Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling.

A carbon-rich black layer, dating to approximately 12.9 ka, has been previously identified at approximately 50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at approximately equal 12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at approximately 12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America.

Appendiceal disease in women with endometriosis and right lower quadrant pain.

STUDY OBJECTIVE: To evaluate the frequency and range of appendiceal disease in women with endometriosis and right lower quadrant (RLQ) pain, and to estimate the value of preoperative gastrograffin enema (GGE) as a screen for the disease. DESIGN: Nonrandomized clinical trial (Canadian Task Force classification II-2). SETTING: University-affiliated hospital with a private practice setting. PATIENTS: A subpopulation of 65 women from a group of 337 patients undergoing laparoscopy for symptomatic endometriosis. INTERVENTION: Preoperative GGE was performed whenever possible in these women. At laparoscopy, the appendix was removed if it appeared abnormal or if the preoperative GGE was positive. MEASUREMENTS AND MAIN RESULTS: Of 65 women (19%) with symptomatic endometriosis and preoperative RLQ pain, 52 (80%) underwent appendectomy as part of surgery. Of these 52 excised appendixes, 39 (75%) had histologically confirmed pathology including appendicitis or periappendicitis, endometriosis, fibrous obliteration, lymphoid hyperplasia, and carcinoid tumor. Preoperative GGE had sensitivity of 74% and specificity of 83% for appendiceal disease. Its positive predictive value was 95% and negative predictive value was 42%. No complications from laparoscopic appendectomy occurred. CONCLUSION: Disease of the appendix is common in women with endometriosis and RLQ pain. Appendectomy is particularly likely if preoperative GGE is positive.

Effect of dietary supplementation of glycine on caries development and lipids in rat molars.

The effect of dietary supplementation of glycine at a level of 4% on caries development and the lipid content of rat molar teeth was studied. The glycine supplementation caused a 65.7% reduction in caries development and a 15.1% reduction in lipid content. In a concurrent balance study, it was noted that the dietary glycine did not have any significant effect on the retention of either calcium or phosphorus by the rat's body. Changes in the fatty acid composition of the tooth and a reduction in growth rate were noted, however.