H-induced platelet and crack formation in hydrogenated epitaxial Si/Si0.98 B0.02 /Si structures

An approach to transfer a high-quality Si layer for the fabrication of silicon-on-insulator wafers has been proposed based on the investigation of platelet and crack formation in hydrogenated epitaxialSi/Si0.98B0.02/Si structures grown by molecular-beam epitaxy. H-related defect formation during hydrogenation was found to be very sensitive to the thickness of the buried Si0.98B0.02 layer. For hydrogenated Si containing a 130nm thick Si0.98B0.02 layer, no platelets or cracking were observed in the B-doped region. Upon reducing the thickness of the buried Si0.98B0.02 layer to 3nm, localized continuous cracking was observed along the interface between the Si and the B-doped layers. In the latter case, the strains at the interface are believed to facilitate the (100)-oriented platelet formation and (100)-oriented crack propagation.

Stress-induced platelet formation in silicon:a molecular dynamics study

The effect of stress on vacancy cluster configurations in silicon is examined using molecular dynamics. At zero pressure, the shape and stability of the vacancy clusters agrees with previous atomistic results. When stress is applied the orientation of small planar clusters changes to reduce the strain energy. The preferred orientation for the vacancy clusters under stress agrees with the experimentally observed orientations of hydrogen platelets in the high stress regions of hydrogen implanted silicon. These results suggest a theory for hydrogen platelet formation. © 2005 The American Physical Society.

Aminoglutethimide-induced leucopenia in a mouse model:effects of metabolic and structural determinates

A model of human leucopenia has been developed further in the female mouse. Following daily administration to female mice of 50 mg/kg of the aromatase inhibitor aminoglutethimide, significant falls in platelet and white cell counts occurred after 2 and 3 weeks. At week 4, drug dosage was stopped and the cell counts recovered at the end of that week, although on rechallenge at the beginning of week 5, both platelet and white cell counts fell rapidly. Administration to the mice of structural analogues of aminoglutethimide, such as WSP-3, glutethimide and 4-nitroglutethimide, showed no reductions in platelet and white cell counts. The haemotoxicity of aminoglutethimide over 21 days was unaffected by the presence of either the P-450 inhibitor SKF-525A or the hepatic P-450 inducer phenobarbitone. However, the co-administration of cimetidine abolished the haemotoxicity of aminoglutethimide in terms of platelet and white cell levels. In in vitro studies, both aminoglutethimide and WSP-3 were oxidised to cytotoxic species, although aminoglutethimide was significantly more cytotoxic than WSP-3. The NADPH-dependent covalent binding of 14C aminoglutethimide to mouse microsomes in vitro was significantly reduced by the presence of cimetidine. The activation of the compound to reactive species in vitro, the inhibitory effects of cimetidine in vivo and in vitro, as well as the rapid fall in the in vivo white cell count on rechallenge with aminoglutethimide suggest that this model illustrates a form of leucopenia which may be related to hapten formation and subsequent immune-mediated platelet and white cell lysis. © 2003 Elsevier B.V. All rights reserved.

Direct design of high channel-count fiber Bragg grating filters with low index modulation

A novel method for designing high channel-count fiber Bragg gratings (FBGs) is proposed. For the first time, tailored group delay is introduced into the target reflection spectra to obtain a more even distribution of the refractive index modulation. This approach results in the reduction of the maximum refractive index modulation to physically realizable levels. The maximum index modulation reduction factors are all greater than 5.5. This is a significant improvement compared with previously reported results. Numerical results show that the thus designed high channel-count FBG filters exhibit superior characteristics including 30 dB channel isolation, a flat-top and near 100% reflectivity in each channel. © 2012 Optical Society of America.

Design of high channel-count fiber Bragg gratings using tailored group delay

A novel method of fiber Bragg grating design based on tailored group delay is presented. The method leads to designs that are superior to the previously reported results. © OSA 2012.

Scalability and process transfer of mesenchymal stromal cell production from monolayer to microcarrier culture using human platelet lysate

Background aims: The selection of medium and associated reagents for human mesenchymal stromal cell (hMSC) culture forms an integral part of manufacturing process development and must be suitable for multiple process scales and expansion technologies. Methods: In this work, we have expanded BM-hMSCs in fetal bovine serum (FBS)- and human platelet lysate (HPL)-containing media in both a monolayer and a suspension-based microcarrier process. Results: The introduction of HPL into the monolayer process increased the BM-hMSC growth rate at the first experimental passage by 0.049 day and 0.127/day for the two BM-hMSC donors compared with the FBS-based monolayer process. This increase in growth rate in HPL-containing medium was associated with an increase in the inter-donor consistency, with an inter-donor range of 0.406 cumulative population doublings after 18 days compared with 2.013 in FBS-containing medium. Identity and quality characteristics of the BM-hMSCs are also comparable between conditions in terms of colony-forming potential, osteogenic potential and expression of key genes during monolayer and post-harvest from microcarrier expansion. BM-hMSCs cultured on microcarriers in HPL-containing medium demonstrated a reduction in the initial lag phase for both BM-hMSC donors and an increased BM-hMSC yield after 6 days of culture to 1.20 ± 0.17 × 105 and 1.02 ± 0.005 × 105 cells/mL compared with 0.79 ± 0.05 × 105 and 0.36 ± 0.04 × 105 cells/mL in FBS-containing medium. Conclusions: This study has demonstrated that HPL, compared with FBS-containing medium, delivers increased growth and comparability across two BM-hMSC donors between monolayer and microcarrier culture, which will have key implications for process transfer during scale-up.