alleged russian interference in last year's presidential election. he's a former head of the fbi, robert mueller. the venezuelan government has reinforced its military presence in the state of tachira along the colombian border which it considers a centre for anti—government radicalism. the defence minister said 2,600 troops would be sent to quell looting and rioting. the number of child migrants and refugees travelling alone around the world has reached record numbers, according to the united nations children's fund, unicef. the un says at least 300,000 children applied for asylum last year and warns many are at risk of being exploited by smugglers and traffickers. now on bbc news, click. this week: regenerating teeth, unusual vegetation, and, goodness gracious, great balls of fire!

energy, as our demand for it grows, the world is faced with a challenge. when we burn coal, the energy that has been stored inside formally and is of years is released, to power cities and machines. but so, of course, is all the bad stuff that is polluting and changing the environment. countries have met and agreed to reduce carbon emissions and invest in clean energy solutions, we are harnessing more

solar and wind energy than ever, and last month the uk had its first day of electricity supply without burning any coal. but, green power is still a long way from taking over from fossil fuels. but what if there was a clean energy source that could release 10 million times more energy than fossil fuels, with an almost limitless supply which could keep the planet running for millions of years. well, turns out, there is, and the answer lies in the stars. in the heart of the sun, under intense pressure and heat, hydrogen atoms change from gas into superhot plasma, and in this burning soup, they fuse together forming helium, and releasing immense amounts of energy. this is nuclearfusion, and this is what scientists have been trying for more than 60 years to recreate down here on earth. we have to do something similar

to a star, which has gravity, and to do that, we use magnetic field, and we're talking about magnetic fields that create more pressure than the water pressure at the bottom of the deepest ocean. so you've got this huge pressure trying to compress the plasma, and you've got to hold it in place for a very long time as well, to get more energy out than you put in. if you can keep the superhot plasma in place for long enough, the energy released can keep everything hot, without the need for external power. the fusion then becomes self—sustaining, that's when the magic happens. that's also the hard bit. we are making progress, though, we have already achieved fusion, and some of the best fusion happens inside machines called tokamaks. what is a tokamak?

this is a tokamak. now this one is just outside oxford, which turns out to be a bit of an epicentre for fusion technology. the world's largest tokamak is just 15 minutes up that way. there is a problem with these machines, and that is that you end up having to put much more energy into these things than you ever get out through fusion. which is fiercely not ideal. but the company here is taking a different route. this is the lab of tokamak energy which is developing relatively small tokamaks, small prototypes can be tested and improved much quicker and more cheaply as the science is understood and the design is understood. this approach means the team may be the first to work out how to produce a net gain of energy. go on then, fire it up. my word! that is a fusion reaction!

inside here, we are generating plasma, which is gas with electricity flowing through it, we are going to fuse atoms together, join them together, generate fusion energy. and this light show isn't even fusion, this isjust a warm up for the next stage which it is hoped will happen in the next year. and then what we're going to do is heated up to over 10 million degrees, up towards 100 million degrees... what will that look like? we won't be able to keep our face this close! because it would get damaged. we will have to be further away outside some sort of concrete barrier. but it will actually start to go transparent, as the plasma gets really hot, ten times the temperature of the sun, 100 times the temperature of the sun. once they have achieved the temperatures, they need to keep the plasma in place long enough for it to become self—sustaining, and this is what the team hopes will create magnetic fields are strong enough to do that.

instead of thick copper cables, a strip of super—thin superconductor made of yttrium barium copper oxide. all this sounds hopeful, but the joke is that nuclear fusion has always been 30 years away, if successful, it will mean the end of our reliance on fossil fuels but there are still a lot of signs to do between now and then. it could be a fantastic source of energy, likely to be the most important source of energy in the 22nd century. the point is, we need it now, and so we want to make faster progress towards this energy. while these guys try and recreate the conditions in the centre of a star, the talk for a few minutes about capturing energy from our sun, solar energy. see, it turns out that india is in the grip of a solar gold rush. money is pouring into the country,

to build solar power plants to try to cater for the skyrocketing demands from about1 billion potential consumers. we send david reid to the southern state of tamil nadu to visit the king of the solar crop, the record—breaking kamuthi power plant. follow the morning sun for two hours in tamil nadu and it will take you to a world first. the planet's largest solar power plant. it's huge. ten square kilometres of glimmering glass and electronics, stretching as far as a drunken sea. stretching as far

as a drone can see. the power company adani threw $700 million into building the plant. and they didn't hang about, up and running injust nine months. but is big beautiful when it comes to solar power, or are the indians just showing off? well, there might be an answer in all those clouds. if you look over there, you can see there is a gathering storm, this is one of the problems with solar power, if the rain comes, if there is too much cloud, your output is drastically reduced. but the sheer size of kamuthi means that this is less of an issue. the plant is covered in 2500 acres of land, one portion of the plant is covered with cloud, that portion, 5%, 10%. the cloud moves, away from the plant, again, it comes back. normally, in a year, we can predict the generation for maximum, ten months.

only two months will there be variations from predictions. each of these panels generate 310 watts of energy. 30 watts is enough for a domestic light bulb, 224 a laptop computer, a plasma tv screen, 333, 350 watts. there are two and a half million of these panels at kamuthi. kamuthi's estimated to make enough power for three quarters of a million people. they are squeezing every last drop of energy out of whatever sun is available. bi—facial panels even generate power from light that bounces

back from the ground. or, even better, snow! not that there's much snow in southern india, nor reliable all year round rain. where water is scarce, washing dust covered panels can be impossible. an israeli company has developed a robot which dry—cleans the panels so they get a regular dusting. as the light fades, so does

the power generated. until they've got the batteries to store something like the 648 megawatts kamuthi produces, solar in india will not replace dirty coal, the noxious gases from which pollute the country and the rest of the world. it's certainly getting cheaper, this week, wholesale prices of solar dropped below coal for the first time. india is aiming to get it solar capacity up from 12 to 100 gigawatts in five years. bids are in to construct a bigger plant than this further north in madhya pradesh, but until then, kamuthi, the planet's largest solar plant, will make the most of its place in the sun.

hello, and welcome to the week in tech. it was the week that microsoft released an urgent software update after discovering a flaw in the windows operating system. the bug could give hackers access by simply sending an e—mail which didn't even need to be opened. a 16—year—old's tweet about chicken nuggets became the most retweeted ever. and 02 customers in the uk were told there would be no more roaming charges in 47 european countries as of next month. take a look at these solar panels. tesla's solar roof tiles are now available. look pricey? well, due to their power harnessing qualities, they're actually being pitched as more affordable than conventional roof tiles. from solar to sonic, a us plane returned to earth this week after two years in space. but its mission remains top secret.

having landed at the kennedy space centre, all that the pentagon declared about the air force's robotic mini space shuttle is that it was performing risk reduction, experimentation and concept of operations development. intriguing...! and finally, hollywood quality animation comes to the masses. 0k, well, not quite... the smartsuit pro with camera free motion tracking system costs a fraction of the pro kit, at $2500, it could prove game changing for independent movie—makers and game designers. cheering. it is one of the biggest fund—raising events of the year. nearly 40,000 people ran this year's london marathon and wealth funds are still being counted, organisers are hopeful they will smash last year's record of £59 million raised. 0nline fundraising platform is now play a big role

in attracting more donations, pushing the charities‘ causes across to users while also enabling them to give money with just one click. justgiving, one of the biggest players, raised just under £350 million last year. this is a figure that charities may not have been able to raise without these sites but these donations are also big business. justgiving takes up to 5% commission, others, like globalgiving, take up to 15%. they say the fees cover operational costs and innovations to ultimately raise more for charities. but for charities, this commission is money that is not going towards their causes. the majority of our funding comes from individualfundraisers, one of our runners is currently on £1500, the commission on that is going to be about £100. and on the ground, that translates into care for ten kids that could have received top to toe checkup, hiv testing, atv testing.

and be insured their health and well—being. it makes a huge difference. starfish is a small charity which helps vulnerable children in south africa, who are affected by hiv and poverty, and a lot of its money goes into running a mobile health clinic. in the uk, the charity big kid helps vulnerable young people in south london to gain leadership skills. both organisations have been experimenting with kind link, a site which promises to give charities although collected donations and will not make its money from commissions. i went to meet its founder, iskren kulev, who traded in corporate life and set up a home office, just south of the thames. kindlink didn't start as a company, kindlink started as an idea to be a social enterprise/ charity which helps charities. it is all about transparency, he wanted to create a platform where charities would post updates. the biggest problem

of the charities is how they communicate with their donors. and do the donors trust were the money is going. about 70% of donors say they would make more if there was transparency with donation. they have also added a feature to show people how much money the charity has received and how much it has spent. how has your background in financial tech helped you to put this together and also to work the system a bit, because it is all about making money, it is about making money now not for businesses but for this? it is always a matter of negotiation, is that the same? i will go firstly through volume is important, how you present volumes to your providers. when i know where they can make a compromise, i can try to come up with a deal which would work for both of us. see, this is a guy you want on your side, because he knows how it all works behind—the—scenes. and so far it's proving

successful, with more than 170 charities signed up. how would you improve on what you are doing on the pitch? for big kid, it's been able to spend more money on its programs, like this one, which trains young people to be football coaches. it has helped me, definitely, especially with school and stuff like that. like, in school, i wasn't the good kid, you understand? so how does kind link cover its costs? well, instead of taking commission from donors, it plans to take the money from businesses. they've developed this platform for companies to build a profile for themselves, showcasing the good causes they support while building the brand name. and the companies will be charged a monthly fee. i think it is quite fitting that kind link have set themselves up just across the river from canary wharf, where the financial industry makes its billions. and i think it takes a certain kind of person to give all of that up and come over here and work for charities. that and a small canoe! what's being created here in this

lab at the university of nottingham could mean that you will be making fewer trips to the dentist in future. they're working on fillings that heal your teeth! whilst they can't actually make a tooth regrow, they aim to encourage the dental pulp stem cells within the tooth to transition into a new healthy cell type. goggles on and time to talk to one of the lead researchers on the project, adam. can you tell me a bit about what you are doing here? yeah, so, we've developed a dental material technology that has been used to restore components of a patient‘s tooth. this is the material we have here, in its solution form, and once uv light is irradiated on this solution, it stiffens into a rigid plastic or a polymer. the substance created is used in the same way as a conventional filling, but the aim is that it

will interact with the dental pulp beneath to heal it as well as prevent further rotting. perfecting the product involves precision and patience. the materials go through many stages of testing. 0nce solidified under a uv light, it is off for its next challenge. is the idea that it will heal all the way up to the point of the filling, so you have a totally healthy tooth remaining? the healing process will only occur if the material is in contact with the cells we screen for, so we have to place this material in contact with the pulp tissue and the pulp tissue contains the cell population, the stem cells, that we are trying to engineer for regeneration. what does this mean for your average person who goes to have a filling? potentially, if a person has severe dental decay and they need a filling, or if it's severe enough they need a root canal, potentially, this technology can be used as an intermediate approach, where we can intervene and reduce the incidence of people

needing root canals. the substance is designed to be used in a similar way to current fillings and is hoped to be available within ten years after various trials and approvals are achieved. and they're not the only ones experimenting with regenerative dentistry. kings college have been working with an alzheimer's drug, aiming to regenerate stem cells, something which could be ready even sooner, in five years. but whilst the wait for what we saw in nottingham may seem long, i am told the materials are cheap, which indicates, if this does becomes a reality, it will do so for more than just the elite few. now, over the last few years, we've reported from silicon valley, as marijuana has gradually been decriminalised in several places across the us. the tech companies in the area have been quick to try and capitalise on changes in the law,

but there have also been some unintended consequences. for example, it turns out there is no reliable way to test whether a driver has been smoking pot. well, as we report, nanotechnology that has previously been used to help detect cancer may now be used by police officers to help keep the roads safe. american police officers are facing a problem with pot as more states legalise it. how to crack down on driving while drugged. we asked the mountain view police department to explain the standard procedure to test for marijuana use. there isn't one. it all depends on whether or not we can smell something. federal law still states that smell alone can allow an officer to investigate further. there is no quick roadside test. pot behaves differently in the body than alcohol. the difference between you and i breaking out alcohol is minimal, whereas, in marijuana cases,

it rapidly leaves the body. at the end of an hour, up to 90% of the marijuana in your system will have been broken down. the police department hopes stanford university can help, scientists there are working on a ‘potalizer‘ — a device which will detect levels of thc, the psychoactive ingredient in marijuana. we have an array of 80 sensors. you can think of each of those sensors as a magnet. and when a chemical reaction occurs, that indicates thc is present, then a magnetic nano particle causes that magnet to flip its polarisation. it's a lot like a computer hard drive, where you have zeros and ones that a read head can read. for us, rather than having a computer flip it from zero to one, we have a biochemical reaction flip it from zero to one. the potalizer tests saliva collected with a swab. it can send results

to a mobile device. this is the first attempt at turning the technology into a hand—held device. in a year's time, the scientists want it to be easy enough to use for police officers in the field. i stop you, you blow into the machine within 15 to 20 minutes of the stop and it tells me your nanogram level right then. 45 minutes later, get your blood drawn, and it is lower. at least i have the original, at the time when my car stopped, you were at this level. and that will help in the prosecution later on. ultimately, researchers want the potalizer to work faster, cost less and it should work on people. yeah, that last requirement is key! because stanford receives us government funding, it must comply with federal drug laws, so potalizer is yet to be tested with humans. the researchers hope it can edge out competing devices, like the thc—detecting breathalyser from hound labs.

marijuana use may rise as loser laws take effect, but the right tool could help police keep streets safe. just before we go, a little tease about next week's click, which is going to be rather epic! can't wait! that's next week. in the meantime, follow us on twitter, and like us on facebook, too. you can see loads of extra content on the facebook page every day of the week. thanks for watching and we will see you soon. hello.

i know many gardeners in england wanted some rain, but i suspect some of those gardens are now water—logged after what happened during wednesday. this is one soggy picture from lincolnshire. and in fact it was at coningsby, in lincolnshire, that was one of the wettest places during wednesday, notching up about 40mm of rain — that is nearly a month worth of rain in 24 hours, but you can see elsewhere widely around 20—40mm of rain from this weather system and clearing now into the north sea. we have a few showers for northern ireland and western scotland, parts of wales, north—west england stayed dry. now we are looking at a fresher feel to things during thursday and for the next few days as we bring in some slightly cooler air.

it is more noticeably fresher, less humid rather than cooler because, actually, in some sunshine, where we had the rain during wednesday, it will feel warmer. the sun will eventually come out after perhaps a cloudy start in east anglia and south—east england. elsewhere, plenty of blue sky to begin the day. take a look at things at 8am. some sunshine in the channel islands after wednesday wet weather. plenty of blue sky in south—west england. again brightening up in the far east of england after perhaps a cloudy start. now there is a chance from the word go of picking up a shower somewhere in wales, north—west england. northern ireland, don't be fooled by a dry bright start, cloud will build quite quickly in the morning, showers break out and there will be one or two across western part of scotland to begin the day. let's go on through thursday and see how the weather develops then. quite quickly the cloud builds in northern ireland. the risk of catching a slow—moving heavy and possibly thundery downpours may come with a bit of hail as well. some beefy showers developing in scotland, too, especially to the north. one or two heavy showers for the afternoon for northern england, for wales and south—west england. maybe an isolated one late in the day in the midlands. much of east anglia and south—east

england staying dry. a fresher feel to things, but again quite pleasant in some sunshine. things cool down when the showers move through. some of the showers continue during thursday evening. but as we go through thursday night and into friday morning, another area of rain running up the eastern side of england. during friday, that could actually move across more of the uk, more of northern england and scotland, as we go on through the day. so there's still some uncertainty about this weather system. keep checking the forecast. elsewhere on friday, we're expecting sunshine, showers again, temperatures into the mid—teens. cooler though where you have any persistent rain rather than showers. we're going to keep low pressure close by going the weekend. perhaps some rain across part of scotland to begin saturday. elsewhere sunshine and showers. throughout the weekend, pleasant in some sunshine. cool with the showers, that could be heavy. fresh—feeling days and there will be some chilly nights.

welcome to bbc news, broadcasting to viewers in north america and around the globe. my name is mike embley. our top stories: a special prosecutor is appointed to investigate allegationds a special prosecutor is appointed to investigate allegations that the trump election campaign colluded with russia, as the president complains about his treatment by the media. no politician in history, and i say this with great surety, has been treated worse or more unfairly. venezuela steps up its military presence along the colombian border as violent anti—government protests spread across the country. the record numbers of children who've fled war and poverty — we speak to the un in new york about the risks of exploitation. and she's a fierce opponent on the court. but this basketball player had to fight a legal action to play hoops in a hijab.