Event-based processing of neutron scattering data at the Spallation Neutron Source

The Spallation Neutron Source at Oak Ridge National Laboratory, USA, ushered in a new era of neutron scattering experiments through the use of event-based data. Tagging each neutron event allows pump–probe experiments, measurements with a parameter asynchronous to the source, measurements with continuously varying parameters and novel ways of testing instrument components. This contribution will focus on a few examples. A pulsed magnet has been used to study diffraction under extreme fields. Continuous ramping of temperature is becoming standard on the POWGEN diffractometer. Battery degradation and phase transformations under heat and stress are often studied on the VULCAN diffractometer. Supercooled Al2O3 was studied on NOMAD. A study of a metallic glass through its glass transition was performed on the ARCS spectrometer, and the effect of source variation on chopper stability was studied for the SEQUOIA spectrometer. Besides a summary of these examples, an overview is provided of the hardware and software advances to enable these and many other event-based measurements

Event-based processing of neutron scattering data at the Spallation Neutron Source

The Spallation Neutron Source at Oak Ridge National Laboratory, USA, ushered in a new era of neutron scattering experiments through the use of event-based data. Tagging each neutron event allows pump–probe experiments, measurements with a parameter asynchronous to the source, measurements with continuously varying parameters and novel ways of testing instrument components. This contribution will focus on a few examples. A pulsed magnet has been used to study diffraction under extreme fields. Continuous ramping of temperature is becoming standard on the POWGEN diffractometer. Battery degradation and phase transformations under heat and stress are often studied on the VULCAN diffractometer. Supercooled Al2O3 was studied on NOMAD. A study of a metallic glass through its glass transition was performed on the ARCS spectrometer, and the effect of source variation on chopper stability was studied for the SEQUOIA spectrometer. Besides a summary of these examples, an overview is provided of the hardware and software advances to enable these and many other event-based measurements

Promoting Catalytic Activity of Boron by Phosphor in Propane Oxidative Dehydrogenation

Metal-free boron-containing materials show excellent performance in the oxidative dehydrogenation of propane (ODHP) reaction, while it remains unclear how the composition of the materials may influence their catalytic activity. Herein, by using boron phosphide (BP) as the test bed, a density functional theory study of the influences of P atoms in the backbone and the extent of surface oxidation on the catalytic activity was reported to address the structure–catalytic activity relationship in the ODHP reaction. The calculations show that (1) the P element in BP may influence the composition of the occupied states of BP (P, 47.3%; O, 98.8%; and N, 81.7%) and bring significant impact on its properties. The influence of O in the B2O3 (O) and N in the h-BN (N) was also analyzed for comparison. (2) The more oxidized surface (BP-H) is more reactive than the less oxidized surface (BP-L) in view of the lower free-energy barrier to the rate-determining step (45.8 vs 57.3 kcal/mol for the dehydrogenation of propane step, respectively). This study explains the role of the P element and the effect of surface oxidation and provides a comprehensive understanding of the structure–activity relationship of boron-containing materials in ODHP

Association of serum glycine levels with metabolic syndrome in an elderly Chinese population

BACKGROUND: Several studies have identified a negative association between serum glycine (Gly) levels and metabolic syndrome (MetS). However, this association has not been fully established in the elderly. METHODS: A total of 472 Chinese individuals (272 males and 200 females, 70.1 ± 6.6 years old) participated in a population-based, cross-sectional survey in Beijing Hospital. The MetS and its components were defined based on the 2006 International Diabetes Federation (IDF) standard for Asians. Serum Gly concentration was determined using isotope dilution liquid chromatography tandem mass spectrometry. RESULT: The proportion of patients with MetS decreased gradually with increasing Gly levels (p for trend < 0.001), and serum Gly concentrations declined gradually with increasing numbers of MetS components (p = 0.03 for trend). After adjusting for age and gender, lower Gly levels were significantly associated with MetS and central obesity, with OR (95% CI) of 0.40 (0.25–0.65) and 0.46 (0.28–0.74). The stratified analysis conducted according to age showed that the OR between serum Gly levels and MetS was greater in those older than 65 (OR = 0.66; 95% CI, 0.51–0.86) than in those younger than 65 (OR = 0.89; 95% CI, 0.54–1.46). In the stratified analysis, using other age cut-off points, the results consistently showed that the association between serum Gly levels and MetS was more remarkable in the older groups. CONCLUSIONS: Gly levels are associated with cardiometabolic characteristics and MetS in the elderly, and the association is more pronounced in very old people than in younger old people

DEMAND, a Dimensional Extreme Magnetic Neutron Diffractometer at the High Flux Isotope Reactor

A two-dimensional (2D) Anger camera detector has been used at the HB-3A four-circle single-crystal neutron diffractometer at the High Flux Isotope Reactor (HFIR) since 2013. The 2D detector has enabled the capabilities of measuring sub-mm crystals and spin density maps, enhanced the efficiency of data collection and phase transition detection, and improved the signal-to-noise ratio. Recently, the HB-3A four-circle diffractometer has been undergoing a detector upgrade towards a much larger area, magnetic-field-insensitive, Anger camera detector. The instrument will become capable of doing single-crystal neutron diffraction under ultra-low temperatures (50 mK), magnetic fields (up to 8 T), electric fields (up to 11 kV/mm), and hydrostatic high pressures (up to 45 GPa). Furthermore, half-polarized neutron diffraction is also available to measure weak ferromagnetism and local site magnetic susceptibilities. With the new high-resolution 2D detector, the four-circle diffractometer has become more powerful for studying magnetic materials under extreme sample environment conditions; hence, it has been given a new name: DEMAND