A theoretical model for single molecule incoherent scanning tunneling spectroscopy

Single molecule scanning tunneling spectroscopy (STS), with dephasing due to elastic and inelastic scattering, is of some current interest. Motivated by this, we report an extended Huckel theory (EHT) based mean-field Non-equilibrium Green's function (NEGF) transport model with electron-phonon scattering treated within the self-consistent Born approximation (SCBA). Furthermore, a procedure based on EHT basis set modification is described. We use this model to study the effect of the temperature dependent dephasing, due to low lying modes in far-infrared range for which hw<<kT, on the resonant conduction through highest occupied molecular orbital (HOMO) level of a phenyl dithiol molecule sandwiched between two fcc-Au(111) contacts. Furthermore, we propose to include dephasing in room temperature molecular resonant conduction calculations.Comment: 12 pages, 5 figure

An Extended Huckel Theory based Atomistic Model for Graphene Nanoelectronics

An atomistic model based on the spin-restricted extended Huckel theory (EHT) is presented for simulating electronic structure and I-V characteristics of graphene devices. The model is applied to zigzag and armchair graphene nano-ribbons (GNR) with and without hydrogen passivation, as well as for bilayer graphene. Further calculations are presented for electric fields in the nano-ribbon width direction and in the bilayer direction to show electronic structure modification. Finally, the EHT Hamiltonian and NEGF (Nonequilibrium Green's function) formalism are used for a paramagnetic zigzag GNR to show 2e2/h quantum conductance.Comment: 5 pages, 8 figure

Polymer brush lubrication of the silicon nitride-steel contact: a colloidal force microscopy study

A greener lubrication solution for the steel–silicon nitride hybrid contact is proposed. The utilisation of surface-initiated (SI) activators-regenerated-by-electron-transfer (ARGET) atom-transfer radical polymerisation (ATRP) is employed to produce an oleophilic polymer brush which is based on methyl methacrylate. The current study presents the synthesis and characterisation of poly methyl methacrylate brushes. X-ray photoelectron spectroscopy, contact angle, gel permeation chromatography and atomic force microscopy were used to characterise the initiators and brushes. The lubricating effects of the polymer brushes under dry and swollen states were elucidated by lateral force microscopy with a steel colloid with a normal load in the nanoscale range. By testing in water and in poly α-olefin (PAO) this work shows that the frictional response of surface initiated polymers is highly dependent on the interaction between polymer brushes and fluid

Strain and field modulation in bilayer graphene band structure

Using an external electric field, one can modulate the bandgap of Bernal stacked bilayer graphene by breaking A-~B symmetry. We analyze strain effects on the bilayer graphene using the extended Huckel theory and find that reduced interlayer distance results in higher bandgap modulation, as expected. Furthermore, above about 2.5 angstrom interlayer distance, the bandgap is direct, follows a convex relation to electric field and saturates to a value determined by the interlayer distance. However, below about 2.5 angstrom, the bandgap is indirect, the trend becomes concave and a threshold electric field is observed, which also depends on the stacking distance.Comment: 3 pages, 5 figures - v1 and v2 are the same, uploaded twice - v3, some typos fixed and a reference adde

Undiagnosed dementia in primary care: A record linkage study

BackgroundThe number of people living with dementia is greater than the number with a diagnosis of dementia recorded in primary care. This suggests that a significant number are living with dementia that is undiagnosed. Little is known about this group and there is little quantitative evidence regarding the consequences of diagnosis for people with dementia.ObjectivesThe aims of this study were to (1) describe the population meeting the criteria for dementia but without diagnosis, (2) identify predictors of being diagnosed and (3) estimate the effect of diagnosis on mortality, move to residential care, social participation and well-being.DesignA record linkage study of a subsample of participants (n = 598) from the Cognitive Function and Ageing Study II (CFAS II) (n = 7796), an existing cohort study of the population of England aged ≥ 65 years, with standardised validated assessment of dementia and consent to access medical records.Data sourcesData on dementia diagnoses from each participant’s primary care record and covariate and outcome data from CFAS II.SettingA population-representative cohort of people aged ≥ 65 years from three regions of England between 2008 and 2011.ParticipantsA total of 598 CFAS II participants, which included all those with dementia who consented to medical record linkage (n = 449) and a stratified sample without dementia (n = 149).Main outcome measuresThe main outcome was presence of a diagnosis of dementia in each participant’s primary care record at the time of their CFAS II assessment(s). Other outcomes were date of death, cognitive performance scores, move to residential care, hospital stays and social participation.ResultsAmong people with dementia, the proportion with a diagnosis in primary care was 34% in 2008–11 and 44% in 2011–13. In both periods, a further 21% had a record of a concern or a referral but no diagnosis. The likelihood of having a recorded diagnosis increased with severity of impairment in memory and orientation, but not with other cognitive impairment. In multivariable analysis, those aged ≥ 90 years and those age

Ultrafast Electronic Energy Transfer in an orthogonal molecular dyad

The St Andrews group acknowledges support from the European Research Council (grant number 321305) and the Engineering and Physical Sciences Research Council (grant EP/L017008/1). I.D.W.S. also acknowledges support from a Royal Society Wolfson Research Merit Award.Understanding electronic energy transfer (EET) is an important ingredient in the development of artificial photosynthetic systems and photovoltaic technologies. Although EET is at the heart of these applications and crucially influences their light-harvesting efficiency, the nature of EET over short distances for covalently bound donor and acceptor units is often not well understood. Here we investigate EET in an orthogonal molecular dyad (BODT4) in which simple models fail to explain the very origin of EET. Based on nonadiabatic ab initio molecular dynamics calculations and fluorescence depolarization experiments we gain detailed microscopic insights into the ultrafast electro-vibrational dynamics following photoexcitation. Our analysis offers molecular-level insights into these processes and reveals that it takes place on timescales ≲ 100 fs and occurs through an intermediate charge-transfer state.PostprintPeer reviewe

Altered matter. Like icons, stored

This thesis proposes research findings that run parallel to my own practice. At the heart of the concepts discussed there is a notion of invention and the transmutation of materials. Attempting to find clear ways of making something with the legitimacy of an artwork. Artists considered along side my practice include Alberto Giacometti, Manfred Pernice, Mike Nelson and Ryan Trecartin. As a result of my academic inquiry, my ideas start to move towards the informational as a way to understand how information and invented symbolism may be inscribed or instilled into something. This may be through constellational choices in joining, script writing or by embracing technological ways to mediate the world and the artwork, extending its quiddity or “thingness” by embracing editing and manipulation. The studio work extends on my previous installation practice:sculptures in a variety of sizes and materials. Sculptures that suggest function in an ambiguous way, mimesis in an uncanny way and have an unclear classification as support, artwork, relic or invention. Amid this ambivalent environment I use constellational choices, inscription into materials and proximity relationships to communicate a fictional language or signs of what may appear to have come from an extraterrestrial culture, in, around and on the sculptures. Some materials appear as “repurposed” through the unusual joining of everyday components. Other materials may have been reduced to mere “matter” by altering them to near unrecognisable states. The sculptures and installation elements have a second mediated form by appearing in still and moving images

Refashioning Service Design : Designing for popular cultural service experience

Services are becoming ever more present in our everyday lives and cultural lifestyles, enabling new practices and shaping new values. In the entanglement of people, experiences, interactions, products, technology and media that shape services, meaning is circulated, and culture formed. This thesis explores a gap between Service Design and concepts from popular culture by inquiring how novel services can be shaped through the uptake and translation of cultural phenomena. It further explores the cultural influence such services have through shaping dynamic relationships between use, production, mediatization and consumption of cultural material and meaning, and circulation of symbolic value. This thesis introduces Trendslation, an experiential Service Design approach that operationalizes a triple-staged semantic transformation of trends, to assist the service designer in designing for experiential services that are culturally informed and enacted. This contribution frames services in consumer and lifestyle domains as popular cultural constructs in the way that they offer mediatized interactions and experiences that are influential in the cultural interplay of meanings, materials and practices. This thesis further contributes with the practical tool of the experience-centric service journey, as a visual narrative and mapping of the flows of meaning that come into play across touchpoints and interactions over time. In light of this service-cultural view the notion of the cultural intermediary is applied as a framework to further unpack how Service Design, and the service designer, may more fully adopt and enact a cultural role in shaping experiential service offerings and details. This contributes to the field and practice of Service Design by highlighting the service designer as a cultural intermediary. The work in this thesis is situated within a commercial business context, where three design explorations have been carried out through the application of an overall qualitative and open-ended Research through Design methodology, in collaboration with three major national and global brands in the areas of food and fashion apparel. Moving between practice and research, and qualitative methods and design techniques, the modes and mechanisms of meaning-construction in a Service Design view have been explored by designing trend-driven and conceptual service design artefacts. The design-led research explorations have further revealed connections between perspectives from Service Design and concepts from Popular Culture that are framed through six new concepts and a model, that jointly offer a positioning of Popular Cultural Service Design, and can be seen as an overall contribution to the field.publishedVersio

Synthesis of and structure–property relationships in zinc complexes of bis‐metaphenylene semiquinone biradical species

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90562/1/poc1917.pd

Elucidating the Structure-Activity Relationships of the Vasorelaxation and Antioxidation Properties of Thionicotinic Acid Derivatives

Nicotinic acid, known as vitamin B3, is an effective lipid lowering drug and intense cutaneous vasodilator. This study reports the effect of 2-(1-adamantylthio)nicotinic acid (6) and its amide 7 and nitrile analog 8 on phenylephrine-induced contraction of rat thoracic aorta as well as antioxidative activity. It was found that the tested thionicotinic acid analogs 6-8 exerted maximal vasorelaxation in a dose-dependent manner, but their effects were less than acetylcholine (ACh)-induced nitric oxide (NO) vasorelaxation. The vasorelaxations were reduced, apparently, in both NG-nitro-L-arginine methyl ester (L-NAME) and indomethacin (INDO). Synergistic effects were observed in the presence of L-NAME plus INDO, leading to loss of vasorelaxation of both the ACh and the tested nicotinic acids. Complete loss of the vasorelaxation was noted under removal of endothelial cells. This infers that the vasorelaxations are mediated partially by endothelium-induced NO and prostacyclin. The thionicotinic acid analogs all exhibited antioxidant properties in both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide dismutase (SOD) assays. Significantly, the thionicotinic acid 6 is the most potent vasorelaxant with ED50 of 21.3 nM and is the most potent antioxidant (as discerned from DPPH assay). Molecular modeling was also used to provide mechanistic insights into the vasorelaxant and antioxidative activities. The findings reveal that the thionicotinic acid analogs are a novel class of vasorelaxant and antioxidant compounds which have potential to be further developed as promising therapeutics