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To determine if prior HPV vaccination contributes to preterm birth risk.Population-based retrospective cohort study.Denmark.243 136 primiparous females born 1961-2004 who had a singleton delivery at22 weeks' gestation occurring in October 2006 to December 2018.High-quality nationwide registries were linked to provide information on demographics, birth outcomes, HPV vaccination status, smoking, BMI, and cervical lesions and treatment history.We assessed the association between HPV vaccination status and spontaneous preterm birth using logistic regression. To address age at vaccination, we performed a stratified analysis by vaccination before and after 17 years old.In age-adjusted and fully-adjusted models, there was a non-significant difference in the odds of spontaneous preterm birth between vaccinated and unvaccinated women (OR: 1.05 [95% CI: 0.99-1.12] and 1.04 [95% CI: 0.98-1.10], respectively). There was no difference in the odds of spontaneous preterm birth in relation to time between vaccination and pregnancy. In contrast, compared to unvaccinated women, the odds of preterm birth were lower among women vaccinated before age 17 (fully-adjusted OR: 0.87, 95% CI: 0.75-1.00). This association was not present for women vaccinated at age17.In this large, population-based cohort, we found reduced odds of spontaneous preterm birth among women HPV vaccinated at an early age compared to those unvaccinated. It seems conceivable that HPV vaccination may not only reduce the incidence of cervical cancer and severe precursors, but also the risk of preterm birth related to HPV infection.

A combined experimental and computational approach is used to investigate the chemical transformations of kaolinite and metakaolin surfaces when exposed to sulfuric acid. These clay minerals are hydrated ternary metal oxides and are shown to be susceptible to degradation by loss of Al as the water-soluble salt Al₂(SO₄)₃, due to interactions between H₂SO₄ and aluminum cations. This degradation process results in a silica-rich interfacial layer on the surfaces of the aluminosilicates, most prominently observed in metakaolin exposed to pH environments of less than 4. Our observations are supported by XPS, ATR-FTIR, and XRD experiments. Concurrently, DFT methodologies are used to probe the interactions between the clay mineral surfaces and H₂SO₄ as well as other sulfur-containing adsorbates. An analysis performed using a DFT + thermodynamics model shows that the surface transformation processes that lead to the loss of Al and SO₄ from metakaolin are favorable at pH below 4; however, such transformations are not favorable for kaolinite, a result that agrees with our experimental efforts. The data obtained from both experimental techniques and computational studies support that the dehydrated surface of metakaolin interacts more strongly with sulfuric acid and provide atomistic insight into the acid-induced transformations of these mineral surfaces.

A condensed phase of zirconium monoxide (ZrO) was detected in YSZ (Zr_(0.92)Y_(0.08)O_(2-δ)) coatings deposited using plasma spray-physical vapor deposition. The rapid cooling rate of this process can result in the condensation of nonequilibrium states that can be kinetically trapped in the coatings. The columnar microstructure contained a mixture of YSZ, ZrO2, and ZrO phases. The ZrO phase was expected to be conductive based on density functional theory calculations, and preliminary impedance measurements were performed that supported this prediction. When heated in an oxygen-containing environment, the ZrO phase remains in the coating until ∼450 K, at which point it disappears quickly, as confirmed by X-ray diffraction and thermogravimetric methods. The loss of ZrO in the coating was also linked to a loss in electrical conductivity. However, it was shown that this phase can persist at elevated temperatures of ∼1000 K in vacuum or inert environments for at least 100 h.

Monomers and polymers from biobased pyrazine underwent post-modification reactions to synthesize a series of novel tailored polyesters with a tunable structure and adjustable physico-chemical properties. Modification by alkylation had limited success. However, controlled oxidative post-modification is possible, without loss of molecular weight. The degree of oxidation has a large effect on the thermal properties of the polyesters. One of the polyesters shows loss of crystallinity combined with an increase in the glass-transition temperature at increasing degrees of oxidation. For the other polyester, oxidation results in an elevated melting point. Weak hydrogen bonds are responsible for the latter observation as demonstrated by infrared spectroscopy. The surface modification of a polymer film results in different wetting behaviors. Our biobased pyrazine building blocks and their ability to be post-modified offer interesting opportunities in added functionality materials of the future.

The hot gas that constitutes the intracluster medium (ICM) has been studied at X-ray and millimeter/submillimeter wavelengths (Sunyaev–Zel’dovich effect) for decades. Fast radio bursts (FRBs) offer an additional method of directly measuring the ICM and gas surrounding clusters via observables such as dispersion measure (DM) and Faraday rotation measure. We report the discovery of two FRB sources detected with the Deep Synoptic Array whose host galaxies belong to massive galaxy clusters. In both cases, the FRBs exhibit excess extragalactic DM, some of which likely originate in the ICM of their respective clusters. FRB 20220914A resides in the galaxy cluster A2310 at z = 0.1125 with a projected offset from the cluster center of 520 ± 50 kpc. The host of a second source, FRB 20220509G, is an elliptical galaxy at z = 0.0894 that belongs to the galaxy cluster A2311 at the projected offset of 870 ± 50 kpc. These sources represent the first time an FRB has been localized to a galaxy cluster. We combine our FRB data with archival X-ray, Sunyaev–Zel'dovich (SZ), and optical observations of these clusters in order to infer properties of the ICM, including a measurement of gas temperature from DM and y SZ of 0.8–3.9 keV. We then compare our results to massive cluster halos from the IllustrisTNG simulation. Finally, we describe how large samples of localized FRBs from future surveys will constrain the ICM, particularly beyond the virial radius of clusters.

Aims: Teenage pregnancy may have negative consequences for the mother and the infant. The aim of the study was to examine whether selected individual factors occurring early in life were associated with teenage pregnancy. Methods: In a population-based, cross-sectional questionnaire study among 34,455 women from Denmark, Norway, and Sweden aged 20–45 years, who had first sexual intercourse (FSI) at age 13–19 years, we assessed the association between early smoking and drinking initiation (i.e., before the age of 13), contraceptive use at FSI, and teenage pregnancy. Log-linear binary regression models were fitted to estimate the relative risk (RR) with 95% confidence intervals (CIs) of teenage pregnancy according to the three exposure variables, overall and by age at FSI. Furthermore, the outcomes of the teenage pregnancies were examined according to age at FSI. Results: Teenage pregnancy occurred in 11% of the population. Both early smoking initiation (RR: 1.6; 95% CI: 1.4–1.8), early drinking initiation (RR: 1.2; 95% CI: 1.0–1.4), and non-use of contraceptives at FSI (RR: 1.9; 95% CI: 1.8–2.0) were associated with teenage pregnancy. The associations for early smoking initiation and non-use of contraceptives remained when analyses were stratified by age at FSI. Almost 60% of all teenage pregnant women had an induced abortion and less than 30% gave birth. Conclusions: Individual factors, including early smoking and drinking initiation, and non-use of contraceptives at FSI, were associated with teenage pregnancy regardless of age at FSI. This emphasizes the necessity of focusing on early risk-taking behavior as a potential modifier to prevent teenage pregnancy.

Cultural heritage materials, ranging from archaeological objects and sites to fine arts collections, are often characterized through their life cycle. In this review, the fundamentals and tools of materials science are used to explore such life cycles—first, via the origins of the materials and methods used to produce objects of function and artistry, and in some cases, examples of exceptional durability. The findings provide a window on our cultural heritage. Further, they inspire the design of sustainable materials for future generations. Also explored in this review are alteration phenomena over intervals as long as millennia or as brief as decades. Understanding the chemical processes that give rise to corrosion, passivation, or other degradation in chemical and physical properties can provide the foundation for conservation treatments. Finally, examples of characterization techniques that have been invented or enhanced to afford studies of cultural heritage materials, often nondestructively, are highlighted.

The effect of gravity on directional solidification was investigated in solution-based freeze casting. A preceramic siloxane-based polymer was freeze-cast with a cyclohexene solvent from two different directions: that against the direction of the gravitational force and that in concert with the gravitational force. Because the density of preceramic polymer is higher than the solvent, the segregated polymer creates a denser solution ahead of the freezing front than the underlying solution when the freezing direction is the same as the gravity direction. This results in convective flow in the liquid phase. This convective flow influences constitutional supercooling, which changes not only the pore size of freeze-cast structure but also the pore morphology from dendritic to cellular pores.

Little is known about risk factors for progression of high-grade anal intraepithelial neoplasia (AIN) to anal squamous cell carcinoma (ASCC). In this large, population-based study, we assess the role of factors related to immune status for the risk of ASCC among individuals from the general population with a diagnosis of AIN3. Individuals diagnosed with AIN3 during 1985-2016 were identified in the Danish Pathology Registry and followed for subsequent development of ASCC. The study population was linked to the National Patient Registry, the Danish Prescription Registry and the Danish HIV Cohort Study for information on autoimmune disease, genital warts and HIV status. To study the progression rate, Cox regression models with hazard ratios (HR) and 95% confidence intervals (CI) were applied with time since AIN3 as the underlying time scale and with adjustment for age at AIN3 diagnosis, year of AIN3 diagnosis and sex. The study population comprised 1222 individuals with AIN3 contributing 12 824 person-years of follow-up. Ninety-seven individuals (7.9%) developed ASCC. Individuals registered with an autoimmune disease or genital warts before and/or after the AIN3 diagnosis had an increased rate of progression to ASCC compared to individuals without these conditions. People living with HIV had a higher progression rate than HIV-negative individuals (HR=4.25; 95% CI: 1.87-9.65) with the highest progression rate among those with CD4 count ≤200 cells/μL. These associations may be caused by an interplay between HPV infection and immunosuppression.

By exploring the manufacturing methods of historic objects, cultural heritage studies can yield new insights into the history of technology. The required tunability of processing steps, however, is often unknown and the underlying physics and chemistry that provide insight into the object’s properties may also be lacking. A case in point is Böttger luster, a purple overglaze decoration famous for its distinctive iridescence, produced in the Meissen Manufactory from its earliest Böttger period (1710–1719) to around 1735. The iridescence of Böttger luster distinguishes it from contemporaneous purple glazes, motivating the exploration of what compositional and structural features give rise to this optical phenomenon. In this study, historic samples of Böttger luster and Purple of Cassius from Meissen are characterized and compared microscopically. The composition of both overglaze enamels is presented, including results from scanning transmission electron microscopy (STEM)-energy-dispersive X-ray spectroscopy (EDX) analyses. It was found that the iridescence and purple color of Böttger luster is due to the presence of gold nanoparticles in the glaze of the porcelain. Of specific interest is how the underlying physics of scattering and interference of the nanoparticle array is responsible for the iridescence that distinguishes Böttger luster from other gold-based purple colorants, including Purple of Cassius. Coupling these results with prior findings of Meissen porcelains, the glazes were recreated and characterized using scanning electron microscopy (SEM)-EDX, X-ray diffraction (XRD), and ultraviolet-visible spectroscopy (UV-Vis), offering insights into compositional requirements to produce purple luster.

In the general population, human papillomavirus (HPV) prevalence is reportedly increased during pregnancy, and emerging evidence suggests that it may be associated with adverse pregnancy outcomes. Women living with HIV (WLWH) experience higher rates of both HPV infection and certain adverse pregnancy outcomes, yet there are no prior reviews of HPV infection during pregnancy in WLWH.We conducted a systematic review and meta-analysis of pooled and type-specific HPV prevalence and associated pregnancy outcomes among pregnant WLWH and, if available, within-study comparators of women without HIV. Subgroup analyses were performed according to polymerase chain reaction primers used and geographic location.Ten studies describing HPV prevalence in 1594 pregnant WLWH were included. The pooled HPV prevalence in pregnant WLWH was 75.5% (95% confidence interval: 50.2 to 90.4) but ranged widely (23%-98%) between individual studies. Among studies that also assessed HPV prevalence in pregnant women without HIV, the pooled prevalence was lower at 48.1% (95% confidence interval: 27.1 to 69.8). Pregnant WLWH had 54% higher odds of being HPV positive compared with pregnant women without HIV. The most common HPV type detected in pregnant WLWH was HPV16. No studies reported pregnancy outcomes by the HPV status.High prevalence of HPV was documented in pregnant WLWH, exceeding the prevalence among pregnant women without HIV. The limited research on this topic must be addressed with further studies to inform the use of HPV testing as a screening modality for this population as well as the role of HPV in adverse pregnancy outcomes.

Reinforcement strategies were applied to solution-based freeze-casting systems to form porous ceramic composites. Multi-walled carbon nanotubes (MWCNT) were used as the reinforcing fillers in a polysiloxane preceramic polymer freeze cast with dimethyl carbonate to produce silicon oxycarbide-based lamellar pore structures. Using a carefully designed dispersion procedure, CNT agglomerates were reduced both in suspension and in pore walls. Electrical conductivity increased by ten orders of magnitude over pure silicon oxycarbide, indicating the preservation of CNTs after pyrolysis. Permeability, compression, and diametral compression (Brazilian disk) tests were performed to demonstrate the reinforcing effect of CNTs without sacrificing the permeability of the final porous structures.

We report the detection and interferometric localization of the repeating fast radio burst (FRB) source FRB 20220912A during commissioning observations with the Deep Synoptic Array (DSA-110). Two bursts were detected from FRB 20220912A, one each on 2022 October 18 and 2022 October 25. The best-fit position is (R.A. J2000, decl. J2000) = (23:09:04.9, +48:42:25.4), with a 90% confidence error ellipse of $\pm2$ arcsec and $\pm1$ arcsec in right ascension and declination respectively. The two bursts have disparate polarization properties and temporal profiles. We find a Faraday rotation measure that is consistent with the low value of $+0.6$ rad m$^{-2}$ reported by CHIME/FRB. The DSA-110 localization overlaps with the galaxy PSO J347.2702+48.7066 at a redshift $z=0.0771$, which we identify as the likely host. PSO J347.2702$+$48.7066 has a stellar mass of approximately $10^{10}M_{\odot}$, modest internal dust extinction, and a star-formation rate likely in excess of $0.1\,M_{\odot}$ yr$^{-1}$. The host-galaxy contribution to the dispersion measure is likely $\lesssim50$ pc cm$^{-3}$. The FRB 20220912A source is therefore likely viewed along a tenuous plasma column through the host galaxy., Comment: 10 pages, 7 figures, 2 tables, submitted to AAS Journals

Freeze-cast porous ceramics are of interest due to a broad range of applications such as filters, bioscaffolds, and catalyst supports. However, achieving the desired mechanical strength while retaining sufficient functionality, such as permeability, has been challenging. In this work, hierarchical structures of bridged lamellar pores were created via two-stage freeze casting of a preceramic polymer to enhance compressive strength of the resulting SiOC. It has been shown that the bridge density can be controlled by changing the concentration of preceramic polymer in solution and compressive strength increased approximately threefold while permeability constants ranged from 9.63 × 10^(−13) to 3.96 × 10^(−12) m^2.

Aqueous alumina slurries with varying solids loading and particle size were freeze-cast under seven freezing conditions to investigate the influence of these on pore network characteristics including pore size and geometric specific surface area. Slurry temperatures were recorded in situ to determine freezing front position and velocity during solidification, which were then analyzed via regression and modeled using solidification theory. Classic mathematical models for the time dependence of freezing front position and velocity were found to hold for freeze-cast slurries. Building on these, a one-phase Stefan problem was used to describe freezing kinetics. Models for freezing front velocity were combined with solidification theory to obtain predictions of microstructural feature size from freezing kinetics. Results showed that, while there may be a dependence on solids loading, the combination of mathematical modeling of solidification and classic solidification theory is applicable to freeze-cast ceramics and accurately describes pore network characteristics from processing parameters.

We present a multiband study of FRB 20180916B, a repeating source with a 16.3 day periodicity. We report the detection of 4, 1 and 7 bursts from observations spanning 3 days using upgraded Giant Metrewave Radio Telescope (300-500 MHz), Canadian Hydrogen Intensity Mapping Experiment (400-800 MHz) and Green Bank Telescope (600-1000 MHz), respectively. We report the first-ever detection of the source in the 800-1000 MHz range along with one of the widest instantaneous bandwidth detection (200 MHz) at lower frequencies. We identify 30 $\mu$s wide structures in one of the bursts at 800 MHz, making it the lowest frequency detection of such structures for this FRB thus far. There is also a clear indication of high activity of the source at a higher frequency during earlier phases of the activity cycle. We identify a gradual decrease in the rotation measure over two years and no significant variations in the dispersion measure. We derive useful conclusions about progenitor scenarios, energy distribution, emission mechanisms, and variation of downward drift rate of emission with frequency. Our results reinforce that multiband observations are an effective approach to study repeaters and even one-off events to better understand their varying activity and spectral anomalies., Comment: 20 pages, 10 figures

International audience; Toughness describes the ability of a material to resist fracture or crack propagation. It is demonstrated here that fracture toughness of a material can be asymmetric, i.e., the resistance of a medium to a crack propagating from right to left can be significantly different from that to a crack propagating from left to right. Such asymmetry is unknown in natural materials, but we show that it can be built into artificial materials through the proper control of microstructure. This paves the way for control of crack paths and direction, where fracture-when unavoidable-can be guided through pre-designed paths to minimize loss of critical components.

We demonstrate that in a recently proposed unified leptoquark model based on the gauge group SU(4)C×SU(2)L×U(1)R significant deviations from the Standard Model values of RK and RK* can be accommodated without any need of extra heavy fermions. Low energy data, in particular lepton-flavor-violating μ decays and KL→eμ, severely constrain the available parameter space. We show that in the allowed part of the parameter space (i) some of the lepton-flavor-violating tau decay branching ratios are predicted to be close to their current experimental limits. (ii) The underlying scalar leptoquarks can be probed at the LHC via their dominant decay modes into tau leptons and electrons and the third generation quarks. (iii) The constraints from meson oscillations imply that the masses of scalar gluons, another pair of colored multiplets around, have to be bigger than around 15 TeV, and thus, they can be probed only at a future 100 TeV collider. In both neutral and charged variants, these scalars decay predominantly into third generation quarks, with up to O(10%) branching ratios into family-mixed final states. Besides that, we comment on the phenomenology of the scalar gluons in the current scenarios in the case that the B-decay anomalies eventually disappear.

The mechanical properties of an alkyd resin filled with zinc oxide pigment were studied at different concentrations over a wide range of time scales using dynamic mechanical analysis, quartz crystal rheometry and nanoindentation. The motivation for this work stems from the interest in accessing the long-term properties of paint coatings by studying the mechanical properties of historic paints. In this foundational work, we compare three different modalities of mechanical measurements and systematically determine the effect of pigment filler loading on the measured properties. Quantitative agreement between the methods is obtained when the characteristic time scales of each of the methods is taken into account. While nanoindentation is the technique most readily applied to historic paint samples, the rheometric quartz crystal microbalance (rheo-QCM) is the best suited for obtaining mechanistic information from measurements of paint properties over time, provided that appropriate thin-film samples can be produced. In these studies we find that ZnO increases the rate of oxidation of the alkyd during the initial stages of cure by an amount that depends on the ZnO content.

The problem of toughening heterogeneous materials with a stiff matrix and compliant inclusions is investigated through numerical simulations and experiments. Specifically, the problem of optimizing a combination of effective toughness and effective elastic modulus in the context of a square array of compliant inclusions in a stiff matrix is explored. Crack propagation in the heterogeneous material is simulated using a variational phase-field approach. It is found that the crack can meander between or get attracted to and trapped in the inclusions. Composite specimens with a stiff matrix and compliant circular inclusions were 3D printed, and their fracture toughness was measured using a specially designed loading fixture. The experimental results show agreement with the numerical predictions by demonstrating the attraction and trapping of cracks in the inclusions. This study demonstrates the potential for significant enhancement of toughness through elastic compliance contrast between the matrix and the inclusion without notably compromising the effective elastic modulus of the composite material.

Shape‐memory ceramics offer promise for applications like actuation and energy damping, due to their unique properties of high specific strength, high ductility, light weight and inertness in harsh environments. To date, shape‐memory behavior in ceramics is limited to micro/submicro‐scale pillars and particles to circumvent the longstanding problem of transformation‐induced fracture which occurs readily in bulk polycrystalline specimens. The challenge, therefore, lies in the realization of shape‐memory properties in bulk ceramics, which requires careful design of three‐dimensional structures that locally mimic pillar structures. In this work, it is demonstrated that with a gradient‐controlled freeze‐casting approach, honeycomb‐like cellular structures can be fabricated with thin and directionally aligned walls to facilitate martensitic transformation under compression without fracture. With this approach, robust bulk shape‐memory ceramics have been demonstrated in a highly porous structure with strengths under compressive stresses of 25 MPa and strains up to 7.5%.

Freeze casting is used for the first time to prepare solid electrolyte scaffolds with oriented porosity and dense ceramic walls made of Li_7La_3Zr_2O_(12) (LLZO), one of the most promising candidates for solid state battery electrolytes. Processing parameters ‐ such as solvent solidification rate, solvent type, and ceramic particle size ‐ are investigated, focusing on their influence on porosity and ceramic wall density. Dendrite‐like porosity is obtained when using cyclohexane and dioxane as solvents. Lamellar porosity is observed in aqueous slurries resulting in a structure with the highest apparent porosity and densest ceramic scaffold but weakest mechanical properties due to the lack of interlamellar support. The use of smaller LLZO particle size in the slurries resulted in lower porosity and denser ceramic walls. The intrinsic ionic conductivity of the oriented LLZ ceramic scaffold is unaffected by the freeze casting technique, providing a promising ceramic scaffold for polymer infill in view of designing new types of ceramic‐polymer composites.

We report the non-detection of dispersed bursts between 4 and 8 GHz from 2.5 hr of observations of FRB 20200120E at 6 GHz using the Robert C. Byrd Green Bank Telescope. Our fluence limits are several times lower than the average burst fluences reported at 600 and 1400 MHz. We conclude that these non-detections are either due to high-frequency bursts being weaker and/or scintillation-induced modulated. It is also likely that our observations were non-concurrent with any activity window of FRB 20200120E.

Freeze casting yttria-stabilized zirconia (YSZ) can be useful in making electrodes for solid oxide fuel cells (SOFCs) by introducing hierarchical porosity to increase triple-phase boundary (TPB) area while maintaining adequate fuel flow. In this study the influence of alcohol additives on pore structure of aqueous YSZ freeze-cast samples was investigated. Slurries with ethanol, iso-propyl alcohol, or methanol as additives were compared to a control sample. Pore characteristics along sample lengths were measured using X-ray computed tomography reconstructions. The control sample showed significant changes in pore size along sample length, whereas pore size of the alcohol additive samples remained similar, indicating that freezing rates of the additive samples remained constant during solidification. Ice lens formation and interactions between alcohols and slurry functional additives (dispersant, surfactant, and binder) resulted in complex pore structures which show promise in increasing SOFC TPB area.

One of the greatest challenges for advancing lithium-ion battery (LIB) technology is to minimize cell degradation during operation for long-term stability. To this end, it is important to understand how cell performance during operation relates to complex LIB microstructures. In this report, transmission X-ray microscopy (TXM) nanotomography is used to gain quantitative three-dimensional (3D) microstructure-performance correlations of LIB cathodes during cycling. The 3D microstructures of LiMn_2O_4 (LMO) electrodes, cycled under different conditions, including cycle number, operating voltage, and temperature, are characterized via TXM and statistically analyzed to investigate the impact of cycling conditions on the electrode microstructural evolution and cell performance. It is found that the number of cracks formed within LMO particles correlated with capacity fade. For the cell cycled at elevated temperatures, which exhibits the most severe capacity fade among all cells tested, mechanical cracking observed in TXM is not the only dominant contributor to the observed degradation. Mn^(2+) dissolution, as verified by detection of Mn on the counter electrode by energy dispersive spectrometry, also contributed. The current work demonstrate 3D TXM nanotomography as a powerful tool to help probe in-depth understanding of battery failure mechanisms, which could be applicable to electrode structure optimization for advancing LIB development.

Freeze casting of traditional ceramic suspensions and freeze casting of preceramic polymer solutions were directly compared as methods for processing porous ceramics. Alumina and polymethylsiloxane were freeze cast with four different organic solvents (cyclooctane, cyclohexane, dioxane, and dimethyl carbonate) to obtain ceramics with ∼70% porosity. Median pore sizes were smaller for solution freeze casting than for suspension freeze casting under identical processing conditions. The pore structures, which range from foam-like to lamellar, were correlated to the Jackson α-factor of the solvent; solvents with low α-factors yielded nonfaceted pore structures, while high α-factors produced more faceted structures. Intermediate α-factors resulted in dendritic pore structures and were most sensitive to the processing method. Small suspended particles ahead of a solid–liquid interface are hypothesized to destabilize the dendrite tip in suspension freeze casting resulting in more foam-like structures. Differences in processing details were highlighted, particularly regarding the improved freezing front observation possible with solution-based freeze casting.

A grain-selection template was applied to freeze casting to control nucleation of pore-forming crystals and achieve ceramics with highly aligned pore structures. A polymethylsiloxane preceramic polymer was freeze cast with cyclohexane as a solvent to produce dendritic pores in SiOC. Image analysis and permeability measurements were performed to quantify the influence of various templates on sample properties. Results show that the percentage of porosity aligned along the freezing axis increased from 13.9% without a template to 92.6% with an optimal template. The Darcian permeability constant increased by more than 6-fold, from 3.4 × 10^(−12) to 2.1 × 10^(−11) m^2.

A multi-element, time-dependent model developed by Childers et al. [A.S. Childers, M.T. Johnson, J. Ramirez-Rico, and K.T. Faber, J. Electrochem. Soc., 160:3093-3102, 2013] for copper infiltration of large (∼50–200 µm diameter), high aspect ratio (∼60) through-hole channels was experimentally tested for validity. The model built on the work of Akolkar and Landau [R. Akolkar and U. Landau, J. Electrochem. Soc., 151:702-711, 2004] for copper deposition in micro-scale integrated circuitry. Childers’ model broadens the original by including the transport and adsorption of all electrolyte species - inhibitors, accelerators, and copper ions. The resulting model is tested experimentally with wood-derived biomorphic carbon materials. Results indicate that model predictions of premature pore choke off are in agreement with quantitative observations of copper infiltration and qualitative imaging of plated pore profiles. Low accelerator concentrations (0.002 ppm) yielded the highest quantity of copper infiltration without premature closure.

Obreimoff reported his first instrumented measurements of the cleavage of muscovite mica in 1930 and that work helped to propel a greater understanding of fracture. This study builds upon that effort by investigating the role of compliance heterogeneities in brittle materials through mica splitting in a manner similar to Obreimoff. The natural layered structure of mica makes it ideal as a model system for studying fracture as crack propagation can be constrained along a single controlled cleavage plane. Cleavage through the insertion of a rounded wedge provides a straightforward mechanical setup that produces stable crack propagation, so long as the effects of friction and wedge geometry are properly considered. First, homogeneous mica sheets of uniform thickness are cleaved in ambient atmosphere to establish a baseline splitting force and critical strain energy release rate, similar Obreimoff’s original work. After establishing this baseline, mica sheets with prescribed thickness heterogeneities are investigated. It is found that the splitting force required to propagate a crack along a specimen with a sharp increase in layer thickness is significantly larger than the analogous homogeneous splitting forces, even though the crack is not deflected. This indicates that a sharp increase in stiffness can produce an increase in toughness in layered structures without the need for any actual toughness contrast between constituent components or any crack deflection. This toughening effect produced by compliance contrast may have implications in the context of layered ceramic composite design, where systems are often composed of a stiff outer shell and a more compliant and damage-tolerant functional layer.

We investigate the fatigue behavior of bulk polycrystalline lead zirconate titanate (PZT) during bipolar electric field cycling. We characterize the frequency- and cycle-dependent degradation in both the effective electro-mechanical properties (specifically, the electrical hysteresis and the macroscopic viscoelastic stiffness and damping measured by Broadband Electromechanical Spectroscopy, BES) and the microstructural damage evolution (quantified via scanning electron microscopy). The BES setup enables the mechanical characterization while performing electrical cycling so as to measure the evolving viscoelasticity without remounting the sample; particularly measuring the viscoelastic damping allows us to gain insight into the ferroelectric domain wall activity across the full electric hysteresis and over the full range of cycles. A clear dependence on the electric cycling frequency is observed in the rates of degradation of all measured properties including an up to 10% increase in dynamic compliance and a 70% decrease in electric displacement magnitude. We quantify the evolving micro-crack density across wide ranges of numbers of cycles and compare with changes in the effective compliance. Interestingly, the observed strong degradation in the ferroelectric hysteresis is contrasted by relatively mild changes in the effective viscoelastic moduli, while samples clearly indicate increasing levels of micro-damage.

A fiber push-in test was adapted to measure the interfacial frictional stresses present in wood-derived biomorphic graphite/copper interpenetrating phase composites. Additionally, a sandwich composite was used to measure the interfacial fracture toughness of the copper/graphite system. Results indicate that due to poor wetting of copper on graphite, the surface roughness and extent of mechanical interlocking between the two phases determine the mechanical characteristics of the interface, and that the values are comparable to other metal-ceramic composite systems with limited bonding. A characterization of the mechanically bonded interfaces is vital to understanding load transfer, thermal cycling effects, contact resistance, and thermal conductivity.

The interaction of calcium-magnesium-aluminosilicates (CMAS) with Yb_2Si_2O_7-based multilayer environmental barrier coatings was studied using a combination of high-energy synchrotron X-ray techniques. Changes in the phase-specific stresses and lattice spacings as a function of temperature were investigated with wide-angle X-ray scattering. Small-angle X-ray scattering was used to study the interaction of CMAS with nanoporosity, while X-ray computed tomography was used to study the formation of cracks in the coating. It was found that CMAS interacts strongly with the Yb_2Si_2O_7 topcoat, leading to changes in lattice spacing, alterations of the ambient temperature stresses, and large cracks in the CMAS that extend through the topcoat.

Three-phase three-dimensional (3D) microstructural reconstructions of lithium-ion battery electrodes are critical input for 3D simulations of electrode lithiation/delithiation, which provide a detailed understanding of battery operation. In this report, 3D images of a LiCoO2 electrode are achieved using focused ion beam-scanning electron microscopy (FIB-SEM), with clear contrast among the three phases: LiCoO2 particles, carbonaceous phases (carbon and binder) and the electrolyte space. The good contrast was achieved by utilizing an improved FIB-SEM sample preparation method that combined infiltration of the electrolyte space with a low-viscosity silicone resin and triple ion-beam polishing. Morphological parameters quantified include phase volume fraction, surface area, feature size distribution, connectivity, and tortuosity. Electrolyte tortuosity was determined using two different geometric calculations that were in good agreement. The electrolyte tortuosity distribution versus position within the electrode was found to be highly inhomogeneous; this will lead to inhomogeneous electrode lithiation/delithiation at high C-rates that could potentially cause battery degradation.

The interactions of two potential topcoat materials for environmental barrier coatings, Yb_2SiO_5 and Yb_2Si_2O_7, with calcium-magnesium-aluminosilicate (CMAS) engine deposits were studied. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron diffraction were used to investigate the phase transformation associated with the exposure of Yb_2SiO_5 and Yb_2Si_2O_7 to CMAS at 1300 °C. It was found that Yb_2SiO_5 strongly reacts with CMAS to completely dissolve the Yb_2SiO_5 and form hexagonal Ca_2Yb_8(SiO_4)_6O_2 deposits. In contrast, no discernable reaction between CMAS and Yb_2Si_2O_7, was observed over the 96-h exposure.

Alumina ceramics were freeze-cast from water- and camphene-based slurries under varying freezing conditions and examined using X-ray computed tomography (XCT). Pore network characteristics, i.e., porosity, pore size, geometric surface area, and tortuosity, were measured from XCT reconstructions and the data were used to develop a model to predict feature size from processing conditions. Classical solidification theory was used to examine relationships between pore size, temperature gradients, and freezing front velocity. Freezing front velocity was subsequently predicted from casting conditions via the two-phase Stefan problem. Resulting models for water-based samples agreed with solidification-based theories predicting lamellar spacing of binary eutectic alloys, and models for camphene-based samples concurred with those for dendritic growth. Relationships between freezing conditions and geometric surface area were also modeled by considering the inverse relationship between pore size and surface area. Tortuosity was determined to be dependent primarily on the type of dispersion medium.

Garnet-type electrolytes with high ionic conductivity and chemical stability against lithium metal show promise as solid-state electrolytes for lithium-ion batteries. However, a high concentration of pores and grain boundaries in air-processed polycrystalline electrolytes makes them prone to dendrite formation and reaction with atmospheric moisture, leading to electrochemical and mechanical instability. In this work, we illustrate that abnormal grain growth, an often-avoided phenomenon in conventional ceramic processing, can be employed as a unique approach to obtain extraordinarily large oligo crystals for minimal grain boundaries. Here we report a straightforward approach to develop a robust Ga-doped garnet, Li_(6.25)Ga_(0.25)La_3Zr_2O_(12) (LGLZO) electrolyte with conventional solid-state sintering in air. By preparing nanopowders without agglomeration through ball milling and freeze drying, we can control the microstructure of air-sintered electrolytes for desirable properties of a high density (98% of theoretical density) and an average grain size of 460 µm. The robust air-processed LGLZO electrolytes demonstrate high ionic conductivity, stability in air, and mechanical robustness relative to other garnet electrolytes offering promise as cost- and performance-competitive solid-state electrolytes for safe lithium-ion batteries.

To better understand the impact of complex structure on mechanical properties in additively manufactured ceramics, truss structures were 3D printed in preceramic polymer and mechanically evaluated in the pyrolyzed SiOC state. Specimens were printed using digital light processing with a siloxane polymer resin blend. Four different designs were printed: two bending-dominant Kelvin cell structures, a stretching-dominant octet structure, and a mixture of the two with geometries chosen for equivalent stiffness. Mechanical characterization was done at multiple length scales: uniaxial compression to evaluate the entire truss structure, and three-point flexure to assess individual beam elements. After pyrolysis, it was found that truss designs exhibited different shrinkages at the beam element scale despite being composed of the same preceramic polymer and exhibiting isotropic shrinkage at the macro-truss scale. This manner of nonuniform shrinkage has rarely, if ever been reported, as it is standard practice in additive manufacturing to report only bulk linear shrinkage. In uniaxial compression, Kelvin structures with thicker beams exhibited the highest strength of 10 MPa, and octet structures exhibited the lowest strength of 3.8 MPa. In beam element flexure however, the octet beams had the highest strength, 1.9 GPa, four times stronger than the Kelvin beam elements and 500 times stronger than the octet bulk structure. Lastly, the implications for interchangeable truss structures are discussed.

Background Up to 40 per cent of patients undergoing oesophagectomy develop pneumonia. The aim of this study was to assess whether preoperative inspiratory muscle training (IMT) reduces the rate of pneumonia after oesophagectomy. Methods Patients with oesophageal cancer were randomized to a home-based IMT programme before surgery or usual care. IMT included the use of a flow-resistive inspiratory loading device, and patients were instructed to train twice a day at high intensity (more than 60 per cent of maximum inspiratory muscle strength) for 2 weeks or longer until surgery. The primary outcome was postoperative pneumonia; secondary outcomes were inspiratory muscle function, lung function, postoperative complications, duration of mechanical ventilation, length of hospital stay and physical functioning. Results Postoperative pneumonia was diagnosed in 47 (39·2 per cent) of 120 patients in the IMT group and in 43 (35·5 per cent) of 121 patients in the control group (relative risk 1·10, 95 per cent c.i. 0·79 to 1·53; P = 0·561). There was no statistically significant difference in postoperative outcomes between the groups. Mean(s.d.) maximal inspiratory muscle strength increased from 76·2(26·4) to 89·0(29·4) cmH2O (P < 0·001) in the intervention group and from 74·0(30·2) to 80·0(30·1) cmH2O in the control group (P < 0·001). Preoperative inspiratory muscle endurance increased from 4 min 14 s to 7 min 17 s in the intervention group (P < 0·001) and from 4 min 20 s to 5 min 5 s in the control group (P = 0·007). The increases were highest in the intervention group (P < 0·050). Conclusion Despite an increase in preoperative inspiratory muscle function, home-based preoperative IMT did not lead to a decreased rate of pneumonia after oesophagectomy. Registration number: NCT01893008 (https://www.clinicaltrials.gov).