Age and growth of mangrove red snapper Lutjanus argentimaculatus at its cool‐water‐range limits

This study investigates the age and growth of Lutjanus argentimaculatus at its southern (cooler) range limits in eastern Australia. Specimens were collected from New South Wales and southern Queensland between November 2011 and December 2013. Fork lengths (L_F) ranged from 190 to 1019 mm, and ages ranged from 2+ to 57+ years. Growth was described by the von Bertalanffy growth function with coefficients L_∞ = 874·92 mm, K = 0·087 year^?1 and t₀ = ?2·76 years. Estimates of the instantaneous natural mortality rate (M) ranged from 0·072 to 0·25. The L_F (mm) and mass (W; g) relationship was represented by the equation: . The maximum age of 57+ years is the oldest reported for any lutjanid and comparisons with tropical studies suggest that the age‐based demography of L. argentimaculatus follows a latitudinal gradient. High maximum ages and low natural mortality rates indicate considerable vulnerability to overexploitation at the species' cool‐water‐range limits. These results demonstrate the need to identify underlying processes driving latitudinal gradients in fish demography.     

Revisiting polarimetry near the isotropic point of an optically active,non‐enantiomorphous,molecular crystal

Accurate polarimetric measurements of the optical activity of crystals along low symmetry directions are facilitated by isotropic points, frequencies where dispersion curves of eigenrays cross and the linear birefringence disappears. We report here the optical properties and structure of achiral, uniaxial (point group D_2d) potassium trihydrogen di‐(cis‐4‐cyclohexene‐1,2‐dicarboxylate) dihydrate, whose isotropic point was previously detected (S. A. Kim, C. Grieswatch, H. Küppers, Zeit. Krist. 1993; 208:219–222) and exploited for a singular measurement of optical activity normal to the optic axis. The crystal structure associated with the aforementioned study was never published. We report it here, confirming the space group assignment I c2, along with the frequency dependence of the fundamental optical properties and the constitutive tensors by fitting optical dispersion relations to measured Mueller matrix spectra. k‐Space maps of circular birefringence and of the Mueller matrix near the isotropic wavelength are measured and simulated. The signs of optical rotation are correlated with the absolute crystallographic directions.     

Optimizing Water Exchange Rates and Rotational Mobility for High‐Relaxivity of a Novel Gd‐DO3A Derivative Complex Conjugated to Inulin as Macromolecular Contrast Agents for MRI

Thanks to the understanding of the relationships between the residence lifetime τ_M of the coordinated water molecules to macrocyclic Gd‐complexes and the rotational mobility τ_R of these structures, and according to the theory for paramagnetic relaxation, it is now possible to design macromolecular contrast agents with enhanced relaxivities by optimizing these two parameters through ligand structural modification. We succeeded in accelerating the water exchange rate by inducing steric compression around the water binding site, and by removing the amide function from the DOTA‐AA ligand [1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid mono(p‐aminoanilide)] ( L ) previously designed. This new ligand 10[2(1‐oxo‐1‐p‐propylthioureidophenylpropyl]‐1,4,7,10‐tetraazacyclodecane‐1,4,7‐tetraacetic acid ( L ₁ ) was then covalently conjugated to API [O‐(aminopropyl)inulin] to get the complex API ‐(GdL ₁ )x with intent to slow down the rotational correlation time (τ_R) of the macromolecular complex. The evaluation of the longitudinal relaxivity at different magnetic fields and the study of the ¹⁷O‐NMR at variable temperature of the low‐molecular‐weight compound ( GdL ₁ ) showed a slight decrease of the τ_M value ( = 331 ns vs.  = 450 ns for the Gd L complex). Consequently to the increase of the size of the API ‐(GdL ₁ )x complex, the rotational correlation time becomes about 360 times longer compared to the monomeric GdL ₁ complex (τ_R = 33,700 ps), which results in an enhanced proton relaxivity.     

Rates and pathways of CH4 oxidation in ferruginous Lake Matano,Indonesia

This study evaluates rates and pathways of methane (CH₄) oxidation and uptake using ¹⁴C‐based tracer experiments throughout the oxic and anoxic waters of ferruginous Lake Matano. Methane oxidation rates in Lake Matano are moderate (0.36 nmol L^?1 day^?1 to 117 μmol L^?1 day^?1) compared to other lakes, but are sufficiently high to preclude strong CH₄ fluxes to the atmosphere. In addition to aerobic CH₄ oxidation, which takes place in Lake Matano's oxic mixolimnion, we also detected CH₄ oxidation in Lake Matano's anoxic ferruginous waters. Here, CH₄ oxidation proceeds in the apparent absence of oxygen (O₂) and instead appears to be coupled to some as yet uncertain combination of nitrate (), nitrite (), iron (Fe) or manganese (Mn), or sulfate () reduction. Throughout the lake, the fraction of CH₄ carbon that is assimilated vs. oxidized to carbon dioxide (CO₂) is high (up to 93%), indicating extensive CH₄ conversion to biomass and underscoring the importance of CH₄ as a carbon and energy source in Lake Matano and potentially other ferruginous or low productivity environments.     

Preparation of cadmium sulfide nanoparticles and their application for improving the properties of the electrochemical sensor for the determination of enrofloxacin in real samples

An advanced electrochemical sensor for the detection of enrofloxacin (ENR) based on the use of a modified electrode containing cadmium sulfide (CdS) nanoparticles (NPs) is reported. The CdS NPs were synthesized and characterized and then coated onto the electrode to fabricate a modified electrode that exhibited a lower limit of detection of 9.5 × 10^?8 mol·L^?1. This detection limit compares with a traditional electrode that exhibited a concentration detection range of 1.0 × 10^?2 to 1.0 × 10^?7 mol·L^?1. This modified electrode demonstrated good selectivity, reproducibility, response time (<40 s), lifetime (up to 12 wk), and pH range (3.3‐7.2) for the determination of ENR in real samples (eg, pig urine).     

Biotransformation of β‐hydroxypyruvate and glycolaldehyde to l‐erythrulose by Pichia pastoris strain GS115 overexpressing native transketolase

Transketolase is a proven biocatalytic tool for asymmetric carbon‐carbon bond formation, both as a purified enzyme and within bacterial whole‐cell biocatalysts. The performance of Pichia pastoris as a host for transketolase whole‐cell biocatalysis was investigated using a transketolase‐overexpressing strain to catalyze formation of l ‐erythrulose from β‐hydroxypyruvic acid and glycolaldehyde substrates. Pichia pastoris transketolase coding sequence from the locus PAS_chr1‐4_0150 was subcloned downstream of the methanol‐inducible AOX1 promoter in a plasmid for transformation of strain GS115, generating strain TK150. Whole and disrupted TK150 cells from shake flasks achieved 62% and 65% conversion, respectively, under optimal pH and methanol induction conditions. In a 300 μL reaction, TK150 samples from a 1L fed‐batch fermentation achieved a maximum l ‐erythrulose space time yield (STY) of 46.58 g L^?1 h^?1, specific activity of 155 U , product yield on substrate (Y_p/s) of 0.52 mol mol^?1 and product yield on catalyst (Y_p/x) of 2.23g . We have successfully exploited the rapid growth and high biomass characteristics of Pichia pastoris in whole cell biocatalysis. At high cell density, the engineered TK150 Pichia pastoris strain tolerated high concentrations of substrate and product to achieve high STY of the chiral sugar l ‐erythrulose. © 2017 The Authors Biotechnology Progress published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers Biotechnol. Prog., 34:99–106, 2018     

Cardiac‐specific overexpression of metallothionein attenuates L‐NAME‐induced myocardial contractile anomalies and apoptosis

Hypertension contributes to the high cardiac morbidity and mortality. Although oxidative stress plays an essential role in hypertensive heart diseases, the mechanism remains elusive. Transgenic mice with cardiac overexpression of metallothionein, a heavy metal‐binding scavenger, were challenged with N^G‐nitro‐L‐arginine methyl ester (L‐NAME) for 14 days prior to measurement of myocardial contractile and intracellular Ca²⁺ anomalies as well as cell signalling mechanisms using Western blot and immunofluorescence analysis. L‐NAME challenge elicited hypertension, macrophage infiltration, oxidative stress, inflammation and cardiac dysfunction manifested as increased proinflammatory macrophage marker F4/80, interleukin‐1β (IL‐1β), intracellular production, LV end systolic and diastolic diameters as well as depressed fractional shortening. L‐NAME treatment reduced mitochondrial membrane potential (MMP), impaired cardiomyocyte contractile and intracellular Ca²⁺ properties as evidenced by suppressed peak shortening, maximal velocity of shortening/relengthening, rise in intracellular Ca²⁺, along with elevated baseline and peak intracellular Ca²⁺. These unfavourable mechanical changes and decreased MMP (except blood pressure and macrophage infiltration) were alleviated by overexpression of metallothionein. Furthermore, the apoptosis markers including BAD, Bax, Caspase 9, Caspase 12 and cleaved Caspase 3 were up‐regulated while the anti‐apoptotic marker Bcl‐2 was decreased by L‐NAME treatment. Metallothionein transgene reversed L‐NAME‐induced changes in Bax, Bcl‐2, BAD phosphorylation, Caspase 9, Caspase 12 and cleaved Caspase 3. Our results suggest that metallothionein protects against L‐NAME‐induced myocardial contractile anomalies in part through inhibition of apoptosis.     

Free radical scavenging activity of novel thiazolidine‐2,4‐dione derivatives

Free radical activity towards superoxide anion radical (), hydroxyl radical (HO^?) and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH^?) of a series of novel thiazolidine‐2,4‐dione derivatives (TSs) was examined using chemiluminescence, electron paramagnetic resonance (EPR) and EPR spin trapping techniques. 5,5‐Dimethyl‐1‐pyrroline‐N‐oxide (DMPO) was applied as the spin trap. Superoxide radical was produced in the potassium superoxide/18‐crown‐6 ether dissolved in dimethyl sulfoxide. Hydroxyl radical was generated in the Fenton reaction (Fe(II) + H₂O₂. It was found that TSs showed a slight scavenging effect (15–38% reduction at 2.5 mmol/L concentration) of the DPPH radical and a high scavenging effect of (41–88%). The tested compounds showed inhibition of HO^? ‐dependent DMPO‐OH spin adduct formation (the amplitude of EPR signal decrease ranged from 20 to 76% at 2.5 mmol/L concentration. Our findings present new group compounds of relatively high reactivity towards free radicals. Copyright © 2012 John Wiley & Sons, Ltd.     

Collagen chirality and three‐dimensional orientation studied with polarimetric second‐harmonic generation microscopy

Polarization‐dependent second‐harmonic generation (P‐SHG) microscopy is used to characterize molecular nonlinear optical properties of collagen and determine a three‐dimensional (3D) orientation map of collagen fibers within a pig tendon. C₆ symmetry is used to determine the nonlinear susceptibility tensor components ratios in the molecular frame of reference and , where the latter is a newly extracted parameter from the P‐SHG images and is related to the chiral structure of collagen. The is observed for collagen fibers tilted out of the image plane, and can have positive or negative values, revealing the relative polarity of collagen fibers within the tissue. The P‐SHG imaging was performed using a linear polarization‐in polarization‐out (PIPO) method on thin sections of pig tendon cut at different angles. The nonlinear chiral properties of collagen can be used to construct the 3D organization of collagen in the tissue and determine the orientation‐independent molecular susceptibility ratios of collagen fibers in the molecular frame of reference.      

Surface‐water availability governs survival of an amphibian in arid mountain streams

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Design of experiment assisted concurrent enantioseparation of bupropion and hydroxybupropion by high‐performance thin‐layer chromatography

A simple and efficient high‐performance thin‐layer chromatographic method was developed for chiral separation of rac ‐bupropion (BUP) and its active metabolite rac ‐hydroxybupropion (HBUP). Design of experiment (DoE)‐based optimization was adopted instead of a conventional trial‐and‐error approach. The Box–Behnken design surface response model was used and the operating variables were optimized based on 17 trials design. The optimized method involved impregnation of chiral reagent, L(+)‐tartaric acid, in the stationary phase with simultaneous addition in the mobile phase, which consisted of acetonitrile : methanol : dichloromethane : 0.50% L‐tartaric acid (6.75:1.0:1.0:0.25, v /v /v /v ). Under the optimized conditions, the resolution factor between the enantiomers of BUP and HBUP was 6.30 and 9.26, respectively. The limit of detection and limit of quantitation for (R)‐BUP, (S)‐BUP, (R,R)‐HBUP, and (S,S)‐HBUP were 9.23 and 30.78 ng spot⁻¹, 10.32 and 34.40 ng spot⁻¹, 12.19 and 40.65 ng spot⁻¹, and 14.26 and 47.53 ng spot⁻¹, respectively. The interaction of L‐tartaric acid with analytes and their retention behavior was thermodynamically investigated using van't Hoff's plots. The developed method was validated as per the International Conference on Harmonization guidelines. Finally, the method was successfully applied to resolve and quantify the enantiomeric content from marketed tablets as well as spiked plasma samples.     

The Aer2 receptor from Vibrio cholerae is a dual PAS‐heme oxygen sensor

The diarrheal pathogen Vibrio cholerae navigates complex environments using three chemosensory systems and 44–45 chemoreceptors. Chemosensory cluster II modulates chemotaxis, whereas clusters I and III have unknown functions. Ligands have been identified for only five V. cholerae chemoreceptors. Here, we report that the cluster III receptor, VcAer2, binds and responds to O₂. VcAer2 is an ortholog of Pseudomonas aeruginosa Aer2 (PaAer2) but differs in that VcAer2 has two, rather than one, N‐terminal PAS domain. We have determined that both PAS1 and PAS2 form homodimers and bind penta‐coordinate b‐type heme via an Eη‐His residue. Heme binding to PAS1 required the entire PAS core, but receptor function also required the N‐terminal cap. PAS2 functioned as an O₂‐sensor [ , 19 μM], utilizing the same Iβ Trp (W276) as PaAer2 to stabilize O₂. The crystal structure of PAS2‐W276L was similar to that of PaAer2‐PAS but resided in an active conformation mimicking the ligand‐bound state, consistent with its signal‐on phenotype. PAS1 also bound O₂ [ , 12 μM], although O₂ binding was stabilized by either a Trp residue or Tyr residue. Moreover, PAS1 appeared to function as a signal modulator, regulating O₂‐mediated signaling from PAS2 and resulting in activation of the cluster III chemosensory pathway.     

New biosourced chiral molecularly imprinted polymer: Synthesis,characterization, and evaluation of the recognition capacity of methyltestosterone

New biosourced chiral cross‐linkers were reported for the first time in the synthesis of methyltestosterone (MT) chiral molecularly imprinted polymers (cMIPs). Isosorbide and isomannide, known as 1,4:3,6‐dianhydrohexitols, were selected as starting diols. The cMIPs were synthesized following a noncovalent approach via thermal radical polymerization and monitored by Raman spectroscopy. These cross‐linkers were fully characterized by ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy and high‐resolution mass spectrometry. The cross‐polarization magic angle spinning ¹³C NMR, Fourier transform infrared spectroscopy, scanning electron microscopy, and specific surface areas following the Brunauer‐Emmett‐Teller (BET) method were used to characterize the cMIPs. The effect of stereochemistry of cross‐linkers on the reactivity of polymerization, morphology, and adsorption‐recognition properties of the MIP was evaluated. The results showed that the cMIP exhibited an obvious improvement in terms of rebinding capacity for MT as compared with the nonimprinted polymer (NIP). The highest binding capacity was observed for cMIP‐Is (27.298 mg g⁻¹) for high concentrations (500 mg L⁻¹). However, the isomannide homologue cMIP‐Im showed higher recovery—up to 65% and capacity for low concentrations (15 mg L⁻¹). The experimental data were properly fitted by the Freundlich adsorption isothermal model.     

Steelhead trout Oncorhynchus mykiss metabolic rate is affected by dietary Aloe vera inclusion but not by mounting an immune response against formalin‐killed Aeromonas salmonicida

The oxygen consumption of two groups of 10° C acclimated steelhead trout Oncorhynchus mykiss was measured for 72 h after they were given a 100 µl kg^?1 intraperitoneal injection of formalin‐killed Aeromonas salmonicida (ASAL) or phosphate‐buffered saline (PBS). In addition, plasma cortisol levels were measured in fish from both groups prior to, and 1 and 3 h after, they were given a 30 s net stress. The first group was fed an unaltered commercial diet for 4 weeks, whereas the second group was fed the same diet but with 0·5% (5 g kg^?1) Aloe vera powder added; A. vera has potential as an immunostimulant for use in aquaculture, but its effects on basal and acute phase response (APR)‐related metabolic expenditures and stress physiology, are unknown. Injection of ASAL v. PBS had no measurable effect on the of O. mykiss indicating that the APR in this species is not associated with any net increase in energy expenditure. In contrast, incorporating 0·5% A. vera powder into the feed decreased routine metabolic rate by c. 8% in both injection groups and standard metabolic rate in the ASAL‐injected group (by c. 4 mg O₂ kg^?1 h^?1; 5%). Aloe vera fed fish had resting cortisol levels that were approximately half of those in fish on the commercial diet (c. 2·5 v. 5·0 ng ml^?1), but neither this difference nor those post‐stress reached statistical significance (P > 0·05).     

NMR‐based conformation and dynamics of a tetrasaccharide‐repeating sulfated fucan substituted by different counterions

The sulfated fucan from the sea urchin Lytechinus variegatus is composed of the repetitive sequence [‐3)‐α‐l ‐Fucp‐4( )‐(1‐3)‐α‐l ‐Fucp‐2,4‐di( )‐(1‐3)‐α‐l ‐Fucp‐2( )‐(1‐3)‐α‐l ‐Fucp‐2( )‐(1‐]_n. Conformation (of rings and chains) and dynamics of this tetrasaccharide‐repeating sulfated fucan substituted by Na⁺, Ca²⁺, and Li⁺ as counterions have been examined through experiments of liquid‐state nuclear magnetic resonance spectroscopy. Scalar coupling and nuclear Overhauser effect (NOE)‐based data have confirmed that all composing units occur as ¹C₄ chair conformer regardless of the cation type, unit position within the repeating sequence, and sulfation type. Chain conformation determined by NOE signal pattern assisted by molecular modeling for a theoretical octasaccharide has shown a similar linear 3D structure for the three differently substituted forms. Data derived from spin‐relaxation measurements have indicated a contribution of counterion type to dynamics. The calcium‐based preparation has shown the highest mobility while the sodiated one showed the lowest mobility. The set of results from this work suggests that counterion type can affect the physicochemical properties of the structurally well‐defined sulfated fucan. The counterion effect seems to impact more on the structural mobility than on average conformation of the studied sulfated glycan in solution.     

Nanodiamond‐Embedded p‐Type Copper(I) Oxide Nanocrystals for Broad‐Spectrum Photocatalytic Hydrogen Evolution

Copper(I) oxide (Cu₂O) is an attractive photocatalyst because of its abundance, low toxicity, environmental compatibility, and narrow direct band gap, which allows efficient light harvesting. However, Cu₂O exhibits poor photocatalytic performance and photostability because of its short electron diffusion length and low hole mobility. Here, it is demonstrated that nanodiamond (ND) can greatly improve the photocatalytic hydrogen evolution reaction (HER) of the p‐type photocatalyst Cu₂O nanocrystals by nanocomposition. Compared with pure Cu₂O nanocrystals, this composite shows a tremendous improvement in HER performance and photostability. HER rates of 100.0 mg NDs‐Cu₂O nanocrystals are 1597 and 824 under the simulated solar light irradiation (AM 1.5, 100 mW cm^?2) and visible light irradiation (420–760 nm, 77.5 mW cm^?2), respectively. The solar‐to‐hydrogen conversion efficiency of this composite is 0.85%, which is nearly ten times higher than that of pure Cu₂O. The quantum efficiency of the composite is high, with values of 0.17% at and 0.23% at . The broad spectral response of ND provides numerous carriers for the subsequent reactions. The electron‐donating ability of ND and suitable band structures of the two components promote electron injection from ND to Cu₂O. These results suggest the broad applicability of ND to ameliorate the photoelectric properties of semiconductors.     

Bradykinin‐mediated Ca2+ signalling regulates cell growth and mobility in human cardiac c‐Kit+ progenitor cells

Our recent study showed that bradykinin increases cell cycling progression and migration of human cardiac c‐Kit⁺ progenitor cells by activating pAkt and pERK1/2 signals. This study investigated whether bradykinin‐mediated Ca²⁺ signalling participates in regulating cellular functions in cultured human cardiac c‐Kit⁺ progenitor cells using laser scanning confocal microscopy and biochemical approaches. It was found that bradykinin increased cytosolic free Ca²⁺ () by triggering a transient Ca²⁺ release from ER IP3Rs followed by sustained Ca²⁺ influx through store‐operated Ca²⁺ entry (SOCE) channel. Blockade of B2 receptor with HOE140 or IP3Rs with araguspongin B or silencing IP3R3 with siRNA abolished both Ca²⁺ release and Ca²⁺ influx. It is interesting to note that the bradykinin‐induced cell cycle progression and migration were not observed in cells with siRNA‐silenced IP3R3 or the SOCE component TRPC1, Orai1 or STIM1. Also the bradykinin‐induced increase in pAkt and pERK1/2 as well as cyclin D1 was reduced in these cells. These results demonstrate for the first time that bradykinin‐mediated increase in free via ER‐IP3R3 Ca²⁺ release followed by Ca²⁺ influx through SOCE channel plays a crucial role in regulating cell growth and migration via activating pAkt, pERK1/2 and cyclin D1 in human cardiac c‐Kit⁺ progenitor cells.     

Exploring a Pool‐seq‐only approach for gaining population genomic insights in nonmodel species

Developing genomic insights is challenging in nonmodel species for which resources are often scarce and prohibitively costly. Here, we explore the potential of a recently established approach using Pool‐seq data to generate a de novo genome assembly for mining exons, upon which Pool‐seq data are used to estimate population divergence and diversity. We do this for two pairs of sympatric populations of brown trout (Salmo trutta): one naturally sympatric set of populations and another pair of populations introduced to a common environment. We validate our approach by comparing the results to those from markers previously used to describe the populations (allozymes and individual‐based single nucleotide polymorphisms [SNPs]) and from mapping the Pool‐seq data to a reference genome of the closely related Atlantic salmon (Salmo salar). We find that genomic differentiation (F_ST) between the two introduced populations exceeds that of the naturally sympatric populations (F_ST = 0.13 and 0.03 between the introduced and the naturally sympatric populations, respectively), in concordance with estimates from the previously used SNPs. The same level of population divergence is found for the two genome assemblies, but estimates of average nucleotide diversity differ ( ≈ 0.002 and  ≈ 0.001 when mapping to S. trutta and S. salar, respectively), although the relationships between population values are largely consistent. This discrepancy might be attributed to biases when mapping to a haploid condensed assembly made of highly fragmented read data compared to using a high‐quality reference assembly from a divergent species. We conclude that the Pool‐seq‐only approach can be suitable for detecting and quantifying genome‐wide population differentiation, and for comparing genomic diversity in populations of nonmodel species where reference genomes are lacking.     

Nitrogen fixation by the diazotroph Cylindrospermopsis raciborskii (Cyanophyceae)

Nitrogen fixation has been proposed as a mechanism that allows the diazotrophic cyanobacterium, Cylindrospermopsis raciborskii, to bloom in nitrogen‐limited freshwater systems. However, it is unclear whether dinitrogen fixation (N₂ fixation) can supplement available dissolved inorganic nitrogen (DIN) for growth, or only provides minimum nitrogen (N) for cell maintenance under DIN deplete conditions. Additionally, the rate at which cells can switch between DIN use and N₂ fixation is unknown. This study investigated N₂ fixation under a range of nitrate concentrations. Cultures were grown with pretreatments of nitrate replete (single dose 941 μmol  · L^?1) and N‐free conditions and then either received a single dose of 941 μmol  · L^?1 (N941), 118 μmol  · L^?1 (N118) or 0 N. Heterocysts appeared from days 3 to 5 when treatments of high were transferred to N free media (N941:N0), and from day 5 in N941 transferred to N118 treatments. Conversely, transferring cells from N0 to N941 resulted in heterocysts being discarded from day 3 and day 5 for N0:N118. Heterocyst appearance correlated with a detectable rate of N₂ fixation and up‐regulation of nifH gene expression, the discard of heterocysts occurred after sequential reduction of nifH expression and N₂ fixation. Nitrate uptake rates were not affected by pretreatment, suggesting no regulation or saturation of this uptake pathway. These data demonstrate that for C. raciborskii, N₂ fixation is regulated by the production or discard of heterocysts. In conclusion, this study has shown that N₂ fixation only provides enough N to support relatively low growth under N‐limited conditions, and does not supplement available nitrate to increase growth rates.     

Energy transfer rate and electron–phonon coupling properties in Eu3+‐doped nanophosphors

A series of controllable emissions SrWO₄:Eu³⁺ and charge‐compensated SrWO₄: (m = 0.01 or 0.20) phosphors was successfully prepared via a simple co‐precipitation method. The energy transfer mechanism was studied based on the Huang's theory. A low magnitude of Huang‐Rhys factor (10^?2) was calculated using phonon sideband spectra. The Judd–Ofelt parameters Ω_λ (λ = 2, 4 and 6) of Eu³⁺‐activated SrWO₄ doped with charge compensation were obtained. The calculated Commission Internationale de l'Eclairage chromaticity coordinates were found to be about (0.67, 0.33) for SrWO₄: and charge‐compensated SrWO₄: phosphors, which coincided with the National Television Standard Committee system standard values for red. A white light emission was obtained under 362 nm excitation. The correlated color temperature was computed by a simple equation to characterize light sources. Thus, warm white light‐emitting diodes with higher Ra can be constructed by combining as‐prepared high efficiency, low correlated color temperature and high color purity phosphor.