Advent Calendar 2019

In the past, when windows were still poorly insulated, it was not unusual to see them on the glass pane on a cold winter morning: ice flowers. While this image evokes ice flowers, this flower is not made of water, but of wax. Chemically speaking, it is made up of long hydrocarbon chains. It was created with the aid of a laser: a so-called combinatorial laser-induced forward transfer (cLIFT) was used to create a tiny hydrophobic (water-repellent) spot on a silicon oxide surface, measuring just 50 micrometers (50 millionth of a meter) in size; from this spot grew a very delicate wax ice flower, four nanometers in thickness. This inexpensive laser method, developed by scientists at the Max Planck Institute of Colloids and Interfaces, allows deeper insights into the physics of melting and freezing of organic microstructures

Noise pollution is not only harmful to humans  – even for birds, a permanently increased noise level does not remain without consequences. In a recent study, ornithologists had a group of pairs of zebra finches each breed in quiet and noisy surroundings. The second group was exposed to traffic noise recorded at several busy intersections in and around Munich during the whole breeding period, with the sounds of heavier traffic during the day and lighter traffic during the night. The result: young chicks raised in a noisy nest grew more slowly than their peers in a quiet environment. Laboratory tests also showed that a persistently high noise level suppresses the increase in stress hormones in the blood of the parent birds. Presumably, this adaptation protects the organism from the negative effects of permanent stress. At the same time, however, a normal, natural stress response of the body – for example in dangerous situations – is prevented. These findings indicate that even bird species that seem to do well in cities can be affected by constant traffic noise.

Read more here: Birds do not habituate traffic noise

Neutron stars are hard dense in the truest sense of the word: a single teaspoonful of their material would weigh about as much as the Zugspitze massif. Occasionally, two of these star corpses, only about 30 kilometres in diameter, come close together and merge in a wild dance into an even more compact object - a black hole. At the birth of such a mass monster, many different signals are emitted that can be observed with different observatories. Which ones are suitable for this? To predict this, researchers at the Max Planck Institute for Gravitational Physics in Potsdam are reconstructing nature with the help of powerful mainframe computers. Here, two neutron stars have merged to form a black hole (centre of image). The black hole is surrounded by a ring of matter, which was ejected into space during the merger. Its decreasing density can be seen here by the colour gradient from green to blue. However, the further fate of this material has already been sealed: it will gradually disappear in the space-time trap.

Read more here New virtual laboratory for merging neutron stars

New human life begins with the fusion of a sperm and an egg. The genetic material of mother and father, stored in the form of chromosomes, unite. While each of these 23 chromosomes is present twice in every normal cell of our body, the germ cells - oocytes and sperm - contain each chromosome only once. After the union, a normal "double" set of chromosomes is again present. For this to work, a special form of cell division, called meiosis, must be used to "dispose" of half of the chromosomes as the egg cell matures: The result is a very small cell, the polar body, into which the surplus chromosomes are discharged. Our picture of an egg cell during meiosis shows the polar body (at the upper edge of the picture), the microtubules (components of the cytoskeleton that also form the machinery that distributes the chromosomes; here stained blue) as well as the chromosomes (green-turquoise) and the cell membrane glowing in magenta. Researchers at the Max Planck Institute for Biophysical Chemistry are investigating the mechanisms that control the process of meiosis. 

Read more here: Fertile Research [PDF]

The fuel in a future fusion power plant - an ultra-thin hydrogen plasma - has an ignition temperature of over 100 million degrees Celsius. Although it is held in suspension by a magnetic field and does not touch the walls of the combustion chamber, these still have to withstand high temperatures and above all short, intense heat pulses from the hot plasma. For this purpose, complex shaped components are developed from tungsten, the metal with the highest melting point. The material has a fine lattice structure, which also gives the heat-resistant tungsten a low thermal conductivity. In this way, the special material can protect the wall sections behind it from thermal overload.

However, such filigree tungsten objects cannot be produced using conventional processes such as milling or pressing. They are "printed out": A computer-controlled laser beam melts tungsten powder layer by layer in the pattern of the desired lattice structure, and the component builds up layer by layer.

 Read more here: From the 3D printer
 

On the fifth day of the voyage, there is a violent storm and the ship is tossed directly towards the magnetic mountain. What the sailors experience in the folk book Duke Ernst from the late 12th century belongs to the realm of fables. But magnetic stars really do exist. These magnetars, compact remnants of supernovae, are the strongest magnets in space. But how do they obtain their unusually high attraction? A team of astrophysicists from Germany and Great Britain has now solved this 70-year-old mystery. On the computer, the researchers merged two stars, each of which possessed a normal magnetic field. The picture illustrates this process, the coloration depicts the strength of the magnetic field, the hatching the field lines. The final product of the simulation was a single, but now extremely strong magnetic star. If one day it explodes as a supernova, a magnetar will be born from the debris.

Read more:  When massive stars collide

The era we live in is often referred to as the "Anthropocene" -  a new Earth age in which humankind has become the most important factor influencing the Earth's biological, geological and atmospheric processes. Is it possible to illustrate the transition to such a human-dominated Earth Age on a regional level? This is precisely the aim of the intercultural research project "Mississippi. An Anthropocene River": The Mississippi - once less a river than an immense floodplain - has changed constantly in the course of containment and navigability in the 20th century, more and more towards an enormous agricultural and industrial corridor. The river passes through complex, constantly changing human-made ecosystems, it is a catchment area for a wide variety of cultures and, last but not least, the scene of historical and historically evolved inequalities.

The motif of the Mississippi project is based on a map from the 1940s that documents the numerous historical changes in the riverbed.

As soon as milder temperatures invite you to stay outdoors in spring, a new era of suffering begins for all those afflicted by allergies. Scientists at the Max Planck Institute for Chemistry are interested in the extent to which air pollutants also play a role in allergies. Air pollutants such as ozone and nitrogen oxides alter protein macromolecules and thus also the two shells that protect a pollen grain.

The outer skeletal layer, called exine, gives the pollen mechanical stability, the inner pollen wall, the intine, protects the actual germ cell. The difference between these two structures is particularly obvious in lily pollen, whose exine forms an ornamental pattern reminiscent of the coat of a giraffe. When viewed under the microscope, the autofluorescence of the two layers - here reddish for the inner pollen wall and green-yellow for the pollen skeleton - reveals which chemical substances are enriched in these structures.

With about 160 micrometres, however, lily pollen are comparatively large and heavy. In contrast to birch, pine and hazel pollen, they are therefore not distributed by the wind, but by insects.

A little flower that unfolds in the middle of winter and deep at night – it is not without reason that this image, which is also part of a famous Christmas carol, is synonymous with a miracle. For even in the life of a plant, much depends on the right timing, from seed germination to growth and flowering. For example, plants can measure the length of the day or the temperature in order to switch from the growth phase to the reproduction phase at a suitable time - in other words, to flower. The image shows how the flowers of a thale cress, botanically called Arabidopsis thaliana, develop from the dome-shaped tissue of the shoot tip.

The thale cress is a so-called long-day plant that blooms in spring. The plant measures the length of the day via its leaves. If the light period is long enough, messenger substances migrate from the leaves into the shoot tips and transmit the flowering signal. In this way, the plant ensures that the flowers are formed at the right time to ensure fertilisation, seed formation and species conservation.

Milky Way systems are the largest building blocks in the universe. Several billion stars shine in such world islands, surrounded by lots of gas and dust clouds. These galaxies have different shapes and the same spindles, ellipses or even spirals as seen here. This picture was not taken by a telescope, but created by a computer. TNG50 is the name of the most detailed large-scale cosmological simulation to date, which covers a cube of space that is more than 230 million light-years across and contains around 20,000 galaxies. In this virtual universe, researchers investigate in detail how galaxies are formed and how they have developed from the time shortly after the Big Bang 13.8 billion years ago until today. But TNG50 also reveals smaller-scale processes, such as galactic gas flows. The computer-generated disk galaxy shown here can be seen in a face-on  view. It corresponds to the view in visible light - and looks deceptively like a real galaxy.

Read more: Cosmic carousels

A broken glass bottle? A glimpse into the interior of a blast furnace? A desert landscape seen from an airplane? None of the descriptions is true:  this picture has a completely different scale - it shows the surface of so-called perovskites, a group of metallic minerals; in this case a mixture of potassium, calcium, and niobium oxide. Scientists at the Max Planck Institute for Iron Research in Düsseldorf are working on these and similar oxides. They are trying to decipher the exact structure and chemistry of these particles, which are in the size range of a millionth of a millimeter, and thus develop novel nanomaterials for a variety of industrial applications. Because of their special crystal structure, lanthanides can be embedded in the perovskites. The latter are a group of "rare earth metals". An important property of lanthanides is luminescence - as soon as energy is supplied from outside, they begin to glow - which is why they are used in mobile phone displays, for example.

Paolo Cirio, Obscurity, archival inkjet on paper, 84 x 105 cm, 2016

They tend to be overshadowed by their far more famous neighbours, and for a long time hardly anyone was interested in them. But without them, nothing in our heads would work at all! We are talking about glial cells, which occur about as frequently in our brain as nerve cells and which take on vital auxiliary and supporting functions. In the case of an injury - for example after a stroke - very specific types of them take action: microglia (here red) and astrocytes (green) support, protect and nourish the nerve cells so that they can regenerate. If the microscope reveals an accumulation of glial cells that have changed shape, it indicates tissue damage. In this image a section of the hippocampus of a mouse - everything is in perfect order: the glial cells are normally distributed and the tissue structures are intact. Under these conditions, the nerve cells (here recognizable as a diagonal band of blue-colored cell nuclei) can optimally perform their own functions.

Electrons move at breathtaking speeds. If you want to observe them, you have to be fast. Researchers at the Max Planck Institute of Quantum Optics use ultra-short light flashes that last only attoseconds, i.e. only a few billionths of a billionth of a second. This allows electrons in atoms and molecules not only to be observed, but even to be photographed or controlled. To generate the ultra-short light pulses, an inert gas is bombarded with a laser beam of very short-wave light. The high-energy light excites electrons in the noble gas atoms - which means that these electrons absorb energy, which they then release again in the form of an attosecond flash.

On the left is a diaphragm of the optical unit that generates the laser beam, and on the right in the foreground is the gas nozzle from which the noble gas flows out. The noble gas atoms are hit by the laser beam and then emit the ultra-short light flashes.

Read more here: The making of a quantum movie