Authoritarian Tendencies in the American Presidency

This thesis attempts to determine if authoritarian tendencies are becoming more or less prevalent in the modern American presidency. Presidential and authoritarian scholars agree that authoritarianism is trending in a more insidious manner in the modern world and that most democracies today are being subverted more inconspicuously by elected officials. The most powerful checks on the power of the president are Congress and the judicial branch, two institutions that do exercise their constitutionally granted powers in some cases, but do not always exert their power in solidarity, leading to discrepancies in the constraint of the president. The presence of conflict leads to the most prevalent usurpation of presidential power, which is unequivocally war powers violations. Through a historical qualitative methodology, I have elaborated upon the major authoritarian tendencies of each modern president, starting with FDR and ending with Donald Trump. There is also a clear distinction between the expansion of state institutions and true attempts to aggrandize the power of the executive which are elaborated upon when necessary. My research has found that authoritarian tendencies absolutely fluctuate in the modern presidency but that the presidents who exhibit the highest degree of authoritarian tendencies are those who serve during times of crisis and conflict. The tendencies of the president to usurp power and disparage democracy came to its zenith under President Donald Trump, who is an anomaly both in his rise to power and his justifications for authoritarian actions. The conclusions that can be drawn from this historical perspective are that even in times of conflict and duress, Congress and the judicial branch must consistently uphold their constitutional responsibility to constrain the president

Mesure directe des constantes de sédimentation de désoxyribonucléase par ultracentrifugation analytique

Dans ce travail, nous décrivons la mesure directe de la constante de sédimentation de la désoxyribonucléase neutre du crabe avec de très faibles concentrations en protéines en utilisant une ultracentrifugeuse analytique et une cellule à séparation fixe. Quelques déterminations ont été effectuées avec une autre désoxyribonucléase, une endonucléase acide extraite du bivalve Glycymeris glycymeris. Dans les deux cas, il y a un bon accord entre les masses moléculaires calculées à partir des résultats de l’ultracentrifugation analytique et mesurées par filtration sur gel de Sephadex G 100

Comparaison des propriétés physicochimiques du DNA natif et du DNA ultrasoné

On a étudié par diffusion de la lumière, ultracentrifugation et dénaturation thermique l’influence de la force ionique (solutions de NaCl 0,0015 M à 1 M) sur la configuration du DNA natif (Mm ~ 6.106) et du DNA fragmenté par sonication en batonnets (Mw ~ 0,6.106). Dans le cas du DNA natif, quand la force ionique du milieu décroît, il y a une augmentation des interactions intermoléculaires (second coefficient du viriel, extrapolation à concentration nulle pour déterminer les constantes de sédimentation). Dans les limites de force ionique étudiées, on n’a pu mettre en évidence aucune perturbation dans le comportement du DNA soniqué

Gammaproteobacterial diazotrophs and nifH gene expression in surface waters of the South Pacific Ocean.

In addition to the cyanobacterial N2-fixers (diazotrophs), there is a high nifH gene diversity of non-cyanobacterial groups present in marine environments, yet quantitative information about these groups is scarce. N2 fixation potential (nifH gene expression), diversity and distributions of the uncultivated diazotroph phylotype γ-24774A11, a putative gammaproteobacterium, were investigated in the western South Pacific Ocean. γ-24774A11 gene copies correlated positively with diazotrophic cyanobacteria, temperature, dissolved organic carbon and ambient O2 saturation, and negatively with depth, chlorophyll a and nutrients, suggesting that carbon supply, access to light or inhibitory effects of DIN may control γ-24774A11 abundances. Maximum nifH gene-copy abundance was 2 × 10(4) l(-1), two orders of magnitude less than that for diazotrophic cyanobacteria, while the median γ-24774A11 abundance, 8 × 10(2) l(-1), was greater than that for the UCYN-A cyanobacteria, suggesting a more homogeneous distribution in surface waters. The abundance of nifH transcripts by γ-24774A11 was greater during the night than during the day, and the transcripts generally ranged from 0-7%, but were up to 26% of all nifH transcripts at each station. The ubiquitous presence and low variability of γ-24774A11 abundances across tropical and subtropical oceans, combined with the consistent nifH expression reported in this study, suggest that γ-24774A11 could be one of the most important heterotrophic (or photoheterotrophic) diazotrophs and may need to be considered in future N budget estimates and models

Nitrogenase (nifH) gene expression in diazotrophic cyanobacteria in the Tropical North Atlantic in response to nutrient amendments

The Tropical North Atlantic (TNAtl) plays a critical role in the marine nitrogen cycle, as it supports high rates of biological nitrogen (N2) fixation, yet it is unclear whether this process is limited by the availability of iron (Fe), phosphate (P) or is co-limited by both. In order to investigate the impact of nutrient limitation on the N2-fixing microorganisms (diazotrophs) in the TNAtl, trace metal clean nutrient amendment experiments were conducted, and the expression of nitrogenase (nifH) in cyanobacterial diazotrophs in response to the addition of Fe, P, or Fe+P was measured using quantitative PCR. To provide context, N2 fixation rates associated with the <10 μm community and diel nifH expression in natural cyanobacterial populations were measured. In the western TNAtl, nifH expression in Crocosphaera, Trichodesmium, and Richelia was stimulated by Fe and Fe+P additions, but not by P, implying that diazotrophs may be Fe-limited in this region. In the eastern TNAtl, nifH expression in unicellular cyanobacteria UCYN-A and Crocosphaera was stimulated by P, implying P-limitation. In equatorial waters, nifH expression in Trichodesmium was highest in Fe+P treatments, implying co-limitation in this region. Nutrient additions did not measurably stimulate N2 fixation rates in the <10 μm fraction in most of the experiments, even when upregulation of nifH expression was evident. These results demonstrate the utility of using gene expression to investigate the physiological state of natural populations of microorganisms, while underscoring the complexity of nutrient limitation on diazotrophy, and providing evidence that diazotroph populations are slow to respond to the addition of limiting nutrients and may be limited by different nutrients on basin-wide spatial scales. This has important implications for our current understanding of controls on N2 fixation in the TNAtl and may partially explain why it appears to be intermittently limited by Fe, P, or both