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The detection and characterization of cell-free DNA (cfDNA) in peripheral blood from neuroblastoma patients may serve as a minimally invasive approach to liquid biopsy. Major challenges in the analysis of cfDNA purified from blood samples are small sample volumes and low cfDNA concentrations. Droplet digital PCR (ddPCR) is a technology suitable for analyzing low levels of cfDNA. Reported here are two quadruplexed ddPCR assay protocols that reliably quantify MYCNand ALKcopy numbers in a single reaction together with the two reference genes, NAGKand AFF3, and accurately estimate ALKF1174L(exon 23 position 3522, C>A) and ALKR1275Q(exon 25 position 3824, G>A) mutant allele fractions using cfDNA as input. The separation of positive and negative droplets was optimized for detecting two targets in each ddPCR fluorescence channel by the adjustment of the probe and primer concentrations of each target molecule. The quadruplexed assays were validated using a panel of 10 neuroblastoma cell lines and paired blood plasma and primary neuroblastoma samples from nine patients. Accuracy and sensitivity thresholds in quadruplexed assays corresponded well with those from the respective duplexed assays. Presented are two robust quadruplexed ddPCR protocols applicable in the routine clinical setting and that require only minimal plasma volumes for the assessment of MYCNand ALKoncogene status.

The room temperature near-normal incidence reflectance spectra for SrTiO3 and BaTiO3 have been measured in the energy region 10 to 32 eV. The optical constants for the region 0 to 32eV have been derived from a Kramers-Kronig analysis by including earlier measurements for the low energy region. For SrTiO3 five peaks in the Ti3d derived conduction band density of states have been found on the basis of experimental data only, neglecting excitonic effects. The energies of these peaks are in excellent agreement with peaks in the density of states calculated by Mattheiss. The results for BaTiO3 could not be interpreted as unambiguously in such a scheme. Alternatively, some of the transitions could be interpreted as being due to core level excitons.

The excitonic spectra associated with the shallow core levels K^+3p, Ga3d, and In4d in potassium halide and iii-v semiconductor single crystals were studied by high resolution reflectivity (ΔE < 10 meV) as a function of temperature down to 20 K. Analysis of the fine structure, transition energies, line profiles, halfwidths, and their temperature dependence yields information on the exciton (electron)–phonon interaction and on the influence of lattice expansion. Strong electron–phonon coupling dominates in the K^+3p excitons as it does in F centers, whereas weak coupling describes the core excitons in semiconductors. The contributions of initial and final states are discussed. Core surface excitons in semiconductors show a significantly smaller temperature coefficient than the volume excitons.