Flow visualization and pressure distributions in a model of the glottis with a symmetric and oblique divergent angle of 10 degrees

Modeling the human larynx can provide insights into the nature of the flow and pressures within the glottis. In this study, the intraglottal pressures and glottal jet flow were studied for a divergent glottis that was symmetric for one case and oblique for another. A Plexiglas model of the larynx (7.5 times life size) with interchangeable vocal folds was used. Each vocal fold had at least 11 pressure taps. The minimal glottal diameter was held constant at 0.04 cm. The glottis had an included divergent angle of 10 degrees. In one case the glottis was symmetric. In the other case, the glottis had an obliquity of 15 degrees. For each geometry, transglottal pressure drops of 3, 5, 10, and 15 cm H2O were used. Pressure distribution results, suggesting significantly different cross-channel pressures at glottal entry for the oblique case, replicate the data in another study by Scherer et al. [J. Acoust. Soc. Am. 109, 1616-1630 (2001b)]. Flow visualization using a LASER sheet and seeded airflow indicated separated flow inside the glottis. Separation points did not appear to change with flow for the symmetric glottis, but for the oblique glottis moved upstream on the divergent glottal wall as flow rate increased. The outgoing glottal jet was skewed off-axis for both the symmetric and oblique cases. The laser sheet showed asymmetric circulating regions in the downstream region. The length of the laminar core of the glottal jet was less than approximately 0.6 cm, and decreased in length as flow increased. The results suggest that the glottal obliquity studied here creates significantly different driving forces on the two sides of the glottis (especially at the entrance to the glottis), and that the skewed glottal jet characteristics need to be taken into consideration for modeling and aeroacoustic purposes.     

Comparative quantitative study of DDT and its metabolites in human milk by gas chromatography with electron capture and mass spectrometric detection

Summary Comparative analytical quantitation of DDE, DDD, and DDT in human milk, by gas chromatography with mass spectrometric and electron capture detection (GC-MS and GC-ECD) has been studied by use of 513 samples of milk from lactating mothers participating in a World Health Organization special study. Although Correlation between thep,p-DDE concentrations measured by GC-ECD and GC-MSD was excellent (r=0.950,P<0.0001) and correlation was significant and moderate forp,p-DDD andp,p-DDT, the best precision was obtained by use of GC-MS. This study has therefore demonstrated that GC-MSD is a useful tool for determining the concentration of DDT and its metabolites, because it enables simultaneous detection and confirmation.     

Intraglottal pressure profiles for a symmetric and oblique glottis with a divergence angle of 10 degrees

Human phonation does not always involve symmetric motions of the two vocal folds. Asymmetric motions can create slanted or oblique glottal angles. This study reports intraglottal pressure profiles for a Plexiglas model of the larynx with a glottis having a 10-degree divergence angle and either a symmetric orientation or an oblique angle of 15 degrees. For the oblique glottis, one side was divergent and the other convergent. The vocal fold surfaces had 14 pressure taps. The minimal glottal diameter was held constant at 0.04 cm. Results indicated that for either the symmetric or oblique case, the pressure profiles were different on the two sides of the glottis except for the symmetric geometry for a transglottal pressure of 3 cm H2O. For the symmetric case, flow separation created lower pressures on the side where the flow stayed attached to the wall, and the largest pressure differences between the two sides of the channel were 5%-6% of the transglottal pressure. For the oblique case, pressures were lower on the divergent glottal side near the glottal entry and exit, and the cross-channel pressures at the glottis entrance differed by 27% of the transglottal pressure. The empirical pressure distributions were supported by computational results. The observed aerodynamic asymmetries could be a factor contributing to normal jitter values and differences in vocal fold phasing.     

Physiochemical properties and novel biological applications of Callistemon viminalis‐mediated α‐Cr2O3 nanoparticles

We report an eco‐friendly synthesis of α‐Cr₂O₃ nanoparticles (NPs) using Callistemon viminalis (Bottle Brush) flower extracts as an efficient reducing and capping agent. NPs of sizes 15 nm and 17 nm were synthesized by annealing them at 400°C and 500°C, respectively, which were characterized by X‐ray diffraction, UV–Vis, Fourier transform‐infrared, high‐resolution‐transmission electron microscopy/scanning electron microscopy, SAED, energy‐dispersive X‐ray spectroscopy and SQUID. Microplate‐based assay was used for examining antibacterial potential against 12 pathogenic bacterial strains, and their minimum inhibitory concentrations were calculated. MTT cytotoxic assay was accomplished on Leishmania tropica amastigotes and promastigotes, which revealed IC₅₀ values of 44 μg/ml and 10.56 μg/ml, respectively. An IC₅₀ value of 46.32 μg/ml was obtained for HepG2 cancer cells. Enzyme inhibition studies indicated good acetylcholinesterase, moderate butyrylcholinesterase and low alpha‐glucosidase inhibition. Hemolytic assay indicated hemocompatibility at low concentration. In addition, good DPPH radical scavenging and moderate reducing power and total antioxidant potential was revealed by α‐Cr₂O₃ NPs.     

A New Cyclopropyl‐Triterpenoid from Ochradenus arabicus

One new cyclopropyl‐triterpenoid ( 1 ), along with four known constituents including octacosan‐1‐ol ( 2 ), pentacosanoic acid ( 3 ), β‐sitosterol ( 4 ), and β‐sitosterol 3‐O‐β‐D ‐glucopyranoside ( 5 ) were isolated from the aerial parts of Ochradenus arabicus for the first time. These compounds were isolated by repeated column chromatography followed by further purification through recycling HPLC. The structure of the new secondary metabolite 1 was established on the basis of UV, IR, 1D‐ (¹H‐ and ¹³C‐) and 2D‐NMR (HMBC and HSQC), and MS spectral data. The molecular mass was determined by HR‐MS, and hence the molecular formula was deduced. The configurations of stereogenic centers in the molecule were assigned by NOESY experiments, along with biogenetic considerations. The structures of the known compounds were confirmed by comparison of their physical and spectroscopic data with those reported in literature.     

Extraction optimization,total phenolic,flavonoid contents,HPLC-DAD analysis and diverse pharmacological evaluations of Dysphania ambrosioides (L.) Mosyakin & Clemants

The present study aims to evaluate phytochemical and pharmacological potentials of Dysphania ambrosioides (L.) Mosyakin & Clemants previously known as Chenopodium ambrosioides L. Extraction was carried out using 14 solvents with wide range of polarity to find out the best solvent system for each bioactivity. Total phenolic and flavonoids contents were measured colorimetrically and polyphenolics were quantified via HPLC-DAD analysis. The samples were screened for inhibitory potentials against free radicals, leishmania, cancer cell lines, protein kinase, α-Amylase enzymes and microbial strains. Among all solvents, maximum percentage of extract was recovered from methanol-water fraction of leaves. HPLC analysis exhibited the presence of rutin, myricetin and quercetin. In DPPH assay, methanolic leaf extract exhibited IC₅₀ value of 130.7 ± 0.57 μg/mL. Considerable α-amylase inhibitory, cytotoxic, leishmanicidal and antimicrobial potentials were exhibited by plant samples. D. ambrosioides revealed significant antioxidant, cytotoxic, antimicrobial and anti-diabetic potentials and thus warrant further detailed studies to find novel drugs.