Effect of isotopic constitution of diamond on its elastic constants: 13C diamond, the hardest known material

Anomalous isotope effect on mechanical properties of single atomic layer Boron Nitride

The ideal mechanical properties and behaviors of materials without the influence of defects are of great fundamental and engineering significance but considered inaccessible. Here, we use single-atom-thin isotopically pure hexagonal boron nitride (hBN) to demonstrate that two-dimensional (2D) materials offer us close-to ideal experimental platforms to study intrinsic mechanical phenomena. The highly delicate isotope effect on the mechanical properties of monolayer hBN is directly measured by indentation: lighter 10B gives rise to higher elasticity and strength than heavier 11B. This anomalous isotope effect establishes that the intrinsic mechanical properties without the effect of defects could be measured, and the so-called ultrafine and normally neglected isotopic perturbation in nuclear charge distribution sometimes plays a more critical role than the isotopic mass effect in the mechanical and other physical properties of materials.

Isotopic dependence of the Casimir force

We calculate the dependence of the Casimir force on the isotopic composition of the interacting objects. This dependence arises from the subtle influence of the nuclear masses on the electronic properties of the bodies. We discuss the relevance of these results to current experiments utilizing the isoelectronic effect to search at very short separations for new weak forces suggested by various unification theories.

Expression of somatostatin receptor subtypes 2 and 4 in human benign prostatic hyperplasia and prostatic cancer

BACKGROUND

The presence of receptor subtypes for the inhibitory peptide somatostatin in prostatic tissue has been a controversial issue with conflicting reports. To elucidate whether prostatic epithelial cells express mRNA for somatostatin receptor (SSTR) subtype 2 and 4, we have investigated the localization of SSTR2 and SSTR4 transcripts in prostatic tissues by in situ hybridization.

METHODS

Nonradioactive in situ hybridization was performed with specific fluorescein-labeled SSTR2 and SSTR4 riboprobes on consecutive sections of benign prostatic hyperplasia (BPH) and prostate cancer tissues.

RESULTS

We report, for the first time, tissue localization of SSTR2 and SSTR4 mRNA in BPH and malignant cells of human prostate. Hybridization signals for SSTR4 mRNA transcripts were confined to the prostatic epithelium (12 of 16 BPH cases, and in 12 of 13 carcinoma cases), whereas SSTR2 transcripts were predominantly localized in the stromal compartment but also were detectable in epithelial cells in a significant number of specimens (11 of 17 BPH cases, and in 12 of 14 carcinoma cases). Furthermore, the staining intensity for SSTR2 and SSTR4 transcripts is stronger in malignant cells compared with adjacent BPH epithelium.

CONCLUSION

The data presented suggest that the expression of SSTR2 and SSTR4 transcripts is up-regulated in malignant cells and that not only SSTR2 agonists, but also compounds targeting the SSTR4 subtype may have a potential role in the treatment of prostate cancer.

X-ray standing wave analysis of the effect of isotopic composition on the lattice constants of Si and Ge

The x-ray standing wave (XSW) technique is used to measure the isotopic mass dependence of the lattice constants of Si and Ge. Backreflection allows substrates of moderate crystallinity to be used while high order reflection yields high accuracy. The XSW, generated by the substrate, serves as a reference for the lattice planes of an epilayer of different isotopic composition. Employing XSW and photoemission, the position of the surface planes is determined from which the lattice constant difference Deltaa is calculated. Scaled to DeltaM = 1 amu we find (Deltaa/a) of -0.36x10(-5) and -0.88x10(-5) for Ge and -1.8x10(-5) and -3.0x10(-5) for Si at 300 and 30 K, respectively.