Biological Assessment and Criteria Improve Total Maximum Daily Load Decision Making

Mandated total maximum daily load (TMDL) analyses present an excellent opportunity to restore the nation’s degraded waters. The current norm for TMDL practice is, however, unlikely to achieve this goal without improved water quality standards plus systematic monitoring and assessment using biological criteria. Better than chemical and physical criteria alone, biological criteria link human actions, their impacts on water bodies, and societal goals, which are expressed as designated uses. To be adequate, monitoring should improve understanding of the connections among stressor, exposure, and response gradients. Water quality standards, monitoring, and assessment can improve water resources because they track water body condition, not the number of TMDLs completed. Federal and state leadership must set policy goals, as required by the Clean Water Act, and provide adequate fiscal and professional resources. States with high-quality programs should serve as models. Administrators should use the advances made in 2 decades of water resource science to improve their water management programs. Without such improvements, those involved in the TMDL process will continue to be frustrated, and the nation’s waters will continue to decline.     

Elastic-plastic fracture by homogeneous microvoid coalescence tearing along alternating shear planes

Mating fracture surfaces developed by slow cracking in salt water and rapid overload fracture were studied by replication and scanning electron microscopy to determine the formation mechanism of the periodic ridges and valleys (“zigzag” fracture) characteristic of surfaces in materials which separate by homogeneous microvoid coalescence. The most significant findings are: 1) The apex of each ridge, which consists of a rim of tear dimples, is sharply defined; while by contrast the bottom of each mating valley is gently rounded, as the mating tear dimples have been severely elongated to form an extensive stretch zone, the back edge of which mates with the peak of the ridge. Thus it appears that this form of fracture is a continuous process in that a moving crack front is maintained, even though the plane of the crack changes orientation with crack length. The crack advances along the first plane inclined to the macroscopic Mode I fracture plane, is then interrupted by a forward stretching step, which is followed by cracking along the second inclined plane. A rationale for this behavior is presented in terms of a simple tension-compression model within a constrained plastic zone. 2) Elongated dimples on each incline are of two types, tear and shear, with the former clearly dominating. This observation implies a strain gradient in the process zone near the crack tip, with the point of maximum strain located at the crack tip. The photomicrographs support a model involving tearing along alternating shear planes.     

Isosurfaces Over Simplicial Partitions of Multiresolution Grids

We provide a simple method that extracts an isosurface that is manifold and intersection‐free from a function over an arbitrary octree. Our method samples the function dual to minimal edges, faces, and cells, and we show how to position those samples to reconstruct sharp and thin features of the surface. Moreover, we describe an error metric designed to guide octree expansion such that flat regions of the function are tiled with fewer polygons than curved regions to create an adaptive polygonalization of the isosurface. We then show how to improve the quality of the triangulation by moving dual vertices to the isosurface and provide a topological test that guarantees we maintain the topology of the surface. While we describe our algorithm in terms of extracting surfaces from volumetric functions, we also show that our algorithm extends to generating manifold level sets of co‐dimension 1 of functions of arbitrary dimension.     

Hierarchical Deformation of Locally Rigid Meshes

We propose a method for calculating deformations of models by deforming a low‐resolution mesh and adding details while ensuring that the details we add satisfy a set of constraints. Our method builds a low‐resolution representation of a mesh by using edge collapses and performs an as‐rigid‐as‐possible deformation on the simplified mesh. We then add back details by reversing edge‐collapses so that the shape of the mesh is locally preserved. While adding details, we deform the mesh to match the predicted positions of constraints so that constraints on the full‐resolution mesh are met. Our method operates on meshes with arbitrary triangulations, satisfies constraints over the full‐resolution mesh and converges quickly.     

Impact of a cleaner‐burning cookstove intervention on blood pressure in Nicaraguan women

Few studies have evaluated the cardiovascular‐related effects of indoor biomass burning or the role of characteristics such as age and obesity status, in this relationship. We examined the impact of a cleaner‐burning cookstove intervention on blood pressure among Nicaraguan women using an open fire at baseline; we also evaluated heterogeneity of the impact by subgroups of the population. We evaluated changes in systolic and diastolic blood pressure from baseline to post‐intervention (range: 273–383 days) among 74 female cooks. We measured indoor fine particulate matter (PM_2.5; N = 25), indoor carbon monoxide (CO; N = 32), and personal CO (N = 30) concentrations. Large mean reductions in pollutant concentrations were observed for all pollutants; for example, indoor PM_2.5 was reduced 77% following the intervention. However, pollution distributions (baseline and post‐intervention) were wide and overlapping. Although substantial reductions in blood pressure were not observed among the entire population, a 5.9 mmHg reduction [95% confidence interval (CI): ?11.3, ?0.4] in systolic blood pressure was observed among women aged 40 or more years and a 4.6 mmHg reduction (95% CI: ?10.0, 0.8) was observed among obese women. Results from this study provide an indication that certain subgroups may be more likely to experience improvements in blood pressure following a cookstove intervention.     

Endothelial cell death on biomaterials: Theoretical and practical aspects of investigation

The use of endothelial cell seeding has been proposed as a solution to increase the patency of blood-contacting devices. While there has been a great deal of research into both biological and mechanical mechanisms of failure, relatively little work involving the effects which biomaterials have on the function of cells seeded on such devices has been conducted. We hypothesize, based on previously published results, that endothelial cells attached to synthetic biomaterials exhibit increased intracellular levels of superoxide and other reactive oxygen species. Previous reports have linked elevated levels of reactive oxygen species to NF-κB activation and subsequent cell death via anoikis, a form of apoptosis. Because of this, it is critical that an understanding of how biomaterials affect cellular behavior is developed, and that this knowledge is used in the creation of future devices which rely on cell seeding and cellular ingrowth.     

Early high dose antioxidant vitamins do not prevent bronchopulmonary dysplasia in premature baboons exposed to prolonged hyperoxia: a pilot study

The effect of two different types of functional ankle-foot orthosis on the gait of patients with spastic hemiplegia was studied. A gap was cut into the conventional stiff orthosis to allow a limited dorsiflexion of 10-15 degrees, while plantarflexion was blocked (spring type). This gap was bridged by an aluminum bar to stiffen the orthosis for the experiment. Fourteen patients of different ages (6.5-20.1 years) walked barefoot and with the orthosis, once springy and once stiff. Kinetics and kinematics were analyzed. Gait was significantly improved into normal pattern by using any type of ankle-foot orthosis. While walking barefoot with a toe-heel-toe gait, the physiological heel-toe gait was restored with any type of orthosis. The spring type of orthosis was significantly superior to the stiff orthosis. This was most clearly expressed in the general parameters of gait-like cadence, velocity, and step length. Kinetic data gave a significant improvement by using any ankle-foot orthosis. Whereas break force was similar with both types, push-off was further improved with the spring type. Kinematics revealed little statistical difference between the two types, although gait was more dynamic and physiological with the spring type of orthosis. Any functional ankle-foot orthosis ameliorates the gait pattern in patients with spastic hemiplegia, but a spring type of orthosis renders the gait more dynamic and best corrects the pathology of gait.     

Abiotic nitrogen reduction on the early Earth

The production of organic precursors to life depends critically on the form of the reactants. In particular, an environment dominated by N2 is far less efficient in synthesizing nitrogen-bearing organics than a reducing environment rich in ammonia. Relatively reducing lithospheric conditions on the early Earth have been presumed to favour the generation of an ammonia-rich atmosphere, but this hypothesis has not been studied experimentally. Here we demonstrate mineral-catalysed reduction of N2, NO2- and NO3- to ammonia at temperatures between 300 and 800 degrees C and pressures of 0.1-0.4 GPa-conditions typical of crustal and oceanic hydrothermal systems. We also show that only N2 is stable above 800 degrees C, thus precluding significant atmospheric ammonia formation during hot accretion. We conclude that mineral-catalysed N2 reduction might have provided a significant source of ammonia to the Hadean ocean. These results also suggest that, whereas nitrogen in the Earth's early atmosphere was present predominantly as N2, exchange with oceanic, hydrothermally derived ammonia could have provided a significant amount of the atmospheric ammonia necessary to resolve the early-faint-Sun paradox.