APIs, or application programming interfaces, are the gateways to the digital world. They link a wide array of software applications and systems. APIs facilitate communication between different software systems, and so power everything from social media – think of the share buttons on webpages – to e-commerce transactions.

At a simple level, APIs are like electrical sockets. A software application that you’re using, say the playback controls for a video on a webpage, is like an appliance. The system that provides data or services that the application needs, say YouTube, is like the electrical grid. The API, in this example the YouTube Player API^[1], is like the standard electrical outlet that lets any appliance plug in to the grid.

APIs are not really so simple, though. Another analogy is a restaurant. The customer is the software application, the chef is the data or service, and the waiter is the API. The waiter brings the customer the menu, which lists available dishes – i.e., options for accessing data or service – and then brings the customer’s request to the chef.

APIs rely on defined rules and protocols that ensure accurate data exchange and effective collaboration. There are APIs for specific uses and software developer preferences.

APIs power various applications and services across many diverse industries. Facebook, Instagram and Twitter, now rebranded as X, let users share their content across these social media platforms. By leveraging their social media credentials, users can log into websites, weather apps and games to simplify their online experiences. Amazon and PayPal depend on APIs for secure payment processing and efficient order fulfillment. Navigation services like Google Maps leverage APIs to provide real-time location data and accurate directions. Even voice-activated smart assistants like Amazon’s Alexa and Google Assistant use APIs to manage and control smart home devices.

Who has access to an API also matters. For example, in March 2023, X began charging a wider range of users for access to its data API^[2], which lets users collect large numbers of tweets to see what people are tweeting about. Businesses use the API for market and competitive research. But many people with limited resources, like developers of some free apps and social science researchers^[3], also rely on it.

APIs are also playing a role in making artificial intelligence widely available. For example, Google^[4], Microsoft^[5] and OpenAI^[6] provide APIs for software developers to incorporate AI in their products.

As APIs continue to shape the digital landscape, developers face challenges. Ensuring the security and privacy of data exchanged through APIs is paramount, given their integration into critical systems. As APIs evolve, managing their complex ecosystems and making sure old programs can use new APIs will be a considerable task.

Biomedical implants – such as pacemakers, breast implants and orthopedic hardware like screws and plates to replace broken bones – have improved patient outcomes across a wide range of diseases. However, many implants fail^[1] because the body rejects them, and they need to be removed because they no longer function and can cause pain or discomfort.

An immune reaction called the foreign body response^[2] – where the body encapsulates the implant in sometimes painful scar tissue – is a key driver of implant rejection. Developing treatments that target the mechanisms driving foreign body responses could improve the design and safety of biomedical implants.

I am a biomedical engineer^[3] who studies why the body forms scar tissue around medical devices. Along with my colleagues Dharshan Sivaraj^[4], Jagan Padmanabhan^[5] and Geoffrey Gurtner^[6], we wanted to learn more about what causes foreign body responses. In our research, recently published in the journal Nature Biomedical Engineering, we identified a gene^[7] that appears to drive this reaction because of the increased stress implants put on the tissues surrounding them.

Mechanics of implant rejection

Researchers hypothesize that foreign body responses are triggered by the chemical and material composition of the implant. Just as a person can tell the difference between touching something soft like a pillow versus something hard like a table, cells can tell when there are changes to the softness or stiffness of the tissues surrounding them as a result of an implant.

The increased mechanical stress^[8] on those cells sends a signal to the immune system that there is a foreign body present. Immune cells activated by mechanical pressure respond by building a capsule made of scar tissue around the implant in an attempt to shield it off. The more severe the immune reaction, the thicker the capsule. This protects the body from getting an infection from injuries like a splinter in your finger.

All biomedical implants cause some level of foreign body response and are surrounded by at least a small capsule. Some people have very strong reactions that result in a large, thick capsule that constricts around the implant, impeding its function and causing pain. Between 10% to 30% of implants^[9] need to be removed because of this scar tissue. For example, a neurostimulator could trigger the formation of a dense capsule of scar tissue that inhibits electrical stimulation^[10] from properly reaching the nervous system.

To understand why the immune systems of some people build thick capsules around implants while others do not, we gathered capsule samples from 20 patients whose breast implants were removed – 10 who had severe reactions, and 10 who had mild reactions. By genetically analyzing the samples, we found that a gene called RAC2^[11] was highly expressed in samples taken from patients with severe reactions but not in those with mild reactions. This gene is found only in immune cells^[12], and it codes for a member of a family of proteins^[13] involved in cell growth and structure.

Because this protein seemed to be linked to a lot of the downstream reactions that lead to foreign body responses, we decided to explore how RAC2 affects the formation of capsules. We found that immune cells activate RAC2 along with other proteins in response to mechanical stress^[14] from implants. These proteins summon additional immune cells to the area that combine into a massive clump^[15] to attack a large invader. These combined cells spit out fibrous proteins like collagen that form scar tissue.

To confirm RAC2’s role in foreign body responses, we artificially stimulated the mechanical signaling proteins surrounding silicone implants surgically placed in mice. This stimulation produced a severe and humanlike foreign body response in the mice. In contrast, blocking RAC2 resulted in an up to threefold reduction^[17] in foreign body responses.

These findings suggest that activating mechanical stress pathways triggers immune cells with RAC2 to generate severe foreign body responses. Blocking RAC2 in immune cells may significantly reduce this reaction.

Developing new treatments

Implant failure is conventionally treated by using biocompatible materials^[18] that the body can better tolerate, such as certain polymers. These don’t completely remove the risk of foreign body reactions, however.

My colleagues and I believe that treatments that target the pathways associated with RAC2 could potentially mitigate or prevent free body responses. Heading off this reaction would help improve the effectiveness and safety of medical implants.

Because only immune cells express RAC2^[19], a drug designed to block only that gene would theoretically target only immune cells without affecting other cells in the body. Such a drug could also be administered via injection or even coated onto an implant to minimize side effects.

A complete understanding of the molecular mechanisms driving foreign body responses would be the final frontier in developing truly bio-integrative medical devices that could integrate with the body with no problems for the recipient’s entire life span.

Flesh-eating bacteria sounds like the premise of a bad horror movie, but it’s a growing – and potentially fatal – threat to people.

In September 2023, the Centers for Disease Control and Prevention issued a health advisory^[1] alerting doctors and public health officials of an increase in flesh-eating bacteria cases that can cause serious wound infections.

I’m a professor^[2] at the Indiana University School of Medicine, where my laboratory^[3] studies microbiology and infectious disease^[4]. Here’s why the CDC is so concerned about this deadly infection – and ways to avoid contracting it.

What does ‘flesh-eating’ mean?

There are several types of bacteria that can infect open wounds and cause a rare condition called necrotizing fasciitis^[5]. These bacteria do not merely damage the surface of the skin – they release toxins that destroy the underlying tissue, including muscles, nerves and blood vessels. Once the bacteria reach the bloodstream, they gain ready access to additional tissues and organ systems. If left untreated, necrotizing fasciitis can be fatal, sometimes within 48 hours.

The bacterial species group A Streptococcus^[6], or group A strep, is the most common culprit behind necrotizing fasciitis. But the CDC’s latest warning points to an additional suspect, a type of bacteria called Vibrio vulnificus^[7]. There are only 150 to 200 cases^[8] of Vibrio vulnificus in the U.S. each year, but the mortality rate is high, with 1 in 5 people succumbing to the infection.

How do you catch flesh-eating bacteria?

Vibrio vulnificus primarily lives in warm seawater but can also be found in brackish water – areas where the ocean mixes with freshwater. Most infections in the U.S. occur in the warmer months, between May and October^[9]. People who swim, fish or wade in these bodies of water can contract the bacteria through an open wound or sore.

Vibrio vulnificus can also get into seafood harvested from these waters, especially shellfish like oysters. Eating such foods raw or undercooked can lead to food poisoning^[10], and handling them while having an open wound can provide an entry point for the bacteria to cause necrotizing fasciitis. In the U.S., Vibrio vulnificus is a leading cause of seafood-associated fatality^[11].

Why are flesh-eating bacteria infections rising?

Vibrio vulnificus is found in warm coastal waters around the world. In the U.S., this includes southern Gulf Coast states. But rising ocean temperatures due to global warming are creating new habitats for this type of bacteria, which can now be found along the East Coast as far north as New York and Connecticut^[12]. A recent study^[13] noted that Vibrio vulnificus wound infections increased eightfold between 1988 and 2018 in the eastern U.S.

Climate change^[14] is also fueling stronger hurricanes and storm surges, which have been associated with spikes in flesh-eating bacteria infection cases.

Aside from increasing water temperatures, the number of people who are most vulnerable to severe infection^[15], including those with diabetes^[16] and those taking medications that suppress immunity, is on the rise.

What are symptoms of necrotizing fasciitis? How is it treated?

Early symptoms^[17] of an infected wound include fever, redness, intense pain or swelling at the site of injury. If you have these symptoms, seek medical attention without delay. Necrotizing fasciitis can progress quickly^[18], producing ulcers, blisters, skin discoloration and pus.

Treating flesh-eating bacteria^[19] is a race against time. Clinicians administer antibiotics directly into the bloodstream to kill the bacteria. In many cases, damaged tissue needs to be surgically removed to stop the rapid spread of the infection. This sometimes results in amputation^[20] of affected limbs.

Researchers are concerned that an increasing number of cases are becoming impossible to treat because Vibrio vulnificus has evolved resistance to certain antibiotics^[21].

How do I protect myself?

The CDC offers several recommendations to help prevent infection^[22].

People who have a fresh cut, including a new piercing or tattoo, are advised to stay out of water that could be home to Vibrio vulnificus. Otherwise, the wound should be completely covered with a waterproof bandage.

People with an open wound should also avoid handling raw seafood or fish. Wounds that occur while fishing, preparing seafood or swimming should be washed immediately and thoroughly with soap and water.

Anyone can contract necrotizing fasciitis, but people with weakened immune systems are most susceptible to severe disease^[23]. This includes people taking immunosuppressive medications or those who have pre-existing conditions such as liver disease, cancer, HIV or diabetes.

It is important to bear in mind that necrotizing fasciitis presently remains very rare^[24]. But given its severity, it is beneficial to stay informed.

Curious Kids^[1] is a series for children of all ages. If you have a question you’d like an expert to answer, send it to This email address is being protected from spambots. You need JavaScript enabled to view it.^[2]. Why does a plane look and feel like it’s moving more slowly than it actually is? – Finn F., age 8, Concord, Massachusetts A passenger jet flies^[3] at about 575 mph once it’s at cruising altitude. That’s nearly nine times faster than a car might typically be cruising on the highway. So why does a plane in flight look like it’s just inching across the sky?I am an aerospace educator^[4] who relies on the laws of physics when teaching about aircraft. These same principles of physics help explain why looks can be deceiving when it comes to how fast an object is moving.Moving against a featureless backgroundIf you watch a plane accelerating toward takeoff, it appears to be moving very quickly. It’s not until the plane is in the air and has reached cruising altitude that it appears to be moving very slowly. That’s because there is often no independent reference point when the plane is in the sky.A reference point is a way to measure the speed of the airplane. If there are no contrails^[5] or clouds surrounding it, the plane is moving against a completely uniform blue sky. This can make it very hard to perceive just how fast a plane is moving. And because the plane is far away, it takes longer for it to move across your field of vision compared to an object that is close to you. This further creates the illusion that it is moving more slowly than it actually is.These factors explain why a plane looks like it’s going more slowly than it is. But why does it feel that way, too?A passenger’s perception on the planeA plane feels like it’s traveling more slowly than it is because, just like when you look up at a plane in the sky, as a passenger on a plane, you have no independent reference point. You and the plane are moving at the same speed, which can make it difficult to perceive your rate of motion relative to the ground beneath you. This is the same reason why it can be hard to tell that you are driving quickly on a highway that is surrounded only by empty fields with no trees.

Watching the speed of a plane’s shadow can help you assess how quickly a plane is moving. Saul Loeb/AFP via GettyImages^[6] However, there are a couple of ways you might be able to understand just how fast you are moving.Can you see the plane’s shadow^[7] on the ground? It can give you perspective on how fast the plane is moving relative to the ground. If you are lucky enough to spot it, you will be amazed at how fast the plane’s shadow passes over buildings and roads. You can get a real sense of the 575 mph average speed of a cruising passenger plane. Another way to understand how fast you are moving is to note how fast thin, spotty cloud cover moves over the wing. This reference point gives you another way to “see” or perceive your speed. Remember though, that clouds aren’t typically stationary^[8]; they’re just moving very slow relative to the plane. Although it can be difficult to discern just how fast a plane is actually moving, using reference points to gain perspective can help tremendously.Has your interest in aviation been sparked? If so, there are a lot of great career opportunities in aeronautics^[9].Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to This email address is being protected from spambots. You need JavaScript enabled to view it.^[10]. Please tell us your name, age and the city where you live.And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Uncommon Courses^[1] is an occasional series from The Conversation U.S. highlighting unconventional approaches to teaching. Title of course:The Design of Coffee: An Introduction to Chemical EngineeringWhat prompted the idea for the course?In 2012, my colleague professor Tonya Kuhl and I were drinking coffee and brainstorming how to improve our senior-level laboratory course in chemical engineering. Tonya looked at her coffee and suggested, “How about we have the students reverse-engineer a Mr. Coffee drip brewer to see how it works?” A light bulb went off in my head, and I said, “Why not make a whole course about coffee to introduce lots of students to chemical engineering?” And that’s what we did. We developed The Design of Coffee as a freshman seminar for 18 students in 2013, and, since then, the course has grown to over 2,000 general education students per year at the University of California, Davis.

A student uses a microscope to look at coffee beans in The Design of Coffee lab. UC Davis What does the course explore?The course focus is hands-on experiments with roasting, brewing and tasting in our coffee lab. For example, students measure the energy they use while roasting to illustrate the law of conservation of energy^[2], they measure how the pH of the coffee^[3] changes after brewing to illustrate the kinetics of chemical reactions, and they measure how the total dissolved solids^[4] in the brewed coffee relates to time spent brewing to illustrate the principle of mass transfer^[5]. The course culminates in an engineering design contest, where the students compete to make the best-tasting coffee using the least amount of energy. It’s a classic engineering optimization problem, but one that is broadly accessible – and tasty.Why is this course relevant now?Coffee plays a huge role in culture^[6], diet^[7] and the U.S.^[8] and global economy^[9]. But historically, relatively little academic work has focused on coffee. There are entire academic programs on wine and beer at many major universities, but almost none on coffee.

Many students who don’t like coffee develop a taste for it over the course of the class. UC Davis The Design of Coffee helps fill a huge unmet demand because students are eager to learn about the beverage that they already enjoy. Perhaps most surprisingly, many of our students enter the course professing to hate coffee, but by the end of the course they are roasting and brewing their own coffee beans at home.What’s a critical lesson from the course?Many students are shocked to learn that black coffee can have fruity, floral or sweet flavors^[10] without adding any sugar or syrups. The most important lesson from the course is that engineering is really a quantitative way to think about problem-solving. For example, if the problem to solve is “make coffee taste sweet without adding sugar,” then an engineering approach provides you with a tool set to tackle that problem quantitatively and rigorously. What materials does the course feature?Tonya and I originally self-published our lab manual, The Design of Coffee: An Engineering Approach^[11], to keep prices low for our students. Now in its third edition, it has sold more than 15,000 copies and has been translated to Spanish^[12], with Korean and Indonesian translations on the way.What will the course prepare students to do?Years ago, a student in our class told the campus newspaper, “I had no idea there was an engineering way to think about coffee!” Our main goal is to teach students that there is an engineering way to think about anything. The engineering skills and mindset we teach equally prepare students to design a multimillion-dollar biofuel refinery, a billion-dollar pharmaceutical production facility or, most challenging of all, a naturally sweet and delicious $3 cup of coffee. Our course is the first step in preparing students to tackle these problems, as well as new problems that no one has yet encountered.

In an exciting milestone for lunar scientists around the globe^[1], India’s Chandrayaan-3 lander^[2] touched down 375 miles (600 km)^[3] from the south pole of the Moon^[4] on Aug. 23, 2023.

In just under 14 Earth days, Chandrayaan-3 provided scientists with valuable new data and further inspiration to explore the Moon^[5]. And the Indian Space Research Organization^[6] has shared these initial results^[7] with the world.

While the data from Chandrayaan-3’s rover^[8], named Pragyan, or “wisdom” in Sanskrit, showed the lunar soil^[9] contains expected elements such as iron, titanium, aluminum and calcium, it also showed an unexpected surprise – sulfur^[10].

Planetary scientists like me^[11] have known that sulfur exists in lunar rocks and soils^[12], but only at a very low concentration. These new measurements imply there may be a higher sulfur concentration than anticipated.

Pragyan has two instruments that analyze the elemental composition of the soil – an alpha particle X-ray spectrometer^[13] and a laser-induced breakdown spectrometer^[14], or LIBS^[15] for short. Both of these instruments measured sulfur in the soil near the landing site.

Sulfur in soils near the Moon’s poles might help astronauts live off the land one day, making these measurements an example of science that enables exploration.

Geology of the Moon

There are two main rock types^[16] on the Moon’s surface^[17] – dark volcanic rock and the brighter highland rock. The brightness difference^[18] between these two materials forms the familiar “man in the moon^[19]” face or “rabbit picking rice” image to the naked eye.

Scientists measuring lunar rock and soil compositions in labs on Earth have found that materials from the dark volcanic plains tend to have more sulfur^[22] than the brighter highlands material.

Sulfur mainly comes from^[23] volcanic activity. Rocks deep in the Moon contain sulfur, and when these rocks melt, the sulfur becomes part of the magma. When the melted rock nears the surface, most of the sulfur in the magma becomes a gas that is released along with water vapor and carbon dioxide.

Some of the sulfur does stay in the magma and is retained within the rock after it cools. This process explains why sulfur is primarily associated with the Moon’s dark volcanic rocks.

Chandrayaan-3’s measurements of sulfur in soils are the first to occur on the Moon. The exact amount of sulfur cannot be determined until the data calibration is completed.

The uncalibrated data^[24] collected by the LIBS instrument on Pragyan suggests that the Moon’s highland soils near the poles might have a higher sulfur concentration than highland soils from the equator and possibly even higher than the dark volcanic soils.

These initial results give planetary scientists like me^[25] who study the Moon new insights into how it works as a geologic system. But we’ll still have to wait and see if the fully calibrated data from the Chandrayaan-3 team confirms an elevated sulfur concentration.

Atmospheric sulfur formation

The measurement of sulfur is interesting to scientists for at least two reasons. First, these findings indicate that the highland soils at the lunar poles could have fundamentally different compositions, compared with highland soils at the lunar equatorial regions. This compositional difference likely comes from the different environmental conditions between the two regions – the poles get less direct sunlight.

Second, these results suggest that there’s somehow more sulfur in the polar regions. Sulfur concentrated here could have formed^[26] from the exceedingly thin lunar atmosphere.

The polar regions of the Moon receive less direct sunlight and, as a result, experience extremely low temperatures^[27] compared with the rest of the Moon. If the surface temperature falls, below -73 degrees C (-99 degrees F), then sulfur from the lunar atmosphere could collect on the surface in solid form – like frost on a window.

Sulfur at the poles could also have originated from ancient volcanic eruptions^[28] occurring on the lunar surface, or from meteorites containing sulfur that struck the surface and vaporized on impact.

Lunar sulfur as a resource

For long-lasting space missions, many agencies have thought about building some sort of base on the Moon^[29]. Astronauts and robots could travel from the south pole base to collect, process, store and use naturally occurring materials like sulfur on the Moon – a concept called in-situ resource utilization^[30].

In-situ resource utilization means fewer trips back to Earth to get supplies and more time and energy spent exploring. Using sulfur as a resource, astronauts could build solar cells and batteries that use sulfur, mix up sulfur-based fertilizer and make sulfur-based concrete for construction^[31].

Sulfur-based concrete^[32] actually has several benefits compared with the concrete normally used in building projects on Earth^[33].

For one, sulfur-based concrete hardens and becomes strong within hours rather than weeks, and it’s more resistant to wear^[34]. It also doesn’t require water in the mixture, so astronauts could save their valuable water for drinking, crafting breathable oxygen and making rocket fuel.

While seven missions^[35] are currently operating on or around the Moon, the lunar south pole region^[36] hasn’t been studied from the surface before, so Pragyan’s new measurements will help planetary scientists understand the geologic history of the Moon. It’ll also allow lunar scientists like me to ask new questions about how the Moon formed and evolved.

For now, the scientists at Indian Space Research Organization are busy processing and calibrating the data. On the lunar surface, Chandrayaan-3 is hibernating through the two-week-long lunar night, where temperatures will drop to -184 degrees F (-120 degrees C). The night will last until September 22.

There’s no guarantee that the lander component of Chandrayaan-3, called Vikram, or Pragyan will survive the extremely low temperatures, but should Pragyan awaken, scientists can expect more valuable measurements.