Chemical degradation of guar gum solutions via the addition of a strong oxidant is a common process step in hydraulic fracturing. Unfortunately, this degradation step leads to the formation of an ...insoluble precipitate which clogs the porous rock formation, reducing efficiency, reducing oil recovery potential, and increasing energy costs. The chemical composition, particle size, and molecular weight distributions of the oxidatively degraded guar (“broken guar”) are largely unknown, making it difficult to develop mitigation strategies. In this work, broken guar gum solutions are systematically analyzed to understand the origin of the observed residue. Our results indicate that cellulose fibers and proteins, rather than galactomannan oligomers, are the two major components (>50%) of the solid residue (the water‐insoluble fraction of broken guar). This finding suggests that removal of the cellulose fiber and proteins from the guar source material may be a potential residue mitigation strategy. Separately, we provide evidence for a potential second mitigation strategy employing chemical additives to reduce aggregation of the insoluble species, effectively reducing their potential to cause formation damage.
Aqueous solutions of guar gum were cleaved by ammonium persulfate and analyzed by monad and protein analyses. Surprisingly, insoluble cellulose fibers and proteins, rather than galactomannan oligomers, were the major components of the water‐insoluble fraction.
The characterization of chemical reactions at the buried interface is critical to understand interfacial molecular interactions and improve interfacial properties like adhesion. Interface-sensitive ...sum frequency generation (SFG) vibrational spectroscopy can probe the buried interface in situ nondestructively. While SFG has been used to study many model polymer interfaces, it has never been applied to study multilayer polymer films produced on commercial coextrusion lines. Here, we apply SFG to elucidate the molecular details of chemical reactions at the buried interface in multilayer cast films consisting of maleic anhydride (MAH)-modified Tie layers promoting the adhesion between polyamide and polyethylene. We demonstrated the utility of SFG to identify the reaction products from the interfacial reaction between MAH and polyamide with varying MAH concentrations and to monitor changes of the interfacial molecular orientation. The developed approach is generally applicable to probe chemical reactions and molecular interactions at buried interfaces in multilayer polymer films.
Silicone elastomers are widely used in many industrial applications, including coatings, adhesives, and sealants. Room-temperature vulcanized (RTV) silicone, a major subcategory of silicone ...elastomers, undergoes molecular structural transformations during condensation curing, which affect their mechanical, thermal, and chemical properties. The role of reactive hydroxyl (−OH) groups in the curing reaction of RTV silicone is crucial but not well understood, particularly when multiple sources of hydroxyl groups are present in a formulated product. This work aims to elucidate the interfacial molecular structural changes and origins of interfacial reactive hydroxyl groups in RTV silicone during curing, focusing on the methoxy groups at interfaces and their relationship to adhesion. Sum frequency generation (SFG) vibrational spectroscopy is an in situ nondestructive technique used in this study to investigate the interfacial molecular structure of select RTV formulations at the buried interface at different levels of cure. The primary sources of hydroxyl groups required for interfacial reactions in the initial curing stage are found to be those on the substrate surface rather than those from the ingress of ambient moisture. The silylation treatment of silica substrates eliminates interfacial hydroxyl groups, which greatly impact the silicone interfacial behavior and properties (e.g., adhesion). This study establishes the correlation between interfacial molecular structural changes in RTV silicones and their effect on adhesion strength. It also highlights the power of SFG spectroscopy as a unique tool for studying chemical and structural changes at RTV silicone/substrate interface in situ and in real time during curing. This work provides valuable insights into the interfacial chemistry of RTV silicone and its implications for material performance and application development, aiding in the development of improved silicone adhesives.
Synthetic crude oils derived from mined oil sands processed via the Clark hot water extraction process do not meet current specifications for pipeline transport and are corrosive to upgrader ...equipment by virtue of the high residual water content (2–5%) and salts. Formulated chemical additives used in this process can improve the oil quality by accelerating and enhancing the separation of water from oil. The identification and selection of these formulated additives is typically based on performance data collected in field testing for each component or blend. Herein, two methods are reported to study the effect of chemical additives on the phase separation behavior of water in diluted bitumen emulsions prepared in microfluidic devices. First, water droplets in diluted bitumen were created in the presence of chemical additives and the kinetics of droplet coalescence were compared for various additives and concentrations. Second, using a custom-made device geometry, water droplets in diluted bitumen were formed and aged prior to the addition of chemical additives. The treated droplets were observed to calculate the kinetics of droplet coalescence. The frequency of coalescence events was the same order of magnitude in both studies. The effectiveness of various additives can be determined by measuring the coalescence time, which is dominated by film drainage in the case of the best chemical additives.
Surface-active asphaltene molecules are naturally found in crude oil, causing serious problems in the petroleum industry by stabilizing emulsion drops, thus hindering the separation of water and oil. ...Asphaltenes can adsorb at water–oil interfaces to form viscoelastic interfacial films that retard or prevent coalescence. Here, we measure the evolving interfacial shear rheology of water–oil interfaces as asphaltenes adsorb. Generally, interfaces stiffen with time, and the response crosses over from viscous-dominated to elastic-dominated. However, significant variations in the stiffness evolution are observed in putatively identical experiments. Direct visualization of the interfacial strain field reveals significant heterogeneities within each evolving film, which appear to be an inherent feature of the asphaltene interfaces. Our results reveal the adsorption process and aged interfacial structure to be more complex than that previously described. The complexities likely impact the coalescence of asphaltene-stabilized droplets, and suggest new challenges in destabilizing crude oil emulsions.
To evaluate the effects of an integrated childbirth education intervention on reducing childbirth fear, anxiety, and depression, and improving dispositional mindfulness.
A two-arm parallel, ...single-blind randomised controlled trial.
A teaching hospital in Northern Taiwan.
Pregnant women ≥ 20 years of age with a singleton pregnancy (12–24 weeks gestation) and their support partners were recruited. All women included in the study had a score of ≥ 7 points on a fear of childbirth visual analogue scale.
The intervention group (n = 53) received an 8-week course in a childbirth education programme, which included (1) childbirth education using simulation-based learning that highlighted coping with labour pain and (2) instruction in mindfulness breathing, body scans, stretching, sitting meditation, and mindfulness walking. Support partners were invited to participate. The control group (n = 53) received the usual standard prenatal care.
The primary outcome of fear of childbirth was assessed using the Wijma Delivery Expectancy/Experience Questionnaire. The secondary outcomes of anxiety, depression, and dispositional mindfulness were assessed with the Edinburgh Postpartum Depression Scale, State-Trait Anxiety Inventory Scale, and the Mindful Attention Awareness Scale, respectively. Repeated data were collected at baseline, 36 weeks gestation, and 1 week postpartum.
Ninety-one mothers completed the study, with a mean age of 33.9 years (SD = 4.4), and most were primipara (n = 83). The baseline measurements did not differ between the groups. Compared with the control group, there were significant differences in all measures from baseline for the intervention group: the scores were significantly lower for fear of childbirth (mean difference (MD) =-14.8 ∼ -23.7, p < .01), symptoms of anxiety (MD =-7.4 ∼ -6.4, p < .01), and depression (MD =-3.7 ∼ -3.5, p < .01); the levels of dispositional mindfulness were significantly higher (MD =4.9 ∼ 5.7, p < .01) at 36 weeks gestation, and 1 week postpartum.
The 8-week integrated childbirth education intervention was effective in reducing the fear of childbirth in pregnant women. The mindfulness techniques were easily learnt and applied by the participants. Using these techniques during pregnancy and labour enhanced participants’ mental health and coping. The integrated childbirth education which includes pregnant women and their support partners could be easily taught by midwives in other contexts.
Molecular transport through nanoporous nuclear-track-etched membranes was investigated with fluorescent probes by manipulating applied electric field polarity, pore size, membrane surface ...functionality, pH, and the ionic strength. Three forces contribute to analyte transport through membranes: ion migration, electroosmosis, and diffusion. Diffusion dominates under field-free conditions with surface hydrophobicity controlling solvent access to the nanochannels and hence the magnitude of transport by diffusion. In low ionic strength solutions (μ ∼ 10 mM), electroosmosis dominates transport when the membranes are biased, and the charge state of the surface determines the direction of flow. At high ionic strength (μ ∼ 1 M), ion migration dominates in hydrophobic membranes, and diffusion is controlling in hydrophilic membranes. The magnitude and polarity of the interior surface charge is controlled by surface functionality and displays the largest impact on molecular transport. The analyte can migrate in opposite directions under the same applied electric field by modifying either membrane surface charge or solution ionic strength. Transport can be fine-tuned by adjusting pH under low ionic strength conditions in either type of membrane. Increasing the surface charge density, σs, enhances the mobile counterion concentration, increasing the electroosmotically driven flux. Comparisons of behavior under different conditions are understood by reference to the product, κa, of the inverse Debye length, κ, and the pore diameter, a.
An electrokinetic injection technique is described which uses a nuclear track-etched nanocapillary array to inject sample plugs from one layer of a microfluidic device into another vertically ...separated layer for electrophoretic separations. Gated injection protocols for analyte separations, reported here, establish nanocapillary array interconnects as a route to multilevel microfluidic analytical designs. The hybrid nanofluidic/microfluidic gated injection protocol allows sample preparation and separation to be implemented in separate horizontal planes, thereby achieving multilayer integration. Repeated injections and separations of FITC-labeled arginine and tryptophan, using 200-nm pore-diameter capillary array injectors in place of traditional cross injectors are used to demonstrate gated injection with a bias configuration that uses relay switching of a single high-voltage source. Injection times as rapid as 0.3 s along with separation reproducibilities as low as 1% for FITC-labeled arginine exemplify the capability for fast, serial separations and analyses. Impedance analysis of the micro-/nanofluidic network is used to gain further insight into the mechanism by which this actively controlled nanofluidic-interconnect injection method works. Gated sample introduction via a nanocapillary array interconnect allows the injection and separation protocols to be optimized independently, thus realizing the versatility needed for real-world implementation of rapid, serial microchip analyses.
Asphaltenes are surface-active molecules that exist naturally in crude oil. They adsorb at the water–oil interface and form viscoelastic interfacial films that stabilize emulsion droplets, making ...water–oil separation extremely challenging. There is, thus, a need for chemical demulsifiers to disrupt the interfacial asphaltene films, and, thereby, facilitate water–oil separation. Here, we examine ethylcellulose (EC) as a model demulsifier and measure its impact on the interfacial properties of asphaltene films using interfacial shear microrheology. When EC is mixed with an oil and asphaltene solution, it retards the interfacial stiffening that occurs between the oil phase in contact with a water phase. Moreover, EC introduces relatively weak regions within the film. When EC is introduced to a pre-existing asphaltene film, the stiffness of the films decreases abruptly and significantly. Direct visualization of interfacial dynamics further reveals that EC acts inhomogeneously, and that relatively soft regions in the initial film are seen to expand. This mechanism likely impacts emulsion destabilization and provides new insight to the process of demulsification.
Low aqueous solubility of active pharmaceutical ingredients (APIs) is an enduring problem in pharmaceutical development, and it is becoming increasingly prevalent among new drug candidates. It is ...estimated that about 40% of drugs in the development pipeline and approximately 60% of the drugs coming directly from discovery suffer from poor aqueous solubility and slow dissolution, thereby reducing their bioavailability and efficacy and thus preventing their commercialization. It is well known that utilizing the amorphous form of a drug can be a useful approach to improve the dissolution rate and solubility of poorly water-soluble APIs. Amorphous compounds are thermodynamically unstable, but they can be stabilized by combining them with a carrier polymer (excipient) to form a solid dispersion. High-throughput Raman spectroscopy was used in this study to identify excipients that promote formation and stabilization of the amorphous drug form in solid dispersions. Four model APIs were used as poorly soluble drug candidates: ketoprofen, danazol, griseofulvin, and probucol. The Raman signals of excipients were generally negligible, and therefore Raman bands from the drugs were used with minimal spectral pre-processing. By comparing Raman spectra collected from the APIs in the crystalline and molten state, appropriate spectral features and regions were identified for the development of semi-quantitative methods to determine the amorphous content for each API. It is demonstrated that methods based on peak intensity ratio, peak width, peak distance, and classical least squares can all be effective methods for the screening of excipients. Interesting excipient-dependent phase transformation behavior was also observed for probucol.
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