The most pressing challenges for light‐driven hydrogel actuators include reliance on UV light, slow response, poor mechanical properties, and limited functionalities. Now, a supramolecular design ...strategy is used to address these issues. Key is the use of a benzylimine‐functionalized anthracene group, which red‐shifts the absorption into the visible region and also stabilizes the supramolecular network through π–π interactions. Acid–ether hydrogen bonds are incorporated for energy dissipation under mechanical deformation and maintaining hydrophilicity of the network. This double‐crosslinked supramolecular hydrogel developed via a simple synthesis exhibits a unique combination of high strength, rapid self‐healing, and fast visible‐light‐driven shape morphing both in the wet and dry state. As all of the interactions are dynamic, the design enables the structures to be recycled and reprogrammed into different 3D objects.
A photoresponsive hydrogel was constructed by using a supramolecular design strategy. A red‐shifted anthracene group furnishes the system with fast photo‐actuation. Hydrogen bonding, π–π interactions, and anthracene photodimerization results in an actuator with high mechanical strength, fast self‐healing, and recyclability.
A novel approach to the design of dirhodium(II) tetracarboxylates derived from (S)‐amino acid ligands is reported. The approach is founded on tailoring the steric influences of the overall catalyst ...structure by reducing the local symmetry of the ligand's N‐heterocyclic tether. The application of the new approach has led to the uncovering of Rh2(S‐tertPTTL)4 as a new member of the dirhodium(II) family with extraordinary selectivity in cyclopropanation reactions. The stereoselectivity of Rh2(S‐tertPTTL)4 was found to be comparable to that of Rh2(S‐PTAD)4 (up to >99 % ee), with the extra benefit of being more synthetically accessible. Correlations based on X‐ray structures to justify the observed enantioinduction are also discussed.
Cyclopropanation catalyst: A series of dirhodium(II) tetracarboxylates derived from N‐protected l‐tert‐leucine ligands have been prepared by tailoring the steric influences of the overall catalyst structure by reducing the local symmetry of the ligand's N‐heterocyclic tether. Of these new complexes, Rh2(S‐tertPTTL)4 shows extraordinary selectivity as a catalyst in cyclopropanation reactions (see scheme) and is easy to synthesise compared with previously prepared dirhodium(II) catalysts of this type.
Visual culture has become one of the most dynamic fields of scholarship, a reflection of how the study of human culture increasingly requires distinctively visual ways of thinking and methods of ...analysis. Bringing together leading international scholars to assess all aspects of visual culture, the Handbook aims to provide a comprehensive and authoritative overview of the subject. The Handbook embraces the extraordinary range of disciplines which now engage in the study of the visual - film and photography, television, fashion, visual arts, digital media, geography, philosophy, architecture, material culture, sociology, cultural studies and art history. Throughout, the Handbook is responsive to the cross-disciplinary nature of many of the key questions raised in visual culture around digitization, globalization, cyberculture, surveillance, spectacle, and the role of art. The Handbook guides readers new to the area, as well as experienced researchers, into the topics, issues and questions that have emerged in the study of visual culture since the start of the new millennium, conveying the boldness, excitement and vitality of the subject.
A crystalline 3D hydrogen bonded framework is assembled in water from tetrahedral tetraamidinium cations and antielectrostatically hydrogen bonded bicarbonate dimers. The framework forms in water, ...and represents a clear demonstration of the potency of these anti-Coulombic hydrogen bonds. Gentle heating of the framework (50 °C) releases CO
2
and water to give the neutral tetraamidine compound.
A 3D hydrogen bonded organic framework was assembled in water from tetraamidinium cations and antielectrostatically hydrogen bonded bicarbonate dimers.
Critique of Accelerationism Gardiner, Michael E.
Theory, culture & society,
01/2017, Letnik:
34, Številka:
1
Journal Article
Recenzirano
The global financial crisis beginning in 2008 has encouraged the revitalization of a wide spectrum of leftist theorizing, but arguably the most audacious is that of ‘accelerationism’. ...Left-accelerationism sees the intensification of certain tendencies in late capitalist society as a way to escape its gravitational orbit and ‘repurpose’ the very material infrastructure of capitalism itself, to universally emancipatory ends. The central task here is to engage accelerationism with a thinker of the post-Autonomist tradition, Franco ‘Bifo’ Berardi. Contrary to Williams and Srnicek, co-authors of the #Accelerate manifesto, Bifo asserts that acceleration per se only augments the power and dynamism of capital, and posits instead a ‘post-politics’ of ironic detachment, aesthetic cultivation, and ‘therapy’. Contrasting Bifo and accelerationism clarifies each of their assumptions and core arguments, and points the way to a more nuanced perspective on these issues, in a contemporaneous moment marked in equal measure by inestimable threat and liberatory promise.
Febrile illnesses, such as malaria and pneumonia, are among the most common causes of mortality in children younger than 5 years in Uganda outside of the neonatal period. Their impact could be ...mitigated through earlier diagnosis and treatment at biomedical facilities; however, it is estimated that a large percentage of Ugandans (70-80%) seek traditional healers for their first line of medical care. This study sought to characterize individual and structural influences on health care-seeking behaviors for febrile children. Minimally structured, qualitative interviews were conducted for 34 caregivers of children presenting to biomedical and traditional healer sites, respectively. We identified six themes that shape the pathway of care for febrile children: 1) peer recommendations, 2) trust in biomedicine, 3) trust in traditional medicine, 4) mistrust in providers and therapies, 5) economic resources and access to health care, and 6) perceptions of child health. Biomedical providers are preferred by those who value laboratory testing and formal medical training, whereas traditional healer preference is heavily influenced by convenience, peer recommendations, and firm beliefs in traditional causes of illness. However, most caregivers concurrently use both biomedical and traditional therapies for their child during the same illness cycle. The biomedical system is often considered as a backup when traditional healing "fails." Initiatives seeking to encourage earlier presentation to biomedical facilities must consider the individual and structural forces that motivate seeking traditional healers. Educational programs and cooperation with traditional healers may increase biomedical referrals and decrease time to appropriate care and treatment for vulnerable/susceptible children.
Acyl bicyclobutanes are shown to engage in strain-promoted cycloaddition reactions with a diverse array of triazolinedione reagents. The synthesis of an orthogonally protected urazole building block ...enabled the facile preparation of amino acid- and peptide-derived triazolinediones that undergo cycloaddition reactions to afford novel peptide conjugates. The additive-free and fully atom-economical nature of the transformation is a promising starting point for the generalization of this cycloaddition reaction for the functionalization of biomolecules.
Rising global demand for fossil resources has prompted a renewed interest in catalyst technologies that increase the efficiency of conversion of hydrocarbons from petroleum and natural gas to ...higher-value materials. Styrene is currently produced from benzene and ethylene through the intermediacy of ethylbenzene, which must be dehydrogenated in a separate step. The direct oxidative conversion of benzene and ethylene to styrene could provide a more efficient route, but achieving high selectivity and yield for this reaction has been challenging. Here, we report that the Rh catalyst (FIDAB)Rh(TFA)(η2–C2H4) FIDAB is N,N′-bis(pentafluorophenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene; TFA is trifluoroacetate converts benzene, ethylene, and Cu(II) acetate to styrene, Cu(I) acetate, and acetic acid with 100% selectivity and yields ≥95%. Turnover numbers >800 have been demonstrated, with catalyst stability up to 96 hours.
This article argues that millennial Scottish culture has been animated in large part by a push to overcome a historiographical compulsion built into the modern British state’s understanding of ...nature. This understanding of nature became the foundational principle of government during the Financial Revolution and British unification in the 1690s–1710, then was made the subject of a universal history by the Scottish Enlightenment of the later eighteenth century, and has remained in place to be extended by neoliberalism. The article argues more specifically that the British association of progress with dominion over the world as nature demands a temporal abstraction, or automation, reducing the determinability of the present, and that correspondingly this idea of nature ‘softens’ conflict in a way that points to weapons carrying perfectly abstracted violence. Nuclear weapons become an inevitable corollary of the nature of British authority. Against this, twenty-first century Scottish cultures, particularly a growing mainstream surrounding independence or stressing national specificity, have noticeably turned against both nuclear weapons and the understanding of nature these weapons protect. These cultures draw from a 1980s moment in which anti-nuclear action came both to be understood as ‘national’, and to stand in relief to the British liberal firmament. These cultures are ‘activist’ in the literal sense that they tend to interrupt an assumption of the eternal that stands behind both nuclear terror and its capture of nature as dominion over the world. A dual interruption, nuclear and counter-natural, can be read in pro-independence cultural projects including online projects like Bella Caledonia and National Collective, which might be described as undertaking a thorough ‘denaturing’. But if the question of nature as resources for dominion has been a topic for debate in the environmental humanities, little attention has been paid to this specifically British ‘worlding’ of nature, or to how later constitutional pressures on the UK also mean pressures on this worlding. Andreas Malm’s Fossil Capital (2016), for example, a powerful account of the automation of production in the British industrial revolution, might be related to the automation of ideas of progress pressed during the Scottish Enlightenment, and entrenching a dualism of owning subject and nature as object-world that would drive extraction in empire. Finally, this article suggests that this dualism, and the nature holding it in place, have also been a major target of the ‘wilderness encounters’ that form a large sub-genre in twenty-first century Scottish writing. Such ‘denaturing’ encounters can be read in writers like Alec Finlay, Linda Cracknell, Thomas A. Clark, and Gerry Loose, often disrupting the subject standing over nature, and sometimes explicitly linking this to a disruption of nuclear realism.
α-Iodo-α,β-unsaturated ketones such as compound 1 serve as vicinal dielectrophiles and react with a range of dinucleophiles including pentane-2,4-dione and 1,3-indandione to produce 3 + 2- and 2 + ...1-adducts such as 5 and 38, respectively. 4 + 2- and 5 + 2-cycloadducts have been obtained from compound 1 by related means. Preliminary studies reveal that α-iodinated α,β-unsaturated esters can also participate in at least some of these same processes.
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