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Smiling is the quintessential facial expression. The simple gesture can communicate honesty, friendship, and positive intent. But as basic and important as smiling is to social creatures like ourselves, it's surprisingly easy to screw up. A misfiring grin can manufacture feelings of unease and distrust.

This conundrum prompts a question: What physical characteristics produce "good" and "bad" smiles? A team of researchers at the University of Minnesota just published a study with some answers.

To uncover those answers, Assistant Professor of Psychology and Statistics Nathaniel E. Helwig and his team took their research out of the lab, venturing to "The Great Minnesota Get Together," the Minnesota State Fair. Setting up shop in the presence of prize-winning swine, carnival attractions, and food stands selling anything and everything fried on-a-stick, they recruited subjects of all ages and backgrounds, avoiding the WEIRD people that plague most psychology studies. The 802 participants who took part in the study were given an iPad loaded with a custom application. The app prompted each subject to rate fifteen random smile animations for their effectiveness, genuineness, and pleasantness.

There were 27 smiles for which data was analyzed. Each was altered based on three parameters: the mouth angle, the smile extent, and the amount of dental show (see figure below).

Helwig et al. / PLoS ONE

Caffeine is the most widely consumed psychoactive drug in the world. Hundreds of millions of people are technically junkies, imbibing that morning brew simply to stave off the fatiguing effects of caffeine withdrawal.

As caffeine is so widely consumed, scientists regularly study the stimulant. (After all, many of them are self-professed junkies, as well, and so nurture a personal interest.) Caffeine boosts athletic performance. Caffeine attenuates symptoms of depression. Caffeine raises blood pressure. The effects are endless.

Yet, an arena that has surprisingly escaped noticeable study is caffeine's link to male infertility. A group of Italian researchers recently filled the information gap with a systematic review published to the Nutrition Journal.

After pouring through the published research, the reviewers turned up 28 relevant studies featuring nearly 20,000 subjects. They then scrutinized each study to uncover caffeine's effects on semen quality, sperm DNA, and the time required to conceive.

A team of scientists from the University of Illinois has uncovered the world's oldest fossil mushroom. Lead author Sam Heads and his colleagues dubbed the specimen Gondwanagaricites magnificus, naming it for the ancient supercontinent Gondwana and the fossil's "magnificent" preservation.

The discovery is detailed in PLoS ONE.

Estimated at between 113 and 120 million years old, G. magnificus is at least 14 million years older than the prior record-holder, but it stands out for more than just its age. Just ten fossils resembling modern-day gilled mushrooms have been unearthed, all from amber. The soft, fleshy bodies of mushrooms simply don't fossilize well, and amber, composed of ancient tree resin, has been the only reliable medium of preservation. G. magnificus, however, is the first and only fossil mushroom found in a mineral layer.

The amazing sedimentary deposit that broke the trend is known as Lagerstatten. In this case, the Lagerstatten layer was composed of laminated limestone from the Crato Formation in northeastern Brazil. In the past, Crato has yielded dinosaurs, pterosaurs, amphibians, and even a variety of fish species with the contents of their stomachs preserved.

Have you ever considered the life of a paleoentomologist? Studying fossil insects is a great gig, but it does present its share of difficulties.

Foremost among those difficulties: finding ancient insects is not nearly as easy as unearthing dinosaurs. Their small size and lack of hard bone make them ill suited to preservation. Dating back 125 million years, insects can be found encased in amber, but before that, there are far fewer to be found.

When scientists do stumble upon insect fossils outside of amber, there's often not much to work with, maybe just a thorax, a head embedded into rock, or rarely, a wing. The incomplete remains leave much open to interpretation.

Such was the case back in 2004, when Michael Engel and David Grimaldi reported in Nature the discovery of Rhyniognatha hirsti, the world's oldest insect. Found in a layer of chert from Aberdeen, Scotland dating to around 400 million years old, the fossil consisted only of a well-preserved head, but according to the duo, the fossil's mandible structure clearly placed the centimeter-sized critter in the category of winged insects.

Running on a treadmill versus running outside: there really isn't a competition. It's always preferable to run somewhere rather than nowhere.

Still, treadmill running offers shelter from the elements in an air conditioned room, often with the opportunity to watch a television show or two, so it's not going out of style anytime soon.

Philosophical, weather, and convenience contentions make up most of the treadmill debate, but what about what really matters? You know, running. Do you get a better workout on a treadmill or outdoors?

In 1996, University of Brighton exercise scientists Jonathan Doust and Andrew Jones measured the energy use of nine trained male runners as they ran outdoors on a flat surface and on a treadmill. They found that running on a treadmill at consistent speeds between 6.7 and 11.1 miles per hour was less energetically demanding compared to running outside, but the disparity could be eliminated by raising the treadmill's incline to a 1% grade. The slight incline accounted for wind resistance.

Scientists at Vanderbilt University are raising a glass to the discovery of a previously ignored source of genetic diversity in wine yeast strains. The finding could explain some of the variation in wine vintages available to consumers and open the door to refining wine flavors and crafting all new vintages.

Many strains of the brewer’s yeast species, Saccharomyces cerevisiae, are responsible for the fermentation of wine from grapes. Different strains of the same species usually share most of their DNA except for key single base variations at a few thousand or million places throughout the genome. These variations can lead to differences between strains that might affect fermentation and the resulting wine.

Given the diverse types and flavor profiles in the wine world, you might expect there to be great genetic variation between the yeast strains that make it, but researchers have struggled to find much genetic evidence to explain the differences in wine fermentation by different yeast strains, since wine yeast strains share most of the same A’s, T’s, C’s, and G’s of the genome.

Dr. Antonis Rokas and graduate student Jacob Steenwyk at Vanderbilt University thought that there must be something hiding in the wine yeast genomes that could explain the differences between the strains. They decided to look at something called “copy number variations” between strains. Unlike single base variations in the genome, copy number variations involve large chunks of DNA that are either amplified or deleted in a strain.

In all likelihood, a Martian colony won't resemble a silver city rising in stark contrast to the planet's signature red soil. Instead, it will blend right in, especially if a new, intriguing discovery pans out.

Engineers from the University of California in San Diego have created bricks composed of simulated Martian regolith (soil). Amazingly, these basic building blocks turned out to be stronger than steel-reinforced concrete!

Creating the bricks was surprisingly simple. Yu Qiao, a Professor of Structural Engineering, and his team dried out simulated Martian soil, compressed it at high pressures in steel molds, and then subsequently allowed it to dry again. The resulting blocks were incredibly strong and had a permeability similar to dense rocks. This latter feature is important, because it means a structure built with the bricks could be adapted to hold an atmosphere, which is vital on a planet as inhospitable as Mars, where the air is extremely thin and the temperature frequently falls to minus 100 degrees F.

Brian J. Chow and Yu Qiao

The secret ingredient allowing for the formation of these bricks seems to be the iron oxide that gives the Martian soil its patented red hue. Under crushing pressure, the iron oxide morphs into a denser form, binding the surrounding regolith together in the process.

Drop a few waxworms of the species Galleria mellonella into a plastic bag, and you may find yourself without a bag. New research published to the journal Current Biology shows that these waxworms, the caterpillar larvae of honeycomb moths, are capable of digesting and biodegrading polyethylene, the most common form of plastic. 

You know polyethylene well. Eighty million metric tons of the stuff are produced each year, most commonly in the form of bags, films, and bottles. You probably also know that polyethylene is not readily biodegradable. The special treatments required to recycle the plastic are very expensive, so the overwhelming majority of waste ends up in landfills.

Enter insects. In 2015, researchers demonstrated that mealworms could eat and digest polystyrene, the plastic synonymous with plates, cups, and take-out boxes, with the aid of their gut bacteria. A year before, that same group showed that bacteria inside the guts of waxworms of the Indian mealmoth can degrade polyethylene.

It was this finding that set the stage for the present study. Scientists Federica Bertocchini, Paolo Bombelli, and Chris Howe noticed that plastic bags containing waxworms rapidly became riddled with holes, so they decided to "feed" the worms in a more controlled fashion. In numerous settings, they left the caterpillars alone with various plastic films and observed what happened. Invariably, the plastic films would end up pockmarked with holes. In the most striking example, the team left one hundred waxworms with a plastic bag. After twelve hours, the hungry critters had devoured 92 milligrams of it.

Current Biology

Most complex animals feel pain, but what about insects? Does the buzzing fly feel the crunch of a swatter? Does the pesky mosquito recoil in agony when stung by a bug zapper? Do experiments on fruit fly gladiators constitute torture?

Seeing as how research on insect pain is scant, those questions remain unanswered. Seeking to begin to fill the information void, researchers based out of the The Queensland Brain Institute at the University of Queensland in Australia conducted a rather ingenious experiment on honeybees. Their efforts are published in the journal Scientific Reports.

Senior Research Technician Julia Groening and her colleagues Dustin Venini and Mandyam Srinivasan conducted two experiments, with 540 bees in each. In the first, the trio affixed clips to the legs of half the bees, to "create the sensation of a continuous pinch, similar to an attack of a biting predator or competitor." The other bees were left unharmed to serve as controls. Then, across nine different replications, thirty pinched bees and thirty control bees were allowed to free feed in a cage with feeders containing pure sucrose solution and feeders containing sucrose solution with morphine.

The researchers also conducted a second experiment, identical but for one difference: Half of the bees had one middle leg amputated, while the other half was left unharmed.

Scientists and journalists have been drawing attention to science's replication crisis for many years now. Unfortunately, the entities with perhaps the most power to affect change inside the scientific literature – journals and publishers – aren't exactly rushing to alter the status quo. That much is apparent from a new analysis just published to the journal Frontiers in Psychology.

In summer 2015, Professor Neil Martin, a psychologist at Regent's University London, and Richard Clarke, a research degree student at the London School of Hygiene and Tropical Medicine, reviewed the instructions to authors and the published aims of 1,151 English-language psychology journals to determine whether the journals indicated that replications were permitted and accepted. Their quest returned a disappointing result.

"Of the 1,151 journals reviewed, 33 specifically stated that replications would be accepted – approximately three percent," the duo report.

Of the rest of the journals, 379 (roughly one-third) implicitly discouraged replications by emphasizing "originality" in submissions. According to the authors, the International Journal of Behavioral Development provided a typical example:

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To anyone who plays video games, it should come as little surprise that female characters have often been portrayed as passive damsels in distress or hypersexualized objects of desire. Lately, game makers have focused on unwinding these unflattering stereotypes, but much work still needs to be done.

The evolution of Lara Croft: Tomb Raider.

Eidos & Square Enix

Given decades of a sexist status quo in video games, a team of French and American researchers sought to find out if young gamers internalize this messaging, and thus are more likely to espouse sexist attitudes towards women.

The researchers surveyed 13,520 French youth aged 11-19 attending public or private schools in Grenoble and Lyon, France. As part of a questionnaire, students were asked to estimate the amount of time they spend watching television and playing video games every day. They were also asked to report how often they attend religious services and how important religion is in their everyday life.

To gauge sexism, students were presented with the statement, “A woman is made mainly for making and raising children," and asked to indicate their level of agreement from fully disagree (1) to fully agree (4).

Significant inequalities pervade modern society, even in the bedroom. For example, women have far fewer orgasms than men.

The divide is especially pronounced between heterosexual men and women. According to a new survey with 52,588 respondents published in the Archives of Sexual Behavior, 95 percent of straight men reported usually or always achieving orgasm when sexually intimate. Only 65 percent of straight women did.

While a significant number of straight women seem to be missing out on the peak of sexual pleasure, far fewer lesbian women are. The overwhelming majority of lesbian women taking part in the survey, 86 percent, reported usually or always reaching orgasm. The disparity between lesbian and straight women clearly hints that heterosexual couples (and especially men) have a thing or two to learn.

Thankfully, the researchers, led by Dr. David Frederick, an Assistant Professor of Psychology at Chapman University, were able to glean a number of pivotal lessons from their survey.

The International Astronomical Union currently defines a planet as:

"a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit."

A newly suggested definition takes a different approach:

"A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters."

Bright, flaring meteors are sometimes accompanied by faint noises. What's strange about these popping, sizzling, rustling, and hissing sounds are that they reportedly occur almost instantly to earthly onlookers. This makes little sense, as meteors are as far as sixty miles away from viewers on the ground, so any sound they make should take several minutes be heard. What's going on? Do meteors somehow defy the laws of physics?

Researcher Richard Spalding and several of his colleagues at Sandia National Laboratories recently set out to study this strange phenomenon, and in a study just published to the journal Scientific Reports, they announce that the sounds are likely created through light.

Meteor fireballs sometimes pulse with light many times brighter than the full Moon, and these blasts can briefly heat the surfaces of objects many miles away. Such sudden temperature changes can actually create sound.

"We suggest that each pulse of light can heat the surfaces of natural dielectric transducers," Spalding and his colleagues write. "The surfaces rapidly warm and conduct heat into the nearby air, generating pressure waves. A succession of light-pulse-produced pressure waves can then manifest as sound to a nearby observer."

Today, in the journal Nature Astronomy, a team of researchers led by Hebrew University cosmologist Yehuda Hoffman has reported that they've found... nothing. To be clear, they've found something, but that something is essentially nothing.

Specifically, Hoffman and his colleagues have spotted an immense, naked region of space which they predict to be largely devoid of galaxies. Since this region is relatively empty of matter, it is exerting a repelling effect on the Local Group of galaxies, which includes Andromeda, the Triangulum Galaxy, and our own Milky Way.

The researchers made the discovery by visualizing the velocities of various galaxies in an area of space extending 1.7 billion light years across. They found that the flow of galaxies was largely directed towards the Shapley Supercluster 650 million light years away. The supercluster is populated by a large number of galaxies, making it gravitationally dense, and thus attractive. Moreover, the researchers found that the flow of galaxies emanated from a distinct region of space, which they dubbed the "Dipole Repeller." They believe this region to be a cosmic void of sorts. Together, it seems that the Shapley Supercluster pulls our Local Group of 54 galaxies while the Dipole Repeller pushes. The result is that our Local Group moves with a velocity of roughly 631 kilometers per second relative to the Cosmic Microwave Background, the leftover radiation from the Big Bang, toward the Shapley Supercluster.

Hoffman et. al. / Nature Astronomy

The cosmic void now called the Dipole Repeller was previously mentioned offhandedly more than a decade ago, when Dale D. Kocevski and Harald Ebeling at the University of Hawaii noted a significant "underdensity" of galaxy clusters in an area of space in the northern hemisphere 490 million light years away.

How did each of the United States get its shape? The answers are as varied and diverse as the states themselves! Oftentimes, geographical barriers like mountains, rivers, or dense forests decided borders, but other times, politics came into play. For example, Michigan gained the Upper Peninsula as compensation when the state was forced to shrink, losing Gary to Indiana and Toledo to Ohio. And most of the western states are similarly sized, boring rectangles because Congress aimed for neat, equal land portions when forming them.

The numerous reasons make for a fascinating history lesson, but they're not exactly very scientific. What if – just for fun – we rearranged states according to a more practical attribute? Economics! In a paper published last November to the journal PLoS ONE, Dr. Alasdair Rae, a senior lecturer in urban studies and planning at Sheffield University, and Garrett Nelson, a postdoctoral fellow in geography at Dartmouth University, did just that.

Nelson and Rae used commuting as a proxy for economic activity, hypothesizing that it would visually demonstrate economic connectivity in a region. For data, they turned to the Census Bureau's American Community Survey, which contains origin and destination information for 4.15 million commutes from 3.5 million addresses between 2006 and 2010.

With such a bounty of data, Nelson and Rae crafted some beautiful figures. Below is a graphical representation of commutes in the region of Minneapolis-St. Paul.

Rae & Nelson, PLoS ONE

The house mouse is a relatively benign animal, feeding almost entirely on plant matter. Its scientific counterpart, the laboratory mouse, is even more so, dieting on nutritive food pellets. But tickle a specific part of its brain, and this humble rodent instantly transforms into a predatory killer.

When Ivan Eid Tavares de Araujo, an Associate Professor of Psychiatry and of Cellular and Molecular Physiology at Yale University, uncovered this fascinating neurological quirk, he wasn't aiming to create a murderous army of super mice. Rather, he was merely curious about the neural mechanisms underlying feeding behaviors in animals. A study published in 2005 pointed to a specific location in the brain that's highly active when hunting prey: the central nucleus of the amygdala. de Araujo hypothesized that manipulating this brain region in mice could produce some fascinating behaviors.

His educated hunch proved to be correct.

de Araujo and his team used optogenetics, a technique that employs laser light to activate specific neurons, to stimulate the central nucleus of the amygdala in lab mice. Upon stimulation, mice attacked and attempted to eat anything in their cages, including wood sticks, bottle caps, tape rolls, tiny robots, and live crickets. They did leave other mice alone, however. When the experimenters switched off the laser light, mice abruptly ceased their attacks.

Physically active people tend to be happier, according to an innovative new study published to PLoS ONE.

Researchers from the University of Cambridge created a smartphone app which allowed users to track their mood and behaviors throughout the day, offering a data-driven tool for introspection. Over ten thousand people downloaded and used it.

The app prompted people to fill out self-reflective surveys at random intervals throughout the day, asking about mood, social interactions, and life satisfaction. Consistent use of the app unlocked additional features.

Along with allowing users to report and track their mood and activities, the app also quietly gathered physical activity data via the devices' accelerometers. An accelerometer measures the acceleration of of a device. The researchers determined the data to be a good proxy for physical activity based on users' self-reported physical activity.