Monsoon-driven Saharan dust variability over the past 240,000 years.

Reconstructions of past Saharan dust deposition in marine sediments provide foundational records of North African climate over time scales of 103 to 106 years. Previous dust records show primarily glacial-interglacial variability in the Pleistocene, in contrast to other monsoon records showing strong precessional variability. Here, we present the first Saharan dust record spanning multiple glacial cycles obtained using 230Th normalization, an improved method of calculating fluxes. Contrary to previous data, our record from the West African margin demonstrates high correlation with summer insolation and limited glacial-interglacial changes, indicating coherent variability in the African monsoon belt throughout the late Pleistocene. Our results demonstrate that low-latitude Saharan dust emissions do not vary synchronously with high- and mid-latitude dust emissions, and they call into question the use of existing Plio-Pleistocene dust records to investigate links between climate and hominid evolution.

African humid periods triggered the reactivation of a large river system in Western Sahara.

The Sahara experienced several humid episodes during the late Quaternary, associated with the development of vast fluvial networks and enhanced freshwater delivery to the surrounding ocean margins. In particular, marine sediment records off Western Sahara indicate deposition of river-borne material at those times, implying sustained fluvial discharges along the West African margin. Today, however, no major river exists in this area; therefore, the origin of these sediments remains unclear. Here, using orbital radar satellite imagery, we present geomorphological data that reveal the existence of a large buried paleodrainage network on the Mauritanian coast. On the basis of evidence from the literature, we propose that reactivation of this major paleoriver during past humid periods contributed to the delivery of sediments to the Tropical Atlantic margin. This finding provides new insights for the interpretation of terrigenous sediment records off Western Africa, with important implications for our understanding of the paleohydrological history of the Sahara.

Reproducibility of transvaginal three-dimensional endometrial volume measurements with virtual organ computer-aided analysis (VOCAL) during ovarian stimulation.

OBJECTIVE: To calculate inter- and intraobserver reliabilities for three-dimensional endometrial volume measurements during in vitro fertilization using virtual organ computer-aided analysis (VOCAL). PATIENTS AND METHODS: Three-dimensional ultrasound measurements of the endometrium using VOCAL software were performed on the day of oocyte retrieval in each of 79 consecutive patients undergoing in vitro fertilization or intracytoplasmic sperm injection. Endometrial volume was calculated every 15 degrees and every 30 degrees by two different observers in order to determine the reproducibility of the technique. RESULTS: Intraobserver reliability for the 15 degrees measurements was 0.97 for both observers; for the 30 degrees measurements, it was 0.93 for one observer and 0.96 for the other. Interobserver reliability was 0.80 for the endometrial volumes calculated every 15 degrees and 0.83 for the volumes calculated every 30 degrees. The intra- and interobserver measurement agreement showed good reproducibility. However, the volumes calculated every 15 degrees were more accurate because the means of differences were close to zero. CONCLUSION: VOCAL provides a reproducible method for the estimation of the endometrial volume.