OAR@UM Collection:

A study of the ionic salt effect upon the photosubstitution reaction between 1,4-dicyanobenzene and 2,3-dimethyl-2-butene

2023-10-05T08:05:42Z

Title: A study of the ionic salt effect upon the photosubstitution reaction between 1,4-dicyanobenzene and 2,3-dimethyl-2-butene Abstract: The photosubstitution reaction between 1,4-dicyanobenzene and 2,3-dimethyl-2-butene was re-investigated with respect to three aspects: irradiation in the presence of the photosensitizer biphenyl; irradiation in the presence of magnesium perchlorate; and irradiation in the presence of both biphenyl and magnesium perchlorate. The photosensitization of this reaction mixture by biphenyl was observed to increase the efficiency and the yield of the products, 1-(4-cyanophenyl)-2,3- dimethyl-2-butene and 3-(4-cyanophenyl)-2,3-dimethyll-butene. The ratio of the products which normally is 1:2 in favour of the terminal alkene changed drastically to 1:18 upon the addition of magnesium perchlorate to the reaction mixture. This dramatic change in product ratio was attributed to the lack of protonation to the 1,4- dicyanobenzene radical anion, a key step in a previously proposed mechanism. It is proposed that this is a result of coordination of the radical anion to the magnesium cation. Description: B.SC.(HONS)

Optimisation of analytical methodology through proficiency testing schemes : trace metal analysis

2023-07-05T07:24:16Z

Title: Optimisation of analytical methodology through proficiency testing schemes : trace metal analysis Abstract: Accurate and precise methods for the determination of trace metals in biological fluids were devised using graphite furnace atomic absorption spectrometry with Zeeman background correction. The five different trace metals investigated were aluminium in plasma and dialysis water, lead in whole blood, and copper, selenium and zinc in bovine serum. For zinc, flame atomic absorption spectrometry was also performed to compare the two methods. For all metals, the methods were based on an appropriate dilution with a mixture of 0.2% Triton X-100 with 0.2% antifoam B. The technique of standard addition was employed to eliminate matrix effects which were present. A palladium (II) chloride modifier was found to be the best modifier in comparison to others as it gave optimum results for lead, copper and selenium. The precision of the results obtained was quite high with %RSD values of<5%. To validate the methods used for the determination of trace metals in biological fluids by GF AAS our laboratory took part in three separate interlaboratory comparison schemes. One scheme was for aluminium, another for lead and the other covering copper, selenium and zinc together. The aim of these interlaboratory testing schemes was to demonstrate the validity of the analytical methods which were devised. The numbers of participants were always greater than 20 in each of these schemes. These numbers were large enough to ensure that the results of the statistical analysis were reliable. The overall results obtained were sufficient for all the metals. Description: B.SC.(HONS)

Interferon-ɑ and sickness behaviour : a study of the dose and time dependency of interferon-ɑ-induced anhedonia and fever

2023-07-05T07:23:29Z

Title: Interferon-ɑ and sickness behaviour : a study of the dose and time dependency of interferon-ɑ-induced anhedonia and fever Abstract: The use of recombinant human Interferon-ɑ2A for the treatment of more than 14 malignancies and virologic diseases is acknowledged world-wide, in over 40 countries. However, its use has been hampered by the many side effects accompanying its therapy, of which depression and suicidal ideations are the extreme cases. Significant research effort has gone into understanding the neural and molecular mechanisms of action of this cytokine, but to date there exist gaps in our understanding of the underlying fine mechanistic details. The side effects of Interferon-a can be described as typical Sickness Behaviour (a coordinated set of behavioural changes that develop in sick individuals during the course of an infection). A Model of Anhedonia was used as the paradigm within which to test and investigate the dose and time dependency of the effects of recombinant human Interferon-a2A (rHIFN-ɑ2A)· The species-specificity of rHIFN-ɑ2A in rats was also studied within this paradigm. The effects of IFN on temperature were used to monitor the activity of the drug in the rats, while anhedonia (measured as a change in the consumption and preference for 1%, 8% and 32% sucrose solutions) was used to assess the impact of IFN on positive reinforcement. From the results obtained rHIFN-ɑ2A was confirmed to be 100 to 1000 times less potent than rat interferon-ɑA (RIFN-ɑA) in rats. More importantly, new insights into the mechanisms of action of rHIFN-ɑ2A on anhedonia and fever were suggested. However, the whole picture is far from complete and this project just represents a first attempt to improve our knowledge of Interferon neurochemistry. This and future studies could eventually lead to the development of appropriate drugs that dampen the undesirable side effects of Interferon-ɑ therapy, allowing patients to make full use of an otherwise effective therapy. Description: B.SC.(HONS)CHEMISTRY&BIOLOGY

Vegetational and other changes at il-Ballut saline marshland : a nature reserve in the making

2023-05-03T13:11:40Z

Title: Vegetational and other changes at il-Ballut saline marshland : a nature reserve in the making Abstract: The historical development of il-ballut saline marshland in Marsaxlokk, together with the recent habitat engineering works as part of a plan to turn the area into a nature reserve, has given rise to three clearly distinguishable sub-regions. These are the saltmarsh itself, which developled from the remains of what once formed a system of fishponds, an abandoned field on the northern side of the marsh, and a recently reclaimed area to the east of this marsh. The distributional pattern of the vegetation of the saltmarsh, is determined by marsh elevation, type of substratum, hydrology of the area over the past few years, and disturbance by human activity. Human interference has also influenced the distribution of the dominant perennial Inula crithmoides and the dominant annual Salsola soda, on the abandoned field. The habitat engineering works, on the reclaimed area created a bare area which was rapidly colonized by a variety of species, the greater part of which were ruderals. The rate and extent of colonization over this area by these species, was largely determined by rainwater floods and differences in soil compactness as a result of the more recent access by heavy vehicles to the region. Description: B.SC.(HONS)