It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Wednesday, December 24, 2025
How greener bus stops can help people beat the heat
UBC study finds it’s not just how hot it is outside—it’s how a place feels
A new University of British Columbia study published in Urban Climate finds that people waiting at bus stops they find visually pleasant are more likely to feel thermally comfortable during hot weather, even when physical heat levels are high.
In other words, how a place looks and feels can shape comfort alongside actual heat exposure.
“Our findings show that thermal comfort isn’t just about air temperature or shade,” said lead author Logan Steinharter, who conducted the research as a master’s student in UBC’s faculty of forestry. “How people perceive a space—its openness, greenery and overall look—can meaningfully influence how comfortable they feel, particularly under extreme heat.”
Aesthetics linked to thermal comfort
The research examined 60 bus stops across Denver, Colorado, a semi-arid city increasingly affected by extreme heat. Researchers combined on-site micrometeorological measurements, including air temperature, radiant heat, and physiological heat stress indices, with surveys of transit users, asking riders how hot or comfortable they felt and how visually pleasant they found each stop.
Visual appeal emerged as one of the strongest predictors of perceived thermal comfort, alongside standard heat measures. Riders were more likely to report feeling comfortable at bus stops they rated as visually pleasant, even when physical heat stress levels were high.
Even at hotter bus stops, people were more likely to feel comfortable if they liked what they were looking at. This didn’t reduce actual heat exposure, but it did change how the heat was experienced.
Greener stops feel more pleasant
The study also examined which features of bus stop environments were associated with higher aesthetic ratings. Bus stops with greater tree canopy cover and more visible vegetation were more likely to be rated as visually pleasant by transit users.
By contrast, conventional bus shelters alone were often rated lower in aesthetic appeal. The researchers caution that shelters still matter for heat protection, but that design and visual quality warrant further attention in transit planning.
“This highlights a design challenge, not a simple solution,” said senior author Dr. Melissa McHale, associate professor of urban ecology and sustainability at UBC. “Shelters are important, but design choices matter. The way infrastructure looks and feels can influence people’s experience of heat, even when physical exposure remains high.”
Implications for heat-resilient transit
As cities across North America grapple with rising temperatures and the need to keep public transit usable and equitable during heat waves, the findings point to the importance of integrating experiential design alongside physical cooling strategies.
“Green infrastructure doesn’t replace the need to reduce heat exposure,” said Dr. McHale, recently awarded a $1-million Wall Fellowship for research that aims to help B.C. communities adapt to a hotter, drier and more fire-prone future. “But it plays a meaningful role in shaping how people experience heat in everyday public spaces. If we want transit systems that are both climate-resilient and people-centred, we need to think beyond bare-bones infrastructure and consider the full experience of waiting for transit.”
The findings underscore that aesthetics alone won’t solve heat risk—but they can make public spaces feel more bearable during extreme heat.
Credit: Courtesy of Prakash Prashanth, Marlene Euchenhofer, et al
Aviation’s climate impact is partly due to contrails — condensation that a plane streaks across the sky when it flies through icy and humid layers of the atmosphere. Contrails trap heat that radiates from the planet’s surface , and while the magnitude of this impact is uncertain, several studies suggest contrails may be responsible for about half of aviation’s climate impact.
Pilots could conceivably reduce their planes’ climate impact by avoiding contrail-prone regions, similarly to making altitude adjustments to avoid turbulence. But to do so requires knowing where in the sky contrails are likely to form.
To make these predictions, scientists are studying images of contrails that have formed in the past. Images taken by geostationary satellites are one of the main tools scientists use to develop contrail identification and avoidance systems.
But a new study shows there are limits to what geostationary satellites can see. MIT engineers analyzed contrail images taken with geostationary satellites, and compared them with images of the same areas taken by low-Earth-orbiting (LEO) satellites. LEO satellites orbit the Earth at lower altitudes and therefore can capture more detail. However, since LEO satellites only snap an image as they fly by, they capture images of the same area far less frequently than geostationary (GEO) satellites, which continuously image the same region of the Earth every few minutes.
The researchers found that geostationary satellites miss about 80 percent of the contrails that appear in LEO imagery. Geostationary satellites mainly see larger contrails that have had time to grow and spread across the atmosphere. The many more contrails that LEO satellites can pick up are often shorter and thinner. These finer threads likely formed immediately from a plane’s engines and are still too small or otherwise not distinct enough for geostationary satellites to discern.
The study highlights the need for a multiobservational approach in developing contrail identification and avoidance systems. The researchers emphasize that both GEO and LEO satellite images have their strengths and limitations. Observations from both sources, as well as images taken from the ground, could provide a more complete picture of contrails and how they evolve.
“With more ‘eyes’ on the sky, we could start to see what a contrail’s life looks like,” says Prakash Prashanth, a research scientist in MIT’s Department of Aeronautics and Astronautics. “Then you can understand what are its radiative properties over its entire life, and when and why a contrail is climatically important.”
The new study appears today in the journal Geophysical Research Letters. The study’s MIT co-authors include first author and graduate student Marlene Euchenhofer, undergraduate Sydney Parke, Ian Waitz, theJerome C. Hunsaker Professor of Aeronautics and Astronautics and MIT’s vice president of research, along with Sebastian Eastham of Imperial College London.
Imaging backbone
Contrails form when the exhaust from planes meets icy, humid air, and the particles from the exhaust act as seeds on which water vapor collects and freezes into ice crystals. As a plane moves forward, it leaves a trail of condensation in its wake that starts as a thin thread that can grow and spread over large distances, lasting for several hours before dissipating.
When it persists, a contrail acts similar to an ice cloud and, as such, can have two competing effects: one in which the contrail is a sort of heat shield, reflecting some incoming radiation from the sun. On the other hand, a contrail can also act as a blanket, absorbing and reflecting back some of the heat from the surface. During the daytime, when the sun is shining, contrails can have both heat shielding and trapping effects. At night, the cloud-like threads have only a trapping, warming effect. On balance, studies have shown that contrails as a whole contribute to warming the planet.
There are multiple efforts underway to develop and test aircraft contrail-avoidance systems to reduce aviation’s climate-warming impact. And scientists are using images of contrails from space to help inform those systems.
“Geostationary satellite images are the workhorse of observations for detecting contrails,” says Euchenhofer. “Because they are at 36,000 kilometers above the surface, they can cover a wide area, and they look at the same point day and night so you can get new images of the same location every five minutes.”
But what they bring in rate and coverage, geostationary satellites lack in clarity. The images they take are about one-fifth the resolution of those taken by LEO satellites. This wouldn’t be a surprise to most scientists. But Euchenhofer wondered how different the geostationary and LEO contrail pictures would look, and what opportunities there might be to improve the picture if both sources could be combined.
“We still think geostationary satellites are the backbone of observation-based avoidance because of the spatial coverage and the high frequency at which we get an image,” she says. “We think that the data could be enhanced if we include observations from LEO and other data sources like ground-based cameras.”
Catching the trail
In their new study, the researchers analyzed contrail images from two satellite imagers: the Advanced Baseline Imager (ABI) aboard a geostationary satellite that is typically used to observe contrails and the higher-resolution Visible Infrared Radiometer Suite (VIIRS), an instrument onboard several LEO satellites.
For each month from December 2023 to November 2024, the team picked out an image of the contiguous United States taken by VIIRS during its flyby. They found corresponding images of the same location, taken at about the same time of day by the geostationary ABI. The images were taken in the infrared spectrum and represented in false color, which enabled the researchers to more easily identify contrails that formed during both the day and night. The researchers then worked by eye, zooming in on each image to identify, outline, and label each contrail they could see.
When they compared the images, they found that GEO images missed about 80 percent of the contrails observed in the LEO images. They also assessed the length and width of contrails in each image and found that GEO images mostly captured larger and longer contrails, while LEO images could also discern shorter, smaller contrails.
“We found 80 percent of the contrails we could see with LEO satellites, we couldn’t see with GEO imagers,” says Prashanth, who is the executive officer of MIT’s Laboratory for Aviation and the Environment (LAE). “That does not mean that 80 percent of the climate impact wasn’t captured. Because the contrails we see with GEO imagers are the bigger ones that likely have a bigger climate effect.”
Still, the study highlights an opportunity.
“We want to make sure this message gets across: Geostationary imagers are extremely powerful in terms of the spatial extent they cover and the number of images we can get,” Euchenhofer says. “But solely relying on one instrument, especially when policymaking comes into play, is probably too incomplete a picture to inform science and also airlines regarding contrail avoidance. We really need to fill this gap with other sensors.”
The team says other sensors could include networks of cameras on the ground that under ideal conditions can spot contrails as planes form them in real time. These smaller, “younger” contrails are typically missed by geostationary satellites. Once scientists have this ground-based data, they can match the contrail to the plane and use the plane’s flight data to identify the exact altitude at which the contrail appears. They could then track the contrail as it grows and spreads through the atmosphere, using geostationary images. Eventually, with enough data, scientists could develop an accurate forecasting model, in real time, to predict whether a plane is heading toward a region where contrails might form and persist, and how it could change its altitude to avoid the region.
“People see contrail avoidance as a near-term and cheap opportunity to attack one of the hardest-to-abate sectors in transportation,” Prashanth says. “We don’t have a lot of easy solutions in aviation to reduce our climate impact. But it is premature to do so until we have better tools to determine where in the atmosphere contrails will form, to understand their relative impacts and to verify avoidance outcomes. We have to do this in a careful and rigorous manner, and this is where a lot of these pieces come in.”
This work was supported in part by the U.S. Federal Aviation Administration Office
Necroprinting nozzle. The tip, made of a mosquito proboscis, is attached with resin.
Credit
c/o Changhong Cao
22-Dec-2025
Mosquitoes’ feeding tubes make ultrafine 3D-printing nozzlesMcGill University
Researchers in McGill’s Department of Mechanical Engineering and at Drexel University have developed an innovative manufacturing technique that makes female mosquito proboscides, or feeding tubes, into high-resolution 3D-printing nozzles. With its unique geometry, structure and mechanics, the proboscis enables printed line widths as fine as 20 microns, or a little smaller than a white blood cell. This is roughly twice as fine as what commercially available printing nozzles can currently produce.
The researchers named the process “3D necroprinting,” where a non-living biological microstructure is directly used as an advanced manufacturing tool. Potential applications include producing tiny scaffolds for cell growth or tissue engineering, printing cell-laden gels, as well as the delicate transfer of microscopic objects like semiconductor chips.
“High-resolution 3D printing and microdispensing rely on ultrafine nozzles, typically made from specialized metal or glass,” said study co-author Jianyu Li, Associate Professor and Canada Research Chair in Tissue Repair and Regeneration at McGill. “These nozzles are expensive, difficult to manufacture and generate environmental waste and health concerns.”
“Mosquito proboscides let us print extremely small, precise structures that are difficult or very expensive to produce with conventional tools. Since biological nozzles are biodegradable, we can repurpose materials that would otherwise be discarded,” added Changhong Cao of McGill, Assistant Professor and Canada Research Chair in Small-Scale Materials and Manufacturing and study co-author.
The study was led by McGill graduate student Justin Puma. He was involved in a previous study using a mosquito proboscis for biomimetic purposes that established a foundation for this research.
Biodegradable and reusable
To develop the nozzles, the researchers examined insect-derived micronozzles and identified the mosquito proboscis – a tiny, naturally evolved microneedle about half of the width of a human hair – as the optimal candidate. The proboscides were harvested from euthanized mosquitoes, sourced from ethically approved laboratory colonies used for biological research at partner institution Drexel University.
Under a microscope, the researchers carefully removed the mosquito’s feeding tube. They then attached this biological needle to a standard plastic dispenser tip using a small amount of resin. The researchers characterized the tips’ geometry and mechanical strength, measured their pressure tolerance and integrated them into a custom 3D-printing setup.
Once connected, the proboscis becomes the final opening through which the 3D printer emits material. The researchers have successfully printed high-resolution complex structures, including a honeycomb, a maple leaf and bioscaffolds that encapsulate cancer cells and red blood cells.
The idea of using biotic materials in advanced manufacturing was inspired by necrobotics research at Rice University. While searching for micronozzles, Cao was also in discussions with Drexel University researchers Megan Creighton and Ali Afify on a separate mosquito-related project. These conversations led the team to explore proboscides for 3D printing.
"Evolutions in bioprinting are helping medical researchers develop unique approaches to treatment. As we look to improve technology, we must also strive to innovate," said Creighton, study co-author and Assistant Professor of Chemical and Biological Engineering at Drexel.
“We found the mosquito proboscis can withstand repeated printing cycles as long as the pressures stay within safe limits. With proper handling and cleaning, a nozzle can be reused many times,” Cao said.
“By introducing biotic materials as viable substitutes to complex engineered components, this work paves the way for sustainable and innovative solutions in advanced manufacturing and microengineering,” Li added.
About the study
“3D Necroprinting: Leveraging biotic material as the nozzle for 3D printing,” by Justin Puma, Megan Creighton, Ali Afify, Jianyu Li, Changhong Cao et al, was published in Science Advances.
