Determination of butyltins in environmental samples using sodium tetraethylborate derivatisation: characterisation and minimisation of interferences

Interferences affecting the determination of butyltin species by sodium tetraethylborate (STEB) derivatisation followed by purge-trap preconcentration were systematically studied using synthetic solutions, natural water samples and sediment extracts. Substances that did not cause interferences included most common cations (apart from those metal ions listed below), anions, metalloids and polar organic compounds. Natural organic matter (NOM) specifically interfered with tributyltin (TBT) due to a mechanism involving partitioning of the butyltin to the hydrophobic portions of the NOM. The metal ions Ag(I) (≥2 μM), Cd(II) (≥2 μM), Cu(II) (≥0.5 μM) interfered predominantly with the determination of monobutyltin (MBT) due to catalytic degradation of the STEB reagent. Pb(II) (≥14 μM) interfered with butyltin determination by an unknown mechanism. Other interferences to the purge-trap method were shown to occur in the presence of chelating agents (e.g. EDTA) or hydrophobic liquids such as diesel fuel. A mixture comprising methanol (MeOH), EDTA and Mn(II) was used to partially mask the effect of interfering NOM and metals. Spike recoveries (mean±S.D. of n=7 different samples) of MBT, dibutyltin (DBT) and TBT in contaminated natural water samples were improved from 70±36,90±11 and 91±24 to 102±10,98±3 and 98±4%, respectively. Spike recoveries (mean±S.D. of n=5 different samples) of MBT, DBT and TBT in aliquots of sediment extracts were improved from 86±17,79±18 and 59±32 to 97±6.2,103±3.6 and 103±5.0%, respectively. The ability to analyse larger aliquots of sediment extracts in the presence of the masking mixture improved the detection limit four-fold if MBT and DBT determination was required and 10-fold if only TBT determination was required.     

New lipids from the soft corals of the Andaman Islands

Sphingolipids and glycolipids including previously unknown (2S,3S,4R)-1,3,4-trihydroxy-2-(2-(R)-hydroxyoctadecanoylamino)octadec-8E-ene, (2S,3R)-1,3-dihydroxy-2-octadecanoylamino-4E,8E-hexadecadiene, and (2-hydroxy-3-hexadecyloxypropyl)--L-fucopyranoside were isolated from soft corals collected on the shelf near the Andaman Islands (Indian Ocean). The structures of all compounds were established by spectroscopic methods and chemical analyses. The lipids possessed antibacterial activity against Bacillus subtilis, Bacillus pumilus, Escherichia coli, and Pseudomonas aeruginosa and antifungal activity against Aspergillus niger, Rhizopus oryzae, and Candida albicans.     

Determination of polycyclic aromatic hydrocarbons (PAHs) in particulate matter collected with low volume samplers

The determination of polycyclic aromatic hydrocarbons (PAHs) contained in samples of particulate matter (PM), collected with low volume pumps, were carried out with an high sensitivity method that comes from several revisions of a previous method. The present work describes how, by using programmable temperature vaporization (PTV) and a mass selective detector with inert ionic source for the GC-MS analysis and the modifications of microwave-assisted extraction (MAE), the sensitivity of the method can be increased.The PAHs chosen for testing the method are: benzo[a]anthracene (BaA), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), indeno[1,2,3-cd]pyrene (Ip) and dibenzo[a,h]anthracene (DbA). They, in fact, belong to that group of substances that are the most harmful for human health for their carcinogenicity.PAHs recoveries for spiked standard solutions at different concentrations were between 95 and 100% with relative standard deviation ranging from 1 to 3%. The revised method was validated using a 1649a urban dust standard reference material (SRM). The results obtained were in good agreement with certified values. The high sensitivity of the method allows to carry out analyses using only a half of the sampled filter (usually 47 mm diameter membranes). In this way, the other half can be used for the characterization of the other components of PM (heavy metals, organic carbon, ions, etc). The last step has been constituted by application of the optimized method on real samples collected in two cities located in Southern Italy (Bari and Taranto).     

Neurofibrillary tangles and plaques are not accompanied by white matter pathology in aged triple transgenic-Alzheimer disease mice

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is the most common cause of dementia in aging populations. Although senile plaques and neurofibrillary tangles are well-established hallmarks of AD, changes in cerebral white matter correlate with cognitive decline and may increase the risk of the development of dementia. We used the triple transgenic (3xTg)-AD mouse model of AD, previously used to show that white matter changes precede plaque formation, to test the hypothesis that MRI detectable changes occur in the corpus callosum, external capsule and the fornix. T₂-weighted and diffusion tensor magnetic resonance imaging and histological stains were employed to assess white matter in older (11–17 months) 3xTg-AD mice and controls. We found no statistically significant changes in white matter between 3xTg-AD mice and controls, despite well-developed neurofibrillary tangles and beta amyloid immunoreactive plaques. Myelin staining was normal in affected mice. These data suggest that the 3xTg-AD mouse model does not develop MRI detectable white matter changes at the ages we examined.     

Temperature dependence of volume and surface symmetry energy coefficients of nuclei

The thermal evolution of the energies and free energies of a set of spherical and near-spherical nuclei spanning the whole periodic table are calculated in the subtracted finite-temperature Thomas–Fermi framework with the zero-range Skyrme-type KDE0 and the finite-range modified Seyler–Blanchard interaction. The calculated energies are subjected to a global fit in the spirit of the liquid-drop model. The extracted parameters in this model reflect the temperature dependence of the volume symmetry and surface symmetry coefficients of finite nuclei, in addition to that of the volume and surface energy coefficients. The temperature dependence of the surface symmetry energy is found to be very substantial whereas that of the volume symmetry energy turns out to be comparatively mild.     

An object-parameter approach to predicting unknown data in incomplete fuzzy soft sets

Incomplete data in soft sets lead to uncertainty and inaccuracy in representing and handling information. This paper introduces notions of complete distance between two objects and relative dominance degree between two parameters. Based on both the notions, an object-parameter method is proposed to predict unknown data in incomplete fuzzy soft sets. The proposal makes full use of known data, including the information from the relationship between known values of all objects on a certain parameter and the information from the relationship between known values of an object on all parameters. The effectiveness of the proposal is verified by many examples under the compared investigation of classical predicted methods.     

Dynamic analysis and regulation of the flexible pipe conveying fluid with a hard-magnetic soft segment

Applied Mathematics and Mechanics - The recently developed hard-magnetic soft (HMS) materials can play a significant role in the actuation and control of medical devices, soft robots, flexible...     

Mildred Dresselhaus and Solid State Pedagogy at MIT

Mildred Dresselhaus is known for her influential research on the physics of carbon. Her wide‐ranging influence as a physics teacher, although well‐known to her students, has been less thoroughly examined. Exploring how Dresselhaus grew into her role teaching solid state physics at MIT reveals much about how that subfield evolved.     

Operators on Soft Inner Product Spaces

In the present paper, self-adjoint operator and completely continuous operator on soft inner product spaces have been introduced and some basic properties of such operators are studied.