Influence of phase behavior on chemical flood transport phenomena

We propose that there are two classes of temporal development in the degradation of permeability of porous media due to deposition of fines: (1) Deposition, and therefore permeability degradation, is localized to bands growing orthogonally to the average local flow direction, and (2) permeability degradation occurs in stripes parallel to the local flow direction. These latter stripes do not influence total permeability much as they develop. When these stripes are allowed to develop, they coalesce and worm holes form. We discuss how imposing different flow conditions such as constant flow and constant pressure influence the deposition process. Our conclusion is that constant pressure conditions typically lead to a slower permeability degradation compared to constant flow conditions as a direct consequence of the formation of low-permeability bands. We test our ideas by numerical simulations on a simple model for fines migration and deposition in porous media.     

The effect of dispersion model on the linear stability of miscible displacement in porous media

Chang and Slattery (1986, 1988b) introduced a simplified model of dispersion that contains only two empirical parameters. The traditional model of dispersion (Nikolaevskii, 1959; Bear, 1961; Scheidegger, 1961; de Josselin de Jong and Bossen, 1961; Peaceman, 1966; Bear, 1972) has three empirical parameters, two of which can be measured in one-dimensional experiments while the third, the transverse dispersivity, must be measured in experiments in which a two-dimensional concentration profile develops. It is found that nearly the same linear stability behavior results from using either model.     

High electron mobility fluorinated indacenodithiophene small molecule acceptors for organic solar cells

Indacenodithiophene (IDT) derivatives are kinds of the most representative and widely used cores of small molecule acceptors (SMAs) in organic solar cells (OSCs). Here we systematically investigate the influence of end-group fluorination density and position on the photovoltaic properties of the IDT-based SMAs IDIC-nF (n = 0, 2, 4). The absorption edge of IDIC-nF red-shifts with the π-π stacking and crystallinity improvement, and their electronic energy levels downshift with increasing n. Due to the advantages of J_sc and FF as well as acceptable V_oc, the difluorinated IDIC-2F acceptor based OSCs achieve the highest power conversion efficiency (PCE) of 13%, better than the OSC devices based on IDIC and IDIC-4F as acceptors. And the photovoltaic performance of the PTQ10: IDIC-2F OSCs is insensitive to the active layer thickness: PCE still keep high values of 12.00% and 11.46% for the devices with active layer thickness of 80 and 354 nm, respectively. This work verifies that fine and delicate modulation of the SMAs molecular structure could optimize photovoltaic performance of the corresponding OSCs. Meanwhile, the thickness-insensitivity property of the OSCs has potential for large-scale and printable fabrication technology.     

A four-dimensional separation approach by offline 2D-LC/IM-TOF-MS in combination with database-driven computational peak annotation facilitating the in-depth characterization of the multicomponents from Atractylodis Macrocephalae Rhizoma (Atractylodes macrocephala)

Plant metabolites represent complex chemical system, which renders it difficult to clarify the chemical composition by conventional liquid chromatography/mass spectrometry (LC/MS) due to the limited selectivity and peak capacity. The rhizomes of Atractylodes macrocephala have been utilized as a traditional Chinese medicine Atractylodis Macrocephalae Rhizoma (Bai-Zhu), and have been reported containing multiple categories of plant metabolites. Targeting the multicomponents from A. macrocephala, an integral approach by offline two-dimensional liquid chromatography/ion mobility quadrupole time-of-flight mass spectrometry (2D-LC/IM-QTOF-MS) was established and validated. By configuring an XBridge Amide column of Hydrophilic Interaction Chromatography and an Atlantis Premier BEH C18AX column of mixed ion exchange and reversed-phase modes, the established 2D-LC/IM-QTOF-MS system showed high orthogonality up to 0.91. Dimension-enhanced, data-independent high-definition MS^E (HDMS^E) in the positive ESI mode was conducted on a Vion IM-QTOF mass spectrometer, and its hyphenation to offline 2D-LC could enable the four-dimensional separation (each dimension in 2D-LC, IM, and MS). Particularly, HDMS^E facilitated the acquisition of high-definition MS¹ and MS² spectra. In-house library-driven computational peak annotation by the bioinformatics platform UNIFI could efficiently process and annotate the HDMS^E data for the structural elucidation. By integrating reference compounds comparison, we could identify or tentatively characterize 251 components from A. macrocephala (including 115 sesquiterpenoids, 90 polyacetylenes, 11 flavonoids, 9 benzoquinones, 12 coumarins, and 14 others), which indicated large improvement in identifying those minor plant components, compared with the conventional LC/MS approach. Conclusively, offline 2D-LC/IM-QTOF-HDMS^E in combination with computational data interpretation proves to be powerful facilitating the in-depth multicomponent characterization of herbal medicine.     

An RP-LC-UV-TWIMS-HRMS and Chemometric Approach to Differentiate between Momordica balsamina Chemotypes from Three Different Geographical Locations in Limpopo Province of South Africa

Momordica balsamina leaf extracts originating from three different geographical locations were analyzed using reversed-phase liquid chromatography (RP-LC) coupled to travelling wave ion mobility (TWIMS) and high-resolution mass spectrometry (HRMS) in conjunction with chemometric analysis to differentiate between potential chemotypes. Furthermore, the cytotoxicity of the three individual chemotypes was evaluated using HT-29 colon cancer cells. A total of 11 molecular species including three flavonol glycosides, five cucurbitane-type triterpenoid aglycones and three glycosidic cucurbitane-type triterpenoids were identified. The cucurbitane-type triterpenoid aglycones were detected in the positive ionization mode following dehydration [M + H − H₂O]⁺ of the parent compound, whereas the cucurbitane-type triterpenoid glycosides were primarily identified following adduct formation with ammonia [M + NH₄]⁺. The principle component analysis (PCA) loadings plot and a variable influence on projection (VIP) analysis revealed that the isomeric pair balsaminol E and/or karavilagen E was the key molecular species contributing to the distinction between geographical samples. Ultimately, based on statistical analysis, it is hypothesized that balsaminol E and/or karavilagen E are likely responsible for the cytotoxic effects in HT-29 cells.     

Electrophoretic mobility of oil droplets in electrolyte and surfactant solutions

Electrophoretic mobility of oil droplets of micron sizes in PBS and ionic surfactant solutions was measured in this paper. The experimental results show that, in addition to the applied electric field, the speed and the direction of electrophoretic motion of oil droplets depend on the surfactant concentration and on if the droplet is in negatively charged SDS solutions or in positively charged hexadecyltrimethylammonium bromide (CTAB) solutions. The absolute value of the electrophoretic mobility increases with increased surfactant concentration before the surfactant concentration reaches to the CMC. It was also found that there are two vortices around the oil droplet under the applied electric field. The size of the vortices changes with the surfactant and with the electric field. The vortices around the droplet directly affect the drag of the flow field to the droplet motion and should be considered in the studies of electrophoretic mobility of oil droplets. The existence of the vortices will also influence the determination and the interpretation of the zeta potential of the oil droplets based on the measured mobility data.     

Determination of thiram residues in canola seeds,water and soil samples using solid-phase microextraction with polypyrrole film followed by ion mobility spectrometer

Thiram fungicide contamination in canola seeds, water and soil samples was monitored using headspace solid-phase microextraction (HS-SPME) combined with ion mobility spectrometer (IMS) to assess its environmental relevance. The influence of the various analytical parameters on microextraction procedure including pH, ionic strength, equilibrium time and temperature has been evaluated and optimised. HS-SPME-IMS allowed the determination of thiram in the concentration range of 10–300 ng mL^?1 (R² > 0.99). The detection limit and relative standard deviation were 6 ng mL^?1 and 8% for five replicate analyses, respectively. The HS-SPME-IMS method with polypyrrole film doped with dodecylsulfate (PPy-DS) as solid phase provided an effective sample clean-up for the monitoring of thiram in canola and soil samples. The main advantages of this method are sensitive, good repeatability, organic solvent-free, less time-consuming and relatively inexpensive.     

Ligand‐Controlled CO2 Activation Mediated by Cationic Titanium Hydride Complexes, [LTiH]+ (L=Cp2, O)

CO₂ activation mediated by [LTiH]⁺ (L=Cp₂, O) is observed in the gas phase at room temperature using electrospray‐ionization mass spectrometry, and reaction details are derived from traveling wave ion‐mobility mass spectrometry. Wheresas oxygen‐atom transfer prevails in the reaction of the oxide complex [OTiH]⁺ with CO₂, generating [OTi(OH)]⁺ under the elimination of CO, insertion of CO₂ into the metal–hydrogen bond of the cyclopentadienyl complex, [Cp₂TiH]⁺, gives rise to the formate complex [Cp₂Ti(O₂CH)]⁺. DFT‐based methods were employed to understand how the ligand controls the observed variation in reactivity toward CO₂. Insertion of CO₂ into the Ti?H bond constitutes the initial step for the reaction of both [Cp₂TiH]⁺ and [OTiH]⁺, thus generating formate complexes as intermediates. In contrast to [Cp₂Ti(O₂CH)]⁺ which is kinetically stable, facile decarbonylation of [OTi(O₂CH)]⁺ results in the hydroxo complex [OTi(OH)]⁺. The longer lifetime of [Cp₂Ti(O₂CH)]⁺ allows for secondary reactions with background water, as a result of which, [Cp₂Ti(OH)]⁺ is formed. Further, computational studies reveal a good linear correlation between the hydride affinity of [LTi]²⁺ and the barrier for CO₂ insertion into various [LTiH]⁺ complexes. Understanding the intrinsic ligand effects may provide insight into the selective activation of CO₂.