Science News
Headlines
. Making clay work as a natural pesticide
. How mammals flourished after dinosaur extinction
. Breeding has given different dogs distinct brain shapes
. Frozen science

. Making clay work as a natural pesticide
Pests are a big problem for farmers, as one swarm of pests can destroy a whole field of crops. Pesticides are used by farmers to kill them. But chemical pesticides cause other problems. They contain high levels of toxicity, and cause risks to human and environmental health. Despite these concerns, pesticides are perceived as necessary and are used.
One big question is to find alternatives to chemical pesticides, and in India, natural bio-pesticides are often suggested. Now Anna Mathis, a high school student from the USA, has demonstrated that kaolin, a natural clay mineral could offer an easily accessible, cost-efficient, and organic alternative. Kaolin is non-toxic, natural, and harmless to humans or animals.
In order to test her hypothesis, Anna obtained micro-filtered and raw kaolin slurries from a company, then applied them to vegetable plants. When combined with water, the kaolin became a liquid that Anna sprayed directly onto the plants.
The micro-filtered and raw kaolin slurries were taken from different mining locations. Anna used two different kaolin filtrations: a fine particle clay and a coarse particle clay. The main difference between the two was the presence of iron in the raw clay, while the micro-filtered slurry was pure kaolin.
For six weeks, Anna exposed the kaolin-covered plants to common pests, such as aphids, beetles, and caterpillars. After six weeks, she analyzed the pest damage on the plants and found that the micro-filtered kaolin (from fine clay) was the more effective of the two, and could be of potential use as a natural pesticide.
When sprayed onto plants, the kaolin forms a thin film that acts as a barrier to insects. Chemical pesticides are applied after the farmer spots plant damage, while kaolin may deter pests from eating plants beforehand. 
This work got Anna a Community Innovation in Science award. She was among the 28 students (from all over the world) who got his award last year. Using the positive results and knowledge gained from her studies, Anna is currently doing research to formulate a natural kaolin pesticide, to prevent insect damage to plants in a safe and healthy way. 
This is the spirit of science, and school students can scientifically study the resources in their own community and attempt to solve its problems.

2. How mammals flourished after dinosaur extinction
We all have read that some 66 million years ago, an asteroid wiped out up to 75 percent of Earth's species. This event is believed to have marked the end of the dinosaurs, but certainly not all life died. Understanding how those survivors fared has been hard. After all, few fossils exist from right after the cataclysm. But one unexpected trove has now turned up in the Denver Basin in Colorado, USA. These fossils offer scientists a glimpse into how mammals, plants and reptiles ultimately came to flourish. Study of these fossils suggest that mammals took over from the dinosaurs.
The Corral Bluffs site in the Denver Basin is the only known locality in the world to have numerous fossils of animals and plants representing a whole series of time slices in the 1 million years following the Cretaceous–Paleogene extinction. Over the last three years, a team of researchers has uncovered more than 7000 fossils there. These include 233 kinds of plants and 16 species of mammals, among which are the earliest known mammals to reach relatively large sizes as they evolved and filled ecological roles previously occupied by dinosaurs. They found that within 700,000 years, some mammals had grown to be 100 times as big as the original survivors. Their research was reported in the October issue of the magazine "Science".
By comparing plant and animal fossils with data on precise dates for rocks, the researchers puzzled together what happened. Ferns and palms quickly came to dominate. Slowly, forests with a much greater diversity of trees replaced them.
Mammals took a little while to recover. But in time they swiftly diversified into a variety of forms and sizes. About the size of a rat, the biggest initial survivors of the impact weighed just 500 grams. But rock from 100,000 years later hosts fossils of raccoon-sized mammals that would have weighed up to 6 kilograms. That weight is apparently not far from some of the biggest mammals that existed before the mass extinction.
By 300,000 years after the impact, some mammals were now 25 to 30 kilograms. This included the beaver-sized Carsioptychus. What led to that growth in their size? A lack of large predators in the post-impact world have helped. So would an explosion in plant diversity, which would have given them a wider array of food choices. By 700,000 years after the mass extinction, these rock deposits held fossils of the earliest known members of the legume, or bean, family. Mammals also appeared weighing nearly 50 kilograms, such as the wolf-size Eoconodon.
The sheer number of fossils and different time slices revealed at Corral Bluffs is astonishing. So also is the number of mammal skulls, at least 40 so far. Skulls are usually very rare. 
Many mammals before the impact were very different from those today. For instance, so-called “placental” mammals came to dominate later. These are animals whose young develops in a womb. Today, they account for some 95 percent of the roughly 6,500 mammal species alive.
Evidence of fossils from another site (in New Mexico) confirms this acceleration of mammals.

3. Breeding has given different dogs distinct brain shapes
For centuries, dog breeders have been experimenting on producing breeds, shaping the way dogs look and behave. It is now becoming clear that meddling in doggy evolution has interfered with the pups' brains, too.
A recent issue of the Journal of Neuroscience reports on a study of brain evolution, in which a team of researchers scanned the brains of 62 pure-bred dogs representing 33 breeds. They used MRI, or magnetic resonance imaging, to map the shapes of brain structures. Their results show that dog brains are not all alike. The shapes of various brain regions can differ broadly by the breed. 
The distinct brain shapes were not simply due to the breed's different head shapes, scientists found. Nor were differences due to the size of the dogs' brains or bodies. Instead, they found that humans' selective breeding of their dogs have shaped the animals' brains, bit by bit.
They found more. Some parts of the brain varied more than others. Smell and taste regions, for instance, varied a lot between breeds. Those areas may support specialized behaviours that often serve people. Such behaviours include hunting by smell, guarding and providing companionship.

4. Frozen science
The film Frozen was very popular when it released some years ago, and now a sequel has come out. In these films, the ice queen Elsa has a magical command over snow and ice. Snowflakes sprinkle from her fingertips. She can blast ice to fight flames. But how closely does Elsa's icy touch approach reality? Can scientists do what Elsa can?
In fact, scientists *can* concoct snowflakes. Architects can also make fantastical structures from ice. Indeed, Disney used Professor Kenneth Libbrecht, a physicist and snowflake expert at California Institute of Technology as a consultant for Frozen.
As ice crystals, snowflakes form only when it is freezing. Elaborate branching patterns form around –15 degrees Celsius. When humidity is high, the air contains a lot of water vapour. High humidity makes conditions ripe for snow. But to kick off the process, snowflakes need a process called nucleation. That means bringing water vapour molecules together to form droplets, usually by condensing onto a particle of dust or something else. Then they freeze and grow. It takes about 100,000 cloud droplets to make one snowflake.
In the laboratory, scientists can spur snowflakes in several ways. For instance, they can let compressed air out of a container. Parts of the air in that expanding gas go to really low temperatures, like –40 to –60 degrees C. At those temperatures, fewer molecules need to unite to start a snowflake. Dry ice, popping bubble wrap and even bolts of electricity can do the trick.
The big advantage Elsa has in the movie is that her fingertips kick off snowflake growth. She is also much faster than nature. Snowflakes take some 15 minutes to an hour to grow in the laboratory. Snowflakes tumbling through the clouds take a similar amount of time.
Elsa builds an ice castle in the movie "Frozen", which also has a time issue. In the space of around three minutes, while Elsa belts out the song "Let It Go", her palace stretches to the sky. How can one do it? By removing heat from a lot of water in the air fast enough to freeze it like this. Unfortunately, not only is such speed difficult, there is simply not that much water in the air.
But if we manage to build it, how does the ice castle hold up? Obviously, ice melts when it is warm. Melting aside, the palace still might not be all that solid. Ice is brittle. A sheet of it shatters when hit by a hammer. Under pressure too, ice can crack and shatter. Even below freezing, ice softens as it warms. It also can deform under pressure. This is what happens with glaciers. Ice at the bottom will eventually deform under a glacier's weight. This is called "creep" and is the main reason that glaciers flow.
Something like this could happen to Elsa's ice palace, especially if it is tall and heavy. With soft and creeping ice at its base, the entire building would start shifting and leaning and cracking apart. 
Elsa could strengthen her castle by adding a second material like cellulose. In fact some scientists at NASA are working on how what to build an ice habitat on Mars for human explorers. Ice walls might even help protect astronauts, because ice can block radiation. They are trying all this because ice is already found on Mars.
Perhaps Elsa could help NASA with freezing ice for the Mars habitat. She would probably be at home there, since the cold does not bother her anyway!
Sources: Scientific American, Science News, Student society for science