Incipient Ferroelectricity in Al‐Doped HfO2 Thin Films

Incipient ferroelectricity is known to occur in perovskites such as SrTiO₃, KTaO₃, and CaTiO₃. For the first time it is shown that the intensively researched HfO₂ thin films (16 nm) also possess ferroelectric properties when aluminium is incorporated into the host lattice. Polarization measurements on Al:HfO₂ based metal–insulator–metal capacitors show an antiferroelectric‐to‐ferroelectric phase transition depending on annealing conditions and aluminium content. Structural investigation of the electrically characterized capacitors by grazing incidence X‐ray diffraction is presented in order to gain further insight on the potential origin of ferroelectricity. The non‐centrosymmetry of the elementary cell, which is essential for ferroelectricity, is assumed to originate from an orthorhombic phase of space group Pbc2₁ stabilized for low Al doping in HfO₂. The ferroelectric properties of the modified HfO₂ thin films yield high potential for various ferroelectric, piezoelectric, and pyroelectric applications. Furthermore, due to the extensive knowledge accumulated by various research groups regarding the HfO₂ dielectric, an immediate relevance of ferroelectric hafnium oxide thin films is anticipated by the authors.     

ChemInform Abstract: Anosovite‐Type V3O5: A New Binary Oxide of Vanadium.

The new anosovite‐type polymorph of the title compound is synthesized by reaction of either V₂F₆·4H₂O or a mixture of 60 wt.% VF₂·4H₂O and 40 wt.% VF₃·3H₂O with a flowing water‐saturated gaseous mixture of 15—20 vol% H₂ in argon (588 K, 14—18 h).     

Cellular uptake studies of two hexanuclear, carboxylate bridged, zinc ring structures using fluorescence microscopy

Two hexanuclear zinc complexes have been structurally characterized, and evaluation against several cells showed selective toxicity. Cellular uptake revealed a non-specific process, resulting in accumulation within the cell cytoplasm.     

Mathematical Modeling of Acid‐Catalyzed 1,3‐Propanediol Polymerization

A reaction mechanism for the polymerization of 1,3‐propanediol is proposed for two acid catalysts. Population and mass balance equations are derived for small molecules and for polymeric species of chain distributions distinguishable in terms of protonation state and end group functionality. Since the sulfuric acid catalyzed process has two types of polymer linkages, the derivation of the moment equations is challenging. The reverse reactions are also accounted thus creating a moment closure problem. A mass transfer model is developed to predict reaction mixture water content. The Sanchez‐Lacombe equation of state is used to calculate phase behavior and species partitioning. Optimization of selected parameters is accomplished by comparison to laboratory data resulting in a fully predictive model.

     

The Role of Co-Adsorbed CO and OH in the Electrooxidation of Formic Acid on Pt(111)

Synergy with potential: Analysis of relevant mechanistic pathways by density functional theory, reveals the synergistic role of co-adsorbed CO and OH in promoting HCOOH electrooxidation on Pt(111). Kinetic models derived from these studies show the atomistic surface phenomena underlying the experimental CV observation in the potential range between 0.0 and 1.2?V.     

Economic implications of poor access to antenatal care in rural and remote Western Australian Aboriginal communities: An individual sampling model of pregnancy

Background

Australian Aboriginal women attend antenatal care less frequently and experience poorer pregnancy outcomes than non-Aboriginal women. Improving access to antenatal care is recognised as a means to improve pregnancy outcomes for mother and baby.

Objective

To estimate the costs of inadequate antenatal care and provide baseline measurements and implications for policy that targets improving access to care in rural and remote Western Australian (WA) Aboriginal communities.

Methods

An individual sampling model of pregnancy was developed that simulated hypothetical women with pregnancy events and outcomes observed in the WA Aboriginal population. Weekly pregnancy events were modelled via logistic regression according to maternal characteristics, events during pregnancy and current gestation, with adequate and inadequate care (?4 and <4 antenatal visits) to reflect differences in outcomes reported in the literature. The pregnancy model simulated clinical management including antenatal visits, hospitalisations, and transfers to tertiary care.

Results

The mean cost of pregnancy was AUD$8985, with a large difference depending on access to antenatal care (AUD$7635 and AUD$10,216 for adequate and inadequate care respectively). The main difference in costs resulted from neonatal care (AUD$1021 vs AUD$3205 for adequate and inadequate care respectively). In a rural community with 150 births per year, up to AUD$123,082 may be spent to improve access to care at no extra cost to the total current expenditure (AUD$1,347,733).

Conclusions

The large difference in pregnancy costs between those receiving adequate and inadequate care demonstrates that additional expenditure on improving access to antenatal care may be cost-effective and should be further investigated.     

High-field QCPMG NMR of strontium nuclei in natural minerals

The only stable NMR-active isotope of strontium, (87)Sr, is a spin-9/2 quadrupolar nucleus that has a low gyromagnetic ratio, a low natural abundance, and a large nuclear electric quadrupole moment. In this work, we utilize the quadrupolar Carr-Purcell-Meiboom-Gill (QCPMG) pulse sequence and a 21.14 T NMR spectrometer at the Pacific Northwest National Laboratory to characterize the strontium sites in the natural minerals strontianite (SrCO(3)) and celestine (SrSO(4)). QCPMG at 21.14 T was found to provide sensitivity enhancements of roughly two orders of magnitude over Hahn-echo experiments at an 11.74 T magnetic field. We extracted the quadrupolar parameters for the strontium nuclei through iterative simulations of the experimental spectra with the SIMPSON program by Bak, Rasmussen, and Nielsen. The data show that the quadrupolar parameters of (87)Sr appear to be highly sensitive to the symmetry of the strontium coordination environment and can thus provide information about the strontium binding environment in complex systems.     

Novel system clock generation from a modulated signal

This paper describes a novel technique to derive a pure-spectral system clock with a common multi-modulus divider from a frequency modulated signal. Therefore, the dividing factor is inverse frequency modulated to compensate the frequency modulation component on the divider input signal. Additionally, $\Upsigma\Updelta$ dithering is applied to the frequency divider. The technique is used for a FM-radio transmitter based on an all-digital phase-locked loop (PLL) to generate a higher-frequency clock for baseband signal processing. It can also be applied to other PLL based transmitters or receivers, especially, if only a slow PLL reference clock is available and a faster system or baseband clock is required. The main factor determining the quality of the generated clock signal is the PLL??s reference quartz oscillator as it determines the accuracy of the PLL??s RF oscillator, which limits then the accuracy of the newly generated clock. In the FM-radio transmitter, a generated ??1?MHz clock signal with 30.58?ppm frequency offset and 515?ps root mean square jitter is generated. The phase noise is determined to ?83.5?dBc/Hz at 10?kHz offset and ?70.5?dBc/Hz at 1?kHz, respectively. The signal can also be used in co-integrated or external circuits.