Two
series of double-chain single-head nonionic surfactants, Guerbet
alcohol ethoxylates (C
m
GA–E
n
; m = 16 and 20, n = 5.7–24.0), were synthesized, and their performances
as surfactants for surfactant–polymer (SP) flooding free of
alkali were evaluated. The products have relatively low critical micelle
concentrations [(6.8 × 10–7)–(1.0 ×
10–5 mol/L)] and a wide range of surface tensions
at the critical micelle concentration (γcmc) values
(30.3–38.0 mN/m) at 25 °C, depending on both the alkyl-chain
length and the number of ethylene oxide (EO) units. When used alone,
these nonionic surfactants are not efficient for reducing crude oil/connate
water interfacial tension (IFT), but their binary mixtures with a
highly hydrophobic zwitterionic surfactant, didodecylmethyl hydroxylpropyl
sulfobetaine (diC12HSB), are very efficient in reducing
Daqing crude oil/connate water IFTs. Ultralow IFTs can be achieved
in a wide total concentration range (0.3–10 mM) at 45 °C,
and the low limit (0.3 mM) can be further reduced to 0.15 mM by adding
an anionic surfactant, α-olefin sulfonate (AOS), to the binary
mixtures at a small mole fraction (0.1). Both the binary and ternary
mixtures display good resistance against adsorption by Daqing sandstone,
and when dissolved in connate water, they prefer to keep the negatively
charged rock surface water-wet and produce a crude-oil-in-water emulsion.
In addition, the incorporation of AOS into the binary mixtures was
found to be beneficial for preventing crystallization of zwitterionic
surfactant and flocculation of nonionic surfactants, as reported previously.
Comparatively, for SP flooding free of alkali, the Guerbet alcohol
ethoxylates are as excellent as the glyceryl ether ethoxylates, nonionic
surfactants with a similar double-alkyl single-head structure, but
are far superior to the conventional nonionic surfactants with monoalkyl
single-head structures.
Rationale:Melioidosis is an emerging infectious disease caused by Burkholderia pseudomallei. To our knowledge, there have been very few cases of splenic abscesses due to melioidosis in Hainan, China.Patient concerns:The patient was a 55-year-old male farmer, who was admitted in our hospital with persistent left epigastric dull pain accompanied by chills and febrile. One month before, the patient presented with persistent abdominal pain. After received anti-infection therapy, the subjective symptoms eased slightly, but recently he suffered from intermittent abdominal pain again.Diagnoses:Bacteria isolated from splenic pus were identified as B. pseudomallei by the Phoenix-100 system and indirect immunofluorescence.Interventions:The patient was treated by surgical excision and anti-infection therapy.Outcomes:The patient was then treated with intravenous ceftazidime and oral trimethoprim-sulfamethoxazole for 2 weeks and his clinical symptoms improved.Lessons:In endemic areas, B. pseudomallei should be considered as a causative organism of splenic abscess in patients with established risk factors. The isolation of B. pseudomallei from abscess sites is crucial to improve clinical outcomes by appropriate antimicrobial therapy coupled with surgical drainage.
PurposeMagnetic submicron particles (MSPs) are pivotal biomaterials for magnetic separations in bioanalyses, but their preparation remains a technical challenge. In this report, a facile one-step coating approach to MSPs suitable for magnetic separations was investigated.MethodsPolyethylene glycol) (PEG) was derived into PEG-bis-(maleic monoester) and maleic monoester-PEG-succinic monoester as the monomers. Magnetofluids were prepared via chemical co-precipitation and dispersion with the monomers. MSPs were prepared via one-step coating of magnetofluids in a water-in-oil microemulsion system of aerosol-OT and heptane by radical co-polymerization of such monomers.ResultsThe resulting MSPs contained abundant carboxyl groups, exhibited negligible nonspecific adsorption of common substances and excellent suspension stability, appeared as irregular particles by electronic microscopy, and had submicron sizes of broad distribution by laser scattering. Saturation magnetizations and average particle sizes were affected mainly by the quantities of monomers used for coating magnetofluids, and steric hindrance around carboxyl groups was alleviated by the use of longer monomers of one polymerizable bond for coating. After optimizations, MSPs bearing saturation magnetizations over 46 emu/g, average sizes of 0.32 μm, and titrated carboxyl groups of about 0.21 mmol/g were obtained. After the activation of carboxyl groups on MSPs into N-hydroxysuccinimide ester, biotin was immobilized on MSPs and the resulting biotin-functionalized MSPs isolated the conjugate of streptavidin and alkaline phosphatase at about 2.1 mg/g MSPs; streptavidin was immobilized at about 10 mg/g MSPs and retained 81% ± 18% (n = 5) of the specific activity of the free form.ConclusionThe facile approach effectively prepares MSPs for magnetic separations.
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