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Abstract In this paper, we demonstrate a strategy to reduce the sintering temperature of titanates through an appropriate amount of Ge substitution for Ti. A series of Li2Mg3Ti1-xGexO6 (x = 0.04, 0.06, 0.08, 0.10, 0.12) ceramics, prepared by a solid-state reaction method, are reported. By controlling the content of the Ge substitution, the sintering temperature of Li2Mg3TiO6 was significantly reduced to 1140 °C. When x = 0.10, the Li2Mg3Ti1-xGexO6 ceramics sintered at 1140 °C for 6 h displayed excellent values of εr = 13.7, Q × f = 131,500 GHz and τf = −34.2 ppm/°C. In addition, the temperature stability was successfully adjusted to be close to zero by adding CaTiO3 to form a composite ceramic. A temperature stable ceramic 0.96Li2Mg3Ti0.9Ge0.1O6-0.04CaTiO3 with τf = −3.5 ppm/°C, εr = 14.9 and Q × f = 68,900 GHz was obtained when sintered at 1180 °C. The good dielectric performances of the CaTiO3-modified Li2Mg3Ti0.9Ge0.1O6 ceramics makes them possible candidates for substrates in microwave integrated circuits.
Abstract Rapid developments of microwave dielectric materials have emerged in recent years due to their wide-spread applications and the revolution in wireless communications. However, many commercial microwave materials are based on titanates, niobates and tantalates which have the disadvantages both of costly raw materials and high sintering temperatures. These result in a production process which is not energy efficient. In this paper we develop a BaO-TiO2-GeO2 ternary system derived from the BaO-TiO2 binary system to obtain low temperature co-fired microwave dielectric ceramics for high frequency applications. The Ba2TiGe2O8 ceramics were prepared via the conventional solid-state route. The X-ray diffraction results showed that Ba2TiGe2O8 belongs to the orthorhombic, Cmm2 space group. The ceramics exhibited a densification of 96.3% after being sintered at 1060 °C. They also exhibited a relative permittivity (εr) of 12.7, a quality factor (Q×f) of 9060 GHz (at 10 GHz), a temperature coefficient of resonant frequency (τf) of −30 ppm/°C and a coefficient of thermal expansion (CTE) of 11.0 ppm/°C. In addition, the Raman spectra and ionic polarizability of Ba2TiGe2O8 unit cells were investigated.
Abstract A low‐permittivity dielectric ceramic Li2GeO3 was prepared by the solid‐state reaction route. Single‐phase Li2GeO3 crystallized in an orthorhombic structure. Dense ceramics with high relative density and homogeneous microstructure were obtained as sintered at 1000‐1100°C. The optimum microwave dielectric properties were achieved in the sample sintered at 1080°C with a high relative density ~ 96%, a relative permittivity εr ~ 6.36, a quality factor Q × f ~ 29 000 GHz (at 14.5 GHz), and a temperature coefficient of resonance frequency τf ~ −72 ppm/°C. The sintering temperature of Li2GeO3 was successfully lowered via the appropriate addition of B2O3. Only 2 wt.% B2O3 addition contributed to a 21.2% decrease in sintering temperature to 850°C without deteriorating the dielectric properties. The temperature dependence of the resonance frequency was successfully suppressed by the addition of TiO2 to form Li2TiO3 with a positive τf value. These results demonstrate potential applications of Li2GeO3 in low‐temperature cofiring ceramics technology.
Abstract A new ultralow dielectric loss cofired CaMgGeO4 dielectric material with olivine structure was fabricated by the solid-state route. The X-ray patterns, Rietveld refinement, and microstructure revealed the characteristics of the synthesized material. CaMgGeO4 ceramic belongs to the orthorhombic system with a Pbmn space group. Sintered at 1300 °C for 6 h, the ceramic exhibited a densification of 96.5%, an ultrahigh quality factor (Q × f) of 124 900 GHz (tan δ = 1.24 × 10–4) at a frequency of 15.5 GHz, a permittivity (εr) of 6.71, and a temperature coefficient of resonant frequency (τf) of −73.7 ppm/°C, and the average coefficient of thermal expansion of CaMgGeO4 was 12.4 ppm/°C. The sintering temperature of the CaMgGeO4 ceramic was reduced from 1300 to 940 °C with the addition of 5 wt % B2O3. The CaMgGeO4 + 5 wt % B2O3 ceramics exhibited favorable microwave dielectric performances: Q × f = 102 000 GHz (at 16.4 GHz), εr = 5.80, and τf = −64.7 ppm/°C, respectively. In addition, the CaMgGeO4 ceramic did not react with Ag electrodes, which could be advantageous in low-temperature cofired ceramic multilayer microwave devices.
Abstract The patch antenna of spinel-olivine composite ceramic (Li2ZnGe3O8-Li2ZnGeO4) is designed, which can realize power ratio (59%) and S11 of -14 dB at 5.7 GHz. The low sintering temperature (< 960 °C), low relative permittivity (8.15) and good microwave dielectric properties (quality factor ~ 32,500 GHz, resonant frequency temperature coefficient ~ -74.8 ppm/ °C) were obtained for spinel-olivine composite ceramic. Li2ZnGe3O8-Li2ZnGeO4 composite microwave dielectric ceramics were synthesized at 900–980 °C using Li2CO3, ZnO and GeO2, which can co-fire with silver electrodes without chemical reaction. These exceptional characteristics enable high-speed signal transmission application of spinel-olivine composite ceramics (Li2ZnGe3O8-Li2ZnGeO4) in 5 GHz Wi-Fi antennas.
Abstract In this paper, BiZn2VO6 doped with sintering aids of B2O3 and Li2CO3 is investigated in order to broaden the options for ultralow temperature cofired ceramics (ULTCC). The sintering behavior, microstructure, and microwave dielectric properties are studied. In combination with 1 wt% B2O3 and 5 wt% Li2CO3 dopants, the sintering temperature of the BiZn2VO6 ceramics was reduced from 780°C to 600°C. The co‐doped BiZn2VO6 ceramics exhibited a low relative permittivity (εr) of 8.9 and a quality factor (Q × f) of 13 000 GHz at a microwave‐range frequency of 9 GHz. The temperature coefficient of resonant frequency (τf) was measured to be −97 ppm/°C. The average linear coefficient of thermal expansion (CTE) was 7.2 ppm/°C. With the low sintering temperature, the co‐doped BiZn2VO6 ceramics are compatible to be cofired with cost‐effective aluminum electrodes. This was proven in a reaction test between the BiZn2VO6‐B2O3‐Li2CO3 and aluminum powders, in which no chemical interaction could be detected. These promising properties make the B2O3‐Li2CO3 co‐doped BiZn2VO6 an ideal candidate for ULTCC applications.
Abstract A cubic rock salt structured ceramic, Li7Ti3O9F, was fabricated via the conventional solid-state reaction route. The synthesis conditions, sintering characteristics, and microwave dielectric properties of Li7Ti3O9F ceramics were investigated by X-ray diffraction (XRD), thermal dilatometer, Scanning Electron Microscopy (SEM) accompanied with EDS mapping, and microwave resonant measurements. Rietveld refinement, selected area electron diffraction (SAED) pattern and high-resolution transmission electron microscopy (HRTEM) confirmed that Li7Ti3O9F adopts a cubic rock-salt structure. The ceramic sintered at 950 °C presented the optimal microwave properties of εr = 22.5, Q×f = 88,200 GHz, and τf = −24.2 ppm/°C. Moreover, good chemical compatibility with Ag was verified through cofiring at 950 °C for 2 h. These results confirm a large potential for Li7Ti3O9F ceramic to be utilized as substrates in the low temperature cofired ceramic (LTCC) technology. This work provides the possibility to exploit low-temperature-firing ceramics through solid solution between oxides and fluorides.
Background: Venous thromboembolism (VTE) and bleeding are serious and potentially fatal complications of surgical procedures. Pharmacological thromboprophylaxis decreases the risk of VTE but increases the risk of major post-operative bleeding. The decision to use pharmacologic prophylaxis therefore represents a trade-off that critically depends on the incidence of VTE and bleeding in the absence of prophylaxis. These baseline risks vary widely between procedures, but their magnitude is uncertain. Systematic reviews addressing baseline risks are scarce, needed, and require innovations in methodology. Indeed, systematic summaries of these baseline risk estimates exist neither in general nor gynecologic surgery. We will fill this knowledge gap by performing a series of systematic reviews and meta-analyses of the procedure-specific and patient risk factor stratified risk estimates in general and gynecologic surgeries. Methods: We will perform comprehensive literature searches for observational studies in general and gynecologic surgery reporting symptomatic VTE or bleeding estimates. Pairs of methodologically trained reviewers will independently assess the studies for eligibility, evaluate the risk of bias by using an instrument developed for this review, and extract data. We will perform meta-analyses and modeling studies to adjust the reported risk estimates for the use of thromboprophylaxis and length of follow up. We will derive the estimates of risk from the median estimates of studies rated at the lowest risk of bias. The primary outcomes are the risk estimates of symptomatic VTE and major bleeding at 4 weeks post-operatively for each procedure stratified by patient risk factors. We will apply the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to rate evidence certainty. Discussion: This series of systematic reviews, modeling studies, and meta-analyses will inform clinicians and patients regarding the trade-off between VTE prevention and bleeding in general and gynecologic surgeries. Our work advances the standards in systematic reviews of surgical complications, including assessment of risk of bias, criteria for arriving at the best estimates of risk (including modeling of the timing of events and dealing with suboptimal data reporting), dealing with subgroups at higher and lower risk of bias, and use of the GRADE approach. Systematic review registration: PROSPERO CRD42021234119.
Abstract Blood pressure (BP) is a major risk factor for cardiovascular disease and more than 200 genetic loci associated with BP are known. Here, we perform a multi-stage genome-wide association study for BP (max N = 289,038) principally in East Asians and meta-analysis in East Asians and Europeans. We report 19 new genetic loci and ancestry-specific BP variants, conforming to a common ancestry-specific variant association model. At 10 unique loci, distinct non-rare ancestry-specific variants colocalize within the same linkage disequilibrium block despite the significantly discordant effects for the proxy shared variants between the ethnic groups. The genome-wide transethnic correlation of causal-variant effect-sizes is 0.898 and 0.851 for systolic and diastolic BP, respectively. Some of the ancestry-specific association signals are also influenced by a selective sweep. Our results provide new evidence for the role of common ancestry-specific variants and natural selection in ethnic differences in complex traits such as BP.
Abstract Glycemic traits are used to diagnose and monitor type 2 diabetes and cardiometabolic health. To date, most genetic studies of glycemic traits have focused on individuals of European ancestry. Here we aggregated genome-wide association studies comprising up to 281,416 individuals without diabetes (30% non-European ancestry) for whom fasting glucose, 2-h glucose after an oral glucose challenge, glycated hemoglobin and fasting insulin data were available. Trans-ancestry and single-ancestry meta-analyses identified 242 loci (99 novel; P < 5 x 10-8), 80% of which had no significant evidence of between-ancestry heterogeneity. Analyses restricted to individuals of European ancestry with equivalent sample size would have led to 24 fewer new loci. Compared with single-ancestry analyses, equivalent-sized trans-ancestry fine-mapping reduced the number of estimated variants in 99% credible sets by a median of 37.5%. Genomic-feature, gene-expression and gene-set analyses revealed distinct biological signatures for each trait, highlighting different underlying biological pathways. Our results increase our understanding of diabetes pathophysiology by using trans-ancestry studies for improved power and resolution.
Abstract In many species, the offspring of related parents suffer reduced reproductive success, a phenomenon known as inbreeding depression. In humans, the importance of this effect has remained unclear, partly because reproduction between close relatives is both rare and frequently associated with confounding social factors. Here, using genomic inbreeding coefficients (FROH) for >1.4 million individuals, we show that FROH is significantly associated (p < 0.0005) with apparently deleterious changes in 32 out of 100 traits analysed. These changes are associated with runs of homozygosity (ROH), but not with common variant homozygosity, suggesting that genetic variants associated with inbreeding depression are predominantly rare. The effect on fertility is striking: FROH equivalent to the offspring of first cousins is associated with a 55% decrease [95% CI 44–66%] in the odds of having children. Finally, the effects of FROH are confirmed within full-sibling pairs, where the variation in FROH is independent of all environmental confounding.
Abstract We study damping signatures at the Jiangmen Underground Neutrino Observatory (JUNO), a medium-baseline reactor neutrino oscillation experiment. These damping signatures are motivated by various new physics models, including quantum decoherence, nu(3) decay, neutrino absorption, and wave packet decoherence. The phenomenological effects of these models can be characterized by exponential damping factors at the probability level. We assess how well JUNO can constrain these damping parameters and how to disentangle these different damping signatures at JUNO. Compared to current experimental limits, JUNO can significantly improve the limits on tau(3)/m(3) in the nu(3) decay model, the width of the neutrino wave packet sigma(x), and the intrinsic relative dispersion of neutrino momentum sigma(rel).
Introduction: Educational attainment, widely used in epidemiologic studies as a surrogate for socioeconomic status, is a predictor of cardiovascular health outcomes. Methods: A two-stage genome-wide meta-analysis of low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), and triglyceride (TG) levels was performed while accounting for gene-educational attainment interactions in up to 226,315 individuals from five population groups. We considered two educational attainment variables: “Some College” (yes/no, for any education beyond high school) and “Graduated College” (yes/no, for completing a 4-year college degree). Genome-wide significant (p < 5 × 10−8) and suggestive (p < 1 × 10−6) variants were identified in Stage 1 (in up to 108,784 individuals) through genome-wide analysis, and those variants were followed up in Stage 2 studies (in up to 117,531 individuals). Results: In combined analysis of Stages 1 and 2, we identified 18 novel lipid loci (nine for LDL, seven for HDL, and two for TG) by two degree-of-freedom (2 DF) joint tests of main and interaction effects. Four loci showed significant interaction with educational attainment. Two loci were significant only in cross-population analyses. Several loci include genes with known or suggested roles in adipose (FOXP1, MBOAT4, SKP2, STIM1, STX4), brain (BRI3, FILIP1, FOXP1, LINC00290, LMTK2, MBOAT4, MYO6, SENP6, SRGAP3, STIM1, TMEM167A, TMEM30A), and liver (BRI3, FOXP1) biology, highlighting the potential importance of brain-adipose-liver communication in the regulation of lipid metabolism. An investigation of the potential druggability of genes in identified loci resulted in five gene targets shown to interact with drugs approved by the Food and Drug Administration, including genes with roles in adipose and brain tissue. Discussion: Genome-wide interaction analysis of educational attainment identified novel lipid loci not previously detected by analyses limited to main genetic effects.
BACKGROUND: Genetic variants within nearly 1000 loci are known to contribute to modulation of blood lipid levels. However, the biological pathways underlying these associations are frequently unknown, limiting understanding of these findings and hindering downstream translational efforts such as drug target discovery. RESULTS: To expand our understanding of the underlying biological pathways and mechanisms controlling blood lipid levels, we leverage a large multi-ancestry meta-analysis (N = 1,654,960) of blood lipids to prioritize putative causal genes for 2286 lipid associations using six gene prediction approaches. Using phenome-wide association (PheWAS) scans, we identify relationships of genetically predicted lipid levels to other diseases and conditions. We confirm known pleiotropic associations with cardiovascular phenotypes and determine novel associations, notably with cholelithiasis risk. We perform sex-stratified GWAS meta-analysis of lipid levels and show that 3-5% of autosomal lipid-associated loci demonstrate sex-biased effects. Finally, we report 21 novel lipid loci identified on the X chromosome. Many of the sex-biased autosomal and X chromosome lipid loci show pleiotropic associations with sex hormones, emphasizing the role of hormone regulation in lipid metabolism. CONCLUSIONS: Taken together, our findings provide insights into the biological mechanisms through which associated variants lead to altered lipid levels and potentially cardiovascular disease risk.