•Landfill leachate (LL) was used as liquid source during HTC of MSWs.•LL resulted in lower hydrochar mass yields than conventional distilled water.•LL had no adverse effect on the fuel ...characteristics of the hydrochars.•The HHV of the hydrochars is comparable to traditional solid fuels.•Use of LL as moisture source can improve the sustainability of HTC processes.
Hydrothermal carbonization (HTC) of yard waste (YW) and food waste (FW) was performed in landfill leachate (LL) to overcome the unnecessary exploitation of our limited natural resources. The physicochemical properties and combustion behavior of the resulting hydrochars were compared with those obtained using distilled water (DW) as reaction medium. Although performing HTC in LL led to lower hydrochar mass yields (43% YWH and 36% FWH) than DW (47.1% YWH and 41.5% FWH), it had minimal impact on the fuel characteristics of the hydrochars. Notably, the higher heating value of the hydrochars prepared in LL (22.8 MJ kg−1 for YWH and 30.2 MJ kg−1 for FWH) is comparable to that of conventional solid fuels, and may, therefore, be considered as inexpensive alternatives to fossil fuels. Overall, the results of this study conclusively suggest that the use of LL as an alternative moisture source can significantly improve the sustainability of HTC technology.
An account of total of 58 plant species including 57 genera and 43 families was reported as useful in ethnomedicine from semi-structured questionnaire survey to the 76 participants of Kaski and ...Baitadi districts, Nepal. Fieldwork and participatory meetings were carried out between September 2017 and January 2018. A total of 419 emic use reports including 150 from Kaski and 269 from Baitadi were reported from 58 ethnomedicinal plant species. Each species was reported for 2-43 use reports and each participant recorded 1-12 use reports. About 25% (n = 104) use reports were associated with the treatment of digestive system disorders followed by 83 for general complaints. Of the species assessed, 53 species had IASc value < 0.25 and only five species had > 0.25. Species Swertia chirayita, Paris polyphylla, Bergenia ciliata, Valeriana jatamansi and Centella asiatica with > 0.25 IASc were found to be highly consented; however they were incongruent between the sample groups and sites. Divergent plant use knowledge specific to each sample district and group was corresponding to the heterogeneity of socio-economy and culture of the sites. Gender, ethnicity, household economy and food availability of the respondents were leading factors affecting the plant use knowledge. Despite the sites were relatively homogenous in eco-physiography, they possessed the distinct plant use knowledge, hinted that the socio-economic factors are more explanatory in plant use knowledge.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We have demonstrated that the electrical property of single-layer molybdenum disulfide (MoS2) can be significantly tuned from the semiconducting to the insulating regime via controlled exposure to ...oxygen plasma. The mobility, on-current and resistance of single-layer MoS2 devices were varied by up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon oxygen plasma exposure, leading to an exponential variation of resistance and mobility as a function of plasma exposure time. The resistance variation calculated using an effective medium model is in excellent agreement with the measurements. The simple approach described here can be used for the fabrication of tunable two-dimensional nanodevices based on MoS2 and other transition metal dichalcogenides.
Display omitted
•Purple bacterial reaction centers with phylloquinone incorporated into the QA binding site were studied.•Vibrational properties of the phyllosemiquinone anion in the protein binding ...site were calculated.•Calculated and experimental spectra agree well.
QA– – QA Fourier transform infrared difference spectra have previously been obtained using purple bacterial reaction centers from Rhodobacter sphaeroides with unlabeled, 18O and 13C isotope labeled phylloquinone (PhQ, also known as vitamin K1) incorporated into the QA protein binding site (Breton, (1997), Proc. Natl. Acad. Sci. USA94 11318–11323). The nature of the bands in these spectra and the isotope induced band shifts are poorly understood, especially for the phyllosemiquinone anion (PhQ–) state. To aid in the interpretation of the bands in these experimental spectra, ONIOM type QM/MM vibrational frequency calculations were undertaken. Calculations were also undertaken for PhQ– in solution. Surprisingly, both sets of calculated spectra are similar and agree well with the experimental spectra. This similarity suggests pigment-protein interactions do not perturb the electronic structure of the semiquinone in the QA binding site. This is not found to be the case for the neutral PhQ species in the same protein binding site. PhQ also occupies the A1 protein binding site in photosystem I, and the vibrational properties of PhQ– in the QA and A1 binding sites are compared and shown to exhibit considerable differences. These differences probably arise because of changes in the degree of asymmetry of hydrogen bonding of PhQ– in the A1 and QA binding sites.
Voltage angle-based torque control of dual three-phase interior permanent magnet synchronous machines (DTP-IPMSMs) in the field weakening (FW) region offers maximum dc voltage utilization, increased ...speed range, and higher torque capability. However, the difference in parameter values between the two three-phase winding sets results in torque limitations during FW operation. This article considers a dual three-phase IPMSM with 0<inline-formula><tex-math notation="LaTeX">^\circ</tex-math></inline-formula> winding displacement (DTP0 IPMSM), where the resistance and leakage inductance of each three-phase winding set are not the same. The effect of this parameter mismatch on the FW performance is discussed in detail. Further, a control scheme is proposed, where a 2-pole torque controller controls the torque dynamics by modifying the voltage angle of one of the inverters, while the other inverter's voltage angle is controlled to minimize the effect of parameter mismatch. The proposed method is implemented on a 3.68 kW DTP0 IPMSM prototype. For a given torque, the current requirement is shown to reduce approximately by 4% in the low and midspeed ranges of the FW region when compared with existing approaches of DTP0 IPMSM control. The performance of the 2-pole controller is also demonstrated, which achieves the desired control system specifications.
γ-Alumina and carbon supported mono and bimetallic Ni and Cu catalysts were synthesized and applied to the reduction of p-cresol and furfural via transfer hydrogenation. The developed reaction system ...was applied to alkyl phenol rich pyrolysis oils produced from the ARS tail gas reactive pyrolysis (TGRP) of switchgrass and oak wood. The catalysts used were characterized pre- and post-reactions using XRD, TPR, TEM and TGA. When isopropanol was used as the hydrogen donor solvent, yields of >95% of a mixture of products from the reduction of p-cresol were achieved using the Ni–Cu/Al2O3 catalyst. This product mixture includes ring hydrogenation products (4-methylcyclohexanol and 4-methylcyclohexanone) as well as deoxygenated products (methylcyclohexane and toluene), with 4-methylcyclohexanol being the major product. The activity remained high in the presence of water with very high levels of water concentration resulting in a higher selectivity towards the ketone product. The system was also effective for the reduction of furfural to furfuryl alcohol, although lower temperatures were required to prevent polymerization of the furfural. When applied to bio-oil, although increases in H/C and C/O ratios and energy content were realized, effective reduction of the alkyl phenols in the bio-oils was below expectation. Rather, solid formation, a result of the polymerization of bio-oil compounds was also observed. Our effort to extend the successes encountered with the model compounds to improve the application of transfer hydrogenation to real bio-oils is the subject of ongoing research.
•Catalytic transfer hydrogenation was studied for stabilization of bio-oil oxygenates.•Ni–Cu catalysts were effective for transfer hydrogenation of p-cresol and furfural.•Isopropanol is a good hydrogen donor for this transformation.•Studied conditions were applied to biomass pyrolysis oils.•Increase in H content and heating value of bio-oil was observed.
By creating defects via oxygen plasma treatment, we demonstrate optical properties variation of single-layer MoS2. We found that, with increasing plasma exposure time, the photoluminescence (PL) ...evolves from very high intensity to complete quenching, accompanied by gradual reduction and broadening of MoS2 Raman modes, indicative of distortion of the MoS2 lattice after oxygen bombardment. X-ray photoelectron spectroscopy study shows the appearance of the Mo6+ peak, suggesting the creation of MoO3 disordered regions in the MoS2 flake. Finally, using band structure calculations, we demonstrate that the creation of MoO3 disordered domains upon exposure to oxygen plasma leads to a direct-to-indirect bandgap transition in single-layer MoS2, which explains the observed PL quenching.
Rationale
Halogenated thiophenes are an important class of compounds mostly used in the synthesis of various materials, showing unusual electronic and optical properties. The Thiophene Ring ...Fragmentation (TRF) process is widely used in synthetic chemistry. In this study, the fragmentation pattern of the molecular cation of halogenated thiophene, namely, 2‐chlorothiophene, was monitored to establish its dissociation mechanism.
Methods
The molecular cation of 2‐chlorothiophene was prepared using multiphoton excitation using a laser at 235 nm. Various product ions upon fragmentation of the molecular ion were mass analyzed using time‐of‐flight mass spectrometry. Laser power dependence studies were also conducted for various product ions to arrive at the dissociation mechanism. Theoretical calculations were carried out to estimate the reaction enthalpies for various reactions and compared with the experimental data available in the literature.
Results
The most abundant product ion was observed as the HCS+ radical cation followed by the C3H3+ ion and the H2CCCCS+ radical cation. Other product ions such as SCCl+, ClHCCS+ radical cations were also observed to a lesser extent in the fragmentation pattern of the parent molecular ion. Various dissociation channels were identified and supported with ab initio calculation. It has been inferred that the TRF process is usually initiated by the H/Cl atom transfer process. The appearance energies of the various fragment ions were also estimated theoretically and compared with literature values.
Conclusions
In conclusion, the fragmentation pattern of the molecular cation of 2‐chlorothiophene was studied and the formation mechanisms of various product ions have been assigned. The appearance energies of the various fragment ions were also calculated. Finally, it is inferred that a TRF process is initiated by the H/Cl atom migration and subsequent ring opening either by C–C or C–S bond cleavage leading to the various isomers and their subsequent fragmentation. The ionization energies were accurately predicted for various species using ab initio calculation.
Type 1, α/β hydrolase-like thioesterase (TE) domains are essential offloading enzymes, releasing covalently bound products from fatty acid, polyketide, and non-ribosomal peptide biosynthetic ...complexes. The release step can occur by attack of an exogenous nucleophile effecting hydrolysis or transesterification or by an intramolecular O-, N-, or C-nucleophile, effecting macrolactonization, macrolactamization or Claisen-like condensation of the product. Thus in addition to ensuring turnover of the pathway, TEs provide access to increased chemical diversity. We review the diversity, structure, and mechanism of PKS and NRPS TEs and discuss recent works that highlight the role of TEs as potential arbitrators in offloading. In particular, we examine cases where TEs act as logic gates that ask a particular question about the substrate and use this information to determine the substrate's fate. As the TE mechanism occurs via two steps, we analyze both the loading and release steps independently as logic gates. The use of logic gates provides an important perspective when evaluating the evolution of TEs within a pathway, as well as highlighting work towards the goal of predicting TE function in unknown and engineered pathways.
PDF
