Measuring the effect of long-term pitfall trapping on the prevalence of epigeal arthropods: A case study in the Pacific Coast of Colombia

Pitfall trapping remains one of the most frequently used methods to assess ground-active arthropods’ diversity and density. Yet, one of its main drawbacks, the possibility that repeated collecting may affect the study objects’ population, has not been formally tested. We studied the effect of a yearlong epigeal pitfall trapping exercise with 22 fortnightly capture events in four differently disturbed areas at the Colombian Pacific coast. A transect of 100 m length with ten equidistant pitfall traps was established in each area, and the traps were operated twice a month for 24 hours. Using count data regression models, we find that trapping did not affect subsequent captures when we analyzed non-ant arthropods. For ants, regression estimates indicate that each subsequent trapping in highly-disturbed environments ended, on average, reducing all ants in between -3.8 and -4.1%, and Ectatomma ruidum between -4.7 and -5.1%. We recommend bio-ecological aspects of the species under study be considered when interpreting results. This is important for future studies that rely on this method to deliver consistent estimates of population sizes or study their dynamics through time. At the same time, it is also a call for scientists to revise more carefully how species’ peculiar traits may limit the reliability of traditional methods

Non-Standard Errors

In statistics, samples are drawn from a population in a data-generating process (DGP). Standard errors measure the uncertainty in estimates of population parameters. In science, evidence is generated to test hypotheses in an evidence-generating process (EGP). We claim that EGP variation across researchers adds uncertainty: Non-standard errors (NSEs). We study NSEs by letting 164 teams test the same hypotheses on the same data. NSEs turn out to be sizable, but smaller for better reproducible or higher rated research. Adding peer-review stages reduces NSEs. We further find that this type of uncertainty is underestimated by participants

Änderung der Mortalitäts- und Amputationsraten bei infrainguinaler Gefäßrekonstruktion unter besonderer Berücksichtigung des chirurgischen Managements

Infektionsraten nach infrainguinalen Bypassoperationen sind nach herrschender Meinung mit hohen Morbiditäts- und Mortalitätsraten verbunden. Insbesondere die Risikofaktoren, die einen derartigen Infekt begünstigen, werden kontrovers diskutiert. Von besonderem Interesse ist auch welches chirurgische Management bei Vorliegen eines infrainguinalen Infektes nach einer Gefäßoperation angewendet werden sollte. Vor diesem Hintergrund ist das Ziel dieser Arbeit eine retrospektive Analyse aller Patienten, die wegen Infektion einer Gefäßprothese im Zeitraum zwischen 01.01.1993 und 31.12.2009 an der Klinik für Herz-, Thorax- und Gefäßchirurgie der Universität Ulm behandelt wurden, anzufertigen. Es sind 115 Bypässe verteilt auf 105 Patienten untersucht worden. Um Entwicklungstendenzen beurteilen zu können sind für die Auswertung zwei Kohorten gebildet worden. In die Gruppe A fallen alle Fälle zwischen 01.01.1993 - 31.12.1999 (52 Fälle) und in die Gruppe B alle Fälle zwischen 01.01.2000 bis 31.12.2009 (63 Fälle). Die erfassten Risikofaktoren sind: Chronisch obstruktive Lungenerkrankung, Niereninsuffizienz, Diabetes mellitus, Herzerkrankung und ein etwaiger Nikotin-abusus. Des Weiteren sind bypassspezifische Daten (Bypassverlauf und Bypassmaterial), der Entzündungsgrad nach Szilagyi, das chirurgisches Management, Amputations- und Mortalitätsraten erfasst worden. Es zeigt sich, dass ein Wundinfekt nach einer infrainguinalen Gefäßoperation ein multifaktorielles Geschehen ist. Generell haben Bypassinfekte hohe Morbiditäts- und Mortalitätsraten. Dies gilt auch für infrainguinale Bypassinfekte, die in dieser Studie untersucht worden sind, aber durch ein konsequentes chirurgisches Management sind sowohl Morbiditäts- als auch Mortalitätsraten akzeptabel

Abstract of: Residual stress distribution in tempered glass with reground edges

Many glass applications require laminated glass to achieve a safe load-bearing behaviour. Beside the structural aspect, glass elements have to meet high aesthetic demands. Laminated glasses often feature an offset between the individual glass panes resulting from the lamination process. With regards to visible or exposed edges, this displacement reduces the aesthetic quality of the glass component. The regrinding of the edge after lamination equalises the offset and thus creates a smooth surface. However, regrinding tempered glass leads to a reduction of the surface compression zone at the edge and may decrease the load-bearing capacity. A research project focuses on the detailed evaluation of the effect of regrinding tempered glass. To attain a precise understanding, three different aspects have to be examined: first the maximum required grinding depth resulting from the edge offset, second the defects on the surface of the edge and third the residual stress distribution. The third part was examined by means of stress measurements at the edge and the surface of different specimens. Glass beams made of fully tempered glass and heat strengthened glass with three different thicknesses (6, 8 and 10 mm) were ground after the tempering process. The regrinding depth was 1, 2 and 3 mm. One group of specimens remain untreated as a reference. The depth of the compression zone and the magnitude of the surface stress at the edge were measured with the help of photoelastic measurements. The experimental approach and the results are the content of this paper. It enables a statement about transformations of the residual stress state at the edge owing to regrinding tempered glass

Comparison of the Residual Stresses at the Edge and Surface of Thermally Toughened Glass

The strength of thermally toughened glass is regulated in EN 12150-1 for fully tempered glass (FTG) and EN 1863-1 for heat-strengthened glass (HSG). The manufacturer has to prove the strength by four-point bending tests based on EN 1288-3. A measurement of the residual stresses of thermally toughened glass is not demanded. Consequently, the determination of the strength is containing the amount of residual stresses. As residual stress is depending on the manufacturing process, the amount and distribution can change within one glass pane and between different glass panes. A research project determined the residual stresses at the surfaces and the edges of HSG and FTG with varying glass thicknesses using photoelastic measurements. Thereby, FTG showed lower values of the residual stresses at the edge compared to the surface. Looking at HSG, the results of the residual stresses at the edge and surface were nearly the same. To analyse the edge strength, four-point bending tests were conducted. Thereby, the load was introduced into the strong axis of the specimens to implement constant tensile stresses along the glass edge. The comparison of the edge strengths showed that the edge strength of FTG is in the same range than HSG. Therefore, the lower residual stress at the edge of FTG reflects in significantly lower edge strengths. The paper includes a detailed presentation of the photoelastic measurements at the edge and the surface as well as the determined residual stresses of more than 80 specimens. In addition, the conducted four-point bending tests are described and the obtained edge strengths are correlated to the measured residual stresses. Based on that, the paper contains a discussion of the standardisations, the process of thermally prestressing and the consequences for the final glass strengths

Influence of Regrinding Depth on Edge Strength of Tempered Glass

Designers use exposed glass edges for decoration, for example within glass steps, glass beams or glass columns. This application requires a mechanical finishing to achieve a high optical quality by compensating a misalignment of the glasses, for example an edge displacement, or a supernatant of the foil resulting from the lamination process of safety glass. Regrinding of annealed glass is allowed without restrictions. In the case of tempered glass there is a risk of premature failure caused by a reduction of the compression zone. During a research project at the Institute of Building Construction, Technische Universität Dresden, the impact of the grinding depth of tempered glass on the bearing capacity of the edge is investigated. The goal is to give a strength value of reground tempered glass edges. We conducted four-point bending tests on glass beams about the strong axis in the style of EN 1288-3. The experimental investigation included 82 glass beams both made from fully tempered and heat strengthened glass in thicknesses of 6 mm with reground edges in varied grinding depths and additional reference specimens. The experimental investigation shows that an increasing grinding depth induces a decrease in edge strength. In the presented case, the result of the test series allows the definition of reduction factors for the calculation of the bending strength of glass beams with reground edges