Investigation of the (001) cleavage plane of potassium bromide with an atomic force microscope at 4.2 K in ultra-high vacuum

We have imaged the (001) surface of KBr with a UHV atomic force microscope at 4.2 K and 300 K. The sample was prepared by cleaving it in UHV along the (001) plane. We achieved atomic resolution at 4.2 K and resolved both the potassium and the bromium ions. We show atomically resolved images of flat terraces as large as 25 nm by 25 nm. Force-versus-distance measurements were taken, and the influence of the loading force acting between sample and cantilever on the appearance of friction effects and sample damage was studied

Theory for an electrostatic imaging mechanism allowing atomic resolution of ionic crystals by atomic force microscopy

An electrostatic imaging mechanism is presented which allows atomic resolution of the surface of ionic crystals by atomic force microscopy (AFM). In the x-y plane the electrostatic field due to the ion charges reflects the periodicity of the surface lattice. If the tip of the AFM stylus is polarizable, an attractive force between tip and sample will exist and allow imaging of the surface in a noncontact mode. It is shown that the decay length of the electrostatic interaction in the z direction is sufficiently short for atomic resolution to be achieved not only with a hypothetical tip consisting of only one atom but also by a more realistic tip of parabolic shape with a radius of 30 nm. The theory is applied to the (001) surface of KBr

A low‐temperature atomic force/scanning tunneling microscope for ultrahigh vacuum

We have built an ultrahigh vacuum atomic force/scanning tunneling microscope that works at 4.2 K. The microscope is incorporated into a very small chamber (100 ml) which can be evacuated and baked to UHV within a few hours by a specially designed valve. The instrument is about 20×20×70 mm3 in size and sturdy enough to operate without vibration isolation. The deflection of a microfabricated cantilever is detected by electron tunneling. Preliminary results show atomic resolution of HOPG in the STM mode and steps in KBr that range from one to four lattice constants in height at UHV conditions and 4.2 K

Tissue Phenomics for prognostic biomarker discovery in low- and intermediate-risk prostate cancer

Tissue Phenomics is the discipline of mining tissue images to identify patterns that are related to clinical outcome providing potential prognostic and predictive value. This involves the discovery process from assay development, image analysis, and data mining to the final interpretation and validation of the findings. Importantly, this process is not linear but allows backward steps and optimization loops over multiple sub-processes. We provide a detailed description of the Tissue Phenomics methodology while exemplifying each step on the application of prostate cancer recurrence prediction. In particular, we automatically identified tissue-based biomarkers having significant prognostic value for low-and intermediate-risk prostate cancer patients (Gleason scores 6-7b) after radical prostatectomy. We found that promising phenes were related to CD8(+) and CD68(+) cells in the microenvironment of cancerous glands in combination with the local micro-vascularization. Recurrence prediction based on the selected phenes yielded accuracies up to 83% thereby clearly outperforming prediction based on the Gleason score. Moreover, we compared different machine learning algorithms to combine the most relevant phenes resulting in increased accuracies of 88% for tumor progression prediction. These findings will be of potential use for future prognostic tests for prostate cancer patients and provide a proof-of-principle of the Tissue Phenomics approach

Imaging of cell membraneous and cytoskeletal structures with a scanning tunneling microscope

AbstractThe first observation of unstained cell membraneous structures by a scanning tunneling microscope is reported. An adhesive preparation method was used for imaging human medulloblastoma cells from the cell line TE 671 and oocytes from the clawed toad Xenopus laevis. The images show filaments, stacks of molecules and hilly structures. The possible identity of the filamentous structures is discussed, although the observed structures cannot yet be fully characterized. The work suggests possible future experiments on various biological structures in their natural environment