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The phenomenon of antimicrobial resistance represents a major public health risk. The activity of integral membrane transporter proteins contributes to antimicrobial resistance in pathogenic bacteria and proton gradient-driven multidrug efflux representatives of the major facilitator superfamily (MFS) of secondary transporters are the dominant antimicrobial efflux proteins in Escherichia coli. In many, but not all, of the characterized MFS multidrug transporters, an aspartic acid residue at position D+5 of the conserved signature Motif A is essential for transport activity. The present work extends those studies to the E. coli MFS multidrug/H+ antiporter MdtM and used a combination of mutagenesis, expression studies, antimicrobial resistance assays, and transport activity measurements to reveal that a negatively charged residue at position D+5 is critical for MdtM transport function.
Quantitative phase analysis is one of the major applications of X-ray powder diffraction. The essential principle of quantitative phase analysis is that the diffraction intensity of a component phase in a mixture is proportional to its abundance. Nevertheless, the diffraction intensities of the component phases cannot be compared with each other directly since the coherent scattering power per unit cell (or chemical formula) of each component phase is usually different. The coherent scattering power per unit cell of a crystal is well represented by the sum of the squared structure factors, which cannot be calculated directly when the crystal structure data is unavailable. Presented here is a way to approximate the coherent scattering power per unit cell based solely on the unit cell parameters and the chemical contents. This approximation is useful when the atomic coordinates for one or more of the phases in a sample are unavailable. An assessment of the accuracy of the approximation is presented. This assessment indicates that the approximation will likely be within 10% when X-ray powder diffraction data is collected over a sufficient portion of the measurable pattern.
Metamaterials, including their two-dimensional counterparts, are composed of subwavelength-scale artificial particles. These materials have novel electromagnetic properties, and can be artificially tailored for various applications. Based on metamaterials and metasurfaces, many abnormal physical phenomena have been realized, such as negative refraction, invisible cloaking, abnormal reflection and focusing, and many new functions and devices have been developed. The effective medium theory lays the foundation for design and application of metamaterials and metasurfaces, connecting metamaterials with real world applications. In this Element, the authors combine these essential ingredients, and aim to make this Element an access point to this field. To this end, they review classical theories for dielectric functions, effective medium theory, and effective parameter extraction of metamaterials, also introducing front edge technologies like metasurfaces with theories, methods, and potential applications. Energy densities are also included.
This Element introduces the exotic wave phenomena arising from the extremely small optical refractive index, and sheds light on the underlying mechanisms, with a primary focus on the basic concepts and fundamental wave physics. The authors reveal the exciting applications of ENZ metamaterials, which have profound impacts over a wide range of fields of science and technology. The sections are organized as follows: in Section 2, the authors demonstrate the extraordinary wave properties in ENZ metamaterials, analyzing the unique wave dynamics and the resulting effects. Section 3 is dedicated to introducing various realization methods of the ENZ metamaterials with periodic and non-periodic styles. The applications of ENZ metamaterials are discussed in Sections 4 and 5, from the perspectives of microwave engineering, optics, and quantum physics. The authors close in Section 6 by presenting an outlook on the development of ENZ metamaterials and discussing the key challenges addressed in future works.
X-ray powder diffraction data, unit-cell parameters, and space group for rivaroxaban, C19H18ClN3O5S, are reported [a = 9.010(3) Å, b = 10.986(6) Å, c = 11.230(1) Å, α = 63.439(5)°, β = 74.355(4)°, γ = 78.133(3)°, unit-cell volume V = 952.87 Å3, Z = 2, ρcal = 1.519 g cm−3, and space group P1]. All measured lines were indexed and are consistent with the P1 space group. No detectable impurities were observed.
It is often assumed that consumers’ willingness to pay (WTP) for eco-labeled products in research settings is not because of a desire for environmental protection, but rather that they are socially compelled to make decisions that reflects favorably on them, limiting the validity of findings. Using a second-price Vickrey experimental auction, this study found higher WTP for an eco-labeled product than a comparable good, but that social desirability bias, measured by the Marlowe–Crowne Social Desirability Scale, was not a significant predictor of WTP. Instead, environmental consciousness, environmental knowledge, education, and available information were stronger predictors of WTP for eco-labeled goods.
Previous research has demonstrated that unique names increased in Japan, which shows a rise in uniqueness-seeking and individualism. To increase the validity of the prior findings, it is important to confirm the robustness of their results. Therefore, this study examined another indicator of historical changes in names in Japan. Specifically, I investigated whether the rates of common names decreased in Japan between 2004 and 2018. The dataset used in the previous study was analyzed. The results consistently showed that the rates of common names decreased for both boys and girls for the period. These results were consistent with the previous research, which further increases the validity of the finding that Japanese culture became more individualistic.
The anthelmintic dinitroaniline oryzalin interferes with the formation of microtubules and inhibits meiosis and mitosis in nematodes. Exposure to oryzalin resulted in deterioration in morphology of the oocytes and loss of synaptonemal complexes at meiotic prophase I. The nuclear matrix and envelope were poorly formed, and the central rachis was diminished. These results provide the basis for the loss of fecundity after treatment with the oryzalin resulting in control of parasitic nematodes.
In this study, we define the cardinal temperatures and thermal time for germination and emergence of pigeonpea genotypes. Seeds of six genotypes were subjected to constant temperatures ranging between 5 and 50°C in petri dishes with filter paper (germination) and with media (emergence) were placed in a thermal gradient plate. A nonlinear bent-stick model fitted to the rate of development to germination and emergence resulted in parameters predicting cardinal temperatures including base (Tb), optimum (To), maximum (Tm), and thermal time. Estimated Tb for 50% germination and emergence were 8.4 and 10.8°C, respectively, with no significant differences between genotypes. Optimum temperatures were 33.8 and 37.9°C for germination and emergence, respectively, with genotypes differing significantly. Thermal time for 50% germination and emergence varied significantly among genotypes. The results suggest that genotypic responses to the temperature are typical for their tropical origin and hence their suitability for cropping in summer dominant rainfall regions insubtropical Australia.
Discover a rigorous treatment of aerogels processing and techniques for characterization with this easy-to-use reference. Presents the basics of aerogel synthesis and gelation to open porous nanostructures, and the processing of wet gels like ambient and supercritical drying leading to aerogels. Describes their essential properties with their measurement techniques and theoretical models used to analyse relations to their nanostructure. Linking the fundamentals and with practical applications, this is a useful toolkit for advanced undergraduates, and graduate students doing research in material and polymer science, physical chemistry, and chemical and environmental engineering.
Compressible magnetohydrodynamic (MHD) turbulence is a common feature of astrophysical systems such as the solar atmosphere and interstellar medium. Such systems are rife with shock waves that can redistribute and dissipate energy. For an MHD system, three broad categories of shocks exist (slow, fast, and intermediate); however, the occurrence rates of each shock type are not known for turbulent systems. Here, we present a method for detecting and classifying the full range of MHD shocks applied to the Orszag–Tang vortex. Our results show that the system is dominated by fast and slow shocks, with far less-frequent intermediate shocks appearing most readily near magnetic reconnection sites. We present a potential mechanism that could lead to the formation of intermediate shocks in MHD systems, and study the coherency and abundances of shocks in compressible MHD turbulence.
Evidence demonstrates increased vulnerability to thoughts and behaviors related to suicide (i.e., suicidal ideation) in students. This study examined the interaction between insomnia-symptoms and student-status (students vs. non-students) on reports of suicidal thoughts of behaviors. A total of 363 (N = 363) university students and 300 (N = 300) members of the general population provided complete data on measures of insomnia-symptoms and suicidal ideation. Students indicated greater reports of both total and lifetime ideation while also considering suicidal behavior within the past year. However, no differences were observed in reports of possible future attempt(s) and the disclosure of suicidal thoughts and behaviors to another person. Moreover, students presenting concurrent symptoms of insomnia reported significantly elevated levels of suicidal ideation relative to nonstudents. These outcomes highlight the possible role of insomnia symptoms in accentuating suicidal thoughts and behaviors in the student population.
Proton electrochemical gradient-driven multidrug efflux activity of representatives of the major facilitator superfamily (MFS) of secondary active transporters contributes to antimicrobial resistance of pathogenic bacteria. Integral to the mechanism of these transporters is a proposed competition between substrate and protons for the binding site of the protein. The current work investigated the competition between protons and antimicrobial substrate for binding to the Escherichia coli MFS multidrug/H+ antiporter MdtM by measuring the quench of intrinsic protein fluorescence upon titration of substrate tetraphenylphosphonium into a solution of purified MdtM over a range of pH values between pH 8.8 and 5.9. The results, which revealed that protons inhibit binding of substrate to MdtM in a competitive manner, are consistent with those reported in a study on the related MFS multidrug/H+ antiporter MdfA and provide further evidence that competition for binding between substrate and protons is a general feature of secondary multidrug efflux.