The iridium double perovskite Sr2YIrO6 revisited: A combined structural and specific heat study

Recently, the iridate double perovskite Sr$_2$YIrO$_6$ has attracted considerable attention due to the report of unexpected magnetism in this Ir$^{5+}$ (5d$^4$) material, in which according to the J$_{eff}$ model, a non-magnetic ground state is expected. However, in recent works on polycrystalline samples of the series Ba$_{2-x}$Sr$_x$YIrO$_6$ no indication of magnetic transitions have been found. We present a structural, magnetic and thermodynamic characterization of Sr$_2$YIrO$_6$ single crystals, with emphasis on the temperature and magnetic field dependence of the specific heat. Here, we demonstrate the clue role of single crystal X-ray diffraction on the structural characterization of the Sr$_2$YIrO$_6$ double perovskite crystals by reporting the detection of a $\sqrt{2}a \times \sqrt{2}a \times 1c$ supercell, where $a$, $b$ and $c$ are the unit cell dimensions of the reported monoclinic subcell. In agreement with the expected non-magnetic ground state of Ir$^{5+}$ (5d$^4$) in Sr$_2$YIrO$_6$, no magnetic transition is observed down to 430~mK. Moreover, our results suggest that the low temperature anomaly observed in the specific heat is not related to the onset of long-range magnetic order. Instead, it is identified as a Schottky anomaly caused by paramagnetic impurities present in the sample, of the order of $n \sim 0.5(2)$ \%. These impurities lead to non-negligible spin correlations, which nonetheless, are not associated with long-range magnetic ordering.Comment: 20 pages, 10 figure

Iridium double perovskite Sr2YIrO6: A combined structural and specific heat study

© 2017 American Physical Society.Recently, the iridate double perovskite Sr2YIrO6 has attracted considerable attention due to the report of unexpected magnetism in this Ir5+ (5d4) material, in which according to the Jeff model, a nonmagnetic ground state is expected. However, in recent works on polycrystalline samples of the series Ba2-xSrxYIrO6 no indication of magnetic transitions have been found. We present a structural, magnetic, and thermodynamic characterization of Sr2YIrO6 single crystals, with emphasis on the temperature and magnetic field dependence of the specific heat. As determined by x-ray diffraction, the Sr2YIrO6 single crystals have a cubic structure, with space group Fm3m. In agreement with the expected nonmagnetic ground state of Ir5+ (5d4) in Sr2YIrO6, no magnetic transition is observed down to 430 mK. Moreover, our results suggest that the low-temperature anomaly observed in the specific heat is not related to the onset of long-range magnetic order. Instead, it is identified as a Schottky anomaly caused by paramagnetic impurities present in the sample, of the order of n∼0.5(2)%. These impurities lead to non-negligible spin correlations, which nonetheless, are not associated with long-range magnetic ordering

Observation of heavy spin-orbit excitons propagating in a nonmagnetic background: The case of (Ba,Sr)2YIrO6

We present a combined experimental and theoretical study of the elementary magnetic excitations in Ba2YIrO6 and Sr2YIrO6 - the two most intensively discussed candidates for a new type of magnetic instability caused by exciton condensation. For both materials, high-resolution resonant inelastic x-ray scattering (RIXS) at the Ir L3 edge reveals sharp excitations around 370 and 650 meV energy loss, which we identify as triplet and quintet spin-orbit excitons. While the momentum-dependent RIXS spectra reveal that both the triplet and the quintet propagate coherently within the nonmagnetic background of the singlet sites, these modes remain fully gapped. The Ir-Ir exchange interactions in both double perovskites are therefore not strong enough to overcome the magnetic gap and, hence, our results exclude an intrinsic magnetic instability due to a condensation of magnetic excitations for both Ba2YIrO6 and Sr2YIrO6

Microvascular decompression as a surgical management for trigeminal neuralgia: A critical review of the literature

Trigeminal neuralgia (TN) is a common pain syndrome and is characterized by recurrent episodes of intense lancinating pain in one or more divisions of the trigeminal nerve. Neurovascular compression (NVC) has been considered as the main cause of TN in the root entry zone (REZ) of the trigeminal nerve in the cerebellopontine angle cistern. Microvascular decompression (MVD) is the surgical procedure of choice for the treatment of medically refractory TN. MVD has also been shown to provide pain relief even in patients without visible neurovascular compression. Additionally, it has been accepted that MVD can provide the highest rate of long-term patient satisfaction with the lowest rate of pain recurrence. We did, systematic review of the subject and also our own experiences

CITRIN DEFICIENCY: AN INFANT INCIDENTALLY DETECTED BY PHENYLKETONURIA SCREENING WITH A NOVEL MUTATION IN SLC25A13 GENE

Citrin deficiency: an infant incidentally detected by phenylketonuria screening with a novel mutation in SLC25A13 gene: We report the first Turkish patient with citrin deficiency detected incidentally by phenylketonuria screening. Mild cholestasis, increased a-fetoprotein level, aminoacidemia including citrulline and coagulation disorder suggested citrin deficiency. Screening the SLC25A13 gene revealed compound heterozygosity harboring a novel mutation, c.851-854de1GTAT (p.M285Pfs*2)/ p.I290T (c.869T>C). Progression to type II citrullinemia was considered due to hyperammonemia episodes resulting from high carbohydrate/low protein diet. High protein/low carbohydrate diet resulted in cessation of hyperammonemia episodes, reversal of hepatic dysfunction and steatohepatitis. Our report illustrates the importance of awareness on citrin deficiency

Effects of melatonin on plasma S-nitrosoglutathione and glutathione in streptozotocin-treated rats

The aim of this study was to determine the effects of streptozotocin-induced diabetes on plasma reduced glutathione (GSH) and S-nitrosoglutathione (CSNO) levels. Further, the study investigated whether an antioxidant, pineal hormone melatonin, could protect against STZ-induced effects. STZ significantly decreased plasma GSH but increased the levels of plasma GSNO. Daily supplementation with melatonin restored plasma thiol to control values. Data suggest that STZ-induced hyperglycemia and compounds that act as scavengers of free radicals and peroxynitrite like melatonin may exert protection against STZ-incluced toxicity

Surgical results of large and giant pituitary adenomas with special consideration of ophthalmologic outcomes

PubMed: 21839965Objective: To analyze functioning and nonfunctioning pituitary adenomas (PAs) >3 cm, with special emphasis on preoperative and postoperative visual functions. Methods: The cases consisted of 49 women and 54 men with mean age of 43.2 years (range 19-66 years). All cases had a macroadenoma >3 cm in diameter. The transsphenoidal approach was performed in 117 procedures, and the transcranial approach was performed in 8 procedures. Radical tumor excision was achieved in 50 of 103 patients. Postoperative evaluation was done in 88 patients. Preoperative and postoperative visual acuity, visual field, and ocular fundi and their relationship with the pattern and duration of the symptoms and the size of the tumor were evaluated. Results: Normalization of visual acuity was obtained in 71.5% of patients, improvement occurred in 13.6%, symptoms persisted in 13.6%, and symptoms worsened in 1%. Postoperative improvement of visual field defects (VFDs) was observed in 74.1% of patients, and visual impairment score improved postoperatively in 92% of patients. Patients operated on <6 months before the onset of vision loss had better and more sustained visual improvement. One patient died, and 15.5% of patients experienced surgery-related complications. Conclusions: This study shows that patients with severe visual impairment may have remarkable improvement if surgical decompression is done early. The transsphenoidal approach should be performed to correct the patient's visual impairment and to relieve the pressure on the optic apparatus caused by macroadenoma of any size. © 2011 Elsevier Inc. All rights reserved