olfaction

Counterintuitive nature of quantum physics leads to a number of paradoxes. One of them is a “quantum vampire” effect consisting in the fact that photon annihilation in a part of a large beam doesn’t change the shape of the beam profile (i. e., doesn’t cast a shadow), but may change the total beam intensity.

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First of all, I can remember very specific odors in extraordinary detail pretty much indefinitely. Moreover, I can conjure the memory of these odors exactly and at will. I have it on excellent authority from several researchers at the Monell Chemical Senses Center that this is a very rare capacity. […]

Secondly, I can mentally and very accurately forecast how the perceived odor of any given substance will change at various levels of concentration. […]

Thirdly and largely because of the two previously mentioned strange abilities, I can imagine discrete odors and know what will happen when I combine and arrange them while adjusting their concentrations – entirely in my head without even opening a bottle or picking up a pipette.

{ CB I Hate Perfume | Continue reading | Thanks Tim }

photo { Robert Mapplethorpe, Jack in the Pulpit, 1988 }

Lift your head up high, and scream out to the world, I know I am someone

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The tendency of people to forge friendships with people of a similar appearance has been noted since the time of Plato. But now there is research suggesting that, to a striking degree, we tend to pick friends who are genetically similar to us in ways that go beyond superficial features.

For example, you and your friends are likely to share certain genes associated with the sense of smell.

Our friends are as similar to us genetically as you’d expect fourth cousins to be, according to the study published Monday in the Proceedings of the National Academy of Sciences. This means that the number of genetic markers shared by two friends is akin to what would be expected if they had the same great-great-great-grandparents. […]

The resemblance is slight, just about 1 percent of the genetic markers, but that has huge implications for evolutionary theory.

{ Washington Post | Continue reading }

polyvinyl chloride, colored with oil, mixed technique and accessories { Duane Hanson, Children Playing Game, 1979 }

Fumbally’s lane that night: the tanyard smells.

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Most humans perceive a given odor similarly. But the genes for the molecular machinery that humans use to detect scents are about 30 percent different in any two people, says neuroscientist Noam Sobel. […] This variation means that nearly every person’s sense of smell is subtly different. [….]

Sobel and his colleagues designed a sensitive scent test they call the “olfactory fingerprint.” […] People with similar olfactory fingerprints showed similarity in their genes for immune system proteins linked to body odor and mate choice. […]

It has been shown that people can use smell to detect their genetic similarity to others and avoid inbreeding, says neuroscientist Joel Mainland of Monell Chemical Senses Center in Philadelphia.  

{ Science News | Continue reading }

photo { Juergen Teller, Octopussy, Rome, 2008 }

‘The world is the totality of facts, not things.’ –Wittgenstein

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A fragrant object lies before you—say, a flower, some stinky cheese, or a smelly sock. Molecules break off from the object, evaporating into the air and floating towards your face. A sniff pulls the molecules into your nostril, where they travel through your nasal cavity towards your olfactory neurons, which extend out through holes in your skull into the mucus layer of your nose. The molecules activate receptors studding the outside layer of individual neurons, which send a message to your brain that something smells.

Humans have around 350 types of receptors on 40 million neurons, which in combination allow us to distinguish more than a trillion different odors. Despite this incredible power of olfaction, the human sense of smell is often neglected, considered a holdover from our animal past or a source of unseemly sensations. It doesn’t help that odors are often literally beneath us; the evolutionary argument goes that when early humans started walking upright, our nose got farther away from the smells on the ground, decreasing the relative importance of olfaction for getting around. Evidence contradicting this story came from a 2006 study which recruited undergraduate students to get on all fours and track the scent of chocolate oil dripped on grass. They were remarkably good at it, showing that our “bad” sense of smell isn’t biologically determined—it’s just that we’re out of practice. […]

We know a lot about how a smell signal travels from an activated receptor on a neuron to the brain. This pathway has been worked out in painstaking detail, with cascades of cellular switches and neural action potentials that signal our brain. […] But how does a smelly molecule activate its receptor in the first place? There is still no satisfactory answer to this question despite nearly a century of research.

{ The New Inquiry | Continue reading }

photo { Juno Calypso, Disenchanted Simulation, 2013 }

In order to remain silent Da-sein must have something to say

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Noise cancellation is a traditional problem in statistical signal processing that has not been studied in the olfactory domain for unwanted odors.

In this paper, we use the newly discovered olfactory white signal class to formulate optimal active odor cancellation using both nuclear norm-regularized multivariate regression and simultaneous sparsity or group lasso-regularized non-negative regression.

As an example, we show the proposed technique on real-world data to cancel the odor of durian, katsuobushi, sauerkraut, and onion.

{ IEEE Workshop on Statistical Signal Processing | PDF }

Further confirming that Burning Man is awful

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Human skin is inhabited and re-populated depending on health conditions, age, genetics, diet, the weather and climate zones, occupations, cosmetics, soaps, hygienic products and moisturizers. All these factors contribute to the variation in the types of microbes. Population of viruses, for example, can include a mixture of good ones - like bacteriophages fighting acne-causing Propionibacterium  - and bad ones  - as highly contagious Mesles. Bacterial communities include thousands of species of Actinobacteria, Bacteroidetes, Cyanobacteria, Proteobacteria, and fungi Malassezia. […]

The major odor-causing substances are sulphanyl alkanols, steroid derivatives and short volatile branched-chain fatty acids.

Most common sulphanyl alkanol in human sweat, 3-methyl-3-sulfanylhexan-1-ol is produced by bacteria in several ways. […] Besides being a major descriptor of human sweat odor,  is also present in beers.

{ Aurametrix | Continue reading }

Tried and true

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Sex pheromones are chemical compounds released by an animal that attract animals of the same species but opposite sex. They are often so specific that other species can’t smell them at all, which makes them useful as a secret communication line for just that species. But this specificity raises an intriguing question: When a new species evolves and uses a new pheromone signaling system, what comes first: the ability to make the pheromone or the ability to perceive it? […]

Any individuals that make a new and different scent would then be perceived by the receivers as being the wrong species and they won’t attract any mates. If you don’t attract mates, you can’t pass on your new genes for your new scent. This produces a strong pressure to make a scent that is as similar as the scent produced by everyone else as possible (this is called stabilizing selection). With this intense pressure to be like everyone else, how did the incredible diversity of species-specific pheromones come to be?

{ Nature | Continue reading }

From the air (dropped by an eagle in flight), by fire (amid the carbonised remains of an incendiated edifice), in the sea (amid flotsam, jetsam, lagan and derelict), on earth (in the gizzard of a comestible fowl)

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On a street in Manhattan’s Lower East Side, an unremarkable gray box protrudes from a telephone pole. Inside the box lies a state-of-the-art airflow-sampling device, one part of an experiment to track how a gas disperses through the city’s streets and subway system. […]

The goal of the project is to develop a model for how a dangerous airborne contaminant, such as sarin gas or anthrax, would spread throughout the city in the event of a terrorist attack or accidental release.

The scientists released tiny amounts of a colorless, nontoxic gas at several locations around the city. The airflow samplers, located at various points throughout the city, measured the gas to determine how fast and how far it spread.

{ LiveScience | Continue reading }

unrelated { Eproctophilia is a paraphilia in which people are sexually aroused by flatulence. The following account presents a brief case study of an eproctophile. | Improbable }

and drew him down to me so he could feel my breasts all perfume

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The sense of smell is one of our most powerful connections to the physical world. Our noses contain hundreds of different scent receptors that allow us to distinguish between odours. When you smell a rose or a pot of beef stew, the brain is responding to scent molecules that have wafted into your nose and locked on to these receptors. Only certain molecules fit specific receptors, and when they slot together, like a key in a lock, this triggers changes in cells. In the case of scent receptors, specialised neurons send messages to the brain so we know what we have sniffed. […]

In the last ten years, however, reports have trickled in from bemused biologists that these receptors, as well as similar ones usually found on taste buds, crop up all over our bodies.

{ BBC | Continue reading }

‘If you want to know yourself, just look how others do it.’ –Schiller

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The objective of this study was to determine test characteristics (i.e., intra- and interobserver variability, intraassay variability, sensitivity, and specificity) of an evaluation of odor from vaginal discharge (VD) of cows in the first 10 days postpartum conducted by olfactory cognition and an electronic device, respectively. […]

The study revealed a considerable subjectivity of the human nose concerning the classification into healthy and sick animals based on the assessment of vaginal discharge.

{ Journal of Dairy Science }

‘Love is a state in which a man sees things most decidedly as they are not.’ –Nietzsche

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Around 1 in 7,500 otherwise healthy people are born with no sense of smell, a condition known as isolated congenital anosmia (ICA). So dominant are sight and hearing to our lives, you might think this lack of smell would be fairly inconsequential. In fact, a study of individuals with ICA published last year showed just how important smell is to humans. Compared with controls, the people with ICA were more insecure in their relationships, more prone to depression and to household accidents.

{ BPS | Continue reading }

photo { Francesca Woodman, Self-portrait talking to Vince, Providence, RI (RISD), 1975-78 }

Smell my hot goathide. Feel my royal weight.

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Men who were born without a sense of smell report having far fewer sexual partners than other men do, and women with the same disorder report being more insecure in their partnerships, according to new research.

The researchers don’t know why romantic difficulties could be tied to smell, but they say one possibility is that people with anosmia, or no sense of smell, are insecure, having missed many emotional signals all their life.

{ LiveScience | Continue reading }

photos { Sarah Pickering, Fuel Air Explosion (L), Land Mine (R) }