A review of carbonatitic magmatism in the Paraná-Angola-Namibia (PAN) system.

Mesozoic to Cenozoic alkaline-carbonatitic complexes from southern Brazil, Angola and Namibia occur along main tectonic lineaments. In general, the alkaline-carbonatite complexes show intrusive/subintrusive, subcircular or oval shaped structures and are indicative of high upwelling energy. Processes of liquid immiscibility from trachytic-phonolitic liquids, starting from parental alkaline mafic magmas are believed to have generated carbonatitic liquids, as suggested by field relationships and geochemical characteristics. Ca-, Mg- and Fe-carbonatites are widespread even in the same complex. The occurrences comprise three main chronogroups, i.e. 1) Early Cretaceous (Eastern Paraguay; Brazil, Ponta Grossa Arch and Anitapolis; Angola and Namibia); 2) Late Cretaceous (Brazil , Ponta Grossa Arch, Lages and Alto Paranaiba. Namibia); 3) Paleogene, Brazil and Namibia Two principal types of associated alkaline rocks are represented, i.e. plagioleucitites l.s. (Eastern Paraguay; Brazil: Ponta Grossa Arch- Angola and Namibia) and kamafugites l.s. (Brazil: alto Paranaiba and Lages; Namibia). Significant variations in O-C isotope compositions are found in primary carbonates , the variations being mainly due to isotope exchange between carbonates and H2O-CO2-rich hydrothermal fluids, whereas magmatic processes, i.e. fractional crystallization or liquid immiscibility, probably affect the delta O-18 and delta C-13 values by not more than 2 delta%.. The isotope exchange model implies that the most significant isotopic variations took place in a hydrothermal environment, e.g. in the range 400-80 degrees C, involving fluids with CO2/H2O ratio ranging from 0.8 to 1. Sr-Nd-Pb isotope systematics highlight heterogeneous mixtures between HIMU and EMI mantle components, similar to the associated alkaline rocks and the flood tholeiites of the Parana-Angola-Etendeka (Namibia) system. This is also consistent with Re-Os systematics on selected mafic samples from the Alto Paranaiba alkaline-carbonatite province. The data relative to the noble gases suggest that the source(s) are similar to other mantle derived magmas (e.g. HIMU and MORB) and that the carbon of carbonatites is unlikely to be subduction-related carbon, and support a C-O fractionation model starting from mantle-derived sources. In spite of the strong variation shown by C-O isotopes, Sr-Nd-Pb-Os isotopic systematics could be related to an isotopically enriched source where the chemical heterogeneities reflect a depleted mantle "metasomatized" by small-volume melts and fluids rich in incompatible elements. These fluids are expected to have promoted crystallization in the mantle of K-rich phases that gave rise to a veined network variously enriched in LILE and LREE (cf. Foley, 1992b). The newly formed veins (enriched component) and peridotite matrix (depleted component) underwent a different isotopic evolution with time as reflected by the carbonatitic rocks. These conclusions may be extended to the whole Parana-Angola-Etendeka system, where isotopically distinct parent magmas were generated following two main enrichment events of the subcontinental lithospheric mantle at 2.0-1.4 and 1.0-0.5 Ga, respectively, as also supported by Re-Os systematics. The mantle sources preserved the isotopic heterogeneities over a long time, suggesting a non-convective lithospheric mantle beneath different cratons or intercratonic regions. Overall the data indicate that the alkaline-carbonatitic magmatism originated from a significant, but small scale heterogeneous subcontinental mantle. In this scenario, the Tristan da Cunha, Walvis Ridge-Rio Grande Rise and Vitoria-Trindade hotspot tracks might reflect the accomodation of stresses in the lithosphere during rifting, rather than continuous magmatic activity induced by mantle plumes beneath the moving lithosphere

Carbonatites from the southern brazilian platform. A review. II. Isotopic evidences

Early and Late Cretaceous alkaline and alkaline– carbonatitic complexes from southern Brazil are located along the main tectonic lineaments of the South America Platform. Calcium-, magnesium-, and ferrocarbonatites are well represented and frequently associated even in the same complex. Primary carbonates present significant variations in C–O isotopic compositions, which are mainly due to isotope exchange with H2O–CO2-rich hydrothermal fluids, whereas fractional crystallization or liquid immiscibility probably affects the δ18O and δ13C values by no more than 2δ‰. Our isotope exchange model implies that the most significant isotopic variations took place in a hydrothermal environment, e.g., in the range 400–80°C, involving fluids with the CO2/H2O ratio ranging from 0.8 to 1. Sr–Nd–Pb isotope systematics highlight heterogeneous mixtures between HIMU and EMI mantle components, similar to the associated alkaline rocks and the flood tholeiites from southern Brazil. In spite of the strong variation shown by C–O isotopes, Sr-Nd–Pb–Os isotopic systematics could be related to an isotopically enriched source where the chemical heterogeneities reflect a depleted mantle “metasomatized” by small-volume melts and fluids rich in incompatible elements. These fluids are expected to have promoted crystallization of K-rich phases in the mantle, which produced a veined network variously enriched in LILE and LREE. The newly formed veins (enriched component) and peridotite matrix (depleted component) underwent a different isotopic evolution with time as reflected by the carbonatites. These conclusions may be extended to the whole Paraná–Etendeka system, where isotopically distinct parent magmas were generated following two main enrichment events of the subcontinental lithospheric mantle at 2.0–1.4 and 1.0–0.5 Ga, respectively, as also supported by Re–Os systematics. The mantle sources preserved the isotopic heterogeneities over a long time, suggesting a non convective lithospheric mantle beneath different cratons or intercratonic regions. Overall, the data indicate that the alkaline–carbonatitic magmatism originated from a locally heterogeneous subcontinental mantle

Carbonatites from the Southern Brazilian platform: I

We present a comprehensive overview of the geochemical characteristics and evolution of the carbo- natites from the southern Brazilian Platform (Paraná Basin). The carbonatites from dierent complexes dis- play large compositional variability in terms of abun- dances of incompatible and rare earth elements. This is in agreement with an origin from heterogeneous litho- spheric sources, as conrmed by isotopic data (see Speziale et al., this issue). The characteristic major and trace element abundances of these carbonatites present compelling evidence for invoking liquid unmixing as the main mechanism of their formation and evolution albeit few exceptions. We propose an evolutionary trend for the Brazilian carbonatites, which can be summarized as following: exsolution of the primary Ca- or Mg-carbona- titic liquids systematically takes place at the phonolite- peralkaline phonolite stage of magma dierentiation; this is followed by progressive Fe-enrichment and by nal emplacement of uorocarbonatites associated with hydrothermal uids

Experimental realization of a single-layer multiferroic

Multiferroic materials have garnered wide interest for their exceptional static and dynamical magnetoelectric properties. Intrinsic type-II multiferroics exhibit an inversion-symmetry-breaking magnetic order which directly induces a ferroelectric lattice distortion through mechanisms such as the inverse Dzyaloshinskii-Moriya interaction. This direct coupling between the magnetic and structural order parameters results in record-strength magnetoelectric effects. Two-dimensional materials possessing such intrinsic multiferroic properties have been long sought for harnessing magnetoelectric coupling in nanoelectronic devices. Here, we report the discovery of type-II multiferroic order in a single atomic layer of transition metal-based van der Waals material NiI2. Using a combination of optical birefringence, second harmonic generation, and Raman spectroscopy in bulk NiI2, we first identified multiple independent and robust signatures of the multiferroic state. Subsequently, we studied the evolution of the optical signatures as a function of temperature and layer number, to find that the multiferroic state is robust down to monolayer NiI2. These observations establish NiI2 as a new platform for studying emergent multiferroic phenomena, chiral magnetic textures and ferroelectricity in the two-dimensional limit

Quantitative risk assessment of human salmonellosis and listeriosis related to the consumption of raw milk in Italy.

Two quantitative risk assessment (RA) models were developed to describe the risk of salmonellosis and listeriosis linked to consumption of raw milk sold in vending machines in Italy. Exposure assessment considered the official microbiological records monitoring raw milk samples from vending machines performed by the regional veterinary authorities from 2008 to 2011, microbial growth during storage, destruction experiments, consumption frequency of raw milk, serving size, and consumption preference. Two separate RA models were developed: one for the consumption of boiled milk and the other for the consumption of raw milk. The RA models predicted no human listeriosis cases per year either in the best or worst storage conditions and with or without boiling raw milk, whereas the annual estimated cases of salmonellosis depend on the dose-response relationships used in the model, the milk storage conditions, and consumer behavior in relation to boiling raw milk or not. For example, the estimated salmonellosis cases ranged from no expected cases, assuming that the entire population boiled milk before consumption, to a maximum of 980,128 cases, assuming that the entire population drank raw milk without boiling, in the worst milk storage conditions, and with the lowest dose-response model. The findings of this study clearly show how consumer behavior could affect the probability and number of salmonellosis cases and in general, the risk of illness. Hence, the proposed RA models emphasize yet again that boiling milk before drinking is a simple yet effective tool to protect consumers against the risk of illness inherent in the consumption of raw milk. The models may also offer risk managers a useful tool to identify or implement appropriate measures to control the risk of acquiring foodborne pathogens. Quantification of the risks associated with raw milk consumption is necessary from a public health perspective

Four-Year Monitoring of Foodborne Pathogens in Raw Milk Sold by Vending Machines in Italy

Prevalence data were collected from official microbiological records monitoring four selected foodborne pathogens (Salmonella spp., Listeria monocytogenes, Escherichia coli O157:H7 and Campylobacter jejuni) in raw milk sold by self-service vending machines in seven Italian Regions (n. 60907 samples from 1239 vending machines) during the years 2008 to 2011. Data of samples analyzed both by culture-based and real-time PCR methods were collected in one Region. A total of 100 raw milk consumers in four regions were interviewed while purchasing raw milk from vending machines. One hundred and seventy eight samples out of 60907 were positive for one of the four foodborne pathogens investigated; overall, 18 samples were positive for Salmonella spp., 83 for L. monocytogenes, 24 for E. coli O157:H7 and 53 for C. jejuni in the seven Regions investigated. There were no significant differences in prevalence among Regions, but a significant increase in C. jejuni prevalence was observed over the years. A comparison of the two different analysis methods showed that real-time PCR is from 2.71 to 9.40 times more sensitive than culture-based method. Data on consumer habits showed that some behaviors may enhance the risk of infection due to raw milk consumption: 37% of consumers do not boil milk before consumption, 93% never use an insulated bag to transport raw milk home, and raw milk is consumed by children under five years of age. The study emphasizes that end-product controls alone are not sufficient to guarantee an adequate level of consumer protection. The beta distribution of positive samples in this study and the data on raw milk consumer habits are useful and appropriate for the development of a National Quantitative Risk Assessment of Salmonella spp., L. monocytogenes, E. coli O157 and C. jejuni related to raw milk consumption

Impact of emergency oral rabies vaccination of foxes in northeastern Italy, 28 December 2009-20 January 2010: preliminary evaluation.

Fox rabies re-emerged in northeastern Italy in 2008, in an area bordering Slovenia. In 2009, the infection spread westward to Veneto region and in 2010 to the provinces of Trento and Bolzano. Aerial emergency oral fox vaccination was implemented in the winter 2009-10. Since this vaccination was performed at altitudes below the freezing level, a statistical analysis was conducted to evaluate its impact. Of the foxes sampled following the vaccination campaign, 77% showed a rabies antibody titre of ≥0.5 IU/ml

Signatures of pressure-enhanced helimagnetic order in van der Waals multiferroic NiI2_2

The van der Waals (vdW) type-II multiferroic NiI$_2$ has emerged as a candidate for exploring non-collinear magnetism and magnetoelectric effects in the 2D limit. Frustrated intralayer exchange interactions on a triangular lattice result in a helimagnetic ground state, with spin-induced improper ferroelectricity stabilized by the interlayer interactions. Here we investigate the magnetic and structural phase transitions in bulk NiI$_2$, using high-pressure Raman spectroscopy, optical linear dichroism, and x-ray diffraction. We obtain evidence for a significant pressure enhancement of the antiferromagnetic and helimagnetic transition temperatures, at rates of $\sim15.3/14.4$ K/GPa, respectively. These enhancements are attributed to a cooperative effect of pressure-enhanced interlayer and third-nearest-neighbor intralayer exchange. These results reveal a general path for obtaining high-temperature type-II multiferroicity via high pressures in vdW materials

Diagnostic and Prognostic Value of Right Ventricular Fat Quantification from Computed Tomography in Arrhythmogenic Right Ventricular Cardiomyopathy

Background: In arrhythmogenic right ventricular cardiomyopathy (ARVC) non-invasive scar evaluation is not included among the diagnostic criteria or the predictors of ventricular arrhythmias (VA) and sudden death (SD). Computed tomography (CT) has excellent spatial resolution and allows a clear distinction between myocardium and fat; thus, it has great potential for the evaluation of myocardial scar in ARVC. Objective: The objective of this study is to evaluate the feasibility, and the diagnostic and prognostic value of semi-automated quantification of right ventricular (RV) fat replacement from CT images. Methods: An observational case-control study was carried out including 23 patients with a definite (19) or borderline (4) ARVC diagnosis and 23 age- and sex-matched controls without structural heart disease. All patients underwent contrast-enhanced cardiac CT. RV images were semi-automatically reconstructed with the ADAS-3D software (ADAS3D Medical, Barcelona, Spain). A fibrofatty scar was defined as values of Hounsfield Units (HU) <-10. Within the scar, a border zone (between -10 HU and -50 HU) and dense scar (<-50 HU) were distinguished. Results: All ARVC patients had an RV scar and all scar-related measurements were significantly higher in ARVC cases than in controls (p < 0.001). The total scar area and dense scar area showed no overlapping values between cases and controls, achieving perfect diagnostic performance (sensitivity and specificity of 100%). Among ARVC patients, 16 (70%) had experienced sustained VA or aborted SD. Among all clinical, ECG and imaging parameters, the dense scar area was the only one with a statistically significant association with VA and SD (p = 0.003). Conclusions: In ARVC, RV myocardial fat quantification from CT is feasible and may have considerable diagnostic and prognostic value