Field-cycling NMR realaxation spectroscopy of poly(di-n-alkylsiloxanes in solid, mesomorphic, and isotropic liquid phases

The frequency dependence of the proton spin-lattice relaxation times T1 and T1., in the laboratory and rotating frames, respectively, is reported for solid and liquid phases of poly(diethylsiloxane) (PDES) and in melts of poly(dimethylsiloxane) (PDMS). The total frequency range is 5 X 102 -3 X 108 Hz and is mainly covered by field-cycling NMR relaxation spectroscopy. The relaxation behavior of PDES in the liquid but ordered mesophase is compared to that of isotropic melts of PDES and PDMS and also to that of nematic main-chain liquid-crystal polymers. The frequency dependences of PDES and PDMS liquids can be represented at low and high frequencies by power laws, section by section. The relaxation behavior in the isotropic melts is entirely equivalent to that previously reported for other polymer species. In the PDES mesophase, the exponents of the power laws are significantly larger and the crossover frequency between the two regimes is reduced. The dynamics in this phase are discussed with respect to the influence of chain modes and order director fluctuations. The main conclusion is, on the whole, that data of the liquid phases are determined by chain modes rather than by local segment fluctuations. The chain dynamics in the PDES mesophase resemble the chain modes in isotropic melts modified for a microstructure with reduced randomness, whereas the influence of order director fluctuations can neither be confirmed nor ruled out

Investigation of the olive mill solid wastes pellets combustion in a counter-current fixed bed reactor

Combustion tests and gaseous emissions of olive mill solid wastes pellets (olive pomace (OP), and olive pits (OPi)) were carried out in an updraft counter-current fixed bed reactor. Along the combustion chamber axis and under a constant primary air flow rate, the bed temperatures and the mass loss rate were measured as functions of time. Moreover, the gas mixture components such as O2, organic carbon (Corg), CO, CO2, H2O, H2, SO2, and NOx (NO + NO2) were analyzed and measured. The reaction front positions were determined as well as the ignition rate and the reaction front velocity. We have found that the exhaust gases are emitted in acceptable concentrations compared to the combustion of standard wood pellets reported in the literature (EN 303-5). It is shown that the bed temperature increased from the ambient value to a maximum value ranging from 750 to 1000 °C as previously reported in the literature. The results demonstrate the promise of using olive mill solid waste pellets as an alternative biofuel for heat and/or electricity production

Investigating the potential to retrieve cloud droplet number concentration from ship-based measurements of spectral solar radiance during EUREC4A

Ship-based cloud remote sensing observations made onboard R/V Meteor during the ElUcidating the RolE of Cloud-Circulation Coupling in ClimAte, EUREC4A, campaign are presented and used to calculate cloud droplet number concentrations. The calculation is based on cloud liquid water path LWP and droplet effective radius reff retrieved from spectral measurements of transmitted solar radiance. It is shown that measurement uncertainties and retrieval assumptions impact the accuracy of the results. A case study indicates that the retrieval of LWP and reff is most affected by 3D-radiative effects in case of shallow cumulus and drizzle, which violates the adiabatic theory and plan-parallel geometry on which the radiative transfer simulations of the retrieval are based. Depending on the cloud thickness, the retrieval of reff might suffers from ambiguity. These retrieval uncertainties and their implications on the estimated cloud droplet number concentration are investigated by a sensitivity study. The analysis showed that most of the uncertainty is introduced by reff, whereas LWP contributes significantly to the uncertainty only for thin clouds. Therefore, it is concluded that only selected cloud cases, which do not violate the retrieval assumption, such as stratiform cloud layers, are suited to apply the retrieval approach in further studies.Fernerkundungsmessungen von Wolken auf dem Forschungsschiff R/V Meteor während der ElUcidating the RolE of Cloud-Circulation Coupling in ClimAte, EUREC4A, Kampagnewerden vorgestellt und zur Berechnung der Tröpfchenanzahlkonzentration verwendet. Die Berechnung basiert auf Messungen des Flüssigwasserpfads LWP und dem effektiven Tröpfchenradius reff, welche aus spektralen Messungen der transmittierten solaren Strahldichte abgeleitet wurden. Es wird gezeigt, dass Messunsicherheiten und Annahmen bei der Ableitung der Wolkeneigenschaften die Genauigkeit der Ergebnisse beeinflussen. Eine Fallstudie zeigt, dass die Ableitung von LWP und reff am stärksten durch 3-dimensionale Strahlungseffekte von flachen Cumuli und Nieselregen beeinflusst wird. Beides wiederspricht den Idealisierungen von adiabatischen Wolken und einer planparallelen Geometrie, auf denen die Strahlungstransfersimulationen des Verfahrens beruhen. Abhängig von der Wolkendicke kann die Ableitung von reff zusätzlich durch Mehrdeutigkeiten beeinflusst sein

Управление процессом контактной точечной микросварки циркониевых сплавов

При контактной точечной сварке тонкостенных деталей стабильность качества соединений зависит от характера выделения тепла, который определяется особенностями изменением общего сопротивления металла между электродами. В настоящей работе проведены экспериментальные исследования по определению влияния алгоритма изменения тока в сварочной цепи на этапе подогрева, а также усилия сжатия и геометрии рабочей поверхности электродов, на величину общего сопротивления металла между электродами. Для этой цели были использованы тонкостенные детали в одном случае из циркониевого сплава Э110 (толщиной 0,25+0,25 мм), а в другом – из нержавеющей стали 12Х18Н10Т (толщиной 0,3+0,3 мм).Quality of resistance spot welded joints depends on heat generation and, in turn, a current profile, dynamic resistance change and its initial value. In the present work, the impact of electrode force and dome radius of hemispherical electrodes on initial resistance between electrodes was investigated. Two combinations of work-pieces of zirconium alloy thickness of 0.25+0.25 mm and austenitic stainless steel thickness of 0.3+0.3 mm were used

Starve to Sustain - An Ancient Syrian Landrace of Sorghum as Tool for Phosphorous Bio-Economy?

Phosphorus (P) is an essential macronutrient, playing a role in developmental and metabolic processes in plants. To understand the local and systemic responses of sorghum to inorganic phosphorus (Pi) starvation and the potential of straw and ash for reutilisation in agriculture, we compared two grain (Razinieh) and sweet (Della) sorghum varieties with respect to their morpho-physiological and molecular responses. We found that Pi starvation increased the elongation of primary roots, the formation of lateral roots, and the accumulation of anthocyanin. In Razinieh, lateral roots were promoted to a higher extent, correlated with a higher expression of SbPht1 phosphate transporters. Infrared spectra of straw from mature plants raised to maturity showed two prominent bands at 1371 and 2337 cm−1, which could be assigned to P-H(H2) stretching vibration in phosphine acid and phosphinothious acid, and their derivates, whose abundance correlated with phosphate uptake of the source plant and genotype (with a higher intensity in Razinieh). The ash generated from these straws stimulated the shoot elongation and root development of the rice seedlings, especially for the material derived from Razinieh raised under Pi starvation. In conclusion, sorghum growing on marginal lands has potential as a bio-economy alternative for mineral phosphorus recycling