Ammonia Neutralization Research Articles

Sol–Gel and Ultrafine Particle Formation via Dielectric Tuning of Inorganic Salt–Alcohol–Water Solutions

Under some conditions, inorganic salts can be as good precursors for sol–gel-type processing as those obtained from expensive metalloorganic precursors such as alkoxides. In this work, the formation of monodispersed hydrous zirconia microsphere particles (particularly nanosized) and gels was achieved in solutions of zirconyl chloride dissolved in alcohol–water mixed solvents. The dielectric property of the mixed alcohol–water solvent directly affects the nucleation and growth of zirconia clusters/particles in homogeneous solutions. A lower dielectric constant of mixed solvent corresponds to a lower solubility of inorganic solute and, thus, a shorter induction period for nucleation as well as higher solid particle growth kinetics. Dynamic light scattering (DLS) was used to monitor the homogeneous nucleation and growth processes, while final particles and gels were studied by scanning electron microscopy (SEM) and high-temperature X-ray diffraction (HTXRD). The sol–gel processes in the mixed solvent system can be adjusted using the processing parameters, including the initial inorganic salt concentration (C), alcohol/aqueous medium volume ratio of the mixed solution (RH), incubation temperature (T), incubation time (t), concentration of hydroxypropyl cellulose (HPC), and ammonia neutralization. Monodispersed submicron and nanoscale (<100 nm) zirconia microspheres/powders were successfully synthesized under conditions of high RH (5) and using HPC (molecular weight of 100,000, 2.0×10−3 g/cm3) and ammonia neutralization. Initial salt concentration affects the particle size significantly. Gel materials were obtained under conditions of low RH (1.0). Microstructure and transparency of gels changed significantly from low (0.05 M) to high (0.2 M) concentration of the metal salt. We have also demonstrated that monodispersed particle production can be achieved not only at low temperatures (<100°C) but also at room temperature using an inorganic salt precursor.

Ammonium in coastal Antarctic aerosol and snow: Role of polar ocean and penguin emissions

Year‐round aerosol samples collected in the boundary layer at coastal Antarctic sites (Dumont D'Urville, Neumayer, and Halley) indicate a seasonal cycle of ammonium concentrations with a minimum in winter (April–September). A large intersite difference appears in the summer (November–February) maxima values, from ∼12.5 ng m−3 at Neumayer to 140–230 ng m−3 at Dumont D'Urville. At Dumont D'Urville, ammonium concentrations are the largest ever reported from Antarctic sites, and the large summer maxima are associated with large enrichments with respect to sea salt for potassium and calcium. In addition, seasonal ammonium variations at Dumont D'Urville are in phase with a well‐marked seasonal cycle of oxalate concentrations which exhibit maxima of 5–10 ng m−3 in spring and summer and minima of less than 0.5 ng m−3 in winter. Such a composition of aerosols present in the boundary layer at Dumont D'Urville in summer is linked to the presence of a large Adélie penguin population from the end of October to March at the site. Ornithogenic soils (defined as guano‐enriched soils), together with the bacterial decomposition of uric acid, are a source of ammonium, oxalate, and cation (such as potassium and calcium) aerosol, in addition to a subsequent large ammonia loss from ornithogenic soils to the atmosphere. The total breeding population of 5 million Adélie penguins widely distributed around the Antarctic continent may emit, at most, some 2.5 × 10−4 Mt of NH3‐N during the summer months. In contrast, Halley and Neumayer Stations are far less exposed to penguin colony emissions. At Neumayer, ammonium concentrations peak from January to March and are in phase with the increase of biogenic sulfur species. Here the NH4+/(MSA + nss SO4−) molar ratio is close to 13% in summer aerosol and to 40% in winter aerosol. Using this summer ratio, which may be related to ammonia and sulfur oceanic emissions occurring south of 50°S in summer and estimated DMS emissions in these regions at this time, we derive an upper limit of 0.064 Mt NH3‐N emitted per year by the high‐latitude Southern Ocean in summer. This study indicates a very limited ammonia neutralization of acidic sulfate aerosols at high southern latitudes, except in the vicinity of ornithogenic soils occupied by large penguin colonies.

Growth and neutralization of sulfate aerosols in human airways.

Evidence derived from in vivo and in vitro laboratory experiments, controlled human exposure studies, and epidemiological studies on mortality and morbidity point to a positive correlation between acid aerosol inhalation and lung impairment. The lung has two important lines of defense against acid aerosols: 1) neutralization by oral or nasal airway ammonia and 2) buffering by mucus lining of the airway. A mathematical model is developed to study the growth and endogenous ammonia neutralization of sulfate-containing aerosol particles in the human respiratory tract. It is shown that an accurate prediction of the luminal ammonia concentration and relative humidity in each generation is essential for quantifying the degree of neutralization of the acidic particles. The model predicts substantial growth and neutralization for small particles (< 0.1 micron), whereas larger particles (> 1.0 micron) experience negligible neutralization. The predicted neutralization of intermediate-sized particles depends on the parameter values used in the model. Water supersaturations that occur in the respiratory tract when ambient conditions are cool and humid cause rapid particle growth and consequently enhance neutralization. Thus the neutralization depends on the particle size as well as on ambient conditions.

Glutamine synthetase (GS) expression is reduced in senile dementia of the Alzheimer type.

Glutamine synthetase (GS), a metabolic marker of the mature astrocyte, was investigated in the temporal neocortex of postmortem brain samples of 8 cases, either not demented or affected by senile dementia of the Alzheimer type. A negative correlation between the GS protein level and the density of both classical beta A4 deposits and senile plaques was evidenced. Such a correlation for GS underlies a dysfunction of the astroglial metabolism and particularly of the glutamate and ammonia neutralization. Since GS is sensitive to oxidative lesioning, the changes in GS level that were observed, occurring at the posttranslational stage, might reflect oxidative damage and have severe consequences on the pathological cascade of events.

Astroglial reactivity in natural scrapie of sheep

Astrogliosis is known to be a common histological feature in experimental scrapie, but astroglial reactivity in natural scrapie of sheep has not yet been precisely studied. We investigated the expression of two markers of glial plasticity, glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS), by Western and Northern blotting, in different areas of the sheep brain. We report that both GFAP-mRNA and GFAP are overexpressed in the cerebellum and the pons. In the thalamus, overexpression of GS was demonstrated for the first time in this disease. The enhancement of this astroglial metabolic marker, essential for glutamate and ammonia neutralization, cellular function and brain detoxification, could represent an attempt by astrocytes to maintain and control the cerebral homeostasis in this area. Our results show that astrocytes: (i) are a target for the scrapie agent even in the early temporal evolution of the disease; (ii) react by overexpressing their intermediate filament major protein, changing their phenotypic appearance and stabilizing their processes in precise brain areas; (iii) overexpress key elements of their metabolism. These changes clearly implicate astrocytes in the pathogenesis of the disease.

Physico-chemical speciation and transformation reactions of particulate atmospheric nitrogen and sulphur compounds

Using X-ray powder diffraction it is possible to identify a number of discrete compounds of nitrogen and sulphur in atmospheric aerosols. The compounds observed include ammonia neutralization products of airborne acids, including mixed ammonium nitrate-sulphate salts. Products of hydrogen halide displacement by HNO 3 and H 2SO 4 are identified both from size-differentiated ion balance studies and X-ray diffraction. A number of mixed metal-ammonium sulphate salts are attributed to reactions of ammonium sulphate subsequent to aerosol coagulation processes.

Newly designed sterilization system for the operating microscope: a technical note.

A new sterilization system for the operating microscope is introduced. The system, which uses formaldehyde vapor, has three advantages: (a) Rapid sterilization can be achieved with the microscope in place in the operating room within one-half hour. (b) The lens assembly of the microscope is protected against damage through ammonia neutralization and fresh air ventilation. (c) The microscope can be used immediately after sterilization without unpleasant odor or irritation of the eyes and nose.

A Thermal study of the precipitates formed in ammonia neutralization of acidic solutions of dissolved phlogopite

The precipitates containing mainly iron, aluminium and magnesium hydroxides, obtained from phlogopite dissolved in nitric acid by means of the neutralization procedure with ammonia, have been investigated by thermal analysis (TG, DTG and DTA). According to the present study, which is part of a larger investigation into the chemical utilization of Finnish mica minerals, the formation of solid solutions between iron and aluminium hydroxides in silt increases with an increasing neutralization temperature. Nitrogen exists mainly in the form of nitrate in silts, and magnesium forms mixed hydroxides with aluminium, which causes a separation between the iron hydroxide and magnesium aluminium hydroxide phases.

Mammalian cell culture mutagenicity and carcinogenicity testing of dimethyl sulfoxide extracts of flame retardant-treated cotton fabrics.

Dimethyl sulfoxide extracts of flame retardant-treated cotton fabrics were tested for ability to mutate and transform mammalian cells in culture. Fabrics were treated with tetrakis(hydroxymethyl)phosphonium chloride (THPC) and tetrakis(hydroxymethyl)-phosphonium sulfate (THPS). Extracts were prepared at the precondensate stage of flame retardant processing and after ammonia neutralization (THPOH-NH3). Unconcentrated or 10-fold concentrated extracts were tested as 0.5 or 1% solutions in cell culture medium. All extracts were mutagenic to V79 hamster lung cells (conversion to ouabain resistance) with or without addition of rat liver microsomes (S9). Up to 84 mutant colonies per 10(6) surviving cells were found with THPS fabric extracts, whereas up to 113 were obtained with THPC fabric extracts. Extracts were also able to transform mammalian cells, as shown in two different assays. Transformation of BHK cells, as measured by colony formation in soft agar, increased more than 20-fold with THPC extracts, but less than 2-fold with THPS extracts. Both the THPC and THPS extracts induced 3T3 cell transformation with linear dose-response. The number of foci of transformed cells per 10(5) survivors was 10--100 times that in the solvent control. Greater numbers of transformed foci were obtained after treatment at the highest doses tested than after treatment with the positive control compounds, benzo[a]pyrene and N-methyl-N-nitro-N-nitrosoguanidine.

Ammonia neutralization in heart muscle

The pathways of ammonia neutralization in rat heart muscle were studied with the aid of15N. The effect of the ammonia concentration in the perfusion fluid on its utilization by the myocardium was studied within the range from 1.6 to 3.4 mM. Neutralized ammonia was found in large quantities in glutamine and glutamic acid and in smaller quantities in alanine and aspartic acid. Isoproterenol-induced necrosis of heart muscle led to a decrease in the binding of ammonia by glutamine (20–40%) and alanine (30–45%). The effect of necrosis on ammonia binding by glutamic acid was not significant, and incorporation of15N into aspartic acid was reduced in the presence of necrosis, but was increased in the presence of high concentrations.

Ammonia neutralization and urea synthesis in cardiac muscle.

Ammonia neutralization and urea synthesis in cardiac muscle.

Ammonia Neutralization and Urea Synthesis in Cardiac Muscle

Ammonia Neutralization and Urea Synthesis in Cardiac Muscle

Chloride Corrosion and Fouling In Catalytic Reformers With Naphtha Pretreaters

Abstract A study was made of chloride corrosion and fouling occurring in low-temperature sections of catalytic reformer naphtha pretreaters. These problems were related to corrosion by aqueous HCl-H 2 S-NH 3 solutions. Laboratory corrosion studies were made with these solutions to establish the effect of pH and composition in the presence or absence of an air atmosphere. Suppression of corrosion by ammonia neutralization and amine-type inhibitors also was studied. Elevated temperature tests were conducted in a nitrogen atmosphere. Field tests were made on six metals in a commercial pretreater reactor effluent stream. The removal of ammonium chloride fouling deposits was discussed briefly. 8.4.3, 4.3.2, 5.7.7, 3.3.2

The presence of glutamine in the urine of children under one year

The content of glutamine in the urine of newborn infants, of premature infants and ontogenetically of children under one year has been studied. The presence of glutamine in the urine of infants from the first day of life has been established; its content fluctuates sharply and is often zero in the case of the youngest. The influence of sleeping and waking on the glutamine content in children of 2 to 3 has been studied. The influence of inhaling oxygen on the glutamine content of the urine has been observed. The possible connection between the changes in glutamine content and the peculiarities of ammonia neutralization in the infant's organism is discussed.

Influence of Soluble Salts on the Solubility of and Plant Response to Dicalcium Phosphate

A considerable part of the phosphorus in most mixed fertilizers is carried as dicalcium phosphate produced as a consequence of ammonia neutralization of the mixture. Agronomic experience with such mixtures suggests that the phosphate produced in situ has a higher nutritive value than separate preparations of dicalcium phosphate. Any increased nutritive value of the dicalcium phosphate must, it would seem, stem mainly from enhancement of phosphorus solubility in the presence of soluble salts. Accordingly, the solubility of a laboratory preparation of dicalcium phosphate was measured in water and several salt solutions. Greenhouse techniques were designed to minimize responses to nutrient constitutents of the salts, change in available soil phosphorus status and physiological effects due to the salts, so that differences in plant response to binary mixtures of dicalcium phosphate and several salts were indicative of differences in solubility of dicalcium phosphate. Alfalfa was used as the test crop on Nunn, Carrington, and Chester soils. In general, salts such as ammonium sulfate, which in laboratory tests markedly increase the solubility of dicalcium phosphate with increasing ionic strength, also gave the greatest crop responses in the greenhouse. Those salts such as the ammonium nitrate type, which increase the solubility only moderately and level off at ionic strengths between 2 and 4, only occasionally gave increased crop response, while salts such as the calcium nitrate type, which decrease the solubility sharply with increasing ionic strengths, usually gave a negative crop response.