Surface reactions of monoethylgermane on Si(100)-(2×1)

The adsorption and decomposition of monoethylgermane (GeH₃Et) on the Si(100)-(2×1) surface was investigated with the intent of elucidating the surface processes leading to the deposition of germanium. The low-temperature adsorption of the molecule was explored, as well as its thermal decomposition. H₂ and C₂H₄ are observed as the desorption products in temperature-programmed desorption experiments. The ethylene is produced by a hydride elimination reaction within the adsorbed ethyl groups. The amount of Ge which can be deposited in a reaction cycle is correlated with the number of sites occupied by the ethyl groups upon the dissociation of GeH₃Et.     

Microwave-assisted acylation of 7-amino-5-aryl-6-cyanopyrido[2,3-d]pyrimidines

A microwave-assisted method is described for monoacylating 7-amino-5-aryl-6-cyanopyrido[2,3-d]pyrimidines using excess acid chlorides in pyridine. A diacylated intermediate is effectively deacylated to the product amide by a macroporous-Tris resin. A small library of 17 amides was prepared to validate the method. The integration of commercial microwave technology into the ArQule chemistry platform is also discussed.     

A Novel Treatment for Hypophonic Voice: Twang Therapy

A hypophonic voice, characterized perceptually as weak and breathy, is associated with voice disorders such as vocal fold atrophy and unilateral vocal fold paralysis. Although voice therapy programs for hypophonia typically address the vocal folds or the sound source, twang voice quality was examined in this study as an alternative technique for increasing vocal power by altering the epilarynx or the sound filter. OBJECTIVE: This study investigated the effect of twang production on physiologic, acoustic, and perceived voice handicap measures in speakers with hypophonia. DESIGN/METHODS: This prospective pilot study compared the vocal outcomes of six participants with hypophonia at pre- and posttreatment time points. Outcome measures included mean airflow rate, intensity in dB sound pressure level (SPL), maximum phonation time, and self-report of voice handicap. RESULTS: All subjects improved in at least three of the four vocal outcome measures. Wilcoxon signed-rank test of paired differences revealed significant differences between pre- and posttherapy group means for airflow rate, SPL, and Voice Handicap Index scores. CONCLUSION: The twang voice quality as a manipulation of the sound filter offers a clinical complement to traditional voice therapies that primarily address the sound source.     

Dual-mode registration of dynamic contrast-enhanced ultrasound combining tissue and contrast sequences

This study proposes a new method for automatic, iterative image registration in the context of dynamic contrast-enhanced ultrasound (DCE-US) imaging. By constructing a cost function of image registration using a combination of the tissue and contrast-microbubble responses, this new method, referred to as dual-mode registration, performs alignment based on both tissue and vascular structures. Data from five focal liver lesions (FLLs) were used for the evaluation. Automatic registration based on the dual-mode registration technique and tissue-mode registration obtained using the linear response image sequence alone were compared to manual alignment of the sequence by an expert. Comparison of the maximum distance between the transformations applied by the automatic registration techniques and those from expert manual registration reference showed that the dual-mode registration provided better precision than the tissue-mode registration for all cases. The reduction of maximum distance ranged from 0.25 to 9.3 mm. Dual-mode registration is also significantly better than tissue-mode registration for the five sequences with p  -values lower than 0.03$0.03$. The improved sequence alignment is also demonstrated visually by comparison of images from the sequences and the video playbacks of the motion-corrected sequences. This new registration technique better maintains a selected region of interest (ROI) within a fixed position of the image plane throughout the DCE-US sequence. This should reduce motion-related variability of the echo-power estimations and, thus, contribute to more robust perfusion quantification with DCE-US.     

Determination of relative response factors of impurities in paclitaxel with high performance liquid chromatography equipped with ultraviolet and charged aerosol detectors

A case study was conducted to determine the relative response factors (RRFs) of paclitaxel-related impurities by high performance liquid chromatography (HPLC) equipped with an ultraviolet (UV) detector and charged aerosol detector (CAD) in tandem. The peak response using CAD was independent of analyte structure in an isocratic analysis for this application. After a sample containing known and unknown impurities was analyzed with HPLC-UV-CAD, an empirical approach was developed to calculate the RRFs for all impurities. The RRFs of known impurities were also determined by linear calibration curves. For known impurities, the RRFs values determined with two approaches are comparable. The new approach is effective yet simpler to determine the RRFs for unknown impurities or degradation products since the need for obtaining authentic pure materials was eliminated.     

Trace element analysis of some shaving powders commonly marketed in Nigeria using instrumental neutron activation analysis

Instrumental neutron activation analysis (INAA) technique has been employed viak ₀ approximation method to determine elemental composition of five shaving powders commonly marketed in Nigeria. Fe displayed the highest concentrations in the range 1000–2000 g·g^–1. Na and Zn concentrations were established in the range 200–400 g·g^–1. Heavy elements like Ga, La, Cr, Co, Ag, Ce and Nd concentrations were noted in the lower range of 1–10 g·g^–1 Br, As, Sb, Sm, Eu, W, Cs, Tb, Yb, Hf, Ta, Th and U concentrations were established in even lower traces in the <1 g·g^–1 range. Results obtained for a certified reference material, CANMET BL-1 and CERT (in house) Kaolin standard compared favourably with the literature values thus establishing the results presented for the shaving powders.     

Peptide sequencing using a patchwork approach and surface-induced dissociation in sector-TOF and dual quadrupole mass spectrometers

Surface-induced ion activation in combination with a database search strategy based on the Patchwork concept is applied to the determination of peptide sequences. Surface-induced dissociation (SID) is performed in a tandem quadrupole mass spectrometer and in a hybrid sector/time-of-flight mass spectrometer in order to evaluate the importance of accurate mass analysis of the SID fragment ions for peptide identification. The modified Patchwork approach is based on piecing together the peptide blocks in a bidirectional way, simultaneously using low-mass fragments originating from the C-terminus and N-terminus of the molecule, and relying on the measurement of the peptide's molecular weight with moderate mass accuracy. The results from this analysis are used as search filters in MASCOT's (http://www.matrixscience.com) Sequence Query search engine, with the simultaneous addition of the full MS/MS peak list. SID is performed with collision targets coated with pure and mixed composition self-assembled monolayers produced by fluorocarbon and hydrocarbon alkanethiolate solutions of varying chemical composition. The resulting MS/MS spectra produced on pure and mixed hydrocarbon SAMs are submitted to the modified version of Patchwork sequencing. It is found that hydrocarbon surfaces improve the relative abundance of larger fragments. Under the moderate mass accuracy conditions (±0.3 u) offered by our linear-TOF-SID instrument, it is found that increasing the abundance of larger fragments dramatically improves the sequencing scores.     

Capillary electrophoresis of single mammalian cells

Capillary electrophoresis (CE) has been established as powerful tool for single cell analysis. Newly developed sampling, separation and detection methods have allowed the investigation of single mammalian cells with CE despite their small size and complex composition. Advances in sample injection techniques include several novel methods for the injection of whole cells and sampling techniques for the study of cellular secretion. CE of single mammalian cells has been applied in a wide range of fields including protein analysis, neuroscience, and oncology. The development of new detection schemes in the analysis of single mammalian cells with CE has included studies of protein expression and the utilization of mass spectrometric and electrochemical detection. Subcellular mammalian cell analysis with CE also has been investigated.     

A competitive displacement assay with quantum dots as fluorescence resonance energy transfer donors

The unique optoelectronic properties of semiconductor quantum dots (QDs) make them well-suited as fluorescent bioprobes for use in various biological applications. Modification of CdSe/ZnS QDs with biologically relevant molecules provides for multipotent probes that can be used for cellular labeling, bioassays, and localized optical interrogation by means of fluorescence resonance energy transfer (FRET). Herein, we demonstrate the use of red-emitting streptavidin-coated QDs (QD₆₀₅) as donors in FRET to introduce a competitive displacement-based assay for the detection of oligonucleotides. Various QD–DNA bioconjugates featuring 25-mer probe sequences diagnostic of Hsp23 were prepared. The single-stranded oligonucleotide probes were hybridized to dye-labeled (Alexa Fluor 647) reporter sequences, which were provided for a FRET-sensitized emission signal due to proximity of the QD and dye. The dye-labeled sequence was designed to be partially complementary and include base-pair mismatches to facilitate displacement by a more energetically favorable, fully complementary recognition motif embedded within a 98-mer displacer sequence. Overall, this study demonstrates proof-of-concept at the nM level for competitive displacement hybridization assays in vitro by reduction of fluorescence intensity that directly correlates to the presence of oligonucleotides of interest. This work demonstrates an analytical method that could potentially be implemented for monitoring of intracellular gene expression in the future.