Chains of Cobalt Doped Magnetosomes Extracted from AMB-1 Magnetotactic Bacteria for Application in AMF hyperthermia

International audienceWe report themagnetic properties and heating efficiency of cobalt doped chains of magnetosomes extracted frommagnetotactic bacteria for applications in alternativemagnetic field cancer therapy. The changes of the magnetic properties of the chains of magnetosomes observed in the presence of cobalt are characterized by an enhancement of the magnetocrystalline anisotropy from Keff ∼ 12 KJ/m3 in the absence of cobalt up to Keff ∼ 104 KJ/m3 in the presence of cobalt. We show that these changes are only observed for the magnetosomes organized in chains. Furthermore, the SAR of the extracted chains of magnetosomes mixed in solution and exposed to an oscillating magnetic field of field amplitude 80 mT and frequency 183 kHz is shown to increase from∼400W/gFe for the undoped chains ofmagnetosomes up to ∼500 W/gFe for the cobalt doped chains of magnetosomes

Expansion of Nature Conservation Areas: Problems with Natura 2000 Implementation in Poland?

In spite of widespread support from most member countries’ societies for European Union policy, including support for the sustainable development idea, in many EU countries the levels of acceptance of new environmental protection programmes have been and, in particular in new member states, still are considerably low. The experience of the countries which were the first to implement union directives show that they cannot be effectively applied without widespread public participation. The goal of this study was, using the example of Poland, to assess public acceptance of the expansion of nature conservation in the context of sustainable development principles and to discover whether existing nature governance should be modified when establishing new protected areas. The increase in protected areas in Poland has become a hotbed of numerous conflicts. In spite of the generally favourable attitudes to nature which Polish people generally have, Natura 2000 is perceived as an unnecessary additional conservation tool. Both local authorities and communities residing in the Natura areas think that the programme is a hindrance, rather than a help in the economic development of municipalities or regions, as was initially supposed. This lack of acceptance results from many factors, mainly social, historic and economic. The implications of these findings for current approach to the nature governance in Poland are discussed

A study of self-assembled InSb quantum dots grown on GaSb

In this thesis, we study the system of self-assembled InSb quantum dots grown on GaSb by metalorganic vapor phase epitaxy. The luminescence of the samples is first studied as a function of different growth parameters. In the series of high growth rate samples, a 'low energy peak' is observed at 0.72-0.74 eV for longer deposition times than 2 seconds and for growth temperatures of 460-500 degC. This peak is attributed to dots that are strongly confined in the growth direction. As the growth rate is halved, a new 'high energy peak' appears in the PL spectra at 0.755-0.79 eV that we assign to another family of big alloyed quantum dots. The luminescence of the high growth rate samples is then studied as a function of excitation power, temperature and magnetic field. When the excitation power is increased the quantum dot transition increases in energy by approx 7-11 meV and further transitions are observed from the wetting layer, bulk acceptor, bound (BE3) and free excitons. Magneto-PL is used to calculate the in-plane dot confinement energies by fitting the data to the ground state of a Fock-Darwin set of energy levels for parabolic dot confinement. For a typical high growth rate sample, the in-plane confinement energy deduced for the quantum dots is relatively small at low power, approx 6 meV, but as the excitation power is increased the average confinement energy increases up to approx 18 meV. This is the same as the increase in quantum dot transition energy and suggests that this is due to a progressive population of a distribution of strongly communicating dots with decreasing lateral sizes and consequently increasing in-plane confinement energies. Further support for this picture comes from the temperature dependence of the quantum dot transition energy which is also found to increase by a relatively similar amount as the temperature is raised from 10 K up to 50 K, following correction for the temperature dependence of the bulk energy band gaps

Tunable mid-IR emission using a novel quantum dot-quantum well coupled system

Low-temperature photoluminescence studies of InSb/GaSb quantum dots strongly coupled to narrow InAs quantum wells are presented. Inclusion of the quantum well has enabled the dot emission energy to be reduced from 0.72 to 0.48 eV. Four-band k.p calculations have been used to illustrate the proposed mechanism. In particular, the importance of the InAs well width and GaSb 'spacer' thickness is discussed in terms of the overall character of the coupled state and the relative intensity of the transition. (C) 2002 Elsevier Science B.V. All rights reserved

Different signatures between chemically and biologically synthesized nanoparticles in a magnetic sensor: A new technology for multiparametric detection

1 - ArticleA magnetic sensor, called MIAplex (R), has been developed by the company Magnisense. This instrument measures a signal, which is proportional to the second derivative of a magnetization curve. We show that this sensor is able to discriminate between the signature of small superparamagnetic nanoparticles produced chemically and that of larger ferromagnetic nanoparticles produced by magnetotactic bacteria. The reason why this distinction is possible comes from the different magnetization curves of these two types of nanoparticles. These results pave the way for the simultaneous detection of different types of biological molecules or living organisms

Self-assembled InSb quantum dots in InAs and GaSb matrices assessed by means of TEM, AFM and PL

Transmission electron microscopy (TEM), atomic force microscopy (AFM) and photoluminescence (PL) with and without additional magnetic fields (magneto-PL) were employed to study metal organic vapour phase epitaxy (MOVPE) grown, self-assembled InSb rich quantum dots (QDs) embedded in InAs and GaSb matrices. Depending on the growth conditions, coherently strained, partly relaxed, and completely relaxed InSb rich agglomerates were observed by means of TEM; AFM delivered more reliable QD number densities and accurate heights of InSb islands on GaSb. For the case of InSb embedded in GaSb, PL showed QD emission at 1.69 mum and wetting layer (WL) emission at 1.61 mum

MOVPE grown self-assembled Sb-based quantum dots assessed by means of AFM and TEM

Self-assembled Sb-based quantum dots (QDs) were grown by metal-organic vapour phase epitaxy and assessed by means of atomic force microscopy, transmission electron microscopy and photoluminescence. Two series of InSb QDs in a GaSb matrix were grown at 490 +/- 10 degrees C and luminesced in the mid-infrared at about 1.7 mu m. Reductions in the III/V ratio and growth rate as used for the second series resulted in a change of the morphology of the InSb islands from hillocks without facets and a low level of order, to dumbbell shaped islands with distinct facets and a higher level of order. Self-assembled GaSb islands were grown on GaAs at 550 degrees C and assessed for comparison by means of AFM