Using stable nitrogen and oxygen isotopes to identify nitrate sources in the Lancang River, upper Mekong.

The Lancang River in China is the headwater of the Mekong River. The impacts of reservoirs on the water, sediment and nutrient trapping in the Lancang River have attracted considerable attention, both locally and abroad. In this research, watershed-scale nitrogen load and nitrate sources along the Lancang River upstream in free-flowing reaches (FFRs) and downstream regulated reaches (RRs) were analyzed using stable nitrogen and oxygen isotopes. The results showed that the nitrogen nutrient (TN, NO3- and NH4+) concentration increased from upstream to downstream along the Lancang River, and the highest values come from large-scale urban samples rather than the reservoirs. Compared to other large rivers in China, such as the Yangtze River, Yellow River and Yalu Tsangpo River, nitrogen nutrient content in the Lancang River is at low level. The nitrate concentration ranged from 0.14 mg/L to 0.63mg/Land increased significantly downstream. The isotopic values ranged from 2.8‰ to 5.2‰ for δ15N-NO3- and from 4‰ to 8.5‰ for δ18O-NO3- along the river, and the δ15N-NO3- value rose significantly downstream. According to the nitrogen and oxygen isotope approach, soil organic nitrogen mineralization was the main source of the nitrate with an average of 51% contribution; domestic sewage was the second largest contributor with an average of 33% but increase downstream, likely due to the significantly larger population in the downstream region. Furthermore, the nitrate concentration decreased and δ15N- and δ18O-NO3- enriched in the Nuozhadu reservoir, indicating that the reservoir may enhance nitrate consumption and reduce nitrogen pollution to downstream reaches. The results provide a perspective of nitrogen nutrient for the trans-border river management and more insight researches are called for understanding the controversial nutrient transport topic in this region.

Chemical and thermal stability of N-heterocyclic ionic liquids in catalytic C-H activation reactions.

(1)H-NMR spectrum analyses are applied to study the chemical and thermal stability of selected N-heterocyclic ionic liquids within the reaction system that can highly efficiently activate a C-H bond of methane and convert it into the C-O bond in methanol. Our results indicate that under such reaction conditions involving using a powerful Pt-based catalyst and strong acidic solvent, the aromatic ring of an imidazolium cation becomes unstable generating an ammonium ion (NH(4)(+)). Our results also suggest that the instability of the imidazolium ring is more chemically (participation in reactions) than thermally based. Modifications of the aromatic ring structure such as pyrazolium and triazolium cations can increase the chemical/thermal stability of ionic liquids under these reaction conditions.

Multidimensional Predictors of Cancer-Related Fatigue Based on the Predisposing, Precipitating, and Perpetuating (3P) Model: A Systematic Review.

Cancer-related fatigue (CRF) is a widespread symptom with high prevalence in cancer patients, seriously affecting their quality of life. In the context of precision care, constructing machine learning-based prediction models for early screening and assessment of CRF is beneficial to this situation. To further understand the predictors of CRF for model construction, we conducted a comprehensive search in PubMed, Web of Science, Embase, and Scopus databases, combining CRF with predictor-related terms. A total of 27 papers met the inclusion criteria. We evaluated the above studies into three subgroups following the predisposing, precipitating, and perpetuating (3P) factor model. (1) Predisposing factors-baseline fatigue, demographic characteristics, clinical characteristics, psychosocial traits and physical symptoms. (2) Precipitating factors-type and stage of chemotherapy, inflammatory factors, laboratory indicators and metabolic changes. (3) Perpetuating factors-a low level of physical activity and poorer nutritional status. Future research should prioritize large-scale prospective studies with emerging technologies to identify accurate predictors of CRF. The assessment and management of CRF should also focus on the above factors, especially the controllable precipitating factors, to improve the quality of life of cancer survivors.

Raman Thermal Maturity of Coal and Type II Kerogen Based on Surface-Enhanced Raman Spectroscopy (SERS).

Low-maturity organic samples generate high levels of fluorescence during Raman detection. This fluorescence will obviously affect the Raman signals from organic matter. Our research shows that surface-enhanced Raman spectroscopy (SERS) can significantly enhance the ratio of the Raman signal from organic matter to the fluorescence background without changing the peak positions. This allows us to obtain more accurate Raman parameters for organic matter. In this study, we conducted Raman testing with SERS on coal and type II kerogen from the USA. We found that for both coal and type II kerogen, the exponential correlation between the thermal maturity and the distance between their D and G bands (Δ(G-D)) in the Raman spectra was good, and the R-squared values were 0.968 and 0.988, respectively. However, the Raman thermal maturity evolution curves for the coal and the type II kerogen were different. Compared with the Raman thermal maturity evolution curve of type II kerogen, that of coal was steeper. The two curves crossed each other at a Δ(G-D) value of 223, which corresponds to a calculated vitrinite reflectance value of 0.61%. This study also shows that the Raman thermal maturity evolution model of organic matter is perhaps related mainly to its type.

Sulfur isotope fractionation during incorporation of sulfur nucleophiles into organic compounds.

(34)S enrichment is shown to occur during sulfurization reactions and for the first time conclusively attributed to an isotope equilibrium effect rather than selective addition of (34)S enriched nucleophiles.

Hollow waveguide quantum cascade laser spectrometer as an online microliter sensor for gas chromatography.

An optical absorption sensor for gas chromatography (GC) is presented. It consists of a quantum cascade laser along with a long piece of Hollow Waveguide for Infrared (HWIR) transmission inserted into the GC line. It measures the infrared absorption in each individual gas peak after separation by the GC column, and maintains the shapes of gas peaks after the HWIR sensor, making the gas samples further available for other sensors. By adding an inline combustion module before the HWIR sensor, the concentrations of many carbon containing compounds can be acquired by measuring CO2 absorption in their peaks. The HWIR sensor detects isotopologues of CO2 separately, and therefore can be used to measure carbon isotope ratios of heavy compounds. Application of the HWIR sensor to the detection of 13CO2 and CDH3 is described.

[Spatial Difference and Causes Analysis of the δ15 N of Suspended Particulate Matter in the Lancang River Basin].

The influence of cascade hydropower construction on the migration and transformation of raw material and ecological problems in the Lancang River Basin is of concern to scholars domestically and internationally. Based on stable isotope technology, this study analyzed the spatial distribution of nitrogen in the Lancang River Basin and explained the cause of this distribution. The results showed that the range of dissolved inorganic nitrogen (DIN) was 0.28-0.60mg·L-1, and that of DIN in the downstream area of the Lancang River was 0.39-1.15mg·L-1. The range of suspended particulate matter δ15 N in the upstream area of this river was 4.52‰-6.72‰, and that in the downstream reservoir section was heavier than that in the upstream reservoir, which varied between 2.3‰ and 11.8‰. This study used Isosource to analyze the source of suspended particulate matter. The results showed that industrial wastewater and sewage, soil organic matter, atmospheric sedimentation, and agrochemicals are the main sources of suspended particulate matter, and their respective total contribution rates are 42.43%, 22.38%, 18.16%, and 17.03%. At the same time, the δ15 N of suspended particulate matter in Xiaowan, Manwan, and Dachaosan dams downstream of the Lancang River were influenced by algal assimilation, it leads to a reduction in the number of δ15 N of suspended particles.

[Distribution Characteristics and Release Fluxes of Phosphorus Forms in Xiangxi Bay Sediments in the Three Gorges Reservoir Before and After Impoundment].

The sediment storage environment in tributaries has been altered by impoundment of water in the Three Gorges Reservoir area, affecting the distribution of phosphorus forms in sediment and processes at the sediment-water interface. Through collection of sediment and overlying water samples in Xiangxi Bay in August 2016 (before impoundment) and October (after impoundment), the distribution characteristics of sedimentary phosphorus and the environmental conditions of storage before and after impoundment were analyzed. Fluxes of PO43--P at the sediment-water interface were also estimated. Results show that pH increased, alkalinity and reducibility were enhanced, and Eh in sediments decreased after impoundment. The relative content of phosphorus in sediments changed as follows:NaOH-P > HCl-P > OP to HCl-P > OP > NaOH-P; this could be attributed to changes in the depositional environment. Compared to pre-impoundment values, TP values after impoundment in sediment, overlying water ρ(PO43--P), and interstitial water ρ (PO43--P) were 1.3 times, 3.7 times, and 8.3 times higher, increasing the risk of nutrient release in sediments of Xiangxi Bay. The manifestation of PO43--P in sendiments of Xiangxi River generally is "source" pre-impoundment and post-impoundment, but the PO43--P diffusive flux increased from -0.0029-0.0059 mg·(m2·d)-1 pre-impoundment to 0.0067-0.1071 mg·(m2·d)-1 post-impoundment. The release of phosphorus from sediments at the bottom of Xiangxi Bay increased after impoundment.

[Effect of the Rainfall on Extinction of Cyanobacteria Bloom and Its Mechanism Analysis].

There were three rainfall events with different intensity in the Xiangxi Bay (XXB) from May 24 to June 2 in 2016. The factors such as hydrodynamics, water temperature, optical properties, and chlorophyll a concentrations during the rainfall events were analyzed. During the May 27 moderate rain period, the upstream flow of the reservoir bay increased by 1.9 times and the average mixing layer depth in the whole reservoir increased 8.2 m, compared to those before the rainfall event. During the June 1 light rain period, the average mixing layer depth in the whole reservoir increased 1.6 m and the average chlorophyll concentration reduced 2.02 µg·L-1, compared with those before the rainfall event. During the June 2 heavy rain period, the upstream flow of the reservoir bay increased by 4 times, the average mixing layer depth in the whole reservoir increased 7.9 m and the average chlorophyll concentration reduced 14.64 µg·L-1, compared with those before the rainfall event. The algae moved from the upstream to the downstream with water that reduced the concentration of algae in the XXB. The water temperature stratification weakened during the rain event and the average mixing layer depth in the whole reservoir increased, destroying the algal growth environment. After the rainfall, under suitable light and temperature conditions for 2-3 d, the water temperature stratification of the reservoir was recovered and rapid growth and reproduction of algae occurred. As a result, the chlorophyll concentrations in the reservoir increased. Rainfall has a periodic inhibitory effect on the outbreak of algal blooms; however, it cannot fundamentally solve the problem of tribal bay blooms.

Wax inhibition by comb-like polymers: support of the incorporation-perturbation mechanism from molecular dynamics simulations.

Deposition of wax on a cold surface is a serious problem in oil production. Progress in developing more effective wax inhibitors has been impeded by the lack of an established mechanism connecting the molecular structure to inhibitor efficiency. Some comb-like polymers having long alkyl side chains are known to decrease the rate of wax formation. Among several possible mechanisms, we investigate here the incorporation-perturbation mechanism. According to this mechanism, the inhibitor molecules in oil are preferentially partitioned (incorporation) toward the wax-rich (amorphous) wax deposits (soft wax), which then serves as a perturbation to slow down the ordering transition of soft amorphous wax into more stable but problematic hard wax crystals. Indeed, molecular dynamics simulations on an effective inhibitor molecule in both the oil phase and in the amorphous wax phase support the idea that the oil-to-wax partition of the inhibitor is energetically favorable. With the inhibitor molecule embedded, the structure of wax crystal is disturbed, significantly decreasing the order and significantly lowering the cohesive energy density relative to that of the pure wax crystal, supporting the slower transition from soft wax to hard wax. Thus, in the presence of an effective wax inhibitor, crystallization (formation of hard wax) is slowed dramatically, so that there is time to flush out the soft wax with a high-pressure flow inside the pipeline. This suggests design principles for developing improved wax inhibitors.

Direct methane conversion to methanol by ionic liquid-dissolved platinum catalysts.

Ternary systems of inorganic Pt salts and oxides, ionic liquids and concentrated sulfuric acid are effective at catalyzing the direct, selective oxidation of methane to methanol and appear to be more water tolerant than the Catalytica reaction.

Biosurfactant produced by novel Pseudomonas sp. WJ6 with biodegradation of n-alkanes and polycyclic aromatic hydrocarbons.

Alkanes and polycyclic aromatic hydrocarbons (PAHs) have threatened the environment due to toxicity and poor bioavailability. Interest in degradation of these hazardous materials by biosurfactant-producing bacteria has been steadily increasing in recent years. In this work, a novel biosurfactant-producing Pseudomonas sp. WJ6 was isolated to degrade a wide range of n-alkanes and polycyclic aromatic hydrocarbons. Production of lipopeptide biosurfactant was observed in all biodegradable studies. These lipopeptides were purified and identified by C18 RP-HPLC system and electrospray ionization-mass spectrometry. Results of structural analysis showed that these lipopeptides generated from different hydrocarbons were classified to be surfactin, fengycin and lichenysin. Heavy-oil sludge washing experiments demonstrated that lipopeptides produced by Pseudomonas sp. WJ6 have 92.46% of heavy-oil washing efficiency. The obtained results indicate that this novel bacterial strain and its lipopeptides have great potentials in the environmental remediation and petroleum recovery.

[Expression of sCD40L in peripheral blood and NF-κBp65 in PBMC of patients with acute progressive cerebral infarction].

AIM: To study the expressional changes of soluble CD40 ligand(sCD40L) in peripheral blood serum and nuclear factor-κB (NF-κB) p65 in peripheral blood mononuclear cells (PBMC) of patients with acute progressive cerebral infarction(APCI). METHODS: We selected ninety-nine patients getting APCI less than 7 d of the onset as APCI group by prospective method. Each 100 cases of patients with acute cerebral infarction(ACI) in the same and with cerebral arteriosclerosis(CAS) in the outpatient were respectively selected as ACI and CAS group. The expressional changes of sCD40L in peripheral blood serum and NF-κBp65 in PBMC of patients with CAS on admission, of patients with APCI and ACI when in hospital, on the course of seventh day, of fourteen and of thirtieth were detected respectively. RESULTS: The expression of sCD40L in peripheral blood serum and NF-κBp65 in PBMC of patients of ACI group on admission were obviously higher all than that of CAS group (P<0.05); The expression of sCD40L in peripheral blood serum and NF-κBp65 in PBMC of patients of APCI group when in hospital, on the course of seventh day, of fourteen and of thirtieth were obviously higher all than that of ACI group (P<0.05 ). CONCLUSION: The inflammatory and apoptotic mechanism mediated by expressional excessive increase of CD40-CD40L signal passage and NF-κB in PBMC might be one of the molecular biology mechanisms of onset and progress for APCI.

Neuropeptide Y polymorphisms and ischemic stroke in Chinese population.

BACKGROUND: Stroke is the second most common cause of death in developed countries and a major cause of adult disability and mortality worldwide. New data strongly suggest that neuropeptide Y (NPY) may be a candidate gene for ischemic stroke. METHODS: We investigated 450 ischemic stroke patients and 423 healthy controls matched for sex and age in a Han Chinese population. Three functional polymorphisms (-883TGins/del, -602G/T and -399 T/C) located in NPY gene promoter were genotyped using DNA sequencing methods. RESULTS: Of 3 NPY polymorphisms investigated in our study, the -399CC genotype (OR: 1.699, 95% CI: 1.124-2.567, P=0.011) and the -399C allele (OR: 1.254, 95% CI: 1.031-1.524, P=0.023) were more frequent among ischemic stroke patients than in controls, especially in the small vessel disease (SVD) subtype patients. The similar results were observed in multivariable logistic regression analysis. Haplotype analysis revealed that the -883ins/-399C haplotype was a risk marker for ischemic stroke (P=0.008). CONCLUSIONS: The C allele of -399 T/C polymorphism in the promoter regions of NPY is an independent risk factor for ischemic stroke, suggesting that NYP system may involve in the mechanisms of stroke pathology.

Partitioning of poly(amidoamine) dendrimers between n-octanol and water.

Dendritic nanomaterials are emerging as key building blocks for a variety of nanoscale materials and technologies. Poly(amidoamine) (PAMAM) dendrimers were the first class of dendritic nanomaterials to be commercialized. Despite numerous investigations, the environmental fate, transport, and toxicity of PAMAM dendrimers is still not well understood. As a first step toward the characterization of the environmental behavior of dendrimers in aquatic systems, we measured the octanol-water partition coefficients (logK(ow)) of a homologous series of PAMAM dendrimers as a function of dendrimer generation (size), terminal group and core chemistry. We find that the logK(ow) of PAMAM dendrimers depend primarily on their size and terminal group chemistry. For G1-G5 PAMAM dendrimers with terminal NH2 groups, the negative values of their logK(ow) indicate that they prefer to remain in the water phase. Conversely, the formation of stable emulsions at the octanol-water (O/ W) interface in the presence of G6-NH2 and G8-NH2 PAMAM dendrimers suggest they prefer to partition at the O/W interface. In all cases, published studies of the cytotoxicity of Gx-NH2 PAMAM dendrimers show they strongly interact with the lipid bilayers of cells. These results suggest that the logK(ow) of a PAMAM dendrimer may not be a good predictor of its affinity with natural organic media such as the lipid bilayers of cell membranes.

Engineering bacteria for production of rhamnolipid as an agent for enhanced oil recovery.

Rhamnolipid as a potent natural biosurfactant has a wide range of potential applications, including enhanced oil recovery (EOR), biodegradation, and bioremediation. Rhamnolipid is composed of rhamnose sugar molecule and beta-hydroxyalkanoic acid. The rhamnosyltransferase 1 complex (RhlAB) is the key enzyme responsible for transferring the rhamnose moiety to the beta-hydroxyalkanoic acid moiety to biosynthesize rhamnolipid. Through transposome-mediated chromosome integration, the RhlAB gene was inserted into the chromosome of the Pseudomonas aeruginosa PAO1-rhlA(-) and Escherichia coli BL21 (DE3), neither of which could produce rhamnolipid. After chromosome integration of the RhlAB gene, the constitute strains P. aeruginosa PEER02 and E. coli TnERAB did produce rhamnolipid. The HPLC/MS spectrum showed that the structure of purified rhamnolipid from P. aeruginosa PEER02 was similar to that from other P. aeruginosa strains, but with different percentage for each of the several congeners. The main congener (near 60%) of purified rhamnolipid from E. coli TnERAB was 3-(3-hydroxydecanoyloxy) decanoate (C(10)-C(10)) with mono-rhamnose. The surfactant performance of rhamnolipid was evaluated by measurement of interfacial tension (IFT) and oil recovery via sand-pack flooding tests. As expected, pH and salt concentration of the rhamnolipid solution significantly affected the IFT properties. With just 250 mg/L rhamnolipid (from P. aeruginosa PEER02 with soybean oil as substrate) in citrate-Na(2)HPO(4), pH 5, 2% NaCl, 42% of oil otherwise trapped was recovered from a sand pack. This result suggests rhamnolipid might be considered for EOR applications.

Alkylation of phenol: a mechanistic view.

The current work utilizes the ab initio density functional theory (DFT) to develop a molecular level of the mechanistic understanding on the phenol alkylation in the presence of a cation-exchange resin catalyst, Amberlyst-15. The catalyst is modeled with the benzene sulfonic acid, and the effect of this acid on olefins such as isopropene (i-Pr) and tributene (t-Bu) in a phenol solution mimics the experimental condition. A neutral-pathway mechanism is established to account for early-stage high concentration of the phenolic ether observed in experiments. The mechanism involves an exothermic reaction between olefin and the benzene sulfonic acid to form ester followed by three reaction pathways leading to direct O-alkylation, o-C-alkylation, and p-C-alkylation. Our calculations conclude that O-alkylation to form the phenolic ether is the most energetically favorable in the neutral condition. An ionic rearrangement mechanism describes intramolecular migrations of the alkyl group from the phenolic ether to form C-alkylphenols, while the positively charged protonation significantly lowers transition barriers for these migrations. The ionic rearrangement mechanism accounts for high yields of o-C-alkylphenol and p-C-alkylphenol. Competition between the H atom and the alkyl R group at the substitutive site of the protonated ortho configuration is found to be the determining factor to the ortho/para ratio of C-alkylation products.