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"Harding, David"
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WikiLeaks : inside Julian Assange's war on secrecy
Traces the history of the online organization WikiLeaks, which released thousands of previously secret or classified documents from numerous government agencies, and examines its impact on world politics and freedom of information.
Book
Neighborhood Effects in Temporal Perspective: The Impact of Long-Term Exposure to Concentrated Disadvantage on High School Graduation
Theory suggests that neighborhood effects depend not only on where individuals live today, but also on where they lived in the past. Previous research, however, usually measures neighborhood context only once and does not account for length of residence, thereby understating the detrimental effects of long-term neighborhood disadvantage. This study investigates effects of duration of exposure to disadvantaged neighborhoods on high school graduation. It follows 4,154 children in the Panel Study of Income Dynamics, measuring neighborhood context once per year from age 1 to 17. The analysis overcomes the problem of dynamic neighborhood selection by adapting novel methods of causal inference for time-varying treatments. In contrast to previous analyses, these methods do not \"control away\" the effect of neighborhood context operating indirectly through time-varying characteristics of the family; thus, they capture the full impact of a lifetime of neighborhood disadvantage. We find that sustained exposure to disadvantaged neighborhoods has a severe impact on high school graduation that is considerably larger than effects reported in prior research. We estimate that growing up in the most (compared to the least) disadvantaged quintile of neighborhoods reduces the probability of graduation from 96 to 76 percent for black children, and from 95 to 87 percent for nonblack children.
Journal Article
Counterfactual Models of Neighborhood Effects: The Effect of Neighborhood Poverty on Dropping Out and Teenage Pregnancy
This article investigates the causal effects of neighborhood on high school dropping out and teenage pregnancy within a counterfactual framework. It shows that when two groups of children, identical at age 10 on observed factors, experience different neighborhoods during adolescence, those in high-poverty neighborhoods are more likely to drop out of high school and have a teenage pregnancy than those in low-poverty neighborhoods. Causal inferences from such associations have been plagued by the possibility of selection bias. Using a new method for sensitivity analysis, these effects are shown to be robust to selection bias. Unobserved factors would have to be unreasonably strong to account for the associations between neighborhood and the outcomes. 10 Tables, 2 Figures, 84 References. (Original abstract - amended)
Journal Article
Incarceration, Prisoner Reentry, and Communities
Since the mid-1970s, the United States has experienced an enormous rise in incarceration and accompanying increases in returning prisoners and in postrelease community correctional supervision. Poor urban communities are disproportionately impacted by these phenomena. This review focuses on two complementary questions regarding incarceration, prisoner reentry, and communities: (a) whether and how mass incarceration has affected the social and economic structure of American communities, and (b) how residential neighborhoods affect the social and economic reintegration of returning prisoners. These two questions can be seen as part of a dynamic process involving a pernicious feedback loop in which mass incarceration undermines the structure and social organization of some communities, thus creating more criminogenic environments for returning prisoners and further diminishing their prospects for successful reentry and reintegration.
Journal Article
Nanoscale Thermosensitive Hydrogel Scaffolds Promote the Chondrogenic Differentiation of Dental Pulp Stem and Progenitor Cells: A Minimally Invasive Approach for Cartilage Regeneration
Several scaffolds and cell sources are being investigated for cartilage regeneration. The aim of the study was to prepare nanocellulose-based thermosensitive injectable hydrogel scaffolds and assess their potential as 3D scaffolds allowing the chondrogenic differentiation of embedded human dental pulp stem and progenitor cells (hDPSCs).
The hydrogel-forming solutions were prepared by adding β-glycerophosphate (GP) to chitosan (CS) at different ratios. Nanocellulose (NC) suspension was produced from hemp hurd then added dropwise to the CS/GP mixture. In vitro characterization of the prepared hydrogels involved optimizing gelation and degradation time, mass-swelling ratio, and rheological properties. The hydrogel with optimal characteristics, NC-CS/GP-21, was selected for further investigation including assessment of biocompatibility. The chondrogenesis ability of hDPSCs embedded in NC-CS/GP-21 hydrogel was investigated in vitro and compared to that of bone marrow-derived mesenchymal stem cells (BMSCs), then was confirmed in vivo in 12 adult Sprague Dawley rats.
The selected hydrogel showed stability in culture media, had a gelation time of 2.8 minutes, showed a highly porous microstructure by scanning electron microscope, and was morphologically intact in vivo for 14 days after injection. Histological and immunohistochemical analyses and real-time PCR confirmed the chondrogenesis ability of hDPSCs embedded in NC-CS/GP-21 hydrogel.
Our results suggest that nanocellulose-chitosan thermosensitive hydrogel is a biocompatible, injectable, mechanically stable and slowly degradable scaffold. hDPSCs embedded in NC-CS/GP-21 hydrogel is a promising, minimally invasive, stem cell-based strategy for cartilage regeneration.
Journal Article