A planetary collision afterglow and transit of the resultant debris cloud.

Planets grow in rotating disks of dust and gas around forming stars, some of which can subsequently collide in giant impacts after the gas component is removed from the disk1-3. Monitoring programmes with the warm Spitzer mission have recorded substantial and rapid changes in mid-infrared output for several stars, interpreted as variations in the surface area of warm, dusty material ejected by planetary-scale collisions and heated by the central star: for example, NGC 2354-ID8 (refs. 4,5), HD 166191 (ref. 6) and V488 Persei7. Here we report combined observations of the young (about 300 million years old), solar-like star ASASSN-21qj: an infrared brightening consistent with a blackbody temperature of 1,000 Kelvin and a luminosity that is 4 percent that of the star lasting for about 1,000 days, partially overlapping in time with a complex and deep, wavelength-dependent optical eclipse that lasted for about 500 days. The optical eclipse started 2.5 years after the infrared brightening, implying an orbital period of at least that duration. These observations are consistent with a collision between two exoplanets of several to tens of Earth masses at 2-16 astronomical units from the central star. Such an impact produces a hot, highly extended post-impact remnant with sufficient luminosity to explain the infrared observations. Transit of the impact debris, sheared by orbital motion into a long cloud, causes the subsequent complex eclipse of the host star.

Orbital period change of Dimorphos due to the DART kinetic impact.

The Double Asteroid Redirection Test (DART) spacecraft successfully performed the first test of a kinetic impactor for asteroid deflection by impacting Dimorphos, the secondary of near-Earth binary asteroid (65803) Didymos, and changing the orbital period of Dimorphos. A change in orbital period of approximately 7 min was expected if the incident momentum from the DART spacecraft was directly transferred to the asteroid target in a perfectly inelastic collision1, but studies of the probable impact conditions and asteroid properties indicated that a considerable momentum enhancement (ß) was possible2,3. In the years before impact, we used lightcurve observations to accurately determine the pre-impact orbit parameters of Dimorphos with respect to Didymos4-6. Here we report the change in the orbital period of Dimorphos as a result of the DART kinetic impact to be -33.0 ± 1.0 (3σ) min. Using new Earth-based lightcurve and radar observations, two independent approaches determined identical values for the change in the orbital period. This large orbit period change suggests that ejecta contributed a substantial amount of momentum to the asteroid beyond what the DART spacecraft carried.

Ammonia disinfection of animal feeds --laboratory study.

Animal feeds may be contaminated, accidentally or maliciously, with a number of zoonotic bacteria. Animal infections with these bacterial agents, whether or not they cause animal disease, may lead to human illnesses. Anhydrous ammonia was introduced on farms in developed countries as a high-nitrogen soil amendment, but later found use in enhancing crude protein in low-quality roughage fed to ruminants and in neutralizing mycotoxins in fungus-infested feed grains. Although ammonia has been known to be effective against bacteria in other contexts (e.g., manure, community sewage sludge, seeds for sprouting, and boneless lean beef trimmings), it appears that the antibacterial effect of ammoniating animal feeds had not been tested. In the present study, samples of roughage (wheat straw, corn silage) and concentrates (corn grain, cottonseed) produced as animal feed were contaminated with dried-on zoonotic bacteria (Salmonella Newport in all; Campylobacte jejuni, E. coli O157:H7, Listeria monocytogenes, Yersinia enterocolitica in corn grain only). Disinfection with anhydrous ammonia gas was conducted for 24 h at room temperature ( 25 degrees C). The treatment was least effective in silage because the silage alone showed strong antibacterial activity, which may have been slightly reduced by ammoniation. In the other three feeds, depending on the initial level of contamination, ammonia destruction of >or= 5 log10 cfu/g (99.999%) of the selected contaminant was usually observed.

Abdominal wall endometrioma after cesarean section: a preventable complication.

The occurrence of abdominal wall scar endometrioma after cesarean section has been reported previously in the literature. However, steps to prevent this complication have not been delineated. A study was undertaken of six patients seen at our general surgical clinic, each of whom had presented with a painful mass at a previous cesarean section site. Ages ranged from 20 to 34 years. The duration of their symptoms ranged from 6 to 84 months. All patients underwent surgical exploration and excision of the mass, which was revealed by histology to be endometrioma. It is strongly recommended that, at the conclusion of the procedure of cesarean section, the abdominal wall wound be cleaned thoroughly and irrigated vigorously with high-jet saline solution before closure.