Alternative opportunities and migration: An exposition

This paper presents a simple migration model which traces the link between individual decision making and observed aggregate migration behavior. The model clarifies and demonstrates the role of alternative opportunities in aggregate migration behavior using both diagrammatical and mathematical presentations. It is shown that the definition of alternative opportunities does not necessarily depend on the distance between origin and destination.The author is indebted to Roger Norton for useful comments.     

Static output-feedback of state-multiplicative systems with application to altitude control

A linear parameter dependent approach for designing a constant output-feedback controller for a linear time-invariant system with stochastic multiplicative Wiener-type noise, that achieves a minimum bound on either the stochastic H ₂ or the H _∞ performance level is introduced. A solution is achieved also for the case where in addition to the stochastic parameters, the system matrices reside in a given polytope. In this case, a parameter dependent Lyapunov function is introduced which enables the derivation of the required constant gain via a solution of a set of linear matrix inequalities that corresponds to the vertices of the uncertainty polytope.

The stochastic uncertainties appear in both the dynamic and the measurement matrices of the system. The problems are solved using the expected value of the standard performance index over the stochastic parameters. The theory developed is applied to an altitude control example.     

Development and Production of Array Barrier Detectors at SCD

XBn or XBp barrier detectors exhibit diffusion-limited dark currents comparable with mercury cadmium telluride Rule-07 and high quantum efficiencies. In 2011, SemiConductor Devices (SCD) introduced “HOT Pelican D”, a 640 × 512/15-μm pitch InAsSb/AlSbAs XBn mid-wave infrared (MWIR) detector with a 4.2-μm cut-off and an operating temperature of ～150 K. Its low power (～3 W), high pixel operability (>99.5%) and long mean time to failure make HOT Pelican D a highly reliable integrated detector-cooler product with a low size, weight and power. More recently, “HOT Hercules” was launched with a 1280 × 1024/15-μm format and similar advantages. A 3-megapixel, 10-μm pitch version (“HOT Blackbird”) is currently completing development. For long-wave infrared applications, SCD’s 640 × 512/15-μm pitch “Pelican-D LW” XBp type II superlattice (T2SL) detector has a ～9.3-μm cut-off wavelength. The detector contains InAs/GaSb and InAs/AlSb T2SLs, and is fabricated into focal plane array (FPA) detectors using standard production processes including hybridization to a digital silicon read-out integrated circuit (ROIC), glue underfill and substrate thinning. The ROIC has been designed so that the complete detector closely follows the interfaces of SCD’s MWIR Pelican-D detector family. The Pelican-D LW FPA has a quantum efficiency of ～50%, and operates at 77 K with a pixel operability of >99% and noise equivalent temperature difference of 13 mK at 30 Hz and F/2.7.     

Bisector curves of planar rational curves

This paper presents a simple and robust method for computing the bisector of two planar rational curves. We represent the correspondence between the foot points on two planar rational curves C₁(t) and C₂(r) as an implicit curve (t,r)=0, where (t,r) is a bivariate polynomial B-spline function. Given two rational curves of degree m in the xy-plane, the curve (t,r)=0 has degree 4m−2, which is considerably lower than that of the corresponding bisector curve in the xy-plane.     

Intersecting a freeform surface with a general swept surface

We present efficient and robust algorithms for intersecting a rational parametric freeform surface with a general swept surface. A swept surface is given as a one-parameter family of cross-sectional curves. By computing the intersection between a freeform surface and each cross-sectional curve in the family, we can solve the intersection problem. We propose two approaches, which are closely related to each other. The first approach detects certain critical points on the intersection curve, and then connects them in a correct topology. The second approach converts the intersection problem to that of finding the zero-set of polynomial equations in the parameter space. We first present these algorithms for the special case of intersecting a freeform surface with a ruled surface or a ringed surface. We then consider the intersection with a general swept surface, where each cross-sectional curve may be defined as a rational parametric curve or as an implicit algebraic curve.     

Relation of visual perception and visual-motor integration for clumsy children

Rac1 small GTPase plays pivotal roles in various cell functions such as cell morphology, cell polarity, and cell proliferation. We have previously identified IQGAP1 from bovine brain cytosol as a target for Rac1 by an affinity purification method. By using the same method, we purified a specifically Rac1-associated protein with a molecular mass of about 140 kDa (p140) from bovine brain cytosol. This protein interacted with guanosine 5'-(3-O-thio)triphosphate (GTPgammaS).glutathione S-transferase (GST)-Rac1 but not with the GDP.GST-Rac1, GTPgammaS.GST-Cdc42, or GTPgammaS.GST-RhoA. The amino acid sequences of this protein revealed that p140 is identified as a product of KIAA0068 gene. We denoted this protein as Sra-1 (Specifically Rac1-associated protein). Recombinant Sra-1 interacted with GTPgammaS.GST-Rac1 and weakly with GDP.Rac1 but not with GST-Cdc42 or GST-RhoA. The N-terminal domain of Sra-1 (1-407 amino acids) was responsible for the interaction with Rac1. Myc-tagged Sra-1 and the deletion mutant capable of interacting with Rac1, but not the mutants unable to bind Rac1, were colocalized with dominant active Rac1(Val-12) and cortical actin filament at the Rac1(Val-12)-induced membrane ruffling area in KB cells. Sra-1 was cosedimented with filamentous actin (F-actin), indicating that Sra-1 directly interacts with F-actin. These results suggest that Sra-1 is a novel and specific target for Rac1.     

CAT administration of language placement examinations

This article describes the development of a computerized adaptive test for Cegep de Jonquiere, a community college located in Quebec, Canada. Computerized language proficiency testing allows the simultaneous presentation of sound stimuli as the question is being presented to the test-taker. With a properly calibrated bank of items, the language proficiency test can be offered in an adaptive framework. By adapting the test to the test-taker's level of ability, an assessment can be made with significantly fewer items. We also describe our initial attempt to detect instances in which "cheating low" is occurring. In the "cheating low" situation, test-takers deliberately answer questions incorrectly, questions that they are fully capable of answering correctly had they been taking the test honestly.     

Fracture toughness and mechanical properties of glass fibre-epoxy composites

The present study investigated fracture properties and various mechanical properties of a set of unidirectional glass fibre-epoxy resin composites. This set was comprised of samples with volume fraction of fibres in the range 0.29 to 0.75. An identical set of composites was water-boil treated for 7 days, and the effect of this treatment on the above properties was examined. The work of fracture (γ _F) and the fracture surface energy of initiation (γ ₁) results were compared with existing theoretical models for the prediction of fracture toughness. It was discovered that theγ _F results agreed with the pull-out model [6], suggesting that this was the major contribution to the fracture energy of the complete process. Theγ ₁ values corresponded generally with the surfaces formation model [9], proposing that the creation of new fibre, matrix and fibre-matrix surfaces controls the stage of fracture initiation.     

Purification,identification and quantification of an egg-weight-depressing factor (vicine) in fababeans (Vicia faba L.)

An egg-weight-depressing factor in fababeans was isolated in pure form from a white precipitate which had been shown in a previous study, to contain a concentrated form of this factor. The analytically pure compound was obtained in colourless, needle crystals. Its melting point was 242-244°C, it contained 17.4% nitrogen but did not react with ninhydrin. The spectra had adsorption maxima at 274, 276 and 269 nm in acidic, neutral, and alkaline solutions, respectively. These and other properties were identical to those of vicine [2,6-diamino-4,5-dihydroxy pyrimidine,5-(β-D-glucopyrano-side)] a compound known to be present in fababeans. Vicine and convicine [2,4,5-trihydroxy, 6-aminopyrimidine,5-(β-D-glucopyranoside)]; compounds having similar chemical and probably physiological activity, were resolved on a cation-exchange column and were detected by monitoring at 280 nm. Quantitative results obtained with the procedure was shown to be similar to those obtained with two other procedures. This method, however, was superior to other methods as it gave individual values for both vicine and convicine rather than a composite value; sample preparation was simple and the method could readily be adapted to automatic analysis.