Comparison of dynamic balance in adolescent male soccer players from rwanda and the United States.

PURPOSE/BACKGROUND: Dynamic balance is an important component of motor skill development. Poor dynamic balance has previously been associated with sport related injury. However, the vast majority of dynamic balance studies as they relate to sport injury have occurred in developed North American or European countries. Thus, the purpose of this study was to compare dynamic balance in adolescent male soccer players from Rwanda to a matched group from the United States. METHODS: Twenty-six adolescent male soccer players from Rwanda and 26 age- and gender-matched control subjects from the United States were screened using the Lower Quarter Y Balance Test during their pre-participation physical. Reach asymmetry (cm) between limbs was examined for all reach directions. In addition, reach distance in each direction (normalized to limb length, %LL) and the composite reach score (also normalized to %LL) were examined. Dependent samples t-tests were performed with significant differences identified at p<0.05. RESULTS: Twenty-six male soccer players from Rwanda (R) were matched to twenty-six male soccer players from the United States (US). The Rwandan soccer players performed better in the anterior (R: 83.9 ± 3.2 %LL; US: 76.5 ± 6.6 %LL, p<0.01), posterolateral (R: 114.4 ± 8.3 %LL ; US: 106.5 ± 8.2 %LL, p<0.01) and composite (R: 105.6 ± 1.3 %LL; US: 97.8 ± 6.2 %LL, p<0.01) reach scores. No significant differences between groups were observed for reach asymmetry. CONCLUSIONS: Adolescent soccer players from Rwanda exhibit superior performance on a standardized dynamic balance test as comparison to similar athletes from the United States. The examination of movement abilities of athletes from countries of various origins may allow for a greater understanding of the range of true normative values for dynamic balance. LEVELS OF EVIDENCE: 3b.

Due to her tender age: Black girls and childhood on trial in South Carolina, 1885-1920

Drawing on local criminal court records in western and central South Carolina, this dissertation follows the legal experiences of black girls in South Carolina courts between 1885 and 1920, a time span that includes the aftermath of Reconstruction and the foundational years of Jim Crow. While scholars continue to debate the degree to which black children were included in evolving conversations about childhood and child protection, this dissertation argues that black girls were critical to turn-of-the century debates about all children's roles in society. Far from invisible in the courts and jails of their time, black girls found themselves in the crosshairs of varying forms of power --including intraracial community surveillance, burgeoning local government, Progressive reform initiatives and military policy -- particularly when it came to matters of sexuality and reproduction. Their presence in South Carolina courts established boundaries between early childhood, adolescence and womanhood and pushed legal stakeholders to consider the legal implication of age, race, and gender in criminal proceedings. Age had a complicated effect on black girls' legal encounters; very young black girls were often able to claim youth and escape harsher punishments, while courts often used judicial discretion to levy heavier sentences to adolescents and violent girl offenders. While courts helped to separate early childhood from the middle years, they also provided a space for African-American children and family to engage a legal system that was moving rapidly toward disenfranchising blacks.

The frequency of voluntary and involuntary autobiographical memories across the life span.

In the present study, ratings of the memory of an important event from the previous week on the frequency of voluntary and involuntary retrieval, belief in its accuracy, visual imagery, auditory imagery, setting, emotional intensity, valence, narrative coherence, and centrality to the life story were obtained from 988 adults whose ages ranged from 15 to over 90. Another 992 adults provided the same ratings for a memory from their confirmation day, when they were at about age 14. The frequencies of involuntary and voluntary retrieval were similar. Both frequencies were predicted by emotional intensity and centrality to the life story. The results from the present study-which is the first to measure the frequency of voluntary and involuntary retrieval for the same events-are counter to both cognitive and clinical theories, which consistently claim that involuntary memories are infrequent as compared with voluntary memories. Age and gender differences are noted.

The Politics of Gender Socialization

This manuscript is comprised of three papers that examine the far-reaching and often invisible political outcomes of gender role socialization in the United States. These papers focus primarily on two areas: political confidence amongst girls and women, and the effects of gender on survey measurement and data quality.

Chapter one focuses on political confidence, and the likelihood that women will run for political office. Women continue to be underrepresented at all levels of political leadership, and their lack of political ambition, relative to men, has been identified as a primary cause. In this paper, I explore the relationship between an individual's masculinity and femininity and her development of political ambition. Using original survey data from the 2012 Cooperative Congressional Election Study (CCES), I first empirically demonstrate that gender (masculinity/femininity) and sex (male/female) are unique elements of identity and, moreover, are both independently related to political ambition. I then explore the relevance of gender for the study of candidate emergence, testing whether and how masculinity and femininity might be related to political ambition are supported empirically. While the results suggest that masculinity is positively associated with the development of political ambition, the relationship between femininity and candidate emergence seems to be more complicated and not what prevailing stereotypes might lead us to expect. Moreover, while the relationship between masculinity and political ambition is the same for men and women, the relationship between femininity and political ambition is very different for women than it is for men. This study suggests that gender role socialization is highly related with both men's and women's desire to seek positions of political leadership.

Chapter two continues this exploration of gendered differences in the development of political ambition, this time exploring how social attractiveness and gendered perceptions of political leadership impact the desire to hold political office.Women are persistently underrepresented as candidates for public office and remain underrepresented at all levels of government in the United States. Previous literature suggests that the gendered ambition gap, gender socialization, insufficient recruitment, media scrutiny, family responsibilities, modern campaign strategies, and political opportunity structures all contribute to the gender imbalance in pools of officeholders and candidates. To explain women's reticence to run, scholars have offered explanations addressing structural, institutional, and individual-level factors that deter women from becoming candidates, especially for high positions in the U.S. government. This paper examines a previously unexplored factor: how dating and socialized norms of sexual attraction affect political ambition. This study investigates whether young, single, and heterosexual women's desire for male attention and fear of being perceived as unattractive or "too ambitious" present obstacles to running for office. The results of these experiments suggest that social expectations about gender, attraction and sexuality, and political office-holding may contribute to women's reticence to pursue political leadership. Chapter two is a co-authored work and represents the joint efforts of Laura Lazarus Frankel, Shauna Shames, and Nadia Farjood.

Chapter 3 bridges survey methodology and gender socialization, focusing on how interviewer sex affects survey measurement and data quality. Specifically, this paper examines whether and how matching interviewer and respondent sex affects panel attrition--respondents dropping out of the study after participating in the first wave. While the majority of research on interviewer effects suggests that matching interviewer and respondent characteristics (homophily) yields higher quality data, little work has examined whether this pattern holds true in the area of panel attrition. Using paradata from the General Social Survey (GSS), I explore this question. My analysis reveals that, despite its broader positive effects on data quality, matching interviewer and respondent sex increases likelihood to attrit. Interestingly, this phenomenon only emerges amongst male respondents. However, while assigning female interviewers to male respondents decreases their propensity to attrit, it also increases the likelihood of biased responses on gender related items. These conflicting outcomes represent a tradeoff for scholars and survey researchers, requiring careful consideration of mode, content, and study goals when designing surveys and/or analyzing survey data. The implications of these patterns and areas for further research are discussed.

Together, these papers illustrate two ways that gender norms are related to political outcomes: they contribute to patterns of candidate emergence and affect the measurement of political attitudes and behaviors.

Prospective Estimation of Radiation Dose and Image Quality for Optimized CT Performance

X-ray computed tomography (CT) is a non-invasive medical imaging technique that generates cross-sectional images by acquiring attenuation-based projection measurements at multiple angles. Since its first introduction in the 1970s, substantial technical improvements have led to the expanding use of CT in clinical examinations. CT has become an indispensable imaging modality for the diagnosis of a wide array of diseases in both pediatric and adult populations [1, 2]. Currently, approximately 272 million CT examinations are performed annually worldwide, with nearly 85 million of these in the United States alone [3]. Although this trend has decelerated in recent years, CT usage is still expected to increase mainly due to advanced technologies such as multi-energy [4], photon counting [5], and cone-beam CT [6].

Despite the significant clinical benefits, concerns have been raised regarding the population-based radiation dose associated with CT examinations [7]. From 1980 to 2006, the effective dose from medical diagnostic procedures rose six-fold, with CT contributing to almost half of the total dose from medical exposure [8]. For each patient, the risk associated with a single CT examination is likely to be minimal. However, the relatively large population-based radiation level has led to enormous efforts among the community to manage and optimize the CT dose.

As promoted by the international campaigns Image Gently and Image Wisely, exposure to CT radiation should be appropriate and safe [9, 10]. It is thus a responsibility to optimize the amount of radiation dose for CT examinations. The key for dose optimization is to determine the minimum amount of radiation dose that achieves the targeted image quality [11]. Based on such principle, dose optimization would significantly benefit from effective metrics to characterize radiation dose and image quality for a CT exam. Moreover, if accurate predictions of the radiation dose and image quality were possible before the initiation of the exam, it would be feasible to personalize it by adjusting the scanning parameters to achieve a desired level of image quality. The purpose of this thesis is to design and validate models to quantify patient-specific radiation dose prospectively and task-based image quality. The dual aim of the study is to implement the theoretical models into clinical practice by developing an organ-based dose monitoring system and an image-based noise addition software for protocol optimization.

More specifically, Chapter 3 aims to develop an organ dose-prediction method for CT examinations of the body under constant tube current condition. The study effectively modeled the anatomical diversity and complexity using a large number of patient models with representative age, size, and gender distribution. The dependence of organ dose coefficients on patient size and scanner models was further evaluated. Distinct from prior work, these studies use the largest number of patient models to date with representative age, weight percentile, and body mass index (BMI) range.

With effective quantification of organ dose under constant tube current condition, Chapter 4 aims to extend the organ dose prediction system to tube current modulated (TCM) CT examinations. The prediction, applied to chest and abdominopelvic exams, was achieved by combining a convolution-based estimation technique that quantifies the radiation field, a TCM scheme that emulates modulation profiles from major CT vendors, and a library of computational phantoms with representative sizes, ages, and genders. The prospective quantification model is validated by comparing the predicted organ dose with the dose estimated based on Monte Carlo simulations with TCM function explicitly modeled.

Chapter 5 aims to implement the organ dose-estimation framework in clinical practice to develop an organ dose-monitoring program based on a commercial software (Dose Watch, GE Healthcare, Waukesha, WI). In the first phase of the study we focused on body CT examinations, and so the patient’s major body landmark information was extracted from the patient scout image in order to match clinical patients against a computational phantom in the library. The organ dose coefficients were estimated based on CT protocol and patient size as reported in Chapter 3. The exam CTDIvol, DLP, and TCM profiles were extracted and used to quantify the radiation field using the convolution technique proposed in Chapter 4.

With effective methods to predict and monitor organ dose, Chapters 6 aims to develop and validate improved measurement techniques for image quality assessment. Chapter 6 outlines the method that was developed to assess and predict quantum noise in clinical body CT images. Compared with previous phantom-based studies, this study accurately assessed the quantum noise in clinical images and further validated the correspondence between phantom-based measurements and the expected clinical image quality as a function of patient size and scanner attributes.

Chapter 7 aims to develop a practical strategy to generate hybrid CT images and assess the impact of dose reduction on diagnostic confidence for the diagnosis of acute pancreatitis. The general strategy is (1) to simulate synthetic CT images at multiple reduced-dose levels from clinical datasets using an image-based noise addition technique; (2) to develop quantitative and observer-based methods to validate the realism of simulated low-dose images; (3) to perform multi-reader observer studies on the low-dose image series to assess the impact of dose reduction on the diagnostic confidence for multiple diagnostic tasks; and (4) to determine the dose operating point for clinical CT examinations based on the minimum diagnostic performance to achieve protocol optimization.

Chapter 8 concludes the thesis with a summary of accomplished work and a discussion about future research.