captioning sponsored by wnet >> sreenivasan: on this edition for saturday, march 21: the united states and iran report new momentum in negotiations to strike a nuclear deal; progress in the battle against alzheimer's; and in our signature segment, taking on isis-- an american army veteran returns to iraq to "defend christianity." >> you can push christians back so far, but, when we do pick up the sword, we fight back. >> sreenivasan: next on pbs newshour weekend. >> pbs newshour weekend is made possible by:

corporate funding is provided by mutual of america-- designing customized individual and group retirement products. that's why we are your retirement company. additional support is provided 1]éy: and by the corporation for public broadcasting and by contributions to your pbs station from viewers like you. thank you. from the tisch wnet studios in lincoln center in new york hari sreenivasan. >> sreenivasan: good evening. thanks for joining us. there are new signs of progress in nuclear negotiations between the world's major powers and iran. officials from both sides said the latest round of talks in switzerland had left the two sides closer to a deal. >> we have not yet reached the finish line, but make no mistake-- we have the opportunity to try to get this right. we have made genuine progress, and we have all lived up to our

obligations. we have worked long and hard to achieve a comprehensive agreement that resolves international concerns about iran's nuclear program. >> sreenivasan: that assessment was echoed by iranian president hassan rouhani. >> ( translated ): in this round of talks, shared points of view emerged in some of the areas where there had been a difference of opinion, which can be a foundation for a final agreement. differences on some of the issues still remain that could have been resolved, but more time is needed. >> sreenivasan: a day after suicide bombers killed at least 137 worshippers in yemen, the united states is reportedly removing the last of its troops out of that country. yemeni officials say the americans evacuated an air base following the capture of a nearby city by al qaeda fighters. the u.s. closed its embassy in the capital city of sanaa last month. authorities in tunisia today arrested 20 suspected militants for their alleged role in the museum attack earlier this week that left nearly two dozen tourists dead.

in tunis today, the victims were remembered during a mass attended by government ministers. the government says the two gunmen killed during the incident had trained at jihadi camps in neighboring libya. a federal judge has ordered the pentagon to release photographs that show the abuse of detainees in iraq and afghanistan. some of the images, taken by american service personnel, reportedly show soldiers pointing guns at the heads of hooded and handcuffed detainees. the government says releasing the photos, taken about a decade ago, will incite attacks against american servicemen overseas. the ruling yesterday by district judge alvin hellerstein gives the defense department two months to appeal. islamic extremists from the group boko haram are said to be behind an atrocity committed in nigeria. a mass grave with at least 70 decomposed bodies was discovered near a town recently taken back from the group. authorities said many of the victims had their throats slit. a federal judge has declared wisconsin's abortion law unconstitutional. the law, challenged by planned parenthood, had required doctors

performing abortions to have admitting privileges at a nearby hospital. supporters of the law, including governor scott walker, said the law would help guarantee the safety of women receiving abortions. opponents said it was really meant to limit access to abortions by making women travel further, especially from rural areas. a new study documents the continuing decline of the nation's middle class. according to pew, every single state saw its percentage of middle class residents shrink between 2000 and 2013. the darker the blue, the steeper the decline. states like ohio, wisconsin and georgia had the steepest declines, all around 5%; idaho, wyoming, hawaii and alaska had the smallest drops. this weekend marks the 70th anniversary of the battle of iwo jima, one of the most brutal and infamous battles of world war ii. more than 30 u.s. veterans, many in their early 90s, attended a ceremony on the tiny japanese island to commemorate the u.s. victory over japanese forces in 1945. 7,000 marines died and more than

20,000 were wounded securing the island. the veterans also visited the hilltop where the iconic photo was taken of the marines raising the u.s. flag. and finally, some ancient history. paleontologists from north carolina state university have discovered remains of what they've dubbed the "carolina butcher," an ancestor of today's crocodile. the "butcher" had sharp teeth was at least nine feet tall and actually walked on its hind legs. scientists believe the beasts died out because they could not ultimately compete with even larger dinosaurs, which preyed on them. in case you're wondering, the carolina butcher may have walked the earth some 230 million years ago. >> sreenivasan: just yesterday came word about what could be a big step forward in the battle against alzheimer's, a new drug that during tests sharply slowed the cognitive decline of people with the debilitating disease. for more, we are joined now by

dr. samuel gandy. he is a neurologist and associate director of the alzheimer's disease research center at mount sinai hospital here in new york city. so, i guess first, what is the drug? what does it do? >> so the drug is aimed at a material that builds up in the brain during alzheimer's disease. it's a normal protein, normal substance of the brain which changes its shape and clumps. and this class of diseases called amyloid disease, or amyloidosis, are notoriously difficult to treat and the idea with this drug is to help the brain clear those clumps away, sort of harnesses the immune system to clear those klumps away. >> sreenivasan: is this just targeted at alzheimer's or are there any formed of dementia that could also benefit from a drug like this? >> in any disease, in in and dementia in this this particular protein builds up, this medicine could be effective. for example not only just alzheimer's disease but what we

call mixed dementias in which alzheimer's and say dementia due to multiple strokes can coexist. in that case, the component due to alzheimer's will still be responsive to this drug. >> sreenivasan: so given that there have been other attempts at this how significant is this sort of advancement? >> well, this is the first drug of any class aimed at amyloid that has shown any convincing signal. so not only have there been antibody trials, but also there are small molecules pills, that are being tested that are aimed at the enzymes that make amyloid, for example. none of those have succeeded so far. so in terms of what we call the amyloid hypothesis of alzheimer's, that amyloid is key to the cause of the disease, this is really important in terms of focusing or sort of confirming that that is a valid target. >> sreenivasan: so why is this particular drug or this particular type of therapy

different? >> this is a biologicallal. it's a protein, what's called a monocolonial antibody, and it's directed specifically at this molecule that builds up. and we've rarely been successful in this sort of medication, in this sort of disease. there's one example of another an lloyd that's treatable. this is the second example where we seem to have a lead on a strategy that looks to be successful. >> sreenivasan: so biogen, the company that made, saw a huge bump in their stock. obviously, investors seem very confident but this is far off from actually getting to market, right? it is. it's a small trial. if you divide it up between-- only about 150, 160 subjects total. they were in six different groups. so in each group, there were only about two dozen patients. so the f.d.a. usually requires at least two much larger trials, and so those would have to now be under at least typical policy those would be required before

it would be approved. the f.d.a. has given some signals they would like to fast track this sort of thing, so they could change those rules. but one would guess, if they ran the two trials in parallel perhaps it would be ready in three, four years. but it's hard to imagine being any faster than that. >> sreenivasan: and that's always side effects to drugs. i mean, are there any known side effects so far? >> there are. and this particular side effect is one that occurs with a number of these biologicals. there are antibodies like this for cancer, for example. and this is a swelling of the brain, or at least a change in the water content of the brain. it's often those symptoms and usually if you sort of decrease the dose of the drug or space out administration, it will resolve spontaneously. but it's fairly important to be-- to survey for it. it's readily detectable on m.r.i., before there are any symptoms so i think it would be

manageable. >> sreenivasan: so this is a category of bilogical drugs you are talking about. are there other drugs-- alzheimer's is so enormous in this country and elsewhere, are there other drugs following this kind of lead or in the clinical trials process? >> in alzheimer's disease this particular strategy has been attempted before and has failed. there was a drug by pfizer a drug from lily, which is still being evaluated but the pfizer drug was abandoned. and it's not quite clear why the biogen trial succeeded where these others have failed. there are a couple of possibilities. the first is that these biologicals can be different. one antibody made by one company may be slightly different from another in ways we may never even know. so it's possible that the biogen antibody is just superior to the others. it's also possible the biogen trial design was the secret because they screened for people who had-- they used amyloid brain scans to select the

subjects. so they knew that the people going in had amyloid in their brain. in previous trials, those folks with amyloid negative or with negative amyloid scans were included. so if they were not responsive to the medication, they would have diluted out the effect. so it's possible that if these other drugs are tested with the same design, they might prove successful. >> sreenivasan: all right, samuel gandy alzheimer's researcher at mount sinai, thank you very much. >> thank you. >> sreenivasan: and now to our signature segment, our original in-depth reports from around the nation and around the world. tonight, the battle to defeat isis. you've no doubt seen reports the past few months about efforts to stop young westerners traveling from the united states and europe to fight alongside the extremists. what you might not know is that some westerners are also signing up to fight against isis, including some motivated to stop the radical islamic group's attacks on christianity in that part of the world.

newshour special correspondent martin himel traveled to northern iraq recently, where he met an american veteran determined to protect christianity. >> reporter: nearly nine years after brett first saw combat here, this detroit native returned to iraq to defend the christian faith he holds so dear. >> hello. >> what's up, buddy? >> hello. >> there are a lot of kids here now. it is awesome. >> reporter: brett asked us to not use his last name for security reasons. in 2006, he served in the u.s. army's 14th mountain division for 15 months in iraq. brett was wounded by a roadside bomb and is a veteran on disability. why come back after all the time you served here and what you've seen? isn't it too much? >> i've seen enough combat to last me a lifetime. i'm trying to do this on humanitarian grounds, trying to help out... to bring the

world view here, trying to help liberate cities, trying to help protect cities. it's just a different mission this time. it is. >> reporter: perhaps his greatest goal is to protect christianity in iraq. brett is a religious catholic. last august, the 28-year-old interrupted his studies and traveled to northern iraq, where he joined the assyrian christian militia dyvekh nawsha, which means "self-sacrifice" in aramaic. >> i miss you. >> reporter: it's a privately funded group numbering in the hundreds under the command of the kurdish peshmerga that is fighting isis in northern iraq and eastern syria. the u.s. military is providing support for the peshmerga. there are several american, british and canadian christian volunteers also serving, most with iraqi battlefield experience. they receive no pay but are provided with free room and board by the assyrian christian militia. >> to me, it means everything. i mean, i come from a country where most people take for granted their freedoms. they don't understand what persecution is.

in this part of the world, to be able to live free and practice your faith without being killed is huge. >> reporter: we caught up with brett in alqosh, a christian town just 30 miles from the isis stronghold in iraq, mosul. alqosh was overrun last summer by isis fighters and then recaptured with the help of kurdish and christian militias this past august. skirmishes with isis persist nearby. >> isis likes to pitch attacks. they're cowards. they like to do it in low visibility, low moonlight, rain, fog, stuff like that. >> we love america too much. >> we love you guys, we love this house, and we love that she stayed here. >> this house is like church. >> it is. it is. >> reporter: basa musafar was the only christian to stay and survive in alqosh when isis took the town. she has transformed her house into a christian shrine, memorializing the fallen.

just as st. george killed the serpent the christian militias are depicting crushing the isis snake. do you think this is a religious war? >> i think it has become a religious war, yes, because the atrocities they are committing are based on their beliefs. and the fact that you can push christians back so far but when we do pick up the sword, we fight back. and we are doing it so far for our faith, we're doing it so far for our beliefs. >> reporter: but for the moment, at least, life in alqosh has returned to something like normal. what does this town mean for you? >> this town signifies a victory. i mean, at one point, this town was completely abandoned except for one person, sometimes two. but now, i mean, the church bells ring again here; people go about their business; people live here. that's the biggest thing. as you can see, shops are open,

business is back, people are going to school. this signifies one of the few victories we have right now. what's terrorism? terrorism is a disruption of your daily life. and i know these people are resilient. they've been able to say, "hey, look, we know you're in the area, but we're not going to let you destroy our lives. we will stay here and die for what we believe in, but we are going to continue to go on and operate our daily life." so, it's a success. >> reporter: assyrian christianity has survived here for nearly 2,000 years despite numerous attempts to destroy its followers. established in syria and iraq assyrian christianity predates the rise of islam by at least 400 years. isis is the latest serious attempt to destroy assyrian christians in the region. isis calls christians the crusaders. how do you feel when they say you're a crusader? >> who was here before islam? the christians.

the assyrian christian population is indigenous to this land, so, to me, it just shows how ignorant they truly are and how uneducated they are, too. >> reporter: dr. yifat monnickendam is an expert on assyrian christianity, a lecturer at hebrew university of jerusalem. >> syrian christians have been here since christianity started in the second century, or the fourth century. it doesn't matter. way before islam and way, way before the crusaders. the crusaders arrived in the 11th century and remained here for 200 years, approximately. the other christian groups in the area were here before and remained even after the crusaders left. >> reporter: though christians once again are worshipping freely in alqosh, they remain under attack in much of iraq and syria and throughout parts of the middle east. 21 egyptian coptic christians recently were beheaded by isis fighters in libya, and isis has

made it a point to publicize its destruction of ancient and precious christian artifacts in iraq. hundreds of christians have been taken hostage, an untold number have been killed and hundreds of thousands of others have been displaced, and yet the christians we met insist they will never surrender to isis. >> ( translated ): we will overcome them. we will never leave. they are evil. they are murderers. they will not defeat us. we will defeat them. >> reporter: while the u.s. government has yet to issue a ruling about the legality of volunteering for these militias, brett says the international community, including christians in the united states, need to do much more to defend people he describes as "their brothers and sisters in christ," people now under attack here. what's the message that you are trying to take to the world? >> they need to open their ears. people are crying. they need to open their eyes. they need to help.

we need funds, we need support. they don't just want to kick us out; they want to kill us, and they are killing us. jesus said, "before they hated you, they hated me. before they persecuted you, they persecuted me. and before they kill you they've killed me." and it shows the resilience of the people here and sends a message to the whole world. >> sreenivasan: who are the assyrian christians? learn more about the group's history on our web site. visit www.pbs.org/newshour. >> sreenivasan: it was a topsy turvy week in the markets, with huge swings in the currency markets and, by week's end another sharp rise in stock prices. the dow and s&p 500 closed yesterday just below their all- time highs. for some insights into the forces at work, we are joined by michael regan of bloomberg news. so, first of all the comments that were made pie the fed everybody kind of thinks about interest rates, but something janetielen said about the price of the dollar seemed to have a huge impact.

why? >> it's sort of counter-intuitive but a stronger currency is not necessarily the best thing for an economy. if you're an american company selling big macs or iphones or whatever in europe unless you raise your prices in euro terms, you'll collect the same amount of euros but when you translate it back to american dollars it's much less on the american dollar side so that creates headwind for a lot of companies that have big overseas businesses which is many american company glars so a lot of these multinational corporations, that means they're not making nearly as much profit overseas right? >> exactly exactly. some are actually doing better because the american spending power is stronger so it's sort of a mixed bag. but on the whole it oftentimes tend too a headwind to the economy and the stock market. >> sreenivasan: besides these huge corporations how does it impact our buying power? i guess on the one hand maybe it's cheaper for me to travel in europe right now, but if that's not my thing how am i actually feeling the impact? >> for one thing, as you said, this is a key issue for policy makers trying to decide the fate

of monetary policy. so at the end of last year, the fed-- their projections for where their interest rate, the federal reserve's rate was going to do was about 1.1% by the end of this year. they've since in the last meeting cut that back down to 0.6%. you think half a percentage point. how big of a deal is that? on wall street it's a huge deal, and potentially a big deal to everyone because, obviously if you-- you know, those rates influence everything-- treasuries, and trickle on down to mortgages and all sorts of commercial loans. so if investors believe i'm not going to make as much investing in the debt market going forward, i might as well try my luck in the stock market. that's part of the reason why we saw this big jump on wednesday and fridays in the stock market is because you know the risk return looks a little bit better in the stock market compared to potential lower interest rates in the debt markets. >> sreenivasan: and this is at a time when our central bank is going one way on the dollar

versus the other banks who trying to suppress their currency. we almost can't stop the power of the dollar getting bigger. >> right. it's almost uncharted territory. the boilerplate on wall street is past performance does not guarantee future results. what does wall street do? they spend all their time annualizing the past trying to figure out what is is going to mean for the future. it's so unprecedented what we've seen, not only the fed lowering interest rates the as low as they dbuying trillions of dollars worth of bonds and the opposite happening where we're sort of backing away from that and europe is doing what we did a few years ago-- they're aggressively-- they're going to buy more than $1 trillion worth of bonds in europe. so it's two forces acting at once to strengthen the dollar, and it's very unprecedented, and it's-- it has a lot of people-- you know maybe not worried but very sort of flummoxed because, again, they look back to these molds based on the past and there's no historical record to base any predictions on. >> sreenivasan: all right mike regan of bloomberg news

thanks so much. >> thank you. >> this is pbs newshour weekend, saturday. >> sreenivasan: and finally tonight, the passing of a remarkable veteran. lucy coffey died earlier this week at the age of 108. she had been the oldest living female veteran. the indiana native was 37 years old when, in 1943, she enlisted in the women's auxiliary army corps, which performed support tasks for the army. >> these women are to take over the jobs of soldiers behind the lines and here at home. >> sreenivasan: coffey served in the pacific theater, earning two bronze stars and rising to the rank of sergeant before being discharged in 1945. after the war, she did civilian work in the army in japan and texas for another 26 years. last july, coffey traveled to washington, d.c., from her home in san antonio and met with both vice president biden and president obama. >> it's so nice to meet you.

>> thank you. >> you're welcome. ( laughter ) >> sreenivasan: vice president biden joked about being upstaged by the president. >> i'm vice president; the president comes in and everybody drops everything. you know what i mean? >> sreenivasan: coffey also visited the women's memorial at arlington national cemetery and the national world war ii memorial where she met fellow veteran and former senator bob dole. coffey was one of about 400,000 women who served in uniform during world war ii. the jobs that women have been allowed to do have dramatically changed since then. in january of 2013, then- secretary of defense leon panetta formally lifted rules that excluded women from ground combat, a change that recognized the danger that many women have faced in afghanistan and iraq since 2001. >> they are fighting and dying together. and the time has come for our policies to recognize that reality. >> sreenivasan: today, women represent about 9% of living veterans. by the middle of this century,

that number is expected to nearly double. >> sreenivasan: some more news before we leave you tonight. authorities say the man who attacked security agents at new orleans international airport last night with wasp and spray and a machete, also was carrying explosives, six molotov cocktails. the incident ended when police shot and wounded him. if your m.c.a.a. basketball bracket has been busted you are not alone. espn has 11 million fans signed up and going into day three of play today only one person was still perfect in their predictions. that's it for this edition of pbs newshour weekend. i'm hari sreenivasan. have a good night. captioning sponsored by wnet captioned by media access group at wgbh access.wgbh.org

>> pbs newshour weekend is made possible by: corporate funding is provided by mutual of america-- designing customized individual and group retirement products. that's why we are your retirement company. additional support is provided by: and by the corporation for public broadcasting and by contributions to your pbs station from viewers like you. thank you.

[reflective music] ♪ ♪ [female vocalizing] ♪ ♪ (female narrator) walking in the light in deep, endless beauty. a memory filters through. carved against the canopy of sky are faces of ancient beings, smiling and familiar.