Public policies should reflect and accommodate as much as possible citizens’ preferences and values. However, it is dicult to know the correct value citizens place on public goods as they are not generally exchanged in the marketplace. For this reason,
non market valuation is increasingly considered to be an important tool for informing policy decisions. In this context, Contingent Valuation (CV) and Discrete Choice Experiments (DCE) are probably the most widely used tools to analyse Stated preferences and retrieve people’s Willingness to Pay (WTP) for improving a particular environmental amenity. Since its introduction as a technique of non-market valuation, the number of CV studies published in peer reviewed journals consistently increased for more than three decades. Then, since the mid to late 1990s, the CV technique has been largely substituted by the DCE method.

Having reviewed the literature, it was decided to focus my Phd on DCE method. Notwithstanding the importance of CV as a useful tool for preference elicitation, DCE proved more appealing, as recent literature have identified a number of exciting research
avenues from a methodological and econometric point of view.
Therefore, the PhD has been mainly focused on developing new tools for accommodating heterogeneity in tastes, variances and heuristics employing Latent Class (LC) analysis. As a result, I formalised a class of LC models that can accommodate heteroscedasticity and/or heterogeneity (depending on assumptions and parameterisation) within each class as well as dierent heuristics across classes. The three essays collected
in this thesis represent the main outcome of this research.

More specifically the first paper, on urban land use, introduces class heterogeneity within a LC model. This is obtained by specifying a discrete mixture of sets of continuous distributions. The model is applied to both simulated and real data in order to
demonstrate its flexibility and the advantages for policy appraisal.

The second paper introduces and formalises the idea of a heteroscedastic LC model using data from a recreational site choice study elicited through stated preference methods
to compare various model specifications. Results show that model fit, welfare estimates and choice predictions are sensitive to the manner in which both types of heterogeneity are accommodated for. This is done in WTP-space to directly compare estimates from continuous and discrete mixture representations as well as to demonstrate the importance of including the scale parameter even under this reparameterisation.

In the third and final paper, on species preservation, the well known problem of preference and variance instability due to learning and fatigue in DCE is tackled by applying a scale-adjusted latent class model to uncover both types of instability simultaneously and probabilistically across the sample. Findings highlight the advantages, in terms of model fit, interpretation and policy implications, that can be achieved when both types
of instability are addressed concurrently. Data collected to estimate the existence value of rare and endangered fish species in Ireland are utilised as an empirical case-study.

Finally conclusions and avenues for possible further research and future applications
of the presented models are drawn.

This paper introduces the discrete choice model-paradigm of Random Regret Minimization (RRM) to the field of health economics. The RRM is a regret-based model that explores a driver of choice different from the traditional utility-based Random Utility Maximization (RUM). The RRM approach is based on the idea that, when choosing, individuals aim to minimize their regret–regret being defined as what one experiences when a non-chosen alternative in a choice set performs better than a chosen one in relation to one or more attributes. Analysing data from a discrete choice experiment on diet, physical activity and risk of a fatal heart attack in the next ten years administered to a sample of the Northern Ireland population, we find that the combined use of RUM and RRM models offer additional information, providing useful behavioural insights for better informed policy appraisal.

The intense process of internationalisation of the food market is giving rise to new competitive scenarios. The growth of market shares by new export countries, along with other consumer and retailer's issues impose different marketing policies for agri-food products. In particular, a wider awareness of consumers for environmental and health issues is modifying the structure of demand for fresh products. In the past, the country of origin and a convenient quality/price ratio were the main strategic strengths for gaining and maintaining international market shares . Nowadays market shares are gained by moving towards new product attributes, namely environment friendliness and food safety. This paper aims to suggesting new and more successful marketing strategies. The case study is the German market of cherry tomatoes. An analysis of German consumer preference was performed on stated choice data. Results provide interesting insights. Product attributes related to the environment are found to be relevant. As these are defined as "faith" attributes, we speculate that German consumers refer to product origin country as a proxy of its environmental aspects. Two separate competitive segments emerge, one with a higher level of environmental quality (Germany and Italy), and Turkey, Spain, France and Holland. Finally, results point out how policies need to be redesigned and focused on new and more complex issues expressed by consumers in modern and developed markets marketing.

Recently, Italian agriculture has been widely characterised by the increasing number of farms and land converting to organic farming. In the slow process of shifting from a "niche" to a broader consu mp tio n in the organic products market deep differences between conventional and organic production, distribution and consum ption became evident. In such a context, the consu me r's behaviour about organic products analysis transpires to be complex as it involves either social-economic and psychogra p hic characteristics. In order to address this issue a research has been carried out in two steps: in the first one, a qualitative analysis step, 45 consumer s of organic products were interviewed by phone using laddering techniques; then, in the second quantitative step, data from a 203 consumer s sample, representative of a region of South of Italy, was analysed by means of a multinomial logit. The research main innovative aspect resides in the two-step approach (qualitative -quantitative analysis), that enabled researchers to identify and quantify the environmental and hygienic compone n t importance in consu me r preferences on organic products.

Within the current Common Agricultural Policy (CAP) framework, Member States are obliged to evaluate their respective Rural Development Plans (RDPs). The aim of the evaluation is to verify the efficiency and efficacy of the implementation process, particularly in terms of integration of environmental issues in the agricultural policy. In this context, a more comprehensive evaluation method is needed, able to integrate in the analysis the spatial structure of the territory the intervention targets. Geographic Information Systems (GIS) have been widely considered a useful tool to encompass the spatial aspects in the evaluation process. GIS, in fact, are able to perform spatial analysis as well as estimate quantitative indicators with reference to different geographic frames. In this short paper we propose a GIS-based analysis of the effects of organic farming support scheme implementation and we report the results of an application of such a methodology. 1

This paper discusses how to develop and manage integration, coordination and cooperation (collective action) in bio-energy supply chains. Farmers decision on whether or not to participate in a contract farming scheme have been investigated, particularly assessing the
trade-offs between the contract attributes and their impact on the likelihood to participate. A stated preference model has been implemented where respondents were asked to choose
between alternative contracts with varying attribute levels to start biomass cultivation. Results show that participation is mainly influenced by minimum price guaranteed, contract length, and re-negotiation before the end of a contract.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Tolueneand naphthalene-dioxygenase-catalysed oxidation of six bicyclic disulfide substrates, using whole cells of Pseudomonas putida, gave the corresponding monosulfoxides with high ee values and enantiocomplementarity, in most cases. Two alcohol-sulfoxide diastereoisomers, formed from the reaction of the (R)-1,3-benzodithiole-1-oxide metabolite with n-butyllithium and benzaldehyde, were separated and stereochemically assigned. Treatment, of enantiopure (1R,3R)-benzo-1,3-dithiole-1,3-dioxide, obtained by chemoenzymatic synthesis, with alkyllithium reagents, resulted in a novel ring-opening reaction which proceeded with inversion of configuration to yield a series of acyclic disulfoxides. q

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A research element of the European Union (EU) sixth Framework project BioCop focused on the development of a surface plasmon resonance (SPR) biosensor assay for the detection of paralytic shellfish poisoning (PSP) toxins in shellfish as an alternative to the increasingly ethically unacceptable mouse bioassay. A biosensor assay was developed using both a saxitoxin binding protein and chip surface in tandem with a highly efficient simple extraction procedure. The present report describes the single laboratory validation of this immunological screening method, for this complex group of toxins with differing toxicities, according to the European Decision 2002/ 657/EC in conjunction with IUPAC and AOAC single laboratory validation guidelines. The different performance characteristics (detection capability CC , specificity/selectivity, repeatability, reproducibility, stability, and applicability) were determined in relation to the EU regulatory limit of 800 µg of saxitoxin equivalents (STX eq) per kg of shellfish meat. The detection capability CC was calculated to be 120 µg/kg. Intra-assay repeatability was found to be between 2.5 and 12.3% and interassay reproducibility was between 6.1 and 15.2% for different shellfish matrices. Natural samples were also evaluated and the resultant data displayed overall agreements of 96 and 92% with that of the existing AOAC approved methods of mouse bioassay (MBA) and high performance liquid chromatography (HPLC), respectively.

A surface plasmon resonance (SPR) optical biosensor method was developed for the detection of paralytic shellfish poisoning (PSP) toxins in shellfish. This application was transferred in the form of a prototype kit to seven laboratories using Biacore Q SPR optical biosensor instrumentation for interlaboratory evaluation. Each laboratory received 20 shellfish samples across a range of species including blind duplicates for analysis. The samples consisted of 4 noncontaminated samples spiked in duplicate with a low level of PSP toxins (240 μg STXdiHCl equivalents/kg), a high level of saxitoxin (825 μg STXdiHCl/kg), 2 noncontaminated, and 14 naturally contaminated samples. All 7 participating laboratories completed the study, and HorRat values obtained were <1 demonstrating that the method performance was acceptable. Mean recoveries expressed as STXdiHCl equivalents/kg were 94.6 ( 16.8% for the low level PSP toxin mix and 98.6 ( 5.6% for the high level of saxitoxin. Relative standard deviations for within-laboratory variations (RSD r : repeatability) and between-laboratory variations (RSD R = reproducibility) ranged from 1.8 to 9.6% and 2.9 to 18.3% respectively. This first ever reported SPR biosensor interlaboratory study demonstrated this PSP application to be an empowering tool in the drive toward the reduction and replacement of the mouse bioassay within Europe.

Saxitoxin and its analogs, the causative agents of paralytic shellfish poisoning (PSP), are a worldwide threat to seafood safety. Effective monitoring of potentially contaminated fishing areas as well as screening of seafood samples is necessary to adequately protect the public. While many analytical methods exist for detecting paralytic shellfish toxins (PSTs), each technique has challenges associated with routine use. One recently developed method [1] that overcomes ethical or performance-related issues of other techniques is the surface plasmon resonance (SPR) bioassay. Notwithstanding the advantages of this method, much research remains in optimizing the sensor substrate and assay conditions to create a robust technique for rapid and sensitive measurement of PSTs. This manuscript describes a more rigorous and stable SPR inhibition immunoassay through optimization of the surface chemistry as well as determination of optimum mixture ratios and mixing times. The final system provides rapid substrate formation (18 h saxitoxin conjugation with low reagent consumption), contains a reference channel for each assay, and is capable of triplicate measurements in a single run with detection limits well below the regulatory action level.

Paralytic shellfish poisoning (PSP) toxins are produced by certain marine dinoflagellates and may accumulate in bivalve molluscs through filter feeding. The Mouse Bioassay (MBA) is the internationally recognised reference method of analysis, but it is prone to technical difficulties and regarded with increasing disapproval due to ethical reasons. As such, alternative methods are required. A rapid surface plasmon resonance (SPR) biosensor inhibition assay was developed to detect PSP toxins in shellfish by employing a saxitoxin polyclonal antibody (R895). Using an assay developed for and validated on the Biacore Q biosensor system, this project focused on transferring the assay to a high-throughput, Biacore T100 biosensor in another laboratory. This was achieved using a prototype PSP toxin kit and recommended assay parameters based on the Biacore Q method. A monoclonal antibody (GT13A) was also assessed. Even though these two instruments are based on SPR principles, they vary widely in their mode of operation including differences in the integrated -fluidic cartridges, autosampler system, and sensor chip compatibilities. Shellfish samples (n = 60), extracted using a simple, rapid procedure, were analysed using each platform, and results were compared to AOAC high performance liquid chromatography (HPLC) and MBA methods. The overall agreement, based on statistical 2 × 2 comparison tables, between each method ranged from 85% to 94.4% using R895 and 77.8% to 100% using GT13A. The results demonstrated that the antibody based assays with high sensitivity and broad specificity to PSP toxins can be applied to different biosensor platforms.

The incorporation of melamine into food products is banned but its misuse has been widely reported in both animal feeds and food. The development of a rapid screening immunoassay for monitoring of the substance is an urgent requirement. Two haptens of melamine were synthesized by introducing spacer arms of different lengths and structures on the triazine ring of the analyte molecular structure. 6-Aminocaproic acid and 3-mercaptopropionic acid were reacted with 2-chloro-4,6-diamino-1,3,5-triazine (CAAT) to produce hapten 1 [3-(4,6-diamino-1,6-dihydro-1,3,5-triazin-2-ylamino) hexanoic acid] and hapten 2 [3-(4,6-diamino-1,6-dihydro-1,3,5-triazin-2-ylthio) propanoic acid], respectively. The molecular structures of the two haptens were identified by 1 H nuclear magnetic resonance spectrometry, mass spectrometry and infrared spectrometry. An immunogen was prepared by coupling hapten 1 to bovine serum albumin (BSA). Two plate coating antigens were prepared by coupling both haptens to egg ovalbumin (OVA). A competitive indirect enzyme-linked immunosorbent assay (ciELISA) was developed to evaluate homogeneous and heterogeneous assay formats. The results showed that polyclonal antibodies with high titers were obtained, and the heterogeneous immunoassay format demonstrated a better performance with an IC 50 of 70.6 ng mL −1 , a LOD of 2.6 ng mL −1 and a LOQ of 7.6 ng mL −1 . Except for cyromazine, no obvious cross-reactivity to common compounds was found. The data showed that the hapten synthesis was successful and the resultant antisera could be used in an immunoassay for the rapid and sensitive detection of this banned chemical.

A fluorescence polarization immunoassay (FPIA) based on a polyclonal antibody was developed for the determination of melamine in milk. To obtain an antibody with improved sensitivity and specificity, 6-hydrazinyl-1,3,5-triazine-2,4-diamine was coupled to bovine serum albumin and used as the immunogen for the rabbit immunization. Three fluorescein-labeled melamine tracers with different structures and spacer bridges were synthesized. The structural effect of the tracers on the assay characteristics was investigated. 6-(4,6-Diamino-1,3,5-triazin-2-ylamino)-N-(2-(3-(3′,6′-dihydroxy-3-oxo-2,3-dihydrospiro[indene-1,9′-xanthene]-5-yl)thioureido)ethyl)hexanamide demonstrated better sensitivity than 5-(2-(4,6-diamino-1,3,5-triazin-2-yl)hydrazinecarbothioamido)-2-(6-hydroxy-3-oxo-3H-xanthen-9-yl)benzoic acid and 3-(4,6-diamino-1,3,5-triazin-2-ylthio)-N-(2-(3-(3′,6′-dihydroxy-3-oxo-3H-spiro[isobenzofuran-1,9′-xanthene]-5-yl)thioureido)ethyl)propanamide. The limit of detection (10% inhibition) of the FPIA was 9.3 ng mL-1 and the IC50 (50% inhibition) value was 164.7 ng mL-1. The antibody in the FPIA showed 21.2% cross-reactivity to the fly-killing insecticide cyromazine, but had no cross-reactivity to other natural structurally related compounds. Recoveries, measured in spiked milk and milk powder samples, ranged from 79.4 to 119.0%. Milk samples fortified with melamine were analyzed by this method and confirmed by high-performance liquid chromatography–mass spectrometry. Excellent recoveries and correlation with spiked levels were observed, suggesting that this immunoassay could be applied to the screening of melamine residues in milk and milk powder after a simple dilution procedure. Figure Figure Performance comparison of tree tracers and two antibodies. (a), antibody A; (b) antibody B