Radioactive isotopes in solid-state physics

Radioactive atoms have been used in solid-state physics and in material science for many decades. Besides their classical application as tracer for diffusion studies, nuclear techniques such as M\"ossbauer spectroscopy, perturbed angular correlation, $\beta$-NMR, and emission channelling have used nuclear properties (via hyperfine interactions or emitted particles) to gain microscopical information on the structural and dynamical properties of solids. During the last decade, the availability of many different radioactive isotopes as a clean ion beam at ISOL facilities such as ISOLDE at CERN has triggered a new era involving methods sensitive for the optical and electronic properties of solids, especially in the field of semiconductor physics. Extremely sensitive spectroscopic techniques like deep-level transient spectroscopy (DLTS), photoluminescence (PL), and Hall effect have gained a new quality by using radioactive isotopes. Because of their decay the chemical origin of an observed electronic and optical behaviour of a specific defect or dopant can be unambiguously identified. The ongoing experiments in solid-state physics using radioactive ions deal with a wide variety of problems in condensed matter physics involving bulk properties, surfaces and interfaces in many different systems like semiconductors, superconductors, surfaces, interfaces, magnetic systems, metals, and ceramics. This article highlights a few examples to illustrate the potential of the use of radiaoctive isotopes for various problems in solid-state physics

Polymorphism of the tumor necrosis factor beta gene in systemic lupus erythematosus

We investigated the Nco I restriction fragment length polymorphism (RFLP) of the tumor necrosis factor beta (TNFB) gene in 173 patients with systemic lupus erythematosus (SLE), 192 unrelated healthy controls, and eleven panel families, all of German origin. The phenotype frequency of the TNFB*I allele was significantly increased in patients compared to controls (63.6% vs 47.1%, RR = 1.96, p <0.002). The results of a two-point haplotype statistical analysis between TNFB and HLA alleles show that there is linkage disequilibrium between TNFB*I and HLA-A1, Cw7, B8, DR3, DQ2, and C4A DE. The frequency of TNFB*I was compared in SLE patients and controls in the presence or absence of each of these alleles. TNFB*I is increased in patients over controls only in the presence of the mentioned alleles. Therefore, the whole haplotypeA1, Cw7, B8, TNFB* I, C4A DE, DR3, DQ2 is increased in patients and it cannot be determined which of the genes carried by this haplotype is responsible for the susceptibility to SLE. In addition, two-locus associations were analyzed in 192 unrelated healthy controls for TNFB and class I alleles typed by serology, and for TNFB and class II alleles typed by polymerase chain reaction/oligonucleotide probes. We found positive linkage disequilibrium between TNFB*I and the following alleles: HLA-A24, HLA-B8, DRBI*0301, DRBI*ll04, DRBI*1302, DQAI*0501, DQBI*0201, DQBI*0604, and DPBI*OIO1. TNFB*2 is associated with HLA-B7, DRBI*1501, and DQB I *0602

Potassium self-diffusion in a K-rich single-crystal alkali feldspar

The paper reports potassium diffusion measurements performed on gem-quality single-crystal alkali feldspar in the temperature range from $1169$ to 1021 \, \mbox{K}. Natural sanidine from Volkesfeld, Germany was implanted with \mbox{}^{43}\mbox{K} at the ISOLDE/CERN radioactive ion-beam facility normal to the (001) crystallographic plane. Diffusion coefficients are well described by the Arrhenius equation with an activation energy of 2.4 \, \mbox{eV} and a pre-exponential factor of 5\times10^{-6} \, \mbox{m}^{2}/\mbox{s}, which is more than three orders of magnitude lower than the \mbox{}^{22}\mbox{Na} diffusivity in the same feldspar and the same crystallographic direction. State-of-the-art considerations including ionic conductivity data on the same crystal and Monte Carlo simulations of diffusion in random binary alloy structures point to a correlated motion of K and Na through the interstitialcy mechanism

Formation of 117In−H^{117}In-H pairs after annealing of GaN implanted with 117Cd(117In)^{117}Cd(^{117}In)

We report on the annealing behaviour of GaN grown on sapphire after implantation of 117Cd(117In). Isochronic annealing has been performed in order to remove the implantation induced lattice damage in evacuated quartz ampoules with additional Al. The extent of the lattice damage is investigated with perturbed gg-angular correlation spectroscopy (PAC). The implantation damage is annealed at temperatures above 1073 K to a large extent. 82(5) % of the probes are found on the Ga-site characterized by a quadrupole coupling constant of 20.9(1) MHz. After H loading, an additional interaction appears which is attributed to 117Cd(117In)-H pairs

Lattice sites of Cd in ferroelectric BaTiO3_3

The radioactive isotope 111mCd was implanted into BaTiO3 in order to measure electric field gradients with Perturbed Angular Correlation spectroscopy (PAC). It is possible to anneal the implantation induced lattice damage to a certain extent. Then, 111mCd probes are positioned at two sites with distinct axially symmetric electric field gradients characterized by the quadrupole coupling constants of 33.9(9) and 69.8(9) MHz. These electric field gradients can be assigned to 111mCd at the Ti- and the Ba-sites

Targeting dendritic cells in pancreatic ductal adenocarcinoma

Dendritic cells (DC) are an integral part of the tumor microenvironment. Pancreatic cancer is characterized by reduced number and function of DCs, which impacts antigen presentation and contributes to immune tolerance. Recent data suggest that exosomes can mediate communication between pancreatic cancer cells and DCs. Furthermore, levels of DCs may serve as prognostic factors. There is also growing evidence for the effectiveness of vaccination with DCs pulsed with tumor antigens to initiate adaptive cytolytic immune responses via T cells. Most experience with DC-based vaccination has been gathered for MUC1 and WT1 antigens, where clinical studies in advanced pancreatic cancer have provided encouraging results. In this review, we highlight the role of DC in the course, prognosis and treatment of pancreatic cancer

Response of the electric field gradient in ion implanted BaTiO3_{3} to an external electric field

Single crystalline, ferroelectric BaTiO$_{3}$ as material with the highest piezoelectric constants among the perovskites with ordered sublattices was implanted with $^{111}$In($^{111}$Cd). The electric field gradient at the Ti position was measured with perturbed $\gamma-\gamma$-angular correlation spectroscopy (PAC) while the crystal was exposed to an external electric field. A quadratic dependence could be observed: $\nu_{Q}$(E) = (34.8(1) + 0.16(4) E/kV/mm + 0.080(2) E$^{2}$/kV$^{2}$/mm$^{2}$) MHz. Point charge model calculations reproduce the linear change of Vzz, but not the quadratic term. The polarizability of the host ions of BaTiO$_{3}$ is known to be nonlinear with respect to an electric field. The resulting quadratic shift of the electron density is reflected in the strength of the EFG