Letter to Editor: Alpo Bites Back

The author critiques the article in IJSAP (1983, 4(2)101-107) addressing the question of the correct amount of protein in a dog’s diet and notes that one of the critics of high protein diets has close ties to a different pet food company that manufactures and sells low protein diets

Origins and Effects of Spartina Wrack in a Virginia Salt Marsh

Movements of mats of tidal wrack (dead Spartina alterniflora) and impacts of the wrack were followed in color infrared aerial photographs of a sloping foreshore salt marsh on Wallops Island, Virginia. Tidal wrack may be stranded in high marsh, where it decomposes, or it may be temporarily stranded at lower elevations. The wrack kills underlying Spartina alterniflora in low marsh and in the transition zone from low to high marsh. Wrack is the major cause of devegetated areas within the marsh, but these areas eventually revegetate, and do not evolve into pans. There are substantial short-term reductions in S. alterniflora marsh productivity. Other effects of wrack are discussed

Distribution of the Marsh Periwinkle Littorina irrorata (Say) in a Virginia Salt Marsh

Littorina irrorata varies over its geographic range in maximum size, preferred elevations relative to tidal datum planes, and in the type of vegetation it inhabits. On Wallops Island, Virginia, postlarvae of Littorina irrorata with shell lengths \u3c 5 mm long live almost exclusively in dead, curled-up leaves of Spartina alterniflora at elevations near mean tide level, below elevations occupied by larger conspecifics. Snails longer than 5 mm in length increase in average size with decreasing elevation. This distribution is opposite to that found by Hamilton (1978) in a marsh in Florida. No difference was found in our study area in growth rate of marked snails at two different elevations, so the size-elevation gradient probably is not caused by differences in growth rate. Snails 15 to 19 mm long are more active when exposed to reduced salinities than snails \u3e 21 mm long. The lowest salinities recorded in the marsh occurred at the highest elevations. This salinity effect, together with mortality from known size-selective predators, may account, at least in part, for the seaward increase in mean shell size

Size-Specific Emergence of the Marsh Snail, Littorina irrorata: Effect of Predation by Blue Crabs in a Virginia Salt Marsh

Marsh periwinkles of 5 to 7 mm in shell height were eaten regularly by blue crabs. Fractures marking unsuccessful crab attacks were present in about 25% of medium-sized (10-16 mm) snails and over 60% of larger snails (over 16 mm). Medium-sized snails, subject to predation, leave the water more frequently than larger snails, but only about a quarter of the snail population leaves the water during high tide. We found no evidence that the snails leave the water because they sense blue crabs in the water

Elevational Variations in the Lowest Limit of Spartina Colonization in a Virginia Salt Marsh

Elevations of lowest colonization of smooth cordgrass, Spartina alterniflora, were surveyed along the edge of a juvenile salt marsh at Wallops Island, Virginia. This lowest limit of Spartina varied over one-third of the local mean tidal range, with lowest occurrences between mean low water and mean low water neaps. Four geographical factors appeared to influence the lowest limit of Spartina: (1) tidal scouring in areas where tidal channels were constricted, (2) scalloping of the marsh edge over a sloping substrate, (3) patterns of historical development of the marsh, and (4) ice scouring of previously colonized Spartina over winter. Marsh edge scallops occurred only in areas of former Spartina thatch islands, and probably resulted from lateral spreading of those islands

Short-Term Accretional and Erosional Patterns in a Virginia Salt Marsh

We estimated 3-year average rates of accretion and erosion in different vegetation zones of a juvenile Spartina alterniflora salt marsh at Wallops Island, Virginia, by precise releveling of a fixed grid. Seaward of the marsh there was extremely variable accretion and erosion in tidal flat, as a result of winter ice scouring and transport. At the lower limit of the marsh, tall Spartina edge marsh accreted at about 6.2 mm yr-1, well in excess of relative sea level rise, supplied by mineral sediments. At the upper limit, levee Spartina and high marsh accreted at about 1.6 mm yr-1, in equilibrium with sea level rise. Accretion there was supplemented by organic sediments from tidal wrack. At mid-elevations, medium Spartina middle marsh eroded slightly at about -0.6 mm yr-1, and low-density Spartina and bare soil eroded rapidly at about -5.3 mm yr-1. These zones may be relatively sediment-starved. The most severe erosion resulted from vegetation diebacks beneath tidal wrack. Patterns of accretion and erosion show that this site is maturing topographically from a juvenile foreshore marsh to a creek-drained marsh

Predicting the Next Best View for 3D Mesh Refinement

3D reconstruction is a core task in many applications such as robot navigation or sites inspections. Finding the best poses to capture part of the scene is one of the most challenging topic that goes under the name of Next Best View. Recently, many volumetric methods have been proposed; they choose the Next Best View by reasoning over a 3D voxelized space and by finding which pose minimizes the uncertainty decoded into the voxels. Such methods are effective, but they do not scale well since the underlaying representation requires a huge amount of memory. In this paper we propose a novel mesh-based approach which focuses on the worst reconstructed region of the environment mesh. We define a photo-consistent index to evaluate the 3D mesh accuracy, and an energy function over the worst regions of the mesh which takes into account the mutual parallax with respect to the previous cameras, the angle of incidence of the viewing ray to the surface and the visibility of the region. We test our approach over a well known dataset and achieve state-of-the-art results.Comment: 13 pages, 5 figures, to be published in IAS-1

Comparative study of visual performance with tinted soft contact lenses vs. clear soft contact lenses and tinted spectacles under bright outdoor conditions; Phase II

Background: Research has clearly shown the advantages of performance tinted CL wear with regard to various measures of objective and subjective responses under various lighting conditions. The current study expanded upon these results. Methods: Subjects were 38 non-presbyopic emmetropes or slight ametropes with distance Snellen acuity of 20/20 or better while wearing -0.50 D spherical Acuvue 2 CLs. Measurements of 6m tachistoscopic stereoacuity and variable distance timed and tachistoscopic texture gradient recognition were obtained with subjects wearing clear CLs, tinted spectacles, and SportSight CLs. Lens modality and test sequence were randomized. Results: Stereoacuity results showed no statistically significant difference in stereolocalization when subjects were wearing clear CLs, SportSight CLs, or tinted spectacles. Texture gradient results using timed and tachistoscopic presentations demonstrated that it was more difficult for subjects to correctly identify the seam orientation at farther distances than nearer distances, and that subjects took more time to try to identify distant target orientation versus near target orientation. In addition, tachistoscopic presentations were not found to be significant with regard to correctness of responses at any distance with any lens modality. Subjective data indicated more physical comfort with either CL modality instead of tinted spectacles. SportSight CLs were also found to be the most visually comfortable modality, followed by tinted spectacles and then clear CLs. Furthermore, a general trend indicated that subjects felt they were able to perform best while wearing the SportSight CLs. This may partially be due to the fact that subjects noted fewer perceptions of stray light with SportSight CLs than with the other modalities. Likewise, subjects reported an equal number of perceived reflections while wearing SportSight CLs and clear CLs but significantly more while wearing tinted spectacles. Conclusion: Objective findings demonstrated that SportSight CLs provide similar performance with regard to distance depth perception and texture gradient recognition to tinted spectacles. Subjective data indicate that visual comfort of the SportSight CLs was superior to tinted spectacles and clear CLs. Additionally, a trend in subjective data demonstrated that the subjects perceived improved performance on the tests while wearing the SportSight CLs