Looking for aliens who might be looking for us
By Bob Sanders and Gail McCormick
Data from a massive search for cosmic radio emissions has allowed astronomers to look for technological signatures of extraterrestrial civilizations that might be looking for us.
The research is inspired by a technique that astronomers use to identify and study planets outside of our solar system called transit photometry. The technique uses sensitive telescopes to detect the dip in a star’s light as orbiting planets pass in front of the star from our line of sight. In this new search, astronomers looked for radio emissions from 20 nearby stars aligned with the plane of Earth’s orbit such that an alien species around those stars could see Earth pass in front of the sun with a telescope of their own.
“This region has been talked about before, but there has never been a targeted search of this region of the sky,” said graduate student Sofia Sheikh.
Using the Green Bank Telescope, the research team checked billions of frequencies for strong radio signals. Ultimately, Sheikh whittled an initial million radio spikes down to a couple hundred, most of which she eliminated as Earth-based human interference. The last four unexplained signals turned out to be from passing satellites.
“Now we know that there isn't anything as strong as our strongest radars beaming something at us,” said Sheikh.
‘Herbivores of the sea’ help keep coral reefs healthy
By Sam Sholtis
Selective fishing can disrupt the delicate balance between corals and algae in Caribbean coral reefs. Removing large parrotfish, which graze on algae like land mammals graze on grasses, can allow the algae to overtake the corals. Maintaining a healthy size distribution of parrotfishes in a sea floor ecosystem through smart fishing practices could help maintain reefs that are already facing decline due to climate change.
“Understanding how fishing impacts coral ecosystems will help us to protect this invaluable resource,” said Andrew A. Shantz, Eberly Postdoctoral Research Fellow.
Researchers set up three different enclosures with different-sized openings on the sea floor around corals in the protected Florida Keys. One enclosure allowed access to fish of any size, the second excluded the largest parrotfish, and the third excluded large and medium parrotfish.
“We found that by excluding large parrotfish, the algae grew four times faster,” said Shantz. “By excluding both large and medium parrotfish, the algae grew ten times faster. So, it’s the larger fish that keep the algae at bay. Unless we can develop and implement fishing strategies that maintain a healthy distribution of fish sizes—for example, a slot-based system with both minimum and maximum size restrictions—the corals in these regions are at risk.”
Herringbone pattern in plant cell walls critical to cell growth
By Gail McCormick
Plant cells tend to grow longer instead of wider due to the alternating angles of the many layers of cellulose that make up their cell walls, according to a new study that may have implications for biofuels research.
“It is generally thought that microtubules—structures that form the ‘skeleton’ of the cell—wrap around the cell like rings on a barrel, restricting growth in width,” said Ying Gu, associate professor of biochemistry and molecular biology. “We found that the story is more complicated than just rings on a barrel.”
Each layer in a cell wall is composed of proteins as well as cellulose microfibers, which are deposited by the cellulose synthase complex, with help from the protein CSI1, as the complex follows along a microtubule. The microfibers in a given layer are deposited at about a 60-degree angle compared to the microfibers in the previous layer, creating a herringbone pattern.
The researchers found that removing CSI1 resulted in the loss of the herringbone pattern and that pharmacological disruption of the herringbone pattern prevented cells from growing normally even in the presence of a growth hormone. These results suggest that CSI1 and the herringbone pattern are integral to cell growth in plants and that existing theories about cell growth are incomplete.
Compartments without borders
By Gail McCormick
A new laboratory method allows researchers to create compartments within a liquid that, like drops of oil in water, are separate but have no physical barrier between them. The method could help researchers understand how human cells use “membraneless compartments” to segregate and concentrate components for important biological functions.
“Disruption of these membraneless compartments has been implicated in diseases such as ALS, Alzheimer's, and Type II Diabetes,” said Gregory Mountain, graduate student in chemistry.
Membraneless compartments within cells form and dissolve as needed and result from the separation of molecules like proteins and RNA into different liquid phases. To create membraneless compartments in the lab, the researchers combined simplified charged polymers of repeating amino acids and/or nucleic acids in water.
As the charged polymers interacted, with opposite charges attracting, separate compartments formed in the liquid with no physical dividers. Combining four polymers allowed the researchers to produce droplets with two compartments as well as compartments within compartments. Combining six polymers produced droplets with three compartments.
“This straightforward method allows us to understand the basic chemistry of how multiphase compartments could form and dissolve within a cell,” said Mountain. “Eventually we hope to control when compartments appear and what types of molecules they contain.”
Including irregular time intervals improves animal movement studies
By Gail McCormick
Studies of animal movement and behavior—including those addressing disease spread and animal conservation—should monitor animals at both regular and irregular time points, according to a new study by Penn State statisticians.
“Tracking animals is one of the major methods of data collection in ecology, but there has been little to no work on the relative benefits of different sampling schemes,” said graduate student Elizabeth Eisenhauer. “In an ideal world, we could collect continuous or really fine-scale data about animal locations, but in reality researchers have to make choices to balance their resources.”
The researchers propose a regime called lattice and random intermediate point sampling (LARI), which involves collecting location data at regular intervals and also at a random time point between each of these intervals. Using three study systems that reflect different kinds of animal movement, they compared very fine-scale data—a gold standard or baseline—with a variety of less-frequent regular and LARI sampling regimes. In nearly every case, the LARI sampling regime provided more-accurate estimates of movement parameters than a regular sampling regime with the same number of data points.
“Using LARI is a relatively easy change for biologists to integrate into their own studies,” said Ephraim Hanks, associate professor of statistics.
The so-called ‘angel particle’ is still a mystery
By Sam Sholtis
A 2017 report of the discovery of a particular kind of Majorana fermion—the chiral Majorana fermion, referred to as the “angel particle”—is likely a false alarm. Majorana fermions are enigmatic particles that act as their own antiparticle. They are of immense interest to physicists because their unique properties could allow them to be used in the construction of a topological quantum computer.
“An important first step toward this distant dream of creating a topological quantum computer is to demonstrate definitive experimental evidence for the existence of Majorana fermions in condensed matter,” said Cui-Zu Chang, assistant professor of physics. “Over the past seven or so years, several experiments have claimed to show such evidence, but the interpretation of these experiments is still debated.”
A team of physicists led by Chang studied more than three dozen devices similar to the one used to produce the angel particle in the 2017 report. They found that the feature that was claimed to be the manifestation of the angel particle was unlikely to be induced by the existence of the angel particle.
“This is an excellent illustration of how science should work,” said Nitin Samarth, Downsbrough Department Head and professor of physics. “Extraordinary claims of discovery need to be carefully examined and reproduced.”
Malaria parasite lives on the edge
By Sam Sholtis
The malaria parasite expresses genes that code for the proteins it will need in later life stages but prevents these proteins from being made until they are needed. Having these mRNAs at the ready is risky: It’s energetically costly, and proteins made prematurely can cause the parasites to become noninfectious.
“The malaria parasite has a complex life cycle in which it is transmitted back and forth between its mosquito and human hosts,” said Scott Lindner, assistant professor of biochemistry and molecular biology. “The parasite can’t predict when these transmissions will happen, so it needs to be able to react quickly.”
The researchers used RNA sequencing and mass spectrometry–based proteomics to identify essentially all of the mRNAs and proteins in the parasite during the transmission from mosquito to human. They demonstrated that the parasites produce mRNAs for genes that they will need in the next stage of their life cycle but then actively repress their translation into proteins.
“Excitingly, we identified two separate translational repression programs that operate simultaneously,” said Lindner. “We are now trying to find how these translational repression programs are controlled in the parasite and if there are weaknesses that we can exploit in this risky strategy that we can use to push the parasite off the edge with new therapeutics.”