Strong field approximation (SFA) is the most important approximation in the analytical theory of intense laser matter interaction. Based on SFA many analytical theories have been developed such that a broad spectrum of strong field physics phenomena can be described. The central idea of SFA-based theories is to approximate the electron propagation in the continuum by the Gordon-Volkov wavefunction - a well studied analytical solution to the time-dependent Schr\"{o}dinger equation where the electron is driven by the laser field only. This approximation captures some of the essential features of strong-field physics, but at the same time causes several problems in the theory. In this thesis a comprehensive study of the SFA has been presented. We introduce the SFA in both the length gauge and the velocity gauge. The adequacy of SFA has been discussed by comparing the theory to the numerical solution to the time-dependent Schr\"{o}dinger equation (TDSE). The numerical method of solving TDSE is presented as a separate chapter. In order to obtain a better understanding of the applicability of SFA-based theory, we tested the major approximations in the theory by using three different models: the zero-range potential, the hydrogen atom and the hydrogen molecular ion. The accuracy of the method of steepest descent (MSD) and other major approximations in the analytical theory have also been examined. Targeting at the generalization of the SFA-based theories, several extensions and improvements of SFA have been proposed. We will review them in detail and bring them into unity. One of the most successful aspect of the SFA-based theories is to describe and decompose electron dynamics into components such that identification of different physical processes becomes possible. For instance, the direct ionization and non-sequential double ionization bear clear definitions only within the SFA-based framework. The physical interpretation becomes more straight forward due to the fact that there is a close connection between the quantum orbital and classical trajectory. The MSD is a mathematical tool to bridge the quantum orbital and the classical trajectory in an SFA-based theory. We will discuss MSD within a systematic framework so that the higher order asymptotic expansion terms can be obtained in a straight forward way. After gaining substantial understanding of the SFA and the MSD we developed a graphic user interface (GUI) software that is capable of calculating strong field ionization rates, photo-electron spectra and high harmonic generation spectra. The software interface and algorithms have been presented in the thesis. Sample calculations were done and compared with the previously obtained results. In the last chapter of the thesis, we further developed the theory to describe a two-laser ionization scheme where one laser is chosen to be resonantly coupled two real states and the other is a strong few-cycle laser pulse. We demonstrate the periodic dependence of the total ionization on the appearance time of the strong few-cycle laser pulse. In the case of few-cycle pulses with lower intensity, we observed side-bands in the photoelectron spectrum, whose intensity vary periodically with the appearance time of the pulse. We show that our extended theory is able to explain these phenomena adequately.

Strong field approximation (SFA) is the most important approximation in the analytical theory of intense laser matter interaction. Based on SFA many analytical theories have been developed such that a broad spectrum of strong field physics phenomena can be described. The central idea of SFA-based theories is to approximate the electron propagation in the continuum by the Gordon-Volkov wavefunction - a well studied analytical solution to the time-dependent Schr\"{o}dinger equation where the electron is driven by the laser field only. This approximation captures some of the essential features of strong-field physics, but at the same time causes several problems in the theory. In this thesis a comprehensive study of the SFA has been presented. We introduce the SFA in both the length gauge and the velocity gauge. The adequacy of SFA has been discussed by comparing the theory to the numerical solution to the time-dependent Schr\"{o}dinger equation (TDSE). The numerical method of solving TDSE is presented as a separate chapter. In order to obtain a better understanding of the applicability of SFA-based theory, we tested the major approximations in the theory by using three different models: the zero-range potential, the hydrogen atom and the hydrogen molecular ion. The accuracy of the method of steepest descent (MSD) and other major approximations in the analytical theory have also been examined. Targeting at the generalization of the SFA-based theories, several extensions and improvements of SFA have been proposed. We will review them in detail and bring them into unity. One of the most successful aspect of the SFA-based theories is to describe and decompose electron dynamics into components such that identification of different physical processes becomes possible. For instance, the direct ionization and non-sequential double ionization bear clear definitions only within the SFA-based framework. The physical interpretation becomes more straight forward due to the fact that there is a close connection between the quantum orbital and classical trajectory. The MSD is a mathematical tool to bridge the quantum orbital and the classical trajectory in an SFA-based theory. We will discuss MSD within a systematic framework so that the higher order asymptotic expansion terms can be obtained in a straight forward way. After gaining substantial understanding of the SFA and the MSD we developed a graphic user interface (GUI) software that is capable of calculating strong field ionization rates, photo-electron spectra and high harmonic generation spectra. The software interface and algorithms have been presented in the thesis. Sample calculations were done and compared with the previously obtained results. In the last chapter of the thesis, we further developed the theory to describe a two-laser ionization scheme where one laser is chosen to be resonantly coupled two real states and the other is a strong few-cycle laser pulse. We demonstrate the periodic dependence of the total ionization on the appearance time of the strong few-cycle laser pulse. In the case of few-cycle pulses with lower intensity, we observed side-bands in the photoelectron spectrum, whose intensity vary periodically with the appearance time of the pulse. We show that our extended theory is able to explain these phenomena adequately.

The above threshold ionization (ATI) spectra provide a diversity of information about a laser-atom ionization process such as laser intensity, pulse duration, carrier envelope phase, and atomic energy level spacing. However, the spatial distribution of intensities inherent in all laser beams reduces the resolution of this information. This research focuses on recovering the intensity-resolved ATI spectra from experimental data using a deconvolution algorithm. Electron ionization yields of xenon were measured for a set of laser pulse intensities using a time of flight (TOF) setup. Horizontally polarized, unchirped, 50fs pulses were used in the ionization process. All laser parameters other than the radiation intensity were held constant over the set of intensity measurements. A deconvolution algorithm was developed based on the experimental parameters. Then the deconvolution algorithm was applied to the experimental data to obtain the intensity-resolved total yield probability and ATI spectra. Finally, an error analysis was performed to determine the stability and accuracy of the algorithm as well as the quality of the data. It was found that the algorithm produced greater contrast for peaks in the ATI spectra where atom specific resonant behavior is observed. Additionally, the total yield probability showed that double ionization may be observed in the ionization yield. The error analysis revealed that the algorithm was stable under the experimental conditions for a range of intensities.

La question de l'eau constitue à l'heure actuelle un enjeu majeur pour nos sociétés. Bien qu'il s'agisse d'une ressource renouvelable, son cycle naturel est soumis à de fortes pressions issues tant de l'activité humaine que des modifications climatiques.Le débit des fleuves constitue une des variables clefs du cycle de l'eau. Sa quantification implique des mesures in situ lourdes. De ce fait, son suivi à l'échelle globale reste problématique, et les techniques de télédétection peuvent représenter un atout majeur. Les techniques satellitaires optiques et radar ne peuvent actuellement que mesurer les variables de surface et n'accèdent pas aux paramètres de fond des cours d'eau. Ce travail propose une méthode d'estimation de ces paramètres hydrauliques de fond à partir des seules mesures des variables de surface, en vue de l'estimation du débit. Cette méthode a été validée sur des données simulées exactes et une étude de sensibilité au bruit de mesure a été menée sur des données simulées bruitées et sur des données réelles.Le second volet de ce travail porte sur le potentiel de l'interférométrie radar temporelle à mesurer la variable de vitesse de surface des fleuves. Une campagne de mesure aéroportée a été réalisée sur le Rhône (ONERA-Cemagref) et a montré des résultats concordants avec les mesures de vitesses réalisées in situ par ADCP. En revanche, le modèle de rétrodiffusion M4S, testé dans le cadre de cette thèse, est apparu peu adapté aux scènes fluviales : il s'avère extrêmement sensible aux conditions de vent, ce qui peut s'expliquer par une faiblesse dans la modélisation des caractéristiques des surfaces de fleuves. Dans le cadre du programme SWOT (NASA-CNES), nous avons développé une méthode de mesure in situ de la rugosité des surfaces fluviales. Validée lors de mesures en laboratoire, cette méthode a été mise en œuvre sur le Rhône, et a ainsi permis de caractériser la surface et l'influence de l'intensité du vent sur les paramètres de rugosité. / The water issue is currently a major challenge for our societies. Even if water is a renewable resource, its natural cycle supports great stresses, both human activity and climate change.River discharge is a key variable of the water cycle, whose quantification requires heavy field measurements. Therefore the global monitoring of river discharge remains problematic and satellite remote sensing techniques could be a major asset. Earth Observation radar techniques are currently limited to the measurement of surface variables and cannot measure river bottom hydraulic parameters. The current study proposes a method to estimate these parameters from surface variables, in order to estimate the river discharge. This method has been validated on exact simulated data and its robustness to measurement noise has been studied on noisy simulated data and on real data.The second part of this work explores the abilities of radar along-track interferometry to measure river surface velocity. Velocity measurements carried out on the Rhône river during an airborne campaign (ONERA-Cemagref) show a strong consistency with ADCP field measurements. M4S backscattering model, tested in the framework of this study, is poorly adapted to river scenes : it appears to be extremely sensitive to wind intensity which could be explained by a poor modeling of surface roughness. As part of the SWOT mission program (NASA-CNES) a method allowing in situ characterization of river surface roughness has been developed. It was validated under laboratory controlled conditions. It was implemented on the Rhône river to characterize water surface and quantify the influence of wind intensity on the water surface roughness parameters.

Health care professionals and nurse educators are concerned about increasing percentage of first time test takers failing the NCLEX-RN exam. The purpose of this retrospective study was to examine predictive accuracy of the Assessment Technologies Institute (ATI) RN Comprehensive Predictor for passing or failing the NCLEX-RN exam in a cohort of nursing students (N = 195). South Eastern Technical College in South Carolina is in jeopardy of losing accreditation for their nursing program because of the low percentage of first time test takers failing. The college's pass rate on the NCLEX-RN exam has been below the national and state averages for the last 2 years. Guided by Bloom's taxonomy and Knowles' andragogical model of learning as the theoretical mainstay, factors that predict success with the NCLEX-RN exam for first time test takers were examined. Inferential and descriptive statistics were used to determine if a relationship existed between NCLEX-RN scores and the independent variables. A Pearson r correlation test was conducted to address whether the ATI Comprehensive Predictor accurately predict student success with the NCLEX-RN exam on first attempt. Multiple regression was employed to test for a significant relationship between prenursing GPA, final GPA, age, gender, and ATI predictor scores. Regression analysis results showed ATI Predictor scores to significantly predict student success with the NCLEX-RN exam on first attempt. Based on findings, a Structured Learning Assistance program was proposed to assist in preparing students for NCLEX-RN success. Positive social change occurs within the community, nursing programs, and health care by increased NCLEX-RN pass rates enhancing the number of nurses entering into health care.

No description available.

Vårdpersonal har kategoriserats som en yrkesgrupp med höga stressnivåer och ungefär 70 % av tillfrågade sjuksköterskor har beskrivit sitt arbete som psykiskt påfrestande. Sjuksköterskestudenter upplever liknande problematik. Tidigare studier har visat att mindfulnessbaserade interventioner (MBI) kan reducera stress, öka mindfulnessförmågor samt främja mer positiva tidsattityder. Befintlig forskning har dock inte undersökt sambanden mellan dessa variabler tillsammans. Syftet i denna studie var att undersöka sambanden mellan tidsattityd, mindfulnessförmåga och grad av stress. Ytterligare syften var att granska effekten av mindfulnessträning på dessa variabler hos sjuksköterskestudenter samt att undersöka om tidsattityd och mindfulness kan predicera stress. Studien var en randomiserad kontrollerad studie med pre-post-kontrollgruppsdesign. Urvalet bestod av 75 sjuksköterskestudenter som genom randomisering delades in i kontrollgrupp (n=37) och experimentgrupp (n=38). Experimentgruppen genomförde ett tvåveckors webbaserat mindfulnessprogram medan kontrollgruppen stod på väntelista. Mätningar genomfördes innan och efter interventionen med formulären Perceived Stress Questionnaire (PSQ), Adolescent Time Inventory (ATI) samtMindful Attention Awareness Scale (MAAS). Resultaten visade på signifikanta interaktioner där experimentgruppen ökade sin mindfulnessförmåga, minskade i grad av stress och fick en mer positiv syn på sin framtid medan det omvända gällde för kontrollgruppen. Mindfulnessförmåga och negativ attityd till nuet predicerade stress. Resultatet stödjer att MBI kan vara en relevant intervention för stressreducering i denna urvalsgrupp.

Satellite observations provide information on land surface processes over a large spatial extent with a frequency dependent on the satellite revisit time. These observations are not subject to the spatial limitations of the traditional point measurements and are usually collected in a global scale. With a reasonable spatial resolution and temporal frequency, the Moderate Resolution Imaging Spectroradiometer (MODIS) is one of these satellite sensors which enables the study of land-atmospheric interactions and estimation of climate variables for over a decade from remotely sensed data. This research investigated the potential of remotely sensed land surface temperature (LST) data from MODIS for air temperature (Ta) and soil moisture (SM) estimation in New Zealand and how the satellite derived parameters relate to the numerical model simulations and the in-situ ground measurements. Additionally, passive microwave SM product from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) was applied in this research. As the first step, the MODIS LST product was validated using ground measurements at two test-sites as reference. Quality of the MODIS LST product was compared with the numerical simulations from the Weather Research and Forecasting (WRF) model. Results from the first validation site, which was located in the alpine areas of the South Island, showed that the MODIS LST has less agreement with the in-situ measurements than the WRF model simulations. It turned out that the MODIS LST is subject to sources of error, such as the effects of topography and variability in atmospheric effects over alpine areas and needs a careful pre-processing for cloud effects and outliers. On the other hand, results from the second validation site, which was located on the flat lands of the Canterbury Plains, showed significantly higher agreement with the ground truth data. Therefore, ground measurements at this site were used as the main reference data for the accuracy assessment of Ta and SM estimates. Using the MODIS LST product, Ta was estimated over a period of 10 years at several sites across New Zealand. The main question in this part of the thesis was whether to use LST series from a single MODIS pixel or the series of a spatially averaged value from multiple pixels for Ta estimation. It was found that the LST series from a single pixel can be used to model Ta with an accuracy of about ±1 ºC. The modelled Ta in this way showed r ≈ 0.80 correlation with the in-situ measurements. The Ta estimation accuracy improved to about ±0.5 ºC and the correlation to r ≈ 0.85 when LST series from spatially averaged values over a window of 9x9 to 25x25 pixels were applied. It was discussed that these improvements are due to noise reduction in the spatially averaged LST series. By comparison of LST diurnal trends from MODIS with Ta diurnal trends from hourly measurements in a weather station, it was shown that the MODIS LST has a better agreement with Ta measurements at certain times of the day with changes over day and night. After estimation of Ta, the MODIS LST was applied to derive the near-surface SM using two Apparent Thermal Inertia (ATI) functions. The objective was to find out if more daily LST observations can provide a better SM derivation. It was also aimed to identify the potential of a land-atmospheric coupled model for filling the gaps in derived SM, which were due to cloud cover. The in-situ SM measurements and rainfall data from six stations were used for validation of SM derived from the two ATI functions and simulated by the WRF model. It was shown that the ATI function based on four LST observations has a better ability to derive SM temporal profiles and is better able to detect rainfall effects. Finally, the MODIS LST was applied for spatial and temporal adjustment of the near-surface SM product from AMSR-E passive microwave observations over the South Island of New Zealand. It was shown that the adjustment technique improves AMSR-E seasonal trends and leads to a better matching with rainfall events. Additionally, a clear seasonal variability was observed in the adjusted AMSR-E SM in the spatial domain. Findings of this thesis showed that the satellite observed LST has the potential for the estimation of the land surface variables, such as the near-surface Ta and SM. This potential is greatly important on remote and alpine areas where regular measurements from weather stations are not often available. According to the results from the first validation site, however, the MODIS LST needs a careful pre-processing on those areas. The concluding chapter included a discussion of the limitations of remotely sensed data due to cloud cover, dense vegetation and rugged topography. It was concluded that the satellite observed LST has the potential for SM and Ta estimations in New Zealand. It was also found that a land-atmospheric model (such as the WRF coupled with the Noah and surface model) can be applied for filling the gaps due to cloud cover in remotely sensed variables.

Pas de résumé fourni. / No summary available.

High attrition rates and a nursing shortage across the nation have led schools of nursing to seek out ways to better identify which applicants will be most successful in graduating from the nursing program and passing the National Council Licensure Examination for Registered Nurses (NCLEX-RN). Nursing programs have historically included standardized entrance exam scores and prerequisite scores among their admission criteria but have not used standardized critical thinking assessments (CTA), even though critical thinking is an integral part of being a successful nursing professional. Using Astin's input-environment-output (I-E-O) model, the purpose of this retrospective correlational study was to determine whether a significant relationship exists between prerequisite grade point average (GPA), Test for Essential Academic Skills (TEAS) composite scores, entrance and exit CTA scores, and nursing GPA and the outcome of interest, passing the NCLEX-RN exam. Archival data for 64 students enrolled in a baccalaureate degree program at a Texas university were analyzed using binary logistic regression. A significant positive relationship was found between prerequisite GPA, TEAS composite scores, entrance and exit CTA scores, and nursing GPA, and the outcome of interest, passing the NCLEX-RN exam. However, in looking at each independent variable separately, no significant relationship was revealed between the individual scores of the prerequisite GPA, TEAS composite, entrance and exit critical thinking assessment, nursing GPA, and the outcome of passing the NCLEX-RN exam on the first attempt. These findings have implications for positive social change by illuminating the complexities of nursing program retention and graduation and informing efforts to train the most talented nurses.