Hydrogen activation in propene polymerization with MgCl2-supported Ziegler-Natta catalysts: the effect of the external donor

¹³C NMR analysis of relatively low-molecular-weight polypropylenes prepared using the catalyst system MgCl₂/TiCl₄/phthalate ester-AlEt₃-external Lewis base has revealed the presence of up to around 20% butyl (n-Bu) chain ends, indicative of regioirregular (2,1-) monomer insertion followed by chain transfer with hydrogen. The effect of hydrogen on catalyst activity depends on the nature of the external donor, and the results indicate that at least part of the observed increase in catalyst activity in the presence of hydrogen can be ascribed to the regeneration of active species via chain transfer at dormant (2,1-inserted) sites.     

Survival and developmental disability in infants with birth weights of 501 to 800 grams, born between 1979 and 1994

OBJECTIVE: Because the survival rate has increased for extremely low birth weight neonates, many have raised the concern that the rate of developmental disability among survivors will also increase. To address this concern, we analyzed changes over time in survival and major neurosensory impairment in a sample of extremely low birth weight infants born between July 1, 1979, and June 30, 1994. METHODS: The study sample included 513 infants with birth weights of 501 to 800 g who were cared for in either of the two neonatal intensive care units that serve a 17-county region in northwest North Carolina and who were born to mothers residing in that region. At 1 year of age (corrected for gestation), survivors were examined by a pediatrician and were tested using the Bayley Scales of Infant Development. Major neurosensory impairment was defined as cerebral palsy, a Bayley Mental Developmental Index <68, or blindness. A total of 209/216 (97%) of survivors were examined at 1 year of age. Epoch of birth was defined as follows: epoch 1, July 1, 1979 to June 30, 1984; epoch 2, July 1, 1984 to June 30, 1989; and epoch 3, July 1, 1989 to June 30, 1994. RESULTS: Survival rates for epochs 1, 2, and 3 were, respectively, 24/120 (20%), 63/175 (36%), and 129/218 (59%). In contrast, the proportions with a major neurosensory impairment did not increase over time; rates for successive epochs were 6/24 (25%), 17/61 (28%), and 26/124 (21%). Rates of cerebral palsy were 3/24 (13%), 12/61 (20%), and 9/124 (7%); rates of delayed mental development were 4/24 (17%), 12/61 (20%), and 17/124 (14%); and rates of blindness were 2/24 (8%), 0/62, and 5/124 (4%), respectively. CONCLUSIONS: This analysis suggests that the increasing survival of extremely low birth weight neonates since the late 1970s has not resulted in an increased rate of major developmental problems identifiable at 1 year of age.     

T cells in patients with chronic Tγ lymphocytosis: Morphology,cytochemistry, ultrastructure and immunological characteristics

Summary We have studied the morphology and cytochemistry in relation to the immunological phenotyping and functional properties of T cells from eight patients with chronic T lymphocytosis. At the light microscopic level the morphology of the patients' lymphocytes was similar to that described for large granular lymphocytes. Ultrastructurally, a division into two groups could be made on differences in the amount of cytoplasm and the location and the more irregular form of the nuclei. The lymphocytes of one group (five patients) had in common the phenotype Fc+, T3+, T4–, T8+, Ia–, M1– and demonstrated (with the exception of one patient) the same functions: presence of K-cell activity, absence of NK, helper and suppressor cell activities. In the other group (three patients), the lymphocytes of one patient showed the same phenotype and functions as those indicated above. The other two patients both lacked the T8 antigen on their lymphocytes but were different with regard to other surface markers. In addition, their cells were functionally identical: both demonstrated NK- and K-cell activity. Thus in this group of eight patients with chronic T lymphocytosis, the immunological and functional subdivision paralleled in part a morphological division at the ultrastructural level.     

Laparoscopic Nissen fundoplication is a good option in patients with abnormal esophageal motility

Background

Patients with gastroesophageal reflux disease (GERD) and abnormal esophageal motility are the most controversial subgroup of surgically treated patients because of potentially increased risk of postoperative dysphagia. Our study aim was to determine if Nissen fundoplication is associated with increased postoperative dysphagia in patients with ineffective esophageal motility.

Methods

Medical records of all adult (>18 years old) patients who underwent laparoscopic Nissen fundoplication for GERD over 8 years were reviewed retrospectively. Of the 151 patients, 28 (group A) met manometric criteria for abnormal esophageal motility (<30 mmHg mean contractile pressure or <80% peristalsis), whereas 63 (group B) had normal esophageal function. Sixty patients had no manometric data and were therefore excluded from analysis. Follow-up time ranged from 1 month to 5 years. Outcomes (postoperative dysphagia, recurrence of GERD symptoms, free of medications) were compared between groups.

Results

Group A had higher age and American Society of Anesthesiologists (ASA) score (p = 0.016 and 0.020), but this did not correlate with outcome. Two patients (7.1%) in group A and three patients (5.3%) in group B had postoperative dysphagia. When adjusted for follow-up time, there was no significant difference between the groups (p = 0.94). Group B had more cases of recurrent heartburn (10.7% versus 3.6%, p = 0.039), and more patients in this group were back on medications (21.4% versus 7.1%, p < 0.05)

Conclusions

This retrospective study found equally low rates of dysphagia following Nissen fundoplication regardless of baseline esophageal motility. Preoperative esophageal dysmotility therefore does not seem to be a contraindication for laparoscopic Nissen fundoplication.     

Subtle lung cancers: impact of edge enhancement and gray scale reversal on detection with digitized chest radiographs

The authors studied the impact of edge enhancement and gray scale polarity reversal on the detection of subtle lung cancers. Three experienced readers reviewed 46 biopsy-proved subtle lung cancers and 46 normal controls on chest radiographs that had been digitized into a 1,024 X 1,536-pixel matrix 8 bits deep. Receiver-operating characteristics (ROC) analysis of 1,656 pooled observations indicated that performance was best with the unmodified images (ROC area = 0.83), degraded by moderate enhancement of medium frequencies (ROC area = 0.80), and markedly impaired by severe enhancement of low frequencies (ROC area = 0.69). Gray scale polarity reversal further degraded performance (unenhanced ROC area = 0.74; moderately enhanced ROC area = 0.76; severely enhanced ROC area = 0.76). The authors conclude that edge enhancement and gray scale polarity reversal can impair the detectability of subtle lung cancers on digitized radiographs of medium resolution.     

Pilot Data on the Endoscopic Placement of Covered Metal Stents to Treat Gastrojejunal Leaks in a Porcine Model

Background  

Placement of stents may be an alternative option to treat gastrojejunal (GJ) anastomotic leaks after Roux-en-Y gastric bypass (RYGB) surgery. The aim was to evaluate the performance of a covered metal stent (Alimaxx-E, 18 × 100 mm) across a GJ leak in a porcine model.     

Influence of High and Low Autonomy-Supportive Climates on Physical Activity in Children with and without Developmental Disability

The aim of this study was to compare the influence of two different instructional climates on the accumulation of moderate-to-vigorous physical activity (MVPA) during a fully-inclusive adapted recreational physical activity program. A total of 32 children (18 typically-developing (TD), and 14 with developmental disabilities (DD) ranging in ages from 5 to 9 years, participated in six, 60-min adapted recreational sessions. Of those six sessions, three incorporated an autonomy-supportive climate (high autonomy), and three incorporated direct instruction (low autonomy). MVPA was measured using accelerometers. A repeated measures ANOVA was conducted to determine significant differences in MVPA between group (TD/DD), climate (autonomy/direct), and a group x climate interaction. Significant group and climate main effects were observed (p?=?0.002 and 0.014, respectively). However, there was not a significant group x climate interaction (p?=?0.313). These results suggest that although the group of children with disabilities spent less time in MVPA compared to their typically-developing peers, all participants spent more time in MVPA for the autonomy-supportive climate compared to the low-autonomous climate. This study is the first to quantitatively assess the efficacy of a fully-inclusive autonomy-supportive climate on physical activity levels in children with and without developmental disabilities.