Co-production is one such buzzword very often used as a rebadging of patient/service user involvement. I see widespread co-option and dilution of more radical concepts like this in order perhaps to be able to slot them into existing structures without the risky and scary business of actual change.
The scale, pace, and intensity of human activity on the planet demands radical departures from the status quo to remain within planetary boundaries and achieve sustainability. The steering arms of society including embedded financial, legal, political, and governance systems must be radically realigned and recognize the connectivity among social, ecological, and technological domains of urban systems to deliver more just, equitable, sustainable, and resilient futures. We present five key principles requiring fundamental cognitive, behavioral, and cultural shifts including rethinking growth, rethinking efficiency, rethinking the state, rethinking the commons, and rethinking justice needed together to radically transform neighborhoods, cities, and regions.
The future is therefore unsurprisingly dominated by dystopian narratives30 that stem from business-as-usual projections of current trends in population, economic, and urban growth (Fig. 1). These narratives exist in prominent future scenarios from global bodies such as the IPCC, IPBES and other31 economic scenarios, and which represent multiple future Anthropocene-related risks, such as from weather-related extreme events (e.g., drought, heat waves, coastal storms, and fires)32. Extreme events do not pose only future risks but are already impacting human and ecological communities33 with complex local, regional, and global feedbacks that challenge human ability to innovatively manage the earth system at scale and alter current negative social and environmental trajectories toward more positive, desirable futures. While a return to past functionality or global climate has limited prospects34,35 owing to its systemic complexity and our fundamental alteration of its dynamic stability, creating, owning, and acting upon positive visions that counter dystopian narratives is possible and critical to chart pathways, create motivation, and drive action in the present16,17,30. However, visions alone are insufficient. More radical transformative thinking is required that provides systemic leverage, actionable ideas, and supportive governance processes to develop pathways for how local, regional, and national innovations can be upscaled to drive global-scale sustainability transformations. Fundamental, and even radical transformations will require creative ways of connecting different types of actions and feedbacks across subsystems to promote positive tipping points36.
We encourage further studies to identify similar SETS couplings, to put forward additional principles that must be re-thought, and to support their mainstreaming together to help initiate and foster the radical transformations toward a good Anthropocene urgently needed.
In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron.With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spontaneously dimerize. Most organic radicals have short lifetimes.
A notable example of a radical is the hydroxyl radical (HO·), a molecule that has one unpaired electron on the oxygen atom. Two other examples are triplet oxygen and triplet carbene (꞉CH2) which have two unpaired electrons.
Radicals may be generated in a number of ways, but typical methods involve redox reactions. Ionizing radiation, heat, electrical discharges, and electrolysis are known to produce radicals. Radicals are intermediates in many chemical reactions, more so than is apparent from the balanced equations.
Radicals are important in combustion, atmospheric chemistry, polymerization, plasma chemistry, biochemistry, and many other chemical processes. A majority of natural products are generated by radical-generating enzymes. In living organisms, the radicals superoxide and nitric oxide and their reaction products regulate many processes, such as control of vascular tone and thus blood pressure. They also play a key role in the intermediary metabolism of various biological compounds. Such radicals can even be messengers in a process dubbed redox signaling. A radical may be trapped within a solvent cage or be otherwise bound.
Radicals are either (1) formed from spin-paired molecules or (2) from other radicals. Radicals are formed from spin-paired molecules through homolysis of weak bonds or electron transfer, also known as reduction. Radicals are formed from other radicals through substitution, addition, and elimination reactions.
Homolysis makes two new radicals from a spin-paired molecule by breaking a covalent bond, leaving each of the fragments with one of the electrons in the bond. Because breaking a chemical bond requires energy, homolysis occurs under the addition of heat or light. The bond dissociation energy associated with homolysis depends on the stability of a given compound, and some weak bonds are able to homolyze at relatively lower temperatures.
Some homolysis reactions are particularly important because they serve as an initiator for other radical reactions. One such example is the homolysis of halogens, which occurs under light and serves as the driving force for radical halogenation reactions.
Radical addition describes when a radical is added to a spin-paired molecule to form a new radical. The figure on the right shows the addition of a bromine radical to an alkene. Radical addition follows the Anti -Markovnikov rule, where the substituent is added to the less substituted carbon atom.
Radical elimination can be viewed as the reverse of radical addition. In radical elimination, an unstable radical compound breaks down into a spin-paired molecule and a new radical compound. Shown below is an example of a radical elimination reaction, where a benzoyloxy radical breaks down into a phenyl radical and a carbon dioxide molecule.
Although organic radicals are generally stable intrinsically (in isolation), practically speaking their existence is only transient because they tend to dimerize. Some are quite long-lived. Generally organic radicals are stabilized by any or all of these factors: presence of electronegativity, delocalization, and steric hindrance. The compound 2,2,6,6-tetramethylpiperidinyloxyl illustrates the combination of all three factors. It is a commercially available solid that, aside from being magnetic, behaves like a normal organic compound.
Organic radicals are inherently electron deficient thus the greater the electronegativity of the atom on which the unpaired electron resides the less stable the radical. Between carbon, nitrogen, and oxygen, for example, carbon is the most stable and oxygen the least stable.
Electronegativity also factors into the stability of carbon atoms of different hybridizations. Greater s-character correlates to higher electronegativity of the carbon atom (due to the close proximity of s orbitals to the nucleus), and the greater the electronegativity the less stable a radical. sp-hybridized carbons (50% s-character) form the least stable radicals compared to sp3-hybridized carbons (25% s-character) which form the most stable radicals.
Most simply, the greater the steric hindrance the more difficult it is for reactions to take place, and the radical form is favored by default. For example, compare the hydrogen-abstracted form of N-hydroxypiperidine to the molecule TEMPO. TEMPO, or (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl, is too sterically hindered by the additional methyl groups to react making it stable enough to be sold commercially in its radical form. N-Hydroxypiperidine, however, does not have the four methyl groups to impede the way of a reacting molecule so the structure is unstable.
Diradicals are molecules containing two radical centers. Dioxygen (O2) is an important example of a stable diradical. Singlet oxygen, the lowest-energy non-radical state of dioxygen, is less stable than the diradical due to Hund's rule of maximum multiplicity. The relative stability of the oxygen diradical is primarily due to the spin-forbidden nature of the triplet-singlet transition required for it to grab electrons, i.e., "oxidize". The diradical state of oxygen also results in its paramagnetic character, which is demonstrated by its attraction to an external magnet. Diradicals can also occur in metal-oxo complexes, lending themselves for studies of spin forbidden reactions in transition metal chemistry. Carbenes in their triplet state can be viewed as diradicals centred on the same atom, while these are usually highly reactive persistent carbenes are known, with N-heterocyclic carbenes being the most common example.
Combustion consists of various radical chain reactions that the singlet radical can initiate. The flammability of a given material strongly depends on the concentration of radicals that must be obtained before initiation and propagation reactions dominate leading to combustion of the material. Once the combustible material has been consumed, termination reactions again dominate and the flame dies out. As indicated, promotion of propagation or termination reactions alters flammability. For example, because lead itself deactivates radicals in the gasoline-air mixture, tetraethyl lead was once commonly added to gasoline. This prevents the combustion from initiating in an uncontrolled manner or in unburnt residues (engine knocking) or premature ignition (preignition).
Many polymerization reactions are initiated by radicals. Polymerization involves an initial radical adding to non-radical (usually an alkene) to give new radicals. This process is the basis of the radical chain reaction. The art of polymerization entails the method by which the initiating radical is introduced. For example, methyl methacrylate (MMA) can be polymerized to produce Poly(methyl methacrylate) (PMMA - Plexiglas or Perspex) via a repeating series of radical addition steps: 2b1af7f3a8