Showing papers by "Worcester Polytechnic Institute published in 1997"
TL;DR: A new study reveals businesses are defining data quality with the consumer in mind, and within this larger context of information systems, data is collected from multiple data sources and stored in databases.
Abstract: ATA-QUALITY (DQ) PROBLEMS ARE INCREASINGLY EVIdent, particularly in organizational databases. Indeed, 50% to 80% of computerized criminal records in the U.S. were found to be inaccurate, incomplete, or ambiguous. The social and economic impact of poor-quality data costs billions of dollars. [5-7, 10]. Organizational databases, however, reside in the larger context of information systems (IS). Within this larger context, data is collected from multiple data sources and stored in databases. From this stored data, useful information is generated for organizational decision-making. A new study reveals businesses are defining data quality with the consumer in mind.
1,296 citations
TL;DR: The authors explored strategic management as a form of fiction and discussed the challenges strategists have faced in making strategic discourse both credible and novel and considered how strategic narratives may change within the "virtual" organization of the future.
Abstract: Using narrative theory, this article explores strategic management as a form of fiction. After introducing several key narrative concepts, we discuss the challenges strategists have faced in making strategic discourse both credible and novel and consider how strategic narratives may change within the "virtual" organization of the future. We also provide a number of narrativist-oriented research questions and methodological suggestions.
986 citations
TL;DR: In this paper, optical vortices that have quasi-point core functions, such as optical vortex solitons, may orbit one another at rates that are orders of magnitude larger than those with nonlocalized cores.
Abstract: Optical vortices in linear and nonlinear media may exhibit propagation dynamics similar to hydrodynamic vortex phenomena. Analytical and numerical methods are used to describe and investigate the interaction between vortices and the background field. We demonstrate that optical vortices that have quasi-point core functions, such as optical vortex solitons, may orbit one another at rates that are orders of magnitude larger than those with nonlocalized cores.
349 citations
TL;DR: In this article, the authors present an in-depth study of blade vibration problems that seriously impact development of advanced gas turbine configurations, and they conclude that structural integrity of power plants is the dominant factor that influences the quality, reliability, and marketability of the product.
Abstract: This paper presents an in-depth study of blade vibration problems that seriously impact development of advanced gas turbine configurations. The motivation for this study arises from the author's conviction that structural integrity of power plants is the dominant factor that influences the quality, reliability, and marketability of the product. Implications of this study in the context of potential R&D challenges and opportunities of interest to industry, governments, and academia are discussed.
313 citations
TL;DR: In this article, a mixed-conducting perovskite dense membrane reactor at 850°C was used for the partial oxidation of methane to synthesis gas (syngas, CO + H2).
Abstract: The partial oxidation of methane to synthesis gas (syngas, CO + H2) was performed in a mixed-conducting perovskite dense membrane reactor at 850°C, in which oxygen was separated from air and simultaneously fed into the methane stream. Steady-state oxygen permeation rates for La1-xA′xFe0.8 Co0.2O3-δ perovskite membranes in nonreacting air/helium experiments were in the order of A′x = Ba0.8 > Ba0.6 > Ca0.6 > Sr0.6. Deep oxidation products were obtained from a La0.2 Ba0.8 Fe0.8 Co0.2 O3–δ disk-shaped membrane reactor without catalyst, with a 4.6% CH4 inlet stream. These products were further reformed to syngas when a downstream catalytic bed was added. Packing the 5% Ni/Al2O3 catalyst directly on the membrane reaction-side surface resulted in a slow fivefold increase in O2 permeation, and a fourfold increase in CH4 conversion. XRD, EDS, and SEM analyses revealed structure and composition changes on the membrane surfaces. Oxygen continuously transported from the air side appeared to stabilize the membrane interior, and the reactor was operated for up to 850 h.
264 citations
17 Aug 1997
TL;DR: An entirely new approach which accelerates the multiplications of points which is the core operation in elliptic curve public-key systems and which proofs to be faster than traditional point multiplication methods is described.
Abstract: This contribution describes three algorithms for efficient implementations of elliptic curve cryptosystems. The first algorithm is an entirely new approach which accelerates the multiplications of points which is the core operation in elliptic curve public-key systems. The algorithm works in conjunction with the k-ary or sliding window method. The algorithm explores computational advantages by computing repeated point doublings directly through closed formulae rather than from individual point doublings. This approach reduces the number of inversions in the underlying finite field at the cost of extra multiplications. For many practical implementations, where field inversion is at least four times as costly as field multiplication, the new approach proofs to be faster than traditional point multiplication methods. The second algorithm deals with efficient inversion in composite Galois fields of the form GF((2n)n). Based on an idea of Itoh and Tsujii, we optimize the algorithm for software implementation of elliptic curves. The algorithm reduced inversion in the composite field to inversion in the subfield GF(2n). The third algorithm describes the application of the Karatsuba-Ofman Algorithm to multiplication in GF((2n)n). We provide a detailed complexity analysis of the algorithm for the case that subfield arithmetic is performed through table look-up. We apply all three algorithms to an implementation of an elliptic curve system over GF((216)11). We provide absolute performance measures for the field operations and for an entire point multiplication.
188 citations
Proceedings Article•
25 Aug 1997TL;DR: The experimental results indicate that BFRJ with global optimizations can outperform the competitor by a significant margin (up to 50%) and this work was supported in part by the University of Michigan ITS Research Center of Excellence grant.
Abstract: R-tree based spatial join is useful because of both its superior performance and the wide spread implementation of R-trees. We present a new R-tree join method called BFRJ (Breadth-First R-tree Join). BFRJ synchronously traverses both R-trees in breadthfirst order while processing join computation one level at a time. At each level, BFRJ creates an intermediate join index and deploys global optimization strategies (ordering, memory management, buffer management) to improve the join computation at the next level. We also present an experimental evaluation of the proposed optimizations as well as a performance comparison between BFRJ and the state-of-the-art approach. Our experimental results indicate that BFRJ with global optimizations can outperform the competitor by a significant margin (up to 50%). This work was supportedin part by the University of Michigan ITS Research Center of Excellence grant (DTFH61-93-X0001i’-Sub) sponsored by the U.S. Dept. of Transportation and by the Michigan Dept. of Transportation. This work was performed while the authors were at the University of Michigan. Permission to copy without fee all OT part of this material is granted provided that the copies are not made OT distributed for direct commercial advantage, the VLDB copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Very Large Data Base Endowment. To copy otherwise, OT to republish, requires a fee and/or special permission from the Endowment. Proceedings of the 23rd VLDB Conference Athens, Greece, 1997
169 citations
TL;DR: In this paper, the stiffness design of laminated plates subjected to single and multiple loads is considered and the stiffness of the laminates is parametrized in terms of the so-called lamination parameters.
159 citations
TL;DR: In this paper, the authors observed the fluid-like rotation of a pair of identical optical vortices (OV's) as they propagate through free space and found that the initial rotation rate is inversely proportional to the squared distance of separation.
Abstract: We have observed the fluidlike rotation of a pair of identical optical vortices (OV's) as they propagate through free space. Similar to vortex filaments in a fluid, the initial rotation rate is found to be inversely proportional to the squared distance of separation. Owing to unusually small vortex cores, we obtained rotation rates that were 2 orders of magnitude larger than expected for ``conventional'' large core OV's.
137 citations
TL;DR: A simple dynamic power management algorithm is developed for fixed quality-of-service constraints and varying channel interference, and shows improved network capacity and stability in addition to substantially improved battery life at the mobile terminals.
Abstract: For fixed quality-of-service constraints and varying channel interference, how should a mobile node in a wireless network adjust its transmitter power so that energy consumption is minimized? Several transmission schemes are considered, and optimal solutions are obtained for channels with stationary, extraneous interference. A simple dynamic power management algorithm based on these solutions is developed. The algorithm is tested by a series of simulations, including the extraneous-interference case and the more general case where multiple, mutually interfering transmitters operate in a therefore highly responsive interference environment. Power management is compared with conventional power control for models based on FDMA/TDMA and CDMA cellular networks. Results show improved network capacity and stability in addition to substantially improved battery life at the mobile terminals.
128 citations
Proceedings Article•
08 Dec 1997TL;DR: Trace-driven simulation of this mechanism on two large, independent data sets shows that PCV both provides stronger cache coherency and reduces the request traffic in comparison to the time-to-live (TTL) based techniques currently used.
Abstract: This paper presents work on piggyback cache validation (PCV), which addresses the problem of maintaining cache coherency for proxy caches. The novel aspect of our approach is to capitalize on requests sent from the proxy cache to the server to improve coherency. In the simplest case, whenever a proxy cache has a reason to communicate with a server it piggybacks a list of cached, but potentially stale, resources from that server for validation.
Trace-driven simulation of this mechanism on two large, independent data sets shows that PCV both provides stronger cache coherency and reduces the request traffic in comparison to the time-to-live (TTL) based techniques currently used. Specifically, in comparison to the best TTL-based policy, the best PCV-based policy reduces the number of request messages from a proxy cache to a server by 16-17% and the average cost (considering response latency, request messages and bandwidth) by 6-8%. Moreover, the best PCV policy reduces the staleness ratio by 57-65% in comparison to the best TTL-based policy. Additionally, the PCV policies can easily be implemented within the HTTP 1.1 protocol.
TL;DR: In this article, a novel class of aluminosilicate-based microporous materials with good adsorption capacity and high selectivity are investigated, and Pillared clays, silicalite and zeolite beta are modified by incorporating a non-ionic surfactant of the general formula C2−14H25−290O (CH2CH20)5H (Tergitol 15S-5).
TL;DR: How established research methods in cognitive psychology can be applied to answer questions about the ability of systems thinking interventions to improve the nature and quality of thought about complex systems is described.
Abstract: This article describes how established research methods in cognitive psychology can be applied to answer questions about the ability of systems thinking interventions to improve the nature and quality of thought about complex systems. The need for and advantages of controlled experimental research on the effects of interventions on mental models and cognitive processes, as well as the limitations of current assessment practices, are discussed. An agenda for collaborative research between cognitive psychologists and researchers interested in dynamic systems, covering the areas of memory, analogical transfer, mental models, decision processes, human–computer interaction, and expertise, is outlined in detail. The article concludes with a discussion of the difficulties and long-term advantages of conducting the described research. © 1997 John Wiley & Sons, Ltd.
TL;DR: An efficient implementation of a nonquadratic objective function for network state estimation that builds naturally on existing least squares software, that is based on an iterative Gauss-Newton solution of the KKT optimality conditions is described.
Abstract: Using a nonquadratic objective function for network state estimation can combine several estimation and bad data rejection techniques into one algorithm: e.g. the benefits of maximum likelihood least squares estimation can be coupled with the bad data rejection properties of least absolute value estimation. For such estimators, we describe an efficient implementation, one that builds naturally on existing least squares software, that is based on an iterative Gauss-Newton solution of the KKT optimality conditions. We illustrate the behavior of a quadratic-linear and a quadratic-constant objective function on a set of test networks. The former is closely related to the Huber M-estimator. The latter shows somewhat better bad data rejection properties, perhaps because it arises from a natural model of meter failure.
TL;DR: In this article, the effect of damping ratio and slope of the torque-speed curve of an elastically mounted unbalanced shaft on a passage/capture threshold is evaluated.
Abstract: Rotation of an elastically mounted unbalanced shaft may be in general affected by its lateral vibration, due to a “vibrational torque”. This interaction is nonlinear, and can be neglected only in case of an unlimited power supply. Whenever the available power of the drive is comparable with power consumption due to vibration, various nonlinear phenomena may be observed, the most well-known of these being the so called Sommerfeld effect – slowing down or complete capture of the shaft at resonance. The corresponding steady-state motions and their stability can be studied by asymptotic methods, as applied to the governing nonlinear set of two second-order equations. However, study of transient motions in general requires numerical solution. This numerical solution is obtained here, and extensive parametric studies are performed of the Sommerfeld effect. In particular, the influence is evaluated of damping ratio and slope of the torque-speed curve of the drive on a passage/capture threshold. The results of numerical simulation, as well as experiments with a physical model, also demonstrate the effect of smooth passage through resonance with a limited power supply, based on using a “switch” of suspension stiffness from a certain artificially increased value to the design one. A brief description is presented also of time-variant components of the resonant amplitude and rotational frequency responses in the case of capture, as observed both in numerical simulation studies and in experiments. Whilst these components are small compared with the corresponding constant ones, i.e. steady-state vibration amplitude and rotational frequency, the above observations indicate the possibility for periodic or chaotic nonstationarity in the system's response.
TL;DR: This study suggests that experimental stroke with silicone-coated sutures (Koizumi's method) provides good reproducibility and reliability, among investigators of varying experience.
TL;DR: A study of the crystallization of the molecular sieve zeolite NaA from clear aluminosilicate solutions is reported in this article, where powder X-ray diffraction is used to determine the only phase in the solid precipitate.
TL;DR: In this article, a nonlinear solution method based on an inexact Newton method with backtracking is proposed for the low Mach number Navier?Stokes equations with heat and mass transport.
TL;DR: The use of an anisotropic material for the boundary truncation of the finite-element method is considered in this article, where a plane-wave incident from free space into the half-space has no reflection, referred to as a perfectly matched layer (PML).
Abstract: The use of an anisotropic material for the boundary truncation of the finite-element method is considered. The anisotropic material properties can be chosen such that a plane-wave incident from free space into the anisotropic halfspace has no reflection. Because there is no reflection, the material is referred to as a perfectly matched layer (PML). The relationship between the anisotropic PML and the original PML proposed by Berenger (see J. Comp. Phys., vol.114, p.185-200, October 1994) is considered. The anisotropic PML is applied to the finite-element solution of electromagnetic (EM) scattering from three-dimensional (3-D) objects. Numerical results are presented to demonstrate the accuracy of the PML.
TL;DR: Investigation of growth kinetics showed that the use of GA3 at 0.01 mg/l (28.9 µM) increased the growth rate of hairy roots of A. annua by 24.9%, and the cultures treated with GA3 reached stationary phase faster than control cultures.
Abstract: Artemisinin (AN), a potent antimalarial drug that has been used for centuries as a folk remedy in China, is an effective treatment against quinine-resistant strains of Plasmodium. It can be produced through the in vitro culture of genetically transformed (hairy) roots. The effect of gibberellic acid (GA3) on the growth and secondary metabolite production of hairy roots of Artemisia annua was investigated. Six different concentrations of GA3 were tested in shaker flasks to determine the optimum concentration. GA3 levels of 0.01–0.001 mg/l (28.9–2.89 µM) provided the most significant increase in biomass, and 0.01 mg/l (28.9 µM) produced the highest amount of AN. Investigation of growth kinetics showed that the use of GA3 at 0.01 mg/l (28.9 µM) increased the growth rate of hairy roots of A. annua by 24.9%. Thus, the cultures treated with GA3 reached stationary phase faster than control cultures.
TL;DR: In this article, the spontaneous moment of a single BMP as a function of temperature and the concentration of BMP's was investigated using magnetization measurements, and it was shown that the BMP susceptibility at low temperatures is quite anisotropic.
Abstract: Bound magnetic polarons (BMP's) in $p$-type ${\mathrm{Cu}}_{2}{\mathrm{Mn}}_{0.9}{\mathrm{Zn}}_{0.1}{\mathrm{SnS}}_{4}$ were investigated using magnetization measurements. The magnetization $M$ was studied from 2 to 60 K in magnetic fields up to 55 kOe. The data show the characteristic features of BMP's in the collective regime. In addition, the onset of antiferromagnetic order in the ``matrix'' surrounding the BMP's leads to anomalies in the BMP susceptibility at the N\'eel temperature of the matrix ${T}_{N}=8$ K. Below 15 K the low-field magnetization of the BMP's is quite anisotropic. A detailed analysis of the isothermal magnetization curves, based on Wolff's work but with some additional assumptions, separates the BMP contributions to $M$ from the contribution of the matrix. The analysis gives the spontaneous moment ${m}_{s}$ of a single BMP as a function of temperature $T$, and the concentration $N$ of BMP's. The value ${m}_{s}=143$ Bohr magnetons/BMP at the lowest temperatures is consistent with the expected radius of the hole orbit, of order 10 \AA{}. The observed $T$ dependence of ${m}_{s}$ is compared with theoretical calculations based on a model that assumes that the wave function in the absence of the $p$-$d$ interaction is hydrogenic. The calculated decrease of ${m}_{s}$ with increasing $T$ is somewhat slower than that deduced from the experimental data. The BMP concentration $N$, from an analysis of the magnetization data, is about $2\ifmmode\times\else\texttimes\fi{}{10}^{19}$ BMP/cm${}^{3}$ in all the samples. This $N$ is consistent with the observed hopping conductivity at low temperatures. High-field magnetization data, up to 300 kOe, show the canted-to-paramagnetic phase transition of the matrix. At 1.4 K the transition is near 225 kOe.
TL;DR: A new approach to spectral response computations of an arbitrary two-dimensional (2-D) waveguide based on the tangential-vector finite-element method in conjunction with the asymptotic waveform evaluation (AWE) technique.
Abstract: This paper describes a new approach to spectral response computations of an arbitrary two-dimensional (2-D) waveguide. This technique is based on the tangential-vector finite-element method (TVFEM) in conjunction with the asymptotic waveform evaluation (AWE) technique. The former is used to obtain modes characteristics for a central frequency, whereas the latter employs an efficient algorithm to compute frequency moments for each mode. These moments are then matched via Pade approximation to a reduced-order rational polynomial, which can be used to interpolate each mode over a frequency band with a high degree of accuracy. Furthermore, the moments computations and subsequent interpolation for a given set of frequency points can be done much more rapidly than just simple simulations for each frequency point.
TL;DR: In this paper, a variational approach for the effective conductivity tensor of anisotropic two-phase electric conductors is proposed. But the authors assume that the interface between phases is highly conducting and they use simple Dirichlet problems inside each phase region.
Abstract: New variational principles are developed for the effective conductivity tensor for anisotropic two-phase electric conductors. Here the interface between phases is assumed to be highly conducting. Extra geometric information is encoded into the principles through the solution operators of simpler transport problems. These operators can be expressed as gradients of simple layer potentials with densities supported on phase interfaces or in terms of simple Dirichlet problems inside each phase region. New upper bounds on the effective conductivity are found that depend upon component volume fractions, a surface energy tensor and a scale-free matrix of parameters. This matrix corresponds to the effective conductivity tensor associated with the same geometry but with perfectly conducting inclusions. New lower bounds are given in terms of two-point correlation functions, component volume fractions, and interfacial geometric parameters. Both upper and lower bounds are found to be optimal for certain choices of interfacial parameters. For isotropic polydisperse suspensions of spheres we are able to estimate the effective conductivity based on measured values of the size distribution of the spheres. Conversely, we are able to characterize the size distribution of the spherical inclusions based on measured values of the effective conductivity.
TL;DR: It is suggested that activation of the PGG‐Glucan‐stimulated factors is not sufficient to stimulate cytokine mRNA transcription, and signal transduction pathways different from those used by LPS are demonstrated.
Abstract: PGG-Glucan (Betafectin) is a novel soluble beta-glucan immunomodulator that enhances leukocyte microbicidal activities without inducing inflammatory cytokines. Although several different receptors for soluble and particulate beta-glucans have been described, the signal transduction pathway(s) used by soluble beta-glucans have not been elucidated. We report that in a murine monocytic cell line (BMC2.3) PGG-Glucan activates nuclear factor-kappaB (NF-kappaB)-like and NF-interleukin-6 (IL-6)-like transcription factors. Electrophoretic mobility shift assays showed that PGG-Glucan activation of the factors is time- and concentration-dependent. The NF-kappaB-like complex includes subunit p65 (rel-A) as one of its components, but apparently not p50 (kappaB1), p52 (kappaB2), p68 (rel-B), or p75 (C-rel) family members. The NF-IL-6-like complex contains subunit C/EBP-beta (NF-IL-6alpha) as one of its components, but apparently not C/EBP-alpha or C/EBP-delta (NF-IL-6beta). As expected, lipopolysaccharide (LPS) activated p65/p50 NF-kappaB and C/EBP-beta NF-IL-6 complexes, increased the nuclear titer of p65 and p50 antigens, and increased cytokine (IL-1beta, tumor necrosis factor alpha) mRNA production. In contrast, PGG-Glucan increased the nuclear titer of p65, but apparently not p50, and did not induce cytokine mRNA production. These data demonstrate that PGG-Glucan utilizes signal transduction pathways different from those used by LPS. The data suggest that activation of the PGG-Glucan-stimulated factors is not sufficient to stimulate cytokine mRNA transcription.
TL;DR: In this paper, heat transfer measurements were reported for packings of full and hollow cylinders in tubes over a tube-toparticle diameter ratio (N) range of 1.8−5.6.
Abstract: New heat transfer measurements are reported for packings of full and hollow cylinders in tubes over a tube-to-particle diameter ratio (N) range of 1.8−5.6. Both high and low thermal conductivity packings were used. These results are analyzed in conjunction with previously-reported data for spheres in the range 1.13 < N < 6.4 and data for cylinders and rings in the range 5.2 < N < 6.9 to provide a comprehensive picture of heat transfer in the region of very low N (< 4) and a comparison to data at higher N. Single-phase heat transfer correlations are critically evaluated with regard to their dependence on N, to determine whether their range of applicability extends to N < 4. The effective radial thermal conductivity kr and wall heat transfer coefficient hw depend on N less strongly for full and hollow cylinders than they do for spheres. For spheres, there is evidence of high rates of radial heat transfer as N approaches unity, and the bed behaves as a single pellet string, but for 2 ≤ N ≤ 4, kr is highly de...
TL;DR: In this article, the energy and momentum densities and currents associated with electromagnetic wave propagation through an absorbing and dispersive diatomic dielectric, which is modeled by a single-resonance Lorentz oscillator, were derived.
Abstract: We calculate the energy and momentum densities and currents associated with electromagnetic wave propagation through an absorbing and dispersive diatomic dielectric, which is modeled by a single-resonance Lorentz oscillator The relative and center-of-mass coordinates of the dielectric sublattices and the electromagnetic field vectors are treated as dynamical variables, while the dielectric loss is modeled by a phenomenological damping force The characteristics of the energy propagation agree with previous work, including the form of the energy velocity The treatment of momentum propagation extends previous work to lossy media, and it is found that the damping plays an important role in the transfer of momentum from the electromagnetic field to the center of mass of the dielectric We discuss the significances of the momentum, the pseudomomentum, and their sum, the wave momentum For each of these quantities we derive the density, the current density, and the appropriate conservation or continuity equation The general expressions are illustrated by applications to a steady-state monochromatic wave and to an excitation in the form of a localized Gaussian pulse The velocities associated with propagation of the various kinds of momentum are derived and discussed @S1063-651X~97!04901-5#
01 Jan 1997
TL;DR: In this article, the entanglement of the particles in a Greenberger-Horne-Zeilingerl (GHZ) state is modelled by a set of interlinked rings known as the Borromean rings.
Abstract: In this paper, I will point out some curious connections between entangled quantum states and classical knot configurations. In particular, I will show that the entanglement of the particles in a Greenberger-Horne-Zeilingerl (GHZ) state is modelled by a set of interlinked rings known as the Borromean rings. It is widely acknowledged that the non-local properties of multiparticle quantum states (such as the GHZ state) derive from their entanglement. By the entanglement of a multiparticle state, I mean simply that the wave function of the state cannot be written as a product of wave functions of the individual particles. Now one of the images conjured up by the term “entanglement” is that of a tangled collection of strings. This led me to enquire whether there might be any similarities between the entanglement of quantum particles and the entanglement of loops of string, or whether the expectation of such a connection is completely far-fetched.
TL;DR: A comparison of published PCR protocols was undertaken, and three cycles of freezing/thawing were sufficient to expose oocyst DNA and resulted in higher sensitivity than proteinase K digestion, sonication or electroporation, andhibition of PCR by surface water from different local sources was entirely associated with the soluble fraction of lake water.
Abstract: Cryptosporidium parvum is an enteric protozoan parasite of medical and veterinary importance. Dissemination of environmentally resistant oocysts in surface water plays an important role in the epidemiology of cryptospridiosis. Although the polymerase chain reaction (PCR) is a well-established technique and is widely used for detecting microorganisms, it is not routinely applied for monitoring waterborne C. parvum. In order to facilitate the application of PCR to the detection of waterborne C. parvum oocysts, a comparison of published PCR protocols was undertaken and different sample-preparation methods tested. The sensitivity of a one-step PCR method, consisting of 40 temperature cycles, was 10 purified oocysts or fewer than 100 oocysts spiked in raw lake water. The detection limit of two primer pairs, one targeting the ribosomal small subunit and another specific for a C. parvum sequence of unknown function, was approximately ten-fold lower than achieved with a primer pair targeting an oocyst shell protein gene. Three cycles of freezing/thawing were sufficient to expose oocyst DNA and resulted in higher sensitivity than proteinase K digestion, sonication or electroporation. Inhibition of PCR by surface water from different local sources was entirely associated with the soluble fraction of lake water. Membrane filtration was evaluated in bench-scale experiments as a means of removing lake water inhibitors and improving the detection limit of PCR. Using gel and membrane filtration, the molecular size of inhibitory solutes from lake water was estimated to less than 27 kDa.
TL;DR: Computed levels of fluid flow suggested a possible load transduction mechanism for cells in the tissue, and the effect of variations in fluid viscosity and permeability of the solid matrix was parametrically explored.
Abstract: The purpose of this study is to describe interstitial fluid flow in axisymmetric soft connective tissue (ligaments or tendons) when they are loaded in tension. Soft hydrated tissue was modelled as a porous medium (using Darcy's Law), and the finite element method was used to solve the resulting equations governing fluid flow. A commercially available computer program (FiDAP) was used to create an axisymmetric model of a biomechanically tested rat ligament. The unknown variables at element nodes were pressure and velocity of the interstitial fluid (Newtonian and incompressible). The effect of variations in fluid viscosity and permeability of the solid matrix was parametrically explored. A transient loading state mimicking a rat ligament mechanical experiment was used in all simulations. The magnitude and distribution of pressure, stream lines, shear (stress) rate, vorticity and velocity showed regular patterns consistent with extension flow. Parametric changes of permeability and viscosity strongly affected fluid flow behaviour. When the radial permeability was 1000 times less than the axial permeability, shear rate and vorticity increased (approximately 5-fold). These effects (especially shear stress and pressure) suggested a strong interaction with the solid matrix. Computed levels of fluid flow suggested a possible load transduction mechanism for cells in the tissue.
01 Nov 1997
TL;DR: This paper presents results from a user interface evaluation of the authors' temporal visual query language (TVQL), which indicates that while subjects took longer to learn TVQL than TForrns, they were more efficient and more accurate in specifying temporal queries with the TVQL interface than with the TForms interface.
Abstract: As new query interfaces emerge for accessing multimedia data, formal user studies are needed to evaluate the usability of such interfaces. In this paper, we present results from a user interface evaluation of our temporal visual query language (TVQL). TVQL is a novel direct manipulation query interface for specifying temporal relationship queries over temporal events such as video data. In our user study, we compare TVQL to a forms-based temporal query language (TForms). Our results indicate that while subjects took longer to learn TVQL than TForrns, they were more efficient and more accurate in specifying temporal queries with the TVQL interface than with the TForms interface.