Development of polyethersulfone phase‐inversion membranes for membrane distillation using oleophobic coatings

Highly porous macrovoid‐free polyethersulfone membranes have been prepared using the phase‐inversion process with water as the non‐solvent. These membranes are of great interest for membrane distillation (MD) after application of a hydrophobic/oleophobic coating. The membrane structure was controlled by optimizing the process conditions and dope composition. Counter intuitively, increasing the polymer concentration favors the formation of larger surface pores under similar process conditions. A symmetric membrane is obtained when a sufficient amount of high‐molecular‐weight polyvinylpyrrolidone was added to the dope solution, which appears to play an important role in the structure formation process. The final membrane shows similar performance compared to commercial MD membranes. However, the membranes developed in this study show an oleophobic character, broadening the applications of MD. Moreover, the compressibility of these membranes is severely reduced compared to stretched membranes, which is expected to result in an improved MD performance at full scale. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45516.     

A comparison of cognitive and organizational classification of publications in the social sciences and humanities

Scientometrics - We study the discrepancy between two ways of classifying publications in the social sciences and humanities (SSH): on the basis of the contents of publications and publication...     

Measurement of the Neutron Lifetime by Counting Trapped Protons

We measured the neutron decay lifetime by counting in-beam neutron decay recoil protons trapped in a quasi-Penning trap. The absolute neutron beam fluence was measured by capture in a thin ⁶LiF foil detector with known efficiency. The combination of these measurements gives the neutron lifetime: τ_n = (886.8 ± 1.2 ± 3.2) s, where the first (second) uncertainty is statistical (systematic) in nature. This is the most precise neutron lifetime determination to date using an in-beam method.     

Certification of a new series of gravimetrically prepared synthetic reference materials for n(236U)/n(238U) isotope ratio measurements

A new series of gravimetrically prepared synthetic isotope reference materials, the so-called IRMM-075 series, with n(²³⁶U)/n(²³⁸U) isotope ratios varying from 10^?4 to 10^?9 has been prepared and certified. This series is suited for calibration of n(²³⁶U)/n(²³⁸U) measurements made by various mass spectrometric techniques such as TIMS (Thermal Ionization Mass Spectrometry), ICPMS (Inductively Coupled Plasma Mass Spectrometry), AMS (Accelerator Mass Spectrometry) and RIMS (Resonance Ionization Mass Spectrometry).Natural uranium with low ²³⁶U isotope abundance and highly enriched ²³⁶U were both purified using well proven chemical methodology. The oxides were calcined into U₃O₈ in an oven installed in a glove-box with controlled humidity. Primary solutions of the same concentration were prepared by dissolving the oxides of ²³⁶U and natural U. From the ²³⁶U solution a series of four dilutions was made by weighing. Weighed amounts of the dilutions of ²³⁶U and weighed amounts of natural U were mixed to form a set of n(²³⁶U)/n(²³⁸U) mixtures at a concentration of 1 mg U g^?1.Verification of the mixtures IRMM-075/1–6 was performed by TIMS measurements using Faraday collectors and a secondary electron multiplier in combination with an energy filter for improved abundance sensitivity. The results agreed well with the certified values obtained from the gravimetrical mixing calculations.The uncertainties of the calculated isotopic ratios are significantly lower compared to typical uncertainties from mass spectrometric techniques such as TIMS and ICPMS and in particular to AMS and RIMS. The methods for the preparation and mixing of the IRMM-075/1–6 series are described and the certification and verification procedures are reported.     

Preparation of drop-deposited quantitative uranium sources with low self-absorption

A source preparation procedure was optimised for ²³⁵U sources of about 1 mg or 100 Bq, to be standardised for their activity concentrations by α-particle counting at a defined solid angle. The aim was to obtain quantitative sources having a thin, homogeneous active layer with low self-absorption of the emitted α-particles. The procedure involves spraying the wetting and seeding agent in a circular shape onto a glass or stainless steel substrate, quantitative drop deposition of active solution onto the sprayed area by the pycnometer method and fast drying of the source on a heating plate. The fraction of heavily scattered and self-absorbed α-particles could be reduced to 0.05-0.1% for a majority of the sources.