Efflux Pumps Might Not Be the Major Drivers of QAC Resistance in Methicillin‐Resistant Staphylococcus aureus

Quaternary ammonium compounds (QACs) are commonly used antiseptics that are now known to be subject to bacterial resistance. The prevalence and mechanisms of such resistance, however, remain underexplored. We investigated a variety of QACs, including those with multicationic structures (multiQACs), and the resistance displayed by a variety of Staphylococcus aureus strains with and without genes encoding efflux pumps, the purported main driver of bacterial resistance in MRSA. Through minimum inhibitory concentration (MIC)‐, kinetic‐, and efflux‐based assays, we found that neither the qacR/qacA system present in S. aureus nor another efflux pump system is the main reason for bacterial resistance to QACs. Our findings suggest that membrane composition could be the predominant driver that allows CA‐MRSA to withstand the assault of conventional QAC antiseptics.     

Effects of Jasmonate-Induced Defenses on Root-Knot Nematode Infection of Resistant and Susceptible Tomato Cultivars

Jasmonates, such as jasmonic acid (JA), are plant-signaling compounds that trigger induced resistance against certain pathogens and a broad range of arthropod herbivores. One goal of this study was to determine the effects of JA-dependent defenses in tomato on root-knot nematodes. Another was to determine if the artificial induction of these defenses could enhance nematode control on plants that carry Mi-1.2, a nematode resistance gene that is present in many tomato cultivars. At moderate soil temperatures, Mi-1.2 can effectively suppress reproduction of most isolates of the common root-knot nematode species Meloidogyne javanica, M. incognita, and M. arenaria. Mi-mediated resistance has its limitations, however. Mi-1.2 is reported to lose its effectiveness at soil temperatures above 28°C, and certain virulent nematode isolates can overcome resistance even at moderate soil temperatures. This study used a foliar application of JA to activate induced resistance in two near-isogenic lines of tomato (Lycopersicon esculentum) with and without Mi-1.2, and evaluated the effects of induced resistance at moderate soil temperatures on one avirulent nematode isolate (M. javanica isolate VW4) and two virulent isolates (M. javanica isolate VW5 and M. incognita isolate 557R). In addition, the effects of induced resistance on avirulent nematode performance were examined at a high temperature (32°C). The results indicate that JA application induces a systemic defense response that reduces avirulent nematode reproduction on susceptible tomato plants. Furthermore, JA-dependent defenses proved to be heat-stable, whereas the effects of Mi-mediated resistance were reduced but not eliminated at 32°C. JA treatment enhanced Mi-mediated resistance at high temperature, but did not suppress either of the virulent nematode isolates tested.     

Glucosinolate and Trichome Defenses in a Natural Arabidopsis lyrata Population

Glucosinolates (GS) and trichomes contribute to plant resistance against insect herbivores in the model Arabidopsis thaliana. The functional and genetic characteristics of herbivore defense, however, can differ even between closely related species. In a quantitative genetic experiment with the out-crossing perennial Arabidopsis lyrata spp. petraea, we measured constitutive GS composition, trichome density, leaf thickness, and plant resistance in four different herbivore interactions. In a single population of A. lyrata, we found heritable variation for trichome density as well as GS amount and carbon side-chain elongation ratios associated with activity in methylthioalkylmalate synthase (MAM). Unexpectedly, heritabilities for indole GS in A. lyrata were high and less affected by differences in plant age and environment than aliphatic GS. We found significant heritability in plant resistance to the specialist Plutella xylostella and generalist Trichoplusia ni, but not to the specialists Pieris brassicae and Phyllotreta cruciferae. Analyses of phenotypic and genetic correlations between candidate defense traits and insect resistance suggested that A. lyrata resistance was conferred by a combination of indole GS amount and trichome density, and, to a lesser extent, aliphatic GS ratios and leaf thickness. Variation in the most abundant compound, the aliphatic 3-hydroxypropyl GS, had little impact on A. lyrata herbivore resistance. The contribution of defense traits to resistance depended on the experimental herbivory context, and resistances were weakly correlated. A diversified defense strategy is likely to be important for long-lived individuals of A. lyrata that are subject to attack by many different herbivores in nature.     

Structure–Function Studies on IMD-0354 Identifies Highly Active Colistin Adjuvants

Infections caused by multidrug-resistant (MDR) bacteria, particularly Gram-negative bacteria, are an escalating global health threat. Often clinicians are forced to administer the last-resort antibiotic colistin; however, colistin resistance is becoming increasingly prevalent, giving rise to the potential for a situation in which there are no treatment options for MDR Gram-negative infections. The development of adjuvants that circumvent bacterial resistance mechanisms is a promising orthogonal approach to the development of new antibiotics. We recently disclosed that the known IKK-β inhibitor IMD-0354 potently suppresses colistin resistance in several Gram-negative strains. In this study, we explore the structure–activity relationship (SAR) between the IMD-0354 scaffold and colistin resistance suppression, and identify several compounds with more potent activity than the parent against highly colistin-resistant strains of Acinetobacter baumannii and Klebsiella pneumoniae.     

Towards a rapid near-infrared technique for prediction of resistance to sugarcane borerEldana saccharina walker (Lepidoptera: Pyralidae) using stalk surface wax

Multiple regression predictive models based on data acquired by near-infrared (NIR) spectrophotometry suggest that stalk surface wax components contribute towards resistance toEldana saccharina Walker in sugarcane. At least 35 sugarcane clones of known resistance were required to calibrate a predictive model that accounted for approximately 54% of the variation in resistance toEldana. Wavelengths chosen in multiple regression models suggest that alcohols and carbonyls are important in the wax contribution. Through the use of wax fractionation and gas chromatography, a high alcohol/aldehyde ratio and shorter carbon chain length appears to be associated with resistance. The use of NIR in the screening of wild germplasm and the early screening of breeding material for resistance, without prior knowledge of the biochemical mechanisms involved, is an exciting prospect. However, cause-and-effect relationships remain to be shown.     

The impedance of alkaline manganese cells and their relationship to cell performance. II. Correlation with short-circuit current and initial pulse discharge behaviour

The theory relating the short-circuit or flash current behaviour of alkaline manganese and Leclanché cells to their internal resistance values has been reviewed. It is shown that the relationship SCC=VOC/R _i pertains for both cell types where SCC is the short-circuit current, VOC the voltage at open circuit andR _i the internal cell resistance which is a composite of several components. In the case of alkaline manganese cells these can be independently resolved usingin situ impedance measurements into three major components: the electrolyte resistance within the anode-separator-cathode porous matrices; the resistance of the cathode (MnO₂ + graphite mixture); and the resistance of the nickel oxide layer on the surface of the nickel-plated steel positive current collector (cell container). In the case of Leclanché cells three components also control the internal resistance, but these cannot be so easily resolved. They are: the electrolyte resistance within the cathode separator matrices; the resistance of the cathode (MnO₂ + carbon); and contact resistance between the cathode and positive current collector (carbon rod). Equivalent circuits for both alkaline manganese and Leclanché cells are proposed.Galvanostatic 2-A pulse discharge measurements have been made on LR20 alkaline manganese cells and directly correlated with the impedance measurements, thus providing confirmatory evidence for the equivalent circuit proposed. It is shown that the resistance calculated from the potential drop at 10 ms correlates closely with the internal resistance and hence short-circuit current value. It is also shown that ohmic polarization at long times (10 s) constitutes 67% of the total potential loss within the cell. Hence for a typical repetitive 2 A/10 s pulse discharge regime, the discharge life is critically dependent on the cell internal resistance value.     

Inheritance Of Resistance To Mammalian Herbivores and Of Plant Defensive Chemistry In A <Emphasis Type="Italic">Eucalyptus</Emphasis> Species

Hybridization in plants provides an opportunity to investigate the patterns of inheritance of hybrid resistance to herbivores, and of the plant mechanisms conferring this resistance such as plant secondary metabolites. We investigated how inter-race differences in resistance of Eucalyptus globulus to a generalist mammalian herbivore, Trichosurus vulpecula, are inherited in their F₁ hybrids. We assessed browsing damage of three-year-old trees in a common environment field trial on four hybrid types of known progeny. The progency were artificial intra-race crosses and reciprocal inter-race F₁ hybrids of two geographically distinct populations (races) of E. globulus; north-eastern Tasmania and south-eastern Tasmania. Populations of trees from north-eastern Tasmania are relatively susceptible to browsing by T. vulpecula, while populations from south-eastern Tasmania are more resistant. We assessed the preferences of these trees in a series of paired feeding trials with captive animals to test the field trial results and also investigated the patterns of inheritance of plant secondary metabolites. Our results demonstrated that the phenotypic expression of resistance of the inter-race F₁ hybrids supported the additive pattern of inheritance, as these hybrids were intermediate in resistance compared to the pure parental hybrids. The expression of plant secondary metabolites in the F₁ hybrids varied among groups of individual compounds. The most common pattern supported was dominance towards one of the parental types. Together, condensed tannins and essential oils appeared to explain the observed patterns of resistance among the four hybrid types. While both chemical groups were inherited in a dominant manner in the inter-race F₁ hybrids, the direction of dominance was opposite. Their combined concentration, however, was inherited in an additive manner, consistent with the phenotypic differences in browsing.     

Inheritance Of Resistance to Mammalian Herbivores and of Plant Defensive Chemistry in an <Emphasis Type="Italic">Eucalyptus</Emphasis> Species

Hybridization in plants provides an opportunity to investigate the patterns of inheritance of hybrid resistance to herbivores, and of the plant mechanisms conferring this resistance such as plant secondary metabolites. We investigated how inter-race differences in resistance of Eucalyptus globulus to a generalist mammalian herbivore, Trichosurus vulpecula, are inherited in their F₁ hybrids. We assessed browsing damage of 3-year-old trees in a common environment field trial on four hybrid types of known progeny. The progeny were artificial intra-race crosses and reciprocal inter-race F₁ hybrids of two geographically distinct populations (races) of E. globulus north-eastern Tasmania and south-eastern Tasmania. Populations of trees from north-eastern Tasmania are relatively susceptible to browsing by T. vulpecula, while populations from south-eastern Tasmania are more resistant. We assessed the preferences of these trees in a series of paired feeding trials with captive animals to test the field trial results and also investigated the patterns of inheritance of plant secondary metabolites. Our results demonstrated that the phenotypic expression of resistance of the inter-race F₁ hybrids supported the additive pattern of inheritance, as these hybrids were intermediate in resistance compared to the pure parental hybrids. The expression of plant secondary metabolites in the F₁ hybrids varied among major groups of individual compounds. The most common pattern supported was dominance towards one of the parental types. Together, condensed tannins and essential oils appeared to explain the observed patterns of resistance among the four hybrid types. While both chemical groups were inherited in a dominant manner in the inter-race F₁ hybrids, the direction of dominance was opposite. Their combined concentration, however, was inherited in an additive manner, consistent with the phenotypic differences in browsing.     

Impedance Spectroscopy Characterization in Bipolar Ta/MnOx/Pt Resistive Switching Thin Films

Impedance spectroscopy was applied to MnO_x‐based thin films prepared in symmetric and asymmetric electrode configurations, i.e., Pt/MnO_x/Pt and Ta/MnO_x/Pt, respectively. Equivalent circuit analysis suggests the presence of higher resistance surface layers adjacent the electrodes, in addition to a higher conductivity component at central portions of the MnO_x thin films. The asymmetric configuration enables the Ta/MnO_x interfacial layer to facilitate the redox transport of oxygen ions, where significant changes in resistance with the electric field are responsible for the higher on/off resistance ratio in Ta/MnO_x/Pt. The higher dielectric constant and bias‐dependent capacitance and resistance support the coexistence of both oxidized surfaces and interfacial layers.     

Anin situ method for determination of internal resistances in fuel cells

Anin situ method has been demonstrated for the determination of internal resistances in electrochemical energy converters without disturbing the test conditions or interrupting the cell operation. While operating the cell at a desired current, the apparent internal resistance and cell voltage are measured following a standardized procedure. A mathematical equation has been derived to calculate the true internal resistance from the observed resistance, cell voltage and operating current. A typical example is given to show the excellent agreement of thein situ measured internal resistances with those obtained by a current interruption technique.     

Root-mediated effects in carrot resistance to the carrot fly,Psila rosae

Field experiments on two different soil types in Ireland assessed the extent and mechanisms of resistance toPsila rosae (F.), the carrot fly, with emphasis on the role of the carrot root. Ten carrot cultivars gave consistent results in terms of resistant and susceptible cultivars. Nonpreference oviposition was confirmed as a mechanism, and the use of egg traps, providing differential exposure of the main root, showed this was regulated by root factors, probably chemical constituents. Independent main root resistance to the larva was also confirmed, and this effect was established as consistent with a chemically mediated nonpreference. Antibiosis by the root was demonstrated. Such effects in three different modes indicate that main root properties are crucial in carrot resistance toPsila and suggest a pervasive influence of root chemicals on such resistance.     

Herbivore- and Elicitor-Induced Resistance in Rice to the Rice Water Weevil (<Emphasis Type="Italic">Lissorhoptrus oryzophilus</Emphasis> Kuschel) in the Laboratory and Field

Feeding by herbivores can change plants in ways that make them more resistant to subsequent herbivory. Such induced responses are better-studied in a number of model dicots than in rice and other cereals. In a series of greenhouse and field experiments, we assessed the effects of prior herbivory by the fall armyworm, Spodoptera frugiperda (J.E. Smith) and of exogenous applications of jasmonic acid (JA) on the resistance of rice plants to the rice water weevil, Lissorhoptrus oryzophilus (Kuschel), the major pest of rice in the United States. Prior feeding by S. frugiperda and treatment of plants with exogenous JA resulted in increases in the resistance of plants to the weevil. Increases in resistance were manifested as reduced numbers of eggs and first-instars associated with armyworm-injured or JA-treated plants relative to control plants. In field experiments, there was a transient but significant reduction in the number of immature L. oryzophilus on JA-treated plants relative to untreated plants. To our knowledge, this is the first example of direct induced resistance in rice demonstrated in small-plot field experiments. We discuss the potential for the use of elicitor induced resistance in rice.     

Extraction resistance and mechanism of a macromolecular hindered phenol antioxidant in natural rubber

Due to low thermal stability, poor migration, and extraction resistances, the antioxidant with low molecular weight is easy to physically lose during processing and long‐term service, and its applications are severely restricted. To increase the molecular weight of antioxidant is one of the promising methods to overcome such drawbacks. In this study, the extraction resistance of a macromolecular antioxidant, namely polyhydroxylated polybutadiene containing thioether binding 2,2′‐thiobis(4‐methyl‐6‐tert‐butylphenol) (PHPBT‐b‐TPH), was investigated by extraction resistance test and equilibrium swelling experiment. The results exhibited that the PHPBT‐b‐TPH offered much better extraction resistance in natural rubber (NR) than the low molecular weight antioxidant TPH. In addition, the extraction resistance of hydroxyl‐terminated polybutadiene (HTPB), polyethylene glycol (PEG), and polypropylene glycol (PPG) in NR were also compared to study the extraction mechanism of the PHPBT‐b‐TPH. It was found that the higher molecular weight of PHPBT‐b‐TPH and the co‐vulcanization between PHPBT‐b‐TPH and NR were the main reasons for the excellent extraction resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44905.     

Ionic conduction in polymer films: II. Inhomogeneous structure of varnish films

Ionic conduction in polymer films is of two types. Inverse conduction, I, occurs when the resistance runs counter to that of the external solution, and Direct conduction, D, when the resistance follows that of the external solution. The distribution of areas having D properties has been established for films of a pentaerythritol alkyd, a phenol-formaldehyde tung oil and a polyamide-cured expoxide varnish, and it is shown that D conduction cannot be ascribed to capillaries, unless they are of molecular dimensions. It is concluded that these films have a very heterogeneous structure and that I and D areas are brought about by differences in crosslinking density within the film.     

Role of cucurbitacin C in resistance to spider mite (Tetranychus urticae) in cucumber (Cucumis sativus L.)

Cucurbitacins are bitter triterpenoid compounds that are toxic to most organisms and occur widely in wild and cultivated Cucurbitaceae. The only cucurbitacin identified in Cucumis sativus is cucurbitacin C. The bitter taste of cucumber has been correlated with resistance to the spider mite Tetranychus urticae, but a quantitative relationship has not been established. We determined the spider mite resistance and cucurbitacin C content in the dihaploid progeny derived from the F₁ generation of a cross between a bitter, spider-mite-resistant cucumber line and a bitter-free, spider-mite-susceptible line. The ratio of the number of bitter to bitter-free dihaploids conformed to the expected 1:1 ratio, based on a monogenic segregation pattern. Genetic analysis ascribed 69% of the variance of the difference in spider mite survival rate to the bitterness locus. Within the group of bitter dihaploids, cucurbitacin C content was significantly correlated with spider mite resistance. Thus, a quantitative relationship between cucurbitacin C content and spider mite resistance could be established.     

Novel gas sensor from polymer‐grafted carbon black: Vapor response of electric resistance of conducting composites prepared from poly(ethylene‐block‐ethylene oxide)‐grafted carbon black

A crystalline block copolymer of poly(ethylene‐block‐ethylene oxide) (PE‐b‐PEO) was successfully grafted onto a carbon black surface by direct condensation of its terminal hydroxyl groups with carboxyl groups on the surface using N,N′‐dicyclohexylcarbodiimide as a condensing agent. The electric resistance of the composite from PE‐b‐PEO (PEO content is above 50 wt %)‐grafted carbon black drastically increased to 10⁴–10⁶ times of the initial resistance in a vapor of dichloromethane, chloroform, tetrahydrofuran, and carbon tetrachloride, which are good solvents for PE‐b‐PEO, and returned immediately to the initial resistance when the composite was transferred in dry air. However, the change of the electric resistance of these composites was less than one‐tenth in a poor solvent vapor at the same condition. The response of the electric resistance was reproducible and stable even after exposure to a good solvent vapor and dry air with 30 cycles or exposure to the vapor over 24 h. The effect of PEO content on the vapor response was also investigated. The composite from PE‐b‐PEO‐grafted carbon black responded to the low vapor concentration with a linear relationship between the electric resistance and the concentration of the vapor in dry air. This indicates that the composite can be applied as a novel gas sensor. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2437–2447, 2000     

Assessment of the Thermal Shock Resistance Figures of Merit of Al2W3O12, a Low Thermal Expansion Ceramic

Zero thermal expansion phases from the A₂M₃O₁₂ and related thermomiotic (negative thermal expansion) families are natural candidates for applications where high thermal shock resistance is the principal requirement. However, their mechanical properties are largely unknown, as are sintering routes for consolidation into bulk objects. Therefore, a preliminary case study on the effect of microstructure on mechanical strength and thermal shock resistance of Al₂W₃O₁₂ has been performed. All thermal and mechanical properties necessary for calculation of thermal shock resistance figures of merit have been measured experimentally. Tensile strengths were measured by four‐point flexural test and analyzed by the Weibull method. The microstructure of bulk specimens, conventionally pressureless sintered at 1273 K, was coarse‐grained, containing microcracks, and inhomogeneous with respect to density due to the agglomeration of nanoparticles, and led to low tensile strength. Despite this, thermal shock resistance features evaluated for Al₂W₃O₁₂ are encouraging. The Hasselman figure of merit for thermal shock resistance for severe heating conditions of Al₂W₃O₁₂ was 120 K, comparable to sapphire, the state‐of‐the‐art material for some advanced thermal shock resistance applications. This study shows that zero thermal expansion phases from the A₂M₃O₁₂ family have potential to be transformed into useful engineering ceramics for thermal shock resistance applications.     

Primary and secondary distributions after a small-amplitude potential step at disk electrode coated with conducting film

The set of equations and boundary conditions for the “primary potential/current distribution” after a small-amplitude potential step has been analyzed for a film-coated disk electrode in contact with an electrolyte. The solution of these equations provides the overall short-time resistance of this system, R_tot, which is determined by the short-time resistance of the electrolyte solution in contact with the bare disk electrode, R_s, and the short-time film resistance to the current passage in the normal direction, (r_o, disk radius; L_f, film thickness; κ_f, its specific conductivity). The deviation of R_tot from the sum of these resistances, R_s + R_f, originates from a three-dimensional potential/current distribution in solution. Procedures to calculate the film resistance and its specific conductivity on the basis of the measured values of R_tot and R_s have been proposed. Similar analysis has also been carried out for the “secondary potential/current distribution” in the same system. The overall resistance for this regime is related to the short-time solution resistance, R_s, and to the total resistance of the electrode, equal to the sum of the resistance, R_f, and two interfacial resistances, R_m/f and R_f/s. A method to determine the bulk-film parameters, R_f and κ_f, from data for the secondary distribution is discussed. Advantages and restrictions of the proposed route to transport parameters of a film at the electrode surface are analyzed, in comparison with existing methods of their determination.     

The electrical resistance of sodium aluminate solutions

Specific resistance data for sodium aluminate solutions at 25° have been obtained. The equation: p = 6.353 + 3.466 R-5.0185 S × 10^?2 + (1.517 + 1.154 R)S² × 10^?4 where p = specific resistance (ohm-cm) S = Na₂O concentration (g/l) R = mass ratio Al₂O₃/Na₂O expresses the effect of sodium hydroxide and alumina concentrations on the specific resistance. The effects of: (a) presence of carbonate and (b) temperature are also discussed. In association with density measurements, specific resistance provides a rapid and continuous means of determining the composition of sodium aluminate solutions.     

Improving the UV resistance of aromatic poly(l,3,4‐oxadiazole) fiber using a disperse dye modified with octavinyl POSS. Part 1: Preparation of dye and dyeing

Modified dyes were obtained by grafting of disperse dyes with octavinyl polyhedral oligomeric silsesquioxanes (POSS) using a Friedel‐Crafts alkylation reaction and using different ratios of POSS and the original disperse dye. The modified dyes are used to dye aromatic poly(l,3,4‐oxadiazole) (p‐POD) fiber to improve its UV resistance. Then the structure of the modified dye is characterized by Fourier transform infrared spectroscopy and NMR, and the effects of the structure of the modified dye and the dyeing conditions on the UV resistance and color strength (K/S value) of the dyed samples are investigated. The results indicated that the UV adsorption peaks of the modified dye solutions are located at the specified UV wavelengths. The UV resistance of the p‐POD fiber dyed with the modified dye (1:3) can be effectively improved, and the dyed p‐POD fiber can obtain a higher K/S value simultaneously. During the dyeing process, increasing the dyeing temperature and prolonging the dyeing time are both beneficial in improving the anti‐UV ability of the dyed p‐POD fiber; these changes can effectively promote the fixation of dye molecules into p‐POD fibers due to stimulating the motion of dye molecules and p‐POD macromolecules. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44745.