baby squid
Celeste Nelson (faculty)
Department of Chemical Engineering
My tissue morphodynamics laboratory studies the dynamic processes that control tissue development. This image of squid (Loligo pealeii) embryos was taken using bright field microscopy.
Desert Butte
Pat Watson, Mike Gaevski, Joe Palmer, Conrad Sylvestre (technical staff)
PRISM micro/nanofabrication laboratory (MNFL)
This is a scanning electron microscope image of an artifact created by a mask defect and found while characterizing a deep Indium Phosphide etch process using a new tool in the PRISM micro/nanofabrication laboratory.
Worm Love
Maria Ciocca '05
University of Pennsylvania School of Medicine
I am a graduate student in a lab that studies the process of asymmetric cell division in the development of model organisms, such as the nematode Caenorhabditis elegans, pictured here. In the process of using immunofluorescence microscopy to study the one- and two-cell stage embryo of this organism, occasionally the slides will contain fully developed worms that were not properly removed in the fixation process. Typically these worms are not imaged and processed - in fact, they do not usually retain a recognizable form.
When I came across this image, it was too good to pass up. The natural shape of this organism does not include such sharp kinks as were found in this case (forming the base of the heart); nor would the worm typically assume a shape resembling a heart.
The staining used here was against the proteasome (green) and alpha-tubulin (red).
Semiconducting Feathers
R. R. Lunt '09
Department of Chemical Engineering
Organic electronics is an emerging field that holds promise for high-quality displays, low-power white lighting, and low-cost photovoltaic applications. This image of an organic semiconducting film was taken using an optical microscope with cross-polarizers and a Nomarski filter. The film is composed of many micron-sized crystallites with a common crystalline stacking direction that was formed through a fast melting/cooling process which led to the formation of feather-like features. The variations in color stem from the anisotropic indices of refraction in combination with the rotation of the crystallites with respect to the polarizer configuration. This film was subsequently incorporated into a thin-film photovoltaic solar cell.
Flying sulphate crystal
Rosa Espinosa (postdoctoral researcher)
Civil and Environmental Engineering
Taken with the optical microscope, this is a work about crystal growth. As a magnesium sulphate solution cools, epsomite and hexahydrite crystals form.
Wrinkles on PDMS in Oil
Oliver Graudejus (research scholar)
Department of Electrical Engineering
The picture shows wrinkles caused by the deposition of a thin film of gold on PDMS, which is the most widely used silicon-based organic polymer and is particularly known for its unusual flow properties. These wrinkles emerge when the compressive stress in the gold is larger than the critical strain for buckling and remain even when the gold is removed from the PDMS, as seen in the dark areas in the picture.
Vortex Waltz
J. Luc Peterson (graduate student) and Greg Hammett (faculty)
Princeton Plasma Physics Laboratory
Two-dimensional fluid vortexes attract, swirling and merging with their partners in a turbulent ballet. This natural behavior influences phenomena ranging from weather patterns in the atmosphere to the performance of nuclear fusion devices. Advanced numerical algorithms and high-performance supercomputers allow for turbulence simulations of unprecedented detail. This snapshot catches the vortexes in the act. Originally entirely separated, the two vortex centers (dark red) have sent out spiral bands and shock waves throughout the background fluid as they've circled each other and combined. If left alone long enough, the two will complete their dance as a single, larger vortex.
All because we live in a finger
Alex Dahlen (graduate student)
Department of Physics
In an attempt to account for what happened before the big bang, as well as the smallness of the cosmological constant, some physicists have been led to a model where our entire observable universe is contained inside a bubble, which is expanding at the speed of light into an exterior space.
But our bubble is not the only one; outside our bubble, there are an infinite number of other bubbles, all expanding just like ours. Sometimes they collide and send waves of death that wash across our universe. In this figure, the regions colored red have already been swept clean by the wave, and the yellow regions can see it coming.
A clear prediction of the model is that Earth resides in the thin sliver, or finger, that forms when two bubbles that have both collided with our bubble narrowly miss one another, indicated here with an arrow. It is thanks to our location here, in a finger, that despite the enormous swaths of our universe decimated by these waves, the odds are exponentially small that they lie in our future. We can all sleep sounder, and it's all because we live in a finger.
I get the blues: on the neurobiology of depression
Barry L. Jacobs (faculty) and Casimir A. Fornal (research scholar)
Princeton Neuroscience Institute
This photomicrograph (at magnification 40X) is of glial cells (glia means "glue" in Greek) from the adult mouse brain in a region called the dentate gyrus. This region is part of a larger brain structure called the hippocampus which is well known to be critical for the formation of new memories.
The dentate gyrus is unique in that it is one of only two brain regions where new brain cells continue to be produced into adulthood, and is therefore believed to be a structure critical for new learning in adults. In 2000, we proposed a theory: that changes in brain cell production in the dentate gyrus were important elements in the descent into, and recovery from, human clinical depression. This image shows hundreds of glial cells stained for a marker protein known as GFAP. The staining uses immunocytochemistry (immunoperoxidase with diaminobenzidine).
Laser Light Through the Eyes of Heat
Fatima Toor (graduate student)
Department of Electrical Engineering
This is the thermal image of a quantum cascade (QC) laser in action -- i.e., lasing. The small bright spot inside the circular window is the laser light. QC laser light is generally invisible to the eye due its emission wavelength, so it is quite fascinating to see it through a thermal camera. The laser is mounted on a cryostat heat sink and held under vacuum using a cryostat holder with a window from which the laser mount is visible. This measurement was taken at -193 C and inside the round window everything is blue except for the bright spot of the laser light.
Light Squared
Lily Yu '12 (undergraduate)
Integrated Science
Light falling through a small circle onto a screen diffracts into rings of differing intensities at different distances. This simulation should have produced a single bull's-eye pattern of wave interference, but a mistake in my MATLAB code created this image instead.
Nimbus
Henry S. Horn (faculty)
Dept. of Ecology and Evolutionary Biology
This is the basal disk from a Redcedar tree that was in competition with a neighboring White Ash. The annual growth rings show that the Redcedar grew well for about 45 years, and then slowed dramatically when the White Ash overtopped it. Markings on the disk record the sizes of roots heading toward neighboring trees and saplings of varied sizes. The heartwood calls to mind an angel, surrounded by a lighter nimbus of sapwood.
surface quasi-geostrophic turbulence
Isaac Held (lecturer with rank of professor)
Atmospheric and Oceanice Sciences Program/Geosciences
A snapshot of a numerical simulation of a distinctive kind of turbulence thought to be relevant to rapidly rotating fluids such as the Earth's atmosphere and oceans.
These simulations, and the equations on which they are based, are used to study the interaction between small- and large-scale structures. In particular, they help us understand the spectra of atmospheric and oceanic turbulent flows -- that is, the relative magnitude of the excitation of different scales of motion.
This is a simulation of a very idealized homogeneous system in which every point in this square domain is physically indistinguishable from every other point. The domain has no walls or boundaries, but is, rather, re-entrant in both dimensions -- as one leaves one side of the domain one enters on the other side. This system is proving to be of interest not only to atmospheric and oceanic scientists, but also to mathematicians, because of the fractal character of its solutions and due to the possibility that it can help us understand how singularities form in fluid flows.
The Persistence of Memory
J. Alex Halderman, Seth D. Schoen, Nadia Heninger, William Clarkson, William Paul, Joseph A. Calandrino, Ariel J. Feldman, Jacob Appelbaum, and Edward W. Felten
Center for Information Technology Policy
Contrary to what most people think, computer memory is not instantly erased when power is cut. Rather, it fades gradually over a period of seconds to minutes as charge leaks out of the DRAM cells.
We loaded a bitmap image into memory on a test computer, then cut power for varying intervals. After 5 seconds (left), the image is nearly indistinguishable from the original; it gradually becomes more degraded, as shown after the computer has been off for 30 seconds, 60 seconds, and 5 minutes. Even after this longest trial, traces of the original remain.
The decay shows prominent patterns. Some areas of the memory chip are wired to interpret lack of charge as a 0 bit, others as a 1 bit -- this results in the alternating horizontal bars. The fainter vertical bands are caused by physical variations in the chip, which cause charge to leak out slightly faster or slower in different areas.
Our research shows that this little-known phenomenon, called memory remanence, has dangerous security implications. For example, it could be used to break the disk encryption on a stolen laptop and reveal sensitive data.
Mad Micelle
Robert Renthal '67 (faculty), Derek Mendez (undergraduate), Liao Chen (faculty)
Department of Biology, University of Texas at San Antonio
To understand the forces involved in the assembly of cell membranes, we pull membrane proteins apart. We embedded a red blood cell protein, glycophorin, in a cluster of detergent molecules called a micelle. Using the computer technique of molecular dynamics simulation, we grabbed glycophorin and pulled it apart. When we displayed the molecular surface of the micelle with the protein shown in outline form, the micelle seemed to be glaring back at us, perhaps giving us a view, at an emotional level, of the forces that hold membranes together.
SU8 flower
Guoguang Fu
Department of Mechanical and Aerospace Engineering
During the development process, the SU8 photoresist -- a commonly used, viscous polymer -- self-organized into these interesting patterns on the silicon surface. This work was done in the cleanroom at Princeton University.
Light Deflection 2b
Joachim Wambsganss (faculty)
Department of Astrophysical Sciences
According to Einstein's Theory of Gravity, a ray of light is attracted by a clump of matter. As a consequence of "gravitational lensing", the light ray changes its direction from a straight line by a minute amount when it passes close to a cosmic object. Stars and planets in our Milky Way or in other galaxies can act as "microlenses": They focus the light of a background source in a very characteristic way. The main effect is a time-variable magnification of the background source due to relative motion.In our research, we simulate the effects of light deflection by tracing light rays backward through a field of lensing objects and calculating their deflection. The colors in the resulting two-dimensional maps in the "source plane" reflect the density of light rays, they indicate the magnification of the background source as a function of its position. The sharp "caustic lines" are locations of very high magnification. When a background star moves across such a pattern, we can measure its variable brightness with our telescopes and deduce properties of dark matter or discover extrasolar planets. Figure 2b: This microlensing pattern indicates the magnification of a distant "quasar" as a function of its position; it is produced by the light deflection of many stars in an intervening galaxy. (Zoom of "Light Deflection 1")
Mouse Retinal Ganglion Cell
Daniel O'Shea '09 (undergraduate)
Department of Electrical Engineering
This is a GFP-tagged mouse retinal ganglion cell (in green), overlaid on a layer of cells with DAPI-stained nuclei (in blue) and ChAT-stained starburst amacrine cells (in red), taken with a tri-channel confocal fluorescence microscope.
I captured this image during a research project supervised by Sebastian Seung at the Massachusetts Institute of Technology and Richard Masland at Harvard. The goal of the collaboration was to develop an improved classification system for ganglion cells based upon their position in the retina and upon the morphology, or architecture, of their dendritic arbors (which behave like antennae).
I developed a series of semi-automated algorithms to digitally reconstruct the 3-D shape of the neuron from a stack of image slices and to calculate the position of the neuron's dendritic arbor in the retina. One issue that has plagued previous attempts to classify ganglion cells is that retinal tissue commonly becomes warped and wrinkled on the slide, which hinders precise localization of the arbor's depth.
Our approach uses the DAPI and ChAT fluorescence channels to mark known landmarks in the retina in the image slices. We can use these markers to unwarp the tissue digitally and thereby obtain improved estimates of each cell's stratification depth. By digitally unwarping the tissue and automating the reconstruction and localization procedure, the classification toolkit I developed this summer will allow ganglion cells to be classified faster and more accurately than was previously possible. With the help of this toolkit, researchers can begin to build a quantitatively accurate retinal "parts list."
Platinum Nano-Forest
Jason Kawasaki '09 (undergraduate) and Craig Arnold (faculty)
Department of Mechanical and Aerospace Engineering and the Princeton Institute for the Science and Technology of Materials (PRISM)
These platinum dendrites were grown via directed electrochemical nanowire assembly (DENA). In the DENA technique, an alternating electric field applied across a salt solution induces the crystallization of metal dendrites. The tree-like structure arises from self-assembly, in which growth along certain crystallographic directions occurs faster than others. The diameter of the main dendrite stem is 500 nanometers.
Social Evolution in Cell Groups
Carey Nadell, Joao Xavier, and Kevin Foster
Department of Ecology and Evolutionary Biology
Expanding clusters of cells are commonplace in the natural world, and depending on the context, they may be beneficial or harmful to humans. Understanding the impact of cell groups on their environment requires that we understand evolution within such cell populations.
Some cell behaviors -- especially those that give the cell group its ability to exploit environmental resources -- are cooperative in nature, and whether or not such behaviors evolve depends on how the group is structured. When genetic relatives are clustered together, cooperative cell behaviors like extracellular enzyme secretion can evolve more easily. Secreted enzymes, in turn, may allow a pathogenic bacterial colony to become more virulent, or a nascent cancerous tumor to become malignant.
Using a computer simulation framework that implements independent cells in explicit space, we have shown that the internal structure of cell groups can depend very heavily on the environment. In the three images shown here, the red and blue cell types do not differ in any way other than their color, which is used to determine whether a cell group remains well-mixed, or whether related cells tend to cluster together.
From left to right, environmental nutrient concentration was decreased from ubiquitous, to moderate, to sparse. As nutrient concentration decreases, the tendency for different genetic lineages to spontaneously segregate increases, which favors the evolution of cooperation. This result may inform our understanding of pathogenic cell groups, in which cooperation between cells is harmful for their host.
Closing in on Thermionic Power
Bruce Alderman (graduate student)
Department of Mechanical and Aerospace Engineering
This is an experiment in the direct conversion of heat to electricity. Practical applications of this device could allow any high-temperature waste heat (such as on the surface of re-entry vehicles, scram-jet combustion chambers, topping units for power plants, and space-based power cells using radioisotopes) to be converted into useful electrical power.
The hot electrode on the left, like any heated metal, has a layer of electrons boiling off of its surface. If these electrons could be collected onto a cooler surface they would effectively generate electrical power.
Unfortunately, under normal circumstances, very little current can be drawn from this sea of boiling electrons. This is because any such extraction creates a negative space-charge effect, making the process self-limiting. By using nanosecond-scale, high-voltage pulses, the xenon gas in the chamber is ignited to form a plasma. This plasma acts as a conduit to allow the electrical current to flow unhindered by any negative space-charge build-up, thus converting the heat into useful electrical power.
Golden Rose
Wenzhe Cao (graduate student)
Department of Electrical Engineering
This is a picture of thin gold film on wrinkled polydimethylsiloxane (PDMS). It was taken with an optical microscope.
Drosophila embryonic neuron
Xin Xu (graduate student)
Department of Molecular Biology
This image shows the organization of Drosophila melanogaster (fruitfly) embryonic neurons. Drosophila embryos have eight abdominal segments, where repeated patterns of peripheral neurons are observed. In order to study the patterns, I used fluorescent immunostaining to label different components of the neurons.
Here, red indicates the axons of neurons and green represents all nuclei in both the central nervous system and the peripheral nervous system. The thick bundle of green cells represents the ventral nerve cord (or central nervous system) which extends throughout the embryo and forms a future head structure at the anterior (upper right in the image).
Laser Forward Transfer
Matt Brown (graduate student)
Department of Mechanical and Aerospace Engineering
Laser forward transfer is a direct-write technique used to print a variety of complex materials, from organic electric precursors to biological materials. In the laser forward process, a transparent substrate is coated with the ink material and a pulsed laser is focused into the ink to initiate the ejection of a small amount of material onto a receiving substrate. Motion of the ink and receiving substrates between successive laser shots allows printing of complex patterns.
Laser printing of stem cells is currently being investigated for tissue engineering applications. This image shows a laser transfer from a model system of 20 micron polystyrene beads in glycerol used to simulate the transfer of human stem cells. The ejected plume is less than 500 microns wide yet moves at tens of meters per second. To freeze the motion, the image is strobed with a 25 nanosecond pulsed plasma lamp, 10 microseconds after the laser hits the ink.
Cement Flower
Hope Connolly '09 (undergraduate)
Department of Chemical Engineering
For my senior thesis in George Scherer's lab, I was investigating the best way to dry cement without doing any damage to the cement's microstructure. I tried drying cement samples in both a desiccator and a 105 degree Celsius oven. The oven-dried samples had hundreds, even thousands, of these cement "flowers," with noticeable "petals" and "buds." The width of this flower is approximately four microns.
Tracer
Kevin Loutherback (graduate student)
Department of Electrical Engineering
Post arrays have shown great promise for separating micron-sized particles from fluid. This particular array, with larger posts interspersed with smaller posts was an attempt to elicit new sorting behaviors. The sorting capabilities of these arrays are typically tested with fluorescent beads. The trace going along the bottom of the panel is the trajectory of a bead as it weaves through the posts in the array.
Collective search behaviour in chaotic flows
Colin Torney (graduate student) and Sepideh Bazazi (graduate student)
Department of Ecology and Evolutionary Biology
Locating the source of an advected chemical signal is a common challenge facing many living organisms. The task becomes particularly difficult when the medium of the flow is chaotic. This image shows how the location of a source can be achieved without assessing the spatial gradient direction, measuring the properties of the flow field, or performing complex calculations. Instead the autonomous, non-communicating individuals (shown as spheres) follow simple social interaction rules which are modified according to the local conditions they are experiencing. Through these context-dependent interactions the group is able to locate the source and displays an awareness of the environment not present at the individual level.
This image shows five snapshots of the time evolution of a group of sixty individuals progressing from a position on a filament to the source of the chemical. Each panel shows the view from above (left) and the concentration profile (right). The work demonstrates the ability of decentralized information processing systems to solve real world problems and also illustrates an alternative pathway to the evolution of higher cognitive capacity via the emergent, group-level intelligence that can result from simple low-level interactions.
Tadpole Vortex Formation
Sepideh Bazazi (graduate student)
Department of Ecology and Evolutionary Biology
These four images show the sequence of tadpole vortex formation in Mexican Spadefoot toad tadpoles, Spea multiplicata.
Vortices form when tadpole density reaches a critical threshold. The flow generated causes detritus matter at the bottom of ponds to be disturbed, facilitating feeding. Therefore the mechanisms leading to the formation of the vortex structure could be a collective foraging strategy.
Initially, individual tadpoles are orientated randomly in space (first panel), but after the detection of food, tadpoles begin to aggregate (second panel). The tadpoles beat their tails quickly and swim into the current generated by others (third panel) until a vortex is fully formed (fourth panel).
Heaters Glowing in Argon Discharge
Robert Kaita, John Timberlake, and the LTX Group
Princeton Plasma Physics Lab
Our group is investigating the use of lithium for use in fusion reactor walls. Lithium is very chemically reactive, so our experiments are conducted in vacuum chambers. Our particular interest is in the properties of liquid lithium, so we need a heated container, which in this case is a circular tray that follows the "doughnut" shape of the magnetic bottle containing the hot fusion plasma. This photograph was taken during a heater test prior to filling the tray with lithium. The glowing regions outline the circular disk heaters underneath the tray.
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发表于 2009-9-19 14:45
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