Wednesday, November 30, 2022

Living With Friends


Above we see a microscopic view of the Paenibacillus bacteria, found in coffee machines and where coffee is prepared. It's been used as a probiotic for both chickens and bees, and might have something to do with the idea that coffee is good for your health. 

But that's just coffee. Onto the real story -- nobody lives alone, and that includes even those of us who don't live with other people. We're talking about the vast array of microbes that share our domestic biome with us. They outnumber us by the billions (uncountable really) and could have a strong influence on our health, maybe even our behavior (looking at you Toxoplasmosis), all by way of the mediating effects between our microbiome and our immune system. And they smell. Not all of them, but where there's life, there's smells. It's our own domestic ecology of smells.  

Each one of us affects the microbiome we live with, depending on who we are, what we eat, what we do for work and in our spare time, how we clean, how often and how thoroughly we clean, ad infinitum. The home is a dynamic place, and very different from a scientific laboratory, in almost every way, and so we don't have a good idea of what's happening in our homes, not on a biological basis, and not even on a chemical basis. 

And then came the HOME house, the HOME Chem model house, a chemical-lab-house, put together by 60 scientists from 13 universities in Austin, Texas circa 2020. They do regular-house things and measure the chemical profile of the air inside the home over time while they cook, clean, eat, sleep. It might sound mundane, but it's the first time we're getting real world indoor air quality data from the domestic frontier.

Most air quality data comes from outside air. We haven't been thinking about the indoor air for very long, and much less resources and scientific inquiry have been devoted to it. The HOME project gives us the first glimpse of what's really happening to our indoor environment while we live there.  


With roommates, it's all about chemistry, molecularly speaking
Jun 2022, phys.org

An experimental test home was erected in Austin, Texas during the summer of 2018. The house was designed for ordinary use and included bathrooms, a kitchen, gathering and work areas. Overnight stays were prohibited, but 45 study participants, plus visitors, spent time in the house, occupying it for approximately six hours per day for 26 days, during which they performed scripted activities, such as cooking, cleaning and socializing.

The house was deep cleaned with a bleach solution. Nonetheless, researchers said traces of molecules associated with humans were still present. After almost of month of human occupation, the house was alive with molecular and microbial abundance and diversity, albeit unevenly distributed.

Not surprisingly, the kitchen and toilet were hotspots of molecular and microbial diversity, though numbers fluctuated with surface cleaning and sanitation. "It appears that, even when a subset of chemistry is removed because of the cleaning, it is only temporary and/or partial, as the sum total of cleaning and human activities overall results in an increase in accumulation of richer chemistry," the authors wrote.

via University of California San Diego, Colorado State (Delphine Farmer), and University of Colorado: Alexander A. Aksenov et al, The molecular impact of life in an indoor environment, Science Advances (2022). DOI: 10.1126/sciadv.abn8016


Here's more links on HOME:

And here's some information on how bad we are at perceiving air quality indoors:
  • Teachers did not accurately perceive mechanical ventilation sufficiency
  • Air quality and temperature are conflated
  • Dramatic difference in IAQ perception (but not quality) in summer vs winter
  • Occupants misperceive temperature as a proxy for indoor air quality; they think cooler air is better, and confuse warm air with "stuffy, stale" air
  • Teachers in classrooms with worse ventilation were more satisfied with classroom temperature
  • Occupants don't understand how the systems work, and think incoming cold air in winter is a defect, for example (when in fact it is the system adding fresh air to the mix); they then say the system isn't working, and therefore they must have bad IAQ; they also think the only time the system brings fresh air is when the AC is on, which is the complete opposite of what's happening
Source: Pistochini T, Mande C, Modera M, et al. Improving Ventilation and Indoor Environmental Quality in California K-12 Schools (CEC-500- 2020-049). Sacramento, CA: California Energy Commission; 2020. https://www.energy.ca.gov/publications/2020/improving-ventilation-and-indoor-environmental-quality-california-schools

Thursday, November 17, 2022

Everyone Likes Vanilla


People around the world like the same kinds of smells
Apr 2022, phys.org

Odor preference is molecular. People share odor preferences regardless of cultural background. Traditionally it has been seen as cultural.

First of all, the thumbnail for this article, of the girl smelling the flower in profile view, is used every time a smell article comes up on phys.org.
Girl Smelling a Flower in Profile - Petr Kratochvil

So I ran it through the Stable Diffusion library at lexica.art, "girl smelling a flower in profile," and got top image above, what I'll call "Woman Eating a Flower by William-Adolphe Bouguereau and Gustav Klimt" [link]

Second of all, look that the list of collaborators here -- this is not your average smell study:

Department of Clinical Neuroscience at Karolinska Institutet, School of Life Sciences at Arizona State, Centre for Languages and Literature at Lund, Department of Anthropology at University College London, Colegio de Ciencias Sociales y Humanidades at Universidad San Francisco de Quito in Ecuador, Instituto de Investigaciones Filológicas at the National Autonomous University of Mexico, School of Languages and Linguistics at University of Melbourne, Monell Chemical Senses Center, Department of Neuroscience at University of Pennsylvania (Asifa Majid as corresponding author)
The secret? 

Many of the researchers are field workers working with indigenous populations. For this present study, the researchers selected nine communities representing different lifestyles: four hunter-gatherer groups and five groups with different forms of farming and fishing. Some of these groups have very little contact with Western foodstuffs or household articles.

"Since these groups live in such disparate odiferous environments, like rainforest, coast, mountain and city, we captured many different types of 'odor experiences'," says Dr. Arshamian.
The results:

The study included a total of 235 individuals, who were asked to rank smells on a scale of pleasant to unpleasant. The results showed variation between individuals within each group, but global correspondence on which odors are pleasant and unpleasant. The researchers showed that the variation is largely explained by molecular structure (41 percent) and by personal preference (54 percent). 

^One other study measured about 30% difference between any two people, this now says 54%, just keeping track.

The odors the participants were asked to rank included vanilla, which smelled best. This was followed by ethyl butyrate, which smells like peaches. The smell that most participants considered the least pleasant was isovaleric acid, which can be found in many foods, such as cheese, soy milk and apple juice, but also in foot sweat.

I think we knew vanilla was the universally liked odor, but this study is likely more reliable. 

via Karolinska Institutet, University of Oxford, Lund University, Stockholm University, University College London, Arizona State University, Monell Chemical Senses, Universidad San Francisco de Quito (Ecuador), University of Melbourne, and National Autonomous University of Mexico: Artin Arshamian, Richard C. Gerkin, Nicole Kruspe, Ewelina Wnuk, Simeon Floyd, Carolyn O’Meara, Gabriela Garrido Rodriguez, Johan N. Lundström, Joel D. Mainland, Asifa Majid, The perception of odor pleasantness is shared across cultures, Current Biology (2022). DOI: 10.1016/j.cub.2022.02.062

AI Art - Emma Watson in a Tunic Holding a Flower by Rubens - 2022
Emma Watson wearing green tunic holding a flower. Painted by Rubens, high detail [link]

Post Script:
(Personal opinion not backed by science) I think cultural influence on odor preference only works for bad smells, and specifically the "quantum hedonic" smells like parmesan cheese, kimchi, durian fruit, etc. That's where the signal is for cultural influence (and if put in the same dataset as vanilla and peaches would get lost).

Thursday, November 10, 2022

The Past Doesn't Smell Like It Used To


Scientists find ways to study and reconstruct past scents
Apr 2022, phys.org

They're trying to develop "an archaeology of scent," which is hard because smells are ephemeral, and last only as long as their source. But because of advances in chromatography, mass spectrometry, sequencing technologies and modern bioinformatics, which include metabolomics, proteomics and genomics; they can identify the organic remains preserved on surfaces like walls, ceramic vessels, incense burners, perfume flasks, cooking pots, dental calculus, mummies, and entire streets:

Advanced biomolecular and ‘omics’ sciences enable more direct insights into past scents, offering new options to explore critical aspects of ancient society and lifeways as well as the historical meanings of smell.

The whole paper is very interesting, and although I encourage anyone interested in ancient history to read it, for those who don't, I bring back only this -- palaeofaeces -- it's a thing in archaeology, and now in olfactory archaeology too: "in an Iron Age roundhouse in Scotland, chemical characterization of floor sediments provided insight into living conditions, hygiene practices and the temporary sheltering of animals in human living areas during this period."
-Mackay, H. et al. J. Archaeol. Sci. 121, 105202 (2020). [pdf]

via the Department of Archaeology at the Max Planck Institute for the Science of Human History in Jena, Germany: Huber, B., Larsen, T., Spengler, R.N. et al. How to use modern science to reconstruct ancient scents. Nat Hum Behav 6, 611–614 (2022). https://doi.org/10.1038/s41562-022-01325-7

via James Gilleard and Justin Gerard

Post Script:
Speaking of human history, the Odeuropa project is taking a completely different angle -- they use computer science to identify, scrape, and coordinate pictures that contain smells in them, either by visually recognizing objects tagged as related to smells, or by reading the text captioned with the image. Sensory mining they call it:

Odeuropa is a European research project which bundles expertise in sensory mining and olfactory heritage. We develop novel methods to collect information about smell from (digital) text and image collections.

Thursday, November 3, 2022

Chemical Intelligence


'E-nose' sniffs out mixtures of volatile organic compounds
Jun 2022, phys.org

Electric nose with porous metal-organic framework films that distinguish xylene isomer mixtures for environmental health monitoring.

Previously, researchers used gas chromatography analysis to identify the three forms of xylene. But this procedure requires large instruments that are expensive, and the analyses are time intensive. 

The researchers prepared six different porous MOF films known to adsorb xylene isomers and applied them to gravimetric sensors in an array called an "e-nose." By analyzing the sensor array data with a machine learning algorithm, the team could determine the composition of the mixtures with 86% accuracy for the 10-ppm mixture and 96% accuracy for the 100-ppm mixture

via Karlsruhe Institute of Technology's Institute of Functional Interfaces and University of Pittsburgh Department of Chemical & Petroleum Engineering: VOC Mixture Sensing with a MOF Film Sensor Array: Detection and Discrimination of Xylene Isomers and Their Ternary Blends, ACS Sensors (2022). DOI: 10.1021/acssensors.2c00301

a detailed blueprint of god, top - secret document 


Nano-sensor detects pesticides on fruit in minutes
Jun 2022, phys.org

Current techniques for detecting pesticides on single products before consumption are restricted in practice by the high cost and cumbersome manufacturing of its sensors.

Uses flame-sprayed nanoparticles made from silver to increase the signal of chemicals, "The flame spray can be used to quickly produce uniform surface-enhanced Raman scattering (SERS) films across large areas, removing one of the key barriers to scalability,"

To test the sensors' practical application, the researchers calibrated them to detect low concentrations of parathion-ethyl, a toxic agricultural insecticide that is banned or restricted in most countries. A small amount of parathion-ethyl was placed on part of an apple. The residues were later collected with a cotton swab that was immersed in a solution to dissolve the pesticide molecules. The solution was dropped on the sensor, which confirmed the presence of pesticides.

via Karolinska Institutet: SERS Hotspot Engineering by Aerosol Self-Assembly of Plasmonic Ag Nanoaggregates with Tunable Interparticle Distance, Advanced Science (2022). DOI: 10.1002/advs.202201133


Damaged plants and fake perfumes can be identified rapidly and reliably in real time
Jun 2022, phys.org

Chiral detection:

Most natural chiral substances are found in two mirror-image forms present in different relative quantities. Therefore, every plant and every perfume must have its own individual chiral signature.

The relative ratios of the two enantiomers of pinene naturally vary in the emissions of such plants, but critically depend on the state of health of the plant.

Fake perfumes will have a chiral signature that differs from that of the originals.

The Mainz-based researchers have developed a cavity-enhanced polarimetric method for optical chiral analysis to detect the differing optical rotation effects of chiral molecules under polarized light. The researchers have been able to achieve a sensitivity that is better than that of the current state-of-the-art equipment by several orders of magnitude.

via Universitaet Mainz and the Max Planck Institute for Chemistry: Lykourgos Bougas et al, Absolute optical chiral analysis using cavity-enhanced polarimetry, Science Advances (2022). DOI: 10.1126/sciadv.abm3749