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The dramatic Tacoma Narrows bridge disaster of 1940 is still very much in the public eye today. Notably, in many undergraduate physics texts the disaster is presented as an example of elementary forced resonance of a mechanical oscillator, with the wind providing an external periodic frequency that matched the natural structural frequency. This oversimplified explanation has existed in numerous texts for a long time and continues to this day, with even more detailed presentation in some new and updated texts. Engineers, on the other hand, have studied the phenomenon over the past half-century, and their current understanding differs fundamentally from the viewpoint expressed in most physics texts. In the present article the engineers' viewpoint is presented to the physics community to make it clear where substantial disagreement exists. First it is pointed out that one misleading identification of forced resonance arises from the notion that the periodic natural vortex shedding of the wind over the structure was the source of the damaging external excitation. It is then demonstrated that the ultimate failure of the bridge was in fact related to an aerodynamically induced condition of self-excitation or 'negative damping' in a torsional degree of freedom. The aeroelastic phenomenon involved was an interactive one in which developed wind forces were strongly linked to structural motion. This paper emphasizes the fact that, physically as well as mathematically, forced resonance and self-excitation are fundamentally different phenomena. The paper closes with a quantitative assessment of the Tacoma Narrows phenomenon that is in full agreement with the documented action of both the bridge itself in its final moments and a full, dynamically scaled model of it studied in the 1950s.

The present study was carried out to explore rooting performance of Punica granatum (Dalim) in Bangladesh through clonal propagation by stem cutting under 3 different doses of rooting hormone IBA (Indole Buetairic Acid) and planted in the perforated plastic tray filled with coarse sand and gravel placed in the non-mist propagator. The experiment was laid out following a Randomized Complete Block Design (RCBD) with 4 treatments and 4 replications (blocks). The treatments were T0= control, T1 = 0.2% IBA, T2 = 0.4% IBA, T3 = 0.8% IBA. The rooting ability of cuttings was significantly influenced by the application of IBA. The results showed that the highest rooting percentage (70%) and longest root length (11.75 cm) of P. granatum stem cuttings were obtained from the cuttings treated with 0.2% IBA followed by 0.4% IBA (47.5% and 7.95 cm respectively) whereas the highest root number (32) and maximum root diameter (2.7 mm) were recorded with 0.4% IBA followed by 0.8% IBA (28 and 2.47 mm respectively). Survival percentage of the cutlings (the rooted cuttings) after 3 months of transferring them into poly bags was also significantly enhanced by exogenous rooting hormone (IBA) application. The highest survival percentage (73.5%) was observed with 0.4% IBA treatment followed by 0.8% IBA (68.5%). Findings of the present study reveal that P. granatum is highly amenable for clonal propagation by stem cuttings using low-cost non-mist propagator and 0.4% IBA treatment may be recommended for mass production of quality planting stocks for the cultivation of the species in homestead agroforestry or in fruit orchards. These outcomes can assist to provide edible fruit to poor rural people of natural disaster vulnerable Bangladesh. [ABSTRACT FROM AUTHOR]

Growing Acacia catechu trees on rice fields is one traditional crop-land Agroforestry system of Rajshahi region in Bangladesh. Farming system was explored with detailed information on farm operations and cropping calendar including system outputs. System dynamics was also evaluated. PRA exercises were conducted for a biophysical assessment. The information was collected on informant wise and cross-checked. Best growth of trees observed under rain-fed conditions. Higher density of trees found in un-irrigated fields. Trees were better managed in small plots. In general, density of khoir trees was found higher in small holdings (less than 2 ha) with secured land tenure. Trees on farms were of uneven age indicating the khoir + rice system biologically sustainable. The ease of establishment of Khoir seedlings, the low cost of its maintenance, and less vulnerability to any serious pest or disease, easy marketability of products rated high in the farmer's preference for khoir. They appreciate the versatility of the wood for a variety of farm uses though its prime economic use to them is for production of lali for katha. They also get pitch khoir as by product of katha (red dyestuff for textiles and paper) production. The multiple products and services offered and the ease of managing the trees on crop fields without causing any immediate or long-term reduction in crop yield seemed to be the most important factors that encourage the farmers to continue this traditional practice. If farmers could be motivated to follow appropriately the silvicultural practices, production could further be increased. [ABSTRACT FROM AUTHOR]

Intersections are high-risk locations on roadways and often experience high incidence of crashes. Better understanding of the factors contributing to crashes and deaths at intersections is crucial. This study analyzed the factors related to crash incidence and crash severity at intersections in San Antonio for crashes from 2013 to 2017 and identified hotspot locations based on crash frequency and crash rates. Binary logistic regression model was considered for the analysis using crash severity as the response variable. Factors found to be significantly associated with the severity of intersection crashes include age of driver, day of the week, month, road alignment, and traffic control system. The crashes occurred predominantly in the highdensity center of the city (downtown area). Overall, the identification of risk factors and their impact on crash severity would be helpful for road safety policymakers to develop proactive mitigation plans to reduce the frequency and severity of intersection crashes.

Reports on hepatitis B vaccination of inmates in Texas correctional facilities which was implemented by the Department of Criminal Justice (TDCJ) from 2000 to 2002. Purpose of establishing hepatitis B vaccination programs in prison and jails; Basis of the decision of TDCJ not to perform prevaccination testing; Information on the dose administration of the vaccine; Comparison between the acceptance rate of vaccine dose in jail and prison inmates; Reason behind the suspension of the vaccination program in December 2002.

OBJECTIVES: Because of the herd-immunity phenomenon, the benefits of immunization against hepatitis A extend beyond those received by those who are vaccinated. This analysis estimates the impact of herd immunity on the cost-effectiveness of routine hepatitis A immunization among US children. PATIENTS AND METHODS: In an economic model, the costs and benefits of hepatitis A immunization were estimated for immunizing all US children at age 1 year over a 10-year period starting in 2005. The future burden of disease from hepatitis A was also estimated with this model, and the fraction that would be prevented by herd immunity was modeled by using a previously published analysis of the relationship between hepatitis A vaccination coverage and declines in hepatitis A incidence. RESULTS: Without accounting for herd-immunity effects, the costs of routine immunization would average 32,000 dollars per quality-adjusted life-year gained for the first 10 cohorts immunized starting with the 2005 birth cohort. Herd-immunity effects would be expected to produce substantial additional benefits, lowering the cost of the immunization program to 1000 dollars per quality-adjusted life-year gained for the first 10 cohorts. Herd-immunity benefits would be greatest for the first few cohorts, more than doubling the benefits of immunization, and would decline over time. In a univariate sensitivity analysis, estimates were most sensitive to vaccination costs but remained below 20,000 dollars per quality-adjusted life-year under all of the assumptions. CONCLUSIONS: Herd-immunity effects more than double the savings from hepatitis A immunization during the first 10 years of the program. After accounting for these effects, immunization is close to cost-neutral on a cost-per-quality-adjusted-life-year basis. [ABSTRACT FROM AUTHOR]

Bicycling is inexpensive, environmentally friendly, and healthful; however, bicyclist safety is a rising concern. This study investigates bicycle crash-related key variables that might substantially differ in terms of the party at fault and bicycle facility presence. Employing 5 year (2014-2018) data from the Texas Crash Record and Information System database, the effect of these variables on bicyclist injury severity was assessed for San Antonio, Texas, using bivariate analysis and binary logistic regression. Severe injury risk based on the party at fault and bicycle facility presence varied significantly for different crash-related variables. The strongest predictors of severe bicycle injury include bicyclist age and ethnicity, lighting condition, road class, time of occurrence, and period of week. Driver inattention and disregard of stop sign/light were the primary contributing factors to bicycle-vehicle crashes. Crash density heatmap and hotspot analyses were used to identify high-risk locations. The downtown area experienced the highest crash density, while severity hotspots were located at intersections outside of the downtown area. This study recommends the introduction of more dedicated/protected bicycle lanes, separation of bicycle lanes from the roadway, mandatory helmet use ordinance, reduction in speed limit, prioritization of resources at high-risk locations, and implementation of bike-activated signal detection at signalized intersections.

Objective: This study assessed the long-term economic implications of a national program to vaccinate all adults treated at sexually transmitted disease (STD) clinics in a single year., Methods: A model was developed to track the long-term disease outcomes and costs among a hypothetical cohort of 2 million STD clinic clients accessing services in one year, using data from published sources and demonstration projects at STD clinics in San Diego (California), Illinois, and Denver (Colorado). The model estimated net economic benefits of a routine hepatitis B vaccination policy at STD clinics nationwide compared with no vaccination., Results: Without a vaccination program, an estimated 237,021 new hepatitis B virus (HBV) infections would occur over the lifetimes of the 2 million STD clinic clients seen in a single year. HBV-related medical costs and productivity losses would be $1.6 billion. In a national program for routine vaccination at STD clinics, 1.3 million adults would be expected to receive at least one vaccine dose, and an estimated 45% of the new HBV infections expected without vaccination would be prevented. The vaccination program would cost $138 million, HBV infections occurring despite the program would cost $878 million, and clients' time and travel would cost $45 million. The net economic benefit (savings) of routine vaccination would be $526 million. If the indirect costs of lost productivity due to HBV infection are not considered, routine vaccination would have a net cost of $28 million., Conclusions: Estimates from this model suggest a national program for routine hepatitis B vaccination of adults at STD clinics would be a cost saving to society.

Background: Despite recent significant achievements in controlling hepatitis B virus (HBV) infection, immunizing high-risk groups against the disease remains a public health challenge in the United States. The aims of this article are to evaluate the projected cost effectiveness of hepatitis B vaccination of adults attending two major types of publicly funded HIV counseling and testing sites (CTSs)-freestanding HIV CTSs and sexually transmitted disease (STD) clinics, and to compare the cost-effectiveness of alternative vaccination and testing strategies in different subgroups in this population., Methods: A decision model was developed to determine the economic and clinical consequences, from a societal perspective, of the following strategies in two hypothetical cohorts of 100,000 adults attending each type of site: (1) routine vaccination without screening, (2) screening for antibody to hepatitis B core antigen with an initial vaccine dose during the first visit, (3) screening and vaccination based on screening results, and (4) no intervention. Life expectancy, expected quality-adjusted life years (QALYs), and medical care costs were estimated for each strategy and at each site., Results: Routine vaccination was both more effective and more cost-effective than either screening strategy; under base-case assumptions, routine vaccination would cost $4400 both per QALY and per life year saved. Results for STD clinics were very similar in magnitude to those for freestanding CTSs. Results were most sensitive to clients' time and travel costs for return visits and the time-discount rate., Conclusions: Routine provision of hepatitis B vaccine at major HIV CTSs would be a highly effective and cost-effective approach to preventing hepatitis B among high-risk adults in the United States.

West Nile virus (WNV) is transmitted by mosquitoes and can cause illness in humans ranging from mild fever to encephalitis. In 2002, a total of 4,156 WNV cases were reported in the United States; 329 were in Louisiana. To estimate the economic impact of the 2002 WNV epidemic in Louisiana, we collected data from hospitals, a patient questionnaire, and public offices. Hospital charges were converted to economic costs by using Medicare cost-to-charge ratios. The estimated cost of the Louisiana epidemic was US 20.1 million dollars from June 2002 to February 2003, including a US 10.9 million dollars cost of illness (US 4.4 million dollars medical and US 6.5 million dollars nonmedical costs) and a US 9.2 million dollars cost of public health response. These data indicate a substantial short-term cost of the WNV disease epidemic in Louisiana.