Such information is important because different substrates reflect and absorb different bands of the electromagnetic spectrum. For example, cloud and surface temperature signals are detected at 3.66-4.08 micron and 10.78-12.27 micron wavelengths, while ocean color and phytoplankton is detected at 405-877 nanometer wavelengths. This property of matter is what makes remote sensing so powerful, but it means that knowing the solar power spectrum and correcting for the absorption and reflectance of the atmosphere--and a myriad of other factors--is critical to proper interpretation of the final signal.
AB - The origin of eukaryotic flagella has long been a mystery. Here we review the possibility that flagella sprouted evolutionarily from the eukaryotic cell proper seems very unlikely because it is hard to imagine what function and benefit in natural selection the flagella would have provided to the cells when they first emerged as simple buds. Lynn Margulis' 1970 spirochete hypothesis, though popular still, has never been confirmed. Moreover, the absence of tubulin and axonemal dynein in the spirochetes and the incapability of the bacterial and eukaryotic membranes' making a continuum now suggest that the hypothesis is outdated. Tubulin genes were recently identified in a new bacteria division, verrucomicrobia, and microtubules have also been found in one of these species, epixenosomes, the defensive ectosymbionts. On the basis of these data, we propose a new symbiotic hypothesis: that the mid-ancestor of eukaryotic cells obtained epixenosomelike verrucomicrobia as defensive ectosymbionts and the ectosymbionts later became endosymbiotic. They still, however, protruded from the surface of their host to play their role. Later, many genes were lost or incorporated into the host genome. Finally, the genome, the bacterial membrane, and the endosymbiotic vesicle membrane were totally lost, and fingerlike protrusions with microtubules formed. As the cells grew larger, the defensive function of the protrusions eventually weakened and then vanished. Some of the protrusions took on a new role in cell movement, which led them to evolve into flagella. The key step in this process was that the dynein obtained from the host evolved into axonemal dyneins, attaching onto the microtubules and forming motile axonemes. Our hypothesis is unproven, but it offers a possible explanation that is consistent with current scientific thought. We hope that our ideas will stimulate additional studies on the origin of eukaryotic flagella and on investigations of verrucomicrobia. Whether such studies confirm, refine, or replace our hypothesis, they should nevertheless further our understanding of the origin of eukaryotic cells.
[An unlikely hypothesis, but a lucid discussion of the issues.]
This investigation analyzes the temporal characteristics of maximal depolarization times for three waveforms: end-plate spikes, fibrillation potentials, and positive sharp waves (PSWs) to provide support for the electrode initiation hypothesis of PSW induction. The maximal depolarization times for PSWs are documented to comprise two distinct populations conforming to relatively short and comparatively longer maximal depolarization times. Those PSWs with short maximal depolarization times were found to be equivalent to end-plate spike maximal depolarization times, whereas those with longer times were comparable to fibrillation potentials. The PSW group with shorter maximal depolarization times was encountered more frequently. The combination of two distinct groups of PSWs with respective times comparable to end-plate spikes and fibrillation potentials supports the hypothesis that the majority of PSWs originate at the recording electrode during insertion, whereas a smaller population of PSWs arises as propagating fibrillation potentials that block at the recording electrode. Subcutaneous compared to intramuscular recordings from denervated muscle document that the recording electrode is necessary to both record and produce PSWs. Hence, this study confirms the proposed hypothesis that the majority of observed PSWs represent a suprathreshold single muscle-fiber discharge induced by, and originating in close proximity to, a perielectrode crushed membrane that then propagate away from the electrode; a smaller population of PSWs conform to that of a blocked fibrillation potential.
How do the stages described in the solar nebula hypothesis ..
Ultimately, our definition of the genus and what species itincludes will determine our view of its center of origins and whether the genusis monophyletic or polyphyletic.
Origin of Life: The Heterotroph Hypothesis - SparkNotes
The dialectic of the First Meditation features a confrontation betweenparticularism and methodism, with methodism emerging the victor. Forexample, the meditator (while voicing empiricist sensibilities) putsforward, as candidates for the foundations of Knowledge, such primafacie obvious claims as “that I am here, sitting by the fire,wearing a winter dressing-gown, holding this piece of paper in my hands,and so on” — particular matters “about whichdoubt is quite impossible,” or so it would seem (AT 7:18). Inresponse (and at each level of the dialectic), Descartes invokes his ownmethodical principles to show that the prima facie obviousness ofsuch particular claims is insufficient to meet the burden of proof.
Origin of Life: The Heterotroph Hypothesis
Descartes is a contextualist in the sense that he allows thatdifferent standards of justification are appropriate to differentcontexts. This is not merely to say the obvious: that depending on thecontext of inquiry, knowledge-worthy justification will sometimes beneeded, but other times not. It's to say something stronger: thatdepending on the context of inquiry, the standards of knowledge-worthyjustification might vary. For example, a contextualist might acceptthat ‘knowledge’-talk is equally appropriate whether oneis describing the best achievements of empirical science, or the bestachievements of mathematics, while acknowledging that the formerrest on weaker standards of proof than the latter. This example ispotentially misleading, in that Descartes appears loath to count mereempirical evidence as knowledge-worthy justification. But uponramping up the standard to what he finds minimally acceptable, thestandard admits of context dependent variation.