Les mesures analítiques i els instruments que les generen poden classificar-se en funció del numero de dades que s'obtenen al mesurar una mostra. Si s'obté una matriu de respostes, s'anomenen dades d'ordre dos.En aquesta tesi es van utilitzar els dades d'ordre dos, obtingudes mitjançant un cromatògraf líquid d'alta resolució amb un detector de diodes en fila (DAD).L'instrument HPLC-DAD és força comú. Tot i això, normalment, per determinar la concentració dels analits d'interès no s'utilitzen totes les dades enregistrades per l'instrument. El mode espectral només s'utilitza per identificar els analits o per verificar la puresa dels pics, mentre que l'àrea o l'alçada del pic s'utilitza per quantificar mitjançant calibratge univariant. Aquesta manera de treballar és molt útil sempre i quan la resposta mesurada sigui selectiva per l'analit d'interès.En analitzar contaminants ambientals en mostres complexes, com poden ser mostres d'aigua de riu, no és senzill obtenir mesures selectives. Quan les respostes no son selectives, els mètodes de calibratge de segon ordre (els que utilitzen dades de segon ordre) es poden utlitzar per a quantificar l'analit d'interès.La present tesi es basa en l'estudi de les propietats del mètode de calibratge de segon ordre Generalized Rank Annihilation Method (GRAM). Aquest mètode fou desenvolupat a mitjans de la dècada dels 80, i té unes propietats molt atractives:1) Per a determinar la concentració de l'analit d'interès en una mostra test només cal una mostra de calibratge o estàndard.2) No calen mesures selectives, amb la qual cosa el temps de la separació es pot reduir de manera considerable.Tot i això, el GRAM té una sèrie de limitacions que fan que no s'apliqui de manera rutinària. L'objectiu de la tesi és estudiar els avantatges i les limitacions del GRAM i millorar els aspectes necessaris per a què és pugui aplicar de manera rutinària.Per emprar GRAM les dades experimentals han de complir una sèrie de requisits matemàtics: (i) la resposta mesurada ha de ser suma de respostes corresponents als diferents analits i (ii) la resposta d'un analit ha de ser proporcional en les diferents mostres: l'analit ha d'eluir exactament al mateix temps de retenció tant en l'estàndard com en la mostra test. Si aquest requisit no es compleix, les prediccions del GRAM son esbiaixades.S'han desenvolupat fórmules de superar aquestes dificultats. S'ha desenvolupat un mètode per alienar pics cromatogràfics, basat en un mètode de resolució de corbes (Iterative Target Transformation Factor Analysis, ITTFA). En sistemes HPLC-DAD, és força habitual que els pics de l'analit d'interès elueixin a diferents temps de retenció.Les diferencies no son gaire grans (pocs segons) però poden ser suficients per fer que els resultats del GRAM siguin incorrectes.El GRAM és un mètode basat en factors, i cal introduir aquest paràmetre per a calcular un model. S'ha desenvolupat un mètode gràfic per a triar el nombre de factors que s'utilitzen per calcular el model GRAM. Està basat en un paràmetre de l'algorisme GRAM (á).Finalment s'ha desenvolupat un criteri per a determinar mostres discrepants (outliers).El criteri desenvolupat per detectar outliers està basat en el Senyal Analític Net (NAS).Tot l'esmentat anteriorment, s'ha aplicat a casos reals, en concret a l'anàlisi de naftalensulfonats i de contaminats polars presents en mostres d'aigua, tant de riu com de depuradora. Així s'ha pogut demostrar la utilitat del GRAM a la cromatografia, i comparar el GRAM amb altres mètodes de calibratge de segon ordre com el PARAFAC i MCR-ALS. Es va trobar que tots tres mètodes produïen resultats comparables. / Analytical measurements and the instruments that generate them can be classified regarding the number of data that are obtained when a sample is measured. When a matrix of response is obtained, it is known as second-order data.In this thesis, second-order data were used, obtained from a high performance liquid chromatography (HPLC) couple with a diode array detector (DAD). This instrument is quite common in the analytical laboratories. However, the concentration of the analytes of interest is normally found without using all the measured data. The spectral model only is used to identify the analytes of for verifying the peak purity, whereas the area or the height of the peak is used to quantify using univariate calibration. This is a very useful strategy. However, the measured response must be selective to the analyte of interest.When environmental pollutants were analyzed, like water samples, it is no so easy to get selective measurements. When the responses are not selective, the analyte on interest can still be quantified by using second-order calibration methods, which are the methods that use second-order data.This thesis is based on the study of the properties of the second-order calibration method Generalized Rank Annihilation Method (GRAM).This method was developed in the mid eighties and has very attractive properties:1) To determine the concentration of the analyte of interest in a test sample, it is only necessary one calibration sample or standard.2) Selective measurements are not necessary, implying the reduce of the separation time.Despite these advantages, GRAM has some limitations which make that it is not applied routinely. The objectives of the thesis are to study the advantages and limitations of GRAM and improve the negative points in order to apply GRAM routinely.To use GRAM the experimental data must accomplish some mathematical requirements: (i) the measured response must be result of the addition due to the different analytes in the peak and (ii) the response of the analyte must be proportional in the different samples: the analyte of interest must elute at the same retention time both in the calibration and in the test sample. When these conditions are not met, the GRAM predictions are biased.Mathematical algorithms have been developed to overcome such difficulties. An algorithm to align chromatographic peaks has been developed, based on curve resolution method (Iterative Target Transformation Factor Analysis, ITTFA). In HPLCDAD systems is quite often that the peaks of the analyte of interest elute at different retention time in the calibration and in the test sample. Even the differences are not big (few seconds), they can be enough to make the GRAM results incorrect.GRAM is a factor based calibration method, and the number of factors has to be introduced as an input to build a GRAM method. A graphical criterion has been selected to determine the number the number of factors, which is base on the use of a parameter of the GRAM algorithm (á).Finally, a criterion to detect outlying samples has been developed, which is based on the Net Analyte Signal (NAS).All the above commented were applied to real cases. Specifically to the analysis of aromatic sulfonates and polar pollutants in water form river samples and waste water plants. We were able to show the applicability of GRAM and to compare GRAM with other second-order calibration methods, such as PARAFAC i MCR-ALS. We found that the three methods provided comparable results.

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Black-Scholes Model is a widely used mathematical model for stock price behaviors, of which the return is assumed to be normally distributed. But this 'normally distributed' assumption is doubted and proved to be not true by realistric data. The main goal of this thesis is to explore polynomial-normal distribution, and use this distribution in the stock return, as a non-normal extension of the Black-Scholes Model. We will develop the properties of polynomial-normal distribtuion in the thesis, and also give the European call and put option price formulas under this model, and show how to use this model to estimate real stock returns.

Bacteriophage (phage), virus of bacteria, has been proposed as a mean to inactivate bacteria that are pathogens of humans. Applied prophylatically to food, phage might decrease the numbers of potential pathogens we ingest. Much active research on using the phages of bacteria to control Gram negative foodborne pathogens are described in the literatures, but comparatively little research describes the phages of Gram positive bacteria and their use as biocontrol agents on food. In this work, previous undescribed phages, able to infect Bacillus cereus and Listeria monocytogenes, were isolated from soil and ruminants faecal material, respectively. As the first step in assessing their potential as biocontrol agents, the isolated phages were purified, concentrated and characterised (albeit to different degrees). The Bacillus phages had a narrow host range while the Listeria phages had a broad host range. Listeria phages also infected L. monocytogenes 2000/47, a strain which recurs in New Zealand clinical cases. Both Bacillus and Listeria phages appeared to be of the Myoviridae family judging by their structure in electron micrographs. The Bacillus FWLBc1 and FWLBc2 phages were lytic phages with a latent period of 106 and 102 min at 37°C, and an average burst size of 322 and 300 phages per infected cell, respectively. Moreover, they both had genomes of approximately 134 kb. All newly isolated and characterized phages were chloroform resistant and survived storage better at 4°C than at room or freezing temperatures. Bacillus phages significantly reduced the bacterial population in mashed potatoes within 24 h at room temperature, when applied at a phage to host ratio of 1000. Listeria phages rapidly inactivated the host population to a low optical density. The findings of this thesis will add to the current knowledge of phages in the context of various environmental conditions for different bacteria and will demonstrate the potential of phages as food safety biocontrol agents.

Thesis (doctoral)--University of Helsinki, 2007. / Includes bibliographical references. Also available on the World Wide Web.

Thesis (M. Med. Sc.)--University of Hong Kong, 2007.

Thesis (M. Med. Sc.)--University of Hong Kong, 2008. / Includes bibliographical references (p. 23-34)

Thesis (M.S.)--Rochester Institute of Technology, 1990. / Includes bibliographical references (leaves 46-48).

Thesis--Washington University (St. Louis). / Musical examples: p. 1-93 (2d group). eContent provider-neutral record in process. Description based on print version record. Bibliography: p. 167-173.