Exergame design for elderly users: the case study of SilverBalance

In this paper, we discuss chances and challenges of game design for an elderly audience with a focus on the development of safe and usable exertion games for frail senior citizens. Based on an analysis of theoretical constraints, we conducted a case study which implements different balance tasks for elderly players featuring the Nintendo Wii Balance Board which encourages users to actively engage in game play. Furthermore, we tested the feasibility of the board as input device for our case study SilverBalance. Our results indicate that age-related impairments influence the use of video games among frail elderly in many respects, hence their needs have to be considered during the design process. In this context, our paper provides a foundation for future research regarding digital games for the elderly. © 2010 ACM

Perceived Stress, Individual Psychological Resources, and Social Resources Among Computer Science Students During the COVID-19 Pandemic

Due to the COVID-19 pandemic, university students worldwide have experienced drastic changes in their academic and social lives, with the rapid shift to online courses and contact restrictions being reported among the major stressors. In the present study, we aimed at examining students’ perceived stress over the course of the pandemic as well as individual psychological and social coping resources within the theoretical framework of the Transactional Model of Stress and Coping in the specific group of STEM students. In four cross-sectional studies with a total of 496 computer science students in Germany, we found that students reported significantly higher levels of perceived stress at both measurement time points in the second pandemic semester (October/November 2020; January/February 2021) as compared to the beginning of the first (April/May 2020), indicating that students rather became sensitized to the constant pandemic-related stress exposure than habituating to the “new normal”. Regarding students’ coping resources in the higher education context, we found that both high (a) academic self-efficacy and (b) academic online self-efficacy as well as low (c) perceived social and academic exclusion among fellow students significantly predicted lower levels of students’ (d) belonging uncertainty to their study program, which, in turn, predicted lower perceived stress at the beginning of the first pandemic semester. At the beginning of the second pandemic semester, we found that belonging uncertainty still significantly mediated the relationship between students’ academic self-efficacy and perceived stress. Students’ academic online self-efficacy, however, no longer predicted their uncertainty about belonging, but instead had a direct buffering effect on their perceived stress. Students’ perceived social and academic exclusion among fellow students only marginally predicted their belonging uncertainty and no longer predicted their perceived stress 6 months into the pandemic. We discuss the need and importance of assessing and monitoring students’ stress levels as well as faculty interventions to strengthen students’ individual psychological and social coping resources in light of the still ongoing pandemic

Generating Potent C–H PCET Donors: Ligand-Induced Fe-to-Ring Proton Migration from a Cp*Fe^(III)–H Complex Demonstrates a Promising Strategy

Highly reactive organometallic species that mediate reductive proton-coupled electron transfer (PCET) reactions are an exciting area for development in catalysis, where a key objective focuses on tuning the reactivity of such species. This work pursues ligand-induced activation of a stable organometallic complex toward PCET reactivity. This is studied via the conversion of a prototypical Cp*Fe^(III)–H species, [Fe^(III)(η⁵-Cp*)(dppe)H]⁺ (Cp* = C₅Me₅⁻, dppe = 1,2-bis(diphenylphosphino)ethane), to a highly reactive, S = 1/2 ring-protonated endo-Cp*H–Fe relative, triggered by the addition of CO. Our assignment of the latter ring-protonated species contrasts with its previous reported formulation, which instead assigned it as a hypervalent 19-electron hydride, [Fe^(III)(η⁵-Cp*)(dppe)(CO)H]⁺. Herein, pulse EPR spectroscopy (^(1,2)H HYSCORE, ENDOR) and X-ray crystallography, with corresponding DFT studies, cement its assignment as the ring-protonated isomer, [Fe^I(endo-η⁴-Cp*H)(dppe)(CO)] ⁺. A less sterically shielded and hence more reactive exo-isomer can be generated through oxidation of a stable Fe0(exo-η⁴-Cp*H)(dppe)(CO) precursor. Both endo- and exo-ring-protonated isomers are calculated to have an exceptionally low bond dissociation free energy (BDFE_(C–H) ≈ 29 kcal mol⁻¹ and 25 kcal mol⁻¹, respectively) cf. BDFE_(Fe–H) of 56 kcal mol⁻¹ for [Fe^(III)(η⁵-Cp*)(dppe)H] ⁺. These weak C–H bonds are shown to undergo proton-coupled electron transfer (PCET) to azobenzene to generate diphenylhydrazine and the corresponding closed-shell [Fe^(II)(η⁵-Cp*)(dppe)CO]⁺ byproduct

Generating Potent C–H PCET Donors: Ligand-Induced Fe-to-Ring Proton Migration from a Cp*Fe^(III)–H Complex Demonstrates a Promising Strategy

Highly reactive organometallic species that mediate reductive proton-coupled electron transfer (PCET) reactions are an exciting area for development in catalysis, where a key objective focuses on tuning the reactivity of such species. This work pursues ligand-induced activation of a stable organometallic complex toward PCET reactivity. This is studied via the conversion of a prototypical Cp*Fe^(III)–H species, [Fe^(III)(η⁵-Cp*)(dppe)H]⁺ (Cp* = C₅Me₅⁻, dppe = 1,2-bis(diphenylphosphino)ethane), to a highly reactive, S = 1/2 ring-protonated endo-Cp*H–Fe relative, triggered by the addition of CO. Our assignment of the latter ring-protonated species contrasts with its previous reported formulation, which instead assigned it as a hypervalent 19-electron hydride, [Fe^(III)(η⁵-Cp*)(dppe)(CO)H]⁺. Herein, pulse EPR spectroscopy (^(1,2)H HYSCORE, ENDOR) and X-ray crystallography, with corresponding DFT studies, cement its assignment as the ring-protonated isomer, [Fe^I(endo-η⁴-Cp*H)(dppe)(CO)] ⁺. A less sterically shielded and hence more reactive exo-isomer can be generated through oxidation of a stable Fe0(exo-η⁴-Cp*H)(dppe)(CO) precursor. Both endo- and exo-ring-protonated isomers are calculated to have an exceptionally low bond dissociation free energy (BDFE_(C–H) ≈ 29 kcal mol⁻¹ and 25 kcal mol⁻¹, respectively) cf. BDFE_(Fe–H) of 56 kcal mol⁻¹ for [Fe^(III)(η⁵-Cp*)(dppe)H] ⁺. These weak C–H bonds are shown to undergo proton-coupled electron transfer (PCET) to azobenzene to generate diphenylhydrazine and the corresponding closed-shell [Fe^(II)(η⁵-Cp*)(dppe)CO]⁺ byproduct

Snapshots of a Migrating H-Atom: Characterization of a Reactive Iron(III) Indenide Hydride and its Nearly Isoenergetic Ring-Protonated Iron(I) Isomer

We report the characterization of an S=1/2 iron π‐complex, [Fe(η⁶‐IndH)(depe)]⁺ (Ind=Indenide (C₉H₇⁻), depe=1,2‐bis(diethylphosphino)ethane), which results via C−H elimination from a transient Fe^(III) hydride, [Fe(η³:η²‐Ind)(depe)H]⁺. Owing to weak M−H/C−H bonds, these species appear to undergo proton‐coupled electron transfer (PCET) to release H₂ through bimolecular recombination. Mechanistic information, gained from stoichiometric as well as computational studies, reveal the open‐shell π‐arene complex to have a BDFE_(C‐H) value of ≈50 kcal mol⁻¹, roughly equal to the BDFE_(Fe‐H) of its Fe^(III)−H precursor (ΔG°≈0 between them). Markedly, this reactivity differs from related Fe(η⁵‐Cp/Cp*) compounds, for which terminal Fe^(III)−H cations are isolable and have been structurally characterized, highlighting the effect of a benzannulated ring (indene). Overall, this study provides a structural, thermochemical, and mechanistic foundation for the characterization of indenide/indene PCET precursors and outlines a valuable approach for the differentiation of a ring‐ versus a metal‐bound H‐atom by way of continuous‐wave (CW) and pulse EPR (HYSCORE) spectroscopic measurements

Light Enhanced Fe-Mediated Nitrogen Fixation: Mechanistic Insights Regarding H_2 Elimination, HER, and NH_3 Generation

Despite their proposed accumulation at the Fe sites of the FeMo-cofactor of MoFe-nitrogenase, the presence of hydride ligands in molecular model systems capable of the nitrogen reduction reaction (N_2RR) appears to diminish catalytic N_2-to-NH_3 conversion. We find that, for an iron-based system bearing the trisphosphine ligand P_2P^(Ph), a dramatic difference in yields is observed for N2RR catalyzed by precatalysts with zero, one, or two hydride ligands; however, irradiating the three different catalysts with a mercury lamp results in similar NH3 yields. Although the efficacy for N2RR versus the hydrogen evolution reaction (HER) is modest for this system by comparison to certain iron (and other metal) catalysts, the system provides an opportunity to study the role of hydrides in the selectivity for N_2RR versus HER, which is a central issue in catalyst design. Stoichiometric reactions with hydride containing precatalysts reveal a hydrogen evolution cycle in which no nitrogen fixation occurs. Irradiation of the dihydride precatalysts, observed during turnover, results in H2 elimination and formation of (P_2P^(Ph))Fe(N_2)_2, which itself is unreactive with acids at low temperature. N_2 functionalization does occur with acids and silyl electrophiles for the reduced species [(P_2P^(Ph))Fe(N_2)]^− and [(P_2P^(Ph))Fe(N_2)]^(2–), which have been characterized independently. The requirement of accessing such low formal oxidation states explains the need for strong reductants. The low selectivity of the system for functionalization at Nβ versus Fe creates off-path hydride species that participate in unproductive HER, helping to explain the low selectivity for N_2RR over HER. The data presented here thus lend further insight into the growing understanding of the selectivity, activity, and reductant strengths relevant to iron (and other) N_2RR catalysts

Snapshots of a Migrating H-atom: Characterization of a Reactive Fe(III) Indenide Hydride and its Nearly Isoenergetic Ring-Protonated Fe(I) Isomer

We report the characterization of an S = ½ iron π‐complex, [Fe(η^6‐IndH)(depe)]^+ (Ind = Indenide (C_9H_(7^‐_), depe = 1,2‐bis(diethylphosphino)ethane), which results via C‐H elimination from a transient Fe^(III) hydride, [Fe(η^3:η^2‐Ind)(depe)H]^+. Owing to weak M‐H/C‐H bonds, these species undergo proton‐coupled electron transfer (PCET) to release H_2 through bimolecular recombination. Mechanistic information, gained from stoichiometric as well as computational studies, reveal the open‐shell π‐arene complex to have a BDFE_(C‐H) value of ≈ 50 kcal mol^(‐1), roughly equal to the BDFE_(Fe‐H) of its Fe^(III)‐H precursor (ΔG^o ≈ 0 between them). Markedly, this reactivity differs from related Fe(η^5‐Cp/Cp^*) compounds, for which terminal Fe^(III)‐H cations are isolable and have been structurally characterized, highlighting the effect of a benzannulated (indene) ring. Overall, this study provides a structural, thermochemical, and mechanistic foundation for the characterization of indenide/indene PCET precursors and out‐lines a valuable approach for the differentiation of a ring‐ versus a metal‐ bound H‐atom by way of continuous‐wave (CW) and pulse EPR (HYSCORE) spectroscopic measurements

On small tension p-branes

This paper deals with p-branes with small but non-zero tension. We prove the existence of canonical transformations, within a perturbation theory, that link specific geometries of p-branes to solvable theories, namely string-like and particle-like theories. The specific shapes correspond to stretched configurations. For configurations linked to string-like theories one will upon quantization get a critical dimension of (25+p).Comment: 7 page