855 research outputs found
Science is perception: what can our sense of smell tell us about ourselves and the world around us?
Human sensory processes are well understood: hearing, seeing, perhaps even tasting and touch—but we do not understand smell—the elusive sense. That is, for the others we know what stimuli causes what response, and why and how. These fundamental questions are not answered within the sphere of smell science; we do not know what it is about a molecule that … smells. I report, here, the status quo theories for olfaction, highlighting what we do not know, and explaining why dismissing the perception of the input as ‘too subjective’ acts as a roadblock not conducive to scientific inquiry. I outline the current and new theory that conjectures a mechanism for signal transduction based on quantum mechanical phenomena, dubbed the ‘swipe card’, which is perhaps controversial but feasible. I show that such lines of thinking may answer some questions, or at least pose the right questions. Most importantly, I draw links and comparisons as to how better understanding of how small (10’s of atoms) molecules can interact so specially with large (10 000’s of atoms) proteins in a way that is so integral to healthy living. Repercussions of this work are not just important in understanding a basic scientific tool used by us all, but often taken for granted, it is also a step closer to understanding generic mechanisms between drug and receptor, for example
Molecular recognition in olfaction
The mechanism by which the chemical identity of odourants is established by olfactory receptors is a matter of intense debate. Here we present an overview of recent ideas and data with a view to summarising what is known, and what has yet to be determined. We outline the competing theories, and summarise experimental results employing isotopes obtained for mammals, insects, and individual receptors that enable us to judge the relative correctness of the theories
Plant population size and isolation affect herbivory of Silene latifolia by the specialist herbivore by parasitoids
TRIS I: Absolute Measurements of the Sky Brightness Temperature at 0.6, 0.82 and 2.5 GHz
At frequencies close to 1 GHz the sky diffuse radiation is a superposition of
radiation of Galactic origin, the 3 K Relic or Cosmic Microwave Background
Radiation, and the signal produced by unresolved extragalactic sources. Because
of their different origin and space distribution the relative importance of the
three components varies with frequency and depends on the direction of
observation. With the aim of disentangling the components we built TRIS, a
system of three radiometers, and studied the temperature of the sky at , and GHz using geometrically scaled antennas
with identical beams (HPBW = ). Observations
included drift scans along a circle at constant declination
which provided the dependence of the sky signal on the
Right Ascension, and absolute measurement of the sky temperature at selected
points along the same scan circle. TRIS was installed at Campo Imperatore (lat.
= N, long.= , elevation = 2000 m a.s.l.) in
Central Italy, close to the Gran Sasso Laboratory.Comment: Accepted for publication in The Astrophysical Journa
Could humans recognize odor by phonon assisted tunneling?
Our sense of smell relies on sensitive, selective atomic-scale processes that
are initiated when a scent molecule meets specific receptors in the nose.
However, the physical mechanisms of detection are not clear. While odorant
shape and size are important, experiment indicates these are insufficient. One
novel proposal suggests inelastic electron tunneling from a donor to an
acceptor mediated by the odorant actuates a receptor, and provides critical
discrimination. We test the physical viability of this mechanism using a simple
but general model. Using values of key parameters in line with those for other
biomolecular systems, we find the proposed mechanism is consistent both with
the underlying physics and with observed features of smell, provided the
receptor has certain general properties. This mechanism suggests a distinct
paradigm for selective molecular interactions at receptors (the swipe card
model): recognition and actuation involve size and shape, but also exploit
other processes.Comment: 10 pages, 1 figur
Numerical analysis of the radio-frequency single-electron transistor operation
We have analyzed numerically the response and noise-limited charge
sensitivity of a radio-frequency single-electron transistor (RF-SET) in a
non-superconducting state using the orthodox theory. In particular, we have
studied the performance dependence on the quality factor Q of the tank circuit
for Q both below and above the value corresponding to the impedance matching
between the coaxial cable and SET.Comment: 14 page
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