A vibrational study of phase transitions in Fe2P2O7 and Cr2P2O7 under high‐pressures

The vibrational properties of synthetic iron diphosphate (Fe₂P₂O₇) and chromium diphosphate (Cr₂P₂O₇) are studied under high‐pressure conditions between ~22 and ~30 GPa, respectively. Each compound's structural response to pressure and pressure‐induced phase transitions are characterized. The chromium‐bearing sample shows coalescence of infrared bands occurring near 6 and 17 GPa: these may be associated with increases in the local symmetry of the P₂O₇ group. The iron sample undergoes a first‐order phase transition near ~9 GPa, and a possible phase transition near 5.5 GPa. At 9 GPa, the initially single, strong symmetric PO₄ stretching mode splits into four modes, and the sole asymmetric PO₄ stretching mode splits into two bands. These changes indicate the presence of multiple tetrahedral environments within a larger volume unit cell, and the relative frequencies of the split vibrations indicate a P₂O₇ environment with a markedly narrowed P–O–P angle. The difference between the behavior of the iron and chromium compounds is probably generated by the smaller iron ion producing a discontinuous decrease in the P–O–P angle at lower pressures than in the analogous chromium compound. Our results demonstrate that the dimerized P₂O₇ group remains stable under compression to over 20‐30 GPa at 300 K.     

Innovative method to produce large-area freestanding functional ceramic foils

Using thick and thin films instead of bulk functional materials presents tremendous advantages in the field of flexible electronics and component miniaturization. Here, a low-cost method to grow and release large-area, microscale thickness, freestanding, functional, ceramic foils is reported. It uses evaporation of sodium chloride to silicon wafer substrates as sacrificial layers, upon which functional lead titanate zirconate ceramic films are grown at 710?°C maximum temperature to validate the method. The freestanding, functional foils are then released by dissolution of the sacrificial sodium chloride in water and have the potential to be integrated into low-thermal stability printed circuits and flexible substrates. The optimization of the sodium chloride layer surface quality and bonding strength with the underlying wafer is achieved thanks to pre-annealing treatment.     

Revisiting the size selective performance of EPA's high-volume total suspended particulate matter (Hi-Vol TSP) sampler

Under the National Ambient Air Quality Standard (NAAQS) for airborne lead, measurements are conducted by means of a high-volume total suspended particulate matter (Hi-Vol TSP) sampler. In the decade between 1973 and 1983, there were 12 publications that explored the sampling characteristics and effectiveness of the Hi-Vol TSP, yet there persists uncertainty regarding its performance. This article presents an overview of the existing literature on the performance of the Hi-Vol TSP, and identifies the reported sampler effectiveness with respect to four factors: particle size (reported effectiveness of 7%–100%), wind speed (?36% to 100%), sampler orientation (7%–100%), and operational state (107%–140%). Effectiveness of the Hi-Vol TSP was evaluated with a solid, polydisperse aerosol in a controlled wind tunnel setting. Isokinetic samplers were deployed alongside the Hi-Vol TSP to investigate three wind speeds (2, 8, and 24 km h^?1), three sampler orientations (0°, 45°, 90°), and two operational states (on, off) for aerosols with aerodynamic diameters from 5 to 35 µm. Results indicate that particle diameter was the largest determining factor of effectiveness followed by wind speed. Orientation of the sampler did not have a significant effect at 2 and 8 km h^?1 but did at 24 km h^?1. In a passive state, the Hi-Vol TSP was collected between 1% and 7% of available aerosol depending on particle size and wind speed. Results of this research do not invalidate results of previous studies but rather contribute to our overall understanding of the Hi-Vol TSP's size-selective performance. While results generally agreed with previous studies, the Hi-Vol TSP was found to exhibit less dependence on these four factors than previously reported.

© 2017 American Association for Aerosol Research     

A predicted three-dimensional structure for the human immunodeficiency virus binding domains of CD4 antigen

A predicted three-dimensional structure of the two N-terminalextracellular domains of human CD4 antigen, a cell surface glycoprotein,is reported. This region of CD4, particularly the first domain,has been identified as containing the binding region for theenvelope gp120 protein of the human immuno-deficiency virus.The model was predicted based on the sequence homology of eachdomain with the variable light chain of immunoglobulins. Theframework ß-sheet regions were taken from the crystalcoordinates of REI. For one region in the first domain of CD4there was an ambiguity in the alignment with REI and two alternatemodels are presented. Loops connecting the framework were modeledfrom fragments selected from a database of main chain coordinatesfrom all known protein structures. Residues identified as involvedin binding gp120 have been located in several other studieswithin the first domain of CD4. Epitopes from eight monoclonalantibodies have been mapped onto residues in both domains. Competitionof these antibodies with each other and with gp120 can be interpretedfrom the structural model.     

EPR Spectroscopy and Imaging of Free Radicals in Food

Electron Paramagnetic Resonance (EPR) is a well-known spectroscopic and imaging technique that can detect free radicals both in vitro and non-invasively in vivo, with high sensitivity. In food, free radicals can be generated by several commonly used industrial processes, such as radiosterilization or heat treatment. EPR spectroscopy has been widely used to detect radioinduced free radicals in food, but is limited to the measurement of the global response of a sample. EPR imaging (EPRI) allows the spin density distribution of free radicals to be mapped within objects. We investigated the possibility of acquiring 2D and 3D EPR images of the distribution of free radicals in various foodstuffs with naturally occurring or induced free radicals, including frogs' legs, tea leaves, coffee beans, and sunflower seeds. Our results demonstrated that the free radicals contained in foodstuffs give EPR signals with characteristics compatible with the acquisition of high-quality images. Small-size structures (e.g., frog bones, 1.0–1.5 mm width) could be delineated with accuracy. The strongest signals came from irradiated samples, but low-intensity signals from naturally occurring free radicals could also be imaged. EPRI is likely to be used when additional information is needed about the spatial distribution of unpaired electrons. The method offers the unique ability to monitor the fate of these free radicals in biological samples and in vivo.     

Structure-conductivity relationship of PrBaMnMoO6-δ through in-situ measurements: A neutron diffraction study

The structural and electrochemical properties of the double perovskite-type oxide, PrBaMnMoO_6-δ, was investigated using neutron diffraction with in-situ conductivity measurement under a dry Argon atmosphere from 25 °C to 700 °C. A Rietveld refinement of the neutron diffraction data confirmed monoclinic symmetry in the P2₁/n space group. Rietveld refinement also confirms the unit cell parameters of a = 5.6567 (1) Å, b = 5.6065 (2) Å, c = 7.9344 (1) Å and β = 84.43° with reliable atomic positions and refinement factors (R-factors). Neutron diffraction data refinement shows two minor phases (<5%), an orthorhombic AB₂O₅ type phase of PrMn₂O₅ in the Pbam (No. 32) space group with unit cell parameters, a = 7.9672 (1) Å, b = 8.9043 (2) Å and c = 5.8540 (1) Å and a scheelite phase of BaMoO₄ in the tetragonal I4₁/a (88) space group with the unit cell parameters, a = b = 5.9522 (1) Å, and c = 12.3211 (2) Å. Morphological images revealed a porous and intertwined microstructure. In-situ conductivity measurement shows that the total conductivity of this material was 130.84 Scm^?1 at 700 °C.     

Specific inhibition of biohydrogen-producing Clostridium sp. after dilute-acid pretreatment of sunflower stalks

Dilute-acid pretreatments are commonly used to solubilize holocelluloses of lignocellulosic materials and represent a promising route to enhance biohydrogen production by dark fermentation. Besides the soluble sugars released, furan derivatives, such as furfural and 5-HMF, as well as phenolic compounds can accumulate in dilute-acid hydrolyzates and that may affect fermentative microbial populations. In this study, biohydrogen production from glucose (5 g VS L⁻¹) in batch tests was investigated in presence of increasing volumes (0% – control, 3.75%, 7.5%, 15% and 35% (v/v)) of dilute acid hydrolyzate generated from sunflower stalks (170 °C, 1 h, 4 g HCl/100 gTS). A sharp decrease of the hydrogen yield was observed from 2.04 mol H₂ mol⁻¹_{eq. hexose initial} in the control to 0 mol H₂ mol⁻¹_{eq. hexose initial} for volumes higher than 15% of added hydrolyzate. Although acetate and butyrate were the main end-products found in the control, ethanol and lactate accumulated accordingly with the increasing addition of hydrolyzate. A clear shift of dominant microbial populations from Clostridium sp. to Sporolactobacillus sp. was concomitantly observed, suggesting a specific inhibition of the biohydrogen-producing bacteria by adding increasing volumes of hydrolyzates.     

People-to-People-to-Geographical-Places: The P3 Framework for Location-Based Community Systems

In this paper we examine an emerging class of systems that link People-to-People-to-Geographical-Places; we call these P3-Systems. Through analyzing the literature, we have identified four major P3-System design techniques: People-Centered systems that use either absolute user location (e.g. Active Badge) or user proximity (e.g. Hocman) and Place-Centered systems based on either a representation of peoples use of physical spaces (e.g. ActiveMap) or on a matching virtual space that enables online interaction linked to physical location (e.g. Geonotes). In addition, each feature can be instantiated synchronously or asynchronously. The P3-System framework organizes existing systems into meaningful categories and structures the design space for an interesting new class of potentially context-aware systems. Our discussion of the framework suggests new ways of understanding and addressing the privacy concerns associated with location aware community system and outlines additional socio-technical challenges and opportunities.     

Hirsch index or Hirsch rate? Some thoughts arising from Liang’s data

Hirsch’s h-index gives a single number that in some sense summarizes an author’s research output and its impact. Since an individual author’s h-index will be time-dependent, we propose instead the h-rate which, according to theory, is (almost) constant. We re-analyse a previously published data set (Liang, 2006) which, although not of the precise form to properly test our model, reveals that in many cases we do not have a constant h-rate. On the other hand this then suggests ways in which deeper scientometric investigations could be carried out. This work should be viewed as complementary to that of Liang (2006).