Effects of surfactants and simulated rainfall on the efficacy of the Engame formulation of glyphosate in johnsongrass, prickly sida and yellow nutsedge

The effects of surfactants and simulated rain were investigated on the efficacy of Engame and Roundup Ultramax formulations of glyphosate on johnsongrass ( Sorghum halepense L.), prickly sida ( Sida spinosa L.) and yellow nutsedge ( Cyperus esculentus L.). Flame surfactant provided the greatest enhancement of Engame efficacy and the effect was species-dependent. Flame enhanced the activity of Engame on johnsongrass and yellow nutsedge but not on prickly sida. Engame and Engame plus Flame were more active than Roundup Ultramax on a glyphosate acid-equivalent basis on johnsongrass without rain, and on yellow nutsedge with or without rain. The Engame and Roundup Ultramax activities on johnsongrass were similar with rain, and rain occurring between five and 30 min after treatment diminished their activities to < 38% of the control. With the addition of Flame surfactant, Engame activity on johnsongrass increased, such that 50% and 80% of the control were realized, even with rain occurring between five and 15 min after treatment, respectively. Engame and Roundup Ultramax provided better control of prickly sida than of johnsongrass following a rain event. The addition of Flame surfactant to Engame did not enhance the activity on prickly sida. Yellow nutsedge control with Engame and Engame plus Flame was greater than with Roundup Ultramax and rain had little effect on control regardless of the length of the rain-free period. These results demonstrated that the activities of Engame, Engame plus Flame and Roundup Ultramax were species-dependent and surfactant-dependent.     

Structure and stability in exploited marine fish communities: quantifying critical transitions

Correlations between time series of the abundance of predator and prey fish species in heavily exploited western North Atlantic marine fisheries vary temporally but are generally positive in southern, warmer waters and negative in northern, colder ones. The correlations provide an index of trophic structure and dynamics. We construct a framework to quantify critical thresholds between states in which the predator–prey correlations are positive or negative. We do so by developing a quantitative model of the distribution of the correlations between predator (15 species) and prey (8 species) functional groups based on the annual predator depletion rates and bottom temperatures (or alternatively species richness). The model accounts for 58% of the variance of the correlations with a root mean square error of 0.3. This index of trophic structure indicates that warmer, species-rich, southern fish populations resist transformation from positive to negative predator–prey correlations at exploitation rates that can be double those in the colder, relatively species-poor, northern areas. The model can be used to set limits for exploitation rates that preserve the functional relationships between predator–prey groups in emerging fisheries, and to assess the potential for and measures required to achieve recovery of degraded fish communities.     

INTRAARTERIAL CONTRAST-ENHANCED COMPUTED TOMOGRAPHY OF THE EQUINE DISTAL EXTREMITY

A technique for regional delivery of contrast medium to the foot of the horse to increase the diagnostic utility of computed tomography (CT) for the characterization of soft tissue structures within the hoof capsule was developed. An intraarterial catheter was placed under ultrasound guidance into the medial palmar artery at the level of the carpus to facilitate a steady-state infusion of iodinated contrast medium. Two 5 mm collimated contiguous acquisition CT scans were performed in 10 horses without lameness or radiographic evidence of distal sesamoid bone degeneration. CT examination was performed before and during regional arterial infusion of iodinated contrast medium administered at a rate of 2 ml/s. Cross-sectional area and mean pre- and post-contrast attenuation of the deep digital flexor tendon and the collateral ligaments of the distal interphalangeal joint were quantified from CT images. Soft tissue anatomy of the foot was also qualitatively characterized from pre- and postcontrast images. Catheterization was successful and without complication in all horses. The evaluated tendons and ligaments were clearly visible and had a small (8-20 Hounsfield Unit) but significant (P < 0.05, paired t-test) increase in attenuation during the steady-state infusion of contrast medium. This study should enhance the diagnostic potential of CT by providing baseline quantitative data for comparison with horses affected with soft tissue injuries in the distal extremity causing lameness that is alleviated with a palmar digital nerve block.     

Femoral Head and Neck Fractures in the Dog and Cat: A Review of 115 Cases

Case histories of 115 dogs and cats with fractures of the femoral head or neck, were reviewed; these animals had been presented to the Ohio State University Veterinary Hospital between 1969 and 1976. Signalment, fracture type by anatomic location, fracture to fixation interval, surgical approaches used, methods of surgical repair, surgical complications, and final results of surgical repair were examined. Avascular necrosis of the femoral head was not a clinically significant problem following internal fixation in this study. Most animals had very good to excellent limb function following fracture repair.     

Obstruction of the Ascending Colon in Cattle: II. An Experimental Model of Partial Bypass of the Large Intestine

Four dairy calves were subjected to partial bypass of the large intestine by uniting the ileum to the distal centrifugal coil of the spiral loop of the ascending colon (spiral colon). Digesta bypassed the distal ileum, cecum, proximal loop of the ascending colon, and the centripetal coils of the spiral colon. The calves survived the surgical procedure and were healthy throughout the 4-week postoperative experimental period. Feces were loose immediately after bypass, but fecal dry matter (DM) gradually increased over the subsequent 2 weeks (P < 0.01), indicating adaptation of remaining bowel to absorb more water. There was no significant change in serum concentration of sodium or chloride. The calves continued to grow and gain weight at acceptable rates after bypass. Necropsy of 3 of the calves demonstrated a decrease in size of the bypassed bowel.     

LONG-TERM CHANGES IN FOREST SOIL ACIDITY IN PENNSYLVANIA,U.S.A.

Forest soil acidification has been reported to cause reduced forest productivity and decline of some tree species. Soil acidification may cause increased bioavailability of Al and Mn, which are potentially phytotoxic. In an attempt to measure whether or not Pennsylvania forest soils have become more acidic, soil samples were collected at 11 undisturbed forested sites in Pennsylvania in 1993. Limited soil chemistry data obtained through 4 previous studies conducted between 1957 and 1979 were available for each site. Soil pH and concentrations of exchangeable Ca and Mg were measured; results were compared to those obtained in earlier studies. Soil exchangeable Al concentrations were determined for 6 sites for which previous data were available. Chemical analysis methods were evaluated to ensure that methods used in 1993 were comparable to those of the original investigators. Mean pH and exchangeable Mg declined most consistently over the study period in the O horizon and the uppermost A horizon. Mean exchangeable AI decreased in the O horizon and increased in the A horizon. Given the high sulfate and nitrate deposition loads in Pennsylvania, it seems likely that the observed changes are at least in part a consequence of acidic deposition.     

State and Local Government Finances: Was There a Structural Break in the Reagan Years?

The Reagan administration's “New Federalism” and tax reform proposals were expected to have chilling effects on growth of state and local government revenues and expenditures. This paper examines the hypothesis that there was a structural break in state and local government fiscal behavior in the 1980s. Although the evidence is far from conclusive, it does suggest some different fiscal patterns in this decade. However, the real structural break appears to have occurred in the late 1970s and these trends have continued during the Reagan years.     

Physical transport of young pollock larvae (Theragra chalcogramma) near Shelikof Strait as inferred from a hydrodynamic model

An advective model was used to simulate the drift of larval walleye pollock ( Theragra chalcogramma ) over a 40-day period (late April through early June) near Shelikof Strait, Alaska. This model was used: (i) to assess how much of the observed change in larval positions during that period can be explained by transport at fixed depth; (ii) to demonstrate that observed change can be related to mean large-scale meteorological forcing; and (iii) to investigate accumulation of larvae in specific areas near the coast. Based on availability of larval and circulation data, three years were studied: 1988, 1989 and 1991. Velocity fields generated from a hydrodynamic model driven by winds and runoff were used to advect particles seeded in accordance with observed larval distributions in late April of each year. The modelled larvae were tracked at 40 m depth, corresponding to the mean depth of sampled larvae and the depth of neutrally buoyant drifters employed in field studies. Specific features observed in late May larval surveys were reproduced by the model, such as the accumulation of larvae in a shoal area downstream of the strait. Differences among the modelled years include extensive flushing of larvae to the south-west in 1988 and 1991, vs. limited flushing in 1989. These differences appear related to the mean large-scale atmospheric pressure patterns for April-May of those years.