Physical Chemistry of the H2SO4/HNO3/H2O System: Implications for Polar Stratospheric Clouds.

Polar stratospheric clouds (PSCs) play a key role in stratospheric ozone depletion. Surface-catalyzed reactions on PSC particles generate chlorine compounds that photolyze readily to yield chlorine radicals, which in turn destroy ozone very efficiently. The most prevalent PSCs form at temperatures several degrees above the ice frost point and are believed to consist of HNO(3) hydrates; however, their formation mechanism is unclear. Results of laboratory experiments are presented which indicate that the background stratospheric H(2)SO(4)/H(2)O aerosols provide an essential link in this mechanism: These liquid aerosols absorb significant amounts of HNO(3) vapor, leading most likely to the crystallization of nitric acid trihydrate (NAT). The frozen particles then grow to form PSCs by condensation of additional amounts of HNO(3) and H(2)O vapor. Furthermore, reaction probability measurements reveal that the chlorine radical precursors are formed readily at polar stratospheric temperatures not just on NAT and ice crystals, but also on liquid H(2)SO(4) solutions and on solid H(2)SO(4) hydrates. These results imply that the chlorine activation efficiency of the aerosol particles increases rapidly as the temperature approaches the ice frost point regardless of the phase or composition of the particles.

Organic nitrate chemistry and its implications for nitrogen budgets in an isoprene- and monoterpene-rich atmosphere: constraints from aircraft (SEAC4RS) and ground-based (SOAS) observations in the Southeast US.

Formation of organic nitrates (RONO2) during oxidation of biogenic volatile organic compounds (BVOCs: isoprene, monoterpenes) is a significant loss pathway for atmospheric nitrogen oxide radicals (NOx), but the chemistry of RONO2 formation and degradation remains uncertain. Here we implement a new BVOC oxidation mechanism (including updated isoprene chemistry, new monoterpene chemistry, and particle uptake of RONO2) in the GEOS-Chem global chemical transport model with ∼25 × 25 km2 resolution over North America. We evaluate the model using aircraft (SEAC4RS) and ground-based (SOAS) observations of NOx, BVOCs, and RONO2 from the Southeast US in summer 2013. The updated simulation successfully reproduces the concentrations of individual gas- and particle-phase RONO2 species measured during the campaigns. Gas-phase isoprene nitrates account for 25-50% of observed RONO2 in surface air, and we find that another 10% is contributed by gas-phase monoterpene nitrates. Observations in the free troposphere show an important contribution from long-lived nitrates derived from anthropogenic VOCs. During both campaigns, at least 10% of observed boundary layer RONO2 were in the particle phase. We find that aerosol uptake followed by hydrolysis to HNO3 accounts for 60% of simulated gas-phase RONO2 loss in the boundary layer. Other losses are 20% by photolysis to recycle NOx and 15% by dry deposition. RONO2 production accounts for 20% of the net regional NOx sink in the Southeast US in summer, limited by the spatial segregation between BVOC and NOx emissions. This segregation implies that RONO2 production will remain a minor sink for NOx in the Southeast US in the future even as NOx emissions continue to decline.

Biofeedback-assisted relaxation to reduce stress in labor.

OBJECTIVE: To test the feasibility and effectiveness of incorporating biofeedback-assisted relaxation techniques into routine instruction in Lamaze classes. DESIGN: A quasi-experimental design (static groups comparison) was used. SETTING: Lamaze classes. PARTICIPANTS: A convenience sample of 33 subjects recruited from 12 Lamaze classes. MEASURES: Duration of first-stage labor, amount of sedation and analgesia during first-stage labor, number of complications, and 1- and 5-minute Apgar scores of the neonates. RESULTS: The experimental subjects reported greater stress during labor than did the control subjects. CONCLUSIONS: Although the supplementary instruction in reducing stress seemed to promote relaxation during the prenatal classes, it did not reduce distress during labor and delivery because no mothers attempted to use the technique at that time.

Evidence for NO(x) control over nighttime SOA formation.

Laboratory studies have established a number of chemical pathways by which nitrogen oxides (NO(x)) affect atmospheric organic aerosol (OA) production. However, these effects have not been directly observed in ambient OA. We report measurements of particulate organic nitrates in Bakersfield, California, the nighttime formation of which increases with NO(x) and is suppressed by high concentrations of organic molecules that rapidly react with nitrate radical (NO(3))--evidence that multigenerational chemistry is responsible for organic nitrate aerosol production. This class of molecules represents about a third of the nighttime increase in OA, suggesting that most nighttime secondary OA is due to the NO(3) product of anthropogenic NO(x) emissions. Consequently, reductions in NO(x) emissions should reduce the concentration of organic aerosol in Bakersfield and the surrounding region.

Photochemical production and release of gaseous NO2 from nitrate-doped water ice.

Temperature-programmed NO2 emissions from frozen aqueous NaNO3 solutions irradiated at 313 nm were monitored as function of nitrate concentration and heating rate, H, above -30 degrees C. Emissions increase nonmonotonically with temperature, displaying transitions suggestive of underlying metamorphic transformations. Thus, NO2 emissions surge at ca. -8 degrees C in frozen [NO3-] > 200 microM samples warmed at H = 0.70 degrees C min(-1) under continuous irradiation, and also in the dark from samples that had been photolyzed at -30 degrees C. The amounts of NO2 released in individual thermograms, SigmaN, increase less than linearly with [NO3-] or the duration of experiments, revealing the significant loss of photogenerated NO2. The actual SigmaN proportional, variant [NO3-]1/2 dependence (at constant H) is consistent with NO2 hydrolysis: 2NO2 + H2O --> NO3- + NO2- + 2H+, overtaking NO2 desorption, even below the eutectic point (-18 degrees C for aqueous NaNO3). The increasingly larger NO2 losses detected in longer experiments (at constant [NO3-]) are ascribed to secondary photolysis of trapped NO2. The relevance of present results to the interpretation of polar NO2 measurements is briefly analyzed.

Factors influencing knowledge, attitudes, and compliance of hypertensive patients.

Using a factorial design, four aspects of an educational program for 160 hypertensive patients were manipulated: number of meetings, patient responsibility and participation, directiveness of the intervention, and emphasis on negative consequences of uncontrolled hypertension. Validity checks on the manipulations included content analysis of the nurse-patient interaction and interview-based measures of the patient's responsibility, participation, and awareness of dangers. Outcome variables included repeated measures of patient knowledge, assessment by the nurse of patient attainment of identified goals, and reduction of the patient's mean arterial blood pressure. High indirect interventions tended to lead to higher goal attainment, particularly in the psychosocial area. Emphasis on negative consequences tended to promote learning for patients with long standing diagnoses, but to retard learning for recently diagnosed patients. Additional meetings and emphasis on patient responsibility were not helpful alone, but in combination they tended to lead to greater learning. Although as a whole, patients in the program tended to reduce their blood pressures, there were no statistically significant main effects or interaction effects of the educational approach variables on blood pressure reduction.

Validation of two experimental nursing approaches using content analysis.

The purpose of this study was to analyze and compare the recorded content of two experimental nursing interventions used in a hypertensive-education program. One intervention was characterized as deliberative or high indirect, the other as task-centered or low indirect. A total of 4,149 nurse-patient interaction units was derived from 62 typed interview transcripts, equally representative of both approaches. Two trained coders categorized the interactions, based upon recurring themes of the teaching content; 24 distinct topical categories were identified. Intercoder agreement above chance for all 4,149 interaction units was k = .68, with confidence limits of 99% +/- .03, p less than .0001. A space-time unit for quantifying the relative amounts of time spent on the various categories also was developed, and analyses were conducted for space-time units as well as interaction units. The main findings showed no definable differences in the frequency of categories or the amounts of time spent in their discussion in the two approaches. These results were contrasted to results obtained when the validity of the nursing approaches was tested previously, and differences between the two interventions in attaining social and health goals were interpreted in light of the findings of the content analysis.

A comparison of traditional approaches to hierarchical linear modeling when analyzing longitudinal data.

Longitudinal designs typically involve repeated time-ordered observations for each individual (or unit). Such designs are uniquely suited to studying changes over time within individuals, and relating these to individual characteristics to identify processes and causes of intra- individual changes and interindividual differences in physiologic and psychological development. The purpose of this paper is to compare and contrast univariate and multivariate ANOVA with repeated measures to hierarchical linear modeling as approaches to analyzing such longitudinal data. This will enable researchers to choose the approach that best meets their research needs, and it will enable them to compare research results that are reported using one analytical approach with results that are reported using the other approach.

Neonatal nurses' knowledge of and attitudes toward caring for cocaine-exposed infants and their mothers.

The knowledge, attitudes, and backgrounds of 215 nurses employed in the nurseries of six hospitals were studied by means of a questionnaire survey. The nurses' attitudes toward the mothers of cocaine-addicted infants were found to be generally negative and/or judgmental and their knowledge to be low. More experience with nursing cocaine-addicted infants and greater acuity of the neonatal unit in which the nurse worked correlated with more positive attitudes toward the infants but not toward their mothers. Knowledge and attitude correlated positively with formal education, inservice education, and self-education, but the correlations were weak.

Psychosocial outcome six months after heart transplant surgery: a preliminary report.

With improvement in survival of patients treated with heart transplant, evaluation of recovery with respect to psychosocial function has become an important issue. In this study, psychosocial functioning of 44 heart transplant recipients pretransplant was compared to their functioning 6 months posttransplant. Before transplantation, patients experienced considerable psychosocial distress attributable to illness. At 6 months after transplantation, the majority of patients showed significant improvement in emotional, domestic, sexual, social, and vocational functioning. However, 25% of patients showed deterioration in psychosocial adjustment and 11% showed an increase in mood disturbance. Further effort is indicated to improve psychosocial outcome of heart transplantation.