Since their introduction in 2004, deep eutectic solvents (DESs) have attracted interest in different fields of chemistry. In the case of biomass, DESs are particularly interesting, not only because ...of their low cost and biodegradability, but also due to their unique property to interact with hydrogen‐bond donors such as renewably sourced polyols or carboxylic acids. Through selected examples, we report the contribution of DESs for the dissolution of biomass, the extraction/purification of bioderived chemicals, and the conversion of carbohydrates to furanic derivatives. In all examples, we discuss how the DES can impact the selectivity of a chemical process and the limitations associated with the use of DES. In particular, impact of the DES viscosity on extraction, the recovery and recycling of DES, and the stabilization of chemical intermediates in DES are among the key aspects that are discussed.
More than just a solvent: The advantages, disadvantages, and challenges offered by the use of deep eutectic solvents (DESs) for biomass valorization are summarized.
To investigate metal oxide surface catalysis, determining an appropriate Hubbard U-correction term is a challenge for the density functional theory (DFT) community and identifying realistic reaction ...intermediates and their corresponding X-ray photoelectron spectroscopy (XPS) shifts is a challenge for experimental researchers, when these methods are used independently. In this study, using CuO as a model transition metal oxide, we demonstrate that when DFT and XPS are applied synergistically, the determination of the U value and the identification of adsorbate/intermediate species on the surface (and their XPS shifts) can be done simultaneously. The experimental O 1s spectra of the as-synthesized CuO 2D-nanoleaves shows the presence of four different peaks with core level binding energies (CLBEs) of 529.7, 531.4, 533.2, and 534.6 eV. DFT is used to calculate the CLBE shifts for probable adsorbed moieties, in various adsorption configurations, on both, clean and vacancy defect containing surfaces. Comparison of experimental and theoretical CLBEs across the entire U value range of 0–9 eV narrows down the list to only four moieties, namely, O2 in the η1(O) configuration, H2O at the surface oxygen vacancy site, and adsorbed HCO3 and HCO2 (resembling adsorbed HCO3). Finally, the U value of 4–4.5 eV reproduces the experimental CLBE shifts correctly and thus, establishes these experimental XPS spectral peaks to the adsorbates and their geometries. The integrated approach elucidated in this article, results in the identification of adsorbates/intermediates (and their CLBEs) for the experimental XPS spectral analysis and the determination of an appropriate U value concurrently, to study metal oxide surface catalysis.
Distributed denial-of-service (DDoS) attacks remain a major security problem, the mitigation of which is very hard especially when it comes to highly distributed botnet-based attacks. The early ...discovery of these attacks, although challenging, is necessary to protect end-users as well as the expensive network infrastructure resources. In this paper, we address the problem of DDoS attacks and present the theoretical foundation, architecture, and algorithms of FireCol. The core of FireCol is composed of intrusion prevention systems (IPSs) located at the Internet service providers (ISPs) level. The IPSs form virtual protection rings around the hosts to defend and collaborate by exchanging selected traffic information. The evaluation of FireCol using extensive simulations and a real dataset is presented, showing FireCol effectiveness and low overhead, as well as its support for incremental deployment in real networks.
Selective transformation of biomass or biomass-based feedstocks into value-added amines is highly desirable and constitutes one of the most important challenges in catalysis. As of today, only few ...amination studies have been reported on biobased substrates, targeting mainly the reductive amination of small platform molecules issued directly from biomass. Here we present a simple and highly efficient system using NH3 or amines as a nitrogen source and molecular hydrogen as reducing agent for the transformation of furan-derived ketones into tetrahydrofuran (THF)-derived amines over Pd/Al2O3 (up to 98% yield). Detailed analysis of the reaction system provided insight into the reaction mechanism. To further realize the production of THF-derived amines, a one-pot, two-step strategy combining C–C and C–N condensation reactions was attempted. A high yield (85%) toward 5-methyl-1-(tetrahydrofuran-2-yl)hexan-3-amine could be successfully achieved starting directly from furfural.
We report here, and rationalize, a synergistic effect between a non-noble metal oxide catalyst (CuO) and high-frequency ultrasound (HFUS) on glucose oxidation. While CuO and HFUS are able to ...independently oxidize glucose to gluconic acid, the combination of CuO with HFUS led to a dramatic change of the reaction selectivity, with glucuronic acid being formed as the major product. By means of density functional theory (DFT) calculations, we show that, under ultrasonic irradiation of water at 550 kHz, the surface lattice oxygen of a CuO catalyst traps H· radicals stemming from the sonolysis of water, making the ring-opening of glucose energetically unfavorable and leaving a high coverage of ·OH radical on the CuO surface, which selectively oxidizes glucose to glucuronic acid. This work also points toward a path to optimize the size of the catalyst particle for an ultrasonic frequency that minimizes the damage to the catalyst, resulting in its successful reuse.
The catalytic hydroarylation of nonactivated alkenes with aniline is a reaction of high interest, aiming at providing C-functionalized aniline derivatives that are important precursors for the ...fabrication of polyurethanes. However, this reaction remains a longstanding goal of catalysis, as it requires one to simultaneously address two important goals: (1) the very low reactivity of nonactivated alkenes and (2) control of the hydroarylation/hydroamination selectivity. As a result, the hydroarylation of aniline is mostly restricted to activated alkenes (i.e., featuring ring strain, conjugation, or activation with electron-donating or -withdrawing groups). Here we show that the combination of bismuth triflate and hexafluoroisopropanol (HFIP) leads to the formation of highly active catalytic species capable of promoting the hydroarylation of various nonactivated alkenes, such as 1-octene, 1-heptene, and 1-undecene, among others, with aniline with high selectivity (71–92%). Through a combined experimental and computational investigation, we propose a reaction pathway where HFIP stabilizes the rate-determining transition state through a H-bond interaction with the triflate anion, thus assisting the acid catalyst in the hydroarylation of nonactivated alkenes. From a practical point of view, this work opens a catalytic access to C-functionalized aniline derivatives from two cheap and abundant feedstocks in a 100% atom-economical fashion.
Once escaped from the quiescence niche, precursor cells interact with stromal components that support their survival, proliferation, and differentiation. We examined interplays between human myogenic ...precursor cells (mpc) and monocyte/macrophages (MP), the main stromal cell type observed at site of muscle regeneration. mpc selectively and specifically attracted monocytes in vitro after their release from quiescence, chemotaxis declining with differentiation. A DNA macroarry-based strategy identified five chemotactic factors accounting for 77% of chemotaxis: MP-derived chemokine, monocyte chemoattractant protein-1, fractalkine, VEGF, and the urokinase system. MP showed lower constitutive chemotactic activity than mpc, but attracted monocytes much strongly than mpc upon cross-stimulation, suggesting mpc-induced and predominantly MP-supported amplification of monocyte recruitment. Determination of 3 Hthymidine incorporation, oligosomal DNA levels and annexin-V binding showed that MP stimulate mpc proliferation by soluble factors, and rescue mpc from apoptosis by direct contacts. We conclude that once activated, mpc, which are located close by capillaries, initiate monocyte recruitment and interplay with MP to amplify chemotaxis and enhance muscle growth.
Despite the growth of prevention techniques, phishing remains an important threat since the principal countermeasures in use are still based on reactive URL blacklisting. This technique is ...inefficient due to the short lifetime of phishing Web sites, making recent approaches relying on real-time or proactive phishing URL detection techniques more appropriate. In this paper, we introduce PhishStorm, an automated phishing detection system that can analyze in real time any URL in order to identify potential phishing sites. PhishStorm can interface with any email server or HTTP proxy. We argue that phishing URLs usually have few relationships between the part of the URL that must be registered (low-level domain) and the remaining part of the URL (upper-level domain, path, query). We show in this paper that experimental evidence supports this observation and can be used to detect phishing sites. For this purpose, we define the new concept of intra-URL relatedness and evaluate it using features extracted from words that compose a URL based on query data from Google and Yahoo search engines. These features are then used in machine-learning-based classification to detect phishing URLs from a real dataset. Our technique is assessed on 96 018 phishing and legitimate URLs that result in a correct classification rate of 94.91% with only 1.44% false positives. An extension for a URL phishingness rating system exhibiting high confidence rate ( > 99%) is proposed. We discuss in this paper efficient implementation patterns that allow real-time analytics using Big Data architectures such as STORM and advanced data structures based on the Bloom filter.
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•Bread waste was valorised for the synthesis of HMF, with yields of 26–27mol%.•Fastest HMF production took place in ACN/H2O and acetonitrile/H2O systems.•Slow glucose isomerization ...hindered HMF formation in DMSO/H2O and THF/H2O.•Similar HMF selectivity was achieved in ACN/H2O, acetonitrile/H2O, and DMSO/H2O.
Valorisation of bread waste for hydroxymethylfurfural (HMF) synthesis was examined in dimethyl sulfoxide (DMSO)-, tetrahydrofuran (THF)-, acetonitrile (ACN)-, and acetone-water (1:1v/v), under heating at 140°C with SnCl4 as the catalyst. The overall rate of the process was the fastest in ACN/H2O and acetone/H2O, followed by DMSO/H2O and THF/H2O due to the rate-limiting glucose isomerisation. However, the formation of levulinic acid (via rehydration) and humins (via polymerisation) was more significant in ACN/H2O and acetone/H2O. The constant HMF maxima (26–27mol%) in ACN/H2O, acetone/H2O, and DMSO/H2O indicated that the rates of desirable reactions (starch hydrolysis, glucose isomerisation, and fructose dehydration) relative to undesirable pathways (HMF rehydration and polymerisation) were comparable among these mediums. They also demonstrated higher selectivity towards HMF production over the side reactions than THF/H2O. This study differentiated the effects of polar aprotic solvent-water mediums on simultaneous pathways during biomass conversion.
The catalytic performance of Aquivion PFSA, a solid superacid, was investigated in the catalytic glycosylation of glucose with fatty alcohols. Four main criteria were considered to evaluate the ...catalytic performance of Aquivion PFSA: (1) the selectivity of the reaction, (2) the turnover frequency, (3) the reactor productivity, and (4) the catalyst stability/recycling. To shed light on the catalytic performance of Aquivion PFSA, it was systematically compared to H2SO4, which is industrially employed in such reactions. We discovered that Aquivion PFSA surpassed the catalytic performance of H2SO4 in terms of activity, selectivity, and reactor productivity. In particular, Aquivion PFSA selectively converted glucose to alkyl polyglucosides (DP = 1.2) with 85% yield, which corresponded to a reactor productivity as high as 477 kg/(m3 h). Conversely to H2SO4, Aquivion PFSA was also capable of selectively producing alkyl polyglucosides directly from glucose syrup, a cheap source of glucose. This result was ascribed to the amphiphilic nature of Aquivion PFSA, which facilitated the Pickering-like emulsification of the biphasic reaction medium. Finally, owing to its high chemical and mechanical properties, Aquivion PFSA was highly stable under our working conditions and could be recycled at least 10 times without obvious loss of its catalytic performance.
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