Major flood disturbance alters river ecosystem evolution

Floods, major formative drivers of channel and floodplain structure and associated riparian and in-stream communities, are increasing in intensity and magnitude with climate change in many regions of the world. However, predicting how floods will affect stream channels and their communities as climate changes is limited by a lack of long-term pre-flood baseline data sets across different organismal groups. Here we show salmon, macroinvertebrate and meiofauna communities, monitored for 30 years in a system evolving owing to glacier retreat, were modified significantly by a major rainfall event that caused substantial geomorphic change to the stream channel. Pink salmon, reduced to one-tenth of pre-flood spawner densities, recovered within two generations. Macroinvertebrate community structure was significantly different after the flood as some pioneer taxa, which had become locally extinct, recolonized whereas some later colonizers were eliminated. The trajectory of the macroinvertebrate succession was reset towards the community structure of 15 years earlier. Meiofaunal abundance recovered rapidly and richness increased post-flood with some previously unrecorded taxa colonizing. Biotic recovery was independent of geomorphological recovery. Markedly different responses according to the organismal group suggest caution is required when applying general aquatic ecosystem theories and concepts to predict flood events

Adhesion of resin cement to dentin:effects of adhesive promoters, immediate dentin sealing strategies, and surface conditioning

PURPOSE: This study evaluated the shear bond strength (SBS) of resin cement to dentin after applying two adhesive (A) systems with a combination of four different immediate dentin sealing (IDS) strategies, and two surface conditioning (SC) methods. MATERIAL AND METHODS: Human third molars (n = 140) were collected and randomly split (n = 70 each) between the two A systems (Clearfil SE Bond; Kuraray [AC] and Optibond FL; Kerr [AO]). The A groups were further divided into four IDS strategies (2 x one adhesive layer (IDS-1L); 2 x two adhesive layers (IDS-2L); 2 x one adhesive layer and one flowable layer (IDS-F); 2 x no adhesive layer (delayed dentin sealing [DDS]). Finally, each strategy group was categorized into one of the two SC methods (only pumice [SC-P] or pumice and silica coating [SC-PS]), except the DDS group, where only SC-P was used. This resulted in 14 groups of 10 specimens each. The occlusal coronal third was removed from each molar crown with a diamond saw (Isomet 1000), and IDS was applied, followed by temporary restorations. These were removed after 2 weeks of water storage, and the IDS surfaces were subsequently conditioned. The standard adhesive procedure (Syntac Primer and Adhesive, Heliobond; Ivoclar Vivadent) was executed, followed by the application of a resin cement (Variolink II; Ivoclar Vivadent) and photopolymerization. All specimens were subjected to thermocyclic aging (10,000 cycles, 5°C to 55°C). Shear force was applied to the adhesive interface in a universal testing machine (1 mm/min). Fracture types and locations after loading were classified. The data were analyzed using analysis of variance (ANOVA) and independent samples t tests. RESULTS: AO groups exhibited higher mean SBS values (14.4 ± 6.43) than AC groups (12.85 ± 4.97) (P = 0.03). ANOVA showed the main effect of the applications on the SBS in the different groups (P = 0.00). Both DDS groups showed significantly lower SBS values compared with all the IDS groups (IDS-1L, IDS-2L, IDS-F). No significant differences in SBS results were found between the IDS groups (P = 0.43) and between the SC methods (P = 0.76). Dentin-cement interface failures diminished with the application of IDS. CONCLUSION: IDS improves the SBS compared with DDS. No significant differences were found between the tested conditioning methods

What Influences Career Choices Among Graduates of a Primary Care Training Program?

OBJECTIVE: To identify factors that influence primary care residents to become generalists or specialists. DESIGN: Structured survey and interview. SETTING: A large university-based, internal medicine residency program in primary care. PARTICIPANTS: Of 92 residency graduates who completed training between 1979 and 1993, 88 (96%) participated. MAIN RESULTS: Although 82% of the participating graduates reported themselves very committed to primary care at the beginning of residency, only 68% pursued generalist careers. Factors influencing career choice that were more important to generalists than specialists included breadth of knowledge used in primary care practice (p = .04), breadth of clinical problems in practice (p = .001), and opportunity for continuity of care (p = .01). Although salary was rated “not important,” 50% of generalists and specialists advocated increased salaries for generalists as a way to increase interest in primary care. Other promoting factors included mentors, increased prestige for generalists, community-based training, lifestyle changes, and decreased paperwork. Seventy-three percent of participants felt it was easier to be a specialist than a generalist. CONCLUSIONS: A substantial minority of primary care residents pursue specialty careers. To produce more generalists, graduates recommend addressing income inequities, providing generalist role models, increasing community-based teaching, and increasing prestige for generalists