Magnetic structure of phase II in U(Ru(0.96)Rh(0.04))2Si2 determined by neutron diffraction under pulsed high magnetic fields.

We report neutron diffraction measurements on U(Ru(0.96)Rh(0.04))(2)Si(2) single crystal under pulsed high magnetic fields up to 30 T applied along the tetragonal c axis. The high-field experiments revealed that the field-induced phase II above 26 T corresponds to a commensurate up-up-down ferrimagnetic structure characterized by the wave vector q=(2/3,0,0) with the magnetic moments parallel to the c axis, which naturally explains the one-third magnetization plateau and the substantially changed Fermi surface in phase II. This a-axis modulated magnetic structure indicates that the phase II near the hidden order phase is closely related to the characteristic incommensurate magnetic fluctuations at Q(1)=(0.6,0,0) in the pure system URu(2)Si(2), in contrast to the pressure-induced antiferromagnetic order at Q(0)=(1,0,0).

Comparison of neonatal outcomes of cesarean sections performed under primary or secondary general anesthesia: a retrospective study.

BACKGROUND: The conversion of neuraxial anesthesia (NA) to general anesthesia (GA) during a cesarean section (CS) may be associated with a higher risk of neonatal morbidity by adding the undesirable effects of both these anesthesia techniques. We aimed to compare the neonatal morbidity of non-elective CS performed after conversion from NA to GA (secondary GA) vs. that after GA from the outset (primary GA). METHODS: We performed a monocentric retrospective study at the Angers University Hospital (France). All non-elective CSs performed under GA between January 2015 and December 2019 were included. The CSs were classified using a three-color coding system (green for non-urgent delivery, orange for urgent CS, and red for very urgent CS). The primary neonatal outcome was a composite of umbilical artery pH <7.10 or 5-min Apgar score <7. The crude and adjusted odds ratios (OR) for the risk of neonatal morbidity associated with secondary GA were estimated. RESULTS: We included 247 patients, of whom 101 (41.3%) had a secondary GA and 146 (58.7%) had primary GA. In the secondary GA group, 86.1% (87/101) had epidural anesthesia and 13.9% (14/101) had spinal anesthesia. Multivariate analysis showed no difference in neonatal morbidity between the two groups (adjusted odds ratio 1.18, 95% CI 0.56 to 2.51). CONCLUSIONS: Our study found insufficient evidence to identify a difference in neonatal outcomes between secondary compared with primary GA for CS, regardless of the level of emergency. However, our study is underpowered and additional studies are needed to confirm these data.

Field-induced freezing of a quantum spin liquid on the kagome lattice.

We report (17)O NMR measurements in the S=1/2 (Cu(2+)) kagome antiferromagnet Herbertsmithite ZnCu(3)(OH)(6)Cl(2) down to 45 mK in magnetic fields ranging from 2 to 12 T. While Herbertsmithite displays a gapless spin-liquid behavior in zero field, we uncover an instability toward a spin-solid phase at sub-Kelvin temperature induced by an applied magnetic field. The latter phase shows largely suppressed moments ≲0.1 µ(B) and gapped excitations. The H-T phase diagram suggests the existence of a quantum critical point at the small but finite magnetic field µ(0)H(c)=1.55(25) T. We discuss this finding in light of the perturbative Dzyaloshinskii-Moriya interaction which was theoretically proposed to sustain a quantum critical regime for the quantum kagome Heisenberg antiferromagnet model.

Biocomposite hydrogels with carboxymethylated, nanofibrillated cellulose powder for replacement of the nucleus pulposus.

Biocomposite hydrogels with carboxymethylated, nanofibrillated cellulose (c-NFC) powder were prepared by UV polymerization of N-vinyl-2-pyrrolidone with Tween 20 trimethacrylate as a cross-linking agent for replacement of the native, human nucleus pulposus (NP) in intervertebral disks. The swelling ratios and the moduli of elasticity in compression of neat and biocomposite hydrogels were evaluated in dependence of c-NFC concentration (ranging from 0 to 1.6% v/v) and degree of substitution (DS, ranging from 0 to 0.23). The viscoelastic properties in shear and the material relaxation behavior in compression were measured for neat and biocomposite hydrogels containing 0.4% v/v of fibrils (DS ranging from 0 to 0.23), and their morphologies were characterized by cryo-scanning electron microscopy (cryo-SEM). The obtained results show that the biocomposite hydrogels can successfully mimic the mechanical and swelling behavior of the NP. In addition, the presence of the c-NFC shows lower strain values after cyclic compression tests and consequently creates improved material relaxation properties compared with neat hydrogels. Among the tested samples, the biocomposite hydrogel containing 0.4% v/v of c-NFC with a DS of 0.17 shows the closest behavior to native NP. Further investigation should focus on evaluation and improvement of the long-term relaxation behavior.

Photon regeneration experiment for axion search using x-rays.

In this Letter we describe our novel photon regeneration experiment for the axionlike particle search using an x-ray beam with a photon energy of 50.2 and 90.7 keV, two superconducting magnets of 3 T, and a Ge detector with a high quantum efficiency. A counting rate of regenerated photons compatible with zero has been measured. The corresponding limits on the pseudoscalar axionlike particle-two-photon coupling constant is obtained as a function of the particle mass. Our setup widens the energy window of purely terrestrial experiments devoted to the axionlike particle search by coupling to two photons. It also opens a new domain of experimental investigation of photon propagation in magnetic fields.

Universal magnetic structure of the half-magnetization phase in Cr-based spinels.

Using an elastic neutron scattering technique under a pulsed magnetic field up to 30 T, we determined the magnetic structure in the half-magnetization plateau phase in the spinel CdCr2O4. The magnetic structure has a cubic P4{3}32 symmetry, which is the same as that observed in HgCr2O4. This suggests that despite their different zero-field ground states a universal field-induced spin-lattice coupling mechanism is at work in the Cr-based spinels.

40-Tesla pulsed-field cryomagnet for single crystal neutron diffraction.

We present the first long-duration and high duty cycle 40-T pulsed-field cryomagnet addressed to single crystal neutron diffraction experiments at temperatures down to 2 K. The magnet produces a horizontal field in a bi-conical geometry, ±15° and ±30° upstream and downstream of the sample, respectively. Using a 1.15 MJ mobile generator, magnetic field pulses of 100 ms length are generated in the magnet, with a rise time of 23 ms and a repetition rate of 6-7 pulses per hour at 40 T. The setup was validated for neutron diffraction on the CEA-CRG three-axis spectrometer IN22 at the Institut Laue Langevin.

Field-induced spin-density wave beyond hidden order in URu2Si2.

URu2Si2 is one of the most enigmatic strongly correlated electron systems and offers a fertile testing ground for new concepts in condensed matter science. In spite of >30 years of intense research, no consensus on the order parameter of its low-temperature hidden-order phase exists. A strong magnetic field transforms the hidden order into magnetically ordered phases, whose order parameter has also been defying experimental observation. Here, thanks to neutron diffraction under pulsed magnetic fields up to 40 T, we identify the field-induced phases of URu2Si2 as a spin-density-wave state. The transition to the spin-density wave represents a unique touchstone for understanding the hidden-order phase. An intimate relationship between this magnetic structure, the magnetic fluctuations and the Fermi surface is emphasized, calling for dedicated band-structure calculations.

Tunnel diode oscillator measurements of the upper critical magnetic field of FeTe(0.5)Se(0.5).

Temperature dependence of the upper critical magnetic field (Hc2) of single crystalline FeTe0.5Se0.5(Tc = 14.5 K) have been determined by tunnel diode oscillator-based measurements in magnetic fields of up to 55 T and temperatures down to 1.6 K. The Werthamer-Helfand-Hohenberg model accounts for the data for magnetic field applied both parallel (H ‖ ab) and perpendicular (H ‖ c) to the iron conducting plane, in line with a single band superconductivity. Whereas Pauli pair breaking is negligible for H ‖ c, Pauli contribution is evidenced for H ‖ ab with Maki parameter α = 1.4, corresponding to Pauli field HP = 79 T. As a result, the Hc2 anisotropy [Formula: see text] which is already rather small at Tc (γ = 1.6) further decreases as the temperature decreases and becomes smaller than 1 at liquid helium temperatures.

[Accidental out-of-hospital deliveries]. / Accouchements inopinés extrahospitaliers.

Unexpected out-of-hospital delivery accounts for 0.5% of the total number of delivery in France. The parturient is placed under constant multiparametric monitoring. Fetus heart rate is monitored thanks to fetal doppler. A high concentration mask containing a 50-to-50 percent mix of O(2) and NO performs analgesia. Assistance of mobile pediatric service can be required under certain circumstances such as premature birth, gemellary pregnancy, maternal illness or fetal heart rate impairment. Maternal efforts should start only when head reaches the pelvic floor, only if the rupture of the membranes is done and the dilation is completed. The expulsion should not exceed 30 min. Episiotomy should not be systematically performed. A systematic active management of third stage of labour is recommended. Routine care such as warming and soft drying can be performed when the following conditions are fulfilled: clear amniotic liquid, normal breathing, crying and a good tonus. Every 30 seconds assessment of heart rate, breathing quality and muscular tonus then guide the care. The redaction of birth certificate is a legal obligation and rests with the attending doctor.

A 31 T split-pair pulsed magnet for single crystal x-ray diffraction at low temperature.

We have developed a pulsed magnet system with panoramic access for synchrotron x-ray diffraction in magnetic fields up to 31 T and at low temperature down to 1.5 K. The apparatus consists of a split-pair magnet, a liquid nitrogen bath to cool the pulsed coil, and a helium cryostat allowing sample temperatures from 1.5 up to 250 K. Using a 1.15 MJ mobile generator, magnetic field pulses of 60 ms length were generated in the magnet, with a rise time of 16.5 ms and a repetition rate of 2 pulses/h at 31 T. The setup was validated for single crystal diffraction on the ESRF beamline ID06.

A 30 T pulsed magnet with conical bore for synchrotron powder diffraction.

We report on the design, construction, and operation of a horizontal field, 30 T magnet system with a conical bore optimized for synchrotron x-ray powder diffraction. The magnet offers ±31° optical access downstream of the sample, which allows to measure a sufficiently large number of Debye rings for an accurate crystal structure analysis. Combined with a 290 kJ generator, magnetic field pulses of 60 ms length were generated in the magnet, with a rise time of 4.1 ms and a repetition rate of 6 pulses/h at 30 T. The coil is mounted inside a liquid nitrogen bath. A liquid helium flow cryostat reaches into the coil and allows sample temperature between 5 and 250 K. The setup was used on the European Synchrotron Radiation Facility beamlines ID20 and ID06.

[Use of the Airtraq by inexperienced physicians supervised during a series of tracheal intubation in adult patient with anticipated difficult airway]. / Utilisation de l'Airtraq par des praticiens inexpérimentés supervisés pour une série de patients adultes prévus difficiles à intuber.

INTRODUCTION: The Airtraq optical laryngoscope (Vygon, Écouen, France) is a new intubation device designed to provide a view of the glottis without alignment of the oral, pharyngeal and laryngeal axes. In recent literature, the efficiency of the Airtraq even in difficult intubation and its short learning curve were characterized. The goal of our study is to evaluate Airtraq efficiency when use by inexperienced physicians in anticipated difficult intubation adult patients. METHODS: The patients showing at least one of the four difficult intubation predictors (history of difficult intubation, thyromental distance less than 60mm, mouth opening less than 35 mm and Mallampati class 3 or 4 were included. Before induction of anaesthesia, the inexperienced physicians participating the study received a short oral formation on the use of the Airtraq. For each intubation manoeuvres, the participant were supervised by an expert in Airtraq handling. The Cormack and Lehane grade of direct laryngoscopy view, the duration times to best glottis view and to intubate the trachea, the success or failure of tracheal intubation, the drop in arterial oxygen saturation of below 95%, the need for external manipulation, and the difficulties met by the operators were noted. RESULTS: Twenty patients were included over a month period. Thirteen had a history of difficult intubation, eight a thyromental distance less than 60mm, nine a mouth opening less than 35 mm and 12 patients were classified as Mallampati IV. The success rate of tracheal intubation with the Airtraq laryngoscope was 80%. Times to best glottis view and to complete tracheal intubation were 28 and 47 s, respectively. Four tracheal intubation failures were encountered. The LMA Fastrach and the flexible fiberoscope were used respectively in one and three patients. DISCUSSION: In the majority of the cases, the insertion of the Airtraq, the visualization of the glottis and the subsequent intubation were easy and rapid, without arterial oxygen desaturation. However, the four tracheal intubation failures associated with prolonged tracheal intubation times in some patients highlight the fact that the Airtraq laryngoscope requires a clinical training process particularly in case of anticipated difficult airway management situations.

Neutron diffraction study on the multiple magnetization plateaus in TbB4 under pulsed high magnetic field.

We present the first application of pulsed high magnetic fields up to 30 T for neutron diffraction experiments. As the first study, field variations of a couple of magnetic Bragg reflections have successfully been measured in the frustrated antiferromagnet TbB4. The results show that the conventional models fail, and a model, which is a mixture of the XY- and the Ising-type moments, matches for the half-magnetization state. We deduce an interaction that stabilizes an orthogonal moment arrangement as an origin of the unusual magnetization plateaus. Our results demonstrate the powerfulness of the present pulsed magnetic fields neutron diffraction system.

(17) O NMR study of the intrinsic magnetic susceptibility and spin dynamics of the quantum kagome antiferromagnet ZnCu3(OH)(6)Cl(2).

We report, through 17O NMR, an unambiguous local determination of the intrinsic kagome lattice spin susceptibility as well as that created around nonmagnetic defects arising from natural Zn/Cu exchange in the S=1/2 (Cu2+) herbertsmithite ZnCu3(OH)6Cl2 compound. The issue of a singlet-triplet gap is addressed. The magnetic response around a defect is found to markedly differ from that observed in nonfrustrated antiferromagnets. Finally, we discuss our relaxation measurements in the light of Cu and Cl NMR data and suggest a flat q dependence of the excitations.

Direct Observation of the High Magnetic Field Effect on the Jahn-Teller State in TbVO4.

We report the first direct observation of the influence of high magnetic fields on the Jahn-Teller (JT) transition in TbVO(4). Contrary to spectroscopic and magnetic methods, x-ray diffraction directly measures the JT distortion; the splitting between the (311)/(131) and (202)/(022) pairs of Bragg reflections is proportional to the order parameter. Our experimental results are compared to mean-field calculations, taking into account all possible orientations of the grains relative to the applied field, and qualitative agreement is obtained.

Dzyaloshinsky-Moriya anisotropy in the spin-1/2 kagome compound ZnCu3(OH)6Cl2.

We report the determination of the Dzyaloshinsky-Moriya interaction, the dominant magnetic anisotropy term in the kagome spin-1/2 compound ZnCu3(OH)6Cl2. Based on the analysis of the high-temperature electron spin resonance (ESR) spectra, we find its main component |Dz|=15(1) K to be perpendicular to the kagome planes. Through the temperature dependent ESR linewidth, we observe a building up of nearest-neighbor spin-spin correlations below approximately 150 K.

Quantum magnetism in the paratacamite family: towards an ideal kagomé lattice.

We report muon spin rotation measurements on the S=1/2 (Cu2+) paratacamite ZnxCu4-x(OH)6Cl2 family. Despite a Weiss temperature of approximately -300 K, the x=1 compound is found to have no transition to a magnetic frozen state down to 50 mK as theoretically expected for the kagomé Heisenberg antiferromagnet. We find that the limit between a dynamical and a partly frozen ground state occurs around x=0.5. For x=1, we discuss the relevance to a singlet picture.

Ground state of the kagomé-like S=1/2 antiferromagnet volborthite Cu3V2O7(OH)2 x 2H2O.

The volborthite compound is one of the very few realizations of S=1/2 quantum spins on a highly frustrated kagomé-like lattice. Low-T SQUID measurements reveal a broad magnetic transition below 2 K which is further confirmed by a peak in the 51V nuclear spin relaxation rate (1/T1) at 1.4 K +/- 0.2 K. Through 51V NMR, the ground state (GS) appears to be a mixture of different spin configurations, among which 20% corresponds to a well defined short-range order, possibly of the sqrt(3) x sqrt(3) type. While the freezing involves all the Cu2+ spins, only 40% of the copper moment is actually frozen which suggests that quantum fluctuations strongly renormalize the GS.