[POPULATION BIOLOGICAL STUDIES] First results of the excavation of the burial mound of Petania, Uvea, Western Polynesia

Author(s):  
Christophe Sand ◽  
Frederique Valentin
Molecules ◽  
2020 ◽  
Vol 25 (22) ◽  
pp. 5443
Author(s):  
Sophie Hoenke ◽  
Immo Serbian ◽  
Hans-Peter Deigner ◽  
René Csuk

The combination of the “correct” triterpenoid, the “correct” spacer and rhodamine B (RhoB) seems to be decisive for the ability of the conjugate to accumulate in mitochondria. So far, several triterpenoid rhodamine B conjugates have been prepared and screened for their cytotoxic activity. To obtain cytotoxic compounds with EC50 values in a low nano-molar range combined with good tumor/non-tumor selectivity, the Rho B unit has to be attached via an amine spacer to the terpenoid skeleton. To avoid spirolactamization, secondary amines have to be used. First results indicate that a homopiperazinyl spacer is superior to a piperazinyl spacer. Hybrids derived from maslinic acid or tormentic acid are superior to those from oleanolic, ursolic, glycyrrhetinic or euscaphic acid. Thus, a tormentic acid-derived RhoB conjugate 32, holding a homopiperazinyl spacer can be regarded, at present, as the most promising candidate for further biological studies.


2020 ◽  
Author(s):  
Tony Reimann ◽  
Mike van Meer ◽  
Hans von Suchodoletz

<p>Chernozems are among the most productive soils in the world, as they unite several favorable factors such as high fertility, favorable pH, a granular structure and high moisture retention capacity. Because of that they are typically characterized by a high agrarian value and often provide long records of intensive human land-use that reach back several millennia. However, despite their high relevance for soil sciences and geoarchaeology, many important aspects regarding chernozem formation – e.g. the question whether natural or human factors were more important - are still poorly understood (Eckmeier et al., 2007). One important drawback in this context is the lack of powerful methods to get grip on timing and rates of chernozem evolution.</p><p>Recently it has been suggested that the nexus of soil mixing and soil evolution can be clarified through single-grain luminescence analyses (Reimann et al., 2017). In this study we apply the suggested protocol for the first time to two chernozem profiles in Central Germany that were buried by the Late Bronze Age burial mound Bornhöck ca. 3.8 ka ago. Our goals are (i) to test the newly developed luminescence methodology, and if successful, (ii) to date the start of chernozem formation and degradation and (iii) to quantify soil formation rates through time.</p><p>First results suggest that chernozem formation of the two profiles started most likely in the early Holocene and ceased between ca. 5.5 and 5.0 ka ago. Furthermore, our data demonstrate that chernozem formation was characterized by very intensive vertical soil mixing, most likely related to intensive bioturbation. In a next step we will calculate corresponding biological soil mixing rates to further detail chernozem evolution. Already at this stage of research, however, we can confidently conclude that we are able to trace key processes of chernozem formation through the analyses of single-grain luminescence data.</p><p> </p><p><strong>References:</strong></p><p>- Eckmeier, E., Gerlach, R., Gehrt, E. & Schmidt, M.W.I.  (2007). Pedogenesis of Chernozems in Central Europe - A review. Geoderma 139, 288-299.</p><p>- Reimann, T., Román-Sánchez, A., Vanwalleghem, T. & Wallinga, J. (2017). Getting a grip on soil reworking–Single-grain feldspar luminescence as a novel tool to quantify soil reworking rates. Quaternary Geochronology 42, 1-14.</p><p> </p>


2005 ◽  
Vol 15 (01n02) ◽  
pp. 41-45 ◽  
Author(s):  
S. MATSUYAMA ◽  
K. ISHII ◽  
S. ABE ◽  
H. OHTSU ◽  
H. YAMAZAKI ◽  
...  

A microbeam analysis system at Tohoku University has been improved in detection efficiency for application to single cell analysis. The system is applicable to STIM analysis and to simultaneous PIXE and RBS analysis. Sample preparation methods suitable for non-adhesive single cell analysis were developed and first results with the improved analysis system are shown.


1976 ◽  
Vol 32 ◽  
pp. 577-588
Author(s):  
C. Mégessier ◽  
V. Khokhlova ◽  
T. Ryabchikova

My talk will be on the oblique rotator model which was first proposed by Stibbs (1950), and since received success and further developments. I shall present two different attempts at describing a star according to this model and the first results obtained in the framework of a Russian-French collaboration in order to test the precision of the two methods. The aim is to give the best possible representation of the element distributions on the Ap stellar surfaces. The first method is the mathematical formulation proposed by Deutsch (1958-1970) and applied by Deutsch (1958) to HD 125248, by Pyper (1969) to α2CVn and by Mégessier (1975) to 108 Aqr. The other one was proposed by Khokhlova (1974) and used by her group.


1976 ◽  
Vol 32 ◽  
pp. 109-116 ◽  
Author(s):  
S. Vauclair

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.


Author(s):  
R. C. Moretz ◽  
D. F. Parsons

Short lifetime or total absence of electron diffraction of ordered biological specimens is an indication that the specimen undergoes extensive molecular structural damage in the electron microscope. The specimen damage is due to the interaction of the electron beam (40-100 kV) with the specimen and the total removal of water from the structure by vacuum drying. The lower percentage of inelastic scattering at 1 MeV makes it possible to minimize the beam damage to the specimen. The elimination of vacuum drying by modification of the electron microscope is expected to allow more meaningful investigations of biological specimens at 100 kV until 1 MeV electron microscopes become more readily available. One modification, two-film microchambers, has been explored for both biological and non-biological studies.


Author(s):  
Murray Vernon King ◽  
Donald F. Parsons

Effective application of the high-voltage electron microscope to a wide variety of biological studies has been restricted by the radiation sensitivity of biological systems. The problem of radiation damage has been recognized as a serious factor influencing the amount of information attainable from biological specimens in electron microscopy at conventional voltages around 100 kV. The problem proves to be even more severe at higher voltages around 1 MV. In this range, the problem is the relatively low sensitivity of the existing recording media, which entails inordinately long exposures that give rise to severe radiation damage. This low sensitivity arises from the small linear energy transfer for fast electrons. Few developable grains are created in the emulsion per electron, while most of the energy of the electrons is wasted in the film base.


Author(s):  
H. Seiler ◽  
U. Haas ◽  
K.H. Körtje

The physical properties of small metal particles reveal an intermediate position between atomic and bulk material. Especially Ag has shown pronounced size effects. We compared silver layers evaporated in high vacuum with cluster layers of small silver particles, evaporated in N2 at a pressure of about 102 Pa. The investigations were performed by electron optical methods (TEM, SEM, EELS) and by Photoacoustic (PA) Spectroscopy (gas-microphone detection).The observation of cluster layers with TEM and high resolution SEM show small silver particles with diameters of about 50 nm (Fig. 1 and Figure 2, respectively). The electron diffraction patterns of homogeneous Ag layers and of cluster layers are similar, whereas the low loss EELS spectra due to plasmon excitation are quite different. Fig. 3 and Figure 4 show first results of EELS spectra of a cluster layer of small silver particles on carbon foil and of a homogeneous Ag layer, respectively.


Author(s):  
Jane K. Rosenthal ◽  
Dianne L. Atkins ◽  
William J. Marvin ◽  
Penny A. Krumm

To comprehend structural changes in cardiac myocytes accompanying adrenergic innervation, it is essential that a three dimensional analysis be performed. To date, biological studies which utilize stereological methods have been limited to cells in tissue and in organs. Our laboratory has utilized current stereological techniques for measuring absolute volumes of individual myocytes in primary culture. Cell volumes are calculated for two distinct groups of cells at 96 hours in culture: isolated myocytes and myocytes innervated with adrenergic neurons (Figure 1).Cardiac myocytes are cultured from the ventricular apices of newborn rats. Cells are plated directly onto tissue culture dishes with or without preplated explants from the paravertebral thoracolumbar sympathetic chain. On day four cultures are photographed and marked for one-to-one cell location. Following conventional fixation and embeddment in eponate-12, the cells are relocated and mounted for microtomy. The cells are completely sectioned at 120nm in their parallel orientation to the surface of the dish (Figure 2). Serial sections are collected on formvar coated slotted grids and are recorded in sequence.


Author(s):  
H.S. von Harrach ◽  
D.E. Jesson ◽  
S.J. Pennycook

Phase contrast TEM has been the leading technique for high resolution imaging of materials for many years, whilst STEM has been the principal method for high-resolution microanalysis. However, it was demonstrated many years ago that low angle dark-field STEM imaging is a priori capable of almost 50% higher point resolution than coherent bright-field imaging (i.e. phase contrast TEM or STEM). This advantage was not exploited until Pennycook developed the high-angle annular dark-field (ADF) technique which can provide an incoherent image showing both high image resolution and atomic number contrast.This paper describes the design and first results of a 300kV field-emission STEM (VG Microscopes HB603U) which has improved ADF STEM image resolution towards the 1 angstrom target. The instrument uses a cold field-emission gun, generating a 300 kV beam of up to 1 μA from an 11-stage accelerator. The beam is focussed on to the specimen by two condensers and a condenser-objective lens with a spherical aberration coefficient of 1.0 mm.


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