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N Kallay

Publications and source records attributed to N Kallay.

11 recordsLinked to original sources

Surface potential at the hematite-water interface.

Construction of a metal oxide electrode enabling measurement of surface potential is described. The electrode was made using a hematite monocrystal, which avoids the problems arising from the possible porosity of the oxide layer. The potential of this electrode was measured as a function of pH. The hematite electrode provides reproducible results, especially in the acidic region. Surface potentials were calculated from electrode potentials using the electrokinetic isoelectric point. The slope of surface potential with respect to pH was found to be lower than the Nernstian, especially in the basic region. The effect was more pronounced at higher ionic strengths. It was shown how the measurement of surface potential can help to interpret the equilibrium data and evaluate the choice of a theoretical model describing the interfacial equilibrium at the metal oxide-water interface.

Journal Article↗

Reversible charging of the ice-water interface. II. Estimation of equilibrium parameters.

Equilibrium parameters characterizing the ice-water interface were obtained from electrokinetic and potentiometric data. The dependency of surface potential on pH was measured by the ice electrode. Electrokinetic zeta potentials were measured by electrophoresis. In the interpretation, the 1-pK and 2-pK concepts of the surface complexation model, developed for metal oxides, were used. The equilibrium parameters (constants of surface reactions) were determined. The results were confirmed by numerical simulations. Both 1-pK and 2-pK models fit the experimental data well.

Journal Article↗

Hemoptysis in patients with renal insufficiency : the role of flexible bronchoscopy.

STUDY OBJECTIVES: To assess the indications, yield, and therapeutic impact of flexible bronchoscopy (FB) in patients with hemoptysis and renal insufficiency. DESIGN: Retrospective cohort analysis. SETTING: Tertiary-care university hospital. PATIENTS: Thirty-four patients over a 7.5-year period who underwent FB to evaluate hemoptysis in the setting of renal insufficiency (ie, serum creatinine level, > 1.5 mg/dL). MEASUREMENTS AND RESULTS: The etiology of hemoptysis was undetermined in 41% of cases. Defined causes of bleeding included infections (29%), pulmonary renal syndromes (15%), airway injury (9%), and pulmonary embolism (6%). No specific bleeding site was identified, but FB lateralized hemorrhaging to one lung in 24% of patients. FB results influenced therapy in 29% of patients overall and in 8% of patients without respiratory tract infection. The hospital survival rate was 47% and did not differ based on the presence or absence (presence vs absence) of the following variables: a defined etiology for hemoptysis (45% vs 50%); lateralized bleeding (38% vs 50%); or management alterations prompted by other FB findings (50% vs 46%). Factors associated with survival included the onset of bleeding prior to hospital admission (80% vs 33%; p = 0.02), the absence of respiratory failure requiring mechanical ventilation at the time of FB (90% vs 29%; p = 0.002), and lack of prohemorrhagic factors (other than uremia) such as disseminated intravascular coagulation, recent treatment with warfarin, heparin, or antiplatelet agents (78% vs 33%; p = 0.05). During the 6 months following hospital discharge, hemoptysis recurred in 14% of patients, and 5 patients died, for an overall mortality rate of 62%. CONCLUSIONS: These data suggest that FB in hospitalized patients with hemoptysis and renal insufficiency, and without radiographic findings suggesting neoplastic disease, has a low yield and limited impact. Whether FB influences outcome in selected patients in this setting requires prospective investigation.

Bronchoscopy↗

Reversible Charging of the Ice-Water Interface.

An ice electrode was constructed in order to measure dependency of the surface potential on pH. The electrode had a Plexiglas body with a platinum plate on the bottom, which was cooled by passing the cooling liquid through a tube mounted inside the electrode. The temperature inside the electrode was -7 degrees C, while the electrolyte solution was kept at 0.02 degrees C, so that an ice layer was formed on the platinum plate. In the acidic region fast equilibration of electrode was observed. The slope dphi(0)/dpH was found to be between -40 and -46 mV. The maximum of the slope was observed at pH 4.4, which coincides with the isoelectric point of ice-water interface. In the basic region the equilibration was slow and more pronounced deviation from the Nernstian behavior was observed. The results were explained on the basis of the surface complexation model, assuming an amphotheric nature of surface OH groups. In the basic region the surface bears high negative charge so that binding of sodium ions at the interface influenced the results. Copyright 2000 Academic Press.

Journal Article↗

Charged Surfaces and Interfacial Ions.

Interfacial charge in a solid/liquid system is due to interactions of ions with surface sites affected by the electrostatic potential that is a consequence of their accumulation. The present theoretical approach is based on the so-called Surface Complexation Model that has several modifications known as either the 1-pK, the 2-pK, or the "MUSIC" model. These models assume different surface reactions and their equilibrium constants, taking into account electrostatic interactions. For that purpose the relationships between potentials affecting the state of interfacial ions and their surface densities need to be known, so that a certain model of the electrical interfacial layer should be introduced. The complexity of the problem results in the use of a variety of different theoretical approaches that cannot be distinguished experimentally. This article discusses several aspects of the problem, such as counterion association, structure of the electrical interfacial layer, potential-charge relationships, surface potentials, the zero charge condition, enthalpy of surface reactions, and the influence of the interfacial ionic equilibrium on the colloid stability. Copyright 2000 Academic Press.

Journal Article↗

Massive left diaphragmatic separation and rupture due to coughing during an asthma exacerbation.

We report a case of herniation of abdominal contents into the left hemithorax in a patient hospitalized with an acute exacerbation of asthma accompanied by paroxysms of coughing. There was no history of trauma. We believe this is the first reported case of diaphragmatic rupture complicating an asthma exacerbation. We review clinical features, pathophysiology, diagnosis, and treatment of diaphragmatic rupture in its most common setting, trauma, and discuss its occasional "spontaneous" occurrence.

Chest Pain↗

Electrostatic Contribution to the Enthalpy of Charging at Hematite/Electrolyte Interface.

A calorimetry study of hematite surface reactions is reported, with special emphasis on the estimation of the electrostatic contribution to the enthalpy of charging. The calorimetry titrations were performed outside the point of zero charge region where the electrostatic contribution is significant. The results were interpreted by the surface complexation model. The interpretation enabled the evaluation of standard protonation and deprotonation enthalpies as well as the electrostatic contribution to these quantities. Copyright 1999 Academic Press.

Journal Article↗

Dissolution of metronidazole from oral and vaginal dosage forms in sink and non-sink conditions.

The pharmaceutical availability of metronidazole from several commercial oral and vaginal dosage forms in sink and non-sink conditions has been examined by measuring the rate of drug dissolution. The results were interpreted by means of reversible and irreversible dissolution models. For non-sink conditions the reversible model was found to better interpret the data. The values of the relative dissolution rate constant, theoretical dissolution time and dissolution efficiency were obtained and discussed.

Administration, Intravaginal↗

Pharmaceutical availability from oral dosage forms: in vitro release of nitrofurantoin from tablets and capsules.

The pharmaceutical availability of nitrofurantoin in three commercial urinary antiseptic preparations for oral use was assessed by an in vitro determination of drug release into a strongly acidic, a weakly acidic and a weakly basic medium. The following parameters are reported: t87.5%, tdiss, X0 (percentage released immediately on contact with medium), krel (relative dissolution rate constant), and dissolution efficiency (DE).

Biological Availability↗

In vitro release of meclozine hydrochloride from lipophilic suppository bases with or without tensides.

Meclozine hydrochloride suppositories were prepared with lipophilic bases, and the release rate of the drug from molten suppositories was investigated in vitro. Among various suppository bases, the highest rate was obtained when Witepsol H 15 was used. The release rates were affected if nonionic tensides (Tween 20 and 80) were incorporated. In comparison to the tensides-free suppositories, the rates obtained with suppositories containing 5, 20 and 30% of tensides were higher, approximately the same, and lower (respectively). The results were interpreted in terms of the micellar solubilization of the drug with nonionic tensides.

Animals↗