The role of environmental context in mapping invasive plants with hyperspectral image data

Lepidium latifolium (perennial pepperweed) is a noxious Eurasian weed invading riparian and wetland areas of the western US. Effective management of Lepidium requires detailed, accurate maps of its distribution, as may be provided by remote sensing, to contain existing infestations and eradicate incipient populations. We mapped Lepidium with 3 m spatial resolution, 128-band HyMap image data in three sites of California's San Francisco Bay/Sacramento–San Joaquin Delta Estuary (Rush Ranch in Suisun Marsh and the Greater Jepson Prairie Ecosystem and the Cosumnes River Preserve in the Delta). These sites are markedly different in terms of hydrology, salinity, species composition, and structural and landscape diversity. Aggregated classification and regression tree models (CART), incorporating the results of mixture tuned matched filter (MTMF) analyses and spectral physiological indexes, were used to map Lepidium at the three sites. This approach was sufficiently flexible and robust to detect Lepidium with similar accuracies (~ 90%) at both Rush Ranch and Jepson Prairie, but was unsuccessful at Cosumnes River Preserve. Comparisons of the behavior of the MTMFs and the CARTs between sites reveal the importance of environmental context in species mapping. Rush Ranch presents the simplest conditions for mapping Lepidium: it is the wettest and least diverse site and Lepidium is spectrally distinct from co-occurring species. At Jepson Prairie, several co-occurring species closely resemble Lepidium spectrally. Nevertheless, hyperspectral data provide sufficient spectral detail to resolve Lepidium even at this challenging site, which is facilitated by phenological separation from the matrix of annual grasses. At Cosumnes River Preserve, however, Lepidium is neither spectrally nor phenologically distinct, and consequently could not be mapped successfully. Evidence suggests that the success of a remote sensing analysis declines as site complexity increases (species, structural, and landscape diversity; spectral variability; etc.), although this relationship is complex, indirect, and may be phenology-dependent.     

Performance of direction-finding systems with sensor gain and phase uncertainties

In this paper we study the performance of direction-finding systems which attempt to estimate unknown array parameters (such as sensor gains and phases) in addition to the estimation of the directions of arrival (DOA), as a way of performing array self-calibration. We develop compact closed form expressions for the Cramér-Rao bound associated with the joint estimation of DOAs, gains, phases, and the signal covariance matrix. By evaluating the Cramér-Rao bound for selected cases we gain some insight into the performance of direction-finding systems in the presence of gain and phase uncertainties.This work was supported by the Army Research Office under Contract No. DAAL03-89-C-0007, sponsored by U.S. Army Communications Electronics Command, Center for Signals Warfare.     

Case study: paradoxical response to naltrexone treatment of self-injurious behavior

Opioid receptor antagonists have been studied in the management of self-injurious behavior (SIB) in developmentally disabled individuals. The authors present a case of a severely retarded, autistic man whose SIB increased dramatically during a trial of naltrexone. A paradoxical increase in SIB, attributed to the extinction burst phenomenon during the initial period of nonreward, is known to occur during treatment with naloxone, a short-acting parenteral opioid antagonist. It has only once been reported during treatment with naltrexone, a long-acting orally administered agent. Opioid analgesic effects and learning theory can explain both increases and decreases in SIB after opioid blockade.     

Representation and selection of relative position.

Part 1 concerns representation: Pop-out for a target that can be distinguished from the distractors only by the relative position of its components was demonstrated, thereby showing that simple shape information is represented preattentively. Findings are discussed in terms of early- vs late-selection debate and in terms of theories of search and texture segregation. Part 2 concerns selection: Strong learning in a varied-mapping paradigm was demonstrated, and it was shown that preattentive shape information can be used for selection. Finally, an account of the learning, namely the group scale hypothesis, is suggested and a final experiment to test it is presented. Results confirm and extend the emphasis placed by J. Duncan and G. W. Humphreys's (1989) attentional engagement theory on grouping processes in visual search. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of supports for the direct synthesis of hydrogen peroxide from H2 and O2 using Au–Pd catalysts

The direct synthesis of hydrogen peroxide from H₂ and O₂ using a range of supported Au–Pd alloy catalysts is compared for different supports using conditions previously identified as being optimal for hydrogen peroxide synthesis, i.e. low temperature (2 °C) using a water–methanol solvent mixture and short reaction time. Five supports are compared and contrasted, namely Al₂O₃, -Fe₂O₃, TiO₂, SiO₂ and carbon. For all catalysts the addition of Pd to the Au only catalyst increases the rate of hydrogen peroxide synthesis as well as the concentration of hydrogen peroxide formed. Of the materials evaluated, the carbon-supported Au–Pd alloy catalysts give the highest reactivity. The results show that the support can have an important influence on the synthesis of hydrogen peroxide from the direct reaction. The effect of the methanol–water solvent is studied in detail for the 2.5 wt% Au–2.5 wt% Pd/TiO₂ catalyst and the ratio of methanol to water is found to have a major effect on the rate of hydrogen peroxide synthesis. The optimum mixture for this solvent system is 80 vol.% methanol with 20 vol.% water. However, the use of water alone is still effective albeit at a decreased rate. The effect of catalyst mass was therefore also investigated for the water and water–methanol solvents and the observed effect on the hydrogen peroxide productivity using water as a solvent is not considered to be due to mass transfer limitations. These results are of importance with respect to the industrial application of these Au–Pd catalysts.     

Post-traumatic stress disorder and smoking: a systematic review.

We conducted a systematic review of what is known about the relationship between post-traumatic stress disorder (PTSD) and smoking to guide research on underlying mechanisms and to facilitate the development of evidence-based tobacco treatments for this population of smokers. We searched Medline, PsychINFO, and the Cochrane Central Register of Controlled Trials and identified 45 studies for review that presented primary data on PTSD and smoking. Smoking rates were high among clinical samples with PTSD (40%-86%) as well as nonclinical populations with PTSD (34%-61%). Most studies showed a positive relationship between PTSD and smoking and nicotine dependence, with odds ratios ranging between 2.04 and 4.52. Findings also suggest that PTSD, rather than trauma exposure itself, is more influential for increasing risk of smoking. A small but growing literature has examined psychological factors related to smoking initiation and maintenance and the overlapping neurobiology of PTSD and nicotine dependence. Observational studies indicate that smokers with PTSD have lower quit rates than do smokers without PTSD. Yet a few tobacco cessation treatment trials in smokers with PTSD have achieved quit rates comparable with controlled trials of smokers without mental disorders. In conclusion, the evidence points to a causal relationship between PTSD and smoking that may be bidirectional. Specific PTSD symptoms may contribute to smoking and disrupt cessation attempts. Intervention studies that test behavioral and pharmacological interventions designed specifically for use in patients with PTSD are needed to reduce morbidity and mortality in this population.     

TES modeling for analysis of a video multiplexer

The transport of video images is likely to be a major application of high-speed networks of the future. These applications are capable of utilizing the high bandwidths that will become available with the advent of B-ISDN. In this paper, we propose a new methodology (called TES) for modeling the frame bitrate stream generated by compressed video sources. The main characteristic of this method is that it can model an arbitrary marginal distribution and approximate the autocorrelation structure of the random bitrate process generated by compressed frames. We present a modeling example utilizing this method, based on data from a video coding algorithm employing a layering technique. Using the source model, we develop a simulation model of a multiplexer of video sources. We show that this model can be used to address a number of design issues that arise in this class of problem. In particular, we show that for a layered video coding algorithm, it is possible to have a gain in the number of sources multiplexed at the cost of some loss of low priority packets.     

A New Approach to Abstract Syntax with Variable Binding

The permutation model of set theory with atoms (FM-sets), devised by Fraenkel and Mostowski in the 1930s, supports notions of ‘name-abstraction’ and ‘fresh name’ that provide a new way to represent, compute with, and reason about the syntax of formal systems involving variable-binding operations. Inductively defined FM-sets involving the name-abstraction set former (together with Cartesian product and disjoint union) can correctly encode syntax modulo renaming of bound variables. In this way, the standard theory of algebraic data types can be extended to encompass signatures involving binding operators. In particular, there is an associated notion of structural recursion for defining syntax-manipulating functions (such as capture avoiding substitution, set of free variables, etc.) and a notion of proof by structural induction, both of which remain pleasingly close to informal practice in computer science. Received October 2000 / Accepted in revised form April 2001