Sediment-moss interactions on a temperate glacier: Falljökull, Iceland

Full text of this article can be found at: http://www.igsoc.org/annals/ Copyright IGS. DOI: 10.3189/172756408784700734We present the results of preliminary investigations of globular moss growth on the surface of Falljökull, a temperate outlet glacier of the Vatnajökull ice cap, southern Iceland. Supraglacial debris has provided a basis for moss colonization, and several large (>500 m2) patches of moss growth (Racomitrium spp.) are observed on the surface of the glacier. Each area of moss-colonized supraglacial debris shows a downslope increase in sphericity and moss cushion size and a decrease in percentage surface coverage of moss-colonized and bare clasts. It is suggested that moss growth on supraglacial debris allows preferential downslope movement of clasts through an associated increase in both overall mass and sphericity. Thermal insulation by moss cushions protects the underlying ice surface from melt, and the resulting ice pedestals assist in downslope sliding and toppling of moss cushions. The morphology and life cycle of supraglacial globular mosses is therefore not only closely linked to the presence and distribution of supraglacial debris, but also appears to assist in limited down-glacier transport of this debris. This research highlights both the dynamic nature of the interaction of mosses with supraglacial sedimentary systems and the need for a detailed consideration of their role within the wider glacial ecosystem.Peer reviewe

The importance of good coding practices for data scientists

Many data science students and practitioners are reluctant to adopt good coding practices as long as the code "works". However, code standards are an important part of modern data science practice, and they play an essential role in the development of "data acumen". Good coding practices lead to more reliable code and often save more time than they cost, making them important even for beginners. We believe that principled coding practices are vital for statistics and data science. To install these practices within academic programs, it is important for instructors and programs to begin establishing these practices early, to reinforce them often, and to hold themselves to a higher standard while guiding students. We describe key aspects of coding practices (both good and bad), focusing primarily on the R language, though similar standards are applicable to other software environments. The lessons are organized into a top ten list

A comparison of the reproducibility of manual tracing and on-screen digitization for cephalometric profile variables

The aim of this investigation was to analyse and compare the reproducibility of manual cephalometric tracings with on-screen digitization using a soft tissue analysis. A random sample of 20 lateral cephalometric radiographs, in the natural head posture, was selected. On-screen digitization using Viewbox (R) 3.1.1.9 cephalometric software and manual tracing on a 1:1 printout of the image was carried out twice in different sessions 1 week apart. Differences were analysed using a repeated measurement analysis of variance with method, session, and method-session interaction as explaining variables. The differences were expressed as an absolute percentage of the overall mean. The findings of the present study indicate that the two measurement methods differ significantly for 11 variables (P = 0.001 to P = 0.042). The area around stomion was the least reproducible. Except for s-n(s)-unt, nasal protrusion, with the manual technique, all mean differences between sessions and between methods were less than 1 degree or 1 mm and were, on-screen, smaller for 13 variables compared with those traced manually. Absolute percentage differences of the overall mean were smaller for seven variables with the digital technique and three variables in the manual technique, while four manual variables and one on-screen variable exceeded 2 per cent of the overall mean. Although small significant differences were found, the clinical relevance remains questionable

Evaluation of elastix-based propagated align algorithm for VOI- and voxel-based analysis of longitudinal F-18-FDG PET/CT data from patients with non-small cell lung cancer (NSCLC)

Background: Deformable image registration allows volume of interest (VOI)- and voxel-based analysis of longitudinal changes in fluorodeoxyglucose (FDG) tumor uptake in patients with non-small cell lung cancer (NSCLC). This study evaluates the performance of the elastix toolbox deformable image registration algorithm for VOI and voxel-wise assessment of longitudinal variations in FDG tumor uptake in NSCLC patients. Methods: Evaluation of the elastix toolbox was performed using F-18-FDG PET/CT at baseline and after 2 cycles of therapy (follow-up) data in advanced NSCLC patients. The elastix toolbox, an integrated part of the IMALYTICS workstation, was used to apply a CT-based non-linear image registration of follow-up PET/CT data using the baseline PET/CT data as reference. Lesion statistics were compared to assess the impact on therapy response assessment. Next, CT-based deformable image registration was performed anew on the deformed follow-up PET/CT data using the original follow-up PET/CT data as reference, yielding a realigned follow-up PET dataset. Performance was evaluated by determining the correlation coefficient between original and realigned follow-up PET datasets. The intra-and extra-thoracic tumors were automatically delineated on the original PET using a 41% of maximum standardized uptake value (SUVmax) adaptive threshold. Equivalence between reference and realigned images was tested (determining 95% range of the difference) and estimating the percentage of voxel values that fell within that range. Results: Thirty-nine patients with 191 tumor lesions were included. In 37/39 and 12/39 patients, respectively, thoracic and non-thoracic lesions were evaluable for response assessment. Using the EORTC/SUVmax-based criteria, 5/37 patients had a discordant response of thoracic, and 2/12 a discordant response of non-thoracic lesions between the reference and the realigned image. FDG uptake values of corresponding tumor voxels in the original and realigned reference PET correlated well (R-2=0.98). Using equivalence testing, 94% of all the voxel values fell within the 95% range of the difference between original and realigned reference PET. Conclusions: The elastix toolbox impacts lesion statistics and therefore therapy response assessment in a clinically significant way. The elastix toolbox is therefore not applicable in its current form and/or standard settings for PET response evaluation. Further optimization and validation of this technique is necessary prior to clinical implementation

Temporal trends and spatial variation in stage distribution of non-small cell lung cancer in the Netherlands

Introduction To explore regional and temporal variation in clinical stage distribution of non-small cell lung cancer (NSCLC) and link the observations to the introduction of positron emission tomography (PET). Method All NSCLC patients diagnosed between 1989 and 2007 were selected from the Netherlands Cancer Registry (n=126,962). Maps of smoothed percentage distribution of clinical stage NSCLC were conducted by period of diagnosis. Join point regression analyses were performed to detect trends over time. Geographic variation in stage distribution was evaluated using spatial scan statistic. To evaluate the impact of PET in regions proportions of stage IV and Estimated Annual Percentage of Change (EAPC) were calculated for two regions in which PET was introduced between 1995 and 2000 and for two regions without a PET scanner during this period. Results The percentage of stage I and unknown decreased with 7.4% and 13.3% between 1989 and 2007, while the percentage of stage IV increased with 23.4%. The most rapid increase in stage I and IV were observed between 1997 and 2003. In two regions with a PET scan the proportion of stage IV increased annually with 10.3 and 8.5% compared to 5.4 and 6.4% in two regions without a PET scan. Conclusion The most rapid changes towards more stage IV NSCLC diagnoses correspond with the implementation of PET. However, trends were already visible before PET was introduced and regions without PET also showed considerable increases in stage IV diagnose, suggesting other factors or improvements in diagnostics also contributed substantially

Endothelial bound lipoprotein lipase (LpL) depletion in hypoalbuminemia results from decreased endothelial binding, not decreased secretion

Hypertriglyceridemia in nephrotic (NS) and Nagase analbuminemic rats (Analb) results from reduced triglyceride clearance. NS and Analb have reduced or absent albumin, reduced plasma oncotic pressure (π), but Analb lack proteinuria. The heparin releasable lipoprotein lipase (LpL) pool in both models is greatly reduced, suggesting reduced LpL is related to low albumin or π and not proteinuria. To determine the cause of endothelial LpL reduction, we studied effectors of endothelial LpL (eLpL) levels from gene expression, to delivery and endothelial binding. eLpL was measured as heparin releasable activity. eLpL and secretion rate was measured in isolated hearts perfused with heparin. mRNA levels were measured in rat hearts by kinetic RT-PCR. Finally, binding of 125I-LpL by competition assays rat endothelial cells measured serum-induced changes in affinity. eLpL in vivo was reduced in nephrotic and Analb rats. While the eLpL pool was reduced in isolated perfused hearts, neither LpL secretion by isolated hearts nor myocardial mRNA was reduced in NS or Analb. Binding of LpL to RAEC preincubated with serum from either NS or Analb was reduced compared to control. LpL mRNA levels and release rate was not altered in hearts from NS rats, while eLpL is depleted, suggesting that reduced eLpL in NS is not the result of reduced delivery. The finding that NS serum alters LpL binding to RAEC suggests LpL depletion results from decreased binding rather than defective delivery. This in turn is a consequence of reduced serum albumin or π but does not require proteinuria