•Theoretical derivation of super-ellipse model for V-I characteristics.•Super-ellipse model as an approximation of standard implicit model.•Model parameters as an approximate function of physical ...parameters.•Effects of temperature and solar irradiance on model parameters.•Compared with other explicit models.
Recently, it has been shown that the super-ellipse model can be used to represent the voltage-current characteristics of illuminated solar PV modules. Since the model is claimed to be empirical in nature, this paper demonstrates that the super-ellipse model can be derived as a theoretical approximation of the physics-based implicit model of solar PV. Further, the model parameters used in the super-ellipse model can be approximated to the physical parameters of the implicit model of solar PV. Here, it is also shown how the model parameters of the super-ellipse model vary with the ambient temperature and solar irradiance. The super-ellipse model is compared with other explicit models for different solar modules and shows satisfactory results in representing the voltage-current (current–density) curve of the solar PV module.
Among hospitals in the NICHD Neonatal Research Network, rates of active treatment of infants born at 22 to 24 weeks of gestation varied substantially and accounted for a substantial proportion of ...between-hospital variation in overall survival and survival without impairment.
The decision to initiate or forgo potentially lifesaving treatment in infants who are born near the limit of viability is extremely difficult.
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Clinicians recognize that in some cases, the infant is too immature for treatment to be effective, whereas in other cases, treatment is clearly indicated. Yet, in many cases, it is unclear whether treatment is in the infant’s best interest.
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Although factors such as the infant’s birth weight and sex, plurality of birth (singleton vs. multiple), and exposure to antenatal glucocorticoids affect the prognosis of extremely preterm infants,
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many groups still make recommendations about active treatment . . .
•J–V characteristics of solar cell.•Rational function form.•Closed form solution of maximum-power-point voltage.
The J–V equation of an illuminated solar cell is implicit and recently it is shown ...that this equation can be expressed explicitly using rational function considering padé approximants. Here an explicit model for J–V characteristic is proposed using equivalent rational function form having two shape parameters. This model allows a simple closed form estimation of maximum power point voltage. The proposed explicit model is validated using wide variety of solar cells.
Objectives To describe and compare the incidence of late-onset sepsis (LOS) and demographic and clinical characteristics associated with LOS in very low birth weight (VLBW) infants from singleton and ...multiple births, and to examine the heritability of susceptibility to LOS among VLBW twins by comparing same-sex and unlike-sex twin pairs. Study design The study group comprised infants with birth weight 401-1500 g seen at clinical centers of the Eunice Kennedy Shriver National Institute of Child and Human Development Neonatal Research Network between 2002 and 2008. Only the first episode of LOS was included in our analysis. Stepwise logistic regression models were fitted separately for singleton and multiple pregnancies to examine the maternal and neonatal factors associated with LOS. LOS due solely to gram-negative bacteria in singleton and multiple pregnancies was also examined in separate models. The heritability of LOS was estimated by examining the concordance of LOS in twins from same-sex and unlike-sex pairs. Results LOS occurred in 25.0% (3797 of 15 178) of singleton and 22.6% (1196 of 5294) of multiple-birth VLBW infants. Coagulase-negative staphylococci were the most common infecting organisms, accounting for 53.2% of all LOS episodes in singletons and 49.2% in multiples. Escherichia coli and Klebsiella species were the most commonly isolated gram-negative organisms, and Candida albicans was the most commonly isolated fungus. Concordance of LOS did not differ significantly between same-sex and unlike-sex twin pairs. Conclusion LOS remains a common problem in VLBW infants. The incidence of LOS is similar for singleton and multiple-birth infants. The similar concordance of LOS in same-sex and unlike-sex twin pairs provides no evidence that susceptibility to LOS among VLBW infants is genetically determined.
This study of temporal trends in mortality among extremely premature infants receiving care in U.S. centers showed declines in overall mortality and in deaths from pulmonary causes, immaturity, ...infection, and CNS injury. Deaths from necrotizing enterocolitis increased.
Although survival among premature infants has improved, prematurity is a leading contributor to neonatal mortality in the United States.
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Approximately one in four extremely premature infants born at 22 to 28 weeks of gestation does not survive the birth hospitalization; mortality rates decrease with each additional week of completed gestation.
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Historically, most extremely premature infants died within a few days after birth.
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Among extremely-low-birth-weight infants born at centers in the National Institute of Child Health and Human Development (NICHD) Neonatal Research Network between 1993 and 1997, immaturity was the leading cause of death within 12 hours after birth, and . . .
► Thermal performance of a new concentric glass vacuum shell as receiver. ► Vacuum shell performs better than non evacuated tube even without selective coating. ► Benefits: lower cost, flexibility in ...choice of selective coatings & receiver material. ► Unlike evacuated tube receivers, structural deformation need not strain vacuum joint. ► Performance comparison of different receiver configurations and their relative merits.
The useful heat gain of a parabolic collector system is directly dependent on the heat loss from the absorber at its operating temperature. Selective coatings with evacuated/non evacuated glass tubes are employed to control radiative and convective heat losses. A concentric glass shell under vacuum is investigated for its thermal performance as this method circumvents the need for direct sealing between the glass envelope and the metal receiver to maintain vacuum and its related technical challenges. The performance is compared against a non evacuated receiver and its influence under different wind velocities; emissivities are calculated by a one dimensional theoretical model and solved by an iterative method.
IMPORTANCE: The Eunice Kennedy Shriver National Institute of Child Health and Human Development Neonatal Research Network (NRN) extremely preterm birth outcome model is widely used for ...prognostication by practitioners caring for families expecting extremely preterm birth. The model provides information on mean outcomes from 1998 to 2003 and does not account for substantial variation in outcomes among US hospitals. OBJECTIVE: To update and validate the NRN extremely preterm birth outcome model for most extremely preterm infants in the United States. DESIGN, SETTING, AND PARTICIPANTS: This prognostic study included 3 observational cohorts from January 1, 2006, to December 31, 2016, at 19 US centers in the NRN (derivation cohort) and 637 US centers in Vermont Oxford Network (VON) (validation cohorts). Actively treated infants born at 22 weeks’ 0 days’ to 25 weeks’ 6 days’ gestation and weighing 401 to 1000 g, including 4176 in the NRN for 2006 to 2012, 45 179 in VON for 2006 to 2012, and 25 969 in VON for 2013 to 2016, were studied. VON cohorts comprised more than 85% of eligible US births. Data analysis was performed from May 1, 2017, to March 31, 2019. EXPOSURES: Predictive variables used in the original model, including infant sex, birth weight, plurality, gestational age at birth, and exposure to antenatal corticosteroids. MAIN OUTCOMES AND MEASURES: The main outcome was death before discharge. Secondary outcomes included neurodevelopmental impairment at 18 to 26 months’ corrected age and measures of hospital resource use (days of hospitalization and ventilator use). RESULTS: Among 4176 actively treated infants in the NRN cohort (48% female; mean SD gestational age, 24.2 0.8 weeks), survival was 63% vs 62% among 3702 infants in the era of the original model (47% female; mean SD gestational age, 24.2 0.8 weeks). In the concurrent (2006-2012) VON cohort, survival was 66% among 45 179 actively treated infants (47% female; mean SD gestational age, 24.1 0.8 weeks) and 70% among 25 969 infants from 2013 to 2016 (48% female; mean SD gestational age, 24.1 0.8 weeks). Model C statistics were 0.74 in the 2006-2012 validation cohort and 0.73 in the 2013-2016 validation cohort. With the use of decision curve analysis to compare the model with a gestational age–only approach to prognostication, the updated model showed a predictive advantage. The birth hospital contributed equally as much to prediction of survival as gestational age (20%) but less than the other factors combined (60%). CONCLUSIONS AND RELEVANCE: An updated model using well-known factors to predict survival for extremely preterm infants performed moderately well when applied to large US cohorts. Because survival rates change over time, the model requires periodic updating. The hospital of birth contributed substantially to outcome prediction.
A prior report on hypothermia for neonatal hypoxic–ischemic encephalopathy showed a reduced rate of death or disability at 18 to 22 months of age. In this report of outcomes at 6 to 7 years, rates of ...death or an IQ below 70 were nonsignificantly lower with hypothermia than with usual care.
Moderate or severe neonatal hypoxic–ischemic encephalopathy is associated with a high incidence of death or motor and sensory disability in children.
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Children with encephalopathy are at risk for cognitive deficits even in the absence of functional deficits. Survivors without disability have delayed entry into primary school and fine-motor dysfunction and behavioral abnormalities.
Hypothermia to 33 to 34°C for 72 hours, when initiated within 6 hours after birth among infants of more than 35 weeks' gestational age with hypoxic–ischemic encephalopathy, has been shown to reduce the risk of death or disability and increase the rate of survival free of disability . . .
To describe the spectrum of cognitive outcomes of children with and without cerebral palsy (CP) after neonatal encephalopathy, evaluate the prognostic value of early developmental testing and report ...on school services and additional therapies.
The participants of this study are the school-aged survivors of the National Institute of Child Health and Human Development Neonatal Research Network randomized controlled trial of whole-body hypothermia. Children underwent neurologic examinations and neurodevelopmental and cognitive testing with the Bayley Scales of Infant Development-II at 18 to 22 months and the Wechsler intelligence scales and the Neuropsychological Assessment-Developmental Neuropsychological Assessment at 6 to 7 years. Parents were interviewed about functional status and receipt of school and support services. We explored predictors of cognitive outcome by using multiple regression models.
Subnormal IQ scores were identified in more than a quarter of the children: 96% of survivors with CP had an IQ <70, 9% of children without CP had an IQ <70, and 31% had an IQ of 70 to 84. Children with a mental developmental index <70 at 18 months had, on average, an adjusted IQ at 6 to 7 years that was 42 points lower than that of those with a mental developmental index >84 (95% confidence interval, -49.3 to -35.0; P < .001). Twenty percent of children with normal IQ and 28% of those with IQ scores of 70 to 84 received special educational support services or were held back ≥1 grade level.
Cognitive impairment remains an important concern for all children with neonatal encephalopathy.
Objective To examine the ability of magnetic resonance imaging (MRI) patterns of neonatal brain injury defined by the National Institute of Child Health and Human Development Neonatal Research ...Network to predict death or IQ at 6-7 years of age following hypothermia for neonatal encephalopathy. Study design Out of 208 participants, 124 had MRI and primary outcome (death or IQ <70) data. The relationship between injury pattern and outcome was assessed. Results Death or IQ <70 occurred in 4 of 50 (8%) of children with pattern 0 (normal MRI), 1 of 6 (17%) with 1A (minimal cerebral lesions), 1 of 4 (25%) with 1B (extensive cerebral lesions), 3 of 8 (38%) with 2A (basal ganglia thalamic, anterior or posterior limb of internal capsule, or watershed infarction), 32 of 49 (65%) with 2B (2A with cerebral lesions), and 7 of 7 (100%) with pattern 3 (hemispheric devastation), P < .001; this association was also seen within hypothermia and control subgroups. IQ was 90 ± 13 among the 46 children with a normal MRI and 69 ± 25 among the 50 children with an abnormal MRI. In childhood, for a normal outcome, a normal neonatal MRI had a sensitivity of 61%, specificity of 92%, a positive predictive value of 92%, and a negative predictive value of 59%; for death or IQ <70, the 2B and 3 pattern combined had a sensitivity of 81%, specificity of 78%, positive predictive value of 70%, and a negative predictive value of 87%. Conclusions The Neonatal Research Network MRI pattern of neonatal brain injury is a biomarker of neurodevelopmental outcome at 6-7 years of age. Trial registration ClinicalTrials.gov : NCT00005772.
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