It is perhaps a matter of taste, but I find analytical solutions, as opposed to numerical ones, more enlightening. Unfortunately, the complexity of photosynthesis means that analytical descriptions can only be achieved at the expense of gross simplification . . . [these models] can be useful aids to understanding, and for prediction, but are also potential hazards when the simplifications involved are forgotten.Graham Farquhar (1989)
Modern engineering design against fracture in “safety -critical” structures generally is based on the concept of defect- or damage-tolerance, where projected life is estimated in terms of the time for an assumed initial defect to propagate to some critical size. Accordingly, from a materials standpoint, increased resistance to failure can be achieved by retarding the sub-critical growth of cracks prior to final failure. In the current paper, an overview is presented of several recent advances in the understanding of the salient mechanisms of such slow crack growth, involving fracture under both monotonie and cyclic loading at ambient and elevated temperatures.
The complexes [BP3R]MX ([BP3R] = PhB(CH2PR2)3–, R = Ph, iPr; M = Ni, Co, Fe; X = halide) were explored as platforms for generation of first-row metal silylene complexes. Direct silylation of [BP3Ph]NiCl or [BP3iPr]CoCl with (THF)2LiSiHMes2 resulted in formation of the silylene complexes [BP3Ph]Ni(μ-H)(SiMes2) and [BP3iPr]Co(μ-H)(SiMes2), respectively. In contrast, [BP3iPr]FeBr reacted with (THF)2LiSiHMes2 to produce the iron-alkyl [BP3iPr]Fe(CH2-2-(SiH2Mes)-3,5-Me2C6H2), a constitutional isomer of the expected silyl or silylene complex. Preparation of the nickel benzyl complex [BP3Ph]Ni(η2-Bn) allowed for exploration of addition–elimination chemistry for access to silylene complexes from simple primary and secondary silanes. Heating toluene solutions of [BP3Ph]Ni(η2-Bn) in the presence of CySiH3 resulted in the formation of a dimeric μ-silylene complex [Ni(μ-BP2Ph)(μ-SiHCy)]2. In the presence of 4-dimethylaminopyridine (DMAP), these conditions led to exclusive formation of the base-stabilized silylene complex [BP3Ph]Ni(μ-H)[SiHCy(DMAP)].
Dehydrochlorination of Cp*Ru(IPr)Cl leads to an unusual C–C bond activation, yielding a cyclometalated Ru complex bearing an NHC-C(sp<sup>2</sup>) ligand. Reactivity studies of cyclometalated Ru complexes were explored.
Fusion constructs as protein overexpression vectors proved to be critical in the heterologous expression of terpene synthases in cyanobacteria. The concept was recently applied to the heterologous overexpression of the β-phellandrene synthase (β- PHLS) from plants, fused to the highly expressed endogenous cpcB gene encoding the β-subunit of phycocyanin. Overexpressed CpcB*PHLS fusion proteins enhanced the heterologous yield of C<sub>10</sub>H<sub>16</sub> β-phellandrene hydrocarbons production in Synechocystis. This work extended the concept of fusion constructs as protein overexpression vectors by showing that highly expressed heterologous genes could also serve as leader sequences for protein overexpression in cyanobacteria. Examined are the kanamycin nptI and chloramphenicol cmR resistance cassettes, both of which are overexpressed in Synechocystis. Evidence showed a dual purpose of the nptI gene, as a leader sequence fused to a heterologous geranyl-diphosphate synthase ( GPPS), promoting its expression, while at the same time serving as a selectable marker for the screening of transformants. The work further showed that enhanced GPPS expression increased the yield of β-phellandrene in Synechocystis transformants harboring the β- PHLS gene. Moreover, the research evaluated the expression efficacy of a DNA fragment comprising 87 nucleotides from the 5' end of the cmR gene in fusion with the GPPS gene. This short fusion construct substantially increased the intracellular geranyl-diphosphate synthase level, suggesting that "short-stretch" cmR leader sequences can be used to drive a higher expression level of heterologous biosynthetic genes, while avoiding undesirable internal recombinations, as these sequences are shorter than the threshold of 200 bp, commonly assumed to be the threshold of high efficiency recombinations.
The phenomenological theory of elastic—plastic response is reconsidered in the light of recent opinion regarding the constitutive character of the constituent elastic and plastic deformations. The primary role of dissipation in the physics of plastic evolution is emphasized and shown to lead to the clarification of a number of open questions. Particular attention is given to the invariance properties of the elastic and plastic deformations, to the kinematics of discontinuities, and to the role of material symmetry in restricting constitutive equations for elastic response, yield and plastic evolution.
Salmonids frequently adapt their feeding and movement strategies to cope with seasonally fluctuating stream environments. Oncorhynchus mykiss tend to drift-forage in higher velocity habitat than other salmonids, yet their presence in streams with seasonally low velocity and drift suggests behavioral flexibility. We combined 3D videogrammetry with measurements of invertebrate drift and stream hydraulics to investigate the drivers of O. mykiss foraging mode and movement during the seasonal recession in a California stream. From May to July (2016), foraging movement rate increased as prey concentration and velocity declined; however, movement decreased in August as pools became low and still. In May, 80% of O. mykiss were drift-foraging, while by July, over 70% used search or benthic-foraging modes. Velocity and riffle crest depth were significant predictors of foraging mode, while drift concentration was a poor univariate predictor. However, top-ranked additive models included both hydraulic variables and drift concentration. A drift-foraging bioenergetic model was a poor predictor of foraging mode. We suggest that infall and benthic prey, as well as risk aversion, may influence late-summer foraging decisions.
