1,721,245 research outputs found
Shear-Induced Crystallization of Colloidal Particles for Narrow Stopband and High Reflectivity
No full textProduction of levulinic acid from wet microalgae in a biphasic one-pot reaction processs
No full textThis work addresses the conversion of wet microalgae to levulinic acid (LA) using a one-pot reaction system. Utilizing moisture in microalgae forms a biphasic system with an organic solvent of 1, 2-dichloroethane (DCE) is formed. This system enhances the LA yield by making an acidic environment through the decomposition of DCE in a small quantity and the recovery of products in each aqueous and organic phase. With lipid-richNannochloropsis gaditanaand carbohydrate-richChlorellaspecies, the effects of reaction variables of temperature, water content, and DCE dosage on the LA production were investigated. The LA yield was 30.13 wt% and 28.15 wt% based on the mass of total hexoses (43-47 wt% of convertible hexoses) for the two types of microalgae at 160 degrees C, while the yield of free fatty acids reached 90.13 w/w% at 180 degrees C based on the esterifiable lipid. This biphasic system facilitates the forward reaction and the product recovery for concurrent reaction and separation.
Scalable Inflatable Origami Robot Modules With Proprioceptive Closed-Loop Shape Control
No full textThis paper introduces a novel pneumatic origami module that embeds a proprioceptive closed-loop shape control through seamless sensor-hardware integration. Each module incorporates a spring along the stretchable airflow passage in conjunction with an individual solenoid valve, enabling intrinsic proprioceptive sensing via inductance measurement while maintaining pneumatic and mechanical reliability. The compact module, measuring 40 x 80 x 35 mm and weighing 55 g, features an adjustable height range of 29 to 71 mm under -25 to 25 kPa pressure. Experimental validation confirmed the notable performance of the module, with a consistent inflation time under various assembly combinations, a maximum extension force of 80.37 N, a low sensing hysteresis error of 7.58%, and sufficient durability to withstand 5,000 activation cycles. The resulting module assembly enables closed-loop shape control in both individual and synchronized multi-module operations, eliminating the need for external sensor attachments and demonstrating a highly responsive, precise, and adaptive shape-morphing process. This compliant, controllable, and straightforward module can serve as an unprecedented foundation for shape-programmable embodied intelligence in emerging autonomous robotic systems.
A Comparative Study of Reinforcement Learning and Analytical Methods for Optimal Control
No full textNumerous reinforcement learning (RL) algorithms have been introduced to resolve challenging tasks like game playing, natural language processing, and control. Particularly, RL can be used to find a good policy for control systems for which the optimal control sequence is difficult to find by analytical methods. This paper compares RL and analytical methods for optimal control in an inverted pendulum environment. Dynamic programming (DP) and model predictive control (MPC) are considered for the analytical methods. The control results of RL, DP, and MPC are qualitatively and quantitatively compared in terms of total reward, state response, and control sequence to investigate the relationships between them. Because they have similar problem formulations, the relationships can be explained by RL parameters: discounting factor and exploration rate. This comparative study is expected to provide insights to those studying RL algorithms and optimal control theories. © 2023 IEEE
Biocompatible amphiphilic Janus nanoparticles with enhanced interfacial properties for colloidal surfactants
No full textEmulsions in which water droplets are dispersed in fluorocarbon oil phase (W/F emulsions) serve as effective means to encapsulate bioactives and precisely execute reactions in confined space due to the gas permeability, chemical inertness, and biocompatibility offered by the continuous phase. While molecular surfactants consisting of perfluorinated polyether (PFPE) and polyethylene glycol (PEG) have been used to stabilize these emulsions, these surfactants cannot effectively prevent coalescence and cross-contamination between the neighboring droplets. Herein, we present Janus nanoparticles (F-SiO2-PEG) as biocompatible colloidal surfactants to achieve excellent stability in W/F emulsions. By utilizing monolayered wax colloidosomes as templates, we show that Janus silica nanoparticles with two distinctive surface wetting properties can be synthesized in high purity. Moreover, we demonstrate that additional PEGylation of these Janus particles allows these colloidal surfactants to strongly adhere at the W/F interface, granting excellent emulsion stability compared to the equivalent randomly functionalized nanoparticles and prevent non-specific adsorption of proteins. As the strategy outlined in this work is general, we anticipate that it can be further extended to prepare Janus particles with tailored interfacial properties for biomedical, cosmetics, and pharmaceutical applications involving emulsions.11Nsciescopu
Heterologous overproduction of oviedomycin by refactoring biosynthetic gene cluster and metabolic engineering of host strain Streptomyces coelicolor
No full textBackground: Oviedomycin is one among several polyketides known for their potential as anticancer agents. The biosynthetic gene cluster (BGC) for oviedomycin is primarily found in Streptomyces antibioticus. However, because this BGC is usually inactive under normal laboratory conditions, it is necessary to employ systematic metabolic engineering methods, such as heterologous expression, refactoring of BGCs, and optimization of precursor biosynthesis, to allow efficient production of these compounds. Results: Oviedomycin BGC was captured from the genome of Streptomyces antibioticus by a newly constructed plasmid, pCBA, and conjugated into the heterologous strain, S. coelicolor M1152. To increase the production of oviedomycin, clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 (CRISPR/Cas9) system was utilized in an in vitro setting to refactor the native promoters within the ovm BGC. The target promoters of refactoring were selected based on examination of factors such as transcription levels and metabolite profiling. Furthermore, genome-scale metabolic simulation was applied to find overexpression targets that could enhance the biosynthesis of precursors or cofactors related to oviedomycin production. The combined approach led to a significant increase in oviedomycin production, reaching up to 670 mg/L, which is the highest titer reported to date. This demonstrates the potential of the approach undertaken in this study. Conclusions: The metabolic engineering approach used in this study led to the successful production of a valuable polyketide, oviedomycin, via BGC cloning, promoter refactoring, and gene manipulation of host metabolism aided by genome-scale metabolic simulation. This approach can be also useful for the efficient production of other secondary molecules encoded by ‘silent’ BGCs.
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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