Coordinative polymerization of p-substituted phenyl glycidyl ethers, 1. Effect of electron-donating groups

A series of p-substituted glycidyl phenyl ethers

1 IUPAC nomenclature: 2,3-epoxypropyl phenyl ether.

with electron donor groups was prepared using a multistep synthetic method. These compounds were polymerized using four of the most common aluminium-based coordinative initiators, (C₂H₅)₃Al/H₂O (the Vandenberg catalyst), (C₂H₅)₃Al/CH₃COCH₂COCH₃/H₂O (the Vandenberg chelate catalyst), [(CH₃)₂CHO&]₂Al? O? Zn? O? Al[OCH(CH₃)₂]₂ (the Teyssié catalyst) and [(CH₃)₂CHO]₃AV/ZnCI₂ (the Price catalyst), all with different Lewis acid character. The influence of the electron-donor group on the characteristics and conversion was studied. Generally speaking, both the Vandenberg and the Teyssié catalysts yield mostly an insoluble polymer fraction, whereas the Price catalyst was shown to be the most stereoselective catalyst. Moreover, the Vandenberg chelate catalyst gave the highest molecular weight, the Price catalyst the lowest. Thermal characteristics of polymers were studied by means of differential thermal analysis to obtain glass transition temperatuures, melting temperatures and fusion enthalpies.     

Polylactones 12. Cationic polymerization of 2,2-dimethyltrimethylene carbonate

The polymerization of 2,2-dimethyltrimethylene carbonate ( 1 ) was initiated with borontrifluoride etherate, trifluoromethanesulfonic acid (triflic acid), methyl triflate and ethyl fluorosulfate. The reaction was studied at 20, 50, 80 and 120°C in 1,2-dichloroethane and nitrobenzene. Methyl triflate and triflic acid turned out to be the most reactive initiators. Yet, due to “black biting” degradation, yields > 80% were never obtained. With BF₃ etherate yields up to 98% and molecular weights (M?_n) up to 5200 g/mol were found. From ¹H NMR and IR spectra it can be deduced that methyl triflate alkylates the exocyclic oxygen (carbonyl group) and the resulting carbenium ion reacts with its counterion by ring-opening of the alkyl-oxygen bond. The oligomers and polymers formed in this way initially possess methyl (or ethyl) carbonate groups at one end and triflate groups at the other end of the chain. Elemental analyses and IR spectra prove that no carbon dioxide is lost in the course of the cationic polymerization. DSC measurements showed that crystallinity and melting points of poly( 1 ) largely depend on the polymerization conditions in contrast to the glass transition temperature.     

Biopsy forceps disinfection technique does not influence Helicobacter pylori culture

Objectives: Culturing Helicobacter pylori ( Hp ) has a low sensitivity rate, and is affected by factors such as the number of biopsies, transport, and culture conditions. Hp detection is also influenced by omeprazole, antibiotics, bismuth salts, or benzocaine use. Disinfection procedures based on glutaraldehyde are highly effective in eliminating any Hp contamination of endoscopic equipment. However, the possibility that some residual glutaraldehyde present in biopsy forceps after decontamination could affect Hp viability has not yet been investigated.
Methods: Antral specimens from 25 patients with active gastric or duodenal ulcer obtained with three forceps (sterilized with ethylene oxide, glutaraldehyde, or glutaraldehyde-phenolate) were streaked on appropriate media, and results of culture evaluated.
Results: Helicobacter pylori was isolated in 17 patients. Positivity of culture was independent of the way the forceps were sterilized, and the number of colonies (mean ± SD) was similar for the three types of forceps (475 ± 312, 533 ± 242, and 550 ± 225 colony-forming units [CFUs] for ethylene oxide, glutaraldehyde, and glutaraldehyde-phenolate, respectively). Moreover, the incubation time since isolation was also similar (6.0 ± 1.3, 5.8 ± 1.2, and 5.7 ± 1.2 days for ethylene oxide, glutaraldehyde, and glutaraldehyde-phenolate disinfected forceps, respectively).
Conclusion: The use of glutaraldehyde to sterilize biopsy forceps is not responsible for the false-negative results of Hp culture.     

New reactive polyethers: preparation and synthetic possibilities

Starting from 4-methoxycarbonylphenyl glycidyl ether and unfunctionalized phenyl glycidyl ether, samples of highly regio- and stereoregular linear homo- and copolymers were synthesized using the ionic coordinative initiator system aluminium isopropoxide/ZnCl₂. The polymers were first transformed into carboxylic acid derivatives and then into highly reactive carboxylic acid chlorides with high yields and conversions. The use of all these synthesized polymers was tested by transforming them into the corresponding 4-nitrobenzyl ester using different synthetic procedures. Finally, the scope of the methodology studied was tested by using it to synthesize a set of new polymers containing different complex groups such as: 18-crown-6, biphenyl-4-carbonitrile, anthraquinone, (1R)-nopol, (-)-inosine and 4-dodecylaniline, which are in general obtained with good yields and conversions.     

Endometrial stromal sarcoma. Is there a place for radiotherapy?

Objectives  

The optimal approach in the management of endometrial stromal sarcoma (ESS) remains unclear. The aim of the present study was to retrospectively report the outcome of patients treated for ESS in our hospital over a 27-year period in order to evaluate the treatment results and the role of radiotherapy.     

MRI prostate contouring is not impaired by the use of a radiotherapy image acquisition set-up. An intra- and inter-observer paired comparative analysis with diagnostic set-up images

PurposeThe use of MRI for radiotherapy planning purposes is growing but image acquisition using radiotherapy set-ups has impaired image quality. Whether differences in image acquisition set-up could modify organ contouring has not been evaluated. Therefore, we aimed to evaluate differences in contouring between paired of image sets that were acquired in the same scanning session using different parameters.Material and methodsTen patients underwent RT treatment planning with MRI co-registration. MRI was carried out using two different set-ups during the same session, MRI radiotherapy set-ups and MRI diagnostic set-ups. Prostates and rectums were retrospectively contoured in both image sets by 5 radiation oncologists and 4 radiologists. Intra-observer analysis was carried out comparing organ volumes, the Dice coefficient and hausdorff distance values between two contouring rounds. Inter-observer analysis was carried out by comparing individual contours to a generated STAPLE consensus contour, which is considered the gold standard reference.ResultsNo significant differences were observed between MRI acquisition set-ups. Significant differences were observed for the dice and hausdorff parameters, comparing individual contours to the STAPLE consensus contour, when analysing diagnostic images between rounds, although raw values were similar.ConclusionProstate and rectum contours did not differ significantly when using diagnostic or radiotherapy MRI acquisition set-ups.