Automated detection of ocular alignment with binocular retinal birefringence scanning

We previously developed a retinal birefingence scanning (RBS) device to detect eye fixation. The purpose of this study was to determine whether a new binocular RBS (BRBS) instrument can detect simultaneous fixation of both eyes. Control (nonmyopic and myopic) and strabismic subjects were studied by use of BRBS at a fixation distance of 45 cm. Binocularity (the percentage of measurements with bilateral fixation) was determined from the BRBS output. All nonstrabismic subjects with good quality signals had binocularity >75%. Binocularity averaged 5% in four subjects with strabismus (range of 0-20%). BRBS may potentially be used to screen individuals for abnormal eye alignment.     

Rapid field screening of soils for heavy metals with spark-induced breakdown spectroscopy

Spark-induced breakdown spectroscopy (SIBS) is a recently developed atomic-fluorescene-based analytical technique that is analogous to laser-induced breakdown spectroscopy. SIBS, however, uses an electrical plasma generation method on nonconductive samples instead of a focused laser beam. Here we describe the basic characteristics of SIBS and its application to the field-screening analysis of soil, using a standard addition analytical approach. Detection limits of approximately 25 mg/kg have been seen for lead, chromium, barium, mercury, and cadmium. A variety of soils have been tested, some cocontaminated with organic material and uranium (238U).     

Parallel components of an equivalent circuit of two-dimensional island gold films

Two-dimensional island gold films [2D-I(Au)Fs] were prepared by the thermal evaporation technique where Corning 7059 glass slides, held at ambient temperature during deposition, were used as substrates. After exposing the films to air at a room temperature of 300 K, the d.c. resistance of the films was monitored until the films attained short-term stability, namely, invariance of resistance over time. The different island gold films were identified by the values of their stabilized surface resistivity ( _s ); these values in units of M/ are 23, 275, 4.4×10³, 23.2×10³ and 37.5×10³. The values of the parallel components (r _p , c _p ) of an equivalent circuit of the investigated films were obtained via a.c. measurements on the films performed by a lock-in amplifier at six temperatures (T) 100, 140, 180, 220, 260, and 300 K, where at each of them the frequency (f) of the a.c. voltage imposed on the film was varied over the range 0.1–80 kHz. It is found that: (i) regarding r _p , its value decreases with the increase in (T) and (f) while it increases as ( _s ) does. (ii) with respect to c _p , its magnitude decreases with the increase in (f) and ( _s ) but increases as (T) does. Our results are interpreted, qualitatively, by relating r _p and c _p to three frequency-independent parameters that reflect what happens physically in an island film when a steady voltage is applied across it. These parameters are R _b , R _g , and C _g ; where R _b is the resistance associated with the conduction of free electrons within the bulk (interior) of islands themselves, R _g is the resistance that accompanies the conduction across the gaps between the islands and C _g is the capacitance resulting from the presence of separated metallic islands at different potentials. To the best of our knowledge, the present results are the first to be reported for 2D-I(Au)Fs.     

Retrospective and prospective validity of aircraft accident risk indicators

Data from a national survey of pilots were used to examine the validity of measures for the prediction of aviation accidents that had occurred prior to the survey (retrospective analysis) and accidents that occurred after the survey (prospective analysis). Separate retrospective and prospective analyses were conducted, and 45 measures from the survey were found to be associated significantly with accident involvement in the retrospective analysis. However, only 13 of those 45 measures achieved significance in the prospective analysis. Most of the measures found to be significantly related to accident involvement concerned aviation exposure; the remaining measures related to pilots' perceived and actual level of caution. The study is unique in its use of a cohort design for the examination of aircraft accident risk prospectively, and the results suggest the need for caution in the interpretation of retrospective analyses in this research domain. Actual or potential applications of this research include the design of aviation safety programs and the design or interpretation of studies that address indicators of aircraft accident risk.     

An assessment of two classification methods for mapping Thames Estuary intertidal habitats using CASI data

The aim of this study was to find the most appropriate method of classification for the Thames intertidal habitat types at Crayford Marsh and Dartford Creek by using Compact Airborne Spectrographic Imager (CASI ) data. Preliminary evaluation of commonly available classification algorithms produced two candidate techniques: the Maximum Likelihood Classifier (MLC) and the Spectral Angle Mapper (SAM). Pre-classification enhancements and the two different classifiers were compared. Ten different dataset combinations were created for two pilot sites: one at Crayford Marsh and one at Dartford Creek. These consisted of the original CASI bandset (15 bands in spatial mode from blue to near-infrared) and nine other combinations resulting from band subsets, Principal Component Analysis (PCA) and Normalized Difference Vegetation Index (NDVI ). Twelve classes were established for each site although only some of these were common to both. Each classified image was accuracy assessed using a combination of field mapping, field photographs and air photograph interpretation as reference data. The most accurate classification (68% for Crayford Marsh and 53% for Dartford Creek) for both sites comprised the use of MLC with a dataset created from PCs 2, 3 and 4 from a PCA carried out on the original 15 band data, combined with an additional NDVI band. CASI data proved useful for the mapping of salt-marsh vegetation and sediments especially in the Crayford Marsh site. In the Dartford Creek site, however, there was significant confusion between some classes. Further work is recommended to test the classification     

Landsat mapping of annual inundation (1979–2006) of the Macquarie Marshes in semi-arid Australia

Measuring inundation over long timeframes is essential for understanding the responses of large floodplain wetlands on regulated rivers, such as the internationally Ramsar listed Macquarie Marshes (2000 km²) in central-eastern Australia. We used near-spring Landsat images (Multispectral Scanner (MSS) and Thematic Mapper (TM) imagery) over 28 years (1979–2006) and classified for inundation, integrating water and vegetation response using Iterative Self-Organizing Data Analysis (ISODATA) clustering. A spatially explicit inundation index showed that zones inundated with high frequency were mostly in the northern region. Change detection of inundation indices over three consecutive water management periods (period 1 (1979–1987), period 2 (1988–1996) and period 3 (1997–2006)) showed that zones inundated with high frequency across the Macquarie Marshes contracted, equating to the loss of three or more spring floods from each 9-year period, despite no corresponding change in annual catchment or local rainfall. Landsat represents the only effective available long-term information for analysing long-term changes in inundation patterns of floodplain wetlands.     

A Genetically-Based Latitudinal Cline in the Emission of Herbivore-Induced Plant Volatile Organic Compounds

The existence of predictable latitudinal variation in plant defense against herbivores remains controversial. A prevailing view holds that higher levels of plant defense evolve at low latitudes compared to high latitudes as an adaptive plant response to higher herbivore pressure on low-latitude plants. To date, this prediction has not been examined with respect to volatile organic compounds (VOCs) that many plants emit, often thus attracting the natural enemies of herbivores. Here, we compared genetically-based constitutive and herbivore-induced aboveground vegetative VOC emissions from plants originating across a gradient of more than 10° of latitude (>1,500 km). We collected headspace VOCs from Asclepias syriaca (common milkweed) originating from 20 populations across its natural range and grown in a common garden near the range center. Feeding by specialist Danaus plexippus (monarch) larvae induced VOCs, and field environmental conditions (temperature, light, and humidity) also influenced emissions. Monarch damage increased plant VOC concentrations and altered VOC blends. We found that genetically-based induced VOC emissions varied with the latitude of plant population origin, although the pattern followed the reverse of that predicted—induced VOC concentration increased with increasing latitude. This pattern appeared to be driven by a greater induction of sesquiterpenoids at higher latitudes. In contrast, constitutive VOC emission did not vary systematically with latitude, and the induction of green leafy volatiles declined with latitude. Our results do not support the prevailing view that plant defense is greater at lower than at higher latitudes. That the pattern holds only for herbivore-induced VOC emission, and not constitutive emission, suggests that latitudinal variation in VOCs is not a simple adaptive response to climatic factors.     

An experimental design strategy for distinguishing among rival mechanistic models an application to the catalytic hydrogenation of propylene

Box and Hill's method was applied to discriminate between two mechanistic models for the catalytic hydrogenation of propylene. A sequential experimental design procedure, this method makes use of a discrimination criterion obtained from information theory.