Morphology assessment of chemically modified cryostructured poly(vinyl alcohol) hydrogel

The morphology of hydrogels based on poly(vinyl alcohol) (PVA) in their frozen hydrated state, modified with biologically active di- and multifunctional molecules was studied by scanning electron microscopy (SEM) with cryo-attachment. The porosity of samples was found to be more regular and ordered in the case of samples containing difunctional, and especially multifunctional carboxylic acids as compared to the neat PVA hydrogel. The morphology is dependent not only from the hydrogel composition but also the number of freezing-thawing cycles. Resulted highly porous and oriented structure has significant influence on materials properties, such as compressive stress and crosslinking density.     

Synthesis and antibacterial activity of 2,3-dehydroofloxacin

The 2,3-dehydro analog 2 of the potent quinolone antibacterial agent ofloxacin ( 1 ) was synthesized by an efficient six step route beginning with ethyl 2,3,4,5-tetrafluorobenzoylacetate. Formation of the oxazine ring of 2 was accomplished by ozonolysis of 1-(1-buten-3-yl)quinolone 5 to the corresponding aldehyde, which cyclized upon treatment with base via intramolecular displacement of the C-8 fluorine to afford tricyclic ester 6 . The antibacterial activities of 2,3-dehydroofloxacin ( 2 ) and ofloxacin ( 1 ) are compared.     

Synthesis of trans-10-hydroxydec-2-enoic acid and related compounds

Syntheses of the two stereoisomeric 10-hydroxydec-2-enoic acids are described. The trans-isomer is identical with the main fatty acid isolated from royal jelly of honeybees.

Some compounds closely related to this trans-acid have also been prepared.

A convenient process for the preparation of 10-acetoxy-decanoic acid from castor oil has been developed.     

A novel humidity sensor using yb-doped SrCeO3 ionic conductor with a au-pd filter

A novel humidity sensor operating at T<580K using Yb-doped SrCeO₃ ionic conductor with a Au-Pd chemical filter has been developed. In this unique design, both the electrodes are exposed to the same test gas and therefore do not require separation of working and reference compartments. A thin layer of impervious Au-Pd alloy on one surface of the perovskite electrolyte allows selective access to oxygen gas, while the other surface coated with porous Pt is exposed to both H₂O and oxygen. Sensor emfs are found to be directly proportional to log pH₂O and independent of pO₂. The design aspects of the sensor, the experimental set-up, some typical results and a postulated mechanism of sensor operation are described in this paper. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996     

The formation of 3(or 5)-methylcyclopent-2-en-2-ol-1-one from acetone

The original observation that 3(or 5)-methylcyclopent-2-en-2-ol-1-one (I) was formed (in low yield) by the treatment of glycidaldehyde with acetone in the presence of aqueous alkali, and speculations concerning the reaction mechanism, led to the realization that the reaction could also be carried out with glyceraldehyde. This suggested an explanation for the previously known formation of I by drastic alkali-treatment of carbohydrates.     

Use of sodium beta alumina in novel processes for the production of metals

Sodium metal is an excellent reductant and can be used to reduce most metallic chlorides and many oxides. However, sodium is relatively expensive and is hazardous to store so that it is only used to reduce titanium tetrachloride to titanium. In-situ electrolytic preparation of sodium from sodium chloride in a reactor is difficult due to the evolution of chlorine, another hazardous substance. A novel cell is described where the sodium salt is separated from the salt to be reduced by a sodium beta alumina membrane. The anode is in the sodium salt and the cathode is in the metallic salt and, on the application of current, it has been found that the metal ions are reduced to the metal and the anion in the sodium salt is oxidised. By using sodium hydroxide or sodium carbonate as the sodium salt, the anodic products are oxygen and water vapour or oxygen and carbon dioxide. Examples are given of electrolytic cells incorporating beta alumina membranes for the production of magnesium and zirconium from the chlorides where the metal is produced and the anodic gases are not toxic. Overall these cells are very efficient as the anodic and cathodic products are separated by the beta alumina membrane and compared with existing cells some of the electrical energy requirement is replaced by chemical energy. The environmental benefits of these cells are very attractive for the production of reactive metals on a small scale. Paper presented at the 4th Euroconference on Solid State Ionics, Connemara, Galway, Ireland, Sept. 13–19, 1997