Tag Archives: DNA sequencing

The Backstreet Boys sing genetics (not really) but their latest album is called “DNA”

Other that the promotional artwork, cover art and the title, the Backstreet Boys pop band does not seem to have taken science or DNA (deoxyribonucleic acid)/genetics to heart in their latest oeuvre. As for what chickens have to do with it, I I gather this is some sort of humorous nod to a past hit song. Still, I am weirdly fascinated by this January 25, 2019 video news item on Billboard,

Having looked at the list of songs on the DNA album (they’re listed in the Billboard news item where they’ve embedded audio samples), I can’t find anything that suggests an interest in genetics but perhaps you can: Don’t Go Breaking My Heart? Nobody Else? Breathe? New Love? Passionate? Is It Just Me? Chances? No Place? Chateau? The Way It Was? Just Like You Like it? OK? Anyone who can figure out how the songs relate to DNA, please let me know in the Comments.

Frankly, that’s as much analysis as I can offer on the topic. Thankfully, Karen James (an independent educator, researcher, and consultant in molecular biology) has written a February 5, 2019 article (I Want DNA That Way; The Backstreet Boys’ new album and tour features a very old-school depiction of DNA) for slate.com where she unpacks the imagery in the promotional material and on the cover (Note: Links have been removed),

The Backstreet Boys are back. Credit: Dennis Leupold [downloaded from https://slate.com/technology/2019/02/backstreet-boys-dna-album-cover-gene-sequencing.html]

The Backstreet Boys released a new album. I never thought I’d start a science article—or any article—with that sentence, but here we are.

We are here because the promotional artwork for the album (above) is a photograph of the boy band (man band?) lit by a projection of DNA bands. The image, and the album’s title, DNA, jumped out of my Twitter timeline because I’m a geneticist, I work with DNA, and I’ve seen countless images just like it in textbooks and research articles. I’ve even made them myself in the lab.

What struck me as funny (both funny-ha-ha and funny-odd) is that the lab methods that could have produced this image are old—older even than the Backstreet Boys’ first album. One of the methods—called Sanger sequencing—was published in 1977, making it even older than two of the Backstreet Boys themselves, scientist Kristy Lamb pointed out. Genetics is a particularly fast-moving science. New technologies are constantly emerging and eclipsing prior ones. Yet this 40-year-old imagery persists, and not just in the promotional artwork for DNA. Just do a Google image search for “DNA sequencing” and you’ll see plenty of images like this mixed in with the double helices and long GATTACA readouts.

After her description of Sanger sequencing James offers another ‘sequencing’ possibility, almost as old as the Sanger technique,

Careful readers might have noticed that I suggested there was more than one method that produces images like this. At first glance, I thought the projection in the Backstreet Boys’ publicity photo was modified from an image made with Sanger sequencing. But when I looked again in preparation for writing this article, I had second thoughts. Why aren’t the lanes clustered in groups of four? Why are some of the bands in adjacent lanes the same size? (They shouldn’t be if you’re doing Sanger sequencing.) It could be that the photo was heavily modified with individual lanes copied and pasted. Indeed, some of the lanes are even identical to each other (*suppresses fake ivory tower scoff*).

Or it could be that this image was made with another old method: DNA fingerprinting. Made famous in so many crime TV shows, DNA fingerprinting was invented in 1984 by Alec Jeffreys, who, though he did not win a Nobel Prize, was made a knight of the British Empire for his contribution to science, among many other prestigious awards, which is nice.

I suspect the Backstreet Boys weren’t going for a tongue-in-cheek reference to their own advancing age. While today’s DNA sequencing methods produce images that scarcely resemble those produced by Sanger sequencing and DNA fingerprinting, the old-school imagery is still everywhere. The Backstreet Boys’ promotional team probably just went with a stock image that looked compelling and worked well as a projection.

James returns to her theme, why use imagery associated with outdated techniques? (Note: Links have been removed),

But that doesn’t answer the real question: Why is 40-year-old imagery still so ubiquitous? As science writer and editor Stephanie Keep tweeted, one reason may be that, despite its age, the Sanger method is still taught in high school classrooms: “It’s so visual and intuitive.” It’s true. When I teach students about DNA sequencing, I always start with Sanger sequencing and use that as the basis for explaining newer technologies, adding more complexity as I go, following the historical timeline.

Another reason the old imagery is still in use may be that the images produced by newer, so-called next-generation sequencing methods aren’t visually scored by a scientist sitting at a lab bench, but by computers. As such, the images themselves often go unseen by human eyes [emphasis mine], despite their colorful beauty.

Interesting, eh? The latest imagery is not seen by human eyes. So the newest imagery is intended for machines. James presents an example of the ‘new’ imagery,

An image generated using a next-generation DNA sequencing method.. Credit: Illumina [downloaded from https://slate.com/technology/2019/02/backstreet-boys-dna-album-cover-gene-sequencing.html]

According to James, this image was not easily obtained according to one of her tweets. [https://twitter.com/kejames/status/1092888034322845696] So, big thanks to Illumina (there’s also a Wikipedia entry about the company). Getting back to James’ and her article, she asks why the band titled their latest album, DNA,

But why did the Backstreet Boys call their album DNA in the first place? The official RCA Records press release announcing the album says, “BSB analyzed their individual DNA profiles to see what crucial element each member represents in the groups DNA.” It links to a YouTube video that supposedly explains “how their individual strains, when brought together, create the unstoppable and legendary Backstreet Boys.”

The video is a futuristic, spy movie–esque montage, complete with a computerized female voice describing the various characteristics of each Backstreet Boy. Reader, I confess: I cringed. There were so many tropes and misconceptions about DNA packed into the 83-second video, I would have to write a follow-up to this just to explore them. The cringeworthiness doesn’t end there, though. The cover of DNA has each Backstreet Boy on his own spiral staircase.

The staircases are surely meant to evoke the structure of DNA: the famous double helix. But there’s a problem, as the social media account for the journal Genome Biology tweeted: The staircases are spiraling in the wrong direction. DNA is usually right-handed. If you stick out your right thumb, your fingers will naturally curl in a right-handed spiral as you move your hand in the direction your thumb is pointing. The Backstreet Boys’ staircases are left-handed.

Here’s the promotional trailer for DNA,

It’s everything James says it is. As for those wrongly spiraling DNA staircases,

RCA Records [downloaded from https://slate.com/technology/2019/02/backstreet-boys-dna-album-cover-gene-sequencing.html]

Thank you to Karen James for this illuminating article. If you have time, I encourage you to read her piece in its entirety:
I Want DNA That Way; The Backstreet Boys’ new album and tour features a very old-school depiction of DNA.

As for why the Backstreet Boys called their album DNA and you likely guessed. it would seem to be a promotional gimmick meant to leverage the perceived interest in commercial DNA testing by companies such as 23andMe and Ancestry, amongst others.

Why not monetize your DNA for 2019?

I’m not a big fan of DNA (deoxyribonucleic acid) companies that promise to tell you about your ancestors and, depending on the kit, predisposition to certain health issues as per their reports about your genetic code. (I regularly pray no one in my family has decided to pay one of these companies to analyze their spit.)

During Christmas season 2018, the DNA companies (23andMe and Ancestry) advertised special prices so you could gift someone in your family with a kit. All this corporate largesse may not be wholly in service of the Christmas spirit. After all, there’s money to be made once they’ve gotten your sample.

Monetizing your DNA in 2016

I don’t know when 23andMe started selling DNA information or if any similar company predated their efforts but this June 21, 2016 article by Antonio Regalado for MIT (Massachusetts Institute of Technology) Review offers the earliest information I found,

“Welcome to You.” So says the genetic test kit that 23andMe will send to your home. Pay $199, spit in a tube, and several weeks later you’ll get a peek into your DNA. Have you got the gene for blond hair? Which of 36 disease risks could you pass to a child?

Run by entrepreneur Anne Wojcicki, the ex-wife of Google founder Sergey Brin, and until last year housed alongside the Googleplex, the company created a test that has been attacked by regulators and embraced by a curious public. It remains, nine years after its introduction, the only one of its kind sold directly to consumers. 23andMe has managed to amass a collection of DNA information about 1.2 million people, which last year began to prove its value when the company revealed it had sold access to the data to more than 13 drug companies. One, Genentech, anted up $10 million for a look at the genes of people with Parkinson’s disease.

That means 23andMe is monetizing DNA rather the way Facebook makes money from our “likes.” What’s more, it gets its customers to pay for the privilege. That idea so appeals to investors that they have valued the still-unprofitable company at over $1 billion. “Money follows data,” says Barbara Evans, a legal scholar at the University of Houston, who studies personal genetics. “It takes a lot of labor and capital to get that information in a form that is useful.”

Monetizing your DNA in 2018 and privacy concerns

Starting with Adele Peters’ December 13, 2018 article for Fast Company (Note: A link has been removed),

When 23andMe made a $300 million deal with GlaxoSmithKline [GSK] in July[2018]–so the pharmaceutical giant could access a vast store of genetic data as it works on new drugs–the consumers who actually provided that data didn’t get a cut of the proceeds. A new health platform is taking a different approach: If you choose to share your own DNA data or other health records, you’ll get company shares that will later pay you dividends if that data is sold.

Before getting to the start-up that would allow you rather than a company to profit or at least somewhat monetize your DNA, I’m including a general overview of the July 2018 GSK/23andMe deal in Jamie Ducharme’s July 26, 2018 article for TIME (Note: Links have been removed),

Consumer genetic testing company 23andMe announced on Wednesday [July 25, 2018] that GlaxoSmithKline purchased a $300 million stake in the company, allowing the pharmaceutical giant to use 23andMe’s trove of genetic data to develop new drugs — and raising new privacy concerns for consumers

The “collaboration” is a way to make “novel treatments and cures a reality,” 23andMe CEO Anne Wojcicki said in a company blog post. But, though it isn’t 23andMe’s first foray into drug discovery, the deal doesn’t seem quite so simple to some medical experts — or some of the roughly 5 million 23andMe customers who have sent off tubes of their spit in exchange for ancestry and health insights

Perhaps the most obvious issue is privacy, says Peter Pitts, president of the Center for Medicine in the Public Interest, a non-partisan non-profit that aims to promote patient-centered health care.

“If people are concerned about their social security numbers being stolen, they should be concerned about their genetic information being misused,” Pitts says. “This information is never 100% safe. The risk is magnified when one organization shares it with a second organization. When information moves from one place to another, there’s always a chance for it to be intercepted by unintended third parties.

That risk is real, agrees Dr. Arthur Caplan, head of the division of medical ethics at the New York University School of Medicine. Caplan says that any genetic privacy concerns also extend to your blood relatives, who likely did not consent to having their DNA tested — echoing some of the questions that arose after law enforcement officials used a genealogy website to find and arrest the suspected Golden State Killer in April [2018].

“A lot of people paid money to 23andMe to get their ancestry determined — fun, recreational stuff,” Caplan says. “Even though they may have signed a thing saying, ‘I’m okay if you use this information for medical research,’ I’m not sure they understood what that really meant. I’m not sure they understood that it meant, ‘Yes, we’ll go to Glaxo, and that’s where we’re really going to make a lot of money off of you.’”

A 23andMe spokesperson told TIME that data privacy is a “top priority” for the company, emphasizing that customer data isn’t used in research without consent, and that GlaxoSmithKline will only receive “summary statistics from analyses 23andMe conducts so that no single individual can be identified.”

Yes the data is supposed to be stripped of identifying information but given how many times similar claims about geolocation data have been disproved, I am skeptical. DJ Pangburn’s September 26, 2017 article (Even This Data Guru Is Creeped Out By What Anonymous Location Data Reveals About Us) for Fast Company illustrate the fragility of ‘anonymized data’,

… as a number of studies have shown, even when it’s “anonymous,” stripped of so-called personally identifiable information, geographic data can help create a detailed portrait of a person and, with enough ancillary data, identify them by name

Curious to see this kind of data mining in action, I emailed Gilad Lotan, now vice president of BuzzFeed’s data science team. He agreed to look at a month’s worth of two different users’ anonymized location data, and to come up with individual profiles that were as accurate as possible

The results, produced in just a few days’ time, range from the expected to the surprisingly revealing, and demonstrate just how “anonymous” data can identify individuals.

Last fall Lotan taught a class at New York University on surveillance that kicked off with an assignment like the one I’d given him: link anonymous location data with other data sets–from LinkedIn, Facebook, home registration and mortgage records, and other online data.
“It’s not hard to figure out who this [unnamed] person is,” says Lotan. In class, students found that tracking location data around holidays proved to be the easiest way to determine who, exactly, the data belonged to. “Basically,” he says, “visits to private homes that are owned and publicly registered.”

In 2013, researchers at MIT and the Université Catholique de Louvain in Belgium published a paper reporting on 15 months of study of human mobility data for over 1.5 million individuals. What they found is that only four spatio-temporal points are required to “uniquely identify 95% of the individuals.” The researchers concluded that there was very little privacy even in raw location data. Four years later, their calls for policies rectifying concerns about location tracking have fallen largely on deaf ears.

Getting back to DNA, there was also some concern at Fox News,

Other than warnings, I haven’t seen much about any possible legislation regarding DNA and privacy in either Canada or the US.

Now, let’s get to how you can monetize your self.

Me making money off me

I’ve found two possibilities for an individual who wants to consider monetizing their own DNA.

Health shares

Adele Peters’ December 13, 2018 article describes a start-up company and the model they’re proposing to allow you profit from your own DNA (Note: Links have been removed),

“You can’t say data is valuable and then take that data away from everybody,” says Dawn Barry, president and cofounder of LunaPBC, the public benefit corporation that manages the community-owned platform, called LunaDNA, which recently got SEC approval to recognize health data as currency. “What we’re finding is that [our early adopters are] very excited about the transparency of this model–that when we all come together and create value, that value flows down to the individuals who shared their data.

The platform shares some anonymized data with nonprofits, such as foundations that study rare diseases. In that case, money wouldn’t initially change hands, but “there could be intellectual property that at some point in time is monetized, and the community would share in that,” says Bob Kain, CEO and cofounder of LunaPBC. “When we have enough data in the near future, then we’ll work with pharmaceutical companies, for instance, to drive discovery for those companies. And they will pay market rates.

The company doesn’t offer DNA analysis itself, but chose to focus on data management. If you’ve sent a tube of spit to 23andMe, AncestryDNA, MyHeritage, or FamilyTree DNA, you can contribute that data to LunaDNA and get shares. (If you’d rather not let the original testing company keep your data, you can also separately take the steps to delete it.

“We looked at a number of different models to enable people to have ownership, including cryptocurrency, which is a proxy for ownership, too,” says Kain. “Cryptocurrency is hard to understand for most people, and right now, the regulatory landscape is blurry. So we thought, to move forward, we’d go with something much more traditional and easy to understand, and that is stock shares, basically.

For sharing targeted genes, you get 10 shares. For sharing your whole genome, you get 300 shares. At the moment, that’s not worth very much–the valuation takes into account the risk that the data might not be monetized, and the fact that the startup isn’t the exclusive owner of your data. The SEC filing says that the estimated fair market value of a whole genome is only $21. Some other health information is worth far less; 20 days of data from a fitness tracker garners two shares, valued at 14¢. But as more people contribute data, the research value of the whole database (and dividends) will increase. If the shareholders ever decided to sell the company itself, they would also make money that way.

Luna’s is a very interesting approach and I encourage you to read the December 13, 2018 article in its entirety.

Blockchain and crypto me

At least one effort to introduce blockchain/cryptocurrency technology to the process for monetizing your DNA garnered a lot of attention in February 2018.

A February 8, 2018 article by Eric Rosenbaum for CNBC (a US cable tv channel) explores an effort by George Church (Note: Links have been removed),

It’s probably wise to be skeptical of anyone who says they have a new idea for a blockchain-based company, or worse still, a company changing its business model to focus on the crypto world. That ice tea company that shifted its model to the blockchain, or Kodak saying its road back to riches was managing photo rights using a blockchain system. Raise eyebrow, or move directly onto outright shake of head

However, when a world renown Harvard geneticist announces he’s launching a blockchain-based start-up, it merits some attention. And it’s not the crypto-angle itself that might make you do a double-take, but the assets that will be managed, and exchanged, using digital currency: your DNA

Harvard University genetics guru George Church — one of the scientists at the forefront of the CRISPR genetic engineering revolution — announced on Wednesday a start-up, Nebula Genomics, that will use the blockchain to not only allow individuals to share their personal genome for research purposes, but retain ownership and monetize their DNA through trading of a custom digital currency.

The genomics revolution has been exponentially advanced by drastic reductions in cost. As Nebula noted in a white paper explaining its business model, the first human genome was sequenced in 2001 at a cost of $3 billion. Today, human genome sequencing costs less than $1,000, and in a few years the price will drop below $100

In fact, some big Silicon Valley start-ups, led by 23andMe, have capitalized on this rapid advance and already offer personal DNA testing kits for around $100 (sometimes with discounts even less)

Nebula took direct aim at 23andMe in its white paper, and one reason why it can offer genetic testing for less

“Today, 23andMe (23andme.com) and Ancestry (ancestry.com) are the two leading personal genomics companies. Both use DNA microarray-based genotyping for their genetic tests. It is an outdated and significantly less powerful alternative to DNA sequencing. Instead of sequencing continuous stretches of DNA, genotyping identifies single letters spaced at approximately regular intervals across the genome. …

Outdated genetic tests? Interesting, eh? Zoë Corbyn provides more information about Church’s plans in her February 18, 2018 article for the Guardian,

“Under the current system, personal genomics companies effectively own your personal genomics data, and you don’t see any benefit at all,” says Grishin [Dennis Grishin, Nebula co-founder]. “We want to eliminate the middleman.

Although the aim isn’t to provide a get-rich-quick scheme, the company believes there is potential for substantial returns. Though speculative, its modelling suggests that someone in the US could earn up to 50 times the cost of sequencing their genome – about $50,000 at current rates – taking into account both what could be made from a lifetime of renting out their genetic data, and reductions in medical bills if the results throw up a potentially preventable disease

The startup also thinks it can solve the problem of the dearth of genetic data researchers have to draw on, due to individuals – put off by cost or privacy concerns – not getting sequenced.

Payouts when you grant access to your genome would come in the form of Nebula tokens, the company’s cryptocurrency, and companies would need to buy tokens from the startup to pay people whose data they wanted to access. Though the value of a token is yet to be set and the number of tokens defined, it might, for example, take one Nebula token to get your genome sequenced. An individual new to the system could begin to earn fractions of a token by taking part in surveys about their heath posted by prospective data buyers. When someone had earned enough, they could get sequenced and begin renting out their data and amassing tokens. Alternatively, if an individual wasn’t yet sequenced they may find data buyers willing to pay for or subsidise their genome sequencing in exchange for access to it. “Potentially you wouldn’t have to pay out of pocket for the sequencing of your genome,” says Grishin.

In all cases, stress Grishin and Obbad [Kamal Obbad, Nebula co-founder], the sequence would belong to the individual, so they could rent it out over and over, including to multiple companies simultaneously. And the data buyer would never take ownership or possession of it – rather, it would be stored by the individual (for example in their computer or on their Dropbox account) with Nebula then providing a secure computation platform on which the data buyer could compute on the data. “You stay in control of your data and you can share it securely with who you want to,” explains Obbad. Nebula makes money not by taking any transaction fee but by being a participant providing computing and storage services. The cryptocurrency would be able to be cashed out for real money via existing cryptocurrency exchanges.

Hopefully, Luna and Nebula, as well as, any competitors in this race to allow individuals to monetize their own DNA will have excellent security.

For the curious, you can find Luna here and Nebula here.Note: I am not endorsing either company or any others mentioned here. This posting is strictly informational.

New nanomapping technology: CRISPR-CAS9 as a programmable nanoparticle

A November 21, 2017 news item on Nanowerk describes a rather extraordinary (to me, anyway) approach to using CRRISP ( Clustered Regularly Interspaced Short Palindromic Repeats)-CAS9 (Note: A link has been removed),

A team of scientists led by Virginia Commonwealth University physicist Jason Reed, Ph.D., have developed new nanomapping technology that could transform the way disease-causing genetic mutations are diagnosed and discovered. Described in a study published today [November 21, 2017] in the journal Nature Communications (“DNA nanomapping using CRISPR-Cas9 as a programmable nanoparticle”), this novel approach uses high-speed atomic force microscopy (AFM) combined with a CRISPR-based chemical barcoding technique to map DNA nearly as accurately as DNA sequencing while processing large sections of the genome at a much faster rate. What’s more–the technology can be powered by parts found in your run-of-the-mill DVD player.

A November 21, 2017 Virginia Commonwealth University news release by John Wallace, which originated the news item, provides more detail,

The human genome is made up of billions of DNA base pairs. Unraveled, it stretches to a length of nearly six feet long. When cells divide, they must make a copy of their DNA for the new cell. However, sometimes various sections of the DNA are copied incorrectly or pasted together at the wrong location, leading to genetic mutations that cause diseases such as cancer. DNA sequencing is so precise that it can analyze individual base pairs of DNA. But in order to analyze large sections of the genome to find genetic mutations, technicians must determine millions of tiny sequences and then piece them together with computer software. In contrast, biomedical imaging techniques such as fluorescence in situ hybridization, known as FISH, can only analyze DNA at a resolution of several hundred thousand base pairs.

Reed’s new high-speed AFM method can map DNA to a resolution of tens of base pairs while creating images up to a million base pairs in size. And it does it using a fraction of the amount of specimen required for DNA sequencing.

“DNA sequencing is a powerful tool, but it is still quite expensive and has several technological and functional limitations that make it difficult to map large areas of the genome efficiently and accurately,” said Reed, principal investigator on the study. Reed is a member of the Cancer Molecular Genetics research program at VCU Massey Cancer Center and an associate professor in the Department of Physics in the College of Humanities and Sciences.

“Our approach bridges the gap between DNA sequencing and other physical mapping techniques that lack resolution,” he said. “It can be used as a stand-alone method or it can complement DNA sequencing by reducing complexity and error when piecing together the small bits of genome analyzed during the sequencing process.”

IBM scientists made headlines in 1989 when they developed AFM technology and used a related technique to rearrange molecules at the atomic level to spell out “IBM.” AFM achieves this level of detail by using a microscopic stylus — similar to a needle on a record player — that barely makes contact with the surface of the material being studied. The interaction between the stylus and the molecules creates the image. However, traditional AFM is too slow for medical applications and so it is primarily used by engineers in materials science.

“Our device works in the same fashion as AFM but we move the sample past the stylus at a much greater velocity and use optical instruments to detect the interaction between the stylus and the molecules. We can achieve the same level of detail as traditional AFM but can process material more than a thousand times faster,” said Reed, whose team proved the technology can be mainstreamed by using optical equipment found in DVD players. “High-speed AFM is ideally suited for some medical applications as it can process materials quickly and provide hundreds of times more resolution than comparable imaging methods.”

Increasing the speed of AFM was just one hurdle Reed and his colleagues had to overcome. In order to actually identify genetic mutations in DNA, they had to develop a way to place markers or labels on the surface of the DNA molecules so they could recognize patterns and irregularities. An ingenious chemical barcoding solution was developed using a form of CRISPR technology.

CRISPR has made a lot of headlines recently in regard to gene editing. CRISPR is an enzyme that scientists have been able to “program” using targeting RNA in order to cut DNA at precise locations that the cell then repairs on its own. Reed’s team altered the chemical reaction conditions of the CRISPR enzyme so that it only sticks to the DNA and does not actually cut it.

“Because the CRISPR enzyme is a protein that’s physically bigger than the DNA molecule, it’s perfect for this barcoding application,” Reed said. “We were amazed to discover this method is nearly 90 percent efficient at bonding to the DNA molecules. And because it’s easy to see the CRISPR proteins, you can spot genetic mutations among the patterns in DNA.”

To demonstrate the technique’s effectiveness, the researchers mapped genetic translocations present in lymph node biopsies of lymphoma patients. Translocations occur when one section of the DNA gets copied and pasted to the wrong place in the genome. They are especially prevalent in blood cancers such as lymphoma but occur in other cancers as well.

While there are many potential uses for this technology, Reed and his team are focusing on medical applications. They are currently developing software based on existing algorithms that can analyze patterns in sections of DNA up to and over a million base pairs in size. Once completed, it would not be hard to imagine this shoebox-sized instrument in pathology labs assisting in the diagnosis and treatment of diseases linked to genetic mutations.

Here’s a link to and a citation for the paper,

DNA nanomapping using CRISPR-Cas9 as a programmable nanoparticle by Andrey Mikheikin, Anita Olsen, Kevin Leslie, Freddie Russell-Pavier, Andrew Yacoot, Loren Picco, Oliver Payton, Amir Toor, Alden Chesney, James K. Gimzewski, Bud Mishra, & Jason Reed. Nature Communications 8, Article number: 1665 (2017) doi:10.1038/s41467-017-01891-9 Published online: 21 November 2017

This paper is open access.