Crystal growth of copper-rich ytterbium compounds: The predicted giant unit cell structures YbCu4.4 and YbCu4.25

Two new phases YbCu4.4 and YbCu4.25 are found as a result of careful phase diagram investigations. Between the congruent and peritectic formation of YbCu4.5 and YbCu3.5, respectively, the phases YbCu4.4 and YbCu4.25 are formed peritectically at 934(2)degC and 931(3)degC. Crystal growth was realised using a Bridgman technique and single crystalline grains of about 50-100 10^{-6}m were analyzed by electron diffraction and single crystal X-ray diffraction. Due to the only slight differences in both compositions and formation temperatures the growth of larger single crystals of a defined superstructure is challenging. The compounds YbCu4.4 and YbCu4.25 fit in Cerny`s (J. Solid State Chem. 174 (2003) 125) building principle {(RECu5)n(RECu2)} where RE = Yb with n = 4 and 3. YbCu4.4 and YbCu4.25 base on AuBe5/MgCu2-type substructures and contain approximately 4570 and 2780 atoms per unit cell. The new phases close the gap in the series of known copper-rich rare earth compounds for n = 1, 2 (DyCu3.5, DyCu4.0) and n = 5 (YbCu4.5, DyCu4.5)

Local atomic order in the vicinity of Cu₂ dumbbells in TbCu₇-type YCu_6.576 studied by Bragg and total scattering techniques

The crystal structure of YCu6.576, a hyperstoichiometric substitution variant of the CaCu5-structure type, was shown to contain Cu2 dumbbells replacing Y-atoms in a fraction s = 0.19 in the formula Y1−sCu5+2s. The structure type TbCu7 is assigned to the disordered structure (P6/mmm, a = 4.96 Å, c = 4.15 Å). The local order in the vicinity of the Cu2-dumbbells has been derived from total scattering X-ray synchrotron data via refinement of the atomic pair distribution function (PDF). The coordinating Cu6-hexagon around the dumbbell site shows a shrinkage of 0.33(1) Å w.r.t. the equivalent environment of the Y-atom. No adjacent Y-atoms are substituted but a hexagonal arrangement of Cu2-dumbbells, separated at least by the vectors √3a and √3b exists in layers perpendicular to c. The stacking along [001] is random and can be modeled locally from the PDF data consistent with both ab- and abc-type stacking. Therefore, the local order is comparable to that in Ni17Th2- and Th2Zn17-structure types. X-ray single crystal analysis and Rietveld refinements of neutron- and X-ray powder data (Bragg diffraction data) of YCu6.576 are consistent with the findings from local crystallography (total scattering data) answering a long-standing question in disordered CaCu5-type based intermetallic structure variants

Management practices for postdural puncture headache in obstetrics : a prospective, international, cohort study

Background: Accidental dural puncture is an uncommon complication of epidural analgesia and can cause postdural puncture headache (PDPH). We aimed to describe management practices and outcomes after PDPH treated by epidural blood patch (EBP) or no EBP. Methods: Following ethics committee approval, patients who developed PDPH after accidental dural puncture were recruited from participating countries and divided into two groups, those receiving EBP or no EBP. Data registered included patient and procedure characteristics, headache symptoms and intensity, management practices, and complications. Follow-up was at 3 months. Results: A total of 1001 patients from 24 countries were included, of which 647 (64.6%) received an EBP and 354 (35.4%) did not receive an EBP (no-EBP). Higher initial headache intensity was associated with greater use of EBP, odds ratio 1.29 (95% confidence interval 1.19-1.41) per pain intensity unit increase. Headache intensity declined sharply at 4 h after EBP and 127 (19.3%) patients received a second EBP. On average, no or mild headache (numeric rating score <= 3) was observed 7 days after diagnosis. Intracranial bleeding was diagnosed in three patients (0.46%), and backache, headache, and analgesic use were more common at 3 months in the EBP group. Conclusions: Management practices vary between countries, but EBP was more often used in patients with greater initial headache intensity. EBP reduced headache intensity quickly, but about 20% of patients needed a second EBP. After 7 days, most patients had no or mild headache. Backache, headache, and analgesic use were more common at 3 months in patients receiving an EBP

Management practices for postdural puncture headache in obstetrics: a prospective, international, cohort study

© 2020 British Journal of AnaesthesiaBackground: Accidental dural puncture is an uncommon complication of epidural analgesia and can cause postdural puncture headache (PDPH). We aimed to describe management practices and outcomes after PDPH treated by epidural blood patch (EBP) or no EBP. Methods: Following ethics committee approval, patients who developed PDPH after accidental dural puncture were recruited from participating countries and divided into two groups, those receiving EBP or no EBP. Data registered included patient and procedure characteristics, headache symptoms and intensity, management practices, and complications. Follow-up was at 3 months. Results: A total of 1001 patients from 24 countries were included, of which 647 (64.6%) received an EBP and 354 (35.4%) did not receive an EBP (no-EBP). Higher initial headache intensity was associated with greater use of EBP, odds ratio 1.29 (95% confidence interval 1.19–1.41) per pain intensity unit increase. Headache intensity declined sharply at 4 h after EBP and 127 (19.3%) patients received a second EBP. On average, no or mild headache (numeric rating score≤3) was observed 7 days after diagnosis. Intracranial bleeding was diagnosed in three patients (0.46%), and backache, headache, and analgesic use were more common at 3 months in the EBP group. Conclusions: Management practices vary between countries, but EBP was more often used in patients with greater initial headache intensity. EBP reduced headache intensity quickly, but about 20% of patients needed a second EBP. After 7 days, most patients had no or mild headache. Backache, headache, and analgesic use were more common at 3 months in patients receiving an EBP