Electrochemical hydrogen charging of duplex stainless steel

This study evaluates the electrochemical hydrogen charging behavior and interaction between hydrogen and the microstructure of a duplex stainless steel. A saturation level of approximately 650 wppm is reached after 10 d of charging. The data are compared with a model resulting in a diffusion coefficient of 2.1 x 10(-14) m(2)/s. A two-step increase of the concentration is observed and ascribed to saturation of ferrite followed by charging of austenite grains. Microstructural changes are observed during charging, i.e., formation and interaction of dislocations, as a result of the high residual stresses inherent to the production process of duplex stainless steels

Fostering Student Agency to Build a Whole Child, Whole School, Whole Community Approach

In this practitioner perspective, we explore the concept of student agency through the implementation of a student government association in a laboratory middle school. Interviews with a social studies teacher and her students offer perspectives of the impact of student voice and choice for student experiences. We describe three major lessons learned through this implementation process: students learn to have healthy conflict and cooperative skills; students learn the appropriate processes to enact change in a democratic society; and students learn to conduct service for their peers, school, and community

Interdisciplinarity: A Catalyst for Faculty Engagement win Internationalization

Despite the benefits of international scholarship to higher education institutions, faculty engagement in internationalization remains a major challenge for many universities. This study sheds light on this problem by investigating the strategies used by two institutions to engage faculty in internationalization through interdisciplinarity. This study found that as interdisciplinarity emphasizes comparative approaches, it prompted faculty to advance the comprehensiveness of their scholarship through the integration of cross-cultural perspectives. Notably, this study presents a model to assist institutions in overcoming endogenous obstacles by providing three infrastructural components--time, place, and financial resources--for faculty to engage in interdisciplinary and international scholarship

Complicated Grief Treatment: What Makes It Work?

This dissertation is an exploration of the putative mediators of complicated grief treatment (CGT) in an effort to gain a better understanding of the mechanisms by which the treatment exerts its effects. This three-paper dissertation utilizes data from an NIMH-funded randomized controlled trial of CGT (Shear et al., 2005), which showed that CGT is more effective than Interpersonal Psychotherapy (IPT) in reducing symptoms of complicated grief (CG). The first paper examines a broad range of ancillary outcomes including symptoms of anxiety, depression, complicated grief and sleep disturbance due to bad dreams. Antidepressant use is examined as a possible moderator since half the sample was taking antidepressants and those taking antidepressants had a marginally better response rate in CGT than those not taking them (59% vs. 42% in CGT and 40% vs. 19% in IPT). CGT was more effective than IPT in reducing cognitive symptoms of anxiety, depression as measured by the Hamilton Rating Scale for Depression (HRSD), somatic symptoms of depression, guilt/self-blame, negative thoughts about the future, avoidance and poor sleep due to bad dreams. The difference in treatment effect on the HRSD for CGT over IPT was more pronounced for participants not taking antidepressants where CGT reduced depression but IPT did not. Paper two examines possible mediators specific to the model of CGT including: guilt/self-blame specific to the death or deceased; negative thoughts about the future; avoidance of reminders of the loss; anxiety and depression (intense negative emotions). Antidepressants are also examined as a potential moderator to explore whether their use affects the mediating role of the identified variables. All of these variables emerged as either full or partial mediators of CGT. Antidepressant use had no effect on the mediating role of these variables. Paper three examines whether alliance (measured at week 4) predicts subsequent change in grief symptoms (controlling for early symptom change) and if so, whether it accounts for the difference in treatment effect between CGT and IPT (mediation). Working alliance emerged as a mediator of CGT, accounting for 28% of the treatment effect found between CGT/IPT and grief symptoms. Discussion sections for each paper summarize study findings, limitations and implications for future research

Moduli Stabilization and Supersymmetry Breaking in Deflected Mirage Mediation

We present a model of supersymmetry breaking in which the contributions from gravity/modulus, anomaly, and gauge mediation are all comparable. We term this scenario "deflected mirage mediation," which is a generalization of the KKLT-motivated mirage mediation scenario to include gauge mediated contributions. These contributions deflect the gaugino mass unification scale and alter the pattern of soft parameters at low energies. In some cases, this results in a gluino LSP and light stops; in other regions of parameter space, the LSP can be a well-tempered neutralino. We demonstrate explicitly that competitive gauge-mediated terms can naturally appear within phenomenological models based on the KKLT setup by addressing the stabilization of the gauge singlet field which is responsible for the masses of the messenger fields. For viable stabilization mechanisms, the relation between the gauge and anomaly contributions is identical in most cases to that of deflected anomaly mediation, despite the presence of the Kahler modulus. Turning to TeV scale phenomenology, we analyze the renormalization group evolution of the supersymmetry breaking terms and the resulting low energy mass spectra. The approach sets the stage for studies of such mixed scenarios of supersymmetry breaking at the LHC.Comment: 33 pages, 8 figures. Published version in Journal of High Energy Physic

Initiation of hydrogen induced cracks at secondary phase particles

The goal of this work is to propose a general mechanism for hydrogen induced crack initiation in steels based on a microstructural study of multiple steel grades. Four types of steels with strongly varying microstructures are studied for this purpose, i.e. ultra low carbon (ULC) steel, TRIP (transformation induced plasticity) steel, Fe-C-Ti generic alloy, and pressure vessel steel. A strong dependency of the initiation of hydrogen induced cracks on the microstructural features in the materials is observed. By use of SEM-EBSD characterization, initiation is found to always occur at the hard secondary phase particles in the materials

Survival of Massive Star-forming Galaxies in Cluster Cores Drives Gas-Phase Metallicity Gradients : The Effects of Ram Pressure Stripping

Recent observations of galaxies in a cluster at z=0.35 show that their integrated gas-phase metallicities increase with decreasing cluster-centric distance. To test if ram pressure stripping (RPS) is the underlying cause, we use a semi-analytic model to quantify the "observational bias" that RPS introduces into the aperture-based metallicity measurements. We take integral field spectroscopy of local galaxies, remove gas from their outer galactic disks via RPS, and then conduct mock slit observations of cluster galaxies at z=0.35. Our RPS model predicts a typical cluster-scale metallicity gradient of -0.03 dex/Mpc. By removing gas from the outer galactic disks, RPS introduces a mean metallicity enhancement of +0.02 dex at a fixed stellar mass. This gas removal and subsequent quenching of star formation preferentially removes low mass cluster galaxies from the observed star-forming population. As only the more massive star-forming galaxies survive to reach the cluster core, RPS produces a cluster-scale stellar mass gradient of -0.05 log(M_*/M_sun)/Mpc. This mass segregation drives the predicted cluster-scale metallicity gradient of -0.03 dex/Mpc. However, the effects of RPS alone can not explain the higher metallicities measured in cluster galaxies at z=0.35. We hypothesize that additional mechanisms including steep internal metallicity gradients and self-enrichment due to gas strangulation are needed to reproduce our observations at z=0.35.Comment: 17 pages, 21 figures, accepted for publication Ap

Extraction of higher-order nonlinear electronic response to strong field excitation in solids using high harmonic generation

State-of-the-art experiments employ strong ultrafast optical fields to study the nonlinear response of electrons in solids on an attosecond time-scale. Notably, a recent experiment retrieved a 3rd order nonlinear susceptibility by comparing the nonlinear response induced by a strong laser field to a linear response induced by the otherwise identical weak field. In parallel, experiments have demonstrated high harmonic generation (HHG) in solids, a highly nonlinear process that until recently had only been observed in gases. The highly nonlinear nature of HHG has the potential to extract even higher order nonlinear susceptibility terms, and thereby characterize the entire response of the electronic system to strong field excitation. However, up till now, such characterization has been elusive due to a lack of direct correspondence between high harmonics and nonlinear susceptibilities. Here, we demonstrate a regime where such correspondence can be clearly made, extracting nonlinear susceptibilities (7th, 9th, and 11th) from sapphire of the same order as the measured high harmonics. The extracted high order susceptibilities show angular-resolved periodicities arising from variation in the band structure with crystal orientation. Nonlinear susceptibilities are key to ultrafast lightwave driven optoelectronics, allowing petahertz scaling manipulation of the signal. Our results open a door to multi-channel signal processing, controlled by laser polarization