ScN/GaN(11Ì 00): A New Platform for the Epitaxy of Twin-Free Metal-Semiconductor Heterostructures.

We study the molecular beam epitaxy of rock-salt ScN on the wurtzite GaN(11̅00) surface. To this end, ScN is grown on freestanding GaN(11̅00) substrates and self-assembled GaN nanowires exhibiting (11̅00) sidewalls. On both substrates, ScN crystallizes twin-free thanks to a specific epitaxial relationship, namely ScN(110)[001]∥GaN(11̅00)[0001], providing a congruent, low-symmetry interface. The 13.1% uniaxial lattice mismatch occurring in this orientation mostly relaxes within the first few monolayers of growth by forming a near-coincidence site lattice, where 7 GaN planes coincide with 8 ScN planes, leaving the ScN surface nearly free of extended defects. Overgrowth of the ScN with GaN leads to a kinetic stabilization of the zinc blende phase, that rapidly develops wurtzite inclusions nucleating on {111} nanofacets, commonly observed during zinc blende GaN growth. Our ScN/GaN(11̅00) platform opens a new route for the epitaxy of twin-free metal-semiconductor heterostructures including closely lattice-matched GaN, ScN, HfN, and ZrN compounds.

T-lymphocyte cytokine production patterns in nonimmune severe hypothyroid state and after thyroid hormone replacement therapy.

The influence of thyroid hormones on the immune system is controversial. We analyzed the cytokine expression pattern of T lymphocytes in patients with severe nonimmune hypothyroidism in order to establish the role of thyroid hormones on the immune system. The study comprised 7 patients (1 male and 6 females) 20 to 76 years of age (mean age, 53 years), without signs of chronic thyroiditis, verified by histology and laboratory data. The patients were studied 5 weeks after total thyroidectomy. Peripheral blood mononuclear cell (PBMC) cultures and intracellular cytokine detection by flow cytometry before and after thyroid hormone replacement therapy were performed (free thyroxine [FT4] 0.030 +/- 0.034 ng/dL, versus FT4: 2.16 +/- 0.68 ng/dL). The control group consisted of 7 healthy subjects (FT4: 1.20 +/- 0.21 ng/dL). We found no significant differences in the cytokine pattern (interferon [IFN]-gamma, IL-2, interleukin [IL]-4, IL-5, IL-6, IL-10, IL-13, tumor necrosis factor [TNF]-alpha, TNF-beta) of CD4+ and CD8+ between the matched groups (hypothyroid subjects versus controls, levothyroxine treated subjects versus controls). Our data show no change in the type 1/type 2 balance of peripheral CD4+ and CD8+ T lymphocytes from patients with nonimmune hypothyroidism. According to our results, the hypothyreotic state does not contribute to the reported changes in cytokine production patterns in Hashimoto's thyroiditis.