A small porous-plug burner for studies of combustion chemistry and soot formation.

We have developed and built a small porous-plug burner based on the original McKenna burner design. The new burner generates a laminar premixed flat flame for use in studies of combustion chemistry and soot formation. The size is particularly relevant for space-constrained, synchrotron-based X-ray diagnostics. In this paper, we present details of the design, construction, operation, and supporting infrastructure for this burner, including engineering attributes that enable its small size. We also present data for charactering the flames produced by this burner. These data include temperature profiles for three premixed sooting ethylene/air flames (equivalence ratios of 1.5, 1.8, and 2.1); temperatures were recorded using direct one-dimensional coherent Raman imaging. We include calculated temperature profiles, and, for one of these ethylene/air flames, we show the carbon and hydrogen content of heavy hydrocarbon species measured using an aerosol mass spectrometer coupled with vacuum ultraviolet photoionization (VUV-AMS) and soot-volume-fraction measurements obtained using laser-induced incandescence. In addition, we provide calculated mole-fraction profiles of selected gas-phase species and characteristic profiles for seven mass peaks from AMS measurements. Using these experimental and calculated results, we discuss the differences between standard McKenna burners and the new miniature porous-plug burner introduced here.

Design and characterization of a linear Hencken-type burner.

We have designed and constructed a Hencken-type burner that produces a 38-mm-long linear laminar partially premixed co-flow diffusion flame. This burner was designed to produce a linear flame for studies of soot chemistry, combining the benefit of the conventional Hencken burner's laminar flames with the advantage of the slot burner's geometry for optical measurements requiring a long interaction distance. It is suitable for measurements using optical imaging diagnostics, line-of-sight optical techniques, or off-axis optical-scattering methods requiring either a long or short path length through the flame. This paper presents details of the design and operation of this new burner. We also provide characterization information for flames produced by this burner, including relative flow-field velocities obtained using hot-wire anemometry, temperatures along the centerline extracted using direct one-dimensional coherent Raman imaging, soot volume fractions along the centerline obtained using laser-induced incandescence and laser extinction, and transmission electron microscopy images of soot thermophoretically sampled from the flame.

Behavioural problems and psychiatric symptoms in 5-13 year-old Swedish children-a comparison of parent ratings on the FTF (Five to Fifteen) with the ratings on CBCL (Child Behavior Checklist).

As part of the validation procedure of a new parent questionnaire ("Five to Fifteen" or the FTF) a random sample of 1500 children aged 5-13 years from the Swedish Population Register (SPAR) was approached. The FTF and the Child Behavior Checklist (CBCL) were sent to the parents of the children together with questions about background conditions. After two reminders the response rate was 55.6%. The final sample had a mean age of 9.12 years (SD=1.89) and a sex distribution with 55% boys and 45% girls. Analysis of attrition did not support overrepresentation of foreigners/immigrants in the attrition population. FTF like CBCL showed sensitivity to sociodemographic variables. On the FTF fewer problems were indicated for girls in all domain scales, whereas this was true for the summary scale Externalizing and Mixed problems of the CBCL. The effects of age and area of residence were slight, but parental education was negatively related to all domain scales of the FTF and to all the CBCL scales. The intercorrelations of the FTF and CBCL scales with common content showed substantial overlap supporting the validity of the FTF scales. The correlation between scales within the FTF however also indicates a substantial comorbidity. This is also supported by the substantial correlation between problem score of the FTF domains perception, language, motor skills and the CBCL scale scores Attention, Social problems as well as the summary scale Mixed problems. These findings indicate that problems with inattention and social relations are shared across the various problem domains. Factor analysis of the FTF subdomain scores resulted in two factors, one representing learning problems and the other behavioural/emotional problems. Despite the low response rate the representativity of the sample was supported by the fact that the total problem score of CBCL was very similar to that of another Swedish sample with a relatively high response rate. The finding of a frequency of AD/HD symptoms in the FTF rating corresponding to the figures of prevalence of AD/HD in several international epidemiological studies could also be seen as support for the relevance of the findings. Thus, the results give support to the usefulness of the FTF questionnaire as an instrument that can help in delineating specific problem areas within the field of child neuropsychiatry. Through the comparison with the CBCL the validity of the FTF for the parts that the two instruments share could be ascertained and the value of tapping a broader problem area could be elucidated.

Sustained performance and regulation of effort in clinical and non-clinical hyperactive children.

OBJECTIVE: To study sustained performance and its relation to regulation of effort among four different groups of children: two clinical subgroups of children diagnosed with attention-deficit hyperactivity disorder (ADHD)--one with and one without comorbid oppositional defiant disorder (ODD); a control sample of children without a diagnosis of ADHD but with parental reports of hyperactivity; and a normal control sample. METHODS: Sustained performance was studied (n=64) using a choice reaction time task with long interstimulus intervals, and hyperactive behaviour and regulation of effort was rated throughout the task. RESULTS: The clinical sample differed from the normal controls regarding all measures of overall, but not initial, performance. When studying performance over time, the ADHD group was shown to differ from the normal controls with regard to omissions, mean reaction time and regulation of effort. No significant differences were found between the ADHD children with or without comorbid ODD. The non-clinical hyperactive children differed from the normal controls with regard to reaction time, initially and overall, and regulation of effort overall. CONCLUSIONS: Deficits in sustained performance among ADHD children appear to be evident when long interstimulus intervals are used, and these deficits are related to poor regulation of effort. Further, the observed differences between ADHD children and normal controls do not appear to be a result of comorbid conduct problems. The non-clinical hyperactive children were more similar to the control group than to the ADHD group.

Social inhibition and overfriendliness: two-year follow-up and observational validation.

Studied socioemotional functioning in 3 groups (n = 15) of high-inhibited, low-inhibited-overfriendly, and low-inhibited-low-overfriendly children at age 9, who were identified by parental ratings in a sample (N = 392) at age 7. Ratings of social inhibition and overfriendliness were stable over the 2-year period from age 7 to age 9. Validity of rated social inhibition and overfriendliness is established with behavioral observations, both predictively and concurrently. The groups are contrasted along the dimensions of social inhibition and overfriendliness with respect to socioemotional distress, social problem solving, empathic ability, and the disinhibitory phenomena of thrill seeking and hyperactivity. The high-inhibited group shows heightened socioemotional distress. The overfriendly group shows heightened levels of thrill seeking and hyperactivity. Social problem solving and empathy are less well developed in the inhibited and in the overfriendly group as contrasted to the low-inhibited-low-overfriendly group. The results are interpreted in terms of risks for socioemotional problems at both ends of the dimension of social inhibition.

Symptoms across pregnancy in relation to psychosocial and biomedical factors.

BACKGROUND: There is current interest in symptoms during pregnancy, but yet little is known about their prevalence and how often they are experienced across pregnancy. The reasons why some women experience more symptoms or experience them more often than others has received limited research attention. OBJECTIVE: To document the prevalence and frequency of 27 pregnancy symptoms and to systematically investigate, cross-sectionally and prospectively, the effect of psychosocial factors on the prevalence and frequency of these symptoms, while controlling for biomedical factors. METHODS: Four hundred and seventy-six nulliparous Scandinavian women who attended routine prenatal care in Uppsala county, Sweden, were studied six times during pregnancy (gestational weeks 10, 12, 20, 28, 32, and 36). RESULTS: The prevalence of symptoms was high, but only a smaller portion of these symptoms were experienced frequently. Psychological stress particularly contributed to the prevalence and frequency of concurrent symptoms and predicted symptoms up to 16 weeks later, independent of medical risk, smoking, and weight gain. CONCLUSIONS: Prevalence rates may be inflated, because many symptoms were experienced only 'occasionally' during each of the 4-week periods we sampled. By examining how frequently symptoms were experienced, we gained an indication of which symptoms are more likely to be bothersome or intrude upon daily activities. Psychosocial variables accounted for individual differences in symptom reports after taking biomedical factors into account. Attention to psychosocial variables in future studies will aid in our understanding of the etiology of pregnancy symptoms.

Social inhibition and overfriendliness as related to socioemotional functioning in 7- and 8-year-old children.

Examined high, medium, and low social inhibition groups in a Swedish sample (N = 815) of 7- and 8-year-old children on the basis of parental reports about their children's reaction to novel social situations. High social inhibition was associated with increased levels of internalizing problems and low social competence. Among the low-inhibited children, we identified a subgroup by using an index of overfriendliness. Overfriendliness was associated with more internalizing, externalizing, and attention problems and lower prosocial orientation. The findings support the notion of high social inhibition as a risk factor for the development of internalizing problems and low social competence but question the view of low inhibition as descriptive of generally well-functioning children. Rather, this is true for low-inhibited children only when they are also low in overfriendliness. Thus, the results point to a need for a better understanding of developmental pathways for both high- and low-inhibited children.

Sex differences in 1-, 3-, and 5-year-olds' toy-choice in a structured play-session.

This cross-sectional study investigated toy-choice in 38 one-year-old, 33 three-year-old, and 35 five-year-old children, who could choose between 10 different toys (four feminine, four masculine, and two neutral) in a structured play-session. The children played alone for 7 minutes and together with their accompanying parent for another 7 minutes (play-status). The results showed that girls and boys chose different toys from as early as the age of one year (Mdn = 12 months). These sex differences were found at all three ages. In contradiction to earlier studies, our results showed that feminine toys became less interesting for both girls and boys with increasing age. The present study showed no consistent effects of play-status. This study contributes to the knowledge of how early behavioral sex differences can be observed, how these differences develop, and it also raises questions concerning what sex differences stem from.

A Longitudinal Study of Perceived Health during Pregnancy: Antecedents and Outcomes.

Perceived health was studied longitudinally in a sample of 364 nulliparous women. Psychosocial, contextual, and biomedical factors were taken into account to predict medically relevant versus benign symptoms which were then used to predict perceived health over time. The results of structural equation modeling showed that pregnancy adjustment and medically relevant symptoms which were affected by social support, perceived stress, and negative affect predicted later perceived health. The outcomes of perceived health were examined during the third trimester in terms of medical care utilization and emergency room visits. Perceived health solely accounted for medical care utilization, while emergency room visits were accounted by medical care utilization and perceived stress.

Measurement of two social competence aspects in middle childhood.

The psychometric properties of a rating measure for parents and teachers for social competence, conceptualized as social skills and behaviors, were studied. The rating measure was constructed from factor analyses on 4 samples of school-age children. Factor analyses identified 2 moderately correlated competence aspects, valid for both sexes and for children from varying socioeconomic backgrounds. The first factor, Prosocial Orientation, captured a style promoting positive social interactions; the second factor, Social Initiative, described initiative as opposed to withdrawal in social situations. Scales based on the 2 factors showed reliability in internal consistency and stability across 1 year, validity in interrater agreement concurrently and across 1 year, correspondence with observed peer behavior, and the capacity to discriminate between children of different peer status.

Interaction between mothers and infants born at risk during the first six months of corrected age.

The effects of preterm birth and the perinatal infant health condition on mother-infant interactions were analysed in 278 mother-infant pairs, divided into four groups according to infants' gestational age at birth: group 1, 23-31 weeks; group 2, 32-36 weeks; group 3, 37-42 weeks; and group 4, a control group of healthy full-term infants. The methodological approach was based on observation of the pairs at 2, 4 and 6 months of infants' corrected age (+/- 1 week) during undressing of the infant and face-to-face interaction. It was found that mother-infant pairs with preterm infants (groups 1 and 2) did not differ in interactional variables from those of the control group. On the other hand, the birth of a full-term infant in need of neonatal intensive care (group 3) affected maternal and infant interactive behaviour. Additionally, infants from group 3 did not show stability in their interactive behaviour between any ages of measurement. This result suggests that interactive behaviour of full-term infants in need of neonatal intensive care are rather unpredictable during their first 6 months of life, which might have contributed to the less optimal interactive pattern observed for their mothers compared with mothers of the control group.

Assessing type a behavior in 8-year-olds: exploring the overlap between the constructs of type a behavior and hyperactivity.

This study attempted to examine, by using behavioral observations, the overlap found between Type A behavior, as measured by the Matthews Youth Test for Health (MYTH) questionnaire, and measures of hyperactivity in children. The sample consisted of 91 children (46 boys and 45 girls) between the ages of 8 and 9 who were part of a longitudinal study in Uppsala, Sweden. Behavioral observations of Type A behavior and various questionnaire data were used. The behaviorally observed Type A behavior correlated significantly with MYTH Type A behavior, whereas only the MYTH Type A behavior correlated with hyperactivity measured by questionnaires. The results indicated that behavioral observations make it possible to measure Type A behavior as distinct from hyperactivity, implying that the MYTH is too indiscriminate a measure of Type A behavior. This has implications for future measurement and perhaps conceptualization of Type A behavior in children, and thereby also for studying the developmental aspects of Type A behavior.

Prevalence studies of problematic behaviors in four-year-olds.

Prevalence rates for specific behaviors in the Problem Behavior Questionnaire (PBQ; Behar & Stringfield, 1974) and for four psychosomatically related behaviors (soiling, day and night wetting, and complaints about bodily aches) were estimated in a sample of 377 Swedish 4-year-olds described by their parents (mainly mothers). The results showed that several of the behaviors classified as outgoing conduct problems were common in this age group; boys showed more problematic behaviors than girls, as did children with older siblings. Firstborn children with younger siblings were more fearful and worried. No systematic differences between children in different types of day care were found. Maternal education had no relationship to reported child behaviors. The findings were discussed in terms of the four-year-age period as a period of transition and with regard to different family situations.

Cardiovascular and sympathoadrenal responses to mental stress: a study of sensory intake and rejection reactions.

Cardiovascular, sympathoadrenal and subjective responses to mental stress induced by two mental challenges eliciting sensory intake (word identification test = WIT) and sensory rejection (colour word conflict test = CWT) reactions were studied in 10 healthy males. Pressor responses to these stressors have been proposed to differ haemodynamically. Sympathoadrenal activity was assessed by arterial and femoral venous plasma catecholamine determinations and direct recordings of muscle sympathetic activity in the right peroneal nerve (MSA). Basal measurements differed little from those made during an active relaxation procedure, with the exception of MSA, which decreased. Both stress tasks elicited increases in heart rate, cardiac output, calf blood flow and brachial and pulmonary arterial blood pressures. WIT and CWT elicited qualitatively similar responses, but the amplitudes of the circulatory responses were lower with WIT, which also was rated as a weaker stressor. MSA increased during CWT, while marginal increases were seen during WIT. Arterial adrenaline showed a transient increase by 0.14 nmol l-1 during WIT. During CWT arterial adrenaline increased significantly by 50%. Increases in arterial adrenaline and subjective stress ratings were related to increases in cardiac output and reductions of systemic vascular resistance. Arterial and femoral venous noradrenaline increased during CWT, while changes during WIT were small. MSA and noradrenaline responses did not correlate to local vascular responses in the calf. Differences in the responses to mental challenges evoking sensory intake or rejection seem to be of a quantitative rather than a qualitative character.

Muscle sympathetic activity and norepinephrine release during mental challenge in humans.

Muscle sympathetic nerve activity (MSA; peroneal nerve) and arterial and femoral venous plasma norepinephrine (NE) were studied in 10 volunteers at rest, during a relaxation procedure (RELAX), and during two mental challenges, a word identification test (WIT) and a color word test (CWT). [3H]NE infusions were used to assess NE spillover to and clearance from plasma. Net NE overflow from the leg was calculated. RELAX reduced MSA and femoral venous NE concentrations. CWT increased blood pressure, cardiac output (thermodilution), and calf flow and reduced systemic vascular resistance. Responses to WIT were less marked. CWT increased MSA by 25%, femoral venous NE concentrations by 25%, and NE overflow from the leg by 26% at 3 min. Fractional epinephrine and [3H]NE extractions were flow related and decreased during CWT. The arterial contribution to femoral venous NE (about half) increased by 10% during CWT. Arterial NE levels and spillover increased, but NE clearance was unchanged. Femoral venous NE concentrations and NE spillover (not based on flow measurements) and regional NE overflow correlated with MSA. Thus NE concentrations in plasma reflect spillover rather than clearance at rest and during mental challenge. Biochemical and neurophysiological indexes of sympathetic activity correlate when assessed in the same region. Mental stress increases sympathetic activity in leg muscle.

Pace variation and control of work pace as related to cardiovascular, neuroendocrine, and subjective responses.

Two studies of paced and self-paced arithmetic performance are reported. Heart rate and blood pressure were recorded and ratings of subjective arousal obtained. In one of the studies, plasma levels of catecholamines and cortisol were determined. Under externally paced experimental conditions pace variation was found to be quantitatively related to changes in systolic and diastolic blood pressure, as well as to ratings of stress and irritation. This was not the case for heart rate or positively evaluated aspects of subjective arousal. Performance was better and ratings of stress and irritation were lower during self-paced than during paced work at a comparable work pace. In one of the studies the diastolic blood pressure increased less when subjects controlled the pace. Plasma catecholamines did not increase significantly during either externally or self-paced work, but adrenaline tended to increase during paced work. Our findings give partial support to the suggestion that personal control may attenuate sympathoadrenal activation and cardiovascular reactivity.

Personal control over work pace--circulatory, neuroendocrine and subjective responses in borderline hypertension.

Cardiovascular and neuroendocrine reactivity during arithmetic task performance were studied in 24 patients with borderline hypertension and normotensive controls. Personal control (self-paced versus externally paced performance) resulted in an attenuated blood pressure (BP) response to task performance in normotensives but not in borderline hypertensives. In response to self-paced work, systolic blood blood pressure (SBP) reactivity was significantly greater in borderline hypertensives, but the heart rate (HR) reactivity was similar in borderline hypertensives and normotensives under the different pacing conditions. Task difficulty (pace variation during external pacing) did not differentially affect reactivity in borderline hypertensives and normotensives. Venous plasma noradrenaline and adrenaline were unaffected by task performance. At rest after the task performance plasma noradrenaline was elevated in both normotensives and borderline hypertensives. The latter group also showed a persistent elevation of diastolic blood pressure after task performance, suggesting a prolonged vasoconstrictor response. The present findings indicate that, in terms of circulatory responses, borderline hypertensives may profit less than normotensives from personal control over environmental demands.