The characteristics of asymmetric pedestrian behavior: A preliminary study using passive smartphone location data

Understanding the movements of people is essential for the design and management of urban areas. This article presents a novel approach to understanding the asymmetry in route choice (i.e., the degree to which people choose different walking routes for their outbound and return journeys). The study utilizes a large volume of traces of individual routes, captured using a smartphone application. The routes are aggregated to a regular grid, and matrix statistics are developed to estimate the aggregate degree of route asymmetry for different types of route (shortest, longest, weekday, weekend, etc.). The results suggest that people change their route approximately 15% of the time. Although this varied little when observing trips made at the weekend or on a weekday, people taking journeys that deviated substantially from the shortest possible path were 6 percentage points less likely to change their routes than those taking journeys that were closest to the shortest path (14 and 20% asymmetry, respectively). The absolute length also impacted on the asymmetry of journeys, but not as substantially. This result is important because, for the first time, it reports a correlation between deviation from shortest route and aggregate pedestrian choice.     

Characterisation of the recreational fishery for southern rock lobster,Jasus edwardsii,in Tasmania,Australia: Implications for management

Southern rock lobster (Jasus edwardsii) support significant commercial and recreational fisheries in Tasmania, Australia. Since the mid 1990s the number of persons holding recreational lobster licences increased by over 80%, with c. 15 500 persons licensed in 2002/03. Assessment of the recreational fishery has been undertaken periodically since 1996 using a telephone‐diary survey method. The fishery was concentrated off the south‐east and east coasts of Tasmania and characterised by strong seasonality in catch and effort, which peaked markedly early in the fishing year (November‐January). Although pots were the most popular fishing method, daily catch rates by divers were more than double those for pots. Divers selectively harvested larger lobsters than those taken by pots and more frequently attained the daily bag limit of 5 lobsters. The estimated recreational harvest increased significantly since 1996/97 and in 2002/03 effectively reached a management trigger level of 10% of the total allowable commercial catch, flagging a review of recreational management arrangements.     

Overview of analogue science activities at the McGill Arctic Research Station,Axel Heiberg Island,Canadian High Arctic

The Canadian High Arctic contains several of the highest fidelity Mars analogue sites in the world. Situated at nearly 80° north, Expedition Fjord on Axel Heiberg Island is located within a polar desert climate, with the surrounding landscape and conditions providing an invaluable opportunity to examine terrestrial processes in a cold, dry environment. Through the Canadian Space Agency's Analogue Research Network program, scientific activities based out of the McGill Arctic Research Station (M.A.R.S.) are extremely broad in scope, representing physical, biological, and technological investigations. Some of the most unique hydrogeologic features under investigation near M.A.R.S. are a series of cold saline springs that maintain liquid-state flow year round regardless of air temperature. Previous studies have examined their geomorphic relation to discharge-related formations, water chemistry, temperature monitoring, discharge rates, and combined flow/thermal modeling. Recent investigations have identified microbial communities and characterized biological activity within the springs and within permafrost sections, having direct relevance to astrobiological analogue research goals. Another main thrust of research activities based at M.A.R.S. pertains to the detection, mapping, and quantification of subsurface ice deposits. A long-term study is presently underway examining polygonal terrain, comparing surficial patterns found in the region with those identified on Mars, and using surface morphology to estimate ice wedge volumes through a combination of aerial photography interpretation and ground-based geophysical techniques. Other technological developments include the use of in situ microscopy for the detection of biomarkers and improved permafrost drilling techniques. This paper presents an overview of previous studies undertaken at M.A.R.S. over the past decades and will describe in detail both present and upcoming work.     

Voyager U.V. spectrometer observations of He 584 Å dayglow at Jupiter

The intensity of Jupiter's He 584 Å airglow has been measured by the Voyager U.V. spectrometers. The disc-averaged brightness is about 4 Rs and limb darkening is present. The intensity probably varies with longitude, the variation being out of phase with the H Lyman-α intensity bulge. Modelling of resonance scattering of the solar He 584 Å line by Jupiter's atmosphere has shown that the hydrogen and helium emissions can be explained about equally well by at least two self-consistent scenarios involving the structure (temperature and eddy diffusion coefficient) and excitation of the atmosphere. All our evidence points to a dramatic change of conditions in the Jovian atmosphere in the time between Pioneer and Voyager encounters.     

Resonance scattering by N2

A study is made of the intensity distribution among the bands of the Meinel and first negative system of N₂⁺ due to resonance scattering of sunlight. Absolute transition probabilities are used to calculate the relative populations among the ion states under resonance scattering conditions; the mean lifetime for deactivation is the parameter which determines the amount of resonance scattering. Photon scattering rates are calculated for most of the ion bands and it is suggested that an appropriate value for the 3914 Å band would be 0·050 photons/ sec per ion. Observations of the Δυ = −1 sequence of the first negative system in the twilight spectrum are reported. Extended vibrational development is detected which indicates that only about 80 per cent of the emission is resonance scattered. Sunlit auroral spectra of N₂⁺, however, which have been generally considered to be due predominantly to resonance scattering, indicates only about 40 per cent of the emission is due to resonance scattering. Measurable effects resulting from a charge-transfer ion source (O⁺(²D)) are predicted.     

Copper-nickel-enriched ferromanganese nodules and associated crusts from the Bauer Basin,northwest Nazca plate

Analysis of a suite of ferromanganese nodules and crusts from the dredge Y73-3-22D in the Bauer Deep (13°40′S, 102°08′W) shows distinct differences between the nodules and crusts. Ultra-slow-scan X-ray diffraction shows that the nodules are more enriched in todorokite while the crusts are more enriched in δ MnO₂. Both have phillipsite and smectite as accessory minerals as well as minor amounts of apatite, barite, and quartz. Chemical analyses show that the nodules also have higher abundances of Mn, Ni, Cu, Zn, and Ba, while crusts are more enriched in Fe, Co, and Ca. We suggest that normal authigenic precipitation of ferromanganese oxyhydroxides from seawater controls the mineralogy and chemistry of the crusts, while nodule mineralogy and chemistry are governed by small-scale diagenetic reactions in the sediment. Todorokite may form because iron in the Fe-Mn oxyhydroxide material dispersed in the sediment reacts with amorphous silica to form iron-rich smectites. The remaining oxyhydroxide material recrystallizes as todorokite.     

A comparison of dimension-adjusted catch data methods for assessment of fish and crab abundance in intertidal salt marshes

Sample collection methods and data standardization techniques accounting for marsh physiography were tested for mobile aquatic fauna in two intertidal pocket salt marshes in Sarah’s Creek, a tributary to the York River in Virginia. Fish and blue crab populations were described and compared as numbers per cubic meter of total marsh volume and numbers per square meter of total marsh area. These methods increase the accuracy of the analyses of sampled populations by relying on fewer assumptions than traditionals random sampling methods. Depending upon the season and the species compared, statistical differences were observed between dimension-adjusted data within the same sampled populations. Our data suggest that accurate population profiles can be determined if collection methods and data adjustments are based on the ecology, behavior, and life-history stage of the target species.     

In search of a gust definition

We propose a simple gust definition based on the theory of excursions by Rice (1944 and 1945). We discuss the relation to the distribution of extreme events and demonstrate theoretically and experimentally that the most probable extreme event is very close to being identical to the gust according to our definition. We demonstrate how it is possible to predict the gust on the basis of the measured mean wind and variance rather than rely on actually measured extreme excursions. Our gust definition also allows us to predict the average duration of a gust.Supported by the Catalonian Research Council (CIRIT), Spain.