Friday, January 13, 2023

Smells Like Covid Part 2

It's been a couple years since the world learned the word "anosmia," so here's some updates:
(but don't forget this post about how parosmia worked with covid)

The first mass screening system for COVID cases has been developed with a sensitivity of 97%
Dec 2022,

Washing your hands with hydroalcoholic gel, smelling it and using a QR code to answer a short questionnaire. These very simple actions make up the world's first patented mass screening system for COVID cases.

Citrus fruits and apples are two of the first aromas that people with the SARS-CoV-2 virus stop detecting.

"Citrus" -- I don't remember seeing this at all, so I looked further into the report: "Based on the literature and habits of our Mediterranean study population, it was determined that the most suitable odoriferous substance was lemon." via Institute for Research in Fundamental Sciences in Iran and R DOty at U Penn: Moein, S. T. et al. Smell dysfunction: A biomarker for COVID-19. Int. Forum Allergy Rhinol. 10, 944–950 (2020).  -- This study used the University of Pennsylvania Smell Identification Test (UPSIT) which has 40 odorants; I can't read the paper because paywall, but I guess "citrus" or "lemon" is one of those odors. The paper wasn't meant to find the most prevalent non-detectable odor, but I guess it was just sitting there in the data?

"The antigen tests on the market have an average sensitivity of 80%, which means that the number of false negatives is 20%. What we have developed is not a diagnostic test, but a screening system that aims to detect the maximum possible number of positives and prevent false negatives," explained the researchers.

via Youcef Azeli et al, A machine learning COVID-19 mass screening based on symptoms and a simple olfactory test, Scientific Reports (2022). DOI: 10.1038/s41598-022-19817-x

Image credit: Stainless steel climate chamber at the Technical University of Denmark, Mikal Schlosser, 2022

Loss of smell following COVID linked to a person's immune reaction to the infection
Dec 2022,

They studied antibody levels in people infected during the early days of the pandemic—in all, they studied blood samples of 306 people who had donated blood for study after recovering from a COVID-19 infection. In comparing the antibody levels with other data provided by the donors and their doctors, the researchers determined that those people who had higher antibody levels tended to be the same people who had reported losing their sense of smell or taste. They found that such patients were twice as likely to lose one or the other sense as those who did not have higher-than-average levels of antibodies in their blood.

via Columbia University Irving Medical Center, the University of Pennsylvania, the National Institute of Alcohol Abuse and Alcoholism and the New York State Psychiatric Institute: Jonathan B. Overdevest et al, Chemosensory deficits are best predictor of serologic response among individuals infected with SARS-CoV-2, PLOS ONE (2022). DOI: 10.1371/journal.pone.0274611

Scientists find key reason why loss of smell occurs in long COVID-19
Dec 2022,

The reason some people fail to recover their sense of smell after COVID-19 is linked to an ongoing immune assault on olfactory nerve cells and an associated decline in the number of those cells, a team of scientists led by Duke Health report.

via Duke University Medical Center: John Finlay et al, Persistent post-COVID-19 smell loss is associated with immune cell infiltration and altered gene expression in olfactory epithelium, Science Translational Medicine (2022). DOI: 10.1126/scitranslmed.add0484.

Thursday, January 12, 2023

Mass Psychogenic Illness

When you have a physical problem that can't be explained by medical science, it's called a "somatic symptom disorder." In other words, it's described as a mental problem that has manifested as a physical problem. Some people will tell you that it's all in your head, and some people think that makes this kind of problem even worse.

Long-covid sufferers know what this is like, but plenty of other people have known it too. Sometimes, lots of people suffer from this together, and that's called "mass psychogenic illness." It's also called "mass sociogenic illness." You might know it as simply "mass hysteria," and recall plagues of hysterical laughter that have been recounted throughout history. 

It's a topic that sits at the intersection of memetic transmission, olfactory perception, and occupational health. It's "memetic" because it's spread through the mind, "olfactory" because that's the sense most susceptible to illusion and cognitive override, and "occupational" because it tends to happen in groups existing in some kind of hierarchy, and although society is one big hierarchy, workplaces are microcosms of social organization.

A couple smelly people on an airplane are real good for sending the entire cabin into a paranoid frenzy over suspicions of a bioterror attack. Too much chlorine in the pool? With the right mixture of hypersensitive olfactory receptors, general distrust in the way the pool is managed, and strong communication networks between the occupants, and you're passing out whether it's the chlorine or not.

Potential carbon monoxide poisoning after six people were sent to the emergency room? Three people in the staff lounge smelled a dead mouse in the wall cavity, couldn't recognize it as a dead-mouse-smell, concocted a scenario about alchemical reactions from the science lab 3 doors down, and spread their paranoia to another group of people eating lunch in another part of the building, who then spread their paranoia to another group somewhere else, until 15 people are asphyxiating at their own thoughts, 6 of whom were not even in the initial group but were sent to the emergency room.

Mass hysteria is a difficult subject to talk about, because it's cruel to dismiss the ill health effects of another person, or especially an entire group of people, as being pure fiction. Yet, there are plenty of stories of this throughout history, where lots of people absolutely confirm they have a physical problem, and yet lots of doctors and special investigators are absolutely certain they've tried everything, looked for everything, and can't find anything wrong.

In fact, and unfortunately, there are many instances of potentially dangerous environmental exposures causing shortness of breath, fainting, blinding migraines, seizures, etc. where the dangerous exposure remains elusive, has no plausible explanation, the investigation is stopped, the cause is recorded as "mass psychogenic illness" and the case is closed. 

Somewhere in the middle is an organization -- be it a church, a workplace, or an entire community -- that has lost its social capital. The hierarchical strata no longer trust each other, they feel powerless to improve their conditions, and are unable to escape. In a world where private industry is valued more than public good, social capital is a liability, not an asset. The next time you hear about an odor sending a whole building full of people to the hospital, consider the social and psychological effects of power and control on a population suffering from a breakdown of social capital. 

Here's a list of qualities of an outbreak of mass psychogenic illness:
  • symptoms with no plausible organic basis;
  • symptoms are transient and benign;
  • symptoms with rapid onset and recovery;
  • occurrence in a segregated group;
  • the presence of extraordinary anxiety;
  • symptoms that are spread via sight, sound or oral communication;
  • a spread that moves down the age scale, beginning with older or higher-status people;
  • a preponderance of female participants.
-"Mass sociogenic illness". Erica Weir (2005). Canadian Medical Association Journal. 172 (1): 36. doi:10.1503/cmaj.045027. PMC 543940. PMID 15632400.

Here's some examples of strong, offensive odors making people sick, or not:

3 custodians treated at N.J. college after chemical smell sweeps through building
Jul 2022, NJ Star Ledger

Three custodians working early Tuesday at Bergen Community College were overcome by chemical fumes and treated on site by paramedics, a college spokesman said.

The incident occurred about 2 a.m. in a building at the campus on Paramus Road in Paramus. The custodians called emergency medical workers because they were concerned about breathing the fumes, the spokesman said.

The spokesman said the smell was caused by a masking agent used to cover a chlorine smell from power-washing a day earlier and the air conditioner carried the masking agent smell throughout the building.

Chlorine fumes at N.J. pool send 14 campers to hospital for observation, officials say
Jul 2022, NJ Star Ledger

Fourteen participants in a soccer camp were taken to the hospital for observation Monday after they became sick while at a pool on Drew University’s campus in Madison, officials said.

The campers experienced chlorine inhalation symptoms when “a small amount of chlorine was accidentally released” at the Simon Forum’s Pool shortly after noon, according to a statement from Madison officials.

The soccer camp participants — ranging in age from 10 to 17 — received medical care at the scene and were taken to a local hospital within an hour, officials said.

Tests at the pool showed normal levels of chlorine and all systems were working properly, according to a school spokesperson.

Some campers reportedly smelled chlorine vapors and were vomiting in a nearby area. It was not immediately clear how the chemical was released, but there was no active leak.

“Initial reports indicated that some of the children were suffering from shortness of breath, difficulty speaking between breaths, nausea and general airway issues,” said Morris County Emergency Management Director Jeffrey Paul.

Dead Zebra Mussels
American Industrial Hygiene Association Catalyst Forum, 2022
I recall an event when workers were cutting through an old cooling water intake from the Hudson River and a strong odor resulted in having to evacuate the building until it was determined that the odor was from torching zebra mussels that had lined the inner surface of the intake!

Here's a study about this phenomenon from 1978 in a journal for nurses:
An investigation was undertaken of an apparent outbreak of contagious psychogenic illness at an electronics plant in which approximately 50 females reported a variety of subjective nonspecific symptoms. The workers believed that the physical symptomatology was triggered by an unidentified odor in the plant which was not verified by environmental sampling for chemicals or by medical evaluations of affected workers. A random sample of non-affected and affected workers was surveyed by means of psychological health status inventories and epidemiological indices to determine the role that life-history, personality characteristics and job dissatisfaction had on susceptibility to illness. Results indicated that those workers reporting the highest level of perceived stress due to job dissatisfaction, family problems, and personal conflict were most likely to experience somatic symptoms. In the present study sources of dissatisfaction identified as potential precipitating factors of the illness outbreak were: 1) working conditions, 2) supervisory style, and 3) personal lifestyle.

The incident, preceded by some form of stress and structural strain, usually is contingent upon several factors including level of environmental stressors, host susceptibility, and mode of rumor transmission, culminating in a collective action.

Work Environment Scale (WES) - ascertain the role of job stress in the etiology of the illness, intended to be predictive of worker satisfaction or adjustment:
  • 1) involvement - the extent to which workers are enthusiastic or committed to their jobs;
  • 2) peer cohesion - the extent to which workers are mutually supportive;
  • 3) staff support - the extent to which management is perceived as supportive by the workers;
  • 4) autonomy - the extent to which the workers feel self-sufficient and independent;
  • 5) task orientation - the extent to which the climate emphasizes productivity and efficiency;
  • 6) work pressure - the extent to which workers perceived pressure to produce;
  • 7) clarity - the extent to which workers know what is expected of them in the perform- ance of their jobs;
  • 8) control - the extent to which management imposes rules and regulations on the workers;
  • 9) innovation - the extent to which variety and new approaches are emphasized in the workplace; and
  • 10) physical comfort - the extent to which the physical surroundings contribute to a pleasant work environment. [19] Moss AH, Insel PM, Humphrey B: Family Work and Group Environment Scales Manual. Palo Alto, Consulting Psychologists Press, Inc, 1974.
  • *Needs: more cohesiveness, more support, less work pressure, more control, less ambiguity of work role; physical comfort is actually negligible.

It appeared that neither the mutual interest of workers for one another nor the relationships between the workers and plant management were conducive to strong interpersonal support and trust.

This lack of trust was reflected in the unwillingness of employees to express their feelings or to reveal their work problems to supervisors. 

Consequently, affected workers perceived no way to resolve the problems facing them; they were locked into a situation with mounting difficulties without any hope of resolution.

When individuals perceive all outlets for help as closed and yet feel compelled to maintain the job, vulnerability to succumb to a mass illness in order to find some relief increases.

Similarly, worker autonomy and innovative approaches were not encouraged. This evident blocking of any outlet for expression by the workers by prohibiting them from contributing their own ideas, sharing their knowledge, or initiating any improvements at their worksite, built up tension and employee anxiety. [hopelessness]

Perceived increased pressure to produce relative to normal population (but may be related to other workers not doing their end of the deal, which multiples the work required on the 'affected' and negates the possibility for pride in work)

A profile of the affected worker emerges from this study as a female, less educated than her peers, who works under great pressure to maintain a job to support her family. Poor relations with supervisors, role ambiguity, work overload, and use of inferior materials are daily stressors. More importantly, opportunities for expressing ideas, grievances, or alleviation of difficulties are stymied so that the worker is without control over her work-life, without pride or self-esteem. Having been left no resource to cope with the situation, an objective physical stressor such as the smell of gas leak, can serve to provide justification to display somatic symptoms severe enough to necessitate a physician's care.

It would therefore appear that the underlying causes of this mass psychogenic illness episode were a function of the employees' working conditions and plant supervision style which produced psychological stress for which no outlets were available, causing anxiety and depression. Over long periods of time such anxiety and depression produced a socially acceptable means of expression - a mass psychogenic reaction with physical symptomatology which was triggered by some undefined toxic agent in the plant environment.
-Cohen, B.G.F., Colligan, M.J., Wester II, W., and Smith, M.J. (1978). An investigation of job satisfaction factors in an incident of mass psychogenic illness at the workplace. Occupational Health Nursing, January 1978:10-16. [pdf].

Here is another old article, this time from a journal of occupational psychology:
The "trigger" is almost always a strange odor, but sometimes bug bites, and one time the threat of staff-wide pregnancy tests, and sometimes related to limited outbreaks of disease in the community such as polio or gonnorhea.

Symptoms are almost always headache, dizziness, nausea, etc., or irritable throat, eyes, coughing, shortness of breath or even skin rashes

The more dramatic symptoms such as catatonic posture, spasms and muscular twitching, and simulated gonorrhoeal vaginitis, were most frequent among adolescent populations.

Most victims appeared to feel a strong need to associate their illness with a physical rather than a psychogenic cause.

Tendency of affecteds to have a history of absenteeism from work prior to the contagious outbreak. It appears, then, that the higher absenteeism rate of affecteds may be more a function of coping style than general health status. It is also possible that the affecteds are hypersensitive to their health state in general.
  • Environment: organized, structured, clear roles, not voluntary, ie, stress daily, escape limited
  • Boredom: repetitive tasks
  • Production pressure: forced overtime, deadlines
  • Physical stressors: noise, lighting, thermal comfort, odors (hypersensitivity?)
  • Labor-management relations: lack of trust
  • Communication: scheduled break times means no meeting friends, noisy means can't hear
The initiator and convergence vs contagion: convergence happens independently of each other instead of passing one to the other (authors saying most mass psychogenic illness is convergence not contagion).

After the first person is visible or vocal with their symptoms, it goes from convergence to contagion real quick, as the initiator disinhibits newly acceptable expression of symptoms.

Sequential decline in symptom severity as the epidemic progressed.
-Colligan, M.J., and Murphy, L.R. (1982). A review of mass psychogenic illness in work settings. In M.J. Colligan, J.W. Pennebaker, and L.R. Murphy (eds.) Mass Psychogenic Illness, NJ: Erlbaum, 171-182.

Here's some written work on the subject:
  • Wheeler, L. (1966). Towards a theory of behavioural contagion. Psychological Review, 73:179-192.
  • Kerckhoff, A.C. and Back, K.W. (1968). The June Bug: A Study in Hysterical Contagion. New York: Appleton-Century-Crofts. 
  • Stahl SM, Lebedun M: Mystery gas: An analysis of mass hysteria. J Health Soc Behav 15:44-50, 1974.
  • Mechanic D: Discussion of research on relations between stressful life events and episodes of physical illness, in Dohrenwend BS, Dohrenwend BP (eds): Stressful Life Events: Their Nature and Effects. New York, John Wiley& Sons, Inc, 1974.
  • Freedman, J.L., and Perlick, D. (1979). Crowding, contagion and laughter. Journal of Experimental Psychology, 15:295-303.
  • Freedman, J.L. (1982). Theories of Contagion as they relate to mass psychogenic illness. In M.J. Colligan, J.W. Pennebaker, and L.R. Murphy (eds.) Mass Psychogenic Illness, N.J: Erlbaum, 171-182.
  • Turner, R.H. and Killian, L.M.(1987). Collective Behavior (3rd ed.) NJ: Prentice-Hall.
  • Goodenough, O. R. and Dawkins, R. (1994). The "St. Jude" mind virus. Nature, 371:23-24 (ask Nature; they'd like you to rent a roughly 30 year old article for $8.99).
  • Jones, M.B., and Jones, D.R. (1995). Preferred pathways of behavioural contagion. Journal of Psychiatric Research, 29:193-209. [Danish twins study, more about criminality, also more about genetics vs contagion.]

Image credits: AI Art - Policeman in Leathery Squid Skin Leaking PVA Glue (set of 5) - 2022

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,

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.

Thursday, November 17, 2022

Everyone Likes Vanilla

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

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
Girl Smelling a Flower in Profile - Petr Kratochvil

So I ran it through the Stable Diffusion library at, "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,

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).

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,

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,

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,

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


Thursday, October 27, 2022

Advances in Olfactory Perception

Scientists use machine learning to predict smells based on brain activity in worms
Jan 2022,

Putting this here because they used graph theory aka network science to decode the otherwise cacophony of neuronal crosstalk involved in smelling.

Also, why C. elegans? It has only 302 neurons, that's why:

Chalasani's team set out to study how C. elegans neurons react to smelling each of five different chemicals: benzaldehyde (almond), diacetyl (popcorn), isoamyl alcohol (banana), 2-nonanone (cheese), and sodium chloride (salt).

The researchers engineered C. elegans so that each of their 302 neurons contained a fluorescent sensor that would light up when the neuron was active. 

By looking at basic properties of the datasets—such as how many cells were active at each time point—Chalasani and his colleagues couldn't immediately differentiate between the different chemicals. So, they turned to a mathematical approach called graph theory, which analyzes the collective interactions between pairs of cells: When one cell is activated, how does the activity of other cells change in response?

The algorithm was able to learn to differentiate the neural response to salt and benzaldehyde but often confused the other three chemicals.

via Salk Institute, Cold Spring Harbor Laboratory and UC San Diego: Javier J. How et al, Neural network features distinguish chemosensory stimuli in Caenorhabditis elegans, PLOS Computational Biology (2021). DOI: 10.1371/journal.pcbi.1009591

a highly detailed, macro shot of a human nose, 8k, depth of field

The art of smell: Research suggests the brain processes smell both like a painting and a symphony
Apr 2022,

"These findings reveal a core principle of the nervous system," using a model to simulate the workings of the early olfactory system. This is a reminder that the olfactory system is an ideal model for understanding the brain.

In their computer simulation, they found that centrifugal fibers switched between two different modes -- one worked on a specific instant in time, while the other worked on the neural patterns across time.

This is where I make a further interpretation, which might be incorrect, but it seems like one is for comparing a smell to the body's repository (is this good or bad for me? have I smelled this before? where? who was I with?) and the other mode is for comparing the smell against itself, over time, perhaps to learn whether it's getting stronger or weaker. One uses autobiographical, physiological memory, and the other uses basic chemotaxis. One ontogeny and the other phylogeny?

Anyway, another reminder by one of the authors that the olfactory system is a good model: "Computational approaches inspired by the circuits of the brain such as this have the potential to improve the safety of self-driving cars, or help computer vision algorithms more accurately identify and classify objects in an image." -Krishnan Padmanabhan, associate professor of Neuroscience at University of Rochester School of Medicine and Dentistry

via University of Rochester Medical Center: Zhen Chen et al, Top-down feedback enables flexible coding strategies in the olfactory cortex, Cell Reports (2022). DOI: 10.1016/j.celrep.2022.110545

Sniffing out the brain's smelling power
Oct 2022,

(Out of order but seemingly related to the above) Here's another way of thinking of the two processes to smelling -- We said mitral cells are what do the smelling, but mostly because those were the ones we could see. Tufted cells were harder to see, up until now -- they find that the mitral cells were faster, more discriminating, and more broadly-tuned. 

The authors think the mitral cells only enhance important smells, but the tufted cells are part of a background process for identity and intensity. 

via Cold Spring Harbor Laboratory: Honggoo Chae et al, Long-range functional loops in the mouse olfactory system and their roles in computing odor identity, Neuron (2022). DOI: 10.1016/j.neuron.2022.09.005

a straight smooth vertical tube with the texture of human skin, highly realistic, hyper-real, 4k, Octane render 

Researchers map mouse olfactory glomeruli using state-of-the-art techniques
Apr 2022,

While other research teams previously examined the organization of glomeruli in the olfactory bulb, so far they only identified the positions of a limited subset of these clusters. As a result, the relationship between the location of glomeruli and odor discrimination has been very difficult to infer.

They used a combination of single-cell RNA sequencing, spatial transcriptomics and machine learning techniques. This allowed them to create a map that outlined the brain regions where most of the sensory neurons in the mouse olfactory bulb sent odor-related information.

via University of Massachusetts Medical School, Broad Institute of Harvard and MIT, and Stanford University: I-Hao Wang et al, Spatial transcriptomic reconstruction of the mouse olfactory glomerular map suggests principles of odor processing, Nature Neuroscience (2022). DOI: 10.1038/s41593-022-01030-8

How mosquito brains encode human odor so they can seek us out
May 2022,

Of the two nerve centers, one responds to many smells including human odor, essentially saying, "Hey, look, there's something interesting nearby you should check out," while the other responds only to humans. Having two may help the mosquitos home in on their targets, the researchers suggest.

First genetically engineer mosquitos whose brains lit up when active, and then deliver human-flavored air (with decanal and undecanal).

"When I first saw the brain activity, I couldn't believe it—just two glomeruli (out of 60) were involved. That contradicted everything we expected, so I repeated the experiment several times, with more humans, more animals. I just couldn't believe it. It's so simple."

via Princeton: Carolyn McBride, Mosquito brains encode unique features of human odour to drive host seeking, Nature (2022). DOI: 10.1038/s41586-022-04675-4