Working paper Documentation of tests on particle size methodologies for laser diffraction compared to traditional sieving and sedimentation analysis

Sieving and sedimentation analyses by pipette or hydrometer are historically the traditional methods for determining particle sizedistributions (PSD). A more informative and faster alternative has for years been laser diffraction (LD). From 2003 to 2013 the authors of this paper have worked intensively with PSD and performed various tests and investigations, using LD, sedimentation (by pipette) and sieving. The aim was to improve and understand the relationship between these various techniques, pre-treatment effects and preferably find a unifying correlation factor.As a result, method comparisons of LD and sieving/sedimentation are difficult, as LD is a 3D optical volume measurement, sieving is a 2D width measurement, and sedimentation is density dependent. Platy particles like clay are generally measured to be coarser than traditional methods when LD is used. For LD the clay-boundary is found at 6 μm.For LD, it seems beneficial to split a soil or sediment sample (<2 mm) into 3 fractions at 63 μm and 250 μm respectively. Well sorted samples (like clay, fine silt or windblown sand) can be measured without splitting into fractions, or by splitting at i.e. 63 μm, depending on the clay content and expected PSD

Description of a nest of Euglossa heterosticta from Peru, with taxonomic notes (Hymenoptera: Apidae)

The nest of Euglossa (Euglossa) heterosticta Moure is described as the first aerial nest in the otherwise cavity-nesting purpurea-group.  Associated adult males and females emerged from the nest permitting taxonomic notes to be provided for the heretofore unknown female of E. heterosticta

Particle Sizing in Geosciences: Explanation of Various Techniques and Pre-treatments

This paper describes different methods for particle characterization, specifically size and shape, from a technical perspective. It emphasizes on analytical procedures in the laboratory, practical challenges and data processing. The content is based on hands-on experience with soil and sediment materials and provides theoretical background information, examples of relevant computations, descriptions of hardware and discussions of using different settings. It is intended to be used as a handbook and may be useful as a guide when designing a local procedure for particle size and shape methods. To achieve results of the highest quality, attention should be given to the importance of sample handling, relevant pretreatment and dispersion into single, free flowing particles. Equally important is the attention to detail, ranging from proper laboratory working conditions to critical evaluation of data. One of the main and most important conclusions is the difficulties in comparing data obtained by techniques that measure different properties. This observation does not only apply to particle characterization but is universally applicable

Retningsbestemmelse af isfremstød i Danmark ud fra analyser af fingrus

På Institut for Geoscience, Aarhus Universitet arbejder forskere, laboranter og studerende med specialiserede metoder indenfor geovidenskaberne. Der forskes bl.a. i sedimenter der kommer fra den danske undergrund og er dannet under de seneste istider eller mellemistider. Heriblandt benyttes en speciel type aflejringer (till) til at kortlægge isens udbredelse i Kvartærtiden ud fra indholdet af fingrus