Neutral dissociation of superexcited molecules in a strong laser field

L'objectif principal de cette thèse est de rendre compte d'une étude expérimentale sur la dissociation neutre de molécules simples dans un champ laser intense créé par un cristal titane saphir. Ces excitations fortement non linéaires nous indiquent que les molécules peuvent être peuplées dans les états hyperexcités. Dans ce travail, un laser titane saphir femtoseconde est utilisé pour amener les molécules de H₂, 0₂, NO, CH₄, C₂H₄, C₃, H₆, 1 — C₄H₈ et cis — 2 — C₄H₈ dans les états très excités. En utilisant une méthode de spectroscopic, on arrive à détecter des signaux de fluorescence. Le diagramme d'énergie des fragments excités et molécules neutres supporte l'excitation des états hyperexcités dans les molécules que nous avons étudiées. La dépendance hautement non linéaire du rendement produit selon la puissance du laser a été observée. En outre, les résultats soutiennent le mécanisme d'hyperexcitation multiphotonique. En utilisant la technique de pompe (800 nm) et sonde (1338 nm) et aussi de la technique de spectroscopie par fluorescence, nous confirmons le mécanisme de hyperexcitation multiphotonique des molécules en présence d'un champ laser intense. Nous arrivons à déterminer la durée de vie des états hyperexcités en regardant l'atténuation des signaux de fluorescence observée à l'aide du faisceau sonde. Nos observations expérimentales ont été également vérifiées à l'aide des calculs semi—empiriques. Nous constatons que certaines impulsions laser provoquent la dissociation neutre de nombreuses molécules

Stochastic memory process and its application to cumulative outage time in nuclear power plants

The safety performance of operating nuclear power plants is strongly affected by the unavailability of safety systems that are designed to mitigate accident conditions. The unavailability of these safety systems during plant operation is controlled by the plant\u27s technical specifications which prescribes limits on the downtime duration (outage time) of the individual safety equipment. In this study, risk- and reliability-based methodologies for the determination of allowable cumulative downtime for safety components and safety systems are developed. The limits on the cumulative downtime durations are determined by taking into account the statistical variations expected from a stochastic process which models both the downtime occurrences as well as the downtime durations. This stochastic process is also expected to track with time, the distribution of the cumulative downtime (or the cumulative residence time while in the failed state). Such processes are referred to as memory processes in the context of this study. Three mathematical models are developed for evaluating the types of processes was developed which can generate thousands of simulations and therefore allows the construction of the cumulative downtime distribution. Various solution techniques for these mathematical models were also developed and applied. The question of partial information was addressed, and the use of the maximum entropy principle in this area was detailed. A solution method for estimating the parameters of maximum entropy distribution using the Laguerre polynomials are also discussed. Finally, these theoretical models were applied to a typical auxiliary feed water system in a pressurized water reactor and a pilot trial for determination of the allowable cumulative downtime for a component and the system was performed

Techniques for data prediction, smoothing, and updating of operator errors in commercial nuclear power plants

http://www.worldcat.org/oclc/533896

The Yin and Yang of Sodium Lauryl Sulfate Use for Oral and Periodontal Health: A Literature Review

Sodium lauryl sulfate (SLS) is an anionic surfactant, which has a wide range of usage in the health sector and in dental pharmaceutical products, especially in toothpastes. The objective of this review was to investigate the effects of SLS containing dentifrices on oral and periodontal health, possible side effects, and its benefits. A thorough literature search was done using databases of PubMed and Google Scholar and finally, 40 articles were included in the study. This narrative review revealed the sources of discrepancy and conflicting results regarding the impact of SLS on oral cavity as well as a lack of sufficient evidence in most topics. Hence, the evidence suggests improved drug bioavailability when used as a solubilizer, improved plaque control, and reduction in bad breath. On the other hand, SLS can serve as a risk indicator of prolonged oral wound healing time, recurrent aphthous stomatitis

Optical gain in rotationally excited nitrogen molecular ions

We pump low-pressure nitrogen gas with ionizing femtosecond laser pulses at 1.5 mu m wavelength. The resulting rotationally excited N-2(+) 2 molecular ions generate directional, forward-propagating stimulated and isotropic spontaneous emissions at 428 nmwavelength. Through high-resolution spectroscopy of these emissions, we quantify rotational population distributions in the upper and lower emission levels. We show that these distributions are shifted with respect to each other, which has a strong influence on the transient optical gain in this system. Although we find that electronic population inversion exists in our particular experiment, we show that sufficient dissimilarity of rotational distributions in the upper and lower emission levels could, in principle, lead to gain without net electronic population inversion.U.S. Air Force Office of Scientific Research under MURI Award [FA9550-16-1-0013]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

A Synoptic analysis for the occurrence of springtime heavy rainfall in the Northwest of Iran

The main purpose of this research is synoptic analysis for the occurrence of springtime heavy rainfall in the Northwest of Iran. Therefore, daily precipitation data were obtained from 15 synoptic stations for a period of 34 years (1981-2014). Then by using percentile index of above 95th, it was identified 98 days with heavy precipitation. So, to determine the synoptic patterns by applied the NCEP/NCAR reanalysis dataset, the maps of geopotential height, sea level pressure, streamlines, vorticity, and specific humidity at different levels were prepared and the regional pattern flow and atmospheric conditions two days before the occurrence of precipitation analyzed. The results indicate that heavy precipitations in North West of Iran are categorized into four synoptic patterns. At the first pattern, the main cause of heavy precipitation in North West is passing cyclone or low-pressure migratory systems and the regional dynamic convergence and its association with cyclonic circulation. The main factor for the transferring of moisture to the inner side of these cyclones is the anti-cyclone stationed in Saudi Arabia. At the second pattern, the couple blocking system in the middle level of troposphere system is caused heavy precipitation with stop-motion circulation systems in the middle and lower levels of the atmosphere. At the third pattern, a deep cyclonic circulation center has not been formed on their area and seems deepening a trough of extratropical and stimulates the local convergence condition dynamically, and is regarded as the main mechanism of precipitations occurrence

Effect of crucible shape on the solution hydrodynamic in the growth of KTiOPO4 single crystals by top-seeded solution growth method: A numerical analysis

Three-dimensional solution flow and temperature field simulations were performed to model the growth of KTiOPO4 single crystals by TSSG method. Steady flow and temperature field for four crucible shapes were computed using finite volume method. Our results show the effect of crucible shape on axial flow which has direct effect on homogeneity of solution, morphology of crystal and mass transport during the growth of crystals from solution. In order to consider the simulation results, KTiOPO4 single crystals were grown by TSSG method in crucibles with different shapes

Investigating the Relationship between the Dimensions and Morphology of Sella Turcica with the Long-Face Growth Pattern and the Vertical Growth Pattern

Introduction. The sella turcica is one of the important landmarks of lateral cephalometry, which is used in orthodontics for the diagnosis, treatment plan, and evaluation of skeletal development and maturity. The purpose of the present study is to investigate the relationship between the dimensions and morphology of sella turcica with the long-face growth pattern and people with an open bite. This study also examines the relationship between sella turcica bridging (STB) and the vertical growth pattern. Methods. As many as 153 radiographs were analyzed using the Romexis software, considering the basal, gonial, and FMA angles to determine the vertical growth pattern of the face. The basal angle was also used to check for an open bite. Of these patients, 80 had a long vertical face growth pattern, and 73 had a normal face growth pattern. The four landmarks of tuberculum sellae, dorsum sellae, sellae floor, and posterior clinoid were determined on the cephalograms to measure the length, depth, and anteroposterior diameter of the sella turcica. Results. In this study, it was found that the chance of developing a long face in people with partial and complete bridging is 8.37 and 1.92, respectively. An increase in the length of the sella turcica for one unit decreases the chance of a long face, and as the depth of the sella turcica increases, the chance of a long face increases. Conclusions. STB is frequently seen in people with long faces. However, this finding should be considered in relation to other diagnostic parameters. The shorter the length and higher the depth of sella turcica, the higher the chance of developing a long face