Catalysts are increasingly finding application in fuel reformation leading to more reactive blends, micro-combustors and nano-catalysts aimed at improving application performance. In the current ...work, the interactions of surface and gas phase reactions in C
2H
6/O
2/N
2 mixtures over a supported platinum catalyst are reported. Experiments were combined with computations featuring comprehensive detailed chemistry for both phases in order to explore the dynamics of the conversion processes using high superficial gas velocities, extended Al
2O
3 foam monoliths up to 60
mm in length and with variable Pt loading of 1% and 3% by weight. The residence time was varied between 1 and 3
ms at different oxygen to carbon weight (0.5
<
O/C
<
0.8) ratios and a constant molar hydrogen to oxygen (H
2/O
2
=
2) ratio. The applied gas phase chemistry features a detailed C
1–C
2 mechanism including low-temperature chemistry. The heterogeneous chemistry is analysed using two independently developed detailed heterogeneous reaction mechanisms
1,2. The study confirms that the heterogeneous chemistry is essential in providing reaction stability and initially contributes to the formation of C
2H
4. It is also shown that increased residence times can result in a consistent heterogeneous consumption of ethylene principally leading to methane, carbon monoxide and carbon deposition. The surface chemistry is analysed in detail and it is shown that residence times can be used to mitigate C
2H
4 loss with the need to balance the stability of the process.
Gastrointestinal peptides, including insulin, glucagon and glucose-dependent insulinotropic polypeptide (GIP) have previously been reported in salivary glands. Recent evidence has suggested they ...might influence postprandial macronutrient metabolism. This study therefore investigated and compared postprandial hormone concentrations in saliva and plasma to determine whether their secretion was influenced by oral food stimuli. In a within-subject randomised cross-over comparison of hormone concentrations in plasma and saliva following a mixed meal, 12 subjects were given two 1708 kJ mixed meals. On one occasion the meal was chewed and swallowed (swallowed meal), on the other it was chewed and expectorated (sham-fed meal). Salivary and plasma levels of immunoreactive insulin, GIP and glucagon-like peptide-1 (GLP-1), total protein, alpha-amylase, glucose and non-esterified fatty acid were measured before and for 90 min following the meals. Saliva total protein and alpha-amylase rose following both meals, indicating that the stimulus for salivary protein release is related to the presence of food in the mouth. GLP-1 was not detected in saliva. Fasting salivary insulin levels were lower in saliva than plasma (28+/-6 vs 40+/-25 pmol/l respectively). Both increased following the swallowed meal but the rise in saliva was slower and less marked than in plasma (peak levels 96+/-18 and 270+/-66 pmol/l for saliva and plasma respectively, P<0.01). Both were unchanged following the sham-fed meal. GIP was detected in saliva. Fasting GIP levels were significantly higher in saliva than plasma (183+/-23 compared with 20+/-7 pmol/l, P<0.01). They decreased in saliva following both swallowed and sham-fed meals to nadirs of 117+/-17 and 71+/-12 pmol/l respectively, but rose following the swallowed meal to peak levels of 268+/-66 pmol/l. These findings are consistent with insulin in saliva being an ultrafiltrate of that circulating in blood, but GIP in saliva being the product of local salivary gland synthesis, whose secretion is influenced, directly or indirectly, by oral stimuli. The function of salivary GIP is unknown, but we speculate that it may play a role in the regulation of gastric acid secretion in the fasting state.
Introduction
We present the ocular features including full-field electroretinography (ff-ERG) and spectral domain optical coherence tomography (SD-OCT) in a 14-month-old infant with congenital ...disorder of glycosylation type 1a (PMM2-CDG).
Methods and results
An infant with failure to thrive, bilateral neurosensory hearing loss, cerebellar hypoplasia, and pericardial effusions was referred to ophthalmic genetics for evaluation. The patient had fix and follow vision, an intermittent esotropia, moderate myopia, a hypo pigmented macula, and mild attenuation of the retinal vasculature. Electroretinography showed severe reduction in both rod and cone-dependent responses with a negative waveform pattern. Handheld SD-OCT revealed severe attenuation of the outer retina throughout the macula, but with preservation of outer retinal structures in the fovea.
Conclusion
PMM2-CDG is a rare congenital disorder for which both ff-ERG and SD-OCT were useful in demonstrating early changes in retinal architecture and function.
Young Sepia officinalis (0-5 months) were studied in the laboratory and in the sea, and their appearance and behaviour compared with that of adult animals. Cuttlefish lay large eggs and the ...hatchlings are miniature replicas of the adults. From the moment of hatching they show body patterns as complex as those of adults and far more elaborate than those shown by most juvenile cephalopods. There are 13 body patterns: 6 of these are ‘chronic’ (lasting for minutes or hours) and 7 are ‘acute’ (lasting for seconds or minutes). The patterns are built up from no fewer than 34 chromatic, 6 textural, 8 postural and 6 locomotor components, used in varying combinations and intensities of expression. Nearly all these components occur in young animals: 26 of the chromatic, all the textural and locomotor, and 6 of the postural components. Nevertheless, patterning does change with age and we have recorded this and correlated the changes with behaviour. The components are built up from units, which themselves comprise four elements organized in precise relation to one another: chromatophores, iridophores, leucophores and skin muscles. The chromatophores are always especially important: they are muscular organs innervated directly from the brain and controlled ultimately by the highest centres (optic lobes). The areas in the Sepia brain that control patterning are already well developed at hatching, for the appearance of the skin is as much part of the brain’s motor program as is the attitude of the arms or fins, or the posture of the entire animal. The iridophores and leucophores develop later and are especially important constituents of many adult patterns, notably the Intense Zebra of the mature male. Experiments confirm that patterning is neurally controlled and apparently mediated exclusively by the visual system. Young cuttlefish use patterning primarily for concealment, utilizing such strategies as general colour resemblance, disruptive coloration, obliterative shading, shadow elimination, disguise and adaptive behaviour. Older animals also conceal themselves but increasingly use patterns for signalling, both interspecifically (warning or ‘deimatic’ displays) and intraspecifically (sexual signalling). Laboratory-reared cuttlefish were released in the sea and observed underwater. They quickly and effectively concealed themselves on the substrate; it was easy for the human observer to lose them and many passing fish behaved as if they were not there. One local predator, Serranus cabrilla, was observed to attack them and no fewer than 35 attacks were recorded, only six of which were successful. Laboratory-reared cuttlefish apparently distinguished between these predators and other, non-predatory, fish the first time they encountered them in nature.
In several species of cephalopod molluscs there is good evidence for the presence of L-glutamate in the central and peripheral nervous system and evidence for both classes of ionotropic receptor, ...AMPA/kainate and NMDA. The best evidence for glutamate being a transmitter in cephalopods comes from pharmacological, immunohistochemical and molecular investigations on the giant fibre system in the squid stellate ganglion. These studies confirm there are AMPA/kainate-like receptors on the third-order giant axon. In the (glial) Schwann cells associated with the giant axons both classes of glutamate receptor occur. Glutamate is an excitatory transmitter in the chromatophores and in certain somatic muscles and its action is mediated primarily via AMPA/kainate-like receptors, but at some chromatophores there are NMDA-like receptors. In the statocysts the afferent crista fibres are also glutamatergic, acting at non-NMDA receptors. In the brain (of Sepia) a neuronal NOS is activated by glutamate with subsequent production of nitric oxide and elevation of cGMP levels. This signal transduction pathway is blocked by D-AP-5, a specific antagonist of the NMDA receptor. Recently immunohistochemical analysis has demonstrated (in Sepia and Octopus) the presence of NMDAR2A /B – like receptors in motor centres, in the visual and olfactory systems and in the learning system. Physiological experiments have shown that glutamatergic transmission is involved in long term potentation (LTP) in the vertical lobe of Octopus, a brain area involved in learning. This effect seems to be mediated by non-NMDA receptors. Finally in the CNS of Sepia NMDA-mediated nitration of tyrosine residues of cytoskeletal protein such as α-tubulin, has been demonstrated.
It has been suggested that the anomalous abundances of Na, Mg and Al observed in globular cluster red giant stars could be the result of a thermally unstable hydrogen shell. Currently accepted ...reaction rates indicate that temperatures of approximately 70–75×106 K are required to produce the observed enhancements in Na and Al along with depletions in Mg. The work presented here attempts to model the H shell instability by a simple mechanism of altering the energy production in the region of the H shell. We show that even extreme cases only give rise to small intermittent temperature increases that have minimal effect on the surface abundances. Full evolutionary modelling incorporating this technique simply accelerates the evolution of the red giant branch (RGB) phase, producing the same surface abundances as other models but at an earlier time. We conclude that, unless hydrogen shell instabilities manifest themselves quite differently, they are unlikely to lead to the required temperatures and alternative explanations of the abundance anomalies are more promising.
The radular apparatus of cephalopods Messenger, J. B.; Young, J. Z.
Philosophical transactions - Royal Society. Biological sciences,
01/1999, Letnik:
354, Številka:
1380
Journal Article
Recenzirano
Odprti dostop
The radular ribbon, which bears many regularly arranged transverse rows of teeth one behind the other, lies in a radular canal
that emerges from the radular sac. Here the radular teeth are formed by ...a set of elongate cells with microvilli, the odontoblasts.
These are organized into two layers, the outer producing the radular membrane and the bases of the teeth, the inner producing
the cusps. The odontoblasts also secrete the hyaline shield and the teeth on the lateral buccal palps, when these are present.
At the front end of the radular ribbon the teeth become worn in feeding and are replaced from behind by new ones formed continuously
in the radular sac, so that the whole ribbon moves forward during ontogeny. Removal of the old teeth is achieved by cells
in the radular organs; these cells, which are formed from modified odontoblasts (‘odontoclasts’), dissolve the teeth and membranes
and absorb them. There is a subradular organ in all cephalopods. In, A characteristic feature of the cephalopod radular apparatus is the pair of large radular support muscles or ‘bolsters’. Their
function seems never to have been investigated, but experiments reported here show that when they elongate, the radular teeth
become erect at the bending plane and splayed, presumably enhancing their ability to rake food particles into the pharynx.
The bolsters of, The buccal mass of, Octopus vulgaris, there are many nerve fibres that may constitute a receptor organ signalling the movements of the radula against hard material.
Such nerves are absent from decapods and from octopods that do not bore holes., This paper describes the ontogeny, breakdown and absorption of the radular teeth of cephalopods and, for the first time, considers
the function of the ‘bolsters’ or radular support muscles., is massive, with heavily calcified tips to the beaks and a wide radular ribbon, with 13 rather than nine elements in each
row. Nevertheless all the usual coleoid features are present in the radular apparatus and the teeth are formed and broken
down in the same way. However,, which bores into mollusc shells and crustacean carapaces, it is especially well–developed and there is also a supraradular
organ., has a unique structure, the radular appendage. This comprises a papillate mass extending over the palate in the mid–line
and forming paired lateral masses that are in part secretory. The organ is attached to the front of the radula by muscles
and connective tissue. Its function is unknown., function as muscular hydrostats: because their volume is fixed, contraction of their powerful transverse muscles causes them
to elongate. In decapods and in nautiloids each bolster contains a ‘support rod’ of semi–fluid material, as well as massive
transverse musculature. This rod may elongate to erect the radular teeth. At the extreme front end of the bolsters in
Sporangial production of Phytophthora cinnamomi buried in gypsum-amended avocado soil for 2 days was reduced by as much as 74% in greenhouse trials. P. cinnamomi sporangial volume was reduced an ...average of 64% in gypsum-amended soil. Soil extracts from gypsum-amended soil reduced in vitro sporangial production and volume. Irrigation with gypsum solutions of buried mycelium in unamended soil also reduced sporangial production and volume. Zoospore production and colony-forming units of P. cinnamomi were reduced in soil amended with calcium sulfate, calcium nitrate, or calcium carbonate. Zoospore encystment or passive movement through soil was not significantly affected by gypsum soil amendments.
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