Classroom peer acceptance, friendship, and victimization: distinct relational systems that contribute uniquely to children's school adjustment?

The proposition that relationships make differential (i.e., unique, redundant, contingent) contributions to adjustment was examined by investigating the linkages between children's participation in different types of peer relationships (i.e., friendship, peer acceptance, peer victimization) and their adjustment to school. Relationship measures were gathered for 5- to 6-year-old children (105 males, 95 females) twice during kindergarten (i.e., fall and spring) and were correlated with adjustment indicators at each time of assessment and used to predict changes in school adjustment over time. Examination of the relative associations between the relationship measures and children's adjustment revealed evidence of both unshared (i.e., unique) and shared (i.e., redundant) linkages, depending on the form of adjustment examined. These findings suggest that adjustment may be influenced by the diverse experiences (i.e., provisions) that children encounter in different forms of relationship, and that certain types of relationships may have greater or lesser adaptive significance depending on the adjustment outcome examined.     

High-precision 40Ar/39Ar geochronology and the advent of North America's Late Cretaceous terrestrial fauna

A densely sampled, diverse new fauna from the uppermost Cedar Mountain Formation, Utah, indicates that the basic pattern of faunal composition for the Late Cretaceous of North America was already established by the Albian-Cenomanian boundary. Multiple, concordant 40Ar/39Ar determinations from a volcanic ash associated with the fauna have an average age of 98.39 +/- 0.07 million years. The fauna of the Cedar Mountain Formation records the first global appearance of hadrosaurid dinosaurs, advanced lizard (e.g., Helodermatidae), and mammal (e.g., Marsupialia) groups, and the first North American appearance of other taxa such as tyrannosaurids, pachycephalosaurs, and snakes. Although the origin of many groups is unclear, combined biostratigraphic and phylogenetic evidence suggests an Old World, specifically Asian, origin for some of the taxa, an hypothesis that is consistent with existing evidence from tectonics and marine invertebrates. Large-bodied herbivores are mainly represented by low-level browsers, ornithopod dinosaurs, whose radiations have been hypothesized to be related to the initial diversification of angiosperm plants. Diversity at the largest body sizes (>10(6) g) is low, in contrast to both preceding and succeeding faunas; sauropods, which underwent demise in the Northern hemisphere coincident with the radiation of angiosperms, apparently went temporarily unreplaced by other megaherbivores. Morphologic and taxonomic diversity among small, omnivorous mammals, multituberculates, is also low. A later apparent increase in diversity occurred during the Campanian, coincident with the appearance of major fruit types among angiosperms, suggesting the possibility of adaptive response to new resources.     

Nationwide survey of fluoroscopy: radiation dose and image quality

PURPOSE: To determine the average abdominal entrance air kerma, low-contrast sensitivity, and spatial resolution in upper gastrointestinal tract fluoroscopy in the United States. MATERIALS AND METHODS: A random sample of fluoroscopic facilities was selected to be surveyed for the Nationwide Evaluation of X-ray Trends program. Measurements were performed by using a newly developed fluoroscopic phantom. The surveys were conducted by state radiation control personnel. RESULTS: Average air kerma rates 1 cm above the tabletop, free in air, were 43 mGy/min (n = 340). The rate increased to 64 mGy/min when a 1.6-mm-thick copper filter, which simulated the use of barium contrast medium, was added to increase attenuation. The average entrance air kerma, free in air, for radiographs was 3.4 mGy, and an average of 12 radiographs were obtained per examination. Of 352 facilities surveyed, 306 (87%) were able to resolve wire mesh with 20 or more lines per inch. Of 339 facilities for which percentage contrast could be calculated, 192 (57%) had minimum percentage contrast values of 4% or more. CONCLUSION: Spatial resolution for fluoroscopy is adequate for most of the facilities surveyed, but a substantial proportion of facilities could not visualize low-contrast test objects, which strongly suggests image quality problems.     

Laparoscopic pelvic lymph node dissection for clinical staging of prostate cancer: encouraging preliminary results

OBJECTIVE: To evaluate the results of the first 72 laparoscopic pelvic lymph node dissections in patients with prostate cancer. DESIGN: Retrospective study of records. SETTING: Netherlands Cancer Institute/Antoni van Leeuwenhoek Hospital, Amsterdam, the Netherlands. METHOD: A retrospective study of records provided data on 72 patients with prostate cancer staged by laparoscopic lymph node dissection in the period 1993-1997. Per- and postoperative complications, operation time, number of removed lymph nodes, pathology result and duration of hospital stay were assessed. A comparison was made between the first series of 36 patients and the second series. RESULTS: In 9 patients the laparoscopic approach was converted to a laparotomy. This occurred six times in the first series of 36 patients and three times in the second series. The postoperative course was complicated six times in the first and four times in the second series. With increasing experience the mean operation time decreased from 140 min to 114 min in the second series (p < 0.0001). The mean number of nodes removed was equal in both series (7.5). Lymph node metastases were found in 20 patients (28%). Hospital stay was 2.9 days in the first series and 2.2 days in the second series (not significant). CONCLUSION: Laparoscopic pelvic lymph node dissection is a minimally invasive method for staging patients with prostate cancer. This staging procedure is of great benefit in patients scheduled for treatment with curative intent because of its accuracy and low morbidity. With increasing experience operation time, hospital stay and number of complications decrease.