High-dose Co implantation in Si, SiO2/Si and Si3N4/Si Part I : Formation of thin silicide surface films

In order to obtain thin CoSi2 surface layers, Si(1 1 1) and Si(1 0 0), covered by SiO2 or Si3N4 with different thickness, have been implanted by Co to normal fluences from 1 x 1016 to 2.6 x 1018 ions cm-2. The Co ions were produced by a high beam current MEtal Vapour Vacuum Arc (MEVVA) ion implantation system with 40 kV acceleration voltage. Time-of-Flight Energy Elastic Recoil Detection (ToF-E ERD) was used to determine the incorporation of Co in the coating materials and silicon substrates. The phase formation and electrical characterisation have been studied by X-ray diffraction (XRD) and a four-point probe system. The results reveal that the oxide and nitride layers are uniformly eroded and no significant N or O transport into the bulk Si is observed. After implantation, a thin surface silicide layer (~80 nm) with both a smooth surface topography and sharp interface could be obtained. The optimum Co normal fluence for producing a flat silicide layer depends on the surface film material and its thickness

Modulation of CEST Images <i>in Vivo</i> by <i>T</i>₁ Relaxation: A New Approach in the Design of Responsive PARACEST Agents

A novel approach for the design of responsive paramagnetic chemical exchange saturation transfer (PARACEST) magnetic resonance imaging (MRI) agents has been developed where the signal is “turned on” by altering the longitudinal relaxation time (<i>T</i>₁) of bulk water protons. To demonstrate this approach, a model Eu­(DOTA-tetraamide) complex (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) containing two nitroxide free radical units was synthesized. The nitroxide groups substantially shortened the <i>T</i>₁ of the bulk water protons which, in turn, resulted in quenching of the CEST signal. Reduction of paramagnetic nitroxide moieties to a diamagnetic species resulted in the appearance of CEST. The modulation of CEST by <i>T</i>₁ relaxation provides a new platform for designing biologically responsive MRI agents

ROIs selected for T2* calculation using the first-echo image.

<p> articular cartilage anterior horn of the medial meniscus posterior horn of the medial meniscus, and femoral subchondral bone marrow.</p

Comparisons of T2^* values in femoral subchondral bone marrow among three groups over 18 weeks using multiple linear regression with generalized estimating equations.

a<p>Group 1 = Control group; Group 2 = ACLX group; Group 3 = Sham group.</p>*<p>The interaction between two variables in the models.</p><p>B: regression coefficient.</p

Histologic confirmation of changes in the articular cartilage and femoral subchondral bone marrow.

<p>In the ACLX group, severe cartilage degeneration including loss of chondrocytes, extracellular matrix deterioration, and fibrovascular proliferation of the subchondral bone marrow are seen in the operated right knee. In contrast, the cartilage and subchondral bone of the femorotibial joint in the other knee joint have a normal histologic appearance.</p

Plots of the T2* values (mean ± SD) in the right knee joints of three groups.

<p>The values are for cartilage (a), anterior horn of the medial meniscus (b), posterior horn of the medial meniscus (c), and femoral subchondral bone marrow (d) at weeks 0, 4, 13, and 18. Asterisks indicate significant differences (<i>p</i><0.05).</p

Plots of the T2* values (mean ± SD) for the ACLX group.

<p>Values are for cartilage (a), anterior horn of the medial meniscus (b), posterior horn of the medial meniscus (c), and femoral subchondral bone marrow (d) at weeks 0, 4, 13, and 18, separately measured in the operated right knees and the intact left knees of all rats. Asterisks indicate significant differences (<i>p</i><0.05).</p

Comparisons of four T2^* values between right (Side 1) and left knees (Side 0) over 18 weeks in the ACLX group using multiple linear regression with generalized estimating equations.

a<p>Side 1 = Right knee and Side 0 = Left knee (the reference knee).</p>*<p>The interaction between two variables in the models.</p><p>B: regression coefficient.</p

An overview of the protocol design in this study.

<p>() MR imaging; () Histologic analysis.</p

The immunohistochemical staining of microvessels of different VEGF isofrom overexpressing tumors and the mock tumors.

<p>Angiogenesis phenotypes of microvessels evaluated by immunohistochemical staining of tumor xenografts overexpressing different VEGF isoforms. (A) Immunohistochemical staining of tumor microvessels (brown color, ×100 in main panel, ×400 in the inset) in tumor xenografts. (B) The microvessel density was highest in the VEGF189-overexpressing tumors, intermediate in the VEGF165-overexpressing tumors, and lowest in the VEGF121-overexpressing tumors. (C) The number of vessels with a diameter larger than 15 µm per tumor section in the tumor xenograft was highest in the VEGF121-overexpressing tumors, intermediate in the VEGF165-overexpressing tumors, and lowest in the VEGF189-overexpressing tumors. Differences between VEGF-overexpressing and mock tumors were significant at the *<i>p</i><0.05, **<i>p</i><0.01, ***<i>p</i><0.001, and ****<i>p</i><0.0001 levels.</p