Error Bars Research Articles

Calibrations without raw data—A response to “Seasonal calibration of the end-cretaceous Chicxulub impact event”

A recent article by DePalma et al. reported that the season of the End-Cretaceous mass extinction was confined to spring/summer on the basis of stable isotope analyses and supplementary observations. An independent study that was concurrently under review reached a similar conclusion using osteohistology and stable isotope analyses. We identified anomalies surrounding the stable isotope analyses reported by DePalma et al. Primary data are not provided, the laboratory where the analyses were performed is not identified, and the methods are insufficiently specified to enable accurate replication. Furthermore, isotopic graphs for carbon and oxygen contain irregularities such as missing data points, duplicate data points, and identical-length error bars for both elements despite different scales, that appear inconsistent with laboratory instrument outputs. A close examination of such methodological omissions and data irregularities can help to raise the standards for future studies of seasonality and prevent inaccurate claims or confirmation bias.

International intercomparison of Radon 222 activity concentration calibration facilities

The Coalition of International Radon Associations (COIRA) organised an inter-comparison of Rn-222 (radon) activity concentrations reported by calibration laboratories. A set of three AlphaGUARDs were used as transfer reference instruments against which to compare reported Rn-222 activity concentrations. Rn-222 activity concentration calibration facilities (sometimes termed chambers) from seven countries (Australia, US, Czech Republic, Spain, England, Sweden, Canada), and three continents participated in this project. The objective of the study was to provide information useful to calibration chamber operators and public health officials in the improvement of measurement and control systems, the maintenance of performance standards for measurements, and regulatory requirements for calibrations. This work builds upon and expands previous interlaboratory comparisons and provides data for estimating and using calibration uncertainty values as part of overall field error estimates and limits. A simple proportional difference between laboratories is presented here, calculated as the average for N hours of each hour’s difference between the laboratory’s concentration and the average of the three reference instruments. This percent difference ranged from less than 0.5% to just less than 8%. This work demonstrates that the ANSI/AARST standards limit of 8% for the estimated unexpanded (one sigma) individual calibration estimated uncertainty for continuous radon monitor calibration facilities in the US is achievable. However, given the few standards regarding calibration of Rn-222 activity concentration measurement instruments that themselves are often used to calibrate secondary and tertiary Rn-222 calibration facilities, there is a great need for continued interlaboratory comparisons to harmonise and document the calibration of Rn-222 activity concentrations.

Exploring γ-Ray Flares from High-Redshift Blazar B3 1343+451 at GeV Energies

We study the temporal and spectral variability properties of the high-redshift blazar B3 1343+451 utilizing Fermi-LAT data from 2008 to 2022 in the energy range of 0.1–300 GeV. We identify six major flares with many substructures and analyze their temporal and spectral properties in detail. The fastest rise and decay timescales are found to be 4.8 ± 0.48 h and 5.28 ± 0.72 h, respectively. The size of the emission region is constrained to be R ∼ 5.18 × 1015–1.56 × 1016 cm with the typical Doppler factors of δ ∼ 10–30. Most of the peaks from the flares exhibit a symmetric temporal profile within the error bars, implying that the rise and decay timescales are dominated by the disturbances caused by dense plasma blobs passing through the standing shock front in the jet region. We also find that four flares are better fitted with a log-parabolic distribution, while two flares are better fitted with a power-law distribution. Our results indicate that the emission regions vary from one flare to another, which is consistent with earlier results.

Driving Forces in the Formation of Biocondensates of Highly Charged Proteins: A Thermodynamic Analysis of the Binary Complex Formation

A thermodynamic analysis of the binary complex formation of the highly positively charged linker histone H1 and the highly negatively charged chaperone prothymosin α (ProTα) is detailed. ProTα and H1 have large opposite net charges (−44 and +53, respectively) and form complexes at physiological salt concentrations with high affinities. The data obtained for the binary complex formation are analyzed by a thermodynamic model that is based on counterion condensation modulated by hydration effects. The analysis demonstrates that the release of the counterions mainly bound to ProTα is the main driving force, and effects related to water release play no role within the limits of error. A strongly negative Δcp (=−0.87 kJ/(K mol)) is found, which is due to the loss of conformational degrees of freedom.

Benchmark computations of nearly degenerate singlet and triplet states of N-heterocyclic chromophores. I. Wavefunction-based methods.

In this paper, we investigate the role of electron correlation in predicting the S1-S0 and T1-S0 excitation energies and, hence, the singlet-triplet gap (ΔEST) in a set of cyclazines, which act as templates for potential candidates for fifth generation organic light emitting diode materials. This issue has recently garnered much interest with the focus being on the inversion of the ΔEST, although experiments have indicated near degenerate levels with both positive and negative being within the experimental error bar [J. Am. Chem. Soc. 102, 6068 (1980), J. Am. Chem. Soc. 108, 17(1986)]. We have carried out a systematic and exhaustive study of various excited state electronic structure methodologies and identified the strengths and shortcomings of the various approaches and approximations in view of this challenging case. We have found that near degeneracy can be achieved either with a proper balance of static and dynamic correlation in multireference theories or with state-specific orbital corrections, including its coupling with correlation. The role of spin contamination is also discussed. Eventually, this paper seeks to produce benchmark numbers for establishing cost-effective theories, which can then be used for screening derivatives of these templates with desirable optical and structural properties. Additionally, we would like to point out that the use of domain-based local pair natural orbital-similarity transformed EOM-coupled cluster singles and doubles as the benchmark for ΔEST [as used in J. Phys. Chem. A 126(8), 1378 (2022), Chem. Phys. Lett. 779, 138827 (2021)] is not a suitable benchmark for these classes of molecules.

Ensemble Monte Carlo calculations with five novel moves

We introduce five novel types of Monte Carlo (MC) moves that brings the number of moves of ensemble MC calculations from three to eight. So far such calculations have relied on affine invariant stretch moves that were originally introduced by Christen (2007) [8], walk moves by Goodman and Weare (2010) [16] and quadratic moves by Militzer (2023) [31,32]. Ensemble MC methods have been very popular because they harness information about the fitness landscape from a population of walkers rather than relying on expert knowledge. Here we modified the affine method and employed a simplex of points to set the stretch direction. We adopt the simplex concept to quadratic moves. We also generalize quadratic moves to arbitrary order. Finally, we introduce directed moves that employ the values of the probability density while all other types of moves rely solely on the location of the walkers. We apply all algorithms to the Rosenbrock density in 2 and 20 dimensions and to the ring potential in 12 and 24 dimensions. We evaluate their efficiency by comparing error bars, autocorrelation time, travel time, and the level of cohesion that measures whether any walkers were left behind. Our code is open source.

Variability of relative treatment effect among populations with low, moderate and high control group event rates: a meta-epidemiological study

BackgroundThe current practice in guideline development is to use the control group event rate (CR) as a surrogate of baseline risk and to assume portability of the relative treatment effect across populations with low, moderate and high baseline risk. We sought to emulate this practice in a very large sample of meta-analyses.MethodsWe retrieved data from all meta-analyses published in the Cochrane Database of Systematic Reviews (2003–2020) that evaluated a binary outcome, reported 2 × 2 data for each individual study and included at least 4 studies. We excluded studies with no events. We conducted meta-analyses with odds ratios and relative risks and performed subgroup analyses based on tertiles of CR. In sensitivity analyses, we evaluated the use of total event rate (TR) instead of CR and using quartiles instead of tertiles.ResultsThe analysis included 2,531 systematic reviews (27,692 meta-analyses, 226,975 studies, 25,669,783 patients).The percentages of meta-analyses with statistically significant interaction (P < 0.05) based on CR tertile or quartile ranged 12–18% across various sensitivity analyses. This percentage increased as the number of studies or range of CR per meta-analysis increased, reflecting increased power of the subgroup test. The percentages of meta-analyses with statistically significant interaction (P < 0.05) with TR quantiles were lower than those with CR but remained higher than expected by chance.ConclusionThis analysis suggests that when CR or TR are used as surrogates for baseline risk, relative treatment effects may not be portable across populations with varying baseline risks in many meta-analyses. Categroization of the continuous CR variable and not addressing measurement error limit inferences from such analyses and imply that CR is an undesirable source for baseline risk. Guideline developers and decision-makers should be provided with relative and absolute treatment effects that are conditioned on the baseline risk or derived from studies with similar baseline risk to their target populations.

Toroidal injection angle dependence of EC assisted plasma initiation at DIII-D

Abstract An experimental scan of the electron cyclotron waves (EC) toroidal injection angle in plasma breakdown is performed at the DIII-D tokamak. The second harmonic, extraordinary mode EC is used for the study. The dependence of n e and T e on the EC injection angle cannot be conclusively drawn from this study due to the large error bars in the n e and T e measurements. On the other hand, high T e data points are observed in some discharges which can be explained by nonlinear heating. The D α emission measurement shows a clear relation between the breakdown time and the injection angle. An experimental investigation of the cause of the dependence of breakdown delay on the EC injection angle suggests that when the injection angle is oblique, the EC heating after the reflection at the inboard wall may become ineffective and cause the breakdown delay even when the EC heating before and directly upon injection remains effective. A preliminary run of the heat and transport balance code DYON indicates that the obtained dataset is suitable for a quantitative validation of EC absorption models.

Simultaneous determination of chlorides, bromides, and fluorides in ion-conducting electrolyte

There are developed the techniques of determining the content of chlorides, bromides and fluorides at their joint presence in two types of solid electrolytes differing in matrix content: the first type contains lithium, the second one — both lithium and aluminium, simultaneously. Determination of bromides mass fraction is fulfilled using a method of iodometric titration of iodic potassium excess after bromides are oxidized until free bromine. The fluorides mass fraction is measured by the gravimetric method in the form of fluoro-chloride of lead, in this case the aluminium interfering influence is eliminated by its precipitation in the form of hydroxide after it is fused with carbonates of potassium and natrium, as well as by the method of potentiometric titration with a fluoride ion-selective electrode using the nitrate lanthanum solution. The absence of aluminium interfering influence on the result of fluorine determination is estimated by the «input – found» method. The mass fraction of chlorides is determined by calculation by difference between results of determining the sum of chlorides and bromides using the method of mercurometric titration and — separately — the bromides mass fraction. Optimal conditions of samples preparation and analysis for each of mentioned methods of analysis were selected. The limits of the relative total error of determining bromides in the range of mass fractions from 28.0 to 41.0% is ±2.1%, chlorides within the mass fraction range from 8.0 to 15.0% — ±3.6%, fluorides within the mass fraction range from 3.0 to 7.0% — ±3.4% using gravimetric method and within the mass fraction range from 5.0 to 8.0% — ±1.5% using a method of potentiometric titration. The developed techniques were certified by a metrological service of the enterprise and are used to control the chemical composition of the ion-conducting electrolyte. The techniques do not require expensive equipment, and can be used in factory laboratories.

Reconstructing and Hindcasting Sea Ice Conditions in Hudson Bay Using a Thermal Variability Framework

The Hudson Bay seasonal sea ice record has been well known since the advent of satellite reconnaissance, with a continuous record since 1971. To extend the record to earlier decades, a thermal variability framework is used with the surface temperature climatological records from four climate stations along the Hudson Bay shoreline: Churchill, Manitoba; Kuujjurapik, Quebec; Inukjuak, Quebec; and Coral Harbour, Nunavut. The day-to-day surface temperature variation for the minimum temperature of the day was found to be well correlated to the known seasonal sea ice distribution in the Bay. The sea ice/thermal variability relationship was able to reproduce the existing sea ice record (the average breakup and freeze-up dates for the Bay) largely within the error limits of the sea ice data (1 week), as well as filling in some gaps in the existing sea ice record. The breakup dates, freeze-up dates, and ice-free season lengths were generated for the period of 1922 to 1970, with varying degrees of confidence, adding close to 50 years to the sea ice record. Key periods in the spring and fall were found to be critical, signaling the time when the changes in the sea conditions are first notable in the temperature variability record, often well in advance of the 5/10th ice coverage used for the sea ice record derived from ice charts. These key periods in advance of the breakup and freeze-up could be potentially used, in season, as a predictor for navigation. The results are suggestive of a fundamental change in the nature of the breakup (faster) and freeze-up (longer) in recent years.

Self-diffusion in Germanium-rich liquid Germanium-Nickel investigated by quasielastic neutron scattering

Abstract We report atomic dynamics in liquid Ge98Ni2 measured using quasielastic neutron scattering. Isotopic substitution enabled to separately determine Ge and Ni self-diffusion with high accuracy. The Ge self-diffusion coefficient in liquid Ge98Ni2 is equal within error bars to that in pure liquid Ge. However, the Ni self-diffusion coefficient lies at least 30% below the Ge self-diffusion coefficient. This behaviour differs from previously reported atomic dynamics in Ge-rich GeAu, GeSi, GeIn and GeCe melts, where no separation of the&amp;#xD;self-diffusion coefficients between the minor component and Ge is observed. The change of the atomic dynamics already at an addition of 2 at% Ni points to electronic and chemical origins in Ge98Ni2. Moreover, the slower self-diffusion of the minor component compared to Ge might be associated with two different local structural environments, as observed in Ge-Ni alloys at higher Ni concentration.

Electrochemical Analysis of Amyloid Plaques and ApoE4 with Chitosan-Coated Gold Nanostars for Alzheimer's Detection.

Monitoring the progression of Alzheimer's disease (AD) is crucial for mitigating dementia symptoms, alleviating pain, and improving mobility. Traditionally, AD biomarkers like amyloid plaques are predominantly identified in cerebrospinal fluid (CSF) due to their concentrated presence. However, detecting these markers in blood is hindered by the blood-brain barrier (BBB), resulting in lower concentrations. To address this challenge and identify pertinent AD biomarkers-specifically amyloid plaques and apolipoprotein E4 (ApoE4)-in blood plasma, we propose an innovative approach. This involves enhancing a screen-printed carbon electrode (SPCE) with an immobilization matrix comprising gold nanostars (AuNSs) coated with chitosan. Morphological and electrical analyses confirmed superior dispersion and conductivity with 0.5% chitosan, supported by UV-Vis spectroscopy, cyclic voltammetry, and Nyquist plots. Subsequent clinical assays measured electrical responses to quantify amyloid-β 42 (Aβ42) (15.63-1000 pg/mL) and APoE4 levels (0.41 to 40 ng/mL) in human blood plasma samples. Differential pulse voltammetry (DPV) responses exhibited peak currents proportional to biomarker concentrations, demonstrating high linear correlations (0.985 for Aβ42 and 0.919 for APoE4) with minimal error bars. Cross-reactivity tests with mixed solutions of amyloid-β 40 (Aβ40), Aβ42, and ApoE4 indicated minimal interference between biomarkers (<3% variation), further confirming the high specificity of the developed sensor. Validation studies demonstrated a strong concurrence with the gold-standard enzyme-linked immunosorbent assay (ELISA), while interference tests indicated a minimal variation in peak currents. This improved device presents promising potential as a point-of-care system, offering a less invasive, cost-effective, and simplified approach to detecting and tracking the progression of AD. The substantial surface binding area further supports the efficacy of our method, offering a promising avenue for advancing AD diagnostics.

The Type VII Secretion System (T7SSb) contributes to interbacterial competition in a murine model of Group BStreptococcus gastrointestinal colonization

Abstract Background Late-onset (LO) disease caused by Group B Streptococcus (GBS) infection is a significant source of morbidity and mortality in neonates. It is believed that gastrointestinal (GI) colonization with GBS plays an important role in the progression to LO disease, although the host-microbial interactions that facilitate GBS GI colonization are poorly understood. The Type VII secretion system (T7SSb) has been identified in several gram-positive bacteria, and its function depends on a membrane-bound ATPase (EssC) which drives secretion of virulence factors. In GBS, the T7SSb has been shown to contribute to vaginal colonization and brain cytotoxicity. We aimed to identify the role of the T7SSb in GBS GI colonization using a murine model and hypothesize that the T7SSb is necessary for sustained GBS GI colonization. Methods Two bacterial strains were used, a wild-type (WT) GBS of A909 background (serotype Ia) and an isogenic T7SSb mutant GBS strain (essC::Himar1, transposon inserted). Monocolonization and co-cocolonization experiments were performed by orally inoculating preweaning C57BL/6J mice (12-14 days of life) with one or both strains, respectively. Euthanasia was performed, rectal swabs collected, and the GI tract harvested at day 7 post infection. For co-colonization experiments, competitive indices were calculated at day 7 post infection to determine the contribution of T7SSb to GBS GI colonization. For monocolonization experiments, colonization status and bacterial burden at day 7 post infection were measured. Results In cocolonization, WT GBS A909 outcompeted the essC::Himar1 mutant at 7-days post infection with a geometric mean competitive index of 8.8, 95% CI [0.2, 350.1] by rectal swab; 35.7, 95% CI [19.2, 66.3] in the small intestine; 87.6, 95% CI [18.9, 407] in the cecum; and 91.7, 95% CI [33.4, 252] in the colon (Figure 1a). In monocolonization, we noted similar rates of colonization (p=NS, Fisher’s exact test) (Figure 1b) and no difference in bacterial burden (p=NS, 2-way ANOVA test) (Figure 1c) across the GI tract at 7 days post infection. Conclusion Our results suggest that T7SSb plays an important role in GBS bacterial competition in the GI tract but is likely not an essential factor for GBS GI colonization. Further exploration of the role of the T7SSb in interbacterial competition may yield relevant information regarding GI colonization dynamics. Figure 1. Establishing the role of T7SSb in a murine model of GI colonization. (a) Wild type (WT) A909 confers an advantage over an isogenic T7SSb mutant (essC::Himar1) strain in a cocolonization model. Data points represent geometric mean competition indices and error bars represent 95% confidence interval. (b) Colonization status by WT A909 and essC::Himar1 mutant in the GI tract 7-days post infection in monocolonization experiments (p-values represent two-sided Fisher’s exact test). (c) Bacterial burden of monocolonization by WT A909 and essC::Himar1 mutant in the GI tract 7-days post infection (p-values represent 2-way ANOVA test).

Green synthesized Cr2O3/Bi2O3 nanocomposites for gamma ray shielding

The quest for advanced materials in gamma radiation shielding has spurred the exploration of environmentally friendly, nanotechnology-based approaches. This study introduces a novel synthesis of Cr2O3/Bi2O3 nanocomposites (NCs) using the solution combustion method, with Aloe vera extract serving as a natural reducing agent. Comprehensive analytical characterization of the synthesized NCs was conducted using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and ultraviolet–visible (UV–Vis) spectroscopy. The gamma radiation shielding properties of the Cr2O3/Bi2O3 NCs are evaluated using a NaI(Tl) detector connected to a multichannel analyzer. Key shielding parameters, including mass attenuation coefficients, mean free path, half-value layer, tenth-value layer, energy buildup factor, and radiation protection efficiency, indicate that Cr2O3/Bi2O3 NCs are highly effective in gamma radiation shielding. The results demonstrated the feasible shielding performance of these nanocomposites across various energies within error limits of 5 %. This study highlights the potential of Cr2O3/Bi2O3 NCs as a promising, sustainable alternative to conventional shielding materials, offering enhanced gamma radiation protection with reduced environmental impact.

Experimental assessments of anthropogenic emissions of nitrogen oxides from the territory of St. Petersburg based on data from long-term mobile measurements

The results of a series of spectroscopic measurements of NO2 content in the troposphere, carried out on a closed route of the ring road (KAD) of St. Petersburg in different seasons of 2012, 2014, 2015 and 2016, are considered. A unified approach to the interpretation of all experimental data using numerical modeling of the dispersion of air pollution and a priori information on the spatial distribution of its anthropogenic sources made it possible to significantly reduce the error in determining the integral NOx emission. The total amount, converted into gross annual anthropogenic emission from the territory of St. Petersburg, constitutes to 81 ± 17 thousand tons of NOx. This value exceeds the official data of the city inventory of air pollution which is 61...63 thousand tons, but is consistent (within the error limits) with the estimate previously obtained on the basis of similar mobile measurements in the spring of 2019 (75 ± 26 thousand tons).

7618 Thyroid Nodules, Normal Thyroid Levels, and Chronic Anxiety: A Case for Sub-Clinical Toxic Multinodular Goiter

Abstract Disclosure: C.M. Barrera: None. Introduction: Chronic anxiety and panic disorders, as described in the Diagnostic and Statistical Manual of Mental Disorders (DSM-V), are the most common psychiatric conditions. Hyperthyroidism is a known cause of both chronic anxiety and panic disorder. Case 1: A 36-year-old overweight Latin female is referred for evaluation of multiple thyroid nodules. The thyroid ultrasound was heterogeneous, with multiple bilateral nodules. In her history, the patient has chronic anxiety with panic attacks resulting in frequent emergency room visits. The TSH and T4 levels were TSH 0.59 mIU/L (0.40-4.5) and T4 10.7 mcg/dL (5.1-11.9). An I[1]23- Thyroid Scan showed a hot nodule with mild suppression and an uptake of 31.8% (The top limit is 35%). The patient started methimazole 2.5 mg daily, and after two months, her chronic anxiety and panic attacks resolved. Post-methimazole TSH rose to 1.18 mIU/L, and T4 10.0 mcg/dL and she has weaned off anxiety medications. Case 2: A 49-year-old overweight Latin female is referred for increased thyroid nodules. She complained of six months of tachycardia and anxiety. The TSH and T4 levels were TSH of 0.828 mIU/L (0.40-4.5) and T4 of 7.9 mcg/dl (4.5-12.0). An I[1]23-Thyroid Scan showed no dominant hot or cold nodules, with an uptake of 36.4% (The top limit is 35%, within normal error limits). She started methimazole 5 mg daily, resolving her tachycardia and anxiety within five weeks. Post-methimazole TSH was 1.64 mIU/L (0.45-4.5), and T4 6.7 mcg/dL (4.5-12.0). Case 3: A 60-year-old overweight Latin female is referred for evaluation of multiple thyroid nodules of ten years. She complained of chronic anxiety and panic attacks for two years. The TSH and T4 were normal at TSH 0.36 mIU/L (0.35- 5.50) and T4 9.7 mcg/dL (4.5-10.9). The thyroid ultrasound showed multiple bilateral nodules. An I[1]23-Thyroid Scan showed a suspected hot nodule without appreciable suppression and an uptake of 33% (The top limit is 35%). The patient started methimazole 5 mg daily. After eight weeks, she reported the resolution of most of her chronic anxiety with post-methimazole TSH 2.39 mIU/L and T4 7.1 mcg/dL (4.5-12.0). Discussion: The normal range of TSH, typically from 0.4-4.5 mIU/L, is calculated by measuring the TSH levels among a normal population. The group range then determines the laboratory reference range. This contrasts with individual values, which have a narrower range, suggesting that each person has a unique thyroid level. This suggests that TSH levels at the extremum, associated with hyperfunctioning nodules contributing to a rise in uptake, may not be normal for that patient and may explain the anxiety and other symptoms. Learning Points: Evolving multiple autonomous thyroid nodules lowers TSH levels while raising thyroid uptake. Symptoms of chronic anxiety and panic attacks can predate abnormal thyroid levels and resolve with low-dose methimazole. Presentation: 6/1/2024

Accuracy of oscillometric blood pressure measurement using a Cardell Touch multiparameter monitor in anesthetized pigs.

To assess the accuracy of an oscillometric monitor in anesthetized pigs and its ability to track changes in mean arterial pressure (MAP) and to detect arterial hypotension and hypertension in reference to direct measurements. Mean arterial pressure was measured simultaneously from a catheter in a femoral artery and with an oscillometric cuff placed over the metatarsus in 9 anesthetized pigs (∼6 months old, 35 to 55 kg). Pigs were subjected to maneuvers to alter MAP. Paired values for invasive and noninvasive MAP (iMAP and NiMAP) were recorded every 2 minutes. Bland-Altman plots with bias, limits of agreement, and percentage error were constructed using each pair and the average of 5 consecutive values. Concordance was calculated using changes in MAP at 20-minute intervals. Receiver operating characteristics (ROC) curves were constructed to test NiMAP for detection of hypotension (< 70 mm Hg) and hypertension (≥ 120 mm Hg). Bias of NiMAP was -8.59 mm Hg for consecutive pairs and -8.85 mm Hg for averaged pairs, relative to iMAP. Limits of agreement and percentage error were reduced for averages (19%) over individual pairs (26%). Concordance was 82%. The area under the ROC curve for detecting hypotension with NiMAP was 0.936, with a best cutoff value of 63 mm Hg NiMAP. The area under the ROC curve for hypertension was 0.940, with a best cutoff value of 101 mm Hg NiMAP. Averaging several consecutive values improves the accuracy of NiMAP measurements. This device correctly tracked changes in MAP approximately 80% of the time and appears reliable for diagnosing arterial hypotension.

Evaluating the Importance of Nitrate‐Containing Aerosols for the Asian Tropopause Aerosol Layer

AbstractThe Asian Summer Monsoon (ASM) convection transports aerosols and their precursors from the boundary layer to the upper troposphere and lower stratosphere (UTLS). This process forms an annually recurring aerosol layer near the tropopause. Recent observations have revealed a distinct property of the aerosol layer over the ASM region, it is nitrate‐rich. We present a newly implemented aerosol formation algorithm that enhances the representation of nitrate aerosol in the Community Aerosol and Radiation Model for Atmospheres (CARMA) coupled with the Community Earth System Model (CESM). The simulated aerosol chemical composition, as well as vertical distributions of aerosol size and mass, are evaluated using in situ and remote sensing observations. The simulated concentrations (ammonium, nitrate, and sulfate) and size distributions are generally within the error bars of data. We find nitrate, organics, and sulfate contribute significantly to the UTLS aerosol concentration between 15°–45°N and 0°–160°E. The two key formation mechanisms of nitrate‐containing aerosols in the ATAL are ammonium neutralization to form ammonium nitrate in regions where convection is active, and condensation of nitric acid in regions of cold temperature. Furthermore, including nitrate formation in the model doubles the surface area density in the tropical tropopause region between 15°–45°N and 0°–160°E, which alters the chlorine partitioning and subsequently impacts the rate of ozone depletion.

A-098 Reducing Hemolyzed Specimen Rejection for Aspartate Aminotransferase (AST): A Quality Improvement Initiative to Further Optimize Concentration-Specific H-index Thresholds

Abstract Background Serum aspartate aminotransferase (AST) is a commonly ordered test useful for diagnosing and monitoring hepatocellular damage. The hemolysis (H) index interference threshold for the Roche Cobas AST reagent is H=20, which is the lowest of all tests on Roche chemistry platforms (Cobas c701, c502, and e801). Previous optimization studies supported the implementation of an AST concentration-specific tiered hemolysis interference threshold schema: AST&amp;lt;100 U/L (H=50), AST=100-200 U/L (H=100), AST=201-300 U/L (H=200) and AST&amp;gt;301 U/L (H=500). This schema significantly reduced redraws; however, a significant number of rejected samples were noted to have AST results within the reference interval (RI). The aim of this study was to establish an H-index threshold for samples with AST results within the RI. Methods Twelve pools of residual serum samples were created with AST concentrations ranging from 17-66 U/L. Each pool was split into 2 aliquots, receiving either 10% of a lab-produced hemolysate solution generating H-indices from 62-508 or 10% of a 0.9% saline control. Aliquots were mixed in equal portions to create a series of 5 samples with increasing hemolysis according to CLSI guideline EP-07 and analyzed in EP Evaluator. Median(interquartile range (IQR)) H-index thresholds were calculated for error limits beginning at +5 U/L and increasing incrementally (+1 U/L) to +10 U/L. Clinical cases with an H-index slightly above the hemolysis interference threshold (50≤H≤70) and results within the RIs (Male:8-48U/L; Female:8-43U/L) were reviewed by the Chemistry Resident/Fellow on-call (n=68) over a period of 8 months. Results were released with a comment if risk of clinical misinterpretation due to a falsely elevated result was low. Previous, non-hemolyzed AST results were compared within 45 days, if available, by paired-Wilcoxon test (Graphpad Prism). Results The median(range) of initial AST results in the serum pools was 20(17-66) U/L. The calculated H-index thresholds (median(IQR)) using error limits of +5, +6, +7, +8, +9, +10 U/L were 49(43-53), 56(52-63), 66(61-78), 78(72-81), 91(84-91) and 101 (96-107), respectively. All slightly hemolyzed AST results (50≤H≤70) within the RI were released with a comment upon chart review. Previously reported AST values (n=23) were compared to current (hemolyzed) concentrations and found to be statistically significantly increased relative to previous results from the same patient (median(range) difference: 3.7(-3.6-11)U/L, p=0.009). However, the median difference was &amp;lt;5U/L or 10%, the laboratory’s criteria used to define a clinically significant difference. Conclusions A median H-index limit of up to 100 can be applied to samples when AST is within the RI. The risk of misinterpretation for results with mild-moderate hemolysis was low in the cases reviewed. Sample rejection rates and reporting delays can be diminished by implementing this practice. Interpretation can be further enhanced by appending the following comment to hemolyzed samples: “Specimen was received with hemolysis slightly above the accepted threshold. This degree of hemolysis is associated with a false increase of approximately 5-10 U/L. Interpret in conjunction with other laboratory and clinical findings.”

B-131 The fallacy of average sigma levels from mixed sample levels

Abstract Background Sigma measures the number of SDs (z-value) from the existing sample mean to the nearest analytical performance standard or allowable error limit. Authors and software programs often measure sigma metrics for each QC sample but use an average sigma to compare methods and select QC strategies. That practice leads to dramatic over or under-estimation of the number of errors reported and the selection of inappropriate QC strategies. Methods Data samples were created to produce sigma values of 3.0, 4.5, and 6.0. Microsoft Excel function NORMSDIST was used to convert sigma to percent to number of errors per million patients. NORMSINV was used to convert the number of errors per million patients to sigma. Results A. Six sigma represents a method with a failure rate of 0.000001% or 0.001 failures of ASP/TEa per million patients. B. Three sigma represents a method with a failure rate of 0.135 percent or 1,350 failures of ASP/TEa per million patients. C. While the average sigma value of samples A and B was 4.5s, the average error rate was 0.0675 percent or 675 failures of ASP/TEa per million patients. D. An error rate was 0.0675 percent converts with the NORMSINV function to a sigma of 3.21. E. A true 4.5 sigma method would have a failure rate of 0.00034 percent or 3.4 failures of ASP/TEa per million patients. Conclusions Sigma studies that present an average sigma value underestimate the true number of errors reported. It would be more scientifically correct to either report the number of errors reported or to report the average sigma value based on the average number of errors. Laboratory professionals should interpret sigma studies and publications cautiously if a single sigma is used to represent two or more data sets.