Top-down design of magnonic crystals from bottom-up magnetic nanoparticles through protein arrays.

We show that chemical fixation enables top-down micro-machining of large periodic 3D arrays of protein-encapsulated magnetic nanoparticles (NPs) without loss of order. We machined 3D micro-cubes containing a superlattice of NPs by means of focused ion beam etching, integrated an individual micro-cube to a thin-film coplanar waveguide and measured the resonant microwave response. Our work represents a major step towards well-defined magnonic metamaterials created from the self-assembly of magnetic nanoparticles.

Pt, Co-Pt and Fe-Pt alloy nanoclusters encapsulated in virus capsids.

Nanostructured Pt-based alloys show great promise, not only for catalysis but also in medical and magnetic applications. To extend the properties of this class of materials, we have developed a means of synthesizing Pt and Pt-based alloy nanoclusters in the capsid of a virus. Pure Pt and Pt-alloy nanoclusters are formed through the chemical reduction of [PtCl4](-) by NaBH4 with/without additional metal ions (Co or Fe). The opening and closing of the ion channels in the virus capsid were controlled by changing the pH and ionic strength of the solution. The size of the nanoclusters is limited to 18 nm by the internal diameter of the capsid. Their magnetic properties suggest potential applications in hyperthermia for the Co-Pt and Fe-Pt magnetic alloy nanoclusters. This study introduces a new way to fabricate size-restricted nanoclusters using virus capsid.

Effective energy barrier distributions for random and aligned magnetic nanoparticles.

Isothermal magnetic relaxation measurements are widely used to probe energy barriers in systems of magnetic nanoparticles. Here we show that the result of such an experiment can differ greatly for aligned and randomly oriented nanoparticles. For randomly oriented cobalt-doped magnetite nanoparticles we observe a prominent low-energy tail in the energy barrier distribution that is greatly attenuated when the particles are magnetically aligned. Monte Carlo simulations show that this behaviour arises for nanoparticles with both cubic and uniaxial magnetic anisotropy energy terms even though for cubic or uniaxial anisotropy alone the energy barrier distribution is independent of nanoparticle orientation.

Protein brownian rotation at the glass transition temperature of a freeze-concentrated buffer probed by superparamagnetic nanoparticles.

For applications from food science to the freeze-thawing of proteins it is important to understand the often complex freezing behavior of solutions of biomolecules. Here we use a magnetic method to monitor the Brownian rotation of a quasi-spherical cage-shaped protein, apoferritin, approaching the glass transition Tg in a freeze-concentrated buffer (Tris-HCl). The protein incorporates a synthetic magnetic nanoparticle (Co-doped Fe3O4 (magnetite)). We use the magnetic signal from the nanoparticles to monitor the protein orientation. As T decreases toward Tg of the buffer solution the protein's rotational relaxation time increases exponentially, taking values in the range from a few seconds up to thousands of seconds, i.e., orders of magnitude greater than usually accessed, e.g., by NMR. The longest relaxation times measured correspond to estimated viscosities >2 MPa s. As well as being a means to study low-temperature, high-viscosity environments, our method provides evidence that, for the cooling protocol used, the following applies: 1), the concentration of the freeze-concentrated buffer at Tg is independent of its initial concentration; 2), little protein adsorption takes place at the interface between ice and buffer; and 3), the protein is free to rotate even at temperatures as low as 207 K.

Fibrose pulmonar na esclerose sistêmica progressiva: frequência e associações clínicas / Pulmonary fibrosis in progressive systemic sclerosis: frequency and clinical associations

A esclerose sistêmica progressiva (ESP) é uma doença crônica caracterizada por vasculopatia disseminada e fibrose tecidual. O envolvimento intersticial pulmonar constitui uma de suas principais causas de morbimortalidade. Foram estudados 22 pacientes (20 mulheres, 2 homens) com ESP (14 com forma limitada, 8 com forma difusa) quanto à presença de fibrose pulmonar através de tomografia computadorizada (TC). Em 13 pacientes (59 por cento), fibrose pulmonar foi documentada tomograficamente. O RX de tórax foi normal em 6 destes 13 pacientes; nos outros 7 casos, as alterações tomográficas foram mais precoces e definidas do que as encontradas no RX de tórax. Em dois terços dos pacientes com fibrose pulmonar o espirograma simples foi alterado. A presença de estertores crepitantes bibasais constitui-se na anormalidade respiratória mais frequente nos pacientes com fibrose pulmonar. Variáveis como sexo, raça, presença de fatores antinucleares (FAN), padrões de FAN, tosse e dispnéia não foram estatisticamente distintos nos pacientes com ou sem fibrose pulmonar. A frequência de fibrose pulmonar nessa casuística de ESP foi intermediária, considerando-se os contrastantes dados de literatura. A TC foi claramente mais sensível do que o RX de tórax no diagnóstico de alterações fibróticas