Preparation and IR Spectra Study of Rare Earth Orthophosphates

By liquid precipitation, lanthanide element orthophosphate was prepared and heat-treated at a series of temperatures. By FT-IR and XRD, it is found that bands near 1000 and 540 cm-1 split above 800 ℃ for the rare earth before Tb, since the system turned from hexagonal phase to monoclinic phase. For those after Tb, obvious tetragonal phase could be found above 800 ℃. In infrared spectra, with the increasing atomic number, bands turned to be blue shift. So rare earth orthophosphates′ absorption bands could be controlled by changing their heat-treating temperature or the proportion of different rare earth ions.

Identification of the amino acid involved in the regulation of bacterial pyruvate, orthophosphate dikinase and phosphoenolpyruvate synthetase

Pyruvate, orthophosphate dikinase (PPDK) and phosphoenolpyruvate synthetase (PEPS) catalyze the conversion of pyruvate to phosphoenolpyruvate (PEP). Both are regulated by a phosphorylation-dephosphorylation mechanism involving a bifunctional serine/ threonine kinase and a pyrophosphorylase (PPDK regulatory protein, PDRP, and PEPS regulatory protein, PSRP, respectively). In plants the regulatory mechanism involves phosphorylation of a threonine residue that is separated by a single amino acid from the histidine residue that forms a phosphorylated intermediate during catalysis. Using antibodies, we demonstrated that the regulation of both Listeria monocytogenes PPDK and Escherichia coli PEP synthetase involves the phosphorylation of a threonine residue located close to the catalytic histidine residue. The amino acid located between the regulatory threonine and the catalytic histidine is highly conserved being serine in PPDK and cysteine in PEPS. Using site-directed mutagenesis we have shown that both PPDK and PEPS in which the serine and cysteine residues, respectively, were substituted with an alanine the enzymes could be regulated indicating that the serine and cysteine residues, respectively, are not essential for regulation. We also demonstrated that altering the intermediate amino acid did not alter the specificity of the regulatory proteins for their protein substrates.

Sonochemical synthesis and characterization of uniform lanthanide orthophosphate(LnPO_4, Ln=La and Ce) nanorods

Uniform lanthanide orthophosphate （LnPO4, Ln = La and Ce） nanorods were successfully synthesized by a simple ultrasonic irradiation method using lanthanide nitrate salt （Ln（NO3）3-6H2O, Ln = La and Ce） and sodium phosphate （Na3PO4） in aqueous solutions with the pH of 1-3. The products were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, high-resolution transmission electron microscopy （HRTEM）, Fourier transform infrared spectrometer （FT-IR）, and UV-visible （UV-Vis） spectroscopy. In this research, the products are nanorods of monoclinic LaPO4 and hexagonal CePOa structures and the vibration modes of PO4^3-, including the strong peaks at 227 nm for LaPO4, and at 225 and 278 nm for CePO4.

Effects of humic acid on residual AI control in drinking water treatment plants with orthophosphate addition

This study aimed to investigate the effects of humic acid （HA） on residual Al control in drinking water facilities that used orthophosphate addition. The results showed that adding orthophosphate was an effective method for residual Al control for the raw water without HA. When orthophosphate was added at 1.0 min before the addition ofpoly aluminum chloride （PAC1）, the concentrations of soluble aluminum （Sol-AI） and total aluminum （Tot-Al） residue were 0.08 and 0.086 mg. L J, respectively; both were reduced by 46% compared with the control experiment. The presence of HA would notably increase the residual Al concentration. For the raw water with 5 mg-L^-1 of HA, the concentrations of Sol-Al and Tot-Al increased from 0.136 and 0.174mg.L^-1 to 0.172 and 0.272 mg.L 1, respectively. For water with a HA concen- tration above 5 mg. L ^-1, orthophosphate was ineffective in the control of residual Al, though there were still parts of orthophosphate were removed in coagulation. The amounts of Al removal were positively correlated with the solids freshly formed in coagulation. Similar to the raw water without HA, the best AI control was obtained with orthophosphate salt added at 1.0 min before PAC1. HA concentrations in the raw water, solution pH, and the orthophosphate dosage suitable for residual Al control by orthopbosphate precipitation were also investigated.

MORPHOLOGICAL AND MICROSTRUCTURAL CHANGES DURING THE HEATING OF SPHERICAL CALCIUM ORTHOPHOSPHATE AGGLOMERATES PREPARED BY SPRAY PYROLYSIS

The microstructural changes taking place during heating of calcium orthophosphate (Ca3(PO4)2) agglom- erates were examined in this study. The starting powder was prepared by the spray-pyrolysis of calcium phosphate (Ca/P ratio=1.50) solution containing 1.8 mol·L-1 Ca(NO3)2, 1.2 mol·L-1 (NH4)2HPO4 and concentrated HNO3 at 600 C, using an o air-liquid nozzle. The spray-pyrolyzed powder was found to be composed of dense spherical agglomerates with a mean diameter of 1.3 μm. This powder was further heat-treated at a temperature between 800 and 1400 C for 10 min. When o the spray-pyrolyzed powder was heated up to 900 C, only β-Ca3(PO4)2 was detected, and the mean pore size of the o spherical agglomerates increased via the (i) elimination of residual water and nitrates, (ii) rearrangement of primary par- ticles within the agglomerates, (iii) coalescence of small pores (below 0.1 μm), and (iv) coalescence of agglomerates with diameters below 1 μm into the larger agglomerates. Among the heat-treated powders, pore sizes within the spherical agglomerates were observed to be the largest (mean diameter: 1.8 μm) for the powder heat-treated at 900 C for 10 min. o With an increase in heat-treatment temperature up to 1000 C, the spherical agglomerates were composed of dense o shells. Upon further heating up to 1400 C, the hollow spherical agglomerates collapsed as a result of sintering via the o phase transformation from β- to α-Ca3(PO4)2 (1150 C), thus leading to the formation of a three-dimensional porous net- o work.

Characterization of maize leaf pyruvate orthophosphate dikinase using high throughput sequencing

In C4 photosynthesis, pyruvate orthophosphate dikinase （PPDK） catalyzes the regeneration of phospho- enolpyruvate in the carbon shuttle pathway. Although the biochemical function of PPDK in maize is well characterized, a genetic analysis of PPDK has not been reported. In this study, we use the maize transposable elements Nlutator and Ds to generate multiple mutant alleles of PPDK. Loss-of- function mutants are seedling lethal, even when plants were grown under 2% CO2, and they show very low capacity for CO2 assimilation, indicating C4 photosynthesis is essential in maize. Using RNA-seq and GC-MS technologies, we exam- ined the transcriptional and metabolic responses to a deficiency in PPDK activity. These results indicate loss of PPDK results in downregulation of gene expression ofenzymes of the C4 cycle, the Calvin cycle, and components of photochemistry. Furthermore, the loss of PPDK did not change Kranz anatomy, indicating that this metabolic defect in the C4 cycle did not impinge on the morphological differentiation of C4 characters. However, sugar metabolism and nitrogen utilization were altered in the mutants. An interaction between light intensity and genotype was also detected from transcriptome profiling, suggesting altered transcriptional and metabolic responses to environmental and endogenous signals in the PPDK mutants.

Enhanced tolerance to drought in transgenic rice plants overexpressing C_4 photosynthesis enzymes

Maize-specific pyruvate orthophosphate dikinase(PPDK) was overexpressed in rice independently or in combination with the maize C4-specific phosphoenolpyruvate carboxylase(PCK). The wild-type(WT) cultivar Kitaake and transgenic plants were evaluated in independent field and tank experiments. Three soil moisture treatments,well-watered(WW), moderate drought(MD) and severe drought(SD), were imposed from 9d post-anthesis till maturity. Leaf physiological and biochemical traits, root activities,biomass, grain yield, and yield components in the untransformed WT and two transgenic rice lines(PPDK and PCK) were systematically studied. Compared with the WT, both transgenic rice lines showed increased leaf photosynthetic rate: by 20%–40% under WW, by45%–60% under MD, and by 80%–120% under SD. The transgenic plants produced 16.1%,20.2% and 20.0% higher grain yields than WT under the WW, MD and SD treatments,respectively. Under the same soil moisture treatments, activities of phosphoenolpyruvate carboxylase(PEPC) and carbonic anhydrase(CA) in transgenic plants were 3–5-fold higher than those in WT plants. Compared with ribulose-1,5-bisphosphate carboxylase, activities of PEPC and CA were less reduced under both MD and SD treatments. The transgenic plants also showed higher leaf water content, stomatal conductance, transpiration efficiency, and root oxidation activity and a stronger active oxygen scavenging system than the WT under all soil moisture treatments, especially MD and SD. The results suggest that drought tolerance is greatly enhanced in transgenic rice plants overexpressing C4photosynthesis enzymes. This study was performed under natural conditions and normal planting density to evaluate yield advantages on a field basis. It may open a new avenue to droughttolerance breeding via overexpression of C4enzymes in rice.

Factors effecting aluminum speciation in drinking waterby laboratory research

Effects of aluminum on water distribution system and human health mainly attribute to its speciation in drinking water. Laboratory experiments were performed to investigate factors that may influence aluminum speciation in water supply system. The concentration of soluble aluminum and its transformation among other aluminum species were mainly controlled by kinetics processes of related reactions. Total aluminum concentration had a notable effect on the concentrations of mononuclear and soluble aluminum in the first 4 day; then its effect became weak. At pH above 7.50, both fluoride and orthophosphate had little effect on aluminum speciation; while, when the solution pH was below 7.50, the concentrations of mononuclear and soluble aluminum were proportional to the concentration of fluoride and inversely proportional to the concentration of orthophosphate. Both mononuclear and polynuclear silicic acids could complex with mononuclear aluminum by forming soluble aluminosilicates. In addition, the adding sequence of orthophosphate and aluminum into drinking water would also affect the distribution of aluminum species in the first 4 day. In order to minimize aluminum bioavailability in drinking water, it was suggested that orthophosphate should be added prior to coagulant process, and that the concentrations of fluoride and silicic acids should be controlled below 2.0 and 25 mg/L, respectively, prior to the treatment. The solution pH in coagulation and filtration processes should be controlled in the range of 6.50-7.50.

Spatial variations of aluminum species in drinking water supplies in Xi'an studied applying geographic information system

This article aimed to investigate the variation of aluminum species and the effects of coagulant type and water quality on aluminum speciation in drinking water. Statistical analysis showed that the concentration of total aluminum （AlT） of drinking water in Xi＇ an ranged from 0.051 to 0.417 mg/L and the concentration of A1T in about 24.7% studied samples was higher than the currently recommended value （0.2 mg/L）. The areas fed by surface water plants had a larger portion （39.4%） of samples over the recommended value. In drinking water treated by alum coagulant, the average concentration of monomeric aluminum （Ala） was higher than that in water treated by poly aluminum chlorine （PACl） and poly aluminum ferric chloride （PAFC）. The average concentrations of polynuclear aluminum （Alb） and colloidal/suspended aluminum （Ale） in the drinking water treated by alum were lower than those in water treated by PACl and PAFC. There was a notable decrease in AlT along with the delivery pipeline away from the plants, with an average decline of about 36 μg/（L-km）. Besides coagulant type, water quality also could affect aluminum speciation. In drinking water without orthophosphate, the concentrations of Ala and AlT were positively correlated with pH; while, in drinking water with orthophospbate, the concentrations of Ala and AlT were negatively correlated with pH. The addition of orthophosphate salts in the drinking water treatment process would be an effective method for aluminum control in pH range 6.5-8.2.

Measuring phosphatidic acid phosphohydrolase (EC 3.1.3.4) activity using two phosphomolybdate-based colorimetric methods

Phosphatidic acid phosphohydrolase (3-sn-phosphatidate phosphohydrolase, EC 3.1.3.4), also known as PAP, catalyzes the dephosphorylation of phosphatidic acid (PtdOH) to form diacylglycerol (DAG) and inorganic orthophosphate. In eukaryotes, the PAP driven reaction is the committed step in the synthesis of triacylglycerol (TAG). Existing methods for measuring PAP activity rely on the use of radioactive PtdOH. These methods are costly and cumbersome. In this report, we describe a simple assay procedure to measure released inorganic orthophosphate, which is a coproduct of the PAP reaction. Each molecule of PtdOH would release one molecule of DAG and one molecule of inorganic orthophosphate (Pi) when subjected to enzymatic breakdown under optimal conditions. Given the published rates of in vitro PAP enzymatic activity from various sources, we proposed that colorimetric determination of released Pi is possible. With this view, we performed in vitro PAP activity assays using freshly isolated enzyme from bitter gourd, Momordica charantia, and measured the released Pi using two spectrophotometric methods. Both methods gave about 2.0 to 2.25 ηkat per mg of protein. Thus, it is now possible to perform PAP activity using a simple procedure that uses nonradioactive substrates, provided the sample is dialyzed extensively to lower the intrinsic concentration of free phosphate. The kinetics data presented in this study is comparable to that of other PAP enzymes reported elsewhere, which gives credence to the notion that non-radioactive methods can be used to perform PAP activity.

A Study of the Yesilirmak River Catchment in Northern Turkey: Spatial Patterns and Temporal Trends in Water Quality

This paper presents a comprehensive study of spatial and temporal patterns of water chemistry (1995-2008) in the Yesilirmak River catchment in Northern Turkey. Biological oxygen demand (BOD), dissolved oxygen (DO) and nutrient concentrations (nitrogen and phosphorus) are variable across the catchment because the upland areas are relatively undisturbed, and the lower catchment is dominated by urban, industrial and agricultural inputs. Seasonally, high nutrient concentrations occur in winter possibly due to flushing from the soil zone. Low summer flow and reduced dilution lead to high orthophosphate concentrations. However, denitrification seems to be more significant than dilution processes and this generates low nitrate concentrations in summer. Nutrient levels since 1995 do not show a significant upward trend. The current water quality status indicates that the river system is in poor condition. The majority of sites fall in the Turkish water classification class II-III and more than half fail the EU standards because of high nutrient concentrations. In order to improve the status of water quality to achieve good chemical and ecological status, there is clearly a need to improve pollution control within the river system by installing waste water treatment plants, while keeping the agricultural pollution to a minimum in the system.

Acknowledgments to reviewers of World Journal of Methodology

Many reviewers have contributed their expertise and time to the peer review,a critical process to ensure the quality of World Journal of Methodology.The editors and authors of the articles submitted to the journal are grateful to the following reviewers for evaluating the articles(including those published in this issue and those rejected for this issue)during the last editing time period.

Structural Studies on Ag₂O-P₂O₅Glasses

Silver phosphate glasses of general formula xAg2O·(100 - x)P2O5 have been investigated over compositional range from x = 40 to 62.5 mol%. The local structure around phosphorus atom has been studied via 31P nuclear magnetic resonance. The distribution of [PO4]Qn species as a function of composition has been shown to slightly deviate from the simple binary alkali phosphate model. An anomalous behavior has been recorded and interpreted in terms of mixed ring-chain effect in metaphosphate composition. The splitting of NMR spectra into sub resonances is assigned to different binding sites characterizing Q1 ring and Q1 chain structure. Higher Ag2O concentration (≥50 mol%) leads to formation of phosphate groups with specific resonance peaks which are mainly related to pyro and orthophosphate species. The rate of change of the chemical shift of the 31P NMR depends on the bond type, which in turn reflects the extent of double bonding between phosphorus and oxygen atoms. Increasing concentration of Q0 with increasing Ag2O content leads to decreasing quantities of bridging and double bonds. As a consequence, specific symmetric resonance peak of higher intensity and chemical shift (Q0) is a feature of silver rich glasses (orthophosphate). The latter species is therefore proposed to compose of separated membered rings,?which cause deshielding of phosphate units.?XRD and EDP studies have shown that, amorphous phosphate network is the dominant structure of glasses containing ≤ 55 mol% Ag2O. Some ordered and well crystallized phases are formed at higher Ag2O concentration. Increasing non-bridging oxygen atoms is shown to have the main effect on crystallization behavior. Orthophosphate composition is the most crystalline one among the other compositions (ultra, meta- and pyrophosphate). Presence of orthophosphate species which typically contains highest concentration from isolated Q0 units is the main reason for building up crystalline Ag3PO4phosphate phase.

Risk assessment and identification of factors influencing the historical concentrations of microcystin in Lake Taihu, China

Understanding the history of microcystins(MCs)pollution in large lakes can help inform future lake management.We collected sediment cores from Lake Taihu to:investigate the long-term record of MCs(MC-LR,MC-YR,and MC-RR),explore the main environmental drivers of MCs,and assess their public health and ecological risks.Results showed that MCs content in all cores increased over time.The core from north Taihu had the highest MC concentrations,with an average total MCs(sum of MC-LR,MC-YR,and MC-RR=TMCs)content of(74.31±328.55)ng/g.The core from eastern Taihu showed the lowest average TMCs content of(2.91±3.95)ng/g.PCA showed that sediment MCs at the three sites were positively correlated with sediment chlorophyll-a.MC-LR and MC-YR in northern and western Taihu negatively correlated with both the sediment total organic carbon/sediment total nitrogen ratio(STOC/STN)andwater nitrate(NO_(3)^(−)-N)concentration,but three MC congeners at eastern Taihu showed positive correlations with water orthophosphate(PO_(4)^(3−)-P),NO_(3)^(−)-N,and STOC/STN.Generalized additive model analysis at each site revealed that NO_(3)^(−)-N was the main TMCs driver in northern andwestern Taihuwhere phytoplankton dominated,whereasPO_(4)^(3−)-P was the main TMCs driver in eastern Taihu where macrophytes dominated.At the whole lake scale,total phosphorus(TP)andPO_(4)^(3−)-P were the most important environmental drivers influencing MCs;TP explained 47.4%,44.2%,and 47.6%while orthophosphate explained 34.8%,31.2%,and 34.7%of the deviance on TMCs,MC-LR,and MC-YR,respectively.NO_(3)^(−)-N also showed a strong effect on MCs variation,especially on MC-YR.Risk assess-ment showed that both ecological and public health risk has increased in recent years.We conclude that while control of phosphorus and nitrogen input should be a major focus for future lake management,lake zone-specificmanagement strategiesmay also be important.

Unusual effects of vacuum annealing on large-area Ag_(3)PO_(4) microcrystalline film photoanode boosting cocatalyst-and scavengerfree water splitting

Ag_(3)PO_(4) as a novel photoanode material,despite its arguably highest photoactivity,suffers for its poor light absorption and stability for photoelectrochemical(PEC)water oxidation.In this work,4.54.5 cm^(2) Ag_(3)PO_(4) microcrystalline films are grown via a room-temperature solution process,and vacuum annealing is proposed to solve the stability and light absorption issues.It is found that the major process below 400℃ of vacuum annealing is the|Recovery|process for Ag_(3)PO_(4) microcrystals,when lattice defects and Ag0 surface species get reduced.Next,|Recrystallization|stage occurs at>40℃.The recovery of native defects of silver vacancies,with both density functional theory calculation and experimental results,could simultaneously improve the light absorption and catalytic activity of Ag_(3)PO_(4).The 400℃-annealed Ag_(3)PO_(4) photoanode,with enhanced light harvesting and crystal quality,exhibits 88% increase in(Jlight-Jdark)value(1.94 mA cm^(-2))than non-annealed photoanode(1.03 mA cm^(-2)).Moreover,it retains>99% current density after a 4000-s stability test.These results suggest that vacuum annealing can substantially improve the PEC performance of Ag_(3)PO_(4) microcrystalline film photoanodes due to mitigated effects of native defects,improved light harvesting,and inhibited Ag_(3)PO_(4) decomposition during water oxidation reaction.

Effect of relaxation on the energetics and electronic structure of clean Ag3PO4(111) surface

The effect of relaxation on the energetics and electronic structure of clean Ag3PO4（111） surface has been studied, carried out using first-principles density functional theory（DFT） incorporating the GGACU formalism.After atomic relaxation of the Ag3PO4（111） surface, it is found that O atoms are exposed to the outermost surface,due to an inward displacement of more than 0.06 nm for the two threefold-coordinated Ag atoms and an outward displacement of about 0.004 nm for three O atoms in the sublayer. The atomic relaxations result in a large transfer of surface charges from the outermost layer to the inner layer, and the surface bonds have a rehybridization, which makes the covalence increase and thus causes the surface bonds to shorten. The calculated energy band structures and density of states of the Ag3PO4（111） surface present that the atomic relaxation narrows the valence band width0.15 e V and increases the band gap width 0.26 e V. Meantime, the two surface peaks for the unrelaxed structure disappear at the top of the valence band and the bottom of the conduction band after the relaxed structure, which induces the transformation from a metallic to a semi-conducting characteristic.

Dielectric relaxation and conduction mechanism of NaMgPO_(4)compound

The polycrystalline NaMgPO_(4)ceramic,synthesized via a high-temperature solid-state reaction route,has been characterized by using different experimental procedures.The X-ray powder diffraction confirmed the phase formation of the synthesized com-pound in the orthorhombic phase.It assumed an olivine-type structure made up of corners linked between tetrahedral PO_(4)and octahedral NaO_(6)and MgO_(6)groups.Infrared and Raman spectroscopies confirmed the presence of PO_(4)^(3−)groups.Local structure and chemical bonding between MgO_(6)octahedral and PO_(4)3−tetrahedral groups investigated by diffusion Raman is the feature in the phase transition at T=693 K.The temperature dependences of the realε′and imaginaryε″parts of dielectric permittivity show a distribution of relaxation times.From Nyquist plots,the presence of grain and grain boundary effect in the material is noticed.The impedance spectroscopy measurement showed a non-Debye-type process.From the impedance data,the determined grain resistance reduces with increment of temperature showing negative temperature coefficient of resistance(NTCR)-type nature of the material which also confirmed from conductivity analysis.The temperature dependence ofσdc reveals an Arrhenius-type behavior with two activation energies,0.98 eV in region I and 0.67 eV in region II.Studied sample’s conduction is assured by Na+ions’hopping in tunnels and its mechanism was discussed.

Capture of phosphates in surface water by TiO_2 nanoparticles under UV irradiation

The capture of orthophosphates and total phosphorus from the Pudong Canal river in the Pudong District of Shanghai by TiO2 nanoparticles is studied using a rotating photoreactor and the nano-TiO2 photocatalyst Degussa P25. The effects of UV irradiation intensity in a range of 20-74 mW/cm^2, the loading of the TiO2 nanoparticles in a range of 0.05-0.1 g/L, irradiation time up to 4 h, and pH values in a range of 2-10.5 on the capture efficiency are investigated. The results show that the capture of orthophosphates and total P are significantly enhanced by UV irradiation; at a loading of 0.1 g/L and an irradiation intensity above 36 mW/cm^2, orthophosphates and total phosphorus are rapidly captured by TiO2 nanoparticles, causing an observed reduction from 0.4 mg/L down to 0.02 mg/L. pH values in a range of 2-10.5 have little effect on the capture efficiency of orthophosphates and total phosphorus.