Laboratory studies of the kinetics of tropospheric and stratospheric atom and radical reactions

Direct measurements of reaction rate constants and branching fractions for elementary reactions necessary in the modeling of the troposphere or stratosphere are provided. Details of reaction mechanisms are elucidated by studying pressure and temperature dependences of reactions, as well as by use of isotopic labels. Measurement techniques are improved for radical species in the laboratory. Progress and results in each area are given

Spatial segmentation of large urban labour markets: Cultures of segregation among the urban poor?

Due to the selective process of suburbanisation of population and firms, a specific distribution of supply and demand categories has appeared within the urban space. The distribution of supply categories is more and more recognizable on the scale of neighbourhoods, both within the central city and the suburbs. The perspective of this paper is that space does not only reflect the differences in labour market chances among supply categories, but that it is also influencing these differences: the process of spatial segmentation. The question is whether the labour market chances of supply categories differs among neighbourhoods, due to personal characteristics like education, gender and etnicity and neighbourhood effects. In this paper two possible neighbourhood effects will be examined. First, the spatial distance between an individual and the location of employment will differ according to the neighbourhood where one lives. If low skilled employment is moving towards the suburbs, low skilled people in the central city will suffer due to the fact that their spatially restricted job search activities is lowering the job opportunities available for them. Second, if the population in the neighbourhood does have a low chance on the urban labour market, people might be influenced in their labour market behaviour by their neighbouring community in a negative way. The discussion of these two effects will help to provide a better insight into the nature of the problems experienced by people from the urban underclass.

Adolescents’ neural reactivity to acute psychosocial stress: dysfunctional regulation habits are linked to temporal gyrus response

Mid-adolescence is a critical time for the development of stress-related disorders and it is associated with significant social vulnerability. However, little is known about normative neural processes accompanying psychosocial stress at this time. Previous research found that emotion regulation strategies critically influence the relationship between stress and the development of psychiatric symptoms during adolescence. Using functional magnetic resonance imaging (fMRI), we examined neural responses to acute stress and analyzed whether the tendency to use adaptive or maladaptive emotion regulation strategies is related to neural and autonomic stress responses. Results show large linear activation increases from low to medium to high stress levels mainly in medial prefrontal, insulae and temporal areas. Caudate and subgenual anterior cingulate cortex, neural areas related to reward and affective valuations, showed linearly decreasing activation. In line with our hypothesis, the current adolescent neural stress profile resembled social rejection and was characterized by pronounced activation in insula, angular and temporal cortices. Moreover, results point to an intriguing role of the anterior temporal gyrus. Stress-related activity in the anterior temporal gyrus was positively related to maladaptive regulation strategies and stress-induced autonomic activity. Maladaptive coping might increase the social threat and reappraisal load of a stressor, relating to higher stress sensitivity of anterior temporal cortices

Microscopic Investigations of the Terahertz and the Extreme Nonlinear Optical Response of Semiconductors

In the major part of this Thesis, we discuss the linear THz response of semiconductor nanostructures based on a microscopic theory. Here, two different problems are investigated: intersubband transitions in optically excited quantum wells and the THz plasma response of two-dimensional systems. In the latter case, we analyze the response of correlated electron and electron-hole plasmas. Extracting the plasma frequency from the linear response, we find significant deviations from the commonly accepted two-dimensional plasma frequency. Besides analyzing the pure plasma response, we also consider an intermediate regime where the response of the electron-hole plasma consists of a mixture of plasma contributions and excitonic transitions. A quantitative experiment-theory comparison provides novel insights into the behavior of the system at the transition from one regime to the other. The discussion of the intersubband transitions mainly focuses on the coherent superposition of the responses from true THz transitions and the ponderomotively accelerated carriers. We present a simple method to directly identify ponderomotive effects in the linear THz response. Apart from that, the excitonic contributions to intersubband transitions are investigated. The last part of the present Thesis deals with a completely different regime. Here, the extreme nonlinear optical response of low-dimensional semiconductor structures is discussed. Formally, extreme nonlinear optics describes the regime of light-matter interaction where the exciting field is strong enough such that the Rabi frequency is comparable to or larger than the characteristic transition frequency of the investigated system. Here, the Rabi frequency is given by the product of the electrical field strength and the dipole-matrix element of the respective transition. Theoretical investigations have predicted a large number of novel nonlinear effects arising for such strong excitations. Some of them have been observed in experiments performed on semiconductors. Previous theoretical works often modeled the semiconductor as an ensemble of independent two-level systems. Such an approach does surely not account for many-body interactions among the carriers. Only very few publications exist that include Coulomb effects in the extreme nonlinear regime. Furthermore, these studies concentrated exclusively on the optically induced interband transitions. For the strong fields considered here, however, the ponderomotive intraband acceleration of the photo-excited carriers cannot be neglected a priori. In our discussion of the extreme nonlinear optical response of semiconductors, we will analyze both the influence of the Coulomb interaction and the effect of carrier accelerations. The Thesis is organized as follows. In Chap. 2, we give an overview of our microscopic theory that has been used to obtain the results presented in this work. Chapter 3 discusses intersubband transitions of optically excited quantum wells. Besides a purely theoretical analysis of excitonic effects, a detailed experiment-theory comparison is presented. Chapter 4 deals with the intraband dynamics in two-dimensional semiconductor systems. Here, our results are also compared to recent experiments. In Chap. 5, we explore the extreme nonlinear optical response of semiconductor nanostructures. Finally, we summarize our findings and give a short outlook in Chap. 6

Trouble in Paradise: Investigating Rape-Collusive Attitudes, Beliefs, and Practices on a Boarding School Campus

From the Washington University Senior Honors Thesis Abstracts (WUSHTA), 2017. Published by the Office of Undergraduate Research. Joy Zalis Kiefer, Director of Undergraduate Research and Associate Dean in the College of Arts & Sciences; Lindsey Paunovich, Editor; Helen Human, Programs Manager and Assistant Dean in the College of Arts and Sciences Mentors: Jami Ake, Mary Ann Dzuback, and Kim Web

The therapeutic importance of understanding mechanisms of neuronal cell death in neurodegenerative disease

Despite major advances in our understanding of the initiating factors that trigger many neurodegenerative disorders, to date, no novel disease-modifying therapies have been shown to provide significant benefit for patients who suffer from these devastating disorders. As most neurodegenerative disorders are late-onset, slowly progressive, and appear to have long relatively asymptomatic prodromal phases, it is possible that therapies optimally targeting the triggers of these disorders may have limited benefit when treatment is initiated in the symptomatic patient. Such therapies may work in the prodromal phase, or when given prophylactically, but in the symptomatic patient there simply may be too much damage to the neuronal networks to restore functionality by reducing or even eliminating the primary stressor. As functional neuronal demise and overt neuronal death are almost certainly the key factors that mediate the functional impairment, it is clear that preventing neuronal death and dysfunction will have a huge clinical benefit. Unfortunately, we lack a detailed understanding of neuronal death pathways in almost all neurodegenerative disorders. To rationally develop new disease modifying therapies that target steps in the degenerative cascade downstream of the disease trigger will require a number of factors. First, we need to refocus our basic research efforts on identifying the precise steps in the pathological cascade that lead to neuronal death in each neurodegenerative disease and, if possible, determine the relative placement of those events within a potentially very complex cascade. Second, we will need to determine which of these steps are potentially targetable. Finally, we will need to develop novel therapies that interfere with these steps and demonstrate that such therapies alone, or in combination with therapies that target the trigger of these devastating diseases, have clinical benefit