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Machines can’t always take the heat − two engineers explain the physics behind how heat waves threaten everything from cars to computers

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Machines can’t always take the heat − two engineers explain the physics behind how heat waves threaten everything from cars to computers

Extreme heat can affect how well machines function, and the fact that many machines give off their own heat doesn’t help.
AP Photo/Abdeljalil Bounhar

Srinivas Garimella, Georgia Institute of Technology and Matthew T. Hughes, Massachusetts Institute of Technology (MIT)

Not only people need to stay cool, especially in a summer of record-breaking heat waves. Many machines, including cellphones, data centers, cars and airplanes, become less efficient and degrade more quickly in extreme heat. Machines generate their own heat, too, which can make hot temperatures around them even hotter.

We are engineering researchers who study how machines manage heat and ways to effectively recover and reuse heat that is otherwise wasted. There are several ways extreme heat affects machines.

No machine is perfectly efficient – all machines face some internal friction during operation. This friction causes machines to dissipate some heat, so the hotter it is outside, the hotter the machine will be.

Cellphones and similar devices with lithium ion batteries stop working as well when operating in climates above 95 degrees Farenheit (35 degrees Celsius) – this is to avoid overheating and increased stress on the electronics.

Cooling designs that use innovative phase-changing fluids can help keep machines cool, but in most cases heat is still ultimately dissipated into the air. So, the hotter the air, the harder it is to keep a machine cool enough to function efficiently.

Plus, the closer together machines are, the more dissipated heat there will be in the surrounding area.

Deforming materials

Higher temperatures, either from the weather or the excess heat radiated from machinery, can cause materials in machinery to deform. To understand this, consider what temperature means at the molecular level.

At the molecular scale, temperature is a measure of how much molecules are vibrating. So the hotter it is, the more the molecules that make up everything from the air to the ground to materials in machinery vibrate.

When metal is heated, the molecules in it vibrate faster and the space between them moves farther apart. This leads the metal to expand.

As the temperature increases and the molecules vibrate more, the average space between them grows, causing most materials to expand as they heat up. Roads are one place to see this – hot concrete expands, gets constricted and eventually cracks. This phenomenon can happen to machinery, too, and thermal stresses are just the beginning of the problem.

A close-up of a street with several cracks running through the asphalt and a white paint stripe.
Streets crack under heat because higher temperatures create more space between vibrating molecules, causing the material to expand and deform.
Priscila Zambotto/Moment via Getty Images

Travel delays and safety risks

High temperatures can also change the way oils in your car’s engine behave, leading to potential engine failures. For example, if a heat wave makes it 30 degrees F (16.7 degrees C) hotter than normal, the viscosity – or thickness – of typical car engine oils can change by a factor of three.

Fluids like engine oils become thinner as they heat up, so if it gets too hot, the oil may not be thick enough to properly lubricate and protect engine parts from increased wear and tear.

Additionally, a hot day will cause the air inside your tires to expand and increases the tire pressure, which could increase wear and the risk of skidding.

Airplanes are also not designed to take off at extreme temperatures. As it gets hotter outside, air starts to expand and takes up more space than before, making it thinner or less dense. This reduction in air density decreases the amount of weight the plane can support during flight, which can cause significant travel delays or flight cancellations.

Battery degradation

In general, the electronics contained in devices like cellphones, personal computers and data centers consist of many kinds of materials that all respond differently to temperature changes. These materials are all located next to each other in tight spaces. So as the temperature increases, different kinds of materials deform differently, potentially leading to premature wear and failure.

Lithium ion batteries in cars and general electronics degrade faster at higher operating temperatures. This is because higher temperatures increase the rate of reactions within the battery, including corrosion reactions that deplete the lithium in the battery. This process wears down its storage capacity. Recent research shows that electric vehicles can lose about 20% of their range when exposed to sustained 90-degree Farenheit weather.

Data centers, which are buildings full of servers that store data, dissipate significant amounts of heat to keep their components cool. On very hot days, fans must work harder to ensure chips do not overheat. In some cases, powerful fans are not enough to cool the electronics.

A white room filled with large black data servers, which look like lockers.
Data centers, which store large quantities of data, can overheat and require large-scale cooling − which adds to their environmental footprint.
AP Photo/Julie Carr Smyth

To keep the centers cool, incoming dry air from the outside is often first sent through a moist pad. The water from the pad evaporates into the air and absorbs heat, which cools the air. This technique, called evaporative cooling, is usually an economical and effective way to keep chips at a reasonable operating temperature.

However, evaporative cooling can require a significant amount of water. This issue is problematic in regions where water is scarce. Water for cooling can add to the already intense resource footprint associated with data centers.

Struggling air conditioners

Air conditioners struggle to perform effectively as it gets hotter outside – just when they’re needed the most. On hot days, air conditioner compressors have to work harder to send the heat from homes outside, which in turn disproportionally increases electricity consumption and overall electricity demand.

An apartment building wall with closed windows, an AC unit in each.
Heat waves can stress air conditioners, which are already working hard to dissipate heat.
AP Photo/Paul White

For example, in Texas, every increase of 1.8 degrees F (1 degree C) creates a rise of about 4% in electricity demand.

Heat leads to a staggering 50% increase in electricity demand during the summer in hotter countries, posing serious threats of electricity shortages or blackouts, coupled with higher greenhouse gas emissions.

How to prevent heat damage

Heat waves and warming temperatures around the globe pose significant short- and long-term problems for people and machines alike. Fortunately, there are things you can do to minimize the damage.

First, ensure that your machines are kept in an air-conditioned, well-insulated space or out of direct sunlight.

Second, consider using high-energy devices like air conditioners or charging your electric vehicle during off-peak hours when fewer people are using electricity. This can help avoid local electricity shortages.

Reusing heat

Scientists and engineers are developing ways to use and recycle the vast amounts of heat dissipated from machines. One simple example is using the waste heat from data centers to heat water.

Waste heat could also drive other kinds of air-conditioning systems, such as absorption chillers, which can actually use heat as energy to support coolers through a series of chemical- and heat-transferring processes.

In either case, the energy needed to heat or cool something comes from heat that is otherwise wasted. In fact, waste heat from power plants could hypothetically support 27% of residential air-conditioning needs, which would reduce overall energy consumption and carbon emissions.

Extreme heat can affect every aspect of modern life, and heat waves aren’t going away in the coming years. However, there are opportunities to harness extreme heat and make it work for us.The Conversation

Srinivas Garimella, Professor of Mechanical Engineering, Georgia Institute of Technology and Matthew T. Hughes, Postdoctoral Associate, Massachusetts Institute of Technology (MIT)

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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As Gaza ceasefire takes hold, Israeli forces turn to Jenin – a regular target seen as a center of Palestinian resistance

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theconversation.com – Maha Nassar, Associate Professor in the School of Middle Eastern and North African Studies, University of Arizona – 2025-01-22 17:42:00

Maha Nassar, University of Arizona

Just two days after a shaky ceasefire took hold in the Gaza Strip, Israel on Jan. 21, 2025, launched a large-scale incursion of the Jenin refugee camp in the West Bank.

Soldiers raided hundreds of homes in the West Bank city in what the Israeli military called a “counterterrorism” operation, aiming to reassert control there. Many analysts have suggested the raid is an attempt by Israeli Prime Minister Benjamin Netanyahu to appease far-right members of his coalition who oppose the ceasefire deal.

Whatever the motive, the offensive has been devastating for many of the camp’s residents. The Israeli military has destroyed infrastructure, closed entrances to local hospitals and forcibly displaced about 2,000 families, according to reports on the raids. As it was, life for inhabitants of the densely populated camp – home to some 24,000 Palestinian refugees – was hard. The West Bank director of UNRWA, the U.N. agency overseeing refugees, recently described camp conditions as “nearly uninhabitable.”

The focus of the latest Israeli operation is not new. The Jenin refugee camp, on the western edge of the town of Jenin in the north of the occupied West Bank, has often experienced violence between Israeli soldiers and Palestinian militants.

That violence has escalated since the Oct. 7, 2023, attacks, when Hamas gunmen led an incursion into Israel in which around 1,200 people were killed. The camp has faced repeated large-scale military operations by Israeli forces, including drone strikes, ground raids, and airstrikes that have caused widespread destruction. Meanwhile, Israeli settlers have torched Palestinian cars and properties, with 64 such attacks in the Jenin area alone since Oct. 7, 2023. Last December, the Palestinian Authority, which coordinates with Israel to oversee security in parts of the West Bank, also attacked local militants.

These events have deepened political tensions and worsened the economic and humanitarian crises in the West Bank. According to the U.N., more than a quarter of the 800-plus Palestinians killed in the West Bank since Oct. 7 attack have come from the Jenin district; several Israeli civilians have also been killed in the West Bank during the same period.

As a scholar of Palestinian history, I see this recent episode as the latest chapter in a much longer history of Palestinian displacement and defiance of Israeli occupation. Understanding this history helps explain why the Jenin camp in particular has become a target of Israeli offensives and a center of Palestinian militant resistance.

Camp conditions

Jenin, an agricultural town that dates back to ancient times, has long been a center of Palestinian resistance. During the 1948 Arab-Israeli War, Arab fighters successfully pushed back Israeli attempts to capture the town.

At the end of that war, the town became a refuge for some of the hundreds of thousands of Palestinian refugees who fled or were expelled from lands that became part of Israel. Jenin, along with the hilly interior of Palestine known as the West Bank, was annexed by Jordan.

The U.N. Relief and Works Agency established the Jenin camp in 1953, just west of the city. Since then, the agency has provided basic services to the camp’s residents, including food, housing and education.

Camp conditions have always been difficult. In the early years of the camp, refugees had to stand in long lines to receive food rations, and for decades their cramped homes lacked electricity or running water.

The Jenin camp soon became the poorest and most densely populated of the West Bank’s 19 refugee camps. And given its location near the “Green Line” – the armistice line that serves as Israel’s de facto border – camp residents who were expelled from northern Palestine could actually see the homes and villages from which they were expelled. But they were prevented from returning to them.

The rise of militancy

Since 1967, Jenin, along with the rest of the West Bank, has been occupied by the Israeli military.

The Israeli occupation of Jenin compounded the difficulties of these refugees. As stateless Palestinians, they couldn’t return home. But under Israeli occupation, they couldn’t live freely in Jenin, either. Human rights groups have long documented what has been described as “systematic oppression,” which includes discriminatory land seizures, forced evictions and travel restrictions.

Seeing no other path forward, many of the camp’s young refugees turned to armed resistance.

In the 1980s, groups such as the Black Panthers, which was affiliated with the Palestinian nationalist Fatah organization, launched attacks on Israeli targets in an effort to end the occupation and liberate their ancestral lands. Throughout the first intifada – a Palestinian uprising lasting from 1987 to 1993 – the Israeli army raided the Jenin camp many times, seeking to arrest members of militant groups. In the process, Israeli forces also sometimes demolished family members’ homes and arrested relatives. Such acts of apparent collective punishment reinforced the idea for many Palestinians that the Israeli occupation could only be ended by force.

A group of men in headscarves stand in front of flags and banners. One holds a pistol up in the air.
Members of the militant group Fatah in Jenin in 1991.
Esaias Baitel/Gamma-Rapho via Getty Images)

The Oslo peace process of the 1990s – which consisted of a series of meetings between Israeli government and Palestinian representatives – led some former militants to hope that the occupation could be ended through negotiations instead. But Jenin’s camp residents remained marginalized in the West Bank and sealed off from Israel, seeing little improvement in their lives, even after the transfer of administrative powers from Israel to the Palestinian Authority in 1995.

Independent projects like the The Freedom Theatre provided some relief to the camp’s refugee children, but it was not enough to overcome the grinding poverty or the violence they faced from Israeli soldiers and settlers. By the time the second intifada broke out in 2000, many of the camp’s teenagers joined militant groups. That included Freedom Theatre co-founder Zakaria Zubeidi, who joined the Fatah-affiliated Al-Aqsa Martyrs Brigade. Like the youth of the 1980s, they, too, concluded that only armed resistance would bring an end to the occupation.

A cycle of violence?

In April 2002, the Israeli army invaded the Jenin camp, hoping to put an end to such armed groups. There were fierce clashes between Israeli soldiers and young Palestinian men in the camp, solidifying Jenin’s reputation among Palestinians as “the capital of the resistance.”

The lack of progress on peace talks since then, Israel’s settlement building on occupied land – deemed illegal under international law – and the inclusion of hard-line Israeli politicians in the government have exacerbated resentment in the camp. Polls show Palestinians increasingly support armed resistance.

Seeking to protect the camp from Israeli incursions, in 2021 a group of local residents formed the Jenin Brigades. While its founder was affiliated with Palestinian Islamic Jihad, the group quickly drew in militants from various political factions. Members acquired weapons, patrolled the streets and fought off Israeli military incursions. By 2022, they had declared parts of the camp to be “liberated” from the Israeli occupation.

Seemingly alarmed by the increase in militancy and the stockpiling of weapons in the camp, Israel dramatically stepped up its raids in 2022. It was during such a raid that Palestinian American journalist Shireen Abu Akleh was killed by an Israeli soldier.

On July 3, 2023, the Israeli military again invaded Jenin, withdrawing after two days of heavy aerial bombardment and a ground invasion that killed 12 Palestinians and wounded over 100.

The latest offensive could well surpass that death toll, with at least 10 killed in the first day of fighting. But the militancy associated with the camp was built on decades of resistance and defiance to occupation that Israel has had little success in extinguishing. Similarly this time, I believe, such militancy within the camp will only increase with the latest deaths and destruction.

This article is an updated version of a story that was first published by The Conversation on July 5, 2023.The Conversation

Maha Nassar, Associate Professor in the School of Middle Eastern and North African Studies, University of Arizona

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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What is seditious conspiracy, which is among the most serious crimes Trump pardoned?

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theconversation.com – Amy Cooter, Director of Research, Academic Development and Innovation at the Center on Terrorism, Extremism and Counterterrorism, Middlebury – 2025-01-22 15:12:00

The Jan. 6, 2021, storming of the Capitol was the result of a planned conspiracy to disrupt the government, prosecutors alleged.
AP Photo/John Minchillo

Amy Cooter, Middlebury

Several of the highest-profile figures in the Jan. 6, 2021, insurrection were charged with, and convicted of, the crime of seditious conspiracy, which is defined as the act of getting together with other people to overthrow the government. They were among the roughly 1,500 people involved in the insurrection who were pardoned or had their prison sentences commuted by Donald Trump on his first day in office.

Seditious conspiracy is a serious crime of conspiring to overthrow the government or stop its normal functioning. Historically, seditious conspiracy has been difficult to successfully prosecute.

In 2009, for example, a state judge ruled that prosecutors had failed to provide sufficient evidence for members of the Michigan Hutaree militia to go to trial on that charge. Certain militia members had been accused of plotting violence against police officers. While some members faced other charges for their actions, the judge determined that a plot against law enforcement was not sufficient to support charges of attempting to overthrow the government.

In contrast, the U.S. Department of Justice charged 18 people associated with the Jan. 6 attack on the U.S. Capitol with that crime, asserting that they had intended to “oppose by force the lawful transfer of presidential power” or had committed other actions that would undermine the entire system of government.

Of those 18, four pleaded guilty, and 10 were found guilty at trial. The remaining four were found not guilty of seditious conspiracy but were convicted of other crimes that were related to the insurrection.

Capitol entry not required

Oath Keepers militia leader Stewart Rhodes’ seditious conspiracy conviction was especially significant because, unlike some other defendants, Rhodes did not physically enter the Capitol building. He was instead in “the restricted area of Capitol grounds,” according to a Justice Department statement.

His conviction was based in part on his communications, including text messages, both before Jan. 6 and on the day itself. Prosecutors successfully argued that these communications were part of a broader conspiracy to disrupt the election certification by organizing and encouraging others to participate in more direct action.

Two men walk in front of a group of masked men with the Washington Monument in the background.
Proud Boys members Joseph Biggs, left, and Ethan Nordean, right with megaphone, walk toward the U.S. Capitol in Washington, D.C., on Jan. 6, 2021.
AP Photo/Carolyn Kaster

Militias respond to convictions – and clemency

Many observers believed successful prosecutions for these charges sent a strong message that violence against a democratically elected government was not acceptable.

Scholars of militia activity like me saw a period of relative quiet through much of Joe Biden’s presidency, which was, in part, likely due to the consequences the Jan. 6 defendants faced.

Some groups, however, continued social media discussions of their beliefs that the 2020 election had been “stolen,” as Trump continues to falsely claim, and which was used as justification by militia members for their attack. Trump himself said publicly he thought the defendants were unjustly persecuted and promised to pardon them if and when he returned to power.

The full effect that the pardons will have on militia actors and related groups in coming years is uncertain: Will the pardons send the message to all Americans that political violence is acceptable, or at least that it can be overlooked or forgiven if the right political figures are in power?The Conversation

Amy Cooter, Director of Research, Academic Development and Innovation at the Center on Terrorism, Extremism and Counterterrorism, Middlebury

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Ozempic and similar weight loss drugs may lower risk of 42 health conditions, but also pose risks

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theconversation.com – Ziyad Al-Aly, Clinical Epidemiologist, Washington University in St. Louis – 2025-01-22 14:11:00

The research shows the health effects of these drugs are significant and wide-ranging.
Mario Tama via Getty Images News

Ziyad Al-Aly, Washington University in St. Louis

Several years ago, a little-known drug named Ozempic – previously used only to treat diabetes – emerged as a promising new drug for weight management.

The Food and Drug Administration’s approval of Ozempic in 2021 for weight loss treatment ushered in a new era for the class of drugs called glucagon-like peptide-1 agonists, or GLP-1.

Today, GLP-1 drugs, including Wegovy, Mounjaro and Zepbound, have become household names and key tools in the fight against obesity: 1 in 8 American adults say they have used a GLP-1 drug, and forecasts show that by 2030, 1 in 10 Americans will likely be using these medications.

Now, research from my lab and others suggests that GLP-1 drugs could help treat dozens of other ailments as well, including cognitive issues and addiction problems. However, my colleagues and I also found previously unidentified risks.

I am a physician-scientist and I direct a clinical epidemiology center focused on addressing public health’s most urgent questions. My team works to address critical knowledge gaps about COVID-19, long COVID, influenza, vaccines, effectiveness and risks of commonly used drugs, and more.

On Jan. 20, 2025, my team published a study of more than 2.4 million people that evaluated the risks and benefits of GLP-1 drugs across 175 possible health outcomes. We found that these drugs lowered risks of 42 health outcomes, nearly a quarter of the total that we analyzed. These include neurocognitive disorders such as Alzheimer’s disease and dementia, substance use and addiction disorders, clotting disorders and several other conditions.

Unfortunately, we also found that GLP-1 drugs come with significant side effects and increase the risk of 19 health conditions we studied, such as gastrointestinal issues, kidney stones and acute pancreatitis, in which the pancreas becomes inflamed and dysfunctional.

Initially, GLP-1 drugs were developed to treat diabetes.

Cognitive benefits

One of the most important health benefits we found was that the GLP-1 drugs lowered the risk of neurodegenerative disorders, including Alzheimer’s disease and dementia. These findings align with other research, including evidence from preclinical studies showing that these drugs may reduce inflammation in the brain and enhance the brain’s ability to form and strengthen connections between its cells, improving how they communicate with one another. These effects contribute to mitigating cognitive decline.

Two other key studies have shown that patients treated with a GLP-1 drug for diabetes had a lower risk of dementia.

All of these studies strongly point to a potential therapeutic use of GLP-1 drugs in treatment of the cognitive decline. Ongoing randomized trials – the gold standard for evaluating new uses of drugs – are looking at the effects of GLP-1 drugs in early Alzheimer’s disease, with results expected later in 2025.

Curbing addiction and suicidal ideation

GLP-1 drugs have also demonstrated potential in reducing risks of several substance use disorders such as those involving alcohol, tobacco, cannabis, opioids and stimulants. This may be due to the ability of these drugs to modulate reward pathways, impulse control and inflammatory processes in the brain.

The effectiveness of GLP-1 drugs in curbing addictive behavior may explain their spectacular success in treating obesity, a chronic disease state that many have suggested is indeed a food addiction disorder.

Our study demonstrated a reduced risk of suicidal thoughts and self-harm among people using GLP-1 drugs. This finding is particularly significant given earlier reports of suicidal thoughts and self-injury in people using GLP-1 drugs. In response to those reports, the European Medicines Agency conducted a review of all available data and concluded that there was no evidence of increased risk of suicidality in people using GLP-1 drugs.

Now at least two studies, including our own, show that GLP-1 drugs actually reduce the risk of suicidality.

Other benefits

In addition to the well-documented effects of GLP-1 drugs in reducing risks of adverse cardiovascular and kidney outcomes, our study shows a significant effect in reducing risk of blood clotting as well as deep vein thrombosis and pulmonary embolism.

One puzzling finding in our study is the reduced risk of infectious diseases such as pneumonia and sepsis. Our data complements another recent study that came to a similar conclusion showing that GLP-1 drugs reduced risk of cardiovascular death and death due to infectious causes, primarily COVID-19.

This is especially important since COVID-19 is regarded as a significant cardiovascular risk factor. Whether GLP-1 drugs completely offset the increased risk of cardiovascular disease associated with COVID-19 needs to be thoroughly evaluated.

GLP-1 drugs may also be useful in treating fatty liver disease and conditions ranging from asthma to chronic obstructive pulmonary disease, sleep apnea, osteoarthritis, depression and eye disorders.

Some doctors are prescribing GLP-1 drugs to help with fertility issues.

Risks and challenges

Despite their broad therapeutic potential, GLP-1 drugs are not without risks.

Gastrointestinal issues, such as nausea, vomiting, constipation and gastroesophageal reflux disease are among the most common adverse effects associated with GLP-1 drugs.

Our study also identified other risks, including low blood pressure, sleep problems, headaches, formation of kidney stones, and gall bladder disease and diseases associated with the bile ducts. We also saw increased risks of drug-induced inflammation of the kidneys and pancreas – both serious conditions that can result in long-term health problems. These findings underscore the importance of careful monitoring in people who are taking GLP-1 medications.

A significant challenge with using GLP-1 drugs is the high rates at which patients stop using them, often driven by their exorbitant cost or the emergence of adverse effects. Discontinuation can lead to rapid weight gain.

That’s a problem, because obesity is a chronic disease. GLP-1 drugs provide effective treatment but do not address the underlying causes of obesity and metabolic dysfunction. As a result, GLP-1 drugs need to be taken long term to sustain their effectiveness and prevent rebound weight gain.

In addition, many questions remain about the long-term effectiveness and risks of these drugs as well as whether there are differences between GLP-1 formulations. Addressing these questions is critical to guide clinical practice.The Conversation

Ziyad Al-Aly, Clinical Epidemiologist, Washington University in St. Louis

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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