Structural and electrical properties of a Ge(111) layer directly grown on a Si(111) substrate are studied. Via optimized two-step growth manner, we form a high-quality relaxed Ge layer, where ...strain-relieving dislocations are confined close to a Ge/Si interface. Consequently, a density of holes, which unintentionally come from crystal defects, is highly suppressed below 4×1016cm−3, which leads to significantly high hole Hall mobility exceeding 1500cm2/Vs at room temperature. By layer transfer of the grown Ge layer, we also fabricate a Ge(111)-on-Insulator, which is a promising template for high-performance Ge-based electronic and photonic devices.
•A high-quality Ge layer is epitaxially grown on a Si(111) by two-step growth manner.•Growth conditions, such as growth temperatures, are optimized.•Very high hole mobility is obtained from Ge(111) grown on Si(111).•High-quality thin Ge-on-Insulator with (111) orientation is obtained.
•Ion-implantation-induced defects can enhance the strain relaxation of SiGe grown on Si(110).•Si ion implantation offers SiGe relaxed layers with much smaller surface roughness than Ar ...implantation.•The strain state of SiGe can be controlled laterally with selective implantation.•Implantation method is promising toward high mobility strained Si/Ge (110) channel pMOSFETS.
We investigate effects of ion implantation on strain relaxation of SiGe(110) layers grown on Si(110) substrates. Ar+ or Si+ ion implantation is carried out before or after the SiGe growth. It is found that the strain relaxation of the SiGe(110) film is largely enhanced due to implantation-induced defects both for Ar and Si implantation. Particularly, the sample with Si implantation after the SiGe growth allows large strain relaxation and smaller surface roughness than Ar implantation. As a result, a 50-nm-thick Si0.79Ge0.21 or Si0.77Ge0.23(110) buffer layer with almost full relaxation and rms surface roughness below 0.5nm was obtained. It is, therefore, expected that high-mobility strained Si/Ge(110) channels can be realized on the SiGe(110) relaxed buffer layers fabricated by Si implantation. It is also demonstrated that the local introduction of the implantation defects allows controlling of lateral strain states and dislocation generation, opening new concepts of engineering of both strain and surface orientation.
We present a method that uses fluorescent cellular barcodes to increase the number of unique samples that can be analyzed simultaneously by microengraving, a nanowell array-based technique for ...quantifying the secretory responses of thousands of single cells in parallel. Using n different fluorescent dyes to generate 2 n unique cellular barcodes, we achieved a 2 n -fold reduction in the number of arrays and quantity of reagents required per sample. The utility of this approach was demonstrated in three applications of interest in clinical and experimental immunology. Using barcoded human peripheral blood mononuclear cells and T cells, we constructed dose–response curves, profiled the secretory behavior of cells treated with mechanistically distinct stimuli, and tracked the secretory behaviors of different lineages of CD4+ T helper cells. In addition to increasing the number of samples analyzed by generating secretory profiles of single cells from multiple populations in a time- and reagent-efficient manner, we expect that cellular barcoding in combination with microengraving will facilitate unique experimental opportunities for quantitatively analyzing interactions among heterogeneous cells isolated in small groups (∼2–5 cells).
Background
The relationship between obesity and bone tissue remains contradictory, especially when the effect of high-fat diet is assessed in experimental models. The aim of this study was to ...evaluate the effects of high-fat diet on bone metabolism of growing rats.
Methods
Twenty weaned female Wistar rats were equally divided into two groups: SD (standard diet) and HFD (high-fat diet with 60 % of energy as fat). After five weeks of the two diets, the rats were euthanized, and the liver, blood and bones extracted. The liver was analysed for malondialdehyde (MDA) and reduced glutathione (GSH) concentrations. Blood was analysed by the ELISA method for osteoprotegerin (OPG) and tumour necrosis factor ligand superfamily member 11 (TNFSF11/RANKL). The bone tissue was analysed by dual-energy X-ray absorptiometry (DXA), mechanical tests, computed microtomography, histological quantitative analysis and scanning electron microscopy. The gene expressions of PPAR-γ Runx-2, RANKL and Cathepsin-K were also evaluated.
Results
HFD caused an increase in the MDA concentration, indicating oxidative stress. It also increased the expression of PPAR-γ, which is the gene that is related to adipocyte differentiation. There was an increase in BMD of the tibia of animals fed with the HFD, but other microstructural and mechanical properties were maintained unaltered. In addition, there were no changes in the gene expressions related to the differentiation of osteoblasts and osteoclasts, as well as no changes to the biochemical markers of bone formation and bone resorption.
Conclusion
Liver and gene parameters are changed in response to the HFD. However, although there was an increase in BMD, the microstructure and function of the bone did not change after a 5-week HFD.
We demonstrate the (111)-oriented Ge-on-Insulator (GOI) formed by Ge epitaxial growth on a Si(111) and the layer transfer technique. The two-step growth manner, involving low-temperature growth of a ...thin Ge layer and subsequent high-temperature growth of a thick Ge layer, enables us to obtain high-quality tensile-strained epitaxial Ge(111) on Si(111). It is found that the strain amount straongly depends on the growth temperatures and we find an optimal growth temperature. We also developed a chemical mechanical polishing (CMP) method modified for Ge, offering the ultra-smooth Ge(111) surface. The polished epitaxial Ge is bonded on a SiO2/Si, followed by the selective etching of Si and the final CMP of Ge. As a result, we achieve the high-quality 200-nm-thick tensile-strained Ge(111)-OI with an ultra-smooth surface, on which, furthermore, we demonstrate the growth of an epitaxial metallic silicide for the metal source/drain in spintronic devices as well as advanced Ge channel devices.
•A high-quality Ge layer is epitaxially grown on a Si(111) by two-step growth manner.•Ultra-smooth Ge surface is obtained with modified chemical mechanical polishing.•Epitaxially grown Ge is transferred onto a SiO2/Si.•High-quality tensile-strained Ge-on-Insulator with (111) orientation is obtained.
The aim of this study was to evaluate the effects of high‐impact physical exercise as a prophylactic and therapeutic means in osteopenic bones of rats submitted to ovariectomy and protein diet ...intake. A total of 64 Wistar rats were divided into eight groups (n = 8 each), being: OVX, ovx, standard diet and sedentary; OVXE, ovx, standard diet and jump; OVXP, ovx, high‐protein diet and sedentary; and OVXEP, ovx, high‐protein diet and jump; SH, sham, standard diet and sedentary; SHE, sham, standard diet and jump; SHP, sham, high‐protein diet and sedentary; and SHEP, sham, high‐protein diet and jump. OVX surgery consists of ovariectomy, and sham was the control surgery. The jumping protocol consisted of 20 jumps/day, 5 days/week. The bone structure was evaluated by densitometry, mechanical tests, histomorphometric, and immunohistochemical analyses. A high‐protein diet resulted in increased bone mineral density (P = .049), but decreased maximal load (P = .026) and bone volume fraction (P = .023). The benefits of physical exercise were demonstrated by higher values of the maximal load in the trained groups compared to the sedentary groups (P < .001). The sham groups had decreased immunostaining of osteocalcin (P = .004) and osteopontin (P = .010) compared to ovx groups. However, the high‐protein diet (P = .005) and jump exercise (P = .017) resulted in lower immunostaining of osteopontin compared to the standard diet and sedentary groups, respectively. In this experimental model, it was concluded that ovariectomy and a high‐fat diet can negatively affect bone tissue and the high‐impact exercise was not enough to suppress the deleterious effects caused by the protein diet and ovariectomy.
CD8+ T cells are a key component of the adaptive immune response to viral infection. An inadequate CD8+ T cell response is thought to be partly responsible for the persistent chronic infection that ...arises following infection with HIV. It is therefore critical to identify ways to define what constitutes an adequate or inadequate response. IFN-γ production has been used as a measure of T cell function, but the relationship between cytokine production and the ability of a cell to lyse virus-infected cells is not clear. Moreover, the ability to assess multiple CD8+ T cell functions with single-cell resolution using freshly isolated blood samples, and subsequently to recover these cells for further functional analyses, has not been achieved. As described here, to address this need, we have developed a high-throughput, automated assay in 125-pl microwells to simultaneously evaluate the ability of thousands of individual CD8+ T cells from HIV-infected patients to mediate lysis and to produce cytokines. This concurrent, direct analysis enabled us to investigate the correlation between immediate cytotoxic activity and short-term cytokine secretion. The majority of in vivo primed, circulating HIV-specific CD8+ T cells were discordant for cytolysis and cytokine secretion, notably IFN-γ, when encountering cognate antigen presented on defined numbers of cells. Our approach should facilitate determination of signatures of functional variance among individual effector CD8+ T cells, including those from mucosal samples and those induced by vaccines.
The ability to explore cell signalling and cell-to-cell communication is essential for understanding cell biology and developing effective therapeutics. However, it is not yet possible to monitor the ...interaction of cells with their environments in real time. Here, we show that a fluorescent sensor attached to a cell membrane can detect signalling molecules in the cellular environment. The sensor is an aptamer (a short length of single-stranded DNA) that binds to platelet-derived growth factor (PDGF) and contains a pair of fluorescent dyes. When bound to PDGF, the aptamer changes conformation and the dyes come closer to each other, producing a signal. The sensor, which is covalently attached to the membranes of mesenchymal stem cells, can quantitatively detect with high spatial and temporal resolution PDGF that is added in cell culture medium or secreted by neighbouring cells. The engineered stem cells retain their ability to find their way to the bone marrow and can be monitored in vivo at the single-cell level using intravital microscopy.
Topography-sensitive deposition, a preferential growth mode in a narrow concave feature, of copper in supercritical solutions is reported. Experiments were carried out in supercritical carbon dioxide ...at 13
MPa with a maximum temperature of 230
°C, using bis(diisobutylmethanate)copper (Cu(dibm)
2) as a precursor. Cu was preferentially deposited in narrow cylindrical features with a diameter less than 100
nm. Copper deposits were mostly rod-like and single-crystalline. In larger features deposition occurred within the inside corner of the features. Nonmetallic residues were also found at locations having a small curvature. Through different visualization experiments, the residues were identified as an unreacted precursor. From these observations, it was concluded that the topography-sensitive deposition proceeds through a capillary condensation of the precursor that is dissolved in the supercritical carbon dioxide at a high concentration, following the conversion to metallic copper.
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