Quantification of Viscosity for Solvents−Heavy Oil/Bitumen Systems in the Presence of Water at High Pressures and Elevated Temperatures

In this study, a new and pragmatic methodology has been developed to accurately predict the viscosity for light solvents (i.e., methane, ethane, propane, n-butane, n-pentane, N2, and CO2)–heavy oil/bitumen/water systems as a function of pressure in the temperature range of 287.9–463.4 K. The LV and ALV (L is the oleic phase, V is the vapor phase, and A is the aqueous phase) phase equilibria of the aforementioned systems are calculated using the Peng–Robinson equation of state (PR EOS) with modified alpha functions and binary interaction parameters (BIPs). The six widely used mixing rules for predicting viscosity of solvents−heavy oil/bitumen systems pertaining to vapor–liquid equilibria are compared and evaluated, while the linear mixing rule is used for hydrocarbons−water mixtures. Plus, effective density is for the first time successfully introduced into the volume-based mixing rules. The volume-based power law, weight-based power law, and weight-based Cragoe’s mixing rules are found to well reproduce the viscosity for the aforementioned systems with AARDs of 15.5%, 19.0%, and 32.6%, respectively. Effective density rather than real density of dissolved gas(es) should be used for all of the volume-based mixing rules, while the adjustable parameter in the power law mixing rule has a potential to achieve high generalization if adequate measurements are made available. Although water has a lower diluting ability than other solvents in the same amount of dissolution, it can outperform methane and CO2 in diluting heavy oil/bitumen at high temperatures due to its high solubility. Addition of water can reduce or increase the viscosity of a solvents–heavy oil/bitumen mixture, depending on the ability of solvents and water to dilute heavy oil/bitumen and effects of water on the solvent dissolution. Water molar fraction in feed can exert an effect on the mixture viscosity in LV equilibria through affecting the solvent dissolution but cannot impose an impact on the mixture viscosity at ALV equilibria

Zinc Improves Functional Recovery by Regulating the Secretion of Granulocyte Colony Stimulating Factor From Microglia/Macrophages After Spinal Cord Injury

While zinc promotes motor function recovery after spinal cord injury (SCI), the precise mechanisms involved are not fully understood. The present study aimed to elucidate the effects of zinc and granulocyte colony stimulating factor (G-CSF) on neuronal recovery after SCI. The SCI model was established by Allen’s method. Injured animals were given glucose and zinc gluconate (ZnG; 30 mg/kg) for the first time at 2 h after injury, the same dose was given for 3 days. A cytokine antibody array was used to screen changes in inflammation at the site of SCI lesion. Immunofluorescence was used to detect the distribution of cytokines. Magnetic beads were also used to isolate cells from the site of SCI lesion. We then investigated the effect of Zinc on apoptosis after SCI by Transferase UTP Nick End Labeling (TUNEL) staining and Western Blotting. Basso Mouse Scale (BMS) scores and immunofluorescence were employed to investigate neuronal apoptosis and functional recovery. We found that the administration of zinc significantly increased the expression of 19 cytokines in the SCI lesion. Of these, G-CSF was shown to be the most elevated cytokine and was secreted by microglia/macrophages (M/Ms) via the nuclear factor-kappa B (NF-κB) signaling pathway after SCI. Increased levels of G-CSF at the SCI lesion reduced the level of neuronal apoptosis after SCI, thus promoting functional recovery. Collectively, our results indicate that the administration of zinc increases the expression of G-CSF secreted by M/Ms, which then leads to reduced levels of neuronal apoptosis after SCI

Binding of dicamba to soluble and bound extracellular polymeric substances (EPS) from aerobic activated sludge: A fluorescence quenching study

Binding of dicamba to soluble EPS (SEPS) and bound EPS (BEPS) from aerobic activated sludge was investigated using fluorescence spectroscopy. Two protein-like fluorescence peaks (peak A with Ex/Em = 225 nm/342-344 nm and peak B with Ex/Em = 275/340-344 nm) were identified in SEPS and BEPS. Humic-like fluorescence peak C (Ex/Em = 270-275 nm/450-460 nm) was only found in BEPS. Fluorescence of the peaks A and B for SEPS and peak A for BEPS were markedly quenched by dicamba at all temperatures whereas fluorescence of peaks B and C for BEPS was quenched only at 298 K. A dynamic process dominated the fluorescence quenching of peak A of both SEPS and BEPS. Fluorescence quenching of peak B and C was governed a static process. The effective quenching constants (log K-a) were 4.725-5.293 for protein-like fluorophores of SEPS and 4.23-5.190 for protein-like fluorophores of BEPS, respectively. Log K-a for humic-like substances was 3.85. Generally, SEPS had greater binding capacity for dicamba than BEPS, and protein-like substances bound dicamba more strongly than humic-like substances. Binding of dicamba to SEPS and BEPS was spontaneous and exothermic. Electrostatic force and hydrophobic interaction forces play a crucial role in binding of dicamba to EPS. (C) 2010 Elsevier Inc. All rights reserved.

Effects of levofloxacin hydrochlordie on photosystem II activity and heterogeneity of Synechocystis sp.

Effects of LH on photosynthesis of Synechocystis sp. were investigated by a variety of in vivo chlorophyll fluorescence. O-2 evolution and the photosystem II (PSII) activity were clearly inhibited by LH. Exposure to LH increased the proportion of PSII beta and this weakened the connectivity between PS11 units and hindered excitation energy-transfer between PSII units. LH decreased the density of the active photosynthetic reaction centers, inhibited electron transport, and increased the dissipated energy flux per reaction center. The inhibitory effect of LH on Q(A)(-) reoxidation process could be divided into several stages. LH first inhibited the electron transfer from Q(A)(-) to Q(B) by weakening the connectivity between Q(A)(-) and Q(B), and PQ binding began taking part in Q(A)(-) reoxidation. At the second stage, the connectivity between Q(A)(-) and PQ pool was broken and inhibition on PQ binding occurred. At this stage, some Q(A)(-) began to be oxidized by S-2(Q(A)Q(B))(-). Finally, when the connectivity between Q(A)(-) and Q(B) and PQ was completely broken, all Q(A)(-) was oxidized through charge recombination. (C) 2009 Elsevier Ltd. All rights reserved

Polymeric core-shell stars with a novel fluorescent, cross-linked and swollen core: Their efficient one-step preparation, further self-assembly into superparticles and application as a chemosensor †

Here we report that block copolymer core-shell stars with a novel fluorescent, cross-linked and swollen core can be efficiently prepared by simply cross-linking the poly(4-vinylpyridine) (P4VP) block of polystyrene (PS)-block-P4VP diblock copolymer in N,N-dimethylformamide (DMF, the common solvent of the copolymer) using propargyl bromide (PB) as the cross-linker. Propargyl bromide first quaternized pyridine groups in the repeat units of the P4VP block chains, grafting propargyl groups onto the P4VP block chains. After the quaternization, the acetylene groups in the grafted propargyl groups were activated and thus could polymerize with each other, which resulted in the cross-linking of the P4VP block chains. The cross-linking reaction forced the aggregation of the P4VP block chains. Meanwhile, with the cross-linking reaction taking place, the PS block chains which were still soluble, gathered around the P4VP aggregates and localized the cross-linking reaction. Therefore, block copolymer core-shell stars with the P4VP/PB cross-linked network as the core and the PS block chains as the shell formed. The average aggregation number of the core-shell stars was determined by static light scattering to be 26, which is much less than that of micelles formed by the same block copolymer with similar structure parameters in a selective solvent for PS. The polymerization of the acetylene groups in the grafted propargyl groups also led to the formation of a fluorescent conjugated polymer polyacetylene in the core. Therefore, the as-prepared core-shell stars have a fluorescent core (the fluorescence of the product of PB and pyridine (or products of PB analogues with pyridine derivatives) has never been reported). We further confirmed that the core of the as-prepared core-shell stars had a loosely aggregated structure and, to a certain extent, swelled in DMF, which made penetration of small molecular species into the core convenient. Therefore, the chromophores within the core could respond promptly to various metallic ions and basic species. It was also due to the loosely aggregated structure that the primary core-cross-linked core-shell stars could further self-assemble into dispersible superparticles in water. Although originally existing as the core, the P4VP/PB cross-linked network acted as the shell of and thus stabilized the superparticles. This simple, yet efficient method for preparing polymeric core-shell stars with a novel fluorescent and loosely aggregated core that can respond promptly to ionic species and further self-assemble into superparticles should show promise to address related problems in the field of materials chemistry

Effectiveness of varicella vaccine as post-exposure prophylaxis: a meta-analysis

Background To evaluate the effectiveness of varicella vaccine (VarV) as post-exposure prophylaxis (PEP) among children during varicella outbreaks. Material and Methods A comprehensive literature search was performed in PubMed, Embase, Web of Science, SinoMed, Wanfang and CNKI. Relevant outcomes included the incidence of varicella. Pooled estimates were calculated using a fixed-effects or random-effects model according to the heterogeneity among studies. Results A total of 15 studies with 7,474 children that received one or two dosages of VarV as PEP and 183,827 children who received no VarV were included in the meta-analysis. In total, one-dose and two-dose VarV as PEP had 43% (95% confidence interval (CI):27%, 55%) and 60% (95%CI: 35%, 75%) efficacy, respectively. When PEP was applied within 3 days, the pooled VarV as PEP for prevention of varicella was 80% (95%CI: 68%, 88%); when PEP was administered beyond 3 days, the pooled VarV as PEP for the prevention of varicella was 50% (95%CI: 11%, 72%). If the PEP was implemented with a coverage of more than 80%, the VarV could prevent 82% of varicella cases from occurring (95%CI: 15%, 96%); if the PEP covered a maximum of 80% of the susceptible cases, the VarV could prevent 65% of varicella cases from occurring (95%CI: 50%, 76%). Conclusion The two-dose VarV had better efficacy than one-dose VarV in the control of varicella outbreaks, especially if PEP was applied within 3 days of an outbreak and in conjunction with a high coverage rate ≥80%

Evaluation of organic matter removal by H2O2 from microplastic surface by nano-physicochemical methods

Microplastics (MPs) are often coated in natural organic matters (NOM) from environments, causing MP identification to become more complicated. Currently, the popular way to remove NOM from MPs is oxidative digestion using hydrogen peroxide (H2O2). However, removal efficiency of NOM on MP surface is still unclear. In this study, we evaluated NOM removal efficiency with digestion time (0, 6, 12 and 24 h) based on physicochemical imaging technologies including Infrared spectra (IR), Thermal Analysis (TA) and Lorentz Contact Resonance (LCR) combined with Atomic Force Microscope (AFM) at nanoscale. Results showed that the changes of C-O-C, -CH2 and -CH3 with digestion time were unreliable for evaluation due to irregular change trends and co-occurrence of these bands in both NOM and MPs. Although AFM-IR signal of C=O was getting weaker on MPs with digestion time, it was insufficient to indicate NOM removal since C=O also presents in weathered environmental MPs. Thermal and mechanical analysis based on TA and LCR at nanoscale showed that the distributions of softening temperature and stiffness tended to be of spatial homogeneity with digestion time, indicating gradual removal of NOM from MP surface. These indicated that a comprehensive IR-thermal-mechanical methods were better to evaluate the efficiency of H2O2 digestion for removal of NOM on MP surface from environment. Therefore, the combination of multiple technologies at nanoscale deserves to be developed for evaluating removal of NOM from MPs in the future. These results can help to provide methodological reference in monitoring and management of MP pollution

A new design of ionic complexation and its application for efficient protection of proteins

Ionic complexation is one of the most important topics in the fields of biology, physics, chemistry, and materials science. An ionic complex normally has an upper critical complexation temperature (UCCT), i.e. the ionic complex disappears above UCCT. Herein we have for the first time demonstrated that a new ionic complex, in contrast to the UCCT complex, has a lower critical complexation temperature (LCCT), which means that the ionic complex exists above UCCT but disappears below LCCT. We have further shown that the LCCT ionic complexation can efficiently protect proteins at the denaturation temperature but automatically release proteins at room temperature to freely interact with the substrates. For example, 70–80% enzymatic activity was retained after heating at 70–75 °C for 60–90 min and cooling to room temperature using this strategy. Thus this new LCCT ionic complexation would provide a cost-effective approach to protecting proteins for various biomedical applications