Pesticide residue analysis by off-line SPE and on-line reversed-phase LC-GC using the through-oven-transfer adsorption/desorption interface

A new method to determine pesticide residue in water is presented. The described method includes using off-line solid-phase extraction (SPE) and on-line reversed-phase liquid chromatography-gas chromatography (RPLC-GC). An interface, based on a modified programmed temperature vaporizer (PTV) injector, packed with a suitable trapping material, is used for on-line RPLC-GC. The changes made in the PTV injector affect the pneumatic system, sample introduction, and solvent elimination. The new interface is easily capable of automation. Methanol/wate (70/30) is used as the eluent in the LC preseparation step. The LC column flow during elution is different from the flow during the transfer step. The transferred volumes range from 500 to 1400 microL (volume of the fractions of interest). Solvent elimination is almost 100% before the sample reaches the GC column. The described system does not show any variation of the peak retention times. The detection limit for real samples ranges from 0.04 to 1.5 ng/L, using NP detection.     

Lattice imaging of structural defects in a chain silicate: The pyroxenoid mineral rhodonite

The pyroxenoid mineral rhodonite has been examined by electron diffraction and high-resolution lattice imaging. Planar defects parallel to (110) and (001) have been observed. The former are comparable to the (100) stacking faults frequently observed in the related mineral wollastonite, whereas the latter involve unit cell strips of the more complex pyroxmangite structure occasionally inserted into the parent rhodonite matrix.     

Grammatical and nongrammatical contributions to closed-class word selection.

Closed-class word selection was investigated by focusing on determiner production. Native speakers from three different languages named pictures of objects using determiner plus noun phrases (e.g., in French "la table" [thefeminineA table], while ignoring distractor determiners printed on the pictures (e.g., "le" [themasculine]. The target and distractor expressed either shared or different grammatical and nongrammatical features (gender, number, and definiteness). A gender-facilitation effect was observed and attributed to noun processing. Crucially, across five experiments, distractors that shared a feature with the target determiner never resulted in longer naming latencies than distractors that were more different. These results indicate that activating related candidates is not detrimental for determiner retrieval, suggesting a noncompetitive mechanism of closed-class word selection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of acid sites on γ-alumina and chlorinated γ-alumina by 31P NMR of adsorbed trimethylphosphine

₃₁P MAS NMR of adsorbed trimethylphosphine (TMP) has been used to characterize the surface acid properties of γ-alumina and chlorinated γ-alumina. Combined with thermodesorption of TMP, NMR has allowed the determination of the strength distribution of Brønsted and Lewis acid sites on these samples. γ-alumina chlorination with 1,2-dichloropropane at 500°C first increases the numbers of ``strong'' Lewis and ``strong'' Brønsted acid sites, second decreases the number of ``weak'' Lewis acid sites. The ``strong'' sites are the ones TMP is desorbed from above 200°C and the ``weak'' sites up to 200°C.     

The Italian quality control study for evaluation of CD4 cells in centres involved in the treatment of HIV-1 patients. Italian CD4 Quality Control Group

We report on the experience of establishing a national network for a quality control programme in evaluating CD4 cell counts in most Italian centres involved in the care of patients with HIV disease. The 68 centres were divided according to their geographical location into eight groups, and twice a year (tests A and B) they received three coded whole blood samples (two were replicates of the same sample) obtained from two informed HIV+ patients, one with CD4 counts/mm3 expected to be < 200 and one with values > 300. The medians of the determinations performed by the labs involved in each of the eight areas were taken as the 'true' values for each sample. Unsatisfactory performances for percentage of CD4 cells were identified as a CD4 analysis with residual values > or = +/- 5% and with deviates > or = +/- 2. For absolute numbers of CD4 cells, an unsatisfactory performance was defined as CD4 counts with residual > +/- 100 CD4 cells/mm3 and with deviates > or = +/- 2. The residual value is the CD4 value reported by each lab minus the median value. The deviate is the residual divided by the modified interquartile range (IQR x 0.75). Most of the centres provided reliable results. However, some labs failed to provide satisfactory results for percentages (6.25% of the tested labs for test A and 6.17% for test B) or absolute numbers (16.25% test A and 12.34% test B). Only 3.7% of the labs gave unsatisfactory results in both tests. Four of the unsatisfactory results from the two tests gave an error in absolute numbers > +/- 200 CD4 cells/mm3. Our data suggest that most Italian labs provide reliable results in evaluating the numbers of CD4 cells in HIV-1+ samples, but the importance of running a quality control programme is highlighted by our experience with those centres which provide unsatisfactory data which may lead to incorrect classification of the patients or assessment of treatment.     

Aerobijels: Ultralight Carbon Monoliths from Cocontinuous Emulsions

Bijels are used to develop a new class of ultralight hierarchically porous aerogels exhibiting multimodal porosity across multiple length scales. Through in situ functionalization of a particle‐laden liquid interface wherein binary liquid pairs are kinetically trapped out of equilibrium through interfacial jamming, monolithic and freestanding carbon electrodes are produced with prescribed bulk densities down to ≈2 mg cm^?3. Exemplary electrokinetic experiments indicate that the bicontinuity of the pore structure is essential for enhancing transport to and from the active electrode surfaces, demonstrating that these materials possess a superior ability to accumulate and transport charge when compared to analogous systems with restricted pore connectivity and fluid throughput. This approach offers a new synthetic route to bicontinuous and hierarchical aerogel materials with nested multimodal porosities. The flexibility of this scheme can address critical issues related to transport‐limited behaviors that arise in many technological fields, ranging from energy and catalysis research to remediation and sensing applications.     

Normal and high pressure synthesis of mixed ruthenium-rhodium oxides of the rutile type

A series of mixed ruthenium-rhodium oxides with general composition Ru_1?xRh_xO_y (O < x < 0.5) has been prepared at normal and — high pressures. The materials obtained at room pressure have a r$\text{u}$ tile structure and y = 2. At 60 Kbar, an orthorhombic distortion of the rutile structure is observed for 0.3 < x < 0.4. At the maximum distortion the unit cell parameters are $\text{a}\text{= 4.429(3)}$$\text{A}\text{?}\text{, —}\text{b}\text{= 4.571(3)}$ Å and $\text{c}\text{= 3.0972(9)}\text{A}\text{?}$.     

Attentional requirements for the selection of words from different grammatical categories.

Two grammatical classes are commonly distinguished in psycholinguistic research. The open-class includes content words such as nouns, whereas the closed-class includes function words such as determiners. A standing issue is to identify whether these words are retrieved through similar or distinct selection mechanisms. We report a comparative investigation of the allocation of attentional resources during the retrieval of words from these 2 classes. Previous studies used a psychological-refractory-period paradigm to establish that open-class word retrieval is supported by central attention mechanisms. We applied the same logic to closed-class word retrieval. French native speakers named pictures with determiner noun phrases while they concurrently identified the pitch of an auditory tone. The ease of noun and determiner retrieval was manipulated independently. Results showed that both manipulations affected picture naming and tone discrimination responses in similar ways. This suggests the involvement of central attentional resources in word production, irrespective of word class. These results argue against the commonly held hypothesis that closed-class retrieval is an automatic consequence of syntactic specific processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)