Presence Of Particulate Material Research Articles

Atmospheric deposition of 10Be in Altzomoni rainfall

The optimization of preparation techniques for 10Be in rainfall samples and the approaches applied to improve the measurement of this radionuclide with the accelerator mass spectrometry (AMS) system were carried out at LEMA-UNAM. A radiochemical procedure has been realized to measure 10Be in smaller samples than those reported in similar studies, reducing the sample volume from 2 L to 250 mL. The 10Be concentrations in the dissolved and particulate fraction of rain from the high-altitude rural site Altzomoni (Mexico) during 2017–2018 were determined for the first time at LEMA. The results show that the presence of particulate material is four orders of magnitude greater than the content of 10Be in the rainfall from Altzomoni. This work shows a mean concentration of (1.9 ± 0.2) × 104 and (3.3 ± 0.6) × 108 atoms per gram of rainfall in dissolved and particulate fractions.

Fractal analysis of the time series of particulate material

The air quality index shows the pollution of the air we breathe, a very low index indicates that we can have respiratory, eye or heart conditions. An index below the minimum levels declared, requires generating strategies such as days without the presence of private vehicles, among others, to reduce pollution. The city of Medellin, Colombia, has shown very low levels in the air quality index due to several factors, mainly the emission produced by vehicles and companies. Due to this, activities have been initiated to reduce the emission of 2.5 micron and 10 microns particulate material, classified as highly harmful to health. The city installed 12 air quality monitoring stations and designed a decontamination proposal for the year 2030. Conducting a study on the persistence of particulate matter in the air according to the data recorded by the stations, will strengthen the proposed strategy or modify it to achieve the goal. In this work, the data collected by a station from July to December 2018 in which a high persistence in the presence of particulate material was analyzed.

Enhancement of cyanobacterial growth by riverine particulate material

Particulate material plays a major role in the transport of sparingly soluble nutrients such as P and Fe in natural surface waters. Microbes might gain access to these nutrients either indirectly through particulate dissolution or directly through microbial attack. As such, it seems reasonable to expect a link between the particulate material concentration and bacterial growth in natural surface waters. To explore this link, a series of microcosm growth experiments were performed in the presence of a typical freshwater cyanobacteria, Synechococcus sp., grown in dilute BG-11 culture media in the presence and absence of basaltic and continental riverine particulate material. Results demonstrate that riverine particulates can increase bacterial biomass by 1) triggering bacterial growth in otherwise unfavourable conditions, 2) increasing total maximum biomass concentration, and 3) inducing bacteria growth during the post-exponential phase. These effects are found to be enhanced by increasing particulate concentration. Results also indicate a positive feedback between the nutrient release from the particulates and growing bacteria, where dissolving particulates enhance bacterial growth, which further promotes particulate dissolution by altering fluid pH. Microscopic analysis showed direct physical contact between particulates and cyanobacteria, suggesting that bacteria attach directly on mineral surfaces to gain required nutrients. Furthermore, frequent bacteria clusters were observed associated with particulates, indicating an increasing aggregation of bacteria in the presence of particulate material, which may facilitate a higher burial efficiency of organic carbon.

CuO/SBA-15 catalyst for the catalytic ozonation of mesoxalic and oxalic acids. Water matrix effects

The depletion of mesoxalic and oxalic acids, two of the main by-products of wastewater ozone treatment, was studied in non-catalytic and catalytic ozonation using copper oxide supported on mesoporous silica SBA-15 as catalyst. The influence of the main inorganic anions present in natural and STP effluents (bicarbonates, sulphates, chlorides and phosphates) was also studied. The non-catalytic reaction rate was strongly dependent on the presence of inorganic anions and it was also almost inhibited by the presence of particulate material. Catalysed ozonation not only accelerates organic acid depletion, but was almost unaffected by the presence of these inorganic anions, or by the presence of suspended solids. The efficiency of catalytic and non-catalytic ozonation for depletion of both acids was studied in a real STP effluent. The depletion of mesoxalic acid was considerably slowed down in non-catalysed reactions, whereas under catalysed conditions it was not affected. Oxalate depletion was dominated by the formation with calcium of an insoluble salt, the precipitation equilibrium of which reversed only in the presence of a catalyst.

ULTRAVIOLET (UV) DISINFECTION OF GREY WATER: PARTICLE SIZE EFFECTS

The impact of water quality on the ultraviolet (UV) disinfection of grey water was investigated with reference to urban water reuse. Direct UV disinfection of grey water did not meet the stringent California State Title 22 criteria for unrestricted urban water reuse due to the presence of particulate material ranging from <1 to ≥2000 μm in size. Grey water was manipulated by settling to produce fractions of varying particle size distributions and blending was employed post‐disinfection to extract particle‐associated coliforms (PACs). The efficacy of UV disinfection was found to be linked to the particle size of the grey water fractions. The larger particle size fractions with a mean particle size of 262μm and above were observed to shield more coliforms from UV light than did the smaller particles with a mean particle size below 119μm. Up to 70% of total coliforms in the larger particle size fractions were particle‐associated following a UV dose (fluence) of 260mJ·cm−2 and would remain undetected by standard coliform enumeration techniques. Implications for urban water reuse are discussed and recommendations made for grey water treatment to ensure removal of particle‐associated indicator bacteria and pathogens prior to UV disinfection.

Fourier Transform Infrared Spectroscopic Analysis of the Polymethoxylated Flavone Content of Orange Oil Residues

Preliminary studies have shown that orange peel polymethoxylated flavones (PMFs) exhibit beneficial biological properties in animals. These properties have increased the demands for these compounds as candidate nutraceuticals and specialty food ingredients. Orange oil residues are a likely commercial source of the PMFs, and a rapid, solvent-free method for the analysis of the PMFs in orange oil residues has been developed based on Fourier transform infrared (FTIR) spectroscopy. The intensities of the FTIR vibrations of the phenyl ring nu(C=C) stretch at 1515 cm(-1) of the PMFs can be used, relative to the intensity of the carbonyl stretch at 1733 cm(-1) of the non-PMF orange oil residue components, to measure PMF content. Excellent correlations for the ratios of the intensities of these vibrations and the total PMF content were observed irrespective of the source, viscosity, and presence of particulate material. The detection limit by this method is approximately 0.1% PMF.

Extent of Excess Far‐Infrared Emission around Luminosity Class III Stars

With the Infrared Space Observatory, we conducted 3 ) 3 pixel imaging photometry of 12 luminosity class III stars, which were previously presumed to have dust particles around them, at far-infrared wave- lengths (60 and 90 km). Eleven out of 12 targets show a peak of excess (above photosphere) far-infrared emission at the location of the star, implying that the dust particles are truly associated with stars. To estimate the size of the excess emission source, the —ux ratio of center to boundary pixels of the 3 ) 3 array was examined. The radius of the dust emission is found to be D3000 to D10,000 AU for a thin shell distribution and D5000 to D25,000 AU for a uniform distribution. We consider three models for the origin of the dust: disintegration of comets, sporadic dust ejection from the star, and emission from nearby interstellar cirrus. The data seem to rule out the —rst model (as far as the ii Kuiper beltlike ˇˇ particles are assumed to be large blackbody grains) but do not enable us to choose between the other two models. Subject headings: circumstellar matterinfrared: starsstars: late-type Zuckerman, Kim, & Liu (1995) correlated the Bright Star Catalogue (Hoffleit & Warren 1991) and the Michigan Spectral Catalogue (Houk, Cowley, & Smith-Moore 1975- 1988) with the IRAS catalogs to determine which, if any, luminosity class III giant stars (—rst-ascent red giants) have associated circumstellar dust particles that radiate at far- infrared (far-IR) wavelengths. Of more than 40,000 class III giant stars in the two catalogs, they found that perhaps 300 have associated dust. The presence of particulate material near premain- sequence, main-sequence, asymptotic giant branch, and supergiant stars may be accounted for in rather straight- forward ways (remnants from the star formation for the for- mer two and mass loss for the latter two). But, there is no obvious way to produce and retain large amounts of dust near —rst-ascent giant stars, which are thought to be too old to still possess much leftover material and insufficiently evolved to have lost a signi—cant amount of their mass. However, one may conjecture that the presence of dust around —rst-ascent giants may involve one or more of the following phenomena: mass loss, binarity, planetary sys- tems, and evaporation of Kuiper belt material. Recently, Jura (1999) has analyzed three models for the dust around eight —rst-ascent giant stars: orbiting dust resulting from the disintegration of comets located in extrasolar analogs of the Kuiper belt, dust sporadically ejected from the star, and emission from particles in the interstellar medium that are accidentally near the star, the ii cirrus hot spot.ˇˇ Among the Zuckerman et al. (1995) list of 100, we observed 12 —rst-ascent giant stars with the PHOT instru- ment of the Infrared Space Observatory (ISO)2 to determine if the excess far-IR emission is truly associated with the stars and to estimate the size of the region that produces the excess far-IR emission.

Particulate material as a prerequisite for rapid cell multiplication in Tetrahymena cultures

1. 1. Tetrahymena pyriformis GL, cultivated axenically in 2 % proteose peptone in slanted test tubes at 28°C, had a population doubling time of more than 40 h when the medium was sterilized by asbestos pad or membrane filtration. Under these conditions the cultures could not be propagated successfully. 2. 2. The doubling time was reduced to 5 h or less when the medium was sterilized in the autoclave instead of by filtration. 3. 3. Various additives improved the growth potential of the sterile-filtered proteose peptone. These included both insoluble materials such as talcum, quartz, clay and calcium carbonate, and water-soluble compounds which through hydrolytic decomposition readily produce insoluble particles in aqueous solution, as, for example, ferrous ammonium sulphate, ferrous sulphate and potassium aluminium sulphate. Other water-soluble compounds such as amino acids, purines, pyrimidines, vitamins and glucose, added either singly or in combination to the sterile-filtered broth, did not significantly improve the rate of cell multiplication. 4. 4. The average number of food vacuoles present in the cells of a culture was observed to be correlated with the growth potential of the medium. 5. 5. On the basis of these observations it is suggested that formation of food vacuoles in Tetrahymena induced by the presence of particulate material is a condition for rapid multiplication of the cells.