Ocean acidification is predicted to impact ecosystems reliant on calcifying organisms, potentially reducing the socioeconomic benefits these habitats provide. Here we investigate the acclimation potential of stony corals living along a pH gradient caused by a Mediterranean CO2 vent that serves as a natural long-term experimental setting. We show that in response to reduced skeletal mineralization at lower pH, corals increase their skeletal macroporosity (features >10 μm) in order to maintain constant linear extension rate, an important criterion for reproductive output. At the nanoscale, the coral skeleton's structural features are not altered. However, higher skeletal porosity, and reduced bulk density and stiffness may contribute to reduce population density and increase damage susceptibility under low pH conditions. Based on these observations, the almost universally employed measure of coral biomineralization, the rate of linear extension, might not be a reliable metric for assessing coral health and resilience in a warming and acidifying ocean.

Magnetic resonance imaging (MRI) is at the forefront of non-invasive medical imaging techniques. It provides good spatial and temporal resolution that can be further improved by the use of contrast agents (CAs), providing a valuable tool for diagnostic purposes. Ultrasmall SuperParamagnetic Iron oxides (USPIOs) nanoparticles are attractive MRI contrast agents due to their negative (T 2 ) contrast enhancement capability and biocompatibility. Clusters of USPIOs with polymer material are of particular interest since they can sustain additional functionalities like drug delivery and targeting. Aiming to establish a relation between the cluster morphology and their efficacy as MRI contrast agent (relaxometric properties), we preparedby using three different maghemite (γ-Fe 2 O 3 ) USPIOs' diametersa series of hybrid copolymer/iron oxide CAs presenting two different geometries (micellar or vesicular). The NMR relaxometry profiles confirmed the nature of the physical mechanisms inducing the increased nuclear relaxation rates at low (magnetic anisotropy) and high (Curie relaxation) magnetic fields. A heuristic model, first proposed by Roch, Muller, Gillis, and Brooks, allowed the fitting of the whole longitudinal relaxivity r 1 () profile, for samples with different magnetic core sizes. We show that both types of cluster exhibit transverse relaxivity (r 2 ) values comparable or higher than those of common contrast agents, over the whole tested frequency range. Moreover, in-depth analysis revealed substantially a linear relation between r 2 and the number of encapsulated USPIOs divided by the diameter of the clusters (N USPIO /D H ), for each USPIOs size. The cluster structure (i.e. micelle or vesicle) appeared to have a mild influence on the transverse relaxivity value. Indeed, the r 2 value was mainly governed by the individual size of the USPIOs, correlated to both the cluster external diameter and the magnetic material volume fraction.

We present the first comparative investigation of the Nuclear Magnetic Resonance (NMR) relaxivity of a series of nanosized cyano-bridged coordination networks stabilized in aqueous solution. These Ln(3+)/[Fe(CN)6](3-) (Ln = Gd, Tb, Y) and M(2+)/[Fe(CN)6](3-) (M = Ni, Cu, Fe) nanoparticles with sizes ranging from 1.4 to 5.5 nm are stabilized by polyethylene glycols (MW = 400 or 1000), polyethylene glycol functionalized with amine groups (MW = 1500), or by N-acetyl-D-glucosamine. The evaluation of NMR relaxivity allowed estimation of the Magnetic Resonance Imaging (MRI) contrast efficiency of our systems. The results demonstrate that Gd(3+)/[Fe(CN)6](3-) nanoparticles have r1p and r2p relaxivities about four times higher than the values observed in the same conditions for the commercial Contrast Agents (CAs) ProHance or Omniscan, regardless of the stabilizing agent used, while nanoparticles of Prussian blue and its analogues M(2+)/[Fe(CN)6](3-) (M = Ni, Cu, Fe) present relatively modest values. The influence of the chemical composition of the nanoparticles, their crystal structure, spin values of lanthanide and transition metal ions, and stabilizing agent on the relaxivity values are investigated and discussed.

A combination of carbon ions/photons irradiation and hyperthermia as a novel therapeutic approach for the in-vitro treatment of pancreatic cancer BxPC3 cells is presented. The radiation doses used are 0–2 Gy for carbon ions and 0–7 Gy for 6 MV photons. Hyperthermia is realized via a standard heating bath, assisted by magnetic fluid hyperthermia (MFH) that utilizes magnetic nanoparticles (MNPs) exposed to an alternating magnetic field of amplitude 19.5 mTesla and frequency 109.8 kHz. Starting from 37 °C, the temperature is gradually increased and the sample is kept at 42 °C for 30 min. For MFH, MNPs with a mean diameter of 19 nm and specific absorption rate of 110 ± 30 W/gFe3o4 coated with a biocompatible ligand to ensure stability in physiological media are used. Irradiation diminishes the clonogenic survival at an extent that depends on the radiation type, and its decrease is amplified both by the MNPs cellular uptake and the hyperthermia protocol. Significant increases in DNA double-strand breaks at 6 h are observed in samples exposed to MNP uptake, treated with 0.75 Gy carbon-ion irradiation and hyperthermia. The proposed experimental protocol, based on the combination of hadron irradiation and hyperthermia, represents a first step towards an innovative clinical option for pancreatic cancer.

Low-temperature specific heat, magnetic susceptibility, and zero-field muon spin resonance (microSR) measurements have been performed in the quasi-one-dimensional molecular helimagnetic compound Gd(hfac)3NITEt. The specific heat presents two anomalies at T(0)=2.19+/-0.02 K and T(N)=1.88+/-0.02 K, which both disappear upon the application of a weak magnetic field. Conversely, magnetic susceptibility and muSR data show the divergence of two-spin correlation functions only at T(N)=1.88+/-0.02 K. These results suggest an experimental validation of Villain's conjecture of a two-step magnetic ordering in quasi-one-dimensional XY helimagnets; i.e., the paramagnetic phase and the helical spin solid phase are separated by a chiral spin liquid phase, where translational invariance is broken without violation of rotational invariance.

No abstract

Nuclear magnetic resonace ͑NMR͒, EPR and magnetization measurements in Na x CoO 2 for 0.65ഛ x ഛ 0.75 are presented. While the EPR signal arises from Co 4+ magnetic moments ordering at T c Ӎ 26 K, 59 Co NMR signal originates from cobalt nuclei in metallic regions with no long range magnetic order and characterized by a generalized susceptibility typical of strongly correlated metallic systems. This phase separation in metallic and magnetic insulating regions is argued to occur below T * ͑x͒ ͑220-270 K͒. Above T * an anomalous decrease in the intensity of the EPR signal is observed and associated with the delocalization of the electrons which for T Ͻ T * were localized on Co 4+ d z 2 orbitals. It is pointed out that the in-plane antiferromagnetic coupling J Ӷ T * cannot be the driving force for the phase separation. PACS number(s): 76.60. Ϫk, 76.30.Ϫv, 71.27.ϩa II. EXPERIMENTAL RESULTS A. Sample preparationNa x CoO 2 (x = 0.65, 0.70, and 0.75) samples were prepared following the "rapid heat-up" method. 12,13 A stoichiometric mixture of 99.99% purity Co 3 O 4 and Na 2 CO 3 was thoroughly ground, and placed in a furnace and preheated at 750°C for 12 hours. The obtained samples were reground and annealed for 15 hours at 850°C in air, followed by slow cooling to room temperature. X-ray powder diffraction measurements confirmed all samples to be single phase of hex-PHYSICAL REVIEW B

We present the magnetic properties and the 1H nuclear magnetic resonance dispersion profiles of Mn-ferrites-based compounds, as possible novel contrast agents (CAs) for magnetic resonance imaging (MRI). The samples consist of nanoparticles (NPs) with the magnetic core made of Mn1+xFe2−xO4, obtained by the rapid decomposition of metalcarbonyl into a hot solvent containing an oxidizer and a coordinating surfactant; by this procedure, monodisperse capped NPs with different sizes have been obtained. We have performed structural and morphological investigation by x-ray powder diffraction and transmission electron microscopy techniques and SQUID magnetometry experiments to investigate the magnetic behaviour of the samples. As required for MRI applications using negative CAs, the samples are superparamagnetic at room temperature, having blocking temperatures in the range 14–80 K. The longitudinal r1 and transverse r2 nuclear relaxivities appear to vary strongly with the magnetic core size, their values being comparable to commercial compounds in the high-frequency range ν > 100 MHz. The experimental results suggest that our samples are suitable for high-frequency MRI imagers in general and in particular for the 3 T clinical imager, as indeed suggested by a recent report (Tromsdorf et al 2007 Nanoletters 7 2422).