Development and Validation of a Convolutional Neural Network Model to Predict a Pathologic Fracture in the Proximal Femur Using Abdomen and Pelvis CT Images of Patients With Advanced Cancer.

BACKGROUND: Improvement in survival in patients with advanced cancer is accompanied by an increased probability of bone metastasis and related pathologic fractures (especially in the proximal femur). The few systems proposed and used to diagnose impending fractures owing to metastasis and to ultimately prevent future fractures have practical limitations; thus, novel screening tools are essential. A CT scan of the abdomen and pelvis is a standard modality for staging and follow-up in patients with cancer, and radiologic assessments of the proximal femur are possible with CT-based digitally reconstructed radiographs. Deep-learning models, such as convolutional neural networks (CNNs), may be able to predict pathologic fractures from digitally reconstructed radiographs, but to our knowledge, they have not been tested for this application. QUESTIONS/PURPOSES: (1) How accurate is a CNN model for predicting a pathologic fracture in a proximal femur with metastasis using digitally reconstructed radiographs of the abdomen and pelvis CT images in patients with advanced cancer? (2) Do CNN models perform better than clinicians with varying backgrounds and experience levels in predicting a pathologic fracture on abdomen and pelvis CT images without any knowledge of the patients' histories, except for metastasis in the proximal femur? METHODS: A total of 392 patients received radiation treatment of the proximal femur at three hospitals from January 2011 to December 2021. The patients had 2945 CT scans of the abdomen and pelvis for systemic evaluation and follow-up in relation to their primary cancer. In 33% of the CT scans (974), it was impossible to identify whether a pathologic fracture developed within 3 months after each CT image was acquired, and these were excluded. Finally, 1971 cases with a mean age of 59 ± 12 years were included in this study. Pathologic fractures developed within 3 months after CT in 3% (60 of 1971) of cases. A total of 47% (936 of 1971) were women. Sixty cases had an established pathologic fracture within 3 months after each CT scan, and another group of 1911 cases had no established pathologic fracture within 3 months after CT scan. The mean age of the cases in the former and latter groups was 64 ± 11 years and 59 ± 12 years, respectively, and 32% (19 of 60) and 53% (1016 of 1911) of cases, respectively, were female. Digitally reconstructed radiographs were generated with perspective projections of three-dimensional CT volumes onto two-dimensional planes. Then, 1557 images from one hospital were used for a training set. To verify that the deep-learning models could consistently operate even in hospitals with a different medical environment, 414 images from other hospitals were used for external validation. The number of images in the groups with and without a pathologic fracture within 3 months after each CT scan increased from 1911 to 22,932 and from 60 to 720, respectively, using data augmentation methods that are known to be an effective way to boost the performance of deep-learning models. Three CNNs (VGG16, ResNet50, and DenseNet121) were fine-tuned using digitally reconstructed radiographs. For performance measures, the area under the receiver operating characteristic curve, accuracy, sensitivity, specificity, precision, and F1 score were determined. The area under the receiver operating characteristic curve was used to evaluate three CNN models mainly, and the optimal accuracy, sensitivity, and specificity were calculated using the Youden J statistic. Accuracy refers to the proportion of fractures in the groups with and without a pathologic fracture within 3 months after each CT scan that were accurately predicted by the CNN model. Sensitivity and specificity represent the proportion of accurately predicted fractures among those with and without a pathologic fracture within 3 months after each CT scan, respectively. Precision is a measure of how few false-positives the model produces. The F1 score is a harmonic mean of sensitivity and precision, which have a tradeoff relationship. Gradient-weighted class activation mapping images were created to check whether the CNN model correctly focused on potential pathologic fracture regions. The CNN model with the best performance was compared with the performance of clinicians. RESULTS: DenseNet121 showed the best performance in identifying pathologic fractures; the area under the receiver operating characteristic curve for DenseNet121 was larger than those for VGG16 (0.77 ± 0.07 [95% CI 0.75 to 0.79] versus 0.71 ± 0.08 [95% CI 0.69 to 0.73]; p = 0.001) and ResNet50 (0.77 ± 0.07 [95% CI 0.75 to 0.79] versus 0.72 ± 0.09 [95% CI 0.69 to 0.74]; p = 0.001). Specifically, DenseNet121 scored the highest in sensitivity (0.22 ± 0.07 [95% CI 0.20 to 0.24]), precision (0.72 ± 0.19 [95% CI 0.67 to 0.77]), and F1 score (0.34 ± 0.10 [95% CI 0.31 to 0.37]), and it focused accurately on the region with the expected pathologic fracture. Further, DenseNet121 was less likely than clinicians to mispredict cases in which there was no pathologic fracture than cases in which there was a fracture; the performance of DenseNet121 was better than clinician performance in terms of specificity (0.98 ± 0.01 [95% CI 0.98 to 0.99] versus 0.86 ± 0.09 [95% CI 0.81 to 0.91]; p = 0.01), precision (0.72 ± 0.19 [95% CI 0.67 to 0.77] versus 0.11 ± 0.10 [95% CI 0.05 to 0.17]; p = 0.0001), and F1 score (0.34 ± 0.10 [95% CI 0.31 to 0.37] versus 0.17 ± 0.15 [95% CI 0.08 to 0.26]; p = 0.0001). CONCLUSION: CNN models may be able to accurately predict impending pathologic fractures from digitally reconstructed radiographs of the abdomen and pelvis CT images that clinicians may not anticipate; this can assist medical, radiation, and orthopaedic oncologists clinically. To achieve better performance, ensemble-learning models using knowledge of the patients' histories should be developed and validated. The code for our model is publicly available online at https://github.com/taehoonko/CNN_path_fx_prediction . LEVEL OF EVIDENCE: Level III, diagnostic study.

Ecological Traits of Fish for Mercury Biomonitoring: Insights from Compound-Specific Nitrogen and Stable Mercury Isotopes.

We coupled compound-specific isotopic analyses of nitrogen (N) in amino acids (δ15NGlu, δ15NPhe) and mercury stable isotopes (δ202Hg, Δ199Hg) to quantify ecological traits governing the concentration, variability, and source of Hg in largemouth bass (LB) and pike gudgeon (PG) across four rivers, South Korea. PG displayed uniform Hg concentration (56-137 ng/g), trophic position (TPcorrected; 2.6-3.0, n = 9), and N isotopes in the source amino acid (δ15NPhe; 7-13‰), consistent with their specialist feeding on benthic insects. LB showed wide ranges in Hg concentration (45-693 ng/g), TPcorrected (2.8-3.8, n = 14), and δ15NPhe (1.3-16‰), reflecting their opportunistic feeding behavior. Hg sources assessed using Hg isotopes reveal low and uniform Δ199Hg in PG (0.20-0.49‰), similar to Δ199Hg reported in sediments. LB displayed site-specific δ202Hg (-0.61 to -0.04‰) and Δ199Hg (0.53-1.09‰). At the Yeongsan River, LB displayed elevated Δ199Hg and low δ15NPhe, consistent with Hg and N sourced from the atmosphere. LB at the Geum River displayed low Δ199Hg and high δ15NPhe, both similar to the isotope values of anthropogenic sources. Our results suggest that a specialist fish (PG) with consistent ecological traits and Hg concentration is an effective bioindicator species for Hg. When accounting for Hg sources, however, LB better captures site-specific Hg sources.

Optimal Intervention for Initial Treatment of Anastomotic Biliary Complications After Right Lobe Living Donor Liver Transplantation.

Background: This study evaluated endoscopic retrograde cholangiopancreatography (ERCP) and percutaneous transhepatic biliary drainage (PTBD) as interventions for patients with anastomotic biliary complications (ABC) after living donor liver transplantation (LDLT). Methods: Prospectively collected data of patients who were diagnosed with ABC after LDLT between January 2013 and June 2017 were retrospectively reviewed. Results: There were 57 patients who underwent LDLT with a right liver graft using duct-to-duct biliary reconstruction and experienced ABC. Among the patients with RAD involvement, there were no significant differences in the intervention success (p = 0.271) and patency rates (p = 0.267) between ERCP and PTBD. Similarly, among the patients with RPD involvement, there were no significant differences in the intervention success (p = 0.148) and patency rates (p = 0.754) between the two procedures. Graft bile duct variation (p = 0.013) and a large angle between the recipient and graft bile duct (R-G angle) (p = 0.012) significantly increased the likelihood of failure of ERCP in the RAD. When the R-G angle was greater than 47.5°, the likelihood of ERCP failure increased. Conclusion: We recommend PTBD when graft bile duct variation is presented in patients with RAD involvement and/or when the R-G angle is greater than 47.5°.

Metalloendopeptidase ADAM-like Decysin 1 (ADAMDEC1) in Colonic Subepithelial PDGFRα+ Cells Is a New Marker for Inflammatory Bowel Disease.

Metalloendopeptidase ADAM-Like Decysin 1 (ADAMDEC1) is an anti-inflammatory peptidase that is almost exclusively expressed in the gastrointestinal (GI) tract. We have recently found abundant and selective expression of Adamdec1 in colonic mucosal PDGFRα+ cells. However, the cellular origin for this gene expression is controversial as it is also known to be expressed in intestinal macrophages. We found that Adamdec1 mRNAs were selectively expressed in colonic mucosal subepithelial PDGFRα+ cells. ADAMDEC1 protein was mainly released from PDGFRα+ cells and accumulated in the mucosal layer lamina propria space near the epithelial basement membrane. PDGFRα+ cells significantly overexpressed Adamdec1 mRNAs and protein in DSS-induced colitis mice. Adamdec1 was predominantly expressed in CD45- PDGFRα+ cells in DSS-induced colitis mice, with only minimal expression in CD45+ CD64+ macrophages. Additionally, overexpression of both ADAMDEC1 mRNA and protein was consistently observed in PDGFRα+ cells, but not in CD64+ macrophages found in human colonic mucosal tissue affected by Crohn's disease. In summary, PDGFRα+ cells selectively express ADAMDEC1, which is localized to the colon mucosa layer. ADAMDEC1 expression significantly increases in DSS-induced colitis affected mice and Crohn's disease affected human tissue, suggesting that this gene can serve as a diagnostic and/or therapeutic target for intestinal inflammation and Crohn's disease.

Extracellular Matrix Biomarkers in Colorectal Cancer.

The cellular microenvironment composition and changes therein play an extremely important role in cancer development. Changes in the extracellular matrix (ECM), which constitutes a majority of the tumor stroma, significantly contribute to the development of the tumor microenvironment. These alterations within the ECM and formation of the tumor microenvironment ultimately lead to tumor development, invasion, and metastasis. The ECM is composed of various molecules such as collagen, elastin, laminin, fibronectin, and the MMPs that cleave these protein fibers and play a central role in tissue remodeling. When healthy cells undergo an insult like DNA damage and become cancerous, if the ECM does not support these neoplastic cells, further development, invasion, and metastasis fail to occur. Therefore, ECM-related cancer research is indispensable, and ECM components can be useful biomarkers as well as therapeutic targets. Colorectal cancer specifically, is also affected by the ECM and many studies have been conducted to unravel the complex association between the two. Here we summarize the importance of several ECM components in colorectal cancer as well as their potential roles as biomarkers.

Tracking nitrate sources in agricultural-urban watershed using dual stable isotope and Bayesian mixing model approach: Considering N transformation by Lagrangian sampling.

A dual isotopes approach and the Bayesian isotope mixing model were applied to trace nitrogen pollution sources and to quantify their relative contribution to river water quality. We focused on two points to enhance the applicability of the method: 1) Direct measurement on the end-members to distinguish "sewage" and "manure" which used to be grouped in one pollution source as their isotope ranges overlap; 2) The Lagrangian sampling method was applied to consider the transport of nitrogen pollutants in a long river so that any fractionation process can be dealt with in the given Bayesian modeling framework. The results of the analysis confirmed the NO3- isotope composition in the river of interest to be within the range of NO3- with origins in "NH4+ in fertilizer", "Soil N", and "Manure and sewage" pollution. This suggests that nitrogen pollution is mostly attributed to anthropogenic sources. The δ18O NO3 value follows the range +2.5∼+15.0‰, implying that NO3- in the river is mainly derived from nitrification, and possible nitrification in groundwater or waterfront other than surface water. The ratio of the concentration of δ15N NO3 to that of δ18O NO3, and the corresponding regression equation indicates that the denitrification effect in surface water was insignificant during the study period. From the results of the contribution ratio of each source, improving the water quality of the discharge from the sewage treatment plants was proved to be the key factor to reduce nitrogen pollution in the river.

Operando Identification of the Chemical and Structural Origin of Li-Ion Battery Aging at Near-Ambient Temperature.

Integrated with heat-generating devices, a Li-ion battery (LIB) often operates at 20-40 °C higher than the ordinary working temperature. Although macroscopic investigation of the thermal contribution has shown a significant reduction in the LIB performance, the molecular level structural and chemical origin of battery aging in a mild thermal environment has not been elucidated. On the basis of the combined experiments of the electrochemical measurements, Cs-corrected electron microscopy, and in situ analyses, we herein provide operando structural and chemical insights on how a mild thermal environment affects the overall battery performance using anatase TiO2 as a model intercalation compound. Interestingly, a mild thermal condition induces excess lithium intercalation even at near-ambient temperature (45 °C), which does not occur at the ordinary working temperature. The anomalous intercalation enables excess lithium storage in the first few cycles but exerts severe intracrystal stress, consequently cracking the crystal that leads to battery aging. Importantly, this mild thermal effect is accumulated upon cycling, resulting in irreversible capacity loss even after the thermal condition is removed. Battery aging at a high working temperature is universal in nearly all intercalation compounds, and therefore, it is significant to understand how the thermal condition contributes to battery aging for designing intercalation compounds for advanced battery electrode materials.

Modified Brachio-basilic/brachial Arteriovenous Fistula Creation with Short-segment Elevation Preserving the Axilla.

BACKGROUND: Brachio-basilic/brachial transposition arteriovenous fistula has emerged as one of the autologous arteriovenous fistula options. However, there have not been many reports on the outcomes of basilic or brachial elevation of arteriovenous fistula compared with those of conventional transposition. We evaluated the efficacy of modified brachio-basilic and brachio-brachial arteriovenous fistula creation with short-segment elevation preserving the axillary area. METHODS: From March 2016 to August 2018, medical records of the patients who underwent short-segment elevation of brachio-basilic or brachio-brachial arteriovenous fistula in the upper arm (sBAE or sBRE) were reviewed retrospectively. RESULTS: Of the 51 patients, 37 underwent sBAE and 14 underwent sBRE. Maturation failure occurred in two patients (3.92%), who underwent sBAE. Stenosis was the most common complication, which developed in 13 patients (25.5%), and there was no significant difference between the sBAE and the sBRE. In the 51 patients, cumulative primary patency rates at 6 and 12 months were 88.3% and 69.1%, respectively. Assisted primary patency rates at 6 and 12 months were 97.8% and 90.7%, respectively. Secondary patency rates at 6 and 12 months were both 100%. There were no significant differences between the sBAE and the sBRE in 1-year primary patency (79.1% vs. 46.7%; P = 0.20), assisted primary patency (91.6% vs. 88.1%; P = 0.36), and secondary patency rates (100% vs. 100%). CONCLUSIONS: Brachio-basilic/brachial arteriovenous fistula with short-segment elevation preserving the axilla showed excellent 1-year patency rate, easier cannulation, and other future advantages, and therefore, is a logical modification of conventional transposition of arteriovenous fistula.

Eupatilin downregulates phorbol 12-myristate 13-acetate-induced MUC5AC expression via inhibition of p38/ERK/JNK MAPKs signal pathway in human airway epithelial cells.

Chronic inflammatory airway diseases, such as chronic rhinosinusitis, chronic obstructive pulmonary disease, and asthma, are associated with excessive mucus production. Hence, the regulation of mucus production is important for the treatment of upper and lower airway diseases. Eupatilin is a pharmacologically active ingredient obtained from Artemisia asiatica Nakai (Asteraceae) and exerts potent anti-inflammatory, anti-allergic, and anti-tumor activities. In the present study, we investigated the effect of eupatilin on phorbol 12-myristate 13-acetate (PMA)-induced MUC5AC and MUC5B expression in human airway epithelial cells. We found that eupatilin treatment significantly inhibited PMA-induced mucus secretion in PAS staining. In addition, qRT-PCR results showed that eupatilin dose-dependently decreased the mRNA expression of MUC5AC in human airway epithelial cells. Western blot and immunofluorescence assay also showed that PMA-induced protein expression of MUC5AC was inhibited by eupatilin treatment. Finally, we investigated MAPKs activity after stimulation with PMA using western blot analysis in human airway epithelial cells. The results showed that eupatilin downregulated the levels of phosphorylated p38, ERK, and JNK. In summary, the anti-inflammatory activities of eupatilin, characterized as the suppression of MUC5AC expression and secretion in human airway epithelial cells, were found to be associated with the inhibition of p38/ERK/JNK MAPKs signaling pathway of MUC5AC secretion.

Synthesis and Characterization of Co-Mn (O)OH Nanosheets Assembled Structure Covered of Reduced Graphene Oxide Hybrid Structures by Hydrothermal Method.

In this study, we prepared cobalt-manganese (oxy) hydroxide nanosheets assembled structure covered of reduced graphene oxide hybrid structure (Co-Mn (O)OH NAS@rGO HS) via reduction and hydroxylation of Mn1.5Co1.5[Co(CN)6]2@graphene oxide (GO). Obtained precursors were optimized at 15 mg GO, and these are hybrid structures in which nanocubes 200-400 nm in size were fully covered by multi-layered GO. The functional group (-COOH, -OH, C-O-C) of GO was removed through reduction by L-ascorbic acid. We obtained MnCOOH, Co(OH)2, and Co-Mn LDH synthesized by hydroxylation of Mn1.5Co1.5[Co(CN)6]2@GO via ion exchange between the CN group and OH-. The hybrid nanostructure between transition-metal oxide/hydroxide and reduced graphene oxide could be used in various fields, including lithium ion batteries, supercapacitors, and electrocatalyst for water splitting.

Comparison of acid extraction and total digestion methods for measuring Cd isotope ratios of environmental samples.

To evaluate the pretreatment processing for Cd isotope analysis of environmental samples, acid extractions and total digestions were examined with various environmental certified reference materials. Four certified reference material samples, including fly ash, polluted soil, domestic sludge, and industrial sludge, were digested by six different acid extraction and total digestion methods, and then Cd was separated to remove other matrix by anion-exchange column. The Cd recovery rates of the acid extraction methods were 2.6-89.1%, while those of the total digestion methods were 21.6-88.7%. In these results, the Cd recovery rates were dependent on the sample type. More than 80% of the Cd in the polluted soil and domestic sludge samples could be recovered regardless of the decomposition method, except one method. On the other hand, the Cd recovery rate from fly ash was low when total digestion was performed using a HF mixture, and the recovery rate by total digestion methods for industrial sludge was higher than that by acid extraction. In our results, Cd isotope ratios tended to be more positive by increasing the Cd recovery rates, suggesting that the light isotope of Cd was decomposed preferentially during the decomposition procedures. However, when more than 80% of the Cd in the samples was recovered, the Cd isotope ratios were determined to be similar. This indicated that at least 80% of the Cd should be recovered from environmental samples to accurately measure the Cd isotopic ratio of environmental samples.

Engineering Titanium Dioxide Nanostructures for Enhanced Lithium-Ion Storage.

Various kinds of nanostructured materials have been extensively investigated as lithium ion battery electrode materials derived from their numerous advantageous features including enhanced energy and power density and cyclability. However, little is known about the microscopic origin of how nanostructures can enhance lithium storage performance. Herein, we identify the microscopic origin of enhanced lithium storage in anatase TiO2 nanostructure and report a reversible and stable route to achieve enhanced lithium storage capacity in anatase TiO2. We designed hollow anatase TiO2 nanostructures composed of interconnected ∼5 nm sized nanocrystals, which can individually reach the theoretical lithium storage limit and maintain a stable capacity during prolonged cycling (i.e., 330 mAh g-1 for the initial cycle and 228 mAh g-1 for the 100th cycle, at 0.1 A g-1). In situ characterization by X-ray diffraction and X-ray absorption spectroscopy shows that enhanced lithium storage into the anatase TiO2 nanocrystal results from the insertion reaction, which expands the crystal lattice during the sequential phase transition (anatase TiO2 → Li0.55TiO2 → LiTiO2). In addition to the pseudocapacitive charge storage of nanostructures, our approach extends the utilization of nanostructured TiO2 for significantly stabilizing excess lithium storage in crystal structures for long-term cycling, which can be readily applied to other lithium storage materials.

Millerite Core-Nitrogen-Doped Carbon Hollow Shell Structure for Electrochemical Energy Storage.

Nickel sulfides have drawn much attention with the benefits of a high redox activity, high electrical conductivity, low cost, and fabrication ease; however, these metal sulfides are susceptible to mechanical degradation regarding their cycling performance. Conversely, hollow carbon shells exhibit a substantial electrochemical steadiness in energy storage applications. Here, the design and development of a novel millerite core-nitrogen-doped carbon hollow shell (NiS-NC HS) structure for electrochemical energy storage is presented. The nitrogen-doped carbon hollow shell (NC HS) protects against the degradation and the millerite-core aggregation, giving rise to an excellent rate capability and stability during the electrochemical charging-discharging processes, in addition to improving the NiS-NC HS conductivity. The NiS-NC HS/18h supercapacitor electrode displays an outstanding specific capacitance of 1170.72 F g-1 (at 0.5 A g-1 ) and maintains 90.71% (at 6 A g-1 ) of its initial capacitance after 4000 charge-discharge cycles, owing to the unique core-shell structure. An asymmetric-supercapacitor device using NiS-NC HS and activated-carbon electrodes exhibits a high power and energy density with a remarkable cycling stability, maintaining 89.2% of its initial capacitance after 5000 cycles.

Accumulation of Microcystin (LR, RR and YR) in Three Freshwater Bivalves in Microcystis aeruginosa Bloom Using Dual Isotope Tracer.

Abstract: Stable isotope tracers were first applied to evaluate the Microcystis cell assimilation efficiency of Sinanodonta bivalves, since the past identification method has been limited to tracking the changes of each chl-a, clearity, and nutrient. The toxicity profile and accumulation of MC-LR, -RR and -YR in different organs (foot and digestive organs) from the three filter-feeders (Sinanodonta woodina, Sinanodonta arcaeformis, and Unio douglasiae) were assessed under the condition of toxigenic cyanobacteria (Microcystis aeruginosa) blooms through an in situ pond experiment using 13C and 15N dual isotope tracers. Chl-a concentration in the manipulated pond was dramatically decreased after the beginning of the second day, ranging from 217.5 to 15.6 µg·L-1. The highest amount of MCs was incorporated into muscle and gland tissues in U. douglasiae during the study period, at nearly 2 or 3 times higher than in S.woodiana and S. arcaeformis. In addition, the incorporated 13C and 15N atom % in the U. douglasiae bivalve showed lower values than in other bivalves. The results demonstrate that U. douglasiae has less capacity to assimilate toxic cyanobacteria derived from diet. However, the incorporated 13C and 15N atom % of S. arcaeformis showed a larger feeding capacity than U. douglasiae and S. wodiana. Our results therefore also indicate that S. arcaeformis can eliminate the toxin more rapidly than U. douglasiae, having a larger detoxification capacity.

Effects of HCl pretreatment, drying, and storage on the stable isotope ratios of soil and sediment samples.

RATIONALE: Stable isotope (δ(13) C, δ(15) N, δ(34) S values) analysis has become increasingly important for tracing contaminant sources in environments. Pretreatment of environmental samples allows accurate analysis of stable isotope ratios. The pretreatment of a sample and its subsequent preservation could either contaminate or create experimental artifacts affecting the validity of the resulting C/N ratios and the elemental isotopic contents of a sample. METHODS: The effects of acid pretreatment (0.1, 0.5, 1, 2, 5, 13 M HCl) and exposure period (2, 6, 12, 24, and 48 h) on the stable isotopic ratios of marine sediment (MS), river sediment (RS) and terrestrial soil (TS) samples were evaluated. The effects of storage temperatures (-80, -20 and 2°C), storage duration (1 week, 1 to 12 months) and washing steps (1, 2, 3, 5, 7 or 12 times) on the stable isotopic ratios were also considered. The %C, %N and %S, as well as the δ(13) C, δ(15) N, and δ(34) S values, of each sample were measured using continuous flow Elemental Analyzer/Isotope Ratio Mass Spectrometry (EA/IRMS). RESULTS: The HCl treatment was applicable for δ(13) C analysis. However, the acid concentration and duration of exposure that brought about total removal of carbonate for the three sample types varied; e.g. the TS sample required stronger acid and a shorter exposure time. Storage time also had an effect: the δ(13) C values were lower and the δ(15) N and δ(34) S values higher after storage for 300 days. CONCLUSIONS: HCl pretreatment effectively eliminates carbonates and thereby helps δ(13) C analysis of the organic fraction. HCl pretreatment is not recommended for δ(15) N and δ(34) S analysis. Freeze-drying of samples is recommended rather than oven drying. A temperature-dependent change in the isotopic ratios of long-term stored samples was observed during this study; therefore, relatively short-term storage (-80°C) of freeze-dried samples is preferable. Copyright © 2016 John Wiley & Sons, Ltd.

Seasonal Changes in Mycosporine-Like Amino Acid Production Rate with Respect to Natural Phytoplankton Species Composition.

After in situ incubation at the site for a year, phytoplanktons in surface water were exposed to natural light in temperate lakes (every month); thereafter, the net production rate of photoprotective compounds (mycosporine-like amino acids, MAAs) was calculated using (13)C labeled tracer. This is the first report describing seasonal variation in the net production rate of individual MAAs in temperate lakes using a compound-specific stable isotope method. In the mid-latitude region of the Korean Peninsula, UV radiation (UVR) usually peaks from July to August. In Lake Paldang and Lake Cheongpyeong, diatoms dominated among the phytoplankton throughout the year. The relative abundance of Cyanophyceae (Anabaena spiroides) reached over 80% during July in Lake Cheongpyeong. Changes in phytoplankton abundance indicate that the phytoplankton community structure is influenced by seasonal changes in the net production rate and concentration of MAAs. Notably, particulate organic matter (POM) showed a remarkable change based on the UV intensity occurring during that period; this was because of the fact that cyanobacteria that are highly sensitive to UV irradiance dominated the community. POM cultured in Lake Paldang had the greatest shinorine (SH) production rate during October, i.e., 83.83 ± 10.47 fgC·L(-1)·h(-1). The dominance of diatoms indicated that they had a long-term response to UVR. Evaluation of POM cultured in Lake Cheongpyeong revealed that there was an increase in the net MAA production in July (when UVR reached the maximum); a substantial amount of SH, i.e., 17.62 ± 18.34 fgC·L(-1)·h(-1), was recorded during this period. Our results demonstrate that both the net production rate as well as the concentration of MAAs related to photoinduction depended on the phytoplankton community structure. In addition, seasonal changes in UVR also influenced the quantity and production of MAAs in phytoplanktons (especially Cyanophyceae).

Atmospheric mercury uptake and accumulation in forests dependent on climatic factors.

The environmental and climatic factors dictating atmospheric mercury (Hg) uptake by foliage and accumulation within the forest floor are evaluated across six mountain sites, South Korea, using Hg concentration and Hg stable isotope analyses. The isotope ratios of total gaseous Hg (TGM) at six mountains are explained by local anthropogenic Hg emission influence and partly by mountain elevation and wind speed. The extent to which TGM is taken up by foliage is not dependent on the site-specific TGM concentration, but by the local wind speed, which facilitates TGM passage through dense deciduous canopies in the Korean forests. This is depicted by the significant positive relationship between wind speed and foliage Hg concentration (r2 = 0.92, p < 0.05) and the magnitude of δ202Hg shift from TGM to foliage (r2 = 0.37, p > 0.05), associated with TGM uptake and oxidation by foliar tissues. The litter and topsoil Hg concentrations and isotope ratios reveal relationships with a wide range of factors, revealing lower Hg level and greater isotopic fractionation at sites with low elevation, high wind speed, and high mean warmest temperature. We attribute this phenomenon to active TGM re-emission from the forest floor at sites with high wind speed and high temperature, caused by turnover of labile organic matter and decomposition. In contrast to prior studies, we observe no significant effect of precipitation on forest Hg accumulation but precipitation appears to reduce foliage-level Hg uptake by scavenging atmospheric Hg species available for stomata uptake. The results of this study would enable better prediction of future atmospheric and forest Hg influence under climate change.

Impact of typhoons on anthropogenic nitrogen sources in Lake Sihwa, South Korea.

This study investigated the nitrate dual isotopic compositions (δ15NNO3 and δ18ONO3) of water samples to trace nitrate sources in Lake Sihwa, which encompasses various land-use types (e.g., urban, industry, wetland, and agriculture). The biogeochemical interactions of anthropogenic nitrogen sources (e.g., soil, road dust, and septic water) were also evaluated through multiple pathways from terrestrial boundaries to the water column. Based on increased concentrations of dissolved total nitrogen (DTN; 3.1 ± 1.6 mg/L) after typhoon, the variation of element stoichiometry (N:P:Si) in this system shifted to the relatively N-rich conditions (DIN/DIP; 14.1 ± 8.1, DIN/DSi; 1.4 ± 1.8), potentially triggering the occurrence of harmful algal blooms. Furthermore, discriminative isotopic compositions (δ15NNO3; 4.0 ± 2.1 ‰, δ18ONO3; 6.1 ± 4.3 ‰) after the typhoon suggested the increased DTN input of anthropogenic origins within Lake Sihwa would be mainly transported from urban sources (76 ± 9 %). Consequently, the isotopic-based approach may be useful for effective water quality management under increased anthropogenic activities near aquatic systems.

Quantitative source tracking for organic foulants in ultrafiltration membrane using stable isotope probing approach.

Quantitatively identifying the primary sources of organic membrane fouling is essential for the effective implementation of membrane technology and optimal water resource management prior to the treatment. This study leveraged carbon stable isotope tracers to estimate the quantitative contributions of various organic sources to membrane fouling in an ultrafiltration system. Effluent organic matter (EfOM) and aquatic natural organic matter (NOM), two common sources, were combined in five different proportions to evaluate their mixed effects on flux decline and the consequent fouling behaviors. Generally, biopolymer (BP) and low molecular weight neutral (LMWN) size fractions - abundantly present in EfOM - were identified as significant contributors to reversible and irreversible fouling, respectively. Fluorescence spectroscopy disclosed that a protein-like component notably influenced overall membrane fouling, whereas humic-like components were predominantly responsible for irreversible fouling rather than reversible fouling. Fluorescence index (FI) and biological index (BIX), common fluorescence source tracers, showed promise in determining the source contribution for reversible foulants. However, these optical indices were insufficient in accurately determining individual source contributions to irreversible fouling, resulting in inconsistencies with the observed hydraulic analysis. Conversely, applying a carbon stable isotope-based mixing model yielded reasonable estimates for all membrane fouling. The contribution of EfOM surpassed 60 % for reversible fouling and increased with its content in DOM source mixtures. In contrast, aquatic NOM dominated irreversible fouling, contributing over 85 %, regardless of the source mixing ratios. This study emphasizes the potential of stable isotope techniques in accurately estimating the contributions of different organic matter sources to both reversible and irreversible membrane fouling.

Identifying the external N and Hg inputs to the estuary ecosystem based on the triple isotopic information (δ15NNO3, Δ17ONO3 and δ18ONO3).

The supply and sources of N and Hg in the Geum estuary of the western coast of Korea were evaluated. Triple isotope proxies (δ15NNO3, Δ17ONO3 and δ18ONO3) of NO3- combined with conservative mixing between river and ocean waters were used to improve isotope finger-printing methods. The N pool in the Geum estuary was primarily influenced by the Yellow Sea water, followed by riverine discharge (821 × 106 mol yr-1) and atmospheric deposition (51 × 106 mol yr-1). The influence of the river was found to be greater for Hg than that of the atmosphere. The triple isotope proxies revealed that the riverine and atmospheric inputs of N have been affected by septic wastes and fossil fuel burning, respectively. From the inner estuary towards offshore region, the influence of the river diminishes, thus increasing the relative impact of the atmosphere. Moreover, the isotope proxies showed a significant influence of N assimilation in February and nitrification in May.