Doctor of Philosophy

dissertationInfrared and resonant two-photon ionization spectroscopy were employed to study the bonding and electronic structure of small gas phase transition metal containing molecules. Rovibrational spectra of NiCO, Ni(CO)3(13CO), and Ni(CO)3(C18O) were collected using a pulsed-discharge slit-jet infrared diode laser spectrometer, while resonant two-photon ionization spectra were collected for ZrF, ZrCl, and PdSi. Analysis of these spectra allowed spectroscopic parameters to be determined, leading to an improved understanding of the chemical bonding in these molecules. Spectra of NiCO, Ni(CO)3(13CO), and Ni(CO)3(C18O) were obtained by exciting a CO vibration in these molecules. For NiCO, band origins of 2010.69289(34) and 2010.64528(23) cm-1 were measured, along with values of B0 = 0.151094(7) and 0.149597(6) cm-1 for 58NiCO and 60NiCO, respectively. These were used to determine bond lengths of r0 (Ni-C) = 1.641(40) A and r0 (C-O) = 1.193(53) A. The ground state constants determined for Ni(CO)3(13CO) are υ0 = 2022.075753(95) cm-1 and B" = 0.034736(2) cm-1. For Ni(CO)3(C18O), υ0 = 2021.93683(18) cm-1 and B" = 0.033764(4) cm-1 are obtained. These values provide bond lengths of r0(Ni-C) = 1.839 ± 0.007 A and r0(C-O) = 1.121 ± 0.010 A. The vibronic spectrum of ZrF revealed many bands in the range from 14700 to 18000 cm-1, several of which can be grouped into three band systems. Rotationally resolved investigations are hampered by perturbations in the excited states, but three unperturbed bands have revealed an Ω″ = 1.5 ground state, and a bond length of r0″ = 1.858 A. Hot bands originating from v″ = 1 provide ΔG1/2″ = 691.45(2) for 90Zr19F. Based on comparisons to ZrCl and ligand-field considerations, the ZrF ground state is assigned as a 2Δ3/2. In addition to the ZrF measurements, vibronically resolved spectra of ZrCl were recorded over the 13000 to 18000 cm-1 range, and four band systems were identified. Three vibronic bands of PdSi have been rotationally resolved and analyzed, two of which are perturbed by interactions with other states. The data show an Ω = 0 ground state and a bond length of r0″ = 2.0824(3) A. Comparisons to density functional (DFT) calculations strongly support a 1Σ+ ground state assignment

Spectroscopy of diatomic ZrF and ZrCl: 760 ? 555 nm

Journal ArticleThe optical spectrum of diatomic ZrF has been investigated, with transitions recorded in the range from 14 700 to 18 000 cm?1. Many bands have been observed, several of which can be grouped into three band systems. Rotationally resolved investigations are hampered by perturbations that are rampant among the excited states, but three unperturbed bands have revealed that the ground state of ZrF has ?" = 3/2, with a bond length of r"e = 1.854(1) ?. Hot bands originating from v" = 1 provide the ground state vibrational interval, ?G"1/2 = 691.45(2) cm?1 for 90Zr19F. Based on comparisons to ZrCl and ligand-field considerations, the ZrF ground state is assigned as a 2?3/2 level deriving from the 3?2 1?1 configuration, in agreement with a previous study. In addition to the measurements on ZrF, vibronically resolved spectra of ZrCl have been recorded over the 13 000 to 18 000 cm?1 range, and four band systems have been identified

Resonant two-photon ionization spectroscopy of jet-cooled PdSi

Journal ArticleThe spectra of diatomic PdSi have been investigated for the first time, using the technique of resonant two-photon ionization spectroscopy. A number of vibronic transitions have been observed in the 20 400?22 000 cm?1 range. It is difficult to group the bands into band systems, although one likely band system has been identified. Three bands have been rotationally resolved and analyzed, two of which are perturbed by interactions with other states. The data show that the ground state of PdSi has ? = 0, and a bond length of r"0 = 2.0824(3) ?. Comparisons to previously published density functional theory calculations provide strong support for the assignment of the ground state to the 1?2 2?2 1?4 1?4 3?2, 1? + term, which is predicted to be the ground state in the alculations. The much shorter bond length and greater bond energy of PdSi, as compared to its isoelectronic counterpart, AlAg, demonstrate that there is strong ? bonding in PdSi, as has been previously found for the other nickel group silicides, NiSi and PtSi

Contenido de calcio y fosforo de especies nativas sometidas a tres frecuencias de corte a lo largo del año

El objetivo del trabajo fue Evaluar el contenido de Calcio y Fósforo de un pastizal nativo, en función a la frecuencia de utilización de la misma a lo largo de un año.CONACYT – Consejo Nacional de Ciencia y TecnologíaPROCIENCI

El problema de la autoconstrucción en Lima Metropolitana

Tener una vivienda donde descansar, refugiarse, sentirse seguro y convivir con las personas más queridas no es solamente un proyecto de vida al que aspiran muchas personas, pues también posibilita el desarrollo económico del país, al ser la construcción una de las actividades económicas que produce más puestos de trabajo. No obstante, ante el problema del alto índice de carencia de viviendas que se presenta en Lima Metropolitana, se genera otro que es la autoconstrucción, y que en los últimos años se ha ido incrementando en gran medida, especialmente en Lima Metropolitana. Debido a ello, el presente trabajo busca analizar el problema de la autoconstrucción en Lima Metropolitana desde distintos aspectos que van desde su impacto en los precios hedónicos del metro cuadrado en las viviendas de cada distrito perteneciente al área, hasta las alternativas de solución que podrían ocuparse de dicho problema. Para ello, se empezará con un análisis sobre la influencia que tiene la autoconstrucción en el valor estético del distrito y la repercusión de este en los precios del metro cuadrado de las viviendas de cada distrito, relación que tiene su respaldo en el concepto de precios hedónicos. Luego, se incluye la problemática de la autoconstrucción en Lima Metropolitana, en donde se explica el origen de esta, la cual se remonta en los años 40, época en la que aconteció la oleada migratoria interna en el país. Se prosigue con la comparación de ciertos países europeos, respecto a la manera en que estos han abarcado el problema de la autoconstrucción que es producto de las oleadas migratorias por las que han pasado. Le contínua el planteaminento de ciertas propuestas de solución que se creen que son las más adecuadas para detener el surgimiento de más viviendas autoconstruidas en la capital. Por último, se presentarán las conclusiones finales sacadas entre todas las autoras respecto a los temas abordados

Depressive Symptoms Among Immigrant Latino Sexual Minorities

To estimate the prevalence and identify correlates of depressive symptoms among immigrant Latino sexual minorities

Infection and coinfection by human papillomavirus, Epstein–Barr virus and Merkel cell polyomavirus in patients with squamous cell carcinoma of the larynx: a retrospective study

Background Human papillomavirus (HPV) is recognized as an important risk factor for laryngeal carcinogenesis. Although HPV-16 and 18 have been strongly implicated, the presence of other high-risk HPV (HR-HPV) genotypes or the coinfection with Epstein-Barr virus (EBV) or Merkel cell polyomavirus (MCPV) may increase the risk, but their etiological association has not been definitively established. Methods We characterized the genotype-specific HPV and the frequency of EBV and MCPV infections through the detection of their DNA in 195 laryngeal specimens of squamous cell carcinoma (SCC) histologically confirmed. Results HPV DNA was detected in 93 (47.7%) specimens. HPV-11 was the most frequent with 68 cases (73.1%), and HPV-52 was the most frequently HR-HPV found with 51 cases, which corresponds to 54.8% of all HPV-positive specimens. EBV DNA was detected in 54 (27.7%) tumor tissue specimens of which 25 (46.3%) were in coinfection with HPV. MCPV DNA was detected only in 11 (5.6%) cases of which 5 (45.4%) were in coinfection with an HR-HPV. No association between the presence of DNA of the three examined viruses and the patient smoking habits, alcohol consumption, age, the keratinization status, differentiation grade, or localization of the tumor in the larynx were found. Discussion HPV-52 was the most prevalent HR-HPV, which may suggest that this and other genotypes in addition to HPV-16 and 18 could be considered for prophylaxis. However, further studies including non-cancer larynx cases and the evaluation of other molecular markers and viral co-infection mechanisms are needed to determine the role of the different HR-HPV genotypes, EBV, and MCPV in the etiology of SCC of the larynx

Selective Depletion of Eosinophils or Neutrophils in Mice Impacts the Efficiency of Apoptotic Cell Clearance in the Thymus

Developing thymocytes undergo a rigorous selection process to ensure that the mature T cell population expresses a T cell receptor (TCR) repertoire that can functionally interact with major histocompatibility complexes (MHC). Over 90% of thymocytes fail this selection process and die. A small number of macrophages within the thymus are responsible for clearing the large number of dying thymocytes that must be continuously cleared. We studied the capacity of thymic macrophages to clear apoptotic cells under acute circumstances. This was done by synchronously inducing cell death in the thymus and then monitoring the clearance of apoptotic thymocytes. Interestingly, acute cell death was shown to recruit large numbers of CD11b+ cells into the thymus. In the absence of a minor CSF-1 dependent population of macrophages, the recruitment of these CD11b+ cells into the thymus was greatly reduced and the clearance of apoptotic cells was disrupted. To assess a possible role for the CD11b+ cells in the clearance of apoptotic cells, we analyzed mice deficient for eosinophils and mice with defective trafficking of neutrophils. Failure to attract either eosinophils or neutrophils to the thymus resulted in the impaired clearance of apoptotic cells. These results suggested that there is crosstalk between cells of the innate immune system that is necessary for maximizing the efficiency of apoptotic cell removal

An investigation of the apparent breast cancer epidemic in France: screening and incidence trends in birth cohorts

<p>Abstract</p> <p>Background</p> <p>Official descriptive data from France showed a strong increase in breast-cancer incidence between 1980 to 2005 without a corresponding change in breast-cancer mortality. This study quantifies the part of incidence increase due to secular changes in risk factor exposure and in overdiagnosis due to organised or opportunistic screening. Overdiagnosis was defined as non progressive tumours diagnosed as cancer at histology or progressive cancer that would remain asymptomatic until time of death for another cause.</p> <p>Methods</p> <p>Comparison between age-matched cohorts from 1980 to 2005. All women residing in France and born 1911-1915, 1926-1930 and 1941-1945 are included. Sources are official data sets and published French reports on screening by mammography, age and time specific breast-cancer incidence and mortality, hormone replacement therapy, alcohol and obesity. Outcome measures include breast-cancer incidence differences adjusted for changes in risk factor distributions between pairs of age-matched cohorts who had experienced different levels of screening intensity.</p> <p>Results</p> <p>There was an 8-fold increase in the number of mammography machines operating in France between 1980 and 2000. Opportunistic and organised screening increased over time. In comparison to age-matched cohorts born 15 years earlier, recent cohorts had adjusted incidence proportion over 11 years that were 76% higher [95% confidence limits (CL) 67%, 85%] for women aged 50 to 64 years and 23% higher [95% CL 15%, 31%] for women aged 65 to 79 years. Given that mortality did not change correspondingly, this increase in adjusted 11 year incidence proportion was considered as an estimate of overdiagnosis.</p> <p>Conclusions</p> <p>Breast cancer may be overdiagnosed because screening increases diagnosis of slowly progressing non-life threatening cancer and increases misdiagnosis among women without progressive cancer. We suggest that these effects could largely explain the reported "epidemic" of breast cancer in France. Better predictive classification of tumours is needed in order to avoid unnecessary cancer diagnoses and subsequent procedures.</p