To assess the early topographic changes after acute transmural myocardial infarction, we studied 28 patients during the first two weeks after infarction by serial two-dimensional echocardiography. Regional end-diastolic segment lengths and wall thicknesses for anterior and posterior left ventricular walls were calculated. Eight patients showed infarct expansion, with disproportionate dilatation and transmural thinning in the infarcted zone, that was significantly different (P less than 0.005) from changes in non-infarcted regions. This regional expansion led to an overall left ventricular dilatation in these eight patients of 25 per cent compared to 5 per cent in the 20 patients without infarct expansion. Although the eight patients with regional expansion did not have significantly higher peak creatine kinase or Killip classification, they had a significantly greater eight-week mortality (four of eight versus none of 20, P less than 0.004). Thus, regional cardiac dilatation may be an early, lethal consequence of transmural infarcts, and appears to be an important mechanism of acute cardiac dilatation after myocardial infarction.

Polymeric materials comprised of all-carbon backbones are ubiquitous to modern society due to their low cost, impressive robustness, and unparalleled physical properties. It is well-known that these materials often persist long beyond their intended usage lifetime, resulting in environmental accumulation of plastic waste. A substantial barrier to the breakdown of these polymers is the relative chemical inertness of carbon–carbon bonds within their backbone. Herein, we describe a photocatalytic strategy for cleaving carbon-based polymer backbones. Inclusion of a low mole percent of a redox-active comonomer allows for a dramatic reduction in polymer molecular weight upon exposure to light. The N-(acyloxy)­phthalimide comonomer, upon reception of an electron from a single-electron transfer (SET) donor, undergoes decarboxylation to yield a backbone-centered radical. Depending on the nature of this backbone radical, as well as the substitution on neighboring monomer repeat units, a β-scission pathway is thermodynamically favored, resulting in backbone cleavage. In this way, polymers with an all-carbon backbone may be degraded at ambient temperature under metal-free conditions.

We report a photomediated disulfide cross-linking strategy for the generation of adaptable hydrogels from telechelic network precursors containing strained cyclic disulfides. Exploiting the intricate stereoelectronic properties of 1,2-dithiolanes arising from the unfavorable four-electron interaction in the disulfide scaffold, amphiphilic poly(ethylene glycol)-1,2-dithiolane conjugates formed free-standing adaptable hydrogels at 10 wt % polymer content upon disulfide photolysis under UV irradiation (λ max = 365 nm). Cross-linking was achieved in less than 10 min with tunable network moduli depending on irradiation time. Investigations into the gelation mechanism suggest the formation of free thiols during light exposure accounting for the dynamic nature of the gels. Furthermore, we successfully expanded this gelation strategy to green light (λ max = 515 nm) by employing the photosensitizer eosin Y, allowing for hydrogel formation open to air.

No abstract

Fluorescent spectroscopy is a convenient method for monitoring the progression of polymerization-induced self-assembly (PISA).