Experimental and Modeling High-Pressure Study of Ammonia-Methane Oxidation in a Flow Reactor.

The present work deals with an experimental and modeling analysis of the oxidation of ammonia-methane mixtures at high pressure (up to 40 bar) in the 550-1250 K temperature range using a quartz tubular reactor and argon as a diluent. The impact of temperature, pressure, oxygen stoichiometry, and CH/NH ratio has been analyzed on the concentrations of NH, NO, NO, NO, N, HCN, CH, CO, and CO obtained as main products of the ammonia-methane mixture oxidation. The main results obtained indicate that increasing either the pressure, CH/NH ratio, or stoichiometry results in a shift of NH and CH conversion to lower temperatures.

A Combined Experimental and Modeling Study on Isopropyl Nitrate Pyrolysis.

Alkyl nitrates thermally decompose by homolytic cleavage of the weak nitrate bond at very low temperatures (e.g., around 500 K at reaction times of a few seconds).

Experimental and Modeling Evaluation of Dimethoxymethane as an Additive for High-Pressure Acetylene Oxidation.

The high-pressure oxidation of acetylene-dimethoxymethane (CH-DMM) mixtures in a tubular flow reactor has been analyzed from both experimental and modeling perspectives. In addition to pressure (20, 40, and 60 bar), the influence of the oxygen availability (by modifying the air excess ratio, λ) and the presence of DMM (two different concentrations have been tested, 70 and 280 ppm, for a given concentration of CH of 700 ppm) have also been analyzed. The chemical kinetic mechanism, progressively built by our research group in the last years, has been updated with recent theoretical calculations for DMM and validated against the present results and literature data.

Experimental Study of the Pyrolysis of NH under Flow Reactor Conditions.

The possibility of using ammonia (NH), as a fuel and as an energy carrier with low pollutant emissions, can contribute to the transition to a low-carbon economy. To use ammonia as fuel, knowledge about the NH conversion is desired. In particular, the conversion of ammonia under pyrolysis conditions could be determinant in the description of its combustion mechanism.

Escaping undesired gas-phase chemistry: Microwave-driven selectivity enhancement in heterogeneous catalytic reactors.

Research in solid-gas heterogeneous catalytic processes is typically aimed toward optimization of catalyst composition to achieve a higher conversion and, especially, a higher selectivity. However, even with the most selective catalysts, an upper limit is found: Above a certain temperature, gas-phase reactions become important and their effects cannot be neglected. Here, we apply a microwave field to a catalyst-support ensemble capable of direct microwave heating (MWH).

Acetylene soot reaction with NO in the presence of CO.

The heterogeneous reaction of soot with NO can be considered as a means of reduction of the emissions of both pollutants from combustion systems. In this paper, the influence of the presence of CO in the soot-NO reaction is studied. Soot was obtained by pyrolysis at 1373 K of 5000 ppmv acetylene in nitrogen.

Mucosal immunization of sheep with a Maedi-Visna virus (MVV) env DNA vaccine protects against early MVV productive infection.

Gene gun mucosal DNA immunization of sheep with a plasmid expressing the env gene of Maedi-Visna virus (MVV) was used to examine the protection against MVV infection in sheep from a naturally infected flock. For immunization, sheep were primed with a pcDNA plasmid (pcDNA-env) encoding the Env glycoproteins of MVV and boosted with combined pcDNA-env and pCR3.1-IFN-gamma plasmid inoculations.

Molecular cloning and mRNA tissue-expression of two isoforms of the ovine costimulatory molecule CD80 (B7-1).

Using RT-PCR and rapid amplification of cDNA ends (RACE), we cloned two putative alternatively spliced transcripts of the sheep CD80 (B7-1) molecule that encode both transmembrane (TM) and secreted (s) forms of CD80 protein. Comparison of the amino acid sequence of the TM form of ovine CD80 with the sequence of cattle, swine and human CD80 indicated that the deduced protein had a higher degree of similarity to cattle (87% of amino acid identity) than to pig (68%) and human sequence (53% of homology). In tissues, RT-PCR using primers for the TM and the sCD80 transcripts indicated that the expression of both CD80 transcripts was almost exclusively expressed in the hematolymphoid system, with the exception of the uterus.

[Severe primary vesicoureteral reflux in infants. A follow-up of 203 cases].

Objective: The aim of our study is to analyze the clinic characteristics and evolution of the primary reflux in infants.

Methods: We studied retrospectively 203 infants in our hospital, diagnosed of severe primary renal reflux. Renal ecography and cyclic mictional cystography were practiced in all cases.

Lipid composition of the intramuscular fat of beef from Spanish cattle breeds stored under modified atmosphere.

The lipid composition of intramuscular fat from 30 young bulls of 5 Spanish cattle breeds (Asturiana de los Valles, Morucha, Parda Alpina, Pirenaica and Retinta) was studied. Steaks from each shortloin were packaged in 60% O(2), 30% CO(2) and 10% N(2) and aged for 0, 5, 10 and 15 days. Lipid classes obtained by thin layer chromatography and total fatty acids obtained by gas chromatography were evaluated.

Formation and destruction of CH2O in the exhaust system of a gas engine.

A computational study of chemical reactions occurring in the exhaust system of natural gas engines has been conducted, emphasizing the formation and destruction of formaldehyde. The modeling was based on a detailed reaction mechanism, developed for describing oxidation of C1-C2 hydrocarbons and formaldehyde. The mechanism was validated against data from laboratory flow reactors and from the exhaust system of a full-scale gas engine.

Shelf life of beef from local Spanish cattle breeds stored under modified atmosphere.

Beef steaks from six Spanish cattle breeds (Asturiana de los Valles, Morucha, Parda Alpina, Pirenaica, Rubia Gallega and Retinta) were packaged under modified atmosphere (60% O(2), 30% CO(2) and 10% N(2)). Water loss, pH, thiobarbituric acid values (TBA), aerobic plate counts, lactic acid bacteria and Enterobacteriaceae counts, CIE L*a*b* colour values and the sensory properties of odour and colour were recorded before packaging (day 0) and after 5, 10 and 15 days of storage. A significant interaction (P<0.

[Intrarenal reflux and kidney damage in essential vesicoureteral reflux].

We had reviewed our series of 59 patients with intrarenal reflux selected out of 596 diagnosed of vesicoureteral reflux. The number of renal units affected of intrarenal reflux was 74. We divided our patients into two groups, in an attempt to clarify the relationship between renal damage and urinary infection; a group include there was prenatal diagnosis of urinary tract dilatation and another group diagnosed for bacterial infection of urine after birth.

[Fetal urinary dilatation due to vesico-ureteral reflux].

We have retrospectively studied 163 newborns referred to us between 1986 and 1990 for sonographic diagnosis of intra-uterine upper urinary tract enlargement. All were studied by paediatric radiologists on days 5th or 6th after birth by means of sonography and voiding cystourethrogram (VCU). Fifty percent had also IVP.

[Syringoceles of Cowper's glands in children].

Some tubular or cystic diverticula observed in the ventral wall of the male bulbous urethra that originate from dilatation of Cowper's gland ducts have been termed "syringoceles". They can cause dysuria, hematuria and obstruction. We report 14 syringoceles and 1 true diverticulum from segmental absence of spongious urethra.

[Primary vesicoureteral reflux. II. Renal growth in kidneys with pyelonephritis].

We have studied kidney growth and function in 38 patients with either unilateral (23) or bilateral (15) vesicoureteral reflux (VUR) and reflux nephropathy (RN). Average follow-up was 38 (range 12-84) months. Surgery was performed in 93.

[Primary vesicoureteral reflux. I: Renal growth in kidneys without pyelonephritis].

We have studied renal growth in 133 children with 195 refluxing ureters (VUR). Average follow-up was 38 (range 12-84) months. Low grade VUR (I-III) were more frequent and left-sided ones predominated among unilateral cases.

[Ventral diverticula of the bulbous urethra].

We report 5 male patients with ventral diverticula of the bulbous urethra. There was urinary infection in 4 cases, urethral obstruction in 1 and voiding disturbances in 1. Urethral catheterism had been performed previously for various reasons in three patients.

[Critical evaluation of cystoscopy in pediatric vesico-ureteral reflux].

Authors report a study on endoscopical evaluation of 110 refluxing ureters in 65 children selected out of a group of 384 with VUR seen between 1977 and 1980. Cystoscopy was only undertaken either in patients with poor response to conservative treatment or in those with associated malformations. Radiologic-endoscopic correlation was rather good: 93% of grade II refluxing orifices were normally located or slightly lateralized, whereas 72% of grade III or IV were so.

[Gastroesophageal reflux with respiratory manifestations. Manometric and pH-metric study].

Gastroesophageal reflux can be found in patients with respiratory tract disease even in the absence of vomiting. A manometric and pH-metric study carried out in 69 children with radiologic reflux (of whom 49 had respiratory symptoms) and 10 normal controls has shown: 1. lower esophageal sphincter pressure was lower in refluxing patients than in controls, but values were significant only for those with vomiting; 2.

[Urology aspects of adrenogenital syndrome].

During the past five years, 10 patients (seven girls and three boys) with virilizing adrenal hyperplasia have been treated in our institution. A thorough urological work-up was preformed in all. We found among the girls one ureteral duplication, three lower urinary obstruction (two of them in girls with high urethro-vaginal confluence) and four bilateral vesico-ureteral refluxes.