A versatile ion beam spectrometer for studies of ion interaction with 2D materials.

We present an ultrahigh vacuum setup for ion spectroscopy of freestanding two-dimensional solid targets. An ion beam of different ion species (e.g., Xe with charge states from 1 to 44 and Ar with charge states from 1 to 18) and kinetic energies ranging from a few 10 eV to 400 keV is produced in an electron beam ion source. Ions are detected after their transmission through the 2D target with a position sensitive microchannel plate detector allowing the determination of the ion's exit charge state as well as the scattering angle with a resolution of approximately 0.04°. Furthermore, the spectrometer is mounted on a swiveling frame covering a scattering angle of ±8° with respect to the incoming beam direction. By utilizing a beam chopper, we measure the time-of-flight of the projectiles and determine the energy loss when passing a 2D target with an energy uncertainty of about 2%. Additional detectors are mounted close to the target to observe emitted secondary particles and are read-out in coincidence with the position and time information of the ion detector. A signal in these detectors can also be used as a start trigger for time-of-flight measurements, which then yield an energy resolution of 1% and an approximately 1000-fold larger duty cycle. First results on the interaction of slow Xe30+ ions with a freestanding single layer of graphene obtained with the new setup are compared to recently published data where charge exchange and energy were measured by means of an electrostatic analyzer.

Surface structure of V_{2}O_{3}(0001) revisited.

In a recent paper [A. J. Window et al., Phys. Rev. Lett. 107, 016105 (2011)], it was proposed that V_{2}O_{3}(0001) is terminated by the so-called O_{3} termination, a reconstruction with a terminating distorted hexagonal oxygen layer. We show that the surface is terminated by vanadyl (V═O) groups instead. This conclusion is based on quantitative low-energy electron diffraction combined with scanning tunneling microscopy, fast atom scattering, and density functional theory employing the Heyd-Scuseria-Ernzerhof functional. New insights into the subsurface sensitivity of ion beam triangulation show that results previously interpreted in favor of the O_{3} termination are reconcilable with vanadyl termination as well.

Ultrasound-guided fine needle aspiration cytology prior to sentinel lymph node biopsy in melanoma patients.

BACKGROUND: Sentinel lymph node biopsy (SLNB) allows early detection of metastases, thereby enabling early treatment in melanoma patients likely to benefit from adjuvant therapies. This prospective study analyzes the possible benefits of additional ultrasound (US) and fine needle aspiration cytology (FNAC) of sentinel nodes (SN) prior to SLNB. METHOD: Over a 2-year period 127 melanoma patients with 151 SN were scheduled for SLNB. All SN were initially identified with lymphoscintigraphy, then identified and evaluated by US and the cells aspirated for cytology (FNAC). US findings and FNAC results were compared to surgical findings. RESULTS: Of 127 patients, 114 had one SN each, 12 had two, and one had three. In vivo US achieved a sensitivity of 79% (95% CI: 62-91%) and a specificity of 72% (95% CI: 62-81%). FNAC showed a sensitivity of 59% (95% CI: 41-76%) and a specificity of 100% (95% CI: 95-100%). The combination of these two in vivo methods achieved an overall sensitivity of 82% (95% CI: 65-93%) and an overall specificity of 72% [95% CI: 62-81%]. CONCLUSION: Combined US and FNAC provides important information prior to SLNB in that both procedures identify metastases in the lymph nodes (sensitivity > 80%). Patients with positive FNAC may proceed directly to complete lymph node dissection (cLND) instead of having initial SLNB. Thus, combined US and FNAC may prevent unnecessary anesthesia and surgical management as well reduce costs. In our study 16% (19/121) fewer SLNB procedures were carried out, subsequently replaced by cLND. For patients with a negative combination of in vivo US and FNAC, SLNB remains the best diagnostic option.

Influence of fast lymphatic drainage on metastatic spread in cutaneous malignant melanoma: a prospective feasibility study.

The concept of sentinel lymph node biopsy in cutaneous malignant melanoma is widely established. Preoperative cutaneous lymphoscintigraphic mapping is a reliable method for identifying the nodal basins at risk of metastases in melanomas. In this prospective study we investigated the correlation between the scintigraphic appearance time and the metastatic involvement of sentinel lymph nodes. In 276 malignant melanoma patients (137 women, 139 men; age 16-93 years), dynamic and static lymphoscintigraphy was performed after strict intracutaneous application of technetium-99m nanocolloid (40-150 MBq; 0.05 ml/deposit) around the tumour or biopsy scar. Analysis of dynamic scans primarily focussed on the appearance time of sentinel lymph nodes. Sentinel lymph node visualisation 20 min as slow drainage. Fast lymphatic drainage was found in 236 patients, of whom 34 (14.4%) had sentinel lymph node metastases. Twenty-two patients showed hybrid (fast and slow) lymphatic drainage, and eight (36.4%) of them had sentinel lymph node metastases. Seven of the latter demonstrated fast lymphatic drainage, while one showed one positive sentinel lymph node with fast and another with slow drainage. The melanomas of 18 patients demonstrated exclusively slow lymphatic drainage, in all cases without sentinel lymph node metastases. This prospective study indicates that the scintigraphic appearance time of sentinel lymph nodes seems to be a clinically relevant factor for prediction of metastatic spread of cutaneous malignant melanoma. Larger numbers of patients need to be examined to truly assess the benefit of the scintigraphic appearance time compared with other predictors of sentinel lymph node tumour positivity.