Determination of the molecular orientation of poly(propylene terephthalate) fibers using polarized Raman spectroscopy: a comparison of methods.

For the first time, four different methods to determine the degree of molecular orientation from polarized Raman spectroscopy measurements are compared. The great influence of molecular orientation on the properties of polymers has driven the development of multiple experimental techniques and procedures. This study is based on the C(1)-C(4) ring stretching vibration of poly(propylene terephthalate) (PPT) at 1614 cm(-1). It is shown that simply ratioing the band intensity obtained with the polarization parallel and perpendicular to the unique axis of the sample provides a good qualitative method to observe the evolution of orientation in a series of similar samples. To quantitatively compare the degree of orientation one needs to utilize a more complex method yielding the second- and fourth-order parameters of the orientation distribution function (P(2) and P(4), respectively). To date, most studies have been based on the assumption of a cylindrically symmetric polarizibility tensor. It is shown that this assumption is highly questionable although this method has been used fairly successfully in the past. This method results in orientation parameters that are clearly different from those obtained with the two more complex procedures. The most complex method, both theoretically and experimentally, requires the most measurements per sample. Major problems have occurred when trying to calculate the desired parameters, in particular for samples with high birefringence. These problems are related to experimental complexities occurring for measurements when the samples are tilted with respect to the polarization direction of the incident light. These measurements are replaced by a simple determination of depolarization ratio in the third method. This method assumes that the depolarization ratio is independent of changes in molecular orientation and structure. It was found that this assumption is not correct. Thus, the most complex method is the method of choice to quantitatively determine the second- and fourth-order parameters of the orientation distribution function, unless one has knowledge of the depolarization ratio of each sample being studied. That knowledge permits the use of an experimentally simpler method to obtain the desired parameters.

Rotational invariants for polarized Raman spectroscopy.

A new method has been developed to determine an orientation-independent Raman scattered intensity based on various polarized Raman measurements. The equivalent term in infrared spectroscopy is the structural absorbance, which has existed for many years. As with the structural absorbance, the calculated Raman intensity allows one to observe spectral changes that are due uniquely to morphological changes in a set of different samples in the presence of orientation differences. The full theoretical development is presented, followed by an example based on a set of polymer fibers processed under different conditions leading to different morphologies and degrees of molecular orientation.

Studying "exposure" to firearms: household ownership v access.

BACKGROUND: Firearm ownership has often been used to measure access to weapons. However, persons who own a firearm may not have access to it and conversely, persons who do not own a firearm may be able to access one quickly. OBJECTIVES: To examine whether using firearm ownership is a reasonable proxy for access by describing the demographic characteristics associated with ownership and access. METHODS: Data are from the 1994 Injury Control and Risk Survey, a national, random digit dial survey. Information about household firearm ownership and ready access to a loaded firearm were collected and weighted to provide national estimates. Adjusted odds ratios for three separate models were calculated using logistic regression. RESULTS: A total of 1353 (27.9%) respondents reported both having a firearm in the household and ready access to one. An additional 313 respondents (8.1%) reported having a firearm, but were not able to access these weapons. Another 421 respondents (7.2%) did not have a firearm in or around their home, yet reported being able to retrieve and fire one within 10 minutes. Based on the logistic regression findings, the demographic characteristics of this latter group are quite different from those who report ownership. Those who do not have a firearm, but report ready access to one, are more likely to be ethnic minorities, single, and living in attached homes. CONCLUSIONS: Asking only about the presence of a firearm in a household may miss some respondents with ready access to a loaded firearm. More importantly, those who do not own a firearm, but report ready access to one, appear to be qualitatively different from those who report ownership. Caution should be exercised when using measures of ownership as a proxy for access.

Prevalence of youth access to alcohol or a gun in the home.

OBJECTIVES: To estimate the national prevalence of youth access to alcohol, a gun, or both alcohol and a gun, in their home and to describe the demographic characteristics associated with access to either alcohol or a gun. METHODS: Cross sectional data from the 1995 in-home survey of the National Longitudinal Study of Adolescent Health, which used a nationally representative randomly selected school based sample (n=18 924) of adolescents in grades 7-12, were analyzed. The current analyses were restricted to those adolescents 12-18 years of age (n=18 454). Crude logistic regression analyses was used to determine the demographic characteristics associated with access to alcohol or a gun in the home. RESULTS: Overall, 28.7% of US adolescents reported having easy access to alcohol in the home. Availability of alcohol was associated with race/ethnicity, mother's education, family structure, and welfare status. Similarly, 24.3% of US adolescents reported easy access to a gun in the home. Availability of a gun in the home was associated with gender, race/ethnicity, mother's education, family structure, and welfare status. Among those that reported that a gun was available in their home, most reported availability of a shotgun (63.0%) followed by a rifle (61.3%), handgun (57.3%), and other gun (16.4%). Ten per cent of adolescents reported availability of both alcohol and a gun in their home. CONCLUSIONS: One quarter of US adolescents reported easy access to either alcohol or a gun in their home. Given the risks associated with the misuse of alcohol and guns among adolescents, efforts to increase public awareness of the availability of alcohol and guns in the home are needed.

Assigning time-linked exposure status to controls in unmatched case-control studies: alcohol use and nearly lethal suicide attempts.

In case-control studies, determination of alcohol consumption by cases immediately prior to the injury event is often conceptually straightforward. However, determination of consumption status by controls is difficult because they lack a reference point, especially when cases and controls are not individually matched. We describe a method of assigning alcohol consumption status to controls using a 24-hour drinking history, the distribution in time of case events, and the random assignment of a specific time period to each control subject. This methodology offers a practical approach for determining alcohol consumption status among control subjects immediately prior to a case event, when controls lack a reference point and have not been individually matched to cases. Published in 2001 by John Wiley & Sons, Ltd.

The prevention of youth violence. The rationale for and characteristics of four evaluation projects.

In response to the magnitude of violence in the United States, a number of violence-prevention programs have been implemented throughout the country. However, relatively few have been rigorously evaluated for effectiveness. To encourage development and evaluation of violence-prevention interventions that focus on young children and their families, the Centers for Disease Control and Prevention (CDC) provided funding to four projects in 1996. This paper briefly describes the rationale for funding these projects, which is based on our understanding of the development of aggressive and violent behavior and on the literature regarding promising approaches to prevent problem behavior in this age group. We provide an overview of the four specific projects funded by the CDC as well as a short discussion of some of the many challenges encountered during their implementation.

Medical conditions and nearly lethal suicide attempts.

Physical illness has been studied as a risk factor for suicidal behavior, but little is known about this relationship among younger persons. We conducted a population-based, case-control study in Houston, Texas, from November 1992 through September 1995. The final sample consisted of 153 case- and 513 control-subjects aged 13 to 34 years. Case patients were identified at hospital emergency departments and met criteria for a nearly lethal suicide attempt. Control subjects were recruited via a random-digit-dial telephone survey. Case patients were more likely than controls to report having any serious medical conditions (crude OR = 3.23; 95% CI = 2.12-4.91). After controlling for age, race/ethnicity, alcoholism, depression, and hopelessness, the adjusted odds ratio for men was 4.76 (95% CI = 1.87-12.17), whereas the adjusted odds ratio for women was 1.60 (95% CI-0.62-4.17), suggesting that young men with medical conditions are at increased risk for nearly lethal suicide attempts. Increased efforts to identify and appropriately refer these patients are needed.

Help-seeking behavior prior to nearly lethal suicide attempts.

The association between help-seeking and nearly lethal suicide attempts was evaluated using data from a population-based, case-control study of 153 13- to 34-year-old suicide attempt case-patients treated at emergency departments in Houston, Texas, and a random sample of 513 control-subjects. Measures of help-seeking included whether the participant sought help for health/emotional problems in the past month, type of consultant contacted, and whether suicide was discussed during the interaction. Overall, friends/family were consulted most frequently (48%). After controlling for potential confounders, case-patients were less likely than control-subjects to seek help from any consultant (OR = 0.5, 95% CI = 0.3-0.8) or a professional (e.g., physician, counselor) consultant (OR = 0.5, 95%CI = 0.29-0.8). Among those who sought help, case-patients were more likely than to discuss suicide (OR = 2.6, 95% CI = 1.2-5.4), particularly with professionals (OR = 11.8, 95% CI = 3.2-43.2). Our findings suggest that efforts to better understand the role of help-seeking in suicide prevention, including help sought from family and friends, deserves further attention.

An unmatched case-control study of nearly lethal suicide attempts in Houston, Texas: research methods and measurements.

This article details the research methods and measurements used in conducting a population-based, case-control study of nearly lethal suicide attempts among persons aged 13-34 years, residing in Houston, Texas. From November 1992 to July 1995, we interviewed 153 case subjects presenting at one of three participating hospital emergency departments and used random digit dialing to identify 513 control subjects residing in the same catchment area in which cases were enlisted. Unlike most research in this area, this study was designed to extend our understanding of suicidal behavior and prevention activities beyond identification and treatment of depression and other mental illnesses. We discuss the overall strengths and weaknesses of our study design and conclude that this methodology is well suited for studying rare outcomes such as nearly lethal suicide.

The role of families and care givers as risk and protective factors in preventing youth violence.

This paper reviews research which discusses the risk and protective functions that families and other caregivers provide in influencing the development of aggressive behavior in youth. Currently, there is an emphasis on providing violence prevention programs in the school environment, typically with little parental or caregiver involvement. By enhancing the role of families and caregivers in youth violence prevention programs, we assert that an unique opportunity exists to both address specific risk factors for violence while enhancing the protective features of the family. Relatedly, the risk literature on youth violence indicates that the most influential risk factors (i.e., the family, community, and peers) have their principle impact on youth aggression outside the school. We suggest a shift in the focus of violence prevention programming that is more inclusive of families as both a risk and protective agent. In support of this position, relevant theory and reviews of exemplary family-involved programs are offered. Challenges to involving youth caregivers are identified and recommendations for overcoming those challenges suggested. Last, recommendations for future research and public policy in the prevention of youth violence are offered.

Oklahoma Firearm-Related Injury Surveillance.

CONTEXT: The magnitude of firearm-related deaths is known, but few studies have evaluated the magnitude and epidemiology of nonfatal firearm-related injuries. The circumstances resulting in fatal versus nonfatal injury are likely very different. No single data source provides complete details on nonfatal shootings. OBJECTIVE: To establish a surveillance system to define the epidemiology of fatal and nonfatal firearm-related injuries. DESIGN: Data were collected on fatal and nonfatal firearm-related injuries that occurred in 1995. SETTING: State of Oklahoma. PARTICIPANTS: Medical Examiner, Vital Statistics, hospital emergency and medical records departments, police departments, newspaper clipping service. MAIN OUTCOME MEASURES: Incidence rate of firearm-related injuries; case-fatality rate; demographic, medical, and epidemiologic data; sensitivity of each reporting source; completeness of reporting. RESULTS: The incidence rate of firearm-related injuries was 45.5 per 100,000 population. The case fatality rate was 35%. Injury rates were highest among adolescents, young adults, males, and African Americans. The Medical Examiner and Vital Statistics reported 87% and 98% of fatal cases, respectively. Passive surveillance of hospital emergency departments identified 72% of patients seeking hospital treatment. Among inpatients, 81% were identified by medical records departments. Newspaper clippings were obtained for 31% of cases. Information on the victim-perpetrator relationship and the type of firearm was available for 79% and 80% of cases, respectively. CONCLUSIONS: Statewide surveillance of firearm-related injuries using multiple data sources is possible and provides a picture of the overall firearm-related injury problem. Strategies to enhance computer linkages of medical and police data should be pursued to maximize the sensitivity of reporting and minimize the costs of surveillance.

Recommended data elements for firearm-related injury surveillance.

During 1994, the Centers for Disease Control and Prevention (CDC) funded seven states to develop and evaluate surveillance systems for firearm-related injuries. In addition, New York City and California had related experience with firearm-related injury surveillance. At the time these nine jurisdictions began developing their surveillance systems, no standardized definitions or recommendations were available about the best methods or procedures of collecting data or suggested data elements of a firearm-related injury surveillance system. The nine jurisdictions and CDC developed a list of recommended data elements (RDEs) for fatal and nonfatal firearm-related injuries. We describe the process used to develop the RDEs, the 21 data elements suggested by the funded projects, the data sources that may be able to provide those data elements, and an indication of which sources may be most useful. We encourage all developing surveillance systems to strive to include these data elements, although some of the elements will be more easily attainable for fatal injury events than nonfatal ones, and no single data source will be able to provide all the desired information about both morbidity and mortality from firearm-related injuries. The RDEs capitalize on the preliminary experiences of the small group of jurisdictions, but they need to be pilot tested and revised as we collect more information about how well these elements capture the desired information and whether the information obtained is useful.

Trends in fatal firearm-related injuries, United States, 1962-1993.

OBJECTIVE: Our objective was to review historical trends in U.S. fatal firearm-related injuries for the years 1962-1993. METHODS: Using mortality data from the National Center for Health Statistics and population estimates projected from census data, we calculated national age-adjusted mortality rates and examined trends over the 32-year period. Data were also examined by type of firearm-related death (unintentional, suicide, homicide, legal intervention, and undetermined intention), race, gender, and age group. RESULTS: During the 32-year period, the total number of firearm-related deaths increased by 137%, from 16,720 in 1962 to 39,595 in 1993. Suicide and homicide were responsible for most firearm fatalities. Rates for both firearm suicides and firearm homicides increased over time, while rates for unintentional, legal intervention, and undetermined intention decreased. The highest rates and widest variation in total firearm-related mortality occurred among African-American men (35.2/100,000 to 84.5/100,000). Persons 15-19, 20-24, and > or = 75 years of age experienced the largest changes in rates during recent years; total firearm mortality was higher for the younger age groups (15-19, 20-24) during 1990 through 1993 than any other time during the 32-year period. CONCLUSIONS: These surveillance data help characterize trends over time and the magnitude of firearm-related mortality and identify groups at risk. However, further efforts to improve our understanding of firearm-related deaths and injuries, such as expansion of current surveillance to include information about morbidity associated with firearms and additional epidemiologic research to identify modifiable individual and societal risk factors, are necessary.

Estimating intruder-related firearm retrievals in U.S. households, 1994.

To estimate the frequency of firearm retrieval because of a known or presumed intruder, the authors analyzed data from a 1994 national random digit dialing telephone survey (n = 5,238 interviews). Three mutually exclusive definitions of firearm retrieval were constructed: (1) retrieved a firearm because there might be an intruder, (2) retrieved a firearm and saw an intruder, and (3) retrieved a firearm, saw an intruder, and believed the intruder was frightened away by the gun. Of 1,678 (34%) households with firearms, 105 (6%) retrieved a firearm in the previous 12 months because of an intruder. National projections based on these self-reports reveal an estimated 1,896,842 (95% CI [confidence interval] = 1,480,647-2,313,035) incidents in which a firearm was retrieved, but no intruder was seen; 503,481 (95% CI = 305,093-701,870) incidents occurred in which an intruder was seen, and 497,646 (95% CI = 266,060-729,231) incidents occurred in which the intruder was seen and reportedly scared away by the firearm. Estimates of the protective use of firearms are sensitive to the definitions used. Researchers should carefully consider both how these events are defined and the study methods used.

Use of multiple reporting sources for perinatal hepatitis B surveillance and follow-up.

The New York State Perinatal Hepatitis B Prevention Program was implemented in New York State (excluding New York City) as a surveillance and control program in 1988. This report describes and evaluates the program and provides data from 1991 regarding hepatitis B surface antigen (HBsAg)-positive mothers and their infants' subsequent hepatitis B vaccination. The program was created using multiple existing surveillance and data collection systems. Completeness of case-ascertainment was estimated by means of the Chandra Sekar-Deming method (J Am Stat Assoc 1949; 44:101-15). An audit of hospital medical records and follow-up by local health departments were used to validate reporting accuracy. Of 158,273 live births in 1991, 363 (0.2%) were born to confirmed HBsAg-positive mothers. Estimated completeness of case-ascertainment was 96%. Thirty-five percent of HBsAg-positive mothers did not report risk factors for hepatitis B, confirming the need for universal testing. Of the infants, 83% received hepatitis B immune globulin and three doses of vaccine within one year of birth. By using existing data collection systems, the program was established quickly, and start-up funding and training requirements were simplified. Multiple reporting increased case-ascertainment to almost 100%. The program effectively identifies and ensures prompt vaccination of infants born to HBsAg-positive mothers.

Nosocomial tuberculosis: an outbreak of a strain resistant to seven drugs.

OBJECTIVE: To evaluate nosocomial transmission of multidrug-resistant (MDR) tuberculosis (TB). DESIGN: Outbreak investigation: review of infection control practices and skin test results of healthcare workers (HCWs); medical records of hospitalized TB patients and mycobacteriology reports; submission of specimens for restriction fragment length polymorphism (RFLP) typing; and an assessment of the air-handling system. SETTING: A teaching hospital in upstate New York. RESULTS: Skin-test conversions occurred among 46 (6.6%) of 696 HCWs tested from August through October 1991. Rates were highest on two units (29% and 20%); HCWs primarily assigned to these units had a higher risk for conversion compared with HCWs tested following previous incidents of exposure to TB (relative risk [RR] = 53.4, 95% confidence interval [CI95] = 6.9 to 411.1; and RR = 37.4, CI95 = 5.0 to 277.3, respectively). The likely source patient was the only TB patient hospitalized on both units during the probable exposure period. This patient appeared clinically infectious, was associated with a higher risk of conversion among HCWs providing direct care (RR = 2.37; CI95 = 1.05 to 5.34), and was a prison inmate with TB resistant to seven antituberculosis agents. The MDR-TB strain isolated from this patient also was isolated from other inmate and noninmate patients, and a prison correctional officer exposed in the hospital. Mycobacterium tuberculosis isolates from all of these patients had matching RFLP patterns. Infection control practices closely followed established guidelines; however, several rooms housing TB patients had marginal negative pressure with variable numbers of air changes per hour, and directional airflow was disrupted easily. CONCLUSIONS: These data strongly suggest nosocomial transmission of MDR-TB to HCWs, patients, and a prison correctional officer working in the hospital. Factors contributing to transmission apparently included prolonged infectiousness of the likely source patient and inadequate environmental controls. Continued urgent attention to TB infection control is needed.