A relatively new class of three-dimensional ordered mesoporous silicates, KIT-6, incorporated with Earth-abundant metals such as Zr, Nb, and W (termed as M-KIT-6), show remarkable tunability of ...acidity and metal dispersion depending on the metal content, type, and synthetic method. The metal-incorporation is carried out using one-pot synthesis procedures that are amenable to easy scale-up. By such tuning, M-KIT-6 catalysts are shown to provide remarkable activity and selectivity in industrially-significant reactions, such as alcohol dehydration, ethylene epoxidation, and metathesis of 2-butene and ethylene. We review how the catalytic properties of M-KIT-6 materials may be tailored depending on the application to optimize performance.
RNAs with 5′-triphosphate (ppp) are detected in the cytoplasm principally by the innate immune receptor Retinoic Acid Inducible Gene-I (RIG-I), whose activation triggers a Type I IFN response. It is ...thought that self RNAs like mRNAs are not recognized by RIG-I because 5′ppp is capped by the addition of a 7-methyl guanosine (m7G) (Cap-0) and a 2′-O-methyl (2′-OMe) group to the 5′-end nucleotide ribose (Cap-1). Here we provide structural and mechanistic basis for exact roles of capping and 2′-O-methylation in evading RIG-I recognition. Surprisingly, Cap-0 and 5′ppp double-stranded (ds) RNAs bind to RIG-I with nearly identical K
d values and activate RIG-I’s ATPase and cellular signaling response to similar extents. On the other hand, Cap-0 and 5′ppp single-stranded RNAs did not bind RIG-I and are signaling inactive. Three crystal structures of RIG-I complexes with dsRNAs bearing 5′OH, 5′ppp, and Cap-0 show that RIG-I can accommodate the m7G cap in a cavity created through conformational changes in the helicase-motif IVa without perturbing the ppp interactions. In contrast, Cap-1 modifications abrogate RIG-I signaling through a mechanism involving the H830 residue, which we show is crucial for discriminating between Cap-0 and Cap-1 RNAs. Furthermore, m7G capping works synergistically with 2′-O-methylation to weaken RNA affinity by 200-fold and lower ATPase activity. Interestingly, a single H830A mutation restores both high-affinity binding and signaling activity with 2′-O-methylated dsRNAs. Our work provides new structural insights into the mechanisms of host and viral immune evasion from RIG-I, explaining the complexity of cap structures over evolution.
This work is a study of tribo-corrosion and engine characteristics of Aegle Marmelos Correa biodiesel and its diesel blends. The tribology results revealed that B50 showed the lowest steady-state ...coefficient of friction (SSCOF) amongst all the other blends. SSCOF of B100 is 23.27% more than B50. Similarly, SSCOF of B90, B60, B20, B10, and diesel are 19%, 8%, 17.23%, 31.9% and 40.11% greater than the SSCOF of B50 respectively. Wear scar diameter (WSD) results also showed that B50, B60, B90, and B100 have lower WSD of around 0.6 mm. Diesel showed the highest WSD of 0.8 mm. Flash temperature parameter (FTP) is inversely related to WSD, and thus B50, B60, B90, and B100 exhibited higher FTP of around 80. On evaluating the corrosion characteristics, B50 exhibited lesser corrosion inducing capability compared to all the other blends. Experimental investigation of the engine showed that B100 yielded lesser thermal efficiency and higher specific fuel consumption than diesel. The CO, HC, NO, and smoke emissions were minimum for B100 when compared to diesel. Finally, all the results revealed that B100 is the ideal blend that can perform efficiently and be a sustainable energy source for diesel engines.
•B50 exhibited the lowest SSCOF compared to other blends.•Wear scar diameter of B50, B60, B90 and B100 is observed similar.•Diesel has the highest WSD and lowest FTP compared to other blends.•Diesel is found to produce less corrosion on metals.•Minimum CO, HC, NO and smoke emissions were obtained for B100.
The development of the world economy goes hand in hand with increased energy consumption and global warming caused by greenhouse gases. These issues can be tackled by implementing promising ...technologies of power generation. They differ from the known ones in that new energy resources are involved, e.g., mixtures of various types of biomass, provided that hazardous gas emissions during the production process are minimized. The development of high-potential energy-efficient and environmentally friendly technologies which use biofuel in the energy industry requires scientific evidence for the mechanisms, conditions, and characteristics of physical and chemical processes during pyrolysis and gasification of biomass, including its multicomponent types. This article analyzes the world technologies and research findings in the field of biomass pyrolysis and gasification. The effect of a group of factors on the intensity and completeness of gasification and pyrolysis of biofuel compositions has been determined. These factors include the size, shape, and surface structure of biomass particles; component composition and properties of fuel mixtures; mechanism and intensity of heat supply; and the temperature field in the reactor filled with solid and gaseous products. The most effective values of these characteristics have been established.
Retinoic-acid-inducible gene-I (RIG-I; also known as DDX58) is a cytoplasmic pathogen recognition receptor that recognizes pathogen-associated molecular pattern (PAMP) motifs to differentiate between ...viral and cellular RNAs. RIG-I is activated by blunt-ended double-stranded (ds)RNA with or without a 5'-triphosphate (ppp), by single-stranded RNA marked by a 5'-ppp and by polyuridine sequences. Upon binding to such PAMP motifs, RIG-I initiates a signalling cascade that induces innate immune defences and inflammatory cytokines to establish an antiviral state. The RIG-I pathway is highly regulated and aberrant signalling leads to apoptosis, altered cell differentiation, inflammation, autoimmune diseases and cancer. The helicase and repressor domains (RD) of RIG-I recognize dsRNA and 5'-ppp RNA to activate the two amino-terminal caspase recruitment domains (CARDs) for signalling. Here, to understand the synergy between the helicase and the RD for RNA binding, and the contribution of ATP hydrolysis to RIG-I activation, we determined the structure of human RIG-I helicase-RD in complex with dsRNA and an ATP analogue. The helicase-RD organizes into a ring around dsRNA, capping one end, while contacting both strands using previously uncharacterized motifs to recognize dsRNA. Small-angle X-ray scattering, limited proteolysis and differential scanning fluorimetry indicate that RIG-I is in an extended and flexible conformation that compacts upon binding RNA. These results provide a detailed view of the role of helicase in dsRNA recognition, the synergy between the RD and the helicase for RNA binding and the organization of full-length RIG-I bound to dsRNA, and provide evidence of a conformational change upon RNA binding. The RIG-I helicase-RD structure is consistent with dsRNA translocation without unwinding and cooperative binding to RNA. The structure yields unprecedented insight into innate immunity and has a broader impact on other areas of biology, including RNA interference and DNA repair, which utilize homologous helicase domains within DICER and FANCM.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•KBr impregnated CaO has been used as heterogeneous catalyst.•Efficient use of waste cooking oil as feedstock.•Response Surface Methodology was used to optimize process parameters.
This research ...paper deals with the synthesis of a heterogeneous catalyst (KBr/CaO) from commercial calcium oxide and potassium bromide by wet impregnation method. This solid catalyst was tested for transesterification of waste cooking oil (WCO). The synthesized catalyst was characterized by Fourier Transform Infrared spectrometry (FTIR), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. Transesterification reaction parameters were varied to obtain the maximum yield of biodiesel. Response Surface Methodology (RSM) using Central Composite Design (CCD) was employed to study the effect of the process variables like methanol to oil ratio, catalyst loading and reaction time. The optimum conditions obtained using regression models were found to be 12:1 methanol: oil ratio, 3wt% catalyst loading and 1.8h reaction time. The composition of FAME was determined using Gas Chromatography–Mass Spectrometry (GC–MS). The performance and emission characteristics for various blends of biodiesel (B10, B20, B50 and B100) were investigated in a four stroke direct injection diesel engine. The results indicated that the brake thermal efficiency, particulate matter, unburned hydrocarbons, carbon monoxide emissions reduced with increased concentration of biodiesel in the fuel blends, whereas the specific fuel consumption, NOx emissions and exhaust gas temperature increased.
A novel wormhole structured mesoporous material containing tin, SnTUD-1, was prepared by a direct hydrothermal synthesis method using triethanolamine (TEA) as an organic inexpensive mesoporous ...structure directing agent. XRD and N sub(2) sorption studies of SnTUD-1 confirmed the amorphous mesoporous nature of SnTUD-1, which possessed a large surface area of 555 m super(2) g super(-1) and a pore diameter of 7.4 nm. HR-TEM further ascertained the disordered pores in their morphology and the presence of nano-domains of SnO sub(2) species. The nature of the Sn super(4+) ion co-ordination with the silica matrix was evaluated by using different techniques including diffuse reflectance UV-Vis, FTIR, super(29)Si MAS NMR and XPS. SnTUD-1 had an interesting Lewis acidity as measured by FTIR of pyridine adsorption which provided excellent activities in one-pot three-component Mannich-type reactions of ketones with aldehydes and amines at room temperature.
We have measured the CO2 volume mixing ratio (VMR) within the planetary boundary layer (PBL) using cloud slicing with an airborne pulsed integrated path differential absorption (IPDA) lidar from ...flight altitudes of up to 13 km. During a flight over Iowa in summer 2011, simultaneous measurement of the optical range and CO2 absorption to clouds and the ground were made using time-resolved detection of pulse echoes from each scattering surface.We determined the CO2 absorption in the PBL by differencing the two lidar-measured absorption line shapes, one to a broken shallow cumulus cloud layer located at the top of the PBL and the other to the ground. Solving for the CO2 VMR in the PBL and that of the free troposphere, we measured a ≈15 ppm (4%) drawdown in the PBL. Both CO2 VMRs were within ≈3 ppm of in situ CO2 profile measurements. We have also demonstrated cloud slicing using scatter from thin, diffuse cirrus clouds and cumulus clouds, which allowed solving for the CO2 VMR for three vertical layers. The technique and retrieval algorithm are applicable to a space-based lidar instrument as well as to lidar IPDA measurements of other trace gases. Thus, lidar cloud slicing also offers promise toward space-based remote sensing of vertical trace gas profiles in the atmosphere using a variety of clouds.
Tungsten, in varying amounts, was incorporated into a SBA-16 structure via a one-pot direct synthesis method under an acidic medium using Pluronic F127 triblock co-polymer as a template and n-butanol ...as a co-surfactant. Tetraethyl orthosilicate (TEOS) and sodium tungstate were used as the Si and W sources, respectively. The resulting materials (denoted as W-SBA-16) are characterized for structural ordering, textural properties, and types of tungsten incorporation by techniques such as small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), N2 sorption, high-resolution transmission electron microscopy (HR-TEM), diffuse-reflectance ultraviolet–visible light (DR-UV-vis) microscopy, temperature-programmed reduction in a hydrogen atmosphere (H2-TPR), and temperature-programmed desorption of ammonia (NH3-TPD). The surface area (823–354 m2/g) and pore volume (0.71–0.44 cm3/g) of the W-SBA-16 materials are found to decrease with an increase in tungsten loading (from 2.7 wt % to 30.4 wt % of the total sample). Isolated framework WO4 species and octahedrally coordinated polytungstate species are observed at all tungsten loadings, while bulk WO3 species are observed only at higher tungsten loadings. The W-SBA-16 materials display significant acidity that is tunable with tungsten loading, and they selectively catalyze the epoxidation of cyclohexene to cyclohexene oxide with H2O2 as an oxidant. The fact that bulk WO3 alone does not catalyze the reaction implies that the framework-incorporated W species and/or the polytungstate species are responsible for the observed catalysis. For this reaction, three-dimensional cubic mesostructured catalysts (W-SBA-16, W-KIT-6, and W-KIT-5) perform better than two-dimensional mesostructured (W-SBA-15) material. The problem of gradual tungsten leaching must be overcome for these catalysts to have practical utility.
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