Immuno-affinity columns versus conventional clean-up: a method-comparison study for the determination of zearalenone in corn

The efficiency of a modern analytical method employing immuno-affinity columns (IACs) is compared to a well established traditional technique with respect to the determination of zearalenone (ZON) in corn in the μg/kg range. Despite of a constant error of about 4 μg/kg in the examined working range of 10–200 μg/kg, analytical data obtained from the analysis of spiked and naturally contaminated samples showed good correspondence for the compared methods. The performance characteristics of immuno-affinity-chromatography as a new clean-up technique for the determination of ZON in corn is reported for the first time and compared to a conventional clean-up procedure     

Microwave‐accelerated Conjugate Addition of 2‐Arylindoles to Substituted β‐Nitrostyrenes in the Presence of Ammonium Trifluoroacetate: An Efficient Approach for the Synthesis of a Novel Class of CB1 Cannabinoid Receptor Allosteric Modulators

2‐Arylindoles, in general, exhibit reduced reactivity towards the conjugate addition to substituted nitrostyrenes, when compared with indoles. We report here an efficient, expeditious, and high‐yielding conjugate addition of 2‐arylindoles to substituted β‐nitrostyrenes in the presence of ammonium trifluoroacetate under microwave irradiation. This method is mild with high and reproducible yields and is selective for addition of β‐nitrostyrenes when compared with other electrophiles. The results obtained from the optimized microwave method consistently provided improved yields in a shorter time compared with those of the conventional heating synthetic route.     

In vivo resistance to photofrin-mediated photodynamic therapy in radiation-induced fibrosarcoma cells resistant to in vitro Photofrin-mediated photodynamic therapy.

The effects of Photofrin-mediated photodynamic therapy (PDT) on the in vitro cell survival and in vivo tumor growth of murine radiation-induced fibrosarcoma (RIF) cell tumors have been examined following in vivo PDT treatment of tumors. The response to in vivo PDT is examined in tumors derived from RIF-1 mouse fibrosarcoma cells and in tumors derived from RIF-8A cells, which show in vitro resistance to PDT. A significant reduction in tumor volume is observed over the first three days following in vivo PDT treatment of either 5 or 10 mg/ kg. The reduction in tumor volume is greater for a 10 compared to a 5 mg/ml dose and occurs to a similar extent for both RIF-1 and RIF-8A tumors. The re-growth is significantly delayed for RIF-1 compared to RIF-8A tumors, indicating a greater response for RIF-1 tumors compared to RIF-8A tumors following PDT. A reduced response of the RIF-8A compared to the RIF-1 tumor cells is also observed in the clonogenic survival of cells from tumors that were excised and explanted in vitro immediately following in vivo PDT treatment. These data indicate that the intrinsic cell sensitivity to PDT is an important component in the mechanism that leads to tumor response following in vivo photodynamic therapy.     

Comparison of catalytic activity of thallium and lead adatoms at the gold electrodeposition and dissolution in cyanide solutions

Catalytic activity of thallium and lead adatoms is compared in electrode processes involving gold in cyanide solutions. It is shown that in the presence of considered atoms on the interface, the gold dissolution is accelerated to the greater extent than its electrodeposition. Lead adatoms are shown to exert a substantially stronger effect on the anodic dissolution rate as compared with thallium adatoms, whereas the opposite trend is observed in the cathodic deposition. An explanation for the fact is proposed.     

The Origin of Shape Sensitivity in Palladium‐Catalyzed Suzuki–Miyaura Cross Coupling Reactions

The shape sensitivity of Pd catalysts in Suzuki–Miyaura coupling reactions is studied using nanocrystals enclosed by well‐defined surface facets. The catalytic performance of Pd nanocrystals with cubic, cuboctahedral and octahedral morphologies are compared. Superior catalytic reactivity is observed for Pd NCs with {100} surface facets compared to {111} facets. The origin of the enhanced reactivity associated with a cubic morphology is related to the leaching susceptibility of the nanocrystals. Molecular oxygen plays a key role in facilitating the leaching of Pd atoms from the surface of the nanocrystals. The interaction of O₂ with Pd is itself facet‐dependent, which in turn gives rise to more efficient leaching from {100} facets, compared to {111} facets under the reaction conditions.     

Comparing the performance of neural networks to well-established methods of multivariate data analysis: the classification of mass spectral data

Summary The performance of neural networks in classifying mass spectral data is evaluated and compared to methods of multivariate data analysis and pattern recognition. Back propagation networks are matched with linear discriminant analysis, Kohonen feature maps are compared to the knearest neighbour clustering algorithm. Eight classifiers were trained, in order to discriminate mass spectra of steroids from eight distinct classes of chemical compounds. The results obtained show slightly better performance of Kohonen networks compared to k-nearest neighbour clustering and equal performance of multi-layer perceptrons and discriminant analysis.     

Determinations of polychlorinated biphenyl isomers by response factor calibration

Quantitative measurement of polychlorinated biphenyl (PCB) isomers by response factor calibration (RFC) is evaluated with gas chromatography and the Hall electrolytic conductivity detector. The procedure requires neither isomer identification nor reference compounds identical to each measured PCB isomer. Weight percent chlorine is determined for five Aroclor mixtures by RFC and compared within a few percent of expected values. Individual PCB isomers are measured and quantitatively compared for Aroclor mixtures. Also, RFC determinations for ten PCB isomers contained in a test material reference solution are compared to the supplier's stated concentrations. These RFC measurements provide quantitative analyses in the absence of a standard for each measured component.     

Application of water as a solvent in microwave-assisted extraction for analysis of PCBs and CBzs in fly ash

Polychlorinated biphenyls (PCBs) and chlorobenzenes (CBzs) are two classes of dioxin precursors formed in municipal solid waste incinerators (MSWIs); they produce negative health effects similar to those of dioxins. Reducing the analytical time required for determining the concentrations of these compounds in MSWIs is important for quickly evaluating their importance and assessing associated health risks. In the present study, water is used as a safe and environmentally friendly solvent in microwave-assisted extraction (MAE) for PCB and CBz analyses. MAE is compared with traditional Soxhlet extraction (SE) to determine the extraction efficiencies. The evaluation of extraction efficiencies shows that MAE has a high extraction efficiency compared with that of SE when water content is lower than 60%. Furthermore, the extraction time and organic solvent consumption are reduced with MAE compared with SE.     

Shape, flexibility and packing of proteins and nucleic acids in complexes

Determining the change in topological properties like shape, flexibility and packing of proteins and nucleic acids on complexation is important in characterizing the role of induced structural changes and various interactions which control the functional specificity of proteins and nucleic acids. To this end, we have analyzed and compared the three dimensional structures of several protein-protein, protein-DNA and protein-RNA complexes available in the Protein Data Bank (PDB) and the Nucleic Acid Data Bank (NDB). The size of complexed proteins and nucleic acids, as measured by the radius of gyration, follows Flory's scaling law. The change in the scaling exponents for proteins, RNA and DNA reflects the changes in their respective sizes due to complexation. The anisotropy in the shape of proteins, DNA and RNA in complexes is measured by considering the asphericity and shape parameter, which are calculated from the eigenvalues of the moment of inertia tensor. The distribution of asphericity and shape shows that complexed proteins are mostly spherically symmetrical, while DNA and RNA in complexed states are largely prolate and considerably more aspherical compared to the proteins. Persistence length characterizes the intrinsic flexibility/rigidity of proteins and nucleic acids. The flexibility of all biomolecules decreases with the chain length. For small DNA molecules (6-147 base pairs), persistence length is larger compared to RNA and proteins in protein-protein and protein-RNA complexes. The flexibility of DNA increases, while RNA decreases, in their respective complexed states as compared to that of proteins which remain almost unchanged. The two body contact analysis confirms that the side-chain-backbone contacts are predominant compared to sidechain-sidechain and backbone-backbone contacts in the complexed proteins. The average packing density of proteins decreases in their complexed states, which is measured by the mean value of the contact density of their alpha carbon atoms. The average number of hydrogen bonds are found to be less in the interface region of protein-protein complexes compared to that in protein-DNA and protein-RNA complexes.     

Phthalocyanine-based field-effect transistors as gas sensors

In this review molecular field-effect transistors are described and compared with their gate-modified inorganic counterparts. The different processes involved in gas sensing are summarized. The advantages of transistors on resistors are demonstrated. The sensitivity of molecular field-effect transistors to strong oxidizing species, for example ozone, is detailed and compared with their sensitivity to humidity and volatile organic compounds. Application to ozone monitoring in urban atmospheres is also described.     

Performance of a sound card as data acquisition system and a lock-in emulated by software in capillary electrophoresis

The performance of fluorescence detectors in capillary electrophoresis is maximized when the excitation light intensity is modulated in time with optimal frequencies. This is especially true when photomultiplier tubes are used to detect the fluorescent light. The photomultiplier tube amplified raw output signal can in principle be captured directly by a personal computer sound card (PCSC) and processed by a lock-in emulated by software. This possibility is demonstrated in the present work and the performance of this new setup is compared with a traditional data acquisition system. The results obtained with this “PCSC and lock-in emulated by software” were of the same quality or even better compared to that obtained by conventional time integrators (Boxcars) and data acquisition boards. With PCSC the limits of detection (LOD) found for both naphthalene-2,3-dicarboxaldehyde-derivatized tyrosine and alanine were 3.3 and 3.5 fmol (injection of 5 nL of samples at 0.66 and 0.70 μmol/L), respectively. This is at least three times better compared to conventional systems when light emitting diodes (LEDs) are used as the excitation source in fluorescence detectors. The PCSC linear response range was also larger compared to conventional data acquisition boards. This scheme showed to be a practical and convenient alternative of data acquisition and signal processing for detection systems used in capillary electrophoresis.     

Reflective blue phase liquid crystal displays with double-side concave-curved electrodes

Reflective blue phase liquid crystal display (BPLCD) is a promising candidate for field sequential colour displays with reflective liquid-crystal-on-silicon (LCoS). However, the issue of high operation voltage still hinders its widespread applications. We propose a reflective BPLCD with double-side concave-curved electrode and research its operation voltage and electro-optic characteristics in simulation, which is compared to the transmissive mode. The effect of double-side electrodes on horizontal electric field and operation voltage is analysed. The improvement of concave-curved electrodes on reflectance is discussed. A reflective BPLCD has two times the optical path difference compared to the transmissive mode. By using double-side concave-curved electrodes, the reflectance increased by 23% and the operation voltage reduced by 32% compared to the traditional in-plane switching mode. This work enables BPLC to be integrated with reflective LCoS.     

The determination of some nebulizer characteristics

An indirect method for measuring nebulizer characteristics is described in detail and is indirectly compared with a direct method described in the literature. Nebulizer characteristics for various cross-flow and concentric nebulizers are compared. The precision of the present indirect method is inferior to that of direct methods, but the accuracy tends to be the same. The efficiencies of cross-flow and concentric nebulizer systems for ICP systems are typically 1–3% and the aerosol concentration tends to be higher for cross-flow nebulizers.     

Liposomal drugs dispersed in hydrogels. Effect of liposome, drug and gel properties on drug release kinetics

Release of calcein and griseofulvin (GRF) from control (gels in which solutes are dissolved in) and liposomal gels was studied using agarose-assisted immobilization as a technique to separate gels from drug-receptor compartments. Liposomes composed of phosphatidylcholine (PC) or distearoyl-glycero-PC and cholesterol (DSPC/Chol), and incorporating calcein or GRF were prepared by thin film hydration. After cleaning the liposomes they were dispersed in different hydrogels (carbopol 974 [1, 1.5 or 2% (w/w)], hydroxylethyl-cellulose (HEC) [4% (w/w)], or a mixture of the two), and release of calcein or GRF was followed by fluorescence or photometric technique, respectively. Results show that calcein release from liposomal gels is slower compared to control gels, and can be further retarded by using rigid-membrane liposomes (faster release from PC-liposome compared to DSPC/Chol-liposome gels). Additionally, calcein release is not affected by the lipid amount loaded (in the range from 2 to 8 mg/ml), therefore solute loading can be controlled according to needs.

Oppositely, GRF release from liposomal gels is determined by drug loading. At high drug loading levels (compared to GRF aqueous solubility), GRF is released with constant rate from liposomal gels irrespective of liposome type (PC or DSPC/Chol). Thereby, for amphiphilic/lipophilic drugs, drug properties (solubility, log P) determine the system behavior.

Calcein and GRF release from control carbopol gels is faster compared to HEC and mixture gels. The same is true for calcein in liposomal gels. Carbopol gel rheological properties were found to be significantly different (compared to the other gels), implying that these characteristics are important for drug diffusion from gels.     

Copolymerization of styrene with vinyl acetate in a construction petroleum bitumen medium and properties of obtained composite materials

The regularities of the copolymerization of styrene (Sr) with vinyl acetate (VA) in a construction petroleum bitumen (CPB) medium are studied. It is established that, in the bitumen medium, the superiority of styrene in terms of reactivity when compared to vinyl acetate is not expressed as critically as in the case of in-bulk copolymerization. Polymer-bitumen composite materials with improved operating performance as compared to bitumen were obtained by copolymerization.     

等速电泳法测定人齿菌斑培养液中乳酸含量

应用等速电泳法分离并测定了人齿菌斑培养液中的乳酸，测定回收率在９４．２％－１０２．２％之间，相对标准偏差小于４．５％，比较了抗龋者与易感龋者的菌斑在相同培养条件下的乳酸产量，并对不同饥饿时间下菌斑所产的乳酸进行了测定与比较。     

On the directionality of anion-π interactions

The directionality of two important noncovalent interactions involving aromatic rings (namely anion-π and cation-π) is investigated. It has been recently published that the anion-π interactions observed in X-ray structures where the anion is located exactly over the center of the ring are scarce compared to cation-π interactions. To explain this behavior, we have analyzed how the interaction energy (RI-MP2/aug-cc-pVDZ level of theory) is affected by moving the anion from the center of the ring to several directions in anion-π complexes of chloride with either hexafluorobenzene or trifluoro-s-triazine. We have compared the results with the directionality of the cation-π interaction in the sodium-benzene complex. The results are useful to explain the experimental differences between both ion-π interactions. We have also computed the van der Waals radii of several halide anions and we have compared them to the neutral halogen atoms.     

Bimetallic nanoparticles as a novel chemiresistor coating

Here, we describe the chemiresistive sensing of some volatile organic compounds with a novel film of chemically synthesized Au–Pt bimetallic nanoparticles (NPs) stabilized with 11-mercaptoundecanoic acid. The chemiresistive sensing properties were measured over a concentration range of 1.4–250 mg L^?1 for methanol, ethanol, ethyl acetate and acetone vapours and the responses were compared with Au and Pt monometallic nanoparticles. It is observed that the sensitivity of bimetallic nanoparticles is increased about 60 % in exposure to methanol and ethanol vapours, but there are no changes in the sensitivity to the other tested vapours. In addition, the detection limit is improved about 80–100 % for all tested vapours in bimetallic nanoparticles compared to AuNPs and 20–30 % compared to PtNPs.     

Side-chain liquid-crystalline copolymers containing charge transfer groups

A series of side-chain liquid crystal copolymers have been prepared based on a polystyrene backbone and having 4-nitro-4'-oxyazobenzenealkyloxy and 4-methoxy-4'-oxyazobenzenealkyloxy pendant groups. All the polymers exhibit solely smectic behaviour. The thermal stability of the smectic phase is significantly enhanced in the copolymers when compared to the homopolymers. This is compared to the behaviour of the analogous monomeric compounds. The enhancement of the thermal stability is attributed to a specific interaction, possibly charge transfer.