Regional aboveground forest biomass using airborne and spaceborne LiDAR in Québec

Aboveground dry biomass was estimated for the 1.3 M km² forested area south of the treeline in the eastern Canadian province of Québec by combining data from an airborne and spaceborne LiDAR, a Landsat ETM+ land cover map, a Shuttle Radar Topographic Mission (SRTM) digital elevation model, ground inventory plots, and vegetation zone maps. Plot-level biomass was calculated using allometric relationships between tree attributes and biomass. A small footprint portable laser profiler then flew over these inventory plots to develop a generic airborne LiDAR-based biomass equation (R² = 0.65, n = 207). The same airborne LiDAR system flew along four portions of orbits of the ICESat Geoscience Laser Altimeter System (GLAS). A square-root transformed equation was developed to predict airborne profiling LiDAR estimates of aboveground dry biomass from GLAS waveform parameters combined with an SRTM slope index (R² = 0.59, n = 1325).Using the 104,044 quality-filtered GLAS pulses obtained during autumn 2003 from 97 orbits over the study area, we then predicted aboveground dry biomass for the main vegetation areas of Québec as well as for the entire Province south of the treeline. Including cover type covariances both within and between GLAS orbits increased standard errors of the estimates by two to five times at the vegetation zone level and as much as threefold at the provincial level. Aboveground biomass for the whole study area averaged 39.0 ± 2.2 (standard error) Mg ha^? 1 and totalled 4.9 ± 0.3 Pg. Biomass distributions were 12.6% northern hardwoods, 12.6% northern mixedwood, 38.4% commercial boreal, 13% non-commercial boreal, 14.2% taiga, and 9.2% treed tundra. Non-commercial forests represented 36% of the estimated aboveground biomass, thus highlighting the importance of remote northern forests to C sequestration. This study has shown that space-based forest inventories of northern forests could be an efficient way of estimating the amount, distribution, and uncertainty of aboveground biomass and carbon stocks at large spatial scales.     

A typology of user liability to IT addiction

To date, information systems (IS) research mainly has provided a monolithic view of information technology (IT) use, considering it to be a desired behaviour with positive outcomes. However, given the dramatic increase in the use of technology during the last few years, susceptibility to IT addiction is increasingly becoming an important issue for technology users and IS researchers. In this paper, we report the results of a study that focuses on identifying variations in user liability to IT addiction, which reflects the susceptibility of individual users to develop IT addiction. First, a review of the literature in different disciplines (e.g. health, psychology and IS) allows us to better understand the concepts of IT addiction and liability to addiction. The literature review also provides an overview of the antecedents and consequences associated with IT addiction. Then, building on the analysis of 15 in‐depth interviews and 182 exploratory open‐ended surveys collected from smartphone users, we apply the concept of liability to addiction in the IT use context and propose a typological theory of user liability to IT addiction. Our typology reveals five ideal types; each can be associated to a user profile (addict, fanatic, highly engaged, regular and thoughtful ). Building upon both the extant literature and our results, we put forth propositions to extend the theoretical contributions of the study. We finally discuss the contributions and implications of our paper for research and practice.     

Cover Picture: Protein Detecting Arrays Based on Cationic Polythiophene–DNA‐Aptamer Complexes (Adv. Mater. 20/2006)

The cover image depicts biochips based on responsive nanoaggregates made from stoichiometric complexes between a cationic polythiophene and an appropriate DNA aptamer. These structures undergo a conformational transition from an unfolded to a folded (G‐quadruplex) structure in the presence of a specific target protein that results in a significant increase of the fluorescence intensity, as reported on p. 2703 by Leclerc and co‐workers.     

Enriching our theoretical repertoire: the role of evolutionary psychology in technology acceptance

Information systems (IS) research has drawn heavily on social and cognitive psychology to explain technology adoption. Indeed, the many variations of the technology acceptance model all share these same theoretical foundations. Focusing exclusively on the socio-cognitive lens can lead to overlooking enhanced explanations of technology acceptance, such that new theoretical perspectives may be warranted. In this qualitative grounded theory study, we discovered how the lens of evolutionary psychology, as embodied in the Four-Drive model, was helpful in understanding technology acceptance across three organizational sites. We contend that evolutionary psychology is an important addition to the theoretical repertoire of IS researchers, and propose including ‘evolved psychological mechanisms’ within traditional models of technology acceptance.     

The Synthesis of Three‐Degree‐of‐Freedom Planar Parallel Mechanisms with Revolute Joints (3‐RRR) for an Optimal Singularity‐Free Workspace

In this paper, a method is presented for the synthesis of 3‐R RR planar parallel mechanisms. The method uses a genetic algorithm while considering three different design criteria: the optimization of the mechanism workspace to approach a prescribed workspace, the maximization of the mechanism's dexterity, and the avoidance of singularities inside the mechanism workspace. It is shown that, for a given mechanism, some working modes do not have any corresponding singularity curves located inside the mechanism workspace. Furthermore, a case is presented where, for a given orientation range of the mechanism's end‐effector, there are no parallel singularities located inside the workspace. Finally, two methods are described and compared to deal with the nonuniform units of the mechanism's Jacobian matrix during the dexterity computation. © 2004 Wiley Periodicals, Inc.     

An empirical examination of self-reported work stress among U.S. managers.

This study proposes that self-reported work stress among U.S. managers is differentially related (positively and negatively) to work outcomes depending on the stressors that are being evaluated. Specific hypotheses were derived from this general proposition and tested using a sample of 1,886 U.S. managers and longitudinal data. Regression results indicate that challenge-related self-reported stress is positively related to job satisfaction and negatively related to job search. In contrast, hindrance-related self-reported stress is negatively related to job satisfaction and positively related to job search and turnover. Future research directions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Asymptotic receiver structures for joint maximum likelihood timedelay estimation and channel identification using Gaussian signals

The problem of jointly estimating the relative time delay and the impulse response linking two received discrete-time Gaussian signals is addressed. Using two different methods, possible structures for the joint maximum-likelihood (ML) estimator are proposed, when the observation interval is long compared to both the delay to estimate and the correlation time, of the various random processes involved. These structures generalize the cross-correlation method with prefiltering that implements the ML estimation of pure time delays     

Nondestructive ion trap mass analysis at high pressure

A method for performing nondestructive ion trap mass analysis at high pressures (>1 mTorr) has been developed using image current measurement with constant dipolar excitation. Instead of monitoring the ion secular motion, a harmonic of the ion motion was used for narrow band image current measurement followed by Fourier Transform. The capability of this technique has been demonstrated with mass analysis using a single measurement at pressures of 10 mTorr or higher. Methods for mixture analysis and tandem mass spectrometry have also been developed for nondestructive mass analysis.