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Cellulose is the most abundant biopolymer on earth, and has qualities that make it suitable for biofuel. There are new tools for the visualisation of the cellulose synthase complexes in living cells, but those do not show their product, the cellulose microfibrils (CMFs). In this study we report the characteristics of cell wall textures, i.e. the architectures of the CMFs in the wall, of root hairs of Arabidopsis thaliana, Medicago truncatula and Vicia sativa and compare the different techniques we used to study them. Root hairs of these species have a random primary cell wall deposited at the root hair tip, which covers the outside of the growing and fully grown hair. The secondary wall starts between 10 ( Arabidopsis) and 40 ( Vicia) μm from the hair tip and the CMFs make a small angle, Z as well as S direction, with the long axis of the root hair. CMFs are 3-4 nm wide in thin sections, indicating that single cellulose synthase complexes make them. Thin sections after extraction of cell wall matrix, leaving only the CMFs, reveal the type of wall texture and the orientation and width of CMFs, but CMF density within a lamella cannot be quantified, and CMF length is always underestimated by this technique. Field emission scanning electron microscopy and surface preparations for transmission electron microscopy reveal the type of wall texture and the orientation of individual CMFs. Only when the orientation of CMFs in subsequent deposited lamellae is different, their density per lamella can be determined. It is impossible to measure CMF length with any of the EM techniques. [ABSTRACT FROM AUTHOR]

Results are presented of a deep optical survey of the Ursa Major cluster, a spiral-rich cluster of galaxies at a distance of 18.6 Mpc which contains about 30 per cent of the light but only 5 per cent of the mass of the nearby Virgo cluster. Fields around known cluster members and a pattern of blind fields along the major and minor axes of the cluster were studied with mosaic CCD cameras on the Canada–France–Hawaii Telescope. The dynamical crossing time for the Ursa Major cluster is only slightly less than a Hubble time. Most galaxies in the local Universe exist in similar moderate-density environments. The Ursa Major cluster is therefore a good place to study the statistical properties of dwarf galaxies, since this structure is at an evolutionary stage representative of typical environments, yet has enough galaxies that reasonable counting statistics can be accumulated. The main observational results of our survey are as follows. (i) The galaxy luminosity function is flat, with a logarithmic slope α=-1.1 for -17R<-11 from a power-law fit. The error in α is likely to be less than 0.2 and is dominated by systematic errors, primarily associated with uncertainties in assigning membership to specific galaxies. This faint-end slope is quite different from what was seen in the Virgo cluster, where α=-2.26±0.14. (ii) Dwarf galaxies are as frequently found to be blue dwarf irregulars as red dwarf spheroidals in the blind cluster fields. The density of red dwarfs is significantly higher in the fields around luminous members than in the blind fields. The most important result is the failure to detect many dwarfs. If the steep luminosity function claimed for the Virgo cluster were valid for Ursa Major, then in our blind fields we should have found ∼103 galaxies with -17R<-11 whereas we have found two dozen. There is a clear deficiency of dwarfs compared with the expectations of hierarchical clustering theory. It is speculated that the critical difference between the Virgo and Ursa Major clusters is the very different dynamical collapse times, which probably straddle the time-scale for reionization of the Universe. Dwarf galaxies in the proto-Virgo environment probably formed before the epoch of reionization. The equivalent dwarf haloes in the proto-Ursa Major environment probably formed only after the epoch of reionization, when the conditions for star formation were inhospitable. [ABSTRACT FROM AUTHOR]

Reports the emission of neutral atomic hydrogen from the galaxy cluster Abell 2218. Use of Westerbrook Synthesis Radio Telescope; Efficiency of the mechanism removing neutral gas from cluster galaxies; Evolution of stellar populations.