Cavitand-functionalized porous silicon as an active surface for organophosphorus vapor detection

This paper reports on the preparation of a porous silicon-based material covalently functionalized with cavitand receptors suited for the detection of organophosphorus vapors. Two different isomeric cavitands, both containing one acid group at the upper rim, specifically designed for covalent anchoring on silicon, were grafted on H-terminated porous silicon (PSi) by thermal hydrosilylation. The covalently functionalized surfaces and their complexation properties were characterized by combining different analytical techniques, namely X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and mass spectroscopy analysis coupled with thermal desorption experiments. Complexation experiments were performed by exposing both active surfaces and a control surface consisting of PSi functionalized with a structurally similar but inactive methylene-bridged cavitand (MeCav) to dimethyl methylphosphonate (DMMP) vapors. Comparison between active and inactive surfaces demonstrated the recognition properties of the new surfaces. Finally, the nature of the involved interactions, the energetic differences between active and inactive surfaces toward DMMP complexation, and the comparison with a true nerve gas agent (sarin) were studied by DFT modeling. The results revealed the successful grafting reaction, the specific host-guest interactions of the PSi-bonded receptors, and the reversibility of the guest complexation.     

The parameter space for the direct spinning of fibres and films of carbon nanotubes

We have recently introduced a method for the continuous spinning of carbon nanotube fibres and films directly from the gas phase of a chemical vapour deposition furnace [Y. Li, et al., Science 304 (2004) 276]. In this work the effect of the process parameters on the ability to spin continuously is studied, with particular focus on the carrier gas and feedstock flow rates. Catalyst dilution by high carrier gas flow rates led to smaller diameter nanotubes but these conditions are found the hardest to spin.     

Preparation of composite materials containing iron in a cross-linked resin host based on styrene and divinylbenzene

Iron composite materials based on styrene/divinylbenzene network hosts were produced using aqueous suspension polymerization. The effects of different kinds of porogen agent, toluene, toluene/n-heptane mixture or a toluene solution of polyphenyleneoxide on the bulk density, swelling in toluene and ferromagnetic properties of these materials were evaluated. The specific area and average porous diameter of network resins were characterized by BET and BJH methods, while the iron content was determined by atomic absorption spectrometry. The morphology of the composites was studied by both optical microscopy and scanning electron microscopy with energy dispersive X-ray analysis. All the spherical beads, irrespective of their sizes, have agglomerated iron particles located only on their surface. The particles have exhibited ferromagnetic behavior, with a coercivity of 328.69 Oe. The porogen agents used affect the iron particle distribution on the bead surfaces.     

1H‐HRMAS NMR study of smoked Atlantic salmon (Salmo salar)

High‐resolution magic angle spinning (HRMAS) NMR spectroscopic data of smoked Atlantic salmon (Salmo salar) were fully assigned by combination of one‐ and two‐dimensional‐HRMAS experiments. Complete representative spectra, obtained after few minutes of analysis time, revealed a large number of minor and major compounds in the sample. The methodology is limited by the low sensitivity of NMR, and therefore HRMAS only enables the determination of the most relevant components. These were fatty acids (FAs), carbohydrates, nucleoside derivatives, osmolytes, amino acids, dipeptides and organic acids. For the first time, spectra were resolved sufficiently to allow semiquantitative determination in intact muscle of the highly polyunsaturated FA 22:6 ω‐3. Additionally, the feasibility of ¹H‐HRMAS NMR metabolite profiling was tested to identify some bioactive compounds during storage. This profiling was carried out by the non‐destructive and direct analysis (i.e. without requiring sample preparation and multiple step procedures) of intact salmon muscle. The proposed procedure can be applied to a large number of samples with high throughput due to the short time of analysis and quick evaluation of the data. Copyright © 2010 John Wiley & Sons, Ltd.     

Unexpected conformational consequences of weak hydrogen bonds on 1,3,7,9,13,15,19,21‐octaazapentacyclo[19.3.1.13,7.19,13.115,19]octacosane monohydrate

In the title compound, C₂₀H₄₀N₈·H₂O, the organic molecule crystallizes with one water molecule located within the molecular cavity of the octaaza macrocycle. The two molecules are linked via two weak O—H...N hydrogen bonds. The assembly has noncrystallographic C₂ axial symmetry.     

Nitrogen Source Optimization for Cellulase Production by Penicillium funiculosum, using a Sequential Experimental Design Methodology and the Desirability Function

The present study aimed at maximizing cellulase production by Penicillium funiculosum using sequential experimental design methodology for optimizing the concentrations of nitrogen sources. Three sequential experimental designs were performed. The first and the second series of experiments consisted of a 2⁴ and a 2³ factorial designs, respectively, and in the third one, a central composite rotational design was used for better visualizing the optimum conditions. The following nitrogen sources were evaluated: urea, ammonium sulfate, peptone, and yeast extract. Peptone and ammonium sulfate were removed from the medium optimization since they did not present significant statistical effect on cellulase production. The optimal concentrations of urea and yeast extract predicted by the model were 0.97 and 0.36 g/L, respectively, which were validated experimentally. By the use of the desirability function, it was possible to maximize the three main enzyme activities simultaneously, which resulted in values for FPase of 227 U/L, for CMCase of 6,917 U/L, and for β-glucosidase of 1,375 U/L. These values corresponded to increases of 3.3-, 3.2-, and 6.7-folds, respectively, when compared to those obtained in the first experimental design. The results showed that the use of sequential experimental designs associated to the use of the desirability function can be used satisfactorily to maximize cellulase production by P. funiculosum.     

Photo-oxidative degradation mechanisms in styrene-ethylene-butadiene-styrene (SEBS) triblock copolymer

The photo-oxidative degradation of poly[styrene-b-ethylene-co-butylene-b-styrene], SEBS, has been studied at wavelengths cut-off below 290 nm, and monochromatic light of 254 nm and 365 nm, using a variety of spectroscopic methods including FTIR, UV and luminescence spectroscopy coupled with crosslinking and hydroperoxide analyses in order to understand the mechanisms involved. A study on polystyrene photodegradation is also compared at varying wavelengths in order to provide an understanding of the light sensitivity of the styrene vs the aliphatic phases in the SEBS. The increase in colour shows evidence for the presence of visible light absorbing chromophores. Hydroperoxide analysis reflects a rapid increase in the hydroperoxide concentration in the olefinic phase. Fluorescence spectroscopy shows a rapid disruption of the polystyrene excimers coupled with the formation of long-wavelength emitting polyconjugated stilbene-type chromophores. Phosphorescence analysis indicates the presence of acetophenone groups while GPC and sol/gel analysis showed that degradation occurs mainly due to chain scission. Changes in the FTIR spectra of the photo-oxidised samples show a predominant absorption associated with carboxylic acids and/or aliphatic esters at 1712 cm⁻¹. Other species such as hydroperoxides, ketones and α,β-unsaturated carbonyls are also formed and mechanisms are proposed.     

Alterations of plasma and cerebrospinal fluid glutamate levels in rats treated with the N-methyl-D-aspartate receptor antagonist, ketamine

It has been reported that the repeated administration of a sub-anesthetic dose of an N-methyl-D-aspartate receptor antagonist, ketamine, can produce an animal model of schizophrenia. Since no information is available on the alterations of the amino acid levels in ketamine-treated rats, we investigated the amino acid composition in the plasma and cerebrospinal fluid of rats that were repeatedly administered with ketamine for 5 consecutive days (30 mg/kg/day). The plasma and cerebrospinal fluid amino acid compositions in the fifth week after cessation of repeated ketamine administration were determined by highperformance liquid chromatography with fluorescence detection using a pre-column fluorescence reagent, i.e. 4-fluoro-7nitro-2,1,3-benzoxadiazole. Among the amino acids investigated in the present study, the level of plasma glutamic acid increased significantly (p < 0.05), while that of the cerebrospinal fluid glutamic acid decreased significantly in the ketamine-treated rats as compared with these levels in control rats injected with saline (p < 0.05, n = 7). These alterations in the glutamic acid level in the plasma and cerebrospinal fluid resemble those in schizophrenic patients, suggesting that ketamine-treated rats may be a useful model for performing research on the pathophysiology of schizophrenia.