Water and sustainable land use at the ancient tropical city of Tikal, Guatemala

The access to water and the engineered landscapes accommodating its collection and allocation are pivotal issues for assessing sustainability. Recent mapping, sediment coring, and formal excavation at Tikal, Guatemala, have markedly expanded our understanding of ancient Maya water and land use. Among the landscape and engineering feats identified are the largest ancient dam identified in the Maya area of Central America; the posited manner by which reservoir waters were released; construction of a cofferdam for dredging the largest reservoir at Tikal; the presence of ancient springs linked to the initial colonization of Tikal; the use of sand filtration to cleanse water entering reservoirs; a switching station that facilitated seasonal filling and release; and the deepest rock-cut canal segment in the Maya Lowlands. These engineering achievements were integrated into a system that sustained the urban complex through deep time, and they have implications for sustainable construction and use of water management systems in tropical forest settings worldwide.     

Survival of short implants is improved with greater implant length, placement in the mandible compared with the maxilla, and in nonsmokers

PURPOSE/QUESTION: What is the 2-year estimated implant survival rate of short (<10 mm) dental implants installed in partially edentulous patients? SOURCE OF FUNDING: Information not available. TYPE OF STUDY/DESIGN: Systematic review with meta-analysis of data. LEVEL OF EVIDENCE: Level 1: Good quality, patient-oriented evidence. STRENGTH OF RECOMMENDATION GRADE: Grade B: Inconsistent or limited-quality, patient-oriented evidence.     

The Medical Management of Pediatric Arrhythmias

OPINION STATEMENT: Arrhythmias are an important cause of morbidity and mortality in children. Despite recent technological advances in treatment, pharmacologic therapy remains the most common treatment modality for pediatric arrhythmias. The choice of antiarrhythmic agent, the duration of therapy, and the dosing schedule depend on multiple factors including the recurrence risk and the arrhythmia burden (the latter being determined by the hemodynamic effect of the arrhythmia), and the frequency and duration of episodes. As with all pediatric medications, consideration must be given to the drug formulation, palatability, adverse effects and adherence issues. There are very few randomized trials available to guide the choice of therapy for pediatric arrhythmias, and thus treatment options often reflect physician or institutional preferences. Although various classification schemes exist, we classify antiarrhythmic agents based on their primary site of action: atrial muscle/accessory pathway (class IA, IC, and III agents); the atrioventricular node (beta-blockers, calcium channel blockers, digoxin, and class III agents); or ventricular muscle (class I and III agents). This type of categorization assists in the approach to treatment required for each type of arrhythmia encountered.