A new method for correlation analysis of compositional (environmental) data - a worked example.

Most data in environmental sciences and geochemistry are compositional. Already the unit used to report the data (e.g., µg/l, mg/kg, wt%) implies that the analytical results for each element are not free to vary independently of the other measured variables. This is often neglected in statistical analysis, where a simple log-transformation of the single variables is insufficient to put the data into an acceptable geometry. This is also important for bivariate data analysis and for correlation analysis, for which the data need to be appropriately log-ratio transformed. A new approach based on the isometric log-ratio (ilr) transformation, leading to so-called symmetric coordinates, is presented here. Summarizing the correlations in a heat-map gives a powerful tool for bivariate data analysis. Here an application of the new method using a data set from a regional geochemical mapping project based on soil O and C horizon samples is demonstrated. Differences to 'classical' correlation analysis based on log-transformed data are highlighted. The fact that some expected strong positive correlations appear and remain unchanged even following a log-ratio transformation has probably led to the misconception that the special nature of compositional data can be ignored when working with trace elements. The example dataset is employed to demonstrate that using 'classical' correlation analysis and plotting XY diagrams, scatterplots, based on the original or simply log-transformed data can easily lead to severe misinterpretations of the relationships between elements.

Nuclear Medicine Imaging of Prostate Cancer.

The new tracer Gallium-68 prostate-specific membrane antigen (Ga-68 PSMA) yields new promising options for the PET/CT diagnosis of prostate cancer (PCa) and its metastases. To overcome limitations of hybrid imaging, known from the use of choline derivatives, seems to be possible with the use of Ga-68 PSMA for PCa. The benefits of hybrid imaging with Ga-68 PSMA for PCa compared to choline derivatives shall be discussed in this article based on an overview of the current literature. Key Points: • Ga-68 PSMA PET/CT can achieve higher detection rates of PCa lesions than PET/CT performed with choline derivatives• The new tracer Ga-68 PSMA has the advantage of high specificity, independence of PSA-level and low nonspecific tracer uptake in surrounding tissue• The new tracer Ga-68 PSMA seems very suitable for MR-PET diagnostic Citation Format: • Schreiter V, Reimann C, Geisel D et al. Nuclear Medicine Imaging of Prostate Cancer. Fortschr Röntgenstr 2016; 188: 1037 - 1044.

A strong enrichment of potentially toxic elements (PTEs) in Nord-Trøndelag (central Norway) forest soil.

Analysis of soil C and O horizon samples in a recent regional geochemical survey of Nord-Trøndelag, central Norway (752 sample sites covering 25,000 km2), identified a strong enrichment of several potentially toxic elements (PTEs) in the O horizon. Of 53 elements analysed in both materials, Cd concentrations are, on average, 17 times higher in the O horizon than in the C horizon and other PTEs such as Ag (11-fold), Hg (10-fold), Sb (8-fold), Pb (4-fold) and Sn (2-fold) are all strongly enriched relative to the C horizon. Geochemical maps of the survey area do not reflect an impact from local or distant anthropogenic contamination sources in the data for O horizon soil samples. The higher concentrations of PTEs in the O horizon are the result of the interaction of the underlying geology, the vegetation zone and type, and climatic effects. Based on the general accordance with existing data from earlier surveys in other parts of northern Europe, the presence of a location-independent, superordinate natural trend towards enrichment of these elements in the O horizon relative to the C horizon soil is indicated. The results imply that the O and C horizons of soils are different geochemical entities and that their respective compositions are controlled by different processes. Local mineral soil analyses (or published data for the chemical composition of the average continental crust) cannot be used to provide a geochemical background for surface soil. At the regional scale used here surface soil chemistry is still dominated by natural sources and processes.

Biogeochemical plant-soil interaction: variable element composition in leaves of four plant species collected along a south-north transect at the southern tip of Norway.

Leaves from four different plant species (birch, willow, juniper, and heather) together with samples of the soil O and C horizons were collected at 44-46 sites along a south-to-north transect extending inland for 200 km from the southern tip of Norway. The transect covers one of the steepest vegetation gradients on Earth, crossing six vegetation zones. Juniper and heather are evergreen, and preferably exclude potentially toxic elements to avoid their accumulation in assimilating tissues, birch and willow shed their leaves in autumn together with the load of potentially toxic elements, and thus can tolerate the uptake of such elements. The plant leaves show the highest concentrations for B, Ca, K, Mg, Mn, P, Rb and S. In the soil O-horizon Ag, Au, As, Bi, Cu, Ge, Hg, In, Pb, Sb, Se, Sn, Te and W are enriched with respect to the C-horizon, whilst Mn and Rb are depleted. Cadmium, Sr and Zn are enriched in willow and Cs, Na and Tl in heather. In terms of concentration gradients from the coast inland, two different patterns are detected: 1) short range with an almost exponential decrease of concentrations from the coast, which appears to be typical for seaspray-related element input, and 2) long range with an almost linear decrease of concentrations with distance from the coast. These patterns differ among the four species, even for one and the same element. Inter-element correlation is different from material to material. Along the transect each of the different plants at the same site individually adapts to the available element combination. High linear correlations in the plants occur between the lanthanides (La, Ce, Y), and interestingly, between P and Ti. The plant/soil system appears highly non-linear and self-regulated.

Anosovite-type V3O5: a new binary oxide of vanadium.

The reaction of either V(2)F(6)·4H(2)O or a mixture of 60 wt % VF(2)·4H(2)O and 40 wt % VF(3)·3H(2)O with a water-saturated gaseous mixture of 15-20 vol % hydrogen in argon leads to the formation of a new polymorph of V(3)O(5) crystallizing in the orthorhombic anosovite-type structure. Quantum-chemical calculations show that the anosovite-type structure is about 15 kJ/mol less stable than the corresponding monoclinic Magnéli phase. In addition, there are no imaginary modes in the phonon density of states, supporting the classification of the anosovite-type phase as a metastable V(3)O(5) polymorph. Susceptibility measurements down to 3 K reveal no hint for magnetic ordering.

Electronic structure and thermodynamics of V2O3 polymorphs.

A metastable bixbyite-type polymorph of vanadium sesquioxide, V(2)O(3), has recently been synthesized, and it transforms to the corundum-type phase at temperatures around 550 °C. The possibility of a paramagnetic to canted antiferromagnetic or even spin-glass-like transition has been discussed. Quantum-chemical calculations on the density-functional theory level including explicit electronic correlation confirm the metastability as well as the semiconducting behavior of the material and predict that the bixbyite-type structure is about 0.1 eV less stable than the well-known corundum-type phase. Nonetheless, quasiharmonic phonon calculations manifest that bixbyite-type vanadium sesquioxide is a dynamically stable compound. Other possible V(2)O(3) polymorphs are shown to be even less suitable candidates for the composition V(2)O(3).

Bixbyite-type V2O3--a metastable polymorph of vanadium sesquioxide.

A metastable polymorph of vanadium sesquioxide was prepared by the reaction of vanadium trifluoride with a water-saturated gaseous mixture of 10 vol % hydrogen in argon. The new polymorph crystallizes in the bixbyite-type structure. At temperatures around 823 K a transformation to the well-known corundum-type phase is observed. Quantum-chemical calculations show that the bixbyite-type structure is about 9 kJ/mol less stable than the known corundum-based one. This result, in combination with the absence of imaginary modes in the phonon density of states, supports the classification of the bixbyite-type phase as a metastable V(2)O(3) polymorph. At ~50 K a paramagnetic to canted antiferromagnetic transition is detected.

Sulphur in the Arctic environment (3): environmental impact.

Long term, high level airborne emissions of pollutants from nickel industries on the Kola Peninsula (NW Russia) have resulted in widespread ecosystem injury up to almost complete vegetation eradication within nearest surroundings of the smelters. Although SO2 is the prevailing component of the emissions, it is only part of a much more complex chemical emission spectrum in the region. In addition to acidic gases, industry also emits potentially toxic elements (e.g. metals) which being less volatile than SO2, are deposited within the immediate region in significant concentrations. Additionally, it appears that sources of base cations (co-emission by smelters, sea aerosols, other industries) are adequate to prevent environmental acidification on the regional scale. Acidification of soils and waters appeared only as single cases in the immediate vicinity of the smelters and is not believed to be a major mechanism of environmental deterioration. Proposed critical concentrations (5 microg/m(3)) of SO2 for the northern ecosystems are exceeded over a large area and direct exposure to SO2 is believed to be the possible mechanism of vegetation damage.

[The future of teleradiology: results of Teleradiology Expert Meeting of the Health Network Congress 2001]. / Die Zukunft der Teleradiologie: Ergebnisse des Expertentreffens Teleradiologie des Gesundheitsnetzkongresses 2001.

Legal prerequisites have substantial influence on the development of teleradiology. At an expert meeting (Mannheim, 8.6.2001) a proposal for a teleradiology article in the new German x-ray ordinance has been set up. An exception of the demand for a doctor trained in radiation protection at the point of examination shall be established for emergency cases. To realize the intended improvement of patient care measurements for quality assurance concerning the medical personnel and processes are necessary. Along with other current developments the basis of secure regional teleradiology networks is now built up.

Sulphur in the arctic environment (2): results of multi-medium regional mapping.

The regional distribution patterns of S in terrestrial moss and in the O-, B-, and C-horizon of podzols have been studied in a 188,000 km2 area in Arctic Europe with both, large natural (marine aerosols) and anthropogenic gradients of S-input. Although the existence of a pollution source is visible in the S-maps for moss, the S-deposition gradient is not depicted. The concentration of S in moss is not at all influenced by input of marine aerosols. In contrast, the O-horizon of podzols shows a coastal enrichment of S but does not reflect the anthropogenic input. Even the coastal pattern visible in the map of S in the O-horizon is, however, not linked to the input of SO4(2-) via sea spray but is rather caused by low litter decomposition rates due to low temperature, increasing total S and decreasing mobile S near coast. S-concentrations as observed in the deeper soil horizons are only locally influenced by both anthropogenic and marine input of S. These results suggest that in undisturbed terrestrial environments no mechanism exists for enriching an additional input of S from anthropogenic or natural sources. A very high local variability in the four sample materials points to small-scale local processes being most important for the observed S-concentrations.

Influence of extreme pollution on the inorganic chemical composition of some plants.

Leaves of nine different plant species (terrestrial moss: Hylocomium splendens and Pleurozium schreberi, blueberry: Vaccinium myrtillus, cowberry: Vaccinium vitis-idaea, crowberry: Empetrum nigrum, birch: Betula pubescens, willow: Salix spp., pine: Pinus sylvestris, and spruce: Picea abies) have been collected from up to nine catchments (size 14-50 km2) spread over a 1,500,000 km2 area in northern Europe. Additional soil samples were taken from the O-horizon and the C-horizon at each plant sample site. All samples were analysed for 38 elements (Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Sb, Sc, Se, Si, Sn, Sr, Th, Tl, U, V, Y, Zn, and Zr) by ICP-MS, ICP-AES or CV-AAS (Hg) techniques. One of the 9 catchments was located directly adjacent (5-10 km S) to the nickel smelter and refinery at Monchegorsk, Kola Peninsula, Russia. The high levels of pollution at this site are reflected in the chemical composition of all plant leaves. However, it appears that each plant enriches (or excludes) different elements. Elements emitted at trace levels, such as Ag, As and Bi, are relatively much more enriched in most plants than the major pollutants Ni, Cu and Co. The very high levels of SO2 emissions are generally not reflected by increases in plant total S-content. Several important macro-(P) and micro-nutrients (Mn, Mg, and Zn) are depleted in most plant leaves collected near Monchegorsk.

Comparison of the element composition in several plant species and their substrate from a 1500000-km2 area in Northern Europe.

Leaves of 9 different plant species (terrestrial moss represented by: Hylocomium splendens and Pleurozium schreberi; and 7 species of vascular plants: blueberry, Vaccinium myrtillus; cowberry, Vaccinium titis-idaea; crowberry, Empetrum nigrum; birch, Betula pubescens; willow, Salix spp.; pine, Pinus sylvestris and spruce, Picea abies) have been collected from up to 9 catchments (size 14-50 km2) spread over a 1500000 km2 area in Northern Europe. Soil samples were taken of the O-horizon and of the C-horizon at each plant sample site. All samples were analysed for 38 elements (Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Sb, Sc, Se, Si, Sn, Sr, Th, Tl, U, V, Y, Zn and Zr) by ICP-MS, ICP-AES or CV-AAS (for Hg-analysis) techniques. The concentrations of some elements vary significantly between different plants (e.g. Cd, V, Co, Pb, Ba and Y). Other elements show surprisingly similar levels in all plants (e.g. Rb, S, Cu, K, Ca, P and Mg). Each group of plants (moss, shrubs, deciduous and conifers) shows a common behaviour for some elements. Each plant accumulates or excludes some selected elements. Compared to the C-horizon, a number of elements (S, K, B, Ca, P and Mn) are clearly enriched in plants. Elements showing very low plant/C-horizon ratios (e.g. Zr, Th, U, Y, Fe, Li and Al) can be used as an indicator of minerogenic dust. The plant/O-horizon and O-horizon/C-horizon ratios show that some elements are accumulated in the O-horizon (e.g. Pb, Bi, As, Ag, Sb). Airborne organic material attached to the leaves can thus, result in high values of these elements without any pollution source.

Sulphur in the Arctic environment (1): results of a catchment-based multi-medium study.

S-concentrations were determined in 9 different sample materials (precipitation (rain and snow), vegetation, O-, E-, B- and C- horizon pf podzols, streams water and ground water) collected in eight small catchments (10-30 km2) at different distances from major SO2 point-source emitters on the Kola Peninsula, Russia. Comparison of the results from these materials, representing different compartments of the ecosystems under varying natural conditions leads to a better understanding of sources, cycling and fate of S in the Arctic environment. More than 300,000 t of SO2 emitted annually from the Kola smelters affect the air quality over a large area. Arctic climatic conditions (cold and dry) and the remote location of the emitters results in considerably lower S-deposition values than those observed in central Europe. The pathways of atmospheric S-deposition in the terrestrial environment vary significantly from summer to winter because different compartments of the ecosystems, with a different capability to accumulate S, are active. The actual S-flux is altered by every component of the ecosystem. When estimating the total S-deposition this effect must be considered.

Critical remarks on the use of terrestrial moss (Hylocomium splendens and Pleurozium schreberi) for monitoring of airborne pollution.

Duplicate samples of the two terrestrial moss species Hylocomium splendens and Pleurozium schreberi, which are widely used to monitor airborne heavy metal pollution, have been collected from eight catchments spread over a 1,500,000 km2 area in northern Europe. These were analysed for a total of 38 elements by inductively coupled plasma-mass spectrometry, inductively coupled plasma-atomic emission spectrometry and cold vapour-atomic absorption spectometry techniques. Results show that the moss species can be combined without interspecies calibration for regional mapping purposes. For the majority of elements the observed within-catchment variation is large--big composite samples over a large area should thus be collected when moss is to be used for monitoring purposes. For the majority of elements the input of dust governs moss chemistry. For a reliable 'contamination' signal over a sizeable area a major source is needed. Some elements show a dependence on climate/vegetation zone. In coastal areas the input of marine aerosols will alter the chemical signal obtained from moss samples.

Hydrochemical distribution patterns in stream waters, Trøndelag, central Norway.

A regional geochemical sampling program of stream waters has been carried out in the Nord-Trøndelag region of central Norway. This area has hitherto been little affected by regional anthropogenic sources of pollution. Hydrochemical trends appear to be dominated by interplay of two main factors: (i) input of sea salts via marine aerosols in precipitation: and (ii) geological sources (mineral weathering). Factor (i) results in a predominance of Na-Cl waters near the coast, and may also be partially responsible (via proton displacement from soil ion-exchange sites by marine cations) for lower pH values in near-coastal waters. Further inland, the importance of marine salts decreases and waters become dominantly Ca-(Na)-HCO3. Sub-regional anomalies in geochemical maps for, e.g. nitrate and copper may indicate anthropogenic sources for these parameters from agriculture or mining activities.

Proteins in vacuo: denaturing and folding mechanisms studied with computer-simulated molecular dynamics.

Mounting evidence from experiments suggests that the native fold in solution is metastable in dehydrated proteins. Results from a number of experiments that use mass spectrometry indicate also that folding-unfolding transitions take place in protein ions even in the absence of water. These observations on anhydrous proteins call for a re-evaluation of our understanding of the folding transition. In this context, computer-assisted simulations are an important complementary tool. Here, we provide an overview of recent progress on the simulation of proteins in vacuo. In particular, we discuss the response of proteins and protein ions to perturbations that trigger unfolding and re-folding transitions. By comparing the general patterns emerging from theory and experiment, we propose a series of new measurements that could help to validate, and improve, current simulation models.

Baltic soil survey: total concentrations of major and selected trace elements in arable soils from 10 countries around the Baltic Sea.

Agricultural soils were collected from 10 European countries over a 1,800,000 km2 area surrounding the Baltic Sea. The sampling density was 1 site/2500 km2. Two samples were taken at each site: topsoil 0-25 cm (ploughing layer, Ap-horizon) and subsoil (bottom samples, usually B- or C-horizon) at an approximate depth of 50-75 cm, well below the ploughed layer. The samples were analysed for total element concentrations of 41 elements by WD-XRF. Analytical results for both layers are quite comparable. Large differences between element concentrations and variations can be observed for most elements when the different countries are compared. The Nordic countries show considerably higher concentrations and variations for quite a number of elements [Al, Fe, (Mg, P), Ti, Ba, Sc, Sr, V] in their agricultural soils. This is an expression of geology, the relatively younger age of the soils here and of the climatic conditions (reduced weathering rates). Regional geochemical maps demonstrate that geology overwhelmingly dominates the total concentration of chemical elements as observed in the agricultural soils. The three (four) large tectonic units (Caledonian mountain chain, Fennoscandian Shield and the northern and southern eastern European Platform) composing this area are all reflected in the regional maps.