But what would happen if one or more leader robots was hacked by a malicious agent and began sending incorrect directions? As follower robots are led farther from the fire, how would they know they had been duped?

The use of blockchain technology as a communication tool for a team of robots could provide security and safeguard against deception, according to a study by researchers at MIT and Polytechnic University of Madrid, which was published today in IEEE Transactions on Robotics. The research may also have applications in cities where multirobot systems of self-driving cars are delivering goods and moving people across town.

A blockchain offers a tamper-proof record of all transactions — in this case, the messages issued by robot team leaders — so follower robots can eventually identify inconsistencies in the information trail.

Leaders use tokens to signal movements and add transactions to the chain, and forfeit their tokens when they are caught in a lie, so this transaction-based communications system limits the number of lies a hacked robot could spread, according to Eduardo Castelló, a Marie Curie Fellow in the MIT Media Lab and lead author of the paper.

“The world of blockchain beyond the discourse about cryptocurrency has many things under the hood that can create new ways of understanding security protocols,” Castelló says.

Not just for Bitcoin

While a blockchain is typically used as a secure ledger for cryptocurrencies, in its essence it is a list of data structures, known as blocks, that are connected in a chain. Each block contains information it is meant to store, the “hash” of the information in the block, and the “hash” of the previous block in the chain. Hashing is the process of converting a string of text into a series of unique numbers and letters.

In this simulation-based study, the information stored in each block is a set of directions from a leader robot to followers. If a malicious robot attempts to alter the content of a block, it will change the block hash, so the altered block will no longer be connected to the chain. The altered directions could be easily ignored by follower robots.

The blockchain also provides a permanent record of all transactions. Since all followers can eventually see all the directions issued by leader robots, they can see if they have been misled.

For instance, if five leaders send messages telling followers to move north, and one leader sends a message telling followers to move west, the followers could ignore that inconsistent direction. Even if a follower robot did move west by mistake, the misled robot would eventually realize the error when it compares its moves to the transactions stored in the blockchain.

Transaction-based communication

In the system the researchers designed, each leader receives a fixed number of tokens that are used to add transactions to the chain — one token is needed to add a transaction. If followers determine the information in a block is false, by checking what the majority of leader robots signaled at that particular step, the leader loses the token. Once a robot is out of tokens it can no longer send messages.

“We envisioned a system in which lying costs money. When the malicious robots run out of tokens, they can no longer spread lies. So, you can limit or constrain the lies that the system can expose the robots to,” Castelló says.

The researchers tested their system by simulating several follow-the-leader situations where the number of malicious robots was known or unknown. Using a blockchain, leaders sent directions to follower robots that moved across a Cartesian plane, while malicious leaders broadcast incorrect directions or attempted to block the path of follower robots.

The researchers found that, even when follower robots were initially misled by malicious leaders, the transaction-based system enabled all followers to eventually reach their destination. And because each leader has an equal, finite number of tokens, the researchers developed algorithms to determine the maximum number of lies a malicious robot can tell.

“Since we know how lies can impact the system, and the maximum harm that a malicious robot can cause in the system, we can calculate the maximum bound of how misled the swarm could be. So, we could say, if you have robots with a certain amount of battery life, it doesn’t really matter who hacks the system, the robots will have enough battery to reach their goal,” Castelló says.

In addition to allowing a system designer to estimate the battery life the robots need to complete their task, the algorithms also enable the user to determine the amount of memory required to store the blockchain, the number of robots that will be needed, and the length of the path they can travel, even if a certain percentage of leader robots are hacked and become malicious.

“You can design your system with these tradeoffs in mind and make more informed decisions about what you want to do with the system you are going to deploy,” he says.

In the future, Castelló hopes to build off this work to create new security systems for robots using transaction-based interactions. He sees it as a way to build trust between humans and groups of robots.

“When you turn these robot systems into public robot infrastructure, you expose them to malicious actors and failures. These techniques are useful to be able to validate, audit, and understand that the system is not going to go rogue. Even if certain members of the system are hacked, it is not going to make the infrastructure collapse,” he says.

The paper was co-authored by Ernesto Jiménez and José Luis López-Presa of the Universidad Politécnica de Madrid. This research was funded by the European Union’s Horizon 2020 Research and Innovation Program, the Regional Government of Madrid, and the MIT International Science and Technology Initiatives Global Seed Fund.

In a look back at data from nearly 179,000 veterans over age 65 who received treatment over two years at VA hospitals nationwide, researchers find that patients have a better chance of sticking to their medication regimen if their doctor maximizes the dosage of one of the drugs they’re already taking. They also found that both strategies decrease blood pressure, but adding a new medication has a very slim advantage over increasing the dose of an existing medication, despite some of the patients being unable to stay on the new medication.

In the end, the researchers say, the new findings could add to discussions between physicians and patients whose blood pressure remains elevated despite starting medication treatment.

The findings, published in the Annals of Internal Medicine by a team from the University of Michigan and the VA Ann Arbor Healthcare System, focus on patients whose initial systolic blood pressure was above 130 mm Hg.

By looking back at VA and Medicare data, the researchers were able to see patterns in treatment and blood pressure readings over time, in a kind of natural experiment. All the patients were taking at least one blood pressure medication at less than the maximum dose and had a treatment intensification at the start of the study period, indicating that their physicians thought they needed more intense treatment.

Because intensification of blood pressure treatment can come with risks — whether a drug interaction if a new drug is added, or an electrolyte imbalance with high doses, or fainting and falling if a person’s pressure gets too low — such decisions must be carefully made.

This is the first time a study has directly compared the effects of the two approaches, said first author Carole E. Aubert, M.D., M.Sc., a general internist from Bern University in Switzerland who performed much of the research while a scholar at the U-M Institute for Healthcare Policy and Innovation.

“There’s increasing guidance on approaches to starting treatment in older adults, but less on to the next steps to intensify treatment, especially in an older and medically complex population that isn’t usually included in clinical trials of blood pressure medication,” she said. “How can we increase medications safely in a population already taking many medications for hypertension and other conditions.”

“Treatment guidelines do suggest starting treatment with multiple medications, and clinicians are comfortable with an approach of ‘starting low and going slow’ in older patients,” said senior author Lillian Min, M.D., M.S.H.S. “But these results show that in older patients, we have further opportunity to tailor choices in intensifying drug therapy for hypertension, depending on the individual patient’s characteristics.”

She continued, “Is the patient more likely to stick to a simpler regimen? Then increase an existing medication. Or is the blood pressure very high and the clinician is more concerned about reducing it? Then consider starting a new medication now.” Min is a geriatrician at the Division of Geriatrics and Palliative Care at Michigan Medicine, U-M’s academic medical center, and the VA Ann Arbor Healthcare System Geriatric Research Education and Clinical Center.

For older adults who already take a range of medications, the added complexity of having to take one more kind of pill may be too much. The risks of polypharmacy, the term for taking multiple medications, are already well-known from other research, Min said. In fact, Medicare covers an annual medication review with a pharmacist for many older adults who take many drugs.

The research was funded by the National Institute on Aging and the Veterans Health Administration. In addition to Aubert and Min, the research team included Jeremy B. Sussman, M.D., M.S.; Timothy P. Hofer, M.D., M.Sc.; William C. Cushman, M.D.; and Jin-Kyung Ha, PhD.

Now, new research has identified proteins called linker histones as the factor that controls whether DNA winds into long and thin chromosomes, made up of many small loops, or short and thick chromosomes with fewer large loops. The findings, published in eLife, are the first to describe how chromosome shape is tuned by linker histones at the molecular level.

“The linker histone was once thought to impact only a narrow range of the genetic material,” says Rockefeller’s Hironori Funabiki. “We have now shown that it controls the number of loops in the chromosome and its ultimate shape, a much larger regulation space than expected.”

Beyond “beads on a string”

Genetic material is organized around a nucleosome — often depicted as a bead on a string, with a length of DNA “string” wound around a central protein “bead.” The string is clamped to its bead by a sort of protein clip — the linker histone — which is also involved in folding multiple nucleosome beads into chromatin fibers. These fibers form chromosomes after they are ratcheted through a molecular motor, the condensin, that organizes chromatin into loops.

Chromosomes come in a wide range of shapes across species and cell types, largely based on the size of each chromatin loop. Funabiki draws an example from the familiar (and frustrating) experience of coiling wired earphones. If you wrap them into many tiny loops, the headphones will fit neatly into your pocket. If, however, you wind the wires into only a few large loops, the earphones form a bulky mass. Similarly, a greater number of small loops will give rise to longer, thinner chromosomes; a few large loops of chromatin will form shorter, thicker chromosomes.

Scientists knew that loop formation lay at the heart of chromosome size and shape, but how various cells tuned this process to form larger or smaller loops remained a mystery.

A new role for linker histone

Funabiki and colleagues set out to solve this mystery. Using a method developed by Job Dekker at the University of Massachusetts Medical School, the team analyzed DNA from frog eggs and found that linker histones — beyond clamping strings to beads and organizing them into fibers — also prevent condensin from binding to nucleosomes and forming chromatin loops.

A picture of loop formation began to emerge, with linker histones at the very heart of the process. Changing the shape of a chromosome, the researchers found, is a simple matter of increasing or decreasing the amount of linker histone available to inhibit condensin.

When a high concentration of linker histone blocks condensin, the protein complex is able to make fewer loops of chromatin. Since only a handful of loops are forming, there’s enough slack in the line for those loops to develop into large coils that will eventually bunch up into short, thick chromosomes. Lower concentrations of linker histone kick off the opposite process: condensin is free to form many more loops, so there is less fiber available to contribute to each loop. The result is a large number of smaller loops, which compress neatly into long, thin chromosomes.

Funabiki speculates that cells may have evolved the ability to tune chromosome length in order to speed up or slow down their growth. “The longer the chromosome is, the more time it takes to separate during cell division,” he says. “Frog eggs are exposed to dangerous environments, so speed is important. Successful reproduction depends on how quickly the eggs can turn into tadpoles and escape. Perhaps frog eggs maintain shorter chromosomes to allow for rapid cell division.”

In the future, Funabiki’s lab will explore whether linker histones play a similar role in influencing the size and shape of human chromosomes. “This initial work only involved frog eggs,” says lead author Pavan S. Choppakatla, a member of the Funabiki lab. “We are now looking at linker histones in human eggs and somatic cells, to see whether our findings are widely applicable.”