Examination of the swelling of heat protective hydrocolloids by DSC

While the basic fermented (sour) milk products, such as yogurt and kefir can be produced only in live flora version, the post heat-treatment is preferred in their flavored variations to increase the storage time. Casein being in sour coagulum precipitates during heat-treatment; therefore protective colloids surrounding the protein should be used to prevent it. Protective colloids are plant extracts, the most known of them are pectin and amylopectin. Basic requirement of protective colloid effect is the lower swelling temperature of hydrocolloid than the temperature of precipitation of sour coagulum. In this work we have examined the precipitation of sour coagulum as a function of the type of lactic acid bacteria cultures applied during fermentation as well as the swelling of heat protective plant hydrocolloids as a function of the composition (mainly of sugar content) of medium. To investigate the precipitation of fermented coagulum skimmed milk was fermented with mesophilic butter culture, thermophilic yogurt culture as well as with exopolysaccharide (EPS)-producing Prebiolact-2 culture. Precipitation was indicated in the increase of great extent of viscosity. Amylopectin was dispersed into aqueous solution of pH 4.5, the saccharose concentration of which was changed during the investigation of the swelling of heat protective hydrocolloids. A definite exothermic peak was assigned to the swelling of hydrocolloids during the DSC experiments. We could conclude that the precipitation temperature was increasing in the mesophilic-thermophilic-EPS producing microbes line, i.e. the heat stability and swelling temperature of hydrocolloids depend on the saccharose content of aqueous medium and they increase with rising the concentration of saccharose.     

History of Analytical Chemistry in Estonia (1800–1950)

The history of analytical chemistry, started in 1802, can be divided into different periods: 1802–1892 the Baltic German period in Universitas Dorpatensis, 1892–1917 the period of russification in the University, 1918–1939 the independent Estonian University of Tartu and opening of the chair of inorganic and analytical chemistry at Tallinn Technical University, 1940–1944 loss of independence and years of war, 1945–1991 the years in the Soviet Union, 1991-up to now the re-establishment of independence. The first chemical laboratory was founded at Universitas Dorpatensis by Prof. Ph. Arzt in 1802. The first practice in analytical chemistry was opened in 1847 by Prof. C. Göbel. The chair of chemistry was separated from pharmacy in 1850. A separate chair of analytical chemistry was opened at Tartu University in 1947.     

Second-order nonlinear optical properties of the Ag(111)/electrolyte interface in the presence of self-assembled monolayers containing conjugated pi systems. I. Alpha-functionalized terthiophene films on Ag(111)

The nonlinear optical properties of self-assembled monolayers obtained from bonding two different alpha-functionalized terthiophenes (alpha-T3) to (111) silver electrode surfaces have been investigated using second harmonic generation (SHG). The two (alpha-T3) compounds used were functionalized with alkane chains of different lengths (C8 and C4), and each was terminated with a thiol anchoring group. A nitrile group was attached to the terminal thiophene ring of the (alpha-T3) compound with the C4 chain. The orientation of the polarization of the incident beam was changed systematically and gradually between "p" and "s" orientation and the SH signal (isotropic and anisotropic contributions) analyzed in both directions ("P" and "S"). The symmetry of the system was reduced by the presence of the adlayers from C3v to C3. The dependence on the applied potential and the incident wavelength has also been studied. The relative magnitudes and phases of the various second-order tensor elements have been estimated and compared with the values for a bare surface. A resonance process in the (alpha-T3) pi moiety has been investigated, and from this, the effective "band-gap" energies of the organic semiconductor SAMs (i.e., the energy difference between the pi-pi bands) have been estimated.     

Reference electrodes based on conducting polymers

Several attempts to produce conducting polymer based all-solid-state reference electrodes are presented. Open circuit potential of conducting polymers is redox sensitive and Donan equilibrium dependent. Therefore, more sophisticated constructions are necessary. Most promising were bilayers composed of conducting polymers with different ion-exchanger properties.     

Nucleocyclitols. Synthesis of substituted purinyl-muco-inositol derivatives

Several carbocyclic nucleoside analogs possessing a 6-substituted purine linked to a mesylated muco-inositol were synthesized. The coupling of triethylamine-activated 6-chloropurine with 2,3-anhydro-l,5,6-tri-O-(methanesulfonyl)-epi-inositol gave a 6-chloro purinyl muco-inositol amenable to further synthetic transformations in the heterocyclic moiety by substitution of the chlorine atom by nitrogen nucleophiles such as methylamino, diethylamino, benzylamino, hydrazino, morpholino, hydroxylamino, piperidino, and glycyl groups.     

Über den Einfluß der Polymorphie auf die Löslichkeit von arzneimitteln

Zusammenfassung Die Möglichkeit einer Verbesserung der Wasserlöslichkeit sowie der Löslichkeit in anderen Lösungsmitteln von Medikamenten durch Verwendung metastabiler (instabiler) Modifikationen wurde aufgezeigt. Bei Sulfathiazol und Tromexan liegt die relative Zunahme der Wasser-Löslichkeit der metastabilen Modifikation gegenüber der stabilen Modifikation in Abhängigkeit vom p_H zwischen 72 und 80%, bei Sulfuno ist der Effekt geringer, er liegt zwischen 8,4 und 15,2%. DiepK _s - Werte der beiden Modifikationen sind sowohl für Sulfathiazol als auch für Sulfuno innerhalb der Fehlergrenze identisch. Für Sulfathiazol wurde die Löslichkeitskurve der beiden Modifikationen in Wasser und Isopropanol bestimmt.

---

Summary The possibility was shown of improving the water-solubility as well as the solubility in other solvents of medicaments through employment of metastable (unstable) modifications. In the case of sulfathiazole and also of tromexan the relative increase of the water-solubility of the metastable modification as compared with the stable modification is between 72 and 80% depending on the p_H the effect is less for sulfuno where it lies between 8.4 and 15.2%. ThepK _s values of the two modifications are identical both for sulfathiazole as for sulfuno, within the limits of error. The solubility curve of sulfathiazole was determined for both modifications in water and in isopropanol.

---

Résumé On présente la possibilité d'améliorer la solubilité de médicaments dans l'eau ainsi que dans d'autres solvants, par emploi de modifications métastables (instables). Dans le cas du sulfathiazole et du «Tromexan», l'augmentation relative de la solubilité dans l'eau de la modification métastable par rapport à celle qui est stable est fonction du p_H entre 72 et 80%, pour le «Sulfuno» l'effet est moindre, entre 8,4 et 15,2%. Les valeurs dupK _s des deux modifications sont identiques tant pour le sulfathiazole que pour le «Sulfuno» dans les limites d'erreurs. La courbe de solubilité des deux modifications a été déterminée pour le sulfathiazole dans l'eau et dans l'isopropanol.

     

Das Spermin-Alkaloid Chaenorpin

The Spermine Alkaloid Chaenorpine Chaenorpine ( 1 ) was isolated from Chaenorhinum minus (Scrophulariaceae). Its structure elucidation was achieved on the basis of chemical degradation and spectroscopic measurements in comparison to the known alkaloid chaenorhine ( 2 ). Structure 1 displays the absolute configuration.     

Synthèses de produits organofluorés VI Solvolyse de chlorofluorocyclopropanes

Fluoro-organic Syntheses VI: The Solvolysis of Chlorofluoro-cyclopropanes 2-Fluoro-allylic carbocations, generated from 1-chloro-1-fluoro-cyclopropanes or 2-fluoro-allyl p-toluene-sulfonates in water or acetic acid, undergo either proton loss or addition of hydroxyl or acetoxyl. In the latter case, an alkyl-substituted 2-fluoro-allyl ion leads predominantly to the more branched product (e.g. 3-fluoro-2-methyl-3-buten-2-ol) which may be converted into the less branched one (e.g. 2-fluoro-3-methyl-2-buten-2-ol) through reversible reactions.     

Notiz zur Darstellung von 4-Hydroxy-6-methyl-5,6-dihydro-2H-pyran-2-on

Meldrum's acid (2) is acylated by diketen affording the acylMeldrum's acid3. In aqueous bicarbonate its 3-oxogroup is selectively reduced by sodium tetrahydroborate giving the alcohol4, which readily undergoes cyclization in refluxing dioxane leading to the title pyrone7. Under identical conditions3 produces the pyrone6 with the pyrone carboxylic acid5 as intermediate.

     

Amperometric determination of hydrogen peroxide in pickling baths for copper and copper alloys by flow injection analysis

The hydrogen peroxide is oxidized at + 1.5 V vs. SCE at a glassy carbon electrode of the wall-jet type. The samples are diluted about 100 times in a dispersion coil before entering the amperometric detector. The calibration curve is linear from 10^?4 to 1 M H₂O₂, when 5-μl samples are used. With 50-μl samples the detection limit decreases to 10^?6 M H₂O₂. Neither metal ions (Cu²⁺, Zn²⁺, Ni²⁺, Al³⁺) up to 0.5 M nor changes in the sulfuric acid concentration of the samples between 0.1 and 1 M interfere with the hydrogen peroxide determination. About 75 samples can be analyzed per hour.