Problems in Hyperland? A Human Factors Perspective

While the potential of hypertext as an information presentation medium is undeniable, its acceptance by users will be determined largely by its usability. The present paper highlights four issues of relevance: reading from screens as opposed to reading from paper; reader behaviour, particularly how and why different texts are read; interface design variables such as display size and manipulation facilities; and user navigation. Existing research is reviewed and implications for the design of hypertext systems are discussed. Suggestions for future work are presented.     

ELECTRONIC BOOKS IN PUBLIC LIBRARIES: A FEASIBILITY STUDY FOR DEVELOPING USAGE MODELS FOR WEB-BASED AND HARDWARE-BASED ELECTRONIC BOOKS

This article is a slightly abridged edited version of a final report detailing the background and implementation of a project that introduced electronic book (e-book) collections to Essex Public Libraries during 2004. The research considered e-book collections available for borrowing on a PDA (HP iPAQ) and collections downloadable on to the borrower's PDA or PC (OverDrive, ebrary). The project, sponsored by The Laser Foundation,1 The Laser (London and South-Eastern Library Region) Foundation was founded in 2002 following the transfer of an operational business to a grant-making body. The Foundation has made a number of grants to public and academic libraries since 2003, and further detail of its activities can be found at: http://www.bl.uk/concord/laser-about.html (accessed 21 February 2005). consisted of a partnership consisting between Loughborough University,2 The Department of Information Science. http://www.lboro.ac.uk/dis/ (accessed 21 February 2005). Essex Public Libraries3 Essex County Libraries operate 73 public libraries and mobile library services in south-eastern England. Their website can be found at: http://194.129.26.30/vip8/ecc/ECCWebsite/display/channels/libraries_channel_134343_Enjoying/index.jsp (accessed 21 February 2005). and Co-East.4 The Co-East Partnership manages acquisition and provision of electronic resources for public libraries in eastern England, including management of the popular ‘Ask a Librarian’ service. Their website can be found at: http://www.co-east.net/ (accessed 22 October 2004). In addition to a discussion of the findings of the research, guidelines are offered to other public library authorities considering the adoption of e-book collections and mobile technology. Two articles based on this research have been published elsewhere considering the evaluation of the iPAQ trials (Dearnley et al., ) and the provision and uptake of OverDrive and ebrary (Dearnley et al., ) collections.     

Monitoring of cropland practices for carbon sequestration purposes in north central Montana by Landsat remote sensing

We used an object-oriented approach in conjunction with the Random Forest algorithm to classify agricultural practices, including tillage (till or no-till (NT)), crop intensity, and grassland-based conservation reserve (CR). The object-oriented approach allowed for per-field classifications and the incorporation of contextual elements in addition to spectral features. Random Forest is a classification tree-based advanced classifier that avoids data over-fitting associated with many tree-based models and incorporates an unbiased internal classification accuracy assessment. Landsat satellite imagery was chosen for its continuous coverage, cost effectiveness, and image accessibility. Classification results for 2007 included producer's accuracies of 91% for NT and 31% for tillage when applying Random Forest to image objects generated from a May Landsat image. Low classification accuracies likely were attributed to the misclassification of conservation-based tillage practices as NT. Results showed that the binary separation of tillage from NT management is likely not appropriate due to surface spectral and textural similarities between NT and conservation-type tillage practices. Crop and CR lands resulted in producer's accuracies of 100% and 90%, respectively. Crop and fallow producer's accuracies were 95% and 82% in the 2007 classification, despite post-senesced vegetation; misclassification within the fallow class was attributed to pixel-mixing problems in areas of narrow (< 100 m) strip management. A between-date normalized difference vegetation index approach was successfully used to detect areas having “changed” in vegetation status between the 2007 and prior image dates; classified “changed” objects were then merged with “unchanged” objects to produce crop status maps. Field crop intensity was then determined from the multi-year analysis of generated crop status maps.     

电子设计发展趋势——开源PCB设计

正电子设计领域的一大趋势是开源硬件及其配套的开源原理图和PCB布局图的使用。使用开源硬件及其配套资源意味着工程师可以方便地使用现有设计方案,从而提高效率并缩短产品上市时间。随着工程师更加深入地了解传统PCB与开源PCB设计之间的区别,该趋势将极有可能获得进一步增长。开源PCB设计较传统PCB设计具有几大优势,其中包括电源和数字部分以及高速数据部分的重复可用性,这使得工程师更加青睐于开源PCB设计。在以往的设计过     

In vivo transposition of mariner-based elements in enteric bacteria and mycobacteria

mariner family transposons are widespread among eukaryotic organisms. These transposons are apparently horizontally transmitted among diverse eukaryotes and can also transpose in vitro in the absence of added cofactors. Here we show that transposons derived from the mariner element Himar1 can efficiently transpose in bacteria in vivo. We have developed simple transposition systems by using minitransposons, made up of short inverted repeats flanking antibiotic resistance markers. These elements can efficiently transpose after expression of transposase from an appropriate bacterial promoter. We found that transposition of mariner-based elements in Escherichia coli produces diverse insertion mutations in either a targeted plasmid or a chromosomal gene. With Himar1-derived transposons we were able to isolate phage-resistant mutants of both E. coli and Mycobacterium smegmatis. mariner-based transposons will provide valuable tools for mutagenesis and genetic manipulation of bacteria that currently lack well developed genetic systems.     

A Body of Circumstantial Evidence for the Irreversible Ectonucleotidase Inhibitory Action of FSCPX,an Agent Known as a Selective Irreversible A1 Adenosine Receptor Antagonist So Far

In previous studies using isolated, paced guinea pig left atria, we observed that FSCPX, known as a selective A₁ adenosine receptor antagonist, paradoxically increased the direct negative inotropic response to A₁ adenosine receptor agonists (determined using concentration/effect (E/c) curves) if NBTI, a nucleoside transport inhibitor, was present. Based on mathematical modeling, we hypothesized that FSCPX blunted the cardiac interstitial adenosine accumulation in response to nucleoside transport blockade, probably by inhibiting CD39 and/or CD73, which are the two main enzymes of the interstitial adenosine production in the heart. The goal of the present study was to test this hypothesis. In vitro CD39 and CD73 inhibitor assays were carried out; furthermore, E/c curves were constructed in isolated, paced rat and guinea pig left atria using adenosine, CHA and CPA (two A₁ adenosine receptor agonists), FSCPX, NBTI and NBMPR (two nucleoside transport inhibitors), and PSB-12379 (a CD73 inhibitor), measuring the contractile force. We found that FSCPX did not show any inhibitory effect during the in vitro enzyme assays. However, we successfully reproduced the paradox effect of FSCPX in the rat model, mimicked the “paradox” effect of FSCPX with PSB-12379, and demonstrated the lipophilia of FSCPX, which could explain the negative outcome of inhibitor assays with CD39 and CD73 dissolved in a water-based solution. Taken together, these three pieces of indirect evidence are strong enough to indicate that FSCPX possesses an additional action besides the A₁ adenosine receptor antagonism, which action may be the inhibition of an ectonucleotidase. Incidentally, we found that POM-1 inhibited CD73, in addition to CD39.     

Optimal discrete filtering for time-delayed systems with respect to mean-square continuous-time error criterion

An optimal linear digital filtering problem for continuous-time dynamic processes is considered. An algorithm for optimal filter design taking into account pure delays in continuous-time networks is presented. The performance of systems, being optimal with respect to discrete-time and continuous-time mean-square errors, is compared. An optimal stochastic model-matching problem is proposed and its solution is presented. © 1998 John Wiley & Sons, Ltd.     

How secure are computers in the U.S.A.? : An analysis of a series of attacks on Milnet computers

For 10 months, we monitored a systematic attack on 450 computers attached to the Defense Data Network. By analyzing the success of these attacks, we can estimate the vulnerability of nodes on the Milnet and (by extrapolation) civilian computers. We analyzed a particular type of attack: an outsider who attempts to log in by guessing at commonly used account name/password combinations.An outsider can expect some degree of access into about 13% of Milnet computers. Access to a programming environment is possible in at least 4%, and system manager privileges can be obtained by strangers in 2% of the sampled sites. Since this is only one of several methods used to enter these systems, these estimates are lower limits; other methods of entry can permit access to still more systems. These weaknesses are due to poor administration of computers, as well as systems distributed by vendors with security features disabled.     

Development and evaluation of multiple regression models for prediction of sweet cherry liking

In two experiments, multiple regression models were developed and evaluated to identify the relevant sensory attributes for cherry liking. In Experiment 1, 16 judges evaluated 18 cherry varieties for seven visual characteristics (colour intensity, uniformity-of-colour, speckles, size, stem length, external firmness and ‘visual’ liking) and seven flavour/texture characteristics (flesh firmness, flesh colour intensity, juiciness, sweetness, sourness, flavour intensity and ‘flavour/ texture’ liking). Stepwise multiple regression was used to develop the most appropriate statistical models for prediction of visual and flavour/texture liking based on visual and flavour/texture characteristics, respectively. Both models were simple and easily understandable with two sensory variables. The best model for visual liking required only size and uniformity-of-colour variables; whereas, the best model for flavour/texture liking required sweetness and flavour intensity variables. In Experiment 2, 18 judges evaluated 30 sweet cherry cultivars, using the same methodology, to create a validation data set. Correlation coefficients (R) and prediction standard errors (PSEs) between the observed (Experiment 2) and predicted (Experiment 1) liking scores were used to evaluate the prediction equations. The prediction equation for flavour/texture liking was most satisfactory (R = 0.85, PSE = 0.61). A new equation developed from the validation data confirmed the importance of sweetness and flavour intensity. In contrast, the prediction equation for visual liking was less satisfactory (R = 0.56) and a new equation developed from the validation data set confirmed only size as an important variable.