A model study of enhanced oil recovery by flooding with aqueous surfactant solution and comparison with theory

With the aim of elucidating the details of enhanced oil recovery by surfactant solution flooding, we have determined the detailed behavior of model systems consisting of a packed column of calcium carbonate particles as the porous rock, n-decane as the trapped oil, and aqueous solutions of the anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT). The AOT concentration was varied from zero to above the critical aggregation concentration (cac). The salt content of the aqueous solutions was varied to give systems of widely different, post-cac oil–water interfacial tensions. The systems were characterized in detail by measuring the permeability behavior of the packed columns, the adsorption isotherms of AOT from the water to the oil–water interface and to the water–calcium carbonate interface, and oil–water–calcium carbonate contact angles. Measurements of the percent oil recovery by pumping surfactant solutions into calcium carbonate-packed columns initially filled with oil were analyzed in terms of the characterization results. We show that the measured contact angles as a function of AOT concentration are in reasonable agreement with those calculated from values of the surface energy of the calcium carbonate–air surface plus the measured adsorption isotherms. Surfactant adsorption onto the calcium carbonate–water interface causes depletion of its aqueous-phase concentration, and we derive equations which enable the concentration of nonadsorbed surfactant within the packed column to be estimated from measured parameters. The percent oil recovery as a function of the surfactant concentration is determined solely by the oil–water–calcium carbonate contact angle for nonadsorbed surfactant concentrations less than the cac. For surfactant concentrations greater than the cac, additional oil removal occurs by a combination of solubilization and emulsification plus oil mobilization due to the low oil–water interfacial tension and a pumping pressure increase

Model Study of Enhanced Oil Recovery by Flooding with Aqueous Solutions of Different Surfactants: How the Surface Chemical Properties of the Surfactants Relate to the Amount of Oil Recovered

© 2016 American Chemical Society. The main aim of this work is to establish how the fraction of oil recovered from an oil-filled calcite powder packed column by injection of aqueous surfactant solution depends on the phase behavior and surface chemical properties of the surfactant system. We have measured the phase behavior, the adsorption of surfactant to the oil-water, calcite-water, and calcite-oil interfaces, tensions, and contact angles for anionic, cationic, and nonionic surfactant/oil/aqueous phase systems. We show how the measured surface chemical properties can be used to approximately predict the fraction of oil recovered as a function of the volume and concentration of the surfactant solutions injected into the column. Measured and calculated plots of %oil recovery versus surfactant concentration show reasonably good agreement for the different surfactant systems. The experimentally validated model for oil recovery provides a sound basis for the rational selection of surfactant type and concentration to achieve maximum oil recovery based on laboratory measurements of the surface chemical properties of candidate surfactants

Generation of very flat optical frequency combs from continuous-wave lasers using cascaded intensity and phase modulators driven by tailored radio frequency waveforms

We demonstrate a scheme, based on a cascade of lithium niobate intensity and phase modulators driven by specially tailored radio frequency waveforms to generate an optical frequency comb with very high spectral flatness. In this work we demonstrate a 10 GHz comb with ~40 lines with spectral power variation below 1-dB and ~60 lines in total. The number of lines that can be generated is limited by the power handling capability of the phase modulator, and this can be scaled without compromising the spectral flatness. Furthermore, the spectral phase of the generated combs in our scheme is almost purely quadratic which, as we will demonstrate, allows for very high quality pulse compression using only single mode fiber.Comment: 12 pages, 3 figures, replaced the older version with the published versio

Supersymmetry and Positive Energy in Classical and Quantum Two-Dimensional Dilaton Gravity

An $N = 1$ supersymmetric version of two dimensional dilaton gravity coupled to matter is considered. It is shown that the linear dilaton vacuum spontaneously breaks half the supersymmetries, leaving broken a linear combination of left and right supersymmetries which squares to time translations. Supersymmetry suggests a spinorial expression for the ADM energy $M$, as found by Witten in four-dimensional general relativity. Using this expression it is proven that ${M}$ is non-negative for smooth initial data asymptotic (in both directions) to the linear dilaton vacuum, provided that the (not necessarily supersymmetric) matter stress tensor obeys the dominant energy condition. A {\it quantum} positive energy theorem is also proven for the semiclassical large-$N$ equations, despite the indefiniteness of the quantum stress tensor. For black hole spacetimes, it is shown that $M$ is bounded from below by $e^{- 2 \phi_H}$, where $\phi_H$ is the value of the dilaton at the apparent horizon, provided only that the stress tensor is positive outside the apparent horizon. This is the two-dimensional analogue of an unproven conjecture due to Penrose. Finally, supersymmetry is used to prove positive energy theorems for a large class of generalizations of dilaton gravity which arise in consideration of the quantum theory.Comment: 21 page

Is the early identification and referral of suspected head and neck cancers by community pharmacists feasible?:A qualitative interview study exploring the views of patients in North East England

INTRODUCTION Head and neck cancer (HNC) is the eighth most common cancer in the United Kingdom. Survival rates improve when the cancer is diagnosed at an early stage, highlighting a key need to identify at-risk patients. This study aimed to explore opportunistic HNC identification and referral by community pharmacists (CPs) using a symptom-based risk assessment calculator, from the perspective of patients with a diagnosis of HNC. METHODS Purposive sampling was used to recruit patients from the HNC pathway in three large teaching hospitals in Northern England. Qualitative methodology was used to collect data through an iterative series of semistructured telephone interviews. Framework analysis was utilised to identify key themes. RESULTS Four main themes were constructed through the analytic process: (1) HNC presentation and seeking help; (2) the role of the CP; (3) public perception of HNC and (4) the role of a symptom-based risk calculator. Participants agreed that CPs could play a role in the identification and referral of suspected HNCs, but there were concerns about access as patients frequently only encounter the medicine counter assistant when they visit the pharmacy. HNC symptoms are frequently attributed to common or minor conditions initially and therefore considered not urgent, leading to delays in seeking help. While there is public promotion for some cancers, there is little known about HNC. Early presentation of HNC can be quite variable, therefore raising awareness would help. The use of a symptom-based risk calculator was considered beneficial if it enabled earlier referral and diagnosis. Participants suggested that it would also be useful if the public were made aware of it and could self-assess their symptoms. CONCLUSION In principle, CPs could play a role in the identification and referral of HNC, but there was uncertainty as to how the intervention would work. Future research is needed to develop an intervention that would facilitate earlier identification and referral of HNC while not disrupting CP work and that would promote HNC and the risk calculator more widely. PATIENT OR PUBLIC CONTRIBUTION Patient and public involvement and engagement (PPIE) was integrated throughout the project. Initially, the proposal was discussed during a Cancer Head and Neck Group Experience (CHANGE) PPIE meeting. CHANGE was set up to support HNC research in 2018. The group is composed of seven members (four female, three male) with an age range of 50-71 years, who were diagnosed at Sunderland Royal Hospital. A patient representative from the University of Sunderland PPIE group and a trustee of the Northern HNC Charity were recruited as co-applicants. They attended project management group meetings and reviewed patient-facing documentation

Worldvolume Superalgebra Of BLG Theory With Nambu-Poisson Structure

Recently it was proposed that the Bagger-Lambert-Gustavsson theory with Nambu-Poisson structure describes an M5-brane in a three-form flux background. In this paper we investigate the superalgebra associated with this theory. We derive the central charges corresponding to M5-brane solitons in 3-form backgrounds. We also show that double dimensional reduction of the superalgebra gives rise to the Poisson bracket terms of a non-commutative D4-brane superalgebra. We provide interpretations of the D4-brane charges in terms of spacetime intersections.Comment: 23 pages; references added, section 4 clarification

No Effect of a Whey Growth Factor Extract during Resistance Training on Strength, Body Composition, or Hypertrophic Gene Expression in Resistance-Trained Young Men

Growth factors can be isolated from bovine milk to form a whey growth factor extract (WGFE). This study examined whether WGFE promoted activation of the AKT/mTOR pathway enabling increased lean tissue mass and strength in resistance trained men. Forty six men with \u3e6 months of resistance training (RT) experience performed 12 weeks of RT. Participants consumed 20 g/day of whey protein and were randomised to receive either 1.6 g WGFE/day (WGFE; n = 22) or 1.6 g cellulose/day (control, CONT; n = 24). The primary outcome was leg press one-repetition maximum (LP1-RM) which was assessed at baseline, 6 and 12 weeks. At baseline and 12 weeks body composition was assessed by dual energy x-ray absorptiometry, and muscle protein synthesis and gene expression were assessed (vastus lateralis biopsy) in a sub-sample (WGFE n = 10, CONT n = 10) pre- and 3 hr post-training. RT increased LP1-RM (+34.9%) and lean tissue mass (+2.3%; p \u3c 0.05) with no difference between treatments (p \u3e 0.48, treatment x time). Post-exercise P70s6k phosphorylation increased acutely, FOXO3a phosphorylation was unaltered. There were no differences in kinase signalling or gene expression between treatments. Compared with CONT, WGFE did not result in greater increases in lean tissue mass or strength in experienced resistance trained men

Geographic Variation in Influenza Vaccination Disparities Between Hispanic and Non-Hispanic White US Nursing Home Residents

BACKGROUND: Disparities in influenza vaccination exist between Hispanic and non-Hispanic White US nursing home (NH) residents, but the geographic areas with the largest disparities remain unknown. We examined how these racial/ethnic disparities differ across states and hospital referral regions (HRRs). METHODS: This retrospective cohort study included >14 million short-stay and long-stay US NH resident-seasons over 7 influenza seasons from October 1, 2011, to March 31, 2018, where residents could contribute to 1 or more seasons. Residents were aged ≥65 years and enrolled in Medicare fee-for-service. We used the Medicare Beneficiary Summary File to ascertain race/ethnicity and Minimum Data Set assessments for influenza vaccination. We calculated age- and sex-standardized percentage point (pp) differences in the proportions vaccinated between non-Hispanic White and Hispanic (any race) resident-seasons. Positive pp differences were considered disparities, where the proportion of non-Hispanic White residents vaccinated was greater than the proportion of Hispanic residents vaccinated. States and HRRs with ≥100 resident-seasons per age–sex stratum per racial/ethnic group were included in analyses. RESULTS: Among 7 442 241 short-stay resident-seasons (94.1% non-Hispanic White, 5.9% Hispanic), the median standardized disparities in influenza vaccination were 4.3 pp (minimum, maximum: 0.3, 19.2; n = 22 states) and 2.8 pp (minimum, maximum: −3.6, 10.3; n = 49 HRRs). Among 6 758 616 long-stay resident-seasons (93.7% non-Hispanic White, 6.5% Hispanic), the median standardized differences were −0.1 pp (minimum, maximum: −4.1, 11.4; n = 18 states) and −1.8 pp (minimum, maximum: −6.5, 7.6; n = 34 HRRs). CONCLUSIONS: Wide geographic variation in influenza vaccination disparities existed across US states and HRRs. Localized interventions targeted toward areas with high disparities may be a more effective strategy to promote health equity than one-size-fits-all national interventions