A study of stellar atmosphere models and the photometric quantity R is presented here, with R being the ratio of the integrated de-reddened fluxes from the two wavelength regions of the International Ultraviolet Explorer (IUE) satellite cameras. The effective temperatures and surface gravities of the stellar atmospheres were calibrated against R and absolute magnitude, using stellar evolution tracks from the literature, and applied to over 156 LMC stars whose masses and mass function are then derived from the results. The results show that the effective temperatures and surface gravities of stars derived from R and absolute magnitude correlate well with those found in the literature. The slope of the initial mass function (IMF) is Gamma = -2.31 for masses 85 Msun > M > 15 Msun. The correlation with R and apparent magnitude could prove useful in better determining the high mass portion of the IMF.

Part I There is some observational evidence of the presence of a pulsating light source in the remnant of the supernova (SN) 1987A [1]. This source is considered to be a rotating neutron star. Fourier analysis of the light intensity of this source reveals a main narrow frequency peak and side bands that are understood as a modulation of the main sinusoidal signal. A particular model of the neutron star invokes a precessing object to explain the modulation. From the Fourier spectrum of the source and changes in the frequency value, we can determine important parameters of the spinning neutron star as rotation frequency, precession frequency and spin-down rate. The neutron star is believed to spin down due to the emission of gravitational waves. We give a precise calculation of the strain value of the gravitational waves reaching earth and discuss the possibility of detection of this radiation by existing and soon on line gravitational waves detectors. Our conclusion is that just a few days of integration time will be sufficient to detect the signal using the next generation detectors as LIGO II. Part II Historically, in the search for burst signals, the ALLEGRO Gravitational Group used a matched filter constructed in the time domain, and with the particular characteristic of separating the information from the two resonant modes of the bar. The information from the two resonant modes is treated separately until the end when the total energy of the response of the bar is estimated, summing each mode output (we call this filter partially matched). We developed a filter (called fully matched) that doesn't separate the two resonant modes and treats the two modes system as a whole. This filter is constructed in the Fourier domain. We compared the performance of partially matched filter with the fully matched filter applying both filters to simulated and real data. The main conclusion is that even in the one mode case, but particularly in the two modes case, the fast filter is more efficient than the slow filter. In addition, we attempt also to explain why the fully matched is a better filter than the partially matched filter.

Aerosol transport in confined spaces was studied via numerical simulation using the dynamic aerosol equation, which is Boltzmann?s transport equation at the hydrodynamic limit. Until recent years, there existed no comprehensive computational tool to predict the spatial distribution and time evolution of aerosol size spectrum. A previously developed code, INDASOL3D, solves the dynamic aerosol equation by using a homogenized control-volume based finite difference method applying the group sectional method on the coagulation dynamics. However, quantitative correctness has not been satisfactory. In this thesis, two new codes (SAEROSA, and CAEROT) were developed. SAEROSA computes the time evolution of the size spectrum in a spatially homogenized aerosol due to coagulation and deposition with user defined arbitrary group sectionalization. CAEROT computes space and time dependent aerosol size spectrum in an enclosed space by solving the lumped parameter integral transport equation along stream tubes. Compared to INDASOL3D, more comprehensive aerosol physics and improved numerical methods were included into CAEROT to resulting in a better prediction. SAEROSA was benchmarked against an existing code, MAEROS, while CAEROT was validated against experimental data obtained at the LSU Nuclear Science Center. Both codes give good results quantitatively and qualitatively.

Ionic complexes between gold and C60 have been observed for the first time. Cations and anions of the type [Au(C60)2]+/- are shown to have particular stability. Calculations suggest that these ions adopt a C60-Au-C60 sandwich-like (dumbbell) structure, which is reminiscent of [XAuX]+/- ions previously observed for much smaller ligands. The [Au(C60)2]+/- ions can be regarded as Au(I) complexes, regardless of whether the net charge is positive or negative, but in both cases, the charge transfer between the Au and C60 is incomplete, most likely because of a covalent contribution to the Au-C60 binding. The C60-Au-C60 dumbbell structure represents a new architecture in fullerene chemistry that might be replicable in synthetic nanostructures. ©

A study of deoxyadenosine crystals (anhydrous form) after irradiation at 10 K found four base-centered radicals and one sugar-centered radical. Radical R1, thermally stable to about 100 K and photobleachable easily with white light, was the product of deprotonation at the amino group by the primary radical cation. Radical R2, also thermally stable to about 100 K, was the product of protonation at N3 of the primary radical anion. Radical R3, stable to about 170 K, was centered in the deoxyribose moiety and evidently was the result of net hydrogen abstraction from C4'. Radicals R4 and RS were the C2 and C8 H-addition products with couplings typical of those species. Both R4 and R5 were formed at 10 K and were stable at room temperature. The behavior of R1 in several systems provides additional evidence for significant involvement of the hydrogen-bonding environment in controlling the stabilization (or formation) of radicals resulting directly from ionization, as described previously (Radiat. Res. 131, 272-284, 1992). From comparison of amino-group hydrogen-bonding environments in which radicals with the structure of R1 were stabilized, we conclude that oxygen atoms as proton acceptors are important in permitting the charge and spin separation necessary for radical stabilization. In particular, oxygens of ROH structures seem most efficient by readily permitting a multi-proton shuffle through a mechanism amounting to proton exchange. The collective results show that stabilization of these products is unlikely unless the charge and spin can be separated by at least one intervening molecule.

Anhydrous single crystals of cytosine hydrochloride (protonated at N3) have been X-irradiated at 10 K and studied using K-band EPR, ENDOR and FSE spectroscopy. At least seven radicals were present at 10 K after X irradiation with a dose of about 150 kGy. Two different protonation states of the one-electron reduced cytosine cation were observed: an amino-protonated species (RI) and the pristine one-electron reduced species (R2) with zero net charge. Apparently three deprotonated versions of the one-electron oxidized cytosine cation were formed: the amino-deprotonated cation (R3), an N3- deprotonated cation (R4) and an N1-deprotonated cation (R5). Finally, two products formed by net hydrogen addition to the cytosine base were observed: a C5 hydrogen-addition radical (R6) and a C6 hydrogen-addition radical (R7). The crystalline lattice of cytosine hydrochloride is characterized in part by a cytosine base initially protonated at the N3-position, thus forming a cytosine base cation, and in part by an extended network of hydrogen bonding involving the chlorine anions. Proton transfer properties of pristine one- electron oxidation and reduction base products in this lattice are discussed and are suggested as explanations of the unusual multitude of positions for deprotonation of the one-electron oxidized species as well as for the two protonation states of the reduction product observed. The magnetic parameters for the amino-protonated species R1 agree well with those extracted from previous studies of cytosine derivatives in frozen solutions and in various glasses.

Single crystals of the co-crystalline complex of 1-methyl-uracil and 9- ethyladenine were X-irradiated and studied using EPR, ENDOR and FSE spectroscopic techniques at 10 K. All together seven radicals were identified, and experimental evidence for at least one more species, as well as for a very low population of radical pairs, is available. Oxidation and reduction products appear to be stabilized at both base constituents of the pair. Of the 1-methyluracil moiety, the product formed by net hydrogen abstraction from the methyl group was observed, together with the 1- methyluracil anion and the 1-methyluracil-5-yl radical. From the 9- ethyladenine moiety, the N3-protonated 9-ethyladenine anion is stabilized. In addition, the 9-ethyladenine cation as well as traces of the amino- deprotonated cation were observed, together with the C8-H hydrogen adduct. The presence of oxidation and reduction products in each of the two bases may indicate that negligible energy transfer takes place between them. This behavior is different from that observed in the similar pair of 1- methylthymine·9-methyladenine. There also seems to be minor proton exchange between the two stacks of molecules: Interbase protonation-deprotonation channeled through the hydrogen-bonding scheme seems to be almost completely suppressed.

Numerous sugar radicals have been observed by EPR and ENDOR spectroscopy in X-irradiated nucleosides and nucleotides. However, no sugar radicals have been observed in irradiated DNA. One possibility exists that sugar radicals may be present in relatively small abundance and therefore have so far escaped detection. Another possibility is that each of the five carbon- centered H-abstraction sugar radicals may exist in a wide range of conformations. Adding together various groups of radicals with different hyperfine couplings and anisotropic g factors may result in very broad EPR lines which would be difficult to detect. Using the crystal structure of a B- DNA dodecamer, the conformations of the five H-abstraction sugar radicals have been computed at all sites. The X-band EPR spectra for each radical were then simulated using typical α-proton and β-proton couplings computed from the various radical conformations. The results suggest considerable broadenings of the EPR lines for the C2, C3, H-abstraction radicals. Composite EPR spectra were simulated by adding 15% of an H-abstraction radical to the DNA spectrum. The results indicate that the outer lines of the C1, radical are visible and should be easy to identify. The broad spectra of the C2, and C3, radicals are barely visible. The simulated spectra of the C4, and C5, radicals are basically doublets and are obscured by the DNA signal.

Single crystals of the complex 1-methylthymine·9-methyladenine were X- irradiated at 10 and at 65 K and studied in the temperature range 10 to 290 K using K-band EPR, ENDOR and field-swept ENDOR (FSE) techniques. The EPR and ENDOR spectra are dominated by two major and four minor resonances. The two major resonances are: MTMA1, the well-known radical formed by net hydrogen abstraction from the C5 methyl group of the thymine moiety, and MTMA2, the radical formed by net hydrogen abstraction from the NI methyl group of the thymine moiety. The latter product has not been observed previously in any 1- methylthymine derivative. The four minor resonances are: MTMA3, the anion of 1-methylthymine, possibly protonated at the 04 position; MTMA4, the well- known species formed by net hydrogen addition to C6 of the thymine moiety; MTMA5, the species formed by net hydrogen addition to C2 of the adenine moiety; and MTMA6, the species formed by net hydrogen addition to C8 of the adenine moiety. Radical MTMA3, the O4-protonated thymine anion, was clearly detected at 10 K, but upon thermal annealing at 40 K the lines began to disappear. In crystals irradiated at 65 K MTMA3 was only weakly present. Radical MTMA2 decayed at about 250 K with no detectable successor, and radical MTMA5 disappeared at about 180 K. It was not possible to learn from the data if MTMA5 transformed into MTMA6. The radical distribution in the 1- methylthymine·9-methyladenine crystal system is different from that in crystals of the individual components. Reasons for this behavior are discussed in light of the hydrogen bonding schemes and molecular stacking interactions in each of the crystals. An important feature is the concept of excited-state transfer from the adenine to the thymine moiety, followed by dehydrogenation at the thymine N1-methyl group, the mechanism resulting in radical MTMA2.

Five free radicals have been detected by detailed ESR/ENDOR experiments on single crystals of deoxyadenosine monohydrate (AdRm), X-irradiated and observed at 10 K. In a previous study of adenosine (Radiat. Res. 117, 367- 378, 1989), only the anion (protonated at N3) and the cation (deprotonated at the exocyclic NH2) were detected at 10 K. In AdRm, Radical R1 is the N3- protonated anion, similar to that observed previously in adenosine. Radical R3 is a C5' hydroxyalkyl radical formed by net H-abstraction from C5'. A second sugar radical is formed by net C1' H-abstraction. Two other base radicals observed in AdRm at 10 K are the C2 and C8 H-addition radicals. The C2 H-addition radical (Radical R5) exhibits inequivalent methylene hydrogen couplings of 5.43 and 3.29 mT, while in the C8 H-addition radical (Radical R6) the couplings are somewhat more equivalent (3.63 and 4.17 mT). No link between Radical R1 and the H-addition radicals has been observed. The reduced base appears to protonate rapidly even at 10 K, while at the same time both H-addition radicals are clearly present. On warming, Radical R1 appears to decay at about 80 K with no apparent successor. Although no base cation was stabilized in AdRm at 10 K, it is interesting to note that Radicals R3 and R4 could both be formed as the result of deprotonation of primary oxidation products.