They are developing a sense of behavioral maturity and learning to control their impulsiveness.

Middle adolescence is marked by the emergence of new thinking skills.

‘Getting along,’ not being different, and being accepted seem somehow pressing to the early adolescent. The worst possibility, from the view of the early adolescent, is to be seen by peers as ‘different’.

Although these stages are common to all teenagers, each child will go through them in his or her own highly individual ways.

Often, these shells are ground oyster shells that are worth significant amounts of money in their own right as irritant catalysts for quality pearls. The resulting core is, therefore, much larger than in a natural pearl

Yet, as long as there are enough layers of nacre (the secreted fluid covering the irritant) to result in a beautiful, gem-quality pearl, the size of the nucleus is of no consequence to beauty or durability.

The only difference between natural pearls and cultured pearls is that the irritant is a surgically implanted bead or piece of shell called Mother of Pearl.

For instance, the pearl was the favored gem of the wealthy during the Roman Empire. This gift from the sea had been brought back from the orient by the Roman conquests. Roman women wore pearls to bed so they could be reminded of their wealth immediately upon waking up. Before jewelers learned to cut gems, the pearl was of greater value than the diamond. In the Orient and Persia Empire, pearls were ground into powders to cure anything from heart disease to epilepsy, with possible aphrodisiac uses as well Pearls were once considered an exclusive privilege for royalty. A law in 1612 drawn up by the Duke of Saxony prohibited the wearing of pearls by the nobility, professors, doctors or their wives in an effort to further distinguish royal appearance.

American Indians also used freshwater pearls from the Mississippi River as decorations and jewelry.

Throughout history, pearls have held a unique presence within the wealthy and powerful.

hey leave vigorous trees that have stayed healthy enough to survive the outbreak.

Another approach that might yield a high amount of low-use wood is a Salvage Cut

Most wood used for energy in Pennsylvania is used to produce heat or electricity through combustion. Many schools and hospitals use wood boiler systems to heat and power their facilities, many homes are primarily heated with wood, and some coal plants incorporate wood into their coal streams to produce electricity. Wood can also be gasified for electrical generation and can even be made into liquid fuels like ethanol and gasoline for lorries and cars. All these products are made primarily from low-use wood.

Several tree- and plant-cutting approaches, which could greatly improve the long-term quality of a forest, focus strongly or solely on the use of wood for those markets.

Wood energy markets can accept less expensive wood material of lower quality than would be suitable for traditional timber markets.

The norm was to remove the stems of highest quality and leave behind poorly formed trees that were not as well suited to the site where they grew. This practice, called ‘high-grading’, has left a legacy of ‘low-use wood’ in the forests. Some people even call these ‘junk trees’, and they are abundant in Pennsylvania. These trees have lower economic value for traditional timber markets, compete for growth with higher-value trees, shade out desirable regeneration and decrease the health of a stand leaving it more vulnerable to poor weather and disease.

Management that specifically targets low-use wood can help landowners manage these forest health issues, and wood energy markets help promote this.

In the past, Pennsylvania landowners were solely interested in the value of their trees as high-quality timber.

he same tree can be valued very differently by each person who looks at it. A large, straight black cherry tree has high value as timber to be cut into logs or made into furniture, but for a landowner more interested in wildlife habitat, the real value of that stem (or trunk) may be the food it provides to animals.

Likewise, if the tree suffers from black knot disease, its value for timber decreases, but to a woodworker interested in making bowls, it brings an opportunity for a unique and beautiful piece of art.

A tree’s ‘value’ depends on several factors including its species, size, form, condition, quality, function, and accessibility, and depends on the management goals for a given forest.

Improvements in the science and technology underpinning green roof development have also led to new variations in the concept. For example, ‘blue roofs’ enable buildings to hold water over longer periods of time, rather than draining it away quickly – crucial in times of heavier rainfall. There are also combinations of green roofs with solar panels, and ‘brown roofs’ which are wilder in nature and maximise biodiversity. If the trend continues, it could create new jobs and a more vibrant and sustainable local food economy – alongside many other benefits. There are still barriers to overcome, but the evidence so far indicates that green roofs have the potential to transform cities and help them function sustainably long into the future.

The success stories need to be studied and replicated elsewhere, to make green, blue, brown and food-producing roofs the norm in cities around the world.

As the expertise about green roofs grows, official standards have been developed to ensure that they are designed, constructed and maintained properly, and function well.

Those responsible for maintaining buildings may have to acquire new skills, such as landscaping, and in some cases, volunteers may be needed to help out. Other considerations include installing drainage paths, meeting health and safety requirements and perhaps allowing access for the public, as well as planning restrictions and disruption from regular activities in and around the buildings during installation. To convince investors and developers that installing green roofs is worthwhile, economic arguments are still the most important.

The term ‘natural capital’ has been developed to explain the economic value of nature; for example, measuring the money saved by installing natural solutions to protect against flood damage, adapt to climate change or help people lead healthier and happier lives.

For green roofs to become the norm for new developments, there needs to be support from public authorities and private investors.

Again, city leaders and authorities have helped push the movement forward – only recently, San Francisco, USA, created a policy requiring new buildings to have green roofs. Toronto, Canada, has policies dating from the 1990s, encouraging the development of urban farms on rooftops. These countries also benefit from having newer buildings than in many parts of the world, which makes it easier to install green roofs. Being able to keep enough water at roof height and distribute it right across the rooftop is crucial to maintaining the plants on any green roof – especially on ‘edible roofs’ where fruit and vegetables are farmed. And it’s much easier to do this in newer buildings, which can typically hold greater weight, than to retro-fit old ones

Having a stronger roof also makes it easier to grow a greater variety of plants, since the soil can be deeper.

In North America, green roofs have become mainstream, with a wide array of expansive, accessible and food-producing roofs installed in buildings.

Research also indicates that green roofs can be integrated with drainage systems on the ground, such as street trees, so that the water is managed better and the built environment is made more sustainable. There is also evidence to demonstrate the social value of green roofs. Doctors are increasingly prescribing time spent gardening outdoors for patients dealing with anxiety and depression.

And research has found that access to even the most basic green spaces can provide a better quality of life for dementia sufferers and help people avoid obesity.

Ongoing research is showcasing how green roofs in cities can integrate with ‘living walls’: environmentally friendly walls which are partially or completely covered with greenery, including a growing medium, such as soil or water.

More and more private companies and city authorities are investing in green roofs, drawn to their wide-ranging benefits. Among the benefits are saving on energy costs, mitigating the risk of floods, making habitats for urban wildlife, tackling air pollution and even growing food. These increasingly radical urban designs can help cities adapt to the monumental problems they face, such as access to resources and a lack of green space due to development. But the involvement of city authorities, businesses and other institutions is crucial to ensuring their success – as is research investigating different options to suit the variety of rooftop spaces found in cities. The UK is relatively new to developing green roofs, and local governments and institutions are playing a major role in spreading the practice.

London is home to much of the UK’s green roof market, mainly due to forward-thinking policies such as the London Plan, which has paved the way to more than doubling the area of green roofs in the capital.

Rooftops covered with grass, vegetable gardens and lush foliage are now a common sight in many cities around the world.

he scans also suggest that Gareyev’s visual network is more highly connected to other brain parts than usual. Initial results suggest that the areas of his brain that process visual images – such as chess boards – may have stronger links to other brain regions, and so be more powerful than normal.

These assessed his ability to hold numbers, pictures and words in mind. One classic test measures how many numbers a person can repeat, both forwards and backwards, soon after hearing them. Most people manage about seven. ‘He was not exceptional on any of these standard tests,’ said Rissman. ‘We didn’t find anything other than playing chess that he seems to be supremely gifted at.’ But next came the brain scans. With Gareyev lying down in the machine, Rissman looked at how well connected the various regions of the chess player’s brain were. Though the results are tentative and as yet unpublished, the scans found much greater than average communication between parts of Gareyev’s brain that make up what is called the frontoparietal control network. Of 63 people scanned alongside the chess player, only one or two scored more highly on the measure. ‘You use this network in almost any complex task.

It helps you to allocate attention, keep rules in mind, and work out whether you should be responding or not,’ said Rissman.

he scientists first had Gareyev perform some standard memory tests

The nature of the game is to run through possible moves in the mind to see how they play out. From this, regular players develop a memory for the patterns the pieces make, the defences and attacks. ‘You recreate it in your mind,’ said Gareyev. ‘A lot of players are capable of doing what I’m doing.’ The real mental challenge comes from playing multiple games at once in the head. Not only must the positions of each piece on every board be memorised, they must be recalled faithfully when needed, updated with each player’s moves, and then reliably stored again, so the brain can move on to the next board. First moves can be tough to remember because they are fairly uninteresting. But the ends of games are taxing too, as exhaustion sets in. When Gareyev is tired, his recall can get patchy.

He sometimes makes moves based on only a fragmented memory of the pieces’ positions.

Accomplished players can develop the skill of playing blind even without realising it

But displays of the feat go back centuries. The first recorded game in Europe was played in 13th-century Florence.

In 1947, the Argentinian grandmaster Miguel Najdorf played 45 simultaneous games in his mind, winning 39 in the 24-hour session.

To the uninitiated, blindfold chess seems to call for superhuman skill.

Tutored by his grandfather, he entered his first tournament aged eight and soon became obsessed with competitions. At 16, he was crowned Asia’s youngest ever chess grandmaster. He moved to the US soon after, and as a student helped his university win its first national chess championship.

In 2013, Gareyev was ranked the third best chess player in the US.

Gareyev learned to play chess in his native Uzbekistan when he was six years old

n the hope of understanding how he and others like him can perform such mental feats, researchers at the University of California in Los Angeles (UCLA) called him in for tests. They now have their first results. ‘The ability to play a game of chess with your eyes closed is not a far reach for most accomplished player,’ said Jesse Rissman, who runs a memory lab at UCLA

But the thing that’s so remarkable about Timur and a few other individuals is the number of games they can keep active at once. To me it is simply astonishing.’

But Gareyev’s prowess has drawn interest from beyond the chess-playing community

While his challengers will play the games as normal, Gareyev himself will be blindfolded. Even by world record standards, it sets a high bar for human performance. The 28-year-old already stands out in the rarefied world of blindfold chess. He has a fondness for bright clothes and unusual hairstyles, and he gets his kicks from the adventure sport of BASE jumping. He has already proved himself a strong chess player, too. In a 10-hour chess marathon in 2013, Gareyev played 33 games in his head simultaneously

He won 29 and lost none. The skill has become his brand: he calls himself the Blindfold King.

Next month, a chess player named Timur Gareyev will take on nearly 50 opponents at once. But that is not the hard part.