Structure, Spin Correlations, and Magnetism of the S = 1/2 Square-Lattice Antiferromagnet Sr2CuTe1-xWxO6 (0 ≤ x ≤ 1).

Quantum spin liquids are highly entangled magnetic states with exotic properties. The S = 1/2 square-lattice Heisenberg model is one of the foundational models in frustrated magnetism with a predicted, but never observed, quantum spin liquid state. Isostructural double perovskites Sr2CuTeO6 and Sr2CuWO6 are physical realizations of this model but have distinctly different types of magnetic order and interactions due to a d10/d0 effect. Long-range magnetic order is suppressed in the solid solution Sr2CuTe1-xWxO6 in a wide region of x = 0.05-0.6, where the ground state has been proposed to be a disorder-induced spin liquid. Here, we present a comprehensive neutron scattering study of this system. We show using polarized neutron scattering that the spin liquid-like x = 0.2 and x = 0.5 samples have distinctly different local spin correlations, which suggests that they have different ground states. Low-temperature neutron diffraction measurements of the magnetically ordered W-rich samples reveal magnetic phase separation, which suggests that the previously ignored interlayer coupling between the square planes plays a role in the suppression of magnetic order at x ≈ 0.6. These results highlight the complex magnetism of Sr2CuTe1-xWxO6 and hint at a new quantum critical point between 0.2 < x < 0.4.

Partitioning the Two-Leg Spin Ladder in Ba2Cu1 - x Zn x TeO6: From Magnetic Order through Spin-Freezing to Paramagnetism.

Ba2CuTeO6 has attracted significant attention as it contains a two-leg spin ladder of Cu2+ cations that lies in close proximity to a quantum critical point. Recently, Ba2CuTeO6 has been shown to accommodate chemical substitutions, which can significantly tune its magnetic behavior. Here, we investigate the effects of substitution for non-magnetic Zn2+ impurities at the Cu2+ site, partitioning the spin ladders. Results from bulk thermodynamic and local muon magnetic characterization on the Ba2Cu1 - x Zn x TeO6 solid solution (0 ≤ x ≤ 0.6) indicate that Zn2+ partitions the Cu2+ spin ladders into clusters and can be considered using the percolation theory. As the average cluster size decreases with increasing Zn2+ substitution, there is an evolving transition from long-range order to spin-freezing as the critical cluster size is reached between x = 0.1 to x = 0.2, beyond which the behavior became paramagnetic. This demonstrates well-controlled tuning of the magnetic disorder, which is highly topical across a range of low-dimensional Cu2+-based materials. However, in many of these cases, the chemical disorder is also relatively strong in contrast to Ba2CuTeO6 and its derivatives. Therefore, Ba2Cu1 - x Zn x TeO6 provides an ideal model system for isolating the effect of defects and segmentation in low-dimensional quantum magnets.

Uncovering the Kagome Ferromagnet within a Family of Metal-Organic Frameworks.

Kagome networks of ferromagnetically or antiferromagnetically coupled magnetic moments represent important models in the pursuit of a diverse array of novel quantum and topological states of matter. Here, we explore a family of Cu2+-containing metal-organic frameworks (MOFs) bearing kagome layers pillared by ditopic organic linkers with the general formula Cu3(CO3)2(x)3·2ClO4 (MOF-x), where x is 1,2-bis(4-pyridyl)ethane (bpe), 1,2-bis(4-pyridyl)ethylene (bpy), or 4,4'-azopyridine (azpy). Despite more than a decade of investigation, the nature of the magnetic exchange interactions in these materials remained unclear, meaning that whether the underlying magnetic model is that of an kagome ferromagnet or antiferromagnet is unknown. Using single-crystal X-ray diffraction, we have developed a chemically intuitive crystal structure for this family of materials. Then, through a combination of magnetic susceptibility, powder neutron diffraction, and muon-spin spectroscopy measurements, we show that the magnetic ground state of this family consists of ferromagnetic kagome layers that are coupled antiferromagnetically via their extended organic pillaring linkers.

Site-Selective d10/d0 Substitution in an S = 1/2 Spin Ladder Ba2CuTe1-xWxO6 (0 ≤ x ≤ 0.3).

Isovalent nonmagnetic d10 and d0 B″ cations have proven to be a powerful tool for tuning the magnetic interactions between magnetic B' cations in A2B'B″O6 double perovskites. Tuning is facilitated by the changes in orbital hybridization that favor different superexchange pathways. This can produce alternative magnetic structures when B″ is d10 or d0. Furthermore, the competition generated by introducing mixtures of d10 and d0 cations can drive the material into the realms of exotic quantum magnetism. Here, Te6+ d10 was substituted by W6+ d0 in the hexagonal perovskite Ba2CuTeO6, which possesses a spin ladder geometry of Cu2+ cations, creating a Ba2CuTe1-xWxO6 solid solution (x = 0-0.3). We find W6+ is almost exclusively substituted for Te6+ on the corner-sharing site within the spin ladder, in preference to the face-sharing site between ladders. The site-selective doping directly tunes the intraladder, Jrung and Jleg, interactions. Modeling the magnetic susceptibility data shows the d0 orbitals modify the relative intraladder interaction strength (Jrung/Jleg) so the system changes from a spin ladder to isolated spin chains as W6+ increases. This further demonstrates the utility of d10 and d0 dopants as a tool for tuning magnetic interactions in a wide range of perovskites and perovskite-derived structures.

1009 nm continuous-wave ytterbium-doped fiber amplifier emitting 146 W.

In this Letter, we demonstrate a single-mode continuous-wave fiber laser amplifier emitting 146 W of average output power at a wavelength of 1009 nm. The wavelength and bandwidth of the seed oscillator are defined by a pair of fiber Bragg gratings. The seed is amplified in a two-stage ytterbium-doped rod-type amplifier to 146 W with a high slope efficiency of 64%, showing excellent beam quality and stability throughout the experiment. The ASE suppression is as high as 63 dB.

Right lower prefronto-parietal cortical dysfunction in akinetic catatonia: a combined study of neuropsychology and regional cerebral blood flow.

BACKGROUND: Catatonia is a psychomotor syndrome that can be characterized by behavioural, affective and motor abnormalities. In order to reveal further underlying pathophysiological mechanisms of psychomotor disturbances in catatonia we investigated neuropsychological function and regional cerebral perfusion (r-CBF) in a combined study. METHODS: Ten catatonic patients were investigated with Tc-99mECD brain SPECT and compared with 10 psychiatric (similar age, sex, medication and underlying psychiatric diagnosis but without catatonic syndrome) and 20 healthy controls. Neuropsychological measures included tests for general intelligence, attention, executive functions and right parietal visual-spatial abilities. Correlational analyses were performed between neuropsychological measures, catatonic symptoms and r-CBF. RESULTS: Catatonic patients showed a significant decrease of r-CBF in right lower and middle prefrontal and parietal cortex compared with psychiatric and healthy controls as well as significantly poorer performance in visual-spatial abilities associated with right parietal function. Correlational analysis revealed significant correlations between visual-spatial abilities and right parietal r-CBF only in psychiatric and healthy controls but not in catatonic patients. In contrast, attentional measures correlated significantly with motor symptoms, visual-spatial abilities and right parietal r-CBF in catatonia only but not in psychiatric or in healthy controls. CONCLUSION: Findings are preliminary but suggest right lower prefronto-parietal cortical dysfunction in catatonia, which may be closely related to psychomotor disturbances.

Somatostatin receptor scintigraphy in small-cell lung cancer: results of a multicenter study.

UNLABELLED: The aims of this study were to determine the accuracy of somatostatin receptor scintigraphy in the detection of the primary tumor and its metastases in small-cell lung cancer (SCLC) in a large patient population, and to investigate the course of somatostatin uptake in primary tumors during therapy. METHODS: In a total of 100 patients, 134 examinations were performed. Twenty-seven of the patients were examined before and after chemotherapy. Planar whole-body images were acquired 4 hr and 24 hr after injection of approximately 200 MBq (111)In-pentetreotide. SPECT of the thorax was performed after 24 hr. Tumor-to-background (T/B) ratios for the primary tumor were averaged from anterior and posterior projections. RESULTS: Compared to conventional investigations, somatostatin receptor scintigraphy (SRS) visualized the primary tumor with varying degrees of uptake in 96% of the examinations. Regional metastases and distant metastases were detected in 60% and 45% of the examinations, respectively. The uptake of the somatostatin analog by the primary tumor was significantly lower in the patients examined during chemotherapy as compared to those examined before treatment (T/B ratio = 1.94+/-0.79 versus 2.35+/-0.9, p < 0.005). A decrease in T/B ratio was noted in patients with remission at the time of SRS (from 2.40+/-1.56 to 1.63+/-0.72, p < 0.05). No difference in the pretreatment uptake of octreotide by the primary tumor was identified between patients with tumor progression and those with partial or complete remission. CONCLUSION: Somatostatin receptor scintigraphy has a high sensitivity in the detection of the primary tumor in SCLC but fails in the detection of metastases. Thus, SRS does not provide useful information for staging of SCLC. Since somatostatin uptake by the primary tumor is affected by chemotherapy, it may be used to follow up on the course of SCLC.

Therapeutic efficacy of L-ornithine-L-aspartate infusions in patients with cirrhosis and hepatic encephalopathy: results of a placebo-controlled, double-blind study.

One hundred twenty-six patients with cirrhosis, hyperammonemia (>50 micromol/L), and chronic (persistent) hepatic encephalopathy (HE), which developed spontaneously without the existence of known precipitating factors, were enrolled in a randomized, double-blind, placebo-controlled clinical trial of intravenously administered L-ornithine-L-aspartate (OA). Patients with subclinical (grade 0, West-Haven criteria) hepatic encephalopathy (SHE), characterized by a prolonged number connection test A (NCT-A) time, and manifest HE (grades I and II, West-Haven criteria) were included in the investigation. The trial was planned as a confirmatory clinical trial OA administered in a dose of 20 g/d, as well as placebo, were dissolved in 250 mL of 5% fructose and infused intravenously for a period of 4 hours during 7 consecutive days with a superimposed protein load at the end of the daily treatment period. Primary variables were postprandial venous ammonia and NCT-A performance time measured following OA or placebo infusions to evaluate the net effect of the treatment on the prevention of the protein-induced hyperammonemia, and on parameters such as NCT-A influenced by hyperammonemia. Mental state gradation, portal systemic encephalopathy index (PSEI), and fasting ammonia levels were estimated as additional efficacy parameters. The data presented are based on the total study sample (intent-to-treat analysis), which included 63 patients in the placebo group and 63 patients in the OA group. Of the 126 patients, 114 met all the criteria for inclusion and completed the trial and treatment as outlined in the protocol (treated-per-protocol analysis). During baseline, the placebo and treatment groups were homogeneous with regard to mental states, NCT-A performance time, fasting venous blood ammonia levels, and Child-Pugh criteria. Although a slight improvement occurred in the placebo group, NCT-A performance times (P < .001) and postprandial venous ammonia concentrations in the OA-treated group showed improvements in comparison with placebo. In addition, venous fasting blood ammonia concentration (P < .01), mental state gradation (P < .001), and PSEI (P < .01), which includes the mental state gradation, NCT-A time, and postprandial venous ammonia in this trial, improved to a much higher degree in the OA group than in the placebo group. In subgroups retrospectively classified according to their initial mental state gradation, OA showed differential but uniformly significant efficacies in patients with manifest HE with respect to ammonia-lowering, improvement in NCT times, and mental state gradation. In patients with initial SHE, OA revealed differences between the medications in the psychometric test used. Adverse events consisting of mild gastrointestinal disturbances were observed in 3 of the OA-treated patients (5%). OA infusion appears to be a safe, effective treatment of chronic (persistent) manifest HE in cirrhotic patients. Additional investigations are required to assess the efficacy of OA in patients with SHE, as well as in patients with more severe grades of HE.

[Findings of combined ventilation/perfusion scintigraphy in children with abnormalities of the bronchi, the lung and lung blood vessels]. / Befunde der kombinierten Ventilations-/Perfusionsszintigraphie bei Kindern mit Fehlbildungen der Bronchien, der Lungen und Lungengefässe.

Combined ventilation/perfusion scintigraphy with 133Xe/99mTc-HAM was performed within the framework of bronchological diagnostics in 38 children suffering from malformations of the bronchi, lungs and pulmonary vessels, and in 9 children after surgery of hernia of the diaphragm. The findings in stenoses, cysts in the bronchial system and in children with pulmonary vessel malformations, in one child with pulmonary agenesia and in a few other malformations, are presented. The significance of these findings in bronchological diagnosis in case of pulmonary malformations or clinical follow-up is discussed. Combined ventilation/perfusion scintigraphy is a valuable contribution to preliminary diagnosis and in follow-up of children with pulmonary malformations.

[Value of bronchography in childhood with special reference to nuclear medicine preliminary examinations]. / Stellenwert der Bronchographie im Kindesalter unter besonderer Berücksichtigung nuklearmedizinischer Vorfelduntersuchungen.

One month to 16 years old 288 children suffering from recurrent and chronic bronchitis, asthma, cystic fibrosis, malformations and various other lung diseases have been undergone 133Xe-Gas/99mTc-HAM lung scintigraphy. By means of results and taking in consideration scintigraphic findings the strategy of bronchographic indication is laid open being of higher load for the children based on anaesthesia and x-ray. Thus the number of bronchographs could be reduced from 47 (1984) via 33 (1985) to 22 (1986) by means of lung-scintigraphic imaging.

[Combined 113Xe/99mTC human serum albumin microspheres lung scintigraphy in children with recurrent and chronic bronchitis]. / Die kombinierte 133Xe-/99mTc-HAM-Lungenszintigraphie bei Kindern mit rezidivierender und chronischer Bronchitis.

A total of 117 children with recurrent and chronic bronchitis aged from 2 months to 16 years were subjected to combined ventilation-perfusion scan of the lungs with 133Xe-gas and 99mTc-HAM. It served as a screening before bronchological examination with the aim to get a more exact indication for bronchography which leads to a higher stress in children because of anaesthesia and radioscopy. Due to combined lung scan, the number of bronchological examinations could be reduced from 109 in 1984 to 79 in 1985 and even to 54 in 1986. Among the 117 children suffering from bronchitis, we found normal scans in 16 cases, perfusion defects in 59 cases, combined ventilation-perfusion defects in 41 cases and one case showed a pure ventilation defect. The lung scan should be applied in the framework of bronchopulmonary standard diagnosis.

[Status of perfusion scintigraphy in the diagnostic strategy in cerebrovascular disorders and space-occupying lesions]. / Die Stellung der Perfusions-szintigraphie in der Diagnosestrategie bei zerebralen Durchblutungsstörungen und Raumforderungen.

The results of an evaluation of the perfusion scintigraphy findings of 350 hospitalised neurological patients and 55 more strictly selected neurosurgical patients with cerebrovascular complaints, revealed an accuraty of 83%, a sensitivity of 89%, and a specificity of 83%. The selection of the patients had no influence on the results as a whole. Compared with contrast-medium angiography, incorrect diagnosis must be expected in 17% of the cases. This includes erroneous negative findings in 10% of the cases. Grounds for misinterpretations are suggested, and the biological and methodological limitations of the method are set forth.

[Results of the complex evaluation of scintigraphy of the intracardiac space in patients with coronary disease]. / Ergebnisse der komplexen Auswertung der Herzbinnenraumszintigraphie bei Patienten mit koronarer Herzkrankheit.

With the help of the comparison of the results of 95 patients with coronary heart disease who were examined by means of the intracardiac space scintigraphy for the purpose of the subjective subdivision according to the NYHA-classification there is no close correlation between the nuclear-medically obtained functional sizes (EF, maximum ejection and filling rate) and the clinical degree of severity of the disease. Only at the degree of severity 3 and 4 a discrimination is possible. In 64 patients laevocardiographic and coronarographic, respectively, findings were present. The trend to the deterioration of the functional parameters and to the increase of the nuclear-medically recognizable disturbances of the kinetics, respectively, with a more intensive expression of the vascular stenoses is distinctly readable. From the examination in rest in the individual case no statement is possible concerning the findings which are to be expected in the invasive diagnostics. When there are discrepancies between the result of the intracardiac space scintigraphy and the clinical and electrocardiographic preliminary investigations in many cases a clarification becomes possible by the immediately following study under submaximal exercise. On the assumption of a close cooperation with experienced cardiologists the relatively little expensive intracardiac space scintigraphy which does not stress the patient provides an essential evidence for the prognosis and estimation of the functional capacity of the patients with coronary heart disease.

[Diagnosis of obliterating vascular processes in the supraaortic area]. / Beitrag zur Diagnostik obliterierender Gefässprozesse im supraaortalen Bereich.

For the diagnostics of obliterating vascular changes in the supraaortic area the invasive diagnostics of the vessels is not to be renounced now as before. The indication to the angiographic investigation results from clinical, perfusion-scintigraphic and Doppler-sonographic-findings. Of 390 patients 289 pathological angiographic findings in the supraaortic vascular area. In 101 patients normal findings were stated. Altogether 509 individual pathological findings were represented. In the comparison of the results of the investigations in the various diagnostic methods the clinical neurological investigation showed itself as particularly evident method. It should be decisive for the indication to the invasive diagnostics. The correspondence between the angiographic findings and the result of the perfusion-scintigraphic and Doppler-sonographic investigations, respectively, was the greater the more expressed the extracranial vascular findings represented themselves. In 127 patients with multiple obliterating vascular changes the size of the pathological changes and their localization could be established only angiographically.