Invariance Violation Extends the Cosmic Ray Horizon ?

We postulate in the present paper that the energy-momentum relation is modified for very high energy particles to violate Lorentz invariance and the speed of photon is changed from the light velocity c. The violation effect is amplified, in a sensitive way to detection, through the modified kinematical constraints on the conservation of energy and momentum, in the absorption process of gamma-rays colliding against photons of longer wavelengths and converting into an electron-positron pair. For gamma-rays of energies higher than 10 TeV, the minimum energy of the soft photons for the reaction and then the absorption mean free path of gamma-rays are altered by orders of magnitude from the ones conventionally estimated. Consideration is similarly applied to high energy cosmic ray protons. The consequences may require the standard assumptions on the maximum distance that very high energy radiation can travel from to be revised.Comment: 14 pages, 1 figure, to be published in Ap J Letter

Investigating the Relationship between Topology and Evolution in a Dynamic Nematode Odor Genetic Network

The relationship between biological network architectures and evolution is unclear. Within the phylum nematoda olfaction represents a critical survival tool. For nematodes, olfaction contributes to multiple processes including the finding of food, hosts, and reproductive partners, making developmental decisions, and evading predators. Here we examine a dynamic nematode odor genetic network to investigate how divergence, diversity, and contribution are shaped by network topology. Our findings describe connectivity frameworks and characteristics that correlate with molecular evolution and contribution across the olfactory network. Our data helps guide the development of a robust evolutionary description of the nematode odor network that may eventually aid in the prediction of interactive and functional qualities of novel nodes

A comparative study of the molecular evolution of signalling pathway members across olfactory, gustatory and photosensory modalities

All sensory modalities serve a similar objective, which is to decode input by making predictions in time and space about an animal’s surroundings. The evolution of sensory modalities is driven by the need to shape effective behavioural outputs, and in turn increase survival. Throughout evolution, sensory systems have undergone a great deal of specialization; and even though some modalities are derived from unique origins within different phyla, they still exhibit many common design features (Strausfeld and Hildebrand 1999; Eisthen 2002; Jacobs et al. 2007). We now have detailed mechanistic data on how sensory systems operate within specific animals (Buck and Axel 1991; Chalasani et al. 2007; Sato et al. 2008; Wicher et al. 2008), however it is still not clear how sensory signalling pathways evolve at the molecular level, and whether these evolutionary mechanisms are shared between diverse taxa. Here we set out to investigate the molecular evolution of signalling pathway members across olfactory, gustatory, and photosensory modalities from very divergent phyla in an attempt to develop a model of molecular evolution for sensory systems. From our pairwise intraphylum analysis we found that sensory signalling pathways unusually undergo high levels of functional constraint that are higher than genomewide global levels of constraint, and this purifying selection is common within the very divergent taxa we examined. We also find that gene duplication events represent a conserved but heterogeneous driver of evolution within sensory signalling pathways. Taken together, we propose a ‘sessile’ mechanism of sensory signalling pathway evolution, which on one side facilitates bursts of gene duplication and relaxed selection and on the other side it is unusually anchored by high levels of selective constraint that preserves core sensory function

A comparative study of the molecular evolution of signalling pathway members across olfactory, gustatory and photosensory modalities

All sensory modalities serve a similar objective, which is to decode input by making predictions in time and space about an animal’s surroundings. The evolution of sensory modalities is driven by the need to shape effective behavioural outputs, and in turn increase survival. Throughout evolution, sensory systems have undergone a great deal of specialization; and even though some modalities are derived from unique origins within different phyla, they still exhibit many common design features (Strausfeld and Hildebrand 1999; Eisthen 2002; Jacobs et al. 2007). We now have detailed mechanistic data on how sensory systems operate within specific animals (Buck and Axel 1991; Chalasani et al. 2007; Sato et al. 2008; Wicher et al. 2008), however it is still not clear how sensory signalling pathways evolve at the molecular level, and whether these evolutionary mechanisms are shared between diverse taxa. Here we set out to investigate the molecular evolution of signalling pathway members across olfactory, gustatory, and photosensory modalities from very divergent phyla in an attempt to develop a model of molecular evolution for sensory systems. From our pairwise intraphylum analysis we found that sensory signalling pathways unusually undergo high levels of functional constraint that are higher than genomewide global levels of constraint, and this purifying selection is common within the very divergent taxa we examined. We also find that gene duplication events represent a conserved but heterogeneous driver of evolution within sensory signalling pathways. Taken together, we propose a ‘sessile’ mechanism of sensory signalling pathway evolution, which on one side facilitates bursts of gene duplication and relaxed selection and on the other side it is unusually anchored by high levels of selective constraint that preserves core sensory function

Multiple lineage specific expansions within the guanylyl cyclase gene family

BACKGROUND: Guanylyl cyclases (GCs) are responsible for the production of the secondary messenger cyclic guanosine monophosphate, which plays important roles in a variety of physiological responses such as vision, olfaction, muscle contraction, homeostatic regulation, cardiovascular and nervous function. There are two types of GCs in animals, soluble (sGCs) which are found ubiquitously in cell cytoplasm, and receptor (rGC) forms which span cell membranes. The complete genomes of several vertebrate and invertebrate species are now available. These data provide a platform to investigate the evolution of GCs across a diverse range of animal phyla. RESULTS: In this analysis we located GC genes from a broad spectrum of vertebrate and invertebrate animals and reconstructed molecular phylogenies for both sGC and rGC proteins. The most notable features of the resulting phylogenies are the number of lineage specific rGC and sGC expansions that have occurred during metazoan evolution. Among these expansions is a large nematode specific rGC clade comprising 21 genes in C. elegans alone; a vertebrate specific expansion in the natriuretic receptors GC-A and GC-B; a vertebrate specific expansion in the guanylyl GC-C receptors, an echinoderm specific expansion in the sperm rGC genes and a nematode specific sGC clade. Our phylogenetic reconstruction also shows the existence of a basal group of nitric oxide (NO) insensitive insect and nematode sGCs which are regulated by O(2). This suggests that the primordial eukaryotes probably utilized sGC as an O(2 )sensor, with the ligand specificity of sGC later switching to NO which provides a very effective local cell-to-cell signalling system. Phylogenetic analysis of the sGC and bacterial heme nitric oxide/oxygen binding protein domain supports the hypothesis that this domain originated from a cyanobacterial source. CONCLUSION: The most salient feature of our phylogenies is the number of lineage specific expansions, which have occurred within the GC gene family during metazoan evolution. Our phylogenetic analyses reveal that the rGC and sGC multi-domain proteins evolved early in eumetazoan evolution. Subsequent gene duplications, tissue specific expression patterns and lineage specific expansions resulted in the evolution of new networks of interaction and new biological functions associated with the maintenance of organismal complexity and homeostasis

What's new in ... capnography monitoring for dental conscious sedation: a clinical review

Capnography monitoring during conscious sedation is not currently required for dentistry in Britain and Ireland. Other countries have introduced guidelines and standards requiring capnography monitoring for procedural sedation. This review highlights the variability of procedural sedation including the setting, the position on the sedation continuum, and the routine use of supplemental oxygen. Specific research is required for conscious sedation in a dental setting to support standards and guidelines with regard to capnography monitoring