Intrinsic Nature of Spontaneous Magnetic Fields in Superconductors with Time-Reversal Symmetry Breaking.

We present a systematic investigation of muon-stopping states in superconductors that reportedly exhibit spontaneous magnetic fields below their transition temperatures due to time-reversal symmetry breaking. These materials include elemental rhenium, several intermetallic systems, and Sr_{2}RuO_{4}. We demonstrate that the presence of the muon leads to only a limited and relatively localized perturbation to the local crystal structure, while any small changes to the electronic structure occur several electron volts below the Fermi energy, leading to only minimal changes in the charge density on ions close to the muon. Our results imply that the muon-induced perturbation alone is unlikely to lead to the observed spontaneous fields in these materials, whose origin is more likely intrinsic to the time-reversal symmetry-broken superconducting state.

Correlated trends of coexisting magnetism and superconductivity in optimally electron-doped oxypnictides.

We report on the recovery of the short-range static magnetic order and on the concomitant degradation of the superconducting state in optimally F-doped SmFe(1-x)Ru(x)AsO(0.85)F(0.15) for 0.1≤x≲0.5. The two reduced order parameters coexist within nanometer-size domains in the FeAs layers and eventually disappear around a common critical threshold x(c)~0.6. Superconductivity and magnetism are shown to be closely related to two distinct well-defined local electronic environments of the FeAs layers. The two transition temperatures, controlled by the isoelectronic and diamagnetic Ru substitution, scale with the volume fraction of the corresponding environments. This fact indicates that superconductivity is assisted by magnetic fluctuations, which are frozen whenever a short-range static order appears, and totally vanish above the magnetic dilution threshold x(c).

Mn-induced Fermi-surface reconstruction in the SmFeAsO parent compound.

The electronic ground state of iron-based materials is unusually sensitive to electronic correlations. Among others, its delicate balance is profoundly affected by the insertion of magnetic impurities in the FeAs layers. Here, we address the effects of Fe-to-Mn substitution in the non-superconducting Sm-1111 pnictide parent compound via a comparative study of SmFe[Formula: see text]Mn[Formula: see text]AsO samples with [Formula: see text] 0.05 and 0.10. Magnetization, Hall effect, and muon-spin spectroscopy data provide a coherent picture, indicating a weakening of the commensurate Fe spin-density-wave (SDW) order, as shown by the lowering of the SDW transition temperature [Formula: see text] with increasing Mn content, and the unexpected appearance of another magnetic order, occurring at [Formula: see text] and 20 K for [Formula: see text] and 0.10, respectively. We attribute the new magnetic transition at [Formula: see text], occurring well inside the SDW phase, to a reorganization of the Fermi surface due to Fe-to-Mn substitutions. These give rise to enhanced magnetic fluctuations along the incommensurate wavevector [Formula: see text], further increased by the RKKY interactions among Mn impurities.

Breaking the ring: 53Cr-NMR on the Cr8Cd molecular nanomagnet.

An accurate experimental characterization of finite antiferromagnetic (AF) spin chains is crucial for controlling and manipulating their magnetic properties and quantum states for potential applications in spintronics or quantum computation. In particular, finite AF chains are expected to show a different magnetic behaviour depending on their length and topology. Molecular AF rings are able to combine the quantum-magnetic behaviour of AF chains with a very remarkable tunability of their topological and geometrical properties. In this work we measure the 53Cr-NMR spectra of the Cr8Cd ring to study the local spin densities on the Cr sites. Cr8Cd can in fact be considered a model system of a finite AF open chain with an even number of spins. The NMR resonant frequencies are in good agreement with the theoretical local spin densities, by assuming a core polarization field A C = -12.7 T µ B -1. Moreover, these NMR results confirm the theoretically predicted non-collinear spin arrangement along the Cr8Cd ring, which is typical of an even-open AF spin chain.

Fast recovery of the pristine magnetic and structural phases in superconducting LaFeAsO0.89F0.11 by Mn/Fe substitution.

We report an experimental study on the effect of Mn impurities in the optimally doped [Formula: see text] compound. The results show that a very tiny amount of Mn, of the order of 0.1%, is enough to destroy superconductivity and to recover at low temperatures both the magnetic ground state and the orthorhombic structure of the pristine LaFeAsO parent compound. The results are discussed within a model where electron correlations enhance the Ruderman-Kittel-Kasuya-Yosida interaction among impurities.

Singling out the effect of quenched disorder in the phase diagram of cuprates.

We investigate the specific influence of structural disorder on the suppression of antiferromagnetic order and on the emergence of cuprate superconductivity. We single out pure disorder, by focusing on a series of [Formula: see text] samples at fixed oxygen content y  = 0.35, in the range [Formula: see text]. The gradual Y/Eu isovalent substitution smoothly drives the system through the Mott-insulator to superconductor transition from a full antiferromagnet with Néel transition [Formula: see text] K at z = 0 to a bulk superconductor with superconducting critical temperature [Formula: see text] K at z = 1, [Formula: see text]. The electronic properties are finely tuned by gradual lattice deformations induced by the different cationic radii of the two lanthanides, inducing a continuous change of the basal Cu(1)-O chain length, as well as a controlled amount of disorder in the active Cu(2)O2 bilayers. We check that internal charge transfer from the basal to the active plane is entirely responsible for the doping of the latter and we show that superconductivity emerges with orthorhombicity. By comparing transition temperatures with those of the isoelectronic clean system we determine the influence of pure structural disorder connected with the Y/Eu alloy.

Magnetic states of MnP: muon-spin rotation studies.

Muon-spin rotation data collected at ambient pressure (p) and at p = 2.42 GPa in MnP were analyzed to check their consistency with various low- and high-pressure magnetic structures reported in the literature. Our analysis confirms that in MnP the low-temperature and low-pressure helimagnetic phase is characterised by an increased value of the average magnetic moment compared to the high-temperature ferromagnetic phase. An elliptical double-helical structure with a propagation vector [Formula: see text], an a-axis moment elongated by approximately 18% and an additional tilt of the rotation plane towards c-direction by [Formula: see text]-8° leads to a good agreement between the theory and the experiment. The analysis of the high-pressure µSR data reveals that the new magnetic order appearing for pressures exceeding 1.5 GPa can not be described by keeping the propagation vector [Formula: see text]. Even the extreme case-decoupling the double-helical structure into four individual helices-remains inconsistent with the experiment. It is shown that the high-pressure magnetic phase which is a precursor of superconductivity is an incommensurate helical state with [Formula: see text].

A simple check valve for microfluidic point of care diagnostics.

Check valves are often essential components in microfluidic devices, enabling automated sample processing for diagnostics at the point of care. However, there is an unmet need for a check valve design that is compatible with rigid thermoplastic devices during all stages of development-from initial prototyping with a laser cutter to final production with injection molding. Here, we present simple designs for a passive, normally closed check valve that is manufactured from commonly available materials with a CO2 laser and readily integrated into prototype and production thermoplastic devices. The check valve consists of a thermoplastic planar spring and a soft elastomeric pad that act together to seal against fluid backflow. The valve's cracking pressure can be tuned by modifying the spring's planar geometry and thickness. Seal integrity is improved with the addition of a raised annular boss beneath the elastomeric pad. To demonstrate the valve's usefulness, we employ these valves to create a finger-operated on-chip reagent reservoir and a finger-actuated pneumatic pump. We also apply this check valve to passively seal a device to enable portable detection of RNA from West Nile virus in a laser-cut device.

Stability of multilead ST-segment "fingerprints" over time after percutaneous transluminal coronary angioplasty and its usefulness in detecting reocclusion.

Multilead ST-segment recordings taken during percutaneous transluminal coronary angioplasty (PTCA) could function as an individualized noninvasive template or "fingerprint," useful in evaluating transient ischemic episodes after leaving the catheterization laboratory. To evaluate the reproducibility of such ST-segment patterns over time, these changes were analyzed in patients grouped according to the time between occlusion and reocclusion. For the patients in group 1, the study required comparing their "fingerprints" in repeat balloon inflation during PTCA (reocclusion in less than 1 hour), for those in group 2, comparing ST "fingerprints" during PTCA with ST changes during spontaneous early myocardial infarction (reocclusion in 24 hours) and in group 3, comparing ST "fingerprints" with ST changes during repeat PTCA for restenosis greater than 1 month after the initial PTCA. The ST "fingerprints" among the 20 patients in group 1 were identical in 14 cases (70%) and clearly related in another 4 (20%). Of the 23 patients in group 2, 12 (52%) had the same and 8 (35%) had related patterns. Of 19 patients in group 3, 8 (42% had the same pattern and 8 (42%) had related patterns. Thus, ST fingerprints were the same or clearly related with reocclusion in the same patient from less than 1 hour to greater than 1 month after initial occlusion in 87% of patients overall, in 90% in less than 1 hour, in 87% in less than 24 hours and in 84% greater than 1 month later. Multilead pattern ST-segment "fingerprints" may serve as a noninvasive marker for detecting site-specific reocclusion.

Transient alterations of the QRS complex and ST segment during percutaneous transluminal balloon angioplasty of the right and left circumflex coronary arteries.

The dynamic QRS amplitude changes that appear during 1-vessel percutaneous transluminal coronary angioplasty of the right and left circumflex coronary arteries were studied in 20 patients using continuous 3-lead electrocardiographic recordings representing leads aVF, V2 and V5. The balloon inflations that produced the greatest extent of ST-segment deviation were identified for each lead ("maximally ischemic periods"). QRS amplitude measurements were performed manually at both the PR and shifted J-ST baselines at 10-second intervals during these periods to determine that baseline from which the R and S waves most nearly maintained their control amplitudes. There was no significant baseline relation for either the R or the S waves in leads V2 and V5 during ischemia. However, the R-wave changes in lead aVF were significantly associated with the PR- versus the J-ST-segment baseline (p = 0.007); the S wave, when it occurred, had no tendency for either baseline. The electrocardiographic records were also examined visually for characteristics of left posterior (inferior) "periischemic block" likely to occur uniquely in patients with a dominant right or left circumflex occlusion. There were 2 patients with obstruction of the right circumflex artery who exhibited the characteristics of periischemic block during percutaneous transluminal coronary angioplasty, as evidenced by an increase in R-wave duration, amplitude or both in lead aVF.

Relaxation rates of paramagnetic solutions: evaluation by nuclear magnetic resonance imaging.

Methods for accurate calculation of nuclear magnetic resonance relaxation times are presented. Data from inversion recovery sequences with different delay times were fitted to derive T1 information on water solutions of paramagnetic ions. T2 values of the same samples were obtained by fitting signals from a multiecho sequence. According to the theory, for the field strength used (0.5 T), T1's and T2's are nearly equal and the enhancement of relaxation rates is found to be directly proportional to molar concentration. Tests performed suggest the opportunity of using the same approach in studies of tissues.

Quantitative magnetic resonance imaging in cervical carcinoma: a report on 30 cases.

T1 and T2 relaxation times were calculated, before radiation therapy, in 30 patients with cervical carcinoma. Eight healthy young women were submitted to magnetic resonance imaging (MRI) to determine T1 and T2 times of the normal cervix. Magnetic resonance imaging was repeated, in 22 patients, during radiation therapy and at follow-up. During treatment and follow-up, patients with complete tumour response showed a significant T1 reduction compared with the pre-treatment values. With persistence of palpable or visible tumour, T1 times showed a small decrease during therapy, and a marked increase at subsequent examinations. The results suggest that the modifications of T1 times, during radiation therapy and follow-up, could be considered as a useful discriminant between patients with differing tumour response.

Puncture wound during CPR from sternotomy wires: case report and discussion of periresuscitation infection risks.

Performing resuscitations presents multiple infectious risks to critical care providers. Potential sources for infection include direct contact with blood and other bodily fluids and possible inoculation through needlestick injuries. In this article, we present a case of a cardiac care unit nurse who, while providing cardiopulmonary resuscitation, suffered a puncture wound to her left hand from the patient's sternotomy wires from previous cardiac surgery. The patient died despite these resuscitation efforts. He was seronegative for human immunodefiency virus, hepatitis B, and hepatitis C, and the nurse's wound healed without complications. This is the first reported case of such an injury occurring during a resuscitation. It demonstrates how a subtle, invisible, and unrecognized physical risk could cause infection in critical care providers.

A semi-automatic algorithm for reducing the time spent on routine follow-up of cardioverter defibrillators.

BACKGROUND: The routine follow-up of cardioverter defibrillators (CD) is a time-consuming procedure. AIM of the STUDY and METHODS: The present study was a prospective randomized cross-over evaluation on the clinical usefulness of a specific semi-automatic software algorithm (Quick Check) for CD follow-up, available in CPI Guidant systems (CD and programmer). Time-saving, while ensuring all the required data and patient safety, was evaluated in a large group of patients (105), recruited in different centers. In the same session and under a physician's supervision all patients underwent a follow-up with the aid of Quick Check or a standard follow-up, in a randomized sequence. Each patient served as his own control. RESULTS: In the overall population of 105 patients, the time spent for follow-up was reduced by Quick Check from 186+/-105 sec to 106+/-67 sec (p<0.0001) (43% reduction). The reduction in time spent for follow-up with Quick Check was the same (43% reduction) in patients with detected episodes (n=38) (from 241+/-144 sec to 138+/-95 sec (p<0.0001)) and in patients without detected episodes (n=67) (from 154+/-52 sec to 88+/-34 sec (p<0. 0001)). No adverse events or deletion of potentially useful data was detected by the supervising physician. CONCLUSIONS: Use of a specific software algorithm for routine follow-up of implanted CDs allows a significant shortening of the time spent on routine follow-up, thus reducing costs. The supervision of a physician is a guarantee of patient safety.

Band filling effect on polaron localization in La1-x(Ca(y)Sr1-y)xMnO3 manganites.

We report on a ìSR and 55 Mn NMR investigation of the magnetic order parameter as a function of temperature in the optimally doped La(5/8)(CaySr(1.y))(3/8)MnO3 and in the underdoped La1.xSrxMnO3 and La1.xCaxMnO3 metallic manganite families. The study is aimed at unravelling the effect of lattice distortions, implicitly controlled by the Ca-Sr isoelectronic substitution, from that of hole doping x on the Curie temperature TC and the order of the magnetic transition. At optimal doping, the transitions are second order at all y values, including the y = 1 (La(5/8)Ca(3/8)MnO3) end member. By contrast, they are first order in the underdoped samples, which show a finite (truncated) order parameter at the Curie point, including La(0.75)Sr(0.25)MnO3 whose TC is much higher than that of La(5/8)Ca(3/8)MnO3. The order parameter curves, on the other hand, exhibit a very minor dependence on x, if truncation is excepted. This suggests that the effective exchange interaction between Mn ions is essentially governed by local distortions, in agreement with the original double-exchange model, while truncation is primarily, if not entirely, an effect of under- or over-doping. A phase diagram, separating in the x.y plane polaron-driven first order transitions from regular second order transitions governed by critical fluctuations, is proposed for the La(1.x)(CaySr(1.y))xMnO3 system.

Crossover between magnetism and superconductivity in LaFeAsO with low H-doping level.

By making a systematic study of the hydrogen-doped LaFeAsO system by means of dc resistivity, dc magnetometry, and muon-spin spectroscopy, we addressed the question of universality of the phase diagram of rare-earth-1111 pnictides. In many respects, the behaviour of LaFeAsO(1-x)H(x) resembles that of its widely studied F-doped counterpart, with H(-) realizing a similar (or better) electron doping in the LaO planes. In an x = 0.01 sample we found a long-range spin-density wave (SDW) order with TN = 119 K, while at x = 0.05 the SDW establishes only at 38 K and, below Tc = 10 K, it coexists at a nanoscopic scale with bulk superconductivity. Unlike the abrupt magnetic-superconducting transition found in the La-1111 compound, the presence of a crossover region makes the H-doped system qualitatively similar to other Sm-1111, Ce-1111, and Nd-1111 families.

A magnetic glassy phase in Fe(1+y)Se(x)Te(1-x) single crystals.

The evolution of magnetic order in Fe1+ySexTe1-x crystals as a function of Se content was investigated by means of ac/dc magnetometry and muon-spin spectroscopy. Experimental results and self-consistent density functional theory calculations both indicate that muons are implanted in vacant iron-excess sites, where they probe a local field mainly of dipolar origin, resulting from an antiferromagnetic (AFM) bicollinear arrangement of iron spins. This long-range AFM phase becomes progressively disordered with increasing Se content. At the same time all the tested samples manifest a marked glassy character that vanishes for high Se contents. The presence of local electronic/compositional inhomogeneities most likely favours the growth of clusters whose magnetic moment 'freezes' at low temperature. This glassy magnetic phase justifies both the coherent muon precession seen at short times in the asymmetry data, as well as the glassy behaviour evidenced by both dc and ac magnetometry.