Electrical Control of Structural and Physical Properties via Strong Spin-Orbit Interactions in Sr_{2}IrO_{4}.

Electrical control of structural and physical properties is a long-sought, but elusive goal of contemporary science and technology. We demonstrate that a combination of strong spin-orbit interactions (SOI) and a canted antiferromagnetic Mott state is sufficient to attain that goal. The antiferromagnetic insulator Sr_{2}IrO_{4} provides a model system in which strong SOI lock canted Ir magnetic moments to IrO_{6} octahedra, causing them to rigidly rotate together. A novel coupling between an applied electrical current and the canting angle reduces the Néel temperature and drives a large, nonlinear lattice expansion that closely tracks the magnetization, increases the electron mobility, and precipitates a unique resistive switching effect. Our observations open new avenues for understanding fundamental physics driven by strong SOI in condensed matter, and provide a new paradigm for functional materials and devices.

Doping Evolution of Magnetic Order and Magnetic Excitations in (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7}.

We use resonant elastic and inelastic x-ray scattering at the Ir-L_{3} edge to study the doping-dependent magnetic order, magnetic excitations, and spin-orbit excitons in the electron-doped bilayer iridate (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7} (0≤x≤0.065). With increasing doping x, the three-dimensional long range antiferromagnetic order is gradually suppressed and evolves into a three-dimensional short range order across the insulator-to-metal transition from x=0 to 0.05, followed by a transition to two-dimensional short range order between x=0.05 and 0.065. Because of the interactions between the J_{eff}=1/2 pseudospins and the emergent itinerant electrons, magnetic excitations undergo damping, anisotropic softening, and gap collapse, accompanied by weakly doping-dependent spin-orbit excitons. Therefore, we conclude that electron doping suppresses the magnetic anisotropy and interlayer couplings and drives (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7} into a correlated metallic state with two-dimensional short range antiferromagnetic order. Strong antiferromagnetic fluctuations of the J_{eff}=1/2 moments persist deep in this correlated metallic state, with the magnon gap strongly suppressed.

Novel magnetism of Ir5+(5d4) Ions in the double perovskite Sr2YIrO6.

We synthesize and study single crystals of a new double-perovskite Sr2YIrO6. Despite two strongly unfavorable conditions for magnetic order, namely, pentavalent Ir5+(5d4) ions which are anticipated to have Jeff=0 singlet ground states in the strong spin-orbit coupling (SOC) limit and geometric frustration in a face-centered cubic structure formed by the Ir5+ ions, we observe this iridate to undergo a novel magnetic transition at temperatures below 1.3 K. We provide compelling experimental and theoretical evidence that the origin of magnetism is in an unusual interplay between strong noncubic crystal fields, local exchange interactions, and "intermediate-strength" SOC. Sr2YIrO6 provides a rare example of the failed dominance of SOC in the iridates.

Tuning magnetic coupling in Sr2IrO4 thin films with epitaxial strain.

We report x-ray resonant magnetic scattering and resonant inelastic x-ray scattering studies of epitaxially strained Sr2IrO4 thin films. The films were grown on SrTiO3 and (LaAlO3)0.3(Sr2AlTaO6)0.7 substrates, under slight tensile and compressive strains, respectively. Although the films develop a magnetic structure reminiscent of bulk Sr2IrO4, the magnetic correlations are extremely anisotropic, with in-plane correlation lengths significantly longer than the out-of-plane correlation lengths. In addition, the compressive (tensile) strain serves to suppress (enhance) the magnetic ordering temperature TN, while raising (lowering) the energy of the zone-boundary magnon. Quantum chemical calculations show that the tuning of magnetic energy scales can be understood in terms of strain-induced changes in bond lengths.

Magnetic field reveals vanishing Hall response in the normal state of stripe-ordered cuprates.

The origin of the weak insulating behavior of the resistivity, i.e. [Formula: see text], revealed when magnetic fields (H) suppress superconductivity in underdoped cuprates has been a longtime mystery. Surprisingly, the high-field behavior of the resistivity observed recently in charge- and spin-stripe-ordered La-214 cuprates suggests a metallic, as opposed to insulating, high-field normal state. Here we report the vanishing of the Hall coefficient in this field-revealed normal state for all [Formula: see text], where [Formula: see text] is the zero-field superconducting transition temperature. Our measurements demonstrate that this is a robust fundamental property of the normal state of cuprates with intertwined orders, exhibited in the previously unexplored regime of T and H. The behavior of the high-field Hall coefficient is fundamentally different from that in other cuprates such as YBa2Cu3O6+x and YBa2Cu4O8, and may imply an approximate particle-hole symmetry that is unique to stripe-ordered cuprates. Our results highlight the important role of the competing orders in determining the normal state of cuprates.

Pair density wave at high magnetic fields in cuprates with charge and spin orders.

In underdoped cuprates, the interplay of the pseudogap, superconductivity, and charge and spin ordering can give rise to exotic quantum states, including the pair density wave (PDW), in which the superconducting (SC) order parameter is oscillatory in space. However, the evidence for a PDW state remains inconclusive and its broader relevance to cuprate physics is an open question. To test the interlayer frustration, the crucial component of the PDW picture, we perform transport measurements on charge- and spin-stripe-ordered La1.7Eu0.2Sr0.1CuO4 and La1.48Nd0.4Sr0.12CuO4 in perpendicular magnetic fields (H⊥), and also with an additional field applied parallel to CuO2 layers (H∥). We detect several phenomena predicted to arise from the existence of a PDW, including an enhancement of interlayer SC phase coherence with increasing H∥. These data also provide much-needed transport signatures of the PDW in the regime where superconductivity is destroyed by quantum phase fluctuations.

Tuning from failed superconductor to failed insulator with magnetic field.

Do charge modulations compete with electron pairing in high-temperature copper oxide superconductors? We investigated this question by suppressing superconductivity in a stripe-ordered cuprate compound at low temperature with high magnetic fields. With increasing field, loss of three-dimensional superconducting order is followed by reentrant two-dimensional superconductivity and then an ultraquantum metal phase. Circumstantial evidence suggests that the latter state is bosonic and associated with the charge stripes. These results provide experimental support to the theoretical perspective that local segregation of doped holes and antiferromagnetic spin correlations underlies the electron-pairing mechanism in cuprates.

In-center daily on-line hemodiafiltration: a 4-year experience in children.

Our daily dialysis program was started in September 2002: in-center daily on-line hemodiafiltration (DIH) was carried out in 3-hour sessions, 5 - 6 times weekly, on-line assessment KT/Vurea of minimal 1.5 per session, polysulfone membranes. 12 children were included: median age 7.4 years (2.10 - 16.8 years), renal residual function less than 3 ml/min/1.73 m2 (Kcreat + Kurea/2), vascular access central catheter (n = 4) or fistula (n = 8), 7/12 being converted from peritoneal dialysis to DIH. Median follow-up on DIH was 11 months (4 - 43 months), endpoint was kidney transplantation (11/12) or transfer to another center (1/12). Monthly assessments of dialysis parameters (KT/Vurea, predialysis phosphatemia), diet survey (3 consecutive days), medications (number of antihypertensive drugs, phosphate chelators, potassium chelators) and statural growth were performed. At start of DIH, diet intake due to medical prescription and limited appetite was restrictive with limitation in water, salt (20 mmol/day), potassium and proteins (median 35 g/day, range 20 - 80 g); only 2/12 children were free of antihypertensive drugs, all received phosphate and potassium chelators, and growth retardation occurred (7/12 in prepubertal children, median height SDS -1.52) despite rhGH therapy (5/12 patients). At the end of DIH, diet was free, protein intake high (2 - 3 g/kg/day, range 30 - 100), 10/12 children were free of antihypertensive drugs, 4/12 received potassium chelators, 1/12 received phosphate chelators. All the prepubertal children at inclusion (n = 7) showed catch-up growth with a median growth rate of 0.8 cm/month (0.5 - 1.6 cm/ month). DIH allowed to maintain predialysis phosphatemia in a low normal range (median 1.23 mmol/l, range 1.65 - 0.63), without (11/12 children) need of phosphate chelators. Thanks to DIH children, parents and team care discovered during DIH a new way of life with motivated children, showing natural compliance (no diet restriction, no or few drugs), and most of all children developing with catch-up of growth.

Immunohistochemical analysis of hepatic ganglioside distribution following a partial hepatectomy and exposure to different hyperbaric oxygen treatments.

Ganglioside GM3(Neu5Ac) expression is highly increased in liver 54h following 15% partial hepatectomy in pre-operatively oxygenated rats. GM3(Neu5Gc), GM2, GalNAc-GM1b and gangliosides of the neolacto-series are less affected. GM3(Neu5Ac) is a potent inhibitor of epidermal growth factor signaling. Since GM3(Neu5Ac) growth inhibitory effect depends on its cellular localization, the aim of this study was to detect ganglioside cellular localization during liver regeneration. The experiment was performed using the same rat model which previously showed increased ganglioside expression and more efficient liver regeneration. Frozen sections of liver were analyzed using confocal microscopy after labeling for binding of five ganglioside-specific antibodies, with or without hepatocyte membrane permeabilization. Ganglioside precursors, ceramide (Cer), monohexaosylceramide and lactosylceramide (LacCer) were determined by high-performance thin-layer chromatography. Apoptosis was assessed by fluorescein-dUTP end-labeling of fragmented DNA. Liver of pre-operative oxygenated rats showed high perinuclear labeling of GM3(Neu5Ac) which was absent in post-operative oxygenated and control animals. In the same group, Cer content was lower, monohexaosylceramide and LacCer were absent, and content of apoptotic cells was significantly the lowest, compared to other groups examined (F=20.36, p=0.0001). These findings indicate that ganglioside GM3(Neu5Ac) may be involved in mediation of beneficial effects of pre-operatively oxygenation during the liver regeneration.

[Clinical and epidemiological profile of pediatric uveitis, course of inflammatory uveitis treated with anti-TNF alpha]. / Profil clinique et épidémiologique des uvéites pédiatriques, évolution des uvéites inflammatoires sous anti-TNF alpha.

INTRODUCTION: Uveitis is the leading cause of acquired childhood blindness with a prevalence of 30 cases per 100,000 inhabitants. There are multiple causes ; nevertheless, there is no standardized etiological assessment. The goal of our study is to define an epidemiological and clinical profile of uveitis diagnosed in a university hospital and their course when treated with anti-tumor necrosis factor (TNF) α. PATIENTS AND METHODS: All cases of uveitis under 18 years old, from 1994 to 2016, were included. Post-traumatic, post-surgical, pseudo-uveitis and retinopathy of prematurity were excluded. Demographic data, patient history, initial ophthalmological status, etiologic assessment data and treatments already underway were collected. RESULTS: Ninety cases of pediatric uveitis were included, among which were 16.7 % infectious uveitis, 38.9 % inflammatory uveitis and 44.4 % idiopathic uveitis. Etiologic investigations were considered incomplete in 45 % of idiopathic uveitis cases. Treatment with anti-TNFα was selected for 15.5 % of patients. In total, 33 % of patients treated with etanercept required other anti-TNFα drugs due to a lack of control of inflammation. Infliximab and adalimumab successfully managed to control inflammation in 28.6 % of cases each. DISCUSSION: Diagnostic criteria based adult systemic disease are sometimes inappropriate for children. The advent of anti-TNFα appears to improve the visual prognosis of inflammatory uveitis resistant to conventional immunosuppressant therapy, but we still need to perfect protocols for their use. CONCLUSION: There are neither standardized etiological assessment nor clear diagnostic and therapeutic protocols for children. TNFα inhibitors are more effective in controlling inflammation in severe pediatric uveitis.

Decoupling of magnetism and electric transport in single-crystal (Sr1-x A x )2IrO4 (A = Ca or Ba).

We report a systematical structural, transport and magnetic study of Ca or Ba doped Sr2IrO4 single crystals. Isoelectronically substituting Ca2+ (up to 15%) or Ba2+ (up to 4%) ion for the Sr2+ ion provides no additional charge carriers but effectively changes the lattice parameters in Sr2IrO4. In particular, 15% Ca doping considerably reduces the c-axis and the unit cell by nearly 0.45% and 1.00%, respectively. These significant, anisotropic compressions in the lattice parameters conspicuously cause no change in the Néel temperature which remains at 240 K, but drastically reduces the electrical resistivity by up to five orders of magnitude or even precipitates a sharp insulator-to-metal transition at lower temperatures, i.e. the vanishing insulating state accompanies an unchanged Néel temperature in (Sr1-x A x )2IrO4. This observation brings to light an intriguing difference between chemical pressure and applied pressure, the latter of which does suppress the long-range magnetic order in Sr2IrO4. This difference reveals the importance of the Ir1-O2-Ir1 bond angle and homogenous volume compression in determining the magnetic ground state. All results, along with a comparison drawn with results of Tb and La doped Sr2IrO4, underscore that the magnetic transition plays a nonessential role in the formation of the charge gap in the spin-orbit-tuned iridate.

Investigations of metastable Ca2IrO4 epitaxial thin-films: systematic comparison with Sr2IrO4 and Ba2IrO4.

We have synthesized thermodynamically metastable Ca2IrO4 thin-films on YAlO3 (110) substrates by pulsed laser deposition. The epitaxial Ca2IrO4 thin-films are of K2NiF4-type tetragonal structure. Transport and optical spectroscopy measurements indicate that the electronic structure of the Ca2IrO4 thin-films is similar to that of Jeff = 1/2 spin-orbit-coupled Mott insulator Sr2IrO4 and Ba2IrO4, with the exception of an increased gap energy. The gap increase is to be expected in Ca2IrO4 due to its increased octahedral rotation and tilting, which results in enhanced electron-correlation, U/W. Our results suggest that the epitaxial stabilization growth of metastable-phase thin-films can be used effectively for investigating layered iridates and various complex-oxide systems.

Expression pattern of PAX3 and PAX6 genes during human embryogenesis.

The expression of human PAX6 and PAX3 genes was investigated in 6 human 6-9 week old conceptuses by in situ hybridization. During human embryonic development (6-8 developmental weeks), PAX6 was expressed in the ventricular zone of telencephalon and diencephalon, and in the ventricular and ventral intermediate zones of medulla oblongata and spinal cord. PAX6 expression was detected in both layers of the optic cup, optic stalk and prospective corneal epithelium. Infundibulum and Rathke's pouch of the pituitary gland showed hybridization signal as well. In the early fetal period (9 developmental weeks) PAX6 expression increased in the spinal cord. In the eye, hybridization signal characterized the corneal and lens epithelium, pigmented and neural retina, while it was missing in the optic disc and nerve. In a 6-week human embryo, transcripts of PAX3 gene were observed in the ventricular zone at the mesencephalic-rhombencephalic border, and in the dorsal part of the ventricular zone and the roof plate of the medulla oblongata and the spinal cord. In the 8-9-week fetus, PAX3 expression increased in dorsal parts of the spinal cord. PAX3 characterized ectomesenchyme of the upper and lower jaw, and tongue. During early human development, PAX6 and PAX3 genes seem to be involved in the brain regionalization and establishment of dorso-ventral polarity of the spinal cord. Additionally, PAX6 participates in organogenesis of the eye and the pituitary gland, and PAX3 in the development of face and neck mesenchyme.

Expression of PAX2 gene during human development.

The expression of human paired-box-containing PAX2 gene was examined in 7 human conceptuses 6 to 9 weeks old by in situ hybridization. The embryos were collected after legal abortions, embedded in paraffin, serially cut in transversal direction and treated with S35 labeled probe for PAX2. In the neural tube of 6-week embryos, PAX2 was expressed in the outer part of the ventricular zone on both sides of the sulcus limitans. At later stages, it was expressed in the intermediate zone of the spinal cord, both in alar and basal plates except in the region of motor neuroblasts. In the brain, expression of PAX2 extended from mesencephalic-rhombencephalic border along the entire rhombencephalon in a manner similar to that described for the spinal cord. Expression of PAX2 gene in the eye was seen in the optic cup and stalk, and later in the optic disc and nerve. In the ear, expression was restricted to the part of the otic vesicle flanking the neural tube and later to the utricle and cochlea. Expression of PAX2 was observed in developing kidneys as well. During human development PAX2 has a spatially restricted expression along the compartmental boundaries of the neural tube, and within developing eye, ear and kidneys. Differentiation of those organs seems to be mediated by PAX2 gene at the defined stages of human development.

Osteoblastic response to the defective matrix in the osteogenesis imperfecta murine (oim) mouse.

This work examines the cellular pathophysiology associated with the weakened bone matrix found in a murine model of osteogenesis imperfecta murine (oim). Histomorphometric analysis of oim/oim bone showed significantly diminished bone mass, and the osteoblast and osteoclast histomorphometric parameters were increased in the oim/oim mice, compared with wild-type (+/+) mice. To assess osteoblast activity, a rat Col1a1 promoter linked to the chloramphenicol acetyltransferase reporter transgene was bred into the oim model. At 8 d and 1 month of age, no difference in transgene activity between oim and control mice was observed. However, at 3 months of age, chloramphenicol acetyl transferase activity was elevated in oim/oim;Tg/Tg, compared with +/+;Tg/Tg and oim/+;Tg/Tg. High levels of urinary pyridinoline crosslinks in the oim/oim;Tg/Tg mice were present at all ages, reflecting continuing high bone resorption. Our data portray a state of ineffective osteogenesis in which the mutant mouse never accumulates a normal quantity of bone matrix. However, it is only after the completion of the rapid growth phase that the high activity of the oim/oim osteoblast can compensate for the high rate of bone resorption. This relationship between bone formation and resorption may explain why the severity of osteogenesis imperfecta decreases after puberty is completed. The ability to quantify high bone turnover and advantages of using a transgene that reflects osteoblast lineage activity make this a useful model for studying interventions designed to improve the bone strength in osteogenesis imperfecta.

Hemodialysis in children: principles and practice.

Hemodialysis has benefited from major progress over the last decade, improvements in technology and in clinical management. The morbidity over the sessions have decreased, seizures being exceptional, hypotensive episodes or headaches rare and pain related to the fistula puncture is effectively prevented by xylocaine ointment. The development of urea kinetic modeling allows the calculation of the dialysis dose Kt/V, and an indirect assessment of the protein intake. Even if the validity of these parameters are questioned their analyse provides an assessment and therefore is a "good thing." The patient also benefited from the technological revolution. The newer machines provide for precise control of ultrafiltration volumetrically assessed, buffered bicarbonate became a standard technique, biocompatible and highly efficient membranes and specific material available for infants have been developed. More recently the concept of ultrapure dialysate, ie, free of microbiological contamination, germs and endotoxins was developed, as was the availability of continuous blood volume monitoring during the session. The hemodiafiltration modality especially with the on line concept, because of all the advantages, should not be limited only to patients at risk.

Prevalence of G-6-PD deficiency in the Croatian Adriatic Coast population.

BACKGROUND: The objective of this study was to determine the prevalence of glucose-6-phosphate dehydrogenase (G-6-PD) deficiency among the population of the Croatian Adriatic Coast, part of the Mediterranean basin. METHODS: The fluorescent spot test was used to screen 2,726 randomly selected high school students in the Croatian Adriatic coastal area. Fluorescence readings were performed at the beginning and at 3, 6, 10, and 25 min of incubation. Results were classified into the following three groups: bright fluorescence (BF), weak fluorescence (WF), and no fluorescence (NF). All NF and WF samples at 3 min were quantitatively measured using the spectrophotometric method. RESULTS: Twelve persons, 10 boys and 2 girls, were found to be deficient in G-6-PD, rendering a 0.44% prevalence of G-6-PD deficiency. All NF samples at fluorescent spot test were G-6-PD-deficient. WF at 3 min of the incubation period was present in 33 (1.2%) subjects, and only 2 (6%) were true positive. Fluorescence reading at 10 min of incubation omits five (41%) of the G-6-PD deficient samples. CONCLUSIONS: Prevalence of G-6-PD deficiency in the Croatian Adriatic coastal population is 0.44%. Fluorescent spot test for moderate enzyme deficiency is reliable in early fluorescence reading.

Normal statural growth in 2 infants on chronic peritoneal dialysis: anecdotal or whole management-related.

AIMS: Growth retardation is usual in children on chronic peritoneal dialysis (CPD). Despite attention to many contributing factors (nutrition, dialysis dose, hemoglobin level, adynamic bone disease, hyperparathyroidism or rickets, growth hormone resistance, etc.), normal growth is rarely obtained in infants on CPD. MATERIALS AND METHODS: We had the chance to observe normal growth over a 1 year period in 2 consecutively treated infants on CPD. Louise (renal hypodysplasia) required CPD at the age of 1 month: creatinine 430 micromol/l; oliguric, creatinine clearance lower than 5 ml/min/1.73 m2. Nutrition was achieved orally with human milk during the first 6 months of life. Tidal peritoneal dialysis allowed a high dialysis dose Kt/V urea 3.8/week and Kcreatinine 105 l/week/1.73 m2. Hemoglobin was maintained over 13 g/dl and low levels of vitamin D analogue were prescribed to avoid adynamic bone disease. At the age of 1 year her height was 75 cm. i.e. in the normal range for age. Madeline (renal hypodysplasia) commenced on CPD at the age of 6 weeks and managed similarly. Her height at 1 year of age was 74 cm. RESULTS: In our 20 years of experience with children on dialysis, these 2 cases of normal statural growth for age at 1 year warrant discussion. As well as nutritional support, the new and recent therapeutic options in our team were: firstly, to avoid high doses of activated vitamin D to control PTH, as high doses are able to induce both a risk of adynamic bone disease and a direct bone cartilage toxicity: secondly, to maintain normal hemoglobin level; and thirdly, to deliver a high dialysis dose (urea, creatinine clearance) based on an individually adapted prescription. CONCLUSION: We feel this management approach is necessary to achieve optimal statural growth in children on chronic peritoneal dialysis. But this management concept only based on clinical anecdotal observations needs further evaluation before its use in clinical guidelines.

Use of intraperitoneal pressure, ultrafiltration and purification dwell times for individual peritoneal dialysis prescription in children.

Tolerance of peritoneal dialysis is, in a part, dependent on intraperitoneal dialysate volume. Measurement of intraperitoneal pressure (IPP) in cm of water is easy to perform especially with the twin bag Y set (Baxter). Today we use IPP for following surgical catheter implantation (delaying, starting and progressing with peritoneal dialysis) and for optimizing ultrafiltration and purification. Efficiency of peritoneal dialysis is dependent on adequate ultrafiltration (UF) and on adequate purification (solute clearances). These two goals seem apparently conflicting in terms of duration of dwells: short dwell time enhances UF capacity and conversely long dwell time enhances solute clearance. Peritoneal equilibration test (PET) allows an approach to the ultrafiltration time: the point at which the overtime dialysate urea saturation and glucose desaturation curves cross, called APEX time. PET allows also an approach of the purification time: the point at which dialysate (D) to plasma (P) concentration ratios over time are high. Because the value of phosphate as uremic factor of morbidity, we have chosen the time for D/P phosphate equal to 0.6 as a purification phosphate dwell time (PPT). A total of 17 patients were studied, over a five-year period allowing 142 determinations. APEX times (range 18 to 71 min) and PPT (range 105 to 238 min) were spread over a wide distribution. PPT and APEX times were significantly shorter in children younger than 3 years of age than in children older than 10 years of age. PPT were nearly four times longer than APEX times. The knowledge of these conflicting ultrafiltration and purification times should help, in our view, in the individual choice of the PD modality: if UF is the major goal, short dwell times should be used (automatic PD); if purification is the major goal, long dwell times should be used (CAPD); if both are the target goal, tidal PD should be discussed.

The optimal approach to peritoneal dialysis prescription in children.

OBJECTIVE: To describe the optimal approach to peritoneal dialysis (PD) prescription in children. DESIGN: Review of the available literature. RESULTS: Unlike the situation in adults, the main method used for PD in children is automated peritoneal dialysis (APD). The prone position, while resting, permits the dialysis prescription to use a higher fill volume (IPV), as in continuous ambulatory peritoneal dialysis (CAPD), and is also probably more effective than PD in an upright position. However, because APD is limited to 10 hours, the dialytic effectiveness of nocturnal APD should avoid two potential risks: (1) use of too high an IPV per exchange, inducing lymphatic reabsorption, a factor in unsuitable water and sodium balance [Fischbach M. Peritoneal dialysis prescription for neonates. Perit Dial Int. 1996; 16(Suppl):S52-4]; and (2) use of too short a dwell time per exchange, limiting the purification of creatinine and phosphate despite an apparently adequate urea purification (Malhotra C, Murota GH, Tzamaloukas AH. Creatinine clearance and urea clearance in PD: What to do in case of discrepancy. Perit Dial Int. 1997; 17:532-5).