Sculpting optical microstructures with slight changes in chemistry

In 2013, materials scientists at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Wyss Institute of Biologically Inspired Engineering grew a garden of self-assembled crystal microstructures. Now, applied mathematicians at the SEAS and Wyss have developed a framework to better understand and control the fabrication of these microstructures.

Together, the researchers used that framework to grow sophisticated optical microcomponents.

The research is published in Science.

An experimental realization of the base shapes for Bragg resonators

Researchers used a new framework to grow sophisticated optical microcomponents, including experimental realizations of the base shapes for Bragg resonators (Credit Wim L. Noorduin/ Harvard University)

When it comes to the fabrication of multifunctional materials, nature has humans beat by miles. Marine mollusks can embed photonic structures into their curved shells without compromising shell strength; deep sea sponges evolved fiber optic cables to direct light to symbiotically living organisms; and brittlestars cover their skeletons with lenses to focus light into the body to “see” at night. During growth, these sophisticated optical structures tune tiny, well-defined curves and hollow shapes to better guide and trap light.

Manufacturing complex bio-inspired shapes in the lab is often time consuming and costly. The breakthrough in 2013 was led by materials scientists Joanna Aizenberg, the Amy Smith Berylson Professor of Materials Science and Chemistry and Chemical Biology and Core Faculty member of the Wyss Institute and former postdoctoral fellow Wim L. Noorduin. The research allowed researchers to fabricate delicate, flower-like structures on a substrate by simply manipulating chemical gradients in a beaker of fluid. These structures, composed of carbonate and glass, form a bouquet of thin walls.

What that research lacked then was a quantitative understanding of the mechanisms involved that would enable even more precise control over these structures.

Enter the theorists.

Inspired by the theory to explain solidification and crystallization patterns, L. Mahadevan, the Lola England de Valpine Professor of Applied Mathematics, Physics, and Organismic and Evolutionary Biology, and postdoctoral fellow C. Nadir Kaplan, developed a new geometrical framework to explain how previous precipitation patterns grew and even predicted new structures.

Mahadevan is also core member of the Wyss Institute.

In experiments, the shape of the structures can be controlled by changing the pH of the solution in which the shapes are fabricated.

“At high pH, these structures grow in a flat manner and you get flat shapes, like side of a vase,” said Kaplan, co-first author of the paper. “At low pH, the structure starts to curve and you get helical structures.”

A helical microstructure made from carbonate-silica coprecipitation patterns

A mathematical model (left) uses a geometrical framework to explain how previous patterns grew and predict new carbonate-silica structures (right, imaged by scanning electron microscopy). (Credit Wim L. Noorduin/ C. Nadir Kaplan/ Harvard University)

When Kaplan solved the resulting equations as a function of pH, with a mathematical parameter standing in for the chemical change, he found that he could recreate all the shapes developed by Noorduin and Aizenberg — and come up with new ones.

“Once we understood the growth and form of these structures and we could quantify them; our goal was to use the theory to come up with a strategy to build optical structures from the bottom up,” said Kaplan.

Kaplan and Noorduin worked together to grow resonators, waveguides and beam splitters.

“When we had the theoretical framework, we were able to show the same process experimentally,” said Noorduin, co-first author. “Not only were we able to grow these microstructures, but we could also demonstrate their ability to conduct light.

Noorduin is now a group lead at the Dutch materials research organization AMOLF.

“The approach may provide a scalable, inexpensive and accurate strategy to fabricate complex three-dimensional microstructures, which cannot be made by top-down manufacturing and tailor them for magnetic, electronic, or optical applications,” said Joanna Aizenberg, co-author of the paper.

“Our theory reveals that, in addition to growth, carbonate-silica structures can also undergo bending along the edge of their thin walls,” said Mahadevan, the senior author of the paper. “This additional degree of freedom is typically lacking in conventional crystals, such as a growing snowflake. This points to a new kind of growth mechanism in mineralization, and because the theory is independent of absolute scale, it may be adapted to other geometrically constrained growth phenomena in physical and biological systems.”

Our theory reveals that, in addition to growth, carbonate-silica structures can also undergo bending along the edge of their thin walls.

Next, the researchers hope to model how groups of these structures compete against each other for chemicals, like trees in a forest competing for sunlight.

The research was coauthored by Ling Li, Roel Sadza and Laura Folkertsma. The research was supported by the National Science Foundation, the Kavli Institute for Bionano Science and Technology at Harvard University and Harvard MRSEC.

Top tips for tax relief

Most of us have heard or read about NISA, pension contribution tax relief, capital gains and personal annual allowance, but do we all use them each year?

I doubt it – many people don’t maximise opportunities for tax relief. There are too many things to worry about – work, shuttling children back and forth to various activities, DIY. There are often much more pressing matters that stand in the way of properly analysing your tax accountability. In fact, most people do what they can to avoid thinking about tax until January, before the annual race to get your tax return in.

But if you knew what to look out for, there are some really good opportunities to reduce your tax liability. Here are some top tips for tax relief:

  • Tax allowance for spouses: in addition to these commonly known allowances, couples now are able to register to shift unused tax allowance between spouses, which could help them save up to £220 a year. If you claim it now, it can be back-dated so you can claim another £212 for 15/16 tax year.
  • Use your tax relief allowance: either to reduce your tax bill, or use your allowances to help loved ones who are just over thresholds such as the Child Benefit Earning threshold or the 20% tax rate threshold. With careful planning, a timely gift to them of a sum of money, which they place in their pension, allows them to use up their pension allowance while reducing their taxable earnings by that same amount. This gift can also help reduce your estate for Inheritance Tax (IHT) purposes if that is something you are interested in doing or help you use your annual gift allowance.
  • Older and wiser: as you get older, there are certain age-related allowances that can reduce your tax. Some are amounts of income that you don’t have to pay tax on, others are amounts that reduce your tax bill. Try to discover some of these this tax year like personal savings allowance and new dividend tax allowance.
  • Capital Gains Tax (CGT): were you aware that in the last budget the rates of capital gains tax – were cut? The CGT rate for basic rate taxpayers will fall from 20 per cent to 10 per cent, while the rate for higher rate taxpayers will fall from 28 per cent to 18 per cent. However, the rates of CGT payable on residential property sales will remain unchanged at 18 per cent for basic rate taxpayers and 28 per cent for higher rate taxpayers.

As the saying goes nothing is as certain as death and taxes. But with some careful planning it’s possible to see some real opportunities to maximise tax relief and drive down your tax liability. Thinking about tax might not be everyone’s cup of tea – but by putting it to the bottom of your to-do-list, you really could be missing a trick. So, why not consider whether these top tips for tax relief are right for you?

Tax treatment set out above is based on our current understanding of UK legislation. It is a broad summary and cannot cover every circumstance, it does not constitute advice. Tax benefits depend upon the investor’s individual circumstances; levels and bases of taxation may be subject to change in the future.

You should not take, or refrain from taking, any action based solely on this article. The investments discussed in this article may not be suitable for all investors. Investors should make their own investment decisions based upon their own financial objectives and financial resources and, if in any doubt, should seek advice from an investment advisor.

Your capital is at risk. The value of investments and the income from them can go down as well as up and you may not get back the amount originally invested.

Opera’s awful role models and the #MeToo moment

A typical work has as much sex and violence as “Game of Thrones”, but a less plausible plot. Should we expose our children to such filth?

Nearly all the great operas are crammed with gore, crudity and all the things from which right-thinking parents seek to shield their precious progeny. And the main characters, especially the female ones, make appalling role models. They fall for the worst sort of men: jealous, violent soldiers (“Carmen”, “Otello”) or unprincipled rakes (“Rigoletto”, “Don Giovanni”). They die horribly: Aida is buried alive; Madame Butterfly stabs herself; Tosca throws herself off a castle parapet. Even the ones who do not die violently succumb to unpleasant diseases (“La Boheme”, “La Traviata”).

Operatic heroines often make awful decisions. Gilda, in “Rigoletto”, sacrifices her life to save the Duke who raped her, because she loves him, even though she overhears him seducing another woman with the same lies he once used on her. Carmen lacks even basic common sense. Confronted by a homicidal ex-boyfriend who whips out a knife and demands to know if she still loves him, she should have played for time. There’s a bullfight nearby, it’s almost over and the crowd will be out in a few minutes. Just keep him talking, for heaven’s sake, and you’ll be safe. Instead, she throws the ring he gave her in his face—whereupon he stabs her to death.

“How can I love an artform that is so consistently, insistently cruel to its female characters?” asks Charlotte Higgins in the Guardian, wondering if opera is “the most misogynistic art form”. She has a point. In the age of #MeToo, some directors have decided to adapt old plots to make them more female-friendly. At the Maggio theatre in Florence this month, Carmen avoids being stabbed by stealing Don Jose’s pistol and shooting him (pictured). “It was just the last 30 seconds and we wanted to draw attention to one of the plagues of our society,” the theatre superintendent told the Financial Times. Changes like this are rare, however. In most productions, it ain’t over till the fat lady bleeds all over the stage. This being the case, can a sensitive, caring dad take his daughter to the opera?

Yes of course, for several reasons. First, as “Rigoletto” so vividly illustrates, over-protective parenting does not work. Gilda’s father, Rigoletto, keeps her sequestered for her entire life and allows her out only to go to church. This backfires spectacularly when the Duke of Mantua, a kind of 16th-century Harvey Weinstein, finds her. Having been shielded from the world, she is so naive that she believes everything he tells her when trying to get her into bed.

Second, operas portray so many honey-voiced but duplicitious seducers that they are a useful inoculation against believing anything a young man says under such circumstances. A young female opera fan who meets a real-life Don Giovanni or Lieutenant Pinkerton will know what to say to him. They don’t teach life skills like that in school.

Third, opera gives young girls a valuable sense of historical perspective. Since the best ones were written at least 100 years ago, they brim with old-fashioned sexist assumptions, such as that a woman who loses her virginity is ruined. A modern listener does not adopt these mores; she marvels at how far women have progressed. Asked if she wanted to copy Gilda’s supremely self-sacrificing approach to romance, your correspondent’s daughter replied: “No, the opera made it quite clear that people who act like Gilda end up shanked and in a bag.”

Finally, and most importantly, the music is sublime. As the daughter put it: “I enjoyed the evil minor key and the cheerful flutes. Overall, it was incredibly sweet to the ear.”

Readers may enjoy this short selection of arias that either celebrate male chauvinism or hint at women’s experiences of it:

“ La donna è mobile”
“Women are fickle”. Sung with brio and hypocrisy by the licentious Duke in Rigoletto
«Madamina, il catalogo è questo”
Don Giovanni’s servant lists his master’s conquests, including 1,003 women in Spain
“Près des remparts de Seville”
To avoid prison, Carmen woos a violent, jealous soldier
«Vissi d’arte»
After being told that she must sleep with Baron Scarpia or he will have her lover executed, Tosca is upset. She later stabs him
«Un bel dì vedremo» 
One fine day, Madame Butterfly sings, my sailor-husband will return. He does, but with a new wife

Why marijuana retailers can’t use banks

Banks cannot handle dope money lest they fall foul of federal rules about money laundering

RECREATIONAL marijuana has been legally sold in California since the start of the year. The state treasury estimates that sales in 2018 will reach $7bn. But it will not collect its fair share, because pot taxes, it turns out, must be paid in cash. This makes tax collection “a nightmare”, as the treasury has described it. The predicament of Oregon, where recreational pot became legal in 2015, is a case in point. Sellers who declare sales have had to bring tax payments in cash every month to a guarded, bulletproof site in Salem, the state capital, no matter the distance they must travel. Operating only one such “cash-transaction unit” saves the revenue department money, but it also reduces the number of sellers who declare sales. So why can’t tax payments be made electronically?

Nearly two-thirds of America’s states have legalised pot sales for certain uses, but the federal government still classifies marijuana as a “Schedule 1” drug, on a par with heroin. Banks that handle marijuana money can be charged with money laundering. Pot businesses, therefore, are on the whole stuck working with cash, which causes problems for more than just tax collection. For starters, cash operations are inefficient. To pay its staff of 200 in cash, CannaCraft, a Californian maker of marijuana products, requires four employees who would otherwise be unneeded. Businesses restricted to cash are “targets for assaults” that endanger the public, laments California’s treasury. And as firms accumulate untraceable cash, some will offer bribes for operating permits, says Fred Timpner, head of the Michigan Association of Police. He expects recent arrests for such corruption in his state to be followed by more.

It may sound like a nightmare for law enforcement. But police are generally happy to keep marijuana money out of banks. That is because “asset-forfeiture” laws allow them to seize cash and, astonishingly, pocket much of it for their departments, even if they merely suspect it of including proceeds from crime. (Cars, homes, and other goods can also be taken, but cash requires less paperwork.) The police do not need to prove that the cash is from crime, or charge that a crime has been committed. Police in Detroit now take so much cash from Michigan’s pot dispensaries that their number has fallen from roughly 500 two years ago to about 200 today, says Rick Thompson, owner of the Michigan Cannabis Business Development Group, a conference organiser in Flint. Sometimes the money can be recovered, but this requires a lot of time and money, as well as a judge who can be amenable to the victim of the asset forfeiture. Pot businesses are only “legal” at state levels, so cash from marijuana is by definition illegal federally. Mr Timpner says that police departments broadly respect state laws and will not routinely seize assets from legal marijuana dispensaries except for those wihch have cut corners. But Mr Thompson also points out that Michigan and California have the most “police-friendly” asset-forfeiture laws in the country.

This sort of asset forfeiture is set to continue. Jeff Sessions, the attorney-general, has directed the Department of Justice to craft seizure policies that increase the cops’ take. Few expect the federal government to reclassify pot, or Congress to protect banks that handle marijuana money, as California’s treasury wishes. Some reckon crypto-currencies like bitcoin may help to solve the problem. But they are volatile and, for many, tricky to use. In the absence of transparent law enforcement and sound legislation, states are left to come up with their own solutions. The California treasury’s Cannabis Banking Working Group is advising government agencies to hire armoured couriers for the collection of businesses’ taxes and permit payments.

Crypto-currencies are in a tailspin

Tough regulation in Asia is to blame

THE past month has seen vertiginous swings in the prices of bitcoin and other crypto-currencies. Most of the moves of late have been downwards, with some days seeing falls of over 20%. News from Asia has driven many of the fluctuations. On January 11th South Korea’s justice minister mooted a plan to ban crypto-currency exchanges, triggering a steep sell-off. Faced with public outcry, the government quickly tried to soften its stance. But last week, the finance minister said the ban remained a “live option”, and bitcoin slid even further.

Although east Asia has generally proven a fertile ground for crypto-currencies, the region’s financial regulators have begun to implement widely divergent policies towards them. China once accounted for over 90% of global bitcoin trading. But alarmed at the way crypto-currencies can evade government oversight, last year it banned domestic exchanges. Japan, by contrast, has given crypto-currencies room to run, deeming them assets that can be used for payments and licensing 11 exchanges.

Virtual currencies have bounced back from past sell-offs, but this has been a big one. At one point bitcoin was down about 50% from its highs in December. Believers in virtual currencies say that one of their selling points is freedom from government meddling. In Asia, the cutting edge of the crypto-world, it is governments that are making—and breaking—their fortunes.