scholarly journals The HIV/STI Epidemic Potential of Dynamic Sexual Networks of Men Who Have Sex With Men in Atlanta and San Francisco

Author(s):  
Emeli J. Anderson ◽  
Kevin M. Weiss ◽  
Martina M. Morris ◽  
Travis H. Sanchez ◽  
Pragati Prasad ◽  
...  

ABSTRACTBackgroundThe potential speed through which a pathogen may circulate in a network is a function of network connectivity. Network features like degree (number of ongoing partnerships) determine the cross-sectional network connectivity. The overall transmission potential of a pathogen involves connectivity over time, which can be measured using the forward reachable path (FRP). We modeled dynamic sexual networks of MSM in San Francisco and Atlanta to estimate the FRP as a predictor of HIV/STI epidemic potential.MethodsWe used exponential random graph models to obtain parameter estimates for each city’s sexual network and then simulated the complete networks over time. The FRP was estimated in each city overall and stratified by demographics.ResultsThe overall mean and median FRPs were higher in San Francisco than in Atlanta, suggesting a greater epidemic potential for HIV and STIs in San Francisco. At one year, in both cities, the average FRP among casual partnerships was highest in the youngest age group and lowest in the oldest age group, contrasting with the cross-sectional network parameters we estimated, where the youngest age category had the lowest mean degree and the oldest age category had the highest mean degree.ConclusionsThe FRP results correspond to the observed STI epidemics but not HIV epidemics between the cities. In San Francisco, rates of HIV have been declining over the last few years, whereas they have been steady in Atlanta. The FRP by age group resulted in fundamentally different conclusions about connectivity in the network compared with the cross-sectional network measures.

2021 ◽  
Vol 12 (2) ◽  
pp. 647-682 ◽  
Author(s):  
Torben G. Andersen ◽  
Martin Thyrsgaard ◽  
Viktor Todorov

We study the temporal behavior of the cross‐sectional distribution of assets' market exposure, or betas, using a large panel of high‐frequency returns. The asymptotic setup has the sampling frequency of returns increasing to infinity, while the time span of the data remains fixed, and the cross‐sectional dimension of the panel is either fixed or increasing. We derive functional limit results for the cross‐sectional distribution of betas evolving over time. We demonstrate, for constituents of the S&P 500 market index, that the dispersion in betas is elevated at the market open and gradually declines over the trading day. This intraday pattern varies significantly over time and reacts to information shocks such as clustered earning announcements and releases of macroeconomic news. We find that earnings news increase beta dispersion while FOMC announcements have the opposite effect on market betas.


1992 ◽  
Vol 36 (2) ◽  
pp. 171-174 ◽  
Author(s):  
Andrew S. Jackson ◽  
Earl F. Beard ◽  
Larry T. Wier ◽  
J. E. Stuteville

The purpose of this study was to develop a multivariate model with cross-sectional data that defined the decline in VO2max over time, and cross-validate the model with longitudinal data. The cross-sectional sample consisted of 1,608 healthy men who ranged in age from 25 to 70 years. VO2max was directly measured during a maximum Bruce treadmill stress test. Regression analysis showed that the cross-sectional age and VO2max relationship was linear, r = 0.45 and the age decline in VO2max was 0.48 ml/kg/min/year. Multiple regression developed the multivariate model from age, percent body fat (%fat), self-report physical activity (SR-PA), and the interaction of SR-PA and %fat (R = 0.793). Accounting for the variance in percent body fat and exercise habits decreased the influence of age on the decline of VO2max to just −0.27 ml/kg/min/year. This showed that much of decline in maximal physical working capacity was due to physical activity level and percent body fat, not aging. The multivariate equation was applied to the data of the longitudinal sample of 156 men who had been tested twice (Mean AgeΔ = 3.1 ± 1.2 years). The correlation between the measured and estimated change in VO2max over time (ΔVO2max) was 0.75. The results of the study showed that changes in body composition and exercise habits had more of an influence on changes in maximal physical working capacity than aging. The developed model provides a useful way to quantify the changes in physical working capacity with aging.


2010 ◽  
Vol 2 (1) ◽  
pp. 100-111 ◽  
Author(s):  
Darrell Duffie ◽  
Gaston Giroux ◽  
Gustavo Manso

We study the “percolation” of information of common interest through a large market as agents encounter and reveal information to each other over time. We provide an explicit solution for the dynamics of the cross-sectional distribution of posterior beliefs. We also show that convergence of the cross-sectional distribution of beliefs to a common posterior is exponential and that the rate of convergence does not depend on the size of the groups of agents that meet. The rate of convergence is merely the mean rate at which an individual agent is matched. (JEL D83)


2004 ◽  
Vol 359 (1443) ◽  
pp. 421-436 ◽  
Author(s):  
S. L. Lewis ◽  
O. L. Phillips ◽  
T. R. Baker ◽  
J. Lloyd ◽  
Y. Malhi ◽  
...  

Several widespread changes in the ecology of old–growth tropical forests have recently been documented for the late twentieth century, in particular an increase in stem turnover (pan–tropical), and an increase in above–ground biomass (neotropical). Whether these changes are synchronous and whether changes in growth are also occurring is not known. We analysed stand–level changes within 50 long–term monitoring plots from across South America spanning 1971–2002. We show that: (i) basal area (BA: sum of the cross–sectional areas of all trees in a plot) increased significantly over time (by 0.10 ±; 0.04 m 2 ha −1 yr −1 , mean ± 95%CI) as did both (ii) stand–level BA growth rates (sum of the increments of BA of surviving trees and BA of new trees that recruited into a plot); and (iii) stand–level BA mortality rates (sum of the cross–sectional areas of all trees that died in a plot). Similar patterns were observed on a per–stem basis: (i) stem density (number of stems per hectare; 1 hectare is 10 4 m 2 ) increased significantly over time ( 0.94 ± 0.63 stems ha −1 yr −1 ); as did both (ii) stem recruitment rates; and (iii) stem mortality rates. In relative terms, the pools of BA and stem density increased by 0.38 ± 0.15% and 0.18 ± 0.12% yr −1 , respectively. The fluxes into and out of these pools—stand–level BA growth, stand–level BA mortality, stem recruitment and stem mortality rates—increased, in relative terms, by an order of magnitude more. The gain terms (BA growth, stem recruitment) consistently exceeded the loss terms (BA loss, stem mortality) throughout the period, suggesting that whatever process is driving these changes was already acting before the plot network was established. Large long–term increases in stand–level BA growth and simultaneous increases in stand BA and stem density imply a continent–wide increase in resource availability which is increasing net primary productivity and altering forest dynamics. Continent–wide changes in incoming solar radiation, and increases in atmospheric concentrations of CO 2 and air temperatures may have increased resource supply over recent decades, thus causing accelerated growth and increased dynamism across the world's largest tract of tropical forest.


2018 ◽  
Vol 14 (2) ◽  
pp. 18-30
Author(s):  
Saman Kapilawanse ◽  
R. P. Bichha ◽  
Sudath Samaraweera ◽  
Nirupa Pallewatte ◽  
Harshni Vitharana ◽  
...  

Introduction: A descriptive cross sectional study was carried out in 5 randomly selected districts i.e Gampaha, Kandy, Badulla, Nuwara Eliya and Ratnapura during the period of March to September 2014. The general objective of the study was to describe the trend of TB among young population over past 6 years in Sri Lanka and to determine contributory factors associated with TB among young population.Methodology: The study was carried out in two stages. The first stage was analysis of the trend of TB over the 6 year period of 2008-2014. The analysis of the trend was carried out using the existing secondary data at the Medical Records Division of the National Programme for Tuberculosis Control and Chest Diseases (NPTCCD). Trend was analyzed for new cases of TB patients of 15--34 years of age and separately for 15-24 and 25-34 age groups and for each type of new TB cases. The second stage was a descriptive cross sectional study which was carried out to determine the associated factors. All the patients (new/ retreatment)in age group of 15-34 years and registered at the selected district chest clinics with confi rmed TB were selected as the study subjects. Operational Definitions were used to identify confi rmed TB cases ie, Sputum smear positive TB, smear negative pulmonary TB and Extra pulmonary TB. The data were collected using a pre tested interviewer administered questionnaire by the District Tuberculosis Control Officers attached to the relevant District Chest Clinics.Result: The main findings of the study were, The two peaks of TB incidence were observed in the trend across age groups and first one was in the age group of 25-34 years second peak in the age group of 45-54.Overall trend of TB in the country is more towards the older age groups (over 45 years), but shift to younger age groups were observed in 15 out of 16 districts in the country. A total of 223 patients were included in the descriptive study. The highest proportion (34%) of study population was from the district of Gampaha while least proportion (10%) of it was from Nuwara Eliya. Nearly 53% of the study population was above 25 years of age with the sex ratio of 1:1. A majority (68%) of the study population was Sinhalese while nearly 70% of the study population has passed the O/L, A/L, Diploma or a degree. About one third of the study population was unemployed. Nearly half (50.4%) of the study population was having monthly income of about Rs. 20,000.00 or above. 31% of the study population were current or past alcohol consumers and 29% were smokers and 7% of the study population were current or past cannabis consumers. Majority (77%) of the study population were under-nourished while 14% of them were less than 15 kg/m2. Nearly three fourth (72%) of the study population have been diagnosed by a consultant. Statistically signifi cant associations were found between the age category and more than 3 family members (χ2=5.063, df=1, p<0.017), ethnicity (χ2=4.229, df=1, p<0.04), employment category (χ2=13.859, df=3, p<0.003). Statistically significant associations were not found between the age category and residing district (χ2=5.962, df=4, p<0.202) and type of house (χ2=1.875, df=1, p<0.110),Conclusion: The study recommends more detailed assessment regarding the dietary habits of the patients, Emphasis on community awareness regarding nutritional aspects. Improving the nutritional status among adolescents and young adults. Modification of risky life style factors, Improvement of socio economic status through enhancement of financial stability, minimizing overcrowding and improvement of housing conditions and involving of non NTP health care providers and health professionals for TB diagnosis and management through capacity building and awareness. SAARC Journal of Tuberculosis, Lung Diseases and HIV/AIDS, Vol. 14, No. 2, 2017, Page: 18-30


Author(s):  
Megan M Sheehan ◽  
Elizabeth R. Pfoh ◽  
Sidra Speaker ◽  
Michael B. Rothberg

Public health recommendations aimed at limiting spread of SARS-CoV-2 have encouraged social distancing and masks as economies across the United States re-open. Understanding adherence to these guidelines will inform further efforts to reduce transmission. In this repeated cross-sectional survey study, we describe changes in social behavior in Ohio during periods of declining and rising cases. While essential activities remained consistent over time, more individuals attended gatherings of 10 or more people as cases rose, particularly in the 18-29 age group. A majority of individuals wore masks. It appears necessary to continue limiting gatherings and encourage mask-wearing, particularly among younger groups.


2021 ◽  
Author(s):  
◽  
Madeleine Brocklesby

<p>Non-Suicidal Self-Injury (NSSI) is defined as the intentional, direct injury to body tissue, undertaken without suicidal intent, and for a purpose that is not socially or culturally sanctioned (International Society for the Study of Self-Injury, 2007; Klonsky & Muehlenkamp, 2007; Muehlenkamp, 2014). NSSI is prevalent in adolescent samples worldwide (Muehlenkamp, Claes, Havertape, & Plener, 2012; Swannell, Martin, Page, Hasking, & St John, 2014) and is typically considered a marker of wider distress. NSSI in adolescents has been associated with numerous poor mental health outcomes, including depression, anxiety, substance abuse, eating disorders, and attempted and completed suicide (Asarnow et al., 2011; Brunner et al., 2014; Claes, Soenens, Vansteenkiste, & Vandereycken, 2012; Fox et al., 2015; Glenn & Klonsky, 2011; Jacobson & Gould, 2007).  In addition, research has demonstrated that perfectionism, defined as the setting of excessively high standards of performance (Frost, Marten, Lahart, & Rosenblate, 1990), is also commonly associated with substantial distress. Unfortunately, perfectionism in adolescents is thought to be on the rise (see Flett & Hewitt, 2014; Portesova & Urbanek, 2013) with many adolescents reporting multi-sourced and relentless pressure to perform highly and adhere to societal ideals. As such, individuals are setting excessively high goals for themselves, and increasingly worrying about the consequences of less than perfect performance. Similar to the research pertaining to NSSI, perfectionism has been shown to also be associated with a raft of poor outcomes including depression, anxiety, eating disorders, and general psychological distress (e.g., Boone, Braet, Vandereycken, & Claes, 2013; Claes et al., 2012; DiBartolo et al., 2007; Lombardo, Mallia, Battagliese, Grano, & Violani, 2013; Vartanian & Grisham, 2011).  Research has shown an association between NSSI and perfectionism (e.g., Hoff & Muehlenkamp, 2009; O’Connor, Rasmussen, & Hawton, 2010). However, this literature is currently very limited and the relationship between NSSI and perfectionism is not well understood. In light of this, I set out to thoroughly explore if, and how, NSSI and perfectionism are related in New Zealand adolescents. Moreover, I aimed to gain insight into the mechanisms that could underpin such relationships.  Of the four studies conducted, the first and second studies established a foundation for my research. Specifically, Study 1 meta-analyses synthesised data from 118 studies investigating the relationship between perfectionism and adaptive and maladaptive outcomes. These analyses demonstrated a robust relationship between negative perfectionism and maladaptive outcomes. More specifically, they revealed a significant, positive summary correlation for the relationship between negative perfectionism and self-injurious thoughts and behaviours.  Study 2 aimed to define the most appropriate conceptualisation of perfectionism for research with New Zealand adolescents. This involved investigating the psychometric properties and factor structure of the Frost Multidimensional Perfectionism Scale (Frost et al., 1990) in 930 adolescents with a mean age of 14 years old. A hierarchical structure with two overarching components (positive perfectionism, negative perfectionism), comprised of four second-level components (concerns and doubts, parental pressure, personal standards, and organisation) was identified and adopted for all following research.  Studies 3 and 4 investigated the cross-sectional and longitudinal relationships between NSSI and perfectionism. Study 3a specifically aimed to ascertain whether negative and positive perfectionism are associated with NSSI in New Zealand adolescents, based on survey data from 930 adolescents in their second year of high school. As expected, negative perfectionism was significantly associated with NSSI in females, however this relationship did not hold for males. On the other hand, positive perfectionism was associated with less engagement in NSSI in both males and females. This suggested that negative perfectionism may represent a risk factor for NSSI, while positive perfectionism may buffer against risk of NSSI. In addition, Study 3b investigated the relationships between perfectionism and the functions of NSSI, indicating that self-punishment functions are particularly relevant for perfectionistic adolescents. As the final component of the cross-sectional analyses, Study 3c illustrated that the association between perfectionism and NSSI is more accurately captured when the interaction between positive and negative perfectionism is also considered.  Study 4 involved the examination of this relationship over time. To do so, another wave of data was collected, resulting in data matched across two times points for 608 adolescents. Longitudinal analyses demonstrated that negative perfectionism prospectively predicted NSSI one year later in females only. Moreover, again for only females, positive perfectionism predicted an increase in negative perfectionism over time. No significant longitudinal relationships were demonstrated for male adolescents.  The ultimate aim of this research was to provide clinicians, school staff and parents with the information required to effectively identify at-risk adolescents, and thereby prevent the onset of NSSI and its vast associated negative outcomes. This research suggests that perfectionism is one such risk factor to be aware of. As such, it is argued that targeted prevention and intervention strategies for perfectionism will help prevent the onset and maintenance of NSSI in females, and are also likely to be of benefit to the wider mental wellbeing of New Zealand adolescents.</p>


Author(s):  
Shi Yu Chan ◽  
Roscoe Brady ◽  
Melissa Hwang ◽  
Amy Higgins ◽  
Kathryn Nielsen ◽  
...  

Abstract Imaging studies in psychotic disorders typically examine cross-sectional relationships between magnetic resonance imaging (MRI) signals and diagnosis or symptoms. We sought to examine changes in network connectivity identified using resting-state functional MRI (fMRI) corresponding to divergent functional recovery trajectories and relapse in early-stage psychosis (ESP). Prior studies have linked schizophrenia to hyperconnectivity in the default mode network (DMN). Given the correlations between the DMN and behavioral impairments in psychosis, we hypothesized that dynamic changes in DMN connectivity reflect the heterogeneity of outcomes in ESP. Longitudinal data were collected from 66 ESP patients and 20 healthy controls. Longitudinal cluster analysis identified subgroups of patients with similar trajectories in terms of symptom severity and functional outcomes. DMN connectivity was measured in a subset of patients (n = 36) longitudinally over 2 scans separated by a mean of 12 months. We then compared connectivity between patients and controls, and among the different outcome trajectory subgroups. Among ESP participants, 4 subgroups were empirically identified corresponding to: “Poor,” “Middle,” “Catch-up,” and “Good” trajectory outcomes in the complete dataset (n = 36), and an independent replication (n = 30). DMN connectivity changes differed significantly between functional subgroups (F3,32 = 6.06, P-FDR corrected = .01); DMN connectivity increased over time in the “Poor” outcome cluster (β = +0.145) but decreased over time in the “Catch-up” cluster (β = −0.212). DMN connectivity is dynamic and correlates with a change in functional status over time in ESP. This approach identifies a brain-based marker that reflects important neurobiological processes required to sustain functional recovery.


2004 ◽  
Vol 50 (3) ◽  
pp. 395-411 ◽  
Author(s):  
Sean Nicholson-Crotty

This article argues that the conclusions of previous research on the impact of sentencing guidelines may be misleading due to the cross-sectional methodologies employed in these studies. This study will suggest that a theoretically driven longitudinal analysis of mandatory guidelines offers a more appropriate way to study these policies. Specifically, the author proposes that over time, guidelines that link sentencing decisions to correctional resources help to mitigate prison populations, while those that do not tend to contribute to growth in that area. An analysis of prison populations in the American states between 1975 and 1998 confirms this proposition. The results suggest that mandatory guidelines have increased both commitment and incarceration rates in states where sentencing decisions are not resource driven. Alternatively, when mandatory guidelines are linked to capacity and expenditures, these policies have had either a negative or an insignificant impact on prison populations.


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