Mie scattering from a sonoluminescing air bubble in water

Applied Optics, Volume 34, No. 15, pp. 2648-2654 (20 May 1995)A single bubble of air in water can emit pulses of blue-white light that have durations of less than 50 ps while it is oscillating in an acoustic standing wave. The emission is called sonoluminescence. A knowledge of the bubble diameter throughout the cycle, and in particular near the time of sonoluminescence emission, can provide important information about the phenomenon. A new Mie scattering technique is developed to determine the size of the bubble through its expansion and collapse during the acoustic cycle. The technique does not rely on an independent means of calibration or on accurate measurements of the scattered intensity.This work was supported in part by the Naval Postgraduate School Research Program and the Office of Naval Research

Influence of hand position on the near-effect in 3D attention

Voluntary reorienting of attention in real depth situations is characterized by an attentional bias to locations near the viewer once attention is deployed to a spatially cued object in depth. Previously this effect (initially referred to as the ‘near-effect’) was attributed to access of a 3D viewer-centred spatial representation for guiding attention in 3D space. The aim of this study was to investigate whether the near-bias could have been associated with the position of the response-hand, always near the viewer in previous studies investigating endogenous attentional shifts in real depth. In Experiment 1, the response-hand was placed at either the near or far target depth in a depth cueing task. Placing the response-hand at the far target depth abolished the near-effect, but failed to bias spatial attention to the far location. Experiment 2 showed that the response-hand effect was not modulated by the presence of an additional passive hand, whereas Experiment 3 confirmed that attentional prioritization of the passive hand was not masked by the influence of the responding hand on spatial attention in Experiment 2. The pattern of results is most consistent with the idea that response preparation can modulate spatial attention within a 3D viewer-centred spatial representation

Improving Highway Work Zone Safety

Highway work zones disrupt normal traffic flow and can create severe safety problems. Due to the rising needs in highway maintenance and construction in the United States, the number of work zones is increasing nationwide. With a total of 1,010 fatalities and more than 40,000 injuries occurring in 2006, improvements in work zone safety are necessary. The three primary objectives of this research project included: 1) to determine the effectiveness of a Portable Changeable Message Sign (PCMS) in reducing vehicle speeds on two-lane, rural highway work zones; 2) to determine the effectiveness of a Temporary Traffic Sign (TTS), (W20-1, “Road Work Ahead”); and 3) to determine motorists’ responses to the signage. To accomplish these objectives, field experiments were conducted at US-36 and US-73 in Seneca and Hiawatha, Kansas, respectively. During the field experiments, an evaluation of the effectiveness of the PCMS was conducted under three different conditions: 1) PCMS on; 2) PCMS off, but still visible; and 3) PCMS removed from the road and out of sight. The researchers also divided the vehicles into three classes (passenger car, truck, and semitrailer) and compared the mean speed change of these classes based on three different sign setups: PCMS on, PCMS off, and the use of the TTS (W20-1, “Road Work Ahead”). A survey was also conducted at the experimental work zones to obtain a general understanding of the motorists’ attitudes as they traveled through the construction areas. Based on the data analysis results, researchers concluded that the presence of the PCMS effectively reduced vehicle speeds on two-lane highway work zones. A slow speed is more likely to reduce the probability of a crash or the severity of a crash. In addition, researchers performed a univariate analysis of the variance test to determine if a significant interaction existed between motorists’ responses and the sign conditions. The results showed a significant interaction between the signs and passenger car vehicles

New insights into the drainage of inundated ice-wedge polygons using fundamental hydrologic principles

The pathways and timing of drainage from the inundated centers of ice-wedge polygons in a warming climate have important implications for carbon flushing, advective heat transport, and transitions from methane to carbon dioxide dominated emissions. Here, we expand on previous research using a recently developed analytical model of drainage from a low-centered polygon. Specifically, we perform (1) a calibration to field data identifying necessary model refinements and (2) a rigorous model sensitivity analysis that expands on previously published indications of polygon drainage characteristics. This research provides intuition on inundated polygon drainage by presenting the first in-depth analysis of drainage within a polygon based on hydrogeological first principles. We verify a recently developed analytical solution of polygon drainage through a calibration to a season of field measurements. Due to the parsimony of the model, providing the potential that it could fail, we identify the minimum necessary refinements that allow the model to match water levels measured in a low-centered polygon. We find that (1) the measured precipitation must be increased by a factor of around 2.2, and (2) the vertical soil hydraulic conductivity must decrease with increasing thaw depth. Model refinement (1) accounts for runoff from rims into the ice-wedge polygon pond during precipitation events and possible rain gauge undercatch, while refinement (2) accounts for the decreasing permeability of deeper soil layers. The calibration to field measurements supports the validity of the model, indicating that it is able to represent ice-wedge polygon drainage dynamics. We then use the analytical solution in non-dimensional form to provide a baseline for the effects of polygon aspect ratios (radius to thaw depth) and coefficient of hydraulic conductivity anisotropy (horizontal to vertical hydraulic conductivity) on drainage pathways and temporal depletion of ponded water from inundated ice-wedge polygon centers. By varying the polygon aspect ratio, we evaluate the relative effect of polygon size (width), inter-annual increases in active-layer thickness, and seasonal increases in thaw depth on drainage. The results of our sensitivity analysis rigorously confirm a previous analysis indicating that most drainage through the active layer occurs along an annular region of the polygon center near the rims. This has important implications for transport of nutrients (such as dissolved organic carbon) and advection of heat towards ice-wedge tops. We also provide a comprehensive investigation of the effect of polygon aspect ratio and anisotropy on drainage timing and patterns, expanding on previously published research. Our results indicate that polygons with large aspect ratios and high anisotropy will have the most distributed drainage, while polygons with large aspect ratios and low anisotropy will have their drainage most focused near their periphery and will drain most slowly. Polygons with small aspect ratios and high anisotropy will drain most quickly. These results, based on parametric investigation of idealized scenarios, provide a baseline for further research considering the geometric and hydraulic complexities of ice-wedge polygons

An Experimental and Analytical Evaluation of Wall And Window Retrofit Configurations: Supporting the Residential Retrofit Best Practices Guide

A Retrofit Best Practices Guide was developed to encourage homeowners to consider energy conservation issues whenever they modify their siding or windows. In support of this guide, an experimental program was implemented to measure the performance of a number of possible wall siding and window retrofit configurations. Both thermal and air-leakage measurements were made for a 2.4 x 2.4 m (8 x 8 ft) wall section with and without a 0.9 x 1.2 m (3 x 4 ft) window. The windows tested were previously well-characterized at a dedicated window test facility. A computer model was also used to provide information for the Best Practices Guide. The experimental data for walls and windows were used in conjunction with this model to estimate the total annual energy savings for several typical houses in a number of different locations

Does the road to happiness depend on the retirement decision? Evidence from Italy

This study estimates the causal effect of retirement decision on well-being in Italy. To do so, the authors exploit the exogenous variation provided by the changes in the eligibility criteria for pensions that were enacted in Italy in 1995 (Dini’s law) and in 1997 (Prodi’s law, from the names of the prime ministers at the time of their introduction). A sizeable and positive impact of retirement decision is found on satisfaction with leisure time and on frequency of meeting friends. Furthermore, the results are generalized, allowing for the estimation of different moments from different data sources

Primate modularity and evolution: first anatomical network analysis of primate head and neck musculoskeletal system

Network theory is increasingly being used to study morphological modularity and integration. Anatomical network analysis (AnNA) is a framework for quantitatively characterizing the topological organization of anatomical structures and providing an operational way to compare structural integration and modularity. Here we apply AnNA for the first time to study the macroevolution of the musculoskeletal system of the head and neck in primates and their closest living relatives, paying special attention to the evolution of structures associated with facial and vocal communication. We show that well-defined left and right facial modules are plesiomorphic for primates, while anthropoids consistently have asymmetrical facial modules that include structures of both sides, a change likely related to the ability to display more complex, asymmetrical facial expressions. However, no clear trends in network organization were found regarding the evolution of structures related to speech. Remarkably, the increase in the number of head and neck muscles – and thus of musculoskeletal structures – in human evolution led to a decrease in network density and complexity in humans