Drop Of Suspension Research Articles

Success and failure of the spreading law for large drops of dense granular suspensions

The spreading of large viscous drops of density-matched suspensions of non-Brownian spheres on a smooth solid surface is investigated experimentally at the global drop scale. The focus is on dense suspensions with a solid volume fraction equal to or greater than $40\,\%$ , and for drops larger than the capillary length, i.e. for which the spreading is governed by the balance of gravitational and viscous forces. Our findings indicate that all liquids exhibit a power-law behaviour typical of gravity-driven dynamics, albeit with an effective suspension viscosity that is smaller than the bulk value. When the height of the drop is of the order of the particle size, the power law breaks down as the particles freeze while the contact line continues to advance.

First Report of Chili Anthracnose Caused by Colletotrichum sojae in South Korea.

Chili (Capsicum annuum L.) is an economically important crop worldwide, valued for its culinary uses. In South Korea, anthracnose caused by Colletotrichum spp. including C. truncatum, C. gloeosporioides, C. coccodes, C. acutatum, and C. scovillei incurs on substantial economic loss (Kim et al. 2008; Oo and Oh 2020). In August 2022, somewhat different types of symptoms that was not typical on chilli fruits were observed in a field in Yereonggwang (GPS: 35.2579° N, 126.4742° E), South Korea. The disease symptoms appeared as sunken, necrotic lesions with dense black spore masses forming in concentric rings. The estimated disease incidence the 0.2 ha field showing up to 1% of fruits affected. To isolate the pathogen, six symptomatic chilli fruits were collected. Small pieces (5 mm²) were cut from the margins of the lesions, surface-sterilized in 70% ethanol for 30 sec, followed by 1% sodium hypochlorite for 1 minute, and then rinsed three times in sterile distilled water. The tissue pieces were placed on potato dextrose agar (PDA) plates and incubated at 25°C in the dark. After 3 to 5 days, emerging fungal colonies were sub-cultured to obtain pure isolates. A total of five isolates were obtained and initially identified as Colletotrichum spp. based on morphological characteristics. Seven-day old colonies were initially white, turning light orange with age on PDA. Setae (observed on lesion) were dark brown, verruculose and septate. Conidia were cylindrical, hyaline, and measured 14.8 to 19.9 × 4.2 to 6.5 µm (mean 16.7 × 5.6 μm, n = 70) in size; appressoria were brown to dark brown and irregularly shaped. These morphological characteristics of the isolates agree with those reported for the morphology of C. sojae by Damm et al. (2019). To confirm the identity of the isolates, DNA was extracted and specific gene regions were amplified and sequenced using the following primer sets: ITS (ITS1 and ITS4), GAPDH (GDF1 and GDR1), ACT (ACT-512F and ACT-783R), TUB (T1 and Bt2b), HIS3 (CYLH3F and CYLH3R), and CHS-1 (CHS-79F and CHS-345R). The resulting sequences were deposited in the NCBI GenBank with accession numbers (LC830742 to LC830766). Maximum likelihood phylogenetic analysis using combine sequences of ITS, GAPDH, ACT, TUB, HIS3 and CHS-1 in MEGA X confirmed the isolates as C. sojae, marking the first report of this pathogen on chilli in South Korea, previously known to infect soybean. Pathogenicity tests were conducted on wound and nonwounded healthy and mature-green chili fruits (cv. Bicksita) to confirm the pathogenicity of the isolated C. sojae. The fruits were surface-sterilized using 70% ethanol and then rinsed with sterile distilled water. The fruits were wounded using a sterile needle to facilitate infection. A conidial suspension (1x106 conidia/mL) was prepared from 7-day-old PDA cultures. Each fruit was inoculated by placing a 10 µL drop of the conidial suspension onto the wounded and nonwounded sites (4 to 5) of the wound and unwound fruits, respectively. Control fruits were inoculated with sterile water. A total of 40 fruits per treatment were used and the experiment repeated twice. The fruits were placed in plastic box lined with moist paper towels to maintain high humidity and incubated at 25°C. Anthracnose symptoms developed on the inoculated fruits within 7 days, while control and unwounded fruits remained symptom-free. Colletotrichum sojae was successfully reisolated from the symptomatic fruits, fulfilling Koch's postulates and confirming its role as the causal agent of the disease. Colletotrichum sojae is known to infect Fabaceae species worldwide such as Glycine max, Medicago sativa, Phaseolus vulgaris, Atractylodes ovata and Vigna unguiculata (Damm et al. 2019; Talhinhas and Baroncelli 2021), Atractylodes ovata in South Korea (Hassan et al. 2021) and chili pepper in China (Zhanget al. 2023). The first report of C. sojae causing chili anthracnose in South Korea represents a new challenge for chili growers. Integrated disease management strategies need to be developed and implemented to mitigate its impact.

Effect of coal suspension concentration and gas-air medium temperature on liquid droplets collisions

Relevance. Understanding the mechanisms of liquid droplets interaction with each other is important for many industrial and technical applications related to solving a range of problems like slag removal in a high-temperature environment, obtaining components of the desired fraction in the food industry, etc. Aim. Establishment of the main patterns of suspension droplets interaction in a gas-air environment with temperature variation. Methods. Using shadow high-speed video recording, the main patterns of the binary collision of suspensions droplets were determined. The paper introduces the results of experimental studies of the characteristics of collisions of droplets of coal-water suspensions in a gas-air environment with a temperature of 90–120°C. Parameters of the generated droplets: radius 1.0–2.2 mm, velocity 0.5–2.0 m/s. Results and conclusions. The authors have determined the modes of collision of droplets of suspensions (coagulation and separation) and the main characteristics of secondary fragments and constructed the maps of the modes of interaction of drops of suspensions with each other when varying the concentration of solid particles in the suspension, the temperature of the gas-air environment and the time the target drop spent in a gas-air environment with an elevated temperature. The conditions were established for the coagulation of droplets, as well as their intensive secondary grinding to intensify their drying, ignition and combustion in boiler furnaces. It was established that an increase in the temperature of the gas-air environment leads to a significant change in the size and properties of droplets, as well as to the occurrence of oscillatory phenomena in the system. It is substantiated that collision of droplets of suspensions in a gas-air environment with elevated temperature is complex and multi-parametric. Its characteristics depend on a combination of factors (surface tension and liquid viscosity, size and shape of droplets, speed of their movement, density and viscosity of gas-air environment). The authors obtained mathematical expressions to describe the boundaries of the modes of the studied processes and schemes for using the results obtained in order to increase the efficiency of the corresponding technological processes.

First Report of Alternaria alternata Causing Postharvest Fruit Rot of Indian Jujube (Ziziphus mauritiana) in China.

Ziziphus mauritiana Lam., commonly known as Indian jujube or ber, is a popular fruit crops grown in tropical and sub-tropical regions of China. It is commonly stored at 4℃, relative humidity of about 90%, combined with waxing or sealing with film bag. In January 2023, a postharvest fruit rot was observed on Indian jujube in three markets located in Nanchang city of Jiangxi province, China, with a disease incidence of 4 to 10%. Initially, brown spots appeared on the surface or base of thefruit, which gradually expanded into irregular brown lesions. Gray-white hyphae developed in the center of the lesions, and ultimately thefruitrotted. To isolate the pathogen, small pieces (5 × 5 mm) of ten infected fruits were surface-sterilized in 75% ethanol for 15 s and then 1% sodium hypochlorite for 30 s, rinsed three times in sterile water, plated onto potato dextrose agar (PDA), and incubated at 25°C for 3 days. Eight strains with similar morphological characteristics were isolated, and one representative isolate (JXAA-1) was used for morphological and molecular characterization. The colonies on PDA were initially olive green with white margins, and later turned dark olive or black with profuse sporulation. Conidia were borne singly or in a chain, brown, with 1 to 5 transverse septa and 0 to 3 longitudinal septa, obclavate to obpyriform, and measured 12.9 to 33.7 × 7.5 to 12.9 μm (n = 30). On the basis of morphological characteristics, the isolates were tentatively identified as Alternaria spp. (Simmons 2007). To confirm the identification, genomic DNA was extracted from the isolate JXAA-1 with the Fungi Genomic DNA Extraction Kit (Solarbio Biotech, China). The 18S nrDNA (SSU), 28S nrDNA (LSU), internal transcribed spacer of the rDNA (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), elongation factor 1-alpha (TEF1), Alternaria major allergen gene (Alt a 1), endopolygalacturonase (EndoPG) and an anonymous gene regions (OPA 10-2) were amplified and sequenced using primers NS1/NS4, LR7/LR0R, ITS5/ITS4, gpd1/gpd2, EF1-728F/EF1-986R, Alt-for/Alt-rev, PG3/PG2b, OPA10-2L/OPA10-2R, respectively (Woudenberg et al. 2015). The obtained DNA sequences (SSU: PP190241; LSU: PP190242; ITS: PP189927; GAPDH: PP196557; TEF1: PP196558; Alt a 1: PP196559; EndoPG: PP196560; and OPA 10-2: PP196561) showed 100% homology with those of A. alternata (GenBank accession nos. MT000349 [1020/1020 bp]; KP940477 [1312/1312 bp]; MK972909 [583/583 bp]; MN615421 [593/593 bp]; MN046379 [280/280 bp]; MN304714 [490/490 bp]; MN698284 [458/458 bp] and MH975214 [701/701 bp]). A maximum likelihood phylogenetic tree was constructed by combining all sequenced loci in IQTREE web servers. The isolate JXAA-1 clustered with Alternaria alternata (CBS 121336). The fungus associated with postharvest fruit rot on Z. mauritiana was thus identified as A. alternata. To evaluate the pathogenicity, six surface sterilized fruits were wounded by a sterile scalpel and inoculated with a 10 μl drop of spore suspension (1 × 105 conidia/ml) of isolate JXAA-1. Another six fruits were inoculated with sterilized ddH2O as control and the experiment was repeated three times. All fruits were incubated at 25°C and 80% relative humidity. After 5 days, all the wounded fruit inoculated with A. alternata showed similar symptoms to those observed previously, while the control fruits remained healthy. A. alternata was consistently reisolated from infected fruit and confirmed by morphological and molecular data, fulfilling Koch's postulates. A.alternata has previously been reported causing leaf spot and fruit rot on Chinese jujube (Ziziphus jujuba) in China (Bai et al. 2015; Li et al. 2021). But to our knowledge, this is the first report of A. alternata causing postharvest fruit rot on Indian jujube (Z. mauritiana) in China. Therefore, managers should pay more attention to postharvest fruit rot of jujube caused by A. alternata, the foam bag is put on after the membrane bag is sealed, the broken or infected fruit is picked out in time to reduce the spread of pathogenic fungus.

First report of Colletotrichum siamense causing anthracnose in Oenocarpus bacaba in Brazil.

Bacaba (Oenocarpus bacaba Mart.) is a native palm tree from Brazilian Amazon and Cerrado biomes. This tree produces a small, rounded fruit with dark skin and approximately 1.5 mm thick pulp, extensively utilized for palm heart extraction, juices, and jellies (De Cól et al. 2021). However, several diseases can adversely impact fruit yield and quality. During the 2021 growing season, anthracnose symptoms were observed in Bacaba fruits, with a disease incidence of 58% in fruits collected from the Abreulândia (9°37'15″ S, 49°9'3″ W) and Gurupi (12°25'46" S; 49°16'42" W) municipalities in Tocantins state, Brazil. A total of 198 fruits exhibiting anthracnose symptoms, characterized by deep necrotic spots, were collected. In the laboratory, symptomatic fruits had their external surfaces sterilized for 30 seconds in 70% ethanol, 1 min in 1.5% NaOCl, and then rinsed with sterile distilled water. Sterilized pieces of the fruit tissue were transferred to PDA medium and incubated for 7 days at 28 ºC with a 12 h photoperiod. After this period, two isolates were obtained from the colonies and were identified both macroscopically and microscopically as Colletotrichum sp. The colonies grown at PDA showed a white to grey cottony mycelia, with straight and fusiform conidia, ranging from 14.0 to 21.0 (mean value of 15.8 ± 1.8) µm in length and 4.0 to 7.0 (mean value of 5.5 ± 0.7) µm in width, (n = 50). For species identification, the intergenic spacer between DNA lyase, mating-type locus MAT1-2-1 (APN2/MAT-IGS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), glutamine synthetase (GS), and β-tubulin (TUB) loci were amplified and sequenced. Resulting sequences were deposited in GenBank (OR333843, OR333844, OR333845 and OR333846). BLAST analysis of the partial APN2/MAT-IGS (99%), GAPDH (99,48%), GS (99,32%) and TUB (99,48%) sequences showed highly similarity to C. siamense isolates (IIFT223 and CBS130147). Maximum likelihood multilocus analysis placed the isolate UFTC16 within the C. siamense clade with 98% bootstrap support, clearly assigning the isolate to this species. Morphological features were consistent with the description of C. siamense (Prihastuti et al., 2009). Inoculation of Bacaba fruits and seedlings was conducted to confirm pathogenicity. The surface of uninjured Bacaba fruits was inoculated with two drops (20 μL) of conidial suspension (106 conidia mL-1). The same methodology was adopted to placed healthy leaves of 35-day-old seedlings grown in plastic tubes. Two drops of sterile distilled water were inoculated on nonwounded healthy fruits and seedlings as a negative control. The fruits and seedlings were incubated for five days in a controlled chamber at 28 °C, 70-80% humidity and a "12-h photoperiod". The experiment was conducted with five replicates (five fruits and five seedlings inoculated per isolate) and repeated once. Typical symptoms of anthracnose were observed in the fruits and leaves of Bacaba seedlings five days after inoculation. No symptoms were observed in the negative control. The pathogen was reisolated from symptomatic fruits and leaves, showing similar morphological characteristics as the original isolate, fulfilling Koch's postulates. The identification of C. siamense as the causal agent of Bacaba anthracnose helps in the diagnosis and disease control strategies of the disease. Colletotrichum siamense is a cosmopolitan species and easily found in cultivated and non-cultivated species (Batista et al. 2023). However, to the best of our knowledge, this is the first report of C. siamense causing anthracnose on Bacaba.

First Report of Leaf Blight Caused by Botryosphaeria dothidea on Aucuba japonica in Zhejiang Province, China.

Aucuba japonica var. variegata Dombrain is a common evergreen cultivated ornamental in China (Li et al. 2016). In December 2022, severe leaf blight on A. japonica was observed next to the Meishiyuan of Zhejiang Normal University (29°8'4″N, 119°37'54″E) in Jinhua City, Zhejiang Province, China. There were seven plants in the surveyed area, and over 50% of leaves were affected. The early symptoms were small gray spot parts with brown borders on the tip of the leaves. Then the grey parts gradually expanded and became brownish black. In severe cases, the whole leaves became black and blighted. To identify the pathogen, 5 symptomatic leaves were randomly collected from 5 plants and cut into small pieces (5 mm × 5 mm), surface disinfected in 1% sodium hypochlorite solution for 3 min, followed by 75% alcohol for 30 s, then rinsed in sterile distilled water thrice. Tissues were cultured on potato dextrose agar (PDA) and incubated at 28°C for 7 days. Pure cultures were obtained by the single-spore method. Thirteen strains were isolates from the tissues, and nine of them showed similar morphological characteristics. Colonies were white initially, then became gray. The undersides of the colonies became black gradually. Hyaline, fusiform conidia (n = 30) were 17.1 to 24.76 µm (average 20.39 ± 1.906 µm) in length and 5.4 to 6.61 µm (average 6.19 ± 0.434 µm) in width. The DNA of nine isolates were extracted by Ezup Column Bacteria Genomic DNA Purification Kit, and their sequences were identical, so they were named QM1. The internal transcribed spacer (ITS) region, translation elongation factor 1-α (TEF1), and β-tubulin (TUB2) genes were amplified with primer pairs ITS1/ITS4, TEF1-728F/TEF1-986R and βt2a/βt2b (Slippers et al. 2004), respectively. The BLAST analysis indicated that ITS (OR215464), TEF1 (OR243689), and TUB2 (OR243688) of the isolate QM1 were 99 to 100% identical to those of Botryosphaeria dothidea (GenBank accession nos. MH329646 for ITS sequences; OL891702 for TEF1 sequences; MK511445 for TUB2 sequences). In addition, the phylogenetic tree based on sequences from ITS, TEF1 and TUB2 was constructed with MEGA 11 by use of the maximum likelihood method with 1,000 bootstrapping iterations. Based on the multi-locus phylogeny and morphological features, the isolate QM1 was identified as B. dothidea. To test the Koch's postulates, ten leaves from three healthy two- to three-year-old A. japonica plants were surface disinfested with 75% ethanol for 30 s, rinsed with ddH2O three times. The leaves were wounded with a sterile needle and inoculated with 2ml drop of the isolate QM1 conidial suspension (106 spores/mL), with sterile distilled water as a control. All plants were placed in a greenhouse at 28°C, >70% relative humidity and 12 h light/day. The experiment was repeated three times. After 7 days, leaves of the inoculated group showed symptoms similar to those observed on the naturally infected leaves, while leaves of the control group remained asymptomatic. The pathogen was reisolated from inoculated leaves and was confirmed as B. dothidea based on morphological and molecular analyses. It has been reported B. dothidea cause leaf disease in a wide range of hosts in China, such as Camellia oleifera (Hao et al. 2023), Kadsura coccinea (Su et al. 2021). To our knowledge, this is the first report of Botryosphaeria dothidea causing leaf blight on Aucuba japonica in Zhejiang Province of China. B. dothidea are usually secondary invaders and are known to cause diseases in stressed plants. The results further expand the host-range of B. dothidea, and would help to establish control strategy against the disease.

Shape deformation, disintegration, and coalescence of suspension drops: Efficient simulation enabled by graph neural networks

Understanding the behaviors of suspension drops (particle swarms) as they settle in a viscous fluid holds significant importance across various applications. Due to hydrodynamic interactions (HIs), suspension drops would undergo a series of intricate behaviors, including shape deformation, disintegration, and coalescence. This work presents the hydrodynamic interaction graph neural network (HIGNN), developed in our prior work (Ma et al., 2022), as an efficient and accurate modeling framework for simulating the dynamics of suspension drops and investigating the various behaviors they exhibit. The HIGNN effectively incorporates the many-body nature of HIs, a feature lacking in most previous simulations that employ the Stokeslet assumption. In the meanwhile, the HIGNN achieves superior computational efficiency compared to traditional, high-fidelity numerical tools such as Stokesian dynamics and PDE solvers. Moreover, the HIGNN, once trained, is applicable to predicting suspension drops across a range of particle concentrations and under diverse forces (such as gravity and Coulombic interactions). Training the HIGNN only requires the data containing a small number of particles, leading to low training cost. Our results demonstrate that the HIGNN can effectively reproduce the various behaviors of suspension drops that were previously reported in literature. More specifically, a single, initially spherical drop slowly evolves into a torus-shaped drop, as particles escape from its rear and form a tail along the sedimenting direction. Subsequently, the torus breaks into secondary droplets, each undergoing a similar transition (deformation into a torus followed by disintegration), thereby leading to a repeating cascade. Further, we quantitatively analyze the correlation between the drop’s sedimentation velocity and volume fraction. We also propose new scaling laws for evaluating both the leakage rate of particles and the expansion rate of the horizontal radius of a suspension drop. For single suspension drops, we also systematically investigate how their dynamics is affected by their initial shapes and the formed tori’s aspect ratios, as well as with or without Coulombic interactions between particles. For a pair of suspension drops, we study the process of coalescence of two vertically aligned particles and examine the effect of introducing a horizontal offset on the subsequent breakup of the coalesced drop. All simulations were executed on a single GPU, with the computation of velocities for several thousand particles requiring less than five seconds per time step. This computational efficiency enables fast and resource-saving simulations of large suspension drops over extended time scales.

Occurence of leaf spot on Narrow-head ragwort (Ligularia stenocephala) caused by Alternaria cinerariae in Korea.

Narrow-head ragwort (Ligularia stenocephala (Maxim.) Matsum. & Koidz.) has been used for medicinal purposes and a leafy vegetable in South Korea (Choi et al., 2007; Debnath et al., 2017). In May 2022, brown spots and blight were observed on the leaves in a farmer's field in Namwon (35°26'58.9"N, 127°28'55.9"E), Korea. About 80% of the plants in a 3000 m2 cultivation area were infected. To isolate the causal agent, small pieces (1 mm2) surface-sterilized (1% NaOCl for 1 min) symptomatic leaf tissues were put onto a water agar (WA) plate and incubated in the dark at 25℃. After five days of incubation, two isolates (FD00021, FD00022) were obtained from diseased leaves using a single spore isolation technique. Morphological characteristics were examined after seven days of incubation at 25℃ in the dark. Colonies were 51.6 to 65.3 mm in diameter, gray-green in the center, and ivory at the edge. Conidiophores were straight or curved and 10 - 34 × 4 - 5 μm. Conidia were solitary or two to four in a chain, long ellipsoid to obclavate, one to thirteen transverse septa, 52 - 169 ×14 - 34 μm, blunt-tapered beak variable in size 4 - 56 × 3 - 10 μm (n=75). The morphological and cultural characteristics of the isolates were consistent with that of Alternaria cinerariae (Nishikawa and Nakashima, 2015; Simmons, 2007). For molecular identification, genomic DNA was extracted from 5-day-old cultures using the Maxwell® RSC PureFood GMO and Authentication Kit (Promega). Five gene regions, including rDNA ITS, GPD, Alt a, RPB2, and EF1-α were amplified and sequenced using ITS1/ITS4, gpd1/gpd2, Alt-a1-for/ Alt-a1-rev, RPB2-5F2/RPB2-7cR, and EF1-728F/EF1-986R primer sets respectively (Wang et al., 2022; Garibaldi et al., 2022). The resulting sequences were deposited in GenBank with accession no. OP785152, OP785153 and OP832000 to OP832007). The concatenated genes (rDNA ITS, GPD, Alt a, RPB2, and EF1-α) sequence identity of the FD00021 and FD00022 against the reference strain A. cinerariae CBS 116495 is 99.92% (2572/2574) and 99.84% (2570/2574), respectively. Maximum Likelihood tree was inferred based on the concatenated sequences of the five gene regions using the Kimura 2-parameter model with 1,000 bootstrap replications. The phylogenetic tree showed that the present strains and A. cinerariae CBS 116495 fell into the same clade with high bootstrap support (100%). Based on morphological characteristics and molecular analysis, the isolates were identified as A. cinerariae. To confirm their pathogenicity, drops (70 μl) of conidial suspension (1×104 spores/ml) were applied on intact healthy leaves (3 leaves/plant) of plants (3 plants/isolate) that had been cultivated for one month after transplantation as seedlings. Controls were treated with sterile distilled water. The treated plants were covered with plastic boxes to maintain humidity around 90% and were maintained in an incubator at 25℃ in a 12-hour light-dark cycle. Symptoms appeared only on inoculated leaves after four days of inoculation, while controls remained asymptomatic. The A. cinerariae isolates were re-isolated from infected tissue of the inoculated leaves, thus fulfilling Koch's postulates. Alternaria cinerariae is an important plant pathogen that can cause leaf spot and blight on a variety of host plants including Cineraria spp. and Tussilago farfara (He et al. 2020). This is the first report on leaf spot on Narrow-head ragwort caused by A. cinerariae in the world. Leaf spot disease caused by Alternaria cinerariae is a significant threat to narrow-head ragwort agriculture in South Korea. Therefore, its control strategies are necessary for increasing productivity.

Accessing the free expansion of a crystalline colloidal drop by optical experiments.

We study poly-crystalline spherical drops of an aqueous suspension of highly charged colloidal spheres exposed to a colloid-free aqueous environment. Crystal contours were obtained from standard optical imaging. The crystal spheres first expand to nearly four times their initial volume before slowly shrinking due to dilution-induced melting. Exploiting coherent multiple-scattering by (110) Bragg reflecting crystals, time-dependent density profiles were recorded within the drop interior. These show a continuously flattening radial density gradient and a decreasing central density. Expansion curves and density profiles are qualitatively consistent with theoretical expectations based on dynamical density functional theory for the expansion of a spherical crystallite made of charged Brownian spheres. We anticipate that our study opens novel experimental access to density determination in turbid crystals.

Versatile Deposition of Complex Colloidal Assemblies from the Evaporation of Hanging Drops.

Existing strategies designed to produce ordered arrangements of colloidal particles on solid supports are of great interest for their wide range of applications, from colloidal lithography, plasmonic and biomimetic surfaces to tags for anti-counterfeiting, but they all share various degrees of complexity hampering their facile implementation. Here, a drastically simplified methodology is presented to achieve ordered particle deposition, consisting in adding micromolar amounts of cationic surfactant to a colloidal suspension drop and let it evaporate in an upside-down configuration. Confinement at the air/water interface enables particle assembly into monolayers, which are then transferred on the substrate producing highly ordered structures displaying vivid, orientation-dependent structural colors. The method is compatible with many particle types and substrates, while controlling system parameters allows tuning the deposit size and morphology, from monocrystals to polycrystalline disks and "irises", from single-component to crystal alloys with Moiré patterns, demonstrating its practicality for a variety of processes.

Bacterial growth on titanium versus zirconia healing caps. An In vitro study.

Objectives To evaluate and compare bacterial growth on zirconia versus titanium healing caps. Material and methods S. sanguinis (Ss) and F. nucleatum (Fn) were grown on titanium and zirconia healing caps that were fixed to the cover of a 96-well microtiter plate. A drop (10 μL) of bacterial suspension was placed on each healing cap and allowed to dry for 1h at 37°C. After this time, the cover was replaced on the plate such that the caps were completely immersed in fresh liquid medium. Each plate contained only one bacterial strain, with 2 control groups. Bacterial growth was monitored over 18h by following the optical density at 650nm. A one-way ANOVA comparison test was used for statistical analysis. Scanning electron microscope (SEM) images of healing caps of each material were taken after a 48h incubation with Ss or Fn to assess bacterial attachment and with no bacteria as control. Results Ss growth was similar in both types of healing cap with no significant differences between these groups and the control (P=0.990). However, there was significantly less growth of Fn on the zirconia caps than on the titanium samples (P<0.0001) or the control (P<0.0001). SEM imaging revealed obvious differences in the surface characteristics of the titanium and zirconia caps. The number of bacteria attached to the rough apical area was particularly high. Conclusions The use of zirconia healing caps may reduce the growth of some bacterial species compared to that seen on titanium healing caps.

First Report of Leaf Spot Caused by Phyllosticta styracicola on Nageia nagi in China.

Nageia nagi (Thunb.) Kuntze belongs to the family Podocarpaceae with shiny green branches and leaves, which is widely distributed in East Asia and the Southern Hemisphere. The leaves, roots and fruits of N. nagi have been used as herbal medicine to treat rheumatism, arthritis and venereal diseases (Abdillahi et al. 2011). In September 2022, leaf spot symptoms were found on approximately 30% of the leaves of N. nagi trees in a community located at the Economic and Technological Development Zone, Nanchang City, Jiangxi Province, China. Following the initial infection, the leaf lesions extended outwards from the top in a circular pattern, appearing as a dark brick color, and later changed to yellow and became dry, with a darker brown margin surrounding them. Ten symptomatic leaves were randomly selected, and a small piece of leaf tissue (5mm ×5mm) located between the health and infected tissues was cut and surface-desinfected with 70% ethanol for 30 s and 1% sodium hypochlorite (NaClO) for 30 s sequentially. After rinsing three times in sterile distilled water, all the small pieces of leaves were placed on potato dextrose agar (PDA) plates, followed by incubation at 28℃ for 3 days. Ten isolates, cultured on each PDA plate, appeared olive green with a granular surface, and an uneven white edge, and finally turned greenish black. The conidia were hyaline, with ellipsoidal to subglobose shapes and spore sizes of 5.5-8.3 × 7.2-12.0 μm (width × length) (=7.2±0.71 × 9.9±1.3 μm, n=40). These morphological characteristics are consistent with those of Phyllosticta species. To confirm the species, three representative isolates, JFRL 03-768, JFRL 03-769 and JFRL 03-770 were selected for further identification. The internal transcribed spacer (ITS) region, actin (ACT), translation elongation factor 1-alpha (TEF1-a), and glyceradehyde-3-phosphate dehydrogenase (GPD) genes of the three isolates were amplified and sequenced with the primers V9G/ITS4 (Carbone and Kohn 1999), ACT-512F/ACT-783R (Carbone and Kohn 1999), EF-728F/EF-2 (O´Donnell et al. 1998) and Gpd1-LM/Gpd2-LM (Myllys et al. 2002; Guerber et al. 2003), respectively. All sequences had been deposited into GenBank (ITS: OQ195332, OQ195333 and OQ195334; ACT: OQ207621, OQ207622 and OQ207623; TEF1-a: OQ207624, OQ207625 and OQ207626; GPD: OQ207627, OQ207628 and OQ207629). A maximum likelihood phylogenetic tree was constructed using the IQtree V1.5.6 (Ngugen et al. 2015) based on the concatenation of multiple sequences (ITS, ACT, TEF1-a and GPD). In the cluster analysis, the representative isolates (JFRL 03-768, JFRL 03-769 and JFRL 03-770) were positioned within a clade comprising of Phyllosticta styracicola. Subsequently, the pathogenicity of P. styracicola was determined by wound inoculation of healthy 2 year-old N. nagi plants, and this experiment was repeated for three times. Briefly, for each isolates, six disinfected leaves were wounded with a sterile scalpel, and then inoculated with 10-μl drop of the conidial suspension (1 × 106 conidia/ml). Another six disinfected leaves were inoculated with 10-μl drop of sterile water as a control group, and all plants were incubated at 28°C with 80% humidity. After 15 days, a similar spot lesion appeared on the leaves of the experimental group. P. styracicola was successfully re-isolated, and then subjected to morphological identification and molecular sequencing (ITS, ACT, TEF1-a and GPD genes). Whilst, the control leaves showed no symptoms. Previous studies have reported that P. styracicola could result in the development of lesions on Styrax grandiflorus leaves in China (Zhang et al. 2013). To our knowledge, this is the first report that P. styracicola can cause leaf spot on N. nagi in China.

The effects of rhamnolipid on the formation of CH4 hydrate and separation of CH4/N2 via hydrate formation

Rhamnolipid (Rha) is an efficient green surfactant that is able to promote hydrate generation, it can be applied to the hydrate method of separating. However, the effect of rhamnolipid on the separation of methane and nitrogen by the hydrate method is not clear. Therefore, in this paper, we investigated the effect of rhamnolipid on methane hydrate formation and the separation between methane and nitrogen via hydrate method. Firstly, the effects of five concentrations (0 ppm, 200 ppm, 400 ppm, 600 ppm and 800 ppm), temperatures and pressures on methane hydrate formation were studied separately. The rate of methane hydrate formation was positively correlated with experimental pressure. The gas consumption increased rapidly with the rhamnolipid concentration, and then increased slowly to a steady state. The final gas consumption above 200 ppm rhamnolipid concentrations could be increased more than five times compared with pure water conditions. The promotion of methane hydrate production is most pronounced at 274.15 K, mainly depending on the diffusion of gas molecules in solution and the ease of hydrate nucleation. Then, the interfacial tension at different concentrations was measured by the suspension drop method, and the relationship between the interfacial tension and the rate of hydrate formation was studied. Hydrate formation rate shows a multiplicative power function with the interfacial tension. What’s more, the kinetics of hydrate formation and gas separation effect of 3:1 CH4/N2 at 274.15 K and 7 MPa were studied with five concentrations. And 200 ppm was found to be the optimum concentration for separation, the separation factor is 8.25. Finally, the kinetics and thermodynamics of hydrate formation and gas separation effect of 1:1 CH4/N2 at 274.15 K and 9 MPa were also investigated, and the separation factor reached a maximum of 12.7 at 800 ppm, and the methane gas recovery rate also reached the maximum at 40.46%. The results of this study can provide some theoretical guidance for the optimal selection of green surfactants in separation by hydrate method.

A new Panax notoginseng Leaf Spot Caused by Boeremia linicola in Yunnan, China.

Panax notoginseng-also known as Tianqi and Sanqi-is one of the most highly valued medicinal perennial herbs in the world (Wang et al. 2016). In August 2021, leaf spot was observed on P. notoginseng leaves in Lincang sanqi base (23º43´10˝N, 100º7´32˝E, 13.33 hm2). Symptoms expanded from water soaked areas on the leaves to form irregular round or oval leaf spots with transparent or grayish-brown centers containing black granular matter, with an incidence of 10 to 20%. To identify the causal agent, ten symptomatic leaves were randomly selected from ten P. notoginseng plants. Symptomatic leaves were cut into small pieces (5 mm2) with asymptomatic tissue margins, disinfected in 75% ethanol for 30s and in 2% sodium hypochlorite for 3 min, and rinsed three times with sterile distilled water. The tissue portions were placed on potato dextrose agar (PDA) plates incubated at 20℃ with a 12 h light/dark photoperiod. Seven pure isolates were obtained with similar colony morphology, dark gray (top view) or taupe (back view) coloration, with flat and villous surfaces. Pycnidia were globose to subglobose, glabrous or with few mycelial outgrowths, dark brown to black, 22.46 to 155.94 (av. 69.57) µm × 18.20 to 130.5 (av. 57.65) µm (n=50) in size. Conidia were ellipsoidal to cylindrical, thinwalled, smooth, hyaline, aseptate, and measured 1.47 to 6.81 (av. 4.29) µm long and 1.01 to 2.97 (av. 1.98) µm thick (n=100). The isolated strains were preliminarily identified as Boeremia sp. based on the morphological characteristics of colonies and conidia. (Aveskamp et al. 2010; Schaffrath et al. 2021). To confirm pathogen identity, the total genomic DNA of two isolates (LYB-2 and LYB-3) was extracted using the T5 Direct PCR kit. The internal transcribed spacer (ITS), 28S large subunit nrRNA gene (LSU), and β-tubulin (TUB2) gene regions were PCR-amplified using primers ITS1/ITS4, LR0Rf/LR5r, and BT2F/BT4R (Chen et al. 2015), respectively. Sequences have been deposited in GenBank (ON908942-ON908943 for ITS, ON908944-ON908945 for LSU, ON929285-ON929286 for TUB2). BLASTn searches of generated DNA sequences from 2 purified isolates (LYB-2 and LYB-3) against GenBank showed high similarity (>99%) with the sequences of Boeremia linicola. Moreover, a phylogenetic tree was constructed based on the neighbor-joining method in MEGA-X (Kumar et al. 2018) and revealed that the 2 isolates were closest to B. linicola (CBS 116.76). Pathogenicity tests were conducted with the 2 isolates (LYB-2 and LYB-3) as described by Cai et al. (2009) with slight modifications. Each isolate was inoculated with three healthy annual P. notoginseng plants, and each leaf was inoculated with three drops of conidia suspension (106 spores/mL). Three P. notoginseng plants inoculated with sterile water were used as controls. All plants were covered with plastic bags incubated in a greenhouse (20℃, 90%RH, 12 h light/dark photoperiod). Fifteen days post-inoculation, all inoculated leaves showed similar lesions, and the symptoms were identical to those in the field. The pathogen was reisolated from symptomatic leaf spots, and the colony characteristics were identical to the original isolates. Control plants remained healthy, and no fungus was re-isolated. Morphological characteristics, sequence alignment and pathogenicity tests confirmed that B. linicola was the cause of P. notoginseng leaf spot disease. This is the first report of B. linicola causing leaf spot on P. notoginseng in Yunnan, China. The identification of B. linicola as the causal agent of the observed leaf spot on P. notoginseng is critical to the prevention and control of this disease in the future.

First report of leaf spot on pecan (Carya illinoinensis) caused by Stemphylium eturmiunum in China.

Pecan [Carya illinoinensis (Wangenh.) K. Koch] is an important nut tree species, which has been widely planted in Jiangsu and Anhui Provinces of China in recent years (Mo et al. 2018). In May 2022, a new leaf spot disease was observed on both young and old leaves of pecan trees in the Luhe area, Nanjing, Jiangsu Province. Approximately 30% of pecan trees suffered from the disease, which affected the growth of young trees and nut production to cause economic loss. Initially, the leaf spots were grayish black and round. Then, disease spots enlarged and joined together, forming irregular lesions with uneven edges. In the last stage, the leaflets were withered. To isolate the pathogen, three symptomatic leaves were collected from each of three different pecan trees. Leaf sections (3 to 4 mm) were excised from the margin of spots, surface sterilized in 75% alcohol for 30 s, then sterilized in 1.5% NaClO for 90 s. After rinsing three times with sterile distilled water, leaf sections were placed on potato dextrose agar (PDA) medium and incubated at 25 °C in a dark environment for 5 days. Pure cultures were obtained by monosporic isolation. A total of 20 isolates were obtained, and 12 isolates were identified as Stemphylium sp. with the same morphological features and ITS sequences. A representative isolate, named LH3-3, was selected for further study. Colonies on PDA were light yellow with dense mycelium and were brownish yellow on the reverse side. Conidia were 16.3 to 34.4 × 8.1 to 16.3 µm) (n=35), muriform, brown, with transverse and longitudinal septa, lightly deformed at the transverse septa. Ascomata were not observed. The morphological characteristics were consistent with the description of Stemphylium eturmiunum (Simmons 2001). The internal transcribed spacer region (ITS) and portions of genes for calmodulin (cmdA) and glyceraldehyde-3-phosphate dehydrogenase (gpd) were amplified and sequenced with the primers ITS1/ITS4 (White et al. 1990), CALDF1/CALDR2 (Xu et al. 2022) and GPD-F/R (Xie et al. 2019), respectively. Sequences were deposited in GenBank under accessions OP482492 (ITS), OP495734 (cmdA), and OP495735 (gpd). BLAST analysis showed that the sequences had 99.67-100% homology to ITS (525/525 bp) of S. eturmiunum strain ST14 (MH843733), cmdA (694/694 bp) of strain CBS122124 (KU850832), and gpd (299/300 bp) of isolate UMSe0030 (MK336876). MEGA 7.0 was used to construct a phylogenetic analysis based on concatenated sequences of ITS, cmdA, and gpd using the neighbor-joining method. The results showed that LH3-3 clustered on the branch of S. eturmiunum, and the support rate was 100%. A spore suspension in sterile water was made from strain LH3-3 grown on PDA, and adjusted to 1×106 spores/mL with a hemocytometer. To test pathogenicity, 20 µl drops of the spore suspension were placed on the left sides of four healthy detached leaflets of mature pecan trees and leaves of three 3-month-old seedlings. The right side of each leaflet was inoculated with 20 µl drops of sterile distilled water as the control. All inoculated seedlings and detached leaflets were covered with a transparent plastic bag and cultured in a greenhouse at 25 °C, 80% relative humidity, and a 12 h light cycle until symptom appeared. The experiment was repeated three times. After 7 days of inoculation, grayish black lesions appeared on all inoculation sites with the spore suspension but not in the controls. The leaf spot symptoms were similar to those observed in orchards. The same fungus, identified by morphological characteristics and sequencing of ITS, cmdA, and gpd, was re-isolated from the diseased spots of the inoculated leaflets to complete Koch's postulates. S. eturmiunum has been reported to infect garlic (Dumin et al. 2022) and tomato (Prencipee et al. 2021), but this is the first report of S. eturmiunum causing leaf spot of C. illinoinensis. This study provides a basis for further study on the biology, epidemiology, and management of the disease.

Comparison of a Urine Antigen Assay and Multiple Examinations with the Formalin-Ethyl Acetate Concentration Technique for Diagnosis of Opisthorchiasis.

Detection of worm antigen in urine is a sensitive diagnostic method for opisthorchiasis, particularly for light-intensity infections; however, the presence of eggs in feces is essential for validating results from the antigen assay. To address the issue of low sensitivity of fecal examination, we modified the protocol for the formalin-ethyl acetate concentration technique (FECT) and compared it against urine antigen measurements for detection of the parasite Opisthorchis viverrini. First, we optimized the FECT protocol by increasing the number of drops for examinations from the standard two drops to a maximum of eight. We were able to detect additional cases after examination of ≥ 3 drops, and the prevalence of O. viverrini saturated after examination of ≥ 5 drops. We then compared the optimized FECT protocol (examining five drops of suspension) against urine antigen detection for the diagnosis of opisthorchiasis in field-collected samples. The optimized FECT protocol detected O. viverrini eggs in 25 of 82 individuals (30.5%) who had positive urine antigen tests but were fecal egg negative by the standard FECT protocol. The optimized protocol also retrieved O. viverrini eggs in 2 of 80 antigen-negative cases (2.5%). In comparison with the composite reference standard (combined FECT and urine antigen detection), the diagnostic sensitivity of examining two and five drops of FECT and the urine assay was 58.2, 67, and 98.8%, respectively. Our results show that multiple examinations of fecal sediment increase the diagnostic sensitivity of FECT and thus provide further support for the reliability and utility of the antigen assay for diagnosis and screening of opisthorchiasis.

First Report of Colletotrichum tropicale Causing Anthracnose on Pitahaya Fruit in Mexico.

Pitahaya (Hylocereus spp.), also called dragon fruit, is a cultivated cactus that is native to Mexico as well as Central and South America. In October 2021, anthracnose symptoms were observed on fruit of pitahaya (Hylocereus costaricensis) in a commercial orchard located in Culiacán, Sinaloa, Mexico. Lesions on fruit were circular, sunken, dark brown and with halo. To fungal isolation, small pieces from adjacent tissue to lesions of symptomatic fruits were surface disinfested by immersion in a 2% sodium hypochlorite solution for 2 min, rinsed in sterile distilled water, and placed in Petri plates containing potato dextrose agar (PDA). The plates were incubated at 25 ºC for 5 days in darkness. Colletotrichum-like colonies were consistently observed on PDA and five monoconidial isolates were obtained. An isolate was selected as a representative for morphological identification, multilocus phylogenetic analysis, and pathogenicity tests. The isolate was deposited as CCLF186 in the Culture Collection of Phytopathogenic Fungi at the Research Center for Food and Development (Culiacán, Sinaloa). On PDA, initially white colonies turned grey with abundant orange conidia masses at 8 days after incubation at 25 ºC. Conidia were cylindrical, with ends rounded, aseptate, hyaline, and measuring 15.2 to 18.9 × 4.3 to 6.4 μm (n= 100). Appressoria were terminal, subglobose to clavate, of 7.4 to 11.6 × 5.9 to 8.2 µm (n= 30). Setae were not observed. These morphological characters were consistent with those reported for the Colletotrichum gloeosporioides species complex (Weir et al. 2012). To determine the phylogenetic identity of the isolate CCLF186, genomic DNA was extracted following the CTAB method (Doyle and Doyle 1990), and the internal transcribed spacer (ITS) region, the ApMat intergenic region, as well as partial sequences of actin (act) and glyceraldehyde-3-phosphate dehydrogenase (gapdh) genes were amplified and sequenced using the primers pairs ITS5/ITS4 (White et al. 1990), AM-F/AM-R (Silva et al. 2012), GDF/GDR, and ACT-512F/ACT-783R (Weir et al. 2012), respectively. The sequences were deposited in GenBank under accession nos. OP269659 (ITS), OP302778 (gapdh), OP302777 (act), and OP302779 (ApMat). BLASTn searches revealed high identity with sequences of C. tropicale (CBS 124949) for ITS (100%), ApMat (100%), act (100%), and gapdh (100%). A phylogenetic tree based on Bayesian inference and Maximum Likelihood methods, including published ITS, ApMat, act, and gapdh sequence datasets for isolates in the Colletotrichum gloeosporioides species complex was generated. The phylogenetic analysis based on the concatenated sequences clustered the isolate CCLF186 with the C. tropicale reference isolates. Pathogenicity of the isolate CCLF186 was confirmed on 10 healthy pitahaya fruits without wounds. A drop of a conidial suspension (1 × 105 spores/ml) was placed on two locations on each fruit. Ten control fruits were treated with sterilized water. The fruits were kept in a moist plastic chamber at 25°C and 12 h light/dark for 8 days. The pathogenicity test was repeated twice. All inoculated pitahaya fruits exhibited sunken and necrotic lesions 6 days after inoculation, whereas no symptoms were observed on the control fruits. The fungus was consistently re-isolated only from the diseased fruits and found to be morphologically identical to the isolate used for inoculation. Recently, C. tropicale causing anthracnose in dragon fruit (Selenicereus monacanthus) was reported from Philippines (Evallo et al. 2022). Now, this is the first report of C. tropicale causing fruit anthracnose in H. costaricensis in Mexico and worldwide. These findings provide a basis for research about the distribution and effective disease-management strategies.

Fully Printed Low-Voltage Field-Effect Transistor Biosensor Array for One-Drop Detection of Shewanella onedensis MR-1 Bacteria

Fast and simple bacterial detection using an in situ measurement technique is indispensable for medical diagnosis, public hygiene, and environmental monitoring. However, current bacterial detection techniques still require large measurement apparatus with complicated analysis. In this work, we propose the use of a full printing process for the fabrication of field-effect-transistor (FET) biosensors using π-junction gold nanoparticle (AuNP) ink and semiconducting single-wall carbon nanotube (sc-SWCNT) ink, which show a low voltage (<1 V) and high field-effect mobility (70 cm2 V–1 s–1), allowing for highly efficient and accurate bacterial detection from a minimal size of the target analyte droplet. This method provides a fully printed sensing platform for the determination of Shewanella onedensis MR-1 bacteria with a linear range of 10–1000 CFU in one drop of bacterial suspension (0.1 μL) (i.e., 105 to 107 CFU/mL), which is promising for the practical application of low-cost and disposable biosensors, especially in the regions with restricted medical conditions.

Drop coating deposition Raman (DCDR) spectroscopy of biologically important molecules

AbstractDrop coating deposition Raman (DCDR) spectroscopy introduces a simple and easily accessible approach to studying biologically important molecules and their mixtures. The method is based on drying a small drop of solution or suspension of studied molecules deposited on a special hydrophobic surface. The drying process efficiently accumulates the molecules in the ‘coffee‐ring’ or any small pattern from which the Raman spectrum can be measured. In this way, a significant (several orders of magnitude) improvement of the Raman detection sensitivity compared with Raman measurement from solution can be reached. Therefore, a small sample volume (several microliters), as well as a low initial concentration of studied molecules in deposited droplets, are important advantages of the DCDR method over the normal Raman one. Recently, many relevant DCDR applications on biomolecules and related molecules have been reported. The mini‐review covers a brief overview of the DCDR method (principle, short history, suitable hydrophobic surfaces and state‐of‐the‐art). It will be followed by a summary of the studies over the last 15–20 years on different biologically important molecules, including proteins, lipids (in the form of liposomes) and small molecules (e.g., porphyrins, anthrax marker dipicolinic acid and food and environmental contaminants). Finally, the application potential and further perspectives of the DCDR method for biomolecular studies will be discussed.

Surfactant-Tunable Nanoparticle Assembly via a Template-Directed Strategy

Nanoparticle (NP) self-assembly from suspension evaporation has been a topic of interest in recent times to fabricate a solid-state structure with diverse functions. We present a simple and facile evaporation-induced strategy for the formation of NP arrays on a flat substrate utilizing a template-directed sandwich system. The lithographic features assist the assembly of the typical nanoparticles (NPs), including SiO2, QDs@PS FMs, and QDs, on the top into circle, stripe, triangle, or square geometries with a fixed width of 2 μm. Additionally, an anionic surfactant, sodium dodecyl sulfonate (SDS), is incorporated into a negatively charged, hydrophilic SiO2 dispersion to govern the aggregation and self-assembly of NPs, fine tuning the morphologies of the residual structures on the substrate. SDS is attributed to modify the nature of SiO2 NPs to be hydrophobic, increase the hydrophobic attraction, dominating particle-particle and particle-interface interactions, and strengthen the particle-particle repulsive electrostatic force that results in the reduction of SiO2 NPs trapped in the separated colloidal suspension drop. Thus, using the SDS surfactant with the concentration ranging from 0 to 1 wt %, the obtained well-ordered SiO2 NP pattern packing on the substrate varies from six layers to one layer.