Optimization of supercritical CO2 extraction of dried Helichrysum italicum flowers by response surface methodology: GC-MS profiles of the extracts and essential oil

Supercritical (SC) CO₂ extraction of dried Immortelle flowers was performed at different process parameters. The optimal extraction conditions related to the yield were determined by response surface methodology (yield 4.09% at 20 MPa and 52°C). The extracts were analyzed by GC-MS and tremetone derivatives dominated: bitalin A, 12-acetoxytremetone, gnaphaliol, 1-[2-(2-methyl-2,3-dihydroxypropyl)-2,3-dihydro-1-benzofuran-5-yl]ethanone, isobutyl bitalin A, and 1-[2-(acetylprop-1-en-2-yl)-3-hydroxy-2,3-dihydro-1-benzofuran-5-yl]ethanone. Striking differences were found among the essential oil and SC-CO₂ extracts composition. The major oil compounds were γ-curcumene, α-pinene, β-selinene, α-selinene, and limonene. Mono- and sesquiterpene were found among minor constituents of the extracts. Neryl acetate was present in the extracts and essential oil.     

MODELLING ADSORPTION EQUILIBRIUM MOISTURE CHARACTERISTICS OF ROUGH RICE

Equilibrium Moisture Content (EMC) data for medium rough rice grain, Lido variety were obtained by equilibrating rice samples at different Equilibrium Relative Humidities (ERH) and Temperatures. The employed models to fit the data were GAB, modified Chung-Pfost, modified Halsey, Modified Henderson, and modified Oswin. The data were evaluated using the standard error of moisture content, mean relative standard error (%P) of the model and the correlation coefficient r². The GAB model by indirect regression described the EMC the best, however its parameters lacked of physical meaning. The modified Chung-Pfost and modified Henderson equations presented a similar fit of the EMCERH relationships. The modified Chung-Pfost equation had lower residual values than the modified Henderson equation and was considered the best model to explain the EMC-ERH relationships.     

Will the numbers add up for sub-7-nm magnetic spacings? Future metrology issues for disk drive lubricants, overcoats, and topographies

To achieve disk drive recording densities greater than one terabit per square inch, future head-media spacings (HMSs) will need to be less than 7 nm. This will place severe demands on the metrology tools used to measure the thickness and topographies of the contributors to the head-media spacing. Here, we first review some of the metrologies used for characterizing overcoats, lubricants, and topographies and discuss some of the limits that will make it difficult to achieve a sub-7-nm HMS. We next show new results for measuring lubricant redistribution on disk surfaces after contact with a small pad on the slider and present a new method for determining wear rates of these slider contact pads.     

Molecular tribology of disk drives

A good molecular level understanding of the tribological properties of the materials at the slider-disk interface is essential to the future development of disk drive technology. This paper provides a short overview of the molecular tribology of disk drives related to the selection of lubricant materials for the slider-disk interface. Besides providing criteria for lubricant selection, this paper briefly discusses our current understanding of stiction and friction forces, lubricant degradation, lubricant mobility, spin-off, and lubricant transfer to sliders. This revised version was published online in June 2006 with corrections to the Cover Date.     

Novel approach for detection of IoT generated DDoS traffic

Wireless Networks - The problem of detecting anomalies in network traffic caused by the distributed denial of service (DDoS) attack so far has mainly been investigated in terms of detection of...     

A flow cytometric assay for global estimation of tyrosine phosphorylation associated with capacitation of spermatozoa from two marsupial species, the tammar wallaby (Macropus eugenii) and the brushtail possum (Trichosurus vulpecula)

The phosphorylation of tyrosine residues in cellular proteins is a major signal transduction event during sperm capacitation. In this study protein phosphorylation was monitored using a fluorescein isothiocyanate (FITC)-labeled antiphosphotyrosine monoclonal antibody and a flow cytometric procedure optimized for sperm. Using this technique, the correlation between tyrosine phosphorylation and sperm capacitation was examined in two marsupial species, the brushtail possum and the tammar wallaby and compared with that of ram spermatozoa. The levels of tyrosine phosphorylation in sperm from all three species were increased by the addition of cyclic AMP (cAMP) and vandate, a phosphotyrosine phosphatase inhibitor and were decreased by the addition of the phosphotyrosine kinase inhibitor, staurosporine. Oviductal conditioned media (CM) induced a progressive increase in tyrosine phosphorylation in both marsupial species and also induced morphological transition from a streamlined to a 'T'-shape configuration in brushtail possum spermatozoa but not in tammar wallaby spermatozoa. Transition to the 'T'-shape orientation associated with capacitation in marsupial spermatozoa was observed by 2 h of incubation in both species when tyrosine phosphorylation was increased by higher levels of cAMP i.e. 5 mM dibutyryl cAMP plus 3 mM pentoxyphylline. Thus the tyrosine phosphorylation trigger with CM may differ in these two marsupial species. Ram sperm tyrosine phosphorylation could be increased by addition of lower levels of cAMP (1 mM). These results support the finding that tyrosine phosphorylation is associated with sperm capacitation in marsupials. Similar results were obtained by using SDS PAGE/Western blot analysis of tyrosine phosphorylation in the brushtail possum spermatozoa. The specificity, efficiency and sensitivity of the procedure described here make it applicable for routine assessment of capacitation in large numbers of samples and in other species.     

Timing of zona pellucida formation in the tammar wallaby (Macropus eugenii) and brushtail possum (Trichosurus vulpecula)

The zona pellucida (ZP) is an extracellular coat that surrounds the mammalian egg, and serves as the primary recognition site for fertilizing spermatozoa. The timetable of ZP formation was examined in two marsupials, the tammar wallaby (Macropus eugenii) and the brushtail possum (Trichosurus vulpecula) using conventional histological methods, immunofluorescence and electron microscopy. Ovaries from tammar wallaby pouch young less than 80 days of age contained only primordial follicles with a single layer of flattened granulosa cells. There was no evidence of ZP formation until 98 days, when a small number of eggs surrounded by a single layer of cuboidal granulosa cells had a ZP detectable by periodic-acid-schiff staining and rabbit anti-pig ZP polyclonal antibody labelling. Possum ovaries at 108 and 114 days also contained a small number of eggs with a ZP and a single layer of cuboidal granulosa cells. The antibody also labelled the peripheral cytoplasm of oocytes at this stage and, occasionally, the granulosa cells. Antral follicles were first detected at 144 days in the wallaby and 125 days in the possum, and always contained an egg surrounded by a ZP. Ovaries from 147, 158, 165, 181, 184 and 210-day-old tammar wallabies contained a range of follicle types from primordial through early antrum formation. Electron microscopy confirmed observations made at the light microscope level. The ZP was first detectable in small primary follicles with a single layer of cuboidal granulosa cells in areas where microvilli had begun to form on the egg plasma membrane. Immunogold labelling indicated the egg cytoplasm as the origin of the ZP proteins. The ZP completely filled the space between the egg and the adjacent granulosa cells in preantral follicles, so that there was no perivitelline space.