Dominant formation of disulfidic linkages in the sulfur cross-linking reaction of isoprene rubber by using zinc stearate as an activator

A linear combination fitting in sulfur K-edge X-ray absorption near edge structure (S-XANES) measurements reveals each fraction of monosulfidic, disulfidic and polysulfidic linkages in solvent extracted sulfur cross-linked isoprene rubbers. The sulfidic linkage of a disulfidic type is found for the first time to be dominant when zinc stearate and N-(1,3-benzothiazol-2-ylsulfanyl)cyclohexanamine are used as the activator and accelerator, respectively, for the sulfur cross-linking reaction at 140 °C. The presence of the bridging bidentate zinc/stearate complex as an intermediate for the sulfur cross-linking reaction is supposed to induce the generation of abundant disulfidic linkages in the rubber networks. This unexpected observation is of use for the material design of high performance rubber products with anti-aging and thermal stabilities. S-XANES is a powerful tool that was used to reveal the characteristics of the sulfur cross-linking of rubber. These results will contribute to the development of rubber science and technology.

The bridging bidentate zinc/stearate complex, an intermediate for the sulfur cross-linking reaction, supposedly induces an abundance of disulfidic linkages in the rubber network.     

Effect of fatty acids on the accelerated sulfur vulcanization of rubber by active zinc/carboxylate complexes

The effect of fatty acids with different aliphatic chain lengths on the accelerated vulcanization reaction of isoprene rubber was investigated through the generation of new intermediates composed of dinuclear bridging bidentate zinc/carboxylate complexes. Using the combination of in situ time-resolved Fourier-transform infrared spectroscopy and in situ time-resolved zinc K-edge X-ray absorption fine structure spectroscopy, the essential complex structure of the intermediates formed during the vulcanization reaction of isoprene rubber was determined to be independent of the aliphatic chain length of fatty acids. However, the reactivity of arachidic acid with ZnO was found to be low, which prolonged the induction period and curing time, and slowed down the curing rate in the vulcanization of isoprene rubber. These results help to understand the complicated vulcanization reaction of rubber, especially natural rubber, which inherently contains various fatty acids. The results obtained in this study are important for developing well-designed high-performance natural rubber products in the future.

The effect of fatty acids with different aliphatic chain lengths on the accelerated vulcanization reaction of isoprene rubber was investigated through the generation of new intermediates composed of dinuclear bridging bidentate zinc/carboxylate complexes.     

Recovery of a Disinserted Medial Rectus Muscle after Pterygium Surgery

Purpose: To report a case of recovery of a medial rectus which was accidentally disinserted after surgical treatment of a recurrent pterygium.

Method: Report of a case of inadvertent medial rectus disinsertion after pterygium excision at a secondary care hospital which was referred to a tertiary care hospital in Northern Thailand.

Result: A 40-year-old healthy woman was referred by a general ophthalmologist at a secondary care center to our hospital. She had undergone recurrent pterygium excision with amniotic membrane transplantation on the nasal side of her right eye. Immediately after the last operation, she complained of horizontal binocular diplopia. On the first postoperative day, the patient could not adduct the eye beyond the primary position. Her measurements in primary position were 45 prism diopters of right exotropia on distant and near. The diagnosis of iatrogenic medial rectus disinsertion was made. Three weeks after pterygium excision, revision surgery was performed; the medial rectus was found and reattached to its normal insertion site. On the first postoperative day, the patient referred a small vertical diplopia in the primary position. Orthoptic examination five months post-operatively demonstrated orthotropia and absence of diplopia in primary position, but minimal horizontal diplopia in right gaze.

Conclusions: Accidental rectus muscle disinsertion after pterygium excision surgery is a serious but rare postoperative complication of pterygium surgery. Great care should be taken intraoperatively to avoid this complication. Reattachment of the disinserted medial rectus will produce a satisfactory resolution of the problem.     

Dietary Intake and Milk Micronutrient Levels in Lactating Women with Full and Partial Breastfeeding

Background

Micronutrient intake and status in lactating women may impact micronutrient levels in milk.

Objectives

This study aimed to determine the micronutrient intake and status in lactating women, and their association with micronutrient levels in human milk.

Methods

Lactating women were enrolled at 4–6 months postpartum. A 24h food recall was examined and nutrient intakes were analyzed using INMUCAL software. Human milk samples were collected to analyze calcium, copper, iron, and zinc levels. Plasma zinc and serum ferritin levels were determined.

Results

Thirty-four women participated; 19 were classified as full breastfeeding and 15 as partial breastfeeding. Mean levels of calcium, copper, iron, and zinc in human milk were 243, 0.2, 0.2, and 1.56 mg/L, respectively. The prevalence of zinc deficiency (plasma zinc?<?10.7 µmol/L) was 11.8%. No lactating women had iron deficiency. Nutrient intakes were lower than the recommended amounts in 38%–70% of participants, and were not correlated with corresponding nutrient levels in human milk. Multiple linear regression showed significant association between zinc levels in human milk and plasma for lactating women with full breastfeeding (β?=?0.034, 95% confidence interval [0.003, 0.067], p?=?0.040).

Conclusions

Lactating women were at risk of micronutrient deficiency. There was an association between zinc levels in human milk and plasma of lactating women with full breastfeeding. As the nutritional status of lactating women influences the quality of human milk, we should encourage good nutrient intake for lactating women.

     

Use of flow field-flow fractionation and single particle inductively coupled plasma mass spectrometry for size determination of selenium nanoparticles in a mixture

Various analytical techniques have been used for size analysis of selenium nanoparticles (SeNPs). These include flow field-flow fractionation (FlFFF), single particle inductively coupled plasma mass spectrometry (SP-ICP-MS), dynamic light scattering (DLS) and transmission electron microscopy (TEM). For hydrodynamic diameter estimation, the FlFFF technique was used and the results were compared with those analyzed by DLS. For core diameter estimation, the results obtained from SP-ICP-MS were compared with those from TEM. Two types of FlFFF channel were employed, i.e., symmetrical FlFFF (Sy-FlFFF) and asymmetrical FlFFF (Asy-FlFFF). Considering the use of FlFFF, optimization was performed on a Sy-FlFFF channel to select the most appropriate carrier liquid and membrane in order to minimize problems due to particle membrane interaction. The use of FL-70 and 10 kDa RC provided an acceptable compromise peak quality and size accuracy for all samples of SeNPs which were coated by proteins (positively charged SeNPs) and sodium dodecyl sulfate (negatively charged SeNPs). FlFFF always yielded the lower estimate of the hydrodynamic size than DLS as a reference method. The results obtained by SP-ICP-MS were consistent with the TEM method for the core diameter estimation. The results from FlFFF and the DLS reference method were significantly different as confirmed by paired t-test analysis, while the results provided by SP-ICP-MS and the TEM reference method were not significantly different. Furthermore, consecutive size analysis by SP-ICP-MS for the fractions collected from FlFFF was proposed for sizing of SeNP mixtures. The combined technique helps to improve the size analysis in the complex samples and shows more advantages than using only SP-ICP-MS.

Various analytical techniques have been used for size analysis of selenium nanoparticles (SeNPs).     

Case Report: Bilateral Granulomatous Anterior Uveitis in HIV-patient with Disseminated Talaromycosis (penicilliosis) Marneffei Infection

ABSTRACT

We report on a 22-years-old Thai male patient with congenital HIV infection. Due to his non-adherence to antiretroviral treatment he developed disseminated Talaromyces marneffei infection and was treated with intravenous amphotericin B. Despite this treatment, he presented with bilateral granulomatous anterior uveitis. Uveitis improved only after intracameral injection of amphotericin B.     

Case Report: Recurrences of Visceral Leishmaniasis Caused by Leishmania siamensis after Treatment with Amphotericin B in a Seronegative Child

We report the first case of visceral leishmaniasis caused by Leishmania siamensis in a seronegative child. She was treated with amphotericin B at 1 mg/kg/day for 3 weeks; however, recurrences occurred twice. The patient was cured after the administration of amphotericin B for 5 weeks and monthly prophylaxis for 6 months.