180 research outputs found

    Controlling Microscopic Friction through Mechanical Oscillations

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    We study in detail the recent suggestions by Tshiprut et al. [Phys. Rev. Lett. 95, 016101 (2005)] to tune tribological properties at the nanoscale by subjecting a substrate to periodic mechanical oscillations. We show that both in stick-slip and sliding regimes of motion friction can be tuned and reduced by controlling the frequency and amplitude of the imposed substrate lateral excitations. We demonstrate that the mechanisms of oscillation-induced reduction of friction are different for stick-slip and sliding dynamics. In the first regime the effect results from a giant enhancement of surface diffusion, while in the second regime it is due to the interplay between washboard and oscillation frequencies that leads to the occurrence of parametric resonances. Moreover we show that for particular set of parameters it is possible to sustain the motion with the only oscillations

    Correction to Quantitative study of the energy changes in voltage-controlled spin crossover molecular thin films [\u3ci\u3eThe Journal of Physical Chemistry Letters\u3c/i\u3e (2020) 11:19 (8231-8237) DOI: 10.1021/acs.jpclett.0c02209]

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    In our recent publication, Figure 5 was published without adequate due diligence. The correct TOC Abstract graphic and Figure 5 are contained here in this correction. The correct on to off current ratios are in the range of 4 to 5, not 100 and the signal to noise ratios are far less than previously shown

    First-Principles Insights into Oxygen Transport in Solid Oxide Fuel Cell Cathode Materials

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    Solid oxide fuel cells (SOFCs) generate electrical power cleanly and efficiently; however, sluggish cathode (oxygen reduction reaction, ORR) kinetics require high operating temperatures (T op > 800°C) [2] Bulk oxygen ion transport depends strongly on the oxygen vacancy concentration and the energy barrier for an oxygen ion to migrate into an adjacent vacant site. Using first-principles density functional theory (DFT) and DFT+U calculations, Oxygen ion transport in perovskite-type (ABO 3 ) cathode materials depends on the material composition. We compare oxygen transport in La 1-x Sr x MO 3 (M=Cr,Mn,Fe,Co) to systematically analyze compositional effects. [4] Specifically, we study how Sr substitution alters the bulk structure, electronic properties, and oxygen vacancy formation energies of these materials. We also present oxygen migration pathways in LaCoO 3 and LaFeO 3 to understand the fundamental physics of the migration process. Our results provide insights for improving oxygen ion conductivities and guidelines for rationally designing new cathode materials. Finally, we show how structure-property relationships in Sr 2 Fe 1-x Mo x O 6 (SFMO), a promising cathode material, [7] We show that oxygen ion transport has a lower barrier in SFMO than in other MIEC cathodes, we explain the origins of this phenomenon, and we discuss how to optimize the Fe/Mo composition to obtain the best oxide ion conductivity

    Rowing against the wind: how do times of austerity shape academic entrepreneurship in unfriendly environments?

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    [EN] Academic spin-offs (ASOs) help universities transfer knowledge or technology through business projects developed by academic staff. This investigation aims at analyzing the critical factors for spin-off creation at universities operating in crisis-raven, entrepreneurship-unfriendly environments. Such factors revolve around four types of resources: environmental, institutional, organizational, and personal. Focusing on a Southern European context, as an example of an unfriendly environment affected by economic crisis, an entrepreneurial university (the Technical University of Valencia in Spain, UPV) is our research setting. Through a case study approach, we examine the potential of UPV as a springboard for ASOs. Our results show an adverse local environment, a rather favorable influence of institutional and organizational drivers, and a mixed role of personal factors. Our findings illustrate that UPV consistently supports spin-off creation due to a greater (rather positive) reflexivity from its institutional, organizational and personal resources than the (negative) imprinting of the unfriendly environment. This helps counter-balance the structural unfriendliness for academic entrepreneurship, and trigger a crisis-led risk-taking attitude by academic staff. Hence, UPV should continue with its current strategy of supporting academic entrepreneurship, and might transfer best practices to other universities also affected by unfavorable environmental conditions. Generally speaking, we would advise universities facing adverse circumstances to develop rules and mechanisms for academic entrepreneurship, carefully revise and improve malfunctions, and become involved throughout the whole process of spin-off development. All in all, our study advances understanding of how the different drivers for ASO creation can be revamped by universities located in unfriendly environments, having in mind the key role that universities play in fostering social and economic development through academic entrepreneurship in such environments.The authors would like to thank the Universitat Politecnica de Valencia (grant PAID-06-12-0916), and the Spanish Ministry of Economy and Competitiveness (grant ECO2011-29863), for their financial support for this research.Seguí-Mas, E.; Oltra, V.; Tormo-Carbó, G.; Sarrión Viñes, F. (2017). Rowing against the wind: how do times of austerity shape academic entrepreneurship in unfriendly environments?. International Entrepreneurship and Management Journal. 1-42. doi:10.1007/s11365-017-0478-zS142Acs, Z. J., Audretsch, D. B., & Lehmann, E. E. (2013). The knowledge spillover theory of entrepreneurship. Small Business Economics, 41, 757–774.Alemany, L. (2011). 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    Advances in ab-initio theory of Multiferroics. Materials and mechanisms: modelling and understanding

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    Within the broad class of multiferroics (compounds showing a coexistence of magnetism and ferroelectricity), we focus on the subclass of "improper electronic ferroelectrics", i.e. correlated materials where electronic degrees of freedom (such as spin, charge or orbital) drive ferroelectricity. In particular, in spin-induced ferroelectrics, there is not only a {\em coexistence} of the two intriguing magnetic and dipolar orders; rather, there is such an intimate link that one drives the other, suggesting a giant magnetoelectric coupling. Via first-principles approaches based on density functional theory, we review the microscopic mechanisms at the basis of multiferroicity in several compounds, ranging from transition metal oxides to organic multiferroics (MFs) to organic-inorganic hybrids (i.e. metal-organic frameworks, MOFs)Comment: 22 pages, 9 figure

    Changes in everyday life after discharge from day care rehabilitation

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    Community-based day care that provides rehabilitation (DCR) targets elderly people with physical disabilities. The goal of these programmes is mainly to improve physical ability in order to enable participants to remain in their ordinary homes. Knowledge of the outcomes of DCR is limited as well as knowledge of what it is that makes a difference for the individual. The aim of this study was to describe what changes in everyday life elderly persons experienced after discharge from a community-based day care rehabilitation centre and to give possible explanations for these changes. Fifteen elderly people were interviewed after that they had been discharged from DCR. A narrative approach was used for analysing the interview data. Four case stories constitute the findings, each of them with unique descriptions of changes in everyday life as well as possible explanations for these changes. The first case story described resumption of daily activities that made the days more eventful and meaningful. The second described how everyday life became an arena for exercising, which create confidence for the future. The third described how an increased sense of certainty and security in the movements led to an increased appetite for life. Finally, the fourth case story described both the stay at the DCR centre and the promise of a new period there as uplifting that made the days easier. Concerning possible explanations for these changes, the findings indicate that it was a combination of several events that together contributed to the changes. Examples were physical training, counselling about how to live in an active and healthy lifestyle, and socialisation with other patients in formal as well as in informal sessions

    Alliances and the innovation performance of corporate and public research spin-off firms

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    We explore the innovation performance benefits of alliances for spin-off firms, in particular spin-offs either from other firms or from public research organizations. During the early years of the emerging combinatorial chemistry industry, the industry on which our empirical analysis focuses, spin-offs engaged in alliances with large and established partners, partners of similar type and size, and with public research organizations, often for different reasons. We seek to understand to what extent alliances of spin-offs with other firms (either large- or small- and medium-sized firms) affected their innovation performance and also how this performance may have been affected by their corporate or public research background. We find evidence that in general alliances of spin-offs with other firms, in particular alliances with large firms, increased their innovation performance. Corporate spin-offs that formed alliances with other firms outperformed public research spin-offs with such alliances. This suggests that, in terms of their innovation performance, corporate spin-offs that engaged in alliances with other firms seemed to have benefitted from their prior corporate background. Interestingly, it turns out that the negative impact of alliances on the innovation performance of public research spin-offs was largely affected by their alliances with small- and medium-sized firms

    Factors associated with spontaneous stone passage in a contemporary cohort of patients presenting with acute ureteric colic. Results from the MIMIC Study (A Multi-centre cohort study evaluating the role of Inflammatory Markers in patients presenting with acute ureteric Colic)

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    Objectives There is conflicting data on the role of white blood cell count (WBC) and other inflammatory markers in spontaneous stone passage in patients with acute ureteric colic. The aim of the study was to assess the relationship of WBC and other routinely collected inflammatory and clinical markers including stone size, stone position and Medically Expulsive Therapy use (MET) with spontaneous stone passage (SSP) in a large contemporary cohort of patients with acute ureteric colic. Subjects and Methods Multi‐centre retrospective cohort study coordinated by the British Urology Researchers in Surgical Training (BURST) Research Collaborative at 71 secondary care hospitals across 4 countries (United Kingdom, Republic of Ireland, Australia and New Zealand). 4170 patients presented with acute ureteric colic and a computer tomography confirmed single ureteric stone. Our primary outcome measure was SSP as defined by the absence of need for intervention to assist stone passage. Multivariable mixed effects logistic regression was used to explore the relationship between key patient factors and SSP. Results 2518 patients were discharged with conservative management and had further follow up with a SSP rate of 74% (n = 1874/2518). Sepsis after discharge with conservative management was reported in 0.6% (n = 16/2518). On multivariable analysis neither WBC, Neutrophils or CRP were seen to predict SSP, with an adjusted OR of 0.97 [95% CI 0.91 to 1.04, p = 0.38], 1.06 [95% CI 0.99 to 1.13, p = 0.1] and 1.00 [95% CI 0.99 to 1.00, p = 0.17], respectively. Medical expulsive therapy (MET) also did not predict SSP [adjusted OR 1.11 [95% CI 0.76 to 1.61]). However, stone size and stone position were significant predictors. SSP for stones 7mm. For stones in the upper ureter the SSP rate was 52% [95% CI 48 to 56], middle ureter was 70% [95% CI 64 to 76], and lower ureter was 83% [95% CI 81 to 85]. Conclusion In contrast to the previously published literature, we found that in patients with acute ureteric colic who are discharged with initial conservative management, neither WBC, Neutrophil count or CRP help determine the likelihood of spontaneous stone passage. We also found no overall benefit from the use of MET. Stone size and position are important predictors and our findings represent the most comprehensive stone passage rates for each mm increase in stone size from a large contemporary cohort adjusting for key potential confounders. We anticipate that these data will aid clinicians managing patients with acute ureteric colic and help guide management decisions and the need for intervention
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