Biaxial nematic and biaxial smectic phases were found in a colloidal model system of goethite (alpha-FeOOH) particles with a simple boardlike shape and short-range repulsive interaction. The macroscopic domains were oriented by a magnetic field and their structure was revealed by small angle x-ray scattering. In accordance with theoretical predictions, biaxiality appears in a system with partic...

We present a short overview of the influence of inter-particle interactions on the properties of magnetic nanoparticles. Strong magnetic dipole interactions between ferromagnetic or ferrimagnetic particles, that would be superparamagnetic if isolated, can result in a collective state of nanoparticles. This collective state has many similarities to spin-glasses. In samples of aggregated magnetic...

Microbial dissimilatory iron reduction (DIR) is widespread in anaerobic sediments and is a key producer of aqueous Fe(II) in suboxic sediments that contain reactive ferric oxides. Previous studies have shown that DIR produces some of the largest natural fractionations of stable Fe isotopes, although the mechanism of this isotopic fractionation is not yet well understood. Here we compare Fe isot...

Adsorption and desorption studies on different types of adsorbents, including natural materials such as teak tree bark powder, rice husk, natural bentonite, different algae like Ecklonia maxima, Escherichia coli, Ascophyllum nodasum, Rhizopus nigricans, Cladophora fascicularis, goethite and soils of three nuclear power plant and artificial materials such as Fe oxide-coated sand, goethite pretre...

We report on the design, operation and data analysis methods employed on the Imaging Spectrometer Instrument as part of the Mars Analog Research and Technology Experiment (MARTE). The Imaging Spectrometer is a hyperspectral scanning pushbroom device sensitive to wavelengths from 400-1000nm. During the MARTE project, the spectrometer was deployed to the Rio Tínto region of Spain. We analyzed sub...

-Fe 57 Mfssbauer spectroscopy has been used to determine the nature of iron-containing minerals in Lower Greensand samples from an experimental lysimeter at Uffington, Oxfordshire, both before and after a three-year irrigation with a synthetic heavy metal leachate. Analysis of the spectra measured at 300 ~ 77 ~ and 4.2~ and at 4.2~ in an applied field of 45 kOe shows that iron is present in the...

In order to study the effect of mineral composition on physical properties lateritic clays, compositions four kinds clay from Guangxi province in China were quantitatively analyzed by means DTA, XRD, SEM, XRF and total chemical element analysis. On this basis, variation law macroscopic was perspective mineralogy. The results show that kaolinite goethite are main minerals clays China. these samp...

The most frequent crystallographic preferred orientations developed during the progressive phase transformation of magnetite-hematite-goethite are described and analyzed in two natural samples banded iron formations from Carajás Mineral Province. Microtextures martitized grains containing three phases microplaty matrix were a scanning electron microscope equipped with detector for backscatter d...