Probing the size dependent chemical properties of metals in reduced dimension

Heterogeneously catalyzed reactions typically start with adsorption and dissociation of reactant molecules on the surface of a solid catalyst. In many instances, this is followed by surface diffusion of the adsorbed species, chemical reaction, and removal of the product molecule. According to the Sabatier principle, optimal catalytic performance requires that the bonding between the adsorbate molecule and the surface should neither be too strong nor too weak. This bonding strength is directly related to the catalyst’s surface electronic structure and hence, electronic structure modification would seem a promising approach for tuning catalytic activity. There have been many studies along this line, including electronic structure modifica- tion via surface alloying, introduction of ’active sites’, size control, and charge transfer between the catalyst and its support. The underlying physics is often expressed within the context of the d-band model by Norskov. Specifically, the bonding strength of adsorbate molecules on transition metal surfaces is strongly influenced by the interaction between the molecular orbitals and the metal d states, which can be parameterized by the location of the d-band center relative to the Fermi level. This model has been successful in explaining trends in catalytic activity of transition metal surfaces but there are exceptions, presumably to competing factors that are structure or element specific, and that are not considered in the model. To firmly establish the validity of the model, we investigated ultrathin Pd and Ru films and tuned the location of the d-band center by changing the film thickness one atomic layer at a time, while keeping all other variables unchanged. Interestingly, while bulk Pd is reactive towards oxygen, Pd(111) films below five monolayer, grown on Ru(0001), are surprisingly inert to oxygen. This trend is fully in line with the d-band model prediction. Here, the shift of the d-band center is associated with the increased band width of the 4dxz [4dxz] and 4dyz [4dyz] orbitals. On the other hand, Ru(0001) films on Pd(111) reveal a more complex behavior which can be attributed to Pd segregation. This study provides an in-depth look at orbital specific contributions to the chemical reactivity, providing new knowledge that could be useful in surface catalysis

Investigating the Usability of the Stylus Pen on Handheld Devices

Many handheld devices with stylus pens are available on the market, however, there have been few studies which examine the effects of the size of the stylus pen on user performance and subjective preferences for hand-held device interfaces. Two experiments were conducted to determine the most suitable dimensions (pen-length, pen-tip width and pen-width) for a stylus pen. In Experiment 1, five pen-lengths (7, 9, 11, 13, 15 cm) were evaluated. In Experiment 2, six combinations of three pen-tip widths (0.5, 1.0 and 1.5mm) and the two pen widths (4 and 7mm) were compared. In both experiments, subjects conducted pointing, steering and writing tasks on a PDA. The results were assessed in terms of user performance and subjective evaluations for all three pointing, steering and writing tasks. We determined that the most suitable pen dimensions were 11 cm for length, 0.5 mm for tip width, and 7mm for pen width

How Are the Differences between Selection Strategies Affected by Changes in Target Size, Distance and Direction?

Fitt's law is commonly used to model target selection. But Fitts' law deals with only one kind of selection strategy. Our question is, do changes in target size, distance and direction to a target affect the differences in performance between target selection strategies? We performed the first empirical tests on a pen-based system to evaluate differences in performance between six selection strategies for selecting a target. Three target sizes, eight pen-movement-directions and three pen-movement-distances were applied to all six strategies. The results show that differences between selection strategies are affected by variations in target size but not by the other parameters (distance and direction)

Designing interactions for the ageing populations – addressing global challenges

We are concurrently witnessing two significant shifts: digital devices are becoming ubiquitous, and older people are becoming a very large demographic group. However, despite the recent increase in related CHI publications, older adults continue to be underrepresented in HCI research as well as commercially. Therefore, the overarching aim of this workshop is to increase the momentum for such research within CHI and related fields such as gerontechnology. For this, we plan to create a space for discussing and sharing principles and strategies to design interactions and evaluate user interfaces (UI) for the ageing population. We thus welcome contributions of empirical studies, theories, design and evaluation of UIs for older adults. Building on the success of last two year’s workshops, we aim to grow the community of CHI researchers across borders interested in this topic by fostering a space to exchange results, methods, approaches, and ideas from research on interactive applications in support of older adults that are reflective of international diversity that is representative of CHI

Designing mobile interactions for the ageing populations

We are concurrently witnessing two significant shifts: mobiles are becoming the most used computing device; and older people are becoming the largest demographic group. However, despite the recent increase in related CHI publication, older adults continue to be underrepresented in HCI research as well as commercially, further widening the digital divide they face and hampering their social participation. This workshop aims to increase the momentum for such research within CHI and related fields such as gerontechnology. We plan to create a space for discussing and sharing principles and strategies to design and evaluate mobile user interfaces for the aging population. We thus welcome contributions to empirical studies, theories, design and evaluation of mobile interfaces for older adults

Genetic Construction of Truncated and Chimeric Metalloproteins Derived from the Alpha Subunit of Acetyl-CoA Synthase from Clostridium thermoaceticum

In this study, a genetics-based method is used to truncate acetyl-coenzyme A synthase from Clostridium thermoaceticum (ACS), an alpha2beta2 tetrameric 310 kda bifunctional enzyme. ACS catalyzes the reversible reduction of CO2 to CO and the synthesis of acetyl-CoA from CO (or CO2 in the presence of low-potential reductants), CoA, and a methyl group bound to a corrinoid-iron sulfur protein (CoFeSP). ACS contains 7 metal-sulfur clusters of 4 different types called A, B, C, and D. The B, C, and D clusters are located in the 72 kda beta subunit while the A-cluster, a Ni-X-Fe4S4 cluster that serves as the active site for acetyl-CoA synthase activity, is located in the 82 kda alpha subunit. The extent to which the essential properties of the cluster, including catalytic, redox, spectroscopic, and substrate-binding properties, were retained as ACS was progressively truncated was determined. Acetyl-CoA synthase catalytic activity remained when the entire alpha subunit was removed, as long as CO, rather than CO2 and a low-potential reductant, was used as a substrate. Truncating an {approx} 30 kda region from the N-terminus of the alpha subunit yielded a 49 kda protein that lacked catalytic activity but exhibited A-cluster-like spectroscopic, redox, and CO binding properties. Further truncation afforded a 23 kda protein that lacked recognizable A-cluster properties except for UV-vis spectra typical of [Fe4S4]2+ clusters. Two chimeric proteins were constructed by fusing the gene encoding a ferredoxin from Chromatium vinosum to genes encoding the 49 kda and 82 kda fragments of the alpha subunit. The chimeric proteins exhibited EPR signals that were not the simple sum of the signals from the separate proteins, suggesting magnetic interactions between clusters. This study highlights the potential for using genetics to simplify the study of complex multi-centered metalloenzymes and to generate new complex metalloenzymes with interesting properties

Rethinking mobile interfaces for older adults

This SIG advances the study of mobile user interfaces for the aging population. The topic is timely, as the mobile device has become the most widely used computer terminal and at the same time the number of older people will soon exceed the number of children worldwide. However, most HCI research addresses younger adults and has had little impact on older adults. Some design trends, like the mantra “smaller is smarter”, contradict the needs of older users. Developments like this may diminish their ability to access information and participate in society. This can lead to further isolation (social and physical) of older adults and increased widening of the digital divide. This SIG aims to discuss mobile interfaces for older adults. The SIG has three goals: (i) to map the state-of-art, (ii) to build a community gathering experts from related areas, and (iii) to raise awareness within the SIGCHI community. The SIG will be open to all at CHI