87 research outputs found
Recent advances in nanoporous materials for renewable energy resources conversion into fuels
The continuous growth in energy production from non-renewable resources in order to meet the ever-increasing energy demand has given rise to serious environmental issues and moving toward renewable energy resources is necessary. Heterogeneous catalysts play a key role in the conversion of renewable resources into fuels and chemicals. The performance of heterogeneous catalysts is directly linked to their surface area, since the number of catalytic sites as well as the activity of each catalytic site increase with increasing effective footprint area of a catalyst. Therefore, nanoporous heterogeneous catalysts are very attractive, owing to their high internal surface areas and high density of active sites generated by curved internal surfaces. The overall catalytic performance of nanoporous heterogeneous catalysts can reach orders of magnitude higher than that of planar catalysts counterparts. This paper reviews recent progress toward the applicability of three-dimensional bulk nanoporous metals and their composites in (electro-)catalytic conversion of renewable resources into fuels and value-added chemicals. The primary focus is given to metal-based materials fabricated through dealloying. Dealloyed nanoporous metals and their composites can be used either directly as high-performance (electro-)catalysts, or indirectly as three-dimensional bulk current collectors along with poorly conducting electro-catalyst materials. Limitations of these material systems such as cost, scalability, and long-term stability in-service are discussed.</p
Le regole del gioco: Primo incontro con l'ingegneria strategica
Cu particles decorated carbon composite
microspheres (CCMs) with
a unique sesame ball structure have been prepared by combining the
mass-producible spray drying technique with calcinations. The conventional
cuprammonium cellulose complex solution obtained by dissolving cellulose
in a cuprammonia solution has been applied as raw materials for the
preparation of CuÂ(NH<sub>3</sub>)<sub>4</sub><sup>2+</sup>/cellulose
complex microspheres via a spray drying process. The resulted CuÂ(NH<sub>3</sub>)<sub>4</sub><sup>2+</sup>/cellulose complex microspheres
are then transformed into the Cu particles homogeneously decorated
porous carbon spheres <i>in situ</i> by calcinations at
450 or 550 °C. The coordination effect between the CuÂ(NH<sub>3</sub>)<sub>4</sub><sup>2+</sup> species and the hydroxyl groups
of the cellulose macromolecules has been exploited for directing the
dispersion of the Cu particles in the resultant composite CCMs. The
antimicrobial effects of the CCMs are evaluated by determining the
minimum growth inhibitory concentrations using Staphylococcus
aureus and Escherichia coli as representatives, respectively. The CCMs show high efficiency
catalytic properties to the conversion of 4-nitrophenol to 4-aminophenol
using NaBH<sub>4</sub> as a reductant in a mild condition. The recyclability
and stability of the CCM catalysts have also been studied
Highly precision carbon dioxide acoustic wave sensor with minimized humidity interference
Extensive applications of carbon dioxide (CO2) in various fields, such as food industry, agricultural production, medical and pharmacological industries, have caused a great demand for high-performance CO2 sensors. However, most existing CO2 sensors suffer from poor performance in a wet environment and often cannot work accurately in a high humidity condition. In this study, a quartz crystal resonator (QCR) coated with a uniform layer of reduced graphene oxide (RGO) is proposed to detect both the concentrations of CO2 and water molecules simultaneously, which can be used to significantly minimize the humidity interference. Unlike the other common gas sensors, the RGO-based CO2 QCR sensor can be operated in different humidity levels and the concentration of CO2 can be quantified precisely and effectively. Moreover, it has a fast response (~0.4 s), which is also suitable for respiration monitoring. Our results showed that before and after a volunteer did a low-intensity exercise, the sensor could detect the differences of concentrations of CO2 in the exhaled breath (i.e., 4.50% and 5.15%, respectively)
Broadband laser polarization control with aligned carbon nanotubes
We introduce a simple approach to fabricate aligned carbon nanotube (ACNT)
device for broadband polarization control in fiber laser systems. The ACNT
device was fabricated by pulling from as-fabricated vertically-aligned carbon
nanotube arrays. Their anisotropic property is confirmed with optical and
scanning electron microscopy, and with polarized Raman and absorption
spectroscopy. The device was then integrated into fiber laser systems (at two
technologically important wavelengths of 1 and 1.5 um) for polarization
control. We obtained a linearly-polarized light output with the maximum
extinction ratio of ~12 dB. The output polarization direction could be fully
controlled by the ACNT alignment direction in both lasers. To the best of our
knowledge, this is the first time that ACNT device is applied to polarization
control in laser systems. Our results exhibit that the ACNT device is a simple,
low-cost, and broadband polarizer to control laser polarization dynamics, for
various photonic applications (such as material processing, polarization
diversity detection in communications), where the linear polarization control
is necessary.Comment: 5 pages, 6 figure
The prognostic value of whole-genome DNA methylation in response to Leflunomide in patients with Rheumatoid Arthritis
ObjectiveAlthough Leflunomide (LEF) is effective in treating rheumatoid arthritis (RA), there are still a considerable number of patients who respond poorly to LEF treatment. Till date, few LEF efficacy-predicting biomarkers have been identified. Herein, we explored and developed a DNA methylation-based predictive model for LEF-treated RA patient prognosis.MethodsTwo hundred forty-five RA patients were prospectively enrolled from four participating study centers. A whole-genome DNA methylation profiling was conducted to identify LEF-related response signatures via comparison of 40 samples using Illumina 850k methylation arrays. Furthermore, differentially methylated positions (DMPs) were validated in the 245 RA patients using a targeted bisulfite sequencing assay. Lastly, prognostic models were developed, which included clinical characteristics and DMPs scores, for the prediction of LEF treatment response using machine learning algorithms.ResultsWe recognized a seven-DMP signature consisting of cg17330251, cg19814518, cg20124410, cg21109666, cg22572476, cg23403192, and cg24432675, which was effective in predicting RA patientâs LEF response status. In the five machine learning algorithms, the support vector machine (SVM) algorithm provided the best predictive model, with the largest discriminative ability, accuracy, and stability. Lastly, the AUC of the complex model(the 7-DMP scores with the lymphocyte and the diagnostic age) was higher than the simple model (the seven-DMP signature, AUC:0.74 vs 0.73 in the test set).ConclusionIn conclusion, we constructed a prognostic model integrating a 7-DMP scores with the clinical patient profile to predict responses to LEF treatment. Our model will be able to effectively guide clinicians in determining whether a patient is LEF treatment sensitive or not
Coâevolutionary adaptations of Acinetobacter baumannii and a clinical carbapenemaseâencoding plasmid during carbapenem exposure
Abstract: OXAâ23 is the predominant carbapenemase in carbapenemâresistant Acinetobacter baumannii. The coâevolutionary dynamics of A. baumannii and OXAâ23âencoding plasmids are poorly understood. Here, we transformed A. baumannii ATCC 17978 with pAZJ221, a blaOXAâ23âcontaining plasmid from clinical A. baumannii isolate A221, and subjected the transformant to experimental evolution in the presence of a subâinhibitory concentration of imipenem for nearly 400 generations. We used population sequencing to track genetic changes at six time points and evaluated phenotypic changes. Increased fitness of evolving populations, temporary duplication of blaOXAâ23 in pAZJ221, interfering allele dynamics, and chromosomal locusâlevel parallelism were observed. To characterize genotypeâtoâphenotype associations, we focused on six mutations in parallel targets predicted to affect small RNAs and a cyclic dimeric (3Ⲡâ 5â˛) GMPâmetabolizing protein. Six isogenic mutants with or without pAZJ221 were engineered to test for the effects of these mutations on fitness costs and plasmid kinetics, and the evolved plasmid containing two copies of blaOXAâ23 was transferred to ancestral ATCC 17978. Five of the six mutations contributed to improved fitness in the presence of pAZJ221 under imipenem pressure, and all but one of them impaired plasmid conjugation ability. The duplication of blaOXAâ23 increased host fitness under carbapenem pressure but imposed a burden on the host in antibioticâfree media relative to the ancestral pAZJ221. Overall, our study provides a framework for the coâevolution of A. baumannii and a clinical blaOXAâ23âcontaining plasmid in the presence of imipenem, involving early blaOXAâ23 duplication followed by chromosomal adaptations that improved the fitness of plasmidâcarrying cells
Robust estimation of bacterial cell count from optical density
Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data
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