The Relationship between Rainfall Pattern and Epilithic Diatoms in Four Streams of Central-Western Korea for Three Years (2013-2015).

To study the effect of rainfall patterns on diatom communities in four major central western streams on the Korean Peninsula during the monsoon seasons of 2013 through 2015, we measured precipitation, environmental factors, and epilithic diatoms at 42 sites before (May) and after (August and September) each monsoon. The Mangyeonggang river and Sapgyocheon stream (SS) had a high percentage of low-permeability soil, and the stream had the highest proportion (49.1%) of surrounding land in urban areas. Precipitation and precipitation frequency was closely correlated with electrical conductivity and nutrients, and this was particularly evident in SS. Epilithic diatom abundance for the most abundant species as, Navicula minima, decreased in the stream in 2013 and 2014 and increased in 2015 when precipitation and precipitation frequency were low. This was not clearly distinguishable in the ecological characteristics of each watercourse's indicator species, except in SS. The dynamic community index was highest in 2015 (ca. 5.50), and the annual changes in the index were clearly shown in SS. The precipitation pattern and the dynamic community index were negatively correlated (r = -0.026~-0.385), and the precipitation within 2 weeks (r = -0.480 for SS) before the second sampling and the frequency of 10 mm of precipitation were closely correlated in the stream (r = -0.450 for SS). The distribution of epilithic diatoms in the four watercourses is therefore affected by monsoon precipitation and precipitation frequency, and the dynamic community index is determined by soil characteristics and land use.

Linker Unit Modulation of Polymer Acceptors Enables Highly Efficient Air-Processed All-Polymer Solar Cells.

A group of regioregular polymer acceptors is synthesized by polymerizing Y6 moieties with different linker units including thiophene, vinylene, 2,2'-bithiophene, and thieno[3,2-b]thiophene, and their optoelectrical properties and photovoltaic performances are studied systematically. It is found that the linker units have significant impacts on the backbone planarity, conjugation, and hence optoelectrical properties of polymer acceptors. The vinylene-based PYF-V-o polymer shows a smaller dihedral angle between the end groups and vinylene units and a more rigid polymer backbone, thus affording bathochromic absorption and better electron-transporting capacity. As a result, the PM6:PYF-V-o based all-polymer solar cells (all-PSCs) are able to achieve the highest power conversion efficiency of 16.4% with an unprecedented small voltage loss of 0.49 V. Moreover, the PM6:PYF-V-o blend exhibits good resistance to environmental stressors and the air-processed PM6:PYF-V-o cells can still maintain a high efficiency of 16.1%, which is the best air-processed all-PSC efficiency reported to date. This study provides the structural-property guidance that can be used to facilitate the development of polymer acceptors for all-PSCs.

A Vinylene-Linker-Based Polymer Acceptor Featuring a Coplanar and Rigid Molecular Conformation Enables High-Performance All-Polymer Solar Cells with Over 17% Efficiency.

State-of-art Y-series polymer acceptors are typically based on a mono-thiophene linker, which can cause some twisted molecular conformations and thus limit the performance of all-polymer solar cells (all-PSCs). Here, a high-performance polymer acceptor based on vinylene linkers is reported, which leads to surprising changes in the polymers' molecular conformations, optoelectronic properties, and enhanced photovoltaic performance. It is found that the polymer acceptors based on thiophene or bithiophene linkers (PY-T-γ and PY-2T-γ) display significant molecular twisting between end-groups and linker units, while the vinylene-based polymer (PY-V-γ) exhibits a more coplanar and rigid molecular conformation. As a result, PY-V-γ demonstrates a better conjugation and tighter interchain stacking, which results in higher mobility and a reduced energetic disorder. Furthermore, detailed morphology investigations reveal that the PY-V-γ-based blend exhibits high domain purity and thus a better fill factor in its all-PSCs. With these, a higher efficiency of 17.1% is achieved in PY-V-γ-based all-PSCs, which is the highest efficiency reported for binary all-PSCs to date. This work demonstrates that the vinylene-linker is a superior unit to build polymer acceptors with more coplanar and rigid chain conformation, which is beneficial for polymer aggregation and efficient all-PSCs.

Prediction of Geosmin at Different Depths of Lake Using Machine Learning Techniques.

Geosmin is a major concern in the management of water sources worldwide. Thus, we predicted concentration categories of geosmin at three different depths of lakes (i.e., surface, middle, and bottom), and analyzed relationships between geosmin concentration and factors such as phytoplankton abundance and environmental variables. Data were collected monthly from three major lakes (Uiam, Cheongpyeong, and Paldang lakes) in Korea from May 2014 to December 2015. Before predicting geosmin concentration, we categorized it into four groups based on the boxplot method, and multivariate adaptive regression splines, classification and regression trees, and random forest (RF) were applied to identify the most appropriate modelling to predict geosmin concentration. Overall, using environmental variables was more accurate than using phytoplankton abundance to predict the four categories of geosmin concentration based on AUC and accuracy in all three models as well as each layer. The RF model had the highest predictive power among the three SDMs. When predicting geosmin in the three water layers, the relative importance of environmental variables and phytoplankton abundance in the sensitivity analysis was different for each layer. Water temperature and abundance of Cyanophyceae were the most important factors for predicting geosmin concentration categories in the surface layer, whereas total abundance of phytoplankton exhibited relatively higher importance in the bottom layer.

Benthic Diatom Communities in Korean Estuaries: Species Appearances in Relation to Environmental Variables.

In the Korean Peninsula's southern estuaries, the distributive characteristics of epilithic diatoms and the important environmental factors predicting species occurrence were examined. The collection of diatoms and measurements of water quality and land-use were performed every May between 2009 and 2016, with no influence from the Asian monsoon and snow. Throughout the study, 564 diatoms were classified with first and second dominant species of Nitzschia inconspicua and N. perminuta. Based on diatom appearance and standing crops, the 512 sampling stations were divided into four groups by cluster analysis, and two regions, namely the West and East Sea. Geographically, G1, G2, G3, and G4 were located in the East Sea, Southeast Sea, West Sea, and Southwest Sea, respectively. Canonical correspondence analysis (CCA) results indicated that environmental factors, such as turbidity, electric conductivity (EC), and total phosphorus (TP), significantly influenced the distribution of epilithic diatoms. A random forest model showed that major environmental factors influencing the diatom species appearance included EC, salinity, turbidity, and total nitrogen. This study demonstrated that the spatial distribution of epilithic diatoms in the southern estuaries of the Korean Peninsula was determined by several factors, including a geographically higher tidal current-driven turbidity increase and higher industrial or anthropogenic nutrient-loading.

Dialectal and gender differences in nasalance for a Mandarin population.

The purpose of this study was to determine whether there are dialectal and gender related differences in nasalance of main Mandarin vowels and three sentences in 400 Chinese normal adults. The mean nasalance score difference for dialect and gender was significant (p < .001) in all speech materials. For different dialects, the average nasalance scores show that Chongqing > Beijing > Shanghai > Guangzhou for the nasal sentence, oro-nasal sentence, /a/, /i/ and /u/. In addition, the average nasalance scores of females were higher than those of males for all speech materials in all dialects. The clinical significance of this study can be helpful in making nasalance clinical decisions for Chinese people with cleft palate, hearing disorders and dysarthria with resonance disorders. It also shows the theoretical and socio-cultural features for linguists considering dialects and gender.

Water quality improvement by natural plant-mineral composites and field temperatures of a eutrophic lake in South Korea.

To improve the water quality of Shingal Reservoir, a eutrophic lake in South Korea, field tests were performed to assess the influence of water temperature on water quality improvement (WQI) ability of domestic plant-mineral composites (PMCs). Interestingly, Cyanobacterium was found to be dominant even in low-temperature seasons, especially winter leading to more effective for diatom growth. Factors such as phytoplankton, biological oxygen demand (BOD) and phosphorous showed high WQI over 70% at 20 degrees C, but declined to 40% at temperatures above 25 degrees C. WQI for Cyanobacteria decreased with increasing water temperature, whereas for diatoms WQI was 90% regardless of water temperature. Additionally, bacterial density and total nitrogen showed very low WQI without water temperature. Collectively, the results indicate that high water temperature decreased WQI ability of a PMC to control phytoplankton (Microcystis aeruginosa) and increased their ability to control diatoms.

Separation of the tip of a coblation wand within the knee joint: a complication of arthroscopic adhesiolysis.

Coblation devices are now widely used in arthroscopic surgery and they show a very low incidence of intraoperative complications. We experienced a case where the tip of the wand separated and migrated into the posterior knee compartment in an arthrofibrotic knee. The free wand tip was identified and then extricated from the popliteal hiatus of the knee with using C-arm fluoroscopic control. To the best of our knowledge, this is the first report of its kind involving coblation wands. We describe this complication to show that the use of coblation devices can lead to unexpected problems and it is imperative to inspect all instruments before and after each surgical use.