In The Physics Teacher, co-published by AIP Publishing and the American Association of Physics Teachers, researcher T. Ryan Rogers designed a hand-held model to demonstrate the concept of entropy for students. Using everyday materials, Rogers’ approach allows students to confront the topic with new intuition — one that takes specific aim at the confusion between entropy and disorder.

“It’s a huge conceptual roadblock,” Rogers said. “The good news is that we’ve found that it’s something you can correct relatively easily early on. The bad news is that this misunderstanding gets taught so early on.”

While many classes opt for the imperfect, qualitative shorthand of calling entropy “disorder,” it’s defined mathematically as the number of ways energy can be distributed in a system. Such a definition merely requires students to understand how particles store energy, formally known as “degrees of freedom.”

To tackle the problem, Rogers developed a model in which small objects such as dice and buttons are poured into a box, replicating a simple thermodynamic system. Some particles in the densely filled box are packed in place, meaning they have fewer degrees of freedom, leading to an overall low-entropy system.

As students shake the box, they introduce energy into the system, which loosens up locked-in particles. This increases the overall number of ways energy can be distributed within the box.

“You essentially zoom in on entropy so students can say, ‘Aha! There is where I saw the entropy increase,'” Rogers said.

As students shake further, the particles settle into a configuration that more evenly portions out the energy among them. The catch: at this point of high entropy, the particles fall into an orderly alignment.

“Even though it looks more orientationally ordered, there’s actually higher entropy,” Rogers said.

All the students who participated in the lesson were able to reason to the correct definition of entropy after the experiment.

Next, Rogers plans to extend the reach of the model by starting a conversation about entropy with other educators and creating a broader activity guide for ways to use the kits for kindergarten through college. He hopes his work inspires others to clarify the distinction in their classrooms, even if by DIY means.

“Grapes and Cheez-It crackers are very effective, as well,” Rogers said.

The findings, published today in the journal Science Advances, shed new light on genomic imprinting, a fundamental, biological process in which a gene from one parent is switched off while the copy from the other parent remains active. Errors in imprinting are linked to a host of diseases, such as the rare disease Silver-Russell syndrome along with certain cancers and diabetes.

“Proper imprinting is crucial for lifelong health but, despite its importance, we still lack a full understanding of the factors that regulate this vital process,” said VAI Associate Professor Piroska Szabó, Ph.D., the study’s corresponding author. “Our findings reveal an RNA mechanism that governs establishment of imprinting and illuminates why it differs between fathers and mothers.”

Our genetic information is encoded in DNA, a long, winding molecule that is tightly packed to form 23 pairs of chromosomes, half of which come from one’s father and half from one’s mother. Sperm and eggs only contain 23 single chromosomes — half of the genetic material required for life. During fertilization, they each contribute their half, resulting in a zygote with a full set of 23 pairs of chromosomes.

But not all instructions in DNA are needed at the same time or in the same places. That’s where epigenetics come in. Epigenetic mechanisms annotate DNA with special chemical tags called methyl groups, which tell certain genes when to be active and when to be silent — all without changing the sequence of DNA itself.

Imprinting occurs when methyl groups are added to certain genes during either sperm or egg formation. This, in turn, is important for determining which parental copy of that gene is expressed in the offspring.

To better understand the processes that govern imprinting, Szabó and colleagues focused on an imprinting control region in the DNA that regulates the Igf2 gene. Igf2 plays key roles in fetal growth and only is active in the chromosome inherited from the father. Too little methylation in the IGF2 control region in humans can result in Silver-Russell syndrome, which is marked by reduced growth and increased risk of metabolic disease.

“If the IGF2 gene’s imprinting control region from one’s father is not methylated, it can result in disease,” Szabó said.

Using genetic models and in-depth genetic sequencing, the team found that the methylation of the Igf2 control region in paternally inherited DNA is governed by an underlying RNA-based process in the male germline.

“We found earlier that RNA similarly runs through other paternally marked imprinted domains in the male germ cells, suggesting that this same process is generally true for paternal imprinting,” Szabó said. “These results suggest a more broadly applicable process, which is exciting and will need to be confirmed in subsequent studies.”

Other authors include Ji Liao, Ph.D., Zhen Fu, Ph.D., Ivan VanderKolk, Brianna M. Busscher and Kin H. Lau, Ph.D., of VAI; Sangmin Song of City of Hope Cancer Center; and Samuel Gusscott, Ph.D., and Julie Brind’Amour, Ph.D., of Université de Montréal.

“These findings indicate that even people with traumatic brain injuries in earlier life who appear to have fully recovered from them may still be at increased risk of cognitive problems and dementia later in life,” said study author Marianne Chanti-Ketterl, PhD, MSPH, of Duke University in Durham, North Carolina. “Among identical twins, who share the same genes and many of the same exposures early in life, we found that the twin who had a concussion had lower test scores and faster decline than their twin who had never had a concussion.”

The study involved 8,662 men who were World War II veterans. The participants took a test of thinking skills at the start of the study when they were an average age of 67 and then again up to three more times over 12 years. Scores for the test can range from zero to 50. The average score for all participants at the beginning of the study was 32.5 points.

A total of 25% of the participants had experienced a concussion in their life.

Twins who had experienced a concussion were more likely to have lower test scores at age 70, especially if they had a concussion where they lost consciousness or were older than 24 when they had their concussion. Those twins with traumatic brain injury with loss of consciousness, more than one traumatic brain injury and who had their injuries after age 24 were more likely to have faster cognitive decline than those with no history of traumatic brain injury.

For example, a twin who experienced a traumatic brain injury after age 24 scored 0.59 points lower at age 70 than his twin with no traumatic brain injury, and his thinking skills declined faster, by 0.05 points per year.

These results took into account other factors that could affect thinking skills, such as high blood pressure, alcohol use, smoking status and education.

“Although these effect sizes are modest, the contribution of TBI on late life cognition, in addition to numerous other factors with a detrimental effect on cognition, may be enough to trigger an evaluation for cognitive impairment,” Chanti-Ketterl said. “With the trend we are seeing with increased emergency room visits due to sports or recreation activity injuries, combined with the estimated half million members of the military who suffered a TBI between 2000 and 2020, the potential long-term impact of TBI cannot be overlooked. These results may help us identify people who may benefit from early interventions that may slow cognitive decline or potentially delay or prevent dementia.”

A limitation of the study was that traumatic brain injuries were reported by the participants, so not all injuries may have been remembered or reported accurately.

The study was supported by the National Institute on Aging and the U.S. Department of Defense.

The study was conducted in the research group of Professor Erez Hasman, head of the Atomic-Scale Photonics Laboratory, in collaboration with Professor Elad Koren, head of the Laboratory for Nanoscale Electronic Materials and Devices in the Department of Materials Science and Engineering, and Professor Ariel Ismach at Tel Aviv University. The two groups at the Technion are in association with the Helen Diller Quantum Center and Russell Berrie Nanotechnology Institute (RBNI). Dr. Kexiu Rong conducted and led the research, and collaborated with Dr. Xiaoyang Duan, Dr. Bo Wang, Dr. Vladimir Kleiner, Dr. Assael Cohen, Dr. Pranab K. Mohapatra, Dr. Avinash Patsha, Dr. Subhrajit Mukherjee, Dror Reichenberg, Chieh-li Liu, and Vladi Gorovoy.

Can we lift the spin degeneracy of light sources in the absence of magnetic fields at room temperature? According to Dr. Rong, “Spin-optical light sources combine photonic modes and electronic transitions and therefore provide a way to study the exchange of spin information between electrons and photons and to develop advanced optoelectronic devices. To construct these sources, a prerequisite is to lift the spin degeneracy between the two opposite spin states either in their photonic or electronic parts. This is usually accomplished by applying magnetic fields under a Faraday or Zeeman effect, although these approaches generally require strong magnetic fields and cannot produce miniaturized sources. Another promising way takes advantage of artificial magnetic fields for photonic spin-split states in momentum space, underpinned by a geometric phase mechanism.

Unfortunately, previous observations of spin-split states have relied heavily on propagation modes with low quality factors, which impose undesired limitations on spatial and temporal coherence of the sources. This approach is also hindered by the spin-controllable properties of a bulk laser gain material being unavailable or nontrivial to access for active control of the sources, especially in the absence of magnetic fields at room temperature.”

To achieve high-Q spin-split states, the researchers constructed photonic spin lattices with different symmetry properties, which comprise an inversion-asymmetry core and inversion-symmetry cladding integrated with a WS₂ monolayer to create laterally confined spin-valley states. The essential inversion-asymmetry lattice the researchers use has two important properties. (1) A controllable spin-dependent reciprocal lattice vector due to space-variant geometric phases from its constituting inhomogeneous-anisotropic nanoholes. This vector splits a spin-degenerate band into two spin-polarized branches in momentum space, being referred to as the photonic Rashba effect. (2) A pair of high-Q symmetry-enabled (quasi-) bound states in the continuum, that is, ±K (corners of the Brillouin zone) photonic spin-valley states, at the band edges of the spin-split branches. Moreover, the two states form a coherent superposition state with equal amplitudes.

Professor Koren noted that, “We used a WS₂ monolayer as the gain material because this direct-bandgap transition metal dichalcogenide possesses unique valley pseudospins, which have been widely investigated as an alternative information carrier in valleytronics. Specifically, their ±K’ valley excitons (radiated as in-plane spin-polarized dipole emitters) can be selectively excited by spin-polarized light according to a valley-contrasted selection rule, thus enabling active control of spin-optical light sources without magnetic fields.”

In the monolayer-integrated spin-valley microcavities, ±K’ valley excitons couple to ±K spin-valley states owing to polarization matching, and spin-optical excitonic lasing is achieved at room temperatures through strong optical feedback. Meanwhile, ±K’ valley excitons (initially without a phase correlation) are driven by the lasing mechanism to find the minimum-loss state of the system, which leads them to re-establish a phase-locked correlation according to the opposite geometric phases of ±K spin-valley states. This lasing-mechanism-driven valley coherence removes the need for cryogenic temperatures to suppress the intervalley scattering. Moreover, the minimum-loss state of the Rashba monolayer laser can be regulated to be satisfied (broken) via a linear (circular) pump polarization, which provides a way to control the lasing intensity and spatial coherence.

“The unveiled photonic spin valley Rashba effect provides a general mechanism to construct surface-emitting spin-optical light sources. The demonstrated valley coherence in the monolayer-integrated spin-valley microcavity makes a step towards achieving entanglement between ±K’ valley excitons for quantum information by means of qubits,” explains Professor Hasman. “For a long time, our group has been working on developing spin optics to harness photonic spin as an effective tool to control the behavior of electromagnetic waves. In 2018, we were attracted by valley pseudospins in two-dimensional materials, and therefore began a long-term project to study the active control of atomic-scale spin-optical light sources in the absence of magnetic fields. We initially tackled the challenge of coherent geometric phase pickup from individual valley excitons by using a non-local Berry-phase defect mode.

However, the underlying coherent addition of multiple valley excitons of the realized Rashba monolayer light sources remained unsolved, owing to the lack of a strong synchronizing mechanism between the excitons. This issue inspired us to think about high-Q photonic Rashba modes. Following innovations in new physical approaches, we achieved the Rashba monolayer laser described here.”

The research was supported by the Israel Science Foundation (ISF), the Helen Diller Foundation and the joint Technion NEVET grant by RBNI. The fabrication was performed at the Micro-Nano Fabrication & Printing Unit (MNF&PU) of the Technion.

The study focuses on a question that still generates debate among neuroscientists: whether infants who have not yet learned to speak (or are developing speech) are capable of logical reasoning. This pioneering research shows that this natural logical reasoning exists from at least 19 months of age, does not depend on knowledge of language and is developed mainly through the strategy of exclusion by elimination. In other words, if toddlers are faced with an unknown reality, they would try to analyse it and reach some conclusion about it by ruling out the options that are not possible, according to their level of knowledge at the time.

The results of the paper are presented in the article entitled The scope and role of deduction in infant cognition, written by Kinga Anna Bohus, Nicolo Cesana-Arlotti, Ana Martín-Salguero and Luca Lorenzo Bonatti. The principal researcher, L. Bonatti (ICREA), is the director of the Reasoning and Infant Cognition (RICO) research group at the Center for Brain and Cognition (CBC) at UPF. Kinga Anna Bohus (main author) also belongs to the group. N. Cesana-Arlotti and Ana Martín-Salguero, previously linked to the CBC at UPF, are currently researchers at Yale University (USA) and at the École Normale Supérieure in Paris.

Toddlers tend to solve uncertainties by ruling out impossible options according to the level of knowledge they have at any given moment

The study analyses the importance of two strategies for infants to deal with uncertainties: association and exclusion (or disjunction elimination). The first strategy would mean that toddlers hearing a new word that may refer to two unfamiliar objects that they can see, mentally associate the term with each of them. Subsequently, they would associate the term with the object with which this name fits better.

The second strategy (exclusion) explains how a toddler can learn a new word through logical reasoning by eliminating alternatives. For example, if they see two objects (A and B) and hear an unknown term that they know is not A (because they know the name of A), they will determine that it is the name of B. This is the predominant strategy, according to the results of the study.

Two experiments to analyse toddlers’ natural logic posed with known and unknown objects and terms

The research team conducted two different experiments, the first with 61 monolingual (26) and bilingual (35) 19-month-old toddlers and the second with 33 (19 mono and 14 bilingual). The analysis of each group was crucial to determine whether deductive processes depend on linguistic experience.

In the first experiment, the participants were shown two objects, which they had to associate with one of the words they heard, through different tests. In the first test, they had to look at two objects they knew (e.g., a spoon and a biscuit) and, upon hearing a term (e.g., spoon), associate it with one of the two. In the second test, the infants were shown an object they knew (e.g., an apple) and an object they did not know (e.g., a carburettor), and they heard the word corresponding to the known object (apple), which they had to identify. The third test was the same as the second, except that the word heard corresponded to the unknown word (e.g., carburettor).

In the second experiment, two objects or animate beings were used (for example, an umbrella and a figure of a boy), each associated with a sound. Subsequently, the two objects were covered so that the infant could not see them and one of them was placed in a glass. When they were uncovered, the toddler could only see one of the two objects and had to guess, by elimination, which one was inside the glass. In a subsequent test (with the two objects covered and without changing their position), the infant listened to the sound associated with one of them and it was analysed whether he/she looked in the direction of the correct object.

In all these tests, their gaze movement patterns were assessed. For example, when reasoning by exclusion, toddlers look at object A and, if they rule out that the term they have heard refers to it, then they turn their gaze towards B. This is known as the double check strategy.

There are no relevant differences in the logic of monolingual and bilingual toddlers

The main author of the research, Kinga Anna Bohus, summarizes the main findings of the study as follows: “We studied the presence of the concept of logical disjunction in 19-month-old infants. In a word-referent mapping task, both bilingual and monolingual infants display a pattern of oculomotor inspection previously found to be a hallmark of disjunctive reasoning in adults and children.”

In short, the results of the study show no relevant differences between the logical reasoning of monolingual and bilingual toddlers, which confirms that it does not depend on linguistic knowledge. This natural logical thinking could be present before the age of 19 months, although there is still not enough scientific evidence to demonstrate its presence at earlier ages.

The team of chemistry professor Claudia Höbartner from Julius-Maximilians-Universität (JMU) Würzburg now presents a newly discovered ribozyme called SAMURI in the journal Nature Chemistry.

SAMURI can precisely modify other RNA molecules. This ability is very helpful for RNA research: “We can use such ribozymes as tools to label RNA with dyes and make it visible,” says JMU researcher Dr. Takumi Okuda. “In this way, the pathways of RNA in the cell and its interactions with other molecules can be studied even better.”

Ribozymes may also be considered for therapeutic use in the future. “We see new possible applications for ribozymes when the enzymes responsible for a specific task are missing or are no longer functional due to mutations,” says Claudia Höbartner.

Details about the new ribozyme

What distinguishes the new ribozyme SAMURI? It modifies other RNA molecules at a precisely defined site of a specific adenine. There it attaches molecules to which, in turn, dyes or other molecules can easily be clicked in — like buckling up a seat belt. Such reactions are known as click chemistry.

SAMURI also has the advantage that it is active under the same physiological conditions that prevail in living cells. This is not the case with other synthetic ribozymes.

Another special feature: SAMURI uses a new synthetic cofactor to make RNA molecules accessible for click chemistry. This cofactor was developed by Dr. Takumi Okuda; it was inspired by the ubiquitous natural cofactor SAM (S-adenosylmethionine). This is also where the name of the new ribozyme comes from: SAMURI stands for “SAM-analogue utilising ribozyme.”

The following steps in research

Claudia Höbartner’s group next wants to elucidate the structure and mechanism of action of SAMURI. She also wants to develop further ribozymes that can modify RNA building blocks other than adenine.