Dimetrodon sp. femur, jaw, teeth, and rib bones were collected at N.E. Frederick, OK, and sectioned for histological examination. This Oklahoma Museum of Natural History site has yielded well-preserved Paleozoic fossils for decades. All bones were heavily infiltrated with calcite and other minerals, yet a reddish-brown mass obstructed many vascular channels. This reddish-brown mass reacted to 374 nm UV illumination by emitting bright blue autofluorescence. This was true for every specimen and indicates a heavy presence of iron. We conclude that the iron in the canals is the crystallized remains of blood that clotted during an asphyxiation event that killed the animal. Remarkably similar reddish-brown obstructive material has also been observed in other histological studies performed on Dimetrodon bones. We conclude that these are also the remains of blood clots and simply await examination under UV fluorescence.

The internal electric field of a 2D P-N junction of a semiconductor is mapped out by two techniques: measuring the deflection of the transmitted beam in micro-STEM mode with acquisition and data fitting of an un-scattered beam image, and through the derivative of electrostatic potential maps by dual lens electron holography. Comparable results of the P-N junction internal electric field measured with these two techniques are reported.

Here, we use a variety of microscopic imaging techniques, including scanning electron microscopy, 3D visible light microscopy, and portable microscopy to capture the topography of rough paper. Paper coated with a model soot was cleaned with either a firm vinyl eraser or softer, putty-like kneaded eraser and reimaged to characterize the disposition of remaining soot. Although both methods remove soot from the upper-most surface of the paper, only the kneaded eraser can conform to the complex topography to remove soot from the interstices between paper fibers.

Temperature is a key parameter in most biological and physical systems. It is, however, an inherent technological challenge to precisely track and control the temperature of small sample volumes when using high- and super-resolution microscopes. Various effects can cause a deviation of the sample temperature from its expected value, specifically in the observed volume or field-of-view. These effects include direct thermal contact of the objective lens and the coverslip via immersion medium, illumination-induced heating, evaporative cooling, or triggered phase transitions. In this paper, we shed light on these phenomena and introduce our newly developed device VAHEAT, which follows a microscopic approach for controlling and measuring the sample temperature. Our system overcomes traditional limitations of temperature sensing and controlling in high-sensitivity microscopy applications, leading to more reproducible experimental results and conquering new experimental parameter ranges.

Cryo-electron tomography (cryo-ET) enables visualization of protein complexes within their native cellular environment at molecular resolution. Most cells and all tissues, however, are too thick to be imaged directly by transmission electron microscopy (TEM). Overcoming this limitation requires the production of thin biological sections called lamellae. The procedure to obtain lamellae of cells, either seeded or grown directly on electron microscopy grids, requires cryo-focused ion beam (cryo-FIB) milling to thin the samples. This method faces an additional challenge when dealing with tissues and multicellular organisms, as these samples must be high-pressure frozen, which embeds the sample in a thick layer of ice. Nonetheless, lamellae can still be prepared from such samples by extracting a small volume and transferring it to a receiver grid for lamella preparation, a process called lift-out. Here, we describe the available workflows to produce lamellae by lift-out at cryogenic conditions and recent developments in gas injection system (GIS)-free approaches to the lift-out transfer. These advances expand the applications of cryo-ET, enabling the investigation of tissues and whole organisms in situ at molecular resolution.