Posts Tagged ‘light’

No ink required to print on this paper — yet look how readable the type is. (Photo: University of California, Riverside/YouTube)


As much as 40 percent of our landfills consist of paper and cardboard, and a major source of that material comes from office supplies. Just think of all the paper that gets used and discarded on a daily basis through the printer in your office alone. Even if that paper gets recycled, it still presents a different sort of problem due to pollution associated with the ink removal process.

Then there’s the concern about deforestation. In the United States, about one-third of all harvested trees are used for paper and cardboard production.

Paper and printing is a problem, to be sure. But now, thanks to a breakthrough from a team of scientists at Shandong University in China, the University of California, Riverside, and Lawrence Berkeley National Laboratory, it might be a problem with a solution.

The researchers have invented a new type of rewritable paper that can be printed with light — no ink required. The paper feels like normal paper to the touch, but it’s coated in color-changing nanoparticles that react to UV light. The technology works simply enough: a UV light printer zaps the paper everywhere except where the text is meant to be. The text then boldly stands out against the clear, light-zapped background.

“The greatest significance of our work is the development of a new class of solid-state photoreversible color-switching system to produce an ink-free light-printable rewritable paper that has the same feel and appearance as conventional paper, but can be printed and erased repeatedly without the need for additional ink,” explained Yadong Yin, chemistry professor at the University of California, Riverside. “Our work is believed to have enormous economic and environmental merits to modern society.”

The researchers published a paper on their work in the journal Nano Letters.

The nanoparticles return to their original background state if left untreated for five days, so the text will disappear naturally. (It certainly beats a paper shredder.) But if you wanted to erase and rewrite onto the same paper sooner than that, it will also revert back if heated for only about 10 minutes at 250 degrees Fahrenheit. It’s kind of like a hardcopy version of Snapchat, assuming you’ve got the proper equipment on hand to erase a message after it’s been read.

“We believe the rewritable paper has many practical applications involving temporary information recording and reading, such as newspapers, magazines, posters, notepads, writing easels, product life indicators, oxygen sensors, and rewritable labels for various applications,” said Yin.

Aside from producing little waste, the technology is also inexpensive. The coating materials are so cheap that they add almost nothing to the cost of a sheet of paper. Meanwhile, the printing technology ought to be cheaper than traditional inkjet printers simply because no ink is required. (Imagine never having to change out your ink cartridge again!)

And of course, because the paper can be re-used more than 80 times before the effect is dulled, the technology saves on the cost of paper as well.

“Our immediate next step is to construct a laser printer to work with this rewritable paper to enable fast printing,” said Yin. “We will also look into effective methods for realizing full-color printing.”

By James Phelps, MD

If light is an antidepressant (true) and antidepressants can make bipolar disorders worse (true), can darkness make bipolar disorders better? Might darkness be anti-manic?

This idea was explored over 2 decades ago, with a stunningly successful case report from the National Institute of Mental Health (NIMH) demonstrating that in at least 1 patient, darkness was indeed a mood stabilizer (1). But the protocol was arduous: 14 hours of enforced darkness every night.

It was so effective, they backed off to 10 hours, from 10 pm to 8 am, which kept the patient well with no medications for over a year. Yet, as clinicians know, patients still resist giving up their electric light, especially their TVs, tablets, and phones.

Hold that thought; and consider a completely separate line of research, which found that all wavelengths of light are not created equal. Blue light is by far the most powerful in setting circadian rhythm.

A new retinal photoreceptor, not a rod or cone, was discovered in 2001; it is sensitive primarily to blue light (2). These receptors connect not to the visual cortex but to the suprachiasmatic nucleus of the hypothalamus, wherein resides the primary biological clock. They are “circadian photoreceptors.”

Now put these 2 lines of research together. At night, when evolutionarily we should have 8 to 14 hours of darkness, one can create “virtual darkness” by blocking just the blue wavelengths of light. This can be done at the source (F.lux for Windows; NightShift for recent Apple products; and for no-blue bulbs and nightlights) or by simply donning a pair of amber-colored safety glasses.

The latter are available as fit-over-glasses, # S0360X; or a stylish version for young people with good eyes, # 3S1933X (purchase from Amazon—or, in a fun twist, from your local Airgas welding shop, ~$9). These safety glasses have been shown to preserve melatonin production at night even in a fully lit environment.3 About 50% of patients responded to wearing the amber lenses with reduced sleep latency and improved sleep quality (4).

But now the acid test: if darkness is a mood stabilizer, and if amber lenses produce physiologic darkness, then can the lenses treat acute mania?

This has just been shown quite conclusively(5) (to the extent that a single randomized trial is conclusive; but note this is a replication of another small inpatient study that used real darkness and found similar, though slightly less robust results (6).

In the new study from Norway, patients being admitted with bipolar mania were randomized to wear amber lenses or control clear lenses whenever they were not in real darkness during the 14-hour period from 6 pm to 8 am.

Thus, they replicated the intervention from the NIMH case report, using either real or “virtual darkness” with the amber lenses. The intervention began near admission and continued for 7 days, during which all participants received other treatments, including anti-manic medications, per usual.

Young Mania Rating Scale (YMRS) scores plummeted in the amber lenses group while those of the control group diminished only slightly: starting from a mean YMRS of 25, reductions were 14.1 vs 1.7, respectively.

Unfortunately, the sample size was smaller than originally intended because of growing public awareness of the effects of blue light and blue light–blocking glasses and consequently the patients knew what effect to expect. Thus, this may be the only such study we’ll ever see, and it took 10 years to replicate the first inpatient study6 of dark therapy.

So I hope that this new Norwegian study will not be dismissed as a pilot. The data are in. Time to move dark therapy into regular practice, as has already been suggested in the latest bipolar-specific psychotherapy, “CBT-IB: A Bipolar-Specific, All-Around Psychotherapy.”

But patients are often hesitant to increase their exposure to darkness: it means giving up things they value, especially television and other electronic entertainment. Blue light blockade can be much more acceptable.

Quick – can you tell where north is? Animals as diverse as sea turtles, birds, worms, butterflies and wolves can, thanks to sensing Earth’s magnetic field.

But the magnet-sensing structures inside their cells that allow them to do this have evaded scientists – until now.

A team led by Can Xie’s at Peking University in China has now found a protein in fruit flies, butterflies and pigeons that they believe to be responsible for this magnetic sense.

“It’s provocative and potentially groundbreaking,” says neurobiologist Steven Reppert of the University of Massachusetts who was not involved in the work. “It took my breath away.”

There used to be two competing theories about magnetic sense: some thought it came from iron-binding molecules, others thought it came from a protein called cryptochrome, which senses light and has been linked to magnetic sense in birds.

Xie’s group was the first to guess these two were part of the same system, and has now figured out how they fit together.

“This was a very creative approach,” says Reppert. “Everyone thought they were two separate systems.”

Xie’s team first screened the fruit fly genome for a protein that would fit a very specific bill.

The molecule had to bind iron, it had to be expressed inside a cell instead of on the cell membrane and do so in the animal’s head – where animals tend to sense magnetic fields – and it also had to interact with cryptochrome.

“We found one [gene] fit all of our predictions,” says Xie. They called it MagR and then used techniques including electron microscopy and computer modelling to figure out the protein’s structure.

They found that MagR and cryptochrome proteins formed a cylinder, with an inside filling of 20 MagR molecules surrounded by 10 cryptochromes.

The researchers then identified and isolated this protein complex from pigeons and monarch butterflies.

In the lab, the proteins snapped into alignment in response to a magnetic field. They were so strongly magnetic that they flew up and stuck to the researchers’ tools, which contained iron. So the team had to use custom tools made of plastic.

The team hasn’t yet tried to remove the MagR protein from an animal like a fruit fly to see if it loses its magnetic sense, but Xie believes the proteins work the same way in a living animal.

Although this protein complex seems to form the basis of magnetic sense, the exact mechanism is still to be figured out.

One idea is that when an animal changes direction, the proteins may swing around to point north, “just like a compass needle,” says Xie. Perhaps the proteins’ movement could trigger a connected molecule, which would send a signal to the nervous system.

Journal reference: Nature Materials, DOI: 10.1038/nmat4484

Thanks to Kebmodee for bringing this to the It’s Interesting community.