Views from aSmall: Specimen #2beta

an applet-based variable size-scale adventure for materials astronomers and/or nano-detectives

Below find a web-interactive "copper TEM grid" (in this case a grid 3 mm in diameter with a 200 line per inch mesh) like that shown in the image on the right next to an ordinary staple. Suspended across the grid you'll find pieces of a 10 nm thick "holey carbon film", like those often used to support a wide variety of particulates. Such grids and carbon films are often used also to mount soft (e.g. tissue or cell) sections sliced by an ultramicrotome. Using your mouse, you can rotate, spin, as well as zoom around on or even inside the structure, thanks to an intersecting-axis goniometer with no rotation limits. The wide tilts, the large focal depth, and the geometric contrast mechanisms of the web-microscope used here allow one to also obtain topographic information of the sort that atomic force and scanning electron microscopes can generate. We have plans to allow you to explore this and other specimens on the micron, nanometer, and even atomic scales in the days ahead, as well as to taylor stories for the use of such models in classrooms from kindergarten through grad school. One objective is to provide visitors with a visceral feel for scale changes that the nano-explorer experiences, in the process of "getting small".

How astute are your observational skills? What information would you bring back from a "fantastic voyage" into the nanoworld? Don't mind the robot in the background. If you look carefully, you may be able to find grid bars and some holey carbon support film, plus a clino-enstatitite lath collected in the earth's stratosphere which contains solar flare tracks from space exposure while in orbit around the sun. Other astrophysical puzzles will be added in days ahead. Of course, unfamiliar contrast mechanisms are needed to observe objects smaller than the wavelength of light, so be prepared for a few surprises.
Note: The mouse allows you to re-orient and or spin the specimen, while the Shift key plus vertical mouse motion allows zooming in on the model for a closer look. The Home key returns you to the original point of view, and the buttons above let you estimate goniometer angles and field-width. The rotation-center may be moved along scope cartesian (xyz) axes by tapping the xXyYzZ keys (hint: rotate between taps). If this version bogs down on zooming (e.g. with an older PC), try a 400x400 or 200x200 window. Try this model for less surface topography, and this model if you wish to rotate "the camera" rather than the specimen plus see objects 2 million lightyears away in the background to boot!

Put on your Sherlock Holmes hat, and ask...

Puzzler #1: If the diameter of the grid is 3[mm], what is it's thickness? Also what is the exact mesh of the grid (i.e. the number of lines per inch)? The manufacturer claimed that it was 200 mesh, but it might be fun to see how close that claim was to the truth. Also, how wide are the grid bars, and what fraction of the grid area is open, i.e. transparent to electrons.

Puzzler #2: Now take a close look at some of the holey carbon film. Can you determine the film thickness experimentally? How large are the holes in this film? What is an average diameter? What is the shape of the holes. Do they vary in size and shape? What is the standard deviation in size? What fraction of the holey film area is comprised of the holes themselves? What is the distribution of hole sizes, i.e. are the sizes normally distributed, does the distribution have multiple peaks, etc.?

Puzzler #3: Next, see if you can locate the enstatite lath. What are the lath's dimensions? What is it's shape? Is it faceted, or irregular in shape? If it has faces, what are the angles between them? What is the lath's volume and surface area?

Puzzler #4: Check out the solar flare tracks in the enstatite lath. Are the tracks randomly distributed, or is there evidence of a preferential orientation which might occur if the lath was buried near the surface of an object much larger than the range of solar flare tracks therein? How many tracks do you find in this grain? How many tracks per unit area was this grain exposed to? If you know that the lath was removed from a 10 micron interplanetary dust particle too small to shield it from track-forming solar flare particles, how much time spent at 1 AU (earth's orbit) around the sun would have been necessary to create the observed track density? What is the uncertainty in this exposure time due to counting statistics alone?

Puzzler #5: Take a close look at the exit and entry holes for the track in that part of the crystal which hangs over the edge of a hole in the carbon film. How has the previously flat surface been disturbed? Can you distinguish the entrance and exit holes? Do the rearranged atoms show signs of order, or disorder? What are the crater diameters, depths, and rim heights? How might one go about determining the ion mass, energy and direction from these surface features?

Puzzler #6: (NOT YET IMPLEMENTED) Decipher the hidden message (an extraterrestrial palimpsest ala Carl Sagan's Contact) buried in the unit-cell ordering of an interstellar silicon carbide grain.

Puzzler #7: (NOT YET IMPLEMENTED) Examine the structure of unlayered graphene in the core of a graphite onion formed in the atmosphere of a red giant star, for clues to precipitation processes in the cool atmosphere of such giant stars.

Storylines for Classroom Use: Suggestions invited.

This is one of several web-based "active mnemonics", designed: (i) to offer complementary perspectives and resources for achieving present day teaching goals among students with a wide range of learning styles; (ii) to do this in the context of emergent topics in modern day science (e.g. nanoscale exploration, information physics, allpaths/action/aging and metric-based anyspeed dynamics), many of which have only begun to work their way into textbooks and curriculum goals; and (iii) to be reliably available for use by individual teachers in class and by students out of class. Nanoworld exploration is especially interesting in this regard since it can offer an open-ended challenge to one's skills at empirical observation and reporting, allowing students to "participate in scientific investigations based on real-life questions that progressively approximate good science". This is, for example, a primary goal of the K-12 Show-Me Standards on scientific inquiry, the basis for Missouri Assessment Program tests. Most classroom challenges instead focus on factual knowledge and skills at theoretical prediction, perhaps since robust empirical challenges have been more difficult to set up.

Frequently Asked Questions: Suggestions invited.
Local links:
Future objectives (for which technology is essentially in hand) include:
This page is Acknowledgement is due particularly to Martin Kraus for his robust Live3D applet and help adapting it to this application. A background image from the Takanishi Lab webpage on robot expressions has been put up temporarily because we don't have a "first specimen" background showing curious students looking at an object in the lab. Yet. Although there are many contributors, the person responsible for errors is P. Fraundorf. This site is hosted by the Department of Physics and Astronomy (and Center for Molecular Electronics) at UM-StL, and is part of the Physics Instructional Resource Association webring (see below). The number of visits here since last reset on 23 Aug 2003 is [broken counter]. Mindquilts site page requests to UM-StL around 2000/day, hence more than 500,000/year. Requests for a "stat-counter linked subset of pages" since 4/7/2005: .

This PIRA Webring site is managed by
P. Fraundorf.

< prev | List Sites | next >