A direct comparison of single-grain and multi-grain aliquot luminescence dating of feldspars from colluvial deposits in KwaZulu-Natal, South Africa

The erosional landscape of the Jojosi dongas in KwaZulu-Natal, South Africa, exposes accretionary slope deposits that preserve important geological and archaeological information. This landscape was occupied by modern humans during the Stone Age for many thousands of years, as evidenced by the presence of numerous stone artefacts on the surface and interbedded within at least three phases of gully cut-and-fill deposits. A contextualisation of the artefacts and their role for human evolution in southern Africa, along with developing an understanding of the environmental conditions that shaped this inhabited landscape, is only made possible by establishing a robust chronological framework. Here, we use luminescence dating of feldspars to constrain the geochronological framework for the sequence of accretionary hillslope deposition at Jojosi at three sampling locations. Measurements of feldspar single grains show low luminescence sensitivity of the individual grains and a variable proportion of grains in saturation. Summing the luminescence signal of individual grains and creating synthetic aliquots enables us to study the effect of signal averaging on the luminescence sensitivity, signal saturation, and dose distributions. We then compare the results from individual grain measurements and synthetic aliquots to true multi-grain aliquots. To allow a quantification of the results, we apply four different dose models, including the Central Age Model (CAM), the Average Dose Model (ADM), BayLum, and a standardised growth curve (SGC) approach, using an averaged Ln/Tn value interpolated onto the SGC. Doses calculated for the different samples range from ∼ 80 to ∼ 800 Gy and contain 6 % to 67 % saturated grains. We evaluate the performance of the different dose models over this range in equivalent doses and relative number of saturated grains. On average, we find good agreement between the results obtained using the different dose models but observe that samples with a large number of saturated grains impact the consistency of the result. Overall, all dose models and data sets give consistent results below a saturated grain threshold of ∼ 15 %, corresponding to a dose of ∼ 120 Gy in this study. Finally, we favour BayLum for age calculations of the single-grain and multi-grain aliquot data sets, representing the opportunity to refine the chronology by including stratigraphic information in the age calculations. We are able to establish a chronology for the three sampled sections within the Jojosi dongas, constraining erosional and depositional processes from ∼ 100 to ∼ 700 ka, and human occupation of the area spanning from early marine isotope stage (MIS) 5 to late MIS 6.</p

High-utilizing Crohn's disease patients under psychosomatic therapy*

<p>Abstract</p> <p>Objective</p> <p>Few studies have been published on health care utilization in Crohn's disease and the influence of psychological treatment on high utilizers.</p> <p>Methods</p> <p>The present sub study of a prospective multi center investigation conducted in 87 of 488 consecutive Crohn's disease (CD) patients was designed to investigate the influence of the course of Crohn's disease on health care utilization (hospital days (HD) and sick leave days (SLD) collected by German insurance companies) and to examine the conditions of high-utilizing patients. Predictors of health care utilization should be selected. Based on a standardized somatic treatment, high health care utilizing patients of the psychotherapy and control groups should be compared before and after a one-year treatment.</p> <p>Results</p> <p>Multivariate regression analysis identified disease activity at randomization as an important predictor of the clinical course (r²= 0.28, p < 0.01). Health care utilization correlated with duration of disease (p < 0.04), but the model was not significant (r²= 0.15, p = 0.09). The patients' level of anxiety, depression and lack of control at randomization predicted their health-related quality of life at the end of the study (r²= 0.51, p < 0.00001). Interestingly, steroid intake and depression (t1) predicted the combined outcome measure (clinical course, HRQL, health care utilization) of Crohn's disease at the end of the study (r²= 0.22, p < 0.001).</p> <p>Among high utilizers, a significantly greater drop in HD (p < 0.03) and in mean in SLD were found in the treatment compared to the control group.</p> <p>Conclusion</p> <p>The course of Crohn's disease is influenced by psychological as well as somatic factors; especially depression seems important here. A significant drop of health care utilization demonstrates the benefit of psychological treatment in the subgroup of high-utilizing CD patients. Further studies are needed to replicate the findings of the clinical outcome in this CD subgroup.</p

Crohn's Disease and Early Exposure to Domestic Refrigeration

Environmental risk factors playing a causative role in Crohn's Disease (CD) remain largely unknown. Recently, it has been suggested that refrigerated food could be involved in disease development. We thus conducted a pilot case control study to explore the association of CD with the exposure to domestic refrigeration in childhood.Using a standard questionnaire we interviewed 199 CD cases and 207 age-matched patients with irritable bowel syndrome (IBS) as controls. Cases and controls were followed by the same gastroenterologists of tertiary referral clinics in Tehran, Iran. The questionnaire focused on the date of the first acquisition of home refrigerator and freezer. Data were analysed by a multivariate logistic model. The current age was in average 34 years in CD cases and the percentage of females in the case and control groups were respectively 48.3% and 63.7%. Patients were exposed earlier than controls to the refrigerator (X2 = 9.9, df = 3, P = 0.04) and refrigerator exposure at birth was found to be a risk factor for CD (OR = 2.08 (95% CI: 1.01-4.29), P = 0.05). Comparable results were obtained looking for the exposure to freezer at home. Finally, among the other recorded items reflecting the hygiene and comfort at home, we also found personal television, car and washing machine associated with CD.This study supports the opinion that CD is associated with exposure to domestic refrigeration, among other household factors, during childhood