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An investigation carried out by the Organisation for the Prohibition of Chemical Weapons (OPCW) has concluded that there are ‘reasonable grounds’ to believe that Islamic State (IS) deployed sulfur mustard in attacks that took place on 1 September 2015 in Syria.

According to the findings of the investigation, which was carried out by the OPCW’s investigation and identification team (IIT) between January 2023 and February 2024, the chemical agent was delivered using one or more artillery pieces from areas under IS control at soldiers primarily from the Syrian Armed Forces. All remnants and munitions observed at several sites across the town of Marea, Syria, were conventional 122mm artillery shells modified to disperse a liquid payload, the report stated.

‘Upon impact, at least six projectiles leaked a black, viscous substance with a distinct “pungent” and “garlic-like” smell,’ the report noted. ‘At least 11 named individuals who came into contact with the liquid substance experienced symptoms consistent with exposure to sulfur mustard.’

The IIT’s comprehensive assessment of the attack included information from the fact-finding mission, relevant countries and interviews, as well as analyses of samples, computer modelling, satellite imagery and videos and photos.

They concluded that no entity other than IS possessed the means, motives and capabilities to deploy sulfur mustard and that the deployment of chemical weapons, as seen in Marea, would only have occurred with direct orders from IS’s leaders.

For the first time, researchers have observed communication between the rotors in a molecular motor. Although the exact mechanism is still a mystery, communicating components could convey complex and controlled movements to molecular machines, better mimicking biological systems.

In molecular motors, external stimuli such as light or heat activate movement. In structures with different rotors, usually each rotation operated independently, however here, ‘[we] show that the rotors have a profound impact on each other’, explains first author Carlijn van Beek, who works in the laboratory of Ben Feringa at the University of Groningen in the Netherlands. The communication between the components affects the behaviour of the overall structure. ‘It’s similar to macroscopic gears, [within] a small molecular system,’ says van Beek. ‘The motor [behaves] as two motorised gears – the two rotors – connected via a third gear, the motor core unit.’

To create the motor van Beek combined fragments of previous molecular motors into a new ‘bridged-isoindigo’ structure. According to the authors, the isoindigo structure ‘revealed another dimension to the traditional mechanism of molecular motors’, where a double metastable intermediate connects the two rotor subunits – effectively creating a communication channel. In traditional molecular motors, one component must complete a rotation before the other is activated, she explains. In contrast, the changes in conformation of one rotor in the isoindigo structure somehow sterically ‘pushes’ the central core unit, which then influences the movement of the other rotor. Moreover, it brought some additional advantages, such as increased solubility and a simpler synthetic process. Nevertheless, the design wasn’t straightforward, says van Beek. ‘In molecular machines … achieving the desired function required a delicate balance of different motions,’ she explains.

‘This system is much more complex [than] other systems in the literature,’ says Aisha Bismillah, an expert in supramolecular chemistry at the University of York, UK. ‘It’s designed in such a clever way,’ she adds. ‘Instead of all the parts of the molecule rotating independently of one another, [they] communicate to one another and influence the rotational motion.’ In part, the communication occurs thanks to the carbon–carbon double bonds that connect the rotor ‘gears’ to the central unit. The study is especially interesting, says Bismillah, as the authors went through ‘a lot of detail to show full understanding of how each of the 12 steps [connecting the eight different isomers] work’.

To investigate the intricate mechanism of the molecular motor, van Beek used a combination of NMR and UV-visible spectroscopy. In both cases, some experiments required temperatures down to -110°C. Cooling the sample slowed down an otherwise extremely fast rotation, facilitating the study of the different steps of the cycle in detail. ‘The design is clever [because] it incorporates a fluorine atom into the structure,’ explains Bismillah. This ‘tag’ added the possibility of using fluorine NMR, which tends to showcase simpler signals.

‘Fluorine NMR spectroscopy studies were very helpful,’ explains van Beek. ‘We could differentiate and follow all eight possible isomers using this technique,’ she says. Additionally, they carried out DFT studies to characterise the conformations of all isomers, particularly the double metastable intermediate, which is key to communication in the coupled rotors. Despite all efforts, the exact explanation for the communication mechanism remained elusive. Yet, the study provides a ‘fundamental understanding’ of the characteristics of coupling in molecular motors, says Bismillah, creating a solid base ‘before moving onto more complex systems [with] several motors working together, such as systems in biology’.

Van Beek says the isoindigo system is a small scale, molecular equivalent of bigger biological machinery like the ATP synthase enzyme, which also exhibits mechanically coupled motion. ‘Although the ATP synthase is clearly capable of much more sophisticated functions than our synthetic motor … the development and control of molecular-level motions will open many possibilities,’ she says. Maybe, artificial molecular motors could present properties ‘beyond biological and macroscopic machines … achieving new functionalities’.

School mathematics teaching is stuck in the past. An adult revisiting the school that they attended as a child would see only superficial changes from what they experienced themselves.

Yes, in some schools they might see a room full of electronic tablets, or the teacher using a touch-sensitive, interactive whiteboard. But if we zoom in on the details – the tasks that students are actually being given to help them make sense of the subject – things have hardly changed at all.

We’ve learnt a huge amount in recent years about cognitive science – how our brains work and how people learn most effectively. This understanding has the potential to revolutionise what teachers do in classrooms. But the design of mathematics teaching materials, such as textbooks, has benefited very little from this knowledge.

Some of this knowledge is counter-intuitive, and therefore unlikely to be applied unless done so deliberately. What learners prefer to experience, and what teachers think is likely to be most effective, often isn’t what will help the most.

For example, cognitive science tells us that practising similar kinds of tasks all together generally leads to less effective learning than mixing up tasks that require different approaches.

In mathematics, practising similar tasks together could be a page of questions each of which requires addition of fractions. Mixing things up might involve bringing together fractions, probability and equations in immediate succession.

Learners make more mistakes when doing mixed exercises, and are likely to feel frustrated by this. Grouping similar tasks together is therefore likely to be much easier for the teacher to manage. But the mixed exercises give the learner important practice at deciding what method they need to use for each question. This means that more knowledge is retained afterwards, making this what is known as a “desirable difficulty”.

Cognitive science applied

We are just now beginning to apply findings like this from cognitive science to design better teaching materials and to support teachers in using them. Focusing on school mathematics makes sense because mathematics is a compulsory subject which many people find difficult to learn.

Typically, school teaching materials are chosen by gut reactions. A head of department looks at a new textbook scheme and, based on their experience, chooses whatever seems best to them. What else can they be expected to do? But even the best materials on offer are generally not designed with cognitive science principles such as “desirable difficulties” in mind.

My colleagues and I have been researching educational design that applies principles from cognitive science to mathematics teaching, and are developing materials for schools. These materials are not designed to look easy, but to include “desirable difficulties”.

They are not divided up into individual lessons, because this pushes the teacher towards moving on when the clock says so, regardless of student needs. Being responsive to students’ developing understanding and difficulties requires materials designed according to the size of the ideas, rather than what will fit conveniently onto a double-page spread of a textbook or into a 40-minute class period.

Switching things up

Taking an approach led by cognitive science also means changing how mathematical concepts are explained. For instance, diagrams have always been a prominent feature of mathematics teaching, but often they are used haphazardly, based on the teacher’s personal preference. In textbooks they are highly restricted, due to space constraints.

Often, similar-looking diagrams are used in different topics and for very different purposes, leading to confusion. For example, three circles connected as shown below can indicate partitioning into a sum (the “part-whole model”) or a product of prime factors.

These involve two very different operations, but are frequently represented by the same diagram. Using the same kind of diagram to represent conflicting operations (addition and multiplication) leads to learners muddling them up and becoming confused.

The “coherence principle” from cognitive science means avoiding diagrams where their drawbacks outweigh their benefits, and using diagrams and animations in a purposeful, consistent way across topics.

For example, number lines can be introduced at a young age and incorporated across many topic areas to bring coherence to students’ developing understanding of number. Number lines can be used to solve equations and also to represent probabilities, for instance.

Unlike with the circle diagrams above, the uses of number lines shown below don’t conflict but reinforce each other. In each case, positions on the number line represent numbers, from zero on the left, increasing to the right.

There are disturbing inequalities in the learning of mathematics, with students from poorer backgrounds underachieving relative to their wealthier peers. There is also a huge gender participation gap in maths, at A-level and beyond, which is taken by far more boys than girls.

Socio-economically advantaged families have always been able to buy their children out of difficulties by using private tutors, but less privileged families cannot. Better-quality teaching materials, based on insights from cognitive science, mitigate the impact for students who have traditionally been disadvantaged by gender, race or financial background in the learning of mathematics.