Synthesis of Dibenzoheteropines of Group 13–16 Elements via Ring-Closing Metathesis

The ring-closing metathesis (RCM) of bis­(2-vinylphenyl)­silanes in the presence of the second-generation Hoveyda–Grubbs catalyst in toluene at 100 °C afforded dibenzo­[<i>b</i>,<i>f</i>]­silepines in excellent yields. Other dibenzoheteropines of group 13–16 elements were also prepared via the RCM of the corresponding heteroatom-tethered dienes

Faster Sorption of Propylene Compared to Propane Using an Elastic Layer-Structured Metal–Organic Framework (ELM-11)

The separation of propane and propylene is the most energy-consuming and difficult separation process in the petrochemical industry because of their extremely similar physical properties. Separating propylene from propane using sorption can considerably reduce the energy consumed by current cryogenic distillation techniques. However, sorption involves several major challenges. An elastic layer-structured metal–organic framework (ELM-11) exhibited a highly efficient propane/propylene sorption separation, owing to its kinetic properties. Under equilibrium conditions, propane and propylene exhibited similar sorption capacities, gate opening pressures, and heats of sorption. Thus, their separation under equilibrium conditions is impractical. However, the sorption rates of the two gases were considerably different, showing different diffusion coefficients, resulting in a high kinetic selectivity (214 at 298 K) of propylene over propane on ELM-11. This kinetic selectivity is considerably higher than those obtained in previous studies. Thus, ELM-11 is a promising sorbent for separation technologies

Fully expanded auxospore in <i>Actinocyclus</i>. A

<p>, E–J, LM. B–E. SEM. <b>A</b>. A spherical auxospore expanded between the hypotheca (top) and epitheca of the oogonium, with peripheral chloroplasts and a nucleus. <b>B</b>. Fully expanded auxospore covered by numerous scales. <b>C</b>. Enlargement of scales, each with a hyaline centre and fimbriate margin (cf. Fig. 9A). <b>D</b>. Broken auxospore wall showing overlap of scales differing in size. <b>E</b>. Initial cell in valve view, still enclosed within the auxospore and containing many stellate chloroplasts and a nucleus near its centre. <b>F</b>. Girdle view of a fully formed initial cell enclosed within the auxospore, showing the ± spherical auxospore wall and the rugby ball–like profile of the initial cell, formed as a result of two lateral contractions of the protoplast. <b>G</b>, <b>H</b>. DAPI-stained auxospore with initial epivalve, showing a nucleus (arrow) and a pyknotic nucleus (arrowhead in Fig. 9G). <b>I</b>. <b>J</b>. DAPI-stained auxospore with both initial epivalve and initial hypovalve, showing a nucleus (arrow) and two pyknotic nuclei (arrowheads in Fig. 9I). the slightly smaller pyknotic nucleus (top) derived from the acytokinetic mitosis preceding formation of the epivalve, the other from the equivalent mitosis preceding formation of the hypovalve. Scale bars = 20 µm. except C, D (2 µm).</p

Repeated evolution of uniparental reproduction in <i>Sellaphora</i> (Bacillariophyceae)

<div><p>Diatoms possess a remarkable life cycle in which cell size decreases slowly during vegetative cell division and then increases rapidly via special expanding cells called ‘auxospores’, which are usually formed as a result of biparental sexual reproduction. However, auxospores are sometimes produced by single unpaired cells, i.e. uniparentally. We examined the nature of uniparental auxosporulation in <i>Sellaphora</i> and used a two-gene dataset to study phylogenetic relationships between uniparental and biparental <i>Sellaphora</i> demes and species; we tested whether uniparental reproduction has evolved once or repeatedly in the genus. In at least two of the uniparental demes auxosporulation occurred through autogamy (i.e. intra-tetrad mating within an undivided cell). Maximum likelihood phylogenies indicated four lineages of uniparental <i>Sellaphora</i> and significance tests of alternative topologies, in which combinations of uniparental <i>Sellaphora</i> were constrained to be monophyletic, coupled with likelihood reconstruction of ancestral character states, led to rejection of the hypothesis that uniparental auxosporulation evolved only once in the genus. Uniparentally reproducing lineages appear to arise not infrequently in diatoms but do not persist. Two small extranuclear bodies, apparently containing DNA and lying outside the chloroplast (one close to each pole of the cell), were revealed by DAPI staining.</p></div

Spermatocyte after meiosis II in <i>Actinocyclus</i>.

<p>A, B, E–G, LM. Figs. C, D, H–K, SEM. A–D. <b>A</b>. Cell with four projections (arrows), each bearing a single flagellum. <b>B</b>. DAPI-stained cell with four separated nuclei. <b>C</b>. Cell with four flagella extending from four projections (arrows). <b>D</b>. Enlargement of a projection with a flagellum with mastigonemes. Note narrower posterior end. <b>E</b>. Final stage of spermatogenesis: sperms separating from the cell (e.g. at arrow). <b>F</b>. Sperm with almost fully elongated flagellum being pinched off from the cell. <b>G</b>. Enlargement of F. <b>H</b>. Four separated sperms (arrows) and a large residual body in a spermatogonium. <b>I</b>. DAPI-stained cell at a similar stage to H, with four sperms in a spermatogonium. <b>J</b>. Spermatogonium with a residual body and uniflagellate sperms (arrowheads) and an apparently fragmentary lid valve around the margin (arrows). <b>K</b>. A spermatogonium with a partly detached lid valve and sperm inside (arrow). All scale bars = 10 µm except Figs. D (2 µm) and G (5 µm).</p

Early stage oogonial structure in <i>Actinocyclus</i>.

<p>A, B, LM. E–F, TEM. <b>A</b>. Peripheral focus of a fully elongated oogonium containing a single nucleus with a nucleolus (arrow), located just beneath the girdle. Scale bar = 10 µm. <b>B</b>. A young oogonium before thin sectioning: note the unequal epi- and hypothecae. Scale bar = 10 µm. <b>C</b>. The same oogonium as in Fig. 5B after thin sectioning. The cell is still fully enclosed by the hypotheca and epitheca. Note a thin layer of scales (appearing as a black line) surrounding the cytoplasm, several scales being formed beneath the cell membrane (circles), and a small discontinuity in the scale layer (arrow). Within the vacuole are several bodies containing ‘frothy’ electron-dense material (double arrows), as well as smaller grey bodies that probably represent lipid. Scale bar = 10 µm. <b>D</b>. Enlargement of <b>C</b> showing a pear-shaped nucleus (with a single nucleolus) elongated towards a centrosome (arrowhead) and overlying split in the scale case (white arrow). Scale bar = 2 µm. <b>E</b>. Detail of the centrosome located at the tip of the nucleus and subtending many radiating microtubules. Scale bar = 1 µm. <b>F</b>. A peripheral part of the cell showing Golgi bodies associated with chloroplasts; note also the mitochondria and a vesicle (arrow) containing a scale beneath the cell membrane. Scale bar = 1 µm.</p

A combined morphological and molecular approach to <i>Nitzschia varelae</i> sp. nov., with discussion of symmetry in Bacillariaceae

<p>A previously unknown member of the Bacillariaceae was discovered almost simultaneously in four different brackish coastal wetlands on the Atlantic and Mediterranean coasts of the Iberian Peninsula. It appears to tolerate a wide range of salinities but was never common in samples where it occurred. The frustules were consistently hantzschioid (i.e. with the raphe systems always on the same side of the frustule) and the valve outline was asymmetrical about the apical plane, two features that have until recently been considered characteristic of <i>Hantzschia</i>. Molecular phylogenies based on <i>rbc</i>L and LSU rDNA indicated, however, that the new species does not belong in <i>Hantzschia</i> but among the several disparate lineages that comprise the paraphyletic genus <i>Nitzschia</i>. This finding, coupled with the recent discovery of other diatoms with constant hantzschioid symmetry but with a morphology very similar to the type species of <i>Nitzschia</i>, is discussed in relation to the status and characterization of <i>Hantzschia</i> as an independent genus. It is concluded that, while a core of hantzschioid species may exist that can be classified together, corresponding to the traditional understanding of the genus <i>Hantzschia</i>, there is no single morphological feature common to all of them that can be used to diagnose the group and differentiate it from the various hantzschioid lineages that are separate from true <i>Hantzschia</i> and currently placed in e.g. <i>Nitzschia</i> or <i>Cymbellonitzschia</i>. Testing whether a hantzschioid species does or does not belong to <i>Hantzschia</i> will in many cases require molecular evidence. Although the new coastal species does not belong to the same lineage as the type species of <i>Nitzschia, N. sigmoidea</i>, it is described for the moment as <i>N. varelae</i> Carballeira, D.G. Mann & Trobajo, <i>sp. nov</i>., until there is a better understanding of generic limits in the Bacillariaceae following a wider molecular and morphological survey of that family.</p

Sperm morphology and flagellar fine-structure in <i>Actinocyclus</i>.

<p>A, B, J, LM. C–I, SEM. <b>A, B</b>. Phase contrast and DAPI images of a sperm showing long anterior uniflagellate and an elongate nucleus occupying most of the sperm ‘body’. Scale bars = 10 µm. <b>C</b>. Two sperm: both are elongate but one is more pointed than the other. Note that one sperm bears a swelling near the tip of the flagellum. Scale bar = 10 µm. <b>D, E</b>. Enlargement of the sperm shown in Fig. 29. Scale bars = 2 µm. <b>F</b>. Enlargement of the swollen portion of one flagellum shown in Fig. 4C: note also the line of mastigonemes (pointing towards the viewer). Scale bar = 1 µm. <b>G</b>. Detail of mastigonemes. Scale bar = 1 µm. <b>H</b>. Detail of mastigonemes lined in a row at both sides of the flagellum. Scale bar = 1 µm. <b>I</b>. Detail of mastigonemes, showing that their tips (arrows) appear branched, because they bear terminal filaments (arrows). Scale bar = 1 µm. <b>J</b>. Many sperms crowding around a broken egg (center). Scale bar = 50 µm.</p

Spermatocyte after meiosis I in <i>Actinocyclus</i>.

<p>A, B, E, F, LM. Figs. C, D, G, H, SEM. A–D. <b>A</b>. Cell with paired flagella (arrows) associated with each nucleus. <b>B</b>. DAPI-stained cell with two separated nuclei. <b>C</b>. Spermatocyte with peripheral vesicles and elongating paired flagella on each side, which have reached about 1/3 of their final length. <b>D</b>. Enlargement of basal area of the paired flagella with mastigonemes. <b>E–H</b>. Spermatocyte during meiosis II. <b>E</b>. Cell undergoing nuclear division with separated flagella (arrows). <b>F</b>. DAPI-stained cell showing dividing nuclei (the median vertical line in the left-hand nucleus marks the position of the spindle). <b>G</b>. Cell with separated flagella on either side of two flat projections where the nuclei are located. <b>H</b>. Enlargement of a flat projection, with flagella extending out on either side. Scale bars = 10 µm except D (1 µm) and H (5 µm).</p

Young auxospore in <i>Actinocyclus</i>.

<p>A, C, LM. B, E–G, TEM. D, SEM. <b>A</b>. A young, partly expanded auxospore, still associated with the oogonium hypotheca and epitheca. Scale bar = 20 µm. <b>B</b>. A thin section of the auxospore illustrated in <b>A</b>, showing organelles arranged peripherally and a large central vacuole. Scale bar = 10 µm. <b>C</b>. A young auxospore showing peripheral chloroplasts and a single nucleus (arrow). Scale bar = 20 µm. <b>D</b>. A young auxospore completely covered by a layer of scales. Scale bar = 20 µm. <b>E</b>. Another thin section of the auxospore shown in Fig. 8A, passing through the centre of nucleus. Note that the nucleus is bigger than that of oogonium. Scale bar = 10 µm. <b>F</b>. Close association of a mitochondrion and a Golgi body producing vesicles with electron-dense contents. Scale bar = 1 µm. <b>G</b>. Scales with a central annulus and branching radial ribs. Scale bar = 1 µm.</p