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Background: With the progress of perinatal medicine and neonatal technology, more and more extremely low birth weight (ELBW) survived all over the world. This study was designed to investigate the short-term outcomes of ELBW infants during their Neonatal Intensive Care Unit (NICU) stay in the mainland of China. Methods: All infants admitted to 26 NICUs with a birth weight (BW) < l000 g were included between January l, 2011 and December 31, 2011. All the data were collected retrospectively from clinical records by a prospectively designed questionnaire. The data collected from each NICU transmitted to the main institution where the results were aggregated and analyzed. Categorical variables were performed with Pearson Chi-square test. Binary Logistic regression analysis was used to detect risk factors. Results: A total of 258 ELBW infants were admitted to 26 NICUs, of whom the mean gestational age (GA) was 28.1 ± 2.2 weeks, and the mean BW was 868 ± 97 g. The overall survival rate at discharge was 50.0%. Despite aggressive treatment 60 infants (23.3%) died and another 69 infants (26.7%) died after medical care withdrawal. Furthermore, the survival rate was significantly higher in coastal areas than inland areas (53.6% vs. 35.3%, P = 0.019). BW < 750 g and GA < 28 weeks were the largest risk factors, and being small for gestational age was a protective factor related to mortality. Respiratory distress syndrome was the most common complication. The incidence of patent ductus arteriosus, intraventricular hemorrhage, periventricular leukomalacia, bronchopulmonary dysplasia, retinopathy of prematurity was 26.2%, 33.7%, 6.7%, 48.1%, and 41.4%, respectively. Ventilator associated pneumonia was the most common hospital acquired infection during hospitalization. Conclusions: Our study was the first survey that revealed the present status of ELBW infants in the mainland of China. The mortality and morbidity of ELBW infants remained high as compared to other developed countries.

The crack growth and stress evolution of single crystal nickel under three different crystal orientations (X[100], Y[010], Z[001]; X[110], Y[10], Z[001]; X[111], Y[10], Z [2]) were studied by introducing a cohesive zone model (CZM) based on molecular dynamics (MD) simulation. The results indicated that different crystal orientations have significant effect on the fracture mechanisms and stress distribution characteristics. Under the X[100], Y[010], Z[001] orientation, void nucleation and growth was observed during the crack propagation; under the X[110], Y[10], Z[001] orientation, atomic configurations basically remained unchanged throughout the crack growth, which represented a brittle process; dissimilarly, blunting and slip bands occurred at the front of the crack tip for the X[111], Y[10], Z[2] orientation. These different mechanisms resulted in different stress distributions along the crack path and crack growth rates. Moreover, based on the calculation of the CZM, the relationship between stress and opening displacement was obtained, which provided useful information for understanding the crystal orientation dependent on the atomic-scale fracture mechanisms and associated mechanical properties.