Characterization of carbon fibrous material from platanus achenes as platinum catalysts support

Carbon materials with developed porosity are usually used as supports for platinum catalysts. Physico-chemical characteristics of the support influence the properties of platinum deposited and its catalytic activity. In our studies, we deposited platinum on carbon fibrous like materials obtained from platanus seeds - achenes. The precursor was chemically activated with different reagents: NaOH, pyrogallol, and H2O2, before the carbonization process. Platinum was deposited on all substrates to study the influence of the substrate properties on the activity of the catalyst. Carbon materials were characterized by nitrogen adsorption/desorption isotherms measurements, X-ray diffraction, and scanning electron microscopy. It was noticed that the adsorption characteristics of carbon support affected the structure of platinum deposits and thus their activity

High-pressure cryogelation of nanosilica and surface properties of cryosilicas

Silica cryogels (cryosilicas) in a powder state were synthesized with different concentrations of fumed silica A-300 (CA-300 = 5-20 wt.%), sonicated in aqueous suspension, then frozen at -14 oC at different pressures in a high-pressure stainless steel reactor (a freezing bomb), and dried in air at room temperature. To analyze the effects of low temperature and high pressure, samples were also prepared at -14 oC or room temperature and standard pressure. The structural and adsorption properties of the powder materials were studied using nitrogen adsorption, high-resolution transmission electron microscopy, infrared spectroscopy, thermogravimetry, low-temperature 1H NMR spectroscopy and thermally stimulated depolarization current. The structural, textural, adsorption and relaxation characteristics of high-pressure cryogel hydrogels and related dried powders are strongly dependent on the silica content in aqueous suspensions frozen at 1, 450 or 1000 atmospheres and then dried. The largest changes are found with CA-300 = 20 wt.% which are analyzed with respect to the interfacial behavior of nonpolar, weakly polar and polar adsorbates using low temperature 1H NMR spectroscopy

Вплив механоактивації сумішей нанопорошків SiO2/Al2O3 на їх морфологію та енергетичний розподіл валентних електронів

The analysis of morphological characteristics of nanoscale structures x-Al2O3 + y-SiO2 (x = 0,2; 0,3; 0,75; y = 0,8; 0,7; 0,25) before and after mechanical activation is hold. During the investigation of spot chemical composition is was revealed that as the consequence of mechanical activation in the structure of composites agglomerates are formed where nanoparticles of silicon and aluminum oxides are present simultaneously. The changes of the structure of morphology are confirmed by the redistribution of valence Ор-, Sisd- та Alsd electrons mixtures as a result of mechanical activation.Проведено аналіз морфологічних характеристик структури нанорозмірних сумішей x-Al2O3+ y-SiO2 (x = 0,2; 0,3; 0,75; y = 0,8; 0,7; 0,25) до і після механоактивації. При дослідженні точкового хімічного складу виявили, що в наслідок механоактивації у структурі композитів утворюються агломерати, де одночасно присутні наночастинки оксидів кремнію та алюмінію. Зміни морфології структури підтверджуються перерозподілом валентних Ор-, Sisd- та Alsd- електронів сумішей в результаті механоактивації

Polyurethane–poly(2-hydroxyethyl methacrylate) semi- IPN–nanooxide composites

Two sets of hybrid polyurethane–poly(2-hydroxyethyl methacrylate) semi-interpenetrating polymer network–nanooxide composites with 0.25 or 3 wt% nanosilica or nanoalumina functionalised with OH, NH2 or CHLCH2 groups were prepared. A combination of atomic force microscopy, infrared spectroscopy, thermally stimulated depolarisation current measurement, differential scanning calorimetry and creep rate spectroscopy analysis of the nanostructure and properties of the composites was performed. The pronounced dynamic heterogeneity and the strong impact of oxide additives, basically suppression of the dynamics and temperature-dependent increasing modulus of elasticity, were observed. The effects correlated with either interfacial interactions (for silica) or the nanostructure (for alumina). A low oxide content strongly affected the matrix due to the formation of an unusual cross-linked, via double covalent hybridisation of three components, structure of the nanocomposites

Individual patient data meta-analysis : Cervical stitch (cerclage) for preventing pregnancy loss in women

BACKGROUND: Cervical cerclage is a surgical procedure involving suturing the cervix with a purse type stitch to keep it closed during pregnancy. This procedure has been used widely in the management of pregnancies considered at high risk of preterm delivery. Several observational studies into the efficacy of cervical cerclage have claimed high rates of successful pregnancy outcome in women with a poor obstetric history attributed to cervical incompetence. However, a recent aggregate data Cochrane review found no such conclusive evidence from seven included randomised studies. Current data suggests that cervical cerclage is likely to benefit women considered to be 'at very high risk' of a second trimester miscarriage due to a cervical factor, however identifying such women remains elusive and many women may be treated unnecessarily. Undertaking an individual patient data (IPD) meta-analysis of the studies will allow us to investigate whether treatment is more effective in particular subgroups. Such an analysis will also provide a more powerful analysis of the predictors of preterm delivery and pregnancy loss, including ultrasound measurement of cervical length, and will allow a more complete analysis of 'time to event' outcomes. METHODS/DESIGN: The analysis will include data from randomised trials comparing the intervention of elective cerclage versus no cerclage or bedrest to prevent miscarriage or pre-term labour. A specific list of data will be requested for each trial, including demographic and obstetric history data. The primary outcomes of interest will be neonatal mortality/morbidity. Attention will also be given to secondary outcomes such as time from randomisation to delivery, preterm delivery before 32 weeks and maternal morbidity. An intention to treat analysis will be performed, with attention paid to assessing clinical and statistical heterogeneity. Multilevel models with patients and trials as the two levels will be explored to investigate treatment effect on various outcomes. Patient-level covariates will be incorporated into the models in an attempt to account for statistical heterogeneity as well as to investigate interactions with treatment effect. DISCUSSION: Predictive models generated from our analysis should lead to more effective counselling of women at risk and a more cost effective use of cerclage

Estimating the mass of a pyrotechnic mixture for burning the launch vehicle nose fairing

It is proposed to carry out burning of the launch vehicle nose fairing after it has completed its mission on the descent trajectory from the moment of separation to an altitude of 5–10 km. Burning is carried out in the Earth atmosphere with additional heating of the faring material due to the reaction of pyrotechnic mixtures. Various pyrotechnic mixtures for use in the nose fairing are discussed

Estimating the mass of a pyrotechnic mixture for burning the launch vehicle nose fairing

It is proposed to carry out burning of the launch vehicle nose fairing after it has completed its mission on the descent trajectory from the moment of separation to an altitude of 5–10 km. Burning is carried out in the Earth atmosphere with additional heating of the faring material due to the reaction of pyrotechnic mixtures. Various pyrotechnic mixtures for use in the nose fairing are discussed

Morphology and Energy Distribution of the Valence Electrons After Mechanochemical Activation SiO2/Al2O3

The analysis of morphological characteristics of nanoscale structures x-Al<sub>2</sub>O<sub>3</sub> + y-SiO<sub>2</sub> (x = 0,2; 0,3; 0,75; y = 0,8; 0,7; 0,25) before and after mechanical activation is hold. During the investigation of spot chemical composition is was revealed that as the consequence of mechanical activation in the structure of composites agglomerates are formed where nanoparticles of silicon and aluminum oxides are present simultaneously. The changes of the structure of morphology are confirmed by the redistribution of valence О р-, Si sd- та Al sd electrons mixtures as a result of mechanical activatio