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Understanding Small-Angle X-Ray Scattering

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Small angle X-ray scattering, or SAXS, is an experimental method where the intensity of the scattered X-rays is measured as a function of the scattering angle. The information obtained in a SAXS experiment can be used to recover information about the bulk microstructure within a sample and is commonly used to study condensed matter systems that are only partially ordered.

Image Credit: Juergen Faelchle/Shutterstock.com

One of the advantages of SAXS for the analysis of nanomaterials is that it can be used to analyze samples on a variety of length scales. In a typical SAXS experiment, the length scales measured can vary from the nanoscale to the mesoscale.

While for nanomaterial studies, some of the unique phenomena exhibited at the smallest length scales, such as enhanced thermal properties, are of primary interest, for many materials applications, the behavior across all length scales can be crucial for ensuring proper device performance.

SAXS Technique

In an X-ray scattering experiment, a sample is illuminated with an incident X-ray beam. Due to the interaction between the X-ray photons and atoms in the sample, some of the incident radiation will be scattered at different angles. Elastic scattering occurs when no energy exchange occurs between the incident X-ray photon and sample, so the scattered radiation is equal in energy to the incident radiation.

Some X-ray photons will be deflected or scattered at different angles to the incident X-ray radiation. By measuring the scattering angle and intensity of the X-ray radiation, information on the structural features of the sample can be recovered, such as particle sizes and distributions or the degree of disorder.

SAXS refers specifically to measuring the elastically scattered X-rays at small (~0 – 10°) angles. There is a related technique, wide-angle X-ray scattering (WAXS), that also measures elastically scattered radiation but at much wider scattering angles (> 10°).

Often, SAXS and WAXS experiments are performed together as changing the relative distance between the detector and the sample is sufficient to switch between a collection of wide or small-angle scattered radiation.

Many SAXS experiments are performed at advanced light source facilities such as synchrotrons as the weak nature of the scattering signal means that a high incident photon intensity is beneficial for improved signal-to-noise and reduced acquisition times in the measurement. However, there are a number of laboratory-based SAXS instruments as well, though acquisition times are typically very long.

Applications of SAXS

SAXS has several applications, including in the analysis of biological materials and nanomaterials. For nanoparticle analysis, SAXS is now often used as an in situ technique to monitor nanoparticle growth and formation. Understanding growth processes is an important part of developing synthesis strategies to grow nanoparticles in a controlled fashion and the structure of the nanoparticles determines their overall properties.

Nanoparticle sizing is a common application of SAXS due to the excellent spatial resolution of the technique that is achievable even in a laboratory environment. SAXS can also be used to extract concentration information from such samples.

SAXS is well-suited to in situ measurements of processes such as nanoparticle growth or materials synthesis as it requires minimal sample preparation and is compatible with a variety of sample types, including disordered solids and colloidal dispersions. In situ measurements require relatively short acquisition times to capture multiple images of the process as it occurs to see its evolution.

Biological applications account for a large number of SAXS studies, as SAXS can be used to determine the protein, nucleic acid and biopolymer structures and sizes.

As many biological systems undergo continual structural changes even at room temperature, one of the advantages of SAXS for biological imaging is that time-resolved variants of the technique can be used to capture processes such as protein folding in action. This makes SAXS an invaluable tool for not just understanding single structures in structural biology but the full landscape of how different conformers and structures are interconnected.

Outlook

As SAXS experiments use 2D detectors, a large amount of data is generated with each image recorded. Finding ways to reduce data sizes, speed up data processing and automate large parts of the analysis procedure has been very important in turning SAXS into a routine analytical tool. It is necessary to use some fitting and reconstruction procedures to convert from the recorded 2D image data to structural information such as particle sizes or distances.

Many of the algorithms for such procedures are available as relatively easy-to-use software packages for simple cases.

Brighter synchrotron sources, more efficient and sensitive detectors and greater degrees of automation of the experimental acquisition and data analysis will all help improve the throughput of SAXS measurements. With advances in nanoscale fabrication methods such as focused ion beams, there will continue to be a great demand for techniques such as SAXS that can characterize materials on the nanoscale reliably.

Time-resolved studies with SAXS are also likely to play an important role with the increasing availability of X-ray free-electron laser sources. Achieving very short (< 100 fs) time resolutions with high photon flux at synchrotrons can be very challenging.

Free-electron lasers, with their high peak brightnesses, also offer the ability to perform SAXS measurements on materials under extreme conditions to understand phenomena such as plasma formation and propagation in materials.

References and Further Reading

Giannini, C., Ladisa, M., Altamura, D., Siliqi, D., Sibillano, T., & Caro, L. De. (2016) X-ray Diffraction : A Powerful Technique for the Multiple-Length-Scale Structural Analysis of Nanomaterials. Crystals, 6, p. 87. https://doi.org/10.3390/cryst6080087

Shi, S., & Russell, T. P. (2018). Nanoparticle Assembly at Liquid – Liquid Interfaces : From the Nanoscale to Mesoscale. Advanced Materials, 30, p. 1800714. https://doi.org/10.1002/adma.201800714

Li, T., Senesi, A. J., & Lee, B. (2016). Small Angle X‑ray Scattering for Nanoparticle Research. Chemical Reviews, 116, pp. 11128–11180. https://doi.org/10.1021/acs.chemrev.5b00690

Garcia, P. R. A. F., Prymak, O., Grasmik, V., Pappert, K., Wlysses, W., Otubo, L., Epple, M., & Oliveira, C. L. P. (2020). SAXS investigation of the formation of silver nanoparticles and bimetallic silver – gold nanoparticles in controlled wet-chemical reduction synthesis. Nanoscale Advances, 2, pp. 225–238. https://doi.org/10.1039/c9na00569b

Pauw, B. R., Ka, C., & Thunemann, A. F. (2017). Nanoparticle size distribution quantification : results of a small-angle X-ray scattering inter-laboratory comparison research papers. Journal of Applied Crystallography, 50, pp. 1280–1288. https://doi.org/10.1107/S160057671701010X

Brosey, C. A., & Tainer, J. A. (2019). Evolving SAXS versatility : solution X-ray scattering for macromolecular architecture , functional landscapes , and integrative structural biology. Current Opinion in Structural Biology, 58, pp. 197–213. https://doi.org/10.1016/j.sbi.2019.04.004

Kluge, T., Rödel, M., Metzkes-ng, J., Pelka, A., Garcia, A. L., Prencipe, I., Rehwald, M., Nakatsutsumi, M., Mcbride, E. E., Schönherr, T., Garten, M., Hartley, N. J., Zacharias, M., Grenzer, J., Erbe, A., Georgiev, Y. M., Galtier, E., Nam, I., Lee, H. J., … Landstraße, B. (2018). Observation of Ultrafast Solid-Density Plasma Dynamics Using Femtosecond X-Ray Pulses from a Free-Electron Laser. Physical Review X, 8(3), p. 31068. https://doi.org/10.1103/PhysRevX.8.031068

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator

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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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Follow AP’s climate coverage at https://apnews.com/hub/climate

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Follow Seth Borenstein on Twitter at @borenbears

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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