In this work we report the preparation of fucan-coated magnetite (Fe3O4) nanoparticles by the co-precipitation method. These nanoparticles were characterized by scanning electron microscopy, ...transmission electron microscopy, X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Mössbauer spectroscopy and magnetic measurements. The nanoparticles showed quasi-spherical morphology with mean sizes around 10nm. XRD and FT-IR confirmed the functionalization of the Fe3O4 nanoparticles with the fucan polysaccharide. Room temperature magnetization measurements and Mössbauer spectroscopy showed that the nanoparticles exhibited superparamagnetic behavior at 300K and the magnetic properties of the Fe3O4 are partly screened by the coating preventing aggregation.
•Syntheses of fucan-coated Fe3O4 nanoparticles were made by co-precipitation method.•The efficiency of polysaccharide coated was analyzed by XRD and FT-IR.•The magnetic nanoparticles mean size was 10–20nm.•The fucan-coated magnetite nanoparticles showed superparamagnetic behavior.
We present new measurements of the cosmic cold molecular gas evolution out to redshift 6 based on systematic mining of the Atacama Large Millimeter/submillimeter Array (ALMA) public archive in the ...COSMOS deep field (A3COSMOS). Our A3COSMOS data set contains ∼700 galaxies (0.3 z 6) with high-confidence ALMA detections in the (sub)millimeter continuum and multiwavelength spectral energy distributions. Multiple gas mass calibration methods are compared, and biases in band conversions (from observed ALMA wavelength to rest-frame Rayleigh-Jeans tail continuum) have been tested. Combining our A3COSMOS sample with ∼1000 CO-observed galaxies at 0 z 4 (75% at z < 0.1), we parameterize galaxies' molecular gas depletion time ( ) and molecular gas to stellar mass ratio ( ) each as a function of the stellar mass ( ), offset from the star-forming main sequence ( ) and cosmic age (or redshift). Our proposed functional form provides a statistically better fit to current data (than functional forms in the literature) and implies a "downsizing" effect (i.e., more-massive galaxies evolve earlier than less-massive ones) and "mass quenching" (gas consumption slows down with cosmic time for massive galaxies but speeds up for low-mass ones). Adopting galaxy stellar mass functions and applying our function for gas mass calculation, we for the first time infer the cosmic cold molecular gas density evolution out to redshift 6 and find agreement with CO blind surveys as well as semianalytic modeling. These together provide a coherent picture of cold molecular gas, star formation rate, and stellar mass evolution in galaxies across cosmic time.
Plants interact with a myriad of microbial cells in the rhizosphere, an environment that is considered to be important for plant development. However, the differential structuring of rhizosphere ...microbial communities due to plant cultivation under differential agricultural practices remains to be described for most plant species. Here we describe the rhizosphere microbiome of grapevine cultivated under conventional and organic practices, using a combination of cultivation-independent approaches. The quantification of bacterial 16S rRNA and nifH genes, by quantitative PCR (qPCR), revealed similar amounts of these genes in the rhizosphere in both vineyards. PCR-DGGE was used to detect differences in the structure of bacterial communities, including both the complete whole communities and specific fractions, such as Alphaproteobacteria, Betaproteobacteria, Actinobacteria, and those harboring the nitrogen-fixing related gene nifH. When analyzed by a multivariate approach (redundancy analysis), the shifts observed in the bacterial communities were poorly explained by variations in the physical and chemical characteristics of the rhizosphere. These approaches were complemented by high-throughput sequencing (67,830 sequences) based on the V6 region of the 16S rRNA gene, identifying the major bacterial groups present in the rhizosphere of grapevines: Proteobacteria, Actinobacteria, Firmicutes, Bacteriodetes, Acidobacteria, Cloroflexi, Verrucomicrobia and Planctomycetes, which occur in distinct proportions in the rhizosphere from each vineyard. The differences might be related to the selection of plant metabolism upon distinct reservoirs of microbial cells found in each vineyard. The results fill a gap in the knowledge of the rhizosphere of grapevines and also show distinctions in these bacterial communities due to agricultural practices.
A study on the preparation of rice bran-based activated carbon was conducted, with and without an acid treatment step prior the activation process. The influence of the activation time on the ...structure of the activated carbons was evaluated. The acid treatment had a significant positive influence on sorption properties. The rice bran-activated carbon presented a BET surface area of 652
m
2
g
−1 and a pore volume of 0.137
cm
3
g
−1, with mesopores predominance (ca. 55%). These experimental results indicated the potential use of rice bran as a precursor in the activated carbon preparation process, thus representing an economically promising material.
The graph shows the action of zeolite on the NAA heavy water. Display omitted
Square 1 - zeolite with sodium promotes ion exchange of calcium and magnesium present in water hard. ► Square 2 - water ...free of calcium and magnesium captured by zeolite. ► Square 3 - calcium and magnesium present in hard water withheld in the sites of adsorption.
Zeolite 4A (LTA) has been successfully synthesized by a hydrothermal method, where kaolin was used as silica and alumina source. The synthesized zeolite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser granulometry, and FTIR spectroscopy. XRD data from the Rietveld refinement method confirmed only one crystallographic phase. Zeolite A morphology was observed by SEM analysis, and it showed well-defined crystals with slightly different sizes but with the same cubic shape. Particle size distribution of the crystals was confirmed by laser granulometry, whereas FTIR spectroscopy revealed significant structural differences between the starting material and the final zeolite product used as water softener.
Context. Extended synchrotron radio sources are often observed in merging galaxy clusters. Studies of the extended emission help us to understand the mechanisms in which the radio emitting particles ...gain their relativistic energies. Aims. We examine the possible acceleration mechanisms of the relativistic particles that are responsible for the extended radio emission in the merging galaxy cluster Abell 520. Methods. We performed new 145 MHz observations with the LOw Frequency ARay (LOFAR) and combined these with archival Giant Metrewave Radio Telescope (GMRT) 323 MHz and Very Large Array (VLA) 1.5 GHz data to study the morphological and spectral properties of extended cluster emission. The observational properties are discussed in the framework of particle acceleration models associated with cluster merger turbulence and shocks. Results. In Abell 520, we confirm the presence of extended (760 × 950 kpc2) synchrotron radio emission that has been classified as a radio halo. The comparison between the radio and X-ray brightness suggests that the halo might originate in a cocoon rather than from the central X-ray bright regions of the cluster. The halo spectrum is roughly uniform on the scale of 66 kpc. There is a hint of spectral steepening from the SW edge towards the cluster centre. Assuming diffusive shock acceleration (DSA), the radio data are suggestive of a shock Mach number of ℳSW = 2.6−0.2+0.3 M SW = 2 . 6 − 0.2 + 0.3 $ \mathcal{M}_{\mathrm{SW}}=2.6_{-0.2}^{+0.3} $ that is consistent with the X-ray derived estimates. This is in agreement with the scenario in which relativistic electrons in the SW radio edge gain their energies at the shock front via acceleration of either thermal or fossil electrons. We do not detect extended radio emission ahead of the SW shock that is predicted if the emission is the result of adiabatic compression. An X-ray surface brightness discontinuity is detected towards the NE region that may be a counter shock of Mach number ℳNEX = 1.52±0.05 M NE X = 1.52 ± 0.05 $ \mathcal{M}_{\mathrm{NE}}^{\mathrm{X}}=1.52\pm0.05 $ . This is lower than the value predicted from the radio emission which, assuming DSA, is consistent with ℳNE = 2.1 ± 0.2. Conclusions. Our observations indicate that the radio emission in the SW of Abell 520 is likely effected by the prominent X-ray detected shock in which radio emitting particles are (re-)accelerated through the Fermi-I mechanism. The NE X-ray discontinuity that is approximately collocated with an edge in the radio emission hints at the presence of a counter shock.
We combine observations from the Atacama Large Millimeter/submillimeter Array and the NOrthern Extended Millimeter Array to assess the redshift and to study the star formation conditions in AzTEC2, ...one of the brightest submillimeter galaxies (SMGs) in the COSMOS field ( mJy). Our high-resolution observations confirm that AzTEC2 splits into two components (namely AzTEC2-A and AzTEC2-B) for which we detect C ii and 12CO(5 → 4) line emission, implying a redshift of 4.626 0.001 (4.633 0.001) for AzTEC2-A (AzTEC2-B) and ruling out previous associations with a galaxy at . We use the 12CO(5 → 4) line emission and adopt typical SMG-like gas excitation conditions to estimate the molecular gas mass, which is for AzTEC2-A, and a factor four lower for AzTEC2-B. With the infrared-derived star formation rate of AzTEC2-A ( yr−1) and AzTEC2-B ( yr−1), they both will consume their current gas reservoir within (30-200) Myr. We find evidence of a rotation-dominated C ii disk in AzTEC2-A, with a deprojected rotational velocity of km s−1, velocity dispersion km s−1, and dynamical mass of . We propose that an elevated gas accretion rate from the cosmic web might be the main driver of the intense levels of star formation in AzTEC2-A, which might be further enhanced by gravitational torques induced by its minor companion (AzTEC2-B). These results strengthen the picture whereby the population of single-dish selected SMGs is rather heterogeneous, including a population of pairs of massive, highly active galaxies in a pre-coalescence phase.
Elastic neutrino scattering on electrons is a precisely known purely leptonic process that provides a standard candle for measuring neutrino flux in conventional neutrino beams. Using a total sample ...of 810 neutrino-electron scatters after background subtraction, the measurement reduces the normalization uncertainty on the ν μ NuMI beam flux between 2 and 20 GeV from 7.6 to 3.9%. This is the most precise measurement of neutrino-electron scattering to date, will reduce uncertainties on MINER ν A's absolute cross section measurements, and demonstrates a technique that can be used in future neutrino beams such as long baseline neutrino facility.
Final-state kinematic imbalances are measured in mesonless production of νμ+A→μ-+p+X in the MINERvA tracker. Initial- and final-state nuclear effects are probed using the direction of the μ- - p ...transverse momentum imbalance and the initial-state momentum of the struck neutron. Differential cross sections are compared to predictions based on current approaches to medium modeling. These models underpredict the cross section at intermediate intranuclear momentum transfers that generally exceed the Fermi momenta. As neutrino interaction models need to correctly incorporate the effect of the nucleus in order to predict neutrino energy resolution in oscillation experiments, this result points to a region of phase space where additional cross section strength is needed in current models, and demonstrates a new technique that would be suitable for use in fine-grained liquid argon detectors where the effect of the nucleus may be even larger.
PDF
