Formation of cyclic structures in the cationic ring-opening polymerization of 1,3-dioxolane

The cationic ring-opening polymerization of acetals is prone to cyclization of the polymer chains. This is also the case for the polymerization of 1,3-dioxolane. Literature states that this cyclization can be reduced by applying the Active Monomer mechanism, at least if no competition with the Active Chain End mechanism occurs. In this work, a detailed characterization of the different distributions resulting from the cationic ring-opening polymerization of 1,3-dioxolane via the Active Monomer mechanism is made by a combination of gel permeation chromatography, ¹H NMR, and for the first time by matrix assisted laser desorption/ionization time of flight mass spectrometry. The influence of monomer addition speed, catalyst to initiator ratio and solvent were studied on both kinetics and composition of the product. Furthermore, it was found that increasing the conversion and monomer to initiator ratios leads to an increased amount of cyclic structures and to broader distributions, in correspondence with the Jacobson–Stockmayer theory. Furthermore, ion trapping experiments using ³¹P NMR provide insights into the actual reaction mechanism. Finally, purification of the products after the reactions led to a reduction of the cyclic fraction.

Elucidating the mechanism of the cationic ring-opening polymerization of dioxolane using gel permeation chromatography, matrix assisted laser desorption/ionization time of flight mass spectrometry and ³¹P NMR.     

The effect of aminophylline on renal colic: a randomized double blind controlled trial

OBJECTIVE: To evaluate the efficacy of aminophylline infusion as a painkiller compared with placebo in patients with acute renal colic. PATIENTS AND METHODS: From March to August 2005, 141 patients with clinical renal colic, who were under 60 years of age, had no history of heart or hepatic failure, asthma, theophylline or beta blocker use, reaction to methylxantines, pregnancy or breast feeding, and were not prescribed spasmolytic or analgesics, entered our study. They were randomly assigned to receive either 375 mg of aminophylline or placebo infusion under double blind conditions. Pain intensity was recorded using a visual analog scale (VAS), before drug administration and 30 and 60 minutes afterwards. The drug effectiveness was defined as > or =40% decrease in pain intensity 60 minutes after the onset of infusion, without exacerbation during the following 4 hours. RESULTS: Seventy patients received aminophylline; it was effective in 45 (64%; 95% confidence interval 52-75%). Alternatively, placebo was effective in 12 of 71 control patients (17%; 95% confidence interval 9-28%); (P < 0.001). Thirty and 60 minutes after administration, aminophylline reduced pain by 24% and 39% respectively, as compared with 6% and 8% pain reduction in the placebo group. CONCLUSION: This prospective study provides remarkable information about the efficacy of aminophylline on pain relief and decreasing narcotic usage in symptomatic urinary calculi. It is safe, inexpensive, with minute side effects and can be considered a good alternative or additive to narcotic analgesics in the management of renal colic.     

Selenium Deficiency After Bariatric Surgery,Incidence and Symptoms: a Systematic Review and Meta-Analysis

Obesity Surgery - This study review the prevalence of selenium deficiency after bariatric surgery, incidence, and symptoms.&nbsp;A systematic literature search and meta-analysis was performed...     

Atherogenic consequence of antiepileptic drugs: a study of intima-media thickness

We intended to evaluate the carotid intima-media thickness (CA-IMT) as a surrogate factor for atherogenesis in epileptic patients on enzyme inducer (EI) antiepileptic drugs (AEDs) or valproate (VA). The study included 71 patients with epilepsy (37 females) aged 27.7 ± 8.1 and 71 age- and sex-matched non-epileptic subjects. Patients with history of at least 2 years antiepileptic treatment were enrolled. Subjects with known history of cardiovascular risk factors were not included. Thirty-eight patients (21 females) were treated with EI medications and 33 (16 females) with VA. CA-IMTs were measured by a single sonography system in all participants. CA-IMT values were compared between patients with epilepsy and the controls and within the patients with epilepsy on VA or EI medications. Duration of epilepsy was 10.1 ± 7.1 years. Patients were treated with their current AED for 6.9 ± 4.8 years. The CA-IMT of patients with epilepsy was higher than non-epileptic control subjects on either left (0.502 ± 0.079 vs. 0.470 ± 0.073 mm; p = 0.012) or right side (0.524 ± 0.078 vs. 0.458 ± 0.068 mm; p < 0.001). Patients on VA were younger than those receiving EI medications (25.8 ± 7.1 vs. 29.4 ± 8.7 years). Age adjusted CA-IMT values of patients on VA did not differ from the values of patients receiving EI medications. Duration of drug administration did not correlate with CA-IMT values. Patients with epilepsy on AEDs are at higher risk for atherogenesis. In the population of this study the increased risk of atherogenesis was not attributable to the administered AED or duration of treatment.     

Cytotoxic and photocatalytic studies of hexagonal boron nitride nanotubes: a potential candidate for wastewater and air treatment

Boron nitride (BN) nanomaterials are rapidly being investigated for potential applications in biomedical sciences due to their exceptional physico-chemical characteristics. However, their safe use demands a thorough understanding of their possible environmental and toxicological effects. The cytotoxicity of boron nitride nanotubes (BNNTs) was explored to see if they could be used in living cell imaging. It was observed that the cytotoxicity of BNNTs is higher in cancer cells (65 and 80%) than in normal cell lines (40 and 60%) for 24 h and 48 h respectively. The influence of multiple experimental parameters such as pH, time, amount of catalyst, and initial dye concentration on percentage degradation efficiency was also examined for both catalyst and dye. The degradation effectiveness decreases (92 to 25%) as the original concentration of dye increases (5–50 ppm) due to a decrease in the availability of adsorption sites. Similarly, the degradation efficiency improves up to 90% as the concentration of catalyst increases (0.01–0.05 g) due to an increase in the adsorption sites. The influence of pH was also investigated, the highest degradation efficiency for MO dye was observed at pH 4. Our results show that lower concentrations of BNNTs can be employed in biomedical applications. Dye degradation properties of BNNTs suggest that it can be a potential candidate as a wastewater and air treatment material.

Photocatalytic degradation studies of methyl orange using BNNTs.