Problem: Priority health-risk behaviors contribute to the leading causes of morbidity and mortality among youth and adults. Population-based data on these behaviors at the national, state, and local levels can help monitor the effectiveness of public health interventions designed to protect and promote the health of youth nationwide.
Public Health Action: YRBSS data are used widely to compare the prevalence of health-risk behaviors among subpopulations of students; assess trends in health-risk behaviors over time; monitor progress toward achieving 20 national health objectives for Healthy People 2020 and one of the 26 leading health indicators; provide comparable state and large urban school district data; and help develop and evaluate school and community policies, programs, and practices designed to decrease health-risk behaviors and improve health outcomes among youth.
Survey procedures for the national, state, and large urban school district surveys were designed to protect students' privacy by allowing for anonymous and voluntary participation. Before survey administration, local parental permission procedures were followed. Students completed the self-administered questionnaire during one class period and recorded their responses directly on a computer-scannable booklet or answer sheet. CDC's Institutional Review Board approved the protocol for the national YRBS.
Statistical analyses were conducted on weighted data using SAS (10) and SUDAAN (11) software to account for the complex sampling designs. Prevalence estimates and confidence intervals were computed for all variables and all data sets. In addition, for the national YRBS data, t tests were used to determine pairwise differences between subpopulations (12). Differences between prevalence estimates were considered statistically significant if the t test p value was
YRBSS is the largest public health surveillance system in the United States monitoring a broad range of health-risk behaviors among high school students. YRBSS data are used widely to compare the prevalence of health-risk behaviors among subpopulations of students; assess trends in health-risk behaviors over time; monitor progress toward achieving national health objectives; provide comparable state and large urban school district data; and help develop, assess, and improve school and community policies, programs, and practices designed to decrease health-risk behaviors and improve health outcomes among youth. Because of its broad scope, YRBSS also allows analysis of the inter-relationships among health-risk behaviors (e.g., how alcohol and other drug use is associated with behaviors that contribute to violence) and a more complete understanding of how health-risk behaviors cluster among various subpopulations of students (e.g., whether tobacco use or sexual behaviors are more likely to occur among males than females or in certain regions of the country). Although these analyses are beyond the scope of this report, they are a particular strength of YRBSS as compared with more narrowly focused surveys.
One of the strengths of YRBSS is that it provides not just national, but state and large urban school district data. These data are more likely to be used to develop, improve, and evaluate state and local policies, programs, and practices because they reflect a more relevant population. It is also possible to compare data from the state and large urban school district surveys because they share similar sample designs, questionnaires, data collection procedures, and data processing procedures.
CDC and other federal agencies use national YRBS data to assess the contributions of HIV and other STD prevention and chronic disease prevention efforts designed to reduce health-risk behaviors among youth and, in a variety of reports and publications, to stimulate support for and improvements in public health interventions. At the state and local level, agencies and nongovernmental organizations use YRBS data in a variety of ways to improve health-related policies, programs, and practices. For example, the San Diego Unified School District used YRBS data to identify symptoms of an unhealthy school environment, including feeling unsafe at school or on the way to or from school, feeling sad or hopeless, considering or planning suicide, or having attempted suicide among all students including sexual minority students. This spurred development of a district-wide Bullying, Harassment, and Intimidation Prohibition Policy that complies with federal and state laws and extensively delineates the types of protections addressed. In Kentucky, after reviewing YRBS data on fruit and vegetable consumption, physical activity, and obesity, the Coordinated School Health Program and Kentucky Action for Healthy Kids collaborated to create Students Taking Charge projects in high schools around the state. This initiative trains high school students to assess their school's nutritional and physical activity environment, develop an action plan to improve it, implement their plan using minigrants, and learn how to advocate for healthier school environments and policies. In Philadelphia, YRBS data on sexual behaviors were cited along with data on the prevalence of chlamydia and gonorrhea to help persuade the Philadelphia Department of Health and the School District of Philadelphia to set up an in-school STD screening program to educate students about STDs and identify and treat chlamydia and gonorrhea among high school students.
YRBSS is an ongoing source of high-quality data at the national, state, and large urban school district levels for monitoring health-risk behaviors that contribute to the leading causes of mortality and morbidity among youth and adults in the United States. In 2013, in addition to the national data, 42 states and 21 large urban school districts obtained data representative of high school students in their jurisdiction. These data have been an important tool for planning, implementing, and evaluating public health policies, programs, and practices in schools and communities. Ongoing support for YRBSS, enhanced training and technical assistance for participating state and local health and education agencies, an increase in the number of states with representative data, more substate surveys at the large urban school district and county- or school-district level, and more universal use of all standard questions on YRBSS will help sustain the surveillance system and the quality of the data it produces and ensure that it continues to inform future efforts designed to protect and promote the health of youth nationwide.
Construction on Millennium Park began in 1999 with the goal to open in time to celebrate the new millennium. Delays and cost overruns meant the park ended up opening in 2004, nearly four years behind schedule. City planners considered several prominent artists before settling on a proposal by Sir Anish Kapoor for a major artistic installation. Concerns about Kapoor's initial designs further delayed construction. Some feared the highly reflective surface might become dangerously hot in the summer or cold in the winter. Others worried it would be too cumbersome to maintain the necessary polish on a sculpture exposed to the elements. All of this meant Cloud Gate was unveiled only in 2006.
Millennium Park lies at the extreme northwest corner of a far larger urban greenspace that comprises Maggie Daley Park, Grant Park, Lakefront Park, and more. That Millennium Park manages to stand out among the others is a testament to the park's design and planning. In addition to the major attraction that is Cloud Gate, Millennium Park also contains the famed Jay Pritzker Pavilion. Designed by legendary architect Frank Gehry, the Pritzker Pavilion is a large bandstand that's home to the Grant Park Symphony Orchestra and Chorus and the Grant Park Music Festival. Gehry's incorporation of flowing shapes and a trellis structure were meant to invoke a futuristic architecture befitting of a new millennium.
Atelier One, a British engineering firm, teamed up with freelance engineer Chris Hornzee to design the internals of the Cloud Gate. The team chose to use a high-density polyurethane foam during construction of the final structure. Sections were prefabricated and transported to Millennium Park for assembly. Under the mirror polished surface of the Bean are several framing components that keep the overall structure standing. The interior was designed in such a way as to avoid structural overload at any one point. The frame allows the Bean to expand and contract along with changes in exterior temperature.
During design and construction of Cloud Gate, the engineers tasked with bringing Sir Anish Kapoor's vision to fruition faced numerous challenges. In considering building materials, stainless steel was quickly rejected due to its tendency to absorb heat from the surrounding environment. Heating during the day followed by cooling at night might well have led to cracks or other imperfections appearing on the sculpture's surface and thereby ruining the design. Ultimately, engineers took inspiration from tried and true methods used in the shipbuilding industry and selected a wooden structure that could expand and contract with changes in temperature. Contrary to some urban legends, there is actually nothing contained inside the Bean aside from the basic structural elements, though at one point there was a rudimentary construction office located inside.
Specimens of a 90 cross-ply glass-reinforced polyester were tested in tension in a direction parallel to one of the directions of reinforcement. Extensive cracking of the transverse ply occurred at strains much lower than the resin failure strain. These cracks formed in a direction parallel to the transverse reinforcement and showed a remarkably even crack spacing. Results of crack spacing measurements are presented against applied stress for specimens with differing transverse-ply thicknesses. The transverse-crack spacing was found to decrease with increasing applied stress and to increase with increasing transverseply thickness. There was no evidence of debonding between the plies during cracking and a multiple cracking theory in which the plies remain elastically bonded has been presented which can account for the results. 153554b96e