Determination of carazolol residues in porcine tissue by radioreceptor assay

A radioreceptor assay was developed for the determination of the p-blocker carazolol in porcine muscle and kidney. The method involves a simple alkaline extraction procedure using diethyl ether followed by a competitive assay between carazolol residues and [H-3]-dihydroalprenolol ([H-3]-DHA) using solubilised beta2-adrenoceptors isolated from a transfected cell line. The limit of detection (LOD) was determined using 20 reference blank samples of pig kidney and pig muscle. LODs for muscle (0.93 mug kg(-1)) and kidney (1.47 mug kg(-1)) were well below their respective European community maximum residue limits, (MRLs 5 and 25 mug kg(-1), respectively). The assay was used to investigate if carazolol residues persisted in pig tissues for up to 30 h post-intramuscular injection at the recommended dose rate (10 mug carazolol/kg body weight). The highest mean +/- S.D. concentrations were detected at 1 h post-injection in kidney (10.84 +/- 1.3 mug kg(-1)) and muscle (3.59 +/- 0.2 mug kg(-1)) which were less than the respective MRLs. It is concluded that this method offers a robust and rapid alternative to other methods for the screening of carazolol residues in pig meat. (C) 2002 Elsevier Science B.V. All rights reserved.

Biosensor assay of sulfadiazine and sulfamethazine residues in pork

Biosensor-based immunochemical screening assays for the detection of sulfadiazine (SDZ) and sulfamethazine (SMT) in muscle extract from pigs were developed. Samples were extracted with aqueous buffer and then centrifuged. This simple and straightforward preparation allowed up to 40 samples to be processed and analysed in 1 d. The limits of detection for the assays were found to be 5.6 ng g(-1) for SDZ and 7.4 ng g(-1) for SMT. These figures were well below the European and US legal limits for sulfonamides (100 ng g(-1)). The precision (RSD) between runs was

DEVELOPMENT OF A SENSITIVE AND SPECIFIC TIME-RESOLVED FLUOROMETRIC IMMUNOASSAY FOR THE BOVINE ACUTE-PHASE PROTEIN HAPTOGLOBIN (HP)

Haptoglobin (Hp) is recognised as a major acute phase protein in the bovidae and its presence in serum is used as an indicator of inflammation. A mouse monoclonal antibody (1D9) specific for bovine Hp was labelled with a lanthanide (Eu) chelate and used to develop a competitive immunoassay. This competitive immunoassay allowed direct measurement of Hp in serum and was validated for intra- and interassay coefficients of variation (below 8%). Cross-reactivity with other serum proteins was measured (less than 0.1%) and limits of detection for Hp in serum were established for adult male (0.344 mu g/ml) and adult female cattle (1.589 mu g/ml). The immunoassay was compared with an established haptoglobin-haemoglobin binding assay.

Production of a monoclonal antibody and its application in an optical biosensor based assay for the quantitative measurement of Pantothenic Acid (Vitamin B5) in foodstuffs

Pantothenicacid (PA), vitamin B5, is an essential B vitamin that may be fortified in food and as such requires robust and accurate methods of detection to meet compliance legislation. This study reports the production and characterisation of the first monoclonalantibody (MAb) specific for PA and the subsequent development of a surface plasmon resonance (SPR) biosensorassay for the quantification of PA. The developed assay was compared with an SPR based commercial kit which utilised a polyclonal antibody (PAb). Foodstuffs, including cereals (n = 43), infant formulas and baby food (n = 10) and fruit juices (n = 48) were analysed by both the MAb and PAb biosensorassays and comparison plots showed good correlation (R2 0.77–0.99). The results indicate that the MAb basedbiosensorassay is suitable for the measurement of PA in foodstuffs and has the added advantage of facilitating a constant, long term supply of identical antibody. Preliminary matrix studies suggest the MAb basedassay is an excellent candidate for further validation studies and routine quality assurance based analysis.

An investigation of clustered radiation-induced lesions in DNA

Recent track structure modelling studies indicate that radiation induced damage to DNA consists of a spectrum of different lesions of varying complexity. There is considerable evidence to suggest that, in repair-proficient systems, it is only the small proportion of more complex forms that is responsible for most of the biological effect. The complex lesions induced consist initially of clustered radical sites and a knowledge of their special chemistry is important in modelling how they react to form the more stable products that are processed by the repair systems. However, much of the current understanding of the chemical stage of radiation has developed from single-radical systems and there is a need to translate this to the more complex reactions that are likely to occur at the important multiple radical sites. With low LET radiation, DNA dsb may derive either from single-radical attack that damages both strands by a transfer mechanism, or from pairs of radical sites induced in close proximity, with one or more radical on each strand. With high LET radiation, modelling studies indicate that there is an increased probability of dsb arising from sites with more than two radical centres, leading to a greater frequency of more complex types of break. The spectrum of these lesions depends on the overall outcome of consecutive physical and chemical processes. The initial pattern of radical damage is determined by the energy depositions on and around the DNA, according to the type of radiation. This pattern is then modified by scavengers that inhibit the formation of radicals on the DNA, and by agents that either chemically repair (e.g. thiols) or fix (e.g. oxygen) a large fraction of these radicals. The reaction kinetics associated with clustered radical sites will differ from those of single sites: (1) because of the opportunities for interactions between the radicals themselves; and (2) because certain endpoints, e.g. a dsb, may require a combination of the products of two or more radicals. Fast response techniques using pulsed low and high LET irradiation have been established to measure the reactions of radical sites on pBR322 plasmid DNA with oxygen and thiols with a view to obtaining information about cluster size. This paper describes experimental approaches to explore the role of the chemical stage of the radiation effect in relation to lesion complexity.

A comparison of the chemical repair rates of free radical precursors of DNA damage and cell killing in Chinese hamster V79 cells.

One of the important temporal stages of radiation action in cellular systems is the chemical phase, where oxygen fixation reactions compete with chemical repair reactions involving reducing agents such as GSH. Using the gas explosion technique it is possible to follow the kinetics of these fast (> 1 ms) reactions in intact cells. We have compared the chemical repair kinetics of the oxygen-dependent free radical precursors leading to DNA single-strand and double-strand breaks, measured using filter elution techniques, with those leading to cell killing in V79 cells. The chemical repair rates for DNA dsb (670s-1 at pH 7.2 and 380s-1 at pH 9.6) and cell killing (530s-1) were similar. This is in agreement with the important role of DNA dsb in radiation induced cell lethality. The rate for DNA ssb precursors was significantly slower (210s-1). The difference in rate between DNA ssb and dsb precursors may be explained on the basis of a dsb free radical precursor consisting of a paired radical, one radical on each strand. The instantaneous probability of one or other of these radicals being chemically repaired and not proceeding to form a dsb will be twice that of a ssb radical precursor. This agrees well with the concept of locally multiply damaged sites (LMDS) produced from clusters of ionizations in DNA (Ward 1985).

Reliability Assessment of 3-D Space Frame Structures Applying Stochastic Finite Element Analysis

Throughout design development of satellite structure, stress engineer is usually challenged with randomness in applied loads and material properties. To overcome such problem, a risk-based design is applied which estimates satellite structure probability of failure under static and thermal loads. Determining probability of failure can help to update initially applied factors of safety that were used during structure preliminary design phase. These factors of safety are related to the satellite mission objective. Sensitivity-based analysis is to be implemented in the context of finite element analysis (probabilistic finite element method or stochastic finite element method (SFEM)) to determine the probability of failure for satellite structure or one of its components.

R-matrix Floquet theory of multiphoton processes:XIII. Resonances in H multiphoton detachment

The results of calculations investigating the effects of autodetaching resonances on the multiphoton detachment spectra of H are presented. The R-matrix Floquet method is used, in which the coupling of the ion with the laser field is described non-perturbatively. The laser field is fixed at an intensity of 10 W cm, while frequency ranges are chosen such that the lowest autodetaching states of the ion are excited through a two- or three-photon transition from the ground state. Detachment rates are compared, where possible, to previous results obtained using perturbation theory. An illustration of how non-lowest-order processes, involving autodetaching states, can lead to light-induced continuum structures is also presented. Finally, it is demonstrated that by using a frequency connecting the 1s and 2s states, the probability of exciting the residual hydrogen atom is significantly enhanced.

Animal group forces resulting from predator avoidance and competition minimization

A new model to explain animal spacing, based on a trade-off between foraging efficiency and predation risk, is derived from biological principles. The model is able to explain not only the general tendency for animal groups to form, but some of the attributes of real groups. These include the independence of mean animal spacing from group population, the observed variation of animal spacing with resource availability and also with the probability of predation, and the decline in group stability with group size. The appearance of "neutral zones" within which animals are not motivated to adjust their relative positions is also explained. The model assumes that animals try to minimize a cost potential combining the loss of intake rate due to foraging interference and the risk from exposure to predators. The cost potential describes a hypothetical field giving rise to apparent attractive and repulsive forces between animals. Biologically based functions are given for the decline in interference cost and increase in the cost of predation risk with increasing animal separation. Predation risk is calculated from the probabilities of predator attack and predator detection as they vary with distance. Using example functions for these probabilities and foraging interference, we calculate the minimum cost potential for regular lattice arrangements of animals before generalizing to finite-sized groups and random arrangements of animals, showing optimal geometries in each case and describing how potentials vary with animal spacing. (C) 1999 Academic Press.</p>

Solution-based synthesis of cobalt-doped ZnO thin films

Undoped and cobalt-doped (1-4 wt.%) ZnO polycrystalline, thin films have been fabricated on quartz substrates using sequential spin-casting and annealing of simple salt solutions. X-ray diffraction (XRD) reveals a wurzite ZnO crystalline structure with high-resolution transmission electron microscopy showing lattice planes of separation 0.26 nm, characteristic of (002) planes. The Co appears to be tetrahedrally co-ordinated in the lattice on the Zn sites (XRD) and has a charge of + 2 in a high-spin electronic state (X-ray photoelectron spectroscopy). Co-doping does not alter the wurzite structure and there is no evidence of the precipitation of cobalt oxide phases within the limits of detection of Raman and XRD analysis. Lattice defects and chemisorbed oxygen are probed using photoluminescence and Raman spectroscopy - crucially, however, this transparent semiconductor material retains a bandgap in the ultraviolet (3.30-3.48 eV) and high transparency (throughout the visible spectral regime) across the doping range. © 2012 Elsevier B.V.

Stable isotope probing analysis of the influence of liming on root exudate utilization by soil microorganisms

Rhizosphere microorganisms play an important role in soil carbon flow, through turnover of root exudates, but there is little information on which organisms are actively involved or on the influence of environmental conditions on active communities. In this study, a (CO2)-C-13 pulse labelling field experiment was performed in an upland grassland soil, followed by RNA-stable isotope probing (SIP) analysis, to determine the effect of liming on the structure of the rhizosphere microbial community metabolizing root exudates. The lower limit of detection for SIP was determined in soil samples inoculated with a range of concentrations of C-13-labelled Pseudomonas fluorescens and was found to lie between 10(5) and 10(6) cells per gram of soil. The technique was capable of detecting microbial communities actively assimilating root exudates derived from recent photo-assimilate in the field. Denaturing gradient gel electrophoresis (DGGE) profiles of bacteria, archaea and fungi derived from fractions obtained from caesium trifluoroacetate (CsTFA) density gradient ultracentrifugation indicated that active communities in limed soils were more complex than those in unlimed soils and were more active in utilization of recently exuded C-13 compounds. In limed soils, the majority of the community detected by standard RNA-DGGE analysis appeared to be utilizing root exudates. In unlimed soils, DGGE profiles from C-12 and C-13 RNA fractions differed, suggesting that a proportion of the active community was utilizing other sources of organic carbon. These differences may reflect differences in the amount of root exudation under the different conditions.

Quantitative and qualitative trapping of arsines deployed to assess loss of volatile arsenic from paddy soil

Arsenic volatilization in the environment is thought to be an important pathway for transfer from terrestrial pools to the atmosphere. However, this phenomenon is not well characterized due to inherent sampling issues in trapping, quantifying and qualifying these arsine gases; including arsine (AsH(3)), monomethyl arsine (MeAsH(2)), dimethyl arsine (Me(2)AsH) and trimethyl arsine (TMAs). To quantify and qualify arsines in air we developed a novel technique based on silver nitrate impregnated silica gel filled tubes. The method was characterized by measuring the recovery of trapped arsines after elution of this chemo-trap with hot boiling diluted nitric acid. Results from three separate experiments, measured by ICP-MS, showed that the method is reproducible and quantitative. Arsine species recovery ranged from 80.1 to 95.6%, with limit of detection as low as 3.8 ng per chemo-trap tube. Moreover, HPLC-ICP-MS analysis of hot boiling water eluted traps showed that the corresponding oxy ions of the arsines were formed with the As-C bonds of the molecule intact, hence, allowing qualification of trapped arsine species. A microcosm study examining volatile arsenic evolution from field contaminated Bangladeshi paddy soils (24.2 mg/kg arsenic) was used to show the application of silver nitrate chemo-trapping approach. Traps were placed on the inlet and the outlet of microcosms containing the soils that were either (cattle derived) manured or not, or flooded or not, in a factorial design. The headspace was purged with air at a flow rate of 12 mL/min. Results showed that as much as 320 ng of arsenic (0.014% of total soil content) could be emitted in a 3 week period for manured and flooded soils and that TMAs was the dominant species evolved, with lesser quantities of Me(2)AsH. No volatile arsenic evolution was observed for nonmanured treatments, and arsine release from the nonflooded, manured treatment was much less than the flooded treatment.

Postglacial dispersal, rather than in situ glacial survival, best explains the disjunct distribution of the Lusitanian plant species Daboecia cantabrica (Ericaceae)

Aim:

The distribution of the Lusitanian flora and fauna, species which are found only in southern and western Ireland and in northern Spain and Portugal but which are absent from intervening countries, represents one of the classic conundrums of biogeography. The aim of the present study was to determine whether the distribution of the Lusitanian plant species Daboecia cantabrica was due to persistence in separate Irish and Iberian refugia, or has resulted from post-glacial recolonization followed by subsequent extinction of intervening populations.

Location:

Northern Spain and Co. Galway, western Ireland.

Methods:

Palaeodistribution modelling using Maxent was employed to identify putative refugial areas for D. cantabrica at the Last Glacial Maximum (LGM). Phylogeographical analysis of samples from 64 locations in Ireland and Spain were carried out using a chloroplast marker (atpB–rbcL), the nuclear ITS region, and an anonymous nuclear single-copy locus.

Results:

The palaeodistribution model indicated areas with a high probability of survival for D. cantabrica at the LGM off the western coast of Galicia in Spain, and in the Bay of Biscay. Spanish populations exhibited substantially higher genetic diversity than Irish populations at all three loci, as well as geographical structuring of haplotypes within Spain consistent with divergence in separate refugia. Spanish populations also exhibited far more endemic haplotypes. Divergence time between Irish and Spanish populations associated with the putative Biscay refugium was estimated as 3.333–32 ka.

Main conclusions:

Our data indicate persistence by D. cantabrica throughout the LGM in two separate southern refugia: one in western Galicia and one in the area off the coast of western France which now lies in the Bay of Biscay. Spain was recolonized from both refugia, whilst Ireland was most likely recolonized from the Biscay refugium. On the balance of evidence across the three marker types and the palaeodistribution modelling, our findings do not support the idea of in situ survival of D. cantabrica in Ireland, contrary to earlier suggestions. The fact that we cannot conclusively rule out the existence of a small, more northerly refugium, however, highlights the need for further analysis of Lusitanian plant species.

Comparing poverty and deprivation dynamics:Issues of reliability and validity

In this paper we seek to establish if earlier findings relating to the relationship between income poverty persistence and deprivation persistence could be due to a failure to take measurement error into account. To address this question, we apply a model of dynamics incorporating structural and error components. Our analysis shows a general similarity between latent poverty and deprivation dynamics. In both cases we substantially over-estimate the probability of exiting from poverty or deprivation. We observe a striking similarity across dimensions for both observed and latent outcomes. In both cases levels of poverty and deprivation persistence are higher for the latent case. However, there is no evidence that earlier results relating to the differences in the determinants of poverty and deprivation persistence are a consequence of differential patterns of reliability. Taking measurement error into account seems more likely to accentuate rather than diminish the contrasts highlighted by earlier research. Since longitudinal differences relating to poverty and deprivation cannot be accounted for by measurement error, it seems that we must accept that we are confronted with issues relating to validity rather than reliability. Even where we measure these dimensions over reasonable periods of time and allow for measurement error, they continue to tap relatively distinct phenomenon. Thus, if measures of persistent poverty are to constitute an important component of EU social indicators, a strong case can be made for including parallel measures of deprivation persistence and continuing to explore the relationship between them. © Springer Science+Business Media, Inc. 2006.

Catalytic performance of sheet-like Fe/ZSM-5 zeolites for the selective oxidation of benzene with nitrous oxide

Hierarchical Fe/ZSM-5 zeolites were synthesized with a diquaternary ammonium surfactant containing a hydrophobic tail and extensively characterized by XRD, Ar porosimetry, TEM, DRUV-Vis, and UV-Raman spectroscopy. Their catalytic activities in catalytic decomposition of NO and the oxidation of benzene to phenol with NO as the oxidant were also determined. The hierarchical zeolites consist of thin sheets limited in growth in the b-direction (along the straight channels of the MFI network) and exhibit similar high hydrothermal stability as a reference Fe/ZSM-5 zeolite. Spectroscopic and catalytic investigations point to subtle differences in the extent of Fe agglomeration with the sheet-like zeolites having a higher proportion of isolated Fe centers than the reference zeolite. As a consequence, these zeolites have a somewhat lower activity in catalytic NO decomposition (catalyzed by oligomeric Fe), but display higher activity in benzene oxidation (catalyzed by monomeric Fe). The sheet-like zeolites deactivate much slower than bulk Fe/ZSM-5, which is attributed to the much lower probability of secondary reactions of phenol in the short straight channels of the sheets. The deactivation rate decreases with decreasing Fe content of the Fe/ZSM-5 nanosheets. It is found that carbonaceous materials are mainly deposited in the mesopores between the nanosheets and much less so in the micropores. This contrasts the strong decrease in the micropore volume of bulk Fe/ZSM-5 due to rapid clogging of the continuous micropore network. The formation of coke deposits is limited in the nanosheet zeolites because of the short molecular trafficking distances. It is argued that at high Si/Fe content, coke deposits mainly form on the external surface of the nanosheets. © 2012 Elsevier Inc. All rights reserved.