Greatly enhanced risk to humans as a consequence of empirically determined lower moist heat stress tolerance.

As heatwaves become more frequent, intense, and longer-lasting due to climate change, the question of breaching thermal limits becomes pressing. A wet-bulb temperature (Tw) of 35 °C has been proposed as a theoretical upper limit on human abilities to biologically thermoregulate. But, recent-empirical-research using human subjects found a significantly lower maximum Tw at which thermoregulation is possible even with minimal metabolic activity. Projecting future exposure to this empirical critical environmental limit has not been done. Here, using this more accurate threshold and the latest coupled climate model results, we quantify exposure to dangerous, potentially lethal heat for future climates at various global warming levels. We find that humanity is more vulnerable to moist heat stress than previously proposed because of these lower thermal limits. Still, limiting warming to under 2 °C nearly eliminates exposure and risk of widespread uncompensable moist heatwaves as a sharp rise in exposure occurs at 3 °C of warming. Parts of the Middle East and the Indus River Valley experience brief exceedances with only 1.5 °C warming. More widespread, but brief, dangerous heat stress occurs in a +2 °C climate, including in eastern China and sub-Saharan Africa, while the US Midwest emerges as a moist heat stress hotspot in a +3 °C climate. In the future, moist heat extremes will lie outside the bounds of past human experience and beyond current heat mitigation strategies for billions of people. While some physiological adaptation from the thresholds described here is possible, additional behavioral, cultural, and technical adaptation will be required to maintain healthy lifestyles.

The latitudinal temperature gradient and its climate dependence as inferred from foraminiferal δ18O over the past 95 million years.

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.

Diuretic Tolerance to Repeated-Dose Furosemide in Infants Born Very Preterm with Bronchopulmonary Dysplasia.

OBJECTIVES: To assess the presence and timing of furosemide diuretic tolerance in infants with bronchopulmonary dysplasia (BPD), and to determine if tolerance is modified by thiazide co-administration. STUDY DESIGN: We performed a retrospective cohort study among infants born very preterm with BPD exposed to repeated-dose furosemide for 72 hours, measuring net fluid balance (total intake minus total output) as a surrogate of diuresis in the 3 days before and after exposure. The primary comparison was the difference in fluid balance between the first and third 24 hours of furosemide exposure. We fit a general linear model for within-subject repeated measures of fluid balance over time, with thiazide co-administration as an interaction variable. Secondary analyses included an evaluation of weight trajectories over time. RESULTS: In 83 infants, median fluid balance ranged between + 43.6 and + 52.7 ml/kg/d in the 3 days prior to furosemide exposure. Fluid balance decreased to a median of + 29.1 ml/kg/d in the first 24 hours after furosemide, but then increased to +47.5 ml/kg/d by the third 24-hour interval, consistent with tolerance (P < .001). Thiazides did not modify the change in fluid balance during furosemide exposure for any time-period. Weight decreased significantly in the first 24 hours after furosemide and increased thereafter (P < .001). CONCLUSIONS: The net fluid balance response to furosemide decreases rapidly during repeated-dose exposures in infants with BPD, consistent with diuretic tolerance. Clinicians should consider this finding in the context of an infant's therapeutic goals. Further research efforts to identify safe and effective furosemide dosage strategies are needed.

Land surface conductance linked to precipitation: Co-evolution of vegetation and climate in Earth system models.

Vegetation and precipitation are known to fundamentally influence each other. However, this interdependence is not fully represented in climate models because the characteristics of land surface (canopy) conductance to water vapor and CO2 are determined independently of precipitation. Working within a coupled atmosphere and land modelling framework (CAM6/CLM5; coupled Community Atmosphere Model v6/Community Land Model v5), we have developed a new theoretical approach to characterizing land surface conductance by explicitly linking its dynamic properties to local precipitation, a robust proxy for moisture available to vegetation. This will enable regional surface conductance characteristics to shift fluidly with climate change in simulations, consistent with general principles of co-evolution of vegetation and climate. Testing within the CAM6/CLM5 framework shows that climate simulations incorporating the new theory outperform current default configurations across several error metrics for core output variables when measured against observational data. In climate simulations for the end of this century the new, adaptive stomatal conductance scheme provides a revised prognosis for average and extreme temperatures over several large regions, with increased primary productivity through central and east Asia, and higher rainfall through North Africa and the Middle East. The new projections also reveal more frequent heatwaves than originally estimated for the south-eastern US and sub-Saharan Africa but less frequent heatwaves across east Europe and northeast Asia. These developments have implications for evaluating food security and risks from extreme temperatures in areas that are vulnerable to climate change.

Synchronous tropical and polar temperature evolution in the Eocene.

Palaeoclimate reconstructions of periods with warm climates and high atmospheric CO2 concentrations are crucial for developing better projections of future climate change. Deep-ocean1,2 and high-latitude3 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 data4-6 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 forcing7,8, rather than changes in ocean circulation9,10, 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 CO2 reconstructions8 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 estimates11.

Human Observer Sensitivity to Temporal Noise During B-Mode Ultrasound Scanning: Characterization and Imaging Implications.

This work measures temporal signal-to-noise ratio (SNR) thresholds that indicate when random noise during ultrasound scanning becomes imperceptible to expert human observers. Visible noise compromises image quality and can potentially lead to non-diagnostic scans. Noise can arise from both stable acoustic sources (clutter) or randomly varying electronic sources (temporal noise). Extensive engineering effort has focused on decreasing noise in both of these categories. In this work, an observer study with five practicing sonographers was performed to assess sonographer sensitivity to temporal noise in ultrasound cine clips. Understanding the conditions where temporal noise is no longer visible during ultrasound imaging can inform engineering efforts seeking to minimize the impact this noise has on image quality. The sonographers were presented with paired temporal noise-free and noise-added simulated speckle cine clips and asked to select the noise-added clips. The degree of motion in the imaging target was found to have a significant effect on the SNR levels where noise was perceived, while changing imaging frequency had little impact. At realistic in vivo motion levels, temporal noise was not perceived in cine clips at and above 28 dB SNR. In a case study presented here, the potential of adaptive intensity adjustment based on this noise perception threshold is validated in a fetal imaging scenario. This study demonstrates how noise perception thresholds can be applied to help design or tune ultrasound systems for different imaging tasks and noise conditions.

The enigma of Oligocene climate and global surface temperature evolution.

Falling atmospheric CO2 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 TEX86 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 CO2 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 CO2 This Oligocene warmth, especially at high latitudes, belies a simple relationship between climate and atmospheric CO2 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.

Impact of COVID-19 on Infants followed after Discharge from the Neonatal Intensive Care Unit Using a Telemedicine Model.

OBJECTIVE: Coronavirus disease 2019 (COVID-19) continues to have a profound impact on infant health care and health outcomes. In this study, we aimed to characterize the social impact of the first COVID-19 lockdown on families in a neonatal follow-up program (NFP). Given the ongoing increased use of telehealth across the medicine, we also evaluated for patient-level differences in virtual visit rates to identify patients at risk of follow-up challenges. STUDY DESIGN: To assess the impact of virtual health care utilization, we conducted a retrospective cohort study to describe challenges associated with telemedicine use in this vulnerable patient population during our telemedicine epoch (March 13, 2020-July 31, 2020). We also looked for patient-level factors associated with attending NFP visits as scheduled. Finally, we summarized caregiver responses to a COVID-19 Obstacles Assessment Survey and assessed for racial disparities in these responses. RESULTS: When comparing patients who completed their virtual visit to those who did not, we found no differences by infants' sex, birthweight, gestational age at birth, or caregiver self-reported race and ethnicity. However, infants whose visits did not occur were more often discharged with equipment or covered by public insurance. Nine percent of families reported food insecurity. CONCLUSION: During the initial COVID-19 lockdown, families with infants discharged from a neonatal intensive care unit (NICU) faced significant obstacles caring for their infants and attending scheduled follow-up visits. Infants in families with lower socioeconomic status or with increased medical complexity faced increased challenges in attending virtual follow-up visits during this epoch. Given the ongoing reliance on telemedicine in health care and the need to better prepare for future epidemics/pandemics, this study offers critical information that can assist neonatal teams in bolstering transitions to home and creating stronger safety nets for their patients after discharge. KEY POINTS: · Telemedicine works well for high-risk neonatal populations.. · Infant medical complexity may be a risk factor for challenges attending neonatal follow-up visits.. · NICUs should work to prevent food insecurity postdischarge..

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

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 m2. 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.

Surface mining and low birth weight in central appalachia.

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.

C4 photosynthesis and climate through the lens of optimality.

CO2, temperature, water availability, and light intensity were all potential selective pressures that determined the competitive advantage and expansion of the C4 photosynthetic carbon-concentrating mechanism over the last ∼30 My. To tease apart how selective pressures varied along the ecological trajectory of C4 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 C4 dominance changed through the course of C4 evolution. The higher stomatal resistance and leaf-to-root ratios enabled by C4 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 CO2 concentration. Through paleoclimate model simulations, we find that water limitation was the primary driver for a C4 advantage, with atmospheric CO2 as high as 600 ppm, thus confirming molecular-based estimates for C4 evolution in the Oligocene. Under these high-CO2 conditions, nitrogen reallocation was necessary. Low CO2 and high light, but not nitrogen reallocation, were the primary drivers for the mid- to late-Miocene global expansion of C4 We also predicted the timing and spatial distribution for origins of C4 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.

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

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.

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

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.

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

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.

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

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.

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

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.

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

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 τd, width τw, and separation τs are used to define portions of the backscatter signal for analysis. The goal of the present study was to investigate how different choices of τd, τw, and τs 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 τd, τw, and τs for each specimen. nMBD and nBAR demonstrated the strongest correlations with apparent bone density (0.48 ≤ Rs ≤ 0.90). Generally, the correlations were found to improve as τw + τs was increased and as τd was decreased. Among the four backscatter difference parameters, the measured values of nMBD were least sensitive to gate choice (<16%).

Acute and Chronic Kidney Disease and Cardiovascular Mortality After Major Surgery.

OBJECTIVE: The aim of the study was to determine the long-term cardiovascular-specific mortality in patients with acute kidney injury (AKI) or chronic kidney disease (CKD) after major surgery. BACKGROUND: In surgical patients, pre-existing CKD and postoperative AKI are associated with increases in all-cause mortality. METHODS: In a single-center cohort of 51,457 adult surgical patients undergoing major inpatient surgery, long-term cardiovascular-specific mortality was modeled using a multivariable subdistributional hazards model while treating any other cause of death as a competing risk and accounting for the progression to end-stage renal disease (ESRD) after discharge. Pre-existing CKD and ESRD, and postoperative AKI were the main independent predictors. RESULTS: Before the admission, 4% and 8% of the cohort had pre-existing ESRD and CKD not requiring renal replacement therapy, respectively. During hospitalization, 39% developed AKI. At 10-year follow-up, adjusted cardiovascular-specific mortality estimates were 6%, 11%, 12%, 19%, and 27% for patients with no kidney disease, AKI with no CKD, CKD with no AKI, AKI with CKD, and ESRD, respectively (P < 0.001). This association remained after excluding 916 patients who progressed to ESRD after discharge, although it was significantly amplified among them. Compared with patients having no kidney disease, adjusted hazard ratios for cardiovascular mortality were significantly higher among patients with kidney disease, ranging from 1.95 (95% confidence interval, 1.80-2.11) for patients with de novo AKI to 5.70 (95% confidence interval, 5.00-6.49) for patients with pre-existing ESRD. CONCLUSIONS: Both AKI and CKD were associated with higher long-term cardiovascular-specific mortality compared with patients having no kidney disease.

Mammalian biodiversity on Madagascar controlled by ocean currents.

Madagascar hosts one of the world's most unusual, endemic, diverse and threatened concentrations of fauna. To explain its unique, imbalanced biological diversity, G. G. Simpson proposed the 'sweepstakes hypothesis', according to which the ancestors of Madagascar's present-day mammal stock rafted there from Africa. This is an important hypothesis in biogeography and evolutionary theory for how animals colonize new frontiers, but its validity is questioned. Studies suggest that currents were inconsistent with rafting to Madagascar and that land bridges provided the migrants' passage. Here we show that currents could have transported the animals to the island and highlight evidence inconsistent with the land-bridge hypothesis. Using palaeogeographic reconstructions and palaeo-oceanographic modelling, we find that strong surface currents flowed from northeast Mozambique and Tanzania eastward towards Madagascar during the Palaeogene period, exactly as required by the 'sweepstakes process'. Subsequently, Madagascar advanced north towards the equatorial gyre and the regional current system evolved into its modern configuration with flows westward from Madagascar to Africa. This may explain why no fully non-aquatic land mammals have colonized Madagascar since the arrival of the rodents and carnivorans during the early-Miocene epoch. One implication is that rafting may be the dominant means of overseas dispersal in the Cenozoic era when palaeocurrent directions are properly considered.

Mortality and Cost of Acute and Chronic Kidney Disease after Vascular Surgery.

BACKGROUND: Both acute kidney injury (AKI) and chronic kidney disease (CKD) are common yet underappreciated risk factors for adverse perioperative outcomes. We hypothesize that AKI and CKD are associated with similar increases in 90-day mortality and cost in patients undergoing major vascular surgery. METHODS: We used multivariable regression analyses to evaluate the associations between AKI and CKD and incremental 90-day mortality and hospital cost in a single-center cohort of 3646 adult patients undergoing major vascular surgery. We defined AKI using Kidney Disease: Improving Global Outcomes criteria as change in creatinine ≥ 0.3 mg/dL or ≥ 50% increase from the reference value. CKD was determined from medical history. Regression models were adjusted for demographic and socioeconomic characteristics, comorbid conditions, surgery type, and postoperative complications. RESULTS: The prevalence of kidney disease among vascular surgery patients is high with 49% of patients developing AKI during hospitalization and 17% presenting with CKD on admission. In risk-adjusted logistic regression analysis, perioperative AKI (odds ratio 2.2, 95% confidence interval 1.5-3.3) was the most significant predictor of 90-day mortality. The risk-adjusted average cost was significantly higher for patients with any type of kidney disease. The incremental cost of having any type of kidney disease ranged from $9100 to $19,100, even after adjustment for underlying comorbidities and other postoperative complications. CONCLUSIONS: Kidney disease after major vascular surgery is associated with significant increases in 90-day mortality and cost with the highest risk observed among patients with AKI regardless of previous CKD.