MRI contrast-dose relationship of manganese(III)tetra(4-sulfonatophenyl) porphyrin with human xenograft tumors in nude mice at 2.0 T

Previously we reported that Mn(III)tetra(4-sulfonatophenyl) porphyrin, MnTPPS₄, is a contrast agent which can effectively enhance tumor detection by MRI. By imaging 30 additional athymic nude mice bearing subcutaneous MCF-7 WT human breast carcinoma xenografts, we have extended dose-contrast relationships over a wide range of intraperitoneal (IP) doses ranging from 0.025 to 0.50 mmol/kg. The benefits of IP injection are higher possible doses on a volume basis and a reduction in toxicity versus IV administration. Full coronal cross-section images have been obtained on a 2-T spectrometer. Although individual tumor masses displayed different distribution patterns, reflective of their internal morphology, single doses of 0.10 mmol/kg or greater were necessary to produce a detectable effect. At a dose of 0.50 mmol/kg, marked enhancement was produced. Multiple small dosages administered over the course of several days before imaging did not produce increased enhancement. Preliminary results on the new porphyrin derivative, MnTPPS₃, indicate that the ratio of the toxic dose to the effective dose may be adjustable to render this class of agents clinically useful.     

Observation of the giant stark effect in boron-nitride nanotubes

Bias dependent scanning tunneling microscopy and scanning tunneling spectroscopy have been used to characterize the influence of transverse electric fields on the electronic properties of boron-nitride nanotubes (BNNTs). We find experimental evidence for the theoretically predicted giant Stark effect. The observed giant Stark effect significantly reduces the band gap of BNNTs and thus greatly enhances the utility of BNNTs for nanoscale electronic, electromechanical, and optoelectronic applications.     

Solitons in nonlinear media with an infinite range of nonlocality: first observation of coherent elliptic solitons and of vortex-ring solitons

We present an experimental study on wave propagation in highly nonlocal optically nonlinear media, for which far-away boundary conditions significantly affect the evolution of localized beams. As an example, we set the boundary conditions to be anisotropic and demonstrate the first experimental observation of coherent elliptic solitons. Furthermore, exploiting the natural ability of such nonlinearities to eliminate azimuthal instabilities, we perform the first observation of stable vortex-ring solitons. These features of highly nonlocal nonlinearities affected by far-away boundary conditions open new directions in nonlinear science by facilitating remote control over soliton propagation.     

An international round-robin calibration protocol for nanoindentation measurements

Nanoindentation has become a common technique for measuring the hardness and elastic-plastic properties of materials, including coatings and thin films. In recent years, different nanoindenter instruments have been commercialised and used for this purpose. Each instrument is equipped with its own analysis software for the derivation of the hardness and reduced Young's modulus from the raw data. These data are mostly analysed through the Oliver and Pharr method. In all cases, the calibration of compliance and area function is mandatory. The present work illustrates and describes a calibration procedure and an approach to raw data analysis carried out for six different nanoindentation instruments through several round-robin experiments. Three different indenters were used, Berkovich, cube corner, spherical, and three standardised reference samples were chosen, hard fused quartz, soft polycarbonate, and sapphire. It was clearly shown that the use of these common procedures consistently limited the hardness and reduced the Young's modulus data spread compared to the same measurements performed using instrument-specific procedures. The following recommendations for nanoindentation calibration must be followed: (a) use only sharp indenters, (b) set an upper cut-off value for the penetration depth below which measurements must be considered unreliable, (c) perform nanoindentation measurements with limited thermal drift, (d) ensure that the load-displacement curves are as smooth as possible, (e) perform stiffness measurements specific to each instrument/indenter couple, (f) use Fq and Sa as calibration reference samples for stiffness and area function determination, (g) use a function, rather than a single value, for the stiffness and (h) adopt a unique protocol and software for raw data analysis in order to limit the data spread related to the instruments (i.e. the level of drift or noise, defects of a given probe) and to make the H and E(r) data intercomparable.