Search results for "bicarbonate"
showing 10 items of 119 documents
Improving the mechanical properties of unidirectional flax fabrics reinforced epoxy composites by sodium bicarbonate treatment
2017
Despite their beneficial effects on the adhesion between natural fibers and polymeric matrices, chemical pretreatments have become less attractive since they are expensive and harmful to environment. The present paper deals with the effect of an eco-friendly and cost effective treatment, based on the use of a sodium bicarbonate solution, on the mechanical performances of flax reinforced epoxy composites. Materials and methods: A commercial epoxy resin and unidirectional flax fabrics (190 g/m2 areal density) were used as matrix and reinforcement, respectively. The fabrics were soaked in 5 and 10 wt% solutions of sodium bicarbonate for 5 days at 25°C, then dried at 105°C for 1 day. By using u…
Automation of the determination of hydrogen peroxide, dichromate, formaldehyde and bicarbonate in milk by flow injection analysis
1992
Automatic flow injection methods for the determination of hydrogen peroxide, dichromate, formaldehyde and bicarbonate in dairy products are proposed. They are based on reaction with vanadium pentoxide, diphenyl-carbazide, fuchsine-sulphur dioxide and alizarin, respectively. Sample pre-treatment (paper and membrane filtration, dialysis) is widely discussed for on-line incorporation. The usefulness of these methods was tested by applying them to different commercial samples, satisfactory results being obtained in all instances.
Continuous flow synthesis of amine oxides by oxidation of tertiary amines
2019
The synthesis of N-methylmorpholine N-oxide by oxidation of N-methylmorpholine with hydrogen peroxide was implemented in a microstructured reactor for increased safety and larger-scale applications. The active oxidant, peroxymonocarbonate HCO4− is formed in situ from the equilibrium reaction of hydrogen peroxide and bicarbonate. The bicarbonate can be induced by hydration of carbon dioxide. Elaborate studies on the influence of the catalyst concentration and temperature were carried out and the observed activation energy was determined. Elevated temperatures up to 60 °C and a carbon dioxide concentrations of 1 wt% led to a conversion for N-methylmorpholine of approximately 98% within 13.90 …
Der Einfluss aliment�rer Acidosen und Alkalosen auf die Wachstumsgeschwindigkeit und die Eiweissausnutzung der Ratte
1958
Die Erzeugung einer alimentaren Acidose mit 200 mAq NH4Cl/kg Futter bei wachsenden Ratten fuhrt bei Mannchen und Weibchen zu einer schlechteren Protein-Efficiency, aber nur bei den Mannchen zu einer geringeren Wachstumsgeschwindigkeit. Eine mit NaHCO3 in analoger Weise induzierte alimentare Alkalose hat weder bei den Mannchen noch bei den Weibchen einen sicheren Einflus auf die Protein-Efficiency und auf die Wachstumsgeschwindigkeit.
Chloride, carboxylate and carbonate transport by ortho-phenylenediamine-based bisureas
2013
Highly potent but structurally simple transmembrane anion transporters are reported that function at receptor to lipid ratios as low as 1 : 1 000 000. The compounds, based on the simple ortho-phenylenediamine-based bisurea scaffold, have been studied for their ability to facilitate chloride/nitrate and chloride/bicarbonate antiport, and HCl symport processes using a combination of ion selective electrode and fluorescence techniques. In addition, the transmembrane transport of dicarboxylate anions (maleate and fumarate) by the compounds was examined. Molecular dynamics simulations showed that these compounds permeate the membrane more easily than other promising receptors corroborating the e…
Secretin—cerulein test and fecal chymotrypsin concentration in children with intestinal giardiasis
1993
We studied six patients with giardiasis (five males, one female), median age 3.5 yr (range 1-11) and 12 healthy control subjects (10 males, 2 females), median age 3.5 yr (range 1-10). Intestinal biopsy and a contemporaneous secretin-cerulein test were performed in all patients, and fecal chymotrypsin was also assayed. Intestinal biopsy was normal in five of the six patients with giardiasis, whereas one of the six presented a partial atrophy of the intestinal villi. The secretin-cerulein test (1 CU/kg of secretin + 75 ng/kg of cerulein) did not show any significant difference between values in the outputs of chymotrypsin, lipase, phospholipase, and bicarbonate obtained in patients and in con…
Valoración de los cambios de los aniones orgánicos que participan en el equilibrio ácido-base al introducir un regimen de biofiltración sin acetato
2011
VALORACIÓN DE LOS CAMBIOS DE LOS ANIONES ORGÁNICOS QUE PARTICIPAN EN EL EQUILIBRIO ÁCIDO-BASE AL INTRODUCIR UN REGIMEN DE BIOFILTRACIÓN SIN ACETATO. La corrección de la situación de acidosis metabólica común a la insuficiencia renal crónica es uno de los objetivos prioritarios del tratamiento de sustitución dialítico. La diálisis es capaz de producir cambios en el perfil metabólico dependientes de la modalidad y del líquido empleados. Realizamos un estudio con 22 pacientes estables en programa de hemodiálisis que se sometieron de forma cruzada a dos modalidades de hemodiafiltracion una con 34 mmol/l de bicarbonato y 3 mmol/l de acetato (HDF) y la otra biofiltración sin acetato (AFB). Según …
Toward Mechanistic Design of Surrogate Buffers for Dissolution Testing of pH-Dependent Drug Delivery Systems
2020
The in vivo dissolution of enteric-coated (EC) products is often overestimated by compendial in vitro dissolution experiments. It is of great interest to mimic the in vivo conditions as closely as possible in vitro in order to predict the in vivo behavior of EC dosage forms. The reason behind this is the overly high buffering capacity of the common compendial buffers compared to the intestinal bicarbonate buffer. However, a bicarbonate-based buffer is technically difficult to handle due to the need for continuous sparging of the media with CO2 to maintain the desired buffer pH. Therefore, bicarbonate buffers are not commonly used in routine practice and a non-volatile alternative is of inte…
Protein Tyrosine Nitration Induced by Heme/Hydrogen Peroxide: Inhibitory Effect of Hydroxycinnamoyl Conjugates
2006
The present study was designed to optimize the experimental conditions that govern the heme-catalyzed nitration of protein tyrosine residues by nitrite, and, within this framework, to study the effects of 3,5-dicaffeoylquinic acid and its methyl ester, both of which have been previously reported to be antioxidants and inhibitors of leukocyte functions. Although the presence of hydrogen peroxide is essential in cell-free systems, an excess of this compound was found to be detrimental, so much so that an increase in hemin concentration actually resulted in an inverse effect on the reaction, depending on the levels of fixed hydrogen peroxide. Unlike previous reports on nitrite-induced albumin …
Nitric oxide: Relation to integrity, injury, and healing of the gastric mucosa
2001
Nitric oxide (NO) plays a multifaceted role in mucosal integrity. The numerous functions of NO and the double-edged role played by NO in most of them provide a great complexity to the NO action. The three enzymatic sources of NO, neuronal NO-synthase (nNOS), endothelial NOS (eNOS), and inducible NOS (iNOS), have been characterised in the gastrointestinal tract. The protective properties of the NO derived from constitutive NO-synthases (eNOS and nNOS) have already been well established. Less clear is the role assigned to iNOS. The simplistic initial view of low levels of NO synthesised by constitutive NOS being protective while exaggerated NO levels after iNOS induction leading irremediably …