A Study of Task Characteristics and User Intention to Use Handheld Devices for Mobile Commerce

Interface design and the selection of appropriate tasks for small-screen mobile applications are issues critical for mobile commerce. Our earlier research has identified five major task factors that may influence user intention to use handheld devices for wireless applications. These factors are: perceived ease of use, perceived usefulness, perceived playfulness, perceived task complexity, and perceived security. We followed up with a questionnairebased empirical study to validate the relative impact of these proposed task factors on user intention to use handheld devices for mobile commerce. This paper confirms significant correlations between the task factors and user intention. However, only three of the five factors -- perceived usefulness, perceived security, and perceived playfulness -- are important to user intention, explaining 30% of the variations in a multiple regression model. This study makes a unique contribution to HCI and MIS research by providing empirical evidence of user perception of task characteristics for mobile commerce

Dual-Modal Presentation of Sequential Information

on human attention, this study intends to design a visualauditory information presentation to: (1) minimize the interference in information processing between visual and auditory channels; and (2) improve the effectiveness of mental integration of information from different modalities. Baddeley suggests that imagery spatial information and verbal information can be concurrently held in different subsystems within human working memory. Accordingly, this research proposes a method to convert sequential textual information into its graphical and verbal representations and hypothesizes that this dualmodal presentation will result in superior comprehension performance and higher satisfaction as compared to pure textual display. Simple T-tests will be used to test the hypothesis. Results of this study will help to address usability problems associated with small-screen computers. Findings may also benefit interface design of generic computer systems by alleviating the overabundance of information output in the visual channel

Measuring Enjoyment of Computer Game Play

This paper reports on the development of an instrument designed to measure the enjoyment of computer game play. Despite the enormous technological progress in the field of computer games, enjoyment of computer game play is still not a welldefined construct. Based on Nabi and Krcmar’s (2004) tripartite model of media enjoyment, a survey questionnaire was developed to measure computer game players’ affective, behavioral, and cognitive reactions. Expert consultation, exploratory and confirmatory card sorting sessions were used to refine the instrument. A survey of computer game players was subsequently conducted to test the instrument. Reliabilities and construct validities were analyzed. Findings and their implications were discussed

User-Centered Guidelines for Design of Mobile Applications

In this study, interviews were conducted to derive user-centered guidelines for the interface design of mobile applications. These guidelines cover general design issues in input, display, navigation, and feedback. They address five out of seven elements that describe effective mobile commerce interface design proposed by Lee and Benbasat [7]. Compared to guidelines obtained in prior studies, the guidelines derived from this study are user-centered and can be apply to multiple form factors. The comparison between e-commerce and mobile commerce design guidelines suggest that the mobile context plays the most important role in designing mobile commerce interfaces

Mid-term follow-up after suture-less aortic heart valve implantation

Background: Aortic stenosis (AS) is the most common valve disease in the adult population and its prevalence increases with age. Unfortunately, older age and comorbidities significantly increase mortality, operative risk and worsen prognosis. In recent years, sutureless bioprosthesis [sutureless-aortic valve replacement (SU-AVR)] has become an alternative to standard AVR or TAVI in high-risk patients. Compared to standard AVR, the advantages of SU-AVR include shorter valve implantation, shorter aortic cross clamp (ACC) and cardiopulmonary bypass (CPB) times and higher valve EOA with more favorable hemodynamic parameters. Good early clinical and hemodynamic outcomes have been reported in several studies. However, although early SU-AVR results reported in the literature are encouraging, there are few results of long term follow-up. The aim of this study is to present long term echocardiographic hemodynamic outcomes of the Enable sutureless bioprosthesis. Methods: The first human implantation of the Enable sutureless bioprosthesis was performed on the 13th January, 2005 by the authors of this manuscript. From that time until July 2008, 25 patients underwent isolated SU-AVR implantation. The median preoperative logistic EuroSCORE was 1.92±0.17 [standard deviation (SD)] and the STS score was 2.96±2.73. Preoperatively, 65.4% of patients were in NYHA class III or IV, the peak/mean gradient transaortic gradient was 84.6/52.1 mmHg. Results: After the SU-AVR procedure, the average peak/mean aortic gradients were respectively: 12.9/7.1 mmHg at the intraoperative time; 18.1/9.5 mmHg at 3–6 months; 18.3/9.6 mmHg at 11–14 months; 16.9/9.3 mmHg at 2 years; 15.3/8 mmHg at 3 years; 13.4/7.1 mmHg at 4 years; 16.7/8.9 mmHg at 5 years follow-up. Other hemodynamic echocardiographic parameters such as LVOT diameter, LVOT peak velocity, LVOT TVI, valve peak velocity and valve TVI were stable during the follow-up period. Conclusions: In summary, sutureless bioprostheses are safe and effective treatments for valve stenosis with excellent outcomes and hemodynamic profile which remained stable during the follow-up period. The peak and mean gradients were 16.7 and 8.9 mmHg, respectively, over a 5-year follow-up period

Acute aquatic toxicity of arsenic-based chemical warfare agents to Daphnia magna

Sea dumping of chemical warfare (CW) took place worldwide during the 20th century. Submerged CW included metal bombs and casings that have been exposed for 50-100 years of corrosion and are now known to be leaking. Therefore, the arsenic-based chemical warfare agents (CWAs), pose a potential threat to the marine ecosystems. The aim of this research was to support a need for real-data measurements for accurate risk assessments and categorization of threats originating from submerged CWAs. This has been achieved by providing a broad insight into arsenic-based CWAs acute toxicity in aquatic ecosystems. Standard tests were performed to provide a solid foundation for acute aquatic toxicity threshold estimations of CWA: Lewisite, Adamsite, Clark I, phenyldichloroarsine (PDCA), CWA-related compounds: TPA, arsenic trichloride and four arsenic-based CWA degradation products. Despite their low solubility, during the 48 h exposure, all CWA caused highly negative effects on Daphnia magna. PDCA was very toxic with 48 h D. magna LC50 at 0.36 mu g x L-1- and Lewisite with EC50 at 3.2 mu g x L-1 . Concentrations at which no immobilization effects were observed were slightly above the analytical Limits of Detection (LOD) and Quantification (LOQ). More water-soluble CWA degradation products showed no effects at concentrations up to 100 mg x L-1.Peer reviewe

Bis[3α,7α,12α-tris­(4-nitro­benzo­yloxy)-5β-cholan-24-yl] disulfide–ethyl acetate–n-hexane (4/4/1)

The crystal structure of the title compound, C90H100N6O24S2·C4H8O2·0.25C6H14, solved and refined against synchrotron diffraction data, contains two formula units in the asymmetric unit with the all-trans n-hexane mol­ecule having half-occupancy and one of the ethyl acetate mol­ecules disordered over two positions. The two symmetry-independent disulfide mol­ecules are assembled by approximate face-to-face and face-to-edge inter­actions between their 4-nitro­benzo­yloxy groups into an inter­twined dimer having a double-helix-type structure. The centrally placed disulfide bridges in the two symmetry-independent mol­ecules exhibit different helicity as shown by the C—S—S—C torsion angles of 71.0 (1) and −92.5 (1)°