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Tiny water-walking bugs provide scientists with insights on how microplastics are pushed underwater

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Tiny water-walking bugs provide scientists with insights on how microplastics are pushed underwater

You may hardly feel a raindrop, but for some tiny insects, one drop can have an intense impact.
Mendowong Photography/Moment via Getty Images

Andrew Dickerson, University of Tennessee

Microplastics are tiny plastic particles that can cause big problems when they enter the water supply. One way my fluid dynamics lab explores microplastic movement is by studying how tiny water-walking insects are pushed underwater by raindrops.

Exposure to microplastic pollution can pose health risks, such as respiratory and digestive problems, increased risk of diabetes and disrupted sleep. But physicists like me can study how they move through water to learn how to clean them up.

Water striders are tiny insects that can walk on water. They’re abundant in humid, rainy areas, and some species go their entire lives without ever touching land. Raindrops can weigh more than 40 times a water strider, and during storms they occasionally strike striders directly. The drops form a tiny crater under the surface of the water that envelops the strider before jettisoning it out as the crater collapses back to the surface.

The water striders have strong exoskeletons that allow them to survive being hit by a raindrop. Because these insects are water-repellent and very lightweight, they usually bounce right back. But sometimes the raindrops will form a second, smaller crater right below the surface. The second crater usually forms from a large, fast drop.

If the water strider finds itself inside this second crater, it could get trapped under the water.

Four photos showing a raindrop colliding with the surface of the water, the first showing a dip below the surface in which a small, long-legged insect floats, the second showing the insect meeting the surface, and the third showing another small sip with the insect inside, and the fourth showing the insect submerged under the water.
Raindrops form two craters, the second of which can submerge striders.
Daren A. Watson and Andrew K. Dickerson, from the Proceedings of the National Academy of Sciences

In my lab’s latest study, we captured water striders from local ponds and released falling drops above their tanks. We used high-speed videography and image analysis to see how fast the insects submerged when the raindrops hit them.

My colleagues and I also measured the acceleration of the second, smaller crater. This crater retracts quickly – according to our measurements, 50 times the acceleration due to gravity. Water striders cannot support themselves inside this second bubble, as the surface they’re on moves upward so quickly, and they might fall underwater and become submerged. If that happens, the water striders make powerful swimming strokes to try to resurface.

Two illustrations show the process of a strider underwater using its legs to kick up to the water's surface.
Striders can often kick back up to the surface if they get submerged, unlike plastic particles.
Daren A. Watson and Andrew K. Dickerson, from the Proceedings of the National Academy of Sciences

Why it matters

Like water striders, microplastics are very light and often water-repellent. They tend to move on top of the water in a similar way, and raindrops can submerge them. When pollutants get submerged, they’re harder to clean up, and marine life might consume them.

Our research tells us that the second crater’s quick acceleration toward the water’s surface plays a big part in sinking tiny particles – water striders and microplastics alike.

Studying how small particles and organisms disperse in water could help scientists figure out how to prevent and mediate microplastic pollution.

What still isn’t known

Water striders are so water-repellent that they carry a bubble around them called a plastron when pushed underwater.

In the lab, the more times they are struck by drops before repelling away the water, the more likely water striders are to remain submerged for extended periods.

Raindrop impacts seem to deplete the plastron. We don’t yet know how many repeated impacts striders can tolerate and how chemical pollutants in waterways affect their resistance to submersion.

What’s next

Future work will replace the water striders in our experiments with floating particles that mimic microplastics, with a range of size, density and water-repellency. We expect larger particles to make the drops break apart upon contact, while the smaller particles will likely get carried into the air, or aerosolized, by the splash.

And the striders aren’t just good models for microplastic movement. Studying water striders’ legs as they swim could also help researchers design underwater robots.The Conversation

Andrew Dickerson, Assistant Professor of Mechanical, Aerospace and Biomedical Engineering, University of Tennessee

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

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Francis − a pope who has cared deeply for the poor and opened up the Catholic Church

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theconversation.com – Mathew Schmalz, Professor of Religious Studies, College of the Holy Cross – 2025-02-24 15:05:00

Francis − a pope who has cared deeply for the poor and opened up the Catholic Church

Pope Francis during the Palm Sunday Mass at St. Peter’s Square on April 2, 2023, in Vatican City.
Antonio Masiello/Getty Images

Mathew Schmalz, College of the Holy Cross

Pope Francis, who remains in critical condition and hospitalized as he battles pneumonia in both lungs, was elected pope on March 13, 2013, after the surprise resignation of Benedict XVI.

Prior to becoming pope, he was Jorge Mario Bergoglio, archbishop of Buenos Aires, and was the first person from the Americas to be elected to the papacy. He was also the first pope to choose Francis as his name, thus honoring St. Francis of Assisi, a 13th-century mystic whose love for nature and the poor have inspired Catholics and non-Catholics alike.

Pope Francis chose not to wear the elaborate clothing, like red shoes or silk vestments, associated with other popes. As a scholar of global Catholicism, however, I would argue that the changes Francis brought to the papacy were more than skin deep. He opened the church to the outside world in ways none of his predecessors had done before.

Care for the marginalized

Pope Francis reached out personally to the poor. For example, he turned a Vatican plaza into a refuge for the homeless, whom he called “nobles of the street.”

A smiling young man, dressed in black, poses for a photo.
The Argentinian Jorge Mario Bergoglio, ordained for the Jesuits in 1969 at the Theological Faculty of San Miguel.
Jesuit General Curia via Getty Images

He washed the feet of migrants and prisoners during the traditional foot-washing ceremony on the Thursday before Easter. In an unprecedented act for a pope, he also washed the feet of non-Christians.

He encouraged a more welcoming attitude toward gay and lesbian Catholics and invited transgender people to meet with him at the Vatican.

On other contentious issues, Francis reaffirmed official Catholic positions. He labeled homosexual behavior a “sin,” although he also stated that it should not be considered a crime. Francis criticized gender theory for “blurring” differences between men and women.

While he maintained the church’s position that all priests should be male, he made far-reaching changes that opened various leadership roles to women. Francis was the first pope to appoint a woman to head an administrative office at the Vatican. Also for the first time, women were included in the 70-member body that selects bishops and the 15-member council that oversees Vatican finances. Shortly before his death, he appointed an Italian nun, Sister Raffaella Petrini, as President of the Vatican City.

Pope Francis holding on to a railing as he greets people.
Pope Francis in St. Peter’s Square on April 18, 2022.
Stefano Spaziani/Mondadori Portfolio via Getty Images

Not shy of controversy

Some of Francis’ positions led to opposition in some Catholic circles.

One such issue was related to Francis’ embrace of religious diversity. Delivering an address at the Seventh Congress of Leaders of World and Traditional Religions in Kazakhstan in 2022, he said that members of the world’s different religions were “children of the same heaven.”

While in Morocco, he spoke out against conversion as a mission, saying to the Catholic community that they should live “in brotherhood with other faiths.” To some of his critics, however, such statements undermined the unique truth of Christianity.

During his tenure, the pope called for “synodality,” a more democratic approach to decision making. For example, synod meetings in November 2023 included laypeople and women as voting members. But the synod was resisted by some bishops who feared it would lessen the importance of priests as teachers and leaders.

In a significant move that will influence the choosing of his successor, Pope Francis appointed more cardinals from the Global South. But not all Catholic leaders in the Global South followed his lead on doctrine. For example, African bishops publicly criticized Pope Francis’ December 2023 ruling that allowed blessings of individuals in same sex couples.

His most controversial move was limiting the celebration of the Mass in the older form that uses Latin. This reversed a decision made by Benedict XVI that allowed the Latin Mass to be more widely practiced.

Traditionalists argued that the Latin Mass was an important – and beautiful – part of the Catholic tradition. But Francis believed that it had divided Catholics into separate groups who worshiped differently.

This concern for Catholic unity also led him to discipline two American critics of his reforms, Bishop Joseph Strickland of Tyler, Texas, and Cardinal Raymond Burke. Most significantly, Carlo Maria Viganò, the former Vatican ambassador, or nuncio, to the United States was excommunicated during Francis’ tenure for promoting “schism.”

Recently, Pope Francis also criticized the Trump administration’s efforts to deport migrants. In a letter to US Bishops, he recalled that Jesus, Mary and Joseph had been emigrants and refugees in Egypt. Pope Francis also argued that migrants who enter a country illegally should not be treated as criminals because they are in need and have dignity as human beings.

Writings on ‘the common good’

In his official papal letters, called encyclicals, Francis echoed his public actions by emphasizing the “common good,” or the rights and responsibilities necessary for human flourishing.

Several people seated in a row watch as the pope washes the feet of one of them.
Pope Francis washes the foot of a man during the foot-washing ritual at a refugee center outside of Rome on March 24, 2016.
L’Osservatore Romano/Pool Photo via AP

His first encyclical in 2013, Lumen Fidei, or “The Light of Faith,” sets out to show how faith can unite people everywhere.

In his next encyclical, Laudato Si’, or “Praise Be to You,” Francis addressed the environmental crisis, including pollution and climate change. He also called attention to unequal distribution of wealth and called for an “integral ecology” that respects both human beings and the environment.

His third encyclical in 2020, Fratelli Tutti, or “Brothers All,” criticized a “throwaway culture” that discards human beings, especially the poor, the unborn and the elderly. In a significant act for the head of the Catholic Church, Francis concluded by speaking of non-Catholics who have inspired him: Martin Luther King Jr., Desmond Tutu and Mahatma Gandhi.

In his last encyclical, Dilexit Nos, or “He Loved Us,” he reflected on God’s Love through meditating on the symbol of the Sacred Heart that depicts flames of love coming from Jesus’ wounded heart that was pierced during the crucifixion.

Francis also proclaimed a special “year of mercy” in 2015-16. The pope consistently argued for a culture of mercy that reflects the love of Jesus Christ, calling him “the face of God’s mercy.”

A historic papacy

Francis’ papacy has been historic. He embraced the marginalized in ways that no pope had done before. He not only deepened the Catholic Church’s commitment to the poor in its religious life but also expanded who is included in its decision making.

The pope did have his critics who thought he went too far, too fast. And whether his reforms take root depends on his successor. Among many things, Francis will be remembered for how his pontificate represented a shift in power in the Catholic Church away from Western Europe to the Global South, where the majority of Catholics now live.The Conversation

Mathew Schmalz, Professor of Religious Studies, College of the Holy Cross

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The murder rate in Venezuela has fallen − but both Trump and Maduro are wrong about why

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theconversation.com – Rebecca Hanson, Assistant Professor of Latin American Studies, Sociology and Criminology, University of Florida – 2025-02-24 07:41:00

The murder rate in Venezuela has fallen − but both Trump and Maduro are wrong about why

Members of government-backed militias take part in a march in Caracas, Venezuela, on Jan. 7, 2025.
AP Photo/Matias Delacroix

Rebecca Hanson, University of Florida

The body of former Venezuelan army officer Ronald Ojeda was found on Feb. 19, 2024, in a suitcase buried under 5 feet of concrete. Ojeda, accused by Venezuela of plotting against the government, had gone missing nine days earlier, when men dressed as police broke into his apartment in the Chilean capital of Santiago and dragged him away.

Following a yearlong investigation, authorities in Chile have now pointed the finger at the Venezuelan gang Tren de Aragua, claiming members carried out the assassination at the behest of that country’s president, Nicolás Maduro.

It comes as the relationship between Maduro’s government and criminal gangs is under increased scrutiny, both among regional governments in Latin America and in the United States.

Conservative media outlets in the U.S. and right-leaning groups such as the Heritage Foundation have accused Maduro of sending gang members into the U.S. to destabilize the country.

President Donald Trump has even suggested that Maduro successfully reduced crime by exporting gang members to the U.S. “Crime is down in Venezuela by 67% because they’re taking their gangs and their criminals and depositing them very nicely into the United States,” he told supporters in April 2024.

According to data from the Venezuelan Ministry of Health, shared with me by scholar of Venezuelan politics Dorothy Kronick, homicide rates have indeed come down in recent years. And this trend is confirmed by the Venezuelan Observatory of Violence.

The fall in homicide rates has coincided with Maduro successfully consolidating his authoritarian rule in Venezuela. And explanations of the drop in crime tend to imply that it is the result of the government co-opting and controlling gangs. Some observers have even referred to Venezuela as a “narcostate,” suggesting that drug trafficking in the country is an organized venture between top officials and criminal groups.

I have studied crime, violence and policing in Venezuela since 2011 and know that this narrative is at best oversimplistic, at worst outright mistruth. As I explore in my new book, “Policing the Revolution: The Transformation of Coercive Power and Venezuela’s Security Landscape During Chavismo,” the case of Venezuela is not one of government control over criminal groups. Rather, it is characterized by an unstable and volatile relationship between the government and multiple competing armed actors, including gangs and the police.

Violent, but becoming less so

Falling homicide rates should not mask the fact that Venezuela is still plagued by violence. Since the mid-2000s it has been ranked as one of the most violent countries in the world.

Former President Hugo Chávez was never able to get a handle on crime, particularly violent crime, which increased exponentially under his government. The trend continued during Maduro’s first years in office after Chávez’s death in 2013.

However, all available evidence suggests that Venezuela’s homicide rate has declined since reaching a peak in 2016 – by around 42%.

But there’s no evidence this is because the government is “offshoring” criminals.

Maduro’s own explanation for this decline portrays the government as handily controlling criminals by means of incredibly lethal police raids carried out between 2015 and 2019. In short, Maduro claims that the police have effectively “wiped out” criminal groups.

Competing police forces …

But rather than “wiping out” criminal organizations, the Maduro government has instead maintained volatile relationships with many armed groups, including gangs, nonstate paramilitary groups and even the country’s own police forces.

These relationships have produced significant conflict and dysfunction within state institutions. This is clear when looking at institutions presumed to be synonymous with state control, such as the police.

Chávez’s and Maduro’s governments put more police and soldiers in the streets. They created security institutions, such as the Policía Nacional Bolivariana, or Bolivarian National Police.

However, rapid growth of the security apparatus, amid competing approaches, has generated more conflict than coordination.

Police officers and police reformers I interviewed referred to state security policies and the changes they produced as akin to Frankenstein’s monster – an aberration rapidly outpacing the creator’s ability to control it.

What they mean is the government had created new security institutions so quickly that it is unable to supervise and control them. As one former police officer and Chavista politician told me: “Our challenge now is how to manage the monster we created.”

People in army fatigues and holding guns stand in front of a building.
Members of the National Guard take part in an anti-gang security operation in Caracas on July 13, 2015.
Federico Parra/AFP via Getty Images

State policies have also generated significant distrust between the police and the government, and among different police forces.

This distrust has even resulted in police forces coming to blows with each other in the streets on multiple occasions. On Feb. 19, 2020, a section of the Prados del Este highway in Caracas was shut down as officers from Venezuela’s National Police and the country’s investigative police brandished weapons, shoving, punching and wrestling each other to the ground.

… cooperating gangs

It is, as such, highly unlikely that falling homicide rates are the result of policing. Indeed, I interviewed over 200 police officers while conducting research for my book, and most believed that the government’s policing initiatives contributed to crime and violence rather than reducing it.

A more plausible explanation for falling homicide figures is that Maduro’s policies have resulted in more consolidated relationships between criminal groups themselves.

Maduro’s government has built relationships with gangs, but this doesn’t necessarily imply control over them. Since 2013 the government has negotiated pacts with some of the country’s largest gangs, including a gang confederation led by the infamous El Koki in Caracas and the Belén gang in the state of Miranda.

The government agreed to tolerate illicit activities within certain areas and prohibit police from entering gang territory. In exchange, gangs agreed to reduce killings and other highly visible crimes such as kidnapping. As my book and previous research with Verónica Zubillaga, Francisco Sánchez and Leonard Gómez shows, these pacts allowed gangs to consolidate control over territory and illicit markets.

Gangs also negotiated agreements among themselves in case the government pacts fell through. For example, they agreed to divide territory and markets to avoid future conflict and share resources such as weapons and ammunition. This produced less conflict between gangs and less disruption in illicit markets, resulting in fewer homicides.

When pacts have ruptured in the past, the spectacularly violent confrontations that ensued between gangs and the police have shown gangs’ capacity to resist government intervention. Still, the overall effect of pacts and gang consolidation has been a reduction in homicides.

As one neighbor living in gang territory put it: “Before, gangs confronted each other; they killed each other. Now they don’t. Now they are growing.”

‘Mother of all infuriations’

Relationships between the government and various nonstate armed groups, including gangs, have generated enormous discontent within police forces.

As one police officer explained in an interview, these pacts represented the “mother of all infuriations.” For many officers, the goverment’s pacts with other armed groups is tantamount to its sponsorship of criminal activities.

And this discontent has produced sporadic violent confrontations. Even when government-gang pacts are in place, the government has been unable to keep police forces from entering gang territory and engaging in deadly shootouts.

Certainly from the outside, it may look like Maduro’s government has co-opted gangs for political purposes. And with the U.S. government adding Tren de Aragua to its list of global terrorist groups, that could put Venezuela in danger of being labeled a “state sponsor of terrorism.”

However, the Ojeda case in Chile should not be taken as evidence that stable and strong ties exist between Maduro’s government and criminal groups – at least not yet.

Instead, authoritarian survival in Venezuela for now seems to depend on volatile relationships between multiple and competing armed groups that collaborate temporarily with the government when their diverse interests overlap.The Conversation

Rebecca Hanson, Assistant Professor of Latin American Studies, Sociology and Criminology, University of Florida

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As Pennsylvania inches toward legalizing recreational cannabis, lawmakers propose selling it in state-owned dispensaries similar to state liquor stores

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theconversation.com – Daniel J. Mallinson, Associate Professor of Public Policy and Administration, Penn State – 2025-02-24 07:37:00

As Pennsylvania inches toward legalizing recreational cannabis, lawmakers propose selling it in state-owned dispensaries similar to state liquor stores

Advocates believe Pennsylvania and Hawaii may be the next fronts in recreational cannabis legalization.
Spencer Platt/Getty Images

Daniel J. Mallinson, Penn State

After a long, largely successful march over 25 years to liberalize cannabis laws in the United States, the movement had a tough election in 2024.

Legalization ballot measures failed in Florida, North Dakota and South Dakota. In Arkansas, votes on legalization were not even counted due to litigation over the measure. The only successful measures were passed in Nebraska. While they are being implemented, litigation on the programs is pending.

Federally, many of President Donald Trump’s nominees in key posts at the Department of Health and Human Services, Department of Justice and Drug Enforcement Administration have made strong anti-cannabis statements. This may not bode well for the effort started by President Joe Biden to reschedule marijuana as a less dangerous drug.

So, what is the future of cannabis legalization in the United States?

As political scientist Lee Hannah and I argued in our 2024 book “Green Rush,” the states are central to the story of cannabis legalization in the United States.

In fact, advocates are looking to places such as Pennsylvania and Hawaii in 2025 as the next fronts in recreational legalization.

Let’s zoom in on Pennsylvania.

Pennsylvania is a middling adopter

Pennsylvania is following about the same trajectory with adult-use recreational legalization as it did with medical marijuana. It is not an innovator but also not a laggard.

When Pennsylvania adopted medical marijuana in 2016, 23 states had already done so.

The political environment is very different in 2025 than 2016, however, which raises the difficulty of passing a bill that makes recreational marijuana use legal, even in a state where legalization is popular.

In 2016, Pennsylvania’s General Assembly was controlled completely by Republicans, and the governor was a Democrat. Now, the Democrats hold a single-seat majority in the House that erodes every time there is a vacancy. Republicans still control the Senate, and Democrat Josh Shapiro is the governor.

A major key to medical cannabis legalization passing in 2016 was Republican state Sen. Mike Folmer’s advocacy within his caucus. Without a Republican champion, it may not have passed.

For legalization of recreational cannabis, state Sen. Dan Laughlin has been the clear Republican champion. He has been working with Democratic state Sen. Sharif Street of Philadelphia to build support and find a policy design that works for Republicans and Democrats.

But Republican Senate leadership has remained cool to the idea. Senate President Pro Tempore Kim Ward is not a supporter and has been pushing the governor to get more involved.

“If (Shapiro) wants something done, he needs to lead on it,” Ward said. “He can’t throw an idea out there, which he did last year, and say, ‘Let the legislature figure it out, I’ll sign it.’”

Expected revenues likely to fall short

For his part, Shapiro has included projected revenues from legalization in his budget proposals since assuming office in 2023.

This year, he projected an even greater first-year haul – US$536 million – if recreational cannabis is legalized. This estimate includes revenue from initial licensing fees.

The assumptions going into these projections aren’t clear. And while cannabis legalization has been lucrative for state revenues in other places, revenues often fall short of what was projected during legalization debates.

Importantly, Pennsylvania is now nearly surrounded by states with legal recreational cannabis. That includes New York, New Jersey, Delaware, Maryland and Ohio, but not West Virginia.

It is no secret that, in the words of Shapiro, “Pennsylvanians who want to buy cannabis are just driving across the border to one of our neighbors.”

Research on how ideas and policies spread makes clear the intense pressure that comes as a state’s neighbors adopt a policy, especially one with major economic ramifications.

But pressure does not determine the result. The internal politics of a state can still block a policy from being adopted.

State-owned cannabis stores

The biggest challenge for legalization in Pennsylvania will be navigating those internal political dynamics – especially finding a compromise that can be supported by both Democrats and Republicans.

Public safety is often raised as a concern during legalization debates. To counter this point, Democrats in the state House have proposed selling legal cannabis in state-owned stores, just like how liquor and some wine is sold in Pennsylvania now.

Man and woman crossing street in front of a store with sign that reads: Fine Wine & Good Spirits
The Pennsylvania Liquor Control Board operates nearly 600 Fine Wine & Good Spirits stores across the state.
Paul Weaver/SOPA Images/LightRocket via Getty Images

No other states do this, and it puts the state on potentially very slippery ground with the federal government, which still considers cannabis to be completely prohibited. State-run stores mean that states are providing a banned substance directly to citizens. That is a significant step further than creating an infrastructure to regulate private entities that are breaking federal law.

Moreover, there has been a decades-long effort in Pennsylvania by conservatives to privatize the state liquor stores. It seems odd that Republicans would support using that model to create a recreational cannabis market.

If privately owned but government-regulated dispensaries are used, there is significant debate among cannabis policy experts as to whether it is wise to give existing medical dispensaries first dibs on recreational licenses. Doing so allows states to open their recreational programs very quickly.

The drawback, however, is that large, multistate operators such as Trulieve, which runs dispensaries in several states, are positioned to gain a significant share of the market. This is why the industry supports the approach to initial licensing. Legalization advocates such as Shaleen Title, however, are very concerned about the development of a “Big Cannabis” that resembles Big Tobacco, with oligopoly control by a few large companies.

Social equity is another challenge facing recreational legalization that was not a major factor in medical. In short, social equity is about ensuring members of marginalized communities that were previously targets of the War on Drugs somehow benefit from the cannabis industry now that it is legal. While the issue was central to recreational legalization debates in neighboring New York and New Jersey, there’s been little public discussion of this particular facet of Pennsylvania’s proposed legalization plans.

While a middling adopter of medical cannabis, Pennsylvania’s program also had important innovations in research and social equity that influenced legislators in other states. Whatever happens in the commonwealth around recreational cannabis may well do so again, especially as fewer states have the option of adopting recreational cannabis via the ballot.

Finding a legislative solution to these thorny issues in a divided government could thus push legalization forward. Or the recent winds against legalization could stall the effort in Pennsylvania, at least for now.

Read more of our stories about Philadelphia and Pennsylvania.The Conversation

Daniel J. Mallinson, Associate Professor of Public Policy and Administration, Penn State

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