Colloidal Assemblies of Oriented Maghemite Nanocrystals and their NMR Relaxometric Properties

Elevated-temperature polyol-based colloidal-chemistry approach allows for the development of size-tunable (50 and 86 nm) assemblies of maghemite iso-oriented nanocrystals, with enhanced magnetization. 1H-Nuclear Magnetic Resonance (NMR) relaxometric experiments show that the ferrimagnetic cluster-like colloidal entities exhibit a remarkable enhancement (4 to 5 times) in the transverse relaxivity, if compared to that of the superparamagnetic contrast agent Endorem, over an extended frequency range (1-60 MHz). The marked increase of the transverse relaxivity r2 at a clinical magnetic field strength (1.41 T), which is 405.1 and 508.3 mM-1 s-1 for small and large assemblies respectively, allows to relate the observed response to the raised intra-aggregate magnetic material volume fraction. Furthermore, cell tests with murine fibroblast culture medium confirmed the cell viability in presence of the clusters. We discuss the NMR dispersion profiles on the basis of relaxivity models to highlight the magneto-structural characteristics of the materials for improved T2-weighted magnetic resonance images.Comment: Includes supporting informatio

Prospective assessment of integrating the existing emergency medical system with automated external defibrillators fully operated by volunteers and laypersons for out-of-hospital cardiac arrest: the Brescia Early Defibrillation Study (BEDS)

AIMS: There are few data on the outcomes of cardiac arrest (CA) victims when the defibrillation capability of broad rural and urban territories is fully operated by volunteers and laypersons. METHODS AND RESULTS: In this study, we investigated whether a programme based on diffuse deployment of automated external defibrillators (AEDs) operated by 2186 trained volunteers and laypersons across the County of Brescia, Italy (area: 4826 km(2); population: 1 112 628), would safely and effectively impact the current survival among victims of out-of-hospital CA. Forty-nine AEDs were added to the former emergency medical system that uses manual EDs in the emergency department of 10 county hospitals and in five medically equipped ambulances. The primary endpoint was survival free of neurological impairment at 1-year follow-up. Data were analysed in 692 victims before and in 702 victims after the deployment of the AEDs. Survival increased from 0.9% (95% CI 0.4-1.8%) in the historical cohort to 3.0% (95% CI 1.7-4.3%) (P=0.0015), despite similar intervals from dispatch to arrival at the site of collapse [median (quartile range): 7 (4) min vs. 6 (6) min]. Increase of survival was noted both in the urban [from 1.4% (95% CI 0.4-3.4 %) to 4.0% (95% CI 2.0-6.9 %), P=0.024] and in the rural territory [from 0.5% (95% CI 0.1-1.6%) to 2.5% (95% CI 1.3-4.2%), P=0.013]. The additional costs per quality-adjusted life year saved amounted to euro39 388 (95% CI euro16 731-49 329) during the start-up phase of the study and to euro23 661 (95% CI euro10 327-35 528) at steady state. CONCLUSION: Diffuse implementation of AEDs fully operated by trained volunteers and laypersons within a broad and unselected environment proved safe and was associated with a significantly higher long-term survival of CA victims

Observation of Mixed Valence Ru Components in Zn Doped Y2Ru2O7 Pyrochlores

We present a study of Y2 12xZnxRu2O7 pyrochlores as a function of the Zn doping level x. X-ray diffraction measurements show that single-phase samples could be obtained for x < 0.2. Within the allowed range for x, dc conductivity measurements revealed a sizable decrease in resistivity at all the investigated temperatures for Zn doped samples with respect to undoped ones. Neutron diffraction data of the x = 0.2 sample showed that replacing Y3+ by Zn2+ does not result in the formation of oxygen vacancies. X-ray photoemission spectroscopy measurements revealed that part of the Ru ions are in the 5+ oxidation state to balance, in terms of electronic charge, the incorporation of Zn2+. The results give experimental evidence that the heterovalent doping promotes the increase of conductivity in the Y2Ru2O7 pyrochlores, making these systems promising as intermediate temperature solid oxide fuel cell cathodes

Elevated Airway Purines in COPD

Adenosine and related purines have established roles in inflammation, and elevated airway concentrations are predicted in patients with COPD. However, accurate airway surface purine measurements can be confounded by stimulation of purine release during collection of typical respiratory samples

Low-temperature anomalies in muon spin relaxation of solid and hollow nanoparticles: a pathway to detect unusual local spin dynamics

By means of muon spin relaxation measurements we unraveled the temperature spin dynamics in monodisperse maghemite spherical nanoparticles with different surface to volume ratio, in two samples with a full core (diameter D∼4 and D∼5nm) and one with a hollow core (external diameter D∼7.4nm). The behavior of the muon longitudinal relaxation rates as a function of temperature allowed us to identify two distinct spin dynamics. The first is well witnessed by the presence of a characteristic peak for all the samples around the so-called muon blocking temperature T$_{B}^{μ+}$. A Bloembergen-Purcell-Pound (BPP)-like model reproduces the experimental data around the peak and at higher temperatures (20<T<100K) by assuming the Néel reversal time of the magnetization as the dominating correlation time. An additional dynamic emerges in the samples with higher surface to volume ratio, namely, full 4 nm and hollow samples. This is witnessed by a shoulder of the main peak for T<20K at low longitudinal field (μ$_{0}$H≈15mT), followed by an abrupt increase of the relaxation rate at T<10K, which is more evident for the hollow sample. These unusual anomalies of the longitudinal relaxation rate for T<T$_{B}^{μ+}$ are suggested to be due to the surface spins’ dynamical behavior. Furthermore, for weak applied longitudinal magnetic field (μ$_{0}$H≈15mT) and T<T$_{B}^{μ+}$ we observed damped coherent oscillations of the muon asymmetry, which are a signature of a quasistatic local field at the muon site as probed by muons implanted in the inner magnetic core of the nanoparticles. The muon spin relaxation technique turns out to be very successful to study the magnetic behavior of maghemite nanoparticles and to detect their unusual local spin dynamics in low magnetic field conditions

Worsening renal function in patients hospitalised for acute heart failure: clinical implications and prognostic significance.

BACKGROUND: Renal function is a powerful prognostic variable in patients with heart failure (HF). Hospitalisations for acute HF (AHF) may be associated with further worsening of renal function (WRF). METHODS AND RESULTS: We analysed the clinical significance of WRF in 318 consecutive patients admitted at our institute for AHF. WRF was defined as the occurrence, at any time during the hospitalisation, of both a > or =25% and a > or =0.3 mg/dL increase in serum creatinine (s-Cr) from admission (WRF-Abs-%). RESULTS: Patients were followed for 480+/-363 days. Fifty-three patients (17%) died and 132 (41%) were rehospitalised for HF. WRF-Abs-% occurred in 107 (34%) patients. At multivariable survival analysis, WRF-Abs-% was an independent predictor of death or HF rehospitalisation (adjusted HR, 1.47; 95%CI, 1.13-1.81; p=0.024). The independent predictors of WRF-Abs-%, evaluated using multivariable logistic regression, were history of chronic kidney disease (p=0.002), LV ejection fraction (p=0.012), furosemide daily dose (p=0.03) and NYHA class (p=0.05) on admission. CONCLUSION: WRF is a frequent finding in patients hospitalised for AHF and is associated with a poor prognosis. Severity of HF and daily furosemide dose are the most important predictors of the occurrence of WRF

1H-NMR study of the spin dynamics of fine superparamagnetic nanoparticles

We report a broadband 1H-NMR study of the temperature spin dynamics of nearly monodisperse dextran-coated \u3b3-Fe2O3 magnetic nanoparticles. We observed a maximum in T1 121(T) that decreases in amplitude and shifts toward higher temperatures with increasing field. We suggest that this is related to the progressive superparamagnetic spin blocking of the ferrite core. The data can be explained by assuming a single electronic spin-spin correlation time and introducing a field-dependent distribution of anisotropy energy barriers

Magnetic properties and hyperfine interactions in Cr8, Cr7Cd, and Cr7Ni molecular rings from 19F-NMR

A detailed experimental investigation of the 19F nuclear magnetic resonance is made on single crystals of the homometallic Cr8 antiferromagnetic molecular ring and heterometallic Cr7Cd and Cr7Ni rings in the low temperature ground state. Since the F - ion is located midway between neighboring magnetic metal ions in the ring, the 19F-NMR spectra yield information about the local electronic spin density and 19F hyperfine interactions. In Cr 8, where the ground state is a singlet with total spin ST = 0, the 19F-NMR spectra at 1.7 K and low external magnetic field display a single narrow line, while when the magnetic field is increased towards the first level crossing field, satellite lines appear in the 19F-NMR spectrum, indicating a progressive increase in the Boltzmann population of the first excited state ST = 1. In the heterometallic rings, Cr7Cd and Cr7Ni, whose ground state is magnetic with ST = 3/2 and ST = 1/2, respectively, the 19F-NMR spectrum has a complicated structure which depends on the strength and orientation of the magnetic field, due to both isotropic and anisotropic transferred hyperfine interactions and classical dipolar interactions. From the 19F-NMR spectra in single crystals we estimated the transferred hyperfine constants for both the F--Ni 2+ and the F--Cd2+ bonds. The values of the hyperfine constants compare well to the ones known for F--Ni 2+ in KNiF3 and NiF2 and for F --Cr3+ in K2NaCrF6. The results are discussed in terms of hybridization of the 2s, 2p orbitals of the F- ion and the d orbitals of the magnetic ion. Finally, we discuss the implications of our results for the electron-spin decoherence

Avian Influenza Virus Glycoproteins Restrict Virus Replication and Spread through Human Airway Epithelium at Temperatures of the Proximal Airways

Transmission of avian influenza viruses from bird to human is a rare event even though avian influenza viruses infect the ciliated epithelium of human airways in vitro and ex vivo. Using an in vitro model of human ciliated airway epithelium (HAE), we demonstrate that while human and avian influenza viruses efficiently infect at temperatures of the human distal airways (37°C), avian, but not human, influenza viruses are restricted for infection at the cooler temperatures of the human proximal airways (32°C). These data support the hypothesis that avian influenza viruses, ordinarily adapted to the temperature of the avian enteric tract (40°C), rarely infect humans, in part due to differences in host airway regional temperatures. Previously, a critical residue at position 627 in the avian influenza virus polymerase subunit, PB2, was identified as conferring temperature-dependency in mammalian cells. Here, we use reverse genetics to show that avianization of residue 627 attenuates a human virus, but does not account for the different infection between 32°C and 37°C. To determine the mechanism of temperature restriction of avian influenza viruses in HAE at 32°C, we generated recombinant human influenza viruses in either the A/Victoria/3/75 (H3N2) or A/PR/8/34 (H1N1) genetic background that contained avian or avian-like glycoproteins. Two of these viruses, A/Victoria/3/75 with L226Q and S228G mutations in hemagglutinin (HA) and neuraminidase (NA) from A/Chick/Italy/1347/99 and A/PR/8/34 containing the H7 and N1 from A/Chick/Italy/1347/99, exhibited temperature restriction approaching that of wholly avian influenza viruses. These data suggest that influenza viruses bearing avian or avian-like surface glycoproteins have a reduced capacity to establish productive infection at the temperature of the human proximal airways. This temperature restriction may limit zoonotic transmission of avian influenza viruses and suggests that adaptation of avian influenza viruses to efficient infection at 32°C may represent a critical evolutionary step enabling human-to-human transmission

The Relationship of Mucus Concentration (Hydration) to Mucus Osmotic Pressure and Transport in Chronic Bronchitis

Rationale: Chronic bronchitis (CB) is characterized by persistent cough and sputum production. Studies were performed to test whether mucus hyperconcentration and increased partial osmotic pressure, in part caused by abnormal purine nucleotide regulation of ion transport, contribute to the pathogenesis of CB