We review studies of the electromagnetic response of various classes of correlated electron materials including transition metal oxides, organic and molecular conductors, intermetallic compounds with $d$- and $f$-electrons as well as magnetic semiconductors. Optical inquiry into correlations in all these diverse systems is enabled by experimental access to the fundamental characteristics of an ensemble of electrons including their self-energy and kinetic energy. Steady-state spectroscopy carried out over a broad range of frequencies from microwaves to UV light and fast optics time-resolved techniques provide complimentary prospectives on correlations. Because the theoretical understanding of strong correlations is still evolving, the review is focused on the analysis of the universal trends that are emerging out of a large body of experimental data augmented where possible with insights from numerical studies.

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Electrodynamics of correlated electron materials

SUMMARY
Current views on membrane construction are presented as a basis for discussing certain modifications of structure that may render membranes leaky, allowing solutes to diffuse from them. Biophysical experiments on dehydrated membranes indicate that, when their water content is reduced below 20%, they no longer adopt the lipid bilayer conformation. When dry seeds, spores or lichens are placed in water, soluble cell constituents leak from them for a few seconds or minutes until membrane integrity is re-established; the same may apply also to the liberation of solutes from pollen grains. Moreover, there are indications that ‘dry’ in this context means having less than about 20% water.

Some plants are sensitive to chilling, their tissues becoming leaky when exposed to temperatures between 0 and 10°C. This chilling-induced leakage, attributed to a phase change in all the phospholipids of which the membrane is composed occurs at a slightly lower temperature than the change in the activation energy of membrane-bound enzymes.

At senescence, leaf tissues become leaky and may eventually dry out. So much phospholipid disappears from senescing cotyledons of cucumber that there is no longer sufficient to fabricate complete and intact membranes around the cells. Treating cucumber cotyledons with iodoacetate also causes a loss of phospholipids, allowing solutes to leak out of the cells.

It is possible that exposing seeds or mature plant tissues to oxygen at pressures of 1 or more atm renders them leaky because of lipid peroxidation.

Phospholipids and plant membrane permeability

CONTENTS PAGE INTRODUCTION I. . . . . 44 FUNGI . . . . . . . . . . . 144 Occurrence and quantitative variation . . . . . I44 Metabolism and physiological role . . . . . . 148 Uptake and utilization . . . . . . . 148 Polyols as natural substrates . . . . . .I49 Polyols as storage products . . . . . . I50 Polyols in spores and spore germination . . . . I51 Intermediary metabolism and enzymology . . . . I53 The role of polyols in storage of reducing power and coenzyme regulation . . . . . . . . . . 56 The control of polyol synthesis . . . . . .I57 ALGAE . . . . . . . . . . . I57 Occurrence and quantitative variation . . . . . 157 Phaeophyta . . . . . . . . . I59 Rhodophyta . . . . . . . . .I6I Chlorophyta . . . . . . . i6I Chrysophyta and Pyrrophyta . . . . . i6i Heterotrophic growth . . . . . . . . i6I Metabolism and physiological role . . . . . . i62 Phaeophyta . . . . . . . . . i62 Other phyla . . . . . . . . .I63 LICHENS . . . . . . . . . . . I64 Occurrence and quantitative variation . . . . . I64 Metabolism and physiological role . . . . . . i66 Accumulation of polyols during photosynthesis . . . i66 Uptake . . . . . . . . . . I67 Endogenous metabolism . . . . . . . I67 HIGHER PLANTS . . . . . . . . . i68 Occurrence and quantitative variation . .. . . I68 Metabolism and physiological role I. . . . . 70 Photosynthesis and translocation . . . . . . I70 Enzymology . . . . . . . . 171 Endogenous metabolism . . . . . . I73 Heterotrophic nutrition . . . . . . . I74 DISCUSSION . . . . . . . . . . 175 Occurrence and quantitative variation . . . . . 175 Carbohydrate storage . . . . . . . . 175 Translocation . . . . . . . . . 176 Osmo-regulation . . . . . . . . . I77 Enzymology and control of synthesis . . . . . 177 Coenzyme regulation and storage of reducing power . . I78 Conclusions . . . . . . . . . I78 ACKNOWLEDGMENTS I. . . . . 78 REFERENCES . . . . . . . . . . I79

Sugar alcohols (polyols) in fungi and green plants

The evidence presented by numerous investigations of the interface between lichens and their rock substrates strongly suggests that the weathering of minerals can be accelerated by the growth of at least some lichen species. The effects of lichens on their mineral substrates can be attributed to both physical and chemical processes. The physical effects are reflected by the mechanical disruption of rocks caused by hyphal penetration, expansion and contraction of lichen thallus, swelling action of the organic and inorganic salts originating from lichen activity. Lichens also have significant impact in the chemical weathering of rocks by the excretion of various organic acids, particularly oxalic acid, which can effectively dissolve minerals and chelate metallic cations. As a result of the weathering induced by lichens, many rock-forming minerals exhibit extensive surface corrosion. The precipitation of poorly ordered iron oxides and amorphous alumino-silica gels, the neoformation of crystalline metal oxalates and secondary clay minerals have been frequently identified in a variety of rocks colonized by lichens in nature. For a better understanding of the impacts of lichens on environments, further work on the comprehensive involvement of the lichen effects on weathering of natural rocks, deterioration of building stones and stonework, and formation of primitive soils should be carried out.

http://www.geo.mtu.edu/KeweenawGeoheritage/BlackLavas/Hunters_Point_files/ChenetalCatena.pdf

Weathering of rocks induced by lichen colonization — a review

The theory of endosymbiosis describes the origin of plastids from cyanobacterial-like prokaryotes living within eukaryotic host cells. The endosymbionts are much reduced, but morphological, biochemical, and molecular studies provide clear evidence of a prokaryotic ancestry for plastids. There appears to have been a single (primary) endosymbiosis that produced plastids with two bounding membranes, such as those in green algae, plants, red algae, and glaucophytes. A subsequent round of endosymbioses, in which red or green algae were engulfed and retained by eukaryotic hosts, transferred photosynthesis into other eukaryotic lineages. These endosymbiotic plastid acquisitions from eukaryotic algae are referred to as secondary endosymbioses, and the resulting plastids classically have three or four bounding membranes. Secondary endosymbioses have been a potent factor in eukaryotic evolution, producing much of the modern diversity of life.

Primary and secondary endosymbiosis and the origin of plastids

Evidence for Two-Component High-Temperature Superconductivity in the Femtosecond Optical Response of YBa 2 Cu 3 O 7-δ

111. Respiration ’ 545 ( I ) Rate of respiration . . . . . . . . . . . . 545 (2) Respiration rate and water content . . . . . . . . ’ 545 (3) Effects of other environmental factors on respiration rate . . . . . 546 (4) Respiratory substrates and respiratory quotients . . . . . . . 546 IV. Photosynthesis . . . . . . . . . . . . . . 547 ( I ) Rate of photosynthesis and net assimilation . . . . . . . ’ 547 (2) Photosynthetic rate and water content . . . . . . . . . 548 . . . 548 (4) Products of photosynthesis . . . . . . . . . . ’ 549 V. Nutrition and metabolism . . . . . . . . . . . . 549 ( I ) General features of nutrient accumulation . . . . . . . . 549 (2) Nitrogen . . . . . . . . . . . . . . 550 (3) Carbon . . . . . . . . . . . . . . 550 (4) Inorganic elements and the action of lichens on their substrata 552 VI. ‘Lichen substances’ . . . . . . . . . . . . ’ 553 ( I ) Introduction . . . . . . . . . . . . . 5 5 3 (2) Biosynthesis . . . . . . . . . . . . . 554 (3) Physiological roles and antibiotic properties . . . . . . . 555 (4) Use in taxonomy . . . . . . . . . . . . 556 VII. Growth rates, longevity and reproduction . . . . . . . . . 557 (I) Growth rates . . . . . . . . . . . . . 557 (2) Longevity . . . . . . . . . . . . . . 558 (3) Reproduction . . . . . . . . . . . . ’ 559 VIII. Resistance to environmental conditions . . . . . . . . . . 560 ( I ) Drought . . . . . . . . . . . . . . 560 (2) Temperature . . . . . . . . . . . . . 561 (3) Other factors . . . . . . . . . . . . . 562

The biology of lichen thalli

Carbohydrate movement from alga to fungus has been compared in the British species of Lobaria. The algal component of these lichens is either Nostoc or Trebouxia, and the pattern of carbohydrate transfer to the fungus depends on which of these algae is present.

Carbohydrate movement between the symbionts of lichens.

SYMBIOTIC chloroplasts have been reported in several sacoglossan opisthobranch gastropods1–4. The chloroplasts are acquired while the animals feed suctorially on the cells of certain siphonaceous algae and they eventually become located inside the cells of the tubules of the digestive diverticulum.

Synthesis of pigment in symbiotic chloroplasts.

We present measurements of the dynamics of the electronic excitations of BSCCO-2212 measured with 150fs resolution using ultrafast time-resolved spectroscopy. The dynamics is clearly different in the normal, pseudogap and superconducting states, and from that measured in YBa
 2
 Cu
 3
 O
 7−δ
 .

D.C. Smith

Papers

Evidence for Two-Component High-Temperature Superconductivity in the Femtosecond Optical Response of YBa 2 Cu 3 O 7-δ

The biology of lichen thalli

Carbohydrate movement between the symbionts of lichens.

Synthesis of pigment in symbiotic chloroplasts.

Femtosecond Dynamics of BSCCO-2212