Advent Calendar 2023

Take a good portion of gas, add dark matter and refine the mixture with gravity and massive neutrinos. Then feed these ingredients into two supercomputers and wait for the result. Well, it wasn't quite that easy for the researchers to recreate the development of the universe and the galaxies within it.. But the recipe worked and delivered the most comprehensive hydrodynamic simulation model of the universe to date. It examines the behavior of liquids and gases under the influence of forces such as flow, pressure and gravity.
This way, the "MillenniumTNG" project was able to model the formation of around one hundred million galaxies in a region with a diameter of almost two and a half billion light years. The image shows a detail from the simulation with gas (top left), dark matter (top right) and starlight (bottom center). Indicated in the two upper sections are the threads of the cosmic web that runs through the cosmos on a large scale. Among other things, the new calculations are intended to contribute to a precision test of the standard cosmological model.
Read more: Putting the universe to the test

Computer simulation

Quarks, leptons, bosons, gluons - at least 37 different elementary particles exist. In order to study them, scientist must first be able to detect them. This is where scintillators come into play, substances that are excited by interactions with high-energy particles and then emit this excitation energy in the form of measurable radiation. Scintillators can be crystals, liquids or polymer solids.
Shown here is a new scintillator material which has been recently developed at the MPI for Nuclear Physics. Its distinctive feature: it can be transparent or opaque, depending on the temperature. This could greatly simplify the detection of neutrinos and antineutrinos. Because by using the opaque material, their signals can be determined much more precisely and distinguished much better from interference signals. It might even make it possible to operate future neutrino detectors on the Earth's surface instead of building them in deep underground laboratories. Another important advantage of the new material: It is much safer and easier to handle than conventional detectors, which are often highly flammable. Using the new scintillator as a candle demonstrates that this is no problem here.

Photography 

Many cells can actively migrate. During embryonic development, wound healing and immune defense, cell migration is vital for the organism's survival. However, the urge of cells to migrate can also have fatal consequences –  for example in the formation of tumour metastases. Researchers at the MPI for the Physics of Complex Systems are investigating how cells migrate in groups and how they orient themselves in the process. They focus on a process called durotaxis, in which cells follow differences in stiffness of the surface they move on. The illustration visualizes the principle: cell aggregates are shown on a substrate with a stiffness varying from soft (left, yellow) to stiff (right, dark blue). On the soft region, cells remain in place forming a spherical aggregate — a living droplet. On the stiffer region, cells begin to move and the aggregate spreads into a thin film. The aggregate then performs durotaxis: It moves towards even stiffer regions. In frog embryos, scientists showed that durotaxis takes place in nature: When forming the face, certain cells orient themselves based on the stiffness of the underlying tissue.

Illustration 

When many similar units interact in such a way that something new is created, we call this emergence. Many biological processes are only made possible by emergent behavior on a range of very different scales – from individual molecules to cells to entire organisms. Here, scientists at the Max Planck Institute for Dynamics and Self-Organization in Göttingen have used a computer simulation to investigate the behavior of rods with a diameter of around one micrometer (the thousandth part of a millimeter) that grow in length and divide – an idealized form of bacteria. The rods in this virtual colony are colored in the image according to their orientation. They interact with each other exclusively by taking up more and more space as they grow, thereby pushing neighboring particles away. Despite this simple rule, large-scale domains of rods with almost identical orientation are formed over time (as seen from their uniform color). These  microdomains are deformed by growth, break up and form again and again. The dynamics strongly depend on the external environment and also influence the shape of the colony as a whole. Using such minimal models, scientists can determine the essential ingredients which enable certain emergent behaviors.

Computer simulation

Unlike conventional alloys, compositionally complex alloys (CCAs) consist of almost equal proportions of multiple metals, blending at the atomic level. This makes it possible to produce materials that combine disparate properties such as strength and ductility. The material shown here is CoCrFeNi, a CCA that retains its superior mechanical properties even at very low temperatures of -200°C.  This material is produced using an additive manufacturing process, often referred to as 3D printing of metals. The decisive factor in this technique is an easy-flowing metal powder to spread uniform thin layers.  Max Planck scientists have therefore added hard ceramic nanoparticles to the metal powder. These increase the flowability of the powder, but also the strength and toughness of the resulting alloy. The image shows a cross-sectional view of such a particle. It consists of a core composed of titanium oxide and a shell of titanium nitride, with a diameter measuring just under 150 nanometres (a nanometre is a millionth of a millimetre).

Electron microscopy, colored

About 45 million light years from Earth lies a galaxy called NGC 1097. It has been the subject of the initial observations by Eris, a special infrared camera mounted on one of the eight-meter telescopes of the European Southern Observatory's Very Large Telescope (VLT) at Cerro Paranal in northern Chile. The new instrument provided an image of the center of the galaxy in unprecedented detail. Clearly visible is a ring of gas and dust measuring around 5500 light years across, in which numerous stars are being born. The bright spots on the outer side of the ring are such stellar nurseries. The brown regions, on the other hand, mark dust trails that show how gas from the outside of the galaxy migrates inwards. This process fuels the birth of stars. Deep in the heart of NGC 1097 lurks a supermassive black hole, which is fed by the spiraling inward flow of gas. Eris, built by a consortium led by the Max Planck Institute for Extraterrestrial Physics, will not only observe galaxies over the next ten years, but also exoplanets orbiting foreign stars and dwarf planets in our own solar system.
Read more: Eris sees “first light”

Telescope image

The entire national territory of Lesotho lies at an altitude of more than 1000 meters above sea level, the vast majority between 1800 and 3000 meters. Hence the nickname "Kingdom in the Sky". In contrast to the surrounding regions in southern Africa, water is abundant here. In winter, the climate is harsh, snow covers the land and the 192-metre-high Maletsunyane waterfall might be frozen.
Scientists at the MPI of Geoanthropology have investigated in the mountainous regions of Lesotho how our ancestors coped with difficult and changing climatic conditions. Because even in the Pleistocene, the last glacial period, the area was inhabited. The researchers analyzed waxes from plant leaves that preserve well in sediments for hundreds of thousands of years. This enabled them to document the vegetation and precipitation conditions over a period of around 60,000 years. Particularly interesting are the last 20,000 years, as climate conditions changed dramatically with the transition from the Pleistocene to the Holocene. As the results show, people used the high-altitude areas of Lesotho continuously, most likely due to the reliable water supply. At the same time, the work shows the unprecedented extent of climate warming and landscape change in this region over the last 200 years.
Read more: Millennia of Ecological Change

Photographie 

Oocytes are among the largest cells in the animal kingdom. They contain plenty of nutrients to give the embryo the best possible start into life. When an egg cell is formed, the progenitor cell divides extremely asymmetrically and undergoes a very particular form of cell division: meiosis. Researchers at the Max Planck Institute for Multidisciplinary Science are investigating how the cell division apparatus has adapted to this special type of segmentation. As one model, they use marine organisms such as starfish, whose eggs are ideal for light microscopy: they are highly transparent, easy to handle and divide fast.
From the fertilized egg cell a new multicellular organism can develop through repeated regular divisions, called mitosis. Here you can see a starfish embryo at the beginning of its life, right in the middle of the second division cycle. The chromosomes are highlighted in magenta, the microtubules in yellow. Microtubules are an essential part of the cytoskeleton. They form the so-called spindle, which during the cell division allocates the chromosomes to the two daughter cells.

Fluorescence microscopy

Anyone designing a new material has to understand it down to the detail. For example, there is the question of which atoms the material is consisting of and how these atoms are positioned and bonded to each other. One crucial thing is to measure how the electrons in the material behave. As part of a solid, electrons take on very specific energy levels that are characteristic of many physical properties – such as the question of whether the material is an electrical conductor or an insulator. By exposing the material to X-rays and measuring the energy of the emitted electrons, scientists can draw conclusions about the energy levels in which the electrons were previously located. To do this, however, they must first thoroughly prepare the sample and clean and smooth its surface at an atomic level. Therefore, the very small sample, which is no more than a few millimeters or even micrometers in size, is heated to 600 degrees Celsius in an ultra-high vacuum chamber. The view through the porthole of the chamber is directed at the approximately two-centimeter-long block-shaped sample holder in the center, which, like the connecting wire, glows purple due to the heat.

Photography

Plants have developed numerous ingenious strategies to disperse their seeds. In the popping cress Cardamine hirsuta, exploding seed capsules propel the seeds in all directions. Max Planck scientists have investigated the mechanism behind this in detail. As they discovered, the polymer lignin (shown here in red) plays a central role. For the slingshot mechanism to work, the polymer must be embedded in the capsule wall (shown here in blue) in a very specific pattern. The micronutrient copper is required for the formation of this pattern. In addition, the researchers have also identified the genes that control the incorporation of lignin into the wall of the seed pod cells. These findings are particularly interesting for the forestry sector, since lignin is the substance that gives wood its strength and rigidity. However, forest soils often have a low copper content, which leads to poor lignification and a weakening of the trees. Understanding the role of copper in the lignification process is therefore also of economic importance.
Read more: Copper makes seed pods explode

Fluorescence microscopy