In this special issue, invited authors with expertise in correctional and forensic psychology (and related disciplines) were offered an opportunity to reflect on the idea of practice frameworks given ...their own research interests, expertise and practice experiences. In this article we provide a commentary on these contributions with the view of further developing the idea of ‘practice frameworks’ in a way which can better help guide theoretical work, empirical research, and practice in the correctional domain. We begin by reflecting on the nature of practice frameworks and why we think that they are important. We then consider each of the three levels that comprise practice frameworks and how these elements are realized in the diverse practice frameworks considered by the contributors to this special issue. We conclude with some thoughts about some important future directions for the idea of practice frameworks.
The Ras GTPases are frequently mutated in human cancer, and, although the Raf kinases are essential effectors of Ras signaling, the tumorigenic properties of specific Ras-Raf complexes are not well ...characterized. Here, we examine the ability of individual Ras and Raf proteins to interact in live cells using bioluminescence resonance energy transfer (BRET) technology. We find that C-Raf binds all mutant Ras proteins with high affinity, whereas B-Raf exhibits a striking preference for mutant K-Ras. This selectivity is mediated by the acidic, N-terminal segment of B-Raf and requires the K-Ras polybasic region for high-affinity binding. In addition, we find that C-Raf is critical for mutant H-Ras-driven signaling and that events stabilizing B-Raf/C-Raf dimerization, such as Raf inhibitor treatment or certain B-Raf mutations, can allow mutant H-Ras to engage B-Raf with increased affinity to promote tumorigenesis, thus revealing a previously unappreciated role for C-Raf in potentiating B-Raf function.
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•C-Raf binds all Ras proteins equivalently, but B-Raf exhibits selectivity for K-Ras•Raf N-terminal segments and Ras HVR sequences determine binding preferences•C-Raf is critical for downstream transmission of H-Ras-driven signaling•Events that increase B-Raf/C-Raf dimerization augment the B-Raf/H-Ras interaction
The Raf kinases bind to active Ras proteins and function to transmit signals that control cell growth and tumorigenesis. The study by Terrell et al. reveals distinct binding preferences between individual Ras and Raf family members and identifies events that can alter these interactions to upregulate Ras-driven cancer signaling.
We analyse organic solar cells with four different photoactive blends exhibiting differing dependencies of short-circuit current upon photoactive layer thickness. These blends and devices are ...analysed by transient optoelectronic techniques of carrier kinetics and densities, air photoemission spectroscopy of material energetics, Kelvin probe measurements of work function, Mott-Schottky analyses of apparent doping density and by device modelling. We conclude that, for the device series studied, the photocurrent loss with thick active layers is primarily associated with the accumulation of photo-generated charge carriers in intra-bandgap tail states. This charge accumulation screens the device internal electrical field, preventing efficient charge collection. Purification of one studied donor polymer is observed to reduce tail state distribution and density and increase the maximal photoactive thickness for efficient operation. Our work suggests that selecting organic photoactive layers with a narrow distribution of tail states is a key requirement for the fabrication of efficient, high photocurrent, thick organic solar cells.
We employed transient absorption spectroscopy (TAS) to investigate the kinetic dependences of photocatalysis in anatase and rutile TiO2 films of varying morphology. In mesoporous films, anatase was ...∼30 times more efficient than rutile in the photocatalytic degradation of an intelligent ink model system. Independent of phase, up to 100 lower levels of photocatalysis were found in dense films. Charge carrier lifetimes were probed by TAS on the microsecond to second time scale. For both rutile and anatase, recombination was independent of morphology. Rutile exhibited up to 10 times slower recombination kinetics than anatase. Efficient, irreversible hole scavenging by alcohols was present in mesoporous anatase alone, resulting in the generation of long-lived electrons (τ ≈ 0.7 s) which, upon the addition of the dye reduction target resazurin, enabled efficient electron transfer (τ ≈ 3 ms). Hole scavenging by alcohols on mesoporous rutile was substantially less efficient and more reversible than anatase, resulting in only a marginal increase in electron lifetime. The lower activity of rutile was not due to differences in recombination but rather to the deficiency of rutile holes to drive efficient and irreversible alcohol oxidation.
Oxygen vacancies are widely used to tune the light absorption of semiconducting metal oxides, but a photophysical framework describing the impact of such point defects on the dynamics of ...photogenerated charges, and ultimately on catalysis, is still missing. We herein use WO3 as a model material and investigate the impact of significantly different degrees of oxygen deficiency on its excited state kinetics. For highly oxygen-deficient films, photoelectron spectroscopy shows an over 2 eV broad distribution of oxygen vacancy states within the bandgap which gives rise to extended visible light absorption. We examine the nature of this distribution using first-principles defect calculations and find that defects aggregate to form clusters rather than isolated vacancy sites. Using transient absorption spectroscopy, we observe trapping of photogenerated holes within 200 fs after excitation at high degrees of oxygen deficiency, which increases their lifetime at the expense of oxidative driving force. This loss in driving force limits the use of metal oxides with significant degrees of sub-stoichiometry to photocatalytic reactions that require low oxidation power such as pollutant degradation, and highlights the need to fine-tune vacancy state distributions for specific target reactions.
We report a study of the effects of polymer optoelectronic properties on the performance of photovoltaic devices consisting of nanocrystalline TiO2 and a conjugated polymer. Three different ...poly(2‐methoxy‐5‐(2′‐ethylhexoxy)‐1,4‐phenylenevinylene) (MEH‐PPV)‐based polymers and a fluorene–bithiophene copolymer are compared. We use photoluminescence quenching, time‐of‐flight mobility measurements, and optical spectroscopy to characterize the exciton‐transport, charge‐transport, and light‐harvesting properties, respectively, of the polymers, and correlate these material properties with photovoltaic‐device performance. We find that photocurrent is primarily limited by the photogeneration rate and by the quality of the interfaces, rather than by hole transport in the polymer. We have also studied the photovoltaic performance of these TiO2/polymer devices as a function of the fabrication route and device design. Including a dip‐coating step before spin‐coating the polymer leads to excellent polymer penetration into highly structured TiO2 networks, as was confirmed through transient optical measurements of the photoinduced charge‐transfer yield and recombination kinetics. Device performance is further improved for all material combinations studied, by introducing a layer of poly(ethylene dioxythiophene) (PEDOT) doped with poly(styrene sulfonic acid) (PSS) under the top contact. Optimized devices incorporating the additional dip‐coated and PEDOT:PSS layers produced a short‐circuit current density of about 1 mA cm–2, a fill factor of 0.50, and an open‐circuit voltage of 0.86 V under simulated AM 1.5 illumination (100 mW cm–2, 1 sun). The corresponding power conversion efficiency under 1 sun was ≥ 0.4 %.
The effects of the exciton‐transport, charge‐transport, and light‐harvesting properties of conjugated polymers on the performance of a polymer/TiO2 hybrid system is studied systematically. Devices made from three different poly(2‐methoxy‐5‐(2′‐ethylhexoxy)‐1,4‐phenylenevinylene)‐based polymers and a fluorene–bithiophene copolymer are compared; it is found that the short‐circuit current density is limited by the photogeneration rate and the quality of the interfaces, rather than by the hole‐transport properties of the polymer. For optimizing performance, dip‐coating is found to lead to excellent polymer infiltration into the porous metal oxide, and the inclusion of a poly(ethylene dioxythiophene):poly(styrene sulfonic acid) layer beneath the top metal contact improves the short‐circuit photocurrent. Devices optimized in such a way show a short‐circuit current density of 1 mA cm–2, a fill factor of 0.50, an open‐circuit voltage of 0.86 V, and an overall power conversion efficiency of ≥ 0.4 % under 1 sun.
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