Circular Spot Research Articles

On the Effects of Atmospheric Particles Contamination and Humidity on Tin Corrosion

The effects of hygroscopic atmospheric particles are investigated in relation to the corrosion of tin. Surface insulation resistance test boards were directly contaminated both with ambient particles sampled in the field at Milan, Italy, and with pure saline particles generated in the laboratory. An innovative particle deposition device was used to uniformly coat circular spots on to the test board surfaces. Deliquescence and crystallization of the water-soluble compounds were detected by observing the impedance response to varying relative humidity (RH) conditions with a gradual and continuous ramps. The effects of the adsorption/desorption kinetics and of the temperature on the deliquescence and crystallization RH values were also investigated. Leakage current measurements at 5-V dc highlighted the ability of atmospheric particles to promote corrosion and electrochemical migration at RH levels far below condensing conditions (100% RH).

First Report ofStemphylium lycopersiciCausing Leaf Spot onSansevieria trifasciatain Malaysia

Sansevieria trifasciata is widely planted in Malaysia as an indoor or outdoor ornamental plant. In June 2016, several S. trifasciata plants exhibiting symptoms of leaf spots were observed and collected from outdoor planting in Tanah Rata, Cameron Highlands, Pahang, Malaysia. Disease severity and incidence were estimated at 25% and 30% (total of 30 plants), respectively. The lesions began as circular brown spots which gradually enlarged, forming oval to irregular chlorotic lesions with reddish- brown borders on the leaves. As the disease progressed, the center of the lesions became sunken and dry. Symptomatic leaf segments (~1 cm2) were surface sterilized in 10% bleach (1% sodium hypochlorite) for 3 minutes, placed on potato dextrose agar (PDA) and incubated at 28°C for 3 to 5 days with a 12-h photoperiod. Fungal mycelia growing from the edges of the leaf segments were transferred onto PDA prior to obtaining pure cultures using a single spore isolation technique. Two isolates were recovered from the sympto...

Curvularia malina causes a foliar disease on hybrid Bermuda grass in China

Hybrid Bermuda grass (Cynodon dactylon × C. transvaalensis) was observed with an unknown foliar disease during a survey conducted in the golf courses of Hainan Province in southern China (during April 2011 to April 2015). Leaves on affected plants initially had small, dark brown, circular or oblong spots. Frequently, the spots would coalesce into large lesions with dark brownish-black margins. Leaf blight may occur under high disease pressure, resulting in black patches 2–15 cm in diameter on close mown turf such as golf course putting greens and fairways. Symptomatic leaf samples were collected from infected plants and cultured on potato dextrose agar. A sterile, filamentous fungus was isolated in pure culture. On the basis of colony morphology and combined sequences of the internal transcribed spacer regions and intervening 5.8S nrDNA (ITS), partial glyceraldehyde-3-phosphate dehydrogenase gene (GAPDH) and partial translation elongation factor 1-alpha gene (TEF-1α), the fungus was identified as Curvularia malina. Pathogenicity testing showed C. malina isolates were pathogenic to healthy hybrid Bermuda grass and Koch’s postulates were fulfilled by re-isolating the pathogen.

First Report of Citrus Black Spot Caused by Phyllosticta citricarpa in Angola

Citrus is an important subsistence crop in Angola, consumed mainly as fresh fruit. In April 2014, fruit symptoms reminiscent of citrus black spot (CBS) consisting of depressed circular spots of about 5 mm in diameter with a light-brown to gray center and black margins surrounded by green rind tissue were observed on a ‘Valencia’ sweet orange (Citrus sinensis) orchard in Bembe, Uige Province, Angola, with a disease incidence of 47%. Dark brown pycnidia were present in fruit lesions, which often coalesced forming sunken blemishes. Symptomatic fruits from this orchard were surface disinfected with 0.5% NaOCl for 2 min. Small fragments from lesions were plated onto potato dextrose agar (PDA) amended with 0.5 g of streptomycin sulfate/liter and incubated for 15 days at 23°C in the dark. Fungal colonies were transferred to PDA and oatmeal agar (OA) and incubated for 30 days at 23°C with 12-h photoperiod for morphological examination. Colonies were black with irregular margins in PDA and surrounded by a yellow pigment in OA. Pycnidia in PDA were aggregated, globose, dark brown, and 210 µm in diameter. Conidia were 9 to 12 × 5 to 7 µm, hyaline, aseptate, guttulate, obovoid to ellipsoid with truncate base, a mucoid layer and apical appendage. Pycnidia and conidia in PDA or fruit lesions were morphologically similar to those of Phyllosticta (Wikee et al. 2013). The ITS1-5.8S-ITS2 region, partial TEF1-alpha region, and LSU were amplified and sequenced as per Wikee et al. (2013) from DNA extracted from the single-spore isolate IIA-GC003NA, obtained from a Valencia sweet orange fruit from Bembe (GenBank accession nos. KY457232, MF693404, and MF693405, respectively). The sequences had 100% identity with those of P. citricarpa (McAlpine) van der Aa (synonym Guignardia citricarpa Kiely) epitype strain CBS 127454 (Glienke et al. 2011) (GenBank accession nos. JF343583, JF343604, and KF206306, respectively). Laboratory pathogenicity tests were performed by injecting the albedo of 30 mature detached fruit of Valencia sweet orange with 100 µl of a suspension of 3.0 × 10⁴ conidia/ml of water of the isolate IIA-GC003NA (Perryman et al. 2014). Fruits treated with sterile distilled water were used as controls. Fruits were maintained in humid chambers for 40 days at 24 to 26°C with 12-h photoperiod, and those inoculated with the fungus developed depressed necrotic lesions after 35 days. Field pathogenicity tests were performed on 12- to 14-week-old Valencia sweet orange fruits covered by waxed paper bags. Leaf disks colonized by the fungus were placed onto the rind of 60 fruits (Baldassari et al. 2009). Sterile leaf discs were used as controls. Symptoms of a false melanose-type consisting of dark brown stipplings were observed after 86 days on fruit inoculated in the field. No symptoms were observed on control fruit in either experiment. P. citricarpa, identified as described above, was reisolated from lesions on inoculated fruit in all experiments, but not from control fruit. The disease was verified as CBS caused by P. citricarpa. To our knowledge, this is the first report of CBS, caused by P. citricarpa, in Angola. P. citricarpa is responsible for large economic losses worldwide, so further studies are needed to map its geographic distribution, population structure, and impact in Angola.

Green synthesis of Silver and Gold Nanoparticles for Enhanced catalytic and bactericidal activity

A rapid one step green synthetic method using kiwi fruit extract was employed for preparation of silver and gold nanoparticles. The synthesized nanoparticles were successfully used as green catalysts for the reduction of 4-nitrophenol (4-NP) and methylene blue (MB). They also exhibited excellent antimicrobial activity against clinically isolated Pseudomonas aeruginosa (P.aeruginosa) and Staphylococcus aureus (S.aureus). It was noticed that with increase in concentration of the aqueous silver and gold solutions, particle size of the Ag and Au NPS showed increase as evidenced from UV-Visible spectroscopy and TEM micrograph. The method employed for the synthesis required only a few minutes for more than 90% formation of nanoparticles when the temperature was raised to 80°C. It was also noticed that the catalytic activity of nanoparticles depends upon the size of the particles. These nanoparticles were observed to be crystalline from the clear lattice fringes in the transmission electron microscopic (TEM) images, bright circular spots in the selected area electron diffraction (SAED) pattern and peaks in the X-ray diffraction (XRD) pattern. The Fourier-transform infrared (FTIR) spectrum indicated the presence of different functional groups in the biomolecule capping the nanoparticles.

The application of axisymmetric lattice Boltzmann two-phase model on simulations of liquid film dewetting

An axisymmetric two-phase lattice Boltzmann method is applied to simulate the dewetting dynamics of a thin liquid film on a substrate. Initially, a circular dry spot exists in the center of the liquid film. A contact line forms around the dry spot and expands outwards. The liquid films dewetting on smooth and rough substrates are investigated. For a smooth substrate, the effects of the contact angle (θeq), Ohnesorge number (Oh), and viscosity ratio (λμ) are studied. It is observed that the contact line recedes with a constant velocity V and that if θeq > 45°, V has a linear relationship with θeq, which has never been mentioned in previous literatures. For a rough substrate, well-distributed pillars are set up to represent the roughness. There are two states for the liquid film dewetting on a rough substrate: Cassie and Wenzel states. By comparison, it is found that the speed of the liquid film dewetting on the rough substrate of the Cassie state is slightly faster than that on the smooth substrate but much faster than that on the rough substrate of the Wenzel state, i.e., Wenzel state can obviously hold back the movement of the receding contact line. The corresponding mechanism is analyzed. The effect of the geometric factors of the pillars on the dewetting speed is discussed in detail. It is indicated that both the width and the depth of the grooves in roughness can significantly affect the dewetting speed. The results are helpful to design structured substrates for controlling the dewetting process of the liquid film.

Studies of the Core Conditions of the Earth and Super-Earths Using Intense Ion Beams at FAIR

Abstract Using detailed numerical simulations, we present the design of an experiment that will generate samples of iron under extreme conditions of density and pressure believed to exist in the interior of the Earth and interior of extrasolar Earth-like planets. In the proposed experiment design, an intense uranium beam is used to implode a multilayered cylindrical target that consists of a thin Fe cylinder enclosed in a thick massive W shell. Such intense uranium beams will be available at the heavy-ion synchrotron, SIS100, at the Facility for Antiprotons and Ion Research (FAIR), at Darmstadt, which is under construction and will become operational in the next few years. It is expected that the beam intensity will increase gradually over a couple of years to its maximum design value. Therefore, in our studies, we have considered a wide range of beam parameters, from the initial beam intensity (“Day One”) to the maximum specified value. It is also worth noting that two different focal spot geometries have been used. In one case, a circular focal spot with a Gaussian transverse intensity distribution is considered, whereas in the other case, an annular focal spot is used. With these two beam geometries, one can access different parts of the Fe phase diagram. For example, heating the sample with a circular focal spot generates a hot liquid state, while an annular focal spot can produce a highly compressed liquid or a highly compressed solid phase depending on the beam intensity.

Resonator-Length Dependence of Electron-Beam-Pumped UV-A GaN-Based Lasers

The dependence of resonator length on the threshold power and emission wavelength of electron-beam-pumped UV-A edge-type emitting lasers is demonstrated. The lowest pump power thresholds are achieved for 100-200 μm long resonators, where there is good overlap of the focused e-beam spot with the resonator cavity. For longer resonator lengths the focused circular e-beam spot excites only a segment of the resonator cavity, yet lasing is observed. Absorption of the e-beam generated photons in the un-pumped sections of the resonator results in increased absorption losses and, consequently, higher laser thresholds. In addition, a significant wavelength shift from 375 nm for the 50 μm resonators to 385 nm for the 600 μm resonators is observed due to absorption of the higher energy photons and re-emission at longer wavelengths in the un-pumped sections.

Multi-image mosaic with SIFT and vision measurement for microscale structures processed by femtosecond laser

In femtosecond laser processing, the field of view of each image frame of the microscale structure is extremely small. In order to obtain the morphology of the whole microstructure, a multi-image mosaic with partially overlapped regions is required. In the present work, the SIFT algorithm for mosaic images was analyzed theoretically, and by using multiple images of a microgroove structure processed by femtosecond laser, a stitched image of the whole groove structure could be studied experimentally and realized. The object of our research concerned a silicon wafer with a microgroove structure ablated by femtosecond laser. First, we obtained microgrooves at a width of 380 µm at different depths. Second, based on the gray image of the microgroove, a multi-image mosaic with slot width and slot depth was realized. In order to improve the image contrast between the target and the background, and taking the slot depth image as an example, a multi-image mosaic was then realized using pseudo color enhancement. Third, in order to measure the structural size of the microgroove with the image, a known width streak ablated by femtosecond laser at 20 mW was used as a calibration sample. Through edge detection, corner extraction, and image correction for the streak images, we calculated the pixel width of the streak image and found the measurement ratio constant Kw in the width direction, and then obtained the proportional relationship between a pixel and a micrometer. Finally, circular spot marks ablated by femtosecond laser at 2 mW and 15 mW were used as test images, and proving that the value Kw was correct, the measurement ratio constant Kh in the height direction was obtained, and the image measurements for a microgroove of 380 × 117 µm was realized based on a measurement ratio constant Kw and Kh. The research and experimental results show that the image mosaic, image calibration, and geometric image parameter measurements for the microstructural image ablated by femtosecond laser were realized effectively.

Tight focusing of laser light using a chromium Fresnel zone plate.

Using near-field scanning microscopy, we demonstrate that a 15-µm zone plate fabricated in a 70-nm chromium film sputtered on a glass substrate and having a focal length and outermost zone's width equal to the incident wavelength λ = 532 nm, focuses a circularly polarized Gaussian beam into a circular subwavelength focal spot whose diameter at the full-width of half-maximum intensity is FWHM = 0.47λ. This value is in near-accurate agreement with the FDTD-aided numerical estimate of FWHM = 0.46λ. When focusing a Gaussian beam linearly polarized along the y-axis, an elliptic subwavelength focal spot is experimentally found to measure FWHMx = 0.42λ (estimated value FWHMx = 0.40λ) and FWHMy = 0.64λ. The subwavelength focal spots presented here are the tightest among all attained so far for homogeneously polarized beams by use of non-immersion amplitude zone plates.

Rectangular Illumination Based on Diffuse Reflective Off-Axis Surface

Diffuse reflective LED lighting system is widely used in many areas, while rectangular illumination is also widely used in various lighting fields because of its regular lighting shapes, but traditional diffuse reflection method can only produce circular spot. This paper first introduced rectangular illumination into design of the diffuse reflective surface, combined the merits of both. A mathematical model of a diffuse reflective off-axis surface based on a single LED chip, desired value of the target plane and energy conservation is established and the shape of the illumination facula is used as the constraint condition. By solving the nonlinear equations, a number of two-dimensional (2-D) curves are obtained and combine these 2-D curves into off-axis surface. The results show that the shape of the illumination facula is close to the standard rectangle, and the efficiency and the uniformity of illumination is higher than traditional diffuse reflectors.

First Report of Phoma herbarum Causing Leaf Spot of Woodland Sage (Salvia nemorosa) in Northern Italy

HomePlant DiseaseVol. 101, No. 10First Report of Phoma herbarum Causing Leaf Spot of Woodland Sage (Salvia nemorosa) in Northern Italy PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Phoma herbarum Causing Leaf Spot of Woodland Sage (Salvia nemorosa) in Northern ItalyG. Gilardi, S. Matic, M. L. Gullino, and A. GaribaldiG. GilardiSearch for more papers by this author, S. MaticSearch for more papers by this author, M. L. Gullino†Corresponding author. E-mail: E-mail Address: marialodovica.gullino@unito.itSearch for more papers by this author, and A. GaribaldiSearch for more papers by this authorAffiliationsAuthors and Affiliations G. Gilardi S. Matic , Centre of Competence for the Agro-Environmental Sector (AGROINNOVA), 10095 Grugliasco, Italy M. L. Gullino † , Centre of Competence for the Agro-Environmental Sector (AGROINNOVA), 10095 Grugliasco, Italy; and DISAFA, University of Torino, 10095 Grugliasco, Italy A. Garibaldi , Centre of Competence for the Agro-Environmental Sector (AGROINNOVA), 10095 Grugliasco, Italy. Published Online:24 Jul 2017https://doi.org/10.1094/PDIS-04-17-0606-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Woodland sage (Salvia nemorosa L.) is a hardy herbaceous perennial plant widely used in parks and public gardens in Italy. During the summer of 2016, a new leaf spot was observed on 90-day-old plants grown in the gardens of the Venaria Castle located in Venaria Reale, near Turin, in Piedmont, northern Italy. At temperatures between 25 and 30°C, 70% of plants of about 100 grown in the garden were affected, though at different levels. First symptoms of the disease appeared as circular brown leaf spots (1 to 3 mm), gradually increased in number to 30 to 40, changing from circular to elliptical or irregular, eventually covering a large percentage of the leaf and causing leaf death. Lesions were dark brown to black, generally surrounded with a yellow halo. As lesions developed, they became gray and scattered black specks appeared in the center of the spots. A fungus was consistently isolated from several isolations carried out on potato dextrose agar amended with 25 mg/liter of streptomycin sulfate from the margin of the necrotic lesions. After 10 days, black pycnidia 52.1 to 64.9 μm and 118.0 to 125.0 μm diameter were observed, releasing masses of hyaline, elliptical conidia measuring 3.4 to 7.7 (avg. 4.5) and 1.3 to 1.9 (avg. 1.5) μm. On the basis of morphological characteristics, it was identified as Phoma sp. (Boerema et al. 2004). DNA from one isolate coded IT36 was obtained using the E.Z.N.A. Fungal DNA Mini Kit (Omega Bio-Tek, Darmstadt, Germany). A PCR reaction was performed using primers ITS1/ITS4 to amplify the internal transcribed spacer, the intergenic region between 28S and 18S sequences of the ribosomal RNA, including the 5.8S sequence. PCR product was purified and sent for sequencing to BMR Genomics (Padova, Italy). BLASTn analysis (Altschul et al. 1997) of the 544-bp sequence showed a 99% identity with the corresponding sequence in GenBank for P. herbarum (accession no. FN868459). The sequence was deposited to GenBank (KY947522). A pathogenicity test was carried out by spraying a conidial suspension of 106 conidia ml–1 from a single-spore culture of strain IT36 onto foliage of 60-day-old S. nemorosa maintained under >90% relative humidity for 72 h after inoculation. Plants (three per treatment) were kept in a glasshouse at an average temperature of 24°C (minimum 20°C, maximum of 28°C). Lesions developed on leaves 8 days after inoculation, while control plants remained healthy. P. herbarum was consistently reisolated from the lesions. The pathogenicity test was carried out twice with the same results. To our knowledge, this is the first report of P. herbarum on S. nemorosa in Italy and worldwide. The wide host range of P. herbarum is well known (Farr and Rossman 2017; Kinsey 2002) and this report extends it to a new host.

Characterization and Quantification of Biosynthesized Gold Nanoparticles Using Chenopodium aristatum L. Stem Extract

A cost-effective, and rapid method to synthesize gold nanoparticles using Chenopodium aristatum L. stem extract was developed in this study. Chenopodium aristatum L. is an obnoxious weed. Their tenacious vitality can provide us enormous biomass for beneficial utilizations. In this paper, its stem extract was used as both capping and reducing agents for the biosynthesis of gold nanoparticles (AuNPs). UV–Vis spectra showed surface plasmon resonance (SPR) band at ~540 nm. The synthesized AuNPs were quantified by the centrifugal ultrafilter method followed with ICP-MS determination. TEM images showed that the shapes of synthesized AuNPs were predominantly spherical. In addition, truncated triangular and small amounts of other shaped NPs were also formed. The results of SAED showed clear circular spots. The face-centered cubic structure of the AuNPs was confirmed by XRD peaks at 38.188°, 44.552°, 64.589°, and 77.584°, which corresponded to (111), (200), (220), and (311) planes, respectively. Zeta (ζ) potential of AuNPs was −22.9 ± 5.56 mV. FTIR spectrum showed the functional groups, such like O–H, N–H, C–H, C=O, were possibly responsible for reducing Au(III) ions and stabilizing nanoparticles. The synthesized AuNPs exhibited good catalytic and antioxidant activities in degradation of 4-nitrophenol and free radical scavenging.

The study of umbral dots in sunspots based on SOT/Hinode observations

To understand the energy transport in sunspots, it is necessary to investigate the dynamic properties of umbral dots (UDs). In this connection, we used high‐resolution SOT/Hinode time‐series images. The intensity oscillations of UDs are determined. We conclude that their periods are in the range of 3–5 min, which may be related to the propagation of p‐modes through them. We follow the motion path of UDs and investigate whether they are oscillating quasi‐periodically. Moreover, we detect their transverse motion and obtain two different periods for these oscillations. Finally, we analyze the diameter of UDs as circular spots. We find that the UDs fluctuate in size.

First Report of Fusarium oxysporum Causing Stem Dry Rot in Astrophytum ornatum in Mexico

HomePlant DiseaseVol. 101, No. 7First Report of Fusarium oxysporum Causing Stem Dry Rot in Astrophytum ornatum in Mexico PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Fusarium oxysporum Causing Stem Dry Rot in Astrophytum ornatum in MexicoA. Quezada-Salinas, M. Moreno-Velázquez, J. L. Cruz-Jaramillo, C. J. García-Avila, and J. A. López-BuenfilA. Quezada-SalinasSearch for more papers by this author, M. Moreno-VelázquezSearch for more papers by this author, J. L. Cruz-JaramilloSearch for more papers by this author, C. J. García-AvilaSearch for more papers by this author, and J. A. López-BuenfilSearch for more papers by this authorAffiliationsAuthors and Affiliations A. Quezada-Salinas M. Moreno-Velázquez J. L. Cruz-Jaramillo C. J. García-Avila J. A. López-Buenfil , Servicio Nacional de Sanidad, Inocuidad y Calidad Agroalimentaria, Unidad Integral de Diagnóstico, Servicios y Constatación Carretera Federal México-Pachuca Km 37.5, Tecámac, Estado de México, C.P. 55740, Mexico. Published Online:14 Apr 2017https://doi.org/10.1094/PDIS-06-16-0941-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Astrophytum ornatum (DC.) Britton & Rose, family Cactaceae, is native to Mexico and is categorized as a threatened species. It has a spherical stem at the beginning of its development, but during growth it becomes columnar. Wild specimens can reach up to 1 m high and 30 cm in diameter, although in cultivation they rarely exceed 30 cm in height. During September 2013, in Texcoco State, Mexico, dry rot symptoms were observed in 8-year-old A. ornatum plants grown in pots and in green spaces. Incidence was ∼30%. Symptoms began as small dots, olive in color, in the younger tissues of the aerial part of the plant; subsequently, they developed semicircular dry spots 3 to 5 cm in diameter, light brown, delimited by a light green margin. In some cases, lesions increased in size and coalesced, and after 240 days, 100% of the plant area was invaded. Eventually, affected tissues collapsed and the plants died. Inner tissue pieces were cut from the healthy-ill transition area, placed in potato dextrose agar (PDA), and incubated for 48 h at 22°C. Mycelium was grown out of infected plant tissue and transferred to PDA dishes. The developed colonies were purified by monoconidial cultures on PDA to determine their cultural and morphological characteristics (Nelson et al. 1983). The isolates were identified as Fusarium oxysporum due to the production of sickle shaped macroconidia 30.4 μm long × 3.28 μm wide with three septa, foot-shaped basal cell and a short apical cell, in branched conidiophores or on the surface of sporodochia; microconidia developed in simple lateral phialides, oval to ellipsoid shaped, straight to curved, and without septa. The colonies were purple (Leslie and Summerell 2006; Nelson et al. 1983). Molecular analysis was performed on two isolates to validate morphological characterization. DNA was extracted from monoconidial cultures and partial ITS1-4 region EF1-α subunit fragments were amplified by PCR with universal primer sequences. BLASTn analysis performed to sequences showed 98 to 99% similarity with the corresponding F. oxysporum sequences deposited in the nr-nucleotide database (Camacho et al. 2009), as well as with the Fusarium-ID database (Geiser et al. 2004); the sequences were deposited as KX398010 (ITS1-4) and KY379852 (EF1-α), respectively. For pathogenicity tests, 4-year-old A. ornatum plants were inoculated with the KX398010 isolate using three methods: i) spraying spores, ii) wound + spraying spores, and iii) subepidermal injection of spores. For control plants, sterile distilled water was used. Wounding was done by causing lesions with a sterile needle. For each method of inoculation, five plants were used, and the pathogenicity test was repeated two times. The inoculation in the aerial part (ribs) of the plant was carried out because the symptoms begin in this zone. For spraying spores, the first symptoms of dry rot were observed 15 days after inoculation as olive colored spots, which developed semicircular dry light brown spots; in the spores’ injection method, the tissues collapsed and died, causing perforations; lastly, by wound plus spraying spores method, they developed circular light brown spots from the damage done. The symptoms were similar to those observed in the first plants with dry rot, which originated this research. F. oxysporum was recovered from infected tissues by reisolation. To our knowledge, this is the first report of F. oxysporum in A. ornatum plants in Mexico. This work has significance in nurseries as well as for the conservation of this cactus, which is a threatened species.

A lattice Boltzmann model for condensation and freezing of dry saturated vapor about a cryogenic spot on an inclined hydrophobic surface

A triple phase-change lattice Boltzmann model, based on a coupling of existing vapor-liquid phase-change model and enthalpy-based liquid-solid phase-change model, is proposed in this paper. Based on this novel model, 3D simulations for transient condensation of a dry saturated vapor and subsequent freezing at a circular cryogenic spot of an inclined hydrophobic surface are carried out. The dynamic morphologies of the droplet and ice are presented. Simulated results show that ice adjacent to the cryogenic spot is formed inside a droplet, and the droplet subsequently moves down along the vertical surface under action of gravity. Effects of droplet’s dynamic behaviors on the growth of ice and averaged heat flux are presented. Temperature distributions in the ice as well as in the water and steam on the middle cross section and local heat flux at the wall are illustrated. Simulations of the triple phase-change phenomena under different tilt angles show that the ice is elongated in the direction of gravity. The wettability of the surface is shown to have important influence on the morphology of droplet but its effect on the growth of ice is small.

Green synthesis and characterization of gold and silver nanoparticles using Mussaenda glabrata leaf extract and their environmental applications to dye degradation.

Plant-derived nanomaterials opened a green approach in solving the current environment issues. Present study focused on rapid microwave-assisted synthesis and applications of gold and silver nanoparticles mediated by aqueous leaf extract of Mussaenda glabrata. The synthesized nanoparticles were characterized by UV-vis, FT-IR, powder XRD, energy-dispersive X-ray spectroscopy (EDX), transmission electron (TEM), and atomic force microscopic techniques (AFM). FCC crystal structure of both nanoparticles was confirmed by peaks corresponding to (111), (200), (220), and (311) planes in XRD spectra and bright circular spots in SAED pattern. IC50 values shown by gold and silver nanoparticles (44.1±0.82 and 57.92±1.33μg/mL) reflected their high free radical scavenging potential. The synthesized gold and silver nanoparticles revealed their potency to inhibit pathogenic microorganisms Bacillus pumilus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Aspergillus niger, and Penicillium chrysogenum. Anthropogenic pollutants rhodamine B and methyl orange were effectively degraded from aquatic environment and waste water sewages of dye industries using the prepared nanocatalysts. The catalytic capacities of the synthesized nanoparticles were also exploited in the reduction of 4-nitrophenol. Graphical abstract.

Synthesis of platinum nanoparticles using seaweed Padina gymnospora and their catalytic activity as PVP/PtNPs nanocomposite towards biological applications

In the recent years, synthesis of nanomaterials using seaweeds and their diverse applications is escalating research in modern era. Among the noble metals, platinum nanoparticles (PtNPs) are of great importance owing to their catalytic property and less toxicity. The significance of this work is a simple one-step synthesis of PtNPs using aqueous extract of Indian brown seaweed Padina gymnospora and their catalytic activity with a polymer Polyvinylpyrrolidone (PVP) as PVP/PtNPs nanocomposite towards antimicrobial, haemolytic, cytotoxic (Artemia salina) and antioxidant properties. Fourier Transform Infrared (FT-IR) spectrum results showed diversified functional groups (biomoeities such as carbohydrates and proteins) present in the seaweed extract is responsible for the reduction of platinum ions (Pt+) to PtNPs. The seaweed mediated PtNPs was characterized by UV–vis spectrophotometer, X-ray diffraction (XRD) pattern, Field Emission Scanning Electron Microscopy (FESEM) equipped with Energy Dispersive X-ray (EDX) spectroscopy and High Resolution Transmission Electron Microscopy (HRTEM) analysis. The synthesized PtNPs was found to be truncated octahedral in shape with the range of 5–50nm. Crystalline nature of the nanoparticles was evidenced by Selected Area Electron Diffraction (SAED) pattern with bright circular spots corresponding to (111), (200), (220) and (311) Bragg’s reflection planes. The size of the PtNPs was further evidenced by Dynamic Light Scattering (DLS) analysis and it is originate to be stable at −22.5mV through Zeta Potential (ZP) analysis. The present study shows that the catalytic behavior of PtNPs as polymer/metal nanocomposite (PVP/PtNPs) preparation for an antibacterial activity against seven disease causing pathogenic bacterial strains with the maximum activity against Escherichia coli (15.6mm) followed by Lactococcus lactis (14.8mm) and Klebsiella pneumoniae (14.4mm). But no haemolytic activity was seen at their effective bactericidal concentration, whereas increase in the haeomyltic activity was seen only in higher concentrations (600, 900 and 1200μgmL−1). On the other hand, PVP/PtNPs nanocomposite has shown cytotoxic activity at 100±4μgmL−1 (LC50) against Artemia salina nauplii. Furthermore, PVP/PtNPs nanocomposite showed an enhanced scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH), superoxide, nitric oxide and hydroxyl radicals.

First Report of Olive Anthracnose, Caused by Colletotrichum gloeosporioides, in Morocco

Ripe and overripe olive fruits (Picholine marocaine) showing circular spots of 5 to 20 mm in diameter, slightly depressed and reddish-brown in color, were collected from two orchards located in the regions of Ouazzane in Morocco. Colletotrichum gloeosporioides was isolated from symptomatic fruits and Koch’s postulate was fulfilled. According to the literature, this is the first report of Colletotrichum gloeosporioides causing anthracnose in olives in Morocco.

Evanescent field interferometric optical tweezers with rotational symmetric patterns

A simple configuration to create optical lattices with N-fold rotational symmetry using the interference of N evanescent fields is proposed. The potential energy of a Rayleigh particle in the generated patterns (optical lattices) is investigated. The results show that by adjusting the relative phases and polarization states of the incident beams, an enormous range of optical lattices can be obtained. When the number of interfering beams is increased, circular spots beyond the diffraction limit can be created. For s-polarization, the intensity landscape has a dark-centered distribution at the origin encircled by a very small bright circular ring whose radius is 120 nm. This intensity distribution acts as a hollow beam and can be used for efficient trapping of low-index particles. We believe that the resulting lattices can find applications in the arrangement of particles, creation of optical lattices, and efficient trapping of very small Rayleigh particles.