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A Tauber

Publications and source records attributed to A Tauber.

6 recordsLinked to original sources
PubMed2000

Sonolysis of aqueous 4-nitrophenol at low and high pH.

The sonolysis of 4-nitrophenol in argon-saturated aqueous solution has been studied at 321 kHz. In order to evaluate separately the effect of OH radicals that are formed in the cavitational bubble and part of which react in the aqueous phase with this substrate, radiolytic studies in N2O-saturated solutions were carried out for comparison. A detailed product study of the sonolysis of 4-nitrophenol solutions shows that at pH 10, where 4-nitrophenol is deprotonated (pKa = 7.1), its sonolytic degradation is fully accounted for by OH-radical-induced reactions in the aqueous phase. At this pH, the sonolytic yield of H2O2 resulting from OH radical recombination in the solution, measured as a function of the 4-nitrophenol concentration, is reduced in line with the scavenging capacity of the 4-nitrophenolate. In contrast, at pH 4 the formation of H2O2 is already fully suppressed when the solution is 7 x 10(-4) mol dm-3 in 4-nitrophenol, and oxidative-pyrolytic degradation predominates, as exemplified by the large yields of CO and CO2 which are accompanied by a large H2 yield. The basis of this difference in behavior is a hydrophobic enrichment of 4-nitrophenol (which is undissociated at pH 4) at the interface of the cavitational bubble by a factor of about 80. The pH dependence of the yields of the pyrolytic products reflects the hydrolytic equilibrium concentration of 4-nitrophenol. The paper also demonstrates that the complexity of this sonochemical system precludes its use a gauge to determine the temperature in the interior of the cavitational bubble.

Journal Article↗
PubMed1998

OH-radical formation by ultrasound in aqueous solution--Part II: Terephthalate and Fricke dosimetry and the influence of various conditions on the sonolytic yield.

Terephthalate and Fricke dosimetry have been carried out to determine the sonolytic energy yields of the OH free radical and of its recombination product H2O2 in aqueous solutions under various operating conditions (nature of operating gas, power, frequency, temperature). For example, in the sonolysis of Ar-saturated terephthalate solutions at room temperature, a frequency of 321 kHz, and a power of 170 W kg-1, the total yield [G(.OH) + 2 G(H2O2)], equals 16 x 10(-10) mol J-1. This represents the total of .OH that reach the liquid phase from gas phase of the cavitating bubble. The higher the solute concentration, the lower the H2O2 production as more of the OH free radicals are scavenged, in competition with their recombination. Fricke dosimetry, in the absence and presence of Cu2+ ions, shows that the yield of H atom reaching the liquid phase is much lower, with G(H.) of the order of 3 x 10(-10) mol J-1. These sonolytic yields are smaller in solutions that are at the point of gas saturation, and increase to an optimum as the initial sonication-induced degassing and effervescence subsides. The probing of the sonic field has shown that the rate of sonolytic free-radical formation may vary across the sonicated volume depending on frequency and power input.

Journal Article↗
PubMed1983

The use of computerized tomography scanning to localize the impalpable testis.

To determine the usefulness of computerized tomography scanning in the preoperative localization of the impalpable undescended testis 5 patients with 8 impalpable testes were studied. In 2 patients the scan correctly outlined 3 impalpable testes inside the internal inguinal ring, in 2 patients the scan correctly localized 4 impalpable testes at or just inside the external inguinal ring and in 1 patient the scan failed to demonstrate a testis, a finding corroborated at an operation. These results suggest that computerized tomography scanning appears to be an effective, simple and less hazardous method to localize impalpable undescended testes than other currently available techniques.

Adolescent↗
PubMed1979

[Animal experimental studies on partial kidney function after temporary tourniquet ischemia with and without blood substitute therapy].

70 rats were subjected to tourniquet ischemia of a hind limb for a period of two and three hours. 12 rats served as controls. After release of the 3 hours tourniquets 20 rats were treated either with Ringer's solution or with hydroxyethyl starch. Kidney function and morphology, systolic blood pressure, hematocrit, serum electrolytes, creatinine and urea were studied as different times of recirculation. 1. Reduction in renal function was only observed after releasing the tourniquets. 2. The extent of reduction in renal function depended on the time of ischemia and time of recirculation. 3 hours of tourniquet with two hours of recirculation led to the largest extent of reduction in renal function and renal parenchymal lesions. 3. If the infusion of HES was applied at the beginning of recirculation, reduction in renal function was prevented, as well as parenchymal lesions. Ringer's infusion, however, did not improve kidney function to a normal range.

Animals↗
PubMed1979

[Effects of dopamine-droperidol interaction on renal function in rats (author's transl)].

The influence of dopamine and droperidol on the glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) was examined in twelve groups (N = 8) of male wistar rats using the double isotope method with a partially-shielded whole-body counter according to Oberhausen. No alterations of GFR and ERPF could be elicited in normovolaemic rats given dopamine 2--4 micrograns/kg/min (i.v.) alone or in combination with droperidol 0.3 mg/kg. The administration of 10 micrograms/kg/min dopamine alone was followed by a significant (p less than or equal to 0.05) reduction of the ERPF, this effect being abolished by the concomitant use of both drugs. In tourniquet shock dopamine administration or the combined use of dopamine and droperidol produced a significant rise in arterial blood pressure and the renal functions described above. The results in the present study indicate that dopamine infusions will be effective in the presence of froperidol.

Animals↗