Magnetic Susceptometry Research Articles

Synthesis of superconducting hcp- ZrH3 under high hydrogen pressure

Zirconium trihydride and, for comparison, trideuteride with hexagonal close-packed (hcp) metal lattices were synthesized at a hydrogen/deuterium pressure of 9 GPa and a temperature of 873 K using toroid-type high-pressure chambers. After a rapid cooling (quenching) to 100 K and lowering the pressure to atmospheric, the quenched sample was removed from the chamber and studied by hot extraction analysis, powder x-ray diffraction, and ac magnetic susceptometry. The hot extraction showed that thermal decomposition of both hcp-${\mathrm{ZrH}}_{3}$ and hcp-${\mathrm{ZrD}}_{3}$ in vacuum begins after heating at a rate of 10 K/min to \ensuremath{\sim}200 K and almost ceases at 270 K, leaving tetragonal $\ensuremath{\varepsilon}\text{\ensuremath{-}}{\mathrm{ZrH}}_{2}/\ensuremath{\varepsilon}\text{\ensuremath{-}}{\mathrm{ZrD}}_{2}$ as a result. The x-ray diffraction study at 85 K gave lattice parameters $a=3.443(2)\phantom{\rule{0.16em}{0ex}}\AA{}$ and $c=5.964(4)\phantom{\rule{0.16em}{0ex}}\AA{}$ for hcp-${\mathrm{ZrH}}_{3}$ and somewhat smaller values of $a=3.430(5)\phantom{\rule{0.16em}{0ex}}\AA{}$ and $c=5.947(5)\phantom{\rule{0.16em}{0ex}}\AA{}$ for hcp-${\mathrm{ZrD}}_{3}$. The measurements of magnetic susceptibility revealed superconductivity with an onset at 11.6(1) K for hcp-${\mathrm{ZrH}}_{3}$ and 9.5(2) K for hcp-${\mathrm{ZrD}}_{3}$.

Scanning SQUID Imaging of Reduced Superconductivity Due to the Effect of Chiral Molecule Islands Adsorbed on Nb

AbstractUnconventional superconductivity was realized in systems comprising a monolayer of magnetic adatoms adsorbed on conventional superconductors, forming Shiba‐bands. Another approach to induce unconventional superconductivity and 2D Shiba‐bands was recently introduced, namely, by adsorbing chiral molecules (ChMs) on conventional superconductors, which act in a similar way to magnetic impurities as verified by conductance spectroscopy. However, the fundamental effect ChMs have on the strength of superconductivity has not yet been directly observed and mapped. In this work, local magnetic susceptometry is applied on heterostructures comprising islands of ChMs (α‐helix L‐polyalanine) monolayers adsorbed on Nb. It is found that the ChMs alter the superconducting landscape, resulting in spatially‐modulated weaker superconductivity. Surprisingly, the reduced diamagnetic response is located along the perimeter of the islands with respect to both their interior and the bare Nb. The authors suggest that topological edge‐states forming at the edges are the source of the reduced superconductivity, akin to the case of magnetic islands. The results pave new paths for the realization of topological‐superconductivity‐based devices with changing order parameter.

Remote Sensing of the Nano-Rheological Properties of Soft Materials Using Magnetic Nanoparticles and Magnetic AC Susceptometry.

We have developed a nano-rheological characterization tool to extract the frequency- and scale-dependent rheological properties of soft materials during oral processing. Taking advantage of AC susceptometry, the dynamic magnetization of magnetic nanoparticles blended in the matrix material is measured. The magnetic AC susceptibility spectra of the particles are affected by the viscosity and mechanical modulus of the matrix material and provide the rheological properties of the matrix. Commercially available iron-oxide magnetic nanoparticles with 80 and 100 nm particle sizes are used as tracers in the frequency range of 1 Hz-10 kHz. The AC susceptibility is measured using two differentially connected coils, and the effects of the sample temperature and distance with respect to the detection coils are investigated. The developed measurement setup shows the feasibility of remote nano-rheological measurements up to 2 cm from the coil system, which can be used to, e.g., monitor the texture of matrix materials during oral processing.

Origin of Ferromagnetism and Magnetic Anisotropy in a Family of Copper(II) Triangles.

Previously reported ferromagnetic triangles (NnBu4 )2 [Cu3 (μ3 -Cl)2 (μ-4-NO2 -pz)3 Cl3 ] (1), (PPN)2 [Cu3 (μ3 -Cl)2 (μ-pz)3 Cl3 ] (2), (bmim)2 [Cu3 (μ3 -Cl)2 (μ-pz)3 Cl3 ] (3) and newly reported (PPh4 )2 [Cu3 (μ3 -Cl)2 (μ-4-Ph-pz)3 Cl3 ] (4) were studied by magnetic susceptometry, electron paramagnetic resonance (EPR) spectroscopy and ab initio calculations to assess the origins of their ferromagnetism and of the magnetic anisotropy of their ground S=3/2 state (PPN+ =bis(triphenylphosphine)iminium, bmim+ =1-butyl-3-methylbenzimidazolium, pz- =pyrazolate). Ab initio studies revealed the d character of the magnetic orbitals of the compressed trigonal bipyramidal copper(II) ions. Ferromagnetic interactions were attributed to weak orbital overlap via the pyrazolate bridges. From the wavefunctions expansions, the ratios of the magnetic couplings were determined, which were indeterminate by magnetic susceptometry. Single-crystal EPR studies of 1 were carried out to extend the spin Hamiltonian with terms which induce zero-field splitting (zfs), namely dipolar interactions, anisotropic exchange and Dzyaloshinskii-Moriya interactions (DMI). The data were treated through both a giant-spin model and through a multispin exchange-coupled model. The latter indicated that ≈62 % of the zfs is due to anisotropic and ≈38 % due to dipolar interactions. The powder EPR data of all complexes were fitted to a simplified form of the multispin model and the anisotropic and dipolar contributions to the ground state zfs were estimated.

Fast and robust optically pumped cesium magnetometer

Abstract We present a fast and robust optically pumped magnetometer that is based on a feedback-controlled spin ensemble of cesium atoms in spin-polarized vapor. The table-top system is intended for operation in unshielded environment, and its design allows conversion into a handheld sensor head. Under strongly disturbed environmental conditions in the laboratory, the sensor exhibits a speed of more than 56 kHz, while having a slew rate of 39 mT/s and a full dynamic range of 10 – 120 μT. Under these conditions a sensitivity of 33 pT / Hz $\text{pT}/\sqrt{\text{Hz}}$ is reached. By reducing the speed to 3.6 kHz the sensitivity can be improved to 6 pT / Hz $\text{pT}/\sqrt{\text{Hz}}$ , which is close to the shot noise limit. We describe the sensor design and its optimization and demonstrate the performance of the sensor under conditions appropriate for magnetic susceptometry measurements.

Dynamics of Superparamagnetic Iron Oxide Nanoparticles with Various Polymeric Coatings.

In this article, the results of a study of the magnetic dynamics of superparamagnetic iron oxide nanoparticles (SPIONs) with chitosan and polyethylene glycol (PEG) coatings are reported. The materials were prepared by the co-precipitation method and characterized by X-ray diffraction, dynamic light scattering and scanning transmission electron microscopy. It was shown that the cores contain maghemite, and their hydrodynamic diameters vary from 49 nm for PEG-coated to 200 nm for chitosan-coated particles. The magnetic dynamics of the nanoparticles in terms of the function of temperature was studied with magnetic susceptometry and Mössbauer spectroscopy. Their superparamagnetic fluctuations frequencies, determined from the fits of Mössbauer spectra, range from tens to hundreds of megahertz at room temperature and mostly decrease in the applied magnetic field. For water suspensions of nanoparticles, maxima are observed in the absorption part of magnetic susceptibility and they shift to higher temperatures with increasing excitation frequency. A step-like decrease of the susceptibility occurs at freezing, and from that, the Brown’s and Néel’s contributions are extracted and compared for nanoparticles differing in core sizes and types of coating. The results are analyzed and discussed with respect to the tailoring of the dynamic properties of these nanoparticle materials for requirements related to the characteristic frequency ranges of MRI and electromagnetic field hyperthermia.

Measurement of the liver iron concentration in transfusional iron overload by MRI R2* and by high-transition-temperature superconducting magnetic susceptometry

PurposeTo compare measurement of the liver iron concentration in patients with transfusional iron overload by magnetic resonance imaging (MRI), using R2*, and by magnetic susceptometry, using a new high-transitiontemperature (high-Tc; operating at 77 K, cooled by liquid nitrogen) superconducting magnetic susceptometer. MethodsIn 28 patients with transfusional iron overload, 43 measurements of the liver iron concentration were made by both R2* and high-Tc magnetic susceptometry. ResultsMeasurements of the liver iron concentration by R2* and high-Tc magnetic susceptometry were significantly correlated when comparing all patients (Pearson's r = 0.91, p < 0.0001) and those with results by susceptometry >7 mg Fe/g liver, dry weight (r = 0.93, p = 0.006). In lower ranges of liver iron, no significant correlations between the two methods were found (0 to <3.2 mg Fe/g liver, dry weight: r = 0.2, p = 0.37; 3.2 to 7 mg Fe/g liver, dry weight: r = 0.41; p = 0.14). ConclusionThe lack of linear correlation between R2* and magnetic susceptibility measurements of the liver iron concentration with minimal or modest iron overload may be due to the effects of fibrosis and other cellular pathology that interfere with R2* but do not appreciably alter magnetic susceptibility.

Liver Iron Measurements with Less Expensive Technology: Comparison of a Room-Temperature Susceptometer with SQUID in 84 Subjects

Introduction. Tissue iron measurements with magnetic resonance imaging (MRI) have given doctors a reliable way to monitor iron overload in thalassemias, sickle-cell disease and other disorders. However, MRI remains too expensive for widespread use in the countries where the largest numbers of patients with these disorders live. This abstract describes a test in human subjects of a potentially less expensive method of quantifying excess iron: measurement of liver iron concentrations (LIC) by magnetic susceptometry, using magnetic sensors that work at room temperature.Methods. The room-temperature susceptometer (RTS) in this study was a close copy of the one described by Maliken et al. [Room-temperature susceptometry predicts biopsy-determined hepatic iron in patients with elevated serum ferritin. Ann. Hepatol. 2012;11:77-84]. LIC measurements with the RTS were compared to those of an existing SQUID (superconducting quantum interference device) biosusceptometer [Starr, TN et. al. A new generation SQUID biosusceptometer. Proceedings, 12th International Conference on Biomagnetism. 2000].84 patients, mostly with transfusion-dependent thalassemia major, participated in this comparison. Their LICs based on SQUID ranged from zero to 5250 μg/g wet weight, with median 920 μg/g and standard deviation 960 μg/g. Body-mass indices ranged from 16.6 to 31.7 kg/m2 (median 21.8 kg/m2, standard deviation 3.1 kg/m2). Liver-skin distances measured by ultrasound imaging ranged from 13.0 to 30.0 mm (median 17.5 mm, standard deviation 3.1 mm). For each patient, SQUID and RTS measurements were done in a single session.The agreement of the two susceptometers was assessed in terms of their Pearson product moment correlation coefficient r and the standard deviation σ of the differences between the SQUID results and the least-squares Deming regression line. This standard deviation was slightly dependent on the value of λ, the ratio of the variances of errors for the two susceptometers, that was assumed in the Deming regression. This dependence was estimated by calculating σ for a range of λ values.Results. LICs from RTS and SQUID had a Pearson product moment correlation coefficient r = 0.93. The differences between the two systems had a standard deviation σ = 363 μg/g assuming that the RTS's variance was four times the SQUID's and 353 μg/g assuming equal variances. As a point of reference, applying a similar analysis to published data yielded r = 0.975 and σ = 320 μg/g for a comparison of the Torino-based SQUID used in this study with another SQUID susceptometer at Hamburg [Engelhardt R et al. Agreement of liver iron quantification measurements with low Tc-SQUID biosusceptometers in Oakland, Torino and Hamburg. Elsevier International Congress Series 2007;1300: 279-282].Conclusions. These results indicate that a less expensive susceptometer using room-temperature magnetic sensors can make liver iron measurements that are well correlated with those of the biopsy-validated SQUID technology. Based on the standard deviation of the differences between the two systems, the RTS used in this study was approaching accuracy levels that would be useful clinically, especially in screening patients for dangerously high iron. Since the RTS's errors in measurements on phantoms are significantly lower than those found in this study on human subjects, the room-temperature susceptometer's accuracy appears to be limited not by the noise of the room-temperature magnetic sensors, but by the relationship of the susceptometer to the patient's body. With improvement in areas such as patient positioning, measurement of the sensor-skin distance, and correction for the magnetic response of tissue between the liver and the susceptometer, low-cost susceptometers may ultimately achieve accuracies comparable to those of existing SQUIDs. Such technologies can potentially improve the management of iron overload, especially in regions where MRI is too expensive for routine use. [Display omitted] DisclosuresPiga:Acceleron: Research Funding; La Jolla: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; Apopharma: Honoraria, Research Funding; Bluebird Bio: Honoraria; Celgene Corp: Membership on an entity's Board of Directors or advisory committees, Research Funding. Avrin:Insight Magnetics: Employment, Other: Proprietor of company developing the study device, Patents & Royalties: Own rights to patents on the study device.

Optimization of an implantable magnetic marker for surgical localization of breast cancer

For small, early-stage or otherwise non-palpable breast tumors, surgeons rely on localization technologies to accurately find and remove the tumor tissue during breast conserving surgery. However, current widely accepted localization technologies either use painful and logistically challenging guidewires, or complex radioactive iodine sources. We have developed an implantable magnetic marker, intended to mark the location of a breast tumor, that can be detected during surgery using a clinical handheld magnetic susceptometry system. Here, we report on the development and optimization of this magnetic marker, focusing on the material, shape and various material assemblies. It was found that the effects of magnetic shape anisotropy may decrease localization precision. This can be circumvented by combining multiple isotropic magnetic elements separated from one another. A final optimized prototype was constructed and compared to a commercially available magnetic marker. Finally, the technology was tested in an ex vivo surgical setting on tissue to assess radiological visibility and surgical feasibility. The marker was successfully detected and removed in all ex vivo sessions, and the technology was found feasible.

Iatrogenic iron overload and its potential consequences in patients on hemodialysis

Iron overload was considered rare in hemodialysis patients until recently, but its clinical frequency is now increasingly recognized. The liver is the main site of iron storage and the liver iron concentration (LIC) is closely correlated with total iron stores in patients with secondary hemosiderosis and genetic hemochromatosis. Magnetic resonance imaging (MRI) is now the gold standard method for estimating and monitoring LIC. Studies of LIC in hemodialysis patients by magnetic susceptometry thirteen years ago and recently by quantitative MRI have demonstrated a relation between the risk of iron overload and the use of intravenous (IV) iron products prescribed at doses determined by the iron biomarker cutoffs contained in current anemia management guidelines. These findings have challenged the validity of both iron biomarker cutoffs and current clinical guidelines, especially with respect to recommended IV iron doses. Moreover, three recent long-term observational studies suggested that excessive IV iron doses might be associated with an increased risk of cardiovascular events and death in hemodialysis patients. It has been hypothesized that iatrogenic iron overload in the era of erythropoiesis-stimulating agents might silently increase complications in dialysis patients without creating obvious, clinical signs and symptoms. High hepcidin-25 levels were recently linked to fatal and nonfatal cardiovascular events in dialysis patients. It has been postulated that the main pathophysiological pathway leading to these events might involve the pleiotropic master hormone hepcidin, which regulates iron metabolism, leading to activation of macrophages in atherosclerotic plaques and then to clinical cardiovascular events. Thus, the potential iron overload toxicity linked to chronic administration of IV iron therapy is now becoming one of the most controversial topics in the management of anemia in hemodialysis patients.

Rare earth ions doped K2Ta2O6 photocatalysts with enhanced UV–vis light activity

Novel rare earth-doped K2Ta2O6 (RE-K2Ta2O6) photocatalysts were successfully synthesized by one-step hydrothermal method. The effect of dopant type (RE=Y, Yb, Ho, Pr, Er) and amount of rare earth precursor (2, 4, 8 and 10mol%) on the physicochemical and photocatalytic properties of RE-K2Ta2O6 have been investigated. All as-prepared materials were subsequently characterized by UV–vis diffuse reflectance spectroscopy (DRS), Brunauer-Emmett-Teller (BET) specific surface area measurement, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, mass magnetic susceptometry and photoluminescence (PL) emission spectroscopy. The photocatalytic activity under UV–vis light irradiation was estimated in phenol degradation in aqueous phase, toluene removal in gas phase and H2 generation from formic acid solution. The experimental results show that, novel RE-K2Ta2O6 exhibits greatly improved degradation efficiency under UV–vis light irradiation compared with pristine K2Ta2O6. The Er-K2Ta2O6 and Pr-K2Ta2O6, obtained by introducing of 2mol% of RE ions during synthesis, reveal the highest photocatalytic activity among prepared samples in aqueous phase (33% of phenol decomposition after 90min of irradiation) and gas phase (45% of toluene removal after 60min of irradiation), respectively. Moreover, both photocatalysts present good stability after subsequent three cycles. The active species trapping test shows that OH and O2− radicals are significantly involved in phenol oxidation under UV–vis light irradiation. The amount of H2 evolution increases with increasing addition of Er dopant into K2Ta2O6 lattice. The highest H2 production is obtained for 10mol% Er-K2Ta2O6 after 240min of UV–vis light irradiation (15.40μmol/min). Enhanced photoactivity performance can be attributed to incorporation of RE ions at K+ lattice site in RE-K2Ta2O6, probably leading to formation of new RE 4f states below the conduction band of K2Ta2O6 structure. To investigate the localization of RE ions in K2Ta2O6 structure, the band structure and partial density of the states (PDOS) have been investigated. Computer simulations were performed using plane-wave based Vienna ab-initio simulation package (VASP) with the generalized gradient approximation (GGA) by Perdew-Burke-Ernzerhof (PBE). Moreover, inclusion of RE ions in K2Ta2O6 causes predominance pyrochlore phase formation over perovskite in regular cubic structure. Summarized, RE-doped K2Ta2O6 is promising material in photocatalytic degradation of organic pollutants and H2 generation processes. Our work may provide valuable information for rare earth doping semiconductor with improved photocatalytic performance.

Selection of potential iron oxide nanoparticles for breast cancer treatment based on in vitro cytotoxicity and cellular uptake.

Superparamagnetic iron oxide nanoparticles (SPIONs) are promising tools for the treatment of different diseases. Their magnetic properties enable therapies involving magnetic drug targeting (MDT), hyperthermia or imaging. Depending on the intended treatment, specific characteristics of SPIONs are required. While particles used for imaging should circulate for extended periods of time in the vascular system, SPIONs intended for MDT or hyperthermia should be accumulated in the target area to come into close proximity of, or to be incorporated into, specific tumor cells. In this study, we determined the impact of several accurately characterized SPION types varying in size, zeta potential and surface coating on various human breast cancer cell lines and endothelial cells to identify the most suitable particle for future breast cancer therapy. We analyzed cellular SPION uptake, magnetic properties, cell proliferation and toxicity using atomic emission spectroscopy, magnetic susceptometry, flow cytometry and microscopy. The results demonstrated that treatment with dextran-coated SPIONs (SPIONDex) and lauric acid-coated SPIONs (SPIONLA) with an additional protein corona formed by human serum albumin (SPIONLA-HSA) resulted in very moderate particle uptake and low cytotoxicity, whereas SPIONLA had in part much stronger effects on cellular uptake and cellular toxicity. In summary, our data show significant dose-dependent and particle type-related response differences between various breast cancer and endothelial cells, indicating the utility of these particle types for distinct medical applications.

Iatrogenic Iron Overload in Dialysis Patients at the Beginning of the 21st Century.

Iron overload used to be considered rare in hemodialysis patients but its clinical frequency is now increasingly realized. The liver is the main site of iron storage and the liver iron concentration (LIC) is closely correlated with total iron stores in patients with secondary hemosideroses and genetic hemochromatosis. Magnetic resonance imaging is now the gold standard method for LIC estimation and monitoring in non-renal patients. Studies of LIC in hemodialysis patients by quantitative magnetic resonance imaging and magnetic susceptometry have demonstrated a strong relation between the risk of iron overload and the use of intravenous (IV) iron products prescribed at doses determined by the iron biomarker cutoffs contained in current anemia management guidelines. These findings have challenged the validity of both iron biomarker cutoffs and current clinical guidelines, especially with respect to recommended IV iron doses. Three long-term observational studies have recently suggested that excessive IV iron doses may be associated with an increased risk of cardiovascular events and death in hemodialysis patients. We postulate that iatrogenic iron overload in the era of erythropoiesis-stimulating agents may silently increase complications in dialysis patients without creating frank clinical signs and symptoms. High hepcidin-25 levels were recently linked to fatal and nonfatal cardiovascular events in dialysis patients. It is therefore tempting to postulate that the main pathophysiological pathway leading to these events may involve the pleiotropic master hormone hepcidin (synergized by fibroblast growth factor 23), which regulates iron metabolism. Oxidative stress as a result of IV iron infusions and iron overload, by releasing labile non-transferrin-bound iron, might represent a ‘second hit’ on the vascular bed. Finally, iron deposition in the myocardium of patients with severe iron overload might also play a role in the pathogenesis of sudden death in some patients.

Effects of Subanesthetic Dose of Nitrous Oxide on Cerebral Blood Flow and Metabolism

Nitrous oxide, in a concentration of 50% or more, is a known cerebral vasodilator. This study investigated whether a lower dose (30%) of nitrous oxide would also increase cerebral blood flow. In addition, the authors wished to study whether the increase in cerebral blood flow was accompanied by an increase in cerebral metabolism. Multimodal Magnetic Resonance Imaging at 3T was performed, and data were obtained in 17 healthy volunteers during three inhalation conditions: medical air, oxygen-enriched medical air (40% oxygen), and 30% nitrous oxide with oxygen-enriched medical air (40% oxygen). Arterial spin labeling was used to derive the primary tissue specific hemodynamic outcomes: cerebral blood flow, arterial blood volume and arterial transit times. Magnetic Resonance Susceptometry and proton Magnetic Resonance Spectroscopy were used for secondary metabolic outcomes: venous oxygenation, oxygen extraction fraction, cerebral metabolic oxygen rate and prefrontal metabolites. Nitrous oxide in 40% oxygen, but not 40% oxygen alone, significantly increased gray matter cerebral blood flow (22%; P < 0.05) and arterial blood volume (41%; P < 0.05). Venous oxygenation increased in both oxygen and nitrous oxide conditions. Compared with medical air inhalation, nitrous oxide condition caused a significantly larger decrease in oxygen extraction fraction than 40% oxygen alone (mean [SD] 11.3 [5.6]% vs. 8.3 [5.9]% P < 0.05), while global cerebral metabolic rate and prefrontal metabolites remained unchanged. This study demonstrates that 30% nitrous oxide in oxygen-enriched air (40% oxygen) significantly increases cerebral perfusion, and reduces oxygen extraction fraction, reflecting a strong arterial vasodilatory effect without associated increases in metabolism.

Intermolecular hydrogen bonds directed tetramer and intramolecular electronic communication: paramagnetic di([5]trovacenyl)arsinous acid

Paramagnetic di([5]trovacenyl)arsinous acid was prepared and characterized by X-ray crystallography, cyclic voltammetry, EPR spectroscopy and magnetic susceptometry. A weak intramolecular electronic communication is observed. XRD demonstrates an intermolecular hydrogen bonds directed tetramer. It represents the first structural characterization of organometallic arsinous acid.

α,ω‐Di([5]trovacenyl) Sulfides TVC–S n –TVC ( n = 1–4) and TVC–SCH 2 S–TVC: a Study in Intramolecular Communication

The oligosulfur-bridged dinuclear paramagnetic complexes di([5]trovacenyl) sulfide (3··), di([5]trovacenyl) trisulfide (5··), di([5]trovacenylthio)methane (6··), and di([5]trovacenyl) tetrasulfide (7··) have been prepared by the metathesis reactions of [5]trovacenyllithium with SCl2, and [5]lithiotrovacenylthiolate (2·) with SCl2, CH2Cl2, and S2Cl2, respectively, in which 2· was obtained by the reaction of [5]trovacenyllithium with 1 equiv. of elemental sulfur at ambient temperature. Combined with the previously reported di([5]trovacenyl) disulfide (4··), these complexes have been systematically investigated by means of cyclic voltammetry, electron paramagnetic resonance (EPR) spectroscopy, magnetic susceptometry, and/or X-ray diffraction analysis, which reveal weak antiferromagnetic spin–spin exchange interactions. The monosulfur-bridged 3··, in particular, displays the strongest intramolecular spin–spin exchange interaction of |JEPR| = 2.8 cm–1 and Jχ = –1.39 cm–1. This study also indicates that with an increasing number of sulfur atoms in the bridge, the intramolecular communication of biradicals throught the 1D saturated sulfur atom bridge significantly weakens both in solution and in the solid state compared to those of unsaturated carbon-based bridges.

Transfused Myelodysplastic Syndromes (MDS) Patients Have Severe Iron Overload and Relevant Improvements in Iron Burden and Liver Function with Deferasirox Treatment: Results From a Pooled Analysis

Abstract 5019 Background:MDS patients receiving chronic transfusions can develop significant iron accumulation in key organs such as the liver following 10–20 transfusions (Porter et al. BJH 2001). The diagnosis and monitoring of iron overload, as well as the effect of iron chelation therapy in MDS patients, is often based on serum ferritin (SF), with limited data on liver iron concentration (LIC), primarily due to the biopsy-related increased risk of bleeding and infections in these patients. However, LIC is clinically a more robust and direct measure of body iron burden and with the availability of non-invasive determination of LIC by MRI, LIC assessment has become more practical in MDS patients. This pooled analysis focuses on LIC assessments from a population of 71 MDS patients who completed 1 year of treatment with deferasirox (Exjade®), including assessment of the relationship between LIC vs SF and alanine aminotransferase (ALT). Methods:Analysis is based on 1-year pooled data from iron-overloaded patients with MDS who were enrolled in 4 open-label single-arm deferasirox studies: US02 (Low/Int-1 MDS patients, starting dose 20 mg/kg/day); 2409 (MDS patients with life expectancy >1 yr, starting dose 10–30 mg/kg/day); 108 (MDS patients with life expectancy >1 yr, dosing 5–40 mg/kg/day), and 2204 (Low/Int-1 MDS patients, starting dose 10–30 mg/kg/day). LIC was assessed in the US02, 2409 and 2204 studies using R2 MRI (St Pierre et al. Blood 2004). In the 108 study, LIC was assessed by magnetic liver susceptometry using a superconducting quantum interference device (SQUID) or ultrasound-guided percutaneous liver biopsy; LIC values obtained by SQUID were multiplied by a factor of 2 to correct for the underestimation of LIC by SQUID compared to biopsy (Porter et al. EJH 2008). Datasets were pooled for baseline (BL) characteristics, as well as LIC, SF and ALT at BL and end of study (EOS). Correlations were evaluated on a Pearson’s correlation coefficient. Results:71 patients (56.3% male) were assessed with a mean age of 65 years (range 16.5–82.0). Mean transfusional iron intake ± SD was 0.31 ± 0.12 mg/kg/day. Mean actual deferasirox dose was 19.6 ± 6.5 mg/kg/day. At BL, mean ± SD LIC was 20.5 ± 14.6 mg Fe/g dw (BL LIC <7 mg Fe/g dw, 21.1%; ≥7 mg–≤15 mg Fe/g dw, 23.9%; and >15 mg Fe/g dw, 54.9%). Median BL SF was 2620 ng/mL (range 538–12,639) (BL SF ≤2500 ng/mL, 47.9%; >2500–≤5000 ng/mL, 32.4%; and >5000 ng/mL, 15.5%). With 1 year of DFX, mean ± SD LIC decreased to 13.9 ± 13.1 mg Fe/g dw (mean absolute change –6.6 mg Fe/g dw). In patients with BL LIC <7 mg Fe/g dw (n=15), LIC was maintained with a mean absolute change of 1.0 ± 2.8 mg Fe/g dw, whereas in patients with BL LIC ≥7 mg Fe/g dw (n=56), LIC was reduced by –8.6 ± 10.7 mg Fe/g dw from BL. The proportion of MDS patients with LIC ≥7 mg Fe/g dw reduced from 78.9% at BL to 59.2% at EOS, with 50.7% of patients achieving a decrease in LIC of ≥30%.Median SF decreased to 2035 ng/mL (range 158–10520 ng/mL) with median absolute change from baseline of –630 ng/mL. There was a significant correlation between BL LIC and SF (R=0.548; P<0.0001). Change in LIC significantly correlated with change in serum ferritin (R=0.336; P=0.0042, Figure A). Mean ALT decreased from 55.9 to 38.9 U/L (absolute change –17.0). The change in LIC correlated with the change in ALT (R=0.397, P=0.0006, Figure B). [Display omitted] Conclusions:This pooled analysis in a large cohort of transfusion-dependent MDS patients with LIC assessment shows significantly elevated LIC, with a high proportion of patients (55%) having severely elevated LIC of >15 mg Fe/g dw, a level known to markedly increase liver dysfunction and other iron overload-related complications. One year of treatment with deferasirox produced relevant reductions in LIC, an outcome possibly indicative of a clinical benefit. SF and ALT (an important indicator of liver function) also decreased, with reductions correlating with those of LIC. These findings indicate that correction of moderate-to-severe iron overload in MDS patients is associated with a parallel improvement in liver function. Disclosures:Gattermann:Novartis Pharma: Honoraria, Research Funding. Greenberg:Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees. Habr:Novartis Pharma: Employment. Kpamegan:Novartis Pharma: Employment. Porter:Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.

Bis([5]trovacenyl)dichalcogenides: Synthesis, Structure, and Study of Intramolecular Communication

AbstractThe paramagnetic bis(5trovacenyl)dichalcogenides(η7‐C7H7)V(η5‐C5H4‐E–E–η5‐C5H4)V(η7‐C7H7) 2·· (E = S), 3·· (E = Se), and 4·· (E = Te) were prepared by a novel path in which the elemental chalcogen atoms serve as suppliers of the hetero‐atoms and as oxidants in the final step. Compounds 2·· and 4·· were analyzed by single‐crystal X‐ray diffraction analyses. Cyclic voltammetry revealed that redox splitting in 2··–4·· is not resolved, i.e. the potential difference of successive redox steps is less than 70 mV. Compound 2·· was studied in detail by EPR spectroscopy and magnetic susceptometry. EPR spectroscopy clearly demonstrated spin exchange coupling of two unpaired electrons, which reside in vanadium centered orbitals (51V, I = 7/2), |JEPR(2··)| = 0.65 cm–1. The considerably larger value Jχ(2··) = –1.36 cm–1 was obtained from magnetic susceptometry. This apparent discrepancy is discussed, based on a comparison of the spacers –S–S–,–CH2–CH2–, and –C(CH3) = C(CH3)–.

Measurement of liver iron overload: Noninvasive calibration of MRI‐R2* by magnetic iron detector susceptometer

An accurate assessment of body iron accumulation is essential for the diagnosis and therapy of iron overload in diseases such as thalassemia or hemochromatosis. Magnetic iron detector susceptometry and MRI are noninvasive techniques capable of detecting iron overload in the liver. Although the transverse relaxation rate measured by MRI can be correlated with the presence of iron, a calibration step is needed to obtain the liver iron concentration. Magnetic iron detector provides an evaluation of the iron overload in the whole liver. In this article, we describe a retrospective observational study comparing magnetic iron detector and MRI examinations performed on the same group of 97 patients with transfusional or congenital iron overload. A biopsy-free linear calibration to convert the average transverse relaxation rate in iron overload (R(2) = 0.72), or in liver iron concentration evaluated in wet tissue (R(2) = 0.68), is presented. This article also compares liver iron concentrations calculated in dry tissue using MRI and the existing biopsy calibration with liver iron concentrations evaluated in wet tissue by magnetic iron detector to obtain an estimate of the wet-to-dry conversion factor of 6.7 ± 0.8 (95% confidence level).

Rapid magnetic resonance measurement of global cerebral metabolic rate of oxygen consumption in humans during rest and hypercapnia

The effect of hypercapnia on cerebral metabolic rate of oxygen consumption (CMRO(2)) has been a subject of intensive investigation and debate. Most applications of hypercapnia are based on the assumption that a mild increase in partial pressure of carbon dioxide has negligible effect on cerebral metabolism. In this study, we sought to further investigate the vascular and metabolic effects of hypercapnia by simultaneously measuring global venous oxygen saturation (S(v)O(2)) and total cerebral blood flow (tCBF), with a temporal resolution of 30 seconds using magnetic resonance susceptometry and phase-contrast techniques in 10 healthy awake adults. While significant increases in S(v)O(2) and tCBF were observed during hypercapnia (P<0.005), no change in CMRO(2) was noted (P>0.05). Additionally, fractional changes in tCBF and end-tidal carbon dioxide (R(2)=0.72, P<0.005), as well as baseline S(v)O(2) and tCBF (R(2)=0.72, P<0.005), were found to be correlated. The data also suggested a correlation between cerebral vascular reactivity (CVR) and baseline tCBF (R(2)=0.44, P=0.052). A CVR value of 6.1%±1.6%/mm Hg was determined using a linear-fit model. Additionally, an average undershoot of 6.7%±4% and 17.1%±7% was observed in S(v)O(2) and tCBF upon recovery from hypercapnia in six subjects.