Turbulent Exchange
Turbulent currents play an important role in climate events, for example in cloud formation or – as calculated and visualized here – in the exchange processes that occur on the surface of water bodies. When the water on the boundary with the air cools down, through convection and uplift, a typical cell-like pattern of the heat distribution in the water arises in the layer underneath. The dark zones in the image are relatively warm areas, which move upwards while cooler areas, often just a few millimeters wide, move down – the light-colored edges of the “cells” here. Tiny whirlpools arise at the network nodes, sometimes even double vortices with opposite directions of rotation.
Steady Nerves
Various long extensions grow from the rounded cell body of a young neuron. The longest one becomes the future axon (green), which transmits signals to other neurons. The short extensions are the future dendrites (red), which will receive signals from other neurons and process them. The microtubuli, a component of the cytoskeleton, are indicated in different colours. These small protein tubes give the neuron its shape and enable it to grow. The colours indicate the stability of the microtubuli: green/yellow means stable, red, on the other hand, unstable. The axon is the only extension that has stable microtubuli and can therefore grow – which is important for the regeneration capacity of neurons. Phase contrast image superimposed on a multichannel fluorescence microscope image
Unleashed Magnetic Force
Plasma at temperatures of several thousand degrees rises from the sun’s interior, cools down and retreats again into its depths. Dark sunspots arise where the plasma is contained by strong magnetic fields. On the edge of the spots thread-like structures can be observed. In these areas, the fields should actually be strong enough to prohibit the plasma flows, so they should appear darker. Scientists at the Max Planck Institute for Solar System Research succeeded in proving that the magnetic field here is relaxed in places. The plasma circulates and generates elongated, brightly shining structures that appear to rotate on their axis.
Digital photograph, Swedish Solar Telescope/La Palma
Caught in the Net
White blood corpuscles play an important role in our immune system. Among these cells, the neutrophil granulocytes – generally referred to as the neutrophils – form the first line of defence. They literally devour bacteria by surrounding the pathogen and digesting it in their cell interior. The neutrophils also have another ingenious trick up their sleeves: they can cast fibrous net-like structures, trap bacteria in them and thereby kill them outside the cell. This image shows Shigella bacteria (red) being caught in a net cast by neutrophils.
Scanning electron microscope image, colored
Ballistic Electronics
Despite the fact that they exit the point contact at completely different angles, electrons that leave a point contact in a two-dimensional semiconductor can be focused on a second contact through an externally applied magnetic field. The lower half of this simulation shows this kind of ideal transverse magnetic focussing. Weak disturbances always arise, however, in real semiconductor crystals. The upper half of the image shows how strongly a weak disorder in the material can affect the electrons’ path.
Larval Images
The zebrafish (Danio rerio) is a popular model organism in developmental biology. It grows from a fertilised egg to a sexually mature animal within a period of three months. The image shows two-day-old larvae, in which the mouth opening can already be clearly identified. However, at first glance, the apertures which look like eyes surrounded by eyelashes are, in fact, the organisms’ future olfactory organs. The scientists at the Max Planck Institute for Developmental Biology study tissue and organ development in zebrafish embryos. A genetic defect in the embryo on the left causes problems in the development of the skin. Scanning electron microscope image, colored
At the Root of a Plant
In order to thrive, plants require sufficient nitrogen. If nitrogen is lacking, they must cut back on photosynthesis and growth. To deal with this, plants have developed various strategies, for example the increased formation of the red leaf dye anthocyanin, which protects against excess light irradiation. Scientists suspect that the mechanisms that regulate anthocyanin also regulate the formation of the leaf hairs, which protect the plant against dehydration. Therefore, as part of studies on the effect of nitrogen deficiency, the size and number of leaf hairs were examined. The image shows just such a leaf hair from the thale cress plant (Arabidopsis thaliana). Confocal microscope image
Web of Dark Matter
Dark matter is not visible, it does not emit any kind of radiation, yet it exists – as its gravitation attracts other, standard matter. This computer simulation makes dark matter visible; it shows a virtual cosmic network of dark matter that connects individual, brightly shining galaxies in the universe with each other. The colourful image is part of the Millennium Simulation Project and demonstrates the enormous variety and complexity that arises from the gravitational dynamics of the dark matter particles. Differences in brightness represent the local density, and the colours represent the different speeds of the matter. Computer simulation
Ingenious Navigation System
Flies are master navigators: their vision is excellent, even while flying. To enable this, their brains must process images extremely quickly – online, so to speak. Yet they manage to steer their course visually using just 120 nerve cells. These receive the signals via several intermediate stations from the photoreceptors in the eyes, are connected with each other, process the movement stimuli and then transmit the signals to the centres which control wing movement. The image shows the back of a fly’s head and provides a view of the neuronal flight control centre of the left side of the brain. Individual nerve cells have been made visible through the injection of a fluorescent dye. Composite photo of superimposed optical microscope images
In the Cosmos of Quanta
Is spacetime a fixed quantity? Quantum theory confirms this; however, according to the general theory of relativity, spacetime is dynamic. Loop quantum gravity is a promising approach for combining the two theories. According to this theory, space consists of tiny intersecting loops with finite extension that can decay and arise temporally. In this image, triangles represent the elementary area elements. The spatial properties arise from the way in which the individual triangles are connected – the crucial dimension is the area of the triangles. The red triangles are small in area, while the violet ones are bigger. Computer animation
The Immune System In Action
What looks like an exotic flower at first glance, is, in fact, the human immune system in action: a white blood corpuscle (shown here in red) is in the process of disarming tuberculosis bacteria (yellow). The pathogens are encircled by the scavenger cell membrane, pulled into the interior of the cell and locked in there – ideally forever. However, Mycobacterium tuberculosis is an extremely tough customer: thanks to a particularly resistant membrane, the bacteria can survive for many years inside the scavenger cells and may be released again if the host immune system is weakened, for example through diseases like AIDS or the effects of aging. Scanning electron microscope image, colored
Hierarchy of Nanocones
Tiny cones of silica gel grow in an ordered arrangement on a glass surface. Inside, they consist of nanometre-sized silica gel tubes that wrap themselves in a spiral around an axis – like liquorice spirals. The central symmetrical axis already exists in the seed of the cone and is responsible for the subsequent appearance and characteristics of the silica forms. The tubes contain ordered organic molecules. Therefore, the entire arrangement has a hierarchical structure. Up to now, hierarchical structures were mainly known from nature, for example from bone development. Scanning electron microscope image, colored
Arms Race in the Plant Kingdom
Powdery mildew (Golovinomyces orontii), a plant pest from the sac fungi group, forms a thread-like mass or mycelium on the leaves of the thale cress (Arabidopsis thaliana). The sporophores which protrude from the mycelium develop stacks of asexual spores at their tips which are spread by the wind. This way, the fungus can infest other plants. Scientists use the interaction between powdery mildew and the thale cress as a model system for studying how plants react to fungal infestations and how the fungi deal with the plant’s defence mechanisms. Scanning electron microscope image, colored
Nano Interference
When two stones are thrown simultaneously and closely together into smooth water, two overlapping, concentric wave fronts form. A similar overlapping effect arises when electrons are scattered at two defects on the surface of a copper crystal. If the surface were perfectly ordered, there would be no interference; however, small disturbances cause the formation of an interference pattern. The interference of electrons on surfaces influences the conductivity and magnetism of the material – effects that can be important for magnetic data storage. Low-temperature scanning tunnelling electron microscope image at minus 266°C
Hairy Feet
With the help of the minute hair-like structures on its feet, the green dock beetle can walk up walls and even sit upside down on the ceiling. This technique developed over millions of years and is based on the distribution of the contact structure in several sub-contacts and the ingenious shape of the hairs, in particular at their extremes. Moreover, researchers have discovered a simple mathematical relation: the greater an animal’s body weight, the smaller and more numerous the contact structures. When searching for optimum adhesion systems, materials researchers try to emulate nature – the resulting ideas range from re-usable adhesive tape to complex climbing robots. Scanning electron microscope image, colored
A Blanket of Hot Plasma
Fusion power plants are supposed to harness energy from the fusion of atomic nuclei, in a similar way to the sun. The fusion fuel, an ultra-thin hydrogen plasma, has an ignition temperature of over 100 million degrees Celsius. Even the vessel walls reach temperatures of a few hundred degrees. Researchers therefore have to develop heat-resistant materials for the construction of such plants. The sample shows a wolfram alloy, into which silicon and chrome have been incorporated to make the material oxidation-resistant. Under the microscope, stress cracks can be seen. These are caused by the different rates of thermal expansion – an effect that should be avoided during subsequent application.. Polarised light microscopy image
The Network in the Brain
The neurons in the brain form a closely interconnected network. The pyramidal cells – as seen here in a mouse – are the most common type of neurons found in the brains of mammals. Neurobiologists can measure the activity of the individual neurons in their natural environment, the cerebral cortex. For this image, they stained a cerebral cortex tissue culture in which the spatial arrangement of the neurons is conserved with potassium dichromate and silver nitrate. A three-dimensional image of the neurons, as they are arranged in the cerebral cortex, is produced using the microscope’s pseudo-phase-contrast setting. Transmitted-light microscopy with pseudo-phase-contrast setting
Disco Ball To Trap Electrons
Scientists use photo electron and photoion spectroscopy to study the electronic properties of solids and gaseous samples: energy-rich light can knock electrons out of matter. Scientist can then draw conclusions about the electronic structure of matter from the flight path and speed of the electrons. The sample in the image, which is being hit by the light beam from a free electron laser (FEL), is located in the brightly shining centre of the ball. Sensors on the walls of the ball, known as time-of-flight spectrometers, trap the electrons. The entire system is cooled using liquid nitrogen, which is trickled onto the middle of the array from above and escapes below it in a cloud. Conventional photograph
A Threat To The Mucous Membrane
The Neisseria bacteria shown here are just one thousandth of a millimeter in size. These pathogens, which are also known as gonococci, cause the sexually transmitted disease gonorrhoea. In the early stages of an infection, they accumulate in sets of two and four at the cells of human mucous membranes. This detailed image clearly shows how the bacteria succeed in being absorbed by the mucous membrane cells: the cell membrane has already closed around some of the gonococci. This marks the beginning of the infection, which can result in inflammation and copious pus discharge. Scanning electron microscope image, colored
Microcosmic Transport System
Pharmaceutical substances are most effective and cause fewest side effects when they are released directly in the diseased area of the body. Max Planck scientists are working on the development of a drug delivery system that only releases drugs when it recognizes the target cells: microcapsules with special recognition molecules dock directly onto diseased cells, e.g. cancer cells. The drugs can escape through the capsule walls as a result of changes in the temperature, pH value or salt content. The image shows different types of such capsules that were exposed to different temperatures: some shriveled to form solid balls (yellow) and others melted to form bigger capsules (green), which collapsed when they dried out. Scanning electron microscope image, colored
Electrons Gone Astray
Small missteps can have major consequences. This also applies to electrons – as demonstrated by this simulation – which spread in all directions from a point-shaped source in a two-dimensional electron gas. The process takes place in a layer of particular semiconductor components, which are just a few millionths of a millimetre thick. This image depicts electron density – the darker the area, the more electrons it contains. Weak faults – small “irregularities” in the conducting layer – cause the electrons to go astray and result in the pronounced ramification of the particle stream. An effect that must be taken into account in the development of future semiconductor components. Computer-aided 2-D simulation
