Sensitivity of the backscattering Mueller matrix to particle shape and thermodynamic phase

The Mueller matrix (M) corresponding to the phase matrix in the backscattering region (scattering angles ranging from 175 degrees to 180 degrees) is investigated for light scattering at a 0.532-microm wavelength by hexagonal ice crystals, ice spheres, and water droplets. For hexagonal ice crystals we assume three aspect ratios (plates, compact columns, and columns). It is shown that the contour patterns of the backscattering Mueller matrix elements other than M11, M44, M14, and M41 depend on particle geometry; M22 and M33 are particularly sensitive to the aspect ratio of ice crystals. The Mueller matrix for spherical ice particles is different from those for nonspherical ice particles. In addition to discriminating between spherical and nonspherical particles, the Mueller matrix may offer some insight as to cloud thermodynamic phase. The contour patterns for large ice spheres with an effective size of 100 microm are substantially different from those associated with small water droplets with an effective size of 4 microm.     

Examining the consistency of products derived from various ocean color sensors in open ocean (Case 1) waters in the perspective of a multi-sensor approach

During its lifetime, a space-borne ocean color sensor provides world-wide information about important biogeochemical properties of the upper ocean every 2 to 4 days in cloudless regions. Merging simultaneous or complementary data from such sensors to obtain better spatial and temporal coverage is a recurring objective, but it can only be reached if the consistency of the sensor-specific products, as delivered by the various Space Agencies, has first been carefully examined. The goal of the present study is to provide a procedure for establishing a coherency of open ocean (Case-1 waters) data products, for which the various data processing methods are sufficiently similar. The development of the procedure includes a detailed comparison of the marine algorithms used (after atmospheric corrections) by space agencies for the production of standard products, such as the chlorophyll concentration, [Chl], and the diffuse attenuation coefficient, K_d. The MODIS-Aqua, SeaWiFS and MERIS [Chl] products agree over a wide range, between ∼ 0.1 and 3 mg m^− 3, whereas increasing divergences occur for oligotrophic waters ([Chl] (from 0.02 to 0.09 mg m^− 3). For the K_d(490) coefficient, different algorithms are in use, with differing results. Based on a semi-analytical reflectance model and hyperspectral approach, the present work proposes a harmonization of the algorithms allowing the products of the various sensors to be comparable, and ultimately, meaningfully merged (the merging procedures themselves are not examined). Additional potential products, obtained by using [Chl] as an intermediate tool, are also examined and proposed. These products include the thickness of the layer heated by the sun, the depth of the euphotic zone, and the Secchi disk depth. The physical limitations in the predictive skill of such downward extrapolations, made from information concerning only the upper layer, are stressed.     

Improving angular error via systematically designed near-circular Gaussian-based feature extraction operators

In image filtering, the ‘circularity’ of an operator is an important factor affecting its accuracy. For example, circular differential edge operators are effective in minimising the angular error in the estimation of image gradient direction. We present a general approach to the computation of scalable circular low-level image processing operators that is based on the finite element method. We show that the use of Gaussian basis functions within the finite element method provides a framework for a systematic and efficient design procedure for operators that are scalable to near-circular neighbourhoods through the use of an explicit scale parameter. The general design technique may be applied to a range of operators. Here we evaluate the approach for the design of the image gradient operator. We illustrate that this design procedure significantly reduces angular error in comparison to other well-known gradient approximation methods.     

The impact of continuing care adherence on environmental risks, substance use, and substance-related problems following adolescent residential treatment.

The effectiveness of adolescent treatment to reduce substance use has been demonstrated by a number of different literature reviews, yet longer term outcome studies have suggested that continued alcohol and other drug use is common. Participation in continuing care services and reductions in environmental risk factors (e.g., peer substance use or alcohol or drug use in the home) have both been found to be associated with improved posttreatment substance use. The authors conducted Path analysis to examine the experimental direct effect of the Assertive Continuing Care Protocol (S. H. Godley, M. D. Godley, & M. L. Dennis, 2001) on general continuing care adherence following residential treatment and the protocol's indirect effect (via general continuing care adherence) on social and environmental risk factors, as well as subsequent substance use and substance-related problems. Supporting previous findings, the final model indicates that greater adherence to continuing care is associated with reductions in environmental risk, which in turn is associated with reduced adolescent substance use and substance-related problems 9 months after discharge from residential treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An examination of factors contributing to a reduction in subgroup differences on a constructed-response paper-and-pencil test of scholastic achievement.

The authors investigated subgroup differences on a multiple-choice and constructed-response test of scholastic achievement in a sample of 197 African American and 258 White test takers. Although both groups had lower mean scores on the constructed-response test, the results showed a 39% reduction in subgroup differences compared with the multiple-choice test. The results demonstrate that the lower subgroup differences were explained by more favorable test perceptions for African Americans on the constructed-response test. In addition, the two test formats displayed comparable levels of criterion-related validity. The results suggest that the constructed-response test format may be a viable alternative to the traditional multiple-choice test format in efforts to simultaneously use valid predictors of performance and minimize subgroup differences in high-stakes testing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motion capture controls negate the violent video-game effect

Considerable research suggests that violent video game play increases players’ aggression. However, few studies have investigated this effect in the now ubiquitous context of motion-capture technology. Study 1 used a 2 × 2 design, with a violent (Soul Calibur) and non-violent (Lego Indiana Jones) game, played under analog (Playstation 3) and motion-capture (Nintendo Wii) conditions. Violent video game play led to less aggression when participants used motion-capture controls. Study 2 eliminated potential confounds by using the only game on the Wii system that can be played identically with or without motion capture (Punch-Out!!). Again, participants who used motion-capture were less aggressive. Study 3 looked for effects of cooperative vs. competitive play during 2-player motion-capture gaming (Soul Calibur, Wii). Participants using motion-capture controls in competitive and cooperative scenarios did not differ from baseline. These results run counter to standard models relating violent video game play to aggressive behavior, highlighting the difficulty in anticipating the effects of newer, more immersive technology.     

Experimental Validation of a Helicopter Autopilot Design using Model-Based PID Control

Autonomous helicopter flight provides a challenging control problem. In order to evaluate control designs, an experimental platform must be developed in order to conduct flight tests. However, the literature describing existing platforms focuses on the hardware details, while little information is given regarding software design and control algorithm implementation. This paper presents the design, implementation, and validation of an experimental helicopter platform with a primary focus on a software framework optimized for controller development. In order to validate the operation of this platform and provide a basis for comparison with more sophisticated nonlinear designs, a PID controller with feedforward gravity compensation is derived using the generally accepted small helicopter model and tested experimentally.     

Timing HIV infection with a simple and accurate population viral dynamics model

Clinical trials for HIV prevention can require knowledge of infection times to subsequently determine protective drug levels. Yet, infection timing is difficult when study visits are sparse. Using population nonlinear mixed-effects (pNLME) statistical inference and viral loads from 46 RV217 study participants, we developed a relatively simple HIV primary infection model that achieved an excellent fit to all data. We also discovered that Aptima assay values from the study strongly correlated with viral loads, enabling imputation of very early viral loads for 28/46 participants. Estimated times between infecting exposures and first positives were generally longer than prior estimates (average of two weeks) and were robust to missing viral upslope data. On simulated data, we found that tighter sampling before diagnosis improved estimation more than tighter sampling after diagnosis. Sampling weekly before and monthly after diagnosis was a pragmatic design for good timing accuracy. Our pNLME timing approach is widely applicable to other infections with existing mathematical models. The present model could be used to simulate future HIV trials and may help estimate protective thresholds from the recently completed antibody-mediated prevention trials.     

Scheduling operations on parallel machine tools

We introduce unique scheduling problems that arise for multiple spindle machine tools. The ability of these machines to perform simultaneous operations on more than one part creates constraints that are not found in the traditional scheduling literature. Two types of solution procedures are introduced for these problems. The first uses priority dispatching rules and a delay factor concept, while the second uses a genetic algorithm with a random keys encoding. The effectiveness of these methods is demonstrated on test problems with comparisons to lower bounds