Light-driven vectorial proton translocation is basic to the mechanism of energy transduction by photosynthetic systems. Bacteriorhodopsin (bR)1 is the simplest known light-driven proton pump and has long served as a model system for understanding how protons may be transported "up hill" against a transmembrane proton motive potential. bR contains seven transmembrane ␣-helices that surround a proton translocation channel lined with strategically placed charged residues (3). Depending upon their protonation states, which change in a well orchestrated cascade as a proton is transported across the cell membrane, these charged residues can serve as either proton donors or proton acceptors. Light activation of the chromophore, an all-trans-retinal molecule covalently attached to Lys-216 in helix G via a protonated Schiff base (the primary proton donor) results in the 13-cis-retinal configuration with two-thirds quantum efficiency. Steric conflicts and mechanical stress resulting from photoisomerization initiate a sequence of conformational changes that can be characterized spectroscopically and that perturb the local environment of several key residues, strongly affecting their pK a values and creating transient pathways for proton transfer.The specific spectral intermediates of the bR photocycle have been well characterized, and a common reaction scheme is: bR 570 3 K 590 7 L 550 7 M 412 7 N 560 7 O 640 3 bR 570 (sub-

Over the last four decades, numerous reports have appeared on the physico‐chemical kinetics, especially crystallization kinetics, based on the Avrami equation, ϕ = exp [−Ktn] where ϕ is the fraction of material unchanged at time t, K is an overall rate constant and “n” is the Avrami exponent indicative of process mechanism. The usage of the Avrami equation has been limited to the determination of “n” and its temperature dependence. It is shown that the evaluation of K and the activation energy (E) using this equation is erroneous since K and E are both influenced by “n” although such would be unexpected from the Avrami equation. On the other hand, if one uses a modified expression, ϕ = exp[−Kt]n, then in addition to the value of “n”, correct values of K and E are obtained. This retains the original correspondence of the Avrami equation to nuclea‐tion and crystal growth processes but extends its applicability to (i) correctly evaluate K and E parameters, and (ii) correctly compare transformation rates when the systems differ in their n values. Experimental data are presented to support these conclusions.

The automotive industry is under increasing pressure to: (1) reduce the weight of vehicles and (2) improve crash performance. ‘Hot stamped’ mild carbon–manganese–boron steel 22MnB5 has become common place in the body structure of the European vehicle over the past decade. The ultrahigh strength martensitic microstructure resulting from hot stamping (proof strength ∼1200 MPa and ultimate tensile strength ∼1500 MPa) enables down gauging while not compromising crash performance. However, with demands for yet higher strength in the final component so to enable further down gauging, novel grades must be developed. In this paper, development of the novel grade 38MnB5 was reported. Following hot stamping, 38MnB5 demonstrated proof strength in excess of 1400 MPa and ultimate tensile strength in excess of 2000 MPa. Owing to the immense strength, the novel grade 38MnB5 was considered to offer significant down gauging and weight reduction opportunities to the automotive industry.

Originating from the early 1970s in Luleå, Sweden, and initially designed for the agricultural industry, hot-stamped sheet steel has developed to become the leading material in a modern state-of-the-art lightweight structural automotive body engineering. This critical review provides a detailed insight into the origins, fundamental metallurgical principles, commercial growth, current legal stronghold on aluminising coatings and latest technological developments. Comparisons to other state-of–the-art ferrous and non-ferrous automotive sheet materials are made, including carbon fibre-reinforced polymer; while the future outlook for hot-stamped sheet steel and opportunities for further technological developments are highlighted.

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