Coupled-oscillator theory of dispersion and Casimir-Polder interactions.

We address the question of the applicability of the argument theorem (of complex variable theory) to the calculation of two distinct energies: (i) the first-order dispersion interaction energy of two separated oscillators, when one of the oscillators is excited initially and (ii) the Casimir-Polder interaction of a ground-state quantum oscillator near a perfectly conducting plane. We show that the argument theorem can be used to obtain the generally accepted equation for the first-order dispersion interaction energy, which is oscillatory and varies as the inverse power of the separation r of the oscillators for separations much greater than an optical wavelength. However, for such separations, the interaction energy cannot be transformed into an integral over the positive imaginary axis. If the argument theorem is used incorrectly to relate the interaction energy to an integral over the positive imaginary axis, the interaction energy is non-oscillatory and varies as r(-4), a result found by several authors. Rather remarkably, this incorrect expression for the dispersion energy actually corresponds to the nonperturbative Casimir-Polder energy for a ground-state quantum oscillator near a perfectly conducting wall, as we show using the so-called "remarkable formula" for the free energy of an oscillator coupled to a heat bath [G. W. Ford, J. T. Lewis, and R. F. O'Connell, Phys. Rev. Lett. 55, 2273 (1985)]. A derivation of that formula from basic results of statistical mechanics and the independent oscillator model of a heat bath is presented.

Judgment of the Quality of Restorative Care as Predictors of Restoration Retreatment: Findings from the National Dental PBRN.

The primary aim of this study was to test the hypothesis that a patient's subjective assessments of the dentist's technical competence, quality of care, and anticipated restoration longevity during a restorative visit are predictive of restoration outcome. This prospective cohort study involved 3,326 patients who received treatment for a defective restoration in a permanent tooth, participated in a baseline patient satisfaction survey, and returned for follow-up. Of the 4,400 restorations that were examined by 150 dentists, 266 (6%) received additional treatment after baseline. Reporting satisfaction with the technical skill of the dentist or quality of the dental work at baseline was not associated with retreatment after baseline. However, patients' views at baseline that the fee was reasonable (odds ratio [OR], 1.6) was associated with retreatment after baseline, whereas satisfaction at baseline with how long the filling would last (OR, 0.6) was associated with less retreatment. These findings suggest that retreatment occurs more often for patients who at baseline are satisfied with the cost or who at baseline have less confidence in the restoration. The authors found no associations between restoration retreatment and the patients' baseline evaluations of the technical skills of their dentists or perceptions of quality care. KNOWLEDGE TRANSFER STATEMENT: Dental patients' ratings of their dentist's skills were not related to a restoration needing retreatment. Patients focus on other aspects of the dental visit when making this judgment.

Respiratory health and lung function in 8-year-old children of very low birth weight: a cohort study.

In comparison with a cohort of normal birth weight children, those of very low birth weight (less than 1501 g birth weight) had more wheezing illnesses and hospital readmissions for respiratory problems in the first 2 years of life; from 2 years to 8 years of age respiratory health was unrelated to birth weight. Lung function measurements at 8 years of age in very low birth weight children were similar to expected values; few children had severely abnormal lung function. On univariate analyses, forced vital capacity (FVC) and forced expired volume in 1 second (FEV1), but not flow rates, were lower in children who had survived bronchopulmonary dysplasia. However, the univariate analyses were misleading, because bronchopulmonary dysplasia occurred more frequently with lower birth weight, and lower birth weight in turn was strongly related to reduced FVC and FEV1. After adjusting for birth weight and other potential confounding variables, FVC and FEV1 were unrelated to bronchopulmonary dysplasia, and to neonatal ventilation. Flow rates were largely uninfluenced by perinatal events, but were reduced in children with asthma or recurrent bronchitis at 8 years of age. Passive smoking was unrelated to lung function at 8 years of age. However, the effects of passive or active smoking, or perinatal events, on respiratory function or health beyond 8 years of age in very low birth weight survivors remain to be determined.

Audiologic assessment of extremely low birth weight infants: a preliminary report.

The aim of this study was to assess all relevant aspects of auditory function, including acuity and perception, of a cohort of extremely low birth weight (< 1000 g) children who survived to 8 years of age; 42 of the 59 consecutive survivors born over a 4-year period from January 1, 1977, had a full auditory assessment. Of the 42 children, 4 (9.5%) had a sensorineural hearing impairment, 5 (11.9%) had a conductive hearing impairment, 24 (57.1%) had figure/ground differentiation problems, and 20 (47.6%) had a short-term auditory memory problem. The 4 children with sensorineural hearing impairments had had significantly higher maximum concentrations of bilirubin in the newborn period (median 167 mumol/L vs 138 mumol/L and had required more intensive care; at 8 years of age they were significantly disadvantaged in verbal ability. The 5 children with conductive hearing impairments were not significantly different on any perinatal or other 8-year outcome variables. The proportion with figure/ground differentiation problems (57.1%) was significantly higher than in a normative population (11.7%, chi 2 = 24.2). Extremely low birth weight children with figure/ground differentiation problems were more likely to be restless in the classroom (45.0% [9/20]) than those without these problems (16.7% [2/12]), but the difference was not statistically significant (chi 2 = 2.7). Children with short-term auditory memory problems had significantly higher maximum bilirubin concentrations in the newborn period (median 152 mumol/L vs 137.5 mumol/L). At 8 years of age they had significantly reduced intelligence and reading ability.(ABSTRACT TRUNCATED AT 250 WORDS)

Very low birth weight and growth into adolescence.

OBJECTIVE: To compare the growth and pubertal development of very low-birth-weight (VLBW) children (birth weight <1500 g) and normal-birth-weight (NBW) children (birth weight >2499 g) to adolescence to determine if, and at what age, VLBW children "catch up." DESIGN: Inception cohort study to age 14 years. SETTING: Royal Women's Hospital, Melbourne, Australia. PATIENTS: Eighty-six consecutive survivors with a birth weight less than 1000 g, 120 consecutive survivors with a birth weight of 1000 to 1499 g, and 60 randomly selected NBW controls. Children with cerebral palsy at age 14 years were excluded. MAIN OUTCOME MEASURES: Weight, height, and head circumference measurements at birth and ages 2, 5, 8, and 14 years converted to z (SD) scores. RESULTS: At age 14 years, pubertal development was similar in NBW and VLBW children. At ages 2, 5, 8, and 14 years, VLBW children were significantly shorter and lighter and had smaller head circumferences than NBW children. The differences in height and weight between VLBW and NBW children were less apparent as SD scores improved in VLBW children over time. Within the VLBW group, compared with children with a birth weight of 1000 to 1499 g, those with a birth weight less than 1000 g had significantly lower weight z scores earlier in childhood but not at age 14 years, significantly lower height z scores only at age 2 years, and significantly lower head circumference z scores throughout childhood. CONCLUSION: This group of VLBW children experienced late catch-up growth to age 14 years but remain smaller than their NBW peers. Arch Pediatr Adolesc Med. 2000;154:778-784

Sensorineural outcome at 2 years for survivors of erythroblastosis treated with fetal intravascular transfusions.

OBJECTIVE: To determine the sensorineural outcome at 2 years of age in a complete cohort of survivors of fetal intravascular transfusions. METHODS: From March 1984 to May 1990, 38 of 52 consecutive fetuses (73%) suffering from severe erythroblastosis survived attempted intravascular transfusions at the Royal Women's Hospital, Melbourne. At 2 years of age, corrected for prematurity where appropriate, the survivors had a psychological assessment, including the mental developmental index of the Bayley scales, and a standardized neurodevelopmental examination. RESULTS: Only one transfused child had a severe sensorineural disability, with severe developmental delay and multiple minor motor seizures. Another child was moderately disabled with spastic hemiplegia. In neither case were complications of an intravascular transfusion the likely explanation for the disability. Only one other child had a mental developmental index in the suspect range. The remaining 35 children (92.1%) had no sensorineural disability. The overall rate of sensorineural impairments and disabilities was lower in the group transfused than in previous reports of survivors of intraperitoneal transfusions. The mean mental developmental index was significantly higher in the transfused group than in a control group of normal birth weight children. CONCLUSION: Children who survive fetal intravascular transfusions compare favorably not only with other high-risk survivors, but also with low-risk children.

Antenatal steroid therapy and 5-year outcome of extremely low birth weight infants.

Over a 63-month period beginning January 1, 1977, 258 infants with birth weights of 500-999 g were born alive at one tertiary perinatal center; 170 were offered full intensive care. The mothers of 67 (39.4%) of these 170 infants had been given betamethasone antenatally to accelerate fetal lung maturation. Of the 67 infants exposed to steroids antenatally, 46 (68.7%) survived their primary hospitalization, compared with 43 (41.7%) of the 103 infants who had not been exposed to steroids. This difference is highly significant (chi 2 = 10.7; P less than .005) but is biased because infants in the steroid group had a better prognosis. After adjustment for discrepancies in birth weight and gestational age and other confounding obstetric variables, survival in the steroid group remained substantially higher (relative odds of survival 1.85, 95% confidence intervals 1.16-2.86; P = .006). The improvements in survival were not at the expense of increased rates of chronic ill health or impairments of growth neurodevelopment up to at least 5 years of age. For extremely immature and extremely low birth weight infants, steroids are rarely contraindicated on fetal grounds.

Changing obstetric practice and 2-year outcome of the fetus of birth weight under 1000 g.

The aim of this study was to assess the outcome up to 2 years of age for the fetus of birth weight 500-999 g, over time and in association with changes in obstetric care. Two consecutive cohorts of infants of birth weight 500-999 g were compared from two eras, 1977-1982 and 1985-1987, and their outcome up to 2 years of age was determined with particular emphasis on the effect of various obstetric interventions at the time of birth, such as cesarean delivery, electronic fetal monitoring, antenatal steroid therapy, and tocolytic therapy. The outcome to 2 years was analyzed by logistic function regression to adjust for imbalances in confounding perinatal variables. In the latter era, the survival rate to 2 years increased significantly by almost 50%, and only 7% of the survivors were severely disabled. The rates of delivery by cesarean and of electronic fetal monitoring both increased significantly in the latter era, but neither was associated with the improved outcome. The only variable associated with an improved outcome that was amenable to obstetric intervention at the time of birth was antenatal steroid therapy, which was used equally in both eras. The obstetrician may aid the fetus of birth weight 500-999 g by giving the mother steroids to accelerate fetal lung maturity, but cesarean cannot be recommended as the routine mode of delivery unless there are recognized maternal or fetal indications.

Cesarean section or vaginal delivery at 24 to 28 weeks' gestation: comparison of survival and neonatal and two-year morbidity.

A large cohort of consecutive live births with gestational ages assessed antenatally from 24 to 28 weeks from one tertiary center was studied to determine the association between mode of delivery and in-hospital mortality and morbidity and morbidity at two years of age. Between 1 January 1977 and 31 March 1982, 52.8% (172 of 326) of such infants survived their primary hospitalization. Obstetric factors independently associated with improved survival were increasing gestational age (P less than .0001), the absence of maternal hypertension (P = .007), singleton pregnancy (P = .007), and antenatal steroid therapy (P = .018). Although 62.7% (32 of 51) of infants delivered by cesarean section survived compared with 50.9% (140 of 275) of infants delivered vaginally, the increased survival was not statistically significant (X 2 = 1.97). Moreover, the trend favoring cesarean section disappeared after adjustment for confounding obstetric factors. In univariate analyses cesarean births more frequently required ventilatory support and there was a trend toward a lower incidence of cerebroventricular hemorrhage; again, however, when adjusted for extraneous factors these associations disappeared. Of the 172 in-hospital survivors, five died at home unexpectedly; 162 of the remaining 167 were traced; 18 (11.1%) had cerebral palsy and two (1.2%) were deaf. Of the 111 children who were fully assessed, 13.5% had major handicaps, 23.4% were suspect, and 63.1% were free of handicap at two years' corrected age. There was no association between mode of delivery and frequency of handicap. Little evidence was found from mortality or morbidity data to support routine delivery of infants of borderline viability by cesarean section.

Changes in lung function between age 8 and 14 years in children with birth weight of less than 1,501 g.

We set out to determine whether lung function of children with a birth weight of <1,501 g changed relative to expectations between the ages of 8 and 14 years. We hypothesized that changes in lung function may differ between those of birth weight above and below 1,000 g. The subjects of this study were born in the Royal Women's Hospital, Melbourne. There were 86 consecutive survivors with birth weights <1,000 g born between January 1, 1977 and March 31, 1982, and 124 consecutive survivors with birth weights 1,000-1,500 g born between October 1, 1980 and March 31, 1982. Lung function was measured at both age 8 and 14 years, corrected for prematurity in 78% (67/86) of those with birth weight <1,000 g, and in 69% (86/124) of those with birth weight 1,000-1,500 g. Overall, lung function was similar to predicted values at both 8 and 14 years of age [e.g., (forced expired volume in 1 s, FEV1% predicted) at age 8 years mean 88.5% (SD 14.7) and at age 14 years, mean 94.9% (SD 13.8)]. There were significant changes, mostly improvements, in lung function between age 8-14 years relative to predicted values: FEV1 (% predicted) increased between 8-14 years of age by a mean of 6.4 (95% confidence interval, 4.4-8.3). The improvements in some lung function variables were significantly greater in those of birth weight <1,000 g compared with those of birth weight 1,000-1,500 g: improvement in FEV1 (% predicted) between age 8-14 years in infants with birth weight <1,000 g had a mean of 10.3 (SD 13.1), and in those with birthweight 1,000-1,500 g a mean of 3.3 (SD 10.1). We conclude that lung function improved significantly relative to predicted values in children of birth weight <1,501 g between age 8-14 years. The improvements were greatest in those of birth weight <1,000 g.

Cognition, school performance, and behavior in very low birth weight and normal birth weight children at 8 years of age: a longitudinal study.

Cognition, school performance, and behavior were assessed at 8 years of age in 132 very low birth weight (VLBW) children free of major sensorineural impairments, and the results were contrasted with a randomly selected control group of normal birth weight (NBW) children. Considering their fragile beginnings, the majority of VLBW children were developing normally and were reading and performing in most academic and social areas as well as the NBW children. However, VLBW children were significantly inferior to NBW children on tests of cognition, including tests of intelligence and visual memory, and on teacher's reports of motor skills and initiative. In addition, proportionally more VLBW children (20.5%) than NBW children (5.9%) were reported by their parents to be not coping at school.

Growth promotion in chickens by interleukin-2.

Chicken interleukin-2 (cIL-2), which was prepared by sensitizing chicken lymphocytes with concanavalin A, was administered to fertile broiler eggs on Day 18 of embryonation (0.1 mg in 200 mL distilled water). Controls (CON) received distilled water. Hatched chicks were reared to 6 wk. Body weight (BW), as well as abdominal fat pad, liver, bursa of Fabricius, a thymic lobe, spleen, and gonads were excised and expressed relative to BW at 2, 4, and 6 wk of age. Additionally, hematocrit (HCT), hemoglobin (HGB), and plasma protein (PP) levels were determined at the three time intervals. Finally, chicks were sensitized against human gamma globulin (HGG) and challenged at 6 wk by intradermal injections into the wattles. Delayed type hypersensitivity (DTH) to HGG was used as a direct measure of cell-mediated immunity. In ovo cIL-2 increased BW consistently, relative fat pad weights at 2 wk, relative bursa and liver weights at 2 and 6 wk, HBG and relative thymic weight at 2 and 4 wk, and PP at 2 wk. Delayed type hypersensitivity to HGG was not affected by cIL-2. Potential metabolic and immunologic mechanisms to explain in ovo cIL-2 effects are discussed.

Lorentz transformation of blackbody radiation.

We present a simple calculation of the Lorentz transformation of the spectral distribution of blackbody radiation at temperature T. Here we emphasize that T is the temperature in the blackbody rest frame and does not change. We thus avoid the confused and confusing question of how temperature transforms. We show by explicit calculation that at zero temperature the spectral distribution is invariant. At finite temperature we find the well-known result familiar in discussions of the 2.7 K cosmic radiation.

Developmental coordination disorder at 8 years of age in a regional cohort of extremely-low-birthweight or very preterm infants.

The aims of this study were to determine the motor outcome of extremely-low-birthweight (ELBW; <1000g) or very preterm (<28wks) children compared with normal birthweight (NBW) children, to establish the perinatal associations of developmental coordination disorder (DCD) and its cognitive and behavioural consequences. Participants were consecutive surviving ELBW or very preterm children and randomly selected NBW(>2499g) children born in the state of Victoria, Australia, in 1991 or 1992. Main outcomes were: (1) results of the Movement Assessment Battery for Children (MABC) at 8 years of age; (2) cognitive function; (3) academic progress; and (4) behaviour. Of 298 consecutive ELBW/very preterm survivors, 255 (85.6%; 117 males, 138 females) had the MABC at a mean age of 8 years 8 months. More ELBW/very preterm children (9.5%) had DCD than the NBW group (2%, p=0.001). Only male sex increased the likelihood of DCD in ELBW/very preterm children (p=0.017). ELBW/very preterm children with DCD had worse cognitive function and academic test scores (up to 1SD below those without DCD); they also had more adaptive behaviour and externalizing problems, but not internalizing problems. DCD is more common in ELBW/very preterm children, has few perinatal correlates, and is associated with poor cognitive and academic performance as well as increased behaviour problems.

A quantum violation of the second law?

An apparent violation of the second law of thermodynamics occurs when an atom coupled to a zero-temperature bath, being necessarily in an excited state, is used to extract work from the bath. Here the fallacy is that it takes work to couple the atom to the bath and this work must exceed that obtained from the atom. For the example of an oscillator coupled to a bath described by the single relaxation time model, the mean oscillator energy and the minimum work required to couple the oscillator to the bath are both calculated explicitly and in closed form. It is shown that the minimum work always exceeds the mean oscillator energy, so there is no violation of the second law.

Optical electric-field enhancement at a metal surface arising from surface-plasmon excitation.

Surface plasmons can be excited on a metal by an external plane-wave beam through the use of prism or grating couplers or by introducing roughness. This can enhance the electric field at the surface compared with that in the incident beam, and it has been suggested that this effect is an important aspect of surface-enhanced Raman scattering. A general upper limit for this field enhancement is derived on the basis of energy conservation. Numerical results are given for Ag, Au, and Cu. With a perfect coupler on a Ag surface, the maximum increase of the square of the electric field in the 2-3-eV range is congruent with300. On randomly roughened surfaces, the estimated enhancements are of the order of unity.

Therapy with parent's lymphocyte transfer factor in children with infection and malnutrition.

Transfer factor (T.F.) prepared from 5 x 10(8) lymphoid cells from 500 ml of a parent's blood was given to 40 Australian aboriginal children aged 2-46 months who had been in hospital with acute infection. Many had protein-calorie malnutrition. These and a control group of 35 similar children were assessed blind for at least 12 months. In T.F.-treated children there were significantly fewer episodes of diarrhoeal disease for periods in excess of 26 weeks. Recurrent moderate diarrhoeal disease was particularly reduced, and the onset of severe gastroenteritis may have been delayed. There was no protection against chest, middle-ear, or skin infection.

Muscular strength at 5 years of children with a birthweight under 1500 g.

The hand-grip strength was measured as part of the 5-year neurodevelopmental assessment of 24 very low birthweight (VLBW) and 18 normal birthweight (NBW) children. Hand-grip strength was significantly lower in the VLBW children for left and right hands tested individually and for both hands used concurrently. Increasing hand-grip strength was significantly related to 5-year weight percentiles and to being in the NBW group. More of the VLBW children weighed less than the 10th percentile. After adjusting for the 5-year weight percentile, the hand-grip strength of VLBW children was still significantly lower than that for NBW children. This is another aspect of development in which VLBW children are disadvantaged.

Inguinal hernia in very low birthweight children: a continuing risk to age 8 years.

The prevalence of inguinal hernia repair up to 8 years of age was determined in 205 inborn children of birthweight less than 1500 g who had survived to the age of 8 years; 37 (18.0%) of the children required surgery for inguinal hernia, significantly more frequently for boys than girls (32.0% and 3.9% respectively). The cumulative percentage of inguinal hernia operations in boys was 8.7% during primary hospitalization, 20.4% by 2 years, 30.1% by 5 years and 32.0% by 8 years; 36.4% (12 of 33) hernias in boys occurred beyond 2 years of age. The risk of hernia in boys was only marginally higher in those who required assisted ventilation and in those of birthweight less than 1000 g. Very low birthweight infants, particularly boys, are at risk of developing an inguinal hernia not only in infancy but also to at least 8 years of age.

Growth and very low birth weight.

Information on the likelihood of catch up growth in poorly grown very low birthweight children is sparse. The centiles for weight, height, and head circumference were recorded at both 2 and 5 years of age for 135 very low birthweight children and 42 normal birthweight children. At both ages significantly more children of very low birth weight were under the 10th centile for weight and height. Children of birth weight under 1000 g were more often under the 10th centile for weight at 5 years compared with those of birth weight 1000-1500 g. Mean incremental weight gain between 2 and 5 years was significantly less for very low birthweight children. Mean increment in weight from 2 to 5 years was less for very low birthweight children who had been under the 10th centile for weight at 2 years; children who had been under the 10th centile for height also had lower mean height increments. The growth centiles achieved by 2 years of age were useful predictors of poor growth at 5 years, with perinatal data of marginal importance. Only six of 43 (14%) children with a weight at 5 years of age under the 10th centile were small for gestational age at birth. Very low birthweight children who had a weight or height under the 10th centile at 2 years of age usually remained in this category at 5 years with no evidence of catch up growth.