A method for the incorporation of parametric uncertainty in the weighted evaluation multi-attribute decision analysis model

We develop an extension of the classic Weighted Evaluation (WE) Multi-Attribute Decision Analysis (MADA) model that allows for uncertainty in the parameters of the model. Uncertainties in attribute importance weights and alternative evaluation ratings are represented by independent uniform, triangular or beta random variables; and an iterative multi-variate integration scheme is used to evaluate the mean, variance and skewness of the resulting Probabilistic Weighted Evaluation (PWE). These moments are used to compute two-term Edgeworth and normal approximations to the distribution of: (a) the PWE for each of several alternatives that are to be analysed separately; or (b) the difference between PWEs for selected alternatives that are to be analysed on a pairwise basis. The proposed methodology is used to compare probabilistically three alternative solutions to the Mexico City Airport Siting Problem of Keeney and Raiffa (Keeney, R. L. and Raiffa, H., Decisions with Multiple Objectives. Wiley, New York, 1976).     

Student Cooperative Learning Workshops Go Mainstream: UMR's Excel Program

We offer cooperative learning workshops to all students enrolled in our largest lower division math and science courses where failure rates are high. Participation in the workshops is related to retention and higher academic achievement among engineering students of various abilities. In the tradition of workshops developed for disadvantaged students in mathematics, science, and engineering, our students meet outside of class in structured group meetings. Our contributions to this tradition include application to a broader range of courses, the inclusion of all types of students, and enhanced training of workshop facilitators in small group communication methods and modern leadership techniques. Our approach is readily adaptable to most institutions.     

Replicating America’s earliest bloomery process

Over the last twenty years, there has been a discernable increase in the number of scholars who have focused their research on metal production, working and use in antiquity, a field of study which has come to be known as archaeometallurgy. Materials scientists and conservators have worked primarily in the laboratory while archaeologists have conducted fieldwork geared to the study of metal technology in a cultural context with laboratory analysis as one portion of the interpretive program.     

Optical Chemical Barcoding Based on Polarization Controlled Plasmonic Nanopixels

Plasmonic devices offer the possibility of passively detecting changes in local chemistry that opens up a wide range of applications from molecular sensing to monitoring water quality. Conventional plasmonics have previously shown great promise as nanoscale chemical sensors through detection of small variations in the local refractive index (RI). The motivation behind using plasmonics for these applications includes the fact that detection is entirely passive and the devices themselves can be readily miniaturized. Previously, a lack of any control over the output of these devices, has fundamentally limited their application to chemicals which produce clearly identifiable resonances within the range of detection. Here it is demonstrated that microfluidic devices, incorporating polarization‐controlled plasmonic nanopixels, allow the device response to be tuned to the particular analyte of interest, anywhere within the visible spectrum. This dramatically increases the effective dynamic range and allows local variations in RI to be perceived directly as color changes by the human eye. Active control over the output of the device also enables clear differentiation between a number of different analytes, paving the way for plasmonics to be used for a wide range of real‐world chemical sensing applications.     

Ant-like Traits in Wingless Parasitoids Repel Attack from Wolf Spiders

A recent study showed that a wingless parasitoid, Gelis agilis, exhibits a suite of ant-like traits that repels attack from wolf spiders. When agitated, G. agilis secreted 6-methyl-5-hepten-2-one (sulcatone), which a small number of ant species produce as an alarm/panic pheromone. Here, we tested four Gelis parasitoid species, occurring in the same food chain and microhabitats, for the presence of sulcatone and conducted two-species choice bioassays with wolf spiders to determine their degree of susceptibility to attack. All four Gelis species, including both winged and wingless species, produced sulcatone, whereas a closely related species, Acrolyta nens, and the more distantly related Cotesia glomerata, did not. In two-choice bioassays, spiders overwhelmingly rejected the wingless Gelis species, preferring A. nens and C. glomerata. However, spiders exhibited no preference for either A. nens or G. areator, both of which are winged. Wingless gelines exhibited several ant-like traits, perhaps accounting for the reluctance of spiders to attack them. On the other hand, despite producing sulcatone, the winged G. areator more closely resembles other winged cryptines like A. nens, making it harder for spiders to distinguish between these two species. C. glomerata was also preferred by spiders over A. nens, suggesting that other non-sulcatone producing cryptines nevertheless possess traits that make them less attractive as prey. Phylogenetic reconstruction of the Cryptinae reveals that G. hortensis and G. proximus are ‘sister’species, with G. agilis, and G.areator in particular evolving along more distant trajectories. We discuss the possibility that wingless Gelis species have evolved a suite of ant-like traits as a form, of mimicry to repel predators on the ground.     

Effect of crosslinking on the elasticity of polyelectrolyte multilayer films measured by colloidal probe AFM

A homemade colloidal probe atomic force microscope was used to perform nanoindentation with a spherical probe of 5 microm in diameter, at different approach velocities in order to extract the Young's modulus, E0, of poly(L-lysine)/hyaluronan (PLL/HA) films. This parameter is of prime importance to control cellular adhesion. The films were either kept in their native form or cross-linked with a mixture of 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide (EDC) and N-hydrosulfosuccinimide (sulfo-NHS), where the EDC concentration was varied from 1 up to 100 mg mL(-1) (approximately from 5 to 500 mM). A model based on Hertz mechanics was used to account for the interactions between film and probe. It is shown that the Young's modulus varies with the approach velocity for the native (PLL/HA) films, whereas for cross-linked ones, E0 is independent from the velocity over the whole range investigated. It is found that for native films, E0 takes a value of 3 kPa at low approach velocities, a velocity domain that should be relevant in cellular adhesion processes. The Young's modulus increases with the EDC concentration used to cross-link the films and levels off at a value of about 400 kPa for EDC concentrations exceeding 40 mg mL(-1). Thus, it is possible by crosslinking PLL/HA films to control their elastic properties with the aim to alter their behavior as to the cellular adhesion.     

Electron microscopy localization and characterization of functionalized composite organic-inorganic SERS nanoparticles on leukemia cells

We demonstrate the use of electron microscopy as a powerful characterization tool to identify and locate antibody-conjugated composite organic-inorganic nanoparticle (COINs) surface enhanced Raman scattering (SERS) nanoparticles on cells. U937 leukemia cells labeled with antibody CD54-conjugated COINs were characterized in their native, hydrated state using wet scanning electron microscopy (SEM) and in their dehydrated state using high-resolution SEM. In both cases, the backscattered electron (BSE) detector was used to detect and identify the silver constituents in COINs due to its high sensitivity to atomic number variations within a specimen. The imaging and analytical capabilities in the SEM were further complemented by higher resolution transmission electron microscopy (TEM) images and scanning Auger electron spectroscopy (AES) data to give reliable and high-resolution information about nanoparticles and their binding to cell surface antigens.     

Fourier Elimination for Compiling Constraint Hierarchies

Linear equality and inequality constraints arise naturally in specifying many aspects of user interfaces, such as requiring that one window be to the left of another, requiring that a pane occupy the leftmost 1/3 of a window, or preferring that an object be contained within a rectangle if possible. For interactive use, we need to solve similar constraint satisfaction problems repeatedly for each screen refresh, with each successive problem differing from the previous one only in the position of an input device and the previous state of the system. We present an algorithm for solving such systems of constraints using projection. The solution is compiled into very efficient, constraint-free code, which is parameterized by the new inputs. Producing straight-line, constraint-free code of this sort is important in a number of applications: for example, to provide predictable performance in real-time systems, to allow companies to ship products without including a runtime constraint solver, to compile Java applets that can be downloaded and run remotely (again without having to include a runtime solver), or for applications where runtime efficiency is particularly important. Even for less time-critical user interface applications, the smooth performance of the resulting code is more pleasing than that of code produced using other current techniques.     

Static Fourier-transform ultraviolet spectrometer for gas detection

We report the design, construction, and evaluation of a static Fourier-transform ultraviolet spectrometer. The spectrometer is based on Wollaston prisms that form an interferogram in the spatial domain, which is recorded with a detector array. We demonstrate the application of the spectrometer to gas detection. Using a deuterium light source, we measured a detection limit, with a 1-s integration time, for hydrogen sulfide and sulfur dioxide, corresponding to 0.2 ppm over a 5-m path length.     

Precision pointing and tracking through random media by exploitation of the enhanced backscatter phenomenon

The active illumination of a target through a turbulent medium with a monostatic transmitter-receiver results in a naturally occurring conjugate wave caused by reciprocal scattering paths that experience identical phase variations. This reciprocal path-scattering phenomenon produces an enhanced backscatter in the retroverse direction (precisely along the boresight of the pointing telescope). A dual aperture causes this intensity enhancement to take the form of Young's interference fringes. Interference fringes produced by the reciprocal path-scattering phenomenon are temporally stable even in the presence of time-varying turbulence. Choosing the width-to-separation ratio of the dual apertures appropriately and utilizing orthogonal polarizations to suppress the time-varying common-path scattered radiation allow one to achieve interferometric sensitivity in pointing accuracy through a random medium or turbulent atmosphere. Computer simulations are compared with laboratory experimental data. This new precision pointing and tracking technique has potential applications in ground-to-space laser communications, laser power beaming to satellites, and theater missile defense scenarios.