Publications by authors named "Matthew Huber"

49 Publications

African Hydroclimate During the Early Eocene From the DeepMIP Simulations.

Paleoceanogr Paleoclimatol 2022 May 16;37(5):e2022PA004419. Epub 2022 May 16.

Climate and Global Dynamics Laboratory National Center for Atmospheric Research Boulder CO USA.

The early Eocene (∼56-48 Myr ago) is characterized by high CO estimates (1,200-2,500 ppmv) and elevated global temperatures (∼10°C-16°C higher than modern). However, the response of the hydrological cycle during the early Eocene is poorly constrained, especially in regions with sparse data coverage (e.g., Africa). Here, we present a study of African hydroclimate during the early Eocene, as simulated by an ensemble of state-of-the-art climate models in the Deep-time Model Intercomparison Project (DeepMIP). A comparison between the DeepMIP pre-industrial simulations and modern observations suggests that model biases are model- and geographically dependent, however, these biases are reduced in the model ensemble mean. A comparison between the Eocene simulations and the pre-industrial suggests that there is no obvious wetting or drying trend as the CO increases. The results suggest that changes to the land sea mask (relative to modern) in the models may be responsible for the simulated increases in precipitation to the north of Eocene Africa. There is an increase in precipitation over equatorial and West Africa and associated drying over northern Africa as CO rises. There are also important dynamical changes, with evidence that anticyclonic low-level circulation is replaced by increased south-westerly flow at high CO levels. Lastly, a model-data comparison using newly compiled quantitative climate estimates from paleobotanical proxy data suggests a marginally better fit with the reconstructions at lower levels of CO.
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http://dx.doi.org/10.1029/2022PA004419DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9321955PMC
May 2022

Long-Term Earth-Moon Evolution With High-Level Orbit and Ocean Tide Models.

J Geophys Res Planets 2021 Dec 1;126(12):e2021JE006875. Epub 2021 Dec 1.

Department of Earth, Atmospheric, and Planetary Sciences Purdue University West Lafayette IN USA.

Tides and Earth-Moon system evolution are coupled over geological time. Tidal energy dissipation on Earth slows rotation rate, increases obliquity, lunar orbit semi-major axis and eccentricity, and decreases lunar inclination. Tidal and core-mantle boundary dissipation within the Moon decrease inclination, eccentricity and semi-major axis. Here we integrate the Earth-Moon system backwards for 4.5 Ga with orbital dynamics and explicit ocean tide models that are "high-level" (i.e., not idealized). To account for uncertain plate tectonic histories, we employ Monte Carlo simulations, with tidal energy dissipation rates (normalized relative to astronomical forcing parameters) randomly selected from ocean tide simulations with modern ocean basin geometry and with 55, 116, and 252 Ma reconstructed basin paleogeometries. The normalized dissipation rates depend upon basin geometry and rotation rate. Faster Earth rotation generally yields lower normalized dissipation rates. The Monte Carlo results provide a spread of possible early values for the Earth-Moon system parameters. Of consequence for ocean circulation and climate, absolute (un-normalized) ocean tidal energy dissipation rates on the early Earth may have exceeded rate due to a closer Moon. Prior to , evolution of inclination and eccentricity is dominated by tidal and core-mantle boundary dissipation within the Moon, which yield high lunar orbit inclinations in the early Earth-Moon system. A drawback for our results is that the semi-major axis does not collapse to near-zero values at 4.5 Ga, as indicated by most lunar formation models. Additional processes, missing from our current efforts, are discussed as topics for future investigation.
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http://dx.doi.org/10.1029/2021JE006875DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9285098PMC
December 2021

Comparison of knowledge acquisition and retention following traditional didactic vs. flipped classroom education utilizing a standardized national curriculum: a randomized controlled trial.

J Perinatol 2022 Jun 3. Epub 2022 Jun 3.

Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.

Objective: Measure the effectiveness of and preference for a standardized, national curriculum utilizing flipped classrooms (FC) in neonatal-perinatal medicine (NPM) fellowships.

Study Design: Multicentered equivalence, cluster randomized controlled trial of NPM fellowship programs randomized to receive standardized physiology education as in-class lectures (traditional didactic, TD arm) or as pre-class online videos followed by in-class discussions (FC arm). Four multiple-choice question quizzes and three surveys were administered to measure knowledge acquisition, retention, and educational preferences.

Results: 530 fellows from 61 NPM fellowships participated. Quiz performance was comparable between groups at all time points (p = NS, TD vs FC at 4 time points). Post intervention, more fellows in both groups preferred group discussions (pre/post FC 42% vs. 58%, P = 0.002; pre/post TD 43% vs. 60%, P = < 0.001). FC fellows were more likely to rate classroom effectiveness positively (FC/TD, 70% vs. 36%, P < 0.001).

Conclusions: FCs promote knowledge acquisition and retention equivalent to TD and FC modalities are preferred by fellows.
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http://dx.doi.org/10.1038/s41372-022-01423-4DOI Listing
June 2022

An Automated Region-Selection Method for Adaptive ALARA Ultrasound Imaging.

IEEE Trans Ultrason Ferroelectr Freq Control 2022 Jul 30;69(7):2257-2269. Epub 2022 Jun 30.

The objective of this work was to develop an automated region of the interest selection method to use for adaptive imaging. The as low as reasonably achievable (ALARA) principle is the recommended framework for setting the output level of diagnostic ultrasound devices, but studies suggest that it is not broadly observed. One way to address this would be to adjust output settings automatically based on image quality feedback, but a missing link is determining how and where to interrogate the image quality. This work provides a method of region of interest selection based on standard, envelope-detected image data that are readily available on ultrasound scanners. Image brightness, the standard deviation of the brightness values, the speckle signal-to-noise ratio, and frame-to-frame correlation were considered as image characteristics to serve as the basis for this selection method. Region selection with these filters was compared to results from image quality assessment at multiple acoustic output levels. After selecting the filter values based on data from 25 subjects, testing on ten reserved subjects' data produced a positive predictive value of 94% using image brightness, the speckle signal-to-noise ratio, and frame-to-frame correlation. The best case filter values for using only image brightness and speckle signal-to-noise ratio had a positive predictive value of 97%. These results suggest that these simple methods of filtering could select reliable regions of interest during live scanning to facilitate adaptive ALARA imaging.
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http://dx.doi.org/10.1109/TUFFC.2022.3172690DOI Listing
July 2022

The latitudinal temperature gradient and its climate dependence as inferred from foraminiferal δO over the past 95 million years.

Proc Natl Acad Sci U S A 2022 03 7;119(11):e2111332119. Epub 2022 Mar 7.

Department of Earth and Planetary Sciences, Yale University, New Haven, CT 06511.

SignificanceThe temperature difference between low and high latitudes is one measure of the efficiency of the global climate system in redistributing heat and is used to test the ability of models to represent the climate system through time. Here, we show that the latitudinal temperature gradient has exhibited a consistent inverse relationship with global mean sea-surface temperature for at least the past 95 million years. Our results help reduce conflicts between climate models and empirical estimates of temperature and argue for a fundamental consistency in the dynamics of heat transport and radiative transfer across vastly different background states.
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http://dx.doi.org/10.1073/pnas.2111332119DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8931236PMC
March 2022

Health Care Professional and Caregiver Attitudes Toward and Usage of Medical Podcasting: Questionnaire Study.

JMIR Pediatr Parent 2022 Feb 1;5(1):e29857. Epub 2022 Feb 1.

Children's Hospital of Philadelphia, Philadelphia, PA, United States.

Background: Podcasts are used increasingly in medicine. There is growing research into the role of podcasts in medical education, but the use of podcasting as a tool for pediatric parent/caregiver health education is largely unexplored. As parents/caregivers seek medical information online, an understanding of parental preferences is needed.

Objective: We sought to explore health care professional and parent/caregiver awareness and views on podcasting as a health education tool.

Methods: This survey study was conducted and distributed via in-person collection from parents/caregivers (≥18 years old) in the waiting room of an academic pediatric primary care clinic, targeted social media promotion, and professional listservs for health care professionals in pediatrics. Statistical analysis included chi-square tests of independence between categorical variables.

Results: In total, 125 health care professionals and 126 caregivers completed the survey. Of those surveyed, 81% (101/125) of health care professionals and 55% (69/126) of parents/caregivers listened to podcasts (P<.001). Health care professionals and parents/caregivers listed the same top 3 quality indicators for medical podcasts. Podcast listeners were more likely to have higher incomes and use professional websites for information. The survey elicited a variety of reasons for podcast nonengagement.

Conclusions: Health care professionals appear to be more engaged in medical education podcasts than parents/caregivers. However, similar factors were valued when evaluating the quality of a pediatric podcast: accuracy, transparency, and credibility. Professional websites may be one avenue to increase podcast uptake. More needs to be done to explore the use of podcasts and digital media for medical information.
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http://dx.doi.org/10.2196/29857DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8848225PMC
February 2022

Occult Regions of Suppressed Coherence in Liver B-Mode Images.

Ultrasound Med Biol 2022 01 23;48(1):47-58. Epub 2021 Oct 23.

Department of Biomedical Engineering, Duke University, Durham, North Carolina, USA; Department of Radiology, Duke University Medical Center, Durham, North Carolina, USA.

Ultrasound is an essential tool for diagnosing and monitoring diseases, but it can be limited by poor image quality. Lag-one coherence (LOC) is an image quality metric that can be related to signal-to-noise ratio and contrast-to-noise ratio. In this study, we examine matched LOC and B-mode images of the liver to discern patterns of low image quality, as indicated by lower LOC values, occurring beneath the abdominal wall, near out-of-plane vessels and adjacent to hyperechoic targets such the liver capsule. These regions of suppressed coherence are often occult; they present as temporally stable uniform speckle on B-mode images, but the LOC measurements in these regions suggest substantially degraded image quality. Quantitative characterization of the coherence suppression beneath the abdominal wall reveals a consistent pattern both in simulations and in vivo; sharp drops in coherence occurring beneath the abdominal wall asymptotically recover to a stable coherence at depth. Simulation studies suggest that abdominal wall reverberation clutter contributes to the initial drop in coherence but does not influence the asymptotic LOC value. Clinical implications are considered for contrast loss in B-mode imaging and estimation errors for elastography and Doppler imaging.
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http://dx.doi.org/10.1016/j.ultrasmedbio.2021.09.007DOI Listing
January 2022

Probing the Ecology and Climate of the Eocene Southern Ocean With Sand Tiger Sharks .

Paleoceanogr Paleoclimatol 2020 Dec 8;35(12):e2020PA003997. Epub 2020 Dec 8.

Department of Earth, Atmosphere, and Planetary Sciences Purdue University West Lafayette IN USA.

Many explanations for Eocene climate change focus on the Southern Ocean-where tectonics influenced oceanic gateways, ocean circulation reduced heat transport, and greenhouse gas declines prompted glaciation. To date, few studies focus on marine vertebrates at high latitudes to discern paleoecological and paleoenvironmental impacts of this climate transition. The Tertiary Eocene La Meseta (TELM) Formation has a rich fossil assemblage to characterize these impacts; , an extinct (†) sand tiger shark, is abundant throughout the La Meseta Formation. Body size is often tracked to characterize and integrate across multiple ecological dimensions. † body size distributions indicate limited changes during TELMs 2-5 based on anterior tooth crown height ( = 450, mean = 19.6 ± 6.4 mm). Similarly, environmental conditions remained stable through this period based on δO values from tooth enameloid ( = 42; 21.5 ± 1.6‰), which corresponds to a mean temperature of 22.0 ± 4.0°C. Our preliminary ( = 4) results indicate an early Drake Passage opening with Pacific inputs during TELM 2-3 (45-43 Ma) based on single unit variation with an overall radiogenic trend. Two possible hypotheses to explain these observations are (1) † modified its migration behavior to ameliorate environmental changes related to the Drake Passage opening, or (2) the local climate change was small and gateway opening had little impact. While we cannot rule out an ecological explanation, a comparison with climate model results suggests that increased CO produces warm conditions that also parsimoniously explain the observations.
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http://dx.doi.org/10.1029/2020PA003997DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8246854PMC
December 2020

Achieving adequate growth in infants with congenital diaphragmatic hernia prior to discharge.

J Pediatr Surg 2021 Dec 26;56(12):2200-2206. Epub 2021 Mar 26.

Division of Neonatology, The Children's Hospital of Philadelphia, Perelman School of Medicine at University of Pennsylvania, 3401 Civic Center Boulevard, Philadelphia, PA 19104, United States.

Background/purpose: To evaluate the enteral feeding requirements, including caloric provisions, of infants with CDH in relation to growth patterns.

Methods: A retrospective observational study was conducted on infants with CDH between August 2012 and March 2017. Electronic medical records were reviewed to extract detailed infant feeding data and anthropometric measurements at monthly intervals until discharge. Statistical methods of analysis included generalized linear models, Pearson correlation coefficient, Analysis of variance (ANOVA), Kruskal-Wallis, Wilcoxon rank sum, and Fisher's Exact tests.

Results: Among 149 infants with CDH, 45% (n = 67) met criteria for malnutrition at discharge. Maternal human milk (HM) was initiated in 95% of infants (n = 142) and continued in 79% of infants (n = 118) at discharge. Overall, 50% received fortification of feeds, including 60% (n = 89) of formula fed infants compared to only 21% (n = 31) of HM fed infants (p<0.001). Infants fed formula had lower weight-for-length z-scores at discharge compared to those fed HM.

Conclusions: Infants receiving HM demonstrated improved growth compared to formula fed infants. However, higher calorie feeding regimens need to be initiated earlier to improve growth velocity. Prompt recognition of malnutrition and growth failure with aggressive supplementation may improve the overall growth of infants with CDH and has the potential to improve long term neurodevelopmental outcomes.
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http://dx.doi.org/10.1016/j.jpedsurg.2021.03.048DOI Listing
December 2021

Delivery room oxygen physiology and respiratory interventions for newborns with cyanotic congenital heart disease.

J Perinatol 2021 09 23;41(9):2309-2316. Epub 2021 Mar 23.

Children's Hospital of Philadelphia, Division of Neonatology, Philadelphia, PA, USA.

Objective: To characterize pulse oxygen saturation (SpO) trajectories and respiratory interventions after birth for newborns with cyanotic congenital heart disease (CCHD).

Study Design: Retrospective single-site study of newborns ≥32 weeks gestation with CCHD: single ventricle with critical aortic obstruction (SV-CAO), critical pulmonic obstruction (CPO), transposition of the great arteries (TGA). Minute-to-minute SpO values and respiratory interventions were summarized and compared.

Results: Two hundred infants were enrolled. SpO at each minute differed across groups (p < 0.01), with the lowest values in TGA. All interventions were most frequent in TGA (p < 0.01). Continuous positive airway pressure was provided in 22% SV-CAO, 23% CPO, and 66% TGA. Positive pressure ventilation occurred in 7% SV-CAO, 14% CPO, and 33% TGA. Intubation occurred in 4% SV-CAO, 10% CPO, and 53% TGA.

Conclusion: We defined SpO trajectories and delivery room respiratory interventions for three CCHD phenotypes. These results inform delivery room management of these high-risk populations.
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http://dx.doi.org/10.1038/s41372-021-01029-2DOI Listing
September 2021

Goals of Care Discussions and Moral Distress Among Neonatal Intensive Care Unit Staff.

J Pain Symptom Manage 2021 09 28;62(3):529-536. Epub 2021 Jan 28.

Division of Neonatology, Department of Pediatrics, The Children's Hospital of Philadelphia and University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA.

Context: The relationship between quality of Goals of Care (GOC) conversations and moral distress among neonatal intensive care unit (NICU) providers is not known.

Objectives: We sought 1) to explore levels of moral distress in providers, 2) to evaluate how staff moral distress changes in relation to GOC discussions, and 3) to identify elements of GOC discussions associated with change in moral distress. We hypothesized that staff moral distress would change after GOC discussions and that change would vary with presence of key discussion elements.

Methods: Prospective cohort study in a level IV NICU in an urban teaching hospital. We administered validated instruments at baseline and following GOC discussions including the Moral Distress Thermometer (MDT) and Williams Instrument (a measure of end-of-life care) to physicians, nurses, and social workers.

Results: We collected data on 79 GOC conversations over a 1-year period from 2018 to 2019. Most providers experienced an increase in moral distress following a GOC discussion. Providers experienced an average increase in moral distress, as measured by the MDT, of 0.84 (+/-3.15; P = 0.002). Physicians experienced an average change in moral distress of 1.1 (+/-3.52; P = 0.01) while nurses experienced an average change of 0.55 (+/-2.66; P = 0.07). Several elements of discussions were associated with the degree of increase in moral distress after the conversation.

Conclusion: Change in moral distress among providers may be a useful metric of quality of GOC discussions. There are identifiable elements of GOC conversations that are associated with high-quality discussions. These elements warrant further study.
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http://dx.doi.org/10.1016/j.jpainsymman.2021.01.124DOI Listing
September 2021

Association Between Kidney Clearance of Secretory Solutes and Cardiovascular Events: The Chronic Renal Insufficiency Cohort (CRIC) Study.

Am J Kidney Dis 2021 08 7;78(2):226-235.e1. Epub 2021 Jan 7.

Kidney Research Institute, Seattle, WA; Department of Medicine, Division of Nephrology, University of Washington, Seattle, WA. Electronic address:

Rationale & Objective: The clearance of protein-bound solutes by the proximal tubules is an innate kidney mechanism for removing putative uremic toxins that could exert cardiovascular toxicity in humans. However, potential associations between impaired kidney clearances of secretory solutes and cardiovascular events among patients with chronic kidney disease (CKD) remains uncertain.

Study Design: A multicenter, prospective, cohort study.

Setting & Participants: We evaluated 3,407 participants from the Chronic Renal Insufficiency Cohort (CRIC) study.

Exposures: Baseline kidney clearances of 8 secretory solutes. We measured concentrations of secretory solutes in plasma and paired 24-hour urine specimens using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Outcomes: Incident heart failure, myocardial infarction, and stroke events.

Analytical Approach: We used Cox regression to evaluate associations of baseline secretory solute clearances with incident study outcomes adjusting for estimated GFR (eGFR) and other confounders.

Results: Participants had a mean age of 56 years; 45% were women; 41% were Black; and the median estimated glomerular filtration rate (eGFR) was 43 mL/min/1.73 m. Lower 24-hour kidney clearance of secretory solutes were associated with incident heart failure and myocardial infarction but not incident stroke over long-term follow-up after controlling for demographics and traditional risk factors. However, these associations were attenuated and not statistically significant after adjustment for eGFR.

Limitations: Exclusion of patients with severely reduced eGFR at baseline; measurement variability in secretory solutes clearances.

Conclusions: In a national cohort study of CKD, no clinically or statistically relevant associations were observed between the kidney clearances of endogenous secretory solutes and incident heart failure, myocardial infarction, or stroke after adjustment for eGFR. These findings suggest that tubular secretory clearance provides little additional information about the development of cardiovascular disease events beyond glomerular measures of GFR and albuminuria among patients with mild-to-moderate CKD.
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http://dx.doi.org/10.1053/j.ajkd.2020.12.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8260620PMC
August 2021

Predictive Value of the BSID-II and the Bayley-III for Early School Age Cognitive Function in Very Preterm Infants.

Glob Pediatr Health 2020 20;7:2333794X20973146. Epub 2020 Nov 20.

Children's Hospital of Philadelphia, Philadelphia, PA, USA.

Objective: To compare the predictive validity of the Bayley Scales of Infant Development, Second Edition (BSID-II) and the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III) for cognitive function at early school age in very preterm infants.

Methods: Seventy-seven former preterm infants (born <32 weeks gestation and ≤2000 g) completed both the BSID-II and the Bayley-III at 2 years corrected age. Children enrolled at hospitals that perform follow-up beyond 2 years had cognitive assessments with the Wechsler Preschool and Primary Scale of Intelligence Fourth Edition (WPPSI-IV). Associations between Bayley and WPPSI scores were assessed using correlation coefficients, linear regression, and Bland-Altman plots.

Results: Thirty-one of 45 eligible children were tested with the WPPSI-IV at 47 ± 11 months. Average BSID-II Mental Development Index (MDI) was 86 ± 19, Bayley-III Cognitive composite score was 101 ± 12 and WPPSI Full Scale IQ (FSIQ) was 96 ± 12. Correlation between MDI and FSIQ was 0.54 ( < .001); correlation between Bayley-III cognitive composite score and FSIQ was 0.31 ( = .03). Bayley-III language composite had a modestly stronger correlation with FSIQ than cognitive composite (correlation coefficient 0.39;  = .005). Linear regression models also demonstrated that BSID-II was more closely correlated with FSIQ than Bayley-III. This bias was consistent across the full range of scores.

Conclusion: The BSID-II underestimated FSIQ and the Bayley-III overestimated FSIQ. Children at risk for impairment might be missed with the Bayley-III. As the Bayley-4 is introduced, clinicians and researchers should be cautious about interpretation of scores until performance of this new measure is fully understood.
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http://dx.doi.org/10.1177/2333794X20973146DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7683841PMC
November 2020

Surface mining and low birth weight in central appalachia.

Environ Res 2021 05 22;196:110340. Epub 2020 Oct 22.

Division of Neonatology, Children's Hospital of Philadelphia, Philadelphia, PA, 19104, USA; Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.

Background: Surface mining has become a significant method of coal mining in the Central Appalachian region of the eastern United States alongside the traditional underground mining. Concerns have been raised about the health effects of this surface mining, particularly mountaintop removal mining where coal is mined upon steep mountaintops by removing the mountaintop through clearcutting forests and explosives.

Methods: We used a control group design with a pretest and a posttest to assess the associations of surface mining in Central Appalachia with low birth weight and other adverse birth outcomes. The pretest period is 1977-1989, a period of low surface mining activity. We consider three posttest periods: 1990-1998, 1999-2011 and 2012-2017, with 1999-2011 as the primary analysis and the other periods as secondary analyses. Surface mining in Central Appalachia increased after 1989, partly resulting from the Clean Air Act Amendments of 1990 which made surface mining in Appalachia more financially attractive. For the primary analysis, we fit a logistic regression model of the primary outcome (low birth weight, <2500 g) on dummy variables for county and year; individual level maternal/infant covariates (maternal race, maternal age, infant sex and whether birth was a multiple birth); and the amount of surface mining during the year of the birth in the maternal county of residence.

Results: Our analysis sample consisted of 783,328 infants -- 482,284 infants born from 1977 to 2017 to women residing in substantial surface mining activity counties and 301,044 infants born from 1977 to 2017 to women residing in matched control counties. Compared to the pre-period of low surface mining from 1977 to 1989, for the primary analysis posttest period of 1999-2011, there was an estimated relative increase in low birth weight in surface mining counties compared to matched control counties that was not statistically significant (odds ratio for a 5 percentage point increase in area disturbed by surface mining: 1.07, 95% confidence interval (0.96, 1.20), p-value: .22). For the secondary analysis posttest period of 1990-1998, there was no increase (odds ratio: 0.91, 95% confidence interval: (0.74, 1.13), p-value: .41). For the secondary analysis posttest period of 2012-2017, there was a statistically significant relative increase (odds ratio: 1.28, 95% confidence interval: (1.08, 1.50), p-value: .004). Qualitatively similar results were found for the outcomes of very low birth weight, preterm birth and small-for-gestational age.

Conclusions: We examined the hypothesis that surface mining activity in Central Appalachia contributes to low birth weight using an observational study. We found evidence in secondary analyses that surface mining was associated with low birth weight in the 2012-2017 time period and potentially beginning in the early to mid 2000's. Evidence for an association was not found prior to 2000. A potential explanation for this pattern of association is that surface mining caused an increase in low birth weight but its onset was delayed. Future research is needed to clarify the findings and if replicated, identify the mechanism necessary to mitigate the impacts of mining on adverse birth outcomes.
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http://dx.doi.org/10.1016/j.envres.2020.110340DOI Listing
May 2021

The enigma of Oligocene climate and global surface temperature evolution.

Proc Natl Acad Sci U S A 2020 10 28;117(41):25302-25309. Epub 2020 Sep 28.

Department of Geology and Geophysics, Yale University, New Haven, CT 06511.

Falling atmospheric CO levels led to cooling through the Eocene and the expansion of Antarctic ice sheets close to their modern size near the beginning of the Oligocene, a period of poorly documented climate. Here, we present a record of climate evolution across the entire Oligocene (33.9 to 23.0 Ma) based on TEX sea surface temperature (SST) estimates from southwestern Atlantic Deep Sea Drilling Project Site 516 (paleolatitude ∼36°S) and western equatorial Atlantic Ocean Drilling Project Site 929 (paleolatitude ∼0°), combined with a compilation of existing SST records and climate modeling. In this relatively low CO Oligocene world (∼300 to 700 ppm), warm climates similar to those of the late Eocene continued with only brief interruptions, while the Antarctic ice sheet waxed and waned. SSTs are spatially heterogenous, but generally support late Oligocene warming coincident with declining atmospheric CO This Oligocene warmth, especially at high latitudes, belies a simple relationship between climate and atmospheric CO and/or ocean gateways, and is only partially explained by current climate models. Although the dominant climate drivers of this enigmatic Oligocene world remain unclear, our results help fill a gap in understanding past Cenozoic climates and the way long-term climate sensitivity responded to varying background climate states.
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http://dx.doi.org/10.1073/pnas.2003914117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7568263PMC
October 2020

Tubular Secretory Clearance Is Associated With Whole-Body Insulin Clearance.

J Clin Endocrinol Metab 2020 11;105(11)

Kidney Research Institute, Seattle, Washington.

Context: The kidneys eliminate insulin via glomerular and peritubular mechanisms; consequently, the kidney contribution to insulin clearance may be underestimated by the glomerular filtration rate (GFR) alone.

Objective: To determine associations of tubular secretory clearance with whole-body insulin clearance and sensitivity in a dedicated study of glucose and insulin metabolism.

Design, Setting, And Participants: We performed an ancillary, cross-sectional study of tubular secretion in the Study of Glucose and Insulin in Renal Disease (SUGAR). Hyperinsulinemic-euglycemic clamps were performed in 57 nondiabetic persons with chronic kidney disease and 38 persons without kidney disease.

Intervention: We measured plasma and 24-hour urine concentrations of endogenous solutes primarily eliminated by tubular secretion. Kidney clearances of secretory solutes were calculated as the amount of blood fully cleared of that solute per minute.

Main Outcome Measures: Whole-body insulin clearance, insulin sensitivity.

Results: Mean whole-body insulin clearance was 924 ± 228 mL/min. After adjustment for age, sex, Black race, fat and fat-free mass, each 20% lower estimated GFR was associated with a 13 mL/min lower insulin clearance (95% confidence interval [CI], 2-24 mL/min lower). Each 20% lower clearance of isovalerylglycine and xanthosine were associated with a 16 mL/min lower (95% CI, 5-26 mL/min lower) and 19 mL/min lower (95% CI, 7-31 mL/min lower) insulin clearance, respectively. Neither estimated GFR nor secretory solute clearances were associated with insulin sensitivity after adjustment.

Conclusions: These results highlight the importance of tubular secretory pathways to insulin elimination but suggest that kidney functions in aggregate contribute only modestly to systemic insulin clearance.
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http://dx.doi.org/10.1210/clinem/dgaa522DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7500476PMC
November 2020

Innovation in Oncology Drug Development.

J Oncol 2019 23;2019:9683016. Epub 2019 Nov 23.

ICON Plc, 79 T.W. Alexander Drive, 4401 Research Commons Bldg., Suite 300, Durham, NC 27709, USA.

Significant progress has been made in our understanding of the molecular lesions responsible for tumor cells to exhibit uncontrolled growth while circumventing normal mechanisms of apoptosis and their ability to migrate and invade normal tissues while evading recognition and destruction by the immune system. This understanding has enabled the development of therapies specifically targeted to these lesions coupled to innovative treatment regimens to most effectively use these new targeted therapies with precision in selected subpopulations of patients. Innovation at the scientific and clinical levels has been appropriately embraced and supported at the FDA, resulting in regulatory innovation to facilitate and adapt to the Precision Medicine environment.
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http://dx.doi.org/10.1155/2019/9683016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6930717PMC
November 2019

Paradoxical impact of sprawling intra-Urban Heat Islets: Reducing mean surface temperatures while enhancing local extremes.

Sci Rep 2019 12 23;9(1):19681. Epub 2019 Dec 23.

Lyles School of Civil Engineering, Purdue University, IN, USA.

Extreme heat is one of the deadliest health hazards that is projected to increase in intensity and persistence in the near future. Here, we tackle the problem of spatially heterogeneous heat distribution within urban areas. We develop a novel multi-scale metric of identifying emerging heat clusters at various percentile-based thermal thresholds and refer to them collectively as intra-Urban Heat Islets. Using remotely sensed Land Surface Temperatures, we first quantify the spatial organization of heat islets in cities at various degrees of sprawl and densification. We then condense the size, spacing, and intensity information about heterogeneous clusters into probability distributions that can be described using single scaling exponents (denoted by β, [Formula: see text], and λ, respectively). This allows for a seamless comparison of the heat islet characteristics across cities at varying spatial scales and improves on the traditional Surface Urban Heat Island (SUHI) Intensity as a bulk metric. Analysis of Heat Islet Size distributions demonstrates the emergence of two classes where the dense cities follow a Pareto distribution, and the sprawling cities show an exponential tempering of Pareto tail. This indicates a significantly reduced probability of encountering large heat islets for sprawling cities. In contrast, analysis of Heat Islet Intensity distributions indicates that while a sprawling configuration is favorable for reducing the mean SUHI Intensity of a city, for the same mean, it also results in higher local thermal extremes. This poses a paradox for urban designers in adopting expansion or densification as a growth trajectory to mitigate the UHI.
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http://dx.doi.org/10.1038/s41598-019-56091-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6928021PMC
December 2019

A Cholecystokinin Receptor Antagonist Halts Nonalcoholic Steatohepatitis and Prevents Hepatocellular Carcinoma.

Dig Dis Sci 2020 01 11;65(1):189-203. Epub 2019 Jul 11.

Department of Medicine, Georgetown University, 4000 Reservoir Rd, NW, Building D, Room 338, Washington, DC, 20007, USA.

Background And Aims: Nonalcoholic steatohepatitis (NASH) is a common inflammatory liver condition that may lead to cirrhosis and hepatocellular carcinoma (HCC). Risk factors for NASH include a saturated fat diet, altered lipid metabolism, and genetic and epigenetic factors, including microRNAs. Serum levels of cholecystokinin (CCK) are elevated in mice and humans that consume a high-saturated fat diet. CCK receptors (CCK-Rs) have been reported on fibroblasts which when activated can induce fibrosis; however, their role in hepatic fibrosis remains unknown. We hypothesized that elevated levels of CCK acting on the CCK-Rs play a role in the development of NASH and in NASH-associated HCC.

Methods: We performed a NASH Prevention study and Reversal study in mice fed a saturated fat 75% choline-deficient-ethionine-supplemented (CDE) diet for 12 or 18 weeks. In each study, half of the mice received untreated drinking water, while the other half received water supplemented with the CCK-R antagonist proglumide. CCK-R expression was evaluated in mouse liver and murine HCC cells.

Results: CCK receptor antagonist treatment not only prevented NASH but also reversed hepatic inflammation, fibrosis, and steatosis and normalized hepatic transaminases after NASH was established. Thirty-five percent of the mice on the CDE diet developed HCC compared with none in the proglumide-treated group. We found that CCK-BR expression was markedly upregulated in mouse CDE liver and HCC cells compared with normal hepatic parenchymal cells, and this expression was epigenetically regulated by microRNA-148a.

Conclusion: These results support the novel role of CCK receptors in the pathogenesis of NASH and HCC.
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http://dx.doi.org/10.1007/s10620-019-05722-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6946881PMC
January 2020

Endogenous Gastrin Collaborates With Mutant KRAS in Pancreatic Carcinogenesis.

Pancreas 2019 08;48(7):894-903

From the Department of Medicine.

Objective: The KRAS gene is the most frequently mutated gene in pancreatic cancer, and no successful anti-Ras therapy has been developed. Gastrin has been shown to stimulate pancreatic cancer in an autocrine fashion. We hypothesized that reactivation of the peptide gastrin collaborates with KRAS during pancreatic carcinogenesis.

Methods: LSL-Kras; P48-Cre (KC) mutant KRAS transgenic mice were crossed with gastrin-KO (GKO) mice to develop GKO/KC mice. Pancreata were examined for 8 months for stage of pancreatic intraepithelial neoplasia lesions, inflammation, fibrosis, gastrin peptide, and microRNA expression. Pancreatic intraepithelial neoplasias from mice were collected by laser capture microdissection and subjected to reverse-phase protein microarray, for gastrin and protein kinases associated with signal transduction. Gastrin mRNA was measured by RNAseq in human pancreatic cancer tissues and compared to that in normal pancreas.

Results: In the absence of gastrin, PanIN progression, inflammation, and fibrosis were significantly decreased and signal transduction was reversed to the canonical pathway with decreased KRAS. Gastrin re-expression in the PanINs was mediated by miR-27a. Gastrin mRNA expression was significantly increased in human pancreatic cancer samples compared to normal human pancreas controls.

Conclusions: This study supports the mitogenic role of gastrin in activation of KRAS during pancreatic carcinogenesis.
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http://dx.doi.org/10.1097/MPA.0000000000001360DOI Listing
August 2019

C photosynthesis and climate through the lens of optimality.

Proc Natl Acad Sci U S A 2018 11 6;115(47):12057-12062. Epub 2018 Nov 6.

Department of Biology, University of Pennsylvania, Philadelphia, PA 19104.

CO, temperature, water availability, and light intensity were all potential selective pressures that determined the competitive advantage and expansion of the C photosynthetic carbon-concentrating mechanism over the last ∼30 My. To tease apart how selective pressures varied along the ecological trajectory of C expansion and dominance, we coupled hydraulics to photosynthesis models while optimizing photosynthesis over stomatal resistance and leaf/fine-root allocation. We further examined the importance of nitrogen reallocation from the dark to the light reactions. We show here that the primary selective pressures favoring C dominance changed through the course of C evolution. The higher stomatal resistance and leaf-to-root ratios enabled by C led to an advantage without any initial difference in hydraulic properties. We further predict a reorganization of the hydraulic system leading to higher turgor-loss points and possibly lower hydraulic conductance. Selection on nitrogen reallocation varied with CO concentration. Through paleoclimate model simulations, we find that water limitation was the primary driver for a C advantage, with atmospheric CO as high as 600 ppm, thus confirming molecular-based estimates for C evolution in the Oligocene. Under these high-CO conditions, nitrogen reallocation was necessary. Low CO and high light, but not nitrogen reallocation, were the primary drivers for the mid- to late-Miocene global expansion of C We also predicted the timing and spatial distribution for origins of C ecological dominance. The predicted origins are broadly consistent with prior estimates, but expand upon them to include a center of origin in northwest Africa and a Miocene-long origin in Australia.
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http://dx.doi.org/10.1073/pnas.1718988115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6255158PMC
November 2018

Epidemiology, outcomes, and management of acute kidney injury in the vascular surgery patient.

J Vasc Surg 2018 09 28;68(3):916-928. Epub 2018 Jun 28.

Department of Medicine, College of Medicine, University of Florida, Gainesville, Fla; Precision and Intelligent Systems in Medicine (PrismaP), University of Florida, Gainesville, Fla. Electronic address:

Objective: Conventional clinical wisdom has often been nihilistic regarding the prevention and management of acute kidney injury (AKI), despite its being a frequent and morbid complication associated with both increased mortality and cost. Recent developments have shown that AKI is not inevitable and that changes in management of patients can reduce both the incidence and morbidity of perioperative AKI. The purpose of this narrative review was to review the epidemiology and outcomes of AKI in patients undergoing vascular surgery using current consensus definitions, to discuss some of the novel emerging risk stratification and prevention techniques relevant to the vascular surgery patient, and to describe a standardized perioperative pathway for the prevention of AKI after vascular surgery.

Methods: We performed a critical review of the literature on AKI in the vascular surgery patient using the PubMed and MEDLINE databases and Google Scholar through September 2017 using web-based search engines. We also searched the guidelines and publications available online from the organizations Kidney Disease: Improving Global Outcomes and the Acute Dialysis Quality Initiative. The search terms used included acute kidney injury, AKI, epidemiology, outcomes, prevention, therapy, and treatment.

Results: The reported epidemiology and outcomes associated with AKI have been evolving since the publication of consensus criteria that allow accurate identification of mild and moderate AKI. The incidence of AKI after major vascular surgery using current criteria is as high as 49%, although there are significant differences, depending on the type of procedure performed. Many tools have become available to assess and to stratify the risk for AKI and to use that information to prevent AKI in the surgical patient. We describe a standardized clinical assessment and management pathway for vascular surgery patients, incorporating current risk assessment and preventive strategies to prevent AKI and to decrease its complications. Patients without any risk factors can be managed in a perioperative fast-track pathway. Those patients with positive risk factors are tested for kidney stress using the urinary biomarker TIMP-2•IGFBP7, and care is then stratified according to the result. Management follows current Kidney Disease: Improving Global Outcomes guidelines.

Conclusions: AKI is a common postoperative complication among vascular surgery patients and has a significant impact on morbidity, mortality, and cost. Preoperative risk assessment and optimal perioperative management guided by that risk assessment can minimize the consequences associated with postoperative AKI. Adherence to a standardized perioperative pathway designed to reduce risk of AKI after major vascular surgery offers a promising clinical approach to mitigate the incidence and severity of this challenging clinical problem.
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http://dx.doi.org/10.1016/j.jvs.2018.05.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6236681PMC
September 2018

Synchronous tropical and polar temperature evolution in the Eocene.

Nature 2018 07 2;559(7714):382-386. Epub 2018 Jul 2.

Department of Earth Sciences, Faculty of Geoscience, Utrecht University, Utrecht, The Netherlands.

Palaeoclimate reconstructions of periods with warm climates and high atmospheric CO concentrations are crucial for developing better projections of future climate change. Deep-ocean and high-latitude palaeotemperature proxies demonstrate that the Eocene epoch (56 to 34 million years ago) encompasses the warmest interval of the past 66 million years, followed by cooling towards the eventual establishment of ice caps on Antarctica. Eocene polar warmth is well established, so the main obstacle in quantifying the evolution of key climate parameters, such as global average temperature change and its polar amplification, is the lack of continuous high-quality tropical temperature reconstructions. Here we present a continuous Eocene equatorial sea surface temperature record, based on biomarker palaeothermometry applied on Atlantic Ocean sediments. We combine this record with the sparse existing data to construct a 26-million-year multi-proxy, multi-site stack of Eocene tropical climate evolution. We find that tropical and deep-ocean temperatures changed in parallel, under the influence of both long-term climate trends and short-lived events. This is consistent with the hypothesis that greenhouse gas forcing, rather than changes in ocean circulation, was the main driver of Eocene climate. Moreover, we observe a strong linear relationship between tropical and deep-ocean temperatures, which implies a constant polar amplification factor throughout the generally ice-free Eocene. Quantitative comparison with fully coupled climate model simulations indicates that global average temperatures were about 29, 26, 23 and 19 degrees Celsius in the early, early middle, late middle and late Eocene, respectively, compared to the preindustrial temperature of 14.4 degrees Celsius. Finally, combining proxy- and model-based temperature estimates with available CO reconstructions yields estimates of an Eocene Earth system sensitivity of 0.9 to 2.3 kelvin per watt per square metre at 68 per cent probability, consistent with the high end of previous estimates.
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http://dx.doi.org/10.1038/s41586-018-0272-2DOI Listing
July 2018

Ultrasonic backscatter difference measurements of cancellous bone from the human femur: Relation to bone mineral density and microstructure.

J Acoust Soc Am 2018 06;143(6):3642

Department of Physics, Rhodes College, Memphis, Tennessee 38112, USA.

Ultrasonic backscatter techniques are being developed to detect changes in cancellous bone caused by osteoporosis. One technique, called the backscatter difference technique, measures the power difference between two portions of a backscatter signal. The goal of the present study is to investigate how bone mineral density (BMD) and the microstructure of human cancellous bone influence four backscatter difference parameters: the normalized mean of the backscatter difference (nMBD) spectrum, the normalized slope of the backscatter difference spectrum, the normalized intercept of the backscatter difference spectrum, and the normalized backscatter amplitude ratio (nBAR). Ultrasonic measurements were performed with a 3.5 MHz broadband transducer on 54 specimens of human cancellous bone from the proximal femur. Volumetric BMD and the microstructural characteristics of the specimens were measured using x-ray micro-computed tomography. Of the four ultrasonic parameters studied, nMBD and nBAR demonstrated the strongest univariate correlations with density and microstructure. Multivariate analyses indicated that nMBD and nBAR depended on trabecular separation and possibly other microstructural characteristics of the specimens independently of BMD. These findings suggest that nMBD and nBAR may be sensitive to changes in the density and microstructure of bone caused by osteoporosis.
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http://dx.doi.org/10.1121/1.5043385DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6014850PMC
June 2018

Aggregation in particle rich environments: a textural study of examples from volcanic eruptions, meteorite impacts, and fluidized bed processing.

Bull Volcanol 2018 2;80(4):32. Epub 2018 Mar 2.

1Ludwig-Maximilians-Universität München LMU, Munich, Germany.

Aggregation is a common process occurring in many diverse particulate gas mixtures (e.g. those derived from explosive volcanic eruptions, meteorite impact events, and fluid bed processing). It results from the collision and sticking of particles suspended in turbulent gas/air. To date, there is no generalized model of the underlying physical processes. Here, we investigate aggregates from 18 natural deposits (16 volcanic deposits and two meteorite impact deposits) as well as aggregates produced experimentally via fluidized bed techniques. All aggregates were analyzed for their size, internal structuring, and constituent particle size distribution. Commonalities and differences between the aggregate types are then used to infer salient features of the aggregation process. Average core to rim ratios of internally structured aggregates (accretionary lapilli) is found to be similar for artificial and volcanic aggregates but up to an order of magnitude different than impact-related aggregates. Rim structures of artificial and volcanic aggregates appear to be physically similar (single, sub-spherical, regularly-shaped rims) whereas impact-related aggregates more often show multiple or irregularly shaped rims. The particle size distributions (PSDs) of all three aggregate types are similar (< 200 μm). This proves that in all three environments, aggregation occurs under broadly similar conditions despite the significant differences in source conditions (particle volume fraction, particle size distribution, particle composition, temperature), residence times, plume conditions (e.g., humidity and temperature), and dynamics of fallout and deposition. Impact-generated and volcanic aggregates share many similarities, and in some cases may be indistinguishable without their stratigraphic context.
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http://dx.doi.org/10.1007/s00445-018-1207-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5834565PMC
March 2018

Characterization of a polymer, open-cell rigid foam that simulates the ultrasonic properties of cancellous bone.

J Acoust Soc Am 2018 02;143(2):911

College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.

Materials that simulate the ultrasonic properties of tissues are used widely for clinical and research purposes. However, relatively few materials are known to simulate the ultrasonic properties of cancellous bone. The goal of the present study was to investigate the suitability of using a polymer, open-cell rigid foam (OCRF) produced by Sawbones. Measurements were performed on OCRF specimens with four different densities. Ultrasonic speed of sound and normalized broadband ultrasonic attenuation were measured with a 0.5 MHz transducer. Three backscatter parameters were measured with a 5 MHz transducer: apparent integrated backscatter, frequency slope of apparent backscatter, and normalized mean of the backscatter difference. X-ray micro-computed tomography was used to measure the microstructural characteristics of the OCRF specimens. The trabecular thickness and relative bone volume of the OCRF specimens were similar to those of human cancellous bone, but the trabecular separation was greater. In most cases, the ultrasonic properties of the OCRF specimens were similar to values reported in the literature for cancellous bone, including dependence on density. In addition, the OCRF specimens exhibited an ultrasonic anisotropy similar to that reported for cancellous bone.
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http://dx.doi.org/10.1121/1.5023219DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5812744PMC
February 2018

Dominant control of agriculture and irrigation on urban heat island in India.

Sci Rep 2017 10 25;7(1):14054. Epub 2017 Oct 25.

Earth, Atmospheric and Planetary Sciences, Purdue University, West Lafayette, IN 47907, USA.

As is true in many regions, India experiences surface Urban Heat Island (UHI) effect that is well understood, but the causes of the more recently discovered Urban Cool Island (UCI) effect remain poorly constrained. This raises questions about our fundamental understanding of the drivers of rural-urban environmental gradients and hinders development of effective strategies for mitigation and adaptation to projected heat stress increases in rapidly urbanizing India. Here we show that more than 60% of Indian urban areas are observed to experience a day-time UCI. We use satellite observations and the Community Land Model (CLM) to identify the impact of irrigation and prove for the first time that UCI is caused by lack of vegetation and moisture in non-urban areas relative to cities. In contrast, urban areas in extensively irrigated landscapes generally experience the expected positive UHI effect. At night, UHI warming intensifies, occurring across a majority (90%) of India's urban areas. The magnitude of rural-urban temperature contrasts is largely controlled by agriculture and moisture availability from irrigation, but further analysis of model results indicate an important role for atmospheric aerosols. Thus both land-use decisions and aerosols are important factors governing, modulating, and even reversing the expected urban-rural temperature gradients.
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http://dx.doi.org/10.1038/s41598-017-14213-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5656645PMC
October 2017

Effect of gate choice on backscatter difference measurements of cancellous bone.

J Acoust Soc Am 2017 08;142(2):540

Department of Physics, Rhodes College, Memphis, Tennessee 38112, USA.

A variety of ultrasonic techniques have been developed to detect changes in bone caused by osteoporosis. One approach, called the backscatter difference technique, analyzes the power difference between two different portions of a backscatter signal. Analysis gates with a certain delay τ, width τ, and separation τ are used to define portions of the backscatter signal for analysis. The goal of the present study was to investigate how different choices of τ, τ, and τ affect four backscatter difference parameters: the normalized mean of the backscatter difference (nMBD), the normalized slope of the backscatter difference (nSBD), the normalized intercept of the backscatter difference (nIBD), and the normalized backscatter amplitude ratio (nBAR). Backscatter measurements were performed on 54 cube shaped specimens of human cancellous bone. nMBD, nSBD, nIBD, and nBAR were determined for 34 different combinations of τ, τ, and τ for each specimen. nMBD and nBAR demonstrated the strongest correlations with apparent bone density (0.48 ≤ R ≤ 0.90). Generally, the correlations were found to improve as τ + τ was increased and as τ was decreased. Among the four backscatter difference parameters, the measured values of nMBD were least sensitive to gate choice (<16%).
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http://dx.doi.org/10.1121/1.4996140DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5552398PMC
August 2017

Optical imaging of propagating Mach cones in water using refracto-vibrometry.

J Acoust Soc Am 2017 03;141(3):EL239

Department of Physics, Rhodes College, 2000 North Parkway, Memphis, Tennessee 38112, USA

Refracto-vibrometry was used to optically image propagating Mach cones in water. These Mach cones were produced by ultrasonic longitudinal and shear waves traveling through submerged 12.7 mm diameter metal cylinders. Full-field videos of the propagating wave fronts were obtained using refracto-vibrometry. A laser Doppler vibrometer, directed at a retroreflective surface, sampled time-varying water density at numerous scan points. Wave speeds were determined from the Mach cone apex angles; the measured longitudinal and shear wave speeds in steel (6060 ± 170 m/s and 3310 ± 110 m/s, respectively) and beryllium (12 400 ± 700 m/s and 8100 ± 500 m/s) agreed with published values.
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http://dx.doi.org/10.1121/1.4977099DOI Listing
March 2017

Extreme warmth and heat-stressed plankton in the tropics during the Paleocene-Eocene Thermal Maximum.

Sci Adv 2017 Mar 3;3(3):e1600891. Epub 2017 Mar 3.

Marine Palynology and Paleoceanography, Laboratory of Palaeobotany and Palynology, Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Heidelberglaan 2, 3584CS Utrecht, Netherlands.

Global ocean temperatures rapidly warmed by ~5°C during the Paleocene-Eocene Thermal Maximum (PETM; ~56 million years ago). Extratropical sea surface temperatures (SSTs) met or exceeded modern subtropical values. With these warm extratropical temperatures, climate models predict tropical SSTs >35°C-near upper physiological temperature limits for many organisms. However, few data are available to test these projected extreme tropical temperatures or their potential lethality. We identify the PETM in a shallow marine sedimentary section deposited in Nigeria. On the basis of planktonic foraminiferal Mg/Ca and oxygen isotope ratios and the molecular proxy [Formula: see text], latest Paleocene equatorial SSTs were ~33°C, and [Formula: see text] indicates that SSTs rose to >36°C during the PETM. This confirms model predictions on the magnitude of polar amplification and refutes the tropical thermostat theory. We attribute a massive drop in dinoflagellate abundance and diversity at peak warmth to thermal stress, showing that the base of tropical food webs is vulnerable to rapid warming.
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http://dx.doi.org/10.1126/sciadv.1600891DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5336354PMC
March 2017
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