Advances in nitrogen transfer reactions involving aziridines

In recent years, our search for new nitrogen transfer reactions has concentrated on aziridine chemistry. This Account highlights our efforts toward the synthesis and functionalization of aziridines. In the course of our research, we have investigated the electrochemical aziridination of olefins, the acid-catalyzed ring opening of aziridines, and the development of transition metal mediated nitrogen allylation, arylation, and alkenylation of unprotected aziridines. Our studies have also involved the synthesis of aziridine-based enamine intermediates and their stereoselective transformations into heterocyclic compounds.     

Towards a Polytheistic Relationship to Landscape: Issues for Contemporary Art

The paper examines the concerns of the art critic and environmentalist Rebecca Solnit with the myth of Eden in the book of Genesis, the assumptions of a Judaeo-Christian monotheism and its secular inheritance, as a means to introduce the need for a 'polytheistic' psychology to advance a genuinely radical understanding of the relationship between issues of place, identity and contemporary landscape art. Drawing on the work of Peter Bishop and Edward S. Casey to identify a body of thinking related, via issues of metamorphosis and ambiguity, to both art historical and geographical contexts relating to a 'conversational' aesthetic are identified. This is seen as making possible a polytheistic conception of art based on imaginal space as an alternative to the dominant traditions of conceptual and Minimal art since the 1960s. Finally, the approaches of specific artists, and in particular the world of Sian Bonnell, are examined in relation to garden traditions in the UK.     

Trap Healing for High‐Performance Low‐Voltage Polymer Transistors and Solution‐Based Analog Amplifiers on Foil

Solution‐processed semiconductors such as conjugated polymers have great potential in large‐area electronics. While extremely appealing due to their low‐temperature and high‐throughput deposition methods, their integration in high‐performance circuits has been difficult. An important remaining challenge is the achievement of low‐voltage circuit operation. The present study focuses on state‐of‐the‐art polymer thin‐film transistors based on poly(indacenodithiophene‐benzothiadiazole) and shows that the general paradigm for low‐voltage operation via an enhanced gate‐to‐channel capacitive coupling is unable to deliver high‐performance device behavior. The order‐of‐magnitude longitudinal‐field reduction demanded by low‐voltage operation plays a fundamental role, enabling bulk trapping and leading to compromised contact properties. A trap‐reduction technique based on small molecule additives, however, is capable of overcoming this effect, allowing low‐voltage high‐mobility operation. This approach is readily applicable to low‐voltage circuit integration, as this work exemplifies by demonstrating high‐performance analog differential amplifiers operating at a battery‐compatible power supply voltage of 5 V with power dissipation of 11 µW, and attaining a voltage gain above 60 dB at a power supply voltage below 8 V. These findings constitute an important milestone in realizing low‐voltage polymer transistors for solution‐based analog electronics that meets performance and power‐dissipation requirements for a range of battery‐powered smart‐sensing applications.     

The Biochemical Assessment of Mitochondrial Respiratory Chain Disorders

Mitochondrial respiratory chain (MRC) disorders are a complex group of diseases whose diagnosis requires a multidisciplinary approach in which the biochemical investigations play an important role. Initial investigations include metabolite analysis in both blood and urine and the measurement of lactate, pyruvate and amino acid levels, as well as urine organic acids. Recently, hormone-like cytokines, such as fibroblast growth factor-21 (FGF-21), have also been used as a means of assessing evidence of MRC dysfunction, although work is still required to confirm their diagnostic utility and reliability. The assessment of evidence of oxidative stress may also be an important parameter to consider in the diagnosis of MRC function in view of its association with mitochondrial dysfunction. At present, due to the lack of reliable biomarkers available for assessing evidence of MRC dysfunction, the spectrophotometric determination of MRC enzyme activities in skeletal muscle or tissue from the disease-presenting organ is considered the ‘Gold Standard’ biochemical method to provide evidence of MRC dysfunction. The purpose of this review is to outline a number of biochemical methods that may provide diagnostic evidence of MRC dysfunction in patients.     

Cell-Like Capsules with “Smart” Compartments

Eukaryotic cells have inner compartments (organelles), each with distinct properties and functions. One mimic of this architecture, based on biopolymers, is the multicompartment capsule (MCC). Here, MCCs in which the inner compartments are chemically unique and “smart,” i.e., responsive to distinct stimuli in an orthogonal manner are created. Specifically, one compartment alone is induced to degrade when the MCC is contacted with an enzyme while other compartments remain unaffected. Similarly, just one compartment gets degraded upon contact with reactive oxygen species generated from hydrogen peroxide (H₂O₂). And thirdly, one compartment alone is degraded by an external, physical stimulus, namely, by irradiating the MCC with ultraviolet (UV) light. All these specific responses are achieved without resorting to complicated chemistry to create the compartments: the multivalent cation used to crosslink the biopolymer alginate (Alg) is simply altered. Compartments of Alg crosslinked by Ca²⁺ are shown to be sensitive to enzymes (alginate lyases) but not to H₂O₂ or UV, whereas the reverse is the case with Alg/Fe³⁺ compartments. These results imply the ability to selectively burst open a compartment in an MCC “on-demand” (i.e., as and when needed) and using biologically relevant stimuli. The results are then extended to a sequential degradation, where compartments in an MCC are degraded one after another, leaving behind an empty MCC lumen. Collectively, this work advances the MCC as a platform that not only emulates key features of cellular architecture, but can also begin to capture rudimentary cell-like behaviors.     

Quasi-1D Polymer Semiconductor–Diarylethene Blends: High Performance Optically Switchable Transistors

Optically switchable field-effect transistors (OSFETs) are non-volatile photonic memory devices holding a great potential for applications in optical information storage and telecommunications. Solution processing of blends of photochromic molecules and π-conjugated polymers is a low-cost protocol to integrate simultaneously optical switching and charge transport functions in large-area devices. However, the limited reversibility of the isomerization of photochromic molecules due to steric hindrance when embedded in ordered polymeric matrices represents a severe limitation and it obliges to incorporate as much as 20% in weight of the photochromic component, thereby drastically diluting the electronic function, limiting the device performance. Herein, a comparative study of the photoresponsivity of a suitably designed diarylethene molecule is reported when embedded in the matrix of six different polymer semiconductors displaying diverse charge transport properties. In particular, this study focuses on three semi-crystalline polymers and three quasi-1D polymers. It is found that 1% w/w of 1,2-bis(5-(3,5-di-tert-butylphenyl)-2-methylthiophen-3-yl)cyclopent-1-ene in a blend with poly(indacenodithiophene-co-benzothiadiazole) is sufficient to fabricate OSFETs combining photo-modulation efficiencies of 45.5%, mobilities >1 cm² V⁻¹s⁻¹, and photo-recovered efficiencies of 98.1%. These findings demonstrate that quasi-1D polymer semiconductors, because of their charge transport dominated by intra-molecular processes, epitomize the molecular design principles required for the fabrication of high-performance OSFETs.     

Developing and testing a cost-effectiveness analysis to prioritize green infrastructure alternatives for climate change adaptation

Green infrastructure has been increasingly identified as an option to help manage climate change impacts in urban areas, although its implementation is still not widely promoted in urban planning. This is because of the lack of detailed analysis for decision-makers regarding construction and maintenance costs for different types and how effective various measures are at managing precipitation at a catchment scale. This paper contributes to fill this gap in knowledge by developing a green infrastructure cost-effectiveness ranking index (GICRI) able to evaluate the stormwater runoff volume reduction of multiple green infrastructure alternatives under different climate change scenarios, over differing spatial configurations and combining this performance data with their construction and maintenance costs. After applying this model over two case study areas, this paper provides three main insights. First, climate change projections have a significant impact on green infrastructure cost-effectiveness. Second, as green infrastructure cost-effectiveness is influenced by the spatial scale, there are different challenges for larger cities and smaller regional towns. Building on this, the paper argues that GICRI can be a simple and fast heuristic to increase the use of green infrastructure by informing decision-makers regarding how and where to prioritize investment or where greater modelling is needed.     

High Performing Solid-State Organic Electrochemical Transistors Enabled by Glycolated Polythiophene and Ion-Gel Electrolyte with a Wide Operation Temperature Range from −50 to 110 °C

The development of organic electrochemical transistors (OECTs) capable of maintaining their high amplification, fast transient speed, and operational stability in harsh environments will advance the growth of next-generation wearable and biological electronics. In this study, a high-performance solid-state OECT (SSOECT) is successfully demonstrated, showing a recorded high transconductance of 220 ± 59 S cm⁻¹, ultrafast device speed of ≈10 kHz with excellent operational stability over 10 000 switching cycles, and thermally stable under a wide temperature range from −50 to 110 °C. The developed SSOECTs are successfully used to detect low-amplitude physiological signals, showing a high signal-to-noise-ratio of 32.5 ± 2.1 dB. For the first time, the amplifying power of these SSOECTs is also retained and reliably shown to collect high-quality electrophysiological signals even under harsh temperatures (−50 and 110 °C). The demonstration of high-performing SSOECTs and its application in harsh environment are core steps toward their implementation in next-generation wearable electronics and bioelectronics.