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- Ougazzaden, A., et al.
(author)
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Growth of GaN by metal organic vapor phase epitaxy on ZnO-buffered c-sapphire substrates
- 2008
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In: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 310:5, s. 944-947
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Journal article (peer-reviewed)abstract
- The materials quality and availability of large-area bulk GaN substrates is currently considered a key problem for the continuing development of improved GaN-based devices. Since industrial fabrication of bulk GaN substrates with suitable materials quality has proven very difficult, the opto-GaN industry is currently based on heteroepitaxy using either c-sapphire or 6H SiC substrates. ZnO is promising as a substrate material for GaN because it has the same wurtzite structure and a relatively small lattice mismatch (similar to 1.8%). In this study, we have successfully grown GaN by MOVPE on ZnO-buffered c-sapphire. The growth conditions required to both prevent ZnO degradation and grow monocrystal thin film of GaN have been obtained. SEM, HRXRD and micro-Raman characterizations underlined the presence of the two layers GaN and ZnO with high structural quality.
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- Yu, A. B., et al.
(author)
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Characterization and optimization of dry releasing for the fabrication of RF MEMS capacitive switches
- 2007
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In: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 17:10, s. 2024-2030
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Journal article (peer-reviewed)abstract
- This paper discusses fabrication aspects of photoresist sacrificial layers for fabricating metal bridges of capacitive radio frequency (RF) microelectromechanical systems (MEMS) switches. First, reflow of the photoresist layer after lithography is investigated for reducing mechanical fracture of the metal layer by smoothing the edges of the sacrificial layer. Second, the dry-etch releasing process of the structures in an O-2 plasma has been investigated by identifying suitable etching parameters. The findings in this paper reveal that the mechanical performance of the released bridges strongly depends on the etch parameters. It is shown that especially the etching power affects the mean stress and the stress gradient in the bridge, which results in buckling and deformed bridge shape for an etching power above 500 W, drastically increasing the actuation voltage and reducing the down-state capacitance. Finally, the paper presents a suitable parameter set for the release etching of capacitive MEMS metal bridges.
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- Feás, Xesús, et al.
(author)
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Application of dummy molecularly imprinted solid-phase extraction in the analysis of cyproheptadine in bovine urine.
- 2009
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In: Journal of Separation Science. - : Wiley. - 1615-9314 .- 1615-9306. ; 32:10, s. 1740-1747
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Journal article (peer-reviewed)abstract
- Due to the difficulty of monitoring trace levels of cyproheptadine (CYP) residues in complicated biological matrices, specific adsorption materials for the preconcentration and clean-up of CYP are indispensable. In this work, CYP was extracted from urine using dummy molecularly imprinted SPE (DMISPE) to avoid leakage of the imprinting molecules during the desorption phase. For synthesis of DMISPE, azatadine (AZA) was employed as the dummy template, methacrylic acid (MAA) as the monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker, 2,2'-azobis(2-methylpropionitrile) (AIBN) as the initiator, and dichloromethane as the porogen solvent. An LC-MS/MS method was used to analyze CYP. Two MRM (multiple reaction monitoring) transitions for each analyte were monitored using diphenylpyraline hydrochloride (DPP.HCl), which was used as an internal standard. The advantages of DMISPE include obtaining less complex chromatograms and reducing ion suppression in ESI. The process efficiencies for DMISPE and SPE were 80% and 12%, respectively. In addition, the demonstrated reusability of the DMISPE cartridges is an advantage compared with single-use SPE cartridges or immunoaffinity materials.
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- Feás, Xesús, et al.
(author)
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Development and validation of LC-MS/MS method for the determination of cyproheptadine in several pharmaceutical syrup formulations.
- 2009
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In: Journal of Pharmaceutical and Biomedical Analysis. - : Elsevier BV. - 0731-7085. ; 50, s. 1044-1049
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Journal article (peer-reviewed)abstract
- A rapid and sensitive liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method was developed and validated for the qualitative and quantitative assay of cyproheptadine (CP) in pharmaceutical samples. Diphenylpyraline hydrochloride (DPP) was used as an internal standard (IS). Two multiple reaction-monitoring (MRM) transitions for each analyte were observed: 288.1/96.1 and 288.1/191.2 for CP and 282.1/167.2 and 282.1/116.3 for DPP. The retention time of the drug was 7.29min. The analytical method was successfully validated for linearity (1-100ng/ml), intra-day precision, inter-day precision, and accuracy. The limit of detection (LOD) and limit of quantification (LOQ) were 0.86 and 0.98ng/ml, respectively. The proposed method was applied to analyse the cyproheptadine content from seven different syrup formulations.
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- Haj-Hosseini, Neda, 1980-, et al.
(author)
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Evaluation of a Fiber-Optic Based Pulsed Laser System for Fluorescence Spectroscopy
- 2008
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In: 14TH NORDIC-BALTIC CONFERENCE ON BIOMEDICAL ENGINEERING AND MEDICAL PHYSICS. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1680-0737. - 9783540693666 ; 20, s. 363-366
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Conference paper (peer-reviewed)abstract
- A fiber optic based continous wave laser setup has been developed to record the 5-aminolevulinic (5-ALA) induced Protoporfyrin IX (PpIX) fluorescence signals from cerebral gliomas. To reduce the energy delivered to the tissue as well as suppression of the ambient lamp artifact from the recorded spectra, a pulsed laser setup has been developed and evaluated. This setup has been calibrated and first evaluations were performed on the 5-ALA treated skin showing PpIX fluorescence peaks from the ALA treated skin at 635 and 704 nm wavelengths. The system controls laser pulses through a computer interface and labview software package. Pulses as short as 50 ms over a period time of 500 ms are generated and optimally detected. The results from primary measurements on skin show an effective suppression of room fluorescent lamp artifact from the recorded spectra.
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- Hosseini Maaf, Bahram, et al.
(author)
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Structural basis for red cell phenotypic changes in newly identified, naturally occurring subgroup mutants of the human blood group B glycosyltransferase.
- 2007
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In: Transfusion. - : Wiley. - 1537-2995 .- 0041-1132. ; 47:5, s. 864-875
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Journal article (peer-reviewed)abstract
- BACKGROUND: Four amino-acid-changing polymorphisms differentiate the blood group A and B alleles. Multiple missense mutations are associated with weak expression of A and B antigens but the structural changes causing subgroups have not been studied. STUDY DESIGN AND METHODS: Individuals or families having serologically weak B antigen on their red cells were studied. Alleles were characterized by sequencing of exons 1 through 7 in the ABO gene. Single crystal X-ray diffraction, three-dimensional-structure molecular modeling, and enzyme kinetics showed the effects of the B allele mutations on the glycosyltransferases. RESULTS: Seven unrelated individuals with weak B phenotypes possessed seven different B alleles, five of which are new and result in substitution of highly conserved amino acids: M189V, I192T, F216I, D262N, and A268T. One of these (F216I) was due to a hybrid allele resulting from recombination between B and O-1v alleles. The two other alleles were recently described in other ethnic groups and result in V175M and L232P. The first crystal-structure determination (A268T) of a subgroup glycosyltransferase and molecular modeling (F216I, D262N, L232P) indicated conformational changes in the enzyme that could explain the diminished enzyme activity. The effect of three mutations could not be visualized since they occur in a disordered loop. CONCLUSION: The genetic background for B-w phenotypes is very heterogeneous but usually arises through seemingly random missense mutations throughout the last ABO exon. The targeted amino acid residues, however, are well conserved during evolution. Based on analysis of the resulting structural changes in the glycosyltransferase, the mutations are likely to disrupt molecular bonds of importance for enzymatic function.
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