetic feed-back loops within a wider public culture engaged in the making and imagining of architecture.4 4 Brian McGrath and Jean Gardner, Cinemetrics: Architectural Drawing Today, London: Wiley-Academy, 2007. This essay argues that this break can only be accomplished by embodying architectural representation through a careful engagement with Gilles Deleuze's philosophy of movement and time images derived from cinema,5 5 Gilles Deleuze, Cinema 1: the movement image, Hugh Tomlinson and Habberjam (trans.), Minneapolis, MN: University of Minnesota, 1986; Cinema 2: the time-image, Hugh Tomlinson and Robert Galeta (trans.), Minneapolis, MN: University of Minnesota, 1989. Henri Bergson's theories of memory, attention and duration,6 6 Henri Bergson, Creative Evolution, Arthur Mitchell (trans.), Lanham, MD: University Press of America, 1991; Henri Bergson, Matter and Memory, M.N. Paul and W.S. Palmer (trans.), New York: Zone Books, 1991. and from Charles Sanders Peirce's pragmatic semiosis.7 7 Charles Sanders Peirce, The Essential Peirce: Selected Philosophical Writings, Vol. 2 (1893-1913), Peirce Edition Project, Bloomington, IN: Indiana University Press, 1998.      

Oxidation Behavior of γ′-Ni3Al-Based Ni–20Al–5Cr Alloys With and Without Reactive Elements Under Different Heating Conditions

Oxidation of Metals - High-temperature oxidation of a model γ′-Ni3Al-based Ni–20Al–5Cr alloy and versions of this alloy doped with Y, Hf, or Si, or some combination of these,...     

On the Validity of the Poisson Assumption in Sampling Nanometer-Sized Aerosols

For a constant aerosol concentration, it is traditionally assumed that a Poisson process describes the behavior of particle detections during sampling and consequently fluctuations in the measured concentration. Recent studies, however, have shown that sampling of micrometer-sized aerosols has non-Poissonian behavior with positive correlations. The validity of the Poisson assumption for nanometer-sized aerosols has not been established and thus was tested in this study. Its validity was tested for four particle sizes—10 nm, 25 nm, 50 nm, and 100 nm—by sampling from indoor air with a differential mobility analyzer-condensation particle counter (DMA-CPC) setup to obtain a time series of particle counts. Five metrics were calculated from the data: pair-correlation function (PCF), scaled clustering index (SCI), coefficient of variation, probability of measuring a concentration at least 25% greater than average, and posterior distributions from Bayesian inference. To identify departures from Poissonian behavior, these metrics were also calculated for 1000 computer-generated Poisson time series with the same mean as the experimental data. For most comparisons, the experimental data fell within the range of 80% of the Poisson-simulation values. Essentially, the metrics for the experimental data were mostly indistinguishable from a simulated Poisson process. The greater influence of Brownian motion for nanometer-sized aerosols may explain the Poissonian behavior observed for smaller aerosols. Although the Poisson assumption was found to be reasonable in this study it must be carefully applied, as the results here do not definitively prove applicability in all sampling situations.

Copyright 2014 American Association for Aerosol Research     

Real-time in situ monitoring of the thermal cure of a bisphenol cyanate: A view toward intelligent processing

A dispersive fiber-optic Raman spectrometer was used to remotely monitor, in real-time, the local temperature and the extent of reaction of a commercial cyanate ester polymer (AroCy L-10). The local temperature was determined by solving the Boltzmann relation governing the intensity ratio of the Raman Stokes and anti-Stokes scattering of a reference mode which does not vary with the reaction chemistry. The extent of the reaction can be monitored using either individual peaks assciated with the reactant or product or by using the entire spectrum and principal component multivariate calibration. The use of principal component analysis has distinct advantages over the single-peak method. © 1996 John Wiley & Sons, Inc.     

Concrete filled high strength steel box columns for tall buildings: Behaviour and design

This paper presents a study of the behaviour and design of concrete filled high strength steel fabricated box columns for use in tall buildings. The many advantages that can be attributed to the use of high strength steel in concrete filled steel box column constructions are presented and discussed. The paper deals with short composite columns and presents guidelines for plate slenderness and overall column slenderness to eliminate local and overall buckling. A proposed design model is developed to calculate the strength of short columns in bending and compression. A method for constructing the strength interaction diagram is presented. Furthermore, to study the ductility of this form of column construction a cross-sectional analysis computer program was developed to consider the moment-thrust-curvature response of such members. This has been undertaken using mild structural steel and high strength steel. The study also shows that, by the use of the method considered, savings can be made in the base column design of a tall building with a negligible penalty in ductility. Finally, recommendations are given for further research into this new method of column construction, which focuses on future experimental work.