Variation in interference relationships have been shown for a number of crop-weed associations and may have an important effect on the implementation of decision support systems for weed management. Multiyear field experiments were conducted at eight locations to determine the stability of corn-foxtail interference relationships across years and locations. Two coefficients (I and A) of a rectangular hyperbola equation were estimated for each data set using nonlinear regression procedures. The I and A coefficients represent percent corn yield loss as foxtail density approaches zero and maximum percent corn yield loss, respectively. The coefficient I was stable across years at two locations and varied across years at four locations. Maximum yield loss (A) varied between years at one location. Both coefficients varied among locations. Although 3 to 4 foxtail plants m−-1 row was a conservative estimate of the single-year economic threshold (Tc) of foxtail density, variation in I and A resulted in a large variation in Tc. Therefore, the utility of using common coefficient estimates to predict future crop yield loss from foxtail interference between years or among locations within a region is limited.

Field studies were conducted at 35 sites throughout the north-central United States in 1998 and 1999 to determine the effect of postemergence glyphosate application timing on weed control and grain yield in glyphosate-resistant corn. Glyphosate was applied at various timings based on the height of the most dominant weed species. Weed control and corn grain yields were considerably more variable when glyphosate was applied only once. The most effective and consistent season-long annual grass and broadleaf weed control occurred when a single glyphosate application was delayed until weeds were 15 cm or taller. Two glyphosate applications provided more consistent weed control when weeds were 10 cm tall or less and higher corn grain yields when weeds were 5 cm tall or less, compared with a single application. Weed control averaged at least 94 and 97% across all sites in 1998 and 1999, respectively, with two glyphosate applications but was occasionally less than 70% because of late emergence of annual grass and Amaranthus spp. or reduced control of Ipomoea spp. With a single application of glyphosate, corn grain yield was most often reduced when the application was delayed until weeds were 23 cm or taller. Averaged across all sites in 1998 and 1999, corn grain yields from a single glyphosate application at the 5-, 10-, 15-, 23-, and 30-cm timings were 93, 94, 93, 91, and 79% of the weed-free control, respectively. There was a significant effect of herbicide treatment on corn grain yield in 23 of the 35 sites when weed reinfestation was prevented with a second glyphosate application. When weed reinfestation was prevented, corn grain yield at the 5-, 10-, and 15-cm application timings was 101, 97, and 93% of the weed-free control, respectively, averaged across all sites. Results of this study suggested that the optimum timing for initial glyphosate application to avoid corn grain yield loss was when weeds were less than 10 cm in height, no more than 23 d after corn planting, and when corn growth was not more advanced than the V4 stage.

A 14 year old boy with scapuloperoneal muscular atrophy, pes cavus, areflexia and distal sensory loss (Davidenkow syndrome) is described. Nerve conduction velocities were diminished. Sural nerve biopsy demonstrated a reduction in the number of myelinated fibers and early “onion-bulb” formation. These observations support the hypothesis that the scapuloperoneal amyotrophy associated with distal sensory loss may represent a variant of type I hereditary motor sensory neuropathy.

Significant new opportunities for astrophysics and cosmology have been identified at low radio frequencies. The Murchison Widefield Array is the first telescope in the southern hemisphere designed specifically to explore the low-frequency astronomical sky between 80 and 300 MHz with arcminute angular resolution and high survey efficiency. The telescope will enable new advances along four key science themes, including searching for redshifted 21-cm emission from the EoR in the early Universe; Galactic and extragalactic all-sky southern hemisphere surveys; time-domain astrophysics; and solar, heliospheric, and ionospheric science and space weather. The Murchison Widefield Array is located in Western Australia at the site of the planned Square Kilometre Array (SKA) low-band telescope and is the only low-frequency SKA precursor facility. In this paper, we review the performance properties of the Murchison Widefield Array and describe its primary scientific objectives.

The levels of four sets of pollutants (heavy-metals, artificial radionuclides, petroleum components, and halogenated hydrocarbons), have been measured in U.S. coastal waters, using bivalves as sentinel organisms. The strategies of carrying out this programme are outlined and the results from the first year's work are given. Varying degrees of pollution in U.S. coastal waters have been indicated by elevated levels of pollutants in the bivalves, which comprised certain species of mussels and oysters and were collected at over one hundred localities.

We advocate primary repair of atrioventricular septal defect with a common atrioventricular orifice in symptomatic children presenting with intractable congestive heart failure. The single patch technique has been utilized as our procedure of choice. A low operative mortality and a low incidence of residual ventricular septal defect and regurgitation of the left atrioventricular valve requiring reoperation has been achieved. This report emphasizes the technical details of the repair. Careful delineation of anatomic detail is considered to be of the utmost importance. Precise suture placement, tailoring the patch, and reconstruction of the left atrioventricular valve are essential to achieve complete closure of the atrial and ventricular septal defects and functional integrity of the left atrioventricular valve.

We report analysis of surgical results in 110 consecutive infants and children who underwent atrial repair of simple complete transposition using the Senning operation between February 1978 and May 1990. Mean age at operation was 5.4 months ± 6.1 (range 1 week to 4 years); 75 were less than 6 months old. There were 72 males and 38 females. Operative mortality rate was 5.5%, with one late death. Average follow-up is 48.1 months with 44 followed greater than 3 years, and 27 greater than 5 years. Postoperative cardiac catheterization was performed in 48 patients. Right ventricular ejection fraction averaged 0.52 ± 0.08 and was normal in 28 patients. Response of right ventricular ejection fraction to afrerload stress was abnormal in 12 of 14 patients tested. Right ventricular ejection fraction increased normally during exercise in 6 patients, but was abnormal in 15. Mild tricuspid regurgitation was noted in 12 patients. Mild obstruction of the superior caval vein was noted in 4 patients. Baffle leak requiring reoperation occurred in one patient. Fifty-seven of 90 patients are in sinus rhythm by latest electrocardiogram. Postoperative electrophysiologic studies were performed in 34 patients, and Holter monitoring in 25. Significant arrhythmia occurred in 26 patients: 6 patients required pacemakers for slow junctional rhythm or complete heart block; 20 additional patients have a junctional rhythm. Six patients have delayed sinus nodal recovery time. At last follow-up, 88 children (98%) are in New York Heart Association functional Class I, and 2 (2%) are in Class II. The Senning operation for compete transposition can be accomplished with a low operative and late mortality. Serious baffle complications requiring reoperation are rare. Surviving patients are clinically well, but arrhythmias and depressed right ventricular function may limit their long-term functional status.