Comparison of membrane assisted liquid–liquid microextraction devices applied to a series of volatile organic compounds in aqueous environmental matrices

An extraction device has been investigated for the separation and preconcentration of a series of volatile organic compounds (CHCl₃, CHCl₂Br, CHClBr₂ and CHBr₃) in aqueous matrices. The device consisted of a microporous membrane system utilising a hollow fibre tube filled with organic solvent directly immersed into the sample solution. The hollow fibre containing 160 µL organic solvent was immersed in a glass vial with 10 mL capacity, and the extraction took place through diffusive transport between the aqueous sample and the small amount of solvent. For validation of the method, some operational conditions, such as extraction solvent, temperature, stirring rate and separation time, were optimised. Limit of detection was at low ppb levels, with GC-MS analysis under selected ion monitoring (SIM), whereas enrichment factors between 22 and 35 were obtained. Good reproducibility with RSDs between 7.2% and 9.8% and large linear dynamic ranges with R ² between 0.996 and 0.998 were also achieved. In addition, the performance of the membrane assisted solvent extraction (MASE) system was compared with two existing configurations: a non-porous membrane separation device, as well as with a comparable microporous configuration. The comparison considered the extraction mechanism and the underlying transport processes. The application to real samples showed a good concordance with classical analytical methods.     

Comparison of adaptive psychometric procedures motivated by the theory of optimal experiments: simulated and experimental results

The wide use of psychometric assessments and the time necessary to conduct comprehensive psychometric tests has motivated significant research into the development of psychometric testing procedures that will provide accurate and efficient estimates of the parameters of interest. One potential framework for developing adaptive psychometric procedures is the Theory of Optimal Experiments. The Theory of Optimal Experiments provides several metrics for determining informative stimulus values based on a model of the psychometric function to be provided by the investigator. In this study, two methods based on a previous implementation of the Theory of Optimal Experiments are presented for comparison to two fixed step size staircase methods and also an existing adaptive method that utilizes a Bayesian framework. The psychometric procedures were used to measure detection thresholds and discrimination limens on two separate psychoacoustic tasks with normal-hearing subjects. Computer simulations were performed based on the outcomes of the experimental psychoacoustic detection task to analyze performance over a large sample size in the case of known truth. Results suggest that the proposed stimulus selection rules motivated by the Theory of Optimal Experiments perform better than previous techniques and also extend estimation to multiple parameters.     

Thermal analysis of Romanian ancient ceramics

The present work is focused on thermoanalytical investigations as thermogravimetric analysis (TG) and derivative thermal analysis (DTG), applied for the characterization of some samples collected from archaeological sites (Brasov and Trofeum Traiani) located in different regions of Romania. New informations derived about ceramic technologies concerning raw materials and binding materials (mineralogical components) have been obtained. All these experimental results have been correlated with related techniques as X-ray diffraction (XRD), energy-dispersive X-ray fluorescence (EDXRF) and inductively coupled plasma—atomic emission spectrometry (ICP-AES). By progressive heating in static air atmosphere and in the temperature range of 20–800 °C, all investigated materials exhibit three main successive processes, associated with the dehydration and thermo-oxidative degradations. The rate of the first thermooxidative process, temperatures corresponding to the maximum rate of the second thermooxidative process and shrinkage temperature were associated with the damage of the investigated materials due to environmental impact. Heating also affects the contact between the fine-sized clay matrix and mineral clast fragments, appearing in reaction rims, sometimes showing newly formed phases. The temperature at which ancient ceramics and pottery were fired varies over a wide range (600–800 °C) depending on the type of clay used, although firing temperatures not above 30–400 °C have also been suggested. Clay minerals, as the main material for production of ceramics and pottery, show some characteristic reactions (dehydroxylation, decomposition, transformation) in the course of firing (heating effects) and several thermoanalytical criteria can be used for reconstruction of former production conditions.     

A note on cocycle-conjugate endomorphisms of von Neumann algebras

We show that two cocycle-conjugate endomorphisms of an arbitrary von Neumann algebra that satisfy certain stability conditions are conjugate endomorphisms, when restricted to some specific von Neumann subalgebras. As a consequence of this result, we obtain a new criterion for conjugacy of Powers shift endomorphisms acting on factors of type

     

Characterization of the perceived sound of trauma-induced tinnitus in gerbils

Tinnitus often develops following inner ear pathologies, like acoustic trauma. Therefore, an acoustic trauma model of tinnitus in gerbils was established using a modulated acoustic startle response. Cochlear trauma evoked by exposure to narrow-band noise at 10 kHz was assessed by auditory brainstem responses (ABR) and distortion product otoacoustic emissions (DPOAE). Threshold shift amounted to about 25 dB at frequencies >?10 kHz. Induction of a phantom-noise perception was documented by an acoustic startle response paradigm. A reduction of the gap-prepulse inhibition of acoustic startle (GPIAS) was taken as evidence for tinnitus at the behavioral level. Three to five weeks after trauma the ABR and DPOAE thresholds were back to normal. At that time, a reduction of GPIAS in the frequency range 16-20 kHz indicated a phantom noise perception. Seven weeks post trauma the tinnitus-affected frequency range became narrow and shifted to the center-trauma frequency at 10 kHz. Taken together, by investigating frequency-dependent effects in detail, this study in gerbils found trauma-evoked tinnitus developing in the frequency range bordering the low frequency slope of the induced noise trauma. This supports the theory of lateral inhibition as the physiological basis of tinnitus.     

A class of essential representations of product systems

We construct a family of essential representations of an arbitrary product system by generalizing some techniques introduced by M. Skeide and W. Arveson. We then classify the resulting E₀-semigroups up to conjugacy, by identifying their tail flows as periodic W^∗-dynamical systems acting on factors of type I_∞. The conjugacy classes of these E₀-semigroups correspond to the orbits of the action of the automorphism group of the product system on unital vectors. In the sequel, this classification shows explicitly that any E₀-semigroup admits uncountably many non-conjugate cocycle perturbations.     

Slippage mutation rates in 15 autosomal short tandem repeat loci for forensic purposes in a Southeastern Brazilian population

Well‐defined estimates of mutation rates in highly polymorphic tetranucleotide STR loci are a prerequisite for human identification in genetics laboratory routines useful for civil and criminal investigations. Studying 15 autosomal STR loci of forensic interest (CSF1PO, D2S1338, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D19S433, D21S11, FGA, TH01, TPOX, and vWA), we detected 193 slippage mutations (189 one‐step and four two‐step mutations) in 148 875 parent‐child allelic transfers from 5171 paternity cases with true biological relationship (15 096 individuals; 4754 trios and 417 duos; 9925 meiosis) from the state of São Paulo, a very representative population of Brazil. The overall mutation rate was 1.3 × 10^?3 and the highest rates were observed at loci vWA (2.8 × 10^?3), FGA and D18S51 (2.7 × 10^?3 for both), while loci TH01 and TPOX did not present any mutations. The mean slippage mutation rate of paternal origin (1.8 × 10^?3) was six times higher than that observed for maternal origin (0.3 × 10^?3).     

Can the provenance of the conflict minerals columbite and tantalite be ascertained by laser-induced breakdown spectroscopy?

Conflict minerals is a term applied to ores mined in conditions of armed conflict and human rights abuse. Niobium and tantalum are two rare metals whose primary natural occurrence is in the complex oxide minerals columbite and tantalite, the ore of which is commonly referred to as coltan. The illicit export of coltan ore from the Democratic Republic of the Congo is thought to be responsible for financing the ongoing civil conflicts in this region. Determining the chemical composition of an ore is one of the means of ascertaining its provenance. Laser-induced breakdown spectroscopy (LIBS) offers a means of rapidly distinguishing different geographic sources for a mineral because the LIBS plasma emission spectrum provides the complete chemical composition (i.e., “chemical fingerprint”) of any material in real time. To test this idea for columbite–tantalite, three sample sets were analyzed. Partial least squares discriminant analysis (PLSDA) allows correct sample-level geographic discrimination at a success rate exceeding 90%.     

Absence of gauge-invariant functionals on spectral C*-algebras

We show that Arveson??s spectral C*-algebra C*(E) of an arbitrary product system E?=?{E(t)} _t>0 admits no non-zero gauge-invariant positive functionals.