An efficient purification method for detonation nanodiamonds

This article reports the purification process of detonation soot to obtain pure nanodiamond powder. Nanodiamonds are synthesized by detonation using a high explosive mixture composed of trinitrotoluene and hexogen. The detonation of the charge leads to a powder containing nanodiamonds as well as metallic impurities and sp² carbon species. Further, to remove metallic particles, an unusual acidic treatment (hydrofluoric/nitric acids; i.e. fluorinated aqua regia) was set up. To eliminate sp² carbon species such as graphite and amorphous carbon, a thermal oxidation treatment was performed at 420 °C under air in a furnace during several hours. Transmission Electronic Microscopy, Raman spectroscopy, X-ray diffraction and Thermo-Gravimetric Analysis showed that this purification process is very efficient. From TGA measurements, a model of the carbon grain combustion was developed by considering graphitic shells surrounding the nanodiamond particles, and was used to demonstrate that the selective oxidation of graphite was experimentally realistic. Moreover, another model was set up from specific area measurements to evaluate the thickness of the functional groups surrounding the nanodiamonds after the oxidation of sp² carbonaceous species. The treatment described herein was achieved on several tens of grams of product and could be easily adapted to the industrial scale.     

MTCLAB: A MATLAB®-based program for traveltime quality analysis and pre-inversion velocity tuning in 2D transmission tomography

A MATLAB^®-based computer code that analyses the traveltime distribution and performs quality analysis at the pre-inversion stage for 2D transmission experiments is presented. The core tools of this approach are the so-called mean traveltime curves. For any general recording geometry, the user may select any pair of subsets of contiguous sources and receivers. The portion of the domain swept by the implied rays defines a zone of analysis, and for each source (receiver) the outcoming (incoming) ray fan is named a source (receiver) gather. The empirical mean traveltime curves are constructed, for each zone, by assigning the average and the standard deviation of the traveltimes in the gathers to the positions of the sources (receivers).The theoretical expressions assume isotropic homogeneous velocity inside each zone. The empirical counterparts use the observed traveltimes and make no assumptions. Isotropic velocity in each zone is inferred by least-squares fitting of the empirical mean traveltime curves. The user may refine the analysis considering different zones (multi-zone analysis). Initially the whole domain is modelled as a single zone. The procedure compares empirical versus theoretical curves. In addition, residuals can be plotted using source–receiver positions as plane coordinates. The results are used to unravel the possible presence of anomalous gathers, heterogeneities, anisotropies, etc. Depending on the kind of anomalies, velocity estimation and mean time residuals are different in the source and receiver gather curves.This software helps to grasp a better understanding of the data variability before the inversion and provides to the geophysicist an approximate zonal isotropic model and a range of velocity variation that can be used in the inverse problem as a priori information (regularization term). Its use is described through tutorial examples. A guided user interface leads the user through the algorithm steps.     

Balance-dendrogram. A new routine of CoDaPack

A statistical analysis of compositional data based on the Aitchison geometry of the simplex requires an appropriate basis for representing the data. A simple and intuitive way of building such a basis employs a sequential binary partition of the compositional vector. The partition, together with some statistical summaries of the coordinates, or balances, can be represented in a dendrogram-type graph. In this paper we introduce an implementation of this methodology inside CoDaPack, which is freeware. An example with real data illustrates the use of the Balance-Dendrogram routine.     

Mapping field density distribution in radiators by microwave noise

In his earlier paper on Active Microwave Radiometry, the author indicated that microwave noise can be used to map field density distribution inside radiators and in antenna systems, without the need for anechoic chambers. The presented paper gives details and results of such experiment. The method is described, details of equipment are given and results are presented with a concluding commentary.     

Embryonal metabolism

It is very difficult to have a clear and homogeneous idea of the embryo metabolism. In fact it may vary from one species to another and also according to the embryonic stage: i.e. before and after genomic activation. Basic compounds such as glucose may be toxic, but obviously, it is more the problem of the quantity introduced in the culture media and an unsuitable balance between the metabolites which may impair the embryonic development. At low concentration glucose is actively metabolised by embryos. High levels of amino acids are deleterious (due to release of ammonia), but they are necessary at low concentrations. Addition of serum or other biological fluids is generally useless. Further knowledge on embryo metabolism is necessary to avoid culture medium related delay or developmental blocks. Sequential media are at least partly the answer.     

Stoffwechselwirkungen von ω-3-Fettsäuren

Metabolic Effects of ω-3 Fatty Acids Biological effects of ω-3 fatty acids are related to their properties as structural components of cell membranes, their role as precursors of eicosanoids and their effects on lipoprotein metabolism. This is the basis for a great variety of metabolic effects, many of which of increasing medical interest. Particularly in the cardiovascular field, ω-3 fatty acids have been shown to have a wide spectrum of potentially antiatherogenic effects. Among these are the inhibition of platelet aggregation, reduction of blood viscosity, lowering of blood pressure and suppression of inflammatory reactions in the arteriosclerotic plaque. The principal actions in lipid metabolism are a reduction in triglycerides and a small increase in HDL₂. The effect on LDL-cholesterol is complex and an adverse LDL-increase may occur in particular hyperlipoproteinemias.     

Effects of Ajoene on lymphocyte and macrophage membrane-dependent functions

An increasing flow of evidences collected on elementary forms of learning processes in selected animal models evidentiates some mechanisms which can represent the basic cellular principles underlying plastic changes: 1. 5HT and second messengers of nucleotide type (like cAMP) have a pivotal role in the learning process. 2. In almost all short-term learning processes the modifications are subserved by a mechanism of protein phosphorylation. 3. In various animal models the modulation of K+ and Ca2+ channels is the molecular mechanism for learning. Experiments performed in sensory T neuron of the leech indicate that the modulation of Na+/K+ electrogenic pump is one of the fundamental mechanism for learning. 4. In long-term plastic changes, the most important finding is that newly synthesized proteins are formed. 5. In addition to what has been observed in the Aplysia model, where changes in synaptic efficacy represent the basic principles of memory storage, in the leech it has been demonstrated that a molecular machinery present in a single neuron can adapt the activity of the cell to environmental stimuli.     

Tests of electric and electromagnetic methods in the travale geothermal field

Within the framework of an EEC project involving ten European laboratories, research on the application of several electric and electromagnetic methods to a geothermal field (Travale, Tuscany), has been undertaken by the B.R.G.M. The objective was to refine the conceptual model of the Travale field and, therefore, to describe the morphology of the basement (down to 2 km depth) and of the Rhaetian reservoir covered by impermeable series.The method best suited to this type of prospection appeared to be electrical dipole — dipole profiling, combined with a 2-D interpretation. Contrasts at more than 2 km depth (500 m long dipoles) could be seen and compared to the depths measured in the boreholes. The EM Melos method (Syscal equipment) should be improved (lower frequencies) to increase the depth penetration. It is, however, a good complementary method for the surface layers. An attempt at a computational interpretation of the self potential profiles gave promising results. To make full advantage of the bipole — dipole measurements efforts should be devoted to their computational interpretation.