in tech, as our documentary series founders, valley holders africa to meet the founders, empowering their continent through digital innovation. transformer, work, and living conditions in their country, and inspiring world with their ideas. only valley africa started february, 13th, or the w. i open your eyes is everything clear? if so, then perhaps you're still young will be taking a look at how the eyes change as we age. but 1st we're digging into the construction industry. a major driver of climate change. there are some solutions,

like poorest concrete recycled materials and cement from plants. ah, hello and welcome to to morrow to day the science program on d. w. the construction industry is booming, more is being built around the world than ever before, with serious consequences for the environment. because almost everything is made from concrete containing the binding agent cement the mind is made in special kills . this combustion process makes it a real climate killer. it's responsible for almost 10 percent of c o. 2 emissions caused by humans, but thus could hopefully change the carbon footprint of concrete could be reduced by using this material. expanded

small air filmed clay balls that are mixed in the concrete to reduce its weight. it also works with glass b. dec who are the driver thing about both materials is helping corporate air into a solid structure. and the more air, the more finely distributed, the better the quality of the i'm so so home in from light concrete contains so much air that it even floats. i at the food is very university and munich. christiane tina's team is testing the formula for their in, for light concrete. first expanding clay than water. and finally cement. this mixture weighs less than a quarter of standard concrete because it's so light,

the material is harder to work with on construction sites. on the team is satisfied is on died. the special feature of concrete is that it has to flow like a fine chocolate mousse, where the concrete can be used to build walls that provide excellent insulation because of the trapped air digging that one's really cold, right? in for light malls don't need extra insulation like polystyrene. and this concrete also helps the climate in other ways. but it does it because it's porous layer containing c o 2, him get inside and then react with the calcium hydroxide in the concrete. so the calcium hydroxide binding, the c o 2 from the air, and so offset some of the sealed to that was released during production of your twice before the group. so, and flags it's pulled through. it's open pours the in for light concrete breathes in the greenhouse gas. the calcium hydroxide contained in the concrete form during

the concrete mixing process absorb c o. 2 from the air and over the years turns back into calcium carbonate or limestone. and yet the concrete remains stable using a scanning electron microscope, the research team observes how needles form inside the concrete, interlocking with each other, and providing stability. yes, shawn, we had, we look at how the micro structure has develop suddenly ever can we see that the strength building needles have formed? well, to produce a highly robust concrete at small and magnifications. we can also see the porosity of the micro structure that there are many mole pulls. and so much more air is contained in the ultra like concrete than in normal, concrete tiredness as it does from am i the talking and, but how strong is ultra light concrete compared to normal concrete, a block of regular concrete is exposed to pressure

from at the freight but only under 60 tons of pressure when it's the turn of ultra light concrete, it franks under just 9 tons of pressure. these affects the ultralight concrete has a stronger overall structure than standard bricks are. is highly robust, as you can see from your way for bridges or skyscrapers. ah, old buildings are often demolished to make way for me once. but what happens to the old building materials most of the time they're disposed of. but almost all the components of

a demolish building can be recycled. this may significantly reduce the carbon footprint of the construction industry. in berlin's shown back district, this student residence has long stood empty. now the old building is set to become something new, a multi generational house, thanks to annabel fund, whiten. lot of other typically it would just be torn down, sissy. exactly, that's why we're happy you're here. so we can go through the building together and see what parts can be kept and we used the aim is to save resources, reusing something avoids having to produce it all over again. it reduces c o 2 emissions but requires more planning as good as this and felt like the good thing is that compared to the much than a granite slabs that were used the loss in the 1990s, the smaller tourette's tiles are about 4 centimeters thick. and they can believe it out quite easily. haven come on above and white and as an urban mining expert for

her site set for demolition. our sources of raw materials for new building projects . i fenced on as lead windows in the problem is often that use a energy saving regulation and sat, sat in one's can no longer believed. they simply can't me to day standards used. building materials can't always be re used in their original form. adhesives, like glue or mortar, make for added complications. the material must be removed, re cleaned and hauled away, which requires more work and often a rethink. during planning. at the calls were institute of technology, professor dia cable teaches butting architects about circular construction. he's been monitoring sustainability in the building trade for over 2 decades. hardly lesson yet seeds in recent decades, if not centuries, yada. we followed

a linear business model name. that means we extract materials from the earth's crust to produce things like buildings. then we demolish them and deposit the materials as waste and landfills. these a thing, this way of thinking must change in the future of diet at 1st because resources will be in short supply coin and 2nd to take responsibility and protect the climate better martyr's visit. so to think circular wouldn't and no longer follow this linear model that's led us to a dead end. denise, what it does, once in the suckers shouldn't switzerland is a pioneer when it comes to resource efficient construction. in basel, they're even considering of voluntary commitment to using recycled building materials, architect, caston. miller and her colleagues have already realised numerous innovative buildings this way, often unsightly and for. we need some advance warning about buildings that are about to be torn down simply so that we can go that early enough. then we have the

time to evaluate the construction component and save them. so i think it's an evaluation for a current project. they're salvaging tons of electricity pylons their real climate killers, to produce recycling the steel supports along the architects to reduce c o. 2 emissions during the entire production process imagined as male male want to name. when noticing that more and more companies are adopting this concept and making the hugs as get at 1st, they're quite skeptical in any fee, the problems and huddles i. but as soon as they've done it once have been through the process, they view it as an opportunity to position themselves from the market and carry it further talk since it wasn't as tough as it looks at 1st. we some on from shined. one of the architecture firms biggest projects is the cup bow holler in the city of into to a 70 percent of the building was made from repurposed materials. yeah. now starsky length we learned from it that you need a launch platform,

felice construction materials. hydrophobic as they come in at different time, and you need an interim storage facility to prepare them for a specific buildings and such an internet platform as being developed in berlin called consular. it creates so called material passports, which include a materials age, condition, shape, and color. they're then posted online. when a property developer finds a component, they can use a matches made soon. it could become even easier if a stance f, as in the inventory that we're doing now as an unnecessary because there aren't any material possible as yet if in future such passports, why required for every new project on the continental platform that just have to be activated at the right time, i wish i'd have been assessing which materials can be recycled and whether it's worth the effort requires experience and know how the architects know that some materials are more popular. on the 2nd hand market than others. steel is sought

after other materials, much less so, and it's too costly to recover and transport materials just to have them sit in storage. there are other hurdles to regulations about warren cheese and liability when employing use building materials still need to be established in germany. sustainable construction requires more than just the will of architects and builders. it also requires a legal framework. thus we got mostly doing isn't just nice to have, it's the future. we must plan and build this way. although be new construction revolution and without no climate revolution, we won't meet the 1.5 degrees target if we don't radically changed the construction industry. so in the near future, the architects 1st job could be see would construction materials are available on the circular marketplace and plan accordingly. concrete can also be recycled. and if it can,

it should be because the manufacturing process is extremely climate damaging. concrete as might have water, sand, gravel and cement. the cement itself is composed of limestone and clay. it's killing, fired at up to $1450.00 degrees celsius. one of the most climate damaging stages of production. the combustion process requires enormous amounts of energy and releases carbon dioxide. c o 2 is also released in the chemical reaction. when limestone, c, a, c o 3 becomes quick, lime c, a o, and c o 2 ave alternative ways to make some main production more environmentally friendly. could there be huge potential locked away in the humble cassava materials researcher voice hum. schmidt wants to use it as raw material for cement,

and use it to produce high quality concrete. cassava, also known as manioc, or euchre. as a starchy tuber grown is food in many countries. but the peel is poisonous, which can cause problems when it rots. we're talking about a little we're, we're making a form of cement from the ash of cassava pio and water. the done. we would later add sand to make it into something like concrete at all. this is like a precursor to concrete. we want to see if we can get the same properties from cassava, peel, ash that we can from the normal cement to mixtures. linesman the one in the middle . schmidt's concrete does contain some cement, but also the ash of cassava, peel, and sand and gravel, like normal concrete miss burn the cassandra appeal to ash and then placed it in a kiln and almost $800.00 degrees celsius. this releases

a substance that's contained in the peel silicon dioxide. and that's the key to schmidt's concrete when the fun of so now it's time for the sand and we've got course medium and fine sailings. and this will pour that all in together now. and then the cement and water and finally, pick a cell, the ash with a silicon dioxide we've on your chart isn't sold on the cassava. peel is also used for cleaning more so in places where it grows allotted, which makes sense, like sierra leone and gonna fit with often with a highland is the biggest exporter of cassava. and huge amounts of had grown brazil among their they call it yoko or mun joker. not was this enough for the seat of the

country grows way more than it eats all. so there's a lot left over that could be used to make some antigen dolls. and then catherine cloth, lam, schmidt's research colleagues, and nigeria are already experimenting with cassava. ash. the technology is improvised by effective simple ovens are used to produce the ash. the cement alternative is already being successfully produced and large quantities listed here. so this is luckily i was issued, it's important that the material flows nicely, but that the air bubbles can escape by themselves. they're not trapped, you know, because that would reduce the strength of the concrete. the i'm, his issue in the contents of life is not, this is a nice consistency. it flows, but it's stable. holding particular, the initial can wouldn't even the course particles don't sink to the bottom. we've

made some good concrete here that only has 50 percent of the normal cement content by replacing it with limestone, powder, and cause sob appeal ash, which has hello shonasha half as much cement as normal means lower c o 2 emissions vol. sam schmidt wants to use test blocks like this to demonstrate its strength. the concrete is put under pressure until it breaks and it manages to withstand the same load as normal concrete. this pavilion at lake os university and nigeria is made of cassava concrete, a solid, new eco friendly alternative in construction. if i'm a blood is red, why i? and now over to you, what have you always wanted to know?

if you had a question about science nature, technology all makes and then just ask if we answer it on the show, we'll send you a little surprise as a thank you rides or send a video message to tomorrow to day at d. w dot come. this week's question comes from will the false nixon in nigeria? oh, how long can a person survive without eating fasting or freely choosing to go without food is a common custom around the world. people up to fax for a certain time for religious health or political reasons. but how long a person can survive without eating depends on many factors. the amount of fact reserves they have, their age and general health,

all play an important role. someone who stops eating and drinking will die within a matter of days. those who go without food but stay hydrated will live longer. for the 1st days, the body goes without food. it draws on its blood sugar reserves, mainly to keep the brain functioning because that requires a lot of glucose under normal circumstances. around half of our daily glucose requirement is consumed by the brain. but if there's no more sugar intake, the brain secures all of the glucose reserves, leaving the rest of the body to go hungry. once the glucose is gone, protein is next. the body starts to break down muscle. it turns amino acids components of muscle proteins into glucose. jermaine chain supplies to the brain, but the body also burns fat until all gone tooth.

o, starvation mode begins. bodily functions gradually shut down the heart rate, blood pressure, and body temperature all sink the body does everything to reduce the amount of calories it burns in order to conserve energy that can prove dangerous for children in particular. like here in the horn of africa, children's bodies react much quicker to mount nutrition. they can starve to death as a result of long periods of drought and failed harvests. if there is no more energy left in the muscles, the body starts to draw on its own organs, which can shrink to half their former size as a result. because the heart muscle is also broken down, starving people often die of heart failure. ah, scientists figure that people can survive for 2 to 3 months without eating,

but going without food for so long results in lasting damage including a weakened immune system, as well as major muscle and memory loss. and now why our vision declines as we become older, usually this happens to adults in the mid forty's. the eyes, accommodation 2 objects near or far away becomes limited. seen, clear without correcting lenses, depends increasingly on light and visibility conditions. but why? what happens? we're about to find out starting with a popular children's game that requires the keen eye is their eyes by with my eyes, isn't i that something that is red? this is child's play for 10 year old emily whose eyes see colors brightly and

details sharply, but not for her grandma. the gain leaves her looking old. i tell you is over there. but why is that? what happens to our eyes as we age emily's? grandma ingrid noticed the 1st changes in her early forties ever since she is increasingly had trouble seeing things clearly up close. a classic case of pres, bio, pia, or age related farsightedness. many think the i muscles, it's a blame, but ophthalmologist antonia chuckle off has more insight. 9 has to be the lens. that's the problem. it gets harder and less flexible as we age. and so the accommodation, the close up focusing no longer works as before, and still only mccord from 20 on during childhood. the lens is still elastic, allowing it to bend to vary the refraction over the years. this ability,

termed accommodation, is lost as the lens harden's, the muscle has a tough a time reshaping it, especially up close. the refraction isn't sufficient to focus light precisely on the retina. the image becomes blood, so emily's grandma keeps her reading glasses at hand. it's an easy way to rectify the problem. yeah, yes, i've got one up to me to are great. but that's not ingrid's only problem. objects and the distance are also blurry and sometimes everything's foggy. and a few rays of sunshine can make her eyes water. that's due to the lenses to childrens are still transparent and clear. but over the course of our lifetimes, certain proteins inside the lenses start to clump together. as a result, they get claudia, causing some of the light to diffuse and become glaring. the image on the

retina then appears to be blurry or foggy or was it? i'm a thinking, ha ha. this clouding of the lens of the i is known as a cataract is in fact the examination of ingrid's eyes shows that she has a mild cataract, but it's not problematic yet. dylan kent's rights are enormous sign of aging. they only become problematic on require surgery. if they lead to subjective impairments of vision for people bless the inability to distinguish colors or contrasts death farms. in contrast, infants foot the changes occur gradually. simenon, can you give me a light blue m. o been even a mild cataracts means colors don't look as bright to her grandmother than to know that the dark name to her white looks yellowish and shades of blue a launch, lee felt it out as

a t closer. the classic problem is that patients dress strangely, they no longer recognize the colors and their clauses, even clarifying all their wash, the drapes constantly because they look so yellow will get a shine. but what worries ingrid far more is not being able to see well in the dark . she can no longer distinguish between slight differences and brightness, which poses a danger while driving. several factors come together to produce what's known as night blindness. first, the cloudy lens absorbs a lot of light, but the retina also shows signs of aging and isn't as well supplied with blood and nutrients. over time, around 30 percent of its photo receptions die above all the rods that are responsible for night vision. it doesn't make for a rosy outlook mackenzie hunger from

a 3rd of the light sensitivity of young people, human mention. but isn't there a way of turning back the clock or at least slowing it down? there's no secret recipe to stop eyes from aging, though, eating lots of fruit and vegetable certainly can't hurt bittman ay and other corrosive nights like looting, which is found in leafy greens, are sensual, the good eye health. otherwise, the best advice is to avoid risk factors. cottage couched onto racks can be triggered or worsened by over exposure to the sun's rays and heavy smoke kendrick or otherwise. there's not really much she can do on this voltage. naturally, a healthy diet is always good and a healthy lifestyle overall, because on the limbs visor and sculpt, and that includes uv protection from a young age. but even the best precautions can't stop the eyes normal aging process . so old eyes don't stand a chance against young ones z advised by with my this lie weiss, emily,

and have grandma might soon have to find a different game to play that. so for this edition of tomorrow to day. but thanks for joining us and see you next time until then. stay curious with ah, ah, with

ah, ah, re examining the way the holocaust is memorialized. there is the culture of remembrance froze and the time is distracting us from honoring other historical atrocities in the future of remembrance, culture and international quest arts 21 in 90 minutes. on d. w. we've got some hot tips for your bucket. list. romantic

cornered tread hotspot for food and some great cultural memorials to boot did w travel off. we go a b currently more people than ever on the move mold wife in such a better life. one of us and so it as a committee god that hard. he goes out national. it does the now here is it america and i got to know the god lazily or for the bench to okay. the thing nanda donation one back to the gun. find out about robina story in for my grand, reliable news for migraines. wherever they may be.

leo, nar, davinci, mysterious masterpiece. is perhaps the greatest leonardo masterpiece in the collection of the louvre. and no, it is not the mona lisa. it is the virgin of the rocks, 2 versions, multiple hidden drawing. was there another symbolic meaning to this beautiful painting that perhaps we just don't understand? a search for answers store to february 10th on d, w. ah .

ah ah ah, this is d w lie for the death toll rises after a suicide bombing and a mosque in the pockets stop. at least 44 people are dead after the attack of the city of peshawar, close to them police officers, pakistani taliban commander has claimed responsibility. all.