First-principles study of the ferroelectric Aurivillius phase Bi2WO6

In order to better understand the reconstructive ferroelectric-paraelectric transition of Bi2WO6, which is unusual within the Aurivillius family of compounds, we performed first principles calculations of the dielectric and dynamical properties on two possible high-temperature paraelectic structures: the monoclinic phase of A2/m symmetry observed experimentally and the tetragonal phase of I4/mmm symmetry, common to most Aurivillius phase components. Both paraelectric structures exhibits various unstable modes, which after their condensation bring the system toward more stable structures of lower symmetry. The calculations confirms that, starting from the paraelectric A2/m phase at high temperature, the system must undergo a reconstructive transition to reach the P2_1ab ferroelectric ground state.Comment: added Appendix and two table

Svensk Insektfauna Trettonde Steklar

Steklarne anses med skäl såsom de högst stående bland in-sekterna. De utmärka sig genom följande kännetecken: Hufvudet mycket rörligt med munöppningen vänd nedåt. Öfverkäkarne kraftigt utbildade, bitande; underkäkarne bilda tillsammans med underläppen en sug- eller slickapparat. Första mellankroppsleden är i allmänhet liten och ofvan oftast orörligt sammanväxt med andra leden, dess sido- och bröstplåtar äro alltid genom en !edgång rörligt förenade med ryggplåten {halsskölden), hvarigenom frambenen blifva mycket rörliga. Vingarne, som sällan saknas, äro fyra, tunna, nakna, hinnaktiga och endast försedda med ett ringa antal slutna vingfält; de bakre kortare och smalare än de främre. Förvandlingen är fullständig. Larverna hafva ett tydligt afsatt hufvud med bitande mundelar och tretton kroppsleder. Puppans kroppsdelar nästan fritt liggande

Svensk Insektfauna Steklar Gaddsteklar Andra Rofsteklar

Hufvudet medelmåttigt eller stort. Ögonen oftast nakna, mycket sällan håriga (Entomognathus), på insidan vanligen hela, sällan med en inskärning (Phila11thus, Trypoxylon); de äro oftast så stora, att de nå ned till mandiblernas rot, hvarigenom kinder komma att saknas; de stå antingen parallella eller närma sig hvarandra uppåt eller nedåt. Punktögonen tre ställda i trekant, vanligen halfklotformiga, de öfre sällan otydliga och långsträckta (T achytes). Öfverläppen är oftast liten och mer eller mindre dold under munskölden, sällan (Bembex) mycket stor och inslagen under mandiblern a. Mandiblerna äro vanligen skärformiga, enkla eller tandade. Underkäkarne och tungan äro korta och bilda således endast en föga utvecklad sug-eller slickapparat

FAUNA BURUANA. COLEOPTERA, Fam. Cerambycidae

abstract not availabl

First-Principles Calculation of Born Effective Charges and Spontaneous Polarization of Ferroelectric Bismuth Titanate

In this study, we present the results of our first-principles calculations of the band structure, density of states and the Born effective charge tensors for the ferroelectric (ground state B1a1) and paraelectric (I4/mmm) phases of bismuth titanate. The calculations are done using the generalized gradient approximation (GGA) as well as the local density approximation (LDA) of the density functional theory. In contrast to the literature, our calculations on B1a1 structure using GGA and LDA yield smaller indirect band gaps as compared to the direct band gaps, in agreement with the experimental data. The density of states shows considerable hybridization among Ti 3d, Bi 6p and O 2p states indicating covalent nature of the bonds leading to the ferroelectric instability. The Born effective charge tensors of the constituent ions for the ground state (B1a1) and paraelectric (I4/mmm) structures were calculated using the Berry phase method. This is followed by the calculation of the spontaneous polarization for the ferroelectric B1a1 phase using the Born effective charge tensors of the individual ions. The calculated value for the spontaneous polarization of ferroelectric bismuth titanate using different Born effective charges was found to be in the range of 55+/-13 $\mu$C/cm2 in comparison to the reported experimental value of (50+/-10 $\mu$C/cm2) for single crystals. The origin of ferroelectricity is attributed to the relatively large displacements of those oxygen ions in the TiO6 octahedra that lie along the a-axis of the bismuth titanate crystal.Comment: 36 pages, 5 figure

Electronic Structure and Valence Band Spectra of Bi4Ti3O12

The x-ray photoelectron valence band spectrum and x-ray emission valence-band spectra (Ti K _beta_5, Ti L_alpha, O K_alpha) of Bi4Ti3O12 are presented (analyzed in the common energy scale) and interpreted on the basis of a band-structure calculation for an idealized I4/mmm structure of this material.Comment: 6 pages + 7 PostScript figures, RevTex3.0, to be published in Phys.Rev.B52 (Oct.95). Figures also available via anonymous ftp at ftp://ftp.physik.uni-osnabrueck.de/pub/apostnik/BiTiO

Functional respiratory imaging assessment of budesonide/glycopyrrolate/formoterol fumarate and glycopyrrolate/formoterol fumarate metered dose inhalers in patients with COPD:the value of inhaled corticosteroids

BACKGROUND: For patients with chronic obstructive pulmonary disease (COPD), greater improvements in lung function have been demonstrated for triple versus dual inhaled therapies in traditional spirometry studies. This study was the first to use functional respiratory imaging (FRI), known for increased sensitivity to airway changes versus spirometry, to assess the effect of the inhaled corticosteroid (ICS) component (budesonide) on lung function in patients with moderate-to-severe COPD and a blood eosinophil count > 150 cells/mm(3). METHODS: Patients in this Phase IIIb (NCT03836677), randomized, double-blind, crossover study received twice-daily budesonide/glycopyrrolate/formoterol fumarate (BGF) 320/18/9.6 μg fixed-dose triple therapy and glycopyrrolate/formoterol fumarate (GFF) 18/9.6 μg fixed-dose dual therapy over 4 weeks, each delivered via a single metered dose Aerosphere inhaler. Primary endpoints were the improvements from baseline for each treatment in specific (i.e. corrected for lobar volume) image-based airway volume (siVaw) and resistance (siRaw) measured via FRI taken at total lung capacity (Day 29). Secondary outcomes included spirometry and body plethysmography. Adverse events were monitored throughout the study. RESULTS: A total of 23 patients were randomized and included in the intent-to-treat analysis (mean age 64.9 years, 78.3% males, 43.5% current smokers, mean predicted post-bronchodilator forced expiratory volume in 1 s [FEV(1)] 63.6%). BGF and GFF both statistically significantly increased siVaw from baseline at Day 29 (geometric mean ratio [GM], 95% confidence interval [CI]: 1.72 [1.38, 2.13] and 1.53 [1.28, 1.83], respectively, both p < 0.0001), with a greater increase observed for BGF versus GFF (GM, 95% CI 1.09 [1.03, 1.16], p = 0.0061). Statistically significant reductions in siRaw were also observed with both BGF and GFF (GM, 95% CI 0.50 [0.39, 0.63] and 0.52 [0.40, 0.67], respectively, both p < 0.0001). Additionally, significant improvements from baseline in post-dose FEV(1) were observed with BGF and GFF (mean 346 mL, p = 0.0003 and 273 mL, p = 0.0004, respectively). Safety findings were consistent with the known profiles of BGF and GFF. CONCLUSIONS: As observed using FRI, triple therapy with BGF resulted in greater increases in airway volume, and reductions in airway resistance versus long-acting muscarinic antagonist/long-acting β(2)-agonist (LAMA/LABA) dual therapy with GFF, reflecting the ICS component’s contribution in patients with moderate-to-severe COPD. Trial registration: ClinicalTrials.gov, NCT03836677. Registered 11 February 2019, https://clinicaltrials.gov/ct2/show/NCT03836677 SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12931-021-01772-2

High-throughput screening of perovskite alloys for piezoelectric performance and thermodynamic stability

We screen a large chemical space of perovskite alloys for systems with optimal properties to accommodate a morphotropic phase boundary (MPB) in their composition-temperature phase diagram, a crucial feature for high piezoelectric performance. We start from alloy end points previously identified in a high-throughput computational search. An interpolation scheme is used to estimate the relative energies between different perovskite distortions for alloy compositions with a minimum of computational effort. Suggested alloys are further screened for thermodynamic stability. The screening identifies alloy systems already known to host an MPB and suggests a few others that may be promising candidates for future experiments. Our method of investigation may be extended to other perovskite systems, e.g., (oxy-)nitrides, and provides a useful methodology for any application of high-throughput screening of isovalent alloy systems

Chemistry of layered d-metal pnictide oxides and their potential as candidates for new superconductors

Layered d-metal pnictide oxides are a unique class of compounds which consists of characteristic d-metal pnictide layers and metal oxide layers. More than 100 of these layered compounds, including the recently discovered Fe-based superconducting pnictide oxides, can be classified into 9 structure types. These structure types and the chemical and physical properties of the characteristic d-metal pnictide layers and metal oxide layers of the layered d-metal pnictide oxides are reviewed and discussed. Furthermore, possible approaches to design new superconductors based on these layered d-metal pnictide oxides are proposed.Comment: 29 pages including 6 tables and 2 figure