Surface Wax Research Articles

Efficient recovery of superhydrophobic wax surfaces on solid wood

Superhydrophobic surface coatings have enormous potential to protect wood from excessive water uptake. Unfortunately, such coatings often require toxic chemicals or complex fabrication methods, and their mechanical stability is very limited. As an alternative, highly water-repellent wood surfaces with mean water contact angles (WCAs) of 160° were prepared by straightforward spray-deposition of alkyl ketene dimer (AKD) wax microparticles. While water repellency was unaffected by static loading with a cast iron weight, prolonged rubbing resulted in a strong reduction in WCA to 125° since the spherical wax microstructure was largely destroyed by the acting shear forces. Thermal treatment of such a degraded surface at 80 °C led to an almost full recovery (WCA 155°) of water repellency. Microscopy and thermal analysis revealed that exposure to temperatures above the melting range and subsequent slow cooling enable self-assembly of AKD into leaf-shaped microstructures, which are responsible for the high WCA observed. It is proposed that the thermally induced self-recovery ability will greatly enhance the utility and service life of AKD-based superhydrophobic wood surfaces and make them suitable for multiple practical applications.

Flower surface wax chemicals in green gram help to stimulate oviposition in Spilosoma obliqua within short distances

AbstractLarvae of Spilosoma obliqua Walker (Lepidoptera: Arctiidae) feed on leaves and flowers of green gram (or mung bean), Vigna radiata (L.) R. Wilczek (Fabaceae), and thereby reduce yield in India. Previously, we demonstrated that leaf surface waxes from three green gram cultivars – PDM 54 (PDM), Pusa Baisakhi (PUSA), and Samrat (SAM) – served as short‐range attractants and oviposition stimulants in S. obliqua. In this study, we aimed to find out whether flower surface waxes have similar roles. We identified the alkanes and free fatty acids in flower surface wax of the three cultivars, created representative blends of synthetic compounds, and tested the effects of crude wax and various blends on attraction and oviposition of S. obliqua. Twenty‐two n‐alkanes (n‐C13 to n‐C36) were identified in PDM, and 23 in the other two cultivars; pentadecane was predominant. Fifteen free fatty acids (C12:0 to C22:0) were detected in the three cultivars; palmitoleic acid (in PDM and PUSA) and pentadecanoic acid (in SAM) were predominant. In Y‐tube olfactometer bioassays, females were attracted to 1 mg flower surface wax of the three cultivars, as well as to blends composed of 3–7 compounds representative of the three varieties (PDM: tricosane, pentacosane, heptacosane, nonacosane, palmitoleic acid, linolenic acid, and stearic acid; PUSA: heptacosane, nonacosane, and stearic acid; and SAM: heptacosane, linolenic acid, and stearic acid). In dual choice tests, the females did not distinguish between surface wax of a variety and its representative synthetic blend. Also, they did not distinguish between the three cultivars. Results of oviposition assays were similar: 1 mg flower surface wax, as well as synthetic blends, stimulated egg laying, but the numbers of eggs were similar in the presence of surface wax of a variety vs. its representative synthetic blend. Also, oviposition was not differentially affected by cultivar. Thus, as in leaves, flower surface waxes act as short‐range attractants and oviposition stimulants in S. obliqua. The blends are potentially of use to develop lures as part of integrated pest management strategies.

METHODS OF UNCREASING OF THE WAX MODEL SURFACE PRIMARY WETTABILITY DURING LOST-WAX CASTING

Lost-wax casting is one of the most advanced ways to obtain geometrically complex castings of high quality. One of the main factors influenced on the casting properties is the quality of the ceramic mold face layer. A uniform deposition of the ceramic slurry can be achieved by condition of the wax surface is well wetted by the suspension dispersion medium. Since the surface of the wax model is hydrophobic and the dispersion medium of ceramic suspension is water, an increase of wettability may be achieved not only by SAS-wetting agent adding in suspension composition but also by activating of the model surface by chemical or physical methods. The paper presents the results of the different ways of chemical activation influence on the wettability of the wax model surface.

Interaction of surfactants with barley leaf surfaces: time-dependent recovery of contact angles is due to foliar uptake of surfactants

Main conclusionTime-dependent contact angle measurements of pure water on barley leaf surfaces allow quantifying the kinetics of surfactant diffusion into the leaf.Barley leaf surfaces were sprayed with three different aqueous concentrations (0.1, 1.0 and 10%) of a monodisperse (tetraethylene glycol monododecyl ether) and a polydisperse alcohol ethoxylate (BrijL4). After 10 min, the surfactant solutions on the leaf surfaces were dry leading to surfactant coverages of 1, 10 and 63 µg cm−2, respectively. The highest surfactant coverage (63 µg cm−2) affected leaf physiology (photosynthesis and water loss) rapidly and irreversibly and leaves were dying within 2–6 h. These effects on leaf physiology did not occur with the lower surfactant coverages (1 and 10 µg cm−2). Directly after spraying of 0.1 and 1.0% surfactant solution and complete drying (10 min), leaf surfaces were fully wettable for pure water and contact angles were 0°. Within 60 min (0.1% surfactant) and 6 h (1.0% surfactant), leaf surfaces were non-wettable again and contact angles of pure water were identical to control leaves. Scanning electron microscopy investigations directly performed after surfactant spraying and drying indicated that leaf surface wax crystallites were partially or fully covered by surfactants. Wax platelets with unaltered microstructure were fully visible again within 2 to 6 h after treatment with 0.1% surfactant solutions. Gas chromatographic analysis showed that surfactant amounts on leaf surfaces continuously disappeared over time. Our results indicate that surfactants, applied at realistic coverages between 1 and 10 µg cm−2 to barley leaf surfaces, leading to total wetting (contact angles of 0°) of leaf surfaces, are rapidly taken up by the leaves. As a consequence, leaf surface non-wettability is fully reappearing. An irreversible damage of the leaf surface fine structure leading to enhanced wetting and increased foliar transpiration seems highly unlikely at low surfactant coverages of 1 µg cm−2.

Individual and Interactive Temporal Implications of UV-B Radiation and Elevated CO2 on the Morphology of Basil (Ocimum basilicum L.)

Temporal and spatial variations in ozone levels and temporal changes in solar radiation greatly influence ultraviolet radiation incidence to crops throughout their growth, yet the interactive effects of CO2 and UV-B radiation on Basil production under sunlight environmental conditions has not been studied. Basil ‘Genovese’ plants grown under sunlit plant growth chambers were subjected to a combination of supplemental UV-B (0 and 10 kJ m−2d−1) and ambient (420 ppm) and elevated (720 ppm) CO2 treatments for 38 days after 14 days of germination. UV-B radiation treatments caused a decrease in basil stem branching, fresh mass, and stem dry mass under both CO2 treatments when harvested after 17 and 38 days of treatment. There was also an increase in basil leaf surface wax under UV-B (10 kJ m−2d−1) treatment compared to controls (0 kJ m−2d−1). Elevated CO2 treatments caused a decrease in morphological features, including specific leaf area and fresh mass. Interactive effects between UV-B and CO2 treatments existed for some morphological features, including plant height, root surface area, and average root diameter. Understanding the impacts that CO2 and UV-B radiation treatments have on basilcan improve existing varieties for increased tolerance while simultaneously improving yield, plant morphology, and physiology.

Desktop scanning electron microscopy in plant-insect interactions research: a fast and effective way to capture electron micrographs with minimal sample preparation.

The ability to visualize cell and tissue morphology at a high magnification using scanning electron microscopy (SEM) has revolutionized plant sciences research. In plant–insect interactions studies, SEM-based imaging has been of immense assistance to understand plant surface morphology including trichomes [plant hairs; physical defense structures against herbivores], spines, waxes, and insect morphological characteristics such as mouth parts, antennae, and legs, that they interact with. While SEM provides finer details of samples, and the imaging process is simpler now with advanced image acquisition and processing, sample preparation methodology has lagged. The need to undergo elaborate sample preparation with cryogenic freezing, multiple alcohol washes, and sputter coating makes SEM imaging expensive, time consuming, and warrants skilled professionals, making it inaccessible to majority of scientists. Here, using a desktop version of SEM (SNE- 4500 Plus Tabletop), we show that the “plug and play” method can efficiently produce SEM images with sufficient details for most morphological studies in plant–insect interactions. We used leaf trichomes of Solanum genus as our primary model, and oviposition by tobacco hornworm (Manduca sexta; Lepidoptera: Sphingidae) and fall armyworm (Spodoptera frugiperda; Lepidoptera: Noctuidae), and leaf surface wax imaging as additional examples to show the effectiveness of this instrument and present a detailed methodology to produce the best results with this instrument. While traditional sample preparation can still produce better resolved images with less distortion, we show that even at a higher magnification, the desktop SEM can deliver quality images. Overall, this study provides detailed methodology with a simpler “no sample preparation” technique for scanning fresh biological samples without the use of any additional chemicals and machinery.

Pivotal role of water molecules in the photodegradation of pymetrozine: New insights for developing green pesticides

Photodegradation of the insecticide pymetrozine (PYM) was studied on surface of wax films, and in aqueous and nonaqueous phase. The half-life of PYM on the wax surface was approximately 250 times longer than in water. Scavenging experiments, laser flash photolysis, and spectra analysis indicated the first singlet excited state of PYM (S1 *PYM) to be the most important photoinduced species initiating the photodegradation. Quantum chemistry calculations identified significant molecular torsion and changes in the structure C–CN–N of S1 *PYM, and the absolute charges of the CN atoms increased and the bond strength weakened. Free energy surface analysis, and O18 labeling experiments further confirmed that the mechanism was two-step photoinduced hydrolysis. The first step is the hydrolysis of S1 *PYM at CN upon reaction with 2–3 water molecules (one H2O molecule as the catalyst). The second step is an intramolecular hydrogen transfer coupled with the cleavage of C–N bond and formation of two cyclic products. During the interactions, water molecules experience catalytic activation by transferring protons, while there is a negligible solvent effect. Clarifying the detailed photodegradation mechanisms of PYM is beneficial for the development of green pesticides that are photostable and effective on leaf surfaces, and photolabile and detoxified in the aquatic environment.

Short-range attraction and oviposition stimulant of a biocontrol agent, Galerucella placida Baly (Coleoptera: Chrysomelidae) toward weed leaf surface waxes.

Two Polygonaceae weeds, Rumex dentatus L. and Polygonum glabrum Willd. are abundant in wheat- and rice-fields, respectively, in India. Galerucella placida Baly (Coleoptera: Chrysomelidae) is a biocontrol agent of these two weeds. The importance of long-chain alkanes and free fatty acids present in leaf surface waxes of these weeds was assessed as short-range attractant and ovipositional stimulant in G. placida females. Extraction, TLC, GC-MS and GC-FID analyses demonstrated 19 n-alkanes from n-C14 to n-C35 and 14 free fatty acids from C12:0 to C22:0 in leaf surface waxes. Hentriacontane was predominant among alkanes in both weeds, while oleic acid and docosanoic acid were predominant among free fatty acids in R. dentatus and P. glabrum, respectively. Females of G. placida were attracted toward one leaf equivalent surface wax of both weeds against the control solvent (petroleum ether) in a short Y-tube olfactometer bioassay. But, the insect could not differentiate between one leaf equivalent surface wax of R. dentatus and P. glabrum, indicating that both weed leaves were equally attractive in females. A synthetic blend of either 2.44, 35.57 and 23.58 μg ml-1 of octadecane, heptacosane and nonacosane, respectively, resembling the amounts present in one leaf equivalent surface wax of R. dentatus or 4.08, 19.54 and 23.58 μg ml-1 of octadecane, palmitoleic acid and docosanoic acid, respectively, resembling the amounts present in one leaf equivalent surface wax of P. glabrum acted as short-range attractant and ovipositional stimulant in G. placida. These results could be a basis for host plant specificity of the biocontrol agent.

Synergism in Host Selection Behavior of Three Generalist Insects Towards Leaf Cuticular Wax of Sesame Cultivars.

Leaf cuticular wax plays important role in host selection, oviposition, and feeding of phytophagous insects. Thus, the role of cuticular wax of sesame (Sesamum indicum) cultivars (Savitri and Nirmala) in host selection of 3 generalist pests (Spilosoma obliqua Walker, Helicoverpa armigera Hübner, and Spodoptera litura Fabricius) was investigated under laboratory conditions. The GC-MS and GC-FID analyses of leaf surface waxes of both cultivars indicated the presence of 14 n-alkanes from n-C9 to n-C44 and 12 free fatty acids (FFAs) from C9:0 to C20:0. The most predominant n-alkane and FFA of the cultivars were n-C26 (94.3 ± 7.27 μg leaf-1) and C18:1 (110.8 ± 10.07 μg leaf-1), respectively present in Savitri cultivar. The generalists used visual (color and shape), olfactory (odorous n-alkanes and FFAs), tactile (surface ultra-structure), and gustatory (cuticular wax) cues in a synergistic manner for their host selection through attraction (adults and larvae) followed by oviposition (adults) and feeding (larvae) on studied cultivars (Savitri > Nirmala). Their olfactory responses were maximum towards 2 leaf equivalent amount, whereas oviposition and feeding preference were maximum towards 4 leaf equivalent amount of the combined synthetic (4 n-alkanes (n-C16, n-C22, n-C24, n-C26) + 3 FFAs (C12:0, C14:0, C18:1)) mixture-treated intact leaf of cultivar Savitri. This finding can suggest that the synthetic blend (4 n-alkanes + 3 FFAs) in leaf equivalent amount (396.6 ± 4.13 μg leaf-1) or more from cultivar Savitri can be used as lures to develop baited trap. In addition, the cultivar Nirmala can be used as a resistant cultivar in the ecological pest management (EPM) framework of these target pest species.

Leaf Surface Wax Chemicals in Trichosanthes anguina (Cucurbitaceae) Cultivars Mediating Short-Range Attraction and Oviposition in Diaphania indica.

Larval Diaphania indica (Saunders) (Lepidoptera: Crambidae) cause complete defoliation of Trichosanthes anguina L. and reduce crop yield in India. Females lay eggs on the leaf surface, and therefore leaf surface waxes are potentially involved in host selection. Alkanes and free fatty acids are the major constituents of leaf surface waxes, so a study was conducted to determine whether these wax constituents from three T. anguina cultivars (MNSR-1, Baruipur Long, and Polo No.1) could act as short-range attractants and oviposition stimulants in D. indica females. Twenty n-alkanes from n-C14 to n-C36 and 13 free fatty acids from C12:0 to C21:0 were detected in the leaf surface waxes of these cultivars. Heptadecane and stearic acid were predominant among n-alkanes and free fatty acids, respectively, in these cultivars. Females showed attraction towards one leaf equivalent surface wax of each of these cultivars against solvent controls (petroleum ether) in Y-tube olfactometer bioassays. A synthetic blend of heptadecane, eicosane, hexacosane, and stearic acid, a synthetic blend of hexacosane and stearic acid, and a synthetic blend of pentadecane and stearic acid comparable to amounts present in one leaf equivalent surface wax of MNSR-1, Baruipur Long, and Polo No.1, respectively, were short-range attractants and oviposition stimulants in D. indica. Female egg laying responses were similar to each of these blends, providing information that could be used to developing baited traps in integrated pest management (IPM) programs.

Drawing inspiration from nature to develop anti-fouling coatings: the development of biomimetic polymer surfaces and their effect on bacterial fouling

Abstract The development of self-cleaning biomimetic surfaces has the potential to be of great benefit to human health, in addition to reducing the economic burden on industries worldwide. Consequently, this study developed a biomimetic wax surface using a moulding technique which emulated the topography of the self-cleaning Gladiolus hybridus (Gladioli) leaf. A comparison of topographies was performed for unmodified wax surfaces (control), biomimetic wax surfaces, and Gladioli leaves using optical profilometry and scanning electron microscopy. The results demonstrated that the biomimetic wax surface and Gladioli leaf had extremely similar surface roughness parameters, but the water contact angle of the Gladioli leaf was significantly higher than the replicated biomimetic surface. The self-cleaning properties of the biomimetic and control surfaces were compared by measuring their propensity to repel Escherichia coli and Listeria monocytogenes attachment, adhesion, and retention in mono- and co-culture conditions. When the bacterial assays were carried out in monoculture, the biomimetic surfaces retained fewer bacteria than the control surfaces. However, when using co-cultures of the bacterial species, only following the retention assays were the bacterial numbers reduced on the biomimetic surfaces. The results demonstrate that such surfaces may be effective in reducing biofouling if used in the appropriate medical, marine, and industrial scenarios. This study provides valuable insight into the anti-fouling physical and chemical control mechanisms found in plants, which are particularly appealing for engineering purposes.

Skin greasiness in apple is caused by accumulations of liquid waxes: Evidence from chemical and thermodynamic analyses

The surface waxes of some apple (Malus × domestica) cultivars can become greasy during storage. Our previous work suggests the accumulation of fluid esters cause the increasing wax fluidity. To provide evidence for the inference, we revealed the effects of chemical changes in the apple epicuticular waxes on their thermodynamic properties. First, the chemical compositions and thermodynamic properties of the epicuticular waxes on ‘Jonagold’ apples were measured using GC-MS and differential scanning calorimetry, respectively. Then, a simulation experiment was performed in which alkanes (representing the epicuticular waxes) were mixed with different proportions of farnesyl linoleate. As skin greasiness in ‘Joangold’ develops, the linoleate and oleate esters (mainly the farnesyl linoleate) increase significantly, which is the most obvious chemical change in the epicuticular waxes. Meanwhile, the thermodynamic properties including the melt temperatures and the enthalpy decrease. In the simulation, the melt temperatures and the enthalpy of alkanes decreased with the increasing farnesyl linoleate. This confirms that the accumulation of farnesyl linoleate in ‘Jonagold’ can cause the decrease in thermodynamic properties of the epicuticular waxes. The results also suggest the esters may raise the wax fluidity of apples, in a manner similar to that of the plasticizer in the polymers.

AaPKAc Regulates Differentiation of Infection Structures Induced by Physicochemical Signals From Pear Fruit Cuticular Wax, Secondary Metabolism, and Pathogenicity of Alternaria alternata.

Alternaria alternata, the casual agent of black rot of pear fruit, can sense and respond to the physicochemical cues from the host surface and form infection structures during infection. To evaluate the role of cyclic AMP-dependent protein kinase (cAMP-PKA) signaling in surface sensing of A. alternata, we isolated and functionally characterized the cyclic adenosine monophosphate-dependent protein kinase A catalytic subunit gene (AaPKAc). Gene expression results showed that AaPKAc was strongly expressed during the early stages of appressorium formation on hydrophobic surfaces. Knockout mutants ΔAaPKAc were generated by replacing the target genes via homologous recombination events. We found that intracellular cAMP content increased but PKA content decreased in ΔAaPKAc mutant strain. Appressorium formation and infection hyphae were reduced in the ΔAaPKAc mutant strain, and the ability of the ΔAaPKAc mutant strain to recognize and respond to high hydrophobicity surfaces and different surface waxes was lower than in the wild type (WT) strain. In comparison with the WT strain, the appressorium formation rate of the ΔAaPKAc mutant strain on high hydrophobicity and fruit wax extract surface was reduced by 31.6 and 49.3% 4 h after incubation, respectively. In addition, AaPKAc is required for the hypha growth, biomass, pathogenicity, and toxin production of A. alternata. However, AaPKAc negatively regulated conidia formation, melanin production, and osmotic stress resistance. Collectively, AaPKAc is required for pre-penetration, developmental, physiological, and pathological processes in A. alternata.

Analytical study of phenotypic and biochemical attributes of onion cultivars in relation to infestation of onion thrips, Thrips tabaci

• Anatomical features of onion cultivar suppress the population of Thrips tabaci . • Fatty alcohols influenced the formation of epicuticular wax in onion cultivars. • Biochemical characteristics of Onion Gawran contribute in resistance to T. tabaci . • Onion Gawran showed tolerance while Onion White was susceptible against T. tabaci. Onion thrips is a major threat to onion crop throughout the world. It is a potential vector of Iris yellow spot virus and causes significant economic damage to bulb production. Phenotypic and biochemical traits of onion cultivars were assessed against Thrips tabaci . Onion Gawran LR-241 (OG) cultivar was tolerant against the infestation of T. tabaci whereas Onion White (OW) was susceptible. Number and size of stomata, cuticle thickness, cell wall thickness and surface wax of onion leaves were studied with the help of scanning electron microscope and quantitative and qualitative analysis was carried out to estimate epicuticular wax and other bio-chemical components through GC/MS. Onion Gawran has thick cell wall, sharp and dense wax crystals, wider central angle and small sized stomata compared to other cultivars. Epicuticular wax components of OG cultivar were heptacosane (5.2%), octacosanol-1 (9.2%), 2-methyl octacosane (4.2%), heptadecanol-1 (5.2%), hexacosanol-1 (4.2%), azulene, 1,4-dimethyl-7-(1-methylethyl) (36.9%), hexadecanoic acid (1.95%), heptadecane (4.2%), triacontanol-1 (5.8%) and hentriacontanone-16 (23.40%). Azulene, 1, 4-dimethy-l-7-(1-methy-l-ethyl) was only found 36.9% in OG but absent in other three cultivars. 2-methyl octacosane was absent in Poona Red Desi and OW cultivars. Hentriacontanone-16, 2-methyl octacosane, fatty alcohols (Octacosanol-1 and Triacontanol-1) and azulene, 1, 4-dimethy-l-7-(1-methy-l-ethyl) were effective in the formation of epicuticular wax in onion cultivars. It implies that phenotypic and biochemical characteristics of OG cultivar proved as resisting features to T. tabaci .

Comparative performance of bio-based coatings formulated with cellulose, chitin, and chitosan nanomaterials suitable for fruit preservation

Sustainable nanomaterials (SNMs) from wood, sugarcane and crab shell were prepared and used to coat selected fruits. The properties of SNMs and selected fruits were characterized and strawberry was used as an example to test antifungal activity and freshness preservation of the SNMs. The SNMs with their nano-structured morphology form strong shear-thinning dispersions for easy spraying on fruit surfaces. The fruit surface free energy was influenced by its surface morphology, predominant surface wax components, and cutin monomers. The antifungal activity of SNMs was influenced by their surface functional groups and particle size (crystals vs fibers). The coblend of wood nanocrystals (WCNCs) and chitosan nanofiber (CSNFs) exhibited the best antifungal property, which was comparable with the performance of the fungicide thiabendazole (80 mg L−1). The weight loss and color change of the WCNC/CSNF coated strawberries decreased by nearly half compared with the control samples, showing coating effectiveness on preserving fruit freshness.

Interrelation between Surface Wax Alkanes from Red Kidney Bean (Phaseolus vulgaris L.) Seeds and Adzuki Bean Weevil [Callosobruchus chinensis (F.)] (Coleoptera: Bruchidae)

Background: Callosobruchus chinensis (Fabricius) (Coleoptera: Bruchidae) is one of the major insect pests of Phaseolus vulgaris L. grains, commonly known as rajma seeds, in Europe and Asia including India. Infestations of these insects destroy majority of legume seeds including rajma which causes a great economic loss. Hence, a proper sustainable pest management measures are necessary for storage of rajma seeds. For this, the study aims to identify and quantify the n-alkane profile from the surface waxes of rajma seeds and their role as olfactory cue in C. chinensis. Individual synthetic alkane followed by the synthetic blends mimicking rajma seed surface wax n-alkanes as olfactory cue was also evaluated.Methods: Collected rajma seeds were solvent extracted to isolate surface waxes. The extract then fractioned by thin-layer chromatography and followed by gas chromatography-mass spectrometry analyses to purify, quantify and identify n-alkanes.Result: Rajma seeds’ surface waxes analysis revealed 18 n-alkanes between n-C15 and n-C33. The predominant alkanes were n-octacosane and n-hexadecane. n-Octadecane was the least abundant alkane in seeds. Total alkane content was 3502.67±12.82µg from 100 g (number 200 ± 5.13) seeds. Adult female C. chinensis elicited attraction towards the surface wax alkanes at concentrations of 0.5, 1, 2, 4 and 6 seed(s) equivalent of rajma seed(s) in the Y-tube olfactometer bioassay, but the highest attraction was observed at 6 seeds equivalent. Hence, a synthetic alkane blend resembling of 6 seeds equivalent, present in seeds’ surface wax alkane or a combination of nine (which elicited positive response) synthetic alkane blend resembling 6 seeds equivalent could be used as lures in developing baited trap in insect pest management programme.

Paper-based antibiotic sensor (PAS) relying on colorimetric indirect competitive enzyme-linked immunosorbent assay for quantitative tetracycline and chloramphenicol detection

Antibiotics such as tetracycline (TET) and chloramphenicol (CAP) are widely used, but their abuse leads to antibiotic residue which is harmful to human health. To obtain sensitive and accurate TET and CAP detections, we design the paper-based antibiotic sensor (PAS) relying on the colorimetric indirect competitive ELISA. PAS can be simply fabricated only via wax printing and surface modification, making the cost of single detection rather cheap as ∼0.15 US dollar; and additionally, it can be fabricated and conserved in good stability. Moreover, the PAS supporting smartphone application with the functions of image recording, correction and analysis is also designed for quantitative antibiotic detections. Using a series of standard solutions, it is proved that the PAS could reach the extremely low limits of detection as 0.5 ng/mL and 0.05 ng/mL as well as the wide effective linear detecting ranges as 1∼103 ng/mL and 0.1∼100 ng/mL in the TET and CAP detections, respectively. Moreover, using milk and fish samples, it was also verified that the PAS could quantify the TET and CAP concentrations accurately even in the practical applications.

Visual and olfactory cues for mate recognition in male pumpkin beetle, Aulacophora foveicollis

Visual and olfactory mediated cues play a major role in mate selection in different groups of insects. This study aimed to observe if there is any role of mate color (under different wavelengths) and/or cuticular hydrocarbons in mate selection of Aulacophora foveicollis. In this study, visual cues and olfactory cues showed a vital role for male A. foveicollis to find mates. Males preferred (81%) orange (similar body colour) coloured glass model than white (52%) and black (49%) under the visible spectrum; whereas under the UV spectrum white coloured model was more preferred (77%) than orange (60%) and black (48%) coloured. In contrast, unresponsive males were very high though white coloured model was still preferred (36.67%) than orange (24.44%) or black (22.22%) coloured under IR spectrum. It was also observed that body surface waxes can play alone an olfactory cue for male mate selection (attraction was 67%) from short distance. Under the visual spectrum, when both visual and olfactory cues were presented, attraction of males toward all orange (93%), white (74%), and black (71%) coloured glass bead model increased. Even under UV and IR spectra attraction increased when body surface extract of female was applied on the glass models though the preference was more towards white coloured model than orange as previous. Male A. foveicollis showed less preference towards black colour. These works provide evidence that both visuals and olfactory cues can act separately as well as synergistically to find mates for male insects. These findings will be helpful for sustainable pest management program.

Dry deposition of particulate matter and its associated soluble ions on five broadleaved species in Taichung, central Taiwan

Many studies have estimated particulate matter (PM) removal by urban trees using dry deposition models; however, few studies have quantified the accuracy of their results. Thus, this study investigated the dry deposition of PM and its associated soluble ions in five broadleaved species in three districts of Taichung, central Taiwan, through field experiments. The total suspended particulate (TSP) dry deposition flux on leaf surfaces varied with sampling time, site, and tree species. By contrast, single-factor effects were observed for PM10 and PM2.5. The average dry deposition velocities of TSPs, PM10, and PM2.5 were 0.63, 0.062, and 0.028 cm s−1, respectively. Moreover, the dry deposition velocities of sulfate and nitrate were estimated to be 0.186 and 0.194 cm s−1, respectively. A significant relationship was observed between the ambient concentration and the dry deposition flux for all size fractions of PM. By contrast, weak and negative correlations were found between particle deposition velocity and wind speed. The measured PM2.5 dry deposition velocity was approximately equal to the dry deposition velocity obtained with the i-Tree model (0.03 cm s−1), which indicated the promising application potential of i-Tree in Taiwan. Compound and rough leaves, such as leaves of the Taiwan golden-rain tree, intercepted a high amount of PM2.5, whereas the pongam tree, which has thin leaves and wax surfaces, exhibited the lowest TSP interception. Species difference mostly occurred in the dry deposition flux of nitrate rather than sulfate; however, the interception of sulfate by trees revealed the possibility of the long-range transport of air pollutants. The results of this study elucidate the dry deposition of PM and its associated soluble ions in real-world situations.

Adhesion and removal of E. coli K12 as affected by leafy green produce epicuticular wax composition, surface roughness, produce and bacterial surface hydrophobicity, and sanitizers

Contaminated leafy vegetables have been associated with high-profile outbreaks causing severe illnesses. A good understanding of the interactions between human pathogen and produce is important for developing improved food safety control strategies. Currently, the role played by produce surface physiochemical characteristics in such interactions is not well-understood. This work was performed to examine the effects of produce physiochemical characteristics, including surface roughness, epicuticular wax composition, and produce and bacteria surface hydrophobicity on attachment and removal of vegetative bacteria. Escherichia coli K12 was used as a model microorganism to evaluate attachment to and removal from five leafy green vegetables after washing with selected sanitizers. A detailed epicuticular wax component analysis was conducted and the changes of wax composition after sanitation were also evaluated. The results showed that E. coli K12 removal is positively correlated with alkanes, ketones, and total wax content on leaf surfaces. Vegetables with high surface wax content had less rough leaf surfaces and more bacterial removal than the low wax produce. Produce surface roughness positively correlated to E. coli K12 adhesion and negatively correlated to removal. The cells preferentially attached to cut vegetable surfaces, with up to 1.49 times more attachment than on leaf adaxial surfaces.