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Large increases in the number of low earth orbit satellites are projected in the coming decades [L. Schulz, K.-H. Glassmeier, Adv. Space Res. 67, 1002–1025 (2021)] with perhaps 50,000 additional satellites in orbit by 2030 [GAO, Large constellations of satellites: Mitigating environmental and other effects (2022)]. When spent rocket bodies and defunct satellites reenter the atmosphere, they produce metal vapors that condense into aerosol particles that descend into the stratosphere. So far, models of spacecraft reentry have focused on understanding the hazard presented by objects that survive to the surface rather than on the fate of the metals that vaporize. Here, we show that metals that vaporized during spacecraft reentries can be clearly measured in stratospheric sulfuric acid particles. Over 20 elements from reentry were detected and were present in ratios consistent with alloys used in spacecraft. The mass of lithium, aluminum, copper, and lead from the reentry of spacecraft was found to exceed the cosmic dust influx of those metals. About 10% of stratospheric sulfuric acid particles larger than 120 nm in diameter contain aluminum and other elements from spacecraft reentry. Planned increases in the number of low earth orbit satellites within the next few decades could cause up to half of stratospheric sulfuric acid particles to contain metals from reentry. The influence of this level of metallic content on the properties of stratospheric aerosol is unknown. [ABSTRACT FROM AUTHOR]

BACKGROUND: Previous studies have reported that ambient temperature may affect perinatal outcomes. However, whether extreme temperature affects the risk of preterm birth (PTB) remains controversial. Studies on the associations of extreme temperature with PTB subtypes are lacking. OBJECTIVES: We aimed to investigate the associations of extreme climate events with the risks of PTB and its subtypes, discerning possible modifiers. METHODS: Data on all singleton deliveries were obtained from the China Labor and Delivery Survey (CLDS), a nationwide investigation implemented in 2015 and 2016. PTB was defined as gestational weeks <37 and then categorized as early (24–34 wk) and late PTBs (35–36 wk), and clinical subtypes [spontaneous PTB, preterm premature rupture of the fetal membranes (PPROM), iatrogenic PTB]. Ambient temperature data were provided by the China National Weather Data Sharing System. Five heat indexes and five cold indexes were used to define heat waves and cold spells. Generalized linear mixed models with a random term by hospital unit were used to assess the associations of short-term prenatal extreme temperature exposure. The Cox proportional hazard regression model was applied to assess the nonlinear associations of low- or high-temperature exposure at the whole and different trimesters of pregnancy with the risk of PTB. Stratified analyses were conducted to assess the possible modification by geographic region and fetal sex. RESULTS: A total of 70,818 singleton births from 96 hospitals in China were included, among which 4,965 (7.01%) were PTBs. Exposure to extreme cold events 1 wk before delivery was associated with an increased PTB risk, with an adjusted odds ratio (aOR) [95% confidence intervals (CIs)] of 1.07 (95% CI: 1.04, 1.10) and 1.06 (1.04, 1.09) for the total days when the daily average temperature below the fifth percentile (fifth-days) and the 10th percentile (10th-days), 1.18 (1.04, 1.34) for the cold spells when the daily average temperature below the fifth percentile for two consecutive days (fifth-2D), 1.09 (1.03, 1.16) and 1.12 (1.06, 1.19) for the cold spells when the daily average temperature below the 10th percentile for three and two consecutive days (10th-3D and 10th-2D), respectively. Results of extreme temperature exposure during 2 weeks before delivery showed similarly significant associations. The association between cold spells and PTB tended to be stronger for late PTB than for early PTB. Cold spells were mainly associated with spontaneous PTB and late PPROM. A stratified analysis indicated that pregnant women in western and northern regions tended to be more sensitive to cold spells, and pregnant women with a female fetus appeared to be at a higher risk of PTB when exposed to cold spells. Pregnant women in late pregnancy were more susceptible to extreme temperatures. No significant or stable association was found between heat waves and preterm birth. DISCUSSION: Exposure to cold spells was associated with an increased risk of PTB, especially late, spontaneous PTB and PPROM. The associations appeared to be more pronounced in the north and west regions and in pregnancies with female fetuses. [ABSTRACT FROM AUTHOR]

Background and Objectives: Few studies have investigated the effects of dietary theobromine intake on the cognitive performance of older adults. Therefore, we investigated these effects in older adults in the United States. Methods and Study Design: In this cross-sectional study, we used data (2011–2014) from the National Health and Nutrition Examination Survey. Intake of theobromine intake was obtained through two 24-h dietary recall interviews and was adjusted by energy. Cognitive performance was assessed using the animal fluency test, Consortium to Establish a Registry for Alzheimer’s Disease Word Learning subtest (CERAD), and Digit Symbol Substitution Test (DSST). Logistic regression and restricted cubic spline models were constructed to evaluate the correlation between the dietary intake of theobromine from different sources and the likelihood of low cognitive performance. Results: The fully adjusted model revealed that compared with the lowest quintile, the odds ratios (with 95% confidence intervals) of cognitive performance in the CERAD test were 0.42 (0.28–0.64), 0.34 (0.14– 0.83), 0.25 (0.07–0.87), and 0.35 (0.13–0.95) for the highest quintile of total theobromine intake and that from chocolate, coffee, and cream, respectively. Dose–response relationship analysis indicated nonlinear correlations between the likelihood of low cognitive performance and dietary theobromine (total intake and that from chocolate, coffee, and cream). An L-shaped relationship was observed between total theobromine intake and cognitive performance in the CERAD test. Conclusions: The dietary intakes of theobromine (total and that from chocolate, coffee, and cream) may protect older adults, particularly men, against low cognitive performance. [ABSTRACT FROM AUTHOR]

Background and Objectives: In daily life, the intake of dietary nutrients is mixed. However, evidence for the association between mixed dietary B vitamin intake and insulin resistance is limited. In this study, we estimated the joint effect of intake of various dietary B vitamins on insulin resistance. Methods and Study Design: This crosssectional study used data from the National Health and Nutrition Examination Survey 2011-2018. We included 1,628 middle-aged and 1,058 older adults without diabetes. Multivariable logistic regression and Bayesian kernel machine regression models were constructed. Results: In the multivariable logistic regression, when all B vitamins were included in the model, the ORs (95% CIs) of insulin resistance were 3.06 (1.00-9.37) and 0.42 (0.19-0.93) for the highest quartile of vitamin B-1 and B-12 intake in the middle-aged group when the lowest quartile was the reference. In the older group, no significant association was observed. In the Bayesian kernel machine regression analysis, a negative trend was noted between mixed B vitamin intake and insulin resistance in both examined groups. The univariate exposure-response function indicated that vitamin B-12 intake was negatively associated with insulin resistance in the middle-aged group, and that vitamin B-6 and dietary folate equivalent intakes were negatively associated with insulin resistance in older group. The bivariate exposure-response function indicated a potential interaction effect between dietary intake of vitamin B-12 and those of vitamin B-1, B-2, niacin, and dietary folate equivalent on insulin resistance in older people. Conclusions: Our results suggest that mixed dietary B vitamin intake tends to decrease the OR of insulin resistance both in middle-aged and older people. [ABSTRACT FROM AUTHOR]