Редактирование: Whole brain emulation (раздел)

== Slicing ==

=== ATLUM ===

The '''Automatic Tape-Collecting Lathe Ultramicrotome''' is currently the fastest way to fully automatically section and scan neural tissue.<ref>Hayworth, Kashturi et al., 2006; Hayworth, 2007</ref>

[[File:ATLUM Prototype.jpg|thumb|right|The Automatic Tape Collecting Lathe Ultramicrotome - [[ATLUM]]]]

Invented by transhumanist [[Ken Hayworth]], the ATLUM is essentially a rotating block of tissue (typically 1 to 2mm in width, 10mm  in length, and 0.5mm in depth) mounted on a steel axle. As the tissue is turned by an ultraprecise [http://en.wikipedia.org/wiki/Fluid_bearing#Air_bearingsair bearing], the microtome (An ultrathin knife) advances by means of a piezoelectric component, creating a spiral cut of 40nm-thikc tissue, which slides onto the water on the back surface of the microtome. The slice is then sandwiched between two Carbon-coated mylar tapes, replacing the need for dexterous undergraduates to manually position the sections on a TEM grid. The tape has the extra benefits of being a sturdy substrate and preventing charging and beam damage during the scan. The position of the knife relative to the axle can be held to within approximately 10nm, so that many square millimeters of tissue can be sectioned.

[[File:ATLUM_Closeup.jpg|thumb|left]]
[[File:ATLUM poster.jpg|thumb]]

After sectioning, the tissue can be preserved for later imaging, or exposed to heavy metals for SEM. This produces greater signal to noise ratios and much faster imaging time that what is provided by SBFSEM and FIBSEM. Imaging can also be done through the SEM backscattering signal, like in SBFSEM and FIBSEM, allowing the ATLUM to work without the need for a TEM grid and disposes of width-of-section limitations.

Images obtained with an ATLUM are of a quality equivalent to that of traditional TEM, with a lateral resolution above 5nm. ATLUM-collected sections can be subject to tomographic tilt (See SSET), giving aditional depth data. This is done by tilting the section at various angles relative to the SEM beam, giving depth resolutions greater than that of the thickness itself.

One of the main differences between the ATLUM and other microtomes is that others engage in discontinuous motion — That is, sweep forward, collect a slice into the water boat, sweep back, repeat. The ATLUM generates a continuous cut by moving in a spiral manner around the sample. There may be some problems reconstructing large volumes from EMs of slices that are flat but must be mapped to tubular surfaces of decreasing diameter (The brain), a problem that is avoided by having straight, one-above-the-other cuts. Another point, related to the above, is that the ATLUM produces a single tape of tissue, while others produce independent slices that must be gather and set in an orderly manner. The ATLUM does not have this problem. In an ordinary ultramicrotome, an accident that randomizes the slices will ruin the entire process. In the ATLUM, one only needs to distinguish one end from the other.

With an ATLUM, one can scan volumes of brain tissue in the range of cubic millimeters, in a completely automated manner: Unlike SSET and SSTEM, which are only semi-automated: The operator must manually recover tissue from the knife's water boat and, again, manually place it into TEM slot grids using an eyelash, a terribly inefficient and unreliable process.

=== KESM ===

[[File:KESM.jpg|thumb|right|The Knife Edge Scanning Microscope - KESM. Texas A&M University.]]

The Knife-Edge Scaning Microscope is a machine that integrates sectioning and imaging into a single process, with the diamond knife and microscope moving together in the same assembly, and can scan large volumes of tissue at high resolution (Below SBFSEM). It would allow for an entire mouse brain (≈1 cm<sup>3</sup>) to be scanned in one hundred hours, producing 15 Terabytes of raw EM data.<ref>McCormick, 2002a; McCormick, 2002b)</ref>

The main limitation is the need to stain inside a volume. The array of stains is at present limited, but genetic modifications may allow for cells to express stains or become fluorescent.

The tissue is fixed and embedded in plastic. As the knife and the microscope move over the tissue, a thin strip of tissue is cut and scanned. The KESM can scan up to 200 megapixels per second, with the width of the EM field being 2.5mm for 64μm resolution and 0.625mm for 32μm resolution<ref>McCormick, Koh et al., 2004</ref>. The sample is cut in a stair-step manner to reduce jittering and use knives larger than the microscope FOV<ref>Koh and McCormick, 2003</ref>.