Erratum: (2x1)-(1x1) Phase Transition on Ge(001): Dimer Breakup and Surface Roughening [Phys. Rev. Lett. 91, 116102 (2003)]

Using low energy electron microscopy, we have investigated the (2×1)-(1×1) phase transition occurring above 925 K on Ge(001). Dimer breakup has been identified as the physical origin of this transition. A quantitative description of the dimer concentration during the transition involves configuration entropy of random monomers within the dimer matrix. The dimer formation energy amounts to 1.2±0.3  eV. Dimer breakup promotes reversible surface disorder by step proliferation and irreversible surface roughening above 1130 K

Alloying, de-alloying and reentrant alloying in (sub-)monolayer growth of Ag on Pt(111)

An in-situ nanoscopic investigation of the prototypical surface alloying system Ag/Pt(111) is reported. The morphology and the structure of the ultrathin Ag-Pt film is studied using Low Energy Electron Microscopy during growth at about 800 K. An amazingly rich dynamic behaviour is uncovered in which stress relieve plays a governing role. Initial growth leads to surface alloying with prolonged and retarded nucleation of ad-islands. Beyond 50% coverage de-alloying proceeds, joined by partial segregation of Pt towards the centre of large islands in violent processes. Upon coalescence the irregularly shaped vacancy clusters are filled by segregating Pt, which then take a compact shape (black spots). As a result at around 85% coverage the strain of the initially pseudo-morphological film is almost completely relieved and Pt-segregation is at its maximum. Further deposition of Ag leads to transient re-entrant alloying and recovery of the pseudo-morphological layer. The black spots persist even in/on several layers thick films. Ex-situ atomic force microscopy data confirm that these are constituted by probably amorphous Pt(-rich) structures. The (sub-)monolayer films are very much heterogeneous

A quantitative evaluation of the dimer concentration during the (2 × 1)-(1 × 1) phase transition on Ge(0 0 1)

We propose a new quantitative model of the high-temperature (2 × 1)-(1 × 1) phase transition on Ge(0 0 1). We demonstrate that the transition is driven by an entropy facilitated breakup of dimers. A full quantitative description of the reversible variation of the dimer concentration requires incorporation of vibration entropy, not only of the topmost atoms, but also of those in two layers beneath. The main ingredients of our new model include the dimer formation energy and the difference in vibration entropy between the reconstructed (2 × 1) and the bulk-terminated (1 × 1)-phase. This entropy difference amounts to about 1.4 meV/K and the obtained dimer formation energy of 1.5 ± 0.2 eV is in good agreement with calculated values

Optical Characterization of Thin Colloidal Gold Films by Spectroscopic Ellipsometry

Spectroscopic ellipsometry and atomic force microscopy (AFM) experiments are employed to characterize nanocolloidal gold films, self-assembled at APTES-derivatized Si/SiO2 surfaces. X-ray fluorescence measurements after deposition confirm that AFM provides a representative means to probe the absolute surface coverage. Optical properties of gold nanocrystal assemblies are investigated both ex situ after drying and in situ prior to evaporation of the solvent. Quantitative optical characterization of these highly inhomogeneous systems is not unambiquous. Conventional effective medium approximations are not applicable to these systems. To enable an accurate analysis, extinction measurements on colloidal suspensions are performed. The limited particle size in relation to the electron mean free path leads to a modification of the dielectric function at longer wavelengths. Ellipsometry spectra of the colloidal gold films are analyzed qualitatively using an optical invariant and principal component analyses. Quantitative results are obtained using a theory which treats the nanocrystals as polarizabilities at the Fresnel interface. Above approximately 20%, the coverages determined from optical spectra are in agreement with what is found from AFM images. At lower coverages, the optical results seem to overestimate the actual nanocrystal density. The discrepancies are discussed in terms of image charge effects arising from the proximity of the substrate

CABA-V7: a prospective biomarker selected trial of cabazitaxel treatment in AR-V7 positive prostate cancer patients

Background: Metastatic castration-resistant prostate cancer (mCRPC) patients with positive AR-V7 expression in their circulating tumour cells (CTCs) rarely derive benefit from abiraterone and enzalutamide. Design: We performed a prospective, multicenter, single arm phase II clinical trial (CABA-V7) in mCRPC patients previously treated with docetaxel and androgen deprivation therapy. Objective: In this trial, we investigated whether cabazitaxel treatment resulted in clinically meaningful PSA response rates in patients with positive CTC-based AR-V7 expression and collected liquid biopsies for genomic profiling. Results: Cabazitaxel was found to be modestly effective, with only 12% of these patients obtaining a PSA response. Genomic profiling revealed that CTC-based AR-V7 expression was not associated with other known mCRPC-associated alterations. CTC-based AR-V7 status and dichotomised CTC counts were observed as independent prognostic markers at baseline. Conclusions: AR-V7 positivity predicted poor overall survival (OS). However, cabazitaxel-treated AR-V7 positive patients and those lacking AR-V7 positivity, who received cabazitaxel as standard of care, appeared to have similar OS. Therefore, despite the low response rate, cabazitaxel may still be an effective treatment in this poor prognosis, AR-V7 positive patient population