Non-innocent side-chains with dipole moments in organic solar cells improve charge separation

Providing sustainable energy is one of the biggest challenges nowadays. An attractive answer is the use of organic solar cells to capture solar energy. Recently a promising route to increase their efficiency has been suggested: developing new organic materials with a high dielectric constant. This solution focuses on lowering the coulomb attraction between electrons and holes, thereby increasing the yield of free charges. In here, we demonstrate from a theoretical point of view that incorporation of dipole moments in organic materials indeed lowers the coulomb attraction. A combination of molecular dynamics simulations for modelling the blend and ab initio quantum chemical calculations to study specific regions was performed. This approach gives predictive insight in the suitability of new materials for application in organic solar cells. In addition to all requirements that make conjugated polymers suitable for application in organic solar cells, this study demonstrates the importance of large dipole moments in polymer side-chains

Exploring Modern Virtue Ethics in the Context of Oral Healthcare

Virtue ethics is established as one of the dominant ethical theories that has application for healthcare practice, including oral health. Attributed to the ancient Aristotelian concepts of living a deeply fulfilled life, virtue ethics draws attention first and foremost, to the significance of character traits, or virtues in the process of ethical decision-making. This focus on character, contrasts with duty-based ethical theories such as deontological ethics (with a primary concern on duties) the principles of biomedical ethics (with a central focus on the principles and the obligations derived from these) and consequentialist ethics (with a primary focus on the consequences of actions).

There is a Silver Lining.

I investigated two unique processes developed throughout this body of work. The first technique is the cracking and lifting of an electroformed layer from a core vessel form. The second process, that I named “crunch-raising”, is used to form vessels. General data is gathered through research of traditional metalsmithing processes. Using an individualized approach, new data is gathered through extensive experimentation to develop a knowledge base because specific reference information does not currently exist. I find that an electroformed layer can be lifted from a core form with extreme torch heat to reveal the underlining vessel. I also find that the “crunch-raising” technique leaves a rippled texture in the surface of a vessel as it is being formed. I conclude that the project is successful. It is quite significant in that it has given me a personal vocabulary to define my current work

Sol-gel preparation of pure and doped TiO₂ films for the photocatalytic oxidation of ethanol in air

Stable sols of TiO2 were synthesized by a non-aqueous sol-gel process using titanium (IV) isopropoxide as precursor. The microstructure, optical and morphological properties of the films obtained by spin-coating from the sol, and annealed at different temperatures, were investigated using scanning electron microscopy, transmission electron microscopy, diffuse reflectance spectroscopy and ellipsometry. The crystalline structure of the films was characterized by X-ray diffraction and their photocatalytic activity was evaluated for the oxidation of ethanol in air. The influence of the calcination temperature, pre-heat treatment and the number of layers was studied. Simultaneous thermo-gravimetric and differential thermal analysis measurements were carried out to ascertain the thermal decomposition behavior of the precursors. In order to obtain a higher photoresponse in the visible region, a series of vanadium-, niobium- and tantalum-doped TiO2 catalysts was synthesized by the same sol-gel method. For V doping two different precursors, a vanadium alkoxide and V2O5, were used. The effect on the crystallization and photocatalytic activity of the doped TiO2 films was investigated. Furthermore, to identify the effective composition of the samples, they were characterized by X-ray photoelectron spectroscopy and the surface area of the powders was measured by N-2 adsorption. The 10 wt.% doped catalysts exhibit high photocatalytic activity under visible light and among them the best performance was obtained for the sample containing Ta as dopant. The crystallite sizes are closely related to the photocatalytic activity

Virtue ethics in dentistry - a model for developing virtuous dental practitioners

There is a renewed appreciation of the contribution of virtue ethics in clinical healthcare practice, including dentistry. This interest in virtue ethics highlights the limitations of only focusing on the development of clinical skills and competence or mere adherence to a set of ethical rules and guidelines. There is also a growing interest and appreciation that an equally important and integral aspect of dental practice is the development of a virtuous character. From this virtue ethics perspective, a virtue is an haracter, a disposition, well entrenched in its possessor

On the relation between local and charge-transfer exciton binding energies in organic photovoltaic materials

In organic photovoltaic devices two types of excitons can be generated for which different binding energies can be defined: the binding energy of the local exciton generated immediately after light absorption on the polymer and the binding energy of the charge-transfer exciton generated through the electron transfer from polymer to PCBM. Lowering these two binding energies is expected to improve the efficiency of the devices. Using (time-dependent) density functional theory, we studied whether a relation exists between the two different binding energies. For a series of related co-monomers, we found that the local exciton binding energy on a monomer is not directly related to that of the charge-transfer exciton on a monomer-PCBM complex because the variation in exciton binding energy depends mainly on the variation in electron affinity, which does not affect in a direct way the charge-transfer exciton binding energy. Furthermore, for the studied co-monomers and their corresponding trimers, we provide detailed information on the amount of charge transfer upon excitation and on the charge transfer excitation length. This detailed study of the excitation process reveals that the thiophene unit that links the donor and acceptor fragments of the co-monomer actively participates in the charge transfer process

Dentistry and COVID-19 - Is there a moral duty of care?

The world is witnessing the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with countless serious and fatal cases of corona virus disease (COVID-19). The impact of this pandemic has been most devastating among the health professionals due to the nature of their work. The risk of COVID-19 is particularly greater among oral health professionals due to their proximity to the oral cavity and production of aerosols. This scenario then raises the question, is there a moral duty for dental professionals to care for patients when doing so exposes them to significant risks of COVID-19

The behaviour of charge distributions in dielectric media

Screened Coulomb interaction in dielectrics is often used as an argument for a lower exciton binding energy and easier exciton dissociation in a high dielectric material. In this paper, we show that at length scales of excitons (10-20 angstrom), the screened Coulomb law is invalid and a microscopic (quantum chemical) description is necessary to describe the medium effect on exciton dissociation. The exciton dissociation energy decreases with increasing dielectric constant, albeit deviating from the inversely proportional relationship. The electron-hole interaction energy, approximated with a point charge model, is apparently not affected by the dielectric constant of the environment. (C) 2014 Elsevier B.V. All rights reserved

arf3DS4: An Integrated Framework for Localization and Connectivity Analysis of fMRI Data

In standard fMRI analysis all voxels are tested in a massive univariate approach, that is, each voxel is tested independently. This requires stringent corrections for multiple comparisons to control the number of false positive tests (i.e., marking voxels as active while they are actually not). As a result, fMRI analyses may suffer from low power to detect activation, especially in studies with high levels of noise in the data, for example developmental or single-subject studies. Activated region fitting (ARF) yields a solution by modeling fMRI data by multiple Gaussian shaped regions. ARF only requires a small number of parameters and therefore has increased power to detect activation. If required, the estimated regions can be directly used as regions of interest in a functional connectivity analysis. ARF is implemented in the R package arf3DS4. In this paper ARF and its implementation are described and illustrated with an example