ALICE shines light into the nucleus to probe its structure

 

In the Large Hadron Collider, proton and lead beams travel close to the speed of light. They carry a strong electromagnetic field that acts like a flux of photons as the beam moves through the accelerator. When the two beams at the LHC pass by close to each other without colliding, one of the beams may emit a photon of very high energy that strikes the other beam. This can result in photon—nucleus, photon—proton, and even photon—photon collisions. The ALICE collaboration studies these collisions to investigate protons and the inner structure of nuclei, and has recently released new results on this topic at the LHCP 2023 conference.

Photons are ideal tools to study the interior of nuclei. Usually when a photon collides with a nucleus, two gluons (force carriers of the strong interaction) are exchanged, which results in the production of a quark-antiquark pair. Researchers further distinguish two different classes of these collisions: when a photon interacts with the whole nucleus (a coherent collision), and when a photon interacts with a single nucleon inside the nucleus (an incoherent collision).

Inside nuclei, scientists look for high numbers of gluons, which indicate high levels of gluon density. Theoretical models suggest that the gluon density inside nuclei increases when they approach the speed of light. If the density increases enough, the nucleus will become saturated with gluonic matter, meaning that the number of gluons in the nucleus cannot increase any further. Directly probing gluonic saturated matter is one of the main outstanding challenges in the field of strong interactions, and observing it could lead to further insight into the inner structure of protons and nuclei.

If a charm quark-antiquark pair is produced in a photon—nucleus collision, this is known as J/ψ meson production. Scientists study how coherent J/ψ production varies with photon energy in order to look for gluon saturation effects. As the photon energy increases, it becomes easier and easier to “see” the gluonic matter inside the nuclei. The new ALICE results on J/ψ production using LHC Run 2 data cover a larger momentum range than previous measurements from Run 1, and are in line with expectations of gluon-saturation models.

Incoherent collisions offer the opportunity to study geometrical configurations of the quantum fluctuations in the internal structure of the proton. The ALICE collaboration achieves this by studying the distribution of momentum that is transferred to the J/ψ meson. In a new study, the collaboration has been able to show that this momentum transfer can only be described when areas of saturated gluonic matter, called gluonic hotspots, are introduced into the models.

The ALICE collaboration will continue to investigate these phenomena in LHC Runs 3 and 4, where high-precision measurements with larger data samples will provide more powerful tools to better understand the role of saturation and gluonic hotspots.

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Next-generation electrochemical sensors to be launched later this year

 Sentek has developed an innovative new design for their highly acclaimed range of electrodes that features zero leakage, fill stopper technology and sensor information displayed clearly on the stem, in an all-new, streamlined cap design, whilst maintaining the same, affordable price..

“We’re thrilled to be launching this exciting new product upgrade which provides our customers with a smart and reliable sensor” commented Kenny Petrie, Sentek’s founder and Technical Director. “At our core, we constantly strive to provide our customers with exceptional quality at a reasonable price, and the features of this new design achieves just that.” 

Whether used for testing biological samples in a lab, monitoring pH in a brewery, or the measurement of soil conductivity, the electrodes, and their striking cap design, brought the dependable experience, that Sentek customers have become accustomed, to an incredible price point. This has always been the purpose of Sentek’s electrodes, and now the product is getting even better.

Along with free technical support for the life of the probe, the upgrade delivers zero solution leakage on re-fillable electrodes, by applying years of hands-on experience. The new electrodes offer durability and easier maintenance using robust, easy-to-clean ABS material and electrode information and specification are conveniently displayed on the electrode stem of key sensors. 

These new electrodes will go into production later this year but are available already for pre-ordering. The new design will be applied to the Sentek branded range of electrodes and will improve the usability of this essential testing equipment significantly.

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‘Dynamic bonds’ reshape the rules of aromaticity and chirality

 New discoveries in ‘dynamic bonds’ could reshape our fundamental understanding of key chemical concepts, including aromaticity and chirality. A team at the University of York in the UK has synthesised a polycyclic molecule whose aromaticity can be switched on and off, as well as a carbon cage where chiral carbon atoms interconvert without breaking bonds at the stereocentre. This ‘subverts our view of carbon-based molecules as fixed objects’, according to lead author Paul McGonigal. In the future, these new concepts could one day underpin ‘new applications for dynamic molecular materials’.

The researchers started by studying fluxional molecules.1 In these species, different functional groups interchange positions but, depending on the velocity of the process and the timescales of the observations, they may appear identical. An example is the extremely fast interconversion between cyclohexane chair and boat conformations. In an attempt to control and condition the interconversion rates of a range of fluxional molecules, researchers at York started overcrowding the structures with bulky and highly crowded systems. ‘We were lucky to observe both phenomena while exploring the effects of bond strain in fluxional molecules,’ explains McGonigal. Previously, the team had used this strategy to create unusual luminescence in strained structures, such as molecular rotors. Now, the results demonstrate dynamism is more common in organic molecules than previously thought.

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A New Experiment Casts Doubt on the Leading Theory of the Nucleus

 

Excited helium nuclei inflate like balloons, offering physicists a chance to study the strong nuclear force, which binds the nucleus’s protons and neutrons.

Anew measurement of the strong nuclear force, which binds protons and neutrons together, confirms previous hints of an uncomfortable truth: We still don’t have a solid theoretical grasp of even the simplest nuclear systems.

To test the strong nuclear force, physicists turned to the helium-4 nucleus, which has two protons and two neutrons. When helium nuclei are excited, they grow like an inflating balloon until one of the protons pops off. Surprisingly, in a recent experiment, helium nuclei didn’t swell according to plan: They ballooned more than expected before they burst. A measurement describing that expansion, called the form factor, is twice as large as theoretical predictions.

“The theory should work,” said Sonia Bacca, a theoretical physicist at the Johannes Gutenberg University of Mainz and an author of the paper describing the discrepancy, which was published in Physical Review Letters. “We’re puzzled.”

The swelling helium nucleus, researchers say, is a sort of mini-laboratory for testing nuclear theory because it’s like a microscope — it can magnify deficiencies in theoretical calculations. Physicists think certain peculiarities in that swelling make it supremely sensitive to even the faintest components of the nuclear force — factors so small that they’re usually ignored. How much the nucleus swells also corresponds to the squishiness of nuclear matter, a property that offers insights into the mysterious hearts of neutron stars. But before explaining the crush of matter in neutron stars, physicists must first figure out why their predictions are so far off.

Bira van Kolck, a nuclear theorist at the French National Center for Scientific Research, said Bacca and her colleagues have exposed a significant problem in nuclear physics. They’ve found, he said, an instance where our best understanding of nuclear interactions — a framework known as chiral effective field theory — has fallen short.

“This transition amplifies the problems [with the theory] that in other situations are not so relevant,” van Kolck said.

The Strong Nuclear Force

Atomic nucleons — protons and neutrons — are held together by the strong force. But the theory of the strong force was not developed to explain how nucleons stick together. Instead, it was first used to explain how protons and neutrons are made of elementary particles called quarks and gluons.

For many years, physicists didn’t understand how to use the strong force to understand the stickiness of protons and neutrons. One problem was the bizarre nature of the strong force — it grows stronger with increasing distance, rather than slowly dying off. This feature prevented them from using their usual calculation tricks. When particle physicists want to understand a particular system, they typically parcel out a force into more manageable approximate contributions, order those contributions from most important to least important, then simply ignore the less important contributions. With the strong force, they couldn’t do that.

Then in 1990, Steven Weinberg found a way to connect the world of quarks and gluons to sticky nuclei. The trick was to use an effective field theory — a theory that is only as detailed as it needs to be to describe nature at a particular size (or energy) scale. To describe the behavior of a nucleus, you don’t need to know about quarks and gluons. Instead, at these scales, a new effective force emerges — the strong nuclear force, transmitted between nucleons by the exchange of pions.

Weinberg’s work helped physicists understand how the strong nuclear force emerges from the strong force. It also made it possible for them to perform theoretical calculations based on the usual method of approximate contributions. The theory — chiral effective theory — is now widely considered the “best theory we have,” Bacca said, for calculating the forces that govern the behavior of nuclei.

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To Battle Climate Change, Scientists Tap Into Carbon-Hungry Microorganisms for Clues

 

Scientists at Lawrence Berkeley National Laboratory (Berkeley Lab) have demonstrated a new technique, modeled after a metabolic process found in some bacteria, for converting carbon dioxide (CO2) into liquid acetate, a key ingredient in “liquid sunlight” or solar fuels produced through artificial photosynthesis.

The new approach, reported in Nature Catalysis, could help advance carbon-free alternatives to fossil fuels linked to global warming and climate change.

The work is also the first demonstration of a device that mimics how these bacteria naturally synthesize acetate from electrons and CO2.

“What’s amazing is that we learned how to selectively convert carbon dioxide into acetate by mimicking how these little microorganisms do it naturally,” said senior author Peidong Yang, who holds titles of senior faculty scientist in Berkeley Lab’s Materials Sciences Division and professor of chemistry and materials science and engineering at UC Berkeley.

“Everything we do in my lab to convert CO2 into useful products is inspired by nature. In terms of mitigating CO2 emissions and fighting climate change, this is part of the solution.”

– Peidong Yang, Berkeley Lab senior faculty scientist, Materials Sciences Division

For decades, researchers have known that a metabolic pathway in some bacteria allows them to digest electrons and CO2 to produce acetate, a reaction driven by the electrons. The pathway breaks CO2 molecules down into two different or “asymmetric” chemical groups: a carbonyl group (CO) or a methyl group (CH3). Enzymes in this reaction pathway enable the carbons in CO and CH3 to bond or “couple,” which then triggers another catalytic reaction that produces acetate as the final product.

Researchers in the field of artificial photosynthesis have wanted to develop devices that mimic the pathway’s chemistry – called asymmetric carbon-carbon coupling – but finding synthetic electrocatalysts that work as efficiently as bacteria’s natural enzymatic catalysts has been challenging.

“But we thought, if these microorganisms can do it, one should be able to mimic their chemistry in the lab,” Yang said.

Advancing artificial photosynthesis with carbon-hungry copper

Copper’s talent for converting carbon into various useful products was first discovered in the 1970s. Based on those previous studies, Yang and his team reasoned that artificial photosynthesis devices equipped with a copper catalyst should be able to convert CO2 and water into methyl and carbonyl groups, and then turn these products into acetate. So for one experiment, Yang and team designed a model device with a copper surface; then, they exposed the copper surface to liquid methyl iodide (CH3I) and CO gas, and applied an electrical bias to the system.

The researchers hypothesized that CO would stick to the copper surface, triggering the asymmetric coupling of CO and CH3 groups to produce acetate. Isotope-labelled CH3I was used in the experiments in order to track the reaction pathway and final products. (An isotope is an atom with more or fewer neutrons (uncharged particles) in its nucleus than other atoms of an element.)

And they were right. Chemical analytical experiments conducted in Yang’s UC Berkeley lab revealed that copper’s pairing of carbonyl and methyl groups produced not only acetate but other valuable liquids, including ethanol and acetone. The isotopic tracking allowed the researchers to confirm that the acetate was formed through the combination of the CO and CH3.

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Biosensor Versatility; From Analytical Chemistry to Diagnostics

 Classical diagnostic methods tend to be better suited for on-the-spot blood measurement. This form of method is conducted periodically, such as twice a year, and it gives you a single measurement. However, some circumstances require biochemical information to be monitored as it fluctuates, such as diabetics.

In diabetics, we have what we call CGM, Continuous Glucose Monitor, which monitors glucose fluctuation. This type of fluctuation must also be monitored for cardiac, stress, wellness, and nutrition.

Measuring blood monthly or quarterly is an insufficient method, as you are unable to get an idea of the overall picture and identify any trends. This is not only the case in medicine, but also in fitness; you want to continuously monitor your hydration or lactate – all of which fluctuate.

There are a lot of temporal variations in kidney and cardiac diseases. Thus, taking just one measurement will not provide useful information.

If you look at the glucose market, it is dominated by electrochemical devices. The beauty of an electrochemical sensor is that it is a small, compact, portable device that is easy to mass produce with a low power requirement, making them very attractive technologies.

For instance, the finger stick blood test, a mobile self-testing or wearable device, relies on electrochemistry because of these unique properties.

We are creating wearable alcohol or opioid sensors to help prevent drunk driving or drug abuse. A sensor that can monitor cortisol levels would also be highly advantageous when it comes to determining stress levels. Other useful targets would be vitamins to aid in monitoring personal nutrition.

We are also hoping to develop a sensor to help identify trace elements and minerals in food supplements. Nerve agents for monitoring the body’s surroundings – such as electrolytes, metabolites, and hormones – are other viable targets.

The beauty of these sensors is that they are non-invasive, as you do not need to physically take a sample of blood. However, everything needs to be validated by comparing to blood, which is the gold standard, so we must also validate without controlled conditions. Other challenges include changes in the surrounding temperature, e.g., when running around in the summer compared to in winter. Common bioreceptor, such as enzymes are not so stable in uncontrolled extreme conditions.

There is also the issue of bio-fouling. In terms of mobility, it is easy to measure your steps, calories, or ECG artery as these are physical characteristics. However, when it comes to chemical sensing, you need a bioreceptor, and you need to immobilize it to make it stable. This is why we do not have many of these except glucose.

It is a great honor to have been presented with this award, especially as I knew Ralph Adam personally. Ralph Adam passed away in 2002; he was a fantastic scientist and, more importantly, a wonderful person. He had a vision and shared my idea to make receptors simple but creative.

He was the first to put electrodes in the brain of small animals and gain insight into the neurochemicals of the brain. This was back in the 70s. At present, I am now putting electrodes in the skin. The progression in this field is astounding, but it would not have been possible without great scientists like Ralph.

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New Unsaturated Fatty Acids Discovered in Human Samples

 

QUT researchers have discovered 103 new unsaturated fatty acids in human derived samples. These findings have doubled the number of these fundamental building blocks of life previously reported in human blood plasma.

In an article in the prestigious journal Nature Communications, QUT researchers and their colleagues in Adelaide and Prague have described their findings and the new analytical technique that enabled the discoveries.

Professor Stephen Blanksby, from the QUT Centre for Materials Science said the human body made its own fatty acids but also took up fatty acids from food that were then modified to make them fit for purpose.

“Lipids play many roles in the body - some form cell membranes, others are precursors for signalling molecules that regulate how the body copes with inflammation and the resolution of inflammation,” Professor Blanksby said.

“This means changes in fatty acids and other lipids (complex fats made from fatty acids) in the body can provide critical clues for health and disease.”

“We know that blood tests report on lipids like cholesterol and triglycerides that are linked to our health status and, with further research, these new molecules could provide critical information about our bodies’ responses to diet or disease.”

Professor Blanksby said QUT researchers developed advanced analytical technology to probe the human lipidome (all lipids in a cell) more deeply than was previously possible.

“The discovery of new lipids and new lipid metabolism using this approach paves the way for more sensitive and selective diagnostic tests,” he said.

Dr Jan Philipp Menzel, a postdoctoral fellow in the QUT School of Chemistry and Physics, said the discoveries were enabled by a combination of liquid chromatography with a mass spectrometer modified to enable a gas-phase reaction with ozone that broke down the carbon-carbon double bonds in unsaturated fatty acids.

Dr Menzel developed custom software to trawl the complex datasets the team obtained to identify the novel lipids.

“It was an innovative approach that allowed us to characterise the structure of unsaturated fatty acids,” Dr Menzel said.

“Using this process we studied human blood plasma, cancer cells, and vernix caseosa, a white layer covering newborns, and found new and different fatty acids in each.

“Some of the newly found fatty acids may not originate from human metabolism but are likely present in blood plasma, for example, after being consumed in food whereas most fatty acids found in vernix caseosa are likely to be a product of human metabolism.

“Our investigation of cancer cell lines included the addition of an enzyme inhibitor to one cell line that helped to assign which fatty acids were formed in increased amounts in laboratory conditions.

“Some of our results show the same trends established in several recent publications and add to the body of evidence that fatty acid metabolism is an important aspect of the metabolism of cancer cells.

“It will take a concerted effort by many scientists around the world to unravel the full biological significance of all the fatty acids that were identified in this study. For example, some new omega-3 fatty acids found in vernix caseosa have unusual patterns of double bonds.

“Fish and seafood, walnuts and flaxseed are well known for essential fatty acids (omega-3 polyunsaturated fatty acids) and their health benefits. However, we currently know very little about the new omega-3 fatty acids we detected on the skin of newborns.”

“The exact structure of a biomolecule determines its biological function, a principle used extensively in biochemistry and biomedical research. Finding biomolecules with new structures (here, differences in the position of double bonds along a fatty acid chain) could be a first step towards studying new metabolic pathways or even develop diagnostic methods or treatments.”

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